Hydroxyl-Modified Binder Inhibits Electrode Swelling
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Solution Overview
Problem
The existing binder compositions for non-aqueous secondary batteries, such as those described in PTL 1, fail to adequately inhibit electrode swelling and lithium dendrite deposition during high-temperature cycling and repeated charging and discharging, particularly in lithium ion secondary batteries.
Innovation Solution
A binder composition for non-aqueous secondary battery electrodes incorporating a water-soluble polymer with a specific monomer unit derived from a monomer represented by the general formula CH2═C(R1)—C═O—NH—R2—OH, where R1 is hydrogen or an alkyl group and R2 is (CHR3)n(O(CHR3)m)l, in a proportion of at least 0.1 mass % and not more than 20 mass %, which includes an N-hydroxyalkyl(meth)acrylamide monomer, an acid group-containing monomer unit, and a (meth)acrylamide monomer unit, to improve high-temperature cycle characteristics and prevent electrode swelling and lithium dendrite deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a binder containing a particulate polymer with acid group-containing monomer units and amide group-containing monomer units is used, then the binder composition can provide some binding function, but it cannot sufficiently inhibit electrode swelling associated with repeated charging and discharging
Solution Approach 1:
The patent changes the chemical composition parameters of the binder by incorporating a water-soluble polymer containing hydroxyl group-containing monomer units (at least 50 mass% of total monomer units). This parameter change in polymer chemistry transforms the binder's properties to effectively inhibit electrode swelling during repeated charging and discharging cycles.
Solution Approach 2:
The patent creates a composite binder system by combining the water-soluble polymer (containing hydroxyl group-containing monomer units) with conventional binders containing acid group-containing and amide group-containing monomer units. This composite material approach synergistically improves both binding function and inhibition of electrode swelling, resolving the technical contradiction.
2Ease of manufacture
If the binder according to PTL 1 is used in formation of a negative electrode, then the electrode can be formed, but it has not been possible to inhibit deposition of lithium dendrites at the surface of the negative electrode
Solution Approach 1:
The patent modifies the binder composition parameters by incorporating a water-soluble polymer with hydroxyl group-containing monomer units at least 50 mass% of total monomer units. This parameter change in the binder's chemical structure enables inhibition of lithium dendrite deposition while maintaining electrode formation capability.
3Ease of manufacture
If conventional binder compositions are used, then the electrode mixed material layer can be formed, but it has not been possible to sufficiently improve secondary battery high-temperature cycle characteristics
Solution Approach 1:
The patent develops a composite slurry composition by integrating the water-soluble polymer (with hydroxyl group-containing monomer units comprising at least 50 mass% of total monomer units) into the conventional slurry system containing electrode active material and solvent. This composite approach maintains ease of manufacture through standard application processes while significantly improving high-temperature cycle characteristics.
Data Source
AI summary
A binder composition for a non-aqueous secondary battery electrode contains a water-soluble polymer including, in a proportion of at least 0.1 mass % and not more than 20 mass %, a monomer unit derived from a monomer represented by general formula (1): CH2═C(R1) —C═O—NH—R2—OH (R1 is hydrogen or an alkyl group and R2 is (CHR3)n(O(CHR3)m)l[n=1 to 10; m=1 to 4; 1=0 to 3; and R3 is hydrogen or an alkyl group having a carbon number of 1 to 4]).