Solid-state lithium battery in-situ electrochemical passivation and repair method

Abstract

To provide an in-situ electrochemical passivation and repair method for a solid-state lithium battery.SOLUTION: A sulfide-based solid-state battery is discharged to a specific lithiation degree according to a specific discharge mode under low current density, so that in-situ electrochemical passivation and / or repair of the battery are / is realized. Through the electrochemical reduction method, the interface of the sulfide-based solid-state battery can be passivated and stabilized, and the sulfide electrolyte is prevented from being continuously decomposed in the charging and discharging process, so that the sulfide solid-state electrolyte can be matched with an oxide positive electrode material with relatively high operating voltage; and an oxidation product generated by decomposition in the cycle process is converted into a lithium-rich reduction product with ion conductivity again, so that the activation and repair effects are achieved, and the battery has more excellent cycle stability.SELECTED DRAWING: Figure 13

Description

Technical Field

[0001] The present invention belongs to the field of solid lithium batteries, and specifically relates to an in-situ electrochemical reduction method for passivating and repairing the cathode interface of sulfide-based solid batteries.

Background Art

[0002] With the rapid development of 3C electronic products, new energy vehicles, and large-scale energy storage systems, higher energy density and safety are required for lithium-ion batteries. Sulfide solid electrolytes have the advantages of high ionic conductivity, excellent thermal stability, processability, and good ductility. Sulfide-based solid lithium batteries manufactured using them instead of conventional flammable organic liquid electrolytes are expected to be significantly improved in terms of energy density and safety.

[0003] However, from theoretical calculations and experimental results, the electrochemical stability window of sulfide solid electrolytes is only about 1.7 - 2.1 V (vs. Li +It is (Li), and it can be seen that it is much lower than the operating voltage range (usually 2.0 to 5.0 V) and the platform voltage (3.3 to 3.8 V) of the currently mainstream commercial layered oxide cathodes (such as lithium nickel cobalt manganese oxide cathodes), polyanion oxide cathodes (such as lithium iron phosphate cathodes), and next-generation high-voltage lithium-rich cathodes (such as lithium-rich manganese-based solid solutions) (see Figure 14). As a result, when a sulfide solid electrolyte and an oxide cathode are combined and operated, the sulfide is oxidized and decomposed, generating electron-ion insulating products such as polysulfide phosphorus and elemental sulfur, which cover the interface, preventing the efficient transport of carriers. Consequently, the interfacial impedance increases rapidly, making it difficult to fully utilize the capacity of the cathode material and resulting in rapid attenuation. Furthermore, many oxide cathode materials themselves have low electronic conductivity and need to be coated with conductive carbon on the surface, which makes the oxidative decomposition of the sulfide electrolyte at the cathode interface even more serious. Currently, means such as surface coating of cathode materials and doping modification of sulfide electrolytes in the industry are not only difficult to fundamentally solve the above problems but also involve issues such as high cost and complex processes in large-scale industrial production. Therefore, in order to achieve stable operation of sulfide solid electrolytes in oxide cathode systems with high operating voltages, it is urgently necessary to develop a simple and effective method for passivating and then repairing the cathode interface of sulfide-based solid-state batteries.

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide an in-situ electrochemical reduction method for passivating and repairing the cathode interface of a sulfide-based solid-state battery, which realizes passivation of the sulfide electrolyte and the oxide cathode interface and then repairs the interface after failure by controlling the charge and discharge procedure, ensuring full utilization of the capacity of the cathode active material and stable cycling.

Means for Solving the Problems

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows.

[0006] In-situ electrochemical passivation and repair method of a solid lithium battery, which realizes in-situ electrochemical passivation and / or repair of the battery by discharging a sulfide-based solid battery to a specific degree of lithiation at a low current density and in a specific discharge mode. By controlling the charge-discharge procedure, a passivation interface is formed between the sulfide solid electrolyte and the cathode material, or an interface that has lost its activity is repaired and activated.

[0007] Preferably, the sulfide-based solid battery is a sulfide-based solid battery assembled with a sulfide solid electrolyte as an electrolyte and an ion conductor in the cathode, and a layered oxide or polyanion oxide as a cathode active material. The electrolyte and the ion conductor in the same battery are not necessarily the same.

[0008] More preferably, the sulfide solid electrolyte is an argyrodite-type electrolyte such as Li6PS5Cl, Li6PS5Br, Li6PS5Cl 0.5 Br 0.5 、Li 5.5 PS 4.5 Cl 1.5 、Li 5.4 PS 4.4 Cl 1.6 and the like, a lithium fast ion conductor such as Li 10 GeP2S 12 、Li 10 SnP2S 12 、Li 6.75 Si 0.75 As 0.25 S5I and the like, a glass-ceramic phase solid electrolyte such as Li3PS4, Li7P3S 11 、xLi2S-(100-x)P2S5 and the like, and includes at least one of other electrolytes manufactured by doping anions and cations based on the above electrolytes or by complexing with a polymer, but is not limited thereto. More preferably, the layered oxide or polyanion oxide cathode is lithium cobalt oxide (LiCoO2), lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O4), lithium nickel cobalt manganese oxide (LiNix Co y Mn 1-x-y (O2), lithium nickel cobalt aluminate (LiNi x Co y Al 1-x-y (O2), lithium-rich manganese-based solid solution (xLi2MnO3·(1-x)LiMO2, M is one or more of Ni, Co, Mn), lithium iron phosphate (LiFePO4), lithium manganese iron phosphate (LiMn x Fe 1-x (PO4), lithium vanadium phosphate (LiVPO4), cathode materials obtained by surface coating modification and doping modification of the above materials, and combinations of one or more of the above cathode materials, but are not limited thereto. More preferably, the anode material of the sulfide-based solid battery includes anode materials such as metallic lithium, lithium indium alloy, graphite, hard carbon, silicon carbon, lithium titanate, niobium titanate, and anode materials obtained by modifying the above materials, and combinations of one or more of the above anode materials, but are not limited thereto. More preferably, the ionic conductor accounts for 1% to 60% of the total mass of the cathode.

