rGO Anode Research Articles

Supramolecular-driven construction of multilayered structure by modified hummers method for robust silicon anode

Rational design of nano-structured silicon (Si)-based composites to enhance the structural stability and electrical conductivity is key to developing high-performance lithium-ion batteries. Here, a supramolecular self-assembly strategy is first adopted to prepare Si@rGO composites with multilayered structure through the modified Hummers method. Experimental results demonstrate that Si@SiOx NPs are uniformly distributed in rGO interlayers by supramolecular interaction. In situ Raman results suggest that the multilayer embedded structure can effectively confine the Si NPs and preserve the integrity of the electrode. Theoretical calculations indicate that the imbalanced charge distribution in inner interface shows enhanced dual-interfacial bonding and charge interactions in the Si@SiOx⊂rGO composite, resulting in an interfacial electric-field between Si NPs and rGO for fast ionic and charge migration. The fabricated MSi@SiOx⊂rGO anode with high Si contents (> 60 wt.% Si) exhibits superior Li-ion reaction kinetics (882.4 mAh g−1 at 8 A g−1), durable structural stability (0.031% per cycle capacity attenuation with an average Coulombic efficiency > 99.7%), and low expansion rate. High-mass-loading electrodes show great potential for commercial applications. Full cells assembled with LiCoO2 cathodes also demonstrate outstanding Li-ion storage properties. This work provides insights into the interfacial design of Si@C anodes for advanced Li-ion battery.

Controllable synthesis of carbon supported cobalt monoxide anode and high-voltage lithium cobalt oxide cathode with enhanced lithium-ion storage

Natural macromolecule amylose (AM) is employed to deoxygenate few-layered graphene oxide (GO) and modulate the surface interaction between GO sheets and Co2+ ions under mild hydrothermal conditions. The obtained Co2+ ions and AM molecule jointly decorated reduced graphene oxide (Co-AM/RGO) sample is further utilized to synthesize both anode and cathode materials with controlled microstructures. To synthesize anode material, the Co-AM/RGO can be directly converted to a hierarchical AM pyrolyzed carbon and RGO supported cobalt monoxide nanocomposite (CoO@AMC/RGO) after a simple inert gas protected thermal treatment. To synthesize cathode material, a carbon coated nano-sized lithium cobalt oxide sample (LiCoO2/C, LCO/C) can be obtained after a solid-state reaction in air by mixing lithium salt with the Co-AM/RGO. The CoO and LCO nanocrystals with significantly controlled sizes are well dispersed in the carbon matrices. The CoO@AMC/RGO anode shows a high reversible capacity of 785.25 mAh·g−1 after 500 cycles at 200 mA·g−1 and 608.25 mAh·g−1 after 700 cycles at 1000 mA·g−1, while the LCO/C cathode delivers a superior reversible capacity of 140.91 mAh·g−1 after 1000 cycles at 1000 mA·g−1 with a high cut-off voltage of 4.6 V. This work provides a new perspective for controllable engineering of electrode materials with enhanced lithium-ion storage performances.

3D-Printed Hierarchically Microgrid Frameworks of Sodiophilic Co3O4@C/rGO Nanosheets for Ultralong Cyclic Sodium Metal Batteries.

Herein, hierarchically structured microgrid frameworks of Co3O4 and carbon composite deposited on reduced graphene oxide (Co3O4@C/rGO) are demonstrated through the three-dimensioinal (3D)printing method, where the porous structure is controllable and the height and width are scalable, for dendrite-free Na metal deposition. The sodiophilicity, facile Na metal deposition kinetics, and NaF-rich solid electrolyte interphase (SEI) formation of cubic Co3O4 phase are confirmed by combined spectroscopic and computational analyses. Moreover, the uniform and reversible Na plating/stripping process on 3D-printed Co3O4@C/rGO host is monitored in real time using in situ transmission electron and optical microscopies. In symmetric cells, the 3D printed Co3O4@C/rGO electrode achieves a long-term stability over 3950 at 1mA cm-2 and 1 mAh cm-2 with a superior Coulombic efficiency (CE) of 99.87% as well as 120h even at 20mA cm-2 and 20 mAh cm-2, far exceeding the previously reported carbon-based hosts for Na metal anodes. Consequently, the full cells of 3D-printed Na@Co3O4@C/rGO anode with 3D-printed Na3V2(PO4)3@C-rGO cathode (≈15.7mg cm-2) deliver the high specific capacity of 97.97 mAh g-1 after 500 cycles with a high CE of 99.89% at 0.5 C, demonstrating the real operation of flexible Na metal batteries.

