A positive electrode lithium supplementing material, a preparation method thereof and a lithium ion battery

Abstract

The application provides a positive electrode lithium supplementing material and a preparation method thereof and a lithium ion battery, relates to the technical field of lithium ion batteries, and the positive electrode lithium supplementing material is a transition metal embedded in a Li2O crystal lattice; the preparation method of the positive electrode lithium supplementing material comprises the following steps: mixing Li2O and a transition metal source according to a mass ratio (0.7-1.5):1, and then ball milling for 12-18 hours under the condition that the rotating speed is 250-350 revolutions per minute. The positive electrode lithium supplementing material provided by the application introduces the transition metal into a local crystal framework to adjust the energy band / energy level structure, so that the oxidation activity of oxygen is enhanced. The injection of the transition metal ion introduces a doping energy level in the band gap of the Li2O, improves the conductivity, weakens the strength of the Li-O bond, is beneficial to the decomposition of the Li2O, and reduces the decomposition potential.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a positive electrode lithium replenishment material, its preparation method, and a lithium-ion battery. Background Technology

[0002] In the global wave of energy structure transformation towards cleaner and lower-carbon energy, energy storage technology is leaping from a supporting role to a core infrastructure of new power systems. Against this backdrop, electrochemical energy storage, with its flexible deployment, rapid response, and modular expansion characteristics, has become a key technological path supporting the high-proportion grid connection of photovoltaic and wind power. Furthermore, lithium-ion batteries are gradually being applied in portable electronic devices, specialized equipment, and other fields. As these applications demand longer battery life and higher specific energy from lithium-ion batteries, continuous improvement of various performance indicators of lithium-ion batteries is of great significance.

[0003] Silicon-oxygen or silicon-carbon anode materials, when used as high-energy-density anode materials, typically exhibit significant active lithium loss during the first charge-discharge cycle due to the formation of a solid electrolyte film. Lithium replenishment technology, as an additional lithium compensation mechanism, can compensate for the active lithium loss caused by the formation of the solid electrolyte film or other side reactions.

[0004] Generally, cathode lithium replenishment materials can be divided into three categories: The first category is binary lithium-containing compounds, such as Li₂O, Li₂O₂, LiF, Li₂S, and Li₃N. Binary lithium-containing compounds have high decomposition potentials, leave residues in the electrode system after decomposition, and have poor air stability. The second category is ternary lithium-containing compounds, such as Li₄FeO₅, Li₆CoO₄, Li₂NiO₂, Li₅ReO₆, Li₂RuO₃, Li₂MnO₃, Li₂MoO₃, and Li 0.65 Ni 1.35 O2 and other substances, after the decomposition of ternary cathode lithium replenishment materials, will leave oxide residues inside the electrode system, reducing the battery energy density. At the same time, the residual inert substances inside the battery will form excess substances, which may have a negative impact on the later use of the battery. The third type is organic lithium salts, such as Li2DHBN and Li2C2O4. The lithium replenishment capacity of organic cathode lithium replenishment materials still needs to be improved. The process of removing the gas generated after decomposition, as well as the impact of gas generation on the electrode, electrolyte and interface, are still uncertain.

[0005] Because it possesses a high theoretical energy density (1794 mAh / g, 2.91 V vs. Li / Li) + Li₂O is a relatively ideal cathode lithiation agent. However, due to its poor conductivity and low electrochemical activity, it results in high charge overpotential / polarization (typically 4.7 V vs. Li / Li). + This is much higher than the upper cutoff voltage of typical cathode materials (usually <4.4 V vs. Li / Li).+ ). Summary of the Invention

[0006] This invention provides a positive electrode lithium replenishment material, its preparation method, and a lithium-ion battery, which solves the defects of poor conductivity and low electrochemical activity of Li2O in the prior art, and achieves the beneficial technical effects of improving the conductivity of Li2O and reducing the decomposition potential.

[0007] In a first aspect, the present invention provides a positive electrode lithium replenishment material in which a transition metal is embedded in a Li2O lattice.

