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Lithium-ion batteries are becoming more popular due to their superior performance like high power density, long lifespan, broad operating range of temperatures, quick charging capabilities, and low self-discharge. The implementation of a Battery Management System (BMS) is crucial in order to guarantee the secure and optimal functioning of electric vehicle batteries. BMS monitors, controls, and maintains the health and performance of rechargeable batteries by monitoring the State of Charge (SoC), State of Health (SoH), and State of Temperature (SoT). SoC quantifies the amount of energy stored in a battery at a certain moment, and it is employed to approximate the remaining distance that may be covered. SoH describe the overall health or state of a rechargeable battery. It reveals how well a battery performs in comparison to its original state. SoT estimation keeps the battery temperature within a safe range, allowing it to reach a higher age and safety, which is critical for battery reliability. In this paper SoC, SoH, SoT estimation models for a lithium-ion battery have been developed using an improved EP-based R110-BLSTM approach. The Emperor Penguin based Residual Network-110 incorporated Bidirectional Long-Short Term Memory (EP-based R110-BLSTM) is ideal for estimating SoC, SoH, and SoT and features great accuracy, a quick estimation speed, and strong generalization capabilities. However, Extreme Learning Machine performance is heavily reliant on proper feature extraction. In order to enhance estimate performance by extracting the best features, Simulated-Annealing-based Golden Eagle optimization is utilized. Electric vehicle drive cycles are used to test the model's resilience to temperature changes. MATLAB 2018b software is used in the execution of this research. The results demonstrate that the proposed model performs better in terms of accuracy and has lower SoC, SoH, and SoT error rates than existing models. A thorough comparison between the recommended model and existing methods is also made, further demonstrating the proposed model's superiority. [ABSTRACT FROM AUTHOR]

Due to advancements in e-mobility technology, more and more people are opting to use electric vehicles. As there is a lack of a backup power supply, energy storage device is especially important for onboard systems. So, battery management systems become an important aspect for these energy storage devices. State-of-charge (SoC) estimation is a vitally significant assessment index in BMS because it is one of the most critical attributes that represents the working state of power batteries in EVs. In addition to the quick display of the remaining battery capacity to the user, accurate knowledge of SoC exerts further control over the charging/discharging process, which may be used to enhance battery life. This can be done in order to increase the longevity of the battery. According to the findings of this study, the error while estimating the SoC has been reduced to near about zero. The effect of resistance, temperature and C-rate on SoC has been also considered in this study. These findings show that the resistance is proportional to SoC below 80%, and after that, it becomes nonlinear. The SoC calculation using optimized deep learning strategy is proposed in this study. This approach helps to limit the margin of error in the calculation of SoC. It has also taken into account the occurrence of changes in SoC as a result of the changing C-rate, temperature, and resistance. Hence, this study helps to offset the negative effects of inaccurate SoC prediction. [ABSTRACT FROM AUTHOR]

Ni-rich layered cathode materials LiNixCoyMn(1-x–y)O2 (x ≥ 0.8) suffer from capacity decay due to structural deterioration during electrochemical cycling. To overcome these problems, the fast-ion conductor Li0.33La0.56TiO3 (LLTO) is coated on the surface of LiNi0.83Co0.12Mn0.05O2 (NCM83) cathodes through the sol–gel method, which can stabilize the electrode/electrolyte interface of cathode materials and facilitate Li+ transport and charge transfer. As a result, the LLTO-coated NCM83 exhibits better cycle stability and higher rate performance. The NCM83 modified by 5 wt% LLTO has the discharge capacity of 185.9 mAh g−1 at 1C rate after 100 cycles and with higher capacity retention of 92.9% than the pristine NCM83 of 86.2%, and as well as the 5 wt% LLTO-coated NCM83 has a higher Li+-insert diffusion coefficient of 1.143 × 10−11 cm2 s−1 than the pristine NCM83 of 8.757 × 10−12 cm2 s−1. Therefore, the fast-ion conductor LLTO coating strategy shows great potential in improving the performance of Ni-rich layered cathode materials. [ABSTRACT FROM AUTHOR]

In order to explore the thermal safety of lithium ion batteries (LIBs), a series of thermal runaway tests for single 32,650 LIB with different state of charges (SOC) and double 32,650 LIBs with different spacings from 0 to 2 D (D is 32 mm) are conducted in this work. It is clearly shown that the increasing SOC decreases the onset and duration time of the jet fire stages, increasing the mass loss and flame area in the jet fire stages. With the spacing decreases, the thermal effect of the flames on the LIBs is enhanced, which decreases the onset and duration time of the jet fire stages, increasing the mass loss and strengthening the combustion in the two second jet fire stages. In addition, according to the flame surface area and mass loss rate (MLR), the heat of combustion of LIB is estimated as Δ H c = 8.21 kJ g - 1 , and a simplified model is derived to predict the heat release rate (HRR) of LIBs. The above results provide a theoretical foundation for quantitative assessment of the fire risk of the LIBs. [ABSTRACT FROM AUTHOR]

The composite membrane (PDFP-POPM) based on the blending of poly(vinylidene fluoride-co-hexafluoropropylene) (PDFP) and POPM (the copolymer of organic palygorskite and methyl methacrylate) was prepared by the phase-inversion method, and a gel polymer electrolyte (GPE) was obtained when the PDFP-POPM was activated by absorbing liquid electrolyte (LE). The SEM morphologies showed that the PDFP-POPM had a porous structure. The XRD results indicated that PDFP-POPM was an amorphous polymer and that the POPM could effectively suppress the crystallization of PDFP. The lithium ion transference number of GPE was higher than that of pristine POPM- and PDFP-based GPE. When the mass concentration of PDFP was 40%, the uptake of the PDFP-POPM and ionic conductivity of GPE reached the maximum values of 164% and 2.37 mS/cm, respectively. The electrochemical stability window of Li/GPE/SS batteries was over 4.7 V (vs. Li+/Li), and the Li/40PDFP-POPM GPE/LiFePO4 battery exhibited good cycling performance. The discharge capacity of the battery was 145mAh g−1 after 100 cycles and the columbic efficiency was over 95%. [ABSTRACT FROM AUTHOR]

We have studied the effect of doping with tin and titanium cations on the electrochemical performance of lithium-rich cathode materials. Samples for this investigation were prepared via coprecipitation of precursors, followed by solid-state reaction with a lithium and tin (titanium) source. The cathode materials have been characterized by X-ray diffraction, scanning electron microscopy, and X-ray microanalysis and tested in lithium half-cells in galvanostatic cycling mode at various current densities. The titanium-doped material had a considerably higher specific discharge capacity (270 mAh/g) in comparison with the undoped and tin-doped materials (230 mAh/g). As the charge/discharge current was raised, the titanium-doped sample exhibited the best cycling stability among all of the materials. In addition, both doped materials had a smaller voltage hysteresis in comparison with the undoped sample. [ABSTRACT FROM AUTHOR]

