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Although aqueous zinc metal batteries (AZMBs) have attractive advantages such as high safety, low cost and eco-friendliness, severe dendrites formation and side reactions of zinc metal anodes cause a serious challenge for commercial applications. Herein, a polyanionic hydrogel electrolyte, poly 2-acrylamido-2-methyl-1-propane sulfonate zinc (PAMPSZn) is firstly designed and synthesized by ion exchange and free-radical polymerization. The PAMPSZn hydrogel electrolyte owns fixed polyanionic chain and restricted Zn2+ transport channels, which can effectively alleviate the side reactions and prevent the formation of Zn dendrites simultaneously. Consequently, the anode-friendly electrolyte not only enables ultra-stable Zn plating/stripping over 4500 h at 1.0 mA cm−2, but also achieves high preferred orientation deposition during the procedure of repeated plating/stripping. It delivers high reversibility with high initial coulombic efficiency (87.5%) and average coulombic efficiency (99.3%) in Zn/Cu cells at 0.5 mA cm−2. Zn/V2O5 cells with the developed electrolyte also possess outstanding cycle stability with capacity retention of 80.2% after 400 cycles at 0.5 A g−1. The PAMPSZn hydrogel electrolyte with unique fixed polyanionic chain and restricted Zn2+ transport channels demonstrates an effective strategy to solve both dendrites formation and side reactions in AZMBs, providing a new opportunity for high performance AZMBs.

Separators play a vital role in electronic insulation and ionic conduction in lithium-ion batteries. The common improvement strategy of polyolefin separators is mostly based on modifications with a coating layer, which is simple and effective to some extent. However, the improvement is often accompanied by negative effects such as the increase of the thickness and the blockage of the porous structure, resulting in the decrease of energy density and power density. The porous structure of the separators serves as a conduction path for ions to travel back and forth between the anode and cathode, which has an important impact on the performance of lithium-ion batteries. If the porous structure of the separators can be modified, it will essentially affect the ionic transport behavior through the whole conduction path. Herein, we provide a simple and effective method to functionalize the porous polyolefin separator via the γ-ray co-irradiation grafting process, where high-energy γ-ray is used to generate active sites on the polymer chain to initiate the grafting polymerization of chosen monomers with selected functional groups. In this work, 4,4,5,5-tetramethyl-2-vinyl-1,3,2-dioxaborolane, a kind of borane molecule with an electron-deficient group, was chosen as the grafting monomer. After the γ-ray co-irradiation grafting process, both the surface and pores of the polyolefin separators were functionalized by electron-deficient groups in the borane molecule and the whole electrolyte conduction path within the separator was activated. Due to the electron-deficient effect of the B atom, the lithium-ion conduction is promoted and the lithium-ion transference number can be increased to 0.5. As a result, the half-cell assembled with the functionalized separator shows better cycle stability and better capacity retention under high current rate.

In this work, a poly(vinylidene fluoride) (PVDF)-based copolymer is synthesized by grafting two kinds of monomer, 2, 2, 3, 4, 4,-hexafluorobutyl methacrylate (HFMA) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS), onto the PVDF powder with pre-irradiation grafting copolymerization. Then a new single lithium-ion conducting polymer electrolyte (SIPE) is prepared by solution casting of the radiation grafted PVDF-based copolymer powder with subsequent lithiation process. Its chemical structure, crystal form, and membrane morphology are characterized by nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM), etc. The mechanical properties exhibit the elongation at break of 72% and the tensile strength of 28 MPa. Comparatively high values of ionic conductivity, up to 2.08 × 10−5 S cm−1 at 30 °C, are obtained, combined with lithium-ion transference number of 0.93 and stable electrochemically oxidation voltage as high as 4.4 V vs Li/Li+. Except for these promising features, the SIPE cell with lithium ion conduction network has a stable charge/discharge cycling performance with various C-rates at room temperature. As-prepared SIPE shows a great prospect for the application in lithium-ion batteries.

Safety is one of the most factors for lithium-ion batteries (LIBs). In this work, a novel kind of ceramic separator with high safety insurance is proposed. We fabricated the core-shell nanofiber separators for LIBs by atomic layer deposition (ALD) of 30 nm Al2O3 on the electrospinning nonwoven fiber of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP). The separators show a pretty high heat resistance up to 200 °C without any shrinkage, an excellent fire-resistant property and a wide electrochemical window. Besides, with higher uptake and ionic conductivity, cells assembled with the novel separator shows better electrochemical performance. The ALD produced separators exhibit great potential in elaborate products like 3C communications and in energy field with harsh requirements for safety such as electric vehicles. The application of ALD on polymer fiber membranes brings a new strategy and opportunity for improving the safety of the advanced LIBs.

