Polyvinyl Pyrrolidone Cathode Mix for High Current Battery Life
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Solution Overview
Problem
Lithium ion secondary batteries with olivine crystal structure cathode active materials face cycle deterioration during high current discharge due to low electron conductivity and increased binder and solvent content, leading to reduced life characteristics.
Innovation Solution
Incorporating polyvinyl pyrrolidone (PVP) into the cathode mix slurry containing the cathode active material, conductive additive, and binder to improve dispersibility and reduce binder and solvent loading, thereby enhancing the life characteristics during high current discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the particle diameter of the active material is decreased to increase specific surface area, then electron conductivity is improved, but binder and solvent content must be increased to stabilize slurry properties, leading to cycle deterioration
Solution Approach 1:
The patent changes the chemical composition parameter of the binder from conventional options to polyvinyl pyrrolidone, which has superior dispersibility and binding characteristics. This parameter change allows the slurry to maintain stability with reduced binder and solvent content, resolving the contradiction between improving conductivity through particle size reduction and avoiding excessive binder/solvent addition that causes cycle deterioration.
2Productivity
If carbon black or fibrous carbon is added to improve electron conductivity, then charge and discharge capacity at high current is increased, but binder content must be increased to maintain slurry stability, causing cycle deterioration
Solution Approach 1:
Polyvinyl pyrrolidone acts as an intermediary substance that enhances the interaction between carbon additives and the active material surface. It provides superior wetting and dispersing capabilities, allowing carbon black or fibrous carbon to be effectively distributed in the slurry with minimal binder content, thus improving charge and discharge capacity without causing cycle deterioration through excessive binder addition.
3Ease of operation
If a binder with high binding power is used to improve adhesiveness, then charge and discharge characteristics at high current are improved, but solvent content must be increased to achieve proper slurry viscosity, leading to cycle deterioration
Solution Approach 1:
The patent changes the binder parameter to polyvinyl pyrrolidone, which possesses both high binding power and excellent slurry stabilization properties. This parameter change allows the formation of stable slurries with reduced solvent content while maintaining adequate adhesiveness, thereby improving charge and discharge characteristics at high current without causing cycle deterioration through excessive solvent addition.
4Ease of manufacture
If binder and solvent content is increased to stabilize slurry properties, then manufacturing is easier, but life characteristics during high current discharge are reduced due to binder swelling and segregation
Solution Approach 1:
The patent changes the binder parameter to polyvinyl pyrrolidone, which provides exceptional slurry stability with minimal content. This parameter change eliminates the need to increase binder and solvent content for manufacturing ease, thereby preventing binder swelling and segregation that would otherwise reduce life characteristics during high current discharge.
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 addition of PVP improves the life characteristics of nonaqueous electrolyte secondary batteries by preventing binder segregation and swelling, resulting in improved performance during high current discharge.
Implementation Method 1
Incorporating polyvinyl pyrrolidone (PVP) into the cathode mix slurry containing the cathode active material, conductive additive, and binder to improve dispersibility
Implementation Method 2
The addition of PVP improves the life characteristics of nonaqueous electrolyte secondary batteries by preventing binder segregation and swelling
Data Source
AI summary
A cathode mix for nonaqueous electrolyte secondary batteries includes a cathode active material having an olivine crystal structure, and polyvinyl pyrrolidone. Also, a nonaqueous electrolyte secondary battery includes: a cathode; an anode; and a nonaqueous electrolyte, wherein the cathode includes: a cathode active material having an olivine crystal structure; and polyvinyl pyrrolidone.