Specific Discharge Energy Research Articles

Classification of cathode materials for lithium-ion batteries of new energy electric vehicles based on safety and dynamic performance

The severe environmental pollution caused by fossil fuels has driven the demand for new energy vehicles. The choice of cathode materials for lithium-ion batteries is a major difficulty to be overcome in the development of new energy vehicles. Based on the performance characteristics of new energy vehicle batteries in actual use, this paper classifies the six most widely used cathode electrode materials in the new energy vehicle market. Firstly, the temperature data of power batteries with different cathode materials in the overcharge experiment and acupuncture experiment were collected to characterize the safety performance of power batteries. Then the maximum specific discharge capacity and operating voltage data of the battery were collected, and the maximum specific discharge energy of the battery was calculated to study the dynamic performance of the vehicle. After that, the safety performance and dynamic performance of each index is compared. Finally, according to the safety performance and dynamic performance of the corresponding power battery, the six cathode materials are divided into three types: power type, safety type, and balanced type. According to the classification results, it can be concluded that the design of balanced cathode materials with both safety and dynamic performance is the best development route for future new energy vehicle batteries.

Metal- and binder-free dual-ion battery based on green synthetic nano-embroidered spherical organic anode and pure ionic liquid electrolyte

Dual-ion batteries (DIBs) have attracted extensive attention and investigations due to their inherent wide operating voltage and environmental friendliness. Nevertheless, the vast majority of DIBs employ metal-based anode active materials or electrolytes, which are relatively costly and unsustainable. Moreover, the utilization of binders and current collectors in the preparation of cathodes and anodes reduces the energy density to a certain extent, which weakens the advantages of DIBs. Here, we synthesized three types of binder-free nano-embroidered spherical polyimide anode materials composed entirely of renewable elements, paired with pure ionic liquid electrolyte without metal elements and flexible self-supporting independent graphite paper cathode without current collector, to construct a class of totally metal and binder-free DIBs. It significantly improves specific discharge capacity, energy density, cyclic stability, and fast charging performance while remarkably reducing costs and self-discharge rate. Additionally, we overcame the drawbacks of conventional synthesis methods and innovatively prepared nanoscale polyimide materials by a green and facile hydrothermal method, which effectively minimizes synthesis costs and avoids risks. This novel battery system design strategy will promote the advancement of low-cost, high-performance DIBs and could be a promising candidate for large-scale energy storage applications.

Enhancing lithium-sulfur battery performance with biomass-derived graphene-like porous carbon and NiO nanoparticles composites

Despite the promising specific discharge capacity and energy density, lithium-sulfur batteries (LSBs) encounter challenges related to the lithium polysulfides (LiPSs) shuttle effect and volume expansion during extended cycling. A pivotal aspect of this research lies in the strategic synthesis of a hybrid of non-polar and polar compounds, creating an effective host and separator modifier tailored for LSBs for improvement of their electrochemical characteristics. Precisely, high-specific surface area graphene-like porous carbon (GPC) was successfully synthesized from inexpensive and abundant rice husk (RH) waste via step-by-step carbonization and thermo-chemical activation, and subsequently used as a porous matrix for sulfur cathode preparation using the melt-diffusion technique. Furthermore, composites based on GPC decorated with NiO nanoparticles were synthesized with varying GPC to Ni(NO3)2 ratios and utilized as an efficient separator modifier. The obtained results revealed that the cell consisting of GPC@S cathode and GPC-NiO-20 modified separator exhibited accelerated LiPSs redox reactions and suppressed the shuttle effect. In particular, the GPC@S/GPC-NiO-20 cell demonstrated excellent initial discharge capacity (1519 mAh g−1 at 0.2 C), promising long-term cycling performance (capacity decay of 0.091 % per cycle over 400 cycles at 1 C), and remarkable rate performance (568 mAh g−1 at 2 C).

