發(fā)布時間：2018-03-04 09:10

  本文選題：LiNi_(0.6)Co_(0.2)Mn_(0.2)O_2　切入點：尿素均相沉淀　出處：《哈爾濱工業(yè)大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：由于高的能量密度以及成本優(yōu)勢,富Ni系鎳鈷錳三元層狀氧化物L(fēng)iNixCoyMnz02 (x0.5,文中簡稱為NCM),已成為主流的下一代鋰離子電池正極材料。在實際應(yīng)用中,為了獲得更高的能量密度,最簡單的辦法是提高截止電壓,但是富鎳氧化物在高壓工作時(4.3 V)會伴隨著快速的容量衰減問題,較差的高壓性能阻礙了富Ni三元層狀氧化物的應(yīng)用前景。為了獲得較好性能的NCM三元材料,本文采用了三種方法進(jìn)行LiNi0.6Co0.2Mn0.202(文中簡稱為NCM622)材料的制備,具體內(nèi)容如下:第一部分采用共沉淀法成功制備出多孔形貌的LiNi0.6Co0.2Mn0.202材料。實驗中探討了陳化時間以及過鋰量的影響。結(jié)果顯示,過鋰量為5%,陳化時間為12h時,陽離子的混排程度小和層狀結(jié)構(gòu)維持得較好。電化學(xué)性能測試顯示由于維持了一種多孔的形貌,所以該材料的倍率性能較好,1 C (1 C=200mA/g)、2C、5C、10C 的比容量分別為 144mAh/g、130mAh/g、112 mAh/g、89mAh/g。第二部分采用尿素均相沉淀法制備出球狀形貌的LiNi0.6Co0.2Mn0.202材料。結(jié)果顯示,在本實驗條件下,除醋酸類過渡金屬鹽受自組裝的影響較弱之外,其余的陰離子在純尿素體系中很難正確的沉淀出LiNi0.6Co0.2Mn0.202材料。通過調(diào)節(jié)溶液的pH值以及聚乙烯吡咯烷酮(PVP)輔助水熱反應(yīng),可以生成正確LiNi0.6Co0.2Mn0.202材料,并且獲得優(yōu)化后的性能。pH=9時,在0.1 C、1 C、2C的倍率下的初始放電容量分別為:163 mAh/g、142mAh/g、102 mAh/g,循環(huán)50圈的能量保持率分別為:91%、93%、92%。160℃的聚乙烯吡咯烷酮(PVP)輔助水熱法在1 C的倍率下的首次放電容量為134 mAh/g,50圈循環(huán)后的容量保持率為80%,比起純尿素體系的68%得到了一定的提升。第三部分采用模版法制備出具有一定形貌的LiNi0.6Co0.2Mn0.202材料。結(jié)果顯示,比起花狀形貌的NiO模版,球狀的模版的結(jié)構(gòu)更加的穩(wěn)定,本實驗成功的合成了以球狀NiO為模版的LiNi0.6Co0.2Mn0.202材料,經(jīng)過高溫?zé)Y(jié)后依舊能夠保持球形形貌,在0.1 C、1C以及2 C倍率下的初始放電比容量分別為:165 mAh/g、117 mAh/g以及93 mAh/g,循環(huán)50圈后的能量保持率分為:88%、84%以及82%。
[Abstract]:Because of its high energy density and cost advantage, Ni-rich nickel-cobalt-manganese ternary layered oxide (LiNixCoyMnz02 x 0.5) has become the mainstream cathode material for the next generation of lithium ion batteries. The easiest way to do this is to increase the cut-off voltage, but nickel rich oxides at high pressure work at 4.3 V) with a rapid capacity decay problem. In order to obtain better properties of NCM ternary materials, three methods were used to prepare LiNi0.6Co0.2Mn0.2022 (referred to as NCM622 in this paper). The main contents are as follows: in the first part, LiNi0.6Co0.2Mn0.202 materials with porous morphology were successfully prepared by coprecipitation. The effects of aging time and the amount of perlithium were discussed. The results showed that the amount of perlithium was 5 and the aging time was 12 hours. The results of electrochemical performance test show that because of maintaining a porous morphology, Therefore, the specific capacity of this material is 144mAh-gr 130mAh / gr 130mAh/ g / 10C, respectively. In the second part, the spherical LiNi0.6Co0.2Mn0.202 material is prepared by urea homogeneous precipitation method. The results show that, under the experimental conditions, the spherical morphology of the LiNi0.6Co0.2Mn0.202 material can be obtained by using urea homogeneous precipitation method. Except for the transition metal salts of acetic acid which are less affected by self-assembly, it is very difficult for the other anions to precipitate LiNi0.6Co0.2Mn0.202 materials correctly in the pure urea system. The hydrothermal reaction is assisted by adjusting the pH value of the solution and polyvinylpyrrolidone (PVP). The correct LiNi0.6Co0.2Mn0.202 material can be produced, and the optimized performance. Ph = 9:00, The initial discharge capacity at the rate of 0.1 C ~ (-1) C ~ (2 C) is 10: 163 mAh/ g ~ (142) mAh/ g ~ (10 ~ 2) mg / g, and the energy retention rate of 50 cycles is: 1 / 91 ~ 932 ~ 932 鈩，

本文編號：1565014