Ultrahigh Specific Capacitance Research Articles

Entrapping polyiodide by using highly N, P co-doping porous carbon framework towards high performance zinc‑iodine batteries

Rechargeable aqueous zinc‑iodine batteries (ZIBs) with low environmental impact and abundant natural reserves have become promising electrochemical energy storage devices. However, the shuttle effect and low conductivity lead to poor electrochemical performance, hindering their practical applications. Herein, a (NH4)3PO4-activated ZIF-8-derived porous carbon (NPPC) is proposed for entrapping iodine species in ZIBs. Benefiting from its abundant porous structure and highly conductive framework, the iodine loading and electron transport of NPPC is greatly enhanced. In addition, the in-situ doping multiple heteroatoms (N, P and O) in the carbon framework can also establish chemical anchoring with iodine species and hence mitigate the shuttle effect. As a result, the ZIBs prepared by the NPPC-1.5/I2 electrode achieves an ultra-high specific capacity of 175 mAhg−1 at 0.1 A g−1, and a specific capacity of 95 mAh g−1 at a high current density of 10 A g−1. An extremely stable cycle performance of 97 % capacity retaining after 6000 cycles at 10 A g−1 is also obtained. This study provides a new strategy for realizing aqueous ZIBs with high capacity and long cycling life.

Evaluating Electronic Properties of Self‐Assembled Indium Phosphide Nanomaterials as High‐Efficient Solar Cell

ABSTRACTGeometries and electronic properties associated with relative stabilities and energy gaps of porous (InP)12n (n = 1–12) nanoclusters (NCs) (nanowires and nanosheets) are systemically studied by density functional method. The relative stabilities of (InP)12n NCs through the calculated fragmentation energies and cluster‐binding energies are determined and discussed. Interestingly, the calculated energy gaps of (InP)12n nanowires and nanosheets are localized at regions of visible light energy ranges. (InP)12n are relatively wide‐band semiconductor solar energy nanomaterial. The calculated density of states reveals large‐sized porous (InP)12n nanosheets and nanowires with narrow pore size distribution and slight thickness and a large surface area manifest ultrahigh specific capacitance of trapping solar light energies and high light‐to‐electricity conversion efficiencies in solar energy absorption or conversion or photovoltaicsm. Particularly, (InP)12n NCs maintain their elemental properties of individual (InP)12 clusters in the energy gaps of (InP)12n (n > 4). NCs are almost independent of variable sizes. Specifically, the size‐dependent charge transfers of In atoms in (InP)12n NCs exhibit that ionic and covalent bonding exist in (InP)12n NCs and can stabilize (InP)12n NCs. Comparison with experiment results available is made.

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.

Ternary g-C3N4/Co3O4/CeO2 nanostructured composites for electrochemical energy storage supercapacitors

Extensive use of fossil fuels causes heavy discharge of carbon dioxide, depleting energy resources and this requires environmentally friendly and effective energy storage materials. Hybrid supercapacitors (HSCs) are recently developed as effective energy storage materials enabling high capacitance retention rate and quick charging. Herein, synthesis of two-dimensional g-C3N4 nanosheets supported onto three-dimensional flower-like Co3O4/CeO2 (CoCe) ternary synergistic heterostructures are developed as effective electrodes for hybrid supercapacitor applications. Addition of g-C3N4 produces substantial surface active sites, enabling its synergistic effect with CoCe to enhance electrochemical performance having exceptional conductivity. The CoCe/g-C3N4 ternary composite electrode exhibits a higher specific capacitance of 1088.3 F g−1 at 1 A g-1 with 96 % of recycling stability over 5000 cycles, which is ∼5.5 and ∼5 folds higher specific capacitance than the pristine g-C3N4 and CoCe electrodes. EIS analysis revealed that CoCe/g-C3N4 electrode offered reduced charge transfer resistance compared to pristine electrodes. The fabricated two-electrode HSC device displays outstanding retention after 10,000 cycles with an ultra-high specific capacitance of 119.8 F g−1, excellent energy density 37.4 Wh kg−1 and power density of 749.9 W kg−1. This research showcases the perspectives of CoCe/g-C3N4 ternary electrodes in hybrid supercapacitors and other renewable energy storage devices.

