Lithium oxalate composite lithium supplement agent and preparation method and application thereof

Abstract

The invention belongs to the technical field of batteries, and particularly relates to a lithium oxalate composite lithium supplement agent, a preparation method thereof, a positive plate, a battery and an electric device. The composite lithium supplement agent comprises composite lithium supplement agent particles, the composite lithium supplement agent particles comprise a lithium oxalate matrix and ion conductors, the ion conductors are distributed in the lithium oxalate matrix, and the concentration of the ion conductors is gradually reduced in the direction from the surfaces of the composite lithium supplement agent particles to the centers of the composite lithium supplement agent particles. The composite lithium supplement agent can obviously reduce the decomposition potential of lithium oxalate, so that the decomposition efficiency of lithium oxalate is obviously improved, and the lithium supplement efficiency is improved.

Description

Technical Field

[0001] This application belongs to the field of battery technology, specifically relating to lithium oxalate composite lithium replenishing agent and its preparation method and application, and more specifically relating to lithium oxalate composite lithium replenishing agent and its preparation method, positive electrode sheet, battery, and electrical device. Background Technology

[0002] While energy density can be improved in existing battery systems by optimizing battery structure or developing high-specific-capacity electrode materials, significant losses of active lithium ions still exist, severely limiting energy density. Currently, sacrificial lithium replenishment additives like Li₂C₂O₄ have attracted widespread attention due to their good stability, low production cost, and high theoretical specific capacity. However, lithium oxalate materials have poor conductivity, and their actual decomposition potential is typically higher than 4.7 V, severely limiting their practical application. Therefore, the technology related to lithium replenishment agents still needs improvement. Summary of the Invention

[0003] This application aims to at least partially address one of the technical problems in related technologies. To this end, this application proposes a lithium oxalate composite lithium replenisher with low decomposition potential and high lithium replenishment efficiency, its preparation method, and its application.

[0004] A first aspect of this application provides a composite lithium supplement agent comprising composite lithium supplement agent particles, the composite lithium supplement agent particles comprising a lithium oxalate matrix and an ion conductor, the ion conductor being distributed in the lithium oxalate matrix, and the concentration of the ion conductor decreasing along the direction from the surface of the composite lithium supplement agent particle to its center.

[0005] This application constructs a structure with a specific ionic conductor distribution in lithium oxalate. On the one hand, it forms a continuous and sufficient lithium-ion transport channel, significantly widening the lithium-ion migration path and greatly enhancing the ionic conductivity of the lithium oxalate matrix. On the other hand, the composite ionic conductor can undergo controlled decomposition simultaneously during the first charging cycle, and the resulting decomposition products can exert a highly efficient catalytic effect, accelerating the decomposition reaction process of lithium oxalate. These effects work synergistically to effectively reduce the decomposition potential of lithium oxalate supplementers, significantly improving the overall decomposition efficiency of lithium oxalate, thereby increasing the overall lithium supplementation efficiency of the composite lithium supplementer particles.

[0006] According to embodiments of this application, the following compounds are included: Li₂C₂O₄·aLi x MO y Among them, Li x MO y The ionic conductor is defined as follows: M represents at least one of Nb, Ta, Al, Zr, and Ti; a is 0.08-0.19; x is 1 or 2; and y is 2 or 3.

[0007] According to an embodiment of this application, along the direction from the surface of the composite lithium replenishing agent particle to its center, the concentration of element M decreases from P1 to P2, wherein the concentration of element M is the atomic percentage of element M content relative to the total content of elements C, O, and M. P1 ranged from 2.4 at% to 5.7 at% P2 is 0.1 at% to 0.3 at%.

[0008] According to embodiments of this application, the ionic conductor includes at least one of LiNbO3, LiTaO3, LiAlO2, Li2ZrO3, and Li2TiO3.

[0009] According to an embodiment of this application, in the XRD spectrum of the composite lithium supplement, the peak intensity ratio Q = I1 / I2 of the first diffraction peak I1 and the second diffraction peak I2 satisfies: 0.32≤Q≤1.75. Wherein, the first diffraction peak is the strongest diffraction peak of the ionic conductor in the XRD spectrum, and the second diffraction peak is the diffraction peak at 2θ of 33.9±0.2° in the XRD spectrum.

[0010] According to an embodiment of this application, the 2θ angle of the first diffraction peak is 23.5±0.3°, 23.6±0.3°, 22.3±0.3°, 42.3±0.3°, or 42.7±0.3°.

[0011] According to embodiments of this application, the above-mentioned composite lithium supplement meets at least one of the following conditions: The Dv50 of the composite lithium supplement particles is 1 μm to 10 μm, specifically 1 μm to 5 μm; The specific surface area of ​​the composite lithium supplement particles is 1 m². 2 / g~10 m 2 / g, specifically 1 m 2 / g~5 m 2 / g.

