Silicon anode cells and electronic devices
By setting an overhang region in the negative electrode active material layer and adding silicon-based compounds to the electrolyte, the problems of reduced electronic conductivity and interfacial side reactions caused by silicon materials are solved, thereby improving the cycle life and energy density of the battery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHENZHEN HIGHPOWER TECH CO LTD
- Filing Date
- 2025-10-22
- Publication Date
- 2026-05-26
AI Technical Summary
Introducing silicon into the negative electrode reduces electronic conductivity and facilitates interfacial side reactions at the electrode edge region during the final stage of charging, affecting battery performance and cycle life.
By setting an overhang region in the negative electrode active material layer and adding silicon-based compounds to the electrolyte, the electrolyte composition and key negative electrode material parameters are synergistically controlled, and a stable interface layer is preferentially constructed in the inactive region of the electrode to suppress side reactions.
Significantly improves battery cycle life and safety, reduces the risk of lithium plating, and increases energy density.
Smart Images
Figure CN120999085B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of battery technology, and more particularly to silicon anode batteries and electronic devices. Background Technology
[0002] The energy density and cycle life of lithium-ion batteries largely depend on the performance of the anode material. Introducing high-capacity materials into the anode has become the mainstream technical approach to improve battery energy density.
[0003] In related technologies, silicon materials are added to the negative electrode to increase the energy density of the battery. However, the addition of silicon materials will reduce the overall electronic conductivity of the negative electrode. Moreover, at the end of charging, interfacial side reactions are prone to occur in the electrode edge area, which not only consumes the active lithium source, but also aggravates the decomposition of the electrolyte, thereby restricting the overall performance of the battery and the improvement of cycle life. Summary of the Invention
[0004] To address or partially address the problems existing in related technologies, this application provides a silicon anode battery and electronic device that can preferentially construct a stable interface layer in the inactive region of the electrode by synergistically controlling the electrolyte composition and key anode material parameters, thereby significantly suppressing side reactions and improving battery cycle life.
[0005] This application provides a silicon anode battery, comprising a positive electrode, a negative electrode, and an electrolyte. The negative electrode includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector, wherein the negative active material layer comprises a negative active material, the negative active material being silicon, and the silicon material having a mass percentage content of m% in the negative active material layer. The positive electrode includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector. The area of the negative active material layer is larger than that of the positive active material layer, and the area difference between the negative active material layer and the positive active material layer is a% of the area of the negative active material layer. The electrolyte includes an additive, the additive being a silicon-based compound, and the silicon-based compound having a mass percentage content of b% in the electrolyte. Wherein, 0.00002 ≤ b / (m×a) ≤ 3.
[0006] As an optional embodiment, 0.0004 ≤ b / (m×a) ≤ 1.
[0007] As an optional embodiment, 1 ≤ a ≤ 30.
[0008] As an optional embodiment, 0.01 ≤ b ≤ 3.
[0009] As an optional embodiment, 0.01 ≤ m ≤ 30.
[0010] As an optional embodiment, the silicon-based compound has the following structural formula:
[0011]
[0012] R1, R2, R3 and R4 are each independently selected from substituted or unsubstituted C1-C5 alkyl groups, substituted or unsubstituted C2-C5 alkenyl groups, and substituted or unsubstituted C2-C6 alkynyl groups, and at least one of R1-R4 is selected from substituted or unsubstituted C2-C5 alkenyl groups.
[0013] As an optional embodiment, the silicon-based compound includes at least one of tetravinylsilane, trivinylethylsilane, divinyldiethylsilane, trivinylethylsilane, vinyltriethylsilane, trivinylethynylsilane, tetrapropylenesilane, trivinylpropylsilane, tripropylenepropylsilane, dipropylenedipropylsilane, and divinyldipropylsilane.
[0014] As an optional embodiment, both sides of the negative current collector are coated with a negative active material layer, and both sides of the positive current collector are provided with a positive active material layer; and the sum of the areas of the negative active material layers on both sides of the negative current collector is greater than the sum of the areas of the positive active material layers on both sides of the positive current collector.
[0015] As an optional embodiment, the silicon material includes at least one of elemental silicon, silicon-carbon materials, and silicon-oxygen materials.
