Silicon Negative Electrode Paste Composition for Lithium-Ion Batteries

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Solution Overview

Problem

Lithium ion secondary batteries using silicon-based negative electrode active materials face challenges in suppressing expansion and contraction during charging and discharging, leading to structural deterioration and uneven distribution of the active material, which affects cycle characteristics.

Innovation Solution

A paste composition for lithium ion secondary battery negative electrodes is developed, comprising a silicon-based negative electrode active material and a water-soluble polymer obtained through polymerization of specific monomers, with a predetermined ratio and degree of swelling, to improve dispersibility and binding properties, thereby enhancing cycle characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If silicon-based negative electrode active material is used to increase battery capacity, then battery capacity is improved, but the material expands and contracts during charging and discharging causing structural deterioration and electrode fracture

Engineering Contradiction:

Improvebattery capacityVSAvoidcycle characteristics

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

A water-soluble polymer coating is applied to the silicon-based negative electrode active material particles. This polymer shell acts as a flexible protective layer that accommodates the expansion and contraction of silicon during lithiation and delithiation, preventing structural fracture and maintaining electrode integrity over repeated charge-discharge cycles.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The negative electrode is constructed as a composite material system combining silicon-based active material particles with a water-soluble polymer binder. The polymer matrix provides mechanical support and flexibility to the brittle silicon particles, creating a composite structure that maintains structural integrity during volume changes while preserving high capacity.

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If silicon-based negative electrode active material is dispersed in water to form slurry, then the slurry can be applied to current collector, but the silicon material easily aggregates causing uneven distribution in the negative electrode mixed material layer

Engineering Contradiction:

Improveslurry applicationVSAvoiduniformity of active material distribution

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

A water-soluble polymer is used as an intermediary substance between the silicon-based active material particles and the aqueous slurry medium. This polymer improves the wettability and dispersibility of hydrophobic silicon particles in water, preventing aggregation and ensuring uniform distribution throughout the slurry and subsequent electrode structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The surface properties of silicon particles are modified by coating with water-soluble polymer, changing their hydrophobicity to hydrophilicity. This parameter change in surface wettability enables better dispersion in aqueous slurry and prevents aggregation during electrode manufacturing processes.

Inventive Principle:

Principle #35Parameter changes

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 effectively suppresses the expansion and contraction of the silicon-based negative electrode active material, improves its dispersibility, and enhances the cycle characteristics and internal resistance of lithium ion secondary batteries, leading to higher battery capacity and stability.

Implementation Method 1

the water-soluble polymer has a degree of swelling in electrolysis solution of less than 120%

Methodology Applied

Scientific EffectSwelling: Hydrogel

Implementation Method 2

a water-soluble polymer obtained through polymerization of a monomer composition including: an ethylenically unsaturated carboxylic acid compound (A)... and a copolymerizable compound (B)

Methodology Applied

Scientific EffectPolymerization: Photopolymerisation

Data Source

PatentEP3214676B1Paste composition for negative electrode for lithium-ion rechargeable battery, composite particles for negative electrode for lithium-ion rechargeable battery, slurry composition for negative electrode for lithium-ion rechargeable battery, negative electrode for lithium-ion rechargeable battery, and lithium-ion rechargeable battery

Publication Date: 2019.03.27 ZEON CORP

AI summary

An objective of the present disclosure is to provide a material for slurry composition-use that allows a lithium ion secondary battery using a silicon-based negative electrode active material to achieve excellent cycle characteristics. The material for slurry composition-use for example is a paste composition including a negative electrode active material that contains a silicon-based negative electrode active material in an amount of at least 30 mass% and a water-soluble polymer in an amount of at least 3 parts by mass and less than 500 parts by mass per 100 parts by mass of the silicon-based negative electrode active material. The water-soluble polymer includes at least 20.0 mass% and no greater than 79.5 mass% of structural units derived from an ethylenically unsaturated carboxylic acid compound (A) and at least 20.0 mass% and no greater than 79.5 mass% of structural units derived from a copolymerizable compound (B) that has an ethylenically unsaturated bond and a water solubility of at least 7 g/100 g at 20°C, and the water-soluble polymer has a degree of swelling in electrolysis solution of less than 120%.