A gradient LiF / Li3N artificial SEI film, a solid electrolyte-SEI-electrode composite material, and a solid-state lithium-ion battery and their preparation.

Abstract

The present application belongs to the field of solid-state lithium ion battery interface engineering and thin film preparation technology, and provides a gradient LiF / Li3N artificial SEI film, a solid-state electrolyte-SEI-pole piece composite material and a solid-state lithium ion battery and preparation thereof. The gradient LiF / Li3N artificial SEI film comprises a bottom layer, an intermediate transition layer and a surface layer which are sequentially stacked; the bottom layer is a Li3N layer; the intermediate transition layer is a layer with gradient change in Li3N and LiF content; the atomic ratio of N and F in the intermediate transition layer gradually changes from 80:20 to 20:80 at a constant speed; one side of the intermediate transition layer with an atomic ratio of N and F of 80:20 is in contact with the bottom layer; and the surface layer is a LiF layer. The gradient LiF / Li3N artificial SEI film has excellent high ionic conductivity and stability, and solves the contradiction between high ionic conductivity and stability.

Description

Technical Field

[0001] This invention relates to the field of interface engineering and thin film preparation technology for solid-state lithium-ion batteries, and particularly to a gradient LiF / Li3N artificial SEI film, a solid electrolyte-SEI-electrode composite material, and a solid-state lithium-ion battery and their preparation. Background Technology

[0002] Lithium metal anodes and silicon-based materials are considered core components of next-generation batteries due to their high theoretical capacities (3860 mAh / g and 4200 mAh / g), but interface instability hinders their practical application. To improve interface stability, existing technologies typically deposit an SEI film on the surface of the lithium metal anode. These SEI films are generally LiF or Li3N layers. Li layers offer high stability but have low ionic conductivity; while Li3N has high ionic conductivity, but its electrochemical window is narrow (less than 3V), resulting in poor stability.

[0003] Therefore, it is necessary to provide an SEI membrane that combines high ionic conductivity and high stability. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a gradient LiF / Li3N artificial SEI film, a solid electrolyte-SEI-electrode composite material, and a solid-state lithium-ion battery, as well as their preparation methods. The gradient LiF / Li3N artificial SEI film provided by this invention possesses both excellent ionic conductivity and stability.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a gradient LiF / Li3N artificial SEI film, comprising a bottom layer, an intermediate transition layer and a top layer stacked sequentially; The bottom layer is a Li3N layer; The intermediate transition layer is a layer with a gradient change in the content of Li3N and LiF; the atomic ratio of N to F in the intermediate transition layer gradually changes from 80:20 to 20:80 at a uniform rate; the side of the intermediate transition layer with an atomic ratio of N to F of 80:20 is in contact with the bottom layer. The surface layer is a LiF layer.

[0006] Preferably, the thickness of the bottom layer is 14.5~15.5 nm, and the ionic conductivity of the bottom layer is ≥10. -5 S / cm; The thickness of the intermediate transition layer is 4.9~5.1 nm; The thickness of the surface layer is 4.5~5.5 nm, and the electrochemical window of the surface layer is ≥4.5 V.

[0007] This invention also provides a method for preparing the gradient LiF / Li3N artificial SEI film described in the above technical solution, comprising the following steps: A precursor is obtained by sequentially sputtering a bottom layer, an intermediate transition layer, and a top layer onto a substrate. The precursor was annealed to obtain the gradient LiF / Li3N artificial SEI film.

[0008] Preferably, the sputtering conditions for the bottom layer include: a Li3N target and a sputtering power density of 2.45~2.55 W / cm². 2 The substrate rotation speed is 0.5 m / min, the deposition rate is 1 nm / s, and the time is 14.5~15.5 s; The sputtering conditions for the intermediate transition layer include: the target materials include a Li3N target and a LiF target, and the sputtering power density of the Li3N target is from 2.50 W / cm². 2 The constant velocity changes to 1.0 W / cm 2 The sputtering power density of the LiF target is from 0 W / cm². 2 The constant velocity changes to 2.0 W / cm 2 The deposition rate was 1 nm / s, and the time to change it was 4.9–5.1 s. The sputtering conditions for the surface layer include: a LiF target and a sputtering power density of 3.45~3.55 W / cm². 2 The deposition rate was 1 nm / s, and the time was 4.5~5.5 s; The annealing temperature is 195~205℃, and the time is 10~30min.

[0009] The present invention also provides a solid electrolyte-SEI-electrode composite material, comprising an electrode, and an SEI film and a solid electrolyte sequentially disposed on the surface of the electrode; The electrode includes a negative electrode; The SEI film is the gradient LiF / Li3N artificial SEI film described in the above technical solution or the gradient LiF / Li3N artificial SEI film prepared by the preparation method described in the above technical solution; The bottom layer of the gradient LiF / Li3N artificial SEI film is in contact with the electrode.

[0010] Preferably, the negative electrode is silicon; The solid electrolyte is lithium lanthanum zirconium oxide; The thickness of the solid electrolyte is 49~51μm.

[0011] This invention also provides a method for preparing the solid electrolyte-SEI-electrode composite material described in the above technical solution, comprising the following steps: An SEI film is prepared on the electrode to obtain an electrode with an attached SEI film; A solid electrolyte is applied to the SEI film of the electrode to which the SEI film is attached, and then hot-pressed to obtain the solid electrolyte-SEI-electrode composite material. The electrode includes a negative electrode.

[0012] Preferably, the hot pressing temperature is 148~152℃, the pressure is 9.9~10.1MPa, and the time is 4~6min.

[0013] The present invention also provides a solid-state lithium-ion battery, comprising a positive electrode and a solid electrolyte-SEI-electrode composite material; wherein the electrode in the solid electrolyte-SEI-electrode composite material is a negative electrode; The positive electrode is NCM811; The positive electrode is in contact with the solid electrolyte in the solid electrolyte-SEI-electrode composite material; The solid electrolyte-SEI-electrode composite material is the solid electrolyte-SEI-electrode composite material described in the above technical solution.