[0016] A second aspect of this application provides an electronic device including the aforementioned silicon anode battery.
[0017] The technical solution provided in this application may include the following beneficial results:
[0018] In this application, b / (m×a) represents the ratio of silicon anode material to silicon-based compound in the electrolyte additive in the overhang region. When b / (m×a) is less than 0.00002, the silicon-based compound content is insufficient, making it difficult to meet the film-forming consumption of the anode during cycling. When b / (m×a) is greater than 3, the impedance of the silicon-based compound on the anode side is too high, which may lead to lithium plating and cause cycle deterioration. Therefore, by controlling 0.00002≤b / (m×a)≤3, this application allows the electrolyte to preferentially and rapidly form a film in the overhang region, effectively reducing side reactions between the overhang region and the electrolyte, thereby effectively improving the cycle performance of the electrochemical device.
[0019] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description
[0020] The above and other objects, features and advantages of this application will become more apparent from the more detailed description of exemplary embodiments thereof in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments thereof.
[0021] Figure 1 This is a schematic diagram of the negative electrode sheet shown in the embodiments of this application;
[0022] Figure 2 This is a schematic diagram of the structure of the positive electrode sheet shown in the embodiments of this application. Detailed Implementation
[0023] The embodiments of this application will now be described in more detail. It should be understood that this application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make this application more thorough and complete, and to fully convey the scope of this application to those skilled in the art.
[0024] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.
[0025] It should be understood that although the terms "first," "second," "third," etc., may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.
[0026] In related technologies, silicon materials are added to the negative electrode to increase the energy density of the battery. However, the addition of silicon materials will reduce the overall electronic conductivity of the negative electrode. Moreover, at the end of charging, interfacial side reactions are prone to occur in the electrode edge area, which not only consumes the active lithium source, but also aggravates the decomposition of the electrolyte, thereby restricting the overall performance of the battery and the improvement of cycle life.
[0027] To address the aforementioned issues, this application provides a silicon anode battery that can preferentially construct a stable interface layer in the inactive region of the electrode by synergistically controlling the electrolyte composition and key anode material parameters, thereby significantly suppressing side reactions and improving battery cycle life.
[0028] This application provides a silicon anode battery, including a positive electrode, a negative electrode, and an electrolyte. The negative electrode includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector. The negative active material layer contains a negative active material, which includes silicon material, and the mass percentage of silicon material in the negative active material layer is m%. The positive electrode includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector. The area of the negative active material layer is larger than that of the positive active material layer, and the area difference between the negative and positive active material layers is a% of the area of the negative active material layer. The electrolyte contains additives, including silicon-based compounds, and the mass percentage of silicon-based compounds in the electrolyte is b%. Wherein, 0.00002 ≤ b / (m×a) ≤ 3.
[0029] This application embodiment improves battery safety and reduces the risk of lithium plating by setting the area of the negative electrode active material layer to be larger than that of the positive electrode active material layer. Furthermore, including silicon as the negative electrode active material increases the battery's energy density.
[0030] Firstly, in the embodiments of this application, the negative electrode active material layer includes an additional overhang region in addition to the area covering the positive electrode active material layer; that is, the area of the negative electrode active material layer is larger than the area of the positive electrode active material layer. By setting the overhang region, the following advantages are available: On the one hand, under harsh conditions such as fast charging and low-temperature charging, lithium ions may not be uniformly embedded between graphite layers, but tend to precipitate and form lithium dendrites in the edge regions with higher current density. The overhang region provides additional embedding sites for these unevenly migrating lithium ions, acting as a buffer and safety pool, effectively reducing the risk of lithium plating and preventing dendrites from piercing the separator and causing internal short circuits. On the other hand, during battery manufacturing (such as winding), there may be slight alignment errors between the positive and negative electrode sheets. The design of the overhang region can tolerate this error, ensuring that no positive electrode active material directly faces the negative electrode current collector (e.g., copper foil). Simultaneously, the overhang region also provides some space for the expansion of the silicon negative electrode.
