Ceramic composite lithium supplementing diaphragm, preparation method and application thereof

Abstract

The application belongs to the technical field of lithium ion batteries, and particularly relates to a ceramic composite lithium supplementing diaphragm and a preparation method and application thereof, and comprises the following steps: dissolving a cobalt source in ethylene glycol, adding polyvinylpyrrolidone and a first sulfur source to obtain a solid-state precursor; calcining the solid-state precursor under a protective atmosphere, mixing with a second sulfur source, and then transferring to a closed container for calcination to obtain a composite material; dispersing the composite material, conductive carbon black and PVDF in a solvent and grinding into a slurry, coating on a diaphragm and drying to obtain a CSP diaphragm; adding an electrolyte on the surface of the CSP diaphragm, covering a lithium sheet and performing in-situ lithiation to obtain an LCSP diaphragm. Compared with the prior art, the application solves the problems of complex process and expensive raw materials in the prior art. The preparation process of the scheme is simple, and the scale production can be further realized through a roll-to-roll mode. The entire manufacturing process of the diaphragm is fully adapted to the production process of the lithium ion battery, and the production cost is reduced.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a ceramic composite lithium-replenishing separator, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries have been widely used in energy storage grids, portable electronic products, and electric vehicles.

[0003] Commercial lithium-ion batteries typically consist of a lithium-containing transition metal oxide cathode (such as lithium cobalt oxide, lithium iron phosphate, and ternary materials) and a lithium-depleted anode (mainly graphite). During the first charge cycle, an irreversible electrochemical reduction reaction occurs in the electrolyte, forming an SEI film on the anode surface. In this process, 5-20% of the active lithium ions at the cathode are typically consumed, leading to a decrease in coulombic efficiency and battery capacity during the first charge cycle. To compensate for this capacity loss, it is necessary to replenish the electrodes with additional active lithium ions before battery assembly.

[0004] Lithium replenishment methods can be divided into negative electrode replenishment and positive electrode replenishment. Negative electrode replenishment methods mainly include chemical lithiation and electrochemical lithiation. Chemical lithiation involves directly contacting lithium metal foil or stable lithium metal powder with the negative electrode, or immersing the negative electrode in a reducing lithium-containing solution. This allows for the pre-intercalation of some lithium ions into the negative electrode through an in-situ chemical reaction, thus compensating for capacity loss. However, the degree of pre-lithiation is difficult to control, and excessive replenishment can lead to lithium plating, posing a safety hazard. Electrochemical pre-intercalation allows for precise control of the pre-lithiation degree, but the process requires battery assembly and disassembly, making it complex and unsuitable for commercial mass production. Another method is to replenish lithium on the positive electrode side, for example, using over-lithiated positive electrode materials (Li5V2(PO4)3, Li...). 1+x Ni 0.5 Mn 1.5 During the first charge, additional lithium ions are released from the positive electrode (such as O4) to compensate for the lithium ion consumption by the SEI film. However, these materials have limited lithium replenishment capacity, and their high voltage plateau makes them prone to electrolyte decomposition, which is detrimental to stable battery cycling.

[0005] Introducing lithium replenishment additives is currently a feasible solution. Their lithium replenishment capacity can be controlled by adjusting the additive content, and the additives can be directly mixed with the cathode material, simplifying the preparation process. Furthermore, cathode lithium replenishment additives are typically low-cost and possess good chemical stability, making them suitable for large-scale commercial applications. An ideal lithium replenishment additive needs to have a lithium storage capacity far exceeding that of the cathode material, its delithiation potential should be lower than the maximum charging potential of the cathode, and it should not re-intercalate lithium within the cathode discharge voltage range. Specifically, the lithium replenishment additive should remain electrochemically inert after delithiation and should not affect subsequent battery cycling.

[0006] However, current lithium replenishment additives, after delithiation, are typically poor conductors of lithium ions and electrons. Introducing them into the positive electrode reduces the overall conductivity of the electrode, hindering subsequent battery capacity development. Modifying the separator with lithium replenishment additives can solve this problem. Furthermore, as an inorganic coating, it can improve the electrolyte wettability of the separator, thereby reducing interfacial impedance.

