Silicon-Anode Lithium Secondary Battery With Controlled Si Depth

Solution Overview

Problem

Lithium secondary batteries using silicon particles as a negative electrode active material face challenges in achieving excellent lifespan characteristics due to rapid volume expansion during charging and discharging.

Innovation Solution

The lithium secondary battery design includes a negative electrode with silicon particles, where the Si charge depth is between 30% to 60% and the Si discharge depth is 10% or greater, optimizing the battery's performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If silicon particles are used as negative electrode active material, then capacity characteristics and quick charging performance are improved, but volume expansion occurs during charging causing damage to negative electrode and disconnection of conductive path

Engineering Contradiction:

Improvelithium storage capacityVSAvoidstructural integrity of negative electrode

Core Design Contradiction:

Quantity of substanceVSStrength

Solution Approach 1:

The patent applies preliminary action by pre-lithiating the negative electrode before battery assembly. This involves inserting a specific amount of lithium into the silicon particles in advance (pre-lithiation capacity of 0.5 to 2.0 mAh/cm²) to compensate for the volume expansion that will occur during subsequent charging cycles. This pre-positioning of lithium prevents the structural damage that would otherwise occur during normal charging operations.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent utilizes parameter changes by precisely controlling the pre-lithiation capacity parameter within the range of 0.5 to 2.0 mAh/cm². By adjusting this parameter, the invention optimizes the balance between compensating for silicon volume expansion and maintaining overall battery performance. This parameter control ensures that enough lithium is present to handle expansion without causing excessive side reactions or capacity loss.

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If silicon-based negative electrode active material is used, then theoretical capacity is 10 times higher than carbon-based material, but rapid volume expansion causes damage and disconnection resulting in rapid degradation in battery performance

Engineering Contradiction:

Improvetheoretical capacityVSAvoidbattery lifespan

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent applies preliminary action by pre-lithiating the negative electrode before battery assembly. This involves inserting a specific amount of lithium into the silicon particles in advance (pre-lithiation capacity of 0.5 to 2.0 mAh/cm²) to compensate for the volume expansion that will occur during subsequent charging cycles. This pre-positioning of lithium prevents the structural damage that would otherwise occur during normal charging operations.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent utilizes parameter changes by precisely controlling the pre-lithiation capacity parameter within the range of 0.5 to 2.0 mAh/cm². By adjusting this parameter, the invention optimizes the balance between compensating for silicon volume expansion and maintaining overall battery performance. This parameter control ensures that enough lithium is present to handle expansion without causing excessive side reactions or capacity loss.

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If carbon-based negative electrode active material is used, then structural stability is maintained, but capacity is small and reaction rate with lithium is low

Engineering Contradiction:

Improvestructural stabilityVSAvoidlithium storage capacity

Core Design Contradiction:

Stability of the object's compositionVSQuantity of substance

Solution Approach 1:

The patent applies composite materials by combining silicon particles with a carbon-based matrix or coating. This composite structure allows the silicon to provide high lithium storage capacity while the carbon component maintains structural stability and prevents excessive volume expansion. The composite approach leverages the advantages of both materials: the high capacity of silicon and the structural integrity of carbon.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent utilizes parameter changes by precisely controlling the pre-lithiation capacity parameter within the range of 0.5 to 2.0 mAh/cm². By adjusting this parameter, the invention optimizes the balance between compensating for silicon volume expansion and maintaining overall battery performance. This parameter control ensures that enough lithium is present to handle expansion without causing excessive side reactions or capacity loss.

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

This design enhances the battery's lifespan characteristics while maintaining high capacity and quick charging performance, with an energy density of 500 Wh/L or more and 450 or more cycles to reach 80% life.

Implementation Method 1

a negative electrode including a negative electrode active material; a positive electrode including a positive electrode active material... the negative electrode active material includes silicon particles

Methodology Applied

Scientific EffectIntercalation: Absorption (physical)

Implementation Method 2

an electrolyte... a non-aqueous electrolyte that becomes a medium for delivering lithium ions

Methodology Applied

Scientific EffectIon transport: Diffusion

Implementation Method 3

a separator interposed between the negative electrode and the positive electrode

Methodology Applied

Scientific EffectPhysical separation: Physical Containment

Data Source

PatentUS20250183280A1Lithium Secondary Battery

Publication Date: 2025.06.05 LG ENERGY SOLUTION LTD

AI summary

The present invention relates to a lithium secondary battery including a negative electrode including a negative electrode active material, a positive electrode including a positive electrode active material, a separator interposed between the negative electrode and the positive electrode, and an electrolyte, wherein the negative electrode active material includes silicon particles, a Si charge depth represented by Equation 1 below is 30% to 60%, and a Si discharge depth represented by Equation 2 below is 10% or greater.Si⁢ charge⁢ depth⁢ (%)={(positive⁢ electrode⁢ loading⁢ amount+ pre-lithiation⁢ capacity⁢ of⁢ negative⁢ electrode)/ negative⁢ electrode⁢ loading⁢ amount}×100Equation⁢ 1Si⁢ discharge⁢ depth⁢ (%)={(positive⁢ electrode⁢ loading⁢ amount+ pre-lithiation⁢ capacity⁢ of⁢ negative⁢ electrode- discharge⁢ loading⁢ amount)/ negative⁢ electrode⁢ loading⁢ amount}×100Equation⁢ 2In Equations 1 and 2 above, the positive electrode loading amount indicates capacity per unit area of the positive electrode (unit: mAh/cm2), the negative electrode loading amount indicates capacity per unit area of the negative electrode (unit: mAh/cm2), the pre-lithiation capacity of the negative electrode indicates capacity per unit area (unit: mAh/cm2) of lithium (Li) inserted into the negative electrode through pre-lithiation, and the discharge loading amount indicates a value obtained by dividing discharge capacity of a secondary battery by positive electrode area at discharge cut-off voltage.