The Caw's Magnetic And Electrical Properties

This dissertation reports the preliminary experimental results of magnetic properties of carbon atom wires (CAWs) and their electrochemical features demonstrated in the anode of lithium-ion secondary batteries A vibrating sample magnetometer (VSM) and an electron paramagnetic resonance (EPR) spectrometer were used in the magnetic investigation and the number of unpaired electrons in CAWs was evaluated. The electrochemical features of the CAW anode for lithium-ion secondary batteries were studied by use of the cyclic voltammetry, constant-current charging-discharging experiments and the AC impedance method. In addition, the effects of nitric acid treatment applied on CAWs were also tested.By a vibrating sample magnetometer, we discovered that magnetic hysteresis loop of CAW in the shape of "S" at the room temperature. The intensity of magnetization increased with the applied magnetic field until saturation, but whose value was much smaller than those of ordinary ferromagnetic materials. The experimental results showed CAWs to be a kind of alike ferromagnetic substance. The abnormal magnetic behaviors probably came from the particular structure of sp hybridization. By means of EPR, we estimated the number of unpaired electrons of CAW and a plenty of unpaired electrons existed in CAWs, as shown in the experiments, in agree with their structure proposed.In the constant-current charging-discharging experiment for a battery composed of a CAW electrode and a piece of Li electrode, the discharging capacity in the first cycle was as great as 999.4mAh/g and the corresponding charging capacity was 369.5mAh/g,.The charging-discharging efficiency began to increase from the 2nd cycle and reached 94.3% at the 10th cycle. The irreversible capacity was reduced gradually and the reversible capacity maintained to be about 300mAh/g finally. From the results, CAWs have a potential application used as an anode in the lithium-ion secondary batteries.Treated by concentrated nitric acid, some carboxylic acid groups on CAWs were produced, which could help to form a solid film arising from the reduction of thesolvent and the electrolyte on the interphase between the electrode and electrolyte solution in the process along with the lithium-ion intercalation. The solid film can reduce the co-intercalation of solvent molecules and inhibit their decomposition. Therefore, the nitric acid treatment can reduce the irreversible capacity and increase the reversible capacity of the CAW electrode.