To solve the volume expansion problem of Fe3O4 nanoparticles (nmFe3O4), a facile, green, and industrializable preparation of N-doped carbon–encapsulated nmFe3O4 (nmFe3O4@N-doped C) is designed. This nmFe3O4@N-doped C is prepared through pyrolysis in nitrogen atmosphere of nmFe3O4 encapsulated by polyaniline (PANI@nmFe3O4) which is obtained through oxidative polymerization of aniline on the surface of nmFe3O4. In comparison with the capacity (113 mAh g−1 at 0.1C) of nmFe3O4, the nmFe3O4@N-doped C electrode exhibits a high reversible capacity of 400 mAh g−1 after 500 cycles. Even at 4C, the nmFe3O4@N-doped C electrode presents 160 mAh g−1 capacity, which is much higher than 30 mAh g−1 of the nmFe3O4 electrode. The results suggest that the N-doped carbon shell layer obtained from PANI is effective to inhibit volume expansion of nmFe3O4 core and maintain the electron and ion transport channels after long cycles. [ABSTRACT FROM AUTHOR]

Fast charging of Lithium ion batteries (LIBs) is expected to boost the extensive electrification of transportation sector. However, fast charging a LIB comes at the cost of increased internal heat generation that results in higher reaction rates of both the necessary as well as unwanted reactions at the electrode–electrolyte interface. This can trigger a chain of events that can possibly lead to thermal runaway. Electrolyte has a critical effect on the internal heating of a LIB and thus plays an inherent role in its safety. We elucidate the role of electrolyte salt in reducing internal heating by evaluating two different salts—Lithium bis(fluorosulfonyl)imide (LiFSI) and Lithium hexafluorophosphate ( LiPF 6 ). Using a physics-based electrochemical–thermal model, we study these electrolyte salts individually in LiCoO 2 (Cathode)/Graphite (Anode) LIB system. Under fast charging conditions, internal heating and polarization were studied in each of the LIB system. The temperature rise seen in the two systems shows that LiFSI is a better electrolyte salt for fast charging application as compared to LiPF 6 . This is primarily due to better transport properties of LiFSI compared to LiPF 6 , as elaborated using polarization studies. This study can aid in choosing the appropriate electrolyte salt for mitigating the internal heating and thermal issues during fast charging. [ABSTRACT FROM AUTHOR]

For the first time, cotton fiber-shaped Cu2O nanoparticles were prepared onto the surface of a commercial copper (Cu) foil via a very simple immersion method at room temperature in which the soaking solution only contained CuSO4, Na2S2O3, and a very little amount of 1-butyl-3-methylimidazolium trifluoroacetate. In this work, the current collectors prepared using 1 mM, 2 mM, and 3 mM Na2S2O3 were, respectively, nominated as current collectors a, b, and c. Interestingly, a cotton fiber-shaped spatial network structure assembled by a large number of 10-nm-sized nanoparticles was presented on the surface of current collector b. The initial discharge capacity (DC) at 0.1 A g−1 of electrode b, namely, the graphite electrode assembled using current collector b, was as high as 467 mAh g−1, almost 1.65 times larger than that of the conventional graphite electrode. Particularly, at 0.5 A g−1 after 10 cycles, the DC value of electrode b (105 mAh g−1) was still about 1.8 times higher than that of the conventional graphite electrode (59 mAh g−1). An immersion method for preparing Cu2O-modified Cu foil at room temperature is developed in this work, which is very meaningful to the development of the Cu foil-based commercial graphite electrode, since no additional energy consumptions and no variations of the electrode preparation process are required. [ABSTRACT FROM AUTHOR]

A nearly saturated 2,2,2-trifluoroethyl acetate (FEA)-based electrolyte solution has a low viscosity and delivers superior charge/discharge performance for LiNi0.8Co0.1Mn0.1O2 (NCM811) positive electrodes for lithium ion batteries. However, FEA has a low flash point, and hence needs to be mixed with an appropriate co-solvent to improve the safety of electrolyte solutions. In this study, two kinds of co-solvent were introduced into LiBF4/FEA electrolyte solutions and the LiBF4 concentration was increased. The mixture ratio of FEA and a co-solvent had a major effect on the charge/discharge performance of NCM811. The resultant nearly saturated electrolyte solution further improved the charge/discharge properties in terms of both cycle- and high rate performance. A very thin protective layer formed on NCM811 to suppress continual decomposition of the electrolyte solution, and did not interfere with interfacial Li+ transfer between the NCM811 electrode and electrolyte solution. In addition, 2,2-difluoroethyl acetate, which has a higher flash point than FEA, was used as a main solvent to study the highly concentrated electrolyte solutions. [ABSTRACT FROM AUTHOR]

In this study, within the defined orthogonal array of Taguchi design, the hydrothermal process parameters have been optimized for fabricating the smallest particle sized iron oxide (Fe2O3) particles. The finest particle size (210 nm) has been achieved when 0.02 M FeCl3 solution at pH 10 is hydrothermally treated for 90 min with an autoclave filling ratio of 100% (D3). Afterwards, to improve the physical properties of iron oxide particles, carbon black powder is added into the precursor solution as the seeding agent before the hydrothermal treatment. Structural and morphological analyses show that upon the existence of carbon in the precursor solution, C-supported Fe2O3 (D5) is fabricated. In the latter, carbon is present in graphitic form and no carbide formation is detected. Electrochemical test results verify that unlike to Fe2O3 (D3), C-supported Fe2O3 (D5) electrode performs lower charge transfer resistance and polarization leading to higher first coulombic efficiency, capacity retention, and improved rate performance, eventually. Thanks to the favorable characteristics of the latter, after 150 cycles, D5 performs 550, 390, and 333 mAh g−1 discharge capacities under loads of 50 mA g−1, 500 mA g−1, and 1.5 A g−1, respectively. Finally, to understand the contribution of capacitive and diffusion-controlled reactions to the total stored charge, an adopted sweep rate method has been used. The calculated voltammograms reveal that fabricating C-supported Fe2O3 particles led to improved rate performance because faradaic reactions that occur at the surface of the material prevail. [ABSTRACT FROM AUTHOR]

