Binder-free Cathode Research Articles

In-situ synthesis AgO/AgNPs composite as binder-free cathode for high-performance aqueous AgO-Al batteries

Aqueous AgO-Al batteries are promising systems due to their ultrahigh specific capacity, energy density, and stable output voltage. However, they still suffer from the low utilization and sluggish kinetics of the cathode. In this study, the binder-free AgO/AgNPs composites were synthesized in-situ using a simple electrodeposition method. Due to the excellent conductivity and rich mesoporous structure of AgO/AgNPs materials, the electron and ion transfer kinetics were enhanced, thereby improving the charge storage performance of the electrode. As expected, the AgO-Al battery with the optimized AgO/AgNPs composite cathode demonstrated excellent rate performance, achieving a high discharge capacity of 325.1 mAh g−1, and a stable operating voltage platform of 1.55 V at the current density of 1000 mA cm−2. The maximum energy and power density were 687 Wh kg−1 and 6.2 kW kg−1, respectively. This work presents an effective strategy for designing high-performance AgO electrode materials for AgO-Al batteries.

Highly asymmetrically configured single atoms anchored on flame-roasting deposited carbon black as cathode catalysts for ultrahigh power density Zn-air batteries

Iron group element-based single atom (SA) catalysts are highly regarded as promising alternatives to commercial Pt/C for catalysis of oxygen reduction reaction (ORR). For applications in rechargeable zinc-air batteries (ZABs), achieving the necessary high catalytic efficiency of the SAs toward oxygen evolution reaction (OER) however remains a significant challenge. Here, highly asymmetrically configured Fe SAs created with N,S co-coordination and anchored on flame-roasting deposited carbon black (CB), Fe-N3S1/CB, are developed, achieving outstanding bifunctional oxygen catalytic efficiency, with an ultra-small potential gap of 0.661 V at 10 mA cm-2 (ΔE10), outperforming the (Pt/C+RuO2) composite catalyst (0.697 V). With a newly proposed binder-free composite air cathode design, the Fe-N3S1/CB based ZAB achieves an ultrahigh power density of 365.7 mW cm-2 at a current density of 511.3 mA cm-2, largely outperforming the (Pt/C+RuO2) based ZAB (225.9 mW cm-2 at 344.7 mA cm-2). Furthermore, the Fe-N3S1/CB based ZAB demonstrates excellent long-term stability, with only 8.2% decay in round-trip efficiency over 1000 (333.3 h) charge-discharge cycles at 10 mA cm-2. Density functional theory calculations elucidate that incorporation of sulfur into the coordination sphere of Fe facilitates the electrochemical dehydroxylation step for ORR and accelerates the electrochemical O2 desorption step for OER, thereby reducing the corresponding free energy differences on Fe SAs for largely enhanced catalytic efficiency.1. A large size hetero-atom element, sulfur, is introduced to create highly asymmetrically configured Fe single atoms for enhancements in catalytic efficiency toward both oxygen reduction reaction and oxygen evolution reaction, and a binder-free composite air cathode design is proposed to improve electrochemical performances of zinc-air batteries.2. An ultra-small potential gap of 0.661 V at 10 mA cm-2 (ΔE10) is achieved for the air cathode, and an ultrahigh discharge power density of 365.7 mW cm-2 at a current density of 511.3 mA cm-2 is acquired for the zinc-air battery.

Electrodeposited Co0.85Se/Ni3Se2 heterostructure as an efficient binder-free cathode for fast electrochemical energy storage devices

In this study, a facile technique was developed to generate a bimetallic Co0.85Se/Ni3Se2 heterostructure through a straightforward one-step electrodeposition process. The resulting structure proved to be an efficient cathode for fast charge/discharge electrochemical energy storage devices. The composition and morphology of the cathode can be easily adjusted by varying the molar ratio of Co/Ni precursors. The optimized Co0.85Se/Ni3Se2 (3:1) electrode demonstrated an impressive specific capacity of 141.9 mAh g−1 at a current density of 1 A g−1. It retained a capacity of 103.5 mAh g−1 at a high current density of 8 A g−1 due to its heterostructure nature. The assembled hybrid supercapacitor (HSC) device based on this optimized cathode achieved remarkable energy and power densities. Additionally, the Co0.85Se/Ni3Se2 (3:1) electrode was successfully demonstrated in micro-HSC (μ-HSC) applications, exhibiting favorable cycling stability during 480-h floating tests. These findings suggest that the synthesized Co0.85Se/Ni3Se2 cathode has great potential for use in high-performance electrochemical energy storage devices.

