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

With an increasing demand for high-energy-density lithium-ion batteries (LIBs), nickel-rich cathodes such as LiNi0.9Mn0.05Co0.05O2 (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(CH3)(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 similar to 10% higher capacity retention, outperforming pristine NMC90 full cells.