Lithium deposition behavior in hard carbon hosts: Optical microscopy and scanning electron microscopy study

Lithium (Li) metal is an ideal anode for the next generation high-energy-density batteries. However, it suffers from dendrite growth, side reactions, and infinite relative volume change. Effective strategies are using porous carbons or surface modification carbons to guide Li deposition into their pores. While the Li deposition behavior is still ambiguous. Here, we systematically determine their deposition behavior in various surface-modified carbons and in different electrolytes via optical microscopy and scanning electron microscopy study. It is found that Li will not spontaneously deposit into the carbon pores, which is significantly dependent on the carbon surface, current density, areal capacity, and electrolyte. Thus, a “lithiophilic” modified commercial hard carbon with Ag is developed as a stable “host” and efficient surface protection derived from the localized high-concentration electrolyte exhibits a pretty low volume change (5.3%) during cycling at a current density of 2 mA·cm⁻² and an areal capacity of 2 mAh·cm⁻². This strategy addresses the volume change and dendrite problems by rationally designed host and electrolyte, providing a broad perspective for realizing Li-metal anode.