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Due to difficulties with scalability and practical utilization, Si/graphene composites are not yet used as anodes for commercially available lithium-ion batteries. In this paper, we report an accessible and cost-effective ball-milling route to synthesize Si and graphene composites. By introducing amino- and carboxyl-groups, covalent linkage between Si nanoparticles and graphene is created, which solves serious issues of hybrids like poor dispersion and weak connection. This composite features a unique structure, where Si nanoparticles are uniformly attached to the surface or embedded into the inter-layers of the graphene. When used as anodes of lithium-ion batteries, this composite can retain a reversible capacity of 1516.23 mAh g−1 after 100 cycles at 100 mA g−1. It also exhibited excellent ultra-long-term cycling stability and high rate performance. The electrochemical performance is superior to most reported Si/graphene composites without chemical bonds at the interface, which indicates that covalent bonding can effectively inhibit the irreversible sliding of Si nanoparticles. In addition, EIS measurement had revealed a lower transfer resistance and faster Li-ions diffusion of Si@APTES/ f -Gr, suggesting the integrity of graphene after functionalization. The proposed functionalization-assisted ball-milling approach, therefore, probably enables the large-scale production of Si/Graphene as anodes in high-performance batteries in the future. [Display omitted] [ABSTRACT FROM AUTHOR]

Ceramic solid electrolytes are crucial for electrochemical devices, including emerging solid-state batteries. However, they are susceptible to degradation and failure under harsh conditions, leading to dendrite growth, cracking and short circuits. While longitudinal lithium dendrites have been identified as a primary degradation mechanism, recent experiments have revealed transverse reduction fronts and bowl-shaped cracks that differ significantly from the longitudinal picture. We propose an electrochemical shock model to explain these transverse degradation modes in solid electrolytes (SE) and mixed ionic-electronic conductors (MIEC), where SE is taken to be the very weakly electronic leaking limit of MIEC. The model describes a transverse layer with an abrupt oxygen potential jump over a short distance, caused by the electronic transport bottleneck on the Brouwer diagram. Using Li 7 La 3 Zr 2 O 12 as an example, we demonstrate that even minor nonuniform lithium distribution associated with an electrochemical shock can induce stress concentrations, resulting in electrolyte cracking and bowl-shaped cracks. The electrochemical shock model highlights the significance of finite electronic conductivity in the degradation of SE and MIEC, providing insights for the design of durable solid electrolytes. [Display omitted] [ABSTRACT FROM AUTHOR]

ABSTRACT: In this paper, poly(lithium acrylate‐co‐butyl acrylate) [P(AALi‐co‐BA)] was synthesized, and a P(AALi‐co‐BA)‐coated polypropylene (PP) separator was prepared by a simple dip‐coating process. In contrast to the conventional thick, dense gel polymer coating layer, a thin P(AALi‐co‐BA) layer was formed on the PP separator, which had less influence on the pore structure of the original PP separator and was beneficial for the migration of lithium ions through the separator. Furthermore, the AALi units in the copolymer could improve the wettability of the separator, while the BA units provided the separator with strong adhesion to the electrodes. As expected, the modified separators showed good wettability, high ionic conductivity, and excellent interface stability. In addition, the cycle stability and rate performance were also improved significantly. This facile, affordable, and effective method has great application potential for the modification of polyolefin‐based separators. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46423. [ABSTRACT FROM AUTHOR]

Surface chemistry of the separator plays an important role in the performance of the lithium ion battery separator, which not only influence the wettability with the electrolyte, but also the lithium ion migration through the separator. Here we developed a simple method to modify the polypropylene separator with tannic acid (TA) and polyethyleneimine (PEI). A thin and uniform TA/PEI layer was formed onto the surfaces of the separator through a simple assembly process without destroyed the microstructure. The modified PP separator showed excellent wettability, high ambient ionic conductivity (0.95 mS cm −1 ) and lithium-ion transference number (0.44), indicating that the TA/PEI layer played a role in the lithium ions migration. The possible mechanism of the surface promoting lithium ion migration was discussed in this paper. The battery performances of the modified separator were also conducted. As a result, cells with the TA/PEI-coated PP separator displayed superior cycle stability and rate capability. [ABSTRACT FROM AUTHOR]

