High Energy Density Requirements Research Articles

Effect of Mechanical Pressure on Rate Capability, Lifetime, and Expansion of Multilayer Pouch Cells with Silicon-Dominant Anodes

Silicon-dominant (Si) anodes with microscale silicon particles meet the requirements of high energy density and low costs due to its ten times higher theoretical electrochemical capacity of 3579 mAh/gSi (Li15Si4) compared to graphite,1 lifetime extension due to partial lithiation,1-2 and high abundance and economic availability due to existing industrial infrastructure.1-2 The major drawback of silicon is the large volume expansion of nearly 300% upon full lithiation. This hinders the broad application of silicon as an active anode material due to continuous SEI (re-) formation and electrochemical milling of particles. Additionally, the volume expansion impacts the overall electrode stability, leading to thickness changes, the disruption of the electronic pathways, and the decoupling of particles. Although the approach of partial lithiation of microscale1 Si eases these effects by lowering the overall volume expansion, these problems still exist.2,3 In this work, the effect of different mechanical cell pressures on lithium-ion batteries with partially lithiated silicon-dominant anodes is investigated with 5.4 Ah multilayer pouch cells as a follow-up study of our previous work with laboratory T-Cells.3 Methodologically, a novel cell holder and pressure device were developed and validated to apply different mechanical cell pressures. Our investigation covers a pressure range from uncompressed as zero (ZP, 0.00 MPa) to high (HP, 0.50 MPa) external cell pressure to determine the optimal pressure for high rate capacity, cyclic lifetime, energy density, and low thickness gain. The cells were tested by checkup cycles at C/10, rate tests up to 3C, and cycled at C/2 until 70% state of health (SoH). Electrochemical impedance spectroscopy was conducted at different SoHs to quantify the effect of mechanical pressures on the impedance response.4 The post-mortem analysis after reaching 70% SoH and operando thickness measurements in a compression test5 bench give insights into the electrode and cell thickness gain.In the electrochemical results, the discharge capacity Q DCH was immediately reduced by decreasing the mechanical pressure from 0.20 MPa to 0.00 MPa or 0.05 MPa, both for the cells in the cell holder (see inset in Figure 1a) and the compression test bench (not shown). This pressure change was also quantified by an increased charge-averaged full cell potential during charging and a decreased charge-averaged full cell potential during discharging. The impedance was reduced for higher mechanical pressure, especially the cathode contact resistance initially and over aging, resulting in lower temperature increases during the rate tests. The capacity retention Q DCH and the total charge throughput were increased to 360 cycles until 70% SoH for higher mechanical pressures at NP (normal pressure, 0.20 MPa) and HP (see Figure 1) compared to 181 cycles for ZP. Overall, applying higher mechanical pressures reduced the thickness increase, as shown by operando thickness measurements and the post-mortem analysis. A dependency of the reversible thickness on the charged capacity was found. Moreover, the porosity decreased with increasing pressure, which was measured with mercury intrusion porosimetry (MIP) and pycnometry. The anode mass increase correlates to the total charge throughput, which is pressure-dependent and the highest for NP.Our findings demonstrate that applying the optimal mechanical cell pressure is significant when using microscale silicon-dominant anodes. We recommend a mechanical pressure of 0.50 MPa for increased rate capacity, minimizing impedance, heat evolution, and thickness gain, and 0.20 MPa for increased energy density. Acknowledgments: S.F. gratefully acknowledges the financial support from the BMBF (Federal Ministry of Education and Research, Germany) under the auspices of the ExZellTUM III project (grant number 03XP0255). The authors want to thank the research battery production team of iwb at TUM for the multi-layer pouch cell production. We also thank Wacker Chemie for kindly providing the microscale silicon material.

Advancements and Challenges in the Synthesis of Oxymethylene Ethers (OMEs) as Sustainable Transportation Fuels.

