High-Nickel Cathode Surface Layer for High-Temperature Stability
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Solution Overview
Problem
High-nickel positive electrode active materials in electrochemical apparatuses experience phase transitions and structural damage due to volume changes, affecting high-temperature storage performance.
Innovation Solution
Incorporating a lithium composite oxide with a rock salt phase structure and a tungsten element surface layer in the positive electrode active material, and using an ionic liquid with specific mass percentages in the electrolyte to stabilize the structure and enhance high-temperature performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-nickel positive electrode active materials are used to increase energy density, then energy density is improved, but structural stability deteriorates due to phase transition and volume changes
Solution Approach 1:
The patent applies local quality by creating a rock salt phase surface layer specifically on the positive electrode active material particles. This surface layer has different structural properties (rock salt phase) compared to the bulk material (layered structure), providing localized structural stability at the surface where phase transitions occur, while maintaining the high-capacity layered structure in the bulk for high energy density.
Solution Approach 2:
The patent creates a composite structure where the positive electrode active material consists of a layered structure core with a rock salt phase surface layer coating. This composite material combines the advantages of both structures: the layered structure provides high capacity for lithium insertion/extraction, while the rock salt phase surface layer provides structural stability and prevents harmful phase transitions.
2Ease of manufacture
If high-nickel positive electrode active materials are used to reduce costs, then cost is improved, but high-temperature storage performance deteriorates due to structural damage
Solution Approach 1:
The patent applies parameter changes by modifying the surface composition and phase structure of the positive electrode active material. By controlling the formation process parameters to create a rock salt phase surface layer with specific tungsten content (0.01-1 mass%), the material achieves improved high-temperature storage performance while maintaining cost-effectiveness through the use of high-nickel composition.
3Stability of the object's composition
If rock salt phase surface layer with tungsten element is formed to improve structural stability, then structural stability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by forming the rock salt phase surface layer during the initial formation process of the positive electrode active material, before the battery enters service. This preliminary structural modification ensures long-term structural stability during cycling and storage without requiring additional complex manufacturing steps later in the production process or during battery operation.
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 controlled rock salt phase and ionic liquid composition improve the structural stability and reduce gas production during high-temperature storage, enhancing the electrochemical apparatus' performance.
Implementation Method 1
as the content of nickel increases, the positive electrode active materials undergo phase transition, which causes volume changes and structural damage
Implementation Method 2
the ionic liquid can be fully dissolved in the electrolyte and complexed with the tungsten element on the surface of a positive electrode, thereby improving high-temperature storage performance
Data Source
AI summary
An electrochemical apparatus includes a positive electrode plate and an electrolyte. The positive electrode plate includes a positive electrode active material layer. The positive electrode active material layer includes a positive electrode active material. The positive electrode active material includes a lithium composite oxide. The lithium composite oxide includes the lithium element and at least one element selected from the cobalt element, the nickel element, the manganese element, and the aluminum element. A surface layer of the positive electrode active material has a rock salt phase structure and includes the tungsten element. Based on a total mass of the positive electrode active material, a mass percentage of the tungsten element is B, where 0.01%≤B≤1%. The electrolyte includes an ionic liquid represented by a formula R: