《Energy Storage Science and Technology》(ESST) (CN10-1076/TK, ISSN2095-4239) is the bimonthly journal in the area of energy storage, and hosted by Chemical Industry Press and the Chemical Industry and Engineering Society of China in 2012,The editor-in-chief now is professor HUANG Xuejie of Institute of Physics, CAS. ESST is focusing on both fundamental and applied aspects of energy storage science and technology. Submissions can be in English or Chinese. It is included in Chinese Sci-tech Core Journal, main indexed by CSCD(China), Ulrichsweb(America), INSPEC(England), CA(America), and others database etc.
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05 March 2020, Volume 9 Issue 2 Previous Issue   
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4.5 V Li-ion battery with a carbonate ester-based electrolyte
Yuanjie ZHAN, Yida WU, Xiaowei MA, Haicong LIANG, Xuejie HUANG
2020, 9 (2):  319-330.  doi: 10.19799/j.cnki.2095-4239.2020.0045
Abstract ( 91 )   HTML ( 12 )   PDF (6265KB) ( 124 )  

LiNi0.5Mn1.5O4 (LNMO) spinel is a cathode material with a voltage plateau of 4.7 V versus Li. An LNMO cell shows an operation voltage that is 1.3 and 0.9 V higher than that of a LiFePO4 and NCM cell, respectively. The LNMO cell has the advantages of higher specific energy and lower cost and can meet the long range per charge and low cost requirements of electric vehicles in the post-subsidy era after 2020. The high operating voltage is undoubtedly a great advantage; however, the extremely high cut-off voltage (4.9 V vs. Li+) is also a huge obstacle in its commercialization. The widely used carbonate ester-based electrolytes are considered unsuitable owing to the intrinsic thermodynamic tendency of these carbonates to decompose at potentials well below the thermodynamic threshold required for the reversible reactions of these high-voltage systems. Alternatives such as fluoride carbonate, thiophene, and ionic liquids were introduced to replace the carbonate solvent used as the electrolyte in present commercial lithium-ion batteries. However, full battery data have not been reported with respect to optimum cycle performance and a sufficiently high coulombic efficiency for practical batteries. In this study, LiNi0.5Mn1.5O4/graphite full cells are demonstrated using an electrolyte that is based on carbonate esters. The side reactions between the electrolyte and interface are inhibited by modifying the interface of lithium nickel-manganate cathode materials to improve the efficiency and cycling performance of the full cells. However, there is still a gap between commercial applications. The side reactions are further inhibited using the GDY electrolyte to improve the efficiency and cycling performance of the full cells. The full cells show superior electrochemical performance compared to that of the reported full cells that use high-voltage-resistant solvents. The capacity retention rate of the full cells can reach 88.02% and the coulombic efficiency can reach 99.93% at 1C and 25 ℃ after 1000 cycles. The capacity retention rate of the full cells can reach 93.88% and the coulombic efficiency is 99.80% at 1C and 55 ℃ after 300 cycles. This performance has already met the requirements of EV applications. In addition, the inhibition effect of material modification and electrolyte optimization on the side reactions between the electrolyte and interface is demonstrated by comparing the median polarization voltage and impedance during cycling. These results indicate that LiNi0.5Mn1.5O4/graphite full cells, which are based on carbonate ester electrolytes, with a working voltage of 4.5 V can be commercialized.

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Effect of electrolyte composition on the performance of sulfur cathode based on solid-phase conversion mechanism
Xiangjiang WU, Feng HE, Yuliang CAO, Xinping AI
2020, 9 (2):  331-338.  doi: 10.19799/j.cnki.2095-4239.2019.0282
Abstract ( 73 )   HTML ( 7 )   PDF (3476KB) ( 72 )  

Lithium-sulfur battery (Li-S) shows a great promise as a new generation electric energy storage technology due to its very high theoretical energy density (2600 W·h/kg). However, fabricating a sulfur cathode with acceptable high electrochemical utilization and long-term cyclability is a great challenge, mainly due to the unavoidable generation, dissolution and deactivation of soluble lithium polysulfide (PS) intermediates generated during the discharge process. Our previous study has demonstrated that the redox chemistry of sulfur cathodes can be converted from dissolution-deposition mechanism to a solid-phase conversion (SPC) reaction by in situ formation of a thin and compact solid electrolyte interface (SEI) on the sulfur surface through a prompt nucleophilic reaction of soluble PSs with vinyl carbonate (VC) molecule specially designed as a co-solvent in the ether-based electrolyte, thus separating the direct contact of electrolyte with the active sulfur and completely suppressing the generation and dissolution of PSs. To obtain the research results more in line with the practical application, we prepared a high-sulfur loading sulfur/carbon composite cathode (7mg/cm2) in this work, and investigated the influence of electrolyte composition, including VC content and LiTFSI concentration, on the performance of solid-phase conversion sulfur electrode. The experimental results demonstrated that, in a co-solvent electrolyte of 2.5 mol/L LiTFSI + VC/DOL/DME (volume ratio is 10:5:5) with high VC content and high LiTFSI concentration, thus-prepared high sulfur loading cathode can exhibit a high reversible specific capacity of 1090 mA·h/g and excellent cycling performance with a capacity retention of 97.2% after 50 cycles. This study provides a new insight for future development of high sulfur loading, structurally and electrochemically stable sulfur cathodes for new generation advanced Li-S batteries.

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Balance between ion migration and electron transport in composite cathodes for all-solid-state lithium-sulfur batteries
Ge YE, Hong YUAN, Chenzi ZHAO, Gaolong ZHU, Lei XU, Lipeng HOU, Xinbing CHENG, Chuanxin HE, Haoxiong NAN, Quanbin LIU, Jiaqi HUANG, Qiang ZHANG
2020, 9 (2):  339-345.  doi: 10.19799/j.cnki.2095-4239.2020.0002
Abstract ( 130 )   HTML ( 8 )   PDF (3062KB) ( 164 )  

All-solid-state lithium-sulfur batteries (ASSLSBs) are strong candidates for next-generation energy-storage systems owing to their high theoretical energy density and the ability to eliminate the shuttle effect. The insulation of sulfur in solid-state cathodes requires additional ionic and electronic conductors, where the balance between ion and electron transport is crucial for a stable electrochemical reaction. In addition, for high-energy-density batteries, it is important to develop composite cathodes with high sulfur content and less amount of inactive substances. Herein, we investigate the balance between ion migration and electron transport by adjusting the content of sulfide electrolyte Li10GeP2S12 (LGPS) and carbon nanotubes (CNTs) under high sulfur content (40% of weight fraction). Sulfur cathodes were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy. The ionic and electronic conductivities of composite cathodes were measured separately. Electrochemical tests indicate that ion transportation is hindered when LGPS content reduces, while the electronic conductivity is limited by the considerable excess of LGPS electrolytes. By comparing the specific capacity in the first cycle and capacity retention in the following cycle, we conclude that the optimal solution should contain 15% CNT and 45% (weight fraction) LGPS. In this case, the discharge specific capacity of ASSLSBs is 621 mA·h·g-1 and the rate of capacity decay is 3%.

