WO2021243648A1 - 负极活性材料及使用其的电化学装置和电子装置 - Google Patents

负极活性材料及使用其的电化学装置和电子装置 Download PDF

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WO2021243648A1
WO2021243648A1 PCT/CN2020/094385 CN2020094385W WO2021243648A1 WO 2021243648 A1 WO2021243648 A1 WO 2021243648A1 CN 2020094385 W CN2020094385 W CN 2020094385W WO 2021243648 A1 WO2021243648 A1 WO 2021243648A1
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active material
negative electrode
electrode active
material layer
negative
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PCT/CN2020/094385
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English (en)
French (fr)
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何丽红
唐佳
董佳丽
谢远森
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宁德新能源科技有限公司
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Priority to JP2021512516A priority Critical patent/JP7250908B2/ja
Priority to EP20938521.0A priority patent/EP3968416B1/en
Priority to KR1020227042981A priority patent/KR20230003290A/ko
Priority to CN202080003323.XA priority patent/CN112335080B/zh
Priority to PCT/CN2020/094385 priority patent/WO2021243648A1/zh
Priority to CN202210287385.9A priority patent/CN114628625A/zh
Publication of WO2021243648A1 publication Critical patent/WO2021243648A1/zh
Priority to US18/073,884 priority patent/US11967718B2/en
Priority to US18/173,295 priority patent/US11936045B2/en
Priority to JP2023045559A priority patent/JP2023068117A/ja

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    • Y02E60/30—Hydrogen technology
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Definitions

  • This application relates to the field of energy storage, in particular to a negative electrode active material and an electrochemical device and electronic device using the same.
  • Electrochemical devices for example, lithium-ion batteries
  • Small-sized lithium-ion batteries are generally used as power sources for driving portable electronic communication devices (for example, camcorders, mobile phones, or notebook computers, etc.), especially high-performance portable devices.
  • portable electronic communication devices for example, camcorders, mobile phones, or notebook computers, etc.
  • Examples of medium-sized and large-sized lithium batteries with high output characteristics have been developed for use in electric vehicles (EV) and large-scale energy storage systems (ESS).
  • EV electric vehicles
  • ESS large-scale energy storage systems
  • the embodiments of the present application provide a negative electrode active material and an electrochemical device and an electronic device using the negative electrode active material to at least some extent solve at least one problem existing in the related field.
  • the present application provides a negative electrode active material, the negative electrode active material comprises a carbon material, wherein the carbon material meets the following relationship: 6 ⁇ Gr/K ⁇ 16, where Gr is the carbon graphitization of the material, obtained by X-ray diffraction method; and K is the peak intensity of the carbon material and the peak intensity of the carbon material Id 1250cm -1 to 1650cm -1 to 1500cm -1 to 1650cm -1 in an Ig The ratio of Id/Ig is measured by Raman spectroscopy, and the K is 0.06 to 0.15.
  • Gr the carbon graphitization of the material, obtained by X-ray diffraction method
  • K is the peak intensity of the carbon material and the peak intensity of the carbon material Id 1250cm -1 to 1650cm -1 to 1500cm -1 to 1650cm -1 in an Ig
  • the ratio of Id/Ig is measured by Raman spectroscopy, and the K is 0.06 to 0.15.
  • the carbon material meets the following relationship: 8 ⁇ Gr/K ⁇ 15. In some embodiments, the carbon material meets the following relationship: 10 ⁇ Gr/K ⁇ 12. In some embodiments, the Gr/K value of the carbon material is 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15. 15.5 or within the range composed of any two of the above values.
  • the carbon material has a K of 0.08 to 0.10. In some embodiments, the K of the carbon material is 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15 or within a range composed of any two of the above values.
  • the graphitization degree Gr is 0.92 to 0.96.
  • the graphitization degree Gr of the carbon material is 0.92, 0.93, 0.94, 0.95, 0.96, or within a range composed of any two of the above values.
  • the carbon material satisfies at least one of the following relationships:
  • La is the crystal size of the carbon material crystal along the horizontal axis measured by X-ray diffraction method, and the unit is nm;
  • Lc is the crystal size of the carbon material crystal along the vertical axis measured by X-ray diffraction method, and the unit is nm;
  • S is the ratio of the peak area C004 of the (004) plane and the peak area C110 of the (110) plane of the negative electrode active material measured by X-ray diffraction pattern;
  • the Lc is less than 45, and the La is greater than 50.
  • the Lc is less than 40. In some embodiments, the Lc is less than 35. In some embodiments, the Lc is less than 30. In some embodiments, the Lc is less than 25. In some embodiments, the Lc is greater than 10. In some embodiments, the Lc is greater than 15. In some embodiments, the Lc is greater than 20. In some embodiments, the Lc is 20, 22, 25, 28, 30, 35, 40, 43 or within the range of any two of the foregoing values.
  • the La is greater than 60. In some embodiments, the La is greater than 80. In some embodiments, the La is greater than 100. In some embodiments, the La is greater than 110. In some embodiments, the La is greater than 120. In some embodiments, the La is greater than 130. In some embodiments, the La is greater than 150. In some embodiments, the La is greater than 180. In some embodiments, the La is greater than 200. In some embodiments, the La is greater than 220. In some embodiments, the La is less than 300. In some embodiments, the La is less than 250. In some embodiments, the La is 55, 60, 70, 80, 90, 100, 120, 150, 180, 200, 230, 250 or within the range of any two of the foregoing values.
  • the Dv10 value and the Dv90 value of the negative electrode active material satisfy the following relationship: Dv90/Dv10+Dv90>23.0. In some embodiments, the Dv10 value and the Dv90 value of the negative active material satisfy the following relationship: Dv90/Dv10+Dv90>25.0. In some embodiments, the Dv10 value and the Dv90 value of the negative active material satisfy the following relationship: Dv90/Dv10+Dv90>28.0. In some embodiments, the Dv10 value and the Dv90 value of the negative active material satisfy the following relationship: Dv90/Dv10+Dv90>30.0.
  • the Dv10 value and the Dv90 value of the negative active material satisfy the following relationship: Dv90/Dv10+Dv90 ⁇ 50.0. In some embodiments, the Dv10 value and the Dv90 value of the negative active material satisfy the following relationship: Dv90/Dv10+Dv90 ⁇ 45.0. In some embodiments, the Dv10 value and the Dv90 value of the negative active material satisfy the following relationship: Dv90/Dv10+Dv90 ⁇ 40.0. In some embodiments, the Dv10 value and the Dv90 value of the negative active material satisfy the following relationship: Dv90/Dv10+Dv90 ⁇ 35.0.
  • the Dv10 value and the Dv90 value Dv90/Dv10+Dv90 of the negative active material are 24, 26, 28, 30, 33, 35 or within the range of any two of the foregoing values.
  • the unit of Dv90 and Dv10 is ⁇ m.
  • the present application provides an electrochemical device, which includes a positive electrode, an electrolyte, and a negative electrode.
  • the negative electrode includes a negative electrode active material layer and a current collector.
  • the negative electrode active material layer includes the The negative active material.
  • the area density of the negative electrode active material layer is 0.077 mg/mm 2 to 0.121 mg/mm 2
  • the compaction density of the negative electrode active material layer is 1.70 g/cm 3 to 1.92 g/cm 3 .
  • the areal density of the negative active material layer is 0.080 mg/mm 2 to 0.120 mg/mm 2 . In some embodiments, the area density of the negative active material layer is 0.085 mg/mm 2 to 0.110 mg/mm 2 . In some embodiments, the areal density of the negative active material layer is 0.090 mg/mm 2 to 0.100 mg/mm 2 . In some embodiments, the surface density of the negative electrode active material layer was 0.077mg / mm 2, 0.080mg / mm 2, 0.085mg / mm 2, 0.090mg / mm 2, 0.095mg / mm 2, 0.100mg / mm 2. 0.105mg/mm 2 , 0.110mg/mm 2 , 0.115mg/mm 2 , 0.120mg/mm 2 , 0.121mg/mm 2 or within the range of any two of the above values.
  • the compacted density of the negative active material layer is 1.75 g/cm 3 to 1.90 g/cm 3 . In some embodiments, the compacted density of the negative active material layer is 1.80 g/cm 3 to 1.85 g/cm 3 . In some embodiments, the compacted density of the negative active material layer is 1.70 g/cm 3 , 1.75 g/cm 3 , 1.78 g/cm 3 , 1.80 g/cm 3 , 1.85 g/cm 3 , 1.85 g/cm 3 cm 3 , 1.88 g/cm 3 , 1.90 g/cm 3 , 1.92 g/cm 3 or within the range of any two of the above values.
  • the S′ of the negative electrode active material layer measured by X-ray diffraction pattern is in the range of 12 to 18 in the fully discharged state.
  • the S′ of the negative electrode active material layer measured by X-ray diffraction spectroscopy is in the range of 14-16 under the fully discharged state.
  • the S′ of the negative electrode active material layer measured by X-ray diffraction pattern is 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or within the range of any two of the above values.
  • the peel strength between the anode active material layer and the anode current collector is 6 N/m to 15 N/m. In some embodiments, the peel strength between the negative active material layer and the negative current collector is 8 N/m to 14 N/m. In some embodiments, the peel strength between the negative active material layer and the negative current collector is 10 N/m to 12 N/m. In some embodiments, the peel strength between the negative active material layer and the negative current collector is 6N/m, 7N/m, 8N/m, 9N/m, 10N/m, 11N/m, 12N/m m, 13N/m, 14N/m, 15N/m or within the range of any two of the above values.
  • the negative active material layer has a porosity of 20% to 40%. In some embodiments, the negative active material layer has a porosity of 25% to 35%. In some embodiments, the negative active material layer has a porosity of 28% to 32%. In some embodiments, the porosity of the negative active material layer is 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, or a ratio of any two of the foregoing values. Within range.
  • the thermal decomposition temperature of the anode active material layer in the fully charged state of the electrochemical device, is not less than 280°C. In some embodiments, in the fully charged state of the electrochemical device, the thermal decomposition temperature of the anode active material layer is not less than 300°C. In some embodiments, in the fully charged state of the electrochemical device, the thermal decomposition temperature of the anode active material layer is not less than 320°C. In some embodiments, in the fully charged state of the electrochemical device, the thermal decomposition temperature of the anode active material layer is not less than 340°C.
  • the thermal decomposition temperature of the anode active material layer in the fully charged state of the electrochemical device, is not less than 130°C. In some embodiments, in the fully discharged state of the electrochemical device, the thermal decomposition temperature of the anode active material layer is not less than 140°C. In some embodiments, in the fully discharged state of the electrochemical device, the thermal decomposition temperature of the anode active material layer is not less than 150°C. In some embodiments, in the fully discharged state of the electrochemical device, the thermal decomposition temperature of the anode active material layer is not less than 160°C.
  • the present application provides an electronic device, which includes the electrochemical device according to the present application.
  • FIG. 1 shows a scanning electron microscope (SEM) image of the negative electrode active material used in Comparative Example 2 at a magnification of 500 times.
  • FIG. 2 shows a scanning electron microscope (SEM) image of the negative electrode active material used in Example 5 at a magnification of 500 times.
  • Figure 3 shows a photograph of the appearance of the negative electrode active material used in Example 5 after cycling, in which there is no lithium evolution phenomenon.
  • Figure 4 shows a photograph of the appearance of the negative electrode active material used in Comparative Example 1 after cycling, which shows the phenomenon of lithium precipitation.
  • Figure 5 shows a photograph of the appearance of the negative electrode active material used in Comparative Example 2 after cycling, which shows a serious lithium precipitation phenomenon.
  • Figure 6 shows the cycle capacity retention curves of the lithium ion batteries of Comparative Example 1, Comparative Example 2 and Example 5 at 25°C with the number of cycles.
  • Figure 7 shows the cycle capacity retention curves of the lithium ion batteries of Comparative Example 1, Comparative Example 2 and Example 5 at 45°C with the number of cycles.
  • Fig. 8 shows the cyclic expansion rate curves of the lithium-ion batteries of Comparative Example 1, Comparative Example 2 and Example 5 at 25°C with the number of cycles.
  • Figure 9 shows the cyclic expansion rate curves of the lithium ion batteries of Comparative Example 1, Comparative Example 2 and Example 5 at 45°C with the number of cycles.
  • a list of items connected by the term "at least one of” can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (exclude B); B and C (exclude A); or all of A, B, and C.
  • Project A can contain a single element or multiple elements.
  • Project B can contain a single element or multiple elements.
  • Project C can contain a single element or multiple elements.
  • the present application provides a negative electrode active material, the negative electrode active material comprises a carbon material, wherein the carbon material meets the following relationship: 6 ⁇ Gr/K ⁇ 16; wherein, Gr is the graphite of the carbon material degree, obtained by X-ray diffraction method; and K is the ratio of the carbon material in the peak intensity of the peak intensity Id Id and the carbon material 1250cm -1 to 1650cm -1 to 1500cm -1 to 1650cm -1 in the Ig- /Ig, measured by Raman spectroscopy, the K is 0.06 to 0.15.
  • the graphitization degree Gr and K of the carbon material meet the following relationship: 8 ⁇ Gr/K ⁇ 15. In some embodiments, the graphitization degree Gr and K of the carbon material meet the following relationship: 10 ⁇ Gr/K ⁇ 12. In some embodiments, the ratio Gr/K of the graphitization degree Gr and K of the carbon material is 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13. , 13.5, 14, 14.5, 15, 15.5 or within the range of any two of the above values.
  • the carbon material has a K of 0.08 to 0.10. In some embodiments, the K of the carbon material is 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15 or within a range composed of any two of the above values.
  • the K of carbon materials can characterize the ratio of surface defects and crystalline regions of the material.
  • the “graphitization degree” of carbon materials refers to the degree to which non-graphitic carbon is transformed into graphite-like carbon at high temperature or during secondary heating.
  • the graphitization degree and K value of the carbon material in the negative electrode active material affect the intercalation and deintercalation of lithium ions.
  • lithium ions migrate to the negative electrode, and the negative electrode accepts lithium ions.
  • the graphitization degree and K value of the carbon material will affect the speed at which lithium ions are inserted into the carbon material particles. Under the condition of high-rate discharge, if lithium ions cannot be quickly inserted into and diffused in the carbon material particles, lithium ions will precipitate on the surface, accelerating the cycle attenuation of the lithium ion battery.
  • lithium ions are extracted from the negative electrode.
