WO2021217331A1 - 一种负极材料及包含其的负极极片、电化学装置和电子装置 - Google Patents

一种负极材料及包含其的负极极片、电化学装置和电子装置 Download PDF

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WO2021217331A1
WO2021217331A1 PCT/CN2020/087205 CN2020087205W WO2021217331A1 WO 2021217331 A1 WO2021217331 A1 WO 2021217331A1 CN 2020087205 W CN2020087205 W CN 2020087205W WO 2021217331 A1 WO2021217331 A1 WO 2021217331A1
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negative electrode
electrode material
carbon
present application
ppm
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French (fr)
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王超
易婷
崔航
谢远森
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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Priority to PCT/CN2020/087205 priority Critical patent/WO2021217331A1/zh
Priority to KR1020227035741A priority patent/KR20220146664A/ko
Priority to CN202080099224.6A priority patent/CN115380404B/zh
Publication of WO2021217331A1 publication Critical patent/WO2021217331A1/zh
Priority to US17/973,865 priority patent/US12573628B2/en
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    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
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    • C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
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Definitions

  • This application relates to the technical field of lithium ion batteries, and in particular to a negative electrode material and a negative electrode piece containing the same, an electrochemical device and an electronic device.
  • Lithium-ion batteries have the characteristics of large specific energy, high working voltage, low self-discharge rate, small size, light weight, etc., and have a wide range of applications in the field of consumer electronics. With the rapid development of electric vehicles and portable electronic equipment, people have higher and higher requirements for the energy density, safety, and cycle performance of lithium-ion batteries. Among them, silicon material has a high theoretical gram capacity (4200mAh/g), and its application in lithium-ion batteries has broad prospects. However, there are some problems in the application of silicon materials. First, the volume expansion can reach 300% when lithium is inserted, which seriously affects its structural stability and cycle stability.
  • the purpose of this application is to provide a negative electrode material and a negative electrode piece, an electrochemical device and an electronic device containing the negative electrode material, so as to improve the battery cycle stability of the lithium ion battery.
  • the first aspect of the present application provides a negative electrode material.
  • the negative electrode material includes SiM x C y , wherein 0.5 ⁇ x ⁇ 2, 0.5 ⁇ y ⁇ 4, and M includes at least one of boron, nitrogen, oxygen, or aluminum.
  • the particle size of the number accumulation degree A% of the SiM x C y is D N A
  • the particle size of the volume accumulation degree B% is D V B
  • the half-value width of the number distribution curve is ⁇ D N ;
  • the range of D N 99 satisfies: 12.0 to 20.0 ⁇ m; the range of D N 1 satisfies: 0.1 to 1.0 ⁇ m, and the range of D V 50 satisfies: 4.0 to 10.0 ⁇ m.
  • the displacement of the silicon element includes -5 ppm, -35 ppm, -75 ppm, and -110 ppm.
  • the specific surface area of the negative electrode material satisfies: 1.0 to 8.0 m 2 /g.
  • the powder conductivity of the negative electrode material is 2.0 to 30 S/cm.
  • the nitrogen adsorption isotherm specified in IUPAC is type III.
  • the surface of the negative electrode material has at least one of carbon, a high molecular polymer, or a compound of the foregoing substances;
  • the carbon includes at least one of amorphous carbon, carbon nanotubes, carbon nanoparticles, vapor-deposited carbon fibers, or graphene;
  • the high molecular polymer includes at least one of polyvinylidene fluoride, carboxymethyl cellulose, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyacrylic acid, polystyrene butadiene rubber, or derivatives of the above substances.
  • the second aspect of the present application provides a negative pole piece, which includes a current collector and the negative electrode material described in any one of the above.
  • the third aspect of the present application provides an electrochemical device, which includes a positive pole piece and the above-mentioned negative pole piece.
  • the fourth aspect of the present application provides an electronic device, which includes the above-mentioned electrochemical device.
  • the negative electrode material provided in the present application improves the particle size distribution, optimizes the compaction density of the negative electrode active material, and improves the cycle performance and energy density of the negative electrode piece, electrochemical device, and electronic device using the negative electrode material.
  • Dv50 refers to the particle size at which the cumulative distribution of particles is 50% based on the volume distribution; that is, the volume of particles smaller than this size accounts for 50% of the total volume of all particles.
  • the particle size is measured with a laser particle size analyzer.
  • DN 99 refers to the particle size whose cumulative distribution of particles is 99% based on the number distribution; that is, the number of particles smaller than this size accounts for 99% of the total number of particles.
  • the particle size is measured with a laser particle size analyzer.
  • D N 1 refers to a particle size whose cumulative distribution of particles is 1% based on the number distribution; that is, the number of particles smaller than this size accounts for 1% of the total number of all particles.
  • the particle size is measured with a laser particle size analyzer.
  • ⁇ D N represents the half-value width of the particle size distribution curve based on the number distribution.
  • Figure 1 is a solid-state nuclear magnetic resonance spectrum of the negative electrode material SiOC of Example 1;
  • Fig. 2 is the nitrogen adsorption isotherm specified in IUPAC for the negative electrode material SiOC of Example 1.
  • a lithium ion battery is used as an example of an electrochemical device to explain the present application, but the electrochemical device of the present application is not limited to a lithium ion battery.
  • the first aspect of the present application provides a negative electrode material.
  • the negative electrode material includes SiM x C y , wherein 0.5 ⁇ x ⁇ 2, 0.5 ⁇ y ⁇ 4, and M includes at least one of boron, nitrogen, oxygen, or aluminum.
