Search

This work presents a novel method for loading phosphorus nanoparticles by gas deposition. A large amount of nano phosphorus is loaded on the carbon matrix by the reaction of phosphine gas heating. The carbon is obtained by carbonization of hemp and has a natural porous structure. The combination of phosphorus and carbon in the form of C–O–P has better stability. The product obtained a stable capacity of 463 mAh/g at 0.04 A/g. There was still a reversible capacity of 270 mAh/g after continuous operation for 6 months at a high current density of 1 A/g, and the capacity retention rate was 96.7%. The excellent cyclic stability is due to new methods of phosphorus deposition. It can reach 10 times the running time of the same type of battery, which provides a new idea for preparing phosphor-doped electrode materials. Assembled into a potassium ion capacitor, an energy density of 294.2 Wh/kg can be obtained. [ABSTRACT FROM AUTHOR]

• NiNb 2 O 6 @NC-2 hollow nanoparticles is used as rate capability anode for LICs. • The NiNb 2 O 6 @NC-2 exhibits a high specific capacity of 435.8 mAh g−1 at 50 mA g−1. • NiNb 2 O 6 decomposes into Ni metal and Li x Nb 2 O 6 in the 1st charge/discharge process. • The NiNb 2 O 6 @NC//AC LICs has a maximum energy density of 123.9 Wh kg−1. Searching for anode materials with fast Li+ intercalation kinetics to mitigate the dynamic imbalance with the rapid capacitive cathode is the fundamental strategy to achieve high energy-power density of Li-ion capacitors (LICs). Hence, NiNb 2 O 6 hollow nanoparticles are first synthesized by hydrothermal method and then sealed with a protective N-doped carbon shell to achieve the target NiNb 2 O 6 @NC composite. As the anode of LICs, the NiNb 2 O 6 @NC sample exhibits a high capacity of 435.8 mAh g−1 at 50 mA g−1 and excellent rate performance of 47.8% capacity retention with the current density increased to 2 A g−1. The lithium storage mechanism of NiNb 2 O 6 is proposed as a combined conversion reaction and an intercalation reaction, which the NiNb 2 O 6 decomposes into Ni metal and Li x Nb 2 O 5 during the 1st discharge/charge process. The irreversible Ni would not contribute to the reversible capacity and will improve the electric conductivity for fast transport of electrons and the Li x Nb 2 O 5 will act as the host for lithium ions by means of the intercalation mechanism. Furthermore, the assembled NiNb 2 O 6 @NC//activated carbon LICs exhibit a maximum energy density of 123.9 Wh kg−1 and the capacity retention reaches 86.1% after 5000 cycles. The superior electrochemical performances indicate that the rationally-designed NiNb 2 O 6 @NC is expected to be a potential anode material for LICs. [ABSTRACT FROM AUTHOR]

• Ultrathin in-plane 1T-2H MoS 2 heterostructures are coaxially arrayed on 3D CFs. • The 1T-2H ultrathin heterostructures exhibit surprising structure stability. • Our ASC device exhibits an ultrahigh energy density of 81.4 Wh kg−1. Metallic 1T MoS 2 is a promising anode candidate for supercapacitors due to its intrinsically excellent electrical conductivity and high electrochemical activity. However, it is quite unstable and hard to be massively synthesized through common methods. Herein, structurally stable ultrathin (1–3 layers) in-plane 1T-2H MoS 2 heterostructures have been rationally modulated and coaxially aligned on three-dimensional carbon nanofibers (MoS 2 /CF) through a facile hydrothermal approach for supercapacitors and electrocatalysis. Benefiting from the unique heterostructure, the MoS 2 /CF composite shows amazing stability with no obvious change after being stored in air for over 36 months. In addition, it presents high specific capacitance of 310 F g−1 and remarkable rate capability of 78% at 100 mV s−1. The fabricated asymmetric supercapacitor delivers an impressive energy density of 81.4 Wh kg−‍‍‍‍‍1 in 1 M Na 2 SO 4 solution attributed to the high specific capacitance and large operating voltage range of 2 V. Moreover, the MoS 2 /CF composite also demonstrates enhanced electrocatalytic activity for hydrogen evolution reaction with a low overpotential of 194 mV at 10 mA cm−2. The work may promote the developments of high-performance bifunctional energy conversion and storage systems in future. [ABSTRACT FROM AUTHOR]

