Internal Resistance Of Cell Research Articles

System-Level Dynamic Model of Redox Flow Batteries (RFBs) for Energy Losses Analysis

This paper presents a zero-dimensional dynamic model of redox flow batteries (RFBs) for the system-level analysis of energy loss. The model is used to simulate multi-cell systems considering the effect of design and operational parameters on energy loss and overall performance. The effect and contribution of stack losses (e.g., overpotential and crossover losses) and system losses (e.g., shunt currents and pumps) to total energy loss are examined. The model is tested by using literature data from a vanadium RFB energy storage. The results show that four parameters mainly affect RFB system performance: manifold diameter, stack current, cell standard potential, and internal resistance. A reduction in manifold diameter from 60 mm to 20 mm reduced shunt current loss by a factor of four without significantly increasing pumping loss, thus boosting round-trip efficiency (RTE) by 10%. The increase in stack current at a low flow rate increases power, while the cell standard potential and internal resistance play a crucial role in influencing both power and energy output. In summary, the modeling activities enabled the understanding of critical aspects of RFB systems, thereby serving as tools for system design and operation awareness.

Ultrasound-enabled adaptive protocol for fast charging of lithium-ion batteries

Abstract This paper introduces an ultrasound-assisted multi-stage constant current (UA-MSCC) charging protocol to enhance the charging performance of lithium-ion batteries. In this approach, ultrasound is applied during the final portion of each multi-stage constant current (MSCC) charging phase. Experimental results demonstrate that ultrasound decreases the internal resistance of pouch cells by up to 7%, leading to significant increase in charging capacity during each MSCC stage. The overall charging time is reduced by 26% compared to the conventional constant current constant voltage (CCCV) protocol. The performance improvement delivered by this ultrasound-assisted charging approach is especially large when the battery is charged at low temperatures and to a partial capacity. Notably, the application of ultrasound improves the coulombic efficiency to levels comparable to that at the room temperature when charging in cold environments (0°C). This approach can be applied to commercial batteries to immediately improve their charging performance, and can be seamlessly integrated into battery management systems. Unlike approaches that necessitate electrode material modifications or electrolyte additives, which require a long development time, this UA-MSCC charging protocol offers a practical and easily applicable solution for improving the battery charging performance.

Effect of Cell-to-Cell Internal Resistance Variations on the Thermal Performance of Lithium-Ion Batteries for Urban Air Mobility

This study examines the thermal behavior of lithium-ion battery modules intended for Urban Air Mobility (UAM), a forthcoming urban transport system designed to facilitate efficient and secure passenger and cargo transport within city centers. UAM applications necessitate batteries with high energy densities capable of sustaining elevated discharge rates during critical phases such as takeoff and landing. The battery module evaluated in this study comprises four cells arranged in series and configured as a submodule for UAM applications. A three-dimensional thermal model was utilized to analyze the impact of external temperature fluctuations and high discharge rates on the performance of the battery module. The numerical findings indicated considerable variations in temperature and internal resistance among the cells, especially under high discharge rates at low temperatures, with a maximum temperature deviation of 32.952 °C observed at an 8 C discharge rate. These thermal non-uniformities were attributed to variations in cell capacity and internal resistance, which were amplified by manufacturing inconsistencies and operational conditions. The study underscores the necessity of robust thermal management strategies to mitigate the risk of thermal runaway and ensure the operational safety and reliability of UAM systems. The results emphasize the critical role of advanced Battery Management Systems (BMS) in monitoring and controlling cell voltage and temperature to achieve consistent performance across the battery module. This research contributes valuable insights into the design of more efficient and reliable battery modules for UAM, highlighting the importance of addressing cell-to-cell performance discrepancies to enhance overall module efficacy and durability.

