High Energy Density Characteristics Research Articles

Performance of Protection Devices Integrated into Lithium-Ion Cells during Overcharge Abuse Test

Lithium-ion batteries currently represent the most suitable technology for energy storage in various applications, such as hybrid and electric vehicles (HEVs and BEVs), portable electronics and energy storage systems. Their wide adoption in recent years is due to their characteristics of high energy density, high power density and long life cycle. On the other hand, they still face challenges from a safety point of view for the possible faults that could generate several problems, ranging from simple malfunctioning to a dangerous thermal runaway. Overcharge is one of the most critical types of faults, and, depending on the level of abuse, it may trigger a thermal runaway. To prevent high levels of overcharge abuse, some cells include integrated protection devices that cut off the circuit when a critical condition is met. In this paper, the performance of these protection devices is evaluated to assess their effectiveness. The cells were tested at different ambient temperatures and current levels. In the worst-case scenarios, the maximum cell temperature slightly exceeded 70 °C and the State of Charge (SOC) reached a peak of 127% when the Current Interruption Device (CID) was activated. These conditions were not critical, so serious events such as thermal runaway were not triggered. These outcomes confirm the effectiveness of the CID, which always intervenes in maintaining a safe state. However, since it never intervened in the overcharge abuse tests, a specific set up was also used to investigate the operation of the other protection device, the Positive Temperature Coefficient.

Zwitterion assisted in-situ grain boundary coating on Li-rich cathode boosting electrochemical performance in Li-ion batteries

High-capacity and high-voltage Li-rich cathode materials are promising candidates for next-generation LIB cathodes due to their high energy density characteristics. However, they face challenges such as electrolyte side reactions at high voltages and slow kinetic properties. To overcome these challenges, this study proposed a one-pot Li2WO4 (LWO) grain boundary coating method. Additionally, a novel synthesis process utilizing zwitterions was introduced to uniformly position heavy tungsten on the surface of a cathode material. Through grain boundary coating, the cathode material was modified not only at the secondary particle level, but also between primary particles by filling grain boundaries with the coating compound. The synthesized LWO grain boundary coated Li-rich cathode exhibited significantly superior rate capability and cycle stability compared to the pristine material. Furthermore, it demonstrated a more stable cycling behavior after high-temperature storage than pristine counterpart. This study presents a primary particle surface modification technique through grain boundary coating and a one-pot synthesis process leveraging zwitterions as a new driving force, providing a new perspective for enhancing the performance of Li-rich cathode materials.

Advanced design strategies for Fe-based metal–organic framework-derived electrocatalysts toward high-performance Zn–air batteries

This article summarizes the regulation strategies of Fe-based MOFs-derived electrocatalysts for ZABs, and provides a prospect for their future development.

Decoding short-range order in cation-disordered rocksalt materials using Metropolis non-negative matrix factorisation

We present a methodology for accessing the cation short-range ordering (SRO) in disordered rocksalt (DRX) materials by decomposing their pair distribution function (PDF) pattern in terms of a set of basis PDFs, pre-determined via Metropolis non-negative matrix factorisation analysis. These basis PDFs, underpinned by structure modelling, point to specific SRO types that subsequently enable identification and quantification of their presence in the DRX structure. Rapid identification of the evolution of SRO addresses a key bottleneck in the analysis and understanding of high energy density characteristics of DRX materials.

Research progress and prospect of polymer dielectrics

With the increasing demand for energy, how to store and release energy efficiently and stably has become an urgent research topic. Polymer dielectrics have become a kind of ideal dielectric materials in electrostatic capacitors for energy storage due to their advantages of light weight, easy fabrication, low cost, and high breakdown strength. It has a wide application prospect in smart power grids, new energy vehicles, pulse power weapons, electromagnetic guns, and lasers. However, existing polymer dielectrics cannot simultaneously possess the characteristics of high energy density, high breakdown field intensity, high charge and discharge efficiency, and low dielectric loss, thus limiting the development of compact, efficient, and reliable electronic power technology. In addition, the inherent thermal/field charge injection, excitation, and transport phenomena of polymer dielectrics make the resistivity and dielectric energy storage properties of polymer dielectrics decrease sharply under the combined action of high temperature and high electric field. In order to optimize the energy storage performance of polymer dielectrics (including room temperature and high temperature dielectrics), it has been obtained excellent dielectric breakdown strength, energy storage density, energy storage charge, and discharge efficiency from polymer nanocomposites, polymer/small molecule composites, polymer/polymer blends, new synthetic polymers, multilayer polymers, and other material systems. Based on these material systems, this review summarizes and compares these material systems, points out their advantages and disadvantages including the key problems, and puts forward suggestions for the future research.

