Li-Ion Battery Electrode Structure With Sputtered Metal Bonding
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Solution Overview
Problem
Lithium-ion secondary batteries face adhesion issues between the metal foil current collector and the negative electrode active material, leading to reduced charge and discharge characteristics and shorter battery life due to insufficient bonding and stress from lithium intercalation and deintercalation.
Innovation Solution
A method involving the application of a slurry containing electrode active material particles on a base, followed by drying and forming a metal film through sputtering to bond the particles and strengthen the interface, which also serves as a buffer layer to enhance adhesion and flexibility, allowing for a novel structure with improved reliability and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a binder is used to bond electrode active material particles to the current collector, then adhesion is improved, but internal resistance increases and battery performance deteriorates
Solution Approach 1:
The invention extracts and eliminates the binder component from the electrode structure. By forming a metal film directly on the electrode active material particles without using organic binders like polyvinylidene fluoride, the patent removes the source of internal resistance while maintaining adhesion through the metal film's inherent bonding properties to both the current collector and active material particles.
2Quantity of substance
If carbon particles are used as negative electrode active material, then battery capacity is achieved, but adhesion to metal foil deteriorates due to water repellent surface and point contact
Solution Approach 1:
The metal film acts as an intermediary layer between the carbon particles and the current collector. This intermediate metal film layer provides a bonding interface that overcomes the water repellent surface of carbon particles, establishing reliable adhesion through the metal film's ability to bond to both the carbon particles and the metal foil current collector.
3Ease of manufacture
If electrode active material particles are directly applied on metal foil, then manufacturing simplicity is maintained, but adhesion deteriorates due to stress from lithium intercalation and deintercalation
Solution Approach 1:
The metal film is applied beforehand as a cushioning layer between the electrode active material particles and the current collector. This pre-applied metal film layer absorbs and distributes the stress generated during lithium intercalation and deintercalation, preventing direct stress transmission that would cause adhesion failure, thereby maintaining bonding stability throughout charge and discharge cycles.
4Loss of energy
If binder amount is reduced to decrease internal resistance, then energy loss is reduced, but adhesion between current collector and electrode active material deteriorates
Solution Approach 1:
The invention completely extracts the binder component from the electrode system. By eliminating the binder entirely and using only a metal film for bonding, the patent achieves zero binder-related internal resistance while maintaining strong adhesion through the metal film's direct bonding capability to both the current collector and electrode active material particles.
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
The approach enhances the adhesion between the current collector and the electrode active material, improving the charge and discharge characteristics and extending the battery's life while enabling a flexible battery design with a curvature radius of up to 150 mm, maintaining mechanical strength and reliability.
Implementation Method 1
forming a metal film by sputtering among other methods to bond the electrode active material particles with each other or strengthen the bond between the electrode active material particles
Implementation Method 2
the carbon particle has an approximately 10% volume change by intercalation and deintercalation of lithium, and stress is generated at the interface between a current collector and the carbon particles that are active material particles
Data Source
AI summary
The adhesion between metal foil serving as a current collector and a negative electrode active material is increased to enable long-term reliability. An electrode active material layer (including a negative electrode active material or a positive electrode active material) is formed over a base, a metal film is formed over the electrode active material layer by sputtering, and then the base and the electrode active material layer are separated at the interface therebetween; thus, an electrode is formed. The electrode active material particles in contact with the metal film are bonded by being covered with the metal film formed by the sputtering. The electrode active material is used for at least one of a pair of electrodes (a negative electrode or a positive electrode) in a lithium-ion secondary battery.