[0008] The cathode lithium replenishment material provided by this invention enhances oxygen oxidation activity by adjusting the band / level structure through the introduction of transition metals into the local crystal framework. The implantation of transition metal ions introduces doped levels into the band gap of Li₂O, improving conductivity and weakening the Li-O bond strength, thus facilitating Li₂O decomposition.

[0009] In some embodiments, the transition metal is selected from at least one of manganese, nickel, cobalt, and iron.

[0010] In some embodiments, the transition metal is selected from at least one of manganese, nickel, and cobalt.

[0011] A second aspect of the present invention provides a method for preparing a positive electrode lithium replenishment material, comprising: Li2O and a transition metal source were mixed at a mass ratio of (0.7~1.5):1 and then ball-milled at a speed of 250~350 rpm for 12~18 h.

[0012] The present invention provides a method for preparing a positive electrode lithium replenishment material, which uses a mechanochemical method to combine Li2O with a transition metal source. The transition metal in the transition metal source is used as a dopant ion to be embedded in the local crystal framework of Li2O. This can reduce the decomposition potential of Li2O, and at the same time, the transition metal source, as a high specific energy material of the positive electrode, can continue to exert its capacity during cycling.

[0013] This invention provides a method for preparing a positive electrode lithium replenishment material. The method involves ball milling a mixture of Li2O and a transition metal source in a specific ratio (mass ratio of Li2O to transition metal source is (0.7~1.5):1) under conditions controlled at a rotation speed of 250~350 rpm for 12~18 h. These conditions are interdependent and closely related, working synergistically to enable the transition metal to effectively embed into the Li2O lattice. This facilitates the catalytic decomposition of Li2O, improves the specific capacity of the positive electrode lithium replenishment material, and enhances its cycle performance as a positive electrode lithium replenishment material for lithium-ion batteries.

[0014] In the method for preparing the positive electrode lithium replenishment material provided by the present invention, the mass ratio of Li2O to the transition metal source is (0.7~1.5):1, for example, it can be 0.7:1, 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0015] In the method for preparing the positive electrode lithium replenishment material provided by the present invention, the ball milling speed is 250~350 rpm, for example, it can be 250 rpm, 260 rpm, 270 rpm, 280 rpm, 290 rpm, 300 rpm, 310 rpm, 320 rpm, 330 rpm, 340 rpm, or 350 rpm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0016] In the preparation method of the positive electrode lithium replenishment material provided by the present invention, the ball milling time is 12~18 h, for example, it can be 12h, 13h, 14h, 15h, 16h, 17h, 18h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0017] In some embodiments, the ball mill rotates at a speed of 300-350 revolutions per minute.

[0018] In some implementations, the ball milling time is 15-18 hours.

[0019] In some implementations, the transition metal source is selected from at least one of lithium-rich manganese-based materials, lithium-ion battery ternary materials, and lithium iron phosphate.

[0020] In some implementations, the transition metal source is a lithium-rich manganese-based material.

[0021] In some embodiments, the ball milling is carried out under conditions where the dew point is ≤-40°C.

[0022] A third aspect of the present invention provides a lithium-ion battery comprising a positive electrode lithium replenishment material as described in the first aspect above or a positive electrode lithium replenishment material prepared by the method described in the second aspect above.

[0023] Compared with the prior art, the beneficial technical effects of the present invention are as follows: This invention uses high-energy ball milling to couple a transition metal source with Li2O. Through mechanochemical reactions and high-energy collisions (generating local heating and pressure effects), the metal source can be broken down (transition metal extraction process) and doped elements can be embedded into the Li2O lattice. This is beneficial for catalyzing the decomposition of Li2O, improving the specific capacity of the cathode lithium replenishment material, and enhancing the cycle performance of the cathode lithium replenishment material in lithium-ion batteries. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 X-ray diffraction (XRD) images of the lithium-ion cathode material prepared for LRM and Example 4.

