Gradient Titanium-Niobium Electrode for Secondary Battery Life

Solution Overview

Problem

Secondary batteries, particularly nonaqueous electrolyte batteries, face challenges in achieving high energy density, input-output performance, and life performance due to side reactions on the electrode surface, where forming a stable film to prevent electrolyte decomposition increases resistance and hinders lithium diffusion, affecting cycle performance.

Innovation Solution

An electrode with a titanium-niobium composite oxide active material-containing layer is designed, where the area ratio of titanium-niobium composite oxide varies across different thickness regions, and the particle diameter distribution is optimized to maintain conductive paths and uniform charge/discharge reactions, reducing the risk of cracking and enhancing performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a stable film is formed on the electrode surface to prevent electrolyte decomposition, then life performance is improved, but resistance increases and input-output performance deteriorates

Engineering Contradiction:

Improvelife performanceVSAvoidinput-output performance

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The patent applies local quality by creating a non-uniform distribution of titanium-niobium composite oxide within the active material-containing layer. The area ratio of titanium-niobium composite oxide varies between a first cross-section (closer to current collector) and a second cross-section (farther from current collector), with the ratio S2/S1 being 0.05 to 0.80. This gradient structure allows different regions to have optimized properties: regions with higher titanium-niobium composite oxide content provide stability and prevent side reactions, while regions with lower content maintain lower resistance and better lithium diffusion, thus resolving the contradiction between life performance and input-output performance.

Inventive Principle:

Principle #3Local quality

2Reliability

If an inorganic material or organic material is coated on the electrode active material to suppress side reactions, then life performance is improved, but lithium diffusion is hindered and input-output performance deteriorates

Engineering Contradiction:

Improvelife performanceVSAvoidlithium diffusion

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The patent employs parameter changes by controlling the area ratio of titanium-niobium composite oxide in different cross-sections of the active material-containing layer. By adjusting the area ratio S2/S1 to be within 0.05 to 0.80, the patent optimizes the balance between suppressing side reactions (improving life performance) and maintaining lithium diffusion (preserving input-output performance). This parameter optimization allows the electrode to achieve both protection and conductivity without the need for thick coating layers that would hinder lithium diffusion.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the degree of coating with inorganic or organic material is increased to prevent side reactions, then life performance is improved, but lithium diffusion is further hindered and cycle performance deteriorates

Engineering Contradiction:

Improvelife performanceVSAvoidcycle performance

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The patent applies local quality by creating a non-uniform distribution of titanium-niobium composite oxide within the active material-containing layer. The area ratio of titanium-niobium composite oxide varies between a first cross-section (closer to current collector) and a second cross-section (farther from current collector), with the ratio S2/S1 being 0.05 to 0.80. This gradient structure allows different regions to have optimized properties: regions with higher titanium-niobium composite oxide content provide stability and prevent side reactions, while regions with lower content maintain lower resistance and better lithium diffusion, thus resolving the contradiction between life performance and input-output performance.

Inventive Principle:

Principle #3Local quality

4Ease of manufacture

If uniform distribution of active material is used, then manufacturing is simplified, but conductive paths are not maintained and charge/discharge reactions become non-uniform

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidcharge/discharge uniformity

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent applies local quality by creating a non-uniform distribution of titanium-niobium composite oxide within the active material-containing layer. The area ratio of titanium-niobium composite oxide varies between a first cross-section (closer to current collector) and a second cross-section (farther from current collector), with the ratio S2/S1 being 0.05 to 0.80. This gradient structure allows different regions to have optimized properties: regions with higher titanium-niobium composite oxide content provide stability and prevent side reactions, while regions with lower content maintain lower resistance and better lithium diffusion, thus resolving the contradiction between life performance and input-output performance.

Inventive Principle:

Principle #3Local quality

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 electrode design achieves improved life performance and uniform charge/discharge reactions, maintaining conductive paths and reducing the risk of cracking, thereby enhancing the battery's energy density and cycle performance.

Implementation Method 1

diffusion of lithium becomes hindered at the coated sections

Methodology Applied

Scientific EffectLithium ion diffusion: Diffusion

Implementation Method 2

uniform charge/discharge reactions

Methodology Applied

Scientific EffectElectrochemical reactions: Redox Reactions

Implementation Method 3

maintaining conductive paths

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS11228031B2Electrode, secondary battery, battery pack, and vehicle

Publication Date: 2022.01.18 KK TOSHIBA

AI summary

According to one embodiment, an electrode includes a current collector and an active material-containing layer. The active material-containing layer contains a titanium-niobium composite oxide. A cross-section of the active material-containing layer includes a first cross-section from the current collector to length 0.5t with respect to a thickness t of the active material-containing layer, and a second cross-section from length 0.5t to length t from the current collector. An area ratio S1 occupied by the titanium-niobium composite oxide within the first cross-section, and an area ratio S2 occupied by the titanium-niobium composite oxide within the second cross-section satisfy 0.8<S2/S1<1. A maximum peak in a particle diameter frequency distribution of the titanium-niobium composite oxide is from 0.5 μm to 3 μm.