Supercapacitors and batteries are considered as the most promising energy storage devices for electric vehicles and renewable energy systems[1,2].Among them,supercapacitors,combined with exceptionally long cycle life and high power density,afford a smart strategy[3-6].As a burgeoning architecture,micro-supercapacitors are of significant importance expecting to couple with micro-batteries in various applications,including AC line- filtering,microelectromechanical system and portable electronics[7-11].Although they can be fabricated using printing and lithography techniques[12-14],continued improvements in lowcost and scalability are required to realize their future commercialization.Recently,Tour et al.report a scalable approach for producing porous graphene films with three-dimensional networks from commercial polymer films using laser irradiation,and they have equipped the graphene in micro-supercapacitors systems[15-18].

Here,we combine the laser irradiation process with subsequent electroless deposition of pseudocapacitive materials for the fabrication of all-solid-state micro-supercapacitors.A CO2 laser is first used to convert the polyimide(PI)into porous graphene with interdigitated architecture,which works as conductive matrix for the deposition of pseudocapacitive materials.Manganese dioxide(Mn O2)representing pseudocapacitive transition metal oxides is chose via self-limiting electroless deposition.Allsolid-state micro-supercapacitors are fabricated with the interdigitated electrodes using gel electrolyte.The fabricated devices exhibit many advantages in performance such as high capacitance,long lifetime and low leakage current.

事实上，港人对此是不信任的，甚至是恐慌和无奈的，“浮城”的身份和夹缝的位置使得这座城市早早地丧失了发言权，香港无法自主表达内心的想法，它就像白粉圈里的小寿郎，虽是“当事人”却也是最大的“旁观者”。

沉箱海测及陆侧抛石棱体范围计划采用1艘8方挖泥船进行开挖，抓斗船平行码头方向布设，与码头预留约2米的安全距离。8方抓斗船吊臂长度大于27米，抓斗更换为4～6方的小斗，放低吊臂从侧面伸入码头后方进行清挖，吊臂与水平面的角度约55°～60°，抓斗可开挖距离大于13米，可满足清挖要求。泥驳靠泊在挖斗船外侧，为了便于抓斗放渣，泥驳靠在抓斗船船尾。一次驻船可同时清挖码头海侧和陆侧区域，海侧和陆侧区域错位距离约12米，为保证沉箱安全，先清挖陆侧区域再清挖海侧区域，且内外标高落差不得大于2米。

The fabrication process of the micro-supercapacitors is detailed shown in Fig.1.In a typical experiment,graphene is obtained from CO2 laser induction and designed to form 8 in-plane interdigitated electrodes(four per polarity)on PI substrate[18].The pseudocapacitive Mn O2 is deposited on the laser-induced graphene to form Mn O2/graphene(Mn O2/G)composite via a self-limiting process[19-21].Brie fly speaking,the laser-induced graphene was immersed in 0.1 mol/L KMn O4 for 15 min.In a p H neutral solution,the reaction between carbon and Mn O4-can be assumed to be:4Mn O4-+3C+H2O→4Mn O2+CO32-+2HCO3-.After cleaned by deionized water,solid-state polymer electrolyte containing poly(vinyl alcohol)(PVA)/H3PO4 is used to complete the fabrication of the devices[22].The effective area of a micro-supercapacitor is about 6 mm 2.

十多年来，浙江省矿产督察制度逐步健全完善，先后制定实施了《浙江省矿产督察工作制度实施细则》《浙江省矿产督察工作程序》《浙江省矿产督察员考核管理办法》，等等。近五年来，原浙江省国土资源厅共组织208个督察组1628人次，完成督察项目488个，下发矿产督察意见380份；对不落实督察意见要求拒绝整改或限期整改不到位的，移交省厅执法监察局下发国土资源违法案件督查通知书8份；因粉尘防治措施落实不到位被省厅责令停采整顿的矿山3家。在党中央、国务院明确要求加强事中事后监管的新形势下，矿产督察作为浙江省矿产资源勘查开采监督管理工作的重要手段，所发挥的作用和成效将愈发明显。