[0014] This invention also provides a method for preparing the solid-state lithium-ion battery described above, comprising the following steps: The solid-state lithium-ion battery is obtained by composite encapsulating the positive electrode and the solid electrolyte-SEI-electrode composite material. The electrode in the solid electrolyte-SEI-electrode composite material is the negative electrode.

[0015] This invention provides a gradient LiF / Li3N artificial SEI membrane.

[0016] In this invention, the bottom layer is a Li3N layer, which gives the artificial SEI membrane an ultra-high ionic conductivity (≥10). -5 S / cm), with added Li + Transmission, enabling Li + diffusion coefficient 10 -6 cm 2 / s; the surface layer is LiF, with an electrochemical window ≥4.5V, exhibiting high stability and the ability to block electrolyte reactions, resulting in a CE ≥99.2%; the intermediate transition layer is a layer with a gradient of Li3N and LiF content, causing the modulus to gradually change from 80GPa to 20GPa, absorbing 300% of the expansion stress of the silicon anode (substrate), thus ensuring that the silicon anode remains crack-free after 1000 cycles; simultaneously, the intermediate transition layer also reduces interfacial stress, lowers the crack rate, and improves the cycle stability of the silicon anode (substrate). The gradient LiF / Li3N artificial SEI film of this invention resolves the contradiction between "high ionic conductivity and stability".

[0017] The gradient LiF / Li3N artificial SEI membrane of the present invention has the following advantages: (1) Using a three-electrode system (1mA / cm) 2 The interfacial impedance of the gradient LiF / Li3N artificial SEI film provided by this invention was tested and found to be as low as 4.8 ± 0.3 Ω·cm. 2 Compared to existing technologies with impedance >15Ω·cm 2 This reduced the interface impedance by 68%.

[0018] (2) According to the full cell test of silicon anode / NCM811, the full cell constructed by the gradient LiF / Li3N artificial SEI film provided by the present invention has a capacity retention rate of 92% after 1000 cycles at 10C rate. Compared with the prior art, the capacity retention rate is <80% after 500 cycles at 3C rate, and the cycle life is improved by 3.3 times.

[0019] (3) The gradient LiF / Li3N artificial SEI film of the present invention has an electrochemical window of 4.5V and no degradation during cycling, and has excellent high voltage stability.

[0020] (4) The low-temperature performance of the gradient LiF / Li3N artificial SEI film was tested by EIS (-40℃~25℃). The results showed that the impedance increased by 2 times at -40℃, to 1.2×10. -4 S / cm.

[0021] (5) According to SEM and in-situ optical observation, the gradient LiF / Li3N artificial SEI film provided by the present invention has a dendrite suppression efficiency of ≥99.3% under 4.5V cycling with zero short circuit, which meets the aerospace-grade battery standard (DO-311A).

[0022] (6) Adiabatic accelerated calorimeter: The thermal runaway temperature of the gradient LiF / Li3N artificial SEI film provided by this invention is 217℃, which is higher and has better high temperature resistance. It has passed the UL2580 electric vehicle battery safety certification.

[0023] (7) The gradient LiF / Li3N artificial SEI film makes the energy density of silicon anode batteries reach 500Wh / kg; the fast charging time is shortened: at 10C, it can be charged to 80% in 6 minutes.

[0024] The present invention also provides a method for preparing the gradient LiF / Li3N artificial SEI film described in the above technical solution. The present invention uses sputtering to prepare the bottom layer, intermediate transition layer and surface layer, which can accurately control the thickness accuracy, avoid local excessive thinness (<10nm) and reduce the risk of dendrite penetration; at the same time, it strictly controls the power density fluctuation to avoid abnormal film crystallinity and breakage of ion conduction path. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a magnetron sputtering device; Figure 2 This is a schematic diagram of a magnetic levitation roll-to-roll continuous production system. Detailed Implementation

[0026] This invention provides a gradient LiF / Li3N artificial SEI film, comprising a bottom layer, an intermediate transition layer and a top layer stacked sequentially; The bottom layer is a Li3N layer; The intermediate transition layer is a layer with a gradient change in the content of Li3N and LiF; the atomic ratio of N to F in the intermediate transition layer gradually changes from 80:20 to 20:80 at a uniform rate; the side of the intermediate transition layer with an atomic ratio of N to F of 80:20 is in contact with the bottom layer. The surface layer is a LiF layer.

[0027] Unless otherwise specified, the raw materials used in this invention are preferably commercially available products.

[0028] The gradient LiF / Li3N artificial SEI film provided by this invention includes a base layer, wherein the base layer is a Li3N layer. In this invention, the thickness of the base layer is preferably 14.5~15.5 nm, more preferably 15 nm. In this invention, the ionic conductivity of the base layer is preferably ≥10. -5 S / cm. In this invention, the bottom layer is a Li3N layer, which gives the bottom layer an extremely high ionic conductivity (≥10). -5 S / cm), accelerating Li + Transmission, enabling Li + The diffusion coefficient reaches 10. -6 cm 2 / s.

[0029] The gradient LiF / Li3N artificial SEI film provided by this invention includes an intermediate transition layer stacked on the underlying layer. The intermediate transition layer is a layer where the contents of Li3N and LiF change gradients. The atomic ratio of N to F in the intermediate transition layer gradually changes from 80:20 to 20:80. The side of the intermediate transition layer with an N:F atomic ratio of 80:20 is in contact with the underlying layer. In this invention, the thickness of the intermediate transition layer is preferably 4.9~5.1 nm. The intermediate transition layer allows the modulus of the gradient LiF / Li3N artificial SEI film to gradually change from 80 GPa on the surface to 20 GPa on the underlying layer, absorbing 300% of the expansion stress of the negative electrode (specifically silicon), thus ensuring that the silicon negative electrode remains crack-free after 1000 cycles. Simultaneously, the intermediate transition layer also eliminates interfacial stress and crack rate, improving the cycle stability of the substrate (specifically the positive and negative electrodes).

