Raw material screening and element loss in-situ monitoring method in rapid synthesis of solid electrolyte

Abstract

The invention belongs to the technical field of sintering in-situ monitoring of inorganic solid electrolyte, and particularly relates to a raw material screening and element loss in-situ monitoring method in rapid synthesis of solid electrolyte, and efficient judgment of preparation quality and high-throughput screening of a raw material formula in a sintering process can be realized by detecting an atomic absorption spectrum in a reaction process. The garnet type electrolyte screened by the method provided by the invention has high atom utilization rate, high ionic conductivity and excellent cycle stability. The in-situ nondestructive testing method designed by the invention is reasonable in structure, convenient to operate, low in cost and good in mobility.

Description

Technical Field

[0001] The present application belongs to the technical field of in-situ monitoring of sintering of inorganic solid electrolytes, and specifically relates to a method for in-situ monitoring of raw material screening and element loss in rapid synthesis of solid electrolytes. Background Art

[0002] Traditional ceramic electrolyte synthesis relies on a muffle furnace for high-temperature steady-state solid-phase reactions. Consequently, the preparation process is complex and the sintering time is excessively long, leading to severe loss of volatile elements and component segregation. This results in the destruction of the electrolyte's stoichiometric ratio and phase separation of the material, which in turn leads to the destruction of the electrolyte's microstructural density and a decrease in the electrolyte's ionic conductivity. Consequently, there is a significant risk of failure when matching solid-state electrolytes with lithium metal electrodes at high operating current densities. Furthermore, the steady-state heating process is a black-box reaction, and the inherent reaction kinetics of materials that have been sealed and treated for hours cannot be directly understood. These issues require reliance on a posteriori methods for material characterization, such as analyzing the material's morphology and bonding information to assess synthesis quality, which results in delayed feedback. Consequently, material synthesis optimization is inefficient and costly, relying heavily on practical experience.

[0003] To address the issue of element loss during ceramic electrolyte synthesis, existing strategies employ masterbatch coating during sintering to compensate for element losses during preparation. While this approach effectively reduces the loss of key elements, it also traps gaseous byproducts generated during high-temperature reactions, leading to the formation of undesirable secondary phases upon cooling, compromising the structural integrity and electrochemical performance of the electrolyte. While various precursors can be used in the synthesis of ceramic electrolyte materials, inconsistent product quality in previous studies has hindered cross-study comparisons. Pre-addition of volatile elements can mitigate element loss during synthesis, but the addition of excessive lithium or sodium can lead to batch-to-batch variability in grain size, sintered density, and microstructural uniformity. Therefore, to better understand and control the synthesis process, optimization efforts have shifted towards the development of in situ diagnostic methods. While laboratory-scale in situ detection methods such as in situ X-ray diffraction and in situ TEM have been employed to investigate electrolyte synthesis processes, their capabilities for real-time loss tracking and adaptive heating control remain limited. This lack of diagnostic tools hinders detailed analysis, process control, and quality optimization of high-performance ceramic electrolytes. Therefore, in situ diagnostic methods that can directly diagnose volatile species during high-temperature synthesis are urgently needed. Summary of the Invention

[0004] To address the deficiencies in the prior art, the present invention aims to provide a method based on in-situ thermal absorption spectroscopy (InSiTAS), which captures the release and evolution of smoke generated during the electrolyte synthesis process, tracks element volatilization in real time, and quantitatively detects the spectrum of the sintering process, rather than directly detecting the ceramic electrolyte itself. This can optimize the synthesis process and solve the problem of element loss in the existing ceramic electrolyte sintering process.

[0005] The technical solution adopted in the present invention is as follows:

[0006] A method for raw material screening and in-situ monitoring of element loss in rapid synthesis of solid electrolytes comprises the following steps: S1. prefabricating electrolyte raw material powder and pressing it into tablets;

[0007] S2. During the heating and sintering process, based on in-situ thermal absorption spectroscopy, the types of elements lost are determined by analyzing the spectral absorption peaks, and the amount of element loss is determined by analyzing the spectral intensity. The specific phase changes are determined by combining the spectral intensity with XRD analysis.

[0008] S3. Complete the screening of raw materials during the transient synthesis of solid electrolyte materials.

[0009] Preferably, the method further includes capturing the release and evolution of smoke generated during the electrolyte synthesis process by a camera, tracking element loss in real time, and calculating the concentration and speed of element loss. The camera needs to be equipped with an infrared cutoff filter.

[0010] Preferably, in step S1, electrolyte powder for analysis is obtained, the prefabricated powder is crushed, the powder is weighed and placed in a mold, press-formed, and pressed using a cold isostatic press at a pressure of 40t for 1-3 minutes to expel residual gas in the sheet and enhance the structural density of the material.

[0011] Preferably, if no obvious smoke is generated during the high-temperature heating process, it means that the material has not undergone serious side reactions; on the contrary, if the raw material produces a large amount of smoke during the high-temperature process and is accompanied by flame combustion until the cooling stage, it means that serious side reactions and element losses occur under high-temperature conditions.

[0012] Preferably, the input voltage is adjusted in a gradient of 5V by a precision power supply system, and the reaction process is monitored in real time using in-situ AAS technology to establish a quantitative relationship model between the amount of element volatilization and the spectral absorption intensity. When the input voltage increases from 15V to 30V, the relative intensity of the absorption peak of the volatile element increases nonlinearly from the low volatilization temperature zone to the intense volatilization temperature zone, and the corresponding lithium residual amount in the system begins to decrease. When the input voltage continues to increase, the sample melts and decomposes, and the sample rapidly shrinks to completely disappear, accompanied by the release of a large amount of smoke. This quantitative relationship model of AAS intensity-volatile element residual amount-impurity phase content realizes the accurate quantification of the high-temperature volatile element loss rate.

