Modified current collector, preparation method and device thereof, pole piece and solid-state battery

Abstract

The invention discloses a modified current collector and a preparation method and device thereof, a pole piece and a solid-state battery, the modified current collector comprises a base material layer, the base material layer comprises a metal foil and a protective layer located on at least one side of the base material layer, the protective layer comprises at least one protective unit, and the protective unit comprises a first layer and a second layer which are stacked in the direction away from the base material layer, the first layer includes TiN and the second layer includes stainless steel. And the TiN and the stainless steel are combined to form the protective layer or the protective unit, so that the modified current collector has excellent corrosion resistance and excellent conductivity and mechanical properties.

Description

Modified current collectors and their preparation methods, apparatus, electrodes, and solid-state batteries Technical Field

[0001] This application relates to the field of electrochemical energy storage technology, specifically to a modified current collector and its preparation method, apparatus, electrode, and solid-state battery. Background Technology

[0002] Solid-state batteries replace the liquid electrolyte and separator in traditional batteries with solid-state electrolytes, offering higher energy density and better safety performance. Solid-state electrolytes are classified by material into: oxide solid-state batteries, sulfide solid-state batteries, polymer solid-state batteries, and composite solid-state batteries. Among these, sulfide solid-state batteries have significant advantages in ionic conductivity, energy density, and interfacial contact at room temperature, and are widely considered by researchers to be the main direction for future development.

[0003] However, because solid-state batteries are in an environment containing trace amounts of moisture, the electrolyte reacts with water to generate hydrogen sulfide (H2S) gas. As the core component in the battery for collecting and conducting current, the current collector, such as copper foil current collector, will have copper detach from the copper foil in sulfide solid-state batteries and combine with H2S in the sulfide to form copper sulfide, which has the disadvantages of poor corrosion resistance and poor interface stability. Summary of the Invention

[0004] In view of this, this application provides a modified current collector and its preparation method, apparatus, electrode, and solid-state battery to solve the above-mentioned technical problems.

[0005] To achieve the above objectives, in a first aspect, this application provides a modified current collector, which includes a substrate layer comprising a metal foil and a protective layer located on at least one side of the substrate layer. The protective layer includes at least one protective unit, and the protective unit includes a first layer and a second layer stacked in a direction away from the substrate layer. The first layer includes a TiN layer, and the second layer includes a stainless steel layer.

[0006] Based on the first aspect, in some possible implementations, the thickness of the first layer is 10 nm to 100 nm.

[0007] Based on the first aspect, in some possible implementations, the thickness of the second layer is 10 nm to 100 nm.

[0008] Based on the first aspect, in some possible implementations, the thickness ratio of the first layer to the second layer is (0.8~2):1.

[0009] Based on the first aspect, in some possible implementations, the thickness of the protective layer is between 20 nm and 1000 nm.

[0010] Based on the first aspect, in some possible implementations, the first layer further includes a passivation layer located on the side of the TiN layer away from the substrate layer, the passivation layer comprising TiO2. 2-x , 0≤X<2, the thickness of the passivation layer is 1 nm to 3 nm.

[0011] Based on the first aspect, in some possible implementations, the second layer also includes a doping element, which includes at least one of yttrium and cerium.

[0012] Based on the first aspect, in some possible implementations, the first layer further includes a first catalytic active unit located on the side of the TiN layer away from the substrate layer. The first catalytic active unit includes transition metal particles with a particle size of 2 nm to 20 nm. The transition metal particles include at least one of cobalt and iron. The mass ratio of the transition metal particles to the TiN layer is greater than 0 and less than or equal to 5%.

[0013] Based on the first aspect, in some possible implementations, the second layer further includes a second catalytic active unit located on the side of the stainless steel layer away from the substrate layer, the second catalytic active unit comprising a Cr-Ni-Mo alloy.

[0014] Based on the first aspect, in some possible implementations, the substrate layer further includes a polymer film, with metal foils located on both sides of the polymer film, and the polymer film is made of at least one of polypropylene, polyethylene, and polyethylene terephthalate.

[0015] Based on the first aspect, in some possible implementations, the metal foil includes copper.

[0016] Based on the first aspect, in some possible implementations, the thickness of the substrate layer is 3 μm to 15 μm.

[0017] Secondly, this application provides a method for preparing the above-mentioned modified current collector, comprising: forming a protective layer on at least one side of a substrate layer by magnetron sputtering.

[0018] Thirdly, this application provides an apparatus for performing the above-described preparation method, the apparatus comprising: a vacuum chamber, a first coating chamber, a second coating chamber, and a transfer mechanism; the first coating chamber is configured to deposit a first layer on at least one side of a substrate layer by magnetron sputtering; the second coating chamber is configured to deposit a second layer on at least one side of the substrate layer by magnetron sputtering; the transfer mechanism is configured to sequentially and continuously transfer the substrate layer through the first coating chamber and the second coating chamber within the vacuum chamber; wherein the first coating chamber and the second coating chamber are both located within the vacuum chamber, and the first coating chamber and the second coating chamber are separated from each other.

