ZnO‐Embedded Expanded Graphite Composite Anodes with Controlled Charge Storage Mechanism Enabling Operation of Lithium‐Ion Batteries at Ultra‐Low Temperatures

Abstract

As lithium (Li)‐ion batteries expand their applications, operating over a wide temperature range becomes increasingly important. However, the low‐temperature performance of conventional graphite anodes is severely hampered by the poor diffusion kinetics of Li ions (Li+). Here, zinc oxide (ZnO) nanoparticles are incorporated into the expanded graphite to improve Li+ diffusion kinetics, resulting in a significant improvement in low‐temperature performance. The ZnO–embedded expanded graphite anodes are investigated with different amounts of ZnO to establish the structure‐charge storage mechanism‐performance relationship with a focus on low‐temperature applications. Electrochemical analysis reveals that the ZnO–embedded expanded graphite anode with nano‐sized ZnO maintains a large portion of the diffusion‐controlled charge storage mechanism at an ultra‐low temperature of −50 °C. Due to this significantly enhanced Li+ diffusion rate, a full cell with the ZnO–embedded expanded graphite anode and a LiNi0.88Co0.09Al0.03O2 cathode delivers high capacities of 176 mAh g−1 at 20 °C and 86 mAh g−1 at −50 °C at a high rate of 1 C. The outstanding low‐temperature performance of the composite anode by improving the Li+ diffusion kinetics provides important scientific insights into the fundamental design principles of anodes for low‐temperature Li‐ion battery operation.