[0013] Preferably, after the reaction is completed, the cross-sectional morphology of the electrolyte is observed using a scanning electron microscope. The densely arranged grain structure on the surface without gas escape after the high-temperature reaction and the cross-sectional transgranular fracture indicate that the material has a high density and is a good raw material for synthetic electrolytes. If the surface of the electrolyte sheet presents a porous structure formed by the necking of small grains, and there are a large number of pores and a continuous rough surface in the cross-sectional area, it indicates that the material has a low degree of densification and is not a good raw material for synthetic electrolytes.

[0014] Preferably, the shrinkage of the pressed sheet is quantified using a spiral micrometer to evaluate the macroscopic density of the sheet. If the shrinkage is less than a set threshold and is accompanied by surface cracks, it indicates that the structural rigidity is poor and the sheet is not a good raw material for synthesizing electrolytes.

[0015] Preferably, the real-time infrared spectrum captured during the heating process is analyzed, and the metered sintering temperature t is obtained from the Boltzmann formula and the spectrum intensity, that is, the metered temperature t is a reliable sintering temperature.

[0016] Preferably, it is suitable for in-situ volatile element monitoring during the preparation of garnet-type, perovskite-type, halide-type, sulfide-type, NASICON-type and LISICON-type inorganic electrolytes.

[0017] Compared with the prior art, this application has the following beneficial effects:

[0018] The present invention has achieved a breakthrough in the real-time, quantitative in-situ monitoring of volatile elements in the high-temperature sintering process. The existing pre-compensation technology of mother powder covering or excessive element addition has significant side effects, and laboratory in-situ detection methods such as in-situ XRD and in-situ Raman have slow response speeds and limited capabilities in tracking element losses. The present invention is the first to apply InSiTAS to the testing of electrolyte high-temperature sintering environments. AAS technology directly and accurately captures volatile elements (such as Li, Na) in the gas phase by detecting characteristic absorption peaks in the specific infrared / visible light region, realizing millisecond to second real-time monitoring of the volatilization process. This highly sensitive real-time feedback breaks through the limitations of traditional a posteriori analysis or slow-responding in-situ technology.

[0019] The present invention can also avoid the side effects of excessive sintering compensation strategies and improve the stability of the material. Although the existing mother powder covering can reduce element loss, it will irreversibly capture the reaction gas, causing the formation of secondary phases during cooling, damaging the integrity and density of the electrolyte grain boundaries, and reducing the ionic conductivity; and the existing pre-compensation strategy requires the addition of excessive volatile elements, which makes the synthesis process difficult to accurately control, resulting in significant differences in grain size, sintering density and micro-uniformity between batches. The present invention uses rapid synthesis technology to achieve transient heating and cooling without relying on a physical covering layer, fundamentally eliminating the root cause of secondary phase formation; through precise in-situ monitoring, real-time monitoring and control of element volatilization, the sintering parameter settings can be optimized, and only a small amount of element compensation is performed when necessary to ensure batch stability and microstructural consistency, greatly improving material uniformity and intrinsic performance, and solving the key problem of inconsistent synthesis methods and product quality that hinders horizontal comparison of materials.

[0020] The present invention can achieve control and dynamic optimization of the synthesis process, significantly improving synthesis efficiency and material quality. Existing in-situ technologies such as XRD, TEM and Raman mainly provide means of state observation, and the real-time control capability of the synthesis process is weak. However, the present invention, combined with rapid sintering technology, can utilize the millisecond-level element loss monitoring and feedback capabilities of this system for real-time regulation. For example, while significantly shortening the sintering time, the loss of bulk elements can be effectively suppressed; when the element loss intensity rate is abnormal, the heating rate, reaction temperature and holding time can be adjusted in real time. This is a real-time feedback and regulation efficiency that is difficult to achieve with ordinary sintering technology.

[0021] Compared with the general synthesis method, the comprehensive performance indicators of the garnet-type solid electrolyte material synthesized by AAS detection are greatly improved compared with the previously published work. The electrolyte prepared by the method of the present invention (such as LLZO) can achieve a core volatile element retention rate of >95%, which is far superior to the conventional sintering process. SEM morphology test shows that the material has achieved high density, few intrinsic defects and complete structure; electrochemical experimental data show that the prepared garnet-type electrolyte has a high conductivity at 0.3mA·cm -2 The researchers achieved stable cycling for over 1400 hours at a current density of 1.5 GHz, demonstrating excellent long-cycle performance, far exceeding that of garnet-type ceramic electrolytes prepared in published literature and meeting the requirements of high-performance solid-state batteries. This directly verifies that this method significantly improves the final electrochemical performance of the material.

[0022] The present invention can provide strong experimental research support for the study of the mechanism of rapid reaction processes. Conventional a posteriori detection methods are used to verify the results of the mechanism, and the results are difficult to directly support the intrinsic mechanism of the reaction process. This method provides direct experimental evidence for understanding the intrinsic connection between phase evolution and element loss during sintering by establishing a correlation model of "spectral absorption-phase evolution". The spectral absorption data obtained by semi-quantitative analysis can provide a real-time monitoring tool for in-depth study of the influence of different sintering parameters (temperature, atmosphere, heating rate), precursor type / morphology on element volatilization dynamics and final phase / microstructure, which can deepen the understanding of the mechanism of high-temperature solid-phase reaction, which is difficult to provide with existing detection technology.