As a mainstream energy storage device, lithium-ion batteries have always been the focus of scientific researchers. As the most promising anode material, lithium metal has the advantages of high capacity and low reduction potential. Unfortunately, lithium dendrites can cause serious safety hazards during cycling. In this study, biomass carbon with a large number of straight holes was embedded with nickel particles as the anode framework. Nickel induces lithium to complete nucleation and growth in the pores and inhibits dendrite growth. Solid electrolyte interface (SEI) film growth, dead lithium, and electrode breakage all occur within the holes to a limited extent. Benefited from this internal reaction, the electrode obtains better electrochemical and cycling performances. The nickel-modified electrode was stably cycled for 1370 h at a current density of 5 mA/cm2 with a capacity of 2 mAh/cm2. Moreover, more massive capacity lithium storage (5 mAh/cm2) was tried, and the cycle was stable for 630 h. Using the same biomass carbon matrix, the pores were filled with sulfur powder as the positive electrode. After 100 periods of the full cell operation, the capacity retention rate is 85%. [ABSTRACT FROM AUTHOR]

K-ion batteries (KIBs) are widely considered as a promising alternative to Li-ion batteries (LIBs) due to the cost effective and earth abundant features of K. However, identifying a potential anode for KIBs showing good capacity and stability is still challenging. Because traditional graphite suffers from poor stability owing to the large volume expansion during the insertion/extraction of K ions. Non-graphite carbon is a good candidate because of the disordered nature. A facile high temperature pyrolysis method was adopted to obtain bio-derived carbon materials. Among different kinds of biomass precursors, the porous dandelion seed with nitrogen doping shows the best electrochemical performance with a specific capacity of 168 mAh g−1. The nitrogen-doped carbon presents good K ion adsorption capability and enhanced wettability, which is demonstrated in Fig.S1. Moreover, after introducing activation agent (KOH) in the carbonization process, the capacity in improved to 243 mAh g−1. Meanwhile, the as-prepared carbon material delivers good capacity retention of 91% after 100 cycles. Therefore, the hierarchically porous doped carbon derived from renewable biomass precursor shows great economical potential as KIBs anode. Unlabelled Image • The bio-derived carbon activated by KOH maintain maintain an integrated porous microstructure. • The heteroatoms-doped bio-derived carbon exhibits high specific capacity as K ions anode. • The abundant bio-mass precursor enables large scale preparation of the carbon materials. [ABSTRACT FROM AUTHOR]

High-quality F-doped graphene as rate capability anode for Li-ion battery is prepared by a one-step arc-discharge method. The in-situ formation of LiF nano-particles in the first lithium insertion process enhance the interlayer spacing of graphene, thus provid enough void for rapid ion diffusion, which is capable to deliver much high reversible capacity, outstanding rate performance, and excellent cycling stability. • A high-quality F-modified graphene as rate capability anode for Li-ion battery is reported. • The structural evolution of F-modified graphene electrode during the Li+ insertion/extraction is investigated. • The F-modified graphene delivers a high reversible capacity, outstanding rate performance, and excellent cycling stability. The application of lithium ion battery (LIB) in portable electronics and electric vehicle has received tremendous attention, however, challenges remain in seeking suitable high-capacity anode materials with excellent rate performance and thus potentially to boost the energy/power density. Here we report an arc-discharge production of high-quality F-modified graphene as anode for LIB with high-rate capability. As a result of F-modified, the acquired graphene exhibits high atomic ratio of C/O, excellent electric conductivity and more crumpled and wrinkled surface. Interestingly, the in-situ formation of LiF nanoparticles during the first Li+ insertion process not only act as barriers to effectively prevent the agglomeration and re-stacking of graphene sheets but also enhance the interlayer spacing, thus providing enough void for rapid Li+ ion insertion/extraction. These optimized features enable the resultant F-modified graphene delivers a high reversible capacity (783.2 mAh g−1 at 100 mA g−1), outstanding rate performance (298.5 mAh g−1 at 10 A g−1), and excellent cycling stability (>91% capacity retention after 1000 cycles), providing great application prospect in high-enegy-power LIB. [ABSTRACT FROM AUTHOR]

