Methods for Raw Material Screening and In-situ Monitoring of Element Loss in Rapid Synthesis of Solid Electrolytes

Abstract

This application belongs to the field of in-situ monitoring technology for inorganic solid electrolyte sintering, specifically relating to an in-situ method for raw material screening and elemental loss monitoring in the rapid synthesis of solid electrolytes. By detecting atomic absorption spectra during the reaction process, efficient judgment of the preparation quality and high-throughput screening of raw material formulations can be achieved. The garnet-type electrolyte screened by this method exhibits high atomic utilization, high ionic conductivity, and excellent cycle stability. The in-situ non-destructive testing method designed in this invention has a reasonable structure, is easy to operate, low in cost, and has good transferability.

Description

Technical Field

[0001] This application belongs to the field of in-situ monitoring technology for inorganic solid electrolyte sintering, specifically relating to a method for in-situ monitoring of raw material screening and element loss in the rapid synthesis of solid electrolytes. Background Technology

[0002] Traditional ceramic electrolyte synthesis relies on high-temperature steady-state solid-state reactions in muffle furnaces. This process is complex and involves excessively long sintering times, leading to severe loss of volatile elements and component segregation. This disrupts the electrolyte's stoichiometry and causes phase separation, resulting in compromised microstructure density and reduced 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, making it impossible to directly understand the intrinsic reaction kinetics occurring in the material after several hours of sealed treatment. These issues necessitate a posteriori methods for material characterization, such as morphological and bonding information analysis, to assess synthesis quality. This leads to feedback delays, resulting in inefficient and costly material synthesis optimization, heavily reliant on practical experience.

[0003] To address the element loss problem during the synthesis of ceramic electrolytes, existing improvement strategies compensate for element losses during sintering by covering the mixture with masterbatch. While this method effectively reduces the loss of key elements, it easily traps gaseous byproducts generated during high-temperature reactions, leading to the formation of undesirable secondary phases upon cooling, which impairs the structural integrity and electrochemical performance of the electrolyte. Different precursors can be used in the synthesis of ceramic electrolyte materials, but inconsistent product quality in previous studies has hindered cross-sectional comparisons. Pre-replenishing volatile elements can mitigate element losses during synthesis, but adding excessive lithium or sodium can cause batch-to-batch variations in grain size, sintering density, and microstructural uniformity. Therefore, to better understand and control the synthesis process, current optimization efforts have shifted towards improving in-situ diagnostic methods. Although laboratory-scale in-situ detection methods such as in-situ X-ray diffraction and in-situ TEM have been used in electrolyte synthesis studies, their real-time loss tracking and adaptive heating control capabilities remain limited. The lack of diagnostic tools restricts detailed detection, process control, and quality optimization of the synthesized high-performance ceramic electrolytes. Therefore, there is an urgent need for in-situ diagnostic methods that can directly diagnose volatile substances during high-temperature synthesis. Summary of the Invention

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

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

[0006] A method for raw material screening and in-situ monitoring of elemental loss in rapid synthesis of solid electrolytes includes the following steps:

[0007] S1. Pre-prepare electrolyte raw material powder and compress it into tablets;

[0008] S2. The Joule heating sintering process is adopted. Based on the in-situ thermal absorption spectroscopy method, the types of elements lost are obtained by analyzing the spectral absorption peaks, and the amount of element loss is obtained by analyzing the spectral intensity. After sintering, XRD analysis is combined to obtain the specific phase changes.

[0009] S3. Complete the screening of raw materials during the transient synthesis of solid electrolyte materials.

[0010] Preferably, the method also includes capturing the release and evolution of smoke generated during electrolyte synthesis using 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.

[0011] Preferably, in step S1, the electrolyte powder for analysis is obtained, the pre-made powder is crushed, the powder is weighed and placed in a mold, pressed and formed, and pressed with a cold isostatic press at a pressure of 40 t for 1-3 minutes to remove residual gas in the sheet and enhance the density of the material structure.

[0012] Preferably, if no obvious smoke is produced during the high-temperature heating process, it indicates that the material has not undergone serious side reactions; conversely, 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.

[0013] Preferably, the input voltage is adjusted in 5V increments using a precision power supply system, and the reaction process is monitored in real time using in-situ AAS technology. A quantitative relationship model between element volatilization and spectral absorption intensity is established. 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 range to the high volatilization temperature range, corresponding to a decrease in the remaining lithium in the system. As the input voltage continues to increase, the sample melts and decomposes, rapidly shrinks until it disappears completely, accompanied by the release of a large amount of smoke. This quantitative relationship model of AAS intensity, remaining volatile element, and impurity phase content enables precise quantification of the high-temperature volatile element loss rate.

[0014] Preferably, after the reaction is completed, the cross-sectional morphology of the electrolyte is observed using a scanning electron microscope. A tightly packed grain structure on the surface after high-temperature reaction without gas escape and a cross-section with transgranular fracture indicate that the material has high density and is a good raw material for synthesizing electrolytes. If the surface of the electrolyte sheet shows a porous structure formed by small grain necks, and the cross-section has a large number of pores and a continuous rough surface, it indicates that the material has low densification and is not a good raw material for synthesizing electrolytes.

