本文選題：鈉離子電池 + NaV_6O_(15)��； 參考：《合肥工業(yè)大學(xué)》2017年碩士論文

【摘要】：鈉離子電池(SIBs)因具有原料儲(chǔ)量豐富,價(jià)格低廉,安全性高等優(yōu)點(diǎn)而備受青睞。其中尋找一種無毒、低成本、高比容量、結(jié)構(gòu)穩(wěn)定的正極材料是發(fā)展SIBs必經(jīng)之路。本論文以此為出發(fā)點(diǎn),對(duì)釩酸鈉及鐵氰化鐵兩種SIBs正極材料進(jìn)行研究。氧化物型正極材料釩酸鈉(NaV_6O_(15))因具備較大的Na+脫嵌空隙和優(yōu)異的電子電導(dǎo)而受到廣泛關(guān)注。為了進(jìn)一步改善其電化學(xué)性能,本研究一方面通過PVP調(diào)控形貌合成NaV_6O_(15)納米棒,另一方面采用一步水熱法制備NaV_6O_(15)/C復(fù)合電極材料。另一種含氰根配位的普魯士藍(lán)類似物(FeFe(CN)_6)因具有獨(dú)特的三維開放式框架結(jié)構(gòu),較高的理論比容量,合成方法簡(jiǎn)單等優(yōu)勢(shì)而成為新型SIBs正極材料。本研究對(duì)比了溶液共沉淀法和單一源沉淀法制備不同質(zhì)量的FeFe(CN)_6電化學(xué)性能,并探討Na+濃度對(duì)其影響。主要取得如下研究成果:1.采用PVP輔助水熱法成功制備NaV_6O_(15)納米棒,探討了 PVP含量對(duì)NaV_6O_(15)形貌及性能的影響。其中添加0.1 g PVP可獲得長(zhǎng)1～2um,寬～100 nm尺寸均一的納米棒,且電化學(xué)性能最佳:在20mAg-1、1.5-3.8V下,首次放電比容量為157 mAh g-1,20次循環(huán)后的容量保持率為71.38%,即使在200 mA g-1高倍率下,仍能釋放121mAhg-1。此外,降低放電深度,在2.0-3.8V內(nèi)測(cè)得2.69/2.40V氧化/還原峰,且樣品的放電比容量為113 mAh g-1,循環(huán)50次后的容量保持率為86.55%,表現(xiàn)出較好的倍率循環(huán)性和高比容量性。交流阻抗法計(jì)算Na+循環(huán)前后的擴(kuò)散速率分別為3.46× 10-12和2.71 × 10-12 cm2 s-1,并結(jié)合NaV_6O_(15)的態(tài)密度計(jì)算,結(jié)果表明NaV_6O_(15)具有較好的離子電導(dǎo)和電子電導(dǎo)。2.以葡萄糖為碳源,采用一步水熱法制備500 nmNaV_6O_(15)/C納米棒復(fù)合材料,探討了C含量對(duì)材料性能的影響。電化學(xué)性能隨C含量的增加先增后減,當(dāng)添加15.67%C時(shí)性能最佳:樣品包覆一層4 nm均勻厚度的無定型碳層,該碳層不僅抑制了 NaV_6O_(15)晶粒的長(zhǎng)大,還提高了它的電子電導(dǎo)率。在20、200 mA g-1下,首次放電比容量分別為169.03、145.8 mAh g-1,且?guī)靷愋示?0%以上。3.以FeCl_3、K_3Fe(CN)_6為原料,采用溶液共沉淀法制備500 nm FeFe(CN)_6納米顆粒。盡管在高倍率(≥5 C)下的容量?jī)H為理論比容量的19%,但0.1 C倍率時(shí)的首次放電比容量為115.467 mA h g-1 200次循環(huán)后的容量保持率為63%,表現(xiàn)出優(yōu)異的循環(huán)性能。而以K_3Fe(CN)_6為單離子源,Na2S203輔助合成150-250nm,晶格較完美的FeFe(CN)_6納米立方塊,在0.1 C下的充/放電比容量為125.12/124.72 mA h g-1,首次庫(kù)倫效率高達(dá)95.6%,且以0.5C倍率循環(huán)100次后的容量保持率為94%。5 C、10C及20 C倍率下的比容量分別為103.24、100.81和85.87 mAh g-1,表現(xiàn)出優(yōu)良的倍率循環(huán)性能。此外增大Na+濃度有利于提高FeFe(CN)_6的放電容量,低倍率下最高可達(dá)134.689 mAh g-1。4.采用第一性原理和非原位XRD探討Fe_3+在3d軌道的充放電機(jī)制。循環(huán)伏安曲線中3.68/3.46 V氧化還原峰對(duì)應(yīng)與C相鄰的低自旋FeLS2+/FeLs3+嵌鈉反應(yīng):FeHS3+[FeLS3+(CN)_6|(?)NaFeHS3+[FeLS2+(CN)_6],而 3.08/2.81 V 峰則對(duì)應(yīng)與 N 相連的高自旋 FeHS2+/FeHS3+嵌鈉反應(yīng):NaFeHS3+[FeLS2+(CN)_6](?)Na2FeHS2+[FeLS2+(CN)_6]。非原位XRD結(jié)果表明在充放電過程中材料的結(jié)構(gòu)很穩(wěn)定,有利于Na+的可逆脫嵌。
[Abstract]:Sodium ion battery (SIBs) is favored because of its rich material reserves, low price and high safety. It is a necessary way to find a nontoxic, low cost, high specific capacity, and stable structure. This paper is the starting point for the study of two SIBs positive materials of sodium vanadate and ferricyanide. Sodium vanadate (NaV_6O_ (15)) of the type cathode material has been widely concerned for its large Na+ inlay gap and excellent electronic conductance. In order to further improve its electrochemical performance, this study on the one hand synthesis of NaV_6O_ (15) nanorods by PVP morphology, on the other hand, uses one step hydrothermal method to prepare NaV_6O_ (15) /C composite electrode material. The Prussian blue analogue containing cyanogen ligand (FeFe (CN) _6) has become a new SIBs cathode material for its unique three-dimensional open frame structure, higher theoretical ratio and simple synthesis method. This study compared the electrochemical properties of FeFe (CN) _6 with different mass by solution co precipitation and single source precipitation, and discussed Na. The main results are as follows: 1. the