Solid electrolyte materials, electrode materials, separator materials and secondary batteries

Abstract

The present invention relates to a solid electrolyte material, an electrode material, a separator material and a secondary battery. The chemical formula of the solid electrolyte material is Li2ADX4, where A is Ca 2+ or Sr 2+ or Ba 2+ or one or more of them, D is Si 4+ or Ge 4+ or Sn 4+ or one or more of them, X is S 2‑ and / or Se 2‑ ; the structure space group of the solid electrolyte material is #imgabs0# where Li occupies the 4d position, A occupies the 2a position, D occupies the 2b position, and X occupies the 8i position.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and in particular, to a solid electrolyte material, an electrode material, a separator material, and a secondary battery. Background Art

[0002] Lithium-ion batteries are widely used in consumer electronic products and transportation vehicles such as electric vehicles because of their advantages such as high working voltage, high energy density, and long cycle life. However, the currently used commercial lithium-ion batteries have safety hazards due to the use of liquid electrolytes containing flammable organic solvents. In order to overcome the problems faced by existing commercial liquid lithium-ion batteries, researchers are vigorously developing solid-state lithium batteries based on solid electrolytes.

[0003] The core material in a solid-state lithium battery is a solid electrolyte. Designing a solid electrolyte material with high ionic conductivity and high stability is the core to promote the development of solid-state lithium batteries. Currently, the commonly used inorganic solid electrolyte materials are mainly divided into two categories: sulfide systems and oxide systems. Compared with oxygen ions, sulfur ions have smaller electronegativity and larger ionic radii. Therefore, sulfide solid electrolyte materials usually have higher ionic conductivity. Among them, the representative sulfide solid electrolyte material Li 10 GeP2S 12 has a room-temperature ionic conductivity (~10 -2 S / cm) even exceeding that of commonly used electrolyte systems. However, sulfide electrolytes generally have problems of air instability and poor compatibility with positive and negative electrode materials. On the other hand, oxide electrolyte materials represented by garnet-structured Li7La3Zr2O 12 , perovskite-structured Li 3x La 2 / 3-x TiO3, NASICON-structured Li 1.3 Ti 1.7 Al 0.3 (PO4)3 have an ionic conductivity of 10 -4 S / cm, but have problems such as being sensitive to water, poor wettability with metallic lithium, and instability to metallic lithium.

[0004] Currently, the commonly used inorganic solid electrolyte materials still have some defects and deficiencies. Therefore, it is particularly important to develop new solid electrolyte materials. Summary of the Invention

[0005] Based on the above problems and current situation, the embodiments of the present invention provide a solid electrolyte material, an electrode material, a separator material, and a secondary battery. This material has high ionic conductivity, and through element doping substitution, the ionic conductivity can be further improved, so that it can be applied to the preparation of secondary batteries with high safety and high specific energy.

[0006] To this end, in a first aspect, an embodiment of the present invention provides a solid electrolyte material, and the chemical formula of the solid electrolyte material is Li2ADX4, where A is Ca 2+ or Sr 2+ or Ba 2+ or one or more of them, D is Si 4+ or Ge 4+ or Sn 4+ or one or more of them, X is S 2- and / or Se 2- ;

[0007] The crystal structure space group of the solid electrolyte material is wherein Li occupies the 4d position, A occupies the 2a position, D occupies the 2b position, and X occupies the 8i position.

[0008] Preferably, in the solid electrolyte material, there are hetero-valent elements Al 3+ and / or Ga 3+ ; that partially replace A at the lattice sites occupied by A; there are hetero-valent elements P 5+ and / or As 5+ ; that partially replace D at the lattice sites occupied by D; there are hetero-valent elements F - and / or Cl - and / or Br - ; that partially replace X at the lattice sites occupied by X; Li ion vacancies are generated by partially replacing the hetero-valent elements at the lattice sites occupied by A and / or D and / or X;

[0009] The doping ratios of the hetero-valent elements at the lattice sites occupied by A or D or X are respectively in the range of 0 to 0.5;

[0010] Partially replacing the lattice sites with hetero-valent elements is used to improve the ionic conductivity of the solid electrolyte material.