[0012] A second aspect of this application provides a method for preparing the composite lithium supplement agent described in the first aspect, comprising: Provide lithium oxalate matrix; The lithium oxalate matrix, the first lithium source, and the M source are first mixed in a first solvent to obtain a first mixture; The first mixture was reacted and dried to obtain a composite lithium supplement precursor. The composite lithium supplement precursor is calcined at 300℃-350℃ for 12h-24h in an oxygen or air atmosphere to obtain the composite lithium supplement.

[0013] Therefore, the above-mentioned method for preparing the composite lithium supplement is simple to operate and easy to implement, and can reduce costs, enabling large-scale preparation.

[0014] According to embodiments of this application, the provision of the lithium oxalate matrix includes: The second lithium source and the oxalic acid source are mixed in a second solvent to obtain a second mixture. The second mixture was spray-dried to obtain the lithium oxalate matrix.

[0015] According to embodiments of this application, the above method satisfies at least one of the following conditions: The first lithium source and the second lithium source each individually include at least one of lithium hydroxide and lithium hydroxide monohydrate; The oxalic acid source includes at least one of oxalic acid and oxalic acid dihydrate; The M source includes at least one of Nb(OC2H5)5, Ta(OC2H5)5, Al(OC2H5)3, Zr(OC2H5)4, Ti(OC2H5)4, Nb(OCH(CH3)2)5, Ta(OCH(CH3)2)5, Al(OCH(CH3)2)3, Zr(OCH(CH3)2)4, and Ti(OCH(CH3)2)4; The first solvent includes at least one of the following: an ethanol solution with a volume fraction of 95%-98%, a methanol solution with a volume fraction of 95%-98%, and an isopropanol solution with a volume fraction of 95%-98%. The second solvent includes pure water.

[0016] According to embodiments of this application, the above method satisfies at least one of the following conditions: The molar ratio of the second lithium source, the oxalic acid source, and the M source is (1.95-2.05):1:(0.08-0.19). The concentration of the first lithium source in the first mixture is 0.1 mol / L-1.0 mol / L, specifically 0.2 mol / L-0.4 mol / L.

[0017] A third aspect of this application provides a positive electrode sheet comprising the aforementioned composite lithium supplement. Thus, the positive electrode sheet includes all the features and advantages of the composite lithium supplement described in the first aspect, which will not be elaborated further here.

[0018] A fourth aspect of this application provides a battery comprising the aforementioned positive electrode. Consequently, this battery exhibits high energy density and long cycle life.

[0019] A fifth aspect of this application provides an electrical device comprising the aforementioned composite lithium replenisher, the aforementioned positive electrode, or the aforementioned battery. Therefore, the electrical device has high energy density and cycle life. Attached Figure Description

[0020] Figure 1 This is the EDS scan spectrum of the composite lithium supplement agent of Example 1 of this application. Detailed Implementation

[0021] The embodiments of this application are described in detail below, with examples of these embodiments illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0022] While existing battery systems can improve energy density by optimizing battery structure or developing high-specific-capacity electrode materials, significant amounts of active lithium ions are still lost, severely limiting energy density and lifespan. To further increase the number of active lithium ions in the battery system and thus improve its energy density and lifespan, pre-lithiation technology has emerged.

[0023] From a process perspective, current pre-lithiation technologies can be divided into negative electrode-side pre-lithiation and positive electrode-side pre-lithiation. Compared to negative electrode-side pre-lithiation (typically using metallic lithium), positive electrode-side pre-lithiation generally attracts widespread attention due to its high safety and good process compatibility. Among these methods, adding sacrificial lithium supplementation additives is the most commonly used pre-lithiation method on the positive electrode side.

[0024] Currently, sacrificial lithium replenishment additives mainly employ inorganic lithium-containing compounds. Their mechanism of action involves the irreversible release of lithium ions during the first charge-discharge cycle of the battery to compensate for the loss of active lithium during cycling. Among numerous candidate materials, lithium oxalate is considered a highly promising cathode lithium replenishment agent due to its advantages such as low theoretical oxidation decomposition potential, high chemical stability, and large specific capacity. However, in practical applications, lithium oxalate exhibits a high oxidation decomposition potential (>4.7 V), significantly exceeding the voltage tolerance range of commonly used battery cathode materials. This results in poor compatibility between lithium oxalate and cathode materials, severely limiting its practical application.

[0025] In view of this, this application proposes a composite lithium supplement agent, comprising composite lithium supplement agent particles, wherein the composite lithium supplement agent particles comprise a lithium oxalate matrix and an ion conductor, the ion conductor being distributed in the lithium oxalate matrix, and the concentration of the ion conductor decreasing along the direction from the surface of the composite lithium supplement agent particles to their center.

