Method to produce li-based crystalline layers using coarse feedstock powder material and dry coating process

Abstract

The present invention relates to a method for producing a Li-conductive layer coating for solid-state battery cells. The method utilizes a powder feedstock material suitable for thermal spray or cold spray processes to apply the Li-conductive layer onto substrates such as anodes, cathodes, or current collectors. By employing plasma spraying, HVOF, HVAF, or cold spraying in a one-step process, the method preserves the crystallinity of the feedstock powder material after deposition. This approach results in a high-density electrolyte layer comprising Li-based oxides, which maintains high crystallinity of the cubic phase. The method allows for optional doping with alloying elements and enables the production of multilayer or graded composition electrolyte layers. Consequently, this versatile technique facilitates the fabrication of complete or partial solid-state battery unit cell coating systems.

Description

[0001] Method to Produce Li-Based Crystalline Layers Using Coarse Feedstock Powder Material and Dry Coating Process

[0002] The present invention relates to a dry process for producing lithium-based crystalline layers for solid state batteries using coarse feedstock powder material and a one-step coating method to preserve the crystallinity of the base material.

[0003] In the rapidly evolving field of battery technology, lithium-based batteries stand out for their high energy density. The advancement to solid-state batteries, which replace liquid electrolytes, aims to address the limitations of traditional lithium-ion batteries. A particular challenge in this domain is achieving a balance between high thermal stability, long cycle life, and high energy density. This balance is crucial, as it is demonstrated for example with lithium iron phosphate (LFP) batteries that are cost- effective but struggle with lower energy density. The emerging solid-state lithium-metal technology shows promise in enhancing energy density while maintaining safety and durability, potentially enabling the application of batteries beyond just electric vehicles. In particular, solid-state lithium metal cells which employ oxide electrolytes, or a combination of oxide and polymer electrolytes offer an attractive option for achieving high energy and power density.

[0004] One possible choice, like Lithium Lanthanum Zirconate (LLZO) electrolyte, comes with some clear benefits. It demonstrates high oxidative stability, making it compatible with cathode materials such as Nickel Manganese Cobalt (NMC), Lithium Iron Phosphate (LFP), and even high voltage Lithium Manganese Nickel Oxide (LMNO) with a redox plateau at around 4.8 V against Li. Moreover, the LLZO electrolyte shows good electrochemical stability against metallic lithium, making it a favored option for electrolytes. However, a key challenge arises when it comes to processing Li-based materials such as LLZO.

[0005] The most matured pathway process to produce LLZO coatings is tape casting, which typically involves three main steps, assuming that the powder feedstock, which is itself a complex manufacturing process, has already been provided. The quality of the feedstock is important to form the basis for the subsequent steps, in order to ensure the desired properties for better solid-state battery performance. Consequently, precise control over synthesis conditions, including precursor particle size, temperature, and ramp rate, significantly influences LLZO powder characteristics.

[0006] Following the preparation of the feedstock, the three main steps involve a) mixing the powder with a binder which is a wet method b) apply the desired layer using tape casting, and c) sintering the applied layer

[0007] Sintering is essential in Li-based coating manufacturing methods such as tape casting as it increases material density, enhances mechanical strength, improves ionic conductivity, and maintains structural integrity, ensuring optimal performance as a solid-state battery electrolyte. However, sintering presents two challenges:

[0008] • The sintering process of Li-based coatings, in particular LLZO typically requires temperatures above 1000°C, raising concerns of lithium evaporation and stoichiometric deviations.

[0009] • It also contributes to heightened scrap rates due to volume shrinkage-induced cracking during the process.

[0010] Furthermore, the resulting consequences, including an additional process and the related increased risks, contribute to the already high capital and operational costs (Capex and Opex) of this process. Finally, tape casting processes are also limited to provide simple solutions to produce multilayer coatings effectively, a key requirement for developing advanced and efficient solid-state battery systems.

[0011] In order to address these technical and economic limitations caused by sintering, several innovative solutions are currently proposed.

[0012] The first method considered is Powder Aerosol Deposition (PAD), also called Aerosol Spray Deposition, which is a method suitable to be used for depositing ceramic solid electrolyte thin films. The process achieves high deposition rates and low-temperature processing. Unlike traditional cold spray processes, PAD uses micron-sized powder aerosol to ensure better film adherence at room temperature without interdiffusion reactions or mechanical failures. It is effective for large areas but faces challenges in film density, technology readiness, and compatibility with lithium metal electrodes, making it a promising yet evolving technique in solid-state battery development.

