CN115036444A - A kind of pre-lithiated, pre-sodiumized composite negative electrode material and its preparation method and application - Google Patents

Abstract

The invention provides a pre-lithium and pre-sodium composite negative electrode material, a preparation method and application thereof, and relates to the preparation of lithium ion or sodium ion half cells and full cells and the improvement of their electrochemical performance. The sheet is in direct contact with the lithium foil or sodium foil, so that lithium and sodium ions are pre-entered into the surface and internal structure of the composite material of the negative pole piece, and the SEI film is constructed on the surface of the negative pole piece, and the structural defects of the composite material are filled; at the same time; By controlling the short-circuit pressure, time, voltage and other conditions of the pre-lithiation and pre-sodiumization process, the first-cycle Coulomb efficiency range of the composite material can be adjusted to meet the matching requirements of the cathode material of the full battery, and the cycle performance of the full battery can be improved. Rate performance is maintained.

Description

A kind of pre-lithiated, pre-sodiumized composite negative electrode material and its preparation method and application

technical field

The invention belongs to the technical field of batteries, and relates to a pre-lithiated and pre-sodiumized composite negative electrode material, a preparation method and application thereof, and in particular to a composite negative electrode capable of controllably improving the first cycle Coulombic efficiency of a two-dimensional composite material for lithium and sodium ion batteries Materials and preparation methods and applications thereof.

Background technique

The 2D composite anode material has a higher reversible capacity (>500mAh/g) than existing commercial graphite anodes due to its unique two-phase interface providing a large number of active sites for the fast storage of Li-ion pseudocapacitive properties. , thereby exhibiting excellent rate performance and cycling stability. However, the large specific surface area of 2D composites will cause a large area of solid electrolyte interface film (SEI film) to be formed on the surface of composite particles during the first charge-discharge process, thus hindering the reversible adsorption and desorption of lithium ions; On the other hand, the structural defects on the surface of the two-dimensional composites also act as part of the "trap" of lithium ions, so that the lithium ions entering the "trap" cannot be reversibly charged and discharged. Based on the above-mentioned structural defects, the Coulomb efficiency of the two-dimensional composite material is low (50-60%) in the first cycle, and it is difficult to be practical.

At present, the commonly used methods to improve the Coulomb efficiency of two-dimensional composite materials in the first cycle include: (1) Coating the surface of the material with a carbon or metal oxide layer to reduce the chemical structural defects on the surface of the material, thereby reducing the entry of lithium ions into the "trap" probability in . However, neither dry coating nor wet coating can stably control the uniformity and integrity of the coating layer; and if the coating layer is too thick, it will increase the battery impedance and reduce the battery capacity; in addition, The cladding process further increases the production cost of the material. (2) Adding a small amount of film-forming additives to the electrolyte, the film-forming additives can be reduced to form a stable SEI film on the surface of the negative electrode material in preference to solvents such as EC and DEC during battery discharge, thereby reducing the entry of lithium ions in the material into the SEI film. The number of ions in the lithium ion can further improve the reversibility of the adsorption and desorption of lithium ions. The above method is simple to operate and can solve the technical problem of the low first-cycle Coulomb efficiency of conventional graphite-based anode materials. However, for two-dimensional composite materials with low first-cycle Coulomb efficiency, the above method is still difficult to make the first-cycle Coulomb efficiency reach the commercial level. (3) Replenishing lithium technology through the negative electrode: For example, lithium powder can be added during the mixing process of the negative electrode slurry or directly sprayed on the surface of the negative electrode pole piece to provide an additional part of lithium ions during the first charging process, thereby improving the efficiency of the battery. The first cycle Coulomb efficiency of the anode material. However, the above method is relatively complicated to operate, and has high requirements on the environment and equipment. Therefore, how to easily, quickly and controllably improve the first-cycle Coulombic efficiency of materials to improve the first-cycle Coulombic efficiency of lithium, sodium half-cells and full cells has become an urgent technical problem to be solved.

SUMMARY OF THE INVENTION

In order to improve the above-mentioned technical problems, the present invention provides a method for preparing a pre-lithiated and pre-sodiumized composite negative electrode material, which comprises attaching a lithium sheet and/or a sodium sheet to a battery negative electrode plate and adding an electrolyte, and pressing to obtain a pre-lithium sheet The composite negative electrode material after sodiumization and/or pre-sodiumization.

According to an embodiment of the present invention, the negative electrode sheet is a sheet-shaped battery negative electrode sheet. Preferably, the thickness of the sheet-shaped battery negative electrode sheet is 5-20 μm, exemplarily 5 μm, 10 μm, 15 μm, and 20 μm.

