Utilization Of Active Material Research Articles

Operando Investigation on the Role of Densification and Chemo‐Mechanics on Solid‐State Cathodes

AbstractAll solid‐state batteries are desirable for a range of energy storage applications which require high energy density. Achieving a high energy density in a solid‐state battery requires the operation of an energy dense anode with a composite solid‐state cathode. Pores and/or voids within a solid state cathode are ion‐blocking and thus control over the concentration and distribution of pores in the initial electrode and cycled electrode is desirable. This study provides an understanding of the interplay between electrode microstructure and mechanics on active material utilization in solid state cathodes composed of NCM 811 and Li6PS5Cl. Decreasing the solid electrolyte particle size leads to greater active material‐electrolyte contact and less total deformation when exposed to an external load. Composite cathodes with greater compliance can potentially decrease strain between the active material and solid electrolyte, decrease delamination events and result in higher overall active material utilization and high capacity retention.

Accelerating Na2S/Na2S2 conversion kinetics by electrolyte additive with high Na2S/Na2S2 solubility for high-performance room-temperature sodium–sulfur batteries

The development of room-temperature sodium sulfur batteries is severely constrained by the sluggish solid-solid conversion kinetics of Na2S/Na2S2 and the accumulation of “dead Na2S/Na2S2”. Here, we accelerate the conversion kinetics of Na2S/Na2S2 as well as reduce the accumulation of “dead Na2S/Na2S2” by 1-butyl-1-methylpyrrolidine trifluoromethanesulfonate ([P14][OTf]) ionic liquid additive that is compatible with metallic Na and has high Na2S/Na2S2 solubility. The results of three-electrode kinetics tests show a significant enhancement of the apparent redox kinetics of Na2S/Na2S2 through increasing its concentration. During battery cycling, the increase in Na2S/Na2S2 concentration can induce the formation of three-dimensional Na2S deposition and reduce the coverage of the electrode effective electroactive area, thus decreasing the battery polarization, especially at high rates. In addition, high Na2S/Na2S2 solubility can promote the reuse of “dead Na2S/Na2S2” and greatly improve the utilization of active material. At 2C rate, 351 mAh g−1 can be maintained after 800 cycles, and the capacity decay per cycle is 0.046 %. The rate and cycle performance of the battery are greatly improved. Further, a mechanism is proposed for the enhancement of battery performance via overpotential and diffusion theories.

Interdigitated supercapacitor with double-layer active material prepared by sacrificial layer method

Increasing the surface area of active materials is a crucial approach to enhance the capacity of supercapacitors. In this study, we present an interdigitated supercapacitor featuring a double-layer active material prepared using a sacrificial layer method. The replacement of the insulating substrate with a gel electrolyte facilitates ion motion between the active electrodes. Finite element analysis (FEA) and electrochemical experiments confirm that the utilization of double-layer active material can significantly improve the capacity (1.5–1.85 times higher than traditional structures). The electrochemical performance of the three active materials has been significantly improved after using the double-layer active material structure, which proves that the method in this paper has strong material compatibility. Furthermore, an interdigital supercapacitor (ISC) is fabricated using electrodes with double-layer active material through the sacrificial layer method and its electrochemical performance is evaluated. At a scan rate of 10 mV·s-1, ISC exhibits an impressive area-specific capacitance as high as 68.4 mF·cm-2. Remarkably, ISC can maintain stable power output even under extreme deformation and fatigue testing conditions. This strategy involving interdigitated supercapacitors with double-layer active materials prepared via the sacrificial layer method presents a promising solution for flexible energy storage devices.

Eco-friendly aqueous binder derived from waste ramie for high-performance Li-S battery

