Pre-lithiated material Li3P, preparation method and application thereof, and lithium ion capacitor

Abstract

The invention provides a pre-lithiation material Li3P, a preparation method and application thereof, and a lithium ion capacitor. The pre-lithiation material Li3P is powdery; the preparation method specifically comprises the following steps: dispersing P powder to the surface of molten metal Li in a protective atmosphere to generate blocky Li3P; and carrying out grinding treatment on the blocky Li3P to obtain the pre-lithiation material Li3P. According to the invention, the pre-lithiation binary material Li3P with high theoretical specific capacity and low decomposition voltage is prepared by violently reacting P with an interlayer spacing of not less than 2.5 with molten Li in an inert atmosphere, and the Li3P obtained by the method has the advantages of short preparation period, high purity and good electrochemical characteristics.

Description

Technical Field

[0001] The present invention relates to the field of electrochemical energy storage and provides a pre-lithiation material Li 3 P and its preparation method and application and lithium ion capacitor. Background Art

[0002] As a new type of energy storage device, lithium-ion capacitors are widely used in rail transportation, renewable energy generation and other fields due to their high power density and ultra-long cycle life. Lithium-ion capacitors are generally composed of lithium-ion battery negative electrodes, supercapacitor positive electrodes and lithium salt electrolytes. They have both high energy density and high power density and are considered to be a promising energy storage device. However, during the charge / discharge cycle, the Li embedded / de-embedded in the negative electrode + Only from the electrolyte, the large specific surface area of ​​the negative electrode material leads to the formation of SEI, which will consume a large amount of active Li + , which in turn reduces the energy density and cycle life of lithium-ion capacitors. Therefore, it is necessary to supplement them with additional lithium sources, namely pre-lithiation, to compensate for the large irreversible capacity loss during the first cycle of charging and improve the energy density, power density and cycle life of lithium-ion capacitors in practical applications.

[0003] Pre-lithiation technology can be divided into two categories: negative electrode and positive electrode. Negative electrode pre-lithiation technology mainly uses materials such as metal lithium sheets, metal lithium powder or lithium-containing compounds to pre-lithiate the negative electrode, but the degree of lithiation of these materials is uncontrollable, and the potential safety issues caused by strong chemical reactivity cannot be ignored. Combining the advantages and disadvantages of actual applications, operational safety, difficulty and cost considerations, using a positive electrode pre-lithiation additive with high specific capacity, low decomposition voltage and no residue after complete decomposition on the positive electrode side is the safest, most efficient and convenient method.

[0004] Li 3 P has a high theoretical specific capacity (1547.61 mAh / g), high ionic conductivity (10 -4 S / cm), lower decomposition voltage (~1.2V). Li 3 When P is used as a pre-lithiation additive for lithium-ion capacitors, after the first week of charging, the product P is retained on the electrode side, which avoids the appearance of cracks and holes in the electrode and also makes the electrode have excellent flame retardancy, which has great application prospects. 3 Most of the preparation methods of P have potential safety hazards, and it is urgent to develop a safe and high-purity Li 3 Preparation method of P. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a pre-lithiation material Li 3The preparation method of the present invention does not use toxic polar solvents, and the Li 3 P has the advantages of short preparation cycle, high purity and good electrochemical properties. 3 P is used as a pre-lithiation material for the positive electrode of lithium-ion capacitors, which can solve the problem of Li + The loss leads to a decrease in the reversible charge and discharge specific capacity, thereby improving the power and energy density of the lithium ion capacitor. 3 P has good chemical stability and is compatible with activated carbon (AC), the positive electrode material of lithium-ion capacitors, which is more beneficial to the actual production of lithium-ion capacitors.

[0006] The present invention also provides Li prepared by the above preparation method. 3 P and its applications.

[0007] The present invention also provides a method using the pre-lithiation material Li 3 Lithium ion capacitor prepared by P.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0009] A pre-lithiation material Li 3 Preparation method of P, the pre-lithiation material Li 3 P is in powder form; the preparation method specifically comprises dispersing P powder onto the surface of molten metal Li under a protective atmosphere to generate bulk Li 3 P; for the bulk Li 3 P is ground to obtain the pre-lithiation material Li 3 P.

[0010] Wherein, the crystal interlayer spacing of the P powder is not less than 2.5Å.

[0011] Wherein, the molar ratio of the metallic lithium to the P powder is not less than 3:1.

[0012] The molten metal Li is obtained by heating metal Li to 180-220° C., preferably 200-220° C.

