High-capacity Energy Storage System Research Articles

Diffusion coefficients of Al<sub>2</sub>Cl<sub>7</sub><sup>–</sup> in low temperature chloroaluminate melt based on triethylamine hydrochloride

With the growing demand for renewable energy sources, much of the research in the battery industry is focused on creating safe and high-capacity energy storage systems that can handle high current loads using inexpensive and readily available materials. The aluminum-ion batteries (AIB) are considered as one of the most promising systems. Such materials as aluminum metal, carbon materials and chloroaluminate ionic liquids are used as anode, cathode and electrolyte, respectively. A low-temperature chloroaluminate melt based on triethylamine hydrochloride (Et3NHCl) is promising and inexpensive electrolytes for AIBs. This melt has the ability to reversibly precipitate/dissolve aluminum metal due to the presence of the Al2Cl7– ion in it. However, the diffusion of Al2Cl7– ions in the Et3NHCl–AlCl3 system has not been studied previously. In the presented work, the concentration dependence of the diffusion coefficients of the Al2Cl7– anion was studied using chronopotentiometry in the concentration range N = 1.3–1.95 (where N is the molar ratio of aluminum chloride to organic salt). It was shown that diffusion coefficients increase with aluminum chloride content growth in the studied melt: from 1.71·10–7 (N = 1.3) to 4.50·10–7 cm2·s–1 (N = 1.95). This behavior can be caused by the viscosity decrease of the melts with Al2Cl7– concentration growth. Based on the obtained results it can be concluded that Et3NHCl–AlCl3 with N = 1.95 is the most suitable electrolyte for AIB. Moreover, it was established that the electrochemical reduction of the Al2Cl7– on the surface of the aluminum electrode is complicated by the nucleation process, which has the lowest overvoltage at N = 1.95.

Synergistic Effects in BFO@NiCoS@CNT//AC Nanocomposite for High-Capacity Energy Storage Systems

Here, we synthesized a nanocomposite electrode material for high-performance asymmetric supercapacitor devices (ASCD) made of bismuth ferrite (BFO) nanocomposite and nickel cobalt sulfide with carbon nanotubes (NiCoS@CNT). To fabricate the BFO@NiCoS@CNT nanocomposite, a simple hydrothermal process was used. Electrochemical impedance spectroscopy, galvanostatic charge/discharge measurements, and cyclic voltammetry were used to evaluate the electrochemical experiments. At a scan speed of 5 mVs−1, the BFO@NiCoS@CNT nanocomposite exhibited a specific capacitance of 2890 Fg−1, surpassing pure BFO@NiCoS. Furthermore, the nanocomposite displayed excellent cyclic stability, retaining around 87.8% of its capacity retention even after 5000 cycles. Another notable property is its energy density (Ed) of 71 Whkg−1 at the power density (Pd) of 2400 Wkg−1. Based on these promising findings, BFO@NiCoS@CNT nanocomposite might be used to fabricate electrodes for high-performance hybrid supercapacitors. Our research indicates that this is the first report of a BFO@NiCoS@CNT nanocomposite used as an asymmetric supercapacitor.

A Gel Polymer Electrolyte with High Uniform Na+ Flux and its Constructed Hybrid Interface Synergistically to Facilitate High-Performance Sodium Batteries.

Sodium metal batteries (SMBs) can be developed on a large scale to achieve low-cost and high-capacity energy storage systems. Gel polymer electrolyte (GPE) can relieve volatilization of liquid electrolyte, adapt to volume changes in electrodes, and better satisfy the requirements of long-term SMBs. Herein, a dense polyurethane-based GPE modified with polyacrylonitrile is synthesized by rapidly swelling two-component polyurethane/polyacrylonitrile electrospun fiber film. Compared to traditional porous GPEs obtained by swelling porous matrixes, the fiber film provides uniform high Na+ flux inside GPE due to its partial solubility property and ability to dissociate salts. Therefore, it can reduce the polarization effect and induce uniform metal deposition under high current in conjunction with its constructed hybrid N/F-containing solid electrolyte interface (SEI) that possesses low ionic diffusion barrier. The study demonstrates that GPE has an ionic conductivity of 1.816 mS cm-1 at 20 °C and an ion transference number of 0.53. The full battery (NVP/GPE/Na) assembled with this GPE and Na3V2(PO4)3 (NVP) cathode shows 90.8% capacity retention rate after 1000 cycles at 10 C. Considering the convenient preparation and outstanding electrochemical performances of the obtained GPE, it can also be matched with other electrodes in the future to expand the application of sodium-based batteries.

