Showing papers on "Power density published in 2015"
TL;DR: The field of supercapacitors (electrochemical capacitors) is constantly evolving and the global motivation is to create devices that possess a significant energy density without compromising the power density as mentioned in this paper.
Abstract: The field of supercapacitors (electrochemical capacitors) is constantly evolving. The global motivation is to create devices that possess a significant energy density without compromising the power density. To achieve this goal, new materials must be discovered and complex electrode architectures developed.
463 citations
TL;DR: This work has successfully realized an ultrahigh-energy and long-life supercapacitor anode by developing a hierarchical graphite foam-carbon nanotube framework and coating the surface with a thin layer of iron oxide (GF-CNT@Fe2O3).
Abstract: Supercapacitor with ultrahigh energy density (e.g., comparable with those of rechargeable batteries) and long cycling ability (>50000 cycles) is attractive for the next-generation energy storage devices. The energy density of carbonaceous material electrodes can be effectively improved by combining with certain metal oxides/hydroxides, but many at the expenses of power density and long-time cycling stability. To achieve an optimized overall electrochemical performance, rationally designed electrode structures with proper control in metal oxide/carbon are highly desirable. Here we have successfully realized an ultrahigh-energy and long-life supercapacitor anode by developing a hierarchical graphite foam–carbon nanotube framework and coating the surface with a thin layer of iron oxide (GF–CNT@Fe2O3). The full cell of anode based on this structure gives rise to a high energy of ∼74.7 Wh/kg at a power of ∼1400 W/kg, and ∼95.4% of the capacitance can be retained after 50000 cycles of charge–discharge. These pe...
411 citations
TL;DR: In this paper, a novel synergistic TiO2-MoO3 (TO-MO) core-shell nanowire array anode has been fabricated via a facile hydrothermal method followed by a subsequent controllable electrodeposition process.
Abstract: A novel synergistic TiO2-MoO3 (TO-MO) core–shell nanowire array anode has been fabricated via a facile hydrothermal method followed by a subsequent controllable electrodeposition process. The nano-MoO3 shell provides large specific capacity as well as good electrical conductivity for fast charge transfer, while the highly electrochemically stable TiO2 nanowire core (negligible volume change during Li insertion/desertion) remedies the cycling instability of MoO3 shell and its array further provides a 3D scaffold for large amount electrodeposition of MoO3. In combination of the unique electrochemical attributes of nanostructure arrays, the optimized TO-MO hybrid anode (mass ratio: ca. 1:1) simultaneously exhibits high gravimetric capacity (ca. 670 mAh g−1; approaching the hybrid's theoretical value), excellent cyclability (>200 cycles) and good rate capability (up to 2000 mA g−1). The areal capacity is also as high as 3.986 mAh cm−2, comparable to that of typical commercial LIBs. Furthermore, the hybrid anode was assembled for the first time with commercial LiCoO2 cathode into a Li ion full cell, which shows outstanding performance with maximum power density of 1086 W kgtotal −1 (based on the total mass of the TO-MO and LiCoO2) and excellent energy density (285 Wh kgtotal −1) that is higher than many previously reported metal oxide anode-based Li full cells.
251 citations
TL;DR: In this paper, a Li-HESC with carbon fiber electrode and carbon fibers positive electrode was designed to achieve a capacity of 280mA h/g at a current density of 0.2A/g in the potential window of 1.0 and 2.1 A/g.
250 citations
TL;DR: Results demonstrate that the TiO(2) NBA//graphene hydrogel LIC exhibits higher energy density than supercapacitors and better power density than Li-ion batteries, which makes it a promising electrochemical power source.
Abstract: A novel hybrid Li-ion capacitor (LIC) with high energy and power densities is constructed by combining an electrochemical double layer capacitor type cathode (graphene hydrogels) with a Li-ion battery type anode (TiO(2) nanobelt arrays). The high power source is provided by the graphene hydrogel cathode, which has a 3D porous network structure and high electrical conductivity, and the counter anode is made of free-standing TiO(2) nanobelt arrays (NBA) grown directly on Ti foil without any ancillary materials. Such a subtle designed hybrid Li-ion capacitor allows rapid electron and ion transport in the non-aqueous electrolyte. Within a voltage range of 0.0-3.8 V, a high energy of 82 Wh kg(-1) is achieved at a power density of 570 W kg(-1). Even at an 8.4 s charge/discharge rate, an energy density as high as 21 Wh kg(-1) can be retained. These results demonstrate that the TiO(2) NBA//graphene hydrogel LIC exhibits higher energy density than supercapacitors and better power density than Li-ion batteries, which makes it a promising electrochemical power source.
