Carbon Negative Electrode SEI Layering for Low-Resistance Li-Ion Cells

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Electrochemical devices using lithium ions face challenges in forming a high-quality solid electrolyte interface (SEI) coating film due to the reactivity of LiPF6 with water, leading to high internal resistance, while LiFSI-based electrolytes result in stable but high-resistance SEI films containing lithium fluoride.

Innovation Solution

The electrochemical device incorporates a negative electrode material layer with a coating region containing a layered structure of lithium carbonate and fluoride, where lithium carbonate is predominantly found deeper within the coating region to reduce internal resistance and lithium fluoride on the surface for stability, using X-ray photoelectron spectroscopy to optimize the distribution and thickness of these components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If LiPF6 is used as the electrolyte, then high reactivity with water is achieved, but HF is generated which disintegrates the SEI coating film leading to high internal resistance

Engineering Contradiction:

Improveease of forming SEI coating filmVSAvoidstability of SEI coating film

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent changes the chemical composition parameters of the electrolyte by replacing LiPF6 with LiFSI, which has lower reactivity with water and does not generate HF, thereby preventing SEI coating film disintegration while maintaining manufacturability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses a simple carbon material for the negative electrode that can be easily manufactured, accepting that a basic SEI coating film forms initially, then improves it through controlled pre-doping to achieve stable, low-resistance performance

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 approach effectively suppresses the increase in internal resistance by maintaining low lithium ion migration resistance and stability of the SEI film, ensuring efficient charging and discharging processes.

Implementation Method 1

a negative electrode active material capable of being reversibly doped with lithium ions

Methodology Applied

Scientific EffectIon doping: Absorption (physical)

Implementation Method 2

When the coating region is measured by X-ray photoelectron spectroscopy, a peak is observed in a range from 530 eV to 534 eV of a binding energy in an O1s spectrum

Methodology Applied

Scientific EffectX-ray photoelectron spectroscopy: Photoelectric Effect

Data Source

PatentUS20240213551A1Electrochemical device

Publication Date: 2024.06.27 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

An electrochemical device includes a positive electrode, a negative electrode, and an electrolyte having lithium ion conductivity. The negative electrode includes a negative current collector and a negative electrode material layer supported on the negative current collector. The negative electrode material layer contains a negative electrode active material capable of being reversibly doped with lithium ions. The negative electrode active material contains a carbon material. The negative electrode material layer includes a coating region on a surface layer portion of the negative electrode material layer. An O1s spectrum for the coating region has a peak in a range from 530 eV to 534 eV of a binding energy in an O1s spectrum. An intensity of the peak in the O1s spectrum increases as a measuring position changes from a surface layer of the coating region toward the inside of the coating region.