A high energy density long life lithium battery and its preparation method

Abstract

The present invention provides a high-energy-density, long-life lithium battery and a method for preparing the same. The negative electrode material of the high-energy-density, long-life lithium battery comprises a pre-lithiation material comprising a composite material of metallic lithium and Mn3O4-graphene oxide. This negative electrode material exhibits extremely high initial coulombic efficiency, excellent energy density, superior cycle performance, and high specific capacity.

Description

Technical Field

[0001] The present invention belongs to the field of lithium batteries, and in particular relates to a high-energy-density, long-life lithium battery and a preparation method thereof. Background Art

[0002] Energy storage devices have attracted increasing attention due to the rise of mobile devices, electric vehicles, and other electric devices. Among these, lithium batteries have attracted significant attention due to their high energy density and excellent cycle performance, leading to their rapid development in recent years. However, with the increasing number of high-energy-consuming devices, the traditional graphite anode material for lithium batteries (372mAh / g) has been unable to keep up with demand, leading to increasing attention on high-capacity anode material alternatives.

[0003] Manganese dioxide and silicon-based materials have great potential as high-capacity negative electrode materials. Although the poor stability caused by their huge volume expansion can be solved by designing nanostructures, the problem of low initial charge and discharge coulombic efficiency of these materials has not been effectively solved. Therefore, designing a treatment method that can improve the initial charge and discharge coulombic efficiency of lithium batteries is the key to bringing these materials to market. Summary of the Invention

[0004] In response to the deficiencies in the prior art, the present invention provides a high-energy-density, long-life lithium battery and a method for preparing the same. The lithium battery prepared from the high-energy-density, long-life lithium battery provided by the present invention can be used normally in a wide range of temperature environments, thereby broadening the application field of the lithium battery.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] On the one hand, the present application provides a long-life lithium battery with high energy density, wherein the negative electrode material of the lithium battery includes a pre-lithiation material, and the pre-lithiation material includes metallic lithium and Mn3O4-graphene oxide composite material.

[0007] Furthermore, the negative electrode material of the lithium battery also includes a binder, a conductive agent and an active material;

[0008] Furthermore, the binder includes one or more of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, polytetrafluoroethylene and polyimide;

[0009] Furthermore, the conductive agent includes one or more of SuperP, acetylene black, conductive graphite, vapor-grown carbon fiber, carbon nanotubes, and graphene;

[0010] Furthermore, the active material includes one or more of silicon-oxygen materials, tin-nickel alloys, and silicon-carbon materials.

[0011] Furthermore, the mass ratio of the binder, the conductive agent, the active material and the pre-lithiation material is 1-3:3-5:90-110:1-20;

[0012] Preferably, the mass ratio of the binder, the conductive agent, the active material and the pre-lithiation material is 2:4:100:1-20;

[0013] More preferably, the mass ratio of the binder, the conductive agent, the active material and the pre-lithiation material is 2:4:100:5-15;

[0014] Furthermore, the preparation method of the pre-lithiation material includes: taking graphene oxide and uniformly dispersing it in deionized water, adding ethanol, and then slowly dripping a KMnO4 solution into the graphene oxide solution, stirring and standing, and then heating the solid intermediate obtained by separation under an inert atmosphere to obtain a Mn3O4-graphene oxide composite material, and then adding metallic lithium and the Mn3O4-graphene oxide composite material to a heater for heating, stirring evenly, and cooling to room temperature to obtain a pre-lithiation material;

[0015] Furthermore, the specific steps of preparing the Mn3O4-graphene oxide composite material in step (1) are: taking graphene oxide, uniformly dispersing it in deionized water by ultrasound, then adding ethanol and stirring for 10-60 minutes, then slowly dripping the KMnO4 solution into the graphene oxide solution, continuing to stir for 8-16 hours, then standing for 3-7 hours, centrifuging, washing and freeze-drying, and then heating the freeze-dried intermediate to 350-400°C under an argon atmosphere, keeping the temperature for reaction for 1-4 hours, to obtain the Mn3O4-graphene oxide composite material;

[0016] Furthermore, the mass ratio of graphene oxide to KMnO4 is 1:1-3, 1:1.5-2.5;

[0017] Furthermore, the mass volume ratio of the graphene oxide to deionized water is 1-4 g:1 L, 1-3 g:1 L;

