WO2021134199A1 - 用于二次电池的硅基负极材料及其制备方法，二次电池 - Google Patents

用于二次电池的硅基负极材料及其制备方法，二次电池 Download PDF

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WO2021134199A1
WO2021134199A1 PCT/CN2019/129890 CN2019129890W WO2021134199A1 WO 2021134199 A1 WO2021134199 A1 WO 2021134199A1 CN 2019129890 W CN2019129890 W CN 2019129890W WO 2021134199 A1 WO2021134199 A1 WO 2021134199A1
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silicon
negative electrode
shell layer
electrode material
secondary battery
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PCT/CN2019/129890
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English (en)
French (fr)
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吴玉虎
马飞
***
魏良勤
吴志红
丁晓阳
李凤凤
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上海杉杉科技有限公司
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Priority to CA3203502A priority Critical patent/CA3203502A1/en
Priority to US16/772,780 priority patent/US11876220B2/en
Priority to CN201980003453.0A priority patent/CN111164803B/zh
Priority to PCT/CN2019/129890 priority patent/WO2021134199A1/zh
Publication of WO2021134199A1 publication Critical patent/WO2021134199A1/zh
Priority to US18/528,588 priority patent/US20240105924A1/en

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Definitions

  • the invention relates to the field of secondary batteries, in particular to a silicon-based negative electrode material for secondary batteries, a preparation method thereof, and secondary batteries.
  • the anode material of the traditional lithium-ion battery is graphite, but the theoretical capacity of graphite is only 372mAh/g, which cannot meet the high energy demand of the current industry for lithium-ion batteries.
  • Silicon is abundantly stored in nature and is environmentally safe and environmentally friendly, which has attracted more and more attention from researchers. Moreover, in theory, the capacity of silicon is high, its capacity can reach 4200mAh/g, the discharge potential is relatively low, the price is low, and it is environmentally friendly. It is an excellent anode material for lithium-ion batteries. However, due to the serious volume effect of silicon-based materials, the cycle performance of silicon-based materials is very poor, which cannot meet commercial applications.
  • SiOx (0 ⁇ x ⁇ 2) materials have high capacity, they also have superior cycle performance than elemental silicon, and have received extensive attention and research.
  • the initial charge and discharge efficiency of SiOx (0 ⁇ x ⁇ 2) materials is still far behind that of graphite, which makes it difficult to adapt to commercial requirements.
  • 5%-20% lithium is used to form a passivation film (SEI), while Si and SiOx (0 ⁇ x ⁇ 2) need to consume 20-50% lithium. Therefore, the implementation of lithium supplementation for SiOx (0 ⁇ x ⁇ 2) anode materials is of great significance to its commercial applications.
  • the lithium layer is usually directly coated on the surface of the electrode pole piece, or the process of electrochemically plating lithium on the surface of the electrode pole piece is used to replenish lithium.
  • the lithium replenishment process will cause Si The excessive growth of crystal grains reduces the cycle life of the electrode.
  • the safety performance of the lithium supplementation process is poor and it is difficult to realize mass production.
  • the first-time coulombic efficiency is low, making it difficult for commercial applications.
  • This application provides a silicon-based anode material for a secondary battery and a preparation method thereof, so as to improve the first charge-discharge cycle capacity of the silicon-based anode material of the secondary battery and reduce the silicon-based anode of the secondary battery Material production cost.
  • a silicon-based negative electrode material for a secondary battery comprising: an inner core including Si particles and silicon oxide SiOx 1 , where 0 ⁇ x 1 ⁇ 2; a first shell layer, so The first shell layer includes a compound of the general formula MySiOz (0 ⁇ y ⁇ 4, 0 ⁇ z ⁇ 5, and z ⁇ x 1 ) and C particles, the first shell layer covers the core, and the The content of M and C in the first shell layer gradually increase from the side close to the inner core to the side far from the inner core; and the second shell layer, which includes a carbon film layer or a carbon film layer and a conductive additive.
  • the composite film layer, the second shell layer covering the first shell layer.
  • M in the first shell layer is any one or more of Li, Na, Mg, Al, Fe, and Ca.
  • the content of M in the silicon-based negative electrode material is 1-15% by mass, and the content of M in the first shell layer is 1-40% by mass.
  • the mass percentage content of M and C in the first shell layer increases in a gradient from the side close to the inner core to the side away from the inner core.
  • the mass percentage content of M on the side close to the inner core accounts for 0 to 5% of the first shell layer, and the mass percentage content of M on the side far from the inner core accounts for 30 to 48% of the first shell layer.
  • the C particle material includes any one or more of hard carbon, soft carbon, or amorphous carbon.
  • the carbon film layer material includes any one or more of hard carbon, soft carbon or amorphous carbon
  • the conductive additive includes carbon nanotubes, graphene, conductive carbon black, and Any one or more of piano black, vapor-grown carbon fiber, acetylene black, and conductive graphite.
  • the mass percentage content of C particles is 0.1-2%, and the mass percentage content of the carbon film layer or the composite film layer formed by the carbon film layer and the conductive additive It is 0.1 to 15%, and the content of the conductive additive is 0 to 5% by mass.
  • the median particle size of the inner core is 1-10 ⁇ m
  • the thickness of the first shell layer is 0.01-2 ⁇ m
  • the thickness of the second shell layer is 0.01-1 ⁇ m.
  • the core particles are uniformly dispersed in the Si SiOx 1.
  • the total mass percentage content of the Si particles, silicon oxide SiOx 1 and MySiOz is 83-99%.
  • Another aspect of the present application provides a method for preparing a silicon-based negative electrode material for a secondary battery, including: preparing a first mixture, the first mixture including silicon-oxygen raw material SiOx (0 ⁇ x ⁇ 2), a metal source A substance and a carbon source substance; calcining the first mixture under non-oxygen conditions to obtain a first product, the first product comprising: an inner core, the inner core including Si particles and silicon oxide SiOx 1 , where 0 ⁇ x 1 ⁇ 2, x 1 >x; and a first shell layer that covers the core, and the first shell layer includes a compound of the general formula MySiOz (0 ⁇ y ⁇ 4, 0 ⁇ z ⁇ 5, and z ⁇ x 1 ) and C particles, the content of M and C in the first shell layer gradually increase from the side close to the inner core to the side away from the inner core, and the content of Si and O increases from the side close to the inner core.
  • the side away from the inner core is gradually reduced; the first product is coated with a carbon source material or a carbon source material and a conductive additive, and then carbonized in a non-oxidizing atmosphere, in the first shell layer
  • the surface is coated with a second shell layer, wherein the second shell layer includes a carbon film layer or a composite film layer formed by a carbon film layer and a conductive additive.
  • the non-oxidizing atmosphere includes at least one of nitrogen, argon, hydrogen, or helium.
  • the mass ratio of the silicon-oxygen raw material SiOx to the metal source material ranges from 100:1 to 100:50, and the mass ratio of silicon oxide SiOx to the carbon source material ranges from 100:1 to 100 : 10;
  • the temperature of the non-oxygen calcination condition is 300-1000°C; the temperature of the carbonization treatment condition is 500-1200°C.
  • the metal source material includes any one or more of metal carbonate, metal nitrate, and metal hydroxide, and the metal includes Li, Na, and Mg. , Al, Fe, Ca.
  • the metal source material includes one or more of lithium citrate, lithium carbonate, lithium hydroxide, or lithium nitrate.
  • the carbon source material includes citric acid, glucose, resin, coal pitch, petroleum pitch, polyvinyl alcohol, epoxy resin, polyacrylonitrile, polymethyl methacrylate, glucose, sucrose Any one or more of polyacrylic acid and polyvinylpyrrolidone.
  • the first mixture is lithium citrate or a mixture of lithium carbonate, citric acid, and SiOx (0 ⁇ x ⁇ 2).
  • the silicon-oxygen raw material SiOx is powder with a median particle size of 1-10 ⁇ m.
  • composition percentages of the metal source material, the carbon source material, and the silicon-oxygen raw material SiOx are 0.1-30% and 0.1-9%, respectively.
  • the present application also provides a secondary battery, the negative electrode of which includes any one of the negative electrode materials described in the embodiments of the present application.
  • the first shell layer (MySiOz and C particles) is formed on the surface of the core (SiOx 1 and Si particles)
  • the first Coulomb efficiency of the silicon negative electrode is improved
  • a second shell layer is coated on the surface of the first shell layer.
  • the second shell layer is, for example, a dense carbon film layer or a carbon film layer and a conductive additive, which improves the cycle performance of the silicon-based negative electrode material, and the conductive additive can
  • the electron migration rate of the silicon-based negative electrode material is enhanced, and the rapid charging capability is improved; the structure of the silicon-based negative electrode material is stable, and mass production can be realized.
  • the method for preparing the silicon-based negative electrode material of the secondary battery in the embodiment of the present application uses the metal source material and the carbon source material to react with SiOx to form the first product, and part of the silicate (MySiOz) is generated during the reaction, thereby improving the silicon
  • the first Coulombic efficiency of the base negative electrode material and then coat the outer layer of the first product with a carbon film layer or a composite film layer of carbon film layer and conductive additive, so that the cycle performance of the prepared silicon-based negative electrode material becomes better; and
  • the preparation method of the secondary battery described in the present application has simple process, low equipment requirements, and low cost; and the obtained silicon-based negative electrode material has a stable structure and can be mass-produced.
  • the secondary battery made of the silicon-based negative electrode material for the secondary battery provided by the embodiments of the present application exhibits high lithium removal capacity, high first coulombic efficiency and good cycle performance.
  • the charge capacity is above 1400mAh/g, and the discharge The capacity is above 1627mAh/g, and the first coulombic efficiency is above 86%.
  • FIG. 1 is a schematic structural diagram of a silicon-based negative electrode material for a secondary battery according to an embodiment of the application;
  • Fig. 3 is a charge-discharge curve of the silicon-based negative electrode material according to the embodiment of the present application.
  • One aspect of the present application provides a silicon-based negative electrode material for secondary batteries. With reference to Figure 1, it includes:
  • the inner core 10 includes Si particles and silicon oxide SiOx 1 , wherein 0 ⁇ x 1 ⁇ 2;
  • the first shell layer 11 includes a compound of the general formula MySiOz (0 ⁇ y ⁇ 4, 0 ⁇ z ⁇ 5, and z ⁇ x 1 ) and C particles.
  • the first shell layer 11 The inner core 10 is covered, and the contents of M and C in the first shell layer 11 gradually increase from the side close to the inner core 10 to the side away from the inner core 10, and the contents of Si and O increase from the side close to the inner core 10 Decrease gradually to the side away from the core 10;
  • the second shell layer 12 includes a carbon film layer or a composite film layer formed by a carbon film layer and a conductive additive, and the second shell layer 12 covers the first shell layer 11.
  • the silicon oxide SiOx 1 (0 ⁇ x 1 ⁇ 2) contained in the core is powder, and the Si particles exist in the state of simple silicon particles, and the Si particles and silicon
  • the oxide SiOx 1 exists in the form of a mixture as the core of the silicon-based negative electrode material, and the Si particles are uniformly dispersed in SiOx 1.
  • the "uniformity" is not strictly uniform, but substantially Disperse evenly.
  • the first shell layer 11 covers the core 10, wherein the coating can be a partial coating or a complete coating.
  • the core 10 can be completely covered by the first shell layer 11.
  • Fig. 1 schematically shows the situation of complete coating.
  • the first shell layer 11 does not have to be a perfect circular ring-shaped covering structure, but the covering thickness of the first shell layer 11 is substantially close.
