新型锂离子电池正极材料LiMnBO_3的制备及其性能

Preparation and characterization of new cathode material LiMnBO_3 for lithium ion battery

以Li2CO3,MnO2和H3BO3为原料,在烧结温度大于800℃时得到了具有六方结构的单相LiMnBO3。充放电测试结果表明:加入高比表面积的碳黑和机械球磨使其比容量和循环性能得到很大改善,但充放电电流的大小会影响其循环性和比容量。800℃烧结温度下得到的LiMnBO3在电流密度为10mA/g和20mA/g时得到的首次放电比容量分别为82.5mAh/g和81.8mAh/g,循环25周后容量的保持率分别为74.7%和66.9%。850℃下得到的LiMnBO3在10mA/g的电流密度下首次放电比容量为62.9mAh/g,第九个循环后比容量仅为29.7mAh/g。扫描电子显微镜(SEM)测试结果显示,烧结温度为850℃时所得产物的粒径明显增大,这是造成其容量衰减严重的主要原因。

LiMnBO3 cathode material was synthesized successfully by one-step solid-state method using Li2CO3, H3BO3, MnO2 and high specific surface carbon black as starting materials. The crystal structure was determined by X-ray diffraction. The SEM image shows that the particles of samples are homogeneous. Electrochemical measurement results show that the initial discharge capacity of 82.5 mAh/g and 81.8 mAh/g can be obtained at the discharge current density of 10 mA/g and 20 mA/g respectively. So the high specific carbon black not only prevented the agglomeration of LiMnBO3 but also enhanced the electronic conductivity and thus, the electrochemical properties of LiMnBO3 can be improved obviously. The results show that the current density have the influence on the cycle performance and specific capacity of LiMnBO3 cathode materials.