  • the graphitization degree and K value of carbon materials will also affect the thickness of the solid electrolyte interface (SEI) film formed during the first cycle of the lithium-ion battery, thereby affecting the first coulombic efficiency of the lithium-ion battery, and thus the energy density of the lithium-ion battery .
  • SEI solid electrolyte interface
  • the carbon material has a higher degree of graphitization (for example, Gr>0.96), the interplanar spacing of the carbon material is reduced, which is not conducive to the deintercalation of lithium ions from the carbon material.
  • the carbon material has a low degree of graphitization (for example, Gr ⁇ 0.92), there are more SP 3 bonds in the carbon material, which makes the layers of the carbon material constrain each other, thereby making the structure of the carbon material more stable.
  • the lithium ion battery has significantly improved energy density, cycle performance, and rate performance.
  • the graphitization degree Gr of the carbon material is 0.92 to 0.96. In some embodiments, the graphitization degree Gr of the carbon material is 0.92, 0.93, 0.94, 0.95, 0.96, or within a range composed of any two of the above values. When the degree of graphitization of the carbon material is within the above range, it helps to further improve the energy density, cycle performance, and rate performance of the lithium ion battery.
  • the carbon material satisfies at least one of the following relationships:
  • La is the crystal size of the carbon material crystal along the horizontal axis measured by X-ray diffraction method, and the unit is nm;
  • Lc is the crystal size of the carbon material crystal along the vertical axis measured by X-ray diffraction method, and the unit is nm;
  • S is the ratio of the peak area C004 of the (004) plane and the peak area C110 of the (110) plane of the negative electrode active material measured by X-ray diffraction pattern;
  • the Lc is less than 45, and the La is greater than 50.
  • the Lc is less than 40. In some embodiments, the Lc is less than 35. In some embodiments, the Lc is less than 30. In some embodiments, the Lc is less than 25. In some embodiments, the Lc is greater than 10. In some embodiments, the Lc is greater than 15. In some embodiments, the Lc is greater than 20. In some embodiments, the Lc is 20, 22, 25, 28, 30, 35, 40, 43 or within the range of any two of the foregoing values.
  • the La is greater than 60. In some embodiments, the La is greater than 80. In some embodiments, the La is greater than 100. In some embodiments, the La is greater than 110. In some embodiments, the La is greater than 120. In some embodiments, the La is greater than 130. In some embodiments, the La is greater than 150. In some embodiments, the La is greater than 180. In some embodiments, the La is greater than 200. In some embodiments, the La is greater than 220. In some embodiments, the La is less than 300. In some embodiments, the La is less than 250. In some embodiments, the La is 55, 60, 70, 80, 90, 100, 120, 150, 180, 200, 230, 250 or within the range of any two of the foregoing values.
  • the crystal size of the carbon material crystal will affect the intercalation and deintercalation of lithium ions during the cycle.
  • the ratio S of the peak area C004 of the (004) plane and the peak area C110 of the (110) plane of the negative active material can characterize the degree of orientation of the negative active material.
  • the larger the S the larger the anisotropy of the negative electrode active material.
  • the smaller the S the greater the isotropy of the negative electrode active material.
  • the Dv10 value and the Dv90 value of the negative active material satisfy the following relationship: Dv90/Dv10+Dv90>23.0, and the unit of Dv90 and Dv10 is ⁇ m.
  • Dv90 refers to the particle size of the negative electrode active material that reaches 90% of the cumulative volume from the small particle size side in the volume-based particle size distribution, that is, the volume of the negative electrode active material smaller than this particle size accounts for 90% of the total volume of the negative electrode active material. %.
  • Dv10 refers to the particle size of the negative active material that reaches 10% of the cumulative volume from the small particle size side in the volume-based particle size distribution, that is, the volume of the negative active material smaller than this particle size accounts for 10% of the total volume of the negative active material. %.
  • the particle size of the negative active material can be measured by a particle size tester (for example, a Malvern particle size tester).
  • the Dv10 value and the Dv90 value of the negative active material satisfy the following relationship: Dv90/Dv10+Dv90>25.0. In some embodiments, the Dv10 value and the Dv90 value of the negative active material satisfy the following relationship: Dv90/Dv10+Dv90>28.0. In some embodiments, the Dv10 value and the Dv90 value of the negative active material satisfy the following relationship: Dv90/Dv10+Dv90>30.0. In some embodiments, the Dv10 value and the Dv90 value of the negative active material satisfy the following relationship: Dv90/Dv10+Dv90 ⁇ 50.0.
  • the Dv10 value and the Dv90 value of the negative active material satisfy the following relationship: Dv90/Dv10+Dv90 ⁇ 45.0. In some embodiments, the Dv10 value and the Dv90 value of the negative active material satisfy the following relationship: Dv90/Dv10+Dv90 ⁇ 40.0. In some embodiments, the Dv10 value and the Dv90 value of the negative active material satisfy the following relationship: Dv90/Dv10+Dv90 ⁇ 35.0. In some embodiments, the Dv90/Dv10+Dv90 of the negative active material is 24, 26, 28, 30, 33, 35 or within the range of any two of the foregoing values. In the above relationship, the unit of Dv90 and Dv10 is ⁇ m.
  • the particle size of the negative electrode active material When the particle size of the negative electrode active material is larger, the specific surface area of the negative electrode active material is smaller, so that the lithium ion battery only needs to consume less lithium ions during the first cycle to form a solid electrolyte interface (SEI) film with the electrolyte. , Thereby improving the first coulombic efficiency of lithium-ion batteries. Larger particle size will also extend the path of lithium ion insertion and extraction, thereby reducing the dynamic performance of lithium ion batteries. In addition, the larger particle size will adversely affect the cyclic expansion of lithium-ion batteries.
  • SEI solid electrolyte interface
  • the particle size of the negative electrode active material is smaller, the specific surface area of the negative electrode active material is larger, so that the lithium ion battery needs to consume more lithium ions and the electrolyte to form an SEI film during the first cycle, thereby reducing the lithium ion battery’s Coulomb efficiency for the first time.
  • the smaller particle size will also shorten the path of lithium ion insertion and extraction, thereby affecting the dynamic performance of lithium ion batteries.
  • the smaller particle size will also adversely affect the cyclic expansion of lithium-ion batteries.
  • the Dv90 and Dv10 of the negative electrode active material meet the above relationship, it helps to balance the performance of the ion battery and further improve the energy density, cycle performance and rate performance of the lithium ion battery.
  • the application also provides an electrochemical device, which includes a positive electrode, a negative electrode, a separator, and an electrolyte.
  • a positive electrode a negative electrode
  • a separator a separator
  • electrolyte an electrolyte
  • the negative electrode used in the electrochemical device of the present application includes a negative electrode current collector and a negative electrode active material layer, and the negative electrode active material layer contains the negative electrode active material according to the present application.
  • the area density of the negative electrode active material layer is 0.077 mg/mm 2 to 0.121 mg/mm 2
  • the compaction density of the negative electrode active material layer is 1.70 g/cm 3 to 1.92 g/cm 3 .
  • the areal density of the negative active material layer is 0.080 mg/mm 2 to 0.120 mg/mm 2 . In some embodiments, the area density of the negative active material layer is 0.085 mg/mm 2 to 0.110 mg/mm 2 . In some embodiments, the surface density of the negative electrode active material layer was 0.090mg / mm 2 to 0.100mg / mm 2. In some embodiments, the surface density of the negative electrode active material layer was 0.077mg / mm 2, 0.080mg / mm 2, 0.085mg / mm 2, 0.090mg / mm 2, 0.095mg / mm 2, 0.100mg / mm 2.
  • the area density of the negative electrode active material layer can be tested by the following methods: discharging the battery to 0SOC%, disassembling the battery, washing, drying, using an electronic balance to test a certain area A of the negative electrode (the negative electrode current collector is coated on both sides of the negative electrode The active material layer) is weighed, and the weight is denoted as W 1 ; the negative active material layer is washed off with a solvent, dried, and the weight of the negative electrode current collector is measured, denoted as W 2 .
  • the areal density of the anode active material layer is calculated by the following formula: (W 1 -W 2 )/(A ⁇ 2).
  • the compacted density of the negative active material layer is 1.75 g/cm 3 to 1.90 g/cm 3 . In some embodiments, the compacted density of the negative active material layer is 1.80 g/cm 3 to 1.85 g/cm 3 . In some embodiments, the compacted density of the negative active material layer is 1.70 g/cm 3 , 1.75 g/cm 3 , 1.78 g/cm 3 , 1.80 g/cm 3 , 1.85 g/cm 3 , 1.85 g/cm 3 cm 3 , 1.88 g/cm 3 , 1.90 g/cm 3 , 1.92 g/cm 3 or within the range of any two of the above values.
  • the compaction density of the negative electrode active material layer can be tested by the following methods: discharging the battery to 0SOC%, disassembling the battery, washing, drying, using an electronic balance to apply an electronic balance to a certain area of the negative electrode (the negative electrode current collector is coated with both sides
  • the negative electrode active material layer is weighed, and the weight is denoted as W 1 , and the thickness T 1 of the negative electrode is measured using a micrometer.
  • W 2 Use a solvent to wash off the negative electrode active material layer, dry, and measure the weight of the negative electrode current collector, denoted as W 2 , and use a micrometer to measure the thickness of the negative electrode current collector T 2 .
  • the weight W 0 and thickness T 0 of the negative electrode active material layer disposed on the negative electrode current collector side and the compaction density of the negative electrode active material layer are calculated by the following formula:
  • T 0 (T 1 -T 2 )/2
  • the S′ of the negative electrode active material layer measured by X-ray diffraction pattern is in the range of 12 to 18 in the fully discharged state.
  • the S′ of the negative electrode active material layer measured by X-ray diffraction spectroscopy is in the range of 14-16 under the fully discharged state.
  • the S′ of the negative electrode active material layer measured by X-ray diffraction pattern is 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or within the range of any two of the above values.
  • S' can characterize the degree of orientation of the negative active material layer. The larger the S', the larger the anisotropy of the negative electrode active material layer. The smaller the S', the greater the isotropy of the negative electrode active material layer.
  • the peel strength between the anode active material layer and the anode current collector is 6 N/m to 15 N/m. In some embodiments, the peel strength between the negative active material layer and the negative current collector is 8 N/m to 14 N/m. In some embodiments, the peel strength between the negative active material layer and the negative current collector is 10 N/m to 12 N/m. In some embodiments, the peel strength between the negative active material layer and the negative current collector is 6N/m, 7N/m, 8N/m, 9N/m, 10N/m, 11N/m, 12N/m m, 13N/m, 14N/m, 15N/m or within the range of any two of the above values.
  • the peel strength between the negative electrode active material layer and the negative electrode current collector can be obtained through a tensile test, as follows: Use an Instron (model 33652) tester to test the bond between the negative electrode active material layer and the negative electrode current collector: take 15 -20mm long pole piece, fix it on the steel plate with 3M double-sided adhesive tape, stick the adhesive tape on the surface of the negative electrode active material layer, connect one side of the adhesive tape to the paper tape of equal width, adjust the limit of the tension machine Block to a suitable position, fold the paper tape upwards and slide it 40mm at a sliding rate of 50mm/min, and test the peel strength between the negative electrode active material layer and the negative electrode current collector at 180° (ie, stretched in the opposite direction).
  • the negative active material layer has a porosity of 20% to 40%. In some embodiments, the negative active material layer has a porosity of 25% to 35%. In some embodiments, the negative active material layer has a porosity of 28% to 32%. In some embodiments, the porosity of the negative active material layer is 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, or a ratio of any two of the foregoing values. Within range.
  • the porosity of the negative electrode active material layer can be obtained according to the standard test of "GB/T24586-2009 Iron Ore Apparent Density and True Density and Porosity Determination".
  • the thermal decomposition temperature of the anode active material layer is not less than 280°C. In some embodiments, in the fully charged state of the electrochemical device, the thermal decomposition temperature of the anode active material layer is not less than 300°C. In some embodiments, in the fully charged state of the electrochemical device, the thermal decomposition temperature of the anode active material layer is not less than 320°C. In some embodiments, in the fully charged state of the electrochemical device, the thermal decomposition temperature of the anode active material layer is not less than 340°C. When the electrochemical device is fully charged, lithium ions are inserted into the vacancies of the negative electrode material.
  • the thermal decomposition temperature of the negative electrode active material layer can represent the high temperature aging degree of the negative electrode, that is, the higher the decomposition temperature of the negative electrode active material, the high temperature aging The lower the degree, the better the high-temperature cycle performance of the lithium-ion battery.
  • the thermal decomposition temperature of the anode active material layer is not less than 130°C. In some embodiments, in the fully charged state of the electrochemical device, the thermal decomposition temperature of the anode active material layer is not less than 140°C. In some embodiments, in the fully discharged state of the electrochemical device, the thermal decomposition temperature of the anode active material layer is not less than 150°C. In some embodiments, in the fully discharged state of the electrochemical device, the thermal decomposition temperature of the anode active material layer is not less than 160°C. When the electrochemical device is fully discharged, all lithium ions are extracted from the negative electrode.
  • the thermal decomposition temperature of the negative electrode active material layer can indirectly characterize the stability of the SEI film, that is, the higher the decomposition temperature of the negative electrode active material, the thermal stability of the SEI film The better the performance, the less lithium ions needed to repair the SEI membrane during the cycling process of the lithium ion battery, and the better the cycling performance of the lithium ion battery.
  • the thermal decomposition temperature of the negative active material layer can be measured by differential scanning calorimetry (DSC). Specifically, a differential scanning calorimeter is used to heat the thermal decomposition temperature of the negative electrode active material layer to be tested at a constant heating rate at 0-800°C.
  • DSC differential scanning calorimetry
  • the negative electrode current collector used in the present application may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, foamed nickel, foamed copper, polymer substrates coated with conductive metals, and combinations thereof.
  • the negative electrode further includes a conductive layer.
  • the conductive material of the conductive layer may include any conductive material as long as it does not cause a chemical change.
  • conductive materials include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanotubes, graphene, etc.), metal-based materials (e.g., metal Powder, metal fibers, etc., such as copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.
  • the negative electrode further includes a binder, and the binder is selected from at least one of the following: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, and diacetyl cellulose , Polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, poly Propylene, styrene butadiene rubber, acrylic (ester) styrene butadiene rubber, epoxy resin or nylon, etc.
  • the binder is selected from at least one of the following: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, and diacetyl cellulose , Polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone
  • the positive electrode includes a positive electrode current collector and a positive electrode active material provided on the positive electrode current collector.
