Tuning Li occupancy and local structures for advanced Co-free Ni-rich positive electrodes
Hang Li, Hao Liu, Shunrui Luo, Jordi Arbiol, Emmanuelle Suard, Thomas Bergfeldt, Alexander Missyul, Volodymyr Baran, Stefan Mangold, Yongchao Zhang, Weibo Hua, Michael Knapp, Helmut Ehrenberg, Feng Pan, Sylvio Indris
Abstract
Abstract Structure evolution and surface reactivity have long been regarded as the most crucial points for studying Ni-rich positive electrodes for Li-ion batteries. Unfortunately, the influence of Li occupancy as a single factor on electro-chemomechanical stability has been overlooked and is missing, owing to the challenge of Li determination in the lattice. Here, a comprehensive analysis reveals different Li occupancies and related structural domains (Ni/Li exchange, Li a XO b , Li/Mn/X(Ni) ordering domains, X = Nb 5+ , W 6+ , and Mo 6+ ) by using a combination of Li-sensitive characterization techniques. By introducing a Li-regulation strategy, the relative ratio of each domain is effectively tuned in the Ni-rich positive electrodes. Through tuning, two specific positive electrodes are designed, exhibiting notable improvement in battery cyclability. The specific Li structural units induce significant changes in redox mechanisms. This Li-occupancy-tuning approach highlights the necessity of focusing on Li distribution and opens up ideas for designing advanced Ni-rich positive electrodes with high durability.