[0007] In the prior art, CN119651057A (a lithium replenishing separator and its preparation method, lithium-ion battery), CN114552125B (a non-destructive lithium replenishing composite separator and its preparation method and application), and CN117936757B (a lithium replenishing material, lithium replenishing separator and its preparation method) have conducted relevant research on lithium replenishing separators. However, the solutions adopted by the prior art have problems such as complex processes and expensive raw materials, which makes it difficult for lithium replenishing separators to be effectively applied in actual production. Summary of the Invention

[0008] The purpose of this invention is to provide a ceramic composite lithium-replenishing separator, its preparation method, and its application to solve at least one of the aforementioned problems, thereby addressing the issues of complex processes and expensive raw materials in existing technologies. This solution modifies the separator with a lithium-replenishing agent to compensate for the capacity loss during the first cycle of the battery. This method has a simple preparation process, can be further mass-produced via roll-to-roll manufacturing, and the entire manufacturing process of the separator is fully compatible with current lithium-ion battery production processes, significantly reducing production costs and showing good prospects for practical applications.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] The first aspect of this invention discloses a method for preparing a ceramic composite lithium-supplementing separator, comprising the following steps:

[0011] S1: Preparation of CoS2 / Co3S4 composite material:

[0012] Cobalt source was dissolved in ethylene glycol, and then polyvinylpyrrolidone and a first sulfur source were added to react and obtain a solid precursor. The solid precursor was calcined under a protective atmosphere, and the black powder obtained after calcination was mixed with a second sulfur source. Then it was transferred to a closed container for calcination to carry out vulcanization and obtain CoS2 / Co3S4 composite material.

[0013] S2: Preparation of CSP membrane:

[0014] CoS2 / Co3S4 composite material, conductive carbon black and PVDF are dispersed together in an organic solvent and ground to form a slurry. The slurry is then coated onto a diaphragm and dried to obtain a CSP diaphragm.

[0015] S3: Preparation of LCSP membrane:

[0016] After adding electrolyte to the surface of the CSP membrane, a lithium sheet is placed on top, and in-situ lithiation is performed by applying pressure to the CSP membrane through the lithium sheet to obtain the LCSP membrane.

[0017] Preferably, step S1 includes one or more of the following:

[0018] i) The cobalt source is one or more of anhydrous cobalt acetate, anhydrous cobalt sulfate, anhydrous cobalt nitrate, anhydrous cobalt carbonate, cobalt naphthenate, anhydrous cobalt chloride, anhydrous cobalt bromide, cobalt borate, and cobalt citrate;

[0019] ii) The first sulfur source is thiourea;

[0020] iii) The mass ratio of cobalt source, polyvinylpyrrolidone and first sulfur source is 6-10:8-12:1-10;

[0021] iv) The second sulfur source is sulfur powder;

[0022] v) The mass ratio of black powder to the second sulfur source is 1 to 6:1.

[0023] Preferably, step S1 includes one or more of the following:

[0024] i) Dissolve cobalt-based ethylene glycol, polyvinylpyrrolidone, and thiourea and reflux them at 120–180 °C for 2–6 h.

[0025] ii) Solid precursors are subjected to argon atmosphere at 1–5 °C·min -1 The temperature is increased to 800℃ at a rate of [missing information] and held at that temperature for 1–6 hours;

[0026] iii) The mixture of black powder and sulfur powder is vulcanized at 200-500°C for 1-6 hours under an argon atmosphere.

[0027] Preferably, in step S1, after the vulcanization is completed, the sealed container is unsealed and calcination continues to allow the excess sulfur to completely volatilize.

[0028] Preferably, after vulcanization, the sealed container is unsealed and calcined at 200–500°C for 1–6 hours to allow excess sulfur to completely volatilize.

[0029] Preferably, step S2 includes one or more of the following:

[0030] i) The conductive carbon black mentioned is Super P;

[0031] ii) The mass ratio of CoS2 / Co3S4 composite material, conductive carbon black and PVDF is 4-8:1-3:1-3;

[0032] iii) The organic solvent mentioned is NMP;

[0033] iv) The diaphragm mentioned is a PP diaphragm.

[0034] Preferably, in step S3, the in-situ lithiation is: applying pressure to the lithium sheet covering the surface of the CSP separator to cause lithiation of the CSP separator, and the duration of the lithiation process is within 45 seconds.

[0035] The second aspect of this invention discloses a ceramic composite lithium-supplementing separator, which is prepared by any of the methods described above.

[0036] The third aspect of this invention discloses the application of a ceramic composite lithium-filling separator as described above in a lithium-ion battery.

[0037] Preferred,

[0038] When the ceramic composite lithium-supplementing separator is assembled in a half-cell, the half-cell is formed by pressing together a positive electrode shell, a positive electrode sheet, a ceramic composite lithium-supplementing separator, a lithium sheet, nickel foam, and a negative electrode shell, wherein an electrolyte is dropped onto the surface of the ceramic composite lithium-supplementing separator.

[0039] When the ceramic composite lithium-replenishing separator is assembled in a full battery, the full battery is formed by pressing together a positive electrode shell, a positive electrode sheet, a ceramic composite lithium-replenishing separator, a negative electrode sheet, a stainless steel sheet, nickel foam, and a negative electrode shell, wherein an electrolyte is dropped onto the surface of the ceramic composite lithium-replenishing separator.

