Battery Controller Lithium Concentration Diffusion Correction
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Solution Overview
Problem
Lithium-ion secondary batteries employing two-phase coexistence type positive electrode active materials face challenges in accurately estimating their internal state due to changes in performance resulting from charge/discharge history, which is not accounted for in existing estimation methods.
Innovation Solution
A battery system that uses a controller to calculate the distribution of lithium concentration in the active material through a diffusion equation, with a corrected diffusion coefficient based on charge/discharge history data, allowing for accurate estimation of the battery's state of charge and internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a diffusion equation is used to estimate lithium concentration distribution without correcting the diffusion coefficient, then the calculation process is simple, but the estimation accuracy deteriorates due to ignoring charge/discharge history effects
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the relationship between charge/discharge history and diffusion coefficient correction values in a lookup table during the battery design phase. During operation, the controller simply retrieves the appropriate correction value based on stored history data, avoiding complex real-time calculations while maintaining high estimation accuracy
Solution Approach 2:
The patent changes the diffusion coefficient parameter dynamically based on charge/discharge history. Instead of using a constant diffusion coefficient, the system adjusts this parameter according to the battery's operational history, allowing the estimation model to adapt to changing battery conditions and maintain accuracy
2Measurement precision
If charge/discharge history data is stored and used for correction, then the estimation accuracy improves, but the memory requirements and data processing complexity increase
Solution Approach 1:
The patent extracts only the essential features of charge/discharge history that influence diffusion coefficient, storing condensed parameters such as integrated charge/discharge amounts and average temperatures rather than complete historical records. This reduction in data dimensionality significantly decreases memory requirements while preserving the information needed for accurate correction
Solution Approach 2:
The patent performs preliminary processing of charge/discharge data to extract key parameters that most strongly correlate with diffusion coefficient changes. By pre-identifying and storing only these critical parameters (such as cumulative charge/discharge capacity and temperature profiles), the system minimizes storage requirements while maintaining estimation accuracy
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system accurately reflects changes in battery performance by updating the diffusion coefficient with history data, enhancing the estimation of lithium concentration and state of charge, thereby improving the accuracy of internal state estimation.
Implementation Method 1
The controller calculates a distribution of concentration of lithium in the active material in the lithium-ion secondary battery, through the use of a diffusion equation in which a boundary condition is set
Data Source
AI summary
[Task] To accurately estimate a distribution of concentration of lithium in an active material.[Means for Solution] A battery system has a lithium-ion secondary battery (1) and a controller (300). The lithium-ion secondary battery (1) employs a two-phase coexistence type positive electrode active material (141b). The controller (300) calculates a distribution of concentration of lithium in an active material (141b, 142b) of the lithium-ion secondary battery, through the use of a diffusion equation in which a boundary condition is set. The controller corrects a diffusion coefficient that is used in the diffusion equation, in accordance with history data indicating a charge/discharge state of the lithium-ion secondary battery to the present time.