A lithium-rich phosphide lithium supplement, a preparation method and application thereof

Abstract

The application discloses a lithium-rich phosphide lithium supplement agent and a preparation method and application thereof. The lithium-rich phosphide lithium supplement agent is prepared from lithium hydride, red phosphorus and a carbon source as raw materials. The lithium-rich phosphide lithium supplement agent is used in a lithium battery system with LFP as a positive electrode and hard carbon as a negative electrode, and through a chemical reaction of trilithium phosphide, active lithium is effectively supplemented in the first charge-discharge process of the lithium battery, the first coulomb efficiency and the first reversible specific capacity of the battery are improved, through further supplement of phosphorus and carbon in the hard carbon gap in the lithium-rich phosphide lithium supplement agent, the stability of the hard carbon negative electrode is increased, so that the site consumption in the structure of the hard carbon is reduced, the lithium ion density of the battery is maintained, and the cycle service life of the battery is improved.

Description

Technical Field

[0001] This invention belongs to the field of battery materials technology, and specifically relates to a lithium-rich phosphide lithium supplement agent, its preparation method, and its application. Background Technology

[0002] Hard carbon, used as an anode material in lithium-ion batteries, offers advantages over traditional graphite anodes, including superior low-temperature performance, resistance to lithium plating, resistance to expansion, high safety, higher reversible capacity, and better fast-charging performance. However, due to its large interlayer spacing and disorder, its compaction density is relatively low, resulting in low initial coulombic efficiency and a significant reduction in overall battery energy density. The main reason for this is that during the initial charge and discharge process, a solid electrolyte interphase (SEI) film forms on the anode surface, leading to irreversible loss of active lithium in the electrolyte. Furthermore, irreversible lithium is consumed at sites within the gaps on the hard carbon surface, resulting in lower initial coulombic efficiency and energy density.

[0003] The main approach to solving this problem is to add lithium replenishing agents to compensate for the irreversible loss of active lithium during the formation of the SEI film, thereby stabilizing the battery's energy density and improving its coulombic efficiency and cycle life. Lithium triphosphide (Li3P), lithium borate (Li3BO3), and lithium ferrite (Li5FeO4) are three representative lithium replenishing agents. These three agents differ significantly in their lithium replenishment performance, environmental stability, process compatibility, and functional characteristics, and their selection directly affects the battery's initial efficiency, cycle stability, safety, and industrial feasibility.

[0004] In terms of lithium replenishment capacity, Li3P performs best, with a theoretical lithium replenishment capacity as high as 1548 mAh / g, far exceeding that of Li3BO3 (approximately 1010 mAh / g) and Li5FeO4 (approximately 867 mAh / g). Regarding lithium release potential and interface characteristics, Li3P has a lithium release potential of approximately 3.8 V. Overall, Li3P exhibits high lithium replenishment capacity and a moderate lithium release potential, demonstrating significant performance advantages. However, its poor dispersibility and excessive reactivity, leading to a high susceptibility to side reactions, limit its application.

[0005] Existing hard carbon anode lithium replenishment agents generally suffer from drawbacks such as severe gas generation, poor electrochemical stability, poor safety, poor compatibility with hard carbon, and limited lithium replenishment effect. Therefore, developing a high-capacity, high-stability hard carbon anode lithium replenishment agent is an urgent technical problem to be solved in this field. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a lithium-rich phosphide lithium supplement agent, its preparation method, and its application. This lithium supplement agent exhibits high specific capacity, good potential matching performance, and strong stability. By acting in the hard carbon anode of lithium batteries, it can effectively improve the energy density of the battery.

[0007] This invention is achieved through the following technical solution: The present invention relates to a lithium-rich phosphide lithium supplement, which is a carbon-coated lithium supplement composed of lithium triphosphide and a carbon layer. The raw materials include lithium hydride, red phosphorus and carbon source.

[0008] According to the lithium-rich phosphide lithium replenishing agent, the particle size distribution of the lithium replenishing agent is D100 of 1 to 10 μm and D50 of 2 to 3 μm; the thickness of the carbon coating layer on the surface of the lithium replenishing agent is 1 to 20 nm.

[0009] According to the lithium-rich phosphide lithium supplement agent, the mass ratio of lithium hydride to red phosphorus is 0.77~0.85:1.

[0010] According to the lithium-rich phosphate supplement agent, the carbon source is any one of glucose, sucrose, starch, phenolic resin, and citric acid, and its amount is 0.15 to 0.25 times the mass of the red phosphorus.

[0011] This invention discloses a method for preparing a lithium-rich phosphide lithium supplement, comprising the following steps: 1) A measured amount of lithium hydride and red phosphorus are ball-milled at 400~500 r / min for 12~16 h under an argon atmosphere, with the temperature controlled at ≤50℃ during the ball milling process; 2) Then add a quantitative amount of carbon source and mix. Under an argon atmosphere, ball mill at a speed of 100~200 r / min for 30~60 min. Then anneal at 450~550℃ with a cooling rate of 2~3℃ / min. Finally, pulverize with nitrogen gas to obtain lithium supplement powder with D100 of 1~5μm and D50 of 2~3μm.