  • the first shell layer 11 includes a compound of the general formula MySiOz (0 ⁇ y ⁇ 4, 0 ⁇ z ⁇ 5, and z ⁇ x 1 ) and C particles, where M can It is any one or more of Li, Na, Mg, Al, Fe, Ca, for example, MySiOz is Li 2 SiO 3 , Li 2 Si 2 O 5 , Li 4 SiO 4 , MgSiO 3 , CaSiO 3 and FeSiO 3, etc. .
  • the content of M and C in the first shell layer 11 gradually increases from the side close to the inner core 10 to the side away from the inner core 10, and the content of Si and O increases from the one close to the inner core 10
  • the side away from the inner core 10 gradually decreases.
  • the gradual increase may be an uneven increase or a uniform monotonic increase
  • the gradual decrease may be an uneven decrease or a uniform monotonic decrease.
  • it can be increased from 3% to 45% according to a linear relationship, or it can be increased from 4% to 30% according to a linear relationship.
  • the mass percentage content of the M element in the first shell layer increases in a gradient from the side close to the inner core to the side away from the inner core.
  • the mass percentage content of M in the first shell layer is first maintained at 3.5% of a certain thickness, then increased to a certain thickness of 11.5%, then increased to a certain thickness of 19.5%, then increased to a certain thickness of 27.5%, and then increased to a certain thickness of 35.5% thickness.
  • the mass percentage content of the M element on the side close to the inner core accounts for 0 to 5% of the first shell layer
  • the mass percentage content of the M element on the side far from the inner core accounts for the first shell layer.
  • the mass of the first shell layer is 1%-40%.
  • the C particle material includes any one or more of hard carbon, soft carbon or amorphous carbon, and the C particle exists in the form of elemental carbon.
  • the function of the C particles is to suppress the size of the silicon particles while improving the conductivity of the first shell layer.
  • the C particles in the first shell layer are uniformly dispersed in MySiOz.
  • the mass percentage content of the M element is 1%-15%, such as 2%, 4%, 5%, 8%, 10% , 12%, 14%, etc.
  • the mass percentage content of C particles is 0.1%-2%, for example, 0.2%, 0.4%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, etc.
  • the total mass percentage content (Wt) of the Si particles, silicon oxide SiOx 1 and MySiOz is 83%-99% , Such as 87%, 90%, 92%, 95%, 97%, etc.
  • the mass percentage content (Wt 2 ) of silicon oxide SiOx 1 ranges from 55 to 75%
  • the mass percentage content (Wt 3 ) of MySiOz compounds ranges from 1 to 20%
  • the second shell layer 12 covers the first shell layer 11.
  • the second shell layer 12 may only include a carbon film layer, or may also include a composite film layer formed by a carbon film layer and a conductive additive, wherein the conductive additive is uniformly dispersed in the carbon film layer to form a composite film layer.
  • the second shell layer completely covers the first shell layer, preventing the silicon-containing materials (including Si particles, silicon oxide SiOx 1 and MySiOz) in the first shell layer and the core from directly contacting the electrolyte, and slowing down
  • the surface of the silicon-based negative electrode material is powdered to prolong the cycle life.
  • the conductive additive is used to increase the conductivity of the silicon-based negative electrode material.
  • the carbon film layer or the composite film layer formed by the carbon film layer and the conductive additive has a mass percentage content of 0.1-15%, and the mass of the conductive additive The percentage content is 0 to 5%.
  • the carbon film layer material includes any one or more of hard carbon, soft carbon or amorphous carbon
  • the conductive additives include carbon nanotubes, graphene, conductive carbon black, Ketjen black, vapor-grown carbon fiber, and acetylene black , Any one or more of conductive graphite.
  • the median diameter of the inner core is 1-10 ⁇ m
  • the thickness of the first shell layer is 0.01-2 ⁇ m
  • the thickness of the second shell layer is 0.01-2 ⁇ m.
  • the first shell layer (MySiOz and C particles) is formed on the surface of the core (SiOx 1 and Si particles)
  • the first Coulomb efficiency of the silicon negative electrode is improved
  • a second shell layer is coated on the surface of the first shell layer.
  • the second shell layer is, for example, a dense carbon film layer or a composite film layer of a carbon film layer and a conductive additive, which improves the cycle performance of the silicon-based negative electrode material.
  • the conductive additive can enhance the electron migration rate of the silicon-based negative electrode material and improve the rapid charging ability; the structure of the silicon-based negative electrode material is stable, and mass production can be realized.
  • the content of M and C in the first shell layer of the silicon-based negative electrode material gradually increase from the side close to the inner core to the side away from the inner core.
  • This change in the material concentration is beneficial to improve the stability of the silicon-based negative electrode material structure. It reduces the expansion stress of the second shell layer.
  • the concentration gradient can better improve the stability of the silicon-based negative electrode material structure and reduce the second shell Expansion stress of the layer.
  • Another aspect of the present application provides a method for preparing a silicon-based negative electrode material for a secondary battery, including:
  • Step S1 preparing a first mixture, the first mixture including silicon-oxygen raw material SiOx, a metal source material, and a carbon source material (where 0 ⁇ x ⁇ 2);
  • the silica raw material SiOx is a powder with a median particle size D50 of 1-10 ⁇ m
  • the method for forming the silica raw SiOx powder is, for example, coarsely crushing and pulverizing the bulk SiOx to obtain SiOx powder.
  • the coarse crushing includes using a jaw crusher, a pair-roll crusher, a cone crusher, a hammer crusher or an impact crusher to coarsely crush the block SiOx.
  • the pulverization includes further pulverizing the coarsely pulverized SiOx using any one of a jet pulverizer, a mechanical pulverizer, a ball mill or a vibration mill, so as to obtain a powder with a median particle size of 1-10 ⁇ m.
  • the method for preparing the first mixture for example, adopts any one of a high-speed disperser, a high-speed stirring mill, a ball mill, a cone mixer, a screw mixer, a stirring mixer, or a VC mixer to combine the powdery silicon-oxygen raw material SiOx It is uniformly mixed with the metal source material and the carbon source material.
  • the metal source material includes any one or more of metal carbonate, metal nitrate, and metal hydroxide, and the metal includes Li, Na, and Mg. , Al, Fe, Ca.
  • the metal source material includes one or more of lithium citrate, lithium carbonate, lithium hydroxide, or lithium nitrate; the carbon source material includes citric acid, glucose, resin, coal pitch, petroleum pitch, and polyethylene. Any one or more of alcohol, epoxy resin, polyacrylonitrile, polymethyl methacrylate, glucose, sucrose, polyacrylic acid, and polyvinylpyrrolidone.
  • the metal source material is lithium citrate or lithium carbonate
  • the carbon source material is citric acid
  • the first mixture is lithium citrate or lithium carbonate and citric acid and SiOx(0 ⁇ x ⁇ 2) mixture.
  • the mass ratio of the silicon-oxygen raw material SiOx to the metal source material is in the range of 100:1 to 100:50, and the mass ratio of the silicon-oxygen raw material SiOx to the carbon source material is in the range of 100:1 ⁇ 100:10. That is, the mass of the silicon-oxygen raw material SiOx is 100 g, the mass of the metal source material is 1-50 g, and the mass of the carbon source material is 1-10 g.
  • Step S2 calcining the first mixture under non-oxygen conditions to obtain a first product, the first product comprising:
  • An inner core comprising Si particles and silicon oxide SiOx 1 , where 0 ⁇ x 1 ⁇ 2, x 1 >x;
  • the non-oxidizing atmosphere means that the reaction gas includes at least one of nitrogen, argon, hydrogen, or helium.
  • the calcination temperature under the non-oxygen condition is 300°C-1000°C, and the calcination time is 1-24 hours.
  • the calcination temperature is 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, etc.
  • the calcination time is 2 hours, 4 hours, hours, 6 hours, 8 hours, 11 hours, 13 hours, 16 Hours, 18 hours, 21 hours, etc.
  • the equipment for performing the calcination process is, for example, any one of a rotary kiln, a roller kiln, a pusher kiln, an atmosphere box furnace or a tube furnace.
  • the embodiment of the present application controls the generation degree of MySiOz and the first shell by adjusting the time, temperature, and reaction concentration ratio of the reaction between the metal source material M and the core material (Si particles and silicon oxide SiOx 1 ).
  • the content of M and C in the layer changes from the side close to the inner core to the side far from the inner core.
  • step S3 the first product is subjected to a coating reaction with a carbon source material or a mixture of a carbon source material and a conductive additive, and then a carbonization treatment is performed in a non-oxidizing atmosphere, and a second shell is coated on the surface of the first shell layer.
  • the equipment that can carry out the coating reaction may be any one of a mechanical fusion machine, a VC mixer, a coating kettle, a spray dryer, a sand mill or a high-speed disperser.
  • the non-oxidizing atmosphere means that the reaction gas includes at least one of nitrogen, argon, hydrogen, or helium.
  • the carbon source material includes citric acid, glucose, resin, coal pitch, petroleum pitch, polyvinyl alcohol, epoxy resin, polyacrylonitrile, polymethylmethacrylate, glucose, sucrose, polyacrylic acid, polyvinylpyrrolidone Any one or more.
  • the carbonization treatment temperature is 500-1200°C, and the treatment time is 1-12 hours.
  • the carbonization treatment temperature is 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C, etc.
  • the calcination time It is 2 hours, 4 hours, hours, 6 hours, 8 hours, 11 hours, etc.
  • the carbon film layer material includes any one or more of hard carbon, soft carbon or amorphous carbon
  • the conductive additives include carbon nanotubes, graphene, conductive carbon black, Ketjen black, vapor-grown carbon fiber, and acetylene black , Any one or more of conductive graphite.
  • the method for preparing the silicon-based negative electrode material of the secondary battery in the embodiment of the present application uses the metal source material and the carbon source material to react with SiOx to form the first product, and part of the silicate (MySiOz) is generated during the reaction, thereby improving the silicon
  • the first Coulombic efficiency of the base negative electrode material and then coat the outer layer of the first product with a carbon film layer or a composite film layer of carbon film layer and conductive additive, so that the cycle performance of the prepared silicon-based negative electrode material becomes better; and
  • the preparation method of the secondary battery described in the present application has simple process, low equipment requirements, and low cost; and the obtained silicon-based negative electrode material has a stable structure and can be mass-produced.
  • the present application also provides a secondary battery, the negative electrode of which includes any one of the negative electrode materials described in the embodiments of the present application.
  • the mass of the silicon oxide raw material SiOx is 1 Kg
  • the mass of the lithium carbonate is 476.8 g
  • the mass of the citric acid is 5 g.
  • the first mixture is calcined in a rotary furnace in an argon atmosphere at a calcining temperature of 750°C and a reaction time of 12 hours to obtain the inner core including SiOx 1 and Si particles, and the first shell layer includes Li 2 SiO 3 and C The first product of particles.
  • the first product is passed through a coating kettle with conductive graphite doped pitch for coating reaction.
  • the coating reaction is carried out in an argon atmosphere, the reaction temperature is 600° C., the reaction time is 10 hours, and finally the inner core is obtained.
  • It includes SiOx 1 and Si particles
  • the first shell layer includes Li 2 SiO 3 and C particles
  • the second shell layer is a silicon-based negative electrode material with a carbon film doped with conductive graphite.
  • the mass percentage content of Li element in the silicon-based negative electrode material is 10%, wherein the mass percentage content of Li inside the first shell layer is 4%, and the mass percentage content of Li outside the first shell layer is 45%.
