Carbon Nanotube Sheet Layer for Dendrite-Resistant Solid-State Batteries

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Solution Overview

Problem

All-solid-state batteries using solid electrolytes have lower energy density compared to lithium-ion batteries with liquid electrolytes, and face challenges such as interfacial bonding issues and lithium dendrite growth, which hinder their commercialization and performance.

Innovation Solution

An all-solid-state battery design featuring a self-standing sheet layer on the negative electrode current collector made of carbon nanotubes with a network structure, including a first layer of unzipped carbon nanotubes for lithium deposition and a second layer of raw carbon nanotubes for structural support, which inhibits lithium dendrite formation and enhances energy density.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If solid electrolyte is used in all-solid-state battery, then battery safety and stability are improved, but energy density decreases compared to liquid electrolyte batteries

Engineering Contradiction:

Improvebattery safetyVSAvoidenergy density

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent employs a porous carbon nanotube sheet layer with controlled porosity (30-80%) as a buffer structure between the solid electrolyte and negative electrode. This porous architecture provides void space that accommodates volume changes during lithium deposition, preventing direct contact and potential short-circuits between the solid electrolyte and lithium metal, thereby maintaining safety while enabling high energy density through efficient lithium utilization.

Inventive Principle:

Principle #31Porous materials

Solution Approach 2:

The patent creates a composite structure combining carbon nanotubes with the solid electrolyte interface. The carbon nanotube sheet layer serves as an intermediate composite material that combines the electrical conductivity and mechanical flexibility of carbon materials with the ionic conductivity requirements at the solid electrolyte interface, resolving the contradiction between safety and energy density.

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If lithium metal is used as negative electrode to increase energy density, then energy density is improved, but lithium dendrite growth and interfacial bonding issues occur

Engineering Contradiction:

Improveenergy densityVSAvoidinterfacial bonding stability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent introduces a carbon nanotube sheet layer as an intermediary between the solid electrolyte and lithium metal negative electrode. This intermediate layer improves interfacial bonding stability by providing a flexible buffer that accommodates volume expansion during lithium deposition, prevents direct harmful interactions, and ensures reliable electrical contact, thereby enabling safe use of lithium metal for high energy density.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The porous structure of the carbon nanotube sheet provides three-dimensional space for lithium deposition and volume expansion buffering. This porous architecture prevents dendrite formation by distributing lithium deposition uniformly across the porous network, while maintaining stable interfacial bonding between the solid electrolyte and negative electrode.

Inventive Principle:

Principle #31Porous materials

3Reliability

If solid electrolyte with higher specific gravity is used, then ionic conductivity is improved, but energy density decreases due to increased weight

Engineering Contradiction:

Improveionic conductivityVSAvoidbattery weight

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The patent employs a thin film carbon nanotube sheet layer that provides essential functions (interface stabilization, dendrite prevention, volume buffering) without adding significant weight. This thin film approach maintains ionic conductivity through the solid electrolyte while minimizing the weight penalty, thereby improving energy density.

Inventive Principle:

Principle #30Flexible shells and thin films

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 battery achieves improved Coulombic efficiency, energy density, and prevents lithium dendrite formation, leading to enhanced performance and durability.

Implementation Method 1

The first layer may have a greater lithiophilicity than the second layer

Methodology Applied

Scientific EffectLithiophilicity:

Implementation Method 2

The sheet layer may have a porosity in a range of about 30% to 80%

Methodology Applied

Scientific EffectPorosity: Porosity

Implementation Method 3

the negative electrode active material layer includes a solid electrolyte allowing migration of lithium ions as well as negative active materials such as graphite therethrough

Methodology Applied

Scientific EffectIon migration:

Data Source

PatentUS20240079597A1All-solid-state battery including self-standing sheet layer

Publication Date: 2024.03.07 HYUNDAI MOTOR CO LTD

AI summary

Proposed is an all-solid-state battery including a self-standing sheet layer positioned on a negative electrode current collector. The all-solid-state battery may include the negative electrode current collector, the self-standing sheet layer positioned on the negative electrode current collector, a solid electrolyte layer positioned on the sheet layer, a positive electrode active material layer positioned on the solid electrolyte layer, and a positive electrode current collector positioned on the positive electrode active material layer. The sheet layer contains carbon nanotubes.