Nano-TiO₂ coated single-crystal LiNi_0.65Co_0.15Mn_0.2O₂ for lithium-ion batteries with a stable structure and excellent cycling performance at a high cut-off voltage

Abstract

Ni-rich ternary layered oxide materials have become the preferred cathode materials for lithium-ion batteries due to their high specific discharge capacity and low price. However, the hierarchical structure of the...

General flux-free synthesis of single crystal Ni-rich layered cathodes by employing a Li-containing spinel transition phase for lithium-ion batteries

“…The low content of Li + sites occupied by Ni 2+ within Li layers will facilitate Li + ion migration during redox reactions. 7,8 The specific surface area of this SC-NCM622 is only 0.56 m 2 g −1 by Brunner–Emmett–Teller (BET) measurement, lower than that of PC-NCM622 (1.92 m 2 g −1 ), as shown in Fig. S9 †.…”

“…1(c) and S3, † suggesting the signicantly damaged layered feature and the aggravated Li + /Ni 2+ cation mixing. 8,[38][39][40] And the NiO rock-salt phase (space group of Fm 3m) segregation was observed when the Ni-rich oxide Li[Ni 0.8 Co 0.1 Mn 0.1 ]O 2 was calcined at 1000 C for 4 h (Fig. S3 †).…”

“…S3 †). 8,32 Therefore, it is not possible to prepare single crystal Ni-rich oxide cathodes by merely increasing the calcination temperature.…”

“…Ni-rich electrodes easily release the active oxygen from the host lattice, which would induce thermal runaway by reacting with the electrolyte, and nally give rise to safety hazards. [5][6][7][8] Differential scanning calorimetry (DSC) analysis is employed to evaluate thermal stability of the delithiated SC-NCM622 and PC-NCM622 electrodes, as shown in Fig. 4(f).…”

“…[1][2][3] Layered lithium transition-metal oxides, especially Ni-rich Li [Ni x Co y Mn 1ÀxÀy ]O 2 (x $ 0.6) with large reversible capacities, high operating voltage, and good high-rate capability, are considered as an ideal class of cathodes for advanced LIBs. [4][5][6][7][8][9] To reduce their side reactions along with dissolution of transition metal (TM) ions, polycrystalline particles assembled by primary grains with a low specic surface area are commonly employed. However, the H2-H3 phase transition at the deep state of charge (SOC) results in large anisotropic changes of lattice volume and further causes strong micro-stress and strain inside polycrystallites, generating microcracks along the grain boundaries.…”