[0015] Preferably, the shrinkage rate of the tablet is measured by micro-quantification using a spiral to assess the macroscopic density of the tablet. If the shrinkage rate is less than a set threshold and is accompanied by surface cracking, it indicates that the structural rigidity is poor and it is not a good raw material for synthetic electrolytes.

[0016] Preferably, the real-time infrared spectrum captured during the heating process is analyzed, and the sintering measurement temperature t is obtained from the Boltzmann formula and the spectral intensity. That is, the measurement temperature t is a reliable sintering temperature.

[0017] Preferably, it is suitable for in-situ monitoring of volatile elements in the preparation process of inorganic electrolytes such as garnet type, perovskite type, halide type, sulfide type, NASICON type and LISICON type.

[0018] Compared with existing technologies, the benefits of this application are as follows:

[0019] This invention achieves groundbreaking real-time, quantitative, in-situ monitoring of volatile elements during high-temperature sintering. Existing pre-compensation techniques involving masterbatch covering or excessive element addition have significant side effects, while laboratory in-situ detection methods such as in-situ XRD and in-situ Raman spectroscopy have slow response times and limited capabilities in tracking element loss. This invention is the first to apply InSiTAS to testing in the high-temperature sintering environment of electrolytes. AAS technology directly and accurately captures volatile elements (such as Li and Na) in the gas phase by detecting characteristic absorption peaks in specific infrared / visible light regions, achieving millisecond to second-level real-time monitoring of the volatilization process. This highly sensitive real-time feedback overcomes the limitations of traditional a posteriori analysis or slow-responding in-situ techniques.

[0020] This invention also avoids the side effects of over-sintering compensation strategies, improving material stability. While existing masterbatch coverings can reduce element loss, they irreversibly trap reactant gases, causing secondary phase formation during cooling, damaging electrolyte grain boundary integrity and density, and reducing ionic conductivity. Existing pre-compensation strategies require the addition of excessive volatile elements, making precise control of the synthesis process difficult and resulting in significant batch-to-batch differences in grain size, sintering density, and microstructure uniformity. This invention achieves transient heating and cooling through rapid synthesis technology, eliminating the need for physical covering layers and fundamentally eliminating the root cause of secondary phase formation. Precise in-situ monitoring allows for real-time control of element volatilization, optimizing sintering parameter settings and requiring only minor element compensation when necessary. This ensures batch stability and microstructure consistency, significantly improving material uniformity and intrinsic properties, and solving the key problem of inconsistent synthesis methods and product quality hindering cross-comparison of materials.

[0021] This invention enables process control and dynamic optimization, significantly improving synthesis efficiency and material quality. Existing in-situ technologies such as XRD, TEM, and Raman spectroscopy primarily provide means of state observation, offering limited real-time control capabilities for the synthesis process. This invention, however, combines rapid sintering technology, leveraging the system's millisecond-level elemental loss monitoring and feedback capabilities for real-time regulation. For example, it effectively suppresses bulk elemental loss while significantly shortening sintering time; when the elemental loss intensity rate is abnormal, the heating rate, reaction temperature, and holding time can be adjusted in real time—a level of real-time feedback and control efficiency difficult to achieve with conventional sintering techniques.

[0022] Compared to conventional synthesis methods, the overall performance of the synthesized garnet-type solid electrolyte material, as determined by AAS, shows a significant improvement over previously published work. The electrolyte (e.g., LLZO) prepared by the method of this invention achieves a retention rate of >95% for core volatile elements, far superior to conventional sintering processes. SEM morphology analysis shows that the material achieves high density, has few intrinsic defects, and possesses a complete structure. Electrochemical experimental data indicate that the prepared garnet-type electrolyte exhibits excellent performance at 0.3 mA·cm⁻¹. -2 Stable cycling for over 1400 hours can be achieved at the proposed current density, demonstrating excellent long-cycle performance, far exceeding that of garnet-type ceramic electrolytes prepared in published literature, thus meeting the requirements of high-performance solid-state batteries. This directly verifies the significant improvement in the final electrochemical performance of the material achieved by this method.

[0023] This invention provides strong experimental support for the study of the mechanisms of rapid reaction processes. Conventional a posteriori detection methods are used to verify the results of these mechanisms, but the results are difficult to directly support the intrinsic mechanisms of the reaction process. This method, by establishing a correlation model of "spectral absorption-phase evolution," provides direct experimental evidence for understanding the intrinsic relationship between phase evolution and element loss during sintering. The spectral absorption data obtained through semi-quantitative analysis provides a real-time monitoring tool for in-depth research on the influence of different sintering parameters (temperature, atmosphere, heating rate), precursor type / morphology on element volatilization kinetics and the final phase / microstructure. This deepens the understanding of high-temperature solid-state reaction mechanisms, which is difficult to achieve with existing detection technologies.

[0024] This method provides a bridge for rapid formulation optimization. Conventional formulation screening relies on post-hoc morphological and structural characterization, or requires extensive electrochemical performance testing to verify material quality. This method, however, can rapidly screen samples based on elemental 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 formulation determination.

