Surface-modified sulfide electrolyte, preparation method thereof and all-solid-state battery

Abstract

The invention provides a surface-modified sulfide electrolyte and a preparation method thereof, and an all-solid-state battery, the surface-modified sulfide electrolyte comprises a sulfide electrolyte and a modification layer coated on the surface of the sulfide electrolyte, the chemical general formula of the modification layer is LiaMbNcXd, 0 < = a < = 3, 0 < = b < = 1, 0 < = c < = 1, 0 < = d < = 6, and 0 < = c < = 1. M is at least one element of magnesium, aluminum, calcium, iron, zirconium, niobium, tantalum, tungsten, gadolinium, yttrium, indium, hafnium, lanthanum and ytterbium, and X is at least one element of oxygen, sulfur, fluorine, chlorine, bromine and iodine. According to the surface-modified sulfide electrolyte, the modification layer with high ionic conductivity and high oxidation potential is coated outside the sulfide electrolyte, so that when the surface-modified sulfide electrolyte is applied to a positive electrode of an all-solid-state battery, the modification layer can improve the oxidation potential of the electrolyte on the premise of not reducing the ionic conductivity of the electrolyte; the effects of improving the interface stability between the positive electrode active material and the sulfide electrolyte and further improving the cycle performance of the battery are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of batteries, in particular to a surface-modified sulfide electrolyte and a preparation method thereof, and a full solid-state battery. BACKGROUND

[0002] Compared with liquid batteries, full solid-state batteries have been regarded as the hope of next-generation energy storage technology due to their higher energy density and safety. At present, in order to build a lithium ion transmission channel in a full solid-state battery, an electrolyte material is usually added to the positive electrode raw material of the battery. Among the electrolyte materials applied to full solid-state batteries, sulfide solid-state electrolytes are favored by researchers due to their high ionic conductivity.

[0003] However, the electrochemical stability of the sulfide electrolyte is poor, and there is a serious interface side reaction between the sulfide electrolyte and the positive active material in the positive electrode material during the battery cycle, which seriously hinders the performance and long-term stability of the battery, and becomes a core problem that must be solved in the industrialization of solid-state batteries.

[0004] Therefore, there is an urgent need for a technology to solve the problem of battery performance deterioration caused by the side reaction between the positive active material and the sulfide electrolyte in the positive electrode of the full solid-state battery. SUMMARY

[0005] The present application provides a surface-modified sulfide electrolyte and a preparation method thereof, and a full solid-state battery. In the scenario of applying the sulfide electrolyte to the positive electrode of the battery, the modification layer in the surface-modified sulfide electrolyte can effectively avoid the direct contact between the sulfide electrolyte and the positive active material, hinder the side reaction between the two, and achieve the effect of improving the interface stability between the positive active material and the sulfide electrolyte.

[0006] In a first aspect, the present application provides a surface-modified sulfide electrolyte, comprising: a sulfide electrolyte and a modification layer coated on the surface of the sulfide electrolyte.

[0007] The chemical formula of the modification layer is Li a M b N c X d , wherein 0≤a≤3, 0≤b≤1, 0≤c≤1, 0≤d≤6, M is at least one element selected from magnesium, aluminum, calcium, iron, zirconium, niobium, tantalum, tungsten, gadolinium, yttrium, indium, hafnium, lanthanum, and ytterbium, and X is at least one element selected from oxygen, sulfur, fluorine, chlorine, bromine, and iodine.

[0008] According to an implementation manner of the present application, the sulfide electrolyte comprises at least one of the following:

[0009] Li x AP y Sz wherein 0

[0010] Li 7-m-n PS 6-m-n Cl m R n wherein 0

[0011] tLi2S·(100-t)P2S5, wherein 70

[0012] uLiI·vLiBr·(100-u-v)·(wLi2S·(100-w)P2S5), wherein 70

[0013] According to an implementation manner of the present application, in the surface-modified sulfide electrolyte, the mass ratio of the modification layer to the sulfide electrolyte is 0.1-30%.

[0014] According to an implementation manner of the present application, the particle size of the sulfide electrolyte is 0.5 50 20 μm.

[0015] In a second aspect of the present application, a preparation method of the above surface-modified sulfide electrolyte is provided, and the method comprises:

[0016] mixing Li3N, Li j X k and MX in a preset proportion to obtain a modification layer precursor;

[0017] mixing the modification layer precursor with a sulfide electrolyte to make the modification layer precursor adhere to the surface of the sulfide electrolyte to form a modification layer, thereby obtaining a surface-modified sulfide electrolyte;

[0018] wherein M is any one of magnesium, aluminum, calcium, iron, zirconium, niobium, tantalum, tungsten, gadolinium, yttrium, indium, hafnium, lanthanum and ytterbium, and X is any one of oxygen, sulfur, fluorine, chlorine, bromine and iodine.

[0019] According to an implementation manner of the present application, the Li j X k is at least one of LiF, LiCl, LiBr, Lil, Li2O, Li2O2 and Li2S;

[0020] and / or,

[0021] The MX is at least one of MgCl2, MgF2, AlCl3, AlF3, CaCl2, FeCl2, FeCl3, ZrCl4, ZrF4, NbF5, NbCl5, TaF5, TaCl5, TaBr5, WCl6, WBr6, WI6, GdCl3, GdBr3, GdF3, GaCl3, GaBr3, GaF3, YCl3, YBr3, YF3, InCl3, HfCl4, LaCl3, YbCl3.

[0022] According to an implementation manner of the present application, the sulfide electrolyte comprises at least one of:

[0023] Li x AP y S z , wherein 0

[0024] Li 7-m-n PS 6-m-n Cl m R n , wherein 0

[0025] tLi2S·(100-t)P2S5, wherein 70

[0026] uLiI·vLiBr·(100-u-v)·(wLi2S·(100-w)P2S5), wherein 70

[0027] According to an implementation manner of the present application, the Li3N, Li j X k , and the mass ratio of MX to the sulfide electrolyte is 0.1-30%.

[0028] According to an implementation manner of the present application, the particle size of the sulfide electrolyte is 0.5 50 m.

