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CN-122025758-A - Solid electrolyte interface structure and preparation method thereof

CN122025758ACN 122025758 ACN122025758 ACN 122025758ACN-122025758-A

Abstract

The invention discloses a solid electrolyte interface structure, which has the total thickness of 0.5-5 mu m, the elastic modulus of 2-10 GPa and the elongation at break of more than 5 percent, and comprises an inner layer and an outer layer, wherein the thickness of the inner layer accounts for 40-60 percent of the total thickness, the inner layer is formed by compounding first inorganic sodium salt and organic components, the mass ratio of the first inorganic sodium salt to the organic components is 85-95 percent, the mass ratio of the first inorganic sodium salt to the organic components is 5-15 percent, the electronic conductivity sigma e of the inner layer is 10 ‑8 ~10 ‑7 S·cm ‑1 ,Na + ionic conductivity sigma i ≥10 ‑4 S·cm ‑1 , the thickness of the outer layer accounts for 40-60 percent of the thickness of the gradient solid electrolyte interface structure, the outer layer is formed by second inorganic sodium salt, the void ratio of the outer layer is less than 1 percent, the layer does not contain organic components, the electronic conductivity sigma e ＜10 ‑9 S·cm ‑1 and the Na+ ionic conductivity sigma i ≥5×10 ‑ 5 S·cm ‑1 of the outer layer, and the gradient transition region has the thickness of 0.1-0.5 mu m, and the electronic conductivity gradually decreases from 10 ‑8 S·cm ‑1 to 10 ‑9 S·cm ‑1 from inside to outside. The invention can inhibit the continuous growth of MCEI, reduce interface impedance, and improve long cycle life and high rate performance.

Inventors

  • GUO QITAO
  • CAI WEIHUA
  • PAN HONGLAN
  • ZHAO JIANMING

Assignees

  • 深圳华钠新材有限责任公司

Dates

Publication Date
20260512
Application Date
20260203

Claims (7)