Silicon (Si) is extensively used as an electrode in lithium (Li) ion batteries for its superiority in the charging capacity. However, the lithiation of Si would induce large deformation and significant stress jump across a two-phase interface in Si electrodes and might eventually lead to structure failure of batteries. To improve the performance and life of Li ion batteries, it is of great importance to exactly model the lithiation process. In the past decade, although many models have been developed for the lithiation, most of them just relate the deformation with the diffusion, without considering the effect of electrochemical reactions, so that they cannot simulate the formation of the two-phase interface. In this paper, we aim to develop a fully coupling diffusion–reaction–deformation model for large deformation cases and apply it to simulate the lithiation process, where a reaction barrier effect is proposed to describe the formation of the two-phase interface due to fast reaction and the mechanical behaviors of Si electrodes such as large plastic flow during lithiation process are predicted. [ABSTRACT FROM AUTHOR]

The morphology and nanosize of cathode materials play a crucial role in the improved electrochemical properties of the electrode material for lithium ion batteries. Herein, we report the synthesis of a novel NH4V3O8 rectangular nanotube via a facile one-pot solvothermal protocol with the use of the mixing solvent containing glycerol, ethanol, and ethylene glycol. The morphology and nanosize evolution of the as-prepared NH4V3O8 materials from the addition of different solvents has been systematically investigated. The electrochemical properties of these materials are closely related to their structure. Compared with other synthesized counterparts with three different morphologies (nanoparticle, ultra-small nanoparticle, and hierarchical microsheet), the resultant NH4V3O8 rectangular nanotube exhibited high reversible capacity with a maximum discharge capacity of 253.8 mAh g−1at 15 mA g−1, and the capacity retention rate is 75% after 50 cycles. This work reveals the relationship between the morphology and electrochemical performance of NH4V3O8 and provides a feasible method for the synthesis of high-performance electrode materials. [ABSTRACT FROM AUTHOR]

Electrode material is a key factor for high-energy storage battery. In this paper, graphene oxide/poly(o-phenylenediamine) (GO/PoPD) hybrid composite is prepared by combining the self-assembly process to form graphene oxide/o-phenylenediamine hydrogel and subsequently the in situ oxidation polymerization, which exhibits the open porous morphology with high BET surface area of 347 m2/g. As the anode of lithium ion battery, GO/PoPD possesses the double lithium storage mechanisms from graphene oxide and poly(o-phenylenediamine). Meanwhile, it exhibits an initial discharge-specific capacity of 1632.4 mAh/g and the improved cycling stability. Even after 43 cycles, it still keeps a capacity of 839.5 mAh/g, which is obviously higher than that of GO and PoPD. Furthermore, GO/PoPD hybrid composite presents the enhanced rate performances with the discharge-specific capacities of 1411.7, 718.2, 621.2, and 576.3 mAh/g at current rates of 50, 100, 200, and 500 mA/g, respectively. The improved electrochemical performances are attributed to the formed stable porous morphology, which facilitates the electrolyte ion to penetrate into the electrode matrix during the redox reaction and then results in the improved cell performances. [ABSTRACT FROM AUTHOR]

The strong demand on high-performance lithium ion batteries has brought up an attention upsurge in the research society and the commercial market. Carbon materials have shown the great potential as anode materials for lithium ion batteries since they are low-cost, safe, abundant, and electrochemically stable. In this work, we report a selenium-doped carbon anode through carbonizing the mixture of selenium and an organic compound of naphthalenetetracarboxylic dianhydride. Benefiting from the porous structure, enlarged BET specific area, and active defects from the doping of Se, the material shows excellent rate capability. It delivers a high specific capacity of 450 mAh g−1 after 580 cycles at the current density of 500 mA g−1 and a specific capacity of 170 mAh g−1 after 2400 cycles at the current density of 1000 mA g−1. The superb performance of this material proves its potential as anode for high-performance lithium ion batteries. [ABSTRACT FROM AUTHOR]

We propose a method of obtaining two-component composite cathodes for lithium ion batteries with active layer based on lithium iron phosphate and redox-active conducting polymeric complexes of nickel with salen-type Schiff bases. The structure and electrochemical characteristics of obtained electrodes have been studied. It is established that metallopolymers in the proposed cathodes (free of traditional binding and conducting additives in the electrode layer) not only successfully perform the functions of binding and conducting components, but also provide reversible charge storage, which can favor an increase in the specific capacitance of cathode layer as compared to that in electrodes of traditional composition. [ABSTRACT FROM AUTHOR]

In this study, the spray-drying technique was used to apply a 0.5 at%, 1 at%, and 1.25 at% of lithium lanthanum zirconium tantalum oxide (Li6.75La3Zr1.75Ta0.25O12) powder coating on the surface of lithium cobalt oxide (LiCoO2) cathode materials. Subsequently, these materials were sintered for either 5 or 10 h at 800 °C to obtain LiCoO2 cathode materials with a rough coating. X-ray diffraction, cyclic voltammetry, electrochemical impedance spectroscopy, and differential scanning calorimetry were then conducted to analyze differences in the structure, electrochemical properties, and thermostability of the materials before and after surface modification. The modified LiCoO2 cathodes with Li6.75La3Zr1.75Ta0.25O12 rough coating had more than twice the discharge capacity as the bare LiCoO2 cathode at a high discharge current density when the cutoff voltage ranged from 2.8 to 4.5 V. In addition, 1 at% Li6.75La3Zr1.75Ta0.25O12 coating and 5 h of sintering at 800 °C resulted in the optimal capacity retention of 85.4% after 80 cycles and a slower exothermic reaction than that of the bare LiCoO2 cathode. Thus, rough coating an adequate quantity of Li6.75La3Zr1.75Ta0.25O12 powder on a LiCoO2 cathode mitigated the reaction between the cathode material surface and electrolyte, stabilizing the main structure and enhancing the ionic conductivity and electrochemical characteristics of the material. [ABSTRACT FROM AUTHOR]

We have studied the performance of nanotubular nickel hydrosilicate and its derivatives as a negative electrode of lithium ion batteries. Nickel hydrosilicate with the composition Ni3Si2O5(OH)4 was synthesized under hydrothermal conditions (350°C, 14 MPa, 10 h). Its derivatives were prepared by thermal annealing at temperatures of 400, 600, and 1000°C. In this process, the tubular structure of the particles persisted up to 600°C, whereas at 1000°C well-crystallized Ni2SiO4 was formed. Charge/discharge cycles were performed in the voltage range 0.05–3 V at a specific current of 10 mA/g. Heat treatment was shown to increase discharge capacity and reversible capacity in the first cycle. The highest performance was offered by the material heat-treated at 400°C: its discharge capacity reached 678 mAh/g and its reversible capacity was 58% in the first cycle and 85% in subsequent cycles. [ABSTRACT FROM AUTHOR]

