Negative electrode and preparation method therefor, secondary battery, and power comsuming apparatus

Abstract

A negative electrode and a preparation method therefor, a secondary battery, and a power consuming apparatus. The negative electrode comprises at least one of an inorganic phosphide, an inorganic boride, polysulfurized chloranilic acid, 81-33-43,4,9,10-perylenetetracarboxylic dianhydride, triquinoline, naphthalene, croconic acid, 1,4,5,8-tetrahydroxy-9,10-anthraquinone, a [5,10,15,20-tetraethynylporphyrin] magnesium complex, conjugated sulfonic acid, triphenylphosphine selenide, calix[6]quinone, tris(4-nitrosophenyl)amine, hexaketocyclohexane, and dipentamethylenethiuram hexasulfide, and a lithium-silicon alloy.

Description

Negative electrode and preparation method thereof, secondary battery and electrical equipment

[0001] This disclosure claims priority to the Chinese patent application filed with the China Patent Office on September 27, 2023, with application number 202311269833.3 and invention name “Negative electrode and preparation method thereof, secondary battery and electrical equipment”, the entire contents of which are incorporated by reference into this disclosure. Technical Field

[0002] The present disclosure relates to the field of battery technology, and in particular to a negative electrode and a preparation method thereof, a secondary battery, and an electrical device. Background Art

[0003] Solid-state batteries have attracted widespread attention due to their light weight and high energy density. Currently, solid-state batteries often use silicon-based anodes, which are susceptible to side reactions with lithium ions during the battery's first charge cycle, leading to irreversible lithium ion consumption and reduced initial cycle efficiency.

[0004] To solve the above problems, the industry often chooses to pre-lithiate the negative electrode to improve the first cycle efficiency of the battery. The industry generally treats it by directly mixing lithium metal strips or lithium metal powder into the negative electrode or pressing it on the surface of the negative electrode active material layer, but this not only has strict requirements on process conditions, but also has safety issues such as flammability and explosion during the processing. In addition, lithium metal will spontaneously react with silicon-based negative electrode active materials to produce lithium-silicon alloys. Therefore, the above preparation method will also result in a large area of ​​lithium-silicon alloys directly exposed to the air in the negative electrode before being assembled into the battery. The large area of ​​lithium-silicon alloys enriched in the air are less stable and flammable in the air, which will cause the above-mentioned negative electrode to have greater safety hazards during storage and battery assembly.

[0005] Summary of the Invention

[0006] In view of this, the present disclosure provides a negative electrode and a preparation method thereof, a secondary battery and an electrical device. The negative electrode has a stable structure and can effectively replenish the consumption of active lithium. In the preparation process of the negative electrode, there is no problem of flammability and explosion of lithium metal, and the risk of large-area enriched lithium-silicon alloy being directly exposed to the air can be fully reduced, thereby achieving negative electrode lithium replenishment while greatly reducing production safety hazards. The secondary battery with the negative electrode has both high first cycle efficiency and good cycle performance.

[0007] In a first aspect, the present disclosure provides a negative electrode, which includes at least one of an inorganic phosphide, an inorganic boride, polysulfide, 81-33-43,4,9,10-perylenetetracarboxylic dianhydride, triquinoline, naphthalene, keto acid, 1,4,5,8-tetrahydroxy-9,10-anthraquinone, [5,10,15,20-tetraethynylporphyrin] magnesium complex, conjugated sulfonyl acid, triphenylphosphine selenide, cuphexaquinone, tris(4-nitrosophenyl)amine, cyclohexanehexaone and dipentamethylenethiuram hexasulfide, as well as a lithium silicon alloy.

[0008] Optionally, the lithium silicon alloy is in granular form, and the D50 particle size of the lithium silicon alloy is less than or equal to 3 μm, and the D50 particle size of the lithium silicon alloy is in the range of 1 μm to 2 μm.

[0009] Optionally, the BET specific surface area of ​​the lithium silicon alloy is 1.0 m 2 / g~2.2m 2 / g range.

[0010] Optionally, the negative electrode further comprises silicon-based negative electrode material particles.

[0011] Optionally, the negative electrode includes at least one of polysulfide benzoic acid, 81-33-43,4,9,10-perylenetetracarboxylic dianhydride, triquinoline, naphthalene, keto acid, 1,4,5,8-tetrahydroxy-9,10-anthraquinone, [5,10,15,20-tetraethynylporphyrin] magnesium complex, conjugated sulfonic acid, triphenylphosphine selenide, cup hexaquinone, tris(4-nitrosophenyl)amine, cyclohexanehexaone and dipentamethylenethiuram hexasulfide.

[0012] Optionally, at least one of the lithium silicon alloy and the inorganic phosphide, inorganic boride, polysulfide, 81-33-43,4,9,10-perylenetetracarboxylic dianhydride, triquinoline, naphthalene, keto acid, 1,4,5,8-tetrahydroxy-9,10-anthraquinone, [5,10,15,20-tetraethynylporphyrin] magnesium complex, conjugated sulfonic acid, selenide triphenylphosphine, cup hexaquinone, tris (4-nitrosophenyl) amine, cyclohexane hexaketone and dipentamethylenethiuram hexasulfide is composed of Li3P, L At least one of i3B, lithium polysulfide ranate, 81-33-43,4,9,10-perylenetetracarboxylic dianhydride lithium, triquinoline lithium, naphthalene lithium, crotonate lithium, 1,4,5,8-tetrahydroxy-9,10-anthraquinone lithium, lithiated [5,10,15,20-tetraethynylporphyrin] magnesium complex, conjugated sulfonate lithium, triphenylphosphine lithium selenide, cuphexaquinone lithium, tris(4-nitrosophenyl)amine lithium, cyclohexanehexaone lithium and bispentamethylenethiuram hexasulfide lithium is reacted in situ with silicon-based negative electrode material particles to generate.

[0013] Optionally, the negative electrode further comprises a solid electrolyte.

[0014] Optionally, the solid electrolyte includes a sulfide solid electrolyte.

[0015] A second aspect of the present disclosure provides a method for preparing a negative electrode, comprising:

[0016] Providing a negative electrode precursor, wherein the negative electrode precursor comprises silicon-based negative electrode material particles and a lithium supplement agent;

[0017] De-lithiation the lithium supplement agent, and the released lithium ions react with the silicon-based negative electrode material particles to obtain a negative electrode comprising a lithium-silicon alloy;

[0018] The lithium supplement comprises at least one of Li3P, Li3B, lithium polysulfide, lithium dianhydride of 81-33-43,4,9,10-perylenetetracarboxylic acid, lithium triquinoline, lithium naphthalene, lithium crotonate, lithium 1,4,5,8-tetrahydroxy-9,10-anthraquinone, lithium [5,10,15,20-tetraethynylporphyrin] magnesium complex, lithium conjugated sulfonate, lithium triphenylphosphine selenide, lithium calixhexaquinone, lithium tris(4-nitrosophenyl)amine, lithium cyclohexanehexatonide and lithium dipentamethylenethiuram hexasulfide.

[0019] Optionally, the lithium supplementation surface capacity of the negative electrode precursor is 0.3 mAh / cm 2 -3.0mAh / cm 2 .

[0020] Optionally, the material of the silicon-based negative electrode material particles includes at least one of silicon element, silicon monoxide and a silicon-carbon composite.

[0021] Optionally, the carbon content of the silicon-carbon composite is less than or equal to 5 wt.%.

[0022] Optionally, the oxygen content of the silicon monoxide is less than or equal to 18 wt.%.

[0023] Optionally, the delithiation of the lithium supplement agent and the reaction of the delithiation with the silicon-based negative electrode material particles to obtain a negative electrode comprising a lithium-silicon alloy includes heating the negative electrode precursor, and the heating includes: drying the negative electrode precursor at 100°C to 150°C for 20min to 40min, and then baking at 100°C to 170°C for 30min to 720min.

