A high-strength stainless steel current collector, its preparation method and application

Abstract

The application discloses a high-strength stainless steel current collector and a preparation method and application thereof, and relates to the technical field of current collectors.The preparation method of the high-strength current collector specifically comprises the following steps: S1: sequentially performing washing, drying and pre-oxidation treatment on a stainless steel mesh to obtain a stainless steel current collector A; S2: performing one-time nitriding treatment on the stainless steel current collector A to obtain a stainless steel current collector B; and S3: performing two-time nitriding treatment on the stainless steel current collector B to obtain a high-strength stainless steel current collector.The stainless steel current collector obtained through the preparation method has improved uniformity of a nitride layer formed on the surface of the current collector, and the stainless steel current collector has excellent strength and cycle retention rate when being used for a lithium battery negative electrode.

Description

Technical Field

[0001] This invention relates to the field of current collector technology, specifically a high-strength stainless steel current collector, its preparation method, and its application. Background Technology

[0002] With the rapid development of the new energy industry, lithium batteries, as a type of rechargeable battery, are widely used in portable electronic devices, electric vehicles, energy storage, and other technological fields due to their high energy density and long cycle life. As batteries trend towards larger capacity and smaller size, the optimization of battery structure is receiving increasing attention. The current collector, as a key structural component of rechargeable batteries, is used to carry active materials and collect conductive current, playing a crucial role in the overall performance of the battery.

[0003] However, during lithium battery use, after multiple cycles, lithium ions tend to form uneven deposits at the negative electrode, resulting in lithium dendrites. This reduces cycle efficiency and can puncture the separator, causing short circuits, thermal runaway, or even fire and explosion. For a long time, copper foil has been the standard choice for lithium battery negative electrodes due to its excellent conductivity and mature processing technology. However, copper foil has poor corrosion resistance, high cost, and cannot suppress the formation of lithium dendrites. Current technologies generally use composite current collectors to improve lithium battery safety. This involves magnetron sputtering a metal seed layer onto an organic polymer film substrate followed by electroplating to obtain a sandwich-structured composite current collector. While this effectively reduces the possibility of lithium dendrites puncturing the separator and causing short circuits and fires, it still cannot prevent the formation of lithium dendrites at the source. Using artificial SEI films can suppress lithium dendrite growth at the source, but production is difficult, and at high current densities, some lithium ions deposit on the SEI film, causing battery failure.

[0004] Among them, stainless steel materials form a dense passivation film on their surface, which has excellent corrosion resistance, low cost, and good conductivity, making it a promising candidate for current collectors in lithium batteries. However, there are still many problems, such as the relatively poor compatibility between stainless steel and lithium, which may lead to separation during the composite process, and the generally low strength of stainless steel foil, which is prone to wrinkling.

[0005] In conclusion, solving the above problems and preparing a high-strength stainless steel current collector is of great significance. Summary of the Invention

[0006] The purpose of this invention is to provide a high-strength stainless steel current collector, its preparation method, and its application, so as to solve the problems mentioned in the background art.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0008] A method for preparing a high-strength stainless steel current collector includes the following steps:

[0009] S1: The stainless steel mesh is washed, dried and pre-oxidized in sequence to obtain stainless steel current collector A;

[0010] S2: Perform a nitriding treatment on stainless steel current collector A to obtain stainless steel current collector B;

[0011] S3: The stainless steel current collector B is subjected to secondary nitriding treatment to obtain a high-strength stainless steel current collector.

[0012] Preferably, during the pre-oxidation treatment, the temperature is 540~560℃, the time is 120~180 seconds, and the gas atmosphere is air.

[0013] Preferably, during the single nitriding process, the temperature is 350~400℃, the time is 10~15min, the gas atmosphere is ammonia, and the gas flow rate is 0.1~0.2m³. 3 / h.

[0014] Preferably, during the secondary nitriding process, the temperature is 350~400℃, the time is 25~30min, the gas atmosphere is ammonia, and the initial gas flow rate is 0.2m³. 3 / h, at 0.05m 3 The speed increases to 0.4~0.6 m per minute. 3 / h.