[0019] Fourthly, this application provides an electrode comprising the modified current collector described above.

[0020] Fifthly, this application provides a solid-state battery, which includes the aforementioned electrode.

[0021] In the modified current collector of this application, TiN possesses excellent chemical inertness and high conductivity, serving as a rapid electron conduction layer. The passivation film formed on the stainless steel surface effectively inhibits sulfidation reactions. The combination of these two elements maintains high conductivity while reducing the corrosion rate at the interface between the metal foil in the substrate layer and the sulfide electrolyte. The TiN layer (first layer) is located outside the metal foil in the substrate layer. A strong physical bond can be formed between TiN and the metal foil in the substrate layer through sputtering, improving the overall bonding effect between the protective layer and the current collector. Furthermore, the resistivity of TiN is lower than that of the stainless steel layer (second layer). Placing it between the substrate layer and the stainless steel layer allows current to be drawn from the metal foil in the substrate layer first through the lower-resistance TiN layer, which helps reduce ohmic losses in the overall laminated structure. In addition, the coefficient of thermal expansion of TiN is typically between that of electrode active materials (such as silicon) and metal foils (such as copper), reducing the risk of interface delamination caused by battery cycling. Meanwhile, a stainless steel layer is placed on the outside of the TiN layer to contact the solid electrolyte. When exposed to sulfur-containing electrolytes, elements such as chromium (Cr) on its surface can spontaneously form a dense oxide / sulfide passivation layer (such as Cr2O3), which actively resists the penetration of sulfur ions and corrosive media. During battery cycling, when the electrode material undergoes volume changes, the outer stainless steel layer, with its better ductility, can absorb some stress through plastic deformation, which helps reduce the risk of cracking in the brittle TiN layer under large strain. Therefore, the protective layer or unit formed by the combination of TiN and stainless steel possesses both excellent corrosion resistance and excellent electrical and mechanical properties. Attached Figure Description

[0022] Figure 1 is a schematic diagram of the structure of the modified current collector provided in one embodiment of this application when it has a single-sided protective layer and a protective unit.

[0023] Figure 2 is a structural schematic diagram of the modified current collector provided in one embodiment of this application when it has a single-sided protective layer and multiple protective units.

[0024] Figure 3 is a schematic diagram of the structure of the modified current collector provided in one embodiment of this application when it has a double-sided protective layer.

[0025] Figure 4 is a schematic diagram of the structure of the modified current collector substrate layer with a polymer film provided in one embodiment of this application.

[0026] Explanation of main component symbols

[0027] Modified current collector 100, first substrate layer 110, second substrate layer 120, polymer film 121, metal foil 122, protective layer 130, protective unit 140, first layer 141, second layer 142.

[0028] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this application. Detailed Implementation

[0029] To facilitate understanding of the technical solutions of this application, a more comprehensive description of the technical solutions of this application will be provided below with reference to the accompanying drawings, which illustrate preferred embodiments of the technical solutions of this application. However, the technical solutions of this application can be implemented in many different forms and are not limited to the embodiments described herein. Rather, these embodiments are provided to enable a more thorough and comprehensive understanding of the disclosure of the technical solutions of this application.

[0030] 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 this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0031] To address the corrosion and interfacial instability issues of copper foil current collectors in sulfide solid-state batteries, related technologies introduce an outer protective layer to isolate H2S and prevent copper foil corrosion. This outer anti-corrosion layer is typically made of highly corrosion-resistant and highly conductive precious metals or refractory metals. On the one hand, this is costly, and on the other hand, internal stress may be generated between different metal layers due to factors such as thermal expansion coefficients and lattice mismatches. During long-term cycling, delamination and peeling are likely to occur, affecting electron conduction and mechanical integrity. When the outer protective layer is damaged, the copper foil will again face the risk of H2S corrosion.

[0032] Therefore, it is necessary to improve the protective layer to achieve better corrosion resistance. Based on this, this application research found that when stainless steel comes into contact with a sulfide electrolyte, a dense oxide layer (passivation film) spontaneously forms on its surface. This passivation film can form a "molecular barrier," reducing the penetration of sulfur ions and thus reducing the occurrence of sulfidation reactions. Furthermore, transition metal nitride films possess good corrosion resistance and excellent conductivity; as a protective film material for current collectors, they also help reduce corrosion and improve conductivity. To solve the above-mentioned technical problems, embodiments of this application form a protective layer based on the above-mentioned materials and having a specific anti-corrosion structure on the outside of a substrate layer containing metal foil. By improving the material and structure of the protective layer, the corrosion resistance of traditional metal foil current collectors in sulfide solid-state batteries is improved, as well as their conductivity and mechanical properties are enhanced.

