Factors affecting the voltage of lithium batteries

Factors affecting the voltage of lithium batteries
The influence of electrode materials
The selection and characteristics of positive and negative electrode materials play a decisive role in the voltage of lithium batteries. Different cathode materials have different REDOX potentials, which directly determine the nominal voltage and operating voltage range of the battery. For instance, the REDOX potential of lithium cobalt oxide is relatively high, which enables lithium batteries with it as the cathode material to have a relatively high nominal voltage. The REDOX potential of lithium iron phosphate is relatively low, so the nominal voltage of lithium iron phosphate batteries is also relatively low. Meanwhile, the performance of the anode material also affects the battery voltage. For instance, the potential change of the graphite anode during charging and discharging is relatively stable, which helps maintain a steady output of the battery voltage. ​
2. The influence of charging and discharging states
The voltage of lithium batteries changes significantly during the charging and discharging process. During the charging process, the battery voltage gradually rises. When it reaches the charging cut-off voltage, the battery is regarded as fully charged. During the discharge process, as the chemical energy inside the battery is continuously converted into electrical energy, the battery voltage gradually decreases. In addition, the magnitude of the charging and discharging current also has an impact on the voltage. Larger charging and discharging currents will intensify the polarization phenomenon inside the battery, causing the battery voltage to rise more rapidly during charging and drop more significantly during discharging, thereby affecting the actual available capacity and service life of the battery. ​
The influence of temperature and aging
The ambient temperature has a non-negligible influence on the voltage of lithium batteries. In a low-temperature environment, the viscosity of the electrolyte inside the battery increases, and the ion transport resistance rises, resulting in an increase in the internal resistance of the battery, a significant drop in voltage, and a considerable reduction in the battery's discharge capacity. In high-temperature environments, although the initial voltage of the battery may increase slightly, the excessively high temperature will accelerate the chemical reactions inside the battery, leading to a faster aging process, reduced voltage stability, and even potential safety issues such as thermal runaway. As the number of battery uses increases, the electrode materials will gradually age, the active substances will decrease, and the internal resistance of the battery will increase. All these will lead to a drop in battery voltage and capacity attenuation, which is manifested as a gradual decrease in the battery's endurance.