碳纳米管作为超大容量离子电容器电极的研究

本文采用碳纳米管作为超大容量离子电容器的电极材料,研究了硝酸改性处理、粘结剂对电极的电容器性能的影响,探讨了其电容的形成机理.当用硝酸改性处理的碳纳米管作电极,用30%(wt)的H₂SO₄作电解质溶液时,所得超大容量离子电容器不仅能形成双电层电容,也能形成赝电容,从而得到了69F/g的比电容;同时碳纳米管电极超大容量离子电容器具有良好的频率响应特性.     

实用化超电容器的制备与电化学性能的研究

使用高比表面积活性炭可以制备不同电容量、不同工作电压的超电容器,高比表面积活性炭的比电容量远高于普通活性炭。10 F(9V)、45 F、600 F的超电容器样品的测试结果表明,高比表面积活性炭电极的孔径结构不会影响电容器大电流充放电容量,电化学性能稳定,高比表面积活性炭是一种待开发的优良的超电容器电极材料。     

Multilayer‐Folded Graphene Ribbon Film with Ultrahigh Areal Capacitance and High Rate Performance for Compressible Supercapacitors

Limited by 2D geometric morphology and low bulk packing density, developing graphene‐based flexible/compressible supercapacitors with high specific capacitances (gravimetric/volumetric/areal), especially at high rates, is an outstanding challenge. Here, a strategy for the synthesis of free‐standing graphene ribbon films (GRFs) for high‐performance flexible and compressible supercapacitors through blade‐coating of interconnected graphene oxide ribbons and a subsequent thermal treatment process is reported. With an ultrahigh mass loading of 21 mg cm^?2, large ion‐accessible surface area, efficient electron and ion transport pathways as well as high packing density, the compressed multilayer‐folded GRF films (F‐GRF) exhibit ultrahigh areal capacitance of 6.7 F cm^?2 at 5 mA cm^?2, high gravimetric/volumetric capacitances (318 F g^?1, 293 F cm^?3), and high rate performance (3.9 F cm^?2 at 105 mA cm^?2), as well as excellent cycling stability (109% of capacitance retention after 40 000 cycles). Furthermore, the assembled F‐GRF symmetric supercapacitor with compressible and flexible characteristics, can deliver an ultrahigh areal energy density of 0.52 mWh cm^?2 in aqueous electrolyte, almost two times higher than the values obtained from symmetric supercapacitors with comparable dimensions.     

Superior Micro‐Supercapacitors Based on Graphene Quantum Dots

Graphene quantum dots (GQDs) have attracted tremendous research interest due to the unique properties associated with both graphene and quantum dots. Here, a new application of GQDs as ideal electrode materials for supercapacitors is reported. To this end, a GQDs//GQDs symmetric micro‐supercapacitor is prepared using a simple electro‐deposition approach, and its electrochemical properties in aqueous electrolyte and ionic liquid electrolyte are systematically investigated. The results show that the as‐made GQDs micro‐supercapacitor has superior rate capability up to 1000 V s^?1, excellent power response with very short relaxation time constant (τ₀ = 103.6 μs in aqueous electrolyte and τ₀ = 53.8 μs in ionic liquid electrolyte), and excellent cycle stability. Additionally, another GQDs//MnO₂ asymmetric supercapacitor is also built using MnO₂ nanoneedles as the positive electrode and GQDs as the negative electrode in aqueous electrolyte. Its specific capacitance and energy density are both two times higher than those of GQDs//GQDs symmetric micro‐supercapacitor in the same electrolyte. The results presented here may pave the way for a new promising application of GQDs in micropower suppliers and microenergy storage devices.     