[0011] Preferably, in the solid electrolyte material, there are hetero-valent elements Al 3+ and / or Ga 3+ ; that partially replace D at the lattice sites occupied by D, and interstitial Li ions are generated by partially replacing the hetero-valent elements at the lattice sites occupied by D;

[0012] The doping ratio of the hetero-valent elements at the lattice sites occupied by D is in the range of 0 to 0.5;

[0013] Partially replacing the lattice sites with hetero-valent elements is used to improve the ionic conductivity of the solid electrolyte material.

[0014] In a second aspect, an embodiment of the present invention provides an electrode material, which includes the solid electrolyte material described in the first aspect above.

[0015] Preferably, the solid electrolyte material is present on the surface and / or inside and / or gaps of the electrode material.

[0016] Preferably, the electrode material is a positive electrode material or a negative electrode material.

[0017] In a third aspect, an embodiment of the present invention provides a separator material, which includes the solid electrolyte material described in the first aspect above.

[0018] Preferably, the solid electrolyte material is present on the surface and / or inside and / or gaps of the separator material.

[0019] In a fourth aspect, an embodiment of the present invention provides a secondary battery, which includes the solid electrolyte material described in the first aspect above.

[0020] Preferably, the secondary battery includes any one of a liquid lithium-ion battery, a liquid sodium-ion battery, a liquid metal lithium battery, a liquid metal sodium battery, a hybrid solid-liquid lithium-ion battery, a hybrid solid-liquid sodium-ion battery, a hybrid solid-liquid metal lithium battery, a hybrid solid-liquid metal sodium battery, a solid-state lithium-ion battery, a solid-state sodium-ion battery, a solid-state metal lithium battery, or a solid-state metal sodium battery.

[0021] The solid electrolyte material proposed by the present invention has the chemical formula Li2ADX4, where A is Ca 2+ or Sr 2+ or Ba 2+ or one or more of them, D is Si 4+ or Ge 4+ or Sn 4+ or one or more of them, X is S 2- and / or Se 2- , and the structure space group is where Li occupies the 4d position, A occupies the 2a position, D occupies the 2b position, and X occupies the 8i position; the material has a low ion migration barrier, lower than 0.56 eV, has a high ionic conductivity, and the ionic conductivity can be further improved through element doping substitution, so that it can be applied to the preparation of secondary batteries with high safety and high specific energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The technical solutions of the embodiments of the present invention will be further described in detail below with reference to the drawings and embodiments.

[0023] Figure 1 It is the crystal structure diagram of the solid electrolyte material Li2ADX4 provided by the embodiment of the present invention;

[0024] Figure 2 It is the crystal structure diagram of the solid electrolyte material Li2SrSiSe4 provided in Embodiment 1 of the present invention;

[0025] Figure 3 It is the electron density of states diagram of the solid electrolyte material Li2SrSiSe4 provided in Embodiment 1 of the present invention;

[0026] Figure 4 It is the schematic diagram of the lithium ion migration channel in the solid electrolyte material Li2SrSiSe4 provided in Embodiment 1 of the present invention;

[0027] Figure 5 It is the curve diagram of the lithium ion migration barrier in the solid electrolyte material Li2SrSiSe4 provided in Embodiment 1 of the present invention;

[0028] Figure 6 It is for the solid electrolyte materials Li2CaSiS4 and Li 1.75 CaSiS 3.75 Cl 0.25 in the curve diagram of the lithium ion diffusion coefficient. Detailed implementation manners

[0029] The present invention will be further described below through the drawings and specific embodiments, but it should be understood that these embodiments are only used for more detailed description and should not be construed as limiting the present invention in any form, that is, it is not intended to limit the protection scope of the present invention.

[0030] The present invention proposes a solid electrolyte material with the chemical formula Li2ADX4, where A is Ca 2+ or Sr 2+ or Ba 2+ or one or more of them, D is Si 4+ or Ge 4+ or Sn 4+ or one or more of them, X is S 2- and / or Se 2- ; The Li2ADX4 solid electrolyte material proposed by the present invention can be regarded as a family of solid electrolyte materials, including at least 18 compounds. This material has good electronic insulation and ionic conductivity.

[0031] The crystal structure of the above solid electrolyte material is as Figure 1 shown, and the space group is where Li occupies the 4d position, A occupies the 2a position, D occupies the 2b position, and X occupies the 8i position.

