Difunctional composite lithium supplement additive as well as preparation method and application thereof

Abstract

The invention discloses a difunctional composite lithium supplement additive and a preparation method and application thereof, and belongs to the technical field of lithium ion batteries. The bifunctional composite lithium supplement additive provided by the invention comprises lithium-rich lithium ferrite as a core layer and a lanthanum gallate coating layer coating the outer surface of the core layer. The lithium supplementing additive prepared by the invention realizes dual inhibition on released high-active oxygen species, the released O2 is captured and fixed in the coating layer through oxygen vacancy adsorption and lattice constraint, and a physical barrier is synchronously formed in the coating layer in a deep lithium removal process to block a migration channel of active oxygen to an electrolyte, so that the lithium supplementing effect is improved. Therefore, the cycling stability of the lithium ion battery is greatly improved, the service life of the lithium ion battery is greatly prolonged, and the application prospect in the lithium ion battery is wide.

Description

Technical Field

[0001] This application belongs to the field of lithium-ion battery technology, and in particular relates to a dual-functional composite lithium supplementation additive, its preparation method and application. Background Technology

[0002] Lithium replenishment technology is a method of pre-storing lithium ions in the electrode to compensate for the initial capacity loss of the battery. It effectively solves the problem of low initial coulombic efficiency and improves battery capacity and cycle stability. Positive electrode lithium replenishment has the most promising industrial application prospects due to its high safety and the fact that it does not require changes to existing battery manufacturing processes. Antifluorite structure lithium-rich lithium iron phosphate (Li5FeO4) (LFO) serves as a new generation of positive electrode lithium replenishment reagent, utilizing Fe... 3+ / Fe 4+ Cation oxidation and O 2- / O2 n- Anion oxidation synergistic mechanism can provide up to 870 mAh g -1 LFOs, with their significantly higher irreversible lithium release capacity compared to traditional lithium-rich materials, have attracted increasing attention. However, the practical application of LFOs still faces some challenges. When the charging voltage exceeds 4.0 V, deep oxidation of lattice oxygen leads to oxygen evolution, causing electrolyte decomposition (such as CO2 production in carbonate electrolytes), a surge in electrode / electrolyte interfacial impedance, and the risk of battery swelling. Furthermore, when LFOs are exposed to humid air, they readily react with H2O / CO2 to form LiOH and Li2CO3 surface layers, reducing the active lithium content and increasing electrode polarization.

[0003] Existing methods for improving the conductivity and stability of lithium supplementation agents include carbon coating or polymer coating. The prior art, disclosed in application publication number CN 116706273 A, provides a lithium supplementation additive for lithium-rich lithium iron phosphate cathodes. This additive improves the conductivity and stability of lithium iron phosphate by coating lithium fluoride particles onto the surface of the lithium-rich lithium iron phosphate. + Improve transmission efficiency and enhance capacity utilization.

[0004] However, existing lithium iron phosphate cathode lithium supplementation additives have the following problems: First, the additives have poor stability in air, which not only easily causes capacity decay during storage or pretreatment, but also brings difficulties to subsequent processing and preparation. Second, lattice oxygen evolution easily causes structural instability, which in turn leads to poor cycle performance. Summary of the Invention

[0005] This application discloses a bifunctional composite lithium supplement additive, its preparation method and application, aiming to solve the technical problems of unstable positive electrode lithium supplement additives in air and poor battery cycle performance caused by oxygen evolution in the crystal lattice.

[0006] To achieve the above objectives, the technical solution of this application is:

[0007] The first aspect of this application provides a bifunctional composite lithium supplementation additive, comprising: a lithium-rich lithium iron phosphate core layer and a lanthanum gallate coating layer encapsulating the outer surface of the core layer.

[0008] Preferably, in conjunction with the first aspect, the molar ratio of lanthanum gallate to lithium iron phosphate is (1-5):100.