Cobalt-Mediated Defect Engineering Endows High Reversible Amorphous VS4 Anode for Advanced Sodium-Ion Storage.

Metal sulfides are promising anode materials for sodium-ion batteries (SIBs) due to their structural diversity and high theoretical capacity, but the severe capacity decay and inferior rate capability caused by poor structural stability and sluggish kinetics impede their practical applications. Herein, a cobalt-doped amorphous VS4 wrapped by reduced graphene oxide (i.e., Co0.5-VS4/rGO) is developed through a Co-induced defect engineering strategy to boost the kinetics performances. The as-prepared Co0.5-VS4/rGO demonstrates excellent rate capacities over 10Ag-1 and superior cycling stability at 5Ag-1 over 1600 cycles, which is attributed to the defects formed by Co doping, the formed amorphous structure and the robust rGO substrate. The great features of Co0.5-VS4/rGO anode are further confirmed in sodium-ion capacitors when the active carbon cathode is used. Additionally, the relationships between metal doping, the derived defects, the amorphous structure, and the sodium storage of VS4 are uncovered. This work provides deep insights into preparing amorphous functional materials and also probes the potential applications of metal sulfide-based electrode materials for advanced batteries.

Rational Design of High-Performance Electrodes Based on Ferric Oxide Nanosheets Deposited on Reduced Graphene Oxide for Advanced Hybrid Supercapacitors.

The core strategy for constructing ultra-high-performance hybrid supercapacitors is the design of reasonable and effective electrode materials. Herein, a facile solvothermal-calcination strategy is developed to deposit the phosphate-functionalized Fe2O3 (P-Fe2O3) nanosheets on the reduced graphene oxide (rGO) framework. Benefiting from the superior conductivity of rGO and the high conductivity and fast charge storage dynamics of phosphate ions, the synthesized P-Fe2O3/rGO anode exhibits remarkable electrochemical performance with a high capacitance of 586.6Fg-1 at 1Ag-1 and only 4.0% capacitance loss within 10000 cycles. In addition, the FeMoO4/Fe2O3/rGO nanosheets are fabricated by utilizing Fe2O3/rGO as the precursor. The introduction of molybdates successfully constructs open ion channels between rGO layers and provides abundant active sites, enabling the excellent electrochemical features of FeMoO4/Fe2O3/rGO cathode with a splendid capacity of 475.4C g-1 at 1Ag-1. By matching P-Fe2O3/rGO with FeMoO4/Fe2O3/rGO, the constructed hybrid supercapacitor presents an admirable energy density of 82.0Whkg-1 and an extremely long working life of 95.0% after 20000 cycles. Furthermore, the continuous operation of the red light-emitting diode for up to 30min demonstrates the excellent energy storage properties of FeMoO4/Fe2O3/rGO//P-Fe2O3/rGO, which provides multiple possibilities for the follow-up energy storage applications of the iron-based composites.

Dynamic Electronic and Ionic Transport Actuated by Cobalt-Doped MoSe2 /rGO for Superior Potassium-Ion Batteries.

Molybdenum selenium (MoSe2 ) has tremendous potential in potassium-ion batteries (PIBs) due to its large interlayer distance, favorable bandgap, and high theoretical specific capacity. However, the poor conductivity and large K+ insertion/extraction in MoSe2 inevitably leads to sluggish reaction kinetics and poor structural stability. Herein, Coinduced engineering is employed to illuminate high-conductivity electron pathway and mobile ion diffusion of MoSe2 nanosheets anchored on reduced graphene oxide substrate (Co-MoSe2 /rGO). Benefiting from the activated electronic conductivity and ion diffusion kinetics, and an expanded interlayer spacing resulting from Co doping, combined with the interface coupling with highly conductive reduced graphene oxide (rGO) substrate through Mo-C bonding, the Co-MoSe2 /rGO anode demonstrates remarkable reversible capacity, superior rate capability, and stable long-term cyclability for potassium storage, as well as superior energy density and high power density for potassium-ion capacitors. Systematic performance measurement, dynamic analysis, in-situ/ex-situ measurements, and density functional theory (DFT) calculations elucidate the performance-enhancing mechanism of Co-MoSe2 /rGO in view of the electronic and ionic transport kinetics. This work offers deep atomic insights into the fundamental factors of electrodes for potassium-ion batteries/capacitors with superior electrochemical performance.