  • the particle size of the number accumulation degree A% of the SiM x C y is D N A
  • the particle size of the volume accumulation degree B% is D V B
  • the half-value width of the particle size distribution curve is ⁇ D N ; in:
  • the inventors of the present application surprisingly found that in-depth study, the present application the negative electrode material SiM x C y, compared to the prior art, the negative electrode material by adjusting the particle size distribution SiM x C y to be applied so that the negative electrode of the negative electrode material While the pole piece has a higher compaction density, it can also ensure a good cycle performance. Without being limited to any theory, the inventor believes that it may be that the uniform distribution of the negative electrode material SiM x C y can increase the compaction density on the one hand, and on the other hand has less adverse effects on the cycle performance.
  • the range of D N 99 satisfies: 12.0 to 20.0 ⁇ m; the range of D N 1 satisfies: 0.1 to 1.0 ⁇ m, and the range of D V 50 satisfies: 4.0 to 10.0 ⁇ m;
  • the inventors have found that, in addition to controlling the negative electrode material SiM x C y of uniform particle size distribution than, the need for a negative electrode material SiM x C y diameter D V 50, D N 99 and D N 1 to be improved. Without being limited to any theory, the inventor believes that the negative electrode material SiM x C y with excessively large particles is easily broken during the process of deintercalating lithium and causes poor circulation, and the negative electrode material with large particles is likely to cause damage to the separator during compression. Self-discharge; the side reaction of the negative electrode material of small particles is violent, which is prone to safety hazards. By controlling the particle size D V 50, D N 99 and D N 1 of the negative electrode material SiM x C y within the above range, a negative electrode sheet with higher compaction density and better cycle performance can be obtained.
  • the displacement of the silicon element includes -5 ppm, -35 ppm, -75 ppm, and -110 ppm.
  • the inventor unexpectedly discovered in research that the negative electrode material SiM x C y of the present application, compared with some existing negative electrode materials such as carbon, silicon, and oxygen, contains -5 ppm in the chemical shift of the silicon element tested by solid nuclear magnetic resonance. Through testing, it is found that the negative electrode material SiM x C y of the present application has lower swellability. Without being limited to any theory, the inventor believes that this may be due to the fact that the negative electrode material SiM x C y of the present application has a different degree of crystallization than the prior art, so it has lower expansibility.
  • Fig. 1 shows a solid nuclear magnetic resonance spectrum of the negative electrode material SiM x C y of the present application; it shows that the displacement of the silicon element includes -5 ppm, -35 ppm, -75 ppm, and -110 ppm.
  • the specific surface area of the negative electrode material satisfies: 1.0 to 8.0 m 2 /g.
  • the inventor found that if the specific surface area of the negative electrode material is too small, the negative electrode material will not be able to release the stress well, and it is easy to be broken in the process of deintercalating lithium. The side reaction is more severe, leading to deterioration of high-temperature cycle performance.
  • the powder conductivity of the negative electrode material is 2.0 to 30 S/cm.
  • the conductivity can be improved, but the compaction density of the prepared negative electrode piece will be reduced, thereby affecting the improvement of the energy density.
  • the powder conductivity of the negative electrode material within the above range, the conductivity, compaction density, and energy density can be well balanced.
  • the nitrogen adsorption isotherm specified in IUPAC is type III.
  • Figure 2 shows the nitrogen adsorption isotherm specified in IUPAC for the anode material of the present application, and it can be seen that it is of type III.
  • the surface of the negative electrode material has at least one of carbon, a high molecular polymer, or a compound of the foregoing substances;
  • the carbon includes at least one of amorphous carbon, carbon nanotubes, carbon nanoparticles, vapor-deposited carbon fibers, or graphene;
  • the high molecular polymer includes at least one of polyvinylidene fluoride, carboxymethyl cellulose, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyacrylic acid, polystyrene butadiene rubber or derivatives of the above substances.
  • the inventor also discovered in research that the presence of carbon on the surface of the negative electrode material can increase the conductivity of the negative electrode material and improve its electrical performance.
  • the manner and content of adding carbon are not particularly limited.
  • carbon can account for 1% to 30% of the mass of the negative electrode material.
  • a second aspect of the present application provides a negative electrode sheet, which includes a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer containing the negative electrode material described in any one of the above embodiments.
  • the negative active material layer can be coated on one or both surfaces of the negative current collector, and those skilled in the art can make specific selections according to actual needs, and this application is not limited herein.
  • the present application does not particularly limit the negative electrode current collector, and any negative electrode current collector known to those skilled in the art can be used.
  • a negative electrode current collector formed of iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum, etc. can be used.
  • copper foil or copper alloy foil is particularly preferred.
  • the above-mentioned materials may be used singly or in combination of two or more in any ratio.
  • the negative electrode active material layer further includes graphite.
  • the graphite may include at least one of natural graphite, artificial graphite, or mesocarbon microspheres.
  • the mixture of the negative electrode material and graphite of the present application is used as the negative electrode active material.
  • the negative active material layer may further include a binder.
  • the adhesive is not particularly limited, and can be any adhesive or combination known to those skilled in the art.
  • it can include polyacrylate, polyimide, polyamide, polyamideimide, polyvinylidene fluoride, butylene.
  • These binders may be used alone or in combination of two or more in any ratio.
  • the negative active material layer may further include a conductive agent.
  • the conductive agent is not particularly limited, and may be any conductive agent known to those skilled in the art or a combination thereof.
  • at least one of a zero-dimensional conductive agent, a one-dimensional conductive agent, or a two-dimensional conductive agent may be used.
  • the conductive agent may include at least one of carbon black, conductive graphite, carbon fiber, carbon nanotube, VGCF (Vapour Grown Carbon Fiber) or graphene.
  • the amount of the conductive agent is not particularly limited, and can be selected according to common knowledge in the art.
  • the above-mentioned conductive agent may be used alone or in combination of two or more in any ratio.
  • the third aspect of the present application provides an electrochemical device, which includes a positive pole piece and the above-mentioned negative pole piece.
  • the electrochemical device of the present application includes, but is not limited to: all kinds of primary batteries, secondary batteries, fuel cells, solar cells or capacitors.
  • a typical electrochemical device is a lithium ion battery, which is a secondary battery.
