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Using a series of electrochemical performance tests and post‐mortem analysis, herein, the performance and aging mechanisms of high‐nickel lithium‐ion batteries after accelerated aging at different discharge rates are investigated. The results show that the loss of lithium ions and the generation of a solid electrolyte interphase are the main causes for capacity fading at relatively low aging discharge rates. When the aging rate increases to 3 C, the performance of the battery deteriorates significantly, and structural damage becomes the main reason for attenuation, which means that the aging mechanism changed. It is expected that this investigation will improve the safety performance of the retired high‐nickel ternary lithium batteries. [ABSTRACT FROM AUTHOR]

• New PCM filling methods with gradient thickness or conductivity were proposed. • PCM thickness optimization was studied via experiments and theoretical calculation. • A parameter of δ ct has been proposed for the PCM application in cylindrical batteries. • How the laying-aside time influenced cooling performance of PCM was studied. Phase change material (PCM) cooling, as an excellent option for ensuring safety via balancing heat distribution, has been widely used in the thermal management of lithium-ion battery. In this work, a simple PCM cooling structure has been designed. Then we systematically investigate its cooling behavior and the influence of several detailed factors on the performance, including the thickness and phase change temperature (PCT) of the PCM, as well as the laying-aside time during dynamic cycling. The experimental results show that a PCM module with a thickness of ∼10 mm presents the optimal cooling performance, consistent with the theoretical calculation, but the lower heat dissipation capability at the bottom of the battery should be taken into account when designing the PCM module. In addition, increasing the laying-aside time is also beneficial to enhancing the cooling efficiency, whereas the selection of the PCT is variable based on different specific applications and comprehensive requirements, particularly those targeting guaranteeing a higher capacity of the batteries. [ABSTRACT FROM AUTHOR]

Biomass/waste‐based porous carbon (PC) has been treated as the potential anodes for lithium‐ion battery (LIB). Nevertheless, significant challenge appears because it usually exhibits low inheritability of the nanostructure upon activation. In this work, we develop a kind of fiber‐like PCs for LIBs application by choosing waste cotton gloves as the carbon source. The obtained activated carbon fiber (ACF) shows a superior inheritable fiber‐like morphology and thus presents a SBET (Brunauer‐Emmett‐Teller surface area) of 1708 m2 g−1 coupled with a macro/meso/microporous structure. This kind of well‐inherited fiber framework is believed to reduce the electron migration resistance, while the hierarchically macro/meso/microporous structure can reduce the diffusion/transport resistance of the electrolyte and simultaneously increase the utilization of the surface area for Li+ storage. As a result, the obtained ACF exhibits attractive lithium storage performances, including a better reversible capacity of 515 mAh g−1 and high‐rate capability in comparison to most biomass/waste‐based PCs. A kind of waste cotton glove‐based activated carbon fiber (ACF) is fabricated. The obtained ACF presents a large surface area coupled with a hierarchically porous structure and a well‐retained fiber‐like skeleton, which can simultaneously minimize the diffusion/transfer resistance of the electrolyte/electron, and maximize the surface area utilization for lithium storage, thus exhibiting excellent lithium storage performances [ABSTRACT FROM AUTHOR]

Abstract: Rechargeable lithium–sulfur batteries have aroused great attention in recent years. Thousands of research articles are published, and among these publications, the majority are dedicated to improving the battery's performance through chemically and physically modifying the sulfur electrode, electrolytes, separator, and lithium anode. However, the single most important aspect, understanding the sulfur redox mechanism, is sparse and overwhelmed by the huge volume of work done on improving the battery's performance. Besides the intrinsic complexity of the sulfur redox chemistry, the most challenging task is to find an effective analytical technique for the quantitative and qualitative determination of the dissolved and solid polysulfides, including elemental sulfur. In this paper, the recent important research aiming to understand the redox mechanism of the sulfur electrode is reviewed in light of the unique analytical techniques used in the research. The review re‐affirms the complexity of the sulfur redox chemistry and lays the background for the future mechanistic research for Li–S batteries. [ABSTRACT FROM AUTHOR]

