Conductive Cathode Particle Coatings for Dry Electrode Loading
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Solution Overview
Problem
Existing secondary battery manufacturing processes face issues such as solvent evaporation rate inconsistencies leading to defects like pinholes or cracks, non-uniform drying, and the need for expensive drying devices, as well as challenges in dispersing conductive materials in dry electrodes, resulting in reduced active material loading and increased conductive material usage.
Innovation Solution
A cathode active material layer with conductive active material particles having a core and a coating, and a fiberized binder forming a 3D mesh structure, which provides electrical conductivity without additional conductive particles, and an electrode mixture film with a conductive path connectivity index (CPCI) of 0.09 to 0.45, ensuring uniform distribution and increased active material loading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a solvent-containing slurry is used to manufacture electrodes, then the electrode active material layer can be formed and applied to current collectors, but defects such as pinholes or cracks are generated due to non-uniform solvent evaporation rates between internal and external portions
Solution Approach 1:
The invention extracts and eliminates the solvent component from the electrode manufacturing process. By using a dry mixing process without solvents, the patent removes the source of non-uniform evaporation that causes pinholes and cracks, thereby resolving the contradiction between ease of manufacture and manufacturing precision.
Solution Approach 2:
The invention changes the physical state parameter of the mixing process from wet (solvent-containing) to dry (solvent-free). This parameter change eliminates evaporation-related defects while maintaining the ability to form electrode active material layers, thus improving manufacturing precision without sacrificing ease of manufacture.
2Ease of manufacture
If N-methyl-2-pyrrolidone (NMP) is used as the solvent in electrode slurry, then the electrode active material layer can be formed, but high heat energy and very long drying furnaces are required due to its high boiling point, making it highly unsuitable for mass production
Solution Approach 1:
The invention extracts and removes NMP solvent from the electrode manufacturing process entirely. By adopting a dry mixing approach, it eliminates the need for high-temperature drying furnaces and long processing times, thereby improving productivity and mass production suitability while still achieving uniform electrode active material layer formation.
Solution Approach 2:
The invention replaces the expensive, time-consuming NMP drying process with a simple, rapid dry mixing process. This substitution uses inexpensive equipment and significantly reduces processing time, making the process highly suitable for mass production while maintaining ease of manufacture.
3Ease of manufacture
If N-methyl-2-pyrrolidone (NMP) is used as the solvent in electrode slurry, then the electrode active material layer can be formed, but N-methyl-2-pyrrolidone is a toxic substance and is harmful to living things, thereby failing to be environmentally friendly
Solution Approach 1:
The invention extracts and eliminates NMP solvent from the manufacturing process. By using a solvent-free dry mixing method, it removes the toxic substance entirely from the process, thereby eliminating environmental harm while still enabling effective electrode active material layer formation.
Solution Approach 2:
The invention converts the harmful effect of NMP by completely removing it from the process. The dry mixing approach transforms a potentially harmful wet process into a beneficial environmentally-friendly process that eliminates toxic emissions while maintaining manufacturing effectiveness.
4Quantity of substance
If linear conductive materials such as CNT are used in dry electrodes, then they have the effect of reducing the amount of conductive material, but they are not dispersed well in the dry process, making it difficult to achieve an increase in active material loading
Solution Approach 1:
The invention uses composite conductive particles consisting of a core material (such as metal powder or conductive oxide) coated with a conductive material layer (such as carbon or metal). This composite structure provides both good dispersion characteristics in dry mixing and sufficient conductivity, allowing reduced conductive material content while maintaining uniform distribution.
Solution Approach 2:
The invention applies conductive material locally as a coating layer on the surface of core particles rather than using bulk linear conductive materials. This local application ensures uniform dispersion throughout the electrode mixture while providing adequate conductivity pathways, resolving the contradiction between reducing conductive material amount and achieving good dispersion.
5Object-affected harmful factors
If a dry electrode process is used without solvents and dispersants, then environmental friendliness and manufacturing simplicity are improved, but materials cannot be dispersed well to ensure uniform distribution, requiring a relatively greater amount of conductive material
Solution Approach 1:
The invention employs composite conductive particles with core-shell structure that provide inherent dispersion capability in dry conditions. The composite structure allows uniform distribution without solvents or dispersants, maintaining environmental friendliness while reducing the total amount of conductive material needed compared to conventional dry electrode processes.
Solution Approach 2:
The invention changes the morphology and surface properties of conductive particles from linear (CNT) to composite spherical/irregular shapes with controlled surface characteristics. This parameter change improves dispersion in dry mixing while maintaining conductivity, allowing reduced conductive material content without compromising uniformity, thus preserving environmental friendliness.
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 enhances electrical conductivity and active material loading, improving battery resistance, lifetime, and capacity characteristics while reducing production costs by eliminating the need for costly dispersing processes and minimizing conductive material usage.
Implementation Method 1
the coating comprises an electrically conductive material
Implementation Method 2
a binder comprising fibers that are generally linear, extend in random orientations, curve or bend randomly, and intersect and connect with one another at random locations, which provides a three-dimensionally networked mesh of fibers
Data Source
AI summary
A cathode active material layer includes conductive active material particles individually with a core and a coating on a surface of the core, wherein the core comprises a cathode active material, and the coating comprises an electrically conductive material; and a binder including fibers that form a three-dimensionally networked mesh of fibers. The cathode active material layer is free or substantially free of electrically conductive particles other than the conductive active material particles. The conductive active material particles are accommodated in the 3D mesh of the binder, and adjacent ones of the conductive active material particles abut one another within the 3D mesh, in which the electrically conductive material of the coating of one of the conductive active material particles makes at least one contact with the electrically conductive material of the coating of one or more adjacent ones of the conductive active material particles.