Incorporation of redox-active polyimide binder into LiFePO4 cathode for high-rate electrochemical energy storage

Abstract

Commercial LiFePO4 (LFP) electrode still cannot meet the demand of high energy density lithium-ion batteries as a result of its low theoretical specific capacity (170 mA h g−1). Instead of traditional electrochemical inert polyvinylidene fluoride (PVDF), the incorporation of multifunctional polymeric binder becomes a possible strategy to overcome the bottleneck of LFP cathode. Herein, a novel polyimide (PI) binder was synthesized through a facile hydrothermal polymerization route. The PI binder exhibits better connection between active particles with uniform dispersion than that of PVDF. The multifunctional PI binder not only shows well dispersion stability in the organic electrolyte, but also contributes to extra capacity because of the existence of electrochemical active carbonyl groups in the polymer chain. Besides, the high intrinsic ion conductivity of PI also results in promoted ion transfer kinetic. Consequently, the LFP cathode using PI binder (LFP–PI) shows larger capacity and better rate capability than LFP cathode with PVDF binder (LFP–PVDF). Meanwhile, the superior binding ability also endows LFP–PI with great cycling stability compared to the LFP–PVDF electrode.

Keywords

• lithium-ion batteries
• lifepo4
• rate capability
• binder
• polyimide