Composite lithium supplementing diaphragm, preparation method thereof and battery with composite lithium supplementing diaphragm

Abstract

The invention discloses a composite lithium supplementing diaphragm, a preparation method thereof and a battery with the composite lithium supplementing diaphragm. The composite lithium supplementing diaphragm comprises a diaphragm base material and a lithium supplementing layer, the lithium supplementing layer is modified on at least one surface of the diaphragm base material, the lithium supplementing layer comprises lithium nitride () micron crystal grains, and the lithium nitride micron crystal grains are phase crystals with (001) crystal face orientation. The method has the advantages of avoiding over-fast decomposition of the lithium supplement agent, reducing side reaction and gas production and improving the safety performance of the battery.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology, specifically relating to lithium battery separators, and more particularly to a composite lithium-replenishing separator, its preparation method, and a battery having the same. Background Technology

[0002] Lithium-ion batteries are widely used in consumer electronics, electric vehicles, and large-scale energy storage due to their high energy density, long cycle life, and lack of memory effect. However, during the first charge and discharge cycle, a solid electrolyte interphase (SEI) film forms on the electrode surface. This process irreversibly consumes lithium ions from the positive electrode, leading to low initial coulombic efficiency and permanent loss of reversible capacity. This problem is particularly severe for high-capacity anode materials such as silicon-based anodes and lithium metal anodes.

[0003] To compensate for initial lithium loss, pre-lithiation (or lithium replenishment) technology has been extensively studied. Among these methods, using compounds with high lithium content (such as lithium-rich materials, lithium foil, lithium powder, Li3N, etc.) as lithium replenishment agents is an effective approach. Lithium nitride (Li3N) has attracted attention due to its extremely high theoretical lithium replenishment capacity (2300 mAh / g) and low lithiation potential. However, traditional Li3N lithium replenishment agents suffer from problems such as extreme sensitivity to air and humidity, poor chemical stability, dissolution in electrolytes, and numerous side reactions, leading to low lithium replenishment efficiency, severe battery gas generation, and incompatibility with existing battery manufacturing processes. To address these issues, a composite lithium replenishment separator, its preparation method, and a battery incorporating it are proposed. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art.

[0005] Therefore, this invention proposes a composite lithium-replenishing separator, its preparation method, and a battery having the same. The composite lithium-replenishing separator has the advantages of avoiding the rapid decomposition of lithium replenishing agents, reducing side reactions and gas production, and improving the safety performance of the battery.

[0006] A composite lithium-replenishing separator according to an embodiment of the present invention includes: a separator substrate and a lithium-replenishing layer; the lithium-replenishing layer is modified on at least one surface of the separator substrate, and the lithium-replenishing layer comprises lithium nitride (… The lithium nitride micron grains are (001) oriented. Phase crystal.

[0007] According to one embodiment of the present invention, the particle size range of the lithium nitride micron grains is 0.1 μm to 5 μm.

[0008] According to one embodiment of the present invention, the lithium replenishment layer is a dense thin film composed of lithium nitride grains with a thickness of 200 nm to 5 μm.

[0009] A method for preparing a composite lithium-supplementing separator, used to prepare the composite lithium-supplementing separator as described in any one of the above-mentioned methods, includes the following steps: S1. Provide a substrate in the evaporation chamber; S2. A lithium replenishment layer is deposited and grown on at least one surface of the diaphragm substrate using a vapor deposition method.

[0010] According to one embodiment of the present invention, in S1, a rewinding mechanism is used to realize the unwinding and rewinding of the diaphragm substrate, and the unwinding point and the rewinding point of the rewinding mechanism are located on both sides above the lithium reaction chamber, so that the diaphragm substrate passes through the lithium reaction chamber.

[0011] According to one embodiment of the present invention, the rewinding mechanism includes an unwinding roller, a take-up roller, and at least one adjusting roller, wherein at least one adjusting roller is located between the unwinding roller and the take-up roller, and at least one adjusting roller is lower than the unwinding roller and the take-up roller.

