Negative pole piece, solid-state battery and electric device

Abstract

The invention relates to the technical field of batteries, in particular to a negative pole piece, a solid-state battery and an electric device. The negative pole piece comprises a negative current collector; the negative electrode active material layer is arranged on the surface of at least one side of the negative electrode current collector, and the negative electrode active material layer comprises silicon carbon material particles, first silicon particles and second silicon particles; the particle size D50 of the silicon carbon material particles is larger than that of the first silicon particles, and the particle size D50 of the first silicon particles is larger than that of the second silicon particles; the first silicon particles have a porous structure. According to the present invention, through the synergistic effect of the particle size gradient compounding and the first silicon particle porous structure, the volume expansion of the silicon during the charge-discharge process can be inhibited and the continuous ion transmission channel can be formed without additionally sacrificing the capacity, such that the capacity performance, the rate performance and the cycle performance of the battery can be simultaneously improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a negative electrode plate, a solid-state battery, and an electrical device. Background Art

[0002] In recent years, due to the increasing requirements for the safety performance of lithium-ion batteries, the use of solid-state electrolytes to replace traditional liquid electrolytes has become an important development direction.

[0003] Silicon is considered a promising anode material for all-solid-state batteries due to its excellent theoretical specific capacity. However, silicon undergoes dramatic volume expansion during charge and discharge, affecting the battery's cycling stability.

[0004] In traditional technologies, the means of suppressing silicon expansion often come at the expense of capacity. For example, by introducing carbon materials to prepare silicon-carbon materials, although the carbon matrix can buffer expansion, it will reduce the overall gram capacity of the negative electrode; the use of nano-silicon particles can alleviate expansion stress, but its extremely high specific surface area requires a large amount of binder, which also reduces the content of active substances in the negative electrode and is not conducive to the conduction of lithium ions; in addition, if silicon-carbon materials and nano-silicon are compounded in the negative electrode, due to the difference in particle size, the particles are not densely packed, and a large number of pores are formed inside the negative electrode, affecting the continuous conduction of lithium ions, and thus affecting the rate performance of the battery. In order to ensure good lithium ion conduction, it is necessary to introduce more solid electrolytes, resulting in a decrease in battery capacity. Summary of the Invention

[0005] Based on this, it is necessary to provide a negative electrode plate, a solid-state battery, and an electrical device that can suppress the volume expansion of silicon during the charge and discharge process without sacrificing additional capacity, form a continuous ion transmission channel, and thereby simultaneously improve the battery's capacity performance, rate performance, and cycle performance.

[0006] In a first aspect of the present application, a negative electrode plate is provided, which includes: a negative electrode current collector; and a negative electrode active material layer, which is arranged on at least one side surface of the negative electrode current collector, and the negative electrode active material layer includes silicon-carbon material particles, first silicon particles and second silicon particles; the particle size D50 of the silicon-carbon material particles is greater than the particle size D50 of the first silicon particles, and the particle size D50 of the first silicon particles is greater than the particle size D50 of the second silicon particles; the first silicon particles have a porous structure.

[0007] In some embodiments, the ratio of the particle size D50 of the silicon-carbon material particles to the particle size D50 of the first silicon particles is in the range of (5-15):1.

[0008] In some embodiments, the ratio of the particle size D50 of the silicon-carbon material particles to the particle size D50 of the second silicon particles is in the range of (50-500):1.

[0009] In some embodiments, the particle size D50 of the silicon-carbon material particles is 4 μm to 10 μm.

[0010] In some embodiments, the particle size D50 of the first silicon particles is 300 nm to 2 μm.

[0011] In some embodiments, the particle size D50 of the second silicon particles is 20 nm to 70 nm.

[0012] In some embodiments, the porosity of the first silicon particles is 10% to 50%.

[0013] In some embodiments, the mass ratio of the silicon-carbon material particles, the first silicon particles, and the second silicon particles is (50-70): (5-35): (5-30).

[0014] In some embodiments, the silicon-carbon material particles include: a porous carbon skeleton; and silicon material disposed in pores of the porous carbon skeleton.

[0015] In some embodiments, the silicon-carbon material particles further include: a silicon layer disposed on the surface of the porous carbon skeleton.

[0016] In some embodiments, the negative electrode active material layer further includes a binder, and the mass percentage of the binder in the negative electrode active material layer is ≤1%;

[0017] In some embodiments, the negative electrode active material layer further includes a solid electrolyte, and the mass percentage of the solid electrolyte in the negative electrode active material layer is ≤10%.

