Coated Lithium Battery Cathode Material for Cycle-Life and Density
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in achieving high active mass density and improved cycle-life characteristics due to limitations in existing positive active materials.
Innovation Solution
A positive active material for rechargeable lithium batteries is developed, comprising a core with a lithium intercalation compound coated with a layered phase of Li2MO3 and a solid electrolyte compound represented by Chemical Formula Li1.3+4xAl0.3M1.7−x(PO4)3, where M is selected from titanium (Ti), chromium (Cr), gallium (Ga), iron (Fe), scandium (Sc), indium (In), yttrium (Y), lanthanum (La), magnesium (Mg), and strontium (Sr), enhancing ion conductivity and electrochemical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating compound is applied on the surface of the core to improve cycle-life characteristics, then the electrochemical performance is enhanced, but the active mass density decreases due to the additional coating layer
Solution Approach 1:
The coating compound is applied only on the surface of the core particles rather than throughout the entire structure. This localized coating provides protective and electrochemical benefits at the interface where reactions occur, while minimizing the overall mass addition and preserving the high active mass density of the bulk core material.
Solution Approach 2:
The positive active material is designed as a composite structure combining a core material (such as lithium cobalt oxide, lithium nickel cobalt manganese oxide, or lithium manganese oxide) with a coating compound containing Li2MO3 and NASICON-type solid electrolyte. This composite structure integrates the high capacity of the core with the improved stability and ion conductivity of the coating, achieving both enhanced cycle-life and maintained mass density.
2Reliability
If the amount of coating compound is increased to improve electrochemical performance, then the cycle-life is extended, but the manufacturing cost and processing complexity increase
Solution Approach 1:
The coating compound is applied in a controlled, moderate amount rather than as a thick uniform layer. This partial coating provides sufficient protective and electrochemical functions to extend cycle-life while avoiding the excessive material usage and processing complexity that would result from heavy coating applications. The coating amount is optimized to achieve the minimum necessary coverage for performance improvement.
3Productivity
If the specific surface area is increased to enhance reaction activity, then the discharge capacity improves, but the side reactions with electrolyte increase reducing cycle-life
Solution Approach 1:
The coating compound is selectively applied on the surface of core particles with higher surface area, creating a protective interface where electrochemical reactions occur. This localized coating suppresses side reactions between the high-surface-area core material and the electrolyte, while still allowing beneficial charge-discharge reactions to proceed efficiently, thus maintaining high discharge capacity without sacrificing cycle-life.
Solution Approach 2:
The coating compound acts as an intermediary layer between the core material and the electrolyte. It facilitates beneficial lithium ion transport and electrochemical reactions while blocking harmful side reactions such as electrolyte decomposition and gas generation. This mediator function allows the high surface area core to maintain high discharge capacity without suffering from excessive side reactions that would reduce cycle-life.
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 proposed positive active material exhibits improved active mass density, increased cycle-life, and enhanced electrochemical performance, including higher discharge capacity and reduced side reactions, while maintaining a low coating compound amount, thus optimizing battery performance and manufacturing efficiency.
Implementation Method 1
the coating compound including Li2MO3 and a solid electrolyte compound represented by Chemical Formula 1... enhancing ion conductivity and electrochemical performance
Implementation Method 2
Lithium-transition metal oxides having structures capable of intercalating lithium ions... which intercalate and deintercalate lithium ions
Data Source
AI summary
A positive active material including a core including a lithium intercalation compound and a coating compound on a surface of the core, the coating compound including Li2MO3 and a solid electrolyte compound represented by Chemical Formula 1 [Li1.3+4xAl0.3M1.7−x(PO4)3], wherein 0≤x≤0.7, and M is an element selected from Ti, Cr, Ga, Fe, Sc, In, Y, La, Mg, Sr, and combinations thereof; and a rechargeable lithium battery includes the positive active material.