Lithium Battery Electrolyte and Silicon Negative Electrode Design

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Solution Overview

Problem

Existing lithium ion secondary batteries face challenges in achieving high energy density, high capacity, and excellent cycle characteristics due to insufficient understanding of the relationship among negative electrode components, binders, electrolyte solutions, electrode structures, and outer casings.

Innovation Solution

A lithium ion secondary battery design featuring a negative electrode formed by binding metal and metal oxide active materials to a current collector with a binder, using a phosphate ester compound-based electrolyte solution with fluorinated carbonate and halogenated phosphate ester compounds, and an outer casing to enhance stability and capacity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If a negative electrode material with high capacity (such as silicon-based materials) is used to increase energy density, then the battery capacity increases, but the volume change of the negative electrode during charge-discharge cycles increases, leading to poor cycle characteristics

Engineering Contradiction:

Improvebattery capacityVSAvoidcycle characteristics

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent applies the nesting principle by placing silicon fine crystals (high capacity material) inside a void space within a porous silicon compound particle. The silicon fine crystals are nested within the porous structure, allowing them to expand and contract during lithium insertion/extraction without damaging the overall particle structure. This nested configuration enables the high capacity of silicon while mitigating its volume expansion problem, thereby improving cycle characteristics.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The patent uses a porous silicon compound as a flexible matrix that can accommodate volume changes of the embedded silicon fine crystals. The porous structure acts as a flexible shell that expands and contracts with the silicon particles during charge-discharge cycles, preventing structural degradation and maintaining electrode integrity over many cycles, thus improving reliability.

Inventive Principle:

Principle #30Flexible shells and thin films

2Productivity

If conventional electrolyte solutions are used with high-capacity negative electrodes, then the battery can operate, but the electrode structure cannot effectively manage volume changes, leading to degradation

Engineering Contradiction:

Improvebattery operationVSAvoidelectrode structure stability

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

The patent changes the structural parameters of the negative electrode material by creating a porous silicon compound matrix with controlled void spaces. This structural parameter change allows the electrode to accommodate volume expansion of silicon during lithium insertion while maintaining overall structural stability. The porous structure's geometry and porosity are optimized to manage volume changes effectively, preventing electrode degradation.

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If three-component negative electrode materials (carbon, metal alloy, oxide) are used to reduce volume change, then volume stability improves, but the relationship among components, binder, electrolyte, and electrode structure is insufficiently optimized, limiting performance

Engineering Contradiction:

Improvevolume stabilityVSAvoidenergy density

Core Design Contradiction:

Stability of the object's compositionVSProductivity

Solution Approach 1:

The patent creates a composite material system consisting of silicon fine crystals dispersed in a porous silicon compound matrix. This composite structure combines the high capacity of silicon with the structural stability of the silicon compound matrix. The composite design allows effective management of volume changes while achieving high energy density, overcoming the limitations of conventional three-component mixtures through optimized component integration at the nanoscale.

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 battery achieves high energy density, high capacity, and improved cycle characteristics, with the electrolyte solution and electrode structure effectively managing volume changes and heat stability.

Implementation Method 1

metal particles capable of forming an alloy with lithium

Methodology Applied

Scientific EffectAlloy formation:

Implementation Method 2

carbon material particles capable of intercalating and deintercalating lithium ions

Methodology Applied

Scientific EffectIntercalation:

Implementation Method 3

oxide particles capable of intercalating and deintercalating lithium ions

Methodology Applied

Scientific EffectIntercalation:

Data Source

PatentUS9012093B2Secondary battery

Publication Date: 2015.04.21 NEC CORP

AI summary

The present invention provides an electrolyte solution for a lithium ion secondary battery comprising 65 to 99% by volume of a phosphate ester compound, 0.01 to 30% by volume of a fluorinated carbonate compound, and 0.1 to 10% by volume of a halogenated phosphate ester compound and/or 0.1 to 30% by volume of a solvent having a specific dielectric constant of 15 or more, and a lithium ion secondary battery having the same.