本文選題：鋰離子電池　切入點：鈉離子電池　出處：《浙江大學》2017年博士論文

【摘要】：本文主要針對層狀結構過渡金屬硫系化合物在儲鋰儲鈉領域中存在的循環(huán)壽命有限,倍率性能差等問題,以MoS2和MoSe2為研究對象,通過納米化、表面修飾及其與碳基材料復合化的手段,構建合理可控的多層結構,改善其電化學儲鋰儲鈉性能,并結合XPS與HRTEM等分析技術,探究層狀結構過渡金屬硫系化合物儲鋰儲鈉反應機制,為硫系化合物的電化學儲能提供理論基礎與技術支持。主要研究內容與結果如下:(1)以氨水為氮源,以PEG-20000為碳源,通過兩次水熱反應過程構建了自支撐多孔結構碳包覆的MoS2與氮摻雜還原氧化石墨烯氣凝膠(C-MoS2/N-doped rGO),碳包覆與石墨烯三維網(wǎng)格骨架對MoS2電極材料的雙修飾效果,使C-MoS2/N-doped rGO電極具有優(yōu)異的電化學儲鋰性能。在200mA/g電流密度下經(jīng)循環(huán)500次,能保持900 mAh/g高可逆比容量,在4 A/g電流密度下循環(huán),仍具有500mAh/g可逆比容量,遠優(yōu)于C-MoS2電極的電化學儲鋰性能。同時,通過XPS與HRTEM相結合的分析技術探究了其電化學儲鋰反應機制。(2)通過溶液聚合法構建了三維網(wǎng)格交聯(lián)結構的MoS2-PPY-rGO/Cu薄膜。厚度為5-10nm的無定型導電聚合物PPY均勻包覆的MoS2納米片,能夠有效抑制MoS2與鋰反應過程中中間相多硫化物溶解問題,同時連接MoS2與石墨烯骨架。而rGO三維骨架有效抑制活性物質的團聚,并提高整個薄膜的導電性。將其薄膜直接剪切為電極進行鋰離子電池性能測試,該復合薄膜電極有優(yōu)異的電化學儲鋰性能。在200mA/g電流密度下循環(huán)400次,能保持1070mAh/g比容量,在2 A/g電流密度下仍有600mAh/g的可逆比容量。同時研究了不同厚度與載量薄膜的儲鋰性能,表明2 mg/cm2量的MoS2-PPY-rGO薄膜具有更優(yōu)異的儲鋰性能,說明薄膜厚度對電化學儲能有重要的影響。(3)受啟于大自然的生物質結構,通過水熱法制備三維多孔狀結構絲瓜絡生物質碳與MoS2殼核結構(LSDCM/MoS2),并利用溶液聚合法與高溫碳化包覆氮摻雜碳(N-C)保護層形成了三明治核殼結構LSDCM/MoS2/N-C復合材料。由于構建了獨特的三元結構,該LSDCM/MoS2/N-C復合電極具有優(yōu)異的電化學儲鋰儲鈉性能。在儲鋰方面,在200 mA/g電流密度下循環(huán)500次,能保持1058 mAh/g的可逆比容量;在4A/g大電流密度下循環(huán),仍能保持600mAh/g可逆比容量。另外,在4 A/g大電流密度下循環(huán),具有優(yōu)異的循環(huán)穩(wěn)定性,即循環(huán)320次,仍保持571 mAh/g,遠高于LSDCM/MoS2,MoS2與LSDCM電極。在儲鈉方面,在200mA/g電流密度下循環(huán)100次,該LSDCM/MoS2/N-C復合電極能保持534 mAh/g的可逆比容量,在4 A/g高電流密度下循環(huán)保持245 mAh/g。(4)構建合理并具有高性能的電極材料,對進一步發(fā)展鈉離子電池具有極其重要的作用。因此,通過以葡萄糖碳源,以氧化石墨烯為骨架,一步水熱法構建了三維多孔交聯(lián)網(wǎng)絡結構C-MoSe2/rGO復合材料。在水熱過程中,碳包覆MoSe2復合納米片(C-MoSe2)均勻嵌入在三維多孔結構還原氧化石墨烯等級結構中,達到了對MoSe2電極材料的雙修飾效果。直接剪切壓制成電極測試,表明該C-MoSe2/rGO電極具有優(yōu)異的電化學儲鈉性能。在200mA/g電流密度下循環(huán)350次,能保持445 mAh/g高可逆比容量,在4 A/g大電流密度下循環(huán),仍具有225 mAh/g的可逆比容量,遠優(yōu)于C-MoS2電極的電化學儲鈉性能。同時,通過非原位的XPS與HRTEM相結合的技術探究其電化學儲鈉反應機制。(5)以等離子體氣相沉積制備的VG為載體骨架,通過水熱法制備了核殼結構VG/MoSe2垂直陣列,隨后采用溶液聚合法與高溫碳化包覆氮摻雜碳(N-C)保護層形成VG/MoSe2/N-C三明治核殼結構陣列。VG與N-C構建的全方位碳修飾的三維骨架,有利于電子和離子的快速轉移,促進反應動力學過程。同時N-C包覆層能夠有效抑制MoSe2在電化學儲能過程中中間相多硒化物的溶解,而VG具有垂直片狀的穩(wěn)定結構與高導電性,作為載體能夠抑制活性物質團聚。因此,VG/MoSe2/N-C復合陣列具有非常優(yōu)異的儲鈉性能。在200 mA/g電流密度下循環(huán)400次,能保持545 mAh/g的可逆比容量,即使在2 A/g的電流密度下循環(huán)仍呈現(xiàn)出295 mAh/g的可逆比容量。更為重要的是,具有優(yōu)異的高倍率循環(huán)穩(wěn)定性,即在1 A/g與2 A/g循環(huán)1000次,仍能分別保持398 mAh/g與298 mAh/g的高可逆比容量。
[Abstract]:This paper focuses on the life cycle there are laminated structures of transition metal chalcogenides in lithium sodium storage in the field is limited, poor rate performance problems, using MoS2 and MoSe2 as the research object, by means of surface modification and nano technology, and carbon based composite material, multilayer structure construction reasonable and controllable, improve its electrochemical storage lithium storage performance of sodium, and the combination of XPS and HRTEM analysis techniques to explore the layered structure of transition metal chalcogenide lithium sodium storage reaction mechanism, to provide theoretical basis and technical support for the electrochemical sulfur compounds. The main research contents and results are as follows: (1) with ammonia as the nitrogen source, using PEG-20000 as carbon the source, through two times of hydrothermal reaction was constructed from MoS2 and nitrogen doped porous carbon coated support reduced graphene oxide aerogel (C-MoS2/N-doped rGO), and carbon coated graphene 3D mesh skeleton of MoS2 electrode Double modification of materials, the C-MoS2/N-doped rGO electrode has excellent electrochemical lithium storage performance. In the current density of 200mA/g after 500 cycles, can maintain a high capacity reversible cycle of 900 mAh/g at the current density of 4 A/g, 500mAh/g still has a reversible capacity, electrochemical lithium storage performance is much better than that of C-MoS2 electrode. At the same time, analysis of technology through the combination of XPS and HRTEM explore the electrochemical reaction mechanism of lithium storage. (2) to construct the MoS2-PPY-rGO/Cu film 3D mesh crosslinking structure by solution polymerization method. MoS2 nano plate shaping conductive polymer PPY uniform coating thickness is 5-10nm, can effectively inhibit MoS2 and lithium in the reaction process of mesophase multi sulfide dissolution problem, while connecting MoS2 and rGO graphene skeleton. The skeleton inhibit active substances and reunion, improve the conductivity of the whole film. The film is electric direct shear Most of the performance of lithium ion battery test, the composite film electrode has excellent electrochemical lithium storage performance. 