[0009] Preferably, discharging to a specific degree of lithiation in the specific discharge mode includes at least one of discharging to a specific potential in a constant current discharge mode, discharging to a specific current in a constant current-constant voltage discharge mode, and discharging to a specific specific capacity in a constant current discharge mode. More preferably, the low current density is 0.1 to 50 mA g -1 (converted by the mass of the ionic conductor of the composite cathode of the battery), the specific potential for discharging is 0.5 to 2.2 V (vs. Li + / Li), the constant current-constant voltage discharge mode means discharging to a specific potential at a constant current and then discharging to a specific current at a constant voltage, and the cut-off condition is that the constant voltage discharge current is 0.1 to 20 mA g -1 (converted by the mass of the ionic conductor of the composite cathode), and the specific specific capacity is 15 to 500 mAh g -1in terms of the mass of the ion-conductive electrode agent of the composite positive electrode.

[0010] Preferably, the charge-discharge procedure for passivating the solid lithium battery includes (1.1) passivating the positive electrode interface of the sulfide-based solid battery, that is, discharging to a specific degree of lithiation at a low current density and in a specific discharge mode, whereby the sulfide electrolyte undergoes appropriate reductive decomposition at the interface to generate lithium-rich decomposition products, covering the highly reactive sites at the interface, and achieving the purpose of maintaining the lithium-ion transport path while passivating the interface; (1.2) performing a normal charge-discharge cycle on the sulfide-based solid battery. More preferably, in step (1.1), the passivation measure for the positive electrode interface is not limited to the first direct discharge passivation, and the passivation can be performed 1 to 10 times. That is, in order to further ensure sufficient passivation of the interface, the discharge passivation process can be selectively included within 1 to 10 cycles of the battery. More preferably, the cycle current of the normal charge-discharge is 0.05 to 20 C (in terms of the mass of the positive electrode active material), and the voltage range of the charge-discharge is the normal charge-discharge voltage range of this positive electrode material.

[0011] Preferably, the charge-discharge procedure for repairing the solid lithium battery includes (2.1) repairing the sulfide-based solid battery, that is, discharging to a specific degree of lithiation at a low current density and in a specific discharge mode, and performing an interface passivation operation to repair the failed battery, and re-reducing the reduction products accumulated at the interface to lithium-rich products having lithium-ion transport characteristics, so that the battery can perform normal charge-discharge cycles. More preferably, the sulfide-based solid-state battery is a battery that has been cycled until its capacity is significantly attenuated. More preferably, the significant attenuation of the capacity includes the case where the discharge capacity is attenuated to 1% to 70% of the rated discharge capacity. More preferably, the repair may be performed on a solid lithium battery that has not undergone the interface passivation step of the present invention, or has adopted other formation or activation processes, or has directly performed charge and discharge cycles. More preferably, the sulfide-based solid-state battery may have undergone the aforementioned interface passivation treatment. In this case, the specific discharge mode, current, cut-off voltage, rated capacity, etc. of the interface repair operation are not necessarily exactly the same as those of the passivation step. More preferably, the cycle current of the normal charge and discharge is 0.05 to 20 C (converted by the mass of the positive electrode active material), and the voltage range of the charge and discharge is the normal charge and discharge voltage range of this positive electrode material.

[0012] In the present invention, by passivating the battery, the sulfide electrolyte undergoes appropriate reductive decomposition, and a passivation interface of a lithium-rich product is formed at the interface between the sulfide electrolyte and the positive electrode, having certain lithium-ion conduction characteristics to ensure the subsequent normal cycling of the battery. Thereby, the problem that the operating voltage range of the oxide positive electrode material exceeds the electrochemical stability window of the sulfide solid electrolyte can be effectively solved. When the capacity is significantly attenuated during the cycling of the battery, an in-situ electrochemical reduction method is used to reconvert the electron-ion insulating oxide products accumulated at the interface into lithium-rich reduction products, thus playing a role in repairing the battery. By this electrochemical reduction method, the interface of the sulfide-based solid-state battery is passivated and stabilized, preventing the continuous decomposition of the sulfide electrolyte during the charge and discharge process, and enabling the sulfide solid electrolyte to be compatible with the oxide positive electrode material with a high operating voltage. Also, the oxide products generated by the decomposition during the cycling process are reconverted into lithium-rich reduction products having ion conductivity, playing a role in activation and repair, thereby giving the battery better cycle stability.

Advantages of the Invention

[0013] Compared with the prior art, the advantageous effects of the present invention are as follows.

