High Conductivity Properties Research Articles

Regulating Interfacial Chemistry to Boost Ionic Transport and Interface Stability of Composite Solid‐State Electrolytes for High‐Performance Solid‐State Lithium Metal Batteries

AbstractComposite solid‐state electrolytes (CSSEs) that combine the benefits of inorganic and polymer electrolytes hold great potential for solid‐state lithium metal batteries (SSLMBs) due to their high ionic conductivity and superior mechanical properties. However, their overall performance is severely hindered by several practical challenges, including inorganic component aggregation, poor interface behavior, and limited Li+ transport. Here, a unique ultrathin coating of triaminopropyl triethoxysilane with a bifunctional structure is introduced that effectively bridges the inorganic fillers (Li1+xAlxTi2‐x(PO4)3, LATP) and the polyvinylidene fluoride hexafluoropropylene /polyethylene oxide polymer matrix, thereby enabling high‐performance CSSEs (referred to as SLPH). This design prevents LATP particle agglomeration, improves interfacial compatibility, and ensures the enrichment and fast transport of Li+ within SLPH. Consequently, the SLPH exhibits a low ionic conduction energy barrier (Ea = 0.462 eV), desirable ionic conductivity (4.19 × 10−4 S cm−1 at 60 °C), and a high Li+ transference number ( = 0.694). As a result, SSLMBs with SLPH, including Li| SLPH |Li symmetric cells, LiFePO4| SLPH |Li coin‐type, and pouch cells, demonstrate superior rate capability and long‐time cycling stability. This work underscores the significance of surface functionalization of inorganic electrolytes to create a stable solid‐solid interface and enhance ionic conduction, paving the way for high‐performance CSSEs in SSLMBs.

Achieving Fast Ionic Transport and High Mechanical Properties of Cellulose-Based Solid-State Electrolyte via a Cationic Chain-Extended Effect for Zinc Metal Batteries.

In recent years, rechargeable aqueous zinc metal batteries have ushered in rapid development, but their large-scale industrial application is hindered by zinc anode dendrite formation and hydrogen evolution reaction. Using a solid-state polymer electrolyte is one of the strategies to solve this problem. Herein, by introducing the chain-expanding effect of zinc salts on oxidized bacterial cellulose, cellulose-based polymer electrolytes with excellent strength and ionic conductivity are prepared. According to the thermogravimetric calculations, the bound water content in prepared electrolytes greatly increases, which slows down the occurrence of side reactions. More importantly, the expanding distance between the fiber chains provides more space for the movement of Zn2+. The obtained solid-state electrolyte displays a high ionic conductivity (38.26 mS cm-1) and good mechanical properties (tensile stress is 592 kPa and tensile strain is 381%). Due to the properties of the solid electrolyte itself, its electrochemical window is expanded to 2.58 V. The assembled Zn∥Zn symmetrical battery maintains an ultralong cycle lifespan over 980 h of 0.5 mA cm-2. The Zn∥NH4V10O10 battery provides the specific capacity (363.1 mAh g-1 at 0.1 A g-1) and shows a satisfactory rate performance.

High sensitivity flexible strain sensor for motion monitoring based on MWCNT@MXene and silicone rubber

