Gradient H-Bonding Supports Highly Adaptable and Rapidly Self-Healing Composite Binders with High Ionic Conductivity for Silicon Anodes in Lithium-Ion Batteries.

An ideal binder for high-energy-density lithium-ion batteries (LIBs) should effectively inhibit volume effects, exhibit specific functional properties (e.g., self-repair capabilities and high ionic conductivity), and require low-cost, environmentally friendly mass production processes. This study adopts a synergistic strategy involving gradient (strong-weak) hydrogen bonding to construct a hard/soft polymer composite binder with self-healing abilities and high battery cell environments adaptability in LIBs. The meticulously designed 3D network structure comprising continuous electron transport pathways buffers the mechanical stresses caused by changes in silicon volume and improves the overall stability of the solid electrolyte interphase film. The Si-based anode with a polymer composite binder poly(acrylic acid-g-ureido pyrimidinone5% )/polyethylene oxide (Si/PAA-UPy5% /PEO) achieves a reversible capacity of 1245 mAh g-1 after 200 cycles at 0.5 C, which is 6.6 times higher than that of the Si/PAA anode. After 200 cycles at 0.2 A g-1 , a half-cell comprising Si/C anode with a polymer composite binder (Si/C/PAA-UPy5% /PEO) has a remaining specific capacity of 420 mAh g-1 and a capacity retention rate of 79%. The corresponding full cell with a Li-based cathode (LiFePO4 /Si/C/PAA-UPy5% /PEO) has an initial area capacity of 0.96 mAh cm-2 and retains an area capacity of 0.90 mAh cm-2 (capacity retention rate = 93%) after 100 cycles at 0.2 A g-1 .

Microencapsulated Paraffin Phase-Change Material with Calcium Carbonate Shell for Thermal Energy Storage and Solar-Thermal Conversion.

A series of microencapsulated phase-change materials (MEPCMs) based on paraffin core and calcium carbonate (CaCO3) shell were synthesized, and the effect of emulsifier type and pH value on morphology, structure, and properties of paraffin@CaCO3 MEPCMs were investigated. The results showed that CaCO3 shell was formed in vaterite and calcite crystalline phase when emulsifier was sodium dodecyl benzene sulfonate and styrene-maleic anhydride (SMA), respectively. When sodium dodecyl sulfate was used as an emulsifier, both vaterite and calcite CaCO3 were formed. The forming mechanism of emulsifier type on CaCO3 crystalline phase was studied. Furthermore, phase-change enthalpy and leakage rate of MEPCMs were related with the type of emulsifier and the pH value of the emulsion. With optimum condition of SMA as emulsifier and pH value of 7, paraffin@CaCO3 MEPCMs had an encapsulation ratio at 56.6% and leakage rate at 2.88%, illustrating its considerable heat storage capability and leakage-prevention property. The 50 heating-cooling cycles test indicated that the MEPCMs owned excellent thermal reliability. The thermal conductivity of MEPCMs was significantly improved due to the existence of CaCO3 shell. In addition to excellent thermal storage ability, the paraffin@CaCO3 MEPCMs also owned good mechanical property and light-to-heat energy conversion efficiency. The characteristics of MEPCMs indicated its potential application in solar energy resource.

Highly efficient replacement of traditional intumescent flame retardants in polypropylene by manganese ions doped melamine phytate nanosheets.

The intumescent flame retardant (IFR) with ammonium polyphosphate (APP) as the main component has many defects in practical applications, more than that, APP can be traced to non-renewable phosphate rock resources. For the foregoing reasons, the melamine phytate supramolecular nanosheet flame retardant incorporating manganese ion (PAMA-Mn) was successfully prepared with a facile and environmental friendly hydrothermal procedure based on renewable bio-based material phytic acid (PA). The flame retardant polypropylene composite (PPI) with 13.5 wt% APP and 4.5 wt% pentaerythritol (PER) failed to the UL-94 test, and its limiting oxygen index (LOI) value was only 26.5%. After 33 wt% of APP was replaced by PAMA-Mn, the PPMn33 incorporating only 18 wt% flame retardant additives passed the UL-94 V-0 rating, and its LOI value was increased to 31.9%. Compared with PP, pHRR and pSPR values of PPMn33 were reduced by 56% and 23%, respectively. The fire retardant mechanism of PPMn33 was thoroughly discussed via a variety of characterization methods. It was found that the peak of the Gram-Schmidt curve of PPMn33 was drastically reduced by 49% relative to that of PPI, indicating a remarkably decrease of combustible volatile products owing to the incorporation of PAMA-Mn, thereby rapidly reducing the fire hazard risk.