Preparation and application of a full-decomposition positive electrode pre-lithiation agent

Abstract

The application relates to preparation and application of a full-decomposition type positive electrode pre-lithium agent, and comprises the following steps: reacting sodium acetonedicarboxylate with a hydrogen ion exchange resin to generate C3O6H4; then adding a lithium source into the C3O6H4 solution to obtain C3O6H2Li2 powder through drying; dissolving the C3O6H2Li2 powder under an inert atmosphere, mixing the solution with a butyl lithium solution, centrifuging the mixed solution to obtain white powder; and cleaning the white powder, and drying the white powder to obtain the full-decomposition type positive electrode pre-lithium agent; compared with the prior art, the application has the advantages of improving the positive electrode capacity and the initial efficiency of a full battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to the preparation and application of a fully decomposable positive electrode pre-lithiation agent. Background Technology

[0002] Lithium-ion batteries, with their high energy density, good cycle stability, compact size, convenience, and environmental friendliness, have become the representative of modern high-performance rechargeable batteries. Currently, portable consumer electronics products such as laptops, cameras, and smartphones all use lithium-ion batteries. In recent years, with the development of emerging markets such as electric vehicles and energy storage power stations, lithium-ion batteries have gained broader application prospects in large-scale energy storage devices and distributed mobile power sources, while also requiring further improvement in the energy density of lithium-ion batteries.

[0003] For existing lithium-ion batteries with graphite-based anodes, side reactions occur during the formation of the solid electrolyte interface (SEI) on the anode surface, accompanied by the decomposition of the liquid electrolyte, resulting in the consumption of active lithium sources from lithium oxide or phosphate cathodes. This leads to a coulombic efficiency below 100% in the initial charge-discharge cycles (initial coulombic efficiency is 80%-90%), significantly reducing the energy density of the lithium-ion battery (LIB). For next-generation high-energy-density LIBs, high-capacity anodes with alloying reaction mechanisms, such as Si, Sn, and P, experience even more severe side reactions and exhibit greater lithium source loss (>20%) in the first cycle compared to graphite-based anodes. Therefore, the reversible capacity and energy density of lithium-ion batteries using these high-capacity anode materials will decrease significantly, severely hindering their practical application.

[0004] Pre-lithiation technology is an effective way to solve the problem of low initial efficiency of lithium-ion battery anode materials. Its main purpose is to counteract the lithium ions consumed during the lithium-ion battery formation process, thereby improving the discharge capacity of the positive electrode. Currently, pre-lithiation is mainly divided into positive electrode pre-lithiation and negative electrode pre-lithiation.

[0005] Negative electrode pre-lithiation involves placing lithium foil on the negative electrode surface and adding lithium powder to the slurry. The addition of lithium powder to the negative electrode primarily utilizes stabilized lithium metal powder (SLMP) to achieve pre-lithiation: as shown in Chinese patent applications CN10832143A and CN110010863A. Lithium powder can be added during the negative electrode slurry preparation process or sprayed onto the negative electrode surface, making the operation relatively simple. Due to the Li2CO3 protective layer covering the Li metal particles, SLMP exhibits stability in dry air. The protective layer can isolate moisture and oxygen in the air, mitigating safety issues associated with Li metal applications to some extent. However, the safety of lithium powder handling remains difficult to guarantee.

[0006] Pre-lithiation of the cathode mainly involves introducing cathode additives to supplement the active lithium source and improve the discharge capacity of the cathode. The selection of cathode additives needs to consider the following two aspects: first, the working voltage of the additive should match the voltage range of the positive and negative electrodes; second, as a sacrificial lithium salt, the decomposition products of the additive should possess chemical and electrochemical stability. Chinese patent application CN112467139A discloses a pre-lithiation method for lithium-ion battery cathode materials, which uses Li... x (Cu y Fe z O2 is used as a pre-lithiation additive and added to the positive electrode slurry to prepare the positive electrode sheet. Its application in lithium-ion secondary batteries can improve the first-cycle coulombic efficiency and energy density. However, the additive has a low capacity, and the pre-lithiation material still exists in the battery after the lithium ions are released, occupying a certain mass and reducing its specific energy.

