Titanium Composite Electrode for High-Capacity Lithium Batteries
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Solution Overview
Problem
Conventional lithium secondary batteries have insufficient electric capacity and cycle stability, particularly with materials like Li4Ti5O12, which limits their energy density and safety during rapid charging, and alternative titanium-based materials like bronze-structure titanium oxide suffer from low packing density and adhesion issues.
Innovation Solution
A titanium-based composite oxide with a tunnel or layered structure, containing niobium and/or phosphorus, is developed, optimizing its composition and structure to enhance charge/discharge capacity and cycle stability, with specific surface areas between 5 to 50 m2/g, and a production method that includes heat treatment and carbon coating to improve conductivity and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If bronze-structure titanium oxide is converted into nanoparticles to increase charge/discharge capacity, then the charge/discharge capacity increases to 200 mAh/g or more, but the packing density of the electrode decreases and adhesion between the coating film and current collector deteriorates
Solution Approach 1:
The patent changes the particle size parameter from nanometer scale to micrometer scale (5-10 μm diameter), which fundamentally alters the balance between capacity and adhesion. The micrometer-scale particles provide sufficient surface area for electrochemical reactions while maintaining adequate mechanical strength and contact area for reliable adhesion to the current collector, resolving the contradiction between high capacity and good adhesion.
Solution Approach 2:
The patent creates particles with non-uniform internal structure, specifically a core-shell type structure where the interior and exterior have different characteristics. The particles have a firm internal framework that provides structural stability and adhesion, while the surface maintains sufficient reactivity for charge/discharge processes, thus locally optimizing different regions for different functions.
2Reliability
If bronze-structure titanium oxide of micron size is used to reduce specific surface area and improve cycle properties, then cycle properties improve with firm particle framework, but the charge/discharge capacity becomes small
Solution Approach 1:
The patent optimizes the particle size parameter to a specific micrometer range (5-10 μm diameter) and controls the specific surface area to fall within 5-50 m²/g. This parameter optimization allows the particles to maintain a firm framework for good cycle properties while preserving sufficient surface area for adequate charge/discharge capacity, achieving a balance between the two contradictory requirements.
Solution Approach 2:
The patent creates a core-shell type structure where the interior provides structural stability and the exterior provides electrochemical reactivity. This local differentiation allows the core to maintain firm framework for cycle stability while the shell maintains sufficient surface area for charge/discharge capacity, resolving the contradiction between cycle properties and capacity.
3Reliability
If Li4Ti5O12 is used as negative electrode material to achieve high potential of 1.5 V and improve safety, then safety is enhanced and cycle properties are satisfactory, but the electric capacity decreases to approximately half of carbon
Solution Approach 1:
The patent develops composite titanium oxide materials that combine the safety advantages of high-potential titanium oxide (1.5 V vs. Li) with enhanced capacity through controlled microporous structures and surface modifications. The composite structure allows simultaneous achievement of safety (through high potential) and improved capacity (through optimized surface area and pore structure), resolving the contradiction between safety and capacity.
4Use of energy by moving object
If carbon-based negative electrodes are used to achieve high energy density, then the voltage and energy density at discharge are high, but lithium metal is deposited during rapid charge increasing the risk of internal short circuiting
Solution Approach 1:
The patent changes the electrode material from carbon-based to titanium oxide-based with potential of 1.5 V vs. Li, which fundamentally changes the electrochemical window and prevents lithium metal deposition. This parameter change (potential level) simultaneously maintains high energy density while eliminating the safety risk of lithium plating during rapid charging, resolving the contradiction between energy density and safety.
Data Source
AI summary
The present invention provides a novel titanium-based composite oxide being usable as an electrode material for a lithium secondary battery and having a high capacity and an excellent cycle stability, a method for producing the same and a lithium secondary battery using the titanium-based composite oxide. Disclosed is a compound obtained by compositing titanium oxide with elements other than titanium, specifically a titanium-based composite oxide wherein the relevant chemical formula is Ti(1-x)MxOy, M is the element Nb or the element P, or a combination of these two elements in an optional ratio therebetween, x is such that 0<x<0.17, y is such that 1.8≦y≦2.1, x is the sum of Nb and P when M is a combination of the element Nb and the element P, and the present invention provides a lithium secondary battery using as an electrode the titanium-based composite oxide.