Fangfang Zou,Xue Xia,Xiaojia Zheng,Xu Su,Wei Guan,Xueqiang Qi,Meng Wang,Lian Wang,Xuebu Hu
The application of Li metal anode in high energy density batteries is hindered by uncontrolled dendrites growth and rapid capacity decline. In this study, 4-aminobenzoic acid (4-ABA) is used as a multifunctional electrolyte additive to effectively stabilise Li anode and extend the cycling life of LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA) cathode in carbonate electrolyte. It is found that 4-ABA facilitates the desolvation of Li + and increases the Li + transference number, leading to an increase in Li + flux on the surface of the Li anode, and finally the growth of Li dendrites is inhibited. The cycling performance of Li||Li symmetric cell is extended from < 400 h to more than 600 h at 1 mA cm −2 with a capacity of 1 mAh cm −2 . For the NCA cathode, 4-ABA is involved in the formation of a thin and uniform cathode electrolyte interphase (CEI) layer, which is conducive to inhibiting the corrosion of electrolyte on NCA cathode and reducing the dissolution of the transition metals Ni and Co. Thus, the electrochemical performances of the Li||NCA cell with the electrolyte containing 0.5% 4-ABA are significantly improved. In particular, the discharge capacity of the cells with the electrolyte containing 0.5% 4-ABA are still 164.9 and 150.7 mAh g −1 compared to only 126.3 and 116.0 mAh/g for the cells with the baseline electrolyte after 200 cycles at 1C and 5C. This study provides a simple and effective strategy for improving the electrochemical performances of Li anodes and NCA cathodes by optimising the electrolyte.
Practical high-voltage lithium metal batteries hold promise for high energy density applications, but face stability challenges in electrolytes for both 4 V-class cathodes and lithium anode. To address this, we delve into the positive impacts of two crucial moieties in electrolyte chemistry: fluorine atom (-F) and cyano group (-CN) on the electrochemical performance of polyether electrolytes and lithium metal batteries. Cyano-bearing polyether electrolytes possess strong solvation, accelerating Li + desolvation with minimal SEI impact. Fluorinated polyether electrolytes possess weak solvation, and stabilize the lithium anode via preferential decomposition of F-segment, exhibiting nearly 6000-h stable cycling of lithium symmetric cell. Furthermore, the electron-withdrawing properties of -F and -CN groups significantly bolster the high-voltage tolerance of copolymer electrolyte, extending its operational range up to 5 V. This advancement enables the development of 4 V-class lithium metal batteries compatible with various cathodes, including 4.45 V LiCoO 2 , 4.5 V LiNi 0.8 Co 0.1 Mn 0.1 O 2 , and 4.2 V LiNi 0.5 Co 0.2 Mn 0.3 O 2 . These findings provide insights into design principles centered around polymer components for high-performance polymer electrolytes.
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