燃料与氧化剂用量比对溶液燃烧法制备尖晶石型高熵氧化物结构和储锂性能的影响

Effect of Fuel to Oxidant Dosage Ratio on Structure and Lithium Storage Properties of Spinel High Entropy Oxides by Solution Combustion Synthesis

以金属硝酸盐为氧化剂、甘氨酸为燃料,采用溶液燃烧法在750℃下制备尖晶石型(K_(1/6)Co_(1/6)Cr_(1/6)Fe_(1/6)Mn_(1/6)Ni_(1/6))_(3)O_(4)高熵氧化物粉体,并将该粉体用作锂离子电池负极材料,研究了燃料与氧化剂的物质的量比(0.2,0.5,1.0,1.5)对产物结构和储锂性能的影响。结果表明:所制备的高熵氧化物化学成分均匀且具有介孔结构;随着燃料与氧化剂的物质的量比的增加,高熵氧化物的结晶度、晶格常数、晶胞体积、比表面积和孔体积均增大,晶粒尺寸先减小后增大,最可几孔径先减小后增大再减小;当燃料与氧化剂的物质的量比为0.5和1.0时,所制备的粉体具有相似的比表面积和类似的孔结构,但是前者具有更小的晶粒尺寸和最可几孔径。当燃料与氧化剂的物质的量比为0.5时,制备的电极在0.2 A·g^(-1)小电流密度下循环100圈后放电比容量最高(1196 mA·h·g^(-1)),这与此时电极材料具有较小的晶粒尺寸和最可几孔径以及适中的结晶度有关;当燃料与氧化剂的物质的量比为1.0时,电极具有最优的倍率性能,在1.0 A·g^(-1)大电流密度下循环400圈后的放电比容量高达1133 mA·h·g^(-1),在3 A·g^(-1)大电流密度下的比容量保持率仍高达59.4%,这主要与较大的晶胞体积有关。

Spinel(K_(1/6)Co_(1/6)Cr_(1/6)Fe_(1/6)Mn_(1/6)Ni_(1/6))_(3)O_(4)high entropy oxide powder was synthesized by solution combustion synthesis method by taking metal nitrate as oxidant and glycine as fuel at 750℃,and was used as anode materials for lithium ion battery.The effect of fuel to oxidant molar ratio on microstructure and lithium storage performance of the products were studied.The results show that the prepared high entropy oxides had uniform chemical composition and a mesoporous structure.With the increase of the molar ratio of fuel to oxidant,the crystallinity,lattice constant,cell volume,specific surface area and pore volume of the high entropy oxides increased,the grain size decreased first and then increased,and the most probable pore size decreased first and then increased and then decreased.When the molar ratio of fuel to oxidant was 0.5 and 1.0,the prepared powder had similar specific surface area and pore structure,but the former had smaller grain size and the most probable pore size.When the molar ratio of fuel to oxidant was 0.5,the prepared electrode had the highest specific discharge capacity(1196 mA·h·g^(-1))after 100 cycles at a low current density of 0.2 A·g^(-1),which was related to the small grain size and the most possible pore size and the moderate crystallicity of the electrode material at this time.When the molar ratio of fuel to oxidant was 1.0,the electrode had the best rate performance.After cycling for 400 cycles at 1.0 A·g^(-1)high current density,the specific discharge capacity reached 1133 mA·h·g^(-1),and the specific capacity retention remained 59.4%at 3 A·g^(-1)high current density,which was mainly related to the larger cell volume.