[0024] Optionally, delithiation of the lithium supplement agent and reaction of the delithiation with the silicon-based negative electrode material particles to obtain a negative electrode comprising a lithium-silicon alloy comprises assembling the negative electrode precursor into a battery cell and chemically forming the battery cell.

[0025] Optionally, the negative electrode precursor further includes a current collector, and providing the negative electrode precursor includes mixing the silicon-based negative electrode material particles and the lithium supplement agent to obtain a mixture, and disposing the mixture on the surface of the current collector.

[0026] Optionally, the mixture includes the silicon-based negative electrode material particles, solid electrolyte, conductive agent and binder in a mass ratio of (60-99): (0-35): (0-5): (1-5).

[0027] A third aspect of the present disclosure provides a secondary battery, wherein the secondary battery includes the negative electrode according to the first aspect, or the secondary battery includes the negative electrode prepared according to the preparation method according to the second aspect.

[0028] Optionally, the secondary battery further includes a positive electrode, and a solid electrolyte disposed between the negative electrode and the positive electrode.

[0029] A fourth aspect of the present disclosure provides an electric device, comprising the secondary battery according to the third aspect. DETAILED DESCRIPTION

[0030] Silicon-based anode materials (e.g., silicon, silicon dioxide, etc.) have high theoretical specific capacity and are often used as anode materials for solid-state batteries. However, because the surface of silicon-based anode material particles or the material itself contains O atoms, C atoms, etc., the silicon-based anode material will react with active lithium ions to produce substances such as Li4SiO4, resulting in irreversible consumption of active lithium ions, which in turn leads to low first-cycle efficiency of the battery. The industry often uses negative electrode lithium replenishment to improve the first-cycle efficiency of solid-state batteries. The industry generally achieves negative electrode lithium replenishment by directly mixing lithium metal strips or lithium metal powder into the anode or pressing it onto the surface of the anode active material layer. However, this not only has strict requirements on process conditions, but also has safety issues such as flammability and explosion during processing. In addition, lithium metal will spontaneously react with the silicon-based anode active material to produce lithium-silicon alloy. Therefore, the above preparation method will also lead to large-scale enrichment of lithium-silicon alloy in the anode. The large-scale enriched lithium-silicon alloy has poor stability in air and is flammable, resulting in a significant safety hazard during storage and battery assembly of the above-mentioned anode.

[0031] There are also literature reports that a separate lithium metal layer is set in the silicon-based negative electrode to supplement lithium, and the lithium metal layer is set between two stacked silicon-based negative electrode active material layers in an attempt to reduce the risk of lithium metal reacting with air. However, if you want to obtain a negative electrode with the above structure, you must first set the first negative electrode active material layer, the lithium metal layer and the second negative electrode active material layer in sequence on the surface of the negative electrode current collector. Because the lithium metal layer will react violently with substances such as water, the second active material layer can only be prepared by a dry method. The current dry preparation technology makes it difficult to achieve a flatness of the active material layer within 1μm, and the low flatness of the active material layer will cause the active material layer to shrink unevenly during the battery charge and discharge cycle, which can easily lead to battery failure. In addition, there is still the problem of large-area enrichment of lithium metal in the above-mentioned negative electrode, so there is still a large safety risk.

[0032] To solve the above problems, the present disclosure provides a method for preparing a negative electrode, comprising:

[0033] Providing a negative electrode precursor, wherein the negative electrode precursor comprises silicon-based negative electrode material particles and a lithium supplement agent;

[0034] The lithium supplement agent is delithiated, and the delithiated lithium ions react with the silicon-based negative electrode material particles to obtain a negative electrode comprising a lithium-silicon alloy. It can be understood that in some embodiments, the lithium-silicon alloy in the negative electrode is in a granular form.

[0035] The lithium supplement comprises at least one of Li3P, Li3B, lithium polysulfide, lithium dianhydride of 81-33-43,4,9,10-perylenetetracarboxylic acid, lithium triquinoline, lithium naphthalene, lithium crotonate, lithium 1,4,5,8-tetrahydroxy-9,10-anthraquinone, lithium [5,10,15,20-tetraethynylporphyrin] magnesium complex, lithium conjugated sulfonate, lithium triphenylphosphine selenide, lithium calixhexaquinone, lithium tris(4-nitrosophenyl)amine, lithium cyclohexanehexatonide and lithium dipentamethylenethiuram hexasulfide.

[0036] In the embodiments of the present disclosure, for the convenience of description, Li3P and Li3B are referred to as "inorganic lithium supplements" in the specification, and the lithium supplements other than Li3P and Li3B are collectively referred to as "organic lithium supplements".

[0037] There is a potential difference between the lithium supplement agent and the silicon-based negative electrode material particles (for example, Li3P and Li3B, etc.), and / or, the functional groups on the surface of the lithium supplement agent (for example, lithiated carboxylic acid groups, carbonyl groups, ester groups, amino groups, thiol groups, sulfonic acid groups, formyl groups, acetyl groups, etc.) undergo redox reactions, which lowers their chemical barriers and forms a chemical potential difference with the silicon-based negative electrode material particles, so that the silicon atoms in the silicon-based negative electrode material particles can react with lithium ions to form an alloy, thereby in situ forming a lithium-silicon alloy in the silicon-based negative electrode material particles, and the product after the lithium supplement agent is delithiated is dispersed in the negative electrode; therefore, even if a reaction occurs between the lithium supplement agent and the silicon-based negative electrode material particles, no vacancies will be generated in the negative electrode, and the resulting negative electrode structure is stable. Furthermore, the lithium-silicon alloy is formed by the reaction of a lithium replenisher with silicon-based negative electrode material particles, thus avoiding the flammability and explosion issues associated with lithium metal raw materials in the prior art. Furthermore, after the lithium replenisher removes lithium, it forms a delithiation product, which is dispersed within the formed lithium-silicon alloy, reducing the risk of lithium-silicon alloy accumulation. Furthermore, the released lithium ions react with substances on the surface of the silicon-based negative electrode material particles, and / or the lithium ions enter the interior of the silicon-based negative electrode material particles and react with silicon atoms to form a lithium-silicon alloy. Therefore, the newly produced lithium-silicon alloy is essentially divided into lithium-rich regions and silicon-rich regions, further reducing the risk of large-scale accumulation of lithium-silicon alloy and exposure to air.

[0038] The above preparation method is simple and easy, with strong process reliability, and realizes one-step lithium replenishment, simplifying the lithium replenishment process; moreover, the above preparation method does not require the introduction of lithium metal to form a lithium-silicon alloy, has relatively loose requirements on the preparation environment, has high production efficiency, greatly improves the safety of the negative electrode during the preparation process, and can realize large-scale industrial production.

[0039] In some embodiments of the present disclosure, delithiation of the lithium replenisher, allowing the released lithium ions to react with the silicon-based negative electrode material particles to produce a negative electrode comprising a lithium-silicon alloy, includes heating the negative electrode precursor. This promotes the formation of the silicon-lithium alloy. In some specific embodiments, during the heating process, some lithium in the lithium replenisher is released to form a lithium-silicon alloy, resulting in no large-scale accumulation of the lithium-silicon alloy in the negative electrode.

[0040] In some embodiments of the present disclosure, the heat treatment includes drying the negative electrode precursor at 100°C to 150°C for 20 to 40 minutes, and then baking it at 100°C to 170°C for 30 to 720 minutes. In some specific embodiments, the negative electrode precursor is vacuum-baked at 105°C to 135°C for 6 to 12 hours. In particular, during the baking process, at the above temperature, the in-situ reaction efficiency of the lithium supplement and the silicon-based negative electrode material particles is high, which is conducive to improving production efficiency. Exemplarily, the drying temperature can be 100°C, 110°C, 120°C, 130°C, 140°C, 145°C, etc., and the drying time can be 20 minutes, 25 minutes, 30 minutes, 35 minutes, etc. Exemplarily, the baking temperature can be 100°C, 110°C, 120°C, 130°C, 140°C, 145°C, 150°C, 160°C, 165°C, etc. Illustratively, the baking time can be 30 min, 35 min, 40 min, 50 min, 60 min, 100 min, 150 min, 200 min, 250 min, 300 min, 350 min, 400 min, 450 min, 500 min, 550 min, 600 min, 650 min, 700 min, etc.