248 citations
TL;DR: In this paper, the authors presented the development and characterization of two inductive energy harvesters which exploit different characteristics of the human gait and achieved an average power output of up to 0.84 mW with two test subjects on a treadmill.
Abstract: Modern compact and low power sensors and systems are leading towards increasingly integrated wearable systems. One key bottleneck of this technology is the power supply. The use of energy harvesting techniques offers a way of supplying sensor systems without the need for batteries and maintenance. In this work we present the development and characterization of two inductive energy harvesters which exploit different characteristics of the human gait. A multi-coil topology harvester is presented which uses the swing motion of the foot. The second device is a shock-type harvester which is excited into resonance upon heel strike. Both devices were modeled and designed with the key constraint of device height in mind, in order to facilitate the integration into the shoe sole. The devices were characterized under different motion speeds and with two test subjects on a treadmill. An average power output of up to 0.84 mW is achieved with the swing harvester. With a total device volume including the housing of 21 cm3 a power density of 40 μW cm−3 results. The shock harvester generates an average power output of up to 4.13 mW. The power density amounts to 86 μW cm−3 for the total device volume of 48 cm3. Difficulties and potential improvements are discussed briefly.
193 citations
TL;DR: In this article, a novel strategy for the synthesis of functional pillared graphene frameworks, in which graphene fragments in-between graphene sheets, through simple thermal-treatment of ozone (O3)-treated graphene oxide at very low temperature of 200 °C is reported.
Abstract: Supercapacitors, also known as electrochemical capacitors, can provide much faster charge–discharge, greater power density, and cyclability than batteries, but they are still limited by lower energy densities (or the amount of energy stored per unit volume). Here, a novel strategy for the synthesis of functional pillared graphene frameworks, in which graphene fragments in-between graphene sheets, through simple thermal-treatment of ozone (O3)-treated graphene oxide at very low temperature of 200 °C is reported. Due to its high packing density, high content of stable oxygen species, and continues ion transport network in-between graphene sheets, the functional pillared-graphene framework delivers not only high gravimetric capacitance (353 F g−1 based on the mass of the active material) and ultrahigh volumetric capacitance (400 F cm−3 based on total mass of electrode material) in aqueous electrolyte but also excellent cyclic stability with 104% of its initial capacitance retention after 10 000 cycles. Moreover, the assembled symmetric supercapacitor achieves as high as 27 Wh L−1 of volumetric energy density at a power density of 272 W L−1. This novel strategy holds great promise for future design of high volumetric capacitance supercapacitors.
178 citations
TL;DR: In this paper, hydrogenated NiCo2O4 double-shell hollow spheres, combining large specific surface area and high conductivity, are prepared, and a specific capacitance increase of >62%, from 445 to 718 ǫ F g−1, is achieved at a current density of 1ǫ Aǫg−1.
Abstract: Hydrogenated NiCo2O4 double-shell hollow spheres, combining large specific surface area and high conductivity, are prepared. A specific capacitance increase of >62%, from 445 to 718 F g−1, is achieved at a current density of 1 A g−1. A full cell combined with NiCo2O4 and activated carbon is assembled, and an energy density of 34.8 Wh kg−1 is obtained at a power density of 464 W kg−1.
174 citations
TL;DR: In this article, binder-free Fe 2 N nanoparticles (Fe 2 N NPs) were synthesized as high performance free-standing anode for full lithium ion batteries (FLIBs).
173 citations
TL;DR: In this paper, a facile yet efficient method to uniformly decorate conductive silver nanoparticles (∼10 nm) on MnO2 nanowires (width of ∼10-20 nm), which leads to a remarkable improvement of the electrical conductivity and the supercapacitive performance of MnO 2-based electrodes.