[0018] A second aspect of the present application provides a solid-state battery, which includes the negative electrode plate provided by the first aspect above.

[0019] A third aspect of the present application provides an electrical device, which includes the solid-state battery provided in the second aspect.

[0020] Compared with traditional technologies, this application has at least the following beneficial effects:

[0021] The negative electrode sheets provided in some embodiments of the present application utilize a composite of silicon-carbon material particles, first silicon particles, and second silicon particles of decreasing particle size. This utilizes the space-filling effect between the multi-scale particles to achieve dense packing of particles within the negative electrode. This eliminates the need for introducing large amounts of inactive materials (such as solid electrolytes or binders) to create efficient, continuous lithium-ion transport channels, with all three contributing to the battery's capacity. Therefore, the densely packed structure formed by the gradient particle size combination can increase the proportion of active material in the negative electrode, effectively improving the battery's capacity and rate performance.

[0022] The applicant further discovered that in the above-mentioned dense stacking structure, the medium-sized first silicon particles serve as the main filling phase between the gaps of large-sized silicon-carbon material particles. Their volume expansion during the charging and discharging process is the main source of destructive stress in the entire dense stacking structure, thereby limiting the cycle life of the battery.

[0023] To this end, the first silicon particles have a porous structure, which provides space for their own volume expansion, so that the expansion stress can be dissipated inward rather than squeezed outward and destroyed by the surrounding particles, effectively suppressing the overall expansion and improving the cycle performance of the battery.

[0024] In summary, the present application can suppress the volume expansion of silicon during the charge and discharge process through the synergistic effect of particle size gradient compounding and the porous structure of the first silicon particles without sacrificing additional capacity, forming a continuous ion transmission channel, thereby simultaneously improving the capacity performance, rate performance and cycle performance of the battery. DETAILED DESCRIPTION

[0025] References to embodiments of the present application will now be provided in detail, one or more examples of which are described below. Each example is provided to illustrate, not to limit, the present application. Indeed, it will be apparent to those skilled in the art that various modifications and variations may be made to the present application without departing from the scope or spirit of the present application. For example, features illustrated or described as part of one embodiment may be used in another embodiment to produce further embodiments.

[0026] Therefore, it is intended that this application covers such modifications and variations that fall within the scope of the appended claims and their equivalents. Other objects, features, and aspects of the present application are disclosed in or are apparent from the following detailed description. Those skilled in the art will appreciate that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of the present application.

[0027] In this application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0028] In this application, when referring to numerical ranges, unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges subsumed therein.

[0029] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0030] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0031] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, it is mentioned that the method may also include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0032] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0033] In a first aspect of the present application, a negative electrode sheet is provided, comprising a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer is disposed on at least one surface of the negative electrode current collector and comprises silicon-carbon material particles, first silicon particles, and second silicon particles. The particle size D50 of the silicon-carbon material particles is greater than the particle size D50 of the first silicon particles, and the particle size D50 of the first silicon particles is greater than the particle size D50 of the second silicon particles. The first silicon particles have a porous structure.

[0034] The negative electrode sheets provided in some embodiments of the present application utilize a composite of silicon-carbon material particles, first silicon particles, and second silicon particles of decreasing particle size. This utilizes the space-filling effect between the multi-scale particles to achieve dense packing of particles within the negative electrode. This eliminates the need for introducing large amounts of inactive materials (such as solid electrolytes or binders) to create efficient, continuous lithium-ion transport channels, with all three contributing to the battery's capacity. Therefore, the densely packed structure formed by the gradient particle size combination can increase the proportion of active material in the negative electrode, effectively improving the battery's capacity and rate performance.

[0035] The applicant further discovered that in the above-mentioned dense stacking structure, the medium-sized first silicon particles serve as the main filling phase between the gaps of large-sized silicon-carbon material particles. Their volume expansion during the charging and discharging process is the main source of destructive stress in the entire dense stacking structure, thereby limiting the cycle life of the battery.

[0036] To this end, the first silicon particles have a porous structure, which provides space for their own volume expansion, so that the expansion stress can be dissipated inward rather than squeezed outward and destroyed by the surrounding particles, effectively suppressing the overall expansion and improving the cycle performance of the battery.