  • Electrochemical devices, such as lithium-ion batteries, generally include a negative pole piece, a positive pole piece, a separator, and an electrolyte.
  • the electrochemical device may be a lithium ion battery provided in the present application.
  • the negative pole piece of this application adopts the negative pole piece provided in this application; and other components, including the positive pole piece, separator, electrolyte, etc., are not particularly limited in this application.
  • the positive electrode material contained in the positive pole piece may include, but is not limited to, lithium cobaltate, lithium manganate, lithium iron phosphate, and the like.
  • the material of the diaphragm may include, but is not limited to, glass fiber, polyester, polyethylene, polypropylene, polytetrafluoroethylene, or a combination thereof.
  • the electrolyte generally includes organic solvents, lithium salts and additives.
  • Organic solvents may include, but are not limited to, carbon ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate , At least one of ethyl propionate.
  • the lithium salt may include at least one of an organic lithium salt or an inorganic lithium salt; for example, the lithium salt may include lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF 4 ), lithium difluorophosphate (LiPO 2 F 2 ), and double trifluorophosphate (LiPF6).
  • Lithium fluoromethanesulfonimide LiN(CF 3 SO 2 ) 2 LiTFSI
  • Lithium bisoxalate borate LiB(C 2 At least one of O 4 ) 2 LiBOB
  • lithium difluorooxalate borate LiBF 2 (C 2 O 4 ) LiDFOB
  • a secondary battery can be manufactured by the following process: overlap the positive electrode and the negative electrode via spacers, and place them in the battery container after winding, folding and other operations as needed, and inject the electrolyte into the battery container and seal it.
  • the negative electrode used is The above-mentioned negative pole piece provided in this application.
  • overcurrent prevention elements, guide plates, etc. can also be placed in the battery container as needed to prevent the internal pressure of the battery from rising and overcharging and discharging.
  • the fourth aspect of the present application provides an electronic device, which includes the above-mentioned electrochemical device.
  • the 29 Si solid-state nuclear magnetic resonance spectrum test was performed on the AVANCE III 400 WB wide-cavity solid-state nuclear magnetic resonance instrument.
  • the rotation rate of 8kHz corresponds to 29 Si.
  • the adsorption amount of the sample monolayer is calculated based on the Brownauer-Ett-Taylor adsorption theory and its formula (BET formula), thereby calculating The specific surface area of the solid.
  • the negative electrode material, conductive carbon black, and binder polyacrylic acid (PAA) are mixed with deionized water at a mass ratio of 80:10:10 to form a slurry, and a 100 ⁇ m thick coating is coated with a doctor blade. After 12 hours of vacuum at 85°C After drying in the drying box, use a punching machine in a dry environment to cut into discs with a diameter of 1 cm. In the glove box, use the metal lithium sheet as the counter electrode. The ceglard composite film is selected as the isolation film, and the electrolyte is added to assemble the button cell. . Use LAND series battery test system to charge and discharge the battery to test its charge and discharge performance.
  • PAA binder polyacrylic acid
  • the test temperature is 25/45°C
  • the battery is charged to 4.4V at a constant current of 0.7C, and charged to 0.025C at a constant voltage. After standing for 5 minutes, it is discharged to 3.0V at 0.5C.
  • the capacity obtained in this step is the initial capacity, and the 0.7C charge/0.5C discharge is carried out for a cycle test, and the capacity at each step is used as the ratio of the initial capacity to obtain the capacity decay curve.
  • the number of cycles from 25°C cycle to 80% of capacity retention is recorded as the room temperature cycle performance of the lithium ion battery, and the number of cycles from 45°C cycle to 80% is recorded as the high temperature cycle performance of the lithium ion battery. By comparing the above two The number of cycles in this case can be used to obtain the cycle performance of the material.
  • GB/T 24533-2009 "Graphite Anode Materials for Lithium Ion Batteries"
  • a certain amount of anode material powder is placed on a special compaction mold (with a known mold diameter), with a hollow upper and lower metal disc in the middle of the mold.
  • the powder is placed between the metal discs, a metal cylinder is placed on the top, the mold is placed on the compaction density instrument, and different pressures are set.
  • the sample is heated and burned in a high-frequency furnace under oxygen-rich conditions to oxidize carbon and sulfur into carbon dioxide and sulfur dioxide. After treatment, the gas enters the corresponding absorption cell, absorbs the corresponding infrared radiation, and then is converted into the corresponding signal by the detector. .
  • This signal is sampled by the computer, after linear correction, it is converted into a value proportional to the concentration of carbon dioxide and sulfur dioxide, and then the value of the entire analysis process is accumulated. After the analysis is completed, the accumulated value is divided by the weight value in the computer, and then multiplied by Correction coefficient, deduct blank, you can get the percentage of carbon and sulfur in the sample.
  • a high-frequency infrared carbon and sulfur analyzer (Shanghai Dekai HCS-140) was used for sample testing.
  • the fixed body resistance is determined by measuring the voltage and the current flowing through the two ends of the resistance to be measured (ie, the sample pressing piece), and the conductivity is calculated by combining the height and the bottom area of the resistance to be measured.
  • ⁇ is the electronic conductivity
  • h is the height of the sample press
  • S is the bottom area of the sample press
  • R is the read resistance
  • the active material LiCoO 2 , conductive carbon black, and binder polyvinylidene fluoride (PVDF) are formulated into a slurry with a solid content of 75% by weight in an N-methylpyrrolidone solvent system at a weight ratio of 96.7:1.7:1.6. And stir well. Coat the slurry uniformly on one surface of the anode current collector aluminum foil with a thickness of 12 ⁇ m, the coating thickness is 115 ⁇ m, dry at 90°C, and cold press to obtain the positive pole piece. The pole piece is cut into a size of 74mm ⁇ The 867mm sheet is ready for use.