Improving the wettability of liquid electrolyte to polyolefin separators plays a significant role in the fabrication of high performance lithium-ion batteries. Herein, we report a facile surface coating method to enhance the wetting capacity of commercially available polypropylene (PP) separator. Natural polyphenol tannic acid (TA) and sodium periodate are selected as the coating precursor and inorganic trigger, respectively. Coating formation is initiated by the absorption of tannin molecules on the separator surface and then triggered by a single contact (5 min) with sodium periodate solution. After being modified, wettability of the separator can be significantly enhanced without damaging its original advantage properties, which accordingly resulted in higher electrolyte uptake and better interfacial compatibility. Furthermore, the LiCoO 2 /graphite full cells assembled with the modified separator displays an excellent cycle stability with coulombic efficiency exceeding 99.9% and superior rate performance. The ease, low cost and scalability of this coating process, combine with the general surface binding affinity of polyphenol, making this surface modification technique suitable to upgrade other inert substrates for various applications. [ABSTRACT FROM AUTHOR]

Long-life property is one of the key factors for wide applications of lithium-ion batteries. Here, Mo-modified Ni-rich cathode material LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM) is synthesized successfully via a solvent evaporating way followed with a calcination method. This strategy delivers two kinds of effects including Mo-doping and Mo-coating. Mo not only intercalates into the crystal lattice of NCM, but also forms a film-like coating layer on the surface to impede side reactions between electrode and electrolyte. Thus, its specific capacity, rate capability and cycle performance are improved simultaneously, especially in terms of long cycling life property. A series of physical and electrochemical characterizations are used to study the modified performance, and the sample with 1.0 wt% Mo modifying presents the best property with an approximate 3.5 nm coating layer surrounding the surface. Besides, the capacity retention ratio reaches to 89.7% even after 500 cycles between 3.0 and 4.3 V. However, Mo-modified samples have an obvious attenuation in the later period after charging to a higher voltage of 4.6 V although they have preferable cycle performance at the preliminary stage. The results indicate that the reaction mechanisms are diverse at different voltage ranges, which may guide subsequent researches. [ABSTRACT FROM AUTHOR]

A microporous poly( m -phenylene isophthalamide) (PMIA) separator with high safety (high-heat resistance and self extinguishing), high porosity and excellent liquid electrolyte wettability was prepared by the traditional nonsolvent introduced phase separation process. Due to the high-heat resistance of PMIA material, the as-prepared separator exhibited a negligible thermal shrank ratio at 160 °C for 1 h. Meanwhile, benefiting from its high porosity and excellent wettability in liquid electrolyte, the liquid electrolyte uptake and the ionic conductivity of the separator were higher than that of the commercial PP-based separators. Furthermore, the cell assembled with this separator showed better cycling performance and superior rate capacity compared to those with PP-based separators. These results suggested that the PMIA separator is very attractive for high-heat resistance and high-power density lithium-ion batteries. [ABSTRACT FROM AUTHOR]

A novel composite nonwoven separator exhibiting high heat resistance, high ionic conductivity and high lithium ion transference number is fabricated by a simple dip-coating and heat treatment method. The thermal stable polyimide (PI) nonwoven matrix is chosen as a mechanical support and contributes to improving the thermal shrinkage of the composite nonwoven separator (abbreviated as IACS). The cross-linked poly(2-acrylamido-2-methylpropanesulfonic acid) PAMPS(Li + ) gel polymer electrolyte (GPE), lithium ion sources of a single ion conductor, is introduced into the PI nonwoven matrix and acts as a functional filler. This PAMPS (Li + ) GPE is proved to be able to provide internal short circuit protection, to alleviate liquid electrolyte leakage effectively, to supply more lithium ions dissociating from PAMPS (Li + ) by liquid electrolyte solvent, to contribute a more stable interfacial resistance, and thus resulting in an excellent cyclability. More notably, the migration and mobility rate of anions could be hindered by the −SO 3 − group in the PAMPS (Li + ) polymer based on electrostatic interaction, giving rise to a very high lithium ion transference number. These fascinating characteristics endow the IACS a great promise for the application in the high power and high safety lithium ion batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] • The reaction/lithiation front in a solid-liquid reaction is localized on the particle surface due to the limited diffusion of Li, resulting a sharp Li-gradient from surface to interior. • The as-obtained Li 1+x Mn 2-x O 4 spinels exhibit a Li-gradient with decreasing Li concentration from surface to interior. • The Li-rich surface provides good cycle stability while the lightly doped bulk can maintain a high capacity. Owing to the rapid Li ion extraction/insertion kinetics, Li-Mn-O spinels are promising candidates for high-power lithium-ion batteries that is required in electric vehicles. However, the Li-Mn-O spinel cathodes always suffer from poor cycling stability in practical due to the dissolution of Mn and Jahn-Teller distortion. Herein, we report on a new design of constructing a Li-gradient in Li-Mn-O spinel, which is achieved by surface treatment with lithium naphthalenide solution. The as-obtained Li 1+x Mn 2-x O 4 spinels exhibit a Li-gradient with decreasing Li concentration from surface to interior. Importantly, the highly doped surface ensures good cycle stability while the lightly doped bulk maintains a relatively high capacity. This work provides a new design for Li-Mn-O spinels to mitigate their stability problem. [ABSTRACT FROM AUTHOR]

