Nickel-Based Cathode Coating for Battery Stability
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Solution Overview
Problem
Nickel-based lithium metal oxide positive active materials in rechargeable lithium batteries face deteriorated cell characteristics due to side-reactions with electrolyte solutions, leading to increased charge transfer resistance and reduced power output.
Innovation Solution
A positive active material is developed with a nickel-based lithium metal oxide having a layered crystal structure and a selective coating layer of lithium-metal oxide on the (003) crystalline plane, minimizing lattice mismatch and preventing charge transfer resistance increase, while maintaining lithium ion intercalation and deintercalation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a nickel-based lithium metal oxide is used as a positive active material to improve capacity characteristics, then the discharge capacity is improved, but the cell characteristics deteriorate due to side-reactions with the electrolyte solution
Solution Approach 1:
A coating layer comprising a lithium-metal oxide is formed on the surface of the nickel-based lithium metal oxide particles. This coating layer acts as an intermediary barrier between the nickel-based lithium metal oxide and the electrolyte solution, preventing direct contact and side-reactions while allowing lithium ion transport, thus improving cell characteristics without sacrificing discharge capacity
Solution Approach 2:
The positive active material is designed as a composite structure combining nickel-based lithium metal oxide core particles with a lithium-metal oxide coating layer. This composite material approach allows the inner core to provide high capacity characteristics while the outer coating provides stability and prevents harmful side-reactions with the electrolyte solution
2Reliability
If a coating layer is formed on the nickel-based lithium metal oxide to prevent side-reactions, then the cell characteristics are improved, but the charge transfer resistance increases
Solution Approach 1:
The coating layer is designed with specific local properties: it comprises a lithium-metal oxide with a crystal structure having a specific lattice parameter ratio (c/a between 2.05 and 2.15), which creates favorable local crystallographic orientation and lattice matching at the interface with the nickel-based lithium metal oxide. This local structural quality enables efficient charge transfer while maintaining the protective function against side-reactions
Solution Approach 2:
The crystal structure parameters of the lithium-metal oxide coating layer are precisely controlled, specifically the lattice parameter ratio (c/a) between 2.05 and 2.15, and the content of the lithium-metal oxide is optimized at 0.1-5 mol% based on the total amount of lithium metal oxide. These parameter optimizations ensure the coating layer provides protection without significantly increasing charge transfer resistance
3Stability of the object's composition
If the lattice mismatch ratio is reduced to improve epitaxial growth, then the coating layer stability is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent specifies a range for the lattice parameter ratio (c/a between 2.05 and 2.15) and the lithium-metal oxide content (0.1-5 mol%) that optimizes lattice matching between the coating layer and the nickel-based lithium metal oxide. By controlling these parameters within specified ranges rather than requiring exact values, the patent achieves good epitaxial growth and coating stability while maintaining practical manufacturing feasibility
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 enhances power output characteristics, improves electrode stability, and reduces gas generation at high voltages, ensuring improved reliability and safety of rechargeable lithium batteries.
Implementation Method 1
the lithium-metal oxide selectively disposed on the (003) crystalline plane of the nickel-based lithium metal oxide and the nickel-based lithium metal oxide may have a layered structure that is epitaxially grown in the same c-axis direction
Implementation Method 2
A lattice mismatch ratio between a (003) plane of the nickel-based lithium metal oxide and a (001) plane (I is 1, 2, or 3) of the lithium-metal oxide may be less than or equal to about 15%
Implementation Method 3
a positive active material that easily intercalates/deintercalates lithium ions
Implementation Method 4
lithium ion intercalation and deintercalation efficiency
Data Source
Figure 1
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Figure 3A
AI summary
Disclosed are a positive active material for a rechargeable lithium battery including a nickel-based lithium metal oxide having a layered crystal structure and a coating layer including a lithium-metal oxide selevtively disposed on (003) crystalline plane of the nickel-based lithium metal oxide, wherein the positive active material includes at least one secondary particle including an agglomerate of two or more primary particles, a method of preparing the same, and a rechargeable lithium battery including the positive active material.