Tracking Degradation of Sulfolane-Based Electrolytes in 5 V LNMO Cells

Lithium-ion batteries (LIBs) are today the most used energy storage for portable electronics and electric vehicles – but are laden with concerns of materials scarcity and availability, alongside performance and cost. The development of high-voltage cobalt-free cathode active materials, such as LiNi0.5Mn1.5O4 (LNMO), represents one promising route for next-generation LIBs, due to a combination of high capacity and low cost. Combining LNMO with conventional LIB electrolytes, based on carbonate solvents, however, typically leads to severe capacity fading due to a range of different degradation mechanisms1, not the least due to the high electrochemical potential reached during charge, up to 5 V vs. Li+/Li°.Here we use a range of sulfolane-based electrolytes to improve the stability2 and track the degradation by intermittent current interruption (ICI), which is a rather new protocol to determine the internal resistance of battery cells during cycling3. The ICI data is presented in the form of heat maps, in order to better visualize the variation of internal resistance as function of the cell voltage. Furthermore, Raman spectroscopy is used to identify the decomposition products resulting from the degradation and the data is correlated with the ICI data. Overall this allows us to shine further light on the prospects of sulfolane-based electrolytes for 5 V cells as compared to conventional LIB electrolytes such as e.g. LP40.References Guo, K. et al. High‐Voltage Electrolyte Chemistry for Lithium Batteries. Small Science 2, 2100107 (2022).Xu, J. Critical Review on cathode–electrolyte Interphase Toward High-Voltage Cathodes for Li-Ion Batteries. Nano-Micro Letters vol. 14 (2022).Yin, L. et al. Implementing intermittent current interruption into Li-ion cell modelling for improved battery diagnostics. Electrochim Acta 427, (2022).

Formation and Cycling of Microscale Silicon Anodes at Elevated Temperatures with FEC-Based and EC-Based Electrolytes

Silicon is a promising candidate to replace graphite (372 mAh g-1) as anode material in lithium-ion batteries (LIBs) due to its high theoretical gravimetric capacity of 3589 mAh g-1.1 Graphite is already partially substituted by silicon in commercial battery applications in order to increase the energy density of LIBs.2 However, a complete transition to silicon is still hindered by the extreme volume expansion of up to 300% upon complete electrochemical lithiation to Li15Si4.3 This causes particle cracking, electrical contact loss of active material, and the continuous (re-)formation of the solid electrolyte interphase (SEI) on the newly formed surface, leading to a continuous loss of cyclable lithium and a fast capacity fading of the cell.One approach to mitigate Si particle cracking is the partial lithiation of microscale silicon, limiting the capacity to ~1200 mAh g-1, i.e., one-third of the theoretical capacity, enabling a cycle-life of more than 200 cycles before reaching 80% state-of-health (SOH).4 While electronic disconnection of lithiated silicon contributes to the overall cyclable lithium losses, the continuous formation of the SEI remains one of the major challenges that limit the lifetime.5 Fluoroethylene carbonate (FEC) has been shown to be one of the most suitable additives for silicon-containing cells to ensure the formation of a suitable SEI and comparably stable cycling performance.6,7 However, especially at elevated temperatures, FEC decomposes to form vinylene carbonate and hydrogen fluoride, which is detrimental to the SEI.8 This study investigated temperature-dependent cycle-life stability of microscale-silicon dominant anodes with EC-based and FEC-based electrolytes at room and elevated temperature. The electrodes consist of 70% silicon (Wacker Chemie AG) with an LiPAA binder (8%) and conductive carbon (2%). Additionally, graphite (8% KS6L, Imerys) was added to enhance the electronic conductivity, whereby within the operating voltage range of the anode, only a minor capacity of the graphite is used. As electrolytes, either 1 M LiPF6 in EC:DEC 1:2 v:v (EC-based) or 1 M LiPF6 in FEC:DEC 2:8 v:v (FEC-based) were used. Full-cells were cycled with a nickel-rich transition metal oxide cathode active material (LiNi0.83Co0.12Mn0.05O2 (NCM831205), BASF SE) based cathode at 25 °C and 45 °C. As shown in Figure 1, cycling in coin cells revealed the expected decreased cycle-life of cells with the FEC-based electrolyte at 45 °C (light blue) compared to 25 °C (dark blue).8 However, cycling cells with the FEC-free, EC-based electrolyte (green) at elevated temperatures, showed the opposite trend. The cycle-life until 80% SOH increased by 110 cycles (+100%), surpassing that of the cells with the FEC-based electrolyte at 45 °C. The charge-averaged mean voltages for both charge and discharge were investigated to identify the main failure mechanisms. This allowed us to differentiate between the loss of cyclable lithium and internal cell resistance build-up.To better understand the contributions of anode and cathode to capacity fading, we assembled Swagelok® T-Cells with the same cell chemistry and cycled them analogously. While the resistance of the cathode remained nearly constant over the whole course of cycling, the resistance of the anode showed an increase with decreasing cell capacity. Furthermore, online electrochemical mass spectrometry (OEMS) was performed to determine the gases evolved during formation with the EC-based electrolyte at 25 °C and 45 °C. This allowed us to gain insights into the overall SEI formation mechanism and to differentiate the formation of suitable SEI components.

