【摘要】：鎳系正極材料因其容量高,資源廣以及環(huán)境友好等優(yōu)勢而成為最具有應用前景的鋰離子電池正極材料之一。然而,化學計量比的鎳酸鋰難以制備,同時在充電過程中高氧化態(tài)的鎳離子易與電解質(zhì)發(fā)生副反應,從而惡化材料的循環(huán)壽命和熱穩(wěn)定性。通過合適的摻雜與包覆等手段可有效地提高鎳系正極材料的電化學性能。本論文采用控制結(jié)晶共沉淀法制備了Co摻雜的LiNi0.8Co0.2O2正極材料和Co-Al共摻雜的正極材料LiNi0.8Co0.15Al0.05O2,探討了制備條件對材料形貌、結(jié)構(gòu)和電化學性能的影響。此外,通過對LiNi0.8Co0.15Al0.05O2正極材料進行導電聚合物聚苯胺包覆來進一步改善其電化學性能。論文的主要工作如下:(1)通過控制結(jié)晶共沉淀法制備了球形前驅(qū)體Ni0.8Co0.2(OH)2,再將其與氫氧化鋰進行混合,經(jīng)過高溫固相反應得到LiNi0.8Co0.2O2正極材料。探討了共沉淀反應體系中pH值和攪拌速率對前軀體的影響,結(jié)果表明:pH值為10.8,攪拌速率為800 rpm時,所得到的前軀體顆粒球形度好、粒徑分布均勻;同時,研究了高溫固相反應過程中煅燒氣氛、Li/M、煅燒溫度和煅燒時間對材料性能的影響。當氧氣流速為60 m L/min,鋰金屬比1.06時,在750℃溫度下煅燒12 h所得到的材料性能最優(yōu)。在3.0~4.3 V、0.1 C(18 mA g-1)充放電條件下,其首次放電容量可達195.3 mAh?g-1,并且經(jīng)過50次循環(huán)后容量保持率為82.6%。(2)以EDTA為Al3+螯合劑,通過控制結(jié)晶共沉淀法制備了球形前驅(qū)體Ni0.8Co0.15Al0.05(OH)2,考察了Li/M、煅燒溫度以及煅燒時間對所制備的LiNi0.8Co0.15Al0.05O2正極材料的影響,結(jié)果顯示最佳的工藝條件為:氧氣流速60m L/min,鋰金屬比1.06,煅燒溫度750℃和煅燒時間12 h。最佳工藝條件下制備的LiNi0.8Co0.15Al0.05O2正極材料,在3.0~4.3 V、0.1 C條件下首次放電容量為193.4mAh?g-1,經(jīng)過50次循環(huán)后容量保持率仍然為90.1%。(3)為了進一步改善Li Ni0.8Co0.15Al0.05O2正極材料的電化學性能,采用導電聚合物聚苯胺對其進行表面包覆,探討了聚苯胺包覆量對材料性能的影響。結(jié)果表明,聚苯胺包覆量為10 wt%時所得到的材料具有最佳的電化學性性。在3.0~4.3 V電壓范圍內(nèi),以0.1 C倍率進行充放電時,其首次放電容量為195.6 mAh?g-1,并且首次庫倫效率高達90.3%。此外,在0.1 C倍率下循環(huán)50次后容量仍然保持有181.3mAh/g,容量保持率高達92.6%;并且2.0 C倍率下的放電比容量仍為143.5mAh?g-1,顯示材料具有優(yōu)異的循環(huán)穩(wěn)定性和倍率性能。
[Abstract]:Nickel cathode materials have become one of the most promising cathode materials for lithium ion batteries due to their advantages of high capacity, wide resources and environmental friendliness. However, the stoichiometric lithium nickelate is difficult to be prepared, and the high oxidized nickel ion can easily react with the electrolyte during the charging process, thus worsening the cycle life and thermal stability of the material. The electrochemical properties of nickel cathode materials can be improved by appropriate doping and coating. In this paper, Co doped LiNi0.8Co0.2O2 cathode materials and Co-Al co-doped cathode materials LiNi0.8Co0.15Al0.05O2, were prepared by controlled crystallization coprecipitation. The effects of preparation conditions on the morphology, structure and electrochemical properties of the materials were investigated. In addition, the electrochemical properties of LiNi0.8Co0.15Al0.05O2 cathode materials were further improved by coating the conductive polymer Polyaniline. The main work of this paper is as follows: (1) the spherical precursor Ni0.8Co0.2 (OH) _ 2 was prepared by controlled crystallization coprecipitation method, and then mixed with lithium hydroxide. The LiNi0.8Co0.2O2 cathode material was prepared by solid state reaction at high temperature. The effects of pH value and stirring rate on the precursor in coprecipitation reaction system were discussed. The results showed that when the pH value was 10.8 and the stirring rate was 800 rpm, the particle size distribution was uniform and spherical. At the same time, the effects of calcination atmosphere, Li/M, calcination temperature and calcination time on the properties of the materials during high temperature solid state reaction were studied. When the oxygen flow rate is 60 mL / min, the ratio of lithium to metal is 1.06, and the calcined temperature is 750 鈩，

本文編號：2408633