Scanning electrochemical microscopy (SECM) is a kind of in-situ analysis technology based on electrochemical principle of ultra-micro electrode. It used the ultra-micro-disc electrode which can move toward three dimensional directions as working probe immersed in the electrolyte solution. As scanning at a few micro meters from the basal position, the varied probe currents can reflect the morphology and properties of the substrate. SECM has several operations modes, and benefit from fast electrochemical responses with high spatial and temporal resolution at non-invasive detection mode, which enables the technology applicated in analysis of Li-ion batteries. This paper mainly introduced the theory and working modes of SECM, and reviewed the research progresses of in situ analysis of SECM in cathode and anode materials in lithium ion batteries. Particularly, SECM analysis of cathode materials mainly focused on kinetics of intercalation/deintercalation of Li+ and its mechanism during charging/discharging processes. On the anode side, the progress of SECM applications in the formation processes and properties of solid electrolyte interface (SEI) are mainly reviewed in this paper.

This bimonthly review paper highlights 100 recent published papers on lithium batteries. We searched the Web of Science and found 2132 papers online from Oct. 1, 2016 to Nov. 31, 2016. 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 analyzing the mechanism for Li storage and SEI formation. In-situ technologies are used to analyze the kinetic process and SEI 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 and BMS technologies.

As an innovative heat transfer fluids, nanofluids attract great attention because of its excellent heat transfer properties. Research progress in thermal conductivity, convective heat transfer, specific heat capacity, shear viscosity, and stability of nanofluids has been systematically discussed. Then the thermal conductivity enhancement mechanism of nanofluids, the influence factors of thermophysical properties and current technical problems are highlighted and discussed. Finally, an outlook for the future development in nanofluids is also given. It is suggested that the combination of the preparation of composite nanomaterials and the properties of nanofluids is a promising approach to enhance the performance of new heat transfer fluids.

Pumped hydro energy storage (PHES) is one of most widely used large-scale energy storage technologies. The traditional pumped hydro energy storage technology requires specific geographic conditions to construct the upper and lower reservoirs, leading to a high investment, damages to the ecological environment and heavily dependence on the use of fresh water. Seawater pumped hydro energy storage (SPHES) technology uses seawater, and the sea as the upper or the lower reservoir. The advantages of such technology include small variation of water level, low construction cost and small influence on environment, and therefore has great potential for applications in islands where fresh water is lacking. This paper will first explain the working principles of the SPHES technology, followed by a review of the state-of-the-art development in the area. Finally, potential applications in China and associated challenges are discussed.

The factors which influence the safety of lithium batteries exist from the choosing of the cell materials to the using situation of the batteries, from the beginning to the end of a battery life, so the reasons are complicated. Reviewing the Cell material themselves, process of the manufacturing, design of the BMS (battery manage system) and the safety parts, together with working conditions form the factors which may be the barrier of safety. We analyzed the factors which influence battery safety, such as the crystal structure/electrode potential/character, the cell manufacture process/growing of SEI, integration and designing of the battery, the abusing like over-charging/discharging/harsh temperature/accident. Proposing the way (integration and design) to make a safer battery.

Flexible electrochemical energy storage is the key technology supporting the development of flexible electronics (like wearable smart electronic devices) and is regarded as the important R&D direction for future electrochemistry. This article reviewes the state of art of the flexible electrochemical energy storage devices, and introduced the key components and current technology by specifying issues in terms of flexible electrode materials (CNT, graphene, carbon cloth/fiber, textiles), electrolytes(liquid, solid, inorganic/organic composite), fabrication techniques(printing, coating and spraying, deposition and weaving) and novel flexible electrochemical energy storage devices with more additional functional versatilities. Generally speaking, flexible electrochemical energy storage technologies are still in the initial stage. The fundamental prerequisite for its future development is maintaining its mechanical performance and service life under corresponding application circumstances (like bending and twisting).The future R&D emphasis will be mainly focused on elevating its performance including gravimetric/volumetric energy density and power density, service life, stability and development of novel energy storage devices with more functionalities and technologies suitable for scale-up mass production. Since flexible electrochemical energy storage technology combines both structural and functional advantages, it can be foreseen that it will draw constant attention for a long time in future and more R&D progress will be expected.

