High Specific Capacitance Research Articles

Modulation of ion-conducting groups in aqueous terpolymer binders to boost the electrochemical performance of silicon-based anodes

Silicon anodes hold great promise for the next-generation energy dense lithium-ion batteries (LIBs) due to their high specific capacity, yet the capacity of silicon anodes rapidly decays during repeated charge/discharge processes, which can hardly be alleviated via conventional binders due to the poor mechanical properties, insufficient ion/electronic conduction, and weak adhesion force. Herein, a random terpolymer (AMS) with fast ion transport and robust adhesion force was developed via the radical polymerization of acrylic acid (AA), acrylamide (AM) and 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and used as aqueous binder for silicon/graphite (Si/C) anodes. The carboxyl and amide groups from AA and AM can form numerous of hydrogen bonds with the silicon particles, leading to a strong adhesion effect, while the sulfonic acid groups can construct fast channels for the rapid transport of lithium ions. Finally, the Si/C anode using the AMS411 binder delivers a high specific capacity of 322.48 mAh g−1 along with the superior operation stability at 0.5C (high-capacity retention ratio of 80.8 % after 500 cycles). This work provides that the incorporation of specific functional groups effectively enhances the overall electrochemical performance of the silicon-based anodes.

Modulation of ion-conducting groups in aqueous terpolymer binders to boost the electrochemical performance of silicon-based anodes

Silicon anodes hold great promise for the next-generation energy dense lithium-ion batteries (LIBs) due to their high specific capacity, yet the capacity of silicon anodes rapidly decays during repeated charge/discharge processes, which can hardly be alleviated via conventional binders due to the poor mechanical properties, insufficient ion/electronic conduction, and weak adhesion force. Herein, a random terpolymer (AMS) with fast ion transport and robust adhesion force was developed via the radical polymerization of acrylic acid (AA), acrylamide (AM) and 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and used as aqueous binder for silicon/graphite (Si/C) anodes. The carboxyl and amide groups from AA and AM can form numerous of hydrogen bonds with the silicon particles, leading to a strong adhesion effect, while the sulfonic acid groups can construct fast channels for the rapid transport of lithium ions. Finally, the Si/C anode using the AMS411 binder delivers a high specific capacity of 322.48 mAh g−1 along with the superior operation stability at 0.5C (high-capacity retention ratio of 80.8 % after 500 cycles). This work provides that the incorporation of specific functional groups effectively enhances the overall electrochemical performance of the silicon-based anodes.

Vanadium sulfide decorated at carbon matrix as anode materials for “fast-charging” lithium-ion batteries

Vanadium sulfide is considered a promising electrode material for achieving rapid lithium storage ascribing to its high specific capacity, unique crystal structure, and abundant valence states. Unfortunately, the structural collapse induced by volume expansion during charging and discharging is the key factor affecting rapid lithium storage. This article prepares composite materials with different morphologies through a strategy of decorating vanadium sulfide at carbon matrix. Among them, graphene oxide modified vanadium tetrasulfide composite materials with three-dimensional conductive networks exhibit excellent electrochemical performance. When the current density is 50 mA g−1, the discharging specific capacity reaches 1, 560 mAh g−1. After 2, 500 cycles at a high current density of 10, 000 mA g−1, the specific capacity is about 188 mAh g−1 with charging time of approximately 70 s. GITT testing indicates that the order of magnitude of the logarithm of the initial diffusion coefficient is 10−11 cm2 s−1 owing to the three-dimensional porous conductive network, which not only shortens ion diffusion path but also provides more active sites for lithium-ion storage, rendering it a promising anode material for “fast-charging” lithium-ion batteries.

Self-Assembled MXene Supported on Carbonization-Free Wood for a Symmetrical All-Wood Eco-Supercapacitor.

