Negative-electrode-free lithium ion battery current collector, preparation method thereof and negative-electrode-free lithium ion battery

Abstract

The invention provides a preparation method and application of a single crystal copper foil current collector for a negative-electrode-free lithium ion battery, and aims to improve the cycling stability and electrochemical performance of the battery. The preparation method comprises the following steps: (1) carrying out ultrasonic cleaning on the commercial copper foil by using hydrochloric acid, absolute ethyl alcohol and deionized water in sequence to remove surface pollutants; (2) a phosphoric acid and absolute ethyl alcohol mixed electrolyte is used for electrochemical polishing, and the surface smoothness and uniformity are improved; (3) performing high-temperature heat treatment on the sapphire substrate in high-purity argon to induce abnormal growth of crystal grains; (4) annealing in a reducing atmosphere of 1000-1100 DEG C to enhance the crystal orientation and crystallinity of Cu (111); and (5) rapidly cooling to room temperature, stabilizing the structure and preventing oxidation. When the obtained single crystal copper foil is used for the negative-electrode-free lithium battery, the single crystal copper foil is used as a negative electrode current collector to electrochemically deposit lithium metal and then is reassembled into the negative-electrode-free battery. The current collector is high in conductivity and stable in structure, lithium deposition uniformity can be remarkably improved, dendritic crystal growth is inhibited, the cycle life is prolonged, and safety is improved.

Description

Technical Field

[0001] The present invention belongs to the field of battery current collectors, and particularly relates to a current collector for a lithium metal-free lithium-ion battery, a preparation method thereof, and a lithium metal-free lithium-ion battery. Background Art

[0002] Lithium metal anodes are considered an ideal choice for next-generation high-energy-density energy storage technologies due to their extremely high theoretical specific capacity (3860 mAh g -1 ) and extremely low electrode potential (-3.04 V vs. standard hydrogen electrode). However, their commercial applications are still limited by safety issues caused by lithium dendrite growth. The formation of lithium dendrites may cause diaphragm puncture, leading to internal short circuits and even thermal runaway. In addition, dendrite growth will trigger the continuous rupture and regeneration of the solid electrolyte interface film, resulting in the accumulation of irreversible "dead lithium", thereby reducing the Coulomb efficiency, intensifying polarization, and ultimately leading to battery failure.

[0003] To address the above problems, researchers have proposed various strategies to optimize the stability of lithium metal anodes, including artificial SEI film construction, optimizing electrolyte composition, designing high-performance diaphragms, and constructing three-dimensional current collectors. In addition, lithium affinity modification of the current collector has been proven to be able to effectively regulate lithium deposition behavior, guide uniform lithium nucleation on the surface of the current collector, and reduce dendrite growth. In recent years, current collector optimization strategies based on crystal orientation control have received extensive attention, among which the surface structure of single-crystal copper current collectors has a particularly significant impact on lithium deposition.

[0004] Traditionally, lithium metal deposition is considered to follow a typical nucleation-growth-termination mode, and its growth process is affected by factors such as mass transfer, charge transfer, and interfacial reactions, usually showing dendritic deposition. However, recent studies have found that the migration characteristics of lithium atoms on the surface of the current collector have an important impact on the deposition morphology. Research has shown that single-crystal Cu(111) foils have an extremely low lithium atom migration barrier, enabling Li atoms to migrate actively on the surface, thereby promoting lateral growth and aggregation and reducing the tendency of dendritic growth. In contrast, due to the presence of grain boundaries and dislocations in polycrystalline Cu current collectors, the lithium deposition rate is uneven in different orientation regions, easily leading to a dendritic structure with vertical growth.

