Modification and characterisation of superior nickel-rich layered oxide cathodes for advanced lithium-ion batteries for EVs application

Abstract

Significant focus has been directed towards Ni-rich cathodes in lithium-ion batteries (LIBs) as they have been shown to become the sustainable electrodes for electric vehicles (EVs) applications. Particularly, Ni-rich layered oxides (NLO) cathodes with stoichiometric ratios of Ni ≥ 80% have gained substantial attention due to their impressive high energy density. Nonetheless, NLO compounds suffer several crucial problems such as Li+/Ni2+ cation mixing, structural degradation, side reactions, and micro-cracks. These problems deteriorate the battery performance, especially at high current density and high voltage. This PhD research focused on modifying polycrystalline NLO to alleviate these crucial problems. To this end, a novel sol/antisolvent method with boron-related materials has been developed to modify the different NLO materials or their precursors. The underlying mechanisms of the modification effects by the proposed sol/antisolvent method for the superior NLO cathodes for EV applications have also been studied. First, a high initial Coulombic efficiency and ultra-stable mechanical integrity of LiNi0.85Co0.1Mn0.05O2 are achieved. This is mainly because the modification with crystalline LiBO2 nanoparticle coating and nanorod wrapping on NLO can provide double protection against electrolytes. Second, the innovative design of a three-in-one effect incorporating radially aligned structure and amorphous LiBO2 coating and B-doping on NLO has proven compelling. This strategy has enabled extremely high discharge capacity and excellent cycling stability in LiNi0.83Co0.05Mn0.12O2 materials. Third, the benefits of radially aligned structure and B-doping extend to the ultra-high Ni content materials such as LiNiO2 with improved Li/Ni ordering, resulting in markedly superior capacity retentions compared to the well-formed and similar-sized single-crystal LiNiO2. This work demonstrates the efficacy of utilizing novel sol/antisolvent treatment with boron-related materials in advancing NLO cathode development. The findings establish viable strategies for creating superior NLO cathodes for the rigorous demands of EV applications.

Date of Award	17 Mar 2025
Original language	English
Awarding Institution	University of Nottingham
Supervisor	Philip Hall (Supervisor), Zheng Wang (Supervisor) & Yonggao Xia (Supervisor)