Laser structuring of high mass loaded and aqueous acid processed Li(Ni0.6Mn0.2Co0.2)O2 cathodes for lithium-ion batteries

Abstract

Aqueous processing of cathode is a practical method to achieve cost reduction for lithium-ion batteries and provide environmentally friendly production by avoiding the use of the state-of-the-art polyvinylidene fluoride binder and toxic N-methyl-2-pyrrolidone solvent. However, the reaction of cathode materials with water leads to lithium leaching and a slurry pH value larger than 8. This results in chemical corrosion on current collector during coating process, leaving cavities inside dried electrodes. In this work, different acid additions were applied during mixing process in order to adjust slurry pH value. Besides, thick-film Li(Ni0.6Mn0.2Co0.2)O2 cathodes were manufactured to achieve a high mass loading of about 35 mg/cm2. X-ray photoelectron spectroscopy and Raman spectroscopy were applied to characterize the electrodes. Meanwhile, three-dimensional (3D) structures were generated in aqueous processed thick-film electrodes by applying ultrafast laser patterning and the active mass loss was adjusted to 7.5 %. Rate capability analyses, long-term performance, impedance spectroscopy, and cyclic voltammetry measurements were conducted to compare the electrochemical performance of cells with different cathode types. Rate capability analyses reveal that cells with structured aqueous processed thick electrodes with phosphoric acid and acetic acid show higher discharge capacity at specific current >80 mA/g in comparison to ones with PVDF. Besides, cells containing structured high mass loaded electrodes with phosphoric acid maintain 72 % capacity, which is 15 % higher than the reference cells with PVDF.