[0009] Preferably, in conjunction with the first aspect, the thickness of the coating layer is 2-50 nm.

[0010] The second aspect of this application provides a method for preparing the bifunctional composite lithium supplementation additive described in the first aspect, the method comprising:

[0011] The lanthanum source and gallium source were dissolved in ethanol and then subjected to ball milling to obtain a precursor solution.

[0012] Lithium-rich lithium iron oxide was added to the precursor solution, and after secondary ball milling and drying, Li5FeO4 powder coated with the precursor was obtained.

[0013] In an inert atmosphere, the Li5FeO4 powder coated with the precursor is calcined and then cooled to room temperature to obtain the bifunctional composite lithium supplementation additive.

[0014] The primary ball milling process and the secondary ball milling process may be the same or different.

[0015] Preferably, in conjunction with the second aspect, the lanthanum source is one or more of La2O3, La(OH)3, La(CH3COO)3, LaCl3, La(NO3)3·xH2O, and La2(C2O4)3·xH2O.

[0016] Preferably, in conjunction with the second aspect, the gallium source is one or more of Ga2O3, Ga(OH)3, GaCl3, and Ga(NO3)3·xH2O.

[0017] In conjunction with the second aspect, preferably, the conditions for the first ball milling process are: a ball-to-material ratio of (5-10):1, a ball milling speed of 300-800 rpm, and a ball milling time of 1-20 h;

[0018] The conditions for the secondary ball milling process are as follows: ball-to-material ratio of (5-10):1, ball milling speed of 300-800 rpm, and ball milling time of 2-20 h.

[0019] Preferably, in conjunction with the second aspect, the calcination treatment conditions are: heating at a rate of 3-10 ℃ / min to 500-900 ℃ and calcining for 5-20 h.

[0020] The third aspect of this application provides a lithium-ion battery cathode, comprising the bifunctional composite lithium supplement additive described in the first aspect or the bifunctional composite lithium supplement additive prepared by the preparation method described in the second aspect.

[0021] A fourth aspect of this application provides a lithium-ion battery, including a positive electrode sheet, said positive electrode sheet comprising the lithium-ion battery positive electrode described in the third aspect.

[0022] Compared with the prior art, the advantages or beneficial effects of the embodiments of this application include at least the following:

[0023] The dual-functional composite lithium replenishment additive provided in this application forms a core-shell structure by encapsulating lanthanum gallate on lithium iron phosphate. On the one hand, through oxygen ion conduction channels and high-concentration oxygen vacancies, it efficiently captures and fixes highly reactive lattice oxygen released during the delithiation process, significantly inhibiting the migration of reactive oxygen to the interface; furthermore, the high-bond-energy La-O bonds in LaGaO3 strongly anchor the generated oxygen molecules, effectively preventing them from escaping the coating layer and entering the electrolyte. On the other hand, during deep delithiation, the released O2 is captured and fixed inside the coating layer, simultaneously forming a physical barrier that blocks the migration channels of reactive oxygen to the electrolyte, thereby effectively improving the overall stability of the battery. Simultaneously, this additive forms an atomically tightly bonded transition layer with excellent chemical stability, a stable crystal structure, and a chemical composition that effectively resists air erosion and prevents material oxidation and degradation; at the same time, it exhibits intrinsic chemical tolerance and stability to acidic substances such as HF in the electrolyte, significantly inhibiting the occurrence of interfacial side reactions, thereby greatly improving the cycle stability and lifespan of the lithium-ion battery. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 SEM image of the A1-bifunctional composite lithium supplementation additive provided in the embodiments of this application;

[0026] Figure 2 SEM image of the B1-additive prepared in the embodiments of this application;

[0027] Figure 3 XRD pattern of the A1-bifunctional composite lithium supplementation additive provided in the embodiments of this application;

[0028] Figure 4Cyclic data of a lithium-ion half-cell with NCM811 as the positive electrode, prepared by A1-bifunctional composite lithium supplementation additive and B1-additive prepared for the embodiments of this application. Detailed Implementation