[0032] In a specific implementation of the solid electrolyte material of the present invention, there are hetero-valent elements Al that partially replace A at the lattice sites occupied by A. 3+ and / or Ga 3+ ; there are hetero-valent elements P that partially replace D at the lattice sites occupied by D. 5+ and / or As 5+ ; there are hetero-valent elements F that partially replace X at the lattice sites occupied by X. - and / or Cl - and / or Br - ; Li ion vacancies are generated by partial substitution of hetero-valent elements at the lattice sites occupied by A and / or D and / or X.

[0033] In another specific implementation of the solid electrolyte material of the present invention, there are hetero-valent elements Al that partially replace D at the lattice sites occupied by D. 3+ and / or Ga 3+ , and interstitial Li ions are generated by partial substitution of hetero-valent elements at the lattice sites occupied by D.

[0034] The doping substitutions of several hetero-valent elements at the lattice sites of A, D, and X in the above first specific implementation can exist simultaneously, two of them can exist simultaneously, only one can exist, or none of them can exist. The doping substitution of hetero-valent elements at the lattice sites of D in the above another specific implementation can exist or not. Among them, by doping hetero-valent elements at the lattice sites of A or D or X in the Li2ADX4 material respectively or simultaneously, the ionic conductivity of the material can be further improved. Therefore, this series of solid electrolyte materials is expected to be used in the preparation of secondary batteries with high safety and high energy density.

[0035] In a specific example, the solid electrolyte material is Li2SrSiSe4, and the space group is wherein Li occupies the 4d position, Sr occupies the 2a position, Si occupies the 2b position, and Se occupies the 8i position.

[0036] In another specific example, the solid electrolyte material is Li2SrGeS4, and the space group is wherein Li occupies the 4d position, Sr occupies the 2a position, Ge occupies the 2b position, and S occupies the 8i position.

[0037] In another specific example, the solid electrolyte material is Li2CaSiS4, and the space group is wherein Li occupies the 4d position, Ca occupies the 2a position, Si occupies the 2b position, and S occupies the 8i position.

[0038] In another specific example, the solid electrolyte material is Li2BaSiS4, and the space group is Among them, Li occupies the 4d position, Ba occupies the 2a position, Si occupies the 2b position, and S occupies the 8i position.

[0039] In yet another specific example, the chemical formula of the solid electrolyte material is Li 2-y Δ y CaSiS 4-y Cl y , where Δ represents an ionic vacancy occupying the Li site, and y can range from 0 to 2. Preferably, y = 0.25, and the chemical formula is Li 1.75 Δ 0.25 CaSiS 3.75 Cl 0.25 . The space group of this solid electrolyte material is where Li and the ionic vacancy at the Li site occupy the 4d position, Ca occupies the 2a position, Si occupies the 2b position, and S and Cl occupy the 8i position.

[0040] In yet another specific example, the chemical formula of the solid electrolyte material is Li 2-y Δ y SrGeS 4-y Cl y , where Δ represents an ionic vacancy occupying the Li site, and y can range from 0 to 2. The space group of this solid electrolyte material is where Li and the ionic vacancy at the Li site occupy the 4d position, Sr occupies the 2a position, Ge occupies the 2b position, and S and Cl occupy the 8i position.

[0041] In yet another specific example, the chemical formula of the solid electrolyte material is Li2δ y SrGe 1-y Al y S4, where δ represents a Li ion occupying an interstitial lattice site, and y can range from 0 to 0.5. The space group of this solid electrolyte material is where Li occupies the 4d position, the interstitial Li ion occupies the interstitial position of the lattice, Sr occupies the 2a position, Al and Ge occupy the 2b position, and S occupies the 8i position.

[0042] In yet another specific example, the chemical formula of the solid electrolyte material is Li 2-y-z Δ y+z SrGe 1-y P y S 4-z Cl z , where Δ represents an ionic vacancy occupying the Li site, y can range from 0 to 0.5, and z can range from 0 to 2. The space group of this solid electrolyte material is Among them, Li and the ionic vacancies at the Li site occupy the 4d position, Sr occupies the 2a position, Ge and P occupy the 2b position, and S and Cl occupy the 8i position.

[0043] In yet another specific example, the chemical formula of the solid electrolyte material is Li 2-y-z Δ y+z Sr 1-y Al y Ge 1-z P z S4, where Δ represents the ionic vacancy occupying the Li site, y can range from 0 to 0.5, and z can range from 0 to 0.5. The space group of this solid electrolyte material is Among them, Li and the ionic vacancies at the Li site occupy the 4d position, Sr and Al occupy the 2a position, Ge and P occupy the 2b position, and S occupies the 8i position.

