Ionic Liquids As Electrolytes for Post Li-Ion Batteries

Due to their potential for high energy density, low cost, and environmental sustainability, zinc-ion batteries (ZIBs) have emerged as a promising energy storage technology. The performance, safety, and overall efficiency of ZIBs are significantly impacted by the properties of the electrolyte, such as ionic conductivity, electrochemical stability window, viscosity, and compatibility with other battery components. The use of ionic liquids (ILs) in ZIBs has gained extensive attention in recent years due to their desirable properties, such as high thermal stability, low volatility, wide electrochemical window, and tunable physicochemical properties. Therefore, this paper provides a bibliometric analysis of recent advances in the use of ILs as electrolytes in ZIBs. Current research trends, authorship patterns, and publications of ILs in ZIBs are analyzed. Our review reveals a growing interest in the use of ILs as electrolytes in ZIBs, and the development of novel ILs with tailored properties to meet the specific requirements of ZIBs is of a specific focus. This paper provides insights into the recent advancements and future research directions in the field of ILs as electrolytes for ZIBs.

Recently the use of Ionic liquids (ILs) in electrochemical investigations have greatly increased due to their excellent properties such as high viscosity, high thermal stability, wide liquid range, tunable solvent properties, good ionic conductivity and wide electrochemical potential window. In the present review the concept of ILs is defined, along with their classification. This review also focused on some of the properties of ILs which are relevant to electrochemical study of compounds and presents recent voltammetric studies on various ionic liquid modified electrodes.

INTRODUCTION The unique properties of ionic liquids (ILs) i.e. high thermal and chemical stability, non-flammability, low vapor pressure, and wider electrochemical window compared to traditional solvents, as well as the prospect that they can be tailored or custom designed for specific requirements make them all the more interesting. In recent years, ILs with organic cations have been suggested for electrolyte applications. Ionic liquids seems to be promising electrolytes in protonic systems as they exhibit good proton conducting properties.The motivation for the presented research was dictated by the growing interest in the field of the use of ionic liquids as electrolytes in metal-hydride batteries (Ni-MH) and other proton batteries (eg. based on the Si anode). The electrolytes based on ionic liquids can reduce the problem of the anode material (eg. AB5 alloy) corrosion in aqueous basic solutions, which may result in the improvement of the operation parameters of the proton batteries.The focus of this study was to check the applicability of ILs as non-aqueous electrolytes through the investigation of hydrogen sorption in Pd limited volume electrode (Pd-LVE) and AB5-LVE. Since protic ILs and their mixtures with other solvents have been recently proposed as electrolytes in metal-hydride batteries, Pd-LVE is a very good model system to carry out the preliminary study of hydrogen electrosorption in ionic liquids in view of the further research with the use of multicomponent alloys. EXPERIMENTAL The electrochemical experiments were conducted in selected, commercially available protic and aprotic ionic liquids (i.a. diethylmethylammonium triflate (DEMA-TFO), ethylammonium nitrate (EAN), 1-ethyl-3-methylimidazolium methanesulfonate (EMIm-MS) under inert gas (Ar) using three-electrode system. Pd-LVE (ca. 0.5 μm thick) or AB5-LVE (ca. 50 μm thick) was a working electrode, Ag wire was a quasi-reference electrode, and Pt or Au spiral was an auxiliary electrode. Pd-LVE were obtained electrochemically from the PdCl2 aqueous solution. AB5 alloy (LaMMNi4.1Al0.3Mn0.4Co0.45) was obtained from VARTA Microbatteries GmbH. To aprotic ionic liquid (EMIm-MS) organic acid of the same anion as in the IL (methanesulfonic acid, HMS) was added as a source of hydrogen and to increase the ionic conductivity of the obtained electrolyte. Cyclic voltammetry (CV), chronoamperometry (CA) and chronopotentiometry (CP) techniques were used to perform the electrochemical measurements. The electrodes were subjected to a hydrogen pretreatment procedure (HPP) and standard hydrogen cyclic voltammetry electrosorption experiment to obtain hydrogen absorption isotherms. RESULTS AND DISCUSSION It was observed, that the reversibility of the hydrogen sorption in Pd is significantly lower in ILs than in aqueous solutions, which may be caused by hindered proton transport due to few reasons. The first one is the high viscosity of IL, the second one is the difference of proton source, and finally the possible interactions of IL ions with the Pd electrode. Multiple hydrogen sorption in ILs (HPP) increases the reversibility of the investigated process. Preliminary HPP performed in aqueous solution of sulfuric acid facilitates further hydrogen sorption only in some cases (i.a. in EAN). Thus, it was found that the rate of hydrogen absorption is controlled rather by surface than the bulk processes. The maximum hydrogen sorption capacity (H/Mmax) obtained for Pd in protic IL (i.e. DEMA-TFO) and aprotic IL with addition of organic acid (EMIm-MS + 0.5 M HMS) is comparable with those obtained in aqueous solutions of acids and bases, reaching the value of ca 0.7. Our preliminary studies of hydrogen sorption in the AB5 alloy in a mixture of an aprotic IL with the organic acid (EMIm-MS + 1 M HMS) revealed that, as in case of Pd-LVE, the electrochemical reversibility of this process is much lower in comparison with the electrosorption measurements performed in concentrated base (Fig.1), which is due to the significant difference in ion conductivity and dynamic viscosity of the tested electrolytes. Fig. 1. Cyclic voltammetry behavior of AB5 electrode in EMIm-MS + 1 M HMS, inset: cyclic voltammetry of AB5 electrode in 6 M KOH; first cycles; 2 mVs-1. CONCLUSIONS Examined protic and aprotic ionic liquids can be effectively used as electrolytes in the hydrogen sorption process as we demonstrated by the exemplary Pd-LVE electrode. The max. H/Pd ratios obtained for DEMA-TFO and nitrate protic ILs are similar (0.6-0.7) and comparable with those measured in aqueous solutions of acids and bases. Hydrogen electrosorption from aprotic ionic liquids (eg. in EMIM-MS) with different concentration of acid gives ability to tune the maximum hydrogen capacity. The max. H/Pd ratios obtained for EMIm-MS (acid concentration ca. 0.5 M) equals to ca. 0.74 (this is the same value that was obtained for this type of electrode from acidic aqueous media). Figure 1

