Multi-Layer Coated Lithium Composite Oxide for Battery Stability
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Solution Overview
Problem
Conventional positive active materials for lithium rechargeable batteries face challenges such as low capacity, high cost, and instability, particularly with manganese-based materials, and nickel-based materials that deteriorate over time, affecting cycle-life and self-discharge.
Innovation Solution
A multi-layer coating structure is applied to a layered lithium composite oxide core, including a magnesium-doped first coating layer, a NiO-phase second coating layer with a rock salt structure, and a lithium magnesium phosphate third coating layer, which stabilizes the surface structure and enhances high-temperature characteristics without compromising room temperature performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a manganese-based positive active material (LiMn2O4, LiMnO2) is used, then the material is easy to synthesize, costs less, and has excellent thermal stability, but it has relatively low capacity
Solution Approach 1:
The patent uses a composite material structure with a manganese-based layered lithium composite oxide core (LiMn1-a-b-c-dNiaCobMn dO2) combined with multiple coating layers. The core provides ease of synthesis and thermal stability, while the coatings (including LiMgPO4 and NiO phases) enhance capacity and electrochemical performance, achieving both low cost and high capacity
2Reliability
If LiCoO2 is used as the positive active material, then it has good electrical conductivity, high cell voltage, and excellent cycle-life, but it is so expensive that it makes up more than 30% of the battery cost
Solution Approach 1:
The patent applies local quality by using a manganese-based layered lithium composite oxide as the core material (which is low cost) and adding functional coating layers (LiMgPO4, NiO phase) only on the surface. This allows the bulk material to be cost-effective while the surface coatings provide the necessary electrochemical performance and stability, achieving low cost with good cycle-life
3Quantity of substance
If LiNiO2 is used to achieve the highest discharge capacity, then it has high capacity, but it is hard to synthesize and nickel is highly oxidized which deteriorates cycle-life and causes severe self discharge
Solution Approach 1:
The patent segments the positive active material into a manganese-based layered lithium composite oxide core with multiple functional coating layers. The core provides structural stability and ease of synthesis, while the outer coatings (including NiO phase and LiMgPO4) provide high capacity and protect against nickel oxidation, achieving high discharge capacity with good cycle-life
4Temperature
If a simple surface coating layer is formed to improve high temperature characteristics, then high temperature performance is improved, but it exposes many problems and has an influence on rate limiting effect at room temperature
Solution Approach 1:
The patent transitions from a single-dimensional simple coating to a multi-dimensional multi-layer coating structure. The multi-layer structure includes inner layers (LiMgPO4) and outer layers (NiO phase) with different thicknesses and compositions, allowing optimization for both high temperature stability and room temperature rate performance by controlling the depth and distribution of each coating layer
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 multi-layer coating significantly improves high-temperature characteristics by over 50% while maintaining initial capacity and cycle-life, making the battery more efficient and cost-effective.
Implementation Method 1
magnesium doped at a lithium site in the core
Implementation Method 2
a first coating layer on the surface of the core and magnesium doped at a lithium site in the core; a NiO-phase second coating layer on the first coating layer
Implementation Method 3
a third coating layer on the second coating layer and including lithium magnesium phosphate
Implementation Method 4
magnesium ions from the bottom of the NiO layer are permeated into the lithium layer during a coating process
Data Source
AI summary
A positive active material for a rechargeable lithium battery, a method of preparing the same, and a rechargeable lithium battery including the same are disclosed, and the positive active material for a rechargeable lithium battery includes: a layered lithium composite oxide core; a first coating layer on the surface of the core and magnesium doped at a lithium site in the core; a NiO-phase second coating layer on the first coating layer wherein the NiO-phase has a rock salt structure; and a third coating layer on the second coating layer and including lithium magnesium phosphate.