Towards better Li metal anodes: Challenges and strategies

Anode materials are key components of batteries that significantly impact their specific energy and power. Li metal is considered as the ultimate anode due to its high theoretical capacity (similar to 3860 mA h/g) and low redox potential (similar to 3.04 V vs. standard hydrogen electrode). Specifically, rechargeable Li metal batteries (LMBs) with enabled safety promise to surpass the energy density of current Li-ion batteries. Unfortunately, the apparently inevitable growth of dendritic Li, electrolyte consumption, the severe volume changes and the connected potential safety risks of LMBs limit their practical application. Recent strategies based on manipulation of electrolyte chemistry, interface engineering, and structure modification of Li host have reportedly achieved improvement. At the moment, the trend is to move towards all-solid-state LMBs. However, there are serious challenges in terms of low ionic conductivity, poor interfacial contact, and sluggish kinetics. While there are excellent reviews available, this review emphasizes problems and provides additional insight in advanced strategies for stabilizing Li metal anodes in liquid, polymer, ceramic and composite electrolytes. New approaches and novel materials to overcome the above challenges are referred. This review aims at raising relevant questions and outlining future strategies for next-generation high-energy storage systems.