Lithium metal batteries and methods of making and using the same

Abstract

The application provides a lithium metal battery, in a negative electrode sheet, the area density of one side of the lithium metal layer is < the first charge gram capacity of the positive electrode * the area density of the active material of the positive electrode * the excess coefficient of the negative electrode / the first charge gram capacity of the negative electrode / the weight proportion of lithium in the lithium metal layer. When lithium ions obtain electrons and deposit, the lithium metal layer can form a stable metal bond with the lithium ions, and the binding force is strong; meanwhile, the area density of the lithium metal layer is reasonably designed by considering the actual combination of the lithium metal layer and the lithium ions, the mass of the lithium metal layer is reduced, thereby the weight of the electrode sheet can be reduced, the internal resistance growth rate of the lithium metal battery can be controlled, and the battery capacity can also be maintained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of new energy, and particularly relates to a lithium metal battery and a preparation method and application thereof. BACKGROUND

[0002] Lithium batteries have higher energy density, stronger discharge capacity and longer service life, and are widely used. Lithium batteries can be divided into lithium metal batteries and lithium ion batteries. The research and development time of lithium ion batteries is longer than that of lithium metal batteries, and the design has formed a relatively perfect standard in the industry, and the lithium metal battery which appears later usually also refers to these standards for structural design.

[0003] However, there are still problems of large weight and large internal resistance of the pole piece in the current lithium metal battery. SUMMARY

[0004] In view of the above problems existing in the prior art, the purpose of the present application is to provide a lithium metal battery and a preparation method and application thereof, the lithium metal battery has low lithium metal layer surface density of the negative pole piece, can maintain the capacity of the lithium metal battery, and can control the internal resistance growth rate of the lithium metal battery.

[0005] To achieve the above purpose, the application adopts the following technical solutions:

[0006] The application provides a lithium metal battery, comprising a positive pole piece and a negative pole piece, the negative pole piece comprising a negative pole current collector and a lithium metal layer laminated on the surface of the negative pole current collector,

[0007] The surface density of the single surface of the lithium metal layer is < positive first charge gram capacity x positive active material single surface density x negative excess coefficient ÷ negative first charge gram capacity ÷ weight proportion of lithium in the lithium metal layer.

[0008] In one embodiment, the surface density of the single surface of the lithium metal layer is less than 1.67 mg / cm 2 .

[0009] In one embodiment, the surface density of the single surface of the lithium metal layer is greater than or equal to 0.267 mg / cm 2 and less than 1.67 mg / cm 2 .

[0010] In one embodiment, the negative pole piece further comprises a sulfide solid electrolyte layer, and the sulfide solid electrolyte layer is laminated on the surface of the lithium metal layer.

[0011] Optionally, the material of the sulfide solid electrolyte layer comprises one or more of Li2S-P2S5, Li2S-SiS2 and Li2S-B2S3.

[0012] In one of the embodiments, the positive electrode sheet comprises a positive electrode current collector, and a positive electrode active layer and a sulfide solid electrolyte layer which are sequentially stacked on the surface of the positive electrode current collector.

[0013] The positive electrode active layer comprises a positive electrode active material, a sulfide solid electrolyte, a conductive agent, and a binder.

[0014] In one of the embodiments, the positive electrode active layer has one or more of the following characteristics:

[0015] (1) The positive electrode active layer comprises the positive electrode active material, the sulfide solid electrolyte, the conductive agent, and the binder in a mass ratio of (75-90):(15-5):(5-1):(5-1);

[0016] (2) The positive electrode active material comprises one or more of LiCoO2, NCM (811), and NCA;

[0017] (3) The conductive agent comprises one or more of conductive carbon black, conductive graphite, super conductive carbon black, acetylene carbon black, Ketjen black, carbon nanotube, nanofiber, and graphene;

[0018] (4) The binder comprises one or more of polytetrafluoroethylene, butadiene rubber, polyvinylidene fluoride, polyimide, polyacrylonitrile, polypropylene, polyethylene, polystyrene, and polypropylene.

[0019] In one of the embodiments, the material of the lithium metal layer comprises one or more of metallic lithium, lithium-silicon alloy, lithium-magnesium alloy, lithium-copper alloy, lithium-silver alloy, lithium-beryllium alloy, lithium-zinc alloy, lithium-cadmium alloy, lithium-aluminum alloy, lithium-gold alloy, and lithium-boron alloy.

[0020] In one of the embodiments, the lithium metal battery is a solid-state lithium metal battery, a quasi-solid-state lithium metal battery, a semi-solid-state lithium metal battery, a gel-state lithium metal battery, or a liquid-state lithium metal battery.

[0021] The present application also provides a preparation method of a lithium metal battery, comprising a preparation step of a positive electrode sheet and a preparation step of a negative electrode sheet; wherein the preparation step of the negative electrode sheet comprises:

[0022] Taking the negative electrode current collector, the material of the lithium metal layer is magnetron sputtered onto the surface of the negative electrode current collector to prepare the lithium metal layer.