The Raman spectrum of the graphene in Fig.2a shows three characteristic peaks for graphene-derived material:The D peak at～1340 cm-1 induced by defectsor disordered bent sites,the Gpeak at～1580 cm-1 showing graphitic sp 2 carbon,and the 2D peak at～2690 cm-1 originating from second-order zone boundary phonons[16].XPS data(Fig.2b)show ed that Mn 2p 3/2 and Mn 2p 1/2 peaks were located at ca.642.2 eV and 653.7 eV,suggesting the element Mn in the sample was present in the chemical state of Mn4+[19,23].Each interdigitated electrode branch is about 200μm,according to the scanning electron microscopy(SEM)image in Fig.2c.Energy-dispersive X-ray spectrometry(EDS)mapping analysis of elements Mn,K,C and O(shown in Fig.2d,respectively)from the select area in Fig.2c con firms the uniform distribution of Mn O2 in the composite.In a magnified image of Fig.2e,the composites present a nanoflake-like structure,with numerous nanopores.Fig.2f show s the crosssectional SEM image of the MnO2/G composite,and the average thickness of the nanocomposite is about 10μm,generally higher enough than pervious graphene-based micro-supercapacitors’electrodes[24,25].

Fig.1.The process illustration of the pseudocapacitive micro-supercapacitors.

The morphology and structural properties of the composites was characterized by scanning electron microscope(FEI Nova Nano450)equipped with an energy dispersive X-ray spectrometer,X-ray photoelectron spectroscope(XPS,ESCALAB 250)and Raman spectrometer(Renishaw in Via,514.5 nm line of an Ar+laser).Electrochemical measurements were performed using a workstation(CHI 660D).The volumetric capacitance is calculated by C V=∮I d U/(2sVΔU)from the cyclic voltammetry(CV)curves,s is the potential scan rate,V is the volume of the micro-supercapacitor(about 6×10-5 cm 3),and ΔU is the potential window.

Fig.2.(a)Representative Raman spectrum of the graphene film and the starting PI film.(b)XPS spectrum of Mn 2p from the Mn O2/G nanocomposites.(c)SEM image of patterned electrode.(d)EDS mapping images from the same area as in(c).(e)Magnified SEM image from(c).(f)Cross-sectional SEM image of the nanocomposites on the PI substrate.

Fig.3.(a)CV curves of Mn O2/G nanocomposites and pure graphene at a scan rate of 100 m V/s.(b)CV curves of Mn O2/G nanocomposites as the scan rate ranging from 10 m V/s to 100 m V/s.(c)Volumetric capacitance of the micro-supercapacitor device and the Ragone plot.(d)Nyquist plot of the devices measuring from 10 m Hz to 100 k Hz.

Fig.4.Electrochemical performance of micro-supercapacitors connected in(a)series and(b)parallel at scan rate of 100 m V/s.(c)Capacitance retention of the device.(d)Leakage current and self-discharge characteristics of the micro-supercapacitor.

We first studied the electrochemical performance of the assembled device using CV experiments in a potential window from 0 to 0.8 V.Fig.3a show s the CV curves of graphene and Mn O2/G devices at a scan rate of 100 m V/s.Since graphene is know n to contribute capacitance by the electric double layer capacitor mechanism,the Mn O2/G device show s much better performance,con firming the necessity of introducing pseudocapacitive materials for designing high performance micro-supercapacitor.As shown in Fig.3b,the Mn O2/G devices demonstrate excellent pseudocapacitive behavior at scan rates ranging from 10 m V/s to 100 m V/s.The specific volumetric capacitance is derived from the CV curves(Fig.3c).At a scan rate of 10 m V/s,the micro-supercapacitor shows a volumetric capacitance of 1.7 F/cm 3,delivering an energy density of 0.15 m Wh/cm 3,which is comparable to previous micro-supercapacitors[26-28].Electrochemical impedance spectroscopy(EIS)is used to characterize the ion transport properties over the frequency ranging from 10 m Hz to 100 k Hz at an open-circuit potential(Fig.3d).The nearly perpendicular line with a small tangential angle shown at lowfrequency region indicates good capacitive behavior of the device.The high-frequency regime exhibits a semicircle,with charge transfer resistance no more than 5Ω/cm 3,indicating the conductivity of the Mn O2/graphene is even better than the pure graphene scaffold.

Stability and reliability of the micro-supercapacitors are evaluated.These devices show stable cycling performance,retaining about 84%of initial capacitance after 10,000 charge/discharge cycles(Fig.4c).Other considerable factors in practical use are leakage current and self-discharge.These issues have received limited concern in the growing literatures of supercapacitors[29,30].It is found from Fig.4d that the leakage current dropped significantly after 1 h(from 1μA to 10 n A).With such small leakage current,the fabricated micro-supercapacitors may be integrated with energy generators to create efficient energy monument systems.The self-discharge curves can be obtained immediately after measuring the leakage current.After charging at 0.8 Vfor 2 h,the open-circuit potential was recorded.After 12 h,the micro-supercapacitor still contains 0.3 V of voltage.The advantages of low self-discharge property and high pow er output can be satisfied for the applications of supercapacitor devices.

