Topological Structure-Modulated Collagen Carbon as Two-in-One Energy Storage Configuration toward Ultrahigh Power and Energy Density

Efficient energy storage devices with suitable electrode materials,that integrate high power and high energy,are the crucial requisites of the renewable power source,which have unwrapped new possibilities in the sustainable development of energy and the environment.Herein,a facile collagen microstructure modulation strategy is proposed to construct a nitrogen/oxygen dual-doped hierarchically porous carbon fiber with ultrahigh specific surface area(2788 m^(2)g^(-1))and large pore volume(4.56 cm^(3)g^(-1))via local microfibrous breakage/disassembly of natural structured proteins.Combining operando spectroscopy and density functional theory unveil that the dual-heteroatom doping could effectively regulate the electronic structure of carbon atom framework with enhanced electric conductivity and electronegativity as well as decreased diffusion resistance in favor of rapid pseudocapacitive-dominated Li^(+)-storage(353 mAh g^(-1)at 10 A g^(-1)).Theoretical calculations reveal that the tailored micro-/mesoporous structures favor the rapid charge transfer and ion storage,synergistically realizing high capacity and superior rate performance for NPCF-H cathode(75.0 mAh g^(-1)at 30 A g^(-1)).The assembled device with NPCF-H as both anode and cathode achieves extremely high energy density(200 Wh kg^(-1))with maximum power density(42600 W kg^(-1))and ultralong lifespan(80%capacity retention over 10000 cycles).

Fluorinated graphene nanoribbons from unzipped single-walled carbon nanotubes for ultrahigh energy density lithium-fluorinated carbon batteries

Lithium-fluorinated carbon(Li-CFx)batteries have become one of the most widely applied power sources for high energy density applications because of the advantages provided by the CFx cathode.Moreover,the large gap between the practical and theoretical potentials alongside the stoichiometric limit of commercial graphite fluorides indicates the potential for further energy improvement.Herein,monolayer fluorinated graphene nanoribbons(F-GNRs)were fabricated by unzipping single-walled carbon nanotubes(SWCNTs)using pure F2 gas at high temperature,which delivered an unprecedented energy density of 2738.45 W h kg^(−1)due to the combined effect of a high fluorination degree and discharge plateau,realized by the abundant edges and destroyed periodic structure,respectively.Furthermore,at a high fluorination temperature,the theoretical calculation confirmed a zigzag pathway of fluorine atoms that were adsorbed outside of the SWCNTs and hence initiated the spontaneous process of unzipping SWCNTs to form the monolayer F-GNRs.The controllable fluorination of SWCNTs provided a feasible approach for preparing CFx compounds for different applications,especially for ultrahigh-energy-density cathodes.

Enlarging ion-transfer micropore channels of hierarchical carbon nanocages for ultrahigh energy and power densities

Increasing the energy density of supercapacitor without sacrificing its high power is an everlasting pursuit in energy storage.Using ionic liquid electrolyte with high operating voltage can increase the energy density but usually at the expense of power density due to the large ion size,low ionic conductivity and high viscosity.Herein we demonstrate a simultaneous increase of the energy and power densities with ionic liquid electrolyte(EMIMBF4)mainly by enlarging the ion-transfer micropore channels of the electrode material,i.e.,the unique hierarchical carbon nanocages(hCNC).Boudouard reaction is adopted to tune the micropore size while remaining the hierarchical framework of hCNC.Meanwhile,the specific surface area,pore volume and conductivity are also increased under optimal activation temperature.Such a unique modification boosts the large-sized ion transfer,leading to the obvious decrease of equivalent series resistance and the dramatic increase of supercapacitive performance thereof.The optimized product exhibits an energy density up to 153.8 W h kg^(-1) at the power density of 1.8 kW kg^(-1),and maintains 54.0 W h kg^(-1) even at an ultrahigh power density of 480.1 kW kg^(-1).This study demonstrates an effective way to explore advanced electrode materials by the fine regulation of micropores and related properties.

