Dry electrode architecture design to push energy density limits at the cell level

Hybrid/Asymmetric EESs based on the mechanism of “faradaic” or “extrinsic/intrinsic pseudocapacitive” can certainly overcome the EDLCs’ energy density limitation [3,4,5]. In light of this, K&W/TUAT group developed an original material processing technology called “ultracentrifugation (UC)” that allows to prepare (mass produce) a variety of ultrafast (Li-insertion) nanomaterials capable of 3-7 fold enhancement in energy density. It’ s been demonstrated that UC process typically under 75,000g (with subsequent heat or hydrothermal treatment) gives spinel Li4Ti5O12 nanocrystal as nanosheet/nanobook that are grown on the surface of carbon matrices like MWCNT, SGCNT [1,2,4]. The “nanohybrid capacitor(NHC)” configured as uc-LTO/LiBF4[PC] /AC tripled the energy density of conventional EDLCs [1,3,4]. Nippon Chemi-con Corp. is now eagerly developing commercial NHC device in order to place them in the market. Other uc-derived nanomaterials will be introduced together with their effective utilization in the 2nd gen. “NanoHybrid Capacitor” (JST NexTEP project, 2013-2018) and 3rd gen. “SuperRedox Capacitor” (JST A-step project, 2016-2021). As for LTO alternative anodes, b-axis (ultrashort) controlled 5-nm uc-TiO2(B) [6] and electrochemically activated uc-Li3VO4 [7], both showed ultrafast (300C) charge-storage performances. As cathode, nano-structured 2-cores/1-shell of [uc-LiFePO4(LFP)/amorphous/defective LFP/graphitic carbon] shows ultrafast and symmetric discharge and charge performance (300-480C) [8]. Finally, the author will present a perspective of the future supercapacitors’ market in the world.

The rapid electrification of transportation and grid systems has placed lithium‐ion batteries (LIBs) at the forefront of energy storage innovation. Lithium‐ion phosphate (LiFePO 4 , LFP), with its superior safety, long cycle life, and cost advantages, has become a cornerstone cathode material. However, the limited energy density (ED), attributed to its relatively low nominal voltage (~3.2 V) and moderate specific capacity (~170 mAh g −1 ), hinders its competitiveness in high‐energy applications. Furthermore, electrochemical characteristics related to poor charge transfer kinetics and material circularity also limit its overall value. This review highlights recent advances in material design, electrode engineering, and system‐level optimization aimed at overcoming these challenges. Key strategies include precision doping, multifunctional coating, and nanostructuring to enhance conductivity and rate performance, development of high‐tap‐density powders and ultra‐thick electrodes for improved ED, and hierarchical electrode architectures and advanced conductive networks for efficient ion/electron transport. Additional focus is given to low‐temperature performance, scalable and sustainable synthesis routes, and recycling pathways that ensure long‐term environmental viability. Emerging directions such as dry electrode processing, solid‐state integration, and artificial intelligence/machine learning‐driven optimization are also discussed as transformative tools for accelerating LFP innovation. By integrating these multidisciplinary strategies, LFP can evolve from a safe and stable cathode into a high‐performance, sustainable solution for electric vehicles, grid storage, and next‐generation energy systems.

The electric vehicle (EV) market has grown very rapidly to meet the demand for net-zero carbon emissions in the transportation sector. The rapid growth of EVs is primarily attributed to the technological advances in lithium-ion batteries, making them the most promising energy storage devices due to their outstanding electrochemical performance. In recent years, the lithium-ion battery industry has made attempts to achieve price and driving range parity between electric vehicles and internal combustion vehicles. Significant efforts have been devoted to developing electrode processes as well as active materials in order to achieve low-cost and high-energy-density lithium-ion batteries. Particularly, the adoption of thick film electrodes is an effective way to increase both energy density and cost efficiency by reducing the amount of inactive materials, such as current collectors, separators, and cell components. In this presentation, we introduce the dry electrode technology to achieve ultra-thick film electrode. Dry electrode technology has the potential to provide a breakthrough in achieving higher loading levels and electrode densities. Moreover, the distribution of binders in dry electrodes does not impede lithium-ion transport, unlike wet electrode binders such as PVdF. Due to these synergistic effects, dry electrode-based electrodes have achieved ultra-high loading levels with lower resistance compared to wet-based electrodes. Additionally, dry electrode technology on the anode side has limitations due to the low low lowest unoccupied molecular orbital level (LUMO) level of the PTFE binder, resulting in side reaction during lithiation. This phenomenon significantly worsens battery performance, affecting factors such as initial Coulombic efficiency and cycle life. We suggest an effective strategy to mitigate the side reactions of dry-electrode technology.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation Jeffrey Peter Segota; The design, construction, and evaluation of a two‐hydrophone intensity probe to determine the feasibility and limitations of underwater intensity, energy density, and impedance measurements. J. Acoust. Soc. Am. 1 February 1992; 91 (2): 1181. https://doi.org/10.1121/1.402596 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAcoustical Society of AmericaThe Journal of the Acoustical Society of America Search Advanced Search |Citation Search

