Li3PO4 Coating Composition for Solid-State Battery Interfacial Stability
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Solution Overview
Problem
In all-solid-state secondary batteries, the interfacial reaction between sulfide-based solid electrolytes and oxide-based positive electrode active materials degrades cell properties, and existing coating materials like Li3PO4 face challenges in forming a uniform coating layer due to poor wettability and vulnerability to moisture, especially with high nickel content active materials.
Innovation Solution
A coating composition comprising a lithium component, polyphosphoric acid as the phosphorus component, and an organic solvent is used to form a thin and uniform Li3PO4 coating layer on the positive electrode active material, which is heat-treated to enhance stability and electrochemical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Li3PO4 coating material is used to stabilize the interface with sulfide-based solid electrolyte, then interfacial stability is improved, but uniform coating formation becomes difficult due to poor wettability
Solution Approach 1:
The patent changes the chemical parameters of the coating composition by using lithium salt and phosphoric acid in an organic solvent system instead of conventional aqueous solutions. This parameter change enables the coating material to achieve both good wettability for uniform coating formation and chemical stability for interface protection against sulfide-based solid electrolytes.
Solution Approach 2:
The patent introduces an organic solvent as an intermediary medium that facilitates uniform distribution and attachment of Li3PO4 coating material on the positive electrode active material surface. The organic solvent acts as a mediator that enables controlled coating formation while maintaining the stability requirements for sulfide-based solid electrolyte interfaces.
2Ease of manufacture
If aqueous solvent is used to dissolve phosphorus source material for coating formation, then coating material can be attached to surface, but wettability is poor and coating uniformity deteriorates
Solution Approach 1:
The patent fundamentally changes the solvent parameter from aqueous to organic solvent system. This parameter change resolves the contradiction by providing both adequate solubility for phosphorus source material and excellent wettability for uniform coating formation on the oxide-based positive electrode active material surface.
3Power
If high nickel content is used in positive electrode active material to improve capacity, then electrochemical performance is enhanced, but vulnerability to moisture increases causing property deterioration
Solution Approach 1:
The patent applies preliminary protective action by forming a Li3PO4 coating layer on the high nickel content positive electrode active material before contact with moisture or sulfide-based solid electrolyte. This preliminary coating prevents direct interaction between moisture and the nickel-containing material, thereby maintaining electrochemical performance and stability.
Solution Approach 2:
The Li3PO4 coating acts as an intermediary protective layer between the moisture-sensitive high nickel positive electrode active material and the external environment. This intermediary layer enables the use of high nickel content materials while preventing moisture-induced deterioration.
4Reliability
If coating layer is formed thickly to improve interface stability, then protection is enhanced, but resistance in electrode rapidly increases
Solution Approach 1:
The patent optimizes the coating composition parameters (lithium salt to phosphoric acid ratio, solvent type, concentration) to enable formation of a thin yet effective coating layer. This parameter optimization achieves interface stability with minimal coating thickness, thereby avoiding excessive electrode resistance while maintaining protective function.
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 solution enables the formation of a stable and uniform Li3PO4 coating layer, improving the electrochemical properties and interfacial stability of the battery, leading to enhanced discharge capacity and high-rate capability while reducing impedance and preventing side reactions.
Implementation Method 1
an organic solvent dissolving the phosphorus component
Implementation Method 2
forming a coating layer including Li3PO4 on the surface of the positive electrode active material
Implementation Method 3
which is heat-treated to enhance stability and electrochemical properties
Data Source
AI summary
Disclosed are a coating composition for a composite positive electrode active material and a method of preparing a composite positive electrode active material using the same.