[0029] According to an implementation manner of the present application, the Li3N, Li j X k , and MX are sufficiently mixed to obtain a modification layer precursor, comprising:

[0030] The Li3N, Li j X k , and MX are put into a ball mill tank for ball milling mixing treatment to obtain a modification layer precursor.

[0031] Correspondingly, the mixing of the modification layer precursor and the sulfide electrolyte to make the modification layer precursor coat the surface of the sulfide electrolyte to form a modification layer, so as to obtain the surface-modified sulfide electrolyte, comprises:

[0032] The sulfide electrolyte is added into the ball mill jar, and the modification layer precursor and the sulfide electrolyte are ball-mixed to obtain a wet mixture.

[0033] Or,

[0034] The Li3N, Li j X k , MX and solvent are weighed according to a preset ratio, and then mixed to obtain the modification layer precursor.

[0035] The Li3N, Li j X k , MX and solvent are weighed according to a preset ratio, and then mixed to obtain the modification layer precursor.

[0036] Correspondingly, the mixing of the modification layer precursor and the sulfide electrolyte to make the modification layer precursor coat the surface of the sulfide electrolyte to form a modification layer, so as to obtain the surface-modified sulfide electrolyte, comprises:

[0037] The sulfide electrolyte is added into the ball mill jar, and the modification layer precursor and the sulfide electrolyte are ball-mixed to obtain a wet mixture.

[0038] The wet mixture is dried to form the modification layer on the surface of the sulfide electrolyte, so as to obtain the surface-modified sulfide electrolyte.

[0039] According to an implementation manner of the present application, the rotation speed of the ball-mixing process is 200-750 rpm; and / or, the time of the ball-mixing process is 4-24 h.

[0040] According to an implementation manner of the present application, the solvent is at least one of anisole, toluene, xylene, heptane, carbon tetrachloride, isobutyl isobutyrate, tetrahydrofuran, acetonitrile, n-butanol, isopropyl alcohol and ethanol.

[0041] And / or, the temperature of the drying process is 70-200℃; and / or, the time of the drying process is 5-24 h.

[0042] In a third aspect of the present application, a cathode film is provided, which includes a cathode active material, a binder, a conductive agent, and a solid-state electrolyte, the solid-state electrolyte being the surface-modified sulfide electrolyte according to the first aspect described above, or the solid-state electrolyte being the surface-modified sulfide electrolyte prepared by the method according to the second aspect described above.

[0043] According to an implementation manner of the present application, the cathode active material includes at least one of:

[0044] LiCoO2; LiMnO2; LiNiO2; LiVO2;

[0045] LiNi a Co b Mn c O2, wherein a+b+c=1, 0≤a<1, 0≤b<1, 0≤c<1;

[0046] LiNi x Co y Al z O2, wherein x+y+z=1, 0≤x<1, 0≤y<1, 0≤z<1;

[0047] nLi2MnO3·(1-n)LiTMO2, wherein 0<n<1, TM is any one of nickel, manganese, cobalt, and aluminum;

[0048] LiMn2O4; Li4Ti5O 12 ; Li(Ni 0.5 Mn 1.5 )O4; LiFePO4; LiMnPO4; LiNiPO4; LiCoPO4;

[0049] LiMn m Fe 1-m PO4, wherein 0<m<1.

[0050] According to a fourth aspect of the present application, a full solid-state battery is provided, which includes a cathode, an electrolyte layer, and an anode;

[0051] The cathode includes a cathode current collector and a cathode film arranged on the surface of the cathode current collector;

[0052] The cathode film is the cathode film according to the third aspect described above.

[0053] According to an implementation manner of the present application, the raw material of the electrolyte layer includes a sulfide electrolyte.

[0054] In a fifth aspect of the present application, an electric device is provided, which includes the electric device subject and the solid-state battery according to the fourth aspect.

[0055] In the implementation of the present application, at least the following advantages are provided:

[0056] The surface modified sulfide electrolyte provided by the present application has a modified layer with high ion conductivity and high oxidation potential coated outside the sulfide electrolyte. When the surface modified sulfide electrolyte is applied to the positive electrode of a full solid-state battery, the modified layer can avoid direct contact between the sulfide electrolyte and the positive electrode active material without reducing the ion conductivity of the electrolyte, hinder the side reaction between the two, improve the interface stability between the positive electrode active material and the sulfide electrolyte, reduce the interface impedance of the battery, and further improve the cycle performance of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0057] The accompanying drawings, which are incorporated into and form part of the specification, illustrate embodiments consistent with the present application and, together with the specification, serve to explain the principles of the application.

[0058] Figure 1 The flowchart of the preparation method of the surface modified sulfide electrolyte provided by the present application is shown.

[0059] The specific embodiments of the present application have been shown in the above drawings, and will be described in more detail hereinafter. These drawings and written descriptions are not intended to limit the scope of the inventive concept in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0060] In order for those skilled in the art to better understand the scheme of the present application, the present application will be further described in detail below. The specific embodiments listed below are only used to describe the principles and characteristics of the present application, and the examples are used to explain the present application, but not to limit the scope of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0061] In order to facilitate the understanding of the technical content of the present application, the background art will be described in detail as follows:

[0062] In the scenario of applying sulfide electrolyte to the positive electrode of the all-solid-state battery, during the electrochemical cycle of the battery, due to the direct contact between the sulfide electrolyte and the positive electrode active material, on the one hand, the high oxidation state transition metal ions on the surface of the positive electrode active material may be partially reduced to a low valence state, destroying the crystal structure on the surface of the positive electrode active material, and then causing active material loss; on the other hand, the transition metal ions migrated out of the positive electrode active material will catalyze the decomposition of the sulfide electrolyte into electron conductive products, causing self-discharge to form a non-active interface layer, consuming active lithium in the positive electrode material and the electrolyte material. It can be seen that the side reaction between the sulfide electrolyte and the positive electrode active material in the positive electrode of the battery will seriously hinder the performance of the battery.

[0063] At present, some technologies improve the chemical and electrochemical stability of the sulfide electrolyte by element doping or component optimization. However, this means not only has limited improvement effect, but also greatly sacrifices the ionic conductivity.