• Low-cost MgFe x Mn 2-x O 4 nanoparticles were prepared via a facile so-gel route. • MgFe 1.33 Mn 0.67 O 4 exhibited good rate ability and cycling stability. • MgFe 1.33 Mn 0.67 O 4 displays Mg-ions diffusion coefficients of 2.55 × 10−7 cm2 s−1. Aqueous Mg-ion batteries attract lots of attention due to its high safety, low cost and potential application for large scale energy storage system. Although spinel-type metal oxides display their capable Mg ions storage behavior, low diffusion ability extremely hinder their practical application. Herein, low-cost MgFe x Mn 2-x O 4 (x = 0.67, 1, 1.33, 1.6) nanomaterials are prepared by a facile sol–gel method. Their electrochemical performance is affected by molar ratio of iron to manganese. The optimized MgFe 1.33 Mn 0.67 O 4 exhibits excellent electrochemical cycling performance and rate capability. Even at high current density of 1000 mA g−1, a specific capacity 88.3 mAh g−1 is obtained after 1000 charge–discharge cycles. The stable structure of MgFe 1.33 Mn 0.67 O 4 promise a cycling stability. Moreover, hydrogen evolution and oxygen evolution of the electrode material during charging-discharging process can be effectively suppressed by regulating the atom ratio of iron to manganese. In addition, it presents a high magnesium diffusion coefficient at two oxidation peaks, leading to a good rate ability. [ABSTRACT FROM AUTHOR]

Strengthening electrical conductivity and multiple atomic interaction are benefit for improving activity of oxygen evolution reaction (OER). Herein, we synthesized Fe-Doped NiSe 2 nanospheres distribute on reduced graphene oxide sheets (Ni 0.7 Fe 0.3 Se 2 /rGO). The optimum ratio (30%) of rGO was ascertained by comparing the properties of catalysts with different rGO amounts. In alkaline electrolyte, the Ni 0.7 Fe 0.3 Se 2 /rGO-30% owns the better OER performance than those of Ni 0.7 Fe 0.3 Se 2 and NiSe 2 , ascribed to the unique architecture that Ni 0.7 Fe 0.3 Se 2 nanospheres decorate rGO. In the architecture, the rGO matrix increases conductivity, enlarges transfer rate of ions and electrons and promotes dispersion of Ni 0.7 Fe 0.3 Se 2. In addition, multiple atomic interaction of Ni/Fe atoms and the synergistic effect between the Ni 0.7 Fe 0.3 Se 2 and rGO enable the compound to be an efficient OER catalyst. Through the rational analysis, Ni 0.7 Fe 0.3 Se 2 /rGO-30% hybrid is promising as an effective non-noble metal catalyst for OER application. • The Ni 0.7 Fe 0.3 Se 2 nanospheres uniformly decorate the rGO. • Multiple atomic interaction contributes to better OER activities. • The rGO increases conductivity of composite and accelerates charge transfer rate. • The content of rGO in composites affects the OER performance. [ABSTRACT FROM AUTHOR]

• A PPy-rGO Janus-faced film is prepared through a facile and scalable method. • The PPy-rGO electrode reveals a ultra-high specific capacitances of 1380 mF cm−2. • The assembled PPy-rGO//PPy-rGO device delivers a high energy density of 31.95 Wh L−1. The flexible supercapacitors have attracted tremendous attention, but challenges still remain in seeking suitable electrode materials to enhance the energy density and other aspects. To this end, a unique Polypyrrole (PPy)-reduced graphene oxide (rGO) Janus-faced film is prepared through a facile and scalable method consisting of the deposition of graphene film on the surface of copper foil via a Cu||GO electrochemical cell followed by the self-assembly of PPy at the heterogeneous interface. Such a distinctive structure, in which the PPy layer acts as the source of high pseudo-capacitance, while the graphene layer is employed as the "high way" for rapid electron transport and as well as the strong π-π coupling effect between graphene and polymer nanosheets, endows the resultant electrode ultra-high specific capacitances (1380 mF cm−2 at 1 mA cm−2) and excellent rate capability (65.1% capacitance retention with the current density increases to 20 mA cm−2). Furthermore, the assembled PPy-rGO//PPy-rGO symmetric supercapacitors deliver a maximum energy density of 31.95 Wh L−1, remarkable cyclic stability (89.7% capacitance retention after 10,000 cycles) and superior mechanical property (82% capacitance retention after 8000 cycles under different bending conditions). [ABSTRACT FROM AUTHOR]