[0030] The gradient LiF / Li3N artificial SEI film provided by this invention includes a surface layer stacked on the intermediate transition layer, wherein the surface layer is a LiF layer. In this invention, the thickness of the surface layer is preferably 4.5~5.5 nm, more preferably 5 nm. In this invention, the electrochemical window of the surface layer is preferably ≥4.5 V. In this invention, the surface layer is a LiF layer, and the electrochemical window is ≥4.5 V, exhibiting high stability, blocking electrolyte side reactions, and achieving an CE >99.2%.

[0031] This invention also provides a method for preparing the gradient LiF / Li3N artificial SEI film described in the above technical solution, comprising the following steps: A precursor is obtained by sequentially sputtering a bottom layer, an intermediate transition layer, and a top layer onto a substrate. The precursor was annealed to obtain the gradient LiF / Li3N artificial SEI film.

[0032] The present invention involves sequentially sputtering a bottom layer, an intermediate transition layer, and a top layer onto a substrate to obtain a precursor.

[0033] In one specific embodiment of the present invention, the substrate is preferably a negative electrode. The preferred material of the negative electrode will be described later.

[0034] In this invention, the substrate is preferably pretreated before sputtering a gradient LiF / Li3N artificial SEI film. The pretreatment preferably includes sequentially mounting and fixing the substrate, performing plasma cleaning, atomic deposition of a pre-film, and surface activation.

[0035] In this invention, the mounting and fixing of the substrate is preferably achieved by placing the substrate on a magnetically levitated substrate holder. In this invention, the vibration of the magnetically levitated substrate holder is preferably <1 μm to avoid mechanical damage.

[0036] In this invention, the plasma cleaning is preferably performed in an radio frequency plasma cleaner, and the electrode spacing of the radio frequency plasma cleaner is preferably 50 mm. The parameters for the plasma cleaning in this invention include: the working gas is preferably argon, the purity of the argon is preferably 99.999%, the flow rate of the argon is preferably 50 sccm, the radio frequency power is preferably 190~210W, more preferably 200W, the frequency is preferably 13.56MHz, and the time is preferably 4.5~5.5 min, more preferably 5 min. In this invention, the plasma cleaning can remove oxides from the substrate surface. The parameter settings result in an oxide removal rate >98%, a surface oxygen content <2 at%, an O / C atomic ratio <0.05, and a surface roughness <2 nm.

[0037] In this invention, the atomic deposition (ALD) pre-lay substrate is preferably a TiO2 film, and the thickness of the TiO2 film is preferably 1.8~2.2 nm, more preferably 2 nm. In this invention, the atomic deposition pre-lay substrate is preferably performed in an atomic layer deposition apparatus. In this invention, the parameters of the atomic deposition pre-lay substrate include: the precursor includes TiCl4 and H2O; the pulse time is preferably 0.1 s, and the purge time is preferably 5 s. In this invention, the specific process of the atomic deposition pre-lay substrate is preferably: TiCl4 pulse for 0.1 s, N2 purge for 5 s, H2O pulse for 0.1 s, N2 purge for 5 s; repeat the above process 19~21 times, i.e., a total of 20~22 times. In this invention, the atomic deposition pre-lay substrate achieves an adhesion of >5 N / cm to the substrate.

[0038] In this invention, the surface activation is preferably ultraviolet ozone activation, which is preferably performed in an ultraviolet ozone cleaning machine. The parameters of the ultraviolet ozone activation include: the light source is dual-wavelength ultraviolet light, and the dual wavelengths of the dual-wavelength ultraviolet light are 254nm and 185nm; the ozone concentration is preferably 100g / m³. 3 The preferred irradiation time is 10 min. In this invention, the surface activation can increase the hydroxyl density on the substrate surface, enhance its adhesion to the SEI film, and does not block ion channels, with a porosity >30%. Data from the examples show that after surface activation, the substrate surface contact angle is <5°, hydrophilicity is improved, and the surface energy is ≥60 mN / m.

[0039] In one specific embodiment of the present invention, the surface oxygen content of the pretreated substrate is <2 at%, a decrease of 87% compared to the surface oxygen content of the substrate before pretreatment (>15 at%); the interfacial adhesion is 5.8 N / cm, an improvement of 383% compared to the interfacial adhesion of the substrate before pretreatment (1.2 N / cm); the surface roughness (Ra) is 1.8 nm, a decrease of 79% compared to the surface roughness (Ra) of the substrate before pretreatment (8.5 nm); and the ion permeability is 1.2 × 10⁻⁶. -8 cm 2 / s, compared to the ion permeability of the substrate before pretreatment (0.3×10⁻⁶). -8 cm 2 / s, an increase of 300%; surface energy increased to 60mN / m.

[0040] In this invention, the pretreatment improves the yield to 99.5%, provides an atomically flat substrate for subsequent sputtering of the SEI film, and ensures the uniformity of the ultrathin SEI film layer.

[0041] After the pretreatment and before the sputtering of the underlying layer, the present invention preferably further includes: sequentially performing wafer mounting and vacuum chamber pretreatment. In the present invention, the wafer mounting is preferably performed by placing the substrate in a magnetic levitation substrate holder. In the present invention, the vibration of the magnetic levitation substrate holder is preferably <1μm to avoid mechanical damage. In the present invention, the vacuum chamber pretreatment preferably includes the following steps: evacuating to 5×10⁻⁶ m / s². -5 Pa, argon gas is introduced to stabilize the pressure to 0.5 Pa; the preferred flow rate of the argon gas is 20 sccm.

[0042] In this invention, the sputtering conditions of the underlying layer include: the target material is preferably a Li3N target, and the purity of the Li3N target is preferably 99.95%; the sputtering power density is preferably 2.45~2.55W / cm³. 2 Further optimized to 2.5W / cm 2 The substrate rotation speed is preferably 0.5 m / min, the deposition rate is preferably 1 nm / s, and the deposition time is preferably 14.5~15.5 s, more preferably 15 s.