The urgent need for sustainable alternatives to fossil fuels in the transportation sector is driving research into novel energy carriers that can meet the high energy density requirements of heavy-duty vehicles without exacerbating the climate change. This concept article examines the synthesis, mechanisms, and challenges associated with oxymethylene ethers (OMEs), a promising class of synthetic fuels potentially derived from carbon dioxide and hydrogen. We highlight the importance of OMEs in the transition towards non-fossil energy sources due to their compatibility with the existing Diesel infrastructure and their cleaner combustion profile. The synthesis mechanisms, including the Schulz-Flory distribution and its implications for OME chain length specificity, and the role of various catalysts and starting materials are discussed in depth. Despite advancements in the field, significant challenges remain, such as overcoming the Schulz-Flory distribution, efficiently managing water as an undesirable byproduct, and improving the overall energy efficiency of the OME synthesis. Addressing these challenges is crucial for OMEs to become a viable alternative fuel, contributing to the reduction of greenhouse gas emissions and the transition to a sustainable energy future in the transportation sector.

Recent advances in separator design for lithium metal batteries without dendrite formation: Implications for electric vehicles

Electric vehicle (EV) technology addresses the challenge of reducing carbon and greenhouse gas emissions. The power battery, which serves as the energy source for EVs, directly impacts their driving range, maximum speed, and service life. Considering the high energy density requirements for future EVs, lithium metal anodes possess several advantages such as high theoretical capacity, high energy and power density, and low electrochemical reduction potential which enable them to be a promising material for next-generation batteries. However, lithium metal anodes suffer from short cycle life and safety concerns due to the formation of dendritic and moss-like metal deposits that impede battery performance and reliability. This review will feature the recent advancement of functional separators to tackle these challenges. Firstly, this review presents a comprehensive review of the growth mechanism of lithium dendrites and delineates the underlying processes leading to battery failure. This aims to deepen understanding, which serves as a fundamental basis for classifying separators. Then, according to the growth of lithium dendrites and the failure process of lithium metal batteries, namely lithium-ion nucleation, growth of lithium dendrites, penetration of lithium dendrites into the separator, thermal runaway and even failure of the battery, four types of functional separators for different stages are proposed. The functions of these types of separators are to prevent the nucleation of lithium ions and regulate the uniform deposition of lithium ions, detect and eliminate dendrites, increase the mechanical strength of the separator and enhance the thermal stability and flame-retardancy of the separators, respectively. Finally, the recent advances of the above strategies are reviewed and discussed, existing critical problems are identified, and the future perspective of functional separators for the safety of lithium metal batteries is also discussed.

Enhanced high-temperature energy storage properties in BNT-based ceramics with well-controlled low dielectric loss

High-temperature resistance is one of the hot topics in the development of high-power density dielectric materials. It is still a great challenge for dielectric materials to meet the requirements of high energy density and low energy loss at high temperature. Based on the philosophy of increasing the Curie temperature and decreasing the dielectric loss at high temperature, a ceramic system of (1-x)Bi0.5Na0.5TiO3-xBi(Mg0.3Zr0.6)O3 ((1-x)BNT-xBMZ) is designed to improve the high-temperature energy storage properties. The Curie temperature was significantly increased from 320 °C to nearly 400 °C, and the dielectric loss was controlled below 5% up to 400 °C in the 0.92BNT-0.08BMZ ceramic. Due to the high Curie temperature and low dielectric loss, the maximum polarization and discharge energy density at 200 °C under 200 kV/cm of the 0.92BNT-0.08BMZ ceramic sample are as high as 48.79 μC/cm2 and 3.73 J/cm3, respectively. With the BMZ content increases, the changing rate of Pmax in the temperature range of 30∼200 °C decreases from 18.76% for the x = 0.06 ceramic to 10.27% for the x = 0.10 ceramic under 120 kV/cm, and the remanent polarization decreases from 5.23 μC/cm2 to 2.55 μC/cm2 at 200 °C, correspondingly. All these characteristics show that (1-x)BNT-xBMZ ceramics have broad application prospects in the field of high-temperature energy storage systems.