Plant–microbial fuel cell for electrical generation through living plants: an internal resistance insight into the plant species used

Abstract Climate change is a global threat, the presence of which has encouraged the development and implementation of renewable energies, including plant–microbial fuel cells, which could generate 6 629 568–33 147 840 MWh per year due to their large-scale applicability. One of the main challenges associated with microbial cells is internal resistance—a parameter whose magnitude is influenced by several factors. In the case of plant–microbial fuel cells, adding a plant positively affects the mitigation of internal resistance. However, the species employed is expected to play an important role. In the present study, the objective was to determine as a general reference the internal resistance of cells using various plant species, among which were tomato (Solanum lycopersicum), black beans (Phaseolus vulgaris), aloe vera (Aloe vera), corn (Zea mays), and moss (Dicranidae). For this purpose, an experimental procedure was carried out to compare the manual voltage measurements with a free cell concerning the voltage obtained by adding an external resistor in series. The internal resistance values were determined as a function of the measured voltage, obtaining 177, 179, 175, 324, and 233 kΩ for aloe vera, corn, tomato, black beans, and moss, respectively. From this, it was shown that the roots of the plants represent an essential addition to the internal resistance of the cell in the short term. In contrast, plants with a C4 photosynthetic metabolism are more favourable, while C3 plants can also benefit from internal resistance during a more extended period of rhizodeposition.

Experimental study of the effect of different pulse charging patterns on lithium-ion battery charging

This study aims to experimentally investigate the impact of different pulse charging patterns on the charging time and performance of lithium-ion batteries at room temperature. Experimental results indicate that most pulse charging protocols have a positive impact on shortening the total charging time compared to the CC-CV charging method with the same input charge capacity. This effect is observed not only in LFP batteries but also in NMC batteries. Three pulse charging patterns are studied: constant current charge (C–C), charge rest (C–R), and charge discharge (C-D). The C-D mode results in the shortest charging time and the smallest cell internal resistance. Compared to the 1C CC-CV baseline, the pulse C-D mode reduces the charging time by approximately 6.8 %, decreases the average pulse internal resistance by about 17.5 %, and increases the remaining discharge capacity ratio by 3.76 % after 800 cycles. Additionally, a pseudo-2D physics model is used to study the internal effects on the battery using the pulse C-D mode. The results show that using the pulse charging method (C-D) results in a more even distribution of electrolyte salt concentration and electrode particle lithium concentration across the cell, thereby improving battery performance.

