Enhanced Electrochemical Properties of LiFePO₄ Cathode Using Waterborne Lithiated Ionomer Binder in Li-Ion Batteries with Low Amount

The poor conductivity of olivine structure LiFePO₄ led to inevitable hindered electrochemical performances and restricted their uses in Li-ion batteries. To overcome the problem, introduction of conductive agents that bind with LiFePO₄ active material is a universal solution. In this paper, a novel waterborne lithiated ionomer binder (PSBA-Li)for Li-ion batteries was originally designed and assembled with the low addition of 1.5% of a LiFePO₄ cathode, showing a high areal capacity of 2.0 mAh cm^-2. During lithiation/delithiation processes, PSBA-Li provided more Li⁺ ions, resulting in enhanced conductivity, which led to better performances. After 200 cycles, the PSBA-Li cathode based battery maintained stable cycling performances with retentions of 108.5%, 103.6%, and 114.9% at rates of 0.5C, 1C, and 2C, respectively, in contrast with a commercially used PVDF-cathode with a retention of only 7% (0.5C). The rate performance of the PSBA-Li cathode is higher than that of the PVDF-cathode, which shows almost no capacity at high rates. For contrastive analysis, SEM indicates a well integrity PSBA-Li cathode structure after cycling. On the contrary, active materials of PVDF-cathode separate from the aluminum foil after cycling. It is believed that the PSBA-Li has significant potential for further application for LiFePO₄ cathodes in Li-ion batteries.