Fluorine Polymer Coated Silicon Anode for Lithium Battery

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Solution Overview

Problem

Lithium secondary batteries using carbon-based negative electrode active materials face limitations in capacity characteristics and cycle lifetime due to volume changes during lithium intercalation/deintercalation, leading to pulverization and loss of reversible capacity.

Innovation Solution

A negative electrode active material comprising a non-carbon-based core, such as silicon or silicon nanotubes, coated with a fluorine-containing organic polymer layer, which reduces volume changes and enhances cycle lifetime and capacity retention by forming a stable solid electrolyte interface layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If inorganic material-based active material (silicon) is used to increase charge capacity, then theoretical capacity increases to 4200 mAh/g, but volume change during intercalation/deintercalation causes pulverization and loss of reversible capacity

Engineering Contradiction:

Improvecharge capacityVSAvoidcycle lifetime

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

A flexible polymer coating layer is applied on the surface of the inorganic material-based active material particles. This coating layer acts as a protective shell that accommodates volume changes during lithium intercalation and deintercalation, preventing pulverization and maintaining structural integrity over multiple charge-discharge cycles.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The invention creates a composite structure combining inorganic material-based active material (such as silicon) with a polymer coating material. This composite approach allows the inorganic core to provide high charge capacity while the polymer coating provides mechanical flexibility and stability, resolving the contradiction between capacity and cycle lifetime.

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If inorganic material-based active material is used to achieve high charge capacity, then capacity increases, but pulverization occurs leading to electrical extraction from current collector and capacity loss

Engineering Contradiction:

Improvecharge capacityVSAvoidstructural stability

Core Design Contradiction:

Quantity of substanceVSStrength

Solution Approach 1:

The polymer coating layer serves as a flexible shell that maintains structural stability during volume expansion and contraction. This shell prevents the inorganic particles from pulverizing and becoming electrically disconnected from the current collector, thereby maintaining both capacity and structural integrity.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The polymer coating is applied beforehand to cushion the mechanical stress that will occur during subsequent charge-discharge cycles. This pre-protective layer absorbs the shock of volume changes before pulverization can occur, preventing structural failure.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Reliability

If carbon-based negative electrode active material is used, then structural stability is maintained, but charge capacity is limited to 360 mAh/g

Engineering Contradiction:

Improvestructural stabilityVSAvoidcharge capacity

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The invention replaces pure carbon-based materials with inorganic material-based active materials (such as silicon, germanium, antimony, or titanium) that offer significantly higher theoretical capacity. The polymer coating compensates for the structural instability of these high-capacity materials, achieving both high capacity and stability.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention changes the material parameter from carbon-based to inorganic material-based active material, which fundamentally increases the charge capacity parameter from 360 mAh/g to up to 4200 mAh/g for silicon. The polymer coating enables this parameter change to occur without sacrificing structural stability.

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 fluorine-containing organic polymer coating improves charge and discharge efficiency, increases cycle lifetime, and maintains high capacity retention by minimizing side reactions and irreversible capacity loss.

Implementation Method 1

coated with a fluorine-containing organic polymer layer, which reduces volume changes and enhances cycle lifetime and capacity retention by forming a stable solid electrolyte interface layer

Methodology Applied

Scientific EffectSolid electrolyte interface formation:

Implementation Method 2

generate electrical energy by a redox reaction occurred when lithium ions are intercalated and deintercalated between the positive electrode and the negative electrode

Methodology Applied

Scientific EffectRedox reaction: Redox Reactions

Implementation Method 3

Methodology Applied

Scientific EffectChemical inertness:

Data Source

PatentUS9812705B2Negative electrode active material for lithium secondary battery and lithium secondary battery comprising the same

Publication Date: 2017.11.07 LG ENERGY SOLUTION LTD

AI summary

Provided is a negative electrode active material comprising (a) a core including one or more non-carbon-based materials selected from the group consisting of silicon, nickel, germanium, and titanium, and (b) an organic polymer coating layer formed of a polymer compound having a content of a fluorine component of 50 wt % or more on a surface of the core.