Graphite-Silicon Battery Anode Binder for Cycle Life

Solution Overview

Problem

Nonaqueous electrolyte secondary batteries using graphite as negative-electrode active materials face limitations in capacity and charge-discharge cycle characteristics due to volume changes in materials like silicon, which reduce electronic conductivity and deteriorate cycle performance.

Innovation Solution

A nonaqueous electrolyte secondary battery design incorporating a negative-electrode active material composed of a mixture of graphite and silicon or silicon compounds, with a polyimide and polyvinylpyrrolidone binder system to enhance adhesion and maintain electronic conductivity during charge-discharge cycles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If silicon or silicon compound is used as negative-electrode active material to increase capacity, then battery capacity is improved, but volume changes during charge-discharge reduce electronic conductivity and deteriorate cycle characteristic

Engineering Contradiction:

Improvebattery capacityVSAvoidcharge-discharge cycle characteristic

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

Silicon particles are embedded within graphite particles, creating a core-shell structure where the inner silicon provides high capacity while the outer graphite layer accommodates volume expansion and maintains structural integrity. This nested configuration allows the high-capacity silicon to function while being protected by the structurally stable graphite matrix.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The invention uses a composite material system combining silicon (or silicon compound) with graphite to create a negative-electrode active material that leverages the high capacity of silicon while utilizing graphite's structural stability and conductivity to maintain electronic conductivity and cycle performance throughout charge-discharge cycles.

Inventive Principle:

Principle #40Composite materials

2Reliability

If graphite material is used as negative-electrode active material to maintain structural stability, then charge-discharge cycle characteristic is improved, but theoretical capacity is limited to 372 mAh/g

Engineering Contradiction:

Improvecharge-discharge cycle characteristicVSAvoidbattery capacity

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

Silicon particles are embedded within graphite particles, creating a core-shell structure where the inner silicon provides high capacity while the outer graphite layer accommodates volume expansion and maintains structural integrity. This nested configuration allows the high-capacity silicon to function while being protected by the structurally stable graphite matrix.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The invention uses a composite material system combining silicon (or silicon compound) with graphite to create a negative-electrode active material that leverages the high capacity of silicon while utilizing graphite's structural stability and conductivity to maintain electronic conductivity and cycle performance throughout charge-discharge cycles.

Inventive Principle:

Principle #40Composite materials

3Quantity of substance

If material capable of forming alloy with lithium ions is used to increase capacity, then battery capacity is improved, but expansion and shrinkage reduce electronic conductivity between active material and current collector

Engineering Contradiction:

Improvebattery capacityVSAvoidadhesion to current collector

Core Design Contradiction:

Quantity of substanceVSStrength

Solution Approach 1:

Silicon particles are embedded within graphite particles, creating a core-shell structure where the inner silicon provides high capacity while the outer graphite layer accommodates volume expansion and maintains structural integrity. This nested configuration allows the high-capacity silicon to function while being protected by the structurally stable graphite matrix.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The invention uses a composite material system combining silicon (or silicon compound) with graphite to create a negative-electrode active material that leverages the high capacity of silicon while utilizing graphite's structural stability and conductivity to maintain electronic conductivity and cycle performance throughout charge-discharge cycles.

Inventive Principle:

Principle #40Composite materials

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 graphite-silicon composite with a polyimide and polyvinylpyrrolidone binder improves the charge-discharge cycle characteristic by maintaining adhesion and preventing reduction in electronic conductivity, thereby enhancing battery performance and capacity retention.

Implementation Method 1

a material capable of forming an alloy with lithium ions, such as silicon, tin, or aluminum

Methodology Applied

Scientific EffectAlloy formation: Chemical Bonding

Implementation Method 2

lithium ions are inserted into and extracted from between the graphite crystal layers in the negative-electrode active material

Methodology Applied

Scientific EffectIntercalation: Absorption (physical)

Implementation Method 3

the carbon particles absorb volume changes of the material, such as silicon or aluminum, with storage and release of lithium ions

Methodology Applied

Scientific EffectVolume change absorption: Elasticity

Data Source

PatentUS9023521B2Nonaqueous electrolyte secondary battery

Publication Date: 2015.05.05 PANASONIC ENERGY CO LTD

AI summary

Provided is a nonaqueous electrolyte secondary battery in which a negative-electrode active material containing a graphite material and silicon or a silicon compound is used and which has an excellent charge-discharge cycle characteristic. In the nonaqueous electrolyte secondary battery, the negative-electrode active material used is an active material containing a graphite material and silicon or a silicon compound, and the negative electrode binder used comprises a polyimide and polyvinylpyrrolidone.