  • the secondary battery made by using the silicon-based negative electrode material has a reversible capacity of 1430 mAh/g, a first coulombic efficiency of 89%, and a 500-week capacity retention rate of 88%.
  • the mass of the silica raw material SiOx is 1 Kg
  • the mass of the lithium citrate is 286.1 g
  • the mass of the citric acid is 5 g.
  • the first mixture is calcined in a rotary furnace in an argon atmosphere at a calcining temperature of 750°C and a reaction time of 12 hours to obtain the inner core including SiOx 1 and Si particles, and the first shell layer includes Li 2 SiO 3 and C The first product of particles.
  • the first product was passed through a coating kettle with conductive graphite-doped pitch for coating reaction.
  • the coating reaction was carried out in an argon atmosphere, the reaction temperature was 600° C., and the reaction time was 10 hours. Finally, the inner core was obtained.
  • the mass percentage content of Li element in the silicon-based negative electrode material is 6%, wherein the mass percentage content of M in the first shell layer is 2.5%, and the mass percentage content of M outside the first shell layer is 36%.
  • the secondary battery made by using the silicon-based negative electrode material has a reversible capacity of 1500 mAh/g, a first coulombic efficiency of 85%, and a 500-week capacity retention rate of 85%.
  • the mass of the silicon-oxygen raw material SiOx is 1 Kg
  • the mass of the lithium carbonate is 95.4 g
  • the mass of the citric acid is 5 g.
  • the first mixture was calcined in a rotary furnace in an argon atmosphere at a calcining temperature of 750°C and a reaction time of 12 hours to obtain an inner core including SiOx 1 and Si particles, and a first shell layer including Li 2 SiO 3 and C The first product of particles.
  • the first product was passed through a coating kettle with conductive graphite doped pitch for coating reaction.
  • the coating reaction was carried out in an argon atmosphere, the reaction temperature was 600°C, the reaction time was 10 hours, and finally the inner core was obtained.
  • the mass percentage content of Li element in the silicon-based negative electrode material is 2%, wherein the mass percentage content of M in the first shell layer is 0.5%, and the mass percentage content of M outside the first shell layer is 21%.
  • the secondary battery made by using the silicon-based negative electrode material has a reversible capacity of 1550 mAh/g, a first coulombic efficiency of 82%, and a 500-week capacity retention rate of 79%.
  • the mass of the silicon oxide raw material SiOx is 1 Kg
  • the mass of the lithium carbonate is 476.8 g
  • the mass of the citric acid is 5 g.
  • the first mixture is calcined in a rotary furnace in an argon atmosphere at a calcining temperature of 850°C and a reaction time of 12 hours to obtain an inner core including SiOx 1 and Si particles, and a first shell layer including Li 2 SiO 3 and Li 2 The first product of Si 2 O 5 and C particles.
  • the first product was passed through a coating kettle with conductive graphite doped pitch for coating reaction.
  • the coating reaction was carried out in an argon atmosphere, the reaction temperature was 600°C, the reaction time was 10 hours, and finally the inner core was obtained.
  • SiOx 1 and Si particles the first shell layer includes Li 2 SiO 3 and Li 2 Si 2 O 5 and C particles
  • the second shell layer is a silicon-based negative electrode material with a carbon film doped with conductive graphite.
  • the mass percentage content of Li element in the silicon-based negative electrode material is 10%, wherein the mass percentage content of Li inside the first shell layer is 4.5%, and the mass percentage content of Li outside the first shell layer is 44.5%.
  • the secondary battery made by using the silicon-based negative electrode material has a reversible capacity of 1430 mAh/g, a first coulombic efficiency of 88%, and a 500-week capacity retention rate of 90%.
  • the mass of the silicon oxide raw material SiOx is 1 Kg
  • the mass of the lithium carbonate is 476.8 g
  • the mass of the citric acid is 5 g.
  • the first mixture is calcined in a rotary furnace in an argon atmosphere, the calcining temperature is 950°C, the reaction time is 12h, the inner core includes SiOx 1 and Si particles, and the first shell layer includes Li 2 SiO 3 and Li 4 The first product of SiO 4 and C particles.
  • the first product was passed through a coating kettle with conductive graphite-doped pitch for coating reaction.
  • the coating reaction was carried out in an argon atmosphere, the reaction temperature was 600° C., and the reaction time was 10 hours. Finally, the inner core was obtained.
  • SiOx 1 and Si particles the first shell layer includes Li 2 SiO 3 and Li 4 SiO 4 and C particles
  • the second shell layer is a silicon-based negative electrode material with a carbon film doped with conductive graphite.
  • the mass percentage content of Li in the silicon-based negative electrode material is 10%, wherein the mass percentage content of Li inside the first shell layer is 5%, and the mass percentage content of Li outside the first shell layer is 43%.
  • the secondary battery made by using the silicon-based negative electrode material has a reversible capacity of 1400 mAh/g, a first coulombic efficiency of 90%, and a 500-week capacity retention rate of 86%.
  • the mass of the silicon oxide raw material SiOx is 1 Kg
  • the mass of the lithium carbonate is 476.8 g
  • the mass of the citric acid is 5 g.
  • the first mixture was calcined in a rotary furnace in an argon atmosphere at a calcining temperature of 750°C and a reaction time of 8 hours to obtain an inner core including SiOx 1 and Si particles, and a first shell layer including Li 2 SiO 3 and C The first product of particles.
  • the first product was passed through a coating kettle with conductive graphite doped pitch for coating reaction.
  • the coating reaction was carried out in an argon atmosphere, the reaction temperature was 600°C, the reaction time was 10 hours, and finally the inner core was obtained.
  • the mass percentage content of Li in the silicon-based negative electrode material is 10%, wherein the mass percentage content of Li inside the first shell layer is 3%, and the mass percentage content of Li outside the first shell layer is 46%.
  • the secondary battery made by using the silicon-based negative electrode material has a reversible capacity of 1350 mAh/g, a first coulombic efficiency of 86%, and a 500-week capacity retention rate of 85%.
  • the mass of the silicon oxide raw material SiOx is 1 Kg
  • the mass of the lithium carbonate is 476.8 g
  • the mass of the citric acid is 5 g.
  • the first mixture was calcined in a rotary furnace in an argon atmosphere at a calcining temperature of 750°C and a reaction time of 16 hours to obtain an inner core including SiOx 1 and Si particles, and a first shell layer including Li 2 SiO 3 and C The first product of particles.
  • the first product was passed through a coating kettle with conductive graphite-doped pitch for coating reaction.
  • the coating reaction was carried out in an argon atmosphere, the reaction temperature was 600° C., and the reaction time was 10 hours. Finally, the inner core was obtained.
  • the mass percentage content of Li in the silicon-based negative electrode material is 10%, wherein the mass percentage content of Li inside the first shell layer is 3%, and the mass percentage content of Li outside the first shell layer is 46%.
  • the secondary battery made by using the silicon-based negative electrode material has a reversible capacity of 1350 mAh/g, a first coulombic efficiency of 86%, and a 500-week capacity retention rate of 85%.
  • the mass of the silica raw material SiOx is 1 Kg
  • the mass of the sodium hydroxide is 193.2 g
  • the mass of the citric acid is 5 g.
  • the first mixture was calcined in an argon atmosphere through a rotary furnace at a calcining temperature of 750°C and a reaction time of 12 hours to obtain an inner core including SiOx 1 and Si particles, and a first shell layer including Na 2 SiO 3 and C The first product of particles.
  • the first product is passed through a coating kettle with conductive graphite doped pitch for coating reaction.
  • the coating reaction is carried out in an argon atmosphere, the reaction temperature is 600° C., the reaction time is 10 hours, and finally the inner core is obtained.
  • It includes SiOx 1 and Si particles, the first shell layer includes Na 2 SiO 3 and C particles, and the second shell layer is a silicon-based negative electrode material with a carbon film doped with conductive graphite.
  • the content of Na by mass in the silicon-based negative electrode material is 10%, wherein the content of Na by mass inside the first shell layer is 2%, and the content of Li outside the first shell layer is 46% by mass.
  • the secondary battery made by using the silicon-based negative electrode material has a reversible capacity of 1200 mAh/g, a first coulombic efficiency of 78%, and a 500-week capacity retention rate of 83%.
  • Magnesium and citric acid are thoroughly mixed in a high-speed stirring mill to prepare a first mixture including magnesium carbonate, citric acid and SiOx.
  • the mass of the silica raw material SiOx is 1 Kg
  • the mass of the lithium carbonate is 466.5 g
  • the mass of the citric acid is 5 g.
  • the first mixture was calcined in a rotary furnace in an argon atmosphere at a calcining temperature of 950°C and a reaction time of 12 hours to obtain an inner core including SiOx 1 and Si particles, and a first shell layer including MgSiO 3 and C particles.
  • the first product was calcined in a rotary furnace in an argon atmosphere at a calcining temperature of 950°C and a reaction time of 12 hours to obtain an inner core including SiOx 1 and Si particles, and a first shell layer including MgSiO 3 and C particles.
  • the first product is passed through a coating kettle with conductive graphite doped pitch for coating reaction.
  • the coating reaction is carried out in an argon atmosphere, the reaction temperature is 600° C., the reaction time is 10 hours, and finally the inner core is obtained.
  • It includes SiOx 1 and Si particles, the first shell layer includes MgSiO 3 and C particles, and the second shell layer is a silicon-based negative electrode material with a carbon film doped with conductive graphite.
  • the content of Mg element in the silicon-based negative electrode material is 12% by mass, wherein the content of Mg inside the first shell layer is 3% by mass, and the content of Mg outside the first shell layer is 46%.
  • the secondary battery made of the silicon-based negative electrode material has a reversible capacity of 1400 mAh/g, a first coulombic efficiency of 82%, and a 500-week capacity retention rate of 85%.
  • the mass of the silica raw material SiOx is 1 Kg
  • the mass of the aluminum hydroxide is 353.1 g
  • the mass of the citric acid is 5 g.
  • the first mixture was calcined in a rotary furnace in an argon atmosphere at a calcining temperature of 1000°C and a reaction time of 12 hours to obtain the inner core including SiOx 1 and Si particles, and the first shell layer including AlSi 1.5 O 4.5 and C The first product of particles.
  • the first product is passed through a coating kettle with conductive graphite doped pitch for coating reaction.
  • the coating reaction is carried out in an argon atmosphere, the reaction temperature is 600° C., the reaction time is 10 hours, and finally the inner core is obtained.
  • It includes SiOx 1 and Si particles
  • the first shell layer includes AlSi 1.5 O 4.5 and C particles
  • the second shell layer is a silicon-based negative electrode material with a carbon film doped with conductive graphite.
  • the content of Al element in the silicon-based negative electrode material is 10% by mass, wherein the content of Al in the inner side of the first shell layer is 4% by mass, and the content of Al in the outer side of the first shell layer is 45% by mass.
  • the secondary battery made by using the silicon-based negative electrode material has a reversible capacity of 1430 mAh/g, a first coulombic efficiency of 89%, and a 500-week capacity retention rate of 88%.
  • the mass of the silica raw material SiOx is 1 Kg
  • the mass of the iron hydroxide is 297.4 g
  • the mass of the citric acid is 5 g.
  • the first mixture is calcined in a rotary kiln in an argon atmosphere.
  • the calcining temperature is 1000° C. and the reaction time is 12 hours.
  • the inner core includes SiOx 1 and Si particles, and the first shell layer includes FeSiO 3 and C particles.
  • the first product is calcined in a rotary kiln in an argon atmosphere.
  • the calcining temperature is 1000° C. and the reaction time is 12 hours.
