A semi-solid-state battery and its preparation method

Abstract

This application relates to a semi-solid-state battery and its preparation method. The semi-solid-state battery includes a positive electrode, a negative electrode, a separator, and a gel electrolyte. The negative electrode comprises a silicon-based negative electrode material; the gel electrolyte comprises a phosphate ester precursor, a crosslinking agent, and a liquid electrolyte, wherein the liquid electrolyte comprises a lithium salt, a flame retardant additive, a sulfur-containing additive, and a lithium salt-type additive. By optimizing the components and their ratios, the semi-solid-state battery exhibits high energy density, good cycle life, high-temperature storage stability, and flame retardant safety.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically a semi-solid-state battery and its preparation method. Background Technology

[0002] Currently, high-energy-density, high-safety, and long-life rechargeable lithium-ion batteries have become one of the hot research directions in new battery technology development. To balance the demands for high energy density and high safety, all-solid-state batteries have emerged as an effective solution. Using a solid electrolyte with high thermal and chemical stability to completely replace the liquid electrolyte can solve problems such as electrolyte leakage and thermal runaway electrolyte combustion. However, they also suffer from low conductivity, excessive solid-solid interface contact resistance, and solid-solid contact failure due to excessive stress deformation during cycling. To effectively combine the high power performance of liquid lithium-ion batteries with the high safety performance of all-solid-state batteries, the development of high-safety, high-energy-density semi-solid-state lithium-ion gel batteries has become a hot topic. These batteries stably confine the liquid electrolyte within a gel polymer network, eliminating free electrolyte in the cell system. Furthermore, their manufacturing process is compatible with existing liquid lithium-ion battery manufacturing processes, allowing for high mass production. Flame-retardant gel electrolytes, as a new type of functional gel electrolyte, are inherently non-flammable and can maintain the stability of the gel network structure at high temperatures. They effectively suppress the violent contact reaction of positive and negative electrode active materials under thermal runaway, reduce the thermal runaway temperature, and improve the safety of semi-solid batteries.

[0003] Existing high-energy-density semi-solid-state lithium-ion gel batteries mainly use high-nickel ternary materials, high-content silicon / graphite anodes, and gel electrolytes. However, their performance still suffers from numerous problems, such as insufficient power performance, short cycle life, and inability to meet safety regulations for tests like thermal runaway and thermal diffusion. The short cycle life is primarily due to two factors: 1) Excessive volume expansion of the silicon anode material during cycling leads to dynamic growth of the SEI film, which the gel electrolyte cannot effectively repair, resulting in accelerated loss of active lithium; 2) Ineffective contact between the gel polymer and the anode interface, and the large expansion and contraction of the silicon anode material during charge-discharge cycles worsens the contact resistance, leading to increased polarization and accelerated reversible capacity loss. The insufficient safety performance, such as thermal runaway and thermal diffusion, mainly stems from the high-energy-density design of the cell system and the thermal stability and flammability of the gel electrolyte under high-temperature conditions. Summary of the Invention

[0004] To address the issues of short cycle life and insufficient safety performance in existing high-energy-density semi-solid gel batteries, this application develops a novel type of phosphate ester precursor (alkenyl phosphate or allyl phosphate, etc.), which can polymerize with cross-linked acrylate precursors to form a flame-retardant gel polymer, thereby improving the thermal stability and flame-retardant properties of the gel electrolyte and enhancing the cycle life, high-temperature gas generation, and safety performance of high-energy-density semi-solid gel batteries.

[0005] A first aspect of this application provides a semi-solid battery, the semi-solid battery comprising a positive electrode, a negative electrode, a separator, and a gel electrolyte;

[0006] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes a silicon-based negative electrode material.

[0007] The gel electrolyte comprises a phosphate ester precursor, a crosslinking agent, and a liquid electrolyte;

[0008] The liquid electrolyte includes a first lithium salt, a second lithium salt, a flame retardant additive, a sulfur-containing additive, and a lithium salt type additive;

[0009] The semi-solid-state battery satisfies:

[0010] ;

[0011] Specifically, the It can be 11.5, 11.8, 12.0, 12.2, 12.5, 12.8, 13.0, 13.2, 13.5, 13.8, 14.0, 14.2, 14.5, 14.8, 15.0, 15.2, 15.5, 15.8, 16.0, 16.2, 16.5, 16.8, 17.0, or a range consisting of any two of the above numbers.

[0012] Wherein, α is the mass fraction of phosphate ester precursor in the gel electrolyte; β is the mass fraction of crosslinking agent in the gel electrolyte; x is the mass fraction of flame retardant additive in the gel electrolyte; y is the mass fraction of sulfur-containing additive in the gel electrolyte; z is the mass fraction of lithium salt additive in the gel electrolyte; PD is the compaction density of the negative electrode active material layer; and w is the mass fraction of silicon-based negative electrode material in the negative electrode active material layer.

[0013] By ensuring that the mass fractions of phosphate ester precursors, crosslinking agents, flame retardants, sulfur-containing additives, and lithium salt additives in the gel electrolyte, the mass fraction of silicon-based anode material in the anode active material, and the compaction density of the anode active material layer satisfy a specific relationship, the cycle life, high-temperature gas generation, and flame retardant performance of high-energy-density semi-solid gel batteries can be improved.