High-loading NaCrO2 @C nanofibers as binder-free cathode for high-stable sodium-ion batteries

A NaCrO2 @C flexible free-standing cathode is designed and fabricated via a facile electrospinning strategy, in which electrochemically active NaCrO2 nanoparticles homogeneously dispersed in the flexible carbon nanofibers. Serving as the binder-free cathode for sodium-ion batteries, the as-constructed NaCrO2@C flexible free-standing cathode delivers a long cycling life (81 % capacity retention after 1000 cycles) with a high loading (7.6 mg cm−2). The enhancements for sodium-ion insertion/desertion is assigned to the dramatically decrease the polarization between electrodes and avoid the volume expansion during high-rate cycling. The NaCrO2@C flexible free-standing cathode opens up exciting possibilities for the development of advanced flexible sodium-ion batteries with both excellent mechanical flexibility and electrochemical properties.

Preparing a binder-free cathode composed of NMC811/sulfonated reduced graphene oxide sheets/carbon black via in-situ electrophoretic deposition to enhance cyclability of Li-ion batteries

Disruption in the restacking of the graphene present in the electrodes could hamper the reduction in the conductivity and also the surface area, which may be a good reason why graphene has not yet performed as predicted. In this research, we employed the scalable electrophoretic deposition (EPD) procedure to make instantly a binder-free Li-ion battery cathode, consisting of LiNi0.8Mn0.1Co0.1O2 (NMC811), sulfonated reduced graphene oxide (SRGO) sheets, and carbon black (CB) particles. The EPD process caused a squeezing force, which not only wrapped the SRGO sheets around the NMC811 nanoparticles, but also inserted the CB particles into the composite in an electrostatically stabilized combination. As evidenced by the electrochemical measurements, the binder-free NMC/SRGO/CB electrode manifested better cycling performance at the current density of 0.2 C, where this electrode delivered discharge capacities of 170.3 and 143.7 mAh g−1, respectively, at the 1st and 200th cycle compared to discharge capacities of 162.3 and 122.6 mAh g−1 acquired for the NMC/SRGO electrode. The excellent cycle stability and rate capability of the optimized binder-free NMC/SRGO/CB cathode can be attributed to withstanding the volume expansion of the active particles during cycling due to wrapping graphene sheets, inhibition of the restacking of graphene sheets by sulfonated groups and CB spacers, electrostatic interaction between sulfonated groups and lithium ions, and efficient electrolyte infiltration by ion and electron conductive channels in the binder-free cathode structure.

In-situ banana fiber-modified carbonized bacterial cellulose as a free-standing and binder-free cathode host for potassium-sulfur batteries

To meet the growing energy demand for large-scale applications, potassium-sulfur batteries (KSBs) have gained enormous attention owing to their high energy density, natural abundance, and specific capacity. Nevertheless, the shuttle effect, the insulating nature of sulfur, and the large volume change hinder the development of KSBs. To address the different challenges of KSBs, we report eco-friendly and biodegradable in-situ banana fiber-modified carbonized bacterial cellulose as a free-standing and binder-free cathode (sulfur) host. The catholyte K2S6 is used as active sulfur for cell fabrication owing to a high sulfur loading and even distribution of active material. However, introducing the catholyte induces the potassium side reaction by reacting to it. Therefore, carbonized bacterial cellulose is used as an interlayer to reduce the notorious polysulfide shuttle effect. As a result, the fabricated cell delivers a specific capacity of 437, 354, and 193 mAh g-1 at the current density of 0.2, 0.7, and 1.2 C, respectively. During the long cycling, the cell shows excellent electrochemical performance for 200 cycles with a capacity retention of 78 % at 0.7 C. This work paves the way to utilize an eco-friendly and cost-effective approach to fabricate a high-performance KSB.

