Improved Energy Density Research Articles

Optimizing Silicon Nanostructures for Enhanced Li-Ion Storage: Microstructure, Binder and Production Technology

The utilization of silicon nanostructures as anodes in lithium-ion batteries (LIBs) presents a promising avenue for improving device performance. However challenges related to prolonged cycling, energy density, and costs need to be addressed. This presentation outlines three strategies employed within the E2MC framework to overcome these challenges: (a) By incorporating high-quality graphene nanosheets, produced through a low-cost and scalable molten salt method, common silicon nanoparticles (generated by commercially available pyrolysis-based methods) can be enveloped in graphene layers with a controllable chemical composition. The graphene-encapsulated silicon nanoparticles exhibit stable electrochemical lithiation/delithiation performance, showcasing significantly improved energy density, even after numerous Li-insertion and extraction cycles, outperforming bare Si nanoparticles; (b) Thermally modified polyimide (PI) is introduced as an efficient binder to enhance the Li-ion storage performance of silicon nanoparticles. An optimized thermal treatment of the electrodes containing Si nanoparticles and PI binder produces an effective charge transfer complex (CTC) structure, improving the electrochemical performance by forming a compact structure that reduces charge transfer impedance. This enhancement significantly boosts the cycling performance of the silicon anode; (c) An ultra-fast shock-wave combustion synthesis approach is introduced for the rapid and low-cost preparation of Si nanostructures using naturally available SiO2 as the silicon feedstock. Completed at an ignition temperature of approximately 550 °C, this method requires virtually no dwell time. The resulting nanostructured Si product exhibits a mesoporous integrated sheet-like morphology, demonstrating excellent and stable Li-ion storage performance. This approach contributes to a more sustainable and cost-effective utilization of elemental Si nanoparticles in LIB applications.

Flexible Supercapacitors With Improved Energy Density Using OPBI-Coated Polyaniline- Carbon Nanotube Blends

Flexible Supercapacitors With Improved Energy Density Using OPBI-Coated Polyaniline- Carbon Nanotube Blends

Design of High‐Entropy Relaxor Ferroelectrics for Comprehensive Energy Storage Enhancement

AbstractFor an ideal electrostatic energy storage dielectric capacitor, the pursuit of simultaneously high energy density and efficiency presents a formidable challenge. Typically, under an applied electric field, an increase in energy density is usually accompanied with a deteriorated energy storage efficiency due to the escalated hysteretic loss, which is harmful to the reliability of the capacitor. Thus, a well‐balanced performance of improved energy density and maintained high efficiency is highly demanded. In this work, a structure with amorphous phases embedded in polycrystalline nanograins using the entropy tactic, leading to a higher transport barrier of carrier is constructed. Hence, the hysteretic loss is largely suppressed at a high electric field and the high polarization is still sustained in the high‐entropy film. Consequently, an ultrahigh energy density of 139.5 J cm−3 with a high efficiency of 87.9%, and a high figure of merit of 1153 are simultaneously achieved in the high‐entropy Ba2Bi4Ti5O18‐based relaxor ferroelectric. This work offers a promising avenue in materials structure design for advanced high‐power energy storage applications.

Cathode Modification of Sodium‐Ion Batteries for Improved energy Density: A Review

AbstractIn recent years, with the large‐scale commercial application of lithium‐ion batteries, the shortage of lithium resource reserves and the rising price limit its development. The sodium‐ion batteries as a new type of secondary chemical power supply, with ample resources, high safety, as well as great electrochemical performance, are expected to form complementary with Lithium‐ion batteries in the domain of extensive electrochemical energy storage and low‐velocity electric vehicles. However, due to its low energy density, it remains challenging to develop high‐performance sodium‐ion batteries. As is well‐known, the cathode material is the essential factor affecting the performance of sodium‐ion batteries. In order to solve these questions, cathode modification of sodium‐ion batteries aroused wide concern for improving the electrochemical performance. Here, the authors first discuss the challenges of sodium‐ion batteries, and review the energy storage mechanism and the causes of the low energy density. Then, recent studies on cathode modification are summarized based on the mainstream cathode materials in sodium‐ion batteries including sodium‐based transition‐metal oxides, polyanionic compounds, and Prussian blue analogues. Finally, the prospects of sodium‐ion batteries are proposed, which provides promising strategies for the development and practical application of cathode materials in the future.