Even the sulfur cathode in lithium-sulfur (Li-S) battery has the advantages of high theoretical energy density, wide source of raw materials, no pollution to the environment, and so on. It still suffers the sore points of easy electrode collapse due to large volume expansion during charge and discharge and low active materials utilization caused by the severe shuttle effect of lithium polysulfides (LiPSs). Therefore, in this work, ramie gum (RG) was extracted from ramie fiber degumming liquid and used as the functional binder to address the above problems and improve the Li-S battery's performance for the first time. Surprisingly, the sulfur cathode using RG binder illustrates a high initial capacity of 1152.2 mAh/g, and a reversible capacity of 644.6 mAh/g after 500 cycles at 0.5 C, far better than the sulfur cathode using polyvinylidene fluoride (PVDF) and sodium carboxymethyl cellulose (CMC) binder. More importantly, even if the active materials loading increased to as high as 4.30 mg/cm2, the area capacity is still around 3.1 mAh/cm2 after 200 cycles. Such excellent performances could be attributed to the abundant oxygen- and nitrogen-containing functional groups of RG that can effectively inhibit the shuttle effect of LiPSs, as well as the excellent viscosity and mechanical properties that can maintain electrode integrity during long-term charging/discharging. This work verifies the feasibility of RG as an eco-friendly and high-performance Li-S battery binder and provides a new idea for the utilization of agricultural biomass resources.

Effect of pre-intercalation on Li-ion diffusion mapped by topochemical single-crystal transformation and operando investigation.

Limitations in electrochemical performance as well as supply chain challenges have rendered positive electrode materials a critical bottleneck for Li-ion batteries. State-of-the-art Li-ion batteries fall short of accessing theoretical capacities. As such, there is intense interest in the design of strategies that enable the more effective utilization of active intercalation materials. Pre-intercalation with alkali-metal ions has attracted interest as a means of accessing higher reversible capacity and improved rate performance. However, the structural basis for improvements in electrochemical performance remains mostly unexplored. Here we use topochemical single-crystal-to-single-crystal transformations in a tunnel-structured ζ-V2O5 positive electrode to illustrate the effect of pre-intercalation in modifying the host lattice and altering diffusion pathways. Furthermore, operando synchrotron X-ray diffraction is used to map Li-ion site preferences and occupancies as a function of the depth of discharge in pre-intercalated materials. Na- and K-ion intercalation 'props open' the one-dimensional tunnel, reduces electrostatic repulsions between inserted Li ions and entirely modifies diffusion pathways, enabling orders of magnitude higher Li-ion diffusivities and accessing higher capacities. Deciphering the atomistic origins of improved performance in pre-intercalated materials on the basis of single-crystal-to-single-crystal topochemical transformation and operando diffraction studies paves the way to site-selective modification approaches for positive electrode design.

A self-assembled carbon nanotube/silicon composite battery anode stabilized with chemically reduced graphene oxide sheets

This study presents a streamlined fabrication process for lithium-ion battery (LIB) electrodes, involving the dispersion of carbon nanotubes (CNT), silicon (Si), and graphene oxide (GO) in an aqueous solution, followed by vacuum filtration to produce self-standing composite electrodes. Two reduction routes are employed to form reduced graphene oxide (rGO). The chemically reduced CNT/Si/rGO-5 %-Chem anode exhibits superior mechanical resilience compared to thermally reduced counterparts, which suffer from reduced strength and structural integrity. Chemical reduction also enhances electrochemical performance, increasing the initial capacity of the non-reduced CNT/Si/GO-5 % composite anode from 1,461 to 2,342 mAh g−1, with improved long-term cycling performance. Electrochemical impedance spectroscopy shows lower pre-cycle charge transfer resistance (148 Ω) and superior solid electrolyte interphase (SEI) resistance (43 Ω) for chemically reduced anodes compared to thermally reduced ones. After cycling, the chemically reduced composite anode exhibits reduced electrolyte resistance and charge transfer resistance, indicating stable electrochemical reactions. The composite structure undergoes adaptive rearrangements during cycling, optimizing active material utilization. In summary, CNTs accommodate silicon swelling, while chemically reduced rGO promotes stable SEI formation, highlighting the benefits of chemical reduction in enhancing mechanical durability and electrochemical performance, making the self-standing CNT/Si/rGO composite film a promising LIB anode.