  • the inner core includes SiOx 1 and Si particles, and the first shell layer includes FeSiO 3 and C particles.
  • the first product is calcined in a rotary kiln in an argon atmosphere.
  • the first product is passed through a coating kettle with conductive graphite doped pitch for coating reaction.
  • the coating reaction is carried out in an argon atmosphere, the reaction temperature is 600° C., the reaction time is 10 hours, and finally the inner core is obtained.
  • It includes SiOx 1 and Si particles, the first shell layer includes FeSiO 3 and C particles, and the second shell layer is a silicon-based negative electrode material with a carbon film doped with conductive graphite.
  • the mass percentage of Fe in the silicon-based negative electrode material is 14%, wherein the mass percentage of Fe inside the first shell layer is 3%, and the mass percentage content of Fe outside the first shell layer is 46%.
  • the secondary battery made by using the silicon-based negative electrode material has a reversible capacity of 1240 mAh/g, a first coulombic efficiency of 75%, and a 500-week capacity retention rate of 65%.
  • the mass of the silica raw material SiOx is 1 Kg
  • the mass of the calcium carbonate is 277.8 g
  • the mass of the citric acid is 5 g.
  • the first mixture is calcined in a rotary kiln in an argon atmosphere.
  • the calcining temperature is 1000° C. and the reaction time is 12 hours.
  • the inner core includes SiOx 1 and Si particles, and the first shell layer includes CaSiO 3 and C particles.
  • the first product is calcined in a rotary kiln in an argon atmosphere.
  • the calcining temperature is 1000° C. and the reaction time is 12 hours.
  • the inner core includes SiOx 1 and Si particles, and the first shell layer includes CaSiO 3 and C particles.
  • the first product is calcined in a rotary kiln in an argon atmosphere.
  • the first product is passed through a coating kettle with conductive graphite doped pitch for coating reaction.
  • the coating reaction is carried out in an argon atmosphere, the reaction temperature is 600° C., the reaction time is 10 hours, and finally the inner core is obtained.
  • It includes SiOx 1 and Si particles, the first shell layer includes CaSiO 3 and C particles, and the second shell layer is a silicon-based negative electrode material with a carbon film doped with conductive graphite.
  • the mass percentage content of Ca in the silicon-based negative electrode material is 10%, wherein the mass percentage content of Ca inside the first shell layer is 2%, and the mass percentage content of Ca outside the first shell layer is 45%.
  • the secondary battery made of the silicon-based negative electrode material has a reversible capacity of 1140 mAh/g, a first coulombic efficiency of 65%, and a 500-week capacity retention rate of 62%.
  • the acid is thoroughly mixed in a high-speed stirring mill to prepare a first mixture including citric acid and SiOx.
  • the mass of the silica raw material SiOx is 1 Kg, and the mass of the citric acid is 5 g.
  • the first mixture is calcined in a rotary kiln in an argon atmosphere at a calcining temperature of 700° C. to obtain a first product with an inner core including SiOx 1 and Si particles and an outer shell of C.
  • the first product was passed through a coating kettle with conductive graphite doped pitch, and the coating reaction was carried out in an argon atmosphere, the reaction temperature was 750 degrees Celsius, the reaction time was 12 hours, and finally the inner core was obtained. It includes SiOx 1 and Si particles, and the outer shell layer is a silicon-based negative electrode material with a carbon film layer doped with conductive graphite.
  • the secondary battery made by using the silicon-based negative electrode material has a reversible capacity of 1650 mAh/g, a first coulombic efficiency of 76%, and a 500-week capacity retention rate of 30%.
  • the acid is thoroughly mixed in a high-speed stirring mill to prepare a first mixture including citric acid and SiOx.
  • the mass of the silica raw material SiOx is 1 Kg
  • the mass of the citric acid is 10 g.
  • the first mixture is calcined in a rotary kiln in an argon atmosphere at a calcining temperature of 700° C. to obtain a first product with an inner core including SiOx 1 and Si particles and an outer shell of C.
  • the first product was passed through a coating kettle with conductive graphite doped pitch, and the coating reaction was carried out in an argon atmosphere, the reaction temperature was 750 degrees Celsius, the reaction time was 12 hours, and finally the inner core was obtained. It includes SiOx 1 and Si particles, and the outer shell layer is a silicon-based negative electrode material with a carbon film layer doped with conductive graphite.
  • the secondary battery made by using the silicon-based negative electrode material has a reversible capacity of 1620 mAh/g, a first coulombic efficiency of 75%, and a 500-week capacity retention rate of 32%.
  • the secondary battery made of the negative electrode material of the secondary battery provided in the examples of this application exhibits high lithium removal capacity, high first-time coulombic efficiency and good cycle performance, with a charging capacity of 1400mAh /g above, the discharge capacity is above 1627mAh/g, the first coulombic efficiency is above 86%.
