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

A novel polymer electrolyte based on CsPbI₃ 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 CsPbI₃ QDs, RT ion conductivity of PIL largely increased from 0.077 to 0.56 mS cm^-1, and its Li-ion transference number ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mi>τ</mml:mi> <mml:mrow><mml:mi>L</mml:mi> <mml:msup><mml:mi>i</mml:mi> <mml:mo>+</mml:mo></mml:msup> </mml:mrow> </mml:msub> <mml:annotation>${{\tau }_{{\mathrm{L}}{{{\mathrm{i}}}^ + }}}$</mml:annotation></mml:semantics> </mml:math> ) from 0.20 to 0.63. It is revealed that the synergistic enhancement of Li-ion transport and interface stability is realized by CsPbI₃ 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 LiFePO₄) and Li|PIL|NCM811 (NCM811 is Li(Ni_0.8Co_0.1Mn_0.1)O₂) 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.