Passivated LLZO Particles for Air-Stable Tape-Cast Films
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Solution Overview
Problem
The production of thin Li7La3Zr2O12 (LLZO) garnet films for solid-state batteries is hindered by the material's reactivity with water and CO2, leading to instability and fragility, and existing methods require complex processes like hot press sintering and long firing cycles, making scaling and consistency challenging.
Innovation Solution
A passivated LLZO particle with a core-shell structure, where the core is optionally doped and surrounded by a shell of H-LLZO, H3O+-LLZO, and/or Li2CO3, is developed, along with a tape casting method using a slip composition with excess lithium sources like Li2CO3, LiOH, and LiCl, allowing for stable processing in air and reducing the need for inert atmospheres.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If tape casting is used to make thin garnet films, then the thickness can be reduced to achieve high volumetric energy density, but the garnet powder reacts with water and CO2 in air causing instability and fragility
Solution Approach 1:
A passivation layer comprising Li2CO3, H-LLZO, and/or H3O+-LLZO is formed on the surface of the garnet particles. This intermediary layer acts as a protective barrier between the reactive LLZO core and the external environment (water and CO2), preventing harmful reactions while allowing the tape casting process to proceed in air without requiring inert atmospheres.
Solution Approach 2:
The invention creates a composite particle structure with a core-shell architecture: an inner LLZO core providing the desired electrochemical properties and an outer passivation layer providing chemical stability. This composite structure combines the benefits of both materials - the high ionic conductivity of LLZO and the environmental stability of the passivation layer.
2Device complexity
If conventional tape casting methods are used with pristine garnet, then the process can be simplified, but special techniques and inert atmospheres are required to prevent reaction with air
Solution Approach 1:
The passivation layer is formed on the garnet particles before the tape casting process. This preliminary action of surface modification ensures that the particles are already protected against environmental degradation, allowing the subsequent tape casting to be performed using conventional equipment and procedures in air, eliminating the need for complex inert atmosphere setups.
3Manufacturing precision
If excess lithium source is added to the tape casting powder, then Li-loss during sintering is compensated and dense films are achieved, but the formulation complexity increases
Solution Approach 1:
The excess lithium source (such as Li2CO3, LiOH, or Li2O) is merged with the passivation layer components. Since the passivation layer already contains Li2CO3 from the carbonation process, additional lithium sources are incorporated into the same protective layer structure, simplifying the overall formulation by combining multiple functions (protection and lithium compensation) into a single integrated component.
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 passivated LLZO particles and tape casting method result in more stable and flexible green tapes with longer shelf life, enabling faster and cost-effective production of dense, fine-grained LLZO films with consistent lithium ion conductivity, overcoming the reactivity issues and complexity of existing methods.
Implementation Method 1
The particle includes a shell including H-LLZO, H3O+-LLZO, and/or Li2CO3
Implementation Method 2
The passivated particles can stabilize the garnet to prevent it from reacting with organic materials in tape casting slips or in green tapes
Implementation Method 3
heating LLZO in air and/or CO2 at 50° C. to 650° C. for a suitable duration to form the passivated particle
Implementation Method 4
heating LLZO in air and/or CO2 at 50° C. to 650° C.
Implementation Method 5
The tape casting slip composition includes an excess lithium source in sufficient quantity such that the tape casting slip composition includes an amount of Li that is 1% to 40% in excess based on a stoichiometric amount of Li in the LLZO core
Implementation Method 6
The passivated particles can stabilize the garnet to prevent it from reacting with organic materials in tape casting slips or in green tapes
Data Source
AI summary
Passivated Li7La3Zr2O12 (LLZO) particles, tape casting powders and slip compositions including the particles, methods of forming the particles, methods of tape casting using the particles, green tapes including the particles, cast LLZO films formed from the particles, and lithium batteries including the cast LLZO film. A passivated LLZO particle includes an LLZO core, wherein the LLZO is optionally doped with one or more elements. The passivated LLZO particle also includes a shell including H-LLZO, H3O+-LLZO, and/or Li2CO3.