高容量電極材料的制備及其電化學(xué)性能研究
發(fā)布時(shí)間：2018-09-03 06:09
【摘要】：鋰離子電池和超級(jí)電容器是儲(chǔ)能的兩個(gè)重要方向,它們的電化學(xué)性能和能量密度決定著它們今后的道路。然而,目前的儲(chǔ)能電極材料一方面在具有高容量的同時(shí),它的電化學(xué)循環(huán)和倍率容量性能卻很差,需要進(jìn)行改性處理；另一方面電極材料的電化學(xué)性能和儲(chǔ)能容量和它的形貌有著密切的關(guān)系,實(shí)現(xiàn)電極材料的形貌最優(yōu)化制備對(duì)提升電極材料電化學(xué)性能和能量密度有著重要意義。 1.金屬氧化物的理論儲(chǔ)鋰容量比較高,是石墨的2-3倍,但是它的循環(huán)性能卻很差,需要進(jìn)行改性處理。可充電鋰離子二次電池的電化學(xué)性能主要和脫嵌鋰電極中Li的固相擴(kuò)散動(dòng)力問題以及材料表面特性相關(guān)。我們以油酸為碳源,發(fā)明了一種新穎的制備氧化鎳／碳復(fù)合納米片的技術(shù),這種以油酸為碳源,氧化鎳納米片為前驅(qū)體制備的NiO@C復(fù)合材料在50次循環(huán)后仍然展現(xiàn)出883mAh g-1的可逆容量,大大改善了NiO在充放電過程中的循環(huán)衰減問題和倍率問題,制備了一種高能量密度且循環(huán)性能優(yōu)異的鋰電負(fù)極材料,并在實(shí)驗(yàn)中比較了兩種不同碳包覆效果對(duì)材料的影響,對(duì)碳包覆表面改性處理方式的差異提供了重要依據(jù)。 2.我們研究了羥磷鐵鋰結(jié)構(gòu)LiFe(PO4)(OH)xF1-x分層微球的形貌-變量的電化學(xué)性能,包括殼結(jié)構(gòu)和中空結(jié)構(gòu)的創(chuàng)建。實(shí)驗(yàn)結(jié)果表明材料的電化學(xué)性能會(huì)隨著其形貌的改變而明顯變化。與其它顆粒相比,由納米棒和多孔微球組成的羥磷鐵鋰微球表現(xiàn)出優(yōu)異的電化學(xué)性能,這可以歸因于鋰離子擴(kuò)散途徑被縮短,材料比表面積增大。據(jù)我們所知,這是第一次就形貌對(duì)可很好定義結(jié)構(gòu)的羥磷鐵鋰電極材料的電化學(xué)活性的影響進(jìn)行系統(tǒng)的研究。這種易于實(shí)現(xiàn)的合成不同形貌羥磷鐵鋰材料的方法能為進(jìn)一步研究羥磷鐵鋰結(jié)構(gòu)LiFe(PO4)(OH)xF1-x形狀-變量材料的電化學(xué)性能研究提供一個(gè)有趣的平臺(tái)。 3.硅是自然界儲(chǔ)鋰容量最高的,但同時(shí)它的循環(huán)性能很差。我們從材料結(jié)構(gòu)設(shè)計(jì)入手,合成了一種柔性外殼包裹彈性內(nèi)核的核殼結(jié)構(gòu)的石墨烯包裹單顆粒硅納米結(jié)構(gòu)。通過對(duì)納米硅進(jìn)行化學(xué)修飾,實(shí)現(xiàn)納米硅與氧化石墨烯的自組裝,然后采用環(huán)保的維生素C(抗壞血酸)在微波輔助下還原氧化石墨烯,形成石墨烯包裹單顆粒納米硅復(fù)合材料。利用石墨烯的高比表面積、良好導(dǎo)電性和多孔結(jié)構(gòu)來抑制硅在脫嵌鋰過程中的體積膨脹,提高其電化學(xué)性能。通過對(duì)它的電化學(xué)性能研究和與純硅性能的對(duì)比驗(yàn)證了石墨烯的包覆能有效改善硅的循環(huán)性能和倍率性能,為制備高能量密度硅基材料提供了思路。 4.為了進(jìn)一步驗(yàn)證材料的顆粒大小和形貌對(duì)儲(chǔ)能材料電化學(xué)性能的影響,我們利用簡(jiǎn)單的靜電紡絲后空氣退火的方法制備出一維(1D)多孔ZnCo2O4納米管(PNTs)并首次應(yīng)用于超級(jí)電容器(SCs),并與ZnCo2O4納米顆粒的超電容性能做了系統(tǒng)的對(duì)比研究,實(shí)驗(yàn)證明這種一維多孔ZnCo2O4納米管的比容量、循環(huán)性能以及倍率性能等明顯優(yōu)于ZnCo2O4納米顆粒。我們的一系列實(shí)驗(yàn)證明通過改變材料的形貌確實(shí)可以實(shí)現(xiàn)優(yōu)化電化學(xué)性能的目的。
[Abstract]:Lithium-ion batteries and supercapacitors are two important directions of energy storage, and their electrochemical properties and energy density determine their future. However, the current energy storage electrode materials have poor electrochemical cycling and rate capacity performance while they have high capacity, so they need to be modified. The electrochemical properties and energy storage capacity of electrode materials are closely related to their morphologies. It is important to optimize the morphology of electrode materials for improving the electrochemical properties and energy density of electrode materials.
