Binder-Bound Silicon-Carbon Anode Particles to Limit Electrode Cracking
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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 binding between the electrode components, 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 binder, where the binder content is 1% or more by mass, to improve 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
1Quantity of substance
If silicon-based negative electrode active material particles are used to improve capacity, then the theoretical capacity increases to 3600 mAh/g, but large volume expansion and contraction occur during charging and discharging, causing electrode cracking and shortened cycle life
Solution Approach 1:
Carbon-based negative electrode active material particles are used as a matrix to embed silicon-based negative electrode active material particles inside, forming composite particles. The carbon matrix accommodates the volume expansion and contraction of the silicon core during lithium ion insertion and extraction, preventing electrode cracking while maintaining high capacity. The nested structure allows the silicon core to expand into the carbon matrix without causing structural failure.
Solution Approach 2:
Composite particles consisting of silicon-based negative electrode active material particles and carbon-based negative electrode active material particles are used as the negative electrode active material. The composite structure combines the high capacity advantage of silicon with the structural stability and crack-resistance of carbon, achieving both high capacity and long cycle life. The carbon component provides mechanical strength and conductivity while the silicon component provides high lithium ion storage capacity.
2Reliability
If graphite-based negative electrode materials are used to ensure long cycle life, then charge and discharge cycle life is improved, but the charge and discharge capacity is limited to 372 mAh/g, which is insufficient for vehicle applications
Solution Approach 1:
The negative electrode uses composite particles containing both silicon-based and carbon-based negative electrode active material particles. The silicon-based material provides high capacity (3600 mAh/g theoretical) while the carbon-based material provides structural stability and long cycle life. This composite approach overcomes the limitations of pure graphite electrodes by combining the advantages of both material types.
Solution Approach 2:
Silicon-based negative electrode active material particles are embedded within carbon-based negative electrode active material particles to form a core-shell or nested structure. The carbon shell protects the silicon core during volume changes while maintaining electrical conductivity and structural integrity, enabling the electrode to achieve both high capacity and long cycle life simultaneously.
3Stability of the object's composition
If a binder is used to bind electrode components to prevent cracks, then electrode structural stability is improved, but the drying step of electrode active material slurry causes cracks to occur, reducing battery performance
Solution Approach 1:
The nested structure of carbon particles surrounding silicon particles provides inherent structural stability without requiring excessive binder. The carbon matrix acts as a pre-formed structural framework that accommodates silicon volume changes, reducing the need for binder-based stabilization and minimizing crack formation during the drying process.
Solution Approach 2:
The composite particle structure provides intrinsic mechanical strength and crack resistance through the carbon-silicon composite architecture. This self-reinforcing structure reduces dependency on external binders and minimizes the harmful effects of binder-related cracking during electrode manufacturing and battery cycling.
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, which are formed by binding negative electrode active material particles containing a silicon-based negative electrode active material and a carbon-based negative electrode active material via a predetermined amount or more of a binder
Implementation Method 2
a material alloying with Li for the negative electrode is expected as a negative electrode material for vehicle applications because the energy density is improved as compared with the carbon/graphite-based negative electrode material in the related art. For example, a Si material occludes and releases 3.75 mol of lithium ions per mol as shown in the following reaction formula (A) during charging and discharging
Implementation Method 3
the carbon-based material to follow the expansion and contraction of the silicon-based material, thus minimizing the cutting of electron conduction paths
Implementation Method 4
minimizing the cutting of electron conduction paths
Data Source
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.