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The particle surface of Li͓Ni 0.8 Co 0.1 Mn 0.1 ͔O 2 was modified with AlF 3 as a coating material to improve the electrochemical properties. The effect of AlF 3 coating on Li͓Ni 0.8 Co 0.1 Mn 0.1 ͔O 2 cathode was extensively studied with respect to the structural and electrochemical properties, and thermal stability. The AlF 3 coating on Li͓Ni 0.8 Co 0.1 Mn 0.1 ͔O 2 particles improved the overall electrochemical properties, such as the cyclability, rate capability, and thermal stability, compared to pristine Li͓Ni 0.8 Co 0.1 Mn 0.1 ͔O 2 . Electrochemical impedance spectroscopy and transmission electron microscopy showed that the AlF 3 coating on Li͓Ni 0.8 Co 0.1 Mn 0.1 ͔O 2 particles played an important role in stabilizing the interface between the cathode and electrolyte.

A variety of advanced electrode structures have been developed lately to address the intrinsic drawbacks of lithium–sulfur batteries, such as polysulfide shuttling and low electrical conductivity of elemental sulfur. Nevertheless, it is still desired to find electrode structures that address those issues through an easy synthesis while securing large sulfur contents (i.e., > 70 wt %). Here, we report an orthogonal, “one-pot” synthetic approach to prepare a sulfur-embedded polybenzoxazine (S-BOP) with a high sulfur content of 72 wt %. This sulfur-embedded polymer was achieved via thermal ring-opening polymerization of benzoxazine in the presence of elemental sulfur, and the covalent attachment of sulfur to the polymer was rationally directed through the thiol group of benzoxazine. Also, the resulting S-BOP bears a homogeneous distribution of sulfur due to in situ formation of the polymer backbone. This unique internal structure endows S-BOP with high initial Coulombic efficiency (96.6%) and robust cyclability (92.7% retention after 1000 cycles) when tested as a sulfur cathode.

User safety is one of the most critical issues for the successful implementation of lithium ion batteries (LIBs) in electric vehicles and their further expansion in large-scale energy storage systems. Herein, we propose a novel approach to realize self-extinguishing capability of LIBs for effective safety improvement by integrating temperature-responsive microcapsules containing a fire-extinguishing agent. The microcapsules are designed to release an extinguisher agent upon increased internal temperature of an LIB, resulting in rapid heat absorption through an in situ endothermic reaction and suppression of further temperature rise and undesirable thermal runaway. In a standard nail penetration test, the temperature rise is reduced by 74% without compromising electrochemical performances. It is anticipated that on the strengths of excellent scalability, simplicity, and cost-effectiveness, this novel strategy can be extensively applied to various high energy-density devices to ensure human safety.