[0012] According to one embodiment of the present invention, S2 includes: S21. Vacuum pumps are used to evacuate the evaporation chamber through the exhaust port. S22. An electron gun is used to heat and evaporate the metallic lithium source in the lithium reaction chamber, generating a gaseous phase of lithium atoms; S23. A mixture of high-purity argon and high-purity nitrogen is introduced into the evaporation chamber, and the ion source is turned on simultaneously to ionize the high-purity argon, high-purity nitrogen and lithium atoms to generate plasma containing argon ions, nitrogen ions, lithium ions and electrons. S24. In the collision between the lithium atom gas phase generated in S22 and the plasma generated in S23, lithium ions and nitrogen ions combine and diffuse freely inside the evaporation chamber, with the diffusion direction facing the surface of the separator substrate. By controlling the deposition parameters, the (001) crystal plane orientation is preferentially grown and deposited on the separator substrate. Lithium nitride thin film.

[0013] According to one embodiment of the present invention, in S1, the speed of the rewinding mechanism is 0.5-20 m / min; the temperature of the diaphragm substrate is 25-80°C; and the diaphragm substrate is located at a position 40 cm or more directly above the lithium reaction chamber.

[0014] According to one embodiment of the present invention, in S21, the vacuum degree is not higher than 5.0 × 10⁻⁶. -3 Pa; In S22, the electron gun power is 100~600 W; In S23, the purity of high-purity argon and high-purity nitrogen is above 99.99%, the volume ratio of the mixed gas of high-purity nitrogen and high-purity argon is 5:1 to 1:1; the flow rate of the mixed gas is 20 to 150 sccm; the ion source power is 50 to 300 W; and the gas pressure in the evaporation chamber during deposition is 0.01 to 0.1 Pa.

[0015] A battery with a composite lithium-replenishing separator includes the composite lithium-replenishing separator described in any one of the above claims, and further includes a casing, a positive electrode, a negative electrode, and an electrolyte. The composite lithium-replenishing separator is located between the positive electrode and the negative electrode. The positive electrode, the composite lithium-replenishing separator, and the negative electrode are wound and disposed inside the casing, and the electrolyte is located inside the casing.

[0016] The beneficial effect of this invention is that it adopts a (001) crystal plane orientation. Lithium nitride micron-sized grains of phase crystal are modified on the separator substrate to avoid the rapid decomposition of lithium replenishment agent, reduce side reactions and gas production, and improve the safety performance of the battery. Using vapor deposition technology, high-purity, highly crystalline membranes with preferred (001) crystal plane orientation were directly grown in situ on the membrane substrate. The Li3N thin film avoids the introduction of inactive substances in the traditional slurry method, has a higher utilization rate of active substances, and has a strong adhesion to the membrane substrate, making it less prone to falling off. By employing an electron gun to react high-energy lithium atoms with nitrogen plasma, the traditional thermal evaporation method breaks the dependence on high temperatures and achieves for the first time the direct epitaxial growth of highly oriented lithium nitride films on commercial polymer membranes at low temperatures (25-80℃), resulting in environmentally controllable and product-consistent performance.

[0017] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention.

[0018] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0019] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of the internal structure of the evaporation chamber of the present invention; Figure 2 This is a schematic diagram of the first charge-discharge and cycle performance of the full battery of the present invention; Figure 3 This is the XRD pattern of the composite lithium-supplementing separator of Embodiment 1 of the present invention; Figure 4These are optical images and SEM images of the composite lithium-supplementing separator of Embodiment 1 of the present invention; Figure 5 This is a comparison chart of the first charge-discharge curves of the full cells in the comparative and example scenarios; Figure 6 These are XPS data graphs of the positive electrode surface CEI of Comparative Example 1 and Example 1 of the present invention; Figure 7 These are XPS data graphs of the SEI on the negative electrode surface of Comparative Example 1 and Example 1 of the present invention; Figure label: 1. Diaphragm substrate; 2. Rewinding mechanism; 3. Lithium reaction chamber; 4. Electron gun; 8. Ion source; 9. Exhaust port. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0021] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, features defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more. In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] The following describes in detail, with reference to the accompanying drawings, a composite lithium-replenishing separator according to embodiments of the present invention, its preparation method, and a battery having the same.