[0007] Considering factors such as battery performance, operability, and safety, researchers have proposed a pre-lithiation method using self-sacrificing lithium salts as cathode additives. These cathode additives include lithium diketosuccinate (Li₂C₄O₆), lithium squaric acid (Li₂C₄O₄), and lithium oxalate (Li₂C₂O₄). During the first charge, anions in the cathode additive lose electrons, generating lithium metal and CO₂ gas. The generated gas does not affect the battery's cycle performance. Simultaneously, it increases the porosity of the cathode material, improving the lithium content. + The mobility of carbon dioxide gas can be discharged after the first cycle, further improving the specific capacity of the positive electrode and the first-cycle efficiency of the full cell. However, lithium oxalate (Li2C2O4) additives have problems such as low specific capacity and high decomposition potential. The incomplete decomposition of byproducts such as lithium diketosuccinate (Li2C4O6) and lithium squaric acid (Li2C4O4) limits their application in industry. Summary of the Invention

[0008] The purpose of this invention is to overcome the defects of the prior art and provide a fully decomposable positive electrode pre-lithiation agent that can improve the specific capacity of the positive electrode and the first-cycle coulombic efficiency of lithium-ion batteries, and its preparation and application.

[0009] The objective of this invention can be achieved through the following technical solutions:

[0010] The preparation of a fully decomposable positive electrode pre-lithiation agent includes the following steps:

[0011] S1: Sodium pyruvate is reacted with hydrogen ion exchange resin to produce C3O6H4;

[0012] S2: Add a lithium source to a C3O6H4 solution and dry to obtain C3O6H2Li2 powder;

[0013] S3: Dissolve C3O6H2Li2 powder under an inert atmosphere, then mix it with butyllithium solution, centrifuge the mixture to obtain a white powder;

[0014] S4: The white powder is washed and dried to obtain the fully decomposed positive electrode pre-lithiation agent, which is 2,2-dilithiumoxyacetone dicarboxylate (C3O6Li4) pre-lithiation agent.

[0015] The preparation of a fully decomposable positive electrode pre-lithiation agent includes the following steps:

[0016] S1: Sodium pyruvate is reacted with hydrogen ion exchange resin to produce C3O6H4;

[0017] S2: Add a lithium source to a C3O6H4 solution and dry to obtain lithium oxalate (C3O5Li2), which is a fully decomposed positive electrode pre-lithiation agent.

[0018] Further, in step S1, the mass-to-volume ratio of sodium pyruvate to hydrogen ion exchange resin is 1.5-1.8 g:100 ml, more preferably 1.8 g:100 ml.

[0019] Furthermore, in step S2, the lithium source includes LiOH or Li2CO3.

[0020] Furthermore, in step S2, the molar ratio of C3O6H4 to the lithium source is 1:2-1:1.

[0021] Further, in step S3, the molar ratio of C3O6H2Li2 to butyllithium is 1:2-1:1.

[0022] Furthermore, in step S4, the drying temperature is 80-120℃.

[0023] The application of a fully decomposable positive electrode pre-lithiation agent includes: mixing the fully decomposable positive electrode pre-lithiation agent with positive electrode active material, conductive agent and binder evenly, and then forming a slurry to obtain a positive electrode sheet.

[0024] Furthermore, the amount of the fully decomposable positive electrode pre-lithiation agent added is 2 to 10% of the mass of the positive electrode active material.

