本文選題：鋰離子電池　切入點(diǎn)：復(fù)合材料　出處：《哈爾濱工業(yè)大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

【摘要】：Sn、SnO2材料分別具有990mAh·g-1、782mAh·g-1的高容量，因此在鋰離子電池電極材料快速發(fā)展的今天受到人們的關(guān)注。但是，材料在充放電過(guò)程中巨大的體積變化，導(dǎo)致電池性能迅速下降，限制材料商業(yè)化應(yīng)用。針對(duì)材料的劣勢(shì)，本文將對(duì)材料進(jìn)行一定的改性研究及相關(guān)性能測(cè)試。 石墨烯因?yàn)榫哂斜缺砻娣e大、導(dǎo)電性好的優(yōu)點(diǎn)被廣泛用于電極材料的載體，本文采用噴霧干燥的實(shí)驗(yàn)方法將SnO2顆粒負(fù)載到石墨烯片層上。實(shí)驗(yàn)結(jié)果表明，5:1比例的SnO2@Graphene復(fù)合材料表現(xiàn)出優(yōu)異的電化學(xué)性能，200mA·g-1的電流密度、100次循環(huán)之后，材料依然具有760mAh·g-1以上的容量；1000mA·g-1的電流密度時(shí)，材料的可逆容量仍保持在730mAh·g-1左右。但是，70次循環(huán)之后SnO2@Graphene復(fù)合材料的容量出現(xiàn)波動(dòng)，表明材料的結(jié)構(gòu)不穩(wěn)定。為了改善復(fù)合材料的循環(huán)穩(wěn)定性，通過(guò)添加粘結(jié)劑PVP增強(qiáng)SnO2與石墨烯之間的結(jié)合力、包覆熱解碳達(dá)到進(jìn)一步緩解SnO2所產(chǎn)生的應(yīng)力的作用。添加0.3g PVP的復(fù)合材料電化學(xué)性能測(cè)試結(jié)果表明，20個(gè)循環(huán)之后材料的循環(huán)性能開(kāi)始穩(wěn)定，40個(gè)循環(huán)之后容量呈緩慢增加的趨勢(shì)，100個(gè)循環(huán)之后材料的可逆容量維持在685mAh·g-1。復(fù)合材料優(yōu)異的性能是因?yàn)�，PVP添加后使復(fù)合材料的結(jié)構(gòu)更加緊湊，充放電過(guò)程開(kāi)始時(shí)，電解液未完全浸潤(rùn)，隨著循環(huán)的進(jìn)行結(jié)構(gòu)有所松動(dòng)，，電解液開(kāi)始慢慢滲透使材料呈現(xiàn)出如此優(yōu)異的電化學(xué)性能。熱解碳的包覆有兩種方式，一是直接噴霧干燥的方式；二是噴霧干燥-水熱的方式。兩種方式制備的復(fù)合材料均具有比原復(fù)合材料更加優(yōu)異的循環(huán)穩(wěn)定性，但是通過(guò)噴霧干燥-水熱的方式制備的SnO2@C/Graphene表現(xiàn)出更加優(yōu)異的性能。SnO2@C/Graphene在200mA·g-1電流密度下，100-300次循環(huán)內(nèi)可逆容量始終維持在800mAh·g-1左右，表現(xiàn)出極其優(yōu)異的循環(huán)穩(wěn)定性；即使在800mA·g-1和1000mA·g-1的高電流密度下，材料的可逆容量仍可達(dá)到850mAh·g-1、815mAh·g-1。如此優(yōu)異的電化學(xué)性能來(lái)源于復(fù)合材料的層級(jí)結(jié)構(gòu)，即負(fù)載有SnO2顆粒的石墨烯片層外包覆有一層熱解碳層。 基于噴霧干燥制備的電化學(xué)性能優(yōu)異的SnO2基復(fù)合材料，通過(guò)高溫H2還原或NaBH4還原，制備Sn基復(fù)合材料以此提高材料的首次庫(kù)倫效率，提高電池電壓。經(jīng)H2高溫或NaBH4與H2結(jié)合所還原出的復(fù)合材料，因?yàn)殄a顆粒從石墨烯表面脫出并熔化團(tuán)聚成微米級(jí)錫球之后，材料的首次庫(kù)侖效率只提升了幾個(gè)百分點(diǎn)，但材料在20個(gè)循環(huán)之后已無(wú)容量可言。只有經(jīng)包碳處理之后，材料中的錫球顆粒呈納米級(jí)且100次循環(huán)之后具有350mAh·g-1的可逆容量，但是材料的循環(huán)穩(wěn)定性依然較差，整個(gè)充放電循環(huán)過(guò)程中材料的容量一直處于衰減狀態(tài)。這說(shuō)明噴霧干燥法由SnO2基材料還原制備Sn基材料是不可行的。
[Abstract]:The SnO _ 2 materials have a high capacity of 990mAh 路g-1C 782mAh 路g ~ (-1), so they have attracted much attention in the rapid development of electrode materials for lithium ion batteries. However, the huge volume change of the materials during the charging and discharging process leads to the rapid decline of the battery performance. In view of the disadvantages of the materials, this paper will study the modification of the materials and test the properties of the materials. Graphene is widely used as a carrier of electrode materials because of its large specific surface area and good conductivity. In this paper, SnO2 particles were loaded on graphene sheets by spray drying method. The experimental results showed that the SnO2@Graphene composites with 5: 1 ratio exhibited excellent electrochemical properties after 100 cycles of current density of 200mA 路g-1. When the material still has the current density of 1000mA 路g-1 or more