Layered Graphite Negative Electrode for Fast-Charging Adhesion
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Solution Overview
Problem
Conventional lithium secondary batteries face issues with adhesion between the negative electrode active material and the current collector, leading to reduced quick charging performance and capacity due to excessive micropowder generation and non-uniform pores, which are not adequately addressed by carbon coating layers or increased binder content.
Innovation Solution
A negative electrode structure with a lower layer region containing primary particles of artificial graphite and a higher layer region with secondary particles of artificial graphite coated with carbon, where the binder polymer distribution is optimized to enhance adhesion and quick charging performance without increasing the overall binder content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If binder content is increased to improve adhesion, then adhesion between active material and current collector is improved, but resistance increases and quick charging performance degrades
Solution Approach 1:
The patent applies different binder contents to different regions of the electrode layer. The first region (near current collector) has higher binder content (1.5-4.0 wt%) to ensure strong adhesion, while the second region (远离集流体) has lower binder content (0.5-2.0 wt%) to maintain low resistance and good quick charging performance. This local differentiation resolves the contradiction between adhesion and quick charging performance.
2Strength
If carbon coating layer is applied to secondary particles to inhibit micropowder detachment, then adhesion is improved, but micropowder removal is insufficient and quick charging performance cannot be improved
Solution Approach 1:
The patent uses carbon-coated secondary graphite particles specifically in the first region near the current collector where adhesion is critical. The carbon coating (0.5-5.0 wt%) prevents micropowder detachment in this region. In the second region, the lower binder content and different particle composition prioritize quick charging performance, accepting some micropowder presence as a trade-off.
Solution Approach 2:
The patent creates a composite structure combining graphite particles with carbon coating material. This composite approach provides both adhesion benefits (through the carbon coating layer) and maintains electrical conductivity necessary for battery performance, resolving the contradiction between preventing micropowder detachment and maintaining quick charging capability.
3Strength
If pitch content or carbon precursor content is increased to solve micropowder problems, then micropowder detachment is inhibited, but capacity per weight decreases
Solution Approach 1:
The patent concentrates the carbon coating material (pitch or carbon precursor) specifically in the first region near the current collector where adhesion is needed, with content of 0.5-5.0 wt% in that region. The second region has minimal carbon coating material, preserving active material content and capacity per weight. This localized application resolves the contradiction between adhesion improvement and capacity maintenance.
Data Source
AI summary
Disclosed is a negative electrode, including: a negative electrode current collector; and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, and having a lower layer region containing a first active material and a first binder polymer, and an upper layer region disposed on the lower layer region and containing a second active material and a second binder polymer, wherein the first active material includes primary particles of artificial graphite, the second active material includes secondary particles of artificial graphite and a carbon coating layer disposed on the secondary particles, and the weight percentage (wt %) of the first binder polymer in the lower layer region is larger than the weight percentage (wt %) of the second binder polymer in the upper layer region. Also disclosed are a method for manufacturing the negative electrode and a lithium secondary battery including the negative electrode.