[0025] Furthermore, the positive electrode active material includes one or more of lithium iron phosphate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0026] This invention synthesizes novel self-sacrificing cathode additives, including lithium oxalate and lithium 2,2-dilithiumoxyacetone dioxide, using an industrially feasible method. Their decomposition potentials are 4.45V and 4.9V, respectively, with delithiation voltages. The anions in the cathode additive lose electrons, generating lithium metal, CO, and CO2 gas. After degassing, the specific capacity is close to that of lithium metal, reaching as high as 3714 mAh / g. This additive can be added to cathode materials such as lithium iron phosphate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and lithium manganese iron phosphate to improve the specific capacity and cycle performance of the entire battery. Complete decomposition occurs after the first cycle, with the generated lithium metal replenishing the active lithium source of the cathode, and the gas being discharged after the first cycle, further improving the battery's energy density. Half-cell and full-cell tests showed that adding 4.8 wt% lithium oxalate or 10 wt% lithium 2,2-dilithiumoxyacetone dioxide to the positive electrode could increase the first-cycle discharge specific capacity of the electrode to 155.8 mAh / g and 163.5 mAh / g, respectively (compared to 147.3 mAh / g for the control group).

[0027] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0028] (1) The lithium oxalate and lithium 2,2-dilithiumoxyacetone diol prelithiate in the fully decomposable positive electrode prelithiate prepared in this invention replenish the positive electrode active lithium source by self-decomposing to generate lithium metal during the use of the electrode, thereby increasing the specific capacity of the material and the first-cycle coulombic efficiency. Experiments show that by adding the above fully decomposable positive electrode prelithiate, the first-cycle discharge specific capacity of the electrode can be increased by about 15%, which is an excellent positive electrode prelithiate additive.

[0029] (2) The present invention adds the pre-lithiation agent to the positive electrode material. The lithium ions released during the first charge cycle form an SEI film on the surface of the negative electrode. The carbon dioxide produced by the decomposition can improve the interface stability of graphite and silicon negative electrode. If the carbon dioxide is discharged, the specific capacity of the positive electrode and the first efficiency of the whole battery can be further improved. Attached Figure Description

[0030] Figure 1 Infrared curve of the C3O6Li4 pre-lithiated material prepared in Example 1;

[0031] Figure 2 SEM image of the C3O6Li4 pre-lithiated material prepared in Example 1;

[0032] Figure 3 A comparison of the charging curves of the batteries prepared in Example 3 and Comparative Example 1;

[0033] Figure 4 This is a comparison graph showing the capacity cycling of the batteries prepared in Example 3 and Comparative Example 1.

[0034] Figure 5A comparison graph of charge-discharge curves for batteries prepared in Example 3 and Comparative Example 1 at different cycle numbers;

[0035] Figure 6 This is a comparison chart of the coulombic efficiencies of the batteries prepared in Example 3 and Comparative Example 1;

[0036] Figure 7 SEM image of lithium oxalate prepared in Example 6;

[0037] Figure 8 The infrared spectrum of lithium oxalate prepared in Example 6;

[0038] Figure 9 The specific capacity of lithium oxalate under different charging rates in Example 9;

[0039] Figure 10 The full-cell cycling curves are for Example 9 and Comparative Example 1. Detailed Implementation

[0040] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0041] To address the problems existing in the prior art, this invention proposes a method for preparing and applying a fully decomposable positive electrode pre-lithiation agent. The positive electrode containing the pre-lithiation agent can improve the specific capacity of the positive electrode and the first-cycle efficiency of the full cell.

[0042] The present invention proposes a fully decomposable positive electrode pre-lithiation agent, wherein the positive electrode pre-lithiation agents are lithium oxalate (C3O5Li2) and lithium 2,2-dilithiumoxyacetone dioxide (C3O6Li4).

