Silicon-Carbon Anode Layering for Fast Charge and Volume Stability

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Solution Overview

Problem

Silicon-based active materials in anodes for secondary batteries have low lithium-ion diffusion rates and high-volume expansion, limiting their quick charge and lifespan characteristics, despite their high discharge capacity.

Innovation Solution

A multilayer anode structure is implemented, with a first carbon-based active material having a high orientation index in the lower layer for high energy density and a low-orientation carbon-based active material in the upper layer for improved lithium-ion intercalation, along with varying silicon-based active material content and conductive material distribution to enhance quick charge and capacity characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If silicon-based active materials are applied to anodes for high discharge capacity, then energy density is improved, but lithium-ion diffusion rate decreases and volume expansion increases

Engineering Contradiction:

Improveenergy densityVSAvoidlithium-ion diffusion rate

Core Design Contradiction:

Use of energy by moving objectVSSpeed

Solution Approach 1:

The anode is divided into multiple layers with different compositions and functions. The first layer contains silicon-based active material for high capacity, while the second layer contains carbon-based active material for fast lithium-ion diffusion. This segmentation allows each layer to specialize in one function, resolving the contradiction between high energy density and fast diffusion rate.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent uses a composite anode structure combining silicon-based active material in the first layer with carbon-based active material in the second layer. This composite approach leverages the high capacity of silicon and the fast diffusion characteristics of carbon, achieving both high energy density and excellent quick charge performance.

Inventive Principle:

Principle #40Composite materials

2Use of energy by moving object

If silicon-based active materials are applied to anodes for high discharge capacity, then energy density is improved, but volume expansion increases

Engineering Contradiction:

Improveenergy densityVSAvoidvolume stability

Core Design Contradiction:

Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

The anode is segmented into layers where the first layer contains silicon-based material (prone to expansion) and the second layer contains carbon-based material (dimensionally stable). This segmentation isolates the volume expansion issue to a specific layer, allowing the overall structure to maintain stability while still achieving high energy density.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the anode are given different properties: the first layer is optimized for high capacity with silicon-based material, while the second layer is optimized for structural stability with carbon-based material. This local differentiation allows the system to achieve high energy density without compromising overall volume stability.

Inventive Principle:

Principle #3Local quality

3Speed

If multilayer anode structure with different carbon-based materials is used, then quick charge characteristics are improved, but device complexity increases

Engineering Contradiction:

Improvequick charge characteristicsVSAvoidanode structure complexity

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The anode is divided into two functional layers: the first layer with silicon-based material for capacity, and the second layer with carbon-based material for fast diffusion. This segmentation achieves quick charge characteristics through the carbon layer's inherent properties without requiring complex additional structures or components.

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 multilayer anode structure achieves excellent quick charge, capacity, and resistance characteristics, enabling high energy density and prolonged lifespan in lithium-ion secondary batteries.

Implementation Method 1

a first carbon-based active material having a high orientation index in the lower layer for high energy density

Methodology Applied

Scientific EffectIntercalation: Absorption (physical)

Implementation Method 2

a low-orientation carbon-based active material in the upper layer for improved lithium-ion intercalation

Methodology Applied

Scientific EffectDiffusion: Diffusion

Implementation Method 3

silicon-based active materials have a low lithium-ion diffusion rate and high-volume expansion rate compared to carbon-based active materials

Methodology Applied

Scientific EffectVolume expansion: Thermal Expansion

Data Source

PatentUS20240063373A1Anode for secondary battery and lithium secondary battery including the same

Publication Date: 2024.02.22 SK ON CO LTD

AI summary

An anode for a secondary battery is disclosed. In some implementations, the anode includes a current collector, a first anode mixture layer formed on at least one surface of the current collector, and a second anode mixture layer formed on the first anode mixture layer. The first anode mixture layer and the second anode mixture layer include a silicon-based active material, respectively. The first anode mixture layer includes a first carbon-based active material. The second anode mixture layer includes a second carbon-based active material. The first carbon-based active material has an OI value greater than or equal to an OI value of the second carbon-based active material.