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Synthesis and performance of P2-O3 composite-phase Li-rich Mn-based cathode materials
Jianyu ZHANG, Liping LU, Zhihui YU, Jin SONG, Dingguo XIA
2020, 9 (2):  346-352.  doi: 10.19799/j.cnki.2095-4239.2020.0021
Abstract ( 83 )   HTML ( 5 )   PDF (2548KB) ( 117 )  

To solve the common issues of voltage decay, low initial coulombic efficiency, and poor rate performance that occur in high-energy lithium-rich cathode materials, a P2-O3 composite-phase cathode material was synthesized by the simple solid-state method. During the first charging and discharging process, this material experienced P2-O2 phase transition, and the O2 phase prevented transition metal migration; thus, voltage decay was effectively mitigated. This P2-O3 composite-phase cathode material delivered a specific capacity of over 290 mA·h/g with an initial coulombic efficiency of 97% under a current density of 0.1C (1C = 200 mA/g) at 2.0—4.6 V. When charged at 200 mA/g, this material released a capacity of about 240 mA·h/g. After 100 cycles, the capacity retention was approximately 80% and the voltage loss was less than 170 mV. This material is easy to synthesize. At 2.0—4.6 V, it delivered a capacity as high as that of traditional lithium-rich materials tested at 2.0—4.8 V, which greatly promotes the adaptation of lithium-rich materials with commercial electrolytes. Furthermore, the cycle performance is relatively optimum and the voltage decay is suppressed to some extent, which strongly promotes the practical application of lithium-rich materials in the electric vehicles market.

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Electrochemical performance of β-Li0.3V2O5 as a lithium-ion battery cathode material
Jian ZOU, Bojun WANG, Jiachao YANG, Xiaobin NIU, Liping WANG
2020, 9 (2):  353-360.  doi: 10.19799/j.cnki.2095-4239.2019.0222
Abstract ( 93 )   HTML ( 0 )   PDF (3267KB) ( 88 )  

With the development of lithium (Li) and all-solid-state batteries, high energy-density Li-free/deficient cathode materials have received considerable attention. In this study, well-crystallized micron-size Li-deficient cathode material β-Li0.3V2O5 is synthesized via a one-step high-temperature solid-state reaction with an electronic conductivity of 2.20 × 10-4 S/cm. This material exhibits good cycling performance. It delivers a specific capacity of 247 mA·h/g when charging/discharging at 0.5 C between 2.2 V and 4.0 V, with a residual specific capacity of 204 mA·h/g after 100 cycles. In addition, β-Li0.3V2O5 shows excellent rate capabilities, i.e., 160 mA·h/g at 10C. Ex situ X-ray diffraction is applied to study phase transformations during the Li insertion/extraction process; five different phases exist in the voltage range of 1.5—4.0 V: β(0<x<0.27) → β′(0.57<x<0.75) → β1(0.57<x<1.92) → β2(0.75<x<1.92) → β3(1.92<x<2.52). The volume undergoes a small change during the cycling

process

a increases by a maximum of 3.1% (β2) and c increases by a maximum of 4.5% (β3).

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Low-temperature molten-salt-assisted recycling of spent LiNi1/3Co1/3Mn1/3O2 cathode materials
Ersha FAN, Li LI, Jiao LIN, Xiaodong ZHANG, Renjie CHEN, Feng WU
2020, 9 (2):  361-367.  doi: 10.19799/j.cnki.2095-4239.2019.0283
Abstract ( 67 )   HTML ( 6 )   PDF (3483KB) ( 85 )  

To resolve the secondary pollution and high energy consumption caused by current recycling technology, a green and efficient method for recycling spent LiNi1/3Co1/3Mn1/3O2 (NCM) cathode materials is proposed. Using ammonium chloride as the co-solvent, the method effectively leaches the valuable metals in the cathode materials through low-temperature roasting conversion and water-leaching at room temperature. The reaction parameters, namely, the roasting temperature, NH4Cl/NCM mass ratio, and roasting time, were investigated in detail. More than 97% of the Li, Ni, Co, and Mn were recovered under the optimum conditions (roasting temperature is 350 ℃, NH4Cl/NCM mass ratio is 3.5∶1, reaction time is 20 min). During the recycling process, the interphase conversion mechanism of the metal in the cathode material was systematically studied by X-ray diffraction analysis, scanning electron microscopy, and X-ray photoelectron spectroscopy. The energy intensity and industrial operability of the proposed recycling technology rivaled those of traditional hydrometallurgical and pyrometallurgical recycling technologies.

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Protective mechanism of the Li alloy film-buffered Li metal anode
Chenglin WANG, Shiji QU, Jingze LI
2020, 9 (2):  368-374.  doi: 10.19799/j.cnki.2095-4239.2020.0062
Abstract ( 87 )   HTML ( 2 )   PDF (3281KB) ( 140 )  

Lithium (Li) is the ideal anode material for next-generation high-energy-density Li batteries. The performance of a Li anode can be improved by coating it with a Li alloy film, the mechanism for which has not been well interpreted. Herein, a Li-Al alloy layer as a mixed conductor, which is formed by sputtering a 74 nm-thick Al film onto a Li sheet, demonstrates a different protection mechanism with respect to those of electron-conducting and ion-conducting protection layers. Scanning electron microscopy images show that Li ions are reduced on the alloy surface and spontaneously diffuse into the alloy layer because the Li+ concentration in the alloy layer is poor. Furthermore, the Li+ diffusion coefficient of the Li-Al alloy is superior to that of the bulk Li. Both factors ensure that Li is not plated on the surface of the alloy layer. A part of the diffused Li atoms is stored in the alloy layer, which considerably increases the layer thickness, and the remaining diffused Li is condensed at the interface between the alloy layer and the Li metal sheet. However, the alloy protection layer cracks after 200 cycles owing to the severe volume variation. Then, a liquid electrolyte can come in contact with Li through the cracks, and the alloy layer is gradually invalidated. This novel protection mechanism, i.e., the isolation of the reduction of Li+ from the nucleation/growth of Li in space, is very promising for improving the cycling performance of the Li metal anode. An ideal alloy-protection layer with high ion conductivity and excellent mechanical stability should guarantee the commercialization of Li anodes in the near future.

