A semi-solid composite negative electrode and a preparation method thereof

Abstract

The application provides a kind of semi-solid composite negative electrode and its preparation method, the semi-solid composite negative electrode includes: negative electrode sheet, polymer electrolyte and diaphragm, polymer electrolyte is located above negative electrode sheet, diaphragm is located above polymer electrolyte, and part of polymer electrolyte is distributed in the internal interstice of diaphragm, part of polymer electrolyte is close to the surface of negative electrode sheet.The preparation method includes: polymer, lithium salt and initiator are added into container according to the ratio, stirred and dissolved to obtain polymer electrolyte solution; polymer electrolyte solution is coated on negative electrode sheet, and after standing for a period of time, diaphragm is covered; constant temperature heating is carried out at 40 DEG C to 100 DEG C to obtain semi-solid composite negative electrode.The semi-solid composite negative electrode in the application has high mechanical strength, good flexibility, easy processing, can inhibit lithium dendrite, can be applied to semi-solid lithium ion battery, metal lithium battery, and the preparation method is environmentally friendly, compatible with modern lithium ion battery production process, suitable for large-scale production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium battery materials, and particularly relates to a semi-solid composite negative electrode and a preparation method thereof. BACKGROUND

[0002] In recent decades, liquid lithium ion batteries have played an increasingly important role in the fields of electric vehicles, consumer electronics and energy storage. However, the development of science and technology puts forward higher requirements for various performance indicators of lithium ion batteries, such as energy density, power density, cycle life, safety, etc. At present, most of the commercialized lithium ion batteries use carbonate organic electrolyte, which is flammable and volatile, and brings serious safety hazards. In order to solve this problem, it is urgent to introduce solid-state electrolyte with better thermal stability and stronger chemical stability to develop all-solid-state batteries.

[0003] However, there are many technical problems in all-solid-state batteries. For example, although inorganic solid-state electrolyte has a relatively high room temperature ionic conductivity, it is mostly in "solid-solid contact" with the positive and negative electrodes, and the interface contact impedance is large, and the rate performance is poor. Although the organic solid-state electrolyte has high processability and flexibility, the room temperature ionic conductivity is low, and the pre-mixing of the active particles with the positive electrode will reduce the energy density of the electrode sheet and the dynamic performance of the battery.

[0004] In order to solve the above problems and make the whole industry transition from liquid lithium ion batteries to all-solid-state lithium batteries, the research of semi-solid batteries is imperative. The side reaction of electrolyte and negative electrode will continuously consume electrolyte and lithium salt, and induce thermal runaway, so it is crucial to stabilize the negative electrode side interface with solid-state electrolyte.

[0005] Therefore, it is urgent to propose an improved technical solution to solve the above problems of the prior art. SUMMARY

[0006] In view of the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide a semi-solid composite negative electrode and a preparation method thereof, which is used to solve the problem that the electrolyte and the negative electrode side interface in the semi-solid battery of the prior art are not tight, resulting in side reaction between the electrolyte and the negative electrode, consumption of electrolyte and lithium salt, and thermal runaway.

[0007] To achieve the above-mentioned purpose and other related purposes, the present application provides a semi-solid composite negative electrode, which comprises: a negative electrode sheet, a polymer electrolyte and a separator, the polymer electrolyte is located above the negative electrode sheet, the separator is located above the polymer electrolyte, and part of the polymer electrolyte is distributed in the internal gap of the separator, and part of the polymer electrolyte is close to the surface of the negative electrode sheet.

[0008] Preferably, the negative electrode sheet is one or a combination of graphite negative electrode material, silicon-carbon negative electrode material, silicon monoxide / carbon composite negative electrode material, and lithium metal negative electrode material.

[0009] Preferably, the separator is a composite film of one or more of polypropylene film, polyethylene film, non-woven fabric separator, fiber separator, and ceramic separator.

[0010] Preferably, one or both sides of the separator is coated with an ion conductor material.

[0011] Preferably, the surface of the separator is not coated with an ion conductor material.

