Loss Of Electrical Contact Research Articles

Synthesis Methods of Si/C Composite Materials for Lithium-Ion Batteries

Silicon anodes present a high theoretical capacity of 4200 mAh/g, positioning them as strong contenders for improving the performance of lithium-ion batteries. Despite their potential, the practical application of Si anodes is constrained by their significant volumetric expansion (up to 400%) during lithiation/delithiation, which leads to mechanical degradation and loss of electrical contact. This issue contributes to poor cycling stability and hinders their commercial viability, and various silicon–carbon composite fabrication methods have been explored to mitigate these challenges. This review covers key techniques, including ball milling, spray drying, pyrolysis, chemical vapor deposition (CVD), and mechanofusion. Each method has unique benefits; ball milling and spray drying are effective for creating homogeneous composites, whereas pyrolysis and CVD offer high-quality coatings that enhance the mechanical stability of silicon anodes. Mechanofusion has been highlighted for its ability to integrate silicon with carbon materials, showing the potential for further optimization. In light of these advancements, future research should focus on refining these techniques to enhance the stability and performance of Si-based anodes. The optimization of the compounding process has the potential to enhance the performance of silicon anodes by addressing the significant volume change and low conductivity, while simultaneously addressing cost-related concerns.

Is Microporous Carbon Confined Nano Si Composite the Best Anode Choice for High-Energy-Density Lithium-Ion Batteries?

Microporous carbon confined nano silicon composites (Si/m-C) are considered to be the best anode materials for high-energy-density lithium-ion batteries compared with the other Si-based materials such as SiO, due to high initial Coulombic efficiency (ICE) and capacity, as well as good cycling stability. However, there is a lack of multilevel comprehensive evaluation of Si/m-C, which poses potential risks to the commercial application. Herein, combined with quantitative titration, mechanical characterization, and bulk/interface evolution analysis, a systematic evolution of commercialized Si/m-C from the particle level to the cylindrical cell level is conducted, revealing the decay mechanism and proposing corresponding solutions. Among them, it is well demonstrated that the Si/m-C still withstands huge volume expansion of over 200% with poor mechanical strength, causing the electrical contact loss of active LixSi and severe interfacial side reactions. Moreover, even blending more than 90% graphite cannot completely suppress its volumetric strain, and the combination of highly flexible single-walled carbon nanotubes (SWCNT) is necessary. In response to this, the 32700-type cylindrical cell with a designed capacity of 9.5 Ah is assembled by mixing Si/m-C with 90% graphite and SWCNT as anode, achieving a long-term cycling stability over 300 cycles at 0.5C with a capacity retention of 94.8%.

A Microstructure Resolved Multi-Material Model for Silico-Graphite Composite Electrode

Silicon (Si) has been considered as the most promising anode material for next-generation high-capacity Li-ion batteries due to its very high theoretical specific capacity. However, the large deformation associated with (de)lithiation and its detrimental consequences like pulverization, loss of electrical contact, and subsequent capacity loss, have long been a roadblock in deploying high-capacity electrodes. Grafting small amounts of Si with graphite has been proven to utilize the higher capacity of silicon and the stability of graphite. The intricacies of interactions between the two active materials and their effect on the overall performance of the composite electrode are still not well known. Here, we present a novel fully coupled multiphysics electrochemical-mechanical model based on 3D microstructure extracted from X-ray tomography scans of Si-C composite electrode. The theoretical framework integrates the large deformation and viscoplastic response of Si, and the two-way coupling between diffusion and interfacial reactions with mechanical stress. The resolution of the pore phase from the silicon and graphite phases allows for the simulation of the Li+ ion kinetics in the composite electrode and influence of the microstructure. The model is employed to study the phenomena of preferential lithiation, crosstalk between active materials, partial utilization due to mechanical influences, and develop strategies to maximize the specific capacity. Lastly, we also explore the potential and avoidance of mechanical damage within active materials and interfacial delamination. The first-of-its-kind 3D microstructure resolved, multi-material model presents a novel tool to simulate the performance of Si-C composite electrode and decode the depth of interactions between the active materials.