Improved Energy Density at High Temperatures of FPE Dielectrics by Extreme Low Loading of CQDs.

Electrostatic capacitors, with the advantages of high-power density, fast charging-discharging, and outstanding cyclic stability, have become important energy storage devices for modern power electronics. However, the insulation performance of the dielectrics in capacitors will significantly deteriorate under the conditions of high temperatures and electric fields, resulting in limited capacitive performance. In this paper, we report a method to improve the high-temperature energy storage performance of a polymer dielectric for capacitors by incorporating an extremely low loading of 0.5 wt% carbon quantum dots (CQDs) into a fluorene polyester (FPE) polymer. CQDs possess a high electron affinity energy, enabling them to capture migrating carriers and exhibit a unique Coulomb-blocking effect to scatter electrons, thereby restricting electron migration. As a result, the breakdown strength and energy storage properties of the CQD/FPE nanocomposites are significantly enhanced. For instance, the energy density of 0.5 wt% CQD/FPE nanocomposites at room temperature, with an efficiency (η) exceeding 90%, reached 9.6 J/cm3. At the discharge energy density of 0.5 wt%, the CQD/FPE nanocomposites remained at 4.53 J/cm3 with an efficiency (η) exceeding 90% at 150 °C, which surpasses lots of reported results.

Analysis of a CRDI diesel engine powered by ternary fuel blends (diesel, biodiesel, and pentanol) doped with alumina nano-additives

Environmental constraints associated with fossil fuels have driven researchers to find a novel, potential and environmentally benign alternative fuel. Biodiesel, vegetable oil, and alcohol have gained rapid momentum thanks to their renewable nature and comparable energy contents in recent years. Accordingly, a Ternary fuel blend is prepared comprising three fuels namely diesel, biodiesel, and pentanol. Waste cooking oil was identified as the source for biodiesel and Pentanol was chosen among various alcohol alternatives due to improved energy density, reduced toxicity. These are endorsed to the enhancement in surface area-volume ratio of nano additives which boosts the catalytic combustion activity and also causing lesser fuel to take part in combustion for maintaining a constant engine speed. The experimentation is done with ternaryfuel blends with varying pentanol and biodiesel concentrations of diesel, biodiesel and pentanol). Upon experimentation, it was observed that, ternary fuel blend ‘TF’ comprising 70% diesel, 20% biodiesel and 10% pentanol, yielded best performance and was used for doping of Alumina oxide (Al2O3) nano additives. The Al2O3 nanoparticles were doped with ternary blends at fractions of 10 ppm, 20 ppm, and 30 ppm. It was observed that 20 ppm Al2O3 nanoparticle blended TF blend improved BTE and lowered BSFC by about 12.01% and 22.57% respectively. The performance tremendously along with lowered the CO emission by 49.21%, HC emission by 18.91% and smoke opacity by 9.02%.

A High Voltage Symmetric Supercapacitor Comprising Concentrated NaCl: PVA Electrolyte and Partially Reduced Graphene Oxide Electrodes

AbstractStrategies to improve energy density in supercapacitors are mainly based on utilizing electrodes providing larger effective surfaces and electrolytes allowing op eration in wider voltage windows. Here, a water‐based, binder‐free, environmentally friendly, high voltage, and quasi‐solid‐state symmetric supercapacitor is presented comprising partially reduced graphene oxide active electrodes and concentrated NaCl: polyvinyl alcohol gel electrolyte. It is shown that the ionic diffusion through the electrode‐electrolyte interface is augmented by the partial reduction of the graphene oxide electrodes up to an optimum level. The safe operation voltage window is 4 V; the high field endurance is attributed to the ion‐saturated hydrogel electrolyte used. At a scan rate of 25 mV/s, the provided capacitance and stored energy are 0.1 F.cm−2 and 5.6 e−5 W.h.cm−2, respectively. The optimized device retains ~90 % of its initial capacitance after 1000 charge‐discharge cycles; no meaningful sign of degradation is detected afterwards up to the 2000 cycles examined. These results place further emphasis on the potentials of the gel polymer electrolytes in the fabrication of environmentally friendly supercapacitors. Our findings are anticipated to accelerate improvements in the properties of the graphene‐based electrodes, particularly in conjunction with the proposed electrolyte.