[0015] Preferably, both the primary and secondary nitriding processes are ion nitriding; during the secondary nitriding process, the rare earth metal needs to be suspended on the cathode plate inside the ion nitriding furnace.

[0016] Preferably, the rare earth metal includes a lanthanum-yttrium alloy, with a lanthanum to yttrium mass ratio of 2 to 3:1.

[0017] Preferably, the stainless steel mesh is a 304 type stainless steel mesh with a pore size of 500~1000 mesh and a thickness of 50~150μm.

[0018] Preferably, the high-strength stainless steel current collector can be used as a composite negative electrode in a lithium battery, specifically including the following steps: bonding a lithium sheet to the surface of the high-strength stainless steel current collector and mechanically pressing them together to obtain a composite negative electrode.

[0019] Preferably, during the pressing process, the pressing pressure is 40~50MPa and the dew point temperature is -50~-70℃.

[0020] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The present invention is based on stainless steel mesh, and performs pre-oxidation, primary nitriding, and secondary nitriding in sequence, which improves the uniformity of the formed nitride layer, so that the stainless steel current collector has excellent strength and cycle retention rate when used as a negative electrode of lithium battery.

[0021] Among them, the stainless steel current collector adopts a stainless steel mesh structure with a porosity of 500~1000 mesh. Its structure is a three-dimensional continuous metal skeleton with certain strength, and the current can be conducted in any direction in this structure, reducing polarization. Compared with stainless steel metal foil, the high specific surface area of ​​stainless steel mesh can serve as a lithium deposition site, increasing the capacity, and uniformly promoting lithium nucleation, reducing the local current density of the electrode, inhibiting the growth of lithium dendrites, and improving the cycle efficiency of the battery.

[0022] Nitriding is a process that uses ion nitriding with ammonia as the working gas. During nitriding, nitrogen atoms enter the crystal lattice of stainless steel, forming a layer of metal nitride on the surface of the stainless steel mesh. This nitride has a strong affinity for lithium and high ionic conductivity, allowing it to react with lithium in situ to form lithium nitride, which promotes lithium-ion deposition. However, because the stainless steel mesh is woven from metal wires with very small diameters, it is prone to brittleness and cracking if conventional nitriding processes are used, rendering it unusable. Furthermore, a stable chromium oxide passivation film forms on the stainless steel surface, hindering nitrogen penetration. Although the passivation film can be removed during ion nitriding, the effect is limited, and it can easily lead to an uneven nitride layer, resulting in a decrease in battery cycle retention. Therefore, this invention sets a rare earth alloy on the cathode plate in the glow discharge ion nitriding furnace. During the ion nitriding process, rare earth atoms are sputtered onto the surface of the stainless steel mesh. Due to the large difference between the atomic size of rare earth elements and iron atoms, the stainless steel lattice is distorted, which promotes the diffusion rate of nitrogen atoms. This shortens the processing time of the stainless steel mesh, relatively reduces the nitrogen concentration on the stainless steel surface, and reduces the amount of brittle phase formation, thereby reducing the impact on the strength of the stainless steel mesh. At the same time, it plays a role in micro-alloying, inhibiting grain growth, refining the grains, increasing strength and corrosion resistance, and thus improving cycle retention rate.

[0023] The rare earth alloy is preferably a lanthanum-yttrium alloy with a mass ratio of 3 to 2:1. Lanthanum provides a reducing environment, promoting the diffusion of nitrogen atoms into the matrix, while yttrium mainly plays a role in nitrogen adsorption and dissociation, improving the generation efficiency of active nitrogen atoms. The two work synergistically to improve the nitriding efficiency. Meanwhile, because the stainless steel mesh wire diameter is small, the nitriding temperature cannot be too high, otherwise it will easily become brittle and unusable. Therefore, this invention uses a ratio of more lanthanum and less yttrium to improve the nitriding efficiency at low temperatures and control the active nitrogen content at a low level, significantly reducing the risk of embrittlement and improving the strength of the stainless steel current collector.

