A positive electrode lithium supplementing material for releasing active lithium and electrolyte additive in coordination, and preparation and application thereof

Abstract

The application relates to a positive electrode lithium supplementing material for synergistically releasing active lithium and an electrolyte additive and preparation and application thereof, wherein the positive electrode lithium supplementing material is composed of boron, lithium fluoride and Ketjen black which are ball-milled under an inert atmosphere. Compared with the prior art, the positive electrode lithium supplementing material provided by the application breaks through the limitation of the existing lithium supplementing agent, can realize efficient lithium release, no byproduct generation and interface structure optimization in a single system simultaneously.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery material technology, and relates to a positive electrode lithium replenishment material that synergistically releases active lithium and electrolyte additives, as well as its preparation and application. Background Technology

[0002] With the rapid development of new energy vehicles and large-scale energy storage industries, lithium-ion batteries have become a core energy storage technology supporting energy transformation. However, the performance of commercial battery systems is gradually approaching their theoretical limits. How to further improve energy density and cycle life while maintaining existing manufacturing systems and cost frameworks has become a key issue that the industry urgently needs to address. Among these issues, the irreversible loss of active lithium during battery cycling is one of the main bottlenecks causing performance degradation. Active lithium is mainly consumed in large quantities during the initial formation of the solid electrolyte interphase (SEI) film at the negative electrode, and is continuously reduced in subsequent cycles due to interface rupture, regeneration, and electrolyte side reactions. This not only leads to a decrease in initial coulombic efficiency but also accelerates capacity decay, severely restricting the improvement of battery life and energy density.

[0003] To address this issue, researchers have proposed a lithium replenishment strategy: introducing a lithium replenishment agent into the battery to compensate for lithium loss by releasing additional active lithium. Existing lithium replenishment technologies can be broadly categorized into negative electrode lithium replenishment and positive electrode lithium replenishment. Negative electrode lithium replenishment primarily uses metallic lithium or lithium alloys, directly replenishing the lithium source; however, its high reactivity can easily lead to safety hazards, and its processing and storage conditions are stringent, limiting its industrial application. In contrast, positive electrode lithium replenishment agents can release lithium ions at higher potentials, possessing both chemical stability and process compatibility, and are considered to have greater practical potential.

[0004] However, existing cathode lithium supplements still have significant shortcomings. While binary lithium compounds such as Li₂O, Li₂S, and Li₃N are rich in lithium, they are extremely sensitive to moisture in the air, requiring stringent application conditions. Lithium-rich transition metal oxides such as Li₅FeO₄ and Li₆CoO₄, although possessing high capacity, have poor stability in air, easily forming residual alkali that causes gelation of the cathode slurry, and releasing oxygen during oxidation, posing safety risks. Organic lithium supplements such as Li₂C₂O₄ and Li₂C₄O₄ exhibit superior air stability, but their decomposition often involves the release of large amounts of gas, causing electrode peeling, battery swelling, and exacerbated side reactions, especially prominent in high-capacity cells.

[0005] Furthermore, Chinese patent application CN115498176A discloses a composite lithium replenishing agent for lithium-ion batteries based on a chemical reaction. It mentions using lithium compounds such as lithium fluoride and reducing agents such as boron, and then electrochemically oxidizing them under an electric field and thermal energy to generate a stable solid compound without side effects, thereby improving lithium replenishment efficiency. This compound is added to the positive electrode slurry of lithium-ion batteries to enhance battery performance. However, the oxidation potential of the composite lithium replenishing agent provided by this patent is relatively high, requiring additional thermal activation to achieve the desired effect. Moreover, the overall preparation process is complex, and its electrochemical stability needs further improvement.

[0006] In summary, current lithium replenishment agents share several common problems: First, they lack air stability, which is detrimental to material storage and cathode slurry preparation. Second, the generation of byproducts is unavoidable. Solid residues after lithium replenishment, such as metal oxides, cover the electrode surface, causing interface passivation and hindering lithium-ion transport. Meanwhile, gaseous byproducts cause safety issues such as battery swelling.