According to an embodiment of the present invention, the current collector of the sheet-shaped battery negative electrode sheet is a pure metal foil or a metal foil made of an alloy material. Pure metal foils are preferred. For example, the pure metal foil is copper foil or aluminum foil.

According to an embodiment of the present invention, the active material of the sheet-shaped battery negative electrode sheet is a two-dimensional material. For example, the two-dimensional material may be selected from TiO ₂ , MnO ₂ , RuO ₂ , V ₂ O ₅ , MoO ₃ , MoS ₂ , WS ₂ , La ₂ TiO ₃ , LaNb ₂ O ₇ , Ca ₂ Nb ₃ O ₁₀ , One, two or more of graphene, C3N4 (graphitic carbon _nitride ), BN (boron nitride), _Mxene (transition metal carbonitride), and LDHs (layered double hydroxide) . Two types are preferred. For example, the two-dimensional material may be selected from _TiO2 and graphene composites.

According to an embodiment of the present invention, the sheet-shaped battery negative electrode further contains a conductive agent and/or a binder.

According to an embodiment of the present invention, the conductive agent is conductive carbon black, acetylene black, carbon black (Super-P), Ketjen black (KT-Black) conductive carbon balls, conductive graphite, carbon nanotubes, conductive carbon fibers, graphite at least one of alkene and reduced graphene oxide.

According to an embodiment of the present invention, the binder is selected from the group consisting of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), sodium alginate, copolymers of vinylidene fluoride-hexafluoropropylene compounds, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyethylene pyrrolidone, polyvinyl ether, polymethyl methacrylate and polyhexafluoropropylene, etc. at least one of them.

According to an embodiment of the present invention, the mixed mass ratio of the active material, the conductive agent and the binder of the sheet-shaped battery negative electrode sheet is (6-9.8):(0.1-3):(0.1-2); preferably is (8~9):(0.5~1):(0.5~1); exemplarily 6:2:2, 7:1.5:1.5, 8:1:1, 9:0.5:0.5, 9.8:0.1: 0.1.

According to an embodiment of the present invention, the preparation method of the sheet-shaped battery negative electrode plate includes the following steps:

The active material of the negative electrode pole piece of the battery is mixed with a conductive agent and a binder, and then a solvent is added to disperse to obtain a negative electrode slurry, and then the negative electrode slurry is coated on the negative electrode current collector, dried, rolled and die-cut to obtain The sheet-shaped battery negative pole piece.

According to an embodiment of the present invention, in the preparation method of the sheet-shaped battery negative pole piece, the rolling pressure is 0-20 MPa, and the time is 0-120 s.

According to an embodiment of the present invention, in the preparation method of the sheet-shaped battery negative electrode sheet, the drying is preferably vacuum drying. Preferably, the drying temperature is 60-110°C, preferably 70-100°C, exemplarily 60°C, 70°C, 80°C, 90°C, 100°C, 110°C. Further, the drying time is 0.5 to 20 hours, preferably 12 to 20 hours, and examples are 12 hours, 14 hours, 16 hours, 18 hours and 20 hours.

According to an embodiment of the present invention, the negative electrode pole piece of the battery is rolled and sliced to form a pole piece of the required size for a button-type or soft pack battery.

According to an embodiment of the present invention, before the lithium sheet and/or sodium sheet is attached to the negative electrode of the battery, it needs to be rolled out into a lithium foil or sodium foil with a smooth surface and a thickness of ≤200 μm. Preferably, under the protection of an inert atmosphere, the lithium sheet and/or the sodium sheet is rolled out into a lithium or sodium foil with a smooth surface and a thickness of ≤200 μm. More preferably, the inert atmosphere is nitrogen or argon atmosphere. For example, work in a glove box under an argon atmosphere. Further, the area of the rolled lithium sheet and/or sodium sheet is larger than the area of the negative electrode sheet, so as to ensure that the lithium sheet and/or the sodium sheet can cover all the negative electrode electrode sheets.

According to an embodiment of the present invention, the amount of the electrolyte solution is 20-400 μL/cm ² , exemplarily 20 μL/cm ² , 50 μL/cm ² , 80 μL/cm ² , 100 μL/cm ² , 150 μL/cm ² , 200 μL /cm ² , 250 μL/cm ² , 300 μL/cm ² , 350 μL/cm ² , 400 μL/cm ² .

According to an embodiment of the present invention, the solute of the electrolyte is a lithium salt or a sodium salt.