Aluminum and its many versatile alloys are routinely used as surface coatings for the corrosion protection of many metals, offering both barrier and sacrificial protection. Among various methods for aluminum coating, electrodeposition is the most attractive one because it leads to thin, economical coatings that usually are adherent and do not affect the structural and mechanical properties of the substrate. Unfortunately, neither aluminum nor its alloys can be electrodeposited from aqueous solutions because hydrogen is evolved before aluminum is plated. Thus, it is necessary to employ nonaqueous solvents (both molecular and ionic) for this purpose. Room-temperature ionic liquids (low-temperature molten salts) possess a unique set of physical properties such as nonflammability, negligible vapor pressure, high ionic conductivity, and high thermal, chemical and electrochemical stability. Therefore, they open the door for the electroplating of reactive elements, which is impossible using aqueous or other organic solvents. Thus far, most research about the use of ionic liquids for electrodeposition of aluminum and its alloys has focused on chloroaluminate anions, which were obtained by mixing anhydrous AlCl3 with organic chloride salt such as 1-ethyl-3-methyl imidazolium chloride (EMImCl) and 1-(1-butyl)pyridinium chloride (N-BPCl) etc. Unfortunately, because of the hygroscopic nature of AlCl3 and the chloroaluminate, the electroplating has to be performed in an inert-gas atmosphere. 1 One way to reduce the moisture sensitivity of the chloroaluminate based ionic liquids for practical application is to form polymer gel electrolytes, either by impregnating liquid electrolytes into the preformed membranes or co-cast polymer and liquid electrolytes, or by copolymerization of monomers in the presence of plasticizers. In this paper, polymer gel membranes were synthesized using the latter approach, that is, copolymerization of monomers in the presence of plasticizers. The gel membranes are transparent with good mechanical properties, which can be used for practical applications. Fig. 1 shows the ionic conductivities of the gel membranes containing different amount of eutectic mixture of AlCl3 and 1-ethyl-3-methylimidazolium chloride (EMIm.Cl) in a molar ratio of 1.5:1. At 20oC the ionic conductivities of the gel membranes containing 50, 60, 70 and 80 wt% of AlCl3-EMIm.Cl are 5.3 x 10-5, 2.0 x 10-4, 8.7 x 10-4 and 1.7 x 10-3 S cm-1, respectively. Fig. 2 shows a typical cyclic voltammetry of the membrane containing 60 wt% of AlCl3-EMIC (1.5:1) with copper plate as the working electrode and aluminum plate as the counter electrode. Reversible aluminum deposition and stripping is clearly observed. It is noticed that the current densities increase with increasing the scan cycles, indicating an activation process, probably due to the residual surface oxide on the Al plate. For rechargeable aluminum ion battery application, reversible aluminum deposition/ stripping with high coulombic efficiency is a necessary step to realize stable cycling performance. Therefore, this gel membrane can also be used for rechargeable aluminum ion batteries. 2More details about the gel membrane will be presented at the meeting. Acknowledgements:This work was funded by the Strategic Environmental research and Development Program (SERDP) (WP2316). 1. Liao, Q.; Pitner, W. R.; Stewart, G.; Hussey, C. L.; Stafford, G. R., J. Electrochem. Soc. 1997, 144 (3), 936. 2. Lin, M. C., Gong, M., Lu, B. , Wu, Y., Wang, D. Y. , Guan, M. Angell, M. , Chen, C. , Yang, J. , Hwang, B. J., Dai, H., Nature, 2015, 520, 324–328 Figure 1