[0044] In the application of the solid electrolyte material of the present invention, it can be used in the positive electrode material or the negative electrode material. As an application in the electrode material, the solid electrolyte material can be present on the surface and / or inside and / or in the gaps of the electrode material.

[0045] In addition, it can also be applied to the separator material. Similarly, the solid electrolyte material can be present on the surface and / or inside and / or in the gaps of the separator material.

[0046] The above solid electrolyte material or the positive electrode material, negative electrode material or separator material applying the solid electrolyte material can all be applied in secondary batteries, including any one of liquid lithium-ion batteries, liquid sodium-ion batteries, liquid metal lithium batteries, liquid metal sodium batteries, hybrid solid-liquid lithium-ion batteries, hybrid solid-liquid sodium-ion batteries, hybrid solid-liquid metal lithium batteries, hybrid solid-liquid metal sodium batteries, solid-state lithium-ion batteries, solid-state sodium-ion batteries, solid-state metal lithium batteries or solid-state metal sodium batteries.

[0047] The following uses some specific examples to elaborate in detail on the properties and applications of the solid electrolyte material of the present invention.

[0048] Example 1

[0049] In this example, the solid electrolyte material is Li2SrSiSe4 in the Sr series of solid electrolyte materials, Figure 2 is a schematic diagram of the crystal structure of Li2SrSiSe4. The space group of this material is Among them, Li occupies the 4d position, Sr occupies the 2a position, Si occupies the 2b position, and Se occupies the 8i position. The lattice constants of the unit cell are approximately α = β = γ = 90°, and the volume is approximately

[0050] Furthermore, the solid electrolyte material is required to have electronic insulation. Therefore, the inventors calculated the electronic density of states of this material using the mBJ exchange-correlation functional form. As Figure 3 shown, the band gap value of this material is at least 3.1 eV, indicating that it is a good electronic insulator material. The wide band gap indicates that it has a wide electrochemical window, so it has good electrochemical stability when working in a battery.

[0051] Furthermore, the lithium-ion transport property is the most critical property of solid electrolytes. The inventors calculated the lithium-ion migration channels of Li2SrSiSe4 using the bond valence method, and the calculation results are shown in Figure 4 . Referring to Figure 4 , it can be seen that there are mainly lithium-ion migration channels along the c-axis

[001] direction in this material.

[0052] Furthermore, the transition mechanism with the lowest activation energy and the corresponding transition barrier shape in this migration channel were obtained through a first-principles-based transition state calculation method. Figure 5 is the transition barrier with the minimum activation energy. The transition mode is that lattice lithium ions pass through the lattice interstitial site to the next lattice lithium-ion vacancy, and the transition activation energy is about 0.24 eV. This indicates that the energy required for lithium ions to overcome during movement is relatively low, and they can quickly transition within the migration channels of this material. Therefore, Li2SrSiSe4 can be an ionic conductor material.

[0053] The solid electrolyte material Li2SrSiSe4 of the present invention can be prepared by a conventional solid-phase synthesis method. First, in a glove box filled with inert gas under anhydrous and anaerobic conditions, Li, Sr, Si, and Se elemental substances are used as source materials, and they are mixed in a molar ratio of 2:1:1:4 and placed in a crucible; then the crucible is placed in a quartz glass tube inside the glove box, and the quartz glass tube is evacuated to a vacuum state, and then the glass tube is sealed using a high-temperature flame; finally, the sealed quartz glass tube is placed in a programmable temperature-controlled furnace for sintering. The specific temperature control program implemented in this example is: the furnace is heated from room temperature to the maximum temperature within about 48 hours, and the maximum temperature can be 600 to 800 degrees, and the actual implementation of the present invention is 700 degrees, then it is kept at the maximum temperature for about 72 hours, and then cooled to room temperature at a rate of about 10 degrees per hour to obtain the polycrystalline powder of this solid electrolyte material.