[0033] Based on this, one embodiment of this application provides a modified current collector, which includes a substrate layer, the substrate layer including a metal foil, and a protective layer located on at least one side of the substrate layer. The protective layer includes at least one protective unit, and the protective unit includes a first layer and a second layer stacked in a direction away from the substrate layer. The first layer includes a TiN layer, and the second layer includes a stainless steel layer.

[0034] In the modified current collector of this application, TiN possesses excellent chemical inertness and high conductivity, serving as a rapid electron conduction layer. The passivation film formed on the stainless steel surface effectively inhibits sulfidation reactions. The combination of these two elements maintains high conductivity while reducing the corrosion rate at the interface between the metal foil in the substrate layer and the sulfide electrolyte. The TiN layer (first layer) is located outside the metal foil in the substrate layer. A strong physical bond can be formed between TiN and the metal foil in the substrate layer through sputtering, improving the overall bonding effect between the protective layer and the current collector. Furthermore, the resistivity of TiN is lower than that of the stainless steel layer (second layer). Placing it between the substrate layer and the stainless steel layer allows current to be drawn from the metal foil in the substrate layer first through the lower-resistance TiN layer, which helps reduce ohmic losses in the overall laminated structure. In addition, the coefficient of thermal expansion of TiN is typically between that of electrode active materials (such as silicon) and metal foils (such as copper), reducing the risk of interface delamination caused by battery cycling. Meanwhile, a stainless steel layer is placed on the outside of the TiN layer to contact the solid electrolyte. When exposed to sulfur-containing electrolytes, elements such as chromium (Cr) on its surface can spontaneously form a dense oxide / sulfide passivation layer (such as Cr2O3), which actively resists the penetration of sulfur ions and corrosive media. During battery cycling, when the electrode material undergoes volume changes, the outer stainless steel layer, with its better ductility, can absorb some stress through plastic deformation, which helps reduce the risk of cracking in the brittle TiN layer under large strain. Therefore, the protective layer or unit formed by the combination of TiN and stainless steel possesses both excellent corrosion resistance and excellent electrical and mechanical properties.

[0035] Understandably, there may be other material layers between the substrate layer and the protective layer of the modified current collector, or there may be none. In some embodiments, the protective layer is located on at least one surface of the substrate layer.

[0036] In some embodiments, the substrate layer of the modified current collector is a first substrate layer composed of metal foil.

[0037] For example, referring to Figure 1, the modified current collector 100 includes a first substrate layer 110 and a protective layer 130 located on one surface of the first substrate layer 110. The protective layer 130 includes a protective unit 140. The protective unit 140 includes a first layer 141 and a second layer 142 stacked in a direction away from the first substrate layer 110. The first layer 141 includes a TiN layer, and the second layer 142 includes a stainless steel layer.

[0038] For example, referring to Figure 2, the modified current collector 100 includes a first substrate layer 110 and a protective layer 130 located on one surface of the first substrate layer 110. The protective layer 130 includes multiple (two shown in the figure) protective units 140. Each protective unit 140 includes a first layer 141 and a second layer 142 stacked in a direction away from the first substrate layer 110. The first layer 141 includes a TiN layer, and the second layer 142 includes a stainless steel layer. The protective layer features alternating layers of TiN / stainless steel structures. The high hardness and high modulus of TiN are alternately combined with the high toughness and plastic deformation-capable stainless steel, forming multiple protective units that combine strength and toughness. The alternating TiN / stainless steel layers within the protective units constitute a performance transition zone. The hardness, modulus, and coefficient of thermal expansion of the synergistic materials exhibit a gradient change, avoiding abrupt performance changes and reducing the risk of peeling due to thermo-mechanical mismatch.

[0039] For example, referring to Figure 3, the modified current collector 100 includes a first substrate layer 110 and a protective layer 130 located on two surfaces of the first substrate layer 110. The protective layer 130 includes one or more (one shown in the figure) protective units 140. The protective unit 140 includes a first layer 141 and a second layer 142 stacked in a direction away from the first substrate layer 110. The first layer 141 includes a TiN layer, and the second layer 142 includes a stainless steel layer.

[0040] In other embodiments, the substrate layer further includes a polymer film, with metal foils located on both sides of the polymer film. In some embodiments, the substrate layer is a second substrate layer composed of a polymer film and metal foils located on both surfaces of the polymer film. The polymer film can serve as an insulating support, effectively absorbing and dispersing stress during charging and discharging, suppressing fatigue fracture of the metal foils, and fundamentally eliminating the risk of short circuits between the two metal layers.