Planar Sodium‐Nickel Chloride Batteries with High Areal Capacity for Sustainable Energy Storage

AbstractHigh‐temperature sodium‐nickel chloride (Na‐NiCl2) batteries are a promising solution for stationary energy storage, but the complex tubular geometry of the solid electrolyte represents a challenge for manufacturing. A planar electrolyte and cell design is more compatible with automated mass production. However, the planar cell design also faces a series of challenges, such as the management of molten phases during cycling. As a result, cycling of planar high‐temperature cells until now focused on moderate areal capacities and current densities. In this work, planar cells capable of integrating cost‐efficient nickel/iron electrodes at a substantially enhanced areal capacity of 150 mAh cm−2 is presented. Due to a low cell resistance during operation at 300 °C, these cells deliver a specific discharge energy of 300 Wh kg−1 at high discharge current densities of 80 mA cm−2 (C/2, 10%–100% state‐of‐charge). This results represent the first demonstration of planar Na‐NiCl2 cells at a commercially relevant combination of areal capacity, cycling rate, and energy efficiency. It is further identified the secondary molten NaAlCl4 electrolyte to contribute to the cell capacity during cycling. Mitigating electrochemical decomposition of NaAlCl4 will play an important role in further enhancing both cycling rates and cycle life of high temperature Na‐NiCl2 batteries.

Transition mechanisms between selective O3 and NO x generation modes in atmospheric-pressure plasmas: decoupling specific discharge energy and gas temperature effects

Two modes of the atmospheric-pressure plasma discharge, distinguished by the dominant O3 and NO x species are studied numerically and experimentally. To investigate the mode transition mechanisms, here we develop a global chemical kinetics model for the atmospheric-pressure dielectric barrier discharge involving 63 species and 750 reactions. Validated by the experimental results, the model accurately describes the mode transition. The N, O, O2(a), and O2(b) are the essential transient intermediate species for the O3 and NO x production and loss reactions. The individual and synergistic effects of the specific discharge energy and the gas temperature on the species density and the relative contributions of the dominant reactions are quantified under the increasing discharge voltage conditions. The modeling results indicate that the gas temperature and specific discharge energy both contributed to the discharge mode transition, while the decisive factors affecting the change of the O3 and NO x density are different in the respective modes. These insights contribute to diverse plasma applications in biomedicine, agriculture, food, and other fields where selective and controlled production of O3 and NO x species is the key for the desired plasma performance.

The preparation of rod-like porous α-Fe2O3 with large interplanar spacing for symmetric supercapacitors

Rod-like porous α-Fe2O3 was synthesized by static hydrothermal treatment at 160°C and used as a symmetric supercapacitor. The phase information, structure, morphology, valence state and composition of the prepared sample were characterized using X-ray diffraction, infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and N2 adsorption–desorption. The results show that the prepared α-Fe2O3 is a rod-like porous material dominated by mesopores. Moreover, the α-Fe2O3 is a hexagonal single crystal with [FeO6] octahedrons and the interplanar crystal spacings are large enough for electrolyte ion diffusion. In both KOH and Na2SO4 electrolytes, the α-Fe2O3 sample displays good pseudocapacitance performance. However, the specific discharge capacity and energy density in KOH are larger than in Na2SO4. In 1 mol L–1 of KOH, remarkable capacities of 139 and 35.5 F g–1 are obtained and an energy density of 3.91 and 1.01 Wh kg–1 is achieved at 1 and 20 A g–1 respectively. After 10 000 cycles, 87.7% of the specific capacitance is still retained at 1 A g–1. The good capacitance properties may attributed to the rod-like porous structure and large interplanar spacing, which provide good ion insertion–exit paths, enough oxidation–reduction active sites and a fast ion transfer velocity.

On the WEDM of WNbMoTaZrx (x = 0.5, 1) Refractory High Entropy Alloys.

