Carbon-Coated Silicon Anode Material for Swelling-Stable Li Batteries

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Solution Overview

Problem

Lithium secondary batteries face issues with mechanical and chemical damage due to expansion and contraction of anode active materials during charging and discharging, leading to reduced conductivity and capacity, as well as side reactions with the electrolyte, which affect their stability and lifespan.

Innovation Solution

An anode active material is developed with a silicon-based core particle coated with carbon, where the carbon coating prevents exposure to the electrolyte, suppresses swelling, and enhances ion conductivity, thereby improving the battery's electrical properties and lifespan.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If silicon-based active material is used to increase energy density, then capacity is improved, but mechanical stability deteriorates due to expansion and contraction during charging and discharging

Engineering Contradiction:

Improveenergy densityVSAvoidmechanical stability

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The patent applies the nesting principle by coating silicon-based active material particles with a carbon layer. The carbon coating acts as a protective shell that encapsulates the silicon core, allowing the high-capacity silicon to undergo volume expansion and contraction during lithium insertion/extraction cycles without suffering mechanical degradation. This nested structure enables the inner silicon particle to maintain its integrity while providing high energy density.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The patent employs composite materials by combining silicon-based active material with carbon coating to create a hybrid structure. The silicon component provides high theoretical capacity (4.2 times that of graphite), while the carbon component provides mechanical strength, electrical conductivity, and structural stability. This composite approach allows the anode to simultaneously achieve high energy density and excellent cycle stability.

Inventive Principle:

Principle #40Composite materials

2Strength

If carbon coating is applied to improve stability, then mechanical strength is improved, but electrical conductivity may deteriorate if coating is too thick

Engineering Contradiction:

Improvemechanical strengthVSAvoidelectrical conductivity

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent applies parameter changes by precisely controlling the thickness of the carbon coating layer. The carbon coating thickness is optimized to be sufficient to provide mechanical protection and structural stability during silicon expansion/contraction, yet thin enough to maintain adequate electrical conductivity for lithium ion transport and electron flow. This parameter optimization balances the competing requirements of mechanical strength and electrical conductivity.

Inventive Principle:

Principle #35Parameter changes

3Duration of action of stationary object

If particle structure is modified to improve stability, then cycle life is improved, but surface area for reaction may decrease

Engineering Contradiction:

Improvecycle lifeVSAvoidsurface area

Core Design Contradiction:

Duration of action of stationary objectVSArea of stationary object

Solution Approach 1:

The patent applies segmentation by using smaller silicon-based active material particles with controlled size distribution. By reducing particle size, the total surface area is increased, providing more reaction sites for lithium insertion/extraction. The segmented small particles also experience reduced mechanical stress during volume changes compared to large particles, improving cycle life. The carbon coating further protects these small particles from aggregation and degradation.

Inventive Principle:

Principle #1Segmentation

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 carbon-coated silicon-based anode active material enhances energy density, charge/discharge capacity, and chemical stability, reducing side reactions and electrolyte consumption, leading to improved long-term performance and high-temperature storage capabilities.

Implementation Method 1

the carbon coating prevents exposure to the electrolyte, suppresses swelling, and enhances ion conductivity

Methodology Applied

Scientific EffectPhysical barrier formation: Physical Containment

Implementation Method 2

the carbon coating prevents exposure to the electrolyte, suppresses swelling

Methodology Applied

Scientific EffectMechanical constraint:

Implementation Method 3

enhances ion conductivity

Methodology Applied

Scientific EffectIon conductivity enhancement: Conduction (electrical)

Data Source

PatentUS20240258511A1Anode active material for lithium secondary battery and lithium secondary battery including the same

Publication Date: 2024.08.01 SK ON CO LTD

AI summary

An anode active material for a lithium secondary battery includes a silicon-based active material that includes a core particle and a carbon coating formed on or over the core particle. The anode active material satisfies a specific relation within a specific range. A lithium secondary battery includes an anode including the anode active material, and a cathode facing the anode.