Novel bouquet-like cobalt phosphate as an ultrahigh-rate and durable battery-type cathode material for hybrid supercapacitors

Red phosphorus(RP)is beneficial to industrialization due to its rich resources,chemical stability and environmental friendliness.However,the low electronic conductivity and large volume expansion limit its application for energy storage.Herein,we first used RP to prepare a novel bouquet-like Co_(3)(HPO_(4))_(2)(OH)_(2) by the hydrothermal approach as cathode materials for hybrid supercapacitors(HSC),which delivered a large specific capacity(119.2 mA h g^(−1) at 1 A g^(−1)),a superb rate capability(83.6 mA h g^(−1) at 100 A g^(−1))and a splendid electrochemical stability(92%capacity retention after 5000 cycles at 10 A g^(−1)).Furthermore,a novel HSC device assembled with Co_(3)(HPO_(4))_(2)(OH)_(2) as the cathode,porous carbon(PC)as the anode showed a high energy density of 44.6 W h kg^(−1) and a remarkable power density of 33.75 kW kg^(−1),along with an exceptional cyclic performance(91.8%capacity retention after 10,000 cycles at 3 A g^(−1)).This study not only develops a novel type of high-performance battery-type cathode material,but also provides a new idea for the industrial application of RP.

Temperature-driven reversible structural transformation and conductivity switching in ultrathin Cu_(9)S_(5)crystals

Two-dimensional(2D)materials with reversible phase transformation are appealing for their rich physics and potential applications in information storage.However,up to now,reversible phase transitions in 2D materials that can be driven by facile nondestructive methods,such as temperature,are still rare.Here,we introduce ultrathin Cu_(9)S_(5)crystals grown by chemical vapor deposition(CVD)as an exemplary case.For the first time,their basic electrical properties were investigated based on Hall measurements,showing a record high hole carrier density of~1022 cm^(-3) among 2D semiconductors.Besides,an unusual and repeatable conductivity switching behavior at~250 K were readily observed in a wide thickness range of CVD-grown Cu_(9)S_(5)(down to 2 unit-cells).Confirmed by in-situ selected area electron diffraction,this unusual behavior can be ascribed to the reversible structural phase transition between the room-temperature hexagonalβphase and low-temperatureβ’phase with a superstructure.Our work provides new insights to understand the physical properties of ultrathin Cu_(9)S_(5)crystals,and brings new blood to the 2D materials family with reversible phase transitions.

Complex atrial tachycardia with alternating cycle length:What is the mechanism?

Background Atrial tachycardia(AT)with cycle length(CL)alternans is uncommon and conventional mapping of this AT remains challenging. We used an ultrahigh density mapping system to rapidly map complicated circuits with sufficient spatial resolution and electrogram quality to elucidate the precise mechanism of this special ATs. Methods Of 210 consecutive patients with clinical ATs who underwent catheter ablation with the ultrahigh density mapping system,4 patients(1.9%)with CL alternans were identified. The AT alternating cycles mapped by the Rhythmia mapping system for long CL were 317±51(range 245-355)ms and for short CL were 282±51(range 235-333)ms. Both long and short cycles followed in 1∶1 sequence in all 4 patients(longshort-long-short). Results By comparing the separate maps with long and short CL,we classified ATs with CL alternans into 2 types. In type 1,CL alternans resulted from an intermittent 2∶1 conduction block through the slow conduction channel in the small circuit. In type 2,CL alternans caused by the alternated conduction velocity passing through the conduction gap were manifested. Ablation at the fractionated potentials contributes to the termination of AT in 3 of the 4 patients. Conclusions Ultrahigh density mapping system can accurately identify the mechanism of complex ATs with alternating CL. The CL alternans may be related to the intermittent conduction block within the channel of the small circuitor different conduction velocity through the identical channel. Fractionated electrogram recorded in the common isthmus or some"conduction gaps"may be a reasonable approach to terminate these ATs.