[0023] like Figure 1-7 As shown, the composite lithium-replenishing separator according to an embodiment of the present invention includes: a separator substrate 1 and a lithium-replenishing layer; the lithium-replenishing layer is modified on at least one surface of the separator substrate 1, and the lithium-replenishing layer comprises lithium nitride (… The lithium nitride micron grains are (001) oriented. Phase crystal.

[0024] In this embodiment, the lithium replenishment layer can be disposed on one or both surfaces of the separator substrate 1. Lithium nitride with a specific crystal orientation is composited onto the separator substrate 1, avoiding the introduction of inactive substances (binders, conductive agents) in traditional slurry methods. This results in higher utilization of active materials and stronger adhesion to the substrate, making it less prone to detachment. Because Li... + The (001) crystal planes perpendicular to the c-axis exhibit a lower migration rate, and this orientation exposes more (001) crystal planes to the reaction interface, effectively prolonging the Li-C reaction time during α-Li3N decomposition. + This reduces the migration time, thereby slowing down the overall decomposition rate, inhibiting premature and rapid decomposition of the lithium replenishing agent in the electrolyte, reducing side reactions, and improving battery safety. Furthermore, this composite lithium replenishing separator not only provides active lithium during charging to compensate for capacity loss during the first charge, but its unique decomposition pathway and products also preferentially and uniformly participate in the formation of CEI and SEI, generating a more stable interface film with higher ionic conductivity. This simultaneously improves the battery's initial efficiency, energy density, cycle life, and safety. It achieves efficient compensation for lithium loss and simultaneously strengthens the electrode interface, comprehensively enhancing battery performance.

[0025] Specifically, the diaphragm substrate 1 is one or a composite of polyethylene (PE) diaphragm, polypropylene (PP) diaphragm, ceramic-coated diaphragm, or non-woven fabric diaphragm. The temperature of the diaphragm substrate 1 is controlled between 25 and 80°C.

[0026] The particle size range of lithium nitride micron-sized grains is 0.1 μm to 5 μm.

[0027] The lithium replenishment layer is a dense thin film composed of lithium nitride grains, with a thickness of 200 nm to 5 μm.

[0028] A method for preparing a composite lithium-supplementing separator, comprising the following steps: S1. Provide a substrate in the evaporation chamber; S2. A lithium replenishment layer is deposited and grown on at least one surface of the separator substrate 1 using a vapor deposition method. High-purity, high-crystallinity lithium with preferred (001) crystal plane orientation is directly grown in situ on the separator substrate 1 using vapor deposition technology. The structure avoids the introduction of inactive substances (binders, conductive agents) in the traditional slurry method, resulting in higher utilization of active substances and strong adhesion to the membrane substrate 1, making it less prone to detachment.

[0029] In S1, a rewinding machine 2 is used to unwind and rewind the diaphragm substrate 1. The unwinding and rewinding points of the rewinding machine 2 are located on both sides above the lithium reaction chamber 3, so that the diaphragm substrate 1 passes through the lithium reaction chamber 3. The lithium reaction chamber 3 can be a crucible.

[0030] The rewinder includes an unwinding roller, a take-up roller, and at least one adjusting roller, wherein the at least one adjusting roller is located between the unwinding roller and the take-up roller, and at least one adjusting roller is lower than the unwinding roller and the take-up roller.

[0031] Specifically, there are two adjusting rollers, which are spaced apart horizontally to increase the deposition area of ​​the diaphragm substrate 1. Furthermore, the distance between the two adjusting rollers is less than the distance between the unwinding roller and the take-up roller, such as... Figure 1 As shown, the diaphragm substrate 1, supported by the rewinding mechanism 2, has a trapezoidal shape that is narrow at the bottom and wide at the top. That is, the diaphragm substrate 1 has inclined surfaces on both the front and back sides of the two adjusting rollers, so that the lithium ion and nitrogen ion combination that floats out of the area between the two adjusting rollers is deposited on the diaphragm substrate 1 outside the two adjusting rollers, thereby improving the utilization rate of lithium ion and nitrogen ion combination.

[0032] S2 includes: S21. Vacuum pumps are used to evacuate the evaporation chamber through the exhaust port 9 of the evaporation chamber.

