Positive electrode slurry composition for secondary battery, and positive electrode for secondary battery and secondary battery which are prepared by using the same
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing positive electrode slurries for secondary batteries face issues with reduced electrode adhesion and degraded high-temperature characteristics due to the use of nitrile-based copolymers that swell in electrolyte solutions, leading to insufficient electrochemical properties and increased resistance.
Innovation Solution
A positive electrode slurry composition using a nitrile-based copolymer with a low electrolyte solution swelling coefficient and a carbon-based conductive agent with a specific surface area of 100-200 m2/g, along with a binder, to maintain electrode adhesion and electrochemical properties at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a nitrile-based copolymer containing a hydrophilic group is used to improve cycle characteristics and output characteristics, then cycle characteristics and output characteristics are improved, but affinity with electrolyte solution increases causing electrode adhesion reduction and high-temperature characteristics degradation
Solution Approach 1:
The patent changes the chemical composition parameters of the nitrile-based copolymer by selecting specific monomer ratios (acrylonitrile 40-70 wt%, butadiene 30-60 wt%) and controlling the electrolyte solution swelling degree to 150-250%, thereby achieving a balance between cycle characteristics and high-temperature stability without requiring hydrophilic functional groups
Solution Approach 2:
The patent uses a composite binder system combining nitrile-based copolymer with polyvinylidene fluoride (PVDF) in specific weight ratios (nitrile-based copolymer 70-95 wt%, PVDF 5-30 wt%), where the PVDF component provides high-temperature adhesion stability while the nitrile-based copolymer contributes to cycle characteristics and output characteristics
2Strength
If the amount of polyvinylidene fluoride binder is increased to improve electrode adhesion, then electrode adhesion is improved, but the amount of positive electrode active material is reduced and electrochemical properties become insufficient
Solution Approach 1:
The patent optimizes the binder composition parameters by using a composite system of nitrile-based copolymer and PVDF in specific ratios, and controls the total binder content at 3-15 wt% of the positive electrode active material, thereby achieving sufficient adhesion while maximizing active material content for electrochemical performance
Solution Approach 2:
The patent employs a composite binder material system where nitrile-based copolymer (70-95 wt% of binder) provides good adhesion and flexibility, while PVDF (5-30 wt% of binder) provides thermal stability and adhesion at high temperatures, achieving synergistic effect that allows lower total binder content while maintaining excellent adhesion properties
3Adaptability or versatility
If a nitrile-based copolymer with high electrolyte solution swelling degree is used to improve affinity with electrolyte solution, then affinity with electrolyte solution is improved, but electrode adhesion is reduced and high-temperature characteristics are degraded
Solution Approach 1:
The patent precisely controls the electrolyte solution swelling degree parameter within the range of 150-250% by selecting specific copolymer composition (acrylonitrile 40-70 wt%, butadiene 30-60 wt%), achieving optimal balance between electrolyte solution affinity and electrode adhesion without excessive swelling that would cause adhesion loss
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 composition achieves minimal electrode adhesion loss and electrochemical property deterioration at high temperatures, with a resistance increase rate of 20% or less after 4 weeks at 60°C, improving high-temperature storability and performance.
Implementation Method 1
affinity with an electrolyte solution is increased due to the presence of the hydrophilic functional group, and, as a result, since electrode adhesion is reduced while the nitrile-based copolymer is swollen by the electrolyte solution
Implementation Method 2
The conductive agent is used to improve conductivity of the positive electrode, wherein carbon black and carbon nanotubes are widely used
Data Source
AI summary
A positive electrode slurry composition for a secondary battery which includes a positive electrode active material, a carbon-based conductive agent having a specific surface area (Brunauer-Emmett-Teller (BET)) of 100 m2/g to 200 m2/g, a binder, and a nitrile-based copolymer which has an electrolyte solution swelling degree defined by Equation (1) of 200% or less and does not contain a functional group other than a cyano group is provided:electrolyte solution swelling degree (%)={(W1−W0)/W0}×100 Equation (1)wherein, W0 is an initial weight of a polymer film prepared from the nitrile-based copolymer, and W1 is a weight of the polymer film which is measured after storing the polymer film at 60° for 48 hours in an electrolyte solution.