[0041] In some embodiments of the present disclosure, the lithium supplement agent is delithiated, and the released lithium ions react with the silicon-based negative electrode material particles to obtain a negative electrode containing a lithium-silicon alloy, which includes assembling the negative electrode precursor into a battery cell and chemically forming the battery cell. In this way, the release of lithium ions from the lithium supplement agent and the generation of lithium-silicon alloys can be fully promoted. It can be understood that even if a large amount of lithium-silicon alloys are generated in the above process, these lithium-silicon alloys are also generated in the closed environment of the battery cell. Even if a large area of ​​lithium-silicon alloys is enriched at this time, there is no problem of these lithium-silicon alloys being directly exposed to the air. It can be understood that for silicon-based negative electrode materials, the surface or the body of the silicon-based negative electrode material carry active sites (for example, O atoms, C atoms, etc.). During the first cycle of the battery, the silicon-based negative electrode material will capture the active lithium ions released from the positive electrode and react with the above-mentioned active sites, resulting in irreversible loss of active lithium ions, causing the first efficiency of the battery to decrease and affecting the cycle performance of the battery. During the above-mentioned formation process, the lithium released by the lithium supplement agent can replace the active lithium ions released from the positive electrode and be captured by the silicon-based negative electrode material particles, thereby improving the first cycle efficiency and cycle performance of the battery cell (i.e., battery). It can be understood that the battery cell also includes a positive electrode and a solid electrolyte layer located between the positive electrode and the negative electrode. The above-mentioned positive electrode and solid electrolyte layer can be selected from any known positive electrode and solid electrolyte layer in the art. Specifically, the material of the above-mentioned solid electrolyte layer is preferably a sulfide solid electrolyte.

[0042] It is understood that in some specific embodiments, delithiation of the lithium supplement agent, and reaction of the released lithium ions with the silicon-based negative electrode material particles to produce a negative electrode comprising a lithium-silicon alloy, comprises first heating a negative electrode precursor, then assembling the heated negative electrode precursor into a battery cell, and then forming the battery cell. The negative electrode precursor is then cooled before being assembled into a battery cell.

[0043] In some embodiments of the present disclosure, the lithium supplementation surface capacity of the negative electrode precursor is 0.3 mAh / cm 2 -3.0mAh / cm 2 In some embodiments of the present disclosure, the lithium replenishment surface capacity of the negative electrode is 0.3 mAh / cm 2 -3.0mAh / cm 2 In the present disclosure, the lithium replenishment surface capacity of the negative electrode precursor refers to the irreversible capacity of the negative electrode precursor before the first charge and discharge cycle. For example, the lithium replenishment surface capacity of the negative electrode precursor can be 0.30 mAh / cm 2 , 0.32mAh / cm 2 , 0.35mAh / cm 2 , 0.40mAh / cm 2 , 0.45mAh / cm 2 , 0.50mAh / cm 2 , 0.80mAh / cm 2 , 0.90mAh / cm 2 、1.00mAh / cm 2 , 1.20mAh / cm 2 、1.50mAh / cm 2 、1.80mAh / cm 2 , 2.00mAh / cm 2 , 2.20mAh / cm 2 , 2.50mAh / cm 2 , 2.80mAh / cm 2 , 2.90mAh / cm 2 In the embodiments of the present disclosure, the lithium replenishment surface capacity of the negative electrode precursor is: when the negative electrode precursor and the positive electrode are assembled into a battery and charged and discharged at a rate of 0.1C, the lithium replenishment surface capacity of the negative electrode precursor = (the initial charge capacity of the battery - the initial discharge capacity of the battery) / the total area of ​​the negative electrode active material layer. The unit of the lithium replenishment surface capacity of the negative electrode precursor is mAh / cm 2. The above-mentioned positive electrode includes a positive electrode current collector and a positive electrode material layer. The positive electrode material layer is composed of a Li3BO3-coated NCM811 positive electrode, a Li6PS5Cl solid electrolyte, a Super P conductive agent, and polytetrafluoroethylene in a mass ratio of 85:13:1.5:0.5. Controlling the lithium replenishing surface capacity of the negative electrode precursor within the above-mentioned range can not only contribute a sufficient amount of active lithium ions during the battery cycle to compensate for the irreversible consumption of active lithium ions and improve the battery's first cycle efficiency; at the same time, it will not affect the reversible capacity of the final negative electrode, thereby helping to ensure a high energy density of the battery. In addition, it can be understood that the lithium replenishing surface capacity of the negative electrode precursor mainly depends on the amount of lithium replenishing agent added during the preparation of the negative electrode precursor. Controlling the lithium replenishing surface capacity of the negative electrode precursor within an appropriate range also controls the amount of lithium replenishing agent added within an appropriate range, thereby effectively reducing the risk of local lithium precipitation during the battery formation process, thereby ensuring good battery cycle performance. In some embodiments, the lithium ions released by the lithium replenishing agent react with some silicon-based negative electrode material particles to form a lithium-silicon alloy. Therefore, at this time, the prepared negative electrode includes the lithium-silicon alloy, silicon-based negative electrode material particles and the product after the lithium supplement agent is delithiated.

[0044] In some embodiments of the present disclosure, the negative electrode precursor further includes a current collector, and providing the negative electrode precursor includes mixing the silicon-based negative electrode material particles and the lithium replenisher to obtain a mixture, and applying the mixture to the surface of the current collector. This allows the silicon-based negative electrode particles and the lithium replenisher to fully contact each other, thereby facilitating a sufficient reaction between the two to form a silicon-lithium alloy.

[0045] In some embodiments of the present disclosure, silicon-based negative electrode material particles and a lithium supplement agent are dispersed in a solvent and mixed to obtain a negative electrode slurry (i.e., the mixture is a negative electrode slurry). In this way, the silicon-based negative electrode material particles and the lithium supplement agent can fully contact each other during the preparation of the negative electrode slurry, and the lithium supplement agent will not react with other substances in the slurry (e.g., the solvent), thereby obtaining a negative electrode slurry with high uniformity and good stability.

[0046] In some embodiments of the present disclosure, silicon-based anode material particles include, but are not limited to, elemental silicon, silicon monoxide (SiOx), and silicon-carbon composites. Silicon-carbon composites include, but are not limited to, mixtures of silicon particles and carbon materials, and silicon particles coated with a carbon layer (silicon as the core).

[0047] In some embodiments of the present disclosure, the silicon-based negative electrode material particles are selected from silicon single substance particles. At this time, the above-mentioned negative electrode will change during the cycle of the battery, and the granular lithium-silicon alloy will gradually fuse into a block-like substance. Specifically, during the formation / charge and discharge cycle of the solid-state battery system, the silicon single substance expands after being amorphized by lithium insertion, and can undergo welding-fusion with other silicon single substance particles to form a block composed of amorphous materials. The block has sufficient electronic conductivity and ionic conductivity, and the structure has considerable stability, so it can circulate relatively stably in the solid-state battery system. In addition, silicon single substance is stable to the electrolyte, and the first efficiency of the battery can be as high as 82-85%.