高分子聚合物超电容器研究

超电容器具有能量密度高,循环寿命长,可大功率充放电等特性,应用前景诱人。导电性聚合物由于可取得较高的容量和价格低廉,是合适的超电容器电极材料。采用不同掺杂方式的导电性聚合物(N型或P型)作为电极材料使相应的超电容器分为三种类型,各具有不同的工作电压及容量特性。笔者综述了聚合物超电容器的工作原理和最新研究进展。     

超电容器复合活性炭电极的制备及性能研究

用高比表面积活性炭作为原料,酚醛树脂为粘结剂,在120℃高温下粘结成型制备系列超电容器用固体活性炭电极,改变酚醛树脂添加量考察不同炭化温度对复合活性炭电极炭化收率的影响。实验发现,随着炭化温度的提高,复合活性炭电极的炭化收率呈逐渐降低的趋势,炭化温度高于800℃时复合活性炭电极比电容量下降。酚醛树脂掺杂量多时收率降低。另外在酚醛树脂中加入固化剂可提高其炭化收率。不同组成的复合活性炭电极中,微孔活性炭含量大,则比电容量高。     

Wearable Supercapacitors Printed on Garments

Electronic garments have garnered considerable attention as a core technology for the upcoming wearable electronics era. To enable ubiquitous operation of electronic garments, they must be monolithically integrated with rechargeable power sources. Here, inspired by printing‐assisted aesthetic clothing designs, a new class of wearable supercapacitors (SCs) is demonstrated that can be directly printed on T‐shirts, which look like letters (or symbols) commonly printed on T‐shirts. The printed SCs consist of activated carbon/multiwalled carbon nanotube/ionic liquid‐based electrodes and ionic liquid/thiol‐ene polymer network skeleton/SiO₂ nanoparticle‐based gel electrolytes. The rheological properties of the electrode/electrolyte pastes are fine‐tuned by varying the colloidal network structure, which affects the printing processability and formation of the nanoscale ion/electron conduction channels. To ensure the seamless unitization and design versatility of the printed SCs, the T‐shirt is sewn with electroconductive stainless steel (SS) threads prior to the printing process. Onto the SS threads acting as shape‐directing current collectors, the electrode/electrolyte pastes are sequentially stencil‐printed and sealed with water‐proof packaging films. The printed SCs exhibit exceptional form factors, flexibility, and thermal stability. Notably, the SC‐printed T‐shirts maintain their electrochemical activity upon exposure to laundering, wringing, ironing, and folding, demonstrating their potential and practical applicability as a promising electronic garment technology.     

Scalable 3D Self-Assembly of MXene Films for Flexible Sandwich and Microsized Supercapacitors

The self-assembly of large-area MXene films is the main step to realize their applications in various energy storage devices. However, the scalable self-assembly of flexible thin MXene films with high conductivity as well as excellent mechanical and electrochemical properties is still a challenge. Herein, a synchronous reduction and self-assembly strategy to fabricate flexible MXene films is developed, where MXene films are synchronously reduced and self-assembled on the Zn foil surface. Furthermore, the self-assembly of MXene films can be scaled up by controlling the area of Zn substrates. By adjusting the patterns of Zn substrates, the interdigital MXene patterns can also be obtained via a selectively reducing/assembling process. The resultant MXene films demonstrate high electrical conductivity, large specific surface area, and excellent mechanical properties. Thus they can serve as the electrodes of flexible supercapacitor devices directly. As a proof of concept, flexible sandwich and microsized supercapacitors are designed based on the above MXene film electrodes. Both sandwich and microsized supercapacitors display stable electrochemical performance under various bending states. This study provides a route to achieve large-area MXene-based films or microsized structures for applications in the field of energy storage.     

Customizable Supercapacitors via 3D Printed Gel Electrolyte

New manufacturing strategies toward customizable energy storage devices (ESDs) are urgently required to allow structural designability for space and weight-sensitive electronics. Besides the macroscopic geometry customization, the ability to fine-tune the ESD internal architectures are key to device optimization, allowing short and uniform electrons/ions diffusion pathways and increased contact areas while overcoming the issues of long transport distance and high interfacial resistance in conventional devices with planar thick electrodes. ESDs with 2D or 3D electrodes filled with liquid or gel-like electrolyte have been reported, yet they face significant challenges in design flexibility for 3D ESD architectures. Herein, a novel method of assembling ESDs with the ability to customizing both external and internal architectures via digital light processing (DLP) technique and a facile sequential dip-coating process is demonstrated. Using supercapacitors as prototype device, the 3D printing of ESDs with areal capacity of 282.7 mF cm⁻² which is higher than a reference device with same mass loading employing planar stacked configuration (205.5 mF cm⁻²) is demonstrated. The printed devices with highly customizable external geometry conveniently allow the ESDs to serve as structural components for various electronics such as watchband and biomimetic electronics which are difficult to be manufactured with previously reported strategies.     

