V6O13 nanosheets self-assembled into 3D hollow microflowers for long-life and high-rate Li-ion batteries

Among vanadium-based materials, V 6 O 13 is considered to be an ideal cathode candidate material due to its high theoretical capacity and energy density. However, as mixed-valence vanadium oxide, it faces the challenge of controllable synthesis, and suffers unsatisfactory cycle performance due to the unstable structure. Constructing 3D micro/nano-structures is a very effective method to solve the above problems. Herein, we report a simple template-free solvothermal method to controllably synthesize 3D hollow microflowers structure formed by self-assembly of thin nanosheets. The growth mechanism of the hollow microflowers is revealed by changing the solvothermal reaction time and the content of ethylene glycol. As a cathode material for Li-ion batteries, the V 6 O 13 hollow microflowers exhibit an initial discharge specific capacity of 326 mAh/g at a current density of 0.1 A/g. Even at a high current density of 1 A/g, the V 6 O 13 hollow microflowers still deliver a discharge capacity of 183.2 mAh/g, and display high capacity retention of 75.6% after 500 cycles. The excellent electrochemical performance benefits from the unique advantages of 3D hollow microflowers structure, that is, large specific surface area, abundant mesopores, and robust structure. These results indicate that the V 6 O 13 hollow microflowers have great potential as the long-life and high-rate cathode materials for the next generation of Li-ion batteries. • V 6 O 13 hollow microflowers assembled from nanosheets were synthesized controllably by a template-free solvothermal method. • The growth mechanism of hollow microflowers is revealed by changing the solvothermal reaction time and the content of ethylene glycol. • V 6 O 13 hollow microflowers exhibit excellent cycle stability and high-rate capability.