Polymer‐in‐Salt Electrolyte Enabled High‐Performance Solid‐State Hybrid Lithium‐Ion Capacitor with 3D Conductive Nb ₂ O ₅ Anode for Energy Storage

To address the safety limitations of liquid electrolytes and performance bottlenecks in conventional energy storage devices, a high‐concentration polymer‐in‐salt polymer solid electrolyte (PiS‐PSE) and a 3D conductive network‐engineered niobium pentoxide (Nb 2 O 5 ) composite anode for solid‐state hybrid lithium‐ion capacitors (HLICs) are developed. The optimized lithium bis(trifluoromethanesulfonyl)imide/poly(vinylidene fluoride ‐co ‐hexafluoropropylene) (LiTFSI/PVDF‐HFP) electrolyte (mass ratio 3:1) achieves an ionic conductivity of 2.09 × 10 − 3 S cm −1 at 20 °C with enhanced electrochemical stability (>4.5 V vs. Li/Li + ). Simultaneously, the Nb 2 O 5 /graphene‐carbon nanotube hybrid anode (NGNT‐90%) exhibits exceptional pseudocapacitive behavior and rate capability (171 mAh g −1 at 0.1C). The integrated solid‐state HLIC delivers a high energy density of 108.3 Wh kg −1 at 100 W kg −1 and maintains 37.63 Wh kg −1 at 500 W kg −1 , which is comparable with reported liquid‐based LICs. Critically, the device demonstrates >80% capacitance retention after 300 cycles at 5C with near‐unity coulombic efficiency (≈99.0%), attributable to stable electrode/electrolyte interfaces and dendrite‐suppressing characteristics of the PiS‐PSE. This work provides a material design paradigm for next‐generation safe, high‐performance electrochemical energy storage systems.