Computational prediction of two dimensional Mo4BC as promising anode material for lithium-ion batteries

The rising demand for high-capacity energy storage systems drives the hunt for cutting-edge lithium-ion batteries. Herein, calculations based on density functional theory have been performed to investigate the properties of two-dimensional (2D) Mo4BC monolayer as an anode material with high stability and storage capacity. Phonon dispersion and ab initio molecular dynamics (AIMD) simulations were performed to determine the dynamic and thermal stability, respectively. A low diffusion barrier of 0.12 eV supports the ultrahigh ionic mobility of Li ions and cycling capability for this material, which is essential for the fast charging/discharging process. In addition, the Li-ion adsorption on Mo4BC shows a high capacity of about 800 mAhg−1 with an average open circuit voltage (Vocv) of 0.03 V. Comprehensive overview of Mo4BC as high-capacity anode material with negligible low diffusion barrier and metallic character provides a significant contribution towards the advancement of energy storage systems such as lithium-ion batteries (LIBs). Our findings suggest Mo4BC as a promising anode material for high-performance LIBs, thus offering valuable insights for exploring innovative anode materials.

Electric propulsion for lifeboat

This paper presents the integration of the electric propulsion technology in the lifeboat maneuvering system to enhance efficiency, reliability and sustainability. The present lifeboat propulsion system often relies on the internal combustion engine which requires fuel to propel and also has various challenges to face such as emissions, maintenance, and overall environmental impact. This paper delves into the design, economics, ergonomics, engineering challenges and performance assessments associated with the successful implementation of electric propulsion for lifeboats. Special emphasis is given to the research and development of lightweight, high-capacity energy storage systems (ESS) and efficient electric motors which are suitable for the maritime emergency evacuation applications. The features of electric propulsion (EP), such as reduced harmful emissions, lowering maintenance requirements and improving maneuverability draws more attention for this research field. The paper also explores the integration of green energy sources such as solar and wind that can be used to supplement the electric propulsion system which enhance the autonomy and sustainability of the lifeboat during emergencies. This work focuses on the overall advancement of maritime emergency safety equipment and will also help in contributing to make maritime services more eco-friendly by offering a comprehensive analysis of electric propulsion integration in lifeboats, providing insights for further future developments.

Designing Metal Complexes for Redox Flow Batteries By High-Throughput Synthesis

Redox flow batteries (RFBs) are an attractive device for high-capacity energy storage systems. Due to the disadvantages of vanadium RFBs such as high cost and limited temperature operability [1], researchers have been developing new redox couples to replace vanadium. The use of relatively inexpensive transition metals (Fe, Cr, Co, etc.) in combination with ligands to form metal-ligand complexes has received considerable attention [2]. The redox potential of a metal ion of a metal-ligand complex can be tuned by forming a complex with a ligand, and the metal-ligand complex form helps alleviate the crossover problem [3].A major challenge in the discovery and development of functional materials is to find and select the most optimized candidates from millions of possible materials [4]. High-throughput Synthesis (HTSy) enables simultaneous screening, synthesis and characterization of a large number of different material classes, providing unprecedented throughput and reproducibility. Therefore, HTSy can save energy, time, and cost for more efficient discovery of advanced functional materials [5]. In this study, based on HTSy methods, we used an automatic synthesis device (OT-2 liquid pipetting robot) to mix and heat metals (Ni, Cr, Cu, etc.) and ligand liquids to automatically design metal complexes. At the same time, a robot platform is developed to perform high-throughput electrochemical tests to quickly select suitable metal complexes for RFBs, and then conduct further related RFBs performance tests.

