Safety issues of lithium-ion batteries are becoming prominent with its application in electric vehicle and large-scale energy storage fields. Flammable gases evolved from electrode|electrolyte interface play an important role on the batteries' safety characteristics. Fortunately, differential electrochemical mass spectrometry (DEMS) as a powerful technology provides exploitable strategies for understanding the gas-related parasitic reaction mechanisms. The review covers the history, basics, know-how, and applications in safety researches of DEMS. In addition, emerging opportunities, critical challenges, future directions and strategies are particularly highlighted.

This bimonthly review paper highlights 100 recent published papers on lithium batteries. We searched the Web of Science and found 4397 papers online from Oct. 1, 2018 to Nov. 30, 2018. 100 of them were selected to be highlighted. This bimonthly review paper highlights 100 recent published papers on lithium batteries. We searched the Web of Science and found 4397 papers online from Oct. 1, 2018 to Nov. 30, 2018. 100 of them were selected to be highlighted. Layered oxide and high voltage spinel cathode materials are still under extensive investigations for the structure evolution and modifications. Large efforts were devoted to metallic lithium anode for investigating the effects of surface modification. Number of papers related to solid state batteries including electrode design and interface construction. There are a few papers related to solid state electrolyte, Li/S battery, Li-air battery, analyses methods, theoretical simulations, and modeling.

The development of multivalent batteries is promising for resolving lithium batteries' bottlenecks, such as safety issue, high cost and limited energy density. Calcium (Ca) is more abundant, and has lower standard reduction potential (-2.87 V) and density than zinc and magnesium. However, Ca-based battery gets less attention than other multivalent batteries, which is mainly due to the limitation of Ca²⁺ transport through the solid electrolyte interphase (passivation layer formed at the interface between Ca anode and organic electrolyte), and thus the inefficient stripping/plating processes. Meanwhile, another challenge in this field concerns the development of Ca²⁺-storage electrode materials and in-depth understanding of the ingress process is required. Here, we introduce recent research progress on the electrochemical behavior of metallic Ca and its alloys in various electrolytes, as well as the intercalation (Prussian blue analogs, vanadium oxides, etc.) and conversion (Ca-sulfur batteries, Ca-oxygen batteries) cathode materials.

Reliable and stable power supply is a key to an effective operation of on-line monitoring equipment of a high voltage (HV) transmission system. This paper reviews power supply technologies commonly used for on-line monitoring terminal of transmission lines with a focus on energy collection and storage. Energy collection technologies include mainly the taking of electricity from the measured system, the taking of electricity from the outside of the measured system, and combining electricity using multiple ways. The energy storage technologies include electrochemical based battery technologies and supercapacitor based storage technologies. The advantages of these technologies and the problems that remain to be resolved are summarized. Based on the above, we discussed future development trends of power supply modes of on-line monitoring systems.

Supercapacitors (SCs) have a fast charge-discharge rate and hence a great potential for high power energy storage applications. However, the low energy density of SCs has limited their developments. On the other hand, the fast development of flexible electronic devices requires flexible energy storage devices. The development of SCs with both high energy and power densities as well as a long cycle life therefore become an area of active research. This article first introduces the principle of SCs and their classification. A review is then performed on the latest progress in electrodes and preparation methods of carbon fibers based flexible SCs. Finally, the prospects and challenges associated with flexible SCs in practical applications are also discussed.

The models of lithium-ion batteries, including equivalent circuit models and electrochemical models, are reviewed. Models are used for the degradation mechanisms analysis, state estimation and life prediction of lithium ion batteries due to the time-effectiveness and applicability. The equivalent circuit models are more applicable for state of charge estimation and the electrochemical models are suitable for the degradation analysis and state of health estimation of lithium ion batteries. The simple and fixed model structure for equivalent circuit models and the complicated model structures and heavy computation for electrochemical models limit their application. The authors summarize the principles and structures of equivalent circuit models and electrochemical models. Then the application of these models is described and the merits and limitations of each model are elaborated. Then, based on the analysis mentioned above and the state-of-the-art modelling theory, the future research direction on more accurate and universal battery models is put forward.