Performance Degradation Mechanism of the Si@N, S-Doped Carbon Anode in Sulfide-Based All-Solid-State Batteries.

Silicon (Si) anode is a promising anode material for all-solid-state lithium batteries with ultra-high theoretical specific capacity and low lithium dendrite risk. However, the inevitable vast volume expansion of Si anode during charge/discharge is recognized as a major limitation preventing its commercial application. Herein, an N, S self-doped amorphous carbon layer coated on porous micron-sized Si (p-mSi@C) is designed to construct an electron/ion conducting network while ensuring structural and interfacial stability. Uneven distribution of von mises stresses during p-mSi lithiation leads to irregular volume expansion and even fragmentation. Meanwhile, the growth of by-products at the interface between p-mSi and electrolyte contact leads to a rapid capacity decay. Compared to p-mSi anode, p-mSi@C reduces the risk of fragmentation thanks to the stress-absorbing effect of amorphous carbon, delivering excellent electrochemical performance (2679.65 mAh g-1 at 0.2 mA cm-2 with initial coulombic efficiency of 84%). More importantly, the chemical failure mechanisms of p-mSi and p-mSi@C composite anodes are revealed through structural characterization, chemical analysis, and simulation, which provides the necessary theoretical guidance for practicalization.

Boosting the Charge Storage Capability of Bi2TeO5 Cathode Using Iodide Ions in Aqueous Zinc-Based Batteries System.

As insertion-type cathode materials of aqueous Zn-based batteries (ABs), bismuth chalcogenides/oxychalcogenides exhibits relatively limited capacities in ZnSO4 baseline electrolyte. This work finds that Bi2TeO5 (BTO) cathode with pre-added I- electrolyte additive can simultaneously achieve conversion and insertion chemistries, which enables aqueous BTO-Zn batteries to deliver an extraordinary electrochemical performance. As shown in the experiment results, the BTO cathode showcases an ultrahigh specific capacity of 534.9mA h g-1 at 0.5 A g-1, excellent rate capability (237.3mA h g-1 at 10 A g-1). In the estimation of cyclic durability, the capacity of the BTO cathode decreases from 271.2 to 171.1mA h g-1 during 2000 cycles at 10 A g-1.

Synergistic promotion of reaction kinetics for LiPSs at high loadings by interfacial built-in electric field and sulfur vacancies of ternary heterostructure for high-performance Li-S batteries

The practical application of lithium-sulfur batteries is significantly impeded by the chaotic migration of lithium polysulfides, sluggish redox-reaction kinetics, and pronounced shuttle effect. Herein, a ternary heterostructure (MoS2-x/MoO2/CoP) is developed with a spontaneous built-in electric field (BIEF) and enriched sulfur vacancies. This heterostructure comprises MoS2-x, which has a high adsorption capability and work function; CoP, noted for its low work function and potent catalytic properties; and MoO2, which features a work function between that of MoS2-x and CoP and serves as a bridge with excellent electronic conductivity. An appropriate combination of the catalyst and adsorbent with sulfur vacancies controls the direction of the BIEF, realizing the “adsorption-directed migration-catalytic” reaction mechanism for sulfur species. Specifically, the synergetic effect of the BIEF and sulfur vacancies enhances electron migration from CoP to MoS2-x, which improves the lithium polysulfide (LiPSs) trapping and accelerates the directional migration of LiPSs to CoP, thereby enabling the efficient catalytic conversion of sulfur species. Consequently, batteries equipped with MoS2-x/MoO2/CoP interlayers that contain sulfur vacancies demonstrate an ultrahigh initial specific capacity of 1356.2 mA h g−1 at 0.2 C, maintaining a capacity of 708.3 mAh g−1 after 1000 cycles at 2 C. Even with sulfur loading increased to 7.13 mg cm−2, these batteries display an initial specific capacity of 7.2 mAh cm−2. This work provides a feasible approach for the rational design of vacancy-containing ternary heterostructure catalysts for commercial lithium-sulfur batteries.

