关键词： nitrogen doping   lithium lanthanum titanate   solid-state electrolyte   lithium battery   composite electrolyte   nanofiber  

摘要： Currently cation doping is common for improving ionic conductivity of metal oxide-based lithium-ion conductors. In this work, anions (nitrogen ions) have been doped to perovskite Li3xLa2/3 - xTiO3 (LLTO) nanofibers by heat treatment in the ammonia-containing atmosphere, and substituted for oxygen anions partially in the perovskite structure. Density-functional theory (DFT) calculation results reveal that nitrogen doping weakens the bonding of Li ions on the A sites in perovskite ABO(3) structure and allows for larger lattice distortion, reducing the activation energy for Li-ion hopping in both the forward and backward jumping directions. Experimental results have also confirmed that nitrogen doping has improved ionic conductivity of LLTO. Nitrogen-doped LLTO nanofibers have been incorporated with a poly (vinylidene fluoride)-co-hexafluoropropylene (PVDF-HFP) polymer to form a solid-state composite electrolyte, which exhibits ionic conductivity of 3.8 x 10(-4) S center dot cm(-1) at room temperature and an electrochemical stability window of up to 4.9 V vs Li divide Li+. The all-solid-state Li metal divide composite electrolyte divide LiFePO4 lithium batteries, which employ nitrogen-doped LLTO nanofibers, show better rate capability and cycling stability at room temperature than the counterparts with pristine LLTO nanofibers.

关键词： ASSLBs   mechanically interlocked polymers   molecular shuttles   polyrotaxane   solid polymer electrolytes  

摘要： The mobility of molecular shuttles inside a mechanically interlocked polymer (MIP) can improve the ionic conductivity and electron transport capacity of a solid polymer electrolyte (SPE) and maintain a mechanically tough structure. The polyrotaxane-based MIP electrolyte with a necklace-like molecular structure exhibits high ionic conductivity (sigma = 5.93 x 10(-3) S cm(-1) at 25 degrees C and 1.44 x 10(-2) S cm(-1) at 60 degrees C), a high Li+ ion transference number (t(+) = 0.71), and high electrochemical oxidation stability (approximate to 4.7 V vs Li+/Li). When SPEs are used in Li-based batteries, a high Coulombic efficiency (>= 98.5%), an excellent rate capability, and fast charging (>= 2C) can be achieved using a "built-in molecular shuttle" design.

关键词： solid state   polymer electrolyte   microporous   wrinkle   polymer blend   Li-ion batteries  

摘要： Solid-state lithium batteries using solid polymer electrolytes can improve the safety and energy density of batteries. Smoother lithium-ion channels are necessary for solid polymer electrolytes with high ionic conductivity. The porosity and channel structure of the polymer film affect the transfer of lithium ions. However, their controllable synthesis remains a big challenge. Here, we developed a simple synthesis approach toward wrinkled microporous polymer electrolytes by combining the amphoteric (water solubility and organic solubility) polymer in three polymer blends. The homogeneous blend solution spontaneously wrinkled to vertical fold channels as the solvent evaporated. Two minor polymers, poly(vinyl pyrrolidone) (PVP) and polyetherimide (PEI), formed close stacks, and Janus PVP was dispersed in the poly(vinylidene fluoride) (PVDF) matrix. The interfacial tensions between the three polymers were different, so stress was produced when they solidified. The solvent was evaporated to the top layer of the polymers when the temperature increased. The bottom layer wrinkled owing to the stress during solidification. The evaporation of the solvent generated micropores to form the lithium-ion channel. They helped Li+ transference and created a wrinkled microporous PVDF-based polymer electrolyte, which achieved an ionic conductivity of 5.1 x 10(-4) S cm(-1) and a lithium-ion transference number of 0.51 at room temperature. Meanwhile, the good flame retardancy and tensile strength of the polymer electrolyte film can improve the safety of the battery. At 0.5C and room temperature, the batteries with a LiFePO4 cathode and the wrinkled microporous LiTFSI/PEI/PVP/PVDF electrolyte reached a high discharge specific capacity of 122.1 mAh g(-1) at the 100th cycle with a Coulombic efficiency of above 99%. The results of tensile and self-extinguishing tests show that the polymer electrolyte film has good safety application prospects.

