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The commercial electrolyte of lithium-ion batteries (LIBs) is usually liquid state supplemented by a porous polyolefin separator to prevent short circuit. Recent years, polymer electrolyte shows great potential for its flexibility and enhanced safety. And novel single-ion conductor gel polymer electrolyte (SIGPE) could effectively suppress the anion polarization by immobilizing anions on the polymer bone. Further enhancing the thermal stability of SIGPE plays a significant role for the safety of the LIBs. Herein, a novel bifunctional core–shell structured composite was prepared, consisting of thermal stable polyimide as core and a composite single-ion conductor polymer. The relations of fiber morphology with spinning parameters and heat-treatment temperature were studied carefully. As a result, the composite core–shell structured membrane shows excellent high dimensional thermal stability up to 190 °C. Moreover, when the charged half battery was stored at 150 °C, the core–shell structured SIGPE cell shows excellent potential stability while ordinary cell quickly short out, greatly enhancing the safety of the LIBs. The ionic conductivity of the plasticized gel electrolyte could reach 1.7*10−5 S cm−1 with a Li-ion transference number of 0.76. The assembled LiFePO4 battery shows stable cycle performance and remained 85% capacity after 100 cycles.

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.

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.

Single ion conductor has been realized as a new path to reduce polarization and improve electrochemical performance of the lithium ion batteries (LIBs). In this work, a novel single ion conductor gel polymer electrolyte (SIGPE) was designed via free radical polymerization, co-electrospinning and plasticizing process. The molecular structure information of the single ion polyanionic salt P(MPEGA-AMPSLi) of the SIGPE is carefully verified. The SIGPE shows high ionic conductivity of around 2.8 × 10−5 S/cm at 25 °C, high lithium ion transference number of 0.75, wide electrochemical window of 4.7 V as well as a stable cycle performance at 25 °C and 60 °C. The plasticizing mechanism of the gel polymer electrolyte has also been modeled and studied theoretically by molecular dynamics simulation. The results display a positive effect of the plasticizing in promoting the ionization of Li ions, increasing the diffusion coefficient of Li ions from 8.05 × 10−11 cm2/s to 1.37 × 10−9 cm2/s.