Constructing sufficient micropores and small mesopores for Li + storage while maintaining a developed hierarchical macro/mesoporous structure for rapid mass transfer are critical for porous carbons in lithium-ion battery (LIB) applications. Herein, a new kind of hierarchical macro–meso–microporous carbon with high surface area (HSHPC) for LIB application is successfully fabricated by using a porous network structured polymer as a precursor. The as-prepared HSHPC presents a 3D continuous macro/mesopore structure and ultrahigh surface area of 2602 m 2 g −1 . As a result, it exhibits a high specific capacity of 660 mAh g −1 and stable cycling performance during 100 cycles at a current density of 0.1 A g −1 . Furthermore, the ideal macro/mesoporous network is able to guarantee rapid ion diffusion and transfer, thus attaining an excellent high-rate performance in contrast to graphite. [ABSTRACT FROM AUTHOR]

For carbon-based anode materials of lithium-ion batteries, guaranteeing high surface area while maintaining developed mesoporosity remains a formidable challenge because the diffusion of electrolyte within mesopores is the rate-performance-limiting step. Herein, mesoporous activated carbon aerogel (MACA) is prepared based on the pore formation and widening effect of HPO. The as-prepared MACA demonstrates a high specific surface area (SSA) of 2161 m g with an extremely high mesopore ratio of 92 %. This well-defined mesopore-dominant nanostructure coupled with high SSA can provide large ion-accessible SSA for Li storage reactions as well as facilitate better mass transfer capability, especially at high charge-discharge rates. In consequence, MACA shows a much higher specific capacity of 610 mAh g at 0.1 A g and an excellent high-rate performance in contrast to other amorphous carbon materials and commercial anode of graphite. These encouraging results reveal the promising application of MACA for high-performance lithium-ion batteries. [ABSTRACT FROM AUTHOR]

Polystyrene-derived carbon with hierarchical macro-meso-microporous structure was prepared via a simple template-free method. As anode materials for lithium-ion batteries, the as-prepared hierarchical porous carbon (HPC) exhibited good electrochemical performance, attaining a stable capacity of 410 mAh g for over 100 cycles. It was also highlighted that, HPC showed an excellent high-rate performance in contrast to other amorphous carbon materials. These good lithium storage performances could be attributed to the developed nanostructures of HPC: (1) The continuous macro-/meso-pores were believed to facilitate rapid ion transport by serving as ion-buffering reservoirs/ion-transport pathways, especially at high current densities; (2) The small-sized nanopores including small mesopores and micropores in carbon nanoparticles provided many active sites for Li storage reaction; and (3) The as-constructed continuous carbon nanonetwork also represented an excellent conductive skeleton throughout the material. We hope that this class of HPC provides new opportunities for anode materials of LIBs. [ABSTRACT FROM AUTHOR]

A class of mesoporous wormholelike carbon (WMC) with controllable nanostructure was prepared by sol–gel method and then used as the anode material of lithium-ion batteries. Based on the experimental results, it is found that the nanostructure of the as-prepared WMC plays an important role in the electrochemical performances. A suitable mesopore size is necessary for a high performance carbon-based anode material since it can not only guarantee effective mass transport channels but also provide large surface area. As a result, F30 with a mesopore size of 4.4 nm coupled with high surface area of 1077 m 2 g −1 shows a reversible capacity of 630 mAh g −1 , much higher than commercial graphite and many other reported nanocarbons. [ABSTRACT FROM AUTHOR]

Carbon aerogel (CA) with 3-D continuous skeleton and mesopore structure was prepared via a microemulsion-templated sol–gel polymerization method and then used as the anode materials of lithium-ion batteries. It was found that the reversible specific capacity of the as-prepared CAs could stay at about 470 mA h g −1 for 80 cycles, much higher than the theoretical capacity of commercial graphite (372 mAh g −1 ). In addition, CA also showed a better rate capacity compared to commercial graphite. The good electrochemical properties could be ascribed to the following three factors: (1) the large BET surface area of 620 m 2 g −1 , which can provide more lithium ion insertion sites, (2) 3-D continuous skeleton of CAs, which favors the transport of the electrons, (3) 3-D continuous mesopore structure with narrow mesopore size distribution and high mesopore ratio of 87.3%, which facilitates the diffusion and transport of the electrolyte and lithium ions. [ABSTRACT FROM AUTHOR]