Li-Ion Batteries with a Binder-Free Cathode of Carbon Nanotubes-LiFePO4-Al Foam

With the increasing demand for Li resources worldwide, the easy recycling of Li-ion batteries materials becomes essential. We report a binder-free cathode consisting of carbon nanotubes (CNTs) and LiFePO4 (LFP) nanoparticles embedded in a 3D Al network. The electrode stability depends on the CNT ratio, where 3% CNT-wrapping LFPs provide a stable structure free of detachment from Al foam, as observed on Al foil. The binder-free cathode sheet exhibited excellent performance for high-rate discharge and long-term cycle life. Materials on the cathode can be easily detached with ultrasonic treatment when immersed in organic solvent, which is advantageous for a green and high-efficiency strategy of recycling all valuable materials compared to the binder-used electrode.

One-Pot Electrochemical Deposition of Polyaniline-MnO2 Hybrids on Carbon Cloth as Binder-Free Cathode for Flexible Zinc Ion Batteries

One-Pot Electrochemical Deposition of Polyaniline-MnO₂ Hybrids on Carbon Cloth as Binder-Free Cathode for Flexible Zinc Ion Batteries

Economical and simple in-situ synthesis of CuS@Cu foam as a binder-free cathode for high-performance hybrid Mg–Li ion batteries

Economical and simple in-situ synthesis of CuS@Cu foam as a binder-free cathode for high-performance hybrid Mg–Li ion batteries

Phase-controllable synthesis of nickel selenide nanostructures decorated on carbon nanotubes as efficient binder-free cathodes for hybrid supercapacitors

In this work, we employed a facile pulse-reversal (PR) electrodeposition route to successfully synthesize nickel selenide nanostructures directly decorated on carbon nanotubes (CNTs) by adjusting different pulse-reversal potentials. The study systematically investigated the effects of PR potential on the morphology and composition of nickel selenides on CNTs. The experimental results suggested that regulating the PR potential could effectively manage the formation of nickel selenide nanostructures on the backbones of CNTs. By decreasing the PR potential from 0.2 to −0.2 V, the composition of nickel selenide nanostructures changed from NiSe2 to Ni0.85Se. The CNTs@NiSe2 electrode outperformed the others with a specific capacity of 125.4 mAh g−1 at 2 A g−1 and an impressive capacity retention of 81.2 % at 16 A g−1. The assembled hybrid supercapacitor using CNTs@NiSe2 as the cathode achieved exceptional performance with a high specific capacity of 42 mAh g−1 at 1 A g−1 and a maximum energy density of 33.6 Wh kg−1 at 800 W kg−1. This work presents an efficient approach that can be widely employed to fabricate one-dimensional carbon material-supported transition metal selenide nanostructures for practical applications in the next generation of energy storage and conversion.

Nanostructured S@VACNTs Cathode with Lithium Sulfate Barrier Layer for Exceptionally Stable Cycling in Lithium-Sulfur Batteries

Lithium-sulfur technology garners significant interest due to sulfur’s higher specific capacity, cost-effectiveness, and environmentally friendly aspects. However, sulfur’s insulating nature and poor cycle life hinder practical application. To address this, a simple modification to the traditional sulfur electrode configuration is implemented, aiming to achieve high capacity, long cycle life, and rapid charge rates. Binder-free sulfur cathode materials are developed using vertically aligned carbon nanotubes (CNTs) decorated with sulfur and a lithium sulfate barrier layer. The aligned CNT framework provides high conductivity for electron transportation and short lithium-ion pathways. Simultaneously, the sulfate barrier layer significantly suppresses the shuttle of polysulfides. The S@VACNTs with Li2SO4 coating exhibit an extremely stable reversible areal capacity of 0.9 mAh cm−2 after 1600 cycles at 1 C with a capacity retention of 80% after 1200 cycles, over three times higher than lithium iron phosphate cathodes cycled at the same rate. Considering safety concerns related to the formation of lithium dendrite, a full cell Si-Li-S is assembled, displaying good electrochemical performances for up to 100 cycles. The combination of advanced electrode architecture using 1D conductive scaffold with high-specific-capacity active material and the implementation of a novel strategy to suppress polysulfides drastically improves the stability and the performance of Li-S batteries.