A fully coupled THMC model for simulating hydrate dissociation by using finite element method

PurposeNatural gas hydrate (NGH) has been regarded as one of the most important resources due to NGH's large amounts of reserve. However, NGH development still faces many technical challenges, such as low production rate and reservoir instability resulting from NGH decomposition. Therefore, developing a fully coupled THMC model for simulating the hydrate decomposition and studying its mechanical behavior is very important and necessary. The purpose of this article is to develop and solve a multi-phase, strong nonlinearity and large-scale fully coupled thermal-hydro-mechanical–chemical (THMC) model for simulating the multi-physics processes involving solid-liquid-gas flow, heat transfer, NGH phase change and rock deformation during NGH decomposition.Design/methodology/approachIn this paper, a multi-phase, strong nonlinearity and large-scale fully coupled THMC model is developed for simulating the multi-physics processes involving solid-liquid-gas flow, heat transfer, NGH phase change and rock deformation during NGH dissociation. The fully coupled THMC model is solved by using a fully implicit finite element method, in which the gas pressure, water pressure, temperature and displacement are taken as basic unknown variables. The proposed model is validated against with the experimental data, showing high accuracy and reliability.FindingsA multi-phase, strong nonlinearity and large-scale fully coupled THMC model is developed for simulating the multi-physics processes involving solid-liquid-gas flow, heat transfer, NGH phase change and rock deformation during NGH decomposition. The proposed model is validated against with the experimental data, showing high accuracy and reliability.Research limitations/implicationsSome assumptions are made to make the model tractable, including (1) the composition gas of hydrate is pure methane; (2) the gas-liquid multi-phase flow in the pore obeys Darcy's law; (3) hydrate occurs on the surface of soil particles, both of them form the composite consolidation material; (4) the small-strain assumption is applied to composite solid materials, which are treated as skeletons and cannot be moved; (5) momentum change caused by phase change is not considered.Practical implications NGH has been regarded as one of the most important resources due to its large amounts of reserve. However, NGH development still faces many technical challenges, such as low production rate and reservoir instability resulting from NGH decomposition. Most of the existing studies decouple the process with solid deformation and seepage behavior, but the accuracy of the numerical results will be sacrificed to certain extent. Therefore, it is very important and necessary to develop a fully coupled THMC model for simulating the hydrate decomposition and studying its mechanical behavior.Social implications NGH, widely distributed in shallow seabed or permanent frozen region, has the characteristics of high energy density and high combustion efficiency (Yan et al., 2020). A total of around 7.5 × 1,018 m3 has been proved to exist around the world and 1 m3 of NGH can release about 160–180 m3 of natural gas (Kvenvolden and Lorenson) under normal conditions. Safely and sustainably extracting NGH commercially can effectively relieve global energy pressure and contribute to achieving carbon reduction goals.Originality/valueThe novelty of the present work lies in mainly two aspects. First, a fully coupled THMC model is developed for studying the multi-physics processes involving solid-liquid-gas flow, heat transfer, NGH phase change and solid deformation during NGH dissociation. Second, the numerical solution is obtained by using a fully implicit finite element method (FEM) and is validated against experimental data.