[0014] The present invention utilizes a simple charge-discharge procedure to control the reversible redox reaction of the sulfide solid electrolyte, achieve the passivation of the interface between the sulfide electrolyte and the oxide cathode, thereby enabling a sulfide electrolyte with a narrow electrochemical stability window to be directly compatible with the mainstream oxide cathode material with a high operating voltage, and avoiding processes such as complicated interface modification and doping modification. Since the discharge of the cathode of a lithium battery corresponds to the lithiation process, during the first discharge, the sulfide electrolyte undergoes reductive decomposition, forming lithium-rich decomposition products such as lithium chloride (or lithium bromide, lithium iodide), lithium sulfide, and lithium phosphide. Different from the ion-electron insulating and lithium-deficient products generated by oxidative decomposition during charging, the above-mentioned lithium-rich decomposition products have electron insulation and ion transport characteristics, and once formed, they are very inert and difficult to be re-oxidized. Thereby, it is expected not only to maintain the transport of lithium ions at the interface and passivate the interface in a metastable state, but also to suppress inherent problems such as lattice oxygen precipitation, structural collapse, and irreversible phase transition of the cathode material, contributing to the subsequent maintenance of the cycle stability of the battery. In addition, the in-situ electrochemical passivation and repair method proposed by the present invention is expected to be directly incorporated into the formation process of conventional lithium batteries, and has great application value and potential in the mass production and commercial application of batteries.

Brief Description of the Drawings

[0015]

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Embodiments for Carrying Out the Invention

[0016] For ease of understanding, specific examples are used to more clearly, completely, and in detail explain the technical solution means and embodiments of the present invention in conjunction with the drawings. It should be noted that the examples described in the present invention are implemented on the premise of the technical solution means of the present invention, and detailed embodiments and specific operation processes are given, but they are only part of the examples of the present invention, not all examples, and the specific embodiments described are only limited to the exemplification and explanation of the present invention, and do not limit the present invention. All other embodiments obtained by those skilled in the art without creative efforts based on the embodiments of the present invention are included within the protection scope of the present invention.

[0017] The experimental methods used in the following examples are conventional methods unless otherwise specified, and the materials, reagents, etc. used in the examples are commercially available unless otherwise specified.

[0018] Example 1 (lithium iron phosphate cathode, passivated by discharging to 1.0 V) In-situ electrochemical passivation and repair method for a solid lithium battery, and the steps of the example are as follows. Step 1: Lithium iron phosphate (LiFePO4, having a carbon coating layer on the surface), Li 5.5 PS 4.5 Cl 1.5 (ionic conductor), vapor-grown carbon fiber (electronic conductor), ethyl cellulose (binder) were mixed at a mass ratio of 70:24:3:3, and using absolute ethanol as a solvent, it was applied to a carbon-coated aluminum foil to obtain a cathode with a loading of the cathode active material of 1-3 mg cm -2 . A cathode was manufactured. Li 5.5 PS 4.5 Cl 1.5 100 mg was used as the solid electrolyte, and a 10 mm diameter metallic lithium was used as the anode, and it was press-molded at 360 MPa to manufacture a solid battery. Step 2: First, the manufactured solid battery was discharged to 1.0 V at a current density of 20 mA g -1 (converted by the mass of the ionic conductor in the composite cathode) to passivate the interface. Step 3: The solid battery with the passivated interface was charged to 4.0 V and discharged to 2.5 V to perform normal charge and discharge cycles, and the current density was 17 mA g -1 (0.1C). The charge and discharge curves of the first cycle and the 50th cycle are shown in Fig. 1. As Comparative Example 1, the same battery was manufactured, and normal charge and discharge were directly performed within the range of 0.1C rate and 2.5 - 4.0 V. From the discharge curves of the first cycle and the 50th cycle shown in Fig. 2, the battery could hardly operate normally, the charge and discharge curves deviated significantly from the typical charge and discharge curves of lithium iron phosphate, and it almost completely failed after 10 cycles. The comparison of the performance of the batteries of Example 1 and the comparative example during the 50-cycle process is shown in Fig. 3. For the positive electrodes of Example 1 (passivated state and charged state after passivation) and Comparative Example 1, characteristic evaluation was carried out by X-ray photoelectron spectroscopy. As shown in Fig. 15, in both the S2p spectrum and the P 2p spectrum, in the in-situ electrochemical passivation method used in Example 1, a passivation interface having lithium sulfide (Li2S) was formed, and oxidation products (-S n (elemental sulfur), polysulfide phosphorus (P2S x )) accumulation was effectively reduced, whereby it was observed that the failure of the interface due to continuous decomposition of the Li 5.5 PS 4.5 Cl 1.5 electrolyte was avoided.

