Halide solid electrolyte stable to negative electrode, preparation method of halide solid electrolyte and solid-state battery

Abstract

The invention provides a halide solid electrolyte stable to a negative electrode, a preparation method of the halide solid electrolyte and a solid-state battery. The structural formula of the halide solid electrolyte is (LinX) aMBy, in the structural formula, the LinX comprises at least one of LiNO3, Li3PO4, Li4SiO4 and LiPF6, and the LiPF6 is at least one of LiNO3, Li3PO4, Li4SiO4 and LiPF6. M is at least one of Zr, Hf, Ta, Nb, Al, Y, Fe and Ga; b is at least one of F, Cl, Br and I; n, a and y are stoichiometric coefficients, 0.5 lt; a < lt >; and y is 3, 4 or 5. The halide solid electrolyte can stably work on the negative electrode side, and is particularly suitable for constructing a high-energy-density and high-safety solid-state battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery materials, and particularly relates to a halide solid-state electrolyte stable to a negative electrode, a preparation method thereof and a solid-state battery. BACKGROUND

[0002] High-energy-density and high-safety secondary batteries are key technologies for the development of high-tech industries such as large-scale energy storage facilities, new energy vehicles, 5G and AI terminals. Solid-state batteries have the advantages of significantly improving energy density and power density due to their potential in multi-layer stacking and matching with lithium metal or silicon negative electrodes. As a core material of solid-state batteries, inorganic solid-state electrolytes are the key to realizing the practicality of solid-state batteries, and the development of inorganic solid-state electrolytes with high ionic conductivity and a wide electrochemical stability window is crucial.

[0003] Inorganic solid-state electrolytes are mainly divided into three categories of oxides, sulfides and halides according to the framework anion. Halide solid-state electrolytes have become the main competitor in the field of solid-state electrolytes due to their excellent oxidation stability, high room-temperature ionic conductivity, and the advantages of not reacting with air to release toxic gases. Since Panasonic first reported Li3YCl6 in 2018, the ionic conductivity of halide solid-state electrolytes has increased from 10 -3 S / cm to 10 -2 S / cm, close to the level of liquid electrolytes and sulfide solid-state electrolytes. In addition, due to the strong oxidation resistance of chlorine / flourine elements, halide solid-state electrolytes can be directly matched with 4V oxide positive electrodes. However, the lower reduction stability of halide solid-state electrolytes is still a bottleneck for their large-scale application, mainly due to the presence of easily reduced high-valence metal ions in halide solid-state electrolytes, which leads to thermodynamic instability between them and lithium metal negative electrodes. Therefore, a layer of sulfide electrolyte is needed to separate the lithium metal negative electrode and the halide electrolyte layer in the current solid-state battery using halide electrolyte, resulting in a complex structure and reduced battery energy density.

[0004] In view of the multiple advantages of halide solid-state electrolytes and the importance of lithium metal negative electrodes in high-energy-density solid-state batteries, it is of important technical value and application prospect to develop a halide solid-state electrolyte material that has high ionic conductivity, electrochemical stability, and can work stably on the negative electrode side. SUMMARY

[0005] In view of the poor stability of halide solid-state electrolytes in the interface of metal lithium and other negative electrodes in the prior art, the application provides a halide solid-state electrolyte stable to a negative electrode, a preparation method thereof and a solid-state battery. The halide solid-state electrolyte can work stably on the negative electrode side, and is particularly suitable for constructing high-energy-density and high-safety solid-state batteries.

[0006] The application is achieved by the following technical solutions: In a first aspect, the application provides a halide solid-state electrolyte stable to a negative electrode, the halide solid-state electrolyte having a structural formula of (Li n X) a MB y ; In the structural formula, Li n X includes at least one of LiNO3, Li3PO4, Li4SiO4 and LiPF6; M is at least one of Zr, Hf, Ta, Nb, Al, Y, Fe and Ga; B is at least one of F, Cl, Br and I; n, a and y are stoichiometric coefficients, 0.5 < a < 3, and y is 3, 4 or 5.

[0007] Preferably, Li n X further includes at least one of Li2S, LiF and LiI.

[0008] Preferably, M is at least one of Zr and Hf.

[0009] Preferably, (Li n X) a MB y is (LiNO3)HfCl4, (LiNO3)(Li2S) 1 / 2 HfCl4, (LiNO3)(LiI) 1 / 2ZrCl4, (Li4SiO4) 1 / 4 (LiPF6) 1 / 2 HfCl4, (LiNO3)(Li2S) 1 / 2 ZrCl4 or (Li3PO4) 1 / 3 (Li2S) 1 / 2 ZrCl4.