Single-walled carbon nanotube (SWCNT) wrapped GeO2/ZnWO4 nanocomposite was prepared by single-step solvothermal method. In this work, GeO2/ZnWO4 nanocomposites were prepared by varying the molar percentage of GeO2 and by further adding SWCNT for the composite to boost the electrochemical performance. The prepared GeO2/ZnWO4 nanocomposites and GeO2/ZnWO4@CNT nanocomposite are used as anode material for lithium-ion battery (LIB). As expected, GeO2/ZnWO4@CNT nanocomposite exhibits higher capacities and good rate capability than the GeO2/ZnWO4 nanocomposite. The GeO2/ZnWO4@CNT nanocomposite exhibits 930 mAh g−1 discharge capacity and 533 mAh g−1 charge capacity for the initial cycle at 100 mAh g−1 in the voltage range of 0.01–3 V (vs. Li+/Li). Even at high current density of 500 mAh g−1, GeO2/ZnWO4@CNT nanocomposite shows 231 mAh g−1 and 257 mAh g−1 charge/discharge capacity which are higher than that of GeO2/ZnWO4 nanocomposite. The GeO2/ZnWO4@CNT nanocomposite delivers 75.8% capacity retention and 100% coulombic efficiency even after 400 cycles at 300 mAh g−1. These results direct that GeO2/ZnWO4@CNT nanocomposite is a good negative electrode for lithium-ion battery. [ABSTRACT FROM AUTHOR]

(1 – n – m)LiCo0.8Ni0.2O2 system was synthesized using the sol–gel method. Stoichiometric weights of the LiNO3, Mn(Ac)2 · 4H2O, Co(Ac)2 · 4H2O, Ni(NO3)2 · 6H2O for preparing of 28 samples have been used as starting materials of lithium, magnesium, cobalt and nickel, in 28 samples of (1 – n – m)LiCo0.8Ni0.2O2, respectively. We exhibited "Li1.333Ni0.4Co0.267Mn0.333O2" is the best composition for cathode material among those compositions. Obviously, the used weight of cobalt in this sample is lower compared with LiCoO2 that is an advantage in view point of cost and toxic problem. Charge–discharge characteristics of the mentioned cathode materials were investigated by performing cycle tests in the range of 2.2–4.5 V. Our results confirmed, although these kind systems can help for removing the disadvantage of cobalt which mainly is its cost and toxic, the performance of these kind systems are similar to LiCoO2 cathode material. [ABSTRACT FROM AUTHOR]

A terahertz chemical microscope has been developed to visualize electric potential distribution on lithium ion battery cathodes during battery operation. A sensing plate comprising a Si film grown epitaxially on a sapphire substrate was used as a terahertz emitter. The amplitude of terahertz radiation from the sensing plate could be related to the electric potential at the exact point where a femtosecond laser illuminated. Here, the sensing plate was integrated into a conventional can-type lithium ion battery and terahertz radiation from the sensing plate was observed during battery operation between 2.7 and 4.2 V. By scanning the laser, the distribution of terahertz amplitude radiated from the sensing plate was observed, which could be related to the electric potential distribution on the electrodes of the batteries. Localized electric potential could be visualized as the amplitude of terahertz radiation generated in the sensing plate, which was integrated beneath the battery electrode. [ABSTRACT FROM AUTHOR]

Ta2O5 is one of the promising anode materials for lithium ion battery application undergoing conversion reaction in combination with an extrinsic pseudocapacitance property. We have synthesized Ta2O5 nanoparticles by hydrothermal method using and without using polyethylene glycol (PEG) as co-solvent. Ta2O5 nanoparticles were characterized by PXRD, SEM, EDAX, BET, and TEM analysis. Electrochemical characterizations like Cyclic voltammetry, galvanostatic charge-discharge process, and rate capability were studied for Ta2O5 NPs. A reversible capability of 130 mA h g−1 is retained after 85 cycles at 0.1C rate by Ta2O5 NPs synthesized using PEG, and reversible capability of 127 mA h g−1 is retained after 40 cycles at 0.1C rate by Ta2O5 NPs synthesized without using PEG. Polyethylene glycol as cosolvent induced enhanced porosity favoring the fast lithium ion transport and better reversible capacity upon cycling. [ABSTRACT FROM AUTHOR]

In this paper, the fire behaviors of 60 Ah LiFePO4/graphite batteries with no safety valve are evaluated using an in situ calorimeter. The batteries experience a stable combustion stage with a small-scale flame rather than immediate jet fire after ignition and the special combustion process is analyzed and discussed in detail. It takes 201 s from ignition to thermal runaway for fully charged battery under an incident heat flux of 11.1 kW m−2. Such a time interval is beneficial for a possible early warning of the battery thermal runaway. Several characteristic parameters, including the ignition time, surface temperature, mass loss, heat release rate (HRR), and flame size are systematically determined. The peak HRR can be as high as 82.3 kW and the maximum average flame height for batteries under an incident heat flux of 11.1 kW m−2 reaches 634.6 mm. The influence of different state of charge (SOC) and incident heat flux are also investigated. The results show that the fully charged batteries exposed to high external heat flux are more vulnerable to have thermal runaway. [ABSTRACT FROM AUTHOR]

The synthesis of ultra-small cobalt-doped (Co-doped) Mn3O4 nanoparticles tiled on multilayer graphene (MLG) surface by one-pot hydrothermal method was reported here. MLG was obtained by the ultrasonication of expanded graphite in mixture solution of N,N-Dimethylformamide (DMF) and H2O and used without any further treatment. Co-doped Mn3O4 nanoparticles were in situ assembled onto MLG surfaces by van der Waals force between metal complex and MLG. The characterization by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy revealed that the as-prepared Co-doped Mn3O4 nanoparticles were homogeneously tiled on MLG with good crystallization and uniform size. The effects of cobalt doping content on the microstructure and electrochemical performance for the composites were studied. For Co0.45Mn2.55O4/MLG composite, a reversible capacity of 906 mAh g−1 is stably delivered at 100 mA g−1 based on the overall weight and it is maintained to 442 mAh g−1 at a high current density of 2 A g−1. Pure and Co-doped Mn3O4 nanoparticles with uniform size were synthesized to be tiled on MLG based on van der Waals force by a one-pot hydrothermal method. The effects of cobalt doping content on the microstructure and electrochemical performance of composite were studied. Co0.45Mn2.55O4/MLG composite exhibits a high reversible capacity, cycling stability and rate capability as anode material for lithium ion battery. [ABSTRACT FROM AUTHOR]

