Zn含量对岩盐型高熵氧化物储锂性能的影响

Effect of Zn Content on Lithium Storage Properties of Rock Salt Type High Entropy Oxides

用溶液燃烧法制备不同Zn含量的岩盐型高熵氧化物(Co_(0.22)Cu_(0.22)Mg_(0.22)Ni_(0.22)Zn_(0.12))O、(Co_(0.2)Cu_(0.2)Mg_(0.2)^(-)Ni_(0.2)Zn_(0.2))O和(Co_(0.18)Cu_(0.18)Mg_(0.18)Ni_(0.18)Zn_(0.28))O,研究了Zn离子浓度对其电化学性能的影响。结果表明:随着Zn含量的提高这类电极材料的电化学性能随之提高。(Co_(0.18)Cu_(0.18)Mg_(0.18)Ni_(0.18)Zn_(0.28))O电极具有优异的电化学性能,其原因是较高的晶格畸变和氧空位浓度使其本征电导率和锂离子扩散系数略微提高。电流密度为200 mA·g^(-1)时这种材料的初始放电比容量(777.06 mAh·g^(-1))和循环稳定性(循环150圈后容量保持率接近100%)最高,电流密度为3000 mA·g^(-1)时比容量为140.2mAh·g^(-1)时其倍率性能优异,即使电流密度为1000 mA·g^(-1)其循环150圈(比容量198.1 mAh·g^(-1))也表现出最高的循环稳定性。(Co_(0.18)Cu_(0.18)Mg_(0.18)Ni_(0.18)Zn_(0.28))O电极优异的电化学性能和循环稳定性,可归因于Zn元素在氧化还原反应中完全转化,含量较高的Zn提供了更多的容量,适当的氧空位浓度和晶格畸变程度为锂离子传输提供了更多的通道。

Rock salt-type high entropy oxide(Co_(0.2)Cu_(0.2)Mg_(0.2)Ni_(0.2)Zn_(0.2))O as anode material for lithium-ion battery has attracted widespread attention due to its unique synergistic effect of multiple elements.Zn and part of Co elements provide the main source of electrode capacities,while MgO stabilizes the crystal structure,Ni,Cu,and the reduced residual Co may form a 3-dimensional network to enhance the conductivities of the oxide.In this study,a series of rock salt-type high entropy oxides(Co_(0.22)Cu_(0.22)Mg_(0.22)Ni_(0.22)Zn_(0.12))O,(Co_(0.2)Cu_(0.2)Mg_(0.2)Ni_(0.2)Zn_(0.2))O and(Co_(0.18)Cu_(0.18)Mg_(0.18)Ni_(0.18)Zn_(0.28))O with different Zn contents were prepared by solution combustion method,while the effect of Zn ion concentration on the electrochemical performance of rock salt-type HEOs was also assessed.The results suggest that with the increasing Zn content,the electrochemical performance of the electrode material was enhanced.Although the(Co_(0.2)Cu_(0.2)Mg_(0.2)Ni_(0.2)Zn_(0.2))O electrode exhibits a higher lattice distortion and oxygen vacancy concentration,resulting in a slightly higher intrinsic conductivity and lithium ion diffusion coefficient,however,the(Co_(0.18)Cu_(0.18)Mg_(0.18)Ni_(0.18)Zn_(0.28))O electrode showed the most excellent electrochemical performance with the highest initial discharge specific capacity(777.06 mAh·g^(-1))and cycling stability(capacity retention rate nearly 100%after 150 cycles)at 200 mA·g^(-1),as well as excellent rate performance(specific capacity of 14_(0.2)mAh·g^(-1)at 3000 mA·g^(-1)),and it even shows the best cycling stability after 150 cycles at a high current density of 1000 mAh·g^(-1)(specific capacity of 198.1 mAh·g^(-1)).The excellent electrochemical performance of the(Co_(0.18)Cu_(0.18)Mg_(0.18)-Ni_(0.18)Zn_(0.28))O electrode may be attributed to the complete conversion of Zn element during the redox reaction.The higher Zn content is beneficial to increase capacities,while the appropriate oxygen vacancy concentration and lattice distortion may provide more channels for Li ion migration,thus resulting in higher cycle stability of the electrode.