[0025] This in-situ detection method also possesses strong universality, applicable to various solid electrolytes containing volatile elements, including sodium metal solid electrolytes, perovskite electrolytes, and NASICON-type electrolytes, as well as advanced ceramic materials requiring high-temperature treatment. In contrast, the muffle furnace sintering process using steady-state heating requires extensive and long-term exploration of the synthesis conditions for different materials to obtain suitable 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.

[0026] This method also has the potential for industrial application. Conventional in-situ or post-hoc detection methods are costly and difficult to implement in batches, while the spectroscopic detection method used in this method has a simpler setup and does not require expensive equipment, making it adaptable to large-scale production processes. The successful validation of this real-time monitoring and process control on a laboratory scale provides a feasible technical path to solve the uniformity and repeatability problems caused by scale effects in materials processing, thus helping to accelerate the industrialization process. Attached Figure Description

[0027] Figure 1 This is a flowchart of the synthesis and detection process for in-situ observation of rapid sintering in this invention;

[0028] Figure 2 This is a schematic diagram of the rapid sintering device for in-situ spectral observation according to the present invention.

[0029] Figure 3 This is a schematic diagram of the temperature control of the synthesis process system in this invention.

[0030] Figure 4 This is a schematic diagram of in-situ densification of ceramic particles in this invention.

[0031] Figure 5 This is a record of the rapid sintering process of LLZO ceramic sheets prepared using different lithium sources in this invention.

[0032] Figure 6 These are SEM images of LLZO sheets obtained using different lithium sources after sintering in this invention.

[0033] Figure 7 This invention describes the macroscopic size shrinkage of LLZO sheets prepared using different lithium sources after reaction.

[0034] Figure 8 This is a diagram illustrating the method of fitting sintering temperature using spectral intensity according to the present invention.

[0035] Figure 9 This is a comparison of the atomic absorption spectra of the systems during the non-equilibrium synthesis of LLZO (I) and (III) in this invention.

[0036] Figure 10 This is a quantitative relationship model between lithium volatilization and spectral absorption intensity established using in-situ AAS technology in this invention.

[0037] Figure 11 This is a schematic diagram of the computational domain for modeling the material loss of smoke in this invention.

[0038] Figure 12 It is a simulation of the Li2O generation process during sintering based on the smoke morphology recorded by the camera.

[0039] Figure 13 It is a modeling and high-temperature state simulation of the component loss during the volatilization process of Li2CO3 in the sintering process.

[0040] Figure 14 This is a structural diagram of a symmetrical battery assembled using an LLZO ceramic electrolyte according to the present invention.

[0041] Figure 15 This is a comparison of the electrochemical performance of LLZO ceramic electrolytes prepared using rapid Joule heating in this invention.

[0042] Figure 16 This is a record of the rapid sintering process for preparing β-Al2O3 electrolyte using different sodium sources in this invention.

[0043] Figure 17 This is a comparison of the atomic absorption spectra of the systems used in the non-equilibrium synthesis of β-Al2O3 with different sodium sources in this invention.

[0044] Figure 18 These are SEM images of β-Al2O3 prepared using different sodium sources after sintering according to this invention.

[0045] Figure 19 This describes the macroscopic dimensional shrinkage of different β-Al2O3 electrolyte sheets after high-temperature reaction according to the present invention.

[0046] Figure 20 This invention relates to the compositional analysis of the β-Al2O3 phase prepared using rapid Joule heating. Detailed Implementation

[0047] The present application will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention, and should not be construed as limiting the scope of protection of the present application.

[0048] A method for raw material screening and in-situ monitoring of elemental loss in rapid synthesis of solid electrolytes includes the following steps:

[0049] S1. Pre-prepare electrolyte raw material powder and compress it into tablets;

[0050] To obtain the electrolyte powder for analysis, the pre-made powder is crushed, weighed and placed in a mold, pressed and formed, and then pressed for 1-3 minutes at a pressure of 40 t using a cold isostatic press to remove residual gas from the sheet and enhance the density of the material structure.

[0051] S2. During the heating and sintering process, based on the in-situ thermal absorption spectroscopy method, the types of elements lost are obtained by analyzing the spectral absorption peaks, and the amount of element loss is obtained by analyzing the spectral intensity; the specific phase changes are obtained by combining the spectral intensity with XRD analysis.

[0052] S3. Complete the screening of raw materials during the transient synthesis of solid electrolyte materials.

[0053] It also includes capturing the release and evolution of fumes generated during electrolyte synthesis using 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.

[0054] If no obvious smoke is produced during the high-temperature heating process, it indicates that the material has not undergone serious side reactions; conversely, 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.

[0055] By adjusting the input voltage in 5V increments using a precision power supply system and monitoring the reaction process in real time using in-situ AAS technology, a quantitative relationship model between element volatilization and 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 nonlinearly increased from the low volatilization temperature range to the high volatilization temperature range, corresponding to a decrease in the remaining lithium in the system. As the input voltage continued to increase, the sample melted and decomposed, rapidly shrinking until it disappeared completely, accompanied by the release of a large amount of smoke. This quantitative relationship model of AAS intensity, remaining volatile element, and impurity phase content enables the precise quantification of the high-temperature volatile element loss rate.

