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.

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

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.

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.

Ultrafast Terahertz Probes of Charge Transfer and Recombination Pathway of CH_3NH_3PbI_3 Perovskites

We use transient terahertz photoconductivity measurements to demonstrate that upon optical excitation of CH_3NH_3PbI_3 perovskite, the hole transfer from CH_3NH_3PbI_3 into the organic hole-transporting material（HTM）Spiro-OMe TAD occurs on a sub-picosecond timescale. Second-order recombination is the dominant decay pathway at higher photo-excitation fluences as observed in neat CH_3NH_3PbI_3 films. In contrast, under similar experimental conditions, second-order recombination weakly contributes the relatively slow recombination between the electrons in the perovskite and the injected holes in HTM, as a loss mechanism at the CH_3NH_3PbI_3/Spiro-OMe TAD interface. Our results offer insights into the intrinsic photophysics of CH_3NH_3PbI_3-based perovskites with direct implications for photovoltaic devices and optoelectronic applications.

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.

自组装杂原子掺杂碳纳米带作为超快充电锌离子混合超级电容器阴极

锌离子混合超级电容器(ZHSs)由于其具有较高安全性,较低成本和超长寿命等优点,适合应用于大型储能设备.然而,目前阴极材料的倍率性能较差,严重阻碍了ZHSs的发展.基于此,本文设计合成了一系列自组装杂原子掺杂(B,N,O)碳纳米带CPTHB-Bx,作为ZHSs的阴极材料.杂原子掺杂可以显著改善碳骨架的化学特性,产生更多的活性位点,并加速电荷传输.除此之外,本文还证明了B–N基团是快速吸附和脱附锌离子的主要活性位点.以CPTHB-B2作为阴极的ZHSs表现出最优异的电化学性能,在0.5 A g^(−1)电流密度下,比电容高达415.3 F g^(−1),当电流密度从0.5增大到100 A g^(−1)时,比电容保留率高达81%,能量密度为131.9 W h kg^(−1),功率密度为42.1 kW kg^(−1).此研究为超快速锌离子存储材料提供了新的设计思路.

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.