关键词： composite solid electrolyte   modified porphyrin   ordered ion channel   intermolecular interaction   solid-state lithium battery  

摘要： Porphyrins and their derivatives are a unique class of multifunctional and modifiable p-conjugated heterocyclic organic molecules, which have been widely applied in the fields of optoelectronic devices and catalysis. However, the application of porphyrins in polymer electrolytes for all-solid-state lithium-ion batteries (ASSLIBs) has rarely been reported. Herein, porphyrin molecules modified by polyether chains are used for composite solid-state polymer electrolytes (CSPEs) for the first time. The introduction of a modified porphyrin in an electrolyte can not only promote the electrochemical properties by constructing ordered ion channels via the intermolecular interaction between pi-conjugated heterocyclic porphyrins, but also significantly improve the mechanical strength and interface contact between the electrolyte membrane and the lithium metal anode. Consequently, the all-solid-state batteries assembled by the modified porphyrin composite polymer electrolyte, LiFePO4 cathodes, and Li anodes deliver a higher discharge capacity of 158.2 mA h g(-1) at 60 degrees C, 0.2 C, which remains at 153.6 mA h g(-1) after 120 cycles with an average coulombic efficiency of similar to 99.60%. Furthermore, the flexible porphyrin-based composite polymer electrolyte can also enable a Li parallel to LiCoO2 battery to exhibit a maximum discharge capacity of 108.6 mA h g(-1) at 60 degrees C, 0.1 C with an active material loading of 2-3 mg cm(-2), which is unable to realize for the corresponding batteries with a pure PEO-based polymer electrolyte. This work not only broadens the application scope of porphyrins, but also proposes a novel method to fabricate CSPEs with improved electrochemical and mechanical properties, which may shed new light on the development of CSPEs for next-generation high-energy-density lithium-ion batteries.

关键词： Cryogenic engineering   Solid polymer electrolytes   All-solid-state lithium batteries   4 V-class   Room temperature  

摘要： Solid polymer electrolytes (SPEs) are promising candidates for all-solid-state lithium batteries (ASSLBs) due to their advantages of good interfacial adhesion and shape flexibility. However, the low ionic conductivity at room temperature (RT) and inferior electrochemical stability at high voltages limit the practical applications of SPEs. In this work, we demonstrate a cryogenic engineering to improve PEO-based SPEs for ASSLBs operated at RT. The rapid in situ cooling process will lead to the uniform formation of PEO crystal nuclei, which can limit the PEO crystal growth in SPEs. The novel crystallization structure could promote the ionic conductivity of SPEs effectively. Such improved cryogenic SPEs display a superior ionic conductivity of 2.17 x 10(-5) S cm(-1) and a superior electrochemical stability at RT. A discharge capacity of 154.9 mAh g(-1) can be achieved at 0.1 C and RT when LiFePO4 (LFP) is used as the cathode. The discharge capacity can remain at similar to 98%, even after 100 cycles performed at 0.1 C. Notably, cryogenic SPEs can be utilized in 4 V-class ASSLBs. A high discharge capacity of 118 mAh g(-1) can be achieved at 0.2 C and RT with the LiNi0.6Co0.2Mn0.2O2 (NCM622) as the cathode and can retain a 94.1% capacity even after 100 cycles. These extraordinary performances of cryogenic SPEs break new ground for the fabrication of ASSLBs operated at RT and high voltages.

关键词： CMC-Li derivative   All-solid-state battery   Polymer electrolyte   PI non-woven fabric   Hybrid membrane  

摘要： A novel PEO/CMC-Li@PI hybrid solid polymer electrolyte membrane was designed/assembled by utilizing the polyethylene oxide (PEO) as matrix, the modified N-carboxymethyl chitosan (CMC-Li) as the facilitator to accelerate the transport of lithium ions and the as-prepared polyimide (PI) non-woven fabric as supporting framework. The CMC-Li was firstly synthesized and then combined with PEO and PI non-woven fabric to assemble PEO/CMC-Li@PI membrane using in all solid-state battery (ASSB). The microscopic morphology of the PEO/CMC-Li@PI hybrid membrane was characterized by SEM images. The membranes thermodynamic behaviors were analyzed by the DSC/TG curves, showing that the T-m of the PEO/CMC-Li@PI decreased to 46.8 degrees C. When assembled into all-solid-state battery, the PEO/CMC-Li@PI membrane demonstrated the high ionic conductivities of 3.16 x 10-5 S/cm (30 degrees C) and 3.15 x 10-4 S/cm (60 degrees C) calculated from EIS spectra. The electrochemical window of the PEO/CMC-Li@PI cell was measured up to similar to 5 V at 60 degrees C. Moreover, the cell with PEO/CMC-Li@PI also delivered excellent electrochemical performances by comparing with other membranes. The high discharge capacities and cycling stability in PEO/CMC-Li@PI cell were assigned to the enhanced ionic conductivity by the added CMC-Li derivative and the improved mechanical properties by the PI non-woven fabric skeleton. The fabrication strategy of the novel PEO/CMC-Li@PI membrane may provide some new design directions for the solid polymer electrolytes in all-solid-state battery. (C) 2021 Elsevier Ltd. All rights reserved.

