A solid-state lithium battery in-situ electrochemical passivation and repair method

Abstract

The present invention belongs to the field of solid-state lithium batteries, and specifically relates to an in-situ electrochemical passivation and repair method for solid-state lithium batteries. The present invention realizes in-situ electrochemical passivation and / or repair of the battery by discharging the sulfide-based solid-state battery to a specific degree of lithiation at a low current density according to a specific discharge mode. Through this electrochemical reduction method, the interface of the sulfide-based solid-state battery can be passivated and stabilized, and the continuous decomposition of the sulfide electrolyte during the charging and discharging process can be avoided, so that the sulfide solid electrolyte can match the oxide positive electrode material with a higher operating voltage; and the oxidation products generated by the decomposition during the cycle are converted back into lithium-rich reduction products with ion conductivity, which play an activation and repair role, so that the battery has better cycle stability. At the same time, the passivation and repair method of the present invention is expected to be directly integrated into the existing lithium battery formation process, and has great application value and potential in the large-scale production and commercial application of batteries.

Description

Technical field:

[0001] The present invention belongs to the field of solid-state lithium batteries, and in particular relates to an in-situ electrochemical reduction method for passivating and repairing the positive electrode interface of a sulfide-based solid-state battery. Background technology:

[0002] With the rapid development of 3C electronic products, new energy vehicles and large-scale energy storage systems, lithium-ion batteries are facing the demand for higher energy density and safety performance. Sulfide solid electrolytes have the advantages of high ionic conductivity, excellent thermal stability, good processability and ductility. Sulfide-based solid-state lithium batteries prepared by replacing traditional flammable organic liquid electrolytes are expected to be greatly improved in terms of energy density and safety.

[0003] However, theoretical calculations and experimental results show that the electrochemical stability window of sulfide solid electrolytes is only about 1.7-2.1V (vs. Li + / Li), which is much lower than the operating voltage range (usually 2.0-5.0V) and platform voltage (3.3-3.8V) of the current mainstream commercial layered oxide cathodes (nickel cobalt manganese oxide ternary cathodes, etc.), polyanion oxide cathodes (lithium iron phosphate cathodes, etc.) and next-generation high-voltage lithium-rich cathodes (lithium-rich manganese solid solutions, etc.) (reference Fig.14 ). This results in the sulfide undergoing oxidative decomposition when the sulfide solid electrolyte and the oxide positive electrode are matched for operation, producing electronic-ion insulating products such as phosphorus polysulfide and elemental sulfur to cover the interface, hindering the effective transmission of carriers, causing a surge in interfacial impedance, and ultimately making it difficult to fully utilize the capacity of the positive electrode material and rapidly decaying. In addition, many oxide positive electrode materials themselves have low electronic conductivity and need to be coated with conductive carbon on the surface, resulting in increasingly serious oxidative decomposition of the sulfide electrolyte at the positive electrode interface. At present, the industry's surface coating of positive electrode materials and doping modification of sulfide electrolytes are not only difficult to fundamentally solve the above problems, but are also subject to high costs and complex processes in large-scale industrial production. Therefore, it is urgent to develop a simple and effective method for passivation and even repair of the positive electrode interface of sulfide-based solid-state batteries to achieve stable operation of sulfide solid electrolytes in oxide positive electrode systems with high operating voltages. Summary of the invention:

[0004] The purpose of the present invention is to provide an in-situ electrochemical reduction method for passivating and repairing the positive electrode interface of a sulfide-based solid-state battery, which can realize the passivation of the interface between the sulfide electrolyte and the oxide positive electrode and even repair the failed interface by regulating the charge and discharge system, thereby ensuring that the capacity of the positive electrode active material is fully utilized and the cycle is stable.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for in-situ electrochemical passivation and repair of solid-state lithium batteries, wherein the method discharges the sulfide-based solid-state battery to a specific degree of lithiation at a low current density according to a specific discharge mode to achieve in-situ electrochemical passivation and / or repair of the battery. By controlling the charge and discharge regime, a passivated interface is formed between the sulfide solid electrolyte and the positive electrode material, or the inactive interface is repaired and activated.

[0007] Preferably, the sulfide-based solid-state battery is a sulfide-based solid-state battery assembled with a sulfide solid electrolyte as the electrolyte and an ion conductor in the positive electrode, and a layered or polyanion oxide as the positive electrode active material; the electrolyte and the ion conductor in the same battery do not have to be the same;

[0008] More preferably, the sulfide solid electrolyte includes but is not limited to 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 Argentite-type electrolyte, Li 10 GeP2S 12 , Li 10 SnP2S 12 , Li 6.75 Si 0.75 As 0.25 Lithium fast ion conductors such as S5I, Li3PS4, Li7P3S 11 , xLi2S-(100-x)P2S5 and other glass-ceramic phase solid electrolytes, and at least one of other electrolytes prepared by using the above electrolytes as a substrate and doping with anions and cations or compounding with polymers;

[0009] More preferably, the layered or polyanion oxide positive electrode includes but is not limited to lithium cobalt oxide (LiCoO2), lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O4), lithium nickel cobalt manganese oxide (LiNi x Co y Mn 1-x-y O2), lithium nickel cobalt aluminum oxide (LiNi x Co y Al 1-x-y O2), lithium-rich manganese solid solution (xLi2MnO3·(1-x)LiMO2, M is one or more of Ni, Co, Mn), lithium iron phosphate (LiFePO4), lithium iron manganese phosphate (LiMn x Fe 1-xPO4), lithium vanadium phosphate (LiVPO4), positive electrode materials derived from surface coating and doping modification of the above materials, and combinations of one or more of the above positive electrode materials;

[0010] More preferably, the negative electrode material of the sulfide-based solid-state battery includes but is not limited to negative electrode materials such as metallic lithium, lithium-indium alloy, graphite, hard carbon, silicon carbon, lithium titanate, titanium niobium oxide, and negative electrode materials derived from the modification of the above materials, and a combination of one or more positive electrode materials mentioned above;

[0011] More preferably, the ion conductive electrode accounts for 1% to 60% of the total mass of the positive electrode.