[0019] Example 2 (lithium iron phosphate positive electrode with high loading, passivated by discharging to 0.8 V) An in-situ electrochemical passivation and repair method for a solid lithium battery, and the steps of the example are as follows. Step 1: Lithium iron phosphate (LiFePO4, having a carbon coating layer on the surface), Li 5.5 PS 4.5 Cl 1.5 (ion conductive agent), vapor-grown carbon fiber (electron conductive agent), polytetrafluoroethylene (binder) were mixed at a mass ratio of 60:34:3:3 to obtain a composite positive electrode, and the loading of the positive electrode active material was 5 mg cm -2 and pressed onto the surface of a carbon-coated aluminum foil. Li 5.5 PS 4.5 Cl 1.5 100 mg was used as the solid electrolyte, a 10 mm diameter metallic lithium was used as the negative electrode, and it was press-molded at 360 MPa to manufacture a solid battery. Step 2: First, the manufactured solid battery was discharged to 0.8 V at a current density of 15 mA g -1 (converted by the mass of the ion conductive agent of the composite positive electrode) to passivate the interface. Step 3: The solid battery with the passivated interface was charged to 3.8 V and discharged to 2.5 V to perform a normal charge-discharge cycle, and the current density was 17 mA g -1It was (0.1C). The charge-discharge curves of the first cycle and the 60th cycle are shown in FIG. 4. As Comparative Example 2, the same battery was directly charged and discharged normally within the range of 0.1C rate and 2.5 to 3.8V, and the charge-discharge curves of the first cycle and the 20th cycle are shown in FIG. 5. The capacity significantly decayed within 20 cycles.

[0020] Example 3 (high-rate lithium iron phosphate cathode, passivated by discharging to 1.0V) A method for in-situ electrochemical passivation and repair of a solid lithium battery, and the steps of the example are as follows. Step 1: Lithium iron phosphate (LiFePO4, having a carbon coating layer on the surface), Li 5.5 PS 4.5 Cl 1.5 (Ionic conductive agent), vapor-grown carbon fiber (electronic conductive agent), ethyl cellulose (binder) were mixed at a mass ratio of 70:24:3:3, and using anhydrous ethanol as a solvent, it was applied to a carbon-coated aluminum foil to manufacture a positive electrode, and the loading amount refers to Example 1. Li 5.5 PS 4.5 Cl 1.5 100 mg was used as a solid electrolyte, and a 10 mm diameter metallic lithium was used as the negative electrode, and it was press-molded at 360 MPa to manufacture a solid battery. Step 2: First, the manufactured solid battery was discharged to 1.0V at a current density of 20 mA g -1 (Converted by the mass of the ionic conductive agent of the composite positive electrode) to passivate the interface. Step 3: The solid battery with the passivated interface was charged to 4.0V and discharged to 2.5V to perform normal charge-discharge cycles, and the current density was 170 mA g -1 (1C). The cycle performance in the 600-cycle process is shown in FIG. 6. The capacity hardly decayed within 600 cycles, indicating that an extremely stable interface was formed kinetically due to in-situ electrochemical passivation.

[0021] Example 4 (lithium-rich manganese-based cathode, passivated by discharging to 1.5V) In-situ electrochemical passivation and repair method for a solid lithium battery, and the steps of the examples are as follows. Step 1: A lithium-rich manganese-based (Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O4) cathode coated with lithium niobate (LiNbO3) as an active material, Li 5.5 PS 4.5 Cl 1.5 (ionic conductor), vapor-grown carbon fiber (electronic conductor), and ethyl cellulose (binder) are mixed at a mass ratio of 60:30:7:3, and coated on a carbon-coated aluminum foil using absolute ethanol as a solvent to manufacture a cathode. The loading amount refers to Example 1. Li 5.5 PS 4.5 Cl 1.5 100 mg of a solid electrolyte and a 10-mm-diameter metallic lithium as the anode are press-molded at 360 MPa to manufacture a solid battery. Step 2: First, the manufactured solid battery is discharged to 1.5 V at a current density of 25 mA g -1 (converted by the mass of the ionic conductor of the composite cathode) to passivate the interface. Step 3: The solid battery with the passivated interface is charged to 4.8 V and discharged to 2.0 V to perform normal charge-discharge cycles, and the current density is 25 mA g -1 (0.1C). The charge-discharge curves of the first cycle and the tenth cycle are shown in Figure 7. After the interface is passivated, the interface tends to be stabilized. After 10 cycles, the capacity does not significantly decay, and about 220 mAh g -1 The capacity can be stably exhibited. As Comparative Example 4, the same battery is directly subjected to a charge-discharge test in the range of 2.0 - 4.8 V at a 0.1C rate without passivation, and the charge-discharge curves of the first cycle and the tenth cycle are shown in Figure 8. For the lithium-rich manganese-based cathode without passivating the interface, the initial discharge capacity is only 70 mAh g -1 , and due to the serious decomposition of the sulfide electrolyte, the capacity after 10 cycles decays to 40 mAh g -1 . When using a lithium-rich manganese-based solid solution (xLi2MnO3·(1 - x)LiMO2, where M is one or more of Ni, Co, and Mn, and 0 < x < 1) as the positive electrode active material, corresponding passivation and / or repair operations are possible and quite effective, but for the sake of brevity, they will not be elaborated here.