[0026] This application constructs a structure with a specific ion conductor distribution in lithium oxalate. On the one hand, the surface-enriched ion conductors can form continuous and sufficient lithium-ion transport channels, significantly widening the lithium-ion migration path and greatly enhancing the ion conductivity of the lithium oxalate matrix. On the other hand, the composite ion conductors can undergo controlled decomposition simultaneously during the first charging cycle, and the resulting decomposition products (such as Nb₂O₅, Ta₂O₅, Al₂O₃, ZrO₂, TiO₂, etc.) can exert a highly efficient catalytic effect, accelerating the decomposition reaction of lithium oxalate. Simultaneously, the low concentration of ion conductors at the center of the composite lithium supplement particles maintains the stability of the internal structure of the particles, ensuring the orderly conduction of the decomposition reaction. These effects work synergistically to effectively reduce the decomposition potential of lithium oxalate, significantly improving the overall decomposition efficiency of lithium oxalate, thereby increasing the overall lithium supplementation efficiency of the composite lithium supplement particles.

[0027] The "concentration decrease of ionic conductors" can be a linear decrease of ionic conductors from the surface of the composite lithium replenishing agent particles toward the center, or it can be a gradient decrease (i.e., a step-like decrease).

[0028] According to embodiments of this application, the composite lithium supplement includes the following compounds: Li₂C₂O₄·aLi x MO y Among them, Li x MO y The ionic conductor is defined as follows: M represents at least one of Nb, Ta, Al, Zr, and Ti; a is 0.08-0.19; x is 1 or 2; and y is 2 or 3.

[0029] Therefore, the composite lithium replenisher with the above structure can effectively reduce the delithiation potential of lithium oxalate, thereby improving the overall lithium replenishment efficiency of the composite lithium replenisher particles. Furthermore, within the range of a above, while maximizing the lithium replenishment function of the lithium oxalate matrix, it provides sufficient lithium-ion transport channels, improving the ion transport capacity of the lithium oxalate matrix.

[0030] According to an embodiment of this application, along the direction from the surface of the composite lithium replenishing agent particle to its center, the concentration of element M decreases from P1 to P2, wherein the concentration of element M is the atomic percentage of element M content relative to the total content of elements C, O, and M.

[0031] According to embodiments of this application, the lithium oxalate matrix comprises 70%-95% by mass based on the total mass of the composite lithium supplement particles. Lithium oxalate has good stability, low production cost, and high theoretical specific capacity, which, within the above range, helps to maintain a high battery capacity.

[0032] According to embodiments of this application, P1 is 2.4 at% to 5.7 at%, specifically 2.4 at%, 3 at%, 4 at%, 5 at%, 5.7 at%, or any range between two of these. Within this range, the ionic conductor has a high concentration on the surface of the composite lithium replenishing agent particles, which can significantly reduce interfacial impedance and preferentially catalyze the decomposition reaction on the surface of the composite lithium replenishing agent particles, rapidly initiating the decomposition of the entire composite lithium replenishing agent particle, thereby improving the overall lithium replenishment efficiency of the composite lithium replenishing agent particles.

[0033] According to embodiments of this application, P2 is 0.1 at% to 0.3 at%, specifically 0.1 at%, 0.15 at%, 0.2 at%, 0.25 at%, 0.3 at%, or any range between two of these. Within this range, sufficient ion transport channels are provided, improving ion transport capability while maintaining low cost.

[0034] According to embodiments of this application, the ion conductor includes at least one selected from LiNbO3, LiTaO3, LiAlO2, Li2ZrO3, and Li2TiO3. Therefore, the aforementioned ion conductor exhibits stable chemical properties, good interfacial compatibility with electrode materials, few side reactions, and can provide a lower energy barrier lithium-ion migration path, thereby enhancing the ion conductivity of lithium oxalate.

[0035] According to an embodiment of this application, in the XRD pattern of the composite lithium supplement, the peak intensity ratio Q = I1 / I2 of the first diffraction peak I1 and the second diffraction peak I2 satisfies: 0.32 ≤ Q ≤ 1.75, specifically within the ranges of 0.32, 0.35, 0.5, 0.8, 1.0, 1.2, 1.4, 1.6, 1.75, or any two thereof. The first diffraction peak is the strongest diffraction peak of the ionic conductor in the XRD pattern, and the second diffraction peak is the diffraction peak at 2θ of 33.9 ± 0.2° in the XRD pattern.

[0036] According to embodiments of this application, the 2θ angle of the first diffraction peak is 23.5±0.3°, 23.6±0.3°, 22.3±0.3°, 42.3±0.3°, or 42.7±0.3°. It should be noted that if there are two or more ionic conductors, then the 2θ angle here refers to the strongest diffraction peak of the first diffraction peak in the XRD pattern.

[0037] According to embodiments of this application, the Dv50 of the composite lithium replenishing agent particles is 1 μm to 10 μm, specifically 1 μm to 5 μm. As an example, the Dv50 of the composite lithium replenishing agent can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or any combination thereof. Within these ranges, it is beneficial to achieve uniform dispersion of the composite lithium replenishing agent particles, resulting in a uniform and consistent lithium replenishment effect.

[0038] Dv50 indicates that particles with a diameter smaller than or larger than this value account for 50% of the total particle volume. This can be tested using a laser particle size analyzer.

[0039] According to an embodiment of this application, the specific surface area of ​​the composite lithium supplement particles is 1 m². 2 / g~10 m 2 / g, specifically 1 m 2 / g~5 m 2 / g. As an example, the specific surface area of ​​the composite lithium supplement can specifically be 1 m². 2 / g、2 m 2 / g、3 m 2 / g、4 m 2 / g、5 m 2 / g、6 m 2 / g、7 m 2 / g、8 m 2 / g、9 m 2 / g、10 m 2 / g or any two of the above ranges. Therefore, within the above range, the composite lithium replenishing agent particles have more reactive sites, allowing for more thorough contact between the particles and the electrolyte. This promotes the lithium-ion desorption reaction, effectively reducing the delithiation potential and improving the efficiency of the lithium replenishment reaction.

[0040] A second aspect of this application provides a method for preparing the composite lithium supplement agent described in the first aspect, comprising: S10: Provides lithium oxalate matrix.

[0041] According to an embodiment of this application, providing the lithium oxalate matrix includes: mixing a second lithium source and the oxalic acid source in a second solvent to obtain a second mixture; and spray-drying the second mixture to obtain the lithium oxalate matrix.

[0042] According to the embodiments of this application, the time and temperature for the second mixing step are not limited, as long as the raw materials are completely dissolved and a clear solution is obtained. Specifically, the selection can be made flexibly according to the actual situation.

[0043] According to embodiments of this application, the second lithium source includes at least one of lithium hydroxide and lithium hydroxide monohydrate. Therefore, the aforementioned lithium source can provide lithium ions and is readily available and inexpensive.

[0044] According to embodiments of this application, the oxalic acid source includes at least one of oxalic acid and oxalic acid dihydrate. Therefore, the aforementioned oxalic acid source can provide oxalate ions and is readily available and inexpensive.

[0045] According to an embodiment of this application, the molar ratio of the second lithium source to the oxalic acid source is (1.95-2.05):1, specifically 1.95:1, 2.00:1, and 2.05:1. Within the above range, a pure lithium oxalate matrix can be generated.

[0046] According to embodiments of this application, the second solvent comprises pure water. This facilitates better dissolution of the second lithium source and oxalic acid source, promoting a uniform and complete reaction.

[0047] As can be understood, spray drying first disperses the mixed solution into uniform droplets through an atomizer. The droplets are then sprayed downwards from the top of the drying tower (or come into contact with the hot air flow in parallel or countercurrent flow), forming sufficient heat and mass transfer contact with the high-temperature hot air flow, and rapidly evaporating the solvent.

[0048] According to an embodiment of this application, the inlet air temperature for spray drying is 190℃-250℃, specifically 200℃~220℃. The inlet air temperature for spray drying can be 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, or any range between two of these. Therefore, within the aforementioned inlet air temperature range, drying efficiency can be effectively improved, solvent can be quickly removed, and the structure of the material can be preserved.

[0049] According to an embodiment of this application, the outlet air temperature of the spray dryer is 90℃-120℃, specifically 90℃~105℃. As an example, the outlet air temperature of the spray dryer can be 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃, or any range between two of these. Therefore, within the above-mentioned outlet air temperature range, the moisture content of the lithium oxalate matrix can be effectively controlled, while also helping to maintain a dry environment inside the equipment, reducing equipment corrosion caused by moisture condensation, and ensuring continuous and stable operation of the equipment.

[0050] According to an embodiment of this application, the spray drying pressure is 0.1 MPa-0.5 MPa, specifically 0.2 MPa-0.4 MPa. As an example, the spray drying pressure can be 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, or any combination thereof. Therefore, within the above range, it is helpful to precisely control the droplet size and distribution, so that the particle size of the lithium oxalate matrix is ​​concentrated in the target range.

[0051] According to embodiments of this application, the feed rate for spray drying is 10 r / min to 50 r / min, specifically 10 r / min to 30 r / min. As an example, the feed rate for spray drying can be 10 r / min, 20 r / min, 30 r / min, 40 r / min, 50 r / min, or any range between two of these. Therefore, within the above range, by reasonably controlling the feed rate, the material dispersion state is improved, enhancing the consistency and sufficiency of the drying effect.

[0052] S20: The lithium oxalate matrix, the first lithium source, and the M source are mixed in a first solvent to obtain a first mixture; the first mixture is reacted and dried to obtain a composite lithium supplement precursor.

[0053] In this step, the above substances are mixed in a certain molar ratio and reacted to generate a composite lithium supplement precursor on the surface of the lithium oxalate matrix.

[0054] According to embodiments of this application, the M source includes at least one of Nb(OC2H5)5, Ta(OC2H5)5, Al(OC2H5)3, Zr(OC2H5)4, Ti(OC2H5)4, Nb(OCH(CH3)2)5, Ta(OCH(CH3)2)5, Al(OCH(CH3)2)3, Zr(OCH(CH3)2)4, and Ti(OCH(CH3)2)4; According to an embodiment of this application, the first solvent includes at least one of an ethanol solution with a volume fraction of 95%-98%, a methanol solution with a volume fraction of 95%-98%, and an isopropanol solution with a volume fraction of 95%-98%.

[0055] For example, this application uses an ethanol solution with a volume fraction of 95%-98% as a solvent. The lithium oxalate matrix, the first lithium source and the M source are dispersed in the ethanol and react to form a composite gel precursor on the surface of lithium oxalate (for example, when M is Nb, a gel-like substance containing Li, Nb and O is formed).

[0056] According to an embodiment of this application, the molar ratio of the second lithium source, oxalic acid source, and M source is (1.95-2.05):1:(0.08-0.19). Within this range, the specific capacity and ion conductivity of the lithium oxalate matrix can be balanced, effectively reducing the delithiation potential of the composite lithium supplement particles, thereby improving the decomposition efficiency of the composite lithium supplement particles.

[0057] According to an embodiment of this application, the concentration of the first lithium source in the first mixture is 0.1 mol / L-1.0 mol / L, specifically 0.2 mol / L-0.4 mol / L. As an example, the concentration of the first lithium source in the first mixture can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, or any two of these ranges. Within the above range, precise stoichiometry of lithium oxalate and the ionic conductor in the chemical formula of the target composite lithium supplement particles can be achieved, generating a pure crystalline phase of the composite lithium supplement.

[0058] According to the embodiments of this application, the reaction temperature is not limited. In some embodiments, the reaction can be carried out at room temperature; in other embodiments, the temperature can be appropriately increased to accelerate the reaction rate. The specific temperature should be flexibly selected according to the actual situation.

[0059] According to embodiments of this application, the reaction time is 2-6 hours, specifically 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, or any combination thereof. Within this range, the reaction is allowed to proceed sufficiently to generate a sufficient amount of the composite lithium supplement precursor.

[0060] According to an embodiment of this application, the process before drying further includes: filtration, removal of the filtered mother liquor, and drying to obtain the composite lithium supplement precursor. This step does not limit the filtration method, as long as solid-liquid separation is achieved.

[0061] According to embodiments of this application, the drying process includes at least one of vacuum drying, forced-air drying, and freeze drying. This removes moisture while simultaneously solidifying the composite lithium supplement precursor, enhancing its bonding with the lithium oxalate matrix, and reducing its impact on subsequent calcination treatment.

[0062] S30: Calcining the composite lithium supplement precursor at 300℃-350℃ for 12h-24h in an oxygen or air atmosphere to obtain the composite lithium supplement.

[0063] In this step, the calcination treatment of the composite lithium supplement precursor is precisely controlled. Under the synergistic effect of the aforementioned temperature and time, ion migration and phase transition are guided in the precursor, while organic components, moisture, and volatile impurities are further removed. During this process, oxygen or air provides an additional oxygen source for lattice construction, promoting the formation of lithium-containing metal oxides and ensuring that the metal element M remains stably in the designed target valence state. The calcination temperature provides the thermodynamic driving force, allowing the ionic conductor to gradually diffuse from the surface of the composite lithium supplement particle towards its center. The appropriate holding time promotes sufficient ion migration and diffusion while reducing or avoiding concentration homogenization caused by excessive migration. Under the synergistic control of temperature and time, a composite structure is ultimately formed where the concentration of the ionic conductor decreases from the surface to the center of the composite lithium supplement particle.

[0064] According to an embodiment of this application, after sintering, the process further includes sieving, for example, using a 200-400 mesh sieve. Sieving can remove larger agglomerated particles and ensure the uniformity of the particle size of the composite lithium supplement in the final product.

[0065] In a third aspect of this application, a positive electrode is proposed, comprising the composite lithium supplement agent of the first aspect. This positive electrode includes all the features and advantages of the composite lithium supplement agent described in the first aspect, which will not be repeated here.