Enhanced Structure/Interfacial Properties of Single‐Crystal Ni‐Rich LiNi0.92Co0.04Mn0.04O2 Cathodes Synthesized Via LiCl‐NaCl Molten‐Salt Method

Arising from the increasing demand for electric vehicles (EVs), Ni‐rich LiNixCoyMnzO2 (NCM, x + y + z = 1, x ≥ 0.8) cathode with greatly increased energy density are being researched and commercialized for lithium‐ion batteries (LIBs). However, parasitic crack formation during the discharge–charge cycling process remains as a major degradation mechanism. Cracking leads to increase in the specific surface area, loss of electrical contact between the primary particles, and facilitates liquid electrolyte infiltration into the cathode active material, accelerating capacity fading and decrease in lifetime. In contrast, Ni‐rich NCM when used as a single crystal exhibits superior cycling performances due to its rigid mechanical property that resists cracking during long charge–discharge process even under harsh conditions. In this paper, we present comparative investigation between single crystal Ni‐rich LiNi0.92Co0.04Mn0.04O2 (SC) and polycrystalline Ni‐rich LiNi0.92Co0.04Mn0.04O2 (PC). The relatively improved cycling performances of SC are attributed to smaller anisotropic volume change, higher reversibility of phase transition, and resistance to crack formation. The superior properties of SC are demonstrated by in situ characterization and battery tests. Consequently, it is inferred from the results obtained that optimization of preparation conditions can be regarded as a key approach to obtain well crystallized and superior electrochemical performances.

How Ammonium Valeric Acid Iodide Additive Can Lead to More Efficient and Stable Carbon‐Based Perovskite Solar Cells: Role of Microstructure and Interfaces?

As perovskite photovoltaic devices can now compete with silicon technology in terms of efficiency, many strategies are investigated to improve their stability. In particular, degradation reactions can be hindered by appropriate device encapsulation, device architecture, and perovskite formulation. Mesoporous device architectures with a carbon electrode offer a plausible solution for the future commercialization of perovskite solar cells. They represent a low‐cost and stable solution with high potential for large‐scale production. Several studies have already demonstrated the potential of the mixed 2D/3D ammonium valeric acid iodide‐based MAPbI3 formulation to increase the lifetime of pure MAPbI3. They can however not describe the mechanisms responsible for the lifetime improvement. Using a full set of characterization techniques in the initial state and as a function of time during damp‐heat aging, new insights into the performance and degradation mechanisms may be observed. With (5‐AVA)0.05MA0.95PbI3, the solar cells are very stable up to 3500 h and the degradation of performances essentially results from the loss of electrical contacts mainly located at the interfaces. In contrast, for the neat MAPbI3, a poor stability is evidenced (T50 = 500 h) and the loss in performance results from the degradation of the bulk perovskite layer itself.

Assembled MXene-Liquid Metal Cages on Silicon Microparticles as Self-Healing Battery Anodes.

In pursuit of higher energy density in lithium-ion batteries, silicon (Si) has been recognized as a promising candidate to replace commercial graphite due to its high theoretical capacity. However, the pulverization issue of Si microparticles during lithiation/delithiation results in electrical contact loss and increased side reactions, significantly limiting its practical applications. Herein, we propose to utilize liquid metal (LM) particles as the bridging agent, which assemble conductive MXene (Ti3C2Tx) sheets via coordination chemistry, forming cage-like structures encapsulating mSi particles as self-healing high-energy anodes. Due to the integration of robust Ti3C2Tx sheets and deformable LM particles as conductive buffering cages, simultaneously high-rate capability and cyclability can be realized. Post-mortem analysis revealed the cage structural integrity and the maintained electrical percolating network after cycling. This work introduces an effective approach to accommodate structural change via a resilient encapsulating cage and offers useful interface design considerations for versatile battery electrodes.

Origins and Importance of Intragranular Cracking in Layered Lithium Transition Metal Oxide Cathodes.

Li-ion batteries have a pivotal role in the transition toward electric transportation. Ni-rich layered transition metal oxide (LTMO) cathode materials promise high specific capacity and lower cost but exhibit faster degradation compared with lower Ni alternatives. Here, we employ high-resolution electron microscopy and spectroscopy techniques to investigate the nanoscale origins and impact on performance of intragranular cracking (within primary crystals) in Ni-rich LTMOs. We find that intragranular cracking is widespread in charged specimens early in cycle life but uncommon in discharged samples even after cycling. The distribution of intragranular cracking is highly inhomogeneous. We conclude that intragranular cracking is caused by local stresses that can have several independent sources: neighboring particle anisotropic expansion/contraction, Li- and TM-inhomogeneities at the primary and secondary particle levels, and interfacing of electrochemically active and inactive phases. Our results suggest that intragranular cracks can manifest at different points of life of the cathode and can potentially lead to capacity fade and impedance rise of LTMO cathodes through plane gliding and particle detachment that lead to exposure of additional surfaces to the electrolyte and loss of electrical contact.

