Role of anions on structure and pseudocapacitive performance of metal double hydroxides decorated with nitrogen-doped graphene

超级电容器因为具有充放电时间短的特点引起了人们的广泛关注.然而,由于电极表面的电荷积聚和化学反应,电容器的比电容及能量密度大大降低,限制了超级电容器的实际应用.本文提出了一种新颖的合成方法用以制备基于镍钴双氢氧化物的复合材料,该复合材料作为超级电容器的电极具有优异的电化学性能.利用氮掺杂石墨烯的缺陷,金属氢氧化物纳米结构在氮掺杂石墨烯表面生长,形成复合结构.通过调节并优化镍钴的元素比以及卤素离子、碳酸根离子的含量,能够改善材料的孔隙度、提高材料结构的稳定性以及促进电化学反应.金属氢氧化物的形成由钴离子的氧化反应引导,并通过定向生长方式形成一维结构.氮掺杂石墨烯有效保护镍钴双氢氧化物的纳米结构,...Electrochemical capacitors (EC) bear faster charge-discharge; however, their real applications are still on a long away due to lower capacitance and energy densities which mainly arise from simple surface charge accumulation or/and reaction. Here, a novel synthesis strategy was designed to obtain the purposeful hybrids of nickel cobalt double hydroxide (NiCoDH) with genetic morphology to improve their electrochemical performance as electrode of EC. Nanostructures of metal hydroxides were grown on the nitrogen-doped graphene (NG) sheets by utilizing defects as nucleation sites and their composition was optimized both by tuning the ratio of Ni:Co as well as the counter halogen and carbonate anions to improve the porosity, stabilize the structure and mediate the redox reaction. The growth of the hybrids was guided by the Co ions through topochemical transformation supported by hoping charge transfer process and olation growth. NG overcoating successfully protects the nanostructure of NiCoDH during electrochemical test and enhances overall conductivity of the electrode, improving the mass and ionic transportations. As a result, the hybrid exhibits excellent capacitance of 2925 F g~(-1) at 1 A g~(-1), as well as long cyclic stability of 10,000 cycles with good capacity retention of 90% at 16 A g~(-1). Furthermore, the hybrid shows excellent energy and power densities of 52 Wh kg~(-1) and 3191 W kg~(-1), respectively at discharge rate of 16 A g~(-1). It is expected that this strategy can be readily extended to other metal hydroxides, oxides and sulphides to improve their electrochemical performances.SCI(E)中国科学引文数据库(CSCD)cbcao@bit.edu.cn; hou@pku.edu.cn02114-1255