Cylindrical secondary battery
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Solution Overview
Problem
Cylindrical secondary batteries face issues with welding impurities, electrode assembly damage, and welding defects due to misalignment and insufficient welding areas when multiple batteries are connected via busbars.
Innovation Solution
The design includes a terminal with a welding groove recessed from its top surface, a coupling part for secure fixation, and gaskets for insulation, preventing foreign substance generation and electrode damage while ensuring stable welding despite misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If welding is performed between terminal and current collector plate, then electrical connection is established, but welding impurities are generated in the case
Solution Approach 1:
The welding groove extracts the harmful welding impurities from the interior space of the case by providing a dedicated recessed area where welding beads and spatter can fall without contaminating the electrode assembly. The groove is positioned such that welding operations occur outside the sealed case environment, separating the welding process from the battery interior.
Solution Approach 2:
The welding groove acts as an intermediary structure between the terminal and the case interior. It provides a controlled interface that allows welding to occur while preventing direct contamination of the case interior, mediating between the electrical connection requirement and the contamination prevention need.
2Reliability
If welding is performed between terminal and current collector plate, then electrical connection is established, but electrode assembly is damaged due to welding heat
Solution Approach 1:
The welding groove extracts the heat-affected zone from the electrode assembly by providing a dedicated recessed area for welding operations. The groove is positioned such that the intense localized heat from welding is confined to the groove area and does not directly impact the electrode assembly, separating the thermal effects from sensitive components.
3Reliability
If a plurality of secondary batteries are welded through busbar, then electrical connection between batteries is established, but welding defects occur due to misalignment
Solution Approach 1:
The flat top surface of the terminal main body serves multiple functions: it provides a stable welding surface for busbar connection, acts as an alignment reference for welding operations, and compensates for dimensional variations. This universal design feature addresses both electrical connection and alignment precision requirements simultaneously.
4Reliability
If a plurality of secondary batteries are welded through busbar, then electrical connection between batteries is established, but resistance increases due to insufficient welding area
Solution Approach 1:
The flat top surface of the terminal main body serves as an expanded welding area that simultaneously provides stable electrical connection and reduces contact resistance. The increased surface area allows for larger welding footprint and better current distribution, addressing both connection reliability and energy loss concerns.
Solution Approach 2:
The design transitions from a narrow groove-based welding interface to a two-dimensional flat top surface for busbar connection. This dimensional expansion from one-dimensional groove to two-dimensional surface increases the effective welding area and improves electrical contact without adding height complexity.
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
Prevents welding impurities and damage, maintains electrical integrity, and facilitates efficient connection of multiple batteries without increased resistance.
Implementation Method 1
a welding groove recessed downward from a top surface of the terminal outside the main body
Implementation Method 2
The lower coupling part may be pressed by riveting
Implementation Method 3
a coupling part disposed outside the main body to fix the terminal to the case
Implementation Method 4
a first gasket disposed between the terminal and the case to electrically separate the terminal and the case from each other
Implementation Method 5
The first current collector plate may be welded outside the terminal through the welding groove
Data Source
AI summary
Embodiments relate to a cylindrical secondary battery. A cylindrical secondary battery includes an electrode assembly including a first electrode plate, a separator, and a second electrode plate, a case that accommodates the electrode assembly and of which a lower end is opened to be electrically connected to the second electrode plate, a first current collector plate disposed between a top surface of the electrode assembly and the case and electrically connected to the first electrode plate, a terminal which passes through a top surface part of the case and of which a lower end is electrically and mechanically coupled to a top surface of the first current collector plate, and a cap plate configured to seal a lower end of the case. The terminal includes a main body having a flat top surface and a welding groove recessed downward from a top surface of the terminal outside the main body.