[0023] In one of the embodiments, the preparation step of the negative electrode sheet further comprises:

[0024] The material of the sulfide solid electrolyte layer is magnetron sputtered onto the surface of the lithium metal layer.

[0025] In one of the embodiments, the preparation step of the positive electrode sheet comprises:

[0026] mixing the positive electrode active material, the sulfide solid electrolyte, the conductive agent, and the binder to prepare a powder of the positive electrode active layer;

[0027] spraying the powder of the positive electrode active layer to the surface of the positive electrode current collector to prepare the positive electrode active layer;

[0028] spraying the material of the sulfide solid electrolyte layer to the surface of the positive electrode active layer.

[0029] The application also provides a lithium metal battery, which comprises the lithium metal battery according to any one of the above embodiments.

[0030] Compared with the prior art, the application has the following beneficial effects:

[0031] The application provides a lithium metal battery, wherein the surface density of one side of the lithium metal layer in the negative electrode sheet is < the positive electrode first charge gram capacity x the positive electrode active material single surface density x the negative electrode excess coefficient ÷ the negative electrode first charge gram capacity ÷ the weight proportion of lithium in the lithium metal layer. Lithium ions can form a stable metal bond with the lithium metal layer when electrons are deposited, and the binding force is strong. At the same time, the surface density of the lithium metal layer is reasonably designed by considering the actual combination of the lithium metal layer and lithium ions, so that the mass of the electrode sheet is reduced, the lithium metal battery internal resistance growth rate can be controlled, and the battery capacity can also be maintained. DETAILED DESCRIPTION

[0032] The lithium metal battery, the preparation method of the lithium metal battery, and the application of the application will be further described in detail below in combination with specific embodiments. The application can be implemented in many different forms, and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the application more thorough and comprehensive.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the application belongs. The terms used in the specification of the application herein are only for the purpose of describing specific embodiments and are not intended to limit the application.

[0034] The application provides a lithium metal battery, which comprises a positive electrode sheet and a negative electrode sheet, the negative electrode sheet comprises a negative electrode current collector and a lithium metal layer laminated on the surface of the negative electrode current collector,

[0035] The surface density of one side of the lithium metal layer is < the positive electrode first charge gram capacity x the positive electrode active material single surface density x the negative electrode excess coefficient ÷ the negative electrode first charge gram capacity ÷ the weight proportion of lithium in the lithium metal layer.

[0036] Wherein, the area density is the mass of the positive electrode coating per unit area; the positive electrode first charging gram capacity is the gram capacity of the positive electrode active material; the negative electrode excess coefficient is the ratio of the actual capacity of the positive and negative electrode materials per unit area under the same stage and the same conditions (for example, lithium battery charging and discharging has two stages, one is the first charging stage, and the other is the discharging stage), and the negative electrode excess coefficient is ≥1 to meet the requirement that the reversible capacity of the negative electrode is greater than that of the positive electrode during the cycle process; and the negative electrode first charging gram capacity is the gram capacity of the metal lithium.

[0037] In the lithium ion battery, the calculation method of the area density of the single side of the negative electrode active material is: the area density of the single side of the negative electrode active material = the positive electrode first charging gram capacity × the positive electrode active material single side area density × the negative electrode excess coefficient ÷ the negative electrode first charging gram capacity × the weight ratio of the negative electrode active material. The area density of the negative electrode active material calculated by this equation can reduce the probability of the deposition of the excess lithium ions on the surface of the negative electrode to form lithium dendrites, so as to ensure the capacity of the lithium ion battery. The lithium metal battery usually refers to the standard of the lithium ion battery for the design of the structure, and therefore it is believed that the single side area density of the negative electrode active material (the material of the lithium metal layer) calculated by this equation can ensure that the capacity of the negative electrode is greater than that of the positive electrode during the cycle process, and thus the capacity of the lithium metal battery is maintained.

[0038] However, the lithium metal battery is different from the lithium ion battery, especially in that the lithium metal layer is used as the negative electrode in the lithium metal battery, while graphite or silicon-carbon material is used as the negative electrode in the lithium ion battery. Based on rich experience and a large number of researches, the inventors of the present application have found that in the traditional lithium ion lithium metal battery using graphite or silicon-carbon as the negative electrode, the graphite or silicon-carbon negative electrode is fully involved in the electrochemical reaction when the positive and negative electrode area densities are designed. Due to the layered structure of the graphite, the lithium ions can be inserted between the layers of the graphite after obtaining electrons, and the graphite particles coated on the surface of the negative electrode current collector can be utilized and combined with the lithium ions. Based on the area density design method of the graphite or silicon-carbon negative electrode, the calculation method of the single side area density of the traditional lithium metal layer is: the single side area density of the lithium metal layer = the positive electrode first charging gram capacity × the positive electrode active material single side area density × the negative electrode excess coefficient ÷ the negative electrode first charging gram capacity ÷ the weight ratio of lithium in the lithium metal layer, which is consistent with the area density design method of the graphite or silicon-carbon negative electrode, and the traditional method believes that this can ensure the gram capacity of the lithium metal battery, but it ignores the fact that the combination mechanism of the lithium ions and the graphite or silicon-carbon is different from that of the lithium ions and the lithium metal. According to the combination mechanism of the lithium ions and the graphite or silicon-carbon negative electrode, the area density of the lithium metal layer is calculated, and the area density of the lithium metal layer designed in this way does not conform to the combination mechanism of the lithium ions and the lithium metal, which causes the increase of the area density of the lithium metal, the weight of the lithium metal layer, and the high internal resistance, which has been ignored by people.

