Prelithiated Li-Si Negative Electrode for SEI Loss and Volume Change

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Solution Overview

Problem

Secondary lithium batteries face issues with active lithium consumption due to solid electrolyte interphase (SEI) formation and volume changes in silicon-based negative electrodes, leading to irreversible capacity loss and reduced cycle life.

Innovation Solution

A method involving a precursor mixture of lithium-silicon alloy particles, electrically conductive carbon particles, and a polymer binder in a nonpolar organic solvent is used to create a negative electrode layer with a core-shell structure, which is then pyrolyzed to form an electrically conductive carbon matrix, reducing porosity and enhancing electrochemical performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If silicon-based negative electrode material is used to increase specific capacity, then energy density is improved, but active lithium is consumed during SEI formation and volume changes occur during cycling

Engineering Contradiction:

Improveenergy densityVSAvoidactive lithium consumption

Core Design Contradiction:

Use of energy by moving objectVSLoss of substance

Solution Approach 1:

Lithium particles are incorporated into the negative electrode during manufacturing to provide preliminary lithium compensation. This preliminary action ensures that excess lithium is available before the battery enters cycling, compensating for the lithium that will be consumed during SEI formation and subsequent volume changes of the silicon-based material.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The stoichiometry of lithium in the negative electrode is deliberately changed from stoichiometric balance to lithium-excess composition. By incorporating additional lithium particles, the negative electrode contains more lithium than theoretically required, creating a lithium reservoir that compensates for ongoing lithium consumption during cycling.

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If silicon-based negative electrode material is used to increase specific capacity, then energy density is improved, but volume changes occur during charging and discharging

Engineering Contradiction:

Improveenergy densityVSAvoidvolume stability

Core Design Contradiction:

Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

A polymer binder matrix is used to create a flexible, compliant structure that can accommodate the volume expansion and contraction of silicon-based particles during lithium insertion and extraction. The polymer matrix acts as a cushioning medium that maintains structural integrity despite the dynamic volume changes of the active material.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The negative electrode is designed as a composite material system combining silicon-based particles, lithium particles, polymer binder, and conductive carbon. This composite structure integrates materials with complementary properties: silicon provides high capacity, lithium provides compensation for volume changes and lithium loss, polymer provides structural flexibility, and carbon provides electrical conductivity.

Inventive Principle:

Principle #40Composite materials

3Reliability

If native SEI forms on negative electrode surface to provide protection, then electrode stability is improved, but active lithium is consumed in the process

Engineering Contradiction:

Improveelectrode stabilityVSAvoidactive lithium consumption

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

Excess lithium is incorporated into the electrode structure in advance to counteract the lithium-consuming SEI formation process. This preliminary anti-action ensures that even though lithium is consumed during SEI formation, the electrode maintains a stoichiometric surplus of lithium, preventing capacity loss and maintaining long-term stability.

Inventive Principle:

Principle #9Preliminary anti-action

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 helps maintain a stoichiometric surplus of lithium, reduces active lithium consumption, and improves capacity retention by creating a robust conductive network, thereby enhancing the stability and performance of the negative electrode.

Implementation Method 1

At least a portion of the polymer binder may be pyrolyzed to form an electrically conductive carbon matrix throughout the negative electrode material layer

Methodology Applied

Scientific EffectPyrolysis: Pyrolysis

Implementation Method 2

At least a portion of the nonpolar organic solvent may be removed from the precursor layer to form a negative electrode layer on the surface of the substrate

Methodology Applied

Scientific EffectEvaporation: Evaporation

Data Source

PatentUS11824186B2Prelithiated negative electrodes including Li—Si alloy particles and methods of manufacturing the same

Publication Date: 2023.11.21 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

In a method of making a negative electrode for an electrochemical cell of a secondary lithium battery, a precursor mixture is prepared that includes electrochemically active Li—Si alloy particles, electrically conductive carbon particles, and an inert polymer binder dissolved in a nonpolar organic solvent.