本文關(guān)鍵詞： 高能量密度 鋰離子電池 硅基負(fù)極材料 電化學(xué)性能　出處：《湖南工業(yè)大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：鋰離子電池已廣泛應(yīng)用于便攜式電子設(shè)備,電動汽車以及儲能領(lǐng)域,但受制于常規(guī)正負(fù)極活性物質(zhì)的比容量,目前商業(yè)化的鋰離子電池很難滿足更高能量密度的需求。根據(jù)中國汽車動力電池發(fā)展路線的規(guī)劃要求,至2015年動力電池模塊的能量密度達(dá)到150Wh/kg(單體在170~190Wh/kg),目前已經(jīng)達(dá)到要求;至2020年動力電池模塊的能量密度達(dá)到250Wh/kg(單體在300Wh/kg以上),以現(xiàn)有的材料體系已經(jīng)無法滿足未來發(fā)展的需求,所以必須要發(fā)展高能量密度的電極材料。硅的理論比容量高達(dá)4200mAh/g,是傳統(tǒng)石墨負(fù)極的十倍多(石墨的理論比容量為372mAh/g),其應(yīng)用可以大幅地提高鋰離子電池的能量密度,因此,硅被認(rèn)為有望成為下一代鋰離子電池大容量負(fù)極材料。然而,硅負(fù)極顆粒在充放電過程中,其體積變化率超過300%,導(dǎo)致活性物質(zhì)結(jié)構(gòu)粉化、脫離集流體而失去活性,以及不穩(wěn)定固體電解質(zhì)界面膜(Solid Electrolyte Interface,簡稱SEI膜)的產(chǎn)生,使得硅基負(fù)極材料的庫倫效率低、循環(huán)性能較差,影響其在全電池中的使用。本文對鋰離子電池的結(jié)構(gòu)與組成、工作原理以及所用負(fù)極材料的進(jìn)展進(jìn)行概述,通過對比微米硅、硅碳復(fù)合、硅鐵合金、硅氧合金四種不同類型的硅基負(fù)極材料的結(jié)構(gòu)和電化學(xué)性能,得到硅氧合金材料中的SiOx可以有效抑制硅顆粒的體積膨脹,循環(huán)性能較好(半電池中0.2C倍率下循環(huán)20次后容量保持率70%),嵌鋰容量較高(首次嵌鋰容量可達(dá)1600mAh/g以上),是比較有希望商業(yè)化應(yīng)用的材料。針對硅氧合金材料的首次效率低、導(dǎo)電性能差的問題,以Si/SiOx為研究對象,采用包覆無定形碳的方式對其進(jìn)行表面改性,得到的Si/SiOx/C的首次庫倫效率提高了10%,循環(huán)容量保持率提高了11%。為進(jìn)一步提高Si/SiOx/C材料的導(dǎo)電性,通過研究Super P、CNTs、Graphene三種單一導(dǎo)電劑和Super P+CNTs、Super P+CNTs+Graphene兩種復(fù)合導(dǎo)電劑的導(dǎo)電網(wǎng)絡(luò)結(jié)構(gòu)對Si/SiOx/C材料的導(dǎo)電性能和電化學(xué)性能的影響,得出綜合性能最好是SP+CNTs復(fù)合導(dǎo)電劑,它具有三維立體導(dǎo)電網(wǎng)絡(luò)結(jié)構(gòu),Si/SiOx/C電極的體電阻率較小,倍率性能最優(yōu)、循環(huán)性能最佳(半電池中0.5C倍率下循環(huán)20次后容量保持率55%)。為改善Si/SiOx/C與導(dǎo)電劑、集流體之間的粘結(jié)性能,研究常規(guī)SBR/CMC常規(guī)粘結(jié)劑體系和PAALi新型粘結(jié)劑對Si/SiOx/C極片的性能影響,在使用Si/SiOx/C/石墨復(fù)合材料的聚合物鋰離子電池(型號為418281)中進(jìn)行對比,得出新型PAALi粘結(jié)劑能提升極片的剝離強度,降低電池的內(nèi)阻、提高電池的倍率、循環(huán)、高低溫性能等。通過對硅基負(fù)極材料的改性、所用導(dǎo)電劑和粘結(jié)劑的優(yōu)化,最終開發(fā)出能量密度高達(dá)737Wh/L,循環(huán)300次后容量保持率為80%,滿足鋰離子電池商業(yè)化應(yīng)用的基本要求,推進(jìn)硅基負(fù)極材料在高能量密度鋰離子電池中的應(yīng)用。
[Abstract]:Lithium ion batteries have been widely used in portable electronic equipment, electric vehicles and energy storage, but limited by the specific capacity of conventional positive and negative active substances. It is difficult to meet the demand of higher energy density for commercial lithium-ion batteries at present. According to the planning requirements of the development route of automobile power battery in China. By 2015, the energy density of the power battery module was 150? In 2020, the energy density of the power battery module reached 250Wh/ kg (the monomer is more than 300Wh/ kg / kg), the existing material system can not meet the future development needs. Therefore, it is necessary to develop high energy density electrode materials. The theoretical specific capacity of silicon is as high as 4200mAh/ g, more than ten times that of the traditional graphite negative electrode (the theoretical specific capacity of graphite is 372mAh/ g). Its application can greatly increase the energy density of lithium-ion batteries. Therefore, silicon is expected to become the next generation of lithium ion batteries large capacity anode materials. However, silicon anode particles in charge and discharge process. Its volume change rate is more than 300, resulting in the structure