[0012] Preferably, the thickness of the separator is 1 μm to 50 μm.

[0013] Preferably, the ion conductor material is one or a combination of LISICON solid-state electrolyte material, NASICON-type solid-state electrolyte material, perovskite-type solid-state electrolyte material, and garnet-type solid-state electrolyte material.

[0014] Preferably, the LISICON solid-state electrolyte is Li 14 A1(B1O4)4, wherein A1 is one or a combination of Zn, Zr, Cr, and Sn, and B1 is one or a combination of Ge, Si, S, and P;

[0015] The NASICON-type solid-state electrolyte is Li 1+x A2 x B2 2-x (PO4)3, wherein x is between 0.01 and 0.5, A2 is one or a combination of Al, Y, Ga, Cr, In, Fe, Se, and La, and B2 is one or a combination of Ti, Ge, Ta, Zr, Sn, Fe, and V;

[0016] The perovskite-type solid-state electrolyte is Li 3y A3 2 / 3-y B3O3, wherein y is between 0.01 and 0.5, A3 is one or a combination of La, Al, Mg, Fe, and Ta, and B3 is one or a combination of Ti, Nb, and Sr;

[0017] The garnet-type solid-state electrolyte is Li 7+m-n-3z Al z La 3-m A4 m Zr 2-n B4 n O 12wherein m, n, z are all between 0 and 1, and m, n, z are not equal to 0, A4 is one or a combination of La, Ca, Sr, Ba, K, and B4 is one or a combination of Ta, Nb, W, Hf.

[0018] Preferably, the polymer electrolyte comprises a polymer and a lithium salt.

[0019] Preferably, the polymer electrolyte comprises a polymer and a lithium salt.

[0020] Preferably, the polymer electrolyte comprises a polymer and a lithium salt.

[0021] A preparation method of the above-mentioned semi-solid composite negative electrode, the preparation method comprising the following steps:

[0022] The polymer, the lithium salt and the initiator are added into a container according to the proportion, stirred and dissolved to obtain a polymer electrolyte solution.

[0023] The polymer electrolyte solution is coated on the negative electrode sheet, and a diaphragm is covered after standing for a period of time.

[0024] The semi-solid composite negative electrode is obtained by constant temperature heating at 40-100℃.

[0025] Preferably, in the obtained polymer electrolyte solution, the concentration of the lithium salt is 0.005-25 mol / L, and the concentration of the initiator is 0.001-1 mol / L.

[0026] Preferably, the initiator comprises one or a combination of azobisisobutyronitrile, dibenzoyl peroxide, bis(4-tert-butylcyclohexyl), peroxydicarbonate, lauroyl peroxide, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and 2,2-dimethoxy-phenyl phenylacetone.

[0027] As mentioned above, the semi-solid composite negative electrode and the preparation method thereof have the following beneficial effects:

[0028] The semi-solid composite negative electrode in the application comprises a negative electrode sheet, a polymer electrolyte and a separator, the polymer electrolyte is coated on the negative electrode sheet, and the separator is covered on the polymer electrolyte, the separator is a porous membrane, part of the polymer electrolyte will be soaked and evenly distributed in the internal interstice of the separator, part of the polymer electrolyte is closely adhered to the negative electrode sheet, the side reaction between the polymer electrolyte and the negative electrode sheet is not easy to occur, and the stability is good; and the semi-solid composite negative electrode in the application has high mechanical strength, good flexibility, is easy to process, can inhibit lithium dendrites, can be applied to semi-solid lithium ion batteries and metal lithium batteries, and the preparation method is environmentally friendly, compatible with modern lithium ion battery production process, and suitable for large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 A structure schematic diagram of the semi-solid composite negative electrode provided in the embodiment 1 of the application is shown.

[0030] Figure 2 A preparation process flow chart of the semi-solid composite negative electrode provided in the embodiment 1 of the application is shown.

[0031] Figure 3 An SEM top view of the semi-solid composite negative electrode provided in the embodiment 1 of the application is shown.