[0029] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0030] In the following description of this embodiment, the term "and / or" is used to describe the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, B existing alone, and A and B existing simultaneously. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0031] In the following description of this embodiment, the term "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0032] Those skilled in the art should understand that, in the following description of the embodiments of this application, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0033] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms "a" and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0034] It should be noted that all raw materials and reagents in the embodiments of this application were purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0035] In a first aspect, embodiments of this application provide a bifunctional composite lithium supplementation additive, comprising: a lithium-rich lithium iron phosphate core layer and a lanthanum gallate coating layer encapsulating the outer surface of the core layer.

[0036] On one hand, lanthanum gallate efficiently captures and fixes highly reactive lattice oxygen released during the delithiation process through oxygen ion conduction channels and high-concentration oxygen vacancies, significantly inhibiting the migration of reactive oxygen to the interface. Furthermore, the high-energy La-O bonds in LaGaO3 strongly anchor the generated oxygen molecules, effectively preventing them from escaping the coating layer and entering the electrolyte. On the other hand, during deep delithiation, the released O2 is captured and fixed within the coating layer, simultaneously forming a physical barrier that blocks the migration channels of reactive oxygen to the electrolyte, thereby effectively improving the overall stability of the battery. Simultaneously, this additive forms an atomically tightly bonded transition layer with excellent chemical stability, a stable crystal structure, and a chemical composition that effectively resists air erosion and prevents material oxidation and degradation. It also exhibits intrinsic chemical tolerance and stability to acidic substances such as HF in the electrolyte, significantly inhibiting interfacial side reactions, thereby greatly improving the cycle stability and lifespan of the lithium-ion battery.

[0037] It should be noted that lanthanum gallate is a perovskite-type oxygen ion conductor. LaGaO3-based materials have excellent chemical stability in CO2 and H2O environments and can be coated on the surface of Li5FeO4 to prevent air erosion. In addition, this coating layer captures and fixes the O2 released by Li5FeO4 during deep delithiation into the coating layer through oxygen vacancy adsorption and lattice confinement, while forming a physical barrier to block the migration channels of active oxygen into the electrolyte, effectively improving the overall stability of the battery.

[0038] It should be noted that the stable crystal structure and chemical composition of LaGaO3 effectively resist air erosion and prevent oxidation and degradation of the material. Furthermore, the perovskite layer, with its intrinsic oxygen ion conduction channels and high concentration of oxygen vacancies, achieves dual suppression of the release of highly reactive oxygen species. Through oxygen vacancy adsorption and lattice confinement, the released O2 is captured and fixed within the coating layer; secondly, it forms a physical barrier, blocking the migration channels of reactive oxygen to the electrolyte. Simultaneously, LaGaO3-based materials possess intrinsic chemical resistance / stability to acidic substances such as HF in the electrolyte, suppressing the occurrence of interfacial side reactions. The pre-lithiation material prepared in this application can be coated together with existing cathode materials to improve the cycle stability and lifespan of the battery.

[0039] In this embodiment, the preferred molar ratio of lanthanum gallate to lithium iron phosphate is (1-5):100. The initial charging capacity gradually decreases with increasing lanthanum gallate coating amount, possibly due to the non-electrochemical activity of LaGaO3, where the coating layer hinders the absorption of Li. +The insertion and extraction of lithium leads to a certain degree of capacity loss. Under air exposure conditions, the unmodified material exhibits significant capacity decay due to the erosion of H2O and CO2 in the environment. In contrast, the LaGaO3-coated material demonstrates excellent capacity retention. This inert coating effectively improves the chemical environmental stability of the material and inhibits interfacial side reactions and the formation of residual lithium compounds (such as Li2CO3 and LiOH).

