Developing High-performance Co-free and Ultra-high Nickel Layered Cathodes through Multi-element Doping Strategy

Description

Lithium-ion batteries as an energy storage system attract much attention because of their high energy density and broad application spectrum in many fields, such as portable electronic devices, electric vehicles (EVs), and stationary energy storage. Driven by the ever-increasing demand of the EVs and clean energy storage market, many works have been done to increase performance and reduce the cost of Li-ion batteries. Cathode materials are the core component of batteries and account for nearly one-third of the total battery cost. To reduce the cost and improve the performance of the batteries, Mn, Ni, and other elements were used to substitute Co in LiCoO2, the first commercialized cathode. In recent years, the nickel-rich LiNixCoyMnzO2 (x≥0.8, referred to as Ni-rich NCMs) layered cathodes have been the focus of research and development worldwide, because substituting Co with Ni could significantly reduce the cost and deliver a higher capacity in the commercial electrolyte working window. However, increasing the Ni content in the cathode is accompanied by structural instability, especially when the Ni content exceeds 80%. Achieving a higher Ni content and long-term high performance simultaneously remains challenging. Based on our previous success in dual-element doped LiCoO2 and inspired by the recent works on cation-disordered rock salt-type high-entropy cathodes and compositionally complex doped Ni-rich layered cathodes (Ni content of 80%), here we propose using a multielement doping strategy to develop high-performance Co-free and ultra-high nickel (CFUHN) layered cathodes. The targeted cathodes will have a Ni concentration higher than 95% with long-term stable cyclic performance. Recently, our preliminary work using this strategy has shown very promising results, as detailed in the main text. In this proposal, we will design and develop multi-element doped CFUHN cathodes that will exhibit reversible capacity ≥ 200 mAh g-1 with a retention rate higher than 92% after 200 cycles. In addition, the underlying mechanisms of doping effects on structural stability and performance improvement will also be investigated and clarified. The final objective of this project is to seek optimal combinations of doping elements, investigate the thermal stability and realize the practical application of high-performance CFUHN cathodes.