Improved Electrochemical Properties of Nickel-Rich, Low-Cobalt Layered Oxide Cathodes Using Dual-Functional Di-tert-butylmethyl Adamantoyl Silane Additives

Abstract

With an increasing demand for high-energy-density lithium-ion batteries (LIBs), nickel-rich cathodes such as LiNi 0.9 Mn 0.05 Co 0.05 O 2 (NMC90) have gained significant interest due to their relatively low cobalt and high specific energy. However, cycling stability is compromised due to parasitic reactions at the electrode−electrolyte interfaces of NMC90. Herein, we demonstrate improved electrochemical properties of NMC90 using di-tert-butylmethyl adamantoyl silane (RSiCOAd: R is tBu(CH 3 ) 2 and Ad is 1-Ad) as an additive in a commercial electrolyte. Upon detailed electrochemical and spectroscopic analysis, we demonstrate that the RSiCOAd additive undergoes in situ decomposition to form a fluorinated organosiloxane passivation layer on the NMC90 surface and enhanced fluorination on the lithium anode surface. This phenomenon could significantly mitigate the parasitic reactions at the cathode−electrolyte interface while improving the electrochemical performances. Furthermore, the practical viability of the RSiCOAd additive is evaluated by full-cell studies with the graphite anode. After prolonged 200 cycles, full cells containing RSiCOAd with the incorporation of just 1% additive demonstrate an impressive ∼10% higher capacity retention, outperforming pristine NMC90 full cells.

Improving the Performance of LiNi0.9Co0.05Mn0.05O2 via Atomic Layer Deposition of ZnxOy Coating

“…The oxidation peaks at ~3.6V, ~3.91V, ~4.09V, and ~4.19V in Figure S4 are attributed to the following phases conversions: hexagonal (H1) to monoclinic (M) phase (H1 $ M), hexagonal to monoclinic (H1 $ M), monoclinic to hexagonal (M $ H2), second hexagonal to third hexagonal (H2 $ H3), respectively. [19,54,55] We can clearly see that the relatively higher intensities in the pristine NMC90 profiles as compared to the Zn x O y @NMC90 samples are due to uncontrolled parasitic reactions at the cathode-electrolyte interfaces. After the formation cycling, the full cells are subjected to cycling at a 0.5 C rate during charge, and 2 C rate during discharge, to evaluate the practical viability of the proposed cathode treatment.…”