【摘要】：近年來(lái),超級(jí)電容器作為一種具有較高的能量密度和較長(zhǎng)循環(huán)使用壽命的新型電化學(xué)能量轉(zhuǎn)換和儲(chǔ)能設(shè)備被廣泛關(guān)注。超級(jí)電容器由電解質(zhì)、隔膜以及兩個(gè)電極組成。電極材料是超級(jí)電容器中最重要的組成部分。一般來(lái)說(shuō),電極材料的形貌、結(jié)構(gòu)及電化學(xué)性能在超級(jí)電容器的研究中起著關(guān)鍵作用。尖晶石鈦酸鋰(Li_4Ti_5O_(12))電極材料因其具有零應(yīng)變性、良好的可逆性、優(yōu)異的循環(huán)性能、結(jié)構(gòu)穩(wěn)定性好、高安全性能、價(jià)格低廉、環(huán)境友好等優(yōu)點(diǎn)被作為超級(jí)電容器電極材料,具有良好的開發(fā)應(yīng)用前景。然而,Li_4Ti_5O_(12)本體的電導(dǎo)率十分低,只有10~(-1)3Scm~(-1)-,嚴(yán)重的阻礙了它的發(fā)展與應(yīng)用。離子摻雜、電極材料的納米化、表面修飾是三種提高Li_4Ti_5O_(12)的電導(dǎo)率最有效的方法。本文以提高Li_4Ti_5O_(12)電極材料的導(dǎo)電性,優(yōu)化Li_4Ti_5O_(12)電極材料的電化學(xué)性能為目標(biāo),制備了具有納米管陣列結(jié)構(gòu)的鈦酸鋰(Li_4Ti_5O_(12)NTA)電極材料,然后通過(guò)離子摻雜、石墨烯(RGO)、碳包覆、氮化鈦(TiN)表面修飾等手段對(duì)Li_4Ti_5O_(12)NTA進(jìn)行改性,制備了氮化鈦-鈦酸鋰納米管陣列(TiN-Li_4Ti_5O_(12)NTA)、石墨烯-碳包覆鈦酸鋰(RGO/C-Li_4Ti_5O_(12) NTA)、氮化鈦-鎂摻雜鈦酸鋰電極材料(TiN-Li_(4-x)Mg_xTi_5O_(12) NTA)三種電極材料。研究了以上電極材料的形貌、結(jié)構(gòu)及其電化學(xué)性能。此外,還研究了三種電極材料在超級(jí)電容器中的應(yīng)用。本論文的研究工作主要包括以下幾個(gè)方面。(1)TiN-Li_4Ti_5O_(12)NTA電極材料的制備及其電化學(xué)性能的研究。TiN-Li_4Ti_5O_(12)NTA電極材料通過(guò)鋰化、高溫煅燒、氮化方式合成。通過(guò)陽(yáng)極氧化的方法在Ti片表面形成Ti02納米管陣列(TiO2 NTA)。然后TiO2 NTA與LiOH發(fā)生鋰化反應(yīng),經(jīng)過(guò)高溫煅燒形成Li_4Ti_5O_(12)NTA。在Li_4Ti_5O_(12)NTA表面上包覆一層Ti02溶膠,在700℃下氮化1 h,形成TiN-Li_4Ti_5O_(12)NTA。掃描結(jié)果顯示,TiN納米顆粒包覆在Li_4Ti_5O_(12)NTA的表面,使形成的TiN-Li_4Ti_5O_(12)NTA的表面變得更為粗糙。TiN-Li_4Ti_5O_(12) NTA與 N-Li_4Ti_5O_(12)NTA 的電導(dǎo)率分別為 39.06 S cm~(-1) 和 14.01 S cm~(-1),表明 TiN-Li_4Ti_5O_(12) NTA具有較高的電導(dǎo)性。在0.5M的Li2S04電解質(zhì)溶液中,在-0.4～0.8V的電勢(shì)窗口下進(jìn)行電化學(xué)性能測(cè)試。當(dāng)電流密度為O.5Ag~(-1)時(shí),TiN-Li_4Ti_5O_(12)NTA電極材料的比電容為143.83 F g~(-1),在3 Ag~(-1)的電流密度下進(jìn)行1000次恒電流充放電后,比電容保持率為82.41%。TiN-Li_4Ti_5O_(12) NTA電極材料提供較大的比表面積,能夠有效地提高TiN-Li_4Ti_5O_(12)NTA電極材料的電容性能�；赥iN-Li_4Ti_5O_(12)NTA電極材料和聚乙烯醇-硫酸鋰(PVA-Li2SO4)凝膠電解質(zhì)制備的全固態(tài)對(duì)稱超級(jí)電容器,其電壓為2.4V。當(dāng)電流密度為0.5Ag~(-1)時(shí),TiN-Li_4Ti_5O_(12) NTA超級(jí)電容器的比能量為32.36 Wh kg~(-1)。體積為10 mm×22 mm×0.5 mm的器件可以點(diǎn)亮工作電壓為2V的LED燈,說(shuō)明TiN-Li_4Ti_5O_(12) NTA電極材料可以作為超級(jí)電容器材料。(2)RGO/C-Li_4Ti_5O_(12)NTA電極材料的制備及其電化學(xué)性能的研究本章主要以分散有RGO的PVA為碳源,在600℃碳化3h,合成了 C-Li_4Ti_5O_(12)/RGO NTA電極材料。利用RGO的高導(dǎo)電性來(lái)提高Li_4Ti_5O_(12) NTA的電導(dǎo)性,以提升其電容性能。掃描結(jié)果顯示,含有石墨烯片的碳層均勻的分布在Li_4Ti_5O_(12)NTA的表面。在0.5 M的Li2SO4中,-0.6～0.6V的電勢(shì)窗下,電流密度為0.5Ag~(-1)時(shí),C-Li_4Ti_5O_(12)/RGONTA電極材料的比電容為210.76 F g~(-1)。在3 A g~(-1)的電流密度下進(jìn)行1000個(gè)恒電流充放電后,C-Li_4Ti_5O_(12)/RGONTA的比電容保持率為89.99%,說(shuō)明RGO包覆在的表面Li_4Ti_5O_(12)NTA使它的電化學(xué)性能有了明顯的提高。RGO/C-Li_4Ti5012 NTA電極材料和PVA-Li2S04凝膠電解質(zhì)制備成全固態(tài)對(duì)稱超級(jí)電容器儲(chǔ)能器件,其測(cè)試電壓為2.4V。