  • the specific types of positive electrode active materials are not subject to specific restrictions, and can be selected according to requirements.
  • the positive electrode active material includes a positive electrode material capable of absorbing and releasing lithium (Li).
  • cathode materials capable of absorbing/releasing lithium (Li) may include lithium cobalt oxide, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium manganate, lithium iron manganese phosphate, lithium vanadium phosphate, lithium vanadyl phosphate, and phosphoric acid. Lithium iron, lithium titanate and lithium-rich manganese-based materials.
  • the chemical formula of lithium cobalt oxide can be as chemical formula 1:
  • M1 represents selected from nickel (Ni), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), Copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), tungsten (W), yttrium (Y), lanthanum (La), zirconium (Zr) and For at least one of silicon (Si), the values of x, a, b, and c are within the following ranges: 0.8 ⁇ x ⁇ 1.2, 0.8 ⁇ a ⁇ 1, 0 ⁇ b ⁇ 0.2, -0.1 ⁇ c ⁇ 0.2.
  • the chemical formula of lithium nickel cobalt manganate or lithium nickel cobalt aluminate can be as chemical formula 2:
  • M2 represents selected from cobalt (Co), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), At least one of copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), tungsten (W), zirconium (Zr), and silicon (Si),
  • the values of y, d, e and f are in the following ranges respectively: 0.8 ⁇ y ⁇ 1.2, 0.3 ⁇ d ⁇ 0.98, 0.02 ⁇ e ⁇ 0.7, -0.1 ⁇ f ⁇ 0.2.
  • the chemical formula of lithium manganate can be as chemical formula 3:
  • M3 represents selected from cobalt (Co), nickel (Ni), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), At least one of copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr) and tungsten (W), with z, g and h values in the following ranges, respectively Inner: 0.8 ⁇ z ⁇ 1.2, 0 ⁇ g ⁇ 1.0 and -0.2 ⁇ h ⁇ 0.2.
  • the weight of the positive active material layer is 1.5 to 15 times the weight of the negative active material layer. In some embodiments, the weight of the positive active material layer is 3 to 10 times the weight of the negative active material layer. In some embodiments, the weight of the positive active material layer is 5 to 8 times the weight of the negative active material layer. In some embodiments, the weight of the positive electrode active material layer is 1.5 times, 2 times, 3 times, 4 times, 5 times, 6 times, 7 times, 8 times, 9 times the weight of the negative electrode active material layer. , 10 times, 11 times, 12 times, 13 times, 14 times or 15 times.
  • the positive active material layer may have a coating on the surface, or may be mixed with another compound having a coating.
  • the coating may include from the oxide of the coating element, the hydroxide of the coating element, the oxyhydroxide of the coating element, the oxycarbonate of the coating element (oxycarbonate) and the hydroxycarbonate of the coating element ( At least one coating element compound selected from hydroxycarbonate).
  • the compound used for the coating may be amorphous or crystalline.
  • the coating element contained in the coating may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, F, or a mixture thereof.
  • the coating can be applied by any method as long as the method does not adversely affect the performance of the positive electrode active material.
  • the method may include any coating method well known to those of ordinary skill in the art, such as spraying, dipping, and the like.
  • the positive active material layer further includes a binder, and optionally, a positive conductive material.
  • the binder can improve the binding of the positive electrode active material particles to each other, and also improve the binding of the positive electrode active material to the current collector.
  • binders include polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl Vinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylic (ester) styrene butadiene rubber, epoxy resin, nylon, etc.
  • the positive electrode active material layer includes a positive electrode conductive material, thereby imparting conductivity to the electrode.
  • the positive electrode conductive material may include any conductive material as long as it does not cause a chemical change.
  • Non-limiting examples of positive electrode conductive materials include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powder, metal fiber, etc., Including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (for example, polyphenylene derivatives), and mixtures thereof.
  • the positive electrode current collector used in the electrochemical device according to the present application may be aluminum (Al), but is not limited thereto.
  • the electrolyte that can be used in the embodiments of the present application may be an electrolyte known in the prior art.
  • the electrolyte that can be used in the electrolyte of the embodiments of the present application includes, but is not limited to: inorganic lithium salts, such as LiClO 4 , LiAsF 6 , LiPF 6 , LiBF 4 , LiSbF 6 , LiSO 3 F, LiN(FSO 2 ) 2, etc.; Fluorine-containing organic lithium salts, such as LiCF 3 SO 3 , LiN(FSO 2 )(CF 3 SO 2 ), LiN(CF 3 SO 2 ) 2 , LiN(C 2 F 5 SO 2 ) 2 , cyclic 1,3- Lithium hexafluoropropane disulfonimide, lithium cyclic 1,2-tetrafluoroethane disulfonimide, LiN (CF 3 SO 2 ) (C 4 F 9 SO 2 ), LiC (CF 3 SO 2 ) 3.
  • inorganic lithium salts such as LiClO 4 , LiAsF 6 , LiPF 6 , Li
  • lithium salt containing dicarboxylic acid complex such as lithium bis(oxalato)borate , Lithium difluorooxalatoborate, tris(oxalato) lithium phosphat
  • the electrolyte includes a combination of LiPF 6 and LiBF 4.
  • the electrolyte includes a combination of an inorganic lithium salt such as LiPF 6 or LiBF 4 and a fluorine-containing organic lithium salt such as LiCF 3 SO 3 , LiN(CF 3 SO 2 ) 2 , and LiN(C 2 F 5 SO 2 ) 2 .
  • the electrolyte includes LiPF 6 .
  • the concentration of the electrolyte is in the range of 0.8 mol/L to 3 mol/L, for example, in the range of 0.8 mol/L to 2.5 mol/L, in the range of 0.8 mol/L to 2 mol/L, 1 mol/L Within the range of L to 2mol/L, for example, 1mol/L, 1.15mol/L, 1.2mol/L, 1.5mol/L, 2mol/L or 2.5mol/L.
  • Solvents that can be used in the electrolyte of the embodiments of the present application include, but are not limited to, cyclic carbonate, chain carbonate, cyclic carboxylic acid ester, chain carboxylic acid ester, cyclic ether, or chain ether.
  • the cyclic carbonate includes, but is not limited to, ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate.
  • the cyclic carbonate has 3-6 carbon atoms.
  • the chain carbonate includes, but is not limited to: dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate (DEC), methyl n-propyl carbonate, ethyl n-propyl carbonate Carbonic acid esters, di-n-propyl carbonate and other chain carbonates, as chain carbonates substituted by fluorine, such as bis(fluoromethyl)carbonate, bis(difluoromethyl)carbonate, bis(trifluoromethyl) ) Carbonate, bis(2-fluoroethyl)carbonate, bis(2,2-difluoroethyl)carbonate, bis(2,2,2-trifluoroethyl)carbonate, 2-fluoroethyl Methyl carbonate, 2,2-difluoroethyl methyl carbonate and 2,2,2-trifluoroethyl methyl carbonate.
  • fluorine such as bis(fluoromethyl)carbonate, bis(difluoromethyl)carbonate,
  • cyclic carboxylic acid esters include, but are not limited to, ⁇ -butyrolactone and ⁇ -valerolactone.
  • part of the hydrogen atoms of the cyclic carboxylic acid ester may be substituted by fluorine.
  • the chain carboxylic acid esters include, but are not limited to: methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, sec-butyl acetate, isobutyl acetate, tertiary acetate Butyl ester, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, methyl isobutyrate, ethyl isobutyrate , Methyl valerate, ethyl valerate, methyl pivalate and ethyl pivalate.
  • part of the hydrogen atoms of the chain carboxylic acid ester may be replaced by fluorine.
  • fluorine-substituted chain carboxylic acid esters include, but are not limited to: methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, and trifluoroacetic acid 2,2 , 2-Trifluoroethyl ester.
  • cyclic ethers include, but are not limited to, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 2-methyl 1,3-dioxolane, 4-methyl 1 , 3-Dioxolane, 1,3-dioxane, 1,4-dioxane and dimethoxypropane.
  • chain ethers include, but are not limited to, dimethoxymethane, 1,1-dimethoxyethane, 1,2-dimethoxyethane, diethoxymethane, 1 ,1-diethoxyethane, 1,2-diethoxyethane, ethoxymethoxymethane, 1,1-ethoxymethoxyethane and 1,2-ethoxymethane Oxyethane.
  • the solvent used in the electrolyte of the present application includes one or more of the above.
  • the solvent used in the electrolyte of the present application includes cyclic carbonate, chain carbonate, cyclic carboxylic acid ester, chain carboxylic acid ester, and combinations thereof.
  • the solvent used in the electrolyte of the present application includes an organic solvent selected from the group consisting of: ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propionic acid Propyl ester, n-propyl acetate, ethyl acetate and combinations thereof.
  • the solvent used in the electrolyte of the present application includes: ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, ⁇ -butyrolactone or a combination thereof .
  • the additives that can be used in the electrolyte of the embodiments of the present application include, but are not limited to, cyclic carbonates containing carbon-carbon double bonds, and compounds containing sulfur-oxygen double bonds.
  • the cyclic carbonate having a carbon-carbon double bond specifically includes, but is not limited to: vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, vinyl ethylene ethylene carbonate Or at least one of carbonic acid-1,2-dimethyl vinylene ester.
  • compounds containing sulfur and oxygen double bonds include, but are not limited to: vinyl sulfate, 1,2-propanediol sulfate, 1,3-propane sultone, 1-fluoro-1,3-propane At least one of sultone, 2-fluoro-1,3-propane sultone or 3-fluoro-1,3-propane sultone.
  • a separator is provided between the positive electrode and the negative electrode to prevent short circuits.
  • the material and shape of the isolation film that can be used in the embodiments of the present application are not particularly limited, and may be any technology disclosed in the prior art.
  • the isolation membrane includes a polymer or an inorganic substance formed of a material that is stable to the electrolyte of the present application, or the like.
  • the isolation film may include a substrate layer and a surface treatment layer.
  • the substrate layer is a non-woven fabric, film or composite film with a porous structure, and the material of the substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide.
  • a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be selected.
  • the porous structure can improve the heat resistance, oxidation resistance and electrolyte infiltration performance of the isolation membrane, and enhance the adhesion between the isolation membrane and the pole piece.
  • a surface treatment layer is provided on at least one surface of the substrate layer, and the surface treatment layer may be a polymer layer or an inorganic substance layer, or a layer formed by a mixed polymer and an inorganic substance.
  • the inorganic layer includes inorganic particles and a binder.
  • the inorganic particles are selected from alumina, silica, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, One or a combination of yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate.
  • the binder is selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, One or a combination of polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.
  • the polymer layer contains a polymer, and the material of the polymer is selected from polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, poly At least one of (vinylidene fluoride-hexafluoropropylene).
  • the present application also provides an electrochemical device, which includes a positive electrode, an electrolyte, and a negative electrode.
  • the positive electrode includes a positive electrode active material layer and a positive electrode current collector.
  • the negative electrode includes a negative electrode active material layer and a negative electrode current collector.
  • the material layer includes the negative active material according to the present application.
  • the electrochemical device of the present application includes any device that undergoes an electrochemical reaction, and specific examples thereof include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors.
  • the electrochemical device is a lithium secondary battery, including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.
  • the application also provides an electronic device, which includes the electrochemical device according to the application.
  • the use of the electrochemical device of the present application is not particularly limited, and it can be used in any electronic device known in the prior art.
  • the electrochemical device of the present application can be used in, but not limited to, notebook computers, pen-input computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, and headsets.
  • Stereo headsets video recorders, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, power assistance Bicycles, bicycles, lighting equipment, toys, game consoles, clocks, power tools, flashlights, cameras, large household storage batteries, lithium-ion capacitors, etc.
  • lithium ion battery is taken as an example and the preparation of a lithium ion battery is described in conjunction with specific examples. Those skilled in the art will understand that the preparation methods described in this application are only examples, and any other suitable preparation methods are described in this application. Within range.
  • the artificial graphite is crushed and sieved to control the particle size distribution so that Dv90 ⁇ 25 ⁇ m to obtain primary particles.
  • the binder is added to the primary particles for bonding, and the particle size is controlled by grading and sieving to make Dv90 ⁇ 45 ⁇ m to obtain secondary particles.
  • the primary particles and the secondary particles are graphitized at 2300-3500° C., and then the processed primary particles and the secondary particles are mixed and sieved to obtain a graphite anode material.
  • the graphitization degree and K of the graphite material in the negative electrode can be controlled by the raw material, particle size, graphitization temperature and the ratio of primary particles to secondary particles.
  • Li x Co a M1 b O 2-c the values of x, a, b, and c are within the following ranges: 0.8 ⁇ x ⁇ 1.2, 0.8 ⁇ a ⁇ 1, 0 ⁇ b ⁇ 0.2, -0.1 ⁇ c ⁇ 0.2;
  • M1 is manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu) ), zinc (Zn), molybdenum (Mo) and combinations thereof), acetylene black and vinylidene fluoride (PVDF) are fully stirred in an appropriate amount of N-methylpyrrolidone (NMP) solvent at a weight ratio of 95:2:3 Mix to form a uniform positive electrode slurry.
  • NMP N-methylpyrrolidone
  • ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) in a weight ratio of 1:1:1, and then add 2% fluorine Substitute ethylene carbonate, 2% 1,3-propane sultone, 2% succinonitrile, dissolve and stir thoroughly, add lithium salt LiPF 6 , mix well to obtain electrolyte, in which the concentration of LiPF 6 is 1 mol/ L.
  • Polyethylene (PE) porous polymer film is used as the isolation membrane.
  • the positive electrode, separator, and negative electrode in order, so that the separator is between the positive electrode and the negative electrode for isolation, and then wind to obtain a bare cell; after welding the tabs, place the bare cell on the outer packaging foil aluminum plastic
  • the electrolyte prepared above is injected into the dried bare cell, and the process of vacuum packaging, standing, forming, shaping, and capacity testing is carried out to obtain a lithium ion battery.
  • the Raman spectroscopy using 523nm light source (light-shielding strength 5%), in the region of 100 ⁇ m ⁇ 100 ⁇ m collection point 100, the peak intensity is calculated carbon material with a carbon material in Id 1250cm -1 to 1650cm -1 to 1500cm -1 in The ratio of the peak intensity Ig at 1650 cm -1 and the average value is the K value of the carbon material.
  • the test conditions are as follows: X-ray adopts CuK ⁇ radiation, and CuK ⁇ radiation is removed by filter or monochromator.
