Study on structural regulation and electrochemical properties of high energy density cathode materials for Lithium-ion battery

Abstract

With the overexploitation of fossil resources and the gradual deterioration of the Earth’s environment, people have begun to focus on new energy sources. Lithium-ion batteries have advantages such as environmental friendliness and low cost. The world is undergoing a new energy revolution, with lithium-ion batteries transforming lifestyles across diverse sectors. Since the energy density, cost, and safety of lithium-ion batteries are constrained by cathode materials, developing next-generation high energy density cathodes is crucial. Nickel-rich cathodes and lithium-rich cathodes are two representative high-energy-density cathode materials, which face severe challenges such as irreversible phase transitions and oxygen evolution, hindering their application and development in high-energy-density lithium-ion barriers.
This thesis explores the regulation of cathode atoms to modify atomic coordination environments and phase transition (or oxygen evolution) processes. Firstly, inspired by architectural structures, a structural modulation strategy is developed for LiNi0.94Co0.055Mn0.005O2 (Ni94) cathodes. This approach employs a simple candle soot coating and subsequent thermal annealing to create a mortise-like disordered surface phase while forming stabilizing “Ni2+ columns” within the bulk material. These features work synergistically to suppress intergranular stress and mitigate the detrimental H2–H3 phase transition. However, the first study has not fully investigated the effect of Li/Ni atomic regulation on anion redox reactions; this effect is examined in detail in the second study. The 2nd work proposes a synergistic competitive redox mechanism between nickel and oxygen. By introducing Ni2+ as an “oxygen anchor”, the hybridization of O 2p orbitals is modulated, lowering the oxygen 2p band center by 0.04 eV and effectively stabilizing lattice oxygen up to 4.5 V. This strategy enables a controlled “Not-gate” cathode electrolyte interphase evolution in modified Ni94. Given the limited energy density of Ni94 and the fact that dry coating may lead to issues such as uneven coating, the third study focuses on lithium-rich cathodes and employs a wet modification strategy. A cation exchange method, completed within 10 min at 50 °C, is applied to modify the surface coordination environment of lithium-rich cathodes. This mild treatment effectively regulates the oxygen redox behaviour, enhancing its reversibility during cycling. This work presents a scalable and efficient strategy for stabilizing anion redox activity in high-capacity lithium-rich cathode materials.

Date of Award	18 Jul 2026
Original language	English
Awarding Institution	University of Nottingham
Supervisor	Binjie Hu (Supervisor), Yonggao Xia (Supervisor) & Guang Li (Supervisor)