Methylene blue intercalated vanadium oxide with synergistic energy storage mechanism for highly efficient aqueous zinc ion batteries

With the rise of aqueous multivalent rechargeable batteries,inorganic-organic hybrid cathodes have attracted more and more attention due to the complement of each other’s advantages.Herein,a strategy of designing hybrid cathode is adopted for high efficient aqueous zinc-ion batteries(AZIBs).Methylene blue(MB)intercalated vanadium oxide(HVO-MB)was synthesized through sol-gel and ion exchange method.Compared with other organic-inorganic intercalation cathode,not only can the MB intercalation enlarge the HVO interlayer spacing to improve ion mobility,but also provide coordination reactions with the Zn^(2+)to enhance the intrinsic electrochemical reaction kinetics of the hybrid electrode.As a key component for the cathode of AZIBs,HVO-MB contributes a specific capacity of 418 mA h g^(-1) at 0.1 A g^(-1),high rate capability(243 mA h g^(-1) at 5 A g^(-1))and extraordinary stability(88%of capacity retention after 2000cycles at a high current density of 5 A g^(-1))in 3 M Zn(CF_(3)SO_(3))_(2) aqueous electrolyte.The electrochemical kinetics reveals HVO-MB characterized with large pseudocapacitance charge storage behavior due to the fast ion migration provided by the coordination reaction and expanded interlayer distance.Furthermore,a mixed energy storage mechanism involving Zn^(2+)insertion and coordination reaction is confirmed by various ex-situ characterization.Thus,this work opens up a new path for constructing the high performance cathode of AZIBs through organic-inorganic hybridization.

KHCO_3 activated carbon microsphere as excellent electrocatalyst for VO^(2+)/VO_2^+ redox couple for vanadium redox flow battery

In this paper,carbon microsphere prepared by hydrothermal treatment was activated by KHCO_3 at high temperature,and employed as the catalyst for VO^(2+)/VO_2^+redox reaction for vanadium redox flow battery(VRFB).Carbon microsphere can be etched by KHCO_3 due to the reaction between the pyrolysis products of KHCO_3 and carbon atoms.Moreover,KHCO_3 activation can bring many oxygen functional groups on carbon microsphere,further improving the wettability of catalyst and increasing the active sites.The electrocatalytic properties of carbon microsphere from hydrothermal treatment are improved by high temperature carbonization,and can further be enhanced by KHCO_3 activation.Among carbon microsphere samples,the VO^(2+)/VO_2^+redox reaction exhibits the highest electrochemical kinetics on KHCO_3 activated sample.The cell using KHCO_3 activated carbon microsphere as the positive catalyst demonstrates higher energy efficiency and larger discharge capacity,especially at high current density.The results reveal that KHCO_3 activated carbon microsphere is an efficient,low-cost carbon-based catalyst for VO^(2+)/VO_2^+redox reaction for VRFB system.

Towards an all-vanadium redox flow battery with higher theoretical volumetric capacities by utilizing the VO^2＋/V^3＋ couple

An all-vanadium redox flow battery with V（IV） as the sole parent active species is developed by accessing the VO2＋/V3＋ redox couple. These batteries, referred to as V4RBs, possess a higher theoretical volumetric capacity than traditional VRBs. Copper ions were identified as an effective additive to boost the battery performance.

System Energy and Efficiency Analysis of 12.5 W VRFB with Different Flow Rates

Vanadium redox flow battery(VRFB)is considered one of the most potential large-scale energy storage technolo-gies in the future,and its electrolyte flow rate is an important factor affecting the performance of VRFB.To study the effect of electrolyte flow rate on the performance of VRFB,the hydrodynamic model is established and a VRFB system is developed.The results show that under constant current density,with the increase of electrolyte flow rate,not only the coulombic efficiency,energy efficiency,and voltage efficiency will increase,but also the capacity and energy discharged by VRFB will also increase.But on the other hand,as the flow rate increases,the power of the pump also increases,resulting in a decrease in system efficiency.The energy discharged by the system does not increase with the increase in flow rate.Considering the balance between efficiency and pump power loss,it is experimentally proved that 120 mL·min-1 is the optimal working flow rate of the VRFB system,which can maximize the battery performance and discharge more energy.