[0013] Wherein, the preparation method comprises the following steps:

[0014] (1) Under a protective gas atmosphere, weigh P powder and metal Li foil in a molar ratio of 1:1;

[0015] (2) The temperature of the heating table is set to 180-220° C. The metal Li foil weighed in step (1) is placed in a crucible and heated on the heating table until the metal Li foil is completely melted;

[0016] (3) quickly dispersing the Black P powder weighed in step (1) onto the surface of the molten metal Li obtained in step (2) to immediately generate irregular block-shaped LiP, stopping heating, and grinding to obtain black LiP powder;

[0017] (4) Continue to weigh 2 mol of metallic lithium foil and place it in the crucible. Set the temperature of the heating table to 180-220 °C and heat the metallic lithium foil in the crucible until it is completely transformed into a molten state.

[0018] (5) The black LiP powder obtained in step (3) is quickly dispersed on the surface of the molten lithium obtained in step (4), and the reaction is violently exothermic, immediately generating bulk Li 3 P, stop heating, grind to get brown Li 3 P powder.

[0019] Wherein, the preparation method is completed in a glove box.

[0020] Wherein, H 2 O, O 2 The content is lower than 0.1 ppm. The protective atmosphere is Ar atmosphere.

[0021] A pre-lithiation material Li 3 P, which uses the above-mentioned pre-lithiation material Li 3 The method for preparing P is used to prepare the product.

[0022] The above-mentioned pre-lithiation material Li 3 The application of P material as a positive electrode pre-lithiation additive in replenishing lithium in lithium-ion capacitors.

[0023] A lithium ion capacitor comprising the above-mentioned pre-lithiation material Li 3 P.

[0024] In summary, the present invention has the following beneficial effects:

[0025] 1. The present invention uses a vigorous reaction between P with an interlayer spacing of not less than 2.5Å and molten Li in an inert atmosphere to prepare a pre-lithiation binary material Li with high theoretical specific capacity and low decomposition voltage. 3 P, Li obtained by this method 3 P has the advantages of short preparation cycle, high purity and good electrochemical properties.

[0026] 2. The dry electrode preparation process of the present invention avoids the use of toxic polar solvents, ensures a more uniform conductive network, and makes Li 3 P achieves an actual specific capacity higher than that of most existing positive electrode pre-lithiation agents.

[0027] 3. Li prepared by the present invention3 P can be directly mixed with the positive electrode material of lithium-ion capacitors. After irreversible decomposition during the first week of charging, a large amount of active Li + , which can effectively improve the energy density and cycle stability of lithium-ion capacitors and has great application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Li prepared in Example 1 3 XRD pattern of P;

[0029] Figure 2 T-Li prepared in Comparative Example 1 3 XRD pattern of P;

[0030] Figure 3 T / R-Li prepared in Comparative Example 2 3 XRD pattern of P;

[0031] Figure 4 The constant current charging curves of Comparative Examples 1 and 2 using the cold pressing method without using a current collector;

[0032] Figure 5 Li prepared in Example 1 3 P is the active material, and the cold pressed Li 3 P / / Li constant current charging curve;

[0033] Figure 6 T-Li prepared in Comparative Example 1 3 P is the active substance, and the cold pressed T-Li 3 P / / Li constant current charging curve;

[0034] Figure 7 Li prepared in Example 1 3 P is the active material, the assembled dry Li 3 Constant current charge / discharge curves of P / / Li in the first 5 weeks;

[0035] Figure 8 T-Li prepared in Comparative Example 1 3 P is the active material, assembled dry T-Li 3 P / / Li's first cycle constant current charging curve;

[0036] Fig. 9 Li prepared in Example 1 3 P is the active material, the assembled dry Li 3 Cyclic voltammetry curves of P / / Li in the first two weeks in the voltage range of 2-4.1V at a scan rate of 0.2mV / s;

[0037] Fig.10Li based on Example 1 3 Li prepared by P and AC 3 P / AC composite dry electrode, assembled Li 3 Constant current charge / discharge curves of the P / AC / / Li half-cell for the first 5 weeks;

[0038] Fig.11 Li based on Example 1 3 Li prepared by P and AC 3 P / AC composite dry electrode, assembled Li 3 Cyclic voltammetry curves of the P / AC / / Li half-cell in the first three weeks in the voltage range of 2-4.1V at a scan rate of 0.2mV / s;

[0039] Fig.12 Li prepared based on Example 1 3 Comparison of rate performance curves of lithium-ion capacitors with different N / P ratios assembled by P;

[0040] Fig.13 Li prepared based on Example 1 3 Comparison of cycle capacity curves of lithium-ion capacitors with different N / P ratios assembled by P. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0042] Example 1

[0043] A pre-lithiation material Li 3 P is prepared by the following steps:

[0044] In a glove box filled with argon, weigh 61.94 mg (~ 2 mol) of P powder and 13.88 mg (~ 2 mol) of Li foil in a 1:1 molar ratio; the crystal interlayer spacing of the P powder is about 3.2 Å. The P powder used is produced under an inert atmosphere with a purity of not less than 99%, and is not exposed to air during transportation.