[0041] For example, referring to Figure 4, the modified current collector 100 includes a polymer film 121 and a metal foil 122 located on both surfaces of the polymer film 121. The polymer film 121 and the metal foil 122 constitute a second substrate layer 120, and a protective layer 130 located on the surface of the metal foil 122 away from the polymer film 121. The protective layer 130 includes one or more (one shown in the figure) protective units 140. The protective unit 140 includes a first layer 141 and a second layer 142 stacked in a direction away from the second substrate layer 120. The first layer 141 includes a TiN layer, and the second layer 142 includes a stainless steel layer.

[0042] In some embodiments, the metal foil includes copper. The selection of copper as the metal foil in the modified current collector of this application balances excellent conductivity, mature processing technology, and controllable cost. Furthermore, based on the excellent protective effect of the protective layer in this application, the copper foil can resist sulfide corrosion while maintaining its core function as a stable and efficient electronic conductor.

[0043] In some embodiments, the polymer film material includes at least one of polypropylene, polyethylene, and polyethylene terephthalate. The inclusion of these materials in the polymer film is beneficial for improving battery energy density, while the resulting substrate structure is flexible and stable, has good compatibility with electrode processing technologies, and offers controllable material costs.

[0044] In some embodiments, the thickness of the substrate layer is from 3 μm to 15 μm. For example, the thickness of the substrate layer can be 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or any value within the range of any two of the above values. Controlling the thickness of the substrate layer within the above range helps to optimize (e.g., minimize) the weight and volume of the current collector to improve battery energy density, and optimize interfacial stress distribution and production costs; when the substrate layer contains a polymer film, it can also provide sufficient support and flexibility to ensure processing and cycle reliability.

[0045] In some embodiments, the stainless steel includes SS316L type stainless steel. SS316L type stainless steel contains about 2%-3% molybdenum (Mo), which is beneficial to improving the corrosion resistance of stainless steel to sulfur-containing media, especially in H2S environments generated in the presence of trace amounts of water. At the same time, SS316L type stainless steel has a similar coefficient of thermal expansion to TiN, thereby reducing the internal stress between multilayer films and improving the overall structural bonding strength and cycle life.

[0046] In some embodiments, the thickness of the first layer is from 10 nm to 100 nm. For example, the thickness of the first layer can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or any value within the range of any two of the above values. Controlling the thickness of the first layer within the above range is beneficial for providing effective physical barrier while ensuring high conductivity, reducing the risk of insufficient protection when the layer is too thin or increased overall impedance and cost when the layer is too thick.

[0047] In some embodiments, the thickness of the second layer is from 10 nm to 100 nm. For example, the thickness of the second layer can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or any value within the range of any two of the above values. Controlling the thickness of the second layer within the above range is beneficial for forming a sufficiently dense passivation film to block sulfide corrosion, while reducing the risk of stress concentration or interface peeling when the layer is thicker.

[0048] In some embodiments, the thickness ratio of the first layer to the second layer is (0.8~2):1. For example, the thickness ratio of the first layer to the second layer can be 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, or any value within the range of any two of the above values. Controlling the thickness ratio of the first layer to the second layer within the above range can balance conductivity and protective functions, which is beneficial for the low-resistance layer to effectively guide current, and at the same time helps to reduce the risk of interface failure due to thickness ratio imbalance.

[0049] In some embodiments, the thickness of the protective layer is from 20 nm to 1000 nm. For example, the thickness of the protective layer can be 20 nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, or any value within the range of any two of the above values. Controlling the thickness of the protective layer within the above range can meet the requirements of different battery systems for protection strength and space occupation, and reduce the risk of protection failure when the thickness is too thin or increased interface impedance when the thickness is too large.

[0050] In some embodiments, the first layer further includes a passivation layer located on the side of the TiN layer away from the substrate layer, the passivation layer comprising TiO2. 2-x 0 ≤ X < 2. In some embodiments, the thickness of the passivation layer is 1 nm to 3 nm. For example, the thickness of the passivation layer can be 1 nm, 1.2 nm, 1.4 nm, 1.6 nm, 1.8 nm, 2 nm, 2.2 nm, 2.4 nm, 2.6 nm, 2.8 nm, 3 nm, or any value within the range of any two of the above values.

[0051] In some embodiments, the second layer further includes a doping element, which includes at least one of yttrium and cerium.

