Entropy Increase in Electrolytes for Practical Anode-Free Lithium Metal Batteries with High-Loading Cathodes and Lean Electrolyte

An effective concept of using entropy increase to regulate the nanoscale solvation structure has been proposed to enhance the cycle performance of anode-free lithium metal batteries (AFLMBs). It includes two mainstream types: entropy increase driven by multiple salts or solvents. However, most current research is based on low-loading cathodes and mAh-level battery systems. The relationship between the increase in entropy and practical battery with different high-loading cathodes and Ah-levels is seldom reported. In this paper, two mainstream methods of entropy increase are compared, and the relationship of their kinetics parameters, solid electrolyte interphase formation, and cycling performances are studied. It is found that the entropy increases driven by multiple-solvents are more favorable to the pouch cell with high-loading cathode and lean electrolytes. The coin cell consists of a copper current collector and a high-loading cathode (10.5 mg cm⁻²) performs 40 cycles at discharge rates of 0.5 C, while the cell with a conventional ester electrolyte only last 10 cycles. A large-capacity pouch cell (4 Ah), with a high-loading cathode (7.6 mAh cm⁻², single side) and lean electrolyte of 1.3 g Ah⁻¹, achieves 500 Wh kg⁻¹ and 20 cycles.