Lithium Ion Battery State Estimation via Freezing Temperature
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Solution Overview
Problem
Existing techniques for estimating the state of deterioration in lithium ion batteries are inaccurate due to errors in charging and discharging history information, making it difficult to differentiate between capacity loss caused by material deterioration and lithium precipitation, which is crucial for effective control and recycling.
Innovation Solution
An apparatus and method that calculate the material deterioration ratio and precipitation deterioration ratio using the freezing temperature and capacity measurements of the lithium ion battery, without relying on charging and discharging history information, by utilizing the correlation between freezing temperature changes and material deterioration, and storing correspondence data between capacity and freezing temperature for precise calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If charging and discharging history information is used to calculate lithium precipitation amount, then calculation can be performed, but errors are accumulated over time and accuracy is lowered
Solution Approach 1:
The patent changes the measurement parameter from charging/discharging history to freezing temperature. By measuring the freezing temperature of the electrolyte, the system can calculate lithium precipitation amount without accumulating errors over time, as freezing temperature is a direct physical property that does not depend on historical data accuracy.
Solution Approach 2:
The patent replaces the computational method (using charging/discharging history calculations) with a physical measurement method (freezing temperature measurement). This substitution eliminates error accumulation by using a direct physical measurement rather than iterative calculations based on historical data.
2Measurement precision
If only whole amount of lowering in capacity is known, then simple assessment is possible, but accurate estimation of material deterioration ratio and precipitation deterioration ratio cannot be achieved
Solution Approach 1:
The patent introduces freezing temperature as an additional measurement parameter to distinguish between material deterioration and lithium precipitation. By measuring freezing temperature alongside capacity, the system can separately estimate material deterioration ratio and precipitation deterioration ratio, achieving accurate differentiation without requiring complex multi-parameter measurements.
3Measurement precision
If freezing temperature measurement is used to calculate material deterioration ratio, then accurate differentiation from lithium precipitation is achieved, but additional measurement equipment is required
Solution Approach 1:
The patent makes the temperature measurement system multi-functional by using it for both capacity assessment (through operating temperature monitoring) and material deterioration assessment (through freezing temperature measurement). This approach reduces the need for completely separate measurement systems, as the same temperature sensing infrastructure serves dual purposes.
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
Accurately calculates the material and precipitation deterioration ratios, enabling better estimation of battery state and future capacity loss, thereby improving battery management and recycling processes.
Implementation Method 1
an amount of increase in freezing temperature (solidification point) of an electrolyte of a lithium ion battery correlates with deterioration of a material
Data Source
AI summary
A control device calculates an amount of increase ΔAm in freezing temperature measurement value Am from an initial freezing temperature Δ0 and calculates an amount of lowering in capacity corresponding to the amount of increase ΔAm in freezing temperature as an amount of lowering in capacity ΔBx due to deterioration of a material. The control device calculates an amount of lowering in capacity measurement value Bm from an initial capacity B0 as a whole amount of lowering in capacity ΔBm and calculates a material deterioration ratio X by using ΔBx and ΔBm. The control device calculates a value resulting from subtraction of ΔBx from ΔBm as an amount of lowering in capacity ΔBy due to precipitation of Li and calculates an Li precipitation deterioration ratio Y by using ΔBy and ΔBm.