High-Voltage Long-Cycling All-Solid-State Lithium Batteries with High-Valent-Element-Doped Halide Electrolytes.

All-solid-state batteries (ASSBs) have garnered considerable attention as promising candidates for next-generation energy storage systems due to their potentially simultaneously enhanced safety capacities and improved energy densities. However, the solid future still calls for materials with high ionic conductivity, electrochemical stability, and favorable interfacial compatibility. In this study, we present a series of halide solid-state electrolytes (SSEs) utilizing a doping strategy with highly valent elements, demonstrating an outstanding combination of enhanced ionic conductivity and oxidation stability. Among these, Li2.6In0.8Ta0.2Cl6 emerges as the standout performer, displaying a superionic conductivity of up to 4.47 mS cm-1 at 30 °C, along with a low activation energy barrier of 0.321 eV for Li+ migration. Additionally, it showcases an extensive oxidation onset of up to 5.13 V (vs Li+/Li), enabling high-voltage ASSBs with promising cycling performance. Particularly noteworthy are the ASSBs employing LiCoO2 cathode materials, which exhibit an extended cyclability of over 1400 cycles, with 70% capacity retention under 4.6 V (vs Li+/Li), and a capacity of up to 135 mA h g-1 at a 4 C rate, with the loading of active materials at 7.52 mg cm-2. This study demonstrates a feasible approach to designing desirable SSEs for energy-dense, highly stable ASSBs.

Design of High-Performance Formyl-Functionalized COF Aerogels as Quasi-Solid Lithium Battery Electrolyte by a Solvent Substitution Strategy.

Covalent organic framework (COF) aerogels with functional groups offer exceptional processability and functionality for various applications. These hierarchical porous materials combine the advantages of COFs with the benefits of aerogels, overcoming the limitations of conventional insoluble and nonfusible COF powders. However, achieving both high crystallinity and shape retention remains a challenge for functionalized COF aerogels. In this work, we develop a novel and general solvent substitution method for the one-step synthesis of formyl-functionalized COF aerogels without harsh vacuum conditions. These aerogels exhibit excellent processing capabilities, superior mechanical strength, and enhanced functionality. As a proof-of-concept, they were used in adsorption and lithium metal battery applications, significantly maximizing the structural advantages of COFs, e.g.: (i) the hierarchical porous structure is fully wetted by the electrolyte to form continuous transport channels; (ii) the polar groups, which are easier to be acquired, help in desolvation and transfer of Li+; (iii) the regular pore structures stabilize deposition of Li+ and inhibit the growth of lithium dendrites. These combined benefits contribute to a lighter battery with improved energy density and enhanced safety.

Ligand substitution as a strategy to tailor cationic conductivity in all-solid-state batteries

An increased electrification of society calls for a revolution of battery technologies to further improve energy densities, safety and reduce dependencies on critical raw materials. Here we present a new type of fast magnesium electrolytes for all solid-state batteries created as solid solutions of two other fast Mg2+ ionic conductors, Mg(BH4)2 ∙ NH3 and Mg(BH4)2 ∙ CH3NH2. However, the different ligands introduce stacking faults in the structures of the solid solutions, which are eliminated upon heating to T > 40 °C. The stacking faults appear to influence ionic conductivity, as the samples are less conductive after heating. Interestingly, the ionic conductivity does not correlate directly with the relative ligand content, as the highest conductivity is observed for the 1:1 molar composition (σ(Mg2+) = 7.3 ∙ 10−6 S cm−1 at 40 °C), which also has the lowest melting point of 60 °C. Thus, this work demonstrates a new approach to increase cationic conductivity using mixed ligand systems to alter conduction pathways and introduce microstructural strain.

