Improving the Performance of All-Solid-State Microbatteries By Conformal Electrodeposition of Polymer Electrolyte into Self-Organized TiO2 Nanotubes

To date, microbatteries are in demand as small power sources to satisfy the market requirements with fast development of microelectronic devices. As more energy is required, a shift to all-solid-state 3D architectures has been proposed as a promising approach to tackle the challenge and achieve both high energy and power densities [1]. Hence, various types of microbatteries have been developed and are under investigation. It has been reported that self-organized TiO2 nanotubes (TiO2nts) can be utilized as anode material for Li-ion microbatteries [2]. The improved electrochemical performance of TiO2nts electrode has been mainly attributed to the larger surface area offered by 3D nanoarchitectured electrodes which is responsible for high reversible capacity, excellent rate capability and long cycle life [3]. To fabricate an all-solid-state Li-ion microbatteries, conventional liquid electrolytes need to be replaced by the solid electrolytes such as polymer electrolyte. We have reported that the electrodeposition of the polymer electrolyte into TiO2nts electrodes through cyclic voltammetry technique leads to the filling of the nanotubes by the thin polymer film [3]. In this work, we report the influence of the conformal electrodeposition on the full microbattery utilizing TiO2nts as anode, LiFePO4 as cathode and a drop-casted layer of methyl ether methacrylate-polyethylene glycol (MA-PEG) acting as electrolyte and separator. Clearly, the polymer-coated TiO2nts vs. LiFePO4 microbattery reaches higher capacity of ~98 mA h g-1 (~48 μAh cm-2 μm-1) compared to the bare TiO2nts vs. LiFePO4 microbattery (~12.5 mA h g-1 , ~6 μAh cm-2 μm-1) over 100 charge-discharge cycles. Galvanostatic charge-discharge profiles revealed the positive influence of electrochemical deposition of the polymer electrolyte into self-organized TiO2nts, as shown in Figure 1(a) and (b). In this communication, we will discuss the fabrication and characterization of all-solid-state microbatteries, as well as the influence of polymer-coated TiO2nts on their electrochemical performance. References[1] S. Ferrari, M. Loveridge, S.D. Beattie, M.Jahn, R.J. Dashwood, R. Bhagat, Latest advances in the manufacturing of 3D rechargeable lithium microbatteries, J. Power Sources. 2015, 28, 25-46. [2] G.F. Ortiz, I. Hanzu, T. Djenizian, P. Lavela, J.L. Tirado and P. Knauth. Alternative Li-Ion Battery Electrode Based on Self-Organized Titania Nanotubes, Chem. Mater. 2009, 21 (1), pp 63–67. [3] N. Plylahan, M. Letiche, M.K. Samy Barr, B. Ellis, S. Maria, T.N.T. Phan, E. Bloch, P. Knauth, T. Djenizian, High energy and power density TiO2 nanotube electrodes for single and complete lithium-ion batteries, J. Power Sources. 2015, 273, 1182–1188 [4] N. Plylahan, M. Letiche, M. K. S. Barr, T. Djenizian, All-solid-state lithium-ion batteries based on self-supported titania nanotubes, Electrochem. Commun. 2014, 4, 1388-2481. Figure 1