• The human hair with high elasticity capable can serve as a promising flexible supporter for the electrode. • The reduced graphene oxide nanosheets can effectively improve the electrical conductivity of the electrode. • The Ni(OH) 2 nanoribbon-intercalated rGO nanosheets shows an interconnected porous structure. • The solid-state flexible supercapacitor delivers high energy density and good cycling stability. The demands for wearable energy storage devices keep growing and novel flexible electrode materials and facile prepared methods for these devices are crucial and attractive. In this work, human hair fiber is employed as the flexible fiber-based material due to the high utilization values of low cost, controllable length and high elasticity capable. Herein, an effective and hazard-free microwave-assisted method is reported to develop superelastic reduced graphene oxide coating human hair (rGO@Hh) to achieve conductive and high-strength fibrous electrode. With the braided rGO@Hh fibers, nickel hydroxide nanoribbon-intercalated rGO nanosheets (Ni(OH) 2 /rGO@Hh) are further prepared through microwave radiation treatment, which shows an interconnected porous structure with outstanding electrochemical performances of high specific capacitance (316 F g−1 at 1 A g−1) and good cycling performance. Moreover, a solid-state fiber-based asymmetric supercapacitor (FASC) is assembled with rGO@Hh fibers and Ni(OH) 2 /rGO@Hh fibers as negative and positive electrodes, which demonstrates a high energy of 27.6 Wh kg−1 and a power density of 699 W kg−1, respectively. The FASC also can be further used for numerous electronic products, presenting its prospect for portable wearable devices with high tensile strength and excellent performances. [ABSTRACT FROM AUTHOR]

Rechargeable aqueous aluminum ion batteries (RAAB) have gained increasing attentions for large scale energy storage system due to their high safety, nontoxicity and low cost. However, lack of capable anode materials extremely hinders their potential application. As we all know, the anodic material of aluminum ion battery was limited, we report poly (3,4,9,10-perylentetracarboxylic diimide) (PPTCDI) under the different synthesis conditions as organic anode material for aqueous RAAB. The aluminum ions intercalation/deintercalation storage mechanism is affected by the different electrolyte concentrations. Upon their high capacity and cycling stability, our work would highlight potential application of conjugated polymer organic electrode materials for aqueous aluminum ion batteries. Unlabelled Image • The PPTCDI as anode in aqueous Al-ion battery was reported for the first time. • The Al-ion battery delivers excellent electrochemical cycling stability. • The aluminum ions intercalation/deintercalation storage mechanism is affected by the different concentrations of electrolyte. [ABSTRACT FROM AUTHOR]

In this work, one-pot hydrothermal method is used to prepare a novel electrode material of nanosheet-like Fe 2 O 3 in-situ grown on Ni foam. The performance of the as-prepared material toward H 2 O 2 oxidation is investigated systematically. The crossed nanosheet-like structure allows a full contact between the electrode surface and electrolyte which is highly beneficial to the sufficient use of H 2 O 2. The catalytic activity of Fe 2 O 3 grown on Ni foam(Fe 2 O 3 /Ni foam) electrode in alkaline medium for H 2 O 2 oxidation is researched by methods of cyclic voltammetry and chronoamperometry. According to the results of cyclic voltammetry in solutions with different H 2 O 2 concentrations, we proposes a possible reaction mechanism that the good ability of Fe3+ to break the oxygen-hydrogen bond in H 2 O 2 leads to the oxidation of H 2 O 2 on the electrode. Meanwhile, Ni foam also has a positive effect on the process of H 2 O 2 oxidation. In a solution of 4 mol L−1 NaOH and 0.4 mol L−1 H 2 O 2 , the current density of H 2 O 2 oxidation on the Fe 2 O 3 /Ni foam electrode is 800 mA cm−2 revealing a desirable catalytic activity toward H 2 O 2 oxidation. Besides, the activation energy of H 2 O 2 oxidation on the Fe 2 O 3 /Ni foam electrode is calculated to be 9.17 kJ mol−1 by studying the influence of temperature on the electrode performance. All the results show that the as-prepared electrode exhibits vast prospect in application. Image 1 • One-pot hydrothermal method was applied to prepare nanosheet-like Fe 2 O 3. • Fe 2 O 3 /Ni foam electrode exhibits good catalytic activity toward H 2 O 2 oxidation. • A possible mechanism of H 2 O 2 oxidation on Fe 2 O 3 /Ni foam electrode was proposed. [ABSTRACT FROM AUTHOR]

