用于锂离子电池的Fe3+O4+_+C+纳米结构的可控制备.pdf
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1、文章编号:摇 1007鄄8827(2014)04鄄0301鄄08用于锂离子电池的 Fe3O4/ C 纳米结构的可控制备邓洪贵1,摇 金双玲2,摇 詹摇 亮1,摇 金鸣林2,摇 凌立成1(1. 华东理工大学 化学工程联合国家重点实验室,上海 200237;2. 上海应用技术学院 材料科学与工程学院,上海 201418 )摘摇 要:摇 采用溶剂热反应并经在氮气中煅烧的方法制备出不同形貌的 Fe3O4/ C 纳米复合物。 无需表面活性剂或模板剂,仅通过调控反应物的浓度,合成出花状、纳米片状、空心球形结构 3 种纳米结构,并对不同形貌的形成机理进行探讨。 此外,三种不同形貌样品的电化学结果表明,花状样
2、品的电化学综合性能显著优于另外两种形貌,在5 C 的充放电电流下,其可逆比容量能达到 227mAh/ g,而空心球形、纳米片状结构样品的容量则分别为 45、10mAh/ g。关键词:摇 Fe3O4;纳米复合材料;负极材料;锂离子电池中图分类号: 摇 TM912. 9文献标识码: 摇 A收稿日期:2014鄄02鄄15;摇 修回日期:2014鄄08鄄12基金项目:国家自然科学基金(20806024, 51002051);中央高校基本科研业务费专项资金(WA1014016).通讯作者:詹摇 亮,副教授. E鄄mail: zhanliang ecust. edu. cn;凌立成,教授. E鄄mail:
3、 lchling ecust. edu. cn作者简介:邓洪贵,博士. E鄄mail: hongguideng gmail. comMorphology鄄controlled synthesis of Fe3O4/ carbonnanostructures for lithium ion batteriesDENG Hong鄄gui1,摇 JIN Shuang鄄ling2,摇 ZHAN Liang1,摇 JIN Ming鄄lin2,摇 LING Li鄄cheng1(1. State Key Laboratory of Chemical Engineering, East China Unive
4、rsity of Science and Technology, Shanghai200237, China;2. School of Materials Science and Engineering, Shanghai Institute of Technology, Shanghai201418, China)Abstract: 摇 Morphology鄄controlled Fe3O4/ carbon nanocomposites were synthesized by a solvothermal reaction followed by calcina鄄tion under a n
5、itrogen atmosphere. Flower鄄like structures, dispersed nanoflakes and hollow microspheres could be readily obtained byadjusting the concentrations of the reactants. Based on the time鄄dependent structure evolution, a possible mechanism for the forma鄄tion of the different morphologies under various con
6、ditions was discussed. The lithium storage properties of the different Fe3O4/ car鄄bon composites were compared. The flower鄄like sample shows the best electrochemical performance with the highest specific capaci鄄ty of 227mAh/ g at a current rate of 5 C while hollow microspheres and dispersed nanoflak
7、es have specific capacities of only 45 and10mAh/ g, respectively.Keywords:摇 Fe3O4; Nanocomposite; Anode material; Lithium鄄ion batteryFoundation item: National Natural Science Foundation of China (20806024, 51002051); Fundamental Research Funds for the Cen鄄tral Universities (WA1014016).Corresponding
8、author: ZHAN Liang, Associate Professor. E鄄mail: zhanliang ecust. edu. cn;LING Li鄄cheng, Professor. E鄄mail: lchling ecust. edu. cnAuthor introduction: DENG Hong鄄gui, Ph. D. E鄄mail: hongguideng gmail. comEnglish edition available online ScienceDirect ( http:蛐蛐www. sciencedirect. com蛐science蛐journal蛐1
9、8725805 ).DOI: 10. 1016/ S1872鄄5805(14)60139鄄61摇 IntroductionNano鄄sized transition metal oxides are one of thecandidates for next鄄generation anode materials for lith鄄ium鄄ion battery due to their high theoretical capaci鄄ties. This category of anode materials assumes a dis鄄tinct lithium storage mechan
10、ism based on conversionreactions: MOx+2x Li圮M+x Li2O (M = Fe, Co,Ni, Cu, Mn, etc. )1. Among the above mentionedtransition metal oxides, recently, magnetite (Fe3O4)has been intensely investigated due to its environmen鄄tal benignity, low cost and natural abundance2鄄9.However, the application of Fe3O4i
11、n practical batter鄄ies is hampered by the poor electronic conductivityand fast capacity fading resulting from severe aggrega鄄摇第 29 卷摇 第 4 期2014 年 8 月新摇 型摇 炭摇 材摇 料NEW CARBON MATERIALSVol. 29摇 No. 4Aug. 2014摇tion of active particles and large volume variation thatinherently accompanies the conversion
12、reactions2.In this context, many efforts have been devotedto synthesize Fe3O4/ carbon nanocomposites, whichinclude (i) embedding Fe3O4nanoparticles into a dis鄄ordered carbon matrix3鄄5or wrapping Fe3O4nanopar鄄ticles with graphene nanosheets6,7, and (ii) coatingcarbon onto Fe3O4particles8,9.During cyc
