Li-Ion Battery Resin Swelling Control

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Solution Overview

Problem

In lithium ion secondary batteries with alloy-formable active materials, the expansion and contraction during charge/discharge cycles lead to uneven distribution of non-aqueous electrolyte, causing deterioration in cycle characteristics and over-discharge of the positive electrode.

Innovation Solution

Incorporating an easily swellable resin with a degree of swelling of 20% or more in the positive electrode and a hardly swellable resin with less than 20% swelling in the negative electrode, ensuring balanced electrolyte distribution and absorption, thereby preventing over-discharge and improving cycle characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If alloy-formable active material is used in the negative electrode, then capacity and energy density are improved, but cycle characteristics deteriorate due to expansion and contraction of the active material

Engineering Contradiction:

ImprovecapacityVSAvoidcycle characteristics

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent applies local quality by creating a resin layer with specific properties at the negative electrode surface that differs from the bulk electrode material. This resin layer has controlled swelling characteristics (less than 20% volume increase) that are locally optimized to suppress electrolyte absorption during alloy expansion, thereby protecting the overall battery cycle characteristics while maintaining high capacity

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses composite materials by combining alloy-formable active material particles with a resin binder to form a composite negative electrode structure. This composite approach allows the resin component to provide mechanical stability and controlled swelling behavior, preventing electrode deformation and maintaining structural integrity during charge-discharge cycles

Inventive Principle:

Principle #40Composite materials

2Stability of the object's composition

If resin coating is formed on negative electrode active material layer, then electrode deformation is suppressed, but non-aqueous electrolyte distribution becomes uneven

Engineering Contradiction:

Improveelectrode structure stabilityVSAvoidelectrolyte distribution uniformity

Core Design Contradiction:

Stability of the object's compositionVSQuantity of substance

Solution Approach 1:

The patent applies parameter changes by carefully controlling the resin layer's swelling parameter (volume increase less than 20%) and thickness (1-10 μm). By optimizing these parameters, the resin layer provides structural stability while maintaining sufficient electrolyte permeability, preventing both electrode deformation and electrolyte distribution imbalance

Inventive Principle:

Principle #35Parameter changes

3Quantity of substance

If non-aqueous electrolyte is absorbed into gaps by capillarity, then local impregnation occurs in positive electrode, but over-discharge and crystal structure disorder accelerate deterioration

Engineering Contradiction:

Improveelectrolyte absorptionVSAvoidpositive electrode durability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent applies preliminary anti-action by using the resin layer at the negative electrode surface to preemptively counteract capillary-driven electrolyte absorption. The resin layer's controlled swelling and surface properties prevent excessive electrolyte accumulation in gaps before it can be drawn into the positive electrode, thereby preventing over-discharge and crystal structure disorder in advance

Inventive Principle:

Principle #9Preliminary anti-action

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

The solution results in a lithium ion secondary battery with enhanced cycle characteristics, high capacity, and improved energy density by maintaining even electrolyte distribution and preventing over-discharge of the positive electrode.

Implementation Method 1

The positive electrode active material layer has an easily swellable resin having a degree of swelling with the non-aqueous electrolyte of 20% or more

Methodology Applied

Scientific EffectSwelling:

Implementation Method 2

the negative electrode active material layer has a hardly swellable resin having a degree of swelling with the non-aqueous electrolyte of less than 20%

Methodology Applied

Scientific EffectSwelling resistance:

Implementation Method 3

the non-aqueous electrolyte contained in the alloy-type secondary battery is absorbed into the gaps by capillarity

Methodology Applied

Scientific EffectCapillarity: Capillary Action

Data Source

PatentUS9153817B2Lithium ion secondary battery

Publication Date: 2015.10.06 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

Disclosed is a lithium ion secondary battery including: a positive electrode including a positive electrode active material layer comprising a positive electrode active material capable of absorbing and releasing lithium ions, and a positive electrode current collector; a negative electrode including a negative electrode active material layer comprising an alloy-formable active material, and a negative electrode current collector; a separator interposed between the positive electrode and the negative electrode; and a non-aqueous electrolyte. The positive electrode active material layer has an easily swellable resin having a degree of swelling with the non-aqueous electrolyte of 20% or more, and the negative electrode active material layer has a hardly swellable resin having a degree of swelling with the non-aqueous electrolyte of less than 20%.