In order to investigate the influences of modification on industrial-grade cathode materials, layered Ti-doped Li(Ni 0.5 Co 0.2 Mn 0.3 ) 1− x Ti x O 2 cathode materials have been synthesized via a simple solid state method using industrial raw materials in bulk scale (>10 kg) in this work. X-ray diffraction (XRD), Rietveld refinement, scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) mapping, particle size distribution and electrochemical tests including cyclic voltammetry (CV) and electrical impedance spectroscopy (EIS) have been used to characterize electrochemical performance of industrial-grade cathode materials. The results of XRD, SEM and EDS mapping characterization indicate that all the modified cathode materials with their Ni, Co and Mn components doped by titanium keep a typical α-NaFeO 2 layered structure with R-3m space group and titanium atoms are uniformly distributed in all series of Ti-doped materials as prepared. Electrochemical characterization confirms that the material of 0.2% Ti doping has the best cycling performance and the least capacity loss because of its best cation ordering figured by Rietveld refinement of XRD. The initial discharge capacity of 0.2% Ti doping material achieves 185.0 mA h/g at 1 C between 2.8 and 4.6 V. Additionally, the capacity retention maintains at 93.4% after 200 charge–discharge cycles. [ABSTRACT FROM AUTHOR]

Abstract: An understanding of the pulse discharge behavior of commercial lithium coin cells in wireless sensing systems (WSs) is critical to prolonging the operating life and/or reducing the size of such systems. This paper is part of an effort to examine, model and optimize battery performance for sensor duty cycles consisting of multiple pulse discharges. The transient behavior of the cells during pulse discharge and the relaxation behavior following the pulse are both investigated with single-pulse experiments, and described with a simple mathematical model. In both cases, the voltage response is characterized by a region of rapid change, associated with ohmic and interfacial resistances, followed by a region of slower change. Solid phase diffusion in the cathode is the major contributor to the “slow” voltage change that occurs during and after a pulse. A simple analytical model, validated for this system, was found to accurately describe the time-dependent voltage and the corresponding non-uniform concentration distribution for the porous electrode. This transient study provides insight into and a description of the factors that influence and control battery behavior during pulsed cycling, and provides a tool to enable the next generation of battery-aware design of autonomous wireless sensing systems. [Copyright &y& Elsevier]

Abstract: To improve the rate performance and cycling stability of LiFePO4, graphene-modified LiFePO4 composite has been developed as Li-ion battery cathode material. The composite is successfully prepared via a novel solvothermal route. C-LiFePO4/graphene, with structure of C-LiFePO4 nanoparticles embedded in graphene matrix, exhibits excellent electrochemical properties, including superior high-rate capability and favorable charge–discharge cycle performance under relative high current density. The size of LiFePO4 nanoparticles can be controlled below 30nm with good reproducibility through this route and due to the synergism of thin carbon film and graphene matrix, the dual coatings exert a significant impact on the electronic conductivity. This novel composite presents excellent electrochemical properties: with reversible capacity of 90mAhg−1 at 10C and 42mAhg−1 at 40C achieved. [Copyright &y& Elsevier]

The separator, as one of the essential components for lithium‐ion batteries (LIBs), has garnered considerable attention because of its significant role in battery performance. Here, an in‐situ coating method to promote the wettability and thermal‐stability of polypropylene (PP) separators was reported. The separator was first dip‐coated with phenolic compound based on biologically inspired surface modification. Then silica layers were in‐situ formed on the separator via a sol–gel process of silicate solution, so that an inorganic–organic hybrid layer was coated on PP separators without the need of any polymer binders. Besides, this method hardly increases the film thickness or sacrifices microporous structure of the pristine separator. Due to the introduction of hybrid layers, the resulted separators showed excellent dimensional thermostability, as the thermal shrinkage was only 20% at 150 °C while that of the bare separator was about 80%. Meanwhile, electrochemical performances of cells with the modified separator were obviously improved, especially the rate performance. At the charge/discharge current density of 5 C, cells with PP separators nearly lost all the capacity, but the modified separator still held 45.7% of the discharge capacity at 0.2 C. This facile yet effective method has great application prospects in the preparation of ceramic‐coated separators. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47277. [ABSTRACT FROM AUTHOR]