On the kinetics of electrodeposition in a magnesium metal anode

Magnesium (Mg) metal batteries are promising for next-generation energy storage due to Mg’s abundance and potential for improved energy densities through two-electron redox in cathodes and thin film anodes supporting high current densities. However, reversible and uniform electrodeposition of Mg necessary for high-energy-density Mg batteries continues to be plagued by challenges traceable to energy barriers to desolvation in liquid electrolytes, the stabilization of passivation layers that impede Mg diffusion at electrified interfaces, and deleterious high-asperity electrodeposition morphologies. Thus, the specific impact and coupling of factors such as (i) composition of the salt solution, (ii) electrode overpotential, and (iii) reversible stripping/plating on the interfacial kinetics of electrodes remains an area of intense interest. This study investigates the effects of overpotential time-transients and electrolyte concentration using experimentally-guided phase-field methods and compares them with an electrochemical spherical cap model. Complex dynamics at the electrode/electrolyte interface involve transient changes in overpotential, influencing nucleation, diffusion, and crystallization, ultimately altering surface evolution. We find that the Damkohler number converges to approximately one for a symmetric Mg-Mg cell using 0.1 M Mg[TFSI]2 in 1:1 v/v diglyme/dimethoxyethane suggesting a subtle balance between reactive and diffusive forces. The results indicate the formation of dendritic structures is primarily driven by limitations in electrolyte transport. In addition, we determine the limiting current density of this cell under various electrolyte concentrations, which is an essential step in successful battery design and operation. Our findings underscore the critical role of overpotentials in underpinning reaction kinetics and non-equilibrium growth dynamics during metal electrodepositon.

Generative learning facilitated discovery of high-entropy ceramic dielectrics for capacitive energy storage

Dielectric capacitors offer great potential for advanced electronics due to their high power densities, but their energy density still needs to be further improved. High-entropy strategy has emerged as an effective method for improving energy storage performance, however, discovering new high-entropy systems within a high-dimensional composition space is a daunting challenge for traditional trial-and-error experiments. Here, based on phase-field simulations and limited experimental data, we propose a generative learning approach to accelerate the discovery of high-entropy dielectrics in a practically infinite exploration space of over 1011 combinations. By encoding-decoding latent space regularities to facilitate data sampling and forward inference, we employ inverse design to screen out the most promising combinations via a ranking strategy. Through only 5 sets of targeted experiments, we successfully obtain a Bi(Mg0.5Ti0.5)O3-based high-entropy dielectric film with a significantly improved energy density of 156 J cm−3 at an electric field of 5104 kV cm−1, surpassing the pristine film by more than eight-fold. This work introduces an effective and innovative avenue for designing high-entropy dielectrics with drastically reduced experimental cycles, which could be also extended to expedite the design of other multicomponent material systems with desired properties.

Finite element modeling simulation of oxygen evolution during charging in lithium-oxygen batteries

The quest for advanced energy storage solutions has intensified the focus on developing next-generation secondary batteries, with lithium-oxygen batteries (LOB) standing out for their superior theoretical gravimetric energy density. This study introduces a novel model-based approach to battery development, enabling the detailed analysis of charge–discharge cycles and oxygen evolution efficiency within a virtual environment. Our model distinctively simulates the oxidative decomposition of lithium peroxide (Li2O2) and differentiates between its formation through solution and surface pathways, addressing the complexities of the charging process and its multiple elementary steps. The developed model further categorizes the oxidative decomposition species into four distinct types, facilitating a comprehensive understanding of their interactions, voltage profile changes, and O2 evolution within the battery's porous cathode. This approach not only enhances the understanding of battery behavior but also aids in refining the design of component materials, thereby propelling forward the development of LOBs with improved energy density and cycle performance.

Ultra‐High Energy Density in Cyanoethyl Biomass Polymers

AbstractDielectric polymers are essential to capacitive capacitors widely used in modern electronic and electrical systems. Most useful dielectric polymers are derived from petroleum while environmentally sustainable dielectric biomass remains mostly unexplored although they are abundant, renewable, and cost‐effective. Here an ultrahigh energy density in cyanoethyl cellulose (CEC) and cyanoethyl pullulan (CEP) obtained by replacing the hydroxyl groups of cellulose and pullulan with cyanoethyl is reported. Large dielectric constants of 16.7 and 20.0 in CEC and CEP due to the strong polarity of cyanoethyl which are comparable to high‐dielectric ferroelectric polymers are shown. CEC and CEP show nearly no degradation of the dielectric constant with increasing electric fields, inhabiting the early polarization saturation and thus leading to improved energy density, which is different from relaxor ferroelectric polymers. Consequently, solution‐processable CEP films exhibit an ultrahigh discharged energy density of 28.2 J cm−3 with an efficiency of 72% at 600 MV m−1, outperforming other all‐organic dielectric biomass materials. The work paves the way for the development of high‐performance dielectric biomass for energy storage applications.

