Battery Cell Diagnosis Using Electrode Profiles for Multi-Phase Degradation

The patent segments the full-cell profile into separate positive electrode profile and negative electrode profile. By dividing the overall battery diagnosis into electrode-specific analyses, the method can accurately track degradation of each electrode independently, particularly for multi-phase characteristics. This segmentation enables precise measurement of electrode participation endpoints and capacity ratios without the interference that plagues conventional full-cell analysis.

The patent introduces a new dimensional approach by plotting voltage against electrode capacity ratio (positive electrode capacity/negative electrode capacity) rather than using traditional full-cell capacity-voltage relationships. This dimensional transformation creates a profile space where multi-phase characteristics can be distinctly identified and tracked, enabling accurate diagnosis even as the battery degrades over time.

The patent applies local quality by analyzing the voltage characteristics at specific local regions of the electrode profiles, particularly focusing on the endpoint voltages of positive and negative electrode participation. Instead of relying on overall electrode design stability, the method extracts localized voltage features that remain reliable indicators of degradation state even as the overall profile evolves. This local feature extraction maintains diagnosis reliability despite profile changes.

The patent transforms the diagnostic parameters from absolute voltage-capacity relationships to normalized electrode capacity ratios and differential voltage features. By changing the parameter space to use ratios and differences rather than absolute values, the method compensates for profile drift and maintains stability. The electrode capacity ratio and endpoint voltage differences serve as stable parameters that reliably indicate degradation regardless of overall profile evolution.