Switchable Supercapacitors with Transistor‐Like Gating Characteristics (G‐Cap)

A novel three‐electrode electrolyte supercapacitor (electric double‐layer capacitor [EDLC]) architecture in which a symmetrical interdigital “working” two‐electrode micro‐supercapacitor array (W‐Cap) is paired with a third “gate” electrode that reversibly depletes/injects electrolyte ions into the system controlling the “working” capacity effectively is described. All three electrodes are based on precursor‐derived nanoporous carbons with well‐defined specific surface area (735 m² g^?1). The interdigitated architecture of the W‐Cap is precisely manufactured using 3D printing. The W‐Cap operating with a proton conducting PVA/H₂SO₄‐hydrogel electrolyte and high capacitance (6.9 mF cm^?2) can be repeatedly switched “on” and “off”. By applying a low DC bias potential (?0.5 V) at the gate electrode, the AC electroadsorption in the coupled interdigital nanoporous carbon electrodes of the W‐Cap is effectively suppressed leading to a stark capacity drop by two orders of magnitude from an “on” to an “off” state. The switchable micro‐supercapacitor is the first of its kind. This general concept is suitable for implementing a broad range of nanoporous materials and advanced electrolytes expanding its functions and applications in future. The integration of intelligent functions into EDLC devices has extensive implications for diverse areas such as capacitive energy management, microelectronics, iontronics, and neuromodulation.     

Origin and Regulation of Self-Discharge in MXene Supercapacitors

MXene-based supercapacitors are promising electrochemical energy-storage devices due to their ultrahigh volumetric capacitance, high-power characteristics, and excellent cyclability. However, they suffer from severe self-discharging behavior while the underlying self-discharging mechanism is still unclear. Here, the self-discharge behavior of MXene-based supercapacitors from surface electronic structure of MXenes is disclosed, and a novel method to mitigate it is proposed. A superficial engineering strategy based on bio-thermal treatment is developed to effectively tailor surface electronic structure of Ti₃C₂T_x MXenes by eliminating hydroxyl terminations. With the evolution of surface electronic structure, as revealed by Kelvin probe force microscope and synchrotron radiation X-ray absorption fine structure analysis, MXene-based supercapacitors with common aqueous electrolytes show >20% decline in self-discharge rate. This decline mechanism originates from the increased work function that induces higher zero-charge potential after the removal of hydroxyl groups in MXenes. Meanwhile, the strengthened surface dipole leads to higher surface free energy between MXene and electrolytes. These two positive effects endow MXenes with weaker self-discharge kinetics. Specifically, the activation-controlled self-discharge process is greatly suppressed. Illuminating the relevance between electronic structure and self-discharge accompanying superficial engineering suppression strategy can guide to development of high-performance energy storage devices.     

Pushing the Cycling Stability Limit of Polypyrrole for Supercapacitors

Polypyrrole (PPy) is a promising pseudocapacitive material for supercapacitor electrodes. However, its poor cycling stability is the major hurdle for its practical applications. Here a two‐prong strategy is demonstrated to stabilize PPy film by growing it on a functionalized partial‐exfoliated graphite (FEG) substrate and doping it with β‐naphthalene sulfonate anions (NS^?). The PPy electrode achieves a remarkable capacitance retention rate of 97.5% after cycling between ?0.8 and 0 V versus saturated calomel electrode for 10 000 cycles. Moreover, an asymmetric pseudocapacitor using the stabilized PPy film as anode also retains 97% of capacitance after 10 000 cycles, which is the best value reported for PPy‐based supercapacitors. The exceptional stability of PPy electrode can be attributed to two factors: 1) the flexible nature of FEG substrate accommodates large volumetric deformation and 2) the presence of immobile NS^? dopants suppresses the counterion drain effect during charge–discharge cycling.     

