Sol-Gel LiTiAlPO4 Solid Electrolyte Density Control
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Solution Overview
Problem
Conventional ceramic solid electrolytes synthesized by the solid-phase method suffer from high porosity, grain boundary resistance, and non-homogeneous mixing, leading to reduced ionic conductivity in lithium rechargeable batteries.
Innovation Solution
The development of a sol-gel method to produce Li(1+x)Ti(2-x)Alx(PO4)3 particles with a true density of 2.20 to 2.50 g/cm3, which enhances ionic conductivity by reducing grain boundary resistance and particle size, allowing for a more efficient charge and discharge process in lithium rechargeable batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a solid-phase method is used to synthesize ceramic solid electrolyte, then the manufacturing process is simple, but the ionic conductivity deteriorates due to high porosity and grain boundary resistance
Solution Approach 1:
The patent changes the synthesis method from solid-phase to sol-gel method, which fundamentally alters the formation parameters of the solid electrolyte. This results in lower porosity and reduced grain boundary resistance, thereby improving ionic conductivity while maintaining manufacturing feasibility
Solution Approach 2:
The patent uses a composite approach by forming a coating layer containing lithium compound on the surface of the solid electrolyte particles. This composite structure improves ionic conductivity at the particle surfaces and interfaces, addressing the grain boundary resistance issue without complicating the overall manufacturing process
2Shape
If heating temperature is increased to coarsen the grain in solid-phase synthesis, then the grain size increases, but the porosity increases and ionic conductivity deteriorates
Solution Approach 1:
The patent changes the synthesis methodology from solid-phase to sol-gel method, which allows for better control of grain growth and porosity formation. The sol-gel process enables homogeneous mixing at molecular level before sintering, resulting in denser structures with lower porosity even at optimized heating temperatures
Solution Approach 2:
The patent performs preliminary mixing of starting materials in a sol-gel state before sintering, ensuring homogeneous distribution of components. This preliminary homogeneous mixing prevents non-reacted phases and reduces porosity formation during subsequent heating, improving ionic conductivity without requiring excessive grain coarsening
3Ease of manufacture
If the mixing state of starting material is not homogeneous in solid-phase method, then the manufacturing process is simpler, but non-reacted phases are easily generated
Solution Approach 1:
The patent changes the mixing state from solid-phase to sol-gel state, allowing molecular-level homogeneous mixing of starting materials. This parameter change ensures complete reaction during sintering, eliminating non-reacted phases while maintaining manufacturing simplicity through the one-step sol-gel process
Solution Approach 2:
The patent uses a sol-gel intermediary state to achieve homogeneous mixing. The liquid sol state acts as a mediator that enables thorough mixing of starting materials at molecular level, which would be difficult to achieve in solid-phase mixing, thereby preventing non-reacted phases without complicating the manufacturing process
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 sol-gel method results in a solid electrolyte with ionic conductivity ranging from 2.33×10−4 S/cm to 2.43×10−4 S/cm at room temperature, improving the charge and discharge characteristics and cycle-life of lithium rechargeable batteries while simplifying the manufacturing process.
Implementation Method 1
The Li(1+x)Ti(2-x)Alx(PO4)3 (0≦x≦1) particles may be formed according to a sol-gel method
Implementation Method 2
mixing a first mixed solution including a lithium source material and a PO4 source material, and a second mixed solution including alcohol, a chelating agent and titanium alkoxide; heating the mixture at about 40° C. to about 80° C. to provide a chelate/metal sol; heating the sol at 200° C. to 300° C. to provide a gel precursor
Implementation Method 3
firing the gel precursor at 650° C. to 950° C.
Implementation Method 4
The solid electrolyte may have a ionic conductivity of about 2.33×10−4 S/cm to about 2.43×10−4 S/cm at a room temperature
Data Source
AI summary
Disclosed is a solid electrolyte including particles comprising Li(1+x)Ti(2-x)Alx(PO4)3 (0≦x≦1) having a true density of about 2.20 to about 2.50 g/cm3.