Zirconium-doped precursor regulates surface-bulk structure of LiCoO2 for stable 4.5 V performance

Abstract

Increasing the cut-off voltages of lithium cobalt oxide (LiCoO2) is crucial for improving its energy density, but this exacerbates bulk structural degradation and interfacial side reactions under high-voltage conditions (≥ 4.5 V). Although various bulk doping and surface coating strategies have been developed to stabilize LiCoO2 at high voltages, most of these involve multi-step processes or are applied after material synthesis, often failing to achieve synergistic strengthening between the bulk and surface phases simultaneously within a single material. Here, we propose an innovative strategy for precursor-doped modification of LiCoO2. Zirconium (Zr) is introduced during the CoCO3 preparation stage via a coprecipitation method, followed by sequential synthesis of Zr-modified Co3O4 and LiCoO2, achieve source-level regulation of LiCoO2. Additionally, during subsequent gradient sintering, Zr simultaneously enters the LiCoO2 lattice and segregates near the surface region, forming Zr-modified LiCoO2 (Zr-LCO) with an integrated structure featuring bulk doping and surface coating. Zr-LCO exhibits significantly enhanced cycle stability (retaining 85% reversible discharge capacity after 100 cycles at 0.5C) and rete capability (89% capacity retention at 5C compared to 0.1C), while the corresponding 3 Ah pouch battery maintains a capacity retention rate of 92.7% after 520 cycles. This study achieved simultaneous control over the bulk and surface structures of LiCoO2 through a precursor modification strategy, providing a new approach with industrialization potential for the development of a high-voltage, long-life LiCoO2 cathode.