High-rate, long-lifespan, sustainable potassium-ion batteries enabled by non-fluorinated solvents

Abstract

Electrolyte solvation chemistry is a key strategy for enhancing battery performance. Herein, we achieve an ultra-high-rate and long-cycle-life potassium-ion battery (PIB) by introducing a fluorine-free ether, (i.e., cyclopentylmethyl ether (CPME)), into a trimethyl phosphate (TMP)-based electrolyte under non-fluorinated and normal-concentration conditions. We discover that CPME and TMP form intermolecular interactions via electropositive hydrogen (δ⁺H) and electronegative oxygen (δ^–O), which effectively weaken the K⁺-TMP interaction. This modification enables highly reversible K⁺ (de-)intercalation within the graphite electrode, not only overcoming the critical challenges of K⁺-solvent co-intercalation in graphite electrodes but also significantly improving the PIB’s rate capability and cycling stability. The newly designed KC₈||3,4,9,10-perylenetetracarboxylic diimide (PTCDI) full cell has sustainable features that can operate stably at 10 C for over 1000 cycles, retaining 84.4 % of its initial capacity. Even at 15 C, it delivers a remarkable capacity of 65.6 mAh g⁻¹, corresponding to 53.0 % of the capacity at 0.2 C. Furthermore, we propose a molecular interface model to analyze the interfacial behavior of K⁺-solvent-anion complexes and elucidate the relationship between intermolecular interactions and graphite electrode performance at the molecular level. This work highlights the importance of solvation structure regulation via intermolecular interactions in developing high-performance PIBs, offering new insights into functionalized metal-ion battery design.