Garnet-PVDF composite film modified lithium manganese oxide cathode and sulfurized carbon anode from polyacrylonitrile for lithium-ion battery
Lithium manganese oxide (LMO) is one of the most promising cathode material for lithium-ion batteries. However, the dissolution of manganese and its deposition on anode surface cause poor cycling stability. To alleviate these issues, a film composed of polyvinylidene difluoride (PVDF) and Li5.6Ga0.26La2.9Zr1.87Nb0.05O12 type garnet (PVDF@LGLZNO) is coated directly on the LMO electrode and it functions as a promising artificial cathode-electrolyte interphase (CEI). The film thickness is optimized concerning the electrospinning-processing time. To realize a cell with good capacity retention, excellent rate capability and resilience under harsher conditions (e.g. elevated temperature or high rates), the coated LMO cathode is coupled with a new anode which consists of sulfurized carbon derived from polyacrylonitrile (S-C(PAN)). The electrode (LMO-30min) coated with PVDF@LGLZNO composite material shows outstanding cycling stability and rate capability, as well as capacity retention when compared to bare electrode both at room temperature (25 °C) and elevated temperature (55 °C). The PVDF@LGLZNO fibrous film coating suppresses the dissolution of manganese both at high C-rates and 55 °C, as supported by XPS, whereas PVDF coated and bare LMO cathodes are not able to prevent the further deterioration of themselves. The film significantly minimizes undesirable side reactions at the cathode-electrolyte interface and reduces charger transfer resistance. The new cell with PVDF@LGLZNO (LMO-30min) modified cathode and S-C(PAN) anode delivers capacity retention of 77% after 1000 cycles at 1 C, corresponding to the average capacity decay of 0.023% per cycle.