[0024] In the pre-oxidation process, the temperature is set at 540~560℃, so that the surface oxidation product is mainly iron(III) oxide (Fe3O4). During nitriding, the iron(III) oxide reacts rapidly with ammonia gas, reducing it to generate primary pig iron and destroying the surface passivation film, thereby promoting nitrogen penetration. Using conventional primary ion nitriding after pre-oxidation, the passivation film on the surface is destroyed during the secondary rare earth ion nitriding process. This increases the penetration rate of rare earth and the uniformity of nitride layer formation during the secondary nitriding process, improves the utilization rate of rare earth, and reduces the nitriding time, thus minimizing the impact on the strength of the stainless steel mesh. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] It should be noted that in the following examples, "parts" refers to parts by weight, and all raw materials used are commercially available.

[0027] Example 1: A method for preparing a high-strength stainless steel current collector includes the following steps:

[0028] S1: Wash the stainless steel mesh to remove surface stains, dry it, transfer it to an air oven, set the temperature to 550℃, and pre-oxidize it for 150 seconds to obtain stainless steel current collector A;

[0029] S2: Transfer the stainless steel current collector A to the glow discharge ion nitriding furnace, set the temperature to 375℃, and the ammonia flow rate to 0.2m³ / h. 3 / h, one nitriding treatment for 15min, to obtain stainless steel current collector B;

[0030] S3: A lanthanum-yttrium alloy (lanthanum to yttrium mass ratio of 3:1) is suspended on the cathode plate in a glow discharge ion nitriding furnace. The temperature is set to 375℃, and the initial ammonia flow rate is 0.2 m³ / s. 3 / h, at 0.05m 3 The speed increases to 0.5 m per minute. 3 / h, the stainless steel current collector B is subjected to secondary nitriding treatment for 30min to obtain a high-strength stainless steel current collector;

[0031] The stainless steel mesh is a 500-mesh stainless steel mesh with a thickness of 60μm.

[0032] Example 2: A method for preparing a high-strength stainless steel current collector includes the following steps:

[0033] S1: Wash the stainless steel mesh to remove surface stains, dry it, transfer it to an air furnace, set the temperature to 550℃, and pre-oxidize it for 120 seconds to obtain stainless steel current collector A;

[0034] S2: Transfer the stainless steel current collector A to the glow discharge ion nitriding furnace, set the temperature to 375℃, and the ammonia flow rate to 0.2m³ / h. 3 / h, one nitriding treatment for 15min, to obtain stainless steel current collector B;

[0035] S3: A lanthanum-yttrium alloy (lanthanum to yttrium mass ratio of 3:1) is suspended on the cathode plate in a glow discharge ion nitriding furnace. The temperature is set to 375℃, and the initial ammonia flow rate is 0.2 m³ / s. 3 / h, at 0.05m 3 The speed increases to 0.5 m per minute. 3 / h, the stainless steel current collector B is subjected to secondary nitriding treatment for 30min to obtain a high-strength stainless steel current collector;

[0036] The stainless steel mesh is a 500-mesh stainless steel mesh with a thickness of 60μm.

[0037] Example 3: A method for preparing a high-strength stainless steel current collector includes the following steps:

[0038] S1: Wash the stainless steel mesh to remove surface stains, dry it, transfer it to an air furnace, set the temperature to 550℃, and pre-oxidize it for 180 seconds to obtain stainless steel current collector A;

[0039] S2: Transfer the stainless steel current collector A to the glow discharge ion nitriding furnace, set the temperature to 375℃, and the ammonia flow rate to 0.2m³ / h. 3 / h, one nitriding treatment for 15min, to obtain stainless steel current collector B;

[0040] S3: A lanthanum-yttrium alloy (lanthanum to yttrium mass ratio of 3:1) is suspended on the cathode plate in a glow discharge ion nitriding furnace. The temperature is set to 375℃, and the initial ammonia flow rate is 0.2 m³ / s. 3 / h, at 0.05m 3 The speed increases to 0.5 m per minute. 3 / h, the stainless steel current collector B is subjected to secondary nitriding treatment for 30min to obtain a high-strength stainless steel current collector;

[0041] The stainless steel mesh is a 500-mesh stainless steel mesh with a thickness of 60μm.