[0048] In some specific embodiments of the present disclosure, the mass percentage of carbon is less than or equal to 5.0% based on the total mass of the silicon-carbon composite. For example, the mass percentage of carbon can be, but is not limited to, 0.1%, 0.5%, 1.0%, 2.0%, 3.0%, 4.0%, 5.0%, etc. Further, in some specific embodiments, the thickness of the carbon layer on the surface of the silicon core is in the range of 3nm to 10nm. For example, the thickness of the above-mentioned carbon layer can be, but is not limited to, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, etc. In this way, lithium ions are facilitated to pass through the carbon layer and react with the silicon core to form a lithium-silicon alloy.

[0049] In some specific embodiments of the present disclosure, SiO x Based on the total mass of the battery, the oxygen content is less than or equal to 18%. In this way, the impact of oxygen on the initial efficiency will be reduced to an acceptable range, reducing the amount of lithium replenishment required, thereby reducing the production cost of the electrode and battery.

[0050] In some embodiments of the present disclosure, the D50 particle size of the silicon-based negative electrode material particles is less than or equal to 3μm. In some specific embodiments, the D50 particle size of the silicon-based negative electrode material particles is in the range of 0.2μm to 2μm. In this way, the silicon-based negative electrode material particles have a more suitable specific surface area, which is conducive to the reaction of lithium ions released from the lithium supplement agent with it / facilitating the diffusion of lithium ions released from the lithium supplement agent to the silicon-based negative electrode material particles, thereby facilitating the rapid formation of lithium-silicon alloys. In addition, because the above-mentioned D50 particle size is a genetic structure, controlling the D50 particle size of the silicon-based negative electrode material particles within the above-mentioned range is also conducive to the extraction / intercalation of active lithium ions during the battery cycle, and thus is beneficial to the rate performance of the battery. In some embodiments of the present disclosure, the BET specific surface area of ​​the silicon-based negative electrode material particles is 1.0m 2 / g~2.2m 2 For example, the BET specific surface area of ​​silicon-based negative electrode material particles can be 1.0 m 2 / g, 1.1m 2 / g, 1.2m 2 / g, 1.3m2 / g, 1.4m 2 / g, 1.5m 2 / g, 1.6m 2 / g, 1.7m 2 / g, 1.8m 2 / g, 1.9m 2 / g, 2.0m 2 / g, 2.1m 2 / g, 2.15m 2 / g, etc. This is beneficial for the reaction with the inorganic lithium supplement during the heating process, and also for the diffusion of lithium ions released by the organic lithium supplement to the silicon-based negative electrode material particles, thereby facilitating the formation of lithium-silicon alloys; at the same time, it is also beneficial for the deintercalation and insertion of lithium ions during the subsequent battery charge and discharge cycles.

[0051] In some embodiments of the present disclosure, a binder, an optional solid electrolyte, and an optional conductive agent are further added to the mixture. For ease of description, the mixture of silicon-based anode material particles, a binder, and any solid electrolyte and conductive agent is referred to as the "first raw material." In some specific embodiments, the first raw material includes the following components in parts by weight: 60 to 99 parts of the silicon-based anode material particles, 0 to 35 parts of the solid electrolyte, 0 to 5 parts of the conductive agent, and 1 to 5 parts of the binder. For example, the weight of the silicon-based anode material particles can be 60, 62, 65, 68, 70, 72, 75, 78, 80, 82, 85, 88, 90, 92, 95, 98, etc. For example, the weight of the solid electrolyte can be 1, 2, 5, 8, 10, 12, 15, 18, 20, 22, 25, 28, etc. For example, the weight percentage of the conductive agent can be 0, 1, 2, 3, 4, 5, etc. For example, the weight percentage of the binder can be 0, 1, 2, 3, 4, 5, etc. In other words, the mixture includes the silicon-based negative electrode material particles, the solid electrolyte, the conductive agent, and the binder in a mass ratio of (60-99): (0-35): (0-5): (1-5).

[0052] In some embodiments of the present disclosure, silicon-based negative electrode material particles, solid electrolyte, conductive agent and binder can be fully mixed to obtain a first raw material, and then the first raw material is mixed with a lithium supplement to obtain the aforementioned mixture.

[0053] In some specific embodiments of the present disclosure, the first raw material, that is, silicon-based negative electrode material particles, solid electrolyte, conductive agent and binder can be mixed by a high-speed disperser to obtain the first raw material. In some specific embodiments, the rotation speed of the high-speed disperser is 500rpm~2000rpm, and the mixing time is 10min~120min, preferably 20min~60min. Then, a small amount of solvent is added to the above-mentioned first raw material and kneaded, and the kneading time is 30min~120min. After the kneading is completed, the solvent is continued to be added to the obtained material so that the solid content of the slurry reaches 40%~60%, and the lithium supplement agent is added at the same time, and stirred under vacuum for 10min~60min to obtain the negative electrode slurry (that is, the aforementioned mixture), and the viscosity of the negative electrode slurry is made to reach 1800Pa / s~3200Pa / s.

[0054] In some embodiments of the present disclosure, the mass percentage of the silicon-based negative electrode material particles is 90% to 99% based on the total mass of the first raw material. For example, the mass percentage of the silicon-based negative electrode material particles in the first raw material may be, but is not limited to, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, etc.

[0055] In some embodiments of the present disclosure, solid electrolytes include but are not limited to Li6PS5Cl, Li 10 GeP2S 12 、 Li 10 Ge 0.5 Si 0.5 P2S 12 、Li7P3S 11 , Li2S·P2S5, Li3YCl6, Li3InCl6 and other lithium ion electrolytes. In some specific implementations, the above solid electrolyte is selected from Li6PS5Cl, Li 10 GeP2S 12 、Li 10 Ge 0.5 Si 0.5 P2S 12 、Li7P3S 11 , Li2S·P2S5 and other sulfide solid electrolytes.

[0056] In some embodiments of the present disclosure, the conductive agent includes but is not limited to one-dimensional conductive agents such as Super P and acetylene black, and one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, etc.

[0057] In some embodiments of the present disclosure, the binder includes, but is not limited to, one or more of AA, PAA-Li, PAA-Na, PI, CMC, SBR, HNBR, PAN, PVDF, PMMA, and PEO. Alternatively, the binder is selected from PAA-Li, PAA-Na, PI, SBR, HNBR, and the like.

[0058] In some embodiments of the present disclosure, the solvent used to disperse the mixture includes but is not limited to water, xylene, anisole, tetrahydrofuran, n-heptane, n-hexane, etc.

[0059] In some embodiments of the present disclosure, the aforementioned mixed material is formed on the surface of the current collector to form a negative electrode material layer precursor, and the lithium replenishing surface capacity (i.e., lithium replenishing surface capacity) of the negative electrode material layer precursor is 0.3 mAh / cm 2 -3.0mAh / cm 2 .

[0060] It can be understood that silicon-based negative electrode material particles include elemental silicon particles, silicon dioxide particles, silicon-carbon composite particles, etc. In general, due to the natural oxidation of silicon elements, the surface and / or interior of the above-mentioned silicon-based negative electrode material particles will have a SiO2 layer several nanometers thick. Specifically, in some embodiments of the present disclosure, when the lithium supplement includes any one of Li3P and Li3B, Li3P and Li3B will react with the SiO2 layer of the above-mentioned silicon-based negative electrode material particles to delithiate and generate lithium-silicon alloys, as well as two inorganic products, inorganic phosphides and inorganic borides. These inorganic products will inherit the position of the above-mentioned inorganic lithium supplement and be dispersed in the negative electrode. In this way, the risk of large-scale enrichment of lithium-silicon alloys can be significantly reduced, the stability of the obtained negative electrode during storage and subsequent battery assembly can be improved, and the risk of safety accidents can be greatly reduced.