[0018] Furthermore, the volume ratio of deionized water to ethanol is 2-6:1;

[0019] Further, the concentration of the KMnO4 solution is 10-40 g / L, 10-30 g / L or 15-25 g / L;

[0020] Further, the freeze-dried intermediate is heated to 370-380° C. under an argon atmosphere;

[0021] Furthermore, the mass ratio of the metallic lithium to the Mn3O4-graphene oxide composite material is 1-3:1;

[0022] Furthermore, the metallic lithium and the Mn3O4-graphene oxide composite material are then added to a heater for heating at a temperature of 200-250° C. and stirred for 5-30 minutes;

[0023] Furthermore, the lithium battery also includes an electrolyte, a positive electrode and a separator;

[0024] Optionally, the electrolyte includes one or more of dimethyl carbonate, diethyl carbonate and ethylene carbonate, the separator includes one or more of PP / PE separator, polyethylene terephthalate separator, poly(p-phenylene benzobisoxazole) separator, polyimide separator, modified glass fiber membrane, coated separator, electrospinning separator, and the material of the positive electrode includes one or more of lithium sheet, lithium iron phosphate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium manganese oxide;

[0025] Optionally, the lithium battery further includes a shell, and the material of the shell is selected from aluminum alloy, steel, aluminum-plastic film, and sheet molding compound material.

[0026] On the other hand, the present application also provides a method for preparing a high energy density and long life lithium battery, comprising the following steps:

[0027] (1) Preparation of pre-lithiation material: graphene oxide is uniformly dispersed in deionized water, ethanol is added, and then KMnO4 solution is slowly dripped into the graphene oxide solution, stirred and allowed to stand, and then the solid intermediate obtained by separation is heated under an inert atmosphere to obtain a Mn3O4-graphene oxide composite material, and then metallic lithium and the Mn3O4-graphene oxide composite material are added to a heater for heating, stirred evenly, and cooled to room temperature to obtain a pre-lithiation material;

[0028] Wherein, the inert atmosphere is one or more of argon atmosphere, nitrogen atmosphere, and helium atmosphere;

[0029] (2) Preparing a negative electrode sheet: taking a binder, a conductive agent, an active material and the pre-lithiation material, grinding them, extruding the evenly dispersed materials into a film at high temperature, and then compounding the obtained film on a current collector to obtain a negative electrode sheet;

[0030] (3) Preparation of a lithium battery: The lithium battery is prepared by using the negative electrode sheet described in step (2) as the negative electrode.

[0031] Furthermore, the specific steps of preparing the Mn3O4-graphene oxide composite material in step (1) are: taking graphene oxide, uniformly dispersing it in deionized water by ultrasound, then adding ethanol and stirring for 10-60 minutes, then slowly dripping the KMnO4 solution into the graphene oxide solution, continuing to stir for 8-16 hours, then standing for 3-7 hours, centrifuging, washing and freeze-drying, and then heating the freeze-dried intermediate to 350-400°C under an argon atmosphere, keeping the temperature for reaction for 1-4 hours, to obtain the Mn3O4-graphene oxide composite material;

[0032] Furthermore, the mass ratio of graphene oxide to KMnO4 is 1:1-3;

[0033] Furthermore, the mass volume ratio of the graphene oxide to deionized water is 1-4 g:1 L;

[0034] Furthermore, the volume ratio of deionized water to ethanol is 2-6:1;

[0035] Furthermore, the concentration of the KMnO4 solution is 10-40 g / L;

[0036] Further, the freeze-dried intermediate is heated to 370-380° C. under an argon atmosphere;

[0037] Furthermore, the mass ratio of the metallic lithium to the Mn3O4-graphene oxide composite material is 1-3:1;

[0038] Furthermore, the metallic lithium and the Mn3O4-graphene oxide composite material are then added to a heater for heating at a temperature of 200-250° C. and stirred for 5-30 minutes;

[0039] Furthermore, the specific steps in step (2) are: weighing each substance according to the mass ratio of the binder, the conductive agent, the active material and the pre-lithiation material of 1-3:3-5:90-110:1-20, grinding, extruding the evenly dispersed material into a film at high temperature, and then compounding the obtained film on the current collector to obtain a negative electrode sheet;

[0040] Preferably, the mass ratio of the binder, the conductive agent, the active material and the pre-lithiation material is 2:4:100:1-20;

[0041] More preferably, the mass ratio of the binder, the conductive agent, the active material and the pre-lithiation material is 2:4:100:5-15;

[0042] Optionally, the current collector is one of a copper foil current collector, a stainless steel current collector, an aluminum foil current collector, a copper mesh, a carbon-coated copper foil / copper mesh, and foamed copper.