than 760mAh 路g-1, the reversible capacity of the material remains around 730mAh 路g-1, but the capacity of SnO2@Graphene composites fluctuates after 70 cycles. In order to improve the cyclic stability of composites, the adhesion between SnO2 and graphene was enhanced by adding binder PVP. The results of electrochemical performance test of composites added 0.3 g PVP show that the cyclic properties of the composites begin to stabilize after 20 cycles, and the capacity of 40 cycles is slow. After 100 cycles, the reversible capacity of the composite was maintained at 685 mAh 路g-1.The excellent properties of the composite were due to the compactness of the structure of the composite with the addition of PVP. At the beginning of the charge-discharge process, the electrolyte was not completely infiltrated. As the structure of the cycle was loosened, the electrolyte began to permeate slowly so that the material showed such excellent electrochemical performance. There were two ways to cover the pyrolytic carbon. One is direct spray drying; the other is spray drying-hydrothermal. The composites prepared by both methods have better cycling stability than the original composite. But the SnO2@C/Graphene prepared by spray drying and hydrothermal method showed better performance. Sno _ 2 @ C _ (r) G _ (ene) kept the reversible capacity of 100mAh 路g ~ (-1) at 200mA 路g ~ (-1) current density, showing excellent cycle stability. Even at the high current density of 800mA 路g-1 and 1000mA 路g-1, the reversible capacity of the composites can reach 850mAh 路g-1N 815mAh 路g-1.The excellent electrochemical properties are derived from the hierarchical structure of the composite, that is, the graphene lamellar coated with SnO2 particles is covered with a layer of pyrolytic carbon layer. Based on the excellent electrochemical properties of SnO2 matrix composites prepared by spray drying, Sn matrix composites were prepared by H _ 2 reduction or NaBH4 reduction at high temperature to improve the first Coulomb efficiency of the composites. Increase battery voltage. Composites reduced by H _ 2 at high temperatures or by NaBH4 combined with H _ 2, because the first Coulomb efficiency of the material increased by only a few percentage points after tin particles were removed from the surface of graphene and melted and agglomerated into micron tin balls, However, after 20 cycles, the material has no capacity. Only after carbon treatment, the tin ball particles in the material are nano-sized and have a reversible capacity of 350 mAh 路g-1 after 100 cycles, but the cyclic stability of the material is still poor. During the whole cycle of charge and discharge, the capacity of the material has been in the state of decay, which shows that it is not feasible to reduce and prepare Sn based material from SnO2 base material by spray drying method.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TM912.9


本文編號(hào)：1636155