The effect of negative-to-positive ratios on the interfacial compatibility for fast-charging lithium-ion batteries

Reversibly cycling Li plating on the graphite (Gr) anode using localized high-concentration electrolytes (LHCEs) is a practical approach to enhance the fast-charging capability of lithium-ion batteries (LIBs). However, the loading boundary of Li plating on the anode surface, necessitating interfacial compatibility and cycling durability, remains unclear in practical full cells. Herein, we investigate the impact of negative-to-positive (N/P) ratios ranging from 0.55 to 1.13 on the fast-charging performance of LiFePO₄||Gr cells using the conventional concentration electrolyte (CCE) and LHCE. The results demonstrate that compared with CCE cells, the LHCE-derived solid electrolyte interphase featuring higher uniformity of species distribution and stable Li-ion flux at the anode interface can facilitate the homogenous and replicable Li plating. With a 0.88 N/P ratio, LHCE cells can maintain long-term cycling stability over 300 cycles at 1–3 C, which is comparable to the conventional type of cells with a higher N/P ratio (1.13). The self-made 40-mAh LiFePO₄||Gr pouch cells with a 0.88 N/P are 3C-cycled in LHCE, exhibiting an excellent capacity retention of 92.8 % over 250 cycles. This study provides insight into the interfacial compatibility of Li plating to enhance the fast-charging efficiency of LIBs while reducing the cost of cell materials.