Multilayer Graphite Anode Layout for Rolling-Induced Pore Loss

Solution Overview

Problem

The rolling process for anode manufacturing reduces the pores in the electrode surface, which decreases the movement path for lithium ions, leading to increased resistance and degraded battery performance, especially when using graphite secondary particles as anode active material.

Innovation Solution

A multilayer anode structure is implemented with a first anode mixture layer on the current collector and a second anode mixture layer on the surface, where the second layer contains a higher content of graphite primary particles than the first layer, to minimize porosity reduction during rolling, thereby improving lithium ion movement and reducing resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a rolling process is used to manufacture the anode, then the electrode surface is flattened and manufacturing efficiency is improved, but pores in the electrode are reduced leading to increased resistance

Engineering Contradiction:

Improvemanufacturing efficiencyVSAvoidbattery performance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The anode active material is segmented into two distinct particle types: primary particles (smaller, less deformed) and secondary particles (larger, more deformed). This segmentation allows different regions of the electrode to have different particle compositions, with the surface region enriched in primary particles that maintain porosity better during rolling, while the bulk can still utilize secondary particles for capacity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention applies local quality by creating a non-uniform distribution of particle types across the electrode thickness. The surface region (second anode mixture layer) has a higher concentration of primary particles that resist deformation and maintain pores, while the underlying region (first anode mixture layer) contains more secondary particles. This localized optimization ensures the critical surface region maintains lithium ion pathways while the bulk provides overall capacity.

Inventive Principle:

Principle #3Local quality

2Quantity of substance

If graphite secondary particles are used as anode active material, then the anode capacity is increased, but the deformation degree during rolling process is high causing significant pore reduction

Engineering Contradiction:

Improveanode capacityVSAvoidparticle deformation

Core Design Contradiction:

Quantity of substanceVSShape

Solution Approach 1:

The invention applies local quality by creating a non-uniform distribution of particle types across the electrode thickness. The surface region (second anode mixture layer) has a higher concentration of primary particles that resist deformation and maintain pores, while the underlying region (first anode mixture layer) contains more secondary particles. This localized optimization ensures the critical surface region maintains lithium ion pathways while the bulk provides overall capacity.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention uses a composite material system combining two types of graphite particles with different properties: primary particles (higher strength, lower deformation) and secondary particles (higher capacity, higher deformation). By compositeing these two particle types in a specific ratio and distribution, the anode achieves both high capacity (from secondary particles) and maintained porosity (from primary particles) after rolling.

Inventive Principle:

Principle #40Composite materials

3Volume of stationary object

If the pores in the electrode are reduced during rolling, then the electrode density is increased, but the movement path of lithium ions decreases and resistance increases

Engineering Contradiction:

Improveelectrode densityVSAvoidresistance

Core Design Contradiction:

Volume of stationary objectVSObject-generated harmful factors

Solution Approach 1:

The invention applies local quality by creating a non-uniform distribution of particle types across the electrode thickness. The surface region (second anode mixture layer) has a higher concentration of primary particles that resist deformation and maintain pores, while the underlying region (first anode mixture layer) contains more secondary particles. This localized optimization ensures the critical surface region maintains lithium ion pathways while the bulk provides overall capacity.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention utilizes porous materials by maintaining a higher porosity in the surface region of the electrode through the use of primary particles that are less deformed during rolling. This porous structure in the critical surface region provides adequate movement paths for lithium ions, reducing resistance while the bulk electrode maintains higher density for overall capacity.

Inventive Principle:

Principle #31Porous materials

Data Source

PatentEP4231378A1Anode and secondary battery including the same

Publication Date: 2023.08.23 SK ON CO LTD

AI summary

An anode for a secondary battery includes a first anode mixture layer disposed on an anode current collector and a second anode mixture layer disposed on a surface of the anode, wherein the first and second anode mixture layers include a graphite-based anode active material of graphite secondary particles, at least the second anode mixture layer includes a graphite-based anode active material of graphite primary particles, and a content [A2] of graphite primary particles included in the second anode mixture layer is greater than a content [A1] of graphite primary particles included in the first anode mixture layer.