As an emerging two-dimensional (2D) material, MXene has garnered significant interest in advanced energy storage systems, yet the stackable structure, poor mechanical stability, and lack of moldability limit its large-scale applications. To address this challenge, herein, the self-assembly of MXene on carbonization-free wood was obtained to serve as high-performance electrodes for symmetrical all-wood eco-supercapacitors by a steam-driven self-assembly method. This method can be implemented in a low-temperature environment, significantly simplifying traditional high-temperature annealing processes and generating minimal impact on the environment, human health, and resource consumption. The environmentally friendly steam-driven self-assembly strategy can be further extended into various wood-based electrodes, regardless of the types and structures of wood. As a typical platform electrode, the optimized MXene@delignified balsa wood (MDBW) achieves high areal capacitance and specific capacitance values of 2.99 F cm-2 and 580.55 F g-1 at an extensive mass loading of 5.16 mg cm-2, respectively, with almost loss-free capacitance after 10,000 cycles at 50 mA cm-2. In addition, an all-solid-state symmetrical all-wood eco-supercapacitor was further assembled based on MDBW-20 as both positive and negative electrodes to achieve a high energy density of 19.22 μWh cm-2 at a power density of 0.58 mW cm-2. This work provides an effective strategy to optimize wood-based electrodes for the practical application of biomass eco-supercapacitors.

A flexible, binder-free electrodes using nickel-cobalt sulfur modified carbon nanofibers for asymmetric supercapacitor applications

The development of high-performance energy storage devices using cost-effective sources are highly important for various applications. Herein, a simple electrodeposition route has been developed for the uniform decoration of nickel-cobalt sulfide (NiCoS) over the carbon nanofibers (CNF). The fabricated NiCoS/CNF has been used as positive electrode with Fe2O3/rGO/CNF as negative electrode to assemble asymmetric supercapacitor (ASC) device. The fabricated ASC device exhibited a good electrochemical performance including high specific capacitance (70 F g-1), excellent cyclic stability (86 % after 10,000 cycles), and good energy density (56.33 Wh kg-1 at 1200 W kg-1). The present simple synthesis process holds a great potential for the design of energy storage devices in various usages.

Protein Interfacial Gelation toward Shuttle-Free and Dendrite-Free Zn-Iodine Batteries.

Aqueous zinc-iodine (Zn-I2) batteries hold potential for large-scale energy storage but struggle with shuttle effects of I2 cathodes and poor reversibility of Zn anodes. Here, an interfacial gelation strategy is proposed to suppress the shuttle effects and improve the Zn reversibility simultaneously by introducing silk protein (SP) additive. The SP can migrate bidirectionally toward cathode and anode interfaces driven by the periodically switched electric field direction during charging/discharging. For I2 cathodes, the interaction between SP and polyiodides forms gelatinous precipitate to avoid the polyiodide dissolution, evidenced by excellent electrochemical performance, including high specific capacity and Coulombic efficiency (CE) (215 mAh g-1 and 99.5% at 1 C), excellent rate performance (≈170 mAh g-1 at 50 C), and extended durability (6000 cycles at 10 C). For Zn anodes, gelatinous SP serves as protective layer to boost the Zn reversibility (99.7% average CE at 2mA cm-2) and suppress dendrites. Consequently, a 500 mAh Zn-I2 pouch cell with high-loading cathode (37.5 mgiodine cm-2) and high-utilization Zn anode (20%) achieves remarkable energy density (80Wh kg-1) and long-term durability (>1000 cycles). These findings underscore the simultaneous modulation of both cathode and anode and demonstrate the potential for practical applications of Zn-I2 batteries.

Enhancing the activation of the Ni2+/Ni3+ redox couple by gradient-tantalum doping for high specific capacity and outstanding interfacial stability

P2-type transition metal layered oxides (TMOs) have gathered significant interest by virtue of their low-cost and excellent cycling stability. However, the extensive practical application of TMOs is constrained by inherent factors, such as inferior rate performance and deficient interfacial stability. Herein, the gradient Ta-doped Na0.78(Ni0.33Mn0.67)1-xTaxO2 (NMT) cathode material was synthesized via a one-step solid-state reaction method to overcome these obstacles. The Ta modification augments the Ni2+/Ni3+ redox couple activity, in accordance with the principle of charge conservation, thus bolstering the reversible capacity of the material. Furthermore, the gradient Ta-doping not only preserves the stability of the bulk phase of TMOs but also serves as a potent suppression against the emergence of deleterious interfacial side reactions. As a result, the NMT cathode delivers an improving initial discharge specific capacity of 105 mAh g−1 at 0.1 C and sustains an excellent capacity retention of 91.4 % after 500 cycles at 5 C within the voltage range of 2.0–4.0 V. Benefiting from the robust Ta–O bond, the highly reversible structure evolution of the gradient Ta-doped material during the Na+ extraction/insertion process is clearly elucidated through in-situ XRD. This research provides a straightforward and efficacious approach to elevate the electrochemical performance of TMOs for sodium-ion batteries (SIBs) in the future.