Modeling of pulse and relaxation of high-rate Li/CFx-SVO batteries in implantable medical devices

We present a Hybrid Multiphase Porous Electrode Theory (Hybrid-MPET) model that accurately predicts the performance of Medtronic’s implantable medical device battery lithium/carbon monofluoride (CFx) - silver vanadium oxide (SVO) under both low-rate background monitoring and high-rate pulsing currents. The distinct properties of multiple active materials are reflected by parameterizing their thermodynamics, kinetics, and mass transport properties separately. Diffusion limitations of Li+ in SVO are used to explain cell voltage transient behavior during pulse and post-pulse relaxation. We also introduce change in cathode electronic conductivity, Li metal anode surface morphology, and film resistance buildup to capture evolution of cell internal resistance throughout multi-year electrical tests. We share our insights on how the Li+ redistribution process between active materials can restore pulse capability of the hybrid electrode, allow CFx to indirectly contribute to capacity release during pulsing, and affect the operation protocols and design principles of batteries with other hybrid electrodes. We also discuss additional complexities in porous electrode model parameterization and electrochemical characterization techniques due to parallel reactions and solid diffusion pathways across active materials. We hope our models can complement future experimental research and accelerate development of multi-active material electrodes with targeted performance.

Experimental Validation of Electrothermal and Aging Parameter Identification for Lithium-Ion Batteries

Modeling and predicting the long-term performance of Li-ion batteries is crucial for the effective design and efficient operation of integrated energy systems. In this paper, we introduce a comprehensive semi-empirical model for Li-ion cells, capturing electrothermal and aging features. This model replicates the evolution of cell voltage, capacity, and internal resistance, in relation to the cell actual operating conditions, and estimates the ongoing degradation in capacity and internal resistance due to the battery use. Thus, the model articulates into two sub-models, an electrothermal one, describing the battery voltage, and an aging one, computing the ongoing degradation. We first propose an approach to identify the parameters of both sub-models. Then, we validate the identification procedure and the accuracy of the electrothermal and aging models through an experimental campaign, also comprising two real cycle load tests at different temperatures, in which real measurements collected from real Li-ion cells are used. The overall model demonstrates good performances in simulating battery characteristics and forecasting degradation. The results show a Mean Absolute Percentage Error (MAPE) lower than 1% for battery voltage and capacity, and a maximum absolute error on internal resistance that is on par with the most up-to-date empirical models. The proposed approach is therefore well-suited for implementation in system modeling, and can be employed as an informative tool for enhancing battery design and operational strategies.

Quantification of internal resistance of microfluidic photosynthetic power cells

Quantification of internal resistance of microfluidic photosynthetic power cells

Assessing the Performance of Continuous-Flow Microbial Fuel Cells and Membrane Electrode Assembly with Electrodeposited Mn Oxide Catalyst

Microbial fuel cells (MFCs) are considered promising energy sources whereby chemical energy is converted into electricity via bioelectrochemical reactions utilizing microorganisms. Several factors affect MFC performance, including cathodic reduction of oxygen, electrode materials, cell internal and external resistances, and cell design. This work describes the effect of the catalyst coating in the air-cathode membrane electrode assembly (MEA) for a microbial fuel cell (MFC) prepared via electrodeposition of manganese oxide. The characterization of the synthesized air-cathode MFC, operating in a continuous mode, was made via electrochemical impedance spectroscopy (EIS) analyses for the determination of the intrinsic properties of the electrode that are crucial for scalability purposes. EIS analysis of the MFCs and of the MEA reveals that the anode and cathode contribute to polarization resistance by about 85% and 15%, respectively, confirming the high catalytic activity of the Mn-based air cathode. The maximum power density of the Mn-based cathode is about 20% higher than that recorded using a Pt/C electrode.

Imidazole-Based Lithium Salt LiHDI as a Solid Electrolyte Interphase-Stabilising Additive for Lithium-Conducting Electrolytes.