[0023] This method can provide a bridge for rapid formulation optimization. While conventional formulation screening relies on a posteriori morphological and structural characterization or requires extensive electrochemical performance testing to verify material quality, this method allows for rapid sample screening based on element loss monitoring results. Furthermore, this method can guide the selection of specific component precursors and precise sintering control at critical stages, leading to more rational sintering processes and precursor formulations.

[0024] This in-situ detection method is also highly universal and applicable to various solid electrolytes containing volatile elements, such as sodium metal solid electrolytes, perovskite-type electrolytes, and NASICON-type electrolytes, as well as advanced ceramic materials requiring high-temperature processing. In contrast, the steady-state heating muffle furnace sintering process requires extensive and long-term exploration of synthesis conditions for different materials before obtaining appropriate sintering parameters. The experimental results obtained using this method can guide more rational precursor design and the determination of universal sintering processes, enabling high-throughput material screening.

[0025] This method also has the potential to be adapted for industrialization. Conventional in-situ or a posteriori detection methods are costly and difficult to implement for mass production. However, the spectral detection method used in this method is relatively simple and does not require expensive equipment, making it amenable to large-scale production processes. The successful validation of this real-time monitoring and process control at the laboratory scale provides a feasible technical path to address the uniformity and repeatability issues caused by scale effects during material process scale-up, helping to accelerate industrialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a flow chart of synthesis and detection of the in-situ observation of the rapid sintering process in the present invention;

[0027] Figure 2 It is a schematic diagram of the rapid sintering device capable of realizing in-situ spectral observation according to the present invention.

[0028] Figure 3 It is a schematic diagram of temperature control of the synthesis process system in the present invention.

[0029] Figure 4 Schematic diagram of the in-situ densification of ceramic particles in the present invention.

[0030] Figure 5 This is a record of the rapid sintering process of LLZO ceramic sheets prepared using different lithium sources in the present invention.

[0031] Figure 6 This is the SEM morphology of the LLZO sheet after sintering prepared using different lithium sources in the present invention.

[0032] Figure 7 This is the macroscopic size shrinkage of the LLZO sheets prepared using different lithium sources in the present invention after the reaction.

[0033] Figure 8 This is a diagram of the method of fitting sintering temperature using spectral intensity in the present invention.

[0034] Figure 9 The figure is a comparison of the atomic absorption spectra of the systems during the non-equilibrium synthesis of LLZO (I) and (III) in the present invention.

[0035] Figure 10 This is a quantitative relationship model between lithium volatilization amount and spectral absorption intensity established by the in-situ AAS technology in the present invention.

[0036] Figure 11 It is a schematic diagram of the calculation domain for modeling the material loss of smoke in the present invention.

[0037] Figure 12 It is a simulation of the generation process of Li2O during sintering based on the smoke morphology of the reaction process recorded by the camera.

[0038] Figure 13 It is a modeling of component loss during the volatilization process of Li2CO3 during the sintering process and a simulation of the high-temperature state.

[0039] Figure 14 This is a diagram of the symmetrical battery structure assembled using LLZO ceramic electrolyte in the present invention.

[0040] Figure 15 This is a comparison of the electrochemical properties of the LLZO ceramic electrolyte prepared using rapid Joule heating in the present invention.

[0041] Figure 16 This is a record of the rapid sintering process of preparing β-Al2O3 electrolyte using different sodium sources in the present invention.

[0042] Figure 17 This is a comparison of atomic absorption spectra of the system during the non-equilibrium synthesis process of preparing β-Al2O3 using different sodium sources in the present invention.

[0043] Figure 18 This is the SEM morphology of β-Al2O3 prepared by the present invention using different sodium sources after sintering.

[0044] Figure 19 This is the macroscopic size shrinkage of different β-Al2O3 electrolyte sheets after high-temperature reaction of the present invention.

[0045] Figure 20 This is the analysis of the β-Al2O3 phase composition prepared by the present invention using rapid Joule heat. DETAILED DESCRIPTION

[0046] The present application will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present application.

[0047] A method for raw material screening and element loss in situ monitoring in rapid synthesis of solid electrolytes comprises the following steps:

[0048] S1. Prefabricating electrolyte raw material powder and tableting;

[0049] Obtain the electrolyte powder for analysis, crush the prefabricated powder, weigh the powder and place it in a mold, press it into shape, and use a cold isostatic press at a pressure of 40t for 1-3 minutes to expel the residual gas in the sheet and enhance the structural density of the material.

[0050] S2. During the heating and sintering process, based on in-situ thermal absorption spectroscopy, the types of elements lost are determined by analyzing the spectral absorption peaks, and the amount of element loss is determined by analyzing the spectral intensity. The specific phase changes are determined by combining the spectral intensity with XRD analysis.

[0051] S3. Complete the screening of raw materials during the transient synthesis of solid electrolyte materials.

[0052] It also includes capturing the release and evolution of smoke produced during electrolyte synthesis through a camera, tracking element loss in real time, and calculating the concentration and rate of element loss. The camera needs to be equipped with an infrared cutoff filter.

[0053] If no obvious smoke is produced during the high-temperature heating process, it means that the material has not undergone serious side reactions; on the contrary, if the raw material produces a large amount of smoke during the high-temperature process and is accompanied by flame combustion until the cooling stage, it means that serious side reactions and element losses have occurred under high-temperature conditions.