[0043] Furthermore, the negative electrode sheet prepared in step (2) is used as the negative electrode, the Li sheet is used as the positive electrode, LiPF6 is selected as the solute, the solvent is an organic solution prepared from dimethyl carbonate, diethyl carbonate and ethylene carbonate in a volume ratio of 1:1:1 as the electrolyte, and the diaphragm is a commercial PP / PE diaphragm, to prepare the lithium battery.

[0044] On the other hand, the present invention also provides a high energy density and long life lithium battery, which is prepared by the above preparation method.

[0045] Beneficial effects of the present invention:

[0046] The present invention provides a high-energy-density, long-life lithium battery and a method for preparing the same. The negative electrode material of the high-energy-density, long-life lithium battery comprises a pre-lithiation material comprising metallic lithium and a Mn3O4-graphene oxide composite material. This negative electrode material exhibits extremely high initial coulombic efficiency, excellent energy density, superior cycle performance, rate capability, and high specific capacity.

[0047] This invention is based on the collaborative design of lithium metal and Mn3O4-graphene oxide (Mn3O4-GO) composite anode materials. The significant improvement in overall performance is likely due to the synergistic interaction between the various materials. First, a pre-lithiation strategy directly compensates for initial lithium loss. Combined with the formation of a dense SEI film on the GO surface, this strategy boosts the initial coulombic efficiency to over 98.6%, breaking through the efficiency bottleneck of traditional high-capacity materials. Second, the synergistic effect of lithium metal's ultra-high theoretical capacity (3860 mAh / g) and the multi-electron reactivity of Mn3O4 (theoretical capacity 936 mAh / g) significantly enhances energy density and specific capacity. Furthermore, the three-dimensional conductive network and nano-confinement effect of GO provide efficient electron transport channels for the active material, suppressing lithium dendrite growth and volume expansion, and ensuring cycling stability. Furthermore, the short-range ion diffusion pathways of the Mn3O4 nanoparticles and the charge transfer acceleration effect of the GO heterointerface jointly optimize rate performance. This material system, through multi-dimensional synergy of component regulation, structural reinforcement and interface optimization, not only solves the problems of volume expansion and low efficiency of high-capacity negative electrodes, but also provides an innovative path for the practical application of next-generation high-energy density and long-life lithium batteries, showing broad application prospects. DETAILED DESCRIPTION

[0048] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention belongs. The terms used in the present specification are intended solely for the purpose of describing specific embodiments and are not intended to limit the present invention. In the description of this application, it should be understood that "and / or" describes an association relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can mean: A exists alone, A and B exist simultaneously, or B exists alone. A and B can be singular or plural. In this application, "at least one" means one or more, and "plurality" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can each be single or plural.

[0050] Example 1

[0051] This embodiment provides a high energy density, long life lithium battery and a preparation method thereof, and the specific steps are as follows:

[0052] (1) Preparation of pre-lithiation material: 8 g of graphene oxide was uniformly dispersed in 4 L of deionized water by ultrasound, and then 1 L of ethanol was added and stirred for 30 min. Then, 0.2 L of KMnO4 solution (20 g / L) was slowly dripped into the graphene oxide solution, and the mixture was stirred for 12 h and then allowed to stand for 5 h. The mixture was centrifuged, washed and freeze-dried. The freeze-dried intermediate was then heated to 375 °C under an argon atmosphere and kept warm for 2 h to obtain a Mn3O4-graphene oxide composite material. 10 g of battery-grade metallic lithium and 5 g of the Mn3O4-graphene oxide composite material were added to a heater with a stainless steel reactor, heated to 230 °C, stirred for 20 min at a stirring speed of 500 r / min, and cooled to room temperature to obtain a pre-lithiation material.

