Glass-Coated Positive Electrode for High-Potential Cycle Stability
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges in achieving stable performance, high charge and discharge capacity, cycle reliability, safety, and cost effectiveness due to the instability of positive electrode active materials at high potentials and temperatures.
Innovation Solution
A positive electrode comprising a first composite oxide, a second composite oxide, and glass with lithium-ion conductivity, where the surface of the first active material is coated with glass and the second active material, and optionally a conductive material like graphene or carbon nanotubes, enhancing stability and cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a high potential is applied to the positive electrode to achieve high capacity, then the charge capacity increases, but the crystal structure stability deteriorates causing significant deterioration in charge and discharge cycles
Solution Approach 1:
A glass coating layer is applied as an intermediary between the positive electrode active material and the electrolyte. This glass layer contains lithium ions and provides lithium-ion conductivity while protecting the electrode material from degradation at high potentials, thereby maintaining both high capacity and cycle stability
Solution Approach 2:
The positive electrode is constructed as a composite system combining the active material (lithium cobalt oxide or lithium nickel-cobalt-manganese oxide) with a glass coating layer. This composite structure allows the electrode to achieve high capacity through the active material while the glass coating provides structural stability and protection during cycling
2Use of energy by moving object
If the positive electrode active material is exposed to high potential to achieve high capacity, then the energy density increases, but the safety deteriorates due to crystal structure reduction
Solution Approach 1:
The glass coating acts as a protective intermediary that prevents direct exposure of the active material to harsh conditions during high potential operation. This intermediary layer maintains safety by preventing structural degradation while allowing the system to operate at high potentials for high energy density
Solution Approach 2:
The glass coating modifies the local chemical and physical parameters at the electrode surface, creating a stable environment that prevents harmful reactions even when the bulk electrode operates at high potentials for high energy density
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 provides a positive electrode active material that maintains stability at high potentials and temperatures, improves charge and discharge cycle performance, and increases the safety and reliability of secondary batteries.
Implementation Method 1
The glass has lithium-ion conductivity
Data Source
AI summary
A positive electrode and a secondary battery with little deterioration due to charge and discharge are provided. A positive electrode and a secondary battery with high electrode density are provided. Alternatively, a positive electrode and a secondary battery with excellent rate characteristics are provided. The positive electrode contains a positive electrode active material and a coating material. The coating material covers at least part of a surface of the positive electrode active material, and the positive electrode active material contains lithium cobalt oxide containing magnesium, fluorine, aluminum, and nickel. The lithium cobalt oxide includes a region with the highest concentration of one or more selected from the magnesium, the fluorine, and the aluminum in a surface portion. The coating material is preferably one or more selected from glass, carbon black, graphene, and a graphene compound.