Single-Particle Cathode Material for High-Nickel Cycle Stability
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Solution Overview
Problem
High nickel positive electrode active materials face issues with structural collapse during charge and discharge, leading to decreased energy density and life characteristics due to microcracks and increased resistance, while single crystal types require high sintering temperatures that can cause phase changes and lithium loss.
Innovation Solution
A positive electrode active material composed of lithium transition metal oxide in a single particle form, characterized by specific boundary ratios and particle sizes, is developed to enhance life and output characteristics. This material includes an outer and inner boundary structure, with controlled crystallinity and a bimodal particle size distribution to improve packing density and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If co-precipitation is used to prepare high nickel positive electrode active material, then the material can be manufactured, but microcracks occur during long-term charge and discharge causing side reactions and degradation
Solution Approach 1:
The invention changes the particle morphology parameter from secondary aggregated structure to single crystal structure, and controls the crystallinity parameter to maintain R-3m layered structure. This resolves the contradiction by preventing microcrack formation while maintaining manufacturability through controlled crystallization processes.
Solution Approach 2:
The invention creates a composite structure with core-shell configuration where the inner core maintains high nickel content (Ni≥0.8) for capacity and the outer shell has reduced nickel content with protective characteristics. This composite approach prevents side reactions at particle interfaces while maintaining overall manufacturability.
2Quantity of substance
If electrode density is increased to improve energy density, then energy density improves, but structural collapse of secondary particles occurs causing degradation in life characteristics
Solution Approach 1:
The invention segments the particle into multiple single crystal grains (2-50 grains per particle) rather than using large secondary aggregates. This segmentation maintains structural integrity at high densities while preserving the benefits of single crystal morphology, preventing structural collapse during charge-discharge cycles.
Solution Approach 2:
The invention changes the particle morphology parameter from secondary aggregated structure to single crystal structure with controlled grain size and distribution. This parameter change enables high electrode density while maintaining structural stability through the inherent strength of single crystal grains.
3Stability of the object's composition
If high sintering temperature is used to prepare single crystal type nickel-based positive electrode active material, then single crystal structure is achieved, but phase change into Fm-3m rock-salt structure occurs and lithium escapes causing increased resistance
Solution Approach 1:
The invention optimizes the sintering temperature parameter to a specific range (900-1000°C) and controls the sintering time parameter to prevent excessive heat treatment. This parameter control maintains the desired crystallinity and single crystal structure while avoiding phase transformation to rock-salt structure and lithium loss, thereby preventing resistance increase.
Solution Approach 2:
The invention performs preliminary crystal structure stabilization before final sintering by controlling the precursor formation and initial heating stages. This preliminary action ensures that the R-3m layered structure is established and maintained throughout the sintering process, preventing subsequent phase changes and lithium escape.
4Reliability
If sintering temperature is decreased to prevent phase change, then resistance is reduced, but the material exists as over-sintered secondary particles failing to achieve expected lifetime improvement
Solution Approach 1:
The invention simultaneously optimizes multiple parameters: sintering temperature (900-1000°C), sintering time (controlled duration), and particle size distribution (2-50 grains per particle). This multi-parameter optimization achieves the desired balance between low resistance and proper particle structure, avoiding both high-temperature phase changes and over-sintered secondary particle formation.
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 single particle lithium transition metal oxide exhibits improved life characteristics and energy density by minimizing lithium ion movement paths and preventing structural collapse, while maintaining high electrode density and reducing resistance.
Implementation Method 1
minimizing lithium ion movement paths
Implementation Method 2
preventing structural collapse
Data Source
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AI summary
The present invention relates to a positive electrode active material including a lithium transition metal oxide in a form of a single particle, and a positive electrode and a lithium secondary battery which include the same, and to a single particle type positive electrode active material, wherein the lithium transition metal oxide in the form of a single particle includes an outer boundary forming an outline of the particle and an inner boundary formed in the particle, and satisfies that 0 < length of the inner boundary/length of the outer boundary < 0.4.