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Electrochemical performance of spinel LiMn2O4 inWater-in-salt aqueouselectrolyte
Xiaolin XIONG, Jinming YUE, Anxing ZHOU, Liumin SUO, Yongsheng HU, Hong LI, Xuejie HUANG
2020, 9 (2):  375-384.  doi: 10.19799/j.cnki.2095-4239.2020.0069
Abstract ( 54 )   HTML ( 10 )   PDF (4764KB) ( 66 )  

Spinel LiMn2O4 cathode is widely used in aqueous lithium-ion batteries whose electrochemical performance are highly dependent on its material properties including the chemical composition, particle size, morphology, crystal structure and so on. In this study, we objectively investigate three typical kinds of spinel LiMn2O4: pure LiMn2O4, LiAl x Mn2- x O4, and Li1+ x Mn2- x O4 respectively in super-high concentrated aqueous electrolytes. The evolution of crystal structure, morphology and chemical composition with the cycles carefully investigate by a series of chemical analysis (ICP), crystal structure (XRD), morphology characterization (TEM, SEM) and multiple electrochemical methods (EIS, CV) whose influence on the electrochemical performances is discussed detailly. It is discovered that pure LiMn2O4 is prone to Mn dissolution and Jahn-teller distortion resulting in the irreversible phase transitions and structure detraction thereby leading to severe capacity fading; the trace amount of Al3+ doping in LiMn2O4 enables to suppress the Jahn-Teller effect of Mn to a certain extent but cannot avoid completely Mn dissolution and lattice deformation whose cycling fading still exists evidently; compared with above-mentioned two kinds of cathodes, lithium-rich Li1+ x Mn2- x O4 presents much better electrochemical performance because the introduction of excessive Li in the crystal structure is favorable to effectively inhibit Mn dissolution and suppress Jahn-Teller distortion, thereby, it is suggested as an ideal cathode candidate for aqueous lithium ion battery.

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Role of Sn doping in layered chromium-based cathode materials for sodium-ion batteries
Jingjing BIAN, Shiyong CHU, Kaiying XI, Shaohua GUO, Haoshen ZHOU
2020, 9 (2):  385-391.  doi: 10.19799/j.cnki.2095-4239.2020.0006
Abstract ( 43 )   HTML ( 1 )   PDF (2880KB) ( 58 )  

The demand for electrochemical energy storage technology has significantly increased. Currently, the large-scale application of lithium-ion batteries can be attributed to their advantages such as high energy density and large power density; however, limited lithium resources restrict the further development of lithium-ion batteries. The potential applications of sodium-ion batteries are expected to solve this problem. Sodium is abundant, widely distributed, cheap, and has physical and chemical properties similar to those of lithium. Sodium can be used as a substitute for lithium in batteries. A Cr-based layered cathode material has the following advantages: abundant raw materials, easy synthesis methods, and controllable composition. However, when the Cr-based layered cathode material is charged to a relatively high voltage, Cr ions migrate from the transition metal layer to the sodium layer, and the structure of sodium chromate will undergo an irreversible structural transformation, which diminishes the capacity. In this study, a new layered material, Na0.7Cr0.85Sn0.15O2, was fabricated by doping Sn, which has a large ionic radius, into sodium chromate. The structure and electrochemical performance of the materials were systematically investigated. The results show that the doped material has a smooth voltage curve and a stable crystal structure. In addition, doping alleviates the serious attenuation of capacity and improves cycle stability. This new layered chromium-based oxide cathode material is expected to provide a new option for the development of cathode materials for sodium-ion batteries.

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Behavior of sodium-ion battery electrolytes based on the co-solvents of polyfluorinated ether and organic carbonates
Haiying CHE, Yan YU, Xinrong YANG, Xiaozhen LIAO, Linsen LI, Yonghong DENG, Zifeng MA
2020, 9 (2):  392-399.  doi: 10.19799/j.cnki.2095-4239.2020.0060
Abstract ( 50 )   HTML ( 1 )   PDF (4182KB) ( 48 )  

Solvents are essential for the ionic conductivity and safety of the electrolytes for lithium/sodium ion batteries. Organic carbonates have been used as solvents in commercial lithium-ion and sodium-ion batteries; however, their thermochemical stability needs to be improved. In this study, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (F-EPE) was first added to the basic electrolyte of NaPF6/EC-DEC-FEC, which partially replaced DEC to form a co-solvent, and a new electrolyte with a different solvent ratio was prepared. The effects of co-solvent F-EPE on the flammability, conductivity, and electrochemical window of the prepared electrolyte were investigated. The prepared electrolyte was applied to study the electrochemical characteristics of NaNi1/3Fe1/3Mn1/3O2 (NFM) cathode materials and to reveal the mechanism of the electrode–electrolyte interface. The influence of the electrolyte on the electrochemical performance of the battery was discussed, and the related interface mechanism was explained. A flammability test revealed that an increase in the content of F-EPE can improve the flame retardancy of the electrolyte and the safety of the corresponding battery. When the content of F-EPE reaches 30%, the electrolyte becomes nonflammable. An electrochemical window test revealed that F-EPE can improve the antioxidation ability and increase the decomposition voltage of the electrolyte. SEM, ICP, EIS, and XPS tests show that a battery with EDH532F has a more stable electrode interface and lower interface impedance compared to one with EC-DEC-FEC as the electrolyte. Thus, the cell with EDH532F has better cycling performance. Moreover, when the F-EPE content is 20%, the cycling performance of the cell is the best, and the capacity retention increases from 75.7% (EC-DEC-FEC) to 82.9% (EDH532F) after 150 cycles.