[0052] This study found that during fast charging or high-temperature operation (>80°C), the passivation film (Cr2O3) on the stainless steel surface of sulfide solid-state batteries may undergo reconstruction or dissolution, leading to a decrease in protective performance. Simultaneously, the high-temperature drying environment during electrode coating may exacerbate the oxidation of the TiN layer (forming TiO2), resulting in increased resistance. Therefore, introducing the aforementioned passivation layer outside the first TiN material layer (e.g., by treating the TiN material layer with controlled oxygen plasma) helps mitigate further oxidation and forms a more stable oxide-metal interface with the subsequently deposited stainless steel layer. Doping the second layer with the aforementioned elements (e.g., doping the stainless steel material with these elements) allows these elements to preferentially diffuse to the surface at high temperatures, facilitating the formation of a more stable Y / Ce-doped chromium oxide passivation film, thereby improving high-temperature stability.

[0053] In some embodiments, the first layer further includes a first catalytic active unit located on the side of the TiN layer away from the substrate layer. The first catalytic active unit includes transition metal particles with a particle size of 2 nm to 20 nm, and the transition metal particles include at least one of cobalt and iron. In some embodiments, the mass ratio of the transition metal particles to TiN is greater than 0 and less than or equal to 5%. For example, the mass ratio can be 0.01%, 0.05%, 0.1%, 0.3%, 0.5%, 0.8%, 1%, 2%, 3%, 4%, 5%, or any value within the range of any two of the above values.

[0054] In some embodiments, the second layer further includes a second catalytic active unit located on the side of the stainless steel layer away from the substrate layer, the second catalytic active unit comprising a Cr-Ni-Mo alloy.

[0055] This study found that the decomposition of trace sulfide electrolytes or interfacial side reactions can still generate insulating products (such as Li₂S) that accumulate on the current collector surface, leading to an increase in interfacial contact resistance over time. Therefore, introducing the aforementioned first catalytic active unit outside the first TiN material layer provides catalytic activity for polysulfide conversion, which helps lower the interfacial reaction energy barrier, thereby further reducing the occurrence of trace sulfide electrolyte decomposition or interfacial side reactions. Introducing the aforementioned second catalytic active unit outside the second stainless steel material layer, for example by enriching the surface of the stainless steel layer with nanocrystalline or amorphous Cr-Ni-Mo alloy phase through high-power pulsed magnetron sputtering, can act as a catalyst to promote the reversible decomposition of Li₂S into Li₂ during charging. + And S, thereby reducing the potential accumulation of Li2S.

[0056] An embodiment of this application also provides a method for preparing the above-mentioned modified current collector, comprising: forming a protective layer on at least one side of a substrate layer by magnetron sputtering.

[0057] Magnetron sputtering can improve overall compactness. Each magnetron sputtering process further compacts the substrate, enhancing overall density. Most thin films may contain microscopic defects such as pinholes; multiple sputterings can reduce defect overlap, thereby reducing the risk of through-hole defects and improving the overall compactness and reliability of the current collector.

[0058] An embodiment of this application also provides an apparatus for performing the above-described preparation method. The apparatus includes: a vacuum chamber, a first coating chamber, a second coating chamber, and a transfer mechanism; the first coating chamber is configured to deposit a first layer on at least one side of a substrate layer by magnetron sputtering; the second coating chamber is configured to deposit a second layer on at least one side of the substrate layer by magnetron sputtering; the transfer mechanism is configured to sequentially and continuously transfer the substrate layer through the first coating chamber and the second coating chamber within the vacuum chamber; wherein the first coating chamber and the second coating chamber are both located in the vacuum chamber, and the first coating chamber and the second coating chamber are separated from each other.

[0059] By using magnetron sputtering, a multi-layer protective layer consisting of TiN and stainless steel is obtained through a one-time molding technique. The magnetron sputtering adopts a multi-compartment design, with each compartment isolated from the others, preventing N2 from entering the stainless steel compartment from the TiN compartment. Continuous coating avoids oxidation of the protective layer surface caused by multiple compartment openings, thereby improving film density, increasing production efficiency, and reducing production costs.

[0060] One embodiment of this application also provides an electrode comprising the modified current collector described above.

[0061] The electrode of this application employs a modified current collector with a multi-layered protective structure, which helps reduce the corrosion rate at the interface between the metal foil and the sulfide electrolyte in the substrate layer, thereby improving the chemical stability of the electrode under harsh environments. Simultaneously, through the synergistic effect of the highly conductive first layer and the passivating protective second layer, the electrode effectively reduces interfacial side reactions while maintaining low resistance, contributing to reduced capacity decay during cycling. Furthermore, the excellent mechanical compatibility of the protective layer can absorb stress generated by electrode volume changes, reducing the risk of delamination or cracking of the electrode during long-term cycling and enhancing structural integrity.

[0062] One embodiment of this application also provides a solid-state battery, which includes the electrodes described above.