Improved BP neural network algorithm to SOC estimation of mine power supply

Since Ni MH battery has the characteristics of high energy density and good stability, it is mainly used as a backup power supply for mining at present, but the accuracy of estimation the SOC of the power supply is poor. To enhance the precision of estimation and extend the lifespan of the battery, based on a single nickel-hydrogen battery, this paper applies a new BP neural network to rise the self-adaption and momentum terms. At the same time, the discharged power is included in the Input feature quantity of the estimation network. The temperature, current and terminal voltage are also included in the input characteristic quantity of the estimation network. There is output during training, and then the momentum term is adjusted based on the Variance of variance error by comparing the actual output. The error of the estimated network should be back propagated from the output to the input to correct the weight. The direction of change in the error determines the adaptive learning rate of the improved BP neural network. The speed of the algorithm is increased by 72% and the error rate is less than 5%, compared to the traditional BP neural network algorithm.

Adaptive Pseudoinverse Control for Constrained Hysteretic Nonlinear Systems and its Application on Dielectric Elastomer Actuator

Flexible smart material actuators, such as dielectric elastomer actuators (DEA) and ionic polymer metal composites, have shown greatly potential applications in the field of soft biomimetic robots and rehabilitation robots due to their human-like muscle softness, large stretch, and high energy density characteristics. In this article, a fuzzy logic system (FLS) and barrier Lyapunov function (BLF) based adaptive pseudoinverse control scheme is proposed for a class of state-constrained hysteretic nonlinear systems, where all the states are always strictly limited in each constrained set. The main features of this article are: 1) the hysteresis nonlinearity in the actuators is considered and mitigated by the proposed pseudoinverse control algorithms, which implies that the direct hysteresis inverse model is not required, instead a searching mechanism of the actual control signal from the temporary control signal; 2) the all-state-constrained control problem of the Preisach hysteresis model is overcome when the control signal is coupled in the double integral functions with the aid of an FLS, BLFs, and the proposed hysteresis pseudoinverse algorithms; and 3) the DEA-based motion control platform is constructed, and the experiments are conducted to validate the effectiveness of our proposed control scheme.

Research on Fuzzy Energy Management Strategy of Hybrid Energy Storage System for Novel Power System

Supercapacitors have great power characteristics and can respond to high-frequency volatility and high-power load of lithium batteries. In a hybrid energy storage system (HESS), the introduction of supercapacitors is an effective scheme to reduce the load pressure and charge/discharge current fluctuation of the battery, which can reflect the high energy density characteristics of lithium batteries and extend the life of lithium batteries. To solve the problem of capacity configuration and energy allocation management of HESS, this paper first researches the dynamic programming model of HESS. Taking the minimum life decay increment of lithium batteries as the optimization objective, the energy distribution scheme of the HESS with the minimum life decay of lithium batteries under different supercapacitor configurations is obtained. Then, according to the decay rate of a unit supercapacitor to the capacity decay increment of lithium batteries, the optimal parameters of supercapacitors are selected, and the fuzzy energy management strategy based on the optimal allocation feature of dynamic programming is proposed. Finally, the simulation results show that compared with the traditional filtering algorithm, the reduction of the lithium battery life attenuation of the proposed scheme is about 2.52 times that of the filtering allocation scheme.

Review on Recent Developments, Challenges, and Perspectives of Mn-Based Oxide Cathode Materials for Aqueous Zinc-Ion Batteries and the Status of Mn Resources in China

Hydroelectrochemical energy storage has the characteristics of high energy density, fast response time, low maintenance cost, flexible and convenient installation, etc., and is a hot development direction of future energy storage technology. Aqueous zinc-ion batteries (AZIBs) with neutral or near-neutral electrolytes have attracted much attention due to their advantages of safety, reliability, abundant resources, and environmental friendliness. Mn-based oxides are widely used as cathode materials for AZIBs due to their high theoretical specific capacity and low toxicity. However, Mn-based oxides face structural collapse during charge–discharge cycles, resulting in rapid capacity decay. This paper reviews the electrochemical characteristics of different Mn-based oxides as cathodes, the energy storage mechanism involved in the charging and discharging process of Mn-based AZIBs, and the advantages of Mn resources. At the same time, combined with the latest research progress, the existing problems and feasible improvement methods are pointed out, and the future development trend is prospected.