[0043] C3O6Li4 possesses a high theoretical specific capacity, with a specific capacity of 3714 mAh / g after degassing. Therefore, only a small amount needs to be added to improve the battery's first-cycle efficiency. For pouch batteries, the degassing and sealing process during manufacturing effectively removes the carbon dioxide generated during pre-lithiation, further improving the battery's specific energy. Simultaneously, the carbon dioxide partially dissolved in the electrolyte after the initial degassing of C3O6Li4 helps form a stable SEI film, which has a beneficial impact on battery cycle life. During the first charge, the C3O6Li4 additive, acting as a pre-lithiation material, undergoes a complete decomposition reaction within the 2-4.9V operating voltage range. The reaction equation is as follows:

[0044] C3O6Li4→3CO2+4Li + +4e -

[0045] Lithium oxalate as a pre-lithiation material: During the first charge, the C3O5Li2 additive, acting as a pre-lithiation material, undergoes a complete decomposition reaction within the 2-4.45V operating voltage range. The reaction equation is as follows:

[0046] C3O5Li2→2CO2+CO+2Li + +2e -

[0047] The generated lithium ions move through the separator to the negative electrode to compensate for the irreversible capacity loss during the formation of the SEI film. After the gas is discharged, the goals of improving the first-cycle coulombic efficiency and ensuring the specific energy of the battery can be achieved simultaneously.

[0048] The preparation of a fully decomposable positive electrode pre-lithiation agent includes the following steps:

[0049] (1): Reaction of 1.8g sodium acetone with excess hydrogen ion exchange resin: Since the active groups of the hydrogen ion exchange resin contain active hydrogen ions, which can be dissociated in water, they can be used to react with Na+. + The exchange process produces C3O6H4;

[0050] (2): Add lithium source to C3O6H4 solution, stir the resulting solution with ultrasonication and spray dry to obtain C3O6H2Li2 powder;

[0051] (3): C3O6H2Li2 powder was dissolved in n-hexane under an inert atmosphere, then mixed with butyllithium solution, heated and stirred for 5-7 days, and the resulting solution was centrifuged to obtain a white powder;

[0052] (4): Dissolve the white powder in n-hexane, centrifuge, remove the supernatant, repeat three times, and dry to obtain C3O6Li4 prelithiating agent;

[0053] In step (2), the obtained C3O6H2Li2 powder is dried in a vacuum drying oven for 10-12 hours at a temperature of 160-200℃ to obtain a light yellow powder, which is the lithium oxalate C3O5Li2 pre-lithiation agent.

[0054] In some specific embodiments of the present invention, the hydrogen ion exchange reaction requires washing with H2SO4 and deionized water 3-5 times. The preferred H2SO4 used is a 1M H2SO4 solution.

[0055] In some specific embodiments of the present invention, the mass-to-volume ratio of sodium pyruvate to hydrogen ion exchange resin is 1.8 g: 100 ml.

[0056] In some specific embodiments of the present invention, the lithium source mentioned in step (2) includes LiOH or Li2CO3:

[0057] When the lithium source is LiOH, the molar ratio of C3O6H4 to LiOH is 1:2;

[0058] When the lithium source is Li2CO3, the molar ratio of C3O6H4 to Li2CO3 is 1:1.

[0059] In some specific embodiments of the present invention, the molar ratio of the C3O6H4 solution to the lithium source in step (2) is 1:2-1:1.

[0060] In some specific embodiments of the present invention, the inlet air temperature of the spray drying in step (2) is 120°C, the peristaltic pump speed is 20 rpm, and the fan frequency is 25 Hz.

[0061] In some specific embodiments of the present invention, the molar ratio of C3O6H2Li2 to butyllithium in step (3) is 1:2-1:1.

[0062] In some specific embodiments of the present invention, the drying temperature in step (4) is 80-120°C and the drying time is 10-12h.

[0063] In some specific embodiments of the present invention, the centrifugation speed in steps (3) and (4) is 2000 rpm and the centrifugation time is 5-8 min.

[0064] This invention also proposes the application of the above-mentioned lithium-ion battery positive electrode pre-lithiation agent in lithium-ion battery positive electrode lithium replenishment. In the positive electrode slurry preparation process, the lithium-ion battery positive electrode pre-lithiation agent is mixed evenly with positive electrode active material, conductive agent and binder, and then coated, dried and rolled to prepare positive electrode sheet.