For example, the lithium salt includes at least one of LiPF ₆ , LiTFSI, LiBOB, LiClO ₄ , LiFSI, LiBF ₄ and LiAsF ₆ ; preferably LiPF ₆ .

For example, the sodium salt includes at least one of NaPF ₆ , NaClO ₄ , NaTFSI and NaFSI; preferably NaClO ₄ .

According to an exemplary embodiment of the present invention, the concentration of the lithium salt and the sodium salt is 1M.

According to an embodiment of the present invention, the solvent of the electrolyte includes ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DEC), diethyl carbonate (DMC), ethyl methyl carbonate (EMC) two or three of the same. For example, when two or three of the above solvents are selected, the volume ratio can be 1:1 or 1:1:1.

According to the embodiment of the present invention, preferably, the smooth side of the lithium foil and/or the sodium foil faces the negative electrode piece, and the lithium foil and/or the sodium foil is completely covered and closely attached to the negative electrode piece. Preferably, the laminating step is carried out under the protection of an inert atmosphere. More preferably, the inert atmosphere is nitrogen or argon atmosphere. For example, work in a glove box under an argon atmosphere.

According to an embodiment of the present invention, the pressing pressure is 0-2 MPa, preferably 0.1-1 MPa, exemplarily 0.1 MPa, 0.15 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.8 MPa, 1.0MPa, 2MPa.

According to an embodiment of the present invention, the standing time of the pressing is 0-120 min, preferably 2-60 min, exemplarily 2 min, 5 min, 10 min, 12 min, 15 min, 20 min, 30 min, 60 min, 90 min.

Where: Time is counted from the start of applying pressure. During the standing process, due to the potential difference, the battery is equivalent to a self-discharge process, and the lithium ions and sodium ions in the lithium foil and/or sodium foil enter the active material surface and internal structure of the negative electrode sheet through the electrolyte.

Further, in the direct short-circuit state, the lithium ions and/or sodium ions in the lithium foil and/or the sodium foil are continuously inserted into the surface and inside of the active material in the negative pole piece, and the lithium ions and/or sodium ions enter the negative pole. The velocity in the sheet is related to the amount of pressure applied. During the pre-lithiation and/or pre-sodiumization process in the short-circuit state, on the one hand, a part of the artificial SEI film is pre-generated on the surface of the material to reduce the lithium ions and/or sodium ions in the counter electrode during the subsequent first cycle of discharge consumption; on the other hand, filling the defects in the two-dimensional material with lithium ions and/or sodium ions can fill the "trap" that cannot be reversibly deintercalated or adsorbed and desorbed on the surface of the two-dimensional material. , which can improve the reversible charge-discharge capacity of the two-dimensional material.

According to an embodiment of the present invention, after pre-lithiation and/or pre-sodiumization, the voltage of the battery composed of lithium foil and/or sodium foil and negative pole piece is 1-2V, preferably 1.2-1.7V, exemplarily 1V , 1.27V, 1.35V, 1.45V, 1.5V, 1.6V, 1.64V, 1.7V, 1.8V, 1.9V, 2.0V. By controlling the voltage of the primary battery after pre-lithiation and/or pre-sodiumization within the range of 1 to 2 V, the first cycle charge-discharge efficiency of the two-dimensional composite can be increased to 80 to 100%.

Among them, during the pre-lithiation and/or pre-sodiumization process, the positive electrode (lithium foil) is separated by separating the short-circuit ground electrodes (lithium foil and/or sodium foil and the negative electrode piece), or by adding a separator between the two electrodes. and/or sodium foil), the negative electrode is connected to a multimeter to detect the voltage changes at both ends of the battery. The battery voltage has a linear relationship with the number and degree of lithium and sodium ions embedded in pre-lithiation and/or pre-sodiumization. Degree of lithiation and/or pre-sodiumization.

According to an embodiment of the present invention, the preparation method further includes the step of separating the pressed lithium foil and/or sodium foil from the negative electrode piece, or adding a separator between the lithium foil and/or sodium foil and the negative electrode piece.

According to an embodiment of the present invention, the preparation method further includes the step of drying or washing the separated negative electrode piece to remove the residual electrolyte on the surface of the negative electrode piece. Preferably, the washing solvent may be DMC.

According to an embodiment of the present invention, the electrolyte on the surface of the lithium foil and/or the sodium foil can be used repeatedly after being sucked dry.

According to an embodiment of the present invention, the preparation method further includes the step of drying the washed negative electrode piece. For example, the drying may be air drying.

The present invention also provides a pre-lithiated and pre-sodiumized composite negative electrode material prepared by the above preparation method. Preferably, the composite negative electrode material is a two-dimensional composite negative electrode material.