Cation-deficient T-Nb2O5/graphene Hybrids synthesized via chemical oxidative etching of MXene for advanced lithium-ion capacitors

Orthorhombic niobium pentoxide (T-Nb2O5) is widely acknowledged as a fast pseudocapacitive material. Nevertheless, its application is hindered by the narrow voltage window (1–3 V vs. Li/Li+) that arises from irreversible phase transformation and sluggish kinetics during deep lithiation. Herein, we demonstrate a unique method for introducing Nb vacancies in T-Nb2O5 nanoparticles via amine-assisted oxidative etching of Nb2CTx MXene, providing extra storage sites and improving structural flexibility by introducing cationic defects. Subsequently reduced graphene oxide (rGO) is employed as substrate to disperse T-Nb2O5 nanoparticles and construct T-Nb2O5/rGO nanohybrids. Multiple characterizations and computational simulations demonstrate that the resulting T-Nb2O5/rGO hybrid anode exhibits rapid and stable multi-electron transfer lithium storage. Owing to the enrichment of Nb vacancies and nanoparticle morphology, even when voltage window of 0.01–3 V (vs. Li/Li+) is extended, T-Nb2O5 exhibits a pseudocapacitive mechanism and integrity of partial crystal structure; effectively tackling the structural collapse and sluggish kinetics of T-Nb2O5. Consequently, the T-Nb2O5/rGO anode shows a superior rate capacity (148 mAh/g at 10 A/g) and cycling stability (3000 cycles at 5 A/g). Remarkably, the assembled lithium-ion capacitors achieve a high energy density of 123.7 Wh/kg, a power density of 22.5 kW/kg, and a capacity retention of 83.6% after 20,000 cycles.

One-step synthesis method of flower-like Si@NiO/rGO composites as high-performance anode for lithium-ion batteries

Si-based materials are the most potential high-capacity anode material for lithium-ion batteries due to their theoretical specific capacity of 4200 mAh g−1, significantly higher than the current commercial graphite anode (372 mAh g−1). However, the significant volume change (>300%) of Si-based materials during the embedding of lithium ions into Si NPs results in various issues, such as short cycle life and low electrical conductivity, which significantly restricts their commercial development. This study introduces a new flower-like Si@NiO/reduced graphene oxide (rGO) ternary composite synthesized using a straightforward and low-pollution one-step synthesis technique. A distinctive composite flower-like structure is created by wrapping Si NPs in NiO nanoflowers and embedding the rGO nanosheets in the NiO "petal" structure. This structure can shorten the lithium-ion transport path, provide a superb conductive network, effectively reduce the electrode's bulk effect and improve the structural stability of the anode material. Additionally, the structure provides more capacity for the electrodes. At a current density of 1 A g−1 and after 700 cycles, the Si@NiO/rGO anode displays a discharge-specific capacity of 1081.34 mAh g−1 thanks to its one-of-a-kind flower-like structure. At various current densities, the Si@NiO/rGO anode likewise demonstrates outstanding electrochemical performance. Additionally, the volume growth of the flower-like Si@NiO/rGO anode material after 700 cycles is approximately 15.08%, substantially less than that of Si NPs. The new flower-shaped Si@NiO/ rGO ternary composite, synthesized in a simple and cost-effective way, offers not only an alternative for the preparation of Si-based electrode materials that can alleviate their drastic volume expansion but also an effort to create new renewable green energy storage devices.

A high-energy hybrid lithium-ion capacitor enabled by a mixed capacitive-battery storage LiFePO4 – AC cathode and a SnP2O7 – rGO anode

In this work we present the development and optimization of a graphene-embedded Sn-based material and an activated carbon/lithium iron phosphate composite for a high-performing hybrid lithium-ion capacitor (LIC).