Graphene powder is an attractive conducting additive for the electrodes of lithium‐ion battery (LIB). However, the practical application of graphene is hampered by the lack of reliable methods for its production. Here, the authors report a promising method for the synthesis of graphene powder, which exhibits the functionalities both in gram‐scale production and high‐quality products. As a validation, the authors show that the introduced graphene matrix can greatly improve the electrochemical activity and cycle stability of the Co3O4 nanoparticles. Typically, when 40 wt% of graphene is introduced, the obtained Co3O4/graphene nanocomposite can stably cycle up to more than 50 cycles with a reversible capacity above 530 mAh g−1. Simultaneously, a limited initial irreversible capacity less than 40 mAh g−1 is also achieved. The attainment of such properties in Co3O4/graphene nanocomposite offers the prospects for the practical applications of graphene in industry for better LIBs. Physical exfoliation of graphite for high quality graphene powder is achieved. The obtained graphene powder can serve as electron conducting additive in Co3O4– anode for LIBs, which prevents the aggregation of Co3O4 nanoparticles, permits efficient electrons transport, and ensures enhanced cycle stability. [ABSTRACT FROM AUTHOR]

Spinel LiMn 2 O 4 has been synthesized by solid state reaction with industrial grade Mn 3 O 4 and Li 2 CO 3 as precursors without purification, and its electrochemical performance for lithium ion battery has been investigated by CR2025 coin cell. The results of X-ray diffraction (XRD) patterns and scanning electron microscope (SEM) images show that the size of LiMn 2 O 4 particles grow up with increasing temperature of calcination, and the sample synthesized at 800 °C for 12 h has the best crystallinity with a submicron size. It can deliver initial capacity of 112.9 mA h/g with capacity retention ratio of 89.1% after 200 cycles at charge/discharge rate of 1 C. The results of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) also show that it has the highest electrochemical activity and lowest charge transfer impedance. [ABSTRACT FROM AUTHOR]

[Display omitted] The growth of lithium (Li) whiskers is detrimental to Li batteries. However, it remains a challenge to directly track Li whisker growth. Here we report in situ observations of electrochemically induced Li deposition under a CO 2 atmosphere inside an environmental transmission electron microscope. We find that the morphology of individual Li deposits is strongly influenced by the competing processes of cracking and self-healing of the solid electrolyte interphase (SEI). When cracking overwhelms self-healing, the directional growth of Li whiskers predominates. In contrast, when self-healing dominates over cracking, the isotropic growth of round Li particles prevails. The Li deposition rate and SEI constituent can be tuned to control the Li morphologies. We reveal a new "weak-spot" mode of Li dendrite growth, which is attributed to the operation of the Bardeen-Herring growth mechanism in the whisker's cross section. This work has implications for the control of Li dendrite growth in Li batteries. [ABSTRACT FROM AUTHOR]

Lithium metal is a promising anode candidate for the next-generation higher energy density batteries. In this work, a detailed study is carried out to clearly explore the influence of separator wettability on ionic conduction and interface properties for lithium-metal anode batteries. Firstly, polyphenol and polyamine are facilely assembled on the surface of polyethylene (PE) separator with the assistant of periodate. Wettability and electrolyte uptake of the polyphenol-polyamine treated PE separator improves significantly, which resulted in the increase of ionic conductivity and lithium-ion transference number (from 0.37 to 0.49). Subsequently, galvanostatic measurements and electrochemical impedance spectra (EIS) are performed on Li symmetric cells to investigate the effect of separator wettability on interface properties. It is found that the modified PE separator favors the electrochemical process by providing lower interfacial resistance, better interface compatibility, and more uniform deposition of Li + , which correspondingly mitigate the formation of Li dendrites. Finally, lithium-metal anode cells (LiCoO 2 (LCO)/Li) assembled with different separators are tested, and superior battery performance is displayed in case of the polyphenol-polyamine treated substrate. These results are expected to be instructive for the design of more durable Li electrodes. [ABSTRACT FROM AUTHOR]

Poor rate capability and cycling performance are the major barriers for Li-rich layered cathode materials to be applied as the next generation cathode materials for lithium-ion batteries. In our work, Li 1.2 Co 0.4 Mn 0.4 O 2 has been successfully synthesized via a self-combustion reaction (SCR) and a calcination procedure. Compared with the material produced by the solid state method (SSM), the one by SCR exhibits both better rate capability and cycling performance. Its initial discharge capacity is 166.01 mA h g −1 with the capacity retention of 85.98% after 50 cycles at a current density of 200 mA h g −1 . Its remarkable performance is attributed to a thin carbon coating layer, which not only slows down the transformation rate of layered to spinel structure, but provides a good electronic pathway to increase the Li + diffusion coefficient. [ABSTRACT FROM AUTHOR]

