Flat Winding Electrode Assembly for Nonaqueous Battery
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Solution Overview
Problem
Nonaqueous electrolytes with high viscosity have difficulty penetrating the central portion of flat winding electrode assemblies in nonaqueous electrolyte secondary batteries, particularly when containing lithium salts with oxalate complexes or LiPF2O2, leading to inefficient electrolyte distribution and potential degradation issues.
Innovation Solution
Incorporating a flat winding electrode assembly with 8 or more layers of separator in the central portion and using lithium salts like LiBOB, along with a prismatic outer body design that allows easy penetration of the electrolyte, ensures effective distribution of the electrolyte within the battery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a nonaqueous electrolyte containing lithium salt with oxalate complex or LiPF2O2 is used to improve battery safety and cycling characteristics, then fire resistance and protective layer formation are improved, but the viscosity of the electrolyte increases making it difficult to penetrate the central portion of the flat winding electrode assembly
Solution Approach 1:
The electrode assembly is segmented into multiple layers (8 or more layers) in the central portion, creating a layered structure that facilitates electrolyte penetration. This segmentation allows the electrolyte to access the central region more effectively despite its high viscosity, while maintaining the beneficial properties of lithium salts with oxalate complexes or LiPF2O2 for safety and cycling characteristics.
2Reliability
If the viscosity of nonaqueous electrolyte is increased by adding lithium salt with oxalate complex or LiPF2O2 to improve protective covering quality, then interface protection and decomposition prevention are improved, but the electrolyte becomes less likely to penetrate the inside of the flat winding electrode assembly
Solution Approach 1:
The central portion of the electrode assembly is divided into 8 or more layers, creating a segmented structure that enhances electrolyte penetration. This segmentation compensates for the high viscosity of the electrolyte containing lithium salts with oxalate complexes or LiPF2O2, ensuring uniform electrolyte distribution throughout the assembly while maintaining the protective interface qualities.
3Productivity
If a flat winding electrode assembly with closely contacted electrodes is used to achieve high capacity and high output characteristics, then space efficiency and power density are improved, but the penetration of nonaqueous electrolyte into the winding electrode assembly is further reduced
Solution Approach 1:
The electrode assembly structure is segmented with 8 or more layers in the central portion, creating pathways that facilitate electrolyte penetration. This segmentation maintains the closely contacted configuration of electrodes for high capacity and output characteristics while ensuring adequate electrolyte distribution throughout the compact structure.
Solution Approach 2:
The central portion of the electrode assembly has a specific local structure with 8 or more layers, creating a region with enhanced electrolyte accessibility. This local quality change allows the electrolyte to penetrate the compact, closely-contacted electrode structure effectively, maintaining both high productivity and reliable electrolyte distribution.
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 enables efficient penetration and distribution of the electrolyte, enhancing the battery's cycling characteristics and safety by preventing direct contact between active materials and the electrolyte, thus improving charge storage and longevity.
Implementation Method 1
a nonaqueous electrolyte is less likely to penetrate the winding electrode assembly in the width direction of the electrode
Implementation Method 2
allows a nonaqueous electrolyte having a high viscosity to easily penetrate the inside of a flat winding electrode assembly
Implementation Method 3
nonaqueous electrolyte secondary batteries typified by lithium ion batteries
Implementation Method 4
LiPF2O2 and lithium react to form a high-quality protective covering on the interfaces of a positive electrode active material and a negative electrode active material
Data Source
AI summary
A prismatic nonaqueous electrolyte secondary battery includes a flat winding electrode assembly formed by winding an elongated positive and negative electrodes with an elongated separator interposed therebetween, and an outer body storing the flat winding electrode assembly and a nonaqueous electrolyte. The positive electrode includes a positive electrode substrate exposed portion formed along a longitudinal direction. The negative electrode includes a negative electrode substrate exposed portion formed along a longitudinal direction. The nonaqueous electrolyte contains at least one of a lithium salt having an oxalate complex as an anion and lithium difluorophosphate (LiPF2O2) at the time of making the nonaqueous electrolyte secondary battery. The flat winding electrode assembly has eight or more layers of a winding portion formed only of the separator in its central portion. This battery can allow a nonaqueous electrolyte having a high viscosity to easily penetrate the inside of a flat winding electrode assembly.