Nickel-Rich Electrode Material with Radial Cobalt Gradient Stability
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Solution Overview
Problem
Existing lithium ion batteries face challenges in safety issues such as low onset temperature and cycling stability, with potential for improvement in volumetric and gravimetric energy densities, and capacity fade, particularly due to exothermic reactions with the electrolyte.
Innovation Solution
Development of particulate electrode active materials with a specific composition and structure, including a gradient of Co content and radial orientation of primary particles, produced through a co-precipitation and thermal treatment process, to enhance safety and cycling stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrode active materials are used, then manufacturing is simpler, but safety behavior deteriorates due to low onset temperature and high cycling stability issues
Solution Approach 1:
The patent applies local quality by creating a radial concentration gradient of cobalt within the particle structure, where the cobalt content varies from the particle center to the surface. This gradient structure provides different local compositions optimized for specific functions: the nickel-rich core provides high capacity while the cobalt-enriched outer shell provides structural stability and safety, resolving the contradiction between safety and material complexity.
Solution Approach 2:
The patent uses composite materials by combining multiple transition metals (nickel, cobalt, and optionally other metals like manganese, magnesium, or aluminum) in a specific radial gradient arrangement. This composite structure with formula Li1+xTM1-xO2 leverages the complementary properties of different metals to achieve both high safety behavior and controlled complexity.
2Quantity of substance
If high nickel content is used to increase capacity, then energy density improves, but cycling stability deteriorates due to capacity fade and cracking
Solution Approach 1:
The patent applies local quality by creating a radial concentration gradient of cobalt within the particle structure, where the cobalt content varies from the particle center to the surface. This gradient structure provides different local compositions optimized for specific functions: the nickel-rich core provides high capacity while the cobalt-enriched outer shell provides structural stability and safety, resolving the contradiction between safety and material complexity.
Solution Approach 2:
The patent applies beforehand cushioning by incorporating a cobalt-enriched outer shell that acts as a protective layer before cycling begins. This cobalt-rich surface layer prevents cracking and structural degradation during subsequent charge-discharge cycles, cushioning against the mechanical stress that would otherwise cause capacity fade in high-nickel materials.
3Speed
If particle size is reduced to improve reaction kinetics, then power density improves, but safety deteriorates due to increased surface area for exothermic reactions
Solution Approach 1:
The patent applies local quality by creating a radial concentration gradient of cobalt within the particle structure, where the cobalt content varies from the particle center to the surface. This gradient structure provides different local compositions optimized for specific functions: the nickel-rich core provides high capacity while the cobalt-enriched outer shell provides structural stability and safety, resolving the contradiction between safety and material complexity.
Solution Approach 2:
The patent applies parameter changes by carefully controlling the particle size parameters (D50 between 2-20 μm) and the compositional gradient parameter (cobalt content variation). By optimizing these parameters, the patent achieves fast reaction kinetics while the cobalt-enriched surface layer suppresses exothermic reactions with the electrolyte.
4Ease of manufacture
If uniform composition is used for simplicity, then manufacturing is easier, but performance deteriorates due to insufficient capacity and safety
Solution Approach 1:
The patent applies local quality by creating a radial concentration gradient of cobalt within the particle structure, where the cobalt content varies from the particle center to the surface. This gradient structure provides different local compositions optimized for specific functions: the nickel-rich core provides high capacity while the cobalt-enriched outer shell provides structural stability and safety, resolving the contradiction between safety and material complexity.
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 resulting electrode active materials exhibit improved safety behavior, high onset temperature, and reduced capacity fade, addressing the limitations of existing lithium ion batteries.
Implementation Method 1
performing a co-precipitation of hydroxides of Ni, Co and - if applicable - at least one more metal selected from Mg, Ti, Zr, Nb, Ta, Mo, Mn, and W by combining an aqueous solution of alkali metal hydroxide and one or more aqueous solution(s) containing water-soluble salts of Ni and of Co
Implementation Method 2
thermally treating the mixture resulting from step (b)
Data Source
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AI summary
Particulate electrode active material with an average particle diameter in the range of from 2 to 20 µm (D50) having a general formula Li1+xTM1-xO2 wherein TM is a combination of Ni, Co and Al, and, optionally, at least one more metal selected from Mg, Ti, Zr, Nb, Ta, Mo, Mn, and W, with at least 80 mole-% of TM being Ni, and wherein x is in the range of from zero to 0.2, where-in the Co content at the outer surface of the secondary particles is higher than at the center of the secondary particles by a factor of at most 5 or by at most 30 mol-%, referring to TM.