Solid Polymer Electrolyte for Safe Lithium Batteries

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Solution Overview

Problem

Current lithium-ion batteries face safety concerns due to flammable liquid electrolytes and limited energy density, with lithium dendrite growth causing short circuits and overheating, and existing solid polymer electrolytes offer high ionic conductivity only at high temperatures, not suitable for room temperature applications.

Innovation Solution

A polymer electrolyte composition with a hard polymer segment having a glass transition temperature greater than 110°C, covalently bound to an ionically-conducting segment with a molecular weight of 800 to 10,000 g/mol, and a salt comprising alkali, alkaline earth metals, zinc, or aluminum, achieving ionic conductivity greater than 1×10−8 S/cm at 25°C, and optionally including a plasticizer to enhance conductivity and charge/discharge rates.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If solid polymer electrolytes with high shear modulus are used to suppress dendrite growth, then dendrite suppression is improved, but ionic conductivity decreases to below 10^-4 S/cm at 25°C

Engineering Contradiction:

Improvedendrite suppressionVSAvoidionic conductivity

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent uses block copolymers consisting of rigid segments (for mechanical strength and dendrite suppression) and flexible ion-conducting segments (for ionic conductivity). This composite structure at the molecular level allows simultaneous achievement of high shear modulus and adequate ionic conductivity at room temperature

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

Different segments of the polymer chain are assigned different functions: rigid segments provide mechanical integrity and dendrite suppression, while flexible segments with appropriate molecular weight provide ion conduction pathways. This local functional differentiation resolves the contradiction between mechanical strength and ionic conductivity

Inventive Principle:

Principle #3Local quality

2Use of energy by moving object

If flammable liquid electrolytes are used in Li-ion batteries, then energy density is improved, but safety deteriorates due to fire hazards

Engineering Contradiction:

Improveenergy densityVSAvoidfire hazard

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent changes the physical state of the electrolyte from liquid to solid polymer, fundamentally altering the safety parameters while maintaining ion conductivity. This phase change eliminates flammability while preserving the ability to conduct lithium ions for high energy density applications

Inventive Principle:

Principle #35Parameter changes

3Quantity of substance

If lithium metal anodes are used instead of lithiated graphite, then storage capacity is improved, but reliability deteriorates due to dendrite formation and short circuits

Engineering Contradiction:

Improvestorage capacityVSAvoidshort circuit prevention

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The rigid polymer matrix is designed in advance to physically constrain lithium deposition, preventing dendrite formation before it can cause short circuits. The high shear modulus of the polymer creates a mechanical barrier that opposes dendrite growth during charge-discharge cycles

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 polymer electrolyte composition provides improved mechanical integrity and ionic conductivity, effectively suppressing lithium dendrite growth and enhancing the safety and energy storage capacity of lithium-based batteries at room temperature, while avoiding flammable organic solvents.

Implementation Method 1

an ionically-conducting segment having a molecular weight of 800 to 10,000 g/mol... wherein said polymer electrolyte composition has an ionic conductivity for an M ion greater than or equal to 1×10−8 S/cm at 25° C.

Methodology Applied

Scientific EffectIonic conduction: Conduction (electrical)

Implementation Method 2

a hard polymer segment having: (a) a glass transition temperature (Tg) greater than or equal to 110° C.

Methodology Applied

Scientific EffectGlass transition:

Implementation Method 3

a salt comprising an element M, wherein M is selected from an alkali metal, an alkaline earth metal, zinc, and aluminum

Methodology Applied

Scientific EffectIonic dissociation: Electrolyte

Data Source

PatentUS10490848B2Solid polymer electrolyte composition

Publication Date: 2019.11.26 CORNELL UNIVERSITY

AI summary

A polymer electrolyte composition includes a hard polymer segment covalently bound to an ionically-conducting segment, and a salt that includes an element M selected from an alkali metal, an alkaline earth metal, zinc, and aluminum. The hard polymer segment has a glass transition temperature (Tg) greater than or equal to 110° C., or a melting temperature (Tm) greater than 110° C. The ionically-conducting segment has a molecular weight of 800 to 10,000 g/mol. The polymer electrolyte composition has an ionic conductivity for an M ion greater than or equal to 1×10−8 S/cm at 25° C. Methods for the preparation of the polymer electrolyte composition are also provided, as are articles (e.g., electrochemical cells and energy storage devices) that contain the polymer electrolyte composition.