具尖晶石結構之 LiMn2O4 (LMO)為一具潛力之鋰離子電池之陰極材料，原因為Mn3+/Mn4+電荷轉換之電化學特性，及結構之穩定性，可用於能量之儲存。LMO 也展現下列優點:如價格低廉、富含錳元素、對環境較少的負面影響。然而，LMO 電容量會隨循環充放電次數逐漸減低，而降低其實用價值。LMO 電容量衰退的原因主要為 Mn離子易溶於電解液，產生 Jahn-Teller 扭曲，進而造成立方體至四方體晶格的轉變。因此，為了改善 LMO 電化學性質，常用的方法包括:添加少量過多的鋰離子，形成富鋰尖晶石、在 LMO 表面加上金屬氧化物鍍層、以過渡金屬添加至LMO 以取代部分錳離子。

在本研究中，鎳添加的方式合成LiMn1.5Ni0.5O4 (鎳添加的 LMO 或 LMNO)。所使用製程包括:溶膠-凝膠 法、軟化學法、固相反應法、及燃燒合成法等。同時也嘗試分階段燃燒合成法，藉以觀察較低溫下合成之LMNO其電化學性質表現。

經由X-ray繞射分析的結果顯示固態法、軟化學法製程等傳統方法，需要較高的鍛燒溫度，才能使反應完全，獲得純相LMNO。相對地，藉由使用燃燒合成法，純相 LMNO 在相差200℃以上溫度，可成功地合成純相 LMNO。

藉由掃描式電子顯微鏡影像觀察，在不同溫度下合成之尖晶石 LMNO，呈現不同粒徑的顆粒。再經由粒子分析儀量測，確認較高鍛燒溫度易造成晶粒成長。

最後，將各種方法合成之LMNO充放電實驗顯示，相對於以傳統單一步驟法與溶膠-凝膠法合成的 尖晶石 LMNO 及以溶膠-凝膠法合成的尖晶石 LMO，由燃燒法合成的尖晶石 LMNO 呈現較優良的電化學特性。尖晶石以兩步驟燃燒法在 600° C、700°C 與 800°C 合成的尖晶石 LMO，其初始放電容量為 123 mAh g-1、124 mAh g-1、128 mAh g-1 與在30圈循環測試後，獲得電容量保留率分別為 74.43%、71.01%、69.65%。

Spinel LiMn2O4 (LMO) is a promising cathode material for lithium-ion battery applications because of its high-power capability and safety that are attributed to the chemical stability of the Mn3+/Mn4+ couple. Other advantages of LMO are the abundance of manganese and its low negative impact to the environment compared to other, layered-oxide cathode materials. However, LMO suffers from high capacity fade, which makes it impractical for commercial use. Known reasons for its capacity fade are the dissolution of Mn2+ to the electrolyte and the Jahn-Teller distortion, which causes the transformation of the crystal lattice from cubic to tetragonal. Various methods of improving the electrochemical performance of LMO include adding excess Li to make a Li-rich cathode, coating the surface of LMO with metal oxide, and doping LMO or substituting Mn with transition metals.

In this study, LiMn1.5Ni0.5O4 (nickel-doped LMO or LMNO) is synthesized using different methods such as sol-gel, soft chemistry, solid state, and combustion synthesis. Two-step combustion synthesis was also performed with the aim of determining if LMNO can be synthesized at a low temperature and still exhibit good electrochemical performance.
X-ray diffraction (XRD) results show that conventional methods such as solid state synthesis and soft chemistry process require high calcination temperatures in order to achieve LMNO without any impurities. Moreover, XRD results also show that pure LMNO was successfully synthesized at lower temperatures using the conventional single-step combustion synthesis and two-step combustion synthesis.
Scanning electron microscopy images of LMNO spinels synthesized using the single-step and two-step combustion methods show the formation of particles of different shapes. Particle size analysis also confirms that increasing the calcination temperature caused grain growth to occur.

The charge-discharge tests show that the LMNO spinels synthesized by two-step combustion method exhibited better electrochemical performance compared to the LMNO spinels synthesized by the conventional single-step method and the sol-gel method as well as the LMO spinel synthesized by the sol-gel method. The spinels synthesized using the two-step combustion method at 600°C, 700°C and 800°C exhibited an initial discharge capacity of 123 mAh g-1, 124 mAh g-1, and 128 mAh g-1 with retention rates of 74.43%, 71.01% and 69.65% after 30 charge/discharge cycles.

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