[0005] Based on this, for lithium metal-free lithium-ion batteries, using high-purity single-crystal Cu(111) foils as current collectors and optimizing their surface structure through electrochemical polishing, direct bonding of copper foils to sapphire substrates, and heat treatment processes can effectively reduce the lithium nucleation overpotential, promote uniform deposition, reduce the generation of dead lithium, and improve the cycle life of the battery. Further combined with laser processing technology, the crystal plane orientation of the Cu foil can be precisely controlled in a local area to achieve directional lithium affinity modification, providing a new idea for constructing high-safety and high-energy-density lithium metal-free lithium-ion batteries. Summary of the Invention

[0006] The present invention relates to a preparation method and application of a single-crystal copper foil current collector for a lithium metal-free anode lithium-ion battery, belonging to the technical fields of new energy materials and battery technologies. Aiming at the problems of lithium dendrite growth, unstable interface, and accumulation of "dead lithium" existing in the existing lithium metal anode during the cycling process, the present invention provides a lithium metal-free anode lithium-ion battery based on a single-crystal copper foil current collector, thereby effectively improving the cycling stability and safety of the battery. For this purpose, the present invention provides a preparation method and application of a single-crystal copper foil current collector for a lithium metal-free anode lithium-ion battery, including:

[0007] The preparation method of the present invention includes the following key steps: Step (1): ultrasonically clean the commercial copper foil, and the cleaning solvents are hydrochloric acid, absolute ethanol, and deionized water in sequence to remove surface contaminants;

[0008] Step (2): electrochemically polish the cleaned copper foil to completely remove surface impurities;

[0009] Step (3): place the polished copper foil sample on a sapphire substrate and perform heat treatment in a quartz tube furnace;

[0010] Step (4): continue heating and perform annealing treatment under a reducing mixed atmosphere;

[0011] Step (5): open the tube furnace after heating to the specified temperature and quickly cool the sample to room temperature. The single-crystal copper foil prepared by this method mainly exhibits a (111) crystal plane orientation, which has excellent electrochemical stability and uniform lithium deposition behavior, can effectively inhibit the growth of lithium dendrites, reduce the interfacial impedance, and improve the cycling life of the lithium metal anode.

[0012] Further, the thickness of the commercial copper foil in step (1) is 4 μm and the purity is 99.8%. The concentration of the hydrochloric acid solution is 0.5 - 2 M, and the treatment time is 3 - 5 min. Then, it is washed repeatedly with absolute ethanol and deionized water and left standing in a vacuum drying oven at 80 °C for 12 h.

[0013] Further, the specific process of the electrochemically polishing step in step (2) is as follows: use an electrolyte with a mass fraction of 85% phosphoric acid and absolute ethanol in a volume ratio of 1:1, and adopt a three-electrode system for electrochemical polishing: the working electrode is a commercial Cu foil, the counter electrode is a platinum electrode, and the reference electrode is a saturated calomel electrode. The selected electrolysis voltage ranges from 2.0 to 3.0 V, and the time is 5 - 10 min. After polishing, take out the Cu foil, rinse it with deionized water, and dry it with N2.

[0014] Further, the sapphire substrate in step (3) has a specification of 2 inches, is c-axis oriented with an error <0.5°, a thickness of 500 μm, and the heat treatment atmosphere is high-purity argon (99.99%). It is held at 800 °C for 1 - 3 h.

[0015] Further, the heating temperature in step (4) is 1000 - 1100 °C, and the time is 1 - 2 h; the annealing atmosphere is a reducing atmosphere of a mixed gas of 95% argon and 5% hydrogen, and the treatment time is 1 - 3 h.

[0016] Further, the temperature in step (5) is 150 °C.

[0017] The present invention provides a single-crystal copper foil current collector, which is prepared by using the above-mentioned preparation method of a current collector for a lithium-ion battery without a negative electrode.

[0018] The present invention also provides a lithium-ion battery without a negative electrode, including a positive electrode, a negative electrode, a current collector, a separator, and an electrolyte. It is characterized in that the negative electrode uses the current collector described in claim 7 deposited with lithium metal, and the positive electrode uses LiNi 0.8 Fe 0.1 Mn 0.1 O2.

