Non-aqueous Electrolyte Battery Separator Porosity Optimization

Solution Overview

Problem

Non-aqueous electrolyte secondary batteries with carboxylic acid esters improve overcharge characteristics but compromise high-temperature cycle characteristics, and the addition of nitrile compounds further reduces shutdown response speed and overcharge characteristics after repeated cycles at high temperatures.

Innovation Solution

A non-aqueous electrolyte secondary battery design incorporating a separator with specific porosity (28-54%) and air permeability (86-450 secs/dl) and a non-aqueous electrolyte containing a carboxylic acid ester and a nitrile compound, such as adiponitrile, to enhance high-temperature cycle characteristics while maintaining shutdown and overcharge functions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a carboxylic acid ester is added to improve overcharge characteristics, then overcharge resistance is improved, but high-temperature cycle characteristics deteriorate

Engineering Contradiction:

Improveovercharge characteristicsVSAvoidhigh-temperature cycle characteristics

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent combines a carboxylic acid ester (for overcharge protection) with a nitrile compound (for high-temperature stability) in the electrolyte composition. This merging of two different additive types allows the system to simultaneously achieve both overcharge resistance and high-temperature cycle characteristics, resolving the contradiction between these two performance aspects.

Inventive Principle:

Principle #5Merging (Combining)

2Stability of the object's composition

If a nitrile compound is added to improve high-temperature cycle characteristics, then high-temperature cycle characteristics are improved, but shutdown response speed deteriorates

Engineering Contradiction:

Improvehigh-temperature cycle characteristicsVSAvoidshutdown response speed

Core Design Contradiction:

Stability of the object's compositionVSSpeed

Solution Approach 1:

The patent optimizes the concentration parameters of both the nitrile compound and carboxylic acid ester in the electrolyte. By carefully controlling the amounts of these additives (within specific ranges), the patent achieves high-temperature cycle characteristics while minimizing the negative impact on shutdown response speed. This parameter optimization resolves the contradiction between these two performance aspects.

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If a nitrile compound is added to reduce electrolyte viscosity, then low-temperature performance is improved, but overcharge characteristics after repeated cycles deteriorate

Engineering Contradiction:

Improvelow-temperature performanceVSAvoidovercharge characteristics after repeated cycles

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent optimizes the concentration parameters of both the nitrile compound and carboxylic acid ester in the electrolyte. By carefully controlling the amounts of these additives (within specific ranges), the patent achieves high-temperature cycle characteristics while minimizing the negative impact on shutdown response speed. This parameter optimization resolves the contradiction between these two performance aspects.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS8679676B2Non-aqueous electrolyte secondary battery having a nitrile compound and a carboxylic acid ester compound

Publication Date: 2014.03.25 PANASONIC ENERGY CO LTD

AI summary

Provided is a non-aqueous electrolyte secondary battery which has excellent high-temperature cycle characteristics, while maintaining the shutdown response speed of the separator and the overcharge characteristics after many repeated cycles at high temperatures. The battery uses a non-aqueous electrolyte containing a carboxylic acid ester and a nitrile compound, and a separator having a porosity of 28 to 54% and an air permeability of 86 to 450 secs/dl.