[0065] In some specific embodiments of the present invention, the amount of the fully decomposable positive electrode pre-lithiation agent added is 2-10% of the mass of the positive electrode active material.

[0066] In some specific embodiments of the present invention, the positive electrode active material includes one or more of lithium iron phosphate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0067] In this invention, the prepared C3O6Li4 cathode pre-lithiation agent has a delithiation voltage of 2 to 4.9 V and an initial coulombic efficiency of 2 to 5%.

[0068] The following embodiments are implemented based on the above-described technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments.

[0069] The following are more detailed implementation examples, which further illustrate the technical solution of the present invention and the technical effects that can be obtained.

[0070] In the following embodiments, unless otherwise specified, the raw materials, reagents or processing techniques are all conventional commercial products or conventional processing techniques in the art.

[0071] Example 1

[0072] This embodiment provides a method for preparing a fully decomposable positive electrode pre-lithiation agent, comprising the following steps:

[0073] S11: React 1.8g of sodium pyruvate with 100ml of hydrogen ion exchange resin. Because the active groups of the hydrogen ion exchange resin contain active hydrogen ions, these ions can dissociate in water and react with Na+. + The exchange process produces C3O6H4;

[0074] S12: Subsequently, LiOH aqueous solution was added to C3O6H4 solution (molar ratio of C3O6H4 to LiOH was 1:2). The resulting reaction solution was ultrasonically stirred and then spray-dried (inlet air temperature was 120℃, peristaltic pump speed was 20rpm, and fan frequency was 25Hz) to obtain C3O6H2Li2 powder.

[0075] S13: C3O6H2Li2 powder was dissolved in 50 ml of n-hexane under an inert atmosphere (argon) and then mixed with butyllithium solution. The molar ratio of C3O6H2Li2 to butyllithium was 1:2. The mixture was heated and stirred for 5 days. The resulting solution was centrifuged (2000 rpm for 8 min) to obtain a white powder.

[0076] S14: Dissolve the white powder in 50 ml of n-hexane, centrifuge (2000 rpm, 8 min), remove the supernatant, repeat three times, and dry to obtain C3O6Li4 pre-lithiation agent.

[0077] like Figure 1 As shown, LMT: C3O6H2Li2; TLMT: C3O6Li4. Infrared spectra show that after reacting with n-butyllithium, the wavelength ranges from 2500 to 3500 cm⁻¹. -1 The disappearance of the corresponding hydroxyl vibration peak proves the formation of the C3O6Li4 pre-lithiation agent. The surface microstructure of the C3O6Li4 pre-lithiation agent is as follows: Figure 2 As shown.

[0078] Example 2

[0079] This embodiment provides an application of a fully decomposable positive electrode pre-lithiation agent, including the following steps:

[0080] C3O6Li4 pre-lithiation agent, lithium iron phosphate positive electrode active material, Super P conductive agent, and Pvdf binder were mixed in a pulping machine at a mass ratio of 2:98:10:10 for 20 minutes. The mixture was then evenly coated onto aluminum foil with a scraper, dried in a vacuum oven at 80℃ for 12 hours, and then rolled to obtain the positive electrode sheet.

[0081] Using lithium sheets as the negative electrode, a CR2025 coin cell was assembled in a glove box and an electrochemical discharge test was conducted.

[0082] A negative electrode sheet was prepared using graphite material with a specific capacity of 370 mAh / g, and assembled into a CR2025 coin cell in a glove box for room temperature cycling testing.

[0083] Comparative Example 1

[0084] The preparation of a positive electrode sheet is the same as that in Example 2, except that C3O6Li4 pre-lithiation agent is not added.

[0085] Using lithium sheets as the negative electrode, a CR2025 coin cell was assembled in a glove box and an electrochemical discharge test was conducted.