[0033] S22. The lithium metal source in the lithium reaction chamber 3 is heated and evaporated by electron gun 4 to generate lithium atom gas phase.

[0034] S23. A mixture of high-purity argon and high-purity nitrogen is introduced into the evaporation chamber, and the ion source 8 is turned on simultaneously to ionize the high-purity argon, high-purity nitrogen and lithium atoms to generate plasma containing argon ions, nitrogen ions, lithium ions and electrons.

[0035] S24. In the collision between the lithium atom gas phase generated in S22 and the plasma generated in S23, lithium ions and nitrogen ions combine and diffuse freely inside the evaporation chamber. The diffusion direction is directly towards the surface of the separator substrate 1. By controlling the deposition parameters, a (001) oriented crystal plane is preferentially grown and deposited on the separator substrate 1. Lithium nitride thin film.

[0036] A high-energy lithium atom beam generated by electron gun 4 reacts with highly reactive nitrogen plasma generated by ion source 8 on the substrate surface. This reaction combination of 'high-energy lithium atoms + highly reactive nitrogen plasma' provides a reaction driving force far higher than that of traditional thermal evaporation methods, allowing lithium nitride crystal growth to occur at temperatures far below the membrane's tolerance limit (even room temperature). Simultaneously, the slight bombardment and cleaning effect of the plasma on the substrate surface not only enhances the adhesion of the thin film but also provides nucleation sites for the epitaxial orientation growth of lithium nitride grains, which is crucial for achieving preferred orientation of the (001) crystal plane.

[0037] In existing technologies, lithium metal is deposited via thermal evaporation followed by a nitriding reaction, forming a two-step process to deposit lithium nitride on the electrode. However, this method has significant limitations: First, the lithium vapor generated by thermal evaporation has low energy and low reaction efficiency with nitrogen, typically requiring a high substrate temperature (>100℃) to obtain a well-crystallized film. This temperature far exceeds the tolerance limit of conventional polyolefin separator substrate 1 (usually <90℃), causing the separator substrate 1 to shrink, melt, or even perforate, rendering it impractical. Second, the fundamental technical contradiction of traditional thermal evaporation lies in the fact that lithium evaporation requires a high vacuum environment (<10℃). -2 The nitriding reaction requires a certain nitrogen pressure (usually >10 Pa), and these two environmental requirements conflict with each other, making it impossible to achieve continuous preparation of high-quality lithium nitride films.

[0038] The use of electron gun 4 to react high-energy lithium atoms with nitrogen plasma breaks the dependence of traditional thermal evaporation methods on high temperatures, achieving for the first time the direct epitaxial growth of highly oriented lithium nitride films on commercial polymer separators at low temperatures (25-80℃). This method offers a controllable environment and good product consistency. Simultaneously, the lithium source is evaporated under high vacuum using electron gun 4, while nitrogen is activated under lower vacuum using ion source 8. This reconciles conflicting environmental requirements within a single process chamber, optimizing the traditional two-step method into a one-step in-situ synthesis of lithium nitride, avoiding contamination and oxidation problems of intermediate products.

[0039] In S1, the rewinder 2 travels at a speed of 0.5-20 m / min; the temperature of the diaphragm substrate 1 is 25-80℃, preferably 40-60℃; the diaphragm substrate 1 is located at a position 40 cm or more directly above the lithium reaction chamber 3, preferably at a distance of 45 cm.

[0040] In S21, the vacuum level is no higher than 5.0 × 10⁻⁶. -3 Pa; In S22, the power of electron gun 4 is 100~600 W, preferably 200~350 W; In S23, the purity of high-purity argon and high-purity nitrogen is above 99.99%, and the volume ratio of the mixed gas of high-purity nitrogen and high-purity argon is 5:1 to 1:1; the flow rate of the mixed gas is 20 to 150 sccm; the power of the ion source 8 is 50 to 300 W, preferably 100 to 200 W; and the gas pressure in the evaporation chamber during deposition is 0.01 to 0.1 Pa, preferably 0.03 to 0.08 Pa.