[0010] In a second aspect, the application provides a preparation method of the halide solid-state electrolyte stable to a negative electrode, comprising the following steps: S1, mixing a lithium salt Li n X with a halide precursor MB y to obtain a mixture; S2, ball milling the mixture to cause a solid-phase reaction, thereby obtaining the halide solid-state electrolyte (Li n X) a MB y .

[0011] Preferably, S1 specifically comprises: mixing the lithium salt Li n X with the halide precursor MB y in an inert atmosphere free of water and oxygen to obtain the mixture; S2 is specifically: placing the mixture in a ball mill jar, adding grinding beads, vacuumizing and sealing the ball mill jar, ball milling to cause solid phase reaction, obtaining halide solid electrolyte (Li n X) a MB y .

[0012] Preferably, in S2, the ball milling speed is 400-800 rpm, and the ball milling time is 1-30 h.

[0013] In a third aspect, the application provides a solid-state battery, comprising a positive electrode sheet, a negative electrode sheet, and a solid-state electrolyte layer between the positive electrode sheet and the negative electrode sheet, the material of the solid-state electrolyte layer being the halide solid electrolyte stable to the negative electrode.

[0014] Preferably, the components of the positive electrode sheet include a positive electrode active material and a positive electrode filler; the positive electrode filler is a combination of one or more of an ion-conducting agent, an electrically conductive agent, and a binder; the ion-conducting agent is the same material as the solid-state electrolyte layer.

[0015] Preferably, the components of the negative electrode sheet include a negative electrode active material, the negative electrode active material being a metal material or a non-metal material, and when the negative electrode active material is a non-metal material, the components of the negative electrode sheet further include a negative electrode filler; when the negative electrode active material is a non-metal material, the negative electrode filler is a combination of one or more of an ion-conducting agent, an electrically conductive agent, and a binder; the ion-conducting agent is the same material as the solid-state electrolyte layer.

[0016] Compared with the prior art, the application has the following beneficial effects: In view of the problem that halide solid electrolyte materials are easily reduced and decomposed at low potential, resulting in the halide solid electrolyte being unable to directly match the negative electrode, the halide solid electrolyte provided by the application has a reaction product of extremely low electronic conductivity when reacting with the lithium metal negative electrode, and these components can block the electronic path, thereby inhibiting the oxidation-reduction reaction between the halide solid electrolyte and the negative electrode, so as to realize the compatibility of the halide solid electrolyte and the negative electrode. The halide solid electrolyte material provided by the application has amorphous characteristics, and compared with the crystalline halide solid electrolyte, the composition and content in the amorphous halide solid electrolyte can be freely adjusted, so as to adjust the compactness and ionic conductivity of the passivation layer by adjusting the type and content of lithium salt. The halide solid electrolyte of the application can match common positive electrode materials while realizing the compatibility with the negative electrode.

[0017] Further, Zr, Hf, and Al are less likely to have reduction reaction on the surface of the negative electrode and are more likely to realize the passivation effect on the surface of the negative electrode due to their lower oxidation-reduction potential compared with Ta, Nb, Fe, and Ga.

[0018] The preparation method of the halide solid electrolyte of the present invention is achieved through a simple solid-phase reaction, has a simple process, is easy to operate, and is suitable for large-scale production.

[0019] Furthermore, in the preparation method of the halide solid electrolyte of the present invention, the lithium salt Li n X and halide precursor MB y Mixing in an inert atmosphere without water or oxygen can prevent oxidation of the lithium salt, thereby reducing the generation of impurities and improving the purity of the product.

[0020] In the solid-state battery of the present invention, the halide solid electrolyte compatible with the negative electrode of the present invention can be directly used without using a double-layer combination of a halide solid electrolyte and a sulfide solid electrolyte, which can simplify the battery assembly process and improve the battery energy density. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 The halide solid electrolyte (LiNO3) (Li2S) synthesized in Example 2 1 / 2 Electrochemical impedance spectrum of HfCl4 at room temperature; in the figure, the horizontal axis represents the real resistance, the unit is ohm (Ω); the vertical axis represents the imaginary resistance, the unit is ohm (Ω).

[0023] Figure 2 The halide solid electrolyte (LiNO3) (Li2S) synthesized in Example 2 1 / 2 X-ray diffraction spectrum of HfCl4. In the figure, the horizontal axis represents the diffraction angle (2 Theta) in degrees (°); the vertical axis represents the diffraction intensity.

[0024] Figure 3 This is the X-ray diffraction spectrum of the halide solid electrolyte Li2HfCl6 synthesized in Comparative Example 1. In the figure, the abscissa represents the diffraction angle (2 Theta), in degrees (°); the ordinate represents the diffraction intensity.