[0086] Negative electrode sheets were prepared using graphite material with a specific capacity of 372 mAh / g and nano-silicon material with a specific capacity of 2300 mAh / g, respectively, and assembled into CR2025 coin cells in a glove box for room temperature cycling tests.

[0087] Example 3

[0088] This embodiment provides an application of a fully decomposable positive electrode pre-lithiation agent. The difference from Embodiment 2 is that the mass ratio of C3O6Li4 pre-lithiation agent to the positive electrode active material lithium iron phosphate is different: it is 10:90. The other steps are the same as in Embodiment 2.

[0089] The batteries prepared in Example 3 and Comparative Example 1 were subjected to charging tests, and the charging curves are shown in the comparison graph. Figure 3 As shown in the figure, the discharge capacity of the lithium iron phosphate / / graphite full cell (LFP+10TLMT / / Gr) increases after adding 10wt% C3O6Li4 pre-lithiation agent to the lithium iron phosphate cathode. The decomposition of the pre-lithiation agent replenishes the irreversible capacity of the full cell in the first cycle. In the figure, LFP / / Gr is the battery without pre-lithiation agent.

[0090] Capacity cycling tests were performed on the batteries prepared in Example 3 and Comparative Example 1 of this invention. The comparison figures are shown below. Figure 4 As shown in the figure, after adding 10wt% C3O6Li4 pre-lithiation agent to the lithium iron phosphate cathode, the discharge capacity of the lithium iron phosphate / / graphite full cell (LFP+10TLMT / / Gr) increases and the cycle performance improves. In the figure, LFP / / Gr is the battery without pre-lithiation agent.

[0091] The batteries prepared in Example 3 and Comparative Example 1 of this invention were subjected to charge-discharge tests with different numbers of cycles. The comparison figures are shown in the figure below. Figure 5As shown in the figure, after adding C3O6Li4 pre-lithiation agent, the charge-discharge curves of the lithium iron phosphate / / graphite full cell (LFP+10TLMT / / Gr) in cycles 1, 2, 4, and 10 are compared with the charge-discharge curve of the battery (LFP / / Gr) without pre-lithiation agent on the left. The polarization of the battery does not increase significantly, indicating that the pre-lithiation agent has no effect on subsequent cycles.

[0092] The coulombic efficiency of the batteries prepared in Example 3 and Comparative Example 1 of this invention was tested, and the comparison is shown in the figure. Figure 6 As shown in the figure, the addition of C3O6Li4 pre-lithiation agent improves the cycle life of the full battery.

[0093] The battery cathodes and battery performance prepared in Examples 2-3 and Comparative Example 1 of this invention were tested, and the test results are shown in Table 1 (all specific capacities mentioned in the table are calculated based on the mass of the cathode; different anodes do not affect the specific capacity of the cathode). As can be seen from the data in Table 1, the delithiation capacity of the cathode in Example 2 during charging is 15% higher than that in Comparative Example 1, indicating that the extra capacity from the cathode pre-lithiation agent has played a role. This portion of capacity can be used to compensate for the lithium ions consumed by the anode in forming the SEI, thus improving the first-stage efficiency of the entire battery.

[0094] Table 1. Battery cathodes and battery performance test results prepared in Examples 2-3 and Comparative Example 1.

[0095] Example 2 220.7 150.1 Example 3 247.3 163.5 Comparative Example 1 171.5 147.3

[0096] Example 4

[0097] This embodiment provides an application of a fully decomposable positive electrode pre-lithiation agent. The difference from Embodiment 2 is that the mass ratio of C3O6Li4 pre-lithiation agent to the positive electrode active material lithium iron phosphate is different: it is 4:96. The other steps are the same as in Embodiment 2.

[0098] Example 5

[0099] This embodiment provides an application of a fully decomposable positive electrode prelithiation agent, which differs from Embodiment 4 in that the positive electrode active material is lithium nickel cobalt manganese oxide, and the other steps are the same as in Embodiment 2.

