Electrode Mixture Slurry Stability with Composite Binder

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Solution Overview

Problem

The electrode active material with an enhanced nickel ratio in lithium-ion secondary batteries tends to settle at the bottom of the container, leading to an uneven solid content concentration and poor handleability during production, due to gelling issues in the electrode mixture slurry.

Innovation Solution

An electrode mixture comprising a lithium metal oxide with a specific composition and a binder composition of vinylidene fluoride copolymer and acrylic polymer, which includes structural units derived from specific monomers, is used to maintain a stable solid content concentration and prevent gelling, ensuring consistent slurry properties during storage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the nickel ratio in the electrode active material is increased to improve discharge capacity, then the charge/discharge capacity is improved, but the electrode mixture slurry becomes prone to gelling and the electrode active material settles

Engineering Contradiction:

Improvecharge/discharge capacityVSAvoidslurry stability

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The patent uses a composite binder system comprising both a vinylidene fluoride-based polymer and a carboxymethyl cellulose-based polymer. This combination of different polymer materials creates a synergistic effect where the vinylidene fluoride polymer provides adhesion and the carboxymethyl cellulose polymer provides steric stabilization, preventing both gelling and settling of high-nickel electrode active material while maintaining high discharge capacity

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent specifies precise compositional parameters for the binder system, including the weight ratio between vinylidene fluoride polymer and carboxymethyl cellulose polymer (1:9 to 9:1), and the content of carboxymethyl cellulose polymer (0.1-10 parts by weight per 100 parts by weight of electrode active material). These parameter optimizations prevent slurry instability while enabling high nickel content electrode materials

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If the electrode active material settles in the container, then the solid content concentration increases at the bottom, but the handleability during electrode production deteriorates

Engineering Contradiction:

Improvesolid content concentration uniformityVSAvoidhandleability

Core Design Contradiction:

Stability of the object's compositionVSEase of operation

Solution Approach 1:

The carboxymethyl cellulose-based polymer acts as an intermediary substance that provides steric stabilization to the electrode active material particles in the slurry. This polymer creates a protective barrier around particles, preventing aggregation and settling, thereby maintaining uniform solid content concentration and ensuring good handleability during electrode production processes

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentEP3796430B1Electrode mixture, electrode mixture production method, electrode structure, electrode structure production method, and secondary battery

Publication Date: 2022.06.15 KUREHA CORPORATION

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AI summary

Provided is an electrode mixture that can suppress changes in solid content concentration during storage of a slurry. The electrode mixture according to the present invention includes an electrode active material and a binder composition, in which the binder composition contains a vinylidene fluoride copolymer and an acrylic polymer, and the electrode active material contains a lithium metal oxide represented by Li1 xMO2.