This paper presented a review on the study of electrode materials for vanadium redox flow battery(VFB), which covered the categories of electrode material, the methods of improving performance in electrode, research progress by modifications, and the aging mechanism of electrode. The methods of electrode modified were presented in detail. The results indicated that improvements of reactivity and active areas of electrode were both effective ways to optimize performance of electrode. Exposure electrodes to acid or heat treatment could increase the reversibility of electrode. Through growing CNTs on the electrode in situ, loading graphene or iridium oxide on surface of electrode, or using porous carbon electrodes prepared from natural waste, the electrodes could exhibit the higher electrochemistry active areas and reversibility at the same time. A practical means to combine bipolar plates with graphite felts as an integrative electrode could obviously reduce the contact resistance, which would benefit for decreasing the polarization voltage. In addition, the aging of electrode could effect on its' service life. The results showed that aging of electrode would have a worse impact on negative electrodes than that on positive electrodes. Finally the present situation and problem for VFB were summarized and the research direction of electrode materials for VFB was prospected.

Li-ion batteries are the most popular portable power source in modern life and promises a broad range of application field, because of its advantages of high energy density, long cycle life, safety, and so on. In order to further improve lithium ion battery and promote its practical process, the study of electrode reaction mechanism is necessary. Atomic force microscope (AFM) can detect the micromorphology of the electrode surface in real time by the interaction between the tip atom and the electrode surface atom. The physical and chemical information of electrode surface is provided on nanometer scale, which provides experimental basis for the optimization modification of electrode material and electrolyte. In this paper, the latest applications of AFM in Li-ion batteries are reviewed, including the morphology changes of electrode materials under electrochemical reaction conditions, nano-mechanical properties and electrical properties, etc. It is concluded that AFM will further promote the research progress of lithium ion batteries.

A distributed combined heating and power (CHP) system is an advanced energy system which is close to end users. The selection of system configuration, capacity and operation strategy has an important impact on energy saving, environmental protection and economics of the system. This research took a building as an example and analyzed the characteristics of the thermal and electric loads using real time data. At the same time, two different configurations were constructed for the CHP system using respectively a micro-turbine and an internal-combustion engine as the power source, and corresponding variable-condition energy balance models were established. Furthermore, the influence of the power unit capacity on the economics, energy saving and environmental protection of the office building was discussed under different operation strategies, such as Following Thermal Load and Following Electric Load, operating under varying operating conditions and rated operation, with and without heat storage, 24-hour continuous operation and early rising and late stopping. Meanwhile, a multi-objective evaluation index was used to evaluate the benefits of the system under different installed capacities and operation strategies, and a chaotic particle swarm optimization algorithm was introduced to find the maximum comprehensive benefits of the system. The results showed that the economic, energy-saving and environmental protection performance of the office building with the CHP system was better than the traditional single function model, and the enhancements were 22.85%, 17.45% and 25.06%, respectively.

The modified expanded vermiculite is used as the adsorbent material, and the lauric acid and stearic acid are used as the phase change materials. The shaped composite phase change material is prepared by melt blending method and vacuum adsorption method, and then mixed into the mortar to prepare the heat storage mortar. The results show that the phase change enthalpy of the composite phase change material after 16 cycles is 167.6 kJ/kg, the change rate is only 3.6%, the thermal stability is good, no leakage phenomenon, and the 28 d strength of the mortar with 30vol% composite phase change material is incorporated. It is 9.2 MPa. The heat storage mortar mixed with the shaped phase change material has excellent thermodynamic properties and can be completely applied to the building envelope to adjust the indoor temperature.

Energy storage technology is one of the key enabling technologies for smart grids. Compressed air energy storage (CAES) technology has the potential to provide a similar storage capacity as a pumped storage power station, which is characterized by a large system capacity, potentially low construction and operation costs, a long lifetime, long storage period and limited site selection. Thermodynamic principles suggest a high efficiency of the CAES with an isothermal operation. Therefore, a virtual pumped storage system (VPSS) based on the isothermal CAES is proposed in this work. A constant power operation control strategy suitable for a steady operation of VPSS and a power adjusting operation control strategy are proposed for the storage system. A simulation model of permanent magnet synchronous linear motor (PMLSM) is built within a MATLAB/SIMULINK environment and a magnetic field vector-oriented control method based on SVPWM is used to control the PMLSM. According to the system operation strategy and linear motor control strategy, the basic model of VPSS based on linear motor are simulated and the simulation results verify the feasibility of the proposed constant power operation control strategy.