[0040] Preferably, the half-cell is a lithium iron phosphate|Li half-cell or a graphite half-cell; the full cell is a lithium iron phosphate|graphite full cell.

[0041] The working principle of this invention is as follows:

[0042] A CoS2 / Co3S4 composite material was synthesized using a simple reflux condensation method. This material exhibits high lithium storage capacity and good structural stability. Super P was then added to form carbon-coated CoS2 / Co3S4 composite nanoparticles. This highly conductive nanostructure accelerates the lithiation reaction rate and improves the degree of lithiation. The resulting CoS2 / Co3S4 composite material retains its nanostructure after the reaction, allowing for faster lithium ion extraction during charging and contributing more capacity. The carbon-coated CoS2 / Co3S4 composite nanoparticles were then applied to commercial PP separators via slurry coating, a process compatible with current lithium-ion battery manufacturing processes.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] This method synthesizes carbon-coated CoS2 / Co3S4 nanoparticles (a CoS2 / Co3S4 composite material coated with conductive carbon black) using a condensation-reflux followed by high-temperature sintering. These nanoparticles are then coated onto a commercial PP separator, and a Li2S / Co lithium supplementation separator (LCSP) is prepared via in-situ lithiation. The manufacturing process of this functional separator is compatible with current lithium-ion battery production processes, making it an ideal method for industrial-scale lithium supplementation.

[0045] The LCSP membrane is fully lithiated in just 45 seconds, and the resulting Li2S / Co coating exhibits a high lithium replenishment capacity (993 mA·h·g). -1 The degree of lithium replenishment can be precisely controlled by adjusting the loading of the lithium replenishment coating.

[0046] LCSP separators can significantly improve the specific capacity of lithium iron phosphate / graphite batteries, and the energy density is also improved accordingly. Attached Figure Description

[0047] Figure 1 XRD patterns of (a) CoS2 / Co3S4 composite material and (b) Li2S / Co product.

[0048] Figure 2 SEM images of the coating surfaces of (a,b) CSP membranes and (c,d) LCSP membranes.

[0049] Figure 3 Specific capacity diagram of negative electrode half-cells assembled with LCSP separator, CSP separator, and PP separator.

[0050] Figure 4 Cross-sectional SEM images and corresponding elemental distribution diagrams of (ac)CSP diaphragm and (df)LCSP diaphragm.

[0051] Figure 5 The cycling performance and charge-discharge curves of the lithium iron phosphate cathode (a) at 0.5C and (b) are shown; the cycling performance and first charge-discharge curve of the graphite anode (c) at 0.5C and (d) are shown.

[0052] Figure 6 The first charge-discharge curves of graphite, lithium iron phosphate half-cells and full cells are shown (the battery capacity is normalized based on the specific capacity of lithium iron phosphate being 1).

[0053] Figure 7 The first charge-discharge curves of LiFePO4|graphite full cells using different separators are shown.

[0054] Figure 8 The cycling performance of (a) LiFePO4|graphite full cells with different separators; charge-discharge curves of full cells assembled with (b) PP separators and (c) LCSP separators at different number of cycles.

[0055] Figure 9 The specific capacity and energy density of the two types of membrane batteries are given. Detailed Implementation

[0056] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0057] Unless otherwise specified, the reagents used in the following description are conventional commercial products, the methods used are well-known in the art, and other matters not covered herein are prior art.

[0058] A method for preparing a ceramic composite lithium-supplementing separator includes the following steps:

[0059] S1: Preparation of CoS2 / Co3S4 composite material:

[0060] Cobalt source was dissolved in ethylene glycol, and then polyvinylpyrrolidone and a first sulfur source were added to react and obtain a solid precursor. The solid precursor was calcined under a protective atmosphere, and the black powder obtained after calcination was mixed with a second sulfur source. Then it was transferred to a closed container for calcination to carry out vulcanization and obtain CoS2 / Co3S4 composite material.

[0061] S2: Preparation of CSP membrane:

[0062] CoS2 / Co3S4 composite material, conductive carbon black and PVDF are dispersed together in an organic solvent and ground to form a slurry. The slurry is then coated onto a diaphragm and dried to obtain a CSP diaphragm.

[0063] S3: Preparation of LCSP membrane:

[0064] After adding electrolyte to the surface of the CSP membrane, a lithium sheet is placed on top, and in-situ lithiation is performed by applying pressure to the CSP membrane through the lithium sheet to obtain the LCSP membrane.

