Recently, Tang Yongbing, a researcher of the Functional Thin Film Materials Research Center of the Institute of Advanced Technology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, and his research team, together with Professor Zhou Zhiming of Chongqing University of Technology, have adopted a high-concentration electrolyte strategy to significantly improve the energy density and cycle stability of dual-ion batteries. Related research results were published online in the international chemical journal "German Applied Chemistry" (Angew. Chem. Int. Ed., 2020, DOI: 10.1002/anie.) under the title Highly Concentrated Electrolyte towards Enhanced Energy Density and Cycling Life of Dual-Ion Battery. 202006595, IF: 12.257).
Compared with traditional lithium-ion batteries, dual-ion batteries (DIB) have the advantages of high voltage, low cost, and environmental friendliness, and have broad application prospects in the field of large-scale energy storage. As a source of active ions, the electrolyte has a decisive influence on the electrochemical performance of DIB including capacity, cycle life, energy density, etc. However, the concentration of the traditional dual-ion battery electrolyte system is limited, which results in a relatively large volume/mass of the electrolyte, which limits the further improvement of the DIB energy density. In addition, the low-concentration electrolyte has insufficient redox stability, resulting in unsatisfactory cycling stability of the battery.
In view of this, after examining the matching behavior of different solvents and electrolyte salts, Tang Yongbing and his team members successfully developed a LiFS/EC:DMC electrolyte system with a high concentration of 7.5 m. Compared with the low-concentration system, the high-concentration electrolyte shows obvious advantages. The intercalation capacity and cycle stability of the anion intercalated graphite cathode are significantly improved; the structural stability of the metal aluminum foil anode during charge and discharge is improved ; Significantly increased the energy density of the battery. Based on the above high-concentration electrolyte, the proof-of-concept dual-ion battery has a discharge capacity of 94.0 mAh g-1 at a current density of 200 mA g-1; and after 500 cycles, the capacity retention rate reaches 96.8%. In addition, with the consideration of both electrode material and electrolyte quality, the DIB energy density reaches ~180 Wh kg-1. This work has important guiding significance for the further development of high-efficiency and low-cost dual-ion batteries.
The research was supported by the National Natural Science Foundation of China, the Guangdong Science and Technology Plan, and the Shenzhen Science and Technology Plan.
Figure (a) A picture of a high-concentration electrolyte obtained after the solvent is dissolved with an electrolyte salt; (b) Comparison of anti-oxidation LSV curves of electrolytes with different concentrations; (c) The original of the anion-intercalated graphite positive electrode in a high-concentration electrolyte system Bit XRD characterization; (d) medium-voltage discharge in the long-cycle process of the dual-ion battery (the inset shows the charge-discharge curve during the long cycle); (e) a comparison of the energy density of the dual-ion battery has been reported.
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