Lithium salt LiHDI (lithium 4,5-dicyano-2-(n-heptafluoropropyl)imidazolide) is proposed as a solid electrolyte interphase-stabilising additive for lithium-ion batteries, which can be added in a smaller amount than fluoroethylene carbonate (FEC) and vinylene carbonate (VC) additives. Electrolytes containing either lithium 4,5-dicyano-2-(trifluoromethyl)imidazolide (LiTDI) or battery-standard LiPF6 were tested with various amounts of LiHDI additive. Chemical stability in the presence of water and the thermal stability of LiHDI are on par with LiTDI. LiHDI additive does not negatively affect the properties of electrolytes. Conductivity measurements of solutions, galvanostatic cycling of graphite-LiFePO4 cells at room temperature, cells' cycling at 60 °C, internal cell resistance monitoring during cycling, and XPS analysis of electrodes' surfaces after cycling have been performed. LiHDI, unlike the FEC-VC mixture, does not negatively affect the properties of the electrolyte. Cycling showed improved capacity retention with LiHDI additive with both graphite and LiFePO4 as capacity-limiting electrodes over samples without additives. At elevated temperatures, samples with LiHDI exhibited better capacity retention during cycling than those with FEC-VC. Internal cell resistance can be correlated with capacity retention. XPS results show changes in the composition of SEI depending on the composition of the electrolyte and the duration of cycling.

A Generic Model for Accurate Energy Estimation of Electric Vehicles

A systematic simulation model is proposed in this research paper to estimate the energy consumption of electric vehicles. The main advantage of this model is that it is made in a generic and simplified way in order to be adaptable to different electric vehicles. The overall electrical power corresponding to the performed maneuver is estimated considering: a tabular form of electric motor efficiency, mechanical power losses, a generalized efficiency map of the power electronics, the auxiliary power losses, and an electro-thermal Lithium-Ion battery pack model. The battery model was developed in a previous work, which simulates the open circuit voltage curves at different temperatures and the alteration in the internal resistance of the battery cells. The proposed model is validated with experimental data from the maneuver tests. The battery model proved high accuracy in estimating the voltage values relevant to the WLTP2 driving cycle on the chassis roller test bench. Furthermore, the mechanical and electrical power were estimated with excellent matching compared to actual test field driving test measurements, giving only the measured vehicle speed and auxiliary power losses. Finally, the state of charge change is predicted accurately along the performed test field dynamic maneuver.

In situ dual-interface layer enabling lower resistance of Ta-doped Li7La3Zr2O12-based thermal battery

Application of Ta-doped Li7La3Zr2O12 (LLZTO) to thermal battery could solve overflow safety hazards caused by molten salt electrolytes. However, the capacity of large current discharge is obstructed by the large interfacial resistance originating from poor solid–solid contact between LLZTO and cathode. In this work, an in-situ dual-interface layer with favorable conductivity and multi-ionic diffusion between LLZTO and cathode is constructed by introducing connection layer in a simple way. The Ni(BrxCl2-x) layer with favorable conductivity would be established at high temperature during discharge for the reaction between the connection layer and NiCl2 cathode; the ionic (Br-,Cl-,O2–) diffusion layer with significant diffused direction among the connection layer, LLZTO layer and cathode layer occurs simultaneously at high temperature during discharge. Besides, the left connection layer with low melting point could form wettable interface as well. Consequently, the internal resistance of the single cell modified by in-situ dual-interface layer is reduced from 3.72 Ω to 1.70 Ω, accompanying with larger discharge current density (from 25 to 100 mA cm−2) and higher specific energy (from 444 to 1050 Wh kg−1) at 500 °C. Comparing with the typical discharge current of LLZTO which is less than 1 mA cm−2, this report provides a new insight to improve the interfacial resistance for the solid–solid contact at ambient temperature and the application for LLZTO on high-temperature battery.

