鋰離子二次電池陰極材料與場發射顯示器用螢光材料之製備與特性分析

本研究成功利用超音波噴霧熱裂解法製備尖晶石相的陰極材料Li1.03Co0.15Mn1.82O4，在750oC溫度下可得良好結晶相之粉體。進一步改變加熱時間可以發現，隨著時間的增加粉體的結晶性也會上升。利用噴霧熱裂解法所得之粉體，其一次粒子會聚集成球型之二次粒子，粉體的表面積則會隨時間增加而減少。在充放電測試當中可知，加熱時間四小時之粉體在60C的充放電速率下相對於0.1C仍然有87%的電容量維持率。推測在高速充放電時，不僅僅粉體的結晶性會影響其表現，粉體的表面積也佔非常重要的因素。而加熱四小時的粉體則符合這個條件。第二部分則是利用微波促使聚醇反應合成Sr2CeO4藍光螢光粉。經過微波處理過後所得之粉體經過加熱處理，在800oC時便可得到粉體之相，當加熱到1200oC時粉體則開始分解。若在1000oC加熱24小時可得單相之螢光粉。與傳統固相合成法比較，微波處理後的粉體可得較高之光激發螢光強度。將激發光譜與放射光譜作分析，分別得到兩個高斯曲線，可從此推測Sr2CeO4的能階構造與發光機制。最後本論文利用SiO2包覆在ZnO:Zn綠光螢光粉表面，發現可以使光激發螢光強度增加，推測是因為包覆作用使表面鈍化，缺陷被填補減少非輻射再結合所致。然而陰極激發光強度卻與光激發光譜相反，可能原因為包覆作用使得表面空乏層厚度改變，影響陰極射線激發光的強度。

關鍵字

鋰電池；陰極材料；螢光材料；鈰酸鍶；氧化鋅

並列摘要

Li1.03Co0.15Mn1.82O4 powders as cathode materials used in lithium-ion battery were synthesized using an ultrasonic spray pyrolysis process. As the time increased at 750oC heating, the crystallinity of the powders enhanced. The nanometered primary particles were aggregated into sphere-like secondary particles. The surface area of the heated samples decreased with an increase in the heating time. During the high C-rate tests, the sample heated for 4 h revealed 87% capacity retention at 60C-rate related to 0.1C. The electrochemical performance of the prepared Li1.03Co0.15Mn1.82O4 powders depends on not only the crystallinity but also the surface area. The sample heated for 4 h may fit this requirement and it exhibited good rate capability. Secondly, Sr2CeO4 phosphors were prepared via the microwave-assisted solvothermal method with post-heating. The blue emission was obtained under an excitation wavelength of 280 nm. Compared with the solid-state method, the powder derived by the microwave-polyol method had higher luminescence intensity. Deconvoluted excitation and emission spectra were also investigated in order to analyze the band structure of Sr2CeO4. Smaller Stokes shift of microwave-derived powders were also observed. Finally, ZnO:Zn phosphors were coated with SiO2 in order to modify the particle surface. The photoluminescence properties show a great enhancement due to the surface passivation. For further coatings the intensity decreased. The cathodoluminescence results showed a different trend. The depletion region of the particle surface determines the CL intensity.

並列關鍵字

Li-ion batteries ； cathode materials ； phosphors ； Sr2CeO4 ； ZnO

參考文獻

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國際替代計量

鋰離子二次電池陰極材料與場發射顯示器用螢光材料之製備與特性分析

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