[0064] Based on the introduction of the above background technology, the inventors found that by coating a modification layer with high ionic conductivity and high oxidation potential on the surface of the sulfide electrolyte, the modification layer not only does not affect the ionic conductivity of the sulfide electrolyte, but also can avoid the direct contact between the sulfide electrolyte and the positive electrode active material under high voltage in the positive electrode, reduce the side reaction between the sulfide and the transition metal elements in the positive electrode material and in the high-voltage charging and discharging process, and effectively improve the comprehensive electrochemical performance of the all-solid-state battery, such as cycle performance.

[0065] Therefore, the present application provides a surface-modified sulfide electrolyte, comprising: a sulfide electrolyte and a modification layer coated on the surface of the sulfide electrolyte.

[0066] The chemical formula of the modification layer is Li a M b N c X d , wherein 0≤a≤3, 0≤b≤1, 0≤c≤1, 0≤d≤6, M is at least one element selected from magnesium, aluminum, calcium, iron, zirconium, niobium, tantalum, tungsten, gadolinium, yttrium, indium, hafnium, lanthanum and ytterbium, and X is at least one element selected from oxygen, sulfur, fluorine, chlorine, bromine and iodine.

[0067] According to the research of the inventors, the chemical formula of the modification layer is Li a M b N c X dThe metal element M and the X element in the substance can ensure the ion conductivity and oxidation resistance of the modification layer, and the combination of the elements determines that the modification layer has high ion conductivity (ion conductivity ≥ 3 mS / cm) and high oxidation potential (greater than 4.0V). Therefore, when the substance is used as a modification layer for coating the surface of the sulfide electrolyte, the sulfide electrolyte can avoid direct contact with the positive active material under high voltage of the positive electrode without reducing the overall ion conductivity of the electrolyte, hindering the catalysis of transition metal ions on the sulfide electrolyte and the reduction of the sulfide electrolyte to transition metal ions, thereby improving the interface stability between the sulfide electrolyte and the positive active material in the positive electrode of the battery, reducing the interface impedance, and improving the cycle performance of the battery.

[0068] It should be understood that in actual applications, the number and selection of elements included in M and X in the above chemical formula, and the selection of the values of a, b, c, and d, should be comprehensively considered and optimized according to the target performance of the electrolyte, the specific needs of the application scenario, and the production cost and other factors.

[0069] Through X-ray energy dispersive spectroscopy (Energy Dispersive Spectroscopy, EDS) detection of the above-mentioned surface-modified sulfide electrolyte, it can be observed that the surface has lithium, nitrogen, M elements and X elements. Among them, the M element includes at least one of magnesium, aluminum, calcium, iron, zirconium, niobium, tantalum, tungsten, gadolinium, yttrium, indium, hafnium, lanthanum, and ytterbium, and the X element includes at least one of oxygen, sulfur, fluorine, chlorine, bromine, and iodine.

[0070] In one possible implementation, the sulfide electrolyte in the above-mentioned surface-modified sulfide electrolyte includes at least one of the following:

[0071] Li x AP y S z , wherein 0 < x, 0 < y, 0 < z, and A is at least one of tin, germanium, and silicon;

[0072] Li 7-m-n PS 6-m-n Cl m R n , wherein 0 ≤ m, 0 ≤ n, and R is at least one of fluorine, bromine, and iodine;

[0073] tLi2S·(100-t)P2S5, wherein 70 ≤ t ≤ 80;

[0074] uLiI·vLiBr·(100-u-v)·(wLi2S·(100-w)P2S5), wherein 70 ≤ w ≤ 80, 0 ≤ u ≤ 30, and 0 ≤ v ≤ 30.

[0075] It should be understood that, in order to improve the overall performance of the surface-modified sulfide electrolyte, the sulfide electrolyte with more excellent performance described above can be preferentially selected to ensure the ion conductivity, electrochemical window, and chemical stability of the modified sulfide electrolyte.

[0076] Specifically, the sulfide electrolyte can be selected from Li x AP y S z , Li 7-m-n PS 6-m-n Cl m R n , tLi2S·(100-t)P2S5, and uLiI·vLiBr·(100-u-v)·(wLi2S·(100-w)P2S5). The number of elements included in A and R in the chemical formula of the above sulfide electrolyte and the selection of the elements, as well as the selection of the values of x, y, z, m, n, t, u, v, and w, should be comprehensively considered and optimized according to the target performance of the electrolyte, the specific requirements of the application scenario, and the production cost and other factors.

[0077] In one possible implementation, in the surface-modified sulfide electrolyte, the mass ratio of the modification layer to the sulfide electrolyte is 0.1-30%.

[0078] For example, the mass ratio of the modification layer to the sulfide electrolyte is, for example, 0.1%, 4%, 8%, 12%, 16%, 20%, 24%, 28%, 30%, or any two of the foregoing values are selected to form a new range, and a value is taken within the new range.

[0079] It should be understood that the mass ratio of the modification layer to the sulfide electrolyte is a key factor affecting the performance of the surface-modified sulfide electrolyte. Specifically, if the mass ratio of the modification layer is too low, the sulfide electrolyte may not be completely coated, affecting the performance of the modification layer; if the mass ratio of the modification layer is too high, the modification layer may be too thick, which may lower the overall ion conductivity of the electrolyte.

[0080] In one possible implementation, the particle size of the sulfide electrolyte is 0.5 μm≤D 50 ≤20 μm.

[0081] For example, the particle size D 50 of the sulfide electrolyte is, for example, 0.5 μm, 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, or any two of the foregoing values are selected to form a new range, and a value is taken within the new range.

[0082] It should be understood that, from the perspective of electrolyte application, the smaller the electrolyte particle size, the better its performance. Therefore, this invention selects sulfide electrolytes with smaller particle sizes as the modifiers, so that the surface-modified sulfide electrolytes obtained after modification also have smaller particle sizes. This allows them to be better dispersed in the positive electrode active material after being applied to the battery positive electrode, further optimizing the ion transport efficiency inside the electrode.

