Silicon is a promising material for anodes in energy-storage devices. However, excessive growth of a solid-electrolyte interphase (SEI) caused by the severe volume change during the (de)lithiation processes leads to dramatic capacity fading. Here, we report a super-concentrated electrolyte composed of lithium bis(fluorosulfonyl)imide (LiFSI) and propylene carbonate (PC) with a molar ratio of 1:2 to improve the cycling performance of silicon nanoparticles (SiNPs). The SiNP electrode shows a remarkably improved cycling performance with an initial delithiation capacity of approximately 3000 mAh g and a capacity of approximately 2000 mAh g after 100 cycles, exhibiting about 6.8 times higher capacity than the cells with dilute electrolyte LiFSI-(PC) . Raman spectra reveal that most of the PC solvent and FSI anions are complexed by Li to form a specific solution structure like a fluid polymeric network. The reduction of FSI anions starts to play an important role owing to the increased concentration of contact ion pairs (CIPs) or aggregates (AGGs), which contribute to the formation of a more mechanically robust and chemically stable complex SEI layer. The complex SEI layer can effectively suppress the morphology evolution of silicon particles and self-limit the excessive growth, which mitigates the crack propagation of the silicon electrode and the deterioration of the kinetics. This study will provide a new direction for screening cycling-stable electrolytes for silicon-based electrodes.

Si has been extensively examined as a potential alternative to carbonaceous negative materials, because it shows exceptional gravimetric capacity and abundance.

Ni-rich cathode (Ni > 0.8) provides a low-cost and high-energy-density solution to the next-generation lithium-ion batteries. Unfortunately, severe capacity fading of Ni-rich cathode caused by the interfacial and bulk structural degradation impeded its application. Herein, Zr doping and Li6Zr2O7 coating are applied to a Ni-rich LiNi0.83Co0.12Mn0.05O2 (NCM) layered cathode material, and the modified material exhibits excellent cycle stability. The 1%Zr-NCM cathode material maintains a discharge capacity of 173.9 mAh g–1 at 1 C after 200 cycles in the 2.5–4.3 V voltage range at 25 °C, corresponding to a capacity retention of 94.6%; however, the unmodified NCM only delivers 129.9 mAh g–1 (capacity retention 68.6%). The synergistic effect of bulk Zr doping and surface Li6Zr2O7 coating improves the cycle stability of the Ni-rich material. Zr doped into the bulk could form a strong Zr–O bond to stabilize the layered structure, and Zr located in the Li layer can act as a pillar to maintain the layered structure and reduce Li+/Ni2+ mixing. In addition, the Li6Zr2O7 coating layer can also play a dual role in promoting Li+ migration and suppressing surface side reactions. This work demonstrates that sufficiently utilizing zirconium to enhance the electrochemical performance of cathode materials is a feasible and promising strategy.