[0061] In some embodiments of the present disclosure, the above-mentioned lithium replenisher includes the above-mentioned organic lithium replenisher. The above-mentioned organic lithium replenisher can spontaneously undergo a delithiation reaction, especially under heating conditions. The released lithium ions will quickly diffuse into the interior of the silicon-based negative electrode material particles and react in situ with the silicon atoms inside the silicon-based negative electrode material particles to form a lithium-silicon alloy. At the same time, the organic lithium replenisher after delithiation is converted into an organic product and dispersed in the gaps between the lithium-silicon alloy (or, between the gaps between the lithium-silicon alloy and the silicon-based negative electrode material particles). In particular, the above-mentioned organic product has a certain viscosity and can help bind the composite active material particles in the negative electrode to improve the structural stability of the negative electrode, thereby also benefiting the cycle performance of the battery. At the same time, the surface of the lithium-silicon alloy particles is a silicon-rich region, which avoids large-scale enrichment of the silicon-lithium alloy in the negative electrode, thereby improving the stability and safety performance of the negative electrode. It can be understood that if the surface of the silicon-based negative electrode material particles has a SiO2 layer, then the surface of the resulting composite active material particles will also have a corresponding SiO2 layer.

[0062] In the present disclosure, it is understood that in extreme cases, the lithium supplement agent may not react completely. In this case, a very small amount of lithium supplement agent may remain in the final negative electrode, which will not affect the performance of the battery.

[0063] An embodiment of the present disclosure provides a negative electrode, including at least one of an inorganic phosphide, an inorganic boride, polysulfide, 81-33-43,4,9,10-perylenetetracarboxylic dianhydride, triquinoline, naphthalene, keto acid, 1,4,5,8-tetrahydroxy-9,10-anthraquinone, [5,10,15,20-tetraethynylporphyrin] magnesium complex, conjugated sulfonyl acid, triphenylphosphine selenide, cup hexaquinone, tris(4-nitrosophenyl)amine, cyclohexanehexaone and dipentamethylenethiuram hexasulfide, and a lithium silicon alloy.

[0064] In some embodiments of the present disclosure, the above-mentioned negative electrode is prepared by the preparation method provided in the examples of the present disclosure.

[0065] As mentioned above, the battery with the above-mentioned negative electrode can achieve a higher first cycle efficiency and better cycle performance, which will not be repeated here. At the same time, the lithium in the silicon-lithium alloy can also make up for the "continuous loss of active lithium due to the difficulty of continuous lithium removal in the ordinary silicon-based negative electrode in the related technology during the cycle", thereby further improving the cycle performance of the battery. In addition, the above-mentioned polysulfide, 81-33-43,4,9,10-perylenetetracarboxylic acid dianhydride, triquinoline, naphthalene, keto acid, 1,4,5,8-tetrahydroxy-9,10-anthraquinone, [5,10,15,20-tetraethynylporphyrin] magnesium complex, conjugated sulfonic acid, selenide triphenylphosphine, cup hexaquinone, tris (4-nitrosophenyl) amine, cyclohexane hexaketone and hexasulfide dipentamethylenethiuram also have a certain viscosity, which can help maintain the structural stability of the negative electrode during the cycle and is also beneficial to the cycle performance of the battery.

[0066] In the present disclosure, Raman, infrared and other testing methods can be used to characterize the presence of inorganic phosphides, inorganic borides, polysulfide, 81-33-43,4,9,10-perylenetetracarboxylic dianhydride, triquinoline, naphthalene, keto acid, 1,4,5,8-tetrahydroxy-9,10-anthraquinone, [5,10,15,20-tetraethynylporphyrin] magnesium complex, conjugated sulfonic acid, triphenylphosphine selenide, cup hexaquinone, tris (4-nitrosophenyl) amine, cyclohexanehexaketone and hexasulfide bispentamethylenethiuram.

[0067] In some embodiments of the present disclosure, the inorganic phosphide includes but is not limited to phosphorus oxide. The inorganic boride includes but is not limited to boron oxide.

[0068] In some embodiments of the present disclosure, the inorganic phosphide and inorganic boride are in granular form. Specifically, the granular inorganic phosphide and inorganic boride are dispersed in the negative electrode and filled in the gaps between the lithium-silicon alloy. In some specific embodiments, the D50 particle size of the inorganic phosphide and inorganic boride is independently 50nm to 800nm. Exemplarily, the D50 particle size of the inorganic phosphide and inorganic boride can be independently 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, etc.

[0069] In some embodiments of the present disclosure, the negative electrode includes at least one of polysulfide, 1-33-43,4,9,10-perylenetetracarboxylic dianhydride, triquinoline, naphthalene, keto acid, 1,4,5,8-tetrahydroxy-9,10-anthraquinone, [5,10,15,20-tetraethynylporphyrin] magnesium complex, conjugated sulfonyl acid, triphenylphosphine selenide, calixhexaquinone, tris(4-nitrosophenyl)amine, cyclohexanehexaone, and dipentamethylenethiuram hexasulfide. Each of these substances has a certain viscosity, which helps maintain the structural stability of the negative electrode and, in turn, improves the cycling stability of the battery. In some embodiments of the present disclosure, each of these substances is distributed between the gaps in the lithium-silicon alloy and provides a certain adhesive effect.

[0070] For the convenience of description, in the following text, inorganic phosphides and inorganic borides are collectively referred to as "first inorganic materials"; polysulfonated ranic acid, 81-33-43,4,9,10-perylenetetracarboxylic dianhydride, triquinoline, naphthalene, ketoic acid, 1,4,5,8-tetrahydroxy-9,10-anthraquinone, [5,10,15,20-tetraethynylporphyrin] magnesium complex, conjugated sulfonic acid, triphenylphosphine selenide, cuphexaquinone, tris(4-nitrosophenyl)amine, cyclohexanehexaone and dipentamethylenethiuram hexasulfide are collectively referred to as "first organic materials"; and the first inorganic material and the first organic material are collectively referred to as "first material".

[0071] In some embodiments of the present disclosure, the negative electrode includes a current collector and a negative electrode material layer disposed on at least one surface of the current collector. The mass percentage of the lithium-silicon alloy in the negative electrode material layer is 90% to 99% based on the total mass of the negative electrode material layer.

[0072] In some embodiments of the present disclosure, the negative electrode further comprises silicon-based negative electrode material particles. In this case, the silicon-based negative electrode material particles are dispersed within the lithium-silicon alloy. As previously mentioned, the presence of silicon-based negative electrode material particles and the mass proportion of silicon-based negative electrode material particles in the negative electrode are related to the amount of lithium supplement added during the negative electrode preparation process and will not be further elaborated here. In this case, the combined mass proportion of the silicon-based negative electrode material particles and the lithium-silicon alloy in the negative electrode material layer is 90% to 99%.

[0073] In some embodiments of the present disclosure, the lithium silicon alloy is in granular form, and the D50 particle size of the lithium silicon alloy is less than or equal to 3 μm. For example, the D50 particle size of the lithium silicon alloy may be, but is not limited to, 0.1 μm, 0.2 μm, 0.5 μm, 0.8 μm, 0.9 μm, 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2.0 μm, 2.2 μm, 2.5 μm, 2.8 μm, etc. In some specific embodiments, the D50 particle size of the lithium silicon alloy is in the range of 1 μm to 2 μm. For example, the D50 particle size of the lithium silicon alloy may be 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, etc. Controlling the D50 particle size of the lithium-silicon alloy within the above range not only facilitates the insertion / extraction of lithium ions, but also increases the compaction density of the negative electrode, which is beneficial to the energy density of the battery. In the embodiments of the present disclosure, the D50 particle size of the lithium-silicon alloy can be measured using a laser particle size analyzer.

[0074] In some embodiments of the present disclosure, when the negative electrode further includes silicon-based negative electrode material particles, the D50 particle size of the silicon-based negative electrode material particles is less than or equal to 3 μm. Based on the negative electrode preparation method, it is not difficult to understand that the D50 particle size of the silicon-based negative electrode material particles is essentially the same as the D50 particle size of the lithium-silicon alloy. Therefore, this description is not repeated here.