[0012] Preferably, the specific discharge mode to discharge to a specific degree of lithiation includes: 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 0.1-50mAg -1 (measured according to the mass of the ionic conductive agent in the battery composite positive electrode); the specific discharge potential is 0.5-2.2V (vs.Li + / Li); the constant current-constant voltage discharge mode is a constant current discharge to a specific potential followed by a constant voltage discharge to a specific current, the cut-off condition is a constant voltage discharge current of 0.1-20mAg -1 (measured according to the mass of the ionic conductive agent in the composite positive electrode); the specific capacity is 15-500mAh g -1 (measured according to the mass of the ion conductive electrode in the composite positive electrode).

[0013] Preferably, the charge and discharge regime for passivating the solid-state lithium battery includes the following:

[0014] (1.1) Passivate the positive electrode interface of the sulfide-based solid-state battery, that is, discharge to a specific degree of lithiation at a low current density according to a specific discharge mode, so that the sulfide electrolyte at the interface undergoes moderate reduction decomposition, and produces lithium-rich decomposition products that cover the interface with strong reaction activity, thereby achieving the purpose of interface passivation and retaining the lithium ion transmission pathway;

[0015] (1.2) Performing normal charge and discharge cycles on sulfide-based solid-state batteries;

[0016] More preferably, in step (1.1), the positive electrode interface passivation measure is not limited to the first direct discharge passivation, and 1-10 passivations can be performed, that is, the discharge passivation process can be selectively included in 1-10 cycles of the battery to further ensure that the interface is fully passivated;

[0017] More preferably, the normal charge and discharge cycle current is 0.05-20C (measured by the mass of the positive electrode active material), and the charge and discharge voltage range is the voltage range of normal charge and discharge of the positive electrode material.

[0018] Preferably, the charging and discharging system for repairing the solid-state lithium battery includes the following:

[0019] (2.1) Repairing sulfide-based solid-state batteries, that is, discharging to a specific degree of lithiation at a low current density according to a specific discharge mode, performing an interface passivation operation to repair the failed battery, and reducing the reduction products accumulated at the interface to lithium-rich products with lithium ion transport properties, so that the battery can resume normal charge and discharge cycles;

[0020] More preferably, the sulfide-based solid-state battery is a battery that has been cycled to a point where its capacity has been significantly attenuated. More preferably, the significant capacity attenuation includes a case where the discharge capacity has been attenuated to 1%-70% of the rated discharge capacity. More preferably, the repair can be performed on a solid-state lithium battery that has not undergone the interface passivation step described in the present invention, or has adopted other formation and activation processes, or has been directly subjected to charge and discharge cycles.

[0021] More preferably, the sulfide-based solid-state battery may also be subjected to the aforementioned interface passivation treatment; at this time, the specific discharge mode, current, cut-off voltage, rated capacity, etc. of the interface repair operation do not have to be completely the same as those in the passivation step;

[0022] More preferably, the normal charge and discharge cycle current is 0.05-20C (measured by the mass of the positive electrode active material), and the charge and discharge voltage range is the voltage range of normal charge and discharge of the positive electrode material.

[0023] The present invention passivates the battery, causing the sulfide electrolyte to undergo an appropriate degree of reduction and decomposition, forming a lithium-rich product passivation interface at the interface between the sulfide electrolyte and the positive electrode, and having certain lithium ion conductivity properties to ensure the subsequent normal circulation of the battery, which can effectively solve the problem that the working voltage range of the oxide positive electrode material exceeds the electrochemical stability window of the sulfide solid electrolyte. After a large capacity decay occurs in the battery cycle, the accumulated electron-ion insulating oxidation products at the interface are converted back into lithium-rich reduction products by an in-situ electrochemical reduction method, which repairs the battery. Through this electrochemical reduction method, the interface of the sulfide-based solid-state battery can be passivated and stabilized, avoiding the continuous decomposition of the sulfide electrolyte during the charge and discharge process, so that the sulfide solid electrolyte can match the oxide positive electrode material with a higher operating voltage; and the oxidation products generated by the decomposition during the cycle are converted back into lithium-rich reduction products with ion conductivity, which play an activation and repair role, so that the battery has better cycle stability.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention utilizes a simple charge and discharge system regulation to manipulate the reversible redox reaction of the sulfide solid electrolyte, realizes the passivation of the interface between the sulfide electrolyte and the oxide positive electrode, so that the sulfide electrolyte with a narrow electrochemical stability window can be directly matched with the mainstream oxide positive electrode material with a higher operating voltage, avoiding cumbersome interface modification, doping modification and other processes. Since the discharge of the positive electrode in the lithium battery corresponds to the lithiation process, the sulfide electrolyte undergoes reduction decomposition during the first discharge to form lithium-rich decomposition products such as lithium chloride (or bromine, iodine), lithium sulfide and lithium phosphide. Different from the lithium-poor product that undergoes oxidation decomposition during charging to produce ion-electronic insulation, the above-mentioned lithium-rich decomposition product has electronic insulation and ion transmission characteristics. Once generated, it has high inertness and is not easy to be reoxidized. It not only maintains the transmission of lithium ions at the interface, passivates the interface to a metastable state, and is expected to suppress intrinsic problems such as lattice oxygen precipitation, structural collapse, and irreversible phase change of the positive electrode material, which is conducive to maintaining the subsequent cycle stability of the battery. At the same time, the in-situ electrochemical passivation and repair method proposed in the present invention is expected to be directly integrated into the existing lithium battery formation process, and has great application value and potential in the large-scale production and commercial application of sulfide-based solid-state lithium batteries. Description of the drawings:

[0026] Figure 1 The charge and discharge curves of the first and 50th cycle processes of the lithium iron phosphate positive electrode in Example 1 of the present invention after being discharged and passivated to 1.0V and then charged and discharged;

[0027] Figure 2 The first and 50th charge-discharge curves of the lithium iron phosphate positive electrode in Comparative Example 1 of the present invention are directly subjected to charge-discharge tests without discharge passivation, as a comparative experiment;

[0028] Figure 3 The cycle performance diagram of the lithium iron phosphate positive electrode in Example 1 of the present invention after discharge passivation and direct charge and discharge at 0.1C during 50 cycles in Comparative Example 1;

[0029] Figure 4 The charge and discharge curves of the first and 60th cycles of the lithium iron phosphate positive electrode after discharge passivation to 0.8V in Example 2 of the present invention;

[0030] Figure 5 The charge-discharge curves of the first and 20th cycles of the normal charge-discharge test of the lithium iron phosphate positive electrode in Comparative Example 2 of the present invention without discharge passivation are used as a comparative experiment;

[0031] Figure 6This is a cycle performance diagram of the lithium iron phosphate positive electrode after passivation in Example 3 of the present invention at 1C and 600 cycles;

[0032] Figure 7 The charge and discharge curves of the first and tenth cycle processes of the lithium-rich manganese-based positive electrode in Example 4 of the present invention after discharge passivation to 1.5V and then charge and discharge;

[0033] Figure 8 The lithium-rich manganese-based positive electrode in Comparative Example 4 of the present invention is directly charged and discharged normally without discharge passivation, and the charge and discharge curves at the 1st and 10th cycles are used as a comparative experiment;

[0034] Fig. 9 The charge and discharge curves of the first and tenth cycle processes of the lithium manganese iron phosphate positive electrode in Example 5 of the present invention after discharge passivation to 1.0V and then charge and discharge;

[0035] Fig.10 The lithium manganese iron phosphate positive electrode in Comparative Example 5 of the present invention is not discharged and passivated, and is directly charged and discharged normally. The charge and discharge curves of the 1st and 10th cycles are used as a comparative experiment;

[0036] Fig.11 The charge and discharge curves of the first and tenth cycle processes of the mixed positive electrode of lithium manganese iron phosphate and lithium nickel cobalt manganese oxide in Example 8 of the present invention after discharge passivation to 1.0V;

[0037] Fig.12 The mixed positive electrode of lithium manganese iron phosphate and lithium nickel cobalt manganese oxide in Comparative Example 8 of the present invention is directly charged and discharged normally without discharge passivation, and the charge and discharge curves at the 1st and 10th cycles are used as a comparative experiment;

[0038] Fig.13 It is a schematic diagram of the implementation steps and principles of the present invention;

[0039] Fig.14 is the oxidation decomposition potential (2.1V (vs.Li) of the sulfide solid electrolyte of the present invention + Comparison of the charge and discharge range of common oxide positive electrode materials;

[0040] Fig.15 This is the X-ray photoelectron spectrum (XPS) of the positive electrode during charging after interface passivation in Example 1 of the present invention and direct normal charging (ie, Comparative Example 1). Specific implementation method:

[0041] For ease of understanding, the technical solutions and implementation methods of the present invention are further described clearly, completely and in detail through specific examples and in combination with the accompanying drawings. It should be noted that the embodiments described in the present invention are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operating processes are given, but they are only part of the embodiments of the present invention, not all of the embodiments. The specific implementation methods described are limited to explaining and interpreting the present invention, and do not limit the present invention. Based on the embodiments in the present invention, all other implementation methods obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0042] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods, and the materials, reagents, etc. used in the examples are all available from commercial sources unless otherwise specified.

[0043] Example 1 (lithium iron phosphate positive electrode, discharge passivation to 1.0V):

[0044] A solid-state lithium battery in-situ electrochemical passivation and repair method, the embodiment steps are as follows:

[0045] In the first step, lithium iron phosphate (LiFePO4, with a carbon coating on the surface), Li 5.5 PS 4.5 Cl 1.5 (ion conductive agent), vapor-grown carbon fiber (electronic conductive agent), and ethyl cellulose (binder) were mixed in a mass ratio of 70:24:3:3 and coated on carbon-coated aluminum foil with anhydrous ethanol as solvent to prepare the positive electrode. The positive electrode active material loading was 1-3 mg cm -2 ; 100 mg of Li 5.5 PS 4.5 Cl 1.5 As a solid electrolyte; metal lithium with a diameter of 10 mm as the negative electrode, pressed at 360 MPa to prepare a solid-state battery;

[0046] In the second step, the prepared solid-state battery is first heated to 20 mAg -1 Discharge at a current density (measured according to the mass of the ionic conductive agent in the composite positive electrode) to 1.0 V for interface passivation;

[0047] In the third step, the solid-state battery after interface passivation is charged to 4.0V and discharged to 2.5V for normal charge and discharge cycles with a current density of 17mAg -1 (0.1C). The charge and discharge curves for the 1st and 50th times are as follows Figure 1 shown.

