炭修饰锂离子电池负极材料的设计及性能研究

发布时间：2018-06-15 18:08

本文选题：锂离子电池 + 负极　；参考：《大连理工大学》2014年博士论文

【摘要】：为了满足节能环保的新能源汽车对锂离子动力电池的需求,发展具有长循环稳定性、高可逆容量、良好的安全性能和快速充放电能力的电极材料成为当务之急。根据电极中活性物质的电化学特性定向设计合适的结构以提高锂离子电池的电化学性能,尤其是循环稳定性,是一个具有挑战性的研究课题。鉴于炭材料在能量储存方面的优势,本论文以纳米电极材料的结构设计为导向,制备一系列多孔炭修饰的金属氧化物／硫化物复合负极材料,旨在提高锂离子电池负极材料的循环稳定性,在此基础上,研究材料的结构特点对其电化学性能和反应机理的影响。具体包括如下几个方面： (1)针对Sn02负极材料在充放电过程中体积膨胀大(250%)和导电性低的问题,以薄壁(-2nm)高孔容(2.16cm3g-1)的管状介孔炭为载体,构筑Sn02颗粒尺寸5nm的Sn02@C复合材料。对Sn02在炭孔道中的填充度进行调变,调变范围为7-27%。当Sn02的负载量高达80wt%时,Sn02纳米颗粒还能高度分散于炭载体的介孔孔道中,且无团聚现象发生。这种管状复合材料表现出高的可逆容量和稳定的循环性能,经过100次循环后,可逆容量为1039mAh g-1,容量保持率为106%。其稳定后的容量高于Sn02的传统理论容量(782mAhg-1),这可能归因于在充放电过程中Sn02与Sn之间发生了可逆的转化反应。 (2)为了从本质上降低Sn02的体积膨胀,将体积变化相对较小的ZnO(体积膨胀：103%)引入到Sn02体相中,制备出ZnSn03(体积膨胀：-191%)负极材料。同时,结合炭材料的优势,设计合成了核壳结构的炭包覆ZnSnO3(ZnSnO3@C)纳米方块。其中,ZnSnO3方块的尺寸为37nm,具有无定形结构和丰富的介孔孔道；外部的炭层相互交联,构成连续的电子导通骨架和相互贯通的大孔通道(74nm)。电化学测试结果表明,ZnSnO3@C复合物的储锂反应综合了合金反应和转化反应的特点(Li4.4Sn与LiZn合金可逆地转变为初始的2ZnSnO3),因而可以提供高的可逆容量。经过100次循环后,可逆容量达到1060mAh g-,并且其容量保持率为93%。 (3)考虑到电极／电解液表界面的稳定性问题,以过渡金属氧化物Fe2O3为研究对象,探索了提高界面稳定性的方法。为了获取稳定的固体电解质界面(SEI)膜,根据各组分的不同功能,采用纳米工程技术将Fe203纳米颗粒、管状介孔炭载体和导电聚吡咯分层次地组装在一起,构筑了一种多功能复合负极材料。在复合物中,Fe203高度分散于炭载体中,同时导电聚吡咯均匀地包覆在Fe203@C的孔道口和外表面,将Fe2O3@C颗粒桥接起来构成一个大的单元。作为锂离子电池负极材料,聚吡咯包覆的Fe2O3@C表现出稳定的循环性能,100次循环后,容量保持率高达97%。另外,复合材料还具有快速的充放电速度、高的Fe203利用率和大的体积比容量。 (4)以负载于管状介孔炭中的硫为起始物质,铜箔代替传统的铝箔作为集流体,依靠恒流充放电过程中的电化学反应在管状介孔炭中原位生成Cu2S纳米颗粒。对反应机理进行研究发现：S颗粒与Li+反应生成的Li2Sn溶解于电解液中变为Sn2-,来自于铜箔的Cu+会与Sn2-反应生成难溶性的CuxS中间产物,随着循环次数的增加,CuxS逐渐转变为最终的Cu2S产物,得到高度分散于管状介孔炭中的Cu2S。这种原位制备的Cu2S/C复合材料表现出稳定的循环性能和优异的倍率性能。在0.2C下循环300次,可逆容量为270mAh g-1,容量保持率为104%。在10C的大电流密度下,可逆容量保持在225mAhg-1左右,是0.2C下可逆容量的86%。
[Abstract]:In order to meet the needs of energy saving and environment-friendly energy vehicles for lithium ion batteries, it is urgent to develop the electrode materials with long cycle stability, high reversible capacity, good safety performance and fast charging and discharging capacity. The design of suitable structure to improve the lithium ion battery according to the electrochemical characteristics of active substances in the electrode The electrochemical performance, especially the cyclic stability, is a challenging research topic. In view of the advantages of carbon materials in energy storage, this paper is guided by the structure design of nanomaterials. A series of porous carbon modified metal oxide / sulfide composite negative materials are prepared to improve the anode of lithium ion batteries. Based on the cyclic stability of materials, the effects of structural characteristics of materials on their electrochemical properties and reaction mechanism are studied.
(1) aiming at the problem of large volume expansion (250%) and low conductivity of Sn02 negative electrode in charge and discharge process, a Sn02@C composite with Sn02 particle size 5nm is constructed with thin-walled (-2nm) high pore volume (2.16cm3g-1) tubular mesoporous carbon as carrier. The filling degree of Sn02 in the carbon channel is adjusted and the adjustment range is 7-27%. when the load of Sn02 is as high as 80W. At t%, Sn02 nanoparticles can also be highly dispersed in mesoporous pore channels of carbon carriers, and no aggregation occurs. This tubular composite exhibits high reversible capacity and stable cycling performance. After 100 cycles, the reversible capacity is 1039mAh g-1, and the capacity retention rate is 106%. with the traditional theoretical capacity of higher than Sn02 (78). 2mAhg-1), which may be attributed to the reversible conversion reaction between Sn02 and Sn in charge discharge process.