[0013] Unfortunately, one major limitation of PAD is the requirement for extremely fine feedstock, finer than 10 pm (D50) to obtain final coating densities above 95%. This fine feedstock increases the environmental footprint due to its energy-intensive production. Also, managing and feeding these fine particles present technical challenges, impacting the stability and efficiency of the coating process.

[0014] Another strategy is to manufacture thin ceramic-based solid electrolytes for solid-state batteries using a two-step coating process by Sequential Decomposition Synthesis (SDS), which offers an alternative to the traditional high-temperature sintering processes. SDS allows producing ceramics, such as crystalline LLZO by spraying a precursor solution onto a heated substrate, where it undergoes controlled pyrolysis to form dense, thin ceramic films without the need for high-temperature sintering. However, it has been shown that for LLZO the proposed method exhibits a more amorphous structure in the as-deposited state, and further annealing process at temperatures below 1000°C is needed to recover the crystallinity. Nevertheless, this method allows the production of films as thin as 1 -10 pm, similar to polymer separators in lithium-ion batteries, at temperatures close to 700°C. SDS offers the advantage of creating unique ceramic microstructures with a broad electrochemical stability window, beneficial for battery performance. However, despite its promising potential, SDS's complex chemistry and labor-intensive process raise scalability and cost concerns.

[0015] Compared to simpler, more scalable spraying techniques, SDS, like tape casting, is a wet process with potential environmental disadvantages. It may face limitations in material variety and production speed, making it a promising yet complex and environmentally impactful option in the future landscape of battery technology.

[0016] As a third state-of-the-art solution in addressing the above-mentioned challenges in solid state electrolyte production is Atmospheric Plasma Spraying (APS), which is a well-known process for other applications that can be used for producing solid-state battery coatings. APS melts feedstock powder material injected in a high-temperature plasma jet and sprays the resulting material in form of droplets onto a surface to create uniform coatings. It has been shown that this method can efficiently produce large- scale, coatings of garnet-type electrolytes, like LLZO onto various type of substrate. APS-made coatings show good electrical conductivity and strength, promising for large-scale battery production.

[0017] However, this process is operating at high temperatures, causing rapid cooling of the molten material on impact against the substrate, which can affect material consistency and crystal structure, which is crucial for battery performance. While lower temperatures help maintain crystallinity, they conflict with the need for high temperatures for deposition efficiency and coating density. Some publications suggest post-heat treatment at temperatures above 1000°C for as long as 10 hours to restore crystallinity, but this is impractical as it is as energy and time-consuming as sintering.

[0018] As shown, the current manufacturing methods for LLZO and similar Li-based coatings in solid-state batteries, in particular the electrolytes, encounter several challenges and limitations. High capital and operational, significant environmental impact due to the wet processes, and energy-intensive processes are major concerns. However, the main problem to be solved for the production of Li-based coatings of solid-state batteries is to efficiently produce dense, cubic crystalline Li-based coatings in a single step, thereby simplifying the production process for these coatings.

[0019] The present invention aims to propose a method for producing lithium-based crystalline layers for solid state batteries using a coarse feedstock powder material and a coating method which preserves the purity of the crystal phase of the base material to the coating. Thus, reducing the steps for manufacturing of Li-based coating to one single step.

[0020] According to one aspect of the present invention, a coarse powder feedstock of Li- based material, in particular LLZO for producing a Li-based electrolyte coating is used. This feedstock, with a nominal composition of Li?La3Zr20i2 and Ta doping of 5 at%, features a particle size distribution between 10 and 45 pm, in particular having a median size, D50, of 20±5pm and comprises over 95% purity of the desired crystalline cubic phase for the final Li-based coating. This starting material is suitable for the inventive method, which comprises any of the spraying methods allowing the coarse powder material to be deposited in a cubic phase onto the substrate. This includes, but is not limited to, thermal spray processes like plasma spraying, flame spray, High Velocity Oxygen Fuel (HVOF), High Velocity Oxygen Fuel (HVAF), as well as kinetic energy processes such as cold spray.