[0007] Therefore, an ideal lithium replenisher should simultaneously possess the following characteristics: high irreversible capacity to fully compensate for lithium loss; a suitable oxidation potential matching the battery system; excellent air stability; no gas or solid residues generated during the reaction to ensure interface stability; and a low-cost, scalable synthesis method. To date, no material has been able to simultaneously meet these requirements; existing solutions generally involve trade-offs between performance and process, and a true breakthrough has not yet been achieved. Summary of the Invention

[0008] The purpose of this invention is to provide a positive electrode lithium replenishment material that synergistically releases active lithium and electrolyte additives, as well as its preparation and application. It can be added to lithium-ion batteries as a lithium replenishment agent, and can simultaneously achieve efficient lithium release, no by-product generation, and interface structure optimization in a single system.

[0009] The objective of this invention can be achieved through the following technical solutions: In a first aspect, the present invention provides a positive electrode lithium replenishment material that synergistically releases active lithium and electrolyte additives, which is ball-milled and compounded from boron, lithium fluoride and Ketjen black in an inert atmosphere.

[0010] In a second aspect, the present invention provides a method for preparing a positive electrode lithium replenishment material that synergistically releases active lithium and electrolyte additives. Boron, lithium fluoride and Ketjen black are weighed, mixed and placed in a ball mill, and ball milled and mixed under an inert atmosphere to obtain a uniform nano-sized composite powder, which is the positive electrode lithium replenishment material (BLF material).

[0011] In a third aspect, the present invention provides the application of a positive electrode lithium replenishing material that synergistically releases active lithium and electrolyte additives as a lithium replenishing agent in lithium-ion batteries.

[0012] Compared with the prior art, the present invention has the following advantages: 1) BLF material (i.e. positive electrode lithium replenishment material) can provide a high lithium replenishment capacity of more than 800mAh / g, which significantly improves the battery energy density and cycle life. It does not produce gaseous byproducts during the oxidation process, avoids battery swelling and gas-induced stripping of active materials, and ensures the safety and interface stability of the cell after lithium replenishment. 2) No solid byproducts remain after the reaction, preventing electrode surface passivation and the reduction of overall battery energy density by inactive solid residues; 3) The in-situ generated LiBF4 directly compensates for the consumption of lithium salt in the electrolyte and can form a boron-containing SEI at the negative electrode, improve the SEI composition, make the interface structure more stable, and reduce the interface side reactions and continuous lithium loss in subsequent cycles. 4) The lithium replenishment material exhibits excellent air stability, making it easy to store and use. The performance of the lithium replenishment agent does not degrade after being placed in air, and it does not cause the positive electrode slurry to gel. 5) Lithium replenishment materials have a wide range of applications and can be adapted to the lithium replenishment needs of different battery systems; 6) It adopts a simple and efficient ball milling process, and the raw materials are widely available and easy to obtain, which can be prepared on a large scale at low cost and has industrialization potential. Attached Figure Description

[0013] Figure 1 The first charge-discharge curve of the BLF half-cell in Example 6 is shown.

[0014] Figure 2 The first charge-discharge curves of the lithium-ion batteries in Example 10 and Comparative Example 1 are shown.

[0015] Figure 3 The rate performance of the lithium-ion battery in Example 10 is shown.

[0016] Figure 4 This is a comparison chart of the cycle performance of lithium-ion batteries in Example 10 and Comparative Example 1.

[0017] Figure 5 XPS spectra of B 1s and F 1s of the graphite anode of the lithium-ion battery in Example 10 after the first cycle.

[0018] Figure 6 The first charge-discharge curves of the BLF half-cells in Examples 6 and 13 are shown.

[0019] Figure 7 The first charge curves of the BLF half-cells in Example 6 and Comparative Example 4 are shown.

[0020] Figure 8The first-cycle charging curves of the BLF half-cells in Example 6 and Comparative Examples 5 and 6 are shown. Detailed Implementation

[0021] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0023] As used herein, the terms "and / or," "or / and," and "and / or" encompass any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected using at least two conjunctions selected from "and / or," "or / and," and "and / or," it should be understood that, in this application, the technical solution undoubtedly includes solutions connected by "logical AND," and also undoubtedly includes solutions connected by "logical OR."

