Positive Electrode Coating for Stable Sulfide Solid-State Battery Interfaces
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Solution Overview
Problem
All-solid-state secondary batteries face issues with increased resistance and deteriorated battery characteristics due to the formation of resistive layers at the interface between the positive electrode active material and sulfide-based solid electrolytes, especially in high-temperature environments, and Li3PO4-based batteries suffer from low lithium ion conductivity and initial resistance.
Innovation Solution
A positive electrode active material is coated with a composition containing compounds with P-O and B-O bonds to prevent the formation of resistive layers and enhance lithium ion conductivity, using compounds like Li3PO4, Li4P2O7, LiTi2(PO4)3, LiLa(PO3)4, LiCs(PO3)2, P2O5 for P-O bonds and Li3BO3, Li2B4O7, LiBO2, Li2B2O4, B2O3, LiBa(B3O5)3 for B-O bonds, with optional S-O bond-containing compounds and inorganic particles to improve conductivity and heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sulfide-based solid electrolyte is used in the positive electrode, then high lithium ion conductivity is achieved, but resistive layers form at the interface with positive electrode active material causing increased resistance
Solution Approach 1:
The patent introduces a coating layer containing P-O and B-O bond compounds as an intermediary substance between the sulfide-based solid electrolyte and positive electrode active material. This coating layer prevents direct contact and chemical reactions between the two materials, thereby suppressing resistive layer formation while maintaining lithium ion conductivity through the intermediate structure.
Solution Approach 2:
The patent uses a composite coating layer containing multiple compounds with P-O bonds (such as Li3PO4, Li4P2O7) and B-O bonds (such as Li3BO3, Li2B4O7). This composite material approach combines the benefits of different compounds to achieve both protection against resistive layer formation and maintenance of lithium ion conductivity.
2Stability of the object's composition
If Li3PO4-based coating is used to prevent resistive layer formation, then interface stability is improved, but lithium ion conductivity decreases
Solution Approach 1:
The patent merges Li3PO4-based compounds with Li3BO3-based compounds in the coating layer. This combination allows the coating to inherit the interface stability benefits of Li3PO4 while the Li3BO3 component contributes to maintaining lithium ion conductivity, thus resolving the contradiction between stability and conductivity.
Solution Approach 2:
The patent creates a composite coating material combining P-O bond compounds and B-O bond compounds. This composite structure provides both the interface stability needed to prevent resistive layer formation and the lithium ion conductivity required for high performance, overcoming the limitations of using Li3PO4 alone.
3Object-generated harmful factors
If the positive electrode active material and solid electrolyte are kept separate with coating layers, then resistive layer formation is suppressed, but contact area between electrode materials is reduced
Solution Approach 1:
The patent applies the coating layer selectively at the interface regions where contact between positive electrode active material and solid electrolyte occurs. This localized coating approach provides protection against resistive layer formation precisely where needed, while minimizing the impact on overall contact area between electrode materials.
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 suppresses resistive layer formation and maintains high lithium ion conductivity, resulting in an all-solid-state secondary battery with high capacity and excellent heat resistance, even in high-temperature conditions.
Implementation Method 1
when a sulfide-based solid electrolyte is used as the solid electrolyte to be contained in the positive electrode mixture, such problems are likely to arise. In the positive electrode of an all-solid-state secondary battery, studies have also been conducted on providing a coating layer containing a niobium composite oxide such as LiNbO3 or other oxides such as Al2O3 or Li3PO4, and the like on the surface of a positive electrode active material
Implementation Method 2
Sulfide-based solid electrolytes with excellent ion conductivity are often used for solid electrolytes of all-solid-state secondary batteries
Data Source
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AI summary
Provided is an all-solid-state secondary battery having a high capacity and excellent heat resistance, and a positive electrode for constituting the all-solid-state secondary battery. The all-solid-state secondary battery according to the present invention is related to Goals 3, 7, 11, and 12 of the SDGs. The positive electrode for an all-solid-state secondary battery according to the present invention contains a positive electrode active material and a sulfide-based solid electrolyte, and at least a portion of the surface of the positive electrode active material is coated with a coating layer having a composition that contains a compound containing a P-O bond and a compound containing a B-O bond. Also, an all-solid-state secondary battery according to the present invention includes: at least one electrode body in which a negative electrode and a positive electrode face each other with a solid electrolyte layer interposed between the negative electrode and the positive electrode, and the positive electrode is the positive electrode for an all-solid-state secondary battery according to the present invention.