LiFePO_4/C多层膜的制备及电化学性能研究
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摘要
目的研究LiFePO_4/C多层膜在不同的调制周期下的电化学性能。方法采用多靶磁控溅射方法,在304不锈钢基底上,先沉积10 nm Ti薄膜作为阻挡层,然后交替沉积LiFePO_4薄膜和C薄膜,制备三组不同调制周期的[LiFePO4/C]n多层膜。通过扫描电子显微镜(SEM)及其附带的EDS能谱仪对退火前和经500℃退火2 h后的不同调制周期[LiFePO_4/C]n多层膜的截面形貌、成分进行表征,利用X射线衍射仪(XRD)对退火前和经500℃退火2 h后的LiFePO_4薄膜及不同调制周期[LiFePO4/C]n多层膜的结构进行表征,利用激光显微拉曼光谱仪(Raman)分析经500℃退火2 h后不同调制周期[LiFePO_4/C]n多层膜中的C结构,利用循环伏安和恒流充放电法对LiFePO_4薄膜和不同调制周期[LiFePO_4/C]n多层膜的电化学性能进行测试。结果调制周期为7.5次的[LiFePO4 (160 nm)/C(16 nm)]7.5多层膜中的碳石墨化程度高于调制周期为15次的[LiFePO4(80 nm)/C(8 nm)]15和调制周期为5次的[LiFePO_4 (240 nm)/C(24 nm)]5多层膜,且具有更好的充放电容量和倍率性能。在0.1 C放电倍率下,[LiFePO_4 (160 nm)/C(16 nm)]7.5多层膜的放电容量为151 mAh/g,在5 C高放电倍率下的放电容量为30 mAh/g。结论适当的调制周期下,LiFePO_4/C多层膜具有良好的电化学性能。
The work aims to study the electrochemical properties of LiFePO_4/C multilayer films in different modulation pe-riods. 10 nm Ti film was deposited on 304 stainless steel as the barrier layer by multi-target magnetron sputtering and then theLiFePO_4/C films were deposited alternately to prepare three [LiFePO_4/C]n multilayer films with different modulation periods.The cross-sectional morphology and composition of [LiFePO_4/C]n multilayer films with different modulation periods before andafter annealing at 500 ℃ for 2 h were characterized by SEM and EDS. The structure of LiFePO_4 film and [LiFePO_4/C]n multilayerfilms with different modulation periods before and after annealing at 500 ℃ for 2 h was characterized by XRD. The C structureof [LiFePO_4/C]n multilayer films with different modulation periods after annealing at 500 ℃ for 2 h was characterized by Raman.The electrochemical property of LiFePO_4 film and [LiFePO_4/C]n multilayer films with different modulation periods was evaluatedby cyclic voltammetry and galvanostatic charge-discharge tests. The degree of graphitization in [LiFePO_4(160 nm)/C(16 nm)]7.5(the modulation cycle of 7.5 times) multilayer was higher than that in [LiFePO_4(80 nm)/C(8 nm)]15(the modulation cycle of15 times) and [LiFePO_4(240 nm)/C(24 nm)]5(the modulation cycle of 5 times) multilayers. The [LiFePO_4(160 nm)/C(16 nm)]7.5 multilayer had better charge-discharge capacity and rate performance than the [LiFePO_4(80 nm)/C(8 nm)]15 and [LiFePO_4(240 nm)/C(24 nm)]5 multilayers. The specific capacity of [LiFePO_4(160 nm)/C(16 nm)]7.5 was 151 mAh/g at 0.1 C, and the specific ca-pacity was 30 mAh/g at 5 C. LiFePO_4/C multilayer has good electrochemical properties under the appropriate modulation period.
The work aims to study the electrochemical properties of LiFePO_4/C multilayer films in different modulation pe-riods. 10 nm Ti film was deposited on 304 stainless steel as the barrier layer by multi-target magnetron sputtering and then theLiFePO_4/C films were deposited alternately to prepare three [LiFePO_4/C]n multilayer films with different modulation periods.The cross-sectional morphology and composition of [LiFePO_4/C]n multilayer films with different modulation periods before andafter annealing at 500 ℃ for 2 h were characterized by SEM and EDS. The structure of LiFePO_4 film and [LiFePO_4/C]n multilayerfilms with different modulation periods before and after annealing at 500 ℃ for 2 h was characterized by XRD. The C structureof [LiFePO_4/C]n multilayer films with different modulation periods after annealing at 500 ℃ for 2 h was characterized by Raman.The electrochemical property of LiFePO_4 film and [LiFePO_4/C]n multilayer films with different modulation periods was evaluatedby cyclic voltammetry and galvanostatic charge-discharge tests. The degree of graphitization in [LiFePO_4(160 nm)/C(16 nm)]7.5(the modulation cycle of 7.5 times) multilayer was higher than that in [LiFePO_4(80 nm)/C(8 nm)]15(the modulation cycle of15 times) and [LiFePO_4(240 nm)/C(24 nm)]5(the modulation cycle of 5 times) multilayers. The [LiFePO_4(160 nm)/C(16 nm)]7.5 multilayer had better charge-discharge capacity and rate performance than the [LiFePO_4(80 nm)/C(8 nm)]15 and [LiFePO_4(240 nm)/C(24 nm)]5 multilayers. The specific capacity of [LiFePO_4(160 nm)/C(16 nm)]7.5 was 151 mAh/g at 0.1 C, and the specific ca-pacity was 30 mAh/g at 5 C. LiFePO_4/C multilayer has good electrochemical properties under the appropriate modulation period.