[0014] In some embodiments, the phosphate precursor has a compound of Formula I:

[0015] ;

[0016] in,

[0017] R1 R 2 R 3 and R 4 Each is independently selected from hydrogen, fluorine, alkyl groups substituted or unsubstituted with X, alkenyl, aryl, heteroaryl, or alkoxy; wherein X is an F, Cl, Br, N, O, S, or P atom;

[0018] The R 1 R 2 R 3 and R 4 Each independently satisfies the general formula: C a H b X c ;

[0019] The a is an integer between 0 and 12; for example, a can be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or any two of the above numbers.

[0020] b is an integer between 0 and 25; for example, b can be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25 or any two of the above numbers.

[0021] c is an integer between 0 and 20; for example, c can be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or any two of the above numbers.

[0022] The n is 0 or 1;

[0023] The mass fraction α of the phosphate ester precursor in the gel electrolyte satisfies the following condition: 0.6 wt% ≤ α ≤ 1.0 wt%. For example, the mass fraction α of the phosphate ester precursor in the gel electrolyte can be 0.6 wt%, 0.8 wt%, 1.0 wt%, or any two of the above values.

[0024] Phosphate ester precursors participate in film formation through side-chain phosphate ester groups, forming a Li3PO4-rich interfacial layer, thereby improving interfacial stability and enabling effective contact between the gel polymer and the anode interface. This mitigates the deterioration of contact resistance caused by the expansion and contraction of the silicon anode material during cycling, thus improving cycle life. Furthermore, the decomposition of the side-chain functional groups during film formation does not affect the structural stability of the gel polymer. Simultaneously, controlling the mass fraction of the phosphate ester precursor optimizes the interfacial film formation effect, avoiding excessive amounts that could increase impedance or affect the degree of gelation.

[0025] In some embodiments, the crosslinking agent is an organic compound containing multiple unsaturated bonds, selected from one or more of ethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, ethoxylated trimethylolpropane triacrylate, tripropoxylated trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetraacrylate, bis(trimethylolpropane) tetraacrylate, polydipentaerythritol pentaacrylate, polydipentaerythritol hexaacrylate, allyl sulfonate, and 1,3-divinyl-1,1,3,3-tetramethoxydisiloxane;

[0026] The mass fraction β of the crosslinking agent in the gel electrolyte satisfies the following condition: 1.0 wt% ≤ β ≤ 3.0 wt%. For example, the mass fraction β of the crosslinking agent in the gel electrolyte can be 1.0 wt%, 1.2 wt%, 1.5 wt%, 1.8 wt%, 2.0 wt%, 2.2 wt%, 2.5 wt%, 2.8 wt%, 3.0 wt%, or any range of two of the above numbers.

[0027] Crosslinking agents can form a three-dimensional gel network structure, improving the structural stability of gel polymers. Controlling the mass fraction of the crosslinking agent balances gel strength and ionic conductivity.

[0028] In some embodiments, the gel electrolyte further includes an initiator; the initiator is selected from one or more of azobisisobutyronitrile, dimethyl azobisisobutyrate, azobisisoheptanenitrile, and azobisisovalerate.

[0029] The mass fraction p of the initiator in the gel electrolyte satisfies the following condition: 0.02 wt% ≤ p ≤ 0.2 wt%. For example, the mass fraction p of the initiator in the gel electrolyte can be 0.02 wt%, 0.036 wt%, 0.04 wt%, 0.05 wt%, 0.06 wt%, 0.08 wt%, 0.10 wt%, 0.12 wt%, 0.14 wt%, 0.16 wt%, 0.18 wt%, 0.20 wt%, or any range of two of the above numbers.

[0030] The addition of the initiator ensures that the phosphate ester precursor and crosslinking agent are effectively polymerized under heating conditions to form a stable gel electrolyte network, thereby improving the cycle life and safety performance of the battery.

[0031] In some embodiments, the liquid electrolyte satisfies at least one of the following conditions (1)-(9):

[0032] (1) The flame retardant additive is a cyclotriphosphazene derivative, selected from one or more of ethoxy(pentafluoro)cyclotriphosphazene, phenoxy(pentafluoro)cyclotriphosphazene and trifluoroethoxy(pentafluoro)cyclotriphosphazene;

[0033] (2) The sulfur-containing additive is selected from one or more of vinyl sulfate, 1,3-propane sulpholactone, 1,4-butane sulpholactone, methylene disulfonate, vinyl disulfate, pentaerythritol bicyclic sulfate, mannitol carbonate sulfate, vinyl sulfite and propylene sulfite.

[0034] (3) The lithium salt additive is selected from one or more of lithium bis(oxalato)borate, lithium difluorooxalato)borate, lithium difluorophosphate, lithium difluorobis(oxalato)borate, lithium tetrafluorooxalato)borate, lithium fluorosulfonate, lithium trifluoromethyl sulfinate, lithium trifluoromethyl sulfonate, lithium difluoromalonic acid borate and lithium difluoro(2,2-difluoromalonic acid)borate;

[0035] (4) The first lithium salt and the second lithium salt are each independently selected from one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bisfluorosulfonylimide, lithium bistrifluoromethanesulfonylimide, lithium bisoxalateborate, lithium difluorooxalateborate, lithium trifluoromethanesulfonate and lithium fluorosulfonate.

[0036] (5) The mass fraction x of the flame retardant additive in the gel electrolyte satisfies: 2.0 wt% ≤ x ≤ 3.5 wt%; for example, the mass fraction x of the flame retardant additive in the gel electrolyte can be 2.0 wt%, 2.2 wt%, 2.5 wt%, 2.8 wt%, 3.0 wt%, 3.2 wt%, 3.5 wt% or any two of the above numbers.