[0063] The solid-state battery of this application integrates the aforementioned electrodes, resulting in more stable interfacial contact and lower interfacial impedance within the sulfide electrolyte system, which is beneficial for improving the battery's rate performance. Simultaneously, the effective blocking of sulfur ion penetration by the electrode protective layer helps reduce the degree of side reactions between the electrolyte and the current collector, thereby contributing to maintaining the battery's capacity retention during long cycles. Furthermore, the internal mechanical stress of the battery is better buffered, which helps reduce the risk of internal short circuits or sudden performance degradation caused by interfacial failure, improving the safety and cycle life of the solid-state battery.

[0064] The present application will be described below through specific embodiments and comparative examples. Those skilled in the art should understand that the preparation methods described in this application are merely examples, and any other suitable preparation methods are within the scope of this application.

[0065] Example 1:

[0066] A modified current collector, the preparation method of which includes:

[0067] Step 1: Provide copper foil with a thickness of 3 μm.

[0068] Step 2: Magnetron sputtering TiN onto one surface of a copper foil, using a Ti target as the raw material (99.99%), with an Ar (99.99%) to N2 (99.99%) ratio of 25:1, and a TiN thickness of 10 nm. During the magnetron sputtering process, argon gas is used to bombard the titanium target to sputter the titanium, and nitrogen gas is used as the reactant gas to react with the sputtered titanium atoms to form TiN, thus obtaining the first layer.

[0069] Step 3: Magnetron sputtering stainless steel onto the surface of the first layer, using SS316L stainless steel target as raw material, Ar (99.99%) as sputtering gas, and stainless steel thickness of 10 nm. The second layer is obtained by magnetron sputtering, resulting in a modified current collector.

[0070] Example 2:

[0071] The difference from Example 1 is that in the first step, the thickness of the copper foil is adjusted to 9 μm; in the second step, the ratio of Ar (99.99%) to N2 (99.99%) is 25:3, and the thickness of TiN is 50 nm; in the third step, the thickness of the stainless steel is 50 nm.

[0072] Example 3:

[0073] The difference from Example 1 is that in the first step, the thickness of the copper foil is adjusted to 15 μm; in the second step, the ratio of Ar (99.99%) to N2 (99.99%) is 25:5, and the thickness of TiN is 10 nm; in the third step, the thickness of the stainless steel is 100 nm.

[0074] Example 4:

[0075] The difference from Example 1 is that, based on Example 1, the following fourth and fifth steps are added, namely, forming two protective units on the surface of the copper foil.

[0076] Step 4: Form the first layer again on the surface of the second layer using the same method.

[0077] Step 5: Using the same method, form a second layer on the surface of the first layer formed in step 4 to obtain the modified current collector.

[0078] Example 5:

[0079] The difference from Example 1 is that, in the second step, after magnetron sputtering TiN, TiO is introduced onto the surface of the formed TiN material layer. 2-x passivation layer, TiO 2-x The passivation layer has a thickness of 2 nm.

[0080] Example 6:

[0081] The difference from Example 1 is that in the third step, when magnetron sputtering stainless steel, yttrium and cerium are doped into SS316L stainless steel, with a total doping mass of 1.0% of the mass of SS316L stainless steel, wherein the mass ratio of yttrium to cerium is 1:1.

[0082] Example 7:

[0083] The difference from Example 1 is that in the second step, after magnetron sputtering TiN, nanoscale cobalt particles and iron particles are introduced on the surface of the formed TiN material layer, and the mass ratio of cobalt particles and iron particles to TiN is 3%.

[0084] Example 8:

[0085] The difference from Example 1 is that in the third step, after magnetron sputtering of stainless steel, the Cr-Ni-Mo alloy phase is enriched on the surface of the formed stainless steel material layer.

[0086] Example 9:

[0087] The difference from Example 1 is that the copper foil is replaced with a composite copper foil of the same thickness, wherein the composite copper foil includes a PET film with a middle layer of 1 μm thickness and copper layers with a thickness of 1 μm on both sides of the PET film.

[0088] Comparative Example 1:

[0089] A modified current collector, the preparation method of which includes:

[0090] Step 1: Provide copper foil with a thickness of 3 μm.

[0091] Step 2: Magnetron sputtering TiN onto one surface of a copper foil, using a Ti target as the raw material (99.99%), with an Ar (99.99%) to N2 (99.99%) ratio of 25:1, and a TiN thickness of 10 nm. During the magnetron sputtering process, argon gas is used to bombard the titanium target to sputter the titanium, and nitrogen gas is used as the reactant gas to react with the sputtered titanium atoms to form TiN, thus obtaining the modified current collector.

[0092] Comparative Example 2:

[0093] A modified current collector, the preparation method of which includes:

[0094] Step 1: Provide copper foil with a thickness of 3 μm.

[0095] Step 2: Magnetron sputter stainless steel onto the surface of copper foil, using SS316L stainless steel target as raw material and Ar (99.99%) as sputtering gas. The stainless steel thickness includes 10 nm, to obtain the modified current collector.