 Lithium-ion battery (LIBs) play a key role in development of Smart City. The commercial electrolyte always restricts application of LIBs due to low melting point and high resistance at low temperature. This paper first reviews the recent development of LIBs low-temperature electrolyte in the aspect of lithium-salt，solvents and additives. And proposes temperature is the critical factor for LIBs capabitity. The challenges and future trends of low-temperature electrolyte are also discussed. Low-temperature electrolyte lithium salts should be developed with new lithium salts system; Low-temperature electrolyte solvents should be developed with EC-PC blend system; Low-temperature electrolyte additives should be connected traditional organic additives with new additives.

Vanadium Redox Battery (VRB) has the advantages of large capacity, long service, safety and environmentally friendly. In order to ensure safe charge-discharge and increase the charge speed of Vanadium Redox Battery (VRB), the three closed-loop flexible charge-discharge control strategy which is based on estimated core voltage is proposed. This strategy uses three closed-loop structure, namely SOC loop, voltage loop and current loop. PI regulator with the limit value is used in these three loops. It determines the battery to charge or discharge by comparing the given SOC value and actual SOC value in SOC outer loop. The estimated core voltage is used as feedback in voltage loop, achieving constant voltage charge of VRB. Current loop can achieve constant current charge of VRB. Kernel voltage can be estimatyed by VRB voltage, charge and discharge current and reference model. Finally, a 5 kW/30 kW·h VRB model is builded on Simulink to verify the characteristic of VRB. The results show that the charge time decreases by nearly 40% via using the control strategy, which also ensures the core voltage non-overshoot and achieves safe charge-discharge of VRB.

Currently batteries have heat-related security issues. Similar problems also exist in lithium-sulfur batteries. Thermal simulation method can be used to predict the temperature distribution of battery under various operating conditions, which will help optimize the performance and structure design of the battery. In this article, thermal simulation of lithium-sulfur battery was undertaken to explore the temperature of the battery during cycling. In order to study the heat generation rate in the use of battery, the open circuit voltage and operating voltage were firstly tested and used. A finite element software COMSOL Multiphysics was employed to simulate transient battery temperature at different ambient temperatures and different discharge rates. It was indicated by the simulation that the battery temperature first decreased and then increased in the discharge process. Furthermore, we proposed that reversible entropy change played a major role in the change of battery temperature.

In order to satisfy the requirement of distributed storage system for high power applications, developing a new high power anode materiel for lithium-ion batteries is necessary. In this paper, a novel carbon composite material was developed through compositing soft with hard carbon precursors using wet synthesis method. The capacity, coulombic efficiency, rate capability and cycle stability were investigated. The structures of the prepared materials were characterized by the techniques of X-ray diffraction (XRD), Raman, Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). It has been found that the composite carbon has both soft and hard carbon’s advantage, and better performance than mechanical mixing carbon with the same ratio. Its excellent rate capability were tested at 2C charge/discharge rates between the potential limit of 0—3.0 V, its 2C capacity can reach 154 mA·h/g and the 2C/0.2C capacity retention is 64.3%, at the meantime, it delivers a 0.2C capacity of 240 mA·h/g, and the initial coulombic efficiency of 82%. The composite carbon is stable for its 0.2C capacity retention can reach 99.8% after 5C charge-discharge. There is some kind of synergistic effect between soft carbon and hard carbon during the compositing process, not just simple mechanical mixing, which was confirmed by XRD, Raman, and TEM.

LiPF6 salt was substituted by new salt LiFSI in the electrolyte and comparing researches between them were done. LiFSI/ EC+EMC+DMC (mass ratio was 1∶1∶1) with different concentrations (0.8—1.6 mol/L) were prepared. The effect of lithium salt concentration and electrolyte physicochemical parameters on the rate performance was studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy(EIS), galvanostatic charge-discharge testing, along with physicochemical parameters testing of Li+ transference number, conductivity and viscosity. It was found that the electronic conductivity and Li+ transference number of LiFSI electrolytes are both larger than LiPF6 electrolyte with same salt concentration. In the range of 0.8 mol/L to 1.6 mol/L, Li-ion batteries using LiFSI electrolytes show better electrochemical performances than those with LiPF6 electrolytes. The optional concentration of LiFSI electrolyte is 1.2 mol/L, when ionic conductivity and Li+ transference number are both the maximum(=12.39 ms/cm, t+=0.6327). Li-ion batteries with 1.2 mol/L LiFSI electrolyts have best rate performance.

