Lithium-Ion Electrode Recess Structure for Thin, Short-Resistant Cells
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Solution Overview
Problem
Conventional lithium-ion batteries face challenges in achieving high energy density due to the increased thickness caused by leads, which also affects safety performance by potentially leading to internal short circuits and lithium precipitation.
Innovation Solution
The design incorporates recesses on the positive and negative plates to receive the leads, with insulating glue layers on the leads and corresponding film surfaces to reduce thickness variations and prevent internal short circuits, thereby enhancing safety and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If leads are soldered on current collectors to conduct current, then electrical connectivity is achieved, but battery thickness increases
Solution Approach 1:
The lead is nested within a recess defined on the current collector, allowing the lead to be accommodated within the existing battery structure rather than adding external thickness. The recess creates a cavity that houses the lead, effectively integrating it into the current collector's volume.
Solution Approach 2:
The current collector is designed with different local properties: a recess area with reduced thickness to accommodate the lead, and other areas maintaining original thickness. This local modification allows lead integration without uniformly increasing battery thickness.
2Length of stationary object
If recesses are defined on current collectors to receive leads, then battery thickness is reduced, but film peeling occurs around recess corners
Solution Approach 1:
An insulating layer is applied to the current collector surface before the active material film is deposited. This preliminary insulation layer prevents direct bonding issues at the recess corners that would otherwise cause film peeling during expansion and contraction cycles.
Solution Approach 2:
The insulating layer acts as an intermediary between the current collector and the active material film, particularly at the recess corners where stress concentration occurs. This intermediate layer prevents direct mechanical bonding that leads to peeling while maintaining electrical functionality.
3Reliability
If no insulating layer is provided on positive area corresponding to recess, then internal short circuit and lithium precipitation occur, but safety performance deteriorates
Solution Approach 1:
An insulating layer is applied to the positive current collector surface at the recess area, serving as a mediator that prevents direct contact between the lead and active material. This intermediate insulating barrier eliminates the pathway for internal short circuits and prevents lithium precipitation that would otherwise occur at the exposed positive current collector surface.
Data Source
AI summary
A lithium-ion battery including a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte. The positive electrode includes a positive current collector and a positive electrode active material layer containing lithium cobalt oxide formed on the positive current collector. The positive electrode active material layer is provided with a first recess accommodating a positive lead coupled with the positive current collector and disposed on a surface of the positive current collector facing a center of the battery. The negative electrode includes a negative current collector and a negative electrode active material layer containing graphite or silicon formed on the negative current collector. The negative electrode active material layer is provided with a second recess accommodating a negative lead coupled with the negative current collector and disposed on a surface of the negative current collector facing away from the center of the battery.