Compatible bridged interphase with enhanced Li ion migration for durable quasi-solid-state lithium metal batteries

Solid-state lithium metal batteries suffer from incompatible interfacial electrochemistry introduced by mismatched lithium ion diffusion rates across the anode/electrolyte, which leads to interface degradation and dendrite formation. Here, we propose an interfacial ion migration modulator to bridge the Li ion transport pathway between ceramic-polymer composite electrolytes and Li metal using a series of different lithiophilic nanoscale metals. With the aid of comprehensive theoretical simulations, different metals are screened via spectroscopic measurements as well as electrochemical tests, where Pt acts best and in situ forms a Li-Pt alloy solid-electrolyte interphase layer with a coherent crystal structure during the electrochemical reaction, reducing the internal Li diffusion energy barrier. As investigated, the distribution of relaxation time analyses reveals that the Li-Pt alloy-based interfacial ion migration modulator regulates and balances the interfacial ion transport and nucleation rate, inhibiting defect formation. Consequently, the symmetric cell with the Pt modulator lasts for 1900 h with a low overpotential of 10.7 mV. Moreover, the Pt@polymer electrolyte-based quasi-solid-state lithium metal battery assembled with the LiFePO₄ cathode displays greatly improved cycling stability (154.6 mAh g^-1 at the 150th cycle, 0.2C). This work clarifies the role of the essential interfacial ion migration modulator in paving the way towards extending the interface lifespan of SSLMBs.