Low Interfacial Resistance Research Articles

Triboelectric Performance of Ionic Liquid, Synthetic, and Vegetable Oil-Based Polytetrafluoroethylene (PTFE) Greases

Within electrical contacts, poor electrical conductivity of lubricants can lead to triboelectric charging, causing electrostatic currents and thermal effects, which accelerate lubrication failure. This study aimed to address these challenges by producing and testing three greases with different base oils: ionic liquid ([Oley][Oleic]), synthetic oil (PAO4), and vegetable oil-based synthetic ester (trimethylolpropane oleate). Each grease was prepared with polytetrafluoroethylene powder as the thickener. The greases were tested using a custom-made tribometer, integrated with a grounded electrical current system, with friction tests conducted with up to a 2 A electrical current flow at a constant voltage supply of 4.5 V. Under triboelectric friction testing, [Oley][Oleic] grease outperformed a commercial perfluoropolyether grease by 27.7% in friction and 16.3% in wear. This grease also showed better performance than formulated lithium grease with extreme pressure additives. The study demonstrates that greases with low interfacial resistance can retain their lubrication capacity under triboelectric conditions. These results indicate that [Oley][Oleic] grease, with its ionic liquid base oil, offers a promising solution for applications involving electrical contacts. This study highlights the potential of using advanced base oils and thickeners to enhance the performance and sustainability of lubricants in demanding environments.

Vanadium-doped Li6.7La3Zr1.7V0.3O12 and PVDF-HFP enhanced the ionic conductivity and cycling stability of composite solid electrolytes for All-Solid-State lithium batteries

Solid electrolytes receive widespread attention due to their high safety, high energy density and simplicity of processing. However, the poor interface stability between the solid electrolyte and the electrode leads to a significant increase in interface resistance, greatly reducing the electrochemical performance of lithium-ion batteries (LIBs). Here we designed and prepared a new type of solid composite electrolytes (SCEs), which were composed of poly (ethylene oxide) (PEO) blended with poly (vinylidene fluoride-hexafluoro propylene) (PVDF-HFP) and doped with cubic phase Li6.7La3Zr1.7V0.3O12 (LLZVO) particles. Compared with our previous work, the addition of PVDF-HFP can further reduce the crystallinity of PEO, limit the formation of lithium dendrites, and make the electrolyte/electrode interface more stable. The SCEs had better ionic conductivity of 2.04 × 10-4 S cm−1 and 2.03 × 10-3 S cm−1 at 30 ℃ and 80 ℃, respectively, and the Li/SCEs/Li symmetrical battery cycled for 1800 h without short circuit. Moreover, the coulombic efficiency of LiFePO4/SCEs/Li battery remained at 98 % after 300 cycles. This opens up a new direction for the research of garnet-type composite solid electrolytes with lower interface resistance.

Improving Zn2+ migration via designing multiple zincophilic polymer electrolyte for advanced aqueous zinc ion batteries

Aqueous zinc ion batteries (AZIBs)-based on Zn metal anode face serious issues of hydrogen evolution, corrosion, and zinc dendrite growth, limiting their practical applications. Polymer-based electrolytes can effectively inhibit the above issue, but usually bring additional interfacial resistance, resulting in slow reaction kinetics. Herein, we report a poly(4-acryloylmorpholine) electrolyte with multiple zincophilic primitives for fast zinc ion transport at bulk and interface of Zn metal anode (zinc ion transfer number of 0.77) via a facile one-pot polymerization. The special electrolyte structure with multiple zincophilic primitives can adhere tightly to the Zn metal anode and induce uniform Zn deposition, resulting in low interface resistance and enhanced cycling life of batteries. Therefore, the symmetric Zn||Zn batteries assembled based on the designed and synthesized polymer electrolyte can be stably cycled for 1400 with low overpotential (∼220 mV) at 0.5 mA cm−2 with a capacity of 0.5 mAh cm−2, and the corresponding V2O5||Zn full batteries exhibit attractive reversibility, rate performance, and cycling stability. The electrolyte engineering in this work paves a new path for the construction of polymer-based electrolytes for safe and stable AZIBs.