Context. Dark energy was first detected from large distances on gigaparsec scales. If it is vacuum energy (or Einstein’s Λ), it should also exist in very local space. Here we discuss its measurement on megaparsec scales of the Local Group. Aims. We combine the modified Kahn-Woltjer method for the Milky Way-M 31 binary and the HST observations of the expansion flow around the Local Group in order to study in a self-consistent way and simultaneously the local density of dark energy and the dark matter mass contained within the Local Group. Methods. A theoretical model is used that accounts for the dynamical effects of dark energy on a scale of ∼ 1M pc. Results. The local dark energy density is put into the range 0.8−3.7ρv (ρv is the globally measured density), and the Local Group mass lies within 3.1−5.8 × 10 12 M� . The lower limit of the local dark energy density, about 4/5× the global value, is determined by the natural binding condition for the group binary and the maximal zero-gravity radius. The near coincidence of two values measured

Extremely low loading of carbon quantum dots for high energy density in polyetherimide nanocomposites

Supercapacitors, also known as electric double-layer capacitors (EDLCs), are able to store energy rapidly and reversibly through the formation of a double-layer of electronic and ionic charge, closely spaced, at the electrode/electrolyte interface.[1-2] Due to the combination of various advantageous properties, such as efficient operation at high power density, long cycle life and improved safety compared to Li-ion batteries,[3,4] supercapacitors are being increasingly used as alternative power sources to rechargeable batteries. However, the implementation of supercapacitors in practical application is still restricted by the limited energy density, typically 5-8 Wh/L,[5] which is much lower than that of lead-acid batteries which can achieve ~50-90 Wh/L.[6] Considering a symmetric configuration, the volumetric energy density (E V) of a supercapacitor is directly proportional to the volumetric capacitance (C V) of a single electrode and the square of operating voltage (U) following the equation, Ev = 1/8(C V·U 2). Therefore, in such a system, there are two ways to improve energy density: boosting capacitance and extending cell voltage window. The operating voltage of EDLCs is typically limited by the stability of electrolyte and thus room temperature ionic liquids (ILs) with large electrochemical stability windows (> 3-4 V) have become promising next-generation electrolytes. However, the relatively high viscosity of ILs results in lower ionic conductivity compared to traditional aqueous or organic electrolytes and also leads to challenges with pore wetting. On the electrode side, materials with a high intrinsic capacitance (C DL) per area and a large ion-accessible surface area (SSA) are needed to achieve high gravimetric capacitance (C G) since C G = C DL·SSA. The potentially high electrical conductivity, surface area, and chemical stability of graphene-based materials make them promising candidate electrode.[7,8] Theoretically, single layer graphene can exhibit SSA as high as 2675 m2/g. While pristine graphene is limited by its low quantum capacitance leading to C DL ~3-4 mF/cm2, more defective and functionalized graphene produced by the chemical or thermal reduction of graphene oxide (GO) have been shown to exhibit C DL > 17 mF/cm2 in non-aqueous electrolyte leading to theoretical gravimetric capacitance, C G,theoretical > 450 F/g if all of graphene’s surface area could be made ion-accessible. To prevent aggregation and restacking of graphene-based materials into lower SSA structures, we demonstrated an IL microemulsion system (Figure 1) that spontaneously assembles on the surface of GO, placing nanometer-sized droplets of a high-performance, hydrophobic IL 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMImTFSI) directly onto the available surface of well-dispersed single GO layers. We first demonstrate that a common non-ionic surfactant, Tween 20 is capable of forming a stable microemulsion with EMImTFSI with a particle size on the order of several nanometers. These surfactant stabilized nano-droplets (microemulsion particles) spontaneously adsorb to GO sheets yielding a dispersion which can be cast directly onto current collectors leading to a dense nanocomposite of GO/IL/Tween 20. Tween 20 is then removed by evaporation, while the GO is thermally reduced leading to what we refer to as layered IL-mediated reduced GO (IM-rGO) electrodes. The approach is found to yield high ion-accessible SSA as evidenced by one of the highest C G ever reported (302 F/g) when the composite contains 80 wt% IL. These results indicate that the microemulsion particles formed were better able to deploy IL as a spacer to prevent rGO sheets from restacking. Reducing the IL content to 60 wt%, resulted in dense electrodes that exhibited a C V = 218 F/cm3, which is the highest value reported to date among all graphene-based supercapacitors leading to exceptional volumetric energy density. Reference (1) Conway, B. E. Electrochemical Supercapacitors: Scientific Fundamentals and Technological Applications. Springer Science & Business Media 2013. (2) Miller, J. R.; Simon, P. Electrochemical capacitors for energy management. Science 2008, 321, 651. (3) Du Pasquier, A.; Plitz, I.; Menocal, S.; Amatucci, G. A comparative study of Li-ion battery, supercapacitor and nonaqueous asymmetric hybrid devices for automotive applications. J. Power Sources 2003, 115, 171. (4) Khaligh, A.; Li, Z. Battery, ultracapacitor, fuel cell, and hybrid energy storage systems for electric, hybrid electric, fuel cell, and plug-in hybrid electric vehicles: State of the art. IEEE transactions on Vehicular Technology 2010, 59, 2806. (5) Burke, A. R&D considerations for the performance and application of electrochemical capacitors. Electrochim. Acta 2007, 53, 1083. (6) Linden, D. Handbook of batteries. Fuel and Energy s 1995, 265. (7) Pope, M. A.; Aksay, I. A. Four-Fold Increase in the Intrinsic Capacitance of Graphene through Functionalization and Lattice Disorder. J. Phys. Chem. C 2015, 119, 20369. (8) Stoller, M. D.; Park, S.; Ruoff, R. S. Graphene-based ultracapacitors. Nano Lett. 2008, 8, 3498. Figure 1