1. The theoretical lithium storage capacity of metal oxides is 2-3 times higher than that of graphite, but its cycling performance is very poor and needs modification. The electrochemical performance of rechargeable lithium-ion secondary batteries is mainly related to the solid-phase diffusion dynamics of Li in the de-intercalated lithium electrode and the surface characteristics of materials. A novel technique for preparing nickel oxide/carbon composite nanosheets was developed. The NiO@C composite prepared with oleic acid as carbon source and nickel oxide nanosheet as precursor still exhibited 883 mAh g-1 reversible capacity after 50 cycles. The cyclic attenuation and rate of NiO during charge-discharge process were greatly improved and a high energy NiO@C composite was prepared. The lithium anode materials with high density and excellent cycling performance were compared in the experiment. The influence of two different carbon coating effects on the materials was also compared.
2. The morphology-variable electrochemical properties of LiFe (PO4) (OH) xF1-x layered microspheres were investigated, including the creation of shell and hollow structures. The experimental results show that the electrochemical properties of the microspheres vary significantly with the morphology of the microspheres. Compared with other particles, lithium hydroxyphosphate consisting of nanorods and porous microspheres is slight. The excellent electrochemical properties of the spheres can be attributed to the shortening of the lithium ion diffusion pathway and the increase of the specific surface area of the materials. The method of lithium materials can provide an interesting platform for further study of the electrochemical properties of LiFe(PO4)(OH)xF1-x shape-variable materials.
3. Silicon has the highest lithium storage capacity in nature, but its cycling performance is very poor. Starting from the material structure design, we synthesized a graphene-encapsulated single-particle silicon nanostructure with flexible shell and elastic core. The self-assembly of nano-silicon and graphene oxide was realized by chemical modification of nano-silicon. Graphene-coated single-particle silicon nanocomposites were prepared by microwave-assisted reduction of graphene oxide with environmentally friendly vitamin C (ascorbic acid). High specific surface area, good conductivity and porous structure of graphene were used to restrain the volume expansion of silicon in the process of lithium deintercalation and improve its electrochemical properties. The comparison between graphene and pure silicon shows that graphene coating can effectively improve the cycling performance and ratio performance of silicon, which provides a new idea for preparing high energy density silicon-based materials.
4. In order to further verify the effect of particle size and morphology on the electrochemical properties of energy storage materials, we fabricated one-dimensional (1D) porous ZnCo2O4 nanotubes (PNTs) by simple electrospinning and air annealing method and applied them to supercapacitors (SCs) for the first time. The supercapacitor properties of the materials were systematically compared with those of ZnCo2O4 nanoparticles. The experimental results show that the specific capacity, cycling performance and rate performance of the one-dimensional porous ZnCo2O4 nanotubes are superior to those of ZnCo2O4 nanoparticles.
