Electrolyte Consumption Research Articles

Degradation Effects in Li4Ti5O12-Based Cells─Learning from Electrode Potential Profiles.

Li4Ti5O12 (LTO) is a promising negative electrode active material for high-power applications of lithium-ion batteries due to its structural and dimensional stability, high safety properties, and rate capability. However, there are still challenges regarding the cyclic aging behavior of LTO-based cells, especially when it comes to the origin of gas evolution that needs to be resolved in order to enable an optimized cell design and prolonged cycle life. Using a three-electrode setup provides operando insights into the cyclic aging behavior of LiNi1/3Co1/3Mn1/3O2 (NCM111)||LTO cells. The results demonstrated that an initial slight increase in specific capacity followed by an intense decrease after 40 cycles could be attributed to a relative shift of the individual electrode potential profiles caused by loss of lithium inventory and associated electrolyte consumption during cyclic aging. By using higher formation temperatures, the capacity decrease, an associated loss of lithium inventory, and continuous electrolyte consumption were successfully suppressed. Moreover, the results suggested that gas evolution in Li4Ti5O12-based cells majorly originates from the reductive decomposition of moisture residues and the electrolyte at the Li4Ti5O12 electrode surface.

On the Volume Expansion of Lithium Ion Battery Electrodes (I) after Wetting, and (II) Selection of the Right Amount of Electrolyte

The electrolyte is necessary for transport of lithium ions between the negative and positive electrode within the battery cell. The lower the amount of electrolyte, the higher the energy density and specific energy. Hence, it is important to understand which cell parameters are relevant to determine the right amount of electrolyte. Here, three different cell designs in 1 to 5 Ah pouch cells where investigated for cell impedance after filling, cell capacity after formation, C-rate performance, and capacity retention for up to 3,000 full cycles. Wetting the cell with electrolyte, the cell pore volume changed between 25%–35% due to changes of 6%–16% in the thickness of the anode and cathode. Although electrolyte volumes >0.85 times the wet cell pore volume showed minimal resistance before formation, only electrolyte volumes of 1.08 times the wet cell pore volume were sufficient for a successful formation process. For long-term cycling, a minimum electrolyte volume of 1.19 times the wet cell pore volume was required to improve long-term cycling performance. Future experiments will investigate the correlation of capacity fade with electrolyte consumption for different electrolytes.

Diagnosis of lithium-ion batteries degradation with P2D model parameters identification: a case study on low temperature charging

The estimation of the state of health (SoH) of a lithium-ion battery is still a hot topic in the scientific research. This publication deals with the combined use of optimized tests, also involving impedance spectroscopy, and physical models to investigate lithium-ion batteries degradation. As a case study, this method is firstly applied on a low-temperature charging degradation campaign, in order to expectedly generate a lithium plating-dominated ageing state. Degradation tests, performed under previously selected combinations of operating conditions, are performed down to 75% SoH on commercial samples, determining severe ageing rate up to 1.5% capacity loss per equivalent full cycle. The proposed interpretation methodology identifies the ageing to be dominated by the loss of lithium inventory, consistently with the expected degradation mechanism. Large electrolyte consumption is also detected, which induces a strongly anisotropic utilization of the electrodes during discharge, as confirmed by pseudo-two-dimensional (P2D) model simulations.This activity contributes to verify the reliability of the methodology, elucidate the effect of lithium plating on the performance and underline the effect of the operating conditions at low temperature, paving the way to the application on real-world conditions.

Ameliorating the sodium storage performance of hard carbon anode through rational modulation of binder

Hard carbon anodes have emerged as promising candidates for sodium-ion batteries due to their inherent advantages. Nevertheless, the surface imperfections in these materials often culminate in irreversible electrolyte consumption, fostering the development of a heterogeneous and fragile solid electrolyte interface (SEI), thereby compromising the initial Coulombic efficiency (ICE). Drawing inspiration from the catalytic potential of C=O (carbonyl) bonds in directing preferential salt reduction, we introduce a novel strategy that leverages the modulation of the binder, a long-term overlooked pivotal components in the electrode process. Specifically, Polymethyl methacrylate (PMMA), abundant in C=O groups, is partially substituted for PVDF, ensuring robust adhesion of the electrode material to the current collector while preserving superior mechanical properties. The accurate combination of two binders with delightful compatibility in the state-of-art electrode process, can promote a uniform formation of the SEI on the hard carbon surface enriched in inorganic components, which can ensure long-term interfacial stability and suppresses excessive solvent decomposition and facilitates Na+ transfer at the interface. Consequently, the initial Coulombic efficiency of the hard carbon anode with 70 %PMMA binder achieves 86 %, with prominent cycling stability (88 % capacity retention over 500 cycles) at a high current density of 1.2 A g−1. When paired with high loading cathodes to assemble the pouch cell, it also demonstrates stable operational scenarios.