of the active substances powdered, away from the fluid collection and lose activity. The formation of solid Electrolyte interface (SEI membrane) makes the Coulomb efficiency of silicon-based anode materials low. In this paper, the structure and composition of Li-ion battery, the working principle and the development of anode materials are summarized, and the micron silicon and silicon-carbon composite are compared. The structure and electrochemical properties of four different types of silicon-based negative electrode materials, ferrosilicon alloy and silicon oxide alloy, the SiOx in silicon-oxygen alloy materials can effectively inhibit the volume expansion of silicon particles. The cycle performance is better (the capacity retention is 70 and the lithium intercalation capacity is high (the first lithium intercalation capacity can be more than 1600mAh/ g) after 20 cycles in the semi-battery with 0.2C ratio). It is a promising material for commercial application. Aiming at the problems of low efficiency and poor conductivity of silicon-oxygen alloy materials, Si/SiOx is taken as the research object. The first Coulomb efficiency of Si/SiOx/C was improved by 10% by coating amorphous carbon on the surface. In order to further improve the electrical conductivity of Si/SiOx/C materials, the cyclic capacity retention rate was increased by the study of Super. Three kinds of Graphene single conductive agent and Super P CNTs. The effect of conducting Network structure of Super P CNTs Graphene on the Conductive and Electrochemical Properties of Si/SiOx/C Materials. It is concluded that the best comprehensive property is SP CNTs composite conductive agent, which has a three-dimensional conducting network structure, the volume resistivity of Si / Sio _ x / C electrode is smaller, and the rate performance is the best. In order to improve the adhesion between Si/SiOx/C and conductive agent, the capacity retention rate is 550.In order to improve the adhesion between Si/SiOx/C and conductive agent, the capacity retention rate is 55% after 20 cycles at 0.5C ratio in the semi-battery, in order to improve the bonding performance between the Si/SiOx/C and the conductive agent. The effects of conventional SBR/CMC binder system and new PAALi binder on the properties of Si/SiOx/C plates were studied. Compared with the polymer lithium-ion battery (type 418281) using Si / Sio _ x / C / graphite composite, the new PAALi binder can improve the peeling strength of the electrode. Reduce the internal resistance of the battery, improve the rate of the battery, cycle, high and low temperature performance. Through the modification of silicon-based anode materials, the use of conductive agent and binder optimization. Finally, the energy density is as high as 737Wh/ L, and the capacity retention rate is 80 after 300 cycles, which meets the basic requirements of commercial application of lithium-ion batteries. Application of silicon based anode materials in high energy density lithium ion batteries.
【學(xué)位授予單位】：湖南工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TM912

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