Functionalized Binders Boost High‐Capacity Anode Materials

AbstractThe burgeoning field of energy storage battery innovation has sparked a relentless pursuit of high‐capacity anode materials to meet the escalating demand for improved energy density. Typically, these materials for batteries experience significant volume changes during cycles, which severely test the structural integrity and lifespan of electrode configurations. High‐performance binders have emerged as a critical component in addressing this challenge. Although they represent a small proportion of the battery's composition, binders play a pivotal role in enhancing electrochemical efficiency, safety, and cost‐effectiveness of batteries. The advancement of high‐capacity anode materials has rendered traditional binders inadequate, prompting the development of functional binders that are increasingly being refined to meet these requirements. This article began by outlining the role and requirements of binders within electrodes, examining cutting‐edge characterization methodologies, and discussing the “structure‐function” paradigm that underpins binder selection. It then showcased the research advancements in identifying suitable binders for high‐capacity anode materials, including silicon (Si), phosphorus (P), tin (Sn), antimony (Sb), and germanium (Ge). In summary, the article contemplated the future direction of binder development and application in high‐capacity electrode materials. The aim is to facilitate the progression of high‐performance, high‐capacity anodes, thereby accelerating the development of high‐energy‐density lithium‐ion and sodium‐ion batteries.

Boehmite-PVDF-CTFE/F-PI composite separator irradiated by electron beam for high-rate lithium-ion batteries

As an important part of the fields such as renewable energy and electric vehicles, electrochemical energy storage technology faces significant challenges in improving energy density, extending battery life and improving safety. We successfully prepared a composite battery separator of polyvinylidene fluoride-chlorotrifluorinylene (PVDF-CTFE) and fluorinated polyimide (F-PI) -based materials, mixed it with different contents of boehmite nanoparticles, and then modified it by different doses of electron beam irradiation to improve the performance, especially to overcome the problem of maintaining capacity decline in high-speed charging environment. The results showed that the prepared battery separators exhibited outstanding thermal stability, electrochemical properties and ionic conductivity with 12 % boehmite nanoparticles. After 1000 high-speed charge and discharge cycles in current density of 10C, the battery based on the modified separator still maintained a capacity retention rate of 84.4 %, with the initial discharge specific capacity of 111.9 mAhg−1. This means that irradiated separators not only maintain a high energy density in a high-speed charging environment, but also overcome the problem of maintaining capacity decline. Electron beam irradiation further improved the comprehensive performance of the separator. After 1000 and 1500 cycles at the current density of 10C and 15C, the specific discharge capacity of the battery can still retain more than 90 % and 80 % of the initial specific discharge capacity, which provides a longer life in practical applications.

Consummating ion desolvation in hard carbon anodes for reversible sodium storage

Hard carbons are emerging as the most viable anodes to support the commercialization of sodium-ion (Na-ion) batteries due to their competitive performance. However, the hard carbon anode suffers from low initial Coulombic efficiency (ICE), and the ambiguous Na-ion (Na+) storage mechanism and interfacial chemistry fail to give a reasonable interpretation. Here, we have identified the time-dependent ion pre-desolvation on the nanopore of hard carbons, which significantly affects the Na+ storage efficiency by altering the solvation structure of electrolytes. Consummating the pre-desolvation by extending the aging time, generates a highly aggregated electrolyte configuration inside the nanopore, resulting in negligible reductive decomposition of electrolytes. When applying the above insights, the hard carbon anodes achieve a high average ICE of 98.21% in the absence of any Na supplementation techniques. Therefore, the negative-to-positive capacity ratio can be reduced to 1.02 for full cells, which enables an improved energy density. The insight into hard carbons and related interphases may be extended to other battery systems and support the continued development of battery technology.