Hollow carbon nanofibers with self-induced internal electric field for high-performance full-carbon sodium ion capacitors

Self-induced internal electric field (SIEF) is crucial to achieve high capacity, high rate and long cycle life of carbon anodes in Na+ storage, but it is also a huge challenge currently. Herein, a template-assisted electrospinning process and subsequent low-temperature pyrolysis method is employed to synthesize S, N co-doped hollow carbon nanofibers (SNHCF) with rich micropores and chemisorption sites. The rich micropores and interconnected macroporous in SNHCF provide large internal availability that effectively exposing the active sites, inhibiting the volume expansion and shortening the Na+ diffusion distance. Besides, S, N co-doping in the carbon skeleton can act as an electron acceptor and electron donor respectively to form a SIEF to boost adsorption of Na+. Theoretical calculation and ex-situ characterizations confirmed that S, N co-doping can regulate the electronic configuration and reduce the diffusion barrier of Na+. As a result, SNHCF anode has ultra-high specific capacity (588.2mAh g−1 at 0.05 A/g) and impressive rate performance (264.3mAh g−1 at 20 A/g). The full-carbon sodium ion capacitors assembled with SNHCF anode and activated carbon cathode exhibits high energy density (119 Wh kg−1) and ultra-long cycle stability (80.06 % capacity retention after 12,000 cycles).

Micron silicon-oxide-carbon coated with TiOx(OH)y layer as better performance anode for lithium-ion batteries

Micron-silicon based material is a promising anode material for high performance lithium batteries due to its ultra-high specific capacity. However, the volume expansion exceeds 300 % during charging and discharging, resulting in the collapse of the electrode structure and a rapid decline in electrochemical performance. Coating the surface of silicon-based materials with flexible ionic conductors is an effective method to maintain their high capacity and suppress swelling. Here, to further improve the electrochemical performance of silicon-based materials, we have deposited a titanate-type ionic conductor layer on a micron-sized silicon-carbon oxide (SiOX-C) material to synthesize the SiOX-C@TiOx(OH)y material. The TiOx(OH)y layer not only exhibits the elastic properties of a superpolymer to mitigate swelling strain, but also has a fast capacitance effect to improve its rate performance. In addition, the interfacial charge transport of SiOX-C@TiOx(OH)y is enhanced due to the structural diversity of the TiOx(OH)y layer. For the above mechanisms, the SiOX-C@TiOx(OH)y has a specific capacity of 278.3 mAh g−1 under high current of 3500 mA g−1. Meanwhile, the SiOX-C@TiOx(OH)y with the capacity retention of 67 % is achieved at 2000 mA g−1 after 100 cycles.

Pyrolysis combined with KOH activation to turn waste apple pruning branches into high performance electrode materials with multiple energy storage functions

In this paper, porous activated carbon is successfully prepared from waste apple pruning branches (PGZ), which demonstrates an ultra-high specific capacity of 505 F g −1 at a current density of 1 A g −1 with excellent rate performance (215 F g −1 at 50 A g−1). The assembled supercapacitor also exhibits excellent specific capacitance of 320 F g −1 (at 0.5 A g−1) and 160 F g −1 (at 20 A g−1), with a high energy density of 12.03 Wh kg −1 at a power density of 250.45 W kg −1 in 6 M KOH. In 1 M Na2SO 4 and 1 M Et4 NBF4/AC electrolytes, high energy densities of 18.8 Wh kg −1 and 44.1 Wh kg −1 could be achieved. It also exhibits high reversible lithium storage capacity of 636.2 mAh g −1 at 0.2 C and retains 390 mAh g −1 after 1000 cycles. Even at 0.8 C, the storage capacity is still as high as 327 mAh g −1, with 282 mAh g −1 retained after 1000 cycles. These excellent electrochemical properties are attributed to the hierarchical porous structure of the sample prepared under the optimum conditions. The large pores in the hierarchical structure will lead to high-speed capacitive properties due to their low ion transport resistance while the small mesopore and micropore provide a large electrode and electrolyte interface, which can facilitate charge transfer reaction. These outstanding performances highlights the first example of using waste apple pruning branches as a sustainable source of raw materials for the preparation of high value-added porous carbon materials with multiple energy storage functions.