• A facile method for synthesis of transition metal oxides/ carbon nanofibers @ transition metal oxides nanostructures through electrospinning, heat treatment, and corrosion. • Co 3 O 4 /C nanofibers @ Co 3 O 4 nanosheets, ZnO/C nanofibers @ ZnO nanoparticles, and CuO/C nanofibers @ CuO nanoneedles are produced from this method showing excellent lithium-ion storage performance. • Full cell tests of Co 3 O 4 /C nanofibers @ Co 3 O 4 nanosheets electrode also show high specific capacity and good cycle stability at high current density. [Display omitted] In this work, a facile and universal synthetic strategy is proposed to synthesize carbon nanofibers/ transition metal oxide composites with a three-dimensional cross-linked structure. The character of its morphology is the carbon nanofiber framework, based on which transition metal oxide nanoparticles and nanosheets (nanoparticles, nanoneedles) can be compounded inside and outside the nanofiber, respectively. The synthesis of this special morphology is achieved by electrospinning, heat treatment, and corrosion. By using this method, a series of hybrid materials including Co 3 O 4 /C nanofibers @ Co 3 O 4 nanosheets (Co 3 O 4 /CFs @ Co 3 O 4), ZnO/C nanofibers @ ZnO nanoparticles (ZnO/CFs @ ZnO), and CuO/C nanofibers @ CuO nanoneedles (CuO/CFs @ CuO) can be successfully synthesized. The capacity of Co 3 O 4 /CFs @ Co 3 O 4 can reach 842.4 mAh g − 1 after 150 cycles, and ZnO/CFs @ ZnO and CuO/CFs @ CuO also show well cycle stability and high specific capacity as 650 mAh g − 1 and 544 mAh g − 1 after 600 cycles at 1 A g − 1. This work can inspire the research of carbon nanofibers framework composite transition metal oxide nanostructure materials for outstanding lithium storage. [ABSTRACT FROM AUTHOR]

• Unique nanocables of T-PVP/SnO 2 @ D -PPy was prepared by a facile combination of electrospinning and chemical synthesis. • The T-PVP/SnO 2 @ D -PPy nanocables have a wrapped nanoarchitecture providing a strong synergistic effect. • The T-PVP/SnO 2 @ D -PPy anode delivered high capacity and excellent cycle performance. SnO 2 is one of the classic high-capacity anode candidates for lithium-ion batteries (LIBs). However, its practical application is limited by its low electrical conductivity and inferior cycling performance, where the poor cycle performance is mainly caused by large volume changes during the charging/discharging process. In this work, unique thermally reshaped polyvinylpyrrolidone/SnO 2 @p-toluenesulfonic acid-doped polypyrrole (T-PVP/SnO 2 @ D -PPy) nanocables have been prepared by a combination of electrospinning and chemical synthesis. The T-PVP/SnO 2 @ D -PPy nanocables have a wrapped nanoarchitecture providing a strong synergistic effect, which results in high conductivity and small volume changes during the charging/discharging processes. The T-PVP/SnO 2 @ D -PPy nanocables could deliver a high reversible capacity of 858.2 mAh g−1 after 200 cycles at a current density of 100 mA g−1, indicating the outstanding electrochemical performance. This work provides an elegant method to improve the electrochemical performance of SnO 2 -based anodes for next-generation lithium-ion batteries and energy storage systems. [ABSTRACT FROM AUTHOR]

• SnO 2 @C nanowires is prepared by a facile simple way of electrospinning method. • The nanowires buffer the volume change of SnO 2 during charge/discharge process. • The SnO 2 @C electrode deliver high capacity and excellent cycle. SnO 2 @Carbon (SnO 2 @C) nanowires were prepared using the method electrospinning. After the heat treatment of the SnCl 2 /polyvinypyrrolidone nanofibers, SnO 2 nanoparticles (~20 nm) were uniformly embedded and distributed on the surface of carbon nanowires. The SnO 2 @C manifested a strong synergistic effect that originated from its wrapped nanoarchitecture, which was proved to be highly conductive with small volume change. This SnO 2 @C nanowires shown high reversible capacity and excellent cycling performance of 680 mAh g−1 at 100 mA g−1 after 50 cycles. [ABSTRACT FROM AUTHOR]