Polyoxometalate Modified Separator for Performance Enhancement of Magnesium–Sulfur Batteries

The magnesium–sulfur (Mg‐S) battery has attracted considerable attention as a candidate of post‐lithium battery systems owing to its high volumetric energy density, safety, and cost effectiveness. However, the known shuttle effect of the soluble polysulfides during charge and discharge leads to a rapid capacity fade and hinders the realization of sulfur‐based battery technology. Along with the approaches for cathode design and electrolyte formulation, functionalization of separators can be employed to suppress the polysulfide shuttle. In this study, a glass fiber separator coated with decavanadate‐based polyoxometalate (POM) clusters/carbon composite is fabricated by electrospinning technique and its impacts on battery performance and suppression of polysulfide shuttling are investigated. Mg–S batteries with such coated separators and non‐corrosive Mg[B(hfip)4]2 electrolyte show significantly enhanced reversible capacity and cycling stability. Functional modification of separator provides a promising approach for improving metal–sulfur batteries

A method to prolong lithium-ion battery life during the full life cycle

Extended lifetime of lithium-ion batteries decreases economic costs and environmental burdens in achieving sustainable development. Cycle life tests are conducted on 18650-type commercial batteries, exhibiting nonlinear and inconsistent degradation. The accelerated fade dispersion is proposed to be triggered by the evolution of an additional potential of the anode during cycling as measured vs. Li$^+$/Li. A method to prolong the battery cycle lifetime is proposed, in which the lower cutoff voltage is raised to 3 V when the battery reaches a capacity degradation threshold. The results demonstrate a 38.1% increase in throughput at 70% of their beginning of life (BoL) capacity. The method is applied to two other types of lithium-ion batteries. A cycle lifetime extension of 16.7% and 33.7% is achieved at 70% of their BoL capacity, respectively. The proposed method enables lithium-ion batteries to provide long service time, cost savings, and environmental relief while facilitating suitable second-use applications

New Insights into Lithium Hopping and Ordering in LiNiO2_2 Cathodes during Li (De)intercalation

In situ$_7$Li and ex situ$_6$Li nuclear magnetic resonance (NMR) spectroscopy is applied to monitor lithium mobility in a LiNiO$_2$ cathode during Li-ion (de)intercalation. In situ X-ray absorption spectroscopy and galvanostatic intermittent titration are also used to capture changes during the Li-ion deintercalation process. A considerable line broadening was first found by $^7$Li NMR spectroscopy. The Jahn–Teller distortion hinders the Li diffusion, thus broadening the NMR signal. The observed NMR shifts are compared to Li/vacancy ordering patterns described earlier by Arroyo y de Dompablo et al. Coupled motions of electrons and Li ions are also discovered by both in situ$_7$Li and ex situ$_6$Li NMR spectroscopy for the first time. They result in local Li environments with an enhanced number of Ni$^{3+}$ neighbors at highly charged states. This opens a new perspective for understanding the highly delithiated structure