[0045] The temperature of the heating table is set to 200°C, and the Li sheet is placed in the crucible and heated on the heating table until the metal Li foil is completely melted and a metallic luster appears on the surface;

[0046] The P powder is quickly dispersed onto the surface of the molten metal Li, the reaction is violently exothermic, and irregular block LiP is immediately generated. The heating is stopped and black LiP powder is obtained after grinding.

[0047] Weigh 27.77 mg (~ 4 mol) of lithium foil and place it in the crucible. Set the temperature of the heating table to 180-220 °C and heat the lithium foil in the crucible until it is completely molten. Quickly disperse the obtained black LiP powder on the surface of the molten lithium. The reaction is violently exothermic and irregular block Li is immediately generated. 3 P;

[0048] Stop heating and grind to obtain brown Li 3 P powder.

[0049] Comparative Example 1

[0050] The pre-lithiation material of this embodiment is prepared by the following steps:

[0051] In a glove box filled with argon, 69.4 mg of metal Li sheet and 154.2 mg of biphenyl (Bp) were dissolved in 10 ml of tetrahydrofuran (THF) solution to obtain 10 ml of 1M Li-Bp / THF solution. After stirring evenly at room temperature and the metal Li sheet was completely decomposed, 10 mg (~0.003 mol) of P powder was dissolved in 1M Li-Bp / THF solution; after stirring overnight, centrifugation was performed, and after washing 3 times with THF solution, brown-yellow powder T-Li was obtained by vacuum drying. 3 P. The crystal interlayer spacing of P powder is about 3.2Å.

[0052] Comparative Example 2

[0053] The pre-lithiation material of this embodiment is prepared by the following steps:

[0054] In a glove box filled with argon, 69.4 mg (~0.01 mol) of metal Li sheet and 154.2 mg of biphenyl (Bp) were dissolved in 10 ml of tetrahydrofuran (THF) solution to obtain 10 ml of 1M Li-Bp / THF solution. After stirring evenly at room temperature and the metal Li sheet was completely decomposed, 10 mg (~0.003 mol) of P powder was dissolved in 1M Li-Bp / THF solution; after stirring overnight, centrifugation was performed, and the mixture was washed 3 times with THF solution and vacuum dried to obtain brown-yellow powder T / R-Li 3 P. The crystal interlayer spacing of P powder is about 1nm.

[0055] Example 2

[0056] A pre-lithiation material Li 3 P is prepared by the following steps:

[0057] In a glove box filled with argon, 61.94 mg (~ 2 mol) of P powder and 13.88 mg (~ 2 mol) of Li foil were weighed in a molar ratio of 1:1; the crystal interlayer spacing of the P powder was about 3.2Å.

[0058] The temperature of the heating table is set to 220°C, and the Li sheet is placed in the crucible and heated on the heating table until the metal Li foil is completely melted and a metallic luster appears on the surface;

[0059] The P powder is quickly dispersed onto the surface of the molten metal Li, the reaction is violently exothermic, and irregular block LiP is immediately generated. The heating is stopped and black LiP powder is obtained after grinding.

[0060] Weigh 27.77 mg (~ 4 mol) of lithium foil and place it in the crucible. Set the temperature of the heating table to 180-220 °C and heat the lithium foil in the crucible until it is completely molten. Quickly disperse the obtained black LiP powder on the surface of the molten lithium. The reaction is violently exothermic and irregular block Li is immediately generated. 3 P;

[0061] Stop heating and grind to obtain brown Li 3 P powder.

[0062] Example 3

[0063] A pre-lithiation material Li 3 P is prepared by the following steps:

[0064] In a glove box filled with argon, 61.94 mg of Black P powder and 41.65 mg of Li foil were weighed in a molar ratio of 1:3. The temperature of the heating table was set to 200 °C, and the Li foil was placed in a crucible and heated on the heating table until the metal Li foil was completely melted and a metallic luster appeared on the surface. The Black P powder was quickly dispersed on the surface of the molten metal Li, and the reaction was violently exothermic, generating irregular blocky Li 3 P, brown Li after grinding 3 P powder, used for electrochemical testing.