[0054] By adjusting the input voltage in a 5V gradient through a precision power supply system and using in-situ AAS technology to monitor the reaction process in real time, a quantitative relationship model between the element volatilization amount and the spectral absorption intensity was established. When the input voltage increased from 15V to 30V, the relative intensity of the absorption peak of the volatile element increased nonlinearly from the low volatilization temperature zone to the intense volatilization temperature zone, corresponding to the beginning of the decrease in the residual lithium amount in the system. When the input voltage continued to increase, the sample melted and decomposed, and the sample rapidly shrank until it completely disappeared, accompanied by the release of a large amount of smoke. This quantitative relationship model of AAS intensity-volatile element residual amount-impurity phase content realizes the precise quantification of the high-temperature volatile element loss rate.

[0055] After the reaction is completed, the cross-sectional morphology of the electrolyte is observed using a scanning electron microscope. The tightly arranged grain structure on the surface without gas escape after the high-temperature reaction and the cross-sectional transgranular fracture indicate that the material has a high density and is a good raw material for synthetic electrolytes. If the surface of the electrolyte sheet presents a porous structure formed by the necking of small grains, and there are a large number of pores and a continuous rough surface on the cross-sectional surface, it indicates that the material has a low degree of densification and is not a good raw material for synthetic electrolytes.

[0056] The shrinkage rate of the pressed sheet can be quantified using a spiral micrometer to evaluate the macroscopic density of the sheet; if the shrinkage rate is less than the set threshold and is accompanied by surface cracks, it means that the structural rigidity is low and it is not a good raw material for synthesizing electrolytes.

[0057] By analyzing the real-time infrared spectrum captured during the heating process, the sintering measurement temperature t is obtained by the Boltzmann formula and the spectrum intensity. That is, the measurement temperature t is the reliable sintering temperature.

[0058] Example 1

[0059] The present invention discloses a method for in-situ detection of absorption spectrum during transient synthesis of garnet-type ceramic solid electrolyte materials, which is specifically implemented according to the following steps:

[0060] S1, La2O3, ZrO2, Ta2O5 and LiOH, LiOH·H2O, Li2CO3 were respectively 6.5 La3Zr 1.75 Ta 0.25 O 12 The molar ratio of the lithium element is 10% in excess to compensate for the loss of lithium element in the powder making process.

[0061] S2, dissolve the powder in an alumina ball mill with isopropyl alcohol (IPA), grind it in a planetary ball mill at 360 rpm for 5 h using alumina balls as a grinding aid, and then dry it in a vacuum drying oven at 120°C. Note that this process should avoid contact with air.

[0062] S3, the powder was ground again and placed in an alumina crucible, and fired at 950°C for 7 h using a muffle furnace with a heating program of 3°C / min. After cooling to room temperature, LLZO preformed powder was obtained.

[0063] S4, crush the pre-made powder, weigh 180 mg of powder and place it in a mold with a diameter of 8 mm, press it under a pressure of 3 tons for 2 minutes to form it, and use a cold isostatic press to press it at a pressure of 40 tons for 1 minute to expel the residual gas in the sheet and enhance the density of the material structure. The process of this synthesis method is as follows: Figure 1 shown.

[0064] S5, assemble the rapid heating device and the detection device, such as Figure 2 As shown, the power output of the power supply is adjusted to burn the carbon felt to a red heat to remove surface impurities and oxygen-containing functional groups on the substrate.

[0065] S6, the LLZO sheet is sandwiched between two pieces of carbon felt, the spectrometer is aligned with the upper surface of the sample, and the electrolyte is sintered using the Joule heating method.

[0066] At step 7, turn on the camera and spectrometer. Note that the camera must be equipped with an infrared cutoff filter to effectively block interfering infrared radiation and maintain image clarity. The spectrometer records the continuous spectral intensity from 178.42 to 883.77 nm at a frequency of 200 ms for a total of 30 seconds.

[0067] S8, low temperature treatment of LLZO sheet at about 500℃ to remove the release agent on the surface during the pressing process; then quickly heat up to 1300℃ and heat for about 20s. At this time, the shrinkage of the ceramic sheet can be observed through the camera; after turning off the power output, the system is quickly cooled down, and the total heat treatment time is about 30s, which can achieve rapid synthesis of electrolyte. The specific reaction temperature changes are as follows: Figure 3 As shown in Figure 2, the densification mechanism of LLZO sheets is as follows: Figure 4 shown.

[0068] S9, the LLZO prepared from LiOH, LiOH·H2O and Li2CO3 precursors are named LLZO(I), LLZO(II) and LLZO(III), respectively. The reaction process is recorded as follows Figure 5 As shown, LLZO(I) exhibited a stable heating state during the high-temperature process, with no volatilization observed. LLZO(II) produced significant smoke during the high-temperature process, and LLZO(III) produced a large amount of smoke during the high-temperature process and burned with flames until the cooling stage, indicating that serious side reactions occurred under high-temperature conditions.

[0069] S10, after the reaction is completed, the morphology of different LLZO sheets is compared using a scanning electron microscope (SEM). Figure 6LLZO (I), which did not experience gas escape after high-temperature reaction, exhibited a tightly packed grain structure. The cross-section of the transgranular fracture indicated that the material had a high density, consistent with the characteristics of typical dense garnet. LLZO (II) exhibited a porous structure formed by the necking of small grains, while the cross-section of LLZO (III) contained a large number of pores and a continuous rough surface, indicating a low degree of material densification and the presence of a Li2CO3 deposition layer on the particle surface. LLZO prepared with LiOH had the densest cross-section and was most suitable for practical use as an electrolyte. However, LiOH·H2O or Li2CO3 are not good raw materials for synthesizing LLZO.