Spinning of Carbon Nanofiber/Ni–Cu–S Composite Nanofibers for Supercapacitor Negative Electrodes

The preparation of composite carbon nanomaterials is one of the methods for improving the electrochemical performance of carbon-based electrode materials for supercapacitors. However, traditional preparation methods are complicated and time-consuming, and the binder also leads to an increase in impedance and a decrease in specific capacitance. Therefore, in this work, we reduced Ni-Cu nanoparticles on the surface of nitrogen-doped carbon nanofibers (CNFs) by employing an electrostatic spinning method combined with pre-oxidation and annealing treatments. At the same time, Ni-Cu nanoparticles were vulcanized to Ni–Cu–S nanoparticles without destroying the structure of the CNFs. The area-specific capacitance of the CNFs/Ni–Cu–S–300 electrode reaches 1208 mF cm−2 at a current density of 1 mA cm−2, and the electrode has a good cycling stability with a capacitance retention rate of 76.5% after 5000 cycles. As a self-supporting electrode, this electrode can avoid the problem of the poor adhesion of electrode materials and the low utilization of active materials due to the inactivity of the binder and conductive agent in conventional collector electrodes, so it has excellent potential for application.

CoNiO2/Co3O4 Nanosheets on Boron Doped Diamond for Supercapacitor Electrodes.

Developing novel supercapacitor electrodes with high energy density and good cycle stability has aroused great interest. Herein, the vertically aligned CoNiO2/Co3O4 nanosheet arrays anchored on boron doped diamond (BDD) films are designed and fabricated by a simple one-step electrodeposition method. The CoNiO2/Co3O4/BDD electrode possesses a large specific capacitance (214 mF cm-2) and a long-term capacitance retention (85.9% after 10,000 cycles), which is attributed to the unique two-dimensional nanosheet architecture, high conductivity of CoNiO2/Co3O4 and the wide potential window of diamond. Nanosheet materials with an ultrathin thickness can decrease the diffusion length of ions, increase the contact area with electrolyte, as well as improve active material utilization, which leads to an enhanced electrochemical performance. Additionally, CoNiO2/Co3O4/BDD is fabricated as the positive electrode with activated carbon as the negative electrode, this assembled asymmetric supercapacitor exhibits an energy density of 7.5 W h kg-1 at a power density of 330.5 W kg-1 and capacity retention rate of 97.4% after 10,000 cycles in 6 M KOH. This work would provide insights into the design of advanced electrode materials for high-performance supercapacitors.

Engineering Detrimental Functional Groups in Conductive Additives Toward High-Performance All-Solid-State Batteries.

Conductive additives are of great importance for the adequate utilization of active materials in all-solid-state lithium batteries by establishing conductive networks in the composite cathode. However, it usually causes severe interfacial side reactions with solid electrolytes, especially sulfide electrolytes, leading to sluggish ion transportation and accelerated performance degradation. Herein, a simple hydrogen thermal reduction process is proposed on a commonly used conductive additive Super P, which effectively removes the surface oxygen functional groups and weakens the interfacial side reactions with sulfide. With a small amount of 1 wt % reduced Super P, ASSLBs demonstrates a competitive capacity of 180.2 mAh g-1 , which is much higher than the 130.8 mAh g-1 of untreated Super P. Impressively, reduced Super P based ASSLBs also exhibit a higher capacity retention of 81.8 % than 64.6 % of untreated Super P. The cathode interfacial chemical evolutions reveal that reduced Super P could effectively alleviate the side reactions of sulfide. Reduced Super P shows better reversible capacity compared to reduced carbon nanofiber with almost no loss of capacity retention, due to its more complete conductive network. Our results highlight the importance of oxygen-containing functional groups for conductive additives, lightening the prospect of low-cost 0D conductive additives for practical ASSLBs.

A Multifaceted Competitive Zn–Cu Battery Unleashed by Optimizing Charge Protocols

AbstractRechargeable alkaline Zn–Cu batteries show great potential for energy storage systems due to their high capacity, cost‐effectiveness, and environmental‐friendliness. However, restricted by the severe dissolution upon charging, rapid capacity decline occurs throughout the cycle. Herein, the charging protocol is adjusted to bypass the dissolution stage of high‐valent states, thereby preserving the optimal reaction section of Zn–Cu batteries and greatly improving cycling stability. Additionally, a self‐activation process in the initial stage led to the spontaneous transformation of the original electroplated Cu particles on nickel foam from 10 to 4 mm, enhancing both conductivity and mass transfer, ultimately increasing the utilization of active materials. The battery achieved a discharge capacity of 349.5 mAh g−1, an ultra‐flat charge–discharge voltage platform, over 92% energy efficiency, a low cost of only $43.25 per kWh, and an exceptionally stable cyclic performance with no noticeable decay over 400 cycles. These 5D improvements position the Cu electrode as a robust candidate for the positive electrode material in the next generation of commercial Zn batteries.

