All-solid-state battery

Abstract

The invention relates to an all-solid-state battery in the technical field of lithium battery production. The all-solid-state battery comprises a negative electrode, a positive electrode and a solid-state electrolyte membrane arranged between the negative electrode and the positive electrode, the negative electrode comprises a negative electrode active material layer; the positive electrode comprises a positive electrode active material layer; the negative electrode active material layer comprises doped silicon; the doped silicon comprises silicon and doped atoms, and the doped atoms comprise at least one of B atoms and P atoms; and the mass ratio of the doped silicon is greater than 90% by taking the mass of the negative electrode layer as 100%. The negative electrode active material adopts the boron (B) / phosphorus (P) doped pure silicon material, so that the powder resistance of the material is effectively reduced, the electron conductivity is improved, the negative electrode dynamics is improved, the lithium precipitation risk is reduced, and meanwhile, the cycling stability of the battery can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery production, and particularly to a all-solid-state battery. Background Art

[0002] Nowadays, the research on high-capacity negative electrode active materials (such as silicon (Si)) as substitutes for graphite-based negative electrode active materials is increasing. Silicon (Si) has high electronic conductivity and exhibits higher capacity characteristics than graphite-based active materials. Therefore, when silicon (Si) is used as the negative electrode active material, a higher battery capacity and a smaller battery size than existing batteries containing graphite-based negative electrodes can be achieved. However, the kinetics of pure silicon is insufficient, and lithium deposition is likely to occur, affecting the cycling performance of pure silicon materials.

[0003] There is an urgent need in the market for a technical solution to solve the above problems. Summary of the Invention

[0004] To solve the above problems, an all-solid-state battery is disclosed in the present invention. By using doped silicon as the negative electrode active material, on the one hand, the electron transfer rate of the negative electrode can be effectively improved to prevent lithium deposition on the negative electrode, and on the other hand, the cycling performance of the battery can be effectively improved. The technical solution of the present invention is implemented as follows:

[0005] The present invention provides an all-solid-state battery, comprising a negative electrode, a positive electrode, and a solid electrolyte membrane disposed between the negative electrode and the positive electrode;

[0006] The negative electrode includes a negative electrode layer;

[0007] The negative electrode layer includes doped silicon;

[0008] The doped silicon includes silicon and a doping atom, and the doping atom includes at least one of a B atom and a P atom;

[0009] Based on the mass of the negative electrode layer being 100%, the mass ratio of the doped silicon is greater than or equal to 90%.

[0010] In some embodiments, in the doped silicon, the mass ratio of the doping atom is 0.01 - 0.2%.

[0011] In some embodiments, in the doped silicon, the distribution concentration of the doping atom is 10 14 ~10 21 n / cm 3 , where n is the number of atoms.

[0012] In some embodiments, based on the mass of the negative electrode layer being 100%, the mass ratio of the doped silicon is greater than or equal to 99%.

[0013] In some embodiments, based on the mass of the negative electrode layer being 100%, the mass proportion of the doped silicon is greater than or equal to 99.9%.

[0014] In some embodiments, the doped silicon is silicon particles, and the particle size of the silicon particles is 0.1 μm to 5 μm.

[0015] In some embodiments, in the negative electrode layer, the porosity of the silicon layer formed by piling up the doped silicon particles is 15% to 35%.

[0016] In some embodiments, the negative electrode layer does not include a carbon-containing conductive material.

[0017] In some embodiments, the negative electrode layer further includes a conductive agent. Based on the mass of the negative electrode layer being 100%, the mass proportion of the conductive agent is less than 1%.

[0018] In some embodiments, no additional conductive agent is added to the negative electrode layer.

[0019] In some embodiments, the negative electrode layer further includes a solid electrolyte. Based on the mass of the negative electrode layer being 100%, the proportion of the solid electrolyte is less than 1%.

[0020] In some embodiments, the negative electrode layer does not include a solid electrolyte.

[0021] In some embodiments, the doped silicon does not have a pore structure.

[0022] In some embodiments, the powder resistivity of the doped silicon is 10 to 100 Ω·cm.

[0023] In some embodiments, the tap density of the negative electrode layer is 0.8 g / cm 3 ~1.8 g / cm 3 .

[0024] The advantages of the present invention are as follows:

[0025] The negative electrode active material of the present invention uses a boron (B) / phosphorus (P)-doped pure silicon material, which effectively reduces the powder resistance of the material, improves the electronic conductivity, improves the negative electrode kinetics, is beneficial to reducing the risk of lithium deposition, and can effectively improve the cycle stability of the battery. Detailed Embodiments

[0026] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts fall within the scope of protection of the present invention.

[0027] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meanings as commonly understood by those of ordinary skill in the technical field to which the present invention pertains; the terms used in the specific embodiments are only for the purpose of describing specific embodiments and are not intended to limit the present invention; the terms "comprising" and "having" and any variations thereof in the specification and claims of the present invention and the above description are intended to cover non-exclusive inclusion.

