Implanting nickel and cobalt phosphide into well-defined carbon nanocages: A synergistic adsorption-electrocatalysis separator mediator for durable high-power Li-S batteries

Abstract

Transition metal phosphides (TMPs) are proposed as promising polysulfides (LiPSs) mediates with simultaneous strong adsorption and fast conversion capabilities, which is essential for high-energy Lithium-sulfur (Li-S) batteries. Unfortunately, the attempts of using TMPs as sulfur hosts in cathodes suffer from low sulfur loading and poor rate performance. Herein, Ni, Co bimetal phosphides are in-situ implanted into hollow carbon nanocages (Ni-Co-P@C) and utilized as the multifunctional separator interlayer to achieve durable Li-S batteries that can work at high current rates. Benefiting from the unique hollow nanocage and abundant synergistic adsorption-electrocatalytic sites, the Li-S battery with Ni-Co-P@C separator achieves ultrastable lifespan with only 0.056% capacity decay per cycle over 1000 cycles at 0.5 C and superior rate capability of 654.5 mAh g−1 at 5 C. Moreover, the Li-S batteries with a high sulfur loading of 4.5 mg cm−2 can still maintain a high areal capacity of 3.7 mAh cm−2 after 85 cycles. This work demonstrates a new strategy to apply TMPs as a multifunctional mediator in separators for durable high-power Li-S batteries.