Enhancing Electrode Performance through Triple Distribution Modulation of Active Material, Conductive Agent, and Porosity.

The increasing demand for large-scale energy storage propels the development of lithium-ion batteries with high energy and high power density. Low tortuosity electrodes with aligned straight channels have proved to be effective in building such batteries. However, manufacturing such low tortuosity electrodes in large scale remains extremely challenging. In contrast, high-performance electrodes with customized gradients of materials and porosity are possible to be made by industrial roll-to-roll coating process. Yet, the desired design of gradients combining materials and porosity is unclear for high-performance gradient electrodes. Here, triple gradient LiFePO4 electrodes (TGE) are fabricated featuring distribution modulation of active material, conductive agent, and porosity by combining suction filtration with the phase inversion method. The effects and mechanism of active material, conductive agent, and porosity distribution on electrode performance are analyzed by experiments. It is found that the electrode with a gradual increase of active material content from current collector to separator coupled with the distribution of conductive agent and porosity in the opposite direction, demonstrates the best rate capability, the fastest electrochemical reaction kinetics, and the highest utilization of active material. This work provides valuable insights into the design of gradient electrodes with high performance and high potential in application.

High-Performance Sulfurized Polyacrylonitrile Cathode by Using MXene as a Conductive and Catalytic Binder for Room-Temperature Na/S Batteries.

Sulfurized polyacrylonitrile (PAN@S) is a promising cathode material for room-temperature Na/S batteries but suffers from low conductivity and insufficient electrochemical activity, resulting in unsatisfactory actual capacity and rate performance. Herein, Ti3C2Tx MXene nanosheets are used as a conductive and catalytic binder to establish the PAN@S electrode, wherein MXene constructs a highly conductive framework for fast charge transport and provides high catalytic effect to improve the active material utilization and accelerate the redox kinetics significantly. Therefore, the PAN@S electrode bonded by MXene shows an electronic conductivity of 5.05 S cm-1, 4 orders of magnitude higher than the conventional electrodes bonded by the insulative polymer binders, and much decreased activation energy barrier and resistance. Consequently, the PAN@S electrode displays superior performance in terms of high capacity (697.3 mAh g-1 at 200 mA g-1), unparalleled rate capability (189.0 mAh g-1 at 20 A g-1), and excellent high-rate cycling performance (a capacity decay rate of ∼0.04% per cycle during 1000 cycles at 5 A g-1). This work provides a high-performance electrode for room-temperature Na/S batteries and shows the promising potential of conductive and catalytic MXene binders in boosting the performance of active materials.

A solid-state electrolyte for electrochemical lithium-sulfur cells.

Post-lithium-ion batteries are designed to achieve high energy density and high safety by modifying their active material and cell configuration. In terms of the active material, lithium-sulfur batteries have the highest charge-storage capacity and high active-material utilization because of the use of a conversion-type sulfur cathode, which involves conversion between solid-state sulfur, liquid-state polysulfides, and solid-state sulfides. In terms of the configuration, solid-state batteries ensure high safety by using a solid-state electrolyte in between the two electrodes. Herein, we use a lithium lanthanum titanate (LLTO) solid-state electrolyte in the lithium-sulfur cell with a polysulfide catholyte electrode. The LLTO, which replaces the conventional liquid electrolyte, is a solid-state electrolyte that offers smooth lithium-ion diffusion and prevents the loss of polysulfides, while the highly active polysulfide electrode, which replaces the solid-state sulfur cathode, improves the reaction kinetics and the active-material utilization. The material and electrochemical analyses confirm the stabilized electrodes exhibit long-lasting lithium stripping/plating stability and limited polysulfide diffusion. Moreover, the morphologically and electrochemically smooth interface between the solid-state electrolyte and catholyte enables fast charge transfer in the cell, which demonstrates a high charge-storage capacity of 1429 mA h g-1, high rate performance, and high electrochemical efficiency.