NaV_6O_ (15) nanorods were successfully prepared by PVP assisted hydrothermal method, and the effect of PVP content on the morphology and properties of NaV_6O_ (15) was investigated. The addition of 0.1 g PVP can obtain a nanoscale rod with a length of 1 to 2um and a wide to 100 nm, and the electrochemical performance is the best: under 20mAg-1,1.5-3.8V, the first The capacity retention rate of the secondary discharge ratio of 157 mAh g-1,20 was 71.38%. Even at the high rate of 200 mA g-1, 121mAhg-1. could still be released, and the discharge depth was reduced. The 2.69/2.40V oxidation / reduction peak was measured in 2.0-3.8V, and the discharge ratio of the sample was 113 mAh g-1, and the capacity retention rate after 50 cycles was 86.55%. The diffusion rate of the Na+ cycle was 3.46 * 10-12 and 2.71 x 10-12 cm2 S-1 respectively before and after the AC impedance method. The results showed that NaV_6O_ (15) had better ionic conductance and electron conductance.2. with glucose as carbon source, and 500 nm was prepared by one step hydrothermal method. NaV_6O_ (15) /C nanorod composite was used to investigate the effect of C content on the properties of materials. The electrochemical performance increased first and then decreased with the increase of C content. When 15.67%C was added, the performance was the best: the sample coated an amorphous carbon layer with a uniform thickness of 4 nm. The carbon layer not only inhibited the growth of NaV_6O_ (15) grain, but also increased its electronic conductivity. At the same time, the electron conductivity was increased. Under 200 mA g-1, the initial discharge specific capacity is 169.03145.8 mAh g-1, and the efficiency of Kulun is more than 80%.3. with FeCl_3, K_3Fe (CN) _6 as raw material and the solution co precipitation method is used to prepare 500 nm FeFe nanoparticles. Although the capacity of the high ratio (> 5) is only 19% of the theoretical specific capacity, the capacity of the first discharge ratio at the 0.1 ratio is the first discharge capacity. The capacity retention rate of 115.467 mA h g-1 200 cycles is 63%, showing excellent cycling performance. With K_3Fe (CN) _6 as a single ion source, Na2S203 assisted synthesis of 150-250nm, and the perfect lattice of FeFe (CN) _6 nano cubic block in lattice, and the capacity of charge / discharge ratio of 125.12 under 0.1 C. The first Kulun efficiency is up to 95.6% After 100 cycles, the capacity retention rate is 94%.5 C, the specific capacity of 10C and 20 C multiplier is 103.24100.81 and 85.87 mAh g-1, respectively, showing excellent multiplier cycle performance. In addition, increasing Na+ concentration is beneficial to improve the discharge capacity of FeFe (CN) _6, and the highest rate of 134.689 mAh is up to the first principle and non in situ exploration. The redox peak of the 3.68/3.46 V in the cyclic voltammetry curve corresponds to the low spin FeLS2+/FeLs3+ sodium reaction adjacent to the C: FeHS3+[FeLS3+ (CN) _6| (?) NaFeHS3+[FeLS2+ (CN) _6]. The results of FeLS2+ (CN) _6]. in situ XRD show that the structure of the material is stable during charging and discharging, which is conducive to the reversible deintercalation of Na+.
【學(xué)位授予單位】：合肥工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TM912

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