Polypyrrole (PPy) used as popular coatings can improve the electrochemical performance of electrodes greatly; however, uniform coatings of PPy on nanostructures is a challenging task in a solution system. Substitution for liquid phase polymerization reaction, herein a developed evaporation method is reported to make pyrrole vapor in situ polymerization on CuO arrays for the uniform PPy coatings. With the help of this uniform PPy coatings, the unique structure of arrayed CuO film can well maintain the stability of mechanical structures and has rapid transmission of lithium ions and electrons during charge/discharge processes, hence harvesting a high lithium storage. Electrochemical tests indicate that PPy can not only enhance the specific capacities of CuO anodes greatly but also improve the cyclic stability at a high-current density. The specific capacity of the CuO@PPy integrated anode can be up to 561 mAh g−1 at 1 C after 100 cycles, which is increased by almost 33% than that of the pure CuO anode. [ABSTRACT FROM AUTHOR]

Studying the kinetics of phase transformation and phase boundary propagation during initial lithiation of silicon electrodes in lithium ion batteries is relevant to understanding their performance. Such studies are usually challenging due to the difficulties in measuring the phase boundary velocity in the interior of the sample. Here we introduce a non-invasive, in situ method to measure the progression of the phase boundary in a planar specimen geometry while maintaining well-controlled lithium flux and potential. We developed an apparatus integrating an electrochemical cell with picosecond ultrasonics to probe the propagating phase boundary in real time. Phase propagation during initial lithiation of crystalline silicon, which is an example of a high capacity anode, is investigated. The primary objective of this manuscript is to report on the experimental technique development and some preliminary results. For lithiation normal to the (100) plane, we observe the phase boundary velocity to be approximately 12 pm/s and x to be 3.73 in LixSi under galvanostatic lithiation with a current density of 40 μA/cm2. The growth rate of the lithiated phase and the reaction rate coefficient are examined using a Deal-Grove type model. [ABSTRACT FROM AUTHOR]

Three-dimensional graphene/amorphous carbon composites have been successfully prepared by using biomass resources as raw materials via a simple method. Most macrostructures for biomass resources are maintained in the obtained three-dimensional graphene/amorphous carbon composites during the synthesis process, but the microstructures for them change significantly. The structure and composition of raw biomass materials significantly influence the amount of adsorbed Ni2+, which could affect the structure and composition for the graphene/amorphous carbon composites. The obtained composites were tested as anode materials for a lithium ion battery. Our results show that the structures for the graphene/amorphous carbon composites play important roles from their electrochemical properties. [ABSTRACT FROM AUTHOR]

A three-dimensionally (3D) ordered macro/mesoporous carbon (3DOMC) is synthesized by one-step template method as a TiO2 supporter, and this TiO2/3DOMC hybrid plays the role of immobilizers and can limit any polysulfides from escaping the cathode. The TiO2/3DOMC exhibits high pore volume and specific surface area, accommodating up to 73.2 wt% in sulfur content. As a sulfur host, S/TiO2/3DOMC composite was able to delivered 1105 mAh g−1 on first discharge and 695 mAh g−1 after 150 cycles at a current rate of 0.5 C. Even though at 2 C this material was able to keep a capacity of 551 mAh g−1. We attribute the superior performance to the good conductivity and structural restriction of carbon and the intense electrostatic attraction between metal-oxygen bond and polysulfides to encapsulate sulfur of the TiO2/3DOMC.Graphical abstractSchematic of the preparation of the S/TiO2/3DOMC [ABSTRACT FROM AUTHOR]

In this study, laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was applied to previously aged carbonaceous anodes from lithium ion batteries (LIBs). The electrodes were treated by cyclic aging in a lithium ion cell set-up with LiNi0.5Mn1,5O4 (LNMO) cathodes and hard carbon (HC)/mesocarbon microbead (MCMB) anodes. An inhomogeneous transition metal deposition pattern could be induced by replacing the spacer in a standard coin cell set-up with a washer. The inhomogeneity pattern matched the dimension of the washer depicted by the hole in the center. These transition metal (TM) patterns were used to optimize higher lateral scanning speeds and frequencies on the spatial resolution of the mapping experiments using LA-ICP-MS. Higher scanning speeds had an observable influence on the resolution of the obtained image and an overall saving of 60% with regard to time and gas consumption could be achieved. Additionally, the optimized method was applied to the cathode and separator in order to visualize the distribution and deposition pattern, respectively. [ABSTRACT FROM AUTHOR]

In this study, LiFePO4-carbon (LFP-C) and LFP-C/reduced graphene oxide (rGO) nanocomposites were prepared by ultrasonic spray pyrolysis technique in different calcination conditions to be used as the cathode-active materials for lithium ion battery (LIB). The structure, morphology and composition of the obtained materials were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), high-resolution transmission electron microscopy (HR-TEM) and energy-dispersive X-ray spectroscopy (EDX). The XRD results reveal that the olivine pure phase was obtained after calcination of the LFP-C. The SEM images of the prepared materials exhibit the spherical morphology with nanometer size and also change in the morphology by applying the calcination step. The electrochemical performances of cathode-active materials were investigated by charge-discharge test, electrochemical impedance spectroscopy and cyclic voltammetry. The obtained results for LFP-C show that the electrochemical performance was improved by adding carbon precursor and calcining step; in the optimum calcination conditions; 700 °C for 3 h, the LFP-C shows good results in terms of electrochemical performance in comparison with LFP alone. The LFP-C/rGO nanocomposite exhibits the best electrochemical performance however: highest rechargeable capacity and cycle stability; discharge capacity (168 mAh/g at 0.1 C and 123.5 mAh/g at 10 C) and capacity retention of 100% after 50 cycles with maximum reversibility and lithium ion (Li+) diffusion coefficient.Graphical Abstract: Schematic representation of preparation of the cathode-active materials. [ABSTRACT FROM AUTHOR]

In this work, the transition metal dissolution (TMD) from the respective ternary layered LiMO2 (M = Mn, Co, Ni, Al) cathode active material was investigated as well as the lithiation degrees of the cathodes after charge/discharge cyclic aging. Furthermore, increased nickel contents in LiNixCoyMnzO2-based (NCM) cathode materials were studied, to elucidate their influence on capacity fading and TMD. It was found, that the TMD from nickel-rich cathode materials, e.g., LiNi0.6Co0.2Mn0.2O2 or LiNi0.8Co0.1Mn0.1O2, did not differ significantly from the TMD from the stoichiometric LiNi1/3Co1/3Mn1/3O2. In detail, the TMD from the cathode did not exceed a maximum of 0.2 wt% and was uniformly distributed on all analyzed cell parts (separator, anode, and electrolyte) using total reflection X-ray fluorescence. Moreover, the investigated electrolyte solutions showed that increased Ni contents come with more nickel dissolution of the respective material. Additionally, inductively coupled plasma optical emission spectroscopy analysis on the respective charge/discharge cyclic-aged cathode active materials revealed lithium losses of 20% after 50 cycles. However, only a minimum amount of capacity loss (= 1.5 mAh g−1) can be attributed to active material loss. [ABSTRACT FROM AUTHOR]