[0026] Figure 2 This is a scanning electron microscope (SEM) image of the positive electrode lithium replenishment material prepared in Example 4.

[0027] Figure 3 The image shows the BET desorption curve of the positive electrode lithium replenishment material prepared in Example 4.

[0028] Figure 4 The image shows the X-ray photoelectron spectroscopy (XPS) analysis of the positive electrode lithium replenishment material prepared in Example 4.

[0029] Figure 5 This is a graph of the density of states of the material.

[0030] Figure 6 This is a graph of the Hamiltonian orbital of a crystal.

[0031] Figure 7 The first-week charging curves of the coin cells prepared from the positive electrode lithium replenishment materials in Examples 1-4 are shown.

[0032] Figure 8 The first-week charging curves of the coin cells prepared from the positive electrode lithium replenishment materials of Example 1 and Comparative Example 2 are shown.

[0033] Figure 9 The first-week charging curves of coin cells made from the positive electrode lithium replenishment materials of Comparative Examples 1-6 are shown.

[0034] Figure 10 The graph shows the full-electric cycle performance of the cathode lithium replenishment material and the blank control example (without cathode lithium replenishment material) prepared in Example 4. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] In this invention, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions that include the listed features.

[0037] In this invention, numerical ranges are involved. Unless otherwise specified, the numerical ranges are considered continuous 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 features or characteristics, 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 included.

[0038] Example 1 This embodiment provides a method for preparing a positive electrode lithium supplementation material, including the following steps: In a drying room with a dew point of -40°C, lithium oxide and lithium-rich manganese-based material (LRM, purchased from GRINM New Energy Materials (Jiangxi) Co., Ltd., PL-6) were mixed at a mass ratio of 1:1 and placed in a zirconium oxide ball mill jar. A planetary ball mill (PBM) was placed in the drying room with a dew point of -40°C and the rotation speed was controlled at 300 rpm. The milling time was 30 minutes per milling cycle, followed by a 5-minute rest, for a total milling time of 12 hours. The ball mill jar was then opened in the drying room, and the obtained positive electrode lithium replenishment material powder was collected.

[0039] Example 2 The difference between the preparation method of the positive electrode lithium replenishment material provided in this embodiment and that in Example 1 is that the lithium-rich manganese-based material is replaced with lithium nickel cobalt manganese oxide (NCM, purchased from Ningbo Ronbay New Energy Technology Co., Ltd., S85EL).

[0040] Example 3 The difference between the preparation method of the positive electrode lithium replenishment material provided in this embodiment and that in Example 1 is that the lithium-rich manganese-based material is replaced with lithium iron phosphate nickel cobalt manganese oxide (LFP, purchased from Shenzhen Defang Nanotechnology Co., Ltd., DY-17).

[0041] Example 4 The difference between the preparation method of the positive electrode lithium replenishment material provided in this embodiment and that in embodiment 1 is that the ball milling speed is controlled at 350 rpm, the ball milling time is 30 minutes, the rest time is 5 minutes, and the total ball milling time is 18 hours.

[0042] Figure 1 X-ray diffraction (XRD) patterns of the LRM and the cathode lithium replenishment material prepared in Example 4, by Figure 1 It can be seen that, by comparing the XRD data of LRM and the positive electrode lithium replenishment material prepared in Example 4, two weaker new peaks were found near 32° and 51°, in addition to the LRM peak and the Li2O peak. This is because the crystal structure was changed after the transition metal was inserted into the Li2O crystal structure, or new substances were formed.

[0043] Figure 2 This is a scanning electron microscope (SEM) image of the positive electrode lithium replenishment material prepared in Example 4. Figure 3 This is the BET desorption curve of the positive electrode lithium replenishment material prepared in Example 4. (From...) Figures 2-3 It can be seen that the particle size of the lithium-rich manganese-based material is refined after ball milling, and the structure of many secondary ball particles is destroyed. BET data shows that the specific surface area of ​​the lithium-rich manganese-based material after ball milling is 1.742 m². 2 / g, after ball milling with Li2O, increased to 8.381m. 2 / g, this conclusion can be corroborated by the SEM data, indicating that ball milling destroys the original structure, reduces the particle size, and increases the specific surface area.

