Silicon-Based Anode Active Material with Phosphate Coating

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Solution Overview

Problem

Lithium secondary batteries face challenges with low initial coulombic efficiency and stability issues due to residual lithium compounds causing pH increases and side reactions during manufacturing, leading to reduced adhesion and stability of the anode slurry.

Innovation Solution

An anode active material comprising a composite of silicon-based lithium silicate and lithium-containing phosphate, with a core-shell structure and controlled phosphorus content, is developed to improve initial coulombic efficiency and stability by suppressing residual lithium elution and hydrogen gas generation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If silicon-based anode material is used to increase capacity, then battery capacity increases, but initial coulombic efficiency decreases due to residual lithium compound elution

Engineering Contradiction:

Improvebattery capacityVSAvoidinitial coulombic efficiency

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

A phosphate coating layer is applied as an intermediary between the silicon-based anode material and the electrolyte. This coating layer mediates the interaction by preventing direct contact between residual lithium compounds and the electrolyte, thereby eliminating the source of harmful pH increases while maintaining the high capacity benefits of silicon-based materials.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The surface chemistry parameters of the silicon-based anode material are changed by introducing a phosphate coating. This coating modifies the surface properties to prevent elution of residual lithium compounds, thereby changing the electrochemical behavior and improving initial coulombic efficiency without sacrificing capacity.

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If residual lithium compound is present in anode slurry, then pH increases causing stability issues, but removing it completely may reduce battery capacity

Engineering Contradiction:

Improveanode slurry stabilityVSAvoidbattery capacity

Core Design Contradiction:

Stability of the object's compositionVSQuantity of substance

Solution Approach 1:

The phosphate coating serves as a protective intermediary that stabilizes the anode slurry composition by preventing pH increases from residual lithium compound elution. Simultaneously, it allows controlled lithium release for capacity while maintaining slurry stability during manufacturing and operation.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The anode material exhibits different properties in different regions: the core silicon-based material provides high capacity, while the surface phosphate coating provides stability by controlling lithium elution. This local differentiation allows simultaneous achievement of high capacity and slurry stability.

Inventive Principle:

Principle #3Local quality

3Reliability

If phosphate coating is applied to suppress residual lithium elution, then initial coulombic efficiency improves, but electrical conductivity may decrease

Engineering Contradiction:

Improveinitial coulombic efficiencyVSAvoidelectrical conductivity

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The parameters of the phosphate coating are optimized to balance protection and conductivity. By controlling coating thickness, composition, and structure, the coating provides sufficient protection against lithium elution while maintaining adequate electrical conductivity for battery performance.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The phosphate coating is designed with a porous or nanostructured morphology that provides protective functions while maintaining electrical conductivity. The porous structure allows lithium ion transport and electron conduction pathways to persist, preventing excessive conductivity loss while still suppressing harmful elution.

Inventive Principle:

Principle #31Porous materials

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 composite anode active material enhances the initial coulombic efficiency and stability of lithium secondary batteries by effectively managing residual lithium and maintaining electrical conductivity, thereby improving battery lifespan and performance.

Implementation Method 1

adding the silicon-based material doped with lithium to a phosphate during a compounding process... suppressing residual lithium elution and hydrogen gas generation

Methodology Applied

Scientific EffectChemical reaction suppression:

Implementation Method 2

treating the silicon-based material with heat to incorporate lithium into the silicon-based material during a doping process thereby generating a lithium silicate

Methodology Applied

Scientific EffectSolid-state diffusion: Diffusion

Data Source

PatentUS20230178718A1Anode Active Material for Secondary Battery and Method of Preparing the Same

Publication Date: 2023.06.08 SK ON CO LTD

AI summary

An anode active material for a lithium secondary battery is provided which includes a composite including: a silicon-based material including a lithium silicate; and a lithium-containing phosphate, wherein a peak intensity ratio B/A is 0.01 to 0.5, wherein A is a peak intensity at 2θ=28.5°, and B is a peak intensity at 2θ=22.3°, when an X-ray diffraction (XRD) analysis is performed using a Cu—Kα ray.