Graphite Anode Composition for Dense, Crack-Resistant Li-Ion Batteries

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Solution Overview

Problem

Lithium secondary batteries face challenges in achieving high energy density and long-term stability due to volume expansion issues with silicon-carbon composite anode materials and limitations in obtaining high-density active material layers with conventional carbon-based materials.

Innovation Solution

An anode active material comprising a mixture of first and second graphite particles with specific diameter ratios and densities, where the second graphite particle has a higher hardness, is used to form a high-density anode layer that suppresses particle deformation and supports the electrode during pressing, enhancing energy density and lifespan.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If silicon-carbon composite anode materials are used to increase capacity, then energy density is improved, but volume expansion occurs during charging and discharging

Engineering Contradiction:

Improveenergy densityVSAvoidvolume expansion

Core Design Contradiction:

Quantity of substanceVSVolume of moving object

Solution Approach 1:

The patent changes the physical parameters of graphite particles by controlling particle size distribution (D10-D90 range of 3-15 μm) and hardness characteristics. This parameter optimization allows the anode material to achieve high energy density while maintaining structural stability and suppressing volume expansion during lithium ion insertion and extraction cycles.

Inventive Principle:

Principle #35Parameter changes

2Volume of stationary object

If high pressure pressing is applied to increase density of active material layer, then discharging capacity per volume is improved, but particle deformation and cracks occur

Engineering Contradiction:

Improvedensity of active material layerVSAvoidparticle deformation resistance

Core Design Contradiction:

Volume of stationary objectVSStrength

Solution Approach 1:

The patent applies local quality by creating a specific particle size distribution where finer particles (D10-D30: 3-6 μm) fill voids between larger particles, and coarser particles (D70-D90: 9-15 μm) provide structural framework. This local differentiation in particle roles allows the layer to achieve high density (≥2.1 g/cm³) while the harder coarser particles resist deformation and prevent crack formation during pressing.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent creates a composite structure within the graphite particle system by combining particles of different sizes and hardness levels. The composite nature of the particle mixture enables simultaneous achievement of high density and high mechanical strength, resolving the contradiction between compressibility and deformation resistance.

Inventive Principle:

Principle #40Composite materials

3Reliability

If conventional carbon-based materials are used for anode, then safety is improved compared to lithium metal, but high-density active material layer is difficult to obtain

Engineering Contradiction:

ImprovesafetyVSAvoiddensity of active material layer

Core Design Contradiction:

ReliabilityVSVolume of stationary object

Solution Approach 1:

The patent optimizes critical parameters of graphite particles including particle size distribution (D10-D90: 3-15 μm), hardness, and density. By precisely controlling these parameters, the invention achieves high active material layer density (≥2.1 g/cm³) while maintaining the inherent safety advantages of carbon-based materials over lithium metal.

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 solution effectively suppresses anode deformation, prevents cracks, and maintains high energy density while ensuring long-term properties and improved charge-discharge efficiency of lithium secondary batteries.

Implementation Method 1

a first graphite particle, and a second graphite particle having a different particle diameter from that of the first graphite particle

Methodology Applied

Scientific EffectParticle size distribution effect:

Implementation Method 2

A pellet density and a tap density of the anode active material satisfy a relation of Equation 1: 1.3≤DP/DT≤1.45

Methodology Applied

Scientific EffectDensity ratio effect:

Implementation Method 3

the second graphite particle may include artificial graphite having a hardness higher than that of the first graphite particle

Methodology Applied

Scientific EffectHardness difference effect:

Implementation Method 4

the anode active material layer including the anode active material as described above

Methodology Applied

Scientific EffectMechanical support effect:

Implementation Method 5

The anode active material formed of the carbon-based material has an electrochemical reaction potential with lithium ions similar to that of the lithium metal, and changes in a crystal structure during continuous insertion/desorption of the lithium ion may hardly occur

Methodology Applied

Scientific EffectIntercalation effect:

Data Source

PatentUS11837728B2Anode active material and lithium secondary battery including the same

Publication Date: 2023.12.05 SK ON CO LTD

AI summary

An anode active material according to an embodiment of the present invention includes a first graphite particle and a second graphite particle having a different particle diameter from that of the first graphite particle. A ratio of a pellet density relative to a. tap density of the anode active material is from 1.3 to 1.45. A particle deformation of the anode is suppressed to achieve a lithium secondary battery having improved long-term and high-energy properties.