• Lengthwise thermal propagation indicating multi-layer propagation was studied. • Detailed propagation mechanism inside battery was studied with infrared imager. • The effects of heating modes on thermal failure propagation were investigated. Because of the multi-layer structure and the diversified connection modes of most battery modules, systematically investigating the thermal failure propagation principles and mechanisms of lithium-ion batteries is critical to provide early warnings and protection for thermal runaway. In this work, a series of experimental studies and mathematical deductions were conducted to investigate the propagation behavior of thermal failures within two types of cells under various heating modes, and their heat transfer mechanisms were analyzed. In general, the thermal runaway phenomenon in Li (Ni 1/3 Co 1/3 Mn 1/3) O 2 cells is more severe than that in LiCoO 2 cells. For different heating modes, lengthwise thermal failure propagation is more unlikely to occur in comparison with transversal thermal failure propagation; however, the former involves a more violent combustion. For different heating positions, heating near the positive pole results in the most violent phenomena. Additionally, a higher T max of 185.6 °C was obtained via middle heating in comparison with that obtained via heating on the poles. The temperature rising rate also varied, taking 1619, 1578, and 1699 s for the temperature to rise from 20 °C to 168.9 °C, 185.6 °C, and 173.4 °C through bottom, middle, and top heating, respectively. These phenomena were consequently ascribed to the different heat transfer rates along different directions inside the cells, including transversal/lengthwise propagation, and positive-pole-directional/negative-pole-directional propagation. These encouraging results may raise concerns about developing more precise and suitable surveillance and control measures to further enhance the thermal safety performance of cells/modules from both external and internal perspectives. [ABSTRACT FROM AUTHOR]

Nanosized silica is drawing attentions in lithium‐ion batteries because of its better cycling stability and lower cost compared to silicon. However, significant challenges appear at the uncontrollable and inhomogeneous nanostructure while coupling silica with carbon. Herein, a series of silica/carbon (S/C) composites with tunable nanostructure are developed based on the mechanism that hydrofluoric acid (HF) can control the gelating process of tetraethylorthosilicate (TEOS). By changing the HF/TEOS ratio, the size of the silica skeleton, surface area and porosity of the composites can be tailored precisely. As a result, the optimal lithium storage performance is obtained on the S/C composite with a silica size of ≈9 nm, surface area of 208 m2 g−1, and total pore volume of 0.24 cm3 g−1, including a specific capacity of 820 mAh g−1, superior cycling performance, and high‐rate capability. This can be attributed to the following reasons: 1) the suitable silica size of ≈9 nm simultaneously minimizes the Li+ migrating distance while maintaining the stability of the silica skeleton; 2) the rigid continuous carbon framework acts as a conductive skeleton and restricts the aggregation and volume change of the silica; 3) the porous structure plays roles in buffering the volume change and facilitating the electrolyte transfer. A series of silica/carbon anodes for lithium‐ion batteries are developed. With controlling their nanostructure via changing the HF amount, the optimal performance is obtained on the anode with a silica size of 9 nm and surface area of 208 m2 g−1, including a capacity of 820 mAh g−1, superior cycling and high‐rate performance. [ABSTRACT FROM AUTHOR]

Organic batteries free of toxic metal species could lead to a new generation of consumer energy storage devices that are safe and environmentally benign. However, the conventional organic electrodes remain problematic because of their structural instability, slow ion-diffusion dynamics, and poor electrical conductivity. Here, we report on the development of a redox-active, crystalline, mesoporous covalent organic framework (COF) on carbon nanotubes for use as electrodes; the electrode stability is enhanced by the covalent network, the ion transport is facilitated by the open meso-channels, and the electron conductivity is boosted by the carbon nanotube wires. These effects work synergistically for the storage of energy and provide lithium-ion batteries with high efficiency, robust cycle stability, and high rate capability. Our results suggest that redox-active COFs on conducting carbons could serve as a unique platform for energy storage and may facilitate the design of new organic electrodes for high-performance and environmentally benign battery devices. [ABSTRACT FROM AUTHOR]