[0044] Figure 4 The image shown is an X-ray photoelectron spectroscopy (XPS) analysis diagram of the cathode lithium replenishment material prepared in Example 4. Figure 4 The disappearance of the XPS peak in Mn2p after ball milling indicates that a new phase was generated during the ball milling process.

[0045] Comparative Example 1 The difference between the preparation method of the positive electrode lithium replenishment material provided in this embodiment and that in Example 1 is that it is entirely composed of lithium oxide (i.e., without a transition metal source).

[0046] Comparative Example 2 The difference between the preparation method of the positive electrode lithium replenishment material provided in this embodiment and that in Example 1 is that lithium oxide and lithium-rich manganese-based material are prepared in a mass ratio of 0.5:1.

[0047] Comparative Example 3 The difference between the preparation method of the positive electrode lithium replenishment material provided in this comparative example and that in Example 1 is that the ball milling speed is controlled at 400 rpm.

[0048] Comparative Example 4 The difference between the preparation method of the positive electrode lithium replenishment material provided in this comparative example and that in Example 1 is that the total ball milling time is 20 h.

[0049] Comparative Example 5 This embodiment provides a positive electrode lithium replenishment material as a mixture of lithium oxide and lithium-rich manganese-based material, wherein the mass ratio of lithium oxide to lithium-rich manganese-based material is 1:1.

[0050] Comparative Example 6 The difference between the preparation method of the positive electrode lithium replenishment material provided in this comparative example and that in Example 1 is that lithium oxide and lithium-rich manganese-based material are prepared in a mass ratio of 3:1.

[0051] Theoretical calculation Experimental methods All calculations were performed within the framework of density functional theory, using the DMol3 module in Materials Studio software, employing a first-principles electronic structure calculation method combining the generalized gradient approximation (GGA) and plane wave expansion (PBE). The cutoff energy for the plane wave was set to 480 eV. In the iterative solutions of the equations, the energy baseline was set to 10 eV. -5 Ha. All structures are relaxed until the residual forces on the atoms drop below 0.002 Ha / Å.

[0052] Experimental results To verify the effect of transition metal incorporation on lithium oxide, first-principles calculations were performed in this experiment. The results are as follows: Figures 5-6 As shown, Figure 5 The density of states curve of the material shows that, compared with the undoped sample, the 3d electron orbitals of the doped atoms (Co 3d or Ni 3d) form new hybrid orbitals between the conduction band and the band gap, which improves the conductivity of the material. Figure 6 The image shows the crystal orbital Hamiltonian curves. The Li-O bond strength was quantitatively evaluated by calculating the negative integral crystal orbital Hamiltonian (-ICOHP). The low -ICOHP values ​​(No_doped: 1.15 eV, Co_doped: 1.09 eV, Ni_doped: 0.84 eV) indicate weaker bond strength after transition metal doping, suggesting a weakened interaction between Li and O, and indicating that the Li-O bond is more easily broken during charging.