[0065] in,

[0066] In step S1:

[0067] The cobalt source is one or more of anhydrous cobalt acetate, anhydrous cobalt sulfate, anhydrous cobalt nitrate, anhydrous cobalt carbonate, cobalt naphthenate, anhydrous cobalt chloride, anhydrous cobalt bromide, cobalt borate, and cobalt citrate; furthermore, the cobalt source is preferably anhydrous cobalt acetate.

[0068] The primary sulfur source is thiourea;

[0069] The mass ratio of cobalt source, polyvinylpyrrolidone, and first sulfur source is 6-10:8-12:1-10; further, the mass ratio is 8:10.8:8.

[0070] The second sulfur source is sulfur powder;

[0071] The mass ratio of black powder to the second sulfur source is 1 to 6:1; further, the mass ratio is 3:1.

[0072] Ethylene glycol, polyvinylpyrrolidone, and thiourea dissolved in cobalt source were refluxed at 120–180 °C for 2–6 h; further, they were refluxed at 150 °C for 4 h.

[0073] Solid precursors were subjected to argon atmosphere at 1–5 °C·min -1 The temperature was increased to 800℃ at a rate of [missing information] and held for 1–6 hours; further, [missing information] at a rate of 2℃·min [missing information]. -1 The temperature was increased to 800℃ at a rate of [missing information] and held at that temperature for 2 hours.

[0074] The mixture of black powder and sulfur powder is vulcanized at 200–500°C for 1–6 hours under an argon atmosphere; further, it is vulcanized at 300°C for 2 hours.

[0075] In step S1, after the vulcanization is completed, the sealed container is unsealed and calcination continues to allow the excess sulfur to completely volatilize. Specifically, after the vulcanization is completed, the sealed container is unsealed and calcination continues at 200-500℃ for 1-6 hours to allow the excess sulfur to completely volatilize. Further, calcination is carried out at 300℃ for 2 hours.

[0076] In step S2:

[0077] The conductive carbon black is Super P;

[0078] The mass ratio of CoS2 / Co3S4 composite material, conductive carbon black and PVDF is 4-8:1-3:1-3; further, the mass ratio is 7:2:1.

[0079] The organic solvent is NMP;

[0080] The diaphragm is a PP diaphragm.

[0081] In step S3:

[0082] In-situ lithiation involves applying pressure to the lithium sheet covering the surface of the CSP separator (applying pressure from the lithium sheet side to the CSP separator) to cause lithiation of the CSP separator. The duration of this lithiation process is less than 45 seconds.

[0083] The ceramic composite lithium-ion separator prepared by the above method can be used in lithium-ion batteries. When assembled as a half-cell, it is formed by pressing together a positive electrode shell, a positive electrode sheet, a ceramic composite lithium-ion separator, a lithium sheet, nickel foam, and a negative electrode shell, wherein an electrolyte is dropped onto the surface of the ceramic composite lithium-ion separator. When assembled as a full-cell, it is formed by pressing together a positive electrode shell, a positive electrode sheet, a ceramic composite lithium-ion separator, a negative electrode sheet, a stainless steel sheet, nickel foam, and a negative electrode shell, wherein an electrolyte is dropped onto the surface of the ceramic composite lithium-ion separator. The half-cell is preferably a lithium iron phosphate (LiFePO4) / LiFePO4 half-cell or a graphite half-cell; the full-cell is preferably a lithium iron phosphate (LiFePO4) / graphite full-cell.

[0084] Example 1

[0085] CoS 2 / Preparation of Co3S4 composite materials

[0086] 8 g of anhydrous cobalt acetate was dissolved in 350 mL of ethylene glycol, then 10.8 g of polyvinylpyrrolidone (PVP, molecular weight 58000) and 8 g of thiourea were added and stirred thoroughly until completely dissolved. The solution was transferred to a round-bottom flask and placed in an oil bath. The solution was refluxed at 150 °C for 4 h. After cooling, the solution was filtered and washed three times with deionized water and dried in an oven at 80 °C for 12 h to obtain the precursor. The precursor was transferred to a tube furnace and held at 800 °C for 2 h in an argon atmosphere at a heating rate of 2 °C / min. -1 The obtained black powder was ground and mixed with sulfur powder at a mass ratio of 3:1. The mixture was then poured into a corundum boat and tightly wrapped with tin foil. It was then sulfurized at 300°C for 2 hours in a tube furnace under an argon atmosphere. Finally, the tin foil was removed and the mixture was treated at 300°C for another 2 hours to volatilize the excess sulfur, yielding the product CoS2 / Co3S4.

