Nonaqueous Battery Anode Particle Alignment for Resistance Stability
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries face an increase in resistance due to repetitive charge and discharge, which hinders the enhancement of battery capacity for vehicle applications.
Innovation Solution
The battery design incorporates a negative electrode active material layer with a mix of first particles having an aspect ratio of 1.5 or less and second particles with a higher aspect ratio, aligned at an angle of 30° or more, along with a nonaqueous electrolyte containing 1-30% carboxylate ester with 4 or less carbon atoms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the density and dimensions of the negative electrode active material layer are increased to enhance battery capacity, then the capacity is improved, but the resistance increases accelerated by repetitive charge and discharge
Solution Approach 1:
The patent applies local quality by creating distinct regions within the negative electrode active material layer. High aspect ratio particles are aligned in specific orientations (with at least 30% having their major axes perpendicular to the current collector surface), while low aspect ratio particles fill the interstices. This spatial differentiation allows the aligned high aspect ratio particles to provide stable electrical contact and low resistance, while the mixed composition maintains high capacity.
Solution Approach 2:
The patent uses composite materials by combining two types of negative electrode active material particles with different aspect ratios. The high aspect ratio particles (such as flake graphite or oriented carbon fibers) provide structural stability and efficient electron transport pathways, while the low aspect ratio particles (such as spherical graphite) fill voids and maintain density. This composite structure achieves both high capacity and resistance stability.
2Quantity of substance
If high aspect ratio negative electrode active material particles are used to enhance capacity, then the capacity is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent applies parameter changes by controlling the aspect ratio distribution and orientation of particles during manufacturing. By specifying that at least 30% of high aspect ratio particles have their major axes perpendicular to the current collector surface (within 60 degrees of normal), the patent transforms the manufacturing challenge into a controllable parameter specification. This can be achieved through conventional slurry preparation and drying processes, avoiding complex alignment equipment.
3Quantity of substance
If the negative electrode active material layer density is increased to enhance capacity, then the capacity is improved, but the resistance increases during repetitive charge and discharge
Solution Approach 1:
The patent applies segmentation by dividing the negative electrode active material into two distinct particle size and shape categories. High aspect ratio particles (flake graphite, oriented carbon fibers) create a percolating network for electron transport, while low aspect ratio particles fill the spaces between them. This segmentation creates a dual-function structure where one particle type primarily provides conductive pathways and the other maximizes capacity density.
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 configuration effectively suppresses the increase in resistance during repetitive charging and discharging, maintaining high input/output performance and power generation efficiency suitable for vehicle driving power supplies.
Implementation Method 1
the nonaqueous solvent contains 1 to 30% by volume of a carboxylate ester having 4 or less carbon atoms
Data Source
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AI summary
Provided is a nonaqueous electrolyte secondary battery capable of suppressing an increase in resistance caused by repetitive charge and discharge. A nonaqueous electrolyte secondary battery disclosed here includes a positive electrode, a negative electrode, and a nonaqueous electrolyte. The negative electrode includes a negative electrode active material layer containing a negative electrode active material. The negative electrode active material includes first negative electrode active material particles each having an aspect ratio of 1.5 or less and second negative electrode active material particles each having an aspect ratio exceeding 1.5. A mass ratio between the first negative electrode active material particles and the second negative electrode active material particles is 50 : 50 to 95 : 5. In addition, 50% or more of the second negative electrode active material particles are aligned such that an angle between a plane direction of the negative electrode active material layer and a major axis of the second negative electrode active material particle is 30° or more. The nonaqueous electrolyte contains a nonaqueous solvent and an electrolyte salt. The nonaqueous solvent contains 1 to 30% by volume of a carboxylate ester having 4 or less carbon atoms.