Sodium element has similar physical and chemical properties with lithium, and sodium resource is abundant in the earth, so research interest on sodium ion batteries has rapidly increased recently, particularly for the grid energy storage. Compared with aqueous sodium-ion batteries, non-aqueous sodium-ion batteries have attracted more attention due to its wider electrochemical window (1.5～4.5 V) and higher energy density (100～350 W·h·kg1). Generally, electrochemical performance of the non-aqueous sodium-ion batteries is evaluated using half cells with metallic sodium as a counter electrode. However, it may cause some potential safety risks when used metallic sodium in sodium-ion batteries, so research on non-aqueous sodium-ion batteries based on the anodes of non-metallic sodium deserves much more attention, which will promote the practical application of sodium-ion battery. Herein, we will introduce some typical sodium-ion batteries based on the anodes of non-metallic sodium, including carbon-based materials, Ti-based compounds, Na-alloys and transition metal oxides. In order to realize the commercialization of sodium-ion batteries, it is needed to explore new cathode and anode materials with better performance and low cost. In addition, mutual matching issues between cathode and anode, designing better electrolyte and binders and separator modification are also important in promoting the commercial applications of sodium-ion batteries in future.

This bimonthly review paper highlights 100 recent published papers on lithium batteries. We searched the Web of Science and found 1880 papers online from Aug. 1, 2017 to Sep. 30, 2017. 100 of them were selected to be highlighted. Layered oxide and spinel cathode materials are still under extensive investigations for the effects of structure evolution and modificationson their cycling property and thermal stability. Large efforts were devoted to Si、Sn and oxides based anode material for improving their cycling propeties with new preparation method. Their capacity fading mechnism is also analyzed. The cycling properties of metallic lithium electrode are improved by designing current collector and surface cover layer. The studies of solid state electrolytes are focus on the method of preparation and the transport mechanism. Additives to liquid electrolyte can help to improve the cell’s stability at elavated temperatures. There are a few papers related to Li/S battery, Li-air battery for improving their cycling performance and more papers related to cell analyses, theoretical simulations, and modeling.

Active distribution networks often face power fluctuation due to intermittent and stochastic characteristics of distributed generations (DGs), as well as uncertainties associated with the spatial and temporal distributions of charge and discharge of electric vehicles (EVs). Energy storage systems (ESS) provide an effective mean to mitigate the power fluctuation in such distribution networks. This paper analyzes the connotation of active distribution networks and the origin of the power fluctuation, and reviews the status of ESS for mitigating the power fluctuation. This includes optimal configuration and control of ESS, and dispatch and control strategy of electric vehicles. The results indicate that the power fluctuation could be successfully mitigated through selection, optimal configuration, and effective control of ESS.

Recycling of metals from spent lithium-ion batteries will bring great environmental and economic benefits. This paper summarizes the current process of metals recovery from lithium-ion batteries, including 4 steps of pre-treatment, battery material sorting, metals enrichment, separation and purification, and each step contains many methods. Development conditions, advantages, disadvantages and applications of these methods are analyzed, and it needs to select and integrate them to get better results in practice. Although above recycling technologies are mature and widely used in 4 kinds of spent lithium-ion batteries (LiCoO2, Ni-Co-Mn ternary materials, LiMn2O4 and LiFePO4) recycling field. The economics of metals recovery from spent lithium ion batteries is analyzed. The results show that LiCoO2 and Ni-Co-Mn ternary batteries have good benefits while LiMn2O4 and LiFePO4 batteries have no profits. It needs to strengthen research of spent batteries recovery technology, reduce costs and improve battery resource utilization to form a green and profitable recycling system of “lithium - ion battery production - sales - recovery - reproduction”.

Hybrid supercapacitors are energy-storage devices with great potential, they typically have high specific power, high cycle stability, high safety and relatively high specific energy, but the aqueous and organic electrolytes they use often suffer from drawbacks such as narrow electrochemical window and high flammability. In the meantime, the unique features of ionic liquids, such as low vapor pressure, non-flammability and wide electrochemical window make them ideal electrolytes for hybrid supercapacitors. This paper reviews the recent applications of ionic liquids in hybrid supercapacitors, including ionic liquids as pure electrolytes, components for mixture electrolytes, solid electrolytes and electrodes. Finally, it is pointed out that future research directions for ionic liquids in hybrid supercapacitor system is to improve its moisture stability and cutting down the cost of preparation. Due to the misunderstandings about the notion of hybrid supercapacitor and asymmetric supercapacitor, there has been many inappropriate descriptions about them. In this paper we try to explain the difference between the above-mentioned two kinds of supercapacitors.