As a potential candidate for the next generation of high-temperature alloys, refractory high entropy alloys (RHEAs) have excellent mechanical properties and thermal stability, especially for high-temperature applications, where the processing of RHEAs plays a critical role in engineering applications. In this work, the wire electrical discharge machining (WEDM) performance of WNbMoTaZrx (x = 0.5, 1) RHEAs was investigated, as compared with tungsten, cemented carbide and industrial pure Zr. The cutting efficiency (CE) of the five materials was significantly dependent on the melting points, while the surface roughness (Ra) was not. For the RHEAs, the CE was significantly affected by the pulse-on time (ON), pulse-off time (OFF) and peak current (IP), while the surface roughness was mainly dependent on the ON and IP. The statistical analyses have shown that the CE data of RHEAs have relatively-smaller Weibull moduli than those for the Ra data, which suggests that the CE of RHEAs can be tuned by optimizing the processing parameters. However, it is challenging to tune the surface roughness of RHEAs by tailoring the processing parameters. Differing from the comparative materials, the WEDMed surfaces of the RHEAs showed dense spherical re-solidified particles at upper recast layers, resulting in larger Ra values. The proportion of the upper recast layers can be estimated by the specific discharge energy (SDE). Following the WEDM, the RHEAs maintained the main BCC1 phase, enriched with the W and Ta elements, while the second BCC2 phase in the Zr1.0 RHEA disappeared. Strategies for achieving a better WEDMed surface quality of RHEAs were also proposed and discussed.

Numerical and experimental study on WEDM of BN-AlN-TiB2 composite ceramics based on a fusion FEM model

Due to the poor machining performances in the traditional machining process for BN-AlN-TiB2 composite ceramics, this paper investigated the influence of electrical parameters and material composition on the machining performances of wire electrical discharge machining, namely material removal rate (MRR), surface roughness, kerf width, and energy efficiency. To find out the optimal process parameters, a fusion thermo-physical model based on the finite element method was proposed to predict the machining performances of BN-AlN-TiB2 with different weight proportions. Compared with experimental results, the accuracy of the novel model was verified within a relative error of 24.56, 16.16, and 1.87% in MRR, surface roughness, and kerf width, respectively. In addition, a series of experiments were conducted to investigate the effects of process parameters on machining performances for WEDM of different BN-AlN-TiB2 composite ceramics with 6, 8, and 10 wt% TiB2. The experimental results demonstrated that machining performances were proportional to the discharge energy. Moreover, MRR and specific discharge energy increased with increase of discharge current and pulse-on time. Considering the machining performances and energy efficiency, an appropriate parameter range with discharge current of 6–8 A, pulse-on time of 10–30 μs, and pulse-on time of 4–6 μs was recommended, and the BN-AlN-TiB2 composite ceramics with 6 wt% TiB2 exhibit better energy efficiency during the WEDM process.

High-capacity polymer electrodes for potassium batteries

We synthesized and investigated a series of six promising polymeric electrode materials, which incorporate multiple redox-active groups enabling high specific discharge capacity and energy density in potassium half-cells.

Understanding the Operating Mechanism of Aqueous Pentyl Viologen/Bromide Redox-Enhanced Electrochemical Capacitors with Ordered Mesoporous Carbon Electrodes.

Compared to traditional electric double-layer capacitors, redox-enhanced electrochemical capacitors (redox-ECs) show increased energy density and steadier power output thanks to the use of redox-active electrolytes. The aim of this study is to understand the electrochemical mechanisms of the aqueous pentyl viologen/bromide dual redox system at the interface of an ordered mesoporous carbon (CMK-8) and improve the device performance. Cells with CMK-8 carbon electrodes were investigated in several configurations using different charging rates and potential windows. The pentyl viologen electrochemistry shows a mixed behavior between solution-based diffusion and adsorption phenomena, with the reversible formation of an adsorbed layer. The extension of the voltage window allows for full reduction of the viologen molecules during charge and a consequent increase in the specific discharge energy delivered by the cell. Investigation of the mechanism indicates that a 1.5 V charging voltage with a 0.5 A g-1 charging rate and fast discharge rate produces the best overall performance.

