摘要
为克服硅在储锂时的剧烈体积膨胀,目前文献报导了许多用石墨烯或碳纳米管等先进碳材料制备硅碳复合材料的研究。这些碳材料的高成本和低产量使它们难以满足工业大生产的需求。本文以水热反应剥离出的甲壳素纳米片(CNs)、聚乙烯醇(PVA)和纳米硅为原材料,通过简单的混合和干燥过程,得到CNs,PVA和纳米硅组成的块状复合材料CNs-Si-PVA,实现PVA和CNs对纳米硅的包覆。高温热解后,CNs衍生的二维碳材料(2DC)和PVA衍生的无定形碳共同包覆纳米硅形成硅碳复合材料2DC-Si-C。碳包覆能有效缓冲硅负极材料在重复脱锂/嵌锂过程中的体积变化,并提高导电性,使合成的2DC-Si-C用作锂离子电池的负极材料时表现出优异的循环稳定性及倍率性能。在1.0 A·g^(-1)的大电流密度下,经过300圈循环后,2DC-Si-C复合材料仍保留760 mAh·g^(-1)的放电比容量;倍率测试中,在2.0 A·g^(-1)的电流密度下,该复合材料首次放电能发挥出865 mAh·g^(-1)的比容量。绿色环保的碳前驱体、简单的加工方法以及优异的储锂性能,使2DC-Si-C复合材料有望成为下一代高性能锂离子电池(LIBs)的负极材料。
Si has been considered as one of the most promising anode materials for the next-generation Li-ion batteries(LIBs)be-cause of its ultrahigh theoretical capacity and low lithiation potential.However,the industrial application of Si anode is hampered by its huge volume change during the lithiation/delithiation process.The huge volume variation leads to the pulverization of Si particles,the over-growth of the solid electrolyte interphase(SEI)layer,loss of electrochemical contact,thus yields fast deterioration of capaci-ty.In addition,the low intrinsic electrical conductivity is also an obstacle for Si anode with excellent electrochemical performances.To improve the cycling stability and rate performance,Si is often combined with advanced carbon materials such as carbon nanotubes(CNT),graphene(G),and so on to construct Si/C composites.However,these advanced carbon materials are limited by their high cost and low output and cannot meet the requirements of industrial applications.In this work,we presented a novel Si/C composite for lithium storage,using polyvinyl alcohol(PVA)and two-dimensional(2D)chitin nanosheets(CNs)as carbon precursors.CNs were exfoliated from commercial chitin powders through a simple and scalable hydrothermal process.Then CNs,PVA and nano Si were mixed in deionized water at 90℃,followed by continuously stirring at this temperature to evaporate the water and obtain the robust in-termediate CNs-Si-PVA.Benefiting from the strong hydrogen bonding effect between CNs,PVA and Si nanoparticles,Si nanoparticles were tightly encapsulated by CNs and PVA.After carbonization at 850℃for 3 h in Ar atmosphere,2DC-Si-C composite was obtained.The phase,structure,morphology and elemental composition of the sample were studied by X-ray diffraction(XRD),thermogravimet-ric(TG)analysis,X-ray photoelectron spectroscopy(XPS),scanning electron microscopy(SEM)and transmission electron microsco-py(TEM).SEM and TEM results demonstrated that Si nanoparticles were dual-confined by~12 nm amorphous carbon layer derived from PVA and 2DC derived from CNs,forming a robust and moderate compact structure.Selected area electron diffraction(SAED)and XRD results indicated that Si nanoparticles remained original crystal structure after high temperature carbonization process.Ener-gy dispersive spectroscopy(EDS)mapping and XPS analysis results revealed that 2DC-Si-C contained Si,O,C and N elements.EDS mapping results also demonstrated that Si,O,C and N were distributed uniformly in 2DC-Si-C composite,implying that Si nanoparti-cles were also evenly dispersed in carbon matrix.TGA results revealed that Si content of 2DC-Si-C was 72.9%.According to N2adsorp-tion and desorption isotherms,Brunauer-Emmett-Teller(BET)specific surface of 2DC-Si-C was determined to be 175 m^(2)·g^(-1).The pore size mainly varied between 1.5 and 5 nm.Such structure could effectively buffer the volume variation of Si and lead to the formation of a stable SEI layer,thus enhance the cycling performance.The lithium storage performance of 2DC-Si-C was assessed in CR2032 coin cells assembled in glove-box filled with Ar.The working electrode was prepared by mixing 2DC-Si-C,Super P and sodium alginate in a weight ratio of 70∶15∶15.The areal loading mass of 2DC-Si-C was 1~1.5 mg·cm^(-2).A Celgard 2400 polypropylene membrane was used as the separator.The used electrolyte LX025 was purchased from DoDoChem.The electrochemical tests were carried out after letting the assembled cells standed for 8 h to ensure full infiltration of the electrolyte.The galvanostatic charge-discharge measurements were carried out on a Neware battery testing system within the voltage range from 0.01 to 2.5 V.2DC-Si-C manifested a discharge capacity of2220,1502,1174 and 865 mAh·g^(-1)at 0.2,0.5,1.0 and 2.0 A·g^(-1),respectively,demonstrating much better rate performance than pure Si anode.The initial Coulombic efficiency of 2DC-Si-C was 78.2%.The relatively low initial Coulombic efficiency could be as-cribed to the formation of SEI layer in the first cycle.At a current density of 1.0 A·g^(-1),2DC-Si-C composite maintains a discharge ca-pacity 1510,975,815 and 765 mAh·g^(-1),after 10,50,200 and 300 cycles,respectively,displaying a much better cycling perfor-mance than pure Si and Si-C anodes.The fast capacity decay in the initial 50 cycles of 2DC-Si-C could be attributed to the pulveriza-tion of the micron-sized particles obtained by sieving.After 50 cycles,Coulombic efficiency of 2DC-Si-C became higher than 99.5%which could be attributed to the dual-confining of the carbon layers that prevented the direct contact of Si and the electrolyte and stabi-lized the SEI layer.The highly improved cycling performance and rate capability of 2DC-Si-C could be attributed to the dual-confining effect of 2DC and amorphous carbon layer derived from PVA.The dual-confining of carbon layers could not only buffer the volume change of Si,leading to the formation of a stable SEI layer,but also effectively improve the electronic conductivity.This work demon-strated that 2DC-Si-C was a potential anode material for next-generation LIBs,and low-cost and green biomass could be used as carbon precursor to build high performance Si/C composite.This work also paved a new way for the for the industrial application of seafood waste derived chitin.
作者
刘大进
麻景淇
高凌峰
蔡杰
余创
谢佳
Liu Dajin;Ma Jingqi;Gao Lingfeng;Cai Jie;Yu Chuang;Xie Jia(State Key Laboratory of Advanced Electromagnetic Engineering and Technology,School of Electrical and Electronic Engineering,Huazhong University of Science and Technology,Wuhan 430074,China;State Key Laboratory of Materials Processing and Die&Mould Technology,School of Materials Science and Engineering,Huazhong University of Science and Technology,Wuhan 430074,China;Hubei Engineering Center of Natural Polymerbased Medical Materials,College of Chemistry and Molecular Sciences,Wuhan University,Wuhan 430072,China)
出处
《稀有金属》
EI
CAS
CSCD
北大核心
2022年第9期1125-1132,共8页
Chinese Journal of Rare Metals
基金
国家自然科学基金项目(51821005,U1966214,21334005,21875170)资助。