[0037] In summary, the present application can suppress the volume expansion of silicon during the charge and discharge process through the synergistic effect of particle size gradient compounding and the porous structure of the first silicon particles without sacrificing additional capacity, forming a continuous ion transmission channel, thereby simultaneously improving the capacity performance, rate performance and cycle performance of the battery.

[0038] Herein, "silicon-carbon material particles" refer to composite material particles comprising carbon material and silicon material. The carbon material can buffer the volume expansion of silicon during charge and discharge, thereby improving electrode conductivity.

[0039] Herein, “first silicon particles”, “second silicon particles”, “silicon material” and “silicon layer” are all simple silicon.

[0040] Herein, "particle size D50" refers to the particle size at which the cumulative particle size distribution of a material reaches 50%. Particle size D50 can be measured using methods known in the art. For example, a Malvern laser particle size analyzer can be used to characterize the particle size according to national standard GB / T19077-2016.

[0041] As used herein, "porosity" refers to the ratio of the intragranular pore volume to the total particle volume. Porosity can be measured using methods known in the art. For example, it can be measured using a fully automatic true density tester in accordance with national standard GB / T 24586-2009. Specifically, porosity = (V1 - V2) / V1 * 100%, where V1 refers to the apparent volume of the material and V2 refers to the true volume of the material. V1 can be measured using mercury intrusion porosimetry, while V2 can be measured using nitrogen gas adsorption.

[0042] In some embodiments, the ratio of the particle size D50 of the silicon-carbon material particles to the particle size D50 of the first silicon particles ranges from (5 to 15):1. For example, the ratio of the particle size D50 of the silicon-carbon material particles to the particle size D50 of the first silicon particles can be, but is not limited to, 5:1, 7:1, 9:1, 10:1, 13:1, or 15:1. By controlling the particle size ratio of the silicon-carbon material particles to the first silicon particles, the first silicon particles can be formed in the pores formed by the accumulation of the silicon-carbon material particles, significantly increasing the packing density of the particles within the negative electrode, increasing the active material content per unit volume, and forming a more efficient and continuous lithium ion transmission channel, thereby effectively improving the battery's capacity and rate performance.

[0043] In some embodiments, the ratio of the particle size D50 of the silicon-carbon material particles to the particle size D50 of the second silicon particles ranges from (50 to 500):1. For example, the ratio of the particle size D50 of the silicon-carbon material particles to the particle size D50 of the second silicon particles can be, but is not limited to, 50:1, 100:1, 150:1, 200:1, 250:1, 300:1, 350:1, 400:1, 450:1, or 500:1. By controlling the particle size ratio of the silicon-carbon material particles to the second silicon particles, the second silicon particles can adhere to the surface of the silicon-carbon material particles, increasing the effective contact points between the particles and forming a more efficient and continuous lithium ion transmission channel, thereby effectively improving the rate performance of the battery.

[0044] In some embodiments, the particle size D50 of the silicon-carbon material particles is between 4 μm and 10 μm. For example, the particle size D50 of the silicon-carbon material particles may be, but is not limited to, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm. Within the above particle size range, the silicon-carbon material particles can serve as the structural framework of the negative electrode, providing sufficient mechanical support for the entire electrode and improving the battery's cycling performance.

[0045] In some embodiments, the particle size D50 of the first silicon particles is between 300 nm and 2 μm. For example, the particle size D50 of the first silicon particles may be, but is not limited to, 300 nm, 600 nm, 1 μm, or 2 μm. Within this particle size range, the first silicon particles can effectively fill the gaps formed by the accumulation of silicon-carbon material particles while also suppressing their own volume expansion to a certain extent.

[0046] In some embodiments, the particle size D50 of the second silicon particles is between 20 nm and 70 nm. For example, the particle size D50 of the second silicon particles may be, but is not limited to, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, or 70 nm. Within this particle size range, the second silicon particles, due to their nano-size effect, can significantly reduce their own volume expansion, thereby improving the cycling performance of the battery.

[0047] Furthermore, by simultaneously controlling the particle sizes of the silicon-carbon material particles, the first silicon particles and the second silicon particles, a structure is formed in which the second silicon particles adhere to the surface of the silicon-carbon material particles to form a composite material, and the first silicon particles are distributed in the gaps formed by adjacent composite materials, thereby giving full play to the graded filling effect, significantly improving the packing density of the particles inside the negative electrode, and increasing the content of active materials per unit volume. At the same time, an efficient and continuous lithium ion transmission channel is formed, thereby effectively improving the capacity performance and rate performance of the battery.

[0048] In some embodiments, the porosity of the first silicon particles is 10% to 50%. For example, the porosity of the first silicon particles may be, but is not limited to, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%. By controlling the porosity of the first silicon particles, the first silicon particles can fully absorb their own volume expansion while maintaining structural stability.

[0049] In some embodiments, the mass ratio of the silicon-carbon material particles, the first silicon particles, and the second silicon particles is (50-70): (5-35): (5-30). For example, the mass ratio of the silicon-carbon material particles, the first silicon particles, and the second silicon particles can be, but is not limited to, 50:20:30, 50:35:15, 60:10:30, 60:20:20, 70:10:20, or 70:25:5. Thus, by controlling the mass ratio of the silicon-carbon material particles, the first silicon particles, and the second silicon particles, the capacity performance, rate performance, and cycle performance of the battery are synergistically improved. Within the above mass ratio range, the silicon-carbon material particles, as the structural skeleton, dominate, providing excellent structural stability and an ion-conducting network foundation for the negative electrode. At the same time, the first silicon particles and the second silicon particles, as fillers, together occupy a considerable mass, effectively increasing the overall specific capacity of the negative electrode. Furthermore, this mass ratio range ensures the formation of a densely packed structure while preventing a decrease in cycle stability due to an imbalance in the proportion of any one component.

[0050] In some embodiments, the silicon-carbon material particles include a porous carbon skeleton and a silicon material. The silicon material is disposed within the pores of the porous carbon skeleton. Thus, the porous carbon skeleton provides space for the silicon material to expand and, by utilizing the excellent electrical conductivity of the carbon skeleton itself, improves electronic contact with the silicon material within.

[0051] In some embodiments, the silicon-carbon material particles further include a silicon layer disposed on the surface of the porous carbon framework. The silicon layer enhances contact between the silicon material in the silicon-carbon material particles and the first and second silicon particles, forming a continuous ion-conducting pathway and further improving the rate performance of the battery.

[0052] In some embodiments, the shape of the silicon-carbon material particles is irregular or spherical. Further, the shape of the silicon-carbon material particles is spherical, which is conducive to stacking.

[0053] In some embodiments, the negative electrode active material layer may further include a binder, wherein the binder comprises ≤1% by mass of the negative electrode active material layer. For example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), styrene-ethylene-butylene-styrene copolymer (SEBS), styrene-butadiene-styrene copolymer (SBS), polyacrylic acid (PAA), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA), sodium alginate, and lithium alginate.

[0054] In some embodiments, the negative electrode active material layer optionally includes a solid electrolyte, with the mass percentage of the solid electrolyte in the negative electrode active material layer being ≤10%. By implementing a gradient silicon particle size in the negative electrode, the amount of solid electrolyte used can be effectively reduced, increasing the battery's energy density. This also reduces side reactions between the solid electrolyte and the silicon material, further improving the battery's cycling performance.

[0055] In some embodiments, the negative electrode active material layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, conductive carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0056] In some embodiments, the negative electrode active material layer may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0057] A second aspect of the present application provides a solid-state battery, which includes the negative electrode plate provided by the first aspect above.

[0058] A solid-state battery includes a positive electrode sheet, a negative electrode sheet, and a solid electrolyte membrane. The solid electrolyte membrane is disposed between the positive and negative electrode sheets.

[0059] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side surface of the positive electrode current collector.

[0060] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is provided on either or both of the two facing surfaces of the positive electrode current collector.

[0061] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate made of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0062] In some embodiments, the positive electrode active material may be a positive electrode active material for a battery that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al 0.05 O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0063] In some embodiments, the positive electrode active material layer may further optionally include a binder. As examples, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), styrene-ethylene-butylene-styrene copolymer (SEBS), styrene-butadiene-styrene copolymer (SBS), polyacrylic acid (PAA), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA), sodium alginate, and lithium alginate.

[0064] In some embodiments, the positive electrode active material layer may further include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, conductive carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0065] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0066] In some embodiments, the solid electrolyte membrane includes a solid electrolyte and a binder. As an example, the binder may include at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polypropylene, polyethylene, and polyimide.