Cathode Electrolyte Interphase (CEI) Endows Mo6 S8 with Fast Interfacial Magnesium-Ion Transfer Kinetics.

Magnesium (Mg) metal secondary batteries have attracted much attention for their high safety and high energy density characteristics. However, the significant issues of the cathode/electrolyte interphase (CEI) in Mg batteries are still being ignored. In this work, a significant CEI layer on the typical Mo6 S8 cathode surface has been unprecedentedly constructed through the oxidation of the chloride-free magnesium tetrakis(hexafluoroisopropyloxy)borate (Mg[B(hfip)4 ]2 ) salt under a proper charge cut-off voltage condition. The CEI has been identified to contain Bx Oy effective species originating from the oxidation of [B(hfip)4 ]- anion. It is confirmed that the Bx Oy species is beneficial to the desolvation of solvated Mg2+ , speeding up the interfacial Mg2+ transfer kinetics, thereby improving the Mg2+ -storage capability of Mo6 S8 host. The firstly reported CEI in Mg batteries will give deeper insights into the interface issues in multivalent electrochemical systems.

Cathode Electrolyte Interphase (CEI) Endows Mo6S8 with Fast Interfacial Magnesium‐Ion Transfer Kinetics

AbstractMagnesium (Mg) metal secondary batteries have attracted much attention for their high safety and high energy density characteristics. However, the significant issues of the cathode/electrolyte interphase (CEI) in Mg batteries are still being ignored. In this work, a significant CEI layer on the typical Mo6S8 cathode surface has been unprecedentedly constructed through the oxidation of the chloride‐free magnesium tetrakis(hexafluoroisopropyloxy)borate (Mg[B(hfip)4]2) salt under a proper charge cut‐off voltage condition. The CEI has been identified to contain BxOy effective species originating from the oxidation of [B(hfip)4]− anion. It is confirmed that the BxOy species is beneficial to the desolvation of solvated Mg2+, speeding up the interfacial Mg2+ transfer kinetics, thereby improving the Mg2+‐storage capability of Mo6S8 host. The firstly reported CEI in Mg batteries will give deeper insights into the interface issues in multivalent electrochemical systems.

Evaluation of a Redox-Active Cu-MOF and Co-MOF as Electrode Materials for Battery–Supercapacitor-Type Hybrid Energy Storage Devices

The emerging supercapattery imparts optimum electrochemical performance by synchronizing the admirable power density and cyclic stability of supercapacitors with the high energy density characteristic of batteries. The strong bonds of a metal center with an organic linker give rise to a unique group of porous materials known as metal–organic frameworks (MOFs). Here, we state the synthesis and electrochemical analyzation of a copper-MOF and cobalt-MOF. The initial specific capacity revealed in the three-electrode assembly for the Cu-MOF and Co-MOF is 451 and 103 C g–1 at 3 mV s–1, respectively. Owing to the favorable characteristics of the Cu-MOF, a supercapattery device is fabricated as Cu-MOF//activated carbon. The device exhibits energy and power densities of 41 Wh g–1 and 2400 W kg–1, respectively, with a reversible capacity retention of 92% and coulombic efficiency of 99%. Moreover, to elucidate the capacitive and diffusive contributions of the battery–supercapacitor, Dunn’s model is adapted. The favorable properties of the Cu-MOF electrode as a battery-grade material may be adapted for future energy storage applications.

Preparation and Combustion Mechanism of Boron-Based High-Energy Fuels

Due to the characteristics of high energy density and a high calorific value, boron has become a high-energy fuel and shows great potential to be a high-performance candidate for propellants. However, the wide applications of boron are still limited by the characteristics of easy oxidization, ignition difficulty, a long combustion duration, and combustion products that readily adhere to the surface and inhibit full combustion. Therefore, how to overcome the shortcomings and improve the combustion efficiencies of boron-based fuels have become the highlights in exploring novel high-performance energetic materials. In this paper, the prevalent preparation methods and the corresponding combustion mechanisms of boron-based energetic materials are briefly summarized. The results showed that the boron-based energetic materials can be prepared by surface coating, mechanical milling, and ultrasonic mixing methods. At the same time, the corresponding ignition delay and combustion efficiency were also analyzed according to different combustion tests. The results showed that the boron-based composites with different additives had different combustion characteristics. The combustion of boron-based energetic materials can be optimized by removing surface oxide layers, providing extra heat, inhibiting the formation of or the rapid removal of the combustion intermediates, and increasing the diffusion rate of oxygen. With the improvement of the combustion efficiency of boron-based energetic materials, boron-based high-energy fuels will become more and more widely adopted in the future.