Ultrahigh areal capacity and long cycling stability of sodium metal anodes boosted using a 3D-printed sodiophilic MXene/rGO microlattice aerogel.

Sodium metal has emerged as a highly promising anode material for sodium-based batteries, owing to its intrinsic advantages, including its high theoretical capacity, low working plateau and low cost. However, the uncontrolled formation of sodium dendrites accompanied by unrestricted volume expansion severely limits its application. To tackle these issues, we propose an approach to address these issues by adopting a three-dimensional (3D) structure of Ti3C2Tx/reduced graphene oxide (Ti3C2Tx/rGO) constructed by a direct-ink writing (DIW) 3D printing technique as the Na metal anode host electrode. The combination of the 3D-printed rGO skeleton offering artificial porous structures and the incorporation of sodiophilic Ti3C2Tx nanosheets provides abundant nucleation sites and promotes uniform sodium metal deposition. This specially designed architecture significantly enhances the Na metal cycling stability by effectively inhibiting dendrite formation. The experimental results show that the designed Ti3C2Tx/rGO electrode can achieve a high coulombic efficiency (CE) of 99.91% after 1800 cycles (3600 h) at 2 mA cm-2 with 2 mA h cm-2. Notably, the adopted electrodes exhibit a long life span of more than 1400 h with a high CE over 99.93% when measured with an ultra-high capacity of 50 mA h cm-2 at 5 mA cm-2. Furthermore, a 3D-printed full cell consisting of a Na@Ti3C2Tx/rGO anode and a 3D-printed Na3V2(PO4)3C-rGO (NVP@C-rGO) cathode was successfully demonstrated. This 3D-printed cell could provide a notable capacity of 85.3 mA h g-1 at 100 mA g-1 after 500 cycles. The exceptional electrochemical performance achieved by the 3D-printed full cell paves the way for the development of practical sodium metal anodes.

Heterogeneous WO2/WS2 microspheres synergized with reduced graphene oxides with high rate capacity for superior sodium-ion capacitors

• Heterogeneous WO 2 /WS 2 microspheres wrapped by reduced graphene oxide are prepared. • WO 2 /WS 2 nanosheets shorten Na + diffusion and WO 2 guarantee high electron conductivity. • RGO provide structure protecting layer and alleviate the volume change of WO 2 /WS 2. • WO 2 /WS 2 -rGO electrode exhibits large capacity, high rate and long cycle life. • A 4.0 V sodium-ion capacitor achieves 140 Wh kg −1 at 200 W kg −1. High rate capacity and long-term cycling stability are the pursuing characteristic of a promising anode for sodium-ion capacitors (SICs). However, the sluggish reaction kinetics and aggregation of volume during sodiation/desodiation process are the main obstacles. In this work, we developed a 3D porous WO 2 /WS 2 -rGO network while urchin-like microspheres self-assembled by WO 2 /WS 2 heterogeneous nanosheets and wrapped by rGO network, demonstrating superior rate properties and cycling stability as the anode of sodium-ion batteries (SIBs). The ultrathin WO 2 /WS 2 nanosheets contribute to shorten the Na + diffusion length, while metallic WO 2 guaranteeing high electric conductivity of nanosheet units and rGO network help to construct the fast dual electron transfer pathways during sodiation/desodiation process. Also, rGO network can provide a stable structure protecting layer and alleviate the volume change of WO 2 /WS 2 . Benefiting from these merits, WO 2 /WS 2 -rGO electrode reveals a dominanting capacitive-controlled process especially at the higher scan rates and achieves 100 mAh g −1 at an ultrahigh current density of 25.6 A g −1 as well as maintains 90% capacity retention over 1000 cycles at 1 A g −1 . The SICs comprising of WO 2 /WS 2 -rGO anode and 3D phosphorus-doped carbon (P C) cathode demonstrate outstanding energy density of 140 Wh kg −1 at 200 W kg −1 along with a reasonable stable cycling of 79% capacity retention over 6000 cycles at 5 A g −1 within the voltage of 0.0–4.0 V. The proposed strategy integrates hierarchical heterogeneous structure and effective dual electron transfer network can be applied to develop promising electrode materials for high performance energy storage systems.

