用于超级电容器的还原氧化石墨烯/Ni_xMn_(1-x)/_2O_2复合材料的电化学性能

Electrochemical properties of reduced graphene oxide/Ni_xMn_(1-x)/_2O_2 composites for supercapacitors

MnO_2为有前景的超级电容器正极材料,具有较高的理论比电容及良好的循环稳定性,但电子电导性不佳限制了其应用。采用一步水热法制备了还原氧化石墨烯(RGO)/Ni_xMn_(1-x)/_2O_2复合材料。通过XRD、SEM、TEM、FTIR、电化学分析等手段对制备的RGO/Ni_xMn_(1-x)/_2O_2物相组成、微观形貌和电化学性能进行了表征和分析。电化学测试结果表明:Ni元素的引入提高了MnO_2的电容性能,以水热法制备的MnO_2的比电容为66F/g(扫描速度10 mV/s),而Ni元素掺杂量x=0.02时,Ni0.02Mn0.99O_2比电容为111F/g;材料中引入RGO后,RGO/Ni_xMn_(1-x)/_2O_2复合材料电容性能进一步提高,加入2wt%的RGO时,RGO/Ni0.02Mn0.99O_2的比电容为136F/g。RGO的引入提高了活性材料的电子迁移速率,Ni元素的掺杂造成了MnO_2晶格中存在适量的点缺陷,提高了其导电性。以RGO/Ni_xMn_(1-x)/_2O_2为正极的超级电容器可同时具备双电层电容器和赝电容器的优点,以Ni掺杂MnO_2和RGO的负载协同提高了该复合材料电化学性能。

As a kind of promising cathode materials of supercapacitor,MnO2 has higher theoretical capacitance and better cycle stability,but its application is limited by poorer electronic conductivity.The reduced graphene oxide（RGO）/NixMn1-x/2O2 composites were synthesized by hydrothermal method.The phase composition,microstructure and electrochemical properties of the prepared RGO/NixMn1-x/2O2 composites were characterized by XRD,SEM,TEM,FTIR and electrochemical analysis.The electrochemical tests show that,the capacitor performance of MnO2 is enhanced by partial substitution of Mn by Ni.The specific capacitance of MnO2 synthesized by hydrothermal method is 66 F/g（scanning speed is 10 mV/s）,when x=0.02,the specific capacitance of Ni0.02 Mn0.99 O2 is111 F/g.When the RGO is added,the capacitance performance of RGO/NixMn1-x/2O2 composites is further improved.As a result,the specific capacitance of 2 wt% RGO/Ni0.02 Mn0.99 O2 is 136 F/g.The addition of RGO increases the electron mobility of the active materials.Meanwhile,the conductivity is enhanced because of the doping of Ni,which results in the existence of appropriate point defects in the MnO2 lattice.The super capacitor with RGO/NixMn1-x/2O2 as the cathode material has advantages of electrical double-layer capacitor and faradaic pseudocapacitor at the same time.The electrochemical properties of RGO/NixMn1-x/2O2 composites are enhanced by the synergistic action of doping of Ni ions and loading of RGO.