Single-Particle Cathode Material With LiCoO2 Islands for Cycle Stability
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Solution Overview
Problem
The degradation of battery characteristics in lithium secondary batteries due to the separation of secondary particles during charge and discharge cycles, leading to increased NiO reduction layers on the positive electrode active material surface, which results in higher resistance and decreased capacity.
Innovation Solution
A positive electrode active material in the form of a single particle, composed of a lithium transition metal oxide with a discontinuous coating of LiCoO2 islands and a controlled NiO reduction layer, achieved through a specific heat treatment process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If sintering is performed at higher temperature to prepare single particle positive electrode active material, then particle integrity is improved, but NiO reduction layer ratio on surface increases
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the interior maintains high Ni content for capacity while the surface develops a controlled LiCoO2 layer to prevent excessive NiO reduction. This localized compositional differentiation resolves the contradiction by protecting the surface from harmful reduction while preserving the bulk properties for high performance.
Solution Approach 2:
The patent uses composite materials by combining LiNi0.8Co0.1Mn0.1O2 bulk material with a LiCoO2 surface layer. This composite structure allows the interior to provide high capacity through Ni content while the exterior LiCoO2 layer suppresses NiO reduction, thus resolving the technical contradiction between particle integrity and surface stability.
2Ease of manufacture
If NiO reduction layer ratio on surface is increased, then sintering temperature can be reduced, but battery resistance increases and capacity decreases
Solution Approach 1:
The patent applies parameter changes by optimizing the sintering temperature to a specific range (700-900°C) and controlling the oxygen partial pressure during sintering. These parameter adjustments enable the formation of an appropriate LiCoO2 surface layer without excessive NiO reduction, thus improving ease of manufacture while maintaining reliable battery performance.
Solution Approach 2:
The patent uses Raman spectroscopy to measure the intensity ratio of LiCoO2 to LiNiO2 peaks as a feedback parameter. By monitoring this ratio and adjusting sintering conditions accordingly, the process achieves optimal surface layer formation while preventing excessive NiO reduction, thus resolving the contradiction between manufacturing ease and battery reliability.
3Ease of manufacture
If secondary particle structure is used, then manufacturing is easier, but particle breaks during charge and discharge causing degraded battery characteristics
Solution Approach 1:
The patent applies segmentation by dividing the positive electrode active material into single particles with controlled internal grain structures. Each single particle consists of multiple fine grains (5-50 grains) that are tightly bound, providing mechanical strength to prevent breakage during charge-discharge cycles while maintaining manufacturability through controlled sintering processes.
Solution Approach 2:
The patent creates a composite microstructure within single particles where multiple fine grains are combined to form mechanically robust units. This composite grain structure within single particles provides both the ease of manufacture associated with aggregated structures and the structural integrity needed to prevent breakage during battery operation.
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
Improves cycle characteristics and reduces resistance, enhancing the performance and durability of lithium secondary batteries.
Implementation Method 1
a positive electrode active material in a form of a single particle which includes a lithium transition metal oxide in a form of a single particle; a coating portion containing cobalt which is formed on the lithium transition metal oxide in the form of a single particle
Implementation Method 2
since sintering at a higher temperature than that when preparing the positive electrode active material in the form of a secondary particle is required
Implementation Method 3
a ratio of an intensity of a peak (550 cm−1 to 620 cm−1) corresponding to an A1g vibration mode of LiCoO2 to an intensity of a peak (500 cm−1 to 600 cm−1) corresponding to an A1g vibration mode of LiNiO2 in a Raman spectrum of the surface
Data Source
AI summary
A positive electrode active material in a form of a single particle includes a lithium transition metal oxide in a form of a single particle, a coating portion containing cobalt which is formed on the lithium transition metal oxide in the form of the single particle, and LiCoO2 in a form of an island which is discontinuously formed on a surface of the positive electrode active material. A ratio of an intensity of a peak ranging from 550 cm−1 to 620 cm−1 corresponding to an A1g vibration mode of LiCoO2 to an intensity of a peak ranging from 500 cm−1 to 600 cm−1 corresponding to an A1g vibration mode of LiNiO2 in a Raman spectrum of the surface is greater than 1. Also provided is a method of preparing the same.