Cu-Doped O3 Cathode Material for Stable Sodium Battery Cycling
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Solution Overview
Problem
O3-type positive electrode active materials for sodium secondary batteries face challenges in structural stability, capacity, and lifespan due to gas generation from electrolyte side reactions and loss of internal sodium during washing.
Innovation Solution
The solution involves improving the structural stability of O3-type positive electrode active materials by calcining and Cu doping during preparation, which enhances particle cohesion, air stability, and water stability, and maintains the O3-type crystal structure even after washing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If O3-type layered oxide is used as positive electrode active material, then energy density is improved, but cycle stability deteriorates due to structural changes during charge/discharge
Solution Approach 1:
The patent modifies the crystal structure parameters by controlling the aspect ratio of primary particles to be within 1:1 to 1:2.5, and adjusting the ratio of average particle diameter of secondary particles to primary particles to be within 2.5 to 10. These parameter changes optimize the balance between energy density and cycle stability by reducing excessive structural changes during charge/discharge while maintaining high sodium content.
Solution Approach 2:
The patent creates a composite structure where multiple primary particles aggregate to form secondary particles with controlled morphology. This composite architecture combines the high energy density advantage of O3-type structure with improved cycle stability through the aggregated particle design, which distributes mechanical stress during electrochemical cycling.
2Quantity of substance
If O3-type oxide particles are washed with water to remove residual Na, then purity is improved, but structural stability deteriorates as internal Na is lost and structure collapses
Solution Approach 1:
The patent performs preliminary surface treatment during the synthesis process to form a stable surface layer that prevents excessive Na leaching during subsequent water washing. The controlled aspect ratio and aggregation structure are established before washing, which protects the internal structure while allowing removal of surface residual Na.
Solution Approach 2:
The aggregated secondary particle structure acts as a protective shell around primary particles, maintaining structural integrity during water washing. The controlled morphology and inter-particle bonding create a flexible yet stable architecture that allows water penetration for Na removal while preventing complete structure collapse.
3Quantity of substance
If primary particle aspect ratio is increased, then capacity characteristics are improved, but particle breakage during washing increases
Solution Approach 1:
The patent optimizes the aspect ratio parameter within the specific range of 1:1 to 1:2.5 to achieve the best balance between capacity characteristics and particle strength. This controlled parameter change ensures that particles have sufficient elongation for high capacity while maintaining adequate structural integrity to resist breakage during washing and handling.
Solution Approach 2:
The patent creates local quality variations in the particle structure by controlling the aggregation of primary particles into secondary particles with specific morphology. The local bonding characteristics and particle arrangement are optimized to provide enhanced strength at critical locations while maintaining the aspect ratio needed for high capacity.
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
This approach results in improved energy density, high voltage stability, extended lifespan characteristics, and enhanced rate characteristics for sodium secondary batteries, while minimizing particle breakage and structural collapse.
Implementation Method 1
Cu doping during preparation, which enhances particle cohesion, air stability, and water stability, and maintains the O3-type crystal structure even after washing
Implementation Method 2
calcining and Cu doping when preparing the positive electrode active material
Implementation Method 3
O3-type layered oxide in which a plurality of primary particles are aggregated, and an aspect ratio of the primary particle ranges from 1:1 to 1:2.5
Data Source
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Figure 2A
AI summary
One embodiment of the present invention provides a positive electrode active material for a sodium secondary battery, including an O3-type sodium composite transition metal oxide containing at least sodium, a transition metal, and a doping metal, wherein the sodium composite transition metal oxide is a secondary particle in which a plurality of primary particles are aggregated, and an aspect ratio of the primary particle ranges from 1: 1 to 1:2.5.