高熵氧化物由于独特的高熵效应、多主元协同效应和可定制的结构, 作为能量存储材料受到广泛地关注. 本研究采用金属硝酸盐为金属源, 甘氨酸为燃料, 通过溶液燃烧法成功合成了一系列无钴的钙钛矿型高熵氧化物La(Cr_0.2Fe_0.2Mn_0.2Ni_0.2M_0.2)O₃ (M=Cu, Mg, Zn)锂离子电池负极材料, 研究了粉体的微观结构和电化学性能. 结果表明: 所制备的钙钛矿型高熵氧化物La(Cr_0.2Fe_0.2Mn_0.2Ni_0.2M_0.2)O₃均为单相钙钛矿结构, 形貌为多孔网状且各组成元素分布均匀, 其中引入非活性元素Mg或活性元素Cu的高熵氧化物电化学性能相近; 无钴化La(Cr_0.2Fe_0.2Mn_0.2Ni_0.2Zn_0.2)O₃电极具有最高的比容量(200 mA•g⁻¹电流密度下循环250圈后可逆比容量为1014 mAh•g⁻¹)、优异的循环稳定性(1000 mA•g⁻¹电流密度下循环1000圈后可逆比容量为450 mAh•g⁻¹且几乎没有容量衰减)以及卓越的倍率性能(100 mA•g⁻¹电流密度下可逆比容量为396 mAh•g⁻¹, 3000 mA•g⁻¹电流密度下可逆比容量为198 mAh•g⁻¹, 容量保持率为47.9%). 电化学性能提升主要归因于活性元素Zn的加入可以在还原过程中形成Li-Zn合金使得电极比容量明显增加; 同时较高的比表面积、介孔结构以及丰富的表面氧空位使其具有较高的电导率(0.14 S•cm⁻¹)、锂离子扩散系数(2.1×10⁻¹² cm²•s⁻¹)和较大的赝电容贡献率, 从而显著提升了材料的比容量和倍率性能. 因此, 引入能够与锂发生合金化反应的元素(如Zn)可以极大地提高电化学性能, 有利于为设计成本低廉、性能优异的无钴化高熵材料提供新的设计理念和思路.

High-entropy oxides (HEOs) have become increasingly popular as energy storage materials owing to their unique high-entropy effect, multi-principal synergy effect and customizable structure. In this study, a series of cobalt-free perovskite high-entropy oxide La(Cr_0.2Fe_0.2Mn_0.2Ni_0.2M_0.2)O₃ (M=Cu, Mg, Zn) lithium-ion battery anode materials were successfully synthesized by solution combustion method using metal nitrate as the metal source and glycine as the fuel. The microstructure and electrochemical properties of the as-prepared powders were investigated. The results show that the as-prepared high- entropy oxides crystalize into single-phase perovskite structure with porous foam-like shape and chemical/microstructural homogeneity. Furthermore, the as-prepared HEOs introducing inactive element Mg or active element Cu possess similar electrochemical performance; while the La(Cr_0.2Fe_0.2Mn_0.2Ni_0.2Zn_0.2)O₃ electrode exhibits a highest reversible capacity (1014 mAh•g⁻¹ at 200 mA•g⁻¹ after 250 cycles), excellent cycling stability (450 mAh•g⁻¹ at 1000 mA•g⁻¹ and almost no capacity decay after 1000 cycles) and outstanding rate performance. Such excellent performance can be attributed to the addition of active element Zn, which can form Li-Zn alloy during the reduction process that makes the specific capacity increase significantly. Meanwhile, its higher specific surface area, mesoporous structure and abundant surface oxygen vacancies result in higher conductivity (0.14 S•cm⁻¹), increased larger lithium ion diffusion coefficient (2.1×10⁻¹² cm²•s⁻¹), and pseudo-capacitance contribution, thus significantly enhances the specific capacity and rate performance of the as-prepared material. Therefore, the introduction of electrochemically active metals, which can react with Li alloying, such as Zn, can improve the electrochemical performance, thereby providing ideas for designing cobalt-free HEOs with low-cost and excellent performance for energy storage.