發(fā)布時間：2018-03-20 14:43

  本文選題：有機電極材料　切入點：鋰離子電池　出處：《電子科技大學(xué)》2017年博士論文　論文類型：學(xué)位論文

【摘要】：鋰離子電池廣泛應(yīng)用于社會生產(chǎn)生活的各個方面,傳統(tǒng)的無機鋰離子電池電極材料由于價格昂貴以及不可再生的過渡金屬的使用等弊端,并不能滿足現(xiàn)代社會對于構(gòu)建“清潔能源社會”的要求。而有機小分子電極材料具有綠色環(huán)保、價格低廉、分子結(jié)構(gòu)多樣化以及較高的理論比容量等特性而被廣泛關(guān)注。但目前該類材料仍然存在許多亟需解決的基礎(chǔ)性科學(xué)問題,主要包括其常規(guī)有機電解液中的溶解導(dǎo)致容量衰減較快、實際比容量較低和倍率性能較差,并且其電化學(xué)反應(yīng)機制仍需要進一步探究。本論文利用理論計算結(jié)合具體實驗,圍繞對苯二甲酸根(TP~(2-))有機小分子負極材料,通過對其物理化學(xué)性質(zhì)調(diào)控、材料改性、離子傳輸通道優(yōu)化以及新型電極材料體系的設(shè)計旨在解決上述問題。主要內(nèi)容和結(jié)果歸納如下:(1)通過簡單的酸堿反應(yīng)一步法制備了一系列基于有機對苯二甲酸鋰(Li_2TP)衍生物鋰鹽,并探討了不同取代基對電極材料的電化學(xué)行為產(chǎn)生的影響。研究表明該類有機共軛二羧酸鋰鹽均能夠可逆的儲鋰,其中對苯二甲酸鋰(Li_2TP)具有較高的理論比容量、明顯的充放電平臺以及可逆的儲鋰通道,是一類具有較大潛力的有機負極材料。對Li_2TP苯環(huán)上引入的取代基后,會對電極材料的分子結(jié)構(gòu)產(chǎn)生誘導(dǎo)效應(yīng)和共軛效應(yīng),從而調(diào)控材料的電化學(xué)平臺。另外,以2,5-二羥基對苯二甲酸(DHTPA)和對應(yīng)的二鋰鹽(Li_2DHTPA)為例,通過XRD、FT-IR等測試對該類材料的儲鋰機理進行了研究,結(jié)果表明有機羧酸DHTPA具有電化學(xué)儲鋰活性但循環(huán)性能較差,DHTPA首周放電過程經(jīng)歷了離子取代過程,其首周循環(huán)后產(chǎn)物為Li_2DHTPA;而化學(xué)法制備的Li_2DHPTA能夠可逆的儲鋰,且循環(huán)穩(wěn)定特性優(yōu)異。創(chuàng)新性的提出通過電化學(xué)取代和化學(xué)取代兩種不同的方式,得到同種有機電極材料的思路。(2)針對Li_2TP在常規(guī)有機電解液中的溶解性問題導(dǎo)致循環(huán)性能較差,通過對Li_2TP進行堿金屬陽離子取代制備另一種有機對苯二甲酸鈉(Na_2TP),研究了Na_2TP作為鋰離子電池負極材料并提供一種簡單的噴霧干燥改性研究方法。簡單的水結(jié)晶法制備的Na_2TP在電解液中的溶解度較低,因而循環(huán)性能與Li_2TP相比得到明顯的改善。針對有機小分子導(dǎo)電性差因而活性位點利用率較低,進一步設(shè)計了一種簡單的噴霧干燥的技術(shù)一步原位制備該有機Na_2TP與碳納米管復(fù)合材料(Na_2TP-SD-MCNTs),電化學(xué)測試表明:循環(huán)50周后,復(fù)合材料容量仍然保持在214 mAh g~(-1),與微米級別的Na_2TP以及未加入碳納米管的純材料相比,其循環(huán)可逆容量得到明顯的提升,倍率性能得到明顯改善。主要原因是:該方法制備的納米復(fù)合材料能夠有效縮短鋰離子在電極材料中的擴散路徑,MCNTs能夠提供良好的導(dǎo)電網(wǎng)絡(luò)并穩(wěn)定電極結(jié)構(gòu),而制備的復(fù)合材料在有機的電解液中的溶解速率能夠有效減緩。(3)考慮到有機電極材料的電化學(xué)性能與其鋰離子傳輸通道有關(guān),實驗首次對Li_2TP進行堿金屬陽離子取代,制備了具有空曠結(jié)構(gòu)的對苯二甲酸鉀(K_2TP),并對比研究了不同堿金屬對苯二甲酸鹽體系(Li、Na、K)的儲鋰特性。由于Li、Na具有較小的離子半徑,Li_2TP與Na_2TP形成較短的金屬-O鍵(1.96?/2.43?)容易造成離子堆垛擁擠現(xiàn)象,離子在電化學(xué)過程中的遷移比較困難。但K_2TP由于其K+半徑較大,從而使得TP~(2-)與K~+形成更加匹配的離子鍵,具有最低的范德華排斥力和非常穩(wěn)定的晶體結(jié)構(gòu)。通過理論計算和實驗表明,K_2TP作為鋰離子電池負極材料,在0.1 C的電流密度下,經(jīng)過100周循環(huán),可逆容量達到第二周容量的77%并且倍率特性非常優(yōu)異。結(jié)合三種有機對苯二甲酸鹽的晶體結(jié)構(gòu)可知,Li_2TP和Na_2TP為一維鋰離子擴散通道,而K_2TP具有空曠的二維離子傳輸通道,因而K_2TP表現(xiàn)出最優(yōu)異的儲鋰循環(huán)穩(wěn)定性和倍率性能。此外,為提高有機材料的實際比容量,實驗制備了K_2TP/石墨烯的納米復(fù)合材料,該材料在8 C電流密度下循環(huán)500周后,比容量仍然能夠保持在122 mAh g~(-1),表現(xiàn)出非常穩(wěn)定的大倍率循環(huán)性能。主要原因是:K_2TP活性物質(zhì)在電解液中十分穩(wěn)定,制備的納米級別的K_2TP能夠有效縮短鋰離子擴散路徑,而其與石墨烯形成的復(fù)合能夠構(gòu)建良好的導(dǎo)電網(wǎng)絡(luò)。(4)為拓展有機電極材料的應(yīng)用領(lǐng)域,本文首次開發(fā)了兩種有機小分子對位二羧酸鉀鹽:K_2TP及衍生物吡啶2,5-二羧酸鉀(K2PC),并研究其作為新型的有機鉀離子電池負極材料。K_2TP和K2PC具有十分合適的儲鉀平臺電位,其儲鉀機理為有機共軛二羧酸鉀鹽的共軛羰基的打開和恢復(fù)過程。K_2TP和K2PC作為鉀離子電池負極材料表現(xiàn)出優(yōu)異的循環(huán)穩(wěn)定性,其循環(huán)100周后可逆容量分別為181mAh g~(-1)和190 mAh g~(-1)。該類有機材料是制備“搖椅式”鉀離子電池理想負極材料。(5)另一方面,考慮到有機材料豐富的結(jié)構(gòu),本論文首次設(shè)計了一類新型有機小分子共軛氰基類化合物,以對苯二腈(DCB)和9,10-二氰基蒽(DCA)為例,研究了其可逆的儲能特性、電化學(xué)行為以及溶解性問題等。與DCB相比,DCA具有更優(yōu)異的電子導(dǎo)電率;其還原態(tài)DCA~-和DCA~(2-)的穩(wěn)定性優(yōu)于DCB。同時,DCB作為二次電池電極材料時,經(jīng)歷連續(xù)可逆的兩電子轉(zhuǎn)移過程。
[Abstract]:The lithium ion battery is widely used in social life and production, the traditional inorganic electrode materials for lithium ion batteries because of transition metal prices and non renewable use etc, and can not meet the modern society to build a "clean energy society". While organic small molecule electrode material with the green environmental protection, low price, molecular the structure of diversification and high theoretical capacity and other characteristics was widespread concern. But the materials still exist many basic scientific problems need to be resolved, including the conventional mechanical solution in dissolved solution leads to the capacity