Modified Positive Electrode Active Material for Battery Stability
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Solution Overview
Problem
Current lithium-ion battery positive electrode active materials face issues such as swelling under high voltage, loss of electrochemical activity after cycles, and safety concerns due to single metal oxide coatings that are non-electrochemically active and poorly conductive, leading to reduced energy density and stability.
Innovation Solution
A modified positive electrode active material is developed, comprising a core coated with a metal oxide layer and a polymer layer, specifically polyacrylic acid, polymethyl methacrylate, or lithium polyacrylate, which enhances structural and thermal stability, improving cycle and safety performance without decreasing energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single metal oxide layer is used to coat the positive electrode active material, then the coating process is simple, but the coating is not uniform and effective, limiting the improvement effect
Solution Approach 1:
The patent uses a composite coating structure consisting of an inner metal oxide layer (Al2O3, TiO2, or ZrO2) and an outer lithium phosphate layer. The metal oxide layer provides structural stability and prevents swelling, while the lithium phosphate layer improves lithium ion conductivity and electrochemical activity. This composite structure resolves the contradiction by achieving both uniform effective coating and improved battery performance.
2Stability of the object's composition
If a metal oxide layer is coated on the positive electrode active material, then surface structure stability is improved, but the non-electrochemically active metal oxide decreases specific capacity and energy density
Solution Approach 1:
The patent applies different functional layers to different regions/depths of the electrode material surface. The inner metal oxide layer (0.1-5 nm thick) provides local structural stabilization at the core interface, while the outer lithium phosphate layer (0.1-10 nm thick) provides local electrochemical activity and ion conductivity at the electrolyte interface. This local differentiation allows each layer to perform its specialized function without compromising overall capacity.
Solution Approach 2:
The composite coating of metal oxide inner layer plus lithium phosphate outer layer creates a synergistic structure where the metal oxide provides structural stability and the lithium phosphate restores electrochemical activity. This composite approach overcomes the limitation of single metal oxide coatings by combining materials with complementary properties, thereby maintaining both stability and capacity.
3Duration of action of stationary object
If a metal oxide layer is coated on the positive electrode active material, then cycle performance under high voltage is improved, but the metal oxide layer is insufficient to cover the material uniformly
Solution Approach 1:
The patent introduces a two-layer coating system where the metal oxide layer acts as an intermediary between the electrode material core and the lithium phosphate outer layer. The metal oxide layer first forms a stable foundation that prevents material swelling, then the lithium phosphate layer is deposited uniformly on top. This intermediary structure facilitates uniform coating formation and enhances cycle performance through combined protective effects.
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 modified material significantly enhances the cycle and safety performance of electrochemical energy storage devices by effectively isolating the core from the electrolyte, promoting ion transport, and maintaining adhesive and electrical contact, thus preventing capacity loss and ensuring stability under high voltage conditions.
Implementation Method 1
adding a salt solution of metal element into the suspension and stirring to react
Implementation Method 2
drying and calcining to make a metal oxide layer coated on a surface
Implementation Method 3
dissolving a polymer in a solvent and then adding the substance obtained in the step (1), stirring to react
Implementation Method 4
after the reaction, standing-by and taking underlayer solid material to dry
Implementation Method 5
promoting ion transport, and maintaining adhesive and electrical contact
Implementation Method 6
effectively isolating the core from the electrolyte
Data Source
AI summary
The present disclosure provides a modified positive electrode active material. The modified positive electrode active material comprises a positive electrode active material inner core; a metal oxide layer comprising a metal oxide and coated on a surface of the positive electrode active material inner core; and a polymer layer comprising a polymer and coated on a surface of the metal oxide layer, the polymer being one or more selected from a group consisting of polyacrylic acid, polymethyl methacrylate, polyacrylamide and lithium polyacrylate. The modified positive electrode active material of the present disclosure has better structure stability and thermal stability, when the modified positive electrode active material is applied in the electrochemical energy storage device, cycle performance and safety performance of the electrochemical energy storage device can be significantly improved without decreasing energy density of the electrochemical energy storage device.