Silicon Alloy Negative Material with Carbon Coating for Battery Lifetime

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Solution Overview

Problem

Lithium secondary batteries using non-carbonaceous materials like Si or Sn face rapid capacity degradation due to volume expansion during charging and discharging, limiting their lifetime.

Innovation Solution

A negative active material comprising a silicon-based alloy with carbon nanoparticles and an amorphous carbonaceous coating layer is developed, where the carbon nanoparticles have a smaller average diameter than the core particle, and the amorphous carbonaceous coating layer surrounds the surface, improving electrical conductivity and capacity retention.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If non-carbonaceous materials such as Si or Sn are used as negative active materials, then capacity density is improved (10 times or more higher than graphite), but capacity retention deteriorates due to rapid capacity decrease from volume expansion during charging and discharging

Engineering Contradiction:

Improvecapacity densityVSAvoidcapacity retention

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent embeds silicon-based alloy nanoparticles within a carbonaceous matrix structure, creating a nested configuration where the high-capacity silicon core is protected by the stable carbon shell. This nested structure allows the silicon to expand and contract during lithium insertion/extraction while maintaining structural integrity and preventing capacity fade.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The patent creates a composite material system combining silicon-based alloy with carbonaceous materials (graphite, amorphous carbon, or hard carbon). The composite structure leverages the high capacity of silicon while the carbon component provides structural stability and conductivity, resolving the contradiction between high capacity and good retention.

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If silicon-based alloy is used to achieve high capacity, then volume expansion occurs during charging and discharging, but this leads to rapid capacity decrease and shortened battery lifetime

Engineering Contradiction:

Improvebattery capacityVSAvoidbattery lifetime

Core Design Contradiction:

Quantity of substanceVSDuration of action of stationary object

Solution Approach 1:

The patent employs a carbonaceous coating layer as a flexible shell surrounding the silicon-based alloy core. This thin film shell can accommodate the volume changes of silicon during lithium insertion and extraction, providing mechanical flexibility that prevents structural degradation and maintains battery performance over extended cycles.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The carbonaceous matrix and coating layer serve as a pre-established cushioning structure that absorbs and distributes the mechanical stress from silicon volume expansion before it can cause damage to the electrode structure, thereby extending battery lifetime.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Reliability

If carbon nanoparticles are added to the surface of core particles, then electrical conductivity is improved, but device complexity increases

Engineering Contradiction:

Improveelectrical conductivityVSAvoidmaterial structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the functions of conductivity enhancement and structural protection by integrating carbon nanoparticles into the carbonaceous matrix that already surrounds the silicon core. This merging approach improves electrical conductivity without requiring separate conductivity-enhancing layers, thereby minimizing additional complexity.

Inventive Principle:

Principle #5Merging (Combining)

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 solution enhances the lifetime characteristics of lithium batteries by reducing volume expansion and maintaining battery capacity through improved electrical conductivity and a stable carbonaceous coating layer.

Implementation Method 1

carbon nanoparticles on a surface of the core particle; and an amorphous carbonaceous coating layer on at least a portion of the surface of the core particle

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

an amorphous carbonaceous coating layer on at least a portion of the surface of the core particle

Methodology Applied

Scientific EffectPhysical containment: Physical Containment

Data Source

PatentUS11539043B2Negative active material, lithium battery including the negative active material, and method of preparing the negative active material

Publication Date: 2022.12.27 SAMSUNG SDI CO LTD

AI summary

A negative active material, a lithium battery including the negative active material, and a method of preparing the negative active material. The negative active material includes: a core particle including a silicon based alloy; carbon nanoparticles disposed on a surface of the core particle; and an amorphous carbonaceous coating layer disposed on at least a portion of a surface of the core particle. The negative active material may improve the lifetime characteristics of the lithium batteries.