Template-free synthesis of flower-like hierarchical vanadium nitride/carbon composites for long cycle-life half and full lithium-ion batteries

Vanadium nitride (VN) is a promising energy storage material due to its high theoretical capacity and good electrical conductivity. However, the unbearable volume expansion due to the lithium insertion impedes its application for lithium-ion batteries (LIBs). Herein, a simple, template-free strategy is developed to synthesize a micron-sized flower-like hierarchical structure made of N-doped carbon layers, embedding VN nanoparticles and outer carbon shell (denoted as VN/NC-MF@C). Profiting from the unique structure, the VN/NC-MF@C composite delivers an excellent reversible capacity (601 mA h g−1 at 0.1 A g−1) and ultra-long cycle durability with retention of 92.6% after 5000 cycles at 2 A g−1. More remarkably, the LiCoO2 || VN/NC-MF@C full LIBs also demonstrate extraordinary long-term cycle stability, retaining 94.8% of the initial capacity after 1300 cycles at 1 A g−1. The excellent electrochemical performance of the composite provides inspirations and strategies for developing new unique hierarchical materials with stable, high-performance properties for commercial use in LIBs.