As a new type of energy storage device, lithium-ion capacitor (LIC) combines the advantages of both supercapacitors and lithium-ion batteries, which can provide high energy density, high power density and stable cyclic life. LICs are considered a promising candidate for energy storage in the fields of electric vehicles, rail transit, smart grids, and mobile electronic devices, ushering in their great prospects. Due to the high theoretical specific capacity, naturally abundance and environmental friendliness, metal oxides are considered as ideal anode materials for LICs. However, the low electronic conductivity and huge irreversible volumetric distortion greatly restrict their potential application. In this review, the preparation methods of metal oxide anode materials are summarized, and their electrochemical performances, advantages and disadvantages for LICs are analyzed. Finally, the future development of metal oxide anode materials is also discussed.

All-solid-state thin film lithium batteries, having perfect electrode/electrolyte solid/solid interface, can effectively improve the safety issue of the current commercial lithium-ion batteries using liquid electrolyte. Their outstanding electrochemical properties, including ultralong cycle life, wide temperature range, and low self-discharge, are superior to those of the bulk solid-state batteries and attract a lot of interest. The high fabrication cost and low energy density per unit area are the two main drawbacks for the current thin film battery technology, which limit their broad applications. In this perspective, we summarize the working principle, key materials, and research progress for thin film lithium batteries. The current commercialization and development bottleneck of solid-state thin film lithium batteries are summarized, and perspectives on future development and application of the next-generation thin film lithium batteries are provided.

This bimonthly review paper highlights 100 recent published papers on lithium batteries. We searched the Web of Science and found 1807 papers online from Apr. 1, 2018 to May 31, 2018. 100 of them were selected to be highlighted. Layered oxide and high voltage spinel cathode materials are still under extensive investigations for studying Li⁺ intercalation-deintercalation mechanism and evolution of surface structure, and the influences of doping, coating and interface modifications on their cycling performances. Large efforts were devoted to Si based composite anode materials for optimizing the electrode and electrolytes. The cycling properties of metallic lithium electrode are improved by using different kinds of surface cover layer. In-situ technologies are used to analyze the interface of solid state batteries and theoretical work covers the machnism for Li storage, kinetics, SEI and solid state electrolytes. There are a few papers related to electrolyte additives, solid state lithium batteries, Li/S batteries, modeling.

Available hydrogen storage technologies are reviewed in this article, mainly including physical and chemical hydrogen storage. The physical hydrogen storage technology incudes high-pressure gaseous hydrogen storage and low-temperature liquified hydrogen storage. These methods have advantages of being low-cost, easy to discharge and with a high hydrogen, but safety can be an issue. The chemical hydrogen storage technology is often based on chemical interactions of hydrogen with a substance. such as organic liquid, ammonia, hydride, inorganic substance and methanol etc. These chemical compounds are stable so have an advantage of high storage safety. However, this type of methods often come across issues of slow discharge process and low hydrogen purity due to by-products. To address the issues associated with the main physical and chemical storage methods, alternative hydrogen storage technologies have been proposed, including absorption and hydrate based gas separation. The most widely used absorbents are metal, carbonaceous material and metal-organic frameworks (MOFs) but high cost and low energy density are the main issues. Hydrate based storage technology is favorable in terms of cost and energy consumption but the energy density is low.

Silicon based anode materials with high specific capacity, low voltage plateau, environmental friendliness and abundant resources, are expected to replace graphite for the next generation lithium-ion batteries with high energy density. However, the conductivity of silicon is poor. Even worse, the huge volume change of Si during charge/discharge process can result in large electrochemical polarization, material pulverization, SEI film reconstitution, low coulombic efficiency and continuous capacity fading. However, silicon and carbon composites can combine their advantages of high capacity and excellent electronic conductivity, forming an anode with stable structure, good cycle stability and high capacity. This paper reviews the research progress of Si/C composite in the structural design, preparation process and electrochemical performance from the view of different dimensions of silicon (SiNPs, SiNTs/SiNWs, SiNFs, Bulk Si), and the Si/C composite materials for future research are also prospected.

With the miniaturization and lighting of the portable electronic products, and the rapid development of electric vehicles and grid energy storage devices, lithium ion batteries with higher energy density and higher performances are increasingly demanded. Cathode materials play a key role in lithium ion batteries and their improvements are crucial for enhancing energy density of lithium ion batteries. Nowadays, cathode materials of high energy density with lower production cost and high safety for lithium-ion batteries has been of great significance. This paper summarizes recent progress in cathode materials from the prospects of enhancing the specific capacity and the working voltage, and mainly focuses on design and preparation of meso-scale structured nickel-rich and lithium-rich layered oxide and spinel oxide cathode materials with tunable electrochemical performances.