Enhancing the charge transfer and redox characteristics in energy storage devices with a layered ZnNbS@graphene nanocomposite electrode material for biomedical application

Hybrid supercapacitors, a type of device that integrates the functionalities of both supercapacitors and batteries, exhibit significantly enhanced power and energy densities. Two-dimensional materials particularly graphene with remarkable characteristics such as conductivity, sensitivity, and storage capacity, have garnered significant attention in the realm of energy storage. Herein, a composite electrode of zinc niobium sulfide (ZnNbS) and graphene (Gr) is designed and measured the electrochemical and biomedical applications. The composite electrode ZnNbS@Gr (75/25 ratio) showed a high value of specific capacity of 1573.01 Cg−1, much better than pristine ZnNbS (854.32Cg−1) because of the improvement in charge transfer and redox characteristics. Further, a hybrid supercapacitor device (ZnNbS@graphene//AC) is designed and achieves a specific capacity (179.2 C/g) at 1.5 A/g. The energy density is establish 42.1 WhKg−1, whereas the power density is 2500 WKg−1. This device is measured up to 5000 charging and discharging cycles, obtained a high value of capacity recantation of 96 %. Besides, this device is used to accurately detect the glucose to a small amount of 0.01 mM. The conclusions of our investigation provide a remarkable beginning for the advancement of high-capacity energy storage systems and biomedical applications.

Analysis of an energy storage system using reversible calcium hydroxide in fluidised-bed reactors

• Conceptual study of new CSP-TCES layouts based on calcium hydroxide reaction. • Single fluidised bed reactor designs simplify plant integration and reduce costs. • Design and operation challenges with different requirements in charge and discharge. • Novel insights for reactor design and thermal integration of the systems. • Competitive round-trip efficiency values of 68% and LCOE values of 67–83 $/MWhe. The widespread use of renewable energy requires the support of high-capacity energy storage systems. This work proposes a thermochemical energy storage system for concentrated solar power plants based on the reversible hydration/dehydration process of the calcium hydroxide. It is a single fluidised bed reactor concept with alternating dehydration-hydration processes, charging and discharging alternating reactions, with superheated steam as fluidising agent. The system has been modelled using Aspen Plus™, including equilibrium data and hydrodynamic performance of the reactor. The model has been used to evaluate the effect of different parameters of the reactor, such as geometry, average particle size, or inlet streams conditions, on the performance of the reactor and the system. The thermal integration of the system was optimised using pinch analysis. For the proposed layouts, round-trip efficiencies values of 68 % are obtained. The economic analyses show specific investment costs between 4170 $/kWe and 3250 $/kWe for plants in the range of 31 MW to 45 MW, which are competitive with those expected for plants with storage of molten salts in this power range. LCOE values between 67 $/MWh and 83 $/MWh were obtained. The analyses show how these values highly depend on the fresh material replacement requirements related to the deactivation of the material and operational strategies. The results show the interest in further developments of this concept for concentrated solar power plants.

High performance rechargeable aqueous zinc-iodine batteries via a double iodine species fixation strategy with mesoporous carbon and modified separator

With the increasing requirement for high capacity energy storage systems, a large amount of recent work has focused on the development of zinc-iodine batteries (ZIBs) on account of high energy density, fast redox kinetics, and excellent reversibility. Nevertheless, low electron conductivity, the shuttle effect, and highly soluble iodine species (I2, I−, and I3−) have impeded their widespread application. In this study, metal organic framework-5 (MOF-5)-derived mesoporous carbon (MPC) loaded iodine (MPC/I2) cathode and the single-sided ketjen black modified cotton fiber (KB@CF) separator are designed to solve the problems mentioned above. That is, the double fixation strategy using MPC and KB@CF separators for iodine species suppresses the shuttle effect. Therefore, the ZIBs constructed with the MPC/I2 cathode and the KB@CF separator can exhibit excellent electrochemical performance. At the current density of 0.1 A g−1, a high discharge specific capacity of 137 mAh g−1 is still available after 300 cycles. Meanwhile, it exhibits a low capacity decay rate at long cycling (0.030% per cycle over 2000 cycles).

Performance Assessment of Low-Temperature A-CAES (Adiabatic Compressed Air Energy Storage) Plants