[0083] In the surface-modified sulfide electrolyte provided in this embodiment of the invention, since a modification layer with high ionic conductivity and high oxidation potential is coated on the outside of the sulfide electrolyte, when it is applied to the positive electrode of an all-solid-state battery, the modification layer can avoid direct contact between the sulfide electrolyte and the positive electrode active material without reducing the ionic conductivity of the electrolyte, thus hindering the side reactions between the two and achieving the effect of improving the interfacial stability of the sulfide electrolyte to the positive electrode active material under high positive electrode pressure.

[0084] Furthermore, Embodiment 2 of the present invention provides a method for preparing the above-mentioned surface-modified sulfide electrolyte. Figure 1 The schematic diagram shows the process for preparing the surface-modified sulfide electrolyte provided by this invention. Figure 1 As shown, the method includes:

[0085] S101, mix Li3N and Li in a pre-defined ratio. j X k The mixture is thoroughly mixed with MX to obtain the precursor of the modified layer.

[0086] Where M is any one of the elements selected from magnesium, aluminum, calcium, iron, zirconium, niobium, tantalum, tungsten, gadolinium, yttrium, indium, hafnium, lanthanum, and ytterbium, and X is any one of the elements selected from oxygen, sulfur, fluorine, chlorine, bromine, and iodine.

[0087] Specifically, it will be based on the chemical formula Li a M b N c X d Determine the chemical formula of the target modification layer, and then determine the required Li based on the chemical formula. j X k And MX, and determine Li3N and Li based on the stoichiometric ratios of each element in the chemical formula. j X k And the proportion of MX. Among them, the chemical formula Li a M b N c X d In the given information, 0≤a≤3, 0≤b≤1, 0≤c≤1, 0≤d≤6, M is at least one element selected from magnesium, aluminum, calcium, iron, zirconium, niobium, tantalum, tungsten, gadolinium, yttrium, indium, hafnium, lanthanum, and ytterbium, and X is at least one element selected from oxygen, sulfur, fluorine, chlorine, bromine, and iodine.

[0088] It should be noted that the selected Li j X k Both MX can be one or more substances, determined according to the chemical formula of the target modification layer.

[0089] Optional, Li j X k It is at least one of LiF, LiCl, LiBr, LiI, Li2O, Li2O2, and Li2S.

[0090] Optionally, MX is at least one of MgCl2, MgF2, AlCl3, AlF3, CaCl2, FeCl2, FeCl3, ZrCl4, ZrF4, NbF5, NbCl5, TaF5, TaCl5, TaBr5, WCl6, WBr6, WI6, GdCl3, GdBr3, GdF3, GaCl3, GaBr3, GaF3, YCl3, YBr3, YF3, InCl3, HfCl4, LaCl3, and YbCl3.

[0091] It should be noted that when Li3N and Li j X k During the thorough mixing of MX, due to the injection of high energy, Li3N and Li j X k The reaction between MX yields a precursor for a modified layer with the chemical formula of the target modified layer.

[0092] S102. The modification layer precursor is mixed with the sulfide electrolyte so that the modification layer precursor adheres to the surface of the sulfide electrolyte to form a modification layer, thereby obtaining a surface-modified sulfide electrolyte.

[0093] In this step, the modification layer precursor needs to be further mixed with the sulfide electrolyte so that the modification layer precursor adheres to the surface of the sulfide electrolyte to form a modification layer, thus obtaining a surface-modified sulfide electrolyte.

[0094] Optionally, the sulfide electrolyte includes at least one of the following:

[0095] Li x AP y S z Where 0 < x, 0 < y, 0 < z, and A is at least one element selected from tin, germanium, and silicon;

[0096] Li 7-m-n PS 6-m-n Cl m R n , where 0≤m, 0≤n, and R is at least one element selected from fluorine, bromine, and iodine;

[0097] tLi2S·(100-t)P2S5, where 70≤t≤80;

[0098] uLiI·vLiBr·(100-uv)·(wLi2S·(100-w)P2S5), where 70≤w≤80, 0≤u≤30, and 0≤v≤30.

[0099] In one possible implementation, the aforementioned Li3N and Li j X k The mass ratio of MX to sulfide electrolyte is 0.1-30%.

[0100] It should be understood that suitable Li3N and Li j X k Furthermore, the mass ratio of MX to sulfide electrolyte can ensure the isolation effect of the modified layer while also ensuring higher performance of the sulfide electrolyte (such as ionic conductivity).

[0101] Optionally, the particle size of the sulfide electrolyte is 0.5 μm ≤ D 50 ≤20μm. It should be understood that selecting sulfide electrolytes with smaller particle sizes can ensure that the resulting surface-modified sulfide electrolytes have smaller particle sizes, thereby enabling them to be better dispersed in the positive electrode active material when applied to the battery positive electrode, shortening the lithium ion transport path during cycling, and further optimizing the ion transport efficiency inside the electrode.

[0102] In practical applications, the above-mentioned "pre-prepared ratio of Li3N and Li" j X k Both "thoroughly mixing MX" and "mixing the modified layer precursor with the sulfide electrolyte" can be achieved using wet mixing or dry mixing methods.

[0103] Among them, wet mixing refers to the process of mixing solid materials (i.e., Li3N, Li) with water during the mixing process. j X k A mixing process in which a liquid medium is added to (MX) and the solid material is fully dispersed in the liquid through stirring, grinding and other methods.

[0104] Dry mixing refers to a mixing process in which solid materials are directly contacted and dispersed in a dry state using only mechanical force (such as stirring, grinding, shearing, vibration, etc.).

[0105] As a specific example, the process of preparing surface-modified sulfide electrolytes using a dry mixing method is as follows:

[0106] Li3N and Li were weighed according to the preset ratio.j X k and MX are put into a ball mill tank for ball milling mixing treatment to obtain the modification layer precursor;

[0107] The sulfide electrolyte is added into a ball mill tank, and the modification layer precursor is ball-mixed with the sulfide electrolyte to coat the modification layer precursor on the surface of the sulfide electrolyte to form a modification layer, thereby obtaining the surface-modified sulfide electrolyte.

[0108] It should be understood that the ball milling treatment can mix Li3N, Li j X k and MX into high energy for reaction, thereby obtaining the modification layer precursor. Further, by ball-mixing the modification layer precursor with the sulfide electrolyte, the modification layer precursor can be uniformly coated on the surface of the sulfide electrolyte to form a uniform and dense modification layer, thereby ensuring that the sulfide electrolyte is completely coated.