ZnS Nanoseeds Sealed in N, P, S Co-Doped Carbon Hollow Rhombic Dodecahedra as a Superlithiophilic Host for Dendrite-Free Lithium Metal Anodes.

Lithium (Li) metal is considered ahopeful anode for next-generation Li-ion batteries thanks to its ultra-high theoretical specific capacity, extra-low theoretical density, and low negative potential. However, the uncontrolled growth of Li dendrites and volume fluctuation during plating/stripping processes severely hamper its commercial application. Herein, ZnS seeds sealed in N, P, S co-doped carbon hollow rhombic dodecahedra (ZnS@NPS-C HRD) is fabricated as a superlithiophilic host for Li metal anodes (LMAs) to solve the above problems. In addition, the Li nucleation and deposition mechanism on ZnS@NPS-C HRD is investigated by in situ optical microscopy, ex-situ X-ray diffraction, scanning electron microscopy, and theoretical calculations. Owing to the synergistic strategy of ZnS seeds-inducing nucleation and Li-limited growth, the as-prepared composite exhibits stability for 300 cycles in asymmetric cells and a long lifespan over 1100h in symmetric cells. Moreover, the ZnS@NPS-C HRD@Li|LiFePO4 full cell demonstrates a reversible capacity of 100.91mAhg-1 after 400 cycles at 1C.

Deciphering the energy storage mechanism of CoS2 nanowire arrays for High-Energy aqueous copper-ion batteries

Transition metal sulfide (TMs) offers ultra-high specific capacity through multi-electron transfer, showing promise for aqueous batteries. However, the poor cycling performance and the uncleared energy storage mechanism are restricted from further development. Herein, CoS2 nanowire arrays grown on carbon cloth (CoS2/CC) are proposed as binder-free and self-supporting electrodes for aqueous copper-ion batteries. The energy storage mechanism is clarified by a series of ex-situ tests: a multi-electron electrode reaction through a three-step reaction of CoS2 → CuS → Cu7S4 → Cu2S. Electrochemical results suggest that the CoS2/CC cathode exhibits excellent long cycle stability (capacity retention of 99.7 % after 1000 cycles at 10 A/g) along with high specific capacity (762.3 mAh g−1 at 1 A/g). The carbon cloth with stable three-dimensional (3D) conductive structure can not only offer high-speed pathways to promote the transfer of electrons but also inhibit the volume change. Meanwhile, CoS2 nanowire arrays with high surface-to-volume ratios can improve wettability of electrolyte and promote redox reactions. Furthermore, an advanced Zn-CoS2/CC hybrid ion aqueous battery reveals an energy density of 724 Wh kg−1 and an output voltage of 1.24 V, providing a promising strategy for the establishment of transition metal sulfide cathode in high-energy aqueous batteries.

Design Unsaturated Selenium Coordinated NbSe2-x as Multifunctional Sulfur Electrocatalyst toward Fast and Durable Sulfur Reduction Reaction.

Lithium-sulfur (Li-S) battery are considered as the next generation energy storage system owing to their ultra-high theoretical specific capacity and energy density. However, the commercialization of Li-S battery is still hindered by the intrinsically low conductivity of sulfur, sluggish catalytic conversion and notorious shuttle effect of polysulfides. The implantation of defects in sulfur electrocatalyst can effectively increase its conductivity and catalytic efficiency of lithium polysulfides, but the current mainstream defective materials are limited and lack of in-depth research. Herein, a defective niobium selenide (NbSe2-x) nanosheet sulfur electrocatalyst is constructed with enriched selenium defects, which demonstrates strong interaction with sulfur species, endowing NbSe2-x with rapid and reliable sulfur reduction reaction. As a result, the Li-S cell with NbSe2-x exhibits excellent multiplicative performance in both coin cell and pouch cell, which maintains stable cycling for over 2000 cycles under 5 C, corresponding to a low-capacity fading rate of 0.024% per cycle. Ah level pouch cell is also fabricated, showing a decent energy density of 378Wh kg-1. This creative strategy not only emphasizes the importance of selenium defect engineering in Li-S batterie toward practical application, but also enlightens the material engineering to realize superior performance in related energy storage and conversion area.