[0024] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0025] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0026] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0027] Unless otherwise specified, the temperature parameters in this application may be either constant temperature processing or processing within a certain temperature range. The constant temperature processing allows temperature fluctuations within the precision range controlled by the instrument, such as ±5°C, ±4°C, ±3°C, ±2°C, or ±1°C.

[0028] In this document, the term "suitable" as used in phrases such as "suitable combination," "suitable method," and "any suitable method" refers to the ability to implement the technical solution of this application, solve the technical problem of this application, and achieve the expected technical effect of this application.

[0029] In this application, terms such as "further," "even further," and "particularly" are used to describe purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0030] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0031] In the description of the application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0032] Unless otherwise specified, all preparations and tests described herein took place at 25°C.

[0033] The terms “comprising,” “including,” “containing,” “having,” “comprising,” or other variations thereof are intended to cover non-closed inclusion, and no distinction is made between these terms. The term “comprising” means that other steps and ingredients may be added without affecting the final result. The compositions and methods / processes of the present invention comprise, consist of, and substantially consist of the essential elements and limitations described herein, as well as any additional or optional ingredients, components, steps, or limitations described herein. No distinction is made between the terms “efficacy,” “performance,” “effect,” and “potency” herein.

[0034] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions. Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical solutions.

[0035] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, but sequentially is preferred.

[0036] In some embodiments, the present invention provides a positive electrode lithium replenishment material that synergistically releases active lithium and electrolyte additives, which is ball-milled and compounded from boron, lithium fluoride, and Ketjen black in an inert atmosphere.

[0037] Optionally, the molar ratio of boron to lithium fluoride is 1:3 to 5, and can be 1:3, 1:4 or 1:5, etc.; the mass content of Ketjen black in the positive electrode lithium replenishment material is 1 wt.% to 5 wt.%, and can be 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, 5 wt.%, etc.

[0038] This invention reveals that, due to the fact that both lithium fluoride and boron are typical electronic insulators or semiconductors, the interfacial kinetics of their solid-state combination reactions are extremely slow. Conventional conductive carbon materials, such as conductive carbon black (Super P), are typically solid spheres with a small specific surface area (only tens of m²). 2 The lithium nanotubes (CNTs) can only form a loose, point-to-point physical contact with the insulating reactants; while carbon nanotubes (CNTs), although possessing one-dimensional high conductivity, easily aggregate into bundles and lack internal pores, forming only a line-to-point network on the outside of insulating particle clusters, unable to penetrate deep into the particles. Neither of these two conventional carbon materials can fundamentally break down the charge transport barrier of the insulating phase; therefore, when combined with lithium fluoride and boron, the lithium replenishment effect of the resulting lithium-replenishing material is relatively limited.

[0039] This invention, by introducing Ketjen Black and utilizing a mechanical ball milling process, forces nano-sized lithium fluoride and boron elements into the extremely rich internal pores and branched structure of Ketjen Black, forming a three-dimensional conductive network with no dead angles. This high degree of coating and spatial confinement not only minimizes the diffusion path of electrons and lithium ions but also avoids secondary agglomeration of nano-insulating particles during subsequent slurry preparation, thereby significantly reducing the oxidation overpotential of the lithium replenishment reaction. This is the core key to ensuring that the lithium replenishing agent achieves thorough and efficient lithium release in the electrode. In other embodiments, this invention also provides a method for preparing a positive electrode lithium replenishing material that synergistically releases active lithium and electrolyte additives. Boron, lithium fluoride, and Ketjen Black are weighed, mixed, and placed in a ball mill under an inert atmosphere to obtain a uniform nano-sized composite powder, which is the positive electrode lithium replenishing material (BLF material).

[0040] Optionally, the inert atmosphere is provided by argon or nitrogen.

[0041] Optionally, during the ball milling process: the ball milling speed is 500~800 rpm, and the time is 6~10h. Here, when the ball milling speed is too low, such as using a low-energy ball mill of 200~300 rpm or conventional mechanical mixing methods such as sand milling or hand milling, the resulting lithium replenishment material cannot initiate the designed lithium replenishment reaction because the components are difficult to adhere tightly at the nanoscale. Specifically, the delithiation initiation oxidation potential of the lithium replenishment material increases significantly (even exceeding the stable window range of conventional electrolytes), and the reaction kinetics are severely hindered; within the normal charging formation voltage range, only the material on the electrode surface can undergo a chemical reaction, resulting in incomplete release of active lithium and a significant decrease in lithium replenishment specific capacity.