[0067] In some embodiments, the solid electrolyte is an inorganic solid electrolyte, including one or more of an oxide solid electrolyte, a sulfide solid electrolyte, a halide solid electrolyte, a hydride solid electrolyte, a boride solid electrolyte, and a nitride solid electrolyte.

[0068] The oxide solid electrolyte comprises one or more garnet ceramics, LISICON type oxides, NASICON type oxides and perovskite type ceramics. For example, one or more garnet ceramics include but are not limited to Li 6.5 La3Zr 1.75 Te 0.25 O 12 、Li7La3Zr2O 12 、Li 6.2 Ga 0.3 La 2.95 Rb 0.05 Zr2O 12 、Li 6.85 La 2.9 Ca 0.1 Zr1.75 Nb 0.25 O 12 、Li 6.25 Al 0.25 La3Zr2O 12 、Li 6.75 La3Zr 1.75 Nb 0.25 O 12 one or more of those in. One or more LISICON-type oxides include, but are not limited to, Li 14 Zn(GeO4)4, Li 3+x (P 1-x Si x )O4 (where 0 < x < 1), Li 3+x Ge x V 1-x O4 (where 0 < x < 1) one or more of those. One or more NASICON-type oxides can be defined by LiMM′(PO4)3, where M and M′ are independently selected from Al, Ge, Ti, Sn, Hf, Zr, and La. For example, in certain variants, one or more NASICON-type oxides include, but are not limited to, Li 1+x Al x Ge 2-x (PO4)3 (LAGP) (where 0 ≤ x ≤ 2), Li 1+x Al x Ti 2-x (PO4)3 (LATP) (where 0 ≤ x ≤ 2), Li 1+ x Y x Zr 2-x (PO4)3 (LYZP) (where 0 ≤ x ≤ 2), Li 1.3 Al 0.3 Ti 1.7 (PO4)3, LiTi2(PO4)3, LiGeTi(PO4)3, LiGe2(PO4)3, LiHf2(PO4)3 one or more of those. One or more perovskite-type ceramics include, but are not limited to, Li 0.33 La 0.56 TiO3, LiSr 1.65 Zr 1.3 Ta 1.7 O9, Li 2x-y Sr 1-x Ta y Zr 1-y O3 (where x = 0.75y and 0.60 < y < 0.75), Li 3 / 8 Sr 7 / 16 Nb 3 / 4 Zr 1 / 4 O3, Li3x La (2 / 3-x) one or more of TiO3 (where 0 < x < 0.25).

[0069] Sulfide solid electrolytes include, but are not limited to, Li2S-P2S5, Li2S-P2S5-MS x (where M is Si, Ge, and Sn and 0 ≤ x ≤ 2), Li 3.4 Si 0.4 P 0.6 S4, Li 10 GeP2S 11.7 O 0.3 、Li 9.6 P3S 12 、Li7P3S 11 、Li9P3S9O3, Li 10.35 Si 1.35 P 1.65 S 12 、Li 9.81 Sn 0.81 P 2.19 S 12 、Li 10 (Si 0.5 Ge 0.5 )P2S 12 、Li 10 (Ge 0.5 Sn 0.5 )P2S 12 、Li 10 (Si 0.5 Sn 0.5 )P2S 12 、Li 10 GeP2S 12 (LGPS), Li6PS5X (where X is selected from Cl, Br, or I), Li7P2S8I, Li 10.35 Ge 1.35 P[[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​

[0070] Halide solid electrolytes include, but are not limited to, one or more of Li2CdCl4, Li2MgCl4, Li2CdI4, Li2ZnI4, Li3OCl, LiI, Li5ZnI4, Li3OCl 1-x Br x (where 0 < x < 1).

[0071] Boride solid electrolytes include, but are not limited to, one or more of Li2B4O7, Li2O-(B2O3)-(P2O5).

[0072] Nitride solid electrolytes include, but are not limited to, one or more of Li3N, Li7PN4, LiSi2N3, LiPON.

[0073] Hydride solid electrolytes include, but are not limited to, one or more of Li3AlH6, LiBH4, LiBH4-LiX (where X is one of Cl, Br, and I), LiNH2, Li2NH, LiBH4-LiNH2.

[0074] In some embodiments, the inorganic solid electrolyte can also be one or more metal oxide particles or lithium-containing compounds, including, but not limited to, one or more of Al2O3, SiO2, TiO2, LiNbO3, Li4Ti5O4, Li3PO4.

[0075] In some embodiments, the solid electrolyte further includes a partial polymer solid electrolyte, a composite solid electrolyte composed of the polymer solid electrolyte and the inorganic solid electrolyte. In the embodiments of the present application, there is no special requirement for the mass ratio of the inorganic solid electrolyte and the polymer solid electrolyte in the composite solid electrolyte, and the user can design according to actual needs. Among them, the polymer solid electrolyte can be at least one of polyvinyl chloride (PVC), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), and polyethylene oxide (PEO).

[0076] In the third aspect of the present application, an electrical device is provided, and the electrical device includes the solid-state battery provided in the second aspect above. The solid-state battery provides power for the electrical device.

[0077] The electrical device of the present application is not particularly limited and may be any electrical device known in the art. For example, the electrical device may include, but is not limited to, a laptop computer, a pen-type computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flashlight, a camera, a large household battery, and a lithium-ion capacitor.

[0078] The present application will be further described below with reference to specific embodiments and comparative examples.

[0079] If no specific techniques or conditions are specified in the examples, the experiments were carried out according to the techniques or conditions described in the literature in the field or according to the product instructions. All reagents or instruments used without specifying the manufacturer are commercially available conventional products.

[0080] Example 1

[0081] Negative electrode:

[0082] (1) Silicon-carbon material particles, first silicon particles, and second silicon particles were added to an N-methylpyrrolidone solvent containing a binder PVDF in a mass ratio of 70:10:20, and mixed using a homogenizer to prepare a negative electrode slurry.

[0083] Among them, the silicon-carbon material particles include a porous carbon skeleton, a silicon material arranged in the pores of the porous carbon skeleton, and a silicon layer arranged on the surface of the porous carbon skeleton. The particle size D50 of the silicon-carbon material particles is 6 μm; the particle size D50 of the first silicon particles is 1 μm, the first silicon particles have a porous structure, and the porosity of the first silicon particles is 20%; the particle size D50 of the second silicon particles is 35 nm; based on the solid content of the negative electrode slurry as 100%, the mass proportion of PVDF is 1%.

[0084] (2) The negative electrode slurry was coated on a 10 μm thick copper film using a scraper and vacuum dried at 80 °C overnight to remove the solvent to form a negative electrode active material layer. The negative electrode sheet was then cut into discs.

[0085] Solid-state batteries:

[0086] The positive electrode sheet, the solid electrolyte membrane and the above-mentioned negative electrode sheet are stacked and assembled in sequence to obtain a solid-state battery.

[0087] The positive electrode is prepared by the following method: LiNi 0.8 Co 0.1 Mn0.1 O2, Li6PS5Cl, polyaniline and polytetrafluoroethylene (PTFE) were mixed in a weight ratio of 78:19.5:2:0.5 and fiberized before roll pressing to obtain the positive electrode.

[0088] The solid electrolyte membrane was prepared by mixing the sulfide solid electrolyte Li6PS5Cl and polytetrafluoroethylene in a mass ratio of 96:4, grinding the mixture for 30 minutes to obtain a sulfide solid electrolyte sheet, and hot rolling the obtained sulfide solid electrolyte sheet to prepare a solid electrolyte membrane.

[0089] Example 2

[0090] The preparation method of the negative electrode plate and the solid-state battery in this embodiment is basically the same as that in Example 1, except that:

[0091] In step (1), the porosity of the first silicon particles is 10%.

[0092] Example 3

[0093] The preparation method of the negative electrode plate and the solid-state battery in this embodiment is basically the same as that in Example 1, except that:

[0094] In step (1), the porosity of the first silicon particles is 50%.

[0095] Example 4

[0096] The preparation method of the negative electrode plate and the solid-state battery in this embodiment is basically the same as that in Example 1, except that:

[0097] In step (1), the particle size D50 of the first silicon particles is 1.5 μm.

[0098] Example 5

[0099] The preparation method of the negative electrode plate and the solid-state battery in this embodiment is basically the same as that in Example 1, except that:

[0100] In step (1), the particle size D50 of the first silicon particles is 600 nm.

[0101] Example 6

[0102] The preparation method of the negative electrode plate and the solid-state battery in this embodiment is basically the same as that in Example 1, except that:

[0103] In step (1), the particle size D50 of the first silicon particles is 4 μm.