[0066] It is understood that the positive electrode sheet includes a positive current collector and a positive electrode material layer disposed on at least one side surface of the positive current collector, the positive electrode material layer including a positive electrode active material. In some embodiments, the aforementioned composite lithium supplement can be directly used as the positive electrode active material; in other embodiments, the positive electrode active material includes the aforementioned composite lithium supplement and the positive electrode active material.

[0067] In some embodiments, the positive electrode active material layer also includes a positive electrode binder and a positive electrode conductive agent. Additives with specific functions and effects, such as positive electrode thickeners, film-forming additives, flame retardants, high-temperature / low-temperature stabilizers, etc., can also be added as needed.

[0068] In some embodiments, when the aforementioned composite lithium supplement is used as the positive electrode active material, additives such as positive electrode binder and positive electrode conductive agent are removed, and the composite lithium supplement accounts for 80%-95% of the mass percentage of the positive electrode active material layer. This helps to obtain a positive electrode sheet with high specific capacity and high ion transport performance.

[0069] As an example, the positive electrode active material may include at least one of lithium iron phosphate, lithium manganese phosphate, lithium iron manganese phosphate, lithium cobalt phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium nickel manganese oxide, and lithium-rich layered oxides or positive electrode active materials commonly used in the art.

[0070] As an example, the positive electrode binder in the positive electrode active material layer may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene-propylene terpolymer, ethylene-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0071] As an example, the positive electrode conductive agent in the positive electrode active material layer may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0072] In a fourth aspect of this application, a battery is proposed, comprising the aforementioned positive electrode. Consequently, this battery exhibits high energy density and long cycle life.

[0073] According to the embodiments of this application, it can be understood that there is no particular limitation on the specific type of battery, which can be a primary battery or a secondary battery; the shape of the battery can be a cylindrical battery, a square battery or other arbitrary shape batteries, and according to the outer packaging, the battery can be a hard-shell battery, a soft-pack battery, etc.; the battery can also be a lithium metal battery, a lithium-ion battery, etc.

[0074] In some embodiments, the battery can be an all-solid-state battery, including the above-mentioned positive electrode, negative electrode, and separator. During the charging and discharging process, lithium ions are inserted and extracted back and forth between the positive electrode and the negative electrode. The separator is disposed between the positive electrode and the negative electrode, mainly to prevent short circuit between the positive electrode and the negative electrode, while allowing lithium ions to pass through.

[0075] In some embodiments, the negative electrode may include a metal sheet, including but not limited to a lithium metal sheet.

[0076] In some embodiments, the negative electrode sheet may include a negative electrode current collector and a negative electrode active material layer disposed on at least one side surface of the negative electrode current collector. As an example, the negative electrode active material layer may include a negative electrode material, a negative electrode thickener, a negative electrode conductive agent, and a negative electrode binder.

[0077] Specifically, the negative electrode current collector can be a metal foil, for example, copper foil. The negative electrode material can include carbon-based materials, silicon-based materials, tin-based materials, etc. The negative electrode binder in the negative electrode material layer can include, but is not limited to, at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS). The negative electrode conductive agent in the negative electrode material layer can include, but is not limited to, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0078] In some embodiments, the separator may be a separator known in the art that can be used in batteries and is stable to the electrolyte used, such as a polyethylene separator, a polypropylene separator, a polyethylene / polypropylene composite separator, etc.

[0079] A fifth aspect of this application discloses an electrical device comprising the aforementioned composite lithium replenisher, the aforementioned positive electrode, or the aforementioned battery. This electrical device exhibits high energy density and cycle life.

[0080] According to embodiments of this application, the specific type of electrical device is not particularly limited and can be any device that uses a battery as a power source or energy storage unit. As examples, electrical devices include, but are not limited to, electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), mobile terminals (e.g., mobile phones, laptops, game consoles, wearable devices, etc.), drones, aerospace equipment, satellites, ships, energy storage systems, and so on.

[0081] It is understood that, in addition to the battery mentioned above, the electrical device also includes other necessary structures and components, all of which can be made with reference to conventional technologies. For example, an electric vehicle may include a body, chassis, tires, navigation system, radar system, steering system, braking system, lubrication system, cooling system, driving system, etc., which will not be described in detail here.

[0082] The embodiments of this application are described in detail below.