[0040] In this embodiment, the thickness of the coating layer is 2-50 nm. If the coating layer is too thin, coating defects are likely to occur, failing to provide effective protection. If the coating layer is too thick, it will significantly increase lithium-ion diffusion resistance, reduce electrode reaction kinetics, and lead to a decrease in rate performance. Furthermore, the thickness of the coating layer can adapt to the stress buffering requirements of the core-shell structure, elastically buffering the stress generated by core expansion during charge-discharge volume changes, preventing the coating layer from cracking or detaching.

[0041] Secondly, embodiments of this application also provide a method for preparing the bifunctional composite lithium supplementation additive described in the first aspect, the preparation method comprising:

[0042] The lanthanum source and gallium source were dissolved in ethanol and then subjected to ball milling to obtain a precursor solution.

[0043] Lithium-rich lithium iron oxide was added to the precursor solution, and after secondary ball milling and drying, Li5FeO4 powder coated with the precursor was obtained.

[0044] In an inert atmosphere, the Li5FeO4 powder coated with the precursor is calcined and then cooled to room temperature to obtain the bifunctional composite lithium supplementation additive.

[0045] The primary ball milling process and the secondary ball milling process may be the same or different.

[0046] It should be noted that the lithium-rich lithium iron ferrite pre-lithiation material used in this application is purchased from the market or prepared according to conventional methods known to those skilled in the art, and the source is not particularly limited. The preferred synthesis method is as follows: Lithium oxide (Li₂O), ferric oxide nanoparticles (Fe₂O₃), and carbon nanotubes (CNTs) are weighed and placed in a ball mill jar, and dry-milled at 500 rpm for 5 hours, wherein the Li / Fe molar ratio is 5.5:1, and the mass of conductive carbon accounts for 5% of the total mass of Li₂O and Fe₂O₃. The ball-milled raw material powder is pressed into tablets using a tablet press at a pressure of approximately 16 T, and then placed under an argon atmosphere. The temperature is first increased to 300 °C at a heating rate of 5 °C / min and held for 2 hours, then increased to 600 °C and held for 12 hours. After cooling to room temperature, the material is crushed to obtain the lithium-rich lithium iron ferrite pre-lithiation material (Li₅FeO₄).

[0047] It should be noted that this application forms an atomically tightly bonded transition layer at the core-shell interface through a high-temperature solid-state reaction, ensuring the structural stability and functional durability of the coating layer.

[0048] In this embodiment, the lanthanum source is preferably one or more of La2O3, La(OH)3, La(CH3COO)3, LaCl3, La(NO3)3·xH2O, and La2(C2O4)3·xH2O. The gallium source is preferably one or more of Ga2O3, Ga(OH)3, GaCl3, and Ga(NO3)3·xH2O. These lanthanum and gallium sources are highly compatible, have good solubility, can form a homogeneous system in water or polar solvents, are suitable for various preparation processes, and can be converted into the target oxide upon heating. The released gas is easily volatile, the generated impurities are easily controlled and can be completely removed in the reaction or subsequent processing, and the raw materials are readily available and highly stable, meeting the preparation requirements.

[0049] In this embodiment, the preferred conditions for the primary ball milling treatment are: a ball-to-material ratio of (5-10):1, a ball milling speed of 300-800 rpm, and a ball milling time of 1-20 h; the preferred conditions for the secondary ball milling treatment are: a ball-to-material ratio of (5-10):1, a ball milling speed of 300-800 rpm, and a ball milling time of 2-20 h. Specifically, when the ball milling speed is below 300 r / min, the energy is insufficient, making it difficult to form a pure-phase compound; when the ball milling speed is above 800 r / min, it easily leads to material agglomeration and excessively large particles.

