Synthesis and electrochemical performance of poly(vinylidene fluoride)/SiO2 hybrid membrane for lithium-ion batteries

A Magnesium Carbonate Hydroxide Nanofiber/Poly(Vinylidene Fluoride) Composite Membrane for High-Rate and High-Safety Lithium-Ion Batteries

Simultaneously high-rate and high-safety lithium-ion batteries (LIBs) have long been the research focus in both academia and industry. In this study, a multifunctional composite membrane fabricated by incorporating poly(vinylidene fluoride) (PVDF) with magnesium carbonate hydroxide (MCH) nanofibers was reported for the first time. Compared to commercial polypropylene (PP) membranes and neat PVDF membranes, the composite membrane exhibits various excellent properties, including higher porosity (85.9%) and electrolyte wettability (539.8%), better ionic conductivity (1.4 mS·cm-1), and lower interfacial resistance (93.3 Ω). It can remain dimensionally stable up to 180 °C, preventing LIBs from fast internal short-circuiting at the beginning of a thermal runaway situation. When a coin cell assembled with this composite membrane was tested at a high temperature (100 °C), it showed superior charge-discharge performance across 100 cycles. Furthermore, this composite membrane demonstrated greatly improved flame retardancy compared with PP and PVDF membranes. We anticipate that this multifunctional membrane will be a promising separator candidate for next-generation LIBs and other energy storage devices, in order to meet rate and safety requirements.

Three-dimensional polyimide nanofiber framework reinforced polymer electrolyte for all-solid-state lithium metal battery

The replacement of traditional liquid electrolytes with polyethylene oxide (PEO) based composite polymer electrolytes (CPEs) is an important strategy to address the current flammability and explosiveness of lithium batteries since PEO CPEs have high flexibility, excellent processability and moderate cost. However, the insufficient ionic conductivity and inferior mechanical strength of PEO CPEs do not suit the operating requirements of all-solid-state lithium metal batteries at room temperature. Herein, three-dimensional (3D) framework composed of interweaved high-modulus polyimide (PI) nanofibers along with functional succinonitrile (SN) plasticizers are employed to synergistically reinforce the ionic conductivity and mechanical strength of PEO CPEs. Impressively, benefitting from the synergistic effects of 3D PI framework and SN plasticizer, PI-PEO-SN CPEs exhibits high ionic conductivity of 1.03 × 10^-4 S cm^-1 at 30 °C, remarkable tensile strength of 4.52 MPa, and superior Li dendrites blocking ability (>400 h at 0.1 mA cm^-2). Such favorable features of PI-PEO-SN CPEs endow LiFePO₄/PI-PEO-SN/Li solid-state prototype cells with high specific capacity (151.2 mA h g^-1 at 0.2 C), long cycling lifespan (>150 cycles with 91.7 % capacity retention), and superior operating safety even under bending, folding and cutting harsh conditions. This work will pave the avenues to design and fabricate new high-performance PEO CPEs for the high energy density and safety all-solid-state batteries.

"Polymer-in-Ceramic" Membrane for Thermally Safe Separator Applications

In this work, a facile casting method was utilized to prepare "polymer-in-ceramic" microporous membranes for thermally safe battery separator applications; that is, a series of composite membranes composed of silicon dioxide (SiO₂) as a matrix and polyvinylidene fluoride (PVDF) as a binder were prepared. The effects of different SiO₂ contents on various physical properties of membranes such as the porosity, electrolyte absorption rate, electrochemical stability, and especially thermal stability of the SiO₂/PVDF composite membranes were systematically studied. Compared with a commercial polypropylene separator, the SiO₂/PVDF membrane has a higher porosity (66.0%), electrolyte absorption (239%), and ion conductivity (1.0 mS·cm^-1) and superior thermal stability (only 2.1% shrinkage at 200 °C for 2 h) and flame retardancy. When the content of SiO₂ in the membrane reached 60% (i.e., PS6), LiFePO₄/PS6/Li half-cells exhibited excellent cycle stability (138.2 mA h·g^-1 discharging capacity after 100 cycles at 1C) and Coulombic efficiency (99.1%). The above advantages coupled with the potential for rapid and large-scale production reveal that the "polymer-in-ceramic" SiO₂/PVDF membrane has prospective separator applications in secondary lithium-ion batteries.

Design and Preparation of Molecularly Imprinted Membranes for Selective Separation of Acteoside

Acteoside (ACT) belongs to a type of phenylethanoid glycosides (PhGs), and it is worthy of obtaining high-purity due to its significant medicinal functions. In this study, a novel class of MIMs was designed and synthesized with PVDF membranes as the base membrane for high selective separation and enrichment of ACT. The effects of the different functional monomers, the amounts of functional monomers, crosslinking agents, and initiators on the separation properties of MIMs were investigated. Furthermore, adsorption ability, permeation capacity, and reusability of MIMs were discussed for ACT. It indicated that MIM7 was the optimal performance of MIMs. The adsorption ability of MIM7 for ACT was 62.83 mg/g, and the selectivity factor (α) of MIM7 was up to 2.74 and its permeability factor (β) was greater than 2.66. Moreover, the adsorption amount of MIM7 was still more than 88.57% of the initial value after five cycles. As an ACT imprinted layer of MIMs only had recognition sites for ACT molecules, which recombined with the recognition sites in the membrane permeation experiment, ACT molecules penetration was hindered. However, the analogs of ECH successfully passed MIMs. It indicated that the selective MIMs for ACT followed the mechanism of delayed permeation. This work provides an important reference for the high permselective separation of natural products.