Rational designed hierarchical dual carbon protected ZnSe anode for advanced sodium-ion hybrid capacitors

With a remarkable advantage of high theoretical capacity and excellent rate performance, zinc selenide (ZnSe) has been regarded as a high-potential electrode for sodium-ion batteries (SIBs). Nevertheless, the practical use of ZnSe as the anode for SIBs is severely limited by the large volumetric expansion and sluggish kinetics during the conversion/alloying reaction process. Herein, we develop a dual-type carbon approach to afford a 3D hierarchical ZnSe@N-doped carbon/reduced graphene oxide (ZnSe@NC/rGO) using simple selenization of ZIF-8 and subsequent incorporation process. Alongside with buffering the volume variation by the in-situ generated NC, the electron and ion transfer can also be accelerated on account of the interconnected graphene network. Therefore, the ZnSe@NC/rGO offers a splendid discharge capacity of 455.3 mAh g−1 at 0.1 A g−1, and exhibits a superior rate capability of 195.1 mAh g−1 at 5 A g−1. Besides, the capacity retains as high as 170.1 mAh g−1 after 500 cycles at 5 A g−1, indicating an outstanding cyclic ability. A full-cell sodium ion hybrid capacitor (SIHC) constructed using a ZnSe@NC/rGO anode and a commercial activated carbon (AC) cathode (ZnSe@NC/rGO//AC SIHC) shows a high energy output of 117.8 Wh kg−1 at 105 W kg−1, and a long lifespan with 86.4% capacity retention over 3000 cycles.

Structural design and optimization of metal-organic framework-derived FeO @C/rGO anode materials for constructing high-performance hybrid supercapacitors

Hybrid supercapacitors are promising energy storage devices that bridge the performance gap between conventional capacitors and batteries. However, the backward development of anode materials is a key issue that hinders the performance improvement of the hybrid supercapacitors. Therefore, this study proposes a strategy to fabricate reliable FeOx-based (Fe2O3 or Fe3O4) anode materials using the Fe-based metal-organic framework (Fe-MOF) as a template. Polyvinyl pyrrolidone (PVP) was used to stabilize and regulate the morphology of the Fe-MOF template to ensure a desirable microstructure of the final product. A series of FeOx@Carbon nanocages/reduced graphene oxide (FeOx@C/rGO) nanocomposites were obtained by calcinating the templates. The optimized Fe2O3@C/rGO–2 nanocomposite possesses considerable specific surface area and pore volume, with ultrasmall Fe2O3 particles (<5 nm) stably embedded in the carbon nanocages. The unique microstructure of the Fe2O3@C/rGO–2 electrode results in improved ion/electron accessibility that ensures an admirable specific capacity (713 C g−1 at 1 A g−1) and rate capability (67.3% retention at 50 A g−1). Meanwhile, the impressive cycling stability (104% retention after 20000 cycles) originates from the dual protection of Fe2O3 particles by the carbon nanocages and rGO. Furthermore, a hybrid supercapacitor constructed from a Fe2O3@C/rGO–2 anode and a nickel foam-supported NiCo2O4 nanoneedles (NiCo2O4–NF) cathode exhibited a maximum energy density of 101.9 Wh kg−1, suggesting that the delicately designed anode material is a promising candidate for constructing advanced energy storage devices.

Ultrathin nickel cobalt nitride nanoflowers embedded in Cu3N porous nanorod arrays for ultrahigh capacitance energy storage

Transition-metal nitrides are selected as potential materials for energy storage due to their excellent theoretical electrochemical properties. However, its structure easily collapses in electrochemical reactions, which hinders their application. Reasonable regulation and unique design of its structure is a feasible strategy. Here, we have constructed a unique layered porous heterostructure through a continuous multi-step method. The prepared Cu3N@NiCo–N/Cu electrode material exhibits excellent electrochemical performance (8.49 F cm−2 at 1 mA cm−2) and outstanding cycle stability (90.1% after 8000 cycles). In particular, the asymmetric supercapacitor device assembled with Cu3N@NiCo–N/Cu cathode and rGO anode provides an excellent energy density of 124.9 μWh cm−2 at a power density of 1.6 mW cm−2. This research expands new methods for constructing high-performance energy storage devices.