Assuming that the energy gain by cosmic-ray (CR) particles is a stochastic process with stationary increments, we derive expressions for the shape of their energy spectrum up to energies E ∼ 1018 eV. In the ultrarelativistic case under study, the energy is proportional to the momentum, whose time derivative is the force. According to the Fermi mechanism, a particle accelerates when it passes through a system of shock waves produced by supernova explosions. Since these random forces act on time scales much shorter than the particle lifetime, we assume them to be delta-correlated in time. In this case, due to the linear energy-momentum relationship, the mean square of the energy (increments) is proportional to the differential scale τ(E) ∼ Eτ(≥E), where τ (≥E) is the cumulative time it takes for a particle to gain an energy ≥E. The probability of finding a particle with energy ≥E somewhere in the system is inversely proportional to the time it takes to gain the energy E. To estimate an upper limit for the space number density of CR particles, we use estimates of the CR volume energy density, a quantity known for our Galaxy. It is taken to be constant in the range 10 GeV ≤ E ≤ 3 × 106 GeV, where the index of the energy spectrum was found to be −8/3 ≈ −2.67 against its empirical value of −2.7. In the range 3 × 106 GeV ≤ E < 109 GeV, the upper limit for the volume energy density is estimated by using the results from the previous range to be −28/9 ≈ −3.11 against its empirical value of −3.1. The numerical coefficients in the suggested shapes of the spectrum can be determined by comparison with observational data. Thus, the CR energy spectrumis the result of the random walks of ultrarelativistic particles in energy/momentum space caused by the Fermi mechanism.

