锂离子电池片状四氧化三钴负极的合成及改性

采用液相沉淀法结合低温固相热解法合成了锂离子电池片状Co3O4负极.通过X射线粉体衍射(XRD)、Brunauer-Emmett-Teller(BET)比表面积分析、扫描电子显微镜(SEM)及恒电流充放电等表征手段,发现该Co3O4为立方相,结晶完整且无杂质,由直径为1.5-3.0μm、厚度约为100-300 nm的不规则片状颗粒组成,比表面积约为30.5 m2·g-1;其比容量高且容量保持率好,在0.1C倍率下,首次放电容量高达1444.5 mAh·g-1,50次循环后充电容量仍大于1100.0 mAh·g-1;但在高倍率(1C)下,50次循环后充电容量保持率仅为75.3%,倍率性能一般.故采用碳纳米管(CNTs)掺杂改性,结果表明:在1C倍率下,70次循环后复合材料充电容量保持率为96.3%;在2C倍率下,50次循环后充电容量保持率仍高达97.0%,倍率性能显著提升.

Synthesis and Modification of a Lamellar Co3O4 Anode for Lithium-Ion Batteries

For advanced performance lithium-ion batteries (LIBs) various novel electrode materials with high energy density have been extensively investigated. Cobaltosic oxide (Co₃O₄), commonly used as an anode in LIBs, has attracted much interest because of its high theoretical specific capacity (890 mAh·g^-1), high tap density, and stable chemical properties. However, its practical use has been hindered because of its low electronic conductivity and poor rate capability. To address these problems, we investigated a liquid phase precipitation method followed by thermal treatment and obtained a unique lamellar Co₃O₄ powder. Its X-ray diffraction (XRD) diffraction peaks match the standard pattern for cubic phase Co₃O₄ with good crystallinity. We found that the Co₃O₄ powder consists of many irregular sheets (1.5-3.0 μm in diameter, 100-300 nm in thickness) with numerous poles by scanning electronmicroscopy (SEM).Additionally, the surface area was about 30.5 m²·g^-1, and this was calculated from BET nitrogen adsorption isotherm measurement data. Remarkably, perfect performance was obtained as evaluated by electrochemical measurements, including a high initial discharge capacity (1444.5 mAh·g^-1 at 0.1C) and excellent capacity retention (charge capacity after 50 cycles was still greater than 1100.0 mAh·g^-1 at 0.1C). However, its rate capability was still not adequate (75.3% of the first charge capacity after 50 cycles at 1C). To improve the rate capability, commercial carbon nanotubes (CNTs) mixed with the Co₃O₄ powder was used to enhance the electronic conductivity. The charge capacity retention ratios were 96.3% after 70 cycles at 1C and 97.0% after 50 cycles at 2C. Therefore, enhanced electrochemical performance with impressive rate capability was obtained, as expected.