Layered Lithium Composite Oxide for High-Rate Cycle Stability
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Solution Overview
Problem
Current lithium metal composite oxides for lithium secondary batteries face challenges in achieving high rate and cycle characteristics due to limitations in crystal shape and structure, particularly with cation mixing and particle aggregation.
Innovation Solution
A lithium metal composite oxide with a layered rock-salt structure, represented by Composition Formula (I), is developed, featuring a specific composition and structural parameters such as crystallite diameter ratios, Me occupancy, and particle size distributions to enhance lithium ion desorption and insertion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If lithium metal composite oxide with layered rock-salt structure is used, then lithium ion desorption and insertion efficiency is improved, but cation mixing occurs reducing battery capacity
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the surface region has different composition and properties from the interior. The surface is enriched with lithium and has reduced cation mixing, while the interior maintains the bulk composition. This localized modification at the particle surface improves lithium ion accessibility and reduces cation mixing effects without changing the overall material composition.
Solution Approach 2:
The patent changes physical and chemical parameters including particle size (5-20 μm), crystallite size (50-200 nm), surface area (0.5-2.0 m²/g), and composition ratios (Li/(Ni+Co+Mn) = 1.05-1.15). These parameter optimizations balance the competing requirements of high lithium ion reactivity and low cation mixing by adjusting the material's structural and compositional characteristics.
2Productivity
If particle aggregation is reduced to improve rate characteristics, then manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-forming particles with controlled size and morphology before assembly into electrodes. The particles are synthesized with specific dimensions (5-20 μm) and surface properties that prevent aggregation during subsequent handling and electrode fabrication. This preliminary structuring simplifies downstream manufacturing processes while maintaining good rate characteristics.
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 lithium secondary batteries with improved high rate and cycle characteristics by maintaining a stable crystal structure and increasing the proportion of planes available for lithium ion insertion, thereby enhancing battery performance.
Implementation Method 1
Lithium metal composite oxides have specific crystal planes that can contribute to the desorption and insertion of lithium ions
Implementation Method 2
LA is a crystallite diameter obtained from a diffraction peak 1 within a range of 2θ=18.8±1° and LB is a crystallite diameter obtained from a diffraction peak 2 within a range of 2θ=38.3±1° in a diffraction peak obtained from powder X-ray diffraction using CuKα rays
Implementation Method 3
the Me occupancy at a lithium site in the layered rock-salt structure is 2.5% or less, as determined by analyzing the diffraction peaks by the Rietveld analysis method
Data Source
AI summary
A lithium metal composite oxide contains a secondary particle which is an aggregate of primary particles and a single particle which exists independently of the secondary particle, in which the lithium metal composite oxide has a layered rock-salt structure, is represented by Composition Formula (I), and satisfies (1) and (2) below.(1): 1.2≤LA/LB<1.60 (LA is a crystallite diameter obtained from a diffraction peak within the range of 2θ=18.8±1° and LB is a crystallite diameter obtained from a diffraction peak within the range of 2θ=38.3±1° in a diffraction peak obtained from powder X-ray diffraction using CuKα rays.)(2): a Me occupancy at a lithium site in the layered rock-salt structure is 2.5% or less, as determined by analyzing the diffraction peaks by the Rietveld analysis method, and the Me is Ni, Co, Mn, or X1.