Mucosal barriers are a natural defense system for preventing the entry of foreign objects into the body; however, they pose obstacles for effective drug delivery. Coated polymer nanoparticles (NPs) have been shown to possess improved rates of diffusion across mucus compared to their uncoated, or bare, counterparts. Choline carboxylic acid-based ionic liquids (ILs) are highly tunable and show high biocompatibility and mucus modulation properties, making them an ideal choice for the improvement of NP diffusion through mucosal barriers. This study aimed to investigate whether the use of choline-based ILs has a positive effect on the dispersibility of poly(lactic-co-glycolic acid) (PLGA), poly(ethylene glycol) methyl ether-block-poly(lactide-co-glycolide) (PEG-PLGA), and poly(ethylene glycol)-poly(lactic acid) (PEG-PLA) NPs through nasal mucus by using a multiple particle tracking method. The samples, according to the IL used, showed altered rates of diffusion in both aqueous and mucosal environments. The use of CA2HE 1:1 with PEG-PLGA NPs slowed NP diffusion, while the use of the same IL increased diffusion for PEG-PLA. Additionally, UV-vis spectroscopy was used to identify the possible formation of complexes between the mucin polymer and NPs. Circular dichroism (CD) spectroscopy was used to analyze any potential changes in the secondary structure of mucin as a result of the introduction of polymeric NPs. It was demonstrated that the use of an IL can stabilize the interactions between polymer NPs and mucin polymers. Isothermal titration calorimetry was used to obtain quantitative measurement of the binding energies between NPs and mucus and serves to confirm the results obtained from CD spectroscopy. Last, an ex vivo porcine nasal mucosa model was used to explore their use in a nasal delivery context, disclosing a possible connection between the use of zwitterionic transport materials and more effective drug delivery. This research demonstrates the potential of choline carboxylic acid-based ILs to control the transport behavior of polymer NPs for intranasal drug delivery.

Ionic liquids (ILs) are organic chemical compounds that are composed only of ions, a large organic cation and a smaller inorganic or organic anion. These are salts whose melting point is lower than the boiling point of water. ILs have many interesting properties, thanks to which they find great practical applications in analytics, electrochemistry, separation techniques, catalysis and others. One of the many areas of application of ionic liquids is sensors especially electrochemical sensors including ion-selective electrodes. In this case, the properties of ILs that are particularly useful include very good electrical conductivity, high electrochemical stability, good extraction properties, hydrophobic character and compatibility with other materials, e. g. polyvinyl chloride plasticizers or carbon nanomaterials. ILs were used as components of ion-selective membranes, both polymeric ones based on PVC and membranes in carbon paste electrodes. ILs performed various functions in these membranes, including lipophilic ionic additive, ionophore/ion exchanger, plasticizer, transducer media and matrix. They were also used as a component of the intermediate layer in solid contact ISEs. The last chapter presents examples of the use of ILs in reference electrodes. This review discusses the use of ionic liquids in ion-selective electrodes (ISEs) and reference electrodes over the last ten years.

