Positive Electrode Material Crystallization Temperature Control
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Solution Overview
Problem
The existing methods for manufacturing positive electrode materials for sodium-ion secondary cells face issues such as excessive particle fusion during high-temperature firing, leading to reduced specific surface area and decreased charge and discharge characteristics, as well as costly barrier layer coatings to prevent reactions between the active material and solid electrolyte.
Innovation Solution
A method involving a positive electrode active material precursor powder with a crystallization temperature of 490°C or lower, thermally treated at 400-600°C for less than three hours in a reductive atmosphere, with controlled particle size and composition to minimize excessive reactions and enhance charge and discharge characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If glass powder is fired at high temperature to reduce Fe ions from trivalent to divalent, then the positive electrode active material develops cell characteristics, but glass powder particles excessively fuse together forming coarse particles with small specific surface area
Solution Approach 1:
The invention changes the chemical composition parameters of the glass powder by controlling the ratios of specific oxides (Fe2O3, P2O5, B2O3, SiO2, Al2O3) within defined ranges. This compositional optimization allows the material to achieve desired cell characteristics at lower firing temperatures (900-1100°C), preventing excessive particle fusion while maintaining functionality.
Solution Approach 2:
The invention performs preliminary classification of glass powder particles to remove coarse particles before firing. This preliminary action ensures that only fine particles with appropriate size distribution undergo thermal treatment, preventing excessive fusion during firing and maintaining high specific surface area in the final product.
2Strength
If positive electrode active material precursor powder and solid electrolyte powder are integrally fired to increase adhesiveness, then excellent discharge characteristic is achieved, but maricite NaFePO4 crystals precipitate reducing charge and discharge capacities
Solution Approach 1:
The invention optimizes the firing temperature parameter within a specific range (900-1100°C) and controls the composition of the positive electrode active material precursor powder. These parameter changes enable sufficient adhesiveness between the active material and solid electrolyte while preventing the precipitation of maricite NaFePO4 crystals that would reduce capacity.
Solution Approach 2:
The invention uses a composite precursor powder containing multiple oxide components (Fe2O3, P2O5, B2O3, SiO2, Al2O3) in specific ratios. This composite composition facilitates controlled reaction with the solid electrolyte during firing, achieving good interfacial adhesion without forming harmful maricite phase.
3Strength
If elements in positive electrode active material precursor powder and solid electrolyte mutually diffuse during firing, then a high-resistance layer is formed, but rate characteristics decrease
Solution Approach 1:
The invention carefully controls the firing temperature within 900-1100°C and optimizes the composition of the precursor powder. These parameter changes limit excessive elemental diffusion between the active material and solid electrolyte, preventing the formation of high-resistance layers while still achieving adequate adhesion for structural integrity.
4Reliability
If alkoxide material coating is applied to prevent reaction between active material and solid electrolyte, then high-resistance layer formation is reduced, but manufacturing cost rises
Solution Approach 1:
The invention replaces expensive alkoxide material coatings with a cost-effective compositional optimization approach. By carefully controlling the oxide ratios in the precursor powder and optimizing firing parameters, the invention achieves equivalent or superior performance in preventing high-resistance layer formation without the added cost of alkoxide coatings.
Solution Approach 2:
The invention changes the chemical composition parameters of the precursor powder and firing conditions to inherently prevent excessive reaction and high-resistance layer formation. This parameter optimization eliminates the need for additional protective coating steps, reducing manufacturing complexity and cost while maintaining charge and discharge characteristics.
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
This approach reduces excessive reactions and increases the specific surface area, resulting in positive electrode materials with improved charge and discharge characteristics and reduced internal resistance, while avoiding the need for expensive barrier layers.
Implementation Method 1
the positive electrode active material precursor powder has a crystallization temperature of 490° C. or lower. With the use of, as a raw material, the positive electrode active material precursor powder having a crystallization temperature as low as 490° C. or lower, the positive electrode active material precursor powder can be promoted in crystallization even when thermally treated (fired) at a low temperature.
Implementation Method 2
it is necessary to fire a glass powder as a precursor of the positive electrode active material at a high temperature to reduce Fe ions in the glass powder from trivalent ions to divalent ions
Data Source
AI summary
The present invention provides a method for manufacturing a positive electrode material for an electricity storage device that can reduce excessive reactions between particles of a positive electrode active material precursor powder and between the positive electrode active material precursor powder and a solid electrolyte during thermal treatment to achieve excellent charge and discharge characteristics. A method for manufacturing a positive electrode material for an electricity storage device includes the step of subjecting a raw material containing a positive electrode active material precursor powder made of an amorphous oxide material to thermal treatment, wherein the positive electrode active material precursor powder has a crystallization temperature of 490° C. or lower.