Microcapsule Electrolyte Additive for High-Temperature Li-Ion Stability

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Solution Overview

Problem

Lithium secondary batteries face performance degradation due to surface damage of nickel-based lithium metal oxide cathodes and side reactions with the electrolyte, especially at high and low temperatures, leading to reduced power and capacity, and stability issues.

Innovation Solution

An electrolyte additive comprising microcapsule particles with a phosphorus-based flame retardant core and a urea-formaldehyde-resorcinol polymer shell is introduced, which provides flame retardancy and physically separates the flame retardant from the electrolyte, preventing thermal runaway and maintaining battery performance at high temperatures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a phosphorus-based flame retardant is added to the electrolyte solution, then flame retardancy and high temperature stability are improved, but the battery performance and capacity may be degraded due to side reactions

Engineering Contradiction:

Improveflame retardancy and high temperature stabilityVSAvoidbattery capacity and power

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The flame retardant is segmented into microcapsule particles with a core-shell structure, where the core contains the phosphorus-based flame retardant and the shell contains a polymer that prevents direct contact with the electrolyte. This segmentation allows the flame retardant to be present in the electrolyte solution without causing harmful side reactions, thus maintaining battery performance while providing flame retardancy.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The polymer shell acts as an intermediary between the phosphorus-based flame retardant and the electrolyte solution. It prevents direct interaction between the flame retardant and electrolyte, avoiding side reactions that would degrade battery capacity, while still allowing the flame retardant to function when needed for thermal runaway prevention.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the flame retardant is directly mixed with the electrolyte, then flame retardancy is improved, but the battery shows instability during repeated charging and discharging due to side reactions

Engineering Contradiction:

Improveflame retardancyVSAvoidbattery stability during charging and discharging

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The flame retardant is divided into microcapsule particles that physically separate the flame retardant from the electrolyte, preventing direct contact and side reactions during charging and discharging cycles. This maintains battery stability while providing flame retardancy.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The polymer shell surrounding the flame retardant core acts as a flexible barrier that prevents direct interaction between the flame retardant and electrolyte during normal battery operation, maintaining compositional stability during repeated charging and discharging.

Inventive Principle:

Principle #30Flexible shells and thin films

3Productivity

If a microcapsule structure is used to prevent side reactions, then battery performance is maintained, but the device complexity increases

Engineering Contradiction:

Improvebattery capacity retentionVSAvoidadditive structure complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The microcapsule particles have controlled parameters including particle diameter (1 μm to 15 μm) and shell thickness (100 nm to 300 nm) that optimize both performance maintenance and structural simplicity. These parameter optimizations balance the complexity of the microcapsule structure with the need to maintain battery capacity.

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 additive enhances the high-temperature stability and lifespan of lithium secondary batteries by stabilizing free radicals and preventing combustion, while maintaining initial performance without degrading the battery's capacity and internal resistance.

Implementation Method 1

stabilizing free radicals and preventing combustion

Methodology Applied

Scientific EffectFree radical stabilization:

Implementation Method 2

physically separates the flame retardant from the electrolyte

Methodology Applied

Scientific EffectPhysical containment: Physical Containment

Data Source

PatentUS20240363903A1Additive for Electrolyte Solution of Secondary Battery, Method of Preparing the Same, Electrolyte Solution Including the Same and Lithium Secondary Battery Including the Same

Publication Date: 2024.10.31 SK INNOVATION CO LTD

AI summary

An additive for an electrolyte solution of a secondary battery includes a microcapsule particle. The microcapsule particle includes a core containing a phosphorus-based flame retardant, and a shell surrounding a surface of the core and including a polymer that includes a urea-derived repeating unit, a formaldehyde-derived repeating unit and a resorcinol-derived repeating unit. An electrolyte solution and a lithium secondary battery including the additive for an electrolyte solution have improved stability, life-span and storage properties at high temperature.