In this work, a method for preparing solid polymer electrolytes with function of single ion conduction (SICs-SPEs) is developed and reported. A solid state ionic conduction path with three-dimensional interpenetrating network was constructed by multi-nozzle electrospinning technology and a followed hot pressed treatment. Here, two components of SICs-SPEs were chosen where one component is a single ion conducting lithium salt with polyanion structure, and the other component is a solid polymer electrolyte matrix with the function of conducting lithium ions in solid state. This stable three-dimensional interpenetrating network structure is beneficial to inhibit the separation of the two components. At the same time, the introduction of hydrophilic and hydrophobic silica (SiO2) reduces the crystallinity of polyethylene oxide (PEO) and promotes the dissociation of lithium ions, respectively, thereby the ionic conductivity of the prepared single-ion conductor solid polymer electrolyte can be increased to 5.4 × 10−5 S cm−1 at 60 °C, and the lithium-ion transference number (tLi+) can be increased to 0.96. This method can also adjust the performance of the solid state polymer electrolyte through balancing the ration of composition by controlling the number of spinning nozzle. It provides a practical way to develop functional solid polymer electrolyte by electrospinning technology with nozzle design.

In lithium-ion batteries (LIBs), benefiting from various functional components, functional separators can possess different capabilities to cope with the risks in complex application scenarios. In this work, a functional separator based on the phosphonate-modified nano-scale silica ceramic particles is fabricated to reduce the safety risks in LIBs. Through an anhydrous polymerization process, dimethyl vinylphosphonate (DMVP), a kind of widely used flame retardants, is grafted on silica (SiO2). Then the modified SiO2 (mSiO2) is coated on the pristine polyethylene separator by a typical coating process. Combining the function of the ceramic and phosphonate, the modified ceramic separator displays substantially enhanced thermal stability, without visual thermal shrink up to 200 °C. The flame resistances of separator itself and pouch cells are also significantly improved, even though flammable electrolyte is added. Different from the case when the phosphonate is used as an additive in electrolyte, the phosphonate is fixed firmly on the separator and not easy to be embedded in carbon anode after battery cycles. The coin cells assembled with the modified separators are away from the irreversible loss of discharge capacity and low Coulombic efficiency for the first cycle, which can be attributed to the firm immobilization of organic phosphonate.

TiO2 nanoparticles with oxygen vacancies (B-P25) prepared by NaBH4 reduction method were coated onto PE separator to construct an active ceramic layer. The effect of the functional layer was carefully studied especially the interaction between oxygen vacancies on B-P25 and species in the liquid electrolyte. The B-P25 not only improves the affinity between the separator and electrolyte, but also improves the lithium ion transference number of the electrolyte, from 0.28 to 0.50. Based on the infrared spectroscopy results, it was found that B-P25 weakened the coordination between Li+ and EC, and partially desolvated the Li+-EC complex. Further theoretical calculation showed that the oxygen vacancies are more likely to adsorb EC molecules and indirectly promote the dissociation of Li+-EC, so that partially solvated Li+ has a stronger mobility and a higher lithium ion conductivity in the electrolyte. Therefore, B-P25 as an active layer assembled in LiFePO4 half-cell has better rate performance.

An effective and practical way to develop the lithium-ion power batteries with better safety performance is to increase the thermal shrinkage resistance of the separator at high temperature. In this work, a ceramic coating separator (CCS-PI) is manufactured by coating Al2O3 ultrafine powder and thermal stable polyimide binder onto the surface of the porous polyethylene (PE) membrane. CCS-PI exhibits no thermal shrinkage up to 160 °C in dry state and maintains stable when packed inner the cells up to 165 °C. Meanwhile CCS-PI hasn't been punctured during the hot metal rod piercing testing. The above results all prove that the CCS-PI has high thermo-stability. In addition, the CCS-PI presents higher electrolyte uptake, better wettability with the electrolyte and enabled high ionic conductance when it is saturated with liquid electrolyte. The cells with this CCS-PI show good cyclic performance. Therefore, as-prepared CCS-PI is a promising separator to improve thermal safety and capacity retention for lithium-ion power batteries.