In recent years, with the growing demands of lithium-ion battery (LIB) in electric vehicles (EV) or hybrid electric vehicles (HEV), the technological requirement on the high capacity and power is becoming stronger. Graphite is the most commonly used anode material in LIB, because of its high energy density, low voltage, good electronic conductivity, abundant resource and low price. However, when the graphite anode is charging at high current, lithium plating and low capacity are common problems, resulting in a low reversible capacity of LIB and serious security issues. In this paper, the research progress of fast-charge graphite material is reviewed, and several methods are proposed to evaluate the fast-charge performance, which can provide theoretical guidance for the development of fast-charge lithium-ion battery.

 Large scale compressed air energy storage systems have the potential for a wide range of applications including peak load shifting, distributed energy systems, and renewable energy utilization. However, such a technology requires the compression system to have a high efficiency and a wide operating range. The use of adjustable vane diffusers provides a compact solution to enlarge the operating regime of the compressor with a high efficiency. In this paper, a centrifugal compressor with a vane diffuser for large scale compressed air energy storage is analyzed. A multi-objective optimization method is applied to the initial diffuser vane. Through numerical modelling, the regulation relationship and the perform curve are obtained The results show that the optimized three dimensional twisted vane can reduce the impact of the non-uniform impeller outlet flow on the diffuser and improve the performance of the compressor. The adjustable range of the vane diffuser is between 8°and +5°at the design speed. The use of the adjustable vane diffuser could improve the operating regime of centrifugal compressors by 117%. Significant improvement could also occur on the compressor performance at off-design conditions.

A thermoelectric energy storage (TEES) system stores electricity in thermal form and the thermal energy converts back to electricity by a Brayton cycle, Rankine cycle or other power cycles during the discharge period. Various working fluids coupled with heat and cold storage mediums have been studied extensively and the use of CO2 as the working fluid is a hot topic in TEES system. This paper first explains the principle of TEES system and examines the effects of thermal integration between the working fluid and the heat and cold storage mediums as well as the isentropic efficiency of turbomachinery on the system round trip efficiency. Applications of different working fluids are then discussed including water, air, argon, ammonia and organic chemicals, and the focus is on systems with CO2 as the working fluid, including system design, system performance study and optimizations, and system realization. Finally, the TEES system is compared with compressed air energy storage (CAES) technology. It is concluded that the TEES not only is independent on the geographical conditions and the use of fossil fuels, but also has a large storage capacity, a long life span, a low capital cost and a high round trip efficiency.

A 1 MW·h electrical heating system with heat storage was constructed based on an modular design. Both a composite phase change material and a magnesium iron oxide based material were used as heat storage materials. The results showed that the composite phase change material outperformed the metal oxide based storage material under the same testing conditions. Based on the results of the 1 MW·h system, a 36 MW·h system was designed, constructed and tested. Similar performance was obtained.

A 1 MW/60 MJ flywheel energy storage system was developed for smoothing load fluctuations of a drilling rig power system. This paper introduces the use of transfer matrix method and the finite element method to model the flywheel rotor-support system, and to calculate the critical speeds and vibration modes of the flywheel shaft. The finite element method was also used to calculate the modal frequency of protective casing of the system. An experimental study was performed on flywheel acceleration and deceleration processes to obtain real-time the amplitude-frequency characteristics. The numerical simulations were in agreement with the experimental results. The results provide basis for the design and improvement of flywheel energy storage systems.

 Mesoporous graphene/carbon black (G/SC) composite conductive additive has been applied for lithium ion capacitor anode. G/SC conductive additive has been comparatively studied with carbon black (SC), graphene nanosheets/carbon nanotube/carbon black conductive slurry (GNC/SC), and carbon nanotube/carbon black (CNC). The morphologies and structures of G, SC, GNC, CNC and hard carbon have been characterized by scanning electron microscopy and X-ray diffraction, respectively. The electrochemical impedance spectra of hard carbon anode shows that the G/SC conductive additive can decrease the charge transfer resistance and the solid electrolyte interphase resistance. Compared with other conductive additives, the hard carbon anode with G/SC has the highest specific capacity (155 mA·h·g1), best rate capability (60 mA·h·g1 at the current density of 2 A·g1). The cyclic voltammetry analysis indicates that the faradaic diffusion of lithium ion in the electrode bulk transforms into rapid diffusion on the anode surface as the scan rate increases, G/SC conductive additive and hard carbon have formed “point-to-plane” conducting network, which promotes the electron transfer in hard carbon anode and the lithium ion diffusion on anode surface.. Lithium ion capacitors have been fabricated with hard carbon anode and activated carbon cathode, which shows excellent electrochemical performances. The energy density of lithium ion capacitor with G/SC is 81.1 W·h·kg1, and the power density is 22.3 kW·kg1, the capacity retention ratio is 98.7% after 2000 cycles at a C-rate of 20 C.