[0053] Specifically, Figure 5 The density of states (DPS) diagrams (a, b, and c) systematically reveal the profound influence of cobalt (Co) and nickel (Ni) doping on the electronic band structure of the material. In the undoped case, such as... Figure 5As shown in Figure a, undoped Li₂O exhibits a wide band gap. This characteristic is typical of the electronic structure of semiconductors or insulators because it means that at absolute zero, the valence band is completely filled with electrons, while the conduction band is completely empty, and there are no quantum states available for electron migration at the Fermi level, resulting in extremely low intrinsic conductivity. However, the situation changes fundamentally when Co or Ni (implanted Li sites) is introduced for doping. Figure 5 As clearly seen in diagrams b and c, a series of new, continuous electronic states appear near the Fermi level (approximately -2 eV to 2 eV). The density of states of these new states is not zero at the Fermi level, implying a narrowing of the band gap. Comparing the contributions of different orbitals reveals that these new states primarily originate from the 3d electron orbitals of the dopant atoms (Co 3d or Ni 3d), and they exhibit significant orbital hybridization with the 2p orbitals of oxygen in the bulk material. This hybridization effect expands the d electron states, originally localized on the dopant atoms, into a shared energy band across the entire crystal lattice. The direct physical consequence is that the Fermi level is no longer in a stateless band gap but extends across this newly formed, partially electron-filled band. According to solid-state physics, such a partially filled band exhibits metallic properties. Therefore, the doping behavior essentially induces a metallization transition, improving the material's conductivity, which makes it possible to apply this material to electrode applications requiring high conductivity.

[0054] The negative integral crystal orbital Hamiltonian (-ICOHP) was calculated to quantitatively evaluate the Li-O bond strength. The results are as follows: Figure 6 The values ​​d, e, and f are shown in the figure. The lower -ICOHP values ​​(No_doped: 1.15 eV, Co_doped: 1.09 eV, Ni_doped: 0.84 eV) indicate weaker bond strength after transition metal doping, suggesting a weakened interaction between Li and O, and indicating that the Li-O bond is more easily broken during charging. The decomposition process of Li₂O involves the dissociation of the Li-O bond and the formation of OO bonds. The calculation results provide theoretical predictions for the experiment, preliminarily confirming the possibility of experimental success.

[0055] Theoretical calculations verify the effectiveness of doping: First-principles calculations show that Co or Ni doping can alter the electronic structure of Li₂O, introducing a continuous density of states near the Fermi level, making the material metallic and improving its conductivity. Simultaneously, crystal orbital Hamiltonian population (-ICOHP) analysis shows that the Li-O bond strength weakens after doping (undoped: 1.15 eV, Co-doped: 1.09 eV, Ni-doped: 0.84 eV), which is beneficial for Li₂O decomposition.

[0056] Performance testing Button production: The positive electrode for coin cells is fabricated by adding positive electrode lithium supplement material, conductive agent (conductive carbon black), and binder (polyvinylidene fluoride, PVDF) in a weight ratio of 40:45:15 into the hopper of a Thinky small homogenizer. Oxalic acid is then added at 2% of the total weight, and finally N-methylpyrrolidone (NMP) is added to adjust the slurry solid content to 40 wt%. Homogenization is then performed using a program set at 800 rpm (1 min) - 1500 rpm (5 min) - 2000 rpm (20 min) - 1500 rpm (1 min). After homogenization, a 300 μm thick coating is applied to a 15 μm aluminum foil, which is then dried in a vacuum oven. After drying, the electrode is cut into 14 mm diameter sheets and rolled using a roller press with a 50 μm gap. The coin cell assembly uses 2032 coin cells, and the negative electrode uses a 16 mm diameter lithium sheet.

[0057] The standard capacity test of the coin cell was conducted using the Blue Battery Performance Testing System, and the electrolyte used was ESIC-1 electrolyte from Guangzhou Tinci Advanced Materials Co., Ltd. The battery was charged and discharged at 0.1C, with a voltage range of 2.5-4.8V.

[0058] Specific capacity = charging capacity / mass of positive electrode lithium replenishment material The first-week charging curves of the above embodiments and comparative examples are shown below. Figures 7-9 As shown in Table 1.