[0031] However, if the overhang region is set too high, the negative electrode active materials (including active materials, conductive agents, and binders) in the overhang region will not participate in the electrochemical reaction, which will reduce the energy density of the battery. Moreover, since the overhang region does not have the constraint of the positive electrode, its electrochemical environment is very special, and the potential is more likely to fluctuate to the window of electrolyte reduction and decomposition. This makes it difficult for a stable SEI film to form on the surface of the overhang region, and it is easy to have side reactions with the electrolyte, which will affect the cycle life of the battery.
[0032] Secondly, the embodiments of this application can improve the energy density of the battery by adding silicon material to the negative electrode. However, the addition of silicon material will reduce the overall electronic conductivity of the negative electrode. Moreover, at the end of charging, the electrode edge area is prone to interfacial side reactions, which not only consume the active lithium source, but also aggravate the decomposition of the electrolyte, thereby restricting the overall performance of the battery and the improvement of cycle life.
[0033] To address the potential risks posed by the overhang region and silicon materials, this application embodiment adds a silicon-based compound to the electrolyte. This silicon-based compound can be reduced to an SEI film at the negative electrode and effectively passivates the silicon-based negative electrode. During the initial charging (formation) of the battery, the current is distributed across the entire negative electrode. However, because the overhang region lacks the constraint of the positive electrode counter, its potential drops more rapidly, reaching the reduction decomposition potential of the silicon-based compound more quickly. Therefore, the silicon-based compound is preferentially and concentratedly reduced in the overhang region, forming a stable interface layer.
[0034] b / (m×a) represents the ratio of silicon anode material to silicon-based compounds in the electrolyte additive in the overhang region. When b / (m×a) is less than 0.00002, the silicon-based compound content is insufficient, making it difficult to meet the film-forming consumption of the anode during cycling. When b / (m×a) is greater than 3, the impedance of the silicon-based compound on the anode side is too high, which may lead to lithium plating and cause cycle deterioration. Therefore, in this embodiment, by controlling 0.00002≤b / (m×a)≤3, the electrolyte can preferentially and rapidly form a film in the overhang region, effectively reducing side reactions between the overhang region and the electrolyte, thereby effectively improving the cycle performance of the electrochemical device.
[0035] As an optional embodiment, 0.0004 ≤ b / (m×a) ≤ 1.
[0036] In this embodiment, by further controlling 0.0004≤b / (m×a)≤1, the side reactions between the Overhang region and the electrolyte can be further reduced, thereby effectively improving the cycle performance of the electrochemical device.
[0037] As an optional embodiment, 1 ≤ a ≤ 30.
[0038] In the embodiments of this application, if the overhang region is too small and the negative electrode excess area is too small, it may lead to an increase in the possibility that the positive electrode cannot be covered in some areas due to process fluctuations, resulting in lithium plating; if the overhang region is too large and the inactive material is too high, the high-temperature performance will deteriorate and the energy density will be affected.
[0039] Wherein, 'a' can be 1, 5, 10, 15, 20, 25, 30, or any value within the above-mentioned range, and this application does not limit it in this regard.
[0040] As an optional embodiment, 0.01 ≤ b ≤ 3.
[0041] In this embodiment, when b is too low, the film formation effect will be poor, affecting the cycle performance; when b is too high, the negative electrode impedance will be high, making lithium plating easy.
[0042] Wherein, b can be 0.01, 1, 2, 3, or any value within the above-mentioned range, and this application does not limit it in this regard.
[0043] As an optional embodiment, 0.01 ≤ m ≤ 30.
[0044] In this embodiment, when m is too low, it will affect the energy density of the battery; when m is too high, it will cause the silicon anode to expand too much, consume the additives too quickly, and at the same time, the risk of strip breakage will increase, affecting the battery cycle.
[0045] Wherein, m can be 0.01, 1, 5, 10, 15, 20, 25, 30, or any value within the above-mentioned range, and this application does not limit it in this regard.
[0046] As an optional embodiment, the structural formula of the silicon-based compound is as follows:
[0047]
[0048] R1, R2, R3 and R4 are each independently selected from substituted or unsubstituted C1-C5 alkyl groups, substituted or unsubstituted C2-C5 alkenyl groups, and substituted or unsubstituted C2-C6 alkynyl groups, and at least one of R1-R4 is selected from substituted or unsubstituted C2-C5 alkenyl groups.
