Battery Cap Assembly Deformable Sheet Pressure Relief
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Solution Overview
Problem
Existing cap assembly designs for secondary batteries face issues with reliability due to loose insulating plastic under the cap plate, leading to decreased connection reliability and increased thickness, which affects energy density, and pose safety risks during nail penetration tests due to low on-resistance between conductive sheets and cap plates.
Innovation Solution
A cap assembly with a deformable sheet connected to a terminal board, an isolator, and a conductive sheet, where the deformable sheet disconnects under increased pressure to prevent overcharging and the isolator connects the conductive sheet to the cap plate, reducing external short-circuit currents during nail penetration tests.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If insulating plastic is used to wrap the conductive sheet, then the conductive sheet is fixed, but the insulating plastic occupies internal space of the case, increasing the thickness of the cap assembly and affecting energy density
Solution Approach 1:
The fixing member serves as an intermediary that provides secure fixation of the conductive sheet without requiring extensive insulating plastic wrapping. This intermediary component enables reliable connection while minimizing the space occupied by insulating materials, thereby preserving internal case space and maintaining energy density
2Reliability
If the conductive sheet is directly welded onto the cap plate, then the on-resistance is very small, but a large external short-circuit current is generated during nail penetration test, causing sparking and safety problems
Solution Approach 1:
The isolator is introduced as an intermediary component between the cap plate and the conductive sheet. This isolator increases the on-resistance of the electrical connection, which limits the magnitude of external short-circuit current that can flow during nail penetration tests, thereby preventing sparking and improving safety while still maintaining reliable electrical connection under normal operating conditions
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 solution enhances connection reliability, maintains energy density, and prevents safety hazards by ensuring the cap assembly can disconnect under pressure and limit external short-circuit currents during testing.
Implementation Method 1
the deformable sheet is configured to deform to be electrically disconnected from the first portion in response to an increase in a pressure inside the secondary battery
Implementation Method 2
an outer peripheral surface of the conductive sheet is surrounded by the isolator, and the conductive sheet is connected with the cap plate through the isolator
Data Source
AI summary
The present disclosure provides a cap assembly for a secondary battery and a secondary battery. The cap assembly for the secondary battery includes a cap plate having an electrode lead-out hole; and a terminal assembly including a terminal board, a fixing member, a deformable sheet, a conductive sheet and an isolator, wherein the deformable sheet is attached to the terminal board; the conductive sheet includes a first portion provided between the terminal board and the cap plate; the terminal board is fixed to a side of the cap plate through the fixing member and covers the electrode lead-out hole, and the terminal board is electrically connected with the first portion through the deformable sheet; the deformable sheet is configured to deform to be electrically disconnected from the first portion in response to an increase in a pressure inside the secondary battery.