Cathode Electrolyte Interphase-Forming Additive for Improving Cycling Performance and Thermal Stability of Ni-Rich LiNi_xCo_yMn_1–x–yO₂ Cathode Materials

Abstract

High-capacity Ni-rich LiNi x Co y Mn1–x–y O2 (NCM) has been investigated as a promising cathode active material for improving the energy density of lithium-ion batteries (LIBs); however, its practical application is limited by its structural instability and low thermal stability. In this study, we synthesized tetrakis(methacryloyloxyethyl)pyrophosphate (TMAEPPi) as a cathode electrolyte interphase (CEI) additive to enhance the cycling characteristics and thermal stability of the LiNi0.8Co0.1Mn0.1O2 (NCM811) material. TMAEPPi was oxidized to form a uniform Li+-ion-conductive CEI on the cathode surface during initial cycles. A lithium-ion cell (graphite/NCM811) employing a liquid electrolyte containing 0.5 wt % TMAEPPi exhibited superior capacity retention (82.2% after 300 cycles at a 1.0 C rate) and enhanced high-rate performance compared with the cell using a baseline liquid electrolyte. The TMAEPPi-derived CEI layer on NCM811 suppressed electrolyte decomposition and reduced the microcracking of the NCM811 particles. Our results reveal that TMAEPPi is a promising additive for forming stable CEIs and thereby improving the cycling performance and thermal stability of LIBs employing high-capacity NCM cathode materials.

Atomic-level insights into the first cycle irreversible capacity loss of Ni-rich layered cathodes for Li-ion batteries

“…80 Additionally, while direct visual evidence of CEI formation 82 during the initial cycle has not been reported, most CEI layers have been detected after significant cycling (more than 50 cycles) at higher voltages above 4.5 V with a typical thickness ranging from 5–30 nm. 83,84 These findings provide support for the idea that IRC loss is primarily due to irreversible structural changes that occur during cycling. Furthermore, our in situ study utilized hard X-rays to probe several microns deep into the material during the first cycle.…”

Non-flammable Gel Polymer Electrolyte for Enhancing the Safety and High-Temperature Performance of Lithium-Ion Batteries

“…Figure c,d shows the electrochemical impedance spectra of the cells before and after cycling at 55 °C. The experimental data were fitted using the equivalent circuits shown in Figure S10, , and the results are summarized in Table S1. Based on these results, the increase in the resistance of the cells is plotted in Figure e.…”

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.…”