[0050] In this embodiment, the preferred calcination conditions are: heating to 500-900℃ at a heating rate of 3-10℃ / min and calcining for 5-20 h. Specifically, La2O3 and Ga2O3 exhibit significant thermal mismatch during rapid heating; controlling the heating rate to ≤10℃ / min reduces interfacial shear stress and prevents cracking of the coating layer. The synthesis temperature of LaGaO3 is greater than 500℃, ensuring sufficient interfacial diffusion to enhance bonding while preventing excessive grain growth due to high temperatures, which could disrupt coating uniformity. Appropriate holding time ensures densification of the coating layer and thoroughly removes residual impurities, improving the structural stability and interfacial compatibility of the mixed coating system.

[0051] Thirdly, this application also provides a lithium-ion battery cathode, comprising the bifunctional composite lithium replenishing additive described in the first aspect or the bifunctional composite lithium replenishing additive prepared by the preparation method described in the second aspect. Based on the fact that the above additives can form a uniform, regular, and stable material structure, the lithium-ion battery cathode is endowed with higher lithium replenishment capacity and stability.

[0052] Fourthly, this application also provides a lithium-ion battery, including a positive electrode sheet, wherein the positive electrode sheet comprises the lithium-ion battery positive electrode described in the third aspect. The aforementioned lithium-ion battery positive electrode possesses excellent lithium replenishment capacity and stability, thereby endowing the lithium-ion battery with high conductivity, excellent rate cycle performance and stability, and strong product competitiveness.

[0053] The technical solution of this application will be further described below with reference to specific embodiments.

[0054] Example 1

[0055] This embodiment provides a method for preparing A1-bifunctional composite lithium supplementation additive, specifically including:

[0056] S101: Mix 0.1 mmol of La2O3 with Ga2O3, add the mixture to a zirconia ball mill jar, add 20 ml of anhydrous ethanol as the medium, and ball mill at 500 rpm for 6 h to obtain the precursor solution; (La2O3+Ga2O3→2LaGaO3).

[0057] S102: Add 0.02 mol of Li5FeO4 pre-lithiation material to the above precursor solution, continue ball milling for 6 h, and then dry at 60 ℃ for 12 h to form Li5FeO4 coated with precursor.

[0058] S103: The dried precursor-coated Li5FeO4 powder was placed in an alumina crucible and calcined in an argon atmosphere. The temperature was increased to 600 ℃ at a heating rate of 5 ℃ / min and held for 10 h. The mixture was then cooled to room temperature in the furnace to obtain the A1-bifunctional composite lithium supplement additive.

[0059] The Al-bifunctional composite lithium supplement additive is a lithium-rich lithium iron oxide supplement material uniformly coated with lanthanum gallate. It is a core-shell structured cathode material with Li5FeO4 as the core layer and LaGaO3 as the shell layer material. The molar ratio of LaGaO3 to Li5FeO4 is 1:100.

[0060] Example 2

[0061] This embodiment provides a method for preparing A2-bifunctional composite lithium supplementation additive, specifically including:

[0062] S201: Mix 0.2 mmol of La2O3 with Ga2O3, add the mixture to a zirconia ball mill jar, add 20 ml of anhydrous ethanol as the medium, and ball mill at 500 rpm for 6 h to obtain the precursor solution.

[0063] S202: Add 0.02 mol of Li5FeO4 pre-lithiation material to the above precursor solution, continue ball milling for 6 h, and then dry at 60 ℃ for 12 h to form precursor-coated Li5FeO4.

[0064] S203: The dried precursor-coated Li5FeO4 powder is placed in an alumina crucible and calcined in an argon atmosphere. The temperature is increased to 600 ℃ at a heating rate of 5 ℃ / min and held for 10 h. The mixture is then cooled to room temperature in the furnace to obtain the A2-bifunctional composite lithium supplement additive.

[0065] The A2-bifunctional composite lithium supplement additive is a lithium-rich lithium iron oxide lithium supplement material uniformly coated with lanthanum gallate. It is a core-shell structured cathode material with Li5FeO4 as the core layer and LaGaO3 as the shell material. The molar ratio of LaGaO3 to Li5FeO4 is 2:100.