Lithium sulfur (Li-S) battery has become a hotspot of next-generation high-performance secondary batteries in recent years, by virtue of the advantages of high energy density, low cost, favorable environmental friendliness. However, low utilization of active materials, rapid capacity decay and serious self-discharge greatly hindered its practical application. Since cathode is a key component of rechargeable battery, it is very necessary to design and construct rationally the constitution and structure of sulfur cathode for improving the cell performances. In this paper, basic principles, existent problems and solving approaches of Li-S battery were analyzed at first. Then, the research progresses on active material, current collector, coating layer, binder and additive of sulfur cathode were reviewed. Finally, the further developing prospects of the battery were discussed. It is pointed out that more attention should be paid to real energy density of sulfur cathode, and research scope of Li-S battery should not be limited to cathode material.

This article reviews the applications of MXene materials used in fuel cells. MXene is a new family of two-dimensional transition metal carbides and carbonitrides materials. This kind of materials can usually be produced by etching the A element from the MAX phases. For the good electrical conductivity, hydrophilicity, transparency and flexibility, MXenes will be good candidates in the fields of catalysis, energy storage, composite materials, sensor, antibiosis and so on. The synthetic methods, structure, chemical stability and electronic characteristics of MXenes are briefly introduced in this paper. The applications of these materials in fuel cells are summarized, especially as Pt catalyst supporters. MXene supported Pt catalysts exhibit high activity and stability for oxygen reduction reaction. At the end of the article, some problems and challenges of MXene used in fuel cells and as catalysts supporters are proposed.

Lithium-ion capacitor (LIC) consists of a battery-type anode and a capacitor-type cathode in the organic electrolyte containing lithium salts, combining the excellent power characteristics of a supercapacitor with the high energy density of a lithium-ion battery. It has a board application prospect on smart grid, rail transportation, hybrid electric vehicles and other fields. Because of a wide range of sources, low prices, stable performance, carbon materials are used as the preferred electrode material of LIC and carbon-based LIC has a competitive industrialization prospects. The negative electrode pre-lithiation technology has a decisive influence on the electrochemical performance of carbon-based LIC. Herein, the progress of pre-lithiation technology for LIC is systematically reviewed from the introduction of lithium source. The key factors in the process of pre-lithiation are also reviewed. It is helpful for the comprehensive understanding of the pre-lithiation technology research status, providing scientific reference for the further development of LIC.

Li metal has the highest specific capacity (3860 mA·h·g^-1), the lowest negative electrochemical potential (-3.040 V vs. the standard hydrogen electrode) and a low density (0.59 g cm^-3), so Li metal is one of the most promising candidates as an anode material for next-generation energy storage systems. But unfortunately, the battery has hardly been commercialized successfully so far because the safety problem and low cycle efficiency of Li metal battery during charge and discharge. Li ion battery has been developed becoming mature nowadays, but its capacity cannot satisfy the advance in new technology. Therefore, it is of great urgent to develop next generation battery, Li metal battery is a good choice. To solve the problem of Li metal battery in application, a buffer layer is proposed in this paper which is inserted between anode and separator. In this paper, carbon nanotube (CNT) and polyaniline-carbon nanotube (PANI-CNT) film were used as buffer layer and inserted into the battery. Rate test and cycle test were taken to compare the rate performance and cycle performance of battery with and without buffer layer. And scanning electron microscopy test was taken to observe the growth of Li dendrites. Experiment shows that buffer layer is useful to suppress the growth of Li dendrite, and it can improve the safety and cycle efficiency of Li metal battery.

ZIF-67, a metal-organic framework (MOF), was grown on expanded graphite (EG) sheet by in-situ precipitation to obtain modified ZIF-67/EG, which, upon calcination, formed a hierarchical porous Co₃O₄/EG hybrid. By using a melting blending and vacuum adsorption methods, stearic acid (SA), SA/Co₃O₄/EG composite phase change material (PCM) was then prepared. The materials were characterized for their microstructure, phase, phase change enthalpy, phase change temperature and charging/discharging behavior. The influence of the microstructure of Co₃O₄/EG on the thermal properties of the SA/Co₃O₄/EG composite PCMs was analyzed. The results showed that the effect of Co₃O₄/EG on the phase transition temperature of SA/Co₃O₄/EG composite PCMs was small, and the phase transition temperature was independent of the amount of Co₃O₄/EG addition. However, the latent heat of the composites PCMs decreased with increasing Co₃O₄/EG content, consistent with the theoretical calculation. The Co₃O₄/EG hierarchical porous structure was shown to be able to prevent the agglomeration of Co₃O₄, providing a high specific surface area and pore volume adsorption of SA. The synergistic effect of the porous structure Co₃O₄ and high thermal conductivity of EG could increase the heat transfer of SA and improve the heat release rate.