A numerical model of a two-stage centrifugal compressor with inter-stage cooling and variable guide vanes has been developed. Analyses are made using the model on the performance of the compressor while the two-stage vanes are adjusted. The results illustrate that when each of the two-stage guide vanes adjusted, they follows the same rules: a positive opening of the guide vane improves the stall features; a negative opening leads to a pressure ratio increase.; but the isentropic efficiency drops for both the positive or negative openings of the vane. When two-stage guide vanes are adjusted jointly using the zero opening as the reference, the pressure ratio increases only when the opening of two-stage guide vanes are all negative whereas the pressure ratio decreases in all other cases. The isentropic efficiency of all opening cases is lower than that at the reference condition. Internal flow analyses suggest that the uniformity of the internal flow of the second stage can be improved through jointly adjusting the two vanes. The effect of adjusting the guide vanes of the two stages is the same on the performance of the two-stage centrifugal compressor. When the opening of first stage guide vane changes from negative to positive, the area of high velocity at the suction surface of the impeller inlet shroud decreases, concentrating on the pressure surface around the shroud.

Binder is indispensable and also has a direct impact on the performance of lithium-ion batteries. The introduction of aqueous binders into the manufacturing process of lithium-ion batteries can be more environmentally friendly, and meanwhile decrease the manufacturing cost and bring great economic benefit by its development and application. In this work two kind of polyacrylate binders LA and LB were used in LiFePO4 electrodes and the electrochemical performance of the prepared electrodes were investigated. Electrochemical test showed that the oxidation potential of the polyacrylate binder was about 4.65 V. Due to its higher oxidation potential, the polyacrylate binder is more suitable for the cathode of lithium-ion batteries. In comparison with LA, the LB binder showed better thermal stability with a decompose temperature of 318 ℃. Lithium ion diffusion coefficients for LA and LB electrodes were 6.2×1014 cm2/s and 1.8×1014 cm2/s, respectively. The effect of LA and LB binders on the electrode manufacturing properties, the battery capacity, rate performance, and cycle life were detailedly investigated and the optimized strategy for the application of aqueous binders in the LiFePO4 based electrodes were obtained. The results indicated that 3% of the LA binder content, 2.5% of the LB binder content, and 2.25 g/cm3 of the compaction density are the optimized condition for the batteries to obtain a best cycle life and overall performance.

The cause of thermal runaway occurrence was analyzed. By the current situation of using AGM as separator in many factories, the possibility of the thermal runaway occurred in gel battery was discussed from two aspects of oxygen evolution from positive electrode and separator. The results showed that the content of fumed silica strongly affected the evolution of oxygen from positive electrode. To diminish the occurrence of thermal runaway in gel battery, the content of fumed silica should be less than 5%. The risk of thermal runaway was rather remarkable when AGM was used as separator in gel battery, which was attributed to its large pores. The importance was emphasized for the development of special separator used in gel battery, by which real and high quality gel battery can be achieved.

The use of electric vehicles and distributed generation increases the complexity of modern distribution network.  This is made more serious with more correlated input of random variables. In this study, we use the Nataf transformation, also called the third order polynomial normal transformations, to transform random variables from a correlated non-normal random vector space (CNNRVS) to a correlated standard normal random vector space (CSNRVS), and use the elementary transformation, also called the orthogonal transformation, to transform random variables from CSNRVS to independent standard normal random vector space (ISNRVS). These lead to the random independent input variables to execute the probabilistic load flow calculations using a 2m+1 point estimate method. Examples was made to simulate an IEEE-33 distribution network with wind power and electric vehicles. Comparison was made between four cases for the correlation among random input variables. The results showed that the Nataf transformation combined with elementary transformation gave the best accuracy.

