3,3‐Diethylene Di‐Sulfite (DES) as a High‐Voltage Electrolyte Additive for 4.5 V LiNi 0.8 Co 0.1 Mn 0.1 O 2 /Graphite Batteries with Enhanced Performances

Electrolyte Engineering Toward High Performance High Nickel (Ni ≥ 80%) Lithium-Ion Batteries

High nickel (Ni ≥ 80%) lithium-ion batteries (LIBs) with high specific energy are one of the most important technical routes to resolve the growing endurance anxieties. However, because of their extremely aggressive chemistries, high-Ni (Ni ≥ 80%) LIBs suffer from poor cycle life and safety performance, which hinder their large-scale commercial applications. Among varied strategies, electrolyte engineering is very powerful to simultaneously enhance the cycle life and safety of high-Ni (Ni ≥ 80%) LIBs. In this review, the pivotal challenges faced by high-Ni oxide cathodes and conventional LiPF6 -carbonate-based electrolytes are comprehensively summarized. Then, the functional additives design guidelines for LiPF6 -carbonate -based electrolytes and the design principles of high voltage resistance/high safety novel electrolytes are systematically elaborated to resolve these pivotal challenges. Moreover, the proposed thermal runaway mechanisms of high-Ni (Ni ≥ 80%) LIBs are also reviewed to provide useful perspectives for the design of high-safety electrolytes. Finally, the potential research directions of electrolyte engineering toward high-performance high-Ni (Ni ≥ 80%) LIBs are provided. This review will have an important impact on electrolyte innovation as well as the commercial evolution of high-Ni (Ni ≥ 80%) LIBs, and also will be significant to breakthrough the energy density ceiling of LIBs.

Sulfur-Rich Additive-Induced Interphases Enable Highly Stable 4.6 V LiNi0.5 Co0.2 Mn0.3 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 LiNi0.5 Co0.2 Mn0.3 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.

Synergistic Effect of Dual-Anion Additives Promotes the Fast Dynamics and High-Voltage Performance of Ni-Rich Lithium-Ion Batteries by Regulating the Electrode/Electrolyte Interface

Combining the Ni-rich layered cathode (Ni ≥ 80%) with high operating voltage is considered as a feasible solution to achieve high-energy lithium-ion batteries (LIBs). However, the working voltage is limited in practical applications due to the poor interface stability in traditional carbonate electrolytes. Herein, LiBF₄ and LiNO₃ are added as film-forming additives and 1.0 M LiPF₆ in SL/FEC/EMC with 0.5 wt % LiBF₄-LiNO₃ (HVE) is obtained. A uniform and inorganic-rich cathode electrolyte interphase (CEI) as well as a dense and Li₃N-LiF-rich solid electrolyte interphase (SEI) could be in situ generated on LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) and graphite (Gr) electrode in HVE, respectively. The robust interface film with electronic insulation and ionic conductivity effectively stabilizes the NCM811/Gr-electrolyte interfaces and improves the Li⁺ diffusion kinetics, enabling the high-load NCM811-Gr to maintain 85.2% capacity (∼180 mA h g^-1) after 300 cycles under 4.4 V. Besides, the 4.2 V NCM811-Gr retains 90.4% of the initial capacity after 200 cycles at 2 C (∼6 mA h cm^-2). Compared with the traditional carbonate electrolyte (LB301), HVE has obvious advantages in terms of high-voltage and fast dynamics performance. Especially, good thermal stability and economy make HVE a promising electrolyte for commercial high-energy LIBs.