The widespread diffusion of renewable energy sources calls for the development of high-capacity energy storage systems as the A-CAES (Adiabatic Compressed Air Energy Storage) systems. In this framework, low temperature (100°C–200°C) A-CAES (LT-ACAES) systems can assume a key role, avoiding some critical issues connected to the operation of high temperature ones.In this paper, two different LT-ACAES configurations are proposed. The two configurations are characterized by the same turbomachines and compressed air storage section, while differ in the TES section and its integration with the turbomachinery. In particular, the first configuration includes two separated cycles: the working fluid (air) cycle and the heat transfer fluid (HTF) cycle. Several heat exchangers connect the two cycles allowing to recover thermal energy from the compressors and to heat the compressed air at the turbine inlet. Two different HTFs were considered: air (case A) and thermal oil (case B). The second configuration is composed of only one cycle, where the operating fluid and the HTF are the same (air) and the TES section is composed of three different packed-bed thermal storage tanks (case C). The tanks directly recover the heat from the compressors and heat the air at each turbine inlet, avoiding the use of heat exchangers.The LT-ACAES systems were modelled and simulated using the ASPEN-Plus and the MATLAB-Simulink environments. The main aim of this study was the detailed analysis of the reciprocal influence between the turbomachinery and the TES system; furthermore, the performance evaluation of each plant was carried out assuming both on-design and off-design operating conditions. Finally, the different configurations were compared through the main performance parameters, such as the round-trip efficiency.A total power output of around 10 MW was set, leading to a TES tank volume ranging between 500 and 700 m3. The second configuration with three TES systems appears to be the most promising in terms of round-trip efficiency since the energy produced during the discharging phase is greater. In particular, the round-trip efficiency of the LT-ACAES ranges between 0.566 (case A) to 0.674 (case C). Although the second configuration assures the highest performance, the effect of operating at very high pressures inside the tanks should be carefully evaluated in terms of overall costs.

Investigation of lithiation/delithiation processes in ceramic solid electrolyte by means of Neutron Depth Profiling

Rechargeable all-solid-state Li batteries with solid electrolytes (SE) are a prospective solution for safe and high-capacity energy storage systems. In recent decades, several types of SE with high ionic conductivity have been developed and tested with different techniques. In this study, we employed a non-destructive nuclear analytical method, Neutron Depth Profiling (NDP), to investigate the response of one of the promising electrolytes, Lithium Conductive Glass Ceramic (LICGC), to the applied voltage +2.8 V. The in-situ NDP measurements made it possible to directly monitor the migration of lithium ions in the electrolyte and to observe and quantify the formation of a space charge layer with depleted Li atoms, which depends on the biasing time.

Hydrogen energy storage systems to improve wind power plant efficiency considering electricity tariff dynamics

One of the limitations of the efficiency of renewable energy sources is the stochastic nature of generation; consequently, it is necessary to use high-capacity energy storage systems such as hydrogen storage for its integration into existing power networks. At the same time, electricity market tariffs for large enterprises change during the day. Therefore, it can be assumed that storing energy during cheaper hours and usage in more expensive hours allows increasing the efficiency of renewable energy sources. Evaluation of the economic efficiency of an energy storage system requires simulation with a step of at least 1 h for several years since the use of averaged production volume and averaged electricity tariffs will not allow obtaining an adequate to the task accuracy. A simulation model and software have been implemented to perform simulations and calculate the economic efficiency of a wind turbine with and without a hydrogen storage device. The methodology has been approved on three-year real data of wind speeds and electricity tariffs in the Novosibirsk region and Krasnodar Territory (Russian Federation).

Peer-to-Peer energy trading strategy for energy balance service provider (EBSP) considering market elasticity in community microgrid

The peer-to-peer (P2P) energy trading technology can effectively promote the mutual exchange and complementation of energy among diversified prosumers in the community microgrid. To further improve the energy resource allocation performance of the P2P energy trading, an energy balance service provider (EBSP) can be involved in the market. EBSP is an independent commercial entity configured with high-capacity energy storage systems (ESS) or auxiliary power sources, participating in the P2P market for profit. The energy shifting ability of EBSP can further improve the overall benefit of the microgrid. However, the scale effect endows the EBSP with comparatively strong market power, which may impose influence on the equilibrium of the P2P market. From the perspective of EBSP, the P2P market can be regarded as a market with elasticity. In the existing researches on optimized pricing and trading strategies of the P2P market, such a characteristic was not fully considered, which may have negative impacts on the economic profit of the EBSP and the overall benefit of the microgrid. Therefore, a P2P energy trading strategy for EBSP considering market elasticity is proposed in this paper. A market equilibrium model for the community microgrid with EBSP is first established, which reflects the elasticity of the market. Then, an optimized pricing model and trading strategy are established and solved to maximize the EBSP’s profit. Numerical results show that the proposed method can improve the profit of EBSP, meanwhile reducing the energy dispatching cost of prosumers, achieving peak load shifting and renewable energy self-consumption of the community microgrid.

