Semi-solid battery and preparation method thereof

Abstract

The invention relates to a semi-solid battery and a preparation method in the technical field of lithium battery production, the semi-solid battery comprises a positive electrode, a negative electrode and an electrolyte, the negative electrode comprises a negative electrode active material, and the negative electrode active material comprises graphite; a solid electrolyte layer is arranged on the surface of one side, close to the electrolyte, of the negative electrode; and the electrolyte comprises a flame retardant additive. The solid electrolyte layer is arranged on the surface of the negative electrode, so that contact between a flame retardant in electrolyte and the graphite negative electrode is isolated, and the problem of gas production caused by contact between graphite and the flame retardant in the electrolyte is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery production, and in particular to a semi-solid battery and a preparation method thereof. Background Art

[0002] Lithium-ion batteries (LIBs) have become an indispensable energy storage method for portable electronic devices, electric vehicles and large-scale energy storage systems due to their high energy density, long cycle life and environmental friendliness. However, the safety issues of LIBs, especially their thermal runaway behavior under high temperature or abuse conditions, have limited their further development in high energy density applications. Existing solutions mainly improve battery safety by improving the composition of the electrolyte. For example, adding new flame retardants, such as phosphorus-containing compounds, interferes with the chain reaction of hydroxyl radicals by capturing free radicals, thereby improving the non-flammability of the electrolyte. Although existing solutions have improved the safety of batteries to a certain extent, some problems still exist. The problem that existing flame retardant additives produce gas at the graphite negative electrode and are incompatible with the graphite system needs to be solved.

[0003] Therefore, developing a high-safety electrolyte that is compatible with the graphite system, improving the negative electrode interface, and fundamentally solving the battery safety problem is an important direction for the current development of lithium-ion battery technology. Summary of the Invention

[0004] In order to solve the above problems, the present invention discloses a semi-solid battery and a preparation method. The technical solution of the present invention is implemented as follows:

[0005] A first aspect of the present invention provides a semi-solid-state battery, comprising a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode comprises a negative electrode active material, and the negative electrode active material comprises graphite;

[0006] A solid electrolyte layer is provided on a surface of the negative electrode close to the electrolyte;

[0007] The electrolyte includes a flame retardant additive.

[0008] Preferably, the solid electrolyte layer includes an oxide solid electrolyte.

[0009] Preferably, the thickness of the solid electrolyte layer is 20 μm to 150 μm.

[0010] Preferably, the flame retardant additive includes at least one of triethyl phosphate, triphenyl phosphate, and perfluoro-2-methyl-3-pentanone.

[0011] Preferably, in the electrolyte, the mass proportion of the flame retardant additive is 5% to 20%.

[0012] Preferably, the electrolyte further includes a second additive, and the second additive includes propane sultone and vinylene carbonate.

[0013] Preferably, the electrolyte further comprises a first lithium salt and a solvent;

[0014] The first lithium salt includes at least two of lithium hexafluorophosphate LiPF6, lithium bis(fluorosulfonyl)imide LiFSI, and lithium bis(oxalatoborate) LiBOB;

[0015] The solvent includes at least two of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, diethyl carbonate, and fluoroethylene carbonate;

[0016] Preferably, in the electrolyte, the mass proportion of the first lithium salt is 10% to 20%.

[0017] Preferably, in the electrolyte, the mass proportion of the second additive is 2% to 5%;

[0018] The second aspect of the present invention discloses a method for preparing a semi-solid-state battery, which is used to prepare the semi-solid-state battery proposed in the first aspect of the present invention, and the method comprises the following steps:

[0019] S1, preparing the positive electrode;

[0020] S2. Preparation of negative electrode:

[0021] S2.1, preparing a negative electrode layer;

[0022] S2.2, preparing a solid electrolyte slurry, coating it on the surface of the negative electrode layer, and drying it to obtain a negative electrode;

[0023] S3. Prepare a semi-solid-state battery: stack the positive electrode, the separator, and the negative electrode in sequence to form a dry cell, inject the electrolyte, and package to form a semi-solid-state battery.