[0065] Example 4

[0066] This example uses the Li prepared in Example 1 3 Preparation of Li 3 P / AC composite dry-process positive electrode.

[0067] Calculation of the required pre-lithiation additive Li based on the mass of AC 3 The mass of P is adjusted to adjust the N / P ratio to prepare different proportions of Li 3P / AC composite dry-process cathode, AC mass loading is 1.5-3.8 mg / cm 2 Changes between.

[0068] Performance testing

[0069] The pre-lithiation sacrificial materials prepared in the above-mentioned Example 1, Comparative Example 1 and Comparative Example 2 are applied to button-type lithium ion half-cells and button-type lithium ion capacitors. The preparation methods of the button-type lithium ion half-cells and button-type lithium ion capacitors are as follows:

[0070] (1) Preparation of dry electrodes and button-type lithium-ion half-cells.

[0071] In the glove box, the temperature of the heating table was set to 80° C. Under heating, the active material prepared in Example 1, Comparative Example 1 and Comparative Example 2, Super C45, and PTFE were evenly mixed in a mortar at a mass ratio of 70:20:10 wt %, and cut into a suitable size to obtain the following dry electrode.

[0072] When the active substance is T-Li 3 P, get T-Li 3 P dry electrode;

[0073] When the active material is Li 3 When P, Li 3 P dry electrode;

[0074] Fixed pre-lithiation additive Li 3 When the actual usage mass of P is 5wt% and the actual usage mass of AC (activated carbon) is 65wt%, Li 3 P / AC composite dry electrode;

[0075] Using 1M LiPF 6 , EC / DMC / DEC=1 / 1 / 1, (volume ratio) electrolyte, polypropylene membrane (Polypropyleneseparator, Celgard 2400) as separator, T-Li 3 P.Li 3 P, Li3P / AC electrode as working electrode, metal lithium sheet as counter electrode, assembled T-Li 3 P / / Li, Li 3 P / / Li, Li 3P / AC / / Li CR2032 button-type lithium-ion half-cell. EC / DMC / DEC is a common lithium-ion battery electrolyte solvent system, consisting of ethylene carbonate (EC), dimethyl carbonate (DMC) and diethyl carbonate (DEC).

[0076] (2) Preparation of cold-pressed electrodes and button-type lithium-ion half-cells.

[0077] In a glove box, the active material, Super C45, and PVDF were mixed evenly in a mortar at a mass ratio of 80:10:10 wt%. The obtained mixture was evenly cold-pressed on one side of a carbon-coated aluminum foil under a pressure of 5 MPa to obtain the following cold-pressed electrode:

[0078] When the active substance is T-Li 3 P, cold pressed T-Li 3 P electrode;

[0079] When the active material is T / R-Li 3 P, cold pressed T / R-Li 3 P electrode.

[0080] Using 1M LiPF 6 , EC / DMC / DEC=1 / 1 / 1, (v / v / v) electrolyte, polypropylene membrane (Polypropyleneseparator, Celgard 2400) as separator, cold pressed T-Li 3 P, Cold Pressed T / R-Li 3 The P electrode is the working electrode, the metal lithium sheet is the counter electrode, and the cold-pressed T-Li 3 P / / Li, cold pressed T / R-Li 3 P / / Li button-type lithium-ion half-cell.

[0081] (3) Preparation of negative electrode and button-type lithium-ion capacitor.

[0082] SC, Super C45 and PVDF were evenly dispersed in NMP solvent at a ratio of 80:10:10 wt%, coated on the surface of the carbon-coated copper foil current collector, dried at 80°C for 1 h, vacuum dried at 100°C for 12 h, compacted, and punched into SC electrodes with a diameter of 11 mm.

[0083] Calculation of the required pre-lithiation additive Li based on the mass of AC 3 The mass of P is adjusted to adjust the N / P ratio to prepare different proportions of Li 3P / AC composite dry-process cathode, AC mass loading is 1.5-3.8 mg / cm 2 Changes between.

[0084] Using 1M LiPF 6 , EC / DMC / DEC=1 / 1 / 1, (v / v / v) electrolyte, polypropylene membrane (Celgard 2400) as separator, Li 3 The P / AC electrode was used as the positive electrode and the SC electrode was used as the negative electrode to assemble the CR2032 button-type lithium-ion capacitor in an argon-filled glove box.