[0028] In the description of the specific embodiments of the present invention, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of the present invention, the meaning of "a plurality of" is more than two, unless otherwise specifically defined.

[0029] Reference to "embodiments" in the present invention means that a particular feature, structure or characteristic described in connection with the embodiments can be included in at least one embodiment of the present invention. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in the present invention can be combined with other embodiments.

[0030] In the description of the embodiments of the present invention, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in the present invention generally represents an "or" relationship between the associated objects before and after.

[0031] Throughout the present invention, numerical values represent approximate measures or limits of ranges, covering minor deviations from a given value as well as embodiments having approximately the mentioned value and embodiments having the exact value mentioned. Except for the working examples provided at the end of the detailed description, all numerical values of parameters (such as mass or conditions) in this specification (including the appended claims) should be understood to be modified in all cases by the term "about", whether or not "about" actually appears before the numerical value. "About" indicates that the stated numerical value allows for some minor inaccuracies (reasonably close to the exact value of the stated value; approximately or reasonably close to the stated value; almost). If the inaccuracy provided by "about" is not otherwise understood in the art in this ordinary meaning, then "about" as used in the present invention indicates at least the variations that can be produced by ordinary methods of measuring and using such parameters. For example, "about" can include variations of less than or equal to 5%, optionally less than or equal to 4%, optionally less than or equal to 3%, optionally less than or equal to 2%, optionally less than or equal to 1%, optionally less than or equal to 0.5%, and in some aspects, optionally less than or equal to 0.1%.

[0032] In addition, the disclosure of a range includes the disclosure of all values within the entire range and further divided ranges, including the endpoints and sub-ranges given for these ranges.

[0033] The kinetics of pure silicon is insufficient, and lithium precipitation is likely to occur. Moreover, it is difficult for pure silicon materials to achieve stable cycling exceeding 100 cycles in all-solid-state batteries.

[0034] To solve the above problems, the present invention proposes a technical solution.

[0035] The present invention proposes an all-solid-state battery. The all-solid-state battery includes a negative electrode, a positive electrode, and a solid electrolyte membrane disposed between the negative electrode and the positive electrode; the negative electrode includes a negative electrode active material layer; the negative electrode active material layer includes doped silicon;

[0036] The doped silicon includes silicon and doped atoms, and the doped atoms include at least one of B atoms and P atoms.

[0037] In a specific application, the doped atom can be a phosphorus atom, can be a boron atom, or can be a combination of both.

[0038] Based on the mass of the negative electrode layer being 100%, the mass ratio of the doped silicon is greater than or equal to 90%.

[0039] The negative electrode active material of the present invention uses a boron (B) / phosphorus (P) doped pure silicon material, which effectively reduces the powder resistance of the material, improves the electronic conductivity, improves the kinetics of the negative electrode, is beneficial to reducing the risk of lithium precipitation, and at the same time effectively improves the cycling stability of the negative electrode active material, thereby effectively improving the cycling stability of the battery.

[0040] Since doped silicon has good electrical conductivity, which is beneficial to the transmission of lithium ions and electrons, in the negative electrode layer, an increase in the mass ratio of doped silicon is conducive to improving the capacity and rate performance of the battery.

[0041] In some embodiments, in the doped silicon, the mass ratio of the doped atoms is 0.01-0.2%.

[0042] In some embodiments, in the doped silicon, the distribution concentration of the doped atoms is 10 14 ~10 21 n / cm 3 , where n is the number of atoms.

[0043] In specific applications, the distribution concentration of the doped atoms can be selected from any value within the range except for the endpoints 10 14 / cm 3 、10 21 / cm 3 . For example, it can also be any value within the above range, such as: 10 15 / cm 3 、10 16 / cm 3 、10 17 / cm 3 、10 18 / cm 3 、10 19 / cm 3 、10 12 / cm 3 etc. The above-listed values are only examples, and the present invention does not impose any restrictions on this.

[0044] In specific applications, the specific measurement method for the distribution concentration of the doped atoms can be selected as the electrochemical capacitance-voltage method (ECV): By measuring the capacitance change of the semiconductor material at a specific voltage to infer the doping concentration and distribution. The ECV test utilizes the capacitance characteristics of the pn junction or Schottky barrier under reverse bias, and by measuring the capacitance change of the semiconductor material at different voltages, to infer the doping concentration and its distribution of the material.

[0045] In some preferred embodiments, based on the mass of the negative electrode layer being 100%, the mass ratio of the doped silicon is greater than or equal to 99%.

[0046] At this time, the porosity of the silicon layer can be approximately regarded as the porosity of the negative electrode layer.

[0047] In some more preferred embodiments, based on the mass of the negative electrode layer being 100%, the mass ratio of the doped silicon is greater than or equal to 99.9%.

[0048] In some embodiments, the doped silicon is silicon particles, and the particle size of the silicon particles is 0.1 μm to 5 μm.