[0059] Table 1

[0060] Figure 7 The figures show the first-week charging curves of the coin cells prepared using the cathode lithium replenishment materials in Examples 1-4. Combined with Table 1, it can be seen that the cathode lithium replenishment materials prepared using the high-energy ball milling mechanochemical method provided by this invention exhibited charging specific capacities of 494 mAh / g, 275.1 mAh / g, and 155.5 mAh / g in Examples 1-3, respectively, using different transition metal sources LRM, NCM, and LFP. Compared to the specific capacity of the transition metal source itself, the actual specific capacity exhibited by the cathode lithium replenishment materials in Examples 1-3 is higher than that of the transition metal source material itself. Therefore, it can be concluded that all three transition metal source materials have a certain catalytic effect. However, using LRM as the transition metal source showed a higher specific capacity, indicating that LRM is more suitable as a transition metal source for catalyzing the decomposition of Li₂O. This is because LRM, as a two-phase solid solution, has lower structural stability than LFP and NCM, and its transition metal is more easily extracted. Meanwhile, comparing Examples 1, 4, 3, and 4, the optimal ball milling time was found to be 18 hours and the optimal ball milling speed was 350 rpm by adjusting the ball milling time and speed.

[0061] Figure 8 The first-week charging curves of the coin cells prepared by the positive electrode lithium replenishment materials of Example 1 and Comparative Example 2 are shown in Table 1. As can be seen from Table 1, changing the ratio of lithium-rich material to Li2O, i.e. reducing the proportion of lithium oxide, will actually reduce the charging capacity.

[0062] Figure 9 The first-week charging curves of the coin cells made from the positive electrode lithium replenishment materials of Comparative Examples 1 to 6 are shown in Table 1. It can be seen from Table 1 that Comparative Example 5, without ball milling, does not show lithium replenishment capacity by simply homogenizing the lithium-rich material and Li2O.

[0063] All-battery construction: (1) By weight, lithium-rich manganese-based material (PL-6) (90 parts), positive electrode lithium replenishment material (5 parts), multi-walled carbon nanotubes (2.4 parts), single-walled carbon nanotubes (0.1 parts), carbon black (5 parts) and oxalic acid (2 parts) are mixed in a pre-prepared PVDF (polyvinylidene fluoride) solution (PVDF is 2.5 parts, and the weight ratio of PVDF to NMP is 10:90) to prepare a positive electrode slurry. The homogenizing equipment is a Hongyun double planetary homogenizer. The obtained positive electrode slurry is uniformly coated on an aluminum foil current collector, and the positive electrode is obtained after drying, rolling, slitting and vacuum drying.

[0064] (2) By weight, a mixture of graphite (80 parts) and silicon carbon (11 parts) (91 parts), multi-walled carbon nanotubes (1.62 parts), single-walled carbon nanotubes (0.8 parts), oxalic acid (0.2 parts) and carbon black (6 parts) were evenly dispersed in a mixed solution of CMC (sodium carboxymethyl cellulose) and PAA (polyacrylic acid) (CMC is 1.6 parts, PAA is 2 parts, and the weight ratio of CMC, PAA and water is 2.3:8.5:97.7). Finally, SBR (styrene-butadiene rubber, 2.9 parts) was added to prepare the negative electrode slurry. The homogenizing equipment used was a Hongyun double planetary homogenizer. The obtained negative electrode slurry was evenly coated on a copper foil current collector, and the negative electrode was obtained after drying, rolling, slitting and vacuum drying.

[0065] (3) The positive and negative electrode sheets are cut into 55×77 mm and 57×79 mm respectively. A separator with a thickness of 12+4μm is used. A 5×6 layer battery is made by stacking the sheets. After drying, liquid injection and formation, a full cell is obtained.

[0066] Cyclic performance testing: In accordance with national standard GB / T 31484 (Cyclic life requirements for power batteries for electric vehicles) and IEC 62660 and other standards, this test is divided into two main stages: First, the battery capacity is calibrated using a 0.33C rate to determine its initial capacity; then, under the same environmental conditions, charge and discharge cycles are performed using a 1C rate until the battery capacity decays to a specified threshold (usually 80% of the initial capacity) to evaluate its cycle life.

[0067] 0.33C Capacity Calibration Procedure The purpose of this step is to accurately determine the initial capacity (C0) of the battery.