[0053] (2) Preparation of negative electrode sheets: Weigh each material according to the ratio of polytetrafluoroethylene: acetylene black (Jiaozuo Hexing Chemical Industry Co., Ltd.): silicon carbon: pre-lithiation material = 2g: 4g: 100g: 10g, place them in a small jet mill and grind them for 2h, extrude the evenly dispersed materials into a film at high temperature, the thickness of the electrode film is 90 microns, and then use a roller press to press and compound it on a copper foil current collector, the thickness of the copper foil is 8 microns, and then cut and shape the obtained electrode sheet to serve as the negative electrode sheet of the pre-lithiation lithium battery;

[0054] (3) Preparation of lithium battery: The negative electrode sheet prepared in step (2) is used as the negative electrode, the Li sheet is used as the positive electrode, LiPF6 is selected as the solute, the solvent is an organic solution prepared by dimethyl carbonate, diethyl carbonate and ethylene carbonate in a volume ratio of 1:1:1 as the electrolyte, and the diaphragm is a commercial PP / PE diaphragm to prepare a lithium battery.

[0055] Example 2

[0056] This embodiment provides a high energy density, long life lithium battery and a preparation method thereof, and the specific steps are as follows:

[0057] (1) Preparation of pre-lithiation material: 8 g of graphene oxide was uniformly dispersed in 4 L of deionized water by ultrasound, and then 1 L of ethanol was added and stirred for 30 min. Then, 0.2 L of KMnO4 solution (20 g / L) was slowly dripped into the graphene oxide solution, and the mixture was stirred for 12 h and then allowed to stand for 5 h. The mixture was centrifuged, washed and freeze-dried. The freeze-dried intermediate was then heated to 375 °C under an argon atmosphere and kept warm for 2 h to obtain a Mn3O4-graphene oxide composite material. 10 g of battery-grade metallic lithium and 5 g of the Mn3O4-graphene oxide composite material were added to a heater with a stainless steel reactor, heated to 230 °C, stirred for 20 min at a stirring speed of 500 r / min, and cooled to room temperature to obtain a pre-lithiation material.

[0058] (2) Preparation of negative electrode sheets: Weigh each material according to the ratio of polytetrafluoroethylene: acetylene black: silicon carbon: pre-lithiation material = 2g: 4g: 100g: 5g, place it in a small jet mill and grind it for 2h, extrude the evenly dispersed materials into a film at high temperature, the thickness of the electrode film is 90 microns, and then use a roller press to press and compound it on a copper foil current collector, the thickness of the copper foil is 8 microns, and then cut and shape the obtained electrode sheet to serve as the negative electrode sheet of the pre-lithiation lithium battery;

[0059] (3) Preparation of lithium battery: The negative electrode sheet prepared in step (2) is used as the negative electrode, the Li sheet is used as the positive electrode, LiPF6 is selected as the solute, the solvent is an organic solution prepared by dimethyl carbonate, diethyl carbonate and ethylene carbonate in a volume ratio of 1:1:1 as the electrolyte, and the diaphragm is a commercial PP / PE diaphragm to prepare a lithium battery.

[0060] Example 3

[0061] This embodiment provides a high energy density, long life lithium battery and a preparation method thereof, and the specific steps are as follows:

[0062] (1) Preparation of pre-lithiation material: 8 g of graphene oxide was uniformly dispersed in 4 L of deionized water by ultrasound, and then 1 L of ethanol was added and stirred for 30 min. Then, 0.2 L of KMnO4 solution (20 g / L) was slowly dripped into the graphene oxide solution, and the mixture was stirred for 12 h and then allowed to stand for 5 h. The mixture was centrifuged, washed and freeze-dried. The freeze-dried intermediate was then heated to 375 °C under an argon atmosphere and kept warm for 2 h to obtain a Mn3O4-graphene oxide composite material. 10 g of battery-grade metallic lithium and 5 g of the Mn3O4-graphene oxide composite material were added to a heater with a stainless steel reactor, heated to 230 °C, stirred for 20 min at a stirring speed of 500 r / min, and cooled to room temperature to obtain a pre-lithiation material.

[0063] (2) Preparation of negative electrode sheets: Weigh each material according to the ratio of polytetrafluoroethylene: acetylene black: silicon carbon: pre-lithiation material = 2g: 4g: 100g: 15g, place it in a small jet mill and grind it for 2h, extrude the evenly dispersed materials into a film at high temperature, the thickness of the electrode film is 90 microns, and then use a roller press to press and compound it on a copper foil current collector, the thickness of the copper foil is 8 microns, and then cut and shape the obtained electrode sheet to serve as the negative electrode sheet of the pre-lithiation lithium battery;

[0064] (3) Preparation of lithium battery: The negative electrode sheet prepared in step (2) is used as the negative electrode, the Li sheet is used as the positive electrode, LiPF6 is selected as the solute, the solvent is an organic solution prepared by dimethyl carbonate, diethyl carbonate and ethylene carbonate in a volume ratio of 1:1:1 as the electrolyte, and the diaphragm is a commercial PP / PE diaphragm to prepare a lithium battery.

