Enabling High-Stability of Aqueous-Processed Nickel-Rich Positive Electrodes in Lithium Metal Batteries

Lithium batteries occupy the large-scale electric mobility market raising concerns about the environmental impact of cell production, especially regarding the use of poly(vinylidene difluoride) (teratogenic) and N-methyl-2-pyrrolidone (NMP, harmful). To avoid their use, an aqueous electrode processing route is utilized in which a water-soluble hybrid acrylic-fluoropolymer together with sodium carboxymethyl cellulose is used as binder, and a thin phosphate coating layer is in situ formed on the surface of the nickel-rich cathode during electrode processing. The resulting electrodes achieve a comparable performance to that of NMP-based electrodes in conventional organic carbonate-based electrolyte (LP30). Subsequently, an ionic liquid electrolyte (ILE) is employed to replace the organic electrolyte, building stable electrode/electrolyte interphases on the surface of the nickel-rich positive electrode (cathode) and metallic lithium negative electrode (anode). In such ILE, the aqueously processed electrodes achieve high cycling stability with a capacity retention of 91% after 1000 cycles (20 °C). In addition, a high capacity of more than 2.5 mAh cm^-2 is achieved for high loading electrodes (≈15 mg cm^-2 ) by using a modified ILE with 5% vinylene carbonate additive. A path to achieve environmentally friendly electrode manufacturing while maintaining their outstanding performance and structural integrity is demonstrated.