Research on flexible strain sensors has grown rapidly and is widely applied in the fields of soft robotics, body motion detection, wearable sensors, health monitoring, and sports. In this study, MXene was successfully synthesized in powder form and combined with multi-walled carbon nanotube (MWCNT) to develop MWCNT@MXene conductive network-based flexible strain sensors with silicone rubber (SR) substrate. Combining MWCNTs with MXene as a conductive material has been shown to significantly improve the sensor performance, due to MXene’s high conductivity properties that strengthen the MWCNT conductive pathway, increase sensitivity, and improve sensor stability. The sensor is fabricated by a sandwich method consisting of three layers, which enables more accurate and reliable detection of strain changes. The main innovation of this research is the utilization of MWCNT@MXene as a conductive material that optimizes the performance of flexible strain sensors, overcomes the limitations of previous materials, and makes it a more effective solution for long-term applications. Furthermore, the sensor was evaluated to test its performance through sensitivity, linearity, response time, and durability tests. The results showed that the sensor exhibited excellent performance with a high sensitivity of 39.97 over a strain range of 0-100% and excellent linearity (0.99) over a strain of 0–50%. The sensor also has a fast response time of about 70 ms, it also has good stability during low (1–5%) and high (20–100%) strain cycle testing and can withstand up to 1200 loading and unloading cycles. In addition, the sensor effectively detects a wide range of body movements, including finger, wrist and knee movements. These findings show that the electromechanical properties of strain sensors are significantly improved through the use of MWCNT@MXene as a conductive material, so these sensors are considered a promising solution for applications in wearables and body motion monitoring.

Downscaling of Non-Van der Waals Semimetallic W5N6 with Resistivity Preservation.

The bulk phase of transition metal nitrides (TMNs) has long been a subject of extensive investigation due to their utility as coating materials, electrocatalysts, and diffusion barriers, attributed to their high conductivity and refractory properties. Downscaling TMNs into two-dimensional (2D) forms would provide valuable members to the existing 2D materials repertoire, with potential enhancements across various applications. Moreover, calculations have anticipated the emergence of uncommon physical phenomena in TMNs at the 2D limit. In this study, we use the atomic substitution approach to synthesize 2D W5N6 with tunable thicknesses from tens of nanometers down to 2.9 nm. The obtained flakes exhibit high crystallinity and smooth surfaces. Electrical measurements on 15 samples show an average electrical conductivity of 161.1 S/cm, which persists while thickness decreases from 45.6 to 2.9 nm. The observed weak gate-tuning effect suggests the semimetallic nature of the synthesized 2D W5N6. Further investigation of the conversion mechanism elucidates the crucial role of chalcogen vacancies in the precursor for initiating the reaction and strain in propagating the conversion. Our work introduces a desired semimetallic crystal to the 2D material library with mechanistic insights for future design of the synthesis.

Dual network ionized hydrogels with high electrical conductivity and strong mechanical properties for wearable drug delivery patches

Dual network ionized hydrogels with high electrical conductivity and strong mechanical properties for wearable drug delivery patches

Multifunctional starch-based conductive hydrogels for smart sensors and flexible supercapacitors.

In order to overcome harsh working environments and meet eco-friendly demands, the development of environmentally tolerant and recyclable hydrogels is necessary. Herein, multifunctional conductive hydrogel was successfully constructed by introducing starch into polyvinyl alcohol (PVA)/glycerin (Gly)/lithium chloride (LiCl) hydrogel. Starch is rich in active sites (-OH groups) that provide a variety of physical interactions for the construction of polymer hydrogels. PSGL hydrogel exhibited high conductivity (40.65 mS cm-1) and outstanding anti-freezing properties (-40 °C). Meanwhile, PSGL hydrogel retained 82.6 % initial weight after 30 days of exposure and 80 % conductivity retention after recycling. The mechanism of Gly and LiCl in inhibiting the freezing and dehydration of hydrogels was further revealed by density functional theory simulations. Moreover, PSGL hydrogel-based sensors had a satisfactory sensitivity (GF = 1.68 at 0-100 %) and accurately detected human motion. Further, by linking the PSGL hydrogel sensors with Internet of Things technology, human-computer interaction was accomplished. Besides, the PSGL hydrogel-based supercapacitors had a specific capacitance of 120.0 mF cm-2 (0.2 mA cm-2) and 98.17 % capacitance retention after 10,000 cycles. PSGL hydrogel-based devices also worked steadily in extreme environments. Therefore, the PSGL hydrogels have great potential for flexible electronics, soft robotics, energy storage etc.

