Gradient Cobalt Single Crystal Cathode for High-Capacity Li-Ion Batteries
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Solution Overview
Problem
High-nickel low-cobalt positive electrode materials face issues such as low capacity, poor cycle life, and safety risks, including high residual lithium content, poor rate performance, and cycling performance.
Innovation Solution
A low-cobalt single crystal positive electrode material with a two-tier cobalt concentration gradient distribution, where the cobalt concentration decreases from the surface to the center, combined with element doping and a controlled sintering process, forms lithium-ion transfer channels and alleviates phase transitions, enhancing lithium-ion diffusion and material stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-nickel low-cobalt positive electrode materials are developed to reduce cost and increase energy density, then cost and energy density are improved, but capacity, cycle life, and rate performance deteriorate
Solution Approach 1:
The patent applies local quality by creating a two-tier cobalt concentration gradient distribution within the positive electrode material particles. The first region (outer layer, 25-425 nm from surface) has a high cobalt concentration gradient (6-20% per 100 nm decrease), while the second region (inner layer, 425 nm to center) has a low cobalt concentration gradient (0.1-6% per 100 nm decrease). This spatial variation in cobalt concentration optimizes different regions for different functions: the outer region enhances lithium-ion diffusion and reduces polarization impedance, while the inner region maintains structural stability, thereby improving both energy density and cycle life simultaneously.
Solution Approach 2:
The patent employs parameter changes by precisely controlling the cobalt concentration gradient parameters in different regions. The first region maintains a steep gradient (6-20% per 100 nm) to maximize lithium-ion diffusion promotion, while the second region uses a shallow gradient (0.1-6% per 100 nm) to preserve structural integrity. This parameter optimization resolves the contradiction between achieving high energy density through low-cobalt formulation and maintaining reliable cycle life.
2Speed
If cobalt concentration is increased to improve lithium-ion diffusion rate, then rate performance is improved, but cost increases and capacity is reduced
Solution Approach 1:
The patent applies local quality by concentrating high cobalt gradients only in the first region (25-425 nm from surface) where lithium-ion diffusion is most critical, while maintaining low cobalt gradients in the second region (425 nm to center). This localized high-cobalt approach maximizes lithium-ion diffusion rate improvement without requiring high overall cobalt content, thus enhancing rate performance while maintaining high capacity and low cost.
Solution Approach 2:
The patent uses parameter changes by optimizing the cobalt concentration gradient parameters spatially. The first region employs a high gradient parameter (6-20% per 100 nm decrease) to accelerate lithium-ion diffusion at the particle surface and outer layers, while the second region uses a low gradient parameter (0.1-6% per 100 nm decrease) to maintain structural stability. This parameter differentiation achieves high rate performance without sacrificing capacity or increasing overall cobalt content.
3Quantity of substance
If lithium intercalation degree is increased to improve capacity, then capacity is improved, but polarization impedance increases and cycle life deteriorates
Solution Approach 1:
The patent applies local quality by creating a cobalt concentration gradient that is highest at the particle surface and outer regions (first region with 6-20% per 100 nm gradient) where lithium-ion insertion occurs, and lowest at the particle center (second region with 0.1-6% per 100 nm gradient). This spatial distribution promotes rapid lithium-ion diffusion into the crystal lattice during intercalation, reducing polarization impedance while enabling high capacity achievement through deep lithium insertion.
Solution Approach 2:
The patent employs parameter changes by optimizing the cobalt concentration gradient parameters to match the lithium concentration gradient effect during intercalation. The high gradient in the first region (6-20% per 100 nm) aligns with the high lithium concentration gradient at the particle surface during charging, maximizing the promoting effect on lithium-ion diffusion and reducing polarization impedance. The low gradient in the second region (0.1-6% per 100 nm) maintains structural stability during deep intercalation, enabling high capacity with improved cycle life.
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 material achieves high capacity and long cycle life, improving intercalation speed and reducing power loss, while maintaining mechanical strength and safety, suitable for automotive batteries in long-range electric vehicles.
Implementation Method 1
a cobalt concentration of the first region is in a gradient distribution, decreasing from outside to inside at a rate of 6% to 20% per 100 nm, and a cobalt concentration of the second region is in a gradient distribution, decreasing from outside to inside at a rate of 0.1% to 6% per 100 nm
Implementation Method 2
a preparation method therefor
Data Source
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AI summary
The present application belongs to the technical field of lithium battery positive electrode materials, and discloses a low-cobalt single crystal positive electrode material with high capacity and long cycle life. The interior of the particle is divided into a first region and a second region, and the cobalt concentrations in the first and second region are in a gradient distribution, decreasing from outside to inside at decreasing rates of 6% to 20% and 0.1% to 6% per 100 nm, respectively. This design can significantly improve the initial charge/discharge capacity and rate performance, and can significantly enhance the high-temperature cycling performance. The method for preparing the low-cobalt single crystal positive electrode material is also provided, which has a simple process and low cost. Through appropriate selection of small particles of high-nickel low-cobalt precursors, combined with element doping, coating modification, and dry sintering processes, the method can regulate particle size morphology and structure of the low-cobalt single crystal positive electrode material, and modify the crystal structure and the surface material, resulting in a two-tier decreasing cobalt concentration gradient distribution from the outside to the inside, which addresses the common issues of high-nickel low-cobalt positive electrode materials, such as high residual lithium content, poor power performance and cycling performance, and inferior safety performance.