Polycrystalline Sodium Titanium Oxide Electrode Synthesis
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Solution Overview
Problem
Current sodium ion secondary batteries face challenges in developing high-capacity, reversible electrode materials, particularly for negative electrodes, due to the use of expensive and safety-concerned lithium and the lack of investigation into polycrystalline sodium titanium oxide synthesis.
Innovation Solution
A method for producing a single-phase polycrystalline sodium titanium oxide (NaxTi4O9) with a one-dimensional tunnel type structure, using a mixture of sodium compounds and metal titanium, fired in a non-oxidizing atmosphere, which can be represented by Na2Ti4O9, facilitating reversible charge/discharge reactions in secondary batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If metal sodium is used for the synthesis of NaxTi4O9, then the material can be produced, but safety concerns and handling difficulties arise due to the high reactivity of metal sodium
Solution Approach 1:
The patent replaces expensive and hazardous metal sodium with inexpensive and safe sodium carbonate (Na2CO3) as the sodium source. This substitution eliminates safety concerns while maintaining the ability to synthesize NaxTi4O9, directly resolving the contradiction between ease of manufacture and safety concerns.
Solution Approach 2:
The patent changes the chemical form of the sodium source from metallic sodium (highly reactive) to sodium carbonate (stable compound). This parameter change in the chemical state of sodium enables safe handling and storage while still achieving the desired synthesis of NaxTi4O9 through controlled reaction with titanium compounds at elevated temperatures.
2Use of energy by moving object
If lithium ion secondary batteries are used, then high energy density is achieved, but cost increases due to the expensive nature of lithium
Solution Approach 1:
The patent substitutes expensive lithium with inexpensive sodium to produce NaxTi4O9 for battery applications. Sodium is abundant and cost-effective, allowing production of high-capacity batteries at lower cost while maintaining performance through the one-dimensional tunnel structure that enables efficient sodium ion insertion/extraction.
Solution Approach 2:
The NaxTi4O9 material developed in this patent serves multiple functions: it can be used in both sodium ion secondary batteries and lithium ion secondary batteries. The one-dimensional tunnel structure accommodates both Na+ and Li+ ions, providing universal applicability across different battery chemistries and enabling cost-effective alternatives to lithium-based systems.
3Quantity of substance
If polycrystalline NaxTi4O9 is synthesized, then high-capacity electrode material is obtained, but synthesis methodology has not been established leading to manufacturing uncertainty
Solution Approach 1:
The patent performs preliminary mixing of sodium carbonate and titanium compounds in specific ratios before firing. This preliminary preparation ensures proper stoichiometry and homogeneous distribution of reactants, leading to consistent synthesis of polycrystalline NaxTi4O9 with controlled composition and desired one-dimensional tunnel structure, thereby establishing a reliable manufacturing methodology.
Solution Approach 2:
The patent optimizes firing parameters including temperature range (800-1600°C), atmosphere (non-oxidizing), and time to produce high-quality polycrystalline NaxTi4O9. By controlling these parameters, the method achieves complete reaction, proper phase formation, and desired crystal structure, establishing a reproducible synthesis methodology for high-capacity material production.
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 method enables the creation of high-capacity, reversibly chargeable and dischargeable sodium ion and lithium ion secondary batteries, with the polycrystalline material demonstrating stable performance over multiple cycles.
Implementation Method 1
a step of firing a raw material containing a sodium compound and at least one of a titanium compound and metal titanium at 800° C. or more but 1600° C. or less
Implementation Method 2
NaxTi4O9 (2≤x≤3) which is a sodium titanium oxide having, similar to Na0.44MnO2, a large one-dimensional tunnel type structure became a candidate for a negative electrode material
Data Source
AI summary
Provided are a sodium ion secondary battery and a lithium ion secondary battery capable of undergoing a reversible large-capacity charge/discharge reaction. The sodium and lithium ion secondary batteries each have a positive electrode, a negative electrode, and an electrolyte. The active substance of the positive or negative electrode of these secondary batteries is a single-phase polycrystal represented by the following chemical formula: NaxTi4O9 (2≤x≤3), preferably Na2Ti4O9, having a one-dimensional tunnel type structure, and belonging to a monoclinic crystal system. This polycrystal is obtained by filling a container made of molybdenum or the like with a raw material containing a sodium compound and at least one of a titanium compound and metal titanium, and firing at 800° C. or more but 1600° C. or less.