Cathode Particle Structure with Dual Coating Layers
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Solution Overview
Problem
Lithium ion battery cathode materials react with electrolytes during charging and discharging, leading to decreased working voltage and cycle life.
Innovation Solution
A particle structure of cathode material with at least two coating layers, where the first coating layer contains potassium and aluminum to enhance lithium ion migration, and the second coating layer contains sulfur to prevent reaction with the electrolyte.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cathode material surface is exposed to electrolyte during charging and discharging, then the battery can operate, but the reaction between cathode material and electrolyte decreases working voltage and cycle life
Solution Approach 1:
A coating layer comprising sulfur and at least one element selected from lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, aluminum, silicon, tin, lead, manganese, iron, chromium, nickel, zinc, zirconium, thallium, and nitrogen is applied to the cathode material surface. This coating layer acts as an intermediary barrier between the cathode material and the electrolyte, preventing direct harmful reactions while allowing lithium ion transport, thereby improving cycle life and working voltage stability
Solution Approach 2:
The coating layer is formed as a composite material combining sulfur with other elements (such as potassium alum mentioned in embodiments). This composite structure provides both protective functions (preventing electrolyte reaction) and functional benefits (facilitating lithium ion migration), resolving the contradiction between protection and electrochemical performance
2Reliability
If a coating layer is added to protect the cathode material, then cycle life is improved, but the device complexity increases
Solution Approach 1:
The coating layer is segmented into different functional zones: an inner layer containing sulfur and specific elements for chemical protection against electrolyte, and potentially an outer layer optimized for lithium ion transport. This segmentation allows each layer to specialize in one function, improving overall effectiveness while maintaining a relatively simple overall structure
Solution Approach 2:
Different regions of the coating layer have different compositions optimized for local functions. The inner coating layer near the cathode material surface contains sulfur and specific elements for chemical stability, while the composition may vary to optimize lithium ion conductivity at different depths, providing locally optimized properties without excessive overall complexity
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 cathode material structure improves the cycle life, capacity, and stability of lithium ion batteries by facilitating lithium ion migration and avoiding electrolyte reactions.
Implementation Method 1
the first coating layer contains potassium and aluminum, it is conducive to the migration of lithium ions
Implementation Method 2
the second coating layer contains sulfur, so that the reaction between the cathode material and the electrolyte during charging and discharging is avoided
Data Source
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AI summary
A particle structure of cathode material and a preparation method thereof is provided. Firstly, a precursor for forming a core is provided. The precursor includes at least nickel, cobalt and manganese. Secondly, a metal salt and a lithium ion compound are provided. The metal salt includes at least potassium, aluminum and sulfur. After that, the metal salt, the lithium ion compound and the precursor are mixed, and a mixture is formed. Finally, the mixture is subjected to a heat treatment step, and a cathode material particle structure is formed to include the core, a first coating layer coated on the core and a second coating layer coated on the first coating layer. The core includes potassium, aluminum and a Li-M-O based material. The first coating layer includes potassium and aluminum, and a potassium content of the first coating layer is higher than a potassium content of the core. The second coating layer includes sulfur.