[0066] Example 3

[0067] This embodiment provides a method for preparing A3-bifunctional composite lithium supplementation additive, specifically including:

[0068] S301: Mix 0.3 mmol of La2O3 with Ga2O3, add the mixture to a zirconia ball mill jar, add 20 ml of anhydrous ethanol as the medium, and ball mill at 500 rpm for 6 h to obtain the precursor solution.

[0069] S302: Add 0.02 mol of Li5FeO4 pre-lithiation material to the above precursor solution, continue ball milling for 6 h, and then dry at 60 ℃ for 12 h to form Li5FeO4 coated with precursor.

[0070] S303: The dried precursor-coated Li5FeO4 powder is placed in an alumina crucible and calcined in an argon atmosphere. The temperature is increased to 600 ℃ at a heating rate of 5 ℃ / min and held for 10 h. The mixture is then cooled to room temperature in the furnace to obtain the A3-bifunctional composite lithium supplement additive.

[0071] The A3-bifunctional composite lithium supplement additive is a lithium-rich lithium iron oxide lithium supplement material uniformly coated with lanthanum gallate. It is a core-shell structured cathode material with Li5FeO4 as the core layer and LaGaO3 as the shell material. The molar ratio of LaGaO3 to Li5FeO4 is 3:100.

[0072] Example 4

[0073] This embodiment provides a method for preparing A4-bifunctional composite lithium supplementation additive, specifically including:

[0074] S401: Mix 0.5 mmol of La2O3 with Ga2O3, add the mixture to a zirconia ball mill jar, add 20 ml of anhydrous ethanol as the medium, and ball mill at 500 rpm for 6 h to obtain the precursor solution.

[0075] S402: Add 0.02 mol of Li5FeO4 pre-lithiation material to the above precursor solution, continue ball milling for 6 h, and then dry at 60 ℃ for 12 h to form Li5FeO4 coated with precursor.

[0076] S403: The dried precursor-coated Li5FeO4 powder is placed in an alumina crucible and calcined in an argon atmosphere. The temperature is increased to 600 ℃ at a heating rate of 5 ℃ / min and held for 10 h. The mixture is then cooled to room temperature in the furnace to obtain the A4-bifunctional composite lithium supplement additive.

[0077] The A4-bifunctional composite lithium supplement additive is a lithium-rich lithium iron oxide lithium supplement material uniformly coated with lanthanum gallate. It is a core-shell structured cathode material with Li5FeO4 as the core layer and LaGaO3 as the shell material. The molar ratio of LaGaO3 to Li5FeO4 is 5:100.

[0078] Meanwhile, to verify the comprehensive performance of the lithium supplementation additives prepared in the above embodiments, this application provides the following comparative examples for detailed illustration.

[0079] Comparative Example 1

[0080] This comparative example provides B1-additive directly using Li5FeO4 as the comparative example, that is, without LaGaO3 encapsulation, to obtain B1-additive.

[0081] Comparative Example 2

[0082] This comparative example provides a material preparation method, component ratio, preparation operation, and process parameters that are basically the same as those in Example 1. The difference is that the molar ratio of LaGaO3 to Li5FeO4 in this comparative example is 6:100, resulting in B2-additive.

[0083] Comparative Example 3

[0084] This comparative example provides a material preparation method, component ratio, preparation operation, and process parameters that are basically the same as those in Example 1. The difference is that the molar ratio of LaGaO3 to Li5FeO4 in this comparative example is 0.5:100, resulting in B3-additive.

[0085] To verify the morphological characteristics of the bifunctional composite lithium-supplementing additive prepared in the examples, the fabricated piezoelectric material was subjected to SEM testing. The test results are as follows: Figures 1 to 2 As shown.