The development of new materials for secondary batteries is nowadays one of the most active fields in the international scientific panorama [1].The state of the art for liquid electrolytes in a lithium-ion cell is typically a mixture of organic carbonates such as ethylene carbonate (EC) or dimethyl carbonate (DMC). The mixture ratio varies depending upon the desired cell properties. These solvents contain solvated lithium ions. The latter are provided by lithium salts, most commonly lithium hexafluorophosphate (LiPF6)[2]. Despite the high conductivity of these electrolytes (s >10-3 S·cm-1 at RT), important drawbacks are associated with the volatility and flammability of liquid solvents and the chemical instability of the LiPF6 salt. The latter undergoes hydrolysis in the presence of water traces, releasing fluoride anions. [3]Ionic liquids (ILs) are salts with melting temperatures lower than 100°C. When they are liquid at room temperature, ILs are classified as room temperature ILs (RTILs). Some typical properties of ILs are: a) a low volatility, a high thermal stability and a negligible flammability; b) a high ion density and conductivity; c) a wide electrochemical stability window; and d) a simple synthesis, carried out by choosing the cation and anion which best comply with the requirements of the intended application. These features make ILs very suitable as solvents in electrolytes for Li batteries[4].Recently, a class of solid-state single-ion conducting materials based on lithiated fluorinated-TiO2 (LiFT) was proposed, which demonstrated its applicability as a nanofiller to obtain nanocomposite polymer electrolytes [5,6]. LiFT consists of fluorinated anatase nanoparticles that are directly surface-functionalized with Li+ through an innovative one-step reaction with molten metallic lithium[7]. The conductivity of LiFT is due to Li+hopping processes between coordination sites present at the nanoparticle grain boundaries. These latter events take place in a very effective way.The use of LiFT nanoparticles as the source of Li+ ions and ILs as the plasticizing agents allowed us to obtain innovative composite electrolytes for application in lithium batteries with a high thermal stability and conductivity. Indeed, the use of imidazolium ILs based on TFSI- and BF4 - anions allowed us to investigate the different ability of these anions to coordinate and dissociate the Li+cations present on the surface of LiFT nanoparticles. For these reasons it has to be highlighted that no conventional Li salts are used in the electrolytes here proposed.In this report, composite electrolytes based on LiFT nanopowder, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4) and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMImTFSI) ILs are proposed. In details, LiFT nanopowder is doped with a known amount of both ILs to obtain two types of electrolytes with formula LiFT/EMImTFSI0.118 and LiFT/EMImBF4 0.200. The resulting electrolytes contain around 25% wt of ILs and show a powder-like consistence.The correlation between structure, thermal properties and conductivity mechanisms of the resulting LiFT/EMImTFSI0.118 and LiFT/EMImBF4 0.200electrolytes is investigated by a variety of techniques: (a) FT-MIR and FIR at different temperatures; (b) Differential Scanning Calorimetry (DSC); (c) Thermogravimetric Analysis (TGA); and (d) Broadband Electrical Spectroscopy (BES).The materials are thermally stable up to 250°C and their conductivities at 30 and 130°C are, respectively, of 1.2x10-2 cm-1 and 4.1x10-2 Scm-1 for LiFT/EMImTFSI0.118 and 1.7x10-3 Scm-1 and 1.7x10-2 Scm-1, for LiFT/EMImBF4 0.200. Finally, the performance of the proposed materials, tested in operating CR2032 coin cells by galvanostatic cycling in a Li4Ti5O12/{LiFT/EMImTFSI0.118}/LiCoO2configuration is shown in Figure 1. Figure 1 Discharge profiles (inset) and capacity vs. cycle number for a Li4Ti5O12/ {LiFT/EMImTFSI0.118}/LiCoO2, CR2032, coin cell (discharge plotted as negative current).

Unraveling the emulsifying activity of bio-based ionic liquids in the formation and stabilization of oil-in-water emulsions

Modeling of H2S solubility in ionic liquids using deep learning: A chemical structure-based approach