[0075] In some embodiments of the present disclosure, the BET specific surface area of ​​the lithium silicon alloy is 1.0 m 2 / g~2.2m 2 For example, the BET specific surface area of ​​the lithium silicon alloy can be 1.0 m 2 / g, 1.1m 2 / g, 1.2m 2 / g, 1.3m 2 / g, 1.4m 2 / g, 1.5m 2 / g, 1.6m 2 / g, 1.7m 2 / g, 1.8m 2 / g, 1.9m 2 / g, 2.0m 2 / g, 2.1m2 / g, 2.15m 2 / g, etc. In this way, it is beneficial for the rapid diffusion of lithium ions at the electrode level when the battery electrode is first intercalated with lithium, and for the deintercalation of active lithium ions during the cycle before complete lithiation of charge and discharge. In the embodiment of the present disclosure, the BET specific surface area of ​​the lithium-silicon alloy is tested by gas adsorption and desorption method, wherein the gas used can be nitrogen. In some specific embodiments, the BET specific surface area of ​​the silicon-based negative electrode material particles is 1.0m 2 / g~2.2m 2 / g range.

[0076] In some embodiments of the present disclosure, the lithium-silicon alloy and the first material are formed by in-situ reaction of at least one of Li3P, Li3B, lithium polysulfide, lithium 81-33-43,4,9,10-perylenetetracarboxylic dianhydride, lithium triquinoline, lithium naphthalene, lithium crotonate, lithium 1,4,5,8-tetrahydroxy-9,10-anthraquinone, lithium [5,10,15,20-tetraethynylporphyrin] magnesium complex, lithium conjugated sulfonate, lithium triphenylphosphine selenide, lithium calixhexaquinone, lithium tris(4-nitrosophenyl)amine, lithium cyclohexanehexatonide, and lithium dipentamethylenethiuram hexasulfide with silicon-based negative electrode material particles. This allows the lithium-silicon alloy to be uniformly dispersed in the negative electrode, greatly reducing the risk of large-scale accumulation of the lithium-silicon alloy and significantly improving the safety and storage stability of the negative electrode.

[0077] In some embodiments of the present disclosure, the negative electrode further comprises a solid electrolyte. In some specific embodiments, the solid electrolyte in the negative electrode is selected from a sulfide solid electrolyte, wherein the sulfide solid electrolyte includes but is not limited to Li6PS5Cl, Li 10 GeP2S 12 、Li 10 Ge 0.5 Si 0.5 P2S 12 、Li7P3S 11 , Li2S·P2S5, etc. In some specific embodiments of the present disclosure, the solid electrolyte in the negative electrode is dispersed in the negative electrode material layer. This solid electrolyte can buffer the expansion of the lithium-silicon alloy and / or silicon-based negative electrode material and provide suitable ionic conductivity, thereby improving the electrochemical performance of the negative electrode.

[0078] The present disclosure also provides a secondary battery comprising the negative electrode provided in the present disclosure, or comprising a negative electrode produced by the negative electrode production method provided in the present disclosure. Due to the negative electrode provided in the present disclosure, the secondary battery has a high first cycle efficiency and good cycle performance.

[0079] In some specific embodiments, when the silicon-based negative electrode material particles are silicon elemental particles, the negative electrode after several charge and discharge cycles includes a negative electrode material layer, the negative electrode material layer includes bulk amorphous silicon, and the first inorganic material and / or first organic material is dispersed in the bulk amorphous silicon.

[0080] In some embodiments of the present disclosure, the secondary battery further includes a positive electrode and a solid electrolyte disposed between the positive electrode and the negative electrode.

[0081] In some embodiments of the present disclosure, the secondary battery is an all-solid-state battery.

[0082] In some embodiments of the present disclosure, the N / P ratio (ratio of the negative electrode capacity to the positive electrode capacity of the battery) of the secondary battery is 1.03-3. For example, the N / P ratio of the secondary battery can be 1.03, 1.05, 1.07, 1.10, 1.13, 1.15, 1.20, 1.50, 2.00, 2.50, 3.00, etc.

[0083] In some embodiments of the present disclosure, the secondary battery has an areal capacity of 4.5-7 mAh / cm 2 , preferably 5mAh / cm 2 -6mAh / cm 2 In the embodiments of the present disclosure, the surface capacity of the secondary battery is controlled by the loading of the positive electrode. A person skilled in the art can select the surface capacity of the battery according to actual needs, and the present disclosure does not impose any limitation on this.

[0084] In the present disclosure, the above-mentioned positive electrode can be any positive electrode known in the art. The positive electrode includes a positive electrode current collector, a positive electrode active material layer arranged on the surface of the positive electrode current collector, wherein the active material layer includes a positive electrode active material, a solid electrolyte, a binder and a conductive agent. In some embodiments of the present disclosure, the mass ratio of the positive electrode active material, the solid electrolyte, the binder and the conductive agent is 70~85:10~25:0.5~3:0.5~2. Exemplarily, the mass ratio of the positive electrode active material, the solid electrolyte, the binder and the conductive agent can be 70:25:2.5:2.5, 70:25:2:3, 75:23:1:1, 80:18:1:1, 85:13:0.5:1.5, etc. In the present disclosure, the positive electrode current collector can be any material known in the art. In some specific embodiments, the current collector is preferably a carbon-coated aluminum foil. In some embodiments of the present disclosure, the positive electrode active material includes LiNi x Co y Mn zO2, wherein x>0, y>0, z>0, x+y+z=1. In some specific embodiments, the positive electrode active material is in a granular form, and the positive electrode active material particles have a coating layer, and the coating layer material includes but is not limited to LiNbO3, Li2O·ZrO2, Li3BO3, Al2O3, BaTiO3, Li 1.3 Al 0.3 Ti 1.7 P3O 12 , LIPON, TiS2, etc. In some specific embodiments, the thickness of the coating layer is 2nm-15nm, preferably 5nm-10nm. For example, the thickness of the coating layer can be, but is not limited to, 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 12nm, 15nm, etc.

[0085] In some embodiments of the present disclosure, the solid electrolyte in the positive electrode active material layer includes but is not limited to Li6PS5Cl, Li 10 GeP2S 12 、Li 10 Ge 0.5 Si 0.5 P2S 12 、Li7P3S 11 , Li2S·P2S5, Li3YCl6, Li3InCl6 and other lithium ion electrolytes.

[0086] In some embodiments of the present disclosure, the binder in the positive electrode active material layer includes, but is not limited to, one or more of nitrile rubber (NBR), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), and polytetrafluoroethylene (PTFE). In some embodiments of the present disclosure, the conductive agent in the positive electrode active material layer includes, but is not limited to, one or more of Super P, acetylene black, multi-walled carbon nanotubes (MWCNTs), vapor-grown carbon fibers (VGCFs), and graphene.

[0087] In the present disclosure, the solid electrolyte layer is any solid electrolyte layer known in the art. In some embodiments of the present disclosure, the solid electrolyte layer includes a solid electrolyte and a binder. The mass ratio of the solid electrolyte to the binder is 90 to 99.5:0.5 to 10. For example, the mass ratio of the solid electrolyte to the binder can be 90:10, 92:8, 95:5, 97:3, 99.5:0.5, etc. For example, the solid electrolyte includes but is not limited to Li6PS5Cl, Li 10 GeP2S 12 、Li 10 Ge 0.5 Si 0.5 P2S 12、Li7P3S 11 , Li2S·P2S5 and other lithium ion electrolytes. Exemplarily, the binder includes, but is not limited to, one or more of PVDF5130, PVDF75130, PVDF21216, PVDF6020, PVDF-HVS900, PVDF-HFP, PVDF-LBG, NBR, HNBR, styrene-butadiene rubber (SBR), styrene-butadiene-styrene block copolymer (abbreviated as SBS), or SEBS.