Tailored Yolk-Shell Design to Silicon Microparticles via Scalable and Template-Free Synthesis for Superior Lithium Storage.

Micrometer-sized Si particles are beneficial to practical lithium-ion batteries in regard to low cost and high volumetric energy density in comparison with nanostructured Si anodes. However, both the issues of electrical contact loss and overgrowth of solid electrolyte interface for microscale Si induced by colossal volume change still remain to be addressed. Herein, a scalable and template-free method is introduced to fabricate yolk-shell structured Si anode from commercially available Si microparticles. The void is created via a one-step alkali etching process with the remaining silicon core as the yolk, and a double-walled shell is formed from simultaneous in situ growth of the conformal native oxide layer and subsequent carbon coating. In this configuration, the well-defined void spaces allow the Si core to expand without compromising structural integrity, while the double-walled shell acts as a static capsule to confine silicon fragments despite likely particle fracture. Therefore, electrical connectivity is maintained on both the particle and electrode level during deep galvanostatic cycling, and the solid-electrolyte interface is stabilized on the shell surface. Owing to the benefits of tailored design, excellent cycling stability (capacity retention of 95% after 100 cycles) and high coulombic efficiency (99.5%) are realized in a practical full-cell demonstration.

High performance carboxymethyl cellulose- polyethylene oxide polymer binder for black phosphorus anode in lithium-ion batteries

Black phosphorus (BP) is regarded as a promising anode material due to its high theoretical specific capacity and fast charging safety. However, the problems of huge volume expansion and moderate electrical conductivity may restrict its performance. In this work, we present a novel 3D network binary polymer binder synthesized from carboxymethyl cellulose (CMC) and polyethylene oxide (PEO) for adapt to lithium-ion batteries of BP and graphite (G) composite anode (BP-G). There are the following characteristics of the binder: CMC and PEO are crosslinked through intermolecular forces; while CMC and PEO are connected to BP through strong intermolecular forces, respectively; BP and graphite are connected through PC and POC bonds to form composite anode. So as to form a sturdy structure and effectively accommodate the volume expansion of BP during charging-discharging processes, while avoiding loss of electrical contact between electrode components. Accordingly, the lithium-ion battery shown an excellent electrochemical performance, such as a high initial discharge capacity of 1602 mA h g−1 at 0.5 A/g.

Modification of Layered Cathodes of Sodium-Ion Batteries with Conducting Polymers

Layered oxides exhibit interesting performance as positive electrodes for commercial sodium-ion batteries. Nevertheless, the replacement of low-sustainable nickel with more abundant iron would be desirable. Although it can be achieved in P2-Na2/3Ni2/9Fe2/9Mn5/9O2, its performance still requires further improvement. Many imaginative strategies such as surface modification have been proposed to minimize undesirable interactions at the cathode–electrolyte interface while facilitating sodium insertion in different materials. Here, we examine four different approaches based on the use of the electron-conductive polymer poly(3,4-ethylene dioxythiophene) (PEDOT) as an additive: (i) electrochemical in situ polymerization of the monomer, (ii) manual mixing with the active material, (iii) coating the current collector, and (iv) a combination of the latter two methods. As compared with pristine layered oxide, the electrochemical performance shows a particularly effective way of increasing cycling stability by using electropolymerization. Contrarily, the mixtures show less improvement, probably due to the heterogeneous distribution of oxide and polymer in the samples. In contrast with less conductive polyanionic cathode materials such as phosphates, the beneficial effects of PEDOT on oxide cathodes are not as much in rate performance as in inhibiting cycling degradation, due to the compactness of the electrodes without loss of electrical contact between active particles.