[0039] Based on the problems existing in the foregoing conventional method, the lithium metal layer single-sided area density < positive electrode first charge gram capacity x positive electrode active material single-sided area density x negative electrode excess coefficient ÷ negative electrode first charge gram capacity ÷ weight percentage of lithium in the lithium metal layer. According to the design of the lithium metal layer, it conforms to the combination mechanism of lithium metal and lithium ion, that is, after the lithium ion gets an electron, it is only deposited on the surface of the lithium metal layer, and the inner layer of lithium metal does not play a role. The area density of the lithium metal sheet layer is reduced to a certain extent, which does not affect the gram capacity of the lithium metal battery. Therefore, only the lithium metal layer single-sided area density < positive electrode first charge gram capacity x positive electrode active material single-sided area density x negative electrode excess coefficient ÷ negative electrode first charge gram capacity ÷ weight percentage of lithium in the lithium metal layer, the area density is lower than that calculated by the conventional method, which can control the lithium metal battery internal resistance growth rate, and at the same time can ensure the battery capacity.

[0040] In one of the examples, the negative electrode excess coefficient is 1.06.

[0041] In one of the examples, the negative electrode excess coefficient is 1.

[0042] In one of the examples, the negative electrode first charge gram capacity is the lithium metal gram specific capacity of 3870mAh / g.

[0043] In one of the examples, the lithium metal layer single-sided area density is less than 1.67mg / cm 2 .

[0044] In one of the examples, the lithium metal layer single-sided area density is greater than or equal to 0.267mg / cm 2 and less than 1.67mg / cm 2 . Specifically, the area density of the lithium metal layer includes but is not limited to 0.267mg / cm 2 , 0.300mg / cm 2 , 0.500mg / cm 2 , 1.000mg / cm 2 , 1.100mg / cm 2 , 1.200mg / cm 2 , 1.300mg / cm 2 , 1.500mg / cm 2 , 1.580mg / cm 2 , 1.600mg / cm 2 , 1.650mg / cm 2 or 1.660mg / cm 2 .

[0045] In one of the examples, the negative electrode sheet further comprises a sulfide solid electrolyte layer laminated on the surface of the lithium metal layer.

[0046] In one of the examples, the material of the sulfide solid electrolyte layer comprises one or more of Li2S-P2S5, Li2S-SiS2, and Li2S-B2S3.

[0047] In one of the examples, the single-sided thickness of the sulfide solid electrolyte layer is 2-4 μm. Understandably, the single-sided thickness of the sulfide solid electrolyte layer can be set to any value in 2-4 μm.

[0048] In one of the examples, the positive electrode sheet comprises a positive electrode current collector, and a positive electrode active layer and a sulfide solid electrolyte layer laminated on the surface of the positive electrode current collector in sequence.

[0049] The positive electrode active layer comprises a positive electrode active material, a sulfide solid electrolyte, a conductive agent, and a binder.

[0050] In one of the examples, the structure of the lithium metal battery is negative electrode current collector / lithium metal layer / sulfide solid electrolyte layer / separator / sulfide solid electrolyte layer / positive electrode active layer / positive electrode current collector.

[0051] In one of the examples, the material of the sulfide solid electrolyte layer laminated on the surface of the positive electrode active layer is the same as that of the sulfide solid electrolyte layer laminated on the negative electrode current collector.

[0052] In one of the examples, the single-sided area density of the positive electrode active layer is 20-30 g / cm 2 . Understandably, the single-sided area density of the positive electrode active layer can be set to any value in 20-30 g / cm 2 .

[0053] In one of the examples, the positive electrode current collector comprises an aluminum foil.

[0054] In one example, the positive active layer includes a positive active material, a sulfide solid-state electrolyte, a conductive agent, and a binder in a mass ratio of (75-90):(15-5):(5-1):(5-1). Understandably, the positive active material, the sulfide solid-state electrolyte, the conductive agent, and the binder can be in any weight ratio of (75-90):(15-5):(5-1):(5-1). Specifically, the weight ratio of the positive active material, the sulfide solid-state electrolyte, the conductive agent, and the binder includes, but is not limited to, 75:15:5:5, 85:10:2:3, 86:10:2:2, 87:9:2:3, 84:10:2:3, 90:5:2:3. By controlling the composition of the positive active material, the sulfide solid-state electrolyte, the conductive agent, and the binder, the components in the active material layer can have good compatibility.

[0055] In one example, the positive active material includes one or more of LiCoO2, NCM (811), and NCA.

[0056] In one example, the conductive agent includes one or more of conductive carbon black, conductive graphite, super conductive carbon black, acetylene carbon black, ketjen black, carbon nanotube, nanofiber, and graphene.