Layered Bismuth Selenide with a Kinetics‐Enhanced Iodine Doping Strategy Toward High‐Performance Aqueous Potassium‐Ion Storage

AbstractAqueous potassium‐ion batteries with inherent safety, high abundance, and competitive hydrated ion‐radius point to future availability in energy storage. However, the extensively studied electrodes (metal‐oxides, Prussian‐blue‐analogues, etc.) typically suffer from undesirable capacities and sluggish kinetics owing to overwhelming ion diffusion barriers. Herein, for the first time, the metal chalcogenide bismuth selenide reinforced by iodine‐doping (I‐Bi2Se3) is implemented for high‐performance aqueous potassium‐ion storage. The co‐intercalation mechanism of potassium‐ion with proton in I‐Bi2Se3 is entirely revealed by operando synchrotron X‐ray diffraction and substantial ex‐situ analysis, and the excellent interlayer diffusion kinetics in the high‐conductive host are further enhanced by iodine‐doping, as proposed by theoretic calculations. Therefore, the resulting high diffusion coefficient and low interfacial transfer resistance endow I‐Bi2Se3 with superior rate performance (109.2 mAh g−1 at 10 A g−1) and cycling stability (91% capacity retention after 1200 cycles). Employing in hybrid‐ion batteries matching zinc metal, the highest reversible aqueous potassium‐ion storage to date of 316.8 mAh g−1 is demonstrated, permitting the establishment of reliable performance pouch cells. The promising aqueous potassium intercalation chemistry built in the improved metal chalcogenide is proven to be extendable to other hybrid‐ion devices, offering novel mechanistic insights and material practices for aqueous energy storage.

Three-Dimensional Nickel Foam-Based Lithiophilic LPP-Ni3S2@Ni Current Collector for Dendrite-Free Lithium Anode.

Lithium metal has been treated as one of the most promising anode materials for next-generation rechargeable batteries due to its extremely high theoretical capacity. However, its practical application is hindered by inhomogeneous lithium deposition and uncontrolled dendrite growth. In this work, we prepared a three-dimensional nickel foam (NF)-based current collector with a lithiophilic interface layer through facile hydrothermal and coating methods. The lithiophilic Ni3S2 array synthesized via a hydrothermal method has been demonstrated to facilitate the nucleation of Li+. Moreover, it has been observed that the outer coating comprising LPP effectively enhances the inward diffusion of Li+. Additionally, this interface layer can serve as an isolating barrier between the electrodes and the electrolyte. The prepared LPP-Ni3S2@Ni shows significant reversibility both in symmetric cells (1200 h, 1 mA cm-2) and half-cells (CE: 99.60%, 500 cycles, 1 mA cm-2) with low interfacial resistance (35 Ω). Full cells with LiFePO4 as a cathode also exhibit promising electrochemical performance with over 76.78% capacity retention over 200 cycles at 1 C.

–C≡N functionalizing polycarbonate-based solid-state polymer electrolyte compatible to high-voltage cathodes

Solid-state polymer electrolytes (SPEs) capable of withstanding high voltage are considered to be key for next-generation energy storage devices with inherent safety as well as high energy density. This study involves the rational design of solid-state –C≡N functionalized P(VEC1-CEA0.3)/LiTFSI@CE SPEs and its synthesis by in-situ free radical polymerization of vinyl ethylene carbonate (VEC) and 2-cyanoethyl acrylate (CEA). In situ polymerization yields electrode/electrolyte interfaces with low interfacial resistance, forming a stable SEI layer enriched with LiF, Li3N, and RCOOLi, ensuring stable Li plating/stripping for over 1400 h. The –C≡N moiety renders the αH on the adjacent αC positively charged, thereby endowing it with the capability to anchor TFSI−. Simultaneously, the incorporation of –C≡N moiety diminishes the electron-donating ability of the C = O, C–O–C, and –C≡N functional groups, facilitating not only the ion conductivity enhancement but also a more rapid Li+ migration proved by DFT theoretical calculations and Raman spectroscopy. At room temperature, tLi+ of 0.60 for P(VEC1-CEA0.3)/LiTFSI@CE SPEs is achieved when the ionic conductivity σLi+ is 2.63 × 10−4 S cm−1 and the electrochemical window is expanded to 5.0 V. Both coin cells with high-areal-loading cathodes and the 6.5-mAh pouch cell, exhibit stable charge/discharge cycling. At 25 °C, the 4.45-V Li|P(VEC1-CEA0.3)/LiTFSI@CE|LiCoO2 battery performs stable cycling over 200 cycles at 0.2 C, with a capacity retention of 82.1%.

