本文選題：錳酸鋰 + 四氧化三錳　； 參考：《中南大學》2014年博士論文

【摘要】：摘要：能源危機、環(huán)境污染、全球變暖等一系列問題嚴重威脅到人類的生存和發(fā)展。為解決以上問題,各國政府紛紛投入大量人力物力開發(fā)利用電動汽車。鋰離子電池具有體積小、電壓高、容量大、壽命長、自放電小、無記憶效應和綠色環(huán)保等優(yōu)點而成為車載動力的首選。磷酸鐵鋰和錳酸鋰作為最可能應用于動力電池的正極材料。然而在我國磷酸鐵鋰熱火朝天的幾年里,世界各大主流汽車廠商電動汽車電池正極材料逐步向以日韓為代表的錳系正極材料轉(zhuǎn)移。但是日本以及韓國對動力LiMn2O4正極材料進行封鎖,在技術(shù)上進行保密,因此,研究開發(fā)出性能優(yōu)越的尖晶石LiMn2O4具有非常重要的現(xiàn)實意義。本文從前驅(qū)體入手,提出采用控制結(jié)晶一步氧化法制備球形四氧化三錳前驅(qū)體,然后聯(lián)合高溫固相法制備球形錳酸鋰,并從資源綜合利用角度出發(fā),采用液相法進行摻雜改性研究。 論述了控制結(jié)晶法合成前驅(qū)體的理論基礎(chǔ)。根據(jù)同時平衡原理和質(zhì)量守恒定律推導,繪制出Mn-NH3-SO42--H2O的φ-pH圖,并對晶粒形成和長大機理進行理論分析,為制備形貌單一、粒徑分布均勻的球形四氧化三錳前驅(qū)體提供理論基礎(chǔ)。 系統(tǒng)研究了控制結(jié)晶一步氧化法制備球形四氧化三錳工藝。研究了反應溫度、反應時間、攪拌速度、MnS04摩爾濃度、氨水濃度、氨錳摩爾比、硫酸錳加料速度對前驅(qū)體物理化學指標的影響,研究結(jié)果表明,在反應溫度為70℃、攪拌速度為500r·min-1、反應時間為12h、硫酸錳濃度為1.25mol·L-1、氨水濃度為2mol·L-1、NH3/Mn摩爾比為2.4、硫酸錳加料速度為600mL·h-1。制備的Mn304純度高達99.74%,粒度分布較好,平均粒徑為11.201μm,振實密度達到2.28g·cm-3。拉曼光譜分析表明所有Raman峰與尖晶石Mn304的特征峰完全吻合。 系統(tǒng)研究了高溫固相法制備球形錳酸鋰。研究結(jié)果表明最佳燒結(jié)工藝為500℃、650℃預燒6h后升溫至800℃燒結(jié)10h,此條件下合成的LiMn204材料顆粒球形度較好、結(jié)晶完善、電化學性能較好,常溫0.1C首次放電比容量高達125.5mAh·g-1,1C首次放電比容量為119.9mAh·g-1,循環(huán)300次后容量保持率為87.66%,高溫(55℃)1C首次放電比容量為114.9mAh·g-1,循環(huán)200次后容量保持率為86.24%。LiMn2O4電極循環(huán)伏安結(jié)果發(fā)現(xiàn)兩對氧化還原峰,與LiMn204電極的充放電曲線的特征平臺表現(xiàn)一致。 研究了聯(lián)合控制結(jié)晶一步氧化高溫固相法制備球形摻鎂錳酸鋰。研究發(fā)現(xiàn)控制NH3/Mn摩爾比,可以得到Mg含量可控、振實密度較大的球形摻Mg的Mn304前驅(qū)體。XRD結(jié)果顯示經(jīng)過高溫固相反應,Mg取代部分Mn成功進入尖晶石LiMn204晶格。鎂摻雜改善了錳酸鋰的循環(huán)性能,當前驅(qū)體中鎂含量約為1.5%時,得到的LiMn2-xMgxO4電化學性能最好,常溫1C首次放電比容量為113.1mAh·g-1,循環(huán)300次后容量保持106.4mAh·g-1；高溫1C首次放電比容量為121.4mAh·g-1,循環(huán)300次后容量保持99.3mAh·g-1。循環(huán)性能基本能滿足動力電池要求。 為進一步改善錳酸鋰的循環(huán)性能、降低原料成本、提高資源綜合回收利用,采用液相法分別對錳酸鋰進行了Ni、Co單一和Ni、Co復合摻雜。XRD結(jié)果表明,Ni、Co成功取代部分Mn進入尖晶石LiMn204晶格,減小了材料的晶格常數(shù)。鉆摻雜錳酸鋰具有較高的放電比容量和較好的循環(huán)性能,當前驅(qū)體中鈷含量為8%時,材料1C首次放電比容量為117.3mAh-g-1,循環(huán)200周后容量保持率為95.82%；鎳摻雜有效改善了LiMn204的循環(huán)性能,但是材料的比容量較低；Ni、Co復合摻雜LiMn204具有較高的比容量和較好的循環(huán)性能,當前驅(qū)體中Ni、Co的百分含量分別為1%左右時,制備的LiMn204常溫和高溫1C首次放電比容量分別為112.8和118.2mAh-g-1,常溫500次循環(huán)后容量保持率為97.52%,高溫300次循環(huán)后容量保持率為90.52%,所有物理化學指標都達到動力電池要求。XPS分析結(jié)果表明,Ni、Co復合摻雜提高了錳的平均價態(tài),Ni、Co復合摻雜樣品中Mn、Ni、Co的價態(tài)分別為+4、+2、+3價。 最后對球形錳酸鋰及Ni、Co復合摻雜錳酸鋰進行中試。中試結(jié)果表明錳酸鋰具有較好的常溫電化學性能,1C首次放電比容量為115.8mAh·g1,循環(huán)500次后容量保持率為89.29%；Ni、Co復合摻雜錳酸鋰具有優(yōu)越的電化學性能,常溫和高溫1C首次放電比容量分別為112.8和111.2mAh-g-1,500次循環(huán)后容量保持率分別為91.22%和83.81%。成本分析認為該工藝具有非常好的經(jīng)濟效益。