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Investigation of the performance and safety degradation caused by slight accumulation of electricity in traction batteries
Tianyi MA, Fang WANG, Dapeng XU, Chunjing LIN, Shiqiang LIU, Liduo CHEN
2020, 9 (2):  400-408.  doi: 10.19799/j.cnki.2095-4239.2020.0010
Abstract ( 35 )   HTML ( 2 )   PDF (3551KB) ( 58 )  

Because the energy density of lithium-ion (Li-ion) batteries for vehicles and grid storage continues to increase, the safety of Li-ion batteries throughout their life cycle has become the key issue for the continuous development of this technology. Electrical abuse behavior considerably affects the performance and safety of batteries; however, the impact of the slight accumulation of electricity is often ignored because the feedback is not considerable in the short term. This study aimed to investigate the slight over-discharge abuse, which is most likely to be encountered in the practical use of electric vehicles and grid storage, by conducting a “material-battery-performance” multi-level analysis by combining electrochemical testing, tomography analysis, and material characterization technologies. In addition, the effect of mild over-discharge accumulation on the lithium state of the battery was analyzed using neutron imaging technology.

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Effect of precursor microstructure on the performance of LiNi0.85Co0.10Mn0.05O2 cathode materials
Long CHEN, Erdong ZHANG, Azhar IQBAL, Daocong LI, Maoping YANG, Xin XIA
2020, 9 (2):  409-414.  doi: 10.19799/j.cnki.2095-4239.2019.0291
Abstract ( 67 )   HTML ( 6 )   PDF (1979KB) ( 111 )  

In this work, the nucleation and crystal growth processes of the precursor can be controlled by adjusting the ammonia concentration and pH value during the co-precipitation processes, and two types of high-nickel Ni0.85Co0.10Mn0.05(OH)2 precursors with different particle structures (agglomerated vs. uniform) are synthesized. The as-synthesized precursors show almost similar physical and chemical properties. After sintering process, the obtained LiNi0.85Co0.10Mn0.05O2 cathodes also showed similar initial charge/discharge capacities and rate performance. However, LiNi0.85Co0.10Mn0.05O2 cathode resulted from the precursor with uniform structure demonstrates better cycling performance (98.3% capacity retention after 50 cycles at 1 C) than that of the cathode with agglomerated structure (96.9%). The LiNi0.85Co0.10Mn0.05O2 cathode with uniform structure shows stable redox peak position and voltage interval after cycle test by dQ ·dV -1 analysis, which indicated the lower polarization loss. Further SEM characterization also revealed the suppression of the microcracks that maintain the mechanical integrity of the particles throughout the cycling process along with the establishment of a stable electrode/electrolyte interface to improved cycling stability.

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SrFeF x O3- x - δ cathode with high catalytic activity for solid oxide fuel cells
Xu DONG, Zhihong DU, Yang ZHANG, Keyun LI, Hailei ZHAO
2020, 9 (2):  415-424.  doi: 10.19799/j.cnki.2095-4239.2020.0011
Abstract ( 47 )   HTML ( 6 )   PDF (5713KB) ( 39 )  

SrFeO3- δ is a widely studied cathode material for solid oxide fuel cells owing to its good mixed electronic and oxygen ionic conductivity and considerable catalytic activity. However, SrFeO3- δ usually has a tetragonal structure at room temperature, and the tetragonal-to-cubic phase transition at high temperatures produces volume change, which poses the risk of structural deterioration. In addition, its catalytic activity toward oxygen reduction needs to be improved further. In this study, fluorine substitution of oxygen was employed to modulate the lattice structure of SrFeO3- δ as a cathode material and improve its various properties. F-ion-doped SrFeF x O3- x - δ (SFF x , x = 0, 0.125, and 0.25) materials were synthesized via the sol-gel process. The effects of F ion doping on the lattice structure, thermal expansion coefficient, electrical conductivity, oxygen surface exchange coefficient, oxygen bulk diffusion coefficient, polarization resistance, electrode reaction kinetics, and cell performance were investigated through X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical characterization techniques. The results show that the partial substitution of O ions by F ions (x = 0.25) can stabilize the cubic structure of SrFeF x O3- x - δ at room temperature owing to a decreased tolerance factor, decreased iron valence, and increased Fe ion size. Both cell parameters and cell volume increase with F ion doping content. The F ion doping decreases the thermal expansion coefficient but increases the electrical conductivity of SFFx. With F ion doping, the oxygen surface exchange coefficient (K ex) and bulk diffusion coefficient (D chem) of the material improve, which is correlated with the effective reduction of the polarization resistance (R p) of the materials by F substitution. By monitoring the impedance change of each component process with a change in oxygen partial pressure, the electrode reaction kinetics study reveals that F ion doping considerably enhances the dissociation process of oxygen molecules on the surface of SFF x . For materials with an F-doping amount of x = 0.25, the R p value is 0.508, 0.173, 0.077, 0.039, and 0.023 Ω·cm2 at 650, 700, 750, 800, and 850 °C, respectively. Single cells were constructed using SFF x and Sm0.2Ce0.8O2- δ (1∶1) as the cathode, La0.9Sr0.1Ga0.8Mg0.2O3- δ (300 μm) as the electrolyte, La0.4Ce0.6O2- δ as the buffer layer, and NiO-Gd0.1Ce0.9O2- δ as the anode. Humidified H2 and air were fed as the fuel and oxidant, respectively. The cell tests show that the F ion doping significantly increases the peak power density of the cells. For materials with x = 0.25, the maximum power density can reach 446 and 962 mW·cm-2 at 700 °C and 850 °C, respectively.