Room temperature ionic liquids (RTILs) are desirable electrolyte materials for advanced batteries because of their unique properties such as non-volatility, non-flammability and high thermal and electrochemical stability. We have reported that glyme-Li salt complexes, comprising equimolar mixtures of a glyme (CH3O(CH2CH2O) n CH3) and a Li salt, have similar properties to RTILs and classified as solvate ionic liquids. Certain glyme-Li salt complexes such as lithium bis(trifluoromethylsulfonyl)amide (Li[TFSA]) and tetraglyme (G4) or triglyme (G3) are liquid at room temperature and show high thermal stability, high lithium ion transference number, and high lithium ion concentration. We demonstrated reversible charge-discharge of lithium secondary batteries using glyme-Li salt complex as an electrolyte. Recently, the similar results were obtained with equimolar mixtures of pentaglyme (G5) and Na[TFSA] abbreviated as [Na(G5)1][TFSA] was able to use as an electrolyte of sodium secondary battery. Elemental sulfur has been studied as the post-lithium ion battery cathode material for its high theoretical capacity of 1672 mAh g-1. However, the major drawback of this material is the poor cycle stability because of dissolution of lithium polysulfides into typical organic electrolyte. One facile approach to overcome this problem is trapping the sulfur inside a polymer network such as poly(acrylonitrile) (PAN) to prevent the dissolution. By mixing PAN and excess amount of sulfur and heating at around 300 °C, cyclization and dehydrogenation of PAN is promoted by sulfur and results in sulfur contained p-conjugated polymer (PAN-S). The PAN-S has been studied as cathode active material with high specific capacity, good efficiency and cycling stability. However, most reports of PAN-S dealt with lithium batteries and not so many reports have been done in PAN-S sodium system. In this study, we tested the charge-discharge property of PAN-S composite cathode with [Na(G5)1][TFSA] electrolyte at 30 °C. The PAN-S was synthesized by mixing PAN and elemental surfur in 1:4 weight ratio and heated at 350 °C for 6 hours under Ar atmosphere. The composite cathode was fabricated by mixing PAN-S, AB, PVA in the weight ratio of 70:20:10 with NMP used as homogenizer to obtain slurry and pasted onto Al sheet. The electrolyte was prepared by mixing pentaglyme (G5) and sodium bis(trifluoromethylsulfonyl)amide (Na[TFSA]) in 1:1 molar ratio ([Na(G5)1][TFSA]) and mixed with a hydrofluoroether (HFE) in 1:4 molar ratio in order to improve ionic conductivity. Anode material Na15Sn4was prepared by mixing sodium metal and Sn powder in 15:4 molar ratio by ball mill for 5 hours, 510 rpm. The result of charge discharge test is shown in the figure. The initial discharge capacity was about 500 mA h g(PANS) -1 and charge-discharge capacity after that was around 400 mA h g(PANS) -1with excellent coulombic efficiency for 30 cycles. Although there are capacity decrease as the cycle number increase, the cycle stability is much improved compared to that of elemental sulfur composite cathode and sodium metal anode system.ReferencesT.Tamura et al., Chem. Lett., 2010, 39, 753.K.Yoshida et al.,J. Am. Chem. Soc., 2011, 133, 13121.X. Yu et al., J. Electroanal. Chem., 2004, 573,121-128

Ionic liquids (ILs) are salts possessing many properties that make them attractive for use in a wide range of applications including batteries. One of the biggest drawbacks of ILs is that they tend to be more viscous than conventional solvents, which means low ionic conductivity when used as electrolytes in batteries. One effective way to lower the viscosities is to mix ILs with low viscosity additives such as molecular solvents. An obvious disadvantage of mixing molecular solvents with ILs is that the extremely low volatility of the IL is compromised by the finite vapor pressure of the diluent. One strategy to overcome this is to mix ILs with molecular solvents that are themselves of very low volatility. One such class of compounds are the glymes, which are oligoethers having a CH3O-(CH2CH2O)n-CH3 structure. In addition to having low volatility, glymes are effective at dissociating salts because of the electron donating nature of their ether oxygen groups. They also tend to have high thermal and electrochemical stability, which has led many groups to investigate mixing glymes with alkali metal salts (most commonly Li+ [NTf2]) for use as electrolytes in batteries. The alkali metal cation tends to coordinate with the oxygen atoms of the glyme, which can significantly lower the melting point of the salt. Such systems usually retain the attractive properties of pure ILs but the transport properties are improved. They are considered a new class of ILs and have been termed “solvate ILs”. Tetraethylene glycol dimethyl ether (tetraglyme or G4) is a particularly promising glyme. While there are many studies devoted to the properties of Li-based solvate ILs, much less work has been done investigating the properties of mixtures containing glymes and more conventional ionic liquids. In the current work, the density and viscosity of the IL [C6mim][NTf2]) and its mixtures with tetraglyme were measured at different temperatures and concentrations. Molecular dynamics (MD) simulations were also carried out on the mixtures in order to compute the density, self-diffusivity, viscosity, ideal ionic conductivity and liquid structure. We find that both the density and viscosity drop with increasing temperature and G4 concentration. Detailed analysis of the simulation results suggests that G4 preferentially solvates the cations, thereby weakening the interactions with the anions and resulting in faster dynamics, particularly for the anions. Such behavior was previously observed in solvate ionic liquids. Based on the simulation results of a model G4 system, it was further revealed that the localized negative charges on the oxygen atoms of G4 are primarily responsible for the preferential solvation of cations. If G4 (or a similar solvent) instead had large localized positive charges, it would tend to preferentially solvate the anions, resulting in increased cation mobility. This suggests a strategy for selecting molecular solvents that will selectively enhance cation dynamics.

