Does Pseudocapactive Charge Storage Take Place in Nanoparticulate TiO2 and Li4Ti5O12 Anodes?

Titanium oxide-based materials, such as TiO₂ and Li₄Ti₅O₁₂ (LTO), are considered as interesting alternative anode materials for lithium ion batteries. In order to increase the interfacial area between TiO₂ particles and the battery electrolyte and in order to reduce the diffusion length for Li⁺ ions within the particles, both materials have been extensively studied. [1], [2] Thereby, indication has been found that the charge storage is not entirely due diffusion-controlled Faradaic charge storage, but also due to pseudocapacitive charge storage. [3], [4]

We studied nanoparticlate LTO electrodes and compared this to Li storage in Nb-doped TiO₂ particles. Using scan rate-dependent cyclic voltammetry, we determined the amount of Faradaic and of pseudocapactive charge with the same method that was reported in the literature [1], [4]. Thereby, we discovered that the application of this method leads to unphysical results, which is originated in the iso-potential plots of the scan-rate dependent current density. We show that even for simple prototype Faradaic reactions, such iso-potential plots yield an apparent pseudocapacitance.

References

[1]   J. Wang, J. Polleux, J. Lim, B. Dunn, J. Phys. Chem. C 111 (2007) 14925–14931.

[2]   D. Wang, X. Wu, Y. Zhang, J. Wang, P. Yan, C. Zhang, D. He, Ceramics International 40 (2014) 3799–3804.

[3]   T. Brezesinski, J. Wang, J. Polleux, B. Dunn, S.H. Tolbert, Journal of the American Chemical Society 131 (2009) 1802–1809.

[4]   P. Yu, C. Li, X. Guo, J. Phys. Chem. C 118 (2014) 10616–10624.