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Numerical study on the air distribution characteristics of the turbine regulating stage in a compressed air energy storage system
Jiahao LIU, Xing WANG, Xuehui ZHANG, Wen LI, Yangli ZHU, Haisheng CHEN
2020, 9 (2):  425-434.  doi: 10.19799/j.cnki.2095-4239.2020.0038
Abstract ( 28 )   HTML ( 0 )   PDF (5108KB) ( 25 )  

Compressed air energy storage is considered the most promising large-scale energy storage system. Because a compressed air energy storage system operates under variable working conditions and is characterized by the long-term pressure loss between the air storage device and the inlet of the turbine, in this study, a nozzle governing mode is proposed to reduce throttling losses. Numerical calculation and analysis of a closed radial turbine in a MW-level compressed air energy storage system were performed by the computational fluid dynamics method. By adjusting the air state at the inlet of each nozzle group, the effects of air distribution on control-stage performance was studied. The results show that under the nozzle governing condition, the flow rate of the turbine varies between 0.86 and 1.42 times that of the rated flow rate, which meets the regulation requirement. The output of the regulating stage can also be increased by 11.2% at the specified flow rate compared with that using throttled governing. The abovementioned results reveal the effects of air distribution on the performance of the radial turbine, which provides a theoretical basis for the design, optimization, and system operation control of a nozzle governing radial turbine.

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Preparation and comparative analysis of thermophysical properties on low melting point mixed nitrate molten salts
Cancan ZHANG, Yuting WU, Yuanwei LU
2020, 9 (2):  435-439.  doi: 10.19799/j.cnki.2095-4239.2020.0023
Abstract ( 22 )   HTML ( 1 )   PDF (1502KB) ( 17 )  

Mixed Nitrates Molten salt as heat transfer and storage medium have been widely applied in commercial solar power plant and thermal energy storage. After more than ten years of independent research and development, our team has successfully obtained LMPS series mixed nitric acid molten salt with low melting point and high decomposition temperature. Firstly, the DSC and TG curves of different mixed nitrates are measured and analyzed in this paper. It is found that the melting point of LMPS II quaternary mixed nitrate salt is the lowest, the decomposition temperature is the highest, and the liquid range was the largest. Secondly, the results of 1200 hours constant high temperature test show that the fluctuation range of melting point is no more than ±4.89% and decomposition temperature of mixed quaternary nitrate salt at low melting point is no more than ±3.54%.The specific heat capacity and thermal conductivity of LMPS II quaternary salt are better than that of LMPS I quaternary salt and LMPS III binary salt. Therefore, in practical engineering applications, the quaternary nitrate salt of LMPS II with low melting point and high decomposition temperature has excellent heat transfer and heat storage performance; it can reduce the operating cost of the system and the risk of freezing.

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Effect of the in situ synthesis of nano-ZnO on the specific heat capacity of solar salt
Feng XIONG, Xiaomin CHENG, Yuanyuan LI, Pei DAI, Xiuli WANG, Hao ZHONG
2020, 9 (2):  440-447.  doi: 10.19799/j.cnki.2095-4239.2019.0297
Abstract ( 15 )   HTML ( 0 )   PDF (3081KB) ( 9 )  

Solar salt as a heat storage material with optimum thermal properties has promising application prospects with respect to the thermal power and heat storage of solar energy. By enhancing the specific heat capacity of solar salt, it is possible to considerably improve the thermal storage capacity. In this study, nano-ZnO flakes were synthesized in situ in solar salt via the hydrothermal method, and granular ZnO was synthesized in situ in solar salt via the combustion method. XRD, EDS, FE-SEM, TEM, and DSC were used to study the effect of nano-ZnO on the structure and properties of solar salt. Results show that the size of ZnO nanosheets is between 50 and 200 nm, the size of ZnO nanoparticles is between 30 and 200 nm, and nano-ZnO has good dispersibility in salt. When the weight content of ZnO nanoflakes in solar salt was 1%, the specific heat of the solid and liquid of modified solar salt reached 2.09 and 1.78 J·(g·℃)-1, which denote an increase of 71.3% and 38.0%, respectively. When the ZnO nanoparticle weight content in solar salt was 0.75%, the solid and liquid specific heat of modified solar salt reached 2.22 and 1.88 J·(g·℃)-1, which denote an increase of 82.0% and 45.7%, respectively. The addition of granular ZnO has a better specific heat capacity enhancement effect on solar salt than that of ZnO nanoflakes.

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Development of strategies for high-energy-density lithium batteries
Wenjun LI, Hangyu XU, Qi YANG, Jiuming LI, Zhenyu ZHANG, Shengbin WANG, Jiayue PENG, Bin ZHANG, Xianglei CHEN, Zhen ZHANG, Meng YANG, Yan ZHAO, Yaoyao GENG, Wenshi HUANG, Zepeng DING, Lei ZHANG, Qiyou TIAN, Huigen YU, Hong LI
2020, 9 (2):  448-478.  doi: 10.19799/j.cnki.2095-4239.2020.0050
Abstract ( 84 )   HTML ( 10 )   PDF (42812KB) ( 261 )  

In recent years, various governments have proposed staged goals for the development of lithium batteries with high energy densities. The main challenge is to identify a balanced solution to satisfy energy density and other characteristics such as safety, cycle life, and rate capability. This paper analyzes the main problems and possible solutions considering the available cathode, anode, electrolyte, and separator materials. A forward cell design is discussed.

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Characterization and testing of key electrical and electrochemical properties of lithium-ion solid electrolytes
Xiao HUANG, Linbin WU, Zhen HUANG, Jiu LIN, Xiaoxiong XU
2020, 9 (2):  479-500.  doi: 10.19799/j.cnki.2095-4239.2019.0296
Abstract ( 80 )   HTML ( 5 )   PDF (12753KB) ( 139 )  

Lithium-ion solid electrolyte is a key material for the development of high-safety solid-state lithium batteries, and its electrochemical performance is closely related to the full batteries. Ionic conductivity, electronic conductivity, electrochemical window, and stability versus lithium interface are the key electrical and electrochemical properties of solid electrolytes. In-depth characterization and analysis can help understand the compatibility between different electrolyte and electrode materials, which facilitates the development of high-performance solid-state lithium batteries. This study introduces different types of lithium-ion solid electrolytes. The key electrochemical performances, methods, principles, and equipment for testing are described. In addition, the analysis of the data is described in combination with specific cases.

