Feasible approaches for anode-free lithium-metal batteries as next generation energy storage systems

As the demand for lithium-ion batteries (LIBs) rapidly increases, there is a need for high-energy-density batteries, which can be achieved through the use of lithium metal (∼3860 mAh g−1) as a higher-capacity anode relative to graphite (∼370 mAh g−1). However, given the low economic efficiency and safety of lithium metal, anode-free lithium-metal batteries (AFLMBs) have been pushed into the spotlight. The energy density of these batteries can be improved by increasing the cathode loading amount as the anode volume decreases. In addition, because anode fabrication is not needed, the unit cost of the battery is significantly reduced. However, serious deterioration that occurs at the interface of the anode lowers the reversibility of the battery and reduces the battery performance. Improving the reversibility of such lithium-metal plating/stripping is the main development goal of AFLMBs. In AFLMBs, the lithium inventory retention rate (LIRR), which means the efficiency of lithium plating/stripping, is the most important performance indicator. Many works have been directed to improve this parameter including electrolyte modification, current-collector modification, artificial solid electrolyte interface (SEI), and excess lithium in the cathode. In this review, we open discussion to improve the reversibility of AFLMBs with different type of electrolytes.