【摘要】：在對高比容量能源需求強烈的當(dāng)下,硅基材料成為了鋰離子電池負極材料的研究寵兒。針對硅負極材料導(dǎo)電性差,體積效應(yīng)大,SEI膜不穩(wěn)定等問題,本文結(jié)合微量摻雜、納米化、硅碳復(fù)合化等改性方法,成功制備了多種比容量高、循環(huán)性能好、首次庫倫效率高的硅/碳復(fù)合鋰電負極材料。一方面,將應(yīng)用于太陽能電池的磷摻雜n型硅作為負極材料,然后進行碳包覆,制備了n-Si/C復(fù)合材料,并對其制備工藝進行了優(yōu)化,電化學(xué)性能作了分析;另一方面,采用不同的硅源,利用石墨烯進行復(fù)合,制備了三種硅/石墨烯復(fù)合材料,并通過電化學(xué)工作站、充放電測試等作了分析表征。此外,對亞微米硅/GNS的內(nèi)在反應(yīng)動力學(xué)還作了初步探討。1、減小顆粒尺寸能夠提高硅的循環(huán)穩(wěn)定性,但改善程度有限;微量P(或B)摻雜不影響硅的結(jié)構(gòu),卻能顯著改善硅的導(dǎo)電性以及循環(huán)性能;n型硅以及亞微米硅是更為理想的硅電極材料。2、采用高溫固相法制備了性能優(yōu)異的n-Si/C復(fù)合材料,其30次后的放電容量為1101.4mAhg-1,首次庫倫效率高達85.6%。對該材料制備工藝及電極制作條件進行了研究,結(jié)果發(fā)現(xiàn):最佳燒結(jié)工藝為600℃/1h,最佳碳源為葡萄糖,最佳n型硅、碳比為1:1;添加石墨后,復(fù)合材料放電比容量增加,循環(huán)穩(wěn)定性大大提高,首次庫倫效率提高至81.1%;二次包覆后,復(fù)合材料循環(huán)可逆性與首次庫倫效率都得到提升,其30次后放電容量為1054.3mAhg-1;在電極片制作中,集流體選用銅箔效果更好,極片干燥溫度使用80℃最佳,極片熱處理也有利于電極性能提升。3、通過原位復(fù)合及直接機械混合的方式制備了循環(huán)性能好、比容量高、導(dǎo)電性好的硅/石墨烯(MS@Si/GNS,nano@Si/GNS,p-Si/GNS)復(fù)合負極材料。重點對MS@Si/GNS進行了工藝參數(shù)的研究,經(jīng)各種測試手段發(fā)現(xiàn):原位復(fù)合制得SG1具有更高的首次容量,庫倫效率以及導(dǎo)電性;隨石墨烯含量的增加,MS@Si/GNS首次放電容量逐漸降低,循環(huán)性能依次提高,阻抗值逐漸減小;CNT的加入以及極片熱處理都有助于MS@Si/GNS循環(huán)性能的改善和導(dǎo)電性的提高。4、通過SSCV研究,EIS分析及鋰離子擴散系數(shù)計算發(fā)現(xiàn),MS@Si/GNS表現(xiàn)出了優(yōu)異的循環(huán)可逆性及高的鋰離子遷移率,DLi可達2.9×10-12 cm2s-1,比純亞微米硅高出一個數(shù)量級,不同次數(shù)的各R值變化較小,電極結(jié)構(gòu)穩(wěn)定性良好。
[Abstract]:At present, silicon-based materials have become the favorite of lithium ion battery anode materials in high specific capacity energy demand. Aiming at the problems of poor electrical conductivity and large volume effect of silicon negative electrode materials and the instability of SEI film, this paper has successfully prepared various kinds of high specific capacity and good cycling performance by combining the modification methods of micro-doping, nanocrystalline and silicon-carbon composite. The first high Coulomb efficiency silicon / carbon composite lithium anode material. On the one hand, phosphorus-doped n-type silicon, which is used in solar cells, is used as negative electrode material, then carbon coating is carried out to prepare n-Si/C composite, and its preparation process is optimized and electrochemical performance is analyzed. Three kinds of silicon / graphene composites were prepared by using different silicon sources and graphene, and were characterized by electrochemical workstation and charge-discharge test. In addition, the intrinsic reaction kinetics of sub-micron silicon / GNS is also discussed. The decrease of particle size can improve the cycling stability of silicon, but the improvement is limited, and the microamount of P (or B) doping does not affect the structure of silicon. However, the electrical conductivity and cycling properties of silicon can be significantly improved. The n-type silicon and sub-micron silicon are more ideal silicon electrode materials. The n-Si/C composites with excellent properties have been prepared by high temperature solid state method. The discharge capacity is 1101.4 mAhg-1 after 30 times, and the first Coulomb efficiency is 85.6%. The results show that the optimum sintering process is 600 鈩，

本文編號：2227035