[0024] Preferably, in S2.2, the specific steps of preparing the solid electrolyte slurry include:

[0025] S100, stirring a binder and a second lithium salt in a solvent until a viscous solution is formed;

[0026] S200, adding ball-milled dispersed solid electrolyte powder to the viscous solution and stirring to obtain a milky white viscous solution;

[0027] S300, performing vacuum degassing on the viscous liquid to obtain the solid electrolyte slurry;

[0028] The second lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(oxalatoborate).

[0029] This invention designs a highly safe semi-solid-state battery. A solid electrolyte layer is placed on the negative electrode surface to isolate the flame retardant in the electrolyte from contact with the graphite negative electrode, thereby preventing the gassing problem caused by contact. This reduces the proportion of flammable organic solvents and also reduces the gassing of the flame retardant additive at the negative electrode interface, which could disrupt the formation of the negative electrode SEI film. This improves the safety of lithium-ion batteries without affecting their electrochemical performance. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0031] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by technicians in the technical field to which the present invention belongs; the terms used in the specific embodiments are only for the purpose of describing specific embodiments and are not intended to limit the present invention; the terms "including" and "having" in the description and claims of the present invention and any variations thereof are intended to cover non-exclusive inclusions.

[0032] In the description of the specific embodiments of the present invention, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the technical features indicated. In the description of the embodiments of the present invention, the meaning of "plurality" is more than two, unless otherwise specifically defined.

[0033] References to "embodiments" in this disclosure mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the disclosure. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0034] In the description of the embodiments of the present invention, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three possible relationships exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exists simultaneously, and B exists alone. In addition, the character " / " in this invention generally indicates that the associated objects are in an "or" relationship.

[0035] Throughout this disclosure, numerical values represent approximate measures or limits of ranges to encompass minor deviations from a given value, as well as embodiments having approximately the stated value and embodiments having the exact value stated. Except for the working examples provided at the end of the detailed description, all numerical values for parameters (e.g., amounts, or conditions) in this specification (including the appended claims) should be understood as being modified in all instances by the term "about," regardless of whether "about" actually appears before the numerical value. "About" indicates that the stated numerical value allows for some minor imprecision (some degree of closeness to the exact value of the stated value; approximately or reasonably close to the stated value; nearly). If the imprecision provided by "about" is not otherwise understood in this ordinary sense in the art, "about," as used herein, at least indicates the variation that can occur due to ordinary methods of measuring and using such parameters. For example, "about" can encompass variations of less than or equal to 5%, optionally less than or equal to 4%, optionally less than or equal to 3%, optionally less than or equal to 2%, optionally less than or equal to 1%, optionally less than or equal to 0.5%, and in certain aspects, optionally less than or equal to 0.1%.

[0036] Additionally, disclosure of ranges includes disclosure of all values within the entire range and further divided ranges, including endpoints and sub-ranges stated for such ranges.

[0037] In order to improve the safety performance of the battery, flame retardant additives are generally added to the electrolyte. For batteries with graphite as the negative electrode, flame retardant additives have poor compatibility with the graphite negative electrode and are prone to decomposition to produce gas, resulting in a decrease in battery capacity, deterioration in cycle performance, battery expansion, and reduced safety.

[0038] A first aspect of the present invention provides a semi-solid-state battery, comprising a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode comprises a negative electrode active material, and the negative electrode active material comprises graphite;

[0039] A solid electrolyte layer is provided on a surface of the negative electrode close to the electrolyte;

[0040] The electrolyte includes a flame retardant additive.

[0041] The present invention provides a solid electrolyte layer on the surface of the negative electrode to isolate the flame retardant in the electrolyte from contacting the graphite negative electrode, thereby avoiding side reactions between the flame retardant and the graphite, and thus achieving compatibility between the flame retardant and the graphite system.