[0037] (6) The mass fraction y of the sulfur-containing additive in the gel electrolyte satisfies: 0.5 wt% ≤ y ≤ 2.5 wt%; for example, the mass fraction y of the sulfur-containing additive in the gel electrolyte can be 0.5 wt%, 0.8 wt%, 1.0 wt%, 1.5 wt%, 1.8 wt%, 2.0 wt%, 2.2 wt%, 2.5 wt% or any two of the above numbers.

[0038] (7) The mass fraction z of the lithium salt additive in the gel electrolyte satisfies: 0.5 wt% ≤ z ≤ 2.5 wt%. For example, the mass fraction z of the lithium salt additive in the gel electrolyte can be 0.5 wt%, 0.8 wt%, 1.0 wt%, 1.5 wt%, 1.8 wt%, 2.0 wt%, 2.2 wt%, 2.5 wt%, or any two of the above numbers.

[0039] (8) The mass fraction r of the first lithium salt in the gel electrolyte satisfies: 10 wt% ≤ r ≤ 20 wt%; for example, the mass fraction r of the lithium salt additive in the gel electrolyte can be 10 wt%, 12.5 wt%, 14 wt%, 16 wt%, 18 wt%, 20 wt%, or any two of the above numbers; or

[0040] (9) The mass fraction s of the second lithium salt in the gel electrolyte satisfies: 1 wt% ≤ s ≤ 10 wt%; for example, the mass fraction s of lithium salt additive in the gel electrolyte can be 1 wt%, 1.5 wt%, 3 wt%, 5 wt%, 6 wt%, 8 wt%, 10 wt% or any two of the above numbers.

[0041] Flame retardant additives impart non-flammable properties to the gel electrolyte, effectively suppressing thermal runaway. Sulfur-containing and lithium salt additives synergistically participate in interfacial film formation, improving SEI film stability and reducing active lithium loss, thereby enhancing safety performance and cycle life. The mass fraction of each additive optimizes film formation and flame retardant effects within specific ranges.

[0042] In some embodiments, the liquid electrolyte further includes organic solvents and drag-reducing additives;

[0043] The organic solvent is a fluorocarbonate, a non-fluorocarbonate, or a non-fluorocarboxylic acid ester, wherein...

[0044] The fluorocarbonate is selected from one or more of fluoroethylene carbonate, 4-trifluoromethyl ethylene carbonate, (trifluoroethyl) methyl carbonate, and di(trifluoroethyl) carbonate;

[0045] The non-fluorinated carbonate is selected from one or more of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dimethyl 2,5-dioxahexanoate, and diethyl 2,5-dioxahexanoate.

[0046] The non-fluorinated carboxylic acid ester is selected from one or more of ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate;

[0047] The drag-reducing additive is selected from one or more of the following: trimethylsilyl phosphate, triethylsilyl phosphate, dimethylsilyl ethyl phosphate, dimethylsilyl propyl phosphate, and 3-bistrimethylsilylaminopropyl phosphate.

[0048] The percentage A of the weight of the fluorocarbonate to the total mass of the fluorocarbonate and the non-fluorocarbonate or non-fluorocarboxylic acid ester satisfies: 8% ≤ A ≤ 25%; for example, A can be 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25% or any two of the above numbers.

[0049] The mass fraction q of the drag-reducing additive in the gel electrolyte satisfies: 0.3 wt% ≤ q ≤ 2.0 wt%. For example, q can be 0.3 wt%, 0.5 wt%, 0.8 wt%, 1.0 wt%, 1.5 wt%, 1.8 wt%, 2.0 wt%, or any range of two of the above numbers.

[0050] Resistance-reducing additives can reduce battery internal resistance, improve interfacial ionic conductivity, and enhance power performance.

[0051] In some embodiments, the phosphate precursor is selected from compounds having the following structural formulas I-1 to I-10:

[0052] ;

[0053] The crosslinking agent is selected from trimethylolpropane trimethacrylate, pentaerythritol tetraacrylate or ethoxylated trimethylolpropane;

[0054] The initiator is azobisisobutyronitrile;

[0055] The flame retardant additive is ethoxy(pentafluoro)cyclotriphosphonium or trifluoroethoxy(pentafluoro)cyclotriphosphonium;

[0056] The sulfur-containing additive is vinyl sulfate;

[0057] The lithium salt type additive is lithium difluorophosphate and lithium difluorooxalate borate;

[0058] The first lithium salt is lithium hexafluorophosphate;

[0059] The second lithium salt is lithium difluorosulfonylimide;

[0060] The organic solvent is diethyl carbonate, methyl ethyl carbonate, propylene carbonate, and fluoroethylene carbonate; and

[0061] The drag-reducing additive is tris(trimethylsilyl) phosphate.

[0062] By selecting specific components, the interfacial film-forming ability and gel thermal stability are synergistically improved, thereby optimizing the battery's room temperature cycle capacity retention, high temperature gas generation performance, and flame retardant performance.

[0063] In some embodiments, the battery satisfies at least one of the following conditions (10)-(14):

[0064] (10) The diaphragm comprises a base membrane and a solid electrolyte coating, wherein the solid electrolyte coating comprises one or more of lithium aluminum titanium phosphate, lithium aluminum germanium phosphate, lithium lanthanum titanate, and lithium lanthanum zirconate; the thickness of the solid electrolyte coating is 3~5 μm;

[0065] (11) The positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector and containing lithium nickel cobalt manganese oxide. In the lithium nickel cobalt manganese oxide, based on the molar amount of metal elements other than lithium, the molar percentage content B of nickel element in the lithium nickel cobalt manganese oxide satisfies: B≥70%; for example, B can be 70%, 75%, 78%, 80%, 82%, 88%, 90%, 92% or any two of the above numbers.

