Doped Sodium Manganese Oxide Cathode for Stable Sodium Ion Batteries
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Solution Overview
Problem
Current lithium-ion batteries face challenges with scarcity of lithium resources, high costs due to cobalt and nickel, and safety concerns such as fire and explosion risks, while sodium-ion batteries are underdeveloped and lack commercial cathode materials with sufficient cycle stability and safety.
Innovation Solution
Development of a sodium transition metal cathode material with a P2 layered bronze crystal structure, composed of abundant sodium and manganese with low-valent dopants like magnesium, lithium, or nickel, which undergoes structural transformation during charging to achieve high reversible capacity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium-ion batteries are used to achieve high energy density, then energy storage performance is improved, but resource scarcity and cost increase
Solution Approach 1:
The patent changes the chemical composition parameters by substituting lithium with sodium and incorporating multi-element doping (magnesium, lithium, nickel) into the manganese oxide structure. This parameter change enables the use of abundant sodium resources while maintaining electrochemical performance through optimized compositional ratios and structural configuration.
Solution Approach 2:
The patent creates a composite cathode material with the formula NaxMO2 where M contains manganese along with magnesium, lithium, and/or nickel elements. This composite structure combines the advantages of different elements: sodium provides abundance, manganese provides high capacity, magnesium stabilizes the structure, lithium enhances conductivity, and nickel improves voltage. The composite material achieves both resource sustainability and high energy density.
2Use of energy by moving object
If cobalt and nickel are used in cathode materials to achieve high energy density, then energy storage performance is improved, but material cost increases
Solution Approach 1:
The patent applies local quality by strategically positioning different dopant elements in the cathode structure. Magnesium, lithium, and nickel are incorporated in specific ratios (0 < x ≤ 0.5 for each) at the M-site of the NaxMO2 structure, creating local compositional variations that optimize both performance and cost. This localized doping approach achieves high energy density without requiring expensive cobalt and nickel in large quantities.
Solution Approach 2:
The patent replaces expensive cobalt and nickel with cheaper alternatives: magnesium and lithium are used as primary dopants, with nickel only as a supplementary element in limited amounts. The formulation NaxMO2 with M = Mn1-x-y-zMgxLiyNiz allows the use of abundant, low-cost elements while maintaining electrochemical performance through optimized stoichiometry and structural design.
3Use of energy by moving object
If lithium-based cathode materials are used to achieve high capacity, then energy storage is improved, but safety concerns arise
Solution Approach 1:
The patent introduces magnesium and nickel as intermediary elements that mediate between the sodium host structure and the electrochemical reactions. Magnesium stabilizes the crystal structure during cycling, preventing catastrophic failures, while nickel modulates the voltage profile and improves electronic conductivity. These intermediary elements enhance safety by creating a more stable and controllable electrochemical environment.
Solution Approach 2:
The patent employs magnesium doping as a preventive measure to stabilize the cathode structure before electrochemical cycling begins. The magnesium atoms occupy specific sites in the NaxMO2 structure, creating a pre-stabilized framework that resists structural degradation, phase transitions, and oxygen release during charging and discharging. This beforehand cushioning prevents safety issues before they occur.
4Quantity of substance
If sodium-ion batteries are developed to reduce cost and improve safety, then resource availability and safety are improved, but cycle stability is insufficient
Solution Approach 1:
The patent optimizes multiple parameters simultaneously: sodium content (x in NaxMO2), dopant ratios (magnesium, lithium, nickel), oxidation states, and crystal structure parameters. By carefully adjusting these parameters, the patent achieves a balance between sodium ion accessibility (for high capacity) and structural stability (for long cycle life). The optimized formulation enables stable cycling while maintaining high sodium content.
Solution Approach 2:
The patent creates a composite cathode material where manganese forms the base structure providing high capacity, while magnesium, lithium, and nickel serve as stabilizing and performance-enhancing components. This composite structure combines the high capacity of sodium-manganese oxide with the structural stability provided by magnesium and the electrochemical performance enhancement from lithium and nickel, achieving both high capacity and long cycle stability.
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 sodium cathode material exhibits a high reversible capacity of over 170 mAh/g, improved air stability, and enhanced cycle stability, potentially replacing lithium-ion batteries with reduced costs and increased safety.
Implementation Method 1
The successful reversible intercalation and de-intercalation of sodium ions in a cathode material (NaxCoO2) has been described already 1981 by Delmas
Implementation Method 2
The Fe—Mn-oxide host structure remains intact during sodium de-intercalation and re-insertion
Data Source
AI summary
A sodium transition metal cathode material for a rechargeable sodium battery having a P2 layered bronze crystal structure, comprising at least 55 mol % manganese, wherein the manganese valence state is at least 3.75. The material undergoes a structural transformation to a secondary cathode material by extraction of sodium during the 1st charge of a rechargeable sodium battery comprising the sodium cathode material. The material has either a composition NaxMO2 where M=Mn1-y-zLiyAz where z<0.2 and y<0.33 and 0.66<x<0.95, and wherein A consists of either one of more elements of the group Ti, Fe, Ni, Mg and Co, or a composition NaxMO2 where M=LiaMn1-a-b-cMgbAc where 0<a<0.2, c<0.2 and 0.2<a+b<0.46 and 0.66<x<0.95, and wherein A consists of either one of more elements of the group Ti, Fe, Ni and Co.