Multilayer Graphite Anode Structure for Adhesion and Output Balance
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving high capacity and stability due to electrode separation issues during manufacturing, which are exacerbated by the use of binders and conductive materials that can decrease adhesion and conductivity when used in excess.
Innovation Solution
A multilayer negative electrode structure is introduced, featuring a first layer with natural graphite for improved adhesion to the current collector and a second layer with artificial graphite for enhanced output characteristics, allowing for a balance of adhesion and capacity retention with reduced binder and conductive material content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the content of binder is increased to improve electrode adhesion, then adhesion is improved, but internal resistance increases and electronic conductivity decreases
Solution Approach 1:
The negative electrode is divided into two distinct layers: a first negative electrode mixture layer containing natural graphite particles that provides excellent adhesion to the current collector, and a second negative electrode mixture layer containing artificial graphite particles that provides high electronic conductivity and capacity. This segmentation allows each layer to optimize its function without compromise.
Solution Approach 2:
Different regions of the electrode are assigned different material compositions tailored to their specific functional requirements. The first layer near the current collector uses natural graphite for maximum adhesion, while the second layer at the surface uses artificial graphite for maximum conductivity and capacity, creating local optimization of properties.
2Power
If the content of conductive material is increased to improve output characteristic, then conductivity is improved, but adhesion is lowered and capacity decreases
Solution Approach 1:
The electrode is segmented into two layers with different conductive material contents and types. The first layer has lower conductive material content focused on adhesion, while the second layer has higher conductive material content optimized for output characteristics, eliminating the need to compromise adhesion to improve power.
Solution Approach 2:
The electrode uses a composite structure combining natural graphite and artificial graphite in specific layers, along with binders and conductive materials, to achieve simultaneous optimization of adhesion, conductivity, and capacity that cannot be obtained with single-material electrodes.
3Quantity of substance
If a large amount of electrode active material is disposed on current collector to produce high capacity, then capacity is improved, but electrode separation occurs during coating and rolling
Solution Approach 1:
The first negative electrode mixture layer containing natural graphite is applied to the current collector before the second layer. This preliminary layer creates a stable, well-adhered foundation that prevents separation during subsequent coating and rolling processes, enabling high capacity loading without stability loss.
4Strength
If natural graphite is used in electrode mixture layer contact with current collector, then adhesion is improved, but output characteristics and lifespan characteristics are reduced
Solution Approach 1:
The electrode is segmented into two layers where natural graphite is confined to the first layer for adhesion, while artificial graphite is placed in the second layer for lifespan and output characteristics, allowing both properties to coexist without compromise.
Solution Approach 2:
Different graphite types are localized to different regions: natural graphite at the current collector interface for adhesion, and artificial graphite at the surface for performance characteristics, creating local optimization that resolves the global contradiction.
Data Source
AI summary
The present disclosure relates to a multilayer negative electrode comprising a negative electrode current collector configured to transfer electrons between an outer lead and a negative electrode active material, a first negative electrode mixture layer formed on one surface or both surfaces of the current collector and containing natural graphite as a negative electrode active material and a second negative electrode mixture layer formed on the first negative electrode mixture layer and containing artificial graphite as a negative electrode active material, and a lithium secondary battery including the same.