  • the working voltage of the X-ray tube is 35-45kV, and the working current is 30-50mA.
  • the scanning speed of the counter is 0.3(°)/min.
  • the scanning range of the diffraction angle 2 ⁇ is 52°-58°.
  • the scanning range of the diffraction angle 2 ⁇ is 70°-79°.
  • the peak area of the negative electrode active material obtained from the (004) plane diffraction line pattern is denoted as C004.
  • the peak area of the negative electrode active material obtained from the (110) plane diffraction line pattern is denoted as C110. Calculate the ratio of C004/C110 of the negative active material and record it as S.
  • the peak area of the negative electrode active material layer obtained from the (004) plane diffraction line pattern is denoted as C004'.
  • the peak area of the negative electrode active material layer obtained from the (110) plane diffraction line pattern is denoted as C110'. Calculate the ratio of C004'/C110' of the negative active material and record it as S'.
  • the X-ray diffractometer was used to analyze the crystal size La along the horizontal axis and the crystal size Lc along the vertical axis of the carbon material in the negative electrode active material.
  • a Malvern particle size tester was used to test the particle size of the negative electrode active material: the negative electrode active material was dispersed in an alcohol dispersant, after 30 minutes of ultrasound, the sample was added to the Malvern particle size tester to test the Dv90 and Dv10 of the negative electrode active material.
  • the areal density of the anode active material layer is calculated by the following formula: (W 1 -W 2 )/(A ⁇ 2).
  • W 1 the weight of the negative electrode current collector
  • W 2 the weight of the negative electrode current collector
  • W 2 a micrometer to measure the thickness of the negative electrode current collector T 2 .
  • the weight W 0 and thickness T 0 of the negative electrode active material layer disposed on the negative electrode current collector side and the compaction density of the negative electrode active material layer are calculated by the following formula:
  • T 0 (T 1 -T 2 )/2
  • an Instron (model 33652) tensile tester to test the bonding between the negative electrode active material layer and the negative electrode current collector: take a 15-20mm long pole piece, fix it on the steel plate with 3M double-sided adhesive tape, and fix it on the steel plate.
  • the adhesive tape is attached to the surface of the negative electrode active material layer.
  • One side of the adhesive tape is connected to the paper tape of equal width.
  • Adjust the limit block of the tensile machine to a suitable position. Fold the tape upward and slide 40mm, and the sliding rate is 50mm /min, the peel strength between the negative electrode active material layer and the negative electrode current collector at 180° (that is, stretched in the opposite direction) is tested.
  • a sample of the negative electrode active material layer was prepared into a complete wafer. Each example or comparative example tested 30 samples, and the volume of each sample was about 0.35 cm 3 .
  • the porosity of the negative electrode active material layer was tested according to the "GB/T24586-2009 Iron Ore Apparent Density, True Density and Porosity Determination" standard.
  • a differential scanning calorimeter was used to heat at a constant temperature rise rate at 0-800°C to test the thermal decomposition temperature of the negative electrode active material layer disassembled in the fully charged or fully discharged state.
  • Cycle capacity retention rate (discharge capacity after cycle/discharge capacity at first cycle) ⁇ 100%.
  • Cycle expansion ratio (thickness after cycle/thickness at first cycle) ⁇ 100%.
  • the disassembled negative electrode is golden-yellow as a whole, and a very small part of the negative electrode can be observed in gray; and the area of the gray area is less than 2%, it is judged that lithium is not precipitated.
  • the disassembled negative electrode is mostly golden yellow, and gray can be observed in some positions; and the area of the gray area is between 2% and 20%, it is judged as slight lithium evolution.
  • the disassembled negative electrode is gray as a whole, golden yellow can be observed in some positions; and the area of the gray area is between 20% and 60%, it is judged to be lithium-deposited.
  • the disassembled negative electrode is gray as a whole and the area of the gray area is greater than 60%, it is judged as serious lithium evolution.
  • Table 1 shows the influence of the characteristics of the negative electrode active material on the performance of the lithium ion battery.
  • Comparative Example 1 when the ratio of the graphitization degree Gr to K of the negative electrode active material Gr/K is less than 6 and K is greater than 0.15, the first coulombic efficiency of the lithium ion battery is very low, and the phenomenon of lithium evolution occurs (as shown in Figure 4). Show), the cycle capacity retention rate is low and the cycle expansion rate is high. As shown in Comparative Example 2, when the ratio of the graphitization degree Gr to K of the negative electrode active material Gr/K is greater than 16 and K is less than 0.06, the first coulombic efficiency of the lithium ion battery is low, and a serious lithium evolution phenomenon occurs (as shown in Figure 5). Shown), the cycle capacity retention rate is very low and the cycle expansion rate is very high.
  • the lithium ion battery when the ratio of the graphitization degree Gr to K of the negative electrode active material Gr/K is in the range of 6 to 16, and K is in the range of 0.06 to 0.15, the lithium ion battery can be significantly improved.
  • the first coulombic efficiency and cycle capacity retention rate significantly reduce the cycle expansion rate of the lithium-ion battery, and significantly reduce the lithium evolution phenomenon of the lithium-ion battery during the cycle (as shown in Figure 3).
  • the significant increase in coulombic efficiency indicates that lithium-ion batteries have a significantly increased energy density.
  • the significant increase in the cycle capacity retention rate and the significant decrease in the cycle expansion rate indicate that the lithium ion battery has significantly improved cycle performance.
  • the improvement of the lithium evolution phenomenon helps to significantly improve the rate performance of lithium-ion batteries. Therefore, the lithium ion batteries of Examples 1-36 have significantly improved energy density, cycle performance, and rate performance.
  • the overall performance is more excellent.
  • the lithium ion battery can be further improved
  • the first coulombic efficiency, cycle capacity retention rate, cycle expansion rate and/or lithium evolution phenomenon of the first time improve the comprehensive performance of lithium-ion batteries.
  • Dv90/Dv10+Dv90 When Dv90/Dv10+Dv90 is greater than 23.0, it helps to further improve the cycle capacity retention rate and lithium evolution of lithium-ion batteries, and enhance the overall performance of lithium-ion batteries.