[0057] In one example, the binder includes one or more of polytetrafluoroethylene, styrene butadiene rubber, polyvinylidene fluoride, polyimide, polyacrylonitrile, polypropylene, polyethylene, polystyrene, and polypropylene.

[0058] In one example, the binder is a composite binder.

[0059] In one example, the composite binder includes polytetrafluoroethylene and styrene butadiene rubber in a weight ratio of (1-4): 1. Specifically, the weight ratio of the polytetrafluoroethylene and the styrene butadiene rubber includes, but is not limited to, 1:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.5:1, 3:1, 3.5:1, 3.8:1, 3.9:1, or 4:1.

[0060] In one example, the material of the lithium metal layer includes one or more of metallic lithium, lithium-silicon alloy, lithium-magnesium alloy, lithium-copper alloy, lithium-silver alloy, lithium-beryllium alloy, lithium-zinc alloy, lithium-cadmium alloy, lithium-aluminum alloy, lithium-gold alloy, and lithium-boron alloy.

[0061] In one example, the lithium metal battery is a solid-state lithium metal battery, a quasi-solid-state lithium metal battery, a semi-solid-state lithium metal battery, a gel-state lithium metal battery, or a liquid-state lithium metal battery.

[0062] In one of the examples, the lithium metal battery, the positive current collector comprises an aluminum foil.

[0063] In one of the examples, the lithium metal battery, the negative current collector comprises a copper foil.

[0064] In one of the examples, the lithium metal battery further comprises a filler, the filler serving as an electrolytic solvent of the lithium metal battery.

[0065] In one of the examples, the filler comprises one or both of ethylene oxide and 1,3-dioxolane.

[0066] In one of the examples, the weight ratio of the filler to the positive active material is (1-4): 1. Understandably, the weight ratio of the filler to the positive active material can be set to any value in (1-4): 1. Specifically, the weight ratio of the filler to the positive active material includes but is not limited to 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 2:1, 2.1:1, 2.2:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 3:1, 3.5:1, 3.8:1, 3.9:1 or 4:1.

[0067] The application also provides a preparation method of a lithium metal battery, comprising a positive electrode sheet preparation step and a negative electrode sheet preparation step; wherein the negative electrode sheet preparation step comprises:

[0068] Selecting the negative current collector, magnetron sputtering the material of the lithium metal layer to the surface of the negative current collector to prepare the lithium metal layer.

[0069] In one of the examples, the process parameters for magnetron sputtering the material of the lithium metal layer to the surface of the negative current collector include: taking the material of the lithium metal layer as the target material, setting the vacuum degree to (4-6) x 10 -5 Pa, setting the sputtering gas pressure to (0.2-0.4) Pa, setting the distance between the target material and the surface of the negative current collector to (45-55) mm, and setting the sputtering power to (4.5-6.5) kW.

[0070] In one of the examples, the negative electrode sheet preparation step further comprises:

[0071] Magnetron sputtering the material of the sulfide solid electrolyte layer to the surface of the lithium metal layer.

[0072] In one of the examples, the process parameters for magnetron sputtering the material of the sulfide solid electrolyte layer to the surface of the lithium metal layer include: taking the material of the sulfide solid electrolyte layer as the target material, setting the vacuum degree to (4-6) x 10-5 Pa, the distance between the target material and the surface of the lithium metal layer is (45-55) mm, and the sputtering power is set to (4.5-6.5) kW.

[0073] In one of the examples, the preparation method of the positive electrode sheet comprises:

[0074] Mixing the positive electrode active material, the sulfide solid electrolyte, the conductive agent, and the binder to prepare a powder of the positive electrode active layer;

[0075] Spraying the powder of the positive electrode active layer onto the surface of the positive electrode current collector to prepare the positive electrode active layer;

[0076] Spraying the sulfide solid electrolyte onto the surface of the positive electrode active layer.

[0077] In one of the examples, the mixing method of the positive electrode active material, the sulfide solid electrolyte, the conductive agent, and the binder is ball milling, and during the ball milling, the mass ratio of the ball milling beads to the total mass of the powder of the positive electrode active layer is (8-15) : 1, the mass ratio of large balls to small balls is (1-3) : 1, and the rotation speed is set to (200-400) r / min.

[0078] In one of the examples, the process parameters for spraying the powder of the positive electrode active layer onto the surface of the positive electrode current collector include: electrostatic voltage 60-80 kV, compressed argon pressure 5-7 kg / cm 2 , electrostatic current 10-20 μA, powder flow rate pressure 0.3-0.7 MPa, atomization pressure 0.2-0.6 MPa, and the spraying distance between the positive electrode current collector and the powder of the positive electrode active layer is 25-45 mm.

[0079] In one of the examples, after the preparation of the positive electrode active layer, the process further comprises high-temperature softening and rolling of the positive electrode active layer, the process parameters of the high-temperature softening include: heating temperature set to 180-250 °C, and heating time (3-10) min; the process parameters of the rolling include: rolling pressure set to (80-100) T, and rolling speed set to (40-60) m / min. Through high-temperature softening, the binder can be softened, and then through rolling, the adhesion between the positive electrode active layer and the positive electrode current collector can be enhanced.

