Initial measurement of ultrafast charge exchange recombination spectroscopy on the EAST tokamak

Ultrafast charge exchange recombination spectroscopy(UF-CXRS)has been developed on the EAST tokamak(Yingying Li et al 2019 Fusion Eng.Des.146522)to measure fast evolutions of ion temperature and toroidal velocity.Here,we report the preliminary diagnostic measurements after relative sensitivity calibration.The measurement results show a much higher temporal resolution compared with conventional CXRS,benefiting from the usage of a prismcoupled,high-dispersion volume-phase holographic transmission grating and a high quantum efficiency,high-gain detector array.Utilizing the UF-CXRS diagnostic,the fast evolutions of the ion temperature and rotation velocity during a set of high-frequency small-amplitude edgelocalized modes(ELMs)are obtained on the EAST tokamak,which are then compared with the case of large-amplitude ELMs.

TiN Paper for Ultrafast-Charging Supercapacitors

Ultrafast-charging energy storage devices are attractive for powering personal electronics and electric vehicles.Most ultrafast-charging devices are made of carbonaceous materials such as chemically converted graphene and carbon nanotubes.Yet,their relatively low electrical conductivity may restrict their performance at ultrahigh charging rate.Here,we report the fabrication of a porous titanium nitride(TiN)paper as an alternative electrode material for ultrafast-charging devices.The TiN paper shows an excellent conductivity of 3.67×104 S m−1,which is considerably higher than most carbon-based electrodes.The paper-like structure also contains a combination of large pores between interconnected nanobelts and mesopores within the nanobelts.This unique electrode enables fast charging by simultaneously providing efficient ion diffusion and electron transport.The supercapacitors(SCs)made of TiN paper enable charging/discharging at an ultrahigh scan rate of 100 V s−1 in a wide voltage window of 1.5 V in Na2SO4 neutral electrolyte.It has an outstanding response time with a characteristic time constant of 4 ms.Significantly,the TiN paper-based SCs also show zero capacitance loss after 200,000 cycles,which is much better than the stability performance reported for other metal nitride SCs.Furthermore,the device shows great promise in scalability.The filtration method enables good control of the thickness and mass loading of TiN electrodes and devices.

Self-assembled carbon nanoribbons with the heteroatom doping used as ultrafast charging cathodes in zinc-ion hybrid supercapacitors

Zinc-ion hybrid supercapacitors(ZHSs)are highly desirable for large-scale energy storage applications owing to the merits of high safety,low cost and ultra-long cycle life.The poor rate performance of cathodes,however,severely hinders their application.Herein,aqueous ZHSs with superior performance were fabricated by employing a series of ultrathin carbon nanobelts modified with B,N,O(CPTHBBx).The heteroatom doping can significantly modify the chemical behaviors of carbon frameworks,which could generate numerous active sites and accelerate the charge transport.The systematic investigation reveals that the B-N groups are active species for fast Zn-ion adsorption and desorption.As a result,the best-performed CPTHB-B2 exhibits an excellent electrochemical performance as cathodes in ZHSs,delivering a high specific capacitance of 415.3 F g^(−1) at 0.5 A g^(−1),a record high capacitance retention of 81%when increasing the current densities from 0.5 to 100 A g^(−1),an outstanding energy density of 131.9 W h kg^(−1) and an exceptionally high power density of 42.1 kW kg^(−1).Our work provides a new cathode design for ultrafast charging Zn-ion storage devices.

3D Carbon Frameworks for Ultrafast Charge/Discharge Rate Supercapacitors with High Energy‑Power Density

Carbon-based electric double layer capacitors(EDLCs)hold tremendous potentials due to their high-power performance and excellent cycle stability.However,the practical use of EDLCs is limited by the low energy density in aqueous electrolyte and sluggish diffusion kinetics in organic or/and ionic liquids electrolyte.Herein,3D carbon frameworks(3DCFs)constructed by interconnected nanocages(10-20 nm)with an ultrathin wall of ca.2 nm have been fabricated,which possess high specific surface area,hierarchical porosity and good conductive network.After deoxidization,the deoxidized 3DCF(3DCFDO)exhibits a record low IR drop of 0.064 V at 100 A g^−1 and ultrafast charge/discharge rate up to 10 V s^−1.The related device can be charged up to 77.4%of its maximum capacitance in 0.65 s at 100 A g^−1 in 6 M KOH.It has been found that the 3DCF-DO has a great affinity to EMIMBF4,resulting in a high specific capacitance of 174 F g^−1 at 1 A g^−1,and a high energy density of 34 Wh kg^−1 at an ultrahigh power density of 150 kW kg^−1 at 4 V after a fast charge in 1.11 s.This work provides a facile fabrication of novel 3D carbon frameworks for supercapacitors with ultrafast charge/discharge rate and high energy-power density.