[0049] In some embodiments, in the negative electrode layer, the porosity of the silicon layer formed by piling up the doped silicon particles is 15% to 35%.

[0050] In specific applications, except for the endpoints 0.1 μm and 5 μm of the above-mentioned range, the particle size of the doped silicon particles can also be any value within the above-mentioned particle size range. For example: 0.2 μm, 0.5 μm, 0.8 μm, 1.0 μm, 1.5 μm, 2.0 μm, 2.5 μm, 3.0 μm, 3.5 μm, 4.0 μm, 4.5 μm, etc.; except for the endpoints 15% and 35% of the porosity, the porosity of the silicon layer formed by piling up the silicon particles can also be any value within the above-mentioned porosity range, such as: 18%, 20%, 24%, 25%, 28%, 30%, 32%, etc. The values listed above are only examples, and the present invention does not make any restrictions thereon.

[0051] By forming voids through the piling up of the doped silicon particles to reserve space for the expansion of the doped silicon, the change of the negative electrode structure can be effectively inhibited, which is beneficial to improving the cycling performance of the battery.

[0052] In some embodiments, the negative electrode layer does not include a carbon-containing conductive material. Exemplarily, the carbon-containing conductive material includes particulate carbon materials such as acetylene black (AB) and Ketjen black (KB), carbon fibers, carbon nanotubes (CNT), carbon nanofibers (CNF), vapor-grown carbon fibers (VGCF), and the like.

[0053] The carbon-containing conductive material will cause the solid electrolyte to decompose, generating by-products with poor ionic conductivity at the interface between the negative electrode and the solid electrolyte membrane, thereby deteriorating the cycling performance and rate performance of the all-solid-state battery.

[0054] In some embodiments, the negative electrode layer further includes a conductive agent. Based on the mass of the negative electrode layer being 100%, the proportion of the conductive material is less than 1%.

[0055] Exemplarily, the conductive material can be a metal oxide, a conductive polymer, etc., such as titanium dioxide, aluminum oxide, zinc oxide, polyaniline, polythiophene, etc. Those skilled in the art can select a combination of two or more or a single conductive agent based on the understanding of the prior art. The present invention does not make any restrictions thereon.

[0056] In some embodiments, no additional conductive agent is added to the negative electrode layer. It can be understood that not adding an additional conductive agent here means that except for the doped silicon, the negative electrode layer does not include other substances that mainly play an electron-conducting role.

[0057] In some embodiments, the negative electrode layer further includes a solid electrolyte. Based on the mass of the negative electrode layer being 100%, the proportion of the solid electrolyte is less than 1%.

[0058] In some embodiments, the negative electrode layer does not include a solid electrolyte.

[0059] Since the present invention dopes boron (B) / phosphorus (P) in silicon-based materials, it not only reduces the powder resistance but also improves the electronic conductivity. Without adding a solid electrolyte and a conductive agent in the negative electrode active material, it can have good electron-conducting and ion-conducting properties. This can not only reduce the production cost but also increase the capacity and energy density of the battery.

[0060] In some more preferred embodiments, the negative electrode layer does not include a conductive agent and a solid electrolyte.

[0061] In some embodiments, the doped silicon does not have a pore structure.

[0062] As used in the present invention, "not having a pore structure" means that there are no holes or channels inside the silicon, and the overall structure is tight and continuous without obvious internal spaces or channels. The "pore structure" referred to in the present invention is not the hollow structure inside the particles but the porous structure of the particle shell layer.

[0063] In some embodiments, the negative electrode layer further includes a negative electrode binder. Based on the mass of the negative electrode layer being 100%, the mass proportion of the negative electrode binder is less than or equal to 1%.

[0064] In specific applications, the negative electrode binder can be selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTEE), styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), etc. On the premise that the above binders do not chemically react with each other, those skilled in the art can select a combination of two or more based on the understanding of the prior art, or select a single binder. The present invention does not impose any restrictions on this.

[0065] In some embodiments, the tap density of the negative electrode layer is 0.8 g / cm 3 ~1.8 g / cm 3 .

[0066] In specific applications, except for the endpoints 0.8 g / cm 3 、1.8 g / cm 3 of the above range, the tap density of the negative electrode layer can also be selected as any value within the above range. For example, 0.9 g / cm 3 、1.0 g / cm 3 、1.2 g / cm 3 、1.4 g / cm 3 、1.6 g / cm 3etc. The above-listed values are only examples, and the present invention does not impose any limitations thereon.

[0067] In some embodiments, the resistivity of the doped silicon powder is 10 - 100 Ω·cm.

[0068] In the all-solid-state battery proposed by the present invention, the preparation method of the negative electrode active material is as follows:

[0069] S1. Mix high-purity silicon and a doping source to form a first mixture, and heat it to a molten state;

[0070] Among them, the doping source includes at least one of a phosphorus source and a boron source;

[0071] Exemplarily, the phosphorus source includes but is not limited to POCl3, PCl3, etc.; the boron source includes but is not limited to boric acid, sodium borate, borax, etc.

