本文選題：鋰-氧電池 + 正極材料��； 參考：《南京航空航天大學(xué)》2016年博士論文

【摘要】：可充電鋰-氧電池被認(rèn)為是取代常規(guī)鋰電池的最有希望的儲(chǔ)能介質(zhì)候選者,其超高的理論能量密度(3485 Wh kg-1),是目前商用鋰離子電池(387 Wh kg-1)的8-10倍。目前,由于碳材料或碳基材料具有大的比表面積和孔容,同時(shí)具有一定的氧還原(ORR)催化活性及放電產(chǎn)物過氧化鋰(Li2O2)的存儲(chǔ)空間,所以常被用來作為鋰-氧電池的正極材料。然而,碳材料對(duì)ORR和析氧催化(OER)的催化性能較差,基于碳材料的正極面臨了諸多嚴(yán)峻的挑戰(zhàn),限制了鋰-氧電池性能的提升。因此,基于碳材料的優(yōu)點(diǎn),我們?cè)O(shè)想通過設(shè)計(jì)具有合理的電極結(jié)構(gòu),并結(jié)合高效的雙功能催化劑,從而大幅提升鋰-氧電池的電化學(xué)性能。本論文嘗試將廉價(jià)、高催化活性的尖晶石型氧化物(Co3O4,NiCo2O4)與多種不同結(jié)構(gòu)的碳材料相結(jié)合,并通過對(duì)電極結(jié)構(gòu)進(jìn)行合理設(shè)計(jì)、調(diào)控,構(gòu)筑了四種碳基正極,研究了電極材料結(jié)構(gòu)、形貌與電催化性能,及作為鋰-氧電池正極的電化學(xué)性能之間的關(guān)系。論文的主要內(nèi)容介紹如下:1、通過溶劑蒸發(fā)誘導(dǎo)自組裝法,經(jīng)800℃氮?dú)饨Y(jié)合300℃空氣兩步熱處理,制備得到Co3O4納米顆粒均勻負(fù)載在氮摻雜有序介孔碳上的復(fù)合材料(Hollow Co3O4/NOMC),其比表面積大(~650 m2 g-1),介孔有序性好,碳載體石墨化程度高,空心結(jié)構(gòu)的Co3O4納米顆粒結(jié)晶度良好。電化學(xué)測(cè)試表明,得益于材料自身特性和結(jié)構(gòu)設(shè)計(jì)上的優(yōu)勢(shì),Hollow Co3O4/NOMC的起始電位和半波電位分別為-0.15 V和-0.23 V,極限擴(kuò)散電流密度達(dá)到4.99 mA cm-2,顯示出良好的ORR催化活性,組裝成電池后測(cè)得其放電比容量為3472 mAh g-1。此外,通過旋涂法將其與碳紙集流體復(fù)合作為無粘結(jié)型一體式正極,電極的電子傳輸能力得到大幅提高,使其可承受大電流(1000 mA g-1)充放電;更多開放的孔洞,使其放電比容量提升至4190 mAh g-1;粘結(jié)劑的摒棄減少了副反應(yīng)的發(fā)生,提高了循環(huán)穩(wěn)定性,在200 mAg-1的電流密度下,1000 mAh g-1定容量充放電達(dá)72次。2、為提升催化劑的催化活性和利用率,加強(qiáng)碳載體的石墨化程度,通過靜電紡絲技術(shù),制備了負(fù)載有過渡金屬氧化物(Fe2O3,Co3O4,NiCo2O4)的氮摻雜碳納米纖維(NCF)膜。其中,20 nm左右的氧化物顆粒均勻負(fù)載在直徑約為250 nm的碳納米纖維表面,氮元素主要以吡啶型氮的形式摻雜,摻雜量較大(7%)。電化學(xué)性能的測(cè)試表明,三種復(fù)合材料中,NiCo2O4@NCF具有最優(yōu)的ORR與OER催化性能,得益于NiCo2O4更高的電催化活性。作為鋰-氧電池正極材料,基于優(yōu)良的電催化性能,NiCo2O4@NCF正極極化度最小,放電比容量最大(5304 mAh g-1)。通過對(duì)比傳統(tǒng)的壓片式導(dǎo)電炭黑正極和純的碳纖維薄膜正極,自支撐無粘結(jié)劑型NiCo2O4@NCF正極均表現(xiàn)出更優(yōu)異的性能,不僅放電容量更大,倍率性能好,循環(huán)壽命也顯著提升,可穩(wěn)定循環(huán)92次(電流密度:200 mAg-1,定容量1000 mAh g-1)。其優(yōu)異的性能主要來源于NiCo2O4@NCF的高催化活性,提供了電子高速傳輸網(wǎng)絡(luò)的碳纖維薄膜,且無粘結(jié)劑引起的副反應(yīng),同時(shí)豐富的分級(jí)孔道利于電解液的浸潤(rùn)、氧氣的擴(kuò)散、及Li2O2的大量?jī)?chǔ)存。3、為近一步提升碳載體的導(dǎo)電性,同時(shí)更大限度的發(fā)揮NiCo2O4的高效ORR和OER催化活性,通過溶劑熱合成法,將NiCo2O4納米顆粒均勻負(fù)載在氮摻雜石墨烯表面(NCO@N-rGO),冷凍干燥后形成三維多孔結(jié)構(gòu)。結(jié)構(gòu)表征顯示約為7nm的NiCo2O4均勻錨定在石墨烯表面,負(fù)載量達(dá)72.4%。與機(jī)械混合的NiCo2O4/石墨烯相比,原位合成的NCO@N-rGO復(fù)合材料作為鋰-氧電池正極材料,表現(xiàn)出更優(yōu)異的電化學(xué)性能。三維多孔的石墨烯不僅可以作為導(dǎo)電網(wǎng)絡(luò),而且提供了大量開放的孔道,便于儲(chǔ)存大量Li2O2,同時(shí)高負(fù)載的NiCo2O4納米顆粒提供了豐富的催化活性位點(diǎn)。因此,NCO@N-rGO放電比容量高達(dá)6716 mAh g-1,能在200 mA g-1的電流密度下,定容量1000 mAh g-1,可穩(wěn)定循環(huán)112次。4、在獲得高導(dǎo)電性碳載體、高催化活性的催化劑的基礎(chǔ)上,為解決碳材料引起的諸多副反應(yīng),利用溶劑熱法,在碳布(CT)上原位生長(zhǎng)針狀NiCo2O4納米線陣列(NCONWAs)。隨著溶劑熱反應(yīng)時(shí)間的增加,NiCo2O4納米線的直徑和長(zhǎng)度顯著增加,16h溶劑熱反應(yīng)得到的NCONWAs/CT復(fù)合材料中,每一根垂直陣列生長(zhǎng)的NiCo2O4納米線均由顆粒尺寸(7~10 nm)的NiCo2O4顆粒組成,形成的介孔納米線比表面積達(dá)90 m2 g-1,孔徑更高達(dá)11 nm。NCONWAs/CT復(fù)合材料相比于常規(guī)需要粘結(jié)劑和導(dǎo)電劑的正極材料,4221 mAh g-1的放電比容量高于常規(guī)電極的3409 mAh g-1。同時(shí),NiCo2O4納米線陣列緊密包裹住碳纖維,有效地防止副反應(yīng)產(chǎn)物L(fēng)i2CO3的形成,加上其分級(jí)的多孔結(jié)構(gòu)和高的催化活性,NCONWAs/CT復(fù)合材料可穩(wěn)定循環(huán)200次(電流密度:200 mA g-1),遠(yuǎn)超過常規(guī)電極材料,并可在大電流密度(1000 mA g-1)下,實(shí)現(xiàn)穩(wěn)定充放電。最后,利用碳布基底的柔韌性,以NCONWAs/CT復(fù)合材料為正極,構(gòu)造了柔性的鋰-氧電池,可在彎曲過程中實(shí)現(xiàn)充放電,并具有優(yōu)異的倍率性能和循環(huán)穩(wěn)定性。
