Electrochemical reaction mechanism of porous Zn2Ti3O8 as a high-performance pseudocapacitive anode for Li-ion batteries

Zn2Ti3O8, as a new type of anode material for lithium-ion batteries, is attracting enormous attention because of its low cost and excellent safety. Though decent capacities have been reported, the electrochemical reaction mechanism of Zn2Ti3O8 has rarely been studied. In this work, a porous Zn2Ti3O8 anode with considerably high capacity (421 mAh/g at 100 mA/g and 209 mAh/g at 5000 mA/g after 1500 cycles) was reported, which is even higher than ever reported titanium-based anodes materials including Li4Ti5O12, TiO2 and Li2ZnTi3O8. Here, for the first time, the accurate theoretical capacity of Zn2Ti3O8 was confirmed to be 266.4 mAh/g. It was also found that both intercalation reaction and pseudocapacitance contribute to the actual capacity of Zn2Ti3O8, making it possibly higher than the theoretical value. Most importantly, the porous structure of Zn2Ti3O8 not only promotes the intercalation reaction, but also induces high pseudocapacitance capacity (225.4 mAh/g), which boosts the reversible capacity. Therefore, it is the outstanding pseudocapacitance capacity of porous Zn2Ti3O8 that accounts for high actual capacity exceeding the theoretical one. This work elucidates the superiorities of porous structure and provides an example in designing high-performance electrodes for lithium-ion batteries.