More and more application scenarios of rechargeable batteries like lithium-ion batteries are set up in high-temperature environments, such as large-scale energy storage, aerospace, oil extraction industry, etc. Besides of electrolyte, the separator is also a vital part of the battery's sustainable operation at high temperature working condition, however traditional polyolefin separators and even ceramic-coated polyolefin separators have poor thermal stability. This article provides a fiber-supported aluminum oxide separator with improved flexibility and thermal stability because of the introduced flexible SiC fiber network skeleton. The ceramic separator exhibits electrochemical performance equivalent to commercial separators at room temperature. What's more, with high-temperature electrolyte system, its conductivity at 120 °C reaches 5.12 mS cm−1, which is 3 times higher than that at room temperature, so that the LiFePO4 half-cell has excellent rate performance that still maintains a specific capacity of 140 mAh g−1 for 200 cycles under a rate of 20C at 120 °C. Specially, the half-cell containing the high temperature stable fiber-supported aluminum oxide separator realizes cycles of charging at a high temperature with high rate as 20C and discharging at a room temperature with normal rate of 1C, which is of great guiding significance to practical application.

A novel way to manufacture single-ion conductor gel polymer electrolyte was reported in this work. Firstly, the γ-ray co-irradiation grafting is introduced to solve the difficulty on how to prepare single-ion conductor with considerable physical and chemical properties. Here, the PVDF-HFP is chosen as the polymer backbone for its excellent performance for polymer electrolyte while 2-acrylamido-2-methylpropanesulfonic acid (AMPS), a common and easily obtained double bond monomer with higher degree of negative charge delocalization, is chose to be the grafting monomer. To further promote the dissociation of Li+ ions from the polyanions, the prepared grafting copolymer is spun into a nonwoven membrane with high porosity. Besides, the grafting copolymer nonwoven fabric transforms the crystal form of PVDF-HFP to a better β-phase with higher polarity and maintains an approximative thermal stability. After plasticized by EC/DMC solvent, this prepared single-ion conductor gel polymer electrolyte (SIC-GPE) presence a high lithium-ion transference number (LTN) of 0.97 with an outstanding electrochemical stability and an appropriate battery performance.

A separator plays a crucial role in ensuring the safety in lithium-ion batteries (LIBs). However, commercial separators are mainly based on microporous polyolefin membranes, which possess serious safety risks, such as their thermal stabilities. Although many efforts have been made to solve these problems, they cannot yet fully ensure the safety of the batteries, especially in large-scale applications. Herein, we report a rational design of separator with substantially enhanced thermal features. We report how, by a simple dip-coating process, polydopamine (PDA) formed an overall-covered self-supporting film, both on the ceramic layer and on the pristine polyolefin separator, which made the ceramic layer and polyolefin separator appear as a single aspect and furthermore, this layer amended the film-forming properties of the separator. Combining the function of the ceramic and PDA, the developed composite-modified separator displays substantially enhanced thermal and mechanical stability, with no visual thermal shrink and can maintain its mechanical strength up to 230 °C when the polyethylene separator acts as the pristine separator.

In this work, the ceramic coating separator (CCS-CS) prepared with polyethylene (PE) separator, Al2O3 inorganic particles, carboxymethyl cellulose sodium (CMC) and styrene-butadiene rubber (SBR) mix binders is further modified by coating with a thin polydopamine (PDA) layer through a simple chemical deposition method. Compared with the bare ceramic coating separator, the PDA-modified CCS-CS (CCS-CS-PDA) exhibits excellent thermal stability, which shows no thermal shrinkage after storing at 200 °C for 30 min. Compared with the PE separator, both the uptake and wettability with the electrolyte and water of CCS-CS-PDA are improved significantly. Meanwhile, when saturated with liquid electrolyte, the CCS-CS-PDA also shows enabled high ionic conductance. Furthermore, the test of the electrochemical impedances changing with the temperatures suggests that only the PE separator exhibits no thermal shutdown behaviors, and the CCS-CS separator only has a shutdown temperature range from 138 to 160 °C, while the CCS-CS-PDA shows a shutdown temperature range from 138 to more than 200 °C. The cells prepared with the CCS-CS-PDA also show stable repeated cycling performance and good rate capacity at room temperature.