A cooperative biphasic MoO_x-MoP_x promoter enables a fast-charging lithium-ion battery.

Abstract

The realisation of fast-charging lithium-ion batteries with long cycle lifetimes is hindered by the uncontrollable plating of metallic Li on the graphite anode during high-rate charging. Here we report that surface engineering of graphite with a cooperative biphasic MoO_x-MoP_x promoter improves the charging rate and suppresses Li plating without compromising energy density. We design and synthesise MoO_x-MoP_x/graphite via controllable and scalable surface engineering, i.e., the deposition of a MoO_x nanolayer on the graphite surface, followed by vapour-induced partial phase transformation of MoO_x to MoP_x. A variety of analytical studies combined with thermodynamic calculations demonstrate that MoO_x effectively mitigates the formation of resistive films on the graphite surface, while MoP_x hosts Li⁺ at relatively high potentials via a fast intercalation reaction and plays a dominant role in lowering the Li⁺ adsorption energy. The MoO_x-MoP_x/graphite anode exhibits a fast-charging capability (<10 min charging for 80% of the capacity) and stable cycling performance without any signs of Li plating over 300 cycles when coupled with a LiNi_0.6Co_0.2Mn_0.2O₂ cathode. Thus, the developed approach paves the way to the design of advanced anode materials for fast-charging Li-ion batteries.