Interplay of chain dynamics and ion transport on mechanical behavior and conductivity in ionogels.

Understanding the interplay among the mechanical behavior, ionic conductivity and chain dynamics of ionogels is essential for designing flexible conductors that exhibit both high conductivity and excellent mechanical properties. In this study, ionogels were synthesized via the radical polymerization of N,N'-dimethylacrylamide (DMAA) and methacrylic acid (MAAc) monomers in the presence of ionic liquid 1-ethyl-3-methylimidazolium trifluoromethane sulfonate ([EMIM][OTf]). By varying the mass content of ionic liquid within ionogels, we investigated the mechanical behavior and ionic conductivity at the macroscopic scale using tensile, rheological testing and electrochemical impedance spectroscopy, as well as the dynamic behavior of chain segments and ions within the network at the microscopic scale using broadband dielectric relaxation spectroscopy (BDS) over a broad temperature range. Our findings revealed that variations in ionic liquid concentration significantly affect mechanical performance, ionic conductivity, complex conductivity spectra, and complex permittivity spectra. These ionogels exhibited remarkable stretchability, adhesion, and strain-sensing capabilities. Analysis of BDS indicated that the temperature dependence of the hopping frequency (ωH), the conductivity of free ions (σdc), and the relaxation time (τs) of chain segments conforms to the Vogel-Tammann-Fulcher (VTF) equation for ionogels with varying ionic liquid content. By correlating τs measured through rheological tests and BDS, we observed a transition from Arrhenius to VTF behavior, which shifts towards lower temperatures with increasing ionic liquid content. This study highlighted a strong coupling between σdc and ωH, as well as between 1/τs and ωH, at low ionic concentrations, facilitating high mechanical performance of the ionogels due to viscoelastic energy dissipation. However, as the ionic concentration increased, a slight decoupling of σdc and ωH was noted, leading to a substantial reduction in the mechanical properties of the ionogels. Ultimately, these ionogels demonstrate potential as polymer electrolytes for applications in flexible wearable devices.

Ultrathin Bioelectrode Array with Improved Electrochemical Performance for Electrophysiological Sensing and Modulation.

To achieve high accuracy and effectiveness in sensing and modulating neural activity, efficient charge-transfer biointerfaces and a high spatiotemporal resolution are required. Ultrathin bioelectrode arrays exhibiting mechanical compliance with biological tissues offer such biointerfaces. However, their thinness often leads to a lack of mechano-electrical stability or sufficiently high electrochemical capacitance, thus deteriorating their overall performance. Here, we report ultrathin (∼115 nm) bioelectrode arrays that simultaneously enable ultraconformability, mechano-electrical stability and high electrochemical performance. These arrays show high opto-electrical conductivity (2060 S cm-1@88% transparency), mechanical stretchability (110% strain), and excellent electrochemical properties (24.5 mC cm-2 charge storage capacity and 3.5 times lower interfacial impedance than commercial electrodes). The improved mechano-electrical and electrochemical performance is attributed to the synergistic interactions within the poly(3,4-ethylenedioxythiophene) sulfonate (PEDOT:PSS)/graphene oxide (GO) interpenetrating network (PGIN), where π-π and hydrogen bonding interactions improve conductive pathways between PEDOT chains and enhance the charge-transfer mobility. This ultrathin bioelectrode is compatible with photolithography processing and provides spatiotemporally precise signal mapping capabilities for sensing and modulating neuromuscular activity. By capturing weak multichannel facial electromyography signals and applying machine learning algorithms, we achieve high accuracy in silent speech recognition. Moreover, the high transparency of the bioelectrode allows simultaneous recording of electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS) signals, facilitating dual-mode brain activity analysis with both high temporal and high spatial resolution.

Flexible, stretchable multifunctional silver nanoparticles-decorated cotton textile based on amyloid-like protein aggregation for electrothermal and photothermal dual-driven wearable heater.