[0086] according to Figure 1 and Figure 2 It is evident that the surface of the material becomes rough after coating with the Al-bifunctional composite lithium supplementation additive, and the CNTs are covered. Li5FeO4, as a lithium supplementation material, has relatively weak electronic conductivity, while CNTs possess excellent electron transport capabilities, enabling the construction of a continuous conductive network within the material and accelerating electron transfer. Especially when an insulating layer may form after lanthanum gallate coating, CNTs can effectively compensate for the influence of the coating layer on conductivity. Although the CNTs may be partially covered by the lanthanum gallate layer after coating, their pre-constructed conductive network can still function through contact points or pores, balancing the insulation brought by the coating with the overall electrochemical performance of the material.

[0087] To verify the structural properties of the bifunctional composite lithium-supplementing additive prepared in the examples, the fabricated piezoelectric material was characterized by XRD. The test results are as follows: Figure 3 As shown.

[0088] according to Figure 3 It can be seen that the characteristic peaks of Li5FeO4 coated with LaGaO3 are consistent with the characteristic peaks of Li5FeO4 on the standard card. This is because the surface coating amount is small and the surface coating does not change the structure of the cathode material.

[0089] To verify the piezoelectric properties of the bifunctional composite lithium supplementation additive prepared in the examples, the additive was subjected to an air stability test.

[0090] Electrode preparation: The positive electrode is prepared by mixing active material, conductive agent Super P, and binder PVDF (5 wt%, solvent NMP) in a mass ratio of 70:20:10 to form a slurry, which is then coated onto the current collector. After vacuum drying at 100°C to remove the solvent, it is cut into circular electrode sheets with a diameter of 12 mm. The pre-lithiated positive electrode is prepared by mixing the positive electrode material and the pre-lithiated material in a mass ratio of 95:5, and the remaining steps are the same as described above.

[0091] Lithium-ion half-cell: The assembly of the half-cell was carried out in a glove box where the water and oxygen content was less than 0.1 ppm. The specific steps were as follows: Take the positive electrode shell of a CR2032 button cell, place the positive electrode sheet (active material side up), and add an appropriate amount of electrolyte (e.g., 1 M LiPF6 in DMC:EC:EMC = 1:1:1 Vol%); cover with a separator (e.g., Celgard 2500, 16 mm in diameter), and add a small amount of electrolyte again to wet the separator; place the lithium metal sheet, and cover with a gasket and spring sheet in sequence, then cover with the negative electrode shell, and press and seal with a battery packaging machine. After standing for 10 hours to allow the electrolyte to fully wet the electrodes and separator, constant current charge-discharge tests were performed on the Blue Battery testing system. The voltage range was 2.5-4.5 V.

[0092] The above additives were exposed to an environment of 28 °C and approximately 40% RH for a period of time, and electrochemical tests were performed. The data obtained are shown in Table 1.

[0093] Table 1. Results of the first charge specific capacity test of the half-cell.

[0094]

[0095] According to the first-cycle charge specific capacity test results of Examples 1-4 and Comparative Example 1 in Table 1, the first-cycle charge capacity of the material decreases with increasing LaGaO3 coating amount. This is attributed to the non-electrochemical activity of LaGaO3, whose coating layer hinders the Li... + The insertion and extraction of lithium leads to a certain degree of capacity loss. However, under air exposure conditions, the unmodified material exhibits significant capacity decay due to the erosion of H2O and CO2 in the environment; in contrast, the LaGaO3-coated material demonstrates excellent capacity retention. This inert coating effectively improves the chemical stability of the material and inhibits interfacial side reactions and the formation of residual lithium compounds (such as Li2CO3 and LiOH).

[0096] Pre-lithiation battery preparation: The lithium replenishing materials prepared in Example 1 and Comparative Example 1 were applied to the cathode material NCM811, with a lithium replenishing material mass ratio of 5 wt%. The remaining steps were the same as those for coin cell preparation. Constant current charge-discharge tests were performed on the Blue Battery testing system, with voltage ranges of 3-4.3 V.

[0097] Table 2. Results of the first charge specific capacity test of the half-cell.

