Ultra‐Stable Polycarbonate‐Based Solid‐State Lithium Metal Batteries Enabled by In Situ Polymerized Ferroelectric Engineering

Abstract The relatively low room‐temperature ionic conductivity and terrible lithium dendrite growth of polycarbonate‐based solid polymer electrolytes (SPEs) seriously restrict their further development for solid‐state lithium metal batteries (SSLMBs). Herein, a polycarbonate‐based SPE is innovatively designed through facile in situ polymerization of ferroelectric poly(vinylidene fluoride‐trifluoroethylene‐chlorotrifluoroethylene) (PVTC) and vinyl ethylene carbonate (VEC) monomer (PVTC‐g‐PVEC). This in situ polymerized PVTC‐g‐PVEC SPE with polar ─CF 2 group and C═O/C─O groups greatly promotes the dissociation of Li salts and enhances the transport of Li + . Moreover, the ferroelectric PVTC‐g‐PVEC SPE can produce spontaneous polarization under external electric fields, which promotes uniform deposition of Li + and suppresses lithium dendrite growth. In addition, the fabricated PVTC‐g‐PVEC SPE facilitates the formation of a stable solid electrolyte interface and cathode electrolyte interface, effectively reducing side reactions at the electrode/electrolyte interfaces. Specifically, the Li|PVTC‐g‐PVEC|Li symmetric cell can exhibit ultra‐long cycle stability for more than 10 000 h (>416 days). The assembled LiFePO 4 |PVTC‐g‐PVEC|Li cell and high‐voltage LiNi 0.8 Co 0.1 Mo 0.1 O 2 |PVTC‐g‐PVEC|Li cell exhibit outstanding cycling stability for 1000 cycles at 2C and 500 cycles at 1C, respectively. The pouch batteries also depict high safety against abusive conditions. This in situ polymerized ferroelectric engineering strategy establishes a new pathway for designing high‐performance solid‐state lithium batteries.