[0025] Figure 4 is the critical current density when the halide solid electrolyte is matched with the lithium metal negative electrode, the horizontal axis represents time, the unit is hour (h), and the vertical axis represents voltage, the unit is volt (V); Figure 5The first three weeks of charge-discharge curves at 0.1 C rate for the solid-state battery provided in Example 1. In the figure, the abscissa represents the specific capacity in milliampere hours per gram (mAh g -1 ); the ordinate represents the voltage (voltage vs. Li+ / Li) in volts (V). DETAILED DESCRIPTION

[0026] Other advantages and benefits of the present application will become apparent to those skilled in the art upon consideration of the disclosure or can be learned by practice of the application. The present application can be realized and achieved by means of the structures and combinations described in this specification and it is therefore to be understood that various embodiments can be made without departing from the scope of the present application.

[0027] It should be noted that the process equipment or devices not specifically mentioned in the following examples are all conventional equipment or devices in the art.

[0028] It should be noted that the terms "comprising" and "having" and any variations thereof are intended to cover a non-exclusive inclusion, for example, a process, method, system, product or apparatus that includes a list of steps or units not necessarily limited to those explicitly listed, but can include other steps or units not expressly listed or inherent to such processes, methods, products or apparatus. In addition, unless otherwise specified, the numbering of the method steps is only a convenient tool for identifying the method steps, and is not intended to limit the arrangement order of the method steps or to limit the scope of the application, and changes or adjustments of the relative relationship, without substantial changes in the technical content, are also considered to be within the scope of the application.

[0029] The present application provides a halide solid-state electrolyte stable to a negative electrode, having a structural formula of (Li n X) a MB y ; In the structural formula, Li n X is selected from one or more of components capable of reacting with metallic lithium to form a component conducive to interface stability, specifically, Li n X is at least one of lithium nitrate (LiNO3), lithium phosphate (Li3PO4), lithium silicate (Li4SiO4), and lithium hexafluorophosphate (LiPF6); In the structural formula, MB y is a high-valence transition metal halide, M is at least one of Zr, Hf, Ta, Nb, Al, Fe, and Ga; B is at least one of F, Cl, Br, and I; n, a, and y are stoichiometric coefficients, 0.5 < a < 3, and y is 3, 4, or 5.

[0030] The halide solid-state electrolyte described in the present application is in an amorphous state or a glass-ceramic state, contains a Li+ conductive network, is rich in Li-X (X=NO3, PF6, etc.) and M-Cl (M=Hf, Zr, Ta, etc.) coordination units in the structure, forms a space-connected ion migration channel, and realizes efficient lithium ion conduction. After the halide solid-state electrolyte contacts with metal lithium and its alloy, a passivation layer with a multiphase composite structure containing an oxide compound can be formed on the surface of the metal lithium and its alloy, realizing the stability of the halide electrolyte to the metal lithium and its alloy. Specifically, the halide solid-state electrolyte described in the present application contains a large amount of Li-X (X=NO3, PF6, etc.), and when a reduction reaction occurs on the surface of the lithium metal negative electrode, a large amount of electron-insulating components (such as LiNO3, etc.) are contained in the interface layer generated, so that the electron transmission between the negative electrode and the halide electrolyte can be isolated, and the chemical stability to the metal lithium negative electrode can be realized. In some preferred embodiments of the present application, Li n X can further include at least one of lithium sulfide (Li2S), lithium fluoride (LiF), and lithium iodide (LiI), so as to improve the ionic conductivity of the halide solid-state electrolyte.

[0031] In some preferred embodiments of the present application, the structural formula is (Li n X) a MB y M is at least one of Zr and Hf.

[0032] As a specific example, in the present application, (Li n X) a MB y is (LiNO3)HfCl4, (LiNO3)(Li2S) 1 / 2 HfCl4, (LiNO3)(LiI) 1 / 2 ZrCl4, (Li4SiO4) 1 / 4 (LiPF6) 1 / 2 HfCl4, (LiNO3)(Li2S) 1 / 2 ZrCl4, or (Li3PO4) 1 / 3 (Li2S) 1 / 2 ZrCl4.

[0033] The halide solid-state electrolyte described in the present application has a Li + ionic conductivity of 10 -4 ~10 -3 S / cm at room temperature, and does not have a sustained side reaction when in contact with a metal lithium, graphite, silicon, etc. negative electrode, and has high stability.

