Anode Composite Layer Particle Size Distribution

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Solution Overview

Problem

Lithium-ion secondary batteries face challenges in increasing energy density without deteriorating battery characteristics, particularly due to the low lithium storage capacity and high reactivity of artificial graphite anodes, which can lead to safety issues and reduced capacity.

Innovation Solution

A non-aqueous electrolyte battery design that uses a mixture of carbonaceous materials with controlled particle size distributions, where the average particle sizes of graphite range from 20 μm to 40 μm for large particles and 5 μm to 16 μm for small particles, ensuring a narrow particle size distribution and optimal surface area to volume ratio, reducing reactivity and enhancing lithium storage capacity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If artificial graphite is used as anode active material to improve battery characteristics and ease of manufacture, then battery safety and manufacturing ease are improved, but lithium storage capacity per unit mass or unit volume decreases

Engineering Contradiction:

Improvebattery safetyVSAvoidlithium storage capacity

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent uses a composite anode structure combining artificial graphite particles with fine powder material. The artificial graphite provides safety and structural stability, while the fine powder material fills voids and increases lithium storage capacity. This composite approach resolves the contradiction by integrating materials with complementary properties.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent utilizes the void spaces naturally present in artificial graphite particle arrangements and fills them with fine powder material. This porous structure utilization increases the effective lithium storage capacity without compromising the safety benefits of the artificial graphite framework.

Inventive Principle:

Principle #31Porous materials

2Quantity of substance

If fine powder is added to increase volume density of anode, then energy density is improved, but reactivity with electrolyte solution increases and battery safety deteriorates

Engineering Contradiction:

Improvevolume densityVSAvoidreactivity with electrolyte

Core Design Contradiction:

Quantity of substanceVSObject-affected harmful factors

Solution Approach 1:

The patent extracts only the necessary amount of fine powder material required to fill the void spaces in the artificial graphite structure, avoiding excessive fine powder addition. This controlled extraction approach increases volume density while limiting the increase in reactivity with electrolyte that would occur with excessive fine powder.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The fine powder material is selectively placed in the void spaces between artificial graphite particles rather than being uniformly distributed throughout the anode. This localized placement increases volume density in specific regions without uniformly increasing reactivity across the entire anode structure.

Inventive Principle:

Principle #3Local quality

3Quantity of substance

If particle size distribution range is widened to increase fine powder content, then volume density of anode is improved, but surface area to volume ratio increases and reactivity with electrolyte increases

Engineering Contradiction:

Improvevolume densityVSAvoidsurface area

Core Design Contradiction:

Quantity of substanceVSArea of moving object

Solution Approach 1:

The patent carefully controls the particle size distribution parameters, specifically limiting the fine powder content to 5-30 mass% and optimizing the D50 and D90 values. This parameter optimization achieves sufficient volume density improvement while constraining the surface area increase and associated reactivity with electrolyte.

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

This design effectively increases energy density while maintaining battery safety and performance by efficiently retaining electrolyte and reducing ionic resistance, leading to improved charging and discharging efficiency and cyclic characteristics.

Implementation Method 1

the clearances in the anode composite mixture layer are efficiently filled with the spherical graphite of the small particle size while spaces capable of retaining a suitable amount of non-aqueous electrolyte solution are left

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Data Source

PatentUS7749659B2Nonaqueous electrolyte battery

Publication Date: 2010.07.06 MURATA MFG CO LTD

AI summary

The present invention uses a mixture of spherical carbonaceous materials having different average particle sizes as an anode active material in an anode composite mixture layer of an anode. The spherical carbonaceous material of large particle size decreases the reaction with non-aqueous electrolyte solution to suppress the decrease in battery capacity, form clearances having suitable sizes in the anode composite mixture layer, and retain the non-aqueous electrolyte solution. The clearances in the anode composite mixture layer are efficiently filled with the carbonaceous material of small particle size while spaces capable of suitably retaining the non-aqueous electrolyte solution are left unfilled. Thus, the volume density of the anode composite mixture layer is improved and the battery capacity is increased. Accordingly, energy density can be increased without deteriorating battery characteristics.