<p>Irreversible lithium plating is a critical degradation mechanism in lithium-ion batteries under low-temperature operation. This paper presented a non-destructive quantitative detection framework for irreversible lithium plating in lithium iron phosphate/graphite batteries. Systematic aging experiments were conducted on commercial cells under − 20 ℃ conditions, where the quantity of irreversible lithium plating was directly quantified using the difference between charge and discharge capacities. Feature extraction was performed using incremental capacity and differential voltage, electrochemical impedance spectroscopy, and distribution of relaxation times analyses. Two characteristic factors, loss of lithium inventory and charge transfer resistance, were identified and exhibited strong correlations with the measured irreversible lithium plating. Consequently, a data fusion strategy was implemented to construct a bivariate quadratic model that couples these features. Independent validation using a “7 + 1” strategy (seven training cells and one independent validation cell) demonstrated that the proposed 3D fusion model achieved an R² ≥ 0.98 and a Mean Absolute Percentage Error of 2.64%. Furthermore, the model’s transferability was preliminarily verified under − 10 ℃ conditions, identifying a notable sensitivity to operating temperature. This paper provides a rigorous laboratory-level benchmark for irreversible lithium plating quantification, facilitating future battery health management strategies.</p> Graphical abstract <p></p>