Doping Engineering in Manganese Oxides for Aqueous Zinc-Ion Batteries.

Manganese oxides (MnxOy) are considered a promising cathode material for aqueous zinc-ion batteries (AZIBs) due to their high theoretical specific capacity, various oxidation states and crystal phases, and environmental friendliness. Nevertheless, their practical application is limited by their intrinsic poor conductivity, structural deterioration, and manganese dissolution resulting from Jahn-Teller distortion. To address these problems, doping engineering is thought to be a favorable modification strategy to optimize the structure, chemistry, and composition of the material and boost the electrochemical performance. In this review, the latest progress on doped MnxOy-based cathodes for AZIBs has been systematically summarized. The contents of this review are as follows: (1) the classification of MnxOy-based cathodes; (2) the energy storage mechanisms of MnxOy-based cathodes; (3) the synthesis route and role of doping engineering in MnxOy-based cathodes; and (4) the doped MnxOy-based cathodes for AZIBs. Finally, the development trends of MnxOy-based cathodes and AZIBs are described.

Na0.4MnO2/MXene nanocomposites as cathodes for high-performance aqueous zinc-ion batteries.

The distinctive configuration of MnO2 renders it an exceptionally promising candidate for cathode materials for aqueous zinc-ion batteries (ZIBs). However, its practical utilization is constrained by the sluggish diffusion kinetics of Zn2+ and the capacity degradation resulting from lattice distortions occurring during charge and discharge cycles. To address these challenges, Na0.4MnO2@MXene with a typical 2 × 4 tunnel structure has been successfully synthesized by a simple hydrothermal method in the presence of 5 M NaCl. The nanorods are about 56 nm in diameter. The zinc-ion batteries (ZIBs) with Na0.4MnO2@MXene displays a specific capacity of 324.6 mA h g-1 at 0.2 A g-1, and have a high reversible capacity of 153.8 mA h g-1 after 1000 charge-discharge cycles at 2 A g-1 with a capacity retention of 91.4%. The unique morphology endows abundant electrochemical active sites and facile ion diffusion kinetics, that contribute to the high specific capacity and stability. The Na0.4MnO2@MXene with a 2 × 4 tunnel structure is a promising candidate as an electrode material for ZIBs.

Na0.4MnO2/MXene nanocomposites as cathodes for high-performance aqueous zinc-ion batteries.

The distinctive configuration of MnO2 renders it an exceptionally promising candidate for cathode materials for aqueous zinc-ion batteries (ZIBs). However, its practical utilization is constrained by the sluggish diffusion kinetics of Zn2+ and the capacity degradation resulting from lattice distortions occurring during charge and discharge cycles. To address these challenges, Na0.4MnO2@MXene with a typical 2 × 4 tunnel structure has been successfully synthesized by a simple hydrothermal method in the presence of 5 M NaCl. The nanorods are about 56 nm in diameter. The zinc-ion batteries (ZIBs) with Na0.4MnO2@MXene displays a specific capacity of 324.6 mA h g-1 at 0.2 A g-1, and have a high reversible capacity of 153.8 mA h g-1 after 1000 charge-discharge cycles at 2 A g-1 with a capacity retention of 91.4%. The unique morphology endows abundant electrochemical active sites and facile ion diffusion kinetics, that contribute to the high specific capacity and stability. The Na0.4MnO2@MXene with a 2 × 4 tunnel structure is a promising candidate as an electrode material for ZIBs.

An aqueous symmetric supercapacitor with wide window and high energy density using redox electrode of Cu-Al-layered double hydroxides and λ-manganese dioxide.