[0070] S11, use a screw micrometer to quantify the shrinkage of the ceramic sheet as follows Figure 7 , which can be used to assess the macroscopic density of the sheet. LLZO(I) exhibited a diameter shrinkage of 14.13% after sintering and exhibited a ceramic luster. LLZO(II) shrank by only 6.11% and exhibited surface cracking, indicating poor structural rigidity. LLZO(III) exhibited surface powdering with a dimensional change of <0.8%.

[0071] S12, analyze the real-time infrared spectrum captured during the heating process. Figure 8 As shown in the figure, due to the significant deviation of conventional temperature measurement tools in high temperature environments, the carbon felt can be equivalent to a black body radiation source due to thermal radiation, and its radiation energy density distribution conforms to the Stefan-Boltzmann law. 2 ) / λ 5 *(1 / (exp(hc / λRT)-1)), where B(λ,T) represents the spectral radiance of the blackbody in W·m -2 ·Sr -1 μm -1 λ is the wavelength of radiation, expressed in μm; T is the absolute temperature of the black body, measured in Kelvin (K), T = t (degrees Celsius) + 273K; c is the speed of light, approximately 2.998×10 8 m·s -1 ; h is Planck's constant, which is approximately 6.626×10 -34 J·S; and K is the Boltzmann constant, which is approximately 1.380×10 -23 J.K. -1 The spectral intensity of the system can be fitted based on the blackbody radiation intensity. The real-time temperature k of the reaction can be expressed as T by decoupling the exponential term of Planck's law and taking the logarithm, which is T=hc / (λk*In(1+(2πhc 2 *(λ 5 *B(λ,T)))), by inputting the temperature measurement value t during sintering, the actual sintering temperature is obtained to be 1359℃.

[0072] S13, Peak comparison of atomic absorption spectra (AAS) of LLZO(I) and (III) systems during non-equilibrium synthesis. Figure 9 a. S13, Peak comparison of atomic absorption spectra (AAS) of LLZO (I) and (III) systems during non-equilibrium synthesis Figure 9 As shown in a. Under normal conditions, atoms are in the ground state. When thermally or electrically excited, atoms will transition from the ground state to the excited state. This process causes the absorption of light of characteristic wavelength. The intensity of transmitted light I is lower than the intensity of incident light I0. The degree of light intensity attenuation is positively correlated with the atomic concentration, that is, I = I0e -KvNL , so absorbance A=log 10 (I0 / I) = K'NL. K' absorption coefficient is related to the element type and wavelength; N is the ground state atomic number density (unit: cm -3 ); L is the thickness of the absorption layer (unit: cm). The energy absorbed during atomic transition ΔE=E2-E1=hν=hcλ -1 , so resonant absorption occurs only when the incident photon energy hν is strictly equal to the energy level difference ΔE.

[0073] The experimental results show that when Li2CO3 is used as a precursor to prepare LLZO, significant spectral absorption appears at 671.1nm, and this peak coincides with the characteristic absorption line of lithium; while only trace element absorption signals are detected in the system using LiOH as a precursor. Figure 9 The continuous in situ spectra in b further reveal that no element loss was detected in LLZO(I) during the entire synthesis process, while the spectral curve of LLZO(III) shows that Li element loss always occurs during the synthesis process using Li2CO3.

[0074] S14, using LLZO(III) precursor as the research object, the input voltage was adjusted in a 5V gradient through a precision power supply system, and the reaction process was monitored in real time using in-situ AAS technology. The quantitative relationship model between the amount of lithium volatilization and the spectral absorption intensity was established as follows Figure 10 As shown in the figure. When the input voltage increases from 15V to 30V, the relative intensity of the Li absorption peak increases nonlinearly from 0.14% in the low volatility temperature zone to 15.60% in the intense volatility temperature zone, corresponding to a sharp drop in the amount of lithium remaining in the system from 95% to 82.0%. When the input voltage is increased to 35V, LLZO melts and decomposes, and the sample shrinks rapidly until it disappears completely, accompanied by the release of a large amount of smoke. This quantitative relationship model of AAS intensity-lithium residue-impurity phase content enables the precise quantification of high-temperature lithium loss rate and the optimization of the LLZO synthesis process.

[0075] To analyze the chemical composition of substances in the sintering atmosphere, S15 used carbon paper to collect condensed smoke particles. X-ray photoelectron spectroscopy (XPS) was used to analyze the chemical state of the deposits on the carbon paper surface. It was found that the deposits were mainly composed of three elements: Li, C, and O. The composition was a mixture of Li2CO3 and Li2O. That is, during the non-steady-state thermal synthesis process, the gaseous CO2 produced by the decomposition of the Li2CO3 precursor carried Li2O out of the bulk phase, resulting in a large amount of lithium loss in the bulk phase. During the cooling stage, some volatile substances reorganized, resulting in the formation of Li2O and Li2CO3 co-deposition products on the carbon paper.