Multicomponent hierarchical Cu-based advanced cathode for ultrahigh capacity rechargeable Cu-Zn battery

Rechargeable aqueous Zn-based batteries (RAZBs) have emerged as a practically attractive option for large-scale energy storage applications due to their cost-effectiveness, safety, eco-friendliness, and high theoretical capacity. Nonetheless, the application of RAZBs at the grid scale is restricted by the drawbacks of cathode that exhibit low capacities and poor durability. In this work, a multicomponent hierarchical Cu@CuO@Cu2O cathode with superior electrochemical energy storage performance has been successfully synthesized by a fairly simple calcination method. Benefiting from its large active area, fast ion diffusion channel, high conductivity, and synergetic effect between different components, the resulting Cu@CuO@Cu2O electrode exhibits ultrahigh specific capacity (40.2 mAh cm−2, 402 mAh cm−3 at 10 mA cm−2), excellent rate capability (24.8 mAh cm−2, 248 mAh cm−3 at 100 mA cm−2) and satisfactory cycling durability (71.5 % capacity retention after 3800 cycles). To our knowledge, such high areal/volumetric specific capacity ranks top among previously reported Cu-based electrode and other aqueous electrodes. Furthermore, the fabricated Cu@CuO@Cu2O//Zn battery achieves an extraordinary energy density of 24.5 mWh cm−2 and a remarkable cyclic capability of 91 % capacity retention after 3000 cycles, highlighting its potential for large-scale energy storage in RAZBs.

Developing a Multifunctional Cathode for Photoassisted Lithium-Sulfur Battery.

Integration of solar cell and secondary battery cannot only promote solar energy application but also improve the electrochemical performance of battery. Lithium-sulfur battery (LSB) is an ideal candidate for photoassisted batteries owing to its high theoretical capacity. Unfortunately, the researches related the combination of solar energy and LSB are relatively lacking. Herein, a freestanding photoelectrode is developed for photoassisted lithium-sulfur battery (PALSB) by constructing a heterogeneous structured Au@N-TiO2 on carbon cloths (Au@N-TiO2/CC), which combines multiple advantages. The Au@N-TiO2/CC photoelectrode can produce the photoelectrons to facilitate sulfur reduction during discharge process, while generating holes to accelerate sulfur evolution during charge process, improving the kinetics of electrochemical reactions. Meanwhile, Au@N-TiO2/CC can work as an electrocatalyst to promote the conversion of intermediate polysulfides during charge/discharge process, mitigating induced side reactions. Benefiting from the synergistic effect of electrocatalysis and photocatalysis, PALSB assembled with an Au@N-TiO2/CC photoelectrode obtains ultrahigh specific capacity, excellent rate performance, and outstanding cycling performance. What is more, the Au@N-TiO2/CC assembled PALSB can be directly charged under light illumination. This work not only expands the application of solar energy but also provides a new insight to develop advanced LSBs.