[0066] (12) The compaction density PD of the negative electrode active material layer in the negative electrode sheet satisfies: 1.55≤PD≤1.75;

[0067] (13) The silicon-based anode material in the anode active material layer is selected from one or more of elemental silicon, silicon-carbon composites, silicon oxides, silicon nitrides, and silicon alloys; or

[0068] (14) The mass fraction w of silicon-based anode material in the anode active material layer satisfies: 10 wt% ≤ w ≤ 30 wt%.

[0069] The solid electrolyte coating on the diaphragm enhances thermal stability and ion conductivity, reducing the risk of thermal runaway; the high-nickel cathode provides high energy density; and the controlled compaction density and silicon content of the anode optimize the balance between volume expansion and anode specific capacity, thereby improving the cycle life and safety of the high-energy-density system.

[0070] A second aspect of this application provides a method for preparing the semi-solid-state battery, the method comprising the following steps:

[0071] S1. Preparation of the positive electrode sheet: The positive electrode active material LiNi... 0.8 Co 0.1 Mn 0.1 O2, conductive agent and binder are mixed in a mass ratio of (90-97):(2-5):(1-5), and N-methyl-2-pyrrolidone is added to disperse and form a slurry. The slurry is coated on both sides of aluminum foil, and the positive electrode sheet is obtained by baking, rolling and cutting.

[0072] S2. Preparation of negative electrode sheet: Graphite, silicon carbide, conductive agent and binder are mixed in a mass ratio of (60-76.8):(19.2-30):(1-5):(3-10), deionized water is added to disperse and prepare a slurry, which is coated on both sides of copper foil, and the negative electrode sheet is obtained by baking, rolling and cutting.

[0073] S3. Electrolyte preparation: Under an inert atmosphere, add the first lithium salt and the second lithium salt to the organic solvent, and then add the phosphate ester precursor, crosslinking agent, initiator, flame retardant additive, sulfur-containing additive, lithium salt type additive and drag-reducing additive in sequence, and stir evenly to obtain the electrolyte.

[0074] S4. Semi-solid battery assembly: The positive electrode, separator and negative electrode are stacked to form a bare cell, which is then encapsulated in an aluminum-plastic film. After baking and dehumidification, electrolyte is injected. After standing, heating and gelling, it undergoes formation, aging, hot pressing, secondary sealing and capacity testing to obtain the semi-solid battery.

[0075] The preparation method ensures that the gel electrolyte is uniformly formed and in good contact with the electrode through a controllable gelation process, thereby achieving high cycle life, low high-temperature gas generation rate and excellent safety performance of the battery.

[0076] A third aspect of this application provides an electrical device including the aforementioned semi-solid-state battery; the electrical device is an electric vehicle, a drone, or a power tool.

[0077] Using the aforementioned semi-solid-state battery as a power source can provide longer cycle life, higher safety, and more stable high-temperature performance in high-power, high-safety-requirement applications such as electric vehicles, drones, and power tools. Detailed Implementation

[0078] To better illustrate the purpose, technical solution, and advantages of this application, specific embodiments will be used to further describe this application below. However, these embodiments do not limit this application in any way. Unless otherwise specified, the reagents, methods, and equipment used in this application are conventional reagents, methods, and equipment in this technical field.

[0079] For the sake of brevity, this document only discloses a few specific numerical ranges for a given parameter. However, any lower limit can be combined with any upper limit to form an unspecified range, and any lower limit can be combined with other lower limits to form an unspecified range; similarly, any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit, combined with any other point or single value, or with other lower or upper limits, to form an unspecified range. It should be understood that this disclosure is not limited to the specific methods, schemes, and reagents described herein, and is itself subject to variation. The terminology used herein is for the purpose of describing specific embodiments or aspects only and is not intended to limit the scope of this disclosure.

[0080] Unless otherwise stated, the terms used in this application have their common meanings as commonly understood by those skilled in the art. Unless otherwise stated, the numerical values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application). Unless otherwise expressly stated, all reagents used in this application are commonly used reagents for chemical analysis or experiments and are derived from conventional commercial suppliers in the art.

[0081] The list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another instance, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single component or multiple components. Item B may contain a single component or multiple components. Item C may contain a single component or multiple components.

[0082] In this application, "semi-solid battery" refers to an electrochemical energy storage device in which the electrolyte system is composed of solid and liquid components and the physical form is a mixture of solid and liquid, such as gel, viscous or wet powder.

[0083] In this application, "phosphate precursor" refers to a polymerizable phosphate compound containing an alkenyl or allyl group.

[0084] In this application, "drag reduction additive" refers to a functional additive used to reduce the internal interface impedance of a battery.

[0085] The raw materials and reagents used in the embodiments of this application, unless otherwise specified in their source or preparation method, were all purchased through legitimate commercial channels and are commercially available products known to those skilled in the art.

[0086] The following are specific embodiments of this application, and the technical solutions of this application will be further described in conjunction with the embodiments, but this application is not limited to these embodiments.

[0087] Example 1

[0088] This embodiment provides a semi-solid-state battery, the preparation method of which includes the following steps:

[0089] 1. Preparation of positive electrode sheet

[0090] LiNi, the positive electrode active material 0.8 Co 0.1 Mn 0.1 O 2、Conductive agent SP and adhesive polyvinylidene fluoride (PVDF) are mixed evenly at a mass ratio of 97:2:1, and then... N A black slurry was uniformly dispersed in methyl-2-pyrrolidone, then coated on both sides of aluminum foil. After baking, rolling, and cutting, the positive electrode sheet was obtained, with a compaction density of 3.5 g / cm³ for the positive electrode active material layer. 3 .

