發(fā)布時(shí)間：2018-01-12 02:36

  本文關(guān)鍵詞：層狀Ni-Co-Mn基正極材料在電化學(xué)儲(chǔ)能中的研究與應(yīng)用　出處：《武漢大學(xué)》2014年博士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 鋰離子二次電池 鈉離子二次電池 流變相法 層狀正極材料 粘接劑 改性

【摘要】：在科技技術(shù)日新月異的今天,鋰離子二次電池的應(yīng)用已經(jīng)逐漸從小型電子產(chǎn)品朝大規(guī)模動(dòng)力型產(chǎn)品方向發(fā)展,但目前商業(yè)應(yīng)用的鋰離子電池還不能完全滿足大規(guī)模動(dòng)力型產(chǎn)品的需求,因此,我們需要開發(fā)高能量、高功率、安全性好的鋰離子電池。在鋰離子二次電池中,正極材料對(duì)其整體電化學(xué)性能起著至關(guān)重要的作用,所以開發(fā)新型正極材料和改善已有正極材料的綜合性能是當(dāng)前的主要任務(wù)。相對(duì)于鈷酸鋰材料,Li-Ni-Co-Mn-O層狀材料作為鋰離子電池正極材料具有較高的比容量、優(yōu)異的循環(huán)性能、適宜的電壓平臺(tái)、較低的工藝成本、穩(wěn)定的熱安全性等特點(diǎn),因此,其成為近年來(lái)研究的熱點(diǎn)。 本論文從應(yīng)用研究的角度,對(duì)計(jì)量比Ni-Co-Mn基層狀材料及富鋰固溶體Ni-Co-Mn基層狀材料在鋰離子電池中的應(yīng)用進(jìn)行了探討研究,重點(diǎn)針對(duì)這類材料在倍率性、安全性等方面的不足,希望通過(guò)各種改性手段的應(yīng)用使其更好發(fā)揮它的實(shí)用價(jià)值,真正應(yīng)用到鋰離子二次電池中。此外,我們對(duì)Na-Ni-Co-Mn基層狀材料的合成及在鈉離子二次電池中的應(yīng)用進(jìn)行了初步探究。綜上,本論文的研究工作主要分為以下幾個(gè)部分： (1) LiNixCoyMn1-x-yO2材料的性能研究 采用流變相法合成了三種計(jì)量比Ni-Co-Mn基層狀材料LiNi1/3Co1/3Mn1/3O2、 LiNi0.6Co0.2Mn0.2O2和LiNi0.4Co0.2Mn0.4O2,將商業(yè)化的Sb203粉末分別與三種計(jì)量比層狀材料直接機(jī)械混合得到混合材料。其中以LiNi1/3Co1/3Mn1/3O2為重點(diǎn),探討分析了Sb203粉末修飾活性材料前后的電化學(xué)性能和熱安全性能。采用粉末衍射光譜儀(XRD)、掃描電子顯微鏡(SEM)及透射電子顯微鏡(TEM)來(lái)檢測(cè)和觀察樣品的結(jié)構(gòu)和表面形貌。根據(jù)充放電數(shù)據(jù)顯示,混合材料Sb2O3/LiNixCoyMn1-x-yO2的循環(huán)性能、倍率性能和熱安全性能均比原材料LiNixCoyMn1-x-yO2有明顯改進(jìn)。通過(guò)對(duì)比混合前后LiNi1/3Co1/3Mn1/3O2材料的充放電曲線可以發(fā)現(xiàn),循環(huán)過(guò)程中混合材料的電極極化明顯減小。進(jìn)一步的阻抗實(shí)驗(yàn)表明,相對(duì)于LiNi1/3Co1/3Mn1/3O2材料電極,混合材料Sb2O3/LiNi1/3Co1/3Mn1/3O2電極具有更小的SEI膜阻抗值Rf和電荷轉(zhuǎn)移阻抗值Rct。我們猜測(cè)混合后材料的性能改進(jìn)主要是由于Sb203的存在抑制了電解液與正極材料間的消極反應(yīng),減少有害物質(zhì)的生成,穩(wěn)定了正極片表層的SEI膜。另外,根據(jù)Sb203不同加入方式的比較,我們認(rèn)為使用Sb203包覆的隔膜將對(duì)電池性能起到相似的積極作用。 (2)Li1.182Ni0.182Co0.091Mn0.545O2的研究 在700-900℃C的不同煅燒溫度條件下,使用流變相法合成了富鋰固溶體材料Li1.182Ni0.182Co0.091Mn0.545O2。XRD、SEM實(shí)驗(yàn)結(jié)果表明：所得到富鋰固溶體材料具有層狀六面體結(jié)構(gòu),陽(yáng)離子混排度較小,顆粒為亞微米級(jí)。隨著煅燒溫度的升高,所得材料的顆粒粒徑逐漸增大,團(tuán)聚現(xiàn)象明顯減小。同時(shí)充放電曲線顯示,隨著煅燒溫度的逐漸升高,所得材料首周的放電比容量逐漸減小,但材料的容量保持率依次增大。在此基礎(chǔ)上,我們嘗試使用階梯升溫法從600-750-8500C逐步升溫煅燒得到Li1.182Ni0.182Co0.091Mn0.545O2材料。實(shí)驗(yàn)表明,這種改進(jìn)既可以有效的抑制材料顆粒生長(zhǎng)過(guò)大,又可以減小材料顆粒的團(tuán)聚,增強(qiáng)樣品的均一性,并且得到的材料具有相對(duì)較好的電化學(xué)性能。 (3)粘接劑對(duì)Li1.182Ni0.182Co0.091Mn0.545O2電極的影響 以流變相法階梯升溫得到的固溶體材料Li[Li0.182Ni0.182Co0.091Mn0.545]O2為活性物質(zhì),分別使用粘接劑羧甲基纖維素鹽(CMC)、聚偏氟乙烯(PVDF)、海藻酸鈉(SA)制得正極電極片,并且與聚四氟乙烯(PTFE)作為粘接劑制得的電極片進(jìn)行電化學(xué)性能對(duì)比。