Room‐Temperature CsPbI ₃ ‐Quantum‐Dot Reinforced Solid‐State Li‐Polymer Battery

Abstract A novel polymer electrolyte based on CsPbI ₃ quantum dots (QDs) reinforced polyacrylonitrile (PAN), named as PIL, is exploited to address the low room‐temperature (RT) ion conductivity and poor interfacial compatibility of polymer solid‐state electrolytes. After optimizing the content of CsPbI ₃ QDs, RT ion conductivity of PIL largely increased from 0.077 to 0.56 mS cm ⁻¹ , and its Li‐ion transference number () from 0.20 to 0.63. It is revealed that the synergistic enhancement of Li‐ion transport and interface stability is realized by CsPbI ₃ QDs through Lewis acid–base interaction, ordered polarization of PAN, and interface chemical regulation. These two effects guarantee the robust solid‐electrolyte interface (SEI) in PIL‐based solid‐state batteries. Consequently, PIL electrolyte enables solid‐state Li‐metal batteries to deliver extraordinary RT cycling performance as verified by excellent cycling stability (>2000 h at 0.1 mA cm ⁻² ) of Li|PIL|Li symmetric batteries. Moreover, Li|PIL|LFP (LFP is LiFePO ₄ ) and Li|PIL|NCM811 (NCM811 is Li(Ni _0.8 Co _0.1 Mn _0.1 )O ₂ ) batteries maintain capacity retention of 81.2% and 77.9%, respectively, after 600 cycles at 0.5 C, as well as good rate‐capability and very high Coulombic efficiency at RT.