Polyanion Coated Positive Electrode for Solid-State Battery Interface
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Solution Overview
Problem
All solid-state batteries face a persistent issue of increasing interfacial resistance over time due to reactions between the positive electrode active material and the solid electrolyte, which affects the battery's performance and durability, especially when transition metals are involved.
Innovation Solution
A composite positive electrode active material is developed, featuring a transition metal-containing positive electrode active material coated with a reaction suppressor made of a polyanion structure-containing compound. This suppressor, with a cation moiety and a center atom covalently bonded to multiple oxygen atoms, forms a thin transition metal-reducing layer on the surface, reducing interfacial resistance and enhancing electrochemical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiNbO3 is coated onto the surface of LiCoO2 to reduce interfacial resistance, then initial interfacial resistance is reduced, but interfacial resistance rises over time due to reactions with solid electrolyte material
Solution Approach 1:
The patent introduces a reaction suppressor layer as an intermediary substance between the positive electrode active material and the solid electrolyte material. This reaction suppressor, composed of a polyanion structure-containing compound, mediates the interface to prevent harmful reactions while maintaining low interfacial resistance over time.
Solution Approach 2:
The patent creates a composite structure consisting of the positive electrode active material (containing transition metal) combined with a reaction suppressor layer. This composite material approach allows the system to benefit from both the electrochemical activity of the transition metal and the stability of the polyanion structure.
2Stability of the object's composition
If a compound with polyanion structural moiety is used to suppress reactions, then electrochemical stability is improved, but interfacial resistance may still rise when transition metal is present
Solution Approach 1:
The patent optimizes specific parameters of the polyanion structure-containing compound, including the electronegativity of the center atom (1.74 or more) and the thickness of the reaction suppressor layer (1 nm to 500 nm). These parameter changes ensure both electrochemical stability and low interfacial resistance.
3Power
If transition metal is used in positive electrode active material, then battery performance is improved, but interfacial resistance rises due to reactions with solid electrolyte
Solution Approach 1:
The patent applies local quality by creating a reaction suppressor layer specifically at the interface region where the positive electrode active material contacts the solid electrolyte. This localized treatment preserves the bulk properties of the transition metal-containing material while protecting the critical interface region.
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 positive electrode active material effectively decreases interfacial resistance and suppresses the formation of high-resistance layers, leading to improved battery performance and durability by maintaining low resistance over time, even when used with high-resistance layer-forming solid electrolytes.
Implementation Method 1
a transition metal-reducing layer which has self-assembled on the surface of the positive electrode active material in contact with the reaction suppressor owing to reaction of the transition metal with the polyanion structure-containing compound
Implementation Method 2
when a compound having a polyanion structural moiety with covalent bonds is used instead of LiNbO3, such a compound substantially does not react with the positive electrode active material and the solid electrolyte material
Data Source
AI summary
A composite positive electrode active material includes: a positive electrode active material which includes a transition metal; and a reaction suppressor which is formed so as to cover a surface of the positive electrode active material, and which is made of a polyanion structure-containing compound having a cation moiety composed of a metal atom that becomes a conducting ion and having a polyanion structural moiety composed of a center atom that is covalently bonded to a plurality of oxygen atoms. A transition metal-reducing layer which has self-assembled on the surface of the positive electrode active material in contact with the reaction suppressor owing to reaction of the transition metal with the polyanion structure-containing compound, has a thickness of 10 nm or less.