Silicon Anode Polyimide Binder for Li-Ion Cycle Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium-ion secondary batteries with silicon as a negative electrode active material face challenges in maintaining cycle characteristics due to volume expansion, which degrades the battery's performance, and existing binders do not adequately address this issue.
Innovation Solution
A lithium-ion secondary battery design that incorporates a negative electrode with silicon or silicon compounds and an aromatic polyimide binder, where the binder is characterized by specific NMR spectroscopy peaks indicating effective lithium interaction, enhancing the battery's cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon or silicon compound is used as negative electrode active material to increase capacity, then the theoretical capacity is significantly improved, but volume expansion occurs during charging which deteriorates cycle characteristics
Solution Approach 1:
The patent introduces a specific binder containing polyimide as an intermediary substance between the silicon-based active material particles and the current collector. This binder acts as a mediator that accommodates the volume expansion of silicon during charging while maintaining structural integrity and electrical connectivity, thereby preventing particle detachment and SEI film degradation that would otherwise occur due to the large volume changes.
Solution Approach 2:
The patent creates a composite structure where silicon or silicon compound particles are bound together with polyimide binder material. This composite approach combines the high capacity advantage of silicon with the structural stability of the polyimide matrix, allowing the negative electrode to withstand volume expansion during cycling while maintaining good cycle characteristics.
2Strength
If conventional binders are used in negative electrode active material layers, then the structure is maintained, but adhesion is insufficient and cycle characteristics are not adequately improved
Solution Approach 1:
The patent specifies precise parameters for the polyimide binder, including molecular weight (10,000 to 100,000) and chemical structure characteristics. By optimizing these parameters, the binder achieves optimal balance between adhesion strength and flexibility, allowing it to maintain strong bonding to both the active material particles and current collector while accommodating volume changes during charging and discharging cycles.
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 use of aromatic polyimide as a binder in lithium-ion secondary batteries improves cycle characteristics by ensuring strong adhesion and uniform lithium occlusion, leading to better capacity retention and overall battery performance.
Implementation Method 1
the binder contains polyimide... uniform lithium occlusion... NMR spectrum of a solid 7 Li nucleus has a first peak, and the first peak has a peak top in a chemical shift range of 0.5 ppm or more and 1.5 ppm or less
Implementation Method 2
The use of aromatic polyimide as a binder in lithium-ion secondary batteries improves cycle characteristics by ensuring strong adhesion...
Data Source
AI summary
This lithium-ion secondary battery may have a positive electrode, a negative electrode, a separator present between the positive electrode and the negative electrode and an electrolytic solution. The negative electrode may contain silicon or a silicon compound and a binder, and the binder may contain polyimide. When the negative electrode after discharging is observed by nuclear magnetic resonance (NMR) spectroscopy using a single-pulse magic-angle spinning method (SP-MAS method) and peaks are separated by a Gaussian function, a Lorentzian function or a Voigt function, an NMR spectrum of a solid7 Li nucleus may have a first peak, and the first peak may have a peak top in a chemical shift range of 0.5 ppm or more and 1.5 ppm or less with Li in LiCoO2 set to −0.5 ppm.