[0056] After the reaction is complete, the cross-sectional morphology of the electrolyte is observed using a scanning electron microscope. The tightly packed grain structure on the surface after the high-temperature reaction without gas escape and the cross-section with transgranular fracture indicate that the material has high density and is a good raw material for synthesizing electrolytes. If the surface of the electrolyte sheet shows a porous structure formed by small grain necks, and the cross-section has a large number of pores and a continuous rough surface, it indicates that the material has low densification and is not a good raw material for synthesizing electrolytes.

[0057] The shrinkage rate of the tablet can be evaluated by using a screw to measure the micro-quantitative shrinkage rate. If the shrinkage rate is less than the set threshold and is accompanied by surface cracking, it indicates that the structural rigidity is poor and it is not a good raw material for synthetic electrolytes.

[0058] The real-time infrared spectrum captured during the heating process is analyzed, and the sintering measurement temperature t is obtained from the Boltzmann formula and spectral intensity. That is, the measurement temperature t is a reliable sintering temperature.

[0059] Example 1

[0060] This invention discloses a method for in-situ detection of the absorption spectrum during the transient synthesis of garnet-type ceramic solid electrolyte materials, specifically implemented according to the following steps:

[0061] S1, La2O3, ZrO2, Ta2O5, LiOH, LiOH·H2O, and Li2CO3 were respectively formulated according to Li 6.5 La3Zr 1.75 Ta 0.25 O 12 The molar ratio of the mixture is 10% excess of Li to compensate for the loss of lithium during the powdering process.

[0062] S2, dissolve the powder in an alumina ball mill jar with isopropanol (IPA), grind with alumina balls as grinding aid in a planetary ball mill at 360 rpm for 5 h, and then dry in a vacuum drying oven at 120 ℃, taking care to avoid contact with air during this process.

[0063] S3, after grinding the powder again, is 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 pre-powder is obtained.

[0064] S4. The pre-formed powder is pulverized, and 180 mg of powder is weighed and placed in a mold with a diameter of 8 mm. It is then pressed at 3 t for 2 minutes to form the sheet. A cold isostatic press is then used to press the sheet at 40 t for 1 minute to remove residual gas and enhance the material's structural density. The process flow of this synthesis method is as follows: Figure 1 As shown.

[0065] S5, assemble the rapid heating device and the detection device, such as Figure 2 As shown, the power output is first adjusted to heat the carbon felt to red-hot to remove surface impurities and oxygen-containing functional groups from the substrate.

[0066] S6. The LLZO sheet is sandwiched between two carbon felts, the spectrometer is aimed at the upper surface of the sample, and the electrolyte is sintered using the Joule heating method.

[0067] S7. 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 wavelength at a frequency of once every 200 ms, for a total of 30 s.

[0068] S8. The LLZO sheets were treated at approximately 500 °C to remove the release agent adhering to the surface during pressing; then the temperature was rapidly increased to 1300 °C for about 20 seconds. During this time, the shrinkage of the ceramic sheets could be observed using a camera. After the power output was turned off, the system was rapidly cooled, with a total heat treatment time of approximately 30 seconds, thus achieving rapid electrolyte synthesis. Specific reaction temperature changes are as follows... Figure 3 As shown, the densification mechanism of LLZO wafers is as follows: Figure 4 As shown.

[0069] S9, the LLZOs prepared from LiOH, LiOH∙H2O, and Li2CO3 precursors were named LLZO (I), LLZO (II), and LLZO (III), respectively. The reaction process was recorded as follows: Figure 5 As shown, LLZO (I) exhibits a stable heating state during high-temperature processes, with no substance volatilization observed. LLZO (II) produces significant fumes during high-temperature processes, while LLZO (III) produces a large amount of fumes during high-temperature processes, accompanied by flame combustion until the cooling stage, indicating severe side reactions occurring under high-temperature conditions.

[0070] S10, after the reaction is complete, the morphology of different LLZO sheets is compared using scanning electron microscopy (SEM) as follows: Figure 6LLZO (I) that did not experience gas escape after high-temperature reaction exhibited a tightly packed grain structure, and the transgranular fracture cross-section indicated high density, consistent with typical dense garnet characteristics. LLZO (II) showed a porous structure formed by small grain necks, while LLZO (III) had numerous pores and a continuously rough surface, indicating low densification and the presence of a Li₂CO₃ deposition layer on the particle surface. LLZO prepared from LiOH had the densest cross-section and was most suitable for practical electrolyte applications. However, LiOH∙H₂O or Li₂CO₃ were not good raw materials for synthesizing LLZO.

[0071] S11, the shrinkage rate of the micro-quantitative ceramic sheet is measured using a spiral. Figure 7 The macroscopic density of the sheet can be assessed. LLZO(I) exhibits a diameter shrinkage rate of 14.13% after sintering and displays a ceramic luster. LLZO(II) shrinks by only 6.11% and is accompanied by surface cracking, with poor structural rigidity. LLZO(III) shows surface powdering and a dimensional change rate of <0.8%.