[0080] In one of the examples, the process parameters for spraying the sulfide solid electrolyte onto the surface of the positive electrode active layer include: taking the positive electrode active layer as the base material, and taking the sulfide solid electrolyte as the target material, the vacuum degree is set to (4-6) x 10 -5 Pa, the distance between the target material and the surface of the lithium metal layer is (45-55) mm, and the sputtering power is set to (4.5-6.5) kW.

[0081] In one of the examples, the preparation method of the lithium metal battery further comprises the following steps:

[0082] After the positive electrode sheet and the negative electrode sheet are combined through the diaphragm, the positive electrode sheet and the negative electrode sheet are placed in a lithium metal battery shell and filled with a filling agent.

[0083] In one of the examples, the filling agent is injected and then a standing treatment is performed, and the process parameters of the standing treatment include that a first standing temperature is set to (40-50) °C, a first standing time is set to (20-30) h, a second standing temperature is set to (55-65) °C, and a second standing time is set to (20-30) h.

[0084] The application also provides a power utilization device comprising the lithium metal battery of any one of the examples.

[0085] The application will be further described in conjunction with specific examples. Unless otherwise specified, the raw materials used in the examples are commercially available.

[0086] Example 1

[0087] Example 1 provides a preparation method of a lithium metal battery. According to the conventional calculation method, the single-side area density of the lithium metal layer = the first charge gram capacity of the positive electrode × the single-side area density of the positive electrode active material × the negative electrode excess coefficient ÷ the lithium metal gram specific capacity = 236 mAh / g × 26 mg / cm 2 × 1.06 / 3870 mAh / g = 1.68 mg / cm 2 . In Example 1, the area density of the lithium metal layer is 0.267 mg / cm 2 , which is only 15.89% of the area density calculated by the conventional method. The specific preparation method is as follows:

[0088] (1) Preparation of the positive electrode sheet

[0089] In an argon dry atmosphere with a water content of less than 1 ppm and an oxygen content of less than 1 ppm, 1700 g of NCA, 200 g of Li2S-P2S5 sulfide solid electrolyte, 40 g of graphene, 40 g of polytetrafluoroethylene, and 20 g of butadiene styrene rubber are weighed. The obtained NCA, Li2S-P2S5 solid electrolyte, graphene, polytetrafluoroethylene, and butadiene styrene rubber are placed in a ball mill jar and ball milled. During the mixing ball milling process, the mass ratio of the ball milling beads to the total mass of the mixture is 10:1, the mass ratio of large balls to small balls is 2:1, the rotation speed is set to 360 r / min, and the ball milling time is 60 min. After ball milling, the powder of the positive electrode active layer is obtained.

[0090] In an argon dry atmosphere with moisture content less than 1 ppm and oxygen content less than 1 ppm, the aluminum foil is hung on a winding shaft as a base material, and the powder of the positive active layer is used as a target material. The powder is sprayed on the surface of the aluminum foil by powder spraying. During the powder spraying process, the electrostatic voltage is set to 70 kV, the compressed argon pressure is set to 6.5 kg / cm 2 , the electrostatic current is set to 15 μA, the powder flow rate pressure is set to 0.45 MPa, the atomization pressure is set to 0.40 MPa, and the distance between the spray gun and the aluminum foil is 40 mm. After the single-sided spraying of the aluminum foil is completed, the single-sided surface density of the positive active layer is 26 g / cm 2 . Then, the second side of the aluminum foil is sprayed, and the steps and parameter settings are as described above. The double-sided surface density of the prepared positive active layer is 52 g / cm 2 .

[0091] The positive electrode sheet containing the positive active layer is placed in a high-temperature furnace for heating and softening. The heating temperature is set to 200 ℃, and the heating time is 5 min. The PTFE and SBR are softened by high-temperature softening, and the NCA, graphene, and Li2S-P2S5 solid-state electrolyte are adsorbed on the aluminum foil. After the positive electrode sheet is heated and softened, the positive electrode sheet is rolled to 133 ± 2 μm by rolling process. During the rolling process, the rolling pressure is set to 90 T, and the rolling speed is 50 m / min. After the rolling is completed, the dry positive electrode sheet is obtained.

[0092] In an argon dry atmosphere with peripheral moisture content less than 1 ppm and oxygen content less than 1 ppm, the Li2S-P2S5 compound solid-state electrolyte is plated on the dry positive electrode sheet by vacuum magnetron sputtering. The specific process conditions of the vacuum magnetron sputtering method are as follows: the background vacuum degree is 5 × 10 -5 Pa, the sputtering gas pressure is 0.3 Pa, the distance between the target material and the base material is 50 mm, and the sputtering power is 5.5 kW. The single-sided thickness of the sulfide solid-state electrolyte layer is 3 μm, and the double-sided thickness is 6 μm. The positive electrode sheet is obtained.

