NANOTECH LAB | YUSHIN GROUP

This review considers key parameters for affordable Li-ion battery (LIB)-powered electric transportation, such as mineral abundance for active material synthesis, raw materials' processing cost, cell performance characteristics, cell energy density, and the cost of cell manufacturing. It analyzes the scarcity of cobalt (Co) and nickel (Ni) resouces available for intercalation-type LIB cathode materials, estimates the demands for these metals by transportation and other industries, and discusses risk factors for their price increase within the next two decades. It also further contrasts perfromance and estimates costs of LIBs based on intercalation materials, such as lithium nicket cobalt manganese oxide (NCM), lithium nickel cobalt aluminum oxide (NCA), lithium iron phosphate (LFP), and other oxide-based cathodes and carbonaceous anodes, with those of LIBs based on conversion-type cathodes and silicon (Si)-based anodes.

High-performance supercapacitor nonwoven separators based on polyvinyl butyral (PVB) with uniformly distributed Al2O3 nanowires (NW) fillers (up to 40 wt %) have been developed using a low-cost casting (stir-pour-dry) technique utilized under ambient conditions for the first time. These novel nonwoven separators with highly porous network demonstrated tensile strength of >30 MPa, extremely high electrolyte absorption (>200 wt. %), low-to-no swelling behavior and stable electrochemical performance, substantially exceeding that of analogous cells with commercial separators. Thermal properties of the produced separators were also exceptional with >15 MPa of ultimate strength, high flexibility and minimal thermal shrinkage maintained at temperatures as high as 200 °C. The one-dimensional (1D) ceramic nanofillers improved PVB's mechanical and thermal properties and enabled formation of highly porous membranes with self-organized nanopores and high ionic conductivity of up to 13.5 mS/cm in 1 M Na2SO4 aqueous electrolyte. This simple and innovative method and separator design is attractive for manufacturing of high-strength, low-cost and flexible separators and suitable for various polymers-ceramic nonwoven compositions for fast charging, high-power and safe electrochemical capacitors, hybrid devices and batteries.

Low‐melting‐point solid‐state electrolytes (SSE) are critically important for low‐cost manufacturing of all‐solid‐state batteries. Lithium hydroxychloride (Li2OHCl) is a promising material within the SSE domain due to its low melting point (mp < 300 °C), cheap ingredients (Li, H, O, and Cl), and rapid synthesis. Another unique feature of this compound is the presence of Li vacancies and rotating hydroxyl groups which promote Li‐ion diffusion, yet the role of the protons in the ion transport remains poorly understood. To examine lithium and proton dynamics, a set of solid‐state NMR experiments are conducted, such as magic‐angle spinning 7Li NMR, static 7Li and 1H NMR, and spin‐lattice T1(7Li)/T1(1H) relaxation experiments. It is determined that only Li+ contributes to long‐range ion transport, while H+ dynamics is constrained to an incomplete isotropic rotation of the OH group. The results uncover detailed mechanistic understanding of the ion transport in Li2OHCl. It is shown that two distinct phases of ionic motions appear at low and elevated temperatures, and that the rotation of the OH group controls Li+ and H+ dynamics in both phases. The model based on the NMR experiments is fully consistent with crystallographic information, ionic conductivity measurements, and Born–Oppenheimer molecular dynamic simulations.

Technologically important composites with enhanced thermal and mechanical properties rely on the reinforcement by the high specific strength ceramic nanofibers or nanowires (NWs) with high aspect ratios. However, conventional synthesis routes to produce such ceramic NWs have prohibitively high cost. Now, direct transformation of bulk Mg‐Li alloys into Mg alkoxide NWs is demonstrated without the use of catalysts, templates, expensive or toxic chemicals, or any external stimuli. This mechanism proceeds through the minimization of strain energy at the boundary of phase transformation front leading to the formation of ultra‐long NWs with tunable dimensions. Such alkoxide NWs can be easily converted in air into ceramic MgO NWs with similar dimensions. The impact of the alloy grain size and Li content, synthesis temperature, inductive and steric effects of alkoxide groups on the diameter, length, composition, ductility, and oxidation of the produced NWs is discussed.