[0034] The present application also provides a preparation method of the above-mentioned halide solid-state electrolyte, which comprises the following steps: S1, adding lithium salt Lin X and the halide precursor MB y mixing to obtain a mixture; S2, ball milling the mixture to occur a solid phase reaction to obtain a halide solid-state electrolyte (Li n X) a MB y .

[0035] To avoid oxidation of the lithium salt Li n X, the mixing process in S1 of the present application is preferably carried out in anhydrous and oxygen-free inert atmosphere (such as Ar or N2), specifically: mixing the lithium salt Li n X and the halide precursor MB y in anhydrous and oxygen-free inert atmosphere to obtain a mixture.

[0036] Similarly, to avoid oxidation of the lithium salt Li n X in the solid phase reaction, the ball milling in S2 of the present application is preferably carried out under vacuum conditions, specifically: placing the mixture in a ball milling tank, adding grinding beads, vacuumizing and sealing the ball milling tank, and ball milling to occur a solid phase reaction to obtain a halide solid-state electrolyte (Li n X) a MB y .

[0037] In some preferred embodiments of the present application, in S2, the ball milling process parameters include: (1) the ball milling time is 1-30 h, as specific examples, the ball milling time can be 1 h, 3 h, 5 h, 7 h, 10 h, 15 h, 20 h, 25 h, 30 h, etc.; more preferably, the ball milling time is 1-10 h, further preferably 1-5 h; (2) the ball milling rotation speed is 400-800 rpm, as specific examples, the ball milling rotation speed can be 400 r / min, 500 r / min, 600 r / min, 700 r / min, 800 r / min, etc.; (3) the ball-to-material ratio is 20:1-60:1, as specific examples, the ball-to-material ratio can be 20:1, 40:1, 60:1, etc.; more preferably, the ball-to-material ratio is 40:1; (4) grinding beads with a diameter of 3-10 mm are used, for example, grinding beads with a diameter of 3 mm, 5 mm, or 8 mm are used; (5) a circulating water cooling method is used in the ball milling process to control the ball milling temperature below 100 o C to prevent crystallization.

[0038] In one specific embodiment of the present application, 3 mm diameter grinding beads are used, the ball-to-material ratio is 40:1, the ball milling rotation speed is 600 rpm, and the ball milling time is 5 h.

[0039] The application can adjust the glass phase / crystal phase ratio of the halide solid-state electrolyte by controlling the raw material ratio and ball milling conditions, including ball milling parameters (ball milling time, rotation speed), raw material ratio, etc. The optimization of each parameter can improve the ionic conductivity of the halide solid-state electrolyte to a certain extent. The higher the relative content of amorphous phase, the higher the Li ion conductivity.

[0040] The application also provides application of the halide solid-state electrolyte material in a solid-state battery.

[0041] The solid-state battery comprises a positive electrode sheet, a negative electrode sheet, and a solid-state electrolyte layer between the positive electrode sheet and the negative electrode sheet. The material of the solid-state electrolyte layer is the halide solid-state electrolyte described above, and the solid-state electrolyte layer can be obtained by cold pressing the halide solid-state electrolyte.

[0042] In some preferred embodiments of the application, the components of the positive electrode sheet comprise a positive electrode active material and a positive electrode filler, and the positive electrode sheet can be obtained by cold pressing or coating the positive electrode active material and the positive electrode filler.

[0043] The positive electrode active material includes but is not limited to cobalt-aluminum oxide, lithium iron phosphate, lithium-rich lithium manganese oxide, lithiated layered oxide, lithiated layered sulfide, or a combination thereof. The positive electrode filler is an ion-conducting agent, an electrically conductive agent, a binder, or a combination thereof. The ion-conducting agent is the same material as the solid-state electrolyte layer. The electrically conductive agent can include graphite, carbon black, acetylene black, ketjen black, carbon fiber, or a combination thereof. The binder can include, for example, styrene-butadiene rubber, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, or a combination thereof. The cold pressing or coating method is a common method for preparing a positive electrode sheet in the art.

[0044] In some preferred embodiments of the application, the components of the negative electrode sheet comprise a negative electrode active material, which refers to a material capable of storing and releasing Li + ions, including but not limited to metal materials, graphite, silicon.

[0045] The negative electrode active material is a metal material or a non-metal material. When the negative electrode active material is a non-metal material (such as graphite or silicon), the components of the negative electrode sheet further comprise a negative electrode filler, and the negative electrode sheet can be obtained by cold pressing or coating the negative electrode active material and the negative electrode filler. The negative electrode filler is a combination of one or more of an ion-conducting agent, an electrically conductive agent, and a binder. The ion-conducting agent is the same material as the solid-state electrolyte layer. The electrically conductive agent can include graphite, carbon black, acetylene black, ketjen black, carbon fiber, or a combination thereof. The binder can include, for example, styrene-butadiene rubber, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, or a combination thereof. The cold pressing or coating method is a common method for preparing a negative electrode sheet in the art.