The design of multifunctional, high-performance wearable heaters utilizing textile substrates has garnered increasing attention, particularly in the development of body temperature and health monitoring devices. However, fabricating these multifunctional wearable heaters while simultaneously ensuring flexibility, air permeability, Joule heating performance, electromagnetic interference (EMI) shielding and antibacterial properties remains a significant challenge. This study utilizes phase transition lysozyme (PTL) film-mediated electroless deposition (ELD) technology to deposit silver nanoparticles (Ag NPs) on the cotton fabrics surface in a mild aqueous solution at room temperature, thereby constructing a wearable heater with long-term stability, high conductivity, and exceptional photothermal properties. The textiles enriched with Ag NPs exhibit remarkable electrothermal and photothermal dual-driven heating capabilities, achieving temperatures exceeding 110 °C within 50s under 2 V, or in merely a few seconds through photothermal conversion. Importantly, these textiles retain the intrinsic flexibility and breathability of the textile substrate. Furthermore, the amyloid-like protein Ag NP integrated textiles demonstrate excellent antibacterial properties, and exhibit a high EMI shielding efficiency of 50 dB within the frequency range of 8.2-12.4 GHz. Therefore, these multifunctional Ag NPs wearable heaters were expected to find applications in areas such as smart wearable clothing and future health management.

Lignin-coated liquid metals-induced synthesis of deep eutectic solvent-based hydrogels with environmentally tolerant for strain sensors

In the work, alkali lignin (AL) was used as a coating layer for dispersing liquid metals (LM) in a ternary DES (choline chloride/ethylene glycol/water) system and generating free radical-catalyzed acrylic acid (AA) polymerization. The preparation of flexible sensors had high electrical conductivity (0.33 S·m-1), excellent self-healing and mechanical properties (84.7 KPa). The presence of AL facilitated the dispersion of LM in the DES system and the formation of a flexible hydrogel without the addition of an initiator. Moreover, DES was used as the liquid component of the PAA-AL2@LM2 hydrogel made it more environmentally tolerant and had better water retention. Even at -20 °C, the hydrogel exhibited low electrical resistance (131.4 Ω). The moisture loss of the prepared hydrogel was only 9% after 7 days at room temperature. This work exploited the significant advantages of DES and lignin-based materials in dispersing LM to provide a new technique for the preparation of metal-polymer composite hydrogels, which has great potential in the field of flexible sensors.

Recent Advances in Potential Biomedical Applications of MXene‐Based Hydrogels

ABSTRACTMXene‐based hydrogels represent a significant advancement in biomedical material science, leveraging the unique properties of 2D MXenes and the versatile functionality of hydrogels. This review discusses recent developments in the integration of MXenes into hydrogel matrices, focusing on their biomedical applications such as wound healing, drug delivery, antimicrobial activity, tissue engineering, and biosensing. MXenes, due to their remarkable electrical conductivity, mechanical robustness, and tunable surface chemistry, enhance the mechanical properties, conductivity, and responsiveness of hydrogels to environmental stimuli. Specifically, MXene‐based hydrogels have shown great promise in accelerating wound healing through photothermal effects, delivering drugs in a controlled manner, and serving as antibacterial agents. Their integration into hydrogels also enables applications in targeted cancer therapies, including photothermal and chemodynamic therapies, facilitated by their high conductivity and tunable properties. Despite the promising progress, challenges such as ensuring biocompatibility and optimizing the synthesis for large‐scale production remain. This review aims to provide a comprehensive overview of the current state of MXene‐based hydrogels in biomedical applications, highlighting the ongoing advancements and potential future directions for these multifunctional materials.

