Recently, a research team from the Beijing Institute of Technology (BIT) has made a remarkable breakthrough in diagnosing lithium plating morphology within lithium batteries. Their findings have been published in the esteemed international chemistry journal, the Journal of the American Chemical Society. This innovative study introduces a quantitative diagnostic method for assessing lithium deposition morphology, leveraging the response characteristics of electrochemical impedance spectroscopy (EIS). By establishing a quantitative link between impedance fitting parameters and deposition morphology, this method facilitates the differentiation of electrochemical traits and the dynamic tracking of various lithium plating morphologies.

The research team conducted a comprehensive analysis of impedance evolution under diverse deposition conditions. They discovered that the evolution of charge transfer impedance (R_ct) adheres to a power-law distribution. Utilizing distribution of relaxation times (DRT) analysis, they successfully deciphered key features of the charge transfer process in the mid-frequency range. By manipulating current density and deposition capacity, the team generated typical lithium deposition morphologies, such as dense deposits and dendritic structures, on copper substrates. They established a correlation between the exponent b in the power-law distribution equation and actual morphologies, defining it as the Lithium Growth Factor (LGF).

Experimental validation confirmed that the LGF model exhibits robust early warning capabilities under extreme conditions, including varying current densities (ranging from 0.02 to 2.0 mA cm⁻²) and low temperatures (as low as -10 °C). For example, at a high current density of 2.0 mA cm⁻², the LGF value spiked to 3.04, signaling a severe propensity for dendrite formation. Similarly, under low-temperature conditions (-10 °C), an LGF value of 2.22 accurately foretold an increased risk of dendrite formation.

Moreover, this diagnostic technology was successfully extended from laboratory-scale Li//Cu half-cells to graphite//lithium half-cells and pouch cell systems. In graphite-based systems, the trend of escalating LGF values and dendrite content was validated as the charge/discharge rate increased from 0.5C to 2C. In pouch cell tests, stable LGF values were calculated with a minimal deposition capacity of approximately 0.3-0.4 mAh cm⁻², obviating the need for time-consuming cycling tests or battery disassembly. This offers a non-destructive detection solution for monitoring dendrite formation during the rapid charging of new energy vehicles.

The research was spearheaded by Professor Huang Jiaqi and Professor Yan Chong from the Beijing Institute of Technology, with master's student Yu Zhixian serving as the first author.