Morphology Controlling of the High-voltage Cathode Materials with Different Co-solvents

Abstract

Cathode material LiCoPO 4 was synthesized by solvothermal method with a variety of water/alcohol solvent mixtures, including ethanol (ET), ethylene glycol (EG), and diethylene glycol (DEG). Focus of this work was set on the effect of the different alcohol solvent on morphology and particle size of material. Composition, crystal structure, morphology and particle size of the as-prepared samples were characterized by X-ray-diffraction, scanning electron microscopy and specific surface area test. The results show that relationship of the average particle size of the LiCoPO 4 samples synthesized with different alcohols solvents is in agreement with solubility of solvent for the precursor, but is inconsistent with the viscosity of solvent. Furthermore, LiCoPO 4 sample synthesized with EG/H 2 O possesses the smallest particle size, great crystallinity and excellent cycle performance. Its initial discharge specific capacities reaches to 130 mAh/g at 0.05C, and it shows a capacity retention of the initial value of 88% in 20th cycle. A variety of shapes are obtained from various co-solvents: hexagonal platelets for LiCoPO 4 obtained from EG, whereas, square platelets for LiCoPO 4 from ET/H 2 O and DEG/H 2 O.

Microwave-assisted Synthesis and Co, Al Co-modification of Ni-rich LiNi0.8Mn0.2O2 Materials for Li-ion Battery Electrode

“…formance 锂离子电池(LIBs)作为一种新型可移动储能 设备，在固定设备储能，智能电网，交通运输等领 域的应用已初见成效 [1][2] ，而其工作电压、能量密 度、输出功率、循环寿命和安全性能在很大程度上 由正极材料所决定 [3][4] 。 层状高镍正极材料 LiNi1-xMxO2(M 为 Co、Mn 等金属元素)，具有接近 自身理论的高比容量、较高的工作电压、相对稳定 的结构和较低的成本，高镍二、三元正极材料仍将 是今后一段时间研究的重点和热点 [5][6][7] 。 尽管研究者们不断对高镍正极材料进行研究 改进， 但材料本身仍然还存在一些需要解决的问题 [8][9][10][11] [12][13][14] 。另外，电极材料表面的 各种副反应对材料的电化学性能同样具有较为重 要的影响， 合成过程中残留在材料表面上过量的锂 在存储和制浆过程中与空气中的 CO2 和 H2O 发生 反应形成 LiOH 和 Li2CO3， 循环过程中这些副产物 与电解液反应， 不断在电极表面形成绝缘材料并消 耗电解液，从而阻碍了 Li + 在材料中的扩散 [15][16][17] 。 为了解决上述问题， 本研究采用微波辅助共沉 淀与高温固相结合的方法制备了高镍 LiNi0.8Mn0.2O2(NM-82)正极材料，相比于目前常见 的高温固相、溶胶凝胶和共沉淀法等，通过微波加 热，可以诱导或加速反应过程，同时提高反应选择 性和产率，得到的材料元素分布均匀，性能良好且 方法简单可控 [18][19] 。研究表明，添加 Co 元素可以 极大地提升正极氧化物的倍率和循环性能 [20][21] ，而 掺杂 Al 可以显著改善材料的整体结构和界面稳定 性 [22][23][24][25] [11,19]…”