Design and manufacture of structure-function integrated carbon fiber reinforced plastics for composite construction

Structure-function integrated composite can replace traditional structural components to bear loads, offering an innovative solution to reduce overall weight while storing energy in aircraft composite wings. The structural electrolyte featuring high ionic conductivity and tough mechanical properties is one of the vital components to realize high-performance multifunctional structural composite batteries. Herein, a functional ternary hydrogel electrolyte (i.e., MAP electrolyte) is elaborately engineered through the strategical incorporation of multiple hydrogen bonding among polyacrylamide (PAM) with rigid-reinforcing aramid nanofibers (ANFs) and ion-conductive Ti3C2Tx MXene nanosheets. Accordingly, the ANFs fortify the fracture toughness and self-healing properties of MAP hydrogel, and the MXene enables a doubled ionic conductivity of MAP electrolyte (32.48 mS cm−1) than that of pure PAM (16.18 mS cm−1). In addition, the capacity retention of the MAP-based full cell (81.9 %) is double of the liquid electrolyte (40.6 %) within 1000 cycles at 1 A g−1. Impressively, the MAP electrolyte remarkably enhances the flexural performance of structural batteries, with a flexural modulus (14.5 GPa) nearly three times that of structural batteries with liquid electrolytes (5.3 GPa) due to hydrogen-bonded ANFs. Simulation results and mechanical-electrochemical tests further underscore the imperative functions of MAP electrolyte as a structural component to empower the stiffness and maintain the integrity of structural batteries. Moreover, fabricating curved wing scaled components utilizing multi-point flexible forming technology demonstrates the practical feasibility of replacing structural components with complex shapes. This work will expedite the exploitation of structural battery prototypes and their real applications in EVs, UAVs, and electric-powered maritime vehicles.

Fabrication of multifunctional cu-coated melamine foam by electroless chemical deposition technique for thermal management, EMI shielding, and antibacterial applications

Melamine foam (MF) inherently possesses excellent flame-retardant properties due to its ability to release nitrogen upon combustion. Its porous and loose structure also contributes to its high flexibility, breathability, and sound absorption capabilities. Incorporating copper nanoparticles (Cu NPs) significantly enhances the material's electrical conductivity, including its electromagnetic shielding effectiveness, thermal conductivity, and antibacterial properties. This, in turn, greatly broadens the material's potential applications. This research investigated the coating of Cu NPs on three-dimensional MF using an electroless chemical deposition technique to fabricate multifunctional materials. The electromagnetic shielding effectiveness (SET) increased to 85 dB as the Cu NPs content rose from 0 to 0.31 g. Similarly, the electrical conductivity increased from 0.19 to 357 S/m. These results indicate that the Cu-coated MF has high EMI shielding and conductivity properties. The strong adhesion of the Cu NPs to the MF surface created a coating with low infrared emissivity, contributing to the material's excellent thermal insulation properties. With a modest supply voltage of around 4 V, the material exhibited promising electrical conductivity, generating additional warmth of up to 74 °C through efficient joule heating. Furthermore, the Cu-coated MF demonstrated 100 % antibacterial activity, making it a promising candidate for a variety of applications.

Ionic liquid modifying conductivity and hydrophobicity of B4C for enhanced electrosynthesis of H2O2

Electrosynthesis of hydrogen peroxide (H2O2) via two-electron oxygen reduction reaction (2e− ORR) is an attractive energy-efficient and decentralized alternative to the conventional anthraquinone process. However, designing non-precious metal catalysts with high activity, selectivity and stability is a great challenge. Here, we report a facile and effective approach to improve the catalytic performance of commercial boron carbide (B4C) by loading ionic liquid (IL), which exploits the complementary properties of high electrical conductivity and hydrophobicity of IL. The B4C catalyst with optimal IL loading possesses the highest conductivity and O2 adsorption, exhibiting high H2O2 selectivity in both neutral (∼96 %) and alkaline (∼93 %) electrolyte, which are nearly ∼34 % and ∼19 % higher than pristine B4C, respectively. Moreover, its production rate is ∼1.5 times that of pristine B4C at 130 mA cm−2 current density, resulting in a high concentration of H2O2 (5.93 wt%) produced in flow-cell reactor. The long-term cycle test demonstrates the desirable stability of IL@B4C/GDE, which is attributed to the high hydrophobicity and tight bonding between IL@B4C and the substrate, giving a strong flood-proof capability at the three-phase interface and avoiding rapid flooding by the electrolyte. This work provides new insights into designing non-precious metal electrocatalysts for efficient electrosynthesis of H2O2, emphasizing the role of IL in interface engineering.