[0104] Example 7

[0105] The preparation method of the negative electrode plate and the solid-state battery in this embodiment is basically the same as that in Example 1, except that:

[0106] In step (1), the mass ratio of the silicon-carbon material particles, the first silicon particles, and the second silicon particles is 60:20:20.

[0107] Example 8

[0108] The preparation method of the negative electrode plate and the solid-state battery in this embodiment is basically the same as that in Example 1, except that:

[0109] In step (1), the mass ratio of the silicon-carbon material particles, the first silicon particles, and the second silicon particles is 60:10:30.

[0110] Example 9

[0111] The preparation method of the negative electrode plate and the solid-state battery in this embodiment is basically the same as that in Example 1, except that:

[0112] In step (1), the mass ratio of the silicon-carbon material particles, the first silicon particles, and the second silicon particles is 50:35:15.

[0113] Example 10

[0114] The preparation method of the negative electrode plate and the solid-state battery in this embodiment is basically the same as that in Example 1, except that:

[0115] In step (1), the mass ratio of the silicon-carbon material particles, the first silicon particles, and the second silicon particles is 50:20:30.

[0116] Example 11

[0117] The preparation method of the negative electrode plate and the solid-state battery in this embodiment is basically the same as that in Example 1, except that:

[0118] In step (1), the mass ratio of the silicon-carbon material particles, the first silicon particles, and the second silicon particles is 40:30:30.

[0119] Comparative Example 1

[0120] Negative electrode:

[0121] (1) Silicon-carbon material particles and second silicon particles were added to an N-methylpyrrolidone solvent containing a binder PVDF in a mass ratio of 70:30, and mixed using a homogenizer to prepare a negative electrode slurry.

[0122] Among them, the silicon-carbon material particles include a porous carbon skeleton, a silicon material arranged in the pores of the porous carbon skeleton, and a silicon layer arranged on the surface of the porous carbon skeleton. The particle size D50 of the silicon-carbon material particles is 6 μm; the particle size D50 of the second silicon particles is 35 nm; based on the solid content of the negative electrode slurry as 100%, the mass proportion of PVDF is 1%.

[0123] (2) The negative electrode slurry was coated on a 10 μm thick copper film using a scraper and vacuum dried at 80 °C overnight to remove the solvent to form a negative electrode active material layer. The negative electrode sheet was then cut into discs.

[0124] Solid-state batteries:

[0125] The positive electrode sheet, the solid electrolyte membrane and the above-mentioned negative electrode sheet are stacked and assembled in sequence to obtain a solid-state battery.

[0126] The positive electrode is prepared by the following method: LiNi 0.8 Co 0.1 Mn 0.1 O2, Li6PS5Cl, polyaniline and polytetrafluoroethylene (PTFE) were mixed in a weight ratio of 78:19.5:2:0.5 and fiberized before roll pressing to obtain the positive electrode.

[0127] The solid electrolyte membrane was prepared by mixing the sulfide solid electrolyte Li6PS5Cl and polytetrafluoroethylene in a mass ratio of 96:4, grinding the mixture for 30 minutes to obtain a sulfide solid electrolyte sheet, and hot rolling the obtained sulfide solid electrolyte sheet to prepare a solid electrolyte membrane.

[0128] Comparative Example 2

[0129] Negative electrode:

[0130] (1) Silicon-carbon material particles, first silicon particles, and second silicon particles were added to an N-methylpyrrolidone solvent containing a binder PVDF in a mass ratio of 70:10:20, and mixed using a homogenizer to prepare a negative electrode slurry.

[0131] Among them, the silicon-carbon material particles include a porous carbon skeleton, a silicon material arranged in the pores of the porous carbon skeleton, and a silicon layer arranged on the surface of the porous carbon skeleton. The particle size D50 of the silicon-carbon material particles is 6 μm; the particle size D50 of the first silicon particles is 1 μm, the first silicon particles are solid silicon particles with a porosity close to 0, and the particle size D50 of the second silicon particles is 35 nm; based on the solid content of the negative electrode slurry as 100%, the mass proportion of PVDF is 1%.

[0132] (2) The negative electrode slurry was coated on a 10 μm thick copper film using a scraper and vacuum dried at 80 °C overnight to remove the solvent to form a negative electrode active material layer. The negative electrode sheet was then cut into discs.

[0133] Solid-state batteries:

[0134] The positive electrode sheet, the solid electrolyte membrane and the above-mentioned negative electrode sheet are stacked and assembled in sequence to obtain a solid-state battery.