Exploring the Full Potential of Functional Si2BN Nanoribbons As Highly Reversible Anode Materials for Mg-Ion Battery

Efficient energy storage devices like rechargeable batteries have a vital role in the modern society to cater for an ever-increasing demand of energy. In this context, magnesium-ion batteries (MIBs) have emerged as high-capacity energy storage systems. However, the progress in this area is hindered due to the lack of suitable anode materials for efficient Mg2+ ion storage and diffusion. In this study, using state-of-the-art density functional theory (DFT) simulations, we have systematically investigated novel one-dimensional Si2BN nanoribbons as anode materials for MIBs applications. Our calculations confirm the structural stability and metallic character of pristine (Si2BN) and hydrogen functionalized (Si2BN-H) nanoribbons upon Mg adsorptions. We find Mg adsorption energies in the ranges of -1.2 to -1.8 (-1.8 to -2.0) eV for 25% (20%) coverages in Si2BN (Si2BN-H), respectively, which are strong enough to mitigate the Mg aggregation. Maximum specific capacities of 661.865 (550.421) mAh g-1 and open-circuit voltages of 0.7-1.1 (0.6-0.8) V are found for Si2BN (Si2BN-H), respectively. Diffusion barrier calculations based on nudge elastic band (NEB) methods reveal a relatively low barrier of 0.14 eV, which guarantees a robust diffusion of Mg ions and faster charge/discharge capability of Si2BN nanoribbons. These intriguing features confirm the potential of functional Si2BN nanoribbons as promising anode materials for MIBs.

A hydrophilic poly(methyl vinyl ether-alt-maleic acid) polymer as a green, universal, and dual-functional binder for high-performance silicon anode and sulfur cathode

Binders could play crucial or even decisive roles in the fabrication of low-cost, stable and high-capacity electrodes. This is especially the case for the silicon (Si) anodes and sulfur (S) cathodes that undergo large volume change and active material loss in lithium-ion batteries during prolonged cycles. Herein, a hydrophilic polymer poly(methyl vinyl ether-alt-maleic acid) (PMVEMA) was explored as a dual-functional aqueous binder for the preparation of high-performance silicon anode and sulfur cathode. Benefiting from the dual functions of PMVEMA, i.e., the excellent dispersion ability and strong binding forces, the as-prepared electrodes exhibit improved capacity, rate capability and long-term cycling performance. In particular, the as-prepared Si electrode delivers a high initial discharge capacity of 1346.5 mAh g−1 at a high rate of 8.4 A/g and maintains 834.5 mAh g−1 after 300 cycles at 4.2 A/g, while the as-prepared S cathode exhibits enhanced cycling performance with high remaining discharge capacities of 663.4 mAh g−1 after 100 cycles at 0.2 C and 487.07 mAh g−1 after 300 cycles at 1 C, respectively. These encouraging results suggest that PMVEMA could be a universal binder to facilitate the green manufacture of both anode and cathode for high-capacity energy storage systems.

Electrochemical Insights, Developing Strategies, and Perspectives toward Advanced Potassium-Sulfur Batteries.

The boosting demand for high-capacity energy storage systems requires innovative battery technologies with low-cost and sustainability. The advancement of potassium-sulfur (K-S) batteries have been triggered recently due to abundant resource and cost effectiveness. However, the functional performance of K-S batteries is fundamentally restricted by the vague understanding of K-S electrochemistry and the imperfect cell components or architectures, facing the issues of low cathode conductivity, intermediate shuttle loss, poor anode stability, electrode volume fluctuation, etc. Inspired by considerable research efforts on rechargeable metal-sulfur batteries, the holistic K-S system can be stabilized and promoted through various strategies on rational physical regulation and chemical engineering. In this review, first an attempt is made to address the electrochemical kinetic concept of K-S system on the basis of the emerging studies. Then, the classification of performance-improving strategies is thoroughly discussed in terms of specific battery component and prospective outlooks in materials optimization, structure innovations, as well as relevant electrochemistry are provided. Finally, the critical perspectives and challenges are discussed to demonstrate the forward-looking developmental directions of K-S batteries. This review not only endeavors to provide a deep understanding of the electrochemistry mechanism and rational designs for high-energy K-S batteries, but also encourages more efforts in their large-scale practical realization.

