【摘要】：隨著智能電網(wǎng)的發(fā)展和清潔可再生能源的并網(wǎng),大型電化學(xué)儲(chǔ)能技術(shù)變得日益重要。它是改善和穩(wěn)定電力系統(tǒng)平穩(wěn)運(yùn)行的有效方法。可以根據(jù)電網(wǎng)的運(yùn)行起到調(diào)整頻率、平滑負(fù)荷、冷啟動(dòng)、電力應(yīng)急和削峰填谷的作用。此外,還能提供局部電力供應(yīng)和無功功率支持等服務(wù)。水系鈉離子電池具有綠色環(huán)保、安全、成本低廉、鈉離子資源豐富等特點(diǎn),在大型電化學(xué)儲(chǔ)能方面有很大的應(yīng)用前景。 水鈉錳礦類錳氧化物,是一類具有Mn06八面體共邊組成二維層狀結(jié)構(gòu)的材料,層與層之間的距離約為7A,允許層間區(qū)域的陽離子快速遷移,同時(shí)為離子在電解液和電極界面的快速動(dòng)力學(xué)移動(dòng)提供可能。因此,這類層狀材料也可以作為水系鈉離子電池的正極材料來進(jìn)行使用。同樣,材料的結(jié)晶性,形貌和結(jié)構(gòu)對(duì)其電化學(xué)性能有很大的影響。在本文中,我們主要通過形貌和結(jié)構(gòu)的設(shè)計(jì)來提高這類材料作為水系鈉離子電池正極材料的電化學(xué)性能。主要研究?jī)?nèi)容和結(jié)果如下： 采用簡(jiǎn)單的局部化學(xué)法制備具有分級(jí)結(jié)構(gòu)的花狀K0.27MnO2通過)RD (X-ray powder diffraction)、FE-SEM (Field emission scanning electron microscope)、TEM (Transmission electron microscopy)等手段,考察熱處理溫度對(duì)得到材料形貌和結(jié)構(gòu)的影響。研究表明材料的層狀結(jié)構(gòu)在700℃時(shí)依然能夠保持。但是,花狀形貌則會(huì)遭到破壞。三電極體系測(cè)試表明,花狀分級(jí)結(jié)構(gòu)的樣品KMO-500具有優(yōu)異的電化學(xué)性能。以K0.27MnO2作為正極,商業(yè)化的活性碳作為負(fù)極,考察材料作為水系二次電池的電化學(xué)性能。研究表明在能量密度為418W h kg-1,電池的功率密度可以達(dá)到180.0Wkg1。此外,經(jīng)過1000次充放電循環(huán)以后其結(jié)構(gòu)和形貌仍然得到很好的保持。這些結(jié)果表明,這種材料具有穩(wěn)定的層狀結(jié)構(gòu),可以用在大型電化學(xué)儲(chǔ)能器件上。 分級(jí)花狀K0.27MnO2具有層狀結(jié)構(gòu),可以作為水系鈉電池正極材料。同樣,采用局部化學(xué)法經(jīng)過500℃熱處理2h得到這種材料。以花狀的K0.27MnO2作為正極,NaTi2(PO4)3作為負(fù)極,在200mAg-1的電流密度下,經(jīng)過100次充放電循環(huán),電池的比容量還有68.5mA h g-1。將這種材料用作水系鈉離子電池正極材料表現(xiàn)出很好的可逆容量、循環(huán)穩(wěn)定性和倍率性能。同時(shí),通過對(duì)充放電循環(huán)前后的材料結(jié)構(gòu)和表面化學(xué)態(tài)進(jìn)行研究,分析鈉離子可能存在的脫嵌機(jī)制。經(jīng)過首次充電過程,鉀離子從電極材料中脫出,后面的充放電循環(huán)主要是鈉離子進(jìn)行嵌入和脫出反應(yīng)�？梢哉f這種廉價(jià),環(huán)境友好的電極材料作為水系鈉離子電池在大型電化學(xué)儲(chǔ)能上具有實(shí)際應(yīng)用前景。 采用乳液聚合得至PS (Polystyrene,聚苯乙烯)球,將其作為前驅(qū)體模版,通過水熱法得到核殼結(jié)構(gòu)的PS@K-δ-MnO2,通過熱處理除去樣品內(nèi)部的PS球,得到具有中空結(jié)構(gòu)的K0.27MnO2。在三電極體系中,對(duì)材料K0.27MnO2的電化學(xué)性能進(jìn)行測(cè)試。在充放電電流密度為200mAg1時(shí),經(jīng)過100次充放電循環(huán),其放電比容量還有40.6mAhg-1,容量保持率幾乎為100%,具有很好的循環(huán)穩(wěn)定性。此外,以中空K0.27MnO2作為正極,NaTi2(PO4)3作為負(fù)極,組裝水系鈉離子電池,其中電壓范圍設(shè)為0～1.8V,對(duì)其電化學(xué)性能進(jìn)行研究。在600mAg1條件下,經(jīng)過10次充放電循環(huán),其放電比容量還在50mA hg1以上。說明這種中空結(jié)構(gòu)能夠有效的減少材料粒徑,增加電極材料和電解液的接觸面積,縮短離子或者電子的傳輸距離,有利于鈉離子的快速嵌入和脫出。 通過水熱法和離子交換反應(yīng)制備含有不同堿金屬離子的層狀MnO2(A-8-MnO2, A:K, Na)。將含有不同堿金屬離子的材料作為正極,NaTi2(PO4)3作為負(fù)極組裝成全電池。研究材料的形貌、結(jié)構(gòu)和組成對(duì)電化學(xué)性能的影響。與無規(guī)則的顆粒相比較來說,花狀結(jié)構(gòu)的材料具有優(yōu)異的電化學(xué)性能。其中,樣品K, Na-8-MnO2作為正極材料表現(xiàn)出很好的循環(huán)和倍率性能,在200mAg1時(shí),經(jīng)過200次充放電循環(huán),其可逆比容量還有-59.6mA h g-1,在電流密度為600mAg1,其放電比容量還有46.6mA h g-1。研究分析經(jīng)過一次充放電循環(huán)后電極材料的化學(xué)態(tài)和化學(xué)成分,探討和揭示電化學(xué)反應(yīng)過程。對(duì)經(jīng)過200次充放電循環(huán)后的K,Na-δ-MnO2電極片,進(jìn)行結(jié)構(gòu)和形貌分析,表明材料的結(jié)構(gòu)比較穩(wěn)定。
