Carbon-coated Li 4 Ti 5 O 12 microspheres synthesized through solid-state reaction in a carbon reduction atmosphere for high-rate lithium-ion batteries

Carbon coating combined with morphological engineering has been considered an effective and economical measure for enhancing the electrochemical properties of Li 4 Ti 5 O 12 . Herein, using cheap and industrial H 2 TiO 3 as titanium reactant, carbon-coated Li 4 Ti 5 O 12 microspheres with high-rate performance were synthesized through solid-state reaction under a carbon reduction atmosphere. The carbon reduction atmosphere was produced from coal ash embedded between two corundum crucibles, instead of utilizing the inert or reduction gases. Assisted by spray-drying method for making spheres, the obtained products were composed of micron-size secondary spheres (2–12 μm) accumulated by submicron scale primary particles (~ 300 nm). As anode material, the LTO/C–C therefore delivered a very satisfying performance: a reversible capacity of 164.21 mAh/g at 0.2 C, and remarkable rate capability of ∼130.94 mAh/g at 5 C rate with little capacity fading (2.5%) after 200 cycles. Compared with pristine LTO and LTO/C-N 2 , the superior electrochemical performances are mainly ascribed to the presence of the thin carbon coating layer, conductive carbon network, and the hybrid valence state of Ti 3+ and Ti 4+ . The findings showed that solid-state reaction in the carbon reducing atmosphere provided with coal ash embedded is a promising candidate for the large-scale industrial production of LTO/C–C microparticles with high-rate capability, which avoids the needs of high-risk gas and high-cost of production equipment under harsh conditions.