Integrating surface modification to improve the electrochemical performance of Li-rich cathode materials,Inorganic Chemistry Frontiers

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Integrating surface modification to improve the electrochemical performance of Li-rich cathode materials
Inorganic Chemistry Frontiers ( IF 6.1 ) Pub Date : 2024-07-16 , DOI: 10.1039/d4qi00769g
Xiaoyuan Zhang _{1,

2,

3} , Yanxiao Gao _{1,

2,

3} , Xiangnan Li _{1,

2,

3} , Wenfeng Liu _{1,

2,

3} , Huishuang Zhang _{1,

2,

3} , Shuting Yang _{1,

2,

3} , Yanhong Yin _{1,

2,

3}

Affiliation

Li-rich cathode materials (LLO) exhibit a high specific capacity, but their application is impeded by their poor cycling stability and rate performance which arises from the irreversible anionic redox reaction and their poor electrical conductivity. In this regard, a simple phytic acid surface treatment technique was employed to form an integrated surface structure comprising Li₃PO₄ and oxygen vacancies (Vos) on the surface of LLO materials. In particular, the effect of the Li₃PO₄ layer on the defect structure and their synergistic effect on the electrochemical performances of LLO were researched through experimental and theoretical calculations. The results prove that the existence of Li₃PO₄ can improve the Vo content obviously. The coating layer and the synchronously formed Vo can also facilitate Li⁺ diffusion, improve the electrical conductivity, and inhibit the irreversible O₂ release effectively, thus increasing the cycling stability and rate performance of LLO. Consequently, the initial coulombic efficiency (ICE) increases from 62.8% to 72%. After 200 cycles at 0.5C, the capacity retention has improved significantly from 78% to 92.3%, accompanied by a minimal voltage fading value of 108.8 mV. The discharge specific capacity still reaches 125 mA h g⁻¹ even at a current density of 5C. This work proves the effect of the Li₃PO₄ coating layer on the defect structure and electrochemical properties of the LLO material and provides an effective clue to improve its performance.

中文翻译：

集成表面改性提高富锂正极材料的电化学性能

富锂正极材料（LLO）表现出高比容量，但由于不可逆的阴离子氧化还原反应和较差的电导率而导致循环稳定性和倍率性能较差，阻碍了其应用。在这方面，采用简单的植酸表面处理技术在LLO材料表面形成包含Li ₃ PO ₄ 和氧空位（Vos）的集成表面结构。特别是，通过实验和理论计算研究了Li ₃ PO ₄ 层对缺陷结构的影响及其对LLO电化学性能的协同作用。结果证明Li ₃ PO ₄ 的存在可以明显提高Vo含量。包覆层和同步形成的Vo还可以促进Li ⁺ 扩散，提高电导率，并有效抑制O ₂ 不可逆释放，从而提高电池的循环稳定性和倍率性能。洛洛。因此，初始库仑效率 (ICE) 从 62.8% 增加到 72%。在 0.5C 下循环 200 次后，容量保持率显着提高，从 78% 提高到 92.3%，同时电压衰减值最小为 108.8 mV。即使在5C电流密度下，放电比容量仍达到125mAh g ⁻¹ 。该工作证明了Li ₃ PO ₄ 包覆层对LLO材料缺陷结构和电化学性能的影响，为提高其性能提供了有效线索。

更新日期：2024-07-16

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