Core-Shell Gradient Cathode Precursor for High-Nickel Stability
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Solution Overview
Problem
Existing methods struggle to uniformly control the internal composition, particularly the molar content of nickel, and stabilize the structure of nickel-based lithium metal oxide particles, especially for large diameter particles, which affects the performance and stability of lithium rechargeable batteries.
Innovation Solution
A core-shell gradient (CSG) structure is introduced for nickel-based metal hydroxide particles, where the core maintains a constant molar content of nickel and the shell has a decreasing nickel concentration, achieved through a controlled co-precipitation process, ensuring uniform composition across different particle sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the molar content of nickel in nickel-based lithium metal oxide is increased to achieve higher capacity, then the battery capacity is improved, but the structure becomes unstable
Solution Approach 1:
The patent applies local quality by creating a core-shell gradient structure where the nickel concentration varies spatially: the core region maintains high nickel content for capacity, while the shell region has reduced nickel content for structural stability. This non-uniform distribution resolves the contradiction by optimizing different regions for different functions.
Solution Approach 2:
The patent creates a composite structure combining regions with different nickel concentrations within a single particle. The core-shell gradient structure effectively combines high-nickel and low-nickel phases, achieving both high capacity and structural stability through material composition design.
2Stability of the object's composition
If doping or coating methods are used to stabilize the structure of high-nickel particles, then structural stability is improved, but uniform control of internal composition becomes very difficult
Solution Approach 1:
The patent applies preliminary action by establishing the desired concentration gradient structure during the co-precipitation synthesis process itself, rather than attempting to modify uniform particles afterward through doping or coating. The gradient is built-in from the beginning through controlled reagent addition, ensuring both stability and uniformity.
Solution Approach 2:
The patent uses parameter changes in the synthesis process, specifically varying the addition rates of metal salt solutions and controlling pH gradients during co-precipitation, to directly create the desired nickel concentration distribution. This process parameter control achieves both structural stability and compositional uniformity simultaneously.
3Stability of the object's composition
If nickel-based lithium metal oxide particles with concentration gradient are used, then structural stability is improved, but the average molar content of nickel varies depending on particle size
Solution Approach 1:
The patent applies feedback control during the co-precipitation process by continuously monitoring and adjusting the addition rates of metal salt solutions and pH levels. This real-time control ensures that particles of different sizes develop consistent concentration gradients with uniform average nickel content, resolving the size-dependent variation problem.
Solution Approach 2:
The patent creates a universal synthesis method that produces consistent core-shell gradient structures across particles of different sizes. The co-precipitation process with controlled reagent addition rates universally generates the desired concentration profile regardless of final particle size, enabling scalable production with uniform properties.
4Quantity of substance
If bi-modal technique is used to increase energy density by mixing particles of different sizes, then energy density is improved, but uniform control of internal composition and nickel content becomes very difficult
Solution Approach 1:
The patent applies segmentation by dividing each particle into core and shell regions with different nickel concentrations, rather than relying on mixing particles of different sizes. This intra-particle segmentation achieves the benefits of composition optimization without the inter-particle variability issues of bi-modal mixing.
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
This approach stabilizes the structure, enhances thermal stability, and improves the capacity and resistance characteristics of lithium rechargeable batteries by maintaining a high nickel concentration in the core and reducing it in the shell, resulting in reduced heat generation and improved performance.
Implementation Method 1
a first co-precipitation step of forming a core portion by supplying the first metal salt aqueous solution to a reactor having a pH that is constantly maintained, to which a chelating agent is supplied; and a second co-precipitation step of forming a shell portion surrounding an outer surface of the core portion
Data Source
AI summary
This proposes a minimum core radius for nickel-based metal hydroxide particles having a core-shell gradient (CSG) in which a concentration of nickel in a core portion is constantly maintained and a concentration of nickel in a shell portion is sharply decreased.