Lithium Electrode Contact Lead Ultrasonic Welding
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Solution Overview
Problem
Existing lithium-based rechargeable batteries face issues with unreliable electrical and mechanical connections between lithium electrodes and contact leads, leading to poor cycling performance and rapid degradation due to lithium deposition on non-lithium substrates and the addition of unnecessary mass from current collectors.
Innovation Solution
A method involving ultrasonic welding of lithium or lithium alloy tabs to a contact lead, forming a direct lithium-to-lithium or lithium alloy weld, eliminating the need for a current collector and preventing lithium deposition on non-lithium surfaces, while ensuring a strong and low-resistance connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a current collector made of non-lithium metal is used to connect lithium electrodes to contact leads, then electrical conductivity and mechanical strength are improved, but lithium deposits on the non-lithium substrate causing dendrite formation and poor cycling performance
Solution Approach 1:
The patent applies homogeneity by ensuring that lithium only deposits on lithium substrates throughout the battery system. The current collector, contact tabs, and contact leads are all made of lithium or lithium alloy, creating a homogeneous lithium environment that prevents heterogeneous deposition and dendrite formation.
Solution Approach 2:
The patent extracts the non-lithium current collector material from the system and replaces it entirely with lithium or lithium alloy materials. This removal of the harmful non-lithium substrate eliminates the root cause of unwanted lithium deposition and dendrite formation.
2Use of energy by moving object
If a current collector is added to provide electrical connection, then electrical conductivity is improved, but unnecessary mass is added reducing specific energy
Solution Approach 1:
The patent applies multi-functionality by having the lithium anode material serve dual purposes: as the electrochemically active material and as the current collector. This eliminates the need for separate current collector components, reducing mass while maintaining electrical conductivity functionality.
Solution Approach 2:
The patent merges the functions of the electrochemically active lithium material and the current collector into a single component. By making the current collector from lithium or lithium alloy, the distinction between active material and conductive substrate disappears, eliminating redundant mass.
3Reliability
If mechanical connection methods are used to join contact leads to contact tabs, then ease of manufacture is improved, but connection reliability degrades due to corrosion layers forming at the interface
Solution Approach 1:
The patent applies homogeneity by using lithium-to-lithium welding, where identical materials are joined together. This eliminates galvanic corrosion and interface degradation problems that occur with dissimilar metal connections, significantly improving long-term connection reliability.
Solution Approach 2:
The patent replaces mechanical connection methods (screws, clips, or press-fit connectors) with ultrasonic welding. This substitution eliminates mechanical wear, contact resistance, and corrosion issues while providing a more reliable electrical connection suitable for rechargeable battery applications.
4Reliability
If ultrasonic welding is used to join lithium tabs to contact leads, then connection strength and electrical conductivity are improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies parameter changes by optimizing ultrasonic welding parameters (frequency, amplitude, power, duration) specifically for lithium-to-lithium and lithium-to-contact lead joints. By establishing standardized welding parameters, the process becomes controllable and repeatable, reducing manufacturing complexity despite the advanced joining technique.
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 provides a reliable, lightweight, and efficient connection that enhances the cycle life and stability of lithium-based batteries by preventing dendrite formation and reducing unnecessary mass, thereby improving the battery's performance and longevity.
Implementation Method 1
the method comprising the steps of: i) positioning the end portion of the contact lead a) on top of the tabs of the electrode stack b) underneath the tabs of the electrode stack, or c) at an intermediate position between the top and the bottom of the electrode stack, and ii) ultrasonically welding the contact zone to the end portion so as to join an electrode to the contact lead
Data Source
AI summary
There is disclosed a method of connecting a lithium electrode to a contact lead in a rechargeable battery. The electrode comprises a sheet or foil of lithium or lithium alloy with a tab protruding from an edge of the sheet or foil. The contact lead comprises an electrically conductive lead with an end portion made of a second metal that does not alloy with lithium and has a plurality of through holes. The end portion of the contact lead and the tab of the electrode are positioned so that there is substantial overlap between the end portion and the tab. The metal of the tab is then caused, for example by pressing and welding, to penetrate through the through holes of the end portion so as to join the electrode to the contact lead. A combination electrode/contact lead assembly made by this method is also disclosed.