Gradient-Aligned Carbon Anode to Suppress Lithium Plating
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Solution Overview
Problem
Lithium secondary batteries experience increased lithium precipitation and internal short circuits due to degradation near the negative electrode tab, leading to safety concerns, especially under high-rate conditions.
Innovation Solution
A negative electrode with a carbon-based active material layer divided into regions with controlled alignment, where the alignment increases from the first region to the nth region, reducing electrical resistance and preventing lithium precipitation by applying a magnetic field with decreasing intensity, resulting in a perpendicular alignment of a-b axis crystal faces to the current collector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the weight and thickness of non-capacity configurations (electrode tabs, separators, current collectors) are reduced to increase energy density, then the rate of redox reactions at electrode tabs increases, but degradation near the negative electrode tab accelerates, leading to increased resistance and capacity degradation
Solution Approach 1:
The patent applies local quality by creating a gradient in the alignment degree of carbon-based active material throughout the negative electrode active layer. The alignment degree varies from the first side portion (near negative electrode tab) to the second side portion (opposite side), with each region having optimized alignment characteristics. This gradient structure allows different regions to have tailored properties: regions near the tab have lower alignment to reduce resistance and prevent degradation, while other regions maintain higher alignment for optimal lithium ion insertion/extraction performance.
2Quantity of substance
If the N/P ratio becomes less than 1 due to capacity degradation near the negative electrode tab, then lithium ions cannot fully intercalate during charging, but lithium precipitation and dendrite formation occur on the negative electrode surface
Solution Approach 1:
The patent employs parameter changes by systematically varying the alignment degree of carbon-based active material across different regions of the negative electrode active layer. This parameter variation (alignment degree) directly influences both electrical resistance and lithium ion insertion/extraction kinetics. By optimizing this parameter spatially, the invention prevents N/P ratio inversion and subsequent lithium precipitation while maintaining high intercalation capacity.
3Speed
If high rate conditions are used for extended periods, then charging and discharging speed increases, but the likelihood of dendrite formation significantly increases, compromising battery safety
Solution Approach 1:
The patent applies preliminary action by pre-establishing a non-uniform alignment degree distribution in the carbon-based active material before the battery undergoes high-rate charging and discharging cycles. This pre-configured gradient structure proactively addresses potential degradation issues by ensuring that regions prone to high current density (near the tab) have lower alignment to reduce resistance and heat generation, thereby preventing dendrite formation before it occurs during extended high-rate operation.
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 solution effectively suppresses lithium precipitation and enhances safety by maintaining high efficiency during charging and discharging, especially under high-rate conditions, by reducing electrode resistance and preventing capacity degradation.
Implementation Method 1
applying a magnetic field with decreasing intensity, resulting in a perpendicular alignment of a-b axis crystal faces to the current collector
Data Source
AI summary
A negative electrode for a lithium secondary battery in which lithium precipitation is suppressed. The negative electrode implements a high degree of orientation of a carbon-based active material contained in a first region of the negative electrode active layer, so that the effect of suppressing lithium precipitation at an end of the negative electrode active layer during charging and discharging of a secondary battery is excellent. Accordingly, a lithium secondary battery including the negative electrode active layer has high safety, and has the advantage of being able to charge and discharge for a long time under high rate conditions. A lithium secondary battery including the negative electrode is also provided.