Phosphorus Coating for Solid-State Cathodes With Lower Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Sulfide solid electrolytes in all-solid-state batteries degrade when directly contacting positive electrode active material particles, leading to increased battery resistance, which is mitigated by forming a coating film but LiNbO3 has higher resistance than desired, necessitating a low-resistance phosphorus-based coating film.
Innovation Solution
A phosphorus-based coating film with a specific composition ratio of lithium, glass network-forming elements, and transition elements is developed, where the elemental concentrations are optimized to achieve low battery resistance and durability under high voltage, using a mixture of boron, silicon, nitrogen, germanium, or hydrogen as glass network-forming elements and lanthanum, cerium, or yttrium as transition elements, ensuring high ionic conduction and coverage of the positive electrode active material particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiNbO3 coating film is used to protect sulfide solid electrolyte from degradation, then durability is improved, but resistance increases beyond acceptable levels
Solution Approach 1:
The patent applies composite materials by combining phosphorus compound with glass network-forming elements (B, Si, Ge) and transition elements (La, Ce, Y) to create a coating film that integrates multiple functional properties: protection against sulfide electrolyte degradation, low resistance, and high ionic conduction, overcoming the limitations of single-material coatings like LiNbO3
Solution Approach 2:
The patent employs parameter changes by precisely controlling the composition ratios of Li, P, glass network-forming elements, and transition elements in the coating film, as well as optimizing deposition parameters to achieve the optimal balance between durability and low resistance, transforming the coating properties to meet both requirements
2Object-affected harmful factors
If phosphorus-based coating film is designed to replace LiNbO3 for lower resistance, then resistance is reduced, but durability under high voltage may be compromised
Solution Approach 1:
The patent uses composite materials by integrating phosphorus compound with specific glass network-forming elements and transition elements, creating a multi-component coating film that simultaneously achieves low resistance through phosphorus compound and high voltage durability through the stabilizing effects of glass network-forming and transition elements
Solution Approach 2:
The patent applies local quality by assigning different functional roles to different components within the coating film: phosphorus compound provides low resistance, while glass network-forming elements and transition elements provide structural stability and high voltage durability, with each component optimized for its specific function within the composite structure
3Reliability
If coating film is formed to prevent sulfide solid electrolyte degradation, then reliability is improved, but battery output may be reduced due to additional resistance
Solution Approach 1:
The patent applies composite materials to create a coating film that provides protection against sulfide solid electrolyte degradation while maintaining low resistance through the synergistic combination of phosphorus compound, glass network-forming elements, and transition elements, thereby preserving battery output
Solution Approach 2:
The patent uses the phosphorus-based coating film as an intermediary layer between the positive electrode active material particles and the sulfide solid electrolyte, providing protection against degradation while the low-resistance composition ensures minimal impact on ionic conduction and battery output
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 phosphorus-based coating film achieves resistance as low as or lower than LiNbO3, enabling both high durability and output by facilitating carrier migration through mixed anion effects and structural defects, while maintaining high ionic conduction and coverage of the positive electrode active material particles.
Implementation Method 1
ionic conduction as high as or higher than that of LiNbO3 may be achieved
Implementation Method 2
Carrier migration can be facilitated by such introduction of the structural defects
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A composite particle (5) includes a positive electrode active material particle (1) and a coating film (2). The coating film (2) covers at least a part of a surface of the positive electrode active material particle (1). The coating film (2) includes a phosphorus compound. The phosphorus compound includes either or both of a first element and a second element, and phosphorus. The first element is a glass network-forming element. The second element is a transition element. The relationship of CLi/(CP + CE1 + CE2) ≤ 2.5 is satisfied, where CLi, CP, CE1, and CE2 represent elemental concentrations obtained by measuring the composite particle by X-ray photoelectron spectroscopy, CLi represents an elemental concentration of lithium, CP represents an elemental concentration of phosphorus, CE1 represents an elemental concentration of the first element, and CE2 represents an elemental concentration of the second element.