Multi-electron reaction and fast Al ion diffusion of δ-MnO2 cathode materials in rechargeable aluminum batteries via first-principle calculations

Rechargeable aluminum batteries with multi-electron reaction have a high theoretical capacity for next generation of energy storage devices. However, the diffusion mechanism and intrinsic property of Al insertion into MnO2 are not clear. Hence, based on the first-principles calculations, key influencing factors of slow Al-ions diffusion are narrow pathways, unstable Al-O bonds and Mn3+ type polaron have been identified by investigating four types of δ-MnO2 (O3, O’3, P2 and T1). Although Al insert into δ-MnO2 leads to a decrease in the spacing of the Mn-Mn layer, P2 type MnO2 keeps the long (spacious pathways) and stable (2.007–2.030 Å) Al-O bonds resulting in the lower energy barrier of Al diffusion of 0.56 eV. By eliminated the influence of Mn3+ (low concentration of Al insertion), the energy barrier of Al migration achieves 0.19 eV in P2 type, confirming the obviously effect of Mn3+ polaron. On the contrary, although the T1 type MnO2 has the sluggish of Al-ions diffusion, the larger interlayer spacing of Mn-Mn layer, causing by H2O could assist Al-ions diffusion. Furthermore, it is worth to notice that the multilayer δ-MnO2 achieves multi-electron reaction of 3|e|. Considering the requirement of high energy density, the average voltage of P2 (1.76 V) is not an obstacle for application as cathode in RABs. These discover suggest that layered MnO2 should keep more P2-type structure in the synthesis of materials and increase the interlayer spacing of Mn-Mn layer for providing technical support of RABs in large-scale energy storage.

Preventing the Distortion of CoO6 Octahedra of LiCoO2 at High-Voltage Operation of Lithium-Ion Battery: An Organic Surface Reinforcement.

Lithium cobalt oxide (LiCoO2, LCO) has been widely used in electronic markets due to its high energy density and wide voltage range applications. Recently, high-voltage (HV, >4.5 V) operation has been required to obey the requirements of high energy density and cycle life in several applications such as electric vehicles and energy storage. However, the HV operation causes structure instability due to the over de-lithiation of LCO, as well as decomposing common carbonate solvents, thereby incurring the decay of battery performance. Moreover, a distortion of the CoO6 octahedra of LCO during de-lithiation induces a rehybridization of the Co 3d and O 2p orbitals. According to above reasons, decreasing the Co-O covalent bond promptly triggers high risks that significantly limit further use of LCO. In this research, an organic surface reinforcement by using bismaleimide-uracil (BU) that electrochemically forms a cathode electrolyte interphase (CEI) on LCO was explored. The results of electrochemical impedance spectroscopy and battery performance, such as the c-rate and cyclability tests, demonstrated that the modified CEI formed from BU significantly prevents the distortion of CoO6 octahedra. X-ray photoelectronic spectroscopy and in situ XAS indicated less LiF formation and higher bond energy of Co-O improved. Finally, the differential scanning calorimetry showed the onset temperature of decomposition of LCO was extended from 245 to 270 °C at 100% state of charge, which is about a 25 °C extension. The exothermic heat of LCO decreased by approximately 30% for high-safety use. This research confirms that the BU is eligible for high voltage (>4.5 V) LCO and presents outstanding electrochemical properties and safety performances.

Lightweight and Flexible 3D ERGO@Cu/PA Mesh Current Collector of Li Metal Battery for Dendrite Suppression

The utilization of 3D Cu current collectors has been approved to be an efficient design to suppress the uncontrolled dendrite growth of Li metal anodes. However, the widely used 3D metallic Cu often has high self-weight and impaired mechanical properties and cannot meet the requirements of high energy density and industrial production. Here, we developed a lightweight, malleable, lithiophilic, and reticular composite Cu-based current collector using a nylon (PA) framework as the 3D substrate, by a synergized approach of combining the conductive Cu/PA with lithiophilic reducing graphene oxide (ERGO) coating. The 3D grid arrangement lowered the regional current density, and the lithiophilic ERGO layer induced Li nucleation, all of which endowed the ERGO@Cu/PA mesh as an anode current collector with attractive performance. The ERGO@Cu/PA composite was applied to display the necessary dendrite-free Li deposition behavior. It delivered an impressive Li plating/stripping behavior and electrochemical performance in half cells and Li/Li symmetric battery tests. The full cell using the ERGO@Cu/PA composite with predeposited Li as the anode and LiFePO4 as the cathode achieved stable cycling and excellent rate performance. Notably, the synergistic combination of light and flexible 3D Cu/PA mesh with lithiophilic ERGO coating proved a valid path to adjust Li anodes in the fields such as flexible wearable devices.