CoFe2O4 nanoparticles modified amidation of N-doped carbon nanofibers hybrid catalysts to accelerate electrochemical kinetics of Li-S batteries with high sulfur loading

Lithium-sulfur battery have been considered as promising energy storage devices because of its superiority in energy density. However, the low active material utilization, low sulfur loading, shuttle effect and torpid kinetics of polysulfides, and poor cycling stability limit its commercial applications. Herein, the functionalized nitrogen doped carbon nanofibers containing amide groups were designed by electrospun and polyamidoamine dendrimer (PAMAM) solution impregnation techniques. The obtained amide groups modified nitrogen-doped carbon nanofibers (ANF) were combined with spinel CoFe2O4 (CFO) nanoparticles (CFOANF) via hydrothermal method to design as membrane electrode containing Li2S6 catholyte for lithium-sulfur batteries. The introduction of nitrogen doped and amide groups modified ANF can increase fibers polarity, which have chemical adsorption capability toward lithium polysulfides. CFO nanoparticles can further absorb the soluble polysulfides by strong chemical interaction due to its intrinsic polarity and also serve as a catalyst to promote the redox kinetics of polysulfides conversion. Benefiting from the synergism of the physical confinement, polar chemical adsorption, and catalytic conversion, the as-prepared CFOANF delivers excellent electrochemical performances at high sulfur loading. The as-prepared CFOANF membrane with 6.3 mg cm−2 sulfur loading delivers a high initial capacity of 940 mAh g−1 and excellent long-term cycling stability up to 450 cycles with a low decay rate 0.059 % per cycle at 0.2C. Remarkably, even at 12.6 mg cm−2 and 16.4 mg cm−2 sulfur loading, the CFOANF membrane electrodes show high capacity of 9.7 mAh cm−2 and 11.8 mAh cm−2, respectively. The results show that the chemically anchoring polysulfides and catalyzing redox reaction by multifunctional CFOANF hybrid composite is promising for assembling with a high sulfur loading electrode, which exhibits a superior electrochemical performance in lithium-sulfur batteries.

Effect of Particle Size Ratio on Microstructure and Active Material Utilization in Argyrodyte All-Solid-State Composite Cathodes

Among next-generation batteries, all-solid-state batteries (ASSB) promise increased energy densities, fast charging properties, and higher safety compared to traditional liquid-based systems. To achieve the demanded high energy densities high mass loadings of the composite cathodes are necessary. These consist of active material (AM), solid electrolyte (SE), and conductive additive as well as binder. Volume changes of intercalation AM and insufficient ionic percolation at low SE contents lead to an increased interfacial resistance and capacity loss. In order to promote cathode AM utilization the particle size ratio of the AM and the SE within the composite cathode needs to be optimized.Theoretical calculations have shown that for high AM utilization at high AM loadings particle size ratio is a crucial parameter [1, 2]. Experimentally, the influence of particle size ratio has so far only been studied at laboratory scale. However, scalable process routes have not considered this important aspect. In this work, we present a solvent-based process route for the preparation of sulfide-based solid-state composite cathodes with NCM622 as AM, starting from the adjustment of the particle size of a commercially available Li6PS5Cl SE by planetary ball mill. Further process steps include the dispersion of SE with AM and conductive additive and doctor blade coating of cathode films. We analyzed the composite cathodes with regard to their internal resistance as well as their microstructure and conducted electrochemical tests in lab-scale test cells. Optimization of the particle size ratio results in an increase of AM utilization by a factor of 5 as well as an enhanced AM-SE-particle contact area and lower porosity.

Lean-Electrolyte Lithium-Sulfur Cells with a Core-Shell Cathode Configuration with High Active-Material Loading and Energy Density