[0072] S12, analyze the real-time infrared spectrum captured during the heating process, such as Figure 8 As shown, conventional temperature measuring tools exhibit significant deviations under high-temperature conditions, while the thermal radiation of carbon felt can be considered equivalent to a blackbody radiation source, and its radiation energy density distribution conforms to the Stefan-Boltzmann law. B(λ, T)=(2πhc 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 blackbody, in Kelvin (K), T = t (degrees Celsius) + 273 K; c is the speed of light, approximately 2.998 × 10⁻⁶. 8 m·s -1 h is Planck's constant, approximately 6.626 × 10⁻⁶. -34 J·S; while K is the Boltzmann constant, approximately 1.380 × 10⁻⁶. -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 obtained by decoupling the exponent term of Planck's law and taking the logarithm, resulting in the expression for temperature T: T = hc / (λk*In(1+(2πhc)). 2 *(λ 5 * B(λ, T)))), by inputting the measured temperature t during sintering, the actual sintering temperature is obtained as 1359 ℃.

[0073] S13, Peak pairs of atomic absorption spectra (AAS) of LLZO (I) and (III) systems during non-equilibrium synthesis, for example... Figure 9 As shown in Figure a. S13, peak pairs of the atomic absorption spectra (AAS) of the LLZO (I) and (III) systems during non-equilibrium synthesis are shown in Figure a. Figure 9 As shown in Figure a. Under normal conditions, atoms are in their ground state. When subjected to thermal or electrical excitation, atoms transition from the ground state to the excited state, a process that involves the absorption of light of a characteristic wavelength. The intensity of the transmitted light, I, is lower than the intensity of the incident light, I0. The degree of attenuation of the light intensity is positively correlated with the atomic concentration, i.e., I = I0e^(-I / I0). -KvNL Therefore, absorbance A = log 10 (I0 / I) = K'NL. K' is related to the element type and wavelength; N is the ground-state atomic number density (unit: cm⁻³); L is the absorption layer thickness (unit: cm). The energy absorbed during atomic transitions is ΔE = E₂ - E₁ = hν = hcλ. -1 Therefore, resonant absorption occurs only when the incident photon energy hν is strictly equal to the energy level difference ΔE.

[0074] Experimental results show that when LLZO is prepared using Li2CO3 as a precursor, a significant spectral absorption occurs at 671.1 nm, which coincides with the characteristic absorption line of lithium. However, only trace amounts of elemental absorption signals were detected in the system using LiOH as a precursor. Figure 9 The continuous in-situ spectra of b further revealed that no elemental loss was detected in LLZO (I) throughout the synthesis process, while the spectral curve of LLZO (III) showed that there was always Li elemental loss in the synthesis process using Li2CO3.

[0075] S14, using LLZO(III) precursor as the research object, employed a precision power supply system with a 5 V gradient to adjust the input voltage and utilized in-situ AAS technology to monitor the reaction process in real time. The established quantitative relationship model between lithium volatilization and spectral absorption intensity is as follows: Figure 10 As shown, when the input voltage increases from 15 V to 30 V, the relative intensity of the Li absorption peak increases nonlinearly from 0.14% in the low volatility temperature region to 15.60% in the violent volatility temperature region, corresponding to a sharp drop in the remaining lithium content in the system from 95% to 82.0%. When the input voltage is increased to 35 V, LLZO melts and decomposes, the sample rapidly shrinks to complete disappearance, and a large amount of smoke is released. This quantitative relationship model of AAS intensity-remaining lithium content-impurity phase content enables accurate quantification of high-temperature lithium loss rate and optimization of LLZO synthesis process.

[0076] To analyze the chemical composition of the substances in the sintering atmosphere, carbon paper was used to collect the condensed smoke particles. X-ray photoelectron spectroscopy (XPS) was used to analyze the chemical state of the deposits on the carbon paper surface. The analysis revealed that the deposits were mainly composed of Li, C, and O, and were a mixture of Li₂CO₃ and Li₂O. This indicates that during the unsteady-state thermal synthesis process, gaseous CO₂ produced by the decomposition of the Li₂CO₃ precursor carried Li₂O out of the bulk phase, resulting in a significant loss of lithium from the bulk phase. During the cooling stage, some volatile substances underwent recombination, leading to the formation of a co-deposited product of Li₂O and Li₂CO₃ on the carbon paper.

[0077] S16 presents a video monitoring and XPS simulation of smoke loss during the high-temperature synthesis of LLZO from Li₂CO₃. A three-dimensional (3d) model was used to simulate the turbulent transport process of Li₂O and CO₂ during the decomposition of Li₂CO₃. The model solved the unsteady, multi-component, reactive, and compressible Navier-Stokes (NS) equations. To accurately capture large-scale turbulence characteristics, a Large Eddy Simulation (LES) dynamic structure model was employed. A Subgrid Scale (SGS) model was used to handle small-scale turbulence effects, improving simulation accuracy. The subgrid kinetic energy transport equations were considered in the LES dynamic structure model, enhancing the predictive ability for turbulent transport processes. The O'Rourke and Amsden models were used to consider the wall heat transfer process. Figure 11 The computational domain is (0.1 × 0.2 m). 2 A cross-sectional view of the computational domain. The initial temperature of the computational domain is 27 °C, the pressure is 1 atm, and the white area at the bottom (10 × 1 mm) is shown. 2 () represents LLZO ceramics on a Li2CO3 substrate. The temperature in this region is 1350 ℃, the same as the heating temperature in the experiment. The concentrations of Li2O and CO2 were calculated based on the Li2CO3 decomposition reaction. A mass flux calculated from the Li2CO3 decomposition rate was set at the top boundary of the ceramic to simulate the upward migration of Li2O and CO2. For the mesh size, the basic mesh was 6 mm. To ensure the stability of the geometry during the flow, a four-layer, two-layer fixed embedding was used in the Li2CO3 decomposition region. Adaptive mesh refinement (AMR) technology was used to adaptively refine the mesh in regions with large velocity 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, where the typical state of Li2O migration is as follows: Figure 12 As shown.

