Sulfonated polyethylene-styrene cation exchange membrane: A potential separator material in vanadium redox flow battery application

We report on the synthesis and characterization of polyethylene-styrene-divinylbenzene-based interpolymer cation exchange membrane (ICEM) and its applicability as a separator in vanadium redox flow battery (VRFB). ICEM preparation involved radical...

Self-Healing of a Covalently Cross-Linked Polymer Electrolyte Membrane by Diels-Alder Cycloaddition and Electrolyte Embedding for Lithium Ion Batteries

Thermally reversible self-healing polymer (SHP) electrolyte membranes are obtained by Diels-Alder cycloaddition and electrolyte embedding. The SHP electrolytes membranes are found to display high ionic conductivity, suitable flexibility, remarkable mechanical properties and self-healing ability. The decomposition potential of the SHP electrolyte membrane is about 4.8 V (vs. Li/Li+) and it possesses excellent electrochemical stability, better than that of the commercial PE film which is only stable up to 4.5 V (vs. Li/Li+). TGA results show that the SHP electrolyte membrane is thermally stable up to 280 °C in a nitrogen atmosphere. When the SHP electrolyte membrane is used as a separator in a lithium-ion battery with an LCO-based cathode, the SHP membrane achieved excellent rate capability and stable cycling for over 100 cycles, and the specific discharge capacity could be almost fully recovered after self-healing. Furthermore, the electrolyte membrane exhibits excellent electrochemical performance, suggesting its potential for application in lithium-ion batteries as separator material.

Preferential lattice expansion of polypropylene in a trilayer polypropylene/polyethylene/polypropylene microporous separator in Li-ion batteries

The abnormal lattice expansion of commercial polypropylene (PP)/polyethylene (PE)/polypropylene (PP) separator in lithium-ion battery under different charging current densities was observed by in-situ X-ray diffraction. Significant lattice changes of both PP and PE were found during the low current density charging. The capacity fading and the resistance value of the cell measured at 0.025 C (5th retention, 92%) is unexpectedly larger than that at 1.0 C (5th retention, 97.3%) from the electrochemical impedance spectroscopic data. High-resolution scanning electron microscopy is employed to witness the pore changes of the trilayered membrane. Density functional theory calculations were used to investigate the mechanism responsible for the irregular results. The calculations revealed that the insertion of Li-ion and EC molecule into PP or PE are thermodynamically favourable process which might explain the anomalous significant lattice expansion during the low current density charging. Therefore, designing a new separator material with a more compact crystalline structure or surface modification to reduce the Li insertion during the battery operation is desirable.

Development of a Two-Stage Pyrolysis Process for the End-Of-Life Nickel Cobalt Manganese Lithium Battery Recycling from Electric Vehicles

With the continuous promotion of electric vehicles, the pressure to scrap vehicle batteries is increasing, especially in China, where nickel cobalt manganese lithium (NCM) batteries have gradually come to occupy a dominant position in the battery market. In this study, we propose a two-stage pyrolysis process for vehicle batteries, which aims to effectively deal with the volatilization of organic solvents, the decomposition of lithium salts in the electrolyte and the removal of the separator material and polyvinylidene fluoride (PVDF) during battery recycling. By solving these issues, recycling is more effective, safe. Through thermogravimetric analysis (TGA), the pyrolysis characteristics of the battery’s internal materials are discussed, and 150 °C and 450 °C were determined as the pyrolysis temperatures of the two-stage pyrolysis process. The results show that in the first stage of pyrolysis, organic solvents EC (C4H3O3), DEC (C5H10O3) and EMC (C4H8O3) can be separated from the electrolyte. In the second stage, the pyrolysis can lead to the separator’s thermal decomposition. The gas products are alkane C2-C6, and the tar products are organic hydrocarbons C15-C36. Meanwhile, the solid residue of the battery’s internal material seems to be very homogeneous. Finally, the potential recovery value and pollution control countermeasures of the products and residues from the pyrolysis process are analyzed. Consequently, this method can effectively handle NCM vehicle battery recycling, which provides the basis for the subsequent hydrometallurgical or pyrometallurgical process for element recovery of the battery material.

Multifunctional structural supercapacitor based on graphene and magnesium phosphate cement

A novel structural supercapacitor is assembled with graphene electrodes and the magnesium phosphate cement separator. Magnesium phosphate cement acts as separator material for the first time due to its high strength and relatively high porosity. Magnesium phosphate cement is synthesized by acid-based reaction between phosphate and magnesia. Effects of processing parameters of magnesium phosphate cement, including M/P ratio and the curing time, on the electrochemical and mechanical properties are investigated. The maximum specific capacitance is as high as 46.38 F g−1 with M/P ratio of 3 at the curing time of 1 day. Moreover, the structural supercapacitor exhibits a specific capacitance of 40.92 F g−1 and simultaneously a compressive strength of 24.59 MPa with the M/P ratio of 3 at the curing time of 28 days. Thus, the optimal M/P ratio is 3 regarding the multifunctionality of structural supercapacitor.

A multi-shelled CoP nanosphere modified separator for highly efficient Li–S batteries

Multi-shelled CoP nanospheres are designed as a new kind of coated separator material for highly efficient Li–S batteries, which exhibits outstanding cycling stability with a capacity degradation of 0.078% per cycle over 500 cycles at 1 C and also excellent rate performances.