Radical Polymer‐based Positive Electrodes for Dual‐Ion Batteries: Enhancing Performance with γ‐Butyrolactone‐based Electrolytes.

Dual‐ion batteries (DIBs) represent a promising alternative for lithium ion batteries (LIBs) for various niche applications. DIBs with polymer‐based active materials, here poly(2,2,6,6‐tetramethylpiperidinyl‐N‐oxyl methacrylate) (PTMA), are of particular interest for high power applications, though they require appropriate electrolyte formulations. As the anion mobility plays a crucial role in transport kinetics, Li salts are varied using the well‐dissociating solvent γ‐butyrolactone (GBL). Lithium difluoro(oxalate)borate (LiDFOB) and lithium bis(oxalate)borate (LiBOB) improve cycle life in PTMA||Li metal cells compared to other Li salts and a LiPF6‐ and carbonate‐based reference electrolyte, even at specific currents of 1.0 A g−1 (≈10C), whereas LiDFOB reveals a superior rate performance, i. e. ≈90 % capacity even at 5.0 A g−1 (≈50C). This is attributed to faster charge‐transfer/mass transport, enhanced pseudo‐capacitive contributions during the de‐/insertion of the anions into the PTMA electrode and to lower overpotentials at the Li metal electrode. [ABSTRACT FROM AUTHOR]