A New TiO with In Situ Transformed Rutile TiO₂ Nanothorns as a Next-Generation Anode Material for Lithium-Ion Battery

Developing new high-performance anodes is highly desired to meet the ever-increasing demands for lithium-ion battery (LIB) systems with large capacity, high-rate capability, and long cycling life. Herein, we present an effective solution for the insufficient reversible capacity issues of titanium oxides largely attributable to the slow Li-ion diffusion, intrinsic low electrical conductivity, and narrow reversible half-cell working potential window, through new material design strategy of unique titanium oxide heterostructure. We report a uniquely integrated hybrid structure of rutile TiO₂ (r-TiO₂) nanothorns <i>in-situ</i> grown over a new porous and conductive TiO core, which is generated from pyrolysis of anatase TiO₂ with Mg metal at 650 degree in centigrade. The TiO is controllably <i>in-situ</i> oxidized to generate r-TiO₂ nanothorns over the TiO surface to form the r-TiO2-TiO hybrid.<br/>The new hybrid exhibits superb LIB performance as an anode with a high reversible capacity and almost no capacity decay during 1000 cycles at a high current density of 20 C (4000 mA g^-1). Two independent reactions of intercalation and interfacial pseudocapacitive interaction are confirmed to occur in the composite of the r-TiO₂ and TiO, respectively. In particular, the excellent rate capability along with long cycle life enables the new hybrid to have ultrafast charging of the system. Furthermore, the hybrid with the job-sharing property exhibits stable charge-discharge performance over a wider potential window range of 0.01 to 3.0 V, particularly even in the low potential range of 1 and 0.01 V, which usually causes irreversible Li-intercalation and rapid capacity decay for pristine TiO₂. All the properties including the wider potential window allows the hybrid to realize the highest electrochemical performance that titanium oxides have ever achieved so far.