P2 Sodium Cathode Composition for Stable High-Manganese Cycling
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Solution Overview
Problem
High-manganese-based sodium ion secondary batteries suffer from phase transitions due to Jahn-Teller distortion, leading to reduced cycle life and capacity, and conventional methods to improve conductivity and stability are not effective.
Innovation Solution
A positive electrode active material is developed using a sodium manganese-based oxide with a P2-type layered structure, incorporating nickel, manganese, and a doping metal, produced through a dry process of simultaneous roasting and doping, which enhances energy density, stability, and cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a high-manganese-based oxide is used to achieve high capacity and price competitiveness, then energy density is improved, but phase transition occurs due to Jahn-Teller distortion leading to deteriorated cycle life and capability rate
Solution Approach 1:
The patent applies parameter changes by controlling the oxidation state of manganese (maintaining Mn3+ without excessive oxidation to Mn4+) and adjusting the ratio of transition metals to suppress Jahn-Teller distortion. By carefully controlling the oxidation roasting conditions and doping composition, the patent modifies the electronic and structural parameters of the high-manganese oxide to prevent phase transitions while preserving high capacity.
Solution Approach 2:
The patent uses composite materials by doping the high-manganese-based oxide with other transition metals (such as nickel, cobalt, or zinc) to create a multi-element composite structure. This composite approach stabilizes the crystal lattice, suppresses Jahn-Teller distortion, and prevents irreversible phase transitions, thereby improving cycle life while maintaining high energy density.
2Reliability
If conventional wet method doping is used to improve stability, then phase transition is suppressed, but productivity decreases due to additional heat treatment and process complexity increases
Solution Approach 1:
The patent merges the doping process with the oxidation roasting process into a single simultaneous operation. By adding doping metal compounds to the precursor mixture before oxidation roasting, the patent combines two separate processes (doping and roasting) into one, eliminating the need for additional heat treatment steps and improving productivity while maintaining phase stability.
Solution Approach 2:
The patent applies preliminary action by pre-mixing the doping metal compounds with the precursor materials before oxidation roasting. This preliminary incorporation of doping metals ensures uniform distribution and effective doping without requiring subsequent separate doping steps, thereby simplifying the process and improving productivity while achieving the desired phase stability.
3Ease of manufacture
If co-precipitation reaction is used to produce ternary transition metal hydroxide precursor, then doping is achieved, but manganese oxides are synthesized in large amount due to high reactivity of manganese leading to non-uniform composition
Solution Approach 1:
The patent applies preliminary action by pre-mixing the doping metal compounds with the precursor materials before oxidation roasting. This preliminary incorporation of doping metals ensures uniform distribution and effective doping without requiring subsequent separate doping steps, thereby simplifying the process and improving productivity while achieving the desired phase 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 solution inhibits phase transitions, improves energy density, voltage stability, and cycle life, while reducing process costs and increasing productivity.
Implementation Method 1
a high-manganese-based (high-Mn) oxide having a P2-type layered structure has a problem of deterioration of electrochemical performance such as a high capability rate and life characteristics due to an irreversible phase produced by Jahn-Teller distortion in a charging and discharging process. The Jahn-Teller distortion is a phenomenon triggered by crystal field stabilized energy
Implementation Method 2
it is preferred to produce a ternary transition metal oxide which further includes a transition metal other than manganese
Implementation Method 3
conventionally, a method of doping a precursor with various transition metals by a wet method is used and the transition metal is doped by a heat treatment in a post-process
Data Source
Figure 1A~1B
Figure 1C
Figure 1D
AI summary
Provided are a positive electrode active material for a sodium secondary battery including: a sodium manganese-based oxide which includes at least sodium (Na), nickel (Ni), manganese (Mn), and a doping metal (MD) and has a manganese content of 55 mol% or more in all metals other than sodium, wherein the sodium manganese-based oxide is a secondary particle formed by agglomeration of at least one primary particle, and the primary particles have an aspect ratio of 1:1 to 1:2.5, a method for producing a positive electrode active material, and a positive electrode for a sodium secondary battery and a sodium secondary battery including the positive electrode active material.