[0096] Comparative Example 3:

[0097] A modified current collector, the preparation method of which includes:

[0098] Step 1: Provide copper foil with a thickness of 3 μm.

[0099] Step 2: Magnetron sputter stainless steel onto the surface of copper foil, using SS316L stainless steel target as raw material and Ar (99.99%) as sputtering gas. The stainless steel thickness includes 10 nm.

[0100] Step 3: Magnetron sputtering TiN onto the surface of the stainless steel material layer formed in Step 2, using a Ti target as the raw material (99.99%), with an Ar (99.99%) to N2 (99.99%) ratio of 25:1, and a TiN thickness of 10 nm. During the magnetron sputtering process, argon gas is used to bombard the titanium target to sputter the titanium, and nitrogen gas is used as the reactant gas to react with the sputtered titanium atoms to form TiN, thus obtaining the modified current collector.

[0101] The testing method for this application is as follows:

[0102] 1. Electrolyte Corrosion Resistance Test: Modified current collector samples were cut into 1 cm × 1 cm pieces and immersed in a mixture of sulfide solid electrolyte (Li6PS5Cl) and trace amounts of water (0.5% by mass) at 25 ℃ for 72 h. The leaching amount of the substrate metal (Cu) in the immersion solution was detected by inductively coupled plasma mass spectrometry (ICP-MS), and the surface morphology of the samples was observed by scanning electron microscopy (SEM). The corrosion rate was calculated using the formula: Corrosion rate (μm / a) = (8.76 × 10⁻⁶) / (μm / a) = 1 / 2.5 × 10⁻⁶. 4(×Δm) / (ρ×S×t), where Δm is the mass loss (g), and ρ is the density of Cu (8.96 g / cm³). 3 S is the surface area of ​​the sample (cm²) 2 ), where t is the soaking time (h).

[0103] 2. Conductivity test: The surface resistivity of the modified current collector was tested using the four-probe method. The test instrument was an RTS-9 dual-electric four-probe tester. The test temperature was 25 ℃ and the humidity was 50%. Five different positions were tested for each sample, and the average value was taken.

[0104] 3. Mechanical performance test: The adhesion between the protective layer and the substrate layer is tested by the cross-cut test (ASTM D3359). The cross-cut spacing is 1 mm. After the tape is peeled off, the edge of the cross-cut is observed to see if it falls off. The rating is 1-5 (1 is the best and 5 is the worst).

[0105] 4. Battery Cycling Test: Using modified current collector as negative electrode current collector, NCM811 as positive electrode, and Li6PS5Cl as solid electrolyte, CR2032 button cell batteries were assembled; charge / discharge rate 0.1 C, voltage range 2.5-4.3 V, temperature 25 ℃, 100 cycles, and the change in internal resistance of the battery before and after 100 cycles was recorded.

[0106] Please refer to Table 1 for the test results above.

[0107] Table 1. Performance test results of Examples 1-9 and Comparative Examples 1-3 of this application

[0108]

[0109] In the modified current collector of this application embodiment, the TiN layer (first layer) is located outside the metal foil in the substrate layer. A strong physical bond can be formed between TiN and the substrate layer (such as the metal foil) through sputtering, improving the overall bonding effect between the protective layer and the current collector. Furthermore, the resistivity of TiN is lower than that of the stainless steel layer (second layer). Placing it between the substrate layer and the stainless steel layer allows current drawn from the metal foil in the substrate layer to first pass through the lower-resistance TiN layer, which helps reduce ohmic losses in the overall laminated structure. In addition, the coefficient of thermal expansion of TiN is typically between that of the electrode active material (such as silicon) and the metal foil (such as copper), reducing the risk of interface delamination caused by battery cycling. Meanwhile, the stainless steel layer is disposed outside the TiN layer for contact with the solid electrolyte. When exposed to sulfur-containing electrolytes, elements such as chromium (Cr) on its surface can spontaneously form a dense oxide / sulfide passivation layer (such as Cr2O3), which actively resists the penetration of sulfur ions and corrosive media. During battery cycling, the electrode materials undergo volume changes. The outer stainless steel layer, with its better ductility, can absorb some stress through plastic deformation, which helps reduce the risk of cracking in the brittle TiN layer under large strain. Therefore, the protective layer or unit formed by the combination of TiN and stainless steel possesses both excellent corrosion resistance and excellent electrical and mechanical properties.

[0110] In Example 5, TiO was further introduced onto the surface of the TiN material layer. 2-x The passivation layer helps to mitigate further oxidation and forms a more stable oxide-metal interface with the subsequently deposited stainless steel layer, thereby further enhancing the stability of the protective layer. In Example 6, yttrium (Y) and cerium (Ce) are further doped into the stainless steel material layer, which helps to form a more stable Y / Ce-doped chromium oxide passivation film, thereby improving high-temperature stability and enhancing the stability of the protective layer under fast charging or high-temperature conditions.