Degradation Diagnostics of Ni-Rich NMC in Lithium-Ion Batteries Aged in Different Degrading Conditions

Ni-rich Nickel Manganese Cobalt Oxides (NMC) such as LiNi0.6Mn0.2Co0.2O2 (NMC622) and LiNi0.8Mn0.1Co0.1O2 (NMC811) have been widely used as the cathode active materials in lithium-ion batteries (LIB) of electric vehicles due to their high capacity. Thus, we can foresee millions of tons of end-of-life LIB will be accumulated by the next decades. This means that the efficient recycling method of batteries material, especially NMC which has the highest value, should be developed to reduce the cost and increase the efficiency of recycling. Direct recycling which is a novel method to recover cathode active materials in lithium-ion batteries by directly regenerating the chemical and physical structure of cathode materials, skipping the usage of harsh chemical and high energy consumption such as those of other recycling methods i.e. pyrometallurgy and hydrometallurgy. Such an attempt to directly reprocess the spent NMC back into the as good as new cathode requires and understanding what has happened with the materials through the battery life. This implies that the understanding of degradation mechanisms of Ni-rich NMC in different usage conditions is required to up-scale the direct recycling of Ni-rich NMC from degraded lithium-ion batteries.In this work, we investigated failure mode in controlled aged samples of LIB cells to understand the degradation mechanism of NMC622 and NMC811 which are to be connected with the method for direct regeneration. Lithium-ion batteries composed of NMC622 or NMC811 cathode active materials were aged through 1C-rate charge/discharge cycling at 25°C, 45°C or 55°C until 20% or 40% capacity fading. The degraded cells were analyzed via incremental capacity analysis (ICA), volume change measurement, electrochemical impedance spectroscopy (EIS). Ex-situ X-ray powder diffraction (XRD), Scanning electron microscopy analysis (SEM), X-ray photoelectron spectroscopy (XPS) and Inductively Coupled Plasma Optical Emission spectroscopy (ICP-OES) were used to characterize the chemical and physical structure of degraded NMC from each different degrading conditions.Inspection of degraded cells shows that NMC811 cells exhibit larger cell expansion compared to NMC622 cells going through the same degrading condition. EIS results show that the solution resistance (R S) does not vary much between the different cells, while solid-electrolyte interphase resistances (R SEI) were found to increase with temperature at approximately similar level for both NMC622 and NMC811. Fig. 1a and Fig. 1b show the contour plot on the variation of charge transfer resistance (R CT) ratio after and before degradation of NMC622 and NMC811 cells. It can be seen that R CT in NMC811 cells were found to increase for the more highly cycled NMC811 coupled with high temperature. However, temperature does not seem to have much role in the increment of R CT in NMC622. Investigating the change in structure of the cycled NMCs at different temperatures and to level of different degradation, it was found that the results show that at the same level of capacity remaining, NMC622 has a much larger change in c/a ratio after vs. before compared to NMC811.The above impedance analysis coupled with the XRD results imply that the main cause of capacity fade of NMC811 cells is likely due to electrolyte decomposition which generates gas, resulting in high degree of cell expansion, causing loss of electrical contact. The electrolyte decomposition in NMC811 cell is further facilitated by the increment of temperature due to the lower onset potential limit for gas evolution in NMC811, causing more capacity fading in NMC811 cell at high temperature [1]. On the other hand, the capacity fading in NMC622 cells is mainly from the chemical/structural change in the cycled NMC622 cathode.These insight information on the degradation mechanism of LIB cells and structural variation of Ni-rich NMC after ageing in each degrading condition is then further inspected to elucidate the method to effectively directly regenerate both NMC622 and NMC811 cathode in the spent Li-ion batteries.

Dilatometric Investigation of Si-Rich Contacting Anode Under External Pressure

Silicon with high abundance and high gravimetric capacity around 3579 mAh.g-1 at Li15Si4 fully lithiated state [1] is one of the attractive anode materials in lithium-ion batteries. Volume expansion of around 300% in the fully intercalated state is the Achilles’ heel of silicon, causing particle pulverisation, continuous formation of solid electrolyte interface (SEI), loss of electrical contact and capacity loss.[2] The use of silicon composite instead of pure silicon, [1,3] limited de/lithiation,[4] and boosting the electrical connection between particles by applying optimal external pressure[5] are practical solutions to mitigate these disadvantages. This study investigates the electrochemical performance and the dilatometric behaviour of a multilayer pouch cells (0.06 to 1.5 Ah) under the external mechanical pressure. Using 1/3 of the Si capacity in order to stabilise the electrochemical performance of a high silicon content anode (70 wt% Si). An irreversible electrode expansion of about 20% after 3 cycles of formation at 0.1C and a 75% electrode thickening after 200 cycles at 0.5C were observed.

