Abstract:

A series of inactive K⁺-doped spinel-type (K _x CoCrFeMnNi)_3/(5+x)O₄ (x=0, 0.5, 1, 1.5) high-entropy oxides lithium-ion battery anode materials were successfully synthesized by solution combustion method, and the effects of K⁺ doping on the structure and lithium storage performance were systematically investigated. The results show that all the synthesized nanocrystalline powders are crystallized as single spinel structure with the increase of K⁺ doping. Among them, the equimolar K⁺-doped (K_1/6Co_1/6Cr_1/6Fe_1/6Mn_1/6Ni_1/6)₃O₄ high-entropy oxide anode material has the highest specific capacity, excellent cycling stability and rate capability. The initial specific discharge capacity of (K_1/6Co_1/6Cr_1/6Fe_1/6Mn_1/6Ni_1/6)₃O₄ is 1295 mA·h·g^-1 at the current density of 200 mA·g^-1 with columbic efficiency of 78%. The specific capacity decreases first and then increases as the cycle proceeds, and after 150 cycles the reversible specific capacity increases to 1505 mA·h·g^-1. Even at a high current density of 1000 mA·g^-1, it still has a reversible specific capacity of 1402 mA·h·g^-1 after 500 cycles, which is much higher than the theoretical specific capacity of 898 mA·h·g^-1. Although the doping of low-valent inactive K⁺ decreases the lattice constant due to the charge compensation effect, entropy-stabilized crystal structure improves the cycling stability, and the abundant surface oxygen vacancies, small grain size and mesoporous structure are beneficial to improve the pseudocapacitive contribution and electron/ion diffusion ability, which significantly improve the specific capacity and rate performance of the as-synthesized (K_1/6Co_1/6Cr_1/6Fe_1/6Mn_1/6Ni_1/6)₃O₄ anode material.

Key words: lithium-ion batteries anode materials, inactive K⁺ doping, high-entropy oxide, spinel structure, nanomaterials, electrochemistry, kinetics

摘要：

通过溶液燃烧法成功合成了一系列非活性K⁺掺杂的尖晶石型 (K _x CoCrFeMnNi)_3/(5+x)O₄(x=0，0.5，1，1.5)高熵氧化物锂离子电池负极材料，系统研究了K⁺掺杂对结构和储锂性能的影响。结果表明：随着K⁺掺杂量的增加，均可制备出具有单一尖晶石结构的纳米晶粉体材料，其中等摩尔K⁺掺杂的 (K_1/6Co_1/6Cr_1/6Fe_1/6Mn_1/6Ni_1/6)₃O₄高熵氧化物负极材料具有最高的比容量、优异的循环稳定性和倍率性能。(K_1/6Co_1/6Cr_1/6Fe_1/6Mn_1/6Ni_1/6)₃O₄电极在200 mA·g^-1电流密度下，首次放电比容量为1295 mA·h·g^-1（首次库仑效率78%）；随着循环的进行，可逆比容量先降低后增加，循环150次可逆比容量增加至1505 mA·h·g^-1；即使在1000 mA·g^-1大电流密度下循环500次后仍具有1402 mA·h·g^-1的可逆比容量（均高于理论比容量898 mA·h·g^-1）。低价非活性K⁺的掺杂由于电荷补偿效应使晶格常数降低，但高构型熵稳定的晶体结构提高了循环稳定性；丰富的表面氧空位、较小的晶粒尺寸和介孔结构，增加了赝电容贡献率和电子/离子传输能力，从而显著提升了材料的比容量和倍率性能。

关键词: 锂离子电池负极材料, 非活性K⁺掺杂, 高熵氧化物, 尖晶石结构, 纳米材料, 电化学, 动力学