[0041] A battery with a composite lithium-replenishing separator, comprising the aforementioned composite lithium-replenishing separator, characterized in that it further comprises a casing, a positive electrode, a negative electrode, and an electrolyte, wherein the composite lithium-replenishing separator is located between the positive electrode and the negative electrode, the positive electrode, the composite lithium-replenishing separator, and the negative electrode are wound and disposed within the casing, and the electrolyte is located within the casing.

[0042] Comparative Example 1: Ordinary diaphragm (without any lithium supplement) (1) Preparation of positive electrode: Lithium cobalt oxide positive electrode material (LiCoO2), conductive carbon black (Super P), and binder polyvinylidene fluoride (PVDF) were added to N-methylpyrrolidone (NMP) solvent at a mass ratio of 96:2:2. The mixture was stirred in a vacuum mixer at a speed of 2000 rpm for 6 hours to obtain a uniform positive electrode slurry. The slurry was uniformly coated onto an aluminum foil current collector, dried by forced air at 80°C for 2 hours, and then vacuum dried at 120°C for 12 hours. After rolling and cutting, the positive electrode was obtained.

[0043] (2) Negative electrode preparation: Graphite negative electrode material, conductive graphite, acetylene black, and binder polyacrylic acid (PAA) are added to deionized water in a mass ratio of 90:3:2:5 and thoroughly mixed to obtain a negative electrode slurry. The slurry is uniformly coated onto a copper foil current collector, first dried in a forced-air dryer at 60°C for 2 hours, and then vacuum dried at 100°C for 12 hours. After rolling and cutting, the negative electrode is obtained.

[0044] (3) Battery assembly: The positive electrode prepared in step (1) is used as the working electrode, the negative electrode prepared in step (2) is used as the counter electrode, Celgard 2320 polypropylene membrane is used as the separator, and 1 mol / L LiPF6 ethylene carbonate (EC) / diethyl carbonate (DEC) (volume ratio 1:1) solution is used as the electrolyte. The CR2032 button cell is assembled in a glove box filled with argon (H2O<0.1 ppm, O2<0.1 ppm).

[0045] Comparative Example 2: Lithium nitride deposition on the cathode surface (cathode lithium replenishment) (1) Preparation of positive electrode: LiCoO2 positive electrode sheet was prepared using the same materials and proportions as in Comparative Example 1 (1).

[0046] (2) Deposition of Li3N thin film on the positive electrode surface: The positive electrode sheet prepared in step (1) is fixed on the sample stage of the vacuum deposition equipment. The deposition chamber is evacuated to a high vacuum of 5.0 × 10⁻⁶. -3 Pa. The sample stage temperature was controlled at 50℃. A lithium atom beam was generated by evaporating a lithium metal source using electron gun 4, while simultaneously introducing 50 sccm of high-purity nitrogen (N2) and 25 sccm of high-purity argon (Ar) into the cavity, and RF ion source 8 (power 150 W) was activated to generate nitrogen plasma. After deposition for 30 minutes, a layer with a (001) oriented crystal plane and a thickness of approximately 1.5 μm was deposited on the surface of the positive electrode. Lithium nitride (Li3N) thin films were prepared and immediately vacuum-sealed after being removed from the substrate.

[0047] (3) Negative electrode preparation: Graphite negative electrode was prepared using the same materials and proportions as in step (2) of Comparative Example 1.

[0048] (4) Battery assembly: The positive electrode with Li3N film deposited in step (2) is used as the working electrode, the negative electrode prepared in step (3) is used as the counter electrode, Celgard 2320 ordinary separator is used as the separator, the electrolyte and assembly environment are exactly the same as those in Comparative Example 1, and a CR2032 button battery is assembled.

[0049] Example 1: (1) Preparation of composite lithium-supplementing membrane (electron gun 4-ion source 8 composite plasma deposition method) Pretreatment of membrane substrate 1: Celgard 2320 PP / PE / PP three-layer composite membrane is selected as membrane substrate 1 and fixed on the rewinding mechanism 2.

[0050] Vacuum preparation: Evaporate the evaporation chamber to a high vacuum, achieving a vacuum level of 5.0 × 10⁻⁶. -3 Pa.