Abstract: Coating the redox-active transition-metal oxides (e.g., MnO2) with a conductive metal layer is one efficient approach to improve the electrical conductivity of the oxide-based electrodes, which could largely boost the energy density and power density of supercapacitors. Here, we report a facile yet efficient method to uniformly decorate conductive silver (Ag) nanoparticles (∼10 nm) on MnO2 nanowires (width of ∼10–20 nm), which leads to a remarkable improvement of the electrical conductivity and the supercapacitive performance of MnO2-based electrodes. For instance, at a low scan rate of 10 mV s−1, the as-designed Ag/MnO2 hybrid electrode delivers a specific capacitance of 293 F g−1, which is twofold higher than that of the bare MnO2 electrode (∼130 F g−1). In addition, the highly conductive Ag nanoparticle layer can also improve the rate capability of the Ag/MnO2 nanowire electrode, delivering a high specific energy density and power density of 17.8 W h kg−1 and 5000 W kg−1, respectively, at a current density of 10 A g−1.
170 citations
TL;DR: In this paper, a magneto-mechano-electric (MME) generator with a colossal power density that can turn on 35 LEDs and drive a wireless sensor network under a weak magnetic field of 5-7 × 10−4 T at a low frequency of 60 Hz.
Abstract: Stray magnetic field considered as harmful noise for the human body can be a ubiquitous energy source. We are surrounded with 50/60 Hz parasitic magnetic noise arising from power delivery infrastructure, but it cannot be readily utilized by traditional electromagnetic harvesters. Here, we introduce a novel magneto-mechano-electric (MME) generator with a colossal power density that can turn on 35 LEDs and drive a wireless sensor network under a weak magnetic field of 5–7 × 10−4 T at a low frequency of 60 Hz. The MME generator is a cantilever structured magnetoelectric (ME) laminate composite in which the 〈011〉 oriented anisotropic single crystal fiber composite (SFC) is bonded to Ni plate and Nd permanent magnet proof mass. The ME laminate composite has a strong ME coupling (αME ∼ 160 V cm−1 Oe−1) even without magnetic bias due to the intrinsic property of Ni. The MME generator is also found to exhibit a colossal output power density of 46 mW cm−3 Oe−2 under a weak magnetic field of 1.6 × 10−4 T at 60 Hz. This MME generator can be a ubiquitous power source for wireless sensor networks, low power electric devices, and wireless charging systems by harvesting tiny amounts of parasitic magnetic energy from our living environment.
TL;DR: An elasto-aerodynamics-driven triboelectric nanogenerator (TENG) based on contact electrification that is utilized to scavenge human breath induced air-flow energy to sustainably power a human body temperature sensor.
Abstract: Efficient scavenging the kinetic energy from air-flow represents a promising approach for obtaining clean, sustainable electricity. Here, we report an elasto-aerodynamics-driven triboelectric nanogenerator (TENG) based on contact electrification. The reported TENG consists of a Kapton film with two Cu electrodes at each side, fixed on two ends in an acrylic fluid channel. The relationship between the TENG output power density and its fluid channel dimensions is systematically studied. TENG with a fluid channel size of 125 × 10 × 1.6 mm3 delivers the maximum output power density of about 9 kW/m3 under a loading resistance of 2.3 MΩ. Aero-elastic flutter effect explains the air-flow induced vibration of Kapton film well. The output power scales nearly linearly with parallel wiring of multiple TENGs. Connecting 10 TENGs in parallel gives an output power of 25 mW, which allows direct powering of a globe light. The TENG is also utilized to scavenge human breath induced air-flow energy to sustainably power a hu...
TL;DR: Multifunctional MoS2 @PANI (polyaniline) pseudo-supercapacitor electrodes consisting ofMoS2 thin nanosheets and PANI nanoarrays are fabricated via a large-scale approach for superior capacitance retention and high energy density.
Abstract: Multifunctional MoS2 @PANI (polyaniline) pseudo-supercapacitor electrodes consisting of MoS2 thin nanosheets and PANI nanoarrays are fabricated via a large-scale approach. The superior capacitance retention is retained up to 91% after 4000 cycles and a high energy density of 106 Wh kg(-1) is delivered at a power density of 106 kW kg(-1) .