Understanding the Effect of Lithium Nitrate as Additive in Carbonate-Based Electrolytes for Silicon Anodes

Due to its high specific capacity, silicon is one of the most promising anode materials for next-generation lithium-ion batteries. However, its large volumetric changes upon (de)lithiation of ∼300% lead to a rupture/re-formation of the solid-electrolyte interphase (SEI) upon cycling, resulting in continuous electrolyte consumption and irreversible loss of lithium. Therefore, it is crucial to use electrolyte systems that form a more stable SEI that can withstand large volume changes. Here, we investigate lithium nitrate (LiNO3) and lithium nitrite (LiNO2) as electrolyte additives. Linear scan voltammetry on carbon black working electrodes in a half-cell configuration with LiNO3-containing 1 M LiPF6 in EC/DEC (1/2 v/v) revealed a two-step reduction mechanism, whereby the first reduction peak could be attributed to the conversion of LiNO3 to LiNO2, while X-ray photoelectron spectroscopy on harvested electrodes suggests the formation of Li3N during the second reduction peak. On-line electrochemical mass spectrometry (OEMS) on carbon black electrodes showed that N2O gas is evolved upon the reduction of LiNO3- and LiNO2-containing electrolytes but that the gassing associated with EC reduction is significantly reduced. Furthermore, OEMS and voltammetry were used to examine the redox chemistry of LiNO2 additive. Finally, LiNO3 and LiNO2 additives significantly improved the cycle-life of Si||NCM622 full-cells.

Modification of LiMn2O4 Cathodes to Boost Kinetics Match via rGO for High-Performance Rocking-Chair Lithium-Ion Capacitors.

The rocking-chair lithium-ion capacitors (RLICs), composed of a battery-type cathode and capacitive-type anode, alleviates the issue of increased internal resistance caused by electrolyte consumption during the cycling process of the lithium-ion capacitors (LICs). However, the poor conductivity of cathode materials and the mismatch between the cathode and anode are the key issues that hinder its commercial application. In this work, a modification simplification strategy is proposed to tailor the conductivity of the cathode and matching characteristic with the anode. The in situ grown lithium manganate (LMO) is featured with a three-dimensional conductive network constructed by reduced graphene oxide (rGO). The optimized LMO/rGO composite cathode demonstrates an excellent rate performance, lithium-ion diffusion rate, and cycling performance. After assembling an RLICs with activated carbon (AC), the RLICs exhibits an energy density of as high as 239.11 Wh/kg at a power density of 400 W/kg. Even at a power density of 200 kW/kg, its energy density can maintain at 39.9 Wh/kg. These excellent electrochemical performances are mainly attributed to the compounding of LMO with rGO, which not only improves the conductivity of the cathode but also realizes a better matching with the capacitive-type anode. This modification strategy provides a reference for the further development of energy storage devices suitable for actual production conditions and application scenarios.

(Invited) Development of Mildly Acidic Aqueous Zinc Batteries: Anode, Cathode, and Electrolyte

Aqueous zinc batteries use earth abundant materials and has stable supply chains, making them one of the promising battery technologies for grid-scale energy storage applications. However, the limited cycle life because of the dendrite formation of zinc anodes, poor reversibility of cathodes, and consumption of electrolyte has greatly hampered its practical application. Recently, extensive research effort has been made on the development of rechargeable alkaline batteries and mildly acidic zinc ion batteries. Novel structured zinc anodes, intercalation cathode materials and new electrolytes have been developed to improve the performance. Here, we would like to present our effort towards aqueous zinc batteries under practical conditions. Zinc alloy anodes, organic cathode materials, and the use of new binders and electrolyte additives will be discussed.