[0046] Example 1 The embodiment provides a halide solid electrolyte (LiNO3)HfCl4, and a specific preparation method thereof comprises the following steps: (1) in the waterless and oxygenless argon atmosphere glove box, LiNO3 is mixed with HfCl4 in a mass ratio of 1:1, and is hand ground for 10 min by using a agate mortar to fully mix; (2) the mixed powder (1 g) is transferred into a 75 mL ball mill jar, and 40 g of grinding beads with a diameter of 3 mm are added accordingly, then the ball mill jar is vacuumized and sealed; the ball mill jar is ball milled on a planetary ball mill at a rotating speed of 600 r / min for 5 h; after the ball milling is completed, the ball mill jar is transferred into the glove box to be opened, and the powder in the jar is taken out, which is the synthesized (LiNO3)HfCl4 solid electrolyte.

[0047] Embodiment 2 The embodiment provides a halide solid electrolyte (LiNO3)(Li2S) 1 / 2 HfCl4, and a specific preparation method thereof comprises the following steps: (1) in the waterless and oxygenless argon atmosphere glove box, LiNO3, Li2S and HfCl4 are mixed in a mass ratio of 1:1 / 2:1, and are hand ground for 10 min by using a agate mortar to fully mix; (2) the mixed powder (1 g) is transferred into a 75 mL ball mill jar, and 40 g of grinding beads with a diameter of 3 mm are added accordingly, then the ball mill jar is vacuumized and sealed; the ball mill jar is ball milled on a planetary ball mill at a rotating speed of 600 r / min for 5 h; after the ball milling is completed, the ball mill jar is transferred into the glove box to be opened, and the powder in the jar is taken out, which is the synthesized (LiNO3)(Li2S) 1 / 2 HfCl4 solid electrolyte.

[0048] Embodiment 3 The embodiment provides a halide solid electrolyte (LiNO3)(LiI) 1 / 2 ZrCl4, and a specific preparation method thereof comprises the following steps: (1) in the waterless and oxygenless argon atmosphere glove box, LiNO3, LiI and ZrCl4 are mixed in a mass ratio of 1:1 / 2:1, and are hand ground for 10 min by using a agate mortar to fully mix; (2) the mixed powder (1 g) is transferred into a 75 mL ball mill jar, and 40 g of grinding beads with a diameter of 3 mm are added accordingly, then the ball mill jar is vacuumized and sealed; the ball mill jar is ball milled on a planetary ball mill at a rotating speed of 600 r / min for 5 h; after the ball milling is completed, the ball mill jar is transferred into the glove box to be opened, and the powder in the jar is taken out, which is the synthesized (LiNO3)(LiI) 1 / 2 ZrCl4 solid electrolyte.

[0049] Example 4 This example provides a halide solid-state electrolyte (Li3PO4) 1 / 3 (Li2S) 1 / 2 ZrCl4, the specific preparation method comprising the following steps: (1) In anhydrous and anaerobic argon atmosphere glove box, Li3PO4, Li2S and ZrCl4 were mixed in a molar ratio of 1 / 3:1 / 2:1, and ground in a agate mortar for 10 min for sufficient mixing; (2) The mixed powder (1 g) was transferred to a 75 mL ball mill jar, and 40 g of grinding beads with a diameter of 3 mm were added accordingly. The ball mill jar was then vacuumed and sealed. The ball milling was carried out on a planetary ball mill at a speed of 600 r / min for 5 h. After the ball milling was completed, the ball mill jar was transferred to the glove box and opened. The powder in the jar was taken out, which was the synthesized (Li3PO4) 1 / 3 (Li2S) 1 / 2ZrCl4 solid-state electrolyte.

[0050] Example 5 This example provides a halide solid-state electrolyte (Li4SiO4) 1 / 4 (LiPF6) 1 / 2 HfCl4, the specific preparation method comprising the following steps: (1) In anhydrous and anaerobic argon atmosphere glove box, Li4SiO4, LiPF6 and HfCl4 were mixed in a molar ratio of 1 / 4:1 / 2:1, and ground in a agate mortar for 10 min for sufficient mixing; (2) The mixed powder (1 g) was transferred to a 75 mL ball mill jar, and 40 g of grinding beads with a diameter of 5 mm were added accordingly. The ball mill jar was then vacuumed and sealed. The ball milling was carried out on a planetary ball mill at a speed of 600 r / min for 5 h. After the ball milling was completed, the ball mill jar was transferred to the glove box and opened. The powder in the jar was taken out, which was the synthesized (Li4SiO4) 1 / 4 (LiPF6) 1 / 2HfCl4 solid-state electrolyte.