A New Model Predictive Current Control Strategy for Hybrid Energy Storage System Considering the SOC of the Supercapacitor

Proportional-integral (PI) control and model predictive control (MPC) are mainly utilized in battery and supercapacitor (SC) hybrid energy storage system (HESS) of dc microgrid. Unfortunately, the regulation time of the PI controller is long, while large current ripples are introduced by MPC when the system frequency is low. This article proposes a new model predictive current control (new MPCC) strategy for HESS based on MPC and PI controllers. This method reduces current ripples, and meanwhile, enhances system stability and rapidity. MPC is adopted as the outer loop and it calculates reference values for the inner PI current loop. Furthermore, the state of charge (SOC) of the SC is considered based on fuzzy control to optimize the reference power of the SC inner controller. First, the topology and mathematical model of HESS in the dc microgrid are analyzed. Then based on PI control and MPC, the new MPCC is proposed, and compared with MPC and PI methods, respectively. Finally, the fuzzy control method takes SOC of SC into account to optimize the SC reference current. Simulation and experimental results show that the proposed new control strategy could effectively decrease current ripples and dynamic processes and entirely perform the high energy density characteristic of batteries and high power density characteristic of SC.

Preparation of elastomeric nanocomposites using nanocellulose and recycled alum sludge for flexible dielectric materials

Flexible dielectric materials with environmental-friendly, low-cost and high-energy density characteristics are in increasing demand as the world steps into the new Industrial 4.0 era. In this work, an elastomeric nanocomposite was developed by incorporating two components: cellulose nanofibrils (CNFs) and recycled alum sludge, as the reinforcement phase and to improve the dielectric properties, in a bio-elastomer matrix. CNF and alum sludge were produced by processing waste materials that would otherwise be disposed to landfills. A biodegradable elastomer polydimethylsiloxane was used as the matrix and the nanocomposites were processed by casting the materials in Petri dishes. Nanocellulose extraction and heat treatment of alum sludge were conducted and characterized using various techniques including scanning electron microscopy (SEM), thermogravimetric analysis/derivative thermogravimetric (TGA/DTG) and X-ray diffraction (XRD) analysis. When preparing the nanocomposite samples, various amount of alum sludge was added to examine their impact on the mechanical, thermal and electrical properties. Results have shown that it could be a sustainable practice of reusing such wastes in preparing flexible, lightweight and miniature dielectric materials that can be used for energy storage applications.

Multiscale modeling for dynamic compressive behavior of polymer bonded explosives

The impact damage behavior of polymer bonded explosives (PBXs) is critical to ensure the safety of explosive systems. PBX 1314 (60 wt% RDX, 16 wt% aluminum, and 24 wt% HTPB) is a popular propellant owing to its characteristics of high energy density and low sensitivity. In this study, the compressive damage evolution rules and the strain rate effect of PBX 1314 were investigated by using a multiscale method. To acquire damage evolution data during loading, a finite element model based on real crystal morphology, with a cohesive zone model (CZM) for describing the damage, was developed. A novel hybrid/inverse optimization strategy was developed to calibrate the cohesive parameters of PBX 1314, and the accuracy of the parameters was verified basis experimental results. Using an as-developed bilinear model, the shift of damage pattern with the variation of strain rate was observed, and the nonlinearity of the stress–strain curve was presented at the mesoscale. The crack parameters and distribution of damaged elements in each mesoscopic component were acquired to quantitively characterize the strain rate dependence of PBX 1314, and the mechanism of crack propagation and the shift of damage mode under various strain rates was illustrated. The findings of this study provide insights for understanding the nonlinearity of macroscopic mechanical behavior and the influence of strain rate on the mesoscopic damage mode of PBXs with high binder content.