[0091] 2. Preparation of negative electrode sheet

[0092] The negative electrode active material graphite, silicon carbon (silicon content 35%~50%), conductive agent conductive carbon black (SP), binder carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) were mixed evenly in a mass ratio of 76.8:19.2:1:2.2:0.8 and uniformly dispersed in deionized water to form a black slurry. This slurry was then coated on both sides of a copper foil, and after baking, rolling, and cutting, the negative electrode sheet was obtained. The compaction density of the negative electrode active material layer was 1.65 g / cm³. 3 .

[0093] 3. Electrolyte preparation

[0094] At room temperature, in an argon-filled glove box (H2O < 1 ppm, O2 < 1 ppm), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), propylene carbonate (PC), and fluoroethylene carbonate (FEC) were mixed uniformly in a mass ratio of 25:43:20:12. Water was removed using a 4 Å molecular sieve. LiPF6, equivalent to 12.5 wt% of the total mass of the gel electrolyte, was added sequentially to the prepared mixed solvent, with continuous stirring and cooling to ensure the electrolyte temperature did not rise by more than 2 °C. Lithium salts could then be added, followed by LiFSI, equivalent to 1.5 wt% of the total mass of the gel electrolyte, in multiple additions. To prepare a colorless and transparent liquid, the following components were added in batches: 0.6 wt% of phosphate precursor I-1, 1.5 wt% of crosslinking agent trimethylolpropane trimethacrylate, 0.036 wt% of azobisisobutyronitrile (AIBN), 2.0 wt% of ethoxy(pentafluoro)cyclotriphosphonium, 1.0 wt% of vinyl sulfate (DTD), 0.3 wt% of lithium difluorophosphate (LiPO2F2), 0.5 wt% of lithium difluorooxalate borate (LiODFB), and 0.5 wt% of tri(trimethylsilyl) phosphate (TMSP). The mixture was stirred until homogeneous to obtain the electrolyte.

[0095] 4. Assembly of lithium-ion semi-solid-state pouch batteries

[0096] The positive electrode, the PI separator with LATP coating (2 μm thickness) and the negative electrode obtained above are stacked in sequence, so that the separator covers the positive and negative electrode. After stacking, a bare cell is obtained. The bare cell is encapsulated in an aluminum-plastic film and baked at high temperature until the moisture content reaches the standard (cell moisture ≤ 200 ppm). 23 g of the prepared electrolyte is injected. After sealing and standing to soak thoroughly, it is placed in an 80°C oven and heated for 2 h to complete gelation. Then, after formation (70% SOC), high temperature aging (45°C, 48 h), hot pressing, secondary sealing and capacity testing, a semi-solid battery is obtained.

[0097] Examples 2-6 and Comparative Example 1

[0098] Examples 2-6 and Comparative Example 1 provide a series of semi-solid-state batteries. The difference between them and Example 1 is the content of flame retardant additives. The other raw materials and preparation methods are the same as those in Example 1. The relevant specific parameters are shown in Table 1.

[0099] Examples 7-10 and Comparative Example 2

[0100] Examples 7-10 and Comparative Example 2 provide a series of semi-solid-state batteries. The difference from Example 1 is the content of phosphate ester precursors. The other raw materials and preparation methods are the same as those in Example 1. The relevant specific parameters are shown in Table 1.

[0101] Examples 11-14 and Comparative Example 3

[0102] Examples 11-14 and Comparative Example 3 provide a series of semi-solid-state batteries. The difference from Example 1 is the content of the crosslinking agent trimethylolpropane trimethacrylate. The other raw materials and preparation methods are the same as those in Example 1. The relevant specific parameters are shown in Table 1.

[0103] Example 15

[0104] Example 15 provides a semi-solid-state battery, which differs from Example 1 in that trifluoroethoxy (pentafluoro)cyclotriphosphononitrile is used instead of ethoxy (pentafluoro)cyclotriphosphononitrile, while the other raw materials and preparation methods are the same as in Example 1.

[0105] Example 16

[0106] Example 16 provides a semi-solid-state battery, which differs from Example 1 in that phenoxy(pentafluoro)cyclotriphosphononitrile is used instead of ethoxy(pentafluoro)cyclotriphosphononitrile, while the other raw materials and preparation methods are the same as in Example 1.

[0107] Example 17

[0108] Example 17 provides a semi-solid-state battery, which differs from Example 1 in that a compound with the structure described in the phosphate ester precursor I-4 is used instead of phosphate ester precursor I-1, while the other raw materials and preparation methods are the same as in Example 1.

[0109] Example 18

[0110] Example 18 provides a semi-solid-state battery, which differs from Example 1 in that a compound with the structure described in the phosphate ester precursor I-5 is used instead of phosphate ester precursor I-1, while the other raw materials and preparation methods are the same as in Example 1.

[0111] Example 19

[0112] Example 19 provides a semi-solid-state battery, which differs from Example 1 in that a compound with the structure described in the phosphate ester precursor I-6 is used instead of phosphate ester precursor I-1, while the other raw materials and preparation methods are the same as in Example 1.

[0113] Example 20

[0114] Example 20 provides a semi-solid-state battery, which differs from Example 1 in that a compound with the structure described in phosphate ester precursor I-9 is used instead of phosphate ester precursor I-1, while the other raw materials and preparation methods are the same as in Example 1.