[0065] Comparative Example 1

[0066] Compared with Example 1, the only difference is that step (1) is omitted, that is, in step (2), only polytetrafluoroethylene, acetylene black and silicon carbon are added, and no pre-lithiation material is added.

[0067] Comparative Example 2

[0068] Compared with Example 1, the only difference is that the Mn3O4-graphene oxide composite material in step (1) is directly used in step (2), that is, the compounding step of metallic lithium and the Mn3O4-graphene oxide composite material is omitted in step (1).

[0069] Test Analysis

[0070] (1) First charge and discharge and charge and discharge cycle test: The pre-lithiated lithium battery is subjected to first charge and discharge and charge and discharge cycle test using a soft pack test instrument, with the test voltage window being 3-4.2V;

[0071] The first efficiency (first coulombic efficiency, ICE) is defined as the ratio of the first discharge capacity to the first charge capacity, that is:

[0072] Initial efficiency = initial discharge capacity / initial charge capacity × 100%. The results are shown in Table 1.

[0073] (2) The lithium batteries prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to room temperature constant current charge and discharge performance tests. The test method was: constant current charge and discharge tests were performed at room temperature at 1C in the range of 3 to 4.2 V. The evaluation method was capacity retention, and the capacity retention was evaluated until it was less than 80%.

[0074] The capacity retention rate is defined as: Capacity retention rate = discharge capacity at the nth cycle / discharge capacity at the first cycle × 100%, where n is the number of cycles. The calculated results are averaged and are shown in Table 1.

[0075] Table 1

[0076] First efficiency Stable cycle (80% capacity retention) 1C discharge specific capacity (mAh / g) Example 1 100.8% 1760 times 498 Example 2 98.6% 1625 times 483 Example 3 99.5% 1690 times 489 Comparative Example 1 90.6% 781 times 178 Comparative Example 2 91.4% 872 times 297

[0077] The experimental results above show that the initial efficiency of the silicon-carbon electrode without pre-lithiation is only 90.6%, while after pre-lithiation, the initial efficiency can reach over 98.6%, which significantly improves the initial efficiency. In addition, the stable cycle times and 1C discharge specific capacity of Examples 1-3 and Comparative Examples 1-2 show that the lithium battery provided in this application also has good energy density, excellent cycle performance, rate performance, and high specific capacity.

[0078] The above is a detailed introduction to a high-energy-density, long-life lithium battery and its preparation method provided by the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the technical solutions and core ideas of the present application; ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A high energy density and long life lithium battery, characterized in that: The negative electrode material of the lithium battery includes a pre-lithiation material, a binder, a conductive agent and an active material, wherein the pre-lithiation material is composed of metallic lithium and a Mn3O4-graphene oxide composite material; Wherein, the mass ratio of the binder, the conductive agent, the active material and the pre-lithiation material is 1-3:3-5:90-110:1-20; The binder includes one or more of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, polytetrafluoroethylene and polyimide; the conductive agent includes one or more of Super P, acetylene black, conductive graphite, vapor-grown carbon fiber, carbon nanotubes, and graphene; the active substance includes one or more of silicon-oxygen material, tin-nickel alloy, and silicon-carbon material.

2. The high energy density and long life lithium battery according to claim 1, characterized in that: The mass ratio of the binder, the conductive agent, the active material and the pre-lithiation material is 2:4:100:1-20.

3. The high energy density and long life lithium battery according to claim 1, characterized in that: The lithium battery further comprises an electrolyte, a positive electrode and a separator; the electrolyte comprises one or more of dimethyl carbonate, diethyl carbonate and ethylene carbonate; the separator comprises one or more of PP / PE separator, polyethylene terephthalate separator, poly(p-phenylene benzobisazole) separator, polyimide separator, modified glass fiber membrane, coated separator and electrospinning separator; the material of the positive electrode comprises one or more of lithium sheet, lithium iron phosphate, lithium cobalt oxide, lithium nickel cobalt manganese oxide and lithium manganese oxide; And / or, the lithium battery further comprises a shell, and the material of the shell is selected from aluminum alloy, steel, aluminum-plastic film, and sheet molding compound material.

