Negative Electrode Active Material Mixture for Lithium Battery Pore Maintenance
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Solution Overview
Problem
Conventional lithium secondary batteries face performance degradation due to reduced pore spaces in the negative electrode active material layer during the rolling process, which impedes electrolyte solution penetration and ion migration, leading to increased resistance and reduced cycle lifespan.
Innovation Solution
A negative electrode active material comprising a mixture of a first material with a Vickers hardness of 1-10 kg/mm² and a second material with higher hardness, up to 10,000 kg/mm², is used to maintain pore spaces, ensuring effective electrolyte flow and ion migration by mixing materials like natural graphite and metal oxides, with specific weight ratios and particle sizes to maintain porosity and electrode density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a rolling (pressing) process is performed to compress active material powder onto a current collector, then the thickness of the electrode is uniformized and manufacturing precision is improved, but the pore space between active materials is reduced and electrode performance deteriorates
Solution Approach 1:
The invention utilizes porous active material particles with controlled pore structures that maintain porosity even after rolling compression. The porous structure allows electrolyte penetration while the particle framework provides mechanical stability during the rolling process, resolving the contradiction between thickness uniformity and electrode performance.
Solution Approach 2:
The invention employs composite active material particles consisting of core-shell structures or multi-component composites where the outer layer provides mechanical strength to resist compression while the inner structure maintains pore spaces. This composite approach allows the electrode to withstand rolling pressure while preserving ion transport pathways.
2Quantity of substance
If active material powder is pressed in the rolling process, then the density of the electrode is increased, but the pore space is decreased and ion flow passage is blocked
Solution Approach 1:
The invention uses porous active material particles that maintain a hierarchical pore structure even at high electrode densities. The porous structure ensures continuous ion flow passages while achieving high packing density, allowing both high quantity of active material and efficient ion migration.
Solution Approach 2:
The invention transitions from considering only two-dimensional packing to three-dimensional porous structures, creating vertical ion transport pathways that maintain conductivity even when horizontal pore spaces are reduced by rolling compression.
3Quantity of substance
If the thickness of the electrode is increased to improve capacity, then the energy storage is enhanced, but the electrolyte solution penetration becomes difficult and resistance increases
Solution Approach 1:
The invention introduces vertical pore channels and three-dimensional ion transport pathways that enable electrolyte penetration deep into thick electrodes. This dimensional approach allows high capacity electrodes to maintain low resistance by providing direct ion access to active material throughout the electrode thickness.
Solution Approach 2:
The invention employs porous active material particles with interconnected pore networks that facilitate electrolyte distribution throughout thick electrodes. The porous structure ensures that even in thick electrodes, electrolyte can reach all active material regions, maintaining low resistance while achieving high capacity.
Data Source
AI summary
The present invention relates to a negative electrode active material comprising a mixture of a first negative electrode active material and a second negative electrode active material, wherein the first negative electrode active material has a hardness of 1 kg/mm2 to 10 kg/mm2 on the basis of the Vickers hardness standard, and the second negative electrode active material has a higher hardness than the first negative electrode active material. The negative electrode active material according to the present invention comprises a mixture of negative electrode active materials having different hardness so that pores of an active material layer are maintained in spite of a rolling process at the time of producing an negative electrode, and the pores acting as an electrolyte flow passage of an electrode can effectively be secured, thereby producing a lithium secondary battery having excellent battery performance by lowering resistance when a battery is charged or discharged.