Why is the O3 to O1 phase transition hindered in LiNiO₂ on full delithiation?

Abstract

Ni-enriched layered materials are utilized as positive electrode materials of high-energy Li-ion batteries. Because electrode reversibility is gradually lost for stoichiometric LiNiO2 on continuous cycles, Ni ions are partly substituted...

High Nickel and No Cobalt─The Pursuit of Next-Generation Layered Oxide Cathodes

“…In fact, perfect layered LNO is hard to achieve, and it is always accompanied by twin intricate disorders in the synthesis process, namely, off stoichiometry and Li/Ni exchange. − The real formula of lithium nickelate should be denoted as Li 1– z Ni 1+z O 2 ( z > 0). The off stoichiometry and Li/Ni exchange are generally considered to be caused by the following various reasons: (a) the loss of lithium from the host structure during high-temperature calcinations due to the high vapor pressure of lithium; (b) the inevitable presence of Ni 2+ ions in the material resulting from the reduction of the Ni 3+ ions at high temperatures; (c) excess Ni 2+ ions trend to reside in the lithium slab because of the slight size difference between the Li + (0.76 Å) and Ni 2+ (0.69 Å) ions .…”

Oxygen-redox activity in non-Li-excess W-doped LiNiO2 cathode

“…[23,27,52,53] The nature, extent and mechanism of this transformation are currently not well understood due to the differences in the pristine material properties, extent of delithiation, and charging protocols. [51] For example, the O3 to O1 transformation has been reported to be suppressed/hindered in LiNiO2 until full delithiation based on operando XRD [54] and first-principles calculations [55]. However, there is ample evidence for the presence of O1-type stacking in highly delithiated LixNiO2.…”

“…This has been previously linked to the migration of Ni from the TM layer to the tetrahedral sites in the Li layer which suppresses the O3 to O1 transformation. [54] However, this is unlikely as significant broadening of the 10l reflections (due to stacking faults) suggest that O1 stacking is present in the structure, which can also lead to the same effect. [23] It is also unlikely that Ni 4+ is stabilised in a tetrahedral site.…”

Highly Graphitic Carbon Coating on Li1.25Nb0.25V0.5O2 Derived from a Precursor with a Perylene Core for High-Power Battery Applications

“…Facing the increasing threat of global climate change, the market of electric vehicles equipped with rechargeable Li-ion batteries (LIBs) as power sources is rapidly increasing to reduce the dependence on fossil fuels. Electrochemical properties of LIBs are restricted by positive electrode materials, and thus advanced positive electrode materials with higher energy and power density are desired. − Increasing attention has been focused on Li-excess cation-disordered rocksalt (DRS) oxides over the last couple of years due to their higher capacity and wider variety of chemistry than present cobalt-/nickel-based oxides with a layered structure, , leading to a beneficial advantage on the further development of LIBs. Unlike the ordered layered oxides which have a two-dimensional network for Li migration paths enabling high power applications, DRS oxides have been considered electrochemically inactive for a long time because there is a less obvious migration path for Li ions associated with the statistical distribution of cationic species.…”