[0049] In this embodiment, the silicon-carbon (Si-C) bond has a certain bond energy, which gives the silicon-based compound relatively good thermal stability. At higher temperatures, the molecular structure of the silicon-based compound is less prone to decomposition, making it suitable for applications requiring thermal stability.
[0050] Furthermore, the structure of the silicon-based compounds provided in this application is tunable, enabling the precise design and synthesis of silicon-based compounds with specific properties according to actual application requirements. For example, to improve the flexibility of the material, longer-chain alkyl groups can be introduced; to impart certain reactivity to the material, alkenyl or alkynyl substituents can be added.
[0051] As a preferred embodiment, the silicon-based compound includes at least one of tetravinylsilane, trivinylethylsilane, divinyldiethylsilane, trivinylethylsilane, vinyltriethylsilane, trivinylethynylsilane, tetrapropylenesilane, trivinylpropylsilane, tripropylenepropylsilane, dipropylenedipropylsilane, and divinyldipropylsilane.
[0052] In the embodiments of this application, the silicon-based compound contains multiple vinyl (-CH=CH2) or propylene (-CH2-CH=CH2) groups. These carbon-carbon double bonds have high chemical potentials and high reduction potentials. During the first charging (formation) of the battery, as the negative electrode potential gradually decreases, these silicon-based compounds undergo electrochemical reduction reactions on the negative electrode surface before other components in the electrolyte (such as solvents like EC and DEC) decompose. This ensures that the silicon-based compound reacts precisely in the Overhang region where the potential decreases the most, forming a dense initial SEI film, thereby effectively preventing the subsequent decomposition of solvent molecules.
[0053] As an optional embodiment, see Figure 1 Both sides of the negative electrode current collector are coated with a layer of negative electrode active material, see [link to relevant documentation]. Figure 2 Both sides of the positive current collector are provided with positive active material layers; and the sum of the areas of the negative active material layers on both sides of the negative current collector is greater than the sum of the areas of the positive active material layers on both sides of the positive current collector.
[0054] In this embodiment, active materials are coated on both sides of the current collector (positive electrode aluminum foil / negative electrode copper foil), which can double the amount of active material that can be contained in the unit volume / weight of the battery, thereby significantly improving the energy density of the battery.
[0055] Furthermore, this embodiment, based on achieving double-sided coating, ensures that the total coating area (A1+A2)×AL on both sides of the negative electrode is greater than the total coating area (C1+C2)×CL on both sides of the positive electrode, which can prevent lithium plating and improve safety. Here, A1 represents the length of the negative active material layer coated on the front side of the negative current collector, A2 represents the length of the negative active material layer coated on the back side of the negative current collector, and AL represents the width of the negative active material layers coated on both sides of the negative current collector; C1 represents the length of the positive active material layer coated on the front side of the positive current collector, C2 represents the length of the positive active material layer coated on the back side of the positive current collector, and CL represents the width of the positive active material layers coated on both sides of the positive current collector. On the one hand, even under harsh conditions such as fast charging and low temperatures, it can provide sufficient buffer space for lithium ions, fundamentally and significantly reducing the risk of lithium plating and short circuits. On the other hand, in the battery winding or stacking process, there may be slight alignment errors between the positive and negative electrode sheets. A larger negative electrode area can accommodate this error, ensuring that no positive electrode active material directly faces the negative electrode current collector (which would cause a local short circuit). Moreover, for materials like silicon-based negative electrodes, which expand significantly during charging and discharging, a larger area also provides some space for expansion, helping to maintain the integrity of the electrode structure.
[0056] As an optional embodiment, the silicon material includes at least one of elemental silicon, silicon-carbon materials, and silicon-oxygen materials.
[0057] The silicon material used in this application embodiment is at least one of elemental silicon, silicon-carbon material, and silicon-oxygen material, which can improve the battery energy density and cycle life.
[0058] In some embodiments, the electrolyte further includes a lithium salt.
[0059] Lithium salts are existing technology and are not limited in this application. For example, the lithium salt can be at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium perchlorate, lithium difluorophosphate, lithium bis(oxalate)borate, lithium difluorooxalateborate, lithium tetrafluoroborate, and lithium difluorodi(oxalate)borate.
