Silicon negative electrode sheet and lithium ion battery

Abstract

The utility model belongs to lithium ion battery technical field especially relates to a kind of silicon negative pole piece and lithium ion battery. Including substrate layer and the active material layer coated in at least one side of substrate layer;The substrate layer includes polymer layer and is set in the copper plating layer of polymer layer surface;The active material layer is provided with groove, and the active material layer is silicon-containing material layer.This application is by using the composite copper foil structure of polymer base material and metal copper plating layer, to reduce substrate layer thickness, increase the relative thickness of active material layer, then form groove in active material layer by laser etching, form micron level pore structure that can absorb silicon particle volume expansion in charge and discharge process, so that, effectively promote battery volume energy density.

Description

Technical Field

[0001] This utility model belongs to the field of lithium-ion battery technology, specifically relating to silicon anode sheets and lithium-ion batteries. Background Technology

[0002] Silicon-based anode materials are among the most promising innovative directions in the field of lithium-ion batteries. Elemental silicon boasts a theoretical specific capacity of up to 4200 mAh / g, more than 10 times that of graphite anodes, and a volumetric specific capacity of up to 2200 mAh / cm³. 3 It is a graphite anode (760mAh / cm²) 3 It is 2.9 times larger than that of silicon anodes. However, the problem of volume expansion has become a technical bottleneck restricting its industrial application. Chinese invention patent publication number CN118335902A discloses a silicon-containing anode sheet and its preparation method, battery, and electrical device. The silicon anode sheet includes: a polymer material and a copper seed layer, forming a composite copper foil as the base layer. At the same time, a multi-layer structure design with silicon thin film layer and carbon thin film layer is provided. Although the silicon thin film layer obtained by the process parameters of this case reduces the particle size of silicon particles, thereby reducing the expansion of silicon anode, the thickness of the base layer in this case is 3μm to 12μm. The thicker polymer base layer will affect the conductivity, mechanical properties, thermal management performance and adhesion to metal coating of copper foil.

[0003] One of the mainstream methods for solving the expansion problem of silicon anodes is laser etching on the electrode sheet. For example, Chinese Patent Publication No. CN118588901A discloses an anode sheet, its preparation method, and a lithium-ion battery. This anode sheet includes a current collector and an active coating. A double-layer coating method is used, and a groove is formed on the active coating using laser etching. This can suppress the expansion of the silicon anode, and the adhesion between the active coating and the current collector is improved by adjusting the proportion of binder in the double-layer coating. However, in this case, the current collector is a copper foil with a thickness of 4μm to 15μm. To improve the volumetric energy density of the battery, the relative thickness of the active coating must be reduced. Although laser etching modification technology can construct micro-nano structures on the surface of silicon materials to buffer volume expansion, it will also destroy the silicon crystal structure. The porous structure formed by etching directly affects the volumetric energy density of the battery. Utility Model Content

[0004] In view of this, this application provides a silicon anode sheet and a lithium-ion battery, which adopts a composite copper foil structure of polymer substrate and metal copper plating layer to reduce the thickness of the substrate layer and increase the relative thickness of the active material layer, so as to ultimately achieve the purpose of improving the volumetric energy density, thereby overcoming the defects of the prior art.

[0005] To achieve the above objectives, the detailed technical solution of this utility model is as follows:

[0006] A silicon anode includes a substrate layer and an active material layer coated on at least one side of the substrate layer; the substrate layer includes a polymer layer and a copper plating layer disposed on the surface of the polymer layer; the active material layer has grooves and is a silicon-containing material layer.

[0007] The thickness of the substrate layer is 1 μm to 3.5 μm, preferably 3 μm;

[0008] The polymer layer is a polyimide (PI) layer, and the thickness of the polymer layer is 0.5 μm to 1.5 μm, preferably 1 μm.

[0009] The thickness of the copper plating layer is 0.5μm to 1μm, preferably 1μm;

[0010] The thickness of the active material layer is 40 μm to 50 μm, preferably 45 μm.

[0011] Preferably, the grooves are obtained by laser etching, and the grooves are spaced apart. Preferably, the groove spacing C is 1-2 mm, and more preferably 2 mm.