Introduction The growing demand for rechargeable batteries with increasingly high energy density and low-cost active material has inspired the research of low-cost cathodes with higher specific capacities than those based on intercalation lithium-ion cathodes. Among these novel energy storage technologies, the lithium-sulfur electrochemical cell is the most promising because of the high energy density, low cost, wide availability, and low environmental impact of the sulfur cathode. However, the high-capacity sulfur cathode forms insulating solid sulfur and lithium sulfide in the fully charged and discharged states. The resulting high cathode resistance limits electrochemical utilization and reversibility, and the resulting low redox kinetics leads to the poor rate performance of sulfur cathodes. Moreover, these solid-state active materials are converted to liquid-state polysulfides during intermediate charging and discharging. The liquid-state polysulfides readily dissolve in the lithium-sulfur battery electrolyte, resulting in irreversible polysulfide loss and poor discharge-charge efficiency of the cell. The inefficient and unstable cell electrochemistry of sulfur can be mitigated by designing appropriate configurations of cathode materials. However, the modification of cathode materials often encounters the inability to accommodate a sufficient amount of sulfur in the cathode under lean electrolyte conditions while maintaining electrochemical stability. Results and Discussion In this presentation, we present the design of a core-shell architecture for the entire cathode, which features a conductive carbon shell having a fabric-like tubular structure to accommodate an active material core and provide fast charge transfer to the active material. In addition to the novel cathode configuration, we present a summary of a number of active material cores, including a pure sulfur core and a pure lithium sulfide core as solid-state active material cores, and a polysulfide catholyte core as a liquid-state active material (Figure 1) [1-3]. With these three different core-shell cathodes, we will comprehensively report the material design with high electrochemical utilization and efficiency, and the designed cell configuration stabilizes the reversible lithium-sulfur electrochemistry. Most importantly, we propose the sulfur core to demonstrate the high-loading sulfur cathode with the highest sulfur loading and content, and the sulfide and polysulfide cores to demonstrate the lean-electrolyte cells with low electrolyte to active material ratios. Specifically, we design a series of lithium-sulfur battery cathodes with a unique cathode material and configuration. In terms of the cathode material, a high-loading sulfur cathode prepared with pure sulfur powder, a high-concentration polysulfide prepared as the catholyte, and a sulfide cathode prepared in an ether-based solvent are reported. The sulfur, polysulfide, and sulfide serve as a high-loading active materials. The conductive carbon shell encapsulates the active material during cycling and resting. The integrated design of the cathode material and configuration enables the core-shell cathodes to achieve high sulfur loadings ranging from of 4 to 30 mg cm−2 and high sulfur contents in the range of 60-70 wt%. The high-loading core-shell cathodes excellent electrochemical utilization of the large amount of active material, showing high peak charge-storage capacity of 600-800 mA∙h g−1 at C/10 rate, long cycle life of 100-200 cycles, and high rate performance of C/10-C/2 rates with long-term cyclability and high capacity retention of 70% after 200 cycles. Moreover, by using polysulfide and sulfide cores, we demonstrate a lean electrolyte cell with low electrolyte/sulfur ratios of 6-3 μL mg-1. Accordingly, the designed core-shell cathodes achieve a high areal capacity of about 10 mA∙h cm-2, high gravimetric capacities of ~500 mA∙h g-1, and an energy density of about 20 mW∙h cm-2. Conclusion In summary, we report in the presentation a summary of our high-loading core-shell sulfur cathodes and the design of their application in the development of the lean-electrolyte lithium-sulfur cells. Our core-shell cathodes exhibit excellent electrochemical utilization and retention of active material in both solid and liquid state, which shows the long cycle life and long shelf life of the high energy density lithium-sulfur cell. Figure 1. Illustration of a lithium-sulfur cell with the core-shell cathode equipped with sulfur, polysulfide, and sulfide cores. References -C. Wu, S.-H. Chung, J. Mater. Chem. A 2023, 10.1039/D3TA00210A.-H. Chung, A. Manthiram, Adv. Energy Mater. 2017, 7, 1700537.-H. Chung, A. Manthiram, Energy Environ. Sci. 2016, 9, 3188. Figure 1

Robust-Dense Composite Cathode with Improved Three-Dimensional Ionic Percolation Network and Electrode/Electrolyte Interface for the Development of All-Solid-State Sodium Batteries