  • FIG. 2 is an SEM image of the silicon-based anode material according to the embodiment of the application, it can be seen from the drawings that the particles of the silicon-based anode material are uniformly dispersed.
  • FIG. 3 it is the charge and discharge curve of the silicon-based anode material according to the embodiment of the application. It can be seen from the drawings that the silicon-based anode material has a high reversible capacity and a high first-time coulombic efficiency.
  • first, second, third, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. Therefore, the first element in some embodiments may be referred to as the second element in other embodiments without departing from the teaching of the present invention.
  • the same reference number or the same reference designator represents the same element throughout the specification.
  • the exemplary embodiments are described by referring to cross-sectional illustrations and/or plan illustrations as idealized exemplary illustrations. Therefore, the difference from the illustrated shape due to, for example, manufacturing technology and/or tolerances is foreseeable. Therefore, the exemplary embodiment should not be interpreted as being limited to the shape of the area shown here, but should include deviations in the shape caused by, for example, manufacturing. For example, an etched area shown as a rectangle will generally have round or curved features. Therefore, the area shown in the figure is schematic in nature, and its shape is not intended to show the actual shape of the area of the device nor to limit the scope of the exemplary embodiment.

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Abstract

用于二次电池的硅基负极材料及其制备方法以及二次电池，所述用于二次电池的硅基负极材料包括：内核（10），所述内核（10）包括Si粒子和硅氧化物SiO x1，其中0＜x1＜2；第一壳层（11），所述第一壳层（11）包括通式为M ySiO z的化合物(0＜y≤4，0＜z≤5，且z≥x1)以及C粒子，所述第一壳层（11）包覆所述内核（10），并且所述第一壳层（11）中M、C的含量由靠近内核（10）的一侧向远离内核（10）的一侧逐渐增加；以及第二壳层（12），所述第二壳层（12）包括碳膜层或者碳膜层与导电添加剂形成的复合膜层，所述第二壳层（12）包覆所述第一壳层（11）。所述硅基负极材料的首次充放电循环能力得到了提高，并且制作成本降低。

Description

用于二次电池的硅基负极材料及其制备方法，二次电池 技术领域
本发明涉及二次电池领域，具体涉及一种用于二次电池的硅基负极材料及其制备方法、以及二次电池。
背景技术
传统的锂离子电池的负极材料是石墨，然而石墨的理论容量只有372mAh/g，不能满足当前产业界对锂离子电池的高能量需求。硅元素在自然界中存储丰富，而且对环境安全环保，得到了研究者越来越多的关注。而且，理论上硅的容量高，其容量可达4200mAh/g，放电电位相对较低，价格低廉，对环境友好，是一种优良的锂离子电池负极材料。但是由于硅基材料有严重的体积效应，导致了硅基材料的循环性能非常差，无法满足商业化应用。
SiOx(0＜x＜2)材料具有高容量的同时，具有比单质硅更优越的循环性能，受到广泛的关注和研究。但是SiOx(0＜x＜2)材料的首次充放电效率相比石墨仍有较大差距，难以适应商业化需求。石墨在首次充放电循环中有质量百分比为5％～20％的锂用于形成钝化膜(SEI)，而Si、SiOx(0＜x＜2)则需要消耗20～50％的锂。因此，对SiOx(0＜x＜2)负极材料实施补锂，对其商业应用有重大意义。
现有技术中，通常采用直接在电极极片表面涂覆锂层，或者在电极极片表面采用电化学方式镀锂的工艺来进行补锂，然而，所述的补锂工艺一方面会导致Si晶粒生长过大，降低电极的循环寿命，另一方面，所述的补锂工艺安全性能差，难以实现量产。而且，由于硅氧材料嵌锂过程中有不可逆物质的生成，导致首次库伦效率偏低，难以商业应用。
发明内容
本申请提供一种用于二次电池的硅基负极材料及其制备方法，以提高所述二次电池的硅基负极材料的首次充放电循环能力，并降低所述二次电池的硅基负极材料的制作成本。
本申请的一方面提供一种用于二次电池的硅基负极材料，包括：内核，所述内核包括Si粒子和硅氧化物SiOx 1，其中0＜x 1＜2；第一壳层，所述第一壳层包括通式为MySiOz的化合物(0＜y≤4，0＜z≤5，且z≥x 1)以及C粒子，所述第一壳层包覆所述内核，并且所述第一壳层中M、C的含量由靠近内核的一侧向远离内核的一侧逐渐增加；以及第二壳层，所述第二壳层包括碳膜层或者碳膜层与导电添加剂形成的复合膜层，所述第二壳层包覆所述第一壳层。
在本申请的一些实施例中，所述第一壳层中M为Li、Na、Mg、Al、Fe、Ca中的任意一种或者多种。
在本申请的一些实施例中，所述硅基负极材料中M的质量百分比含量1～15％，其中，M占第一壳层的质量百分比含量为1～40％。
在本申请的一些实施例中，所述第一壳层中M、C的质量百分比含量由靠 近内核的一侧向远离内核的一侧呈梯度增加。
在本申请的一些实施例中，靠近内核的一侧M的质量百分比含量占第一壳层的0～5％，远离内核的一侧M的质量百分比含量占第一壳层的30～48％。
在本申请的一些实施例中，所述C粒子材料包含硬碳、软碳或者无定形碳中任意一种或者多种。
在本申请的一些实施例中，所述碳膜层材料包含硬碳、软碳或者无定形碳中任意一种或者多种，所述导电添加剂包括碳纳米管、石墨烯、导电炭黑、科琴黑、气相生长碳纤维、乙炔黑、导电石墨中的任意一种或多种。
在本申请的一些实施例中，所述硅基负极材料中，C粒子的质量百分比含量为0.1～2％，所述碳膜层或者碳膜层与导电添加剂形成的复合膜层的质量百分比含量为0.1～15％，所述导电添加剂的质量百分比含量为0～5％。
在本申请的一些实施例中，所述内核中值粒径为1～10μm，所述第一壳层的厚度为0.01～2μm，所述第二壳层的厚度为0.01～1μm。
在本申请的一些实施例中，所述内核中Si粒子均匀分散在SiOx 1中。
在本申请的一些实施例中，以所述硅基负极材料的质量为100％计，所述Si粒子、硅氧化物SiOx 1和MySiOz的质量百分比含量之和为83～99％。
本申请的另一方面提供一种用于二次电池的硅基负极材料的制备方法，包括：制备第一混合物，所述第一混合物包括硅氧原料SiOx(0＜x＜2)、金属源物质和碳源物质；将所述第一混合物在非氧条件下煅烧，得到第一产物，所述第一产物包括：内核，所述内核包括Si粒子和硅氧化物SiOx 1，其中0＜x 1＜2，x 1＞x；以及第一壳层，所述第一壳层包覆所述内核，并且所述第一壳层包括通式为MySiOz的化合物(0＜y≤4，0＜z≤5，且z≥x 1)和C粒子，所述第一壳层中 M、C的含量由靠近内核的一侧向远离内核的一侧逐渐增加，Si、O的含量由靠近内核的一侧向远离内核的一侧逐渐降低；将所述第一产物通过碳源物质或者碳源物质和导电添加剂进行包覆反应，然后在非氧化气氛中进行碳化处理，在所述第一壳层表面包覆第二壳层，其中，所述第二壳层包括碳膜层或者碳膜层与导电添加剂形成的复合膜层。
在本申请的一些实施例中，所述非氧化气氛包括氮气、氩气、氢气或氦气中的至少一种。
在本申请的一些实施例中，所述硅氧原料SiOx与金属源物质的质量比范围为100∶1～100∶50，硅氧化物SiOx与碳源物质的质量比范围为100∶1～100∶10；所述非氧煅烧条件温度为300-1000℃；所述碳化处理条件的温度为500-1200℃。
在本申请的一些实施例中，所述金属源物质包括金属的碳酸盐，金属的硝酸盐，以及金属的氢氧化物中的任意一种或者多种，所述金属包括Li、Na、Mg、Al、Fe、Ca。
在本申请的一些实施例中，所述金属源物质包括柠檬酸锂、碳酸锂、氢氧化锂或者硝酸锂中的一种或者多种。
在本申请的一些实施例中，所述碳源物质包括柠檬酸、葡萄糖、树脂、煤沥青、石油沥青、聚乙烯醇、环氧树脂、聚丙烯腈、聚甲基丙烯酸甲酯、葡萄糖、蔗糖、聚丙烯酸、聚乙烯吡咯烷酮中的任意一种或者多种。
在本申请的一些实施例中，所述第一混合物为柠檬酸锂或者碳酸锂和柠檬酸和SiOx(0＜x＜2)的混合物。
在本申请的一些实施例中，所述硅氧原料SiOx为粉体，中值粒径为 1～10μm。
在本申请的一些实施例中，所金属源物质和碳源物质与硅氧原料SiOx的组分百分比分别为0.1～30％、0.1～9％。
本申请还提供一种二次电池，其负极包括本申请实施例所述的任意一种负极材料。
本申请实施例所述的用于二次电池的硅基负极材料，在内核(SiOx 1和Si粒子)表面形成第一壳层(MySiOz和C粒子)后，提高了硅负极的首次库伦效率；在第一壳层表面包覆第二壳层，所述第二壳层例如为致密的碳膜层或者碳膜层和导电添加剂，提高了所述硅基负极材料的循环性能，而且导电添加剂能增强所述硅基负极材料的电子迁移速率，提高快速充电能力；所述硅基负极材料的结构稳定，可实现量产。
本申请实施例二次电池的硅基负极材料的制备方法采用金属源物质和碳源物质与SiOx进行反应生成第一产物，反应过程中生成部分硅酸盐(MySiOz)，从而提高了所述硅基负极材料材料的首次库伦效率；再在所述第一产物外层包覆碳膜层或者碳膜层和导电添加剂的复合膜层，从而使制备的硅基负极材料的循环性能变好；而且，本申请所述的二次电池的制备方法工艺简单、对设备要求低，成本低廉；并且得到的硅基负极材料结构稳定，可实现量产。
采用本申请所述的实施例提供的二次电池硅基负极材料制成的二次电池，表现出高脱锂容量、高首次库伦效率和良好的循环性能，充电容量在1400mAh/g以上，放电容量在1627mAh/g以上，首次库伦效率在86％以上。
