A novel zwitterionic polymer binder with enhanced ionic conductivity for water-processable LiFePO4 cathodes

Abstract

Current olivine structure LiFePO₄ possesses poor conductivity, which makes it unsuitable for unparalleled battery applications. This issue can be solved by improved design concepts of binder systems. Herein, an original waterborne binder polymer with efficient functional groups is designed and fabricated for LiFePO₄ cathodes of lithium-ion batteries (LIBs). Compared to universal lithiated ionomer binders, the introduction of the zwitterionic structure of the ionomer enhances the ionic conductivity by nearly 100-fold. LiFePO₄ cathodes assembled with limited 1.5 wt% lithiated zwitterionic ionomer (LZI) maintain markedly stable cycling performances with 95.62% retention at 1C after 250 cycles. Also, LZI-cathodes preserve good integrity structures after cycling, as confirmed by morphology analysis. In sum, LZI-cathodes look promising for potential applications in LIBs due to their numerous advantageous characteristics.