[0076] S16 is a simulation of the smoke loss process based on the video monitoring and XPS results of the high-temperature synthesis process of LLZO prepared by Li2CO3. A three-dimensional (3D) model is used to simulate the turbulent transport process of Li2O and carbon dioxide CO2 during the decomposition of Li2CO3. The model solves the unsteady, multi-component, reactive, and compressible Navier-Stokes (NS) equations; in order to accurately capture the large-scale turbulence characteristics, the large eddy simulation (LES) dynamic structure model is used; the sub-grid scale (SGS) model is used to deal with the small-scale turbulence effects, which improves the simulation accuracy. The sub-grid kinetic energy transport equation is considered in the LES dynamic structure model, which improves the prediction ability of the turbulent transport process. The O'Rourke and Amsden model is used to consider the wall heat transfer process, Figure 11 The calculation domain (0.1×0.2m 2 ). The initial temperature of the calculation area is 27℃, the pressure is 1atm, and the white area at the bottom (10×1mm 2 ) represents the LLZO ceramic on the Li2CO3 substrate. The temperature in this area is 1350℃, which is the same as the heating temperature in the experiment. The concentrations of Li2O and CO2 are calculated based on the Li2CO3 decomposition reaction. The mass flux calculated by the Li2CO3 decomposition rate is set at the top boundary of the ceramic to simulate the upward migration of Li2O and CO2. For the grid size, the basic grid is 6mm. In order to ensure the stability of the geometric structure during the flow process, four layers of two layers of fixed embedding are used in the Li2CO3 decomposition area. The adaptive mesh refinement (AMR) technology is used to adaptively refine the grid in areas with large velocity gradients and temperature gradients during the turbulent transport of Li2O and CO2. Based on the above theoretical system, the migration behavior of Li2O and CO2 and the lithium loss mechanism in the high-temperature reaction of LLZO (III) materials can be analyzed, among which the typical states of Li2O migration are as follows Figure 12 As shown. The concentration of substances in the gas can be simply abstracted as

[0077] When the rate of material loss in the gas phase and the system temperature reach the decomposition threshold of Li2CO3, lithium begins to gasify and escape. The typical state of Li2O and CO2 migration is as follows: Figure 13As shown. When the reaction proceeds to 0.5s, the gas phase transmission distance reaches 0.1m, and the surface Li2O transport rate reaches 0.1m·s -1 When the reaction proceeded to 1.1s, the lithium generation rate in the central region surged to 0.3m·s due to the vortex core acceleration effect. -1 , forming a significant spatial concentration gradient, and Li2O is continuously transported into the atmosphere.

[0078] S17, the surfaces of the synthesized samples were polished continuously with 500, 1000, and 2000 mesh boron nitride sandpaper to obtain a ceramic electrolyte sheet with a smooth surface and no oxide layer. Lithium metal was deposited on the surface of the LLZO electrolyte using a high-temperature titanium heating table to form a sandwich structure. Care was taken to strictly control the lithium deposition area to avoid lateral short circuits. After the electrolyte cooled to room temperature, the battery was assembled using a CR2032 button cell shell. A carbon felt buffer layer was pre-placed to prevent the sealing pressure (20 MPa) from damaging the electrolyte. The schematic diagram of the symmetrical battery structure is shown in the figure. Figure 14 .

[0079] S18, Figure 15 To compare the electrochemical performance of different LLZOs, the impedance and ionic conductivity of LLZO were tested by electrochemical impedance spectroscopy (EIS). The constant current charge-discharge cycle test of the symmetrical battery was carried out to verify the interfacial stability of LLZO prepared with different Li sources during the lithium deposition / stripping process. The step current method (step size 0.05 mA cm) was used to measure the interfacial stability of LLZO prepared with different Li sources during the lithium deposition / stripping process. -2 The critical current density (CCD) of the symmetrical battery was tested (process step 0.3h) to measure the ability of the LLZO interface prepared from different raw materials to resist lithium dendrites. The ionic conductivity of LLZO(I) prepared from LiOH is significantly higher than that of LLZO(III). The CCD of LLZO(I) is 11.5 times that of LLZO prepared from Li2CO3 under the same conditions, which greatly improves the battery performance. The battery based on LLZO(III) has a high conductivity at 0.1mA·cm -2 At 0.3 mA·cm, LLZO(I) exhibited a significant increase in polarization voltage and short circuit failure after only 1.17 h of cycling. -2 It can operate stably for more than 1400 h at a constant current density, and the polarization voltage fluctuation amplitude is maintained at around 100 mV, confirming that the LLZO(I) electrolyte synthesized with LiOH as a precursor exhibits the best lithium dendrite suppression ability and interface durability.

[0080] Example 2

[0081] The present invention discloses a method for in-situ detection of absorption spectrum during transient synthesis of layered sodium metal solid electrolyte β-Al2O3 material, which is specifically implemented according to the following steps:

[0082] S1, Na2CO3 or NaOH were mixed with Li2CO3 and γ-Al2O3 respectively according to Al 10 Na2Li 0.5 O 17 The molar ratio of the mixture is 10% (Na and Li sources are in excess).

[0083] S2 is the same as the specific implementation method 1.

[0084] S3, the ground powder was placed in an alumina crucible and calcined at 1250 °C for 2 h using a muffle furnace at a temperature ramp of 3 °C / min to obtain β-Al2O3 preformed powder.

[0085] S4, taking 100 mg of pre-made powder to prepare tablets, the rest of the points are the same as those in the specific implementation method 1.

[0086] S5-7 are the same as the specific implementation method 1.

[0087] In step S8, the Al2O3 sheet is treated at a low temperature of approximately 500°C to remove the release agent. The temperature is then rapidly raised to 1500°C and heated for approximately 20 seconds. The temperature calculation method is the same as in step S12 of the first embodiment. The electrolytes prepared using NaOH and Na2CO3 as raw materials are named β-Al2O3(I) and β-Al2O3(II), respectively.

[0088] S9, the reaction process is recorded as follows Figure 16 As shown in the figure, β-Al2O3(I) exhibits steady-state thermal radiation characteristics at 1500℃, the surface of the sheet is uniformly red and no gas release is observed, while β-Al2O3(II) prepared using Na2CO3 generates smoke in the early stage of thermal synthesis, and produces violent flames accompanied by large amounts of smoke release at 1000℃, which disappears when the temperature is lowered to about 500℃.

