Block Copolymer Binder for Lithium Ion Battery Electrodes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium ion secondary batteries using graphite as an anode active material face issues such as decomposition and deterioration due to reactions with carbonate ester compounds in the electrolyte, leading to reduced charge/discharge efficiency, cycle characteristics, and safety concerns, while existing binders like polyvinyl alcohol and acrylic polymers result in electrode polarization and productivity issues.
Innovation Solution
A battery electrode is produced using a block copolymer with a vinyl alcohol polymer block as the binder, which reduces polarization and improves charge/discharge properties, cycle characteristics, and productivity by incorporating a (meth)acrylic polymer block, allowing for a more efficient active material layer formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyvinyl alcohol or acrylic polymer is used as a binder, then the electrode can be formed, but electrode polarization increases and charge/discharge properties deteriorate
Solution Approach 1:
The patent uses a block copolymer comprising a polyvinyl alcohol block and a polyacrylic acid block, combining the advantages of both polymers. The polyvinyl alcohol block provides coordination ability with lithium ions to reduce polarization, while the polyacrylic acid block contributes to film formation and structural stability, achieving both low polarization and good charge/discharge properties
Solution Approach 2:
The binder is divided into two distinct functional blocks: a polyvinyl alcohol block (5-50 mass%) responsible for coordinating lithium ions and reducing polarization, and a polyacrylic acid block (50-95 mass%) responsible for film formation and structural integrity. This segmentation allows each block to optimize its specific function while working together as a unified binder system
2Ease of manufacture
If polymethacrylic acid is used as a binder, then solubility in organic solvent is improved, but workability decreases due to need for organic solvent
Solution Approach 1:
The patent changes the solvent parameter from organic solvent to water by using polyvinyl alcohol as the main component of the block copolymer. Polyvinyl alcohol is water-soluble, allowing the slurry to be prepared with water instead of organic solvents, improving workability and eliminating the need for organic solvent removal steps
Solution Approach 2:
The block copolymer structure acts as an intermediary that combines the water-solubility of polyvinyl alcohol with the film-forming ability of polyacrylic acid. This intermediary structure enables the use of water as solvent while maintaining the necessary binder performance for electrode formation
3Use of energy by moving object
If graphite is used as anode active material with carbonate ester electrolyte, then energy density is improved, but decomposition and deterioration occur reducing cycle characteristics
Solution Approach 1:
The block copolymer binder performs preliminary protective action by forming a stable film on the graphite surface before electrolyte decomposition can occur. The polyvinyl alcohol block coordinates with lithium ions and the polyacrylic acid block forms a protective matrix, preventing direct contact between graphite and carbonate ester, thus preventing decomposition and improving cycle characteristics while maintaining energy density
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 a block copolymer with a vinyl alcohol and (meth)acrylic polymer block combination results in a less polarized battery with excellent charge/discharge properties and cycle characteristics, enhancing electrode and battery productivity while preventing cracks and improving processability.
Implementation Method 1
a polymer having an oxygen-containing functional group capable of coordinating to a lithium ion in a molecular structure such as polyvinyl alcohol
Data Source
Figure 1
AI summary
There are provided a battery electrode wherein an active material layer is formed on a collector surface, and the layer contains an active material and a block copolymer having a vinyl alcohol polymer block; and a lithium ion secondary battery having a laminate structure in which a pair of electrodes having an active material layer are disposed in such a manner that the active material layers face each other via a separator, and an electrolyte composition containing a lithium-containing electrolyte salt fills the gaps between the pair of electrodes and the separator, wherein at least one of the pair of electrodes is the above battery electrode. Thus, there can be provided a lithium ion secondary battery which can be easily produced and be less polarized, exhibiting excellent charge/discharge properties and cycle characteristics.