非简谐振动对石墨烯量子电容和热稳定性的影响

采用固体物理理论和方法,研究了单层石墨烯的量子电容和它的温度稳定性随温度和电压的变化规律,探讨原子非简谐振动对它的影响.结果表明:(1)当电压一定时,单层石墨烯的量子电容和温度稳定性系数均随温度升高发生非线性变化,电压小于2.3 V时,量子电容随温度升高而增大,温度稳定性系数随温度升高由缓慢变化到很快增大,电压高于2.3 V时,量子电容随温度升高先增大后减小,而其温度稳定性系数随温度升高由缓慢变化到很快减小.温度一定时,量子电容只在电压值为0.4～2.8 V范围内才变化较小,而电压值大于2.8 V时,量子电容迅速减小并趋于0;(2)与简谐近似相比,非简谐项会使石墨烯量子电容有所增大,且温度愈高,两者的差愈大,非简谐效应愈显著,温度为300 K时,非简谐的量子电容要比简谐近似的值大0.33%,而温度为1 000 K时,差值增大到1.47%;(3)电压在1.5～1.8 V之间,而温度低于800 K时,石墨烯量子电容的温度稳定性系数最小且不随温度而变,储能性能的温度稳定性最好;(4)非简谐项会使它的量子电容热稳定性系数比简谐近似的值增大,且增大的情况与温度有关,当温度为400 K时量子电容热...

Effect of anharmonic vibration on graphene quantum capacitance and thermal stability

Using solid-state physics theories and methods, the quantum capacitance of single-layer graphene and the variation of its temperature stability with temperature and voltage are studied, and the influence of atomic anharmonic vibration on it is discussed. The results show that the quantum capacitance and temperature stability coefficient of single-layer graphene both change nonlinearly with increasing temperature when the voltage is constant. The quantum capacitance increases with increasing temperature when the voltage is less than 2.3 V. The stability coefficient slowly changes to quickly increases with increasing temperature. The quantum capacitance increases and then decreases with increasing temperature when the voltage is higher than 2.3 V, and its temperature stability coefficient changes slowly to quickly with increasing temperature. When the temperature is constant, the quantum capacitance changes only when the voltage value is within the range of 0.4 to 2.8 V, and when the voltage is greater than 2.8 V, the quantum capacitance rapidly decreases and tends to zero. Compared with the simple harmonic approximation, the anharmonic term will increase the graphene quantum capacitance, and the higher the temperature, the greater the difference between the two, and the more significant the anharmonic effect. When the temperature is 300 K, The an-harmonic quantum capacitance is 0.33% larger than the harmonic approximation value, and when the temperature is 1000 K, the difference increases to 1.47%. When the voltage is between 1.5 and 1.8 V and the temperature is lower than 800 K, the temperature stability coefficient of the graphene quantum capacitor is the smallest and does not change with temperature, and the temperature stability of the energy storage performance is the best. The anharmonic term will increase the thermal stability coefficient of its quantum capacitor compared to the harmonic approximation, and the increase is related to the temperature, when the temperature is 400 K, the thermal stability coefficient of the quantum capacitor will increase by 67.47%, while it increases by 22.36% when the temperature is 1000 K. The quantum capacitance result obtained in this paper is not only close to the result of the literature, but also shows the law and the analytical formula of quantum capacitance and its temperature stability coefficient with temperature, this has reference value for the application of graphene in the energy storage performance of supercapacitors.