電流密度從0.5Ag~(-1)增加到10Ag~(-1),功率密度從0.6 kW kg~(-1)升高到12 kW kg~(-1),能量密度從39.98 Wh kg~(-1)降低到12.36 Wh kg~(-1),體積為10 mm × 20 mm× 0.5 mm的器件可以點(diǎn)亮工作電壓為2 V的LED燈,說(shuō)明RGO/C-Li_4Ti_5O_(12) NTA電極材料可以作為有效的超級(jí)電容器材料。(3)TiN-Li_(4-x)Mg_xTi_5O_(12)NTA電極材料的制備及其電化學(xué)性能的研究本章采用以硝酸鎂(Mg(NO_3)_2)為鎂源對(duì)Li_4Ti_5O_(12) NTA進(jìn)行Mg2+摻雜,合成了Li_(4-x)Mg_xTi_5O_(12) NTA,然后將TiO2溶膠包覆在Li_(4-x)Mg_xTi_5O_(12) NTA表面,在700℃下氮化1h,形成TiN-Li_(4-x)Mg_xTi_5O_(12)NTA。掃描結(jié)果顯示Mg2+摻雜后,Li_4Ti_5O_(12)NTA的形貌沒有發(fā)生明顯的改變,仍呈納米管陣列結(jié)構(gòu)。氮化后Li_(4-x)Mg_xTi_5O_(12)NTA表面覆蓋了一層細(xì)小的顆粒。EDS檢測(cè)結(jié)果顯示,TiN-Li_(4-x)Mg_xTi_5O_(12)NTA電極材料的EDS譜圖中檢測(cè)到了 Ti、O、Mg以及N。在0.5 M的Li2S04為電解質(zhì)溶液中,-0.4～0.8 V的電勢(shì)窗下,進(jìn)行電化學(xué)恒電流充放電測(cè)試。當(dāng)電流密度為0.5 A g~(-1)時(shí),TiN-Li_(4-x)Mg_xTi_5O_(12) NTA電極材料的比電容為224.58 F g~(-1)。在3 A~(-1)的電流密度下進(jìn)行1000次循環(huán)充放電后,TiN-Li_(4-x)Mg_xTi_5O_(12) NTA的電容保持率為89.53%,說(shuō)明Mg2+摻雜和TiN有效地改善了電極材料的電化學(xué)性能�；赥iN-Li_(4-x)Mg_xTi_5O_(12)NTA電極材料和聚乙烯醇-硫酸鋰(PVA-Li2SO4)凝膠電解質(zhì)制備的全固態(tài)對(duì)稱超級(jí)電容器,其測(cè)試電壓窗口為2.4 V。當(dāng)電流密度為0.5 A g~(-1)時(shí),TiN-Li_(4-x)Mg_xTi_5O_(12) NTA 電容器的比能量 42.61 Wh kg~(-1)。體積為 30 mm× 10 mm×0.5 mm的器件可以點(diǎn)亮工作電壓為2 V的LED燈,說(shuō)明TiN-Li_(4-x)Mg_xTi_5O_(12)NTA電極材料表現(xiàn)出優(yōu)異的儲(chǔ)能性能。
[Abstract]:In recent years, as a new type of electrochemical energy conversion and storage equipment with high energy density and long cycle life, supercapacitor is widely concerned. It consists of electrolyte, diaphragm and two electrodes. Electrode material is the most important part of supercapacitor. Spinel lithium titanate (Li_4Ti_5O_ (12)) electrode materials have been used as electrode materials for supercapacitors because of their zero strain, good reversibility, excellent cycling performance, good structural stability, high safety performance, low cost and environmental friendliness. However, the conductivity of Li_4Ti_5O_ (12) bulk is very low, only 10-1_ 3Scm_ (1) -, which seriously hinders its development and application. Ion doping, nanocrystallization of electrode materials and surface modification are the three most effective methods to improve the conductivity of Li_4Ti_5O_ (12). In this paper, the Li_4Ti_5O_ (12) electrode materials are studied. To optimize the electrochemical performance of Li_4Ti_5O_ (12) electrode materials, lithium titanate (Li_4Ti_5O_ (12) NTA) electrode materials with nanotube arrays were prepared. Then Li_4Ti_5O_ (12) NTA was modified by ion doping, graphene (RGO), carbon coating and surface modification of titanium nitride (TiN). Nanotube arrays (TiN-Li_4Ti_5O_ (12) NTA), graphene-carbon coated lithium titanate (RGO/C-Li_4Ti_5O_ (12) NTA), titanium nitride-magnesium doped lithium titanate electrode materials (TiN-Li_ (4-x) Mg_xTi_5O_ (12) NTA) were