[0083] Example 1 1. Preparation of composite lithium supplement: (1) Lithium hydroxide monohydrate and oxalic acid dihydrate were weighed at a molar ratio of 2:1, mixed evenly, and then added to pure water. After stirring until a clear solution was obtained, the mixture was spray-dried. The inlet air temperature of the spray dryer was 195℃, the outlet air temperature was 95℃, the pressure was 0.3 MPa, and the feed rate was set to 25 r / min to obtain the Li2C2O4 matrix. (2) The above Li2C2O4 matrix was dispersed in 95% ethanol by volume, and then lithium hydroxide monohydrate powder was added until the lithium hydroxide solution concentration reached 0.3 mol / L; (3) Nb(OC2H5)5 was then added, wherein the molar ratio of lithium hydroxide monohydrate, oxalic acid dihydrate and niobium ethanol in step (1) was 2:1:0.1. The mixture was stirred and reacted, and after filtration, a composite lithium supplement precursor was obtained. (4) Subsequently, the above precursor was vacuum dried, placed in an oxygen atmosphere, and calcined at 330℃ for 18 h. After sieving, Li₂C₂O₄·0.1LiNbO₃ was obtained. The resulting composite lithium supplement particles had a Dv₅₀ of 2.9 μm and a specific surface area of ​​4.1 m². 2 / g; 2. Preparation of the positive electrode sheet: The above-mentioned composite lithium supplement (as the positive electrode active material), conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are mixed in N-methylpyrrolidone solvent at a mass ratio of 95:2:3 to obtain a positive electrode slurry. The above positive electrode slurry is coated on one side of the positive electrode current collector aluminum foil, dried at 120°C for 6 hours, and then stamped into an electrode sheet with a diameter of 11 mm under a pressure of 100 MPa to obtain the positive electrode sheet; 3. Battery Assembly: A lithium metal sheet with a diameter of 16 mm and a thickness of 1 mm is used as the negative electrode; a Celgard 2400 porous membrane with a thickness of 25 μm is used as the separator; the electrolyte consists of ethylene carbonate (EC), ethyl methyl carbonate (DEC), and LiPF6, with a volume ratio of EC to DEC of 3:7 and a LiPF6 concentration of 1 mol / L. The positive electrode, separator, negative electrode, and electrolyte are assembled into a coin cell in an argon-filled glove box with a water content and oxygen content of less than 5 ppm.

[0084] The specific differences between Examples 2-12 and Comparative Examples 1-3 are shown in Table 1, while other parameters are the same as in Example 1. The composite lithium replenishing agent and coin cells in the aforementioned examples and comparative examples were tested as follows, and the test results are shown in Table 2.

[0085] Performance testing Peak intensity ratio Q: The phases of different composite lithium supplements were analyzed using X-ray powder diffraction. The strongest diffraction peak of the ionic conductor was located at 2θ between 23.5±0.3° (LiNbO3), 23.6±0.3° (LiTaO3), 22.3±0.3° (LiAlO2), 42.3±0.3° (Li2ZrO3), or 42.7±0.3° (Li2TiO3). In the composite lithium supplement, the first diffraction peak is the strongest diffraction peak of the ionic conductor in the XRD pattern, and the second diffraction peak is the diffraction peak at 2θ of 33.9±0.2° in the XRD pattern. The peak intensity ratio of the first diffraction peak I1 and the second diffraction peak I2 is Q = I1 / I2.

[0086] Concentration of ionic conductors: An analytical region was set at a depth of 0.5 μm from the surface of the composite lithium supplement particle towards the center. Four measurement points were uniformly selected within each analytical region, and the concentrations of element M, element C, and element O were measured at each point. Four measurement points were uniformly selected in the region (0 μm-0.5 μm), and the concentration at each point was measured using energy dispersive spectroscopy (EDS). The average concentration of element M at the four measurement points in the 0 μm-0.5 μm region was calculated as the concentration P1 of the ionic conductors on the surface of the composite lithium supplement particle. Similarly, four measurement points were uniformly selected in the core region (0.5 μm-5.0 μm), and the average concentration of element M at the four measurement points was calculated using the same method. This average concentration was taken as the concentration P2 of the ionic conductors at the center of the composite lithium supplement particle.

[0087] Dv50: Detected using a laser particle size analyzer.

[0088] Specific surface area: Measured using a specific surface area analyzer.

[0089] Decomposition potential: The assembled coin cell was charged and discharged at 25°C with a current density of 20 mA / g, where the electrochemical window was 1.0 V to 4.95 V. The charging decomposition plateau was read from the test software and recorded as the decomposition potential.

[0090] Battery capacity: The assembled coin cells were charged and discharged at 25°C with a current density of 20 mA / g, where the electrochemical window was 1.0 V to 4.95 V. The specific charge capacity was read from the test software and recorded as the battery capacity.

[0091] Table 1

[0092] Table 2

[0093] Table 3

[0094] Figure 1 The EDS scan image of Embodiment 1 of this application was obtained through testing, and the data in Table 3 is shown below. Figure 1 Spectrum of measurement points Figure 1 Spectra 2, 3, and 4 represent surface measurement points. Calculations show that the Nb concentration on the surface of the composite lithium supplement particle is 2.94 at%. Spectra 9, 10, 11, and 12 represent central region measurement points. Calculations show that the Nb concentration at the center of the composite lithium supplement particle is 0.17 at%. The data in the table also show that the Nb concentration decreases from the surface to the center of the composite lithium supplement particle.