[0032] Figure 4 An SEM side view of the semi-solid composite negative electrode provided in the embodiment 1 of the application is shown.

[0033] The reference signs: 100, negative electrode sheet layer; 200, first polymer electrolyte layer; 300, separator layer. DETAILED DESCRIPTION

[0034] The embodiments of the application will be described in detail with specific reference being made to certain particular examples. The skilled person can easily understand other advantages and effects of the application from the content disclosed in the specification. The application can also be implemented or applied by means of other different specific embodiments, and the details in the specification can be modified or changed in different ways without departing from the spirit of the application.

[0035] Please refer to Figures 1 to 4 It should be noted that the diagrams provided in the embodiments only schematically illustrate the basic concept of the application, and the diagrams only show the components related to the application, not the number, shape and size of the components when actually implemented. The type, number and proportion of the components when actually implemented can be arbitrarily changed, and the layout type of the components can be more complex.

[0036] The semi-solid composite negative electrode in the application comprises a negative electrode sheet, a polymer electrolyte and a separator, the polymer electrolyte is coated on the negative electrode sheet, and the separator is covered on the polymer electrolyte, the separator is a porous membrane, part of the polymer electrolyte is soaked and uniformly distributed in the internal interstice of the separator, and the other part of the polymer electrolyte is closely adhered to the negative electrode sheet, so that the side reaction between the polymer electrolyte and the negative electrode sheet is difficult to occur, and the stability is good; the semi-solid composite negative electrode in the application has high mechanical strength, good flexibility and easy processing, can inhibit lithium dendrites, can be applied to semi-solid lithium ion batteries and metal lithium batteries, and the preparation method is environmentally friendly and compatible with modern lithium ion battery production process, and is suitable for large-scale production.

[0037] The application provides a semi-solid composite negative electrode, which at least comprises: a negative electrode sheet, a polymer electrolyte and a separator, the polymer electrolyte is located above the negative electrode sheet, and the separator is located above the polymer electrolyte, and part of the polymer electrolyte is distributed in the internal interstice of the separator, and the other part of the polymer electrolyte is close to the surface of the negative electrode sheet.

[0038] Specifically, referring to Figure 1 Fig. 1 shows a structure schematic diagram of the semi-solid composite negative electrode, the negative electrode sheet is located in the lowermost layer (referred to as: negative electrode sheet layer 100); part of the polymer electrolyte is close to the surface of the negative electrode sheet and is located above the negative electrode sheet layer, and this part of the polymer electrolyte is referred to as the first polymer electrolyte layer 200; part of the polymer electrolyte is distributed in the internal interstice of the separator, forming the separator layer 300.

[0039] As an example, the negative electrode sheet is one or a combination of graphite negative electrode material, silicon-carbon negative electrode material, silicon monoxide / carbon composite negative electrode material and metal lithium negative electrode material.

[0040] As an example, the separator is one or a combination of polypropylene film, polyethylene film, non-woven fabric separator, fiber separator and ceramic separator.

[0041] Specifically, the separator is a porous membrane, but the porosity and pore size of the specific porous membrane are not limited here, and can meet the actual use requirements.

[0042] As an example, the separator is coated with an ion conductor material on one side or both sides.

[0043] As an example, the surface of the separator is not coated with an ion conductor material.

[0044] As an example, the thickness of the separator is 1 μm to 50 μm.

[0045] Specifically, the thickness of the diaphragm can include any value within 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 45 μm, 50 μm, etc., and is adjusted according to actual conditions. In addition, the thickness of the diaphragm refers to the total thickness of the diaphragm when the diaphragm is coated with an ion conductor material on one side, coated with an ion conductor material on both sides, or not coated with an ion conductor material.

[0046] As an example, the ion conductor material is one or a combination of LISICON solid electrolyte material, NASICON type solid electrolyte material, perovskite type solid electrolyte material, and garnet type solid electrolyte material.

