Flat Winding Electrode Assembly for Uniform Reaction in Lithium Batteries
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries with large width positive and negative electrodes experience non-uniform reactions, leading to inadequate formation of protective coverings and suboptimal cycling characteristics, especially when using lithium salts with oxalate complexes as anions.
Innovation Solution
A flat winding electrode assembly with a positive electrode and negative electrode, each wound 30 or more times, where the exposed portions are welded and connected to collectors, ensuring uniform reaction and formation of a stable protective covering on the negative electrode surface using lithium salts like LiBOB and LiPF2O2, enhancing cycling characteristics and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a flat winding electrode assembly with large width positive and negative electrodes is used to achieve high capacity and output, then the battery capacity and output characteristics are improved, but the reaction inside the electrode occurs in a non-uniform manner, leading to inadequate formation of protective coverings and suboptimal cycling characteristics
Solution Approach 1:
The electrode assembly is divided into multiple winding layers (30 or more windings), creating a segmented structure that allows uniform electrolyte distribution and reaction progression throughout the electrode. This segmentation prevents non-uniform reactions that would occur in a single large electrode, thereby maintaining both high capacity and excellent cycling characteristics.
Solution Approach 2:
The patent transitions from a two-dimensional electrode layout to a three-dimensional wound structure. By winding the electrodes multiple times (30 or more windings), the battery achieves high capacity through increased electrode surface area in the third dimension while maintaining uniform reaction conditions through the concentric wound geometry, which ensures consistent electrolyte access to all electrode surfaces.
2Reliability
If lithium salt with oxalate complex as anion is added to improve cycling characteristics, then a stable protective covering is formed on the negative electrode surface, but the protective covering is less likely to be formed uniformly when reaction inside the electrode occurs in a non-uniform manner
Solution Approach 1:
The wound electrode structure ensures that each local region of the electrode receives uniform electrolyte access and undergoes consistent reactions. The concentric winding geometry creates uniform local conditions throughout the electrode assembly, enabling uniform protective covering formation by lithium salts with oxalate complexes on all negative electrode surfaces, thereby achieving both reliable cycling characteristics and uniform manufacturing quality.
3Quantity of substance
If the winding number is increased to achieve high capacity, then the battery capacity is improved, but the reaction inside the electrode becomes more non-uniform, making protective covering formation even more inadequate
Solution Approach 1:
The electrode assembly is divided into multiple winding layers (30 or more windings), creating a segmented structure that allows uniform electrolyte distribution and reaction progression throughout the electrode. This segmentation prevents non-uniform reactions that would occur in a single large electrode, thereby maintaining both high capacity and excellent cycling characteristics.
Solution Approach 2:
The concentric wound structure creates homogeneous conditions throughout the electrode assembly. Each winding layer experiences similar electrolyte access, current distribution, and reaction conditions, ensuring uniform protective covering formation even at high winding numbers. This homogeneity is achieved through the geometric consistency of the wound structure, where all electrode surfaces are positioned at comparable distances from the center, enabling uniform lithium salt deposition and protective covering formation throughout the entire electrode assembly.
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 enables nonaqueous electrolyte secondary batteries to achieve high capacity and output while maintaining excellent cycling characteristics and safety, even with large winding numbers, by ensuring uniform reaction and protective covering formation across the electrodes.
Implementation Method 1
a lithium salt having an oxalate complex as an anion is added to a nonaqueous electrolyte in order to improve cycling characteristics... a protective layer including a lithium ion conductive layer that is thin and extremely stable is formed on the surface of a carbon negative electrode active material
Implementation Method 2
nonaqueous electrolyte secondary batteries typified by lithium ion batteries... lithium ion conductive layer
Data Source
AI summary
A nonaqueous electrolyte secondary battery includes a flat winding electrode assembly including a positive electrode substrate exposed portion on one end and a negative electrode substrate exposed portion on the other end. The winding numbers of the positive and the negative electrode substrate exposed portions are each 30 or more. The positive and negative electrode substrate exposed portions each have an outermost surface welded and connected with a positive and a negative electrode collectors, respectively. A nonaqueous electrolyte used to fabricate the battery contains a lithium salt having an oxalate complex as an anion. At the welded connection portions, all of the layers of the positive electrode substrate exposed portion are melted to be welded and connected to the positive electrode collector, and all of the layers of the negative electrode substrate exposed portion are melted to be welded and connected to the negative electrode collector.