[0042] Example 4: A method for preparing a high-strength stainless steel current collector includes the following steps:

[0043] S1: Wash the stainless steel mesh to remove surface stains, dry it, transfer it to an air oven, set the temperature to 550℃, and pre-oxidize it for 150 seconds to obtain stainless steel current collector A;

[0044] S2: Transfer the stainless steel current collector A to the glow discharge ion nitriding furnace, set the temperature to 350℃, and the ammonia flow rate to 0.2m³ / h. 3 / h, one nitriding treatment for 15min, to obtain stainless steel current collector B;

[0045] S3: A lanthanum-yttrium alloy (lanthanum to yttrium mass ratio of 3:1) is suspended on the cathode plate in a glow discharge ion nitriding furnace. The temperature is set to 350℃, and the initial ammonia flow rate is 0.2 m³ / s. 3 / h, at 0.05m 3 The speed increases to 0.5 m per minute. 3 / h, the stainless steel current collector B is subjected to secondary nitriding treatment for 30min to obtain a high-strength stainless steel current collector;

[0046] The stainless steel mesh is a 500-mesh stainless steel mesh with a thickness of 60μm.

[0047] Example 5: A method for preparing a high-strength stainless steel current collector includes the following steps:

[0048] S1: Wash the stainless steel mesh to remove surface stains, dry it, transfer it to an air oven, set the temperature to 550℃, and pre-oxidize it for 150 seconds to obtain stainless steel current collector A;

[0049] S2: Transfer the stainless steel current collector A to the glow discharge ion nitriding furnace, set the temperature to 400℃, and the ammonia flow rate to 0.2m³ / h. 3 / h, one nitriding treatment for 15min, to obtain stainless steel current collector B;

[0050] S3: A lanthanum-yttrium alloy (lanthanum to yttrium mass ratio of 3:1) is suspended on the cathode plate in a glow discharge ion nitriding furnace. The temperature is set to 400℃, and the initial ammonia flow rate is 0.2 m³ / s. 3 / h, at 0.05m 3 The speed increases to 0.5 m per minute. 3 / h, the stainless steel current collector B is subjected to secondary nitriding treatment for 30min to obtain a high-strength stainless steel current collector;

[0051] The stainless steel mesh is a 500-mesh stainless steel mesh with a thickness of 60μm.

[0052] Example 6: A method for preparing a high-strength stainless steel current collector includes the following steps:

[0053] S1: Wash the stainless steel mesh to remove surface stains, dry it, transfer it to an air oven, set the temperature to 550℃, and pre-oxidize it for 150 seconds to obtain stainless steel current collector A;

[0054] S2: Transfer the stainless steel current collector A to the glow discharge ion nitriding furnace, set the temperature to 375℃, and the ammonia flow rate to 0.2m³ / h. 3 / h, one nitriding treatment for 15min, to obtain stainless steel current collector B;

[0055] S3: A lanthanum-yttrium alloy (lanthanum to yttrium mass ratio of 3:1) is suspended on the cathode plate in a glow discharge ion nitriding furnace. The temperature is set to 375℃, and the initial ammonia flow rate is 0.2 m³ / s. 3 / h, at 0.05m 3 The speed increases to 0.5 m per minute. 3 / h, the stainless steel current collector B is subjected to secondary nitriding treatment for 30min to obtain a high-strength stainless steel current collector;

[0056] The stainless steel mesh is a 1000-mesh stainless steel mesh with a thickness of 150μm.

