Overlithiated Oxide Core with Spinel and Titanium Coatings
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Solution Overview
Problem
Rechargeable lithium batteries face challenges with high manufacturing costs and unstable supply of traditional positive active materials like LiCoO2, and alternative materials such as nickel-based compounds have issues with structural stability and thermal stability due to reactions with electrolyte solutions, leading to capacity deterioration and irreversible reactions.
Innovation Solution
A positive active material for rechargeable lithium batteries is developed, comprising a core overlithiated oxide coated with a compound having a spinel structure and a second coating layer containing titanium, which improves ion conductivity and prevents side reactions with the electrolyte, enhancing cycle-life characteristics and rate capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiCoO2 is used as the positive active material, then the battery has high energy density and stable performance, but the manufacturing cost is high and the supply is unstable due to cobalt scarcity
Solution Approach 1:
The patent replaces expensive LiCoO2 with cheaper nickel-based or manganese-based positive active materials that have lower cost and more stable supply chains, accepting that these materials require additional protective measures (coating layers) to achieve acceptable performance
Solution Approach 2:
The patent creates a composite structure by coating the positive active material surface with aluminum oxide and aluminum hydroxide layers, combining the high capacity of nickel/manganese-based materials with the protective properties of aluminum-based coatings to achieve both cost reduction and performance stability
2Quantity of substance
If nickel-based positive active material is used, then the battery achieves high capacity and high voltage, but the structure becomes unstable and thermal stability decreases due to reaction with electrolyte solution
Solution Approach 1:
The patent introduces aluminum oxide and aluminum hydroxide coating layers as intermediary substances between the nickel-based positive active material and the electrolyte solution, preventing direct harmful reactions while allowing beneficial lithium ion transport to maintain high capacity
Solution Approach 2:
The patent applies thin film coatings (aluminum oxide and aluminum hydroxide layers with controlled thickness) on the positive active material surface, creating a protective shell that maintains structural stability and thermal stability while preserving electrochemical performance
3Quantity of substance
If overlithiated oxide is used to increase capacity, then lithium ions are released at high voltage (≥4.5 V), but oxygen gas is generated during reaction causing irreversible reactions
Solution Approach 1:
The patent converts the harmful oxygen gas generation issue into a beneficial outcome by using aluminum-based coating materials that react with the generated oxygen to form stable aluminum oxide layers, thereby preventing irreversible reactions and actually improving battery stability and cycle life
Solution Approach 2:
The patent applies protective coating layers before battery operation to prevent harmful reactions in advance, creating a barrier that stops oxygen gas from causing irreversible reactions with the electrolyte solution while allowing the overlithiated oxide to function at high voltage
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 results in a rechargeable lithium battery with high capacity, good rate capability, and improved cycle-life characteristics at high voltages, while maintaining capacity without substantial deterioration.
Implementation Method 1
a positive electrode including a positive active material capable of intercalating/deintercalating lithium ions
Implementation Method 2
a second coating layer coated (e.g. surrounding) the first coating layer and including a compound represented by Chemical Formula 2... improves ion conductivity
Implementation Method 3
treating the first mixture with a primary heat treatment to obtain an overlithiated oxide represented by Chemical Formula 1
Implementation Method 4
co-precipitating a nickel (Ni) source, a cobalt (Co) source and a manganese (Mn) source with ammonium hydroxide (NH4OH) or sodium hydroxide (NaOH) to obtain a precipitate
Data Source
AI summary
A positive active material for a rechargeable lithium battery includes a core including an overlithiated oxide represented by Chemical Formula 1, a first coating layer on the core and including a compound having a spinel structure, and a second coating layer on the first coating layer and including a compound represented by Chemical Formula 2. The compound having a spinel structure shows a peak between about 2.6 V and about 2.7 V in a graph of differential capacity dQ/dV vs. voltage, where the voltage is between about 4.7 V and about 2.5 V. In Chemical Formula 1, 0<x<1, 0<a<1, 0<b<1, 0<c<1, and a+b+c=1. In Chemical Formula 2, 0≦d<1 and 0<e≦1.xLi2MnO3.(1−x)LiNiaCobMncO2, Chemical Formula 1LidTieO2. Chemical Formula 2