[0042] However, if the ball milling speed is too high (such as reaching 1000 rpm or more), it will not only be difficult to promote further performance improvement, but also may damage the microcrystallineity and hollow structure of Ketjen black due to the huge mechanical shear force and local thermal effect, leading to the amorphous collapse of the conductive network. In addition, especially due to the fact that it is difficult to completely isolate oxygen, the drastic temperature rise caused by high speed may cause a dense oxide layer to form on the boron surface, resulting in a large decrease in the final lithium replenishment capacity.

[0043] In addition, the ball mill can be an existing device such as a planetary high-energy ball mill, and its structure itself is not an innovative point of protection of this invention, so it will not be described in detail here.

[0044] In other embodiments, the present invention also provides the application of a positive electrode lithium replenishing material that synergistically releases active lithium and electrolyte additives as a lithium replenishing agent in lithium-ion batteries.

[0045] The positive electrode lithium replenishment material of the present invention will produce the following reaction during the charging and discharging process of a lithium-ion battery: B + 4LiF → LiBF4 + 3Li + + 3e - The generated active lithium ions are directly used to compensate for lithium loss in the electrode system, while the in-situ generated LiBF4 can quickly dissolve in the electrolyte and participate in the construction of the negative electrode SEI.

[0046] Optionally, the positive electrode material in the lithium-ion battery is one or more of lithium iron phosphate (LFP), lithium manganese iron phosphate (LMFP), lithium cobalt oxide (LCO), and lithium nickel cobalt manganese oxide (NCM), preferably a polyanionic positive electrode such as lithium iron phosphate (LFP) or lithium manganese iron phosphate (LMFP).

[0047] Optionally, the negative electrode material is one or more of graphite, silicon carbide, or silicon.

[0048] Optionally, the process of adding the positive electrode lithium replenishment material to the lithium-ion battery is as follows: The positive electrode lithium replenishing material is combined with a conductive agent, a binder, and a solvent to form a lithium replenishing slurry, which is then coated onto the surface of a separator to prepare a functionalized lithium replenishing separator. During assembly, the side of the functionalized lithium replenishing separator containing the positive electrode lithium replenishing material faces the positive electrode of the lithium-ion battery.

[0049] More specifically, the solvent can be one or a mixture of two of N-methylpyrrolidone (NMP) and dimethylformamide (DMF).

[0050] More specifically, the conductive agent is one or a mixture of Super-P, mesoporous carbon, Ketjen black, carbon nanotubes and graphene.

[0051] More specifically, the adhesive is one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and polyethyl methacrylate (PEMA).

[0052] More specifically, the mass ratio of the positive electrode lithium replenishment material to the conductive agent and binder is (80~95):(2~10):(3~10).

[0053] Optionally, the positive electrode lithium replenishment material can also be directly doped into the positive electrode of a lithium-ion battery as an additive, specifically, its doping amount can be 2 wt.%~5 wt.%.

[0054] When the positive electrode lithium replenishment material is added to a lithium-ion battery, the applicable charging rate of the lithium-ion battery is 0.02C~0.1C, and the cutoff voltage is 4.3~4.5V. When the charging rate is high or the cutoff voltage is low, the capacity performance of the lithium-ion battery using the lithium replenishment material of this invention will be significantly reduced.

[0055] The present invention will be further described below with reference to specific embodiments.

[0056] In the following embodiments, unless otherwise specified, the raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in the art.

[0057] Example 1: Preparation of BLF complex Boron powder and lithium fluoride were accurately weighed at a molar ratio of 1:3, and 2 wt.% of Ketjen black was added as a conductive agent. The mixture was then ball-milled at 600 rpm for 6 h in a planetary high-energy ball mill under an argon atmosphere to obtain BLF composite powder with a particle size distribution of 60–100 nm. Example 2: Preparation of BLF complex The molar ratio of boron to lithium fluoride was adjusted to 1:4, and the rest was the same as in Example 1.