Porous core-shell B-doped silicon–carbon composites as electrode materials for lithium ion capacitors

Development of anode materials of high capacities, rate capability, and cycling stability is critical for lithium ion capacitors (LICs). Composite electrode design, combining advantages of constituent component materials, is a promising approach for the purpose. Porous core-shell B-doped silicon-carbon spheres, B–Si@1RFC, of small sizes (150 nm) and high specific capacities are successfully synthesized with a one-pot method, followed by carbonization, magnesiothermic reduction, and B-doping, to be composited with reduced graphene oxide (rGO) porous structure of excellent structural and electrical properties to serve as an outstanding anode material, B–Si@1RFC/rGO, for LICs. The LIC, assembled by coupling the B–Si@1RFC/rGO anode with a glucose-derived carbon nanosphere cathode of ultrahigh specific surface areas (1947 cm2 g−1) and pore volumes (2.04 cm3 g−1), delivers a high energy density of 149 Wh kg−1 at a power density of 0.328 kW kg−1 and maintains a decent energy density of 82.1 kW kg−1 at a high power density of 49.3 kW kg−1, together with an excellent cycling stability of retaining 74.4% of the initial energy density after 10,000 cycle operations at 5 A g−1.

Thiophene-diketopyrrolopyrrole-based polymer derivatives/reduced graphene oxide composite materials as organic anode materials for lithium-ion batteries

In this work, we synthesized thiophene-diketopyrrolopyrrole-based (TDPP-based) polymer derivatives/reduced graphene oxide (RGO) composites. The interaction between the carboxyl groups on polymer and the hydroxyl groups on graphene oxide endows the composite excellent electrochemical performance as anode for lithium-ion batteries (LIBs). The participation of RGO decreases the discharge voltage, enhances electronic conductivity, and improves the capacity retention for P(C-TDPP-AC)/RGO (contains carbazole (C) and acetyl (AC)) and P(F-TDPP-AC)/RGO (contains fluorene (F)) composite anode. More than that, P(C-TDPP-AC)/RGO anode possesses excellent comprehensive electrochemical performance for LIBs. The discharge specific capacity for P(C-TDPP-AC)/RGO anode is as high as 857 mAh g−1 at 1000 mA g−1 for 1000 cycles, while its cyclic stability is up to 83 % and its energy density and power density are 643 Wh kg−1 and 774 W kg−1, respectively. Therefore, P(C-TDPP-AC)/RGO electrode has great potential to become a candidate for promising anode for LIBs.

Construction of hierarchical NiS@C/rGO heterostructures for enhanced sodium storage

Transition metal sulfides have attracted considerable interest as anode for sodium ion batteries (SIBs) in view of their high theoretical capacity and decent redox reversibility. However, their practical application is hindered by the low intrinsic conductivity and large volume effects during the conversion-type sodiation/desodiation process, which remain great challenges for achieving high performance SIBs. Nanostructure engineering and carbon hybridization have been reported as effective strategies for constructing advanced electrode materials with enhanced electrochemical properties. Herein, we report the designed synthesis of a multilevel-carbon supported NiS anode material (NiS@C/rGO) with a complex hierarchical hollow structure via a simple hydrothermal-heat treatment method. With the compositional and structural merits, the prepared NiS@C/rGO anode manifests excellent sodium storage performance in terms of high reversible specific capacity (472.3 mAh g−1 at 0.1 A g−1), enhanced rate capability (324.1 mAh g−1 at 1 A g−1) and superior cycling stability 240.2 mAh g−1capacity retention after 500 cycles). The greatly improved electrochemical performance of NiS@C/rGO demonstrates the importance of electrode engineering by coupling multilevel carbon modification and hierarchical structure design for SIBs.

Co-doped amorphous NiMoS4 modified with rGO for high-rate performance and long-cycling stability of hybrid supercapacitors.

