Direct-contact prelithiation (PL) is a facile, practical, and scalable method to overcome the first-cycle loss and large volume expansion issues for silicon anode (with 30 wt % Si loading) material, and a detailed study is absent. Here, an understanding of direct-contact PL as a function of the PL time, and the effects of externally applied pressure (weight), microstructure, and operating temperature have been studied. The impact of PL on the Si–C electrode surfaces has been analyzed by electrochemical techniques and different microstructural analyses. The solid electrolyte interface (SEI) layer thickness increases with the increase in PL time and decreases after 2 min of PL time. The ideal PL time was found to be between 15 (PL-15) and 30 (PL-30) min with 83.5 and 97.3% initial Coulombic efficiency (ICE), respectively, for 20 g of externally applied weight. The PL-15 and PL-30 cells showed better cyclic stability than PL-0 (without prelithiation), with more than 90% capacity retention after 500 cycles at 1 A g–1 current density. The discharge capacities for PL-15 and PL-30 have been observed as highest at 45 °C operating temperature with limited cyclability. We propose here a synchronization strategy in prelithiation time, pressure, and temperature to achieve excellent cell performance.

Lithium cobalt oxide (LCO) is yet a preferred choice because of its unique structure and electrochemical relationship. However, LCO sacrifices its structural stability and associated battery safety at higher voltage and a high rate of operation in current battery technology. To mitigate such problems, a targeted strategy has been adopted with a thin lithium cobalt manganese oxide (LiCo0.5Mn1.5O4, LCMO) coating on the LCO cathode by easy and inexpensive microwave-assisted synthesis. The as-prepared cathode structure showed a tiny amount of manganese­(III) ion (Mn3+) diffusion into the bulk of LCO, which resulted in the increase of its lattice parameter and favoring the Li-ion diffusion in LCO cathode and enables a faster cycling rate 3C (20 min charging–discharging) for longer periods of time. The structural entropy estimation has been utilized to evaluate the arrangement of Li ions and the vacancy in the LCO lattice at different states of charge to investigate the stability of coated LCO at higher voltage. A comprehensive study at higher rate capability at 3C, 5C (12 min), and even at 10C (6 min) current rates and stability at a higher cutoff voltage for modified LCO has been reported here. Finally, the current study is ended with full-cell fabrication with silicon-carbon anodes and LCMO-coated-LCO cathodes in two-layer pouch-type cell format (∼15 mAh capacity) and displayed a commercial feasibility.

No abstract

Li 10 GeP 2 S 12 (LGPS) solid electrolyte is not affordable due to the high cost of Ge metal, making it economically unviable despite being a lithium superionic conductor. The synthesis of such solid electrolytes is much more time-and energyconsuming and needs an inert environment. Here, we report Si (silicon)-based composition [Li 10 SiP 2 S 12 (LSiPS)] to make it cost-effective through microwave heating (MW). The total time for synthesis processes, including ball milling, heating rate, and heating dwell time, is ∼120 min, much less than the previous reports. We have also avoided vacuum sealing/Ar-purging to reduce the synthesis cost further. During MW heating, the densification process dominates over coarsening, resulting in a dense nanoflake morphology with a finer crystallite size. The synthesized LSiPS has a high fraction (∼89%) of more conducting tetragonal phase as identified by NMR analysis. Further, we modified the interface between the Li anode and LSiPS by forming a lithiophobic and lithiophilic kind of gradient interlayer to reduce the reduction of LSiPS and suppress the side reactions. The interface modification resulted in a better Li/LSiPS/Li cyclic performance for 1800 h at 0.2 mA/cm 2 and 500 h at 1.0 mA/cm 2 . All-solid-state lithium-metal batteries (ASSLIB) have been developed against a high-voltage cathode (LCMO-coated LCO) and showed an excellent cycling performance with a reversible capacity of ∼110 mAh/g after 300 cycles.

No abstract