A 10‐μm Ultrathin Lithium Metal Composite Anodes with Superior Electrochemical Kinetics and Cycling Stability

Lithium metal is a promising candidate for the promotion of the next generation high energy density batteries. The employment of ultrathin Li metal anode with controllable thickness could enable a higher efficiency of Li utilization. Herein, a simple method to fabricate free‐standing 10 μm ultrathin Li metal anode is developed in this work. A three‐dimensional MnOx‐coated CNT framework is constructed through a facile hydrothermal process, utilizing as a host for molten Li infusion, which could not only put forward a simple strategy to modulate the thickness of Li metal film but also restricts the volume expansion. The abundant MnOx nanoparticles acting as lithiophilic sites reduce the Li nucleation barrier and optimize the electrochemical kinetics at the anode/electrolyte interface. As a result, the ultrathin Li composite anode exhibits a superior lifespan expanded to 2000 cycles in a symmetric cell, as well as a better capacity and rate capability than that of bare Li anode in full cell, fulfilling the requirements of high energy density and stable cycling life. Furthermore, a wave‐shaped Li metal pouch cell based on the ultrathin Li composite anode is assembled that exhibits remarkable mechanical bending toleration and cyclic stability, demonstrating large potential application in the field of flexible wearable devices.

Bowl-shaped carbon loaded Co9S8 nanoparticles connected by carbon nanotubes with excellent rate performance for sodium-ion batteries

Sodium-ion batteries (SIBs) are expected to replace lithium-ion batteries in the energy storage sector owing to their low cost and abundant resources. However, developing suitable anode materials to meet the high energy density requirements of SIBs remains an ongoing challenge. Herein, we design a hollow nitrogen-doped bowl-like carbon decorated with Co9S8 nanoparticles linked by carbon nanotubes (HNBC@Co9S8@CNTs) as an anode material for SIBs. The HNBC@Co9S8@CNTs electrode exhibits impressive rate performance (449.3 mAh g−1 at 5 A g−1) and cycling stability (426.5 mAh g−1 after 500 cycles at high current density of 1 A g−1) due to the advantages of highly conductive three-dimensional (3D) interconnected structures. In addition, its pseudo-capacitance and sodium storage diffusion kinetics are analyzed in depth using Cyclic Voltammetry (CV) and galvanostatic intermittent titration technique (GITT). The results elucidate that the partially surface-induced capacitive sodium storage, highly conductive 3D interconnected structures, and fast reaction kinetics synergistically contribute to the high-rate performance. This work may provide new insights for the fabrication of various metal sulfide or sulfide composites with high sodium storage capacity.

Thermal design of standalone miniature thermo-electric power conversion system using variable area liquid fuel combustor

The novel standalone miniature thermo-electric power conversion system using variable area liquid fuel combustor is proposed in the present work. There is a need to provide an alternative energy source for portable electronic devices to cater to its need for high energy density requirements, and the proposed system is a feasible option for the same. The various critical parameters required for designing a thermoelectric power conversion system are identified as per the requirement of standalone nature and flame stabilization. The 15 W thermo-electric power conversion system is designed based on these parameters. The variable area combustor and the concentric fuel tube helps for the natural circulation of fuel and air inside the combustor and flame stability. The temperature of liquid fuel film over the fuel orifice exit is calculated by equating mass diffusion transfer number with thermal diffusion transfer number at steady state condition assuming the Lewis number unity. The Thin metallic porous media of ∼ 10 mm diameter is suggested based on the thermal analysis over the fuel orifice exit to enhance the fuel evaporation rate.

