Silicon Negative Electrode Adhesion via Copper Silicide Interface
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Solution Overview
Problem
The existing techniques for forming a negative electrode with silicon as the active material on a copper foil face issues of poor adhesion due to strain and shearing stress, leading to increased electrode resistance and reduced discharge capacity at the initial stage of charge-discharge cycles, particularly because of the weak interaction between copper and silicon.
Innovation Solution
A method involving plasma treatment of the copper foil to form an intermetallic compound of copper and silicon at the interface with the active material layer, enhancing adhesion and preventing separation during charge-discharge cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as the negative electrode active material to achieve high energy density, then the capacity is improved, but the adhesion between the active material and current collector deteriorates due to expansion and contraction during lithium ion storage/release
Solution Approach 1:
The invention uses a composite structure where silicon particles are embedded in a carbon matrix, and this composite is then integrated with the copper current collector. The carbon matrix acts as a buffer that accommodates silicon expansion/contraction while maintaining structural integrity and adhesion to the current collector, thus preserving both high capacity and reliable adhesion.
Solution Approach 2:
The invention changes the physical and chemical parameters of the interface between silicon and copper current collector by forming an intermediate layer or modifying the surface properties. This parameter change allows the interface to withstand the mechanical stress from silicon volume changes while maintaining strong adhesion, preventing peeling during charge-discharge cycles.
2Ease of manufacture
If the negative electrode active material layer is formed by deposition, sintering, or coating, then the manufacturing process is simplified, but shearing stress is applied to the binder during lithium intercalation/deintercalation, causing peeling from the current collector
Solution Approach 1:
The invention applies local quality enhancement by creating a specialized interface region between the active material layer and current collector. This interface has different properties (e.g., enhanced bonding, gradient composition) compared to the bulk material, allowing it to specifically resist shearing stress from binder expansion/contraction while maintaining ease of manufacture through standardized coating processes.
3Duration of action of stationary object
If carbon is used as the negative electrode material, then the charge-discharge cycle life is improved, but the capacity is limited to around theoretical capacity with no significant increase expected
Solution Approach 1:
The invention merges the advantages of both carbon and silicon by combining them into a composite negative electrode. Carbon provides the stable structure and long cycle life, while silicon contributes high capacity. The composite structure allows silicon particles to be embedded in the carbon matrix, enabling the electrode to achieve both extended cycle life and significantly enhanced capacity beyond what carbon alone can provide.
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 effectively suppresses the increase in electrode resistance and maintains discharge capacity by forming a strong interaction between the copper foil and the silicon-based active material, preventing peeling and ensuring stable performance during charge-discharge cycles.
Implementation Method 1
forming an intermetallic compound of copper and silicon at an interface between the copper foil and the active material
Implementation Method 2
subjecting a copper foil to a plasma treatment
Data Source
AI summary
A method for producing a negative electrode, including a step of subjecting a copper foil to a plasma treatment, a step of coating the copper foil subjected to the plasma treatment, with a slurry including an active material containing a silicon atom, and a step of subjecting the copper foil coated with the slurry to a heat treatment to form an intermetallic compound of copper and silicon at an interface between the copper foil and the active material. A negative electrode including a copper foil, an active material layer including an active material containing a silicon atom on the copper foil, and copper silicide at an interface between the copper foil and the active material.