本文選題：鋰離子電池 + 硅基負(fù)極材料��； 參考：《陜西科技大學(xué)》2017年碩士論文

【摘要】：硅的理論比容量高達(dá)4200 mAh/g,有望成為新一代的高容量負(fù)極材料之一。但鋰離子在嵌鋰和脫鋰過程中,引起硅顆粒體積膨脹和電極結(jié)構(gòu)崩破,導(dǎo)致硅與集流體的導(dǎo)電性變?nèi)?影響電池的電化學(xué)性能。為了改善這一個問題,本文通過研究海藻酸鈉在不同硅基復(fù)合負(fù)極材料(硅負(fù)極材料、硅/石墨烯負(fù)極材料、硅/鐵負(fù)極材料)中的電化學(xué)性能,并分析負(fù)極材料與海藻酸鈉復(fù)合漿料的流變特性。試圖改善電極結(jié)構(gòu),探索出比容量高、電極循環(huán)穩(wěn)定好的鋰離子電池。本論文主要工作及結(jié)果如下:(1)制備了3種不同海藻酸鈉粘結(jié)劑含量的鋰離子電池硅負(fù)極漿料,并對其漿料進(jìn)行流變性和觸變性測試與比較,篩選出海藻酸鈉粘結(jié)劑合適含量為20%,該含量下負(fù)極漿料顆�？尚纬删鶆�,穩(wěn)定的分散結(jié)構(gòu)。測試了該體系電化學(xué)性能,結(jié)果表明,當(dāng)負(fù)極材料(納米硅)、導(dǎo)電劑、粘結(jié)劑質(zhì)量比是6:2:2時,首次放電比容量為2200 mAh/g,庫倫效率達(dá)到87%。但循環(huán)50圈后,放電比容量低于800 mAh/g。鋰離子電池在嵌鋰和脫鋰過程中,硅會發(fā)生體積膨脹,導(dǎo)致硅材料粉化、剝落、失去電接觸,因此容量衰減很快,循環(huán)穩(wěn)定性較差。(2)為了改善硅負(fù)極鋰離子電池的循環(huán)穩(wěn)定性,可通過改善硅顆粒與集流體之間的電接觸來實(shí)現(xiàn)。本文在硅負(fù)極中引入導(dǎo)電性能優(yōu)異的石墨烯材料,制得硅/石墨烯負(fù)極材料。測試了3種不同海藻酸鈉粘結(jié)劑含量的硅/石墨烯負(fù)極漿料的流變性和觸變性,選擇出最佳海藻酸鈉粘結(jié)劑含量仍為20%。在負(fù)極材料、導(dǎo)電劑、粘結(jié)劑質(zhì)量比是6:2:2的基礎(chǔ)上,測試了含量分別為10%、20%、30%的3種硅/石墨烯鋰離子電池的電化學(xué)性能。實(shí)驗(yàn)結(jié)果顯示,石墨烯含量減小,比容量增大,內(nèi)阻降低。10%含量的硅/石墨烯鋰離子電池在循環(huán)50圈后,放電比容量大于1800 mAh/g;循環(huán)100圈后,放電比容量在1650 mAh/g左右,因此適量的石墨烯有利于提高鋰離子的循環(huán)性。(3)為了提高硅基鋰離子電池的循環(huán)穩(wěn)定性,可通過制備多孔硅/金屬復(fù)合材料為硅體積的膨脹預(yù)留空間。本文通過酸化處理硅鐵合金制備了多微孔硅/鐵合金負(fù)極材料。測試了基于海藻酸鈉粘結(jié)劑的多微孔硅/鐵負(fù)極漿料的流變性和觸變性,確定了海藻酸鈉粘結(jié)劑合適含量為20%。當(dāng)負(fù)極材料(多微孔硅/鐵)、導(dǎo)電劑、粘結(jié)劑質(zhì)量比分別為6:2:2時,首次放電比容量高達(dá)2600 mAh/g,循環(huán)50圈后,充放電比容量大約為1250 mAh/g。比容量有所下降,但多孔的結(jié)構(gòu)有效的增強(qiáng)了循環(huán)性能的穩(wěn)定性。
[Abstract]:The theoretical specific capacity of silicon is as high as 4200 mAh/ g, which is expected to be one of the new generation of high capacity anode materials. However, during the process of lithium intercalation and delithium removal, the volume expansion of silicon particles and the breakdown of electrode structure lead to the weakening of the conductivity of silicon and collector, which affects the electrochemical performance of the battery. In order to improve this problem, the electrochemical properties of sodium alginate in different silicon based composite anode materials (silicon anode material, silicon / graphene negative electrode material, silicon / iron negative electrode material) were studied. The rheological properties of negative electrode material and sodium alginate composite slurry were analyzed. This paper attempts to improve the electrode structure and explore the lithium ion battery with high specific capacity and stable electrode cycle. The main work and results of this paper are as follows: (1) three kinds of sodium alginate binders were prepared, and the rheological properties and thixotropy of the slurry were measured and compared. The suitable content of sodium alginate binder is 20%, under which the particles of negative electrode slurry can form uniform and stable dispersion structure. The electrochemical properties of the system have been tested. The results show that when the mass ratio of nanocrystalline silicon, conductive agent and binder is 6:2:2, the first discharge specific capacity is 2200 mg / g, and the Coulomb efficiency is 87%. But after 50 cycles, the specific discharge capacity is less than 800 mg / g. In the process of lithium intercalation and delithium removal, the volume expansion of silicon will occur, which will cause the silicon material to be powdered, peeled off, and lose electrical contact. Therefore, the capacity of lithium ion battery decreases rapidly and the cycle stability is poor.) in order to improve the cycle stability of silicon anode lithium ion battery, This can be achieved by improving the electrical contact between silicon particles and collecting fluids. In this paper, silicon / graphene anode materials are prepared by introducing graphene materials with excellent conductivity into silicon anode. The rheology and thixotropy of three kinds of silicon / graphene negative paste with different content of sodium alginate binder were tested, and the optimum content of sodium alginate binder was still 20. On the basis of 6:2:2 mass ratio of negative electrode material, conductive agent and binder, the electrochemical properties of three kinds of silicon / graphene lithium-ion batteries with the content of 10% and 20% were tested. The experimental results show that the specific discharge capacity of silicon / graphene lithium-ion battery with the content of graphene decreases and the specific capacity increases, and the specific discharge capacity of the silicon / graphene lithium ion battery containing 10% lower internal resistance is greater than 1800 mg / g after 50 cycles, and the discharge specific capacity is about 1650 mAh/g after 100 cycles. In order to improve the cycle stability of silicon-based lithium-ion batteries, porous silicon / metal composites can be prepared to reserve space for silicon volume expansion. In this paper, multiporous silicon / ferroalloy anode materials were prepared by acidification treatment of ferrosilicon alloys. The rheological properties and thixotropy of multipore silicon / iron negative paste based on sodium alginate binder were tested. The suitable content of sodium alginate binder was determined to be 20%. When the mass ratio of multipore silicon / iron, conductive agent and binder is 6:2:2, the initial discharge specific capacity is up to 2600 mAh-g, and after 50 cycles, the charge / discharge capacity is about 1250 mAh/ g. The specific capacity decreased, but the porous structure effectively enhanced the stability of the cycle performance.
【學(xué)位授予單位】：陜西科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TB332;TM912

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本文編號：1964465