[0012] Preferably, the etching depth B of the groove is 4μm to 25μm, and more preferably, the etching depth B is 12μm and the etching width A is 80μm.

[0013] When the active material layer is disposed on both sides of the substrate layer, the grooves on the upper and lower sides of the substrate layer are staggered. Preferably, the misalignment distance D of the grooves is 1 / 2 of the spacing distance C.

[0014] Preferably, the active material layer comprises graphite, silicon, a conductive agent, and a binder, wherein the mass ratio of graphite:silicon:conductive agent:binder is (80-97):(1-20):(0.1-5):(2-10), and preferably, the mass ratio of graphite:silicon:conductive agent:binder is 86.55:10:0.25:3.2.

[0015] The conductive agent is carbon black and carbon nanotubes, and the mass ratio of carbon black to carbon nanotubes is 4:1.

[0016] The adhesive is a mixture of polyacrylic acid (PAA), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR), with a mass ratio of PAA:CMC:SBR of 1:1:2.

[0017] A method for preparing a silicon anode sheet, characterized by comprising the following steps:

[0018] S1, Use a plasma cleaner to clean the polymer layer;

[0019] S2, A copper layer is deposited on the surface of the polymer layer by magnetron sputtering using a magnetron sputtering device to achieve a preset thickness and obtain the base layer.

[0020] S3, Prepare the active material layer by mixing graphite, silicon, conductive agent and binder in the mass ratio and homogenizing until the slurry is uniform and free of agglomeration;

[0021] S4, the slurry is evenly coated on the surface of the substrate to obtain the active material layer, and the electrode is compacted by the rolling process;

[0022] S5, grooves are formed on the surface of the active material layer using laser etching.

[0023] A lithium-ion battery comprising the negative electrode sheet described above.

[0024] Compared with the prior art, the beneficial effects of this utility model are:

[0025] The technical solution of this application utilizes a composite structure of a polymer substrate and a metal coating to form a PI / Cu composite copper foil as the substrate layer, aiming to reduce the thickness of the substrate layer. Simultaneously, an active material layer is coated on at least one side of the substrate layer; preferably, the active material layer is coated on both sides of the substrate layer. Due to the reduced thickness of the substrate layer, the relative thickness of the active material layer increases. Furthermore, grooves are formed in the active material layer using laser etching, creating a micron-sized porous structure that can absorb the volume expansion of silicon particles during charging and discharging. This effectively improves the volumetric energy density of the battery. Attached Figure Description

[0026] Figure 1 A schematic diagram of a single-sided coated electrode structure with a PI / Cu substrate layer and a laser-etched active material layer.

[0027] Figure 2 A schematic diagram of an electrode structure with a PI / Cu substrate layer and a laser-etched active material layer coated on both sides;

[0028] Figure 3 A schematic diagram of a double-sided coated electrode structure on a PI / Cu substrate;

[0029] Figure 4 Schematic diagram of a double-sided coated electrode with copper foil and laser-etched active material layer;

[0030] Figure 5 for Figure 2 A schematic diagram of the electrode size markings. Detailed Implementation

[0031] To enable those skilled in the art to better understand the technical solution of this utility model, the present utility model will be further described in detail below with reference to the accompanying drawings and preferred embodiments.

[0032] Figure 1 A silicon anode is shown, comprising a substrate layer and an active material layer coated on one side thereof; the substrate includes a polymer layer and a copper plating layer disposed on the surface of the polymer layer; grooves are formed on the active material layer; the grooves are formed by laser etching. The groove etching depth B is 12 μm, the etching width A is 80 μm, and the groove spacing C is 2 mm.

[0033] Figure 2 The diagram shows a silicon anode sheet, including a substrate layer and active material layers coated on both sides thereon; the substrate includes a polymer layer and a copper plating layer disposed on the surface of the polymer layer; the active material layer is provided with grooves; the grooves are obtained by laser etching, and the grooves are staggered, preferably, the groove stagger distance D is 1 / 2 of the interval distance C.

[0034] Figure 3 The control group 1 shown is different from the experimental group in that the active material layers on both sides of the substrate are not laser-etched.

[0035] Figure 4 The control group 2 shown is different from the experimental group in that the base layer is copper foil.

[0036] Figure 5 The diagram shows the electrode size marking structure involved in this case. Where: A: etching width, B: etching depth, C: spacing distance, D: misalignment distance.

