Nonaqueous electrolyte secondary battery

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Solution Overview

Problem

Non-aqueous electrolyte secondary batteries experience a decrease in battery capacity after high-temperature storage due to decomposition reactions of the electrolyte solution at the electrodes.

Innovation Solution

The battery design includes a negative electrode active material layer with specific porosity distribution and the use of a phosphoric acid ester compound in the electrolyte solution, where graphite particles with low internal porosity are predominantly on the outer surface, and the electrolyte contains a phosphoric acid ester compound to suppress decomposition reactions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional carbon materials with uniform porosity are used in the negative electrode, then the battery structure is simple, but the battery capacity decreases significantly after high-temperature storage due to electrolyte decomposition

Engineering Contradiction:

Improvebattery capacity retention after high-temperature storageVSAvoidnegative electrode structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies local quality by creating a negative electrode with non-uniform porosity distribution. Graphite particles with different internal porosities (first porosity in the inner half, second porosity in the outer half) are selectively distributed to different regions of the electrode. This spatial variation in porosity allows the electrode to have different functional characteristics in different regions, suppressing electrolyte decomposition at the outer surface while maintaining overall battery performance.

Inventive Principle:

Principle #3Local quality

2Reliability

If graphite particles with low internal porosity are used throughout the negative electrode, then electrolyte decomposition is suppressed, but the battery capacity is insufficient

Engineering Contradiction:

Improvesuppression of electrolyte decompositionVSAvoidbattery capacity

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent resolves this contradiction by applying local quality through spatially differentiated porosity. The inner half of the negative electrode contains graphite particles with first internal porosity (5-20%) for adequate capacity, while the outer half contains graphite particles with second internal porosity (0-5%) for suppressing electrolyte decomposition. This local differentiation allows each region to optimize for its specific function.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent segments the negative electrode into two distinct regions based on porosity characteristics. By dividing the electrode thickness into an inner half and an outer half with different graphite particle porosity distributions, the patent creates functionally distinct zones that collectively solve both the capacity and decomposition suppression requirements.

Inventive Principle:

Principle #1Segmentation

3Reliability

If the entire negative electrode surface is exposed to electrolyte, then electrolyte decomposition occurs at all locations, but limiting electrolyte contact reduces active material exposure and capacity

Engineering Contradiction:

Improvesuppression of electrolyte decomposition at negative electrodeVSAvoidnegative electrode active material utilization

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent applies local quality by creating a surface layer (outer half) with graphite particles having low internal porosity (0-5%). This surface layer acts as a protective interface with the electrolyte, suppressing decomposition reactions. The bulk interior (inner half) contains graphite particles with higher porosity (5-20%) that provide adequate capacity while being shielded from direct electrolyte contact by the low-porosity surface layer.

Inventive Principle:

Principle #3Local quality

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

This configuration effectively reduces the decrease in battery capacity after high-temperature storage by minimizing electrolyte decomposition at both positive and negative electrodes.

Implementation Method 1

the non-aqueous electrolyte solution contains a phosphoric acid ester compound represented by general formula (I)... effectively reduces the decrease in battery capacity after high-temperature storage by minimizing electrolyte decomposition at both positive and negative electrodes

Methodology Applied

Scientific EffectDecomposition reaction suppression:

Data Source

PatentUS12531271B2Nonaqueous electrolyte secondary battery

Publication Date: 2026.01.20 PANASONIC ENERGY CO LTD

AI summary

A nonaqueous electrolyte secondary battery according to one embodiment of the present disclosure comprises a positive electrode, a negative electrode and a nonaqueous electrolyte solution; the negative electrode comprises a negative electrode collector and a negative electrode active material layer that is provided on the negative electrode collector; the negative electrode active material layer contains, as negative electrode active materials, graphite particles A and graphite particles B; the graphite particles A have an internal void fraction of 5% or less; the graphite particles B have an internal void fraction of from 8% to 20%; if the negative electrode active material layer is halved in the thickness direction, a region on the half closer to the outer surface contains more graphite particles A than a region on the half closer to the negative electrode collector.