Interface Engineering and Understanding for the Next-Generation Batteries

Lithium-ion batteries (LIBs) have become the most widely used energy storage systems for portable electronic devices and electric vehicles. With the increasing requirements of high energy density, next-generation batteries, including Li-metal batteries, Na-metal batteries and solid-state batteries, have received huge attention in recent years. For most batteries, the interfacial issues between the electrolyte (both liquid and solid) and electrodes are critical factors affecting the performance of the batteries. Atomic and molecular layer deposition (ALD and MLD) are considered as ideal strategies for overcoming the interfacial issues for the batteries.In this talk, I will introduce our research about interface engineering and understanding for next-generation batteries. i) The interface is one of the key factors for the Li and Na deposition behaviors and battery performances. We developed ALD and MLD approaches to fabricate the artificial interface with significantly improved electrochemical performances and reduced dendrite formation for Li/Na metal anodes. ii) We further design different ALD/MLD thin films to stabilize the interfaces for solid-state Li batteries. iii) We have also developed ex-situ and in-situ synchrotron X-ray techniques for next-generation batteries.

Thermal safety and thermal management of batteries

AbstractElectrochemical energy storage is one of the critical technologies for energy storage, which is important for high‐efficiency utilization of renewable energy and reducing carbon emissions. In addition to the higher energy density requirements, safety is also an essential factor for developing electrochemical energy storage technologies. Lithium‐ion batteries (Li‐ion batteries) are commercialized as power batteries in electric vehicles (EVs) because of their advantages (such as high energy density, long life span, etc.), while for future electrochemical energy storage markets, lithium–sulfur (Li–S) and lithium–air (Li–air) batteries can be promising candidates for high energy density requirements. Therefore, this paper summarizes the present or potential thermal hazard issues of lithium batteries (Li‐ion, Li–S, and Li–air batteries). Moreover, the corresponding solutions are proposed to further improve the thermal safety performance of electrochemical energy storage technologies.

Stable lithium metal anode achieved by shortening diffusion path on solid electrolyte interface derived from Cu2O lithiophilic layer

• We found the lithiation of Cu 2 O film would participate in the SEI generation. • The thickness of Cu 2 O film can affect Li + diffusion path in the derived SEI layer. • The oxidation state/thickness of Cu 2 O film can be tuned by oxygen plasma rapidly. The stable operation of lithium metal batteries is crucial for high energy density requirements, but it is plagued by Li dendrite growth and unstable solid electrolyte interphase (SEI). Lithiophilic transition metal oxides (TMOs) have been studied extensively on Cu current collectors to stabilize lithium metal anodes by decreasing the Li nucleation overpotential, yet less is known about the SEI derived from the lithiation reaction of TMOs. Here we report a novel approach to regulate the SEI interface precisely, especially to construct a nanoscale inorganic-dominated SEI with shortened diffusion path by controlling the oxidization state of Cu 2 O film on Cu current collector. The highly stable cyclic performance is achieved by generating the thin SEI that contains dense inorganic inner layer and organic layer. Consequently, the lithium metal anode based on Cu 2 O/Cu current collector exhibits low and stable polarization voltage for an ultralong life-span (∼22.5 mV at 1 mA cm −2 for 3000 h). This work elucidates the relationship between lithiation reaction of oxides modified layer and derived SEI, guiding for constructing stable lithium metal batteries.

Experimental investigations on the correlations between the structure and thermal‐electrochemical properties of over‐discharged ternary/ Si‐C power batteries

The thermal safety of power lithium-ion batteries (LIBs) has seriously affected the booming development of electric vehicles (EVs). Especially, owing to the requirement of high energy density, thermal runaway (TR) easily occurs in LIBs, resulting in a higher heat generation rate. Over-discharging is recognized as a common cause for TR. In the present research, the correlations between the structure and thermal-electrochemical properties of an over-discharged ternary/Si-C battery at room and high temperatures were investigated. The heat generation mechanisms of the batteries due to the maximum surface temperature and peak temperature difference variations during fast charging and discharging processes were investigated. Moreover, the electrochemical performances parameters of the batteries, such as voltage changing trend, discharge time, discharge capacity, internal resistance, electrochemical impedance spectroscopy (EIS) spectra, were analyzed. When the battery was discharged at 2.0C and 55°C, its maximum temperature and highest temperature difference reached 91.34°C and 13.24°C, respectively, finally resulting in a sharp decline in electrochemical performance. Furthermore, the root reasons for performance degradation and heat generation intensification of the over-discharged battery were analyzed by scanning electron microscopy and X-ray diffraction. The cause of the aforementioned phenomenon is due to irreversible damage to the electrode materials. This research not only reveals the relevant relationship between the thermal behavior and the microscopic structure of the over-discharged ternary/Si-C battery under various temperature conditions but also provides valuable insights for improving the safety of LIBs modules even packs.

