Cathode Precursor Gradient Layer With Barrier for Thermal Stability
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Solution Overview
Problem
Conventional methods for manufacturing lithium secondary battery positive active materials struggle to maintain a continuous concentration gradient during thermal treatment, leading to instability and degradation due to metal ion diffusion, and existing solutions fail to achieve desired thermal stability and reproducibility.
Innovation Solution
A method involving a reactor process where a chelating agent solution, core forming solution, and barrier layer forming solution are input to form a core and barrier layer, followed by a shell forming solution to create a concentration gradient layer, with a barrier layer between the core and shell, and thermal treatment in an oxidation atmosphere to stabilize the composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating layer is applied to the surface of positive active material particles, then thermal stability is improved, but the coating effect deteriorates over time due to sharp composition difference between coated layer and bulk particles
Solution Approach 1:
The patent applies local quality by creating a concentration gradient layer where the metallic composition transitions gradually from the core to the surface. The layer has different compositions at different positions: Ni-rich at the core interface and Mn-rich at the surface, with a continuous gradient in between. This gradual composition change eliminates the sharp interface problem while maintaining thermal stability throughout the particle structure.
Solution Approach 2:
The patent changes the composition parameter continuously through the particle radius, creating a gradient distribution of metallic elements. By controlling the concentration of Ni, Co, and Mn atoms to vary continuously from core to surface, the material achieves both thermal stability (through surface Mn enrichment) and long-term durability (through gradual composition transition that prevents stress concentration and structural degradation).
2Manufacturing precision
If thermal treatment is performed to form a solid solution on the surface, then coating uniformity is improved, but composition homogeneity deteriorates due to metal ion diffusion
Solution Approach 1:
The patent applies preliminary action by pre-forming the concentration gradient layer with the desired composition distribution before thermal treatment. The sol-gel process creates a controlled gradient structure in advance, and subsequent thermal treatment merely densifies and crystallizes the pre-established gradient rather than creating it through diffusion. This prevents the formation of sharp composition interfaces that would occur if coating were applied after sintering.
Solution Approach 2:
The patent replaces the conventional mechanical mixing and coating methods with a chemical sol-gel process. By using controlled hydrolysis and condensation reactions of metal alkoxides in a solvent system, the desired concentration gradient is formed chemically at the molecular level during precipitation, achieving uniform distribution without mechanical disruption or subsequent diffusion-induced homogenization.
3Reliability
If a double layer structure with core and shell is created, then thermal stability is improved, but continuity of concentration distribution at the interface deteriorates
Solution Approach 1:
The patent segments the particle structure into multiple functional zones with distinct composition characteristics: a Ni-rich core for capacity, a gradient transition zone for stability, and an Mn-enriched surface layer for thermal protection. This segmentation is achieved through controlled precipitation during sol-gel processing, where different metal ions precipitate at different rates and positions, creating a multi-zone structure with continuous composition transitions between zones.
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 method ensures a continuous concentration distribution across the interface between the core and shell, enhancing thermal stability and reproducibility of the lithium secondary battery positive active material, while reducing primary particle size and improving charge/discharge characteristics.
Implementation Method 1
a chelating agent solution, core forming solution and barrier layer forming solution are input into the reactor at the same time to form a core and barrier layer
Implementation Method 2
thermal treatment in an oxidation atmosphere to stabilize the composition
Data Source
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AI summary
Disclosed are a method for manufacturing a lithium secondary battery positive active material exhibiting a concentration gradient and a lithium secondary battery positive active material exhibiting a concentration gradient, manufactured by the method, and more particularly, a method for manufacturing a lithium secondary battery positive active material exhibiting a concentration gradient and a lithium secondary battery positive active material exhibiting a concentration gradient, manufactured by the method, the method being characterized by forming a barrier layer so as to maintain a concentration gradient layer even in case of thermal diffusion by a subsequent thermal treatment process.