Thermal properties of paraffin wax (PA) and paraffin/expanded graphite (97% PA/3%EG and 95% PA/5%EG) composite materials were investigated. Heat release performance of thermal energy storage (TES) units with different diameters containing the phase change materials were studied at a drying media temperature of 25℃ and a media velocity of 0.8 m·s^-1. The results showed that the thermal conductivity of the composites was increased by 178.10% and 214.30% respectively compared with that of PA, which could shorten the TES unit discharge time. The diameter of the TES unit had a significant effect on the heat release performance. An increase in the diameter of the PA based TES unit leads to a linear increase in the heat release time, whereas an increased EG content reduces the heat release time of the unit for a given TES unit diameter. The effect of EG on the heat release performance of the TES unit increases first and then decreases with increasing diameter, leading to an optimal TES unit diameter of 35 mm under the conditions of this study.

The high specific capacity with high rate characteristic graphite anode was synthesized by nitrogen doping and secondary particle bonding technologies. The reversible capacity of the obtained graphite was 359.8mAh/g. The full pouch cells with the minimal energy density of 230Wh/Kg (650Wh/L) were assembled to evaluate the electrical performance. The charging capacity can research 51% within 10 minutes, and 100% within 30 minutes, demonstrating an excellent fast charging characteristics. The fast charge cycle test with 3C-rate charge and 1C-rate discharge was conducted at room temperature. It shows that even after 1000 cycles, there is still 88% of the initial capacity, and the maximum swelling rate is 10.1%, which can meet the demand of most electron devices and electric vehicles.

Applying styrene butadiene rubber-carboxymethyl cellulose (SBR-CMC) and polyvinylidene fluoride (PVDF) as anode binder, respectively, the influence of different anode binders on the high power li-ion battery performance was researched. Glass transition temperature of PVDF, SBR and CMC was tested by the method of differential scanning calorimetry (DSC), and the values were -51.7℃, -42.18℃ and -55.82℃, respectively. Pouch cells were prepared with the two kinds of binder. The rate performance testing result showed no obvious difference at room temperatures. However, due to the different glass-transition temperature of the two binders, the sample cells with PVDF binder exhibited superior performance in low temperature discharge. The cells were discharged at 0.5 C at the temperature of 20℃ and -40℃, and 1 C at -40℃, respectively, the discharge capacity ratio of cell with SBR-CMC binder to that of the with PVDF binder cell were 1.004, 0.706 and 0.589.

Ti₃C₂T_x MXene sheets were prepared by etching Ti₃AlC₂ MAX ceramic powders, followed by intercalation and ultrasonic exfoliation. With an ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate, as a heteroatom-doped N and B source, a new type of N, B-doped MXene (N, B-Ti₃C₂T_x) was synthesized by heat treatment of the MXene at different temperatures, and used as an electrode material for supercapacitor fabrication. The influence of annealing temperature to capacitive performance was studied, and the results indicates that the capacitance performance was effectively improved at a calcination temperature of 300℃. The mass capacitance of N, B-Ti₃C₂T_x-300℃ was measured to be 65 F/g at a scan rate of 100 mV/s, which was 5.5 times higher than that of Ti₃C₂T_x. The EIS showed that the contact resistance of N, B-Ti₃C₂T_x-300℃ was 0.52 Ω. The capacitance retained 84% at a current density of 2 A/g after 1000 cycles.

Dynamic ice storage is a latent heat storage technology in the field of energy storage. A small type experimental device for dynamic preparation of ice slurry was designed and built based on the flat scraping method. The effects of crystallization time, coolant temperature, type and concentration of additives, and scraping speed on the dynamic crystallization characteristics of the ice slurry were analyzed by testing the dynamic crystallization cooling curve of the ice making solution, and the ice content with crystal equivalent diameter at different crystallization moments.The results show that the scraping speed is lower than 200 r/min, and the degree of crystallization supercooling of the solution increases with the increase of the scraping speed. The ice content of the ice slurry and the ice crystal grain size increase with the crystallization time. When the ice crystal size is large, the scraping action causes the ice crystal particles to coalesce and break, which causes the degree of ice crystal size increase to slow down or even reduce.With the increase of additive concentration, the increase rate of ice content in ice slurry and the increase of ice crystal size were both decreased, and the effect of strong polar inorganic compounds on ice crystal growth was stronger than that of glycol and other alcohol compounds.

