流变相法制备海藻酸基碳包覆Li_3V_2(PO_4)_3材料的电化学性能（英文）

Synthesis and Electrochemical Performance of Alginic Acid-Based Carbon-Coated Li_3V_2(PO_4)_3 Composite by Rheological Phase Method

以海藻酸为碳源,采用流变相法制备出碳包覆改性的Li_3V_2(PO_4)_3/C(LVP/C)正极材料。X射线衍射(XRD)结果显示所合成样品均为标准的单斜结构Li_3V_2(PO_4)_3。扫描电子显微镜(SEM)和透射电子显微镜(TEM)图像显示所合成的LVP/C活性材料颗粒尺寸较均匀。海藻酸质量分数为10%的LVP/C样品展现出最优的循环稳定性。0.1C放电电流下,首次放电容量为117.5 m Ah?g^(-1),50周循环后容量保持在116.5m Ah?g^(-1)。LVP/C-10%材料在3.0–4.3 V和3.0–4.8 V电压范围内循环50周后的容量保持率分别为99.1%和76.8%,明显优于未包覆的LVP材料。海藻酸基碳包覆层可以有效增加材料的电子导电性、缓冲活性材料在脱嵌锂过程产生的机械损伤,进而提高材料的电化学性能。

Li3V2（PO4）3/C （LVP/C） cathode materials were successfully prepared by a rheological phase method using alginic acid as the carbon source. The X-ray diffraction （XRD） patterns demonstrate that all the samples contain pure LVP with the same monoclinic structure. The scanning electron microscopy （SEM） and transmission electron microscopy （TEM） images show that LVP/C materials have a uniform particle size. The LVP/C sample with 10% （w） alginic acid shows the best cycling stability. It delivers a discharge capacity of 117.5 mAh.g-1 （3.0-4.3 V）, which can be maintained at 116.5 mAh·g-1 after 50 cycles at a rate of 0.1C. Its capacity retentions of 99.1% （3.0-4.3 V） and 76.8% （3.0-4.8 V） after 50 cycles are prominently higher than those of pristine Li3V2（PO4）3, which are 89.7% （3.0-4.3 V） and 62.39% （3.0- 4.8 V）. These outstanding electrochemical performances are mainly attributed to the alginic acid-basedcarbon coating, which can increase the electronic conductivity of materials and buffer the mechanical damage of the active materials during the Li ion insertion/extraction process, thus improving the electrochemical performance of the LVP/C samples.