A mathematical model was established for a 500 kW-TICC energy storage system using the lumped parameter method. An algorithm was built to solve the model  with a C-language based program. The program was integrated into the North China Electric Power University’s Star-90 simulation support system for real-time dynamic modelling of the cold start of the 500 kW-TICC system. Analyses were done on the dynamics of various components including compressor, heat exchanger, storage tank, and thermal store. The simulation results show a significant impact of the intake air flow rate on the system parameters at the storage phase, whereas the effect on the gas temperature change in the gas chamber is relatively flat. This simulation errors were found to meet the actual needs of the dynamic system characteristics.

With an increased pace in energy transition, high penetration of renewables in the power grid is becoming an inevitable trend. Advanced energy storage is one of the important methods to facilitate the integration of renewables to the power grids. This paper focuses on energy storage technologies for power grid-scale applications. Various energy storage technologies are analyzed first. The technical characteristics of these technologies are then analyzed together with their economic aspects. This is followed by expert interviews and surveys. Finally, a roadmap is proposed on the basis of these outputs for large scale energy storage in China for 2020, 2030 and after 2030, including the expected scale, technical development and economic features of these energy storage technologies.

Parallel operation of a storage-based wind farm and a thermal power unit can play a positive effect on improving the recovery rate of a local power grid is black-started using the wind farm as the power source to drive the thermal power unit. This paper presents a control strategy for such a hybrid system in order to maintain the network stability. In such an approach, the following are proposed: (a) smooth switching control is achieved through following the state of the Battery Energy Storage System (BESS) P/Q controller, and the switching point of the BESS from V/f to P/Q; (b) using an additional inertial controller and an additional frequency droop controller in the BESS control unit to improve frequency stability of the wind-battery-thermal unit hybrid system; and using an additional voltage droop controller in DFIG control unit to improve the voltage stabilith of the wind-battery-thermal unit hybrid network. Simulation results showed that the use of the proposed control strategy can realize smooth switching of BESS control and effectively improve the voltage and frequency stability of the wind-battery-thermal unit hybrid network.

The speed of generator is adjusted through the gearbox in traditional compressed air energy storage (CAES) technology, thus enables the output of the generator to meet the demand. However, the expander does not always work in accordance with the maximum efficiency point when flowrate changes in such a configuration. Furthermore, the use of the gearbox leads to increased system loss, footprint and maintenance cost, and reduced system efficiency. This work considers the use of a converter instead of a gearbox due to the flexibility of speed control and power control capability of the converter, and control strategy for tracking the maximum efficiency point of the expander-generator system. Such a strategy takes into account heat, gas and electricity, and is based on the similarity theory. A model is built for the expander-generator system and simulation using the model shows that converter has the expected flexible control ability and the expander-generator system can operate stably under different grid requirements. At the same time, the speed control can be done using the real-time tracking as reference value, making the expander work at the highest efficiency under different power demands and expander-generator system operate under the best working conditions.

Ministry of Science and Technology of the People’s Republic of China organizes “nano science and technology” key implementation project in Feb. 2016 and releases the annual project declaration Guide. Totally 43 projects focusing on seven different research areas are announced in Jun. 2016. A research team led by Prof. PENG Dongliang from Xiamen University with the project title of “Basic research on high efficiency energy storage devices based on nanostructured materials” has been funded. In this project, scientific and technological issues concerning advanced lithium ion batteries will be studied, aiming to greatly improve their energy density (400 W·h/kg) and cycling stability (500 cycles).

Ministry of Science and Technology of the People’s Republic of China (MOST) initiates national new energy vehicles pilot project in 2015 for next 5 years. Totally 19 projects are announced in 2016. The project 1.1 is a 5-year fundamental research type project (2016—2020) with a 32M ￥ budget，aiming to increase the energy density of EV batteries. Two targets are purposed: 400 W·h/kg for Li-ion batteries and 500 W·h/kg for new batteries. After 3 rounds review and defense, a team led by Peaking University wins the project. The title of the project is “Key technology and basic science problem reach for high energy density lithium batteries”. Scientific problems and technologies of three types batteries will be studied: 400 W·h/kg lithium ion batteries, 500 W·h/kg Li-S batteries and 500 W·h/kg Li-air batteries. This project includes 10 institutes and two companies as partners.