Sodium-Blocking Layer on Titanium Composite Oxide Electrode
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries, particularly those using titanium-based negative electrodes, face challenges with low energy density and high operating potential, leading to reduced battery voltage and increased number of batteries required in series for high-voltage applications, along with instability at high temperatures due to sodium ion elution and side reactions.
Innovation Solution
The use of a sodium-containing titanium composite oxide with a monoclinic titanium dioxide sodium ion-blocking layer, which has a crystal structure belonging to the space group Cmca or Fmmm, is introduced to stabilize lithium insertion/extraction reactions at a lower potential, suppress sodium ion elution, and enhance battery performance at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxide of titanium is used as negative electrode active material, then rapid charge-and-discharge performance and long-term reliability are improved, but energy density decreases due to higher potential and lower capacity per weight
Solution Approach 1:
The patent changes the crystal structure parameter of titanium oxide from conventional phases to a specific phase with space group Cmca or Fmmm, which has lower potential vs. Li/Li+ and higher capacity per weight, thereby improving energy density while maintaining reliability
Solution Approach 2:
The patent uses a composite material consisting of titanium-including composite oxide with specific crystal phases (Cmca or Fmmm) combined with sodium-containing titanium composite oxide, achieving both high energy density and stable rapid charge-discharge performance
2Reliability
If material with high potential relative to metallic lithium is used as negative electrode material, then voltage becomes lower than conventional batteries, but this requires more batteries in series for high-voltage applications
Solution Approach 1:
The patent changes the electrochemical potential parameter of the negative electrode material by adopting a specific crystal phase (Cmca or Fmmm) of titanium oxide, which operates at lower potential vs. Li/Li+ (improving voltage) while maintaining stability through the unique crystal structure
3Use of energy by moving object
If sodium-containing titanium composite oxide is used to improve energy density, then sodium ion elution occurs at high temperatures causing side reactions and instability
Solution Approach 1:
The patent introduces a sodium ion-blocking layer as an intermediary between the sodium-containing titanium composite oxide and the electrolyte, preventing sodium ion elution and side reactions at high temperatures while allowing the high-energy-density material to function
Solution Approach 2:
The patent creates a composite structure combining sodium-containing titanium composite oxide (for high energy density) with sodium ion-blocking layer materials (for thermal stability), achieving both high energy density and stability at elevated temperatures
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 configuration results in a secondary battery with improved energy density, higher voltage, and extended life performance at elevated temperatures by stabilizing lithium insertion reactions and reducing side reactions, while maintaining high-rate discharge efficiency.
Implementation Method 1
a sodium ion-blocking layer formed on a surface of the active material-containing layer... the sodium ion-blocking layer contains a material impermeable to sodium ions
Implementation Method 2
stabilize lithium insertion/extraction reactions at a lower potential... the active material-containing layer contains a sodium-containing titanium composite oxide
Data Source
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AI summary
According to one approach, there is provided an electrode construct including an active material-containing layer and a sodium ion-blocking layer (8). The active material-containing layer contains a sodium-containing titanium composite oxide having a crystal structure belonging to a space group Cmca or a space group Fmmm. The sodium ion-blocking layer (8) is disposed on a surface of the active material-containing layer. The sodium ion-blocking layer (8) contains a material impermeable to sodium ions.