[0085] Perform the following test:

[0086] Test 1: After the button-type lithium-ion half-cell is activated for 5 weeks at a voltage range of 2-4.1V and a low current of 0.05mA, a constant current charge and discharge test is performed at a low current of 0.2mA.

[0087] Test 2: Cyclic voltammetry of the button-type lithium-ion half-cell at a scan rate of 0.2 mV / s in the voltage range of 2-4.1 V;

[0088] Test 3: The assembled LICs with different N / P ratios were subjected to constant current charge / discharge tests in the voltage range of 2-4.1V and the current density of 0.05-5A / g.

[0089] Lithium ion capacitor positive electrode pre-lithiation material Li prepared based on the above embodiments and comparative examples 3 P.T-Li 3 P, T / R-Li 3 The test results of button-type lithium-ion half-cells and lithium-ion capacitors assembled by P are shown in Figure 4-Figure 13 shown.

[0090] Figures 1 to 3 The XRD diagrams are obtained by performing XRD tests on Example 1 and Comparative Examples 1 and 2. Figure 1 For Example 1, Li prepared by reaction of molten Li with Black P 3 P sample and Li 3 The diffraction results of P standard card PDF#74-1160 are consistent, with good purity and crystallinity, and the base peak of the tape is around 18.5°. Figure 2 For Comparative Example 1, Black P was used to prepare T-Li with 1M Li-Bp / THF solution. 3 XRD curves of P and Li 3 The diffraction results of P standard card PDF#74-1160 are consistent, with good crystallinity and a base peak of the tape at around 18.5°. Figure 3 For comparative example 2, Red P was used to prepare T / R-Li 3 XRD curves of P and Li 3 The diffraction results of P standard card PDF#74-1160 are consistent, with good crystallinity and a base peak of the tape at around 18.5°.

[0091] Figure 4 The constant current charging curves of Comparative Examples 1 and 2 using the cold pressing method without using a current collector. Under the same conditions, after eliminating the influence of the current collector, the T-Li prepared in Comparative Example 1 3 P and T / R-Li prepared in Comparative Example 2 3 The actual charge capacity of P shows that the T-Li prepared in Comparative Example 1 3 P is compared with T / R-Li prepared in Comparative Example 2 3 P has a higher specific charge capacity, but also has a larger polarization.

[0092] Figure 5 and Figure 6 are Li prepared in Example 1 3 P is the active material and T-Li prepared in Comparative Example 1 3 P is the active material, and the cold pressed Li 3 P / / Li, cold pressed T-Li 3 P / / Li constant current charging curve. It can be seen that under the same electrode preparation method, cold pressed T-Li 3 Although P has a larger specific capacity, its polarization phenomenon is more severe than that of cold-pressed Li. 3 P was significant.

[0093] Figure 7 and Figure 8 are Li prepared in Example 1 3 P is the active material and T-Li prepared in Comparative Example 1 3 P is the active material, the assembled dry Li 3 Constant current charge / discharge curves of P / / Li in the first 5 weeks and dry T-Li 3 The first week charging curve of P / / Li shows that compared with the electrode prepared by cold pressing, the polarization phenomenon of dry electrode is smaller. 3 The first cycle charge capacity of the P electrode reached 1078 mAh / g, which is much higher than that of dry T-Li 3 P electrode, and basically no specific capacity is provided in subsequent cycles. This shows that the Li prepared by using P as raw material and molten metal Li in combination with the dry electrode process 3 P (Example 1) releases a large amount of Li after irreversible decomposition during the first week of charging. +, with good pre-lithiation performance.

[0094] Fig. 9 Li prepared in Example 1 3 P is the active material, the assembled dry Li 3 The cyclic voltammetry curve of P / / Li in the first two weeks in the voltage range of 2-4.1V at a scan rate of 0.2mV / s. It can be seen that Li 3 P only irreversibly decomposes during the first week of charging, releasing a large amount of Li + .

[0095] Fig.10 is Li of Example 1 3 Li composed of P and AC 3 P / AC composite dry electrode, assembled Li 3 The constant current charge / discharge curve of the P / AC / / Li half-cell in the first 5 weeks. It shows that during the first week of charging, when the voltage is higher than 3.7V, the Li 3 P begins to irreversibly decompose, releasing a large amount of active Li + Until 4.1V charging is completed; subsequently, the specific capacity is provided only by the physical adsorption of AC, and Li 3 After the irreversible decomposition of P is complete, there will be no adverse effects on subsequent cycles.

