Which Layered Cathode Suits More for Nanosilica Protection, Ni-Rich LiNi_0.8Co_0.1Mn_0.1O₂ or Li-Rich Li_1.2Mn_0.54Co_0.13Ni_0.13O₂?

Abstract

Both Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) and Li-rich Li1.2Mn0.54Co0.13Ni0.13O2 (LLO), the most-promising cathodes for the next-generation Li-ion battery, suffer from severe interfacial side reactions inducing the continual capacity fading and voltage reduction upon cycling. Although protecting them with inert silica proves effective to stabilize electrode interfaces and lessen the corrosion/dissolution reactions, the subtle silica thickness control and core–shell matching effects are rarely explored. We herein develop a general silica thickness-tuned method to make preferable cathodes. The cell testing reveals that the 4 nm silica coating is optimal for either NCM811- or LLO-based cathode systems; their basic behaviors such as long-term cyclability, rate capabilities, and midpoint voltage sustaining are all promoted. The postmortem analysis shows such a conformal silica coating indeed strengthens the mechanical/chemical properties of cathodes against particle cracking/fracturing and the electrolyte corrosion. Particularly, the moderate silica coating is more compatible with NCM811 cathodes, since it markedly prompts the vital long-cyclic behaviors without sacrificing their rate capabilities or midpoint voltage. This work unearths the understanding of the role of silica in distinct cathode systems, offering a useful interface-engineering technique to regulate the cathode kinetics.