[0047] As an example, the LISICON solid electrolyte is Li 14 A1(B1O4)4, wherein A1 is one or a combination of Zn, Zr, Cr, and Sn, and B1 is one or a combination of Ge, Si, S, and P;

[0048] The NASICON type solid electrolyte is Li 1+x A2 x B2 2-x (PO4)3, wherein x is between 0.01 and 0.5, A2 is one or a combination of Al, Y, Ga, Cr, In, Fe, Se, and La, and B2 is one or a combination of Ti, Ge, Ta, Zr, Sn, Fe, and V; specifically, x can include any value within 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, etc., and is adjusted according to actual conditions; for example, the NASICON type solid electrolyte is Li 1.3 A1 0.3 Ti 1.7 (PO4)3, etc.

[0049] The perovskite type solid electrolyte is Li 3y A3 2 / 3-y B3O3, wherein y is between 0.01 and 0.5, A3 is one or a combination of La, Al, Mg, Fe, and Ta, and B3 is one or a combination of Ti, Nb, and Sr; specifically, y can include any value within 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, etc., and is adjusted according to actual conditions.

[0050] The garnet type solid electrolyte is Li 7+m-n-3z Al z La 3-m A4 m Zr 2-n B4 n O 12Wherein m, n, z are all between 0-1, and m, n, z are not equal to 0, A4 is one or combination of La, Ca, Sr, Ba, K, B4 is one or combination of Ta, Nb, W, Hf; Specifically, m, n, z can include 0.01, 0.1, 0.3, 0.5, 0.7, 0.9, 1, etc. Any value within the range, and the actual adjustment is made; The values of m, n, z can be the same or different, and m, n, z are not equal to 0.

[0051] As an example, the polymer electrolyte includes a polymer and a lithium salt;

[0052] Wherein, the polymer includes one or combination of polyethylene oxide (PEO), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVDF), polycyanoacrylate (PCA), polyethylene glycol diacrylate (PEGDA), polyethylene glycol methacrylate (PEGMEA), polyvinylidene carbonate, polyvinylidene sulfite, polyacrylate, polyvinyl acetate and polyimide;

[0053] The lithium salt includes one or combination of lithium bisoxalate borate (LiBOB), lithium difluoro oxalate borate (LiDFOB), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium trifluoromethylsulfonate (LiCF3SO3), lithium bis-trifluoromethylsulfonimide (LiTFSI), lithium bisfluorosulfonimide (LiFSI), lithium nitrate (LiNO3), lithium carbonate (Li2CO3) and lithium fluoride (LiF).

[0054] For better understanding of the semi-solid composite negative electrode in the present application, refer to Figure 2 The present application also provides a preparation method of the semi-solid composite negative electrode, which comprises the following steps:

[0055] S1, the polymer, the lithium salt and the initiator are added into the container according to the proportion, stirred and dissolved to obtain a polymer electrolyte solution;

[0056] S2, the polymer electrolyte solution is coated on the negative electrode sheet, and after standing for a period of time, the diaphragm is covered;

[0057] S3, constant temperature heating at 40-100℃, to obtain a semi-solid composite negative electrode.

[0058] Specifically, in step S1, the lithium salt and the initiator are both dissolved in the polymer to form a polymer electrolyte solution through stirring; in step S2, the polymer electrolyte solution is coated on the negative electrode sheet, and the coating method can be drop coating, nozzle spraying or soaking; in step S3, the constant temperature heating temperature can include any value within the range of 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, etc., and is adjusted according to the actual situation.

[0059] For example, in the obtained polymer electrolyte solution, the concentration of the lithium salt is 0.005 mol / L to 25 mol / L, and the concentration of the initiator is 0.001 mol / L to 1 mol / L.

[0060] Specifically, in the obtained polymer electrolyte solution, the concentration of the lithium salt can include any value within the range of 0.005 mol / L, 0.5 mol / L, 1 mol / L, 5 mol / L, 10 mol / L, 15 mol / L, 20 mol / L, 25 mol / L, etc., and is adjusted according to the actual situation; the concentration of the initiator can include any value within the range of 0.001 mol / L, 0.005 mol / L, 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.5 mol / L, 1 mol / L, etc., and is adjusted according to the actual situation.