Intrinsically Safe Lithium Metal Batteries Enabled by Thermo-Electrochemical Compatible In Situ Polymerized Solid-State Electrolytes.

In situ polymerized solid-state electrolytes have attracted much attention due to high Li-ion conductivity, conformal interface contact, and low interface resistance, but are plagued by lithium dendrite, interface degradation, and inferior thermal stability, which thereby leads to limited lifespan and severe safety hazards for high-energy lithium metal batteries (LMBs). Herein, an in situ polymerized electrolyte is proposed by copolymerization of 1,3-dioxolane with 1,3,5-tri glycidyl isocyanurate (TGIC) as a cross-linking agent, which realizes a synergy of battery thermal safety and interface compatibility with Li anode. Functional TGIC enhances the electrolyte polymeric level. The unique carbon-formation mechanism facilitates flame retardancy and eliminates the battery fire risk. In the meantime, TGIC-derived inorganic-rich interphase inhibits interface side reactions and promotes uniform Li plating. Intrinsically safe LMBs with nonflammability and outstanding electrochemical performances under extreme temperatures (130°C) are achieved. This functional polymer design shows a promising prospect for the development of safe LMBs.

Carboxymethyl Cellulose – Polyvinyl Alcohol Composite-Based Gel Polymer Electrolyte for Rechargeable Zn-Air Batteries

The high ionic conductivity, lower interfacial contact resistance, enhanced safety, non-toxicity, and biodegradability bring the gel polymer electrolytes (GPEs) as a prospective electrolyte for applications in high-energy density flexible Zn-air batteries (ZABs). The present study comprehensively optimizes the procedures to obtain carboxymethyl cellulose (CMC)–polyvinyl alcohol (PVA) composite-based GPEs holding a maximum KOH amount in the polymer matrix. Optimization of the GPE has been performed and demonstrated by an in-house-developed rechargeable ZAB cells using MnO2-based air cathode and Zn anode. The optimization parameters include the ratio of PVA:CMC, concentration of PVA-CMC in DI water, and thickness of the gel polymer electrolyte. Results show that a 4mm thick GPE prepared from a polymer membrane synthesized using PVA:CMC ratio of 5:2 at a concentration of 0.063 g ml−1 in DI water displayed the highest 6M KOH uptake, least charge transfer resistance of the device, higher discharge plateau, and 5–6 times more cycling compared to GPE made of PVA only. The “as-synthesized GPE” demonstrates high stability of GPE over 100h for a Zn-air battery device. The findings of this work shall speed up the development of Zn air batteries for applications as energy storage systems.

Screening of Pd-Co-Ni catalyst arrays by scanning electrochemical microscopy and characterization of the potential catalyst for formic acid oxidation

BackgroundAppropriate anodic catalyst is one of the key points in improving the performance of direct formic acid fuel cells (DFAFCs). This study utilizes the concept of a combination method to design and screen anodic catalysts for formic acid oxidation. MethodsThe tip generation-substrate collection (TG-SC) mode of scanning electrochemical microscopy (SECM) was employed to screen the Pd-Co-Ni ternary catalyst array for catalyzing formic acid oxidation. The potential catalyst was further characterized by scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Significant findingsThe composition ratios of the prepared Pd-Co-Ni ternary catalyst array matched the concentration ratios set by the precursor solution. SECM screening revealed that the optimal ratio for formic acid oxidation was the Pd2Co6Ni2 catalyst. The cyclic voltammograms and CO stripping voltammograms indicate that the Pd2Co6Ni2 electrode exhibits lower onset potentials for the oxidation of formic acid and its intermediates than the pure Pd electrode. Electrochemical impedance spectroscopy (EIS) confirms that the Pd2Co6Ni2 electrode possesses lower interfacial resistance than the Pd electrode, with its pseudo-inductive behavior at high potential aligning with the outcomes observed in cyclic voltammograms and CO stripping voltammograms.