[0042] This invention combines an electrolyte with a solid electrolyte membrane to reduce side reactions of flame retardant additives at the negative electrode, protect the negative electrode interface, and achieve a balance between battery safety and electrochemical performance. This addresses the problem that existing solutions, while improving battery safety, often lead to a decrease in electrochemical performance, such as charge and discharge efficiency and cycle stability.

[0043] In some embodiments, the solid electrolyte layer includes an oxide solid electrolyte.

[0044] In specific applications, the oxide solid electrolyte can be selected from: perovskite type, garnet type, LISICON type, NASICON type, among which the perovskite type solid electrolyte material is preferably Li 0.33 La 0.56 TiO3 (LLTO), garnet-type solid electrolyte material is preferably Li7La3Zr2O 12 (LLZO), NASICON (sodium super ion conductor) type solid electrolyte material is preferably Li 1.3 Al 0.3 Ti 1.7 At least one of (PO4)3(LATP).

[0045] The term "at least one" as used in the present invention means that any one element can be selected from the listed elements as a technical solution, or a combination of two or more elements can be used as a technical solution. Such a combination will not exceed the understanding of those skilled in the art, and therefore the form of combination can be freely selected as needed, up to a maximum of all combinations of the listed elements.

[0046] In some preferred embodiments, the oxide solid electrolyte includes at least one of lithium lanthanum zirconium oxide, lithium lanthanum titanate, and lithium aluminum titanium phosphate.

[0047] When the oxide solid electrolyte is at least one or a combination of two or three of the above materials, the oxide solid electrolyte has the best performance in the semi-solid battery disclosed in the present invention.

[0048] In some embodiments, the solid electrolyte layer has a thickness of 20 μm to 150 μm.

[0049] In specific applications, the thickness of the solid electrolyte layer can be selected as: 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm, 150μm, etc.; the above-listed values are only examples and are not limiting. Without exceeding the prior art understanding of those skilled in the art, those skilled in the art can freely implement any value within the range of 20μm to 150μm.

[0050] In some embodiments, the flame retardant additive includes at least one of triethyl phosphate (TEP), triphenyl phosphate (TPP), and perfluoro-2-methyl-3-pentanone (PFPN).

[0051] The flame retardant additives listed in the present invention can decompose in the electrolyte to produce phosphorus or fluorine free radicals, which can remove active hydrogen / hydroxide free radicals that may be generated during thermal runaway of the battery, thereby improving the non-flammability of the electrolyte.

[0052] In some preferred embodiments, the flame retardant additive is perfluoro-2-methyl-3-pentanone PFPN.

[0053] When the flame retardant additive is perfluoro-2-methyl-3-pentanone PFPN, the overall performance of the electrolyte is optimal.

[0054] In some embodiments, the flame retardant additive accounts for 5% to 20% by mass in the electrolyte.

[0055] In specific applications, the mass proportion of the flame retardant additive in the electrolyte can be selected to be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc.; the percentage values listed above are only examples and are not limiting. Without exceeding the prior art understanding of those skilled in the art, those skilled in the art can freely implement any percentage value within the range of 5% to 20%.

[0056] In some embodiments, the electrolyte further includes a second additive, and the second additive includes propane sultone and vinylene carbonate.

[0057] In the present invention, the second additive is a conventional additive, including conventional film-forming additives such as propane sultone and vinylene carbonate, which help form a stable SEI film on the surface of the negative electrode and improve the cycle stability and safety of the battery.

[0058] In some embodiments, the electrolyte further comprises a first lithium salt and a solvent;

[0059] The first lithium salt includes at least two of lithium hexafluorophosphate LiPF6, lithium bis(fluorosulfonyl)imide LiFSI, and lithium bis(oxalatoborate) LiBOB;

[0060] The solvent includes at least two of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, diethyl carbonate, and fluoroethylene carbonate.