[0043] In this invention, the sputtering conditions for the intermediate transition layer include: the target material comprises a Li3N target and a LiF target, wherein the purity of the Li3N target is preferably 99.95%, and the purity of the LiF target is preferably 99.99%; the sputtering power density of the Li3N target is preferably 2.50 W / cm³. 2 The constant velocity changes to 1.0 W / cm 2 The sputtering power density of the LiF target is preferably from 0 W / cm². 2 The constant velocity changes to 2.0 W / cm 2 The deposition rate is preferably 1 nm / s, and the variation time is preferably 4.9~5.1s, more preferably 5s.

[0044] In this invention, the sputtering conditions for the surface layer include: the target material is preferably a LiF target, and the purity of the LiF target is preferably 99.99%; the sputtering power density is preferably 3.45~3.55W / cm³. 2 Further preferred is 3.5W / cm 2 The deposition rate is 1 nm / s, and the deposition time is preferably 4.5~5.5 s, more preferably 5 s.

[0045] In this invention, the sputtering of the substrate, intermediate transition layer, and surface layer is preferably controlled in real time using a dual closed-loop monitoring system. This dual closed-loop monitoring system preferably includes a thickness control system and a composition control system. The thickness control system is preferably a quality control machine (QCM), and the composition control system is preferably an optical emission spectrometer (OES), with a wavelength resolution of 0.01 nm. In this invention, during the sputtering of the substrate, intermediate transition layer, and surface layer, when the QCM detects a thickness deviation > 0.2 nm, the deposition time is automatically compensated by ±0.05 s; when the OES spectral analysis of the Li / F signal ratio shows a deviation > 0.5%, the target power is preferably dynamically adjusted using a PID controller, with a correction value preferably ±0.03 W / cm². 2 .

[0046] In this invention, the sputtering underlayer, intermediate transition layer, and surface layer are preferably located in... Figure 1 The process is carried out in the magnetron sputtering equipment shown.

[0047] The precursor prepared by this invention exhibits excellent performance in terms of thickness uniformity, ionic conductivity, LiF:Li3N ratio, interfacial impedance, and film defect density, with the measured values ​​showing little difference from the target values. In one specific embodiment of this invention, the target thickness is 20±2 nm, and the measured value is 20.1±1.8 nm, achieving a success rate of 99.5%; the target LiF:Li3N ratio is 70:30±0.5%, and the measured value is 70.2:29.8±0.3%, achieving a success rate of 100%; the target ionic conductivity (25℃) is >1×10⁻⁶. -4 S / cm, measured value is 1.2×10 -4 S / cm, achieving a success rate of 120%; target interface impedance value <5Ω·cm 2 The measured value is 4.8 ± 0.3 Ω·cm. 2 The achievement rate was 100%; the target value for film defect density was <0.1 defects / μm. 2 The measured value was 0.05 particles / μm. 2 The achievement rate was 200%.

[0048] In this invention, the sputtering conditions reduce the thickness fluctuation of the precursor to ±1.8 nm, increase ionic conductivity by 20%, and reduce the LiF to Li3N ratio error in the intermediate transition layer to 0.3%. In this invention, sputtering achieves a target utilization rate of 85% and reduces solid waste by 30%.

[0049] After obtaining the precursor, the present invention anneals the precursor to obtain the gradient LiF / Li3N artificial SEI film.

[0050] In this invention, the annealing temperature is preferably 195~205℃, more preferably 200℃; the annealing time is preferably 10~30min, specifically 10min, 20min, or 30min; the atmosphere is preferably nitrogen, and the nitrogen flow rate is preferably 9.8~10.2L / min, more preferably 10L / min. In this invention, the annealing is preferably carried out in a tubular annealing furnace. In this invention, the energy consumption is reduced by 50% compared to the existing annealing temperature of 400℃.

[0051] The annealing process achieves an internal stress relief rate >90% (residual stress <50MPa), and a stable modulus gradient that changes uniformly from 80GPa to 20GPa. Simultaneously, it prevents Li3N decomposition and maintains an ionic conductivity >10. -4 S / cm.

[0052] The present invention also provides a solid electrolyte-SEI-electrode composite material, comprising an electrode, and an SEI film and a solid electrolyte sequentially disposed on the surface of the electrode; The electrode includes a negative electrode; The SEI film is the gradient LiF / Li3N artificial SEI film described in the above technical solution or the gradient LiF / Li3N artificial SEI film prepared by the preparation method described in the above technical solution; The bottom layer of the gradient LiF / Li3N artificial SEI film is in contact with the electrode.

[0053] The solid electrolyte-SEI-electrode composite material provided by this invention includes an electrode, wherein the electrode includes a negative electrode. In this invention, the negative electrode is preferably silicon.

[0054] The solid electrolyte-SEI-electrode composite material provided by this invention includes an SEI film disposed on the electrode. In this invention, the SEI film is the gradient LiF / Li3N artificial SEI film described in the above-described technical solution or the gradient LiF / Li3N artificial SEI film prepared by the preparation method described in the above-described technical solution. In this invention, the bottom layer of the gradient LiF / Li3N artificial SEI film is in contact with the electrode.

[0055] The solid electrolyte-SEI-electrode composite material provided by this invention includes a solid electrolyte disposed on the SEI film. In this invention, the solid electrolyte is preferably lithium lanthanum zirconium oxide. In this invention, the thickness of the solid electrolyte is preferably 49-51 μm, more preferably 50 μm.

[0056] This invention incorporates a solid electrolyte onto the SEI film of the electrode, enabling atomic-level fusion of the SEI film and the solid electrolyte at the interface, seamlessly connecting the ion transport paths, with interface porosity <50nm, thereby reducing impedance by 68%.

[0057] This invention also provides a method for preparing the solid electrolyte-SEI-electrode composite material described in the above technical solution, comprising the following steps: An SEI film is prepared on the electrode to obtain an electrode with an attached SEI film; A solid electrolyte is applied to the SEI film of the electrode to which the SEI film is attached, and then hot-pressed to obtain the solid electrolyte-SEI-electrode composite material.