[0088] In some embodiments of the present disclosure, the thickness of the solid electrolyte layer is 20 μm to 50 μm. In some specific embodiments, the thickness of the solid electrolyte layer is 25 μm to 35 μm. For example, the thickness of the solid electrolyte layer can be, but is not limited to, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, etc.

[0089] In some embodiments of the present disclosure, when assembling a secondary battery, the negative electrode (or, negative electrode precursor), solid electrolyte layer and positive electrode provided in the embodiments of the present disclosure are assembled and then pressure packaged. In some embodiments, after assembling the battery, the battery is placed in a warm isostatic press for pressure packaging, and the temperature setting range is 50°C to 160°C. In some specific embodiments, the packaging temperature is 80°C to 140°C. In some embodiments, the packaging pressure is 5MPa to 700MPa. In some specific embodiments, the packaging pressure is 300MPa to 650MPa. In some embodiments, the pressure holding time of packaging is 1 to 360min. In some specific embodiments, the pressure holding time of packaging is 10min to 120min. The isostatic pressing pressure packaging is repeated 1 to 10 times, preferably 1 to 3 times. After the battery pressure packaging is completed, the battery is taken out and wiped clean to complete the assembly of the above-mentioned secondary battery.

[0090] The present disclosure also provides an electric device, which includes the secondary battery. Due to the secondary battery provided by the present disclosure, the electric device has good market competitiveness.

[0091] In some embodiments of the present disclosure, the above-mentioned electrical equipment includes but is not limited to 3C electronic products, vehicles, etc.

[0092] The technical solution of the present disclosure is further illustrated below with multiple embodiments.

[0093] Example 1

[0094] (1) Preparation of negative electrode precursor: Weigh nano-silicon (D50 particle size is 1.0μm), Li6PS5Cl solid electrolyte, NBR binder and Super P conductive agent in a mass ratio of 70:20:3:7. Fully dissolve NBR in n-heptane solvent. Pre-dry-mix micron silicon, Li6PS5Cl solid electrolyte and Super P conductive agent by a 2000rpm degassing machine. After mixing evenly, drop an appropriate amount of NBR solution and an appropriate amount of n-heptane solvent into the mixture and knead the mixture for 60 minutes. After kneading, add an appropriate amount of n-heptane solvent and triquinoline lithium to the mixture. The amount of triquinoline lithium added corresponds to a lithium supplement amount of 1mAh / cm 2 , bringing the solids content to 55%. After 30 minutes of dispersion at 2000 rpm, the slurry reached a viscosity of 2300 Pa / s before coating on the copper-based current collector. After coating, air-dry at 120°C for 30 minutes. The completed electrode sheet was roller-compacted and then baked in a vacuum oven at 150°C for 12 hours to obtain the negative electrode precursor.

[0095] (2) Preparation of positive electrode: Li3BO3-coated NCM811 positive electrode, Li6PS5Cl solid electrolyte, Super P conductive agent, and PTFE binder were weighed in a mass ratio of 85:13:1.5:0.5. The powder was mixed and ground in a high-speed disperser at 2000 rpm for 60 min, and then dry-rolled to form a film and transferred to a carbon-coated aluminum foil by rolling. The surface capacity of the positive electrode was 5 mAh / cm 2 .

[0096] (3) Preparation of solid electrolyte layer: Li6PS5Cl solid electrolyte and HNBR binder were weighed in a mass ratio of 98:2. The hydrogenated nitrile rubber (HNBR) binder was pre-dissolved in xylene, and then the Li6PS5Cl solid electrolyte was added and mixed by ball milling. The resulting slurry was directly coated on the prepared negative electrode surface and dried at 120°C under a forced air condition for 30 minutes. After dyeing, the solid electrolyte layer was dried at 110°C under vacuum for 360 minutes to obtain the solid electrolyte layer.

[0097] (4) Battery Assembly: The composite electrode sheets of the positive electrode and solid electrolyte layer-negative electrode precursor prepared above were laminated, bonded, and welded to the tabs for packaging. Warm isostatic pressing was performed twice at 120°C and 600 MPa for 30 minutes to obtain the battery of Example 1. The N / P ratio of this battery was 1.03.

[0098] Example 2

[0099] (1) Preparation of negative electrode precursor: Weigh micron silicon (D50 particle size is 1.6μm), Li6PS5Cl solid electrolyte, PAA (polyacrylic acid) binder and Super P conductive agent in a mass ratio of 95:0:3:2. Fully dissolve PAA in water solvent. Pre-dry micron silicon, Li6PS5Cl solid electrolyte and Super P conductive agent by a 2000rpm degassing machine. After mixing evenly, drop an appropriate amount of PAA solution and an appropriate amount of water solvent into the mixture and knead the mixture for 60 minutes. After kneading, add an appropriate amount of water and naphthalene lithium to the mixture. The amount of naphthalene lithium added corresponds to a lithium supplement amount of 1.2mAh / cm 2 , bringing the solids content to 50%. After 30 minutes of dispersion at 2000 rpm, the slurry reached a viscosity of 2100 Pa / s before coating on the copper-based current collector. After coating, air dry at 120°C for 30 minutes. The completed electrode sheet was roller-compacted and then baked in a vacuum oven at 160°C for 12 hours to obtain the negative electrode precursor.

[0100] (2) Preparation of positive electrode: Li3BO3-coated NCM811 positive electrode, Li6PS5Cl solid electrolyte, Super P conductive agent, and PTFE binder were weighed in a mass ratio of 85:13:1.5:0.5. The powder was mixed and ground in a high-speed disperser at 2000 rpm for 60 min, and then dry-rolled to form a film and transferred to a carbon-coated aluminum foil by rolling. The surface capacity of the positive electrode was 6 mAh / cm 2 .

[0101] (3) Preparation of solid electrolyte layer: Li6PS5Cl solid electrolyte and HNBR binder were weighed at a mass ratio of 98:2. The HNBR binder was pre-dissolved in xylene, and then the Li6PS5Cl solid electrolyte was added and mixed by ball milling. The resulting slurry was coated on a polyethylene terephthalate (PET) film and dried at 120°C for 30 minutes under a forced air conditioner to obtain a solid electrolyte layer.

[0102] (4) The solid electrolyte layer and the negative electrode were laminated and bonded, and warm isostatic pressing was performed twice at 80°C and 500 MPa for 10 minutes. The solid electrolyte-negative electrode precursor composite electrode was laminated and bonded to the positive electrode, and the tabs were welded and packaged. Warm isostatic pressing was performed once at 120°C and 600 MPa for 30 minutes to obtain the battery of Example 2. The N / P ratio of the battery was 1.03.

[0103] Example 3

[0104] The difference from Example 1 is that the added lithium supplement is Li3P.

[0105] Example 4

[0106] The difference from Example 1 is that the added lithium supplement is lithium polysulfide.

[0107] Example 5

[0108] The difference from Example 2 is that the lithium supplement agent added is Li3B.

[0109] Example 6

[0110] The difference from Example 2 is that the added lithium supplement is lithium crotonate.

[0111] Example 7

[0112] The difference from Example 1 is that the amount of lithium triquinoline added corresponds to a specific capacity of 0.3 mAh / cm 2 Lithium replenishment capacity.

[0113] Example 8

[0114] The difference from Example 1 is that the amount of lithium triquinoline added corresponds to a specific capacity of 3 mAh / cm 2 Lithium replenishment capacity.

[0115] Example 9

[0116] The difference from Example 5 is that the added lithium supplement Li3B has a specific capacity of 0.3 mAh / cm 2 Lithium replenishment capacity.

[0117] Example 10

[0118] The difference from Example 5 is that the added lithium supplement Li3B has a specific capacity of 3 mAh / cm 2 Lithium replenishment capacity.