[0109] Optionally, the rotation speed of the ball-mixing treatment is 200-750 rpm; and / or, the ball-mixing treatment time is 4-24 h.

[0110] For example, the rotation speed of the ball-mixing treatment is 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, 650 rpm, 700 rpm, 750 rpm, or any two of the above values are selected to form a new range, and the values in the new range are taken; and / or, the ball-mixing treatment time is 4 h, 6 h, 8 h, 10 h, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h, or any two of the above values are selected to form a new range, and the values in the new range are taken.

[0111] It should be noted that the above "ball-mixing treatment of Li3N, Li j X k and MX" is to make the raw materials fully react, and the above "ball-mixing treatment of the modification layer precursor and the sulfide electrolyte" is to coat the modification layer precursor on the surface of the sulfide electrolyte. It can be seen that the two mixing processes have different processing requirements, and therefore the rotation speed and time of the two ball-mixing treatments are different. In actual application, the rotation speed condition of the "ball-mixing treatment of Li3N, Li j X k and MX" is usually higher and the time is longer.

[0112] As another specific example, the implementation process of preparing the surface-modified sulfide electrolyte by the wet mixing method is as follows:

[0113] Li3N, Li j X k , MX and the solvent into a ball mill tank for ball milling mixing treatment to obtain a modification layer precursor;

[0114] The sulfide electrolyte is added into the ball mill tank, and the modification layer precursor is ball-mixed with the sulfide electrolyte to coat the modification layer precursor on the surface of the sulfide electrolyte to obtain wet mixing;

[0115] The wet mixing is subjected to drying treatment to form a modification layer on the surface of the sulfide electrolyte to obtain a surface-modified sulfide electrolyte.

[0116] Optionally, the solvent is at least one of anisole, toluene, xylene, heptane, carbon tetrachloride, isobutyl isobutyrate, tetrahydrofuran, acetonitrile, n-butanol, isopropyl alcohol, and ethanol.

[0117] Specifically, the solvent can be one of anisole, toluene, xylene, heptane, carbon tetrachloride, isobutyl isobutyrate, tetrahydrofuran, acetonitrile, n-butanol, isopropyl alcohol, and ethanol, or a combination of any two or more thereof.

[0118] It should be noted that after the wet mixing is obtained by mixing the above-mentioned solid substances with the solvent, the wet mixing needs to be subjected to drying treatment to volatilize the solvent therein.

[0119] Optionally, the temperature of the drying treatment is 70-200℃, and / or the time of the drying treatment is 5-24h. For example, the temperature of the drying treatment is 70℃, 90℃, 110℃, 130℃, 150℃, 170℃, 190℃, 200℃, or any two of the foregoing values are selected to form a new range, and the values taken within the new range, and / or the time of the drying treatment is 5h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h, or any two of the foregoing values are selected to form a new range, and the values taken within the new range.

[0120] The surface-modified sulfide electrolyte provided by the embodiment of the present application is first obtained by mixing Li3N, Li j X k and MX in a predetermined ratio to make the three raw material components uniformly dispersed and react to generate a modification layer precursor; then the modification layer precursor is mixed with the sulfide electrolyte to make the precursor uniformly adhere to the surface of the sulfide electrolyte by mechanical action such as contact and adsorption during the mixing process, forming a continuous and dense modification layer structure, and finally obtaining a surface-modified sulfide electrolyte capable of isolating the side reaction with the positive active material.

[0121] Further, the third embodiment of the present application provides a positive electrode film, which comprises a positive electrode active material, a binder, a conductive agent, and a solid-state electrolyte, wherein the solid-state electrolyte is the surface-modified sulfide electrolyte in the above-mentioned embodiments.

[0122] It should be understood that, in the positive electrode film, the modification layer coated on the sulfide electrolyte in the solid-state electrolyte can isolate the side reaction between the sulfide electrolyte and the positive electrode active material.

[0123] The materials of the above-mentioned positive electrode active material, conductive agent, and binder can be the materials commonly used in lithium ion batteries. Specifically, the conductive agent can be selected from at least one of carbon black, acetylene black, graphene, ketjen black, and carbon fiber; and the binder can be selected from at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polyethylene, polypropylene, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, an oxirane-containing polymer, polyvinylpyrrolidone, and polyurethane.

[0124] According to an implementation manner of the present application, the positive electrode active material comprises at least one of:

[0125] LiCoO2; LiMnO2; LiNiO2; LiVO2;

[0126] LiNi a Co b Mn c O2, wherein a+b+c=1, 0≤a<1, 0≤b<1, 0≤c<1;

[0127] LiNi x Co y Al z O2, wherein x+y+z=1, 0≤x<1, 0≤y<1, 0≤z<1;

[0128] nLi2MnO3·(1-n)LiTMO2, wherein 0

[0129] LiMn2O4; Li4Ti5O 12 ; Li(Ni 0.5 Mn 1.5 )O4; LiFePO4; LiMnPO4; LiNiPO4; LiCoPO4;

[0130] LiMn m Fe 1-m PO4, wherein 0

[0131] Specifically, in the preparation of the positive electrode film, for example, the conductive agent, the positive electrode active material, the binder and the surface-modified sulfide electrolyte can be mixed in an inert gas, and then the positive electrode film is prepared by a rolling film process.

[0132] The surface-modified sulfide electrolyte in the positive electrode film is dispersed in the positive electrode active material, which can construct lithium ion channels, ensure the ion transmission efficiency of the positive electrode, and has good interface stability with the positive electrode active material, thereby ensuring the performance of each material.

[0133] Further, the fourth embodiment of the present application provides a full solid-state battery, which comprises a positive electrode, an electrolyte layer and a negative electrode; the positive electrode comprises a positive electrode current collector and a positive electrode film arranged on the surface of the positive electrode current collector;

[0134] The positive electrode film is the positive electrode film provided in the above embodiments. In addition, the positive electrode current collector can be a commonly used material for lithium ions, such as at least one of aluminum foil and nickel foil.