根據(jù)充放電性能、循環(huán)性能、倍率性能、電壓衰退情況及庫(kù)倫效率等數(shù)據(jù)來(lái)看,我們認(rèn)為相對(duì)于其他幾種粘接劑來(lái)說(shuō),使用海藻酸鈉(SA)作為粘接劑的固溶體電極片具有相對(duì)較優(yōu)的綜合電化學(xué)性能。此外,通過(guò)測(cè)試比較使用不同粘接劑的電極片的膨脹性能及循環(huán)后電極的表面形貌,我們發(fā)現(xiàn)以聚偏氟乙烯(PVDF)為粘接劑制得的富鋰固溶體電極由于吸收了較多的電解液,極片內(nèi)部發(fā)生膨脹,電極表面出現(xiàn)裂紋,從而造成活性材料與導(dǎo)電劑或者電極片與集流體之間接觸不好,影響了電極片的整體導(dǎo)電性,材料的循環(huán)性能逐漸惡化。 (4)Li1.2Ni0.16Co0.08Mn0.56O2的改性研究 采用流變相法合成了富鋰固溶體材料Li1.2Ni0.16Co0.08Mn0.56O2,使用不同濃度的過(guò)硫酸銨溶液對(duì)其進(jìn)行浸泡處理,從而改進(jìn)了Li1.2Ni0.16Co0.08Mn0.56O2材料的首周庫(kù)倫效率及倍率性能。通過(guò)XRD、拉曼光譜及ICP-AES表征了富鋰固溶體材料處理前后的結(jié)構(gòu)變化及元素含量變化。根據(jù)實(shí)驗(yàn)結(jié)果發(fā)現(xiàn),處理后的活性材料保持著基底材料的層狀結(jié)構(gòu)框架,但隨著過(guò)硫酸銨處理濃度的增加,材料中鋰離子的含量有所減少,說(shuō)明有部分鋰離子從材料的結(jié)構(gòu)空間中脫出。根據(jù)XPS數(shù)據(jù)和首周充放電曲線,可以說(shuō)明過(guò)硫酸銨處理后的富鋰固溶體材料中過(guò)渡金屬陽(yáng)離子沒(méi)有發(fā)生明顯的價(jià)態(tài)變化,脫出的鋰離子主要來(lái)自于材料中的Li2MnO3相。使用過(guò)硫酸銨處理后的富鋰固溶體材料雖然初始放電比容量略低,但在隨后的循環(huán)過(guò)程中放電比容量會(huì)逐漸增大,并保持良好的循環(huán)性能。通過(guò)綜合比較,我們認(rèn)為過(guò)硫酸銨使用量為活性材料質(zhì)量的30%-40%時(shí),所得材料的電化學(xué)性能總體最優(yōu)。其中采取30%的過(guò)硫酸銨處理量,得到的最終產(chǎn)物不僅具備優(yōu)異的循環(huán)穩(wěn)定性,而且在4C時(shí)放電比容量仍接近200mAh g-1。 (5)的研究 通過(guò)流變相法在700-900℃的不同煅燒溫度條件下,一步煅燒得到層狀材料NaxNi1/3Co1/3Mn1/3O2,使用XRD和SEM檢測(cè)了所得材料的結(jié)構(gòu)和形貌。SEM實(shí)驗(yàn)和充放電結(jié)果表明,隨著煅燒溫度的逐漸升高,三種材料的顆粒粒徑逐漸增大,形貌由塊狀轉(zhuǎn)變?yōu)槠瑺?首周放電比容量逐漸增大,循環(huán)性能總體較好。其中,900℃煅燒得到的Na-Ni-Co-Mn基材料具有較優(yōu)的電化學(xué)性能。根據(jù)其XRD分析和首周充放電曲線,認(rèn)為900℃煅燒得到的Na-Ni-Co-Mn基層狀材料中鈉元素的含量x小于1,此材料為缺鈉材料。
[Abstract]:In the science and technology change rapidly today, the application of lithium ion secondary battery two has been gradually from small electronic products toward large-scale power product development, but the current lithium ion battery business applications can not fully meet the needs of large-scale power products, therefore, we need to develop a high energy and high power lithium ion battery safety two. In the lithium ion secondary battery, cathode material plays a vital role in the overall electrochemical properties of cathode materials, comprehensive performance so the development of new cathode materials and improve the existing is the main task at present. Compared with the lithium cobalt oxide material, Li-Ni-Co-Mn-O layered materials as cathode materials for lithium ion batteries with high specific capacity. Excellent cycling performance, voltage platform for the process of low cost, stable characteristics, thermal safety etc. Therefore, it has become a research hotspot in recent years.
