Lithium Ion Battery Insulator Placement for Lithium Plating Prevention
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Solution Overview
Problem
Conventional lithium ion secondary batteries experience performance degradation due to the separation of lithium compounds on the negative electrode surface, which occurs when lithium ions are not fully intercalated, leading to reduced battery efficiency.
Innovation Solution
The battery design includes a positive electrode mixture layer, a negative electrode mixture layer, and an electrolyte layer, with an insulator covering a region from the positive electrode current collector to the gradually-decreasing portion of the positive electrode mixture layer, featuring a tangent line with contact points and a depressed part, ensuring controlled lithium ion flow and preventing lithium compound separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If insulating tape is used to prevent short-circuiting between electrodes, then electrical insulation is improved, but lithium ion flow control is insufficient leading to performance degradation
Solution Approach 1:
The insulator is positioned specifically at the gradually-decreasing portion of the positive electrode mixture layer where thickness varies, providing localized insulation precisely where needed to prevent short-circuiting while maintaining lithium ion flow control in other regions. This selective placement ensures electrical insulation without compromising battery efficiency.
Solution Approach 2:
The insulator acts as an intermediary element between the positive and negative electrodes, preventing direct contact and short-circuiting while allowing the system to maintain proper lithium ion flow through the electrolyte. This mediator approach resolves the contradiction by providing insulation without blocking ionic pathways.
2Ease of manufacture
If insulator position is not optimized, then manufacturing is simpler, but lithium compound separation occurs on negative electrode surface
Solution Approach 1:
The insulator is pre-positioned at the gradually-decreasing portion of the positive electrode mixture layer before battery operation begins. This preliminary placement ensures that lithium ion flow is properly controlled from the start, preventing compound separation on the negative electrode while maintaining a manufacturable design.
Solution Approach 2:
The invention replaces complex mechanical positioning systems with a simplified insulator placement strategy based on the geometric feature of the gradually-decreasing portion. This substitution maintains manufacturing simplicity while achieving reliable lithium ion intercalation control through the defined tangent line contact points.
3Reliability
If insulator covers entire positive electrode surface, then short-circuit prevention is maximized, but lithium ion flow is restricted
Solution Approach 1:
The insulator covers only the gradually-decreasing portion of the positive electrode mixture layer rather than the entire surface, providing localized short-circuit prevention while leaving other regions open for lithium ion flow. This selective coverage resolves the contradiction between maximum insulation and adequate ionic transport.
Solution Approach 2:
The insulator provides partial coverage of the positive electrode surface, specifically targeting the gradually-decreasing portion where thickness variation creates short-circuit risk. This partial action approach prevents over-insulation that would block lithium ion flow while still providing sufficient protection against short-circuiting.
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 configuration effectively prevents the degradation of battery performance by managing lithium ion flow, reducing the amount of lithium ions that separate as metal or compounds on the negative electrode surface, thereby maintaining battery efficiency.
Implementation Method 1
a positive electrode active material intercalating or deintercalating lithium ions
Implementation Method 2
a negative electrode active material intercalating or deintercalating lithium ions
Implementation Method 3
an electrolyte layer provided between the positive electrode mixture layer and the negative electrode mixture layer
Data Source
AI summary
A lithium ion secondary battery according to an embodiment of this disclosure includes: a positive electrode mixture layer provided on a main plane of a positive electrode current collector; a negative electrode mixture layer provided on a main plane of a negative electrode current collector; and an insulator covering a region of a part of a surface of a gradually-decreasing portion included in the positive electrode mixture layer. The portion has thickness gradually decreasing toward a terminal of the positive electrode mixture layer; the surface of the portion has a tangent line in contact with the surface in at least two contact points, and has a depressed part between any adjacent two contact points on the tangent line; and an end of the insulator is positioned between the contact points closest to and farthest from the terminal of the positive electrode mixture layer along the tangent line.