The electrochemical performance of hybrid capacitors is seriously affected by the slow charging and discharging of the bulk phase. Here, Co-doped amorphous NiMoS4 modified with reduced graphene oxide (rGO) was prepared by a simple one-step hydrothermal method, and the obtained Co-doped NiMoS4/rGO nanocomposite (Ni1-xCoxMoS4/rGO) exhibits a high specific surface area, realizing the redox reaction from the bulk to the surface. Owing to the doping of Co with abundant redox active sites and the support of rGO sheets with high conductivity and a stable structure, the Ni1-xCoxMoS4/rGO anode assembled with an oxidized needle coke (NCO) cathode shows an excellent energy density of 28.9 W h kg-1 at a power density of 968.3 W kg-1. In addition, the hybrid supercapacitor displays a superior cycling performance with a capacity retention of 92.4% after 10 000 cycles. The construction of the Co-doped NiMoS4/rGO nanocomposite provides an effective strategy to boost the activity and stability of amorphous NiMoS4 for high-performance hybrid supercapacitors.

Regulating high specific capacitance NCS/α-MnO2 cathode and a wide potential window α-Fe2O3/rGO anode for the construction of 2.7 V for high performance aqueous asymmetric supercapacitors

The long-term durability, safety, and high specific power, supercapacitors (SCs) hold unlimited promise for replacing non-renewable energy sources. Aqueous asymmetric supercapacitors (AASCs) offer numerous economic and environmental benefits. The small voltage of AASCs, however, limits their progress for large-scale industrial applications. AASCs with voltage windows (>2.0 V) have made significant progress in the last few years. Herein, a novel hierarchical α-Fe2O3 ultra-thin nanowires grown on rGO aerogel (denoted as α-Fe2O3/rGO) composite was designed as the anode. Taking advantage of the rGO aerogel protective layer, the α-Fe2O3/rGO anode reveals a prolonged voltage window up to -1.5–0 V, which considerably boosts capacitance up to (270 F g−1@1 A g−1), and (106.7 F g−1@ 10 A g−1) along with superb stability owing to the good integration of rGO network and α-Fe2O3. Moreover, NiCo2S4 nanosheets coated on α-MnO2 nanorods (denoted as NCS/α-MnO2) as a protection layer to complement the wide potential cathode, as a result, the NCS/α-MnO2 composite displays an optimized voltage window of 0–1.2 V, a high capacitance (594 F g−1@1 A g−1), and outstanding cycling stability. More importantly, the assembled NCS/α-MnO2//α-Fe2O3/rGO AASC device functions in an optimized voltage (2.7 V) by means of ultra-high specific energy of 142.1 Wh kg−1, at the specific power of 1350 W kg−1 with the downfall of the specific energy of 18.75 Wh kg−1 at the specific power of 67,500 W kg−1 with exceptional stability (79% of its initial capacitance retention). Additionally, we demonstrated a single AASC device with enough energy to light a 20 mW green LED and emitted light over 40 s, which opens up possible realistic applications. Finally, this study provides an avenue for fabricating and designing a wide voltage using a compositing technique, which seems to be one of the promising route to increase specific energy of AASCs.

Ultrafast presodiation of graphene anodes for high‐efficiency and high‐rate sodium‐ion storage

AbstractThe low initial Coulombic efficiency (ICE) is a significant problem hindering the practical uses of carbon anodes in sodium‐ion batteries (SIBs), especially for the carbons with large surface area. Presodiation is an effective way to solve the above problem, but it always needs complicated operations and cannot suppress the unavoidable electrolyte decomposition in the assembled battery. Herein, we develop an ultrafast chemical presodiation method for reduced graphene oxide (rGO) using sodium naphthalene (Na‐Nt) dissolved in dimethoxyethane (DME) solvent as a presodiation reagent. The presodiation effectively improves the ICE of rGO to 96.8% and forms an artificial solid electrolyte interphase (SEI) on its surface due to the decomposition of the formed complex between Na+ and DME. The formed artificial SEI suppresses the excessive decomposition of electrolytes in the assembled battery, leading to a formation of uniform and inorganic component–rich SEI on rGO surface, which enables a rapid interfacial ion transfer. Therefore, the presodiated rGO showed excellent rate performance with a high capacity of 198.5 mAh g−1 at 5 A g−1. Moreover, excellent cycle stability indicated by the high capacity retention of 68.4% over 1000 cycles was also achieved, showing the potential to promote the practical uses of high‐rate rGO anode in SIBs.image