Binder-Bound Silicon-Carbon Negative Electrode for Crack-Resistant Cycling
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Solution Overview
Problem
The existing methods for producing lithium ion secondary batteries using silicon-based and carbon-based negative electrode active materials face challenges in achieving high cycle characteristics due to the lack of binder in the electrode production process, leading to cracks and reduced battery performance.
Innovation Solution
The use of composite secondary particles formed by binding silicon-based and carbon-based negative electrode active material particles with a predetermined amount of binder, where the binder content is 1% or more by mass, helps in improving the cycle characteristics by allowing the carbon-based material to follow the expansion and contraction of the silicon-based material, thus minimizing the cutting of electron conduction paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a binder is not used in electrode production to avoid drying cracks, then manufacturing simplicity is improved, but electrode structural stability deteriorates leading to cracks and reduced battery performance
Solution Approach 1:
The patent uses a specific binder (carboxymethyl cellulose or starch derivative) as an intermediary substance to bind active material particles together. This binder acts as a mediator that provides structural stability and prevents cracks during charging-discharging cycles, while still allowing the electrode to be produced without complex drying processes. The binder content is controlled at 1-10 mass% to achieve the right balance between structural integrity and manufacturing simplicity.
2Quantity of substance
If silicon-based negative electrode active material is used to increase capacity, then energy density is improved, but cycle durability deteriorates due to large volume expansion and contraction
Solution Approach 1:
The patent changes the physical and chemical parameters of the electrode structure by controlling binder content (1-10 mass%) and using specific binder types (carboxymethyl cellulose or starch derivative). These parameter changes allow the electrode to accommodate the large volume expansion and contraction of silicon-based materials during charging-discharging cycles, maintaining structural integrity and improving cycle durability while preserving high capacity.
Solution Approach 2:
The patent creates a composite electrode structure by combining silicon-based negative electrode active material particles with a binder matrix. This composite structure allows the binder to provide mechanical support and flexibility, enabling the electrode to withstand the repeated expansion and contraction of silicon during lithium ion insertion and extraction, thereby improving cycle durability while maintaining high capacity.
3Reliability
If binder content is increased to improve electrode structural stability, then cycle durability is improved, but electron conduction paths are cut leading to reduced discharge capacity
Solution Approach 1:
The patent optimizes the binder content parameter to a specific range (1-10 mass%) to achieve the right balance. Within this range, there is sufficient binder to provide structural stability and prevent cracks during cycling, but not so much that it blocks electron conduction paths. This precise parameter control allows simultaneous achievement of high cycle durability and high discharge capacity.
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
This approach enhances the cycle characteristics and discharge capacity of the battery, providing a balance between high capacity and durability while preventing electrode cracking.
Implementation Method 1
composite secondary particles formed by binding silicon-based and carbon-based negative electrode active material particles with a predetermined amount of binder
Implementation Method 2
allowing the carbon-based material to follow the expansion and contraction of the silicon-based material, thus minimizing the cutting of electron conduction paths
Data Source
Figure 1
Figure 2~3
AI summary
Provided is a technique capable of further improving the cycle characteristics in a negative electrode for a non-aqueous electrolyte secondary battery in which a silicon-based negative electrode active material and a carbon-based negative electrode active material are used in combination as a negative electrode active material, and constituent components of the electrode are not bound to each other via a binder. The negative electrode for a non-aqueous electrolyte secondary battery according to the present invention has a configuration in which a negative electrode active material layer containing a negative electrode active material is formed on a surface of a current collector. The negative electrode active material contains composite secondary particles in which silicon-based negative electrode active material particles and carbon-based negative electrode active material particles are bound to each other via a binder. Here, the content of the binder in the composite secondary particles is 1% by mass or more with respect to the total mass of the silicon-based negative electrode active material particles and the carbon-based negative electrode active material particles. Further, in the negative electrode active material layer, the composite secondary particles are characterized to exist in a state of being not bound to each other via a binder.