[0022] Example 5 (lithium iron manganese phosphate positive electrode, passivated by discharging to 1.0 V) An in-situ electrochemical passivation and repair method for a solid lithium battery, and the steps of the example are as follows. Step 1: Mix lithium iron manganese phosphate (LiFe 0.5 Mn 0.5 PO4) positive electrode, Li 5.5 PS 4.5 Cl 1.5 , vapor-grown carbon fiber, and ethyl cellulose in a mass ratio of 50:40:7:3, use absolute ethanol as the solvent, coat it on carbon-coated aluminum foil to manufacture the positive electrode, and refer to Example 1 for the loading amount. Li 5.5 PS 4.5 Cl 1.5 100 mg is used as the solid electrolyte, a 10-mm-diameter metallic lithium is used as the negative electrode, and it is pressed at 360 MPa to form a solid battery. Step 2: First, discharge the manufactured solid battery to 1.0 V at a current density of 15 mA g -1 (converted based on the mass of the ion conductor in the composite positive electrode) to passivate the interface. Step 3: Charge the solid battery with the passivated interface to 4.3 V and discharge it to 2.5 V to perform normal charge and discharge cycles, and the current density is 17 mA g -1 (0.1C). The charge and discharge curves of the first cycle and the tenth cycle are shown in Figure 9. After the interface is passivated, the initial discharge capacity is about 150 mAh g -1 , and the capacity did not significantly decay within 10 cycles. As Comparative Example 5, the same battery was directly tested for charge and discharge within the range of 2.5 - 4.3 V at a 0.1C rate without passivation, and the charge and discharge curves of the first cycle and the tenth cycle are shown in Figure 10. For this battery, the charge and discharge capacity is 30 mAh g-1 is less than that, and shows a large polarization because the intense oxidation and decomposition of the electrolyte make it difficult for the battery to operate. Lithium manganese iron phosphate (LiFe x Mn 1-x PO4, 0 < x < 1) as the positive electrode active material, the corresponding passivation and / or repair operations are possible and have considerable effects, but for the sake of space, they will not be described in detail here.

[0023] Example 6 (Repair of Lithium Nickel Cobalt Manganese Oxide Ternary Positive Electrode) An in-situ electrochemical passivation and repair method for a solid lithium battery, and the steps of the example are as follows. Step 1: Mix lithium nickel cobalt manganese oxide (LiNi 0.8 Co 0.1 Mn 0.1 O2) positive electrode, Li 5.5 PS 4.5 Cl 1.5 (ion conductive agent), vapor-grown carbon fiber (electronic conductive agent), ethyl cellulose (binder) in a mass ratio of 60:30:7:3, and use absolute ethanol as the solvent to coat on a carbon-coated aluminum foil to manufacture the positive electrode. Refer to Example 1 for the loading amount. Li 5.5 PS 4.5 Cl 1.5 100 mg of solid electrolyte and a 10-mm-diameter metallic lithium as the negative electrode are pressed at 360 MPa to form a solid battery. Step 2: Charge and discharge this solid battery within the voltage range of 2.5 - 4.3 V at a current density of 250 mA g -1 (1C, converted based on the loading amount of lithium nickel cobalt manganese oxide) for 100 cycles. The initial discharge capacity is 122 mAh g -1 . Step 3: After 100 cycles of the solid battery are completed, the capacity is significantly attenuated to 52 mAh g -1 . Discharge it to 1.8 V at a small current of 20 mA g -1 (converted based on the mass of the ion conductive agent in the composite positive electrode) to reduce the oxidation products accumulated at the interface to lithium-rich products with a certain ionic conductivity, thereby completing the repair of the ternary positive electrode. Step 4: When the 1C high-rate cycle was restored, the capacity after repair returned to a high level of 98 mAh g -1 and then. Normal charge and discharge cycles can be performed thereafter. After another 300 cycles, the capacity is higher than 80 mAh g -1 Thus, the performance of the battery is effectively restored and more stable than the conventional performance. When lithium nickel cobalt manganese oxide (LiNi x Co y Mn 1-x-y O2, 0 < x < 1, 0 < y < 1, 0 < 1 - x - y < 1) is used as the positive electrode active material, the corresponding passivation and / or repair operations are possible and quite effective. However, for the sake of space, it will not be described in detail here.

[0024] Example 7 (Repair of high-voltage lithium cobalt oxide positive electrode) An in-situ electrochemical passivation and repair method for a solid lithium battery, and the steps of the example are as follows. Step 1: Mix lithium cobalt oxide (LiCoO2) positive electrode, Li 5.5 PS 4.5 Cl 1.5 (ionic conductor), vapor-grown carbon fiber (electronic conductor), ethyl cellulose (binder) in a mass ratio of 60:30:7:3, and use absolute ethanol as the solvent, apply it to carbon-coated aluminum foil to manufacture the positive electrode, and refer to Example 1 for the loading amount. Li 5.5 PS 4.5 Cl 1.5 100 mg of solid electrolyte and a 10 mm diameter lithium metal as the negative electrode were pressed at 360 MPa to form a solid battery. Step 2: For this solid battery, within the voltage range of 2.5 to 4.7 V, at a current density of 270 mA g -1 (1C, converted based on the lithium cobalt oxide loading amount), cycle 100 times, and the initial discharge capacity is 85 mAh g -1 is. Step 3: After 100 cycles of the solid battery were completed, the capacity decreased significantly to 30 mAh g -1 By 20 mA g -1(Converted by the mass of the ion conductor in the composite cathode) Discharge at a small current to 1.8 V to reduce the oxidation products accumulated at the interface to lithium-rich products with a certain ionic conductivity, thereby completing the repair of the high-voltage lithium cobalt oxide cathode. Step 4: Restore the 1C high-rate cycle, and the capacity after repair is 78 mAh g -1 returned to a high level. After that, normal charge and discharge cycles can be performed. After another 300 cycles, the capacity is 60 mAh g -1 higher than this, and thus the performance of the battery is effectively restored and more stable than the conventional performance.