[0061] For example, the initiator includes one or a combination of azobisisobutyronitrile (AIBN), dibenzoyl peroxide (BPO), bis(4-tert-butylcyclohexyl), peroxydicarbonate (BBP), lauroyl peroxide (LPO), 2-hydroxy-2-methyl-1-phenyl-1-propanone (HMPP), 2,2-dimethoxy-phenyl phenylacetone (DMPA).

[0062] The semi-solid composite negative electrode and the preparation method thereof will be described below with reference to specific examples, and it should be noted that these examples are merely descriptive and do not limit the present application in any way.

[0063] Example 1

[0064] The present embodiment provides a semi-solid composite negative electrode, which includes: a negative electrode sheet, a polymer electrolyte and a separator, the polymer electrolyte is located above the negative electrode sheet, the separator is located above the polymer electrolyte, and part of the polymer electrolyte is distributed in the internal gap of the separator, and part of the polymer electrolyte is close to the surface of the negative electrode sheet; wherein the negative electrode sheet is a metal lithium negative electrode; the separator is a polyethylene film, and Li 1.3 A1 0.3 Ti 1.7polymer electrolyte includes polyethylene glycol methacrylate and lithium difluoro(oxalato)borate.

[0065] The embodiment also provides a preparation method of the above semi-solid composite negative electrode, and the preparation method comprises the following steps:

[0066] S1, a polymer, a lithium salt and an initiator are added into a container according to a proportion, and are stirred and dissolved to obtain a polymer electrolyte solution; wherein the polymer is polyethylene glycol methacrylate, the lithium salt is lithium difluoro(oxalato)borate, and the initiator is azobisisobutyronitrile; the concentration of the lithium salt in the polymer electrolyte solution is 1 mol / L, and the concentration of the initiator is 0.05 mol / L;

[0067] S2, the negative electrode sheet is laid on a polytetrafluoroethylene plate, and the polymer electrolyte solution is drop-coated on the negative electrode sheet, and a separator is covered after standing for a period of time; wherein the negative electrode sheet is a lithium sheet;

[0068] S3, constant temperature heating is performed at 80℃ to obtain a semi-solid composite negative electrode.

[0069] Referring to Figure 3 is a SEM top view of the semi-solid composite negative electrode, and thus it can be known that the polymer electrolyte is uniformly distributed in the separator; referring to Figure 4 is a SEM side view of the semi-solid composite negative electrode, and thus it can be known that the polymer electrolyte is integrated with the separator, and is closely adhered to the negative electrode sheet.

[0070] The semi-solid composite negative electrode prepared in the embodiment is subjected to performance testing, an electrochemical workstation (ZENNIUM, ZAHNER) is used to test the ionic conductivity of the semi-solid composite negative electrode, an atomic force microscope (AFM, MultiMode8-HR) is used to test the mechanical strength of the semi-solid composite negative electrode, and it is tested that the ionic conductivity of the semi-solid negative electrode is as high as 4.5×10 -4 S cm -1 , and the mechanical strength is as high as 16.7 MPa, which can effectively inhibit the growth of lithium dendrites.

[0071] Embodiment 2

[0072] The embodiment provides a semi-solid composite negative electrode, which is different from that in embodiment 1 in that a Li 1.3 A1 0.3 Ti 1.7 (PO4)3 solid-state electrolyte is coated on one side of the separator adjacent to the negative electrode sheet; and the others are the same as those in embodiment 1, which will not be described herein again.

[0073] The embodiment also provides a preparation method of the above-mentioned semi-solid composite negative electrode, which is different from that in the embodiment 1 in that: the polymer in the step S1 is PEO, the lithium salt is LiTFSI, the initiator is BPO, the concentration of the lithium salt in the polymer electrolyte solution is 3 mol / L, and the concentration of the initiator is 0.1 mol / L; the constant temperature heating temperature in the step S3 is 60 DEG C; and the other steps and methods are the same as those in the embodiment 1.