A Coupled NMR and Differential Capacity Study of the Consumption of Electrolyte and Additive Components during the Formation Cycle of Li-Ion Pouch Cells

Understanding the side reactions occurring inside lithium-ion cells remain a significant challenge, presenting opportunities for innovation. In this context, we developed a coupled 1H NMR (nuclear magnetic resonance) and dQ/dV (differential capacity) analysis method aimed at enhancing our understanding of these reactions during the formation cycle. Using deuterated acetonitrile as an extraction solvent, we measured the relative consumption of electrolyte components inside different electrolyte, including in 1.2M LiPF6 EC:EMC 3:7 2% VC and 1.2M LiPF6 EC:EMC 3:7 2% VC + 1% DTD electrolytes at different voltage. Our NMR observations were subsequently compared with electrochemical data to better understand and validate the results. These findings offer valuable insights into lithium-ion cell dynamics and mark a significant step towards the advancement of diagnostic techniques.

Uncovering Reduction Mechanisms of Fluoroethylene Carbonate

Energy storage plays an integral role in climate change mitigation, given that many promising alternatives to fossil fuel-based technologies rely on intermittent energy sources like the sun or wind. Particularly, lithium metal batteries (LMBs) are a promising technology due to lithium’s high theoretical specific capacity and low reduction potential, which can result in batteries with energy densities surpassing current state of the art lithium-ion batteries.1 Electrolyte design is a key strategy to improve the cycling stability and Coulombic efficiency of LMBs, where the highly reductive lithium metal anode reacts with the electrolyte during cycling, resulting in capacity loss. These reactions form a solid electrolyte interphase (SEI), and many successful electrolyte engineering strategies have involved tuning the SEI to be mechanically and chemically stable to prevent further reactions.In this research, we focus on fluoroethylene carbonate (FEC), a highly effective electrolyte solvent in LMBs.2 Although prior research has illuminated key reduction products of FEC2,3, including lithium fluoride (LiF), there remains a gap in understanding regarding the mechanism by which FEC and other similar fluorinated solvents are reduced to form an SEI. Furthermore, recent research has demonstrated that a preformed SEI comprised solely of LiF breaks down during cycling, illustrating that bulk chemical and mechanical properties of SEI components may not translate to their function within the SEI.4 In this work, we employ electron paramagnetic resonance (EPR) spectroscopy to study intermediate generation during FEC reduction. We pursued both a chemical reduction using lithium naphthalenide and an electrochemical approach to reduce FEC. The use of EPR with spin traps enables insight into the radical species formed during FEC reduction, which we hypothesize are precursors to cross-linked polymer networks that are key to a high performing SEI. Here, we employed conventional post-mortem SEI analysis like X-ray Photoelectron Spectroscopy (XPS) in addition to EPR to clarify reduction mechanisms of FEC and form a framework for studying electrolyte reduction intermediates. Ultimately, this approach affords insight into electrolyte breakdown mechanisms to form an effective SEI which can both accommodate volume expansion and inhibit parasitic electrolyte consumption. This will guide electrolyte design for high Coulombic efficiency LMBs in the future.References K. G. Gallagher et al., Energy Environ. Sci., 7, 1555–1563 (2014).X.-Q. Zhang, X.-B. Cheng, X. Chen, C. Yan, and Q. Zhang, Advanced Functional Materials, 27, 1605989 (2017).Y. Jin et al., J. Am. Chem. Soc., 139, 14992–15004 (2017).M. He, R. Guo, G. M. Hobold, H. Gao, and B. M. Gallant, Proceedings of the National Academy of Sciences, 117, 73–79 (2020).

Deciphering the Impact of Current, Composition, and Potential on the Lithiation Behavior of Graphite in Silicon-Graphite Anodes

