Ultrathin Li–Si–O Coating Layer to Stabilize the Surface Structure and Prolong the Cycling Life of Single-Crystal LiNi_0.6Co_0.2Mn_0.2O₂ Cathode Materials at 4.5 V

Abstract

Single-crystal LiNi1–x–y Co x Mn y O2 cathode materials can effectively suppress intergranular cracks that usually is seen in commercial polycrystal LiNi1–x–y Co x Mn y O2 cathode materials. However, the surface structure degradation for single-crystal LiNi1–x–y Co x Mn y O2 cathode materials is still aggravated at a higher cutoff voltage (over 4.5 V). In this work, we prepare single-crystal LiNi0.6Co0.2Mn0.2O2 cathode materials via a solid-state method and then coat an ultrathin Li–Si–O layer on their surface by a wet coating method. The results show that the single-crystal LiNi0.6Co0.2Mn0.2O2 cathode materials with a Li–Si–O coating layer deliver excellent cycling performance even at a higher cutoff voltage of 4.5 V. The optimized Li–Si–O-modified sample displays a capacity retention of 90.6% after 100 cycles, whereas only 68.0% for unmodified single-crystal LiNi0.6Co0.2Mn0.2O2. Further analysis of the cycled electrodes reveals that the surface structure degradation is the main reason for the decrease of electrochemical performance of single-crystal LiNi0.6Co0.2Mn0.2O2 at a high voltage (4.5 V). In contrast, with Li–Si–O coating, this phenomenon can be suppressed effectively to maintain interfacial stability and prolong the cycling life.

Nano-TiO2 coated single-crystal LiNi0.65Co0.15Mn0.2O2 for lithium-ion batteries with a stable structure and excellent cycling performance at a high cut-off voltage

“…2). The single crystal material synthesized in this work has a particle size range of 3-5 mm, which is much more uniform and larger than in the literature 17,18,20,[22][23][24][25][26][27][28][29][30] and implies a more authentic single crystal. Fig.…”

Reduction of Surface Residual Lithium Compounds for Single-Crystal LiNi0.6Mn0.2Co0.2O2 via Al2O3 Atomic Layer Deposition and Post-Annealing

“…Compared with the bare and the 2AL NCM622 cathode, the 2AL-A NCM622 cathode exhibits the best capacity retention (92.2%) and the highest final capacity (128.4 mAh/g). To the best of our knowledge, the NCM622 cathode modified by Al 2 O 3 ALD and post-annealing shows outstanding capacity retention compared with NCM622 cathodes modified by other methods reported in literature (Table S1) [17,[44][45][46][47][48][49][50]. It shows only 0.026% capacity loss per cycle, which is lower than most NCM622 cathodes modified by other methods.…”

Elucidating and Mitigating High-Voltage Interfacial Chemomechanical Degradation of Nickel-Rich Lithium-Ion Battery Cathodes via Conformal Graphene Coating

“…This behavior is consistent with trends for other reports utilizing comparatively larger single-crystal NMC particles. 32 Second, the high upper cutoff voltage exacerbated the severity of these interfacial chemical degradation mechanisms and promoted additional bulk chemomechanical degradation associated with layered oxides at high SOCs. 5,33 Nonetheless, the observed capacity fading reinforces the need for mitigation strategies that can enable improved high-voltage operation.…”

“…The extremely poor cycle life observed for the NMC-CBPVDF control electrode was attributed to two factors. First, the high primary particle surface area provided ample surfaces upon which electrolyte decomposition reactions or surface phase formation could occur. ,,, Compared to conventional electrodes fabricated using secondary particles of NMC, the NMC-CBPVDF electrode, which utilizes submicron particles with no surface protection, exhibits a precipitous decline in cycle life. This behavior is consistent with trends for other reports utilizing comparatively larger single-crystal NMC particles .…”

“…First, the high primary particle surface area provided ample surfaces upon which electrolyte decomposition reactions or surface phase formation could occur. ,,, Compared to conventional electrodes fabricated using secondary particles of NMC, the NMC-CBPVDF electrode, which utilizes submicron particles with no surface protection, exhibits a precipitous decline in cycle life. This behavior is consistent with trends for other reports utilizing comparatively larger single-crystal NMC particles . Second, the high upper cutoff voltage exacerbated the severity of these interfacial chemical degradation mechanisms and promoted additional bulk chemomechanical degradation associated with layered oxides at high SOCs. , Nonetheless, the observed capacity fading reinforces the need for mitigation strategies that can enable improved high-voltage operation.…”