[0058] The present invention prepares an SEI film on an electrode to obtain an electrode with an SEI film attached.

[0059] In this invention, the electrode includes a negative electrode, which is preferably silicon. In this invention, the method for preparing the SEI film is preferably consistent with the method for preparing the gradient LiF / Li3N artificial SEI film described in the above technical solution, and will not be repeated here.

[0060] After obtaining the electrode with the SEI film attached, the present invention applies a solid electrolyte to the SEI film of the electrode with the SEI film attached and performs hot pressing to obtain the solid electrolyte-SEI-electrode composite material.

[0061] In this invention, the electrode with the SEI film attached is preferably preheated before the solid electrolyte is applied. The preheating temperature is preferably 79~81°C, and more preferably 80°C.

[0062] In this invention, the preferred method of application is spraying.

[0063] In this invention, the temperature of the hot pressing is preferably 148~152℃, more preferably 150℃; the pressure is preferably 9.9~10.1MPa, more preferably 10MPa; and the time is preferably 4~6min.

[0064] After hot pressing, the present invention preferably further includes cutting and finishing. The present invention does not specifically limit the parameters and operations of cutting and finishing, and operations well known to those skilled in the art can be used.

[0065] This invention provides a solid-state lithium-ion battery, comprising a positive electrode and a solid electrolyte-SEI-electrode composite material; wherein the electrode in the solid electrolyte-SEI-electrode composite material is the negative electrode; The positive electrode is NCM811; The positive electrode is in contact with the solid electrolyte in the solid electrolyte-SEI-electrode composite material; The solid electrolyte-SEI-electrode composite material is the solid electrolyte-SEI-electrode composite material described in the above technical solution.

[0066] The solid-state lithium-ion battery provided by this invention includes a positive electrode. In this invention, the positive electrode is NCM811.

[0067] The solid-state lithium-ion battery provided by this invention includes a solid electrolyte-SEI-electrode composite material; the electrode in the solid electrolyte-SEI-electrode composite material is the negative electrode; the solid electrolyte-SEI-electrode composite material is the solid electrolyte-SEI-electrode composite material described in the above-mentioned technical solution. In this invention, the positive electrode is in contact with the solid electrolyte in the solid electrolyte-SEI-electrode composite material.

[0068] The present invention also provides a method for preparing the solid-state lithium-ion battery described in the above technical solution, characterized by comprising the following steps: The solid-state lithium-ion battery is obtained by composite encapsulating the positive electrode and the solid electrolyte-SEI-electrode composite material. The electrode in the solid electrolyte-SEI-electrode composite material is the negative electrode.

[0069] The present invention does not specifically limit the operation and parameters of the composite packaging; those skilled in the art can set them according to actual needs.

[0070] In this invention, the processes for preparing the solid electrolyte-SEI-electrode composite material and the solid lithium-ion battery are preferably carried out in the following manner: Figure 2 The magnetic levitation roll-to-roll continuous production system shown in the diagram begins with the sputtered precursor and proceeds with continuous production. The following section combines... Figure 2 The continuous production process of solid electrolyte-SEI-electrode composite materials and solid lithium-ion batteries is described: The precursor is placed on a magnetic levitation conveyor platform and fed into a tubular annealing furnace under the transmission of an electromagnetic levitation conveyor. It is then annealed under N2 protection by infrared radiation heating, preheated by a hot air heater, and then sent to a deposition device where a solid electrolyte (LLZO powder) is applied. The thickness is then measured using a β-ray thickness gauge and then sent to a hot press packaging machine. Under the action of heated upper pressure rollers and room temperature pressure rollers, a solid electrolyte-SEI-electrode composite material is formed. The positive electrode and the solid electrolyte-SEI-electrode composite material are transported to the packaging device via a packaging conveyor for composite packaging to obtain a solid lithium-ion battery; the electrode in the solid electrolyte-SEI-electrode composite material is the negative electrode.

[0071] In this invention, the transmission speed of the electromagnetic levitation transmission device is preferably 0.5±0.02m / min, the vibration is preferably <1μm, and the tension fluctuation is preferably <1N.

[0072] In this invention, the hot-press packaging machine preferably further includes a laser cutting unit and an online quality inspection system arranged sequentially. In this invention, the laser cutting unit preferably performs cutting and post-processing. In this invention, the online quality inspection system preferably includes a laser thickness gauge, the accuracy of which is preferably ±1μm. In this invention, the online quality inspection system can achieve online thickness detection. In this invention, an automatic winding unit is preferably also provided after the online quality inspection system. In this invention, the automatic winding unit is provided to achieve mass production of solid electrolyte-SEI-electrode composite materials.

[0073] In this invention, the composite encapsulation is carried out under magnetic levitation transmission conditions, achieving zero-contact transmission (tension 20±1N), avoiding the rupture of the brittle SEI film (damage rate <0.01%), and making the yield >99.3%; at the same time, the scrap material is <0.5%.

[0074] The methods for preparing gradient LiF / Li3N artificial SEI films, solid electrolyte-SEI-electrode composite materials, and solid lithium-ion batteries provided by this invention are all solvent-free processes, with no organic solvents and zero VOC emissions.

[0075] In this invention, the use of continuous production equipment enables mass production, achieving a daily production capacity of 1000m³ per machine. 2 The packaging efficiency is 99.3%, with a yield improvement of 16.8%; energy consumption is 3.5 kWh / m³. 2 Costs reduced 18 / kWh.

[0076] The following detailed description, with reference to embodiments, of the gradient LiF / Li3N artificial SEI film, the solid electrolyte-SEI-electrode composite material, and the solid lithium-ion battery and their preparation methods provided by the present invention, should not be construed as limiting the scope of protection of the present invention.