[0093] (2) Preparation of negative electrode sheet

[0094] The copper foil is hung on a winding shaft as a base material. First, the metal lithium is used as a target material, and the excited metal lithium is uniformly magnetron sputtered onto the copper foil to form a lithium metal beam and a lithium metal layer on the copper foil. The specific process conditions of the magnetron sputtering are as follows: the background vacuum degree is 5 × 10 -5 Pa, the sputtering gas pressure is 0.3 Pa, the distance between the target material and the base material is 50 mm, and the sputtering power is 5.5 kW. The single-sided surface density of the obtained lithium metal layer is 0.267 mg / cm 2 .

[0095] Secondly, the Li2S-P2S5 sulfide solid electrolyte is used as a target material, and the Li2S-P2S5 sulfide solid electrolyte is uniformly magnetron sputtered on the lithium metal layer after being excited, so as to form a sulfide solid electrolyte on the lithium metal layer, the sulfide solid electrolyte completely covers the lithium metal layer, and the thickness of the sulfide solid electrolyte layer is 3 μm on a single side. -5 The specific process conditions of the vacuum magnetron sputtering method are as follows: a base vacuum degree is 5*10-3 Pa, a sputtering gas pressure is 0.3 Pa, a distance between the target material and the substrate is 50 mm, and a sputtering power is 5.5 kW. After the coating on the first side of the copper foil substrate is completed, the coating on the second side of the copper foil is performed, and the coating sequence is still the lithium metal layer and the Li2S-P2S5 sulfide solid electrolyte layer. The double-sided surface density of the lithium metal layer is 0.534 mg / cm 2 , the thickness of the double-sided sulfide solid electrolyte layer is 6 μm, and the negative electrode sheet is prepared.

[0096] (3) The above negative electrode sheet and the positive electrode sheet are wound to form a 1254 button type lithium metal battery, and 1,3-dioxolane is injected into the lithium metal battery. The mass ratio of the positive electrode active material NCA and the 1,3-dioxolane is 1:0.4. The lithium metal battery is placed at 45°C for 24 h, and then placed at 60°C for 24 h to complete the in-situ polymerization of the 1,3-dioxolane.

[0097] Example 2

[0098] Example 2 is basically the same as Example 1, and the main difference is that: (2) in the preparation of the negative electrode sheet, the single-sided surface density of the obtained lithium metal layer is 0.534 mg / cm 2 , and the double-sided surface density of the lithium metal layer is 1.068 mg / cm 2 . The surface density of the lithium metal layer in the negative electrode sheet is only 31.79% of the surface density calculated by the traditional method.

[0099] Example 3

[0100] Example 3 is basically the same as Example 1, and the main difference is that: (2) in the preparation of the negative electrode sheet, the single-sided surface density of the obtained lithium metal layer is 0.801 mg / cm 2 , and the double-sided surface density of the lithium metal layer is 1.602 mg / cm 2 . The surface density of the lithium metal layer in the negative electrode sheet is only 47.68% of the surface density calculated by the traditional method.

[0101] Example 4

[0102] Example 4 is basically the same as Example 1, and the main difference is that: (2) in the preparation of the negative electrode sheet, the single-sided surface density of the obtained lithium metal layer is 1.068 mg / cm 2 , and the double-sided surface density of the lithium metal layer is 2.136 mg / cm2 The areal density of the lithium metal layer in the negative electrode sheet is only 63.57% of the areal density calculated by the conventional method.

[0103] Example 5

[0104] Example 5 is basically the same as Example 1, the main difference being that: (2) in the preparation of the negative electrode sheet, the single-sided areal density of the obtained lithium metal layer is 1.335 mg / cm 2 , and the double-sided areal density of the lithium metal layer is 2.67 mg / cm 2 . The areal density of the lithium metal layer in the negative electrode sheet is 79.94% of the areal density calculated by the conventional method.

[0105] Comparative Example 1

[0106] Comparative Example 1 is basically the same as Example 1, the main difference being that: (2) in the preparation of the negative electrode sheet, the single-sided areal density of the obtained lithium metal layer is 0 mg / cm 2 , and the double-sided areal density of the lithium metal layer is 0 mg / cm 2 . The specific preparation steps are as follows:

[0107] (1) Preparation of the positive electrode sheet

[0108] In an argon dry atmosphere with a water content of less than 1 ppm and an oxygen content of less than 1 ppm, 1700 g of NCA was weighed, 200 g of Li2S-P2S5 sulfide solid-state electrolyte was weighed, 40 g of graphene was weighed, 40 g of polytetrafluoroethylene was weighed, and 20 g of butadiene-styrene rubber was weighed. The weighed NCA, Li2S-P2S5 solid-state electrolyte, graphene, polytetrafluoroethylene, and butadiene-styrene rubber were placed in a ball mill jar for ball milling. During the mixing and ball milling process, the mass ratio of the ball milling beads to the total mass of the mixture was 10:1, the mass ratio of large balls to small balls was 2:1, the rotation speed was set to 360 r / min, and the ball milling time was 60 min. After ball milling, the powder of the positive electrode active layer was obtained.