引文
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[25]罗绍华,田勇,唐子龙,等.热解碳结构对LiFePO4/C复合电极性能的影响[J].稀有金属材料与工程,2009,38(2):13-15.LUO Shao-hua,TIAN Yong,TANG Zi-long,et al.Effect of the structure of pyrolytic carbon on the performance of LiFePO4/C composite cathode material[J].Rare metal materials and engineering,2009,38(2):13-15.
[2]ANDERSSON A S,THOMAS J O.The source of firstcycle capacity loss in LiFePO4[J].Journal of power sources,2001,97(3):498-502.
[3]WANG C S,HONG J.Ionic/electronic conducting characteristics of LiFePO4 cathode materials[J].Electrochemical and solid-state letters,2007,10(3):A65-A69.
[4]LU Z G,CHENG H,LO M F,et al.Pulsed laser deposition and electrochemical characterization of LiFePO4-Ag composite thin films[J].Advanced functional materials,2010,17(18):3885-3896.
[5]EFTEKHARI A.Electrochemical deposition and modification of LiFePO4 for the preparation of cathode with enhanced battery performance[J].Journal of the electrochemical society,2004,151(11):263-273.
[6]LU Z G,LO M F,CHUNG C Y.Pulse laser deposition and electrochemical characterization of LiFePO4-Ccomposite thin films[J].Journal of physical chemistry,2008,112(17):7069-7078.
[7]CHIU K F,CHEN P Y.Structural evolution and electrochemical performance of LiFePO4/C thin films deposited by ionized magnetron sputtering[J].Surface and coatings technology,2008,203(5-7):872-875.
[8]LIU Y Y,LIU D W,ZHANG Q F,et al.Lithium iron phosphate/carbon nanocomposite film cathodes for high energy lithium ion batteries[J].Electrochimica acta,2011,56(5):2559-2565.
[9]ZHOU N,UCHAKER E,LIU Y Y,et al.Effect of carbon content on electrochemical performance of LiFePO4/Cthin film cathodes[J].International journal of electrochemical science,2012,7(12):12633-12645.
[10]CHIU K F,TANG H Y,LIN B S.High conductivity LiFePO4/C composite thin films with Ti underlayers deposited by radio frequency sputtering[J].Journal of the electrochemical society,2007,154(4):A364-A368.
[11]BAJARS G,KUCINSKIS G,SMITS J,et al.Physical and electrochemical properties of LiFePO4/C thin films deposited by direct current and radiofrequency magnetron sputtering[J].Solid state ionics,2011,188(1):156-159.
[12]WANG D Y,LI H,SHI S Q,et al.Improving the rate performance of LiFePO4 by Fe-site doping[J].Electrochimica acta,2005,50(14):2955-2958.
[13]AHN C W,CHOI J J,RYU J,et al.Microstructure and electrochemical properties of graphite and C-coated LiFePO4 films fabricated by aerosol deposition method for Li ion battery[J].Carbon,2015,82(82):135-142.
[14]KUCINSKIS G,SMITS J,KLEPERIS J,et al.Characterization of LiFePO4/C composite thin films using electrochemical impedance spectroscopy[J].Materials science and engineering,2012,38:1-5.
[15]XIE J,IMANISHI N,ZHANG T,et al.Li-ion diffusion kinetics in LiFePO4 thin film prepared by radio frequency magnetron sputtering[J].Electrochimica acta,2009,54(20):4631-4637.
[16]CHIU K F.Optimization of synthesis process for carbonmixed LiFePO4 composite thin-film cathodes deposited by bias sputtering[J].Journal of the electrochemical society,2007,154(2):A129-A133.
[17]LIU Y H,ZHANG W,ZHU Y J,et al.Architecturing hierarchical function layers on self-assembled viral templates as 3D nano-array electrodes for integrated Li-ion microbatteries[J].Nano letters,2013,13(1):293-300.
[18]DOMINKO R,BELE M,GOUPIL J,et al.Wired porous cathode materials:A novel concept for synthesis of LiFePO4[J].Chemistry of materials,2007,19(12):2960-2969.
[19]DOMINKO R,BELE M,GABERSCEK M,et al.Porous olivine composites synthesized by sol-gel technique[J].Journal of power sources,2006,153(2):274-280.
[20]LIU X W,FENG T Z,CHEN S H,et al.Effects of different templates on electrochemical performance of Li Fe PO4/C prepared by supercritical hydrothermal method[J].International journal of electrochemical science,2016,11:2276-2283.
[21]CHEN Y,XIANG K,ZHOU W,et al.Li Fe PO4/Cultra-thin nano-flakes with ultra-high rate capability and ultra-long cycling life for lithium ion batteries[J].Journal of alloys and compounds,2018,749:1063-1070.
[22]LU C Z,FEY T K,KAO H M.Study of LiFePO4 cathode materials coatedwith high surface area carbon[J].Journal of power sources,2009,189(1):155-162.
[23]WANG D Y,LI H,WANG Z X,et al.New solid-state synthesis routine and mechanism for LiFePO4 using LiFas lithium precursor[J].Journal of solid stae chemistry,2004,177(12):4582-4587.
[24]LIN Y,GAO M X,ZHU D,et al.Effects of carbon coating and iron phosphides on the electrochemical properties of LiFePO4/C[J].Journal of power sources,2008,184(2):444-448.
[25]罗绍华,田勇,唐子龙,等.热解碳结构对LiFePO4/C复合电极性能的影响[J].稀有金属材料与工程,2009,38(2):13-15.LUO Shao-hua,TIAN Yong,TANG Zi-long,et al.Effect of the structure of pyrolytic carbon on the performance of LiFePO4/C composite cathode material[J].Rare metal materials and engineering,2009,38(2):13-15.
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