Graphite is the most used anode material for current-generation lithium-ion batteries due to its beneficial cycle life, availability and reasonable rate capability. Still, the modest capacity of 372 mAhg-1 represents a bottleneck in the pursuit of high-energy density anodes. Enabling much higher theoretical capacities of 3600 mAhg-1 [1], silicon represents a promising candidate as anode material for next generation batteries. However, the alloying-based lithiation mechanism of silicon is accompanied by a large volumetric change of up to 300% upon cycling, leading to fast degradation due to electrode pulverization, continuous SEI formation and extensive electrolyte consumption. Even though shallow cycling of silicon anodes has been demonstrated in laboratory scale cells [2], the mixing of silicon with graphite is considered the most viable approach to lift energy density while maintaining appropriate cycle life.Due to the fundamentally different kinetics and potentials of Li insertion and extraction of both materials, the development of silicon-graphite composite electrodes is not straightforward. One of the key questions for optimization is how the incorporation of silicon impacts the (de)lithiation behavior of graphite as a function of the silicon:graphite mass ratio, operating current and electrode potential. While lithiation of graphite in composite electrodes of 15 wt% silicon has been shown to occur in a similar manner as pure graphite, higher fractions of silicon are expected to exert more stress on the graphite and represent kinetic barriers for Li diffusion. This study presents results from in-situ X-ray diffraction experiments (XRD) of silicon-graphite/Li half cells conducted at the European Synchrotron Radiation Facility (ESRF). Serving as a reference, the current-dependent (de)lithiation behavior of a pure graphite/Li half cell has been thoroughly investigated and systematically compared to the (de)lithiation behavior of two selected silicon-graphite composite anodes (silicon:graphite ratio of 30:70 and 70:30, respectively) exposed to the same formation cycle and C-rate protocol. An optimized and novel measurement setup was used, based on a perforated current collector of the anode, providing a complete picture of the graphite in-plane and interplanar structural changes as well as the evolution of semicrystalline silicon peaks which would usually be obscured by the current collector signal.By correlating the electrochemical features (voltage curve and differential capacity plot) with the in-situ diffraction data, it was possible to identify and assign the occurrence and absence of dilute-stage and ordered graphite intercalation compounds (GICs) for the respective electrodes, yielding an in-depth insight into the graphite state of charge upon (de)lithiation and how it is influenced by the silicon content and applied C-rate.As expected, the silicon is (de)lithiated within the entire potential range, whereas graphite is most electrochemically active at potentials lower than 260 mV. In both composite electrodes, graphite attains a lower lithiation degree compared to pure graphite. This is because the high theoretical capacity of silicon results in high specific currents, ultimately challenging the rate capability of graphite. Moreover, the high delithiation overpotential encountered in the composite electrodes results in a highly asymmetrical lithiation/delithiation behavior of graphite. Also, graphite lithiation is less uniform in the composite anodes, indicated by the coexistence of dilute GICs upon (de)lithiation, compared to pure graphite where dilute phases are fully consumed (formed) as (de)lithiation progresses. Surprisingly, the in-situ XRD studies did not reveal signs of structural degradation and strain of graphite as a result of mechanical interaction with silicon. Instead, the volume change of graphite is well correlated with the amorphization of crystalline, unreacted silicon and the volume evolution of silicon crystallites upon charge-discharge.To mitigate the observed effects, the work suggests nanostructuring and advanced electrode architectures towards higher utilization and more homogeneous lithiation of graphite. Overall, the study provides a demonstration of a suitable operando cell for studies of anodes for Li-based systems, and aids the rational design of silicon-graphite composite anodes.

A Robust Network Sodium Carboxymethyl Cellulose-Epichlorohydrin Binder for Silicon Anodes in Lithium-Ion Batteries.

Silicon (Si), as an ideal anode component for lithium-ion batteries, is susceptible to substantial volume changes, leading to pulverization and excessive electrolyte consumption, ultimately resulting in a rapid decline in the cycle stability. Herein, a new sodium carboxymethyl cellulose-epichlorohydrin (CMC-ECH) binder featuring a three-dimensional (3D) network cross-linked structure is synthesized by a simple ring-opening reaction, which can effectively bond the Si anode through abundant covalent and hydrogen bonds to mitigate its pulverization. Benefitting from the merits of the CMC-ECH binder, the electrochemical performance is significantly enhanced compared to the CMC binder. The CMC-ECH binder is applied to Si anodes, a specific capacity of 1054.2 mAh g-1 can be maintained at 0.2 C following 200 cycles under an elevated Si mass loading of around 1.0 mg cm-2, and the corresponding capacity retention is 65.6%. In the case of the LiFePO4//Si@CMC-ECH full battery, the cycle stability exhibits a substantial enhancement compared with the LiFePO4//Si@CMC full battery. Furthermore, the CMC-ECH binder demonstrates compatibility with micron-Si anode materials. Based on the above, we have successfully developed a facilely prepared water-based CMC-ECH binder that is suitable for Si and micron-Si anodes in lithium-ion batteries.