[0057] Comparative Example 1: Based on Example 1, 304 stainless steel foil was used as the current collector, and the rest of the process remained unchanged, as follows:

[0058] S1: Wash the stainless steel foil to remove surface stains, and dry it to obtain a high-strength stainless steel current collector;

[0059] The thickness of the 304 stainless steel foil is 60 μm.

[0060] Comparative Example 2: Based on Example 1, an untreated stainless steel mesh was used as the current collector, with the remaining processes unchanged, as follows:

[0061] S1: Wash the stainless steel mesh to remove surface stains, dry it, and obtain a high-strength stainless steel current collector;

[0062] The stainless steel mesh is a 500-mesh stainless steel mesh with a thickness of 60μm.

[0063] Comparative Example 3: Based on Example 1, the nitriding temperature was increased while the rest of the process remained unchanged, as follows:

[0064] S1: Wash the stainless steel mesh to remove surface stains, dry it, transfer it to an air oven, set the temperature to 550℃, and pre-oxidize it for 150 seconds to obtain stainless steel current collector A;

[0065] S2: Transfer the stainless steel current collector A to the glow discharge ion nitriding furnace, set the temperature to 510℃, and the ammonia flow rate to 0.2m³ / h. 3 / h, one nitriding treatment for 15min, to obtain stainless steel current collector B;

[0066] S3: A lanthanum-yttrium alloy (lanthanum to yttrium mass ratio of 3:1) is suspended on the cathode plate in a glow discharge ion nitriding furnace. The temperature is set to 510℃, and the initial ammonia flow rate is 0.2 m³ / s. 3 / h, at 0.05m 3 The speed increases to 0.5 m per minute. 3 / h, the stainless steel current collector B is subjected to secondary nitriding treatment for 30min to obtain a high-strength stainless steel current collector;

[0067] The stainless steel mesh is a 500-mesh stainless steel mesh with a thickness of 60μm.

[0068] Comparative Example 4: Based on Example 1, the ratio of the two components in the lanthanum-yttrium alloy was exchanged, while the other processes remained unchanged, as follows:

[0069] S1: Wash the stainless steel mesh to remove surface stains, dry it, transfer it to an air oven, set the temperature to 550℃, and pre-oxidize it for 150 seconds to obtain stainless steel current collector A;

[0070] S2: Transfer the stainless steel current collector A to the glow discharge ion nitriding furnace, set the temperature to 375℃, and the ammonia flow rate to 0.2m³ / h. 3 / h, one nitriding treatment for 15min, to obtain stainless steel current collector B;

[0071] S3: A lanthanum-yttrium alloy (lanthanum to yttrium mass ratio of 1:3) is suspended on the cathode plate in a glow discharge ion nitriding furnace. The temperature is set to 375℃, and the initial ammonia flow rate is 0.2 m³ / s. 3 / h, at 0.05m 3 The speed increases to 0.5 m per minute. 3 / h, the stainless steel current collector B is subjected to secondary nitriding treatment for 30min to obtain a high-strength stainless steel current collector;

[0072] The stainless steel mesh is a 500-mesh stainless steel mesh with a thickness of 60μm.

[0073] Comparative Example 5: Based on Example 1, the secondary nitriding time was increased, while the rest of the process remained unchanged, as follows:

[0074] S1: Wash the stainless steel mesh to remove surface stains, dry it, transfer it to an air oven, set the temperature to 550℃, and pre-oxidize it for 150 seconds to obtain stainless steel current collector A;

[0075] S2: Transfer the stainless steel current collector A to the glow discharge ion nitriding furnace, set the temperature to 375℃, and the ammonia flow rate to 0.2m³ / h. 3 / h, one nitriding treatment for 15min, to obtain stainless steel current collector B;

[0076] S3: A lanthanum-yttrium alloy (lanthanum to yttrium mass ratio of 3:1) is suspended on the cathode plate in a glow discharge ion nitriding furnace. The temperature is set to 375℃, and the initial ammonia flow rate is 0.2 m³ / s. 3 / h, at 0.05m 3 The speed increases to 0.5 m per minute. 3 / h, the stainless steel current collector B is subjected to secondary nitriding treatment for 2h to obtain a high-strength stainless steel current collector;

[0077] The stainless steel mesh is a 500-mesh stainless steel mesh with a thickness of 60μm.