[0135] The negative electrode specifically comprises a negative electrode current collector and a negative electrode film arranged on the surface of the negative electrode current collector. For example, the negative electrode current collector can be at least one of copper foil, foamed nickel and foamed copper.

[0136] In the preparation of the negative electrode film, the negative electrode active material can be mixed with the conductive agent and the binder to press the negative electrode film. For example, the conductive agent can be at least one of natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber and graphene; and the binder can be at least one of carboxymethyl cellulose, butadiene rubber, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing oxirane, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyvinyl alcohol and sodium polyacrylate.

[0137] As a specific example, the above full solid-state battery can be prepared by the following method:

[0138] The electrolyte is mixed with the binder to press the electrolyte layer. The raw material of the electrolyte layer (i.e. the electrolyte) is preferably a sulfide electrolyte.

[0139] The above positive electrode current collector, positive electrode film, electrolyte layer, negative electrode film and negative electrode current collector are stacked in order and then pressed to obtain a battery cell, and finally packaged to obtain a full solid-state battery.

[0140] The full solid-state battery provided by the embodiments of the present application has excellent interface stability between the positive electrode active material and the surface-modified sulfide electrolyte in the positive electrode, so that the battery has a lower interface impedance, and further has good comprehensive performance, such as cycle performance and rate performance.

[0141] Embodiment four of the present application provides a power consuming device, comprising a power consuming device body and the solid-state battery provided by the present application.

[0142] It should be noted that the present application does not particularly limit the type of power consuming device, which can be any power consuming equipment including the battery, including but not limited to electric vehicles, mobile phones, portable devices, notebook computers, electric bicycles, electric toys, energy storage devices, etc.

[0143] The present application will be further described below through specific embodiments.

[0144] Embodiment 1

[0145] Anisole was used as a solvent, 0.1109 g of Li3N, 0.0337 g of LiCl and 1.8553 g of ZrCl4 were weighed in a ball milling jar, and ball milling mixing treatment was performed, wherein the rotation speed of the ball milling mixing treatment was 600 rpm, and the time was 20 h; D 50 The sulfide electrolyte Li 5.5 PS 4.5 Cl 1.5 The material 10 g was subjected to ball milling mixing treatment, and then dried to obtain the surface modified sulfide electrolyte Li 1.3 ZrN 0.4 Cl 4.1 @Li 5.5 PS 4.5 Cl 1.5 , wherein the rotation speed of the ball milling mixing treatment was 550 rpm, the time was 2 h, the temperature of the drying treatment was 110°C, and the time was 12 h.

[0146] Embodiment 2:

[0147] 1.0920 g of TaCl5, 0.1034 g of LiCl, 0.7105 g of ZrCl4, 0.0212 g of Li3N and 0.0729 g of Li2O were weighed in a ball milling jar, and ball milling mixing treatment was performed, wherein the rotation speed of the ball milling mixing treatment was 650 rpm, and the time was 18 h; D 50 The sulfide electrolyte Li 10 GeP2S 12 The material 10 g was subjected to ball milling mixing treatment to obtain the surface modified sulfide electrolyte Li 1.5 Zr 0.5 Ta 0.5 Cl 4.9 O 0.4 N 0.1 @Li 10 GeP2S12 wherein the rotation speed of the ball-milling mixing treatment is 600 rpm and the time is 1 h.

[0148] Example 3:

[0149] Li3N, 0.0872 g of LiBr, 2.1051 g of ZrCl4, and 0.1679 g of ZrF4 were weighed into a ball mill jar, and a ball-milling mixing treatment was performed thereon, wherein the rotation speed of the ball-milling mixing treatment was 700 rpm and the time was 16 h; D 50 A sulfide electrolyte 15LiBr·10LiI·75(0.75Li2S·0.25P2S5) material 10 g with a particle size of 2 μm was subjected to a ball-milling mixing treatment to obtain a surface-modified sulfide electrolyte Li 1.3 ZrN 0.4 Cl 3.8 F 0.4 @15LiBr·10LiI·75(0.75Li2S·0.25P2S5), wherein the rotation speed of the ball-milling mixing treatment was 650 rpm and the time was 1 h.

[0150] Example 4:

[0151] Li3N, 0.0872 g of LiBr, 2.1051 g of ZrCl4, and 0.1679 g of ZrF4 were weighed into a ball mill jar, and a ball-milling mixing treatment was performed thereon, wherein the rotation speed of the ball-milling mixing treatment was 700 rpm and the time was 16 h; D i3 N and 0.9596 g of TaCl5 were weighed into a ball mill jar, and a ball-milling mixing treatment was performed thereon, wherein the rotation speed of the ball-milling mixing treatment was 750 rpm and the time was 12 h; D 50 A sulfide electrolyte Li 5.4 PS 4.4 Cl 1.6 material 10 g with a particle size of 0.5 μm was subjected to a ball-milling mixing treatment to obtain a surface-modified sulfide electrolyte Li 1.3 N 1.3 / 3 ·TaCl5@Li 5.5 PS 4.5 Cl 1.6 wherein the rotation speed of the ball-milling mixing treatment was 550 rpm and the time was 2 h.

[0152] Comparative Example 1:

[0153] D 50 A sulfide electrolyte Li 5.5 PS 4.5 Cl 1.5 was weighed into a ball mill jar, and a ball-milling mixing treatment was performed thereon, wherein the rotation speed of the ball-milling mixing treatment was 500 rpm and the time was 2 h.

[0154] Comparative Example 2:

[0155] Take 10 g of D 50 sulfide electrolyte Li 10 GeP2S 12 In a ball mill jar, a ball milling mixing process was carried out, wherein the rotation speed of the ball milling mixing process was 600 rpm, and the time was 1 h.

[0156] Comparative Example 3:

[0157] Take 10 g of D 50 sulfide electrolyte 15LiBr·10LiI·75(0.75Li2S·0.25P2S5) with a particle size of 2 μm was subjected to a ball milling mixing process in a ball mill jar, wherein the rotation speed of the ball milling mixing process was 650 rpm, and the time was 1 h.