  • PVDF polyvinylidene fluoride
  • the negative electrode materials prepared in each example and comparative example were mixed with graphite in a certain proportion to obtain negative active material powder with a designed mixing capacity of 500mAh/g.
  • the negative active material powder, conductive agent acetylene black, and PAA were mixed in a weight ratio of 95: 1.2:3.8
  • a slurry with a solid content of 45% by weight is obtained, which is coated on both surfaces of a copper foil current collector with a thickness of 10 ⁇ m, with a coating thickness of 100 ⁇ m;
  • the sheet is cold pressed, and the double-sided compaction density is 1.8 g/cm 3 to obtain a negative pole piece.
  • the pole piece is cut into a sheet with a size of 74 mm ⁇ 867 mm for use. .
  • a PE porous polymer film with a thickness of 15 ⁇ m is used as the separator.
  • the positive pole piece, the isolation film, and the negative pole piece are stacked in order, so that the isolation film is in the middle of the positive and negative electrodes for isolation, and the electrode assembly is wound by winding.
  • the carbon source including at least one of glucose or sucrose
  • the organosilicon including polysiloxane, polycarbosilane, polysilazane, polycarborane methyl
  • At least one of siloxane or polysilazaborazane is added in a certain proportion, stirred for 4h, so that the carbon source solution and the organosilicon solution are completely immersed, then stirred and heated at 80°C to remove the solvent, and then the product is placed at 80°C Dry in an oven for 24 hours.
  • the resulting product is put into a tube furnace for high-temperature cracking.
  • the heating program is: heating at 1°C/min to 500°C, holding for 30min, further heating at 3°C/min to 900 to 1500°C for 3h, high temperature cracking to obtain the anode material SiM x C y .
  • SiOC silicon-oxy-carbon ceramic material
  • the rest is the same as in Example 1.

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Abstract

本申请提供一种负极材料及包含其的负极极片、电化学装置和电子装置。其中，所述负极材料为SiMxCy，0.5≤x≤2，0.5≤y≤4，M包括硼、氮、氧或铝中的至少一种；所述SiMxCy的数量累积度A％的粒径为DNA，体积累积度B％的粒径为DVB，数量分布曲线的半峰宽为ΔDN；其中：2μm≤（DV50-DN50）≤6μm，1≤(DN99-DN1)/ΔDN≤1.3。采用本申请的负极材料，及包含其的负极极片、电化学装置和电子装置均具有良好的循环性能和能量密度。

Description

一种负极材料及包含其的负极极片、电化学装置和电子装置 技术领域
本申请涉及锂离子电池技术领域，具体涉及一种负极材料及包含其的负极极片、电化学装置和电子装置。
背景技术
锂离子电池具有比能量大、工作电压高、自放电率低、体积小、重量轻等特点，在消费电子领域具有广泛的应用。随着电动汽车和可移动电子设备的高速发展，人们对锂离子电池的能量密度、安全性、循环性能等相关要求越来越高。其中，硅材料具有高的理论克容量(4200mAh/g)，在锂离子电池中的应用有着广阔的前景。但硅材料在应用时也存在着一些问题，一是嵌锂时其体积膨胀可达到300％，从而严重影响其结构稳定性和循环稳定性，同时也容易引起隔膜的破坏而形成微短路；二是其表面会持续生成副产物，不断消耗电解液中的锂源，尤其在高温时会加快电解液的消耗，从而影响锂离子电池的循环性能。
