Rational Design of the Li⁺-Solvation Structure Contributes to Constructing a Robust Cathode-Electrolyte Interphase for a 5 V High-Voltage LiNi_0.5Mn_1.5O₄ Cathode

Abstract

Spinel oxide LiNi0.5Mn1.5O4 (LNMO) presents great potential for lithium-ion batteries (LIBs) due to its high working potential (∼4.7 V vs Li/Li+) and low cost. Nevertheless, the lack of a competent electrolyte restricts its application. We develop a battery of LiPF6-based localized high-concentration electrolytes containing dimethyl carbonate (DMC) and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE). As the volume ratio of TTE to DMC augments, the percentage of free DMC and PF6 – and the solvation number of Li+ reduce. The proper Li+-solvation structure contributes to forming a robust PF6 –-derived LiF enriched cathode-electrolyte interphase (CEI). The Li||LNMO cell in the 1M LiPF6-DMC/TTE (1:2, V/V) (1M-DT12) electrolyte exhibits wonderful cycling stability (97.5%, after 100 cycles at 1C), superior rate capability (124.0 mA h/g at 5C), and significantly enhanced low-temperature performance (83.1 mA h/g, 0.1C at −30 °C). This work illustrates the rational design of the Li+-solvation structure in the LiPF6-based electrolyte to obtain robust PF6 –-derived LiF enriched CEI for a high-voltage LNMO cathode.

Sulfide-Based Flexible Solid Electrolyte Enhancing Cycling Performance of All-Solid-State Lithium Batteries

“…In contemporary times, lithium-ion batteries (LIBs) have evolved into indispensable energy storage devices utilized in mobile electronics, electric vehicles, and large-capacity energy storage systems. − However, significant technological challenges persist in enhancing energy density and safety within the realm of LIBs. − Consequently, a growing interest has been observed in all-solid-state lithium batteries (ASSLBs) that circumvent the use of flammable organic solvents. − Notably, research on sulfide-based solid electrolytes, such as Li 6 PS 5 Cl, Li 10 GeP 2 S 12 , and Li 3 PS 4 , characterized by high ionic conductivities (on the order of 10 –2 S cm –1 ) and suitable mechanical properties, has been actively pursued. − Despite these advancements, successful development of sulfide-based ASSLBs faces hurdles, including the fabrication of thin and flexible solid electrolytes with high ionic conductivity to achieve high energy density. − At the laboratory scale, ASSLBs are assembled using cold-pressed sulfide-based solid electrolyte pellets, which typically exceed 600 μm in thickness due to brittleness, hindering the fabrication of thin electrolytes. Additionally, the poor interfacial adhesion and stability between the rigid solid electrolyte pellets and electrodes arise from substantial volume changes in electrodes during charge and discharge cycles.…”