本文關鍵詞： 鋰離子電容器 二硫化鉬 水熱法 碳氮復合　出處：《哈爾濱工業(yè)大學》2017年碩士論文　論文類型：學位論文

【摘要】：碳材料是目前廣泛使用的商用鋰離子電池負極材料,但其放電容量低、易產生鋰枝晶,無法滿足高功率、高能量、高容量等需求。二硫化鉬是一種類石墨烯的層狀化合物,其二維結構方便鋰離子的嵌入與脫出。同時,二硫化鉬制作工藝相對簡單,且其作為儲能器件負極時具有較高容量,目前受到廣泛關注。本文對制備的二硫化鉬進行了XRD、SEM、XPS等物理表征和循環(huán)伏安、交流阻抗、充放電等電化學測試,從結構、形貌、電化學性能等方面對二硫化鉬進行研究。采用水熱法合成二硫化鉬,通過對硫源、鉬源的比例,添加劑的使用、反應溫度、反應時間等條件進行工藝優(yōu)化,制得具有規(guī)則形貌的二硫化鉬。電化學測試結果表明:二硫化鉬電極在1 A g-1的電流密度下,首次放電比容量可以達到337mAhg~(-1),1000次循環(huán)過后保留比容量為57mAhg~(-1),明顯優(yōu)于商業(yè)碳材料。電池比容量的提高與二硫化鉬具有規(guī)則的立方體結構相關,層狀結構和較大的比表面積有利于電解液與電極的充分接觸,降低了電池內阻、提高了倍率性能以及循環(huán)性能。以活性炭為正極、二硫化鉬為負極、1 mol L-1的Li PF6-PC作為有機電解液,組裝成混合電容器。組裝后Mo S2/AC鋰離子混合電容器工作電壓為0-3.4 V,功率密度與能量密度較高,容量保持率較好。盡管二硫化鉬具有規(guī)則形貌和相對穩(wěn)定的電化學性能,但是隨著充電截止電壓的升高,電池循環(huán)性能逐漸變差;且在高電流密度下極化增加,容量衰減加快。通過煅燒聚吡咯制備了二硫化鉬與碳氮復合材料,并對包覆后的材料進行電化學測試。測試結果表明:經過復合后的材料,不僅電池容量有所提高,且在充放電過程中的穩(wěn)定性也明顯增強。在大電流密度1 A g-1的條件下,經500次循環(huán)后容量仍能達到230mAhg~(-1);未經包覆二硫化鉬經過500次循環(huán)后,剩余容量僅有65mAhg~(-1)。碳氮包覆層增強了材料的導電性以及結構穩(wěn)定性,進而保證了材料較好的電化學性能。
[Abstract]:Carbon materials are widely used as anode materials for commercial lithium-ion batteries at present, but their discharge capacity is low and lithium dendrites are easily produced, which can not meet the needs of high power, high energy, high capacity, etc. Molybdenum disulfide is a layered compound of graphene. The two-dimensional structure facilitates the intercalation and removal of lithium ions. At the same time, the fabrication process of molybdenum disulfide is relatively simple, and it has a high capacity as a negative electrode for energy storage devices. The preparation of molybdenum disulfide has been characterized by XRDX SEM XPS and electrochemical measurements such as cyclic voltammetry, AC impedance, charge / discharge, etc. The electrochemical properties of molybdenum disulfide were studied in this paper. Molybdenum disulfide was synthesized by hydrothermal method. The conditions such as sulfur source, proportion of molybdenum source, additive, reaction temperature and reaction time were optimized. Molybdenum disulfide with regular morphology was prepared. The electrochemical measurement results showed that the current density of molybdenum disulfide electrode was 1 A g ~ (-1). The specific discharge capacity of the first discharge can reach 337mAhgGN ~ (-1) ~ (-1). After 1000 cycles, the reserved specific capacity is 57m Ahg ~ (-1), which is obviously superior to that of commercial carbon materials. The increase of the specific capacity of the battery is related to the regular cubic structure of molybdenum disulfide (MoS _ 2). The layered structure and large specific surface area are beneficial to the full contact between electrolyte and electrode, reduce the internal resistance of the battery, improve the performance of the rate and cycle. The active carbon is the positive electrode. Li PF6-PC, with 1 mol L-1 molybdenum disulfide as organic electrolyte, was assembled into a hybrid capacitor. The operating voltage of Mo S 2 / AC lithium ion hybrid capacitor was 0-3.4 V, and the power density and energy density were high. Although molybdenum disulfide has regular morphology and relatively stable electrochemical performance, the cycle performance of the battery becomes worse with the increase of charging cutoff voltage, and polarization increases at high current density. After calcination of polypyrrole, molybdenum disulfide and carbon nitrogen composites were prepared, and the coated materials were tested by electrochemical test. The results showed that the composite material not only increased the capacity of the battery, but also increased the battery capacity. Under the condition of high current density of 1 A g ~ (-1), after 500 cycles, the capacity of molybdenum disulfide can still reach 230 m 路g ~ (-1), and after 500 cycles without coating, the capacity of molybdenum disulfide can reach 230m 路g ~ (-1). The residual capacity is only 65 m 路g ~ (-1). The carbon and nitrogen coating enhances the electrical conductivity and structural stability of the material, thus ensuring the better electrochemical performance of the material.
【學位授予單位】：哈爾濱工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TQ136.12;TM53

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本文編號：1539408