Lithium Battery Deterioration Detection via External Voltage Measurement

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Solution Overview

Problem

Rechargeable lithium batteries using silicon or tin as negative active materials suffer from significant capacity deterioration due to charge/discharge cycles, making it difficult to maintain optimal discharge cutoff potential without complicating the battery structure and requiring additional electrodes.

Innovation Solution

A method to detect and estimate battery deterioration by measuring closed-circuit and open-circuit voltages, calculating an evaluation value, and comparing it to a reference value to control charging and discharging, thereby suppressing capacity loss and extending battery life.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a reference electrode of lithium is provided in the battery to control discharge potential of the negative electrode, then the discharge cutoff potential can be controlled to suppress deterioration, but the battery structure becomes complicated requiring an additional third electrode terminal

Engineering Contradiction:

Improvecycle characteristicsVSAvoidbattery structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The invention extracts the reference electrode from the battery structure, performing potential control measurements externally without requiring an additional electrode terminal inside the battery. This resolves the contradiction by maintaining reliability through external measurement while simplifying the battery structure.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention introduces an external measurement system as an intermediary between the battery and the control system. This mediator measures the potential difference between the positive and negative electrodes without requiring internal modification of the battery structure, thus maintaining reliability while avoiding structural complexity.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the discharge cutoff potential is set to 0.6 V or lower relative to the positive electrode, then deterioration suppression is intended, but it is difficult to confirm whether the potential is actually maintained due to changing potential ranges as materials deteriorate

Engineering Contradiction:

Improvecapacity retentionVSAvoidpotential measurement accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The invention implements a feedback control system that continuously measures the actual potential difference between electrodes and adjusts the discharge cutoff dynamically. This ensures accurate potential control by comparing measured values against target values and making real-time adjustments, resolving both reliability and measurement precision requirements.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The invention changes the control parameter from a fixed potential value (0.6 V) to a dynamically adjusted potential based on actual battery state and deterioration level. This allows the system to maintain accurate potential control despite material deterioration by adapting the cutoff potential to current battery characteristics.

Inventive Principle:

Principle #35Parameter changes

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 estimates battery deterioration and suppresses capacity loss by controlling charge/discharge cycles, allowing for repeated use while maintaining large capacity.

Implementation Method 1

a positive electrode having a positive active material that absorbs and emits lithium ions

Methodology Applied

Scientific EffectIon absorption and emission: Absorption (physical)

Implementation Method 2

lithium-ion conductive electrolyte provided between the positive electrode and the negative electrode

Methodology Applied

Scientific EffectIonic conduction: Conduction (electrical)

Data Source

PatentUS8102152B2Deterioration detecting method and deterioration suppressing method for rechargeable lithium batteries, deterioration detector, deterioration suppressor, battery pack, and charger

Publication Date: 2012.01.24 PANASONIC HOLDINGS CORP

AI summary

According to a deterioration detecting method for rechargeable lithium batteries, battery voltages of a rechargeable lithium battery before and after the completion of charging or discharging are measured. An evaluation value is calculated based on the measured battery voltages. This evaluation value is compared with a reference value of the rechargeable lithium battery stored in advance. A deterioration level of the rechargeable lithium battery is estimated based on this comparison result. In addition, further deterioration can be suppressed by controlling charging and discharging of the rechargeable lithium battery based on the estimated deterioration level.