  • FIG. 1 shows a scanning electron microscope (SEM) image of the negative electrode active material used in Comparative Example 2 at a magnification of 500 times.
  • the negative active material in Comparative Example 2 only includes primary particles.
  • FIG. 2 shows a scanning electron microscope (SEM) image of the negative electrode active material used in Example 5 at a magnification of 500 times.
  • the negative electrode active material in Example 5 includes a certain ratio of primary particles and secondary particles, and the graphitization degree and K value of the carbon material can be adjusted by adjusting the ratio.
  • Figure 6 shows the cycle capacity retention curves of the lithium ion batteries of Comparative Example 1, Comparative Example 2 and Example 5 at 25°C with the number of cycles.
  • Figure 7 shows the cycle capacity retention curves of the lithium ion batteries of Comparative Example 1, Comparative Example 2 and Example 5 at 45°C with the number of cycles. The results show that, compared with Comparative Examples 1 and 2, the cycle capacity retention rate of the lithium ion battery of Example 5 at 25° C. and 45° C. is always maintained above 90%. As the number of cycles increases, the difference in the retention rate of the cycle capacity between Example 5 and Comparative Examples 1 and 2 gradually increases.
  • Table 2 shows the influence of the characteristics of the negative active material layer on the performance of the lithium ion battery. Examples 37-44 are improvements based on Example 5 in Table 1, and the difference lies only in the parameters listed in Table 2.
  • the overall performance of the battery may also be affected by the compaction density of the negative electrode active material layer, the isotropy of the negative electrode active material layer (S′ reduction), porosity, The influence of the peel strength between the negative electrode active material layer and the negative electrode current collector.
  • the S′ of the lithium ion battery in the fully discharged state is 10 To 20
  • the peel strength between the negative electrode active material layer and the negative electrode current collector is 6N/m to 15N/m
  • the porosity of the negative electrode active material layer is 20% to 40%
  • the heat of the negative electrode active material layer in the fully charged state When the decomposition temperature is not less than 280°C, and/or the thermal decomposition temperature of the negative electrode active material layer in the fully discharged state is not less than 130°C, it will help to further improve the first coulombic efficiency, cycle capacity retention rate, and cycle expansion of lithium-ion batteries.
  • references to “embodiments”, “partial examples”, “one embodiment”, “another example”, “examples”, “specific examples” or “partial examples” throughout the specification mean that At least one embodiment or example in this application includes the specific feature, structure, material, or characteristic described in the embodiment or example. Therefore, descriptions appearing in various places throughout the specification, such as: “in some embodiments”, “in an embodiment”, “in one example”, “in another example”, “in an example “In”, “in a specific example” or “exemplified”, which are not necessarily quoting the same embodiment or example in this application.
  • the specific features, structures, materials, or characteristics herein can be combined in one or more embodiments or examples in any suitable manner.

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Abstract

一种负极活性材料及使用其的电化学装置和电子装置。所述负极活性材料，其包括碳材料，所述碳材料的特定峰强度比值K以及石墨化度Gr和K的比例在特定范围内。所述负极活性材料可显著改善电化学装置的能量密度、循环性能和倍率性能。

Description

负极活性材料及使用其的电化学装置和电子装置 技术领域
本申请涉及储能领域，具体涉及一种负极活性材料及使用其的电化学装置和电子装置。
背景技术
电化学装置(例如，锂离子电池)由于具有环境友好、工作电压高、比容量大和循环寿命长等优点而被广泛应用，已成为当今世界最具发展潜力的新型绿色化学电源。小尺寸锂离子电池通常用作驱动便携式电子通讯设备(例如，便携式摄像机、移动电话或者笔记本电脑等)的电源，特别是高性能便携式设备的电源。具有高输出特性的中等尺寸和大尺寸锂例子电池被发展应用于电动汽车(EV)和大规模储能系统(ESS)。随着锂离子电池的广泛应用，其能量密度、循环性能和倍率性能已成为亟待解决的关键技术问题。改进极片中的活性材料是解决上述问题的研究方向之一。
有鉴于此，确有必要提供一种改进的负极活性材料及使用其的电化学装置和电子装置。
发明内容
本申请实施例通过提供一种负极活性材料及使用其的电化学装置和电子装置以在至少某种程度上解决至少一种存在于相关领域中的问题。
根据本申请的一个方面，本申请提供了一种负极活性材料，所述负极活性材料包含碳材料，其中所述碳材料符合以下关系：6＜Gr/K＜16，其中，Gr为所述碳材料的石墨化度，通过X射线衍射法测定得到；且K为所述碳材料在1250cm -1至1650cm -1的峰强度Id与所述碳材料在1500cm -1至1650cm -1的峰强度Ig的比值Id/Ig，通过拉曼光谱法测定得到，所述K为0.06至0.15。
在一些实施例中，所述碳材料符合以下关系：8＜Gr/K＜15。在一些实施例中，所述碳材料符合以下关系：10＜Gr/K＜12。在一些实施例中，所述碳材料的Gr/K值为6.5、7、7.5、8、8.5、9、9.5、10、10.5、11、11.5、12、12.5、13、 13.5、14、14.5、15、15.5或在以上任意两个数值所组成的范围内。
在一些实施例中，所述碳材料的K为0.08至0.10。在一些实施例中，所述碳材料的K为0.06、0.07、0.08、0.09、0.10、0.11、0.12、0.13、0.14、0.15或在以上任意两个数值所组成的范围内。
根据本申请的实施例，所述碳材料的，所述石墨化度Gr为0.92至0.96。在一些实施例中，所述碳材料的石墨化度Gr为0.92、0.93、0.94、0.95、0.96或在以上任意两个数值所组成的范围内。
根据本申请的实施例，所述碳材料满足以下关系中的至少一种：
Lc/S＜9；
La/S＞20，
其中：
La为由X射线衍射法测定的所述碳材料晶体沿水平轴的晶体尺寸，单位为nm；
Lc为由X射线衍射法测定的所述碳材料晶体沿垂直轴的晶体尺寸，单位为nm；
S为由X射线衍射图谱测定得到的所述负极活性材料的(004)面的峰面积C004和(110)面的峰面积C110的比值；
所述Lc小于45，所述La大于50。
在一些实施例中，Lc/S＜8。在一些实施例中，Lc/S＜7。在一些实施例中，Lc/S＜6。在一些实施例中，Lc/S＞2。在一些实施例中，Lc/S＞3。在一些实施例中，Lc/S为3、3.5、4、4.5、5、5.5、6、6.5、7、7.5、8、8.5或在以上任意两个端点值所组成的范围内。
在一些实施例中，La/S＞22。在一些实施例中，La/S＞25。在一些实施例中，La/S＞28。在一些实施例中，La/S＞30。在一些实施例中，La/S＜60。在一些实施例中，La/S＜55。在一些实施例中，La/S＜50。在一些实施例中，La/S为22、25、28、30、35、40、45、50或在以上任意两个端点值所组成的范围内。
在一些实施例中，所述Lc小于40。在一些实施例中，所述Lc小于35。在一些实施例中，所述Lc小于30。在一些实施例中，所述Lc小于25。在一些实施例中，所述Lc大于10。在一些实施例中，所述Lc大于15。在一些实施例中，所述Lc大于20。在一些实施例中，所述Lc为20、22、25、28、30、35、40、 43或在上述任意两个数值的范围内。
在一些实施例中，所述La大于60。在一些实施例中，所述La大于80。在一些实施例中，所述La大于100。在一些实施例中，所述La大于110。在一些实施例中，所述La大于120。在一些实施例中，所述La大于130。在一些实施例中，所述La大于150。在一些实施例中，所述La大于180。在一些实施例中，所述La大于200。在一些实施例中，所述La大于220。在一些实施例中，所述La小于300。在一些实施例中，所述La小于250。在一些实施例中，所述La为55、60、70、80、90、100、120、150、180、200、230、250或在上述任意两个数值的范围内。
根据本申请的实施例，所述负极活性材料的Dv10值与Dv90值满足以下关系：Dv90/Dv10+Dv90＞23.0。在一些实施例中，所述负极活性材料的Dv10值与Dv90值满足以下关系：Dv90/Dv10+Dv90＞25.0。在一些实施例中，所述负极活性材料的Dv10值与Dv90值满足以下关系：Dv90/Dv10+Dv90＞28.0。在一些实施例中，所述负极活性材料的Dv10值与Dv90值满足以下关系：Dv90/Dv10+Dv90＞30.0。在一些实施例中，所述负极活性材料的Dv10值与Dv90值满足以下关系：Dv90/Dv10+Dv90＜50.0。在一些实施例中，所述负极活性材料的Dv10值与Dv90值满足以下关系：Dv90/Dv10+Dv90＜45.0。在一些实施例中，所述负极活性材料的Dv10值与Dv90值满足以下关系：Dv90/Dv10+Dv90＜40.0。在一些实施例中，所述负极活性材料的Dv10值与Dv90值满足以下关系：Dv90/Dv10+Dv90＜35.0。在一些实施例中，所述负极活性材料的Dv10值与Dv90值Dv90/Dv10+Dv90为24、26、28、30、33、35或在上述任意两个数值的范围内。在上述关系式中，Dv90和Dv10的单位为μm。
根据本申请的另一方面，本申请提供一种电化学装置，其包括正极、电解液和负极，所述负极包括负极活性材料层和集流体，所述负极活性材料层包括根据本申请所述的负极活性材料。
根据本申请的实施例，所述负极活性材料层的面密度为0.077mg/mm 2至0.121mg/mm 2，所述负极活性材料层的压实密度为1.70g/cm 3至1.92g/cm 3。
在一些实施例中，所述负极活性材料层的面密度为0.080mg/mm 2至0.120mg/mm 2。在一些实施例中，所述负极活性材料层的面密度为0.085mg/mm 2至0.110mg/mm 2。在一些实施例中，所述负极活性材料层的面密度为0.090 mg/mm 2至0.100mg/mm 2。在一些实施例中，所述负极活性材料层的面密度为0.077mg/mm 2、0.080mg/mm 2、0.085mg/mm 2、0.090mg/mm 2、0.095mg/mm 2、0.100mg/mm 2、0.105mg/mm 2、0.110mg/mm 2、0.115mg/mm 2、0.120mg/mm 2、0.121mg/mm 2或在上述任意两个数值的范围内。
在一些实施例中，所述负极活性材料层的压实密度为1.75g/cm 3至1.90g/cm 3。在一些实施例中，所述负极活性材料层的压实密度为1.80g/cm 3至1.85g/cm 3。在一些实施例中，所述负极活性材料层的压实密度为1.70g/cm 3、1.75g/cm 3、1.78g/cm 3、1.80g/cm 3、1.85g/cm 3、1.85g/cm 3、1.88g/cm 3、1.90g/cm 3、1.92g/cm 3或在上述任意两个数值的范围内。
