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Lithium‐ion batteries (LIBs) have gained widespread attention due to their numerous advantages, including high energy density, prolonged cycle life, and environmental friendliness. Nevertheless, their electrochemical performance deteriorates rapidly under extreme temperature conditions, accompanied by a series of safety issues. Electrolyte optimization has emerged as a crucial and feasible strategy to expand the operational temperature range of LIBs. This review comprehensively summarizes the challenges, advances, and characterization methodologies of electrolytes at both subzero and elevated temperatures. Initially, it discusses the degradation mechanisms of different types of electrolytes at extreme temperatures, integrates recent advances, and offers insights into future research directions. Subsequently, various experimental techniques are systematically presented to evaluate the fundamental physical properties, stability, and dynamic behaviors of electrolytes in non‐ambient environments. Finally, it also provides relevant computational methods across the electronic, molecular, and macroscopic scales, and explores the application of high‐throughput techniques in this field. This review offers valuable guidance for breaking the working temperature limits of electrolytes and promoting the development of next‐generation LIBs. [ABSTRACT FROM AUTHOR]

Cross‐linked polyethylene glycol‐based resin (c‐PEGR) is constructed by a ring‐opening reaction of polyethylene glycol diglycidyl ether (PEGDE) with epoxy groups and polyether amine (PEA) with amino groups. By confining the hydroxyl groups with inferior oxidative stability to the c‐PEGR backbone, the oxidation potential of the PEG‐based polymer material with reduced reactivity is boosted to 4.36 V. The c‐PEGR based gel electrolyte shows excellent flexibility, lithium‐ion transport, lithium compatibility, and enhanced oxidation stability, and is successfully applied to a 4.35 V lithium cobaltate (LCO)||lithium (Li) battery system. A quasi‐static linear scanning voltammetry (QS‐LSV) method is proposed for the first time to accurately measure the oxidation potential and electrochemical stability window of materials with low conductivities such as polymers, which possesses the advantages of high accuracy and short test time. This work provides new insights and research techniques for selecting polymer electrolytes for high‐voltage flexible lithium‐ion batteries (LIBs). [ABSTRACT FROM AUTHOR]

Cross-stacked super-aligned carbon nanotube (SACNT) films are promising for use as current collectors in lithium-ion batteries because of their outstanding capability to decrease the weight and thickness of inactive material and strong adhesion to the electrodes. However, the relatively poor conductivity of SACNT films may limit their application to large-size electrodes or at high current rate. Herein, a facile approach is proposed to improve the conductivity of SACNT films by electron-beam deposition of a thin metal film on their surface. Such modification lowers the sheet resistance by three orders of magnitude while keeping the extremely small fraction of SACNT current collectors. The metal-coated SACNT films strongly inhibit polarization during the electrochemical reaction, resulting in improved cell performance compared with that of metal and uncoated CNT current collectors. The improvement in conductivity and cell performance achieved by this approach is so large that the effect of the increase of inactive material is overwhelmed, leading to increased gravimetric energy density. [ABSTRACT FROM AUTHOR]

Abstract: Super-aligned multi-walled carbon nanotubes (MWCNTs), which had been produced in large-scale, were oxidized by H2O2 and HNO3. The surface defects and oxygen-containing functional groups introduced during the oxidizing process were characterized by Raman spectroscopy and X-ray photoelectron spectroscopy. The surface modification of MWCNTs improved the electrochemical properties. As a result, H2O2-treated and HNO3-treated MWCNTs displayed reversible capacities of 364mAh/g and 391mAh/g, respectively, after 80 galvanostatic cycles, corresponding to 143% and 154% improvements compared with pristine MWCNTs. The rate capability was also increased. At a current density of 3500mA/g, H2O2-treated and HNO3-treated MWCNTs exhibited reversible capacities of 66mAh/g and 156mAh/g, respectively. In contrast, pristine MWCNTs were only able to deliver 27mAh/g at this current density. [Copyright &y& Elsevier]

Abstract: Mn3O4 nanoparticles anchored on continuous super-aligned carbon nanotube (SACNT) films are synthesized by decomposition of Mn(NO3)2. In the Mn3O4/SACNT composite electrodes, SACNT film is capable of serving as both the conductive pathway and structural scaffold, therefore no binder, extra conductive agent, or current collector is needed. The electrochemical performance of the Mn3O4/SACNT composite electrode is significantly affected by the particle size of Mn3O4. With smaller particle size, the electrode displays smaller voltage hysteresis and much improved reversibility and rate capability. The Mn3O4/SACNT electrodes with particle size of Mn3O4 less than 10 nm show a capacity retention of 95% after 100 cycles at 1 C and a high rate capacity of 342 mAh g−1 at 10 C (based on the total mass of the electrode), suggesting their advantages over the commercial graphite anode and potential in practical applications. [Copyright &y& Elsevier]

Abstract: Porous Li4Ti5O12 nanoclusters with high surface area are synthesized by a facile solution-based method followed by low-temperature calcination. The Li4Ti5O12 nanoclusters present the key characteristics needed to serve as high-performance negative electrodes for lithium ion batteries, including nano-sized dimension of the Li4Ti5O12 clusters (50–100 nm) for short ion and electron transfer path, and high surface area (142 m2 g−1) with mesoporosity (pore diameter 2–6 nm) for easy access to the electrolyte and efficient ion transport. Based on these characteristics, the Li4Ti5O12 electrode delivers an initial capacity of 173 mAh g−1 at the rate of 0.5 C, comparable to its theoretical capacity. Excellent cycling stability at high rates is achieved in the Li4Ti5O12 electrode, offering potential to serve as a negative electrode material for high rate lithium ion battery applications. [Copyright &y& Elsevier]