Corrosion Enhanced By Hydrogenotrophic Methanogens Differently Enriched on Copper Alloys

Copper and its alloys, such as brass and bronze, are widely used in heat exchangers valves, fitting, and other components of industrial facilities due to their corrosion resistance, high conductivity, and biocide properties. However, they can suffer of microbial corrosion like or more than other non-toxic materials, as several bacteria and archaea can settle and form thick biofilm on them. Nowadays, there is a growing interest in studying the metabolisms of methanogens and their effects for materials [1], due to the pivotal role that these microorganisms play in the biotechnological processes. The production of methane by CO2 and H2, for instance, is one of the most promising bioprocesses addressing the energy transition [2].In this context, the aim of this work is to evaluate, and underline, the corrosiveness of biofilm growth on different copper alloys, starting from a common microbial pool enriched of bacteria and hydrogenotrophic archaea, treated at different temperatures and autoclaved. The study was evaluated based on 16 days test on the surface of two different copper materials, a pure Cu and a CuZn brass (40 wt. % Zn). Electrochemical investigations were performed using a three-electrode cell consisting of a working electrode (test alloy), a reference electrode (saturated Ag/AgCl electrode) and a counter electrode (titanium mesh). Investigations included open circuit potential (OCP) monitoring and electrochemical impedance spectroscopy (EIS). Chemical characterizations of the corrosion products and post-experiment observations were performed by SEM and micro-Raman spectroscopy (μRS). Molecular analysis by next generation sequencing (NGS) of 16S RNA was performed by swabbing the surface of the material and identifying the microorganisms constituting the microbial communities for each case. Results evidenced a different corrosion behavior of materials, which corresponded to different enrichment of microorganisms and different corrosion products, depending on the material and the treatment of the inoculum. [1] Lahme S, Mand J, Longwell J, Smith R, Enning D. Severe Corrosion of Carbon Steel in Oil Field Produced Water Can Be Linked to Methanogenic Archaea Containing a Special Type of [NiFe] Hydrogenase. Appl Environ Microbiol. 2021 Jan 15;87(3) [2] Hirano SI, Ihara S, Wakai S, Dotsuta Y, Otani K, Kitagaki T, Ueno F, Okamoto A. Novel Methanobacterium Strain Induces Severe Corrosion by Retrieving Electrons from Fe0 under a Freshwater Environment. Microorganisms. 2022 Jan 25;10(2):270.