因此，亟需一种能够进一步提高锂离子电池循环稳定性和降低锂离子电池体积膨胀的负极材料。
发明内容
基于现有技术的缺陷，本申请的目的是提供一种负极材料及包含其的负极极片、电化学装置和电子装置，以提升锂离子电池的电池循环稳定性能。
本申请的第一方面，提供了一种负极材料，所述负极材料包括SiM xC y，其中，0.5≤x≤2，0.5≤y≤4，M包括硼、氮、氧或铝中的至少一种；所述SiM xC y的数量累积度A％的粒径为D NA，体积累积度B％的粒径为D VB，数量分布曲线的半峰宽为ΔD N；其中：
2μm≤(D V50-D N50)≤6μm，1≤(D N99-D N1)/ΔD N≤1.3。
在本申请第一方面的一些实施方式中，其中，D N99范围满足：12.0至20.0μm；D N1范围满足：0.1至1.0μm，D V50范围满足：4.0至10.0μm。
在本申请第一方面的一些实施方式中，其中，固体核磁共振测试所述负极材料中，硅元素的位移包括-5ppm，-35ppm，-75ppm，-110ppm。
在本申请第一方面的一些实施方式中，其中，所述负极材料的比表面积满足：1.0至8.0m 2/g。
在本申请第一方面的一些实施方式中，其中，所述负极材料的粉末电导率为2.0至30S/cm。
在本申请第一方面的一些实施方式中，其中，在IUPAC中规定的氮吸附等温线为III型。
在本申请第一方面的一些实施方式中，其中，所述负极材料的表面存在碳、高分子聚合物或上述物质复合物中的至少一种；
所述碳包括无定形碳、碳纳米管、碳纳米粒子、气相沉积碳纤维或石墨烯中的至少一种；
所述高分子聚合物包括聚偏氟乙烯、羧甲基纤维素、羧甲基纤维素钠、聚乙烯基吡咯烷酮、聚丙烯酸、聚丁苯橡胶或上述物质衍生物中的至少一种。
本申请的第二方面提供了一种负极极片，其包括集流体以及上述任一项所述的负极材料。
本申请的第三方面提供了一种电化学装置，其包括正极极片和上述的负极极片。
本申请的第四方面提供了一种电子装置，其包括上述的电化学装置。
本申请所提供的负极材料改进了粒径分布，优化了负极活性材料的压实密度，提升了应用该负极材料的负极极片、电化学装置和电子装置的循环性能和能量密度。
本文中，术语“Dv50”表示以体积分布为基准，颗粒累积分布为50％的粒径；即小于此粒径的颗粒的体积占全部颗粒总体积的50％。所述粒径用激光粒度仪进行测定。
术语“D N99”表示以数量分布为基准，颗粒累积分布为99％的粒径；即小于此粒径的颗粒的数量占全部颗粒总数量的99％。所述粒径用激光粒度仪进行测定。
术语“D N1”表示以数量分布为基准，颗粒累积分布为1％的粒径；即小于此粒径的颗粒的数量占全部颗粒总数量的1％。所述粒径用激光粒度仪进行测定。
术语“ΔD N”表示以数量分布为基准，颗粒粒径的数量分布曲线的半峰宽。
附图说明
为了更清楚地说明本申请实施例和现有技术的技术方案，下面对实施例和现有技术中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1是实施例1的负极材料SiOC的固体核磁共振谱图；
图2是实施例1的负极材料SiOC在IUPAC中规定的氮吸附等温线。
具体实施方式
为使本申请的目的、技术方案、及优点更加清楚明白，以下参照附图并举实施例，对本申请进一步详细说明。显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
需要说明的是，本申请的具体实施方式中，以锂离子电池作为电化学装置的例子来解释本申请，但是本申请的电化学装置并不仅限于锂离子电池。
本申请的第一方面，提供了一种负极材料，所述负极材料包括SiM xC y，其中，0.5≤x≤2，0.5≤y≤4，M包括硼、氮、氧或铝中的至少一种；所述SiM xC y的数量累积度A％的粒径为D NA，体积累积度B％的粒径为D VB，颗粒粒径数量分布曲线的半峰宽为ΔD N；其中：
2μm≤(D V50-D N50)≤6μm，1≤(D N99-D N1)/ΔD N≤1.3。
本申请的发明人于深入研究中意外发现，本申请的负极材料SiM xC y，与现有技术相比，通过调整负极材料SiM xC y的粒径分布，可以使得应用该负极材料的负极极片具有更高压实密度的同时，还可保证很好的循环性能。不限于任何理论，发明人认为，可能是负极材料SiM xC y的分布均匀一方面可以提升压实密度，另一方面对于循环性能的不良影响较小。
在本申请第一方面的一些实施方式中，其中，D N99范围满足：12.0至20.0μm；D N1范围满足：0.1至1.0μm，D V50范围满足：4.0至10.0μm；
发明人发现，除了控制负极材料SiM xC y的粒径分布均匀以外，还需对负 极材料SiM xC y的粒径D V50、D N99和D N1加以改进。不限于任何理论，发明人认为，过大颗粒的负极材料SiM xC y在脱嵌锂过程中容易破碎而导致循环变差，且大颗粒的负极材料在压片时容易对隔膜造成破坏而产生自放电；小颗粒的负极材料的副反应剧烈，容易产生安全隐患。通过控制负极材料SiM xC y的粒径D V50、D N99和D N1在上述范围内，可以得到压实密度更高，循环性能更好的负极极片。
在本申请第一方面的一些实施方式中，其中，固体核磁共振测试所述负极材料中，硅元素的位移包括-5ppm，-35ppm，-75ppm，-110ppm。
发明人在研究中意外地发现，本申请的负极材料SiM xC y，与现有的一些碳硅氧等的负极材料相比，采用固体核磁共振测试硅元素的化学位移中包含了-5ppm。而经测试发现，本申请的负极材料SiM xC y具有更低的膨胀性。不限于任何理论，发明人认为，这可能是由于本申请的负极材料SiM xC y的晶化程度相别于现有技术，所以具有更低的膨胀性。
图1示出了本申请的负极材料SiM xC y固体核磁共振谱图；其中示出了硅元素的位移包括-5ppm，-35ppm，-75ppm，-110ppm。
