High Energy and Power Density TiO2 Nanotube Electrodes By Conformal Electrodeposition of Polymer Electrolyte

Due to high surface area and improved charge transport, self-supported nanostructured materials based on transition metal oxides can be used as electrode for Li-ion batteries (LIBs). Their use is particularly interesting when considering the miniaturization of energy storage systems and the development of micropower sources [1]. For example, it has been reported that self-organized titania nanotubes (TiO2NTs) are potential candidates as negative 3D self-supported electrodes for Li-ion microbatteries [2]. In the prospect of developing all-solid-state batteries, it has been also demonstrated that electrodeposition technique (EDP) is a viable approach to achieve the deposition of polymer electrolytes on nanostructured electrode materials [3,4].

In this work, we study the conformal electrodeposition of PMMA-(PEO)₅ copolymer on TiO2NTs by electrochemical techniques. The physical and chemical analyses of the electrodeposited polymer carried out by SEM, TEM, XPS, TGA, and NMR will be discussed in order to understand the relationship existing between the EDP parameters and the properties of the polymers.

Then, the benefits of the conformal coating of polymer electrolyte on the electrochemical performance in terms of energy density and power density will be highlighted. Actually, due to better electrode/electrolyte interface, we show that the capacity of the half cell is improved by 45% at 1 C compared to bare TiO₂NTs (Fig. 1). Furthermore, we report that the polymer-coated TiO₂nts tested in the full cell deliver an average capacity of ∼30 μA h cm⁻² (120 mA h g⁻¹) with LiNi_0.5M_1.5O₄, ∼25 μA h cm⁻² (100 mA h g⁻¹) with LiFePO₄ and ∼23 μA h cm⁻² (90 mA h g⁻¹) with LiCoO₂, respectively during 50 cycles (Fig. 2).

References

1. B. L. Ellis, P. Knauth, and T. Djenizian, Adv. Mater, 26, 3368, (2014).

2. T. Djenizian, I. Hanzu, P. Knauth, J. Mater. Chem.,  21, 9925, (2011).

3. N. A. Kyeremateng, F. Dumur, P. Knauth, B. Pecquenard, and T. Djenizian, Electrochem. Commun., 13, 894 (2011).

4. N. Plylahan, N.A. Kyeremateng, M. Eyraud, F. Dumur, H. Martinez, L. Santinacci, P. Knauth, T. Djenizian, Nanoscale Res. Lett., 7, 349,  (2012).