Lithium Battery Negative Electrode Protrusions for Expansion Control

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Solution Overview

Problem

Lithium secondary batteries face challenges in reducing the expansion of the negative electrode due to lithium metal deposition, leading to degraded discharge capacity and cycle characteristics, as existing solutions like porous current collectors do not effectively limit volume change.

Innovation Solution

Incorporating a negative electrode current collector with protrusions, where at least one protrusion is made of an insulative material, to create spaces for lithium deposition, reducing volume expansion and internal short-circuits, and enhancing charge/discharge efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If lithium metal is deposited on the negative electrode during charge, then the capacity of the battery is increased, but the negative electrode expands and degrades discharge capacity

Engineering Contradiction:

Improvelithium metal depositionVSAvoidnegative electrode expansion

Core Design Contradiction:

Quantity of substanceVSVolume of moving object

Solution Approach 1:

The negative electrode current collector is divided into multiple protrusions separated by grooves, creating segmented structures. This segmentation allows lithium metal to deposit in isolated regions within the grooves, preventing continuous expansion across the entire electrode surface and accommodating volume changes locally.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The grooves are formed as recesses within the protrusions structure, creating nested geometries. lithium metal deposits within these nested groove spaces, allowing the electrode to accommodate deposition volume without expanding outward, as the nested structure provides internal accommodation space.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Quantity of substance

If lithium metal is deposited on the negative electrode during charge, then the capacity of the battery is increased, but internal short-circuits occur due to dendritic deposition

Engineering Contradiction:

Improvelithium metal depositionVSAvoidinternal short-circuit prevention

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The protrusions and grooves create segmented deposition zones that isolate lithium metal growth. This segmentation prevents dendritic structures from bridging across the electrode, as each groove acts as an independent containment region, thereby eliminating the continuous conductive paths that cause internal short-circuits.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The grooves act as intermediary spaces between protrusions, serving as controlled regions for lithium deposition. These intermediary groove structures mediate the deposition process by providing defined boundaries that prevent uncontrolled dendritic growth and subsequent short-circuiting.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Quantity of substance

If the surface of the negative electrode current collector is made rough to accommodate lithium deposition, then the deposition space is increased, but the manufacturing precision is reduced

Engineering Contradiction:

Improvelithium deposition spaceVSAvoidsurface roughness control

Core Design Contradiction:

Quantity of substanceVSManufacturing precision

Solution Approach 1:

Instead of creating a uniformly rough surface, the invention segments the surface into discrete protrusions and grooves. This segmentation allows for controlled, localized roughness features that can be precisely manufactured using standard techniques like embossing or molding, avoiding the need for high-precision rough surface control while still providing adequate deposition space.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the surface parameter from continuous roughness to discrete geometric features (protrusions and grooves with specific dimensions). This parameter transformation allows the use of conventional manufacturing tolerances for creating the geometric features, rather than requiring tight control over continuous surface roughness parameters.

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 solution effectively reduces negative electrode expansion, improves discharge capacity, and enhances safety by accommodating lithium metal deposition and facilitating efficient charge/discharge reactions.

Implementation Method 1

lithium metal is deposited on a negative electrode during charge

Methodology Applied

Scientific EffectElectrochemical reduction: Electrodeposition

Implementation Method 2

the lithium metal dissolves in a nonaqueous electrolyte during discharge

Methodology Applied

Scientific EffectElectrochemical oxidation: Electrodeposition

Data Source

PatentUS11024874B2Lithium secondary battery including nonaqueous electrolyte having lithium-ion conductivity

Publication Date: 2021.06.01 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

A lithium secondary battery includes a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte having lithium-ion conductivity. The positive electrode contains a positive electrode active material containing lithium. The negative electrode faces the positive electrode. The separator is disposed between the positive and negative electrodes. The negative electrode includes a negative electrode current collector. The negative electrode current collector includes a layer and protrusions. The layer has a first surface on which lithium metal is deposited during charge. The protrusions protrude from the first surface. At least one of the protrusions includes a conductive material and an insulative material.