The present invention also provides the application of the pre-lithiated and pre-sodiumized composite negative electrode material in a lithium battery. It is preferably used as the negative electrode of lithium battery.

The present invention also provides a lithium battery or a sodium battery, which contains the above-mentioned pre-lithiated and pre-sodiumized composite negative electrode material and/or negative electrode pole piece. Preferably, the lithium battery or the sodium battery may be a half battery or a full battery. For example, the half cell may be a 2032 coin half cell.

According to an embodiment of the present invention, the half-cell further comprises lithium and/or sodium sheets.

According to an embodiment of the present invention, the half-cell further includes a separator. Preferably, the separator may be at least one of PP, PE, PP/PE/PP, glass fiber, and the like. More preferably, the separator is a single-sided and/or double-sided ceramic-coated separator. For example, the charge-discharge range of the separator is 0.005-3V.

According to an embodiment of the present invention, the full cell further includes a positive electrode sheet. Preferably, the positive electrode material of the positive electrode sheet includes at least one of ternary positive electrode materials such as lithium cobalt oxide, lithium iron phosphate, sodium vanadium phosphate and cobalt nickel manganese.

Preferably, the capacity ratio of the negative electrode and the positive electrode is 1.0-1.2, exemplarily 1.0, 1.10, 1.2, preferably 1.10.

The invention can match the specific capacity of the negative electrode after pre-lithiation and pre-sodiumization according to the first cycle discharge capacity requirement of the half-battery after pre-lithiation and pre-sodiumization; and the charge-discharge interval of the whole battery can refer to the commonly used charge-discharge interval range of positive electrode materials.

According to an embodiment of the present invention, the full cell further includes an electrolyte and a separator.

According to an embodiment of the present invention, the electrolyte may be a conventional electrolyte known in the art for lithium batteries and/or sodium batteries, preferably 1M LiPF ₆ + EC/DEC (lithium battery) with a volume ratio of 1:1 battery), 1M NaClO ₄ + EC/PC (sodium battery) with a volume ratio of 1:1.

According to an embodiment of the present invention, the separator can be a commercially available separator known in the art, preferably Celgard 2500.

Beneficial effects of the present invention:

(1) In the present invention, by performing pre-lithiation or pre-sodium treatment on the two-dimensional composite negative electrode material, the first cycle of charge and discharge of the half-cell assembled from the two-dimensional composite negative electrode material after pre-lithiation or pre-sodium treatment can be performed. The efficiency is increased to 80-100% (while the first-cycle charge-discharge efficiency of the half-cell assembled with the two-dimensional composite anode material without pre-lithiation or without pre-sodiumization is 50-60%); and by pre-lithiation, or The first-cycle charge-discharge efficiency of the full battery formed by the pre-sodiumized two-dimensional composite anode material can reach the first-cycle charge-discharge efficiency comparable to that of commercial graphite and other anode materials. At the same time, after the pre-lithiation or pre-sodium-treated two-dimensional composite negative electrode material of the present invention is assembled into a full battery, not only the capacity of the positive electrode material can be fully utilized (the two-dimensional composite negative electrode material without pre-lithiation or pre-sodium treatment , which will waste more than 40% of the capacity of the positive electrode material), and compared with the negative electrode material such as graphite (theoretical capacity is 372mAh/g), the weight of the negative electrode used in the present invention can also be reduced by 40-50%, so it can significantly improve the overall The energy density of the battery.

(2) Compared with lithium supplementary processes such as adding lithium powder to materials or pole pieces, the process route is more complicated, and large-scale equipment such as spraying devices need to be added. Internal, thus limiting the further improvement of the first effect. The process route of the invention is simple to operate, convenient for process amplification, can be continuously produced, supplemented lithium ions or sodium ions can enter the internal structure of the material, the first effect can be increased by nearly 100%, and the lithium foil or sodium foil can be Repeated use, low production cost.

(3) The two-dimensional material pre-lithium or pre-sodium is carried out by using the positive and negative short-circuit contact method. By increasing the pre-lithiation process pressure, a rapid pre-lithium or pre-sodium process can be performed, and the total time is controlled within 5-15 minutes. Greatly improved production efficiency and productivity.

(4) Through the pressure control of the short-circuit pre-lithium process and the voltage control of the half-cell, the stability and repeatability of the process are improved, and the consistency of the first cycle efficiency and discharge capacity of different batches is improved by stably controlling the cut-off voltage, Meet the actual production requirements.