4. The high energy density and long life lithium battery according to claim 1, characterized in that: The mass ratio of the binder, the conductive agent, the active material and the pre-lithiation material is 2:4:100:5-15; The preparation method of the pre-lithiation material includes: taking graphene oxide, uniformly dispersing it in deionized water by ultrasound, then adding ethanol and stirring for 10-60 minutes, then slowly dripping a KMnO4 solution into the graphene oxide solution, continuing to stir for 8-16 hours, then standing for 3-7 hours, centrifuging, washing and freeze-drying, then heating the freeze-dried intermediate to 350-400°C under an argon atmosphere, keeping the temperature for reaction for 1-4 hours to obtain a Mn3O4-graphene oxide composite material, then adding metallic lithium and the Mn3O4-graphene oxide composite material into a heater for heating, stirring evenly, and cooling to room temperature to obtain a pre-lithiation material.

5. A method for preparing a high energy density and long life lithium battery, characterized in that: The following steps are involved: (1) Preparation of pre-lithiation material: Graphene oxide is uniformly dispersed in deionized water by ultrasound, and then ethanol is added and stirred for 10-60 minutes. Then, KMnO4 solution is slowly dripped into the graphene oxide solution, and the stirring is continued for 8-16 hours. After standing for 3-7 hours, centrifugation, washing and freeze-drying, the freeze-dried intermediate is then heated to 350-400 ° C under an argon atmosphere and kept warm for 1-4 hours to obtain a Mn3O4-graphene oxide composite material. Then, metallic lithium and the Mn3O4-graphene oxide composite material are added to a heater for heating, stirred evenly, and cooled to room temperature to obtain a pre-lithiation material; (2) Preparation of negative electrode sheets: Weigh each material according to the mass ratio of the binder, conductive agent, active material and the pre-lithiation material of 1-3:3-5:90-110:1-20, grind, extrude the evenly dispersed material into a film at high temperature, and then composite the obtained film on the current collector to obtain a negative electrode sheet; wherein the binder includes one or more of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, polytetrafluoroethylene and polyimide; the conductive agent includes one or more of Super P, acetylene black, conductive graphite, vapor-grown carbon fiber, carbon nanotubes, and graphene; the active material includes one or more of silicon oxide material, tin-nickel alloy, silicon-carbon material (3) Preparation of a lithium battery: The lithium battery is prepared by using the negative electrode sheet described in step (2) as the negative electrode.

6. The method for preparing a high energy density and long life lithium battery according to claim 5, characterized in that: The mass ratio of graphene oxide to KMnO4 is 1:1-3; The mass volume ratio of the graphene oxide to deionized water is 1-4 g:1 L; The volume ratio of deionized water to ethanol is 2-6:1; The concentration of the KMnO4 solution is 10-40 g / L.

7. The method for preparing a high energy density and long life lithium battery according to claim 5, characterized in that: The mass ratio of the metallic lithium to the Mn3O4-graphene oxide composite material is 1-3:1; The mass ratio of the binder, the conductive agent, the active material and the pre-lithiation material is 2:4:100:1-20.

8. The method for preparing a high energy density and long life lithium battery according to claim 5, characterized in that: Then, the metallic lithium and the Mn3O4-graphene oxide composite material are added into a heater for heating at a temperature of 200-250° C. and stirred for 5-30 minutes.

9. The method for preparing a high energy density and long life lithium battery according to claim 5, characterized in that: The mass ratio of the binder, the conductive agent, the active material and the pre-lithiation material is 2:4:100:5-15; The current collector is one of a copper foil current collector, a stainless steel current collector, an aluminum foil current collector, a copper mesh, a carbon-coated copper foil / copper mesh, and a foamed copper.

10. The method for preparing a high energy density and long life lithium battery according to claim 5, characterized in that: The negative electrode sheet prepared in step (2) is used as the negative electrode, the Li sheet is used as the positive electrode, LiPF6 is selected as the solute, the solvent is an organic solution prepared from dimethyl carbonate, diethyl carbonate and ethylene carbonate in a volume ratio of 1:1:1 as the electrolyte, and the diaphragm is a commercial PP / PE diaphragm to prepare the lithium battery.