All solid-state sodium batteries (AS3Bs) attract immense attention due to their excellent energy and power density, cycle life and thermal security [1]. However, the practical realization of AS3Bs is greatly affected by low to moderate ionic conductivity of the solid electrolyte, unstable electrode/electrolyte interface and poor ion and electron transport between the cathode active materials [2,3]. The unstable electrode/electrolyte interface with point contact leads to huge charge transfer resistance, stress generation and the delamination of the electrode/electrolyte interface during electrochemical reactions. The ion percolation network in the cathode structure is also a critical part. Liquid electrolyte fills the pores present in the cathode and leads to a good Na+ percolation network; however, Na+ percolation cannot be possible in the case of AS3Bs due to the non-fluidity nature of solid electrolyte. This results in low capacity contribution from the cathode owing to fewer cathode active material utilization during electrochemical cycling [4]. Due to the above mentioned issues, the long-cycle stability of AS3Bs is poor.Here we have first prepared Mg doped Na1+3xZr2(SixP1-xO4)3 (NZSP-0.05Mg) with improved ionic conductivity (4.1 mS cm-1 25 ℃) by minimizing the secondary impurity phase. Further, we have utilized an innovative approach to develop a composite cathode by directly firing sodium vanadium fluoro phosphates (NVPF) with Na3.1Zr1.95Mg0.05Si2PO12 (NZSP-0.05Mg) solid electrolyte in the optimized size and weight ratio leading to the robust and dense structure with 3D ionic and electronic percolation network. Additionally, the pores present in the composite cathode is addressed by incorporating polymer electrolyte which further improves the ionic percolation network. The intimate contact between the solid electrolyte and the electrodes was further improved by using a composite solid electrolyte, and the full cell is fabricated by using NVPF composite cathode, composite solid electrolyte and Na metal. The cell delivers a discharge capacity of 103 mAh g-1 after 500 cycles with a Coulombic efficiency of 98 % at 0.1 C and shows excellent capacity retention of 67 mAh g-1 at 2C. The post-mortem XPS analysis confirms the electrochemical stability between the NVPF composite cathode and CSE as well as the Na metal and CSE. Our research provides a new prospective for the preparation of composite cathode and full cell design which can be utilized in solid state sodium and lithium batteries. This work can contribute to a safer battery with long cycle life.

Cathode Design and Evaluation for the High-Sulfur-Loading, Lean-Electrolyte Lithium–Sulfur Battery

Sulfur is a promising active material for the lithium rechargeable batteries because of its high theoretical capacity, a relatively low cost, and an environmentally friendly nature. Lithium–sulfur battery with a high-energy-density is regarded as a third-generation rechargeable battery with high potential for commercialization. The well charged and discharged lithium–sulfur battery can generate specific energy density of up to 600 W∙h kg−1. However, the charging product, sulfur, and the discharging product, lithium sulfide, both have low conductivity, which lead to low active material utilization and excessive addition of conductive materials, lowering the active material content and performance in the cathode region. The liquid active material, polysulfides, formed in the middle of the cycling reaction will dissolve in the electrolyte, causing leakage to the lithium anode to form a non-reactive lithium sulfide layer, causing severe capacity fading. Furthermore, the repeated transformation of sulfur (solid-state), polysulfides (liquid-state), and lithium sulfur (solid-state) active materials led to the sluggish battery reaction and irreversible electrolyte consumption. All and all, the chemical and physical properties of the sulfur and the combination with lithium resulted in low active material utilization, low cycling ability, low capacity-retention rate, and shortened cycle life.To fully realize the potential of the high-energy-density lithium–sulfur battery, the cathode material, configuration, and fabrication must be carefully considered. Herein, a sulfur cathode fabricated by a hot-pressing method and the evaluation of different porous substrate was also conducted. Porous conductive network is a common cathode material, which provides a large surface area and great polysulfides absorbability. However, as a result of high-sulfur-loading and lean-electrolyte cathode batteries, a low specific capacity and short cycle life are discovered, which is affected by the high electrolyte consumption. Accordingly, a carbon electrospun substrate with a non-nanoporous structure was introduced as the conductive network to achieve the high-energy-density battery design. To fabricate the free-standing sulfur cathode, sulfur powder was loaded between two porous carbon electrospun substrate by a hot-pressing technique. The cathode consists of three layers: carbon current collector, melt-in sulfur layer, and carbon interlayer, forming a sandwich-like cathode.With this design, we can accommodate high areal loading of sulfur (8 mg cm−2) in the cathode area while lessening the conductive additive (sulfur content of 73 wt%). The hot-pressed electrospun cathode, conducted under low electrolyte usage (i.e., the low electrolyte-to-sulfur ratio of 7 µL mg−1) can achieve excellent energy density (11.8 mW∙h cm−2) with a stable areal capacity up to 5.9 mA∙h cm− 2 let alone with an extended cycle life over 200 cycles. Furthermore, this devised cathode can also retain excellent cycling ability with lower ratios of electrolyte to sulfur (6–4 µL mg−1) and great rate dependent performance up to C/2 cycling rate. Figure 1