(5) The negative pole piece treated by the pre-lithium or pre-sodium process can maintain the cycle performance and rate performance after forming a half cell or a full cell, and will not have any side effects on the electrochemical performance of the two-dimensional composite material.

(6) Through the pre-lithium or pre-sodium time, pressure, and voltage control, it is convenient to adjust the discharge capacity of the first effect and the first cycle, so as to adapt and match the positive electrode materials of different first effects to form a full battery, so as to give full play to the positive and negative electrode materials. capacity, further improving the energy density of the full battery.

Description of drawings

1 is a first-cycle charge-discharge curve diagram of a half-cell assembled from a two-dimensional composite negative electrode material after pre-lithiation in Example 1.

FIG. 2 is the first cycle charge-discharge curve diagram of the full battery assembled with the two-dimensional composite negative electrode material before and after pre-lithiation in Example 2. FIG.

FIG. 3 is a cycle performance diagram of the full battery assembled with the two-dimensional composite negative electrode material before and after pre-lithiation in Example 2. FIG.

FIG. 4 is a rate performance diagram of the full battery assembled from the two-dimensional composite negative electrode material before and after pre-lithiation in Example 2. FIG.

FIG. 5 is a first cycle charge-discharge curve diagram of a full battery assembled from the two-dimensional composite negative electrode material after pre-lithiation in Example 4. FIG.

Detailed ways

The technical solutions of the present invention will be described in further detail below with reference to specific embodiments. It should be understood that the following examples are only for illustrating and explaining the present invention, and should not be construed as limiting the protection scope of the present invention. All technologies implemented based on the above content of the present invention are covered within the intended protection scope of the present invention.

Unless otherwise stated, the starting materials and reagents used in the following examples are commercially available or can be prepared by known methods.

In the following examples of the present invention, the two-dimensional material used is TiO ₂ and graphene composite material (TiO ₂ /C), and the preparation method can refer to the method disclosed in Example 2 of Patent Application Publication No. CN112125334A.

Example 1

(1) According to the mass ratio of TiO ₂ /C:carbon black (Super-P):PVDF=8:1:1, each raw material was weighed, and NMP solvent was added to prepare a negative electrode slurry with a solid content of 40%, and then According to the dosage of 2 mg/cm ² , it was uniformly coated on the conductive copper foil with a thickness of 9 μm to form a negative pole piece with a coating thickness of 100 μm. After rolling at 20 MPa and vacuum drying at 100 °C, it was cut into pieces. A pole piece with a diameter of 10mm;

(2) Add electrolyte (1M LiPF ₆ , EC/DEC with a volume ratio of 1:1) dropwise to the surface of the pole piece prepared in step (1) according to 100 μL/cm ² to wet the pole piece, and then apply a stainless steel rod to the surface of the pole piece. Roll out the lithium foil (purchased from Duoduo Reagent) with a thickness of 150 μm and press it on the surface of the pole piece (wherein: the lithium foil and the pole piece are all bonded together), the pressure is 0.2MPa, the time is 5min, and the open circuit voltage is 1.6V after completion. ;

(3) Separate the lithium foil and the pole piece, rinse the residual electrolyte on the surface of the pole piece with solvent DMC, and dry the pole piece;

(4) Assemble the pole piece obtained in step (3) into a 2032 button-type half-cell, the diaphragm is Celgard2500 (purchased from Duoduo Reagent), the counter electrode is a lithium piece, the electrolyte is 1M LiPF ₆ , and the volume ratio is 1:1 EC/DEC.

The half-cell assembled in this example was charged and discharged at 130 mA/g, and the results are shown in FIG. 1 . It can be seen from the figure that the charge-discharge range of the half-cell assembled from the pre-lithiated two-dimensional composite negative electrode material in this example is 0.005-3V, the discharge capacity of the first cycle is 712mAh/g, and the charge-discharge efficiency of the first cycle is 102 %.

Example 2

(1) According to the weight ratio of TiO ₂ /C: KT-black PVDF=9:0.5:0.5, each raw material was weighed, and NMP solvent was added to prepare a negative electrode slurry with a solid content of 35%, then According to the dosage of 3 mg/cm ² , it was uniformly coated on a conductive copper foil with a thickness of 9 μm to form a negative pole piece with a coating thickness of 200 μm. After rolling at 15 MPa and vacuum drying at 110 ° C, it was cut into pieces. A pole piece with a diameter of 12mm;