Thermal Modelling and Multi Decision Making Optimization of EDM of Non Conductive SiC-CNT Ceramic Composite Used for Li-ion Battery and Sensor

In this research work the thermal modeling of a nonconductive Silicon carbide Ceramic matrix composite (CMC) machined by Die Sinking Electric Discharge Machining (EDM) has been done. Though SiC is a non-conductive material but the presence of CNT makes it a conductive material which can be machined with EDM. The modeling procedure carried out by considering some realistic approach like Gaussian heat Flux, Specific Discharge Energy, Variable Latent heat etc. For this analysis a 2D continuum has been designed as work domain. By simulating the work domain model by a Finite Element Analysis (FEA) Software (COMSOL), material removal rate (MRR) has been estimated with variable thermal properties. Parametric analysis of effect of Variable Specific heat on MRR by considering different current, Voltage and Pulse-On time has been performed. The effect of different input parameters (peak current and Pulse-on time) on Crater geometry has been done. A new concept of Specific discharge energy has been introduced during modelling to make it a more realistic model which can also be used as electrode support for electrochemical energy devices as Polymer Electrolyte Membrane Fuel Cells on Li-ion battery. Desirability analysis has been done to get an optimize set of input parameters for I= 3A, V=30V, Ton= 75 µs for machining ceramic matrix composite by EDM. The optimized MRR at this setting is 7.25 mm3/min whereas PFE is 87%. The experimental analysis has been also performed to strengthen the thermal and mathematical modelling.

Rechargeable Lithium Metal Pouch Cell Development

Commercially available Li-ion batteries using graphite or graphite-silicon blended anodes are currently approaching a cell level specific energy of 300 Wh kg−1. The use of lithium metal instead as an anode an intriguing possibility to further increase cell level specific energies to 400 Wh kg−1 and beyond. Lithium is an ideal anode because it is the lightest metal and highly electronegative. However, attempts to commercialize cells using lithium metal anodes have been slowed by poor cycle life and safety issues. This is because nonuniform lithium plating leads to the growth of dendrites that cause loss of active lithium and can eventually lead to internal cell shorts. Safe cell cycle life must be improved to 50-100 cycles for special purpose applications like unmanned aerial vehicles, >300 cycles for portable power applications and >1000 cycles for electric vehicle applications.The performance of prototype cells developed at EaglePicher Technologies using lithium metal anode will be highlighted. The figure below on the left shows the specific discharge energy of a 2.5 Ah prototype pouch cell using a lithium anode, high nickel cathode and nonaqueous electrolyte. The cell demonstrates an extremely high specific energy of >400 Wh kg−1 at low rates. The effect of electrolyte on capacity retention is shown in the figure below on the right. The optimized electrolyte demonstrates good retention to >50 cycles. This presentation will focus on design considerations for pouch cells with lithium anodes, as well as improving the cycle life and safety characteristics of these cells. Prototype performance data including cycle life, rate capability, temperature effects and safety testing will be presented.EaglePicher Technologies would like to acknowledge the US Army DEVCOM C5ISR Center in Aberdeen Proving Ground, Maryland for funding this research. Figure 1

A short review on dissolved lithium polysulfide catholytes for advanced lithium-sulfur batteries

Lithium-sulfur battery (LSB) technology has drawn enormous attention during the last decade. Benefitting from the high theoretical specific discharge capacity (1,675 mAh g−1) and energy density (2,600 Wh kg−1), LSBs have proved to be a suitable candidate for electric vehicles and large-scale power grid electrical energy storage systems. However, the commercialization of LSB is hindered by various barriers, which include the high insulating nature of sulfur and its discharge products, severe polysulfide shuttling phenomenon, extreme volume expansion during charging/discharging, and poor stability of Li metal anodes. Additionally, LSB technology faces considerable battery design challenges, which allows high sulfur content and/or sulfur-loading while simultaneously maintaining a low electrolyte/sulfur ratio. Therefore, in this review, we highlight recent effective strategies that lead to more practical and commercial LSBs. We restrict ourselves to various cathode architectures designed specifically to absorb dissolved polysulfide catholyte. The integration of dissolved lithium polysulfide catholyte with specially designed cathode substrates efficiently allows ultra-high sulfur loading and/or sulfur-content with low electrolyte/sulfur ratio while still exhibiting reasonable electrochemical performance and cycling stability. The effect of concentration variation of dissolved lithium polysulfide catholyte on the cell performance is also discussed in detail. Therefore, the present review encapsulates feasible strategies with practical parameters to address the problems associated with LSBs.

