Lithium Deposition Detection via Voltage Coefficient Analysis

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Solution Overview

Problem

Existing methods for determining lithium deposition in nonaqueous electrolyte type lithium ion secondary batteries require disassembly, making it difficult to assess whether deposition has occurred and preventing its occurrence only in low temperature states, failing to address deposition outside these conditions.

Innovation Solution

A system that calculates coefficients from charging and discharging voltage data to determine the possibility of lithium deposition without disassembly, using symmetry and intersection phenomena in coefficient plots to assess battery health.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the battery is disassembled to confirm lithium deposition, then the determination accuracy is improved, but the ease of operation deteriorates and the battery cannot be reused

Engineering Contradiction:

Improvelithium deposition determination accuracyVSAvoidbattery disassembly convenience

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The patent replaces the mechanical disassembly method with an electrical measurement system. By measuring voltage changes during charging and discharging cycles and analyzing coefficient variations in quadratic approximation curves, the system can determine lithium deposition without physically opening the battery, thus maintaining determination accuracy while improving ease of operation and battery reusability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces voltage measurement data and coefficient analysis as an intermediary between the battery and the determination process. Instead of directly observing the battery's internal state through disassembly, the system uses voltage coefficients as a mediator to indirectly detect lithium deposition, enabling non-invasive assessment

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If the battery is kept in use without disassembly, then the productivity is improved, but the ability to detect lithium deposition deteriorates

Engineering Contradiction:

Improvebattery usage continuityVSAvoidlithium deposition detection capability

Core Design Contradiction:

ProductivityVSDifficulty of detecting and measuring

Solution Approach 1:

The patent enables continuous monitoring of battery health by performing voltage measurements during normal charging and discharging operations. The system continuously calculates voltage coefficients and analyzes their variations over multiple sampling periods, allowing lithium deposition detection to occur continuously without interrupting battery usage, thus maintaining both productivity and detection capability

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The patent implements a feedback mechanism where voltage measurement results and coefficient variations are continuously analyzed to provide information about lithium deposition status. This feedback loop allows the system to detect deposition trends over time while the battery remains in service, maintaining both continuous operation and detection capability

Inventive Principle:

Principle #23Feedback

3Reliability

If the battery is made to internally generate heat to raise temperature before low temperature state, then the prevention of lithium deposition in low temperature is improved, but the ability to treat deposition outside low temperature conditions deteriorates

Engineering Contradiction:

Improvelithium deposition prevention in low temperatureVSAvoidapplicability to various temperature conditions

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent detects lithium deposition by analyzing changes in voltage coefficients under various operating conditions rather than controlling temperature to prevent deposition. The system monitors coefficient variations during charging and discharging at different temperatures, enabling detection and assessment of lithium deposition across a wide range of temperature conditions, thus improving adaptability while maintaining reliability through comprehensive parameter monitoring

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP2485318B1Nonaqueous electrolyte solution type lithium-ion secondary battery system, method for determining lithium precipitation by the system, and vehicle having the system mounted therein

Publication Date: 2018.01.24 TOYOTA JIDOSHA KK

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AI summary

It is arranged to obtain charging voltage when charging voltage is applied to a nonaqueous electrolyte type lithium ion secondary battery and discharging voltage when a discharging current is generated by the battery. A coefficient of a quadratic term of an approximated curve of a quadratic function with respect to changes in value within a sampling period for each of the charging voltage and the discharging voltage is calculated. This calculation is repeated over a plurality of the sampling periods. Based on occurrence situations of symmetry phenomenon and intersection phenomenon in the calculated coefficients, it can be determined whether or not there is a possibility of lithium deposition without disassembling the battery.