[0072] The heating temperature satisfies being greater than or equal to 1400 °C.

[0073] Step S1 further includes putting the first mixture into a heating device, evacuating the heating device, and introducing an inert gas as a protective gas, where the inert gas is argon.

[0074] Furthermore, by introducing the inert gas argon and combining with the pumping of the vacuum pump, an argon flow under a reduced-pressure atmosphere is formed inside the heating device.

[0075] S2. Insert a seed crystal with a certain crystal orientation into the molten silicon melt, and obtain a silicon ingot doped with element M through seed crystal introduction, shoulder release, shoulder turning, equal diameter, tailing, and cooling;

[0076] S4. Process the silicon ingot to form doped silicon particles with a size of 0.1 μm - 5 μm; the doped silicon particles are the negative electrode active material.

[0077] In addition, the present invention does not impose any limitations on the doping method, and the eutectic method, master alloy doping method, or other known methods that can achieve the same purpose and effect can be selected.

[0078] In some specific embodiments, in step S3, the processing technology includes jaw crusher crushing, roll crusher crushing, and air jet milling.

[0079] In some embodiments, the positive electrode includes a positive electrode layer.

[0080] In some preferred embodiments, the positive electrode layer does not include a carbon-containing conductive material.

[0081] In some embodiments, the positive electrode layer includes a solid electrolyte.

[0082] In some preferred embodiments, the type of the solid electrolyte in the positive electrode layer is the same as the type of the solid electrolyte forming the solid electrolyte film.

[0083] The embodiments of the present invention will be described more specifically below through examples and comparative examples. In addition, in all examples and comparative examples, for the preparation of doped silicon particles, samples were taken after preparation to measure the respective concentrations of doped atoms. Since the measurement method has been described above, it will not be elaborated here.

[0084] In all examples and comparative examples, the measurement and determination methods are the same.

[0085] It should be noted that the embodiments of the present invention are not limited to these examples.

[0086] Example 1

[0087] I. Preparation of the negative electrode active material

[0088] S1, Mix high-purity silicon raw material and POCl3 to form a first mixture, and then put it into a graphite crucible in a single crystal furnace. After the single crystal furnace is evacuated, an inert protective gas argon is introduced, and it is heated to above 1400 °C until the internal materials are melted;

[0089] The mass ratio of phosphorus atoms is 0.01 wt%.

[0090] By introducing the inert gas argon and combining with the pumping of the vacuum pump, an argon flow under a reduced pressure atmosphere is formed in the graphite crucible;

[0091] S2, Insert a seed crystal with a certain crystal orientation into the molten silicon melt, and after seeding, shoulder release, shoulder turning, equal diameter, ending, and cooling, a silicon ingot doped with P atoms is obtained; the distribution concentration of P atoms is 10 16 n / cm 3 ; The test method for the doping ratio is the electrochemical capacitance-voltage method (ECV).

[0092] S3, Process the silicon ingot into doped silicon particles with a size of 5 μm; the doped silicon particles are the negative electrode active material.

[0093] II. Material selection for the negative electrode layer

[0094] Use the negative electrode active material prepared in step one for the negative electrode layer. The negative electrode active material layer does not contain a carbon conductive material and does not contain a solid electrolyte material. Based on the weight of the negative electrode active material layer being 100%, the weight ratio of the binder is 1%. The binder is PVDF.

[0095] III. Preparation of the negative electrode sheet

[0096] Add the negative electrode active material (particle size 5 μm) to the N-methyl-2-pyrrolidone solution of PVDF and mix to form a slurry. Among them, the weight ratio of the negative electrode active material to PVDF is 99:1.

[0097] The slurry is coated on the copper foil, dried, and pressed to obtain the negative electrode sheet. The compaction density of the negative electrode layer is 1.6 g / cm 3 , and the porosity of the silicon layer formed by the accumulation of doped silicon particles is 25%.

[0098] IV. Preparation of the positive electrode sheet

[0099] NCM811, Li6PS5Cl, polyaniline, and polytetrafluoroethylene (PTFE) are mixed in a weight ratio of 78:19.5:2:0.5 and fibrillated, and then roll-pressed to obtain the positive electrode.

[0100] V. Preparation of the solid electrolyte membrane

[0101] Li6PS5Cl and polytetrafluoroethylene (PTFE) are mixed in a weight ratio of 99:1, fibrillated, and then roll-pressed to obtain the solid electrolyte membrane.

[0102] VI. Preparation of the all-solid-state battery

[0103] The positive electrode, the solid electrolyte membrane, and the negative electrode are assembled in sequence to form the all-solid-state battery.