[0054] Example 2

[0055] In this example, the solid-state electrolyte material is Li2SrGeS4 in the Sr series of solid electrolyte materials, and the space group of this material is Among them, Li occupies the 4d position, Sr occupies the 2a position, Ge occupies the 2b position, and S occupies the 8i position. The lattice constants of the unit cell are approximately α = β = γ = 90°, and the volume is approximately

[0056] Furthermore, the inventors calculated the electronic density of states of this material using the mBJ exchange-correlation functional form. The calculation results show that the band gap value of this material is at least 3.6 eV, indicating that it has good electronic insulation and meets the basic conditions for becoming a solid electrolyte material.

[0057] Furthermore, the inventors combined the bond valence method and the transition state calculation method to obtain the lithium ion migration channel in Li2SrGeS4, the transition mechanism with the lowest activation energy in this migration channel, and the corresponding shape of the transition barrier. The calculation results show that the transition mode of lithium ions is that lattice lithium ions pass through the interstitial site to the next lattice lithium ion vacancy, and the activation energy of the transition is about 0.37 eV. This indicates that the energy that lithium ions need to overcome during movement is relatively low, and they can quickly transition within the migration channel of this material. Therefore, Li2SrGeS4 can be an ionic conductor material.

[0058] Similarly, the solid electrolyte material Li2SrGeS4 of the present invention can also be prepared by a conventional solid-phase synthesis method. Using Li, Sr, Ge, and S elemental substances as source materials, mixing them evenly according to the required molar ratio and sintering them can obtain polycrystalline powders of Li2SrGeS4. It has been described in detail in Example 1 and will not be elaborated here.

[0059] Example 3

[0060] In this example, the solid electrolyte material is Li2CaSiS4 in the Ca series of solid electrolyte materials. The space group of this material is Among them, Li occupies the 4d position, Ca occupies the 2a position, Si occupies the 2b position, and S occupies the 8i position. The lattice constants of the unit cell are approximately α = β = γ = 90°, and the volume is approximately

[0061] Furthermore, the inventors calculated the electronic density of states of this material using the mBJ exchange-correlation functional form. The calculation results show that the band gap value of this material is at least 3.9 eV, indicating that it is a good electronic insulator material and meets the electronic insulation requirements of solid electrolyte materials.

[0062] Furthermore, the inventors combined the bond valence method with the transition state calculation method to obtain the lithium ion migration channels in Li2CaSiS4, the transition mechanism with the lowest activation energy in this migration channel, and the corresponding transition barrier shape. The calculation results show that there are mainly lithium ion migration channels along the c-axis

[001] direction in this material. The transition mode of lithium ions in this material is that lattice lithium ions pass through the lattice interstitial sites to the next lattice lithium ion vacancy, and the activation energy of the transition is about 0.25 eV. This indicates that lithium ions only need to overcome relatively low energy to rapidly transition within the migration channels during movement. Therefore, Li2CaSiS4 can be an ionic conductor material.

[0063] Similarly, the solid electrolyte material Li2CaSiS4 of the present invention can also be prepared by a conventional solid-phase synthesis method, which will not be elaborated here.

[0064] Example 4

[0065] In this example, the solid-state electrolyte material is Li2BaSiS4 in the Ba series of solid electrolyte materials. The space group of this material is where Li occupies the 4d position, Ba occupies the 2a position, Si occupies the 2b position, and S occupies the 8i position. The lattice constants of the unit cell are approximately α = β = γ = 90°, and the volume is approximately

[0066] Furthermore, the inventors calculated the electronic density of states of this material using the mBJ exchange-correlation functional form. The calculation results show that the bandgap value of this material is at least 4.1 eV, indicating its good electronic insulation. The wide bandgap indicates its wide electrochemical window and it can be a solid electrolyte material.

[0067] Furthermore, the inventors combined the bond valence method with the transition state calculation method to obtain the lithium ion migration channels in Li2BaSiS4, the transition mechanism with the lowest activation energy in this migration channel, and the corresponding transition barrier shape. The calculation results show that there are mainly lithium ion migration channels along the crystal c-axis direction in this material. The transition mode of lithium ions is that lattice lithium ions pass through the lattice interstitial sites to the next lattice lithium ion vacancy, and the activation energy of the transition is about 0.44 eV. This indicates that the energy that lithium ions need to overcome during movement is relatively low and they can rapidly transition within the migration channels of this material. Therefore, Li2BaSiS4 can be an ionic conductor material.