Ultrafast Laser Patterning of Silicon/Graphite Composite Electrodes to Boost Battery Performance

The ever-increasing share of electric vehicles in the mobility sector urgently calls for an increase in the production capacity of high-power and high-energy lithium-ion batteries with low production costs. A gravimetric energy density of about 350 Wh/kg flanked by a volumetric energy densities of at least 750 Wh/L were defined as ambitious goals from the European Union to be achieved by 2025. For this purpose, novel, high-capacity anode materials containing significant silicon content should be utilized in next generation batteries. At room temperature, silicon has a theoretical specific capacity of 3579 mAh/g which is one order of magnitude higher compared to the state-of-the-art graphite anode material (372 mAh/g). The volume change which silicon undergoes during lithiation and delithiation and the thereby caused mechanical stresses inside the composite electrode, which lead to loss of electrical contact and delamination, are an obstacle for its implementation in industrial battery production. While many researchers focus on other promising approaches to facilitate the usage of silicon in electrodes, for example pre-lithiation, the usage of graphite-silicon composites, or carbon coating on the silicon particles, here, the implementation of additional porosity via laser patterning is pursued. A water-based silicon/graphite slurry concept for the large-scale electrode production is used. There, the silicon nanoparticles’ agglomerates are destroyed and the silicon is finely dispersed using a ball mill, while the slurry homogenization is finalized using a disk stirrer. This facilitates the production of electrode sheets on a roll-to-roll coater, delivering enough material for the high power, high repetition rate roll-to-roll laser patterning process, both of which exhibit a technology readiness level of 5 to 6. The slurry and electrode characterizations are performed using laser induced breakdown spectroscopy (LIBS) for both the binder and lithium spatial distribution, the cyclability and lifetime of the electrodes is assessed in pouch cells with NMC 622 as counter electrode, and the lithiation of the composite material is determined with cyclic voltammetry. Scanning electron, digital and light microscopy are used for the characterization of the laser patterning, while chemical analysis is used to assess the composition of the electrode and the silicon oxidation during water-based manufacturing.

Superionic Conductor Enabled Composite Lithium with High Ionic Conductivity and Interfacial Wettability for Solid‐State Lithium Batteries

AbstractThe urgent demand for high energy and safety batteries has generated the rapid development of Li6.4La3Zr1.4Ta0.6O12 (LLZTO) type solid‐state lithium metal batteries. However, severe dendritic lithium growth, which is caused by poor interfacial contact of the Li/LLZTO interface and loss of electrical contact during cycles due to low intrinsic Li+ diffusion coefficient of lithium, greatly hampers its practical application. Here, from the point of view of reducing surface tension and improving ion diffusion of lithium, a composite lithium anode (CLA) with high wettability and ion diffusion coefficient is prepared by adding GaP into molten lithium, thus strengthening the CLA/LLZTO interface even in cycling. As envisioned, compared to pure lithium, CLA presents lower surface tension, larger adhesion work, and higher ion diffusion coefficient, ensuring close contact of the CLA/LLZTO interface. Therefore, the assembled symmetric cells exhibit a low area specific resistance of 4.5 Ω cm2, a large critical current density of 2.5 mA cm−2, and ultra‐long lifespan of 5700 h at 0.3 mA cm−2 at 25 °C. Meanwhile, full cells coupled with LiFePO4 cathode show a high‐capacity retention of 97.32% after 490 cycles at 1C. This work provides a new solution to the interfacial challenges of solid‐state lithium‐metal batteries.

