A UV cross-linked gel polymer electrolyte enabling high-rate and high voltage window for quasi-solid-state supercapacitors

Serving as a promising alternative to liquid electrolyte in the application of portable and wearable devices,gel polymer electrolytes(GPEs)are expected to obtain more preferable properties rather than just be satisfied with the merits of high safety and deformability.Here,an easy-operated method is employed to fabricate cross-linked composite polymer membranes used for GPEs assisted by UV irradiation,in which N-doped carbon quantum dots(N-CQDs)and TiO2are introduced as photocatalysts and additives to improve the performances of GPEs.Specifically,N-CQDs participate as a cross-linker to construct the inner porous structure,and TiO2nanoparticles serve as a stabilizer to improve the electrochemical stability of GPEs under high voltage(3.5 V).The excellent thermal and mechanical stability of the membrane fabricated in this work guarantee the safety of the supercapacitors(SCs).This GPE based SC not only exhibits prominent rate performance(105%capacitance retention at the current density of 40A g^(-1))and cyclic stability(85%at 1 A g^(-1)under 3.5 V after 20,000 cycles),but also displays remarkable energy density(42.88 Wh kg^(-1))with high power density(19.3 k W kg^(-1)).Moreover,the superior rate and cycling performances of the as-prepared GPE based flexible SCs under flat and bending state confirm the feasibility of its application in flexible energy storage devices.

Dual carbon Li-ion capacitor with high energy density and ultralong cycling life at a wide voltage window

Using the same materials for the cathode and anode in energy storage devices could greatly simplify the technological process and reduce the device cost significantly.In this paper,we assemble a dual carbon-based Li-ion capacitor with the active materials derived entirely from a single precursor,petroleum coke.For the anode,petroleum cokederived carbon(PCC)is prepared by simple ball milling and carbonization,having a massive tap density(1.80 g cm^(-3))and high electrical conductivity(11.5 S cm^(-1)).For the cathode,the raw petroleum coke is activated by KOH(petroleum cokeactivated carbon(PC-AC)sample)to achieve a well-developed pore structure to meet a rapid capacitive behavior.As a result,in addition to the robust structural stability of both the anode and cathode,the assembled dual carbon Li-ion capacitor shows a high energy density(231 W h kg^(-1)/206 W h L^(-1))and ultralong cycling life(up to 3000/10,000 cycles)at a wide voltage window.The excellent electrochemical response and simple production process make the PCC materials have great potential for practical application.

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.

New types of hybrid electrolytes for supercapacitors

Supercapacitors(SCs)are emerging as efficient energy storage devices but still suffering from limited energy density compared with batteries.Electrolytes have been regarded as the key to determine the energy storage performance of SCs.However,none of the conventional electrolytes can fully meet the increasing requirements of SCs in terms of high ion conductivity,excellent stability,wide voltage window and operating temperature range,as well as environmentally friend concerns.To this end,hybrid electrolytes have sprung up in recent years,which are believed to be the candidate to solve these shortcomings.Herein,the state-of-the-art types of hybrid electrolytes for SCs,including the combination of aqueous and organic,aqueous and gel polymer,ionic liquids(ILs)and organic,and ILs and gel polymer hybrid electrolytes,are reviewed.The effects of different hybrid systems on the performance of SCs and the underlying mechanisms are among the focal points of the review,and prospects and possible directions are discussed as well to provide further insight into the future development of this field.

Electrochemical characteristics of ternary and quadruple lithium silicon nitrides as anode material for lithium ion batteries:the influence of precursors

Ternary and quadruple lithium silicon nitride anode materials for lithium ion batteries with different precursors were prepared by the simple process of high-energy ball milling. High capacity and excellent cyclability were obtained. The influence of precursor introduction on the electrochemical performance of products was investigated. This research reveals that the electrochemical performance of lithium silicon hitilde can be enhanced significantly by doping O. The cyclability of quadruple lithium silicon nitfide can be optimized remarkably by controlling the introduction quantity of the precursors. It is possible for the composite to be used as a capacity compensator within a wide voltage cut-off window.

Activated carbon clothes for wide-voltage high-energy-density aqueous symmetric supercapacitors

Commercial carbon clothes have the potential to be utilized as supercapacitor electrodes due to their low cost and high conductivity.However,the negligible surface area of the carbon clothes serves as a serious impediment to their utilization.Herein,we report a facile calcination activation method for carbon cloths to realize remarkable comprehensive electrochemical performance.The activated carbon cloths deliver a high areal capacitance(1700 mF/cm^2),good rate capability,and stable cycling performance up to 20,000 cycles.Owing to the stability in the wide potential window,a designed symmetric capacitor can function in a cell voltage of 2.0 V and delivers high volumetric and gravimetric energy densities of 7.62 mWh/cm^3 and 18.2 Wh/kg,respectively.The remarkable electrochemical performance is attributed to rich microporosity with high surface area,superior electrolyte wettability,and stability in wide potential window.