The power battery safety problem brought about by the rapid growth of electric vehicles has become the focus of the industry. The rapid safety inspection of power batteries has become the demand of the current market. This paper designs a power battery charge and discharge detection system based on bidirectional inverter hardware module and C#.NET host computer software module. The system is tested for electric vehicle power batteries and second use batteries, which are characterized by rapid detection and in-depth inspection. The rapid performance shows that the battery pack insulation safety and monomer consistency are detected within two minutes, and it obtains the distribution map of opening circuit voltage (OCV) of battery cells and direct current (DC) internal resistance to quickly diagnose the battery consistency problem according to the DC internal resistance detection module. The data of each detection module finally generates an electronic test report and is saved in Excel format for further analysis as well. The system is reliable and can provide a reference for the promotion and application in the field of energy storage.

A mathematical model was developed for a flywheel system based on the characteristics of a switched reluctance motor (SRM) and simulated under a Matlab/Simulink environment. The influence of the maximum permissible current and the breaking angle on the system performance was analyzed. Based on the analyses, a control mode of charging and discharging of the system was designed. During charging, the current chopper control and angle position control were adopted; whereas in discharging, the current chopper control was adopted. The simulation results showed that the charging and discharging processes had the characteristics of a fast response speed and a high steady state precision with the proposed control method. Finally, the feasibility of using SRM based flywheel as an uninterruptible power supply was verified by simulation.

An ionic liquid of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF₄) was employed to fabricate two high-voltage electrolytes for applications in large-capacity cylindrical supercapacitors. The capacity, resistance (ESR) and cycle performance of the devices were investigated, and the heat generation behavior during high-voltage cycling were analyzed. Compared to commercial high-voltage electrolyte, the two as-prepared electrolytes with a suitable ionic conductivity increased the energy density of the device to a certain extent, but the power density decreased due to an increased ESR. It is difficult for the commercial high-voltage electrolyte to cycle normally at a voltage of exceeding 2.85 V due to rapidly-increased surface temperature. However, the two as-prepared electrolytes significantly reduced the temperature rise and improved the high-voltage cycle performance of the device. In addition, decreasing the current density also effectively controlled the temperature rise rate of the supercapacitor. All the supercapacitors maintained stable cycles at a upper voltage of 3V. The electrolyte of EMIBF₄/AN even provided a favorable cycle at a upper voltage of 3.2V, with maximum energy density and power density (based on total mass of the device) of 8.62 Wh/kg and 16.18 kW/kg, respectively.

In order to improve the speed and efficiency of the capacitive equalization method, a charge-discharge combination strategy for establishing voltage drop is proposed. The working process of the combination strategy and the conventional scheme is analyzed. The difference of equalization speed between the two schemes is compared. The equalization circuit is equivalent to the full-response RLC circuit. The relationship between energy loss rate and circuit parameters is analyzed by formula deduction and Matlab calculation. The effect of different charge-discharge combinations on equalization efficiency is compared. The results show that the drop combination strategy can significantly improve the speed of capacitive equalization, and the equalization efficiency can be improved by optimizing the charge-discharge combination. The proposed scheme is analyzed and verified by experiments. The results show that the method can effectively solve the problem of unbalanced battery pack.

Molten salts play a key role in thermal energy storage of solar thermal utilization. The higher the upper limit of the usable temperature of molten salt, the greater the heat storage density and the higher the energy transfer efficiency. This work uses both experiments and quantum chemical calculations to study factors affecting the stability of two molten salts of Solar Salt and HITEC at a high temperature. Solar Salt and HITEC were firstly prepared, which involved drying of NaNO₃ and KNO₃ powder in a vacuum oven at 120℃ for 24 hours; mixing the dried NaNO₃ and KNO₃ in a mortar with 60%:40% (mass ratio) followed by grinding of the mixture; heating the ground powder mixture in a resistance furnace at 400℃ for 12 hours; cooling the molten salt down and grounding the sample to a powder form. The resulting material gave the Solar Salt. The HITEC were prepared by using the same method with mass ratio of KNO₃, NaNO₃ and NaNO₂ being 53%:7%:40%(weight fraction). High-temperature stabilities of samples were studied by DSC-TG analyses. The decomposition of the products was analyzed by XPS. The nitrate decomposition into nitrite was simulated by a software based on B3LYP functional with a base group of 6-31+G^*. Finally factors affecting the stability of the nitrate salts were discussed from the reaction mechanisms. The results showed that, when heated to 600℃, Solar Salt and HITEC mass losses were 2% and 1%, respectively. No metal oxides were produced or the production rate is too low to be observed. The difference in the metal ion proportion and the difference in the acid radical proportion were regarded as possible factors for the difference in the stabilities of the molten salts. The radii of the metal ions were found to be different, leading to different energies of intermediates and transition states. The movement of chemical equilibrium, caused by reactant, was considered as an additional reason for the different thermal stabilities of the Solar Salt and HITEC.

