Colloid Electrolyte with Changed Li+ Solvation Structure for High-Power, Low-Temperature Lithium-Ion Batteries.

Lithium-ion batteries currently suffer from low capacity and fast degradation under fast charging and/or low temperatures. In this work, a colloid liquid electrolyte (CLE) is designed, where the trace amount of lithium thiocarbonate (LTC) colloids in commercial carbonate electrolyte (1 m LiPF6 in ethylene carbonate/dimethyl carbonate) not only boosts up σLi+ but also improves the Li+ transfer kinetics at LiNi0.8 Co0.15 Al0.05 O2 (NCA) cathode/electrolyte interface. The competitive coordination of LTCs with anions and solvents facilitates the dissociation of lithium salts and Li+ decoupling, dramatically enhancing the σLi+ (15 to 4.5 mS cm-1 at 30 and -20 °C, respectively); meanwhile, the desolvation process is accelerated. It demonstrates that LTC colloids induce an ≈5 nm ultrathin Li2 CO3 -rich cathode electrolyte interface and infuse the grain boundary of NCA particles, enhancing interfacial Li+ transfer and inhibiting the particle cracks during cycling. Consequently, the Li||CLE||NCA battery delivers a maximum capacity of 135 mAh g-1 at a 10 C rate with 80% retention after 2000 cycles. Moreover, the fast-charging capability under a sub-zero environment is proved (122 mAh g-1 with 90% retention after 400 cycles at 2 C and -10 °C). This strategy for tailoring the interfacial charge transfer appears generalizable and can practically be extended to next-generation energy-storage systems.

Unraveling Atomic-Scale Origins of Selective Ionic Transport Pathways and Sodium-Ion Storage Mechanism in Bi2 S3 Anodes.

It is a major challenge to achieve a high-performance anode for sodium-ion batteries (SIBs) with high specific capacity, high rate capability, and cycling stability. Bismuth sulfide, which features a high theoretical specific capacity, tailorable morphology, and low cost, has been considered as a promising anode for SIBs. Nevertheless, due to a lack of direct atomistic observation, the detailed understanding of fundamental intercalation behavior and Bi2 S3 's (de)sodiation mechanisms remains unclear. Here, by employing in situ high-resolution transmission electron microscopy, consecutive electron diffraction coupled with theoretical calculations, it is not only for the first time identified that Bi2 S3 exhibits specific ionic transport pathways preferred to diffuse along the (110) direction instead of the (200) plane, but also tracks their real-time phase transformations (de)sodiation involving multi-step crystallographic tuning. The finite-element analysis further disclosed multi-reaction induced deformation and the relevant stress evolution originating from the combined effect of the mechanical and electrochemical interaction. These discoveries not only deepen the understanding of fundamental science about the microscopic reaction mechanism of metal chalcogenide anodes but also provide important implications for performance optimization.

Atomic-Scale Tracking of Dynamic Nucleation and Growth of an Interfacial Lead Nanodroplet.

Revealing the evolutional pathway of the nucleation and crystallization of nanostructures at the atomic scale is crucial for understanding the complex growth mechanisms at the early stage of new substances and spices. Real-time discrimination of the atomic mechanism of a nanodroplet transition is still a formidable challenge. Here, taking advantage of the high temporal and spatial resolution of transmission electron microscopy, the detailed growth pathway of Pb nanodroplets at the early stage of nucleation was directly observed by employing electron beams to induce the nucleation, growth, and fusion process of Pb nanodroplets based on PbTiO3 nanowires. Before the nucleation of Pb nanoparticles, the atoms began to precipitate when they were irradiated by electrons, forming a local crystal structure, and then rapidly and completely crystallized. Small nanodroplets maintain high activity and high density and gradually grow and merge into stable crystals. The whole process was recorded and imaged by HRTEM in real time. The growth of Pb nanodroplets advanced through the classical path and instantaneous droplet coalescence. These results provide an atomic-scale insight on the dynamic process of solid/solid interface, which has implications in thin-film growth and advanced nanomanufacturing.