[0051] Example 6 This example provides a halide solid-state electrolyte (LiNO3)(LiI) 1 / 2 ZrCl4, the specific preparation method comprising the following steps: (1) In anhydrous and anaerobic argon atmosphere glove box, LiNO3, LiI and ZrCl4 were mixed in a molar ratio of 1:1 / 2:1, and ground in a agate mortar for 10 min for sufficient mixing; (2) The mixed powder (1 g) was transferred to a 75 mL ball mill jar, and 40 g of grinding beads with a diameter of 3 mm were added accordingly. Then the ball mill jar was vacuumized and sealed. The ball milling was performed on a planetary ball mill at a rotation speed of 400 r / min for 30 h. After the ball milling was completed, the ball mill jar was transferred to the glove box to be opened, and the powder in the jar was taken out, which was the synthesized (LiNO3)(Li2S) 1 / 2 ZrCl4 solid-state electrolyte.

[0052] Example 7 This example provides a halide solid-state electrolyte (LiNO3)(Li2S) 1 / 2 HfCl4 was synthesized according to the preparation method provided in Example 2, with the only difference being that the grinding beads were changed to 8 mm and the ball milling time was changed to 1 h.

[0053] Example 8 This example provides a halide solid-state electrolyte (LiNO3)(Li2S) 1 / 2 HfCl4 was synthesized according to the preparation method provided in Example 2, with the only difference being that the grinding beads were changed to 60 g.

[0054] Example 9 This example provides a halide solid-state electrolyte (LiNO3)(Li2S) 1 / 2 HfCl4 was synthesized according to the preparation method provided in Example 2, with the only difference being that the ball milling time was changed to 10 h.

[0055] Comparative Example 1 This comparative example provides a halide solid-state electrolyte, and the specific preparation method is as follows: In an anhydrous and oxygen-free argon atmosphere glove box, LiCl and HfCl4 were mixed in a molar ratio of 2:1. The mixed powder (1 g) was transferred to a 75 mL ball mill jar, and 40 g of grinding beads with a diameter of 3 mm were added accordingly. Then the ball mill jar was vacuumized and sealed. The ball milling was performed on a planetary ball mill at a rotation speed of 600 r / min for 5 h. After the ball milling was completed, the ball mill jar was transferred to the glove box to be opened, and the powder in the jar was taken out, which was the synthesized Li2HfCl6 halide solid-state electrolyte.

[0056] Application Example 1 This example provides a solid-state lithium metal battery Li-LiNi 0.88 Co 0.09 Mn 0.03 O2 (Li-NMC88) battery, which was assembled using the halide solid-state electrolyte (LiNO3)(Li2S) 1 / 2 HfCl4 provided in Example 2. Step 1: Take 10 mg of the lithium intercalation layered oxide LiNi 0.88 Co 0.09 Mn 0.03 O2(as a positive active material), (LiNO3)(Li2S) 1 / 2 HfCl4(as an ion conductor) and carbon black (as an electron conductor) in a mass ratio of 7:3:0.1, and manually grind them in a mortar for 10 min until they are uniformly mixed to form a composite positive electrode.

[0057] Step 2: Take 100 mg of the (LiNO3)(Li2S) 1 / 2 HfCl4powder synthesized in Example 3, and cold-press it into a solid electrolyte sheet with a diameter of 10 mm at a pressure of 100 MPa for 2 min.

[0058] Step 3: Take 10 mg of the composite positive electrode prepared in Step 1, and uniformly spread it on one side surface of the (LiNO3)(Li2S) 1 / 2 HfCl4solid electrolyte sheet prepared in Step 2, and cold-press it at a pressure of 350 MPa for 2 min.

[0059] Step 4: Use a commercially available lithium sheet (with a diameter of 10 mm and a thickness of 500 μm) as a negative active material, and attach it to the other side surface of the (LiNO3)(Li2S) 1 / 2 HfCl4solid electrolyte sheet prepared in Step 2 to form a three-layer structure of "positive electrode sheet-solid electrolyte sheet-negative electrode sheet", and assemble the whole to obtain a full-solid-state lithium metal battery.

[0060] The steps 1 to 4 are all performed in an argon glove box in anhydrous and oxygen-free atmosphere.