[0089] S10, the non-steady-state synthesis process of β-Al2O3 was recorded in situ by AAS. Figure 17 As shown. The characteristic absorption peak of β-Al2O3(II) prepared using Na2CO3 at 589.2nm corresponds to the atomic absorption spectrum of Na atoms, and remains at a high level of 9.3% during the 20s sintering cycle, indicating the existence of continuous sodium volatilization. Only a weak absorption signal is detected for β-Al2O3(I) in the infrared / visible light wavelength range, that is, the loss of sodium during the sintering process is effectively suppressed. The above spectral differences provide atomic-scale theoretical support for the development of a synthetic formula for β-Al2O3 with low material loss.

[0090] S11, Comparison of SEM morphologies of different β-Al2O3 electrolyte sheets Figure 18As shown in the figure, β-Al2O3(I) has a typical layered β-Al2O3 dense structure with no micron-sized pores, confirming that the rapid sintering process achieved densification. However, β-Al2O3(II) exhibits porous structural defects and a large number of micron-sized pores, indicating that no densification occurred during the high-temperature synthesis process.

[0091] S12, quantitative changes in the size of the sodium electrolyte sheet before and after sintering Figure 19 The diameter shrinkage of β-Al2O3(I) reaches 12.0%, while that of β-Al2O3(II) prepared using Na2CO3 with the same size only shrinks by 5.0%.

[0092] S13, the phase composition of the product after rapid sintering is analyzed as follows Figure 20 The main diffraction peak of β-Al2O3(I) corresponds to a β-Al2O3 phase standard card (COD#96-101-0018), indicating that β-Al2O3 was formed during the rapid sintering process. The characteristic peaks of the Na2CO3-based sample closely match those of the α-Al2O3 standard card (PDF#35-0438), indicating excessive sodium loss during the high-temperature reaction. These results demonstrate that using NaOH instead of traditional Na2CO3 as the Na source can promote the synthesis of β-Al2O3 phase during non-equilibrium rapid sintering. Furthermore, the combination of the in-situ process visualization monitoring advantages of AAS and ultrafast sintering technology provides a rapid screening paradigm for materials screening in high-temperature solid-state reactions.

[0093] Example 3

[0094] The present invention discloses a method for in-situ detection of absorption spectrum during transient synthesis of chloride solid electrolyte Li2ZrCl6, which is specifically implemented according to the following steps:

[0095] S1, LiCl and ZrCl4 powders were mixed in a 1:1 mass ratio in a glove box.

[0096] S2 is the same as the specific implementation method 1. During the process, care should be taken to avoid contact with air to prevent the chloride from reacting with oxygen and water vapor in the air and deteriorating.

[0097] S3, taking 200 mg of the pre-prepared powder to prepare tablets, the rest of the points are the same as S4 of the specific implementation method 1.

[0098] S4-6 is the same as S5-7 of the specific implementation method 1.

[0099] In step S7, the Li2ZrCl6 sheet is rapidly heated using Joule heating. Initially, the sheet is treated at 200°C to remove the release agent contaminated on the surface during sheet production. The temperature is then rapidly raised to 700°C for approximately 20 seconds. The power supply is then turned off and the system is rapidly cooled. The total treatment time is approximately 30 seconds.

[0100] S8, similar to S13-14 of the specific implementation method one, establishes a linear correlation model between spectral absorption intensity and element volatilization amount by analyzing the signal intensity of the atomic absorption spectrum at the characteristic absorption peak of lithium element (670.8nm) and the absorption band of chlorine element (134.7nm). Based on this, the degree of loss of lithium and chlorine elements is determined in real time, achieving non-destructive and rapid evaluation of the synthesis quality, and providing a quantitative basis for the optimization of sintering process parameters.

[0101] Example 4

[0102] The present invention discloses a method for in-situ detection of the absorption spectrum of a perovskite solid electrolyte LLTO material during transient synthesis, which is basically the same as the third implementation method, except that:

[0103] Press Li 0.5 La 0.5 Ti 0.92 Zr 0.08 Li2CO3, La2O3, TiO2, and ZrO2 were weighed in a stoichiometric ratio of 10 mol% Li2CO3 to compensate for lithium loss during the powder making process. The raw materials were mixed with ethanol solvent and ball milled for 12 hours to ensure uniform dispersion of the components. The milled mixture was pre-sintered at 1000°C in air for 12 hours to obtain LLTO pre-powder. The pre-sintered powder was ground and pressed into a green body with a diameter of 8 mm. It was sintered at 1000°C for 1 minute using Joule heating to obtain Li 0.5 La 0.5 Ti 0.92 Zr 0.08 The element loss and densification degree of LLTO in the O3 solid electrolyte are measured by capturing the Li element atomic absorption spectrum at 670.8nm by a spectrometer.

[0104] Example 5

[0105] The present invention discloses a method for in-situ detection of absorption spectrum during transient synthesis of NASICON solid electrolyte LATP material. The synthesis process is basically the same as that of the third implementation method, except that:

[0106] Press Li 1.3 Al 0.3 Ti 1.7Li2CO3, Al2O3, TiO2, and H9N2O4P powders were weighed in a stoichiometric ratio of (PO4)3, of which Li2CO3 needed to be 10wt% in excess to compensate for the lithium loss during the powder making process. The raw materials were mixed with ethanol solvent and ball-milled for 12 hours to ensure that the components were evenly dispersed. The slurry was thoroughly dried in an oven at 78°C to remove the ethanol. The mixture after ball milling was pre-sintered at 800°C in air for 4 hours at a heating rate of 5°C / min to obtain LATP pre-powder. 200mg of the ground pre-powder was pressed into a green embryo with a diameter of 8mm and sintered at 800°C for 30s using Joule heat method to obtain Li 1.3 Al 0.3 Ti 1.7 (PO4)3 solid electrolyte, in which the atomic absorption spectrum intensity of the Li element at 670.8nm is captured by a spectrometer to measure the synthesis quality of LATP.

