Al-doping enables high stability of single-crystalline LiNi_0.7Co_0.1Mn_0.2O₂ lithium-ion cathodes at high voltage

Abstract

In this work, the single-crystalline LiNi0.7Co0.1Mn0.2O2 materials with stable and ordered crystal structure have been synthesized by Al-doping, which display the advanced Li+-ion storage property.

Effects of a Solid Solution Outer Layer of TiO2 on the Surface and Electrochemical Properties of LiNi0.6Co0.2Mn0.2O2 Cathodes for Lithium-Ion Batteries through the Use of Thin-Film Electrodes

“…Two selected areas with different depths were studied by the fast Fourier transform (FFT) method to reveal the differences in the surface structure. From the boxed area labeled I in Figure c, the diffraction spot with a layer distance of 0.289 nm was indexed to the 022s spinel-like phase as the main component, , although 003 and 101 planes corresponding to the layered rhombohedral structure were also observed. − These findings suggest that a large amount of spinel-like phase induced from the oxygen vacancy exists as a derivative phase in the NCM622-bare thin-film electrode, and is especially concentrated at the surface region, which was identical to the results in Figure .…”

Single‐Crystalline Cathodes for Advanced Li‐Ion Batteries: Progress and Challenges

“…In contrast, a batch co‐precipitation method is required to synthesize small‐sized single‐crystalline precursors to shorten the residence time and alleviate agglomeration, which increases cost and waste water production. [ 76a,78 ] But it is difficult to synthesize the small precursors with particle size distribution as narrow as those via a continuous co‐precipitation method. In addition, the small‐sized precursors also can be obtained by ball grinding large size precursors.…”

“…Doping is an important method to improve the performance of cathode materials, [ 78,129 ] which has four positive effects: 1) Substitution of unstable elements, such as, Li and Ni; [ 40a,130 ] 2) preventing cation mixing between Ni 2+ and Li + considering the ionic radius and the ionic valence state; [ 108,131 ] 3) inhibiting the structural collapse and the release of lattice oxygen by increasing the bonding energy between oxygen and TM ions; [ 78 ] and 4) improving Li + and electronic transport by introducing larger radius ions to increase the interlayer distance. [ 2,85 ] Both transition and non‐transition metal ions have been widely applied as doping elements.…”

“…[ 2 ] Non‐transition element aluminum has been widely used to dope cathode metals, which can not only improve the thermal stability but also effectively stabilize structure and interface to improve the cycling performance. [ 40a,78,130 ] Chen et al [ 78 ] reported that the Al‐doped single‐crystalline NCM712 could alleviate the structural collapse of the cathode during the charging process and exhibited a capacity of 80.26% after 90 cycles at 1 C with a high cut‐off voltage (4.4 V). Al 3+ has also been reported to displace active nickel more readily than cobalt and manganese and stabilize the interface by reducing the number of nickel ions on the surface, which helps to inhibit the formation of oxygen and rock‐salt phase.…”

Effects of Co/Mn Content Variation on Structural and Electrochemical Properties of Single-Crystal Ni-Rich Layered Oxide Materials for Lithium Ion Batteries

“…However, P-NCMs have a detrimental inherent defect, i.e., the structures of the agglomerated secondary particles will rupture during the charging and discharging process, , and the primary particles will separate from each other at the grain boundaries and trigger side reactions at the electrode–electrolyte interface. − To tackle this problem, many research groups have attempted single-crystal strategies . Similar to the family of agglomerated counterparts, the corresponding single-crystal NCMs (S-NCMs) with different Ni, Co, and Mn contents, such as LiNi 0.6 Co 0.2 Mn 0.2 O 2 , − LiNi 0.65 Co 0.15 Mn 0.2 O 2 , LiNi 0.7 Co 0.1 Mn 0.2 O 2 , , LiNi 0.8 Co 0.1 Mn 0.1 O 2 , − LiNi 0.9 Co 0.05 Mn 0.05 O 2 , , and other single crystals with higher Ni contents, have also been synthesized, and some have even surpassed the performances of polycrystalline materials, as expected. − These newly developed S-NCMs, which are modified by similar measures to their agglomerated counterparts, exhibit further improved cycling performances, thus taking the development of NCMs a step further. It is not difficult to conclude that the modification measures for P-NCMs are often applicable to S-NCMs.…”