Advances in carbon-based composite anodes with gradients of lithiophilicity and conductivity used for stable lithium metal batteries

To address the issues of non-uniform Li plating/stripping and the large volume fluctuations during their repeated cycling, Li metal anodes, a composite Li anode with a three-dimensional (3D) host has been proposed as a promising strategy to improve the uniformity of Li plating/stripping and relieve volume fluctuations. One key strategy in this area is to develop 3D carbon hosts with gradients of lithiophilicity and conductivity to guide Li deposition from bottom to top, thus maximizing the positive effect of this composite Li anode. Such anodes have recently received significant attention due to the flexibility, adjustability, (electro)chemical stability and light weight of the carbon hosts. This review summarizes recent advances in these anodes, categorizing them into those that have hosts with a lithiophilicity gradient, hosts with a conductivity gradient, and those that have both. Latest research findings are discussed and these different anode categories are reviewed. Prospects for the design of such anodes to promote the use of Li metal anodes in high-energy-density rechargeable batteries are presented.