Phosphorus-Coated Positive Electrode Particles for Stable Low Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing all-solid-state batteries face challenges in reducing initial resistance and post-endurance-test resistance increment, particularly in sulfide-type batteries, where conventional coating films like Li3PO4 increase initial resistance while niobium compounds lead to high post-endurance-test resistance.
Innovation Solution
A composite particle is developed with a phosphorus compound coating film on the positive electrode active material, where the lithium to phosphorus concentration ratio (CLi/CP) is maintained at 2.5 or less, achieved by using a coating liquid with diphosphorus pentoxide in a mass fraction of 72% or more, which forms a coating film with high covering rate and low initial resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional coating film material (Li3PO4) is used, then the coating film provides protective coverage, but the initial resistance becomes high
Solution Approach 1:
The patent changes the compositional parameters of the coating film by controlling the Li/P concentration ratio to 2.5 or less and using a coating liquid with diphosphorus pentoxide at 72% mass fraction or more. This parameter optimization reduces initial resistance while maintaining protective coverage, resolving the contradiction between reliability and harmful factors.
Solution Approach 2:
The patent employs a composite coating film composed of phosphorus compounds with specific composition ratios rather than using a single conventional material like Li3PO4. This composite approach allows simultaneous achievement of low initial resistance and adequate protective coverage by balancing lithium and phosphorus concentrations.
2Object-affected harmful factors
If a niobium compound coating film (LiNbO3) is used, then the initial resistance decreases, but the post-endurance-test resistance increment becomes great
Solution Approach 1:
The patent changes the material composition parameters by using phosphorus compounds with controlled Li/P ratios instead of niobium compounds. This substitution maintains low initial resistance while significantly reducing post-endurance-test resistance increment, resolving the contradiction between initial performance and long-term stability.
Solution Approach 2:
The patent replaces niobium compound coating films with phosphorus compound-based coatings that are more stable over time. Although phosphorus compounds may have different initial properties, their long-term stability and lower resistance increment make them superior for sustained battery operation.
3Object-affected harmful factors
If the lithium to phosphorus concentration ratio (CLi/CP) is increased to improve Li-ion conductivity, then initial resistance decreases, but the covering rate decreases
Solution Approach 1:
The patent optimizes the Li/P concentration ratio parameter to 2.5 or less, which represents a specific parameter setting that balances Li-ion conductivity and covering rate. This optimized parameter achieves low initial resistance while maintaining high covering rate, resolving the contradiction between conductivity and coverage area.
Solution Approach 2:
The patent uses a coating liquid containing diphosphorus pentoxide at 72% mass fraction or more to pre-establish an optimal coating composition before battery assembly. This preliminary optimization of coating composition ensures that the final coating film achieves both low initial resistance and high covering rate without requiring post-processing adjustments.
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 particle with a phosphorus compound coating film significantly decreases initial resistance and minimizes post-endurance-test resistance increment, enhancing the battery's performance by maintaining a high covering rate and optimal lithium to phosphorus composition.
Implementation Method 1
a coating film covers at least part of a surface of the positive electrode active material particle. The coating film includes a phosphorus compound
Implementation Method 2
A coating film is required to have Li-ion conductivity. The higher the Li-ion conductivity is, the more decreased the initial resistance is expected to be
Implementation Method 3
By using X-ray photoelectron spectroscopy (XPS), it is possible to identify the composition of a particle surface (namely, the composition of the coating film)
Data Source
AI summary
A composite particle includes a positive electrode active material particle and a coating film. The coating film covers at least part of a surface of the positive electrode active material particle. The coating film includes a phosphorus compound. The composite particle satisfies a relationship of “CLi/CP≤2.5”. “CLi” represents a concentration of Li element measured by XPS. “CP” represents a concentration of P element measured by XPS.