[0021] The process parameters for the inventive method are selected in such a manner that the molten droplets from the injected coarse powder into the plasma jet or gas flow do not transform their corresponding crystal phase purity below 95% on the resulting Li- based coating. This indicates that there is no phase transformation of the powder after its injection into the spray gun, during its in-flight trajectory, or throughout the deposition onto the substrate and subsequent cooling. Additionally, the process parameters may be adjusted so that when depositing Li-based electrolyte coatings, the resulting coating density is above 95%. Consequently, the inventive method is an efficient one-step method for depositing Li-based coatings, in particular LLZO, eliminating the need for any pre- or post-treatment of the material or coating.

[0022] The resulting coating by this inventive method exhibits surfaces with particle count below 1 in a 100x50 pm representative surface area and the corresponding surface roughness, Ra, is between 2.0 and 4.0 pm. These particles which are considered impurities coming from potential overspray re-deposition are an efficient measurement of the quality of a coating which is crucial for applications in batteries.

[0023] In a preferred embodiment, HVOF is the selected method of deposition, offering a balance between being colder than plasma spraying yet highly efficient for depositing dense materials. It has been found that this method serves as an optimal compromise between cold spraying, PAD, and plasma spraying. It allows for high-density deposition without altering the crystal phase, due to the very short travel time of particles in the fast-moving gas jet. HVOF also simplifies powder feedstock preparation, as it does not require complex, fine powder distribution like the ones used in PAD. For this purpose, readily available commercial powders can be employed. HVOF coating is known to be used in industries like aerospace, machinery, and petrochemicals for its outstanding wear resistance and the creation of hard coatings. This method significantly improves the durability and longevity of metal surfaces by enhancing their resistance to wear and tear, a key factor in the longevity and performance of industrial components. Despite its extensive industrial applications, its use in areas like battery technology is not well-established.

[0024] Another preferred embodiment of the present invention involves the use of dopants to enhance the properties of the Li-based coating, in particular the electrolyte layer, such as LLZO doped with alloying elements such as Ta (Tantalum), Al (Aluminum), Nb (Niobium), and Y (Yttrium). This doping method can be extended to include elements from groups III, IV, V, and VI of the periodic table. The introduction of these dopants into oxide Li-based coatings, such as LLZO matrix significantly improves their ionic conductivity and overall electrochemical stability. Such enhancements are crucial for achieving high-performance solid electrolytes, making them more efficient and reliable for use in advanced energy storage systems.

[0025] Another preferred embodiment of the present invention, the resulting Li-based coating forms a solid electrolyte layer, which is produced through a composite blend of polymer and oxide materials provided as powder feedstock material. The polymer component contributes flexibility and processability, while the oxide element, typically a lithium-based metal oxide, provides structural integrity and ensures efficient ionic conductivity. This innovative combination not only enhances the mechanical strength and durability of the electrolyte layer but also optimizes its electrochemical performance, making it well-suited for high-demand applications.

[0026] Another embodiment of this invention uses the proposed coating method to create multilayer electrolytes, such as a combination of two or more Li-based oxides, improving the interfaces between the electrolyte and the cathode and / or anode. For example, a multilayer electrolyte structure, comprising layers of Lithium Lanthanum Zirconate Oxide (LLZO), Lithium Aluminum Titanium Phosphate (LATP), and Lithium Phosphorus Oxynitride (LiPON), can be provided to smoothly transition from the cathode to the anode. This configuration optimizes the interface between each layer, ensuring efficient ion transport and improved overall battery performance.

[0027] Another embodiment of this invention uses the proposed coating method to provide graded compositions between the Li-based coatings, such as for example Lithium Lanthanum Zirconate Oxide (LLZO), Lithium Aluminum Titanium Phosphate (LATP), and Lithium Phosphorus Oxynitride (LiPON). This approach aims to reduce even more surface contact loss that often occurs with distinct layers. By seamlessly transitioning the material composition at each interface, a more integrated and stable structure is achieved. This not only enhances the ion transport efficiency but also significantly improves the overall performance and durability of the battery.

[0028] Building on the previous aspects of the present invention and since the resulting layers are all Li-based coating, another embodiment uses the proposed coating method to provide a complete or partial coating system composing a unit cell of a solid state battery, such as a combination of anode / electrolyte / cathode or partially just anode / electrolyte and / or cathode / electrolyte coating systems. Similar to the embodiment about the multilayer structure of an electrolyte, such embodiment not only streamlines the battery's architecture but also enhances its overall efficiency and connectivity.