[0087] Preparation of CSP membrane

[0088] CoS2 / Co3S4 composite, Super P, and PVDF were dispersed in NMP solvent at a mass ratio of 7:2:1 and ground to obtain a fine and uniform slurry. This slurry was then coated onto a commercial PP separator using a doctor blade and subsequently dried in a 50°C vacuum oven to obtain a CSP separator. Different loading capacities of coated separators can be obtained by adjusting the doctor blade thickness.

[0089] Preparation of LCSP membrane

[0090] The CSP membrane was cut into 19mm diameter discs, and after adding an appropriate amount of electrolyte, a lithium sheet was placed on top, and a certain pressure was applied. After reacting for a certain period of time, the lithium sheet was removed, yielding the LCSP lithium-added membrane. The reaction was carried out under an inert atmosphere in a glove box.

[0091] Comparative Example 1

[0092] Preparation of CoS2 / Co3S4 composite materials

[0093] 8 g of anhydrous cobalt acetate was dissolved in 350 mL of ethylene glycol, then 10.8 g of polyvinylpyrrolidone (PVP, molecular weight 58000) and 8 g of thiourea were added and stirred thoroughly until completely dissolved. The solution was transferred to a round-bottom flask and placed in an oil bath. The solution was refluxed at 150 °C for 4 h. After cooling, the solution was filtered and washed three times with deionized water and dried in an oven at 80 °C for 12 h to obtain the precursor. The precursor was transferred to a tube furnace and held at 800 °C for 2 h in an argon atmosphere at a heating rate of 2 °C / min. -1 The obtained black powder was ground and mixed with sulfur powder at a mass ratio of 3:1. The mixture was then poured into a corundum boat and tightly wrapped with tin foil. It was then sulfurized at 300°C for 2 hours in a tube furnace under an argon atmosphere. Finally, the tin foil was removed and the mixture was treated at 300°C for another 2 hours to volatilize the excess sulfur, yielding the product CoS2 / Co3S4.

[0094] Preparation of CSP membrane

[0095] The CoS2 / Co3S4 complex, Super P, and PVDF were dispersed in NMP solvent at a mass ratio of 7:2:1.

[0096] The mixture was ground to obtain a fine and uniform slurry, which was then coated onto a commercial PP separator using a scraper. The slurry was then dried in a 50°C vacuum oven to obtain a CSP separator. The CSP separator was then cut into round pieces with a diameter of 19mm.

[0097] Comparative Example 2

[0098] Preparation of PP membrane

[0099] Commercial PP diaphragms are placed in a 50°C vacuum oven for baking, and then cut into round pieces with a diameter of 19mm.

[0100] Preparation of electrode sheets

[0101] Lithium iron phosphate electrode: Lithium iron phosphate, Super P, and PVDF are added to a vacuum mixer in a mass ratio of 94:2:4. An appropriate amount of NMP solvent is added and stirred to obtain a fine and uniform slurry. This slurry is then coated onto carbon-coated aluminum foil using a scraper and dried overnight in a 70°C oven. The electrode is then compacted using a roller press and cut into the required size for later use.

[0102] The preparation method of graphite electrode sheets is basically the same as that of lithium iron phosphate electrode sheets, except that the binder is replaced with PAALi and the current collector is replaced with copper foil.

[0103] The lithium iron phosphate electrode loading is 12-15 mg·cm³. -2 The graphite electrode loading is 6-8 mg·cm³. -2 .

[0104] Battery assembly and testing

[0105] Battery assembly

[0106] The battery assembly was carried out in a glove box under an argon atmosphere, with water and oxygen content not exceeding 0.1 ppm.

[0107] The coin cell model used in this scheme is CR2032. For a half-cell, the positive electrode and the separator prepared in Example 1, Comparative Example 1, or Comparative Example 2 are stacked sequentially on the positive electrode shell. After adding electrolyte, a lithium sheet and nickel foam are stacked on top. The negative electrode shell is then covered, and the cells are transferred to a packaging machine for pressing and molding. When assembling a lithium-ion full cell, the lithium sheet is replaced with a negative electrode, and a stainless steel sheet is added between it and the nickel foam. In the above, the positive electrode is a lithium iron phosphate electrode, and the negative electrode is a graphite electrode.

[0108] The electrolyte used in the test battery was a 1M lithium hexafluorophosphate (LiPF6) ethylene carbonate (EC) / diethyl carbonate (DEC) solution (volume ratio 1:1), with 5wt% fluoroethylene carbonate (FEC) added as an additive. The electrolyte volume was 50 μL (coin cell).

[0109] When assembling a full battery, the negative electrode capacity should be 10% excess to match the capacity of the positive electrode.

