Lithium Battery Negative Electrode Protrusions for Expansion Control

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Solution Overview

Problem

Lithium secondary batteries with wound electrode groups face challenges in reducing negative electrode expansion during charging, leading to stress and uneven deposition of lithium metal, which decreases charge/discharge efficiency and capacity.

Innovation Solution

The battery design incorporates a negative electrode current collector with first and second protrusions on its surfaces, where the second protrusions have a higher average height than the first, creating spaces for lithium deposition, thereby reducing apparent volume expansion and enhancing charge/discharge efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If lithium metal is deposited on a flat negative electrode current collector, then the battery structure is simple, but the negative electrode expands significantly during charging, causing stress and reducing charge/discharge efficiency

Engineering Contradiction:

Improvenegative electrode structureVSAvoidcharge/discharge efficiency

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent applies preliminary action by pre-forming protrusions on the negative electrode current collector before lithium metal deposition. These protrusions create predetermined spaces that anticipate and accommodate the expansion of lithium metal during charging, preventing stress and maintaining charge/discharge efficiency without complicating the overall battery structure

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent employs dimensionality change by transitioning from a flat two-dimensional current collector surface to a three-dimensional structure with protrusions. This adds vertical dimensionality that creates accommodation spaces for lithium metal expansion, effectively managing volume changes while maintaining structural simplicity

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Ease of manufacture

If the negative electrode current collector has uniform protrusions on both surfaces, then the structure is symmetric and simple to manufacture, but lithium metal deposits unevenly, causing peeling and reducing stability

Engineering Contradiction:

Improvecurrent collector fabricationVSAvoidlithium metal adhesion

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies asymmetry by designing the negative electrode current collector with protrusions of different heights on opposite surfaces. The first surface has protrusions with a first average height, while the second surface has protrusions with a second average height that differs from the first. This asymmetric configuration ensures uniform lithium metal deposition density across both surfaces, preventing peeling and enhancing reliability

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent employs local quality by varying the protrusion height at different locations (surfaces) of the current collector. Each surface has protrusions optimized for its specific position, with the first surface having one average height and the second surface having another, creating locally optimized conditions for lithium metal deposition and adhesion

Inventive Principle:

Principle #3Local quality

3Quantity of substance

If high-capacity lithium-ion batteries use graphite and alloy active materials, then the battery capacity increases, but the capacity increase is reaching its limit

Engineering Contradiction:

Improvebattery capacityVSAvoidfurther capacity improvement potential

Core Design Contradiction:

Quantity of substanceVSAdaptability or versatility

Solution Approach 1:

The patent applies parameter changes by transitioning from lithium-ion batteries (using graphite and alloy active materials) to lithium secondary batteries (using lithium metal). This fundamental parameter change in the negative electrode material enables significantly higher capacity while providing adaptability for further improvements through the protrusion structure that manages lithium metal deposition and expansion

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

This design effectively reduces negative electrode expansion, maintains high discharge capacity, and minimizes lithium metal peeling, resulting in improved charge/discharge efficiency and stability.

Implementation Method 1

Lithium metal is deposited on the first surface and the second surface by charging

Methodology Applied

Scientific EffectElectrochemical reduction: Electrodeposition

Data Source

PatentUS10916809B2Lithium secondary battery including lithium-ion conductive nonaqueous electrolyte

Publication Date: 2021.02.09 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

A lithium secondary battery includes a wound electrode group and a lithium-ion conductive nonaqueous electrolyte. The wound electrode group includes a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode. The negative electrode includes a negative electrode current collector. The negative electrode current collector includes: a layer having a first surface facing outward of the winding of the electrode group and a second surface facing inward of the winding of the electrode group; first protrusions protruding from the first surface; and second protrusions protruding from the second surface. Lithium metal is deposited on the first surface and the second surface by charging. A second average height of the second protrusions is higher than a first average height of the first protrusions.