[0074] The polymer electrolyte in the semi-solid composite negative electrode prepared in the embodiment is uniformly distributed in the diaphragm, and a small part of the polymer electrolyte is located between the diaphragm and the negative electrode sheet, and most of the polymer electrolyte is integrated with the diaphragm; the semi-solid composite negative electrode prepared in the embodiment is tested, the test method is the same as that in the embodiment 1, and the test result shows that the ion conductivity of the semi-solid negative electrode is as high as 8.5*10 -4 S cm -1 , and the mechanical strength is as high as 14.3 MPa, so that the growth of lithium dendrites can be effectively inhibited.

[0075] Embodiment 3

[0076] The embodiment provides a semi-solid composite negative electrode, which is different from that in the embodiment 1 in that: the negative electrode sheet is a silicon-carbon negative electrode material, and the side of the diaphragm adjacent to the negative electrode sheet is coated with Li7La3Zr2O 12 solid electrolyte; and the other steps and methods are the same as those in the embodiment 1.

[0077] The embodiment also provides a preparation method of the above-mentioned semi-solid composite negative electrode, which is different from that in the embodiment 1 in that: the polymer in the step S1 is PEGMEA, the lithium salt is LiBF4, the initiator is BBP, the concentration of the lithium salt in the polymer electrolyte solution is 10 mol / L, and the concentration of the initiator is 0.2 mol / L; the constant temperature heating temperature in the step S3 is 100 DEG C; and the other steps and methods are the same as those in the embodiment 1.

[0078] The polymer electrolyte in the semi-solid composite negative electrode prepared in the embodiment is uniformly distributed in the diaphragm, tightly adhered and penetrated into the negative electrode, and most of the polymer electrolyte is integrated with the diaphragm; the semi-solid composite negative electrode prepared in the embodiment is tested, the test method is the same as that in the embodiment 1, and the test result shows that the ion conductivity of the semi-solid negative electrode is as high as 9.6*10 -4 S cm -1 , and the mechanical strength is as high as 12.6 MPa, so that the growth of lithium dendrites can be effectively inhibited.

[0079] Embodiment 4

[0080] The embodiment provides a semi-solid composite negative electrode, which is different from that in the embodiment 1 in that the negative electrode is a graphite negative electrode, the separator is coated with Li 0.5 La 0.5 TiO3 solid electrolyte; the others are the same as those in the embodiment 1 and will not be repeated here.

[0081] The embodiment also provides a preparation method of the semi-solid composite negative electrode, which is different from that in the embodiment 1 in that the polymer used in the step S1 is PAN, the lithium salt is LiFSI, the initiator is LPO, the concentration of the lithium salt in the polymer electrolyte solution is 25 mol / L, and the concentration of the initiator is 0.5 mol / L; the constant temperature heating temperature in the step S3 is 90 DEG C; and the others are the same as those in the embodiment 1 and will not be repeated here. -3 S cm -1 The semi-solid composite negative electrode prepared in the embodiment has a high ionic conductivity of 1.2*10

[0082] Embodiment 5

[0083] The embodiment provides a semi-solid composite negative electrode, which is different from that in the embodiment 1 in that the negative electrode is a silicon monoxide / carbon composite negative electrode, one side of the separator is coated with Li 0.5 La 0.5 TiO3 solid electrolyte, and the other side is coated with Li 1.3 A1 0.3 Ti 1.7 (PO4)3, and the side of the Li 1.3 A1 0.3 Ti 1.7 (PO4)3 coating is adjacent to the negative electrode sheet; and the others are the same as those in the embodiment 1 and will not be repeated here.

[0084] The embodiment also provides a preparation method of the semi-solid composite negative electrode, which is different from that in the embodiment 1 in that the polymer used in the step S1 is PMMA, the lithium salt is LiClO4, the initiator is HMPP, the concentration of the lithium salt in the polymer electrolyte solution is 5 mol / L, and the concentration of the initiator is 1.0 mol / L; the constant temperature heating temperature in the step S3 is 50 DEG C; and the others are the same as those in the embodiment 1 and will not be repeated here.