[Abstract]:Rechargeable lithium - oxygen battery is considered as the most promising candidate for energy storage medium to replace conventional lithium batteries. Its ultra high theoretical energy density (3485 Wh kg-1) is 8-10 times the current commercial lithium ion battery (387 Wh kg-1). At present, the carbon material or carbon based material has a large specific surface area and Kong Rong, and has a certain oxygen reduction (ORR ) the catalytic activity and the storage space of the lithium peroxide (Li2O2) of the discharge products are often used as positive materials for lithium oxygen batteries. However, the catalytic performance of carbon materials for ORR and oxygen evolution Catalysis (OER) is poor. The cathode based on carbon materials faces many severe challenges and limits the performance of lithium oxygen batteries. Therefore, carbon materials are based on carbon materials. In this paper, we try to combine the cheap, high catalytic active spinel oxide (Co3O4, NiCo2O4) with a variety of different structure carbon materials and through the electrode structure. Four kinds of carbon based positive poles were designed and regulated reasonably. The structure, morphology and electrocatalytic properties of the electrode materials were studied, and the relationship between the electrochemical properties of the positive electrode of the lithium oxygen battery. The main contents of the paper were as follows: 1, the self assembly method was induced by solvent evaporation, and the Co was treated by two steps by two steps of nitrogen combined with 300 centigrade air. 3O4 nanoparticles are uniformly loaded on nitrogen doped ordered mesoporous carbon (Hollow Co3O4/NOMC), with a large specific surface area (~650 M2 g-1), good mesoporous order, high degree of graphitization of carbon carriers and good crystallinity of Co3O4 nanoparticles in hollow structures. The electrochemical test chart is shown to benefit from the advantages of the material itself and the structural design advantages, Hol. The starting potential and the half wave potential of low Co3O4/NOMC are -0.15 V and -0.23 V respectively. The limit diffusion current density reaches 4.99 mA cm-2, showing a good ORR catalytic activity. After assembling the battery, the discharge specific capacity is 3472 mAh g-1.. The electrode is combined with the carbon paper collector as an unbonded integral positive pole by spin coating. The electronic transmission capacity is greatly improved, making it able to withstand large current (1000 mA g-1) charging and discharging; more open holes to increase the discharge ratio to 4190 mAh g-1; the abandonment of the binder reduces the occurrence of side reactions and improves the cycle stability. Under the current density of 200 mAg-1, 1000 mAh g-1 capacity is charged and discharged to 72 times.2, The catalytic activity and utilization of the catalyst were enhanced and the degree of graphitization of the carbon carrier was strengthened. By electrospinning, a nitrogen doped carbon nanofiber (NCF) membrane loaded with transition metal oxides (Fe2O3, Co3O4, NiCo2O4) was prepared. Among them, the oxide particles around 20 nm were uniformly loaded on the surface of carbon nanofibers with a diameter of about 250 nm. The elements are doped mainly in the form of pyridine type nitrogen, and the amount of doping is larger (7%). The electrochemical performance test shows that NiCo2O4@NCF has the best catalytic performance of ORR and OER in the three composites, and is benefited from the higher electrocatalytic activity of NiCo2O4. As a cathode material for lithium oxygen battery, the NiCo2O4@NCF positive polarity is the least, based on the excellent electrocatalytic properties. The maximum discharge specific capacity (5304 mAh g-1). By comparing the traditional compression conductive carbon black positive electrode and pure carbon fiber film positive pole, the self supporting NiCo2O4@NCF positive pole without adhesive type shows better performance, not only the discharge capacity is greater, the multiple performance is better, the cycle