[0061] The term "at least two" as used herein refers to a mixture of at least two of the listed elements as a technical solution. These options include combinations of more elements that, through synergistic cooperation, enhance the performance of the electrolyte. It should be noted that the selection of the above elements is within the purview of those skilled in the art, and those skilled in the art may make any selection based on their needs in accordance with their understanding of the prior art.

[0062] The combination of the first lithium salt is designed to balance the conductivity and thermal stability of the battery, where LiPF6 provides good conductivity and LiFSI and LiBOB provide higher thermal stability and oxidation resistance.

[0063] The combination of solvents is designed to optimize the viscosity, melting point and electrochemical window of the electrolyte to suit different operating temperature and voltage requirements.

[0064] The synergistic effect of the two lithium salts can effectively compensate for the deficiencies of a single lithium salt, thereby optimizing the electrolyte's ionic conductivity, electrochemical stability, interfacial compatibility, and safety. For example, the combination of LiPF6 and LiFSI forms multiple ion transport channels after mixing. LiPF6 provides rapidly dissociated Li+, while LiFSI optimizes the solvation structure and improves overall conductivity. At the same time, the two decompose together to form a gradient SEI layer, significantly improving the cycling stability of the negative electrode.

[0065] In some embodiments, the mass percentage of the first lithium salt in the electrolyte is 10% to 20%.

[0066] In specific applications, the mass proportion of the first lithium salt in the electrolyte can be selected as: 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc. The percentage values listed above are only examples and are not limiting. Those skilled in the art may freely implement any percentage value within the range of 10% to 20% without exceeding the prior art understanding of those skilled in the art.

[0067] In some embodiments, in the electrolyte, the mass proportion of the second additive is 2% to 5%;

[0068] In specific applications, the mass percentage of the second additive in the electrolyte can be selected as: 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc. The percentage values listed above are only examples and are not limiting. Those skilled in the art can freely implement any percentage value within the range of 2% to 5% without exceeding the existing technical understanding of those skilled in the art.

[0069] The second aspect of the present invention discloses a method for preparing a semi-solid-state battery, which is used to prepare the semi-solid-state battery proposed in the first aspect of the present invention, and the method comprises the following steps:

[0070] S1, preparing the positive electrode;

[0071] S2. Preparation of negative electrode:

[0072] S2.1, preparing a negative electrode layer;

[0073] S2.2. Prepare a solid electrolyte slurry, apply it on the surface of the negative electrode layer, and obtain the negative electrode after drying.

[0074] S3. Prepare a semi-solid-state battery: stack the positive electrode, the separator, and the negative electrode in sequence to form a dry cell, inject the electrolyte, and package to form a semi-solid-state battery.

[0075] In some embodiments, the separator includes one or more of a polyolefin separator, a coated polyester membrane, a cellulose membrane, a polyimide membrane and a polyamide membrane, a spandex or aramid membrane, a non-woven membrane, and an inorganic nanocomposite membrane.

[0076] In some embodiments, the step S1 is as follows: mixing the positive electrode active material with the positive electrode conductive agent and the positive electrode binder by a solution blending method, and coating the mixture on an aluminum foil to form a positive electrode.

[0077] In specific applications, the positive electrode active material can be selected from any one or a combination of at least two of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese oxide, lithium iron manganese phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium iron phosphate, lithium titanate, or a lithium-rich manganese elastic-based material. The above are all common positive electrode active materials in the field and are only examples and not limitations.

[0078] In specific applications, the positive electrode conductive agent may include any conductive material as long as it does not cause chemical changes. Conductive materials include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powder, metal fiber, etc., including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof. The above are all common conductive agents in the art, which are only examples and not limitations.

[0079] In specific applications, the positive electrode binder may include at least one of polyvinylidene fluoride, poly(vinylidene fluoride-hexafluoropropylene), polyvinyl alcohol, polyacrylic acid, polyethylene glycol, polyethylene oxide, poly(p-phenylene oxide), poly(methyl methacrylate), polyacrylonitrile, or polyvinyl chloride (PVC). The above are all common binders in the art and are only examples and not limitations.