[0111] Example 7 further introduces a first catalytic active unit on the surface of the TiN material layer, which has catalytic activity for polysulfide conversion and helps to reduce the interfacial reaction energy barrier, thereby further reducing the decomposition of trace sulfide electrolytes or the occurrence of interfacial side reactions; Example 8 further introduces a second catalytic active unit into the stainless steel material layer, which can act as a catalyst to promote the reversible decomposition of Li2S into Li during charging. + And S, thereby reducing the potential accumulation of Li2S.

[0112] Compared to Examples 1-9 of this application, Comparative Example 1 uses only TiN as a protective layer, and Comparative Example 2 uses only stainless steel as a protective layer. A single material protective layer cannot simultaneously achieve corrosion resistance, electrical conductivity, and mechanical properties.

[0113] Compared to Examples 1-9 of this application, Comparative Example 3 first plates stainless steel on the copper foil surface and then plates TiN. The current will first pass through the second layer with higher resistivity, which will significantly increase the overall ohmic loss of the current collector, resulting in an increase in battery internal resistance and a decrease in energy efficiency. At the same time, the brittle and chemically inert first layer is placed on the outside and directly contacts the sulfide electrolyte. It is difficult to form an effective passivation film on its surface, which will lead to intensified interface corrosion. In addition, the outer first layer is more prone to cracking under battery cycle stress due to its brittleness, thus losing its overall protective function.

[0114] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0115] The embodiments described above are merely illustrative of several implementations of the technical solution of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the technical solution of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A modified current collector, characterized in that, The modified current collector includes: a substrate layer comprising a metal foil; and a protective layer located on at least one side of the substrate layer, the protective layer comprising at least one protective unit, the protective unit comprising a first layer and a second layer stacked in a direction away from the substrate layer, the first layer comprising a TiN layer and the second layer comprising a stainless steel layer.

2. The modified current collector as described in claim 1, characterized in that, The protective layer satisfies at least one of the following conditions: (1) the thickness of the first layer is 10 nm to 100 nm; (2) the thickness of the second layer is 10 nm to 100 nm; (3) the thickness ratio of the first layer to the second layer is (0.8~2):1; (4) the thickness of the protective layer is 20 nm to 1000 nm.

3. The modified current collector as described in claim 1, characterized in that, The protective layer also satisfies at least one of the following conditions: (1) the first layer further includes a passivation layer located on the side of the TiN layer away from the substrate layer, the passivation layer comprising TiO2. 2-x , 0≤X<2, the thickness of the passivation layer is 1 nm to 3 nm; (2) the second layer further includes a doping element, the doping element includes at least one of yttrium and cerium; (3) the first layer further includes a first catalytic active unit located on the side of the TiN layer away from the substrate layer, the first catalytic active unit includes transition metal particles, the particle size of the transition metal particles is 2 nm to 20 nm, the transition metal particles include at least one of cobalt and iron, the mass ratio of the transition metal particles to the TiN layer is greater than 0 and less than or equal to 5%; (4) the second layer further includes a second catalytic active unit located on the side of the stainless steel layer away from the substrate layer, the second catalytic active unit includes a Cr-Ni-Mo alloy.

4. The modified current collector as described in claim 1, characterized in that, The substrate layer further includes a polymer film, with the metal foil located on both sides of the polymer film. The polymer film is made of at least one of polypropylene, polyethylene, and polyethylene terephthalate.

5. The modified current collector as described in claim 1, characterized in that, Metal foils include copper.

6. The modified current collector as described in claim 1, characterized in that, The thickness of the substrate layer is 3 μm to 15 μm.

7. A method for preparing a modified current collector as described in any one of claims 1-6, characterized in that, include: The protective layer is formed on at least one side of the substrate layer by magnetron sputtering.

8. An apparatus for performing the preparation method as described in claim 7, characterized in that, The apparatus includes: a vacuum chamber; a first coating chamber configured to deposit a first layer on at least one side of a substrate layer by magnetron sputtering; a second coating chamber configured to deposit a second layer on at least one side of a substrate layer by magnetron sputtering; and a transport mechanism configured to sequentially and continuously transport the substrate layer through the first coating chamber and the second coating chamber within the vacuum chamber; wherein the first coating chamber and the second coating chamber are both located within the vacuum chamber, and the first coating chamber and the second coating chamber are isolated from each other.

9. An electrode sheet, characterized in that, The electrode includes the modified current collector as described in any one of claims 1-6.

10. A solid-state battery, characterized in that, The solid-state battery includes the electrode as described in claim 9.

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