life is also significantly improved, and the stable cycle is 92 times (the current density: 200 mAg-1). It has a fixed capacity of 1000 mAh g-1). Its excellent performance mainly comes from the high catalytic activity of NiCo2O4@NCF, which provides the carbon fiber film of the electronic high-speed transmission network, and the side effects caused by the non binder. At the same time, the rich hierarchical channel is beneficial to the infiltration of the electrolyte, the diffusion of oxygen, and the large storage of.3 in the Li2O2, for the promotion of the carbon carrier in a close step. Electrical conductivity, at the same time, give full play to the high efficient ORR and OER catalytic activity of NiCo2O4. Through the solvent thermal synthesis, the NiCo2O4 nanoparticles are uniformly loaded on the surface of the nitrogen doped graphene (NCO@N-rGO) and freeze-drying to form a three-dimensional porous structure. The structural characterization shows that the NiCo2O4 uniform of about 7Nm is anchored on the surface of graphene with a load of 72.4%.. Compared with the mechanically mixed NiCo2O4/ graphene, the in-situ synthesized NCO@N-rGO composite exhibits excellent electrochemical performance as a cathode material for the lithium oxygen battery. The three-dimensional porous graphene can not only be used as a conductive network, but also provide a large number of open channels to facilitate the storage of a large number of Li2O2 and high load NiCo2O4 nanoscale. The particles provide a rich catalytic activity site. Therefore, the specific capacity of NCO@N-rGO discharge is up to 6716 mAh g-1, and can be fixed at a capacity of 1000 mAh g-1 at the current density of 200 mA g-1, and can circulate 112 times.4. On the basis of high conductivity carbon carrier and high catalytic activity catalyst, many side reactions caused by carbon materials are solved and solvent is used to use solvent. The needle like NiCo2O4 nanowire array (NCONWAs) was grown on the carbon cloth (CT) by thermal method. The diameter and length of the NiCo2O4 nanowires increased significantly with the increase of the solvent thermal reaction time. In the NCONWAs/CT composites obtained by the 16h solvothermal reaction, each vertical array of NiCo2O4 nanowires grew by the particle size (7~10 nm) NiCo2O4 particles. The mesoporous nanowires have a specific surface area of 90 M2 g-1, and the pore size is up to 11 nm.NCONWAs/CT, compared to the normal material requiring binder and conductive agent, the discharge specific capacity of 4221 mAh g-1 is higher than the 3409 mAh g-1. of the conventional electrode, and the NiCo2O4 nanowire array tightly encapsulated carbon fiber, effectively preventing the side reaction. The formation of the product Li2CO3, with its graded porous structure and high catalytic activity, can be stabilized by NCONWAs/CT composites for 200 times (current density: 200 mA g-1), far exceeding the conventional electrode materials, and can achieve stable charge and discharge at a high current density (1000 mA g-1). Finally, the flexibility of the carbon substrate is used as a NCONWAs/CT composite. For the positive electrode, a flexible lithium oxygen battery is constructed, which can realize charging and discharging in bending process, and has excellent rate performance and cycle stability.

【學(xué)位授予單位】：南京航空航天大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：TM911.41;TB332

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1 薛海榮;鋰—氧電池碳基正極材料的設(shè)計(jì)、制備及其性能研究[D];南京航空航天大學(xué);2016年

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本文編號(hào)：1851623