Manganese oxide is a potential agent in the field of energy storage owing to its changeable redox characteristics, high theoretical specific capacitance and valence shells for charge transfer. On the other hand, due to huge surface area, affordability, customisable composition, layered structure and high theoretical specific capacitance, layered double hydroxides, or LDHs, have drawn a lot of interest. This study employs a three-electrode setup to investigate the supercapacitive performance of λ-manganese dioxide/Cu-Al LDH composite at different compositional ratios. To enhance the adhesive and conductivity capabilities, 10% of CNT additive and PVDF binder are added for the composites. Out of all the composites, the one with the greatest weight percentage of λ-manganese dioxide shows the best electrode performance with a superior specific capacitance of 164 F/g at a scan rate of 10mV/s. Additionally, using a symmetrical two-electrode setup, the best-performing electrode is examined. The result shows an exceptional potential window of 2.7V in a basic electrolyte, a power density of 4.04kW/kg at 3 A/g, an energy density of 20.32 Wh/kg at 1 A/g, and a specific capacitance of 37 F/g.

Cross-linkable binder for composite silicon-graphite anodes in lithium-ion batteries

Silicon (Si) is a promising substitute for graphite anode due to the high theoretical specific capacity (4200 mAh g−1). However, too large volume change exists during the lithiation/delithiation process. Composite anode, prepared by mixing Si with graphite, can realize higher specific capacity than graphite and much better cycle performance than Si anode. However, the capacity decay caused by pulverization of Si particles is still a great challenge. Here, a cross-linkable binder rich in nitrile, carboxyl and hydroxyl groups is designed for composite silicon-graphite (Si-C) anode. The nitrile and hydroxyl groups can be in situ cross-linked in the batteries through Ritter reaction. The cross-linked binder has excellent resilience and good adhesion to the active materials and current collector. The cycle performance of the cell with cross-linked binder is much better than the counterpart. Scanning electron microscopy results of the cycled Si-C anode show that the cross-linked binder can suppress the volume expansion and pulverization. Moreover, the investigation with X-ray photoelectronic spectrum and density function theory calculation demonstrate that the decomposition of ester solvent and LiPF6 on Si anode has been mitigated and more stable SEI film is formed on the Si-C anode. Our strategy of in situ cross-linking binder in the batteries has provided a feasible way for designing the next generation of silicon-based anodes with higher specific capacity and longer cycling life.

Highly graphitized coal tar pitch-derived porous carbon as high-performance lithium storage materials.

Because of its high specific capacity and superior rate performance, porous carbon is regarded as a potential anode material for lithium-ion batteries (LIBs). However, porous carbon materials with wide pore diameter distributions suffer from low structural stability and low electrical conductivity during the application process. During this study, the calcium carbonate nanoparticle template method is used to prepare coal tar pitch-derived porous carbon (CTP-X). The coal tar pitch-derived porous carbon has a well-developed macroporous-mesoporous-microporous hierarchical porous network structure, which provides abundant active sites for Li+ storage, significantly reduces polarization and charge transfer resistance, shortens the diffusion path and promotes the rapid transport of Li+. More specifically, the CTP-2 anode shows high charge capacity (496.9 mAh g-1 at 50 mA g-1), excellent rate performance (413.6 mAh g-1 even at 500 mA g-1), and high cycling stability (capacity retention rate of about 100% after 1,000 cycles at 2 A g-1). The clean and eco-friendly large-scale utilization of coal tar pitch will facilitate the development of high-performance anodes in the field of LIBs.

Dynamically regulated redox shuttling and nucleation of lithium polysulfides through the built-in ferroelectric field

Sulfur is highly desired for energy storage devices by virtue of its high theoretical specific capacity and natural abundance. Yet the lithium-sulfur battery becomes practically unstable due to the migration of lithium polysulfides (LiPSs), which is the major challenge for its widespread application. Here, we demonstrate that the polysulfide redox shuttling can be kinetically buffered, which relies on a rational design of ferroelectric/carbon interfaces in a silica-based host structure. In situ TEM observation shows that a robust sulfur host is constructed by spatially embedding ferroelectric BaTiO3 nanodots within both the shell and bulk of a yolk-shell microsphere. During the electrochemical cycling process, the as-prepared composite material functions as a LiPSs pocket. It facilitates the reversible LiPSs conversion, giving rise to long-term stabilization of lithium-sulfur battery. This is due to the synergetic effect of the built-in polarization electric field and abundant LiPSs nucleation sites at internal ferroelectric/carbon interfaces. Furthermore, we show that the nucleation and growth of Li2Sn can be regulated by the designed polarization electric field in the yolk-shell structure. This study further highlights the potential of physical field towards high-performance lithium-slfur batteries.