[0077] The electrochemical tests in the following examples were performed under three-electrode, full-cell, or symmetrical cell conditions. The working electrode of the three-electrode system was a silicon anode with a gradient LiF / Li3N SEI film deposited on its surface, and the counter electrode was an NCM811 cathode. The reference electrode was a lithium metal microelectrode, and the electrolyte was an LLZO solid electrolyte with a thickness of 50±1μm. The electrolyte was bonded to the working electrode by hot pressing and then to the counter electrode.

[0078] The negative electrode of the full cell is a silicon negative electrode with a gradient LiF / Li3N SEI film deposited on its surface, and the positive electrode is an NCM811 positive electrode; the electrolyte is an LLZO solid electrolyte with a thickness of 50 μm; the electrolyte is bonded to the negative electrode by hot pressing, and then to the positive electrode.

[0079] Assemble a symmetrical cell according to Li@SEI-electrolyte-SEI@Li.

[0080] Example 1 Gradient LiF / Li3N ratio optimization verification Step 1: Electrode (silicon wafer or lithium wafer) pretreatment 1.1 The process parameters and equipment configuration for pretreatment are shown in Table 1.

[0081] Table 1. Process parameters and equipment configuration for pretreatment

[0082] 1.2 Specific Implementation Process of Preprocessing 1.2.1 Mounting and fixing: The electrode is placed on a magnetic levitation substrate frame (vibration <1μm) to avoid mechanical damage; 1.2.2 Ar + Plasma cleaning: Ar gas was introduced (flow rate 50 sccm), and radio frequency bombardment was performed at 200W for 5 minutes to remove organic residues and oxides (SEM verification showed surface roughness <2nm). 1.2.3 Atomic deposition of TiO2: TiCl4 pulse (0.1s) → N2 purging (5s) → H2O pulse (0.1s) → N2 purging (5s), cycle 20 times → form a dense substrate film; 1.2.4 Ultraviolet ozone activation: Dual-wavelength ultraviolet irradiation for 10 minutes → increases surface hydroxyl density and enhances SEI film adhesion.

[0083] The implementation effects and indicators of the pretreatment are shown in Table 2.

[0084] Table 2. Implementation Results and Indicators of Pretreatment

[0085] Step 2: Fabrication of the bottom layer, intermediate transition layer, and surface layer by magnetron sputtering 2.1 The process and equipment parameters for magnetron sputtering are shown in Table 3.

[0086] Table 3 Process and equipment parameters for magnetron sputtering

[0087] 2.2 Specific Implementation Process of Magnetron Sputtering 2.2.1 Gradient film preparation: Preparation of the 7:3 group: (1): Using silicon or lithium wafers as electrodes, start the Li3N target (2.5W / cm²). 2), deposit a 15nm bottom layer (15s); (2): Dual-target co-sputtering (5s), the power of Li3N increased from 2.5 W / cm² in 5s. 2 Linear reduction to 1.0 W / cm 2 The power of LiF increased from 0 W / cm² in 5 seconds. 2 Linear increase to 2.0 W / cm 2 ; (3): The Li3N target was turned off, and the LiF target power was increased to 3.5 W / cm. 2 A 5nm surface layer was deposited (5s).

[0088] Preparation of the 5:5 group: (1): Using silicon or lithium wafers as electrodes, start the Li3N target (2.5W / cm²). 2 ), depositing a 4nm substrate (4s); (2): During dual-target co-sputtering for 1 second, the power of Li3N increased from 2.5 W / cm² in 1 second. 2 Linear reduction to 1.0 W / cm 2 The power of LiF increases from 0 W / cm² in 1 second. 2 Linear increase to 2.0 W / cm 2 A 1 nm intermediate transition layer was deposited. (3): The Li3N target was turned off, and the LiF target power was increased to 3.5 W / cm. 2 A 5nm surface layer was deposited (5s).

[0089] Preparation of the 8:2 group: (1): Using silicon or lithium wafers as electrodes, start the Li3N target (2.5W / cm²). 2 ), depositing a 7nm substrate (7s); (2): During dual-target co-sputtering for 1 second, the power of Li3N increased from 2.5 W / cm² in 1 second. 2 Linear reduction to 1.0 W / cm 2 The power of LiF increases from 0 W / cm² in 1 second. 2 Linear increase to 2.0 W / cm 2 A 1 nm intermediate transition layer was deposited. (3): The Li3N target was turned off, and the LiF target power was increased to 3.5 W / cm. 2 A 2nm surface layer was deposited (2s).

[0090] 2.2.2 Real-time feedback adjustment: If the OES detects a Li / F signal ratio deviation >0.5%, the target power will be dynamically adjusted using PID control (correction value ±0.03 W / cm²). 2 ); QCM thickness fluctuation >0.2nm → automatic compensation deposition time ±0.1s.

[0091] 2.2.3 Annealing treatment Annealing temperature 200℃, nitrogen gas (flow rate 10L / min) protection, time 10min.

[0092] Three samples were taken from each batch and analyzed by XPS depth profiling (sputtering rate 0.1 nm / s, Ar). + (Beam current 1μA).

[0093] 2.2.4 Preparation of solid electrolyte-SEI-electrode composite material: After annealing, the SEI electrode is placed in a nitrogen atmosphere glove box, and a solid electrolyte LLZO is deposited on the SEI film of the SEI electrode. The electrode is then hot-pressed at 10 MPa and 150 °C for 5 min to form a solid electrolyte-SEI electrode composite material.

[0094] Different solid electrolyte-SEI-electrode composite materials were assembled into corresponding battery systems, and impedance (1 mA / cm²) was measured. 2 ) and ionic conductivity testing.

[0095] The results showed that the impedance rise rate of group 7:3 was only 8%; the crack density was 0.05 cracks / μm. 2 ; Ionic conductivity 1.2×10 -4 S / cm. 5:5 group: High Li3N content → decomposition at 4.5V (XPS detected Li3N → Li2O conversion); 8:2 group: High LiF content → ion blocking (TEM showed Li... + The transmission path is broken.

[0096] Conclusion: The LiF:Li3N=7:3 ratio resolves the impedance-stability contradiction through the synergistic effect of the surface LiF resisting high voltage and the bottom Li3N fast conduction, supporting 10C fast charging cycle (capacity retention >95% after 500 cycles).

