Alkali Carbonate Layer on Graphite for Lithium Battery SEI

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Solution Overview

Problem

Graphite-based negative electrode active materials in lithium secondary batteries react adversely with propylene carbonate, leading to degradation and limited low-temperature performance, necessitating the development of a technique to mitigate this side reaction.

Innovation Solution

A negative electrode active material is developed by forming an alkali carbonate layer on the surface of graphite, which reduces the side reaction with propylene carbonate, improving low-temperature performance and initial efficiency through the creation of a stable solid electrolyte interface.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If propylene carbonate is added to the electrolyte solution to improve low-temperature performance, then low-temperature performance is improved, but the graphite-based active material is destroyed by exfoliation of graphite layers

Engineering Contradiction:

Improvelow-temperature performanceVSAvoidgraphite layer stability

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

A coating layer comprising a polymer and a metal oxide is introduced as an intermediary between the graphite-based active material and the propylene carbonate in the electrolyte solution. This coating layer prevents direct contact and adverse reactions between propylene carbonate and graphite, while still allowing lithium ion intercalation and deintercalation to proceed efficiently, thus maintaining both low-temperature performance and graphite layer stability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The surface properties of the graphite-based active material are modified by forming a coating layer with specific chemical and physical parameters. The coating layer has controlled porosity, conductivity, and chemical composition that allow it to be permeable to lithium ions while blocking harmful interactions with propylene carbonate, effectively changing the interface parameters to resolve the contradiction

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If a high-temperature activation process is performed to enable the use of propylene carbonate, then propylene carbonate can be used in the electrolyte, but the preparation time and cost are increased

Engineering Contradiction:

Improveelectrolyte composition flexibilityVSAvoidpreparation time

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The coating layer is formed on the graphite-based active material during the electrode manufacturing process, before the battery assembly and activation stages. This preliminary formation of the protective coating eliminates the need for subsequent high-temperature activation treatments, allowing propylene carbonate to be used in the electrolyte from the first charge without additional processing time or cost

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The coating formation process uses controlled deposition parameters (such as solution concentration, deposition time, and drying conditions) to create a functional coating layer at moderate temperatures. This approach achieves the same effect as high-temperature activation but under milder conditions, reducing energy consumption and processing time while enabling electrolyte flexibility

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 alkali carbonate layer on the graphite surface enhances the stability of the solid electrolyte interface, allowing the use of propylene carbonate without degradation, thereby improving the lithium secondary battery's low-temperature performance and initial efficiency.

Implementation Method 1

the alkali carbonate layer contributes to the formation of a stable solid electrolyte interface (SEI) to reduce a side reaction with an electrolyte solution including propylene carbonate

Methodology Applied

Scientific EffectSolid electrolyte interface formation:

Implementation Method 2

the graphite has an ID/IG ratio of 0.05 to 0.3 in Raman spectroscopy

Methodology Applied

Scientific EffectRaman spectroscopy:

Data Source

PatentUS10604410B2Negative electrode active material for lithium secondary battery and method of preparing the same

Publication Date: 2020.03.31 LG ENERGY SOLUTION LTD

AI summary

The present invention relates to a negative electrode active material for a lithium secondary battery, which comprises graphite having an alkali carbonate layer formed on a surface thereof, wherein the graphite has an ID/IG ratio of 0.05 to 0.3 in Raman spectroscopy, and a method of preparing the same, wherein, since the negative electrode active material for a lithium secondary battery of the present invention includes the graphite having an alkali carbonate layer formed on the surface thereof, the alkali carbonate layer contributes to the formation of a stable solid electrolyte interface (SEI) to reduce a side reaction with an electrolyte solution including propylene carbonate. Thus, since low-temperature performance and initial efficiency of the lithium secondary battery may be improved, the negative electrode active material for a lithium secondary battery of the present invention is suitable for the preparation of the lithium secondary battery.