400 cycles at the current density of 200mA/g, to maintain the 1070mAh/g capacity, under the current density of 2 A/g 600mAh/g still reversible capacity of lithium storage properties were also studied. Different thickness and load the film, show MoS2-PPY-rGO film 2 mg/cm2 amount has more excellent lithium storage performance, which shows that the film thickness has an important influence on the electrochemical energy storage. (3) by the biomass structure and on the nature, through the hydrothermal synthesis of 3D porous structure of Luffa raw material of carbon and MoS2 core-shell structure (LSDCM/MoS2), and by solution polymerization high temperature carbonization method and coated nitrogen doped carbon protective layer (N-C) formed a sandwich LSDCM/MoS2/N-C core-shell structure composite materials. Because of the unique structure of the construction of three yuan, the LSDCM/MoS2/N-C composite electrode has excellent electrochemical The lithium storage performance of sodium. In lithium storage, 500 cycles at the current density of 200 mA/g, 1058 mAh/g can maintain a reversible capacity; cycle in 4A/g under high current density, 600mAh/g can still maintain a reversible capacity. In addition, circulation at 4 A/g under high current density, excellent cycling stability, i.e. 320 cycles, still maintain 571 mAh/g, much higher than that of LSDCM/MoS2, MoS2 and LSDCM electrodes. In sodium storage, 100 cycles at the current density of 200mA/g, the LSDCM/MoS2/N-C composite electrode can keep 534 mAh/g reversible capacity, on environmental protection to 245 mAh/g. at 4 A/g under the condition of high current density (4) to construct reasonable electrode materials with high performance, to the further development of sodium ion battery plays a very important role. Therefore, by using glucose as carbon source, graphene oxide skeleton, one-step hydrothermal method to construct the three-dimensional porous crosslinked network structure of C-MoSe2/rGO composite material in the water. In the process of heat, carbon coated MoSe2 nano composite film (C-MoSe2) embedded in a uniform three-dimensional porous structure of graphene grade structure, achieves the double effect of MoSe2 modified electrode material. The direct shear test show that the pressed electrode, C-MoSe2/rGO electrode has excellent electrochemical performance of sodium. 350 cycles at a current density 200mA/g next, can maintain a high capacity reversible cycle in 445 mAh/g, 4 A/g high current density is 225 mAh/g, the reversible capacity, the electrochemical behavior of sodium is much better than that of C-MoS2 electrode. At the same time, to explore through the combination of XPS and HRTEM non in situ phase of the electrochemical reaction mechanism of sodium storage technology. (5) to plasma chemical vapor deposition preparation of VG vector backbone, were prepared by hydrothermal method with core-shell structure of VG/MoSe2 vertical array, followed by solution polymerization and carbonization of coated nitrogen doped carbon (N-C) protective layer formation VG/MoSe The full range of carbon skeleton 2/N-C array sandwich core-shell structure of.VG and N-C to build the modified, fast transfer to electron and ion dynamics. At the same time, promote the N-C coating layer can effectively inhibit MoSe2 in electrochemical energy storage solution of mesophase selenide multi process, and stable structure with vertical sheet VG with high conductivity, as a carrier of active substances can inhibit agglomeration. Therefore, VG/MoSe2/N-C composite sodium storage array has very excellent performance. 400 cycles at the current density of 200 mA/g, 545 mAh/g can maintain a reversible capacity, even at the current density of 2 A/g cycle is still showing a reversible specific capacity of 295 mAh/g. More importantly, with excellent high rate cycling stability, i.e. 1000 cycles at 1 A/g and 2 A/g respectively, can still maintain a high reversible 398 mAh/g and 298 mAh/g capacity.

【學位授予單位】：浙江大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：TB33;O646

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本文編號：1659423