Lithium-Ion Battery SOH Estimation From Incremental Capacity Peaks
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Solution Overview
Problem
Existing methods for determining the state of health (SOH) of lithium-ion batteries require a full charge and discharge cycle, which is impractical during normal use, and often involve destructive physical inspections to assess degradation modes.
Innovation Solution
A method that determines SOH by analyzing the relationship between incremental capacity and terminal voltage of the battery, identifying key peaks, and calculating degradation modes without full charging, using a diagnostic device with software to analyze incremental capacity curves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a full charge and discharge cycle is performed to determine battery state of health, then measurement precision is improved, but loss of time and productivity deteriorate
Solution Approach 1:
The patent performs incremental capacity analysis during a partial charging process (typically 0-80% or 0-90% charge) rather than requiring a complete full charge and discharge cycle. By analyzing the incremental capacity curve (dQ/dU) obtained during this partial charging, the system can determine state of health and degradation modes without completing the entire charge-discharge cycle, thus reducing time while maintaining sufficient measurement accuracy
Solution Approach 2:
The patent performs preliminary incremental capacity analysis during the charging process itself, before the battery reaches full charge. By extracting state of health information from the charging phase data (incremental capacity vs. voltage curves), the system obtains diagnostic information in advance, eliminating the need for separate full discharge and recharging cycles that would otherwise be required
2Measurement precision
If physical inspection methods are used to determine degradation modes, then measurement precision is improved, but device complexity and ease of operation worsen due to destructive testing requirements
Solution Approach 1:
The patent replaces physical/mechanical inspection methods (opening the battery, visually inspecting electrodes, physical testing) with an electrical analysis method. By measuring electrical parameters (voltage, current, incremental capacity dQ/dU during charging) and analyzing the resulting curves, the system identifies degradation modes such as lithium plating, SEI growth, and electrode material degradation without any physical disassembly or destructive testing
Solution Approach 2:
The patent uses incremental capacity analysis as an intermediary method between direct electrical measurement and physical inspection. The dQ/dU curve serves as an intermediate diagnostic tool that translates electrical charging behavior into degradation mode identification, providing accurate information without requiring direct physical contact with or damage to the battery components
Data Source
AI summary
A method for determining the state of health (SOH) of a lithium-ion battery includes: a first step (E1) of determining a function (f) of the incremental capacity of the battery, a second step (E2) of identifying peaks (P1, P2, P3) of the function (f) determined in the first step (E1), a third step (E3) of determining voltages (U1, U2, U3) across the terminals of the battery (1) for which said peaks (P1, P2, P3) are obtained, a fourth step (E4) of determining the amplitudes of said peaks (P1, P2, P3), a sixth step (E6) of determining the state of health (SOH) of the battery (1) on the basis of a degradation mode of the battery and on the basis of the amplitudes determined in the fourth step (E4).