(2) Add electrolyte (1M LiPF ₆ , EC/DEC with a volume ratio of 1:1) dropwise to the surface of the pole piece prepared in step (1) according to 500 μL/cm ² to wet the pole piece, and then use a stainless steel rod Roll out to a lithium foil with a thickness of 100 μm (purchased from Duoduo Reagent) and press it all on the surface of the pole piece (wherein: the lithium foil and the pole piece are all bonded together), the pressure is 0.1MPa, and the time is 12min. After completion, the open circuit voltage is detected as 1.45V;

(3) Separate the lithium foil and the pole piece, rinse the residual electrolyte on the surface of the pole piece with solvent DMC, and dry the pole piece;

(4) Assemble the pole piece obtained in step (3) into a 2032 button-type full battery: the positive electrode of the full battery uses lithium iron phosphate (LiFePO ₄ ), the negative electrode/positive electrode capacity is N/P=1.10, and the separator is alumina ceramic double-sided Coated with PP separator (purchased from Xingyuan material, the thickness of PP coating layer is 4 μm), the electrolyte is 1M LiPF ₆ , and the volume ratio is EC/DEC of 1:1.

The full battery assembled in this example was subjected to a charge-discharge test, and the results are shown in FIG. 2 . It can be seen from the figure that the charge-discharge range of the full battery assembled from the pre-lithiated two-dimensional composite negative electrode material in this example is 1-3.7V, the current is 0.1C (17mA/g), and the Coulomb efficiency of the first cycle is was 81.7%, and the discharge capacity was 145.4 mAh/g. The discharge capacity after 30 cycles is 144.8mAh/g, and the capacity retention rate is 99%.

As a comparison, the LiFePO ₄ -TiO ₂ /C full cell without lithiation was charged and discharged, and the results are shown in Fig. 3 . It can be seen from the figure that the first cycle discharge capacity of the full battery assembled with the two-dimensional composite anode material without lithiation is only 97.1mAh/g, the first cycle charge and discharge efficiency is only 57.8%, and the discharge after 27 cycles The capacity is only 55.9mAh/g left. This shows that the present invention can fully utilize the capacity of the positive electrode material after assembling the two-dimensional composite negative electrode material after pre-lithiation or pre-sodiumization into a full battery, so as to significantly improve the authorized coulombic efficiency and cycle performance of the full battery.

Example 3

(1) According to the weight ratio of TiO ₂ /C: Ketjen black (KT-black): PVDF=8:1:1, each raw material was weighed, and NMP solvent was added to prepare a negative electrode slurry with a solid content of 32%, and then According to the dosage of 1 mg/cm ² , it was uniformly coated on the conductive copper foil with a thickness of 9 μm to form a negative pole piece with a coating thickness of 80 μm. After rolling at 12 MPa and vacuum drying at 90 °C, it was cut into pieces. A pole piece with a diameter of 14mm;

(2) Add electrolyte (1M LiPF ₆ , EC/DEC with a volume ratio of 1:1) dropwise to the surface of the pole piece prepared in step (1) according to 400 μL/cm ² to wet the pole piece, and then use a stainless steel rod Roll out to a lithium foil with a thickness of 120 μm (purchased from Duoduo Reagent) and press it all on the surface of the pole piece (wherein: the lithium foil and the pole piece are all bonded together), the pressure is 0.3MPa, and the time is 20min. After completion, the open circuit voltage is detected as 1.64V;

(3) Separate the lithium foil and the pole piece, and dry the residual electrolyte on the surface of the pole piece;

(4) Assemble the pole piece obtained in step (3) into a 2032 button-type full battery: the positive electrode of the full battery uses lithium cobalt oxide, the negative electrode/positive electrode capacity N/P=1.10, and the separator is alumina ceramic double-coated PP separator (Purchased from Xingyuan Material, the thickness of PP coating layer is 4 μm), the electrolyte is 1M LiPF ₆ , and the volume ratio is EC/DEC of 1:1.

The full battery assembled in this example was subjected to a charge-discharge test, and the results are shown in FIG. 4 . It can be seen from the figure that the charge-discharge range of the full battery assembled from the pre-lithiated two-dimensional composite negative electrode material in this example is 0.005-4.4V (0.1C becomes 0.005-4.2V), and the current is 0.1C ( 18mA/g), the first cycle Coulomb efficiency is 93.4%, the discharge capacity is 159.6mAh/g, the 0.2C (36mA/g) discharge capacity is 167.7mAh/g, and the 0.5C (90mA/g) discharge capacity is 141.4mAh/g , 1C (180mA/g) discharge capacity is 119.8mAh/g, 2C (360mA/g) discharge capacity is 98.6mAh/g, 5C (900mA/g) discharge capacity is 71.6mAh/g.