[0095] In the description of this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0096] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "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 this application. 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. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0097] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A composite lithium supplement, characterized in that, The invention includes composite lithium supplement particles, which comprise a lithium oxalate matrix and an ion conductor. The ion conductor is distributed within the lithium oxalate matrix, and its concentration decreases along the direction from the surface of the composite lithium supplement particle to its center.

2. The composite lithium supplement agent according to claim 1, characterized in that, The composite lithium supplement includes the following compounds: Li2C2O4·aLi x B.C y Among them, Li x MO y The ionic conductor is defined as follows: M represents at least one of Nb, Ta, Al, Zr, and Ti; a is 0.08-0.19; x is 1 or 2; and y is 2 or 3.

3. The composite lithium supplement agent according to claim 2, wherein, along the direction from the surface of the composite lithium supplement agent particle to its center, the concentration of element M decreases from P1 to P2, wherein, The concentration of element M is the atomic percentage of element M relative to the total content of elements C, O, and M. P1 ranged from 2.4 at% to 5.7 at% P2 is 0.1 at% to 0.3 at%.

4. The composite lithium supplement agent according to claim 2, characterized in that, The ionic conductor includes at least one of LiNbO3, LiTaO3, LiAlO2, Li2ZrO3, and Li2TiO3.

5. The composite lithium supplement agent according to claim 1, characterized in that, In the XRD pattern of the composite lithium supplement, the peak intensity ratio Q = I1 / I2 of the first diffraction peak I1 and the second diffraction peak I2 satisfies: 0.32≤Q≤1.75; Wherein, the first diffraction peak is the strongest diffraction peak of the ionic conductor in the XRD spectrum, and the second diffraction peak is the diffraction peak at 2θ of 33.9±0.2° in the XRD spectrum.

6. The composite lithium supplement agent according to claim 5, characterized in that, The 2θ angle of the first diffraction peak is 23.5±0.3°, 23.6±0.3°, 22.3±0.3°, 42.3±0.3° or 42.7±0.3°.

7. The composite lithium supplement agent according to claim 1, characterized in that, At least one of the following conditions must be met: The Dv50 of the composite lithium supplement particles is 1 μm to 10 μm, preferably 1 μm to 5 μm; The specific surface area of ​​the composite lithium supplement particles is 1 m². 2 / g~10 m 2 / g, preferably 1 m 2 / g~5 m 2 / g.

8. A method for preparing the composite lithium supplement agent according to any one of claims 1 to 7, characterized in that, include: Provide lithium oxalate matrix; The lithium oxalate matrix, the first lithium source, and the M source are first mixed in a first solvent to obtain a first mixture; The first mixture was reacted and dried to obtain a composite lithium supplement precursor. The composite lithium supplement precursor is calcined at 300℃-350℃ for 12h-24h in an oxygen or air atmosphere to obtain the composite lithium supplement.

9. The method according to claim 8, characterized in that, The provision of the lithium oxalate matrix includes: mixing a second lithium source and an oxalate source in a second solvent to obtain a second mixture; The second mixture was spray-dried to obtain the lithium oxalate matrix.

10. The method according to claim 9, characterized in that, At least one of the following conditions must be met: The first lithium source and the second lithium source each individually include at least one of lithium hydroxide and lithium hydroxide monohydrate; The oxalic acid source includes at least one of oxalic acid and oxalic acid dihydrate; The M source includes at least one of Nb(OC2H5)5, Ta(OC2H5)5, Al(OC2H5)3, Zr(OC2H5)4, Ti(OC2H5)4, Nb(OCH(CH3)2)5, Ta(OCH(CH3)2)5, Al(OCH(CH3)2)3, Zr(OCH(CH3)2)4, and Ti(OCH(CH3)2)4; The first solvent includes at least one of the following: an ethanol solution with a volume fraction of 95%-98%, a methanol solution with a volume fraction of 95%-98%, and an isopropanol solution with a volume fraction of 95%-98%. The second solvent includes pure water.

11. The method according to claim 10, characterized in that, At least one of the following conditions must be met: The molar ratio of the second lithium source, the oxalic acid source, and the M source is (1.95-2.05):1:(0.08-0.19). The concentration of the first lithium source in the first mixture is 0.1 mol / L-1.0 mol / L, preferably 0.2 mol / L-0.4 mol / L.

12. A positive electrode plate, characterized in that, The composite lithium supplement agent includes any one of claims 1 to 7.

13. A battery, characterized in that, Includes the composite lithium supplement agent according to any one of claims 1 to 7 or the positive electrode sheet according to claim 12.

14. An electrical appliance, characterized in that, It includes the composite lithium replenishing agent according to any one of claims 1 to 7, the positive electrode sheet according to claim 12, or the battery according to claim 13.

Images