Impact of Electrolyte on Direct-Contact Prelithiation of Silicon-Graphite Anodes in Lithium-Ion Cells with High-Nickel Cathodes.

Silicon-based anodes offer high specific capacities to enhance the energy density of lithium-ion batteries, but are severely hindered by the immense volume expansion and subsequent breakage of the solid-electrolyte-interphase (SEI) during cycling. Herein, we utilize an effective strategy, known as direct-contact prelithiation, to mitigate the challenges associated with expansion and surface instability in SiOx/graphite (SG) anodes. It involves introducing lithium into the anode via physical contact with lithium metal and electrolyte before cycling. Prelithiation of SG anodes with an advanced localized high-concentration electrolyte is shown to develop a mechanically robust artificial SEI that tolerates better the electrode volume expansion. The modified SG anode paired with the high-Ni cathode LiNi0.90Mn0.05Co0.05O2 delivers a high initial capacity of 191 mA h g-1 with 80% capacity retention over 150 cycles, compared to 46% retention with a conventional electrolyte. The bolstered SEI layer with reduced surface reactivity is due to the reduced electrolyte consumption and regulated SEI formation during cycling. Furthermore, the advanced electrolyte and fortified SG anode help reduce cathode degradation, transition-metal dissolution, and loss of active lithium. This study highlights viable prelithiation strategies to stabilize Si-based anodes for high-energy-density batteries through electrolyte design.

Lightweight Electrolyte Design for Li/Sulfurized Polyacrylonitrile (SPAN) Batteries.

Sulfurized polyacrylonitrile (SPAN) recently emergesas a promising cathode for high-energy lithium (Li) metal batteries owing to its high capacity, extended cycle life, and liberty from costly transition metals. As the high capacities of both Li metal and SPAN lead to relatively small electrode weights, the weight and specific energy density of Li/SPAN batteries are particularly sensitive to electrolyte weight, highlighting the importance of minimizing electrolyte density. Besides, the large volume changes of Li metal anode and SPAN cathode require inorganic-rich interphases that can guarantee intactness and protectivity throughout long cycles. This work addresses these crucial aspects with an electrolyte design where lightweight dibutyl ether (DBE) is used as adiluent for concentrated lithium bis(fluorosulfonyl)imide(LiFSI)-triethyl phosphate (TEP) solution. The designed electrolyte (d = 1.04g mL-1) is 40%-50% lighter than conventional localized high-concentration electrolytes (LHCEs), leading to 12%-20% extra energy density at the cell level. Besides, the use of DBE introduces substantial solvent-diluent affinity, resulting in a unique solvation structure with strengthened capability to form favorable anion-derived inorganic-rich interphases, minimize electrolyte consumption, and improve cell cyclability. The electrolyte also exhibits low volatility and offers good protection to both Li metal anode and SPAN cathode under thermal abuse.

Cyclability Investigation of Anode-Free Lithium-Metal Batteries

Lithium (Li) is a sought-after element for thrift, and considerable effort is being invested in conserving, reusing, and optimizing its chemical capabilities as a key material for energy storage systems. Anode-free lithium-metal batteries (AFLMB) provide the ability to utilize the exact amount of Li in the battery, thereby increasing both the specific capacity and safety of the battery. AFLMBs are widely recognized and investigated due to their promised benefits but have not yet become commercial, primarily because they suffer from uneven Li deposition. This issue results in Li dendrite formation, electrolyte consumption due to poor solid electrolyte interphase properties, and, generally, safety concerns. Overcoming these challenges would bring humanity one step closer to a desirable zero-carbon emission future, as more energy could be stored in less volume and weight. In this study, we examined an AFLMB system and investigated different physical and electrochemical factors to understand their effects on the nature of Li deposition/dissolution processes and on the cyclability of the battery. The effects of electrode architecture, cycling temperature, current density in the first charge, and salt composition on the battery were investigated using electrochemical impedance spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy.