[0135] The positive electrode is prepared by the following method: LiNi 0.8 Co 0.1 Mn 0.1 O2, Li6PS5Cl, polyaniline and polytetrafluoroethylene (PTFE) were mixed in a weight ratio of 78:19.5:2:0.5 and fiberized before roll pressing to obtain the positive electrode.

[0136] The solid electrolyte membrane was prepared by mixing the sulfide solid electrolyte Li6PS5Cl and polytetrafluoroethylene in a mass ratio of 96:4, grinding the mixture for 30 minutes to obtain a sulfide solid electrolyte sheet, and hot rolling the obtained sulfide solid electrolyte sheet to prepare a solid electrolyte membrane.

[0137] Performance Testing

[0138] Electrochemical tests were performed on the solid-state batteries of the above embodiments and comparative examples:

[0139] (1) Rate performance test

[0140] At 25°C, a fully charged battery is discharged at a current of 0.1C to a cut-off voltage of 3.0V, and the capacity obtained by the test is C0. At 25°C, a fully charged battery is discharged at a current of 1C to a cut-off voltage of 3.0V, and the capacity obtained by the test is C1. C1 / C0 is the capacity retention rate of 1C.

[0141] (2) Cyclic performance test

[0142] Charge to 4.25 V at a charging current of 0.33 C, charge at constant voltage until the cutoff current is 0.05 C. Then discharge to 3.0 V at 0.33 C, cycle until the capacity decays to 80% of the initial capacity, and record the number of cycles.

[0143] The test results are shown in Table 1.

[0144] Table 1

[0145]

[0146] As shown in Table 1, by comparing Examples 1 to 11 and Comparative Examples 1 to 2, it can be seen that the negative electrode sheets provided in some embodiments of the present application improve the rate performance and cycle performance of the battery.

[0147] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0148] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the technical concept of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A negative electrode plate, characterized in that: include: negative electrode current collector; as well as A negative electrode active material layer is provided on at least one side of the negative electrode current collector, wherein the negative electrode active material layer comprises silicon-carbon material particles, first silicon particles and second silicon particles; The particle size D50 of the silicon-carbon material particles is greater than the particle size D50 of the first silicon particles, and the particle size D50 of the first silicon particles is greater than the particle size D50 of the second silicon particles; The first silicon particles have a porous structure.

2. The negative electrode sheet according to claim 1, characterized in that: At least one of the following conditions is met: (1) The ratio of the particle size D50 of the silicon-carbon material particles to the particle size D50 of the first silicon particles is in the range of (5-15):1; (2) The ratio of the particle size D50 of the silicon-carbon material particles to the particle size D50 of the second silicon particles is in the range of (50-500):

1.

3. The negative electrode sheet according to claim 2, characterized in that: One of the following conditions is met: (1) The particle size D50 of the silicon-carbon material particles is 4 μm to 10 μm; (2) The particle size D50 of the first silicon particles is 300 nm to 2 μm; (3) The particle size D50 of the second silicon particles is 20 nm to 70 nm.

4. The negative electrode sheet according to any one of claims 1 to 3, characterized in that: The porosity of the first silicon particles is 10% to 50%.

5. The negative electrode sheet according to any one of claims 1 to 3, characterized in that: The mass ratio of the silicon-carbon material particles, the first silicon particles and the second silicon particles is (50-70): (5-35): (5-30).

6. The negative electrode sheet according to any one of claims 1 to 3, characterized in that: The silicon-carbon material particles include: porous carbon framework; and The silicon material is disposed in the pores of the porous carbon skeleton.

7. The negative electrode sheet according to claim 6, characterized in that: The silicon-carbon material particles further include: The silicon layer is arranged on the surface of the porous carbon skeleton.

8. The negative electrode sheet according to any one of claims 1 to 3, characterized in that: At least one of the following conditions is met: (1) The negative electrode active material layer further includes a binder, and the mass percentage of the binder in the negative electrode active material layer is ≤1%; (2) The negative electrode active material layer further includes a solid electrolyte, and the mass percentage of the solid electrolyte in the negative electrode active material layer is ≤10%.

9. A solid-state battery, characterized in that: Comprising the negative electrode sheet as described in any one of claims 1 to 8.

10. An electrical device, characterized in that: Including the solid-state battery as described in claim 9.

Images