[0058] Example 3: Preparation of BLF complex The molar ratio of boron to lithium fluoride was adjusted to 1:5, and the rest was the same as in Example 1.

[0059] Example 4: Preparation of BLF complex Using the formulation from Example 2, the ball mill speed was increased to 800 rpm, and the ball milling time was 6 hours.

[0060] Example 5: Preparation of BLF complex Using the formulation of Example 2, the ball milling speed was 600 rpm, and the ball milling time was extended to 10 h.

[0061] Example 6: Electrochemical performance testing of BLF complex 1) Positive electrode preparation: The BLF composite obtained in Example 2, the conductive agent Super P, and the binder PVDF were mixed at a mass ratio of 80:10:10. N-methylpyrrolidone (NMP) solvent was added to a solid content of 35 wt.%, and the mixture was dispersed in a homogenizer at 2000 rpm for 20 min to obtain a slurry. The slurry was coated onto an aluminum foil current collector with a 100 μm doctor blade, vacuum dried at 80℃ for 12 h, and then cut into 12 mm diameter electrode sheets.

[0062] 2) Battery assembly: The BLF electrode obtained in step 1 was used in an argon glove box (H2O < 0.1 ppm, O2 < 0.1 ppm) with a lithium metal sheet as the counter electrode and Celgard 2500 as the separator. Electrolyte (1 M LiPF6 in EC:DMC = 3:7 vol.% + 2 wt.% VC) was injected to assemble a CR2032 coin cell.

[0063] 3) Performance Testing: After standing for 12 hours, constant current charge-discharge testing was performed on the Xinwei testing system (voltage window 2.0-4.5 V, 0.02C rate). For example... Figure 1 As shown, the BLF exhibits a charging plateau at approximately 4.2 V, with an initial charge capacity of 822 mAh / g, a discharge capacity of only 12 mAh / g, and an effective lithium replenishment capacity exceeding 800 mAh / g.

[0064] Example 7: Application of BLF complex in cathode lithium supplementation 1) Cathode preparation: Lithium iron phosphate, conductive agent Super P, binder PVDF and BLF lithium supplementer prepared in Example 2 were mixed in a mass ratio of 77:10:10:3, dispersed in NMP to form a slurry (solid content of about 35 wt.%), coated on aluminum foil current collector and dried; 2) Anode preparation: Graphite (Gr), Super P and PVDF are mixed in a ratio of 90:5:5 and dispersed in NMP solvent to prepare anode slurry, which is then coated on copper foil and dried to obtain anode sheet; 3) Battery assembly: Assemble the positive and negative electrode sheets obtained in steps 1) and 2) with the PP separator into a button cell. The electrolyte is 1 M LiPF6 in EC:DMC=3:7 vol.% + 2 wt.% VC. After standing for 12 h, perform constant current charge and discharge test.

[0065] Example 8: Application of BLF complex in cathode lithium supplementation 1) Cathode preparation: Lithium cobalt oxide, conductive agent Super P, binder PVDF and BLF lithium supplementer prepared in Example 2 were mixed in a mass ratio of 77:10:10:3, dispersed in NMP to form a slurry, coated on aluminum foil current collector and dried; 2) Anode preparation: Graphite, Super P and PVDF are mixed in a ratio of 90:5:5 and dispersed in NMP solvent to prepare anode slurry, which is then coated on copper foil and dried to obtain anode sheet; 3) Battery assembly: Assemble the positive and negative electrode sheets obtained in steps 1) and 2) with the PP separator into a button cell. The electrolyte is 1 M LiPF6 in EC:DMC=3:7 vol.% + 2 wt.% VC. After standing for 12 h, perform constant current charge and discharge test.

[0066] Example 9: Application of BLF complex in cathode lithium supplementation 1) Cathode preparation: Lithium nickel cobalt manganese oxide (NCM811), conductive agent Super P, binder PVDF and BLF lithium supplementer prepared in Example 2 were mixed in a mass ratio of 75:10:10:5, dispersed in NMP to form a slurry, coated on aluminum foil current collector and dried. 2) Anode preparation: Silicon carbon (Si / C, the third-generation vapor-deposited silicon carbon of Lanxi Zhide New Energy Materials Co., Ltd., in which silicon accounts for 50%), Super P and CMC are mixed in a ratio of 80:10:10 and dispersed in an aqueous solvent to prepare anode slurry, which is then coated on copper foil and dried to obtain anode sheet. 3) Battery assembly: Assemble the positive and negative electrode sheets obtained in steps 1) and 2) with the PP separator into a button cell. The electrolyte is 1 M LiPF6 in EC:DMC=3:7 vol.% + 2 wt.% FEC. After standing for 12 h, perform constant current charge and discharge test.