[0107] This experimental method is also applicable to the in-situ monitoring of volatile elements in the preparation process of other inorganic electrolytes such as garnet, perovskite, halide, sulfide, NASICON and LISICON, so as to reflect the sintering quality in real time during the synthesis process, solving the problems of process black box and time-consuming and energy-consuming problems of traditional methods, and providing a technical path for high-throughput development and rapid performance verification of solid-state electrolytes.

[0108] The applicant of the present invention has made a detailed explanation and description of the implementation examples of the present invention in conjunction with the drawings in the specification. However, those skilled in the art should understand that the above implementation examples are only preferred implementation plans of the present invention, and the detailed description is only to help readers better understand the spirit of the present invention, and is not a limitation on the scope of protection of the present invention. On the contrary, any improvements or modifications based on the inventive spirit of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for raw material screening and in-situ monitoring of element loss in rapid synthesis of solid electrolytes, characterized in that: The following steps are involved: S1. Prefabricating electrolyte raw material powder and tableting; S2. During the heating and sintering process, based on in-situ thermal absorption spectroscopy, the types of elements lost are determined by analyzing the spectral absorption peaks, and the amount of element loss is determined by analyzing the spectral intensity. The specific phase changes are determined by combining the spectral intensity with XRD analysis. S3. Complete the screening of raw materials during the transient synthesis of solid electrolyte materials.

2. The method for raw material screening and element loss in-situ monitoring in rapid synthesis of solid electrolytes according to claim 1, characterized in that: The release and evolution of smoke produced during electrolyte synthesis is captured by a camera, element loss is tracked in real time, and the concentration and rate of element loss are calculated. The camera needs to be equipped with an infrared cutoff filter.

3. The method for raw material screening and element loss in-situ monitoring in rapid synthesis of solid electrolytes according to claim 1, characterized in that: In step S1, the electrolyte powder for analysis is obtained, the prefabricated powder is crushed, the powder is weighed and placed in a mold, press-formed, and pressed using a cold isostatic press at a pressure of 40t for 1-3 minutes to expel residual gas in the sheet and enhance the structural density of the material.

4. The method for raw material screening and element loss in-situ monitoring in rapid synthesis of solid electrolytes according to claim 2, characterized in that: If no obvious smoke is produced during the high-temperature heating process, it means that the material has not undergone serious side reactions; on the contrary, if the raw material produces a large amount of smoke during the high-temperature process and is accompanied by flame combustion until the cooling stage, it means that serious side reactions and element losses have occurred under high-temperature conditions.

5. The method for raw material screening and element loss in-situ monitoring in rapid synthesis of solid electrolytes according to claim 1, characterized in that: By adjusting the input voltage in a 5V gradient through a precision power supply system and using in-situ AAS technology to monitor the reaction process in real time, a quantitative relationship model between the element volatilization amount and the spectral absorption intensity was established. When the input voltage increased from 15V to 30V, the relative intensity of the absorption peak of the volatile element increased nonlinearly from the low volatilization temperature zone to the intense volatilization temperature zone, corresponding to the beginning of the decrease in the residual lithium amount in the system. When the input voltage continued to increase, the sample melted and decomposed, and the sample rapidly shrank until it completely disappeared, accompanied by the release of a large amount of smoke. This quantitative relationship model of AAS intensity-volatile element residual amount-impurity phase content realizes the precise quantification of the high-temperature volatile element loss rate.

6. The method for raw material screening and element loss in-situ monitoring in rapid synthesis of solid electrolytes according to claim 2, characterized in that: After the reaction is completed, the cross-sectional morphology of the electrolyte is observed using a scanning electron microscope. The tightly arranged grain structure on the surface without gas escape after the high-temperature reaction and the cross-sectional transgranular fracture indicate that the material has a high density and is a good raw material for synthetic electrolytes. If the surface of the electrolyte sheet presents a porous structure formed by the necking of small grains, and there are a large number of pores and a continuous rough surface on the cross-sectional surface, it indicates that the material has a low degree of densification and is not a good raw material for synthetic electrolytes.

7. The method for raw material screening and element loss in-situ monitoring in rapid synthesis of solid electrolytes according to claim 2, characterized in that: The shrinkage rate of the pressed sheet can be quantified using a spiral micrometer to evaluate the macroscopic density of the sheet; if the shrinkage rate is less than the set threshold and is accompanied by surface cracks, it means that the structural rigidity is low and it is not a good raw material for synthesizing electrolytes.

8. The method for raw material screening and element loss in-situ monitoring in rapid synthesis of solid electrolytes according to claim 2, characterized in that: By analyzing the real-time infrared spectrum captured during the heating process, the sintering measurement temperature t is obtained by the Boltzmann formula and the spectrum intensity. That is, the measurement temperature t is the reliable sintering temperature.

9. The method for raw material screening and element loss in-situ monitoring in rapid synthesis of solid electrolytes according to any one of claims 1 to 8, characterized in that: It is suitable for in-situ volatile element monitoring in the preparation process of garnet, perovskite, halide, sulfide, NASICON and LISICON inorganic electrolytes.

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