In consideration of practical application,combination of the supercapacitors is demonstrated for the purpose of increasing the operating voltage and output current.Figs.4a and b show the CV curves of micro-supercapacitors in both series and parallel con figurations.The tandem devices exhibit essentially rectangular CV curves pro files.The increase of voltage and currents in series and parallel combination,respectively,con firms them to the pure capacitor characteristics.

In summary,we have demonstrated a simple route to make allsolid-state pseudocapacitive micro-supercapacitors.The room temperature laser induction is follow ed by Mn O2 electrodeless deposition.The solid-state micro-supercapacitors based on Mn O2/G nanocomposites deliver high volumetric capacitances,promising energy density,good stability and low leakage current.The simplicity of the approach and considerable electrochemical performance hold the micro-supercapacitors promising potential for energy storage devices in portable microelectronics.

Acknowledgments

This work is financially supported by the National Natural Science Foundation of China(Nos.51706016,51506014),and the China Postdoctoral Science Foundation(No.2017T100677)

References

[1]B.E.Conway,Electrochemical Supercapacitors:Scientific Fundamentals and Technological Applications,Kluwer Academic/Plenum,New York,1999.

[2]B.Dunn,H.Kamath,J.M.Tarascon,Science 334(2011)928-935.

[3]X.Lu,M.Yu,G.Wang,et al.,Energy Environ.Sci.7(2014)2160-2181.

[4]P.Yang,W.Mai,Nano Energy 8(2014)274-290.

[5]P.Simon,Y.Gogotsi,B.Dunn,Science 343(2014)1210-1211.

[6]T.Zhai,L.Wan,S.Sun,et al.,Adv.Mater.29(2017)1604167.

[7]Z.S.Wu,K.Parvez,X.Feng,K.Müllen,Nat.Commun.4(2013)2487.

[8]J.Chmiola,C.Largeot,P.L.Taberna,et al.,Science 328(2010)480-483.

[9]K.Wang,W.Zou,B.Quan,et al.,Adv.Energy Mater.1(2011)1068-1072.

[10]B.Hsia,J.Marschew ski,S.Wang,et al.,Nanotechnology 25(2014)055401.

[11]T.Huang,K.Jiang,D.Chen,G.Shen,Chin.Chem.Lett.29(2018)553-563.

[12]K.U.Laszczyk,K.Kobashi,S.Sakurai,et al.,Adv.Energy Mater.5(2015)1500741.

[13]Y.Wang,Y.Shi,C.X.Zhao,et al.,Nanotechnology 25(2014)094010.

[14]J.Han,Y.C.Lin,L.Chen,et al.,Adv.Sci.2(2015)1500067.

[15]Z.Peng,J.Lin,R.Ye,et al.,ACS Appl.Mater.Interfaces 7(2015)3414-3419.

[16]Z.Peng,R.Ye,J.A.Mann,et al.,ACS Nano 9(2015)5868-5875.

[17]L.Li,J.Zhang,Z.Peng,et al.,Adv.Mater.28(2016)838-845.

[18]J.Lin,Z.Peng,Y.Liu,et al.,Nat.Commun.5(2014)5714.

[19]P.Yang,X.Xiao,Y.Li,et al.,ACS Nano 7(2013)2617-2626.

[20]P.Yang,Y.Chen,X.Yu,et al.,Nano Energy 10(2014)108-116.

[21]A.E.Fischer,K.A.Pettigrew,D.R.Rolison,et al.,Nano Lett.7(2007)281-286.

[22]X.Xiao,T.Li,P.Yang,et al.,ACS Nano 6(2012)9200-9206.

[23]P.Yang,Y.Li,Z.Lin,et al.,J.Mater.Chem.A 2(2014)595-599.

[24]J.Chang,S.Adhikari,T.H.Lee,et al.,Adv.Energy Mater.5(2015)1500003.

[25]Z.S.Wu,Z.Liu,K.Parvez,et al.,Adv.Mater.27(2015)3669-3675.

[26]D.Pech,M.Brunet,H.Durou,et al.,Nat.Nanotechnol.5(2010)651-654.

[27]Z.S.Wu,K.Parvez,S.Li,et al.,Adv.Mater.27(2015)4054-4061.

[28]W.Gao,N.Singh,L.Song,et al.,Nat.Nanotechnol.6(2011)496-500.

[29]P.Yang,D.Chao,C.Zhu,et al.,Adv.Sci.3(2016)1500299.

[30]M.F.El-Kady,R.B.Kaner,Nat.Commun.4(2013)1475.