TL;DR: Li et al. as discussed by the authors designed and fabricated a Li-ion capacitor device, which is composed of an electrochemical double layer capacitance electrode as the positive electrode and a Li ion battery type electrodes as the negative electrode.
TL;DR: By limiting the voltage cutoff window in an appropriate range, the obtained Ge anode exhibits excellent lithium storage performance in half- and full-cells, which can be mainly attributed to the designed nanostructured current collector with good conductivity, enough buffering space for the volume change, and shortened ionic transport length.
Abstract: Germanium is a highly promising anode material for lithium-ion batteries as a consequence of its large theoretical specific capacity, good electrical conductivity, and fast lithium ion diffusivity. In this work, Co3O4 nanowire array fabricated on nickel foam was designed as a nanostructured current collector for Ge anode. By limiting the voltage cutoff window in an appropriate range, the obtained Ge anode exhibits excellent lithium storage performance in half- and full-cells, which can be mainly attributed to the designed nanostructured current collector with good conductivity, enough buffering space for the volume change, and shortened ionic transport length. More importantly, the assembled Ge/LiCoO2 full-cell shows a high energy density of 475 Wh/kg and a high power density of 6587 W/kg. A high capacity of 1184 mA h g(-1) for Ge anode was maintained at a current density of 5000 mA g(-1) after 150 cycles.
TL;DR: In this paper, the authors presented a frequency up-converted electromagnetic energy harvester that generates significant power from human-limb motion (hand-shaking) by mechanical impact.
TL;DR: In this article, a flexible wire-shaped fiber asymmetric supercapacitor (WFASC) was fabricated using these materials as the positive and negative electrodes, respectively, and it exhibited a perfect stability after 5000 cycles at a current density of 30 mA cm−2, meanwhile, it could withstand the bending test and drive a LED under bending states.
Abstract: Due to high capacitance resulting from the redox character of the MnO2–PPy–carbon and V2O5–PANI–carbon fiber composites, a flexible wire-shaped fiber asymmetric supercapacitor (WFASC) was fabricated using these materials as the positive and negative electrodes, respectively. Especially, the large work function difference between MnO2 and V2O5 help the device to exhibit a wide potential window of 2.0 V and a high areal capacitance of 0.613 F cm−2. As a result, the WFASC showed a maximum energy density of 0.340 mW h cm−2 at a power density of 1.5 mW cm−2 and a maximum power density of 30 mW cm−2 at an energy density of 0.294 mW h cm−2. Furthermore, the device exhibited a perfect stability after 5000 cycles at a current density of 30 mA cm−2, meanwhile, it could withstand the bending test and drive a LED under bending states. All of the above results prove the potential application of WFASC devices.
TL;DR: In this paper, a facile preparation method for orthorhombic phase niobium oxide (T-Nb2O5) nanowire structure with ultra-thin carbon coating is reported, which shows stable high rate Li+ storage ability.
TL;DR: In this paper, a high capacitance of 225 F g−1 at 2 A g− 1 was achieved with a high current density of 20 A G−1 in an aqueous electrolyte, and an energy density of 7 W h kg−1 was achieved at a power density of 5000 W kg− 1.
Abstract: Yogurt is used as a novel precursor to synthesize high quality heavily nitrogen doped porous carbon for supercapacitor applications. It is an easily scalable and manufactureable food item containing casein as the major protein, in addition to some whey proteins. The yogurt forming process is mediated by bacteria, and thus this precursor has a high nitrogen content that can get doped into carbon upon controlled precursor pyrolysis. Indeed our material retains a high (12 wt%) nitrogen percentage even after high temperature pyrolysis in the presence of an activating agent. A surface area of 1300 m2 g−1 is attained with a good density of mesopores, apart from abundant micropores. The material offers a high capacitance of 225 F g−1 at 2 A g−1, which decreases only to 200 F g−1 even at a high current density of 20 A g−1 in an aqueous electrolyte. An energy density of 7 W h kg−1 is delivered at a power density of 5000 W kg−1. We have also examined the cathode performance of our material vs. nickel cobalt sulfide (NCS) in an asymmetric configuration. The energy density in an asymmetric assembly goes as high as 27 W h kg−1 at a power density of 364 W kg−1 and 17.8 W h kg−1 at a power density of 6400 W kg−1.
