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鋰離子電池正極材料LiCoMnO4製備及其電化學性能研究

Optimized Synthesis and Electrochemical Performance of LiCoMnO4 Cathode Material for Lithium-Ion Batteries

  • 摘要: 尖晶石結構的LiCoMnO4由於含有Li離子和價態可變的Co離子、Mn離子🏄‍♀️,可以作為鋰離子電池的正極*️⃣,在輸出電壓為5.3 V左右時具有高能量密度優勢。但其合成過程中產生的Li2MnO3非活性雜質,會影響其充放電容量。采用正交試驗研究方法,討論了鋰過量程度🆘、原料球磨粒徑🍧、成型壓力💅🏼、燒結溫度4個因素對LiCoMnO4相純度的影響🧜🏿。通過研究得到優化的材料合成方案,並對其樣品進行了電化學性能測試分析🔻。對比實驗結果顯示,LiCoMnO4優化方案中的樣品17#,其電池首次放電容量為99.7 mAh·g–1,首圈庫倫效率達到93.3%👌🏿;而樣品1#首次放電容量為94.6 mAh·g–1,首圈庫倫效率為94.2%。優化工藝對容量保持率有很大影響,循環100圈後,17#樣品容量保持率為79.4%💝,而1#樣品容量保持率為41.6%👩🏽‍🍳。對於倍率特性,優化後的17#樣品在5 C充放電條件下還具有67.2 mAh·g–1的比容量。上述結果顯示,優化的材料合成方案提高了LiCoMnO4材料的電化學性能;此類材料有望成為新一代鋰離子電池高電位正極材料👄。

     

    Abstract: With a spinel structure, LiCoMnO4 has been developed as a cathode material for lithium-ion batteries due to the existence of lithium-ion and valence-variable Co and Mn cations. The potential advantages for this cathode material come from the high energy density caused by the output voltage around 5.3 V. However, Li2MnO3 inactive impurity is generated during the synthesis, which affects its charge and discharge capacity. The effects of Li excess, particle size of precursor materials, forming pressure and sintering temperature on the purity of synthesized LiCoMnO4 were discussed by orthogonal experimental study. An optimized material synthesis approach is obtained through the study and related electrochemical performance of the prepared samples were tested. The results show that, the initial specific capacity of the optimized 17# cathode material can be improved to 99.7 mAh·g–1, with a coulombic efficiency of 93.3%. For the 1# cathode material, the specific capacity is 94.6 mAh·g–1 and the value for coulombic efficiency is 94.2%. Big difference is observed for capacity retention after 100 cycles. Sample 17# showed high capacity retention of 79.4% when compared to the value of 41.6% for 1# sample. For the rate performance, the sample 17# presents a high capacity of 67.2 mAh·g–1 even at 5 C current density. Such results indicate that the electrochemical performance of the material is greatly prompted, showing the high potential to serve as a candidate cathode for a new generation of lithium-ion batteries.

     

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