Nafion-Based Quasi-Solid-State Polymer Electrolyte for Lithium-Sulfur Batteries

Lithium-sulfur batteries are considered a strong contender for next-generation high-energy battery systems given their high gravimetric energy density. However, this battery chemistry is still facing challenges such as the polysulfide shuttle effect caused by the high solubility of long-chain lithium polysulfides (Li2Sn) resulting in active material loss and compromised cycle life. Solid-state polymer electrolytes (SPEs) represent a promising pathway to address this issue by preventing the formation and transport of these undesirable polysulfide intermediates.1,2 Moreover, the application of flexible polymer electrolytes promotes safe high energy batteries for smart textiles.In this study, single lithium-ion conducting solid polymer electrolytes (SLIC-SPEs) based on lithiated Nafion membrane have been investigated, utilizing the chemical and thermal stability of this kind of ionomers. Among others, a mixture of ethylene carbonate (EC) and propylene carbonate (PC) was tested as organic aprotic swelling solvent offering advantageous characteristics such as great chemical stability and high ion mobility while avoiding phase separation issues and undesired leaching.Sulfur-infiltrated ultramicroporous carbon composite cathodes were utilized in combination with the investigated SLIC-SPEs, facilitating a quasi-solid-state lithium-sulfur full cell with carbonate-solvent compatibility and high active material utilization.3 Electrochemical performance of the full cell was investigated elaborately and compared with a reference system using solely the liquid EC:PC solvent. While rapid capacity fading can be observed for the liquid electrolyte cell, an enduring high capacity is found in the lithiated-Nafion system. For better understanding of these effects, cycling analysis was accompanied by implementing impedance spectroscopy upon galvanostatic cycling. The electrochemical characterization indicates the formation of a stable film and high degree of reversibility during cycling of the lithiated-Nafion cell whereas an increased film resistance due to sulfur cross-over and electrolyte decomposition was observed within the liquid electrolyte system.(1) Z. Li, W. Lu, N. Zhang, Q. Pan, Y. Chen, G. Xu, D. Zeng, Y. Zhang, W. Cai, M. Yang, J. Mater. Chem. A 2018, 6 (29), 14330-14338.(2) X. Hao, H. Wenren, X. Wang, X. Xia, J. Tu, J. Colloid Interface sci. 2020, 558, 145-154,(3) M. Nojabaee, B. Sievert, M. Schwan, J. Schettler, F. Warth, N. Wagner, B. Milow, K. A. Friedrich, J. Mater. Chem. A 2021, 9 (10), 6508-6519,

An Overview on Polymer-Based Electrolytes with High Ionic Mobility for Safe Operation of Solid-State Batteries

Liquid electrolytes used in commercial Li-ion batteries are generally based on toxic volatile and flammable organic carbonate solvents, thus raising safety concerns in case of thermal runaway. The most striking solution at present is to switch on all solid-state designs exploiting polymer materials, films, ceramics, low-volatile, green additives, etc. The replacement of liquids component with low-flammable solids is expected to improve the safety level of the device intrinsically. Moreover, a solid-state configuration is expected to guarantee improved energy density systems. However, low ionic conductivity, low cation transport properties and issues in cell manufacturing processes must be overcome [1].Electrochemical performance in lab-scale devices can be readily improved using different RTILs or specific low-volatile additives. Here, an overview is offered of the recent developments in our labs on innovative polymer-based electrolytes allowing high ionic mobility, particularly attractive for safe, high-performing, solid-state Li-metal batteries, and obtained by different techniques, including solvent-free UV-induced photopolymerization. Cyclic voltammetry and galvanostatic charge/discharge cycling coupled with electrochemical impedance spectroscopy exploiting different electrode materials (e.g., LFP, Li-rich NMC, LNMO, Si/C) demonstrate specific capacities approaching theoretical values even at high C-rates and stable operation for hundreds of cycles at ambient temperature [2,3]. Direct polymerization procedures on top of the electrode films are also used to obtain an intimate electrode/electrolyte interface and full active material utilization in both half and full-cell architectures. In addition, results of composite hybrid polymer electrolytes [4] and new single-ion conducting polymers [5] are shown, specifically developed to attain improved ion transport and high oxidation stability for safe operation with high voltage electrodes even at ambient conditions.