本申请中另外的特征将部分地在下面的描述中阐述。通过该阐述，使以下 附图和实施例叙述的内容对本领域普通技术人员来说变得显而易见。本申请中的发明点可以通过实践或使用下面讨论的详细示例中阐述的方法、手段及其组合来得到充分阐释。
附图说明
以下附图详细描述了本申请中披露的示例性实施例。其中相同的附图标记在附图的若干视图中表示类似的结构。本领域的一般技术人员将理解这些实施例是非限制性的、示例性的实施例，附图仅用于说明和描述的目的，并不旨在限制本公开的范围，其他方式的实施例也可能同样的完成本申请中的发明意图。应当理解，附图未按比例绘制。其中：
图1为本申请实施例所述用于二次电池的硅基负极材料的结构示意图；
图2为本申请实施例所述的硅基负极材料的SEM图；
图3为采用本申请实施例所述的硅基负极材料的充放电曲线。
具体实施方式
以下描述提供了本申请的特定应用场景和要求，目的是使本领域技术人员能够制造和使用本申请中的内容。对于本领域技术人员来说，对所公开的实施例的各种局部修改是显而易见的，并且在不脱离本公开的精神和范围的情况下，可以将这里定义的一般原理应用于其他实施例和应用。因此，本公开不限于所示的实施例，而是与权利要求一致的最宽范围。
下面结合实施例和附图对本发明技术方案进行详细说明。
本申请的一方面提供一种用于二次电池的硅基负极材料，参考附图1，包 括：
内核10，所述内核10包括Si粒子和硅氧化物SiOx 1，其中0＜x 1＜2；
第一壳层11，所述第一壳层11包括通式为MySiOz的化合物(0＜y≤4，0＜z≤5，且z≥x 1)以及C粒子，所述第一壳层11包覆所述内核10，并且所述第一壳层11中M、C的含量由靠近内核10的一侧向远离内核10的一侧逐渐增加，Si、O的含量由靠近内核10的一侧向远离内核10的一侧逐渐降低；
第二壳层12，所述第二壳层12包括碳膜层或者碳膜层与导电添加剂形成的复合膜层，所述第二壳层12包覆所述第一壳层11。
在本申请的一些实施例中，所述内核中包含的硅氧化物SiOx 1(0＜x 1＜2)为粉体，而Si粒子以单质态的硅粒子状态存在，所述Si粒子和硅氧化物SiOx 1以混合物形态存在，作为所述硅基负极材料的内核，并且所述Si粒子均匀的分散在SiOx 1中，所述的“均匀”并非严格意义上的均匀，而是大体上的均匀分散。
所述第一壳层11包覆所述内核10，其中，所述的包覆可以是部分包覆，也可以是完全包覆。可选的，在多数硅基负极材料的制作工艺中，都可以实现所述第一壳层11对所述内核10的完全包覆。在图1中示意性的表示出完全包覆的情形。然而，所述的第一壳层11也不一定是正圆环形的包覆结构，只是大体上实现所述第一壳层11的包覆厚度接近。
在本申请的一些实施例中，所述第一壳层11包括通式为MySiOz的化合物(0＜y≤4，0＜z≤5，且z≥x 1)以及C粒子，其中，M可以是Li、Na、Mg、Al、Fe、Ca中的任意一种或者多种，例如MySiOz为Li 2SiO 3、Li 2Si 2O 5、Li 4SiO 4、MgSiO 3、CaSiO 3以及FeSiO 3等。
在本申请的一些实施例中，所述第一壳层11中M、C的含量由靠近内核10 的一侧向远离内核10的一侧逐渐增加，Si、O的含量由靠近内核10的一侧向远离内核10的一侧逐渐降低。其中，所述的逐渐增加可以是不均匀的增加，也可以是均匀的单调增加，所述的逐渐降低可以是不均匀的降低，也可以是均匀的单调降低。例如，按照线性关系从3％增加至45％，或者，也可以按照线性关系从4％增加至30％等。
在本申请的其他一些实施例中，所述第一壳层中M元素的质量百分比含量由靠近内核的一侧向远离内核的一侧呈梯度增加。例如，第一壳层中M的质量百分比含量先保持在3.5％一定厚度，然后增加至11.5％一定厚度，再增加至19.5％一定厚度，再增加至27.5％一定厚度，再增加至35.5％一定厚度。
在本申请的一些实施例中，整体上，靠近内核的一侧M元素的质量百分比含量占第一壳层的0～5％，远离内核的一侧M元素的质量百分比含量占第一壳层的30％～48％。以所述第一壳层的质量为100％计，所述M元素占第一壳层的质量百分比含量的整体平均为1％～40％。
在本申请的一些实施例中，所述C粒子材料包含硬碳、软碳或者无定形碳中任意一种或者多种，所述C粒子以单质碳的形式存在。C粒子的作用是抑制硅粒子尺寸的大小，同时改善所述第一壳层的导电性能。所述第一壳层中C粒子均匀分散在MySiOz中。
所述硅基负极材料中(以所述硅基负极材料的质量为100％计)，M元素的质量百分比含量1％～15％，例如2％，4％，5％，8％，10％，12％，14％等。C粒子的质量百分比含量为0.1％～2％，例如0.2％，0.4％，0.6％，0.8％，1％，1.2％，1.4％，1.6％，1.8％等。
在本申请的一些实施例中，以所述硅基负极材料的质量为100％计，所述Si 粒子、硅氧化物SiOx 1和MySiOz的质量百分比含量之和(Wt)为83％～99％，例如87％，90％，92％，95％，97％等。其中硅氧化物SiOx 1的质量百分比含量(Wt 2)范围是55～75％，MySiOz的化合物的质量百分比含量(Wt 3)范围为1～20％，Si粒子的质量百分比含量Wt 1范围为(Wt 1＝Wt-Wt 2-Wt 3)。
在本申请的一些实施例中，第二壳层12包覆所述第一壳层11。所述第二壳层12可以仅包括碳膜层，还可以包括碳膜层与导电添加剂形成的复合膜层，其中，所述的导电添加剂均匀的分散再所述碳膜层中，共同组成所述第二壳层。所述的第二壳层完全包覆所述第一壳层，防止所述第一壳层以及内核中的含硅材料(包括Si粒子、硅氧化物SiOx 1和MySiOz)直接接触电解液，减缓所述硅基负极材料的表面粉化，延长循环寿命。所述导电添加剂用于增加所述硅基负极材料的导电性。
在本申请的一些实施例中，所述硅基负极材料中，所述碳膜层或者碳膜层与导电添加剂形成的复合膜层的质量百分比含量为0.1～15％，所述导电添加剂的质量百分比含量为0～5％。
所述碳膜层材料包含硬碳、软碳或者无定形碳中任意一种或者多种，所述导电添加剂包括碳纳米管、石墨烯、导电炭黑、科琴黑、气相生长碳纤维、乙炔黑、导电石墨中的任意一种或多种。
在本申请的一些实施例中，所述内核中值粒径为1～10μm，所述第一壳层的厚度为0.01～2μm。所述第二壳层的厚度为0.01～2μm。
本申请实施例所述的用于二次电池的硅基负极材料，在内核(SiOx 1和Si粒子)表面形成第一壳层(MySiOz和C粒子)后，提高了硅负极的首次库伦效率；在第一壳层表面包覆第二壳层，所述第二壳层例如为致密的碳膜层或者 碳膜层和导电添加剂的复合膜层，提高了所述硅基负极材料的循环性能，而且导电添加剂能增强所述硅基负极材料的电子迁移速率，提高快速充电能力；所述硅基负极材料的结构稳定，可实现量产。
进一步，所述硅基负极材料的第一壳层中M、C的含量由靠近内核的一侧向远离内核的一侧逐渐增加，这种材料浓度的变化有利于改善硅基负极材料结构的稳定性，减小第二壳层的膨胀应力。更进一步，所述M、C的含量由靠近内核的一侧向远离内核的一侧呈梯度增加时，所述浓度梯度能够更好的改善硅基负极材料结构的稳定性，减小第二壳层的膨胀应力。
本申请的另一方面提供一种用于二次电池的硅基负极材料的制备方法，包括：
步骤S1，制备第一混合物，所述第一混合物包括硅氧原料SiOx、金属源物质和碳源物质(其中0＜x＜2)；
其中，所述硅氧原料SiOx为中值粒径D50在1～10μm的粉末，形成所述硅氧原料SiOx粉末的方法例如为：将块状SiOx通过粗碎、粉碎得到SiOx粉末。所述粗碎包括采用颚式破碎机、对辊破碎机、园锥破碎机、锤式破碎机或者反击式破碎机对所述块状SiOx进行粗碎处理。所述粉碎包括采用气流粉碎机、机械粉碎机、球磨机或者振动磨中的任意一种对粗碎后的SiOx进行进一步粉碎，从而得到中值粒径在1～10μm的粉末。
制备所述第一混合物的方法例如采用高速分散机、高速搅拌磨、球磨机、锥形混合机，螺旋混合机，搅拌式混合机或VC混合机中的任意一种将粉末状的硅氧原料SiOx与金属源物质和碳源物质进行均匀混合。
在本申请的一些实施例中，所述金属源物质包括金属的碳酸盐，金属的 硝酸盐，以及金属的氢氧化物中的任意一种或者多种，所述金属包括Li、Na、Mg、Al、Fe、Ca。例如，所述金属源物质包括柠檬酸锂、碳酸锂、氢氧化锂或者硝酸锂中的一种或者多种；所述碳源物质包括柠檬酸、葡萄糖、树脂、煤沥青、石油沥青、聚乙烯醇、环氧树脂、聚丙烯腈、聚甲基丙烯酸甲酯、葡萄糖、蔗糖、聚丙烯酸、聚乙烯吡咯烷酮中的任意一种或者多种。
在本申请的一些实施例中，所述金属源物质为柠檬酸锂或者碳酸锂，所述碳源物质为柠檬酸，所述第一混合物为柠檬酸锂或者碳酸锂和柠檬酸和SiOx(0＜x＜2)的混合物。
在本申请的一些实施例中，所述硅氧原料SiOx与金属源物质的质量比范围为100∶1～100∶50，所述硅氧原料SiOx与碳源物质的质量比范围为100∶1～100∶10。也就是说，所述硅氧原料SiOx的质量以100g计，所述金属源物质的质量为1～50g，所述碳源物质的质量为1～10g。
步骤S2，将所述第一混合物在非氧条件下煅烧，得到第一产物，所述第一产物包括：
内核，所述内核包括Si粒子和硅氧化物SiOx 1，其中0＜x 1＜2，x 1＞x；以及
第一壳层，所述第一壳层包覆所述内核，并且所述第一壳层包括通式为MySiOz的化合物(0＜y≤4，0＜z≤5，且z≥x 1＞x)和C粒子，所述第一壳层中M、C的含量由靠近内核的一侧向远离内核的一侧逐渐增加，由此，所述Si、O的含量由靠近内核的一侧向远离内核的一侧逐渐降低。
在本申请的一些实施例中，所述非氧化气氛意为反应气体中包括氮气、氩气、氢气或氦气中的至少一种。在本申请的一些实施例中，所述非氧条件下煅烧的温度为300℃-1000℃，煅烧时间为1-24小时。例如，所述煅烧温度为 400℃，500℃，600℃，700℃，800℃，900℃等，煅烧时间为2小时，4小时，小时，6小时，8小时，11小时，13小时，16小时，18小时，21小时等。
进行所述煅烧工艺的设备例如为回转炉、辊道窑、推板窑、气氛箱式炉或管式炉中的任意一种。通过调整进行反应的第一混合物与所述金属源物质和碳源物质的含量以及煅烧的时间和温度，使所述第一壳层中M、C的含量由靠近内核的一侧向远离内核的一侧逐渐增加，所述Si、O的含量由靠近内核的一侧向远离内核的一侧逐渐降低。也就是说，本申请实施例通过金属源物质M与内核物质(Si粒子和硅氧化物SiOx 1)反应的时间、温度、反应浓度比等调控手段来控制MySiOz的生成程度以及所述第一壳层中M、C含量从接近内核一侧到远离内核一侧的变化。
步骤S3，将所述第一产物通过碳源物质或者碳源物质和导电添加剂的混合物进行包覆反应，然后在非氧化气氛中进行碳化处理，在所述第一壳层表面包覆第二壳层，其中，所述第二壳层包括碳膜层或者碳膜层与导电添加剂形成的复合膜层。
在本申请的一些实施例中，可进行所述包覆反应的设备可以是机械融合机、VC混合机、包覆釜、喷雾干燥、砂磨机或高速分散机中的任意一种。所述非氧化气氛意为反应气体中包括氮气、氩气、氢气或氦气中的至少一种。
所述碳源物质包括柠檬酸、葡萄糖、树脂、煤沥青、石油沥青、聚乙烯醇、环氧树脂、聚丙烯腈、聚甲基丙烯酸甲酯、葡萄糖、蔗糖、聚丙烯酸、聚乙烯吡咯烷酮中的任意一种或者多种。所述进行碳化处理的温度为500-1200℃，处理时间为1-12小时，例如，进行碳化处理的温度为600℃，700℃，800℃，900℃，1000℃，1100℃等，煅烧时间为2小时，4小时，小时，6小时， 8小时，11小时等。
所述碳膜层材料包含硬碳、软碳或者无定形碳中任意一种或者多种，所述导电添加剂包括碳纳米管、石墨烯、导电炭黑、科琴黑、气相生长碳纤维、乙炔黑、导电石墨中的任意一种或多种。
本申请实施例二次电池的硅基负极材料的制备方法采用金属源物质和碳源物质与SiOx进行反应生成第一产物，反应过程中生成部分硅酸盐(MySiOz)，从而提高了所述硅基负极材料材料的首次库伦效率；再在所述第一产物外层包覆碳膜层或者碳膜层和导电添加剂的复合膜层，从而使制备的硅基负极材料的循环性能变好；而且，本申请所述的二次电池的制备方法工艺简单、对设备要求低，成本低廉；并且得到的硅基负极材料结构稳定，可实现量产。
本申请还提供一种二次电池，其负极包括本申请实施例所述的任意一种负极材料。
实施例1