[0115] Example 21

[0116] Example 21 provides a semi-solid-state battery, which differs from Example 1 in that a compound with the structure described in the phosphate ester precursor I-10 is used instead of phosphate ester precursor I-1, while the other raw materials and preparation methods are the same as in Example 1.

[0117] Example 22

[0118] Example 22 provides a semi-solid-state battery, which differs from Example 1 in that the cross-linked precursor pentaerythritol tetraacrylate is used instead of trimethylolpropane trimethacrylate, while the other raw materials and preparation methods are the same as in Example 1.

[0119] Example 23

[0120] Example 23 provides a semi-solid-state battery, which differs from Example 1 in that the cross-linked precursor ethoxylated trimethylolpropane triacrylate is used instead of trimethylolpropane trimethacrylate, while the other raw materials and preparation methods are the same as in Example 1.

[0121] Examples 24-25

[0122] Examples 24-25 provide a series of semi-solid-state batteries, which differ from Example 1 in that the mass fraction w of silicon-based anode material in the anode active material is different. The relevant specific parameters are shown in Table 1. The other raw materials and preparation methods are the same as in Example 1.

[0123] Examples 26-27

[0124] Examples 26-27 provide a series of semi-solid-state batteries. The difference from Example 1 is that the compaction density (PD) of the negative electrode active material is different. The other raw materials and preparation methods are the same as those in Example 1. The relevant specific parameters are shown in Table 1.

[0125] Examples 28-30 and Comparative Example 4

[0126] Examples 28-30 and Comparative Example 4 provide a series of semi-solid-state batteries. The difference from Example 1 is the content of sulfur-containing additive DTD. The other raw materials and preparation methods are the same as those in Example 1. The relevant specific parameters are shown in Table 1.

[0127] Examples 31-34 and Comparative Example 5

[0128] Examples 31-34 and Comparative Example 5 provide a series of semi-solid-state batteries. The difference from Example 1 is the content of lithium salt additives. The other raw materials and preparation methods are the same as those in Example 1. The relevant specific parameters are shown in Table 1.

[0129] Table 1. Relevant parameters of Examples 1-34 and Comparative Examples 1-5

[0130]

[0131]

[0132]

[0133] The performance of the semi-solid-state batteries obtained in the above embodiments and comparative examples was tested. The specific test items, test methods, and results are shown below:

[0134] 1. Room temperature DCR test:

[0135] At 25±2℃, the semi-solid-state batteries obtained in the examples and comparative examples were charged to 4.25V at a constant current of 0.5C, then charged at a constant voltage until the current became 0.05C, then discharged at a current of 1C for 30 minutes to adjust to 50% SOC, and then pulsed discharged at a constant current of 2.5C for 10 seconds and then charged for 10 seconds. The DCR was calculated as (voltage before pulse discharge - voltage after pulse discharge) / discharge current. The results are shown in Table 2.

[0136] 2. Room temperature cycling performance test:

[0137] At 25±2℃, the semi-solid-state batteries obtained in the examples and comparative examples were subjected to charge-discharge cycle tests at a charge-discharge current of 0.5C / 1C within a voltage range of 2.5~4.25V. The discharge capacity of the battery in the first cycle and the discharge capacity after 500 cycles at room temperature were recorded. Capacity retention after 500 cycles = discharge capacity after 500 cycles / discharge capacity in the first cycle. 100%, and the recorded data is shown in Table 2.

[0138] 3. High-temperature gas production performance test:

[0139] At 25±2℃, the semi-solid-state batteries obtained in the examples and comparative examples were charged at a constant current of 0.5C to 4.25V, and then charged at a constant voltage until the current became 0.05C, so that the cell reached a fully charged state. The volume of the fully charged cell before storage was measured and recorded as V0. The cell was then placed in an oven at 60±2℃ for 30 days. After being removed and cooled to room temperature, the volume of the cell after storage was measured and recorded as V1. The volume expansion rate was calculated as (V1-V0) / V0. 100%, and the recorded data is shown in Table 2.

[0140] Table 2. Performance test results of the semi-solid-state batteries prepared in Examples 1-34 and Comparative Examples 1-5

[0141]

[0142]

[0143] The results above show that:

[0144] As can be seen from the above embodiments and comparative examples, this application can improve the cycle life, high-temperature gas generation and safety performance of high-energy-density semi-solid-state batteries by optimizing the mass fraction and structure of phosphate ester precursors, the mass fraction of crosslinking agents, the mass fraction of flame retardant additives, the mass fraction of sulfur-containing additives, the mass fraction of lithium salt additives, the compaction density of the negative electrode active material, and the mass fraction of silicon-based negative electrode material in the negative electrode active material to satisfy a specific relationship.

[0145] A comparison of Examples 1-6 and Comparative Example 1 revealed that adjusting the mass fraction of the flame retardant additive ethoxy(pentafluoro)cyclotriphosphazene could... The values ​​vary. Specifically, when the value is between 11.5 and 17.0, the gel electrolyte is non-flammable and the cell exhibits superior performance in room temperature cycling and high-temperature gas generation. When the value is too low, the initial DCR at room temperature is better, but both room temperature cycling and high-temperature gas generation deteriorate, and the gel electrolyte becomes flammable. This may be mainly due to the inability to form stable SEI and CEI films when the flame retardant additive content is too low, and the inability to effectively block the chain reaction, leading to the flammability of the gel electrolyte. When the value is too high, the high-temperature gas generation and flame retardant performance are excellent, but both the initial DCR and room temperature cycling performance deteriorate. This may be mainly due to the severe film decomposition at the positive and negative electrode interfaces when the flame retardant additive content is too high, resulting in a deterioration in the growth of both the initial DCR and the cycling DCR at room temperature.

