Sodium-Ion Cathode Material Stabilized for Na Deintercalation
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Solution Overview
Problem
Existing sodium-ion batteries using layered transition metal oxides suffer from poor initial coulombic efficiency and cycling performance due to structural instability during sodium deintercalation, leading to irreversible changes and side reactions with the electrolyte.
Innovation Solution
A positive electrode active material composed of Na x Mn a Fe b M c N d O 2+δ-e F e, where cations with an ionic potential greater than or equal to 5 Å -1<, including manganese, iron, and N ions, are used, forming strong covalent bonds with oxygen to stabilize the structure during sodium deintercalation, thereby improving initial coulombic efficiency and cycling performance.
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 structural stability during sodium deintercalation deteriorates, leading to poor initial coulombic efficiency and cycling performance
Solution Approach 1:
The patent introduces ions with high ionic potential (≥5 Å⁻¹) at specific lattice positions within the layered transition metal oxide structure. These localized high-ionic-potential sites create strong electrostatic fields that stabilize the oxygen sublattice during sodium deintercalation, preventing structural collapse while preserving the high-capacity layered framework
Solution Approach 2:
The patent creates a composite cathode material by combining layered transition metal oxides (such as Na₀.₆[Mn₀.₈Ni₀.₁Co₀.₁]O₂) with ions of high ionic potential (such as Al³⁺, Ti⁴⁺, Ta⁵⁺, or Nb⁵⁺). This composite structure integrates the high capacity of layered oxides with the structural stabilization effect of high-ionic-potential ions, achieving both high capacity and improved cycling performance
2Quantity of substance
If layered transition metal oxides undergo sodium deintercalation, then the battery can deliver high capacity, but side reactions with the electrolyte increase, deteriorating initial coulombic efficiency
Solution Approach 1:
The patent applies preliminary anti-action by introducing high-ionic-potential ions before battery operation to preemptively stabilize the cathode structure. This pre-stabilization prevents oxygen release and structural degradation that would otherwise trigger harmful side reactions with the electrolyte during subsequent cycling, thereby improving initial coulombic efficiency
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 proposed active material enhances the structural stability of sodium-ion batteries, reducing side reactions and improving both initial coulombic efficiency and cycling performance by stabilizing the structure during sodium deintercalation.
Implementation Method 1
cations with an ionic potential greater than or equal to 5 Å -1, including manganese, iron, and N ions, are used, forming strong covalent bonds with oxygen to stabilize the structure during sodium deintercalation
Implementation Method 2
The positive electrode active material maintains structural stability during deintercalation of sodium
Data Source
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AI summary
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: NaxMnaFebMcNdO2+δ-eFe, where 0.5 ≤ x ≤ 1.1, a ≥ 0, b ≥ 0, c ≥ 0, d > 0, a + b + c + d = 1, -0.1 ≤ δ ≤ 0.1, and e ≥ 0; M ions include at least one of Ni2+, Ni3+, Cu2+, Cu+, Zn2+, Mg2+, Y3+, La3+, In3+, Sb3+, Li+, Sn2+, and Ag+; ΣBi × I14 ≥ 1500 Å-4, where Bi is a molar fraction of cations, Ii is an ionic potential of the cations, in unit of Å-1, and the cations include manganese ions, iron ions, M ions, and N ions; and the ionic potential of the N ions is greater than or equal to 5 Å-1.