[0104] Example 2

[0105] I. Preparation of the negative electrode active material

[0106] S1. The high-purity silicon raw material and POCl3 are mixed to form the first mixture, which is then loaded into the graphite crucible in the single crystal furnace. After the single crystal furnace is evacuated, an inert protective gas, argon, is introduced, and the temperature is raised to above 1400 °C until the internal materials are melted;

[0107] The mass ratio of phosphorus atoms is 0.01 wt%;

[0108] By introducing the inert gas argon and combining with the pumping of the vacuum pump, an argon flow under a reduced pressure atmosphere is formed in the graphite crucible;

[0109] S2. A seed crystal with a certain crystal orientation is inserted into the molten silicon melt. After seeding, shoulder release, shoulder turning, equal diameter, tailing, and cooling, a silicon ingot doped with P atoms is obtained; the doping ratio of P atoms is 10 16 n / cm 3 ; the test method for the doping ratio is the electrochemical capacitance-voltage method (ECV).

[0110] S3. The silicon ingot is processed into doped silicon particles with a size of 3 μm, and the doped silicon particles are the negative electrode active material.

[0111] II. Material selection for the negative electrode layer

[0112] The negative electrode active material prepared in Step 1 is used in the negative electrode layer. The negative electrode active material layer does not contain a carbon conductive material and does not contain a solid electrolyte material. Based on the weight of the negative electrode active material layer being 100%, the weight ratio of the binder is 1%. The binder is PVDF.

[0113] III. Preparation of the negative electrode sheet

[0114] The selected negative electrode active material (particle size 3 μm) from Step 2 is added to a solution of PVDF in N-methyl-2-pyrrolidone and mixed to form a slurry. The weight ratio of the doped silicon powder to PVDF is 99:1.

[0115] The slurry is coated on a copper foil, dried, and pressed to obtain the negative electrode sheet. The tap density of the negative electrode layer is 1.6 g / cm 3 , and the porosity of the silicon layer formed by the accumulation of doped silicon particles is 24%.

[0116] IV. Preparation of the positive electrode sheet

[0117] NCM811, Li6PS5Cl, polyaniline, and polytetrafluoroethylene (PTFE) are mixed in a weight ratio of 78:19.5:2:0.5, fibrillated, and then roll-pressed to obtain the positive electrode.

[0118] V. Preparation of the solid electrolyte membrane

[0119] Li6PS5Cl and polytetrafluoroethylene (PTFE) are mixed in a weight ratio of 99:1, fibrillated, and then roll-pressed to obtain the solid electrolyte membrane.

[0120] VI. Preparation of the all-solid-state battery

[0121] The positive electrode, the solid electrolyte membrane, and the negative electrode are assembled in sequence to form the all-solid-state battery.

[0122] Example 3

[0123] I. Preparation of the negative electrode active material

[0124] S1, Mix high-purity silicon raw material and POCl3 to form a first mixture, then put it into a graphite crucible in a single crystal furnace. After the single crystal furnace is evacuated, an inert protective gas argon is introduced, and it is heated to above 1400 °C until the internal materials are melted;

[0125] The mass ratio of phosphorus atoms is 0.1 wt%;

[0126] By introducing the inert gas argon and combining with the pumping of the vacuum pump, an argon flow under a reduced pressure atmosphere is formed in the graphite crucible;

[0127] S2. A seed crystal with a certain crystal orientation is inserted into the molten silicon melt. After seeding, shoulder opening, shoulder turning, equal diameter growth, end finishing, and cooling, a silicon ingot doped with P atoms is obtained. The doping ratio of P atoms is 10 18 n / cm 3 ; The testing method for the doping ratio is the electrochemical capacitance-voltage method (ECV).

[0128] S3. The silicon ingot is processed into doped silicon particles with a size of 2 μm; the doped silicon particles are the anode active material.

[0129] II. Material Selection for the Anode Layer

[0130] The anode active material prepared in Step 1 is used in the anode layer. The anode active material layer does not contain a carbon conductive material and does not contain a solid electrolyte material. Based on the weight of the anode active material layer being 100%, the weight ratio of the binder is 1%. The binder is PVDF.

[0131] III. Preparation of the Anode Sheet

[0132] The anode active material (particle size 2 μm) is added to a solution of PVDF in N-methyl-2-pyrrolidone and mixed to form a slurry. Among them, the weight ratio of the doped silicon powder to PVDF is 99:1.

[0133] The slurry is coated on a copper foil, dried, and pressed to obtain an anode sheet. The compaction density of the anode layer is 1.5 g / cm 3 , and the porosity of the silicon layer formed by the accumulation of doped silicon particles is 22%.

[0134] IV. Preparation of the Cathode Sheet

[0135] NCM811, Li6PS5Cl, polyaniline, and polytetrafluoroethylene (PTFE) are mixed in a weight ratio of 78:19.5:2:0.5, and after being fibrillated and roll-pressed, a cathode is obtained.

[0136] V. Preparation of the Solid Electrolyte Membrane

[0137] Li6PS5Cl and polytetrafluoroethylene (PTFE) are mixed in a weight ratio of 99:1, fibrillated, and roll-pressed to obtain a solid electrolyte membrane.

