鋰硫電池硫基正極材料與隔膜改性研究
發(fā)布時間：2018-07-27 15:27
【摘要】：鋰硫電池作為一種新型的能量儲存系統(tǒng),理論能量密度高達2600 Wh/kg,受到研究者的廣泛關(guān)注,并且活性物質(zhì)單質(zhì)硫具有環(huán)境友好、價格低廉和資源豐富的特點。與傳統(tǒng)的鋰離子電池相比,鋰硫電池優(yōu)勢明顯。到目前為止,鋰硫電池還處于實驗室研發(fā)階段,可實現(xiàn)的能量密度遠低于理論值,并存在容量衰減快,循環(huán)壽命短等問題,限制了其大規(guī)模工業(yè)生產(chǎn)。從鋰硫電池的結(jié)構(gòu)和工作原理進行分析,活性物質(zhì)單質(zhì)硫為絕緣體,電子導(dǎo)電率不高和中間產(chǎn)物多硫化物易溶于電解液,引發(fā)的穿梭效應(yīng)是主要原因。本論文針對鋰硫電池存在的關(guān)鍵問題,從硫基正極和隔膜改性兩方面開展研究。將鍍鎳碳納米管作為硫的載體應(yīng)用于正極改性;研究了氮化鈦/硫復(fù)合正極的電化學(xué)性能;在商用隔膜表面涂覆導(dǎo)電氧化物Ti4O7,制備Ti4O7改性隔膜。具體研究內(nèi)容如下:(1)通過加熱熔融的方法使升華硫進入鍍鎳碳納米管的孔隙,制得鍍鎳碳納米管/硫復(fù)合正極材料。作為硫的載體,鍍鎳碳納米管相互交錯,構(gòu)成了三維導(dǎo)電網(wǎng)絡(luò)。其中碳納米管具有中空結(jié)構(gòu),比表面積和孔隙率高,能對多硫化物產(chǎn)生物理吸附作用,并適應(yīng)活性物質(zhì)在充放電過程中的體積變化。鎳顆粒均勻分布在碳納米管的表面,縮短電子傳輸路徑,增強了復(fù)合正極的電子電導(dǎo);并在電化學(xué)反應(yīng)中起到催化作用,有利于多硫化物向Li2S的轉(zhuǎn)化。(2)采用二氧化鈦碳熱還原氮化的方法制備氮化鈦顆粒,氮化鈦導(dǎo)電性良好,與硫-胺化學(xué)方法制備的納米硫進行復(fù)合,制備氮化鈦/硫復(fù)合正極。氮化鈦與多硫化物之間存在化學(xué)鍵合作用,減少多硫化物的穿梭效應(yīng)。通過CV和阻抗分析可知,氮化鈦能夠降低電池的電荷轉(zhuǎn)移電阻,促進電化學(xué)反應(yīng)的進行,有利于提升電池的電化學(xué)性能。1 C下充放電循環(huán)200次,還保留602 mAh/g的可逆比容量。(3)通過高溫碳熱還原金紅石二氧化鈦的方法制備了Ti4O7粉體,均勻涂覆在Celgard 2400隔膜表面,涂層的厚度為5μm。作為物理阻擋層,可以抑制多硫化物向鋰負極的擴散。Ti4O7涂層還具有二次集流體的作用,提高了硫的利用率,減少了容量的損失。與使用普通隔膜的電池相比,Ti4O7改性隔膜電池在循環(huán)和倍率性能方面有了大幅度的提升,在1 C下充放電循環(huán)600次,還保留565 mAh/g的可逆比容量;在大倍率4 C下,放電比容量達到528 mAh/g。
[Abstract]:As a new type of energy storage system, the theoretical energy density of lithium-sulfur battery is as high as 2600 Wha / kg, which has attracted extensive attention of researchers. The simple sulfur, an active substance, has the characteristics of environmental friendliness, low price and abundant resources. Compared with the traditional lithium ion battery, lithium sulfur battery has obvious advantages. Up to now, the lithium-sulfur battery is still in the stage of laboratory research and development, the energy density is far lower than the theoretical value, and there are some problems such as fast capacity attenuation, short cycle life and so on, which limits its large-scale industrial production. The structure and working principle of lithium-sulfur battery are analyzed. It is found that the simple sulfur is an insulator, the electronic conductivity is not high and the intermediate product polysulfide is easily dissolved in the electrolyte. The main reason is the shuttle effect. In this paper, the key problems of lithium-sulfur battery are studied from two aspects: sulfur positive electrode and membrane modification. Nickel coated carbon nanotubes were used as carrier of sulfur to modify positive electrode. Electrochemical properties of titanium nitride / sulfur composite positive electrode were studied. Conductive oxide Ti4O7 was coated on the surface of commercial diaphragm to prepare Ti4O7 modified diaphragm. The main contents are as follows: (1) by heating and melting, sublimated sulfur enters the pores of nickel coated carbon nanotubes, and the nickel coated carbon nanotubes / sulfur composite cathode materials are prepared. As the carrier of sulfur, nickel-coated carbon nanotubes intersect with each other to form a three-dimensional conductive network. Carbon nanotubes have hollow structure, high specific surface area and porosity, which can produce physical adsorption to polysulfide and adapt to the volume change of active substances during charge and discharge. Nickel particles distribute uniformly on the surface of carbon nanotubes, shorten the electron transport path, enhance the electronic conductivity of the composite positive electrode, and play a catalytic role in the electrochemical reaction. (2) Titanium nitride particles were prepared by carbothermal reduction and nitridation of titanium dioxide. Titanium nitride particles had good electrical conductivity. Titanium nitride / sulfur composite positive electrode was prepared by compounding with nano-sulfur prepared by sulfur-amine chemical method. There is a chemical bond cooperation between titanium nitride and polysulfide to reduce the shuttle effect of polysulfide. The results of CV and impedance analysis show that titanium nitride can reduce the charge transfer resistance of the battery, promote the electrochemical reaction, and improve the electrochemical performance of the battery. The reversible specific capacity of 602 mAh/g was also retained. (3) the Ti4O7 powder was prepared by carbothermal reduction of rutile TIO _ 2 at high temperature. The Ti4O7 powder was uniformly coated on the surface of the Celgard 2400 diaphragm. The thickness of the coating was 5 渭 m. As a physical barrier layer, the diffusion of polysulfide to lithium negative electrode can be inhibited. Ti4O7 coating also has the effect of secondary fluid collection, which improves the utilization rate of sulfur and reduces the loss of capacity. Compared with the battery with ordinary diaphragm, Ti4O7 modified membrane battery has a great improvement in cycle and rate performance. It has a reversible specific capacity of 565 mAh/g at 1 C for charge / discharge cycles, and at a large rate of 4 C, The specific discharge capacity is 528 mg / g.