NiS 2 is a promising anode material for sodium-ion batteries (SIBs) and capacitors (SICs). However, the sluggish Na+ diffusion and large volume change of bulk NiS 2 during sodiation/de-sodiation lead to poor rate capability and fast capacity decay, limiting its practical application. Herein, we design and prepare well-oriented NiS 2 nanosheets on porous carbon microtubes (denoted as NiS 2 /pCMT) as a novel anode material for SIBs/SHCs. The unique porous hollow carbon tubes and NiS 2 nanosheets can well relieve the repeated stress/strain and maintain the structural integrity of the composite anode during long-term charging/discharging. As a confirmation, a modelled SHC is constructed by using the NiS 2 /pCMT composite as anode and coupling with an activated carbon cathode, delivering a high energy density of 136 Wh kg−1 and good cycling stability. The first-principles density functional theory (DFT) calculations confirm that the NiS 2 nanosheets surface has a high chemical affinity towards Na+ ions, promising the concentration of Na+ ion on/nearby the surface for fast redox reactions during sodiation/de-sodiation of NiS 2. This work provides some new insights for the design and fabrication novel composite electrode materials for applications in beyond lithium-ion batteries/capacitors. • The carbon microtubes have unique tubular structure and good conductivity. • NiS 2 nanosheets uniformly grow on both sides of the carbon microtubes. • The layered NiS 2 nanosheets facilitate the intercalation of the Na+ ions. • The sodium-ion hybrid capacitor delivers high energy and power densities. [ABSTRACT FROM AUTHOR]

• The triple-layered heterostructure provides abundant active sites for urea electrooxidation. • The synergistic effect between MnCo 2 O 4.5 and Ni(OH) 2 promotes the electrooxidation of urea. • The as-prepared MnCo 2 O 4.5 @Ni(OH) 2 /NF exhibits much better stability and activity towards urea electrooxidation. Urea oxidation reaction (UOR) is considered as a prospective technology for hydrogen generation and degradation of urea-rich wastewater concurrently. In theory, nickel-based catalysts exhibit superior activity in this regard. However, the intrinsically low conductivity and limited active sites on usual nickel-based catalysts impede their applications in UOR. Hence, a hierarchical triple-layered heterostructure, which consists of MnCo 2 O 4.5 nanosheets seamlessly sandwiched between a bottom layer of Ni foam substrate and a top layer of Ni(OH) 2 nanosheets, are directly synthesized via a successive hydrothermal-calcination-hydrothermal process (MnCo 2 O 4.5 @Ni(OH) 2 /NF). Taking advantages of the distinctive sandwich structure and the synergistic effect between MnCo 2 O 4.5 and Ni(OH) 2 , the resulting MnCo 2 O 4.5 @Ni(OH) 2 /NF electrode presents superior electrocatalytic activity with a small onset potential of 0.19 V versus Ag/AgCl as well as a current density of 650 mA cm−2 in 5 M KOH and 0.33 M urea electrolyte. This work provides a promising platform for designing an effective hybrid material toward a wide range of electrochemical applications. [ABSTRACT FROM AUTHOR]

Highlights: A freestanding MXene-derived defect-rich TiO2@reduced graphene oxides (M-TiO2@rGO) foam electrode was fabricated. M-TiO2@rGO presents fast Na+ storage kinetics due to capacitive contribution. M-TiO2@rGO foam electrode displays a capacity retention of 90.7% after 5000 cycles. Sodium ion batteries and capacitors have demonstrated their potential applications for next-generation low-cost energy storage devices. These devices's rate ability is determined by the fast sodium ion storage behavior in electrode materials. Herein, a defective TiO2@reduced graphene oxide (M-TiO2@rGO) self-supporting foam electrode is constructed via a facile MXene decomposition and graphene oxide self-assembling process. The employment of the MXene parent phase exhibits distinctive advantages, enabling defect engineering, nanoengineering, and fluorine-doped metal oxides. As a result, the M-TiO2@rGO electrode shows a pseudocapacitance-dominated hybrid sodium storage mechanism. The pseudocapacitance-dominated process leads to high capacity, remarkable rate ability, and superior cycling performance. Significantly, an M-TiO2@rGO//Na3V2(PO4)3 sodium full cell and an M-TiO2@rGO//HPAC sodium ion capacitor are fabricated to demonstrate the promising application of M-TiO2@rGO. The sodium ion battery presents a capacity of 177.1 mAh g−1 at 500 mA g−1 and capacity retention of 74% after 200 cycles. The sodium ion capacitor delivers a maximum energy density of 101.2 Wh kg−1 and a maximum power density of 10,103.7 W kg−1. At 1.0 A g−1, it displays an energy retention of 84.7% after 10,000 cycles. [ABSTRACT FROM AUTHOR]