[0146] A comparison of Examples 7-10 and Comparative Example 2 revealed that adjusting the mass fraction of the phosphate ester precursor could... The value varies. Specifically, when the value is between 11.0 and 17.0, the performance of room temperature cycling and high temperature gas generation is better. However, when the value is too low, the gel electrolyte is flammable. This is mainly because when the content of phosphate ester precursors is too low, the flame retardant properties of the gel polymer are poor. The 2.0wt% ethoxy(pentafluoro)cyclotriphosphazene flame retardant additive in the gel electrolyte cannot effectively inhibit the combustion of the gel electrolyte.

[0147] A comparison of Example 1 and Examples 17-21 reveals that, When the values ​​are the same, the gel electrolytes are all non-flammable when using phosphate ester precursors with different structures, but there are differences in gas production during room temperature cycling and high temperature cycling. Among them, I-10 has the best performance, mainly because it can form a polymer network structure on the negative electrode surface to improve interfacial stability, and it can form a cross-linked gel polymer to improve the thermal stability of the gel electrolyte.

[0148] The above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit the scope of protection of this application. Although this application has been described in detail with reference to preferred embodiments, modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the substance and scope of the technical solutions of this application.

Claims

1. A semi-solid-state battery, characterized in that, The semi-solid battery comprises a positive electrode, a negative electrode, a separator, and a gel electrolyte; The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes a silicon-based negative electrode material. The gel electrolyte comprises a phosphate ester precursor, a crosslinking agent, and a liquid electrolyte; The phosphate ester precursor has a compound as shown in Formula I: ； in, R 1 R 2 R 3 and R 4 Each is independently selected from hydrogen, fluorine, substituted or unsubstituted alkenyl, aryl, heteroaryl, alkyl or alkoxy; wherein X is an F, Cl, Br, N, O, S or P atom; The R 1 R 2 R 3 and R 4 Each independently satisfies the general formula: C a H b X c ; Where a is an integer between 0 and 12; b is an integer between 0 and 25; c is an integer between 0 and 20; and n is 0 or 1. The mass fraction α of the phosphate precursor in the gel electrolyte satisfies: 0.6 wt% ≤ α ≤ 1.0 wt%; The liquid electrolyte includes a first lithium salt, a second lithium salt, a flame retardant additive, a sulfur-containing additive, and a lithium salt type additive; The flame retardant additive is a cyclotriphosphazene derivative, selected from one or more of ethoxy(pentafluoro)cyclotriphosphazene and trifluoroethoxy(pentafluoro)cyclotriphosphazene; The mass fraction x of the flame retardant additive in the gel electrolyte satisfies: 2.0 wt% ≤ x ≤ 3.5 wt%; The semi-solid-state battery satisfies: ； Wherein, α is the mass fraction of phosphate ester precursor in the gel electrolyte; β is the mass fraction of crosslinking agent in the gel electrolyte; x is the mass fraction of flame retardant additive in the gel electrolyte; y is the mass fraction of sulfur-containing additive in the gel electrolyte; z is the mass fraction of lithium salt additive in the gel electrolyte; PD is the compaction density of the negative electrode active material layer; and w is the mass fraction of silicon-based negative electrode material in the negative electrode active material layer.

2. The semi-solid-state battery as described in claim 1, characterized in that, The crosslinking agent is an organic compound containing multiple unsaturated bonds, selected from one or more of the following: ethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, ethoxylated trimethylolpropane triacrylate, tripropoxylated trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetraacrylate, bis(trimethylolpropane) tetraacrylate, polydipentaerythritol pentaacrylate, polydipentaerythritol hexaacrylate, allyl sulfonate, and 1,3-divinyl-1,1,3,3-tetramethoxydisiloxane. The mass fraction β of the crosslinking agent in the gel electrolyte satisfies: 1.0 wt% ≤ β ≤ 3.0 wt%.

3. The semi-solid-state battery as described in claim 1, characterized in that, The gel electrolyte also includes an initiator; The initiator is selected from one or more of azobisisobutyronitrile, dimethyl azobisisobutyrate, azobisisoheptanenitrile, and azobisisovalerate. The mass fraction p of the initiator in the gel electrolyte satisfies: 0.02 wt% ≤ p ≤ 0.2 wt%.

4. The semi-solid-state battery as described in claim 1, characterized in that, The liquid electrolyte satisfies at least one of the following conditions (1)-(7): (1) The sulfur-containing additive is selected from one or more of vinyl sulfate, 1,3-propane sulpholactone, 1,4-butane sulpholactone, methylene disulfonate, vinyl disulfate, pentaerythritol bicyclic sulfate, mannitol carbonate sulfate, vinyl sulfite and propylene sulfite; (2) The lithium salt additive is selected from one or more of lithium bis(oxalato)borate, lithium difluorooxalato)borate, lithium difluorophosphate, lithium difluorobis(oxalato)borate, lithium tetrafluorooxalato)borate, lithium fluorosulfonate, lithium trifluoromethyl sulfinate, lithium trifluoromethyl sulfonate, lithium difluoromalonic acid borate and lithium difluoro(2,2-difluoromalonic acid)borate; (3) The first lithium salt and the second lithium salt are each independently selected from one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bisfluorosulfonylimide, lithium bistrifluoromethanesulfonylimide, lithium bisoxalateborate, lithium difluorooxalateborate, lithium trifluoromethanesulfonate and lithium fluorosulfonate; (4) The mass fraction y of the sulfur-containing additive in the gel electrolyte satisfies: 0.5 wt% ≤ y ≤ 2.5 wt%; (5) The mass fraction z of the lithium salt additive in the gel electrolyte satisfies: 0.5 wt% ≤ z ≤ 2.5 wt%; (6) The mass fraction r of the first lithium salt in the gel electrolyte satisfies: 10 wt% ≤ r ≤ 20 wt%; or (7) The mass fraction s of the second lithium salt in the gel electrolyte satisfies: 1 wt% ≤ s ≤ 10 wt%.