【學(xué)位授予單位】：江蘇大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TM912
本文編號：2148271
[Abstract]:As a new type of energy storage system, the theoretical energy density of lithium-sulfur battery is as high as 2600 Wha / kg, which has attracted extensive attention of researchers. The simple sulfur, an active substance, has the characteristics of environmental friendliness, low price and abundant resources. Compared with the traditional lithium ion battery, lithium sulfur battery has obvious advantages. Up to now, the lithium-sulfur battery is still in the stage of laboratory research and development, the energy density is far lower than the theoretical value, and there are some problems such as fast capacity attenuation, short cycle life and so on, which limits its large-scale industrial production. The structure and working principle of lithium-sulfur battery are analyzed. It is found that the simple sulfur is an insulator, the electronic conductivity is not high and the intermediate product polysulfide is easily dissolved in the electrolyte. The main reason is the shuttle effect. In this paper, the key problems of lithium-sulfur battery are studied from two aspects: sulfur positive electrode and membrane modification. Nickel coated carbon nanotubes were used as carrier of sulfur to modify positive electrode. Electrochemical properties of titanium nitride / sulfur composite positive electrode were studied. Conductive oxide Ti4O7 was coated on the surface of commercial diaphragm to prepare Ti4O7 modified diaphragm. The main contents are as follows: (1) by heating and melting, sublimated sulfur enters the pores of nickel coated carbon nanotubes, and the nickel coated carbon nanotubes / sulfur composite cathode materials are prepared. As the carrier of sulfur, nickel-coated carbon nanotubes intersect with each other to form a three-dimensional conductive network. Carbon nanotubes have hollow structure, high specific surface area and porosity, which can produce physical adsorption to polysulfide and adapt to the volume change of active substances during charge and discharge. Nickel particles distribute uniformly on the surface of carbon nanotubes, shorten the electron transport path, enhance the electronic conductivity of the composite positive electrode, and play a catalytic role in the electrochemical reaction. (2) Titanium nitride particles were prepared by carbothermal reduction and nitridation of titanium dioxide. Titanium nitride particles had good electrical conductivity. Titanium nitride / sulfur composite positive electrode was prepared by compounding with nano-sulfur prepared by sulfur-amine chemical method. There is a chemical bond cooperation between titanium nitride and polysulfide to reduce the shuttle effect of polysulfide. The results of CV and impedance analysis show that titanium nitride can reduce the charge transfer resistance of the battery, promote the electrochemical reaction, and improve the electrochemical performance of the battery. The reversible specific capacity of 602 mAh/g was also retained. (3) the Ti4O7 powder was prepared by carbothermal reduction of rutile TIO _ 2 at high temperature. The Ti4O7 powder was uniformly coated on the surface of the Celgard 2400 diaphragm. The thickness of the coating was 5 渭 m. As a physical barrier layer, the diffusion of polysulfide to lithium negative electrode can be inhibited. Ti4O7 coating also has the effect of secondary fluid collection, which improves the utilization rate of sulfur and reduces the loss of capacity. Compared with the battery with ordinary diaphragm, Ti4O7 modified membrane battery has a great improvement in cycle and rate performance. It has a reversible specific capacity of 565 mAh/g at 1 C for charge / discharge cycles, and at a large rate of 4 C, The specific discharge capacity is 528 mg / g.
【學(xué)位授予單位】：江蘇大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TM912
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