A new cobalt free LiFeO2–Li2MnO3 based solid solution with a composition of Li(Li0.23Mn0.47Fe0.2Ni0.1)O2 is developed to obtain high capacity and better cycling stability. A new citric acid assisted sol–gel process including three-step of “preparation of wet gel—formation of spray-dried gel—annealing at high temperature” is proposed. The results show that uniform Li(Li0.23Mn0.47Fe0.2Ni0.1)O2 solid solution with pure hexagonal phase (or monoclinic phase) can be successfully prepared even at low temperature of 600 °C. Increasing the annealing temperature can improve the crystallization and cation-ordering of Li(Li0.23Mn0.47Fe0.2Ni0.1)O2, but severe agglomeration to form large size secondary particles (1–10 μm) over 750 °C leads to the decreased capacity. The sample annealed at optimized temperature of 700 °C shows uniform fine well-crystallized particles with 100–200 nm diameters, high capacity of 277.4 mAh g−1 at 10 mA g−1 (0.04C) and better cycling stability at different rate. It presents a capacity of 188 mAh g−1 at 75 mA g−1 (0.3C) and 90.4% capacity retention after charge–discharged 100 cycles. [ABSTRACT FROM AUTHOR]

Abstract: A glycol based solvothermal process combined with carbon coating is attempted to prepare nano particle LiFePO4 cathode materials for Li-ion batteries. Different concentration of starting materials, process time, pH values and process temperature are tried. Samples are characterized by XRD and SEM analysis. A carbon coating process with sucrose is used to make LiFePO4/C composites. The optimized sample delivers capacity retention of 100% after 100 cycles at 100% depth of discharge with initial columbic efficiency of 98.9%, cycling capacity of about 163 mAh g−1 at 0.1 C-rate, 159 mAh g−1 at 0.5 C-rate, 157.8 mAh g−1 at 1 C-rate, and 145.9 mAh g−1 at 5 C-rate, under the electrode formula of 80% LiFePO4/C composites, 10% carbon black and 10% binder. This study shows that proposed process can be a potential promising way to prepare high performance LiFePO4 cathode materials for lithium ion batteries. [Copyright &y& Elsevier]

Abstract: Super-aligned carbon nanotube (SACNT) films drawn from SACNT arrays are uniformly introduced into LiCoO2–Super P composite cathodes by a cold-rolling method, and a hybrid conductive network consisting of SACNTs and carbon black powders is obtained. This attempt results in reduced percolation threshold and increased conductivity of the LiCoO2–Super P cathodes with addition of less than 0.01 wt% of SACNTs. The strength and flexibility of the LiCoO2–Super P–SACNT composites can be improved significantly due to the excellent mechanical properties of SACNTs. The continuous SACNT films play an important role for the formation of a homogeneous network for long-range conductive pathways. Super P is also an essential component to form short-range conductive pathways. By comparing with control samples that only contain Super P or SACNT films, we demonstrate that the LiCoO2–Super P–SACNT composites possess the best cycling stability (150 mA h g−1 at 0.1 C with a capacity retention of 99.7% after 50 cycles) and rate capability (87 mA h g−1 at 5 C). Combining both short-range and long-range conduction, the hybrid Super P-SACNT conductive network manifests itself as a promising strategy to improve the battery performances with a minimum amount of conductive fillers. [Copyright &y& Elsevier]

A uniform Fe3O4sheath is magnetronsputteredonto aligned carbon nanotube (CNT) scaffolds that are directly drawnfrom CNT arrays. The Fe3O4–CNT compositeelectrode, with the size of Fe3O4confined to5–7 nm, exhibits a high reversible capacity over 800 mAh g–1based on the total electrode mass, remarkable capacityretention, as well as high rate capability. The excellent performanceis attributable to the superior electrical conductivity of CNTs, theuniform loading of Fe3O4sheath, and the structuralretention of the composite anode on cycling. As Fe3O4is inexpensive and environmentally friendly, and the synthesisof Fe3O4–CNT is free of chemical wastes,this composite anode material holds considerable promise for high-performancelithium ion batteries. [ABSTRACT FROM AUTHOR]

The research in high performance flexible lithium ion batteries (FLIBs) thrives with the increasing demand in novel flexible electronics such as wearable devices and implantable medical kits. FLIBs share the same working mechanism with traditional LIBs. Meanwhile, FLIBs need to exhibit flexibility and even bendable and stretchable features. The development of FLIBs highly relies on the improvement of flexible electrodes and battery designs to achieve high performance and stability under mechanical deformation. In this review, recent advances and progress on the development of FLIBs are concerned. Two specific research strategies of FLIBs are discussed in detail: preparation of flexible battery components (including electrodes, current collectors, and electrolytes) and flexible structure designs or assembly methods of FLIBs. Finally, challenges and perspectives for developing high performance FLIBs are presented. • The latest progress of flexible lithium batteries (FLIBs) is reviewed. • Two research routes to achieve FLIBs are summarized. • The challenges of FLIBs in material selection and structural design are analyzed. • The key points of future development of FLIBs are listed. [ABSTRACT FROM AUTHOR]