Graphite Anode Composite Structure for Electrolyte Permeation
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Solution Overview
Problem
The densification process for negative electrodes in lithium ion secondary batteries often results in reduced permeation of the electrolytic solution due to particle crushing, which deteriorates the battery's performance.
Innovation Solution
A negative electrode material comprising composite particles, each consisting of a spherical graphite particle and flat graphite particles with non-parallel orientation planes, which satisfy specific pore volume and pore distribution conditions to maintain excellent liquid permeation properties even after densification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If artificial graphite particles having a secondary particle structure are used to increase negative electrode density, then energy density is improved, but particle crushing occurs during densification which deteriorates electrolytic solution permeation
Solution Approach 1:
The patent uses composite particles comprising both spherical graphite particles and flake graphite particles. The spherical particles provide high density and good packing characteristics, while the flake particles create interconnected pore structures. This composite structure allows the negative electrode to achieve high energy density while maintaining sufficient electrolytic solution permeation pathways, resolving the contradiction between density improvement and permeation deterioration.
2Quantity of substance
If high pressure pressing is applied to densify the negative electrode, then energy density is improved, but particle crushing occurs which deteriorates electrolytic solution permeation
Solution Approach 1:
The patent changes the physical and chemical parameters of the graphite particles by creating composite structures with specific pore volume distributions (0.03-0.20 mL/g total pore volume, with specific distributions of micropores, mesopores, and macropores). This parameter optimization allows the particles to withstand high pressure pressing without crushing, maintaining both high energy density and electrolytic solution permeation.
3Quantity of substance
If particle size is reduced to increase density, then energy density is improved, but pore structure is compromised which deteriorates electrolytic solution permeation
Solution Approach 1:
The patent applies local quality by creating different pore size distributions within the composite particle structure. The composite particles contain micropores (0.003-0.02 μm), mesopores (0.02-2 μm), and macropores (2-50 μm) in specific proportions. This hierarchical pore structure provides both high density from fine particles and adequate permeation pathways from larger pores, resolving the contradiction between density improvement and pore structure preservation.
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 proposed solution enables lithium ion secondary batteries to maintain excellent liquid permeation properties after densification, enhancing their performance and efficiency.
Implementation Method 1
the pore volume in a range of a pore diameter of from 0.10 to 8.00 μm obtained by a mercury intrusion method is from 0.20 to 1.00 mL/g
Implementation Method 2
maintain excellent liquid permeation properties even after densification
Data Source
AI summary
A negative electrode material for a lithium ion secondary battery, including composite particles, each of the composite particles including: a spherical graphite particle; and flat graphite particles that are gathered or bound together such that the flat graphite particles have non-parallel orientation planes, wherein the composite particles satisfy the following (1) and (2): (1) a pore volume in a range of a pore diameter of from 0.10 to 8.00 μm obtained by the mercury intrusion method is from 0.20 to 1.00 mL/g; and (2) in a log differential pore volume distribution obtained by the mercury intrusion method, at least two peaks appear in a range of a pore diameter of from 0.10 to 8.00 the two peaks including a first peak P1 and a second peak P2 at a higher diameter than the first peak P1.