Electrochemical Characteristics of Co-Substituted α- and β-Li₅AlO₄ as High-Specific Capacity Positive Electrode Materials

Abstract

Electric vehicles and hybrid electric vehicles require batteries with higher energy densities than conventional batteries. Anion redox-type active materials have been proposed as new high-capacity positive electrode materials for Li-ion batteries with high-energy densities. Co-substituted Li 5 AlO 4 is a novel and promising high-capacity positive electrode material for Li-ion batteries. In this study, we investigated the influence of different synthesis conditions on the enhancement of the specific capacity. The material prepared via mechanical alloying of β-Li 5 AlO 4 with LiCoO 2 at 300 rpm for 24 h exhibited a higher specific capacity than that prepared from α-Li 5 AlO 4 and LiCoO 2 . Co-substituted β-Li 5 AlO 4 demonstrated a specific capacity of approximately 250 mA h g –1 . The specific capacity of Co-substituted α and β-Li 5 AlO 4 increased with increasing Co content in the samples. According to X-ray absorption near edge structure measurements, the irreversible oxygen redox reaction and a reversible reaction involving the formation and consumption of peroxide were responsible for the charge compensation of Co-substituted β-Li 5 AlO 4 and α-Li 5 AlO 4 , respectively.

Cation-Disorder-Assisted Reversible Topotactic Phase Transition between Antifluorite and Rocksalt Toward High-Capacity Lithium-Ion Batteries

“…Antifluorite structure-based oxides such as Li 5 FeO 4 and Li 6 CoO 4 also have much potential as high-capacity cathode materials because of their rich lithium content. Their cathode performances were first reported in 1999, and subsequently, the electrochemical performances of these types of species and the analyses of the relevant redox reactions have been widely reported. − In Li 5 FeO 4 , the transformation to disordered rocksalt Li 3 FeO 3.5 proceeds, whereas in Li 6 CoO 4 , the transformations to Li 4 CoO 4 , or CoO 2 are feasible, by the extraction of two Li ions. However, in each case, reversibility is poor, resulting in discharge capacity contributed by a one-electron reaction, which is due to only TM redox.…”

Universal solid-state oxygen redox in antifluorite lithium oxidesviatransition metal doping

“…Enhancing the energy densities of the cathodes in LIBs by utilizing the redox reactions of oxide ions in cathode materials has recently attracted extensive attention. [1][2][3][4][5] For instance, Li-rich layered rocksalts (Li 2 MnO 3 , [6][7][8][9][10][11][12] Li 2 RuO 3 , [13][14][15] Li 2 IrO 3 , [16][17][18] and their solid solutions with LiTMO 2 (TM: transition metal) [19][20][21][22][23] ), disordered rocksalts (Li 3 NbO 4 -LiTMO 2 , 24 Li 2 TiO 3 -LiTMO 2 , 25 and Li 4 Mn 2 O 5 26,27 ), and antifluorites (Li 5 FeO 4 , [28][29][30][31][32][33][34][35][36][37] Li 6 CoO 4 , 28,38 and Li 5 AlO 4 39,40 ) facilitate an increase in capacity by using partial oxygen redox along with transition metal redox. Among them, antifluorite Li 2 O exhibits the highest possible theoretical capacity of 897 mA h g À1 , which is based on the solid-state oxygen redox reaction given by…”