Example 4

(1) according to the weight ratio of TiO ₂ /C: Ketjen black (KT-black): PVDF=8:1:1, each raw material was weighed, and NMP solvent was added to prepare a negative electrode slurry with a solid content of 35%, Then, it was uniformly coated on the conductive copper foil with a thickness of 9 μm according to the dosage of 2 mg/cm ² to form a negative pole piece with a coating thickness of 100 μm, which was then cut after rolling at 15 MPa and vacuum drying at 90 °C. into a pole piece with a diameter of 10mm;

(2) dropping electrolyte (1M NaClO ₄ , EC+PC+5% volume FEC with a volume ratio of 1:1) on the surface of the pole piece prepared in step (1) according to 300 μL/cm ² to wet the pole piece, Then, the sodium foil with a thickness of 200μm was rolled out with a stainless steel stick and pressed on the surface of the pole piece (wherein: the lithium foil and the pole piece were all attached), the pressure was 0.15MPa, the time was 30min, and the open circuit voltage was 1.27V after completion;

(3) Separate the sodium foil from the pole piece, rinse the pole piece with residual electrolyte on the surface of the pole piece with solvent DMC, and dry the pole piece;

(4) Assemble the pole piece obtained in step (3) into a 2032 button-type full battery: the positive electrode of the full battery is sodium vanadium phosphate, the negative electrode/positive electrode capacity is N/P=1.05, and the separator is Whatman glass fiber (purchased from Duoduo Reagent) , the electrolyte is 1M NaClO ₄ , and the volume ratio is 1:1 EC+PC+5% volume FEC.