Catalytic Combustion Type H2 Gas Sensor Based on Cerium Oxide

Hydrogen gas is the most promising clean energy source, but its use carries an explosion hazard (LEL: 4 vol%). Therefore, the real-time and accurate detection of H2 gas leakage at every emitting site is required with the compact sensor to prevent a critical accident. Among the compact H2 gas sensors proposed, the catalytic combustion type gas sensor using precious metal-loaded γ-Al2O3 such as Pt/Al2O3 as the catalyst is one of the sensors in practical use because of its long life and low-cost features. However, platinum is an expensive and scarce resource, and its use is desired to be reduced. Therefore, for the realization of the coming hydrogen society, the development of novel catalytic combustion type sensor using a noble-metal-free catalysts is important.In this study, we focused on CeO2, Fe2O3, Co3O4, NiO as H2 oxidation catalyst and investigated the sensing performance of these metal oxides. In addition, we applied CeNbO4 +δ [1], having high oxide ion conductivity and redox property, as a promoter for CeO2 catalyst, and the H2 gas sensing performance of the sensor with 4 wt% CeO2/CeNbO4 +δcatalyst was investigated.Among the sensors applied metal oxide (CeO2, Fe2O3, Co3O4, NiO), the sensor with CeO2 showed highest sensor output which is over 2 times higher than the sensors with other metal oxides. This is due to high specific surface area and low heat capacity of CeO2. Although the sensor using CeO2 showed good sensing performance, quantitative detection of H2 required a temperature of 105 °C or higher, which is still high for practical use.To improve the H2 oxidation activity of CeO2, we applied CeNbO4 +δ as a promoter and the sensor with 4 wt% CeO2/CeNbO4 +δcatalyst. Figure 1(a) displays the response curves to H2 gas concentration change for the sensor applied 4 wt% CeO2/CeNbO4 +δ and CeO2. The sensor with 4 wt% CeO2/CeNbO4 +δcatalyst showed about 2.6 times higher sensor output compared to the sensor with only CeO2, indicating that the combination of CeNbO4 +δ improves H2 oxidation activity. Furthermore, the sensor with 4 wt% CeO2/CeNbO4 +δcatalyst was able to detect H2 gas concentration quantitatively even at 75 °C (Fig. 1(b)) with a 90% response time of about 14 seconds. The sensitivity to other gases such as carbon monoxide, methane, ethanol, and acetaldehyde was examined, and the sensor showed excellent selectivity for H2 at 75 °C.[1] Y. Jin, Y. Quan, J. Liu, C. Qui, P. Pan, B. Shan, H. Luo, and P. Yang, J. Solid State Chem., 313, 123318 (2022). Figure 1

Flammability (Flash point) of Gel Polymer Electrolytes

Gel polymer electrolytes offer a promising pathway for the rapid commercialization of next-generation batteries. These electrolytes are composed of a polymeric matrix in which a solvent is trapped. The liquid component provides high ionic conductivity and favorable interfacial properties , while the polymeric matrix enhances electrolyte safety by reducing flammability. Most of the flammability tests that are performed on gel polymer electrolytes are neither standardized nor quantitative. This makes it difficult to compare materials and evaluate the safety of different electrolyte components. Our group has confronted this issue by developing new methodology to quantify the flammability of gel polymer electrolytes by adapting flash point measurements to gel systems [1]. The methodology that was used to measure the flashpoint of gel polymer electrolytes is presented here. A series of gel polymer electrolytes are analyzed to determine how intermolecular interactions that are present in these systems influence the flash point temperature of the gel polymer electrolytes. The objective is to understand which factors influence flammability, and ultimately, how to achieve a balance between a high flash point and high ionic conductivity in these systems. St-Antoine, C., et al., Relationship between the intermolecular interactions of carbonyl (PC) with nitrile (HNBR) functional groups and the flash point of a gel polymer electrolyte. Journal of Materials Chemistry A, 2023. 11(20): p. 10984-10992.

(Invited) Extrinsic and Intrinsic Methods to Increase the Rate Performance of MnO2 Electrodes