VOx@MoO3 Nanorod Composite for High‐Performance Supercapacitors

Vanadium oxide is a promising pseudocapacitive electrode, but their capacitance, especially at high current densities, requires improvement for practical applications. Herein, a VO_x@MoO₃ composite electrode is constructed through a facile electrochemical method. Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy demonstrate a modification on the chemical environment and electronic structure of VO_x upon the effective interaction with the thin layer of MoO₃. A careful investigation of the electrochemical impedance spectroscopy data reveals much enhanced power capability of the composite electrode. More charge storage sites will also be created at/near the heterogeneous interface. Due to those synergistic effects, the VO_x@MoO₃ electrode shows excellent electrochemical performance. It provides a high capacitance of 1980 mF cm⁻² at 2 mA cm⁻². Even at the high current density of 100 mA cm⁻², it still achieves 1166 mF cm⁻² capacitance, which doubles the sum of single electrodes. The MoO₃ layer also helps to prevent VO_x structure deformation, and 94% capacitance retention over 10 000 cycles is obtained for the composite electrode. This work demonstrates an effective strategy to induce interactions between heterogeneous components and enhance the electrochemical performance, which can also be applied to other pseudocapacitive electrode candidates.     

电动汽车用超级储能电容试验方法研究

超级电容己成为世界各国竞相研究的热点,为加速我国电动车用超级电容器的应用,文中通过对电动汽车用超级储能电容进行容量、循环工况、温度特性、循环寿命、恒功率放电、大电流恒流放电等一系列试验方法研究,并对电动车用储能电容进行充放电仿真实验,估算了其漏电电流,建立了一套适用于电动汽车用超级储能电容的试验规范。     

Strong,Machinable Carbon Aerogels for High Performance Supercapacitors

Designing macroscopic, 3D porous conductive materials with high mechanical strength is of great importance in many fields, including energy storage, catalysis, etc. This study reports a novel approach to fabricate polyaniline‐coated 3D carbon x‐aerogels, a special type of aerogels with mechanically strong, highly cross‐linked structure that allows the originally brittle aerogels machinable. This approach is accomplished by introducing a small amount of graphene into the sol–gel process of resorcinol and formaldehyde, followed by physical activation and subsequent cross‐linking with polyaniline via electropolymerization. The resulting x‐aerogels are not only porous and conductive, but also mechanically robust with high compressibility and fast recovery. The strong combination of these properties makes the x‐aerogels promising for high performance supercapacitors that are designed to provide additional functionality for wearable and portable electronics. Such multi‐functionality leads to a significant increase in electrochemical performance, in particular high volumetric capacitance, which results from the more densely packed electroactive structure in three dimensions. More importantly, monoliths of carbon x‐aerogels are machinable into thin slices without losing their properties, thus enabling effective integration into devices with different sizes and shapes.     

Flexible MXene/Graphene Films for Ultrafast Supercapacitors with Outstanding Volumetric Capacitance

A strategy to prepare flexible and conductive MXene/graphene (reduced graphene oxide, rGO) supercapacitor electrodes by using electrostatic self‐assembly between positively charged rGO modified with poly(diallyldimethylammonium chloride) and negatively charged titanium carbide MXene nanosheets is presented. After electrostatic assembly, rGO nanosheets are inserted in‐between MXene layers. As a result, the self‐restacking of MXene nanosheets is effectively prevented, leading to a considerably increased interlayer spacing. Accelerated diffusion of electrolyte ions enables more electroactive sites to become accessible. The freestanding MXene/rGO‐5 wt% electrode displays a volumetric capacitance of 1040 F cm^?3 at a scan rate of 2 mV s^?1 , an impressive rate capability with 61% capacitance retention at 1 V s^?1 and long cycle life. Moreover, the fabricated binder‐free symmetric supercapacitor shows an ultrahigh volumetric energy density of 32.6 Wh L^?1, which is among the highest values reported for carbon and MXene based materials in aqueous electrolytes. This work provides fundamental insight into the effect of interlayer spacing on the electrochemical performance of 2D hybrid materials and sheds light on the design of next‐generation flexible, portable and highly integrated supercapacitors with high volumetric and rate performances.