Pre-Lithiated Negative Electrode Coating for Initial Capacity Loss

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Solution Overview

Problem

Lithium secondary batteries face significant initial irreversible capacity loss due to the formation of a solid electrolyte interface (SEI) on the negative electrode active material, leading to reduced lithium ion diffusion and increased oxidation susceptibility, which hampers the battery's initial reversibility and overall electrochemical performance.

Innovation Solution

A negative electrode design featuring a first active material layer, a polymer coating layer, and a second lithiated active material layer, where the polymer coating protects lithium ions from moisture and oxidation, allowing for effective pre-lithiation and improved lithium diffusion into the first active material layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If pre-lithiation is performed to reduce initial irreversible capacity loss, then battery capacity and initial reversibility are improved, but lithium ions are lost due to moisture and oxidation

Engineering Contradiction:

Improveinitial reversibilityVSAvoidlithium ion loss

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The patent uses a composite structure consisting of a polymer coating layer and a lithiated negative electrode active material layer. The polymer coating layer (made from materials like polyacrylic acid, polyvinyl alcohol, or polymethyl methacrylate) combines with the lithiated active material to create a protective composite that prevents lithium ion loss while maintaining pre-lithiation benefits. This composite structure resolves the contradiction by providing both protection against moisture/oxidation and effective pre-lithiation functionality.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies a thin polymer coating layer over the lithiated negative electrode active material. This flexible protective film acts as a barrier against moisture and oxygen while allowing lithium ion diffusion. The coating layer provides the necessary protection without significantly increasing electrode thickness, thus preventing lithium ion loss while maintaining the pre-lithiation effect that improves initial reversibility.

Inventive Principle:

Principle #30Flexible shells and thin films

2Loss of substance

If a polymer coating layer is added to protect lithium ions, then lithium ion loss is prevented, but device complexity increases

Engineering Contradiction:

Improvelithium ion lossVSAvoidelectrode structure complexity

Core Design Contradiction:

Loss of substanceVSDevice complexity

Solution Approach 1:

The polymer coating layer is applied in advance during electrode manufacturing, before the electrode is assembled into the battery. This preliminary coating action ensures lithium ion protection is built-in from the start, preventing loss during storage and initial battery operation. By performing the protection action during manufacturing rather than requiring additional components or steps later, the patent minimizes the effective complexity added to the device.

Inventive Principle:

Principle #10Preliminary action

3Quantity of substance

If lithium metal is used as negative electrode active material, then theoretical capacity is high, but lithium atoms grow on surface causing damage to separator and battery

Engineering Contradiction:

Improvetheoretical capacityVSAvoidlithium dendrite formation

Core Design Contradiction:

Quantity of substanceVSObject-affected harmful factors

Solution Approach 1:

The patent applies pre-lithiation specifically to the negative electrode active material layer, creating a localized lithium reservoir at the electrode surface. This local quality change allows the electrode to compensate for initial lithium loss without requiring bulk lithium metal that would form dendrites. The lithiated active material provides high capacity locally where needed while maintaining the safety advantages of oxide-based materials.

Inventive Principle:

Principle #3Local quality

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 proposed design enhances the initial reversibility and electrochemical performance of lithium secondary batteries by preventing lithium ion loss and oxidation, thereby reducing irreversible capacity loss and improving cycle characteristics.

Implementation Method 1

the polymer coating protects lithium ions from moisture and oxidation

Methodology Applied

Scientific EffectPhysical barrier protection: Physical Containment

Implementation Method 2

allowing for effective pre-lithiation and improved lithium diffusion into the first active material layer

Methodology Applied

Scientific EffectIonic diffusion: Diffusion

Data Source

PatentEP3754757B1Negative electrode for lithium secondary battery, method of producing the same and lithium secondary battery including the same

Publication Date: 2023.12.13 LG ENERGY SOLUTION LTD

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AI summary

The present invention relates to a negative electrode for a lithium secondary battery, a method of producing the negative electrode, a method of producing a pre-lithiated negative electrode by pre-lithiation of the negative electrode, and a lithium secondary battery including the negative electrode. Specifically, the negative electrode according to the present invention can increase the capacity of a battery and improve the electrochemical performance by securing the initial reversibility of a negative electrode by pre-lithiation, and allow lithium ions to be diffused into a negative electrode active material layer during pre-lithiation without being lost.