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Recent progress in interfaces of all-solid-state lithium batteries based on sulfide electrolytes
Jinghua WU, Xiayin YAO
2020, 9 (2):  501-514.  doi: 10.19799/j.cnki.2095-4239.2020.0065
Abstract ( 40 )   HTML ( 5 )   PDF (1990KB) ( 59 )  

All-solid-state lithium batteries, in which the liquid organic electrolytes are replaced by nonflammable inorganic solid electrolytes, are expected to ultimately resolve the combustion and leakage safety issues of lithium batteries. Meanwhile, a lithium anode is anticipated to improve the energy density. In recent years, breakthroughs in ionic conductivity have identified sulfide electrolyte as a promising ion conductor. However, many challenges in this field remain unsolved, including the stability of sulfide electrolytes, the instability of electrolyte/electrode interfaces, and lithium dendrite formations within the electrolyte. Therefore, a stable solid electrolyte/electrode interface is the keystone of all-solid-state lithium batteries with high performance. Considering the challenges and opportunities for all-solid-state lithium batteries based on sulfide electrolytes, we summarize various interface problems and interface modification strategies. Possible research directions and development trends of sulfide-based all-solid-state lithium batteries are also discussed.

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Na-ion batteries: From fundamental research to engineering exploration
Xiaohui RONG, Yaxiang LU, Xingguo QI, Quan ZHOU, Weihe KONG, Kun TANG, Liquan CHEN, Yongsheng HU
2020, 9 (2):  515-522.  doi: 10.19799/j.cnki.2095-4239.2020.0054
Abstract ( 65 )   HTML ( 4 )   PDF (3020KB) ( 80 )  

With the increasing demand for low-cost energy storage systems, more and more researchers and engineers have been involved in the fundamental research and engineering exploration of Na-ion batteries (NIBs), which grew rapidly in the past decade. This article firstly analyzes the situation of global lithium resource, especially the potential risks in China. Then we review the history of NIBs and introduce their global industrialization status in recent years. According to the latest research progress in this field, we summarize seven advantages of NIBs in terms of cost, performance, etc., which endows NIBs with huge development potential. Finally, we focus on introducing our work on the development and mass production of low-cost electrode materials such as copper-based layered oxide cathodes and disordered carbon anodes, as well as the application demonstration and engineering scale-up of NIBs. The successful demonstration of Ah-grade cells and battery packs for NIBs has initially proved their feasibility. By optimizing electrode materials, electrolytes, manufacturing and integration, and battery management, it is expected to further improve the comprehensive performance of NIBs, and realize the practical applications in low-speed electric vehicles, data center backup power supplies, communication base stations, household/industrial energy storage systems, and large-scale energy storage.

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Recent progress on the Li7La3Zr2O12 LLZO solid electrolyte
Pengfeng JIANG, Yuansheng SHI, Kangwan LI, Baichuan HAN, Liquan YAN, Yang SUN, Xia LU
2020, 9 (2):  523-537.  doi: 10.19799/j.cnki.2095-4239.2019.0286
Abstract ( 91 )   HTML ( 6 )   PDF (5127KB) ( 91 )  

Solid-state batteries with high safety, high energy density, and long lifespan are considered one of the most important next-generation energy storage technologies to replace traditional organic rechargeable Li-ion batteries. The development of such solid batteries is limited by the solid electrolytes that are compatible with solid-solid interfaces. Since it’s discovered in 2007, the garnet Li7La3Zr2O12 (LLZO) solid electrolyte has demonstrated a promising application in solid batteries owing to its superior ionic conductivity (ca. 10-3 S/cm at room temperature) and highly stable chemical/electrochemical activities. Therefore, this review systematically summarizes the recent progress on the structural manipulation, elemental doping, and the fundamentals of fast ionic migration. In addition, this paper introduces an approach to optimize the interface structure between the positive/negative electrodes and the garnet-type solid electrolyte, improve the interface wettability and compatibility with LLZO electrodes, and presents the history of Li-rich garnet solid electrolytes. The new results on the development of high-performance LLZO-based solid batteries are also included to outline the path for building better solid batteries. This paper sheds new light on promoting the practical application of all-solid-state lithium-ion batteries.

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Research progress on high-voltage electrolytes for ternary NCM lithium-ion batteries
Shulan MAO, Qian WU, Zhuoya WANG, Yingying LU
2020, 9 (2):  538-550.  doi: 10.19799/j.cnki.2095-4239.2019.0287
Abstract ( 98 )   HTML ( 7 )   PDF (4603KB) ( 118 )  

LiNixCoyMn1-x-yO2 (NCM) cathodes have large reversible capacity, high operating voltage, and good rate capability, which are essential in the field of electric vehicles (EVs). The requirements of endurance mileage of electric vehicles can be met by increasing the energy density of lithium-ion batteries for which the cut-off working voltage must be increased. However, the narrow electrochemical window of current electrolytes could result in poor cycle performance at high voltage. This review focuses on NCM battery electrolytes under high working voltage. Starting from the frontier orbital theory related to the decomposition of electrolytes and the interface reactions between electrodes and electrolytes, this review identifies approaches to improve the high-voltage working performance of lithium-ion batteries with ternary positive materials. Moreover, the design progress of non-aqueous electrolytes in solvents, Li salts, additives and other aspects and the application of solid electrolytes and ionic liquids in NCM batteries at high working voltages are summarized. Finally, improvement strategies are proposed for the practical application of electrolytes under high working voltage and the development trend of solid electrolyte in the future is prospected.

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Research progress on dual-ion batteries
Xiaolong ZHOU, Xuewu OU, Qirong LIU, Yongbing TANG
2020, 9 (2):  551-568.  doi: 10.19799/j.cnki.2095-4239.2019.0252
Abstract ( 115 )   HTML ( 4 )   PDF (7507KB) ( 133 )  

As a significant intermittent supporter, traditional rocking-chair batteries [lithium-ion batteries (LIBs)] have been widely used in consumer electronics, electric vehicles, and energy storage power stations owing to their long-term cycle life and absence of the memory effect. However, owing to the shortage and uneven global distribution of lithium and cobalt resources and the growing unprecedented demand for power batteries in electric vehicles and grid-scale energy storage stations, it is essential to develop novel energy storage technologies that are efficient, low-cost, safe, and reliable, for example, secondary batteries based on non-lithium cations (e.g., Na+, K+, Mg2+, Ca2+, Zn2+, and Al3+), zinc-air batteries, and dual-ion batteries (DIBs). Among them, DIBs are emerging energy-storage systems, which are different from traditional LIBs, in that both cations and anions participate in the electrochemical redox reactions of the anode and cathode, respectively. This feature endows these novel energy-storage systems with more options for electrode materials and the advantages of a high working voltage, wide working temperature range, optimum safety, low cost, and environment friendliness; therefore, these novel energy-storage systems show considerable application prospects in large-scale energy storage applications. Herein, we first present the development history of DIBs. Furthermore, on the basis of the working principle of DIBs, we systematically reviewed state-of-the-art materials and identify the challenges of using them in DIBs.