[0078] Comparative Example 6: Based on Example 1, the pre-oxidation temperature was increased, while the rest of the process remained unchanged, as follows:

[0079] S1: Wash the stainless steel mesh to remove surface stains, dry it, transfer it to an air furnace, set the temperature to 600℃, and pre-oxidize it for 150 seconds to obtain stainless steel current collector A;

[0080] S2: Transfer the stainless steel current collector A to the glow discharge ion nitriding furnace, set the temperature to 375℃, and the ammonia flow rate to 0.2m³ / h. 3 / h, one nitriding treatment for 15min, to obtain stainless steel current collector B;

[0081] S3: A lanthanum-yttrium alloy (lanthanum to yttrium mass ratio of 3:1) is suspended on the cathode plate in a glow discharge ion nitriding furnace. The temperature is set to 375℃, and the initial ammonia flow rate is 0.2 m³ / s. 3 / h, at 0.05m 3 The speed increases to 0.5 m per minute. 3 / h, the stainless steel current collector B is subjected to secondary nitriding treatment for 30min to obtain a high-strength stainless steel current collector;

[0082] The stainless steel mesh is a 500-mesh stainless steel mesh with a thickness of 60μm.

[0083] Comparative Example 7: Based on Example 1, without pre-oxidation treatment, the remaining processes remain unchanged, as follows:

[0084] S1: Wash the stainless steel mesh to remove surface stains, and dry it to obtain stainless steel current collector A;

[0085] S2: Transfer the stainless steel current collector A to the glow discharge ion nitriding furnace, set the temperature to 375℃, and the ammonia flow rate to 0.2m³ / h. 3 / h, one nitriding treatment for 15min, to obtain stainless steel current collector B;

[0086] S3: A lanthanum-yttrium alloy (lanthanum to yttrium mass ratio of 3:1) is suspended on the cathode plate in a glow discharge ion nitriding furnace. The temperature is set to 375℃, and the initial ammonia flow rate is 0.2 m³ / s. 3 / h, at 0.05m 3 The speed increases to 0.5 m per minute. 3 / h, the stainless steel current collector B is subjected to secondary nitriding treatment for 30min to obtain a high-strength stainless steel current collector;

[0087] The stainless steel mesh is a 500-mesh stainless steel mesh with a thickness of 60μm.

[0088] Comparative Example 8: Based on Example 1, without performing a single nitriding treatment, the remaining processes remain unchanged, as follows:

[0089] S1: Wash the stainless steel mesh to remove surface stains, dry it, transfer it to an air oven, set the temperature to 550℃, and pre-oxidize it for 150 seconds to obtain stainless steel current collector A;

[0090] S2: Transfer the stainless steel current collector A to the glow discharge ion nitriding furnace. Suspend the lanthanum-yttrium alloy (lanthanum to yttrium mass ratio 3:1) on the cathode plate within the furnace. Set the temperature to 375℃ and the initial ammonia flow rate to 0.2 m³ / s. 3 / h, at 0.05m 3 The speed increases to 0.5 m per minute. 3 / h, nitriding treatment for 45min, to obtain high-strength stainless steel current collector;

[0091] The stainless steel mesh is a 500-mesh stainless steel mesh with a thickness of 60μm.

[0092] Performance testing: (1) The stainless steel current collector samples prepared in each embodiment and comparative example were pressed together with lithium sheets to obtain a composite negative electrode. Lithium iron phosphate was used as the positive electrode material and coated on the surface of the aluminum foil current collector as the positive electrode. The samples were assembled into lithium batteries and the capacity retention rate was measured after 200 cycles at a 3C charging rate. (2) The stainless steel current collector samples prepared in each embodiment and comparative example were subjected to brittleness testing: a hard metal ball with a radius of 5 mm was pressed into the sample surface, and the critical load at which cracks were generated on the surface of the stainless steel mesh of the current collector was measured. The experimental data are shown in the table below.

