Charge–Discharge Behavior of Lithium-Ion Batteries Using a Polymer Electrolyte Bearing High-Density Functional Groups

Lithium-ion batteries (LIBs) have become crucial for various applications, but carbonate-based liquid solvents, commonly used in their electrolytes, suffer from the flammability and exchange dynamic of lithium-ion movement in electrolytes. To address these issues, poly(ethoxycarbonylmethylene) (PECM) with a dense distribution of functional ester groups was evaluated as a polymer electrolyte in LIBs. The polymer was shown to be polar aprotic with an ET(30) value of 43.85 kcal mol–1 and to offer improved solvation of cations. Polymer electrolytes (PEs) in combination with LiTFSI showed a glass transition temperature in the range of 10–33 °C. PEs demonstrated good ionic conductivity within the range of 9.76 × 10–5–3.08 × 10–4 S cm–1 at 51 °C, lithium-ion transference number between 0.80 and 0.98, and activation energy of diffusion within 27.4–43.0 kJ mol–1. The PECM-based cathodic half-cell exhibited good rate capacity at varied current densities, and long-cycle performance showed 80% capacity retention at 0.2 C for more than 100 cycles. The effect of polarity on the conductivity and transport number and interfacial compatibility with the cathode show promise as an alternative electrolyte material for future lithium-ion battery applications.