5. The semi-solid-state battery as described in claim 3, characterized in that, The liquid electrolyte further includes an organic solvent and a drag-reducing additive; the organic solvent is a fluorocarbonate, a non-fluorocarbonate, or a non-fluorocarboxylic acid ester, wherein... The fluorocarbonate is selected from one or more of fluoroethylene carbonate, 4-trifluoromethyl ethylene carbonate, (trifluoroethyl) methyl carbonate, and di(trifluoroethyl) carbonate; The non-fluorinated carbonate is selected from one or more of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dimethyl 2,5-dioxahexanoate, and diethyl 2,5-dioxahexanoate. The non-fluorinated carboxylic acid ester is selected from one or more of ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate; The drag-reducing additive is selected from one or more of the following: trimethylsilyl phosphate, triethylsilyl phosphate, dimethylsilyl ethyl phosphate, dimethylsilyl propyl phosphate, and 3-bistrimethylsilylaminopropyl phosphate. The percentage A of the weight of the fluorocarbonate to the total mass of the fluorocarbonate and the non-fluorocarbonate or non-fluorocarboxylic acid ester satisfies: 8% ≤ A ≤ 25%; The mass fraction q of the drag-reducing additive in the gel electrolyte satisfies: 0.3 wt% ≤ q ≤ 2.0 wt%.

6. The semi-solid-state battery as described in claim 5, characterized in that, The phosphate ester precursors are selected from compounds having the following structural formulas I-1 to I-10: ； The crosslinking agent is selected from trimethylolpropane trimethacrylate, pentaerythritol tetraacrylate or ethoxylated trimethylolpropane; The initiator is azobisisobutyronitrile; The flame retardant additive is ethoxy(pentafluoro)cyclotriphosphonium or trifluoroethoxy(pentafluoro)cyclotriphosphonium; The sulfur-containing additive is vinyl sulfate; The lithium salt type additive is lithium difluorophosphate and lithium difluorooxalate borate; The first lithium salt is lithium hexafluorophosphate; The second lithium salt is lithium difluorosulfonylimide; The organic solvent is diethyl carbonate, methyl ethyl carbonate, propylene carbonate, and fluoroethylene carbonate; and The drag-reducing additive is tris(trimethylsilyl) phosphate.

7. The semi-solid-state battery as described in claim 1, characterized in that, The battery satisfies at least one of the following conditions (8)-(12): (8) The diaphragm comprises a base membrane and a solid electrolyte coating, wherein the solid electrolyte coating comprises one or more of lithium aluminum titanium phosphate, lithium aluminum germanium phosphate, lithium lanthanum titanate, and lithium lanthanum zirconate; the thickness of the solid electrolyte coating is 3~5 μm; (9) The positive electrode sheet comprises a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector and comprising lithium nickel cobalt manganese oxide, wherein, based on the molar amount of metal elements other than lithium, the molar percentage content B of nickel element in the lithium nickel cobalt manganese oxide satisfies: B≥70%; (10) The compaction density PD of the negative electrode active material layer in the negative electrode sheet satisfies: 1.55≤PD≤1.75; (11) The silicon-based anode material in the anode active material layer is selected from one or more of elemental silicon, silicon-carbon composites, silicon oxides, silicon nitrides, and silicon alloys; or (12) The mass fraction w of silicon-based anode material in the anode active material layer satisfies: 10 wt% ≤ w ≤ 30 wt%.

8. A method for preparing a semi-solid-state battery as described in claim 5 or 6, characterized in that, The method includes the following steps: S1. Preparation of the positive electrode sheet: The positive electrode active material LiNi... 0.8 Co 0.1 Mn 0.1 O2, conductive agent and binder are mixed in a mass ratio of (90-97):(2-5):(1-5), and N-methyl-2-pyrrolidone is added to disperse and form a slurry. The slurry is coated on both sides of aluminum foil, and the positive electrode sheet is obtained by baking, rolling and cutting. S2. Preparation of negative electrode sheet: Graphite, silicon carbide, conductive agent and binder are mixed in a mass ratio of (60-76.8):(19.2-30):(1-5):(3-10), deionized water is added to disperse and prepare a slurry, which is coated on both sides of copper foil, and the negative electrode sheet is obtained by baking, rolling and cutting. S3. Electrolyte preparation: Under an inert atmosphere, add the first lithium salt and the second lithium salt to the organic solvent, and then add the phosphate ester precursor, crosslinking agent, initiator, flame retardant additive, sulfur-containing additive, lithium salt type additive and drag-reducing additive in sequence, and stir evenly to obtain the electrolyte. S4. Semi-solid battery assembly: The positive electrode, separator and negative electrode are stacked to form a bare cell, which is then encapsulated in an aluminum-plastic film. After baking and dehumidification, electrolyte is injected. After standing, heating and gelling, it undergoes formation, aging, hot pressing, secondary sealing and capacity testing to obtain the semi-solid battery.

9. An electrical device, characterized in that, Including the semi-solid-state battery as described in any one of claims 1-7; The electrical device is an electric vehicle, a drone, or a power tool.

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