Ultraporous, Ultrasmall MgMn2O4 Spinel Cathode for a Room-Temperature Magnesium Rechargeable Battery

Hiroaki Kobayashi; Yu Fukumi; Hiroto Watanabe; Reona Iimura; Naomi Nishimura; Toshihiko Mandai; Yoichi Tominaga; Masanobu Nakayama; Tetsu Ichitsubo; Itaru Honma; Hiroaki Imai

doi:10.1021/acsnano.2c12392

Ultraporous, Ultrasmall MgMn₂O₄ Spinel Cathode for a Room-Temperature Magnesium Rechargeable Battery

ACS Nano. 2023 Feb 14;17(3):3135-3142. doi: 10.1021/acsnano.2c12392. Epub 2023 Jan 20.

Authors

Affiliations

¹ Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan.
² Department of Applied Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522, Japan.
³ Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-Cho, Koganei, Tokyo 184-8588, Japan.
⁴ Center for Green Research on Energy and Environmental Materials, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.
⁵ Department of Advanced Ceramics, Nagoya Institute of Technology, Gokiso, Showa-ku, Nagoya, Aichi 466-8555, Japan.
⁶ Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan.

Abstract

Magnesium rechargeable batteries (MRBs) promise to be the next post lithium-ion batteries that can help meet the increasing demand for high-energy, cost-effective, high-safety energy storage devices. Early prototype MRBs that use molybdenum-sulfide cathodes have low terminal voltages, requiring the development of oxide-based cathodes capable of overcoming the sulfide's low Mg²⁺ conductivity. Here, we fabricate an ultraporous (>500 m² g^-1) and ultrasmall (<2.5 nm) cubic spinel MgMn₂O₄ (MMO) by a freeze-dry assisted room-temperature alcohol reduction process. While the as-fabricated MMO exhibits a discharge capacity of 160 mAh g^-1, the removal of its surface hydroxy groups by heat-treatment activates it without structural change, improving its discharge capacity to 270 mAh g^-1─the theoretical capacity at room temperature. These results are made possible by the ultraporous, ultrasmall particles that stabilize the metastable cubic spinel phase, promoting both the Mg²⁺ insertion/deintercalation in the MMO and the reversible transformation between the cubic spinel and cubic rock-salt phases.

Keywords: cathode materials; cubic metastable spinel; freeze-drying; magnesium battery; porous nanoparticles.