decay faster, lower than the actual capacity and poor rate capability, and the electrochemical reaction mechanism still needs to be this paper further explored. By theoretical calculation with the experiment, around the root of terephthalic acid (TP~ (2-)) of small organic molecules through the cathode material. A regulation on the physical and chemical properties, material modification, design of ion transmission channel optimization and new electrode material system to solve the above problems. The main contents and results are summarized as follows: (1) through one step method of simple acid-base reaction to synthesize a series of organic based on benzene two lithium formate (Li_2TP) derivatives and salts. To investigate the effect of different substituted groups on the electrochemical behavior of produced electrode materials. The results indicate that this kind of organic conjugated carboxylic acid lithium salt can two reversible lithium storage, including lithium terephthalate (Li_2TP) has high theoretical capacity, obvious charge discharge and the reversible lithium storage channel, is a kind of organic cathode materials with larger the potential of Li_2TP. By introducing substituents on the benzene ring, the molecular structure of the electrode materials will produce inductive effect and conjugated effect, thereby regulating the electrochemical platform. In addition to 2,5- Two hotp (DHTPA) and the corresponding two lithium salt (Li_2DHTPA) as an example, through the XRD, FT-IR and other tests were carried out to study on the mechanism of lithium storage in this kind of materials, the results showed that organic carboxylic acid DHTPA with electrochemical lithium storage activity but poor cycle performance, DHTPA first discharge process through ion substitution process, the first cycle after the product is Li_2DHTPA; and the chemical preparation of Li_2DHPTA can reversible lithium storage, and excellent cyclic stability. Proposed by electrochemical and chemical substitution to replace the two different ways, the same material obtained electromechanical ideas. (2) aiming at the problem of Li_2TP solubility in conventional organic electrolyte. Lead to poor cycle performance, preparation of another organic terephthalic acid sodium by alkali metal cations on the substitution of Li_2TP (Na_2TP), the effects of Na_2TP as lithium ion battery cathode material and provide a simple The spray drying method. The modified simple water crystal prepared by Na_2TP solubility in the electrolyte is low, so the cycle performance compared with Li_2TP significantly improved. For small organic molecules and poor conductivity of the active site of low utilization rate, further design a simple spray drying technique in situ the preparation of organic Na_2TP and carbon nanotube composite material (Na_2TP-SD-MCNTs), electrochemical tests show that after 50 cycles, the composite capacity remained at 214 mAh g~ (-1), and the micron level Na_2TP and without adding carbon nano tube materials pure meters compared to the cycle of reversible capacity improved obviously, rate performance improved obviously. The main reason is: the diffusion path method of nanocomposites can effectively shorten the lithium ion in the electrode material, the MCNTs can provide good and stable conductive network The electrode structure, and the dissolution rate of prepared composite materials in organic electrolyte can effectively slow down. (3) considering the electrochemical properties and organic electrode materials of lithium ion transmission channel, the experiment of Li_2TP for the first time the alkali metal cation