  1. 1. A solid state electrolyte interface structure characterized by: The gradient solid electrolyte interface structure has the thickness of 0.5-5 mu m, and has the characteristics of elastic modulus of 2-10 GPa and elongation at break of more than 5%; The gradient solid electrolyte interface structure comprises an inner layer (21) with a buffer effect and an outer layer (23) with a blocking effect, wherein the thickness of the inner layer (21) accounts for 40% -60% of the thickness of the gradient solid electrolyte interface structure, the inner layer (21) is mainly formed by compounding a first inorganic sodium salt with a mechanical strength enhancing effect and an organic component capable of improving the flexibility and the adhesive force of the interface layer, the mass ratio of the first inorganic sodium salt to the organic component is 85% -95%, the mass ratio of the first inorganic sodium salt to the organic component is 5% -15%, and the electronic conductivity sigma e of the inner layer (21) is 10 -8 ~10 -7 S·cm -1 ,Na + ion conductivity sigma i ≥10 -4 S·cm -1 ; The thickness of the outer layer (23) accounts for 40% -60% of the thickness of the interface structure of the gradient solid electrolyte, the outer layer (23) is mainly composed of a second inorganic sodium salt, the void ratio of the second inorganic sodium salt is less than 1%, the layer does not contain organic components, the electronic conductivity sigma e ＜10 -9 S·cm -1 ,Na + ion conductivity sigma i ≥5×10 -5 S·cm -1 of the outer layer (23), and the inner layer (21) and the outer layer (23) form a gradient transition zone (22) between the inner layer and the outer layer through in-situ electrochemical conversion in the non-forming stage of the precursor; The thickness of the gradient transition region (22) is 0.1-0.5 mu m, and the electron conductivity of the gradient transition region gradually and continuously decreases from 10 -8 S·cm -1 to 10 -9 S·cm -1 from the layer to the outer layer (23) along the Na + ion transmission direction.
  2. 2. The gradient solid state electrolyte interface structure of claim 1, wherein: The first inorganic sodium salt is NaF and NaCl or Na 2 O, wherein the mass ratio of NaF is more than or equal to 60 percent.
  3. 3. The gradient solid state electrolyte interface structure of claim 1, wherein: The organic component is at least one of polyvinylidene fluoride, aluminoxane or polyethylene glycol.
  4. 4. The gradient solid state electrolyte interface structure of claim 1, wherein: The second inorganic sodium salt is NaF and Na 2 O or Na 3 PO 4 , wherein the mass ratio of NaF is more than or equal to 80%.
  5. 5. The gradient solid state electrolyte interface structure of claim 1, wherein: The thickness of the gradient solid electrolyte interface structure is 1-3 mu m.
  6. 6. A method of preparing a gradient solid electrolyte interface structure according to any one of claims 1-5, characterized in that: The preparation method comprises the following specific preparation steps: S1, selecting and grading preparation of precursor materials 1. And (3) designing a precursor component: (1) Mixing the precursors of the inner layer (21) according to the mass ratio of 'inorganic sodium salt precursor: organic elastic precursor=85:15-95:5'; (2) The precursor of the outer layer (23) is mainly an inorganic sodium salt precursor with the purity more than or equal to 99.9 percent and does not contain organic components, wherein the mass ratio of the sodium difluorophosphate is more than or equal to 90 percent; 2. step forming of the precursor layer: (1) The preparation of the precursor film of the inner layer (21) comprises the steps of mixing and stirring the precursor mixture of the inner layer (21) and a solvent according to the mass ratio of 1:3-1:5 to form uniform slurry, coating the slurry on the surface of a sulfide solid electrolyte, controlling the thickness of a wet film to be 1-2 mu m, drying in a vacuum oven at 80-100 ℃ for 4-6 hours, removing the solvent to form the precursor film of the inner layer (21), and drying to obtain the film with the thickness of 0.5-1 mu m; (2) The preparation of the precursor film of the outer layer (23) comprises the steps of mixing and dispersing the precursor of the outer layer (23) and a solvent according to a mass ratio of 1:2-1:4 for 30-60 min to form a uniform suspension, coating the suspension on the surface of the precursor film of the inner layer (21), drying in a vacuum oven at 80-100 ℃ for 2-4 h after spraying to form the precursor film of the outer layer (23), and finally obtaining a graded precursor layer with a total thickness of 1-2 mu m after drying; S2 assembling of all solid-state battery In an inert atmosphere glove box, tightly contacting the solid electrolyte coated with the precursor layer on the surface with a sodium metal or sodium alloy anode to assemble an all-solid-state battery; s3, in-situ electrochemical conversion of gradient solid electrolyte interface structure (1) Applying constant current or constant voltage conditions to the assembled battery cells in a first cycle or pre-formation stage, wherein the conversion process should be performed at a lower current density to ensure uniform Na + deposition; (2) The electrochemical potential of the Na anode is regulated by controlling the cut-off voltage or current density of the activation process, so that the reduction reaction of the precursor layer is not completely uniform, thereby forming an electron conductivity gradient in the thickness direction.
  7. 7. The method of manufacturing according to claim 6, wherein: in the step S1, the inorganic sodium salt precursor of the inner layer (21) is sodium difluorophosphate, sodium chloride or sodium carbonate, and the organic elastic precursor is polyvinylidene fluoride powder or aluminoxane precursor; The inorganic sodium salt precursor in the precursor of the outer layer (23) is sodium difluorophosphate, sodium hexafluorophosphate or sodium fluorosulfonyl imide.