TL;DR: In this paper, a Li-ion capacitor (LIC) is constructed with Li4Ti5O12/C hybrid as the negative electrode and 3D porous graphene macroform (PGM) as the positive electrode.
TL;DR: In this paper, the authors reported the synthesis of TiO2/BiFeO3 nanoheterostructure (NH) arrays by anchoring BFO nanoparticles on the TiO 2 nanotube surface and investigate their pseudocapacitive and photoelectrochemical properties considering their applications in green energy fields.
Abstract: Here, we report the synthesis of TiO2/BiFeO3 nanoheterostructure (NH) arrays by anchoring BiFeO3 (BFO) nanoparticles on TiO2 nanotube surface and investigate their pseudocapacitive and photoelectrochemical properties considering their applications in green energy fields. The unique TiO2/BFO NHs have been demonstrated both as energy conversion and storage materials. The capacitive behavior of the NHs has been found to be significantly higher than that of the pristine TiO2 NTs, which is mainly due to the anchoring of redox active BFO nanoparticles. A specific capacitance of about 440 F g–1 has been achieved for this NHs at a current density of 1.1 A g–1 with ∼80% capacity retention at a current density of 2.5 A g–1. The NHs also exhibit high energy and power performance (energy density of 46.5 Wh kg–1 and power density of 1.2 kW kg–1 at a current density of 2.5 A g–1) with moderate cycling stability (92% capacity retention after 1200 cycles). Photoelectrochemical investigation reveals that the photocurrent ...
TL;DR: In this article, a class of sandwich-structured nanocomposites are prepared by a facile hot-pressing method, and an ultrahigh energy density of 14.6 J/cm3 is achieved.
TL;DR: It has been demonstrated that the output volume power density from a HNG can drive several colour light emitting diodes and a charge capacitor that powers up a calculator, indicating an effective means of energy harvesting power source with high energy conversion efficiency for portable electronic devices.
Abstract: A high-performance flexible piezoelectric hybrid nanogenerator (HNG) based on lead-free perovskite zinc stannate (ZnSnO3) nanocubes and polydimethylsiloxane (PDMS) composite with multiwall carbon nanotubes (MWCNTs) as supplement filling material is demonstrated. Even without any electrical poling treatment, the HNG possesses an open-circuit voltage of 40 V and a short-circuit current of 0.4 μA, respectively, under repeated human finger impact. It has been demonstrated that the output volume power density of 10.8 μW cm(-3) from a HNG can drive several colour light emitting diodes (LEDs) and a charge capacitor that powers up a calculator, indicating an effective means of energy harvesting power source with high energy conversion efficiency (∼1.17%) for portable electronic devices.
TL;DR: In this paper, the authors evaluate the ability of gallium nitride transistors to improve efficiency and output power density in high frequency resonant and soft-switching applications, and experimentally verify the benefits of replacing Si MOSFETs with enhancement mode GaN transistors (eGaNFETs).
Abstract: The emergence of gallium nitride (GaN)-based power devices offers the potential to achieve higher efficiencies and higher switching frequencies than possible with mature silicon (Si) power MOSFETs. In this paper, we will evaluate the ability of gallium nitride transistors to improve efficiency and output power density in high frequency resonant and soft-switching applications. To experimentally verify the benefits of replacing Si MOSFETs with enhancement mode GaN transistors (eGaNFETs) in a high frequency resonant converter, 48–12 V unregulated isolated bus converter prototypes operating at a switching frequency of 1.2 MHz and an output power of up to 400 W are compared using Si and GaN power devices.
TL;DR: In this paper, a Nafion® dispersion was applied to fabricate proton exchange membranes for polymer electrolyte fuel cells, which completely substitutes the commonly used membrane foil.
