In situ synthesis of a graphene/titanium nitride hybrid material with highly improved performance for lithium storage

Abstract

A graphene/titanium nitride (G/TiN) hybrid as an anode material of lithium ion batteries is prepared by a simple in situhydrolysis method combined with ammonia annealing. TiN nanoparticles as obtained are ∼5 nm in size and homogeneously anchored on G. The G/TiN hybrid anode delivers a reversible capacity as high as 646 mA h g⁻¹ at 20 mA g⁻¹ and exhibits an enhanced initial coulombic efficiency of 75%, much higher than that of pure graphene (G: 52%) in the first cycle. The capacity retention is as much as 86% after 200 cycles. At a current density of 2000 mA g⁻¹, the hybrid anode still retains 325 mA h g⁻¹ while that of G is only 98 mA h g⁻¹. It is demonstrated that the G/TiN hybrids display a superior electrochemical performance owing to the highly efficient mixed (electron and Li⁺) conducting network. The internal defects between G layers induced by nitrogen-doping in G/TiN may improve reversible Li storage, whereas the catalytic sites on the surface of G related to the decomposition of the electrolyte may be occupied by TiN, leading to a decreased irreversible capacity. Moreover, the formation of Li₃N in the interface is beneficial to interface transport, which is confirmed by aberration-corrected scanning transmission electron microscopy. The anchoring of TiN nanoparticles on G is promising prospect for energy storage applications in high performance lithium-ion batteries.