Lithium Ion Battery Negative Electrode Particle Orientation
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Solution Overview
Problem
Lithium ion secondary batteries experience increased internal resistance due to electrolyte being pushed out during high-rate charge and discharge, leading to inefficient battery reactions and potential lithium metal deposition at low temperatures.
Innovation Solution
The battery design includes a negative active material layer with flat-shaped graphite particles oriented by a magnetic field, where the non-facing portion has an orientation degree of 1.2 or higher and the facing portion has an orientation degree of 0.8 or less, preventing electrolyte expulsion and enhancing lithium ion insertion at high currents and low temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high-rate charge and discharge are performed, then power output is improved, but electrolyte is pushed out of the electrode body causing internal resistance to increase
Solution Approach 1:
The patent applies different orientation degrees of graphite particles to different regions of the negative active material layer. The non-facing portion (edge regions) has a higher orientation degree (1.2 or higher) to prevent electrolyte expulsion, while the facing portion (central region) has a lower orientation degree (0.8 or less) to facilitate lithium ion insertion. This local differentiation resolves the contradiction by optimizing each region for its specific function.
2Power
If electrolyte is pushed out during high-rate discharge, then power delivery is improved, but battery reaction efficiency decreases due to reduced retained electrolyte
Solution Approach 1:
The patent creates a spatial differentiation in particle orientation within the negative active material layer. By orienting particles vertically at edges (non-facing portion) and horizontally in the center (facing portion), it simultaneously maintains electrolyte retention for efficient battery reactions and enables high power delivery through controlled electrolyte movement.
3Stability of the object's composition
If stored electrolyte interacts with pushed-out retained electrolyte, then electrolyte distribution is improved, but concentration changes cause internal resistance to increase
Solution Approach 1:
The patent preemptively prevents harmful electrolyte concentration changes by orienting graphite particles vertically in the non-facing portion. This orientation creates a barrier that prevents retained electrolyte from being pushed out and mixing with stored electrolyte, thereby maintaining stable concentration and preventing internal resistance increase before the problem can occur.
4Reliability
If flat-shaped graphite particles are oriented vertically, then electrolyte retention is improved, but lithium ion insertion efficiency may decrease
Solution Approach 1:
The patent resolves this contradiction by applying different orientation requirements to different spatial regions. The non-facing portion uses vertical orientation (high orientation degree) for electrolyte retention, while the facing portion uses horizontal orientation (low orientation degree) for efficient lithium ion insertion, achieving both objectives simultaneously through spatial differentiation.
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 maintains electrolyte within the battery, reducing internal resistance changes during high-rate discharge and preventing lithium metal deposition, thus ensuring stable battery performance.
Implementation Method 1
the negative active material particles are flat-shaped particles containing graphite and being able to be oriented by a magnetic field
Data Source
AI summary
In a lithium ion secondary battery, a negative electrode sheet is made of a metal foil and an active material layer containing active material particles. The negative active material layer includes a facing portion that faces a positive active material layer and a non-facing portion that does not face the same. The negative active material particles can be oriented in a magnetic field direction. When an angle between an extending direction of a major axis of the cross section of each particle and the metal foil is θ, the number of particles with the angle θ of 60°-90° is MA, the number of negative active material particles with the angle θ of 0°-30° is MB, and a value MA/MB is assumed to be an orientation degree (AL) of particles, the negative active material layer is made such that an orientation degree (AL1) in the non-facing portion is 1.2 or more.