Hybrid Equalization Topology for Battery Management Systems Applied to an Electric Vehicle Model

This paper presents a hybrid equalization (EQ) topology of lithium-ion batteries (LIB). Currently, LIBs are widely used for electric mobility due to their characteristics of high energy density and multiple recharge cycles. In an electric vehicle (EV), these batteries are connected in series and/or parallel until the engine reaches the voltage and energy capacity required. For LIBs to operate safely, a battery management system (BMS) is required. This system monitors and controls voltage, current, and temperature parameters. Among the various functions of a BMS, voltage equalization is of paramount importance for the safety and useful life of LIBs. There are two main voltage equalization techniques: passive and active. Passive equalization dissipates energy, and active equalization transfers energy between the LIBs. The passive has the advantage of being simple to implement; however, it has a longer equalization time and energy loss. Active is complex to implement but has fast equalization time and lower energy loss. This paper proposes the combination of these two techniques to implement simultaneously to control a pack of LIBs, equalizing voltage between stacks and at the cell level. For this purpose, a pack of LIBs was simulated with sixty-four cells connected in series and divided into eight stacks with eight battery cells each. The rated voltage of each cell is 3.7 V, with a capacity of 106 Ah. The total pack has a voltage of 236.8 V and 25 kW. Some LIBs were fitted with different SOC values to simulate an imbalance between cells. In the simulations, different topologies were evaluated: passive and active topology at the cell level and combined active and passive equalization at the pack level. Results are compared as a response time and state of charge (SOC) level. In addition, equalization topologies are applied in an EV model with the FTP75 conduction cycle. In this way, it is possible to evaluate the autonomy of each equalization technique simulated in this work. The hybrid topology active at the stack level and passive at the module level showed promising results in equalization time and autonomy compared with a purely active or passive equalization technique. This combination is a solution to achieve low EQ time and satisfactory SOC when compared to a strictly active or passive EQ.

Research on Control Strategy of Transient Disturbance Based on the Three-level Hybrid Energy Storage Converter

This paper proposes a control strategy of transient disturbance based on the three-level hybrid energy storage converter. The hybrid energy storage control strategy switches to the supercapacitor when the voltage sag occurs. Its characteristics of high power density can provide rapid and smooth voltage support for the distribution network so that the distribution network system will not be greatly affected by the impact. In the case of long-term voltage sag or power failure, it is important to switch to the energy storage battery and use its characteristics of high energy density to provide an emergency power supply to support the continuous operation of essential equipment. The control strategy proposed in this paper can realize the coordinated working between supercapacitor and energy storage battery and the fast and stable switching between two different working states of the energy storage system, which effectively solves voltage sag in the main power grid. Finally, a prototype is built, and the simulation and experimental results both verify the correctness and feasibility of the proposed control strategy.

Health-aware multi-stage charging strategy for lithium-ion batteries based on whale optimization algorithm

Lithium-ion batteries are widely used in electronics, new energy electric vehicles and energy storage plants. They have become ideal energy storage devices for their excellent characteristics of high energy density, low self-discharge rate, low carbon and environmental protection. Thus, research on lithium-ion batteries has wide scientific and engineering significance. To promote the application of lithium-ion batteries, the charging speed and aging rate of the lithium-ion batteries should be optimized to improve the convenience and economics for using them. Therefore, in this paper, a health-aware multi-stage charging strategy is presented based on the whale optimization algorithm. Specifically, the electrical model, thermal model, and the semi-empirical aging model are established firstly. Then the multi-stage charging optimization strategy considering charging time and battery health loss is proposed. The whale optimization algorithm is presented to obtain the optimal current value at each stage, followed by exploring the factors affecting the charging performance which include fitness function weight, cut-off voltage and current stage number. Compared with constant current (CC) charging, the total fitness function loss decreased by 34.64%, and the charging time decreased by 11.45%. This paper provides audiences with a strategy to meet the trade-off between charging rapidity and battery life in different scenarios by setting the optimization weights.