Bimetallic oxide CoMn 2 O 4 with nano-peony structure is prepared on Ni foam by a traditional hydrothermal process. Then constant-potential electrodeposition is applied to anchor Pd nanoparticles on CoMn 2 O 4 to form an electrode of Pd nanoparticles modified CoMn 2 O 4 (PCMN electrode) for H 2 O 2 electroreduction. The combination of Pd and CoMn 2 O 4 effectively reduces the dosage of noble metal. Besides, no binder is involved in the preparation which cuts the electrode cost and avoids the poor stability of traditional electrodes produced with binders. Scanning electron microscopy, X-ray diffraction and transmission electron microscopy are operated to investigate the structure and composition of the electrode. And the electrochemical behavior of the electrode is characterized by cyclic voltammetry and chronoamperometry. In 0.7 mol L−1 H 2 O 2 and 3 mol L−1 NaOH, a reduction current density of 580 mA cm−2 (normalized by geometric area) at −0.8 V on the electrode is obtained which reveals large capacity for actual application in H 2 O 2 -based fuel cell. A binder-free electrode of Pd nanoparticles anchored to nano-peony CoMn 2 O 4 was prepared and the synergy effect of Co, Mn and Pd highly improved the catalytic activity toward H 2 O 2 reduction. Unlabelled Image • Pd modified CoMn 2 O 4 electrode with special nano-peony structure was synthesized. • The special nano-peony structure provides more active sites for H 2 O 2 reduction. • The synergy effect of Co, Mn and Pd highly improved the catalytic activity. [ABSTRACT FROM AUTHOR]

Lithium-ion capacitors (LICs) by combines the virtues of lithium-ion batteries and supercapacitor have received intensive attention owing to their preeminent energy density, outstanding power density and uncompromised cycle life. However, the practical application of LICs has been greatly hampered by the lack of efficient anode materials. Herein, a facile strategy including hydrothermal reaction and subsequent thermal calcination has been carefully designed for constructing MnO porous spheres with a N-doped carbon coated layer (MnO@N-C). The resultant MnO@N-C electrode delivers a high capacity of 903 mA h g−1 and excellent cyclic performance with 96.2% capacity retention after 1000 cycles. Furthermore, the assembled MnO@N-C//AC LICs displays an excellent energy density of 125.3 Wh kg−1 and superior power density of 19.9 KW kg−1, as well as long cyclic lifetime of 5000 cycles with 83.2% capacity retention, outperforming those of recently reported metal oxide based LICs. Image 1 • MnO@N-C is obtained through a hydrothermal reaction and subsequent thermal calcination. • The MnO@N-C displays a high capacity of 903 mA h g−1 and outstanding stability with 96.2% capacity retention. • The assembled MnO@N-C//AC LICs reveals an excellent energy density of 125.3 Wh kg−1. [ABSTRACT FROM AUTHOR]