[0048] As comparative example 1, the same battery was prepared and directly charged and discharged normally in the range of 2.5-4.0V at a rate of 0.1C. The first and 50th charge and discharge curves are as follows: Figure 2 As shown in the figure, the battery can hardly operate normally, and the charge and discharge curve deviates seriously from the typical charge and discharge curve of lithium iron phosphate. After 10 cycles, it is almost completely ineffective. Performance comparison of the battery of Example 1 and the comparative example during 50 cycles Figure 3 shown.

[0049] The positive electrodes of Example 1 (including the passivated state and the charged state after passivation) and Comparative Example 1 were characterized by X-ray photoelectron spectroscopy. Fig.15 As shown in the S2p and P2p spectra, it is observed that the in-situ electrochemical passivation method used in Example 1 forms a passivation interface with lithium sulfide (Li2S), which effectively alleviates the charged state oxidation product (elemental sulfur (-S n -), phosphorus polysulfide (P2S x )) accumulation, thus avoiding Li 5.5 PS 4.5 Cl 1.5 Interfacial failure caused by continued decomposition of the electrolyte.

[0050] Example 2 (high-load lithium iron phosphate positive electrode, discharge passivation to 0.8V):

[0051] A solid-state lithium battery in-situ electrochemical passivation and repair method, the embodiment steps are as follows:

[0052] In the first step, lithium iron phosphate (LiFePO4, with a carbon coating on the surface), Li 5.5 PS 4.5 Cl 1.5 (ion conductive agent), vapor-grown carbon fiber (electronic conductive agent), and polytetrafluoroethylene (binder) were mixed in a mass ratio of 60:34:3:3 to form a composite positive electrode. -2 The positive electrode active material loading is pressed on the surface of carbon-coated aluminum foil; 100 mg of Li 5.5 PS 4.5 Cl 1.5 As a solid electrolyte; metal lithium with a diameter of 10 mm as the negative electrode, pressed at 360 MPa to prepare a solid-state battery;

[0053] In the second step, the prepared solid-state battery is first heated to 15 mAg -1 Discharge at a current density (measured according to the mass of the ionic conductive agent in the composite positive electrode) to 0.8V for interface passivation;

[0054] In the third step, the solid-state battery after interface passivation is charged to 3.8V and discharged to 2.5V for normal charge and discharge cycles with a current density of 17mAg-1 (0.1C). The charge and discharge curves for the 1st and 60th times are as follows Figure 4 shown.

[0055] As comparative example 2, the same battery is directly charged and discharged normally in the range of 2.5-3.8V at a rate of 0.1C. The charge and discharge curves of the first and 20th times are as follows: Figure 5 As shown, the capacity decayed significantly within 20 cycles.

[0056] Example 3 (High rate lithium iron phosphate positive electrode, discharge passivation to 1.0V)

[0057] A solid-state lithium battery in-situ electrochemical passivation and repair method, the embodiment steps are as follows:

[0058] In the first step, lithium iron phosphate (LiFePO4, with a carbon coating on the surface), Li 5.5 PS 4.5 Cl 1.5 (ion conductive agent), vapor-grown carbon fiber (electronic conductive agent), and ethyl cellulose (binder) were mixed in a mass ratio of 70:24:3:3 and coated on carbon-coated aluminum foil with anhydrous ethanol as solvent to prepare a positive electrode. The loading was based on Example 1; 100 mg of Li 5.5 PS 4.5 Cl 1.5 As a solid electrolyte; metal lithium with a diameter of 10 mm as the negative electrode, pressed at 360 MPa to prepare a solid-state battery;

[0059] In the second step, the prepared solid-state battery is first heated to 20 mAg -1 Discharge at a current density (measured according to the mass of the ionic conductive agent in the composite positive electrode) to 1.0 V for interface passivation;

[0060] In the third step, the solid-state battery after interface passivation is charged to 4.0V and discharged to 2.5V for normal charge and discharge cycles with a current density of 170mAg -1 (1C). Cyclic performance during 600 cycles is as follows Figure 6 As shown, there is almost no capacity decay over 600 cycles, indicating that this in situ electrochemical passivation forms a kinetically stable interface.

[0061] Example 4 (lithium-rich manganese-based positive electrode, discharge passivation to 1.5V):

[0062] A solid-state lithium battery in-situ electrochemical passivation and repair method, the embodiment steps are as follows:

[0063] In the first step, lithium-rich manganese-based (LiNbO3) coated with lithium niobate (Li 1.2 Mn 0.54 Ni0.13 Co 0.13 O4) positive electrode as active material, Li 5.5 PS 4.5 Cl 1.5 (ion conductive agent), vapor-grown carbon fiber (electronic conductive agent), and ethyl cellulose (binder) were mixed in a mass ratio of 60:30:7:3 and coated on carbon-coated aluminum foil with anhydrous ethanol as solvent to prepare a positive electrode. The loading was based on Example 1; 100 mg of Li 5.5 PS 4.5 Cl 1.5 As a solid electrolyte; metal lithium with a diameter of 10 mm as the negative electrode, pressed at 360 MPa to prepare a solid-state battery;

[0064] In the second step, the prepared solid-state battery is first heated to 25 mAg -1 Discharge at a current density (measured according to the mass of the ionic conductive agent in the composite positive electrode) to 1.5 V for interface passivation;

[0065] In the third step, the solid-state battery after interface passivation is charged to 4.8V and discharged to 2.0V for normal charge and discharge cycles with a current density of 25mAg -1 (0.1C). The charge and discharge curves for the 1st and 10th times are as follows Figure 7 After the interface is passivated, the interface becomes stable, and the capacity does not decay significantly after 10 cycles, and can stably exert a capacity of nearly 220 mA hg -1 capacity.