[Abstract]:Abstract: a series of problems, such as energy crisis, environmental pollution, global warming, seriously threaten the survival and development of human beings. In order to solve the above problems, governments have invested a lot of human and material resources to develop and utilize electric vehicles. Lithium ion batteries have small size, high voltage, large capacity, long life, small self discharge, no memory effect and green environmental protection. It has become the first choice of vehicle power. Lithium phosphate and lithium manganese dioxide are most likely to be used as positive materials for power batteries. However, in the years in China, the positive materials of electric vehicle batteries in the world's major automotive manufacturers have gradually shifted to the manganese cathode materials with Japan and South Korea as their behalf. South Korea has blocked the power LiMn2O4 cathode materials and secrecy in technology. Therefore, it is of great practical significance to study and develop the spinel LiMn2O4 with superior performance. This paper, starting from the former, proposed to prepare spherical four oxidation three manganese precursor by controlled crystallization and one step oxidation method, and then combined with high temperature solid state method to prepare the ball. Lithium manganese oxide is studied from the perspective of comprehensive utilization of resources.
The theoretical basis of controlling the synthesis of precursor by crystallization method is discussed. According to the principle of simultaneous equilibrium and the law of mass conservation, the phi -pH diagram of Mn-NH3-SO42--H2O is drawn, and the mechanism of grain formation and growth is theoretically analyzed to provide a theoretical basis for the preparation of a spherical four oxidation three manganese precursor with single morphology and uniform particle size distribution.
The effects of reaction temperature, reaction time, stirring speed, MnS04 molar concentration, ammonia water concentration, ammonia and manganese molar ratio, manganese sulphate feed rate on precursors physical and chemical indexes are studied. The results show that the reaction temperature is 70 degrees C and the stirring speed is 500r min. The results of the study show that the reaction temperature is 70, and the stirring speed is 500r. Min -1, the reaction time is 12h, the concentration of manganese sulfate is 1.25mol. L-1, the concentration of ammonia water is 2mol. L-1, the NH3/Mn molar ratio is 2.4, the Mn304 purity of Mn304 is 99.74%, the particle size distribution is better and the average particle size is 11.201 mu m. The characteristic peak coincides completely.