MnO 2 is regarded as an ideal material of supercapacitor since its low-cost, environment friendly and high specific capacitance but hindered by its poor electrical conductivity. Developing a composite electrode that combines nano-structure MnO 2 with a conductive skeleton such as carbon materials could make up for the shortcomings. Here, porous activated carbon (PAC) is synthesized by using low-cost wheat bran as biomass carbon precursor and a mixture of NaCl/ZnCl 2 as combined solvent-porogen. The resultant PAC sample presents a hierarchical porous structure and large specific surface area up to 1058 m2 g−1. Afterwards, MnO 2 nanosheets decorated PAC (MnO 2 @PAC) is prepared via an in-situ hydrothermal deposition. It is a key finding that the ion/electron transfer kinetics of MnO 2 @PAC could be effectively improved by the addition of hierarchical porous carbon. Thus, the MnO 2 @PAC electrode displays a high specific capacitance (258 F g−1 at 1 A g−1) and superior rate performance (82.8% capacitance retention with the current density ranging from 1 A g−1 to 20 A g−1). Furthermore, an asymmetric supercapacitor is assembled by employing the MnO 2 @PAC as the positive electrode and PAC as negative electrode, which exhibits a high energy density of 32.6 Wh kg−1 and as well as 93.6% capacity retention at over 10,000 charge/discharge cycles. • Porous activated carbon (PAC) is synthesized by a controllable molten salt method. • MnO 2 nanosheets were deposited on the PAC through a simple hydrothermal reaction. • The MnO 2 @PAC displays high specific capacitance and outstanding stability. • The PAC//MnO 2 @PAC asymmetric supercapacitor exhibits energy density of 32.6 Wh kg−1. [ABSTRACT FROM AUTHOR]

Developing advanced supercapacitors with both high areal and volumetric energy densities remains challenging. In this work, self‐supported, compact carbon composite electrodes are designed with tunable thickness using 3D printing technology for high‐energy‐density supercapacitors. The 3D carbon composite electrodes are composed of the closely stacked and aligned active carbon/carbon nanotube/reduced graphene oxide (AC/CNT/rGO) composite filaments. The AC microparticles are uniformly embedded in the wrinkled CNT/rGO conductive networks without using polymer binders, which contributes to the formation of abundant open and hierarchical pores. The 3D‐printed ultrathick AC/CNT/rGO composite electrode (ten layers) features high areal and volumetric mass loadings of 56.9 mg cm−2 and 256.3 mg cm−3, respectively. The symmetric cell assembled with the 3D‐printed thin GO separator and ultrathick AC/CNT/rGO electrodes can possess both high areal and volumetric capacitances of 4.56 F cm−2 and 10.28 F cm−3, respectively. Correspondingly, the assembled ultrathick and compact symmetric cell achieves high areal and volumetric energy densities of 0.63 mWh cm−2 and 1.43 mWh cm−3, respectively. The all‐component extrusion‐based 3D printing offers a promising strategy for the fabrication of multiscale and multidimensional structures of various high‐energy‐density electrochemical energy storage devices. The all‐graphene‐oxide (GO)‐based symmetric supercapacitor is assembled with a thin GO separator and compact active carbon/carbon nanotube/reduced graphene oxide composite electrodes with tunable thickness, which are fabricated using the advanced extrusion‐based 3D printing technology. The 3D‐printed ultrathick and compact symmetric supercapacitor with a high mass loading can achieve both high areal and volumetric energy densities. [ABSTRACT FROM AUTHOR]

Composites of LiFePO4 and activated carbon (LFP-AC) were prepared by a ball milling method. Their morphologies were investigated by scanning electronic microscopy and energy dispersive spectroscopy. Hybrid supercapacitors were assembled using the LFP-AC composites as the positive electrode and Li4Ti5O12 as the negative electrode (LFP-AC/Li4Ti5O12). Effects of the positive electrode composition (ratio of LiFePO4 to AC) on the performance of LFP-AC/Li4Ti5O12 were investigated via constant current charge-discharge tests. The results demonstrated that the specific capacity and the specific power of the LFP-AC/Li4Ti5O12 hybrid supercapacitor significantly depend upon the content of LiFePO4 in the LFP-AC positive electrode. At 0.5 A g-1 charge-discharge current, the specific capacity of the LFP-AC/Li4Ti5O12 with 30 wt. % LiFePO4 and 70 wt. % AC in the positive electrode is 42% higher than that of AC/Li4Ti5O12, and the two supercapacitors have the same specific power. After 500 charge-discharge cycles at 1.0 A g-1, the specific capacity of the LFP-AC/Li4Ti5O12 with 80 wt. % LiFePO4 and 20 wt. % AC in the positive electrode is 53% higher than that of AC/Li4Ti5O12. The hybrid device stores electric energy via both the double-layer electrostatic adsorption and the intercalation/deintercalation of lithium ions. [ABSTRACT FROM AUTHOR]