This paper from the application point of view, the application of layered materials iometric Ni-Co-Mn based layered Li rich material and Ni-Co-Mn based solid solution in lithium ion batteries was studied, focusing on this kind of material in the rate, lack of security and other aspects of the application, hope through a variety of modified methods to make it better its practical value to the real application of lithium ion secondary battery two. In addition, we based on Na-Ni-Co-Mn layered material synthesis and in two sodium ion battery applications were discussed. In conclusion, the research work of this thesis is mainly divided into the following sections:
(1) properties of LiNixCoyMn1-x-yO2 materials
The three kinds of measurement than LiNi1/3Co1/3Mn1/3O2 Ni-Co-Mn based layered materials synthesized by rheological phase method, LiNi0.6Co0.2Mn0.2O2 and LiNi0.4Co0.2Mn0.4O2, Sb203 powder commercial respectively with three kinds of measurement than the direct mixing of layered materials mixed materials. The LiNi1/3Co1/3Mn1 /3O2 as the key to investigate the electrochemical properties and thermal safety performance of Sb203 powder before and after modification of the activated material analysis the powder diffraction spectrometer. (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) structure and surface morphology to detect and observe the samples. According to the charge and discharge data show that the cycle performance of the hybrid Sb2O3/LiNixCoyMn1-x-yO2 materials, heat rate performance and safety performance are better than the original LiNixCoyMn1-x-yO2 material. Through the charging and discharging LiNi1/3Co1/3Mn1/3O2 curve of the contrast of materials before and after mixing can be found in the process of mixing cycle The electrode polarization material significantly reduced. Further experiments show that the impedance of electrode materials, compared with LiNi1/3Co1/3Mn1/3O2, the resistance of SEI hybrid material Sb2O3/LiNi1/3Co1/3Mn1/3O2 electrode has a smaller value of Rct. after mixing we guess improvement of material performance is mainly due to the presence of Sb203 inhibited the negative reaction of electrolyte and cathode materials between Rf and charge transfer resistance, reduce the generation of harmful the material, stable SEI film cathode surface. In addition, according to the Sb203 of different adding methods of comparison, we believe that the use of diaphragm coated Sb203 the positive effect to similar to the battery performance.