[0080] In some embodiments, the step S1 is as follows: mixing the positive electrode active material with the positive electrode conductive agent and the positive electrode binder, and forming the positive electrode through fiberization and roller pressing.

[0081] In some embodiments, in S2.2, the specific steps of preparing the solid electrolyte slurry include:

[0082] S100, stirring a binder and a second lithium salt in a solvent until a viscous solution is formed;

[0083] By adding the second lithium salt and cooperating with the solid electrolyte, the ion transmission capacity of the solid electrolyte layer is improved. Dispersing the binder and the second lithium salt first is beneficial to improving the dispersion uniformity of the second lithium salt in the solid electrolyte layer and preventing the second lithium salt from agglomerating.

[0084] S200, adding ball-milled dispersed solid electrolyte powder to the viscous solution and stirring to obtain a milky white viscous solution;

[0085] S300, performing vacuum degassing on the viscous liquid to obtain the solid electrolyte slurry;

[0086] Through vacuum degassing treatment, the uniformity of the slurry can be effectively improved and the density of the solid electrolyte layer can be increased. Especially for oxide solid electrolytes, degassing can reduce the residual pores in the sintering process and improve the ionic conductivity of the electrolyte layer.

[0087] The second lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(oxalatoborate);

[0088] The solid electrolyte powder includes at least one of LLZO, LATP, and LLTO.

[0089] This application improves the preparation method of the solid electrolyte on the negative electrode side, effectively improving the uniformity of the solid electrolyte layer and the lithium ion transmission capacity.

[0090] In some embodiments, the negative electrode includes a negative electrode conductor and a negative electrode binder.

[0091] In specific applications, the negative electrode conductive agent may include any conductive material as long as it does not cause chemical changes. Conductive materials include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powder, metal fiber, etc., including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof. The above are all common conductive agents in the art and are only examples and not limitations.

[0092] In specific applications, non-limiting examples of negative electrode binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1,1-difluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0093] The embodiments of the present invention will be described in detail below through examples and comparative examples. All examples and comparative examples are groups of semi-solid-state battery samples prepared using the same process, with 20 samples in each group.

[0094] Example 1:

[0095] 1. Preparation of positive electrode:

[0096] The positive electrode active material LMO (lithium manganate), the positive electrode binder PVDF, and the positive electrode conductive agent Super-P are formed into a slurry through a solution blending method and applied on an aluminum foil to form a positive electrode.

[0097] 2. Preparation of negative electrode:

[0098] 1. Preparation of negative electrode sheet: Mix the negative electrode active material graphite with the negative electrode conductive agent Super-P and the negative electrode binder CMC, and apply them on copper foil to form a negative electrode sheet;

[0099] 2. Prepare a solid electrolyte slurry: Heat and stir the binder polyvinylidene fluoride and the second lithium salt in an N-methylpyrrolidine solvent at 40°C until a viscous solution is formed. Add ball-milled and dispersed solid electrolyte powder lithium lanthanum zirconium oxide (LLZO) to the viscous solution, and continue stirring for 20 minutes to obtain a milky white viscous liquid. Vacuum degas the viscous liquid for 10 minutes to obtain a solid electrolyte slurry; the mass proportion of the solid electrolyte powder in the slurry is 80%.

[0100] 3. Preparation of negative electrode: Apply the solid electrolyte slurry to the negative electrode sheet and dry it at 90°C to obtain a negative electrode composited with a solid electrolyte membrane. In this embodiment, the thickness of the negative electrode solid electrolyte is 60 μm.

[0101] 3. Assemble dry cells:

[0102] The positive electrode, separator and negative electrode are combined to form a dry battery cell.

[0103] 4. Preparation of semi-solid-state batteries:

[0104] The electrolyte is injected into the dry battery cell and encapsulated into a semi-solid-state battery.

[0105] The electrolyte includes a first lithium salt, a solvent, conventional additives and a flame retardant additive.