[0068] Charging: At 25℃, charge at a constant current of 0.33C until the battery charging cutoff voltage of 4.45V, then switch to constant voltage charging until the charging current drops to 0.05C and charging is stopped.

[0069] Rest: After charging is complete, let the battery rest for 30 minutes.

[0070] Discharge: Discharge at a constant current of 0.33C until the discharge cutoff voltage of 2.5V, and record the discharge capacity. This capacity is the rated capacity C0.

[0071] Rest: After charging is complete, let the battery rest for 30 minutes.

[0072] Repeat: Usually, the above charge and discharge process is repeated 2-3 times, and the average value of the stable discharge capacity is taken as the final calibrated capacity.

[0073] 1C Cycle Life Test Procedure Based on the calibrated capacity, perform cyclic testing at 1C rate.

[0074] Charging: Charge at a constant current of 1C until the charging cutoff voltage is reached, then switch to constant voltage charging until the current drops to 0.05C to cut off.

[0075] Let stand: After charging is complete, let stand for 30 minutes.

[0076] Discharge: Discharge at a constant current of 1C until the discharge cutoff voltage is reached, and record the discharge capacity.

[0077] Let stand: After the discharge is complete, let stand for 30 minutes.

[0078] Cycle: Repeat steps 1-4 to form a complete charge-discharge cycle. Record the discharge capacity in each cycle.

[0079] Test termination condition: Stop the test when the battery's discharge capacity decays to 80% of the initial rated capacity (C0). Record the number of cycles completed at this point, which is the battery's cycle life at 1C rate.

[0080] The cycle performance test results of the full cells prepared using the positive electrode lithium replenishment material and the blank control (without positive electrode lithium replenishment material) in Example 4 are as follows: Figure 10 As shown.

[0081] Figure 10 This is a cycle performance curve of the full cell prepared using the positive electrode lithium replenishment material in Example 4 and the blank control example (without the positive electrode lithium replenishment material). Figure 10It can be seen that the retention rate after 600 cycles increased from 62% in the blank control example to 85% in Example 4.

[0082] This invention provides a positive electrode lithium replenishment material and its preparation method, which successfully reduces the decomposition potential and improves the electrochemical performance, providing technical support for the industrial application of lithium batteries.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention 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 of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A positive electrode lithium replenishment material, characterized in that, Transition metals are embedded in the Li2O lattice.

2. The positive electrode lithium replenishment material according to claim 1, characterized in that, The transition metal is selected from at least one of manganese, nickel, cobalt, and iron.

3. The positive electrode lithium replenishment material according to claim 2, characterized in that, The transition metal is selected from at least one of manganese, nickel, and cobalt.

4. A method for preparing a positive electrode lithium replenishment material, characterized in that, include: Li2O and a transition metal source were mixed at a mass ratio of (0.7~1.5):1 and then ball-milled at a speed of 250~350 rpm for 12~18 h.

5. The method for preparing the positive electrode lithium replenishment material according to claim 4, characterized in that, The ball mill rotates at a speed of 300-350 revolutions per minute.

6. The method for preparing the positive electrode lithium replenishment material according to claim 4 or 5, characterized in that, The ball milling time is 15-18 hours.

7. The method for preparing the positive electrode lithium replenishment material according to any one of claims 4 to 6, characterized in that, The transition metal source is selected from at least one of lithium-rich manganese-based materials, lithium-ion battery ternary materials, and lithium iron phosphate.

8. The method for preparing the positive electrode lithium replenishment material according to any one of claims 4 to 6, characterized in that, The transition metal source is a lithium-rich manganese-based material.

9. The method for preparing the positive electrode lithium replenishment material according to any one of claims 4 to 7, characterized in that, The ball milling was carried out under conditions where the dew point was ≤-40℃.

10. A lithium-ion battery, characterized in that, The positive electrode lithium replenishment material includes the positive electrode lithium replenishment material as described in any one of claims 1 to 3 or the positive electrode lithium replenishment material prepared by the preparation method as described in any one of claims 4 to 9.

Images