Co-B合金粉体的制备和电化学行为  

PREPARATION AND ELECTROCHEMICAL BEHAVIORS OF Co-B ALLOY POWDERS

作　　者：吕东生[1,2] 李伟善[1,2] 谭春林[1,2] 曾荣华[1] 

机构地区：[1]华南师范大学化学与环境学院,广州510631 [2]广东省高等学校电化学储能和发电技术重点实验室,广州510006

出　　处：《金属学报》2010年第3期346-351,共6页Acta Metallurgica Sinica

基　　金：广东省高校优秀青年教师培养计划(育苗工程)资助项目~~

摘　　要：通过NaBH_4还原CoSO_4溶液制备了Co_(0.68)B_(0.32),Co_(0.55)B_(0.45)和Co_(0.50)B_(0.50)一系列超细非晶态Co-B合金粉体.电化学测试表明,在300 mA/g的高电流密度下,3种合金电极的首次放电容量分别高达510.6,666.4和667.2 mA·h/g,经60次循环后,放电容量仍分别有331.6,379.5和390.5 mA·h/g.3种合金电极还表现出良好的高率放电性能,在1200 mA/g的放电电流密度下,放电容量分别为336.2,373.4和390.1 mA·h/g.较高的B含量有助于提高合金的电化学性能,这是因为B的氧化溶解能提高合金电极的实际电化学反应面积.Alkaline rechargeable batteries,such as Ni/Cd batteries and Ni/MH batteries have been widely used as power sources,however,their further applications are limited due to contamination of Cd in Ni/Cd batteries and lower discharge capacities of Ni/MH batteries.Some metal borides, such as Co-B,Ni-B,Fe-B,V-B and Ti-B,have been known to own very high discharge capacity in alkaline aqueous solution,in which Co-B alloy exhibits the highest reversible discharge capacity and the best cyclic stability.However,the reversible capacity of Co-B alloy prepared by arc melting process is usually less than 250 mA·h/g,which is only one fourth of the theoretical capacity of the alloy electrode（908 mA·h/g）.In the present study,chemical reduction method was used to prepare Co-B alloy to further enhance the electrochemical capacity of the alloy.A series of ultrafine powders of amorphous Co-B alloys,Co0.68B0.32,Co0.55B0.45 and Co0.50B0.50,were prepared by reducing CoSO4 with solution of NaBH4.Electrochemical measurements indicate that the prepared alloys exhibit excellent electrochemical properties.At a high current density of 300 mA/g,the initial discharge capacities of these alloys are 510.6,666.4 and 667.2 mA·h/g,respectively,their discharge capacities still keep 331.6,379.5 and 390.5 mA·h/g after 60 cyc,respectively.Even at a discharge current density as high as 1200 mA/g,the three alloys still deliver reversible capacities of 336.2,373.4 and 390.1 mA·h/g,respectively.In the Co-B alloy electrodes,the boron atoms have two functions.First, boron can be oxidized to BO3^3-,thereby partly contributes to the discharge capacity.Second,most importantly,the gradual dissolution of boron into the electrolyte（in the form of BO3^3-） during the charging/discharging creates a new surface in the electrodes,which can effectively increase the surface area of the active material in contact with the electrolyte.The alloy with higher boron content thereby can produce a larger reaction surface area by boron dissolution than the alloy prepared

关 键 词：Co-B合金 非晶粉体 化学还原 电化学性能 

分 类 号：TQ174[化学工程—陶瓷工业]