Lithiophilic pore-gradient structured and oxygen-enriched carbon fiber as dense lithium nucleation enabler for stable lithium metal batteries

Abstract

Lithium (Li) metal is the ultimate anode material for next generation batteries, thanks to its ultrahigh theoretical specific capacity and lowest reduction potential. However, an unstable solid electrolyte interphase caused by uneven Li deposition and infinite volume expansion of Li obstruct the commercialization of Li metal anodes. Herein, we introduce a unique strategy to tune lithiophobic carbon fiber (CF) to lithiophilic pore-gradient structured and oxygen-enriched carbon fiber (PGOCF) as dense Li nucleation enabler. The simultaneous regulation of surface chemistry and structure of CF is simply achieved by using CoAl layered double hydroxide as an etchant-protectant agent in thermal treatment, in which the porosifying role of Co and the protecting role of Al elements synergistically affect the morphology of PGOCF. The O enriched PGOCF (the atomic O ratio of 10.55%) can exhibit strong Li absorption, lowering Li nucleation barrier, and the pore-gradient structure of PGOCF can effectively lower Li nuclei-substrate contact angle, leading to dense and uniform Li electrodeposition. As a result, PGOCF exhibits an impressive electrochemical performance. When paired with a LiFePO4 cathode, Li@PGOCF delivers a specific capacity of 138.3 mA h g−1 at 2C with an exceptional capacity retention of 98.3% for 500 cycles.