[0100] Example 6

[0101] This embodiment provides a method for preparing a fully decomposable positive electrode pre-lithiation agent, comprising the following steps:

[0102] S21: React 1.8g of sodium pyruvate with excess hydrogen ion exchange resin. Because the active groups of the hydrogen ion exchange resin contain active hydrogen ions, these ions can dissociate in water and react with Na+. + The exchange process produces C3O6H4;

[0103] S22: Subsequently, the LiOH aqueous solution was slowly added to the C3O6H4 solution, with a molar ratio of C3O6H4 to LiOH of 1:2. The resulting reaction solution was ultrasonically stirred and then spray-dried to obtain C3O6H2Li2 powder.

[0104] S23: The obtained powder was dried in a vacuum drying oven at 165℃ for 10 hours to obtain a light yellow powder, which is lithium oxalate C3O5Li2. Figure 7 , 8 As shown, by Figure 8 As can be seen in the figure, NMT is the raw material sodium acetone, LMTS120 is C3O6H2Li2 obtained by spray drying at 120℃, and LMTS120H165 is sodium oxalate obtained by vacuum drying LMTS120 at 165℃. It can be seen that sodium oxalate has a thickness of 3500–2500 cm⁻¹. -1 The hydroxyl stretching vibration peak at that location completely disappeared.

[0105] Example 7

[0106] This embodiment provides an application of a fully decomposable positive electrode pre-lithiation agent, including the following steps:

[0107] The C3O5Li2 prelithiation agent, positive electrode active material lithium iron phosphate, conductive agent Super P, and binder Pvdf prepared in Example 6 were mixed in a pulping machine at a mass ratio of 4:96:10:10 for 20 minutes. The mixture was then evenly coated onto aluminum foil with a scraper, dried in a vacuum oven at 80°C for 12 hours, and then rolled to obtain a positive electrode sheet.

[0108] Using lithium sheets as the negative electrode, a CR2025 coin cell was assembled in a glove box and an electrochemical discharge test was conducted.

[0109] A negative electrode sheet was prepared using graphite material with a specific capacity of 370 mAh / g, and assembled into a CR2025 coin cell in a glove box for room temperature cycling testing.

[0110] Example 8

[0111] This embodiment provides an application of a fully decomposable positive electrode pre-lithiation agent. The difference from Embodiment 7 is that the mass ratio of C3O5Li2 pre-lithiation agent to the positive electrode active material lithium iron phosphate is different: it is 6:94. The other steps are the same as in Embodiment 7.

[0112] Example 9

[0113] This embodiment provides an application of a fully decomposable positive electrode pre-lithiation agent. The difference from Embodiment 7 is that the mass ratio of C3O5Li2 pre-lithiation agent to the positive electrode active material lithium iron phosphate is different: it is 4.8:95.2. The other steps are the same as in Embodiment 7.

[0114] Example 10

[0115] This embodiment provides an application of a fully decomposable positive electrode prelithiation agent, which differs from Embodiment 8 in that the positive electrode active material is lithium nickel cobalt manganese oxide, and the other steps are the same as in Embodiment 7.

[0116] Example 11

[0117] This embodiment provides an application of a fully decomposable positive electrode pre-lithiation agent, which differs from Embodiment 9 in that:

[0118] During room temperature cycling tests: A negative electrode sheet was prepared using nano-silicon material with a specific capacity of 2300 mAh / g, and assembled into a CR2025 coin cell in a glove box. Other steps were the same as in Example 7.

[0119] Performance testing

[0120] Figure 9 The figure shows the specific capacity and voltage curves of the batteries prepared in Example 9 at different rates. As can be seen from the figure, as the rate increases, the specific capacity of the lithium oxalate electrode does not differ significantly and no obvious polarization is observed.