在本申请第一方面的一些实施方式中，其中，所述负极材料的比表面积满足：1.0至8.0m 2/g。
发明人经过深入研究发现，负极材料的比表面积过小，则负极材料不能很好地释放应力，在脱嵌锂过程中易破碎；而负极材料的比表面积过大，在高温时与电解液的副反应更加剧烈，导致高温循环性能恶化。
在本申请第一方面的一些实施方式中，其中，所述负极材料的粉末电导率为2.0至30S/cm。
在本申请中，通过对负极材料中C(碳)含量的增加，可以提升导电性，但会降低制备负极极片的压实密度，从而影响能量密度的提升。通过将负极材料的粉末电导率控制在上述范围内，可以良好平衡导电性、压实密度和能量密度。
在本申请第一方面的一些实施方式中，其中，在IUPAC中规定的氮吸附等温线为III型。
图2示出了本申请的负极材料在IUPAC中规定的氮吸附等温线，可以看 出，其为III型。
在本申请第一方面的一些实施方式中，其中，所述负极材料的表面存在碳、高分子聚合物或上述物质复合物中的至少一种；
所述碳包括无定形碳、碳纳米管、碳纳米粒子、气相沉积碳纤维或石墨烯中的至少一种；
所述的高分子聚合物包括聚偏氟乙烯、羧甲基纤维素、羧甲基纤维素钠、聚乙烯基吡咯烷酮、聚丙烯酸、聚丁苯橡胶或上述物质衍生物中的至少一种。
发明人在研究中还发现，负极材料表面存在碳可以增加负极材料的导电性，改善其电性能。在本申请中，对添加碳的方式和含量不做特殊的限定，例如碳可以占负极材料质量的1％至30％。
本申请的第二方面提供了一种负极极片，其包括负极集流体以及负极活性物质层，所述负极活性物质层含有上述任一实施方式中所述的负极材料。
负极活性物质层可以涂布于负极集流体的一个或两个表面上，本领域技术人员可根据实际需要具体选择，本申请在此不做限制。
本申请对负极集流体没有特别限制，可以采用本领域技术人员公知的任何负极集流体。例如，可以使用由铁、铜、铝、镍、不锈钢、钛、钽、金、铂等形成的负极集流体。其中，特别优选铜箔或铜合金箔。上述材料可以单独使用一种，也可以将两种以上以任意比例组合使用。
在本申请的一些实施方式中，负极活性物质层中还包含石墨，所述石墨可以包括天然石墨、人造石墨或中间相碳微球中的至少一种，在本申请的一些实施方式中，可以采用本申请的负极材料和石墨的混合物作为负极活性物质。
在本申请的一些实施方式中，负极活性物质层中还可以包含粘合剂。粘合剂没有特别限制，可以是本领域技术人员公知的任何粘合剂或其组合，例如可以包括聚丙烯酸酯、聚酰亚胺、聚酰胺、聚酰胺酰亚胺、聚偏氟乙烯、丁苯橡胶、海藻酸钠、聚乙烯醇、聚四氟乙烯、聚丙烯腈、羧甲基纤维素钠、羧甲基纤维素钾、羟甲基纤维素钠或羟甲基纤维素钾中的至少一种。这些粘合剂可以单独使用一种，也可以将两种以上以任意比例组合使用。
在本申请的一些实施方式中，负极活性物质层还可以包含导电剂。导电 剂没有特别限制，可以是本领域技术人员公知的任何导电剂或其组合，例如，可以采用零维导电剂、一维导电剂或二维导电剂中的至少一种。优选地，导电剂可以包括炭黑、导电石墨、碳纤维、碳纳米管、VGCF(气相法生长碳纤维)或石墨烯中的至少一种。导电剂的用量没有特别限制，可以根据本领域公知常识进行选择。上述导电剂可以单独使用一种，也可以将两种以上以任意比例组合使用。
本申请的第三方面提供了一种电化学装置，其包括正极极片和上述的负极极片。
本申请的电化学装置包括但不限于：所有种类的一次电池、二次电池、燃料电池、太阳能电池或电容。一种典型的电化学装置就是锂离子电池，其是一种二次电池。电化学装置，例如锂离子电池一般包含有负极极片、正极极片、隔膜及电解液。
进一步，电化学装置可以是本申请提供的锂离子电池。
本申请提供的电化学装置，其负极极片采用本申请提供的负极极片；而其它的组成部分，包括正极极片、隔膜及电解液等，本申请对此没有特别的限制。例如，正极极片所包含的正极材料可以包括但不限于钴酸锂、锰酸锂、磷酸铁锂等。隔膜的材质可以包括但不限于玻璃纤维、聚酯、聚乙烯、聚丙烯、聚四氟乙烯或其组合。电解液一般包括有机溶剂、锂盐和添加剂。有机溶剂可以包括但不限于碳碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)、碳酸二甲酯(DMC)、碳酸亚丙酯、丙酸乙酯中的至少一种。锂盐可以包括有机锂盐或无机锂盐中的至少一种；例如，锂盐可以包括六氟磷酸锂(LiPF6)、四氟硼酸锂(LiBF 4)、二氟磷酸锂(LiPO 2F 2)、双三氟甲烷磺酰亚胺锂LiN(CF 3SO 2) 2(LiTFSI)、双(氟磺酰)亚胺锂Li(N(SO 2F) 2)(LiFSI)、双草酸硼酸锂LiB(C 2O 4) 2(LiBOB)或二氟草酸硼酸锂LiBF 2(C 2O 4)(LiDFOB)中的至少一种。
电化学装置的制备过程为本领域技术人员所熟识的，本申请没有特别的限制。例如二次电池可以通过以下过程制造：将正极和负极经由间隔件重叠，并根据需要将其卷绕、折叠等操作后放入电池容器，将电解液注入电池容器并封口，其中所用的负极为本申请提供的上述负极极片。此外，也可以根据 需要将防过电流元件、导板等置于电池容器中，从而防止电池内部的压力上升、过充放电。
本申请的第四方面提供了一种电子装置，其包括上述的电化学装置。
测试方法
固体核磁：
29Si固体核磁共振光谱测试在仪器AVANCE III 400 WB宽腔固体核磁共振仪上进行，旋转速率8kHz对应 29Si。
粒度测试：
50ml洁净烧杯中加入约0.02g各样品粉末，加入约20ml去离子水，再滴加几滴1％的表面活性剂，使负极材料粉末完全分散于水中，120W超声清洗机中超声5分钟，利用MasterSizer 2000测试粒度分布。
负极材料比表面积测试：
在恒温低温下，测定不同相对压力时的气体在固体表面的吸附量后，基于布朗诺尔-埃特-泰勒吸附理论及其公式(BET公式)求得试样单分子层吸附量，从而计算出固体的比表面积。
充放电性能测试：