Simplified modelling of nonlinear electromethanogenesis stack for power-to-gas applications

Abstract Bioelectrochemical systems performing electromethanogenesis (EMG-BES) represent an emerging technology for Power-to-gas as well as wastewater treatment. Moreover, EMG-BES can be used as a high-capacity energy storage system to absorb surplus energy in the electrical grid. This paper presents a modelling approach, which is based on building an equivalent electric circuit of the EMG-BES, which can be used to emulate static and dynamic non-linear behaviour of EMG-BES for different input voltages, which is advantageous if compared to other existing models. This model is a suitable choice for future studies in the development of the electric converters for EMG-BES plants connected to the electrical grid. The proposed model consists of practical and commercial elements, including capacitors, resistors, voltage sources, and a diode. The modelling of non-linear behaviour is achieved by adding a diode to the model. Four simple tests were performed to determine the equivalent circuit parameters in a medium-scale EMG-BES prototype. This prototype was built by stacking 45 cells together and connecting them in parallel, and it was long-term operated and tested under different electric inputs to determine the model parameters. A comparative study was finally conducted as reported in this paper in order to validate the proposed model against experimental results and values collected with other models.

Polymer Electrolyte Film as Robust and Deformable Artificial Protective Layer for High-Performance Lithium Metal Anode.

Lithium (Li) metal anode is a promising candidate for next-generation high capacity energy storage systems. Unfortunately, the uneven deposition/dissolution of Li metal hinders its wide applications. Herein, a robust and deformable polymer electrolyte film as the advanced protective layer on Li metal is developed by a simple tape-casting method, in which the polymer endows a comfortable interfacial contact as well as membrane flexibility to adapt the volume change, while the coordination between the polymer and Li salt provides fast Li+ ion diffusion channels. The modified Li metal anodes deliver a stable cycling over 1000 cycles under a high current density of 3 mA cm-2 in the ether-based electrolyte. The enhanced cycling performance at high current densities are mainly attributed to the Li plating occurred beneath the ion-conducting protective layer, which facilitates Li+ ion uniform distribution and further suppresses Li dendrite growth. Accordingly, constructing a polymer electrolyte protective film onto the Li metal anodes is a facile and low-cost methodology to drive the Li metal anode toward practical application.

Sodium-ion batteries: Electrochemical properties of sodium titanate as negative electrode

Abstract Lithium-ion technology is a well known and widely used technology. The basis of this technology is the transport of lithium ions during charging or discharging from one electrode to another, this principle is called “rocking chair”. Nowadays, this leading battery technology finds a wide range of applications ranging from mobile phones through electric vehicles up to high capacity stationary storage systems. With the growing field of applications of lithium-ion batteries, the demand arising from individual applications brings a new perspective and requirements for the lithium-ion technology. For example, the field of renewable energy, together with the use of energy produced, requires them to store large amounts of energy, because all these resources are non-dispatchable. Currently, the lithium-ion technology has a majority share in these applications, but the technology has its limitations. The main one is the lithium element itself. Lithium production has been growing very fast in the last few years and new sources of lithium ore are being sought. However, lithium production is not large enough to meet the growing demand, which leads to an increase in the price of lithium. Every renewable energy source must be supported by a high capacity energy storage system, which is environmentally friendly and cost effective. These are some, but not all of the essential characteristics required from a new generation of energy storage systems. As one of the most promising system, sodium-ion appears to eliminate the cost and environment risk and looks like a promising candidate for a large-scale renewable energy storage system.

Metamodel-Based Optimization of a Lithium-Ion Battery Cell for Maximization of Energy Density with Evolutionary Algorithm

The demand for lithium-ion batteries is gradually increasing, not only in the field of portable electronic devices but also in high-capacity energy storage systems and electric vehicles, owing to such advantages as a high capacity and high power. Accordingly, power and capacity improvements of lithium-ion batteries are required. To achieve such improvements, it is very effective to optimize the electrode thickness, porosity, separator thickness, and active particle size. In this study, maximization of the specific energy density is achieved using metamodel-based global optimization. The capacity and power of the design variables are calculated using an electrochemical-thermal model. The sampling points for the generation of a metamodel are obtained using an optimal Latin hypercube design, and a radial basis function-based metamodel is generated. Furthermore, the global optimal solution is obtained using an evolutionary algorithm. As the results of the optimization show, unnecessary mass reduction, increased negative/positive capacity ratio, and decreased internal resistance, thereby improving the specific energy density without changing the specific power density.