Research on high energy density portable power supply based on metal-air battery

Because of the increasing number of personal electronic devices, there is an urgent demand for portable power supplies with high energy density. Metal-air batteries have the advantages of high energy density, high safety, good infrared concealment, no vibration and noise, low self-discharge rate. They can effectively meet the needs of users. In this paper, we studied the influence of electrode distance, single cell structure and battery module of magnesium-air battery on battery discharge performance, and designed a battery module structure to meet the requirements of high energy density. The results show that, the mass energy density of the module assembled with cells consisting of two positive electrodes and one negative electrodes cell is higher than other modules, and the discharge performance is best when the electrode distance is in the range of 2 mm to 3.5 mm.

The robust carbon shell to improve stability of porous Si anodes for high-performance lithium-ion batteries

Silicon (Si) anode with high theoretical capacity can meet the requirements of high energy density. However, Si anodes suffer from considerable volume expansion and low electron conductivity, resulting in low rate performance and poor cycle stability for Lithium-ion batteries (LIBs). Herein, the carbon coating porous Si (P-Si@C) materials are obtained via decomposition of C2H2 deposition on the surface of porous interconnected Si nanoparticles. Due to the porous structure mitigating Si expansion and the highly robust carbon shell enhancing overall electrical conductivity to improve Li+ diffusivity and ultra-high electron conductivity in Si electrodes. Therefore, the P-Si@C electrodes deliver a high initial Coulombic efficiency (defined as ICE = 83.2%) and long life (high discharge capacity of 1424 mA h/g) at 4 A/g after 600 cycles. As a result, the assembled P-Si@C // LiFePO4 full cell shows a high discharge capacity of 85 mA h/g at 1 C after 200 cycles, corresponding to high retention 88.5%.

Thermal Simulation Analysis of a Lithium-Ion Battery

Lithium – Ion batteries are now extensively used in electric vehicles (EV) as well as in renewable power generation applications for both on-grid and off grid storage. Some of the major challenges with batteries for electric vehicles are the requirement of high energy density, compatibility with high charge and discharge rates while maintaining high performance, and prevention of any thermal runaway conditions. The objective of this research is to develop a computer simulation model for coupled electrochemical and thermal analysis and characterization of a lithium-ion battery performance subject to a range of charge and discharge loading, and thermal environmental conditions. The electrochemical model includes species and charge transport through the liquid and solid phases of electrode and electrolyte layers along with electrode kinetics. The thermal model includes several heat generation components such as reversible, irreversible and ohmic heating, and heat dissipation through layers of battery cell. Simulation is carried out to evaluate the electrochemical and thermal behavior with varying discharge rates. Results demonstrated a strong variation in the activation and ohmic polarization losses as well as in higher heat generation rates. Results show variation of different modes and order of cell heat generation rates that results in a higher rate of cell temperature rise as battery cell is subjected to higher discharge rates. The model developed will help in gaining a comprehensive insights of the complex transport processes in a cell and can form a platform for evaluating number new candidates for battery chemistry for enhanced battery performance and address safety issues associated with thermal runaway.

