High capacity MgH 2 composite electrodes for all- solid-state Li-ion battery operating at ambient temperature Fernando Cano-Banda a,b , Ana Gallardo-Gutierrez a,b , Luis Luviano-Ortiz b , Abel Hernandez-Guerrero b , Ankur Jain c,* , Takayuki Ichikawa a,c,** a Graduate School of Engineering, Hiroshima University, Higashi-Hiroshima, 739-8527, Japan b Mechanical Engineering Department, University of Guanajuato, Salamanca, 36885, Mexico c Natural Science Center for Basic Research and Development, Hiroshima University, Higashi-Hiroshima, 739-8530, Japan highlights  Room temperature all-solid-state Li-ion batteries.  ASS-LIB using MgH 2 as conversion reaction electrode material.  LiBH 4 , 3LiBH 4 LiI and 80Li 2 S-20P 2 S 5 electrolytes operating at room temperature. article info Article history: Received 30 June 2020 Received in revised form 15 September 2020 Accepted 24 September 2020 Available online 22 October 2020 Keywords: Lithium-ion battery Metal hydride Magnesium hydride Negative electrode Conversion reaction electrode All-solid-state battery abstract MgH 2 with a theoretical capacity of 2036 mAh/g has been studied using LiBH 4 as solid electrolyte with remarkable results. However, LiBH 4 conductivity is reduced drastically from ~10 3 to ~10 8 Scm 1 when operating at temperatures below ~117  C, due to the crystal structural transition. This change in the conductivity limits the range of operating temperatures of the battery. In order to have all-solid-state lithium ion batteries operating at room temperature, some alternatives were explored in this work. In this study, different batteries compositions were tested for operating temperatures from 30  C to 120  C, using LiBH 4 , 3LiBH 4 $LiI and 80Li 2 Se20P 2 S 5 to find a workable configuration for all-solid-state lithium-ion battery with MgH 2 as the active material for the working electrode. The cell MgH 2 /3LiBH 4 $LiI/Acetylene Black carbon | 80Li 2 Se20P 2 S 5 | Li, shown the best performance with an initial capacity of 1570 mAh/g operating at 30  C. © 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. * Corresponding author. ** Corresponding author. Graduate School of Engineering, Hiroshima University, Higashi-Hiroshima, 739-8527, Japan. E-mail addresses: ankur.j.ankur@gmail.com (A. Jain), tichi@hiroshima-u.ac.jp (T. Ichikawa). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 46 (2021) 1030 e1037 https://doi.org/10.1016/j.ijhydene.2020.09.202 0360-3199/© 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.