Gradient-Doped High-Nickel Cathode for Stable Cycling and Fewer Microcracks
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Solution Overview
Problem
High-nickel layered oxide positive-electrode materials face challenges such as unstable Ni 4+ ions causing side reactions, microcrack formation due to lattice expansion, and Ni 2+ migration, leading to lithium deactivation and irreversible phase transitions, which current surface coating and bulk-phase doping methods fail to adequately address.
Innovation Solution
A gradient-doped high-nickel layered oxide material with a high-entropy surface and medium-entropy interior is prepared by multiple metal sources for bulk-phase doping and surface reconstruction, forming a superlattice structure to stabilize the interfacial structure and alleviate lattice mismatch during volume expansion and contraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If surface coating and bulk-phase doping are used to modify high-nickel layered oxide, then electronic conductivity and cycling stability are improved, but microcrack formation occurs due to volume expansion mismatch between coating layer and bulk phase
Solution Approach 1:
The patent implements gradient doping where the doping concentration varies spatially: higher doping concentration at the surface to suppress microcrack formation and side reactions, and lower doping concentration in the bulk to maintain high capacity. This local quality variation resolves the contradiction by optimizing each region's properties for its specific function.
Solution Approach 2:
The patent changes the doping concentration parameter from uniform to gradient distribution. By controlling the doping concentration to decrease from surface to bulk, the volume expansion mismatch is reduced at the interface, suppressing microcrack formation while maintaining the benefits of doping in both regions.
2Use of energy by moving object
If high-nickel layered oxide is used to achieve high energy density, then reversible specific capacity is improved, but side reactions occur due to unstable Ni 4+ ions
Solution Approach 1:
The patent applies preliminary anti-action by introducing dopant elements at the surface that preemptively stabilize the Ni 4+ ions before they can participate in harmful side reactions. The gradient doping creates a protective surface layer that counteracts the instability of Ni 4+ ions, preventing oxygen release and electrolyte decomposition while maintaining high capacity.
3Use of energy by moving object
If high-nickel layered oxide is used to achieve high energy density, then reversible specific capacity is improved, but microcrack formation occurs due to lattice expansion during charging and discharging
Solution Approach 1:
The patent implements local quality by applying higher doping concentration at the surface where microcrack formation is most likely to occur during volume expansion. The dopant elements at the surface accommodate the expansion stress, preventing crack propagation while the bulk maintains its high-capacity structure.
Solution Approach 2:
The patent creates a composite structure with gradient doping, forming a core-shell like architecture where the surface region has different compositional properties than the bulk. This composite structure combines the high capacity of high-nickel bulk with the structural stability of doped surface region, resolving the contradiction between energy density and structural integrity.
4Reliability
If surface coating is applied to protect the electrode-electrolyte interface, then stability is improved, but volume expansion mismatch causes microcrack formation
Solution Approach 1:
The patent merges the surface coating function with bulk-phase doping by implementing gradient doping that extends from the surface into the bulk. This unified approach eliminates the interface between separate coating and bulk phases, removing the source of volume expansion mismatch and microcrack formation while maintaining both interface stability and structural integrity.
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 enhances cycling stability and reduces side reactions, microcrack formation, and maintains discharge specific capacity, demonstrating improved electrochemical performance and industrial applicability.
Implementation Method 1
The bulk-phase doping can modify the electronic structure outside the transition metals, strengthening the bond energy of the transition metal ion and oxygen bond, improving the electronic conductivity of the material
Implementation Method 2
The high-entropy reconstruction layer on the surface can utilize the synergistic effects of multiple elements to form a superlattice structure on the surface, so as to reduce the valence state of surface nickel, thereby stabilizing the interfacial structure
Implementation Method 3
the gradient structure of the surface high-entropy reconstruction layer and the interior medium-entropy doping structure can alleviate the lattice mismatch in the process of volume expansion and contraction, so as to reduce the formation of microcracks
Implementation Method 4
subjecting the mixture to primary sintering in a modified atmosphere within an atmosphere-controlled furnace
Data Source
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AI summary
The present invention belongs to the technical field of lithium-ion battery electrode materials, specifically relating to a gradient-doped high-nickel layered oxide positive-electrode material with high-entropy surface and medium-entropy interior and a preparation method thereof. According to the present invention, the preparation method of the gradient-doped high-nickel layered oxide positive-electrode material with high-entropy surface and medium-entropy interior, involves doping the surface of the material with five or more elements to form a surface high-entropy reconstruction layer, while the interior of the material is doped with four elements to form a medium-entropy doping structure. The high-entropy reconstruction layer on the surface utilizes the synergistic effects of multiple elements to form a superlattice structure on the surface, so as to reduce the valence state of surface nickel, thereby stabilizing the interfacial structure and minimizing side reactions with the electrolyte. Through this method, the cycling stability of nickel-rich layered oxide positive-electrode materials can be significantly improved. It is a simple in process, low-cost, easy-to-operate, and high-performance method with promising prospects for industrial production and application.