Performance of redox flow battery systems in Japan

Renewable energies, such as solar and wind power, are increasingly being introduced as alternative energy sources on a glosbal scale toward a low-carbon society. For the next generation power network, which uses a large number of these distributed power generation sources, energy storage technologies will be indispensable. Among these technologies, battery energy storage technology is considered to be most viable. Sumitomo Electric Industries, Ltd. has developed a redox flow battery system suitable for large scale energy storage, and carried out several demonstration projects on the stabilization of renewable energy output using the redox flow battery system. This paper describes the advantages of the redox flow battery and reviews the demonstration projects.

A bipolar verdazyl radical for a symmetric all-organic redox flow-type battery

A symmetric all-organic non-aqueous redox flow-type battery was investigated employing the neutral small molecule radical 3-phenyl-1,5-di-p-tolylverdazyl,which can be reversibly oxidized and reduced in one-electron processes,as the sole charge storage material.Cyclic voltammetry of the verdazyl radical in 0.5 M tetrabutylammonium hexa fluoro phosphate(TBAPF6)in acetonitrile revealed redox couples at-0.17 V and-1.15 V vs.Ag+/Ag,leading to a theoretical cell voltage of 0.98 V.From the dependence of peak currents on the square root of the scan rate,diffusion coefficients on the order of 4 x 10 6 cm2 s-1 were demonstrated.Cycling performance was assessed in a static cell employing a Tokoyuma AHA anion exchange membrane,with 0.04 M verdazyl as catholyte and anolyte in 0.5 M TBAPF6 in acetonitrile at a current density of 0.12 mA cm-2.Although coulombic efficiencies were good(94%-97%)throughout the experiment,the capacity faded gradually from high initial values of 93%of the theoretical discharge capacity to 35%by the 50th cycle.Voltage and energy efficiencies were 68%and 65%,respectively.Postcycling analysis by cyclic voltammetry revealed that decomposition of the active material with cycling is a leading cause of cell degradation.

High performance of zinc-ferrum redox flow battery with Ac^-/HAc buffer solution

A green low-cost redox flow battery using Zn/Znredox couple in HAc/NaAc medium and Fe/Feredox couple in HSOmedium was first proposed and investigated for potential stationary energy storage applications. The presence of HAc/NaAc in the negative electrolyte can keep the pH between 2.0 and 6.0even when a large amount of Hions move into negative electrolyte from positive electrolyte through ion exchange membrane. In the pH range of 2.0–6.0, the chemical reaction of Zn species with Hspecies is very insignificant; furthermore, the electroreduction of Hion on the negative electrode is significantly suppressed at this pH range. The zinc-ferrum redox flow battery（Zn/Fe RFB） operated within a voltage window of 0.5–2.0 V with a nearly 90% utilization ratio, and its energy efficiency is around 71.1% at room temperature. These results show that Zn/Fe RFB is a promising option as a stationary energy storage equipment.

基于深度确定性策略梯度与模糊PID的直流微电网VRB储能系统就地层功率控制

针对直流微电网全钒液流电池(vanadium redox flow battery,VRB)储能系统在实际运行时就地控制层中的功率控制器存在时滞、精度低及抗干扰能力差等问题,提出了一种基于深度确定性策略梯度与模糊PID的功率跟踪控制策略。首先,建立VRB的等效电路模型来描述功率传输特性,并设计了由模糊PID与深度确定性策略梯度(deep deterministic policy gradient,DDPG)算法组成的复合控制器。将模糊PID作为主控制器对功率环进行控制,DDPG作为辅助控制器来补偿功率跟踪误差。然后,设计了VRB储能系统就地层功率跟踪控制器,采用麻雀搜索算法(sparrow search algorithm,SSA)对PID参数和模糊规则进行优化,并通过阶跃信号对优化后的系统输出响应进行测试。同时将分配指令功率与储能单元给定功率偏差作为数据集在DDPG中进行训练,以提高主控制器的响应速度和抗干扰能力。最后,通过在3种不同场景的算例下进行仿真,验证了控制策略的有效性及稳定性。结果表明:所提控制策略在电池充放电时,能够快速地跟踪到功率指令值;实时跟踪时,跟踪功率值与调度指令值偏差小于±2%;受到扰动时,能准确修正功率偏差,满足实际要求。