[0078] When the rate of mass loss in the gas phase reaches the decomposition threshold of Li₂CO₃, lithium begins to vaporize and escape. The typical migration patterns of Li₂O and CO₂ are as follows: Figure 13As shown, when the reaction proceeded for 0.5 s, the gas phase transport distance reached 0.1 m, and the surface Li₂O transport rate reached 0.1 m·s⁻¹. -1 When the reaction proceeded for 1.1 s, the lithium formation rate in the central region surged to 0.3 m·s due to the vortex acceleration effect. -1 This creates a significant spatial concentration gradient, allowing Li2O to be continuously transported into the atmosphere.

[0079] S17, the surfaces of the synthesized samples were continuously polished using 500, 1000, and 2000 grit boron nitride sandpaper to obtain ceramic electrolyte sheets with smooth surfaces and no oxide layer. Lithium metal was deposited onto the LLZO electrolyte surface using a high-temperature titanium heating stage 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 casing. A pre-placed carbon felt buffer layer was used to prevent damage to the electrolyte from the sealing pressure (20 MPa). A schematic diagram of the symmetrical battery structure is shown below. Figure 14 .

[0080] S18, Figure 15 To compare the electrochemical performance of different LLZOs, the impedance and ionic conductivity of LLZOs were measured by electrochemical impedance spectroscopy (EIS). Constant current charge-discharge cycle tests of symmetric cells were conducted to verify the interfacial stability of LLZOs prepared from different Li sources during lithium deposition / stripping. A stepped current method (step size 0.05 mA·cm⁻¹) was used. -2 The critical current density (CCD) of the symmetric cell was tested over a 0.3 h process to measure the resistance of the LLZO interface prepared from different raw materials to lithium dendrite formation. The ionic conductivity of LLZO(I) prepared from LiOH was significantly higher than that of LLZO(III). The CCD of LLZO(I) was 11.5 times that of LLZO prepared from Li₂CO₃ under the same conditions, greatly improving the cell performance. The LLZO(III)-based cell achieved a CCD of 0.1 mA∙cm⁻¹. -2 Short-circuit failure occurred after only 1.17 h of cycling, and LLZO (II) exhibited a significant increase in polarization voltage and rapid short-circuiting. LLZO (I) at 0.3 mA∙cm -2 It can operate stably for more than 1400 h under a constant current density, while the polarization voltage fluctuation range is maintained at around 100 mV, which confirms that the LLZO (I) electrolyte synthesized with LiOH as a precursor exhibits the best lithium dendrite suppression ability and interface durability.

[0081] Example 2

[0082] This invention discloses a method for in-situ detection of the absorption spectrum during the transient synthesis of layered sodium metal solid electrolyte β-Al2O3 material, specifically implemented according to the following steps:

[0083] S1, react Na2CO3 or NaOH with Li2CO3 and γ-Al2O3 respectively according to Al 10 Na2Li 0.5 O 17 The molar ratio of Na and Li sources is mixed (Na and Li sources are in excess by 10%).

[0084] S2 is the same as the specific implementation method one.

[0085] S3. The ground powder was placed in an alumina crucible and calcined in a muffle furnace at 1250 °C for 2 h using a heating program of 3 °C / min to obtain β-Al2O3 pre-powder.

[0086] S4, take 100 mg of pre-made powder to make tablets, and the other key points are the same as in Specific Implementation Method 1.

[0087] S5-7 is the same as the specific implementation method one.

[0088] S8. The Al2O3 sheet is treated at a low temperature of about 500 °C to remove the release agent; then the temperature is rapidly increased to 1500 °C and heated for about 20 s. The temperature calculation method is the same as that in S12 of the specific implementation method. The electrolytes prepared from NaOH and Na2CO3 are named β-Al2O3 (I) and β-Al2O3 (II), respectively.

[0089] S9, the reaction process is recorded as follows: Figure 16 As shown, β-Al2O3 (I) exhibits steady-state thermal radiation characteristics at 1500 ℃, with the sheet surface uniformly red-hot and no gas release observed. In contrast, β-Al2O3 (II) prepared using Na2CO3 produces smoke in the early stages of thermal synthesis, and generates a violent flame with a large amount of smoke at 1000 ℃. This phenomenon disappears when the temperature is lowered to about 500 ℃.