Effect of the graphene-based material on the conductivity and corrosion behaviour of PTFE/graphene-based composites coatings on titanium for PEM fuel cell bipolar plates

Titanium is widely used as a material for bipolar plates (BP) PEM fuel cells, but they require conductive coatings that help with corrosion and have low interfacial contact resistance (ICR). Among many materials, polymer composites reinforced with graphene nanoparticles have the potential to become an effective coating, but the influence of different types of graphene-based materials on the performance remains has not been properly established. In this study, different nanoparticles (graphene monolayers, reduced graphene oxide and few-layer graphene) were used to process PTFE/graphene composite coatings for Ti, and their performance was evaluated. Most of the coating formulations improved the corrosion resistance of the Ti in one or two orders of magnitude, but only the combination of few-layer graphene and carbon black as additive resulted in an ICR of 12 mΩcm2, in range with the target values.

Electrospun polyimide nanofiber‐based separators containing carboxyl groups for lithium‐ion batteries

AbstractA lithium‐ion battery separator facilitates lithium‐ion transportation and prevents direct contact between the cathode and anode. Polyimide separators exhibited superior thermal stability and electrolyte wettability. In this study, carboxylated polyimide separators were prepared by electrospinning carboxyl group‐containing monomers. Polyimide separators were prepared with different content of carboxyl group‐containing monomer. Moreover, the thermal property, mechanical property, and electrochemical performance of separators were studied. The carboxylated polyimide separators exhibited lower interfacial resistance and higher ionic conductivity compared with polyimide separators. Moreover, the LiFePO4/Li half‐cell assembled using the carboxylated polyimide exhibited enhanced cycling stability and rate capability. Therefore, carboxylated polyimide separators with superior electrochemical performances are promising candidates for lithium‐ion batteries.

Design of Soft/Hard Interface with High Adhesion Energy and Low Interfacial Thermal Resistance via Regulation of Interfacial Hydrogen Bonding Interaction.

Adhesion ability and interfacial thermal transfer capacity at soft/hard interfaces are of critical importance to a wide variety of applications, ranging from electronic packaging and soft electronics to batteries. However, these two properties are difficult to obtain simultaneously due to their conflicting nature at soft/hard interfaces. Herein, we report a polyurethane/silicon interface with both high adhesion energy (13535 J m-2) and low thermal interfacial resistance (0.89 × 10-6 m2 K W-1) by regulating hydrogen interactions at the interface. This is achieved by introducing a soybean-oil-based epoxy cross-linker, which can destroy the hydrogen bonds in polyurethane networks and meanwhile can promote the formation of hydrogen bonds at the polyurethane/silicon interface. This study provides a comprehensive understanding of enhancing adhesion energy and reducing interfacial thermal resistance at soft/hard interfaces, which offers a promising perspective to tailor interfacial properties in various material systems.

Effect of hydroxy-terminated hyperbranched polymer coated separator on the lithium-ion battery performances

Abstract The hydrophobicity of polyolefin separators causes poor compatibility with the internal environment of lithium-ion batteries and thus elevates lithium-ion migration barriers. In this research, hydroxy-terminated hyperbranched polymer (HTHP) coated separators are fabricated successfully based on the simple and easy-on impregnation method. Abundant hydroxyl groups in HTHP reinforce separator electrolyte affinity, generating the much lower contact angle and higher electrolyte uptake. Accordingly, HTHP-coated separators show broader electrochemical window and superior ionic conductivity and Li+ transport number, which facilitate the Li+ migration within porous pathways and hence maximally weaken counteranions-induced polarizations. The lower interfacial resistances also guarantee the Li+ accelerated diffusion via the separator–electrodes interfaces. Therefore, batteries containing modified separators exhibit optimized C-rate capacity and cycling stability. However, immoderate HTHP coating blocks partial pores and thus restricts Li+ transference, which deteriorates C-rate capacity and cycling durability in turn. This separator modification scheme possesses advantages of simple preparation, environment-friendly, and low manufacturing cost, providing practical guidance for low-cost and high-performance separator manufacture.