[0098]

[0099] The data in Table 2 show that the LaGaO3-coated high-nickel ternary cathode material prepared in Example 1 exhibits significantly better capacity retention after 100 cycles than the NCM811 material in Comparative Example 1. The rapid capacity decay of the NCM811 material during cycling is mainly attributed to the irreversible precipitation of lattice oxygen (O2) under deep delithiation. The precipitated active oxygen triggers severe oxidative decomposition of the electrolyte, generating gas and consuming active lithium. In contrast, the LaGaO3 oxygen ion conductor coating layer effectively inhibits the accumulation of active oxygen at the interface by promoting oxygen ion conduction, blocking its direct contact and reaction with the electrolyte, thereby significantly reducing electrolyte decomposition side reactions and improving the cycling stability of the material.

[0100] Therefore, the lithium supplement additive prepared in this application is made by encapsulating Li5FeO4 with LaGaO3. Through oxygen vacancy adsorption and lattice binding, the released O2 is captured and fixed inside the coating layer. During the deep delithiation process, the released O2 is captured and fixed inside the coating layer to simultaneously form a physical barrier, blocking the migration channels of active oxygen to the electrolyte. This achieves dual inhibition of the release of highly active oxygen species, thereby significantly improving the cycle stability and service life of lithium-ion batteries and showing broad application prospects in lithium-ion batteries.

[0101] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0102] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.

Claims

1. A bifunctional composite lithium supplement additive, characterized in that, include: A lithium iron phosphate core layer and a lanthanum gallate coating layer wrapped around the outer surface of the core layer.

2. The bifunctional composite lithium supplement additive according to claim 1, characterized in that, The molar ratio of lanthanum gallate to lithium iron ferrite is (1-5):

100.

3. The bifunctional composite lithium supplement additive according to claim 1, characterized in that, The thickness of the coating layer is 2-50 nm.

4. A method for preparing a bifunctional composite lithium supplement additive according to any one of claims 1-3, characterized in that, The preparation method includes: The lanthanum source and gallium source were dissolved in ethanol and then subjected to ball milling to obtain a precursor solution. Lithium-rich lithium iron oxide was added to the precursor solution, and after secondary ball milling and drying, Li5FeO4 powder coated with the precursor was obtained. In an inert atmosphere, the Li5FeO4 powder coated with the precursor is calcined and then cooled to room temperature to obtain the bifunctional composite lithium supplementation additive. The primary ball milling process and the secondary ball milling process may be the same or different.

5. The preparation method of the bifunctional composite lithium supplementation additive according to claim 4, characterized in that, The lanthanum source is one or more of La2O3, La(OH)3, La(CH3COO)3, LaCl3, La(NO3)3·xH2O, and La2(C2O4)3·xH2O.

6. The preparation method of the bifunctional composite lithium supplementation additive according to claim 4, characterized in that, The gallium source is one or more of Ga2O3, Ga(OH)3, GaCl3, and Ga(NO3)3·xH2O.

7. The preparation method of the bifunctional composite lithium supplementation additive according to claim 4, characterized in that, The conditions for the first ball milling process are: ball-to-material ratio of (5-10):1, ball milling speed of 300-800 rpm, and ball milling time of 1-20 h; The conditions for the secondary ball milling process are as follows: ball-to-material ratio of (5-10):1, ball milling speed of 300-800 rpm, and ball milling time of 2-20 h.

8. The preparation method of the bifunctional composite lithium supplementation additive according to claim 4, characterized in that, The calcination conditions are as follows: calcination at 500-900 ℃ for 5-20 h with a heating rate of 3-10 ℃ / min.

9. A lithium-ion battery positive electrode, characterized in that, The additive comprises the bifunctional composite lithium supplementation additive according to any one of claims 1-3 or the bifunctional composite lithium supplementation additive prepared by any one of claims 4-8.

10. A lithium-ion battery, characterized in that, It includes a positive electrode sheet, which comprises the lithium-ion battery positive electrode as described in claim 9.

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