Enhancing Li+ Transport in NMC811||Graphite Lithium-Ion Batteries at Low temperatures by Using Low-Polarity-Solvent Electrolytes

LiNixCoyMnzO2 (x+y+z=1)||graphite lithium-ion battery (LIB) chemistry promises practical applications. However, its low-temperature (<= -20 degrees C) performance is poor because the increased resistance encountered by Li+ transport in and across the bulk electrolytes and the electrolyte/electrode interphases induces capacity loss and battery failures. Though tremendous efforts have been made, there is still no effective way to reduce the charge transfer resistance (R-ct) which dominates low-temperature LIBs performance. Herein, we propose a strategy of using low-polarity-solvent electrolytes which have weak interactions between the solvents and the Li+ to reduce R-ct, achieving facile Li+ transport at sub-zero temperatures. The exemplary electrolyte enables LiNi0.8Mn0.1Co0.1O2||graphite cells to deliver a capacity of approximate to 113 mAh g(-1) (98 % full-cell capacity) at 25 degrees C and to remain 82 % of their room-temperature capacity at -20 degrees C without lithium plating at 1/3C. They also retain 84 % of their capacity at -30 degrees C and 78 % of their capacity at -40 degrees C and show stable cycling at 50 degrees C.

Automated summary

Using low-polarity-solvent electrolytes is proposed as a strategy to reduce the capacity loss of lithium-ion batteries at low temperatures. The weak interactions between solvents and Li+ ions in the electrolyte help to reduce charge transfer resistance and facilitate Li+ transport. Experiments show that this electrolyte enables high capacity retention at low temperatures and stable cycling performance.