Prussian blue analogues-Derived Iron-Cobalt carbon fiber Binder-Free electrodes for electrocatalytic nitrate reduction

Developing a highly selective and efficient electrocatalytic system for nitrate reduction reaction (NO3RR) is of great significance but still remains challenging for environmental remediation and energy utilization. Herein, we constructed a binder-free cathode consisted of iron-cobalt Prussian blue analogues-based bimetal derived carbon fiber (FC-PBAFC) to enhance NO3RR performances. Significantly, high NO3−-N removal capacity of 169.1 mgN h−1 gcat-1, excellent ammonia Faradic efficiency (FE) of 83.2 ± 0.7 % and high ammonia selectivity of 99.3 ± 0.6 % were achieved by FC-PBAFC binder-free cathode. The excellent NO3RR performance was attributed to the rational polymer tethering strategy for the binder-free cathode construction. The introduction of polyacrylonitrile for electrospinning shaping essentially regulated the structural and compositional distribution of binder-free electrode during followed pyrolysis. The in-situ infrared spectroscopy and DFT calculation demonstrated that the Fe and Co regulation optimized the adsorption energy of key intermediate products with suppressing the side reactions. The bimetal binder-free cathode offers a promising strategy for selective and effective electroreduction of nitrate for ammonia synthesis.

Binder-Free Three-Dimensional Porous Graphene Cathodes via Self-Assembly for High-Capacity Lithium-Oxygen Batteries.

The porous architectures of oxygen cathodes are highly desired for high-capacity lithium-oxygen batteries (LOBs) to support cathodic catalysts and provide accommodation for discharge products. However, controllable porosity is still a challenge for laminated cathodes with cathode materials and binders, since polymer binders usually shield the active sites of catalysts and block the pores of cathodes. In addition, polymer binders such as poly(vinylidene fluoride) (PVDF) are not stable under the nucleophilic attack of intermediate product superoxide radicals in the oxygen electrochemical environment. The parasitic reactions and blocking effect of binders deteriorate and then quickly shut down the operation of LOBs. Herein, the present work proposes a binder-free three-dimensional (3D) porous graphene (PG) cathode for LOBs, which is prepared by the self-assembly and the chemical reduction of GO with triblock copolymer soft templates (Pluronic F127). The interconnected mesoporous architecture of resultant 3D PG cathodes achieved an ultrahigh capacity of 10,300 mAh g-1 for LOBs. Further, the cathodic catalysts ruthenium (Ru) and manganese dioxide (MnO2) were, respectively, loaded onto the inner surface of PG cathodes to lower the polarization and enhance the cycling performance of LOBs. This work provides an effective way to fabricate free-standing 3D porous oxygen cathodes for high-performance LOBs.

Enhanced bioelectroremediation of heavy metal contaminated groundwater through advancing a self-standing cathode

