Cerium-Coated High-Nickel Cathode Material for Stable Li-Ion Cycling
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Solution Overview
Problem
Secondary batteries using nickel-containing positive electrode materials with high nickel content suffer from low initial Coulombic efficiency, low initial discharge capacity, and poor high-temperature performance due to surface issues such as high content of low-activity residual lithium and disordered rock-salt layers, which hinder lithium ion re-intercalation and cause side reactions with electrolytes.
Innovation Solution
A positive electrode active material is developed with a lithium-containing nickel-based transition metal oxide core coated with a cerium-containing layer, optionally including cobalt and fluorine, to activate lithiated rock-salt structures and form a compact coating that enhances lithium-ion transmission and reduces erosion by electrolyte byproducts, accompanied by a second coating layer of aluminum and boron to suppress oxygen defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If nickel-containing positive electrode materials with high nickel content are used, then energy density is increased, but initial Coulombic efficiency deteriorates
Solution Approach 1:
A coating layer comprising cerium element is applied on the surface of the high-nickel positive electrode active material. This coating layer acts as an intermediary between the high-nickel material and the electrolyte, preventing harmful interactions while maintaining the high energy density benefits of the nickel-rich core material.
Solution Approach 2:
The coating layer changes the surface chemical composition and structure of the positive electrode material. By introducing cerium element and forming compounds like LiCeO2 with high ionic conductivity, the surface parameters are optimized to improve initial Coulombic efficiency while preserving the bulk high-nickel composition for energy density.
2Use of energy by moving object
If nickel-containing positive electrode materials with high nickel content are used, then energy density is increased, but high-temperature performance deteriorates
Solution Approach 1:
The cerium-containing coating layer serves as a protective intermediary that shields the high-nickel core material from thermal degradation and electrolyte decomposition at high temperatures. This coating stabilizes the interface and prevents harmful side reactions that would otherwise occur at elevated temperatures.
Solution Approach 2:
The positive electrode material is structured as a composite with a high-nickel core for energy density and a cerium-containing coating layer for thermal and chemical stability. This composite structure combines the advantages of both materials: the nickel-rich core provides high capacity while the cerium-based shell provides high-temperature performance.
3Quantity of substance
If high nickel content is used, then capacity is improved, but surface stability deteriorates due to residual lithium and rock-salt layers
Solution Approach 1:
The coating process effectively removes or transforms the unstable residual lithium and disordered rock-salt layers on the surface of the high-nickel material. By reacting with these surface impurities and forming stable cerium-based compounds, the coating extracts the harmful surface components and replaces them with stable structures.
Solution Approach 2:
The coating layer fundamentally changes the surface chemical parameters by introducing cerium elements that form stable compounds. This transforms the unstable surface composition (with residual lithium and rock-salt structures) into a stable surface layer that maintains structural integrity and prevents further degradation.
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 initial Coulombic efficiency, reduces direct current internal resistance, and enhances high-temperature cycling and storage performance by activating lithium and forming protective layers on the core surface.
Implementation Method 1
the oxide containing cerium element can react with residual lithium on the core surface to form LiCeO2 with high ionic conductivity
Implementation Method 2
the cerium element can activate a lithiated rock-salt structure on the core surface, making lithium in the lithiated rock-salt structure more active
Implementation Method 3
the oxide containing cerium element is likely to form a compact coating layer on the core surface, which can reduce erosion of active sites of the core by electrolyte byproducts
Data Source
AI summary
A positive electrode active material, a preparation method thereof, a positive electrode plate, a secondary battery, and an electric apparatus. The positive electrode active material includes: a core and a first coating layer applied on at least a portion of an outer surface of the core, the core includes a lithium-containing nickel-based transition metal oxide, and the first coating layer includes cerium element. In the lithium-containing nickel-based transition metal oxide, a molar proportion of nickel element among all elements excluding lithium element and oxygen element ranges from 50% to 100%.