[0158] Comparative Example 4:

[0159] Take 10 g of D 50 sulfide electrolyte Li 5.4 PS 4.4 Cl 1.6 In a ball mill jar, a ball milling mixing process was carried out, wherein the rotation speed of the ball milling mixing process was 550 rpm, and the time was 2 h.

[0160] The solid-state electrolytes obtained in the above examples and comparative examples were subjected to the following performance tests:

[0161] 1. Ionic conductivity: 150 mg of powder was weighed and placed in a battery mold (inner diameter 10 mm), a pressure of 400 MPa was applied, and an electrochemical workstation was used to test the alternating current impedance, an external voltage of 10 mV was applied in the frequency range of 1 Hz to 7 MHz. The ionic conductivity of the solid-state electrolyte was calculated, and the test results are shown in Table 1.

[0162] 2. Test of battery cycle performance:

[0163] 1) Preparation of all-solid-state battery:

[0164] Preparation of positive electrode film: The prepared solid-state electrolyte was added with conductive agent VGCF and positive electrode active material, and was subjected to a ball milling mixing process in an argon atmosphere at a rotation speed of 300 rpm for 2 h, then a further mixing process was carried out after adding adhesive PTFE, and a rolling film process was carried out to obtain a positive electrode film; wherein the mass of the solid-state electrolyte, VGCF and PTFE was 20%, 2% and 0.05% of the total mass, respectively.

[0165] Preparation of electrolyte layer: sulfide electrolyte Li 5.5 PS 4.5 Cl 1.5 was mixed with adhesive PTFE in a ratio of 99:1 and rolled into an electrolyte layer.

[0166] Preparation of negative electrode film:

[0167] The graphite, sulfide electrolyte Li6PS5Cl and binder PTFE were mixed in a ratio of 60:40:1 and then rolled to prepare the negative electrode film.

[0168] Preparation of battery:

[0169] The battery was assembled in the order of negative electrode current collector, negative electrode film, electrolyte layer, positive electrode film, positive electrode current collector, and packaged into a full solid-state battery.

[0170] It should be noted that all the above preparation processes are carried out in an environment with a dew point < -50℃ to avoid side reactions of the electrolyte.

[0171] 2) Test of cycle performance:

[0172] First charge-discharge test: The full solid-state battery was tested for 1 cycle at 0.1C constant current charge-discharge at 25℃, and the voltage range was 2.7-4.3V. The test results are shown in Table 2.

[0173] Long cycle test: The full solid-state battery was tested for 100 cycles at 0.1C constant current charge-discharge at 25℃, and the voltage range was 2.7-4.3V. The test results are shown in Table 1.

[0174] Table 2 Test results of ionic conductivity of solid-state electrolyte

[0175]

[0176] According to the data in Table 1, the ionic conductivity of the modified solid-state electrolyte in Examples 1-4 is significantly higher than that of the unmodified solid-state electrolyte in Comparative Examples 1-4. It can be seen that the surface-modified sulfide electrolyte provided by the present application has good ionic conductivity, and the introduction of the modification layer does not cause the overall ionic conductivity of the electrolyte to decrease.

[0177] Table 2 Test results of cycle performance of full solid-state battery

[0178]

[0179] According to the data in Table 2, the initial discharge specific capacity, the first coulombic efficiency and the capacity retention rate after 100 cycles of the modified solid-state electrolyte in Examples 1-4 are significantly higher than those of the unmodified solid-state electrolyte in Comparative Examples 1-4. It can be seen that the surface-modified sulfide electrolyte provided by the present application can significantly improve the cycle performance of the battery.

[0180] In conclusion, the surface modified sulfide electrolyte, the preparation method thereof and the all-solid-state battery provided by the present application avoid direct contact between the sulfide electrolyte and the positive active material through the modification layer on the surface of the sulfide electrolyte, the modification layer has high ion conductivity and will not affect the overall ion conductivity of the electrolyte, in addition, the modification layer has high oxidation potential and strong high oxidation resistance, can alleviate the decomposition of the sulfide electrolyte under high voltage, reduce the side reaction of the sulfide and the transition metal elements in the positive active material and in the high-voltage charging and discharging process, is conducive to improving the interface stability between the positive active material and the sulfide electrolyte, reducing the interface impedance of the battery, and then improving the cycle performance and rate performance of the all-solid-state battery.

[0181] It should be understood, however, that the scope of the present application is not limited to the specific embodiments described herein, but includes any and all modifications, and equivalents thereof, within the scope of the present application. The present application is based on Japanese priority patent application No. 2018- 230, 1 filed on December 19, 2018 and Japanese priority patent application No. 2019- 230, 1 1 filed on December 19, 2019, the contents of which are incorporated herein by reference in their entirety.

Claims

1. A surface-modified sulfide electrolyte, characterized in that, include: Sulfide electrolyte and the modification layer coating the surface of the sulfide electrolyte; The chemical formula of the modified layer is Li. a M b N c X d Wherein, 0≤a≤3, 0≤b≤1, 0≤c≤1, 0≤d≤6, M is at least one element selected from magnesium, aluminum, calcium, iron, zirconium, niobium, tantalum, tungsten, gadolinium, yttrium, indium, hafnium, lanthanum, and ytterbium, and X is at least one element selected from oxygen, sulfur, fluorine, chlorine, bromine, and iodine.

2. The surface-modified sulfide electrolyte according to claim 1, characterized in that, The sulfide electrolyte includes at least one of the following: Li x AP y S z Where 0 < x, 0 < y, 0 < z, and A is at least one element selected from tin, germanium, and silicon; Li 7-m-n PS 6-m-n Cl m R n , where 0≤m, 0≤n, and R is at least one element selected from fluorine, bromine, and iodine; tLi2S·(100-t)P2S5, where 70≤t≤80; uLiI·vLiBr·(100-uv)·(wLi2S·(100-w)P2S5), where 70≤w≤80, 0≤u≤30, and 0≤v≤30.

3. The surface-modified sulfide electrolyte according to claim 1 or 2, characterized in that, In the surface-modified sulfide electrolyte, the mass ratio of the modification layer to the sulfide electrolyte is 0.1~30%.

4. The surface-modified sulfide electrolyte according to claim 1 or 2, characterized in that, The sulfide electrolyte has a particle size of 0.5 μm ≤ D 50 ≤20μm.