Advancing supercapacitor performance: a comprehensive review of electrochemical conversion of coconut shells into activated carbon nanofibers

This assessment provides a comprehensive evaluation of the limitations associated with the application of supercapacitors, along with the imperative to enhance their functionality. Following this, the advantages of Electrochemical Double Layer Capacitors (EDLC) are discussed in comparison to other types utilized in supercapacitor contexts. The transformation of coconut shells into carbon nanofibers is extensively investigated through various methodologies, highlighting both their benefits and limitations. It becomes evident that the current utilization of coconut shells has not yet achieved optimal sustainability or viability for energy storage purposes. Nevertheless, coconut shells offer a widely available and sustainable resource that can be converted into Activated Carbon nanofibers for energy storage applications. Diverse techniques have been employed to produce these ACB nanofibers, each targeting specific objectives including improved energy density, adaptable diameter, reduced energy consumption, and faster charging times. Despite these accomplishments, it is evident that numerous significant properties of carbon nanofibers derived from coconut shells remain unexplored, leading to substantial knowledge gaps that must be addressed for each technique. Therefore, further research is warranted to advance the comprehension of key parameters associated with various methods, ultimately facilitating the development of highly desirable carbon nanofibers sourced from coconut shells and catering to the requirements of sustainable energy storage applications.

Multifunctional Additive Enables a "5H" PEO Solid Electrolyte for High-Performance Lithium Metal Batteries.

The solid-state battery with a lithium metal anode is a promising candidate for next-generation batteries with improved energy density and safety. However, the current polymer electrolytes still cannot fulfill the demands of solid-state batteries. In this work, we propose a "5H" poly(ethylene oxide) (PEO) electrolyte via introducing a multifunctional additive of tris(pentafluorophenyl)borane (TPFPB) for high-performance lithium metal batteries. The addition of TPFPB improves the ionic conductivity from 6.08 × 10-5 to 1.54 × 10-4 S cm-1 via reducing the crystallinity of the PEO electrolyte and enhances the lithium-ion transference number from 0.19 to 0.53 via anion trapping due to its Lewis acid nature. Furthermore, the fluorine and boron segments from TPFPB can optimize the composition of the solid-electrolyte interphase and cathode-electrolyte interphase, providing a high electrochemical stability window over 4.6 V of the PEO electrolyte along with significantly improved interface stability. At last, TPFPB can ensure improved safety through a self-extinguishing effect. As a result, the "5H" electrolyte enables the Li/Li symmetric cells to achieve a stable cycle over 2200 h at the current density of 0.2 mA cm-2 with a capacity of 0.2 mA h cm-2; the LiFePO4/Li full cells with a high LFP loading of 8 mg cm-2 exhibits decay-free capacity of 140 mA h g-1 (99% capacity retention) after 100 cycles; and the NCM811/Li cells exhibit a high capacity of 160 mA h g-1 after 50 cycles at 0.5 C. This work presents an innovative approach to utilizing a "5H" electrolyte for high-performance solid-state lithium batteries.

Silicon Solid State Battery: The Solid‐State Compatibility, Particle Size, and Carbon Compositing for High Energy Density

AbstractSolid‐state battery research has gained significant attention due to their inherent safety and high energy density. Silicon anodes have been promoted for their advantageous characteristics, including high volumetric capacity, low lithiation potential, high theoretical and specific gravimetric capacity, and the absence of lethal dendritic growth. Addressing concerns such as low conductivity, pulverization, fracture, dense solid electrolyte interface layer, and low coulombic efficiency has substantially improved the use of silicon electrodes in solid‐state batteries. Researchers have explored carbon additions, solid electrolyte suitability for Si anodes, pressure optimization, and particle size effects (nano/micro) to enhance energy density. Recent studies have investigated the conductivity mechanism, stack pressure, and anode‐solid electrolyte compatibility to improve energy density. Micro‐ and nano‐sized silicon have attracted attention in carbon‐based composites due to their exceptional conductivity, uniform distribution, efficient electron migration, and diffusion channels. The development of solid‐state batteries with high energy density, safety, and extended lifespan has been a major focus. This review sheds light on significant insights and strategic approaches for researchers working on solid‐state silicon‐based systems to overcome existing challenges.