[0066] As comparative example 4, the same battery was not passivated and was directly charged and discharged at a rate of 0.1C in the range of 2.0-4.8V. The charge and discharge curves of the first and tenth times are as follows: Figure 8 As shown. Without interfacial passivation, the first discharge capacity of the lithium-rich manganese-based cathode is only 70 mAh g -1 Due to the severe decomposition of the sulfide electrolyte, the capacity decayed to 40 mAh g after 10 cycles. -1 .

[0067] Lithium-manganese-rich solid solutions (xLi2MnO3·(1-x)LiMO2, M is one or more of Ni, Co, Mn, 0<x<1) as positive electrode active materials can all undergo corresponding passivation and / or repair operations and have comparable effects, which will not be elaborated here due to space limitations.

[0068] Example 5 (Lithium manganese iron phosphate positive electrode, discharge passivation to 1.0V)

[0069] A solid-state lithium battery in-situ electrochemical passivation and repair method, the embodiment steps are as follows:

[0070] The first step is to convert 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, ethyl cellulose were mixed in a mass ratio of 50:40:7:3, and anhydrous ethanol was used as solvent to coat the carbon-coated aluminum foil to prepare the positive electrode. The loading was based on Example 1; 100 mg of Li 5.5 PS 4.5 Cl 1.5 As a solid electrolyte; 10mm diameter lithium metal as the negative electrode, pressed at 360MPa to form a solid-state battery;

[0071] In the second step, the prepared solid-state battery is first heated to 15 mAg -1 Discharge at a current density (measured according to the mass of the ionic conductive agent in the composite positive electrode) to 1.0 V for interface passivation;

[0072] In the third step, the solid-state battery after interface passivation is charged to 4.3V and discharged to 2.5V for normal charge and discharge cycles with a current density of 17mAg -1 (0.1C). The charge and discharge curves for the 1st and 10th times are as follows Fig. 9 After interface passivation, the first discharge capacity is close to 150 mAh g -1 , there is no obvious capacity decay within 10 cycles.

[0073] As comparative example 5, the same battery was directly tested for charge and discharge at a rate of 0.1C in the range of 2.5-4.3V without passivation. The charge and discharge curves of the first and tenth times are as follows: Fig.10 Its charge and discharge capacity is less than 30 mAh g -1 , and exhibits large polarization, which is due to the severe oxidative decomposition of the electrolyte, making it difficult for the battery to operate.

[0074] Lithium manganese iron phosphate (LiFe x Mn 1-x PO4, 0<x<1) as the positive electrode active material can be subjected to corresponding passivation and / or repair operations and have considerable effects, which will not be elaborated here due to space limitations.

[0075] Example 6 (Repair of Nickel-Cobalt-Lithium-Manganese Oxide Ternary Positive Electrode)

[0076] A solid-state lithium battery in-situ electrochemical passivation and repair method, the embodiment steps are as follows:

[0077] The first step is to convert lithium nickel cobalt manganese oxide (LiNi 0.8 Co 0.1 Mn 0.1 O2) positive electrode, Li5.5 PS 4.5 Cl 1.5 (ion conductive agent), vapor-grown carbon fiber (electronic conductive agent), and ethyl cellulose (binder) were mixed in a mass ratio of 60:30:7:3 and coated on carbon-coated aluminum foil with anhydrous ethanol as solvent to prepare a positive electrode. The loading was based on Example 1; 100 mg of Li 5.5 PS 4.5 Cl 1.5 As a solid electrolyte; 10mm diameter lithium metal as the negative electrode, pressed at 360MPa into a solid-state battery;

[0078] In the second step, the solid-state battery is charged at 250mAg in the range of 2.5-4.3V. -1 (1C, calculated based on the loading of lithium nickel cobalt manganese oxide) The current density was cycled 100 times, and the first discharge capacity was 122 mAh g -1 ;

[0079] In the third step, after the solid-state battery has completed 100 cycles, the capacity has dropped significantly to 52 mAh g -1 , at 20mA g -1 (measured according to the mass of the ionic conductive agent in the composite positive electrode) discharge with a small current to 1.8V, reduce the oxidation products accumulated at the interface to lithium-rich products with a certain ionic conductivity, and complete the repair of the ternary positive electrode;

[0080] Step 4: Restore 1C high rate cycle. After repair, the capacity is restored to 98mAh g -1 The battery can then be charged and discharged normally, and after 300 cycles, the capacity is higher than 80 mAh g -1 , the battery performance has been effectively repaired and is more stable than before.

[0081] Lithium Nickel Cobalt Manganese Oxide (LiNi x Co y Mn 1-x-y O2, 0<x<1, 0<y<1, 0<1-xy<1) as positive electrode active materials can all be subjected to corresponding passivation and / or repair operations with considerable effects, which will not be elaborated here due to space limitations.

