Interface design for positive active material LiNi0.6Mn0.2Co0.2O2 via Al2O3-coatings using magnetron sputtering for improved electrochemical performance and safety properties.

Layered transition metal oxides received a lot of attention as positive active material for lithium ion batteries (LIBs) because of high specific capacity, low cost and relatively high operating potential. However, LiNixMnyCozO2-type materials (NMC, x+y+z=1) still face a lot of challenges: 1) Moisture uptake and formation of impurities at the particle surface“;“ 2) Cation mixing leading to phase transformation and particle cracking“;“ 3) Transition metal (TM) dissolution during charge/discharge cycling and/or at elevated temperatures [1]. Surface coatings are reported to have a promising effect on overcoming these issues. Coatings can act as physical barrier to prevent direct electrode/electrolyte contact, mitigating parasitic side reactions and enhancing electrochemical performance. Lithium reactive coatings diminish residual lithium species from the surface and reduce decomposition products. Ionically conductive and active coatings improve ionic conductivity and reduce charge transfer resistance [1][2].&nbsp“;“

In this study Al2O3 coatings with different thicknesses were deposited on NMC-622 particles using a magnetron sputtering device to enhance the electrochemical and safety performance. Uniformity and homogeneity of coatings were analyzed using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). Electrochemical performance analysis showed a significant increase in cycling stability and capacity retention for coated samples. Post-mortem analysis after 200 cycles was performed using TEM, electron energy-loss spectroscopy (EELS) and Thermo gravimetric analysis (TGA) to understand the role of coatings in performance enhancement.

References

[1] Becker, Dina, et al. ACS applied materials & interfaces 11.20 (2019).

[2] Nisar, Umair, et al. Energy Storage Materials 38 (2021).