[0060] In some embodiments, the electrolyte further includes a solvent, which includes at least one selected from ethylene carbonate, propylene carbonate, butene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, diphenyl carbonate, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, propyl acetate, ethyl butyrate, propyl propionate, γ-butyrolactone, 1,3-dioxolane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.
[0061] It should be noted that this application does not impose any particular limitation on the preparation method of the electrolyte. Those skilled in the art can prepare the electrolyte using conventional technical means, such as mixing the raw materials evenly according to the specified ratio.
[0062] As an optional embodiment, the positive electrode active material includes a transition metal lithium oxide with the chemical formula Li. （1+x） Ni y Co z M （1-y-z） O2, where -0.1≤x≤1; 0≤y≤1, 0≤z≤1, and 0≤y+z≤1; where M is selected from one or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr.
[0063] In this application, there is no particular limitation on the type of positive electrode current collector; it can be any known material suitable for use as a positive electrode current collector. In one embodiment, the positive electrode current collector includes metallic materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum, as well as carbon materials such as carbon cloth and carbon paper. In one embodiment, the positive electrode current collector is a metallic material.
[0064] In some embodiments, the positive electrode active material layer further includes a positive electrode conductive agent, a positive electrode binder, and a solvent.
[0065] In some embodiments, the type of positive conductive agent mentioned in the present application is not limited, and any known conductive agent can be used.
[0066] In some embodiments, the positive electrode conductive agent mentioned in the embodiments of this application includes at least one of carbon materials such as natural graphite, artificial graphite, acetylene black, needle coke, carbon nanotubes, and graphene.
[0067] In one embodiment, there is no limitation on the type of positive electrode binder mentioned in the embodiments of this application, and any known positive electrode binder can be used.
[0068] In some embodiments, the positive electrode binder includes at least one of polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose.
[0069] As an optional embodiment, the negative electrode active layer includes a negative electrode active material, which includes artificial graphite and / or silicon-carbon composite materials.
[0070] In the embodiments of this application, there are no particular restrictions on the negative electrode current collector, as long as it can achieve the purpose of this application, such as copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or composite current collector, etc.
[0071] In some preferred embodiments, the negative current collector comprises copper foil.
[0072] In some embodiments, the negative electrode active layer may further include a negative electrode conductive agent, a negative electrode binder, a thickener, and a solvent.
[0073] The negative electrode conductive agent includes at least one of the following carbon materials: natural graphite, artificial graphite, acetylene black, needle coke, carbon nanotubes, and graphene. The negative electrode binder includes styrene-butadiene latex, and the thickener includes CMC. The solvent includes deionized water.
[0074] In the lithium-ion batteries mentioned in this application, a separator is typically provided between the positive and negative electrodes to prevent short circuits. There are no particular restrictions on the material and shape of the separator, as long as it does not significantly impair the effectiveness of this application.
[0075] In some embodiments, the diaphragm includes a porous sheet-like or non-woven material with excellent liquid retention properties. The diaphragm includes resin or glass fiber diaphragm materials, including but not limited to polyolefins, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, etc.
[0076] In some embodiments, the lithium-ion battery may include an outer packaging that can be used to encapsulate the electrode assembly and electrolyte described above.
[0077] In some implementations, the outer packaging of a lithium-ion battery can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of a lithium-ion battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.
[0078] This application does not impose any particular restrictions on the shape of the lithium-ion battery; it can be cylindrical, square, or any other arbitrary shape.
[0079] On the other hand, one embodiment of this application provides an electrical device including the lithium-ion battery described above.
[0080] For example, the aforementioned electrical devices may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.
[0081] To further understand the embodiments of this application, the following description is based on the embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of this application.
