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 LiNi_0.88Co_0.09Al_0.03O₂ 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.