In Situ Polymerized Polysiloxane Enables Cohesive Solid‐Electrolyte Interphase for Practical Lithium‐Metal Batteries

The mechanical instability of nanostructured solid-electrolyte interphase (SEI) on lithium (Li)-metal anodes severely limits the cycle life of Li-metal batteries because SEI undergoes endless cracking and regeneration due to anode volume fluctuations. Here, a cohesive SEI nanostructure is proposed to enhance SEI mechanical stability. The inorganic nanoparticles with weak interparticle cohesion in SEI are glued using polysiloxane, in situ formed from hexamethylcyclotrisiloxane (CTS) as an electrolyte additive. This approach strengthens interparticle cohesion of inorganic components, and the elastic modulus of SEI increases by 109%, significantly improving its tolerance to anode volume fluctuations. As a result, Li-metal coin cells with glued SEI exhibit an extended cycle life of 320 cycles, compared with 183 cycles with routine SEI, under practical conditions. Furthermore, a prototype 505 Wh kg^-1 Li-metal pouch cell with glued SEI achieves 175 cycles. Specifically, the pouch cell with glued SEI exhibits superior high-rate discharge capabilities, as demonstrated by its capacity to power a micro-unmanned aerial vehicle, advancing Li-metal batteries towards practical applications. This work presents a generalizable strategy to in situ reinforcement of SEI for high-energy-density Li-metal batteries.