MnO2 is one of the most well studied pseudocapacitive material for aqueous supercapacitors owing to the surface and near surface-confined redox processes. However, due to its poor electronic conductivity, a large amount of conducting additive, needs to be added to achieve high-rate charge storage. Since the conducting additive does not contribute much to the specific capacitance, this leads to decrease in total energy density of the cell in terms of both mass and volume. In addition, polymeric binders are also necessary to fabricate rigid electrode with good contact.As an alternative to these typical conductive binders and polymer binders, we have studied the possibility of using RuO2 nanosheets as a novel inorganic binder with polymeric properties, high electronic conductivity and excellent pseudocapacitive properties. For example, by adding a small amount of RuO2 nanosheets to particulate MnO2, a large synergetic effect is observed leading to a high utilization of MnO2 pseudocapacitance.1 The optimized amount of RuO2 in the composite was 13 wt%, which is much lower than the amount generally used for conductive carbon additives. The size of nanosheet binders also affects the properties of the electrode. Using MnO2 nanosheets and RuO2 nanosheets with different lateral sizes, it has been shown that larger sized nanosheets affords better conductive binder properties through a better electronic conduction network structure.Asides from using conductive binders, heterogeneous doping can increase the intrinsic conductivity of MnO2. We have shown that Ir-doped Birnessite shows faster redox behavior than pristine MnO2 and this enhanced kinetics are reflected on the exfoliated nanosheets. These properties can be discussed based on the electronic interaction between Mn and Ir.The pseudocapacitive performance of MnO2 can also be manipulated by inducing cationic defects in Birnessite. Low temperature annealed MnO2 with higher number of defects shows higher specific capacitance at low rate, albeit at the loss of high-rate performance. This trade-off is discussed based grain-boundary resistance dominating the rate performance. Acknowledgments This work was supported in part by ISHIFUKU Metal Industry Co., Ltd. and a Japan Science and Technology Agency Program on Open Innovation Platform with Enterprises,Research Institute and Academia (JST OPERA JPMJOP1843).

Strategies for Design and Synthesis Novel Sulfide-Type Na-Ion Conductors

Solid-state superionic conductors play a significant role to achieve the high potential of all-solid-state batteries with high energy density and enhanced safety. Sulfide-type solid electrolytes have attracted strong interest in the past decade due to their advantages of high ionic conductivity and favorable mechanical properties. The ion transport in sulfide-type solid electrolytes is influenced by several factors, including crystal structure, synthesis approach, annealing temperature, as well as chemical doping. Specifically, anion or cation doping may cause the crystal structure changes and thus affect the conductive properties of sulfide solid electrolytes.In this talk, we will discuss the strategies and doping chemistry in Na3MCh4 (M: P or Sb; Ch: S or Se) family conductors. For these sulfide-type Na-ion conductors, different anion or cation dopants will be introduced, and the doping effects on the synthetic process, crystal structures, as well as ionic conductivity will be systematically discussed. Moreover, the isovalent and aniovalent dopants will be compared to understand the doping strategy to design and realizer highly conductive sulfide-type solid electrolytes for solid-state Na batteries.

Li Metal Surface Modification to Stabilize Lithium-Argyrodite Interface for Sulfide-Based All-Solid-State Lithium Metal Batteries

Since the commercialization of lithium-ion batteries, they have faced limitation in safety and energy density. All-solid-state lithium metal batteries (ASSLMBs) can be a solution to address these issues. Among many types of solid electrolytes, sulfide-based solid electrolytes have been attracted great attention because of their high ion conductivity and ductile property. However, many researchers have reported that the interface between lithium metal and solid electrolyte is highly unstable. The lithium dendrite growth can be also occurred in the ASSLMBs by voids, cracks, grain boundaries in solid electrolyte and side reactions between lithium metal and solid electrolyte. Therefore, it is imperative to develop a protective layer that can suppress lithium dendrites and side reactions.In our work, we removed native resistive surface layer formed on pristine lithium metal and reconstructed solid electrolyte interphases (SEI) with uniform, ion-conductive and excellent physical properties by dipping solution containing lithium nitrate in nitromethane and dimethoxyethane. The modified lithium metal is denoted as Li@NDL (lithium @ nitromethane-dimethoxyethane-lithium nitrate). We confirmed that nitromethane reacted with LiOH and Li2O on native surface of lithium to form Li3N and organic layer, which enhanced ionic conductivity and mechanical strength. The symmetric lithium cell with Li@NDL increased critical current density to 2.8 mA cm-2 and exhibited outstanding cycling stability without short circuit over 1000 hours. ASSLMB comprising Li@NDL anode and 4 mAh cm-2 NCM composite cathode maintained 80% retention after 200th cycles at 0.5 C, demonstrating our work can provide a novel surface modification of lithium metal for ASSLMBs.