[0037] The following specific embodiments illustrate the implementation scheme of this patent.

[0038] Experimental group 1

[0039] A method for preparing a silicon anode sheet comprises the following steps:

[0040] S1, The PI layer with a thickness of 1μm is cleaned using a plasma cleaner;

[0041] S2, A copper layer is deposited on the PI layer surface by magnetron sputtering using a magnetron sputtering device, so that the copper plating on both sides reaches a preset thickness of 1μm, and the total thickness of the substrate layer is 3μm.

[0042] S3, Prepare the active material layer by mixing graphite, silicon carbide or silicon oxide, conductive agent (carbon black + carbon nanotubes in a mass ratio of 4:1) and binder (PAA + CMC + SBR in a mass ratio of 1:1:2) in a mass ratio of 86.55:10:0.25:3.2, and homogenize the mixture until it is uniform and free of agglomerates.

[0043] S4, the slurry is evenly coated on the surface of PI / Cu composite copper foil, and the electrode is compacted by the rolling process;

[0044] S5. A groove with a spacing of 2 mm, an etching depth of 12 μm, and an etching width of 80 μm is formed on the surface of the active coating by laser etching.

[0045] Experimental group 2

[0046] A method for preparing a silicon anode sheet comprises the following steps:

[0047] S1, The PI layer with a thickness of 1μm is cleaned using a plasma cleaner;

[0048] S2, A copper layer is deposited on the PI layer surface by magnetron sputtering using a magnetron sputtering device, so that the copper plating on both sides reaches the preset thickness of 1μm; at this time, the total thickness of the substrate layer is 3μm.

[0049] S3, Prepare the active substance layer, in the same proportion as experimental group 1;

[0050] S4, the slurry is evenly coated on the surface of PI / Cu composite copper foil, and the electrode is compacted by the rolling process;

[0051] S5, grooves with a spacing of 1 mm are formed on the surface of the active coating using a laser etching method.

[0052] Experimental group 3

[0053] A method for preparing a negative electrode sheet comprises the following steps:

[0054] S1, The PI layer with a thickness of 1μm is cleaned using a plasma cleaner;

[0055] S2, A copper layer is deposited on the PI layer surface by magnetron sputtering using a magnetron sputtering device, so that the copper plating on both sides reaches the preset thickness of 1μm; at this time, the total thickness of the substrate layer is 3μm.

[0056] S3, Prepare the active substance layer, in the same proportion as experimental group 1;

[0057] S4, the slurry is evenly coated on the surface of PI / Cu composite copper foil, and the electrode is compacted by the rolling process;

[0058] S5, grooves with a spacing of 3 mm are formed on the surface of the active coating using a laser etching method.

[0059] Experimental group 4

[0060] A method for preparing a silicon anode sheet comprises the following steps:

[0061] S1, The PI layer with a thickness of 0.5μm is cleaned using a plasma cleaner;

[0062] S2, A copper layer is deposited on the PI layer surface by magnetron sputtering using a magnetron sputtering device, so that the copper plating on both sides reaches the preset thickness of 0.5μm; at this time, the total thickness of the substrate layer is 1.5μm.

[0063] S3, Prepare the active substance layer, in the same proportion as experimental group 1;

[0064] S4, the slurry is evenly coated on the surface of PI / Cu composite copper foil, and the electrode is compacted by the rolling process;

[0065] S5, using laser etching to form grooves with a spacing of 2mm on the surface of the active coating.

[0066] Experimental group 5

[0067] A method for preparing a silicon anode sheet comprises the following steps:

[0068] S1, The PI layer with a thickness of 1μm is cleaned using a plasma cleaner;

[0069] S2, A copper layer is deposited on the PI layer surface by magnetron sputtering using a magnetron sputtering device, so that the copper plating on both sides reaches the preset thickness of 0.5μm; at this time, the total thickness of the substrate layer is 2μm;

[0070] S3, Prepare the active substance layer, in the same proportion as experimental group 1;

[0071] S4, the slurry is evenly coated on the surface of PI / Cu composite copper foil, and the electrode is compacted by the rolling process;

[0072] S5, using laser etching to form grooves with a spacing of 2mm on the surface of the active coating.

