Coated Lithium Battery Cathode Core for Thermal Stability
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Solution Overview
Problem
Current positive active materials for lithium rechargeable batteries face challenges in terms of cost, thermal stability, and cycle-life, particularly at high temperatures and high voltages, with manganese-based materials offering low capacity and LiCoO2 being expensive, while LiNiO2 has synthesis difficulties and stability issues.
Innovation Solution
A positive active material is developed with a core portion doped with metals like Zr, Ti, or combinations, coated with an island-type layer containing Al and B, which improves thermal stability and cycle-life by selectively reacting with active sites and controlling side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If LiCoO2 is used as positive active material, then electrical conductivity and discharge capacity are improved, but cost increases significantly
Solution Approach 1:
The patent uses composite materials by combining LiCoO2 core with a coating layer containing Al and B elements. This composite structure maintains the high discharge capacity of LiCoO2 while the coating layer reduces cost and improves stability, resolving the contradiction between performance and cost.
2Ease of manufacture
If manganese-based material is used as positive active material, then cost and thermal stability are improved, but discharge capacity decreases
Solution Approach 1:
The patent creates a composite structure with manganese-based material as the core and adds a coating layer containing Al and B. This composite approach preserves the cost advantage and thermal stability of manganese-based materials while attempting to enhance discharge capacity through the coating layer.
3Power
If LiNiO2 is used as positive active material, then discharge capacity is improved, but stability and cycle-life deteriorate
Solution Approach 1:
The patent uses LiNiO2 as the core material to achieve high discharge capacity, then applies a coating layer containing Al and B elements. This composite structure aims to protect the unstable LiNiO2 core, reducing nickel oxidation and improving cycle-life while maintaining high discharge capacity.
Solution Approach 2:
The coating layer acts as an intermediary between the LiNiO2 core and the electrolyte environment. It mediates the interaction by preventing direct contact and harmful reactions, thereby protecting the core material's stability while allowing electrochemical function to proceed.
4Power
If high voltage operation is implemented, then energy density is improved, but thermal stability and life-span deteriorate at high temperature
Solution Approach 1:
The patent employs a composite structure with the positive active material core and a protective coating layer. This composite design enables high voltage operation for improved energy density while the coating layer provides thermal stability and protects against degradation at high temperatures, extending life-span.
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 material exhibits enhanced life-span characteristics and thermal stability at high temperatures and voltages, with improved battery performance compared to conventional materials, including reduced surface energy and increased capacity retention.
Implementation Method 1
the coating layer comprises Al and B... which improves thermal stability and cycle-life by selectively reacting with active sites and controlling side reactions
Implementation Method 2
a material reversibly intercalating or deintercalating lithium ions during charge and discharge reactions
Data Source
AI summary
A positive active material for a rechargeable lithium battery, a method for manufacturing the same, and a rechargeable lithium battery including the same are provided. A positive active material for a rechargeable lithium battery includes a compound that is capable of reversibly intercalating or deintercalating lithium, wherein the compound is formed of a core portion and a coating layer, the core portion is doped with M, and the coating layer includes Al and B, wherein M is Zr, Ti, Mg, Ca, Al, B, V, Zn, Mo, Ni, Co, Mn, or a combination thereof.