Lithium Ion Battery Voltage Curve

1. The Voltage Curve of Lithium Ion Batteries

Lithium ion batteries are widely used due to their high energy density, long cycle lifespan, and stable performance. Understanding their voltage curve is crucial for proper use and maintenance. The voltage vs. state of charge (SOC) curve is key.

The voltage vs. SOC curve is also known as the discharge curve. It includes other aspects like voltage vs. specific capacity. For example, as the SOC decreases, the voltage drops. However, the curve’s slope is steep at 0%-10% and 90%-100% SOC. In the 10%-90% range (the plateau), the slope is very small. This means the battery is stable in this range. Keeping the SOC within 10%-90% helps maintain performance and lifespan. Overcharging or discharging beyond this range can harm the battery. Installing a battery management system (BMS) can help monitor and manage this.

2. Factors Affecting the Voltage Curve

2.1 Aging of the Battery

Aging affects the voltage curve. As the battery ages, active materials decrease, impacting chemical reactions and the voltage curve. Periodic re-measurement of the voltage curve helps adjust charging strategies and extend battery lifespan.

2.2 Operating Temperature

Temperature impacts the voltage curve. Lower temperatures reduce working voltage, while higher temperatures increase it. Lithium ion batteries work best between 0℃ and 40℃. Avoid extreme temperatures to ensure stable operation.

2.3 Manufacturing Process

The manufacturing process affects the voltage curve. Different brands have different internal structures, leading to variations in voltage curves. Consult the manufacturer to understand the actual voltage curve of your battery.

2.4 Self Discharge Rate

Lithium ion batteries naturally discharge over time. A higher self discharge rate leads to a steeper voltage drop, while a lower rate results in a more gradual drop. This affects the shape of the voltage curve.

2.5 Electrolyte Type

Common electrolytes include LiPF6 and LiFSI. Different electrolytes affect internal resistance, which in turn impacts voltage. Higher resistance results in lower voltage. Consider electrolyte type when analyzing the voltage curve.