Organic salt-derived phosphorus-doped mesoporous carbon for high performance supercapacitors

Phosphorus-doped mesoporous carbons(PMCs)were prepared using a self-doping and self-templating approach via direct pyrolysis of sodium phytate(C_(6)H_(17)NaO_(24)P_(6)).The one-pot method allows simultaneous carbonization and P doping,eliminating the need for pre-synthesis or post-activation treatment.The C_(6)H_(17)NaO_(24)P_(6)is the source of both carbon and phosphorus,and the nano-Na_(4)P_(2)O_(7)particles produced during pyrolysis act as hard templates for the honeycomb mesoporous structure with high specific surface area(884–827m^(2)/g),large mesopore volume ratio(67%–75%)and rich phosphorus content(0.53–2.34 at%).As electrodes of supercapacitors in 6 mol/L KOH,the PMCs showed outstanding performance with a high capacitance of 202 F/g and excellent rate performance of 148 F/g at 30 A/g.In addition,the PMCs-based symmetrical supercapacitors can operate in an expanded working voltage of 0–1.6 V in 3mol/L H_(2)SO_(4)aqueous electrolytes with high-density energy of 11.8 Wh/kg.

A pseudocapacitive molecule-induced strategy to construct flexible high-performance asymmetric supercapacitors

The combination of high-voltage windows and bending stability remains a challenge for supercapacitors.Here,we present an“advantage-complementary strategy”using sodium lignosulfonate as a pseudocapacitive molecule to regulate the spatial stacking pattern of graphene oxide and the interfacial architectures of graphene oxide and polyaniline.Flexible and sustainable sodium lignosulfonate-based electrodes are successfully developed,showing perfect bending stability and high electronic conductivity and specific capacitance(521 F·g^(−1)at 0.5 A·g^(−1)).Due to the resulting rational interfacial structure and stable ion-electron transport,the asymmetric supercapacitors provide a wide voltage window reaching 1.7 V,outstanding bending stability and high energy-power density of 83.87 Wh·kg^(−1)at 3.4 kW·kg^(−1).These properties are superior to other reported cases of asymmetric energy enrichment.The synergistic strategy of sodium lignosulfonate on graphene oxide and polyaniline is undoubtedly beneficial to advance the process for the construction of green flexible supercapacitors with remarkably wide voltage windows and excellent bending stability.

Enabling 2.4-V aqueous supercapacitors through the rational design of an integrated electrode of hollow vanadium trioxide/carbon nanospheres

Aqueous supercapacitors(SCs)exhibit several advantages,including high-power density,cycling durability,and safety;however,the shortage of low energy density inhibits their further application.Acquiring an excellent performance upon using simple strategies would be beneficial,but remains challenging.Here,an integrated electrode of hollow V_(2)O_(3)/carbon nanospheres(H-V_(2)O_(3)/C)was designed and synthesized for SCs.The introduction of carbon can increase the conductivity and stability,whereas the hollow structure endows H-V_(2)O_(3)/C with a high specific surface area and rapid transport of ions.Moreover,the H-V_(2)O_(3)/C integrated electrode can simultaneously work in both negative and positive potential windows.Benefiting from these advantages,the H-V_(2)O_(3)/C integrated electrode exhibits a specific capacitance as high as 708.6 F g^(-1) in a wide voltage window of-1.1-1.3 V.Furthermore,stemming from the multiple energy storage mechanisms,the aqueous integrated full SC device exhibits a wider potential window and higher energy density than the traditional(a)symmetric ones.Therefore,the proposed device delivers a wide voltage window of 2.4 V with an energy density of 96.8 W h kg^(-1) at a power density of 1204.6 W kg^(-1),as well as superior cycling stability.This study enlightens the design and preparation of electrode materials,opening up a possible approach for developing wide-voltage aqueous SCs.

Rational construction of phosphate layer to optimize Cu-regulated Fe_(3)O_(4) as anode material with promoted energy storage performance for rechargeable Ni-Fe batteries

Flexible aqueous energy storage devices with high security and flexibility are crucial for the progress of wearable energy storage.Particularly,aqueous rechargeable Ni-Fe batteries owning a large theoretical capacity,low cost and outstanding safety characteristics have emerged as a promising candidate for flexible aqueous energy storage devices.Herein,Cu-doped Fe_(3)O_(4)(CFO)with 3D coral structure was prepared by doping Cu^(2+) based on Fe_(3)O_(4)nanosheets(FO).Furthermore,the Fe-based anode material(CFPO)grown on carbon fibers was obtained by reconstructing the surface of CFO to form a low-crystallization shell which can enhance the ion transport.Excitingly,the newly developed CFPO electrode as an innovative anode material further exhibited a high capacity of 117.5 mAh g^(-1)(or 423 F g^(-1))at 1 A g^(-1).Then,the assembled aqueous Ni-Fe batteries with a high cell-voltage output of 1.6 V deliver a high capacity of 49.02 mAh g^(-1) at 1 A g^(-1) and retention ratio of 96.8%for capacitance after 10000 continuous cycles.What’s more,the aqueous quasi-solid-state batteries present a remarkable maximal energy density of 45.6 Wh kg^(-1) and a power density of 12 kW kg^(-1).This work provides an innovative and feasible way and optimization idea for the design of high-performance Fe-based anodes,and may promote the development of a new generation of flexible aqueous Ni-Fe batteries.