[0019] The present invention also provides a preparation method of a lithium-ion battery without a negative electrode. It is characterized in that the current collector described in claim 8 is first punched into a pole piece, and LiNi 0.8 Fe 0.1 Mn 0.1 O2 is used as the counter electrode, and the battery is assembled using a separator and an electrolyte. Then, the battery is charged to 4.4 V for lithium deposition; when the lithium metal is completely deposited on the current collector, the battery is disassembled, and the current collector deposited with lithium metal is taken out as the negative electrode, and LiNi 0.8 Fe 0.1 Mn 0.1 O2 material is used as the positive electrode, and it is reassembled using a new separator and electrolyte to obtain a lithium-ion battery product without a negative electrode.

[0020] By constructing a single-crystal copper foil current collector, the present invention improves the deposition behavior of lithium metal, avoids the short-circuit risk caused by dendrite growth, and enhances the cycle stability of the lithium metal negative electrode, providing an efficient and feasible solution for the commercial application of lithium-ion batteries without a negative electrode. Description of the Drawings

[0021] Figure 1 It is the XRD pattern of the single-crystal copper foil in Example 1.

[0022] Figure 2 It is the SEM pattern of the single-crystal copper foil in Example 1.

[0023] Figure 3It is the cycle performance graph of the non-anode lithium-ion battery in Example 1.

[0024] Figure 4 It is the XRD graph of the commercial copper foil in Comparative Example 1.

[0025] Figure 5 It is the SEM graph of the single-crystal copper foil in Comparative Example 1.

[0026] Figure 6 It is the cycle performance graph of the non-anode lithium-ion battery in Comparative Example 1.

[0027] Figure 7 It is the cycle performance graph of the non-anode lithium-ion battery in Example 2. Detailed implementation manners

[0028] To facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings of the specification and preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments.

[0029] Example 1

[0030] A preparation method of a single-crystal copper foil current collector for a non-anode lithium-ion battery includes the following steps:

[0031] Step (1): Ultrasonically clean a commercial copper foil with a thickness of 4 μm and a purity of 99.8% for 0.5 h. The cleaning solvents are 0.5 M hydrochloric acid in sequence, and the treatment time is 3 - 5 min. Then, wash it repeatedly with absolute ethanol and deionized water and leave it standing in a vacuum drying oven at 80 °C for 12 h to remove surface contaminants;

[0032] Step (2): Electrochemically polish the cleaned copper foil. Use an electrolyte with a mass fraction of 85% phosphoric acid and absolute ethanol in a volume ratio of 1:1. Adopt a three-electrode system for electrochemical polishing: the working electrode is a commercial Cu foil with a thickness of 4 μm and a purity of 99.8%, the counter electrode is a platinum electrode, and the reference electrode is a saturated calomel electrode. The selected electrolysis voltage ranges from 2.0 - 3.0 V, and the time is 10 min. After polishing, take out the Cu foil, rinse it clean with deionized water, and blow it dry with N2.

[0033] Step (3): Place the polished copper foil sample on a 2-inch sapphire substrate with a c-axis orientation, an error <0.5°, and a thickness of 500 μm, and perform heat treatment in a quartz tube at 800 °C for 1 h under the atmosphere of high-purity argon (99.99%);

[0034] Step (4): Continue heating to 1050 °C for 1 h, and then keep it warm for 1 h under the reducing mixed atmosphere of 95% argon and 5% hydrogen;

[0035] Step (5): After cooling down to 150 °C, open the tube furnace to rapidly cool the sample to room temperature. Further,

[0036] Punch the above copper foil current collector into a pole piece, and use commercial LiNi 0.8 Fe 0.1 Mn 0.1 O2 as the positive electrode, and the electrolyte is LB-037. Then, at a current density of 0.1 C (1 C = 200 mAg -1 ), charge the battery to 4.4 V for lithium deposition; after the lithium metal is completely deposited on the current collector, disassemble the battery and reassemble it with a new separator and positive electrode pole piece to obtain a non-aqueous button cell product. The button cell is charged and discharged at 25 °C within the voltage range of 2.8 V to 4.4 V.

[0037] Figure 1 XRD pattern of the single-crystal copper foil prepared in Example 1. As can be seen from the figure, it can be seen that the obtained single-crystal copper foil has only the (111) crystal plane. Figure 2 SEM image of the single-crystal copper foil in Example 1.