used as electrode materials. The morphology, structure and electrochemical properties of the above electrode materials were studied. The research work of this paper mainly includes the following aspects: (1) Preparation of TiN-Li_4Ti_5O_ (12) NTA electrode material and its electrochemical properties. TiN-Li_4Ti_5O_ (12) NTA electrode material is synthesized by lithium, high temperature calcination and nitridation. Ti02 nanotube array (TiO2) is formed on the surface of Ti sheet by anodic oxidation method. TiN-Li_4Ti_5O_ (12) NTA was prepared by lithium reaction between titanium dioxide NTA and LiOH. TiN-Li_4Ti_5O_ (12) NTA was coated on the surface of Li_4Ti_5O_ (12) NTA and nitrided at 700 C for 1 h to form TiN-Li_4Ti_5O_ (12) NTA. Scanning results showed that TiN nanoparticles were coated on the surface of Li_4Ti_5O_ (12) NTA and formed TiN-Li_4Ti_5O_ (12) NTA. The conductivities of TiN-Li_4Ti_5O_ (12) NTA and N-Li_4Ti_5O_ (12) NTA were 39.06 S cm ~(-1) and 14.01 S cm ~(-1), respectively, indicating that TiN-Li_4Ti_5O_ (12) NTA had higher conductivity. The electrochemical properties of TiN-Li_4Ti_5O_ (12) NTA were tested in Li2S04 electrolyte solution of 0.5 M at a potential window of - 0.4 to 0.8 V. (1) The specific capacitance of TiN-Li_4Ti_5O_ (12) NTA electrode material is 143.83 F g~(-1), and the specific capacitance of TiN-Li_4Ti_5O_ (12) NTA electrode material is 82.41% after 1000 times of constant current charging and discharging at the current density of 3Ag~(-1). TiN-Li_4Ti_5O_ (12) NTA electrode material provides a large specific surface area, which can effectively improve the capacitance performance of TiN-Li_4Ti_5O_ (12) NTA electrode material. All-solid-state symmetrical supercapacitors based on TiN-Li_4Ti_5O_ (12) NTA electrode materials and polyvinyl alcohol-lithium sulfate (PVA-Li2SO_4) gel electrolytes have a voltage of 2.4V. When the current density is 0.5Ag~(-1), the specific energy of TiN-Li_4Ti_5O_ (12) NTA supercapacitors is 32.36 Wh kg~(-1). Devices with a volume of 10 mm *22 mm *0.5 mm can be brightened. The working voltage of LED lamp is 2V, indicating that TiN-Li_4Ti_5O_ (12) NTA electrode material can be used as supercapacitor material. (2) Preparation of RGO/C-Li_4Ti_5O_ (12) NTA electrode material and its electrochemical properties. In this chapter, the C-Li_4Ti_5O_ (12)/RGO NTA electrode material was synthesized by carbonization of PVA with RGO at 600 for 3h. Scanning results show that the carbon layer containing graphene sheet is uniformly distributed on the surface of Li_4Ti_5O_ (12) NTA. In Li_2SO_4 of 0.5 M, - 0.6-0.6 V potential window, the specific capacitance of C-Li_4Ti_5O_ (12)/RGONTA electrode material is 210. 