With the excellent energy density and power density, power-based supercapacitor has been regarded as the most important devices for energy storage and saving system. After simulated the electrolyte leakage situation, using the commercial power-based supercapacitor as the target, the comparison between leakage and no-leakage electrolyte cells have been analyzed, and its high temperature accelerated life test also been discussed. It shows that silver crystal appears, and once the leakage amount is more than 12 g, cell's capacitance and ESR will decrease dramatically. When the amount is over 28.5 g, cell's capacitance and ESR will drop off near 12.1% and 31.3%, respectively. The accelerated life test (Cap-4) also revealed that the over leakage cell will represent more gas release times, and its capacitance will decrease 38.4% and ESR reaches 85.1%.

The development of rechargeable Li-O₂ battery (LOB) has encountered bottlenecks at this stage. One of the biggest challenges is to lower the oxidation potential of Li₂O₂, the insulating and insoluble discharge product. In this paper, 1, 3-Dimethyl-2-imidazolidinone (DMI) is first to be used as electrolyte in LOB, which can increase the solubility of lithium peroxide, promote its solvation, and improve the contact between Li₂O₂ and cathode, resulting in an improved battery performance. Compared to the traditional TEGDME electrolyte, DMI can increase the charge capacity by 1.5 times, while decrease the charge overpotential by 0.6 V, which suppress the side reaction caused by high potential. At the same time, by adding oxygen inhibitors, the oxygen radicals in the solvent are stabilized, the nucleophilic attack on the DMI by the discharge intermediate product is reduced, and the cycle performance of the battery is significantly improved.

Concentrated solar power systems provide a high temperature heat source by concentrating solar radiation for electricity generation. To ensure a stable output, plants with molten salt-based energy storage system have been developed. This study aims to understand the dynamic response of the molten salt loop of a 50MW power plant by modelling and simulation. Such a loop includes a receiver, a hot and a cold storage tanks and a steam generator (heat exchanger). The work was done with the Modelica programming language and Dymola under different working conditions. The simulation results showed that the receiver could reach steady state in 30 s. However, it took~5.5 hours for the storage tank to reach the steady state. The response of the heat exchanger was found to also be very quick with a steady-state reached within~1500 s to reach a completely steady state.

The thermal properties of a Ca(NO₃)₂-KNO₃ (0.47:0.53) based nitrate molten salt with an additive (0.1% to 15%) was prepared, characterized and cost-analyzed. Such a system has a low melting point, a high specific heat capacity and a high thermal decomposition temperature. It was shown that the new formulation had a melting point of 120.1℃ with a latent heat of fusion of 76.37 J·g^-1, a decomposition temperature of 588℃, and an average specific heat of 1.598 J·(g·K)^-1, illustrating an enhanced performance than traditional solar salt and Hitec formulations. The results also suggested a cost of RMB 108 yuan per kW·h.

Conjugated carbonyl compounds have become the one of the most widely studied class of organic electrode materials due to its good ion and electron transport properties and high reversibility. The sodium salt of 3, 4, 9, 10-perylenetetracarboxylic acid (Na₄C₂₄H₈O₈, Na-PTCA) was synthesized by the reaction between 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) precursor with NaOH solution. Na-PTCA exhibits a stable cycling performance, which discharge specific capacity remains 468 mA·h·g^-1 after 100 cycles at a current density of 50 mA·g^-1 in the voltage range of 0.01~2 V vs. Li⁺/Li. Meanwhile, the redox sites of carboxylate groups (C=O) showing discharge/charge plateaus at about 1.10/1.38 V deliver a high cyclic reversibility and reveal a reversible capacity of 148 mA·h·g^-1 after 100 cycles. These results provide a design strategy for expanding the families of anode electrode materials for lithium ion batteries.

A new binary organic phase change material with a phase change temperature of 0~3℃ was developed. The material was mad by mixing tetradecane and octanoic acid around their eutectic point predicted by a theoretical calculation, which also gave the latent heat. A differential scanning calorimeter, a step cooling curve measurement device, and a hot disk thermal analyzer were used to measure the thermal properties of the formulations. A cyclic thermal testing box was used for understanding the cycle stability of the formulations. The results showed that the eutectic point was 1.0℃ at a molar mass ratio of tetradecane to octanoic acid of 51:49 with a latent heat of 191.8 J·g^-1, and a thermal conductivity of 0.3790 W·(m·K)^-1. The phase change material was shown to have a good cycle stability:the phase change temperature was 0.9℃ and the latent heat was 191.5 J·g^-1, after 100 cycles.

