Lithium-ion batteries are in focus of research around the world, due to their high volumetric and gravimetric energy density. For inorganic all-solid-state batteries since many years considerable effort has been devoted to the development of thin film batteries for their application in microelectronics [1, 2]. Recent research activities are directed to develop high capacity all solid state batteries for automobile applications (Toyota) [3, 4]. These kinds of applications of all-solid-state lithium-ion batteries require high cycling performance, high thermal stability, high capacity and high rate capacity.

The main objective of the current work is to build up an all-solid-state battery system which meets the previously listed. Electroactive phosphate materials with different microstructures were synthesized. Based on several combinations of materials, three phosphate compounds were synthesized and used as electrolyte and electrode materials, respectively. The carbon coated cathode (Li₃V₂(PO₄)₃/C) and anode (LiTi₂(PO₄)₃/C) materials were first investigated in half-cells that use metallic lithium foil as counter electrode and reference electrode, 1 M LiPF₆ in a 1:1 solvent mixture of ethylene carbonate (EC)/dimethyl carbonate (DMC) (LP30) was used as electrolyte. Afterwards, the selected electrode materials were used to make full cells by using LP30 liquid electrolyte. The working voltage, capacity as well as high-rate performance of the full cells were characterized. The optimum ratio of Li₃V₂(PO₄)₃/C and LiTi₂(PO₄)₃/C in the full cell was investigated based on the electrochemical performances. Finally, an all-phosphate solid-state lithium-ion battery was made by using the electrode materials and Li_1.3Al_0.3Ti_1.7(PO₄)₃ solid state electrolyte. The electrochemical behavior of the all-phosphate solid-state lithium-ion battery was investigated and compared with a full cell using liquid LP30 electrolyte. The working voltage of the Li₃V₂(PO₄)₃/C-LiTi₂(PO₄)₃/C battery is in the range of 0.2-2.2V, which well matched with the electrochemical window of the solid electrolyte Li_1.3Al_0.3Ti_1.7(PO₄)₃. Applying materials with high Li-ion conductivities such as Li₃V₂(PO₄)₃ and LiTi₂(PO₄)₃provides the advantage of high rate capability for all solid state batteries.

Reference

   [1]  M. Koo, K. Park, S. H. Lee, M. S. Duh, D. Y. Jeon, J. W. Choi, K. Kang and K. J. Lee, Nano Lett., 2012, 12, 4810–4816.

   [2]  Y. J. Nam, S. J. Cho, D. Y. Oh, J. M. Lim, S. Y. Kim, J. H. Song, Y. G. Lee, S. Y. Lee and Y. S. Jung, Nano Lett., 2015, 15, 3317–3323.

   [3]  M. S. Beal, B. E. Hayden, T. L. Gall, C. E. Lee, X. Lu, M. Mirsaneh, C. Mormiche, D. Pasero, D. C. A. Smith, A. Weld, C. Yada and S. Yokoishi, ACS Comb. Sci., 2011, 13, 375–381.

   [4]  C. Yada, C. E. Lee, D. Laughman, L. Hannah, H. Iba and B. E. Hayden, J. Electrochem. Soc., 2015, 162, A722–A726.