Introduction
In modern electronic devices and energy storage systems, lithium batteries have become the preferred power solution due to their high energy density, long cycle life and relatively low self-discharge rate . The performance of lithium batteries can be evaluated in many ways, among which the plateau voltage is a key indicator. This article will explore the concept of platform voltage, the main factors that affect its stability and height, and the characteristics of platform voltage. In addition, it will discuss the discharge rate, a parameter closely related to platform voltage, and delve into the essence of lithium battery discharge platform, explaining the scientific principles of voltage performance when electrochemical reactions reach dynamic equilibrium.
1. The concept of platform voltage
A plateau in a battery basically means that the charge/discharge curve of the battery is a plateau (flat). For example, the charge/discharge curve of a lithium-ion battery using lithium iron phosphate as the positive electrode material (positive electrode active material) and graphite as the negative electrode material has a plateau region. The discharge process of a fully charged lithium battery usually includes three stages: the initial voltage drop, the subsequent stable period (plateau period), and the final voltage drop again. Among these three stages, the stable period is the longest. The longer it lasts, the higher the discharge platform of the battery, which is usually closely related to the manufacturing process of the battery .
2.Main influencing factors
For ternary lithium batteries , under constant voltage conditions, stop charging when the voltage reaches 4.2V and the current is less than 0.01C, then leave it for 10 minutes. At any rate of discharge current, when the battery is discharged to 3.7V, the length of time it takes to discharge is an important indicator of battery quality. However, don't blindly pursue a high platform. Sometimes the platform voltage is high but the capacity is reduced, because the platform voltage is different under different rate conditions .
Battery manufacturing process: Different lithium battery manufacturers have different market positioning and technical process means, which leads to differences in the controlled discharge platform, thus affecting the quality of the battery .
Battery materials: The characteristics of the positive electrode material directly affect the discharge platform phenomenon. For example, the potential of solid solution materials such as lithium cobalt oxide changes little with the lithium ion concentration, while materials such as lithium iron phosphate that form a two-phase structure through phase change show a clear platform area during charge and discharge.
Charge and discharge rate: The discharge rate will affect the voltage change during battery discharge. The higher the discharge rate, the lower the battery discharge voltage platform may be.