Multielectron reaction electrode materials using partial oxygen redox can be potentially used as cathodes in lithium-ion batteries, as they offer numerous advantages, including high reversible capacity and energy density and low cost. Here, a reversible three-electron reaction is demonstrated utilizing topotactic phase transition between antifluorite and rocksalt in a cation-disordered antifluorite-type cubic Li 6 CoO 4 cathode. This cubic phase is synthesized by a simple mechanochemical treatment of conventionally prepared tetragonal Li 6 CoO 4 . It displays a reversible capacity of 487 mAh g −1 , a high value because of a reversible three-electron reaction using Co 2+ /Co 3+ , Co 3+ /Co 4+ , and O 2− /O 2 2− redox, occurring without O 2 gas evolution. The mechanochemical treatment is assumed to reduce its lattice distortion by cation-disordering and facilitate a reversible topotactic phase transition between antifluorite and rocksalt structures via a dynamic cation pushing mechanism.

We previously proposed a lithium-ion battery system based on redox reactions between Li 2 O 2 and Li 2 O by producing a Co-doped Li 2 O (CDL) cathode. CDL is synthesized by the mechanochemical method with Li 2 O and Co-dopant as the source materials in a planetary ball mill. Here, we aim to reveal the relation between the planetary ball milling conditions (the number and size of media balls, rotational speed, and processing time) and the characteristics of CDL. Moreover, we intend to optimize these conditions to improve the performance of CDL. While CDL decomposes into Li 2 O and LiCoO 2 when the impact energy from the collision of balls is too high, we successfully suppress the decomposition reaction of CDL to obtain CDL with higher Co-doping levels than that previously reported by optimizing synthetic conditions. The CDL prepared under optimal conditions delivers a specific capacity of 450 mAh g -1 and exhibits stable discharge behavior for at least 30 cycles.

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In the originally published article, the following values were presented incorrectly:1) The values of the Si impurity concentration ([Si]) and the electron concentration (n) are slightly erroneous for the heavily Si-doped GaAsN, which are described as 6 × 10 19 cm -3 and 9 × 10 18 cm -3 , respectively. The correct values of them are 2 × 10 19 cm -3 and 6 × 10 18 cm -3 , respectively. Figure 1 and 2 with the correct values are presented below.2) The value of n is applied for the evaluation of electron effective mass (m e * ) in the paper. The correct values of the decreased energy of the bandgap narrowing (ΔE BGN ) and the increased energy of the Burstein-Moss effect (E fn ) are 120 meV and 140 meV instead of 140 meV and 160 meV, respectively. Consequently, for the heavily Si-doped GaAsN, the correct value of m e * is 0.11m 0 instead of 0.098m 0 , where m 0 is the electron mass. Figure 2 with the correct value is presented below. Figure 1. PL spectra of heavily Si-doped GaAsN with [Si] of 2 × 10 19 cm −3 and [N] of 0.6% as a function of temperature. Black arrows indicate PL peak energy on each PL spectrum.