[0067] Example 10: Application of BLF complex in membrane lithium supplementation 1) Cathode preparation: Lithium iron phosphate, conductive agent Super P, and binder PVDF are mixed in a mass ratio of 80:10:10, dispersed in NMP to form a slurry, coated on an aluminum foil current collector and dried; 2) Anode preparation: Graphite, Super P and PVDF are mixed in a ratio of 90:5:5 and dispersed in NMP solvent to prepare anode slurry, which is then coated on copper foil and dried to obtain anode sheet; 3) Separator preparation: The BLF powder prepared in Example 2, the conductive agent Super P, and the binder PVDF were mixed at a mass ratio of 80:10:10 and dispersed in NMP to form a slurry (solid content of about 35 wt.%). The slurry was coated on the PP separator using a wire rod coater and dried. The coating thickness was 4 μm. After drying, the BLF lithium supplemental separator was obtained. 4) Battery assembly: Assemble the above positive and negative electrode sheets with the prepared lithium-filling separator into a coin cell. The side of the separator with the BLF coating faces the positive electrode. The electrolyte is 1 M LiPF6 in EC:DMC=3:7 vol.% + 2 wt.% VC. After standing for 12 h, constant current charge and discharge test is performed.

[0068] like Figure 2 As shown, BLF contributes an additional 60 mAh / g of specific capacity in the 4-4.5 V voltage range, effectively compensating for the lithium loss caused by SEI formation in the first cycle, thus increasing the first discharge specific capacity of the LFP||Gr full cell by 17 mAh / g. Figure 3 and Figure 4 As shown, the battery in Example 10 also exhibited good rate performance and cycle stability. The battery from Example 10 was disassembled after the first cycle, and the SEI composition of the negative electrode was analyzed using XPS, as shown... Figure 5 As shown, the formation of boron-containing components in the SEI can be observed from the B 1s and F 1s spectra. Since the electrolyte used itself does not contain boron, the formation of this component demonstrates the formation of boron-containing lithium salt LiBF4 and its role in SEI formation, while also further improving interfacial stability.

[0069] Example 11: BLF complex is used for lithium replenishment in separators. The preparation methods for the positive and negative electrode sheets and the lithium-filling separator are the same as in Example 10, except that the positive and negative electrode materials are replaced with NCM811 and silicon-carbon, respectively, and the BLF coating thickness is increased to 8 μm, as detailed below: 1) Positive electrode preparation: NCM811, conductive agent Super P, and binder PVDF are mixed in a mass ratio of 80:10:10, dispersed in NMP to form a slurry, coated on an aluminum foil current collector and dried; 2) Anode preparation: Silicon carbon, Super P and CMC are mixed in a ratio of 80:10:10 and dispersed in an aqueous solvent to prepare anode slurry, which is then coated on copper foil and dried to obtain anode sheet; 3) Separator preparation: The BLF powder prepared in Example 2, the conductive agent Super P, and the binder PVDF were mixed at a mass ratio of 80:10:10 and dispersed in NMP to form a slurry (solid content of about 35 wt.%). The slurry was coated on the PP separator using a wire rod coater and dried. The coating thickness was 4 μm. After drying, the BLF lithium supplemental separator was obtained. 4) Battery assembly: The above positive and negative electrode sheets are assembled with the prepared lithium-filled separator into a button cell. The side of the separator with BLF coating faces the positive electrode. The electrolyte is 1 M LiPF6 in EC:DMC=3:7 vol.% + 2 wt.% FEC. After standing for 12 h, a constant current charge-discharge test is performed.

