Layered Electrode Structure for Battery Adhesion and Capacity

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Solution Overview

Problem

Lithium titanium oxide with a monoclinic β-type structure, when used alone as a negative electrode material, suffers from reduced adhesion to the current collector, leading to separation and poor cycle characteristics in nonaqueous electrolyte batteries.

Innovation Solution

A layered electrode structure is implemented, with a first layer of lithium titanium oxide having a spinel structure on the current collector and a second layer of monoclinic β-type titanium composite oxide, enhancing adhesion and diffusion of lithium ions, thereby improving rate performance and cycle life.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If monoclinic β-type titanium composite oxide is used alone as the negative electrode active material, then the theoretical capacity is improved (about 330 mAh/g), but the adhesion between the active material layer and current collector is reduced, leading to separation and poor cycle characteristics

Engineering Contradiction:

Improvetheoretical capacityVSAvoidcycle characteristics

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The negative electrode active material layer is divided into two distinct layers: a first layer containing spinel lithium titanium oxide (providing strong adhesion to current collector) and a second layer containing monoclinic β-type titanium composite oxide (providing high capacity). This segmentation allows each layer to perform its specialized function, resolving the contradiction between adhesion and capacity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention uses a composite structure combining two different titanium-based materials with complementary properties: spinel lithium titanium oxide (Li4Ti5O12) for structural stability and adhesion, and monoclinic β-type titanium composite oxide for high lithium ion capacity. The composite layered structure enables simultaneous achievement of strong adhesion and high theoretical capacity.

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If monoclinic β-type titanium composite oxide is used alone, then the reversible capacity is improved (about 240 mAh/g), but the adhesion is reduced causing separation from the current collector

Engineering Contradiction:

Improvereversible capacityVSAvoidadhesion strength

Core Design Contradiction:

Quantity of substanceVSStrength

Solution Approach 1:

The active material layer is segmented into two functional layers: the first layer (spinel lithium titanium oxide) provides strong mechanical adhesion to the current collector, while the second layer (monoclinic β-type titanium composite oxide) provides high reversible capacity. This segmentation resolves the contradiction between adhesion strength and reversible capacity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the active material layer are assigned different properties: the first layer near the current collector has high adhesion strength but lower capacity, while the second layer has high reversible capacity. This local differentiation of material properties allows the electrode as a whole to achieve both strong adhesion and high reversible capacity.

Inventive Principle:

Principle #3Local quality

3Device complexity

If a single-layer structure is used, then the device complexity is reduced, but the rate performance and cycle life are insufficient

Engineering Contradiction:

Improveelectrode structure complexityVSAvoidrate performance

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The electrode is segmented into two layers with distinct functions: the first layer ensures structural integrity and adhesion, while the second layer optimizes lithium ion diffusion and capacity. This segmentation improves rate performance and cycle life despite increased structural complexity, as the layered design enables better electrolyte permeation and ion transport pathways.

Inventive Principle:

Principle #1Segmentation

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 layered structure achieves high capacity, long cycle life, and excellent rate performance by promoting electrolyte permeation and lithium ion diffusion, while maintaining adhesion to the current collector.

Implementation Method 1

Lithium titanium oxide having a spinel structure (Li4Ti5O12), which is in actual use, has three lithium ions capable of absorbing and releasing per unit chemical formula

Methodology Applied

Scientific EffectLithium ion absorption and release: Absorption (physical)

Implementation Method 2

enhancing adhesion and diffusion of lithium ions, thereby improving rate performance and cycle life

Methodology Applied

Scientific EffectLithium ion diffusion: Diffusion

Implementation Method 3

nonaqueous electrolyte battery including a positive electrode, a negative electrode, and a nonaqueous electrolyte

Methodology Applied

Scientific EffectIonic conduction: Conduction (electrical)

Data Source

PatentUS9257700B2Electrode, nonaqueous electrolyte battery and battery pack

Publication Date: 2016.02.09 KK TOSHIBA

AI summary

According to one embodiment, an electrode includes a current collector and an active material-including layer. The active material-including layer includes a first layer and a second layer. The first layer is provided on a surface of the current collector and includes lithium titanium oxide having a spinel structure. The second layer is provided on the first layer and includes a monoclinic β-type titanium composite oxide.