[0082] Example 7 (Repair of high voltage lithium cobalt oxide positive electrode)

[0083] A solid-state lithium battery in-situ electrochemical passivation and repair method, the embodiment steps are as follows:

[0084] The first step is to prepare the lithium cobalt oxide (LiCoO2) positive electrode, Li 5.5 PS 4.5 Cl 1.5(ion conductive agent), vapor-grown carbon fiber (electronic conductive agent), and ethyl cellulose (binder) were mixed in a mass ratio of 60:30:7:3 and coated on carbon-coated aluminum foil with anhydrous ethanol as solvent to prepare a positive electrode. The loading was based on Example 1; 100 mg of Li 5.5 PS 4.5 Cl 1.5 As a solid electrolyte; 10mm diameter lithium metal as the negative electrode, pressed at 360MPa into a solid-state battery;

[0085] In the second step, the solid-state battery is charged at 270mAg in the range of 2.5-4.7V. -1 (1C, calculated based on lithium cobalt oxide loading) Current density cycled 100 times, first discharge capacity 85 mAh g -1 ;

[0086] The third step is to wait until the solid-state battery completes 100 cycles and the capacity is greatly increased to 30 mAh g -1 , at 20mAg -1 (measured according to the mass of the ion conductive agent in the composite positive electrode) discharge with a small current to 1.8V, reduce the oxidation products accumulated at the interface to lithium-rich products with a certain ion conductivity, and complete the repair of the high-voltage lithium cobalt oxide positive electrode;

[0087] Step 4: Restore 1C high rate cycle, and the capacity is restored to 78 mAh g after repair. -1 The battery can then be charged and discharged normally, and after 300 cycles, the capacity is higher than 60 mAh g -1 , the battery performance has been effectively repaired and is more stable than before.

[0088] Example 8 (Mixed lithium iron manganese phosphate and ternary positive electrode, discharged and passivated to 1.0V)

[0089] A solid-state lithium battery in-situ electrochemical passivation and repair method, the embodiment steps are as follows:

[0090] The first step is to convert 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 positive electrode is mixed with positive electrode in a mass ratio of 1:1, Li 5.5 PS 4.5 Cl 1.5 , vapor-grown carbon fiber, and polytetrafluoroethylene were mixed in a mass ratio of 50:40:7:3 as a composite cathode, with a concentration of 5 mg cm -2 The positive electrode active material loading is pressed on the surface of the carbon-coated aluminum foil current collector; 100 mg of Li 5.5 PS4.5 Cl 1.5 As a solid electrolyte; 10mm diameter lithium metal as the negative electrode, pressed at 360MPa into a solid-state battery;

[0091] In the second step, the prepared solid-state battery is first heated to 15 mAg -1 Discharge at a current density (measured according to the mass of the ionic conductive agent in the composite positive electrode) to 1.0 V for interface passivation;

[0092] In the third step, the solid-state battery after interface passivation is charged to 4.3V and discharged to 2.5V for normal charge and discharge cycles with a current density of 18.5mAg -1 (0.1C). The charge and discharge curves for the 1st and 10th times are as follows Fig.11 After interface passivation, the first discharge capacity is close to 110 mAh g -1 , there is no obvious capacity decay within 10 cycles.

[0093] As comparative example 8, the same battery was directly charged and discharged at a rate of 0.1C in the range of 2.5-4.3V. The charge and discharge curves of the first and tenth times are as follows: Fig.12 As shown. Its charge and discharge capacity is relatively low, and the first discharge capacity is 62mAhg -1 After 10 cycles, the discharge capacity is 38 mAh g -1 , and exhibits large polarization. Due to the severe oxidative decomposition of the electrolyte in the carbon layer on the surface of lithium manganese iron phosphate, the capacity of lithium manganese iron phosphate is difficult to exert, and the low capacity exerted is only contributed by the nickel cobalt manganese oxide ternary positive electrode (because there is no carbon coating layer on the surface of lithium nickel cobalt manganese oxide).

[0094] 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-xy<1) mixed (including mixing according to other mass ratios) as positive electrode active materials can all perform corresponding passivation and / or repair operations and have considerable effects, which will not be elaborated here due to space limitations.

[0095] Example 9 (Lithium iron phosphate positive electrode, constant current-constant voltage discharge mode passivation)

[0096] A solid-state lithium battery in-situ electrochemical passivation and repair method, the embodiment steps are as follows:

[0097] In the first step, lithium iron phosphate (LiFePO4, with a carbon coating on the surface), Li 10 GeP2S 12(ion conductive agent), vapor-grown carbon fiber (electronic conductive agent), and polytetrafluoroethylene (binder) were mixed in a mass ratio of 60:34:3:3 to form a composite positive electrode. -2 The positive electrode active material loading is pressed on the surface of the carbon-coated aluminum foil current collector; 100 mg of Li 10 GeP2S 12 As a solid electrolyte; a lithium-indium alloy with a diameter of 10 mm as the negative electrode was pressed at 360 MPa to prepare a solid-state battery;

[0098] In the second step, the prepared solid-state battery is first heated to 10 mAg -1 The battery was discharged at a current density of 1.5 V (calculated according to the loading of the ion conductor in the composite positive electrode) to 1.5 V (to lithium potential), and then discharged at a constant voltage of 1.5 V, with the cut-off condition being a current less than 2 mAg -1 (calculated according to the loading amount of the ion conductive agent in the composite positive electrode), performing interface passivation;

[0099] In the third step, the solid-state battery after interface passivation is charged to 4.0V (to lithium potential) and discharged to 2.5V (to lithium potential) for normal charge and discharge cycles with a current density of 17mAg -1 (0.1C), and after the first 5 charge and discharge cycles, the interface passivation operation as described in step 2 was performed again. After the discharge passivation was completed, the first discharge capacity was 154mAh g -1 After 50 cycles, the capacity is 133 mAh g -1 .

