【摘要】：隨著人類文明的不斷進(jìn)步和全球社會(huì)的經(jīng)濟(jì)發(fā)展，人類對(duì)各類新能源的需求與消耗與日俱增，而新能源的儲(chǔ)藏、轉(zhuǎn)移和利用，都需要以高性能的儲(chǔ)能設(shè)備作為支撐。鋰離子電池作為新一代儲(chǔ)能設(shè)備，以其工作電壓高、自放電小、無記憶效應(yīng)、環(huán)保等優(yōu)點(diǎn)成為移動(dòng)電源的首選。磷酸鐵鋰作為最有前途的鋰離子電池正極材料之一，具有價(jià)格低廉、容量高、壽命長(zhǎng)、熱穩(wěn)定性好等諸多優(yōu)點(diǎn)。但是，，LiFePO4的電子電導(dǎo)率和鋰離子擴(kuò)散速率很低，導(dǎo)致其實(shí)際比容量不高且高倍率性能很差，極大地限制了該電極材料在動(dòng)力電池領(lǐng)域的大規(guī)模應(yīng)用。目前，提高該材料電化學(xué)性能的改性方法主要有三種：減小顆粒尺寸，晶體摻雜和表面修飾。本論文采用水熱合成法制備了LiFePO4/C材料，并通過離子摻雜對(duì)晶體進(jìn)行改性。 首先，利用正交試驗(yàn)法研究了Ni2+、Mn2+摻雜實(shí)驗(yàn)中摻雜濃度、水熱反應(yīng)溫度和水熱反應(yīng)時(shí)間對(duì)LiFePO4/C電化學(xué)性能的影響。結(jié)果表明，以0.1C充放電倍率下材料的性能為試驗(yàn)指標(biāo)時(shí)，鎳摻雜濃度對(duì)材料性能影響最大，在最佳合成工藝條件下合成的材料，首次放電比容量為150.9mAh g-1；錳摻雜正交試驗(yàn)中，試驗(yàn)各因素主要影響了材料的高倍率性能，其中水熱反應(yīng)溫度影響最大，在最優(yōu)合成工藝下，材料的10C充放電倍率下比容量為127mAh g-1。 其次，研究了鎳摻雜改性磷酸鐵鋰的過程中，水熱反應(yīng)溫度對(duì)于摻雜過程和材料性能的影響。通過ICP、FTIR等方法研究發(fā)現(xiàn)，水熱反應(yīng)溫度影響了摻雜離子鎳在產(chǎn)品晶格中的含量，同時(shí)影響了摻雜后晶格內(nèi)的錯(cuò)位情況。當(dāng)水熱反應(yīng)溫度高于210℃時(shí)，鎳摻雜能對(duì)材料起到積極的改性作用；水熱反應(yīng)溫度為240℃時(shí)，材料具有最優(yōu)異的電化學(xué)性能：20C充放電倍率下比容量為98.5mAh g-1，且循環(huán)性能也得到一定的改善。 最后，進(jìn)一步考察了高價(jià)態(tài)的摻雜離子如Al3+和Ti4+對(duì)磷酸鐵鋰摻雜改性過程中溫度的影響。結(jié)果顯示，高價(jià)態(tài)的離子在水熱環(huán)境中由于水解作用，影響了水熱反應(yīng)中晶體的生長(zhǎng)環(huán)境，進(jìn)而對(duì)材料的純度、產(chǎn)品的形貌和尺寸產(chǎn)生影響，而隨著反應(yīng)溫度的升高，這一影響逐漸減弱。然而，Al3+和Ti4+摻雜后材料的電化學(xué)性能并未得到改善。
[Abstract]:With the progress of human civilization and the economic development of global society, the demand and consumption of all kinds of new energy are increasing day by day, and the storage, transfer and utilization of new energy need to be supported by high-performance energy storage equipment. As a new generation of energy storage equipment, lithium ion battery has become the first choice of mobile power supply because of its high working voltage, small self-discharge, no memory effect, environmental protection and so on. As one of the most promising cathode materials for lithium ion batteries, lithium iron phosphate has many advantages, such as low price, high capacity, long life, good thermal stability and so on. However, the electronic conductivity and lithium ion diffusion rate of LiFePO4 are very low, which leads to its low specific capacity and poor performance of high rate, which greatly limits the large-scale application of the electrode material in the field of power battery. At present, there are three main ways to improve the electrochemical properties of the material: reduction of particle size, crystal doping and surface modification. In this paper, LiFePO4/C materials were prepared by hydrothermal synthesis, and the crystals were modified by ion doping. Firstly, the effects of doping concentration, hydrothermal reaction temperature and hydrothermal reaction time on the electrochemical properties of Ni2 and Mn2 were studied by orthogonal test. The results show that the nickel doping concentration has the greatest influence on the properties of the material when the performance of the material under 0.1 C charge-discharge ratio is taken as the test index, and the first discharge specific capacity of the material synthesized under the optimum synthetic conditions is 150.9mAh g-1. In the manganese-doped orthogonal experiment, the experimental factors mainly affect the high rate performance of the material, and the hydrothermal reaction temperature has the greatest influence on the material. Under the optimum synthesis process, the specific capacity of the material is 127mAh g-1 at the charge / discharge rate of 10C. Secondly, the effect of hydrothermal reaction temperature on the doping process and properties of nickel doped lithium ferric phosphate was studied. By means of ICP,FTIR and other methods, it is found that the hydrothermal reaction temperature affects the content of doped nickel in the product lattice and the dislocation in the doped crystal lattice. When the hydrothermal reaction temperature is higher than 210 鈩

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