13、ling,however, the nanoparticles in the hybrid structures arefound to be aggregated strongly, which is unstableand detrimental to the cyclability and/ or rate perform鄄ance of Fe3O4. To further enhance the performance ofFe3O4, Fe3O4/ carbon composite with rationally de鄄signed nanostructure is necessar
14、y.Recently we have reported a two鄄step method tosynthesize a flower鄄like Fe3O4/ carbon nanocomposite,in which the carbon is in鄄situ generated during the cal鄄cination from the organic components of the ironalkoxide precursor prepared by solvothermal reac鄄tion10. Such an approach successfully avoids t
15、he needto separately prepare iron oxides nanostructures and ad鄄ditional steps of coating or hybridization with carbon.The carbon framework formed in Fe3O4/ carbon com鄄posite is demonstrated to favorably maintain the goodperformance of anode material, probably because itprevents the detachment of car
16、bon and aggregation ofFe3O4nanoparticles during cycling.In the presentwork, we extended this synthetic method to control themorphology of Fe3O4/ carbon nanostructures, and fur鄄ther investigated their electrochemical properties.2摇 Experimental2. 1摇 Materials preparationFe3O4/ carbon nanostructures we
17、re prepared by asample method. Briefly, 0. 4 g of FeCl36H2O and1. 0g of hexamethylenetetramine (HMT) were addedto 60mL of ethylene glycol under magnetic stirring togive a cloudy solution.The resulting mixture wasplaced into a 90mL Teflon鄄lined autoclave. Then theautoclave was sealed and heated at 16
18、0益 for 6h. Af鄄ter cooling, the product was harvested by centrifuga鄄tion and washed with alcohol for several times beforedrying at 60 益 in an oven overnight. Subsequently,the obtained product was heated to 450益 at a rate of5益 / min and held at this temperature for 3h under thenitrogen flow to obtain
19、the black powder. Three sam鄄ples with different morphologies can be obtained byadjusting the weight of FeCl36H2O and HMT, andthe detail synthesis conditions are listed in Table 1.Table 1摇 Experimental conditions and morphologies of the products.SamplesmFeCl36H2O/ gmHMT/ gSolvothermal temperature/ ti
20、meMorphologyI0.41.0160益 /6hFlower鄄likeII0.40.25160益 /9hDispersed nanoflakesIII0.82.0160益 /6hHollow microspheres2. 2摇 Materials characterizationThe crystal phase of products was characterizedby X鄄ray powder diffraction (XRD) on a Rigaku D/max鄄2500 diffractometer using a Cu K琢 radiation.The morphology
21、 and structure of the products wereobservedunderascanningelectronmicroscope(SEM, FEI Quanta 200F) and a transmission elec鄄tron microscope (TEM, JEOL 2100F). The specificsurface area was measured by the Brunauer鄄Emmett鄄Teller (BET) method using nitrogen adsorption iso鄄therms on a Micrometrics ASAP 20
22、20 system.2. 3摇 Electrochemical measurementThe working electrodes were prepared by disper鄄sing in N鄄methyl鄄2鄄pyrrolidone (NMP) a blend of as鄄obtained active material, acetylene black, and polyvi鄄nylidene difluoride (PVDF) at a weight percent ratioof 75 颐15 颐10. The counter electrode and the referenc
23、eelectrode is lithium foil, the separator is Celgard 2400, and a solution of 1mol/ L LiPF6in ethylene car鄄bonate ( EC) / dimethyl carbonate ( DMC) / diethylcarbonate (DEC) (1 颐1 颐1, mass ratio) is the electro鄄lyte. The discharge鄄charge tests were performed in avoltage range of 0. 01鄄3. 0 V (vs. Li/
24、Li+) at currentrates from 0. 2 to 5 C. Note that both the current den鄄sity and specific capacity were calculated on the baseof mass of the composite rather than that of Fe3O4,unless otherwise stated.3摇 Results and discussion3. 1摇 Morphology of precursorsFig. 1 shows the SEM and TEM images of thealko
25、xide precursors obtained by varying the reactantconcentrations. Fig. 1a depicts the general morphologof the sample I, revealing that it contains a relativelyuniform 3D flower鄄like architecture with a diameter ofabout 2滋m. The entire architecture is made of severaldozens of nanoflakes with smooth sur
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