[0097] Example 2 Step 1: Electrode (lithium or silicon) pretreatment is the same as in Example 1.

[0098] Step 2: Fabrication of the bottom layer, intermediate transition layer, and top layer by magnetron sputtering.

[0099] 2.1 The process and equipment parameters for magnetron sputtering are shown in Table 4.

[0100] Table 4. Magnetron sputtering process and equipment parameters

[0101] 2.2 Specific Implementation Process of Magnetron Sputtering 2.2.1 Thickness-group deposition (fixed LiF:Li3N=7:3): 20nm: Bottom layer: 11.5nm, transition layer: 5nm, surface layer: 3.5nm; 25nm: bottom layer 15.0nm, transition layer 5.0nm, surface layer 5.0nm; 30nm: bottom layer 18.5nm, transition layer 5.0nm, surface layer 6.5nm.

[0102] 2.2.2 Real-time thickness compensation: If the QCM detects a thickness deviation >0.2nm, it will automatically extend / shorten the deposition time (in 0.05s steps). Example: 20nm group measured 19.8nm → 0.2s of additional deposition to 20.0±0.1nm.

[0103] 2.2.3 Annealing treatment Annealing temperature 200℃, nitrogen gas (flow rate 10L / min) protection, time 10min.

[0104] Three samples were taken from each batch and analyzed by XPS depth profiling (sputtering rate 0.1 nm / s, Ar). + (Beam current 1μA).

[0105] 2.2.4 Preparation of solid electrolyte-SEI-electrode composite material: After annealing, the SEI electrode is placed in a nitrogen atmosphere glove box, and a solid electrolyte LLZO is deposited on the SEI film of the SEI electrode. The electrode is then hot-pressed at 10 MPa and 150 °C for 5 min to form a solid electrolyte-SEI electrode composite material.

[0106] 2.2.5 Electrochemical testing: Solid electrolyte-SEI-electrode composite materials were assembled into corresponding batteries, and performance tests were conducted. Dendrite observation: in-situ microscopic imaging every 100 weeks (local current density 5 mA / cm²) 2 ).

[0107] The implementation results and indicators are shown in Table 5.

[0108] Table 5 Implementation Results and Indicators

[0109] As can be seen from Table 5, the ionic conductivity of the 25nm group is 1.2 × 10⁻⁶. -4 S / cm (20% higher than 20nm / 30nm) → Li +Transmission channel optimization; dendrite penetration <0.1% (competitors >12%) → elimination of local weak points (AFM verification shows no <10nm region). 20nm group: localized excessive thinness (SEM shows thickness fluctuation ±2.5nm) → increased risk of dendrite penetration; 30nm group: excessive thickness leading to ion blockage (TEM shows Li... + (Path bend) → Impedance rises to 6.2 Ω·cm 2 .

[0110] 2.2.6 Industrial-grade accuracy verification: Pilot production line (1000m) 2 Thickness fluctuation ±2.1nm (CPK>1.67) → Mass production feasibility confirmed.

[0111] Conclusion: Optimal balance is achieved at a thickness of 25nm. (1) ±1.8nm uniformity (magnetic levitation + QCM closed-loop control) → eliminate dendrite penetration; (2) Ionic conductivity 1.2×10 -4 S / cm (gradient structure without breaks) → impedance as low as 4.8Ω·cm 2 ; (3) 92% capacity retention after 1000 cycles at 10C (7% higher than competing thick film solutions).

[0112] Example 3 Step 1: Electrode (silicon wafer or lithium wafer) pretreatment is the same as in Example 1.

[0113] Step 2: Magnetron sputtering of the bottom layer, intermediate transition layer, and top layer.

[0114] Step 3 In Figure 2 The solid electrolyte-SEI-electrode composite material is continuously prepared in the magnetic levitation roll-to-roll continuous production system shown.

[0115] 3.1 The process and equipment parameters for continuous preparation of solid electrolyte-SEI-electrode composite materials are shown in Table 6.

[0116] Table 6 Process and Equipment Parameters

[0117] 3.2 Specific process for continuous preparation of solid electrolyte-SEI-electrode composite materials 3.2.1 Continuous Transfer and Annealing: An electromagnetic levitation transmission device pulls the precursor (speed 0.5m / min), and a laser correction system dynamically adjusts the positional deviation (<10μm). Annealing treatment: The precursor obtained in step 2 is fed into a tubular annealing furnace via an electromagnetic levitation conveyor and annealed at a constant speed of N2 (10L / min) and 200℃ for 10min to eliminate internal stress (residual stress <50MPa).

[0118] 3.2.2 LLZO spraying and hot pressing: Then, after preheating by a hot air heater, it is sent to a deposition device to spray LLZO powder (50nm particle size) onto the SEI film surface, and then the thickness is detected by a β-ray thickness gauge. Then it is sent to a hot press packaging machine, and under the action of heated upper pressure roller and room temperature pressure roller, it is hot pressed at 150℃ and 10MPa for 5 minutes. Then it is sent to a laser cutting unit for cutting and finishing, and then sent to an online quality inspection system for online thickness detection to form a 50μm dense layer. Finally, it is sent to an automatic winding unit for winding to obtain a solid electrolyte-SEI-electrode composite material. Pressure fluctuation >0.05MPa → Automatic hydraulic compensation (adjustment rate 0.2MPa / s).

[0119] 3.2.3 Closed-loop quality control: Laser thickness gauge checks LLZO thickness → out of tolerance ±1μm → adjust spray flow rate ±5%; CCD detection of film defects → detection of cracks / pores → automatic marking and removal of defective segments (removal accuracy ±1cm).

[0120] The implementation effects and indicators of continuous preparation of solid electrolyte-SEI-electrode composite materials are shown in Table 7.

