Sodium-Treated Silicon-Carbon Anode for Expansion and Lithium Loss

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Solution Overview

Problem

Rechargeable lithium batteries using crystalline carbon as a negative electrode material face limitations in energy density and suffer from irreversible lithium capacity losses and volume expansion issues due to silicon-based active materials, leading to electrode detachment and electrolyte depletion.

Innovation Solution

A silicon-carbon composite negative electrode active material is developed, featuring nano-silicon primary particles coated with amorphous carbon and a sodium element, prepared through a method involving mixing silicon with sodium raw materials, heat treatment, and immersion in a sodium solution to form sodium silicate and carbide, reducing irreversible lithium capacity losses and suppressing volume expansion.

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 initial efficiency deteriorates and volume expansion occurs causing electrode detachment

Engineering Contradiction:

Improveenergy densityVSAvoidlifecycle characteristics

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent uses a composite structure consisting of silicon primary particles, carbon coating layer, and secondary particles. The silicon provides high capacity while the carbon coating and secondary particle structure suppress volume expansion and improve structural stability, resolving the contradiction between energy density and reliability

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The carbon coating layer acts as a flexible shell surrounding the silicon primary particles, accommodating volume changes during lithiation/delithiation while preventing electrode detachment. This thin film structure allows the silicon to expand and contract without compromising the overall electrode integrity

Inventive Principle:

Principle #30Flexible shells and thin films

2Quantity of substance

If silicon-based active material is used to increase energy density, then capacity is improved, but volume expansion occurs during charging and discharging

Engineering Contradiction:

Improveenergy densityVSAvoidvolume expansion

Core Design Contradiction:

Quantity of substanceVSVolume of moving object

Solution Approach 1:

The patent employs a nested structure where silicon primary particles are embedded within carbon-coated secondary particles. This nested architecture allows the inner silicon to expand and contract while the outer secondary particle structure maintains overall volume stability, preventing electrode detachment

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The carbon coating layer serves as a flexible shell that accommodates the volume expansion of silicon during lithiation while maintaining structural integrity. This flexible shell allows volume change without causing electrode detachment or electrolyte depletion

Inventive Principle:

Principle #30Flexible shells and thin films

3Stability of the object's composition

If crystalline carbon is used as negative electrode material, then structural stability is maintained, but energy density is limited

Engineering Contradiction:

Improvestructural stabilityVSAvoidenergy density

Core Design Contradiction:

Stability of the object's compositionVSQuantity of substance

Solution Approach 1:

The patent creates a composite material combining silicon (high capacity) with carbon (structural stability). The silicon primary particles provide high energy density while the carbon coating and secondary particle structure provide structural stability, achieving both goals simultaneously

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

Different regions of the composite material have different functions: the silicon primary particles provide high capacity locally, while the carbon coating and secondary particle structure provide structural stability locally. This local differentiation allows the overall material to achieve both high energy density and structural stability

Inventive Principle:

Principle #3Local quality

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 charge/discharge efficiency and improves battery lifecycle characteristics by minimizing irreversible reactions and volume changes, resulting in increased energy density and reduced irreversible capacity losses.

Implementation Method 1

an amorphous carbon coating layer on the surface of the secondary particles

Methodology Applied

Scientific EffectVolume expansion suppression:

Implementation Method 2

a sodium element on the surface of the nano-silicon primary particle and the amorphous carbon coating layer

Methodology Applied

Scientific EffectIrreversible capacity loss reduction:

Implementation Method 3

performing heat treatment

Methodology Applied

Scientific EffectHeat treatment: Heat Treatment

Data Source

PatentUS20250323276A1Negative electrode active material, preparation method thereof, and rechargeable lithium batteries

Publication Date: 2025.10.16 SAMSUNG SDI CO LTD

AI summary

Examples of the disclosure include a negative electrode active material, a method of preparing the negative electrode active material, and a rechargeable lithium battery. The negative electrode active material includes a silicon-carbon composite including secondary particles in which a plurality of nano-silicon primary particles are assembled, and an amorphous carbon coating layer on the surface of the secondary particles, and a sodium element on the surface of the nano-silicon primary particle and the amorphous carbon coating layer.