Lithium Ion Battery Negative Electrode Peel Strength
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Solution Overview
Problem
Conventional lithium ion secondary batteries face issues with cycle characteristics and longevity due to peeling of the negative electrode active material and current collector foil during charging and discharging, leading to internal short-circuits and reduced battery life.
Innovation Solution
A manufacturing method for a lithium ion secondary battery that involves forming a negative electrode active material layer on a copper foil current collector with specific tensile strength, ensuring a high peel strength between the active material and the current collector, which is achieved by applying and drying a mixture of active material, binder, and conductive agent in controlled temperature conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If single metal aluminum, silicon, germanium or the like is used as negative electrode active material to increase capacity, then battery capacity is improved, but copper foil current collector drastically changes in shape and internal short-circuiting easily occurs
Solution Approach 1:
The invention changes the material parameter of the current collector from conventional copper foil to stainless steel foil, which has different mechanical and thermal properties. This parameter change allows the current collector to maintain structural stability when used with high-capacity active materials like silicon or aluminum, preventing the shape changes and internal short-circuiting that occur with copper foil.
Solution Approach 2:
The invention uses a composite structure consisting of stainless steel foil as the current collector substrate, which provides mechanical strength and dimensional stability, combined with high-capacity active materials like silicon, aluminum, or germanium. This composite approach allows the system to achieve high capacity while maintaining structural integrity and preventing short-circuits.
2Ease of manufacture
If conventional copper foil is used as negative electrode current collector, then manufacturing process is simple, but negative electrode active material and current collector peel apart during charging and discharging
Solution Approach 1:
The invention changes the material parameter of the current collector from copper foil to stainless steel foil. This material substitution fundamentally alters the interaction between the current collector and active material, resulting in significantly improved peel strength and adhesion during charging and discharging cycles, while still maintaining manufacturing feasibility.
3Reliability
If stainless steel foil is used as negative electrode current collector to improve peel strength, then cycle characteristics are improved, but manufacturing cost increases
Solution Approach 1:
The invention changes the current collector material parameter from copper to stainless steel, which provides superior mechanical properties, corrosion resistance, and adhesion characteristics. These parameter changes result in improved cycle characteristics and battery longevity, with the added benefit of reduced sensitivity to manufacturing variations.
Data Source
Figure 1
AI summary
A lithium ion secondary battery includes: a power generating element including an electrolyte solution, and an electrode stack including a positive electrode including a positive electrode active material layer and a positive electrode current collector foil and a negative electrode including a negative electrode active material layer and a negative electrode current collector foil, the positive electrode and the negative electrode being stacked with a separator interposed therebetween; and a package that internally seals this power generating element. The negative electrode current collector foil is a copper foil, and the negative electrode has a tensile strength of 17.6 N/mm2 or more and 20.0 N/mm2 or less.