[Abstract]:The technology of large-scale electrochemical energy storage is becoming more and more important with the development of the smart grid and the grid of clean and renewable energy sources. It is an effective method to improve and stabilize the stable operation of the power system. The function of adjusting frequency, smoothing load, cold start, electric power emergency and peak clipping can be achieved according to the operation of the power grid. In addition, services such as local power supply and reactive power support can also be provided. The water system sodium ion battery has the characteristics of being green, environment-friendly, safe, low in cost, rich in sodium ion resource and the like, and has great application prospect in large-scale electrochemical energy storage. The manganese oxide of the water-sodium manganese ore is a material with a two-dimensional layered structure composed of a common edge of the Mn06 octahedron, the distance between the layer and the layer is about 7A, the cation of the interlayer area is allowed to be rapidly migrated, and meanwhile, the rapid kinetic movement of the ions in the electrolyte and the electrode interface can be provided. Thus, such a layered material can also be made as a positive electrode material of an aqueous sodium ion battery, In the same way, the crystallinity, morphology and structure of the material have a great shadow on its electrochemical performance. In this paper, we mainly improve the electrochemical property of this kind of material as the cathode material of the water-based sodium ion battery by the design of the shape and structure. Energy. Main research content and results such as In this paper, a simple partial chemical method was used to prepare the flower-like K0.27 MnO2 with a graded structure. The morphology and structure of the obtained material were investigated by means of RD (X-ray power diffractions), FE-SEM (Field emensable electron microscope), and TEM (Transmission electron microcopy). The study shows that the layered structure of the material can still be at 700 鈩，

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