Dry-processed cathode with Li+-carrier composite binder fiber for high energy density lithium-ion battery

Abstract

The application of high energy density battery presents challenges for high loading electrode to achieve good performance. Polytetrafluoroethylene fibrillation results in unique advantages including high tap density, non-pollution, and thick electrodes. However, with an increase in electrode thickness, Li + transport within a dry cathode with a low porosity is particularly limited. Additionally, the binder currently used in the dry-film process suffers from poor conductivity and viscosity, resulting in a lithium-ion battery with poor cycling stability and rate performance. In this study, we developed a dry ultra-high-loading cathode using a Li⁺-carrier composite binder, which facilitated Li⁺ migration and ensured good interfacial contact between the active material particles (LiNi_0.5Co_0.2Mn_0.3O₂). This was attributed to the high dispersion performance of polyacrylonitrile and its interactions with Li⁺. Density functional theory analysis revealed that the composite binder exhibited a homogeneous electrostatic potential profile and narrow lowest unoccupied molecular orbital-highest occupied molecular orbital energy gap, thus enhancing its effectiveness in facilitating electron mobility. Therefore, the thick cathode fabricated with the composite binder displayed a high discharge capacity of 170.4 mAh g⁻¹ (200 μm, 9 mAh cm⁻²) at 0.1C and a stable cycling performance, retaining 80.8 % of its initial capacity after 250 cycles at 0.5C. The single-layer lithium-metal pouch cell exhibited a high energy density of 300 Wh kg⁻¹, and 85.5 % of the capacity was retained after 150 cycles at 0.1C.