5. A method for preparing a surface-modified sulfide electrolyte as described in any one of claims 1 to 4, characterized in that, The method includes: The pre-mixed ratio of Li3N and Li j X k And MX are thoroughly mixed to obtain the precursor of the modified layer; The modified layer precursor is mixed with the sulfide electrolyte so that the modified layer precursor adheres to the surface of the sulfide electrolyte to form a modified layer, thereby obtaining a surface-modified sulfide electrolyte. Where M is any one of the elements selected from magnesium, aluminum, calcium, iron, zirconium, niobium, tantalum, tungsten, gadolinium, yttrium, indium, hafnium, lanthanum, and ytterbium, and X is any one of the elements selected from oxygen, sulfur, fluorine, chlorine, bromine, and iodine.

6. The method according to claim 5, characterized in that, The Li j X k It is at least one of LiF, LiCl, LiBr, LiI, Li2O, Li2O2, and Li2S; And / or, The MX is at least one of MgCl2, MgF2, AlCl3, AlF3, CaCl2, FeCl2, FeCl3, ZrCl4, ZrF4, NbF5, NbCl5, TaF5, TaCl5, TaBr5, WCl6, WBr6, WI6, GdCl3, GdBr3, GdF3, GaCl3, GaBr3, GaF3, YCl3, YBr3, YF3, InCl3, HfCl4, LaCl3, and YbCl3.

7. The method according to claim 5, characterized in that, The sulfide electrolyte includes at least one of the following: Li x AP y S z Where 0 < x, 0 < y, 0 < z, and A is at least one element selected from tin, germanium, and silicon; Li 7-m-n PS 6-m-n Cl m R n , where 0≤m, 0≤n, and R is at least one element selected from fluorine, bromine, and iodine; tLi2S·(100-t)P2S5, where 70≤t≤80; uLiI·vLiBr·(100-uv)·(wLi2S·(100-w)P2S5), where 70≤w≤80, 0≤u≤30, and 0≤v≤30.

8. The method according to any one of claims 5 to 7, characterized in that, The Li3N, Li j X k The mass ratio of MX to the sulfide electrolyte is 0.1-30%.

9. The method according to any one of claims 5 to 7, characterized in that, The sulfide electrolyte has a particle size of 0.5 μm ≤ D 50 ≤20μm.

10. The method according to any one of claims 5 to 7, characterized in that, The pre-mixed ratio of Li3N and Li j X k And MX are thoroughly mixed to obtain the modified layer precursor, including: Li3N and Li were weighed according to the preset ratio. j X k MX was placed in a ball mill jar for ball milling and mixing to obtain the precursor of the modified layer; Accordingly, the step of mixing the modified layer precursor with the sulfide electrolyte to coat the surface of the sulfide electrolyte with the modified layer precursor to form a modified layer, thereby obtaining a surface-modified sulfide electrolyte, includes: The sulfide electrolyte is added to the ball milling jar, and the modification layer precursor and the sulfide electrolyte are ball milled and mixed to coat the surface of the sulfide electrolyte with the modification layer precursor to form the modification layer, thereby obtaining a surface-modified sulfide electrolyte. or, The pre-mixed ratio of Li3N and Li j X k And MX are thoroughly mixed to obtain the modified layer precursor, including: Li3N and Li were weighed according to the preset ratio. j X k MX and solvent are placed in a ball mill jar for ball milling and mixing to obtain the modified layer precursor; Accordingly, the step of mixing the modified layer precursor with the sulfide electrolyte to coat the surface of the sulfide electrolyte with the modified layer precursor to obtain the surface-modified sulfide electrolyte includes: The sulfide electrolyte is added to the ball mill jar, and the modified layer precursor and the sulfide electrolyte are ball-milled and mixed to coat the surface of the sulfide electrolyte with the modified layer precursor, thus obtaining a wet mixture. The wet mixture is dried to form the modification layer on the surface of the sulfide electrolyte, thereby obtaining the surface-modified sulfide electrolyte.

11. The method according to claim 10, characterized in that, The ball milling mixing process is performed at a speed of 200-750 rpm; and / or the ball milling mixing process is performed for a time of 4-24 hours.

12. The method according to claim 10, characterized in that, The solvent is at least one selected from anisole, toluene, xylene, heptane, carbon tetrachloride, isobutyl isobutyrate, tetrahydrofuran, acetonitrile, n-butanol, isopropanol, and ethanol. And / or, the drying temperature is 70~200℃; and / or, the drying time is 5~24h.

13. A positive electrode membrane, characterized in that, The positive electrode membrane includes a positive electrode active material, a binder, a conductive agent, and a solid electrolyte, wherein the solid electrolyte is a surface-modified sulfide electrolyte as described in any one of claims 1 to 4, or the solid electrolyte is a surface-modified sulfide electrolyte prepared by the method described in any one of claims 5 to 12.

14. The positive electrode film according to claim 13, characterized in that, The positive electrode active material includes at least one of the following: LiCoO2; LiMnO2; LiNiO2; LiVO2; LiNi a Co b Mn c O2, where a+b+c=1, 0≤a<1, 0≤b<1, 0≤c<1; LiNi x Co y Al z O2, where x+y+z=1, 0≤x<1, 0≤y<1, 0≤z<1; nLi2MnO3·(1-n)LiTMO2, where 0<n<1, and TM is any one of nickel, manganese, cobalt, and aluminum; LiMn2O4;Li4Ti5O 12 ;Li (Ni 0.5 Mn 1.5 )O4;LiFePO4;LiMnPO4;LiNiPO4;LiCoPO4; LiMn m Fe 1-m PO4, where 0 < m < 1.

15. An all-solid-state battery, characterized in that, It includes a positive electrode, an electrolyte layer, and a negative electrode; the positive electrode includes a positive electrode current collector and a positive electrode membrane disposed on the surface of the positive electrode current collector; Wherein, the positive electrode film is the positive electrode film as described in claim 13 or 14.

16. The all-solid-state battery according to claim 15, characterized in that, The raw material for the electrolyte layer includes sulfide electrolytes.

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