Forced Air Cooling for Battery Module on Series Connected Batteries: Temperature Variation Due to Non-Uniform Flow Across Channel

Cells in battery pack for electric vehicle are typically connected in series to meet system voltage requirement. In series connection, each cell will experience identical amount of current drawn, therefore the amount of heat generation for each cell will be relatively similar. Nevertheless, this depends on the cell internal resistance which causes joule heating. To mitigate increase in temperature in the pack, cooling system is necessary. Forced air cooling is the most straightforward cooling system as it pulls cool air from inside the vehicle cabin, and the air will be channeled through cooling routes in the battery module. Typically, the cell located close to the inlet of the cooling system gets the maximum cooling rate, and the cooling capacity reduces as air passes towards the last cell in the module. Two cooling designs are explored in which air velocity is varied by changing the cross-sectional area of inlet air whilst keeping the same mass flow rate. This causes the inlet air velocity to change, to which the airspeed for a small air inlet will be higher than a larger inlet. It shows that higher air speed promotes better cooling only at the first and last cell in the module with a temperature gradient up to 15°C. A battery module with a higher cross-sectional area provides a more uniform heat transfer rate whereby the individual cell temperature is relatively similar with 50% more consistent than the smaller cross-sectional area. This demonstrates that having a higher air speed is not the key attribute in determining the cooling factor of a battery module/pack.

Fast Estimation of Entropy Profiles for Lithium-Ion Batteries

The operating temperature of a lithium-ion battery (LIB) has strong effects on its electrochemical performance, safety, and lifetime. Reliable predictions of cell temperature and heat generation are required for the design and thermal management of battery systems. During the normal operation of LIBs, heat sources can be classified into irreversible heat from resistive losses such as ohmic resistance, charge-transfer overpotentials, and mass-transfer limitations; and reversible heat from entropy change . The irreversible heat generation is related to the cell's internal resistance and the applied current. The reversible heat depends on the entropy variation of electrode materials, the state of charge (SoC), and the temperature. An accurate measurement of entropy-variation will not only help to improve the battery operation under optimal thermal conditions but can also be used to diagnose the battery aging since it can reveal crystal structure changes in the electrodes [1, 2].Techniques for measuring the entropy of a battery can mainly be classified into potentiometric [3] and calorimetric methods. The potentiometric method measures the open circuit voltage (OCV) changes while the cell temperature is varied at different SoCs. This method requires a long relaxation time to obtain the OCV equilibrium state following each SoC point and temperature step. The calorimetric method [4-6] is based on measuring the heat generation during charge and discharge, and various models are applied to differentiate between and quantify the reversible and irreversible heat sources. The entropy variation with SOC is obtained via the reversible heat rate.Recent improved methods include e.g., Schmidt et al. [4] who proposed a reversible heat extraction method based on electrothermal impedance spectroscopy (ETIS) and Damay et al. [5] proposing a fast calorimetric method to obtain a continuous entropy profile. The cell surface temperature is monitored while the battery is charged and discharged continuously. A thermal balance is used to estimate the heat generation from the monitored cell temperature changes during charge and discharge. The benefit of this method can be low cost, fast and high resolution. Bedürftig et al. [6] proposed a calorimetric method named ‘Double Pulse Method’ to measure reversible heat in lithium-ion battery cells by exciting the cell with charge and discharge current pulses.Here we present a new entropy characterization method via charge and discharge cycles of a LIB at low constant C-rates using simple insulating condition. Through monitoring the variations of cell surface temperature and voltage with the state of charge, the continuous variation of entropy with the state of charge can be extracted. These results were compared to classical entropy measurements obtained through the potentiometric method as shown in Figure 1. In addition, the extracted entropy variation data is input into a LIB modelling approach, combining a P2D-electrochemical sub-model for battery operation and a 3D-finite-element sub-model for thermal behavior while battery charge and discharge. The model predictions on the cell outer surface temperature variation while charge and discharge under different C-rates are compared with the data obtained in the battery characterization tests as shown in Figure 2. Good agreements between the model predictions and tests are achieved.