[0038] Figure 3 Cycling curve of the battery assembled with the single-crystal copper foil prepared in Example 1 at a current density of 100 mA / g. From Figure 3 it can be seen that within the voltage range of 2.8 V to 4.4 V, after 80 cycles, its discharge specific capacity decreases from 197.1 mAh g -1 to 0 mAhg -1 .

[0039] Comparative Example 1

[0040] Step (1): Ultrasonically clean a commercial copper foil with a thickness of 4 μm and a purity of 99.8% for 0.5 h. The cleaning solvents are 0.5 M hydrochloric acid in sequence, and the treatment time is 3 - 5 min. Then, wash it with anhydrous ethanol and deionized water multiple times and leave it standing in a vacuum drying oven at 80 °C for 12 h to remove surface contaminants;

[0041] Punch the above copper foil current collector into a pole piece, and use commercial LiNi 0.8 Fe 0.1 Mn 0.1 O2 as the positive electrode, and the electrolyte is LB-037. Then, at a current density of 0.1 C (1 C = 200 mAg -1 ), charge the battery to 4.4 V for lithium deposition; after the lithium metal is completely deposited on the current collector, disassemble the battery and reassemble it with a new separator and positive electrode pole piece to obtain a non-aqueous button cell product. The button cell is charged and discharged at 25 °C within the voltage range of 2.8 V to 4.4 V.

[0042] Figure 4 XRD pattern of the commercial copper foil of Comparative Example 1. As can be seen from the figure, the obtained is a polycrystalline copper foil with multiple crystal plane orientations. Figure 5 SEM image of the commercial copper foil of Comparative Example 1.

[0043] Figure 6 Cycling curve of the battery assembled with the single crystal copper foil prepared in Comparative Example 1 at a current density of 100 mA / g. From Figure 6 it can be seen that in the voltage range of 2.8 V to 4.4 V, after 20 cycles, its discharge specific capacity decreases from 197.1 mAh g -1 to 0 mAh g -1 .

[0044] Example 2

[0045] A method for preparing a current collector of a single crystal copper foil for a lithium-ion battery without a negative electrode includes the following steps:

[0046] Step (1): Ultrasonically clean a commercial copper foil with a thickness of 4 μm and a purity of 99.8% for 0.5 h. The cleaning solvents are 1.5 M hydrochloric acid in sequence, and the treatment time is 3 - 5 min. Then wash it repeatedly with absolute ethanol and deionized water and leave it standing in a vacuum drying oven at 80°C for 12 h to remove surface contaminants;

[0047] Step (2): Electrochemically polish the cleaned copper foil. Use an electrolyte with a mass fraction of 85% phosphoric acid and absolute ethanol in a volume ratio of 1:1. Adopt a three-electrode system for electrochemical polishing: the working electrode is a commercial Cu foil with a thickness of 4 μm and a purity of 99.8%, the counter electrode is a platinum electrode, and the reference electrode is a saturated calomel electrode. The selected electrolysis voltage range is 2.0 - 3.0 V, and the time is 10 min. After polishing, take out the Cu foil, rinse it with deionized water, and dry it with N2.

[0048] Step (3): Place the polished copper foil sample on a 2-inch sapphire substrate with a c-axis orientation, an error <0.5°, and a thickness of 500 μm, and perform heat treatment in a quartz tube at 800°C for 2 h under an atmosphere of high-purity argon (99.99%);

[0049] Step (4): Continue heating to 1080°C for 2 h, and then keep it warm for 2 h under a reducing mixed atmosphere of 95% argon and 5% hydrogen;

[0050] Step (5): After cooling to 150°C, open the tube furnace to quickly cool the sample to room temperature. Further,

[0051] Punch the above copper foil current collector into a pole piece, and use commercial LiNi 0.8 Fe 0.1 Mn 0.1Using O2 as the positive electrode and electrolyte LB-037, the battery was then charged to 4.4V at a current density of 0.1C (1C = 200 mA g -1 ) for lithium deposition; after the lithium metal was completely deposited on the current collector, the battery was disassembled and reassembled with a new separator and positive electrode sheet to obtain a non-negative button battery product. The button battery was charged and discharged at 25°C within a voltage range of 2.8V to 4.4V.