• H-bond cross-linked Cellulose/PI-COOH composite separator is first prepared. • Cellulose/PI-COOH separator has 3D interconnected network from H-bond crosslinking. • Cellulose/PI-COOH separator possesses superior mechanical and thermal properties. • H-bond enhances the affinity and wettability of the separator toward electrolyte. • Cellulose/PI-COOH separator shows excellent cycle and rate performance in LIBs. Polyimide (PI) membranes with superior chemical resistance, insulation and self-extinguishing are attracting numerous attentions as the separators of lithium-ion batteries (LIBs), but significant challenges of low mechanical strength and poor electrolyte affinity still remain. Herein, a new kind of environmentally friendly hydrogen-bond (H-bond) cross-linked cellulose/carboxylated PI (Cellulose/PI-COOH) nanofiber composite separator is prepared via electrospinning followed by imidization and alkaline hydrolysis. Besides inheriting the high porosity of the pristine PI separator to absorb the electrolyte, the three-dimensional interconnected structure resulting from H-bond cross-linking is beneficial to improving the mechanical properties of the composite separator, and thereby delivers a tensile strength of 34.2 MPa, 5 times higher than that of the pristine PI separator (6.8 MPa). Meanwhile, the exposed hydroxyl groups on the cellulose, and carboxyl and imino groups on the carboxylated PI can also enhance the electrolyte affinity and wettability of the Cellulose/PI-COOH separator, which plays an important role in increasing the ionic conductivity (0.51 mS cm−1) and widening the electrochemical stability window (∼5.1 V). Consequently, compared with the polypropylene separator and PI separator, the H-bond cross-linked Cellulose/PI-COOH separators show better cycle performance and rate performance when adopted in lithium iron phosphate (LiFePO 4) and lithium cobaltate (LiCoO 2) half-cells. For example, the Cellulose/PI-COOH-based LiFePO 4 half-cell demonstrates the highest initial discharge capacity of 166.2 mAh g−1 and capacity retention rate of 90%, much higher than the pristine PI-based LiFePO 4 half-cell (114.6 mAh g−1, 86%). Furthermore, the much enhanced tensile strength, flexibility, thermal stability and flame-resistance of the Cellulose/PI-COOH separator are believed to greatly enhance the safety performance of the obtained LIBs. [ABSTRACT FROM AUTHOR]

To conquer the intrinsic drawbacks of commercial polyolefin-based separators, cross-linked fiber porous membranes made of heat-resistant polymers are recently developed to meet the demands of advanced lithium-ion batteries (LIBs) with high energy density and safety. Herein, for the first time, we present the recent progress of cross-linked fiber membranes as separators for LIBs. We briefly introduce the basic functions and performance requirements of porous separators for LIBs, and highlight the superiority of the cross-linked fiber porous separators compared to the conventional fiber separators. Then, we elaborate on the existing preparation techniques of cross-linked fiber separators in a separate section, including the thermal crosslinking, adhesion and alkaline hydrolysis methods, along with commenting on their respective advantages and functions. Meanwhile, several typical cross-linked fiber separators reported recently are discussed. On the above basis, the current research gaps and future research challenges of cross-linked fiber separators are summarized and prospected. [ABSTRACT FROM AUTHOR]

Abstract: Monoclinic phase LiFeSO4F has a triplite like structure in which Li+/Fe2+ is fully mixing. Not 100% Li can be extracted from the lattice easily even at a rate of C/20, and the valence of Fe changes between ca +2 and +2.5 observed by XANES for a Li/LiFeSO4F cell cycled between 2.2 and 4.6 V. Two-phase reaction mechanism is verified by GITT due to the appearance of a flat plateau, and large polarization appears after more than 50% Li extracted from triplite-LiFeSO4F. A core–shell model has been mentioned to explain its extreme polarization. In the fully mixing structure, there is no intact long-range pathway for Li+, so leading to sluggish kinetics effect and “inert” Li+ in the lattice. [Copyright &y& Elsevier]

Abstract: Nanosized LiVPO4F/C cathode material is synthesized by heating the precursor obtained through a sol–gel method with mechanical blending assist. XRD and SEM results indicate that LiVPO4F/C composite is pure phase, possesses good crystallinity and uniform particle size distribution. The average size of LiVPO4F/C is about 40nm. In the range of 3.0–4.6V, the LiVPO4F/C electrode presents excellent cyclic performance. At 0.1C rate, it delivers initial discharge capacity of about 138.3mAhg−1 and maintains 135.7mAhg−1 after 50 cycles. Even carried out at 55°C, this composite displays discharge capacities of 119.3mAhg−1 at the rate of 0.5C and 104.1mAhg−1 at the rate of 1C, and maintains about 115.5 and 97.4mAhg−1 after 30 cycles, respectively. [Copyright &y& Elsevier]