[0073] Experimental group 6

[0074] A method for preparing a silicon anode sheet comprises the following steps:

[0075] S1, The PI layer with a thickness of 1.5μm is cleaned using a plasma cleaner;

[0076] S2, A copper layer is deposited on the PI layer surface by magnetron sputtering using a magnetron sputtering device, so that the copper plating on both sides reaches the preset thickness of 1μm; at this time, the total thickness of the substrate layer is 3.5μm;

[0077] S3, Prepare the active substance layer, in the same proportion as experimental group 1;

[0078] S4, the slurry is evenly coated on the surface of PI / Cu composite copper foil, and the electrode is compacted by the rolling process;

[0079] S5, using laser etching to form grooves with a spacing of 2mm on the surface of the active coating.

[0080] Control group 1

[0081] A method for preparing a silicon anode sheet comprises the following steps:

[0082] S1, The PI layer with a thickness of 1μm is cleaned using a plasma cleaner;

[0083] S2, A copper layer is deposited on the PI layer surface by magnetron sputtering using a magnetron sputtering device, so that the copper plating on both sides reaches the preset thickness of 1μm; at this time, the total thickness of the substrate layer is 3μm.

[0084] S3, Prepare the active substance layer, in the same proportion as experimental group 1;

[0085] S4. The slurry is evenly coated on the surface of the PI / Cu composite copper foil, and the electrode is compacted by the rolling process.

[0086] Control group 2

[0087] A method for preparing a silicon anode sheet comprises the following steps:

[0088] S1, Use a plasma cleaner to clean a copper foil with a thickness of 6μm;

[0089] S2, Prepare the active substance layer, in the same proportion as experimental group 1;

[0090] S3, the slurry is evenly coated on the surface of the copper foil, and the electrode sheet is compacted through a rolling process;

[0091] S4. Use laser etching to form grooves with a spacing of 2 mm on the surface of the active coating.

[0092] To demonstrate the advantages of this patented solution, a comparison is made between thickness expansion rate and volumetric energy density:

[0093] 1. Thickness Expansion Rate: Silicon anode sheets undergo thickness expansion after charge-discharge cycles, which is measured using the thickness expansion rate. The lower the thickness expansion rate, the better the battery performance. At 45℃, after charging to the maximum voltage of 4.53V at 1C stage, cutting off at 0.05C, resting for 10 minutes, and discharging to 3V at 0.5C stage, the thickness expansion rate after 400 cycles is shown in Table 1 below.

[0094] Table 1

[0095] 50 times 100 times 200 times 300 times 400 times Experimental group 1 5.12％ 6.11％ 7.42％ 8.75％ 9.89％ Experimental group 2 5.10％ 6.0％ 7.35％ 8.70％ 9.80％ Experimental group 3 5.25％ 6.4％ 7.7％ 8.8％ 10.2％ Experimental group 6 5.13％ 6.06％ 7.40％ 8.72％ 9.82％ Control group 1 5.82％ 7.0％ 8.5％ 10.0％ 11.6％ Control group 2 5.35％ 6.5％ 7.8％ 8.9％ 10.5％

[0096] Table 1 shows that the silicon anode sheets in experimental groups 1, 2, and 6 exhibited good battery performance after charge-discharge cycles. In experimental group 3, the groove spacing was 3mm, exceeding the optimal range, resulting in a larger thickness expansion rate during charge-discharge cycles and a decrease in battery performance. In control group 1, the lack of laser etching to form grooves led to rapid expansion of the silicon anode, resulting in a larger thickness expansion rate. In control group 2, the copper foil substrate caused significant volume expansion of the silicon anode during charge-discharge. Although laser etching was used to form grooves, which suppressed the expansion, the overall cycle stability and capacity retention of the battery were still inferior to those in experimental groups 1, 2, and 6. Experimental groups 4 and 5 were not tested due to their poor safety.

[0097] 2. Volumetric Energy Density: The volumetric energy density of a battery is an important indicator of its energy storage capacity per unit volume, usually expressed in watt-hours per liter (Wh / L). A controlled variable method was used to compare the volumetric energy densities of the experimental and control groups. With all other parameters kept constant, the energy density of the experimental group was used as a baseline for comparison with other groups, and the average value was taken from five experiments.