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Research progress on nano silicon-carbon anode materials for lithium ion battery
Junhua ZHOU, Fei LUO, Geng CHU, Bonan LIU, Hao LU, Jieyun ZHENG, Hong LI, Xuejie HUANG, Liquan CHEN
2020, 9 (2):  569-582.  doi: 10.19799/j.cnki.2095-4239.2020.0012
Abstract ( 100 )   HTML ( 13 )   PDF (13233KB) ( 137 )  

High-energy-density lithium-ion batteries are of great importance in alleviating the energy and environmental crisis. The theoretical specific capacity of silicon-based materials is much higher than that of graphite, which is now recognized as the next generation of anode materials for lithium-ion batteries. Since 1999, when the Institute of Physics of the Chinese Academy of Sciences first reported the important role of nanotechnology in improving the performance of silicon negative electrode, it has continued to explore many basic scientific issues and industrial applications of nano silicon-based materials by mainly focusing on the electrochemical mechanism of nano silicon-based negative electrode materials, the dynamic evolution process of their structure and morphology, generation of stress accumulation and cracks, and the three-dimensional feasibility of solid electrolyte interface (SEI) visual research. In this paper, some of these works are summarized and some opinions on the future development of anode materials are present.

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Research on high-safety electrolytes and their application in lithium-ion batteries
Xiaoxia CHEN, Kai LIU, Baoguo WANG
2020, 9 (2):  583-592.  doi: 10.19799/j.cnki.2095-4239.2020.0027
Abstract ( 56 )   HTML ( 3 )   PDF (4706KB) ( 78 )  

Lithium-ion batteries (LIBs) have emerged as the most widely used energy storage devices owing to their high energy density and excellent cycling stability. Unfortunately, their safety problems considerably prohibit their large-scale production and application. Recently, considerable efforts have been made to investigate the mechanism of the LIB thermal runaway. In this study, we summarize highly stable electrolytes, including flame-retardant electrolytes, intrinsically nonflammable electrolytes, aqueous electrolytes, and smart electrolytes. We believe this review sheds light on the design and synthesis of highly stable electrolytes for organic fluid flow battery systems and other high-capacity energy storage systems.

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Challenges on practicalization of lithium sulfur batteries
Weikun WANG, Anbang WANG, Zhaoqing JIN
2020, 9 (2):  593-597.  doi: 10.19799/j.cnki.2095-4239.2019.0295
Abstract ( 89 )   HTML ( 10 )   PDF (641KB) ( 103 )  

In view of the slow progress in the industrialization of lithium sulfur batteries, the basic problems restricting the development of lithium sulfur batteries are analyzed from the practical level, W·hich are the low surface capacity of cathode, the high electrolyte ratio, the poor rate performance and the instability of lithium anode. According to their own work, the authors put forward the solution of these problems.

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Opinions on the reuse of retired power batteries
Xiaokang LAI
2020, 9 (2):  598-602.  doi: 10.19799/j.cnki.2095-4239.2019.0269
Abstract ( 67 )   HTML ( 1 )   PDF (529KB) ( 73 )  

Currently, there is a controversy about the reuse of power batteries. One view is that retired batteries do not have any secondary use value and should be recycled. Another view is that most retired batteries can be used. This study explains the author's views on the judgment standard of whether power batteries can be secondary-used, the key problems in the secondary use batteries, and the future work that should be undertaken. Whether power batteries can be secondary-used should be judged in terms of safety and economy. The key issues to be considered include the rapid diagnosis of the battery state, battery reorganization, and the selection of application scenarios. Currently, the development of breakthrough technologies to evaluate the safety risk of retired power batteries, small-scale demonstration applications, and improvement in data systems is required.

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Reviews of 100 selected recent papers on lithium batteriesDec 1, 2019 to Jan 31, 2020
Hua ZHANG, Mengyu TIAN, Hongxiang JI, Feng TIAN, Wenbin QI, Zhou JIN, Yida WU, Yuanjie ZHAN, Yong YAN, Hailong YU, Liubin BEN, Yanyan LIU, Xuejie HUANG
2020, 9 (2):  603-616.  doi: 10.19799/j.cnki.2095-4239.2020.0079
Abstract ( 40 )   HTML ( 1 )   PDF (767KB) ( 71 )  

This bimonthly review paper highlights 100 recently published papers on lithium batteries. The 100 papers were selected among 3412 online publications in the Web of Science archive from Dec. 1 of 2019 to Jan. 31 of 2020. The failure mechanisms and effects of surface modifications on layered oxides, especially Ni-rich (or even Ni-only) cathode materials, are being extensively investigated. Li-rich and high voltage LiCoO2-layered cathode materials are also studied, although less frequently than layered oxides. Among the anode materials, Si-based composites are thought to improve the cycling performance and columbic efficiency by inhibiting the volume expansion without losing their electron conductivity. Meanwhile, the cycling properties of metallic lithium anodes have been improved by applying various surface-covering layers, electrolyte additives, and current collector modifications. Solid state electrolytes (both inorganic and organic) and their compositions are intensively researched, and new additives and lithium salts have been proposed as liquid electrolytes. Solid state Li-S and Li-O2 batteries remain in the early stage of development, but new electrode preparation methods that maintain the conducting network and reaction reversibility have been proposed. The dynamic changes in morphology, lithium, and potential distribution have been observed by various in situ technologies. The mechanism of SEI has been theoretically analyzed, and the mechanical and thermal properties of solid-state batteries have been explored in mesoscopic and macroscopic models.