[0029] It is important to note that these embodiments are not limited to the specific compositions mentioned before, such as LLZO, LATP, LiPON. The scope of this invention extends to similar coatings that possess Li-ion conductive properties and needs the conservation of the crystallinity during the coating process. This flexibility allows for the exploration and utilization of a wide range of materials, broadening the potential for innovative battery design and application. These embodiments are also only possible due to the inventive one-step method which would not be possible using conventional coating processes used in solid state batteries.

[0030] The invention will now be described with an example and with reference to the figures.

[0031] The following example provides the one-step process of forming LLZO dense layers with a phase purity of the cubic crystal structure above 95%. In this example LLZO powder with a size distribution of D50=20±5pm is provided having a nominal composition Li?La3Zr20i2 and Ta doping of 5 at%, which is also commonly written as LLZTO. A SEM micrograph of the powder is shown in Figure 1 a) and its corresponding measured physical properties, including cubic phase in wt%, XRD and particle size distribution in Figure 1 b). In order to show the advantage of the inventive method, two different thermal spray processes have been selected to produce the desired coating on steel substrates: HVOF and Plasma Spray-Thin Film (PS-TF), which is an extension of the well-known Low Pressure Plasma Spraying (LPPS) but operated at lower pressure, typically between 0.5 and 20 mbar, in particular for this example 1.5 mbar. For the sake of simplicity this process will be further mentioned as LPPS. The as-sprayed samples are shown in Figure 2 with the LLZO coating using HVOF process (23B0381 ) in Figure 2 a) and "LPPS" process (23T0153) in Figure 2 b). The corresponding light microscope micrographs are shown in Figure 2 c) for the HVOF coated LLZO and Figure 2 d) for the LLZO coating using LPPS. Here it can be shown that independently of the surface roughness of the substrate, both processes will produce coatings with a smoother surface than the initial substrate roughness. Both processes are known for this feature since the particle velocities are much higher compared to conventional thermal spray processes such as APS. It is also known that the primary distinction between HVOF and LPPS, particularly when considering the coating material, is the much lower processing temperatures for the injected powder feedstock in HVOF, as opposed to the higher enthalpy process encountered in LPPS. The resulting advantage of HVOF is the possibility to produce a coating with less thermal effects, thus reducing the transformation of the crystallinity of the base feedstock powder material.

[0032] For the LPPS process, an 03CP plasma gun with a combination of process gases of 80 / 10 NLPM Ar / He and electrical current of 1500 A has been used. It has to be noted that the current range for this comparison has been held low in order to avoid the potential of change in the crystallinity due to the high power of the plasma spray process. The corresponding net power for the trial was about 25 kW, the coating process was done in 4'30". Unlike other processes, a surface preparation, such as grit blasting is not always necessary when using LPPS. However, to ensure a good adherence on the substrate a pre-heating has to be done prior coating. The preheating is usually done using the same parameters than the coating parameters, just not injection the powder material. In this case the pre-heating time was 2 minutes so that the substrate can reach a temperature of about 400°C which corresponds to the temperature during the coating process. During the coating process the powder is injected at 2x20 g / min with a carrier gas of 2x6 NLMP Ar. The plasma gun moves in a tilting movement, allowing a back and forth movement of the spray spot over the surface of the substrates. The spray distance in such low pressures is quite high and was for this trial 1300 mm, which produces a large plasma spot, that can be advantageous for upscaling process.

[0033] On the other hand, the HVOF coating process was done using a Diamond Jet, DJA gun operated with a gas mixture of 208 NLPM O2 and 574 NLPM H2 fuel gas with an addition of 690 NLPM Air flow. The resulting lambda value was 1.53. The powder is injected axially inside the gun at a federate of 15 g / min and a carrier gas between 12.5 and 40 NLPM. Depending on the substrate surface roughness an additional pretreatment of the surface by grit blasting is necessary to ensure a good adhesion of the coating layer onto the substrate. Grit blasting also allows the cleaning of oxides on the surface prior coating process. Grit of F36 has been used at a jet pressure of 3 bar and angle 70°. The coating time for this specific coating process was typically between 30 to 60 seconds.