[0106] Among them, the first lithium salt is a mixture of LiPF6 and LiFSI; the conventional additive is a mixture of VC and PS; and the flame retardant additive is a mixture of TEP and PFPN.

[0107] In the electrolyte, the mass ratio of the above substances is as follows:

[0108] LiPF 6: LiFSI:VC:PS:TEP:PFPN=10:5:1:1:2:8.

[0109] The mass ratio of LiPF6 in the electrolyte is 10wt%.

[0110] The solvent is a mixture of EC and DMC, wherein the mass ratio of EC to DMC is 1:1.

[0111] Example 2: The process for preparing a semi-solid-state battery in this example is basically the same as that in Example 1, except that, in this example, the first lithium salt in the electrolyte is a mixture of LiPF6, LiFSI and LiBOB, and the flame retardant additive is a mixture of TPP and PFPN; in the electrolyte, LiPF6:LiFSI:LiBOB:TPP:PFPN=10:4:1:2:8.

[0112] The mass ratio of LiPF6 in the electrolyte is 10wt%.

[0113] The solvent is a mixture of EC, DMC and EMC, wherein the mass ratio of EC, DMC and EMC is 1:1:1.

[0114] Example 3: The process for preparing a semi-solid-state battery in this example is basically the same as that in Example 1, with the only difference being that, in this example, the mass proportions of the various substances in the electrolyte are different. The specific proportions are as follows:

[0115] LiPF 6: LiFSI:VC:PS:TEP:PFPN=8:4:0.8:0.8:2:5.

[0116] The mass ratio of LiPF6 in the electrolyte is 8wt%.

[0117] Example 4: The process for preparing a semi-solid-state battery in this example is basically the same as that in Example 1, with the only difference being that, in this example, the mass proportions of the various substances in the electrolyte are different. The specific proportions are as follows:

[0118] LiPF 6: LiFSI:VC:PS:TEP:PFPN=10:5:1:1:5:20.

[0119] The mass ratio of LiPF6 in the electrolyte is 10wt%.

[0120] Example 5: The process for preparing a semi-solid-state battery in this example is substantially the same as that in Example 1, with the only difference being that, in this example, the solid electrolyte powder accounts for 96% of the total mass of the solid electrolyte slurry.

[0121] Example 6: The process for preparing a semi-solid-state battery in this example is basically the same as that in Example 1, with the only difference being that in this example, the solid electrolyte powder accounts for 50% of the total mass of the solid electrolyte slurry.

[0122] Example 7: The process for preparing a semi-solid-state battery in this example is basically the same as that in Example 1, with the only difference being that in this example, the thickness of the solid electrolyte layer is 150 μm.

[0123] Example 8: The process for preparing a semi-solid-state battery in this example is basically the same as that in Example 1, with the only difference being that in this example, the thickness of the solid electrolyte layer is 20 μm.

[0124] Example 9: The process for preparing a semi-solid-state battery in this example is basically the same as that in Example 1, with the only difference being that the formula and mass proportion of the electrolyte in this example are different. The specific proportions are as follows:

[0125] LiPF6:VC:PS:TEP=15:1:1:10.

[0126] Comparative Example 1: The process for preparing the semi-solid-state battery in this comparative example is basically the same as that in Comparative Example 2, except that: in this comparative example, the negative electrode of this embodiment does not have a solid electrolyte layer.

[0127] A total of 11 groups of samples, including Example 1 to Example 8 and Comparative Example 1 to Comparative Example 3, were tested as follows. All test results were averaged, and some results were rounded off.

[0128] 1. Acupuncture temperature test:

[0129] At a temperature of 25°C (room temperature), the battery cell was charged to 100% SOC. After standing for 1 hour, the battery cell was fixed and punctured with a steel needle, and the temperature of the battery cell after puncture was recorded.