Hexavalent chromium (Cr(VI)) contamination in groundwater poses a substantial global challenge due to its high toxicity and extensive industrial applications. While the bioelectroremediation of Cr(VI) has attracted huge attention for its eco-friendly attributes, its practical application remains constrained by the hydrogeochemical conditions of groundwater (mainly pH), low electron transfer efficiency, limitations in electrocatalyst synthesis and electrode fabrication. In this study, we developed and investigated the use of N, S co-doped carbon nanofibers (CNFs) integrated on a graphite felt (GF) as a self-standing cathode (NS/CNF-GF) for the comprehensive reduction of Cr(VI) from real contaminated groundwater. The binder free cathode, prepared through electro-polymerization, was employed in a dual-chamber microbial fuel cell (MFC) for the treatment of Cr (VI)-laden real groundwater (40 mg/L) with a pH of 7.4. The electrochemical characterization of the prepared cathode revealed a distinct electroactive surface area, more wettability, facilitating enhanced adsorption and rapid electron transfer, resulting in a commendable Cr(VI) reduction rate of 0.83 mg/L/h. The MFC equipped with NS/CNF-GF demonstrated the lowest charge transfer resistance (Rct) and generated the highest power density (155 ± 0.3 mW/m2) compared to control systems. The favorable electrokinetics for modified cathode led to swift substrate consumption in the anode, releasing more electrons and protons, thereby accelerating Cr(VI) reduction to achieve the highest cathodic coulombic efficiency (C.Eca)of80 ± 1.3 %. A similar temporal trend observed between Cr(VI) removal efficiency, COD removal efficiency, and C.Eca, underscores the effective performance of the modified electrode. The reusability of the binder free cathode, exemption from catholyte preparation and the absence of pH regulation requirements highlighted the potential scalability and applicability of our findings on a larger scale.

In Situ Electrophoretic Decorated Cactus-Type Metallic-Phase MoS2 on CaMn2O4 Nanofibers for Binder-Free Next-Generation LIBs.

Ternary manganese-based oxides, such as CaMn2O4 (CMO) nanofibers fabricated via the electrospinning technique, have the potential to offer higher reversible capacity through conversion reactions in comparison to that of carbon-based anodes. However, its poor electrical conductivity hinders its usage in lithium-ion batteries (LIBs). Hence, to mitigate this issue, controlled single-step in situ decoration of highly conducting metallic-phase MoS2@CMO nanofibers has been achieved for the first time via the electrophoretic deposition (EPD) technique and utilized as a binder-free nanocomposite anode for LIBs. Further, the composition of MoS2@CMO nanofibers has also been optimized to attain better electronic and ionic conductivity. The morphological investigation revealed that the flakes of MoS2 nanoflowers are successfully and uniformly decorated over the CMO nanofibers' surface, forming a cactus-type morphology. As a binder-free nanocomposite LIB anode, CMOMS-7 (7 wt % MoS2@CMO) demonstrates a specific capacity of 674 mA h g-1 after 60 cycles at 50 mA g-1 and maintains a capacity of 454 mA h g-1 even after 300 cycles at 1000 mA g-1. Further, the good rate performance (102 mA h g-1 at 5000 mA g-1) of CMOMS-7 can be ascribed to the enhanced electrical conductivity provided by the metallic-phase MoS2. Moreover, the feasibility of CMOMS-7 is thoroughly investigated by using a full Li-ion cell incorporating a binder-free cathode of LiNi0.3Mn0.3Co0.3O2 (NMC). This configuration showcases an impressive energy density of 154 Wh kg-1. Thus, the hierarchical and aligned structure of CMO nanofibers combined with highly conductive MoS2 nanoflowers facilitates charge transportation within the composite electrodes. This synergistic effect significantly enhances the energy density of the conversion-based nanocomposites, making them highly promising anodes for advanced LIBs.

Crystallinity transformation engineering of hydrous cobalt nickel phosphate cathodes for hybrid supercapacitor devices: Extrinsic/battery to intercalation type pseudocapacitors

The necessitating strategies of rationalizing nanostructures and crystallinity of electrode material are crucial to developing high-efficiency hybrid energy storage devices. To enhance the energy storage performance of bimetal phosphates, it is important to have a strategic blend of metal cations that can work together synergistically. So, this work describes the scalable preparation of binder-free cobalt nickel phosphates thin film cathodes with cations variation (Co/Ni) via the facile Successive Ionic Layer Adsorption and Reaction (SILAR) process. The distinct roles of cations in cobalt nickel phosphate electrodes resulted in a noteworthy structural transformation from crystalline to amorphous with an increment of Ni content. The change in cations composition influences the pseudocapacitive performance from extrinsic/battery to intercalation type, and cobalt nickel phosphate electrode with an ideal cations composition (Co:Ni) ratio of approximately 1:1 attain the highest specific capacitance (SCs) of 2142 F g−1 (1071 C g−1). To fulfil the demand for high-performance hybrid supercapacitor devices, aqueous (HASC) and solid-state (HSSC) supercapacitors are assembled using optimized cobalt nickel phosphate (S-CNP5) as a cathode. The HASC device represents maximum SCs of 120 F g−1 with specific energy (SE) and specific power (SP) of 42.59 Wh kg−1 and 1600 W kg−1, respectively. The flexible HSSC device shows impressive SCs of 89 F g−1 and SE of 31.54 Wh kg−1 at SP of 2057.14 W kg−1. The practical demonstration of an HSSC device to power a 12-white LED lamp suggests that the SILAR strategy offers commercializing insights for fabricating high-specific capacity hydrous cobalt nickel phosphate thin film cathodes.