[0068] Similarly, the solid electrolyte material Li2BaSiS4 of the present invention can also be prepared by a conventional solid-phase synthesis method, which will not be elaborated here.

[0069] Examples 1, 2, 3, and 4 above mainly introduced the basic properties and synthesis methods of solid electrolyte materials represented by Li2SrSiSe4, Li2SrGeS4, Li2CaSiS4, and Li2BaSiS4 in the Li2ADX4 family. Next, in Examples 5, 6, 7, 8, and 9, the doping effects in Li2ADX4 solid electrolyte materials will be mainly introduced.

[0070] Example 5

[0071] In this example, taking the doping of Cl element in Li2CaSiS4 as an example, the doping of hetero-valent elements is introduced. Cl - element is mainly doped at the lattice sites where S 2- is located. In order to maintain charge balance, lithium ion vacancies will be generated at the lattice sites where Li is located. A certain concentration of lithium ion vacancies can improve the lithium ion conductivity. When the doping concentration of Cl is y, the concentration of generated lithium ion vacancies is y, and the corresponding chemical formula is Li 2-y Δ y CaSiS 4-y Cl y , where Δ represents the ionic vacancy occupying the Li site, and the range of y is between 0 and 2. The preferred doping concentration of Cl in this example is 0.25, and the corresponding chemical formula is Li 1.75 Δ 0.25 CaSiS 3.75 Cl 0.25 . The space group of this doped material is where the ionic vacancies of Li and Li sites occupy the 4d position, Ca occupies the 2a position, Si occupies the 2b position, and S and Cl occupy the 8i position.

[0072] Furthermore, the inventors calculated the electronic density of states of Li 1.75 Δ

[0073] 0.25 CaSiS 3.75 Cl 0.25 using the mBJ exchange-correlation functional form. The calculation results show that the band gap value of this material is at least 2.9 eV, indicating that it is a good electronic insulator material and can be a solid electrolyte material.

[0074] Furthermore, the inventors obtained the ionic diffusion coefficients of Li2CaSiS4 and Li 1.75 Δ 0.25 CaSiS 3.75 Cl 0.25 materials using the molecular dynamics calculation method and estimated their room-temperature ionic conductivities. As Figure 6 shown, by fitting the Arrhenius curve, Li2CaSiS4 and Li1.75 Δ 0.25 CaSiS 3.75 Cl 0.25 has a room-temperature lithium-ion conductivity of about 10 -7 S / cm and 10 -4 S / cm. That is, the doping of Cl element under this concentration condition can increase the ionic conductivity of the material by at least three orders of magnitude. This shows that Li 1.75 Δ 0.25 CaSiS 3.75 Cl 0.25 can be a fast-ion conductor material.

[0075] The solid electrolyte material Li 1.75 Δ 0.25 CaSiS 3.75 Cl 0.25 of the present invention can also be prepared by a conventional solid-phase synthesis method. Using LiCl, Li, Ca, Si, and S as source materials, mixing them evenly according to the required molar ratio and sintering them can obtain Li 1.75 Δ 0.25 CaSiS 3.75 Cl 0.25 polycrystalline powder. The specific synthesis method and process have been described in detail in Example 1 and will not be elaborated here.

[0076] Example 6

[0077] In this example, taking the doping of Cl element in Li2SrGeS4 as an example, the doping of hetero-valent elements is introduced. The Cl - element is mainly doped at the lattice site where S 2- is located. To maintain charge balance, lithium-ion vacancies will be generated at the lattice site where Li is located. A certain concentration of lithium-ion vacancies can increase the lithium-ion conductivity. When the doping concentration of Cl is y, the concentration of generated lithium-ion vacancies is y, and the corresponding chemical formula is Li 2-y Δ y SrGeS 4-y Cl y where Δ represents the ionic vacancy occupying the Li site, and the range of y is between 0 and 2. In this example, the doping concentration of Cl is 0.25, and the corresponding chemical formula is Li 1.75 Δ 0.25 SrGeS 3.75 Cl 0.25 . The space group of this doped material is where Li and the ionic vacancy at the Li site occupy the 4d position, Sr occupies the 2a position, Ge occupies the 2b position, and S and Cl occupy the 8i position.