关键词： 锂离子电池   聚合物   电解质   室温  

摘要： 目前,大多数聚合物固态电解质在室温下离子电导率较低,约为10^(–8)~10^(-6) S/cm,且对温度存在着较大的依赖性,仍无法满足高性能室温固态锂电池的实际应用需要。基于此,本文先介绍了室温聚合物电解质在锂离子电池中应用的主要研究进展及其优缺点。然后,从物理调控、化学调控等多角度重点阐述了室温聚合物电解质(包括全固态聚合物电解质、准固态聚合物电解质)的制备工艺、优化与改性方法、作用机理等在电池中应用的主要研究进展和现状。最后,对锂离子电池用室温聚合物电解质存在的挑战和未来可能发展趋势进行了展望。

关键词： applications   batteries and fuel cells   polyelectrolytes   waterborne polyurethane  

摘要： Solid polymer electrolyte (SPE)-based lithium batteries have easy processing and safety for energy vehicles and storage. However, the preparation process of SPEs mostly used a lot of organic solvents, which will threaten human living space and body health. Herein, a novel green solid polymer electrolyte (ionic liquid type waterborne polyurethane, IWPUS) without no organic solvents was prepared from hybrids of ionic liquid-based waterborne polyurethane (IWPU) and LiClO4. The structure and properties of IWPUS were investigated by IR, SEM, XRD, TGA, ion conductivity test. The results showed that Li+ of LiClO4 could coordinate with -C(sic)O- and -C-O-C- in the polyurethane matrix. LiClO4 had been well dispersed in IWPU. The conductivity of IWPUS increased with the increase of LiClO4 content. The higher conductivity of IWPUS with 20% LiClO4 at 80 degrees C was 1.8 x 10(-4) s center dot cm(-1). IWPUS based on ionic liquid-based waterborne polyurethane would be promised to become an environmentally friendly candidate for all solid-state lithium ion batteries.

关键词： 聚合物电解质   锂负极   界面   枝晶   固态锂电池  

摘要： 动力电池领域对锂二次电池的能量密度和安全性提出了更高要求,研究高能量密度固态锂电池对发展新能源产业具有重要意义。相比传统的有机电解液锂离子电池,采用聚合物固体电解质的聚合物固态锂电池不但具有明显提升的安全性,而且能够匹配高容量电极材料,实现能量密度的有效提升。聚合物固态锂电池是最有前景的锂二次电池之一,然而聚合物固体电解质与锂负极间仍存在严重的界面副反应、锂负极表面易生长枝晶等问题。近年来,通过电解质成分调控、电解质力学性能提升、电解质/锂负极界面调控和匹配三维锂负极等手段,聚合物基固态锂电池性能明显提升。基于此,本文介绍了常见的聚合物固体电解质及其与锂负极间的界面挑战,从添加无机填料、使用高强度基底膜、分级层状结构设计、构筑界面缓冲层、交联网络设计以及固态锂负极保护等几个方面综述了提升聚合物基电解质/锂负极界面稳定性的最新研究成果,最后对解决聚合物固体电解质/锂负极界面兼容性的研发方向和发展趋势进行了展望。

关键词： solid-state electrolytes   space-charge models   Li-ion batteries   polymer-ceramic electrolyte   molecular dynamics   solid-solid interface   GSHMC  

摘要： Unlocking the full potential of solid-state electrolytes (SSEs) is key to enabling safer and more-energy dense technologies than today's Li-ion batteries. In particular, composite materials comprising a conductive, flexible polymer matrix embedding ceramic filler particles are emerging as a good strategy to provide the combination of conductivity and mechanical and chemical stability demanded from SSEs. However, the electrochemical activity of these materials strongly depends on their polymer/ceramic interfacial Li-ion dynamics at the molecular scale, whose fundamental understanding remains elusive. While this interface has been explored for non-conductive ceramic fillers, atomistic modeling of interfaces involving a potentially more promising conductive ceramic filler is still lacking. We address this shortfall by employing molecular dynamics and enhanced Monte Carlo techniques to gain unprecedented insights into the interfacial Li-ion dynamics in a composite polymer-ceramic electrolyte, which integrates polyethylene oxide plus LiN(CF3SO2)(2) lithium imide salt (LiTFSI), and Li-ion conductive cubic Li7La3Zr2O12 (LLZO) inclusions. Our simulations automatically produce the interfacial Li-ion distribution assumed in space-charge models and, for the first time, a long-range impact of the garnet surface on the Li-ion diffusivity is unveiled. Based on our calculations and experimental measurements of tensile strength and ionic conductivity, we are able to explain a previously reported drop in conductivity at a critical filler fraction well below the theoretical percolation threshold. Our results pave the way for the computational modeling of other conductive filler/polymer combinations and the rational design of composite SSEs.