根据本申请的实施例，在满放状态下，由X射线衍射图谱测定得到的所述负极活性材料层的(004)面的峰面积C004′和(110)面的峰面积C110′的比值S′在10至20的范围内。在一些实施例中，在满放状态下，由X射线衍射图谱测定得到的所述负极活性材料层的S′在12至18的范围内。在一些实施例中，在满放状态下，由X射线衍射图谱测定得到的所述负极活性材料层的S′在14至16的范围内。在一些实施例中，在满放状态下，由X射线衍射图谱测定得到的所述负极活性材料层的S′为10、11、12、13、14、15、16、17、18、19、20或在上述任意两个数值的范围内。
根据本申请的实施例，所述负极活性材料层与所述负极集流体之间的剥离强度为6N/m至15N/m。在一些实施例中，所述负极活性材料层与所述负极集流体之间的剥离强度为8N/m至14N/m。在一些实施例中，所述负极活性材料层与所述负极集流体之间的剥离强度为10N/m至12N/m。在一些实施例中，所述负极活性材料层与所述负极集流体之间的剥离强度为6N/m、7N/m、8N/m、9N/m、10N/m、11N/m、12N/m、13N/m、14N/m、15N/m或在上述任意两个数值的范围内。
根据本申请的实施例，所述负极活性材料层具有20％至40％的孔隙率。在一些实施例中，所述负极活性材料层具有25％至35％的孔隙率。在一些实施例中，所述负极活性材料层具有28％至32％的孔隙率。在一些实施例中，所述负极活性材料层的孔隙率为20％、22％、25％、28％、30％、32％、35％、38％、40％或在上述任意两个数值的范围内。
根据本申请的实施例，在所述电化学装置满充状态下，所述负极活性材料层 的热分解温度不小于280℃。在一些实施例中，在所述电化学装置满充状态下，所述负极活性材料层的热分解温度不小于300℃。在一些实施例中，在所述电化学装置满充状态下，所述负极活性材料层的热分解温度不小于320℃。在一些实施例中，在所述电化学装置满充状态下，所述负极活性材料层的热分解温度不小于340℃。
根据本申请的实施例，在所述电化学装置满放状态下，所述负极活性材料层的热分解温度不小于130℃。在一些实施例中，在所述电化学装置满放状态下，所述负极活性材料层的热分解温度不小于140℃。在一些实施例中，在所述电化学装置满放状态下，所述负极活性材料层的热分解温度不小于150℃。在一些实施例中，在所述电化学装置满放状态下，所述负极活性材料层的热分解温度不小于160℃。
根据本申请的又一个方面，本申请提供了一种电子装置，其包括根据本申请所述的电化学装置。
本申请的额外层面及优点将部分地在后续说明中描述、显示、或是经由本申请实施例的实施而阐释。
附图说明
在下文中将简要地说明为了描述本申请实施例或现有技术所必要的附图以便于描述本申请的实施例。显而易见地，下文描述中的附图仅只是本申请中的部分实施例。对本领域技术人员而言，在不需要创造性劳动的前提下，依然可以根据这些附图中所例示的结构来获得其他实施例的附图。
图1展示了对比例2中使用的负极活性材料放大500倍的扫描电子显微镜(SEM)图。
图2展示了实施例5中使用的负极活性材料放大500倍的扫描电子显微镜(SEM)图。
图3展示了实施例5中使用的负极活性材料在循环后的外观照片，其中没有析锂现象。
图4展示了对比例1中使用的负极活性材料在循环后的外观照片，其中显示出析锂现象。
图5展示了对比例2中使用的负极活性材料在循环后的外观照片，其中显示出严重析锂现象。
图6展示了对比例1、对比例2和实施例5的锂离子电池在25℃下随循环圈数的循环容量保持率曲线。
图7展示了对比例1、对比例2和实施例5的锂离子电池在45℃下随循环圈数的循环容量保持率曲线。
图8展示了对比例1、对比例2和实施例5的锂离子电池在25℃下随循环圈数的循环膨胀率曲线。
图9展示了对比例1、对比例2和实施例5的锂离子电池在45℃下随循环圈数的循环膨胀率曲线。
具体实施方式
本申请的实施例将会被详细的描示在下文中。在本申请说明书中，将相同或相似的组件以及具有相同或相似的功能的组件通过类似附图标记来表示。在此所描述的有关附图的实施例为说明性质的、图解性质的且用于提供对本申请的基本理解。本申请的实施例不应该被解释为对本申请的限制。
在具体实施方式及权利要求书中，由术语“中的至少一者”连接的项目的列表可意味着所列项目的任何组合。例如，如果列出项目A及B，那么短语“A及B中的至少一者”意味着仅A；仅B；或A及B。在另一实例中，如果列出项目A、B及C，那么短语“A、B及C中的至少一者”意味着仅A；或仅B；仅C；A及B(排除C)；A及C(排除B)；B及C(排除A)；或A、B及C的全部。项目A可包含单个元件或多个元件。项目B可包含单个元件或多个元件。项目C可包含单个元件或多个元件。
随着电化学装置(例如，锂离子电池)的广泛应用，对其性能的要求不断提升。能量密度、循环性能和倍率性能是评价锂离子电池性能的重要指标。迄今为止，尚未研发出能够同时改善锂离子电池的能量密度、循环性能和倍率性能的有效手段。
本申请通过优化负极活性材料以解决上述问题。具体而言，本申请提供了一种负极活性材料，所述负极活性材料包含碳材料，其中所述碳材料符合以下关系：6＜Gr/K＜16；其中，Gr为所述碳材料的石墨化度，通过X射线衍射法测定得到；且K为所述碳材料在1250cm -1至1650cm -1的峰强度Id与所述碳材料在1500cm -1至1650cm -1的峰强度Ig的比值Id/Ig，，通过拉曼光谱法测定得到，所述K为0.06至0.15。
在一些实施例中，所述碳材料的石墨化度Gr和K符合以下关系：8＜Gr/K＜15。在一些实施例中，所述碳材料的石墨化度Gr和K符合以下关系：10＜Gr/K＜12。在一些实施例中，所述碳材料的石墨化度Gr和K的比值Gr/K为6.5、7、7.5、8、8.5、9、9.5、10、10.5、11、11.5、12、12.5、13、13.5、14、14.5、15、15.5或在以上任意两个数值所组成的范围内。
在一些实施例中，所述碳材料的K为0.08至0.10。在一些实施例中，所述碳材料的K为0.06、0.07、0.08、0.09、0.10、0.11、0.12、0.13、0.14、0.15或在以上任意两个数值所组成的范围内。
碳材料的K可表征材料的表面缺陷和结晶区域的比例。K可由拉曼光谱法测定：采用523nm光源(遮光强度5％)，在100μm×100μm区域采点100个，计算碳材料在1250cm -1至1650cm -1的峰强度Id与碳材料在1500cm -1至1650cm -1的峰强度Ig的比值，取平均值，即为碳材料的K值。
碳材料的“石墨化度”是指碳材料在高温下或二次加热过程中非石墨炭转变为类石墨炭的程度。碳材料的石墨化度可通过以下方法得到：采用高纯硅粉作为内标校准，通过X射线衍射法测试碳材料的002面的面间距(d002)，根据以下公式计算碳材料的石墨化度Gr：Gr＝(0.344-d002)/0.086×100％。
负极活性材料中的碳材料的石墨化度和K值会影响锂离子的嵌入和脱嵌。例如，在锂离子电池的循环放电过程中，锂离子向负极迁移，负极会接受锂离子，碳材料的石墨化度和K值会影响锂离子嵌入碳材料颗粒的速度。当在大倍率放电的条件下，若锂离子不能迅速嵌入碳材料颗粒内部并在其中扩散，锂离子则会在表面析出，加速锂离子电池的循环衰减。在锂离子电池的循环充电过程中，锂离子从负极脱出。若锂离子不能迅速脱出负极，其会在碳材料颗粒内部形成死锂，同样会加速锂离子电池的循环衰减。碳材料的石墨化度和K值还会影响锂离子电池在首次循环过程中形成的固体电解质界面(SEI)膜的厚度，从而影响锂离子电池的首次库伦效率，进而影响锂离子电池的能量密度。
当碳材料具有较高的石墨化度(例如，Gr＞0.96)时，碳材料的晶面间距减小，不利于锂离子从碳材料中脱嵌。当碳材料具有较低的石墨化度(例如，Gr＜0.92)时，碳材料中的SP 3键较多，使碳材料的各层之间相互牵制，从而使碳材料的结构更稳定。
当碳材料的石墨化度Gr以及碳材料的石墨化度和K的比值Gr/K在上述范 围内时，锂离子电池具有显著改善的能量密度、循环性能和倍率性能。
根据本申请的实施例，所述碳材料的石墨化度Gr为0.92至0.96。在一些实施例中，所述碳材料的石墨化度Gr为0.92、0.93、0.94、0.95、0.96或在以上任意两个数值所组成的范围内。当碳材料的石墨化度在上述范围内时，有助于进一步改善锂离子电池的能量密度、循环性能和倍率性能。
根据本申请的实施例，所述碳材料满足以下关系中的至少一种：
Lc/S＜9；
La/S＞20，
其中：
La为由X射线衍射法测定的所述碳材料晶体沿水平轴的晶体尺寸，单位为nm；
Lc为由X射线衍射法测定的所述碳材料晶体沿垂直轴的晶体尺寸，单位为nm；
S为由X射线衍射图谱测定得到的所述负极活性材料的(004)面的峰面积C004和(110)面的峰面积C110的比值；
所述Lc小于45，所述La大于50。
在一些实施例中，Lc/S＜8。在一些实施例中，Lc/S＜7。在一些实施例中，Lc/S＜6。在一些实施例中，Lc/S＞2。在一些实施例中，Lc/S＞3。在一些实施例中，Lc/S为3、3.5、4、4.5、5、5.5、6、6.5、7、7.5、8、8.5或在以上任意两个端点值所组成的范围内。
在一些实施例中，La/S＞22。在一些实施例中，La/S＞25。在一些实施例中，La/S＞28。在一些实施例中，La/S＞30。在一些实施例中，La/S＜60。在一些实施例中，La/S＜55。在一些实施例中，La/S＜50。在一些实施例中，La/S为22、25、28、30、35、40、45、50或在以上任意两个端点值所组成的范围内。
在一些实施例中，所述Lc小于40。在一些实施例中，所述Lc小于35。在一些实施例中，所述Lc小于30。在一些实施例中，所述Lc小于25。在一些实施例中，所述Lc大于10。在一些实施例中，所述Lc大于15。在一些实施例中，所述Lc大于20。在一些实施例中，所述Lc为20、22、25、28、30、35、40、43或在上述任意两个数值的范围内。
在一些实施例中，所述La大于60。在一些实施例中，所述La大于80。在 一些实施例中，所述La大于100。在一些实施例中，所述La大于110。在一些实施例中，所述La大于120。在一些实施例中，所述La大于130。在一些实施例中，所述La大于150。在一些实施例中，所述La大于180。在一些实施例中，所述La大于200。在一些实施例中，所述La大于220。在一些实施例中，所述La小于300。在一些实施例中，所述La小于250。在一些实施例中，所述La为55、60、70、80、90、100、120、150、180、200、230、250或在上述任意两个数值的范围内。
碳材料晶体的晶体尺寸会影响循环过程中锂离子的嵌入和脱嵌。根据X射线衍射图谱，负极活性材料的(004)面的峰面积C004和(110)面的峰面积C110的比值S可表征负极活性材料的取向度。S越大，负极活性材料的各向异性越大。S越小，负极活性材料的各向同性越大。当碳材料的晶体尺寸及其与取向度的比值在上述范围内时，有助于进一步改善锂离子电池的能量密度、循环性能和倍率性能。
根据本申请的实施例，所述负极活性材料的Dv10值与Dv90值满足以下关系：Dv90/Dv10+Dv90＞23.0，Dv90和Dv10的单位为μm。“Dv90”指的是负极活性材料在体积基准的粒度分布中从小粒径侧起达到体积累积90％的粒径，即，小于此粒径的负极活性材料的体积占负极活性材料总体积的90％。“Dv10”指的是负极活性材料在体积基准的粒度分布中从小粒径侧起达到体积累积10％的粒径，即，小于此粒径的负极活性材料的体积占负极活性材料总体积的10％。负极活性材料的颗粒尺寸可采用粒度测试仪(例如，马尔文粒度测试仪)测试得到。
在一些实施例中，所述负极活性材料的Dv10值与Dv90值满足以下关系：Dv90/Dv10+Dv90＞25.0。在一些实施例中，所述负极活性材料的Dv10值与Dv90值满足以下关系：Dv90/Dv10+Dv90＞28.0。在一些实施例中，所述负极活性材料的Dv10值与Dv90值满足以下关系：Dv90/Dv10+Dv90＞30.0。在一些实施例中，所述负极活性材料的Dv10值与Dv90值满足以下关系：Dv90/Dv10+Dv90＜50.0。在一些实施例中，所述负极活性材料的Dv10值与Dv90值满足以下关系：Dv90/Dv10+Dv90＜45.0。在一些实施例中，所述负极活性材料的Dv10值与Dv90值满足以下关系：Dv90/Dv10+Dv90＜40.0。在一些实施例中，所述负极活性材料的Dv10值与Dv90值满足以下关系：Dv90/Dv10+Dv90＜35.0。在一些实施例中，所述负极活性材料的Dv90/Dv10+Dv90为24、26、28、30、33、35或在上述任 意两个数值的范围内。在上述关系式中，Dv90和Dv10的单位为μm。
当负极活性材料的颗粒尺寸较大时，负极活性材料的比表面积较小，使得锂离子电池在首次循环过程中只需消耗较少的锂离子即可与电解液形成固体电解质界面(SEI)膜，从而提升锂离子电池的首次库伦效率。较大的颗粒尺寸还会延长锂离子嵌入和脱嵌的路径，从而降低锂离子电池的动力学性能。另外，较大的颗粒尺寸还会对锂离子电池的循环膨胀产生不利影响。反之，当负极活性材料的颗粒尺寸较小时，负极活性材料的比表面积较大，使得锂离子电池在首次循环过程中需消耗较多的锂离子与电解液形成SEI膜，从而降低锂离子电池的首次库伦效率。较小的颗粒尺寸还会缩短锂离子嵌入和脱嵌的路径，从而影响锂离子电池的动力学性能。另外，较小的颗粒尺寸还会对锂离子电池的循环膨胀产生不利影响。当负极活性材料的Dv90和Dv10满足上述关系时，有助于平衡离子电池的各项性能，进一步改善锂离子电池的能量密度、循环性能和倍率性能。
本申请还提供了一种电化学装置，其包括正极、负极、隔离膜和电解液。以下说明可用于本申请中正极、负极、隔离膜和电解液。
负极
本申请的电化学装置所使用的负极包括负极集流体和负极活性材料层，所述负极活性材料层包含根据本申请所述的负极活性材料。
根据本申请的实施例，所述负极活性材料层的面密度为0.077mg/mm 2至0.121mg/mm 2，所述负极活性材料层的压实密度为1.70g/cm 3至1.92g/cm 3。
在一些实施例中，所述负极活性材料层的面密度为0.080mg/mm 2至0.120mg/mm 2。在一些实施例中，所述负极活性材料层的面密度为0.085mg/mm 2至0.110mg/mm 2。在一些实施例中，所述负极活性材料层的面密度为0.090mg/mm 2至0.100mg/mm 2。在一些实施例中，所述负极活性材料层的面密度为0.077mg/mm 2、0.080mg/mm 2、0.085mg/mm 2、0.090mg/mm 2、0.095mg/mm 2、0.100mg/mm 2、0.105mg/mm 2、0.110mg/mm 2、0.115mg/mm 2、0.120mg/mm 2、0.121mg/mm 2或在上述任意两个数值的范围内。负极活性材料层的面密度可通过以下方法测试得到：将电池放电至0SOC％，拆解电池，清洗，烘干，使用电子天平对一定面积A的负极(负极集流体的双面涂覆有负极活性材料层)进行称重，重量记为W 1；使用溶剂洗掉负极活性材料层，烘干，测量负极集流体的重量，记为W 2。通过以下公式计算负极活性材料层的面密度：(W 1-W 2)/(A×2)。
在一些实施例中，所述负极活性材料层的压实密度为1.75g/cm 3至1.90g/cm 3。在一些实施例中，所述负极活性材料层的压实密度为1.80g/cm 3至1.85g/cm 3。在一些实施例中，所述负极活性材料层的压实密度为1.70g/cm 3、1.75g/cm 3、1.78g/cm 3、1.80g/cm 3、1.85g/cm 3、1.85g/cm 3、1.88g/cm 3、1.90g/cm 3、1.92g/cm 3或在上述任意两个数值的范围内。负极活性材料层的压实密度可通过以下方法测试得到：将电池放电至0SOC％，拆解电池，清洗，烘干，使用电子天平对一定面积A的负极(负极集流体的双面涂覆有负极活性材料层)进行称重，重量记为W 1，并使用万分尺测得负极的厚度T 1。使用溶剂洗掉负极活性材料层，烘干，测量负极集流体的重量，记为W 2，并使用万分尺测得负极集流体厚度T 2。通过下式计算设置在负极集流体一侧的负极活性材料层的重量W 0和厚度T 0以及负极活性材料层的压实密度：
W 0＝(W 1-W 2)/2
T 0＝(T 1-T 2)/2
压实密度＝W 0/(T 0×A)。
根据本申请的实施例，在满放状态下，由X射线衍射图谱测定得到的所述负极活性材料层的(004)面的峰面积C004′和(110)面的峰面积C110′的比值S′在10至20的范围内。在一些实施例中，在满放状态下，由X射线衍射图谱测定得到的所述负极活性材料层的S′在12至18的范围内。在一些实施例中，在满放状态下，由X射线衍射图谱测定得到的所述负极活性材料层的S′在14至16的范围内。在一些实施例中，在满放状态下，由X射线衍射图谱测定得到的所述负极活性材料层的S′为10、11、12、13、14、15、16、17、18、19、20或在上述任意两个数值的范围内。S′可表征负极活性材料层的取向度。S′越大，负极活性材料层的各向异性越大。S′越小，负极活性材料层的各向同性越大。
