Ternary Cathode Composite Coating for Solid-State Battery Interfaces
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Solution Overview
Problem
Existing ternary NCM materials for lithium-ion batteries face issues such as low discharge efficiency, poor high-rate battery performance, and poor cycle stability due to lithium-nickel cation mixing and interfacial reactions with solid electrolytes, which affect the battery's cycling capacity.
Innovation Solution
A ternary composite material is developed by in-situ coating a fast ion conductor, represented by the formula LixMyFx+3y, on the surface of the ternary material, where M is a trivalent metal ion, improving the interfacial contact and lithium ion conductivity, and using a method involving mixing lithium and fluorine sources with a trivalent metal compound, followed by sintering in a pure oxygen atmosphere to enhance the coating's stability and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If surface coating modification is applied using traditional coating materials (Al2O3, TiO2, SiO2, ZrO2, La2O3, Y2O3, ZnO), then the surface stability is improved, but the ionic conductivity is insufficient and the electrochemical reaction rate is not accelerated
Solution Approach 1:
The patent changes the chemical composition parameters of the coating material by introducing lithium-containing compounds (such as LiF, Li2SiO3, Li3PO4) combined with traditional coating materials. This parameter change enables the coating to simultaneously achieve surface stability and high ionic conductivity, resolving the contradiction between stability and reliability.
Solution Approach 2:
The patent employs composite coating materials that combine lithium-containing compounds with traditional coating materials like Al2O3, TiO2, or SiO2. This composite approach allows the coating to exhibit both the surface stability of traditional materials and the ionic conductivity of lithium-containing compounds, effectively resolving the technical contradiction.
2Ease of manufacture
If dry coating method is used to directly mix and sinter nano-sized coating material with substrate, then the manufacturing process is simplified, but the coating adhesion is poor and coatings are easily peeled off
Solution Approach 1:
The patent applies preliminary action by performing surface treatment on the substrate before coating to enhance surface energy and roughness. This preliminary preparation creates better anchoring conditions for the coating, significantly improving adhesion strength while maintaining the simplicity of the dry coating process.
Solution Approach 2:
The patent introduces a bonding agent or coupling agent as an intermediary layer between the substrate and the coating material. This intermediary enhances the chemical bonding between the substrate surface and the coating, preventing peeling while keeping the manufacturing process relatively simple.
3Quantity of substance
If ternary NCM material is used with high nickel content for ultra-high capacity, then the capacity is improved, but the lithium-nickel cation mixing increases and cycle stability deteriorates
Solution Approach 1:
The patent applies local quality by creating a gradient or core-shell structure where the interior maintains high nickel content for capacity while the surface layer has modified composition to prevent cation mixing. This local differentiation allows the material to simultaneously achieve ultra-high capacity and good cycle stability.
Solution Approach 2:
The patent uses composite structure combining high-nickel ternary NCM material with surface-modified layers or dopants. This composite approach allows the bulk material to provide high capacity while the surface modification prevents lithium-nickel cation mixing, thereby maintaining cycle stability.
4Reliability
If contact between ternary NCM and solid electrolyte is increased to improve interface contact, then the interfacial resistance decreases, but interfacial reactions occur and cycling capacity is reduced
Solution Approach 1:
The patent introduces a lithium-containing compound coating as an intermediary layer between the ternary NCM and the solid electrolyte. This intermediary layer improves interfacial contact and reduces resistance while simultaneously acting as a protective barrier that prevents harmful interfacial reactions, thus resolving the contradiction between good contact and reaction prevention.
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 improves the high-voltage resistance and cycle stability of the battery, reduces side reactions, and enhances lithium ion conduction capacity, leading to improved charge-discharge performance and capacity retention.
Implementation Method 1
the fast ion conductor being represented by formula (I); LixMyFx+3y where M is a trivalent metal ion; 1≤x≤3, 1≤y≤3
Implementation Method 2
sintering in a pure oxygen atmosphere to enhance the coating's stability and conductivity
Data Source
AI summary
The present application provides a ternary composite material for an all-solid-state battery, including a ternary material and a fast ion conductor of LixMyFx+3y in-situ coated on the surface of the ternary material; the application also provides a preparation method for ternary composite material and its application. On the one hand, the presence of LixMyFx+3y in the ternary composite material provided by the present application improves the interfacial contact between the ternary positive electrode material and the solid electrolyte, improves the high-voltage resistance performance of the solid electrolyte, and reduces side reactions between the ternary positive electrode and the solid electrolyte and the electrolyte decomposition caused by high voltage. On the other hand, the fast ion conductor property of LixMyFx+3y effectively improves the lithium ion conductivity of the ternary positive electrode material and reduces the residual lithium on the surface of the ternary positive electrode material.