[0052] Figure 7 Cycling curve of the battery assembled with the single crystal copper foil prepared in Example 2 at a current density of 100 mA / g. From Figure 7 it can be seen that within the voltage range of 2.8V to 4.4V, after 60 cycles, its discharge specific capacity decreased from 194.3 mAh g -1 to 0 mAh g -1 .

Claims

1. A method for preparing a current collector of a non - negative electrode lithium - ion battery, characterized in that, It includes the following steps: Step (1): Ultrasonically clean the commercial copper foil, and the cleaning solvents are hydrochloric acid, absolute ethanol, and deionized water in sequence to remove surface contaminants; Step (2): Electrochemically polish the cleaned copper foil to completely remove surface impurities; Step (3): Place the polished copper foil sample on a sapphire substrate and perform heat treatment in a quartz tube furnace; Step (4): Continue heating and perform annealing treatment under a reducing mixed atmosphere; Step (5): After heating to the specified temperature, open the tube furnace to quickly cool the sample to room temperature.

2. A preparation method as described in claim 1, characterized in that, In step (1), the thickness of the commercial copper foil is 4 μm and the purity is 99.8%. The concentration of the hydrochloric acid solution is 0.5 - 2 M, and the treatment time is 3 - 5 min. Then, wash it with absolute ethanol and deionized water multiple times and leave it standing in an 80°C vacuum drying oven for 12 h.

3. A preparation method as described in claim 1, characterized in that, The specific process of the electrochemically polishing step in step (2) is as follows: Use an electrolyte with a volume ratio of 1:1 of phosphoric acid with a mass fraction of 85% and absolute ethanol. Adopt a three - electrode system for electrochemical polishing: the working electrode is the commercial Cu foil, the counter electrode is the platinum electrode, and the reference electrode is the saturated calomel electrode. The selected electrolysis voltage range is 2.0 - 3.0 V, and the time is 5 - 10 min. After polishing, take out the Cu foil, rinse it with deionized water, and dry it with N2.

4. A preparation method as described in claim 1, characterized in that, The specifications of the sapphire substrate in step (3) are 2 inches, c - axis orientation, error <0.5°, thickness 500 μm, the heat treatment atmosphere is high - purity argon (99.99%), and keep it at 800°C for 1 - 3 h.

5. A preparation method as described in claim 1, characterized in that, In step (4), the heating temperature is 1000 - 1100°C, and the time is 1 - 2 h; the annealing atmosphere is a mixed gas of 95% argon and 5% hydrogen as the reducing atmosphere, and the treatment time is 1 - 3 h.

6. A preparation method as described in claim 1, characterized in that, The temperature in step (5) is 150°C.

7. A single-crystal copper foil current collector for a lithium-ion battery without a negative electrode, characterized in that, It is prepared by using the preparation method of a current collector for a non - negative lithium - ion battery described in claims 1 - 6.

8. Application of the single - crystal copper foil current collector described in claim 7 in the preparation of a non - negative lithium - ion battery.

9. A lithium-ion battery without a negative electrode, comprising a positive electrode, a negative electrode, a current collector, a separator, and an electrolyte, characterized in that, The negative electrode adopts the current collector of claim 7 on which lithium metal is deposited, and the positive electrode adopts LiNi 0.8 Fe 0.1 Mn 0.1 O2.

10. The method for preparing a non-anode lithium-ion battery according to claim 9, characterized in that, First, the current collector described in claim 8 is punched into a pole piece, LiNi 0.8 Fe 0.1 Mn 0.1 O2 is used as the counter electrode, and a battery is assembled using a separator and an electrolyte. Then, the battery is charged to 4.4V for lithium deposition. After the lithium metal is completely deposited on the current collector, the battery is disassembled, and the current collector with the deposited lithium metal is taken out as the negative electrode, LiNi 0.8 Fe 0.1 Mn 0.1 O2 material is used as the positive electrode, and a new separator and electrolyte are used to reassemble to obtain a non-negative electrode battery product.

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