[0051] Deposition parameter settings: Control the temperature of the unwinding roller or regulating roller of rewinder 2 at 50℃. Adjust the power of electron gun 4 to evaporate metallic lithium (source material) to generate a stable atomic beam. Simultaneously, introduce high-purity nitrogen (N2) and high-purity argon (Ar) into the evaporation chamber, control the flow rate at 75 sccm (volume ratio 2:1), and turn on the radio frequency ion source 8 (power 150 W) to ionize the argon and nitrogen into plasma.

[0052] Deposition process: Deposition was carried out under the above conditions for 30 minutes. Lithium atoms collided with the plasma, reacted, and diffused freely towards the membrane substrate 1, forming an epitaxial growth with (001) oriented crystal plane. The lithium nitride thin film was prepared by rewinding mechanism 2 at a speed of 1.5 m / min. A dense Li3N thin film with a thickness of approximately 1.5 μm was ultimately obtained.

[0053] Post-processing: After deposition, the sample is taken out in a vacuum environment and immediately vacuum-sealed to obtain the composite lithium replenishment membrane.

[0054] (2) Preparation of positive electrode: LiCoO2 positive electrode sheet was prepared using the same materials and proportions as in Comparative Example 1 (1).

[0055] (3) Negative electrode preparation: Graphite negative electrode was prepared using the same materials and proportions as in step (2) of Comparative Example 1.

[0056] Battery assembly: Using the composite separator with Li3N film deposited in step (1) as the separator, the positive electrode prepared in step (2) as the working electrode, and the negative electrode prepared in step (3) as the counter electrode, the electrolyte and assembly environment are exactly the same as those in Comparative Example 1, and a CR2032 button cell is assembled.

[0057] The preparation method of Example 2 differs from that of Example 1 in that the speed of the rewinding mechanism 2 is adjusted to 0.75 min, and the deposition thickness of Li3N particles on the membrane surface is adjusted to 3.0 μm.

[0058] Test results, such as Figure 2 As shown, both Example 1 and Example 2 can effectively improve the first-efficiency and cycle performance of the battery.

[0059] Performance testing and results analysis: Battery Testing Methods: All assembled button cells underwent charge-discharge testing. Testing was conducted using either Newwell or BlueChip battery testing systems. Full Cell Testing Conditions: The first charge-discharge cycle was performed at a rate of 0.05C (1C = 200 mA / g), with a voltage range of 3.0–4.55 V. Subsequent cycles were performed at a rate of 0.5C, with the same voltage range. The initial charge-discharge capacity, coulombic efficiency, and capacity retention after 200 cycles were recorded.

[0060] First charge / discharge test: The first charge-discharge test was conducted at a rate of 0.05C. The results are as follows: Figure 2 , 5 As shown.

[0061] Comparative Example 1 (without lithium replenishment): The initial efficiency was 83.2%, the first discharge specific capacity was the lowest (195.6 mAh / g), and the irreversible capacity loss was severe.

[0062] Comparative Example 2 (Positive Electrode Lithium Compensation): The initial efficiency was 80.6%, and the first discharge specific capacity was the highest (213.8 mAh / g), proving that Li3N provided a large amount of active lithium, and the compensation effect was very significant.

[0063] The first-cycle discharge specific capacities of Examples 1 and 2 (diaphragm lithium replenishment) were 205.3 and 210.5 mAh / g, respectively, indicating good lithium replenishment performance, which was between the two.

[0064] Analysis: Comparative Example 2 showed the highest initial efficiency because Li3N was directly coated on the positive electrode surface, allowing for highly efficient decomposition and replenishment of the lithium source during the initial charging phase. In Examples 1 and 2, the Li3N was located in the separator, and the specific (001) crystal orientation delayed the release of active lithium, resulting in higher safety and slightly lower efficiency, but still significantly better than Comparative Example 1 without lithium replenishment. Furthermore, the capacity retention rates of the examples after 100 cycles were 86.1% and 87.6%, respectively, higher than Comparative Example 1 (85.1%) and Comparative Example 2 (84.9%). XPS data analysis shows that… Figure 6-7 This is because of the partial decomposition of lithium nitride (Li). 3-x N and the byproduct N2 participate in the formation of the positive electrode CEI and SEI components (nitrogen-containing compounds) which have more favorable electrochemical stability, thereby improving the cycle stability of the full cell.