Influence of Polypyrrole on Phosphorus- and TiO2-Based Anode Nanomaterials for Li-Ion Batteries.

Phosphorus (P) and TiO2 have been extensively studied as anode materials for lithium-ion batteries (LIBs) due to their high specific capacities. However, P is limited by low electrical conductivity and significant volume changes during charge and discharge cycles, while TiO2 is hindered by low electrical conductivity and slow Li-ion diffusion. To address these issues, we synthesized organic-inorganic hybrid anode materials of P-polypyrrole (PPy) and TiO2-PPy, through in situ polymerization of pyrrole monomer in the presence of the nanoscale inorganic materials. These hybrid anode materials showed higher cycling stability and capacity compared to pure P and TiO2. The enhancements are attributed to the electrical conductivity and flexibility of PPy polymers, which improve the conductivity of the anode materials and effectively buffer volume changes to sustain structural integrity during the charge and discharge processes. Additionally, PPy can undergo polymerization to form multi-component composites for anode materials. In this study, we successfully synthesized a ternary composite anode material, P-TiO2-PPy, achieving a capacity of up to 1763 mAh/g over 1000 cycles.

Ultralong Lifespan Zero‐Cobalt/Nickel Prussian Blue Analogs Cathode Realized by Solid Solution Reaction Sodium Storage Mechanism

AbstractDespite their low cost and high specific capacity, the practical use of monoclinic Mn‐based Prussian blue analogs (Mn‐PBAs) is limited by poor cycling stability, primarily due to the structural degradation caused by the multiple phase transitions and Jahn–Teller effect associated with Mn3+ ions throughout the entire cycle. Herein, by synergistic incorporation of low‐cost Cu and Fe into the manganese sites of Mn‐PBAs, the ternary PBAs (T‐PBAs) achieve solid solution reaction of Na+ extraction and insertion, successfully eliminating the inherent multi‐phase transition from the sodium storage mechanism of T‐PBAs. Ex situ analysis and density functional theory calculations are employed to confirm that T‐PBAs consistently maintain a cubic phase with smaller lattice distortion rather than occur in conventional three‐phase transition during the charging and discharging processes, forcefully inhibiting the structural degradation of T‐PBAs. Therefore, the T‐PBAs showcase unprecedented cycling stability at both room temperature (10 000 cycles at 1 A g−1) and −20 °C (over 3000 h, 4200 cycles at 0.2 A g−1 without distinct capacity degradation), More importantly, when paired with commercial hard carbon, the T‐PBAs based sodium‐ion batteries exhibit excellent capacity retention (2000 cycles 76.8%), showcasing their immense potential in practical applications.

Phosphorous - Containing Activated Carbon Derived From Natural Honeydew Peel Powers Aqueous Supercapacitors.

The introduction of phosphorous (P), and oxygen (O) heteroatoms in the natural honeydew chemical structure is one of the most effective, and practical approaches to synthesizing activated carbon for possible high-performance energy storage applications. The performance metrics of supercapacitors depend on surface functional groups and high-surface-area electrodes that can play a dominant role in areas that require high-power applications. Here, we report a phosphorous and oxygen co-doped honeydew peel-derived activated carbon (HDP-AC) electrode with low surface area for supercapacitor via H3PO4 activation. This activator form phosphorylation with cellulose fibers in the HDP. The formation of heteroatoms stabilizes the cellulose structure by preventing the formation of levoglucosan (C6H10O5), a cellulose combustion product, which would otherwise offer a pathway for a substantial degradation of cellulose into volatile products. Therefore, heteroatom doping has proved effective, in improving the electrochemical properties. The improved performance is attributed to the high phosphorous doping with a hierarchical porous structure, which enables the transportation of ions at higher current rates. The high specific capacitance of 486, and 478 F/g at 0.6, and 1.3 A/g in 1M H2SO4 electrolyte with a prominent retention of 98% is observed for 2M H3PO4 having an impregnation ratio of 1:4.

An ionically cross-linked composite hydrogel electrolyte based on natural biomacromolecules for sustainable zinc-ion batteries.