[0070] Example 12: Application of BLF composites in pouch cells Using the BLF-coated separator from Example 10, with lithium iron phosphate and graphite as the positive and negative electrodes respectively, the cells were stacked and assembled into a pouch cell. After electrolyte injection, the cells were allowed to stand for 24 hours, followed by constant current charge-discharge testing.

[0071] Comparative Example 1: The preparation methods for the positive and negative electrode sheets and the lithium-ion battery provided in this comparative example are the same as those in Example 7. The difference is that the positive electrode sheet used does not contain BLF lithium supplementer, and its composition is LFP: Super P:PVDF=8:1:1.

[0072] Comparative Example 2: The preparation methods for the positive and negative electrode sheets and the lithium-ion battery provided in this comparative example are the same as those in Example 8. The difference is that the positive electrode sheet used does not contain BLF lithium supplementer, and its composition is LCO: Super P:PVDF=8:1:1.

[0073] Comparative Example 3: The preparation methods for the positive and negative electrode sheets and the lithium-ion battery provided in this comparative example are the same as those in Example 9. The difference is that the positive electrode sheet used does not contain BLF lithium supplementer, and its composition is NCM811: Super P:PVDF=8:1:1.

[0074] Table 1 shows the first discharge specific capacity and cycle capacity retention of Examples 7-11 and Comparative Examples 1-3, demonstrating that the BLF prepared by this invention can effectively compensate for the loss of active lithium in the battery and extend the battery life.

[0075] Example 13: The BLF composite prepared in Example 2 was placed in air for 24 h, and then an electrode was prepared according to the method described in Example 6, and its electrochemical performance was tested. Figure 6 As shown, the charging capacity of BLF did not decrease significantly after being placed in the air, demonstrating its good air stability.

[0076] Table 1

[0077] By comparing the above examples with the comparative examples, it can be seen that the BLF composite exhibits excellent performance in both cathode lithium replenishment and separator lithium replenishment. It can effectively compensate for the first irreversible capacity loss, improve the SEI composition of the anode, and extend the cycle life of the battery for different battery systems.

[0078] Comparative Example 4: Compared to Example 2, it is almost identical, except that boron is not added and only LiF is ball-milled. Figure 7 As shown, Comparative Example 2 showed almost no capacity utilization, indicating that the designed reaction could not occur without elemental B, and LiF could not be used alone as a lithium supplement.

[0079] Comparative Example 5: Most of the components are the same as in Example 2, except that the molar ratio of boron to lithium fluoride is adjusted to 1:5.

[0080] Comparative Example 6: Most aspects are the same as in Example 2, except that the molar ratio of boron to lithium fluoride is adjusted to 1:3. Figure 8 As shown, the charge specific capacity of the BLF complexes in Comparative Examples 5 and 6 was lower than that in Example 6, indicating that excess B or LiF has an adverse effect on the specific capacity. The excess component cannot continue to participate in the subsequent reaction and reduces the overall specific capacity as an inert component.

[0081] Comparative Example 8: The process was largely the same as in Example 2, except that Ketjen black was replaced with an equal mass of carbon nanotubes. The electrode was then prepared and its electrochemical performance was tested according to the method described in Example 6.

[0082] Comparative Example 9: The process was largely the same as in Example 2, except that the ball milling speed was adjusted to 300 rpm, and then the electrode was prepared and its electrochemical performance was tested according to the method described in Example 6.

[0083] Comparative Example 10: The process was largely the same as in Example 2, except that the ball milling speed was adjusted to 1000 rpm, and then the electrode was prepared and its electrochemical performance was tested according to the method described in Example 6.

[0084] Comparative Example 11: The process was largely the same as in Example 2, except that the ball milling process was replaced with sand milling for 6 hours, and then the electrode was prepared and its electrochemical performance was tested according to the method described in Example 6.