Efficient solid dielectric electrochemical polishing with minimal electrolyte consumption and reusable conductive media

Electrochemical polishing finds wide application across various industries, including manufacturing, biomedicine, and semiconductors. However, this technology requires substantial water usage and results in environmental pollution due to the generation of waste electrolytes containing highly corrosive acids and heavy metal ions. Herein, we propose an electrochemical polishing method (SDEP) that employs solid dielectrics consisting of macroreticular ion exchange resin (MIER) solid particles and phosphoric acid electrolyte as an alternative to traditional liquid conductive media. Maintaining a polishing current of 0.4–0.5 A requires only an electrolyte consumption of 10–20 mL/h, leading to a more than 65% reduction in electrolyte usage compared to liquid electrochemical polishing. Meanwhile, this method can be applied to polish additively manufactured metal parts with an initial roughness Ra>10 μm. The achievable surface finish features Ra = 0.778 ± 0.078 μm, Rq = 0.960 ± 0.121 μm, and Rz = 4.175 ± 1.111 μm after 1-h polishing, with a material removal rate of 0.15–0.19 mm3/min. The improvement of Ra, Rq, and Rz are 92.3%, 92.1%, and 92.0%, respectively. With the EDS and XPS analysis, rod-shaped by-products adhering to the surface of MIER particles generated during the SDEP process are confirmed as Fe3+, PO43−, and PO3−. Furthermore, the MIER particles can be reused after cleaning, exhibiting polishing performance comparable to fresh MIER. This method reduces the use of electrolytes at the source of electropolishing, and MIER particles can be recycled, pointing towards the development of eco-friendly electrochemical polishing.

Spatial confinement of Co1.67Te2 nanoparticles within porous carbon nanofibers enabling fast kinetics and stability for sodium dual-ion batteries

Owing to favorable cell voltage exceeding 3 V and cost-effectiveness, sodium dual-ion batteries (Na-DIBs) have gained increasing emphasis, however, they are hampered by the availability of suitable anode. Here, an exotic Na-DIB anode, composed of Co1.67Te2 nanoparticles embedded within porous carbon nanofibers (Co1.67Te2@PCFs), has been developed by a combination of electrostatic spinning and a specialized thermal etching process. The Co1.67Te2 nanoparticles within the confined space and porous carbon layers show energetic capability for Na+ storage and enhanced kinetic behavior of the cell, further verified by the density functional theory (DFT) calculations. Additionally, the formed thin, uniform, and inorganic-rich solid electrolyte interphase (SEI) on the surface of Co1.67Te2@PCFs after cycling reduces electrolyte consumption and facilitates the uniform flow of Na+. Electrochemically, the Co1.67Te2@PCFs anode exhibits a superior reversible capacity of 383.5 mAh g-1 and maintains stable cycling performance over 1000 cycles at 1 A g-1. Furthermore, the assembled Na-DIB can power a “SUST” pattern comprising 242 light-emitting diodes (LEDs) for two minutes, showcasing its operational potential. This study introduces a promising anode material for Na-DIBs and paves the way for spatially confined energy storage.

Quasi-Solid-State Electrolyte Induced by Metallic MoS2 for Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are a promising high-energy-density technology for next-generation energy storage but suffer from an inadequate lifespan. The poor cycle life of Li-S batteries stems from their commonly adopted catholyte-mediated operating mechanism, where the shuttling of dissolved polysulfides results in active material loss on the sulfur cathode and surface corrosion on the lithium anode. Here, we report in situ formation of a quasi-solid-state electrolyte (QSSE) on the metallic 1T phase molybdenum disulfide (MoS2) host that extends the lifetime of Li-S batteries. We find that the metallic 1T phase MoS2 host is able to initiate the ring-opening polymerization of 1,3-dioxolane (DOL), forming an integrated QSSE inside batteries. Nuclear magnetic resonance analysis reveals that the QSSE consists of ∼13% liquid DOL in a solid polymer matrix. The QSSE efficiently mediates sulfur redox reactions through dissolution-conversion chemistry while simultaneously suppressing polysulfide shuttling. Therefore, while ensuring high sulfur utilization, it avoids degradation of both electrodes, as well as the concomitant electrolyte consumption, leading to enhanced cycling stability. Under a practical lean electrolyte condition (electrolyte-to-sulfur ratio = 2 μL mg-1), Li-S pouch cell batteries with the QSSE demonstrate a capacity retention of 80.7% after 200 cycles, much superior to conventional liquid electrolyte cells that fail within 70 cycles. The QSSE also enables Li-S pouch cell batteries to operate across a wider temperature range (5 to 45 °C), together with improved safety under mechanical damage.