[0100] As comparative example 9, the same battery was charged and discharged directly according to the normal process without passivation, and the first discharge capacity was 50 mAh g -1 After 50 cycles, the capacity is less than 10 mAh g -1 .

[0101] Example 10 (lithium-rich manganese-based positive electrode, 130 mAh g -1 Constant volume mode discharge passivation)

[0102] A solid-state lithium battery in-situ electrochemical passivation and repair method, the embodiment steps are as follows:

[0103] In the first step, lithium niobate (LiNbO3) coated lithium-rich manganese-based (Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O4) positive electrode active material, Li7P3S 11 (ion conductive agent), vapor-grown carbon fiber (electronic conductive agent), and polytetrafluoroethylene (binder) were mixed in a mass ratio of 60:34:3:3 to form a composite positive electrode.-2 The positive electrode active material loading is pressed on the surface of the aluminum foil current collector; 100 mg of Li7P3S 11 As a solid electrolyte; a lithium sheet with a diameter of 10 mm is used as the negative electrode, which is pressed and formed at 360 MPa to prepare a solid-state battery;

[0104] In the second step, the prepared solid-state battery is first heated to 10 mAg -1 The discharge was carried out at a current density of 130 mAh g (measured according to the mass of the ionic conductive agent in the composite positive electrode) for 13 hours, that is, the discharge was carried out to the rated capacity of 130 mAh g -1 (measured according to the mass of the ionic conductive agent in the composite positive electrode), performing interface passivation;

[0105] In the third step, the solid-state battery after interface passivation is charged to 4.8V and discharged to 2.0V for normal charge and discharge cycles with a current density of 25mAg -1 (0.1C). The first discharge capacity is 194mAh g -1 After 50 cycles, the capacity is 160 mAhg -1 .

[0106] As a comparison, the same battery was charged and discharged directly according to normal procedures without passivation. Due to the high operating voltage range, the sulfide electrolyte decomposed severely and the battery could not operate normally.

[0107] Example 11 (High Voltage LiMnO4 Positive Electrode, Passivation in Constant Current-Constant Voltage Discharge Mode)

[0108] A solid-state lithium battery in-situ electrochemical passivation and repair method, the embodiment steps are as follows:

[0109] The first step is to convert lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O4) positive electrode, Li3PS4 (ion conductive agent), vapor-grown carbon fiber (electronic conductive agent), and polytetrafluoroethylene (binder) were mixed in a mass ratio of 60:34:3:3 as a composite positive electrode, with a concentration of 5 mg / cm -2 The positive electrode active material loading is pressed on the surface of the aluminum foil current collector; 100 mg of Li3PS4 is used as the solid electrolyte; a lithium sheet with a diameter of 10 mm is used as the negative electrode, and is pressed and formed at 360 MPa to prepare a solid-state battery;

[0110] In the second step, the prepared solid-state battery is first heated to 10 mAg -1 The current density is discharged to 1.3V (measured according to the mass of the ionic conductive agent in the composite positive electrode), and then a constant voltage discharge is performed at 1.3V. The cut-off condition is that the current is less than 2mAg -1 (measured according to the mass of the ionic conductive agent in the composite positive electrode), performing interface passivation;

[0111] In the third step, the solid-state battery after interface passivation is charged to 5.2V and discharged to 3.0V for normal charge and discharge cycles with a current density of 14.6mAg -1 (0.1C). The first discharge capacity is 113 mAh g -1 After 50 cycles, the capacity is 90 mAh g -1 .

[0112] As a comparison, the same battery was charged and discharged directly according to normal procedures without passivation. Due to the high operating voltage range, the sulfide electrolyte decomposed severely and the battery could not operate normally.

[0113] Example 12 (High voltage lithium nickel manganese oxide positive electrode, 130 mAh g -1 Constant volume mode discharge passivation)

[0114] A solid-state lithium battery in-situ electrochemical passivation and repair method, the embodiment steps are as follows:

[0115] The first step is to prepare the lithium nickel manganese oxide positive electrode (LiNi 0.5 Mn 1.5 O4), Li7P3S 11 (ion conductive agent), vapor-grown carbon fiber (electronic conductive agent), and polytetrafluoroethylene (binder) were mixed in a mass ratio of 60:34:3:3 as a composite positive electrode, with a concentration of 5 mg / cm -2 The positive electrode active material loading is pressed on the surface of the aluminum foil current collector; 100 mg of Li7P3S 11 As a solid electrolyte; a lithium sheet with a diameter of 10 mm is used as the negative electrode, which is pressed and formed at 360 MPa to prepare a solid-state battery;

[0116] In the second step, the prepared solid-state battery is first heated to 10 mAg -1 The discharge was carried out at a current density of 130 mAh g (measured according to the mass of the ionic conductive agent in the composite positive electrode) for 13 hours, that is, the discharge was carried out to the rated capacity of 130 mAh g -1 (measured according to the mass of the ionic conductive agent in the composite positive electrode), performing interface passivation;

[0117] In the third step, the solid-state battery after interface passivation is charged to 5.2V and discharged to 3.0V for normal charge and discharge cycles with a current density of 14.6mAg -1 (0.1C). The first discharge capacity is 105mAh g -1 After 50 cycles, the capacity is 84 mAh g -1 .