采用对辊破碎机将块状SiOx(x＝0.9)进行粗碎，并将粗碎后的原料通过气流粉碎机进行粉碎，得到粒径D50为5μm的SiOx粉末，并将所述SiOx粉末与碳酸锂和柠檬酸在高速搅拌磨中进行充分混合，制备成包括碳酸锂，柠檬酸和SiOx的第一混合物。其中，所述硅氧原料SiOx的质量为1Kg，所述碳酸锂的质量为476.8g，所述柠檬酸的质量为5g。
将所述第一混合物在氩气氛围中，通过回转炉进行煅烧，煅烧温度为750℃煅烧，反应时间为12h，得到内核包括SiOx 1和Si粒子，第一壳层包括Li 2SiO 3和C粒子的第一产物。
将所述第一产物通过掺杂了导电石墨的沥青用包覆釜进行包覆反应，所述包覆反应在氩气气氛中进行，反应温度为600℃，反应时间为10小时，最终得到内核包括SiOx 1和Si粒子，第一壳层包括Li 2SiO 3和C粒子，第二壳层为掺杂了导电石墨的碳膜层硅基负极材料。
所述硅基负极材料中Li元素的质量百分比含量为10％，其中，第一壳层内侧Li的质量百分比含量为4％，第一壳层外侧Li的质量百分比含量为45％。采用所述硅基负极材料制作的二次电池，其可逆容量为1430mAh/g，首次库仑效率为89％，500周容量保持率为88％。
实施例2
采用对辊破碎机将块状SiOx(x＝0.9)进行粗碎，并将粗碎后的原料通过气流粉碎机进行粉碎，得到粒径D50为5μm的SiOx粉末，并将所述SiOx粉末与碳酸锂和柠檬酸在高速搅拌磨中进行充分混合，制备成包括碳酸锂，柠檬酸和SiOx的第一混合物。其中，所述硅氧原料SiOx的质量为1Kg，所述柠檬酸锂的质量为286.1g，所述柠檬酸的质量为5g。
将所述第一混合物在氩气氛围中，通过回转炉进行煅烧，煅烧温度为750℃煅烧，反应时间为12h，得到内核包括SiOx 1和Si粒子，第一壳层包括Li 2SiO 3和C粒子的第一产物。
将所述第一产物通过掺杂了导电石墨的沥青用包覆釜进行包覆反应，所述包覆反应在氩气气氛中进行，反应温度为600℃，反应时间为10h，最终得到内核包括SiOx 1和Si粒子，第一壳层包括Li 2SiO 3和C粒子，第二壳层为掺杂了导电石墨的碳膜层硅基负极材料。
所述硅基负极材料中Li元素的质量百分比含量为6％，其中，第一壳层 内测M的质量百分比含量为2.5％，第一壳层外侧M的质量百分比含量为36％。采用所述硅基负极材料制作的二次电池，其可逆容量为1500mAh/g，首次库仑效率为85％，500周容量保持率为85％。
实施例3
采用对辊破碎机将块状SiOx(x＝0.9)进行粗碎，并将粗碎后的原料通过气流粉碎机进行粉碎，得到粒径D50为5μm的SiOx粉末，并将所述SiOx粉末与碳酸锂和柠檬酸在高速搅拌磨中进行充分混合，制备成包括碳酸锂，柠檬酸和SiOx的第一混合物。其中，所述硅氧原料SiOx的质量为1Kg，所述碳酸锂的质量为95.4g，所述柠檬酸的质量为5g。
将所述第一混合物在氩气氛围中，通过回转炉进行煅烧，煅烧温度为750℃煅烧，反应时间为12h，得到内核包括SiOx 1和Si粒子，第一壳层包括Li 2SiO 3和C粒子的第一产物。
将所述第一产物通过掺杂了导电石墨的沥青用包覆釜进行包覆反应，所述包覆反应在氩气气氛中进行，反应温度为600℃，反应时间为10h，最终得到内核包括SiOx 1和Si粒子，第一壳层包括Li 2SiO 3和C粒子，第二壳层为掺杂了导电石墨的碳膜层硅基负极材料。
所述硅基负极材料中Li元素的质量百分比含量为2％，其中，第一壳层内测M的质量百分比含量为0.5％，第一壳层外侧M的质量百分比含量为21％。采用所述硅基负极材料制作的二次电池，其可逆容量为1550mAh/g，首次库仑效率为82％，500周容量保持率为79％。
实施例4
采用对辊破碎机将块状SiOx(x＝0.9)进行粗碎，并将粗碎后的原料通 过气流粉碎机进行粉碎，得到粒径D50为5μm的SiOx粉末，并将所述SiOx粉末与碳酸锂和柠檬酸在高速搅拌磨中进行充分混合，制备成包括碳酸锂，柠檬酸和SiOx的第一混合物。其中，所述硅氧原料SiOx的质量为1Kg，所述碳酸锂的质量为476.8g，所述柠檬酸的质量为5g。
将所述第一混合物在氩气氛围中，通过回转炉进行煅烧，煅烧温度为850℃煅烧，反应时间为12h，得到内核包括SiOx 1和Si粒子，第一壳层包括Li 2SiO 3和Li 2Si 2O 5和C粒子的第一产物。
将所述第一产物通过掺杂了导电石墨的沥青用包覆釜进行包覆反应，所述包覆反应在氩气气氛中进行，反应温度为600℃，反应时间为10h，最终得到内核包括SiOx 1和Si粒子，第一壳层包括Li 2SiO 3和Li 2Si 2O 5和C粒子，第二壳层为掺杂了导电石墨的碳膜层硅基负极材料。
所述硅基负极材料中Li元素的质量百分比含量为10％，其中，第一壳层内侧Li的质量百分比含量为4.5％，第一壳层外侧Li的质量百分比含量为44.5％。采用所述硅基负极材料制作的二次电池，其可逆容量为1430mAh/g，首次库仑效率为88％，500周容量保持率为90％。
实施例5
采用对辊破碎机将块状SiOx(x＝0.9)进行粗碎，并将粗碎后的原料通过气流粉碎机进行粉碎，得到粒径D50为5μm的SiOx粉末，并将所述SiOx粉末与碳酸锂和柠檬酸在高速搅拌磨中进行充分混合，制备成包括碳酸锂，柠檬酸和SiOx的第一混合物。其中，所述硅氧原料SiOx的质量为1Kg，所述碳酸锂的质量为476.8g，所述柠檬酸的质量为5g。
将所述第一混合物在氩气氛围中，通过回转炉进行煅烧，煅烧温度为950℃ 煅烧，反应时间为12h，得到内核包括SiOx 1和Si粒子，第一壳层包括Li 2SiO 3和Li 4SiO 4和C粒子的第一产物。
将所述第一产物通过掺杂了导电石墨的沥青用包覆釜进行包覆反应，所述包覆反应在氩气气氛中进行，反应温度为600℃，反应时间为10h，最终得到内核包括SiOx 1和Si粒子，第一壳层包括Li 2SiO 3和Li 4SiO 4和C粒子，第二壳层为掺杂了导电石墨的碳膜层硅基负极材料。
所述硅基负极材料中Li元素的质量百分比含量为10％，其中，第一壳层内侧Li的质量百分比含量为5％，第一壳层外侧Li的质量百分比含量为43％。采用所述硅基负极材料制作的二次电池，其可逆容量为1400mAh/g，首次库仑效率为90％，500周容量保持率为86％。
实施例6
采用对辊破碎机将块状SiOx(x＝0.9)进行粗碎，并将粗碎后的原料通过气流粉碎机进行粉碎，得到粒径D50为5μm的SiOx粉末，并将所述SiOx粉末与碳酸锂和柠檬酸在高速搅拌磨中进行充分混合，制备成包括碳酸锂，柠檬酸和SiOx的第一混合物。其中，所述硅氧原料SiOx的质量为1Kg，所述碳酸锂的质量为476.8g，所述柠檬酸的质量为5g。
将所述第一混合物在氩气氛围中，通过回转炉进行煅烧，煅烧温度为750℃煅烧，反应时间为8h，得到内核包括SiOx 1和Si粒子，第一壳层包括Li 2SiO 3和C粒子的第一产物。
将所述第一产物通过掺杂了导电石墨的沥青用包覆釜进行包覆反应，所述包覆反应在氩气气氛中进行，反应温度为600℃，反应时间为10h，最终得到内核包括SiOx 1和Si粒子，第一壳层包括Li 2SiO 3和C粒子，第二壳层为 掺杂了导电石墨的碳膜层硅基负极材料。
所述硅基负极材料中Li元素的质量百分比含量为10％，其中，第一壳层内侧Li的质量百分比含量为3％，第一壳层外侧Li的质量百分比含量为46％。采用所述硅基负极材料制作的二次电池，其可逆容量为1350mAh/g，首次库仑效率为86％，500周容量保持率为85％。
实施例7
采用对辊破碎机将块状SiOx(x＝0.9)进行粗碎，并将粗碎后的原料通过气流粉碎机进行粉碎，得到粒径D50为5μm的SiOx粉末，并将所述SiOx粉末与碳酸锂和柠檬酸在高速搅拌磨中进行充分混合，制备成包括碳酸锂，柠檬酸和SiOx的第一混合物。其中，所述硅氧原料SiOx的质量为1Kg，所述碳酸锂的质量为476.8g，所述柠檬酸的质量为5g。
将所述第一混合物在氩气氛围中，通过回转炉进行煅烧，煅烧温度为750℃煅烧，反应时间为16h，得到内核包括SiOx 1和Si粒子，第一壳层包括Li 2SiO 3和C粒子的第一产物。
将所述第一产物通过掺杂了导电石墨的沥青用包覆釜进行包覆反应，所述包覆反应在氩气气氛中进行，反应温度为600℃，反应时间为10h，最终得到内核包括SiOx 1和Si粒子，第一壳层包括Li 2SiO 3和C粒子，第二壳层为掺杂了导电石墨的碳膜层硅基负极材料。
所述硅基负极材料中Li元素的质量百分比含量为10％，其中，第一壳层内侧Li的质量百分比含量为3％，第一壳层外侧Li的质量百分比含量为46％。采用所述硅基负极材料制作的二次电池，其可逆容量为1350mAh/g，首次库仑效率为86％，500周容量保持率为85％。
实施例8
采用对辊破碎机将块状SiOx(x＝0.9)进行粗碎，并将粗碎后的原料通过气流粉碎机进行粉碎，得到粒径D50为5μm的SiOx粉末，并将所述SiOx粉末与氢氧化钠和柠檬酸在高速搅拌磨中进行充分混合，制备成包括氢氧化钠，柠檬酸和SiOx的第一混合物。其中，所述硅氧原料SiOx的质量为1Kg，所述氢氧化钠的质量为193.2g，所述柠檬酸的质量为5g。
将所述第一混合物在氩气氛围中，通过回转炉进行煅烧，煅烧温度为750℃煅烧，反应时间为12h，得到内核包括SiOx 1和Si粒子，第一壳层包括Na 2SiO 3和C粒子的第一产物。
将所述第一产物通过掺杂了导电石墨的沥青用包覆釜进行包覆反应，所述包覆反应在氩气气氛中进行，反应温度为600℃，反应时间为10小时，最终得到内核包括SiOx 1和Si粒子，第一壳层包括Na 2SiO 3和C粒子，第二壳层为掺杂了导电石墨的碳膜层硅基负极材料。
所述硅基负极材料中Na元素的质量百分比含量为10％，其中，第一壳层内侧Na的质量百分比含量为2％，第一壳层外侧Li的质量百分比含量为46％。采用所述硅基负极材料制作的二次电池，其可逆容量为1200mAh/g，首次库仑效率为78％，500周容量保持率为83％。
实施例9
采用对辊破碎机将块状SiOx(x＝0.9)进行粗碎，并将粗碎后的原料通过气流粉碎机进行粉碎，得到粒径D50为5μm的SiOx粉末，并将所述SiOx粉末与碳酸镁和柠檬酸在高速搅拌磨中进行充分混合，制备成包括碳酸镁，柠檬酸和SiOx的第一混合物。其中，所述硅氧原料SiOx的质量为1Kg，所述 碳酸锂的质量为466.5g，所述柠檬酸的质量为5g。
将所述第一混合物在氩气氛围中，通过回转炉进行煅烧，煅烧温度为950℃煅烧，反应时间为12h，得到内核包括SiOx 1和Si粒子，第一壳层包括MgSiO 3和C粒子的第一产物。
将所述第一产物通过掺杂了导电石墨的沥青用包覆釜进行包覆反应，所述包覆反应在氩气气氛中进行，反应温度为600℃，反应时间为10小时，最终得到内核包括SiOx 1和Si粒子，第一壳层包括MgSiO 3和C粒子，第二壳层为掺杂了导电石墨的碳膜层硅基负极材料。
所述硅基负极材料中Mg元素的质量百分比含量为12％，其中，第一壳层内侧Mg的质量百分比含量为3％，第一壳层外侧Mg的质量百分比含量为46％。采用所述硅基负极材料制作的二次电池，其可逆容量为1400mAh/g，首次库仑效率为82％，500周容量保持率为85％。
实施例10
采用对辊破碎机将块状SiOx(x＝0.9)进行粗碎，并将粗碎后的原料通过气流粉碎机进行粉碎，得到粒径D50为5μm的SiOx粉末，并将所述SiOx粉末与氢氧化铝和柠檬酸在高速搅拌磨中进行充分混合，制备成包括氢氧化铝，柠檬酸和SiOx的第一混合物。其中，所述硅氧原料SiOx的质量为1Kg，所述氢氧化铝的质量为353.1g，所述柠檬酸的质量为5g。
将所述第一混合物在氩气氛围中，通过回转炉进行煅烧，煅烧温度为1000℃煅烧，反应时间为12h，得到内核包括SiOx 1和Si粒子，第一壳层包括AlSi 1.5O 4.5和C粒子的第一产物。
将所述第一产物通过掺杂了导电石墨的沥青用包覆釜进行包覆反应，所 述包覆反应在氩气气氛中进行，反应温度为600℃，反应时间为10小时，最终得到内核包括SiOx 1和Si粒子，第一壳层包括AlSi 1.5O 4.5和C粒子，第二壳层为掺杂了导电石墨的碳膜层硅基负极材料。
所述硅基负极材料中Al元素的质量百分比含量为10％，其中，第一壳层内侧Al的质量百分比含量为4％，第一壳层外侧Al的质量百分比含量为45％。采用所述硅基负极材料制作的二次电池，其可逆容量为1430mAh/g，首次库仑效率为89％，500周容量保持率为88％。