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Recent progresses in non-aqueous redox flow batteries
Xueqi XING, Qinghua LIU, John LEMMON
2020, 9 (2):  617-625.  doi: 10.19799/j.cnki.2095-4239.2019.0237
Abstract ( 16 )   HTML ( 2 )   PDF (3798KB) ( 4 )  

Redox flow batteries (RFBs) are promising large-scale energy storage devices with high safety, long cycling life, decoupled power and energy, and high efficiency. RFBs are applied to the reduction of renewable curtailment, auxiliary service, transmission and distribution, distributed energy sources, and user side. Most traditional RFBs that are based on water have optimum safety; however, their energy density is lower than 50 W·h/L because of the narrow electrochemical window of water, which limits the application of RFBs. Non-aqueous RFBs enable higher cell voltage and higher concentration of active species, and it has become a hot topic in the flow battery research area. In this study, the progress of non-aqueous RFBs in recent years is briefly reviewed. On the basis of the active materials used, the non-aqueous flow batteries are divided into non-aqueous metal complex RFBs, organic RFBs, polymer RFBs, and lithium/organic hybrid RFBs. The advantages and challenges of each type of non-aqueous system are briefly described. Recently, some non-aqueous RFBs have exhibited an open circuit voltage of 3 V and the theoretical energy density over 200 W·h/L. These results show the advantage of high energy density, which allows RFBs to be applied as power batteries in electric vehicles (EVs). Here RFBs may provide a dual advantage: the flow battery application scenarios can be considerably changed and technical routes for EV can be considerably enriched.

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Effect of pre-lithiation on storage life of lithium-ion batteries
Guangyu CHENG, Xinwei LIU, Honghui GU, Lei GAO, Ke WANG
2020, 9 (2):  626-632.  doi: 10.19799/j.cnki.2095-4239.2019.0253
Abstract ( 86 )   HTML ( 0 )   PDF (2744KB) ( 98 )  

In an attempt to expand the storage life of Li-ion batteries, two soft pack Li-ion batteries with a nominal capacity of 2.0 A·h were prepared by a pre-lithiation process. For comparison, a control battery was prepared by the normal process. The effects of pre-lithiation on the rate performance, cycle performance, and storage life were evaluated. The pre-lithiation effectively reduced the self-discharge and enhanced the cycle capacity, but reduced the battery’s rate performance in an indirect way. Based on the design of the soft pack Li-ion battery, a 2.0 A·h 18650 type Li-ion battery was also prepared by pre-lithiation. When discharged at 10 C, the battery retained 99.8% of its capacity at 0.2 C, showing outstanding rate performance. After 8 months’ storage at 55 ℃, 86.6% of the primary capacity was retained. According to the storage-test fitting results, the storage life of the battery at 55 ℃ was more than 2.5 times that of commercial batteries. In addition, the capacity was not attenuated after 300 charge-discharge cycles, revealing excellent cycle performance.

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Composition and Toxicity detection standard method of lithium ion battery thermal runaway leakage Draft
Jie SUN, Jigang LI, Tian ZHOU, Shouping WEI, Hongjia XIE, Na TANG, Shengnan DANG, Kai YANG, Hong LI, Xinping QIU, Liquan CHEN
2020, 9 (2):  633-637.  doi: 10.19799/j.cnki.2095-4239.2020.0055
Abstract ( 40 )   HTML ( 4 )   PDF (531KB) ( 42 )  

With the steady development of Li-ion battery industry and electric vehicle industry at home and abroad, the toxic problem of thermal runaway leakage of Li-ion battery is gradually being solved under close attention. With the support of INBCD, State Grid Corporation of China, National Natural Science Foundation of China and the Ministry of Science and Technology of the People′s Republic of China, the research on the composition and toxicity detection standard method of Li-ion battery thermal runaway leakage has been carried out. The draft has been submitted to the project office of "Power Battery Test and Evaluation Technology", a key project of the Ministry of Science and Technology, and is to be submitted to EVS-GTR. This draft is an informal text.

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Cycle life test and analysis of lithium iron phosphate based traction batteries
Shiqiang LIU, Fang WANG, Tianyi MA, Chunjing LIN, Guangli BAI, Zhen WEI, Liduo CHEN
2020, 9 (2):  638-644.  doi: 10.19799/j.cnki.2095-4239.2020.0007
Abstract ( 33 )   HTML ( 2 )   PDF (2031KB) ( 45 )  

With the extension of the life cycle of electric vehicles, the traction battery has gradually entered the scrapping stage. In this paper, the lithium iron phosphate chemistry traction battery is taken as the research object. Based on the electrical conditions of the communication base station, the available cycle test verification of the temperature and constant voltage charging is carried out. The research results show that when the ambient temperature of the standby electrical condition increases, the performance degradation of the sample is obviously accelerated, and the trend of nonlinear acceleration attenuation occurs. When the constant voltage charging of the standby electrical condition changes, the difference in the available capacity attenuation trend of the sample is small, and the variation of the internal resistance of the discharge DC is significant. The research results show that when the lithium iron phosphate traction battery is reused in the standby electrical condition, it is necessary to control the ambient temperature and the constant voltage charging according to the actual working conditions.

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Analysis of modeling and flow characteristics of vanadium redox flow battery
Junkang SHAO, Xin LI, Yanqing MO, Ya QIU, Xueping DONG, Haoyu ZHU
2020, 9 (2):  645-655.  doi: 10.19799/j.cnki.2095-4239.2019.0215
Abstract ( 46 )   HTML ( 0 )   PDF (4814KB) ( 124 )  

To improve the operation efficiency of a vanadium redox flow battery (VRB) system, flow rate, which is an important factor that affects the operation efficiency of VRB, must be considered. The existing VRB model does not reflect the coupling effect of flow rate and ion diffusion and cannot fully reflect the operation characteristics of the VRB system. Therefore, this paper establishes the hybrid model of the VRB, and hydrodynamic and electrochemical models are added to the equivalent circuit model. The equivalent circuit model reflects the electrical performance of the vanadium battery, the hydrodynamic model reflects the influence of the flow rate on the VRB system, and the electrochemical model reflects the chemical properties of the vanadium battery. The performance of VRB is demonstrated more comprehensively and accurately by synthesizing the characteristics of the three models, and the accuracy of the hybrid model is verified by their comparison. The influence of flow rate on the efficiency of the battery system is analyzed using the hybrid model. It is found that the optimal flow rate is a function of the state of charge (SOC) during charging and discharging. The optimal flow under different SOC is obtained by simulation, and the use of the SOC segment controls the flow rate and effectively improves the efficiency of the battery system.

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