76 F g~(-1). The specific capacitance of C-Li_4Ti_5O_ (12)/RGO NTA was maintained at 89.99% after 1000 constant current charges and discharges at 3 A g~(-1) current density, indicating that the electrochemical performance of RGO coated surface Li_4Ti_5O_ (12) NTA was significantly improved. RGO/C-Li_4Ti5012 NTA electrode material and PVA-Li2S04 gel electrolyte were prepared into solid state. A state-symmetrical supercapacitor energy storage device has a test voltage of 2.4 V. The current density increases from 0.5 Ag~(-1) to 10 Ag~(-1), the power density increases from 0.6 kW kg~(-1) to 12 kW kg~(-1), the energy density decreases from 39.98 Wh kg~(-1) to 12.36 Wh kg~(-1), and the device with a volume of 10 mm (3) Preparation of TiN-Li_ (4-x) Mg_xTi_5O_ (12) NTA electrode material and its electrochemical properties. In this chapter, Li_ (4-x) Mg_xTi_5O_ (12) NTA was synthesized by Mg2+ doping of Li_4Ti_5O_ (12) NTA with Mg (NO_3) _2 as the Mg source. TiN-Li_ (4-x) Mg_xTi_5O_ (12) NTA was formed by sol-coated Li_ (4-x) Mg_ (4-x) Mg_xTi_5O_ (12) NTA after nitriding for 1 h at 700 C. Scanning results showed that the morphology of Li_4Ti_5O_ (12) NTA did not change significantly after doping with Mg2 +, but remained as a nanotube array structure. The results show that the EDS spectra of TiN-Li_ (4-x) M g_xTi_5O_ (12) NTA electrode materials show that the specific capacitance of TiN-Li_ (4-x) M g_xTi_5O_ (12) NTA electrode materials is 224.4 when the current density is 0.5 A g~(-1) and the specific capacitance of TiN-Li_ (4-x) M g_xTi_5O_ (12) NTA electrode materials is 0.5 M in Li2S04 electrolyte solution and - 0.4-0.8 V potential window. 58 F g~(-1). After 1000 cycles of charging and discharging at the current density of 3A~(-1), the capacitance retention of TiN-Li_ (4-x) Mg_xTi_5O_ (12) NTA was 89.53%, indicating that Mg2+ doping and TiN effectively improved the electrochemical performance of electrode materials. Based on TiN-Li_ (4-x) Mg_xTi_5O_ (12) NTA electrode materials and polyvinyl alcohol-lithium sulfate (PVA-Li2SO4) gel electrolysis The specific energy of TiN-Li_ (4-x) Mg_xTi_5O_ (12) NTA capacitor is 42.61 Wh kg~(-1). A device with a volume of 30 mm 10 mm 0.5 mm can turn on the LED lamp with a working voltage of 2 V, indicating that TiN-Li_ (4-x) Mg_xTi_5O_ (12) NTA electrode can be turned on when the current density is 0.5 A g~(-1). The materials exhibit excellent energy storage properties.
【學(xué)位授予單位】：東南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TQ131.11;TM53

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本文編號(hào)：2193103