Study On The Magnetic Response Effect Of Co₃O₄-based Supercapacitors

The magnetic response of supercapacitors（SCs）in complex magnetic environments has become an important topic in practical applications and fundamental research.However,the complex interaction of electric field forces and Lorentz force at the non-homogeneous electrolyte/electrode interface results in the complexity of ion transport.In this work,morphology-controlled Co₃O₄ is prepared by solvothermal method,and then used to study the morphology-dependent magnetic response under magnetic fields.After analyzing the effect of ion transport on the magnetic response,graphene was employed to optimize the ion transport,which allows SCs to operate stably and efficiently in magnetic field environment.The main research contents of this thesis are as follows:Co₃O₄ electrodes with different morphologies（needle-like,weed-like,cotton-like）were synthesized in situ on nickel foam substrates by a one-step hydrothermal method in different solvents,and the effect of morphology on the magnetic response of SCs was investigated.The results show that the specific capacity of the needle-and weed-Co₃O₄ electrodes varies from5.8%to-23.2%and 12.8%to-5.1%under the 4000Gs magnetic field,respectively,while the specific capacity of the cotton-like Co₃O₄ electrode varies from 45.3%～41.3%.In addition,coin-cell supercapacitors（Co₃O₄//AC CR2032 SCs）were assembled and their specific capacity under magnetic field was evaluated,which was similar to the results of the three-electrode system.The different magnetic responses are attributed to the effect of electrolyte convection in different paths at the interface under an external magnetic field.Therefore,regulating the morphology of electrode materials to optimize the magnetic response of SCs is of great significance for fundamental research and practical applications in the field of electrochemistry or magnetism.Co₃O₄@EGO composite films with different content ratios（noted CO40@EGO,CO30@EGO,and CO20@EGO,respectively）were prepared using a self-assembly method.Electrochemical measurements under magnetic field shows that the magnetic response of CO40@EGO film electrode varies from-15%to 2%.However,the magnetic responses of CO30@EGO and CO20@EGO films only changed in the range of-2%～2%,indicating that the CO30@EGO and CO20@EGO composite films have more stable magnetic response under the magnetic field.To further investigate the magnetic stability of the composite films in practical applications,coin-cell supercapacitors（CO30@EGO//AC CR2032 SCs）were assembled and electrochemically tested.The results show that the increase of its magnetic response also varies from-2%to 2%,which can effectively“shield”the side effects caused by the magnetic response.Moreover,it can maintain a specific capacitance of 36%under high current density.Therefore,CO30@EGO//AC CR2032 SCs can not only improve their rate performance in practical applications,but also operate efficiently and stably in complex magnetic field environments.