Positive Electrode CNT Bundle Network for Low DCR Battery Cycling

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Solution Overview

Problem

The growth of direct current resistance (DCR) in secondary battery positive electrode plates during charge-and-discharge cycles leads to deterioration of rate performance and rapid life fading, which existing technologies have not effectively addressed.

Innovation Solution

Incorporating carbon nanotube bundles with specific length-to-diameter ratios and densities into the positive electrode plate to maintain a conductive network integrity and reduce DCR growth, along with the addition of second carbon nanotubes for improved battery life.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional conductive networks are used in the positive electrode plate, then the initial DCR can be kept low, but the conductive network integrity deteriorates during cycling leading to rapid DCR growth

Engineering Contradiction:

Improveconductive network integrityVSAvoidDCR growth

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent uses a composite conductive network comprising carbon nanotube bundles (with length-to-diameter ratio of 2.5-100) combined with traditional conductive carbon materials. This composite structure leverages the high aspect ratio and strength of carbon nanotube bundles to maintain network integrity while providing adequate electrical conductivity, preventing DCR growth during battery cycling.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies carbon nanotube bundles specifically at critical locations where conductive network integrity is most needed, such as between active material particles and within the electrode matrix. This localized application ensures network stability without requiring excessive amounts of conductive material throughout the entire electrode.

Inventive Principle:

Principle #3Local quality

2Productivity

If the positive electrode plate structure is optimized for low initial DCR, then charging speed can be improved, but cycle life deteriorates due to network disruption

Engineering Contradiction:

Improvecharging speedVSAvoidcycle life

Core Design Contradiction:

ProductivityVSDuration of action of stationary object

Solution Approach 1:

The composite of carbon nanotube bundles with traditional conductive carbon creates a dual-function network that simultaneously enables fast electron transport (improving charging speed) and maintains structural stability during expansion-contraction cycles (extending cycle life).

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The high aspect ratio (length-to-diameter ratio of 2.5-100) of the carbon nanotube bundles creates a curved, flexible conductive pathway that can accommodate the volume changes of active material during cycling without breaking, unlike rigid linear conductive paths.

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Ease of manufacture

If traditional carbon materials are used for conductivity, then manufacturing is simple, but the conductive network cannot withstand expansion and shrinking during cycling

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidconductive network strength

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The patent changes the key parameter of the conductive material from traditional isotropic carbon particles to anisotropic carbon nanotube bundles with specific length-to-diameter ratios (2.5-100). This parameter change provides inherent mechanical strength and flexibility to the conductive network, enabling it to withstand cycling stresses while maintaining manufacturability through conventional slurry coating 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 carbon nanotube bundles and second carbon nanotubes effectively reduce initial DCR, enhance cycle life, increase charging speed, and improve low-temperature performance by forming a robust conductive network and ensuring efficient ion transport.

Implementation Method 1

The positive electrode plate includes a current collector and a positive active material layer. The positive active material layer includes a positive active material and a carbon material. The carbon material includes carbon nanotube bundles with a length-to-diameter ratio of 2.5 to 100.

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

Methodology Applied

Scientific EffectIon transport: Ion Exchange

Data Source

PatentUS20230282835A1Secondary battery and electronic device

Publication Date: 2023.09.07 NINGDE AMPEREX TECHNOLOGY LTD

AI summary

A secondary battery includes a positive electrode plate. The positive electrode plate includes a current collector and a positive active material layer. The positive active material layer includes a positive active material and a carbon material. The carbon material includes carbon nanotube bundles with a ratio of an average length of the carbon nanotube bundles to an average diameter of the carbon nanotube bundles being in a range of 2.5 to 100. The carbon nanotube bundle includes a plurality of first carbon nanotubes. The carbon nanotube bundles reduce an initial direct-current resistance of the battery, ensure integrity of a conductive network during cycling, effectively reduce the growth of the direct current resistance, and increase the charging speed.