A stress-adaptive interlinked 3D network binder for silicon anodes via tailored chemical bonds and conformation of functionalized poly(vinylidene fluoride) (PVDF) terpolymers

Lithium-ion batteries (LIBs) incorporating silicon (Si) anodes offer high energy density; however, they confront challenges arising from large volumetric fluctuations during charge/discharge processes. This leads to the pulverization of the Si particles and loss of electric contact in the Si anodes, resulting in reduced cycle stability and degraded capacity retention. Herein, we propose a conceptually designed binder strategy for chemically modified poly(vinylidene fluoride) (PVDF) by introducing double bonds into the PVDF terpolymer (denoted as PVTD), which can produce crosslinked 3D-network structures (denoted as PVTDX) through a simple heat treatment during the anode fabrication process. Notably, the presence of randomly distributed double bonds in PVTD induces irregular conformations, reducing the crystallinity of PVTD by impairing intra- and inter-chain interactions, which in turn improved the solubility of PVTD in organic solvents such as N-methyl-2-pyrrolidone (NMP) and enabled uniform dispersion of PVTD in the Si anode composition. Additionally, PVTD exhibits a strong affinity for electrolytes and considerable chemical and thermal stability owing to the presence of fluorine atoms. Notably, PVTDX effectively mitigates volumetric changes in Si particles because of its enhanced adhesive force and robust network structure. By leveraging these advantageous characteristics of the PVTDX binder, the structural integrity of the Si anode is in good preservation during cycling, resulting in enhanced specific capacity and reliable long-term cycling performance. This innovative and pragmatic design holds significant promise for advancing the development of high-performance Si-anode-based LIBs.

Sulfonic Group Modified Binder Endows Rapid Lithium‐Ion Diffusion for SiOx Microparticle Anode

Silicon‐based materials have been regarded as the most flourishing anode materials owing to the incomparable specific capacity. However, their commercial application is obstructed by huge volume expansion and particle pulverization, which subsequently lead to the stress concentration and the loss of electrical contact, eventually resulting in poor cycling stability and lousy rate performance. Herein, an ion‐conductive binder with boosted ion‐conductivity is proposed by free radical polymerization between acrylic acid and lithiated 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (LiAMPS). With the aid of ample sulfonic acid anionic groups, rapid lithium‐ion diffusion can be achieved to improve the transport kinetics and rate performance. Meanwhile, superior mechanical properties of binder can alleviate the stress concentration to avoid particle pulverization by noncovalent hydrogen bond. The synergistic strategy of constructing lithium‐ion diffusion pathway and alleviating the stress concentration can make a preeminent improvement on Li+ diffusion coefficient and maintain a high structural integrity of electrode. Benefiting from the synergistic effect, the SiOx microparticle anode delivers a high capacity of 587.8 mAh g−1 after 400 cycles at 1C and preeminent rate performance of 648.6 mAh g−1 at 5C. Such a synergistic design strategy endows P(AA‐co‐LiAMPS) binder with a promising potential for high energy density silicon‐based anodes.

3D-printed, aptamer-based microneedle sensor arrays using magnetic placement on live rats for pharmacokinetic measurements in interstitial fluid

Molecular monitoring in the dermal interstitial fluid (ISF) is an attractive approach to painlessly screen markers of health and disease status on the go. One promising strategy for accessing ISF involves the use of wearable patches containing microneedle sensor arrays. To date, such microneedle sensors have been fabricated via various manufacturing strategies based on injection molding, machining, and advanced lithography to name a few. Our groups previously reported 3D-printed microneedles as a convenient and scalable approach to sensor fabrication that, when combined with aptamer-based molecular measurements, can support continuous molecular monitoring in ISF. However, the original platform suffered from poor patch stability when deployed on the skin of rodents in vivo. We identified that this problem was due to the rheological properties of the rodent skin, which can contract post microneedle placement, physically pushing the microneedles out of the skin. This sensor retraction caused a loss of electrical contact between working and reference needles, irreversibly damaging the sensors. To address this problem, we report here an innovative approach that allows magnetic placement of microneedle sensor arrays on the skin of live rodents, affixing the patches under light pressure that prevents needle retraction. Using this strategy, we achieved sensor signaling baselines that drift at rates comparable to those seen with other in vivo deployments of electrochemical, aptamer-based sensors. We illustrate real-time pharmacokinetic measurements in live Sprague-Dawley rats using SLA-printed, aptamer-functionalized microneedles and demonstrate their ability to support drift correction via kinetic differential measurements. We also discuss future prospects and challenges.

Expanding the Potential of Identical Location Scanning Transmission Electron Microscopy for Gas Evolving Reactions: Stability of Rhenium Molybdenum Disulfide Nanocatalysts for Hydrogen Evolution Reaction.