Abstract: We apply drop-on-demand inkjet printing to fabricate proton exchange membranes for polymer electrolyte fuel cells. This completely substitutes the commonly used membrane foil. A Nafion® dispersion is deposited directly onto the catalyst layers of anode and cathode gas diffusion electrodes, and the two electrodes are pressed together with the membrane layers facing each other. Fuel cells constructed utilizing this method reveal a thin overall membrane thickness of 8–25 μm and a good adhesion of membrane and catalyst layers. This results in a membrane ionic resistance of only 12.7 mΩ cm2 without compromising hydrogen crossover, which was determined to be less than 2 mA cm−2. We achieve a cell power density exceeding 4 W cm−2 with pure oxygen as cathode fuel, which, to our knowledge, is the highest reported power density with a Nafion® membrane hydrogen fuel cell. The membrane shows a stable performance over the entire range of reactant gas humidification from 0 to 100% relative humidity. Power densities exceeding 1.0 W cm−2 are achieved under dry operation with air as cathode fuel. A 576 hour combined mechanical and chemical accelerated stress test reveals no significant degradation in terms of hydrogen crossover, indicating a promising lifetime of the membrane.
TL;DR: In this paper, the design, fabrication and testing of thermoelectric generator (TEG) devices using dispenser printer is discussed. And the prototype presented in this paper demonstrates the feasibility of deploying a printable and perpetual power solution for practical wireless sensor network (WSN) applications.
TL;DR: In this article, a micron-sized plate-like copper-substituted layered P2-type Na0.67CuxMn1−xO2 is demonstrated to rapidly charge and discharge within 5 minutes while giving a capacity of more than 90 mA h g−1.
Abstract: While sodium-ion batteries (SIBs) are considered as a next-generation energy storage device because of the higher abundance and lower cost of sodium compared to those of lithium, developing high-power and stable cathode materials remains a great challenge. Here, micron-sized plate-like copper-substituted layered P2-type Na0.67CuxMn1−xO2 is demonstrated to rapidly charge and discharge within 5 minutes while giving a capacity of more than 90 mA h g−1, corresponding to a half-cell energy density of 260 W h (kg cathode)−1 at a power density of 3000 W (kg cathode)−1, which is comparable to that of high-power lithium-ion cathodes. The materials show excellent stability, retaining more than 70% of the initial capacity after 500 cycles at 1000 mA g−1. The good cycle and rate performances of the materials are attributed to copper in the lattice, which stabilizes the crystal structure, increases the average discharge potential and improves sodium transport. This makes Na0.67CuxMn1−xO2 an ideal choice as a cathode for high-power sodium-ion batteries.
TL;DR: In this article, a bow-tie-shaped core was designed to produce a much lower demagnetization factor (hence more power) than that of the conventional solenoid, and the selection of core material was studied and found that Mn-Zn ferrite is the most suitable core material because it greatly reduces the eddy current losses and also has high permeability.
Abstract: Condition monitoring for overhead power lines is critical for power transmission networks to improve their reliability, detect potential problems in the early stage, and ensure the utilization of the transmitting full capacity. Energy harvesting can be an effective solution for autonomous self-powered wireless sensors. In this paper, a novel bow-tie-shaped coil is proposed, which is placed directly under overhead power lines to scavenge the magnetic field energy. Compared to the conventional method by mounting the energy harvester on the power lines, this approach provides more flexibility and space to power bigger sensors such as the weather station. As the harvesting coil cannot entirely enclose the power lines, the demagnetization factor that is closely related to the core geometry should be considered and optimized. Thus a new bow-tie-shape core is designed to produce a much lower demagnetization factor (hence more power) than that of the conventional solenoid. The selection of core material is studied and found that Mn–Zn ferrite is the most suitable core material because it greatly reduces the eddy current losses and also has high permeability. Experiment results show that the bow-tie coil could have a power density of 1.86 μW/cm 3 when placed in a magnetic flux density of 7 $\mu{\rm T_{rms}}$ . This value is 15 times greater than the reported results under the same condition. If a longer bow-tie coil with more turns is placed in a magnetic flux density of $11 \mu{\rm T_{rms}}$ , the produced power density is 103.5 μW/cm3, which is comparable to a solar panel working during a cloudy day. Thus, the proposed solution is a very efficient and attractive method for harvesting the magnetic field energy for a range of monitoring applications.
TL;DR: In this article, the LaxSr1−xNiO3−δ (0.3≤x≤1) nanofibers (LNF-x) samples are prepared by using electrospun method.