Two electron utilization of methyl viologen anolyte in nonaqueous organic redox flow battery

Methyl viologen （MV） as a bench-mark anolyte material has been frequently applied in aqueous organic redox flow batteries （AORFBs） towards large-scale renewable energy storage. However, only the first re- duction of MV was utilized in aqueous electrolytes because of the insoluble MV0generated from the second reduction of MV. Herein, we report that methyl viologen with bis（trifluoromethane）sulfonamide counter anion, MVTFSI, can achieve two reversible reductions in a nonaqueous supporting elec- trolyte. Paired with （Ferrocenylmethyl）trimethylammonium bis（trifluoromethanesulfonyl）imide, FcNFFSI, as catholyte, the MVTFS/FcNTFSI nonaqueous organic redox flow battery （NOARFB） can take advantage of either one electron or two electron storage of the methyl viologen moiety and provide theoretical energy density of 24.9Wh/L and a cell voltage of up to 1.5V. Using a highly conductive LiTFSI/CH_3CN supporting electrolyte and a porous Daramic separator, the NOARFB displayed excellent cycling performance, includ- ing up to a 68.3g energy efficiency at 40 mA/cm2, and more than 88g total capacity retention after 100 cycles.

Soft Template-Induced Porous Polyvinylidene Fluoride Membrane for Vanadium Flow Batteries

Vanadium flow batteries(VFBs)are considered ideal for grid-sc ale,long-duration energy storage applications owing to their decoupled output power and storage capacity,high safety,efficiency,and long cycle life.However,the widespread adoption of VFB s is hindered by the use of expensive Nafion membranes.Herein,we report a soft template-induced method to develop a porous polyvinylidene fluoride(PVDF)membrane for VFB applications.By incorporating water-soluble and flexible polyethylene glycol(PEG 400)as a soft template,we induced the aggregation of hydrophilic sulfonated poly(ether ether ketone),resulting in phase separation from the hydrophobic PVDF polymer during membrane formation.This process led to the creation of a porous PVDF membrane with controllable morphologies determined by the polyethylene glycol content in the cast solution.The optimized porous PVDF membrane enabled a stable VFB performance for 200 cycles at a current density of 80 mA/cm^(2),and the VFB exhibited a Coulombic efficiency of 95.2%and a voltage efficiency of 87.8%.These findings provide valuable insights for the development of highly stable membranes for VFB applications.

模块化VRB-EC混合储能系统配置与控制的优化

提出了一种适用于全钒液流电池-电化学电容器(VRB-EC)混合储能系统(HESS)的控制策略,分析了EC的最优配置数量及HESS的最小成本。根据风电预测数据设计HESS总充放电功率,通过设定EC的动作区间以降低对VRB的损耗,通过排序法实现对VRB各单元充电任务的合理分配。基于某风电场30 d实测及预测数据,仿真分析了EC配置数量对HESS成本的影响,得到了HESS的最优配置及最小成本,为工程应用中VRB-EC混合储能系统运行方式的制定和配置的选择提供了参考依据。

VRB用季铵化聚醚砜阴离子交换膜

对聚醚砜(PES)进行氯甲基化、季铵化改性,制备了季铵化PES(QAPES)阴离子交换膜,考察了不同离子交换容量(IEC)膜的含水率、面电阻(R)、化学稳定性及单体全钒氧化还原液流电池(VRB)的性能。IEC为1.47 mmol/g的QAPES膜的R为0.66Ω.cm2,在1.5 mol/L VO2+溶液中浸泡30 d,质量损失为4.5%,单体VRB的能量效率可达84.4%。