[0065] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0066] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A composite lithium-supplementing separator, characterized in that, include: Diaphragm substrate (1); A lithium replenishment layer is applied to at least one surface of a separator substrate (1), the lithium replenishment layer comprising lithium nitride microcrystals, and the lithium nitride microcrystals having a (001) crystal plane orientation. Phase crystal.

2. The composite lithium-supplementing separator according to claim 1, characterized in that, The particle size range of the lithium nitride micron grains is 0.1 μm to 5 μm.

3. The composite lithium-supplementing separator according to claim 1, characterized in that, The lithium replenishment layer is a dense thin film composed of lithium nitride grains, with a thickness of 200 nm to 5 μm.

4. A method for preparing a composite lithium-supplementing separator, used to prepare the composite lithium-supplementing separator according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Provide a substrate in the evaporation chamber; S2. A lithium replenishment layer is deposited and grown on at least one surface of the diaphragm substrate (1) using a vapor deposition method.

5. The method for preparing the composite lithium-supplementing separator according to claim 4, characterized in that, In S1, a rewinding mechanism (2) is used to unwind and rewind the diaphragm substrate (1), and the unwinding and rewinding points of the rewinding mechanism (2) are located on both sides above the lithium reaction chamber (3) so that the diaphragm substrate (1) passes through the lithium reaction chamber (3).

6. The method for preparing the composite lithium-supplementing separator according to claim 5, characterized in that, The rewinding mechanism (2) includes an unwinding roller, a take-up roller, and at least one adjusting roller, wherein at least one adjusting roller is located between the unwinding roller and the take-up roller, and at least one adjusting roller is lower than the unwinding roller and the take-up roller.

7. The method for preparing the composite lithium-supplementing separator according to claim 6, characterized in that, S2 include: S21. Vacuum the evaporation chamber by using a vacuum pump set through the exhaust port (9) of the evaporation chamber; S22. The lithium metal source in the lithium reaction chamber (3) is heated and evaporated using an electron gun (4) to generate a lithium atom gas phase; S23. A mixture of high-purity argon and high-purity nitrogen is introduced into the evaporation chamber, and the ion source (8) is turned on simultaneously to ionize the high-purity argon, high-purity nitrogen and lithium atoms to generate plasma containing argon ions, nitrogen ions, lithium ions and electrons. S24. In the collision between the lithium atom gas phase generated in S22 and the plasma generated in S23, lithium ions and nitrogen ions combine and diffuse freely inside the evaporation chamber, with the diffusion direction facing the surface of the separator substrate (1). By controlling the deposition parameters, the (001) crystal plane orientation is formed by reactive deposition and preferential growth on the separator substrate (1). Lithium nitride thin film.

8. The method for preparing the composite lithium-supplementing separator according to claim 7, characterized in that, In S1, the rewinding mechanism (2) travels at a speed of 0.5-20 m / min; the temperature of the diaphragm substrate (1) is 25-80℃; the diaphragm substrate (1) is located at a position 40 cm or more directly above the lithium reaction chamber (3).

9. The method for preparing the composite lithium-supplementing separator according to claim 8, characterized in that, In S21, the vacuum level is no higher than 5.0 × 10⁻⁶. -3 Pa; In S22, the power of the electron gun (4) is 100~600 W; In S23, the purity of high-purity argon and high-purity nitrogen is above 99.99%, and the volume ratio of the mixed gas of high-purity nitrogen and high-purity argon is 5:1 to 1:1; the flow rate of the mixed gas is 20 to 150 sccm; the power of the ion source (8) is 50 to 300 W; and the gas pressure in the evaporation chamber during deposition is 0.01 to 0.1 Pa.

10. A battery having a composite lithium-replenishing separator, comprising the composite lithium-replenishing separator according to any one of claims 1-3, characterized in that, It also includes a housing, a positive electrode, a negative electrode, and an electrolyte. The composite lithium-replenishing separator is located between the positive electrode and the negative electrode. The positive electrode, the composite lithium-replenishing separator, and the negative electrode are wound and disposed inside the housing. The electrolyte is located inside the housing.

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