[0025] Example 8 (blend of lithium iron manganese phosphate and ternary cathode, discharging to passivation at 1.0 V) In-situ electrochemical passivation and repair method for a solid lithium battery, and the steps of the example are as follows. Step 1: A cathode obtained by mixing lithium iron manganese phosphate (LiFe 0.5 Mn 0.5 PO4) and lithium nickel cobalt manganese oxide (LiNi 0.8 Co 0.1 Mn 0.1 O2) ternary cathodes in a mass ratio of 1:1, Li 5.5 PS 4.5 Cl 1.5 , a composite cathode obtained by mixing vapor-phase carbon fiber and polytetrafluoroethylene in a mass ratio of 50:40:7:3, and pressing it on the surface of a carbon-coated aluminum foil current collector so that the loading amount of the cathode active material is 5 mg cm -2 . Press 100 mg of Li 5.5 PS 4.5 Cl 1.5 as a solid electrolyte and a 10 mm diameter metallic lithium as the anode at 360 MPa to form a solid battery. Step 2: First, discharge the manufactured solid battery to 1.0 V at a current density of 15 mA g -1 (Converted by the mass of the ion conductor in the composite cathode) to passivate the interface. Step 3: Charge the passivated solid battery to 4.3 V and discharge it to 2.5 V to perform normal charge-discharge cycles, and the current density is 18.5 mA g -1 (0.1C). The charge-discharge curves of the first cycle and the tenth cycle are shown in Fig. 11. After the interface is passivated, the initial discharge capacity is about 110 mAh g -1 and the capacity did not significantly decay within 10 cycles. As Comparative Example 8, the same battery was directly subjected to charge-discharge tests within the range of 0.1 C rate and 2.5 - 4.3 V, and the charge-discharge curves of the first cycle and the tenth cycle are shown in Fig. 12. All of its charge-discharge capacities are low, the initial discharge specific capacity is 62 mAh g -1 and the discharge specific capacity after 10 cycles is 38 mAh g -1 showing a large polarization. Since the electrolyte is violently oxidized and decomposed by the carbon layer on the surface of lithium iron manganese phosphate, it is difficult for the capacity of lithium iron manganese phosphate to be exerted, and the low capacity exerted is only due to the lithium nickel cobalt manganese oxide ternary cathode (because there is no carbon coating layer on the surface of lithium nickel cobalt manganese oxide). Lithium iron manganese phosphate (LiFe x Mn 1-x PO4, 0 < x < 1) and lithium nickel cobalt manganese oxide (LiNi x Co y Mn 1-x-y O2, 0 < x < 1, 0 < y < 1, 0 < 1 - x - y < 1) blends (including those mixed in other mass ratios) as the cathode active material, corresponding passivation and / or repair operations are possible and quite effective, but for the sake of space, it will not be described in detail here.

[0026] Example 9 (Lithium iron phosphate cathode, passivated in constant current-constant voltage discharge mode) A method for in-situ electrochemical passivation and repair of a solid lithium battery, and the steps of the example are as follows. Step 1: Lithium iron phosphate (LiFePO4, having a carbon coating layer on the surface), Li 10 GeP2S 12(Ionic conductive agent), vapor-grown carbon fiber (electronic conductive agent), and polytetrafluoroethylene (binder) were mixed at a mass ratio of 60:34:3:3 to form a composite positive electrode, and the loading amount of the positive electrode active material was 5 mg cm -2 and pressed onto the surface of a carbon-coated aluminum foil current collector so that it became 10 LiGeP2S 12 100 mg was used as the solid electrolyte, and a lithium-indium alloy with a diameter of 10 mm was used as the negative electrode, and it was press-molded at 360 MPa to manufacture a solid battery. Step 2: First, the manufactured solid battery was discharged to 1.5 V (vs lithium potential) at a current density of 10 mA g -1 (converted based on the loading amount of the ionic conductive agent in the composite positive electrode), and then discharged at a constant voltage of 1.5 V until the current was less than 2 mA g -1 (converted based on the loading amount of the ionic conductive agent in the composite positive electrode) to passivate the interface under the cut-off condition. Step 3: The solid battery with the passivated interface was charged to 4.0 V (vs lithium potential) and discharged to 2.5 V (vs lithium potential) to perform normal charge and discharge cycles, and the current density was 17 mA g -1 (0.1C). Also, after each of the first 5 charge and discharge cycles, the interface passivation operation as described in Step 2 was performed. After the discharge passivation was completed, the initial discharge capacity was 154 mAh g -1 and the capacity after 50 cycles was 133 mAh g -1 . As Comparative Example 9, the same battery was charged and discharged directly according to the normal process without passivation. The initial discharge capacity was 50 mAh g -1 and the capacity after 50 cycles was less than 10 mAh g -1 .

