As electric vehicle technology advances into the fast charging era, lithium-ion batteries face increasingly severe challenges regarding safety and lifespan under high-rate charging. One of the most critical concerns is the phenomenon of lithium plating—when the charging current is too high or the temperature is too low, lithium-ions fails to intercalate effectively into the anode and instead deposit as metallic lithium on the surface of the graphite. This leads to capacity degradation, thickening of the solid electrolyte interphase (SEI) layer, and may even cause internal short circuits and thermal runaway. These safety risks, originating from microscopic electrochemical reactions, cannot be adequately investigated using the conventional two-electrode structure of lithium-ion batteries. As it provides only combined voltage-capacity data, this structure does not allow for distinguishing between the independent behaviors of the anode and the cathode. As a result, the mechanism of lithium plating becomes difficult to identify. This is where the advantages of a three-electrode testing setup become particularly significant.

Decoupled Observation of Electrode Behavior for Accurate Detection of Lithium Plating 

By introducing a non-current-carrying reference electrode (RE), the three-electrode system enables stable measurement of the potentials of both the cathode and anode relative to the RE. This setup effectively decouples the otherwise combined reactions of the cathode and anode (Figure 1). Such a design allows researchers to independently observe potential shifts, polarization behavior, impedance changes, and electrochemical instabilities of each electrode during fast charging. This is particularly useful for detecting abnormal behaviors in the anode, such as potential dropping close to 0V vs. Li/Li⁺ or increasing polarization—key indicators of potential lithium metal plating.

▲Figure 1. Schematic comparison of two-electrode and three-electrode battery test configurations

Investigating Lithium Plating Mechanisms During Fast Charging: Application Goals and Measurement Requirements of the Three-Electrode System

When automotive and battery cell manufacturers conduct three-electrode experiments to study lithium plating, their primary objective is to clarify the critical conditions and boundaries under which lithium deposition occurs. These experiments often involve adjusting charging rate, cutoff voltages, and operating temperatures, or simulating real-world charge/discharge cycling conditions to induce internal battery aging and observe changes in the anode potential relative to the reference electrode.  In a journal published by The Electrochemical Society (ECS), Wenlong Xie, Shichun Yang, and others conducted rapid charging at different C-rates by decomposing lithium batteries into three-electrode batteries [1] and observed differences in anode potential based on the degree of lithium plating (Figure 2).

To accurately identify such microscopic phenomena, the voltage measurement equipment used to monitor the anode vs. reference electrode potential must offer high precision, high stability, and high resolution—especially within the sub-millivolt range. It is essential that the system maintains stable long-term measurements in this narrow voltage window to reliably detect the onset and extent of lithium plating. These insights provide a critical foundation for subsequent material development and charging strategy optimization.

▲Figure 2. Schematic diagram showing the evolution of the electromotive force of lithium plating on the anode during CC-CV charging.

Chroma's High-Precision Three-Electrode Testing Solution: An Ideal Tool for Lithium Plating Research

Chroma has developed the A172013 Multi-Channel Voltage Data Logger (Figure 3), offering a reliable testing solution tailored for lithium plating studies. The A172013 is equipped with a 24-bit ADC and features six built-in voltage ranges, enabling detection of voltage changes down to the microvolt (µV) level. This high resolution allows researchers to accurately identify the onset and boundary conditions of lithium plating at the anode. With a measurement accuracy of up to ±0.015% of F.S., it ensures long-term test precision. Additionally, a single unit integrates 16 independent measurement channels, allowing for simultaneous, real-time data acquisition without delay. When paired with the Chroma 17216M-10-6 Programmable Charge/Discharge Testing System, which includes four current ranges (6A/200mA/6mA/200µA), the setup is especially suited for laboratory testing of coin cells, small pouch cells, and 18650 cylindrical cells with three-electrode configurations. Using Chroma's integrated testing platform, researchers can accurately identify lithium plating risks and degradation mechanisms to optimize battery formulations and charging strategies.

▲Figure 3. Integrated setup of 17216M-10-6 combined with A172013

To learn more about the Chroma 17216M-10-6 Programmable Charge/Discharge Tester and the A172013 Multi-Channel Voltage Data Logger used in a decoupled three-electrode testing system, please click the link below and share your requirements. Our team will be happy to provide you with dedicated technical support.

[1]Source: Wenlong Xie, Shichun Yang, Journal of The Electrochemical Society, (170), 2023