[0085] Table 2

[0086] Table 2 shows that the type of conductive carbon and the ball milling speed significantly affect the coating and dispersion of particles and the enhancement of interfacial contact during ball milling. Specifically, regarding the type of conductive carbon, compared to conventional carbon nanotubes, Ketjenblack, after ball milling and composite formation, not only constructs a highly efficient conductive network but also achieves particle coating and dispersion during the ball milling process, enhancing interfacial contact. Its porous structure further promotes electrolyte wetting and ion transport, thereby optimizing the local reaction environment and electron-ion synergistic transport, and improving overall reaction kinetics and rate performance. This effectively increases specific capacity and reduces decomposition potential. For ball milling speed, if the speed is too low, the particle size reduction will be limited, and the interfacial contact between different components will be insufficient. This will cause the delithiation initiation oxidation potential of the lithium-replenishing material to increase significantly (even exceeding the stable window range of conventional electrolytes), severely hindering the reaction kinetics. Furthermore, the lithium-replenishing agent will not be able to exert its lithium-replenishing effect in subsequent applications, resulting in low capacity. If the speed is too high, the capacity will not be further improved, and excess energy will be consumed. In fact, the huge mechanical shear force and local thermal effect may even damage the microcrystallineity and hollow structure of Ketjen black, leading to the amorphous collapse of the conductive network.

[0087] 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 positive electrode lithium replenishment material that synergistically releases active lithium and electrolyte additives, characterized in that, It is composed of boron, lithium fluoride, and Ketjen black in an inert atmosphere.

2. The positive electrode lithium replenishment material with synergistic release of active lithium and electrolyte additives according to claim 1, characterized in that, The molar ratio of boron to lithium fluoride is 1:3~5.

3. The positive electrode lithium replenishment material with synergistic release of active lithium and electrolyte additives according to claim 1, characterized in that, The mass content of Ketjen black in the cathode lithium supplementation material is 1 wt.%~5 wt.%.

4. The method for preparing the positive electrode lithium replenishment material with synergistic release of active lithium and electrolyte additive as described in any one of claims 1-3, characterized in that, Boron, lithium fluoride, and Ketjen black were weighed, mixed, and placed in a ball mill. The mixture was then ball-milled under an inert atmosphere to obtain a uniform nano-sized composite powder, which is the positive electrode lithium supplement material.

5. The preparation method of a positive electrode lithium replenishment material with synergistic release of active lithium and electrolyte additives according to claim 4, characterized in that, During the ball milling process: the ball milling speed is 500~800 rpm, the time is 6~10h, and the ball-to-material ratio is 10~20:

1.

6. The application of the positive electrode lithium replenishing material that synergistically releases active lithium and electrolyte additives as described in any one of claims 1-3 as a lithium replenishing agent in lithium-ion batteries.

7. The application of the positive electrode lithium replenishment material with synergistic release of active lithium and electrolyte additives according to claim 6, characterized in that, The positive electrode material in the lithium-ion battery is one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, and lithium nickel cobalt manganese oxide, and the negative electrode material is one or more of graphite, silicon carbon, or silicon.

8. The application of the positive electrode lithium replenishment material with synergistic release of active lithium and electrolyte additives according to claim 6, characterized in that, The process of adding the positive electrode lithium replenishment material to the lithium-ion battery is as follows: The positive electrode lithium replenishing material is combined with a conductive agent, a binder, and a solvent to form a lithium replenishing slurry, which is then coated onto the surface of a separator to prepare a functionalized lithium replenishing separator. During assembly, the side of the functionalized lithium replenishing separator containing the positive electrode lithium replenishing material faces the positive electrode of the lithium-ion battery. It can also be directly added as an additive to the positive electrode of lithium-ion batteries, with a doping amount of 2 wt.% to 5 wt.%.

9. The application of the positive electrode lithium replenishment material with synergistic release of active lithium and electrolyte additives according to claim 8, characterized in that, The solvent is one or a mixture of two of N-methylpyrrolidone and dimethylformamide; The conductive agent is one or more of Super-P, mesoporous carbon, Ketjen black, carbon nanotubes and graphene, or a mixture thereof. The adhesive is one or more of polyvinylidene fluoride, polytetrafluoroethylene, and polyethyl methacrylate; The mass ratio of positive electrode lithium replenishment material to conductive agent and binder is (80~95):(2~10):(3~10).

10. The application of the positive electrode lithium replenishment material with synergistic release of active lithium and electrolyte additives according to claim 6, characterized in that, When the positive electrode lithium replenishment material is added to the lithium-ion battery, the applicable charging rate of the lithium-ion battery is 0.02C~0.1C, and the cutoff voltage is 4.3~4.5V.

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