Lithium-metal-based solid-state batteries (Li-SSBs) are one of the most promising energy storage devices due to their high energy densities. However, under insufficient pressure constraints (<MPa-level), Li-SSBs usually exhibit poor electrochemical performances owing to the continuous interfacial degradation between the solid-state electrolyte (SSE) and electrodes. Herein, a phase-changeable interlayer is developed to construct the self-adhesive and dynamic conformal electrode/SSE contact in Li-SSBs. The strong adhesive and cohesive strengths of the phase-changeable interlayer enable Li-SSBs to resist up to 250 N pulling force (=1.9 MPa), affording Li-SSBs ideal interfacial integrality even without extra stack pressure. Remarkably, this interlayer exhibits a high ionic conductivity of 1.3 × 10-3 S cm-1 , attributed to the shortened steric solvation hindrance and optimized Li+ coordination structure. Furthermore, the changeable phase property of the interlayer endows Li-SSBs with a healable Li/SSE interface, accommodating the stress-strain evolution of the lithium metal and constructing the dynamic conformal interface. Consequently, the contact impedance of the modified solid symmetric cell exhibits a pressure-independent manner and does not increase over 700 h (0.2 MPa). The LiFePO4 pouch cell with the phase-changeable interlayer shows 85% capacity retention after 400 cycles at a low pressure of 0.1 MPa.
Keywords: interlayer; lithium battery; phase-changeable electrolyte; pressure-free; solid-state battery.
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