Insights into the Electrochemical Degradation of Aluminum Dual-Ion Batteries: Influence of Internal Cell Resistance & Applied Current Density

To face the upcoming demand on high-power energy storage systems, e.g, for high-dynamic grid-stabilization , stationary devices as used in photovoltaics, and mobile applications led to invention of various battery technologies like sodium-ion batteries (SIB), zinc-ion batteries (ZIB) and high-power lithium-ion batteries (LIBs). Especially the several lithium-ion battery technologies have in common that currently used raw materials like lithium-salts and heavy metals (Ni, Co, Mn) are becoming increasingly scarce and therefore expensive. Without substitution by less-critical materials the ongoing energy system transformation cannot be successfully achieved.One promising system that gained attention in the last few years is the so-called aluminum graphite dual-ion battery (AGDIB). The active electrodes are made of cheap and abundant materials like graphite as cathode material and an aluminum-foil as anode1. During operation chloroaluminate anions from the electrolyte, which is currently based on ionic liquids like 1-ethyl-3-methylimidazoliumchloride ([EMIm]Cl) and AlCl3 in stoichiometric ratios as well as deep-eutectic solvents based on mixtures of urea and AlCl3, are (de)intercalated in the graphitic host-structure while on the anode metallic aluminum is electrochemically deposited and dissolved see equation (1) and (2), respectively2, 3. The overall mechanism is quite comparable with Li-metal batteries, where metallic Li is reversibly dissolved and deposited.The big advantages of AGDIBs are cheap electrode materials (graphite & aluminum), electrolytes based on urea and an extraordinary high-power cell-chemistry. Recent publications showed charging rates up to 20 A g-1 Graphite equal to 9 kW kg-1 Graphite in laboratory-scaled cells. Also, the lifetime of those batteries seems to be non-competitive, cycles up to half a million were reported with negligible capacity fading or degradation effects.4 To develop scalable and more representative battery cells, we established the AGDIB cell chemistry in a new corrosion-stable pouch bag design. Due to the significant increased electrode surface area and overall capacity, hitherto unknown effects were observed which limited the end of lifetime (EOL) of those batteries to less than 8,000 cycles. Herein, we report on a detailed analysis of the cell failure, including several electrochemical in-situ techniques like galvanostatic intermittent titration techniques (GITT), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV).5 The obtained data will allow a fundamental understanding of the cell operation under low (≤ 1 C-rates) and very high C-rates ≥ 15 C, which is important for establishing a durable AGDIB with high cycling stability.References M.-C. Lin, M. Gong, B. Lu, Y. Wu, D.-Y. Wang, M. Guan, M. Angell, C. Chen, J. Yang, B.-J. Hwang and H. Dai, Nature, 520(7547), 325–328 (2015). M. L. Agiorgousis, Y.-Y. Sun and S. Zhang, ACS Energy Lett., 2(3), 689–693 (2017). M. Angell, G. Zhu, M.‐C. Lin, Y. Rong and H. Dai, Adv. Funct. Mater., 30(4), 1901928 (2020). G. A. Elia, N. A. Kyeremateng, K. Marquardt and R. Hahn, Batteries & Supercaps, 2, 83–90 (2019).M. Safari and C. Delacourt, J. Electrochem. Soc., 158(10), A1123 (2011). Figure 1

Steps towards the ideal CV and GCD results with biodegradable polymer electrolytes: Plasticized MC based green electrolyte for EDLC application

