本文關鍵詞：釩系正極材料的制備及其儲鈉性能的研究　出處：《南開大學》2016年碩士論文　論文類型：學位論文

  更多相關文章： 鈉離子電池 正極材料 釩酸鈉 五氧化二釩 電化學性能

【摘要】：近年來,鈉離子電池因鈉元素分布廣泛和價格低廉而受到越來越多的關注。但是,由于鈉離子的半徑較大,使其難以在循環(huán)過程中快速的脫嵌。缺少性能優(yōu)異的儲鈉材料,尤其是正極材料是鈉離子電池發(fā)展和商業(yè)化的瓶頸。目前鈉離子電池正極材料的研究主要集中在過渡金屬氧化物,聚陰離子型化合物等材料上,但是,這些材料的容量較低,一般限制在90-130 mAh g-1。因此,尋找新型高性能的鈉離子電池正極材料極為重要。釩基氧化物及其衍生物以其多變的結構,較高的容量,豐富的資源和便宜的價格受到越來越多的關注。但是釩系材料存在導電性差,釩易在有機電解液中溶解等問題,造成其循環(huán)穩(wěn)定性和高倍率性能不足。本文針對以上問題,利用包覆導電聚合物,合理設計結構等手段對釩系材料進行了改性研究,具體內容和研究成果如下:1.采用化學氧化聚合的方法合成了聚吡咯(PPy)包覆的NaV3O8納米片。首次將NaV3O8@PPy納米復合材料用作鈉離子電池的正極,與純NaV3O8相比,表現(xiàn)出明顯提高的循環(huán)與倍率性能。進一步對PPy包覆量進行了優(yōu)化,發(fā)現(xiàn)NaV3O8@10%PPy的樣品具有最優(yōu)異的儲鈉性能。在1.5-4.0 V,80 mA g-1的條件下,該電極循環(huán)60周后,仍能保持99 mAh g-1的放電容量,遠遠大于純NaV3O8樣品的放電容量52 mAh g-1。利用電化學和XPS技術,對NaV3O8的儲鈉機理進行研究,結果表明放電中的兩個平臺都對應著V5+向V4+的轉變。2.采用靜電紡絲的方法制備了一維多孔的V2O5納米纖維(F-V2O5)。對煅燒條件進行了優(yōu)化,確定最佳煅燒條件為:在Ar中,煅燒溫度500℃,升溫速率1℃/min,預煅燒時間2 h,使材料結構穩(wěn)定;然后在空氣中,煅燒溫度400℃,升溫速率1℃/min,煅燒時間30 min,使紡絲前驅體充分氧化為V2O5。當將F-V2O5納米纖維用作鈉離子電池正極時,其表現(xiàn)出優(yōu)異的電化學性能。與商業(yè)化的B-V2O5相比,F-V2O5的循環(huán)穩(wěn)定性和倍率性能都有了明顯的提升。在1.5-4.0 V,40 mA g-1的條件下,F-V2O5電極循環(huán)50次后,仍能保持89.5 mAh g-1的放電比容量,遠遠大于B-V2O5的32.7 mAh g-1的放電容量。
[Abstract]:In recent years, the sodium ion battery has attracted more and more attention because of Na wide distribution and low price. However, the sodium ion radius is larger, making it difficult to quickly in the circulation process. The lack of deintercalate sodium storage material with excellent properties, especially the cathode materials of sodium ion battery is the bottleneck of the development and commercialization of at present the study of cathode materials of sodium ion battery is mainly concentrated in transition metal oxide, poly anionic compounds and other materials, but these materials lower capacity is generally limited to 90-130 mAh g-1. so, looking for a new high performance cathode materials of sodium ion battery is very important. Vanadium oxide and its derivatives with its varied the structure, high capacity, rich resources and cheap prices has attracted more and more attention. But the vanadium material has poor conductivity, easy to dissolve in organic electrolyte of vanadium and other problems caused by The cycle stability and high rate performance. Aiming at the above problem, the use of coated conductive polymer, reasonable structure design method research on modification of vanadium materials, concrete contents and results are as follows: 1. by chemical oxidative polymerization of polypyrrole synthesized (PPy) NaV3O8 nanosheets coated NaV3O8@PPy cathode for the first time. Nano composite materials used for sodium ion batteries, compared with pure NaV3O8, showed the cycle and rate performance significantly improved. Further PPy coating amount were optimized, found that the NaV3O8@10%PPy sample has the best performance of sodium storage. In 1.5-4.0 V, 80 mA g-1 under the condition of the electrode after 60 cycles, the discharge the capacity can still maintain 99 mAh g-1 52 mAh g-1., the discharge capacity of the electrochemical and XPS technology is far greater than that of the pure NaV3O8 samples, study of sodium storage mechanism of NaV3O8, the discharge of The two platforms are corresponding to V5+ transition to the.2. V4+ by electrospinning V2O5 nanofiber porous synthesized (F-V2O5). The calcination conditions were optimized to determine the best conditions for calcination in Ar, calcination temperature of 500 DEG C, the heating rate of 1 DEG /min, pre calcination time 2 h the material, the structure is stable; and in the air, the calcination temperature is 400 degrees centigrade, the heating rate of 1 DEG /min, calcination time 30 min, the spinning precursor fully oxidized to V2O5. when the F-V2O5 nano fiber as cathode sodium ion batteries, which exhibit excellent electrochemical performance. Compared with commercial B-V2O5, cycle stability and the rate performance of F-V2O5 has been significantly improved. In 1.5-4.0 V, 40 mA g-1, the F-V2O5 electrode after 50 cycles, still can maintain 89.5 mAh g-1 discharge capacity, discharge capacity is far greater than that of B-V2O5 32.7 mAh g-1.

【學位授予單位】：南開大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：TQ343.5;TM912

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