A Gradient Doping Strategy toward Superior Electrochemical Performance for Li-Rich Mn-Based Cathode Materials,Small

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A Gradient Doping Strategy toward Superior Electrochemical Performance for Li-Rich Mn-Based Cathode Materials
Small ( IF 13.0 ) Pub Date : 2023-02-20 , DOI: 10.1002/smll.202207797
Puheng Yang _{1,

2} , Shichao Zhang ₁ , Ziwei Wei ₁ , Xianggang Guan ₁ , Jun Xia ₁ , Danyang Huang ₃ , Yalan Xing ₁ , Jia He ₃ , Bohua Wen ₄ , Bin Liu ₅ , Huaizhe Xu ₂

Affiliation

Lithium-rich layered oxides (LLOs) are concerned as promising cathode materials for next-generation lithium-ion batteries due to their high reversible capacities (larger than 250 mA h g⁻¹). However, LLOs suffer from critical drawbacks, such as irreversible oxygen release, structural degradation, and poor reaction kinetics, which hinder their commercialization. Herein, the local electronic structure is tuned to improve the capacity energy density retention and rate performance of LLOs via gradient Ta⁵⁺ doping. As a result, the capacity retention elevates from 73% to above 93%, and the energy density rises from 65% to above 87% for LLO with modification at 1 C after 200 cycles. Besides, the discharge capacity for the Ta⁵⁺ doped LLO at 5 C is 155 mA h g⁻¹, while it is only 122 mA h g⁻¹ for bare LLO. Theoretical calculations reveal that Ta⁵⁺ doping can effectively increase oxygen vacancy formation energy, thus guaranteeing the structure stability during the electrochemical process, and the density of states results indicate that the electronic conductivity of the LLOs can be boosted significantly at the same time. This strategy of gradient doping provides a new avenue to improve the electrochemical performance of the LLOs by modulating the local structure at the surface.

中文翻译：

一种梯度掺杂策略可提高富锂锰基正极材料的电化学性能

^{富锂层状氧化物 (LLO) 因其高可逆容量（大于 250 mA hg -1}）而被视为下一代锂离子电池的有前途的阴极材料。然而，LLO 存在严重的缺点，例如不可逆的氧气释放、结构退化和反应动力学差，这些都阻碍了它们的商业化。^{在此，通过梯度 Ta 5+}掺杂调整局部电子结构以提高 LLO 的容量能量密度保持和倍率性能。结果，容量保持率从 73% 提高到 93% 以上，能量密度从 65% 提高到 87% 以上，LLO 在 1 C 下经过 200 个循环后进行修改。此外，Ta ⁵⁺掺杂的 LLO 在 5 C 下的放电容量为 155 mA hg⁻¹，而裸 LLO 仅为 122 mA hg ⁻¹。理论计算表明，Ta ⁵⁺掺杂可以有效提高氧空位形成能，从而保证电化学过程中的结构稳定性，态密度结果表明同时可以显着提高LLOs的电子电导率。这种梯度掺杂策略为通过调节表面的局部结构来提高 LLO 的电化学性能提供了一条新途径。

更新日期：2023-02-20

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