[0034] Figure 3 shows the XRD comparison between the feedstock powder material and the coatings produced using HVOF (23B0381 ) and LPPS (23T0153); the black arrow highlights a secondary phase in the coatings that is absent in the feedstock material. The outcome indicates that the layer produced by HVOF exhibits significant crystallinity. Nonetheless, this HVOF layer also presents a secondary peak, indicated by the black arrow and a somewhat amorphous bulge around 2 Theta, from 25 to 30 degrees. It is important to note the intensity of this secondary peak surpasses that of the neighboring cubic phase, which is detrimental to its functionality. Additionally, the density of layers estimated from image analysis of Figure 2 b) and d) are 96 % for HVOF, and 95 % for LPPS. This demonstrates that the exclusive use of a low- temperature coating technique is insufficient for ensuring high purity in the cubic crystal phase of the lithium-based coating, particularly in achieving values above 90%.

[0035] Consequently, further investigation has enabled the inventors to identify specific process parameters, as illustrated in Figure 4 which presents the LLTO layers deposited on stainless steel substrates using improved HVOF processes, demonstrated in runs 23B0485 (a, b) and 23B0488 (c, d), along with corresponding optical light microscope micrographs of the coating-substrate cross sections. The coating parameter used in this case were found to be effective in diminishing the amorphous hump and reducing the intensity of the secondary phase to less than 5 % of total count of cubic phase.

[0036] It should be noted that for both batches, the intensity of the secondary peak shown in Figure 5 is significantly less than that of the adjacent cubic phase. Additionally, the calculation of the integrated intensity of the cubic phase reveals that the secondary peak constitutes only 3%. This indicates that the coating produced from the runs 23B0485 and 488 have preserved 97% of the cubic phase from the feedstock. Additionally, the density of the coating estimated from image analysis of Figure 4 b) and d) are 96 % for both 23B0485, and 488. Which is one of the requirements for electrolyte layers.

[0037] This was achieved by increasing in a first step between run 23B0381 and 23B0485, the shroud gas (Air) from 325 NLPM to 700 NLPM and slightly reduce the fuel gas (H2) from 574 to 460 NLPM, which increases the acceleration of the powder particles, significantly reducing their time of flight into the hot gas. This advantageously minimizes the duration of any potential crystallinity transformation and at the same time improves the coating's density.

[0038] In a second fine tuning step, between run 23B0485 and 23B0488, the carrier gas flow has been increased from 12.5 to 40 NLPM and the air flow of the shroud gases slightly reduced from 700 to 690 NLPM. The higher carrier gas flow rate can facilitate better transport of the powder to the substrate, resulting in increased deposition efficiency, the effect is also that the dispersion of the powder is improved, leading to better coating uniformity. However, the most wanted effect was to increase the coating density by increasing the kinetic energy of the powder, this has a double advantage that the powder in-flight is shortened even more which has a beneficial effect on keeping possible transformation of the crystallinity as short as possible and at the same time to improve the density of the coating thanks to the higher kinetic flow provided during operation. It is remarkable that this achievement, a 97% preservation of the cubic phase from the feedstock in the layers from runs 23B0485 and 488, was accomplished in a single- step process without any pre- or post-treatment, as detailed in spray run parameter.

[0039] One notable additional benefit of the proposed method is to ensure surface cleanliness which is shown in Figure 6 for the different runs. The presence of unwanted particles on the surface which are considered as impurities in battery applications, come from potential overspray re-deposition. This criterion is crucial for preventing impaired layer functionality, like cell short-circuiting. There is less than one particle measured in a representative scan area of 150x 100 pm for the inventive coatings 23B0485, and 488. Vacuum processes, such as represented by the run 23T0153, exhibit higher surface impurities due to increased potential for overspray particle recirculation, due to the reduced drag force of gas in the low pressure environment, unlike atmospheric processes where overspray is absorbed by dedicated suction systems. It has to be noted that the run which gives the highest crystallinity retention during the process and highest coating density, also presents no impurities on the coated surface.

[0040] Figure 7 illustrates surface roughness measurements for the coatings presented, with the different thermal spray methods ranging from Ra 2.2 to 4.4. The optimal run by HVOF shows slightly higher values of Ra of 3.9 to 4.4 pm, which can be beneficial for solid electrolyte layers by enabling mechanical interlocking with the counter cathode layer, thus reducing interface contact.