[0078] The solid electrolyte material Li 1.75 Δ0.25 SrGeS 3.75 Cl 0.25 It can also be prepared by a conventional solid-phase synthesis method. Using LiCl, Li, Sr, Ge, and S as source materials, mixing them evenly according to the required molar ratio and sintering them can obtain Li 1.75 Δ 0.25 SrGeS 3.75 Cl 0.25 polycrystalline powder.

[0079] Example 7

[0080] In this example, taking the doping of Al element in Li2SrGeS4 as an example, the doping of hetero-valent elements is introduced. Al 3+ element is mainly doped at the lattice site where Ge 4+ is located. In order to maintain charge balance, interstitial lithium ions will appear at the interstitial positions of the lattice. A certain concentration of interstitial lithium ions can improve the lithium ion conductivity. When the doping concentration of Al is y, the concentration of the generated interstitial lithium ions is y, and the corresponding chemical formula is Li2δ y SrGe 1-y Al y S4, where δ represents the Li ions occupying the lattice interstitial sites, and y can range from 0 to 0.5. In this example, the doping concentration of Al is 0.125, and the corresponding chemical formula is Li2δ 0.125 SrGe 0.875 Al 0.125 S4. The space group of this doped material is where Li occupies the 4d position, the interstitial Li ions occupy the lattice interstitial positions, Sr occupies the 2a position, Al and Ge occupy the 2b position, and S occupies the 8i position.

[0081] The solid electrolyte material Li2δ 0.125 SrGe 0.875 Al 0.125 S4 of the present invention can also be prepared by a conventional solid-phase synthesis method. Using Li, Sr, Ge, Al, and S as source materials, mixing them evenly according to the required molar ratio and sintering them can obtain Li2δ 0.125 SrGe 0.875 Al 0.125 S4 polycrystalline powder.

[0082] Example 8

[0083] In this example, taking the simultaneous doping of P and Cl elements in Li2SrGeS4 as an example, the simultaneous doping of hetero-valent elements is introduced. P 5+ element is mainly doped at the lattice site where Ge 4+ is located, and Cl -The elements are mainly doped at the lattice sites where S is located. To maintain charge balance, lithium ion vacancies will be generated at the lattice sites where Li is located. A certain concentration of lithium ion vacancies can improve the lithium ion conductivity. When the doping concentration of P is y and the doping concentration of Cl is z, the generated lithium ion vacancy concentration is y + z, and the corresponding chemical formula is Li 2- Δ 2-y-z Δ y+z SrGe 1-y P y S 4-z Cl z , where Δ represents the ionic vacancies occupying the Li sites. The range of y is between 0 and 0.5, and the range of z is between 0 and 2. In this embodiment, the doping concentrations of P and Cl are 0.0625 and 0.25 respectively, and the corresponding chemical formula is Li 1.6875 Δ 0.3125 SrGe 0.9375 P 0.0625 S 3.75 Cl 0.25 . The space group of this doped material is where Li and the ionic vacancies at the Li sites occupy the 4d positions, Sr occupies the 2a position, Ge and P occupy the 2b positions, and S and Cl occupy the 8i positions.

[0084] The solid electrolyte material Li 1.6875 Δ 0.3125 SrGe 0.9375 P 0.0625 S 3.75 Cl 0.25 of the present invention can also be prepared by a conventional solid-phase synthesis method. Using LiCl, Li, Sr, Ge, P2S5, and S as source materials, mixing them evenly according to the required molar ratio and sintering them can obtain Li 1.6875 Δ 0.3125 SrGe 0.9375 P 0.0625 S 3.75 Cl 0.25 polycrystalline powder.

[0085] Example 9

[0086] In this embodiment, taking the simultaneous doping of Al and P elements in Li2SrGeS4 as an example, the case of simultaneous doping of hetero-valent elements is introduced. Al 3+ The element is mainly doped at the lattice sites where Sr 2+ is located, and P 5+ The element is mainly doped at the lattice sites where Ge 4+In order to maintain charge balance, the lattice point where Li is located will produce lithium ion holes. A certain concentration of lithium ion holes can improve the lithium ion conductivity. When the doping concentration of Al is y and the doping concentration of P is z, the concentration of lithium ion holes generated is y+z, and the corresponding chemical formula is Li 2-y-z Δ y+z Sr 1-y Al y Ge 1-z P z S4, where Δ represents the ion vacancy occupying the Li position, y ranges from 0 to 0.5, and z ranges from 0 to 0.5. In this embodiment, the doping concentrations of Al and P are 0.125 and 0.0625 respectively, and the corresponding chemical formula is Li 1.8125 Δ 0.1875 Sr 0.875 Al 0.125 Ge 0.9375 P 0.0625 S4. The space group of the doping material is Among them, Li and Li ion vacancies occupy the 4d position, Sr and Al occupy the 2a position, Ge and P occupy the 2b position, and S occupies the 8i position.