Recent scientific studies are rapidly advancing novel technological improvements and engineering developments that demonstrate the ability to minimize, eliminate, or facilitate the removal of various contaminants and green house gas emissions in power generation. The Integrated Gasification Combined Cycle (IGCC) shows promise for carbon dioxide mitigation not only because of its higher efficiency as compared to conventional coal firing plants, but also due to a higher driving force in the form of high partial pressure. One of the novel technological concepts currently being developed and investigated is membranes for carbon dioxide (CO2) separation, due to simplicity and ease of scaling. A challenge in using membranes for CO2 capture in IGCC is the possibility of failure at elevated temperatures or pressures. Our earlier research studies examined the use of ionic liquids on various supports for CO2 separation over the temperature range, 37°C-300°C. The ionic liquid, 1-hexyl-3methylimidazolium Bis(trifluoromethylsulfonyl)imide, ([hmim][Tf2N]), was chosen for our initial studies with the following supports: polysulfone (PSF), poly(ether sulfone) (PES), and cross-linked nylon. The PSF and PES supports had similar performance at room temperature, but increasing temperature caused the supported membranes to fail. The ionic liquid with the PES support greatly affected the glass transition temperature, while withmore » the PSF, the glass transition temperature was only slightly depressed. The cross-linked nylon support maintained performance without degradation over the temperature range 37-300°C with respect to its permeability and selectivity. However, while the cross-linked nylon support was able to withstand temperatures, the permeability continued to increase and the selectivity decreased with increasing temperature. Our studies indicated that further testing should examine the use of other ionic liquids, including those that form chemical complexes with CO2 based on amine interactions. The hypothesis is that the performance at the elevated temperatures could be improved by allowing a facilitated transport mechanism to become dominant. Several amine-based ionic liquids were tested on the cross-linked nylon support. It was found that using the amine-based ionic liquid did improve selectivity and permeability at higher temperature. The hypothesis was confirmed, and it was determined that the type of amine used also played a role in facilitated transport. Given the appropriate aminated ionic liquid with the cross-linked nylon support, it is possible to have a membrane capable of separating CO2 at IGCC conditions. With this being the case, the research has expanded to include separation of other constituents besides CO2 (CO, H2S, etc.) and if they play a role in membrane poisoning or degradation. This communication will discuss the operation of the recently fabricated ionic liquid membranes and the impact of gaseous components other than CO2 on their performance and stability.« less

Battery state-of-health estimation based on a metabolic extreme learning machine combining degradation state model and error compensation

With the aim of reducing the volume, weight and cost of conventional hybrid energy storage system (HESS) while properly exploring the complementary features of different energy storage devices for DC microgrid applications, this paper proposes a multiple-port three-level DC/DC converter. It possesses multiple ports sharing one front-end three-level DC/DC converter with an inductor and supercapacitor bank. Different types of batteries and/or multiple battery banks can be interfaced through the multiple terminals. This converter structure facilitates the cooperation of different energy storage devices to satisfy demands of DC microgrids with intermittent renewable generation. Moreover, it allows power sharing among different energy storage devices, which enables more efficient cooperation of different battery banks or different types of batteries. Experimental results are presented to verify the efficacy of the proposed converter structure and its control.

There are various types of used batteries recovered from electric and hybrid vehicles, such as lithium-ion (LiB) batteries, nickel-metal hydride (NiMH) batteries, and lead-acid batteries. These different types of batteries have different characteristics, such as storage capacity, charge/discharge voltage range, and operating temperature range, making it difficult to combine them in parallel in an energy storage system. However, by combining the features of batteries with different power and energy densities and temperature characteristics, the weaknesses of the energy storage system can be complemented to achieve operation suitable for a variety of applications. In this paper, the effectiveness of the proposed intelligent hot plug switch (IHS) is verified in a compact model of an energy storage system consisting of a new LiB with a new and a used MiMH batteries connected in parallel. As a result, the charging and discharging times were increased by 43 and 12 points in each by using IHS. Furthermore the current flowed into the LiB with high-energy density was suppressed by combining the NiMH with high power density.