A Molecularly Engineered Cathode Lithium Compensation Agent for High Energy Density Batteries.

Abstract

Prelithiating cathode is considered as one of the most promising lithium compensation strategies for practical high energy density batteries. Whereas most of reported cathode lithium compensation agents are deficient owing to their poor air-stability, residual insulating solid, or formidable Li-extracting barrier. Here, this work proposes molecularly engineered 4-Fluoro-1,2-dihydroxybenzene Li salt (LiDF) with high specific capacity (382.7 mAh g-1 ) and appropriate delithiation potential (3.6-4.2V) as an air-stable cathode Li compensation agent. More importantly, the charged residue 4-Fluoro-1,2-benzoquinone (BQF) can synergistically work as an electrode/electrolyte interface forming additive to build uniform and robust LiF-riched cathode/anode electrolyte interfaces (CEI/SEI). Consequently, less Li loss and retrained electrolyte decomposition are achieved. With 2wt% 4-Fluoro-1,2-dihydroxybenzene Li salt initially blended within the cathode, 1.3 Ah pouch cells with NCM (Ni92) cathode and SiO/C (550 mAh g-1 ) anode can keep 91% capacity retention after 350 cycles at 1 C rate. Moreover, the anode free of NCM622+LiDF||Cu cell achieves 78% capacity retention after 100 cycles with the addition of 15wt% LiDF. This work provides a feasible sight for the rational designing Li compensation agent at molecular level to realize high energy density batteries.