[0093]

[0094] Conclusion: As shown in the table above, the present invention, based on stainless steel mesh, sequentially performs pre-oxidation, primary nitriding, and secondary nitriding, which improves the uniformity of the formed nitride layer, resulting in excellent strength and cycle efficiency of the stainless steel current collector when used as a lithium battery anode.

[0095] In Comparative Example 1, using 304 stainless steel foil as the current collector failed to suppress lithium dendrite formation, resulting in a lower cycle retention rate compared to Comparative Example 2, which used untreated stainless steel mesh. In Comparative Example 3, increasing the nitriding temperature caused severe embrittlement of the stainless steel mesh, rendering it unusable. In Comparative Example 4, changing the ratio of lanthanum and yttrium in the alloy reduced the nitriding effect, increased active nitrogen content, and decreased strength and cycle retention rate. In Comparative Example 5, increasing the secondary nitriding time also caused embrittlement of the stainless steel mesh, rendering it unusable. In Comparative Example 6, increasing the pre-oxidation temperature resulted in an oxide layer primarily composed of iron oxide, with a loose structure, decreased density, and a significantly reduced cycle retention rate. In Comparative Example 7, without pre-oxidation treatment, the presence of a passivation film resulted in poor nitriding performance and a significant decrease in cycle retention rate. In Comparative Example 8, without primary nitriding treatment, the oxide layer on the stainless steel mesh surface remained intact, reducing rare earth utilization, decreasing penetration rate and uniformity, and consequently, lowering the cycle retention rate.

[0096] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method of making a high strength stainless steel current collector, characterized by: The method comprises the following steps: S1: sequentially washing, drying and pre-oxidizing the stainless steel mesh to obtain a stainless steel current collector A; wherein, during the pre-oxidizing process, the temperature is 540-560 DEG C, the time is 120-180 seconds, and the gas atmosphere is air; S2: subjecting the stainless steel current collector A to a first nitriding treatment to obtain a stainless steel current collector B; wherein, in the first nitriding treatment, the temperature is 350-400 DEG C, the time is 10-15 min, the gas atmosphere is ammonia, and the gas flow rate is 0.1-0.2 m 3 / h; S3: the stainless steel current collector B is subjected to secondary nitriding treatment to obtain a high-strength stainless steel current collector; wherein, in the process of the secondary nitriding treatment, the temperature is 350-400 DEG C, the time is 25-30 min, the gas atmosphere is ammonia, the initial flow rate of the gas is 0.2 m 3 / h, and the flow rate is increased to 0.4-0.6 m 3 / h per 1 min. 3 / h per 1 min. wherein, the first nitriding treatment and the second nitriding treatment are both ion nitriding; during the second nitriding treatment, the rare earth metal needs to be hung on the cathode disc in the ion nitriding furnace; wherein, the rare earth metal comprises a lanthanum-yttrium alloy, and the mass ratio of lanthanum to yttrium is 2-3:

1.

2. The method of making a high strength stainless steel current collector of claim 1, wherein: The stainless steel mesh is a 304 type stainless steel mesh, the porosity is 500-1000 mesh, and the thickness is 50-150 mu m.

3. A high strength stainless steel current collector characterized by: The high-strength stainless steel current collector is prepared by the preparation method of any one of claims 1-2.

4. Use of a high-strength stainless steel current collector according to claim 3, characterized in that: The composite negative electrode applied in the lithium battery specifically comprises the following steps: compounding a lithium sheet on the surface of the high-strength stainless steel current collector, and mechanically pressing to obtain a composite negative electrode.

5. Use of a high-strength stainless steel current collector according to claim 4, characterized in that: During the pressing process, the pressing pressure is 40-50 MPa, and the dew point temperature is-50--70 DEG C.

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