Modifying the Surface of a High-Voltage Lithium-Ion Cathode

Abstract

Ni-rich lithium nickel manganese cobalt oxides (LiNi x Mn y Co1–x–y O2, NMCs) suffer from poor cycling stability at potentials above 4.2 V vs Li/Li+. This degraded cyclability at high potentials has been largely ascribed to the parasitic reactions between the delithiated cathode and the nonaqueous electrolyte. In this study, we mitigated the performance degradation of high-voltage NMC 622 by designing a functional interfacial layer that consists of a surface doping by Ti4+ and a TiO2 coating at the same time. The doping of Ti4+ near the surface of NMC can suppress the irreversible phase transformation, while the TiO2 coating can kinetically reduce the rate of the electron-transfer reaction between the delithiated cathode and the solvent. It is revealed that this interfacial engineering approach significantly enhanced both the cycling stability and the rate performance of NMC 622.

Enhanced Electrochemical and Structural Stability of Ni‐rich Cathode Material by Lithium Metaborate Coating for Lithium‐Ion Batteries

“…Also, as shown in Table 1, the lithium‐ion diffusion coefficient of NCMA88@0.2B is significantly greater than that of NCMA88. Similar result is previously reported, and the D Li ‐voltage relationship is related to the phase transition [34] . The D Li evolutions of NCMA88 and NCMA88@0.2B could result from the side‐reactions occurred on the surface of the cathode materials.…”

“…Similar result is previously reported, and the D Li -voltage relationship is related to the phase transition. [34] The D Li evolutions of NCMA88 and NCMA88@0.2B could result from side-reactions occurred on the surface of the cathode materials. As the lithium metaborate coating layer could effectively reduce the direct contact between the cathode and the electrolyte, the NCMA88@0.2B shows improved D Li and CEI stability.…”

On the Sensitivity of the Ni-rich Layered Cathode Materials for Li-ion Batteries to the Different Calcination Conditions

“…All of these may cause a deterioration of the electrochemical performance of cathode powders. Nevertheless, the significant benefits in terms of battery capacity that are achievable using these types of high-nickel material are the main reason for the continuous attempts to synthesize them and to improve their properties, e.g., by doping or surface coating [ 17 , 31 , 32 , 33 , 34 , 35 , 36 ]. There are many known methods for obtaining cathode materials, e.g., solid state reaction [ 37 ], co-precipitation [ 38 ], wet-impregnation [ 39 , 40 ], combustion [ 41 ], and spray-drying [ 42 ].…”

A limitation map of performance for porous electrodes in lithium-ion batteries

“…For instance, a significant share of short-range polarization which was revealed for the electrodes considered in this study (Figures 2C, 2F, and 2I) highlights the relatively low intrinsic conductivity of the NMC particles which could be improved by a strategy such as particle coating with a conductive layer (Yu et al, 2019;Kalluri et al, 2017;Wang et al, 2015). We showcased such an approach by covering the NMC particles with a thin TiO 2 layer, known as a good conductor (Chen et al, 2014;Gao et al, 2018b;Wu et al, 2009), with the aid of atomic-layer deposition (see supplemental information) (Chen et al, 2010;Meng et al, 2012). The ALD-coated particles were used to make 16 new electrodes of similar formulation to the original batch and analyzed for the electrochemical performance.…”