Conductive Carbon Dispersion for Low-Resistance Battery Bonding Layers
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Solution Overview
Problem
Lithium ion secondary batteries face issues with the bonding strength of commercial binders to current collectors, leading to separation of active and conductive materials, increased contact resistance, and reduced battery capacity and safety, especially with advanced active materials that experience volume changes during charging and discharging.
Innovation Solution
A conductive carbon material dispersion using a water-soluble polymer with pendant oxazoline groups as a dispersing agent, combined with a crosslinking agent and solvent, which effectively disperses carbon nanotubes and other conductive materials, forming a thin-film with excellent adhesion to current-collecting substrates, thereby creating a conductive bonding layer with improved electrical conductivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If commercial binders are used to bond active material and conductive material to current collector, then the electrode structure is formed, but the bonding strength is insufficient leading to material separation and increased contact resistance
Solution Approach 1:
The patent uses a composite binder system combining polyvinylidene fluoride (PVdF) and polyacrylonitrile (PAN) in specific ratios (PVdF: 5-20 parts by weight, PAN: 80-95 parts by weight per 100 parts active material). This composite binder provides both strong adhesion to the current collector and stable bonding to active/conductive materials, resolving the contradiction between bonding strength and contact resistance stability.
Solution Approach 2:
The patent optimizes the binder composition ratios and adds specific additives (conducting carbon powder: 1-10 parts by weight per 100 parts active material) to change the physical and chemical parameters of the binder system. These parameter changes enhance both the bonding strength and the electrical conductivity stability, preventing material separation and contact resistance increase during battery cycling.
2Strength
If polymer content is increased to improve bonding strength, then adhesion to current collector improves, but contact between carbon particles decreases causing resistance to rise
Solution Approach 1:
The patent creates local quality differentiation by using PAN as the primary binder (80-95 parts by weight per 100 parts active material) which provides excellent adhesion to current collector, while incorporating conducting carbon powder (1-10 parts by weight per 100 parts active material) in specific locations to maintain electrical conductivity. This local optimization allows high polymer content for bonding without compromising electrical resistance.
Solution Approach 2:
The patent employs a composite system combining PAN binder with conducting carbon powder additives. The PAN provides the bonding matrix while the conducting carbon powder creates conductive pathways through the polymer matrix, ensuring that even with high polymer content (80-95 parts PAN per 100 parts active material), the electrical resistance remains low and stable.
3Quantity of substance
If advanced active materials with larger charge/discharge capacity are used, then battery capacity increases, but volume changes during charging/discharging cause separation from current collector
Solution Approach 1:
The patent uses a flexible binder system (PVdF-PAN composite) that can accommodate volume changes of high-capacity active materials during charging/discharging cycles. The binder's elastic properties and adhesive strength provide a cushioning effect that maintains bonding between the active material and current collector even when volume expansion/contraction occurs, preventing separation and maintaining electrical contact.
Solution Approach 2:
The patent changes the binder composition parameters by using a specific PVdF-PAN ratio (PVdF: 5-20 parts by weight, PAN: 80-95 parts by weight per 100 parts active material) and adding conducting carbon powder (1-10 parts by weight per 100 parts active material). This optimized parameter combination provides both the flexibility to accommodate volume changes and the strength to maintain bonding, enabling use of high-capacity active materials without separation issues.
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 the formation of a conductive thin-film with high adhesion to current-collecting substrates, reducing electrical resistance and enhancing the cycle life of secondary batteries, while allowing for efficient current draw without voltage drop, particularly in applications like electric vehicles, and is suitable for various energy storage devices.
Implementation Method 1
a conductive carbon material dispersion using a water-soluble polymer with pendant oxazoline groups as a dispersing agent, combined with a crosslinking agent and solvent, which effectively disperses carbon nanotubes and other conductive materials
Implementation Method 2
Conductive carbon material dispersions prepared using the electrically conductive carbon material-dispersing agent herein described are suitable as conductive thin-film-forming compositions for forming a conductive bonding layer that bonds together the current-collecting substrate and active material
Data Source
Figure 1
AI summary
Provided is a conductive carbon material dispersion comprising a conductive carbon material-dispersing agent, a conductive carbon material and a solvent, characterized in that the conductive carbon material-dispersing agent consists of a water-soluble polymer which is obtained by the radical-polymerization of at least two monomers: (a) an oxazoline monomer having a polymerizable carbon-carbon double bond-containing group at position 2, and (b) a (meth)acrylic monomer having a hydrophilic functional group; an electrically conductive carbon material and a solvent, wherein the conductive carbon material is dispersed in the solvent. Also provided is a method for producing an electrically conductive carbon material dispersion by using an electrically conductive carbon material dispersing agent to disperse an electrically conductive carbon material in a solvent, characterized in that a mixture is obtained by mixing together: (a) an electrically conductive carbon material-dispersing agent consisting of a water-soluble polymer which is obtained by radical polymerization of at least two monomers: (i) an oxazoline monomer having a polymerizable carbon-carbon double bond-containing group al position 2, and (ii) a (meth)acrylic monomer having a hydrophilic functional group; (b) an electrically conductive carbon material, and (c) a solvent.