Fast Ionic Conductor Coating for High-Voltage Li-Ion Cathodes
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Solution Overview
Problem
Lithium-ion battery cathode materials face issues with corrosion and structural instability due to direct contact with electrolytes, leading to rapid capacity decay and safety concerns, as existing coatings like Al2O3 and AlPO4 either reduce electronic conductivity or fail to protect against high-voltage corrosion.
Innovation Solution
A fast ionic conductor coated lithium-transition metal oxide material with a chemical formula (1−x)Li1+a(Ni(1−m−n)ConMnm)1−bMbO2·xLicAldTieM′fM″g(PO4)3 is developed, featuring a layered structure and a preparation method involving solid-phase calcination and precipitation-calcination processes to enhance lithium ion conductivity and structural stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal oxide coating materials (Al2O3, TiO2, ZrO2) are used to protect cathode material, then structural stability and corrosion resistance are improved, but electronic conductivity decreases and capacity is reduced
Solution Approach 1:
The patent uses a composite coating structure combining metal oxide layer (Al2O3, TiO2, or ZrO2) with lithium phosphate (Li3PO4) layer. The metal oxide provides structural stability and corrosion resistance, while the lithium phosphate layer maintains electronic conductivity and facilitates lithium ion transport. This composite approach resolves the contradiction by combining materials with complementary properties.
Solution Approach 2:
The coating is applied as a thin layer (1-10 nm) on the surface of the cathode material particles, providing protection only where needed at the material-electrolyte interface. This localized coating maintains the bulk electronic conductivity of the cathode material while protecting the surface from corrosion and electrolyte contact.
2Reliability
If phosphate coating materials (AlPO4, Li3PO4) are used to improve capacity retention and lithium ion diffusion, then capacity retention rate and thermal stability are improved, but protection ability under high voltage is limited
Solution Approach 1:
The patent combines metal oxide coating (providing high voltage stability and corrosion resistance) with lithium phosphate coating (providing capacity retention and lithium ion diffusion). The metal oxide component specifically addresses high voltage corrosion protection, while the lithium phosphate component maintains capacity retention, together resolving the limitation of phosphate coatings alone.
3Reliability
If Al2O3 coating layer is formed to inhibit side reactions with electrolyte, then cycle performance and safety are improved, but internal resistance increases and specific discharge capacity is sacrificed
Solution Approach 1:
The patent uses an ultra-thin Al2O3 coating layer (1-10 nm) that provides sufficient protection against side reactions and improves cycle performance, while minimizing the increase in internal resistance. The thin layer is thick enough to provide protection but thin enough to allow efficient lithium ion transport and maintain low resistance.
Solution Approach 2:
The combination of ultra-thin metal oxide layer with lithium phosphate layer creates a composite coating that provides protection against side reactions while maintaining low internal resistance. The lithium phosphate component facilitates lithium ion transport, compensating for any resistance increase from the metal oxide layer.
4Loss of substance
If coating materials are applied to reduce contact area between cathode material and electrolyte, then dissolution of transition metals is reduced, but coating uniformity and adhesion become problematic
Solution Approach 1:
The patent applies the coating to the surface of pre-formed cathode material particles through precipitation methods. The coating precursors are introduced before final calcination, allowing uniform distribution and adhesion to the particle surface, thereby reducing transition metal dissolution while achieving consistent coating coverage.
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 provides improved cycle performance and safety at high voltages, with lower impedance and enhanced lithium ion conductivity, reducing the risk of surface layer delamination and corrosion, while maintaining capacity retention.
Implementation Method 1
a fast ionic conductor coated lithium-transition metal oxide material... enhanced lithium ion conductivity
Implementation Method 2
preparation method involving solid-phase calcination and precipitation-calcination processes
Implementation Method 3
Coating other materials on the surface of lithium-containing transition metal oxide cathode materials can effectively reduce the contact area between the cathode material and an electrolyte, reduce the dissolution amount of the transition metals
Data Source
AI summary
The invention belongs to the technical field of lithium ion battery materials, and discloses a fast ionic conductor coated lithium-transition metal oxide material having a chemical formula of (1−x)Li1+a (Ni(1−m−n)ConMnm) 1−bMbO2·xLicAldTieM′fM″g (PO4)3 and a preparation method thereof. The fast ionic conductor coated lithium-transition metal oxide material of the present invention has lower impedance, excellent cycle performance and safety performance under high voltage, especially when the charging voltage is greater than 4.62V, 4.65V, or higher. The Lithium-transition metal oxide can be obtained by a primary calcination, and the final product of lithium-transition metal oxide material coated with fast ionic conductor can be obtained by a secondary calcination.