[0109] In an argon dry atmosphere with a water content of less than 1 ppm and an oxygen content of less than 1 ppm, aluminum foil was used as the substrate and hung on the unwinding shaft, and the powder of the positive electrode active layer was used as the target material. The powder was sprayed onto the surface of the aluminum foil by powder spraying. During the powder spraying process, the electrostatic voltage was set to 70 kV, the compressed argon gas pressure was set to 6.5 kg / cm 2 , the electrostatic current was set to 15 μA, the powder flow rate pressure was set to 0.45 MPa, the atomization pressure was set to 0.40 MPa, and the distance between the spray gun nozzle and the aluminum foil was 40 mm. After completing the single-sided spraying of the aluminum foil, the single-sided areal density of the positive electrode active layer was 26 g / cm 2, and then the second surface of the aluminum foil is sprayed, and the steps and parameters are as shown above. The double-sided surface density of the prepared positive electrode active layer is 52 g / cm 2 .

[0110] The positive electrode sheet containing the positive electrode active layer is placed in a high-temperature furnace for heating and softening. The heating temperature is set to 200°C, and the heating time is 5 min. The polytetrafluoroethylene and the butadiene-styrene rubber are softened by high-temperature softening, and the NCA, graphene, and Li2S-P2S5 solid-state electrolyte are adsorbed on the aluminum foil. After the positive electrode sheet is heated and softened, the positive electrode sheet is rolled to 133±2 μm by a rolling process. During the rolling process, the rolling pressure is set to 90T, and the rolling speed is 50 m / min. After the rolling is completed, a dry positive electrode sheet is obtained.

[0111] In an argon dry atmosphere with a peripheral moisture content of less than 1 ppm and an oxygen content of 1 ppm, a Li2S-P2S5 compound solid-state electrolyte is plated on the dry positive electrode sheet by a vacuum magnetron sputtering method. The specific process conditions of the vacuum magnetron sputtering method are as follows: a background vacuum degree of 5×10 -5 Pa, a sputtering gas pressure of 0.3 Pa, a distance between the target material and the substrate of 50 mm, and a sputtering power of 5.5 kW. The single-sided thickness of the sulfide solid-state electrolyte layer is 3 μm, and the double-sided thickness is 6 μm, thereby obtaining a positive electrode sheet.

[0112] (2) Preparation of a negative electrode sheet

[0113] The Li2S-P2S5 sulfide solid-state electrolyte is used as a target material, and the Li2S-P2S5 sulfide solid-state electrolyte is uniformly magnetron sputtered on a copper foil after excitation. A sulfide solid-state electrolyte layer is formed on the copper foil, and the sulfide solid-state electrolyte completely covers the copper foil. The single-sided thickness of the sulfide solid-state electrolyte layer is 3 μm. The specific process conditions of the vacuum magnetron sputtering method are as follows: a background vacuum degree of 5×10 -5 Pa, a sputtering gas pressure of 0.3 Pa, a distance between the target material and the substrate of 50 mm, and a sputtering power of 5.5 kW. After the plating of the first surface of the copper foil substrate is completed, the second surface of the copper foil is plated. The thickness of the double-sided sulfide solid-state electrolyte layer is 6 μm, thereby preparing a negative electrode sheet.

[0114] (3) The above-mentioned negative electrode sheet and positive electrode sheet are wound to prepare a 1254 button lithium metal battery. 1,3-dioxolane is injected into the lithium metal battery. The mass ratio of the positive electrode active material NCA and 1,3-dioxolane is 1:0.4. The lithium metal battery is placed at 45°C for 24 h, and then placed at 60°C for 24 h to complete the in-situ polymerization of 1,3-dioxolane.

[0115] Comparative Example 2

[0116] Comparative Example 2 is substantially the same as Example 1, with the main difference being that: (2) in the preparation of the negative electrode sheet, the single-sided area density of the obtained lithium metal layer is 1.67 mg / cm 2 , and the double-sided area density of the lithium metal layer is 3.36 mg / cm 2 . The area density of the lithium metal in Comparative Example 2 is the area density value calculated according to the conventional method.

[0117] Electrochemical performance test

[0118] The internal resistance of the button cell was tested by a battery internal resistance tester.

[0119] The capacity of the button cell was tested under a current density of 0.5 C, and the specific capacity = capacity of the button cell / electrode material weight.

[0120] The button cell was subjected to 50 cycles of charge and discharge under a current density of 0.5 C, and the cycle performance of the button cell was tested.

[0121] The electrochemical performance test results of Examples 1-4 and Comparative Examples 1 and 2 are as follows:

[0122] The capacity and cycle performance test results of the button cell are as follows:

[0123]

[0124] The internal resistance test results of the button cell are as follows:

[0125]

