Partial Cathode Coating for Ni-Rich Surface Stability
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Solution Overview
Problem
Lithium ion batteries face issues with undesired reactions on the surface of cathode active materials, leading to electrolyte decomposition and stability problems, particularly in nickel-rich electrode active materials used in all-solid-state batteries, where existing solutions do not consistently improve the electrochemical properties.
Innovation Solution
A process involving sequential treatments of electrode active materials with metal alkyl compounds, oxidants, and specific alkoxide compounds in the gas phase, resulting in a partially coated material with a non-homogeneous coating that protects the surface while maintaining lithium exchange efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If nickel-rich electrode active materials are used to increase energy density, then energy density is improved, but surface stability deteriorates leading to undesired reactions and electrolyte decomposition
Solution Approach 1:
A coating layer comprising lithium aluminate (LiAlO3) and/or lithium titanate (Li2TiO3) is applied to the surface of the nickel-rich electrode active material. This coating acts as an intermediary barrier between the reactive nickel-rich material and the electrolyte, preventing direct contact and undesired reactions while allowing lithium ion exchange to proceed, thus resolving the contradiction between high energy density and surface stability
Solution Approach 2:
The coating is applied selectively to the surface region of the electrode active material particles, creating a localized protective layer with different chemical composition and properties than the bulk material. The surface region contains the stable lithium aluminate and/or lithium titanate phases, while the interior maintains the high-nickel composition for energy density, thus achieving local optimization of both stability and energy storage capability
2Reliability
If the surface is coated to protect against reactions, then surface stability is improved, but lithium exchange efficiency deteriorates
Solution Approach 1:
The coating layer is designed with specific compositional parameters (lithium aluminate and/or lithium titanate) and controlled thickness (0.1-5 nm, 6-15 nm, or 16-50 nm) to optimize its properties. By adjusting these parameters, the coating provides sufficient protection against reactions while maintaining adequate lithium ion conductivity, thus resolving the contradiction between surface stability and lithium exchange efficiency
3Quantity of substance
If washing with water is performed to remove free LiOH or Li2CO3, then surface purity is improved, but electrochemical properties deteriorate
Solution Approach 1:
Instead of water washing which damages electrochemical properties, a dry coating process using lithium aluminate and/or lithium titanate is applied as an intermediary protective layer. This approach removes harmful surface compounds through the coating process itself without requiring water washing, thus maintaining electrochemical properties while achieving surface purification
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 process achieves excellent electrochemical properties, including long-term cycling stability and thermal stability, for nickel-rich electrode active materials, especially in all-solid-state batteries, with improved energy density and retention rates.
Implementation Method 1
treating said electrode active material with at least one metal alkyl compound or at least one metal alkoxide... treating the material obtained in step (b) with an oxidant or moisture... treating the material obtained from step (c) with a compound according to formula M1OR1... wherein steps (b) to (e) are performed in the gas phase
Implementation Method 2
treating the material obtained in step (b) with an oxidant or moisture
Data Source
AI summary
Disclosed herein is a process for making an at least partially coated electrode active material. The process includes:(a) providing an electrode active material according to general formula Li1+xTM1−xO2, where TM includes Ni, Mn and, optionally, Co and at least one metal selected from Al, Nb, Ta, Zr, Ti and Zr, where x is between 0.05 and 0.2, and where the Ni content is at least 55 mol-% referring to TM,(b) treating said electrode active material with a metal alkyl compound,(c) treating the material obtained in step (b) with an oxidant or moisture,(d) treating the material obtained from step (c) with a compound according to formula M1OR1 where M1 is selected from the group consisting of Li, Na and K and where R1 is selected from the group consisting of isopropyl, n-butyl and tert.-butyl, and(e) repeating the sequence of steps (b) to (d) from 1-30 times.