Enhancing Electrochemical Stability of Silicon-Carbon and NMC based Lithium-Ion Batteries through the Synergistic Impact of Charge Balance and Direct-Contact Pre-Lithiation Strategy

Abstract

The commercial feasibility of silicon (Si) anodes (≥ 30%) in full-cell systems is constrained by poor cyclic stability and capacity balancing due to continuous active lithium (Li) consumption in each cycle. We proposed a capacity balancing approach by adding additional Li at the cathode side (i.e., ratio of capacity at negative to positive electrode (N/P) ∼ 0.9) and anode side (i.e., pre-lithiated Si) before full-cell fabrication. This approach provided a capacity-balanced full-cell with 91.7% of initial Coulombic efficiency (ICE) and stability up to 50 cycles. In-situ electrochemical impedance spectroscopy (EIS) and distribution of relaxation times (DRT) analysis have been utilized to examine the interface of bare and balanced full cells. In a large format cell, electrolyte wettability is an issue and it has been investigated even at high temperature (50 °C). The post-cycle investigation also indicates the Si particles retained their integrity after cycling. A 110 mAh pouch cell has been constructed, and the pouch cell demonstrated exceptional cyclic stability up to 200 cycles, with a capacity retention of 83.2% at a current rate of 0.1 C. These findings present a capacity balancing approach for high-loading silicon-based anodes that eventually can scale up to high-quality and long-cycle life lithium-ion batteries.