Sulfur-Rich Additive-Induced Interphases Enable Highly Stable 4.6 V LiNi_0.5 Co_0.2 Mn_0.3 O₂ ||graphite Pouch Cells

High-voltage lithium-ion batteries (LIBs) have attracted great attention due to their promising high energy density. However, severe capacity degradation is witnessed, which originated from the incompatible and unstable electrolyte-electrode interphase at high voltage. Herein, a robust additive-induced sulfur-rich interphase is constructed by introducing an additive with ultrahigh S-content (34.04 %, methylene methyl disulfonate, MMDS) in 4.6 V LiNi_0.5 Co_0.2 Mn_0.3 O₂ (NCM523)||graphite pouch cell. The MMDS does not directly participate the inner Li⁺ sheath, but the strong interactions between MMDS and PF₆ ^- anions promote the preferential decomposition of MMDS and broaden the oxidation stability, facilitating the formation of an ultrathin but robust sulfur-rich interfacial layer. The electrolyte consumption, gas production, phase transformation and dissolution of transition metal ions were effectively inhibited. As expected, the 4.6 V NCM523||graphite pouch cell delivers a high capacity retention of 87.99 % even after 800 cycles. This work shares new insight into the sulfur-rich additive-induced electrolyte-electrode interphase for stable high-voltage LIBs.