Zinc-ion batteries (ZIBs) are regarded as promising power sources for flexible and biocompatible devices due to their good sustainability and high intrinsic safety. However, their applications have been hindered by the issues of uncontrolled Zn dendrite growth and severe water-induced side reactions in conventional liquid electrolytes. Herein, an ionically cross-linked composite hydrogel electrolyte based on natural biomacromolecules, including iota-carrageenan and sodium alginate, is designed to promote highly efficient and reversible Zn plating/stripping. The abundant functional groups of macromolecules effectively suppress the reactivity of water molecules and facilitate uniform Zn deposition. Moreover, the composite hydrogel electrolyte exhibits a high ionic conductivity of 5.89 × 10-2 S cm-1 and a Zn2+ transference number of 0.58. Consequently, the Zn‖Zn symmetric cell with the composite hydrogel electrolyte shows a stable cycle life of more than 500 h. Meanwhile, the Zn‖NH4V4O10 coin cell with the composite hydrogel electrolyte retains a high specific capacity of approximately 200 mA h g-1 after 600 cycles at 2 A g-1. The Zn‖NVO pouch cell based on the composite hydrogel electrolyte also shows a high specific capacity of 246.1 mA h g-1 at 0.5 A g-1 and retains 70.7% of its initial capacity after 150 cycles. The pouch cell performs well at different bending angles and exhibits a capacity retention rate of 98% after returning to its initial state from 180° folding. This work aims to construct high-performance hydrogel electrolytes using low-cost natural materials, which may provide a solution for the application of ZIBs in flexible biocompatible devices.

Cu-Doped Spherical P2-Type Na0.7Fe0.23-xCuxMn0.77O2 Cathode for High-Performance Sodium-Ion Batteries.

Sodium-ion batteries (SIBs), owing to their abundant resources and cost-effectiveness, have garnered considerable interest in the realm of large-scale energy storage. The properties of cathode materials profoundly affect the cycle stability and specific capacity of batteries. Herein, a series of Cu-doped spherical P2-type Na0.7Fe0.23-xCuxMn0.77O2 (x = 0, 0.05, 0.09, and 0.14, x-NFCMO) was fabricated using a convenient hydrothermal method. The successful doping of Cu efficaciously mitigated the Jahn-Teller effect, augmented the electrical conductivity of the material, and diminished the resistance to charge transfer. The distinctive spherical structure remained stable and withstood considerable volumetric strain, thereby improving the cyclic stability of the material. The optimized 0.09-NFCMO cathode exhibited a high specific capacity of 168.6 mAh g-1 at 100 mA g-1, a superior rate capability (90.9 mAh g-1 at 2000 mA g-1), and a good cycling stability. This unique structure design and doping approach provides new insights into the design of advanced electrode materials for sodium-ion batteries.

Tuning the microstructure of biomass-derived hard carbons by controlling the impurity removal process for enhanced Na ion storage performance

Biomass-derived hard carbons are promising anode materials of sodium-ion batteries (SIBs) due to their low cost, renewability and high specific capacity. However, there are inevitably some impurities in biomasses that may not only affect the purity, but microstructure and electrochemical performance of hard carbons. Although the impurities can be removed by appropriate treatments after carbonization, the microstructure of hard carbons can hardly be changed. In this work, taking ficus macrophylla leaves (FMLs) as the model biomass, the effects of impurities and their removing process on the microstructure and Na ion storage performance of hard carbons are investigated. It is found that the presence of Ca and Si-bearing impurities in FMLs results in more graphite-like structure in hard carbons because of their catalytic graphitization effect. The acid and base washing processes after carbonization can mostly get rid of the inorganic impurities is unable to increase the plateau region capacities associating to Na ion insertion in the interlayer of graphitic microcrystals and Na metal filling in micropores. By contrast, by stepwisely removing the Ca and Si-bearing impurities from raw materials before carbonization, hard carbons with high purity, larger interlayer space and more micropores are produced, which exhibit a high reversible specific capacity of 336 mAh g−1 at 20 mA g−1, a high initial Coulombic efficiency of 93 %, excellent rate capability (245 mAh g−1 at 2 A g−1) and robust cycle stability. This study implies that controlling the impurity removal process can simultaneously tune the microstructure of hard carbon anodes derived from biomasses towards high performance Na ion storage.