[0061] Application Example 2 This example provides a lithium-lithium symmetric battery Li-Li battery, which is assembled by using the solid electrolyte (LiNO3)(Li2S) 1 / 2 HfCl4provided in Example 2. Step 1: Take 100 mg of the (LiNO3)(Li2S) 1 / 2 HfCl4powder synthesized in Example 2, and cold-press it into a solid electrolyte sheet with a diameter of 10 mm at a pressure of 100 MPa for 2 min.

[0062] Step 2: Use a commercially available lithium sheet (with a diameter of 10 mm and a thickness of 500 μm) to attach it to both side surfaces of the (LiNO3)(Li2S) 1 / 2 HfCl4solid electrolyte sheet prepared in Step 2, and apply a pressure of 10 MPa to the whole to complete the assembly to obtain a lithium-lithium symmetric battery.

[0063] The steps 1~2 are both carried out in anhydrous and anaerobic argon glove box.

[0064] As a control, the Li3InCl6 halide solid electrolyte of Comparative Example 1 is assembled into a lithium-lithium symmetric battery by the same method as in Application Example 2.

[0065] I. Characterization analysis 1. Ion conductivity characterization analysis (1) Characterization method In anhydrous and anaerobic argon glove box, the halide solid electrolyte powder prepared in Examples 1~9 and Comparative Example 1 is filled into a cylindrical tablet mold (diameter 10 mm); and cold-pressed at a pressure of 375 MPa for 2 min to obtain a solid electrolyte sheet with a thickness of 0.5~1.5 mm and a diameter of 10 mm; after gold plating on the upper and lower surfaces of the solid electrolyte sheet, two stainless steel blocking electrodes are used to clamp the upper and lower surfaces, and connected to an electrochemical workstation to test the electrochemical impedance spectrum at room temperature; the room temperature Li + ion conductivity is extracted from the measured electrochemical impedance spectrum.

[0066] (2) Characterization results Table 1 shows the ion conductivity of the halide solid electrolyte synthesized in Examples 1~9 and Comparative Example 1. Figure 1 (LiNO3)(Li2S) 1 / 2 HfCl4 electrochemical impedance spectrum at room temperature.

[0067] Table 1 Ion conductivity of halide solid electrolyte

[0068] As can be seen from the data in Table 1, the ion conductivity of the halide solid electrolyte of the examples is higher than that of the halide solid electrolyte of the comparative examples.

[0069] Table 2 shows the effect of optimizing the ball milling conditions on the ion conductivity.

[0070]

[0071] As can be seen from the data in Table 2, by optimizing the ball milling conditions, the ion conductivity of the electrolyte material can be controlled, and after optimizing the ball milling conditions, the ion conductivity of the (LiNO3)(Li2S) 1 / 2 HfCl4 electrolyte is the highest, reaching 1.08 10 -3 S cm -1 .

[0072] 2. Structure characterization (1) Characterization method The solid-state electrolyte prepared in Example 2 and Comparative Example 1 was characterized using an X-ray diffractometer.

[0073] (2) Characterization results Figure 2 and Figure 3 are (LiNO3)(Li2S) and Li2HfCl6 synthesized in Example 2, respectively. 1 / 2 The crystal structure of the HfCl4 and Li2HfCl6 halide solid-state electrolyte synthesized in Comparative Example 1.

[0074] Figure 2 The results show that the (LiNO3)(Li2S) halide solid-state electrolyte synthesized in Example 2 exhibits a broad diffraction peak, indicating that the halide solid-state electrolyte is an amorphous phase with disorder. 1 / 2 The HfCl4 halide solid-state electrolyte exhibits a broad diffraction peak, indicating that the halide solid-state electrolyte is an amorphous phase with disorder. Figure 3 The results show that the Li2HfCl6 halide solid-state electrolyte provided by Comparative Example 1 has a distinct diffraction peak, indicating that the halide solid-state electrolyte is a crystalline phase of Li2HfCl6.

[0075] II. Electrochemical performance test 1. Critical current density test (1) Test method At room temperature, the lithium-lithium symmetric battery provided by Example 2 and the lithium-lithium symmetric battery assembled by the Li2HfCl6 of Comparative Example 1 were subjected to variable current charge-discharge test using a blue electric battery test system, and the current density was gradually increased to evaluate the critical current density of the halide solid-state electrolyte matched with the lithium metal negative electrode.

[0076] (2) Test results The test results are shown in Figure 4 The critical current density of the Li2HfCl6 of Comparative Example 1 matched with the metal lithium negative electrode is 0.8 mA cm -2 , and the (LiNO3)(Li2S) 1 / 2 HfCl4 of Example 2 has a critical current density of 1.2 mA cm -2 when matched with the metal lithium negative electrode, and the performance is better than that of the Li2HfCl6 of Comparative Example 1. This result shows that compared with the halide solid-state electrolyte of Comparative Example 1, the halide solid-state electrolyte prepared by the present application has significantly improved matching effect with the metal lithium negative electrode, which can significantly improve the stability of the halide solid-state electrolyte at the interface of the metal lithium negative electrode, thereby improving the battery performance.