将负极材料、导电炭黑与粘结剂聚丙烯酸(PAA)按照质量比80：10：10加去离子水经过搅成浆料，利用刮刀涂层100μm厚度的涂层，85℃经过12小时真空干燥箱烘干后，利用在干燥环境中用冲压机切成直径为1cm的圆片，在手套箱中以金属锂片作为对电极，隔离膜选择ceglard复合膜，加入电解液组装成扣式电池。运用蓝电(LAND)系列电池测试系统对电池进行充放电测试，测试其充放电性能。
循环性能测试：
测试温度为25/45℃，以0.7C恒流充电到4.4V，恒压充电到0.025C，静置5分钟后以0.5C放电到3.0V。以此步得到的容量为初始容量，进行0.7C充电/0.5C放电进行循环测试，以每一步的容量与初始容量做比值，得到容量 衰减曲线。以25℃循环截至到容量保持率为80％的圈数记为锂离子电池的室温循环性能，以45℃循环截至到80％的圈数记为锂离子电池的高温循环性能，通过比较上述两种情况下的循环圈数而得到材料的循环性能。
K值测试：
测试锂离子电池容量后，将其室温下静置48h，测量其电压为V1；再将上述锂离子电池再静置48h后，测量其电压V2；则K值根据以下公式算出：K＝(V1-V2)/48；单位mV/h。
负极材料压实密度测试：
采用GB/T 24533-2009《锂离子电池石墨类负极材料》，将一定量的负极材料粉末放于压实专用模具上(已知模具直径)，模具中间空心上下各一片金属圆片。粉末放于金属圆片之间，顶部放一根金属圆柱，将模具放在压实密度仪器上面，设置不同压力，在设备上可以读出不同压力下负极材料粉末的厚度，通过ρ＝m/v，计算出负极材料的压实密度。
碳含量测试：
样品在富氧条件下由高频炉高温加热燃烧使碳、硫氧化成二氧化碳、二氧化硫，该气体经处理后进入相应的吸收池，对相应的红外辐射进行吸收再由探测器转化成对应的信号。此信号由计算机采样，经线性校正后转换成与二氧化碳、二氧化硫浓度成正比的数值，然后把整个分析过程的取值累加，分析结束后，此累加值在计算机中除以重量值，再乘以校正系数，扣除空白，即可获得样品中碳、硫百分含量。利用高频红外碳硫分析仪(上海徳凯HCS-140)进行样品测试。
负极材料粉末电子电导率测试：
采用四线两端子法，通过测量待测电阻(即样品压片)两端电压和流经电流确定定体电阻，结合待测电阻的高度和底面积计算电导率。取一定量负极材料粉末加入到测试模具中，轻轻震平后，再将模具上的垫片放置在样品上；装样完毕后将模具置于电子压力试验机工作台面上，以5mm/min的速率升至500kg(159Mpa)，恒压60s，再卸压至0；当样品恒压至5000±2kg(升压到达5000kg后约15至25秒)时记录样品压力，并读取样品变形高度，记录此时 的电阻测试仪(苏州晶格电子ST-2255A)显示数值，即可采用如下公式计算电子电导率：
δ＝h/(S*R)/1000
式中，δ为电子电导率，h为样品压片的高度，S为样品压片的底面积，R为读取的电阻。
以下，基于实施例对本申请进行具体地说明，但本申请并不限于这些实施例。
全电池制备
制备例1正极极片的制备：
将活性物质LiCoO 2、导电炭黑、粘结剂聚偏二氟乙烯(PVDF)按重量比96.7：1.7：1.6在N-甲基吡咯烷酮溶剂体系中，调配成为固含量为75wt％的浆料，并搅拌均匀。将浆料均匀涂覆在厚度为12μm正极集流体铝箔的一个表面上，涂布厚度为115μm，90℃条件下烘干，冷压，得到正极极片，将极片裁切成规格为74mm×867mm的片材待用。
制备例2负极极片的制备：
将各实施例和对比例制备的负极材料与石墨按一定比例混合，得到设计混合克容量为500mAh/g的负极活性材料粉末，将负极活性材料粉末、导电剂乙炔黑、PAA按照重量比95：1.2：3.8在去离子水溶剂体系中充分搅拌混合均匀后，得到固含量为45wt％的浆料，涂覆于厚度为10μm的铜箔集流体的两个表面上，涂布厚度100μm；将极片烘干后冷压，双面压实密度为1.8g/cm 3，得到负极极片，将极片裁切成规格为74mm×867mm的片材待用。。
制备例3锂离子电池的制备：
以厚度为15μm的PE多孔聚合薄膜作为隔离膜。将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正负极中间起到隔离的作用，并卷绕得到电极组件。
将电极组件置于外包装中，注入配好的电解液(EC:DMC:DEC＝1:1:1vol％，10wt％FEC，1mol/L LiPF 6)并封装，经过化成，脱气，切边等工艺流程得到锂离子电池。
负极材料制备
将碳源(包括葡萄糖或蔗糖中的至少一种)溶解在二甲苯溶剂中，待完全溶解后将有机硅(包括聚硅氧烷、聚碳硅烷、聚硅氮烷、聚碳硼烷甲基硅氧烷或聚硅硼氮烷中的至少一种)按一定比例加入其中，搅拌4h，使碳源溶液与有机硅溶液完全浸渍，随后80℃搅拌加热去除溶剂，再将产物放入80℃烘箱干燥24h。
将得到的产物放入管式炉中高温裂解。以氮气或者氩气为保护气氛，升温程序为：以1℃/min升温至500℃，保温30min，进一步以3℃/min升温至900至1500℃保持3h，高温裂解得到负极材料SiM xC y。
实施例1
将50g葡萄糖溶解在100mL二甲苯溶剂中，然后将50g聚硅氧烷加入其中，搅拌4h使葡萄糖溶液与聚硅氧烷溶液完全浸渍，随后80℃搅拌加热去除溶剂，再将产物放入80℃烘箱干燥24h。将得到的产物放入管式炉中高温裂解，具体地，以Ar为保护气氛，以1℃/min升温至500℃，保温30min，进一步以3℃/min升温至900℃保持3h，高温裂解得到负极材料SiOC(硅氧碳陶瓷材料)。
将制得的负极材料SiOC置于球磨罐中，以50Hz转速球磨40min，然后以200目的过滤筛过滤。使用振动筛子筛选得到粒径分布为D V50＝8μm、D N50＝5μm、D N99＝15μm、D N1＝0.5μm、ΔD N＝13μm，BET为5m 2/g，电导率为15S/cm的负极材料SiOC。
实施例2
除了将筛选出负极材料SiOC的D V50变为10μm以外，其余与实施例1相同。
实施例3至4
除了将筛选出负极材料SiOC的D N50分别变为3μm、6μm以外，其余与实施例1相同。
实施例5至6