Ternary molten salt based on bis(fluoroalkylsulfonyl)amide anions (LiFSA-KFSA-CsFSA) as a new class of electrolyte was applied in lithium-air batteries. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and combustion experiments were employed to explore the electrochemical and physical properties of this molten salt electrolyte. The electrochemical performance of molten salt-based lithium air battery was analyzed by means of charge-discharge measurement coupled with scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicat that LiFSA-KFSA-CsFSA（LKC）molten salt has much higher ionic conductivity and showed good electrochemical stability. With no carbon component, LKC inorganic molten salt was nonflammable. Furthermore, LKC salt could prevent the formation of insulate and insoluble lithium carbonate originated from electrolyte decomposition during cycling. The lithium-air batteries based on LKC molten salt had an initial discharge capacity of 4 258 mA·h·g1, a charge potential of 3.83 V and the coulombic efficiency was 95% at 50 mA·g1, performing better than the common organic electrolyte-based lithium air battery.

Prussian blue and its analogues (PBAs) are considered as promising cathode materials of alkali metal-ion or alkaline earth metal-ion batteries due to their simple preparation process, high rate performance and low cost. Firstly, we prepared a series of PBAs containing Fe and Co, and then the crystal structure, morphology and electrochemical performance were characterized through XRD, SEM and electrochemical technologies. Finally, the interaction between Fe and Co in different structures was explored. The results suggested that in the structures of “M1—N≡≡C—M2”, by changing transition metal M1 can notable influence the electrochemical activity of transition metal M2.

Variable geometrical characteristics of the four stage radial inflow turbines and heat exchangers are analysed using the computational fluid dynamics (CFD) method. The China’s first MW scale supercritical compressed air energy storage test system is used as an example in the analyses. The results show that an increase in the third stage guide vane opening gives the greatest change in the expansion ratio of the third stage , followed by that of second stage, and the isentropic efficiencies of the two stages vary greatly. When the guide vane opening of first and third stages increases, the expansion ratio tends to be evenly distributed across each stage, and the mass flow rate, the total power, the average isentropic efficiency and the specific work are all seen to increase. When the system is run with a changing load, the joint regulation of the guide vane opening of the first and third stages can increase the range of flow rate and the total power of multistage turbine. In the same time, a wide range of adjustment can be achieved by adjusting the opening of the first stage guide vane, whereas the fine-tuning can be achieved by changing the third stage guide vane opening. When the total pressure of the first stage is lower than the design value, the system can operate efficiently in a wide range of operating conditions with improved isentropic efficiency and total power occurring at 80% first and third guide vane opening.

In order to solve problem about heat dissipation during the process of the Li-ion batterys in electric vehicle, we made simulation and optimized the thermal management of battery pack. Firstly, research was done on the heat generating mechanism and the heat transfer mechanism of Li-ion cell and a three-dimensional thermal model for battery was established. Secondly, the temperature distribution and temperature curve of the cell are simulated. Then the surface temperature during the working process was compared the thermal model was modified. Finally, the modified model was applied to a battery pack to simulate the temperature distribution, then forced cooling equipment on battery pack was added to reduce the temperature of the cells in the pack and the pack structure was optimized. According to the simulation results we found when the ambient temperature is 20℃and the cooling air inlet area is 6 times the area of a single cell profile area and the mass flow of cooling air is 1 kg·s1, the cooling effect is better and more economical.

Cupric acid (CA)-palmitic acid (PA) based phase change material (PCM) was adsorbed by porous diatomite to form shape-stabilized PCM. The shape stable PCM was then mixed with gypsum to form gypsum composite. A differential scanning calorimetry (DSC) was used to measure the phase change temperature and the enthalpy of the composite PCM and the gypsum composite containing PCM in diatomite. The thermal storage material was further tested for the stability, strength, and water absorption behavior. The results showed that the phase change temperature and the enthalpy of the shape-stable are respectively 26.44 ℃and 83.71 J·g1. An increase in the addition of the PCM in the gypsum increases the phase change enthalpy, whereas the strength and the rate of water absorption decrease. It is found that the gypsum composite with 25% of shape-stable phase change materials being the best with a phase change temperature of 22.76 ℃, a phase change enthalpy of 8.42 J·g1, a 7-day oven dry compressive strength of 5.93 MPa, a 7-day full water compressive strength of 4.59 MPa, and a bibulous rate of 15.0%.