[0027] Example 10 (Lithium-rich manganese-based positive electrode, discharged and passivated in constant capacity mode) -1 A method for in-situ electrochemical passivation and repair of a solid lithium battery, and the steps of the example are as follows. Step 1: A lithium-rich manganese-based (Li coated with lithium niobate (LiNbO3)1.2 Mn 0.54 Ni 0.13 Co 0.13 O4) cathode active material, Li7P3S 11 (Ionic conductive agent), carbon fiber by vapor phase method (electronic conductive agent), polytetrafluoroethylene (binder) were mixed at a mass ratio of 60:34:3:3 to form a composite cathode, and the loading amount of the cathode active material was 5 mg cm -2 and pressed onto the surface of the aluminum foil current collector. Li7P3S 11 100 mg was used as the solid electrolyte, and a lithium sheet with a diameter of 10 mm was used as the anode, and it was pressed and formed at 360 MPa to manufacture a solid battery. Step 2: First, the manufactured solid battery was discharged at a current density of 10 mA g -1 (converted by the mass of the ionic conductive agent in the composite cathode) for 13 hours, that is, discharged to a rated capacity of 130 mAh g -1 (converted by the mass of the ionic conductive agent in the composite cathode) to passivate the interface. Step 3: The solid battery with the passivated interface was charged to 4.8 V and discharged to 2.0 V to perform normal charge and discharge cycles, and the current density was 25 mA g -1 (0.1C). The initial discharge capacity was 194 mAh g -1 and the capacity after 50 cycles was 160 mAh g -1 . As a comparative example, the same battery was charged and discharged directly according to the normal process without passivation. Due to the high operating voltage range, the sulfide electrolyte was severely decomposed and the battery could not operate normally.

[0028] Example 11 (Lithium nickel manganate cathode, passivation in constant current - constant voltage discharge mode) In-situ electrochemical passivation and repair method of a solid lithium battery, and the steps of the example are as follows. Step 1: Lithium nickel manganate (LiNi 0.5 Mn 1.5(O4) A composite cathode was prepared by mixing a cathode, Li3PS4 (ionic conductor), carbon fibers prepared by vapor phase method (electronic conductor), and polytetrafluoroethylene (binder) at a mass ratio of 60:34:3:3. The loading of the cathode active material was 5 mg cm -2 and it was pressed onto the surface of an aluminum foil current collector. Using 100 mg of Li3PS4 as the solid electrolyte and a lithium sheet with a diameter of 10 mm as the anode, a solid-state battery was fabricated by pressing at 360 MPa. Step 2: First, the fabricated solid-state battery was discharged to 1.3 V at a current density of 10 mA g -1 (converted based on the mass of the ionic conductor in the composite cathode), and then discharged at a constant voltage of 1.3 V until the current was less than 2 mA g -1 (converted based on the mass of the ionic conductor in the composite cathode) to passivate the interface. Step 3: The solid-state battery with a passivated interface was charged to 5.2 V and discharged to 3.0 V to perform normal charge-discharge cycles at a current density of 14.6 mA g -1 (0.1C). The initial discharge capacity was 113 mAh g -1 and the capacity after 50 cycles was 90 mAh g -1 . As a comparative example, the same battery was charged and discharged directly according to the normal process without passivation. Due to the high operating voltage range, the sulfide electrolyte was severely decomposed and the battery could not operate normally.

[0029] Example 12 (High-voltage lithium nickel manganate cathode, discharging in constant capacity mode for passivation) -1 A method for in-situ electrochemical passivation and repair of a solid lithium battery, and the steps of the example are as follows. Step 1: A composite cathode was prepared by mixing lithium nickel manganate cathode (LiNi Mn 0.5 O4), Li7P3S 1.5 (ionic conductor), carbon fibers prepared by vapor phase method (electronic conductor), and polytetrafluoroethylene (binder) at a mass ratio of 60:34:3:3. The loading of the cathode active material was 5 mg cm 11 and it was pressed onto the surface of an aluminum foil current collector. Using 100 mg of Li3PS4 as the solid electrolyte and a lithium sheet with a diameter of 10 mm as the anode, a solid-state battery was fabricated by pressing at 360 MPa. -2Pressed onto the surface of the aluminum foil current collector so as to achieve [the desired state]. Li7P3S 11 Using 100 mg of solid electrolyte and a lithium sheet with a diameter of 10 mm as the negative electrode, a solid battery was fabricated by pressing at 360 MPa. Step 2: First, the fabricated solid battery was discharged at a current density of 10 mA g -1 (converted based on the mass of the ion conductor in the composite cathode) for 13 hours, i.e., discharged to a rated capacity of 130 mA h g -1 (converted based on the mass of the ion conductor in the composite cathode) to passivate the interface. Step 3: The solid battery with the passivated interface was charged to 5.2 V and discharged to 3.0 V to perform normal charge-discharge cycles, and the current density was 14.6 mA g -1 (0.1C). The initial discharge capacity was 105 mAh g -1 and the capacity after 50 cycles was 84 mAh g -1 . As a comparative example, for the same battery, charge and discharge were directly performed according to the normal process. Due to the high operating voltage range, the sulfide electrolyte was severely decomposed and the battery could not operate normally.

