Rational design of hollow Ti₂Nb₁₀O₂₉ nanospheres towards High-Performance pseudocapacitive Lithium-Ion storage

Ti₂Nb₁₀O₂₉, as one of the most promising anode materials for lithium-ion batteries (LIBs), possesses excellent structural stability during lithiation/delithiation cycling and higher theoretical capacity. However, Ti₂Nb₁₀O₂₉ faces some challenges, such as insufficient ion diffusion coefficient and poor electronic conductivity. To overcome these problems, this study investigates the effect of applying nanostructure engineering on Ti₂Nb₁₀O₂₉ and the lithium storage behaviors. We successfully synthesized hollow Ti₂Nb₁₀O₂₉ nanospheres (h-TNO NSs) via solvothermal method using phenolic resin nanospheres as the template. The effects of using a template or not and the annealing atmospheres on the microstructures of the as-prepared Ti₂Nb₁₀O₂₉ are investigated. Different nanostructures (porous Ti₂Nb₁₀O₂₉ nanoaggregates (p-TNO NAs) without a template and core-shelled Ti₂Nb₁₀O₂₉@C nanospheres (cs-TNO@C NSs)) were formed through annealing in Ar. When examined as anodes for LIBs, the h-TNO NSs electrode with hollow spherical structure displayed a better lithium storage performance. Compared to its counterparts, p-TNO NAs and cs-TNO@C NSs, h-TNO NSs electrode exhibited a higher reversible capacity of 282.5 mAh g^-1 at 1C, capacity retention of 79.5% (i.e., 224.6 mAh g^-1) after 200 cycles, and a higher rate capacity of 173.1 mAh g^-1 at 10C after 600 cycles. The excellent electrochemical performance of h-TNO NSs is attributed to the novel structure. The hollow nanospheres with cavities and thin shells not only exposed more active sites and improved ion diffusion, but also buffered the volume variation upon cycling and facilitated electrolyte penetration. This consequently enhanced the lithium storage performance of the electrode and its high pseudocapacitive contribution (90% at 1.0 mV s^-1).