[0082] Example 1
[0083] I. Preparation of Lithium-ion Batteries
[0084] 1. Preparation of negative electrode sheet: The negative electrode active material artificial graphite, silicon material, conductive agent Super P, and negative electrode binder sodium carboxymethyl cellulose are mixed in a mass ratio of 96-15:15:1.5:2.5. Deionized water is added and stirred evenly to obtain a negative electrode slurry with a solid content of 40wt%. The negative electrode slurry is evenly coated on one surface of the negative electrode current collector copper foil and then dried at 110℃. The above steps are repeated on the other surface of the negative electrode current collector. After cold pressing, the negative electrode sheet is die-cut into a negative electrode sheet with two or more negative electrode tabs on one side of the negative electrode current collector and a specification of 75mm×865mm.
[0085] 2. Preparation of the positive electrode sheet: The positive electrode active material LiCo2O4, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are mixed at a mass ratio of 98:1:1. N-methylpyrrolidone (NMP) is added as a solvent, and the mixture is stirred under vacuum until a homogeneous positive electrode slurry with a solid content of 75 wt% is formed. The positive electrode slurry is uniformly coated onto the positive electrode current collector aluminum foil and dried at 85°C. The above steps are repeated on the other surface of the positive electrode current collector. After cold pressing, the positive electrode sheet is die-cut into a positive electrode sheet with two or more positive electrode tabs on one side of the positive electrode current collector, and a size of 74 mm × 867 mm. The area of the negative electrode active material layer is larger than that of the positive electrode active material layer, and the area difference between the negative and positive electrode active material layers accounts for 1% of the area of the negative electrode active material layer.
[0086] 3. Electrolyte Preparation: In an argon-atmospheric glove box with a water content <10ppm, ethylene carbonate, propylene carbonate, and propyl propionate (PP) were mixed evenly to obtain the base solvent. Thoroughly dried lithium salt LiPF6, tetravinylsilane, adiponitrile (ADN), 1,3,6-hexanetrionitrile (HTCN), lithium salt additive, and fluoroethylene carbonate (FEC) were dissolved in the above base solvent and mixed evenly to obtain the electrolyte. The electrolyte contained in the following composition: LiPF6 mass percentage was 12.5%; solvent ratio EC:PC:PP = 2:1:7; tetravinylsilane mass percentage was 0.5%; LiPF6 mass percentage was 0.5%; FEC mass percentage was 10%; ADN mass percentage was 1%; and HTCN mass percentage was 2%.
[0087] Examples 2-32 and Comparative Examples 1-9
[0088] The basic content of Examples 2-32 and Comparative Examples 1-9 is the same as that of Example 1, with the differences shown in Tables 1.1 to 1.5.
[0089] II. Performance Testing
[0090] 1. Cyclic capacity retention test
[0091] The lithium-ion battery was placed in a 45℃ constant temperature test chamber and left to stand for 30 minutes to allow it to reach a constant temperature. The battery was then charged at a constant current of 1C until the voltage reached 4.53V, followed by constant voltage charging at 4.53V until the current was less than or equal to 0.05C. Finally, it was discharged at a constant current of 1C until the voltage reached 2.8V. This constitutes one charge-discharge cycle, and the discharge capacity obtained at this point is recorded as the initial discharge capacity C0. Using the initial discharge capacity as 100%, the charge-discharge cycles were repeated. After 700 cycles, the test was stopped, and the discharge capacity of the lithium-ion battery at this point was recorded as the discharge capacity after 700 cycles, C1. The 45℃ charging capacity retention rate is then calculated as C1 / C0. The test results are shown in Tables 1.1 to 1.5.
[0092]
[0093]
[0094]
[0095]
[0096]
[0097] Referring to Tables 1.1 to 1.5, and comparing Examples 1 to 32, as well as Comparative Examples 7 and 8, it can be seen that when b / (m×a) is less than 0.00002, the content of silicon-based compounds is insufficient, making it difficult to meet the film-forming consumption of the negative electrode during cycling; when b / (m×a) is greater than 3, the impedance of the silicon-based compounds on the negative electrode side is too high, which may lead to lithium plating and cause cycle deterioration. Therefore, by controlling 0.00002≤b / (m×a)≤3, the electrolyte can preferentially and rapidly form a film in the Overhang region, effectively reducing the side reactions between the Overhang region and the electrolyte, thereby effectively improving the cycle performance of the electrochemical device.
