Hetero-Phase MoO<sub>2</sub>/Cu<sub>2–<i>x</i></sub>Se Nanocomposites Distributed in Porous Octahedral Carbon Networks for High-Performance Lithium Storage
Ming Zhong, Xue Guo, Lingling Li, Yun‐Wu Li, Kun Zhao, Hui Peng, Xiaobo Zhang
Abstract
Owing to the mixed insertion and multielectron conversion reaction mechanisms, nonstoichiometric copper selenide (Cu 2– x Se) has been known as a potential anode for lithium-ion batteries. However, huge volume changes during discharge and charge limit its ability for lithium-ion storage. Constructing heterophase nanocomposite uniformly distributed in the carbon network has been recognized as an effective approach to address the above issue. In this work, polyoxometalate-based metal–organic frameworks were used as the self-template to derive octahedral mesoporous carbon-coated heterophase copper selenide and molybdenum dioxide (MoO 2 /Cu 2– x Se@C) nanocomposites, and the phase transformation of copper selenides from CuSe to Cu 2– x Se can be achieved by tuning the pyrolysis temperature, thus optimizing the electrochemical performance. As a result, the optimized electrode delivers a high reversible specific capacity of 864.8 mAh g –1 at 0.2 A g –1 after 100 cycles, an excellent rate capability with a capacity of 480.9 mAh g –1 at 2.0 A g –1, and a long-term stability up to 500 cycles with a capacity decay rate per cycle of only 0.003%. Also, the reaction mechanism and structural stability after cycling were analyzed in detail.