[0110] The test voltage range for graphite half-cells is 0.01-2V, while the test voltage range for lithium iron phosphate|Li half-cells and lithium iron phosphate|graphite full cells is 2.5-4V. The CV curve test voltage range is 2.5-4V, with a scan rate of 0.1mV·s. -1 All battery tests were conducted at 25°C.

[0111] Figure 1 (a) shows the XRD pattern of the synthesized CoS2 / Co3S4 composite material. The peaks of the sample correspond perfectly to the standard cards for CoS2 (PDF#70-2866) and Co3S4 (PDF#42-1448), proving the successful preparation of the composite material and the absence of other impurity phases. The large peak widths in the figure indicate that the material particles are small, which is beneficial to the rapid progress of the subsequent lithiation reaction. Figure 1 As shown in (b), the product after in-situ lithiation treatment has two small diffraction peaks at 27.0° and 44.9°, proving the formation of Li2S after the reaction. No diffraction peaks of elemental Co were observed, possibly because the Co particles are too small and the diffraction peaks are masked by the background (the peak at around 18° is the diffraction peak of the polyimide tape used during sample preparation).

[0112] The CSP membrane was characterized by SEM, such as... Figure 2As shown in (a,b), the CoS2 / Co3S4 composite material consists of uniformly sized nanoparticles with a diameter of about 50 nm, which are evenly and evenly distributed on the membrane substrate. Figure 2 (c, d) are SEM images of the LCSP membrane coating. The images show that the overall morphology of the coating remains largely unchanged after lithiation; the particle distribution is still smooth and uniform, only the size is slightly larger, and the adhesion between particles is tighter. The nanoscale particle structure facilitates rapid lithiation and results in a higher degree of lithiation. Furthermore, lithium ions can be rapidly extracted during charging, providing greater replenishment capacity.

[0113] from Figure 3 It can be seen that the capacity of the LCSP membrane is much higher than that of the CSP membrane and the commercial PP membrane, indicating that the LCSP membrane has achieved in-situ lithiation through brief contact with the lithium metal segment, replenishing a large amount of lithium. Meanwhile, the capacities of the CSP membrane and the commercial PP membrane are almost identical, indicating that the CoS2 / Co3S4 composite material has good cycle stability and does not consume additional lithium ions.

[0114] from Figure 4 (ac) Cross-sectional SEM images and corresponding X-ray energy dispersive spectroscopy (EDS) analysis of the CSP separator show that the CSP separator coating thickness is only 2.4 μm, and the CoS2 / Co3S4 composite material is uniformly distributed within it. In contrast, in the LCSP separator after in-situ lithiation... Figure 4 (d) Due to the introduction of lithium ions, the particle size of the material increases and the coating thickness also increases accordingly, but it is still only 3μm, which does not have a significant impact on the volumetric energy density at the battery scale. Figure 4 The EDS energy spectrum (e,f) shows that the lithiation product Li2S / Co remains uniformly distributed in the coating.

[0115] The electrochemical performance of the LCSP lithium supplementation membrane was studied using a lithium iron phosphate|graphite full cell system. Figure 5 The graphite and lithium iron phosphate half-cells were tested at 0.5C (graphite: 1C = 372 mA·g). -1 Lithium iron phosphate: 1C = 170 mA·g -1 The cycling performance and charge-discharge curves of different cycles were shown. The lithium iron phosphate cathode voltage rapidly rose to 3.45V during charging and remained stable, corresponding to the phase transition from iron phosphate to lithium iron phosphate. The voltage increased again until all lithium ions were completely desorbed, and then stopped at the upper charging voltage limit. Its first-cycle specific capacity was 153 mA·h·g. -1 After 250 cycles, it still has 151 mA·h·g. -1 The capacity decay was essentially zero, and the positive electrode charge-discharge curve remained almost unchanged. The first-cycle discharge capacity of the graphite negative electrode was 424 mA·h·g. -1However, the charging specific capacity is only 372 mA·h·g -1 The initial coulombic efficiency was 88%. The capacity loss primarily stemmed from the irreversible capacity loss resulting from the formation of the SEI film on the surface during the first discharge. The graphite anode retained 83% of its capacity after 200 cycles, maintaining a stable charge-discharge curve with only a slight decrease in capacity. Both the positive and negative electrodes exhibited good cycling and structural stability; therefore, the influence of electrode materials and processes on performance could be eliminated in the electrochemical testing of the full cell.

[0116] A graphite-based lithium iron phosphate full cell was then assembled, with the Li2S / Co coating mass matched to 5% of the cathode material mass. Its first-cycle charge-discharge curve is shown below. Figure 6 As shown in the figure, all curves are normalized with the capacity of lithium iron phosphate (LFP) set to 1. The negative and positive electrodes in the full cell are matched at a capacity ratio of 1.1:1. The shading indicated by number 1 in the graphite charge-discharge curve represents the capacity loss caused by the formation of the first SEI film. After assembling the graphite with an LFP positive electrode into a full cell, this irreversible capacity will consume the active lithium ions in the LFP positive electrode. This corresponds to the difference in discharge specific capacity between the LFP half-cell and the LFP|graphite full cell in the figure, i.e., the shading indicated by number 2.