实施例11
采用对辊破碎机将块状SiOx(x＝0.9)进行粗碎，并将粗碎后的原料通过气流粉碎机进行粉碎，得到粒径D50为5μm的SiOx粉末，并将所述SiOx粉末与氢氧化铁和柠檬酸在高速搅拌磨中进行充分混合，制备成包括氢氧化铁，柠檬酸和SiOx的第一混合物。其中，所述硅氧原料SiOx的质量为1Kg，所述氢氧化铁的质量为297.4g，所述柠檬酸的质量为5g。
将所述第一混合物在氩气氛围中，通过回转炉进行煅烧，煅烧温度为1000℃煅烧，反应时间为12h，得到内核包括SiOx 1和Si粒子，第一壳层包括FeSiO 3和C粒子的第一产物。
将所述第一产物通过掺杂了导电石墨的沥青用包覆釜进行包覆反应，所述包覆反应在氩气气氛中进行，反应温度为600℃，反应时间为10小时，最终得到内核包括SiOx 1和Si粒子，第一壳层包括FeSiO 3和C粒子，第二壳层为掺杂了导电石墨的碳膜层硅基负极材料。
所述硅基负极材料中Fe元素的质量百分比含量为14％，其中，第一壳层内侧Fe的质量百分比含量为3％，第一壳层外侧Fe的质量百分比含量为 46％。采用所述硅基负极材料制作的二次电池，其可逆容量为1240mAh/g，首次库仑效率为75％，500周容量保持率为65％。
实施例12
采用对辊破碎机将块状SiOx(x＝0.9)进行粗碎，并将粗碎后的原料通过气流粉碎机进行粉碎，得到粒径D50为5μm的SiOx粉末，并将所述SiOx粉末与碳酸钙和柠檬酸在高速搅拌磨中进行充分混合，制备成包括碳酸钙，柠檬酸和SiOx的第一混合物。其中，所述硅氧原料SiOx的质量为1Kg，所述碳酸钙的质量为277.8g，所述柠檬酸的质量为5g。
将所述第一混合物在氩气氛围中，通过回转炉进行煅烧，煅烧温度为1000℃煅烧，反应时间为12h，得到内核包括SiOx 1和Si粒子，第一壳层包括CaSiO 3和C粒子的第一产物。
将所述第一产物通过掺杂了导电石墨的沥青用包覆釜进行包覆反应，所述包覆反应在氩气气氛中进行，反应温度为600℃，反应时间为10小时，最终得到内核包括SiOx 1和Si粒子，第一壳层包括CaSiO 3和C粒子，第二壳层为掺杂了导电石墨的碳膜层硅基负极材料。
所述硅基负极材料中Ca元素的质量百分比含量为10％，其中，第一壳层内侧Ca的质量百分比含量为2％，第一壳层外侧Ca的质量百分比含量为45％。采用所述硅基负极材料制作的二次电池，其可逆容量为1140mAh/g，首次库仑效率为65％，500周容量保持率为62％。
比对例1
采用对辊破碎机将块状SiOx(x＝0.9)进行粗碎，并将粗碎后的原料通过气流粉碎机进行粉碎，得到粒径D50为5μm的SiOx粉末，并将所述SiOx 粉末与柠檬酸在高速搅拌磨中进行充分混合，制备成包括柠檬酸和SiOx的第一混合物。其中，所述硅氧原料SiOx的质量为1Kg，所述柠檬酸的质量为5g。
将所述第一混合物在氩气氛围中，通过回转炉进行煅烧，煅烧温度为700℃煅烧，得到内核包括SiOx 1和Si粒子，外壳为C的第一产物。
将所述第一产物通过掺杂了导电石墨的沥青用包覆釜进行包覆反应，所述包覆反应在氩气气氛中进行，反应温度为750摄氏度，反应时间为12小时，最终得到内核包括SiOx 1和Si粒子，外壳层为掺杂了导电石墨的碳膜层硅基负极材料。
采用所述硅基负极材料制作的二次电池，其可逆容量为1650mAh/g，首次库仑效率为76％，500周容量保持率为30％。
比对例2
采用对辊破碎机将块状SiOx(x＝0.9)进行粗碎，并将粗碎后的原料通过气流粉碎机进行粉碎，得到粒径D50为5μm的SiOx粉末，并将所述SiOx粉末与柠檬酸在高速搅拌磨中进行充分混合，制备成包括柠檬酸和SiOx的第一混合物。其中，所述硅氧原料SiOx的质量为1Kg，所述柠檬酸的质量为10g。
将所述第一混合物在氩气氛围中，通过回转炉进行煅烧，煅烧温度为700℃煅烧，得到内核包括SiOx 1和Si粒子，外壳为C的第一产物。
将所述第一产物通过掺杂了导电石墨的沥青用包覆釜进行包覆反应，所述包覆反应在氩气气氛中进行，反应温度为750摄氏度，反应时间为12小时，最终得到内核包括SiOx 1和Si粒子，外壳层为掺杂了导电石墨的碳膜层硅基 负极材料。
采用所述硅基负极材料制作的二次电池，其可逆容量为1620mAh/g，首次库仑效率为75％，500周容量保持率为32％。
Figure PCTCN2019129890-appb-000001
从表1可以看出，采用本申请所述的实施例提供的二次电池负极材料制成的二次电池，表现出高脱锂容量、高首次库伦效率和良好的循环性能，充电容量在1400mAh/g以上，放电容量在1627mAh/g以上，首次库伦效率在86％以上。
参考附图2所示，为本申请实施例所述的硅基负极材料的SEM图，从附图可以看出，该硅基负极材料的颗粒分散均匀。
参考附图3所示，为采用本申请实施例所述的硅基负极材料的充放电曲线，从附图可以看出，该硅基负极材料的可逆容量高、首次库仑效率高。
综上所述，在阅读本详细公开内容之后，本领域技术人员可以明白，前述详细公开内容可以仅以示例的方式呈现，并且可以不是限制性的。尽管这里没有明确说明，本领域技术人员可以理解本申请意图囊括对实施例的各种合理改变，改进和修改。这些改变，改进和修改旨在由本公开提出，并且在本公开的示例性实施例的精神和范围内。
应当理解，本实施例使用的术语“和/或”包括相关联的列出项目中的一个或多个的任意或全部组合。应当理解，当一个元件被称作“连接”或“耦接”至另一个元件时，其可以直接地连接或耦接至另一个元件，或者也可以存在中间元件。
类似地，应当理解，当诸如层、区域或衬底之类的元件被称作在另一个元件“上”时，其可以直接在另一个元件上，或者也可以存在中间元件。与之相反，术语“直接地”表示没有中间元件。还应当理解，术语“包含”、“包含着”、“包括”和/或“包括着”，在此使用时，指明存在所记载的特征、整体、步骤、操作、元件和/或组件，但并不排除存在或附加一个或多个其他特征、整体、步骤、操作、元件、组件和/或它们的组。
还应当理解，尽管术语第一、第二、第三等可以在此用于描述各种元件，但是这些元件不应当被这些术语所限制。这些术语仅用于将一个元件与另一个元件区分开。因此，在没有脱离本发明的教导的情况下，在一些实施例中的第一元件在其他实施例中可以被称为第二元件。相同的参考标号或相同的参考标志符在整个说明书中表示相同的元件。
此外，通过参考作为理想化的示例性图示的截面图示和/或平面图示来描述示例性实施例。因此，由于例如制造技术和/或容差导致的与图示的形状的不同是可预见的。因此，不应当将示例性实施例解释为限于在此所示出的区域的形状，而是应当包括由例如制造所导致的形状中的偏差。例如，被示出为矩形的蚀刻区域通常会具有圆形的或弯曲的特征。因此，在图中示出的区域实质上是示意性的，其形状不是为了示出器件的区域的实际形状也不是为了限制示例性实施例的范围。

Claims (21)

  1. 一种用于二次电池的硅基负极材料，包括：
    内核，所述内核包括Si粒子和硅氧化物SiOx 1，其中0＜x 1＜2；
    第一壳层，所述第一壳层包括通式为MySiOz的化合物(0＜y≤4，0＜z≤5，且z≥x 1)以及C粒子，所述第一壳层包覆所述内核，并且所述第一壳层中M、C的含量由靠近内核的一侧向远离内核的一侧逐渐增加；以及
    第二壳层，所述第二壳层包括碳膜层或者碳膜层与导电添加剂形成的复合膜层，所述第二壳层包覆所述第一壳层。
  2. 如权利要求1所述的用于二次电池的硅基负极材料，其特征在于，所述第一壳层中M为Li、Na、Mg、Al、Fe、Ca中的任意一种或者多种。
  3. 如权利要求1所述的用于二次电池的硅基负极材料，其特征在于，所述硅基负极材料中M的质量百分比含量1～15％，其中，M占第一壳层的质量百分比含量为1～40％。
  4. 如权利要求1所述的用于二次电池的硅基负极材料，其特征在于，所述第一壳层中M、C的质量百分比含量由靠近内核的一侧向远离内核的一侧呈梯度增加。
  5. 如权利要求4所述的用于二次电池的硅基负极材料，其特征在于，靠近内核的一侧M的质量百分比含量占第一壳层的0～5％，远离内核的一侧M的质量百分比含量占第一壳层的30～48％。
  6. 如权利要求1所述的用于二次电池的硅基负极材料，其特征在于，所述C粒子材料包含硬碳、软碳或者无定形碳中任意一种或者多种。
  7. 如权利要求1所述的用于二次电池的硅基负极材料，其特征在于，所述碳膜层材料包含硬碳、软碳或者无定形碳中任意一种或者多种，所述导电添加剂包括碳纳米管、石墨烯、导电炭黑、科琴黑、气相生长碳纤维、乙炔黑、导电石墨中的任意一种或多种。
  8. 如权利要求1所述的用于二次电池的硅基负极材料，其特征在于，所述硅基负极材料中，C粒子的质量百分比含量为0.1～2％，所述碳膜层或者碳膜层与导电添加剂形成的复合膜层的质量百分比含量为0.1～15％，所述导电添加剂的质量百分比含量为0～5％。
  9. 如权利要求1所述的用于二次电池的硅基负极材料，其特征在于，所述内核中值粒径为1～10μm，所述第一壳层的厚度为0.01～2μm，所述第二壳层的厚度为0.01～1μm。
  10. 如权利要求1所述的用于二次电池的硅基负极材料，其特征在于，所述内核中Si粒子均匀分散在SiOx 1中。
  11. 如权利要求1所述的用于二次电池的硅基负极材料，其特征在于，以 所述硅基负极材料的质量为100％计，所述Si粒子、硅氧化物SiOx 1和MySiOz的质量百分比含量之和为83～99％。
  12. 一种用于二次电池的硅基负极材料的制备方法，其特征在于，包括：
    制备第一混合物，所述第一混合物包括硅氧原料SiOx(0＜x＜2)、金属源物质和碳源物质；
    将所述第一混合物在非氧条件下煅烧，得到第一产物，所述第一产物包括：
    内核，所述内核包括Si粒子和硅氧化物SiOx 1，其中0＜x 1＜2，x 1＞x；以及
    第一壳层，所述第一壳层包覆所述内核，并且所述第一壳层包括通式为MySiOz的化合物(0＜y≤4，0＜z≤5，且z≥x 1)和C粒子，所述第一壳层中M、C的含量由靠近内核的一侧向远离内核的一侧逐渐增加；以及
    将所述第一产物通过碳源物质或者碳源物质和导电添加剂进行包覆反应，然后在非氧化气氛中进行碳化处理，在所述第一壳层表面包覆第二壳层，其中，所述第二壳层包括碳膜层或者碳膜层与导电添加剂形成的复合膜层。
  13. 如权利要求12所述的用于二次电池的硅基负极材料的制备方法，其特征在于，所述非氧化气氛包括氮气、氩气、氢气或氦气中的至少一种。
  14. 如权利要求12所述的用于二次电池的硅基负极材料的制备方法，其特征在于，
    所述硅氧原料SiOx与金属源物质的质量比范围为100∶1～100∶50，硅氧原料 SiOx与碳源物质的质量比范围为100∶1～100∶10。
  15. 如权利要求12所述的用于二次电池的硅基负极材料的制备方法，其特征在于，所述金属源物质包括金属的碳酸盐，金属的硝酸盐，以及金属的氢氧化物中的任意一种或者多种，所述金属包括Li、Na、Mg、Al、Fe、Ca。
  16. [根据细则91更正 14.01.2020]　
    权利要求15所述的用于二次电池的硅基负极材料的制备方法，其特征在于，所述金属源物质包括柠檬酸锂、碳酸锂、氢氧化锂或者硝酸锂中的一种或者多种。
  17. 如权利要求12所述的用于二次电池的硅基负极材料的制备方法，其特征在于，所述碳源物质包括柠檬酸、葡萄糖、树脂、煤沥青、石油沥青、聚乙烯醇、环氧树脂、聚丙烯腈、聚甲基丙烯酸甲酯、葡萄糖、蔗糖、聚丙烯酸、聚乙烯吡咯烷酮中的任意一种或者多种。
  18. 如权利要求12所述的用于二次电池的硅基负极材料的制备方法，其特征在于，所述非氧煅烧条件的温度为300-1000℃；所述碳化处理条件的温度为500-1200℃。
  19. 如权利要求12所述的用于二次电池的硅基负极材料的制备方法，其特征在于，所述第一混合物为柠檬酸锂或者碳酸锂和柠檬酸和硅氧原料SiOx(0＜x＜2)的混合物。
  20. 如权利要求12所述的用于二次电池的硅基负极材料的制备方法，其特征在于，所述硅氧原料SiOx为粉体，中值粒径为1～10μm。
  21. 一种二次电池，其特征在于，其负极包括权利要求1～11所述的任意一种负极材料。
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