A mathematical model is established based on the analyses of energy storage technologies and the structural traits of a power grid for accommodating intermittent renewable resources, subject to constraints of the maximum amount of power the grid can release for the renewable generation and the reduction of wind wind/PV curtailments. The analyses consider energy storage system investment and return due to the increase of renewable energy related income. Two provincial power grids (which mainly accommodates wind and PV generation) are used as examples for the validation of analyses.

sing α-Al₂O₃ and Li₂TiO₃ as safety additives in the positive and negative electrodes of Li-ion battery respectively, a mechanism model of safety additives has been proposed, and the effects of these two additives on the electrochemical performances and safety performances were investigated systematically. The electrochemical performance test results showed that energy density of Li-ion battery will reduce slightly as a result of safety additive; meanwhile, the rate performance is not affected. 82.3% capacity retention at 5C discharge rateis obtained and the battery's cycle life is expected to reach 2409 times (calculated as 80% DOD) compared with 896 times of the control battery. The safety performance test results showed that the battery with electrode safety additives could pass strict safety tests such as punch test, shock test and external short circuit test. The presence of safety additives could avoid the occurrence of local hot spots inside the battery effectively and turn the uncontrollable internal short circuit into controllable low rate discharge, which improves the battery's safety significantly, demonstrating a good application prospects in commercialization.

To investigate the temperature-variation of the soft package lithium-ion battery during discharge, based on the basic heat generation model, through internal resistance test and temperature rise experiment under 0.5 C discharge, the transient heat rate curve is calculated and entropy coefficient is obtained. A transient thermal model can be established and the heating rate varies with the depth of discharge changing. The temperature variation was simulated by using this model and compared with the experiment. It shows that the simulation results are consistent with the experiment. This model can simulate the battery temperature change process under different discharge ratio very well, which has guiding mean for the battery temperature variation analysis and the thermal management.

This numerical study aims to reduce pressure loss and improve thermal efficiency of a regenerator of an aluminum smelting furnace. A porous medium based model with a modified source item of the momentum equation, coupled with energy equations for both gas and solid phases, which upon using suitable, was established for modelling the regenerative process in Fluent environment. The mathematical model was used to investigate the effects of 4 main parameters on the thermal storage process, storage efficiency and pressure loss of the stratified regenerator. The results were analyzed by using the orthogonal experiments and variance analysis, and the collocation scheme for an optimal regenerative efficiency and pressure loss minimization. It was found that an optimal regenerative efficiency occurs with an entrance mass flow of 1.65 kg·s^-1, a particle size combination of 26 mm-18 mm-26 mm, whereas the optimal pressure drop takes place with an entrance mass flow of 1.65 kg·s^-1, a particle size combination of 32 mm-24 mm-32 mm, and the upper middle and lower layer high ratio at 2:1:2.

A battery-supercapacitor hybrid energy storage system (HESS) is applied to a PV grid-connected system to deal with fluctuation and intermittency of the PV microgrid to achieve smooth photovoltaic system power output, balance and improve grid power quality. Considering the upper limit of the battery power and the state of charge (SOC) of the supercapacitor, a power distribution strategy is proposed for the hybrid energy storage system. The strategy uses the SOC of the supercapacitor and the output of the power allocation unit as a reference value to design the hybrid energy storage system charge and discharge processes. The supercapacitor and the battery are connected to the 500 V DC bus using a Bi-direction DC/DC converter. The supercapacitor controls the DC bus voltage through a double closed-loop control strategy. The simulation results show that the proposed power allocation strategy can rationally distribute the power of the hybrid energy storage system, achieve the grid connection of unit power factor and stabilize the DC bus voltage.

Electrochemical impedance spectroscopy (EIS) is an important electrochemical measurement method. It is widely used in the field of electrochemistry, especially in lithium ion batteries, such as measuring the electrical conductivity, apparent chemical diffusion coefficient, growth and evolution of SEI, charge transfer and the mass transfer process. This paper mainly focused on the basic principle of electrochemical impedance spectroscopy (EIS), the testing methods, the matters needing attention and the equipment used in the electrochemical impedance measurement. Finally, the application of the electrochemical impedance spectroscopy in the lithium ion battery is introduced in a practical case.

The separator is an important material for ensuring the safety and the performances of the battery. With a rapid development of the separator industry in China, the production capacity of separator has been the 1^st position in the world. Serialization, standardization of quality, and standardization of testing standards are necessary steps. This article analyzes the related standards related to separator and mainly explains the method of testing and reference standards.

The nationality distribution, applicant distribution and the technical means and technical efficacy distribution of lithium-ion battery polyolefin multilayer separator were investigated from the view of patents. The result shows that Japan, China, South Korea and the United States are main technology exporter, Toray, Asahi, Sumitomo from Japan, LG from South Korea, Senior technology material Co., LTD and Chinese academy of science from China are the main applicants. Using a specific components in a layer, the design of modified layer, as well as the regulation of pore-forming process are the main technical approaches, aiming at the improvement of permeability, porosity, pore uniformity, heat resistance, heat shrinkage, heat closed performance, mechanical strength and ion permeability.