[0118] As a comparison, the same battery was directly charged and discharged according to the normal process steps. Due to the high operating voltage range, the sulfide electrolyte decomposed severely and the battery could not operate normally.

[0119] Example 13 (lithium iron phosphate positive electrode, interface passivation and repair strategy combined case):

[0120] In the first step, lithium iron phosphate (LiFePO4, with a carbon coating on the surface), Li 5.5 PS 4.5 Cl 1.5 (ion conductive agent), vapor-grown carbon fiber (electronic conductive agent), and polytetrafluoroethylene (binder) were mixed in a mass ratio of 60:34:3:3 and 5 mg / cm -2 The positive electrode was prepared by pressing the carbon-coated aluminum foil; 100 mg of Li 5.5 PS 4.5 Cl 1.5 As a solid electrolyte; metal lithium with a diameter of 10 mm as the negative electrode, pressed at 360 MPa to prepare a solid-state battery;

[0121] In the second step, the prepared solid-state battery is first heated to 20 mAg -1 Discharge at a current density of 1.0 V (measured according to the mass of the ionic conductive agent in the composite positive electrode) to perform interface passivation;

[0122] In the third step, the solid-state battery after interface passivation is charged to 4.0V and discharged to 2.5V for normal charge and discharge cycles with a current density of 170mAg -1 (1C). The initial discharge capacity is 105 mAh g -1 After 200 cycles, the capacity did not significantly decay, reaching 94 mAh g -1 After 1000 cycles, the capacity decayed to 53 mAh g due to the destruction of the passivation layer during the long-term cycling process and the re-accumulation of oxidation products produced by electrolyte decomposition at the interface. -1 ;

[0123] Step 4: 20mAg -1 Discharge with a small current to 1.5V to reduce the oxidation products accumulated at the interface to lithium-rich products with a certain ionic conductivity, thus completing the repair of the lithium iron phosphate positive electrode (passivated);

[0124] Step 5: Restore 1C high rate cycle. After repair, the capacity is restored to 85mAh g -1 The battery can be charged and discharged normally again, and can be cycled 500 times, still retaining >77mAh g -1 The discharge capacity.

[0125] In order to further compare the superiority of the technical solution of the present invention, the performance of the batteries prepared in each embodiment and the comparative example are compared as follows (Table 1):

[0126] Table 1

[0127]

[0128]

[0129] The comparison results indicate that the technical solution of the present invention performs significantly better 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, so that the sulfide electrolyte can be successfully matched with more high-voltage oxide positive electrode materials, and the passivated / repaired interface has excellent kinetic stability during long-term cycling.

[0130] The above is only a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A solid-state lithium battery in-situ electrochemical passivation and repair method, characterized in that: The method is to discharge the sulfide-based solid-state battery to a specific degree of lithiation in a specific discharge mode at a low current density to achieve in-situ electrochemical passivation and / or repair of the battery; the discharge mode to discharge to a specific degree of lithiation includes: 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 is 0.1-50 mAg -1 , the low current density is measured according to the mass of the ionic conductive agent in the positive electrode of the battery; the specific discharge potential is 0.5-2.2V (vs.Li + / Li); the specific current is 0.1-20mAg -1 The current is measured according to the mass of the ionic conductive agent in the positive electrode of the battery; the specific capacity is 15-500mAh g -1 The specific capacity is measured according to the mass of the ion conductor in the positive electrode of the battery; the sulfide-based solid-state battery is a sulfide-based solid-state battery assembled with a sulfide solid electrolyte as the electrolyte and an ion conductor in the positive electrode, and a layered or polyanion oxide as the positive electrode active material.

2. The solid-state lithium battery in-situ electrochemical passivation and repair method according to claim 1, characterized in that: The sulfide solid electrolyte includes at least one of argyrodite-type electrolytes, lithium fast ion conductors, glass-ceramic phase solid electrolytes, and other electrolytes prepared by using the above electrolytes as a base and doping with anions and cations or compounding with polymers.

3. The solid-state lithium battery in-situ electrochemical passivation and repair method according to claim 1, characterized in that: The layered or polyanion oxide positive electrode includes lithium cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese-rich solid solution, lithium iron phosphate, lithium vanadium phosphate, and a combination of one or more positive electrode materials derived from the surface coating modification and / or doping modification of the above materials.

4. The in-situ electrochemical passivation and repair method of a solid-state lithium battery according to claim 1, characterized in that: The charge and discharge regime for passivation of solid-state lithium batteries includes the following: (1.1) Passivating the positive electrode interface of the sulfide-based solid-state battery, that is, discharging to a specific degree of lithiation at a low current density according to a specific discharge mode; (1.2) Perform normal charge and discharge cycles on the sulfide-based solid-state battery.

5. The solid-state lithium battery in-situ electrochemical passivation and repair method according to claim 4, characterized in that: In step (1.1), the passivation is performed 1 to 10 times.

6. The solid-state lithium battery in-situ electrochemical passivation and repair method according to claim 1, characterized in that: The charging and discharging system for repairing solid-state lithium batteries includes the following: (2.1) Repairing the sulfide-based solid-state battery, that is, discharging it to a specific lithium degree at a low current density according to a specific discharge mode, and then resuming the normal charge and discharge cycle of the battery.

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

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