Failure Mechanism for Silicon-NMC Batteries

The ongoing development of renewable energy storage requires commercial lithium ion batteries with high energy density. Compared to the all-graphite (Gr) electrodes used in conventional lithium-ion batteries, silicon-based electrode is considered as an attractive alternative due to the high capacity-storage of silicon (Si). But the quick degradation of Si upon lithiation/delithiation is a critical problem that prevents its application. This presentation will investigate the failure mechanism of the full cell with a blended Si-Gr composite anode using multiple approaches. And a key finding is that the utilization of graphite plays an important role to maintain the reversible capacity in full cell, the increased voltage slippage will cause the reduced utilization of Gr. Based on these finding, we demonstrate that surface modification together with voltage controlled prelithiation facilitate the long-term cycling of Si-based anode in full cell. This enables a highly reversible Si-Gr anodes (mass loading, 2.5 mAh/cm2) in full cell demonstration with a specific capacity of 165 mAh/gNMC, and energy density of 450 Wh/kg, a cycling CE of 99.9% over 200 cycles, which shows great potential for commercial battery application.