根据本申请的实施例，所述负极活性材料层与所述负极集流体之间的剥离强度为6N/m至15N/m。在一些实施例中，所述负极活性材料层与所述负极集流体之间的剥离强度为8N/m至14N/m。在一些实施例中，所述负极活性材料层与所述负极集流体之间的剥离强度为10N/m至12N/m。在一些实施例中，所述负极活性材料层与所述负极集流体之间的剥离强度为6N/m、7N/m、8N/m、9N/m、10N/m、11N/m、12N/m、13N/m、14N/m、15N/m或在上述任意两个数值的范围内。
负极活性材料层与负极集流体之间的剥离强度可通过拉伸测试得到，具体如下：使用Instron(型号为33652)测试仪进行测试负极活性材料层与负极集流体之间的粘结：取15-20mm长的极片，用3M双面胶纸将其固定于钢板上，将胶纸贴在负极活性材料层表面，该胶纸一侧与其等宽的纸带相连接，调整拉力机限位块至合适位置，将纸带向上翻折及滑移40mm，滑移速率为50mm/min，测试180°下(即，反方向拉伸)负极活性材料层与负极集流体之间的剥离强度。
根据本申请的实施例，所述负极活性材料层具有20％至40％的孔隙率。在一些实施例中，所述负极活性材料层具有25％至35％的孔隙率。在一些实施例中，所述负极活性材料层具有28％至32％的孔隙率。在一些实施例中，所述负极活性材料层的孔隙率为20％、22％、25％、28％、30％、32％、35％、38％、40％或在上述任意两个数值的范围内。负极活性材料层的孔隙率可根据《GB/T24586-2009铁矿石表观密度真密度和孔隙率的测定》标准测试得到。
在负极活性材料层的面密度一定的情况下，降低负极活性材料层的压实密度会降低负极活性材料层的各向异性和孔隙率并且降低负极活性材料层与负极集流体之间的剥离强度。在负极活性材料层的压实密度一定的情况下，降低负极活性材料层的面密度会增大负极活性材料层的各向异性、降低负极活性材料层的孔隙率并且降低负极活性材料层与负极集流体之间的剥离强度。当负极活性材料的面密度、压实密度、取向度S′、孔隙率和/或负极活性材料与负极集流体之间的剥离强度在上述范围内时，有助于进一步改善锂离子电池的能量密度、循环性能和倍率性能。
根据本申请的实施例，在所述电化学装置满充状态下，所述负极活性材料层的热分解温度不小于280℃。在一些实施例中，在所述电化学装置满充状态下，所述负极活性材料层的热分解温度不小于300℃。在一些实施例中，在所述电化学装置满充状态下，所述负极活性材料层的热分解温度不小于320℃。在一些实施例中，在所述电化学装置满充状态下，所述负极活性材料层的热分解温度不小于340℃。当电化学装置处于满充状态下，锂离子嵌入负极材料空位，此时的负极活性材料层的热分解温度可代表负极的高温老化程度，即，负极活性材料的分解温度越高，其高温老化程度越轻微，锂离子电池的高温循环性能好。
根据本申请的实施例，在所述电化学装置满放状态下，所述负极活性材料层的热分解温度不小于130℃。在一些实施例中，在所述电化学装置满放状态下， 所述负极活性材料层的热分解温度不小于140℃。在一些实施例中，在所述电化学装置满放状态下，所述负极活性材料层的热分解温度不小于150℃。在一些实施例中，在所述电化学装置满放状态下，所述负极活性材料层的热分解温度不小于160℃。当电化学装置处于满放状态下，锂离子全部从负极脱出，负极活性材料层的热分解温度可间接表征SEI膜的稳定性，即，负极活性材料的分解温度越高，SEI膜的热稳定性越好，在锂离子电池循环过程用于修复SEI膜所需消耗的锂离子越少，锂离子电池的循环性能好。
负极活性材料层的热分解温度可通过示差扫描量热法(DSC)测量。具体地，采用示差扫描量热仪以恒定升温速率在0-800℃加热待测试负极活性材料层的热分解温度。
用于本申请所述的负极集流体可以选自铜箔、镍箔、不锈钢箔、钛箔、泡沫镍、泡沫铜、覆有导电金属的聚合物基底和它们的组合。
根据本申请的实施例，所述负极进一步包括导电层。在一些实施方案中，所述导电层的导电材料可以包括任何导电材料，只要它不引起化学变化。导电材料的非限制性示例包括基于碳的材料(例如，天然石墨、人造石墨、碳黑、乙炔黑、科琴黑、碳纤维、碳纳米管、石墨烯等)、基于金属的材料(例如，金属粉、金属纤维等，例如铜、镍、铝、银等)、导电聚合物(例如，聚亚苯基衍生物)和它们的混合物。
根据本申请的实施例，所述负极进一步包括粘结剂，所述粘结剂选自以下的至少一种：聚乙烯醇、羧甲基纤维素、羟丙基纤维素、二乙酰基纤维素、聚氯乙烯、羧化的聚氯乙烯、聚氟乙烯、含亚乙基氧的聚合物、聚乙烯吡咯烷酮、聚氨酯、聚四氟乙烯、聚偏1，1-二氟乙烯、聚乙烯、聚丙烯、丁苯橡胶、丙烯酸(酯)化的丁苯橡胶、环氧树脂或尼龙等。
正极
正极包括正极集流体和设置在所述正极集流体上的正极活性材料。正极活性材料的具体种类均不受到具体的限制，可根据需求进行选择。
在一些实施方案中，正极活性材料包括够吸收和释放锂(Li)的正极材料。能够吸收/释放锂(Li)的正极材料的例子可以包括钴酸锂、镍钴锰酸锂、镍钴铝酸锂、锰酸锂、磷酸锰铁锂、磷酸钒锂、磷酸钒氧锂、磷酸铁锂、钛酸锂和富锂锰基材料。
具体的，钴酸锂的化学式可以如化学式1：
Li xCo aM1 bO 2-c化学式1
其中M1表示选自镍(Ni)、锰(Mn)、镁(Mg)、铝(Al)、硼(B)、钛(Ti)、钒(V)、铬(Cr)、铁(Fe)、铜(Cu)、锌(Zn)、钼(Mo)、锡(Sn)、钙(Ca)、锶(Sr)、钨(W)、钇(Y)、镧(La)、锆(Zr)和硅(Si)中的至少一种，x、a、b和c值分别在以下范围内：0.8≤x≤1.2、0.8≤a≤1、0≤b≤0.2、-0.1≤c≤0.2。
镍钴锰酸锂或镍钴铝酸锂的化学式可以如化学式2：
Li yNi dM2 eO 2-f化学式2
其中M2表示选自钴(Co)、锰(Mn)、镁(Mg)、铝(Al)、硼(B)、钛(Ti)、钒(V)、铬(Cr)、铁(Fe)、铜(Cu)、锌(Zn)、钼(Mo)、锡(Sn)、钙(Ca)、锶(Sr)、钨(W)、锆(Zr)和硅(Si)中的至少一种，y、d、e和f值分别在以下范围内：0.8≤y≤1.2、0.3≤d≤0.98、0.02≤e≤0.7、-0.1≤f≤0.2。
锰酸锂的化学式可以如化学式3：
Li zMn 2-gM3 gO 4-h化学式3
其中M3表示选自钴(Co)、镍(Ni)、镁(Mg)、铝(Al)、硼(B)、钛(Ti)、钒(V)、铬(Cr)、铁(Fe)、铜(Cu)、锌(Zn)、钼(Mo)、锡(Sn)、钙(Ca)、锶(Sr)和钨(W)中的至少一种，z、g和h值分别在以下范围内：0.8≤z≤1.2、0≤g＜1.0和-0.2≤h≤0.2。
在一些实施例中，所述正极活性材料层的重量是所述负极活性材料层的重量的1.5至15倍。在一些实施例中，所述正极活性材料层的重量是所述负极活性材料层的重量的3至10倍。在一些实施例中，所述正极活性材料层的重量是所述负极活性材料层的重量的5至8倍。在一些实施例中，所述正极活性材料层的重量是所述负极活性材料层的重量的1.5倍、2倍、3倍、4倍、5倍、6倍、7倍、8倍、9倍、10倍、11倍、12倍、13倍、14倍或15倍。
在一些实施例中，正极活性材料层可以在表面上具有涂层，或者可以与具有涂层的另一化合物混合。所述涂层可以包括从涂覆元素的氧化物、涂覆元素的氢氧化物、涂覆元素的羟基氧化物、涂覆元素的碳酸氧盐(oxycarbonate)和涂覆元素的羟基碳酸盐(hydroxycarbonate)中选择的至少一种涂覆元素化合物。用于涂层的化合物可以是非晶的或结晶的。在涂层中含有的涂覆元素可以包括Mg、Al、Co、 K、Na、Ca、Si、Ti、V、Sn、Ge、Ga、B、As、Zr、F或它们的混合物。可以通过任何方法来施加涂层，只要所述方法不对正极活性材料的性能产生不利影响即可。例如，所述方法可以包括对本领域普通技术人员来说众所周知的任何涂覆方法，例如喷涂、浸渍等。
在一些实施方案中，正极活性材料层还包含粘合剂，并且可选地还包括正极导电材料。
粘合剂可提高正极活性材料颗粒彼此间的结合，并且还提高正极活性材料与集流体的结合。粘合剂的非限制性示例包括聚乙烯醇、羟丙基纤维素、二乙酰基纤维素、聚氯乙烯、羧化的聚氯乙烯、聚氟乙烯、含亚乙基氧的聚合物、聚乙烯吡咯烷酮、聚氨酯、聚四氟乙烯、聚偏1，1-二氟乙烯、聚乙烯、聚丙烯、丁苯橡胶、丙烯酸(酯)化的丁苯橡胶、环氧树脂、尼龙等。
正极活性材料层包括正极导电材料，从而赋予电极导电性。所述正极导电材料可以包括任何导电材料，只要它不引起化学变化。正极导电材料的非限制性示例包括基于碳的材料(例如，天然石墨、人造石墨、碳黑、乙炔黑、科琴黑、碳纤维等)、基于金属的材料(例如，金属粉、金属纤维等，包括例如铜、镍、铝、银等)、导电聚合物(例如，聚亚苯基衍生物)和它们的混合物。
用于根据本申请的电化学装置的正极集流体可以是铝(Al)，但不限于此。
电解液
可用于本申请实施例的电解液可以为现有技术中已知的电解液。
可用于本申请实施例的电解液中的电解质包括，但不限于：无机锂盐，例如LiClO 4、LiAsF 6、LiPF 6、LiBF 4、LiSbF 6、LiSO 3F、LiN(FSO 2) 2等；含氟有机锂盐，例如LiCF 3SO 3、LiN(FSO 2)(CF 3SO 2)、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2、环状1，3-六氟丙烷二磺酰亚胺锂、环状1，2-四氟乙烷二磺酰亚胺锂、LiN(CF 3SO 2)(C 4F 9SO 2)、LiC(CF 3SO 2) 3、LiPF 4(CF 3) 2、LiPF 4(C 2F 5) 2、LiPF 4(CF 3SO 2) 2、LiPF 4(C 2F 5SO 2) 2、LiBF 2(CF 3) 2、LiBF 2(C 2F 5) 2、LiBF 2(CF 3SO 2) 2、LiBF 2(C 2F 5SO 2) 2；含二羧酸配合物锂盐，例如双(草酸根合)硼酸锂、二氟草酸根合硼酸锂、三(草酸根合)磷酸锂、二氟双(草酸根合)磷酸锂、四氟(草酸根合)磷酸锂等。另外，上述电解质可以单独使用一种，也可以同时使用两种或两种以上。在一些实施例中，电解质包括LiPF 6和LiBF 4的组合。在一些实施例中，电解质包括LiPF 6或LiBF 4等无机锂盐与LiCF 3SO 3、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2等含氟有机锂盐的组合。 在一些实施例中，电解质包括LiPF 6。
在一些实施例中，电解质的浓度在0.8mol/L至3mol/L的范围内，例如0.8mol/L至2.5mol/L的范围内、0.8mol/L至2mol/L的范围内、1mol/L至2mol/L的范围内，又例如为1mol/L、1.15mol/L、1.2mol/L、1.5mol/L、2mol/L或2.5mol/L。
可用于本申请实施例的电解液中的溶剂包括，但不限于，环状碳酸酯、链状碳酸酯、环状羧酸酯、链状羧酸酯、环状醚或链状醚。
在一些实施例中，环状碳酸酯包括，但不限于，碳酸亚乙酯(ethylene carbonate，EC)、碳酸亚丙酯(propylene carbonate，PC)和碳酸亚丁酯。
在一些实施例中，环状碳酸酯具有3-6个碳原子。
在一些实施例中，链状碳酸酯包括，但不限于：碳酸二甲酯、碳酸甲乙酯、碳酸二乙酯(diethyl carbonate，DEC)、碳酸甲基正丙基酯、碳酸乙基正丙基酯、碳酸二正丙酯等链状碳酸酯，作为被氟取代的链状碳酸酯，例如双(氟甲基)碳酸酯、双(二氟甲基)碳酸酯、双(三氟甲基)碳酸酯、双(2-氟乙基)碳酸酯、双(2，2-二氟乙基)碳酸酯、双(2，2，2-三氟乙基)碳酸酯、2-氟乙基甲基碳酸酯、2，2-二氟乙基甲基碳酸酯和2，2，2-三氟乙基甲基碳酸酯。
在一些实施例中，环状羧酸酯包括，但不限于，γ-丁内酯和γ-戊内酯。在一些实施例中，环状羧酸酯的部分氢原子可被氟取代。
在一些实施例中，链状羧酸酯包括，但不限于：乙酸甲酯、乙酸乙酯、乙酸丙酯、乙酸异丙酯、乙酸丁酯、乙酸仲丁酯、乙酸异丁酯、乙酸叔丁酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丙酸异丙酯、丁酸甲酯、丁酸乙酯、丁酸丙酯、异丁酸甲酯、异丁酸乙酯、戊酸甲酯、戊酸乙酯、特戊酸甲酯和特戊酸乙酯。在一些实施例中，链状羧酸酯的部分氢原子可被氟取代。在一些实施例中，氟取代的链状羧酸酯包括，但不限于：三氟乙酸甲酯、三氟乙酸乙酯、三氟乙酸丙酯、三氟乙酸丁酯和三氟乙酸2，2，2-三氟乙酯。
在一些实施例中，环状醚包括，但不限于，四氢呋喃、2-甲基四氢呋喃、1，3-二氧戊环、2-甲基1，3-二氧戊环、4-甲基1，3-二氧戊环、1，3-二氧六环、1，4-二氧六环和二甲氧基丙烷。
在一些实施例中，链状醚包括，但不限于，二甲氧基甲烷、1，1-二甲氧基乙烷、1，2-二甲氧基乙烷、二乙氧基甲烷、1，1-二乙氧基乙烷、1，2-二乙氧基乙烷、乙氧基甲氧基甲烷、1，1-乙氧基甲氧基乙烷和1，2-乙氧基甲氧基乙烷。
在一些实施例中，本申请的电解液中使用的溶剂包括如上所述的一种或多种。在一些实施例中，本申请的电解液中使用的溶剂包括环状碳酸酯、链状碳酸酯、环状羧酸酯、链状羧酸酯及其组合。在一些实施例中，本申请的电解液中使用的溶剂包含选自由下列物质组成的群组的有机溶剂：碳酸亚乙酯、碳酸亚丙酯、碳酸二乙酯、丙酸乙酯、丙酸丙酯、乙酸正丙酯、乙酸乙酯及其组合。在一些实施例中，本申请的电解液中使用的溶剂包含：碳酸亚乙酯、碳酸亚丙酯、碳酸二乙酯、丙酸乙酯、丙酸丙酯、γ-丁内酯或其组合。
可用于本申请实施例的电解液中的添加剂包括，但不限于，含碳碳双键的环状碳酸酯、含硫氧双键的化合物。
在一些实施例中，具有碳-碳双键的环状碳酸酯具体包括，但不限于：碳酸亚乙烯酯、碳酸甲基亚乙烯酯、碳酸乙基亚乙烯酯、乙烯基碳酸乙烯亚乙酯或碳酸-1，2-二甲基亚乙烯酯中的至少一种。
在一些实施例中，含硫氧双键的化合物包括，但不限于：硫酸乙烯酯、1，2-丙二醇硫酸酯、1，3-丙磺酸内酯、1-氟-1，3-丙磺酸内酯、2-氟-1，3-丙磺酸内酯或3-氟-1，3-丙磺酸内酯中的至少一种。
隔离膜
在一些实施方案中，正极与负极之间设有隔离膜以防止短路。可用于本申请的实施例中使用的隔离膜的材料和形状没有特别限制，其可为任何现有技术中公开的技术。在一些实施方案中，隔离膜包括由对本申请的电解液稳定的材料形成的聚合物或无机物等。
例如，隔离膜可包括基材层和表面处理层。基材层为具有多孔结构的无纺布、膜或复合膜，基材层的材料选自聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯和聚酰亚胺中的至少一种。具体的，可选用聚丙烯多孔膜、聚乙烯多孔膜、聚丙烯无纺布、聚乙烯无纺布或聚丙烯-聚乙烯-聚丙烯多孔复合膜。多孔结构可以提升隔离膜的耐热性能、抗氧化性能和电解质浸润性能，增强隔离膜与极片之间的粘接性。
基材层的至少一个表面上设置有表面处理层，表面处理层可以是聚合物层或无机物层，也可以是混合聚合物与无机物所形成的层。
无机物层包括无机颗粒和粘结剂，无机颗粒选自氧化铝、氧化硅、氧化镁、氧化钛、二氧化铪、氧化锡、二氧化铈、氧化镍、氧化锌、氧化钙、氧化锆、氧化钇、碳化硅、勃姆石、氢氧化铝、氢氧化镁、氢氧化钙和硫酸钡中的一种或几 种的组合。粘结剂选自聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯和聚六氟丙烯中的一种或几种的组合。
聚合物层中包含聚合物，聚合物的材料选自聚酰胺、聚丙烯腈、丙烯酸酯聚合物、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯醚、聚偏氟乙烯、聚(偏氟乙烯-六氟丙烯)中的至少一种。
电化学装置
本申请还提供了一种电化学装置，其包括正极、电解液和负极，所述正极包括正极活性材料层和正极集流体，所述负极包括负极活性材料层和负极集流体，所述负极活性材料层包括根据本申请所述的负极活性材料。
本申请的电化学装置包括发生电化学反应的任何装置，它的具体实例包括所有种类的一次电池、二次电池、燃料电池、太阳能电池或电容器。特别地，该电化学装置是锂二次电池，包括锂金属二次电池、锂离子二次电池、锂聚合物二次电池或锂离子聚合物二次电池。
电子装置
本申请另提供了一种电子装置，其包括根据本申请的电化学装置。
本申请的电化学装置的用途没有特别限定，其可用于现有技术中已知的任何电子装置。在一些实施方案中，本申请的电化学装置可用于，但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