Calculation of the parameters of the magnetic-pulse connection of the tip and multi-wire cable

The main provisions of the calculation method and the results of numerical modeling of the process of compression of the tubular shell of the tip onto a stranded wire by the pressure of a pulsed magnetic field are presented. The analysis of the features of the deformation process at different intensity of force loading is carried out. The rational modes of loading and the necessary conditions for minimizing the specific discharge energy while ensuring a high assembly density are determined.

Comparative machinability characterization of wire electrical discharge machining on different specialized AISI steels

In this work, we have attempted to prepare a comparative machinability study of wire electrical discharge machining of different difficult-to-machine materials, viz., stainless steel (SS) 316, H21 hot work tool steel and M42 high-speed steel (HSS). The key features, which are compared during the analysis, are mainly material removal rate, average surface roughness, kerf width, wire consumption rate (WCR), recast layer (RL), elemental diffusion, surface morphology and micro-hardness of the machined surface. They are found to be greatly influenced by pulse energy. The pulse energy is calculated in terms of ‘specific discharge energy’. Apart from the discharge energy, the thermal conductivity of the material also plays an important role in the formation of RL and inclusion of foreign elements such as carbon, oxygen, copper and zinc in RL. H21 steel has been found to be more prone to thermal defects due to its high-thermal conductivity and high tensile residual stresses, whereas more re-solidification of foreign materials is observed in SS316 and M42 HSS due to their high adhesive properties and low-thermal conductivity. But, in low-energy cutting, more uniform surfaces are observed in H21 steel in comparison with other two types of steel.

Improvement of the machining characteristics in WEDM based on specific discharge energy and magnetic field–assisted method

This paper is aimed at investigating and improving material removal rate (MRR) and surface quality in wire electrical discharge machining (WEDM) based on specific discharge energy and magnetic-assisted method. A set of a single-factor experiment is implemented to analyze the effects of carbon content and discharge parameters on machining characteristics. The concept of specific discharge energy (SDE) is proposed to reveal the fundamental influence of workpiece material properties on material removal rate and to obtain the optimal machining feed rate. The mathematical model between SDE and the physical properties of workpiece material is also fitted out. Additionally, it can be found that, in subsurface material, the recast layer is with the maximal hardness followed by bulk material and heat-affected zone. Ra and RLT firstly increase and then decrease with the increase of carbon content, and they have a positive correlation with discharge peak current and pulse-on time. Finally, verified experiment shows that, comparing with other machining feed rates, the method of optimal machining feed rate according to SDE can simultaneously achieve the fastest actual machining speed and the lowest surface roughness. In addition, the method of magnetic-assisted trim cutting can almost eliminate recast layer and reduce heat-affected zone to less than 20 μm.

Shock-tube study of dimethyl ether ignition by high-voltage nanosecond discharge

A shock tube with a discharge cell was used to experimentally analyze the kinetics of dimethil ether (DME) ignition in DME:O2:Ar and DME:O2:Ar:He mixtures at temperatures from 1075 to 1860 K. We measured ignition delay time in lean and stoichiometric mixtures after a reflected shock wave. Measurements were made in the mixtures activated by a high-voltage nanosecond discharge and without discharge plasma. The dominant mechanisms of DME ignition were studied on the basis of a numerical simulation of the discharge and ignition stages. We calculated the densities of chemically active species generated in the discharge and used these data to model ignition. The calculated ignition delay times agreed reasonably with the measured data for autoignition and plasma-assisted ignition. The limiting processes during the discharge and ignition were shown using sensitivity analysis. It was demonstrated that the partial replacement of Ar with He in the mixtures studied allowed the same values of plasma-assisted ignition delay times at much lower gas temperatures being opposite to ignition without plasma where the delay time was not sensitive to the replacement of Ar with He. Calculations showed that this is explained by an increased specific discharge energy spent on the excitation of DME, O2 and Ar, whereas the excitation of He was negligible. It followed from the calculations that electron-impact ionization of DME molecules is of great importance for the production of active species in the discharge phase and consequently for ignition with plasma. The electron-impact ionization cross section of DME is poorly known and its variation influences the calculated ignition delay time. In addition, at reduced gas temperatures, the effect of plasma nonuniformity is important for shock-tube studies.