The structural and electrochemical effects of electrospun V2O5 with selected redox-inactive dopants (namely Na+, Ba2+ and Al3+) have been studied. The electrospun materials have been characterised via a range of analytical methods including X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller surface area measurements and scanning and transmission electron microscopy. The incorporation of dopants in V2O5 was further studied with computational modelling. Structural analysis suggested that the dopants had been incorporated into the V2O5 structure with changes in crystal orientation and particle size, and variations in the V4+ concentration. Electrochemical investigations using potentiodynamic, galvanostatic and impedance spectroscopy analysis showed that electrochemical performance might be dependent on V4+ concentration, which influenced electronic conductivity. Na+- or Ba2+-doped V2O5 offered improved conductivities and lithium ion diffusion properties, whilst Al3+ doping was shown to be detrimental to these properties. The energetics of dopant incorporation, calculated using atomistic simulations, indicated that Na+ and Ba2+ occupy interstitial positions in the interlayer space, whilst Al3+ is incorporated in V sites and replaces a vanadyl-like (VO)3+ group. Overall, the mode of incorporation of the dopants affects the concentration of oxygen vacancies and V4+ ions in the compounds, and in turn their electrochemical performance.ᅟ [ABSTRACT FROM AUTHOR]

A fully coupling model for the diffusion induced finite elastoplastic bending of bilayer electrodes in lithium-ion batteries is proposed. The effect of the mechanical stress on the lithium diffusion is accounted for by the mechanical part of the chemical potential derived from the Gibbs free energy along with the logarithmic stress and strain. Eight dimensionless parameters, governing the stress-assisted diffusion and the diffusion induced elastoplastic bending, are identified. It is found that the finite plasticity starting from the interface of the bilayer increases the chemical potential gradient and thereby facilitates the lithium diffusion. The full plastic flow makes the abnormal lithium concentration distribution possible, i.e., the concentration at the lithium inlet can be lower than the concentration at the interface (downstream). The increase in the thickness of the active layer during charging is much larger than the eigen-stretch due to lithiation, and this excess thickening is found to be caused by the lithiation induced plastic yield. [ABSTRACT FROM AUTHOR]

Abstract: Hierarchical hollow structures are of great interest as electrode materials for lithium ion batteries. They can provide enlarged surface area for efficient contact between electrode and electrolyte, endow the electrodes with fast electron and ion transfer and accommodate the volume change resulted from charge/discharge cycling. Herein, we report the synthesis of urchin-like NiCo2O4 hollow nanospheres based on a special stepwise co-precipitation method. The hollow nanostructures result from the non-equilibrium mass diffusion induced by a rationally designed stepwise co-precipitation reaction. Owning to the hierarchical hollow architectures, the as-prepared urchin-like NiCo2O4 hollow nanospheres exhibit excellent electrochemical properties as anode materials for lithium-ion batteries, with a large discharge capacity of 1232.3 mAh/g at 0.1 C, a high initial coulombic efficiency of 78.4% and a high capacity retention of 95.6% at 0.5 C after 100 cycles.Graphical Abstract: Based on a special stepwise co-precipitation method, we have successfully synthesized hierarchical hollow urchin-like NiCo2O4 nanospheres as anode material caused by cross-layer non-equilibrium diffusion. The unique hierarchical hollow structure can provide efficient electrode-electrolyte contact and endow the electrodes with fast electron and ion transfer enhancing the rate performance of the anode material. Also, the hollow structure can suppress the volume change during the repeated Li+ insertion/extraction in the host corresponding to the enhanced cycling performance. [ABSTRACT FROM AUTHOR]

Intercalation of lithium ions into the electrodes of lithium ion batteries is affected by the stress of active materials, leading to energy dissipation and stress dependent voltage hysteresis. A reaction-diffusion-stress coupling model is established to investigate the stress effects under galvanostatic and potentiostatic operations. It is found from simulations that the stress hysteresis contributes to the voltage hysteresis and leads to the energy dissipation. In addition, the stress induced voltage hysteresis is small in low rate galvanostatic operations but extraordinarily significant in high rate cases. In potentiostatic operations, the stresses and stress induced overpotentials increase to a peak value very soon after the operation commences and decays all the left time. Therefore, a combined charge-discharge operation is suggested, i.e., first the galvanostatic one and then the potentiostatic one. This combined operation can not only avoid the extreme stress during operations so as to prevent electrodes from failure but also reduce the voltage hysteresis and energy dissipation due to stress effects. [ABSTRACT FROM AUTHOR]

In this study, spheroid LiNi1/3Co1/3Mn1/3O2 (NCM111) cathode material were synthesized using LiOH with Ni0.5Co0.2Mn0.3(OH)2 precursor by a simple solid-state reaction, and characterized by X-ray diffraction and scanning electron microscopy. Electrochemical behavior of NCM111 was investigated by electrochemical impedance spectroscopy (EIS) combining with cyclic voltammogram (CV) and charge/discharge test in the 1 M LiPF6-EC:EMC electrolyte with ethylene sulfate (DTD) and methylene methanedisulfonate (MMDS) additives either singly or in combination with high cutoff voltage of 3.0-4.5 V at room temperature of 25 °C or elevated temperature of 55 °C. It was found that DTD additive can increase the initial coulombic efficiency of NCM111, and the spheroid NCM111 can obtain the maximum initial discharge capacity of 177.81 mAh/g with the 2 wt% DTD, and keep 92.29% capacity retention after 80 cycles. The MMDS additives would decrease the initial discharge capacity of the NCM111, and enhance significantly long cycle life of the NCM111 with the capacity retention of 99.23% over 80 cycles at high voltage of 4.5 V. The additive combination 2 wt% DTD + 1 wt% MMDS was an optimal additive combination, demonstrating the 102.2% capacity retention over 80 cycles at room temperature and the 94.2% capacity retention over 70 cycles at elevated temperature of 55 °C. EIS results revealed that the additive blend of 2 wt% DTD + 1 wt% MMDS can drastically lower the kinetics impedance and suppress the growth rate of Rct for the NCM111 electrode. [ABSTRACT FROM AUTHOR]

