Layered Lithium Metal Phosphate Cathode Coating for Cycle Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium iron phosphate cathode active materials in lithium-ion batteries face challenges such as low energy density, poor capacity utilization, and poor cycle performance due to issues like low electronic and ionic conductivity and structural instability, particularly exacerbated by the Jahn-Taylor effect and transition metal dissolution.
Innovation Solution
A cathode active material is developed with a lithium metal phosphate core coated by a hexagonal fast ion conductor and an orthorhombic fast ion conductor, along with a carbon layer, optimizing the material composition and phase structure to enhance conductivity and stability, using a simple preparation method involving sintering treatments in controlled atmospheres.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium metal phosphate is used as cathode active material to improve theoretical specific capacity and operating voltage platform, then energy density is improved, but capacity utilization and cycle performance deteriorate due to poor ionic and electronic conductivity
Solution Approach 1:
The patent applies composite materials by creating a core-shell structure where lithium metal phosphate core is coated with lithium phosphate shell. This composite structure combines the high energy density advantage of lithium metal phosphate with the good stability and ionic conductivity of lithium phosphate, thereby improving both energy density and cycle performance simultaneously
Solution Approach 2:
The patent applies local quality by modifying only the surface region of the cathode active material particles with a lithium phosphate coating layer. The core maintains its high-capacity lithium metal phosphate composition while the surface shell provides improved ionic conductivity and structural stability, resolving the contradiction between energy density and cycle performance through localized property modification
2Use of energy by moving object
If doping elements are added to improve theoretical specific capacity and operating voltage platform, then energy density is improved, but capacity utilization deteriorates due to poor ionic and electronic conductivity
Solution Approach 1:
The patent uses composite materials by forming a lithium phosphate coating shell around the doped lithium metal phosphate core. This composite structure compensates for the poor ionic and electronic conductivity caused by doping, thereby improving capacity utilization while maintaining the high energy density benefits of the doped core material
Solution Approach 2:
The lithium phosphate coating shell acts as an intermediary layer that facilitates ion and electron transport between the doped lithium metal phosphate core and the electrolyte. This intermediary coating improves the interfacial ionic and electronic conductivity, thereby enhancing capacity utilization without compromising the energy density of the doped core
3Reliability
If simple coating methods are used to improve ionic and electronic conductivity, then conductivity is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges the coating process with the sintering process by performing both operations in a single continuous manufacturing step. The slurry containing lithium phosphate coating precursors is applied to the lithium metal phosphate particles, and then both coating formation and sintering are accomplished simultaneously in one thermal treatment process, reducing manufacturing complexity while improving conductivity
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 cathode active material exhibits improved ionic and electronic conductivity, structural stability, and enhanced cycle performance, leading to higher energy density and safety in lithium-ion batteries.
Implementation Method 1
a first coating layer covering at least part of a surface of the core; and a second coating layer covering at least part of a surface of the first coating layer. the first coating layer includes a hexagonal fast ion conductor; and/or the second coating layer includes an orthorhombic fast ion conductor
Implementation Method 2
mixing a first lithium source, a first metal source, and a first phosphorus source to obtain a first slurry, and performing a first sintering treatment on the first slurry in an inactive atmosphere to obtain a core
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Provided are a cathode active material and a preparation method therefor, and a battery. The cathode active material includes: a core including lithium metal phosphate; a first coating layer covering at least part of a surface of the core; and a second coating layer covering at least part of a surface of the first coating layer. An XRD intensity at a 2θ diffraction angle in a range of 35.5° to 35.7° of the cathode active material is S1, an XRD peak intensity at a 2θ diffraction angle in a range of 24.1° to 25.4° of the cathode active material is S2, and S2/S1 is (0.005 to 0.05): 1. An XRD peak intensity at a 2θ diffraction angle in a range of 28.8° to 29.2° of the cathode active material is S3, and S3/S1 is (0.005 to 0.05): 1.