[0138] VI. Preparation of the All-Solid-State Battery

[0139] The cathode, solid electrolyte membrane, and anode are assembled in sequence to form an all-solid-state battery.

[0140] Example 4

[0141] I. Preparation of the Anode Active Material

[0142] S1. Mix high-purity silicon raw materials and POCl3 to form a first mixture, and then put the mixture into a graphite crucible in a single crystal furnace. After the single crystal furnace is evacuated, introduce an inert protective gas, argon, and heat it to above 1400 °C until the internal materials are melted;

[0143] The mass ratio of phosphorus atoms is 0.1 wt%;

[0144] By introducing the inert gas argon and combining with the pumping of a vacuum pump, an argon gas flow is formed in the graphite crucible under a reduced pressure atmosphere;

[0145] S2. Insert a seed crystal with a certain crystal orientation into the molten silicon melt. After seeding, shoulder release, shoulder turning, equal diameter, ending, and cooling, a silicon ingot doped with P atoms is obtained; the doping ratio of P atoms is 10 18 n / cm 3 ; The test method for the doping ratio is the electrochemical capacitance-voltage method (ECV).

[0146] S3. Process the silicon ingot into 1-μm doped silicon particles; the doped silicon particles are the anode active material.

[0147] II. Material Selection for the Anode Layer

[0148] Use the anode active material prepared in Step 1 for the anode layer. The anode active material layer does not contain a carbon conductive material and does not contain a solid electrolyte material. Based on the weight of the anode active material layer being 100%, the weight ratio of the binder is 0.1%. The binder is PVDF.

[0149] III. Preparation of the Anode Sheet

[0150] Add the anode active material (particle size 1 μm) selected in Step 2 to the N-methyl-2-pyrrolidone solution of PVDF and mix to form a slurry.

[0151] Among them, the weight ratio of the anode active material to PVDF is 99.9:0.1.

[0152] Coat the slurry on the copper foil, dry it, and press it to obtain the anode sheet. The compaction density of the anode layer is 1.6 g / cm 3 , and the porosity of the silicon layer formed by the accumulation of doped silicon particles is 22%.

[0153] IV. Preparation of the Cathode Sheet

[0154] Mix NCM811, Li6PS5Cl, polyaniline, and polytetrafluoroethylene (PTFE) in a weight ratio of 78:19.5:2:0.5, perform fibrillation treatment, and then roll and press to obtain the cathode.

[0155] V. Preparation of the Solid Electrolyte Membrane

[0156] Li6PS5Cl and polytetrafluoroethylene (PTFE) were mixed at a weight ratio of 99:1 and fibrillated, and then roll-pressed to obtain a solid electrolyte membrane.

[0157] VI. Preparation of All-Solid-State Battery

[0158] The positive electrode, the solid electrolyte membrane, and the negative electrode were assembled in sequence to form an all-solid-state battery.

[0159] Example 5

[0160] I. Preparation of Negative Electrode Active Material

[0161] S1. High-purity silicon raw material and POCl3 were mixed to form a first mixture, which was then loaded into a graphite crucible in a single crystal furnace. After the single crystal furnace was evacuated, an inert protective gas, argon, was introduced, and the temperature was raised to above 1400 °C until the internal materials melted.

[0162] The mass ratio of phosphorus atoms was 0.2 wt%.

[0163] By introducing inert gas argon and combining with the pumping of a vacuum pump, an argon flow under a reduced pressure atmosphere was formed in the graphite crucible.

[0164] S2. A seed crystal with a certain crystal orientation was inserted into the molten silicon melt. After seeding, shoulder release, shoulder turning, equal diameter, end finishing, and cooling, a silicon ingot doped with P atoms was obtained; the doping ratio of P atoms was 10 19 / cm 3 ; the test method for the doping ratio was electrochemical capacitance-voltage method (ECV).

[0165] S3. The silicon ingot was processed into doped silicon particles with a size of 0.1 μm; the doped silicon particles were the negative electrode active material.

[0166] II. Material Selection for Negative Electrode Layer

[0167] The negative electrode active material prepared in Step 1 was used in the negative electrode layer. The negative electrode active material layer did not contain a carbon conductive material and did not contain a solid electrolyte material. Based on the weight of the negative electrode active material layer being 100%, the weight ratio of the binder was 1%. The binder was PVDF.

[0168] III. Preparation of Negative Electrode Sheet

[0169] The negative electrode active material (particle size 0.1 μm) selected in Step 2 was added to a solution of PVDF in N-methyl-2-pyrrolidone and mixed to form a slurry.

[0170] Among them, the weight ratio of doped silicon powder to PVDF was 99:1.

[0171] The slurry was coated on a copper foil, dried, and pressed to obtain a negative electrode sheet. The compaction density of the negative electrode layer was 1.7 g / cm3 , the porosity of the silicon layer formed by the accumulation of doped silicon particles is 18%.

