Effects of Cell Geometry on Rate Performance of Secondary Batteries

3D geometries for microbattery applications have been explored to increase capacity per footprint area, relevant for small footprint area micro devices [1] [2]. Simulations of interdigitated Li-ion batteries suggest 4 orders of magnitude increase in areal capacity at 330 C-rate from 0.58 Ah/m 2 in the conventional geometry to 318 Ah/m 2 for the 3D geometry [3]. Realization of practical 3D battery designs can potentially decouple their power and energy [4], properties that are historically coupled in conventional battery design, which might have significant implications for high power devices. Using commonly found commercially available materials and tools, we designed and conducted a simple experiment to elucidate how battery performance can be improved by varying the relative arrangements of the active and inactive components. Examples include using Li/LiCoO 2 2032-type coin cells with 1M LiPF 6 and carbonate containing electrolytes. The maximum active ion diffusion length required to fully delithiate the LiCoO 2 electrodes during cycling was increased by 400-6500 μm compared with standard reference cells, and the effect on rate performance was measured between C/24 and C/3. Results suggest that extending the maximum active ion diffusion path length by >1600 μm still allows for attaining specific capacity that matches that of the reference cell at C/24. We discuss possible new geometries and optimized designs in the framework of battery performance. [1] C. Liu, E.I. Gillette, X. Chen, A.J. Pearse, A.C. Kozen, M.A. Schroeder, K.E. Gregorczyk, S.B. Lee, G.W. Rubloff. Nature Nanotechnology 9 (2014) 1031-1039. [2] T.S. Arthur, D.J. Bates, N. Cirigliano, D.C. Johnson, P. Malati, J.M. Mosby, E. Perre, M.T. Rawls, A.L. Prieto, B.Dunn. MRS Bulletin 36 (2011) 523-531. [3] D. Miranda, C.M. Costa, A.M. Almeida, S. Lanceros-Méndez. Applied Energy 165 (2016) 318-328. [4] N. Cirigliano, G. Sun, D. Membreno, P. Malati, C.J. Kim, B. Dunn. Energy Technology 2 (2014) 362-369.