[0090] S10, the unsteady synthesis process of β-Al2O3 recorded in situ by AAS, as follows: Figure 17 As shown, β-Al₂O₃(II) prepared using Na₂CO₃ exhibits a characteristic absorption peak at 589.2 nm, corresponding to the atomic absorption spectrum of Na atoms. This peak remained at a high level of 9.3% throughout the 20 s sintering cycle, indicating continuous sodium volatilization. In contrast, β-Al₂O₃(I) showed only a weak absorption signal in the infrared / visible wavelength range, suggesting that sodium loss during sintering was effectively suppressed. These spectral differences provide atomic-scale theoretical support for developing a synthesis formulation of β-Al₂O₃ with low material loss.

[0091] S11, SEM morphology comparison of different β-Al2O3 electrolyte sheets, for example Figure 18As shown, β-Al2O3 (I) exhibits a typical layered β-Al2O3 dense structure without micron-sized pores, confirming that densification was achieved during the rapid sintering process. In contrast, β-Al2O3 (II) displays a porous structure with numerous micron-sized pores, indicating that densification did not occur during the high-temperature synthesis process.

[0092] S12, quantified changes in the size of the sodium electrolyte sheet before and after sintering, as shown in... Figure 19 The diameter shrinkage rate of β-Al2O3 (I) reached 12.0%, while that of β-Al2O3 (II) prepared using Na2CO3 at the same size only shrank by 5.0%.

[0093] S13, Phase composition analysis of the product after rapid sintering is as follows: Figure 20 The main diffraction peak of β-Al2O3 (I) corresponds to the standard card of β-Al2O3 phase (COD#96-101-0018), indicating that β-Al2O3 was generated during rapid sintering. The characteristic peaks of the Na2CO3-based sample highly match the standard card of α-Al2O3 (PDF#35-0438), indicating that sodium element was excessively lost during the high-temperature reaction. These results indicate that using NaOH instead of traditional Na2CO3 as the Na source can advance the synthesis of β-Al2O3 phase in non-equilibrium rapid sintering. Furthermore, the combination of the in-situ process visualization monitoring advantage of AAS and ultrafast sintering technology provides a rapid screening paradigm for material screening in high-temperature solid-state reactions.

[0094] Example 3

[0095] This invention discloses a method for in-situ detection of the absorption spectrum during the transient synthesis of the chloride solid electrolyte Li₂ZrCl₆, specifically implemented according to the following steps:

[0096] S1, mix LiCl and ZrCl4 powders in a glove box at a mass ratio of 1:1.

[0097] S2 is the same as the specific implementation method one. During this period, 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.

[0098] S3, take 200 mg of pre-made powder to make tablets, and the other key points are the same as S4 of the specific implementation method one.

[0099] S4-6 is the same as S5-7 in Specific Implementation Method 1.

[0100] S7. The Li2ZrCl6 sheet was rapidly heated using the Joule heating method. First, it was treated at a low temperature of 200 °C to remove the release agent adhering to the surface during the sheet preparation process; then, the temperature was rapidly increased to 700 °C and heated for about 20 seconds. The power output was then turned off, and the system was rapidly cooled. The total treatment time was about 30 seconds.

[0101] S8, similar to S13-14 of Specific Implementation Method 1, establishes a linear correlation model between spectral absorption intensity and element volatilization by analyzing the signal intensity of atomic absorption spectra at the characteristic absorption peak of lithium (670.8 nm) and the absorption band of chlorine (134.7 nm). Based on this, the degree of loss of lithium and chlorine can be determined in real time, realizing a non-destructive and rapid assessment of synthesis quality and providing a quantitative basis for optimizing sintering process parameters.

[0102] Example 4

[0103] This invention discloses a method for in-situ detection of the absorption spectrum during the transient synthesis of perovskite-type solid electrolyte LLTO materials, which is basically the same as implementation method three, except that:

[0104] According to Li 0.5 La 0.5 Ti 0.92 Zr 0.08 The stoichiometric proportions of Li₂CO₃, La₂O₃, TiO₂, and ZrO₂ were weighed, with Li₂CO₃ in 10 mol% excess to compensate for lithium loss during the powdering process. The raw materials were mixed with ethanol solvent and ball-milled for 12 h to ensure uniform dispersion of the components. The ball-milled mixture was pre-calcined in air at 1000 °C for 12 h to obtain LLTO pre-powder. The pre-calcined powder was ground and pressed into green embryos with a diameter of 8 mm, then sintered at 1000 °C for 1 min using the Joule heating method to obtain Li₂CO₃. 0.5 La 0.5 Ti 0.92 Zr 0.08 The elemental loss and densification degree of LLTO in the O3 solid electrolyte were measured by capturing the atomic absorption spectra of Li at 670.8 nm using a spectrometer.

[0105] Example 5

[0106] This invention discloses a method for in-situ detection of the absorption spectrum during the transient synthesis of NASICON-type solid electrolyte LATP material. The synthesis process is basically the same as that in Method 3, except that:

[0107] According to Li 1.3 Al 0.3 Ti 1.7Li₂CO₃, Al₂O₃, TiO₂, and H₉N₂O₄P powders were weighed according to the stoichiometric ratio of (PO₄)₃, with Li₂CO₃ in 10 wt% excess to compensate for lithium loss during powdering. The raw materials were mixed with ethanol solvent and ball-milled for 12 h to ensure uniform dispersion of the components. The slurry was thoroughly dried in an oven at 78 °C to remove ethanol. The ball-milled mixture was pre-calcined in air at 800 °C for 4 h at a heating rate of 5 °C / min to obtain LATP pre-powder. 200 mg of the ground pre-powder was pressed into green embryos with a diameter of 8 mm and sintered at 800 °C for 30 s using the Joule heating method to obtain Li 1.3 Al 0.3 Ti 1.7 The (PO4)3 solid electrolyte, in which the atomic absorption spectral intensity of Li at 670.8 nm is captured by a spectrometer to measure the quality of LATP synthesis.