[0126] As can be seen from the test results of Examples 1-5 and Comparative Example 1 in the table, the lithium metal layer stacked on the negative current collector can effectively prevent the failure of the lithium metal battery. In Examples 1-5 and Comparative Example 2, the area density of the lithium metal layer in Examples 1-4 is lower than the area density calculated according to the conventional method in Comparative Example 2, but the first week discharge specific capacity and the 50th week discharge specific capacity after cycling are close, and the internal resistance of the cell also shows the same characteristics. As can be seen from the test results of Examples 1-5 and Comparative Example 2 in the table, the single-sided area density of the lithium metal layer is 0.267 mg / cm 2 -1.335 mg / cm 2 , at this time the area density of the lithium metal layer is lower than the area density calculated according to the conventional method, but the first week discharge specific capacity in Examples 1-5 is close to that of Comparative Example 2, and at the same time, the specific capacity after 50 cycles is also close, and has a good specific capacity retention rate; at the same time, the first week discharge specific capacity and the 50th week discharge specific capacity performance in Example 3 are both better than those of Comparative Example 2. The internal resistance of the cell also shows the same performance, the area density of the lithium metal layer in Examples 1-5 is lower than the area density calculated according to the conventional method, and the internal resistance growth rate measured in Examples 1-5 is less than that of Comparative Example 2.

[0127] Any combination of the technical features in the above-described embodiments can be made. For the sake of brevity, the foregoing description is not intended to be exhaustive or to limit the scope of the application to the precise form disclosed. Modifications and alterations can occur to others upon reading and understanding the disclosure. Accordingly, the scope of the application is intended to be limited only by the appended claims.

[0128] The above-described embodiments only express several implementation manners of the application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the patent scope of the application. It should be pointed out that, for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the application, and these all belong to the protection scope of the application. Therefore, the patent protection scope of the application should be subject to the appended claims.

Claims

1. A lithium metal battery comprising a positive electrode sheet and a negative electrode sheet, characterized by, The negative electrode sheet is composed of a negative electrode current collector and a lithium metal layer and a sulfide solid electrolyte layer laminated on the surface of the negative electrode current collector, and the sulfide solid electrolyte layer is laminated on the surface of the lithium metal layer. The areal density of the single side of the lithium metal layer is < the first charge gram capacity of the positive electrode × the areal density of the positive electrode active material on the single side × the excess coefficient of the negative electrode ÷ the first charge gram capacity of the negative electrode ÷ the weight proportion of lithium in the lithium metal layer. The areal density of the lithium metal layer is greater than or equal to 0.267 mg / cm 2 and less than 1.67 mg / cm 2 .

2. The lithium metal battery of claim 1, wherein, The material of the sulfide solid electrolyte includes one or more of Li2S-P2S5, Li2S-SiS2 and Li2S-B2S3.

3. The lithium metal battery of claim 1, wherein, The positive electrode sheet includes a positive electrode current collector and a positive electrode active layer and a sulfide solid electrolyte layer laminated on the surface of the positive electrode current collector in sequence. The positive electrode active layer includes a positive electrode active material, a sulfide solid electrolyte, a conductive agent and a binder.

4. The lithium metal battery of claim 3, wherein, The positive electrode active layer has one or more of the following characteristics: (1) The positive electrode active layer includes a positive electrode active material, a sulfide solid electrolyte, a conductive agent and a binder in a mass ratio of (75-90):(15-5):(5-1):(5-1); (2) The positive electrode active material includes one or more of LiCoO2, NCM (811) and NCA; (3) The conductive agent includes one or more of conductive carbon black, conductive graphite, carbon nanotubes, nanofibers and graphene; (4) The binder includes one or more of polytetrafluoroethylene, butadiene rubber, polyvinylidene fluoride, polyimide, polyacrylonitrile, polyethylene, polystyrene and polypropylene. 5.The lithium metal battery of any one of claims 1-4, wherein, The material of the lithium metal layer includes one or more of metallic lithium, lithium-silicon alloy, lithium-magnesium alloy, lithium-copper alloy, lithium-silver alloy, lithium-beryllium alloy, lithium-zinc alloy, lithium-cadmium alloy, lithium-aluminum alloy, lithium-gold alloy and lithium-boron alloy. 6.The lithium metal battery of any one of claims 1-4, wherein, The lithium metal battery is a solid-state lithium metal battery, a quasi-solid-state lithium metal battery, a semi-solid-state lithium metal battery, a gel-state lithium metal battery or a liquid-state lithium metal battery.

7. A method of producing the lithium metal battery according to any one of claims 1 to 6, characterized in that, The preparation steps of the positive electrode sheet and the preparation steps of the negative electrode sheet; The preparation steps of the negative electrode sheet include: Taking the negative electrode current collector, magnetron sputtering the material of the lithium metal layer to the surface of the negative electrode current collector to prepare the lithium metal layer.

8. The preparation method according to claim 7, characterized in that, The preparation steps of the negative electrode sheet further include: Magnetron sputtering the material of the sulfide solid electrolyte layer to the surface of the lithium metal layer.

9. The preparation method according to claim 7, characterized in that, The preparation steps of the positive electrode sheet include: Mixing the positive electrode active material, the sulfide solid electrolyte, the conductive agent and the binder to prepare the powder of the positive electrode active layer; Spraying the powder of the positive electrode active layer to the surface of the positive electrode current collector to prepare the positive electrode active layer; Spraying the material of the sulfide solid electrolyte layer to the surface of the positive electrode active layer.

10. An electrical device, characterized by The lithium metal battery includes the lithium metal battery of any one of claims 1-6.

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