Description

Solid electrolyte interface structure and preparation method thereof Technical Field The invention relates to the technical field of sodium ion solid-state batteries, in particular to a solid-state electrolyte interface structure and a preparation method thereof. Background Sodium Ion Batteries (SIBs) are considered a viable alternative or complementary to Lithium Ion Batteries (LIBs) because of their abundant sodium resources and low cost. The all-solid-state sodium battery (ASSSIBs) adopts the solid electrolyte (SSEs) to replace inflammable organic liquid electrolyte, so that the safety and the energy density of the battery are fundamentally improved. Sulfide-based solid state electrolytes, such as Na 3PS4 or Na 3SbS4, are considered very promising electrolyte systems in ASSSIBs due to their high ionic conductivity and good mechanical ductility. Although sulfides SSEs possess excellent bulk properties, in practical applications, they have poor interfacial compatibility when in contact with the highly active sodium metal anode, facing the following key technical pain points: (1) Thermodynamic instability and sustained decomposition sodium metal has a very strong reducibility, which is thermodynamically unstable with sulfide SSEs. This instability causes irreversible reductive decomposition of the SSE at the interface. (2) Continuous growth of mixed conducting phases (MCEI) the products of the decomposition reaction typically form an electron and ion mixed conducting phase (MCEI), such as conductive Na 3 P. The MCEI layer cannot realize self-limiting passivation, but continuously grows, thereby continuously consuming active materials and electrolytes, resulting in an irreversibly large increase in interfacial resistance, severely deteriorating long-term cycle performance of the battery. (3) Dendrite penetration and high CCD requirements sulfide SSEs has low mechanical stiffness, is easily penetrated by Na dendrite, and limits the Critical Current Density (CCD) of the cell. The prior art often employs a prefabricated artificial SEI film to physically isolate the Na anode. However, these methods generally rely on complex and costly manufacturing processes and do not fundamentally eliminate the thermodynamic driving force for sustained MCEI growth, primarily by kinetic inhibition of decomposition. Disclosure of Invention The main purpose of the invention is to provide an interface structure and a simple preparation method thereof, so as to actively regulate and control electrochemical reaction at an Na/sulfide SSE interface and realize self-limiting passivation of an electronic conductive phase, thereby greatly reducing interface impedance and improving the long service life and high rate performance of ASSSIBs. The technical problems of high interface resistance and short cycle life of the existing Na/SSE interface caused by continuous growth of an electron-ion mixed conducting phase (MCEI) are solved by constructing a gradient solid electrolyte interface structure (called G-SEI hereinafter) between a sodium metal anode and a sulfide solid electrolyte. Based on this, a solid electrolyte interface structure is provided. Another object of the present invention is to provide a method for preparing the above solid electrolyte interface structure. In order to achieve the above purpose, the invention adopts the following specific technical scheme: The technical terms related in the invention are as follows: Sodium Ion Battery (SIBs) Lithium Ion Battery (LIBs) All-Solid Sodium battery (ASSSIBs, all-Solid-State Sodium-Ion Batteries) Solid Electrolyte (SSEs) Mixed conductive phase (MCEI, mixed Conducting Electrolyte Interface) Critical Current Density (CCD) Gradient solid electrolyte interface Structure (G-SEI) Polyvinylidene fluoride (PVDF) Aluminoxane (alucone) Polyethylene glycol (PEG) Sodium difluorophosphate (NaDFP) Sodium chloride (NaCl) Sodium carbonate (Na 2CO3) Sodium hexafluorophosphate (NaPF 6) Sodium fluorosulfonyl imide (NaFSI) N-methylpyrrolidone (NMP) Sodium thiophosphate (NPS, na 3PS4) Chemical Vapor Deposition (CVD) Solid Electrolyte Interface (SEI) The solid electrolyte interface structure comprises: The G-SEI is a multifunctional gradient interface layer formed between a sodium metal/sodium alloy anode and sulfide SSE, is formed by in-situ electrochemical conversion of a precursor layer, has the synergistic function of 'inner layer (21) buffer-outer layer (23) blocking', and presents continuously-changed electronic conductivity gradient along the Na + ion transmission direction (from the Na anode to the SSE direction). The total thickness of the G-SEI is controlled to be 0.5-5 mu m, preferably 1-3 mu m, so that not only is enough interface regulation space ensured, but also the increase of initial ion transmission impedance caused by overlarge thickness is avoided. The G-SEI simultaneously meets three core functions, namely ① electron blocking performance (electronic conductivity sigma e＜10-9S·cm-1）