(2) in order to reduce the volume expansion of Sn02 in essence, the ZnO (volume expansion: 103%), which has a relatively small volume change, is introduced into the Sn02 body phase and the ZnSn03 (volume expansion: -191%) negative electrode is prepared. At the same time, the carbon coated ZnSnO3 (ZnSnO3@C) nano block of the nuclear shell structure is designed and synthesized by combining the advantages of the carbon material. Among them, the ruler of the ZnSnO3 square block is designed. The 37nm has an amorphous structure and a rich mesoporous channel, and the external carbon layers cross linked together to form a continuous electronic conduction skeleton and a large pore channel (74nm). The electrochemical test results show that the lithium storage reaction of the ZnSnO3@C complex synthesizes the characteristics of the alloy reaction and the conversion reaction (Li4.4Sn and LiZn alloy reversible transformation. For the initial 2ZnSnO3, it can provide high reversible capacity. After 100 cycles, the reversible capacity reaches 1060mAh g-, and its capacity retention rate is 93%.
(3) taking into account the stability of the electrode / electrolyte surface interface, a method for improving the stability of the interface is explored with the transition metal oxide Fe2O3 as the research object. In order to obtain a stable solid electrolyte interface (SEI) film, Fe203 nanoparticles, tubular mesoporous carbon carriers and conductance are used in accordance with the different functions of each component. Polypyrrole is assembled together to construct a multi-functional composite negative material. In the complex, the Fe203 is highly dispersed in the carbon carrier. At the same time, the conductive polypyrrole is evenly coated on the orifice and the outer surface of the Fe203@C, and the Fe2O3@C particles are bridged to form a large unit. As a anode material for lithium ion batteries, polypyrrole (PPy) The coated Fe2O3@C shows a stable cycle performance. After 100 cycles, the capacity retention rate is up to 97%., and the composite also has rapid charge discharge speed, high Fe203 utilization and large volume specific capacity.
(4) the sulfur in the tubular mesoporous carbon is used as the starting material, and the copper foil is replaced by the traditional aluminum foil as the collector. The Cu2S nanoparticles are produced in situ by the electrochemical reaction in the constant current charge discharge process. The reaction mechanism was studied. The reaction of the S particles and the Li+ reaction was found to be dissolved in the electrolyte to Sn2-, The Cu+ from copper foil reacts with Sn2- to produce insoluble CuxS intermediates. With the increase of the number of cycles, CuxS gradually transforms into the final Cu2S product, and the Cu2S., which is highly dispersed in the tubular mesoporous carbon, has a stable cycling performance and excellent multiplier performance. 300 cycles under 0.2C are circulate under 0.2C. The reversible capacity is 270mAh g-1, and the capacity holding rate is 104%.. Under the high current density of 10C, the reversible capacity remains at 225mAhg-1, which is 86%. under the reversible capacity of 0.2C.
【学位授予单位】：大连理工大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM912

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