[0012] The application of a lithium-rich phosphide lithium supplement agent in lithium battery anode materials.

[0013] According to the application, the application is used in a lithium battery with hard carbon as the negative electrode, and the amount of the lithium replenishing agent added to the hard carbon negative electrode material is 1~5wt.

[0014] Beneficial effects of this invention: The lithium-rich phosphide lithium replenisher provided by this invention effectively replenishes active lithium during the first charge and discharge process of a lithium battery system with LFP as the positive electrode and hard carbon as the negative electrode through the chemical reaction of trilithium phosphide, thereby improving the battery's initial coulombic efficiency and initial reversible specific capacity. Furthermore, the addition of phosphorus and carbon in the hard carbon interstitial spaces by the lithium-rich phosphide lithium replenisher increases the stability of the hard carbon negative electrode, thereby reducing site consumption in the hard carbon structure, maintaining the battery's lithium-ion density, and ultimately improving the battery's cycle life. Attached Figure Description

[0015] Figure 1The particle size distribution diagram prepared in Example 1; Figure 2 The SEM image is from Example 1. Detailed Implementation

[0016] The following is a further explanation of the content of this invention: This invention relates to a lithium-rich phosphide lithium supplement, a carbon-coated lithium supplement composed of lithium triphosphide and a carbon layer. The raw materials include lithium hydride, red phosphorus, and a carbon source. The particle size distribution of the lithium supplement is D100 of 1–10 μm and D50 of 2–3 μm; the thickness of the carbon coating layer on the surface of the lithium supplement is 1–20 nm. The mass ratio of lithium hydride to red phosphorus is 0.77–0.85:1. The carbon source is any one of glucose, sucrose, starch, phenolic resin, or citric acid, and its amount is 0.15–0.25 times the mass of the red phosphorus.

[0017] The method for preparing the lithium-rich phosphide lithium supplement of the present invention includes the following steps: 1) A measured amount of lithium hydride and red phosphorus are ball-milled at 400~500 r / min for 12~16 h under an argon atmosphere, with the temperature controlled at ≤50℃ during the ball milling process; 2) Then add a quantitative amount of carbon source and mix. Under an argon atmosphere, ball mill at a speed of 100~200 r / min for 30~60 min. Then anneal at 450~550℃ with a cooling rate of 2~3℃ / min. Finally, pulverize with nitrogen gas to obtain lithium supplement powder with D100 of 1~5μm and D50 of 2~3μm.

[0018] The application of the lithium-rich phosphide lithium replenishing agent of the present invention in lithium battery anode materials, specifically in lithium batteries with hard carbon as the anode, wherein the amount of the lithium replenishing agent added to the hard carbon anode material is 1~5wt.

[0019] All raw materials used in this invention are commercially available.

[0020] The preparation process of the lithium-rich phosphide lithium supplement of the present invention is described with specific parameters. I. Preparation of lithium-rich phosphide lithium supplement Example 1

[0021] 23.85g of lithium hydride and 30.97g of red phosphorus were added to a ball mill and ball-milled for 12 hours at 400 rpm under an argon atmosphere. The ball milling process was cooled by alternating 20-minute and 10-minute intervals to control the ball milling temperature to ≤50℃. 4.8g of glucose was added, and the ball milling was continued at 100 rpm for 30 minutes under an argon atmosphere. The material was then transferred to an atmosphere furnace and annealed at 450℃ under an argon atmosphere at a cooling rate of 2℃ / min until it reached room temperature. The material was then pulverized using a nitrogen gas flow to obtain 55.96g of the target product, lithium-rich phosphide lithium supplement, denoted as A.

[0022] The product was tested and found to have a moisture content of 0.01%; the particle size D50 was 2.33 μm and the D100 was 4.51 μm.

[0023] Example 2

[0024] 26.23g of lithium hydride and 30.97g of red phosphorus were added to a ball mill and ball-milled at 500 rpm for 12 hours under an argon atmosphere. During the ball milling process, heat was dissipated by ball milling for 20 minutes and then intermittently for 10 minutes to control the ball milling temperature to ≤50℃. 7.2g of starch was added, and the mixture was ball-milled at 200 rpm for 60 minutes under an argon atmosphere. The material was then transferred to an atmosphere furnace and annealed at 550℃ under an argon atmosphere, with a cooling rate of 3℃ / min until the temperature reached room temperature. The material was then pulverized using a nitrogen gas flow to obtain 59.61g of the target product, lithium-rich phosphide lithium supplement, denoted as B.

[0025] The product was tested and found to have a moisture content of 0.01%; the particle size D50 was 2.51 μm and the D100 was 4.72 μm.