[0121] Capacity cycling tests were performed on the batteries prepared in Example 9 and Comparative Example 1 of this invention. The comparison figures are shown below. Figure 10 As shown in the figure, after adding 4.8 wt% C3O5Li2 pre-lithiation agent to the lithium iron phosphate cathode, the discharge capacity of the lithium iron phosphate / / graphite full cell (LFP+4.8% DLMT / / Gr) increases, the cycle performance improves, and the cycle efficiency is high. In the figure, LFP / / Gr is the battery without the added pre-lithiation agent.

[0122] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a fully decomposable positive electrode pre-lithiation agent, characterized in that, Includes the following steps: S1: Sodium pyruvate is reacted with hydrogen ion exchange resin to generate C3O6H4; wherein the mass-volume ratio of sodium pyruvate to hydrogen ion exchange resin is 1.5-1.8g:100ml. S2: Add a lithium source to a C3O6H4 solution and spray dry to obtain C3O6H2Li2; wherein the lithium source includes LiOH or Li2CO3; S3: C3O6H2Li2 was dissolved in n-hexane under an inert atmosphere, then mixed with butyllithium solution, and the mixture was centrifuged to obtain a white powder; S4: The white powder is washed and dried to obtain the fully decomposed positive electrode pre-lithiation agent C3O6Li4; The fully decomposable positive electrode pre-lithiation agent C3O6Li4 undergoes a full decomposition reaction in the operating voltage range of 2-4.9V: C3O6Li4→3CO2+4Li + +4e - .

2. The preparation method of the fully decomposable positive electrode pre-lithiation agent according to claim 1, characterized in that, In step S3, the molar ratio of C3O6H2Li2 to butyllithium is 1:2-1:

1.

3. The preparation method of the fully decomposable positive electrode pre-lithiation agent according to claim 1, characterized in that, In step S4, the drying temperature is 80-120℃.

4. The preparation method of the fully decomposable positive electrode pre-lithiation agent according to claim 1, characterized in that, In step S2, when the lithium source is LiOH, the molar ratio of C3O6H4 to LiOH is 1:2; when the lithium source is Li2CO3, the molar ratio of C3O6H4 to Li2CO3 is 1:

1.

5. A method for preparing a fully decomposable positive electrode pre-lithiation agent, characterized in that, Includes the following steps: S1: Sodium pyruvate is reacted with hydrogen ion exchange resin to generate C3O6H4; wherein the mass-volume ratio of sodium pyruvate to hydrogen ion exchange resin is 1.5-1.8g:100ml. S2: Add a lithium source to a C3O6H4 solution, and obtain C3O5Li2 by spray drying and vacuum drying, which is a fully decomposed positive electrode pre-lithiation agent; wherein, the lithium source includes LiOH or Li2CO3; The fully decomposable positive electrode pre-lithiation agent C3O5Li2 undergoes a full decomposition reaction within the operating voltage range of 2-4.45V: C3O5Li2→2CO2+CO+2Li + +2e - .

6. The method for preparing the fully decomposable positive electrode pre-lithiation agent according to claim 5, characterized in that, In step S2, when the lithium source is LiOH, the molar ratio of C3O6H4 to LiOH is 1:2; when the lithium source is Li2CO3, the molar ratio of C3O6H4 to Li2CO3 is 1:

1.

7. The application of a fully decomposable positive electrode pre-lithiation agent prepared by any one of claims 1-6, characterized in that, The fully decomposable positive electrode pre-lithiation agent is used to prepare positive electrode sheets for lithium batteries. The preparation method includes: mixing the fully decomposable positive electrode pre-lithiation agent with positive electrode active material, conductive agent and binder evenly, and then slurrying to obtain the positive electrode sheet.

8. The application of the fully decomposable positive electrode pre-lithiation agent according to claim 7, characterized in that, The amount of the fully decomposable positive electrode pre-lithiation agent added is 2-10% of the mass of the positive electrode active material.

9. The application of the fully decomposable positive electrode pre-lithiation agent according to claim 7, characterized in that, The positive electrode active material includes one or more of lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and lithium manganese iron phosphate.

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