A Hybrid Mineral Battery: Energy Storage and Dissolution Behavior of CuFeS2 in a Fixed Bed Flow Cell.

The development of a hybrid system capable of storing energy and the additional benefit of Cu extraction is discussed in this work. A fixed bed flow cell (FBFC) was used in which a composite negative electrode containing CuFeS2 (80 wt %) and carbon black (20 wt %) in graphite felt was separated from a positive (graphite felt) electrode by a proton-exchange membrane. The anolyte (0.2 m H2 SO4 ) and catholyte (0.5 m Fe2+ in 0.2 m H2 SO4 with or without 0.1 m Cu2+ ) were circulated in the cell. The electrochemical activity of the Fe2+ /Fe3+ redox couple over graphite felt significantly improved after the addition of Cu2+ in the catholyte. Ultimately, in the CuFeS2 ∥Fe2+ /Cu2+ (CFeCu) FBFC system, the specific capacity increased continuously to 26.4 mAh g-1 in 500 galvanostatic charge-discharge (GCD) cycles, compared to the CuFeS2 ∥Fe2+ (CFe) system (13.9 mAh g-1 ). Interestingly, the specific discharge energy gradually increased to 3.6 Wh kg-1 in 500 GCD cycles for the CFeCu system compared to 3.29 Wh kg-1 for the CFe system in 150 cycles. In addition to energy storage, 10.75 % Cu was also extracted from the mineral, which is an important feature of the CFeCu system as it would allow Cu extraction and recovery through hydrometallurgical methods.

Cathode Materials for Hybrid Supercapacitors Based on Ozonated Reduced Graphene Oxide

A carbon material capable of reversible electrochemical oxidation and reduction with relatively high electrical conductivity was prepared by ozonation of thermally reduced graphene oxide. The specific discharge energy for such materials used in lithium ion electrochemical cell cathodes with non-aqueous electrolytes (LP-71) can reach 540 W h/kg at 40 mA/g current, while the average specific discharge power is 11.5 kW/kg at 5 A/g current. The specific charge after 2500 charge/discharge cycles at 5 A/g current was at a level of 93% of the initial value. The obtained materials appear promising for the design of new electricity storage systems.

High performance of LiMn1-x Fe x PO4/C (0 ≤ x ≤ 0.5) nanoparticles synthesized by microwave-assisted solvothermal method

High specific energy olivine LiMn1-x Fe x PO4/C (0 ≤ x ≤ 0.5) nanoparticles have been synthesized in 20 min at extremely low temperature 160 °C by microwave-solvothermal method. The obtained cathode materials are orthorhombic solid solutions with size of 30–100 nm. Electrochemical test shows that Fe substitution could significantly increase the initial specific capacity and specific energy, as well as cycling performance and rate capability. LiMn0.8Fe0.2PO4/C exhibits the best reversible specific discharge capacity of 165.9 mA h g−1 and specific discharge energy of 643.1 W h kg−1 at 0.1 C. Its discharge capacity remains 95.7% of its initial value of 129.0 mA h g−1 after 50 cycles at 0.5 C. According to the electrochemical impedance spectroscopic analysis, the performance improvement is mainly attributed to the enhancement of Li+ diffusion coefficient (D Li) by Fe substitution. D Li is 4.43 × 10−14 and 1.34 × 10−12 cm2 s−1 for LiMnPO4/C and LiMn0.5Fe0.5PO4/C, respectively.