[0085] The polymer electrolyte in the semi-solid composite negative electrode prepared in this embodiment is uniformly distributed in the separator, closely adheres and penetrates into the negative electrode, and most of the polymer electrolyte is integrated with the separator; performance test is conducted on the semi-solid composite negative electrode prepared in this embodiment, the test method is the same as in Embodiment 1, and it is tested that the ionic conductivity of the semi-solid negative electrode is as high as 1.8×10 -4 S cm -1 , the mechanical strength is as high as 15.2 MPa, and the growth of lithium dendrites can be effectively inhibited.

[0086] Embodiment 6

[0087] This embodiment provides a semi-solid composite negative electrode, which is different from that in Embodiment 1 in that the negative electrode is a composite material of graphite negative electrode material and silicon-carbon negative electrode material, and the separator is not coated with ion conductor material; the others are the same as in Embodiment 1 and will not be repeated here.

[0088] This embodiment also provides a preparation method of the above semi-solid composite negative electrode, which is different from that in Embodiment 1 in that the polymer used in step S1 is PVDF, the lithium salt is LiNO3, the initiator is DMPA, the concentration of the lithium salt in the polymer electrolyte solution is 0.05 mol / L, and the concentration of the initiator is 0.002 mol / L; the constant temperature heating temperature in S3 is 100°C; the other steps and methods are the same as in Embodiment 1 and will not be repeated here.

[0089] The polymer electrolyte in the semi-solid composite negative electrode prepared in this embodiment is uniformly distributed in the separator, closely adheres and penetrates into the negative electrode, and most of the polymer electrolyte is integrated with the separator; performance test is conducted on the semi-solid composite negative electrode prepared in this embodiment, the test method is the same as in Embodiment 1, and it is tested that the ionic conductivity of the semi-solid negative electrode is as high as 7.8×10 -5 S cm -1 , the mechanical strength is as high as 20.2 MPa, and the growth of lithium dendrites can be effectively inhibited.

[0090] Comparative Example 1

[0091] This comparative example provides a blank control, and the negative electrode in this comparative example is pure lithium sheet without semi-solid treatment.

[0092] Performance test is conducted on the negative electrode in this comparative example, the test method is the same as in Embodiment 1, and it is tested that the mechanical strength of the artificial SEI on the surface of the negative electrode in this comparative example is only 0.045 MPa, which cannot effectively inhibit the growth of lithium dendrites, a large number of dendrites grow on the surface of the negative electrode, and the battery rapidly short-circuits and fails.

[0093] In summary, the semi-solid composite negative electrode in the application comprises a negative electrode sheet, a polymer electrolyte and a separator, the polymer electrolyte is coated on the negative electrode sheet, and the separator is covered on the polymer electrolyte, the separator is a porous membrane, part of the polymer electrolyte is soaked and uniformly distributed in the internal interstice of the separator, and the other part of the polymer electrolyte is closely adhered to the negative electrode sheet, the side reaction between the polymer electrolyte and the negative electrode sheet is not easy to occur, and the stability is good; and the semi-solid composite negative electrode in the application has high mechanical strength, good flexibility, easy processing, can inhibit lithium dendrite, can be applied to semi-solid lithium ion batteries and metal lithium batteries, and the preparation method is environment-friendly, compatible with modern lithium ion battery production process, and suitable for large-scale production. Therefore, the application effectively overcomes the shortcomings of the prior art and has high industrial utilization value.

[0094] The above embodiments only exemplarily illustrate the principles and effects of the application, and are not used to limit the application. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the application. Therefore, all equivalent modifications or changes completed by those skilled in the art without departing from the spirit and technical thought disclosed by the application should be covered by the claims of the application.

