Lithium-Ion Battery Capacity Estimation via Electrode Segmentation
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Solution Overview
Problem
Existing methods for estimating the capacity of lithium-ion batteries are not sophisticated enough to accurately account for capacity fade, which is critical for applications like electric and hybrid-electric vehicles.
Innovation Solution
A method and system that use a parameter estimation technique based on terminal voltage and charge current to estimate the capacity of lithium-ion batteries by modeling the state of charge and open circuit potentials of both the positive and negative electrodes, allowing for more accurate capacity estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional capacity estimation algorithms are used based on terminal voltage, charge current, and temperature, then the estimation is accurate enough for most applications, but it is not sophisticated enough to accurately account for capacity fade in applications like electric and hybrid-electric vehicles
Solution Approach 1:
The patent segments the battery capacity estimation into two independent components: negative electrode capacity (C_-) and positive electrode capacity (C_+). By modeling each electrode separately with its own state of charge (SOC_- and SOC_+) and open circuit potential (U_- and U_+), the algorithm can track capacity fade in each electrode independently, providing more accurate overall capacity estimation without excessive complexity
Solution Approach 2:
The patent introduces a new dimension to traditional capacity estimation by separately modeling the positive and negative electrodes as independent entities with separate SOC and OCP variables. This dimensional expansion allows the algorithm to capture asymmetric capacity fade patterns in different electrodes, improving measurement precision while maintaining manageable computational complexity through modular structure
2Reliability
If extended cycling is performed to determine battery capacity, then capacity fade becomes apparent, but the loss of active material, degradation of electrodes, and other factors make accurate capacity estimation challenging
Solution Approach 1:
The patent performs preliminary action by establishing separate electrochemical models for the positive and negative electrodes before capacity fade occurs. By pre-defining the relationship between SOC, OCP, and capacity for each electrode, the system is prepared to detect and measure capacity fade as it happens during cycling, rather than attempting to measure it after degradation has already occurred
Solution Approach 2:
The patent implements feedback mechanisms by continuously monitoring terminal voltage, charge current, and temperature, then using these measurements to update the separate SOC and OCP estimates for each electrode. This feedback loop allows the system to detect capacity fade in real-time and adjust capacity estimates accordingly, making reliable capacity fade detection feasible despite the complexity of underlying degradation mechanisms
Data Source
AI summary
A method of estimating at least one parameter of a lithium-ion battery cell includes determining a terminal voltage (V eq ) of the lithium-ion battery cell during an equilibrium condition of the lithium-ion battery cell with a voltage sensor and determining a charge current (/) of the lithium-ion battery cell during a charging operation of the lithium-ion battery cell with a current sensor. The method also includes using a parameter estimation technique to estimate at least one of a capacity (CO+) to store lithium ions of the positive electrode, a capacity (CO -) to store lithium ions of a negative electrode, and a total amount of lithium ions (n Li ) stored by the electrochemical battery cell based on an electrochemical model of the lithium-ion battery cell.