Ionic Conductivity Analysis of NASICON Solid Electrolyte Coated with Polyvinyl-Based Polymers

The global environmental crisis necessitates reliable, sustainable, and safe energy storage solutions. The current systems are nearing their capacity limits due to the reliance on conventional liquid electrolytes, which are fraught with stability and safety concerns, prompting the exploration of solid-state electrolytes, which enable the integration of metal electrodes. Solid-state sodium-ion batteries emerge as an appealing option by leveraging the abundance, low cost, and sustainability of sodium. However, low ionic conductivity and high interfacial resistance currently prevent their widespread adoption. This study explores polyvinyl-based polymers as wetting agents for the NASICON-type NZSP (Na3Zr2Si2PO12) solid electrolyte, resulting in a combined system with enhanced ionic conductivity suitable for Na-ion solid-state full cells. Electrochemical impedance spectroscopy (EIS) performed on symmetric cells employing NZSP paired with different wetting agent compositions demonstrates a significant reduction in interfacial resistance with the use of poly(vinyl acetate)—(PVAc-) based polymers, achieving an impressive ionic conductivity of 1.31 mS cm−1 at room temperature, 63.8% higher than the pristine material, notably reaching 7.36 mS cm−1 at 90 °C. These results offer valuable insights into the potential of PVAc-based polymers for advancing high-performance solid-state sodium-ion batteries by reducing their total internal resistance.

Highly Efficient and Scalable p-i-n Perovskite Solar Cells Enabled by Poly-metallocene Interfaces.

Inverted p-i-n perovskite solar cells (PSCs) are easy to process but need improved interface characteristics with reduced energy loss to prevent efficiency drops when increasing the active photovoltaic area. Here, we report a series of poly ferrocenyl molecules that can modulate the perovskite surface enabling the construction of small- and large-area PSCs. We found that the perovskite-ferrocenyl interaction forms a hybrid complex with enhanced surface coordination strength and activated electronic states, leading to lower interfacial nonradiative recombination and charge transport resistance losses. The resulting PSCs achieve an enhanced efficiency of up to 26.08% for small-area devices and 24.51% for large-area devices (1.0208 cm2). Moreover, the large-area PSCs maintain >92% of the initial efficiency after 2000 h of continuous operation at the maximum power point under 1-sun illumination and 65 °C.

Rational design of low interfacial resistance between NiS2 cathode and electrolyte for high-performance Li thermal battery

As one of the main components of the cathode and electrolyte for Li thermal batteries (LTBs), conventional binders typically employ high thermal stability MgO to maintain LTBs structure stability, but MgO has the disadvantage of high resistance, which can result in a high resistance at the cathode-electrolyte interface. Thus, it is crucial to optimize the cathode-electrolyte interface for NiS2 to achieve high performance LTBs. Herein, Li7La3Zr2O12 (LLZO) with high thermal stability and excellent ionic conductivity was adopted in the cathode and electrolyte to replace the conventional binders, aiming to build a low resistance interface between the cathode and electrolyte, promoting the Li+ transport kinetics. More importantly, LLZO also plays a vital role in reducing molten salt leakage and enhancing the stability of the cathode-electrolyte interface in LTBs, which contributed to increasing the discharge capacity of the NiS2 cathode material. Consequently, LTB containing LLZO delivers a high discharge specific capacity of 635.1 mAh g−1 with a cut off voltage of 1.4 V at 100 mA cm−2 at 500 °C, retaining 72.8 % of the theoretical capacity of NiS2, which is 25.5 % higher than LTB with MgO. These findings indicate that optimizing the NiS2 electrode and LLZO electrolyte interface would be an effective way to enhance the performance of LTBs.

Application of triblock copolymers in lithium-ion batteries based on solid electrolyte

In the future, all-solid Li-ion batteries are expected to gain widespread acceptance in larger markets due to their high safety and excellent electrochemical performance. However, it is important to acknowledge their drawbacks, including the inadequate compatibility between the electrode and electrolyte interface and the low ionic conductivity at room temperature. This paper reviews the specific methods and the latest research progress of triblock copolymers to solve the above problems. Block copolymerization is an effective way to enhance the efficiency and performance of electrolyte. Its advantage is that two or more monomers with different properties can be polymerized into the same structure, which is conducive to the ionic conductivity of polymer electrolyte. In the latest research results, straight-chain block copolymers have been synthesized, which have better physical and chemical properties compared to traditional comb block copolymers. However, the electrochemical properties of the straight-chain block copolymer electrolyte and the stability of the interface between the electrode and the solid electrolyte are rarely reported. Therefore, it is particularly important to systematically study the electrochemical properties and interface properties of block copolymer electrolytes. In the future, more attention should be drawn to not only improving the properties of SPEs but also building a stable interface with low interface resistance.