High mass-loading CoO@NiCo-LDH//FeNiS flexible supercapacitor with high energy density and fast kinetics

The rapidly growing market of portable and wearable smart electronics has created strong interest in flexible electrode materials with high specific capacitance and fast charging/discharging properties. However, high mass-specific capacitance active materials are often limited by the low areal mass-loading required. High areal capacity electrodes can make more efficient use of the limited internal space of these miniature devices by minimizing the volume and weight taken by current collectors and separators. Herein, a method is proposed to prepare a nickel–cobalt layered double hydroxide binder-free cathode on flexible carbon cloth with a mass loading of 20 mg cm−2. This core–shell hybrid structure prepared using a MOF self-sacrificing template, achieves a high energy density using thick electrodes while improving their slow kinetics by enhancing both the ion diffusion process and charge transfer dynamics. The areal capacitance reaches a staggering 4.42 mAh cm−2 (31.79 F cm−2) at a current density of 8 mA cm−2. Furthermore, a one-step hydrothermal method to prepare the FeNi-S anode (1.67 mAh cm−2, 2 mA cm−2) is proposed. Upon assembling with the gel electrolyte, this flexible device possesses an impressive energy density of 3.29 mW h cm−2 (3 mW cm−2). It can readily supply energy to watches, wireless e-paper, LEDs, and can be anticipated to be widely used in next-generation high-performance portable and wearable devices.

Cover: Journal of the Chinese Chemical Society 02/2024

The figure highlights the fundamental model of a rechargeable zinc‐ion battery, featuring the reaction mechanism of a hydrothermally synthesized binderfree cathode. This 3D model of the battery system showcases its main components and the reversible nature of the process. Both are crucial keys for RZIB's continuous innovations and further development. More details about this figure will be discussed by Dr. Ryan D. Corpuz and his co‐workers on page 140‐154 in this issue.image

Binder-free barium-implanted MnO2 nanosheets on carbon cloth for flexible zinc-ion batteries.

The intrinsically low electrical conductivity and poor structural fragility of MnO2 have significantly hampered the zinc storage performance. In this work, Ba2+-implanted δ-MnO2 nanosheets have been hydrothermally grown on a carbon cloth (Ba-MnO2@CC) as an extremely stable and efficient cathode material of aqueous zinc-ion batteries. The three-dimensionally porous architecture composed of interwoven thin MnO2 nanosheets effectively shortens the electron/ion transport distances, enlarges the electrode/electrolyte contact area, and increases the active sites for the electrochemical reaction. Meanwhile, Ba2+ could function as an interlayer pillar to stabilize the crystal structure of MnO2. Consequently, the as-optimized Ba-MnO2@CC exhibits remarkable Zn2+ storage capabilities, such as a high capacity (305 mAh g-1 at 0.2Ag-1), prolonged lifespan (95% retention after a 200-cycling test), and superb rate capability. The binder-free cathode is also applicable for flexible energy storage devices with attractive properties. The present investigation provides important insights into designing advanced cathode materials toward wearable electronics.

In situ growth of δ-MnO2/C fibers as a binder-free and free-standing cathode for advanced aqueous Zn-ion batteries

δ-MnO2 anchored in N-doped carbon fibers, derived from coal, was prepared using an electrospinning method, demonstrating enhanced performance in AZIBs.