本文選題：磷酸鐵鋰 + 單分散��； 參考：《蘭州大學(xué)》2014年碩士論文

【摘要】：鋰離子電池是新一代的綠色電源,它具有比能量大、工作電壓高、工作溫度范圍寬、循環(huán)壽命長(zhǎng)、無(wú)記憶效應(yīng)、自放電小等優(yōu)點(diǎn),已被廣泛應(yīng)用于多種便攜式電子產(chǎn)品的移動(dòng)電源以及電動(dòng)車和混合動(dòng)力電動(dòng)車等的電源。 鋰離子電池中,其正極材料對(duì)鋰離子蓄電池性能起到了關(guān)鍵性的作用。傳統(tǒng)的鋰離子蓄電池的正極材料主要集中在鋰的過(guò)渡金屬氧化物如LiMO2Ni、Mn)和LiMn2O4。但LiCoO2成本較高、毒性較大、耐過(guò)充性差、資源貧乏；LiNiO2熱穩(wěn)定性差、制備比較困難；LiMn2O4雖然資源豐富、對(duì)環(huán)境無(wú)毒、價(jià)格便宜,但其容量較低,高溫穩(wěn)定性能和循環(huán)穩(wěn)定性能較差。因此,研發(fā)新型的鋰離子正極材料成為目前的重點(diǎn)和熱點(diǎn)。 自從Padhi的研究小組在1997年提出鋰離子電池的正極材料磷酸鐵鋰以來(lái),具有橄欖石結(jié)構(gòu)的LiFePO4材料作為鋰離子電池的正極材料,由于其具有低的成本、毒性小、原材料來(lái)源比較豐富和適應(yīng)高溫工作環(huán)境等優(yōu)點(diǎn)而成為目前的研究熱點(diǎn)之一。但是,LiFePO4在實(shí)際的應(yīng)用中還存在下列不足：第一,較低的電子傳導(dǎo)率(10-7～10-9S·cm-1),這導(dǎo)致在鋰離子電池的充放電過(guò)程中,電子不能及時(shí)的轉(zhuǎn)移,產(chǎn)生了較大容抗,從而影響了磷酸鐵鋰的電化學(xué)性能；第二,較小的Li+擴(kuò)散速率(1.8×10-16～2.2×10-14cm2·s-1),這導(dǎo)致在鋰離子電池的充放電過(guò)程中,鋰離子脫嵌滯后,從而降低了磷酸鐵鋰的容量性能和倍率性能；第三,較低的振實(shí)密度(一般商用1.0g·cm-3左右),導(dǎo)致磷酸鐵鋰體積比能量較低。 可以使用三種方法去解決上述問(wèn)題。第一,通過(guò)包覆導(dǎo)電層(碳、納米銅和納米銀)和金屬離子摻雜(Ni+)來(lái)提高電子導(dǎo)電率鋰離子擴(kuò)散速率。第二,通過(guò)調(diào)節(jié)合成參數(shù)來(lái)減小顆粒尺寸,這樣可以縮短鋰離子的擴(kuò)散距離,進(jìn)而提高擴(kuò)散速率。第三,通過(guò)制備球形的顆粒來(lái)提高振實(shí)密度。 本碩士論文主要包括下面三個(gè)方面的內(nèi)容： (1)使用分析純的FeSO4·7H2O, H3PO4和LiOH·H2O為原料,檸檬酸為絡(luò)合劑,通過(guò)水熱合成法制備了具有孔隙結(jié)構(gòu)的單分散微米球形磷酸鐵鋰。在制備過(guò)程中,檸檬酸的加入起到非常關(guān)鍵的作用；研究了鐵離子的濃度,反應(yīng)溫度,反應(yīng)時(shí)間,檸檬酸和磷酸用量對(duì)磷酸鐵鋰顆粒形貌的影響,通過(guò)調(diào)節(jié)以上參數(shù)最終成功制備了由片狀納米顆粒堆積而成的微米尺度單分散球形磷酸鐵鋰顆粒,掃描電子顯微鏡的結(jié)果表明：微米球的平均粒徑尺寸是18μm,而構(gòu)成球形結(jié)構(gòu)的片狀顆粒的厚度是50nm；這種球形顆粒具有較高的比表面積(15.3m2g-1),因此,增大了顆粒與電解液的接觸面積,從而大幅度的提高材料的電化學(xué)性能；這種合成方法為其他由片狀顆粒堆積而成的球形顆粒的制備提供了新的方向。 (2)Ni+摻雜量(LiFe1-xNixPO4,x=0.075,0.100,0.125,0.150,0.175)對(duì)(1)中制備的LiFePO4球形顆粒形貌的影響。Ni+的摻雜量影響了球形顆粒的形貌和組成球形顆粒的納米片的疏密程度。當(dāng)x=0.075,0.100時(shí),保持了球形顆粒的形貌；當(dāng)x=0.125,0.150時(shí),顆粒形貌呈現(xiàn)類球形；當(dāng)x=0.175時(shí),大部分球形顆粒的形貌被破壞。 (3)采用溶膠-凝膠法,通過(guò)Fe(NO3)3-9H2O和H3PO4混合溶液陳化制備得到單分散球形納米FePO4-2H2O粉體。發(fā)現(xiàn)隨著FeNO3-9H2O濃度的增大,制得樣品的顆粒尺寸有變小的趨勢(shì),分散性沒有明顯的變化：隨著保溫時(shí)間的延長(zhǎng),制得樣品的顆粒尺寸有沒有明顯的變化,分散性和均一性變好；以FePO4-2H2O為前驅(qū)體(?)LiOH·H2O混合在650℃氬氣(95%)和氫氣(5%)保護(hù)下煅燒12h合成了納米單分散球形LiFePO4粉體。
[Abstract]:The lithium ion battery is a new generation of green power supply , which has the advantages of large specific energy , high working voltage , wide working temperature range , long cycle life , no memory effect , small self - discharge , and the like , and has been widely applied to the mobile power supply of various portable electronic products and the power supply of electric vehicles and hybrid electric vehicles .

