Polysulfide Barrier Separator for Lithium-Ion Battery Cells

Solution Overview

Problem

Lithium-ion batteries face issues with polysulfides migrating from the cathode to the anode, causing contamination and potential short circuits, and existing separators either allow ion conduction but are permeable to polysulfides or are impermeable but have low ion conductivity.

Innovation Solution

A separator with a protective layer that is impermeable to polysulfides, composed of chemically reactive particles, and an ion-conducting copolymer layer that includes a stabilizing phase and an ionically conductive phase, preventing polysulfide migration while maintaining high ion conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If a separator is made from organic materials (polyethylene or polypropylene), then it is highly ionically conductive, but it is permeable to polysulfides

Engineering Contradiction:

Improveionic conductivityVSAvoidpolysulfide permeability

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The separator combines organic polymer materials (for ionic conductivity) with inorganic materials (for polysulfide impermeability) to create a composite structure that simultaneously achieves high ion conduction and polysulfide blocking capability

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The separator features a protective layer with specifically tailored properties (impermeable to polysulfides) applied to the side facing the cathode, while the bulk material maintains high ion conductivity, creating localized functional zones

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If a separator is made from inorganic materials, then it is impermeable to polysulfides, but it has relatively low conductivity for ions

Engineering Contradiction:

Improvepolysulfide impermeabilityVSAvoidionic conductivity

Core Design Contradiction:

Object-affected harmful factorsVSUse of energy by moving object

Solution Approach 1:

The separator combines organic polymer materials (for ionic conductivity) with inorganic materials (for polysulfide impermeability) to create a composite structure that simultaneously achieves high ion conduction and polysulfide blocking capability

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The separator features a protective layer with specifically tailored properties (impermeable to polysulfides) applied to the side facing the cathode, while the bulk material maintains high ion conductivity, creating localized functional zones

Inventive Principle:

Principle #3Local quality

3Ease of operation

If a separator is designed to be thin and flexible for assembly, then it is easy to install, but it may be more susceptible to dendrite penetration

Engineering Contradiction:

Improveassembly flexibilityVSAvoiddendrite resistance

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The separator features a protective layer with specifically tailored properties (impermeable to polysulfides) applied to the side facing the cathode, while the bulk material maintains high ion conductivity, creating localized functional zones

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The separator combines organic polymer materials (for ionic conductivity) with inorganic materials (for polysulfide impermeability) to create a composite structure that simultaneously achieves high ion conduction and polysulfide blocking capability

Inventive Principle:

Principle #40Composite materials

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 separator effectively prevents polysulfide contamination and dendrite growth, ensuring reliable battery operation by acting as a barrier to gases, liquids, and chemicals, while maintaining mechanical strength and flexibility for assembly.

Implementation Method 1

The chemically reactive particles of the protective layer, for example, contain an alkali metal or an alkali metal compound or they are made from an alkali metal or an alkali metal compound

Methodology Applied

Scientific EffectChemical reaction: Chemical Bonding

Implementation Method 2

Ions, in particular lithium ions, migrate from one electrode to the other during the charging and discharging of the battery cell. For this purpose, the separator is designed to be ionically conductive

Methodology Applied

Scientific EffectIon conduction: Conduction (electrical)

Implementation Method 3

The protective layer includes an inorganic substance... The inorganic substance of the protective layer includes composite particles that are situated close together, multiple of the composite participles being in contact with each other. This results in a tight bond which is impermeable to liquids and chemicals, in particular to polysulfides

Methodology Applied

Scientific EffectPhysical barrier: Physical Containment

Data Source

PatentUS10431797B2Separator including a polysulfide barrier layer for a battery cell, and battery cell

Publication Date: 2019.10.01 ROBERT BOSCH GMBH

AI summary

A vehicle traction battery includes a battery cell, the battery cell including a cathode, and anode, and a separator the anode and cathode. The separator includes at least one protective layer that is impermeable to polysulfides and at least one ion-conducting conductive layer whose composition is different than that of the protective layer and that is designed as a copolymer which includes a stabilizing phase and an ionically conductive phase, the protective layer including an inorganic substance.