[0117] Constant current charge-discharge tests were performed on both sets of batteries. Figure 7 The first charge-discharge curves of the batteries at 0.1C are shown. During charging, the PP membrane battery and the LCSP membrane battery begin to delithigate and contribute capacity at approximately 2V and 0.5V, respectively, which is consistent with the results of the cyclic voltammetry curves. The specific capacity of the PP membrane battery during the first charge cycle is 163.1 mA·h·g. -1 The discharge specific capacity is 112.6 mA·h·g. -1 In comparison, the LCSP separator boasts a first-cycle specific capacity of up to 195.5 mA·h·g. -1 The increase in charging capacity mainly comes from the capacity contributed by the lithium insertion / extraction of the lithium-ion replenishing membrane. Meanwhile, the discharge specific capacity of the LCSP membrane reaches 150.3 mA·h·g. -1 It is basically on par with the maximum capacity that lithium iron phosphate batteries can actually achieve, and 37.7 mA·h·g higher than PP membrane batteries. -1 Thanks to the replenishment of active lithium ions by the LCSP separator during the first charge cycle, the discharge specific capacity of the lithium iron phosphate|graphite full battery has been significantly improved.

[0118] Figure 8(a) Cycling performance of a lithium iron phosphate|graphite full cell assembled with PP and LCSP separators at 0.5C. The first two cycles used a small current of 0.1C to activate the cell and allow the lithium ions in the lithium-replenishing coating to be completely removed. The compensation of active lithium ions by the LCSP separator in the first cycle improved the discharge capacity of the cell. In addition, the LCSP separator cell still has a capacity of 103.5 mA·h·g after 200 cycles. -1 The LCSP (Lithium-ion SP) separator achieved a capacity retention of 74.8% and an average coulombic efficiency of 99.8%. In contrast, the PP (Polypropylene) separator battery only retained 60% of its capacity and achieved a coulombic efficiency of 99.3% after 200 cycles. This result further demonstrates the excellent chemical and electrochemical stability of the LCSP separator during cycling, indicating that the introduction of the lithium-ion coating did not negatively impact battery performance. On the contrary, the coulombic efficiency and cycle stability of the LCSP separator battery were improved. Figure 8 As shown in (c), the charge-discharge curves of LCSP membrane batteries at different cycle counts largely overlap, with the capacity gradually decreasing as the number of cycles increases. In contrast, PP membrane batteries not only experience faster capacity decay, but their polarization voltage also gradually increases. Figure 8 (b) The reason for this may be that the introduction of the inorganic lithium-replenishing coating improves the wettability of the membrane to the electrolyte, and the lithium ions migrate at a faster rate at the electrode-electrolyte interface, thereby accelerating the electrode reaction kinetics.

[0119] Figure 9 The first-cycle specific capacity and gravimetric energy density of batteries with different separators were compared. The energy density was calculated based on the total mass of the positive and negative electrodes, while the mass of the lithium replenishment coating was taken into account in the LCSP separator. During the first charge cycle of the LCSP separator battery, lithium ions from the Li2S / Co lithium replenishment coating were released and migrated to the negative electrode. These lithium ions, along with those released from the positive electrode, participated in the SEI film formation and the electrode reactions at the negative electrode, compensating for the irreversible capacity loss during the first cycle. Therefore, the battery's first-cycle discharge specific capacity reached as high as 150.3 mA·h·g. -1 Compared to the 112.6 mA·h·g of PP membrane batteries -1 The increase reached 33.5%. Even taking into account the quality of the lithium replenishment coating, the battery using the LCSP separator still exhibited 285 Wh·kg⁻¹. -1 The high energy density of PP membrane batteries, while that of PP membrane batteries is only 220Wh / kg. -1 The energy density increased by 29.5%, mainly due to the high lithium replenishment capacity of the Li2S / Co composite material.

[0120] In summary, this method synthesized a CoS2 / Co3S4 composite material using a high-temperature sintering method following condensation reflux, and coated it onto a commercial PP separator. An in-situ lithiation process was then employed to prepare a Li2S / Co lithium supplementation separator (LCSP). The manufacturing process of this functional separator is compatible with current lithium-ion battery production processes, making it an ideal industrial-scale lithium supplementation method. Complete lithiation of the LCSP separator requires only 45 seconds, and the resulting Li2S / Co coating exhibits a high lithium supplementation capacity (993 mA·h·g). -1 By adjusting the loading of the lithium-filling coating, the degree of lithium replenishment can be precisely controlled. The LCSP separator significantly improves the specific capacity of lithium iron phosphate|graphite batteries, and the energy density is also correspondingly increased.

