Multilayer Polymer Electrolyte for Lithium Battery Safety

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Solution Overview

Problem

Lithium secondary batteries face challenges in achieving high energy density and safety due to the trade-off between mechanical strength and ionic conductivity in polymer electrolytes, leading to issues like internal short circuits and reduced capacity.

Innovation Solution

A multilayer polymer electrolyte structure is developed, with a first layer providing mechanical strength and a second layer ensuring lithium ion conduction, using varying weights of organic electrolyte with ionic salt in each layer to balance flexibility and conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the amount of organic electrolyte is increased to enhance ionic conductivity, then ionic conductivity is improved, but mechanical/physical properties are significantly deteriorated

Engineering Contradiction:

Improveionic conductivityVSAvoidmechanical/physical properties

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent divides the polymer electrolyte into multiple layers with different organic electrolyte content. The first layer has lower organic electrolyte content (0-60 wt%) to provide mechanical strength, while the second layer has higher organic electrolyte content (60-400 wt%) to provide high ionic conductivity. This segmentation allows each layer to optimize for its specific function without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the polymer electrolyte are assigned different compositions tailored to local requirements. The first layer near the electrode interface has lower organic electrolyte content for structural integrity, while the second layer has higher organic electrolyte content for ion transport. This local quality differentiation resolves the contradiction by matching material properties to functional requirements in different spatial locations.

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

The multilayer polymer electrolyte enhances both mechanical strength and ionic conductivity, preventing internal short circuits and improving battery performance, including high cycle durability and uniform electrolyte wetting, thus addressing safety and efficiency concerns.

Implementation Method 1

a second polymer layer to secure a conduction path for lithium ions, wherein the first polymer layer includes an organic electrolyte containing an ionic salt

Methodology Applied

Scientific EffectDiffusion: Diffusion

Implementation Method 2

a second polymer layer to secure a conduction path for lithium ions

Methodology Applied

Scientific EffectIonic conduction: Conduction (electrical)

Data Source

PatentEP2713432B1Novel polymer electrolyte and lithium secondary battery including same

Publication Date: 2017.08.09 LG CHEM LTD

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Figure 2~3

AI summary

Disclosed is a polymer electrolyte having a multilayer structure including a first polymer layer providing mechanical strength against external force and a second polymer layer to secure a conduction path for lithium ions, wherein the first polymer layer includes an organic electrolyte containing an ionic salt in an amount of 0 wt% to 60 wt% based on a weight of a polymer matrix of the first polymer layer and the second polymer layer includes an organic electrolyte containing an ionic salt in an amount of 60 wt% to 400 wt% based on a weight of a polymer matrix of the second polymer layer, and a lithium secondary battery including the same.