[0030] Example 13 (Example combining a lithium iron phosphate cathode with countermeasures for interface passivation and restoration) Step 1: Lithium iron phosphate (LiFePO4 with a carbon coating layer on the surface), Li 5.5 PS 4.5 Cl 1.5 (ion conductor), vapor-grown carbon fiber (electronic conductor), and polytetrafluoroethylene (binder) were mixed at a mass ratio of 60:34:3:3, and pressed onto a carbon-coated aluminum foil so that the loading amount was 5 mg cm -2 to fabricate a cathode. Li 5.5 PS 4.5 Cl 1.5 Using 100 mg of solid electrolyte and metallic lithium with a diameter of 10 mm as the negative electrode, a solid battery was fabricated by pressing at 360 MPa. Step 2: First, the fabricated solid battery was discharged to 1.0 V at a current density of 20 mA g -1 (converted based on the mass of the ion conductor in the composite cathode) to passivate the interface. Step 3: Charge the passivated solid battery to 4.0 V and discharge it to 2.5 V to perform a normal charge-discharge cycle, and the current density is 170 mA g -1 (1C). The initial discharge capacity is 105 mAh g -1 and within 200 cycles, the capacity is 94 mAh g -1 and it is clearly not decayed. After 1000 cycles, due to the long-term cycling process, the passivation layer is destroyed, the electrolyte is decomposed, oxidation products are generated and accumulated on the interface again, so the capacity decays to 53 mAh g -1 . Step 4: Discharge at a small current of 20 mA g -1 to 1.5 V to reduce the oxidation products accumulated on the interface to lithium-rich products with a predetermined ionic conductivity, thus completing the repair of the lithium iron phosphate cathode (after passivation). Step 5: Restore the 1C high-rate cycle, and the capacity after repair returns to a high level of 85 mAh g -1 and thereafter, normal charge and discharge could be performed. Even after 500 more cycles, the discharge specific capacity was maintained at >77 mAh g -1 . To further compare the advantages of the technical solution of the present invention, the performance of the batteries manufactured in each example and comparative example is compared as follows (Table 1).

[0031]

Table 1

[0032] As is clear from the comparison results, the technical solution of the present invention shows significantly better performance than the comparative example in terms of discharge specific capacity and cycle stability. By implementing the technical solution of the present invention, the unstable interface between the sulfide electrolyte and the oxide can be effectively passivated or repaired. Thereby, the sulfide electrolyte can be better compatible with more high-voltage oxide cathode materials, and the passivated / repaired interface exhibits excellent dynamic stability even during a long-term cycling process.

[0033] The above are only preferred embodiments of the present invention. For those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as within the protection scope of the present invention.

Claims

1. 1. A method for in situ electrochemical passivation and repair of a solid-state lithium battery, comprising: Discharging the sulfide-based solid-state battery to a specific degree of lithiation at a low current density and in a specific discharge mode to achieve in situ electrochemical passivation and / or repair of the battery; Discharging to a particular degree of lithiation in the discharge mode includes: The method includes at least one of discharging to a specific potential in a constant current discharge mode, discharging to a specific current in a constant current-constant voltage discharge mode, and discharging to a specific specific capacity in a constant current discharge mode, the low current density being between 0.1 and 50 mA g －１ is calculated based on the mass of the ion conductive agent in the battery positive electrode, and the specific potential to be discharged is 0.5 to 2.2 V (vs. Li ＋ / Li), and the specific current is 0.1 to 20 mA g －１ The current is calculated based on the mass of the ionic conductive agent in the battery positive electrode, and the specific capacity is 15 to 500 mAh g －１ The specific capacity is calculated based on the mass of the ionic conductive agent in the battery positive electrode. The sulfide-based solid-state battery is a sulfide-based solid-state battery assembled with a sulfide solid electrolyte as an electrolyte and an ion conductive agent in a positive electrode, a layered oxide or a polyanion oxide as a positive electrode active material.

2. The in-situ electrochemical passivation and repair method for solid-state lithium batteries according to claim 1, characterized in that the sulfide solid electrolyte is at least one of argyrodite-type electrolyte, lithium fast ion conductor, glass-ceramic phase solid electrolyte, and other electrolytes prepared by doping anions and cations or complexing with polymers based on the above electrolytes.

3. 2. The method of in situ electrochemical passivation and repair of solid-state lithium batteries according to claim 1, characterized in that the layered oxide or polyanion oxide positive electrode comprises one or a combination of positive electrode materials selected from the group consisting of lithium cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium-rich manganese-based solid solutions, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, and positive electrode materials obtained by surface coating modification and / or doping modification of the above materials.

4. The charge-discharge procedure for passivating solid-state lithium batteries is as follows: (1.1) Passivating the positive electrode interface of a sulfide-based solid-state battery, i.e., discharging the battery to a specific degree of lithiation at a low current density and in a specific discharge mode; (1.2) A step of subjecting the sulfide-based solid-state battery to a normal charge-discharge cycle. The method for in-situ electrochemical passivation and repair of a solid-state lithium battery according to claim 1, further comprising the steps of:

5. The in-situ electrochemical passivation and repair method for solid-state lithium batteries as claimed in claim 4, characterized in that in step (1.1), the passivation is carried out 1-10 times.

6. The charging and discharging procedure to repair a solid-state lithium battery is as follows: (2.1) The in-situ electrochemical passivation and repair method for a solid-state lithium battery according to claim 1, characterized in that it comprises the step of repairing the sulfide-based solid-state battery, i.e., discharging the battery to a specific degree of lithiation at a low current density and in a specific discharge mode, and re-running a normal charge-discharge cycle of the battery.

7. The method for in-situ electrochemical passivation and repair of a solid-state lithium battery according to claim 6, wherein the sulfide-based solid-state battery is a battery that has been cycled until its capacity has significantly faded.

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