[0087] The solid electrolyte material Li of the present invention 1.8125 Δ 0.1875 Sr 0.875 Al 0.125 Ge 0.9375 P 0.0625 S4 can also be prepared by conventional solid phase synthesis. Li, Sr, Al, Ge, P2S5, and S are used as source materials, mixed evenly in the required molar ratio, and sintered to obtain Li 1.8125 Δ 0.1875 Sr 0.875 Al 0.125 Ge 0.9375 P 0.0625 S4 polycrystalline powder.

[0088] Through the research process of the present invention, it is found that the solid electrolyte material Li2ADX4 proposed by the present invention is a family of solid electrolyte materials with a crystal structure, which is not only rich in element reserves and low in cost, but also has high ionic conductivity. By further optimizing the doping of such materials, their ionic conductivity can be further improved, so that they can be expected to be used in the preparation of secondary batteries with high safety and high specific energy.

[0089] The specific embodiments described above further elaborate on the objective, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only for the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. Application of a material, characterized in that, The chemical formula of the said material is Li2ADX4, where A is Ca 2+ or Sr 2+ or Ba 2 + or one or more of them, D is Si 4+ or Ge 4+ or Sn 4+ or one or more of them, X is S 2- and / or Se 2- ; The structure space group of the said material is where Li occupies the 4d position, A occupies the 2a position, D occupies the 2b position, and X occupies the 8i position; The said material is used as a solid electrolyte material.

2. Use of the material according to claim 1, characterized in that, In the said material, there are hetero-valent elements Al 3+ and / or Ga 3+ partially substituting A at the lattice sites occupied by A; there are hetero-valent elements P 5+ and / or As 5+ partially substituting D at the lattice sites occupied by D; there are hetero-valent elements F - and / or Cl - and / or Br - partially substituting X at the lattice sites occupied by X; Li ion vacancies are generated by partial substitution of hetero-valent elements at the lattice sites occupied by A and / or D and / or X; The doping ratio of hetero-valent elements at the lattice sites occupied by A or D or X is respectively in the range of 0 to 0.5; Partial substitution of the lattice sites with hetero-valent elements is used to improve the ionic conductivity of the said solid electrolyte material.

3. The application of the material according to claim 1, characterized in that, In the said material, there are some hetero-valent elements Al 3+ and / or Ga 3+ that partially replace D at the lattice sites occupied by D, and interstitial Li ions are generated by the partial replacement of the hetero-valent elements at the lattice sites occupied by D; The doping ratio of hetero-valent elements at the lattice sites occupied by D is in the range of 0 to 0.5; Partial substitution of the lattice sites with hetero-valent elements is used to improve the ionic conductivity of the said solid electrolyte material.

4. An electrode material, characterized in that, The said electrode material includes the solid electrolyte material described in claim 1 above.

5. The electrode material according to claim 4, wherein, The said solid electrolyte material exists on the surface and / or inside and / or in the gaps of the said electrode material.

6. The electrode material according to claim 4, characterized in that, The said electrode material is a positive electrode material or a negative electrode material.

7. A separator material, characterized in that, The said separator material includes the solid electrolyte material described in claim 1 above.

8. The separator material according to claim 7, wherein The said solid electrolyte material exists on the surface and / or inside and / or in the gaps of the said separator material.

9. A secondary battery, characterized in that, The said secondary battery includes the solid electrolyte material described in claim 1 above.

10. The secondary battery according to claim 9, wherein The said secondary battery includes any one of a liquid lithium-ion battery, a liquid sodium-ion battery, a liquid metal lithium battery, a liquid metal sodium battery, a hybrid solid-liquid lithium-ion battery, a hybrid solid-liquid sodium-ion battery, a hybrid solid-liquid metal lithium battery, a hybrid solid-liquid metal sodium battery, a solid lithium-ion battery, a solid sodium-ion battery, a solid metal lithium battery or a solid metal sodium battery.

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