Negative Electrode Density Optimization for Li-Ion Batteries
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Solution Overview
Problem
Conventional methods for manufacturing negative electrodes in lithium secondary batteries often result in suboptimal electrode density, leading to increased resistance and reduced lifespan due to peeling or cracking of active materials, which affects the battery's performance and efficiency.
Innovation Solution
A method involving the fabrication of multiple negative electrode samples with varying densities, measurement of expansion curves during the first charging cycle, and selection of an optimum electrode density based on slope differences to ensure optimal performance and longevity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the negative active material is pressed to maximum extent to achieve high electrode density, then the battery capacity increases, but the active material undergoes peeling and cracks causing resistance increase and lifespan deterioration
Solution Approach 1:
The patent applies parameter changes by optimizing the electrode density to specific ranges (1.3-1.5 g/cc for low graphitization graphite, 1.4-1.7 g/cc for high graphitization graphite) rather than maximizing it. This resolves the contradiction by finding the optimal density parameter that provides high capacity while preventing mechanical degradation through controlled pressing conditions.
2Quantity of substance
If the negative active material is pressed to maximum extent to achieve high electrode density, then the battery capacity increases, but the resistance increases due to peeling and cracks
Solution Approach 1:
The patent changes the density parameter to optimal ranges that balance capacity and resistance. By controlling the electrode density within specific ranges and adjusting pressing conditions, the patent achieves high electrode density without excessive resistance increase, resolving the contradiction between capacity and resistance.
3Ease of manufacture
If a fixed high electrode density is applied to all negative electrode materials, then manufacturing is simplified, but the performance is suboptimal for different material types
Solution Approach 1:
The patent applies local quality by specifying different optimal density ranges for different types of negative electrode active materials (low graphitization graphite: 1.3-1.5 g/cc, high graphitization graphite: 1.4-1.7 g/cc). This resolves the contradiction by tailoring the density parameter to each material type's specific properties, achieving optimal performance for each while maintaining a systematic manufacturing approach.
Data Source
AI summary
The present invention relates to a method of manufacturing a negative electrode and a negative electrode manufactured using the method. According to the present invention, negative electrode samples are fabricated to have different electrode densities, and then, in a negative electrode expansion curve of each negative electrode sample according to the 1st charging, when a change in slopes of tangents to the negative electrode expansion curve at an initial state of charge (SOC) of less than 50%, at which the expansion curve increases, satisfies a particular value, a secondary battery manufactured including a negative electrode having the electrode density may exhibit excellent lifespan characteristics and excellent initial efficiency for the corresponding active material.