[0121] Table 7 Implementation Results and Indicators

[0122] 3.2.4 Data Analysis 1. Breakthrough in transmission stability: Magnetic levitation tension fluctuation <0.5N (competitor's mechanical roller >5N) → membrane damage rate 0.007% (competitor's 5%); Correction accuracy <10μm (competitors >50μm) → Packaging alignment error is almost zero (no misalignment on SEM verification interface).

[0123] 2. Hot-press interface fusion effect: HRTEM revealed an atomically fused interface (lattice continuity, porosity <50 nm) → impedance stabilized at 4.8 ± 0.3 Ω·cm. 2 ; Competitor's mechanical pressing has a pore size >100nm → impedance >15Ω·cm 2 .

[0124] 3. Mass production cost advantages are shown in Table 8.

[0125] Table 8. Mass Production Cost Advantages

[0126] in conclusion: Roll-to-roll mass production technology achieves a three-in-one breakthrough: "zero-damage transmission - atomic-level packaging - full inspection closed loop". (1) 1050m 2 / day production capacity (single unit meets 1GWh annual demand) + 99.3% yield (competitors ≤85%); (2) Magnetic levitation tension control 20±0.5N → solves the problem of brittle SEI film damage (damage rate ↓714 times); (3) Hot-pressed interface pores <50nm → ensuring ultra-low impedance (4.8Ω·cm) 2 It can be stably reproduced in mass production.

[0127] Industrialization significance: Driving down the cost of silicon anode batteries 18 / kWh (competitor) (50+), accelerating the commercialization of 500Wh / kg batteries.

[0128] Industrialization significance: Measured production capacity of Example 3: 1050m³ 2 / day → Meets the annual battery production capacity of 1GWh (0.1m³ / kWh is required per kWh) 2 SEI membrane); cost reduced to 18 / kWh (competitive ALD process) 50 / kWh).

[0129] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A gradient LiF / Li3N artificial SEI film, comprising a bottom layer, an intermediate transition layer and a top layer stacked sequentially; The bottom layer is a Li3N layer; The intermediate transition layer is a layer with a gradient change in the content of Li3N and LiF; the atomic ratio of N to F in the intermediate transition layer gradually changes from 80:20 to 20:80 at a uniform rate; the side of the intermediate transition layer with an atomic ratio of N to F of 80:20 is in contact with the bottom layer. The surface layer is a LiF layer.

2. The gradient LiF / Li3N artificial SEI film according to claim 1, characterized in that, The thickness of the substrate is 14.5~15.5 nm, and the ionic conductivity of the substrate is ≥10. -5 S / cm; The thickness of the intermediate transition layer is 4.9~5.1 nm; The thickness of the surface layer is 4.5~5.5 nm, and the electrochemical window of the surface layer is ≥4.5 V.

3. The method for preparing the gradient LiF / Li3N artificial SEI film according to claim 1 or 2, characterized in that, Includes the following steps: A precursor is obtained by sequentially sputtering a bottom layer, an intermediate transition layer, and a top layer onto a substrate. The precursor was annealed to obtain the gradient LiF / Li3N artificial SEI film.

4. The preparation method according to claim 3, characterized in that, The sputtering conditions for the underlying layer include: a Li3N target and a sputtering power density of 2.45~2.55 W / cm². 2 The substrate rotation speed is 0.5 m / min, the deposition rate is 1 nm / s, and the time is 14.5~15.5 s; The sputtering conditions for the intermediate transition layer include: the target materials include a Li3N target and a LiF target, and the sputtering power density of the Li3N target is from 2.50 W / cm². 2 The constant velocity changes to 1.0 W / cm 2 The sputtering power density of the LiF target is from 0 W / cm². 2 The constant velocity changes to 2.0 W / cm 2 The deposition rate was 1 nm / s, and the time to change it was 4.9–5.1 s. The sputtering conditions for the surface layer include: a LiF target and a sputtering power density of 3.45~3.55 W / cm². 2 The deposition rate was 1 nm / s, and the time was 4.5~5.5 s; The annealing temperature is 195~205℃, and the time is 10~30min.

5. A solid electrolyte-SEI-electrode composite material, characterized in that, It includes an electrode, and an SEI film and a solid electrolyte sequentially disposed on the surface of the electrode; The electrode includes a negative electrode; The SEI film is the gradient LiF / Li3N artificial SEI film according to claim 1 or 2, or the gradient LiF / Li3N artificial SEI film prepared by the preparation method according to claim 3 or 4; The bottom layer of the gradient LiF / Li3N artificial SEI film is in contact with the electrode.

6. The solid electrolyte-SEI-electrode composite material according to claim 5, characterized in that, The negative electrode is silicon; The solid electrolyte is lithium lanthanum zirconium oxide; The thickness of the solid electrolyte is 49~51μm.

7. The method for preparing the solid electrolyte-SEI-electrode composite material according to claim 5 or 6, characterized in that, Includes the following steps: An SEI film is prepared on the electrode to obtain an electrode with an attached SEI film; A solid electrolyte is applied to the SEI film of the electrode to which the SEI film is attached, and then hot-pressed to obtain the solid electrolyte-SEI-electrode composite material. The electrode includes a negative electrode.

8. The preparation method according to claim 7, characterized in that, The hot pressing temperature is 148~152℃, the pressure is 9.9~10.1MPa, and the time is 4~6min.

9. A solid-state lithium-ion battery, characterized in that, The composite material includes a positive electrode and a solid electrolyte-SEI-electrode composite material; the electrode in the solid electrolyte-SEI-electrode composite material is the negative electrode. The positive electrode is NCM811; The positive electrode is in contact with the solid electrolyte in the solid electrolyte-SEI-electrode composite material; The solid electrolyte-SEI-electrode composite material is the solid electrolyte-SEI-electrode composite material as described in claim 5 or 6.

10. The method for preparing a solid-state lithium-ion battery according to claim 9, characterized in that, Includes the following steps: The solid-state lithium-ion battery is obtained by composite encapsulating the positive electrode and the solid electrolyte-SEI-electrode composite material. The electrode in the solid electrolyte-SEI-electrode composite material is the negative electrode.

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