Cross-Linked Poly(Ethylene Carbonate/Ethylene Oxide) Electrolyte for Solid-State Li-Ion Batteries Exploiting Membrane-Electrode Assembly

Safety concerns of flammable liquid electrolytes as well as challenges related to the use of high-capacity anodes, such as silicon-based ones, are among the bottlenecks for achieving next-generation Li-ion batteries. Herein, we synergistically blend poly(ethylene carbonate) and poly(ethylene oxide) copolymers with complementary molecular weights and cross-linking densities into membranes with lithium bis(fluorosulfonyl)imide (LiFSI) salt concentrated up to 140 mol %. The process leads to membranes without any electrochemical performance-enhancing additive, denoted as additive-free in this work. The thin, mechanically robust, and self-standing cross-linked polymer electrolyte membrane (CP-EM) isused in an all-solid-state battery (ASSB), with scalable LiFePO4 membrane-electrode assembly (LFP-MEA), and a prelithiated silicon oxide-carbon (LiySiOxC) anode. Electrochemical characterization reveals a CP-EM with a high lithium-ion transference number (t+) of 0.61, a low activation energy (Ea) of 0.110 eV, anodic stability exceeding 4.0 V, and a suitable interphase with the lithium metal. The integration of the CP-EM into the proof-of-concept full cell with the LFP-MEA and LiySiOx is conducted with a practical N/P ratio of 1.16. The full cell delivers an initial reversible capacity of ∼140 mAh g–1 at 70 °C, with an average working voltage of 3.2 V and limited polarization. Despite stability and rate capability still needing further improvements, this study offers a synergic design for blending distinct macromolecular architectures, with a specific balance between segmental flexibility for ion transport and structural integrity. The outcomes demonstrate the practical viability of the integrated MEA in scalable full cells operating at relatively high temperatures.