【學(xué)位授予單位】：湖南大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TM912
本文編號(hào)：2219094
[Abstract]:Lithium-ion batteries and supercapacitors are two important directions of energy storage, and their electrochemical properties and energy density determine their future. However, the current energy storage electrode materials have poor electrochemical cycling and rate capacity performance while they have high capacity, so they need to be modified. The electrochemical properties and energy storage capacity of electrode materials are closely related to their morphologies. It is important to optimize the morphology of electrode materials for improving the electrochemical properties and energy density of electrode materials.
1. The theoretical lithium storage capacity of metal oxides is 2-3 times higher than that of graphite, but its cycling performance is very poor and needs modification. The electrochemical performance of rechargeable lithium-ion secondary batteries is mainly related to the solid-phase diffusion dynamics of Li in the de-intercalated lithium electrode and the surface characteristics of materials. A novel technique for preparing nickel oxide/carbon composite nanosheets was developed. The NiO@C composite prepared with oleic acid as carbon source and nickel oxide nanosheet as precursor still exhibited 883 mAh g-1 reversible capacity after 50 cycles. The cyclic attenuation and rate of NiO during charge-discharge process were greatly improved and a high energy NiO@C composite was prepared. The lithium anode materials with high density and excellent cycling performance were compared in the experiment. The influence of two different carbon coating effects on the materials was also compared.
2. The morphology-variable electrochemical properties of LiFe (PO4) (OH) xF1-x layered microspheres were investigated, including the creation of shell and hollow structures. The experimental results show that the electrochemical properties of the microspheres vary significantly with the morphology of the microspheres. Compared with other particles, lithium hydroxyphosphate consisting of nanorods and porous microspheres is slight. The excellent electrochemical properties of the spheres can be attributed to the shortening of the lithium ion diffusion pathway and the increase of the specific surface area of the materials. The method of lithium materials can provide an interesting platform for further study of the electrochemical properties of LiFe(PO4)(OH)xF1-x shape-variable materials.
3. Silicon has the highest lithium storage capacity in nature, but its cycling performance is very poor. Starting from the material structure design, we synthesized a graphene-encapsulated single-particle silicon nanostructure with flexible shell and elastic core. The self-assembly of nano-silicon and graphene oxide was realized by chemical modification of nano-silicon. Graphene-coated single-particle silicon nanocomposites were prepared by microwave-assisted reduction of graphene oxide with environmentally friendly vitamin C (ascorbic acid). High specific surface area, good conductivity and porous structure of graphene were used to restrain the volume expansion of silicon in the process of lithium deintercalation and improve its electrochemical properties. The comparison between graphene and pure silicon shows that graphene coating can effectively improve the cycling performance and ratio performance of silicon, which provides a new idea for preparing high energy density silicon-based materials.
4. In order to further verify the effect of particle size and morphology on the electrochemical properties of energy storage materials, we fabricated one-dimensional (1D) porous ZnCo2O4 nanotubes (PNTs) by simple electrospinning and air annealing method and applied them to supercapacitors (SCs) for the first time. The supercapacitor properties of the materials were systematically compared with those of ZnCo2O4 nanoparticles. The experimental results show that the specific capacity, cycling performance and rate performance of the one-dimensional porous ZnCo2O4 nanotubes are superior to those of ZnCo2O4 nanoparticles.
【學(xué)位授予單位】：湖南大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TM912
【參考文獻(xiàn)】
相關(guān)期刊論文 前3條
1 徐仲榆,鄭洪河;鋰離子蓄電池碳負(fù)極/電解液的相容性研究進(jìn)展Ⅱ電解液組成與碳負(fù)極/電解液的相容性[J];電源技術(shù);2000年05期
2 賴瓊鈺,盧集政,鄒宏如;搖椅鋰離子二次電池及其嵌入式電極材料[J];化學(xué)研究與應(yīng)用;1998年01期
3 杜霞;薛衛(wèi)東;趙睿;陳野川;;石墨烯/硅負(fù)極材料的制備及其電化學(xué)性能的研究[J];化工科技;2013年05期
，本文編號(hào)：2219094
本文鏈接：http://sikaile.net/kejilunwen/dianlilw/2219094.html
最近更新
教材專著
