Nanostructured SnO₂@TiO₂ Core-Shell Composites: A High-Rate Li-ion Anode Material Usable without Conductive Additives

Increasing the power density of lithium-ion batteries at the materials level is still the preferred strategy for meeting the requirements of large-scale applications such as electric vehicles and grid-scale energy storage. This paper reports a method to produce reversible Li-ion storage hosts as nanoparticles furnished with their own current collectors. The consequent decrease in interparticle electrical resistance enabled SnO₂ to be used as a lithium-ion battery anode without conductive additives, even surpassing the rate performance of SnO₂ with 10 wt % (typical value) carbon black conductive additive. The “current collector” in this case was a thin, conductive Li_yTi_1−yO₂ shell on a core aggregated from SnO₂ nanoparticles. Good electrical connectivity in the electrode was maintained even with the expansion and contraction of the Li-ion storage host during discharging and charging. The composite fabricated as such delivered a charge (delithiation) capacity of 743 mAh g⁻¹ at 0.2 A g⁻¹ in the first cycle and 518 mAh g⁻¹ at the end of 30 cycles without conductive additives. The charge capacity after increasing the current density by a factor of five was similar: 735 mAh g⁻¹ at 1 A g⁻¹ in the first cycle and 505 mAh g⁻¹ at the end of 30 cycles. Hence the design was effective in minimizing the capacity loss in cycling at high current densities. Impendence measurements indicated that the charge transfer resistance of the composite without conductive additives was even smaller than the charge transfer resistance of pristine SnO₂ mixed with carbon black. The TiO₂-coating method can therefore be an effective approach for the preparation of conductive additive-free high-power-density anode materials.