[0026] Example 3

[0027] 25g of lithium hydride and 30.97g of red phosphorus were added to a ball mill and ball-milled for 14 hours at 450 rpm under an argon atmosphere. During the ball milling process, heat was dissipated by ball milling for 20 minutes and then intermittently for 10 minutes to control the ball milling temperature to ≤50℃. 6g of citric acid was added, and the ball milling was continued at 150 rpm for 45 minutes under an argon atmosphere. The material was then transferred to an atmosphere furnace and annealed at 500℃ under an argon atmosphere at a cooling rate of 2.5℃ / min until it reached room temperature. The material was then pulverized using a nitrogen gas flow to obtain 58.02g of the target product, lithium-rich phosphide lithium supplement, denoted as C.

[0028] The product was tested and found to have a moisture content of 0.01%; the particle size D50 was 2.48 μm and the D100 was 4.46 μm.

[0029] The application process of the lithium-rich phosphide lithium supplement agent of the present invention is described with specific parameters. Preparation of positive electrode sheet: LFP, PVDF and Sp are mixed evenly in NMP solution at a mass ratio of 94:3:3 and then coated onto aluminum foil; the aluminum foil is dried in a vacuum oven at 120℃, then rolled and cut into positive electrode sheets with a diameter of 1.2cm and sealed for storage.

[0030] Preparation of negative electrode: Hard carbon (HC-300), SP, CMC+SBR, and A / B / C were mixed evenly in deionized water at a mass ratio of 94:2:2:2, and then vacuum degassed. After passing through a 200-mesh sieve, the slurry was coated onto the surface of Cu foil and dried in a vacuum oven at 80℃ for 2 hours to obtain the negative electrode. The negative electrode was then rolled and cut into negative electrode sheets with a diameter of 1.4 cm, sealed and stored. The negative electrode sheets were designated as HC-A / HC-B / HC-C (the amount of lithium supplementer added to the blank hard carbon negative electrode sheet was zero, and the mass ratio of hard carbon (HC-300), SP, and CMC+SBR was 96:2:2).

[0031] Assembly and testing of full cells: LFP cells were assembled with blank hard carbon negative electrode sheets, HC-A, HC-B, and HC-C to form CR2032 cells. The ratio of the negative electrode capacity per unit area to the positive electrode capacity per unit area was 1.15:1. Charge and discharge tests were performed in the LANBTS test cabinet within the voltage range of 2.5-3.8 V.

[0032] The test results are shown in the table below: , , The results in Tables 1 and 2 show that the lithium battery using the lithium-rich phosphide provided by this invention as the negative electrode lithium replenishment agent has a significantly higher first-charge specific capacity than the lithium battery without the lithium replenishment agent. In comparison, the lithium battery improves the first coulombic efficiency by about 7%, while also exhibiting better capacity retention and extending battery life.

[0033] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A lithium-rich phosphide lithium supplement, characterized in that it is... A carbon-coated lithium supplement composed of lithium triphosphide and a carbon layer, the raw materials of which include lithium hydride, red phosphorus and carbon source.

2. The lithium-rich phosphide lithium supplement agent according to claim 1, characterized in that, The lithium replenishing agent has a particle size distribution of D100 of 1–10 μm and D50 of 2–3 μm; the thickness of the carbon coating layer on the surface of the lithium replenishing agent is 1–20 nm.

3. The lithium-rich phosphide lithium supplement agent according to claim 1, characterized in that, The mass ratio of lithium hydride to red phosphorus is 0.77~0.85:

1.

4. The lithium-rich phosphide lithium supplement agent according to claim 1, characterized in that, The carbon source is any one of glucose, sucrose, starch, phenolic resin, or citric acid, and its amount is 0.15 to 0.25 times the mass of the red phosphorus.

5. A method for preparing a lithium-rich phosphide lithium supplement agent according to any one of claims 1-4, characterized in that, Includes the following steps: 1) A measured amount of lithium hydride and red phosphorus are ball-milled at 400~500 r / min for 12~16 h under an argon atmosphere, with the temperature controlled at ≤50℃ during the ball milling process; 2) Then add a quantitative amount of carbon source and mix. Under an argon atmosphere, ball mill at a speed of 100~200 r / min for 30~60 min. Then anneal at 450~550℃ with a cooling rate of 2~3℃ / min. Finally, pulverize with nitrogen gas to obtain lithium supplement powder with D100 of 1~5μm and D50 of 2~3μm.

6. The method for preparing airflow pulverizer according to claim 5, characterized in that, Step 2) The crushing pressure is 0.8 MPa, the feeding speed is 3 kg / h, and the classifying wheel speed is 10000 r / min.

7. The application of the lithium-rich phosphide lithium supplement agent as described in claim 1 in lithium battery anode materials.

8. The application according to claim 7, characterized in that, The application is in lithium batteries with hard carbon as the negative electrode, and the amount of the lithium replenishing agent added to the hard carbon negative electrode material is 1~5wt.

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