The requirement of energy-storage equipment needs to develop the lithium ion battery (LIB) with high electrochemical performance. The surface modification of commercial LiFePO4 (LFP) by utilizing zeolitic imidazolate frameworks-8 (ZIF-8) offers new possibilities for commercial LFP with high electrochemical performances. In this work, the carbonized ZIF-8 (CZIF-8) was coated on the surface of LFP particles by the in situ growth and carbonization of ZIF-8. Transmission electron microscopy indicates that there is an approximate 10 nm coating layer with metal zinc and graphite-like carbon on the surface of LFP/CZIF-8 sample. The N2 adsorption and desorption isotherm suggests that the coating layer has uniform and simple connecting mesopores. As cathode material, LFP/CZIF-8 cathode-active material delivers a discharge specific capacity of 159.3 mAh g-1 at 0.1C and a discharge specific energy of 141.7 mWh g-1 after 200 cycles at 5.0C (the retention rate is approximate 99%). These results are attributed to the synergy improvement of the conductivity, the lithium ion diffusion coefficient, and the degree of freedom for volume change of LFP/CZIF-8 cathode. This work will contribute to the improvement of the cathode materials of commercial LIB. [ABSTRACT FROM AUTHOR]

A biodegradable composite polymer membrane is fabricated by synthesizing polyvinylpyrrolidone (PVP) on the matrix of lignin, and then the corresponding gel polymer electrolyte (LP-GPE) is further prepared by absorbing the liquid electrolyte. The morphology, mechanical property, and thermal stability of the composite lignin-PVP membrane and the electrochemical properties of LP-GPE are investigated. The results of the investigation present that the mechanical property of the membrane is remarkable improved (670%) and the composite membrane exhibits a better thermal security. For electrochemical properties, a high ionic conductivity of 2.52 × 10−3 S cm−1 at room temperature, excellent lithium-ion transference number of 0.56, and outstanding electrochemical stability of LP-GPE are confirmed. Moreover, the C-rate performance and capacity retention based on Li/LP-GPE/LiFePO4 cell are superior to that of the commercial Celgard 2730 cell. Consequently, all these results demonstrate that LP-GPE can be applied as a novel electrolyte for lithium ion battery with high-performance, low-cost, and environment-friendly properties.ᅟ [ABSTRACT FROM AUTHOR]

The electrochemical performances of LiMnNiCoO cathode material are enhanced through hydrothermal approach using NaS solution as a medium. Furthermore, the influence of contents of NaS solution on the morphology, structure, and electrochemical performances is fully investigated. The results indicate that a high content of NaS solution results in the formation of spinel particles which are detected by SEM, XRD, and HR-TEM measurements. The formation of spinel particles leads to a deterioration of electrochemical performances. However, a low content of NaS solution results in a slight structure change from layered phase to spinel one near the edge of LiMnNiCoO particles. This slight structure change facilitates the decrease of charge transfer resistance, which contributes to the enhanced rate capability of NaS-treated LiMnNiCoO. [ABSTRACT FROM AUTHOR]

LiTiO/LiTiO composite nanofibers with the mean diameter of ca. 60 nm have been synthesized via facile electrospinning. When the molar ratio of Li to Ti is 4.8:5, the LiTiO/LiTiO composite nanofibers exhibit initial discharge capacity of 216.07 mAh g at 0.1 C, rate capability of 151 mAh g after being cycled at 20 C, and cycling stability of 122.93 mAh g after 1000 cycles at 20 C. Compared with pure LiTiO nanofibers and LiTiO nanofibers, LiTiO/LiTiO composite nanofibers show better performance when used as anode materials for lithium ion batteries. The enhanced electrochemical performances are explained by the incorporation of appropriate LiTiO which could strengthen the structure stability of the hosted materials and has fast Li-conductor characteristics, and the nanostructure of nanofibers which could offer high specific area between the active materials and electrolyte and shorten diffusion paths for ionic transport and electronic conduction. Our new findings provide an effective synthetic way to produce high-performance LiTiO anodes for lithium rechargeable batteries. [ABSTRACT FROM AUTHOR]

A novel disk-like shape of CoO with high porosity was synthesized by a facile hydrothermal approach followed by calcination at 485 °C for 2 h. In order to further confirm the crystal structure, morphology, particle size, surface area, and porosity of the sample, a series of corresponding characterization techniques were used. The disk-like shape of CoO as an anode delivered excellent rate capability such as 510.5 mAh g at 4.0 C, which is much higher than the theoretical capacity of commercial graphite anode (372 mAh g). However, the electrode could not recover the high capacity during the long-term cycling at various higher current rates due to the deformation of the structure as confirmed by the ex situ studies. It is believed that the obtained remarkable structural feature with numerous void pores within the structure may be helpful for short-term cycling due to the large contact areas between the electrode and the electrolyte and a shorter diffusion length for lithium ion insertion but unable to act as a buffer to relax the volume expansion/contraction and alleviate the structural damage of the electrode during long-term cycling. [ABSTRACT FROM AUTHOR]

A Ni-Co-Al ternary oxide precursor with a trigonal structure, which can be used to synthesize LiNiCoAlO cathode material, was prepared by calcining Ni-Co-Al composite oxalates formed by using a facile chemical approach. The LiNiCoAlO cathode material calcined at a temperature as low as 650 °C had acceptable electrochemical performance with an initial discharge capacity of 183.9 mAh g. The sample prepared at 750 °C possessed the highest initial discharge capacity of 196.0 mAh g, while the sample calcined at 700 °C showed the optimal capacity retention (89.9%) after 100 cycles under 1 C. To prepare a pure LiNiCoAlO phase by a conventional solid-state reaction, the calcination temperature should exceed 750 °C, and the highest initial discharge capacity was only 185.4 mAh g. We suggest that the ternary oxide precursor with trigonal structure accelerates lithiation and, therefore, promotes the generation of LiNiCoAlO with high crystallinity at a lower temperature. This study provides a facile way to synthesize layered cathode material with good electrochemical performance at a lower calcination temperature. [ABSTRACT FROM AUTHOR]

Electrophoretically deposited (EPD) lithium ferrophosphate (LFP) electrodes (LiFePO) containing either soft Mg(OH) or rigid PVdF binders have been fabricated and tested in LiSO aqueous solution. The use of Electrochemical Quartz-Crystal Microbalance with dissipation monitoring (EQCM-D) was shown to be extremely advantageous to distinguish between the effectively viscoelastic and rigid states of LFP and LFP/PVdF electrodes, respectively, based already on the raw EQCM-D (i.e. recording resonant frequency and resonance width changes of the electrode on multiple overtone orders). The approach that we developed for testing composite battery and supercapacitor electrodes is quite general, and includes mechanical characterizations of the electrodes in air, in contact with liquids and electrolyte solutions, and most importantly, during combined electrochemical and mechanical characterization of battery electrodes subjected to Li-ions insertion/extraction. A new theory of hydrodynamic admittance of porous semispherical bumps has been developed and successfully applied for the characterization of rigid porous LFP/PVdF composite electrode in its both intercalated and deintercalated states. We show that the extended Voight-type viscoelastic model describes quantitatively the intercalated and deintercalated states of LFP electrode coating containing soft Mg(OH) binder. The approach based on non-gravimetric application of EQCM-D developed in this work is unique and quite promising for in-situ mechanical characterization of a large variety of battery and supercapacitor electrodes for energy-storage devices. [ABSTRACT FROM AUTHOR]