[0077] 2. Solid-state lithium metal battery charge-discharge test (1) Test method At room temperature, the solid-state battery provided in Application Example 1 was subjected to constant current charge-discharge test using a blue light battery test system, the voltage range was 2.5 V~4.3 V (voltage relative to Li + / Li), and the cycle rate was 0.1 C.

[0078] (2) Test results The test results are shown in Figure 5 .

[0079] The solid-state lithium metal battery provided in Application Example 1 had a reversible capacity of 166.6 mAhg -1 (the data of the third week) at a rate of 0.1 C, and the efficiencies of the first three weeks were 78.7%, 96.6% and 97.0%, respectively.

[0080] The results show that the solid-state lithium metal battery assembled using the electrolyte in Example 2 can be stably cycled, and the matching of the electrolyte layer and the metal lithium negative electrode is achieved.

[0081] The above content only illustrates the technical idea of the present application and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical scheme falls within the protection scope of the claims of the present application.

Claims

1. A halide solid electrolyte that is stable to the negative electrode, characterized in that: The structural formula of the halide solid electrolyte is (Li n X) a MB y ; In the said structural formula, Li n X includes at least one of LiNO3, Li3PO4, Li4SiO4 and LiPF6; M is at least one of Zr, Hf, Ta, Nb, Al, Y, Fe and Ga; B is at least one of F, Cl, Br and I; n, a and y are stoichiometric coefficients, 0.5 < a < 3, and y is 3, 4 or 5.

2. The negative electrode-stable halide solid electrolyte according to claim 1, characterized in that: Li n X further includes at least one of Li2S, LiF and LiI.

3. The negative electrode-stable halide solid electrolyte according to claim 1, characterized in that: M is at least one of Zr and Hf.

4. The negative electrode-stable halide solid electrolyte according to claim 1, wherein: (Li n X) a MB y is (LiNO3)HfCl4, (LiNO3)(Li2S) 1 / 2 HfCl4, (LiNO3)(LiI) 1 / 2 ZrCl4, (Li4SiO4) 1 / 4 (LiPF6) 1 / 2 HfCl4, (LiNO3)(Li2S) 1 / 2 ZrCl4 or (Li3PO4) 1 / 3 (Li2S) 1 / 2 ZrCl4.

5. The method for preparing the negative electrode-stable halide solid electrolyte according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1, lithium salt Li n X and halide precursor MB y mixing to obtain a mixture; S2, ball milling the mixture to produce a solid phase reaction to obtain a halide solid electrolyte (Li n X) a MB y .

6. The method for preparing a negative electrode-stable halide solid electrolyte according to claim 5, wherein: S1 is specifically as follows: in an inert atmosphere without water or oxygen, lithium salt Li n X and halide precursor MB y mixing to obtain a mixture; S2 is specifically as follows: placing the mixture in a ball mill, adding grinding beads, evacuating the ball mill, sealing the ball mill, and ball milling to cause a solid phase reaction to obtain a halide solid electrolyte (Li n X) a MB y .

7. The method for preparing a halide solid electrolyte stable to a negative electrode according to claim 5, characterized in that: In S2, the ball milling speed was 400–800 rpm, and the ball milling time was 1–30 h.

8. A solid-state battery, characterized in that: The invention comprises a positive electrode sheet, a negative electrode sheet and a solid electrolyte layer located between the positive electrode sheet and the negative electrode sheet, wherein the material of the solid electrolyte layer is the halide solid electrolyte stable to the negative electrode as claimed in any one of claims 1 to 4.

9. The solid-state battery according to claim 8, characterized in that The components of the positive electrode sheet include positive electrode active material and positive electrode filler; the positive electrode filler is a combination of one or more of an ion conductor, a conductive agent and an adhesive; the ion conductor and the solid electrolyte layer are made of the same material.

10. The solid-state battery according to claim 8, characterized in that The components of the negative electrode sheet include a negative electrode active material, which is a metal material or a non-metallic material. When the negative electrode active material is a non-metallic material, the components of the negative electrode sheet also include a negative electrode filler; the negative electrode active material is a non-metallic material, and the negative electrode filler is a combination of one or more of an ion conductor, a conductive agent and an adhesive; the ion conductor and the solid electrolyte layer are the same material.

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