[0041] In summary, the inventive method, such as the HVOF process, offers a solution to the challenges faced in fabricating oxide-based electrolytes like LLZO for solid-state cells. Unlike current methods, it has been shown that HVOF allows obtaining coating thicknesses ranging from 10 to 30 pm in a single step dry process, with over 90% crystallinity and density, which is excellent for the requirement of Li-based electrolyte coatings. It has been found that the HVOF process, traditionally employed in mechanical and industrial applications, has emerged as a robust technique for electrochemical applications like solid-state batteries. This discovery highlights its already known versatility, utilizing simpler to manufacture powder materials to achieve dense coatings efficiently. With its proven performance and scalability, HVOF presents significant promise for practical implementation in the electrochemical domain, demonstrating its potential to address key challenges in solid-state battery technology.

[0042] Figures Description

[0043] Figure 1 : a) SEM micrograph of Ta-doped LLZO powder material; b) Physical properties of LLZO powder

[0044] Figure 2: a) and c): LLTO layer deposited on the stainless steel substrate using HVOF (23B0381 ) and corresponding optical light microscope micrograph of the coating-substrate cross section; b), and d): the same as above but using LPPS (23T0153).

[0045] Figure 3: XRD comparison between the feedstock powder material and produced coatings using HVOF (23B0381 ) and LPPS (23T0153). The black arrow marks a secondary phase which is not observed in the feedstock material.

[0046] Figure 4: LLTO layer deposited on the stainless steel substrate using improved and inventive HVOF processes illustrated by the runs 23B0485 a), b) and 23B0488 c), d), and corresponding optical light microscope micrograph of the respective coatingsubstrate cross-section;

[0047] Figure 5: XRD comparison between the feedstock powder material and the improved produced coatings using HVOF (23B0485) and LPPS (23B0488). The black arrow marks a secondary phase which is not observed in the feedstock material.

[0048] Figure 6: Optical micrograph of representative coating surface with the presence of unwanted particles

[0049] Figure 7: Tabular summary of the measured surface roughness of the presented layers produced by different spray methods and parameters.

Claims

Claims1. A method for producing a coating comprising at least one Li-conductive layer for a solid-state battery cell, the method comprising the steps of:- providing a powder feedstock material, wherein the feedstock comprises a size distribution suitable for a thermal spray process or cold spraying, wherein the feedstock has the desired high purity of the crystal structure of the Li-conductive layer,- applying the Li-conductive layer onto a substrate using a coating process, including a thermal spray process selected from the group consisting of plasma spraying, HVOF, HVAF, or cold spraying using the provided feedstock material, wherein the substrate is an anode, cathode or current collector composing the solid-state battery cell, characterized in that, the at least one Li-conductive layer is produced by the said coating process carried out in one-step in such a way that during the coating process the crystallinity of the feedstock powder material is preserved subsequent to its deposition onto the substrate.

2. Method according to claim 1 , further comprising maintaining at least 95% crystallinity of the cubic phase of the resulting coating layer.

3. Method according to any of the preceding claims, wherein the powder feedstock material comprises a size distribution between 10 and 45 pm, preferably between 10 and 25 pm.

4. Method according to any of the preceding claims, wherein the Li-conductive layer is an electrolyte layer, comprising Li-based oxides, preferably LLZO, LMO, LMNO, LFP.

5. Method according to any of the preceding claims, wherein the Li-conductive layer is an electrolyte layer having a density of at least 90%.

6. Method according to any of the preceding claims, wherein the Li-conductive layer is an electrolyte layer doped with alloying elements including elementsfrom groups III, IV, V, and VI of the periodic table, preferably Ta (Tantalum), Al (Aluminum), Nb (Niobium), and Y (Yttrium).

7. Method according to any of the preceding claims, wherein the Li-conductive layer comprises an electrolyte multilayer layer, comprising a combination of two or more Li-based oxides, providing an interface between the electrolyte and the cathode and / or anode.

8. Method according to any of the preceding claims, wherein the Li-conductive layer comprises electrolyte layers, wherein the composition changes in a graded way between the electrolyte layers.

9. Method according to any of the preceding claims, characterized in that the coating process is HVOF operating with a process gas mixture of 02 and H2 and an Ar shroud gas of at least 600 NLPM flow and carrier gas of at least 20 NLPM.

10. Method according to any of the preceding claims, wherein the Li-conductive layer is a complete or partial coating system composing a unit cell of a solid state battery, such as a combination of anode / electrolyte / cathode or partially anode / electrolyte and / or cathode / electrolyte coating systems.

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