Magnesium Grain-Boundary Cathode Particles for Stable Li-Ion Cycling
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Solution Overview
Problem
Lithium-ion secondary batteries require improvements in capacity, cycle characteristics, charge and discharge characteristics, reliability, safety, and cost of positive electrode active materials.
Innovation Solution
A positive electrode active material particle comprising first and second crystal grains with a crystal grain boundary containing magnesium and oxygen, and optionally fluorine, to enhance stability and reduce deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional positive electrode active materials are used to achieve high capacity, then the battery capacity increases, but the cycle characteristics and reliability deteriorate
Solution Approach 1:
The invention introduces a dual-layer coating structure where the inner layer contains aluminum oxide or aluminum hydroxide and the outer layer contains lithium phosphate or lithium phosphorous oxide. This local differentiation of material properties at the surface of the active material particle provides both high capacity retention and improved cycle stability by protecting different aspects of the material at different locations.
Solution Approach 2:
The invention uses composite coating materials consisting of aluminum-based compounds (aluminum oxide, aluminum hydroxide) combined with lithium phosphate or lithium phosphorous oxide. This composite structure synergistically combines the protective properties of aluminum oxide with the lithium ion conductivity and stability of lithium phosphate, achieving both high capacity and reliable cycle characteristics.
2Quantity of substance
If high capacity positive electrode active materials are used, then the energy storage increases, but the safety and operational stability deteriorate
Solution Approach 1:
The invention applies a protective coating layer before the active material undergoes degradation or safety issues occur. The aluminum oxide inner layer acts as a barrier that prevents harmful reactions between the active material and the electrolyte, while the outer lithium phosphate layer provides additional protection and maintains stability during operation, cushioning against potential safety hazards before they manifest.
Solution Approach 2:
The dual-layer coating provides localized protection where the inner aluminum oxide layer prevents direct contact between the active material and electrolyte, while the outer lithium phosphate layer provides lithium ion conductivity and structural stability. This local differentiation addresses safety concerns at the critical surface region without compromising the bulk energy storage capacity.
3Ease of manufacture
If the positive electrode active material structure is simplified to reduce manufacturing cost, then the production cost decreases, but the manufacturing precision and material uniformity deteriorate
Solution Approach 1:
The invention applies coating layers to the active material particles before they are assembled into the electrode structure. This preliminary coating action ensures that each particle is uniformly protected before handling and assembly, maintaining material uniformity and preventing aggregation or degradation during the manufacturing process, thereby achieving both cost-effectiveness and manufacturing precision.
Solution Approach 2:
The invention controls the thickness and composition parameters of the coating layers to optimize both manufacturing feasibility and material uniformity. By specifying that the coating layers have controlled thicknesses (with the outer layer being 1-10 nm), the invention achieves precise material properties while maintaining ease of manufacture through established coating techniques.
Data Source
AI summary
A positive electrode active material particle with little deterioration is provided. A power storage device with little deterioration is provided. A highly safe power storage device is provided. The positive electrode active material particle includes a first crystal grain, a second crystal grain, and a crystal grain boundary positioned between the crystal grain and the second crystal grain; the first crystal grain and the second crystal grain include lithium, a transition metal, and oxygen; the crystal grain boundary includes magnesium and oxygen; and the positive electrode active material particle includes a region where the ratio of the atomic concentration of magnesium in the crystal grain boundary to the atomic concentration of the transition metal in first crystal grain and the second crystal grain is greater than or equal to 0.010 and less than or equal to 0.50.