Synthesis, characteristics, and electrochemical performance of N,N-(p-phenylene)bismaleamate and its fluorosubstitution compound on organic anode materials in lithium-ion batteries

Conventional lithium-ion batteries (LIBs) comprise lithium transition metal oxide as a cathode and graphite as an anode. Because of global climate change, growth in the electric vehicle industry, carbon reduction policies, and high energy density requirements, several graphite replacements for LIBs, such as metalloid and organic compounds, have been studied. However, metalloids cause substantial problems when alloys with lithium ions, including volume expansion and electrochemical irreversibility. Organic compounds also have drawbacks, such as low electronic conductivity and low thermal stability. In this study, bismaleamate and its fluorosubstitution polymer are synthesized and evaluated to prevent the aforementioned problems. Calculations of electrochemical performance indicate that the bismaleamate fluorosubstitution significantly reduced the energy band gap to approximately 0.02 eV, and the battery had a capacity of 430.0 mAh g−1 after 350 cycles. The rate performance is significantly improved because of the low energy band gap when the battery operated at 10 C/10 C (190 mAh g−1). The Brunauer–Emmett–Teller analysis indicates that the bismaleamate fluorosubstitution had four times the surface area and 10 times the pore size of bare bismaleamate. The fluorosubstitution produced an obvious three-dimensional steric effect and an asymmetrical structure, which facilitates excellent ionic transfer. X-ray photoelectron spectroscopy revealed that the weak electron-acceptance effect of the fluorosubstitution considerably inhibites solid electrolyte interphase formation and deliveres a notable reaction mechanism for its structure rearrangement. Operando X-ray diffraction patterns confirme changes in the crystal phase of the two bismaleamates. As new organic anode materials, bismaleamates have demonstraed excellent performance in terms of battery capacity, rate, and life cycle. Therefore, bismaleamates have potential applications in lithium-ion and beyond-lithium secondary batteries.

Hierarchically Divacancy Defect Building Dual‐Activated Porous Carbon Fibers for High‐Performance Energy‐Storage Devices

AbstractRenewable and environmentally friendly biomass‐based carbon electrode materials naturally possess fast ion transport, high adsorption, and excellent chemical stability for high‐performance energy‐storage devices. However, intelligently building the effectively biomass‐transferred carbon materials for the requirement of high energy density is still a big challenge to date. Here, a hierarchically divacancy defect building platform is reported for effectively biomass‐transferred and highly interconnected 3D dual‐activated porous carbon fibers (DACFs) based on the internal−external dual‐activation function of the pre‐embedded KOH and CO2 molecular. This uniquely interconnected frameworks not only fully provide the abundant active sites for ion interaction, but also efficiently guarantee the substantial accommodation for ion storage. Based on this, the as‐prepared DACFs‐based supercapacitors deliver a high energy density of 61.3 Wh kg−1 at a power density of 875 W kg−1 in the EMIMBF4 ionic liquid. This work not only provides a simple and efficient technique to enhance the energy density of carbon materials, but also probably promotes its additional application in environmental remediation.

Optimizing high voltage Na3V2(PO4)2F3 cathode for achieving high rate sodium-ion batteries with long cycle life

Sodium-ion batteries have gained an intense attention as a promising alternate for Li-ion batteries due to their low cost, and abundant availability. To meet high energy density requirements, developing a high voltage cathode with ultra-long cycle life is of great importance. Na3V2(PO4)2F3 (NVPF) features a high working voltage, fast sodium-ion diffusion channels, and small volume change during the cycling process. However, the practical performance of NVPF cathode is currently hindered by poor Na+ ion diffusion at high voltage, low cycle life, and limited rate behavior. Herein, we evaluate the effect of synthesis conditions in sol–gel technique, binders (PVDF, PAI and CMC), and electrolytes (ether, and ester based solvents) to overcome the diffusion limitation in high voltage NVPF cathode. Benefiting from the synergistic effect of CMC binder, and DEGME electrolyte, and reduced graphene oxide composite, NVPF effectively overcome the potential barrier during Na+ ion insertion/extraction at high voltage. NVPF with CMC binder and DEGDME electrolyte displayed a high Na+ ion diffusion kinetics, low cell resistance, and delivered an excellent electrochemical performance. NVPF delivered a high coulombic efficiency (92%), long cycle life (10,000 cycles), and an excellent rate performance (50 C), outperforming the conventional PVDF binder, and carbonate based electrolytes. Furthermore, the full-cell constructed by NVPF cathode, and Na3V2(PO4)3 anode delivered an capacity retention. The current study provides new insights for overcoming the kinetic barrier during sodium ion storage in high voltage cathode that could direct the research development towards high energy sodium-ion batteries.