Lithium-Ion Battery Separator Porous Layer for High-Rate Discharge

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Nonaqueous electrolyte secondary batteries, particularly lithium-ion batteries, face limitations in charge capacity after high-rate discharge, requiring enhancement in their charge capacity characteristics.

Innovation Solution

Incorporating a polyolefin porous film separator with a polyvinylidene fluoride-based resin, a positive electrode plate with specific capacitance, and a negative electrode plate with tailored capacitance, along with a porous layer containing a polyvinylidene fluoride-based resin, to optimize ion permeability and polarization states for improved discharge performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional nonaqueous electrolyte secondary battery is used, then basic battery functions are achieved, but charge capacity after high-rate discharge is insufficient

Engineering Contradiction:

Improvecharge capacity after high-rate dischargeVSAvoiddischarge rate performance

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent employs a porous layer containing polyvinylidene fluoride-based resin with specific porosity characteristics to enhance ion permeability during high-rate discharge. The porous structure allows faster ion transport while maintaining charge capacity, directly addressing the contradiction between discharge rate performance and charge capacity retention.

Inventive Principle:

Principle #31Porous materials

Solution Approach 2:

The patent optimizes specific parameters including the capacitance of electrode plates (positive electrode: 0.5-5.0 mAh/cm², negative electrode: 1.0-10.0 mAh/cm²), the piercing strength of the polyolefin porous film (≥2.0 mN/μm²), and the ratio T/M (0.3-1.5) to achieve both high discharge rate performance and maintained charge capacity after high-rate discharge.

Inventive Principle:

Principle #35Parameter changes

2Strength

If the polyolefin porous film has higher piercing strength, then separator durability is improved, but ion permeability may be compromised

Engineering Contradiction:

Improvepiercing strength of separatorVSAvoidion permeability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent applies local quality by introducing a porous layer with specific resin composition and porosity characteristics in contact with the electrode plates, while the polyolefin porous film maintains its structural integrity and piercing strength. This localized optimization allows the porous layer to handle ion permeability while the separator handles mechanical strength requirements.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent creates a composite structure combining the polyolefin porous film separator with a porous layer containing polyvinylidene fluoride-based resin. This composite material system allows the separator to provide mechanical strength and the porous layer to provide enhanced ion permeability, resolving the contradiction between strength and ion permeability.

Inventive Principle:

Principle #40Composite materials

3Quantity of substance

If electrode plate capacitance is increased to improve charge capacity, then energy storage is enhanced, but polarization effects increase reducing discharge output

Engineering Contradiction:

Improvecharge capacity of electrode platesVSAvoiddischarge output

Core Design Contradiction:

Quantity of substanceVSPower

Solution Approach 1:

The patent optimizes the capacitance parameters of electrode plates within specific ranges (positive electrode: 0.5-5.0 mAh/cm², negative electrode: 1.0-10.0 mAh/cm²) and combines them with a porous layer having controlled porosity (30-80%) to achieve a balance between charge capacity and discharge output, minimizing polarization effects while maximizing energy storage.

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

The solution enhances the charge capacity and discharge output of nonaqueous electrolyte secondary batteries, particularly under high-rate discharge conditions, by controlling the capacitance of electrode plates and using a porous layer with a high α-form polyvinylidene fluoride content to promote solvation and desolvation of ions.

Implementation Method 1

using a porous layer with a high α-form polyvinylidene fluoride content to promote solvation and desolvation of ions

Methodology Applied

Scientific EffectSolvation: Solvation

Implementation Method 2

a separator for a nonaqueous electrolyte secondary battery including a polyolefin porous film

Methodology Applied

Scientific EffectPermeation: Permeation

Data Source

PatentUS11038208B2Nonaqueous electrolyte secondary battery

Publication Date: 2021.06.15 SUMITOMO CHEM CO LTD

AI summary

A nonaqueous electrolyte secondary battery includes: a separator including a polyolefin porous film; a porous layer containing a polyvinylidene fluoride-based resin; a positive electrode plate having a capacitance falling within a specific range; and a negative electrode plate having a capacitance falling within a specific range. The polyolefin porous film has a given piercing strength, having a value of not less than 0.00 and not more than 0.54, the value being represented by the following expression: |1−T/M|, where T and M are distances at which a critical load is reached in a scratch test in which the polyolefin porous film is moved in transverse and machine directions, respectively, under a constant load of 0.1N. The polyvinylidene fluoride-based resin contains an α-form polyvinylidene fluoride-based resin in an amount of not less than 35.0 mol %.