Fluorine-Phosphorus Coating for High-Voltage Solid-State Cathodes
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Solution Overview
Problem
High-voltage all-solid-state batteries face increased resistance post-endurance-test, which is not adequately addressed by existing technologies that coat positive electrode active material particles with inorganic solid electrolytes.
Innovation Solution
A composite particle is developed with a coating film containing fluorine (F) and at least one of phosphorus (P) or a glass network forming element, such as boron (B), silicon (Si), nitrogen (N), sulfur (S), germanium (Ge), or hydrogen (H), with specific concentration ratios to reduce resistance increment, and optionally including metallic elements like aluminum (Al), titanium (Ti), or zirconium (Zr), applied to the surface of positive electrode active material particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating film is formed on the surface of a positive electrode active material particle to inhibit direct contact between sulfide-based solid electrolyte and the particle, then initial resistance is decreased, but post-endurance-test resistance increment remains high under high voltage conditions
Solution Approach 1:
The patent changes the chemical composition parameters of the coating film by incorporating fluorine (F) at specific concentrations (0.1-5.0 at%, preferably 0.5-2.0 at%) along with phosphorus (P) and glass network forming elements. This parameter modification transforms the coating film's properties to achieve both low initial resistance and minimal resistance increment after endurance testing under high voltage conditions.
Solution Approach 2:
The patent creates a composite coating film structure combining multiple elements (F, P, glass network forming elements like B, Si, Ge, and optionally metallic elements like Al, Ti, Zr) to achieve synergistic effects. This composite material approach allows the coating to simultaneously provide initial conductivity and long-term stability under high voltage, resolving the contradiction between initial performance and endurance.
2Device complexity
If the coating film includes only inorganic solid electrolyte materials, then the structure is simple, but the resistance increment under high voltage cannot be sufficiently decreased
Solution Approach 1:
The patent modifies the compositional parameters of the coating film by introducing fluorine at controlled concentrations alongside phosphorus and glass network forming elements. This parameter change enables the coating to achieve superior resistance stability under high voltage without requiring complex multi-layer structures, thus maintaining structural simplicity while improving reliability.
3Duration of action of stationary object
If fluorine concentration in the coating film is increased to decrease resistance increment, then endurance under high voltage is improved, but the coating film stability may be compromised
Solution Approach 1:
The patent optimizes the fluorine concentration parameter within a specific range (0.1-5.0 at%, preferably 0.5-2.0 at%) to achieve the best balance between endurance improvement and coating stability. This controlled parameter modification ensures that fluorine provides sufficient resistance increment reduction while maintaining the coating film's structural integrity and compositional stability.
Solution Approach 2:
The patent distributes fluorine atoms locally within the coating film structure at controlled concentrations rather than uniformly throughout. This local quality approach allows fluorine to exert its beneficial effect on resistance stability at specific sites while the overall coating composition remains stable, preventing excessive fluorine from compromising the coating's structural integrity.
Data Source
AI summary
A composite particle comprising: a positive electrode active material particle; and a coating film, wherein the coating film covers at least part of a surface of the positive electrode active material particle, and the coating film includes fluorine and at least one selected from the group consisting of phosphorus and a glass network forming element.