 When electrochemical energy storage systems are applied on-grid, the energy storage devices need to work under constant power(CP) conditions, which is different from the usual constant current(CC) testing methods. In order to know the performance of different kinds of energy storage devices under CP and CC testing conditions, commercial Supercapacitors, Valve Regulated Sealed Lead-acid Batteries(VRLA) and LiFePO4 batteries(LFP) were measured under CC and CP conditions at different rates respectively, with parameters such as voltage-capacity curves, capacity, energy and efficiency analyzed. It is found that the three kinds of energy storage devices revealed quite different performances. Supercapacitors exhibit excellent rate performance and high energy efficiency. There is no obvious difference between the CC and CP modes, while the energy efficiency is higher under the CP condition, which can reach its maximum at a certain rate. VRLA shows a poor rate performance and lower energy efficiency. Large current/power higher than 6 h-rate should be avoided for practical application, and the relevant parameters under power-based conditions need to be checked for correction. LFP battery has high energy density and outstanding rate performance, with quite similar performance under CC and CP conditions, exhibiting an excellent comprehensive property.

The state of charge (SOC) of battery is an important parameter for battery capacity state, the accurate and real-time prediction is one of the most essential performances of for battery management system (BMS). Firstly, according to the open circuit voltage (OCV) characteristic of LiFePO4 battery, the identification zone for SOC is determined. Under different aging conditions, ambient temperature and charge/discharge ratio, the differential curve of voltage versus capacity (dV/dQ vs. Q) against the charging progress was analyzed. Based on analysis results, the correction algorithm of SOC is proposed using the differential curve. Finally, the lithium battery energy storage system is built, the accuracy and applicability of the algorithm is verified  by the experimental results .

Phosphorus@carbon composite anode material has high specific capacity, good safety and low cost. It is expected to be applied to high specific energy battery, but its large volume expansion during lithiation/delithiation shows a great challenge to electrodes process. In this paper, the application of polyacrylic acid (PAA) binder in high specific capacity phosphorous based anode electrodes of lithium ion battery was discussed. The results show that the PAA binder is superior to PVDF binder for phosphorus-carbon composite electrodes according to electrochemical performance evaluation. The first cycle efficiency of the electrodes can reach 85.5%, and the average cycle capacity efficiency is as high as 99.7%. In particular, the bonding strength between the binder and the current collector is the key issue for the electrode performance. This study is helpful to promote the application of the high-capacity phosphorus-based anode and enrich the technology development of high energy density battery.

Based on the PWM(pulse-width modulation) wave and VISA(virtual instrument software architecture) interface, a battery experimental system which is used to study the thermal characteristics of batteries is designed. The system can be used to carry out various discharging experimental in which batteries discharge by different drive cycles, such as NEDC(new european driving cycle), UDDS(urban dynamometer driving schedule), etc., and can collect the temperature information during the experiment, as well as its sampling frequency can be customized according to actual needs. The working principle of the PWM wave in the system is discussed. According to the NEDC, the PWM wave array with sampling accuracy of 0.1s is used to control the discharge of the battery, also verifies the reliability of the system when conduct experiment of thermal characteristics of the single-cell lithium battery with high-rate discharge. There is a new type of symmetrical DC/DC(direct current to direct current converter) which can achieve two-way step-up and down to facilitate the simulation of drive cycles; and a PWM wave generator to produce NEDC condition control signal to control the implementation of the PWM actuator. The reliability and accuracy of critical components of the system is also verified. Finally, NEDC experiments are conducted for the domestic mainstream 18650 batteries and discharge temperature curves are obtained.

BiFeO3 (BFO) thin films were prepared by sol-gel method and the pure phase BFO crystals were obtained by a layer-by-layer annealing process. Reduced graphene oxide (RGO) and octadecyltrichlorosilane (C18H37SiCl3, OTS) were used as interfacial modifiers to study the effect of various interfacial materials on the structure and photovoltaic property of BFO film based photovoltaic devices. The results show that the RGO can increase the device open circuit voltage (Voc, from 0.67 V to 0.84 V), but also significantly improve the fill factor (FF, from 0.664 to 0.965) and the photoelectric conversion efficiency (PCE, from 1.03 to 1.67). Though the OTS film cannot improve the FF and PCE, it is effective in improving the Voc (from 0.67 V to 1.15 V). The RGO and OTS modified layers have different effects on the photovoltaic performance of the BFO film.

Instability of photovoltaic power generation is one of main factors affecting its applications. Integration of an energy storage system (ESS) into grid-connected photovoltaic power stations not only effectively smooths the power output, but also improves power demand management, leading to the use of more renewable energy. Taking a 1MW solar PV plant as an example, the smoothing strategy was studied on the basis of the PV plant output and the time-sharing-control scheduling strategy was established by using the output power and the state of charge (SOC) of the ESS. Meanwhile, the operating characteristics of the ESS with different connection modes to photovoltaic power stations and the effect of the ESS on the load characteristics of the PV connected power grid were investigated, and an optimized solution for ESS design was proposed.

 This paper introduces the application of key equipments for industrialization used in the synthesis, filtration, washing, drying of precursor and mixing, sintering, crushing, removing iron of ternary material.The advantages and disadvantages of different equipment are compared. These provide important reference for industrialization of the ternary material and precursor.