[0172] IV. Preparation of the positive electrode sheet

[0173] NCM811, Li6PS5Cl, polyaniline and polytetrafluoroethylene (PTFE) are mixed at a weight ratio of 78:19.5:2:0.5 and processed by fibrillation and then roll-pressed to obtain the positive electrode.

[0174] V. Preparation of the solid-state electrolyte membrane

[0175] Li6PS5Cl and polytetrafluoroethylene (PTFE) are mixed at a weight ratio of 99:1 and processed by fibrillation and then roll-pressed to obtain the solid-state electrolyte membrane.

[0176] VI. Preparation of the all-solid-state battery

[0177] The positive electrode, the solid-state electrolyte membrane, and the negative electrode are assembled in sequence to form the all-solid-state battery.

[0178] Example 6

[0179] I. Preparation of the negative electrode active material

[0180] S1. The high-purity silicon raw material and sodium borate are mixed to form the first mixture, which is then put into a graphite crucible in a single crystal furnace. After the single crystal furnace is evacuated, an inert protective gas argon is introduced, and it is heated to above 1400 °C until the internal materials are melted;

[0181] The mass ratio of boron atoms is 0.01 wt%.

[0182] By introducing the inert gas argon and combining with the pumping of the vacuum pump, an argon gas flow is formed in the graphite crucible under a reduced pressure atmosphere;

[0183] S2. A seed crystal with a certain crystal orientation is inserted into the molten silicon melt. After seeding, shoulder release, shoulder turning, equal diameter, tailing, and cooling, a silicon ingot doped with B atoms is obtained; the doping ratio of B atoms is 10 16 n / cm 3 ; the test method for the doping ratio is the electrochemical capacitance-voltage method (ECV).

[0184] S3. The silicon ingot is processed into doped silicon particles with a size of 5 μm; the doped silicon particles are the negative electrode active material.

[0185] II. Material selection for the negative electrode layer

[0186] The B-doped silicon prepared in step one is used in the negative electrode layer. The negative electrode active material layer does not contain a carbon conductive material and does not contain a solid-state electrolyte material. Based on the weight of the negative electrode active material layer being 100%, the weight ratio of the binder is 1%. The binder is PVDF.

[0187] III. Preparation of the negative electrode sheet

[0188] Add the negative electrode active material (particle size 5 μm) selected in Step II to the N-methyl-2-pyrrolidone solution of PVDF and mix to form a slurry.

[0189] Among them, the weight ratio of doped silicon powder to PVDF is 99:1.

[0190] Coat the slurry on the copper foil, dry it, and press it to obtain the negative electrode sheet. The compaction density of the negative electrode layer is 1.6 g / cm 3 , and the porosity of the silicon layer formed by the accumulation of doped silicon particles is 25%.

[0191] IV. Preparation of the positive electrode sheet

[0192] Mix NCM811, Li6PS5Cl, polyaniline, and polytetrafluoroethylene (PTFE) in a weight ratio of 78:19.5:2:0.5, perform fibrillation treatment, and then roll-press to obtain the positive electrode.

[0193] V. Preparation of the solid electrolyte membrane

[0194] Mix Li6PS5Cl and polytetrafluoroethylene (PTFE) in a weight ratio of 99:1, perform fibrillation treatment, and then roll-press to obtain the solid electrolyte membrane.

[0195] VI. Preparation of the all-solid-state battery

[0196] Assemble the positive electrode, the solid electrolyte membrane, and the negative electrode in sequence to form the all-solid-state battery.

[0197] Test the porosity of the silicon layer in Examples 1-6:

[0198] First, obtain the cross-sectional SEM image of the negative electrode layer. From the obtained SEM image, use image analysis software to identify the pores and calculate the area of the negative electrode layer.

[0199] Porosity (%) = 100% × (pore area in Region A) / (area of Region A).

[0200] In Examples 1-6, the proportion of doped silicon in the negative electrode layer is about 99% or 99.9%. Therefore, the porosity of the negative electrode layer is approximately equal to the porosity of the silicon layer.

[0201] The following are the parameters of the negative electrode active materials in Examples 1-6

[0202]

[0203] Comparative Example 1

[0204] I. Preparation of the negative electrode active material

[0205] S1. Process high-purity silicon raw materials into silicon particles with a size of 5 μm; the silicon particles are the anode active material.

[0206] II. Material Selection for the Anode Layer

[0207] Use the silicon particles prepared in Step 1 in the anode layer. The anode active material layer does not contain a carbon conductive material and does not contain a solid electrolyte material. Based on the weight of the anode active material layer being 100%, the weight ratio of the binder is 1%. The binder is PVDF.

[0208] III. Preparation of the Anode Sheet

[0209] Add the silicon particles (particle size 5 μm) selected in Step 2 to the N-methyl-2-pyrrolidone solution of PVDF and mix to form a slurry.

[0210] Among them, the weight ratio of silicon particle powder to PVDF is 99:1.

