LFP Cathode Coating with NASICON and Carbon for Higher Energy Density
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Solution Overview
Problem
Conventional lithium iron phosphate-based lithium ion secondary batteries suffer from low energy density due to poor electronic and ionic conductivity, which limits their application in large-scale electric devices.
Innovation Solution
A positive active material is developed with a substrate of LiFe1-aM1aPO4 and a coating layer comprising a fast ion conductor of a NASICON structure and a carbon coating layer, enhancing both ionic and electronic conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional lithium iron phosphate material is used, then safety performance and cycle performance are improved, but energy density deteriorates
Solution Approach 1:
The patent applies composite materials by creating a core-shell structure where lithium iron phosphate particles are coated with a dual-layer coating comprising a fast ion conductor layer and a carbon coating layer. This composite structure combines the safety and cycle performance advantages of lithium iron phosphate with enhanced ionic and electronic conductivity, thereby improving energy density while maintaining reliability
Solution Approach 2:
The patent applies local quality by modifying only the surface region of the lithium iron phosphate particles through the coating process, while preserving the bulk material properties. The coating layers are applied locally on the particle surface to enhance conductivity without altering the core lithium iron phosphate structure, thus maintaining safety and cycle performance while improving energy density
2Ease of manufacture
If conventional lithium iron phosphate material is used, then cost is reduced, but energy density deteriorates
Solution Approach 1:
The patent uses composite materials with cost-effective components - the fast ion conductor layer uses commonly available materials like Li3PO4 or Li2SiO3, and the carbon coating layer uses standard carbon sources. This approach maintains low manufacturing cost while significantly improving energy density through enhanced conductivity
Solution Approach 2:
The patent applies parameter changes by optimizing the thickness and composition parameters of the coating layers. The fast ion conductor layer thickness is controlled at 1-10 nm and carbon coating at 1-5 nm, with specific compositional ratios that maximize energy density improvement while minimizing material cost and manufacturing complexity
3Duration of action of stationary object
If lithium iron phosphate material is used, then cycle performance is improved, but ionic conductivity deteriorates
Solution Approach 1:
The patent introduces a fast ion conductor layer as an intermediary between the lithium iron phosphate particles and the electrolyte. This intermediate layer with higher ionic conductivity facilitates faster lithium ion transport while maintaining the stable crystal structure of lithium iron phosphate, thereby improving both ionic conductivity and cycle performance
Solution Approach 2:
The dual-layer coating creates a composite structure where the fast ion conductor layer provides high ionic conductivity pathways and the carbon coating layer provides electronic conductivity and structural stability. This composite approach simultaneously enhances ionic conductivity and maintains excellent cycle performance
4Reliability
If lithium iron phosphate material is used, then electronic conductivity is improved, but energy density deteriorates
Solution Approach 1:
The patent applies composite materials by adding a carbon coating layer on the outer surface of the fast ion conductor layer. This carbon layer provides excellent electronic conductivity while the thin film structure (1-5 nm) ensures that the majority of the active lithium iron phosphate material remains available for electrochemical reactions, thus improving energy density while enhancing electronic conductivity
Solution Approach 2:
The carbon coating is applied locally on the particle surface to provide electronic conductivity pathways at the interface with the electrolyte and current collector, while the bulk lithium iron phosphate material maintains its high capacity characteristics. This localized modification improves electronic conductivity without sacrificing energy density
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 improved active material significantly increases the energy density of lithium ion secondary batteries while maintaining excellent cycle performance, addressing the limitations of conventional lithium iron phosphate batteries.
Implementation Method 1
the coating layer includes a fast ion conductor layer and a carbon coating layer... the fast ion conductor layer includes a fast ion conductor of a NASICON structure
Implementation Method 2
the coating layer includes a fast ion conductor layer and a carbon coating layer... solving defects of poor electronic conductivity and ionic conductivity
Implementation Method 3
the fast ion conductor layer includes a fast ion conductor of a NASICON structure as shown in formula (II), Li3-bFe2-bM2b(PO4)3
Data Source
AI summary
A positive active material is provided. In some embodiments, the positive material includes: a substrate and a coating layer coating the substrate, wherein the coating layer includes a fast ion conductor layer and a carbon coating layer, the substrate includes more than one compound of formula (I): LiFe1-aM1aPO4 formula (I), in formula (I), M1 is more than one selected from Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb and Ti, and 0≤a≤0.01; the fast ion conductor layer includes a fast ion conductor of a NASICON structure shown in formula (II), Li3-bFe2-bM2b(PO4)3 formula (II), in formula (II), M2 is more than one selected from Ti, Zr, Hf, Ge and Sn with valence of +4, and 0≤b≤1.