流道结构与电解液流动状态对VRB性能的影响

设计了两种不同的流道结构，考察了在平流和穿流情况下，电解液流动状态对全钒液流电池（VRB）性能的影响。改变电解液的循环流量，考察了活性物质的供应量和流动状态对充放电电压的影响。穿流结构的流道可增加电极的有效面积，改善电解液流动的均匀性，提高能量效率1．5％-5．0％。电解液流动状态对能量效率的影响约在1．5％以内，弱于流动方式和流道结构的影响。

全钒液流电池用磺化聚芴醚酮质子交换膜的制备及性能

首先,将9,9-二(3,5-二甲基-4-羟基苯基)芴(DMBHF)、9,9-双(4-羟苯基)芴(BHF)和4,4’-二氟二苯甲酮(DFB)在高温下缩聚,得到聚芴醚酮(PFEK-x)(x=30、40、50,x为DMBHF含量,以DFB的物质的量计,下同);接着,利用溴代反应将PFEK-x的甲基功能化为溴甲基;然后,通过4-羟基苯磺酸钠的SN2亲核取代制得具有不同离子交换容量的磺化聚芴醚酮(SPFEK-x);最后,通过溶液浇铸法成膜并酸化,制得新型低成本质子交换膜(PEMs)。采用^(1)HNMR、FTIR、TGA对其进行了表征,并对其性能进行了测试。结果表明,SPFEK-40膜具有较高的质子传导率及离子选择性、较低的钒离子渗透率及面电阻,综合性能优异。以SPFEK-40膜组装的全钒液流电池(VRFB)在电流密度为80 m A/cm^(2)时的能量效率为88.2%,高于以Nafion 212膜组装的VRFB的84.8%。此外,以SPFEK-40膜组装的VRFB在30次循环后放电容量保持率为84.3%,远高于以Nafion 212膜组装的VRFB(66.1%)。该合成路线的原料来源广泛,价格低廉,不涉及危险的磺化反应,易于工业放大。制得的SPFEK-x均具有良好的机械性能和氧化稳定性。

VRB储能系统对风电场LVRT特性影响分析

为满足电网规定的并网风电场必须具有低电压穿越能力(LVRT)要求,提出一种在风电场并网点加入直接功率控制的钒液流电池(VRB)储能系统的拓扑结构来提高风电场LVRT。根据目前风电机组发展趋势风电场采用基于全功率双脉宽调制AC/DC/AC控制策略的逆变器的永磁直驱风电机组(PMSG),VRB储能系统逆变器采用DC/AC双向功率流动的控制策略。所提出的控制策略通过协调控制风电机组机侧整流器、网侧逆变器和VRB变换器,实现平抑风电场出力和电压跌落时PCC点电压稳定控制及向电网提供一定的无功补偿。仿真结果表明,风速波动和系统电压跌落时,提出的方案可以有效平抑风电场出力波动,提高风电场LVRT能力,减小对系统安全稳定运行的负面影响。

VRB-Boost变换器系统非线性行为对储能系统的影响特性

在钒液流电池Boost变换器系统中,系统参数尤其是钒液流电池(vanadium redox flow batteries,VRB)荷电状态(state of charge,SOC)和负载对系统非线性行为影响较大,是系统安全稳定运行面临的主要问题之一。为此,基于VRB的电气特性建立其数学模型,采用频闪映射方法建立了电流型Boost变换器离散迭代映射模型,结合以上模型建立了VRB-Boost变换器系统统一模型。在系统统一模型基础上分析了SOC和负载R影响系统非线性行为的原因,编程仿真得到系统输出随钒电池SOC和负载R变化的分岔图,通过系统输出分岔图之间的对比,得出钒电池SOC和负载R对系统非线性行为的影响规律,试验结果验证了理论分析的正确性。

