Cathode Active Material Coating for Solid-State Battery Contact
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Solution Overview
Problem
Existing methods for manufacturing all-solid-state batteries fail to achieve sufficient close contact between the active material and electrolyte, leading to inadequate ion and electrical conductivity, which affects battery performance and safety.
Innovation Solution
A composite for a positive electrode active material is formed by coating the surface and pores of the active material with a mixture of solid electrolyte and electrically conductive material using a dry coating process, ensuring close contact and improved conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high pressure is applied to form close contact between active material and electrolyte, then ion conductivity is improved, but the electrode and/or solid electrolyte may be damaged
Solution Approach 1:
The invention applies local quality by creating a coating layer with specific composition (solid electrolyte and electrically conductive material in defined ratios) on the surface and in pores of the active material. This localized modification ensures close contact and high ion conductivity at the interface without requiring global high-pressure compression that could damage the electrode structure.
Solution Approach 2:
The invention uses composite materials by combining solid electrolyte powder (0.2-2 μm) with electrically conductive material powder (0.02-2 μm) in a weight ratio of 9:1 to 1:9 within the coating layer. This composite structure simultaneously provides ion conductivity from the solid electrolyte and electrical conductivity from the conductive material, resolving the contradiction between ion conductivity and structural integrity.
2Device complexity
If simple mixing of components is used for electrode manufacturing, then device complexity is reduced, but resistance of the electrode cannot be sufficiently lowered
Solution Approach 1:
The invention applies preliminary action by pre-forming a coating layer on the active material particles before electrode assembly. The coating layer is prepared in advance with the optimal mixture of solid electrolyte and electrically conductive material, ensuring low resistance contacts are established before the electrode is assembled into the battery, thus avoiding complex post-assembly processing.
Solution Approach 2:
The invention utilizes porous materials by forming a coating layer that penetrates into and coats the pores of the active material particles. This porous coating structure increases the surface area for contact between the active material, solid electrolyte, and electrically conductive material, thereby reducing electrode resistance without requiring complex manufacturing processes.
3Reliability
If close contact between active material and electrolyte is achieved by high pressure, then ion conductivity is improved, but manufacturing precision is compromised due to potential damage
Solution Approach 1:
The invention applies parameter changes by controlling the particle size of solid electrolyte (0.2-2 μm) and electrically conductive material (0.02-2 μm) within specific ranges, and by optimizing their weight ratio (9:1 to 1:9). These parameter optimizations enable the formation of a fine, uniform coating layer that achieves close contact without requiring high-pressure compression, thus maintaining manufacturing precision.
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 composite provides enhanced ion and electrical conductivity, resulting in improved battery capacity, charging and discharging characteristics, and extended lifetime.
Implementation Method 1
The lithium-ion conductivity of the solid electrolyte is still lower than that of the liquid electrolyte, however, theoretically, since it has been reported that the ion conductivity in solid is higher than in liquid
Implementation Method 2
close contact between the active material and the electrically conductive material is required
Data Source
Figure 1
AI summary
The present invention provides a composite for a positive electrode active material, comprising: a positive electrode active material; and a coating layer formed on the pores and the surface of the positive electrode active material, wherein the coating layer is formed of a coating composition containing a powder of the electrically conductive material and a powder of a solid electrolyte having a particle diameter (D50) of 0.3 µm to 2 µm, and an electrode for a secondary battery comprising the same, and a secondary battery comprising the electrode.