Supplementary Materials: Ultrafast charge transfer in dual graphene-WS_2 van der Waals quadrilayer heterostructures

1. The transient absorption spectra of the WS2 monolayer sample.In the measurement of the transient absorption spectra of the WS2 monolayer sample, A 400-nm (3.1eV) pump pulse with a peak fluence of about 10μJ/cm2excites the electrons from the valence band into the conduction band,the

Ultrafast charge transfer in dual graphene-WS_2 van der Waals quadrilayer heterostructures

Using dual graphene–WS2 quadrilayer heterostructures as an example, we find that the ultrafast transfer of electrons from WS2 to graphene takes place within 114 fs, and the Coulomb field of the charge can effectively affect the interlayer electron transfer. This effect illustrates that the charge transfer in such van der Waals heterostructures may be controlled by an externally applied electric field for promising applications in photoelectric devices.

Surface-Engineered Li4Ti5O12 Nanostructures for High-Power Li-Ion Batteries

Materials with high-power charge–discharge capabilities are of interest to overcome the power limitations of conventional Li-ion batteries.In this study,a unique solvothermal synthesis of Li4Ti5O12 nanoparticles is proposed by using an off-stoichiometric precursor ratio.A Li-deficient off-stoichiometry leads to the coexistence of phaseseparated crystalline nanoparticles of Li4Ti5O12 and TiO2 exhibiting reasonable high-rate performances.However,after the solvothermal process,an extended aging of the hydrolyzed solution leads to the formation of a Li4Ti5O12 nanoplate-like structure with a self-assembled disordered surface layer without crystalline TiO2.The Li4Ti5O12 nanoplates with the disordered surface layer deliver ultrahighrate performances for both charging and discharging in the range of 50–300C and reversible capacities of 156 and 113 mAh g−1 at these two rates,respectively.Furthermore,the electrode exhibits an ultrahigh-charging-rate capability up to 1200C(60 mAh g−1;discharge limited to 100C).Unlike previously reported high-rate half cells,we demonstrate a high-power Li-ion battery by coupling Li4Ti5O12 with a high-rate LiMn2O4 cathode.The full cell exhibits ultrafast charging/discharging for 140 and 12 s while retaining 97 and 66% of the anode theoretical capacity,respectively.Room-(25℃),low-(−10℃),and high-(55℃)temperature cycling data show the wide temperature operation range of the cell at a high rate of 100C.

A Voltage-supportive Controller for Ultra-fast Electric Vehicle Chargers in Islanded DC Microgrids

This paper presents a controller for fast and ultrafast electric vehicle(EV)charging stations.Without affecting the charging efficiency,the proposed controller enables the charger to provide support to the interconnection voltage to counter and damp its transients.Existing solutions are either hardware-based such as using supercapacitors and flywheels which increase the cost and bulkiness of the charging station,or software-based such as P/V droop methods which are still unable to provide a robust and strong voltage support.This paper proposes an emulated supercapacitor concept in the control system of the ultra-fast EV charger in an islanded DC microgrid.Thus,it converts the EV from a static load to a bus voltage supportive load,leading to reduced bus voltage oscillations during single and multiple ultra-fast EV charging operations,and rides through and provides supports during extreme external disturbances.Detailed analysis and design guidelines of the proposed controller are presented,and its effectiveness and improved performance compared with conventional techniques are shown for different case studies.

Intelligent nanogels with self-adaptive responsiveness for improved tumor drug delivery and augmented chemotherapy

For cancer nanomedicine,the main goal is to deliver therapeutic agents effectively to solid tumors.Here,we report the unique design of self-adaptive ultrafast charge-reversible chitosan-polypyrrole nanogels(CH-PPy NGs)for enhanced tumor delivery and augmented chemotherapy.CH was first grafted with PPy to form CH-PPy polymers that were used to form CH-PPy NGs through glutaraldehyde cross-linking via a miniemulsion method.The CH-PPy NGs could be finely treated with an alkaline solution to generate ultrafast charge-reversible CH-PPy-OH-4 NGs(R-NGs)with a negative charge at a physiological pH and a positive charge at a slightly acidic pH.The R-NGs display good cytocompatibility,excellent protein resistance,and high doxorubicin(DOX)loading efficiency.Encouragingly,the prepared R-NGs/DOX have prolonged blood circulation time,enhanced tumor accumulation,penetration and tumor cell uptake due to their self-adaptive charge switching to be positively charged,and responsive drug delivery for augmented chemotherapy of ovarian carcinoma in vivo.Notably,the tumor accumulation of R-NGs/DOX(around 4.7%)is much higher than the average tumor accumulation of other nanocarriers(less than 1%)reported elsewhere.The developed self-adaptive PPy-grafted CH NGs represent one of the advanced designs of nanomedicine that could be used for augmented antitumor therapy with low side effects.