[0121] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a ceramic composite lithium-supplementing separator, characterized in that, Includes the following steps: S1: Preparation of CoS2 / Co3S4 composite material: A cobalt source was dissolved in ethylene glycol, and then polyvinylpyrrolidone and a first sulfur source were added to react and obtain a solid precursor. The solid precursor was calcined under a protective atmosphere, and the black powder obtained after calcination was mixed with a second sulfur source. The mixture was then transferred to a closed container for calcination to carry out vulcanization, resulting in a CoS2 / Co3S4 composite material. In this process, ethylene glycol containing a cobalt source, polyvinylpyrrolidone, and thiourea as the first sulfur source were refluxed at 120-180°C for 2-6 hours. S2: Preparation of CSP membrane: CoS2 / Co3S4 composite material, conductive carbon black and PVDF are dispersed together in an organic solvent and ground to form a slurry. The slurry is coated on a diaphragm and dried to obtain a CSP diaphragm. The mass ratio of CoS2 / Co3S4 composite material, conductive carbon black and PVDF is 4~8:1~3:1~3. S3: Preparation of LCSP membrane: After adding electrolyte to the surface of the CSP membrane, a lithium sheet is placed on top, and in-situ lithiation is performed by applying pressure to the CSP membrane through the lithium sheet to obtain the LCSP membrane.

2. The method for preparing a ceramic composite lithium-supplementing separator according to claim 1, characterized in that, Step S1 includes one or more of the following: i) The cobalt source is one or more of the following: anhydrous cobalt acetate, anhydrous cobalt sulfate, anhydrous cobalt nitrate, anhydrous cobalt carbonate, cobalt naphthenate, anhydrous cobalt chloride, anhydrous cobalt bromide, cobalt borate, and cobalt citrate; ii) The mass ratio of cobalt source, polyvinylpyrrolidone and first sulfur source is 6~10:8~12:1~10; iii) The second sulfur source is sulfur powder; iv) The mass ratio of black powder to the second sulfur source is 1~6:

1.

3. The method for preparing a ceramic composite lithium-supplementing separator according to claim 1, characterized in that, Step S1 includes one or both of the following: i) Solid precursors are subjected to argon atmosphere at 1~5℃·min -1 The temperature is increased to 800℃ at a rate of [missing information] and held at that temperature for 1-6 hours. ii) The mixture of black powder and sulfur powder is vulcanized at 200~500℃ for 1~6h under an argon atmosphere.

4. The method for preparing a ceramic composite lithium-supplementing separator according to claim 1, characterized in that, In step S1, after the vulcanization is completed, the sealed container is unsealed and calcination continues to allow the excess sulfur to completely volatilize.

5. The method for preparing a ceramic composite lithium-supplementing separator according to claim 4, characterized in that, After vulcanization, the sealed container is unsealed and calcined at 200-500℃ for 1-6 hours to allow excess sulfur to completely volatilize.

6. The method for preparing a ceramic composite lithium-supplementing separator according to claim 1, characterized in that, Step S2 includes one or more of the following: i) The conductive carbon black mentioned is Super P; ii) The organic solvent mentioned is NMP; iii) The diaphragm mentioned is a PP diaphragm.

7. A ceramic composite lithium-supplementing separator, characterized in that, It is prepared by the method described in any one of claims 1-6.

8. The application of the ceramic composite lithium-filling separator as described in claim 7 in a lithium-ion battery.

9. The application according to claim 8, characterized in that, When the ceramic composite lithium-supplementing separator is assembled in a half-cell, the half-cell is formed by pressing together a positive electrode shell, a positive electrode sheet, a ceramic composite lithium-supplementing separator, a lithium sheet, nickel foam, and a negative electrode shell, wherein an electrolyte is dropped onto the surface of the ceramic composite lithium-supplementing separator. When the ceramic composite lithium-replenishing separator is assembled in a full battery, the full battery is formed by pressing together a positive electrode shell, a positive electrode sheet, a ceramic composite lithium-replenishing separator, a negative electrode sheet, a stainless steel sheet, nickel foam, and a negative electrode shell, wherein an electrolyte is dropped onto the surface of the ceramic composite lithium-replenishing separator.

10. The application according to claim 9, characterized in that, The half-cell is a lithium iron phosphate|Li half-cell or a graphite half-cell; the full cell is a lithium iron phosphate|graphite full cell.

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