(2) research on Li1.182Ni0.182Co0.091Mn0.545O2
Different calcination temperature conditions at 700-900 DEG C, using rheological phase synthesis of lithium rich solid solution materials Li1.182Ni0.182Co0.091Mn0.545O2.XRD, SEM experimental results show that the lithium rich solid solution material having a layered hexahedral structure, cation mixing of small particles is sub micron. With the increase of calcination temperature, the materials of the the particle size increases, agglomeration significantly reduced. At the same time the charge discharge curves showed that gradually increased with the calcination temperature, the first week of the discharge specific capacity of the material decreases, but the capacity retention rate of the materials increases. On this basis, we try to use the ladder temperature method from 600-750-8500C gradually heating and calcining to obtain Li1.182Ni0.182Co0.091Mn0.545O2 material. Experiments show that this improvement can not only inhibit the growth of material particles is too large, and can reduce material particles, enhance the sample The homogenization of the products and the obtained materials have relatively good electrochemical performance.
(3) the effect of the adhesive on the Li1.182Ni0.182Co0.091Mn0.545O2 electrode
The rheological phase method of step temperature obtained solid solution material Li[Li0.182Ni0.182Co0.091Mn0.545]O2 as active material, respectively using adhesive carboxymethyl cellulose salt (CMC), polyvinylidene fluoride (PVDF), sodium alginate (SA) to prepare a positive electrode sheet, and polytetrafluoroethylene (PTFE) as electrode adhesive prepared for electrochemical performance comparison according to the charge and discharge performance, cycle performance, rate capability, voltage and efficiency decline of Kulun data, we believe that compared to other kinds of binders, using sodium alginate (SA) as the adhesive solid solution electrode with electrochemical properties are relatively better. In addition, through the test electrode using the comparison of different adhesives after the cycle expansion performance and electrode surface morphology, we found that using polyvinylidene fluoride (PVDF) as the adhesive prepared by lithium rich solid solution electrode by absorption The more electrolytes, the internal expansion of the electrode plates, the cracks on the electrode surface, resulting in a bad contact between the active material and conductive agent or electrode and collector, which affects the overall conductivity of the electrode, and the cycling performance of the material gradually deteriorates.
(4) research on the modification of Li1.2Ni0.16Co0.08Mn0.56O2
The lithium rich solid solution material Li1.2Ni0.16Co0.08Mn0.56O2 was synthesized by rheological phase method, using different concentrations of ammonium persulfate were soaked in the first week of Kulun so as to improve the efficiency and rate performance of Li1.2Ni0.16Co0.08Mn0.56O2 materials. By XRD, Raman spectroscopy and ICP-AES characterization of the lithium rich solid solution changes and structural change of element content before and after the body material processing. According to the experimental results, the active material after treatment maintained a layered structure of substrate material framework but with the increase of ammonium persulfate, the concentration of lithium ion content in the material decreased, indicating that some lithium ion to emerge from the spatial structure of the material. According to the XPS data and the first charge discharge curve. Can be explained with ammonium sulfate after lithium rich solid solution materials in transition metal cation valence changes did not occur, lithium ion becomes the main. From the material in the Li2MnO3 phase. Used with ammonium sulfate after lithium rich solid solution materials although the initial discharge capacity is slightly lower, but the discharge during the subsequent cycle capacity will gradually increase, and maintain a good cycle performance. By comparison, we think that the amount of ammonium persulfate used as active materials the quality of 30%-40%, the electrochemical properties of the material. The overall optimal income taken with ammonium sulfate 30%, finally the product not only has excellent cycle stability and discharge capacity in 4C than 200mAh is still close to g-1.
(5) research
The rheological phase method at 700-900 DEG C under different calcination temperature, calcination step layered materials NaxNi1/3Co1/3Mn1/3O2, XRD and SEM were detected using the materials of the structure and morphology of.SEM and charge discharge experiment results show that when increasing the calcination temperature, three kinds of material particle size increases, the morphology of the massive transformation for the first week of flake, the discharge capacity increases gradually, the cycle performance is generally good. Among them, Na-Ni-Co-Mn based materials 900 C calcined has better electrochemical performance. According to the XRD analysis and the first week of the charge discharge curves, X sodium content of Na-Ni-Co-Mn based layered materials of 900 DEG C calcined in this less than 1. Material for sodium deficient material.

【學(xué)位授予單位】：武漢大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：O646;TM912

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1 韓增輝;層狀Ni-Co-Mn基正極材料在電化學(xué)儲(chǔ)能中的研究與應(yīng)用[D];武漢大學(xué);2014年

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1 李文珍;Ni-Co、Ni-Co-Mn電極的制備及其析氧性能研究[D];湖南大學(xué);2012年

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本文編號(hào)：1412355