Aqueous Fe-ion hybrid capacitors, with high safety, low cost, and environmental friendliness, have attracted considerable attention as an emerging energy storage device. However, Fe-ion-based energy storage systems still face challenges, such as narrow voltage windows, limited energy density, and harsh fabrication conditions. To address these issues, this work fabricates an aqueous Fe-ion hybrid capacitor using low-cost activated carbon as the anode, manganese dioxide (MnO2) as the cathode, with an FeSO4 + NH4Cl aqueous electrolyte, successfully expanding the voltage window to 0-1.2 V. The atomic molecular dynamics simulations confirm the potential of MnO2 as a cathode material, and the spiny nanostructured MnO2 shows a large specific surface area and a stable tunnel structure, which facilitates the intercalation/deintercalation of Fe2+ ions. Consequently, the assembled device achieved a specific capacitance of 835 mF cm-2 at 1 mA cm-2 and a surface energy density of 167 μWh cm-2 with a capacitance retention of 97.2% after 3000 cycles. Furthermore, to meet wearable electronics requirements, a flexible device was assembled by integrating a carboxymethyl cellulose-poly(vinyl alcohol) hydrogel soft-packaging material. The results show that the flexible device exhibits excellent bending resistance. The further assembled flexible Fe-ion supercapacitors demonstrate a high energy storage potential. Under a current density test of 1 mA cm-2, the calculated specific capacitance is 682.4 mF cm-2, and the areal energy density is 136.48 μWh cm-2. The further assembled flexible Fe-ion supercapacitors demonstrate high energy storage potential. Under a current density test of 1 mA cm-2, the calculated specific capacitance is 682.4 mF cm-2, and the areal energy density is 136.48 μWh cm-2. Similarly, in the cycling performance test, the device retains 92.6% of its capacity after 3000 cycles. This study provides technical references for the development and practical application of flexible Fe-ion-based energy storage devices.

Na superionic conductor structured Na 3 V 2 (PO 4 ) 3 cathodes have attracted great interest due to their long cycling lifespan and high thermal stability rendered by the robust 3D framework. However, their practical application is still hindered by the high cost of raw materials and limited energy density. Herein, a doping strategy with low‐cost Fe 2+ is developed to activate V 4+ /V 5+ redox, in an attempt to increase the energy density of phosphate cathodes. It is also revealed that reversible activation of V 4+ /V 5+ redox is related to the Na positions (Na1, 6b; Na2, 18e). Only the V‐based compounds with enough Na2 content can activate the V 4+ /V 5+ reversibly. More importantly, without presodiation treatment and addition of any sodiation agent, Na 3.4 V 1.6 Fe 0.4 (PO 4 ) 3 is delicately designed as both cathode and the Na self‐compensation agent in full cells, allowing a promising energy density of ≈260 Wh kg −1 . This work sheds light on enhancing the energy density, and designing Na self‐compensation for practical Na‐ions batteries.

Lithium-ion intercalation batteries offer high energy densities but are limited in power density, while capacitors provide high power capabilities with limited energy densities. Pseudo-capacitors bridge this gap by offering moderate power and energy densities through their hybrid energy storage mechanism: combining both bulk intercalation with surface storage. Despite their potential, the precise mechanisms of energy storage and charge partitioning in pseudo-capacitors remain unclear. This study investigates the charge storage mechanisms in MnO2 pseudo-capacitors using galvanostatic intermittent titration and cyclic voltammetry, alongside electrochemical simulations. Our findings reveal that both charge-transfer mechanisms can be modeled using independent Butler-Volmer kinetic expressions. The exchange-current density is higher for the capacitive process, while the intercalation process exhibits more favorable thermodynamics. This modeling framework provides an accurate description of MnO2 pseudo-capacitor performance across a wide range of conditions.

MoS2@Ti3C2Tx Heterostructure: A new negative electrode material for Li-Ion hybrid supercapacitors

The dry‐processing method using polytetrafluoroethylene (PTFE) binders is considered a promising approach in fabricating high‐loading electrodes for high‐energy‐density lithium‐ion batteries (LIBs). However, the fluorinated surface of PTFE resists wetting by conventional electrolytes, hindering ion transport and inducing nonuniform electrochemical reactions across the entire electrode. Here, an innovative strategy is presented to convert the hydrophobic surface of fibrillated PTFE, even those deeply embedded in thick electrodes, into an electrolyte‐compatible interface bearing hydrophilic ─COOH and ─C═O groups, via direct application of electron beam (EB) irradiation to postfabricated dry electrodes. This EB irradiation strategy applied to the fabricated dry electrodes is rapid, solvent‐free, and highly penetrable. Thus, it is highly compatible with the dry electrode manufacturing process, directly addressing sustainability and cost challenges. Benefiting from the improved wettability, the EB‐irradiated dry electrodes exhibited markedly enhanced and uniform Li‐ion migration throughout the thick electrode, thereby delivering superior electrochemical performance even for hyper‐loaded electrodes (100 mg cm −2 , 22.6 mAh cm −2 ), exhibiting stable cycling performance with 89.51% capacity retention, achieving cell‐level energy density of 449.4 Wh kg −1 . This strategy offers a crucial pathway toward high‐energy‐density batteries as it overcomes the inherent challenges of dry electrodes without compromising the environment‐friendly and sustainable nature of dry processing.