基于LC振荡电路的串联型VRB均衡控制策略

针对串联型全钒液流电池组(S-VRBs)在运行过程中会导致电池有效使用容量降低、循环寿命缩短等问题,提出一种基于LC振荡电路的均衡控制策略。该策略利用电容电感储能使能量由高SOC单体电池向低SOC单体电池转移,研究不同LC电路参数和开关频率对均衡性能的影响,选择合适参数,并与传统电容型电路比较。将基于LC振荡电路的电池组模型在静置工况、充电工况以及放电工况下进行仿真分析。在MATLAB/Simulink上进行仿真对比验证,结果表明,该均衡控制策略均衡速度快,能量转移效率高,在充放电过程中能使不同性能的VRB单体SOC趋于一致,S-VRBs电压保持在某一分散度之下,能够有效地提高电池利用率及系统效率。

采用VRB-UDVR提升1 MW光伏发电系统柔性故障穿越能力的仿真研究

为改善1 MW光伏发电系统(PVG)柔性故障穿越(FFRT)能力,提出了基于全钒液流电池(VRB)储能的三相解耦型不间断动态电压恢复器(UDVR)拓扑结构。在对并网型PVG系统、VRB的等效电路模型和充放电特性、双向DC/DC变换器小信号数学模型和UDVR的工作原理进行理论分析的基础上,建立了VRB储能三相解耦UDVR与2路500 k W PVG并网系统仿真模型。PVG正常运行时UDVR处于旁路备用,检测到公共耦合点(PCC)电压故障时UDVR投入运行。依据国家最新光伏电站并网技术标准中规定的最严重电压故障边界条件,设计了6类代表性电网对称/不对称跌落/骤升故障工况,分别对投入UDVR时PVG系统的运行特性进行了深入分析。结果表明:针对各类PCC电压故障,三相解耦型UDVR均可灵活地向电网注入相应的补偿电压,维持了负荷端电压稳定,在宽电压故障范围实现了1 MW PVG系统FFRT运行。

储能电池建模与状态估计研究进展

储能电池具有能够平滑可再生能源输出,提高电力系统灵活性和应对电力需求峰谷等优势,有助于推动可再生能源发展,从而应对环境污染和能源紧缺的双重压力。目前市场主流的储能电池为锂离子电池,具有高比能特性,同时新型储能电池也在蓬勃发展,其中全钒液流电池具有高安全性的优势,液态金属电池具有超长循环寿命,在电力储能领域具有重要应用前景。储能电池的建模和状态估计对提高储能电池系统性能,确保其安全性以及优化维护效率至关重要,因此文中对锂离子电池、全钒液流电池和液态金属电池的建模和状态估计进行综述。首先,介绍了储能电池状态估计的整体框架,对基于实验的方法、基于模型的方法和基于数据驱动的方法进行整体介绍,并对荷电状态(state of charge,SOC)、健康状态(state of health,SOH)和剩余使用寿命(remaining useful life,RUL)进行概括;然后,从原理出发,分别总结了不同储能电池体系的内部工作过程、模型构建、状态估计与电池管理过程;最后,对不同储能电池体系的主要工作特性进行横向对比和总结,旨在为储能电池选择和发展提供启示。

Highly stable side-chain-type cardo poly(aryl ether ketone)s membranes for vanadium flow battery

Vanadium flow batteries(VFBs)have drawn considerable attention as an emerging technology for largescale energy storage systems(ESSs).One of the pivotal challenges is the availability of eligible ion exchange membranes(ICMs)that provide high ion selectivity,proton conductivity,and stability under rigorous condition.Herein,a‘side-chain-type’strategy has been employed to fabricate highly stable phenolphthalein-based cardo poly(arylene ether ketone)s(PAEKs)membrane with low area resistance(0.058Ωcm^(2)),in which flexible alkyl spacers effectively alleviated inductive withdrawing effect from terminal ion exchange groups thus enabling a stable backbone.The assembled VFBs based on PAEKs bearing pendent alkyl chain terminated with quaternary ammonium(Q-PPhEK)demonstrated an energy efficiency above 80%over 700 cycles at 160 mA/cm^(2).Such a remarkable results revealed that the side-chain-type strategy contributed to enhancing the ICMs stability in strong oxidizing environment,meanwhile,more interesting backbones would be woken with this design engaging in stable ICMs for VFBs.