A Fluorine-Free and Biodegradable Cathode Binder toward LiFePO ₄ -Based Lithium Batteries

The improper disposal of lithium batteries is leading to increasingly severe and unavoidable pollution, as their daily use becomes more widespread and frequent. As a conventional cathode binder, poly(vinylidene fluoride) (PVDF) is difficult to degrade, leading to long-term environmental pollution from discarded batteries. Herein, a novel fluorine-free cathode binder (denoted as EMTO) was designed for degradation by environmental microorganisms. This innovative binder features an organic polymer derived from natural-product-based molecules with polysiloxane. This composition imparts exceptional adhesive strength and antioxidant properties that help to enhance the cycle performance of batteries. The sterically hindered phenolic motif in the as-developed binder can effectively reduce the chemical degradation of electrolyte by capturing singlet oxygen (1O2), thereby extending the battery cycle stability. Galvanostatic Intermittent Titration Technique (GITT) tests reveal that the lithium iron phosphate (LiFePO4) cathode integrated with this binder demonstrates superior Li+ diffusion coefficients. Both half cells and full cells with EMTO as the cathode binder demonstrate higher cycling stability than those with PVDF as the binder. Impressively, the discharge specific capacity of the EMTO binder-based full cell remains stable at 160 mAh g–1 for over 240 cycles. Furthermore, microbial culturing experiments indicate that Aspergillus niger can effectively colonize the binder membrane and degrade its organic components. This unique feature allows the EMTO binder to re-enter the ecosystem innocuously, conducive to advancing environmental protection and sustainable development.