The preparation of spherical lithium manganate by high temperature solid state method is systematically studied. The results show that the optimum sintering process is 500 degrees C, the temperature of 6h at 650 C is heated to 800 C for 10h. Under this condition, the particles have better sphericity, perfect crystallization and better electrochemical performance, and the first discharge ratio of 0.1C at normal temperature is up to the first discharge ratio of 125.5mAh. G-1,1C. The capacity is 119.9mAh g-1 and the capacity retention rate is 87.66% after 300 cycles. The initial discharge ratio of 1C at high temperature (55 C) is 114.9mAh. G-1. After 200 cycles, the capacity retention rate is two pairs of redox peaks of 86.24%.LiMn2O4 electrode cyclic voltammetry, which is in accordance with the characteristic platform of the charge discharge curve of LiMn204 electrode.
Study on the preparation of spherical magnesium manganese doped lithium manganese oxide by a combined controlled crystallization and one step oxidation. It is found that the control of the NH3/Mn molar ratio can be controlled by the Mg content. The.XRD results of a spherical Mg doped Mn304 precursor show that the Mg substituted part of Mn has successfully entered the spinel LiMn204 lattice after a high temperature solid reaction. The magnesium doping is improved. The cycle performance of lithium manganate, when the content of magnesium is about 1.5% in the current drive, has the best electrochemical performance of LiMn2-xMgxO4. The first discharge specific capacity of 1C at normal temperature is 113.1mAh. G-1, and the capacity is 106.4mAh. G-1 after 300 cycles. The first discharge ratio of 1C is 121.4mAh. G-1 at high temperature 1C, and the capacity maintains 99.3mAh. G-1. cycle performance base after 300 cycles. Instinct meets the power battery requirements.
In order to further improve the cycle performance of lithium manganate, reduce the cost of raw materials and improve the comprehensive recovery and utilization of resources, Ni, Co single and Ni, and Co compound.XRD have been carried out by liquid phase method, respectively. The results show that Ni and Co have succeeded in replacing partial Mn into the spinel LiMn204 lattice and reducing the lattice constant of the material. The doping of lithium manganate is higher. The discharge specific capacity and good cycling performance of the current drive are 8%, the initial discharge ratio of 1C is 117.3mAh-g-1, and the capacity retention rate is 95.82% after 200 weeks. The nickel doping improves the cycle performance of LiMn204 effectively, but the specific capacity of the material is low; Ni, Co composite LiMn204 has higher specific capacity and comparison. With good cyclic performance, when the content of Ni and Co in the current drive is about 1% respectively, the initial discharge specific capacity of LiMn204 at normal temperature and high temperature 1C is 112.8 and 118.2mAh-g-1 respectively. The capacity retention rate is 97.52% after 500 cycles at normal temperature and 90.52% after 300 cycles of high temperature, and all physical and chemical indexes reach the power battery. The results of.XPS analysis showed that the average valence state of manganese was increased by Ni and Co composite doping. The valence states of Mn, Ni and Co in Ni and Co composite doped samples were +4, +2, and +3, respectively.
The results showed that lithium manganate and Ni, Co compound doped lithium manganate were in the middle test. The results showed that lithium manganate had good electrochemical performance at normal temperature. The initial discharge specific capacity of 1C was 115.8mAh. G1, and the capacity retention rate was 89.29% after 500 cycles; Ni, Co compound doped lithium manganate had excellent electrochemical performance, and the first discharge at normal temperature and high temperature 1C was the first discharge. The capacity retention rate after 112.8 and 111.2mAh-g-1500 cycles respectively is 91.22% and 83.81%. cost analysis shows that the process has very good economic benefits.
【學位授予單位】：中南大學
【學位級別】：博士
【學位授予年份】：2014
【分類號】：TM912

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