Rare-Earth Doped Cathode Material for Stable Sodium-Ion Capacity
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Solution Overview
Problem
Existing sodium-ion batteries using layered transition metal oxides exhibit low capacity retention rates due to structural damage from moisture penetration, lattice oxygen release, and phase transitions during high-voltage charging.
Innovation Solution
A positive electrode active material composed of NiFeMn doped with a rare earth element M1 and a doping element M2, with controlled doping ratios, forms a dense surface layer to block moisture and suppress lattice oxygen release, while M2 forms strong chemical bonds to stabilize the structure and reduce Na ion deintercalation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If layered transition metal oxides are used as positive electrode active materials, then the battery can achieve high capacity, but the capacity retention rate is low due to structural damage from moisture penetration, lattice oxygen release, and phase transitions
Solution Approach 1:
The patent uses a composite material system with layered transition metal oxide (containing Ni, Fe, Mn) as the base material, doped with rare earth elements (M1) and other elements (M2). This composite structure combines the high capacity of layered transition metal oxides with the stabilizing effects of rare earth doping, which suppresses phase transitions and structural degradation during cycling, thereby improving capacity retention while maintaining high capacity
Solution Approach 2:
The patent applies local quality by doping rare earth elements (M1) and other elements (M2) at specific sites within the layered transition metal oxide structure. The doping ratios are precisely controlled (0.001≤d/c≤0.05 for M1 to Mn, and 0.001≤e/c≤0.05 for M2 to Mn) to locally modify the crystal structure and electronic properties, enhancing structural stability and suppressing lattice oxygen release at critical positions without compromising overall capacity
2Quantity of substance
If high-voltage charging is applied to achieve high capacity, then the battery capacity increases, but phase transitions and structural damage occur reducing cycling performance
Solution Approach 1:
The patent changes the chemical composition parameters of the positive electrode active material by introducing rare earth element doping (M1) and other element doping (M2) with controlled ratios. This parameter modification alters the crystal structure stability, electronic conductivity, and electrochemical properties, enabling the material to maintain structural integrity during high-voltage charging while achieving high capacity
Solution Approach 2:
The rare earth elements (M1) and other elements (M2) act as intermediaries that mediate between the high-voltage charging conditions and the layered transition metal oxide structure. These dopant elements buffer the structural stress, suppress phase transitions, and stabilize the crystal lattice during high-voltage operation, allowing high capacity to be achieved without severe structural damage
3Ease of operation
If the positive electrode active material is exposed to air, then the material can be handled easily, but moisture penetration causes structural damage reducing air stability
Solution Approach 1:
The patent creates a composite material where rare earth elements (M1) and other elements (M2) are doped into the layered transition metal oxide structure. This composite structure provides inherent stability against moisture penetration and air exposure, allowing the material to be handled more easily without severe protective measures while maintaining structural integrity and preventing degradation from atmospheric exposure
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
Enhances the capacity retention rate of sodium-ion batteries by improving structural stability and cycling performance through the use of a NiFeMn-based active material with controlled doping, leading to improved air stability and reduced phase transitions.
Implementation Method 1
M1 includes a rare earth element... can form a dense and uniform doping layer on the surface of the positive electrode active material, reducing the probability of phase transitions
Implementation Method 2
M2 includes at least one of a group IA element, a group IIA element, a group IIIA element, a group IVA element, a group VA element, a group VIA element, and a transition element... can form strong chemical bonds with O in the positive electrode active material, suppressing the deintercalation of Na elements
Data Source
AI summary
The present application discloses a positive electrode active material and a preparation method thereof, a positive electrode plate, a battery, and an electric device. The positive electrode active material includes:where M1 includes a rare earth element; M2 includes at least one of a group IA element, a group IIA element, a group IIIA element, a group IVA element, a group VA element, a group VIA element, and a transition element; and 0.6≤x≤1.2, 0<a≤0.5, 0<b≤0.4, 0.3≤c≤0.75, 0.001≤d≤0.05, 0≤e≤0.3, −0.1≤δ≤0.1, 0≤f≤0.1, 0.005≤d/c≤0.05, and a+b+c+d+e=1.