[0119] In order to highlight the beneficial effects of the embodiments of the present disclosure, the following comparative examples are provided.

[0120] Comparative Example 1

[0121] The difference from Example 1 is that no lithium supplement agent is added.

[0122] Comparative Example 2

[0123] The difference from Example 2 is that no lithium supplement agent is added.

[0124] Performance testing:

[0125] (1) First cycle efficiency test: The assembled battery is charged and discharged at a rate of 0.1C, and the charge capacity Q is obtained respectively. charge and discharge capacity Q discharge , the first cycle efficiency is Q discharge / Q charge .

[0126] (2) Cyclic performance test: The batteries of each embodiment and comparative example were charged and discharged 100 times at a rate of 0.33C at 25±2°C, and the discharge capacity of the 100th cycle was compared with the discharge capacity of the 1st cycle.

[0127] The test results are shown in Table 1.

[0128] Table 1

[0129] It can be seen from the data in Table 1 that the secondary battery with the negative electrode according to the embodiment of the present disclosure has both high first cycle efficiency and excellent cycle performance.

[0130] The above is an exemplary embodiment of the present disclosure. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made thereto without departing from the principles of the present disclosure. These improvements and modifications are also considered to be within the scope of protection of the present disclosure.

Claims

1. A negative electrode, characterized in that: It includes at least one of inorganic phosphide, inorganic boride, polysulfide ranic acid, 81-33-43,4,9,10-perylenetetracarboxylic acid dianhydride, triquinoline, naphthalene, keto acid, 1,4,5,8-tetrahydroxy-9,10-anthraquinone, [5,10,15,20-tetraethynylporphyrin] magnesium complex, conjugated sulfonyl acid, selenide triphenylphosphine, cup hexaquinone, tris(4-nitrosophenyl)amine, cyclohexanehexaone and dipentamethylenethiuram hexasulfide, and lithium silicon alloy.

2. The negative electrode according to claim 1, characterized in that The lithium silicon alloy is in a granular form, and the D50 particle size of the lithium silicon alloy is less than or equal to 3 μm, and the D50 particle size of the lithium silicon alloy is in the range of 1 μm to 2 μm.

3. The negative electrode according to claim 1 or 2, characterized in that The BET specific surface area of ​​the lithium silicon alloy is 1.0 m 2 / g~2.2m 2 / g range.

4. The negative electrode according to any one of claims 1 to 3, characterized in that The negative electrode further comprises silicon-based negative electrode material particles.

5. The negative electrode according to any one of claims 1 to 4, characterized in that The negative electrode includes at least one of polysulfide ranic acid, 81-33-43,4,9,10-perylenetetracarboxylic dianhydride, triquinoline, naphthalene, keto acid, 1,4,5,8-tetrahydroxy-9,10-anthraquinone, [5,10,15,20-tetraethynylporphyrin] magnesium complex, conjugated sulfonyl acid, selenide triphenylphosphine, cup hexaquinone, tris(4-nitrosophenyl)amine, cyclohexanehexaone and dipentamethylenethiuram hexasulfide.

6. The negative electrode according to any one of claims 1 to 5, characterized in that The lithium silicon alloy and at least one of the inorganic phosphide, inorganic boride, polysulfide, 81-33-43,4,9,10-perylenetetracarboxylic acid dianhydride, triquinoline, naphthalene, keto acid, 1,4,5,8-tetrahydroxy-9,10-anthraquinone, [5,10,15,20-tetraethynylporphyrin] magnesium complex, conjugated sulfonyl acid, selenide triphenylphosphine, cup hexaquinone, tris (4-nitrosophenyl) amine, cyclohexanehexaone and dipentamethylenethiuram hexasulfide are Li3P, Li3 B. At least one of lithium polysulfide ranic acid, 81-33-43,4,9,10-perylenetetracarboxylic acid dianhydride lithium, triquinoline lithium, naphthalene lithium, crotonate lithium, 1,4,5,8-tetrahydroxy-9,10-anthraquinone lithium, lithiated [5,10,15,20-tetraethynylporphyrin] magnesium complex, conjugated sulfonyl lithium, selenide triphenylphosphine lithium, cuphexaquinone lithium, tris(4-nitrosophenyl)amine lithium, cyclohexanehexaone lithium and dipentamethylenethiuram hexasulfide lithium is reacted in situ with silicon-based negative electrode material particles.

7. The negative electrode according to any one of claims 1 to 6, characterized in that The negative electrode also includes a solid electrolyte.

8. The negative electrode according to claim 7, characterized in that The solid electrolyte includes a sulfide solid electrolyte.

9. A method for preparing a negative electrode, characterized in that: include: Providing a negative electrode precursor, wherein the negative electrode precursor comprises silicon-based negative electrode material particles and a lithium supplement agent; The lithium supplement agent is de-lithiated, and the de-lithiated lithium ions react with the silicon-based negative electrode material particles to obtain a negative electrode comprising a lithium-silicon alloy; The lithium supplement includes Li3P, Li3B, lithium polysulfide, 81-33-43,4,9,10-perylenetetracarboxylic acid dianhydride lithium, At least one of lithium quinoline, lithium naphthalene, lithium crotonate, 1,4,5,8-tetrahydroxy-9,10-anthraquinone lithium, lithiated [5,10,15,20-tetraethynylporphyrin] magnesium complex, conjugated sulfonyl lithium, lithium triphenylphosphine selenide, lithium calixhexaquinone, lithium tris(4-nitrosophenyl)amine, lithium cyclohexanehexatonide and lithium dipentamethylenethiuram hexasulfide.

10. The preparation method according to claim 9, characterized in that: The lithium replenishing surface capacity of the negative electrode precursor is 0.3 mAh / cm 2 -3.0mAh / cm 2 .

11. The preparation method according to claim 9 or 10, characterized in that: The material of the silicon-based negative electrode material particles includes at least one of silicon, silicon oxide and silicon-carbon composite.

12. The preparation method according to claim 11, characterized in that: The carbon content of the silicon-carbon composite is less than or equal to 5 wt.%.

13. The preparation method according to claim 11, characterized in that: The oxygen content of the silicon oxide is less than or equal to 18 wt.%.

14. The preparation method according to any one of claims 9 to 13, characterized in that: The process of removing lithium from the lithium supplement agent and reacting the removed lithium ions with the silicon-based negative electrode material particles to obtain a negative electrode comprising a lithium-silicon alloy includes heating the negative electrode precursor, and the heating includes: drying the negative electrode precursor at 100°C to 150°C for 20min to 40min, and then baking at 100°C to 170°C for 30min to 720min.

15. The preparation method according to any one of claims 9 to 14, characterized in that: The step of removing lithium from the lithium supplement agent and reacting the removed lithium ions with the silicon-based negative electrode material particles to obtain a negative electrode comprising a lithium-silicon alloy includes assembling the negative electrode precursor into a battery cell and chemically forming the battery cell.

16. The preparation method according to any one of claims 9 to 15, characterized in that: The negative electrode precursor further includes a current collector, and providing the negative electrode precursor includes mixing the silicon-based negative electrode material particles and the lithium supplement agent to obtain a mixed material, and disposing the mixed material on the surface of the current collector.

17. The preparation method according to claim 16, characterized in that: The mixture includes the silicon-based negative electrode material particles, a solid electrolyte, a conductive agent and a binder in a mass ratio of (60-99): (0-35): (0-5): (1-5).

18. A secondary battery, characterized in that: The secondary battery comprises the negative electrode according to any one of claims 1 to 8, or the secondary battery comprises the negative electrode prepared by the preparation method according to any one of claims 9 to 17.

19. The secondary battery according to claim 18, characterized in that: The secondary battery further includes a positive electrode, and a solid electrolyte disposed between the negative electrode and the positive electrode.

20. An electrical equipment, characterized in that: The electric device includes the secondary battery according to claim 18 or 19.

Images