The full battery assembled in this example is subjected to a charge and discharge test, and the results are shown in FIG. 5 . It can be seen from the figure that the charge-discharge range of the full battery assembled from the pre-sodiumized two-dimensional composite negative electrode material in this example is 2-4.2V, the current is 0.1C (20mA/g), and the Coulomb efficiency of the first cycle is was 95.4%, and the discharge capacity was 145.4mAh/g.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. a preparation method of pre-lithiation, pre-sodiumization composite negative electrode material, is characterized in that, comprises that lithium sheet and/or sodium sheet and battery negative pole piece are attached and add electrolyte, obtain pre-lithiation and/or by pressing Or pre-sodiumized composite anode material. Preferably, the negative pole piece is a sheet-shaped battery negative pole piece. Preferably, the thickness of the sheet-shaped battery negative electrode sheet is 5-20 μm. Preferably, the current collector of the sheet-shaped battery negative electrode sheet is a pure metal foil or a metal foil made of an alloy material. Pure metal foils are preferred. For example, the pure metal foil is copper foil or aluminum foil. 2 . The preparation method according to claim 1 , wherein the active material of the sheet-shaped battery negative electrode plate is a two-dimensional material. 3 . Preferably, the two-dimensional material is selected from TiO ₂ , MnO ₂ , RuO ₂ , V ₂ O ₅ , MoO ₃ , MoS ₂ , WS ₂ , La ₂ TiO ₃ , LaNb ₂ O ₇ , Ca ₂ Nb ₃ O ₁₀ , One, two or more of graphene, C3N4 (graphitic carbon _nitride ), BN (boron nitride), _Mxene (transition metal carbonitride), and LDHs (layered double hydroxide) . Two types are preferred. For example, the two-dimensional material may be selected from _TiO2 and graphene composites. 3 . The preparation method according to claim 1 or 2 , wherein the sheet-shaped battery negative electrode plate further contains a conductive agent and/or a binder. 4 . Preferably, the conductive agent is conductive carbon black, acetylene black, carbon black (Super-P), Ketjen black (KT-Black) conductive carbon spheres, conductive graphite, carbon nanotubes, conductive carbon fibers, graphene and reduction oxidation At least one of graphene. Preferably, the binder is selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), sodium alginate, vinylidene fluoride-hexafluoropropylene copolymer, polyamide , at least one of polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyethylene pyrrolidone, polyvinyl ether, polymethyl methacrylate and polyhexafluoropropylene, etc. kind. Preferably, the mixed mass ratio of the active material, the conductive agent and the binder of the sheet-shaped battery negative electrode sheet is (6～9.8):(0.1～3):(0.1～2); preferably (8～9.8) 9):(0.5～1):(0.5～1). 4. The preparation method according to any one of claims 1-3, wherein the preparation method of the sheet-shaped battery negative pole piece comprises the following steps: The active material of the negative electrode pole piece of the battery is mixed with a conductive agent and a binder, and then a solvent is added to disperse to obtain a negative electrode slurry, and then the negative electrode slurry is coated on the negative electrode current collector, dried, rolled and die-cut to obtain The sheet-shaped battery negative pole piece. Preferably, in the preparation method of the sheet-shaped battery negative pole piece, the rolling pressure is 0-20 MPa, and the time is 0-120 s. Preferably, in the preparation method of the sheet-shaped battery negative electrode sheet, the drying is preferably vacuum drying. Preferably, the drying temperature is 60-110°C, preferably 70-100°C. Further, the drying time is 0.5-20h, preferably 12-20h. Preferably, the negative electrode pole piece of the battery is rolled and sliced to form a pole piece of the required size for a button-type or soft pack battery. Preferably, before the lithium sheet and/or the sodium sheet is attached to the negative electrode of the battery, it needs to be rolled out into a lithium foil or sodium foil with a smooth surface and a thickness of ≤200 μm. Preferably, under the protection of an inert atmosphere, the lithium sheet and/or the sodium sheet is rolled out into a lithium or sodium foil with a smooth surface and a thickness of ≤200 μm. Preferably, the area of the rolled lithium sheet and/or sodium sheet is larger than the area of the negative electrode. 5 . The preparation method according to claim 1 , wherein the amount of the electrolyte solution is 20-400 μL/cm ² . 6 . Preferably, the solute of the electrolyte is a lithium salt or a sodium salt. Preferably, the lithium salt includes at least one of LiPF ₆ , LiTFSI, LiBOB, LiClO ₄ , LiFSI, LiBF ₄ and LiAsF ₆ ; the sodium salt includes at least one of NaPF ₆ , NaClO ₄ , NaTFSI and NaFSI. Preferably, the solvent of the electrolyte includes two of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DEC), diethyl carbonate (DMC), ethyl methyl carbonate (EMC) and the like species or three. Preferably, the smooth side of the lithium foil and/or the sodium foil is preferably directed toward the negative electrode piece, and the lithium foil and/or the sodium foil are completely covered and tightly attached to the negative electrode piece. Preferably, the laminating step is carried out under the protection of an inert atmosphere. Preferably, the pressing pressure is 0-2 MPa, preferably 0.1-1 MPa. Preferably, the standing time of the pressing is 0-120 min, preferably 2-60 min. Preferably, after pre-lithiation and/or pre-sodiumization, the voltage of the battery composed of lithium foil and/or sodium foil and negative pole piece is 1-2V, preferably 1.2-1.7V. 6. The preparation method according to any one of claims 1-5, wherein the preparation method further comprises a step of separating the pressed lithium foil and/or sodium foil from the negative electrode, or in the lithium foil And/or a separator is added between the sodium foil and the negative pole piece. Preferably, the preparation method further includes the step of drying or washing the separated negative electrode plate, so as to remove the residual electrolyte on the surface of the negative electrode plate. Preferably, the washing solvent may be DMC. Preferably, the preparation method further includes the step of drying the washed negative electrode piece. 7. A pre-lithiated and pre-sodiumized composite negative electrode material prepared by the preparation method according to any one of claims 1-6. Preferably, the composite negative electrode material is a two-dimensional composite negative electrode material. 8. Application of the pre-lithiated and pre-sodiumized composite negative electrode material prepared by the preparation method according to any one of claims 1 to 6 in a lithium battery or a sodium battery. It is preferably used as the negative electrode of lithium battery. 9. A lithium battery or a sodium battery, characterized in that it contains the pre-lithiation, pre-sodium composite negative electrode material and/or negative pole piece obtained by the preparation method described in any one of claims 1-6 . Preferably, the lithium battery or the sodium battery may be a half battery or a full battery. For example, the half cell may be a 2032 coin half cell. 10 . The lithium battery or sodium battery according to claim 9 , wherein the half-cell further comprises lithium sheets and/or sodium sheets. 11 . Preferably, the half-cell further comprises a separator. Preferably, the separator may be at least one of PP, PE, PP/PE/PP, glass fiber, and the like. More preferably, the separator is a single-sided and/or double-sided ceramic-coated separator. For example, the charge-discharge range of the separator is 0.005-3V. Preferably, the full battery further includes a positive electrode sheet. Preferably, the positive electrode material of the positive electrode sheet includes at least one of ternary positive electrode materials such as lithium cobalt oxide, lithium iron phosphate, sodium vanadium phosphate and cobalt nickel manganese. Preferably, the capacity ratio of the negative electrode and the positive electrode is 1.0-1.2. Preferably, the full battery further includes an electrolyte and a separator.

Images