Rolling strategy for highly efficient preparation of phosphating interface enabled the stable lithium anode

Lithium metal anode has an ultra-high theoretical specific capacity and the lowest reduction potential, regarded as the next-generation anode material for high-energy-density batteries. However, the lithium metal anode suffers from the severe side reaction and Li dendrite growth caused by the inhomogeneous deposition of Li+ on the anode during the electrochemical cycling. Herein, a strategy is proposed to design an artificial solid electrolyte interface (SEI) by rolling with the organic phosphating lubricant. The obtained phosphating interface with high surface energy and surface Young’s modulus significantly induces the dense deposition of Li+ and results in a stable cycling. The phosphating interface enables the symmetric cells to cycle stably for 750 h at 1 mA cm−2 with 1 mA h cm−2 and for 450 h at 3 mA cm−2 with 3 mA h cm−2 using ester-based electrolyte. The full cell with high single-side mass loading (10 mg cm−2) of LiCoO2 achieves a capacity retention rate of 77.7 % after 165 cycles at 1 C and 75.6 % after 120 cycles at 2 C. This work paves a path to construct a green fluorine-free interface and provide a large-scale modification for practical lithium strips.

Enhancing novel electrode of MnCo2O4 nanowire/Ni2.5Mo6S6.7 nanosheet arrays for hybrid capacitor

Rationally synthesizing promising electrode material with nano-morphologies for excellent practical hybrid capacitor application lingers as a challenge. To complete the assignment, we design MnCo2O4@Ni2.5Mo6S4.7 electrode via facial hydrothermal approach assisted with calcination and vulcanization processes in which the nano-structured material anchors on the nickel substrate. An ultrahigh specific capacitance of 3164 F g−1 at 1 A g−1 is delivered by the cathode electrode material. The specific capacitance of MnCo2O4@Ni2.5Mo6S6.7 remains 97.2 % even after 8000 cycles. The as-fabricated hybrid capacitor (HC) produces 75.2 Wh kg−1 energy density at 2700 W kg−1 power density. The device shows high stability rate (87.5 % at 8 A g−1 of its original capacitance throughout 8000 cycles. The outcome of MnCo2O4@Ni2.5Mo6S6.7 structure design demonstrates its potential utilizations in future smart micro/nano energy storage device.

A Nanofibrous Polypyrrole Membrane with an Ultrahigh Areal Specific Capacitance and Improved Energy and Power Densities.

For conductive polymers to be competitive with carbon-based electrode materials, it is critical to increase their surface area and electroactivity. In this work, a thick nanofibrous polypyrrole (PPy) membrane with communicating interfiber spaces was prepared through one-pot interfacial polymerization for the first time. The electrochemical properties and conductivity of the membrane were studied with cyclic voltammetry, electrochemical impedance spectroscopy, and a four-point probe. Its morphology, chemistry, and thermostability were evaluated by scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The areal specific capacitances measured between 0.0 and 0.8 V at 1 mA/cm2 were 19179, 13264, 7238, and 4458 mF/cm2 for the membranes doped with docusate sodium (AOT), camphor-10-sulfonic acid (β) (CSA), Cl-, and poly(sodium 4-styrenesulfonate) (PSS), respectively. The capacity retentions after 1000 cycles were 83, 74, 67, and 61% for the AOT-, CSA-, PSS-, and Cl--doped membranes, respectively. The Coulombic efficiency was above 99% for all of the membranes. They showed energy densities of 1.7, 1.2, 0.7, and 0.4 mWh/cm2 and power densities of 0.61, 0.75, 0.66, and 0.62 mW/cm2 for the AOT-, CSA-, Cl--, and PSS-doped membranes, respectively. The ultrahigh areal specific capacitance of PPy-AOT is due to its nanofibrous structure. A mechanism has been proposed to explain how this structure is formed based on the role of AOT as the surfactant. This nanofibrous PPy membrane is easy to prepare and metal-free and offers a very high areal specific capacitance, making it an excellent candidate to construct electrodes in pseudosupercapacitors.