substituted potassium terephthalic acid with open structure was prepared (K_2TP), and contrast effects of different alkali metal salts of terephthalic acid (Li, Na, K) of the lithium storage properties. Due to Li, Na has a smaller ionic radius, Li_2TP and Na_2TP formed -O bond metal short (1.96? /2.43?) can cause ion stacking crowding, migration in the electrochemical process of ion but difficult. K_2TP K+ because of its large radius, so that the TP~ (2-) ionic bond formation, and more K~+, Fan Dehua has the lowest repulsion and very stable crystal structure. Through theoretical calculation and experimental results show that the K_2TP as lithium ion Battery cathode material, current density at 0.1 C, after 100 cycles, the reversible capacity reached second and 77% week capacity rate performance is excellent. The crystal structure of three kinds of organic combination of terephthalic acid salt, Li_2TP and Na_2TP for one-dimensional lithium ion diffusion channel, and K_2TP has a two-dimensional ion transfer channels open, so K_2TP showed the most excellent lithium storage cycle stability and rate performance. In addition, in order to improve the actual organic material than the capacity of K_2TP/ graphene nanocomposites were prepared and the material circulation of 500 weeks under the current density of 8 C, specific capacity can still keep at 122 mAh g~ (-1). Show a big circulation performance is very stable. The main reason is: the K_2TP activity is very stable in the electrolyte, the prepared nano level K_2TP can effectively shorten the diffusion path of lithium ion, and its formation and graphene The composite can build good conductive network. (4) for the expansion of the application of organic electrode materials, this paper developed two kinds of small molecule organic carboxylic acid salts: two para K_2TP and 2,5- two derivatives of pyridine carboxylic acid potassium (K2PC), and studied as a new organic potassium ion battery cathode materials.K_2TP and K2PC with storage the platform is very suitable for the potassium potential, the storage mechanism of potassium for conjugated carbonyl organic conjugated carboxylic acid salts of the two open and recovery process of.K_2TP and K2PC as anode materials for lithium ion batteries exhibit excellent cycle stability. After 100 cycles the reversible capacity was 181mAh g~ (-1) and 190 mAh g~ (-1). Type of organic materials is the preparation of "rocking chair" potassium ion battery ideal cathode material (5). On the other hand, considering the structure of organic rich materials, this is the first time to design a new class of small molecule organic conjugated cyanide base. In two, the benzene nitrile (DCB) and 9,10- (DCA) two cyano anthracene as an example, to study the reversible storage characteristics, electrochemical behavior and solubility problems. Compared with DCB, DCA has more excellent electronic conductivity; the reduced DCA~- and DCA~ (2-) is more stable than DCB. at the same time, as the DCB two battery electrode materials, through two consecutive reversible electron transfer process.

【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：TM912

【參考文獻】

相關(guān)期刊論文 前3條

1 羅飛;褚賡;黃杰;孫洋;李泓;;鋰離子電池基礎(chǔ)科學(xué)問題(Ⅷ)——負極材料[J];儲能科學(xué)與技術(shù);2014年02期

2 馬璨;呂迎春;李泓;;鋰離子電池基礎(chǔ)科學(xué)問題(VII)——正極材料[J];儲能科學(xué)與技術(shù);2014年01期

3 王詩文;陶占良;陳軍;;鋰離子電池有機共軛羰基化合物電極材料研究進展[J];科學(xué)通報;2013年31期

相關(guān)博士學(xué)位論文 前2條

1 王詩文;A_4C_8H_2O_6(A=Li/Na)與聯(lián)苯醌類羰基化合物的制備及鋰/鈉離子電池性能研究[D];南開大學(xué);2014年

2 宋智平;鋰二次電池有機電極材料的研究[D];武漢大學(xué);2011年

相關(guān)碩士學(xué)位論文 前1條

1 陳言慧;色散力修正的密度泛函理論研究鋰離子電池有機電極材料[D];北京工業(yè)大學(xué);2015年

，

本文編號：1639549