A thermoresponsive composite separator loaded with paraffin@SiO_(2) microparticles for safe and stable lithium batteries

Lithium-ion batteries (LIBs)-related accidents have been reported for years and safety issues are stumbling blocks for the practical applications of lithium metal batteries (LMBs) with higher energy density. More effective strategies to shut down the battery at the early stage of thermal runaway with less side effects on the electrochemical performance are greatly desired. In this work, the core–shell structural paraffin@SiO_(2) microparticles were synthesized by in situ emulsion interfacial hydrolysis and polycondensation and the paraffin@SiO_(2)-loaded separator (PSS) was prepared by a facile filtration method. The introduction of hydrophilic silica shells in paraffin@SiO_(2) enhanced the wettability of carbonate electrolyte with the composite separator and improved the processability of soft paraffin. As a result, when used in LMBs at room temperature, the cell with PSS inside had a more uniform deposition of lithium, a much lower overpotential and a more stable electrochemical performance than the cell with the blank separator or the conventional pure paraffin-loaded separator inside. More significantly, when a heating stimulation (i.e. 115 ℃) was subjected to the cell with PSS inside, the paraffin in the core of paraffin@SiO_(2) could be released, blocking the gaps between particles and the pores in the separator and efficiently stopping the transportation of Li+ between two electrodes, resulting in the thermally-induced shutdown of the cell below the melting temperature of PE (~135 ℃) in the Celgard2325 separator. The core–shell structure of paraffin@SiO_(2) enables the maintaining of each component’s benefits while avoiding each one’s drawbacks by elaborating microstructural design. Therefore, the conventional dilemma between the electrochemcial performance and safety of LMBs could be solved in the future.

Preliminary 3D printing of large inclined-shaped alumina ceramic parts by direct ink writing

Three dimensional(3D)printing technology by direct ink writing(DIW)is an innovative complex shaping technology,possessing advantages of flexibility in fabrication,high efficiency,low cost,and environmental-friendliness.Herein,3D printing of complex alumina ceramic parts via DIW using thermally induced solidification with carrageenan swelling was investigated.The rheological properties of the slurry under different thermally-induced modes were systematically studied.The solidification properties of thermally-induced pastes with varying contents of carrageenan were optimized.The experimental results showed that the optimized paste consisting of 0.4 wt%carrageenan could be rapidly solidified at about 55℃,which could print inclined-plane more than 60°in vertical without support,resulting in better homogeneity of the green body.A nearly pore-free structure was obtained after sintering at 1600℃ for 2 h.

Competition between Liquid-liquid De-mixing, Crystallization, and Glass Transition in Solutions of PLA of Different Stereochemistry and DEET

Liquid-liquid(L-L)de-mixing and vitrification of solutions of either crystallizable poly(L-lactic acid)(PLLA)or non-crystallizable poly(D/L-lactic acid)(PDLLA)with 50 m%N,N-diethyl-3-methylbenzamide(DEET)were analyzed by calorimetry and cloud-point measurements,which allows drawing conclusions about the effect of polymer stereochemistry on the phase behavior.Regardless of the PLA stereochemistry,vitrification of the solutions on fast cooling,hindering crystallization of PLLA,occurred below-20℃ and suppressed prior L-L de-mixing.The experimental results prove that crystallization in samples containing crystallizable PLLA,observed at around 55℃ on slow cooling,is not preceded by L-L de-mixing.