[0108] This experimental method is also applicable to in-situ monitoring of volatile elements in the preparation process of other inorganic electrolytes such as garnet, perovskite, halide, sulfide, NASICON, and LISICON types. It allows for real-time reflection of sintering quality during synthesis, solving the problems of process black box and time-consuming and energy-intensive processes in traditional methods. This provides a technical path for high-throughput development and rapid performance verification of solid electrolytes.

[0109] The applicant of this invention has provided a detailed description of the embodiments of the invention in conjunction with the accompanying drawings. However, those skilled in the art should understand that the above embodiments are merely preferred embodiments of the invention. The detailed description is only intended to help readers better understand the spirit of the invention and is not intended to limit the scope of protection of the invention. On the contrary, any improvements or modifications made based on the inventive spirit of the invention should fall within the scope of protection of the invention.

Claims

1. A method for raw material screening and in-situ monitoring of element loss in rapid synthesis of solid-state electrolytes, characterized in that, Comprising the following steps: S1. Preparing electrolyte raw material powder and tabletting; S2. Using Joule heating method to heat the sintering process, based on in-situ thermal absorption spectrum method, the lost element types are obtained by analyzing the spectral absorption peaks, and the element loss amount is obtained by spectral intensity analysis; the release and evolution of smoke generated during the synthesis of electrolyte are captured by the camera, the element loss is tracked in real time, the concentration and speed of element loss are calculated, and the camera needs to be installed with an infrared cutoff filter; after sintering, the specific phase change is obtained by combining XRD analysis; S3. Screening of raw materials during the transient synthesis process of solid electrolyte materials: After the reaction is completed, the cross-sectional morphology of the electrolyte is observed using a scanning electron microscope, the surface of the grain structure after high-temperature reaction does not occur gas escape, the cross-section of transgranular fracture shows that the material has high density, which is a good synthesis electrolyte raw material; if the electrolyte sheet surface presents a porous structure formed by small crystal grains, and there are a large number of pores and continuous rough surfaces in the cross-section, it indicates that the material has low degree of densification, which is not a good synthesis electrolyte raw material; Or, The shrinkage rate of the tablet is quantified by using a screw micrometer, which can evaluate the macroscopic density of the sheet; if the shrinkage rate is less than the set threshold value, and is accompanied by surface cracking, it indicates that the structure has poor rigidity and low, which is not a good synthesis electrolyte raw material.

2. The method for raw material screening and in-situ monitoring of elemental loss in rapid synthesis of solid-state electrolytes according to claim 1, wherein, In step S1, the electrolyte powder for analysis is obtained, the pre-prepared powder is crushed, the powder is weighed and placed in a mold, and a cold isostatic press is used to press at a pressure of 40t for 1-3min to expel the residual gas in the sheet and enhance the material structure density.

3. The method for raw material screening and in-situ monitoring of elemental loss in rapid synthesis of solid state electrolytes according to claim 1, wherein, If no obvious smoke is generated during high-temperature heating, it indicates that the raw material has not undergone serious side reactions; on the contrary, if the raw material generates a large amount of smoke during high-temperature process and is accompanied by flame burning until the cooling stage, it means that serious side reactions and element loss occur under high-temperature conditions.

4. The method for raw material screening and in-situ monitoring of elemental loss in rapid synthesis of solid state electrolytes according to claim 1, wherein, The input voltage is adjusted by a precision power supply system with a gradient of 5V, and the reaction process is monitored in real time by using in-situ AAS technology, and a quantitative relationship model of element volatilization amount and spectral absorption intensity is established. When the input voltage increases from 15V to 30V, the relative intensity of the absorption peak of the volatilized element increases from the low volatilization temperature zone to the intense volatilization temperature zone, and the corresponding lithium remaining amount in the system begins to decrease. When the input voltage continues to rise, the sample melts and decomposes, the sample shrinks rapidly to complete disappearance, and a large amount of smoke is released; the quantitative relationship model of AAS intensity, remaining amount of volatilized element and impurity phase content realizes the accurate quantification of the volatilization rate of high-temperature volatilized element.

5. The method for feedstock screening and in-situ monitoring of elemental loss in rapid synthesis of solid state electrolytes according to claim 1, wherein, The real-time infrared spectrum captured during the heating process is analyzed, and the sintering metering temperature t is obtained from the Boltzmann formula and the spectral intensity, that is, the metering temperature t is the reliable sintering temperature.

6. The method for raw material screening and in-situ monitoring of elemental loss in rapid synthesis of solid state electrolytes according to any one of claims 1-5, wherein, It is suitable for in-situ monitoring of volatile elements during the preparation process of garnet-type, perovskite-type, halide-type, sulfide-type, NASICON-type and LISICON-type inorganic electrolytes.

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