[0130] 2. 100-cycle battery capacity retention test:

[0131] At 25°C (room temperature), charge at 1C to a cut-off voltage of 4.25V. Switch to constant voltage charging to a cut-off current of 0.05C, let stand for 0.5h, then discharge at 1C to a cut-off voltage of 2.5V. Let stand for 0.5h before entering the next charge-discharge cycle. Repeat this cycle for a total of 100 charge-discharge cycles. Capacity retention = discharge capacity after 100 cycles / initial discharge capacity.

[0132] 3. Thickness test of soft-pack battery cells after 100 cycles:

[0133] After the 100-cycle battery capacity retention test, measure and record the thickness of the soft-pack battery cell using a thickness gauge.

[0134] 4. Electrolyte DSC decomposition temperature test:

[0135] Take 10-20 mg of electrolyte, seal it in a high-pressure corrosion-resistant crucible, perform temperature increase test, and obtain DSC curve.

[0136] The comparative test results are shown in the following table:

[0137]

[0138] According to the above table, compared with Comparative Example 1, the batteries in Examples 1 to 9 all have good cycle performance and effectively suppress battery gas production.

[0139] Compared to Examples 1 and 9, the addition of perfluoro-2-methyl-3-pentanone (PFPN) to the electrolyte improves the electrolyte formulation, effectively suppressing the temperature rise after acupuncture. This improved electrolyte formulation, combined with the addition of a solid electrolyte layer to the negative electrode, effectively enhances the battery's safety and cycling performance.

[0140] It should be pointed out that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A semi-solid-state battery comprising a positive electrode, a negative electrode and an electrolyte, characterized in that: The negative electrode includes a negative electrode active material, and the negative electrode active material includes graphite; A solid electrolyte layer is provided on a surface of the negative electrode close to the electrolyte; The electrolyte includes a flame retardant additive.

2. The semi-solid-state battery according to claim 1, characterized in that The solid electrolyte layer includes an oxide solid electrolyte.

3. The semi-solid-state battery according to claim 1, characterized in that The thickness of the solid electrolyte layer is 20 μm to 150 μm.

4. The semi-solid-state battery according to claim 1, characterized in that The flame retardant additive includes at least one of triethyl phosphate, triphenyl phosphate, and perfluoro-2-methyl-3-pentanone.

5. The semi-solid-state battery according to claim 1 or 4, characterized in that: In the electrolyte, the mass proportion of the flame retardant additive is 5% to 20%.

6. The semi-solid-state battery according to claim 1, characterized in that The electrolyte further includes a second additive; The second additive includes propane sultone and vinylene carbonate.

7. The semi-solid-state battery according to claim 1, characterized in that The electrolyte further includes a first lithium salt and a solvent; The first lithium salt includes at least two of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(oxalatoborate); The solvent includes at least two of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, diethyl carbonate, and fluoroethylene carbonate; In the electrolyte, the mass proportion of the first lithium salt is 10% to 20%.

8. The semi-solid-state battery according to claim 6, characterized in that: In the electrolyte, the mass proportion of the second additive is 2% to 5%.

9. A method for preparing the semi-solid battery according to claim 1, characterized in that: The steps include: S1, preparing the positive electrode; S2. Preparation of negative electrode: S2.1, preparing a negative electrode layer; S2.2, preparing a solid electrolyte slurry, coating it on the surface of the negative electrode layer, and drying it to obtain a negative electrode; S3. Prepare a semi-solid-state battery: stack the positive electrode, the separator, and the negative electrode in sequence to form a dry cell, inject the electrolyte, and package to form a semi-solid-state battery.

10. The method according to claim 9, characterized in that The specific steps of preparing the solid electrolyte slurry include: S100, stirring a binder and a second lithium salt in a solvent until a viscous solution is formed; S200, adding ball-milled dispersed solid electrolyte powder to the viscous solution and stirring to obtain a milky white viscous solution; S300, performing vacuum degassing on the viscous liquid to obtain the solid electrolyte slurry; The second lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(oxalatoborate).

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