[0096] Fig.11 is Li of Example 1 3 Li composed of P and AC 3 P / AC composite dry electrode, assembled Li 3 Cyclic voltammetry curves of the P / AC / / Li half-cell in the first three weeks in the voltage range of 2-4.1V at a scan rate of 0.2mV / s. During the first week of charging, the obvious oxidation peak at 3.7V again indicates that Li 3 P only works during the first week of charging. 3 After the irreversible decomposition of P is complete, it no longer plays a role, and the specific capacity is only provided by the physical adsorption of AC.

[0097] Fig.12 Based on Li prepared in Example 1 3 P, rate performance comparison of LICs with different N / P ratios assembled, where LIC 133 Representative Li 3 The mass ratio of P:AC:SC is 1:3:3, with Li 3 The P / AC composite dry electrode is the positive electrode, and the SC is the negative electrode assembled LIC; LIC 163 Representative Li 3 The mass ratio of P:AC:SC is 1:6:3, with Li 3The P / AC composite dry electrode is the positive electrode, and the SC is the LIC assembled at the negative electrode. The other samples are explained in the same way. 3 When the mass ratio of P:AC:SC is 1:3:3, LIC 133 Has the best rate performance.

[0098] Fig.13 Based on Li prepared in Example 1 3 P, the cycle performance comparison of LICs with different N / P ratios assembled, it can be seen that when Li 3 When the mass ratio of P:AC:SC is 1:3:3, LIC 133 The first cycle charge capacity is the highest. After 5000 cycles at a current density of 0.2A / g, the capacity retention rate is as high as 89.72%, which has excellent cycle stability.

[0099] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

[0100] The parts not elaborated in detail in the description of the present invention belong to the known technology in the art. The above embodiments are provided only for the purpose of describing the present invention, and are not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims. Various equivalent substitutions and modifications made without departing from the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A method for preparing a pre-lithiation material Li3P, characterized in that: The pre-lithiation material Li3P is in powder form; the preparation method is specifically to disperse P powder on the surface of molten metal Li under a protective atmosphere to generate bulk Li3P; and the pre-lithiation material Li3P is obtained by grinding the bulk Li3P.

2. The method for preparing the pre-lithiation material Li3P according to claim 1, characterized in that: The crystal interlayer spacing of the P powder is not less than 2.5Å.

3. The method for preparing the pre-lithiation material Li3P according to claim 1, characterized in that: The molar ratio of the metallic lithium to the P powder is not less than 3:

1.

4. The method for preparing the pre-lithiation material Li3P according to claim 1, characterized in that: The molten metal Li is obtained by heating metal Li to 180-220°C.

5. The method for preparing the pre-lithiation material Li3P according to claim 1, characterized in that: The preparation method comprises the following steps: (1) Under a protective gas atmosphere, weigh P powder and metal Li foil in a molar ratio of 1:1; (2) The temperature of the heating table is set to 180-220° C. The metal Li foil weighed in step (1) is placed in a crucible and heated on the heating table until the metal Li foil is completely melted; (3) quickly dispersing the Black P powder weighed in step (1) onto the surface of the molten metal Li obtained in step (2) to immediately generate irregular block-shaped LiP, stopping heating, and grinding to obtain black LiP powder; (4) Continue to weigh 2 mol of metallic lithium foil and place it in the crucible. Set the temperature of the heating table to 180-220 °C and heat the metallic lithium foil in the crucible until it is completely transformed into a molten state. (5) The black LiP powder obtained in step (3) is quickly dispersed on the surface of the molten lithium obtained in step (4). The reaction is highly exothermic and bulk Li3P is immediately generated. The heating is stopped and brown Li3P powder is obtained after grinding.

6. The method for preparing the pre-lithiation material Li3P according to claim 1, characterized in that: The preparation method is completed in a glove box.

7. The method for preparing the pre-lithiation material Li3P according to claim 1, characterized in that: The contents of H2O and O2 in the protective atmosphere are both lower than 0.1 ppm.

8. A pre-lithiation material Li3P, characterized in that It is prepared by the preparation method of the pre-lithiation material Li3P according to any one of claims 1 to 7.

9. Use of the pre-lithiation material Li3P according to claim 8 as a positive electrode pre-lithiation additive in replenishing lithium in lithium ion capacitors.

10. A lithium ion capacitor, characterized in that: Including the pre-lithiation material Li3P as described in claim 8.

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