Core-Shell LiCoO2 Cathode and Electrolyte Film for High-Voltage Stability

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Solution Overview

Problem

Lithium cobalt-based positive electrode active materials in lithium secondary batteries suffer from low structural stability and rapid gas and cobalt dissolution when operated at high voltages, limiting their cycle characteristics and high-temperature durability.

Innovation Solution

A lithium secondary battery design incorporating a positive electrode with a core-shell structure, where the core is a lithium cobalt-based oxide and the shell is a lithium cobalt-based oxide with doping elements like aluminum, zirconium, magnesium, or titanium, combined with a non-aqueous electrolyte solution containing lithium difluorophosphate and a dinitrile-based compound, which forms a durable film on the electrode surface, reducing interfacial resistance and preventing side reactions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If lithium cobalt-based oxide is used as positive electrode active material, then high energy density and operating voltage are achieved, but structural stability deteriorates and gas/cobalt dissolution occurs rapidly at high voltage

Engineering Contradiction:

Improveenergy densityVSAvoidstructural stability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent uses a composite material structure where lithium cobalt-based oxide particles are coated with a lithium-rich lithium cobalt-based oxide shell. This composite structure allows the core to provide high energy density while the shell provides structural stability and suppresses gas/cobalt dissolution at high voltage operations

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies local quality modification by creating a shell layer with different composition (lithium-rich lithium cobalt-based oxide) on the surface of the particles. This shell has higher lithium content and different properties than the core, providing localized protection at the surface where electrochemical reactions occur, while maintaining the high-capacity core material

Inventive Principle:

Principle #3Local quality

2Quantity of substance

If lithium defect portion is formed on surface by adding dopant, then initial capacity is improved, but gas and cobalt dissolution occur rapidly at voltage of 4.45 V or higher

Engineering Contradiction:

Improveinitial capacityVSAvoidhigh-temperature storability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent changes the compositional parameter by creating a lithium-rich shell layer with higher lithium content than the core. This parameter change (increased lithium content in the shell) modifies the surface properties to suppress side reactions and cobalt dissolution at high voltage, while still maintaining good initial capacity

Inventive Principle:

Principle #35Parameter changes

3Volume of stationary object

If large particle diameter is used to increase packing density, then energy per unit volume is improved, but lithium transfer rate decreases due to two-dimensional layered structure

Engineering Contradiction:

Improvepacking densityVSAvoidlithium transfer rate

Core Design Contradiction:

Volume of stationary objectVSSpeed

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent introduces a porous structure within the shell layer, creating a hierarchical porous architecture. This porous structure provides multiple pathways for lithium ion transport, significantly enhancing the lithium transfer rate while maintaining large particle diameter for high packing density

Inventive Principle:

Principle #31Porous 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

This configuration enhances the structural stability of the positive electrode, improves high-temperature storage characteristics, and maximizes cycle characteristics by minimizing gas and cobalt dissolution, making the battery suitable for high-voltage applications.

Implementation Method 1

a non-aqueous electrolyte solution containing lithium difluorophosphate and a dinitrile-based compound, which forms a durable film on the electrode surface

Methodology Applied

Scientific EffectFilm formation: Deposition (physical)

Implementation Method 2

a lithium secondary battery including a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode

Methodology Applied

Scientific EffectLithium ion transfer: Ion Exchange

Data Source

PatentUS20240291018A1Lithium Secondary Battery

Publication Date: 2024.08.29 LG ENERGY SOLUTION LTD

AI summary

The present disclosure provides a lithium secondary battery comprising a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte solution, wherein the positive electrode active material includes a core including a lithium cobalt-based oxide represented by Formula 1; and a shell including a lithium cobalt-based oxide represented by Formula 2 which is disposed on a surface of the core, and the non-aqueous electrolyte solution may include a lithium salt, an organic solvent, lithium difluorophosphate, and a dinitrile-based compound represented by Formula 3:wherein all the variables are described herein.