Strain- and humidity-insensitive, stretchable hydrogel-based oxygen sensor with corrosion-free electrodes for wireless oxygen detection

As the public puts higher and higher demands on wearing comfort, wearable gas sensors rapidly advance toward intrinsic flexibility and stretchability. However, many challenges arise during the development of intrinsically stretchable sensors. The deformation of the sensor following the movement of the wearer and uncertain changes in environmental humidity can cause additional interference signals. In addition, severe electrode corrosion also challenges the long-term continuous monitoring of sensors. Here, a stretchable strain- and humidity-insensitive O2 sensor is proposed by adopting a serpentine hydrogel fiber structure and hydrophobic elastomer encapsulation strategy. Besides, the introduction of the Pt/C electrode and salt immersion strategy effectively eliminate electrode corrosion and electrolyte consumption, significantly prolonging hydrogel sensor's lifespan. Importantly, we propose, for the first time, an oxygen pump mechanism to elucidate positive current transferring and electrode corrosion-free in hydrogel oxygen sensors, which is further validated through well-designed experiments. Optimized sensor exhibits a wide detection range (30 ppm-100%), linear sensitivity (0.03%/ppm), exceptional repeatability and remarkable tolerance towards environmental variations. Integrating oxygen sensor with Bluetooth circuit further enables wireless monitoring of oxygen while confirming its practicality. This research provides insights into improving the interference immunity and longevity of flexible oxygen sensors while showcasing their potential in wearable applications.

Suppression of potasside reaction in localized high concentration electrolytes utilizing fluorine-substituted benzene as bifunctional additive for potassium-metal batteries

Localized high-concentration electrolytes (LHCEs) have unique solvation structures that do not affect the original salt–solvent coordination from highly concentrated electrolytes. LHCEs enable a wide electrochemical voltage window and mitigate the extensive dendritic growth of metallic anodes. However, in K metal batteries, LHCE undergoes undesirable side reactions because of potasside (K−), triggering aggressive chemistry with a diluent, represented as hydrofluoroethers (HFEs), eventually resulting in poor cycle life. In this study, 1, 3, 5-trifluorobenzene (TFB) was introduced as a functional additive to prevent the parasitic K− reaction. The three symmetrically substituted fluorines prevented TFB from disrupting the as-formed solvation structure of LHCE located in the outer sphere. This characteristic increases the reaction energy barrier between K− and HFE, suppressing the deterioration of the metal anode by adding only 3 wt.% of TFB in LHCE. Moreover, TFB preferentially decomposes at each electrode because of its molecular energy level and increases the reversibility of the cell, reducing unnecessary consumption of electrolytes with a stable interface. This study discusses a novel method to prevent the K− reaction at the electrolyte level and the utilization of LHCE in K batteries to pursue higher energy densities, sustaining the advantage of using a metal anode.

Proton Self‐Limiting Effect of Solid Acids Boosts Electrochemical Performance of Zinc‐ion Batteries

AbstractAt present, aqueous rechargeable Zn–MnO2 batteries have attracted widespread attention as green potential application for renewable energy storage devices. MnO2 cathode has great potential for application, but its proton reaction results in side reactions of cathode, electrolyte consumption, and dramatic pH value changes, suffering from capacity degradation. To address the issues caused by proton deficit, a proton–limited domain strategy is proposed by integrating solid acids (Sulfonic acid type polystyrene–divinylbenzene, SATP) with proton exchange reactions into MnO2. SATP can act as a new proton source increasing the amount of H+ and reducing the generation of zinc hydroxide sulfate, by–product of proton at the cathode interface, via proton exchange reactions of ‐HSO3– group. As a result, Zn–MnO2/SATP battery delivered with excellent rate performance (218.4 mAh g–1 at 2 A g–1) and high cycling stability (the retained capacity of 115.8 mAh g–1 after 500 cycles at a current density of 1 A g–1. This work provides an innovative strategy for high performance aqueous Zn–MnO2 batteries.