Abstract
Mixed transition metal oxides (MTMOs) are deemed as promising anode materials for lithium-ion batteries (LIBs) because of the high theoretical capacity and low cost. However, the low electrical conductivity, agglomeration effects, and huge volume variation during discharging/charging still seriously restrict the actual applications of MTMOs as anode materials. Herein, a novel core-shell structure of CoSnO3@carbon-caged NiCo2O4 nanobox (CNC) is rationally designed. It starts from the preparation of CoSnO3@ZIF-67 core-shell nanocubes, followed by chemical etching/anion exchange, dopamine coating and carbonization at high temperature in sequence. It is shown that the CNC achieves high activities from the applied MTMOs components, excellent relief of volume variation from the unique double hollow structure, improved conductivity and inhabited aggregations from the uniform-coated outmost carbon shell, and effective ion/electron transfer rates from the synergetic effects. As a result, the CNC exhibits a discharge capacity of 1548 mA h g−1 at the first cycle and a retention capacity of 992 mA h g−1 after 100 cycles at 0.1 A g−1. In addition, it exhibits a high reversible capacity of about 670 mA h g−1 after 500 cycles at a current density of 1 A g−1. The improved Li+ storage performances of CNC demonstrates that such rational design of double hollow structure could be a novel strategy to apply MTMOs as anode materials of LIBs.
Highlights
Today, over-exploitation of non-renewable fossil energy has serious impacts on our environment [1,2]
During this process, ZIF-67 was gradually etched by protons generated from the hydrolysis of Ni2+ ions, and the Ni-Co LDH was simultaneously formed through Ni2+ ions coprecipitating with the released Co2+ ions (Fig. 2g-i) [28,33]
We successfully prepare the multi-shell hollow structure caged NiCo2O4 nanobox (CNC) nanomaterial by using simple coprecipitation and a one-step calcination method. When it is served as the anode material of lithium-ion batteries (LIBs), the CNC exhibits a high initial capacity of 1548 mA h g− 1 at the current density of 0.1 A g− 1 and it stabilizes around 992 mA h g− 1 after 50 cy cles
Summary
Over-exploitation of non-renewable fossil energy has serious impacts on our environment [1,2]. After annealing, the LDH layers were feasibly converted to ternary nickel cobaltite (NiCo2O4), which is another active MTMOs being applied as effective anodic materials of LIBs owing to its advantages, such as high electrical conductivity, abundant availability, low costs, and nontoxic nature [29,30,31]. Among these TMOs candidates, NiCo2O4 pos sesses a higher electrical conductivity (0.1–0.3 S cm− 1) and better electrochemical performance. The excellent Li+ storage performances benefit from the meticulously designed double hollow structure composed of CoSnO3 nanobox and NiCo2O4 nanocage
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