Identical location (scanning) transmission electron microscopy provides valuable insights into the mechanisms of the activity and degradation of nanocatalysts during electrochemical reactions. However, the technique suffers from limitations that hinder its widespread use for nanocatalysts of gas evolving reactions, e.g., the hydrogen evolution reaction (HER). The main issue is the production of bubbles that cause the loss of electric contact in identical location measurements, which is critical for the correct cycling of the nanocatalysts and interpretation of the electron microscopy results. Herein, we systematically evaluate different set-ups, materials, and tools to allow the facile and reliable study of the stability of HER nanocatalysts. The optimized conditions are applied for the study of layered rhenium molybdenum disulfide (Re0.2Mo0.8S2) nanocatalysts, a relevant alternative to Pt catalysts for the HER. With our approach, we demonstrate that although the morphology of the Re0.2Mo0.8S2 catalyst is maintained during HER, chemical composition changes could be correlated to the electrochemical reaction. This study expands the potential of the IL(S)TEM technique for the construction of structure-property relationships of nanocatalysts of gas evolving reactions.

Pristine SWCNT Based Cathode Materials for Solid-State Li-Sulfur Batteries

Lithium-Sulfur is a long-studied, but yet to be practically implemented battery chemistry which carries a promise of creating high energy density batteries. It uses cheap and abundant materials, but faces major technological challenges. One of the key challenges is that sulfur as the cathode material has negligible electronic conductivity (5x10-28 S/m), preventing electron exchange in the cathode during battery charge/discharge cycling. The other challenge is the significant (up to 80%) volume changes of sulfur during battery cycling that leads to cracking, delamination, voids formation and loss of electrical contacts, therefore limiting battery durability. To overcome these problems, we have developed a solution-free technology of manufacturing composite self-standing electrodes by in-situ mixing of the aerosolized phases and co-deposition [1]. The electrodes consist of sulfur and catholyte particles imbedded in a 3D network of as grown, pristine single-walled carbon nanotubes. The electrodes are flexible and do not include current collector metal foils or binders. They can be produced up to 1 mm thick, up to 200 mgsulfur/cm2 loading, or 330 mAh/cm2 capacity without the loss of the SWCNT network 3D structure. The macroscopic electrical conductivity of the material increases 30 orders of magnitude compared to that of sulfur, and reaches 102-104 S/m, depending on the SWCNT concentration. The presence of SWCNT network not only solves the electrical conductivity challenge but also durability issue, since flexible/stretchable SWCNT network accommodates the volume change of the sulfur active particles without disruption of the cathode integrity. The electrodes fabricated by this method are being studied as perspective cathodes for solid-state LiS batteries. A. Kuznetsov, S. Mohanty, E. Pigos, G. Chen, W. Cai, A.R. Harutyunyan, High energy density flexible and ecofriendly lithium-ion smart battery. Energy Storage Materials, 2023 (54) 266-275, ISSN 2405-8297, doi.org/10.1016/j.ensm.2022.10.023

A Multifunctional Interlocked Binder with Synergistic In Situ Covalent and Hydrogen Bonding for High-Performance Si Anode in Li-ion Batteries.

Silicon has garnered significant attention as a promising anode material for high-energy density Li-ion batteries. However, Si can be easily pulverized during cycling, which results in the loss of electrical contact and ultimately shortens battery lifetime. Therefore, the Si anode binder is developed to dissipate the enormous mechanical stress of the Si anode with enhanced mechanical properties. However, the interfacial stability between the Si anode binder and Cu current collector should also be improved. Here, a multifunctional thiourea polymer network (TUPN) is proposed as the Si anode binder. The TUPN binder provides the structural integrity of the Si anode with excellent tensile strength and resilience due to the epoxy-amine and silanol-epoxy covalent cross-linking, while exhibiting high extensibility from the random coil chains with the hydrogen bonds of thiourea, oligoether, and isocyanurate moieties. Furthermore, the robust TUPN binder enhances the interfacial stability between the Si anode and current collector by forming a physical interaction. Finally, the facilitated Li-ion transport and improved electrolyte wettability are realized due to the polar oligoether, thiourea, and isocyanurate moieties, respectively. The concept of this work is to highlight providing directions for the design of polymer binders for next-generation batteries.