[0098] 3. Needle Penetration Test: The battery electrode needle penetration test is a test method used to evaluate the safety performance of lithium-ion batteries or other types of batteries. It mainly simulates the risk of thermal runaway when a short circuit occurs due to mechanical damage inside the battery (such as foreign object puncture). Because PI material has greater dynamic flexibility, the needle penetration test has a higher pass rate and better safety. The needle penetration test speed is 50 mm / sec, and each area is punctured only once.

[0099] As shown in Table 2:

[0100] Table 2

[0101]

[0102]

[0103] Table 2 shows that, on the one hand, compared with experimental groups 4 and 5, although all experimental groups 1, 2, 3, and 6 have a PI layer in their silicon anode substrate, the thickness of the silicon anode substrate in experimental groups 1, 2, and 3 (3 μm) and experimental group 6 (3.5 μm) is greater than that in experimental groups 4 (1.5 μm) and 5 (2 μm). Therefore, the pass rate in the needle penetration test is higher. Control groups 1 and 2 also indicate that using PI / Cu composite copper foil in the silicon anode substrate performs better in the needle penetration test. On the other hand, experimental groups 1-6, compared with control groups 1 and 2, show superior performance in terms of full-charge expansion rate and volumetric energy density. Among them, experimental groups 4 and 5, due to their thinner silicon anode substrate, have smaller cell thicknesses and higher calculated volumetric energy densities. However, the thinner electrode affects the pass rate in the needle penetration test, thus impacting the battery's safety performance. Control group 2 also reflects from another perspective that using copper foil as the substrate layer inevitably increases the thickness of the substrate layer, but this increase in thickness severely affects the volumetric energy density of the battery and reduces its safety performance. Therefore, all of these factors must be considered comprehensively when manufacturing battery cells.

[0104] In summary, experimental group 1 showed the best results. Specifically, the negative electrode used a PI / Cu composite copper foil as the substrate layer with a thickness of 3 μm, an active material layer with a thickness of 45 μm, and grooves were formed on the surface of the active material layer using laser etching. The groove spacing was 2 mm, the etching depth was 12 μm, and the etching width was 80 μm.

[0105] It should be noted that the above embodiments are merely preferred embodiments of the present invention. Any simple modifications, alterations, and substitutions made to the above embodiments based on the technical essence of the present invention shall fall within the scope of the technical solution of the present invention.

Claims

1. A silicon anode sheet, characterized in that: It includes a substrate layer and an active material layer coated on at least one side of the substrate layer; the substrate layer includes a polymer layer and a copper plating layer disposed on the surface of the polymer layer; the active material layer has grooves and is a silicon-containing material layer.

2. The silicon anode sheet according to claim 1, characterized in that: The thickness of the substrate layer is 1 μm to 3.5 μm; the thickness of the polymer layer is 0.5 μm to 1.5 μm; the thickness of the copper plating layer is 0.5 μm to 1 μm; and the thickness of the active material layer is 40 μm to 50 μm.

3. A silicon anode sheet according to claim 2, characterized in that: The thickness of the substrate layer is 3 μm; the thickness of the polymer layer is 1 μm; the thickness of the copper plating layer is 1 μm; and the thickness of the active material layer is 45 μm.

4. A silicon anode sheet according to claim 1, characterized in that: The grooves are spaced apart, and the groove spacing C is 1-2mm.

5. A silicon anode sheet according to claim 4, characterized in that: The groove spacing distance C is 2mm.

6. A silicon anode sheet according to claim 1, characterized in that: The etching depth B of the groove is 4μm to 25μm, and the etching width A is 70 to 90μm.

7. A silicon anode sheet according to claim 6, characterized in that: The etching depth B of the groove is 12 μm, and the etching width A is 80 μm.

8. A silicon anode sheet according to claim 1, characterized in that: When the active material layer is disposed on both sides of the substrate layer, the grooves on the upper and lower sides of the substrate layer are misaligned.

9. A silicon anode sheet according to claim 8, characterized in that: The misalignment distance D of the groove is 1 / 2 of the interval distance C.

10. A lithium-ion battery, characterized in that, Includes the negative electrode sheet as described in any one of claims 1-9.

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