Advanced materials are a primary focus of many research groups for applications in energy storage devices. Natural polymers, as a branch of advanced materials, are currently a hot topic to produce clean energy and reduce microplastics problems in the ocean and their potential harm to human health through ingestion. A novel biodegradable green polymer electrolyte was selected for energy storage in the current investigation. The MC polymer was impregnated with a fixed weight percent (40 %) of sodium thiocyanate (NaSCN) and different amount of glycerol to produce flexible films of solid polymer electrolytes (SPEs) using solution casting method. The XRD test reveals that the lowest degree of crystallinity is present in the most conductive electrolyte with increasing plasticizer. According to the electrochemical impedance spectroscopy (EIS) results, the sample that was incorporated with 50 % glycerol displayed the highest conductivity. FTIR was employed to observe the interaction of electrolyte components. Ions were found to be the primary species contributing to conduction, with transference numbers of 0.958 and 0.042 for ions (tion) and electrons (te), respectively. The results obtained from the linear sweep voltammetry (LSV) data confirm that the sample can withstand a voltage of approximately 2.54 V. This voltage level is suitable for extensive practical applications. The shape of the CV pattern was almost comparable to an ideal rectangular shape at low scan rates. A slight increase in the internal resistance (ESR) of the EDLC cell was observed, which increased from 59 to 68 Ω. The battery cycler was used to charge and discharge the designed EDLC device and some key parameters, including capacitance (110 F.g−1), energy density (15 Wh.Kg−1), and power density (1300 W.Kg−1) were determined from the discharge curve. Ultimately, based on the study of the assembled cell, it has been suggested that supercapacitors have emerged as potential alternative to replace environmentally harmful Li-ion batteries in advancing green energy.

Status and prospects for the development of mobile power sources

The physicochemical foundations of the basic structures and technologies for the production of promising electrolytic cells for the accumulation of electrical energy with a specific energy intensity for reusable cells of 350–500 W ⋅ h/kg at the first stage and 1000 W ⋅ h/kg at the second stage have been developed. Along with traditional chemical current sources and ionistors, supercapacitive capacitor structures with a thin dielectric in a double electric layer and hybrid capacitors appear, in which energy is accumulated both in a double electric layer and due to electrochemical processes. This approach makes it possible to reduce the internal resistance of electrolytic cells, which leads to a decrease in heat generation during operation and, accordingly, an increase in specific energy consumption, operational safety, a decrease in charging time, and an increase in specific power. A promising anode is a nanostructured electrode material, which is a carbon-based matrix filled with a nanostructured reactive material. Promising materials for filling the carbon matrix are Li and its alloys, Si, Al, Na, Sn, Mg, Zn, Ni, Co, Ag, and a number of other materials and their compounds. The influence of the specific area of the carbon material, dielectric constant, addition of a chemically active substance on the specific energy consumption has been studied. The theoretical values of the specific energy capacity of hybrid capacitors with a metal-air system are calculated. A thin-film technological complex has been developed that ensures the creation of a new generation of electrode materials, the design of which is a carbon matrix with a highly developed surface, in which there is a tunnel-thin dielectric, on the surface of which a chemically active material is placed.

Investigation on topographic, electrochemical and thermal features of aging lithium-ion cells induced by overcharge/over-discharge cycling

The present study prepared five types of cells (the fresh cells, the cells degraded to 90 % and 80 % SOH (state of health) after overcharge cycling and the cells degraded to 90 % and 80 % SOH after over-discharge cycling) to illustrate the topographic, electrochemical and thermal features of aged cells induced by overcharge and over-discharge cycling. Cell's internal resistance aggravates significantly after overcharge and over-discharge cycling, notably for the charge transfer impedance and Warburg impedance. Both electrodes become expanded along the overcharge and over-discharge cycle. The lattice of positive electrode materials varies and the graphite degree of the negative electrode material decreases following the overcharge and over-discharge cycle; meanwhile, the passivation layer of the positive electrode material is revealed to grow obviously and the transition metal dissolution is found to aggravate. The thermal stability of the aged positive electrode materials is somewhat decreased, which further leads to the aggravation of thermal runaway behaviors for the aged cells; moreover, the severity exacerbates with the deepening of cell aging. In comparison with overcharge, the aging induced by over-discharge seems to decline the safety of cells more.