Dense integration of chlorocatechols crosslinked polyphenylene sulfide solid-state separator for Li Metal-Free Batteries

Lithium-ion (Li-ion) batteries have been ubiquitously utilized in the modernized world in portable electronic, electrical vehicles, and grid-scale energy storage. However, demand satisfaction for traditional Li-ion batteries is becoming difficult due to their limited capacity and energy density. Moreover, there are challenges related to the availability of non-renewable critical materials for Li-ion batteries such as Co, Ni, and graphite, and environmental pollution during battery creation and recycling. Further neglect of these problems will lead to dramatic consequences at which batteries will become a part of the environmental problems but not a solution to these problems as they should be. Therefore, it is highly imperative to explore novel battery systems that show high energy density, low production cost and low environmental pollution during production, use and recycling. One of the most promising candidates is the lithium-sulphur (LiS) battery, which offers various advantages such as high energy density, high theoretical specific capacity, and affordable cost, because of the high availability of elemental sulphur and carbon used in this type of battery. The theoretical gravimetric energy density of LiS batteries is 2567 Wh/kg which is 4.5 times higher than the energy density of conventional Li-ion batteries. Despite the richness of sulphur in the Earth’s crust and its prominent merits in energy density and cost, several problems have restricted the development of LiS batteries for commercialization. The most notorious and intractable problem is the high solubility of the sulphur species (Li2Sx, 3≤x≤8) in common Li-ion battery electrolytes that leads to the so-called lithium polysulfide (LiPS) shuttle effect and loss of battery capacity, Li metal anode corrosion, and low coulombic efficiency during interaction of the LiPS with Li metal anode. The most prospective solution to address the above drawbacks is sulphur incorporation with a porous, high-conductive carbon host that will tolerate sulphur volume expansion, improve the conductivity of the electrode, prevent the shuttle effect, and allow reversible lithium-ion migration during charging and discharging.However, to achieve the excellent operation performances of the porous carbon host its properties should be carefully tuned and the LiPS absorption ability of the carbon host should be improved for example by metal oxide doping. Many different strategies for the creation of the required material were proposed in recent years. Unfortunately, many proposed synthetic methods require a hard template to provide fine control of the pore distribution in the materials, which is a significant drawback as in this case harsh conditions are required for template removal. In addition, the formation of doped carbons with good electrical conductivity often demands high temperatures, simultaneously causing the undesirable reduction of metal cations to their metallic state followed by the aggregation to form nanoparticles, together with the collapse of the carbon matrices. Therefore, it still urgently needs to find a new strategy to produce a porous carbon host for the sulfur with fine porosity and good lithium polysulfide absorption ability, which purpose to accelerate the successful commercialization of this battery technology on the market.In our current work, we are investigating the possibility to synthesize finely dispersed metal oxide catalysts on hollow N-doped porous carbon capsules produced from zeolitic imidazolate framework (ZIF-8). The coating of the ZIF-8 with metal–tannic acid coordination polymer allows to uniformly dispersed metal oxide nanoparticles, such as Fe2O3, MnO, CoO etc., on hollow carbon capsules after the pyrolysis process. Moreover, the carbon produced by ZIF-8 pyrolysis is expected to be both doped with nitrogen and highly porous, which should have a positive effect on the maximum sulfur loading possibility in the carbon host and lithium polysulfide absorption ability. In addition, the used approach for the synthesis of the hollow N-doped porous carbon allows the distribution of multicomponent metal oxide nanoparticles on the surface of the hollow carbon capsules, which may have a synergetic effect and improve the lithium polysulfide absorption ability of the produced materials. The structural, compositional, and morphological properties of the created material are investigated using SEM, EDS, XPS, Raman spectroscopy, FTIR and TGA techniques. The effect of the different metal oxide nanoparticles and their combinations on the lithium polysulfide absorption ability of the synthesized materials are investigated by analysis of the electrochemical performances of the Li-S batteries, where synthesized material was used as the sulfur host during the creation of the Li-S battery cathode.