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Improvement of the Electrochemical Performance of LiNi₀.₈Co₀.₁Mn₀.₁O₂ via Atomic Layer Deposition of Lithium-Rich Zirconium Phosphate Coatings

Sri Harsha Akella, Sarah Taragin, Yang Wang, Hagit Aviv, Alexander C. Kozen, Melina Zysler, Longlong Wang, Daniel Sharon, Sang Bok Lee, Malachi Noked
ACS applied materials & interfaces 2021 v.13 no.51 pp. 61733-61741
batteries, cathodes, electric vehicles, electrochemistry, energy density, interphase, lithium, mass spectrometry, phosphates, zirconium
Owing to its high energy density, LiNi₀.₈Co₀.₁Mn₀.₁O₂ (NMC811) is a cathode material of prime interest for electric vehicle battery manufacturers. However, NMC811 suffers from several irreversible parasitic reactions that lead to severe capacity fading and impedance buildup during prolonged cycling. Thin surface protection films coated on the cathode material mitigate degradative chemomechanical reactions at the electrode–electrolyte interphase, which helps to increase cycling stability. However, these coatings may impede the diffusion of lithium ions, and therefore, limit the performance of the cathode material at a high C-rate. Herein, we report on the synthesis of zirconium phosphate (ZrₓPOy) and lithium-containing zirconium phosphate (LiₓZryPOz) coatings as artificial cathode–electrolyte interphases (ACEIs) on NMC811 using the atomic layer deposition technique. Upon prolonged cycling, the ZrₓPOy- and LiₓZryPOz-coated NMC811 samples show 36.4 and 49.4% enhanced capacity retention, respectively, compared with the uncoated NMC811. Moreover, the addition of Li ions to the LiₓZryPOz coating enhances the rate performance and initial discharge capacity in comparison to the ZrₓPOy-coated and uncoated samples. Using online electrochemical mass spectroscopy, we show that the coated ACEIs largely suppress the degradative parasitic side reactions observed with the uncoated NMC811 sample. Our study demonstrates that providing extra lithium to the ACEI layer improves the cycling stability of the NMC811 cathode material without sacrificing its rate capability performance.