Cyclic electrochemical reactions on a Li-metal negative electrode having a low-resistance interface with a solid-state electrolyte

Li metal is a promising negative-electrode material for high-energy-density all-solid-state batteries. However, the surface of Li metal is prone to oxidation, which results in the formation of a contamination layer at the Li metal–solid electrolyte interface. This interfacial contamination layer is the root cause of short-circuiting and poor cycle stability, thus hindering the development of all-solid-state batteries. Prior studies have not quantitatively assessed the effect of the above layer on battery performance. Herein, the degradation mechanisms affecting the interface are investigated using alternating-current impedance measurements and Li plating–stripping cycle tests for a symmetric cell. A thin contamination layer results in a Li–electrolyte interface with a low resistance of 0.20 kΩ cm2 and stable Li plating–stripping behavior at a current density of 3 mA cm−2, whereas a thick contamination layer results in a high interfacial resistance of 2.0 kΩ cm2. The thinning of the contamination layer on Li metal enhances the stability of the Li–electrolyte interface and Li plating–stripping kinetics.

A novel synthetic strategy of mesoporous Ti4O7-coated electrode for highly efficient wastewater treatment

Suboxidized titanium, as a promising anode for electrocatalytic oxidation reactions in wastewater treatment, presents a viable pathway to solve the challenging water pollution. However, current suboxidized titanium anodes are primarily fabricated hot pressing of by suboxidized titanium powders, further hampering their application in wastewater treatment due to high costs and complex shaping processes. To overcome these limitations, this work employs the plasma electrolytic oxidation (PEO) technology to in-situ fabricate porous TiO2 coating precursors on commercial pure titanium substrates, followed by an annealing process to carefully reduce the TiO2 coatings with hydrogen gas, and finally achieving the cost-effective production of high-purity Magnéli phase Ti4O7-coated electrode. The obtained Ti4O7-coated electrodes exhibit a highly ordered granular structure, good crystallinity, wide electrochemical window, and low interfacial charge transfer resistance. Importantly, the Ti4O7-coated electrodes also offer a simple fabrication process, lower energy consumption, and reduced costs compared to advanced boron-doped diamond (BDD) and bulk Ti4O7 electrode. The electrochemical oxidation tests also demonstrate that Ti4O7-coated electrodes can achieve the complete degradation of 100 mg/L phenol within 240 minutes, exhibiting excellent catalytic activity and potential applications in wastewater treatment.

Spatial confinement of Co3O4 in hollow carbon sphere to boost peroxymonosulfate activation for effective degradation of organic pollutants

Herein, hollow carbon sphere (HCS) is constructed via hard template method for loading the Co3O4, and obtained catalyst (namely Co3O4/HCS) is then employed to activate peroxymonosulfate (PMS) for the removal of tetracycline (TC). Owing to high specific surface area and good conductivity of HCS, Co3O4 modified with HCS exhibits low interface resistance and fast charge transfer rate. Meanwhile, hollow structure of HCS can provide spatial confinement effect for Co3O4 and accelerate the mass transfer process between Co3O4 and PMS. As predicted, peroxy bond break of PMS over Co3O4/HCS is significantly boosted compared with pure Co3O4, so reaction system can produce more SO4•–, OH•, 1O2 and high-valent metal complexes to conduct TC degradation. Importantly, Co3O4/HCS-mediated electron transfer process between PMS and TC is also involved in TC degradation. As a result, Co3O4/HCS shows excellent performance in TC degradation, and the highest removal efficiency of TC is more than 95 % within 10 min. Benefiting from the protective effect of HCS, only a small amount of Co ion is released from Co3O4/HCS during the reaction process. Besides, Co3O4/HCS possesses good reusability and anti-interference ability. In short, current work provides a promising catalyst for PMS activation to treat wastewater containing antibiotic.