Accurate and reliable recognition of abnormal batteries is of vital to ensure the stable and safe operation of the battery system. However, it is difficult to deduce the internal information of the battery such as internal resistance and capacity from the limited external information of real-time measured current, voltage and temperature, and consequently to identify abnormal cells. In this paper, based on the voltage measurement of each cell in series lithium-ion batteries pack, an abnormal battery recognition method is proposed, in which dynamic time warping and multi-dimensional scaling strategy are properly combined. The dynamic time warping strategy is used to calculate the dynamic time warping distance to eliminate the effect of inconsistent state of charge in the battery pack, and then the multi-dimensional scaling method is used to extract the abnormal features to achieve visual recognition of abnormal batteries. The effectiveness of the proposed method is demonstrated by battery system simulation results. The results show that the proposed method is a potential promising technology for on-line recognition of abnormal batteries.

In this study, a pouch lithium ion battery was fabricated by using NCM as cathode material and LTO as anode material. Four different N/P ratios were designed by changing the capacity of LTO anode. The battery capacity, high temperature storage and cycling performance were studied, and the results show that increasing the N/P ratio can improve the initial discharge capacity of the battery. However, increasing the N/P ratio will increase the potential of the positive electrode, and the electrolyte will be easily oxidized on the positive electrode side, especially near the fully charged state. The low N/P ratio may ensure that the positive electrode has a lower electrode potential, which reduces the side effects of the LTO battery and improves the high temperature storage and cycling performances.

Utilizing the abandoned mine to construct pumped storage plant is not only a new form of exploration, but also a bidirectional product on account of the demand of power market and ecological environment restoration. Based on the clear definition of three utilization patterns to different mines, three aspects including mine site selection, kinetic energy estimation, and project layout have been researched and verified in the typical case in the technical feasibility analysis. And the purpose of this paper is to provide reference for further design and project layout optimization of pumped storage plant utilizing abandoned mine.

An increased attention has been paid on supercapacitors around the world due to some desirable properties for energy storage. We investigated the development trend of the technology, research hotspots, research and development directions and competition patterns by using analysis tools including the Thomson Data Analyzer(TDA), the Patsnap and the Derwent Innovations Index (DⅡ) of ISI WoK.The results show that the number of patent applications for supercapacitor technologies has experienced a rapid increase from 2009; the main research and development directions have been focused on electrode materials and electrolytes; and the research hotspots have been mainly on double-layer capacitors, capacitor electrodes, and electrolytes, etc. Top three countries for patent applications are China, Japan and the United States, and top three organizations for patent applications are PANASONIC CORP, NIPPON CHEMICON CORP, and MEIDENSHA CORP.

The application trend, nationality distribution, major applicants, the technical means and technical efficacy distribution and the key patent of aluminum plastic film for lithium-ion battery were investigated from the perspective of patents. The result shows that patent applications increased rapidly since 2011. Japan, China, and South Korea are main technology exporter, and Japan has an absolute technological advantage while China and South Korea are emerging forces. Toppan Printing, DIC, Showa Denko, and DNP are major applicants, the gap between Chinese applicants and these applicants is huge. Using aluminum foil, sealant layer, adhesive layer or additional layer to improve peeling strength and corrosion resistance, using aluminum foil, base material layer, additional layer to improve molding performance, using additional layer to improve barrier and mechanical performance of the aluminum-plastic film are technical research hotspot.

With the rise of the lithium-ion batteries (LIBs) industry, its anode materials have also been booming. China's market share in the field of LIBs only lags behind Japan and South Korea, and many manufacturers of anode materials have reached the international advanced level. In order to promote the healthy development of anode material industry, China has promulgated relevant standards since 2009, including raw materials, products and detection methods. The specific technical indexes of physical and chemical properties are put forward, and the corresponding testing methods are given, which have played a guiding role in the actual production and application of anode materials. This paper introduces the main contents of these standards, including crystal structure, particle size, density, specific surface area, pH, moisture content, main element content, impurity element content, first discharging specific capacity and efficiency of anode materials. In addition, it also puts forward some suggestions for future setting work of standards.