[0211] Coat the slurry on the copper foil, dry, and press to obtain the anode sheet. The compaction density of the anode layer is 1.6 g / cm 3 , and the porosity of the silicon layer formed by the accumulation of doped silicon particles is 25%.

[0212] IV. Preparation of the Cathode Sheet

[0213] Mix NCM811, Li6PS5Cl, polyaniline, and polytetrafluoroethylene (PTFE) in a weight ratio of 78:19.5:2:0.5, perform fibrillation treatment, and then roll-press to obtain the cathode.

[0214] V. Preparation of the Solid Electrolyte Membrane

[0215] Mix Li6PS5Cl and polytetrafluoroethylene (PTFE) in a weight ratio of 99:1, perform fibrillation treatment, and then roll-press to obtain the solid electrolyte membrane.

[0216] VI. Preparation of the All-Solid-State Battery

[0217] Assemble the cathode, solid electrolyte membrane, and anode in sequence to form the all-solid-state battery.

[0218] In the battery, the compaction density of the battery is 1.6 g / cm 3 , and the porosity of the silicon layer formed by the accumulation of doped silicon particles is 25%.

[0219] Comparative Experiment

[0220] Take a total of three groups of samples from Example 1, Example 6, and Comparative Example 1, with 20 samples in each group, and conduct the following tests respectively.

[0221] Powder Resistivity Test:

[0222] The negative electrode active materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 were tested for resistivity.

[0223] The four-probe method was selected as the test method for powder resistivity.

[0224] The four-probe method is a test method applicable to powder samples of different sizes and shapes. This method uses four probes, where two probes apply voltage and the other two probes measure current. By measuring the resistance value, the powder resistivity can be calculated.

[0225] Cycling performance test under 1C condition:

[0226] In a 45°C constant temperature oven, charge at a constant current of 1C to 4.2V, then switch to constant voltage charging until the cut-off current is 0.05C, and then discharge at a constant current of 1C to 3.0V. Stop the test when the capacity retention rate reaches 80%, record the number of cycles of all samples and take the average value, rounding off values less than 1.

[0227] The test data of powder resistivity and cycling performance under 1C condition are finally summarized in the following table.

[0228]

[0229] As can be seen from the above table:

[0230] Compared with the non-doped P or B, pure silicon powder particles as the negative electrode active material have too high powder resistivity and low cycling performance. It is proved that the doped carbon doped with B or P can effectively improve the battery performance, and stable cycling exceeding 100 times can be achieved without the negative electrode solid electrolyte material and carbon conductive agent.

[0231] In addition, according to Examples 1-5, changing the amount of doped elements in the doped silicon or the particle size of silicon will affect the porosity of the negative electrode layer (i.e., the void ratio of the silicon layer). Therefore, by controlling the amount of doped elements and the particle size of silicon, a negative electrode layer with the desired porosity and a all-solid-state battery can be obtained.

[0232] It should be noted that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A all-solid-state battery, comprising a negative electrode, a positive electrode, and a solid electrolyte membrane disposed between the negative electrode and the positive electrode; the negative electrode comprises a negative electrode layer, characterized in that, the negative electrode layer comprises doped silicon; the doped silicon comprises silicon and doping atoms, and the doping atoms comprise at least one of B atoms and P atoms; Based on the mass of the negative electrode layer being 100%, the mass proportion of the doped silicon is greater than or equal to 90%.

2. The all-solid-state battery according to claim 1, wherein In the doped silicon, the mass proportion of the doping atoms is 0.01-0.2%.

3. The all-solid-state battery according to claim 1, wherein Based on the mass of the negative electrode layer being 100%, the mass proportion of the doped silicon is greater than or equal to 99%.

4. The all-solid-state battery according to claim 1, characterized in that, Based on the mass of the negative electrode layer being 100%, the mass proportion of the doped silicon is greater than or equal to 99.9%.

5. The all-solid-state battery according to claim 1, wherein The doped silicon is in the form of particles, and the particle size of the doped silicon is 0.1 μm to 5 μm.

6. The all-solid-state battery according to claim 1, characterized in that, In the negative electrode layer, the porosity of the silicon layer formed by the stacking of the doped silicon particles is 15% to 35%.

7. The all-solid-state battery according to claim 1, wherein The negative electrode layer does not include a carbon-containing conductive material.

8. The all-solid-state battery according to claim 1, characterized in that, The negative electrode layer further comprises a conductive agent, and based on the mass of the negative electrode layer being 100%, the mass proportion of the conductive agent is less than 1%; and / or, No additional conductive agent is added to the negative electrode layer.

9. The all-solid-state battery according to claim 1, characterized in that, The negative electrode layer further comprises a solid electrolyte, and based on the mass of the negative electrode layer being 100%, the proportion of the solid electrolyte is less than 1%; and / or, The negative electrode layer does not include a solid electrolyte.

10. The all-solid-state battery according to claim 1, characterized in that, The doped silicon material does not have a pore structure.

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