Claims

1. A method for producing a semi-solid composite negative electrode, characterized by, The preparation method comprises the following steps: adding the polymer, lithium salt and initiator according to the proportion into a container, stirring and dissolving to obtain a polymer electrolyte solution; coating the polymer electrolyte solution on a negative electrode sheet, standing for a period of time, and covering a separator; heating at a constant temperature of 40-100 DEG C to obtain a semi-solid composite negative electrode; The semi-solid composite negative electrode comprises a negative electrode sheet, a polymer electrolyte and a separator, the polymer electrolyte is located above the negative electrode sheet, the separator is located above the polymer electrolyte, and part of the polymer electrolyte is distributed in the internal gap of the separator, and part of the polymer electrolyte is close to the surface of the negative electrode sheet; one side or both sides of the separator are coated with an ion conductor material; the ion conductor material is one or a combination of LISICON solid electrolyte material, NASICON type solid electrolyte material, perovskite type solid electrolyte material and garnet type solid electrolyte material.

2. The method of claim 1, wherein the semi-solid composite negative electrode is prepared by: The negative electrode sheet is one or a combination of graphite negative electrode material, silicon-carbon negative electrode material, silicon monoxide / carbon composite negative electrode material and metal lithium negative electrode material.

3. The method of claim 1, wherein the semi-solid composite negative electrode is prepared by: The separator is a composite film of one or more of polypropylene film, polyethylene film, non-woven fabric separator, fiber separator and ceramic separator.

4. The method of claim 1, wherein the semi-solid composite negative electrode is prepared by: The thickness of the separator is 1-50 microns.

5. The method of claim 1, wherein the semi-solid composite anode is prepared by: The LISICON solid-state electrolyte is Li 14 A1(B1O4)4, wherein A1 is one or a combination of Zn, Zr, Cr, Sn, and B1 is one or a combination of Ge, Si, S, and P; The NASICON-type solid-state electrolyte is Li 1+x A2 x B2 2-x (PO4)3, wherein x is between 0.01 and 0.5, A2 is one or a combination of Al, Y, Ga, Cr, In, Fe, Se, La, and B2 is one or a combination of Ti, Ge, Ta, Zr, Sn, Fe, V, Hf. The perovskite solid-state electrolyte is Li 3y A3 2 / 3-y B3O3, wherein y is between 0.01 and 0.5, A3 is one or a combination of La, Al, Mg, Fe, Ta, and B3 is one or a combination of Ti, Nb, Sr, Pr. The garnet solid-state electrolyte is Li 7+m-n-3z Al z La 3-m A4 m Zr 2-n B4 n O 12 , wherein m, n, and z are each between 0 and 1, and m, n, and z are not equal to 0, A4 is one or a combination of La, Ca, Sr, Ba, and K, and B4 is one or a combination of Ta, Nb, W, and Hf.

6. The method of claim 1, wherein the semi-solid composite anode is prepared by: The polymer electrolyte comprises a polymer and a lithium salt; The polymer comprises one or a combination of polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, polyvinylidene fluoride, polycyanoacrylate, polyethylene glycol diacrylate, polyethylene glycol methacrylate, polyvinylidene carbonate, polyvinylidene sulfite, polyacrylate, polyvinyl acetate and polyimide; The lithium salt comprises one or a combination of lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium trifluoromethylsulfonate, lithium bis(trifluoromethylsulfonylimide), lithium bis(fluorosulfonylimide), lithium nitrate, lithium carbonate and lithium fluoride.

7. The method of claim 1, wherein the semi-solid composite negative electrode is prepared by: In the obtained polymer electrolyte solution, the concentration of the lithium salt is 0.005-25 mol / L, and the concentration of the initiator is 0.001-1 mol / L.

8. The method of claim 1, wherein the semi-solid composite anode is prepared by: The initiator comprises one or a combination of azobisdimethyl isobutyronitrile, dibenzoyl peroxide, bis(4-tert-butylcyclohexyl)peroxide, peroxydicarbonate, lauroyl peroxide, 2-hydroxy-2-methyl-1-phenyl-1-propanone and 2,2-dimethoxy-phenyl phenylacetone.

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