Highly entangled P(VDF-TrFE) solid-state electrolytes for enhanced performance of solid-state lithium batteries

Solid polymer electrolytes (SPEs) offer a promising solution to the safety concerns of lithium metal batteries (LMBs). While poly(vinylidene fluoride) (PVDF)-based SPEs possess advantageous mechanical and thermal properties, their prevalent trans-gauche (TGTG) and TTTG conformations create tortuous ion pathways within chains, and insufficient chain entanglement leads to discontinuous transport between chains, fostering non-uniform current distribution and lithium dendrite growth. This work addresses both limitations by employing a novel poly(vinylidene fluoride-co-trifluoroethylene), P(VDF-TrFE) copolymer as the matrix of SPEs. By utilizing an ultrahigh molecular weight (2.37 × 10⁶ g mol^-1) P(VDF-TrFE) synthesized via suspension polymerization, we simultaneously achieve: (1) stabilized TTTT conformation (β-phase), which forms continuous, low-resistance electronegative fluorine channels for efficient intra-chain Li⁺ transport, and (2) significantly enhanced chain entanglement density, which establishes a 3D interconnected ion transport network that eliminates inactive microregions, homogenizes Li⁺ flux, and improves mechanical resilience. Consequently, Li//Li symmetric cells based on this SPE exhibit exceptional cycling stability exceeding 5000 hours at 0.1 mA cm^-2 and 25 °C, a 16-fold improvement over a lower molecular weight (0.49 × 10⁶ g mol^-1) P(VDF-TrFE) SPE counterpart (∼300 hours). LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811)//Li full cells also demonstrate good cycling stability. This dual optimization of molecular conformation and topological structure provides an effective strategy for enhancing ion transport continuity and uniformity in solid-state LMBs.