Bifunctional composite separator with redistributor and anion absorber for dendrites-free and fast-charging lithium metal batteries

Abstract Li metal anode has been considered as “Holy Grail” for next-generation high energy density batteries owing to its extremely high theoretical capacity and low potential. However, the growth of Li dendrites caused by the uneven Li deposition would lead to poor electrochemical performance and batteries safety risks, which seriously hinders the practical applications of Li metal batteries (LMBs). Herein, a scalable modification with a PVDF-HFP/Y0.08Zr0.92O2-δ composite coating on commercial polypropylene (PP) separators is proposed for dendrites-free Li metal batteries. The porous PVDF-HFP matrix derived by phase inversion can act as a redistributor to regulate Li+ flux, while the oxygen vacancies in Y0.08Zr0.92O2-δ nanoparticles act as anion absorbers to increase the lithium ion transference number which promotes a homogenous Li deposition and fast-charging capability. The synergetic effects of Li redistributor and anion absorber can make LMBs achieve a high average coulombic efficiency (98.4% over 500 cycles), prolonged life span (over 1000 h) and enhanced rate performance (155 mAh g−1 at 10 C). This work provides a feasible strategy for separator modification (e.g. changing the anion absorber to a polysulfide absorber for lithium sulfur batteries) to construct dendrite-free and fast-charging LMBs.