除了将筛选出负极材料SiOC的D N99分别变为14μm、17μm以外，其余 与实施例1相同。
实施例7至8
除了将筛选出负极材料SiOC的D N1分别变为0.1μm、1μm以外，其余与实施例1相同。
实施例9
除了将筛选出负极材料SiOC的ΔD N变为14μm以外，其余与实施例1相同。
实施例10
除了将筛选出负极材料SiOC的D V50变为5μm，D N50变为3μm，D N99变为13μm，D N1变为0.4μm，ΔD N变为10μm以外，其余与实施例1相同。
实施例11
除了将筛选出负极材料SiOC的D V50变为10μm，D N50变为6μm，D N99变为18μm，D N1变为1μm，ΔD N变为14μm以外，其余与实施例1相同。
实施例12
除了将筛选出负极材料SiOC的D V50变为7μm，D N50变为4μm，D N99变为14μm，D N1变为0.4μm，ΔD N变为12μm以外，其余与实施例1相同。
实施例13
除了将筛选出负极材料SiOC的D V50变为4μm，D N50变为1.5μm，D N99变为11μm，D N1变为0.2μm，ΔD N变为9μm以外，其余与实施例1相同。
实施例14
除了将筛选出负极材料SiOC的电导率变为30S/cm以外，其余与实施例1相同。
对比例1
除了将筛选出负极材料SiOC的D V50变为6μm以外，其余与实施例1相同。
对比例2
除了将筛选出负极材料SiOC的D N50变为1μm以外，其余与实施例1相同。
对比例3
除了将筛选出负极材料SiOC的D N99变为22μm以外，其余与实施例1相同。
对比例4
除了将筛选出负极材料SiOC的D N1变为0.01μm以外，其余与实施例1相同。
对比例5
除了将筛选出负极材料SiOC的ΔD N变为3μm以外，其余与实施例1相同。
对比例6
除了将筛选出负极材料SiOC的D V50变为14μm，D N50变为7μm，D N99变为15μm，D N1变为0.5μm，ΔD N变为13μm以外，其余与实施例1相同。
对比例7
除了将筛选出负极材料SiOC的D V50变为3μm，D N50变为2μm以外，其余与实施例1相同。
各实施例和对比例的参数以及测试结果见表1和表2。
表1各实施例和对比例的参数以及测试结果
Figure PCTCN2020087205-appb-000001
Figure PCTCN2020087205-appb-000002
表2各实施例和对比例的测试结果
Figure PCTCN2020087205-appb-000003
通过实施例1至4以及对比例1和对比例2可以看出，当(D V50-D N50)过小时(如对比例1)，由于颗粒粒径分布较集中，使得压实密度较低；当(D V50-D N50)过大时(如对比例2)，颗粒分布中细粉较多，使得压实密度较低 的同时高温循环性能也较差。
通过实施例1、5至6以及对比例3可以看出，当D N1与ΔD N不变而D N99过大时(如对比例3)，一方面会导致颗粒分布不均匀，从而导致压实密度较低，另一方面会使得较大的颗粒较多，从而循环性能和K值都会变差。
通过实施例7和8以及对比例4可以看出，当D N99与ΔD N不变，随着D N1变大，一方面颗粒分布越均匀，使压实密度升高；另一方面使得较小的颗粒越少，从而改善高温循环性能；D N1过小时(如对比例4)，使压实密度低，高温循环性能变差。
通过实施例1、9以及对比例5可以看出，当D N99与D N1不变而ΔD N越大时，会使得颗粒分布越均匀，从而可以有效地提高压实密度，同时对循环性能的影响较小。
通过实施例10至13可以看出，随着负极材料粉末平均粒径(D V50)变小，粉末BET变大，从而使得粉末压实密度越大，K值越小。
通过对比例6和7可以看出，过小的BET(如对比例6)由于平均粒径较大，颗粒应力较大而容易破裂，会使得循环性能较差，过大的BET(如对比例7)会使得副反应增加，从而使循环性能恶化。
通过实施例1至14以及对比例6可以看出，电导率在2～30S/cm范围内负极材料的粉末压实密度更高。
以上所述仅为本申请的较佳实施例，并不用以限制本申请，凡在本申请的精神和原则之内，所做的任何修改、等同替换、改进等，均应包含在本申请保护的范围之内。

Claims (10)

  1. 一种负极材料，其中，所述负极材料包括SiM xC y，0.5≤x≤2，0.5≤y≤4，M包括硼、氮、氧或铝中的至少一种；
    2μm≤(D V50-D N50)≤6μm，1≤(D N99-D N1)/ΔD N≤1.3。
  2. 根据权利要求1所述的负极材料SiM xC y，其中，D N99范围满足：12.0至20.0μm；D N1范围满足：0.1至1.0μm，D V50范围满足：4.0至10.0μm。
  3. 根据权利要求1或2所述的负极材料，其中，固体核磁共振测试所述负极材料中，硅元素的位移包括-5ppm，-35ppm，-75ppm，-110ppm。
  4. 根据权利要求1所述的负极材料，其中，所述负极材料的比表面积满足：1.0至8.0m 2/g。
  5. 根据权利要求1所述的负极材料，其中，所述负极材料的粉末电导率为2.0至30S/cm。
  6. 根据权利要求1所述的负极材料，其中，在IUPAC中规定的氮吸附等温线为III型。
  7. 根据权利要求1所述的负极材料，其中，所述负极材料的表面存在碳、高分子聚合物或上述物质复合物中的至少一种；
    所述碳包括无定形碳、碳纳米管、碳纳米粒子、气相沉积碳纤维或石墨烯中的至少一种；
    所述的高分子聚合物包括聚偏氟乙烯、羧甲基纤维素、羧甲基纤维素钠、聚乙烯基吡咯烷酮、聚丙烯酸、聚丁苯橡胶或上述物质衍生物中的至少一种。
  8. 一种负极极片，其包括集流体以及权利要求1-7任一项所述的负极材料。
  9. 一种电化学装置，其包括正极极片和根据权利要求8所述的负极极片。
  10. 一种电子装置，其包括根据权利要求9所述的电化学装置。
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