Constructing nitrogen-doped graphene quantum dots embedded in CNT supported layered (Ni0.5Co0.5)3V2O8 self-supporting film for high-performance supercapacitor

To improve the electrochemical performance of positive electrode materials, constructing graded nanostructures is a worthwhile approach. This study successfully synthesized nitrogen-doped graphene quantum dots (NGQD) modified (Ni0.5Co0.5)3V2O8 on a carbon nanotube (CNT) substrate to construct self-supporting electrodes for high-performance supercapacitors. The (Ni0.5Co0.5)3V2O8 nanosheets were successfully wrapped onto the CNT surface through a solution impregnation process, which increased the specific surface area and interlayer spacing of the material. Furthermore, the electrochemical properties of the electrode material underwent significant enhancement due to the synergistic interplay between metal ions and the numerous redox centers. The embedding of the NGQD enriched the materials with active sites and further improved its specific capacity without compromising the structure intergrity of the layer configuration. Using CNT as the substrate ensured the self-supporting nature of the electrode. Consequently, the (Ni0.5Co0.5)3V2O8/NGQD@CNT composite exhibits an ultra-high specific capacitance of 3018.2 F g−1 at 1 A g−1 and 2332 F g−1 at 10 A g−1. The asymmetric supercapacitor constructed with (Ni0.5Co0.5)3V2O8/NGQD@CNT and activated carbon (AC) presented an impressive energy density of 160.2 Wh kg−1 at a power density of 800 W kg−1. After 8000 charge–discharge cycles, the capacity retention rate was 78.5 %, with a Coulo mbic efficiency consistently above 98 %.

Stress-Relieving Carboxylated Polythiophene/Single-Walled Carbon Nanotube Conductive Layer for Stable Silicon Microparticle Lithium-Ion Battery Anodes

Silicon is one of the most promising anode materials for next generation Lithium ion batteries (LIBs) on account of its ultrahigh specific capacity (4200 mAh g-1) and relatively low working potential of 0.3 V (vs. Li+/Li). However, practical commercial implementation of silicon poses a great challenge due to technical difficulties such as low conductivity (10-5-10-3 S cm-1), low initial Coulombic efficiency (50-80%) and stress-induced fracture, along with SEI accumulation due to severe volume changes (~400%) inherent in silicon-based anodes.To address these challenges and advance the next generation of LIBs, we present poly[3-(potassium-4-butanoate)thiophene] (PPBT) and single-walled carbon nanotube (SWNT) coated silicon microparticles (Si MPs) (PPBT/SWNT@Si MPs) as active materials for highly stable Si-based anodes for LIB systems. The water-soluble conjugated polymer, PPBT, was selected for its ability to serve as an ion and electron conducting physical/chemical linker (10-5 S cm-1 vs. PVDF; ~ 10-8 S cm-1) to the surface of various high capacity anode active materials systems. In consideration of current practical requirements for Si-based anode materials, Si MPs were selected as starting materials due to their lower surface area than the nanoscale analogs, a characteristic that can further improve LIB bulk capacity. In addition, Si MPs are known to have high initial Coulombic efficiency and industrial compatibility. With the help of PPBT, which facilitates unraveling of entangled single-walled carbon nanotubes, SWNTs were successfully attached to the surface of the active materials. PPBT carboxylate substituents were found to be chemically bound to the Si MP surface, providing an electrochemically conductive environment in intimate contact with the 1D SWNTs and Si MPs.Due to facilitated ion/electron transport kinetics, PPBT/SWNT@SiMP anodes exhibited superior capacity retention and higher reversible capacities, even at a high current density of 8 A g-1, compared to bare Si MP anodes. Improved initial Coulombic efficiency and stable cycling performance over 300 cycles were achieved. In situ Raman spectroscopy was employed to investigate the evolution of stress on the SWNTs during lithiation/delithiation, which elucidated the mechanism underlying the enhancement in PPBT/SWNT@Si MP anode cycling performance. The single-walled carbon nanotubes within the PPBT/SWNT@Si MP anodes consistently exhibited reversible stress recovery and 45 % less tensile stress variation after the 10th cycle than SWNT@Si MP control anodes fabricated by direct mixing of the microparticles with SWNTs to create SWNT@Si MPs.Combined, the results suggest that a well-developed conductive interface can enhance the rate performance, and improve electrode stability and Coulombic efficiency. Furthermore, the PPBT/SWNT coating directly bound to the Si MP surface provides for efficient stress relaxation of Si-based electrodes, resulting in reversible lithiation/delithiation, low electrode resistance, and reduced SEI layer formation.