The positive electrode material of the lithium ion battery plays a key role in the performance of the lithium ion battery . The positive electrode material of the traditional lithium ion battery is mainly concentrated in the transition metal oxide ( such as LiMO2Ni , Mn ) and limn4 , but the cost is higher , the toxicity is large , the overcharge resistance is poor , and the resource is poor ;
poor thermal stability of linioO2 and difficult preparation ;
Although the resources are abundant , the environment is non - toxic , the price is low , but the capacity is low , the high - temperature stability and the cycle stability can be poor . Therefore , the research and development of the novel lithium - ion cathode material becomes the current focus and hot spot .

Since Padhi ' s research team put forward the positive pole material lithium iron phosphate of Li - ion battery in 1997 , LiFePO4 material with olivine structure has become one of the current research hotspots due to its low cost , low toxicity , abundant raw material source and adaptability to high - temperature working environment . However , LiFePO4 also has the following disadvantages in practical application : first , lower electron conductivity ( 10 - 7 - 10 - 9S 路 cm - 1 ) , which leads to the failure of timely transfer of electrons in the charge and discharge process of lithium ion battery , thus affecting the electrochemical performance of lithium iron phosphate .
The second , smaller Li + diffusion rate ( 1.8 脳 10 - 16 ~ 2.2 脳 10 - 14 cm ~ 2 路 s - 1 ) , which leads to the lithium ion deintercalation lag during the charge and discharge of the lithium ion battery , thus reducing the capacity and rate performance of lithium iron phosphate .
Third , lower tap density ( typically around 1.0 g 路 cm - 3 ) results in a lower volume of lithium iron phosphate than energy .

First , by coating the conductive layer ( carbon , nano copper and nano silver ) and metal ion doping ( Ni + ) to improve the electron conductivity lithium ion diffusion rate . Second , by adjusting the synthesis parameters to reduce the particle size , the diffusion distance of lithium ions can be shortened , and the diffusion rate can be improved . Thirdly , the solid density can be improved by preparing spherical particles .

This Master ' s thesis mainly includes the following three aspects :

( 1 ) using analytically pure FeSO4.7H2O , H3PO4 and LiOH.H2O as raw materials , citric acid as a complexing agent , and preparing monodisperse micron spherical lithium iron phosphate with pore structure by hydrothermal synthesis .
The effects of concentration of iron ions , reaction temperature , reaction time , citric acid and phosphoric acid on the morphology of lithium iron phosphate particles were studied .
The spherical particles have higher specific surface area ( 15.3 m2g - 1 ) , therefore , the contact area between the particles and the electrolyte is increased , so that the electrochemical performance of the material is greatly improved ;
The synthetic method provides a new direction for the preparation of other spherical particles which are piled up by sheet - shaped particles .

( 2 ) The influence of Ni + doping amount ( LiFePO4 1 - xNixPO4 , x = 0.075 , 0.100 , 0.125 , 0.150 , 0.175 ) on the morphology of spherical particles of LiFePO4 prepared in ( 1 ) . The doping amount of Ni + affected the morphology of spherical particles and the density of spherical particles .
When x = 0.125 , 0.150 , the morphology of the particles is spherical ;
When x = 0.175 , the morphology of most spherical particles was destroyed .

( 3 ) By the sol - gel method , the monodisperse spherical nano FePO4 - 2H2 powder was prepared by aging of Fe ( NO3 ) 3 - 9H2O and H3PO4 . It was found that with the increase of the concentration of FeNO3 - 9H2O , the particle size of the prepared sample was smaller .
Nano monodisperse spherical LiFePO4 powder was synthesized by calcining at 650 鈩，

本文編號(hào)：2023828