We report the facile, one-step acetonitrile-mediated synthesis and self-assembly of β-AgVO nanowires into three-dimensional (3D) porous spongy-like hydrogel (~ 4 cm diameter) as cathode material for lithium ion battery of high performance and long-term stability. 3D structures made with superlong, very thin, and monoclinic β-AgVO nanowires exhibit high specific discharge capacities of 165 mAh g in the first cycle and 100 mAh g at the 50th cycle, with a cyclic capacity retention of 53% at a current density of 50 mA g. 3D structures are synthesized by reaction between ammonium vanadate and silver nitrate solution containing 5 mL of acetonitrile followed by a hydrothermal treatment at 200 °C for 12 h. Acetonitrile (used here for the first time in the silver vanadate synthesis) plays an important role in the self-assembly of the silver vanadate nanowires. A tentative growth mechanism for the 3D structure and lithium ions intercalation into β-AgVO nanowires has been discussed and described. [ABSTRACT FROM AUTHOR]

Ni-rich LiNiMnCoO (NCM811) is one of the most promising electrode materials for Lithium-ion batteries (LIBs). However, its instability at potentials higher than 4.3 V hinders its use in LIBs. To overcome this barrier, we have prepared a core-shell material composed of a core of NCM811 ( R-3m) and a monoclinic ( C2/m) LiMnO shell. The structure is confirmed by XRD, TEM, and XPS. This core-shell is very different from the conventional core-shell materials. In comparison, the conventional core-shell materials are layered R-3m structures which are instable at highly delithiated state (>4.5 V) due to the high repulsion between the two oxygen atoms facing each other across the empty Li site, while our synthesized material can be safely cycled at high upper cut-off potential of 4.7 V with high capacity retention. Compared to previously reported materials, the materials show substantially improved performance in terms of discharge capacity, energy density, and thermal stability. The upper cut-off potential is elevated from 4.3 to 4.7 V. Differential scanning calorimetry (DSC) results show that the exothermic peak of the core-shell structured material appears at 360 °C with a heat evolution of 575.1 J g, while that of the pristine material appears at 250 °C with a heat evolution of 239.1 J g. [ABSTRACT FROM AUTHOR]

A binder-free carbon nanofibres web over stainless-steel wafer current collector was fabricated by controlled pyrolysis of electrospun SU-8 photoresist nanofibres. Electrochemical performance of the as-prepared carbon nanofibres webwas investigated by performing charge–discharge experiments at different current densities. At lowcurrent density (37.2 mA g−1,0.1C), SU-8-derived carbon nanofabric showed a large initial discharge capacity (1417 mAh g−1) with sufficiently higher initial coulombic efficiency (∼55%). More importantly, this carbon nanofibres web also exhibited excellent rate performance with considerably higher specific capacities at higher current densities (358 mAh g−1 at 1C). This superior electrochemical performance, in particular at high current rates, can be attributed to small lithium ion diffusion length and resilience in entangled carbon nanofibres to accommodate volume changes during charging and discharging. [ABSTRACT FROM AUTHOR]

Negative electrode comprised of CuO nanoparticles (CuO-NPs), with an average particle size of 50 nm have been successfully synthesized by simple and convenient chemical precipitation method. XRD, SEM, FTIR and TEM have been employed for physical characterization. The electrochemical performances have been evaluated by galvanostatic charge-discharge and cyclic voltammetry. During the cycling test at 200 mA g, the CuO-NPs exhibited a stable discharge capacity of 516 mA h g, with 84% capacity retention. This superior electrochemical performance of CuO-NPs is mainly attributed to the nano-dimension of the particles, which benefit electron and Li ion transportation, with large electrode-electrolyte contact area. [ABSTRACT FROM AUTHOR]

Hierarchical porous carbon-TiO composites have been successfully synthesized via evaporation-induced self-assembly and in situ crystallization. The titania content and calcination temperature play significant roles in the structures, pore textures (micropore and mesopore) and electrochemical properties. The prepared composites as anode materials for lithium ion batteries show superior discharge capacity, cycling performance and rate capability. The composite of HPCT-600-5 exhibits the highest reversible capacity of 376.9 mAh g after 50 cycles at a rate of 0.1 C, and retains the capacity of 240.5, 180.2 and 117.0 mAh g even at the higher rates of 0.5, 1 and 2 C, respectively (1 C = 350 mA g). This outstanding electrochemical performance is attributed to the synergistic effects of hierarchical porous carbon and titania due to the unique structures, such as higher specific surface area and pore volume, fine TiO particles, appropriate distribution of hierarchical pore size and optimum content of TiO. The special structures of the composites can improve the wettability of the electrolyte, provide a large storage space for the Li ion, enhance the initial charge-discharge efficiency and reduce the resistance of the charge transfer and the diffusion of Li ions. [ABSTRACT FROM AUTHOR]

A sponge-like poly(vinylidene fluoride)/high density polyethylene (PVDF/HDPE) separator exhibiting high ionic conductivity and transference number of Li ion for lithium ion battery has been prepared by non-solvent induced phase separation (NIPS) method. HDPE fillers with size smaller than 250 nm are prepared with moderated reverse phase emulsion. The ion conductivity of PVDF/HDPE separator saturated with 1.0 M LiPF-ethylene carbonate (EC)/dimethyl carbonate (DMC)/ethyl methyl carbonate (EMC) (1:1:1, v/ v/ v) can be up to 2.54 mS cm at 25 °C, which is higher than that of pristine PVDF separator (1.85 mS cm). The transference number of lithium ion with PVDF/HDPE separator is 0.495, better than that with commercial PP separator (0.33) and pristine PVDF separator (0.27). What is more, LiCoO/Li cells assembled with PVDF/HDPE separator show good C-rate and cycling performance which indicates great potential in serving as a good candidate of polymer separator for lithium ion batteries application. [ABSTRACT FROM AUTHOR]

A series of LiV(PO)/C composites with different amounts of carbon are synthesized by a combustion method. The physical and electrochemical properties of the LiV(PO)/C composites are investigated by X-ray diffraction, element analysis, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy and electrochemical measurements. The effects of carbon content of LiV(PO)/C composites on its electrochemical properties are conducted with cyclic voltammetry and electrochemical impedance. The experiment results clearly show that the optimal carbon content is 4.3 wt %, and more or less amount of carbon would be unfavorable to electrochemical properties of the LiV(PO)/C electrode materials. The results would provide some basis for further improvement on the LiV(PO) electrode materials. [ABSTRACT FROM AUTHOR]