[0098] Further comparison of Examples 1 to 23, 27 and 28, and Examples 24 to 26 shows that when 0.0004≤b / (m×a)≤1 is further satisfied, the side reactions between the Overhang region and the electrolyte can be further reduced, thereby effectively improving the cycle performance of the electrochemical device.
[0099] By comparing Examples 1 to 11 and Comparative Example 9, it can be seen that when the silicon-based compound is selected from the compounds provided in the embodiments of this application, the improvement effect is basically the same.
[0100] By comparing Examples 18 to 21, and Examples 30 and 31, it can be seen that if the overhang region is too small, the excess area of the negative electrode is too small, which may lead to the increase of local areas that cannot cover the positive electrode due to process fluctuations, resulting in lithium plating; if the overhang region is too large, the inactive material content is too high, which deteriorates the high-temperature performance and affects the energy density. When 1≤a≤30 is satisfied, the high-temperature performance can be improved without affecting the energy density.
[0101] By comparing Examples 22 to 25 and Example 32, it can be seen that when b is too low, the film formation effect is poor, affecting cycle performance; when b is too high, the negative electrode impedance is high, making lithium deposition easy. When 0.01≤b≤3 is satisfied, the cycle performance of the battery can be improved.
[0102] Comparing Examples 12 to 17 and Example 29, it is evident that when m is too low, it affects the battery energy density; when m is too high, it leads to excessive expansion of the silicon anode, excessive consumption of additives, and an increased risk of strip breakage, thus affecting battery cycle life. When 0.01 ≤ m ≤ 30, the battery's cycle performance can be improved.
[0103] Although this application has been described with reference to preferred embodiments, those skilled in the art will understand that various changes can be made and equivalents can be substituted for the elements, as long as they do not depart from the scope of this application. Furthermore, many modifications can be made to adapt particular situations or materials to the teachings of this application, as long as they do not depart from the essential scope of this application. Therefore, this application is not intended to be limited to the specific embodiments disclosed as the best mode of carrying out this application as conceived, but rather this application will include all embodiments falling within the scope of the appended claims.
[0104] All scopes disclosed in this application include endpoints, and endpoints can be combined with each other.
[0105] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.
Claims
1. A silicon anode battery, characterized in that, The electrolyte comprises a positive electrode, a negative electrode, and an electrolyte. The negative electrode includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector. The negative active material layer contains a negative active material, which includes silicon, and the silicon content in the negative active material layer is m% by mass. The positive electrode includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector. The area of the negative active material layer is larger than that of the positive active material layer, and the area difference between the negative and positive active material layers is a% of the area of the negative active material layer. The electrolyte contains an additive, which includes a silicon-based compound, and the silicon-based compound in the electrolyte is b% by mass. Wherein, 1≤a≤25, 0.01≤b<0.5, 0.01≤m≤30, and 0.01≤b / (m×a)≤1. The structural formula of the silicon-based compound is as follows: R1, R2, R3 and R4 are each independently selected from substituted or unsubstituted C1-C5 alkyl groups, substituted or unsubstituted C2-C5 alkenyl groups, and substituted or unsubstituted C2-C6 alkynyl groups, and at least one of R1-R4 is selected from substituted or unsubstituted C2-C5 alkenyl groups.
2. The silicon anode battery according to claim 1, characterized in that, The silicon-based compound includes at least one of tetravinylsilane, trivinylethylsilane, divinyldiethylsilane, trivinylethylsilane, vinyltriethylsilane, trivinylethynylsilane, tetrapropylenesilane, trivinylpropylsilane, tripropylenepropylsilane, dipropylenedipropylsilane, and divinyldipropylsilane.
3. The silicon anode battery according to claim 1, characterized in that, Both sides of the negative electrode current collector are coated with a negative electrode active material layer, and both sides of the positive electrode current collector are provided with a positive electrode active material layer; and the sum of the areas of the negative electrode active material layers on both sides of the negative electrode current collector is greater than the sum of the areas of the positive electrode active material layers on both sides of the positive electrode current collector.
4. The silicon anode battery according to claim 1, characterized in that, The silicon material includes at least one of elemental silicon, silicon-carbon materials, and silicon-oxygen materials.
5. An electronic device, characterized in that, Including the silicon anode cell as described in any one of claims 1 to 4.