下面以锂离子电池为例并且结合具体的实施例说明锂离子电池的制备，本领域的技术人员将理解，本申请中描述的制备方法仅是实例，其他任何合适的制备方法均在本申请的范围内。
实施例
以下说明根据本申请的锂离子电池的实施例和对比例进行性能评估。
一、锂离子电池的制备
1、负极的制备
将人造石墨粉碎，分级筛分以控制粒度分布，使得Dv90＜25μm，得到一次颗粒。将粘结剂添加至一次颗粒中进行粘结，分级筛分以控制粒度，使得Dv90＜45μm，得到二次颗粒。将一次颗粒和二次颗粒在2300-3500℃下进行石墨化处理，然后将处理后的一次颗粒和二次颗粒混合筛分，得到石墨负极材料。
将上述制备的石墨负极材料、添加剂、粘结剂丁苯橡胶(SBR)和增稠剂羧甲基纤维素钠(CMC)按照97∶1.51.5的重量比混合，在适量的去离子水中充分搅拌混合，使其形成均匀不沉降的负极浆料。将负极浆料涂覆重量涂覆于负极集流体(铜箔)上，烘干、冷压得到负极活性材料层，之后再经过裁片、分切后，得到负极。
负极中的石墨材料的石墨化度和K可通过原料、粒度、石墨化处理温度和一次颗粒与二次颗粒的配比来控制。
2、正极的制备
将钴酸锂(Li xCo aM1 bO 2-c，x、a、b和c值分别在以下范围内：0.8≤x≤1.2、0.8≤a≤1、0≤b≤0.2、-0.1≤c≤0.2；M1为锰(Mn)、镁(Mg)、铝(Al)、硼(B)、钛(Ti)、钒(V)、铬(Cr)、铁(Fe)、铜(Cu)、锌(Zn)、钼(Mo)及其组合)、乙炔黑和偏二氟乙烯(PVDF)按照95∶2∶3的重量比在适量的N-甲基吡咯烷酮(NMP)溶剂中充分搅拌混合，使其形成均匀的正极浆料。将此浆料涂覆于正极集流体铝箔上，烘干、冷压得到正极活性材料层，之后再经过裁片、分切后，得到正极。
3、电解液的制备
在干燥的氩气气氛手套箱中，将碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸二乙酯(DEC)按照1∶1∶1的重量比进行混合，接着加入2％的氟代碳酸乙烯酯，2％的1，3-丙烷磺内酯，2％的丁二腈，溶解并充分搅拌后加入锂盐LiPF 6，混合均匀后获得电解液，其中LiPF 6的浓度为1mol/L。
4、隔离膜的制备
以聚乙烯(PE)多孔聚合物薄膜作为隔离膜。
5、锂离子电池的制备
将正极、隔离膜、负极按顺序叠好，使隔离膜处于正极和负极之间起到隔离的作用，然后卷绕得到裸电芯；焊接极耳后将裸电芯置于外包装箔铝塑膜中，将上述制备好的电解液注入到干燥后的裸电芯中，经过真空封装、静置、化成、整 形、容量测试等工序，获得锂离子电池。
二、测试方法
1、碳材料的K值的测试方法
根据拉曼光谱法，采用523nm光源(遮光强度为5％)，在100μm×100μm区域采点100个，计算碳材料在1250cm -1至1650cm -1的峰强度Id与碳材料在1500cm -1至1650cm -1的峰强度Ig的比值，取平均值，即为碳材料的K值。
2、碳材料的石墨化度的测试方法
采用高纯硅粉(纯度≥99.99％)作为内标校准，按照碳材料∶硅＝5∶1的重量比进行混合，研磨均匀，压片制样。使用X射线衍射仪(Cu Kα靶材)测试碳材料002面的面间距(d002)，通过以下公式计算碳材料的石墨化度Gr：
Gr＝(0.344-d002)/0.086×100％。
3、负极活性材料的取向度S和负极活性材料层的取向度S′的测试方法
按照中华人民共和国机械行业标准JB/T 4220-2011《人造石墨的点阵参数测定方法》测试负极活性材料和负极活性材料层的X射线衍射图谱中的(004)面衍射线图形和(110)面衍射线图形。试验条件如下：X射线采用CuKα辐射，CuKα辐射由滤波片或单色器除去。X射线管的工作电压为35-45kV，工作电流为30-50mA。计数器的扫描速度为0.3(°)/min。在记录(004)面衍射线图形时，衍射角2θ的扫描范围为52°-58°。在记录(110)面衍射线图形时，衍射角2θ的扫描范围为70°-79°。
由(004)面衍射线图形得到的负极活性材料的峰面积记为C004。由(110)面衍射线图形得到的负极活性材料的峰面积记为C110。计算负极活性材料的C004/C110的比值，记为S。
由(004)面衍射线图形得到的负极活性材料层的峰面积记为C004′。由(110)面衍射线图形得到的负极活性材料层的峰面积记为C110′。计算负极活性材料的C004′/C110′的比值，记为S′。
4、碳材料的晶体尺寸的测试方法
使用X射线衍射仪分析测试负极活性材料中碳材料的沿水平轴的晶体尺寸La和沿垂直轴的晶体尺寸Lc。
5、负极活性材料的粒径的测试方法
采用马尔文粒度测试仪测试负极活性材料的粒径：将负极活性材料分散在乙 醇分散剂中，超声30分钟后，将样品加入到马尔文粒度测试仪内，测试负极活性材料的Dv90和Dv10。
6、负极活性材料层的面密度的测试方法
将电池放电至0S0C％，拆解电池，清洗，烘干，使用电子天平对一定面积A的负极(负极集流体的双面涂覆有负极活性材料层)进行称重，重量记为W 1；使用溶剂洗掉负极活性材料层，烘干，测量负极集流体的重量，记为W 2。通过以下公式计算负极活性材料层的面密度：(W 1-W 2)/(A×2)。
7、负极活性材料层的压实密度的测试方法
将电池放电至0S0C％，拆解电池，清洗，烘干，使用电子天平对一定面积A的负极(负极集流体的双面涂覆有负极活性材料层)进行称重，重量记为W 1，并使用万分尺测得负极的厚度T 1。使用溶剂洗掉负极活性材料层，烘干，测量负极集流体的重量，记为W 2，并使用万分尺测得负极集流体的厚度T 2。通过下式计算设置在负极集流体一侧的负极活性材料层的重量W 0和厚度T 0以及负极活性材料层的压实密度：
W 0＝(W 1-W 2)/2
T 0＝(T 1-T 2)/2
压实密度＝W 0/(T0×A)。
8、负极活性材料层与负极集流体之间的剥离强度的测试方法
使用Instron(型号为33652)拉伸测试仪进行测试负极活性材料层与负极集流体之间的粘结：取15-20mm长的极片，用3M双面胶纸将其固定于钢板上，将胶纸贴在负极活性材料层表面，该胶纸一侧与其等宽的纸带相连接，调整拉力机限位块至合适位置，将纸带向上翻折及滑移40mm，滑移速率为50mm/min，测试180°下(即，反方向拉伸)负极活性材料层与负极集流体之间的剥离强度。
9、负极活性材料层的孔隙率的测试方法
将负极活性材料层样品制备成完整圆片。每个实施例或对比例测试30个样品，每个样品体积为约0.35cm 3。根据《GB/T24586-2009铁矿石表观密度真密度和孔隙率的测定》标准进行测试负极活性材料层的孔隙率。
10、负极活性材料层的浸润时间的测试方法
将1mL电解液滴加至负极活性材料层上，开始计时。待负极活性材料层表面的电解液完全消失时，停止计时。每个实施例或对比例测试100个数据，取平 均值，记为负极活性材料层的浸润时间。
11、负极活性材料层的热分解温度的测试方法
采用示差扫描量热仪以恒定升温速率在0-800℃加热测试满充或满放状态下拆解的负极活性材料层的热分解温度。
12、锂离子电池的循环容量保持率的测试方法
在45℃下，将锂离子电池静置10分钟，然后以0.7C的电流恒流充电至4.4V，以4.4V恒压放电至0.05C，静置10分钟。随后以0.7C的电流恒流充电至3.0V，静置10分钟。此为一个循环，记录首次循环的放电容量。重复上述步骤400次，记录循环后放电容量。通过下式计算锂离子电池的循环容量保持率：
循环容量保持率＝(循环后放电容量/首次循环的放电容量)×100％。
采用基本相同的步骤测试锂离子电池在25℃下的循环容量保持率，区别在于操作温度为25℃，循环次数为800次。
13、锂离子电池的循环膨胀率的测试方法
在45℃下，将锂离子电池静置10分钟，然后以0.7C的电流恒流充电至4.4V，以4.4V恒压放电至0.05C，静置10分钟。随后以0.7C的电流恒流充电至3.0V，静置10分钟。此为一个循环，记录首次循环的锂离子电池的厚度。重复上述步骤400次，记录循环后的锂离子电池的厚度。通过下式计算锂离子电池的循环膨胀率：
循环膨胀率＝(循环后的厚度/首次循环的厚度)×100％。
采用基本相同的步骤测试锂离子电池在25℃下的循环膨胀率，区别在于操作温度为25℃，循环次数为800次。
14、锂离子电池的析锂现象的测试方法
在25℃下，将锂离子电池以0.5C的电流恒流放电至3.0V，静置10分钟。然后以1.5C的电流恒流充电至4.1V，以4.1V的电压恒压充电至0.05C，以0.7C的电流恒流充电至4.3V，以4.3V的电压恒压充电至0.05C，以0.5C的电流恒流充电至4.4V，以4.4V的电压恒压充电至0.05C，最后以0.5C的电流恒流放电至3.0V，静止10分钟。重复上述充放电过程10次。在干燥条件下拆解，拍照记录负极的状态。
根据以下标准判断锂离子电池的析锂程度：
当拆解后的负极整体呈现金黄色，极少部分可观察到灰色；且灰色区域的面 积＜2％，则判定为不析锂。
当拆解后的负极大部分呈现金黄色，部分位置可观察到灰色；且灰色区域的面积在2％至20％之间，则判定为轻微析锂。
当拆解后的负极整体呈现为灰色，部分位置可观察到金黄色；且灰色区域的面积在20％至60％之间，则判定为析锂。
当拆解后的负极整体呈现灰色且灰色区域的面积＞60％时，则判定为严重析锂。
三、测试结果
表1展示了负极活性材料的特性对锂离子电池的性能的影响。
如对比例1所示，当负极活性材料的石墨化度Gr与K的比值Gr/K小于6且K大于0.15时，锂离子电池的首次库伦效率很低、出现析锂现象(如图4所示)、循环容量保持率较低且循环膨胀率较高。如对比例2所示，当负极活性材料的石墨化度Gr与K的比值Gr/K大于16且K小于0.06时，锂离子电池的首次库伦效率较低、出现严重析锂现象(如图5所示)、循环容量保持率很低且循环膨胀率很高。
如实施例1-36所示，当负极活性材料的石墨化度Gr与K的比值Gr/K在6至16的范围内且K在0.06至0.15的范围内时，可显著提高锂离子电池的首次库伦效率和循环容量保持率，显著降低锂离子电池的循环膨胀率，并且显著减轻锂离子电池在循环过程中的析锂现象(如图3所示)。首次库伦效率的显著提高表明锂离子电池具有显著提升的能量密度。循环容量保持率的显著升高以及循环膨胀率的显著降低表明锂离子电池具有显著改善的循环性能。析锂现象的改善有助于显著提高锂离子电池的倍率性能。因此，实施例1-36的锂离子电池具有显著改善的能量密度、循环性能和倍率性能。
当负极活性材料的石墨化度Gr在0.92至0.96的范围内时，综合性能更为优异。
当负极活性材料中碳材料的晶体尺寸与负极活性材料材料的取向度满足以下关系时：Lc/S＜9、La/S＞20、Lc＜45且La＞50时，可进一步改善锂离子电池的首次库伦效率、循环容量保持率、循环膨胀率和/或析锂现象，提升锂离子电池的综合性能。
当Dv90/Dv10+Dv90大于23.0时，有助于进一步改善锂离子电池的循环容 量保持率和析锂现象，提升锂离子电池的综合性能。
图1展示了对比例2中使用的负极活性材料放大500倍的扫描电子显微镜(SEM)图。如图所示，对比例2中的负极活性材料仅包括一次颗粒。图2展示了实施例5中使用的负极活性材料放大500倍的扫描电子显微镜(SEM)图。如图所示，实施例5中的负极活性材料包括一定比例的一次颗粒和二次颗粒，通过调整其比例可调节碳材料的石墨化度和K值。
图6展示了对比例1、对比例2和实施例5的锂离子电池在25℃下随循环圈数的循环容量保持率曲线。图7展示了对比例1、对比例2和实施例5的锂离子电池在45℃下随循环圈数的循环容量保持率曲线。结果表明，相比于对比例1和2，实施例5的锂离子电池在25℃和45℃下的循环容量保持率始终保持在90％以上。随着循环圈数的增加，实施例5与对比例1和2的循环容量保持率差异逐渐增大。图8展示了对比例1、对比例2和实施例5的锂离子电池在25℃下随循环圈数的循环膨胀率曲线。图9展示了对比例1、对比例2和实施例5的锂离子电池在45℃下随循环圈数的循环膨胀率曲线。结果表明，相比于对比例1和2，实施例5的锂离子电池在25℃下的循环膨胀率始终小于8％，在45℃下的循环膨胀率始终小于10％。随着循环圈数的增加，实施例5与对比例1和2的循环膨胀率差异逐渐增大。上述结果表明实施例5的锂离子电池在室温和高温下的循环过程中均具有显著提升的循环性能。
表2展示了负极活性材料层的特性对锂离子电池的性能的影响。实施例37-44是基于表1中的实施例5的改进，其区别仅在于表2中所列参数。
结果表明，在负极活性材料层的面密度一定的情况下，电池的综合性能还可能受到负极活性材料层的压实密度，负极活性材料层的各向同性(S′减小)、孔隙率、负极活性材料层与负极集流体之间的剥离强度的影响。当负极活性材料层的面密度为0.077mg/mm 2至0.121mg/mm 2且压实密度为1.70g/cm 3至1.92g/cm 3、锂离子电池在满放状态下的S′为10至20、负极活性材料层与负极集流体之间的剥离强度为6N/m至15N/m、负极活性材料层的孔隙率为20％至40％、满充状态下的负极活性材料层的热分解温度不小于280℃、和/或在满放状态下的负极活性材料层的热分解温度不小于130℃时，有助于进一步改善锂离子电池的首次库伦效率、循环容量保持率、循环膨胀率和/或析锂现象，提升锂离子电池的综合性能。在负极活性材料层的压实密度一定的情况下，负极活性材料层 的面密度为0.100mg/mm 2的锂离子电池具有较为优异的综合性能。
整个说明书中对“实施例”、“部分实施例”、“一个实施例”、“另一举例”、“举例”、“具体举例”或“部分举例”的引用，其所代表的意思是在本申请中的至少一个实施例或举例包含了该实施例或举例中所描述的特定特征、结构、材料或特性。因此，在整个说明书中的各处所出现的描述，例如：“在一些实施方案中”、“在实施例中”、“在一个实施例中”、“在另一个举例中”，“在一个举例中”、“在特定举例中”或“举例”，其不必然是引用本申请中的相同的实施例或示例。此外，本文中的特定特征、结构、材料或特性可以以任何合适的方式在一个或多个实施例或举例中结合。
尽管已经演示和描述了说明性实施例，本领域技术人员应该理解上述实施例不能被解释为对本申请的限制，并且可以在不脱离本申请的精神、原理及范围的情况下对实施例进行改变，替代和修改。
Figure PCTCN2020094385-appb-000001
Figure PCTCN2020094385-appb-000002
Figure PCTCN2020094385-appb-000003

Claims (12)

  1. 一种负极活性材料，所述负极活性材料包含碳材料，其中所述碳材料符合以下关系：6<Gr/K<16，
    其中，Gr为所述碳材料的石墨化度，通过X射线衍射法测定得到；且
    K为所述碳材料在1250cm -1至1650cm -1的峰强度Id与所述碳材料在1500cm -1至1650cm -1的峰强度Ig的比值Id/Ig，通过拉曼光谱法测定得到，所述K为0.06至0.15。
  2. 根据权利要求1所述的负极活性材料，其中所述石墨化度Gr为0.92至0.96。
  3. 根据权利要求1所述的负极活性材料，其中所述碳材料满足以下关系中的至少一种：
    Lc/S<9；
    La/S>20，
    其中：
    La为由X射线衍射法测定的所述碳材料晶体沿水平轴的晶体尺寸，单位为nm；
    Lc为由X射线衍射法测定的所述碳材料晶体沿垂直轴的晶体尺寸，单位为nm；
    S为由X射线衍射图谱测定得到的所述负极活性材料的(004)面的峰面积C004和(110)面的峰面积C110的比值；
    所述Lc小于45，所述La大于50。
  4. 根据权利要求1所述的负极活性材料，其中所述负极活性材料的Dv10值与Dv90值满足以下关系：Dv90/Dv10+Dv90>23.0，Dv90和Dv10的单位为μm。
  5. 一种电化学装置，其包括正极、电解液和负极，所述负极包括负极活性材料层和集流体，所述负极活性材料层包括根据权利要求1-4中任一权利要求所述的负极活性材料。
  6. 根据权利要求5所述的电化学装置，其中所述负极活性材料层的面密度为0.077mg/mm 2至0.121mg/mm 2，所述负极活性材料层的压实密度为1.70g/cm 3至1.92g/cm 3。
  7. 根据权利要求5所述的电化学装置，其中在满放状态下，由X射线衍射图谱测定得到的所述负极活性材料层的(004)面的峰面积C004'和(110)面的峰面积C110'的比值S'为10至20。
  8. 根据权利要求5所述的电化学装置，其中所述负极活性材料层与所述负极集流体之间的剥离强度为6N/m至15N/m。
  9. 根据权利要求5所述的电化学装置，其中所述负极活性材料层具有20％至40％的孔隙率。
  10. 根据权利要求5所述的电化学装置，其中在所述电化学装置满充状态下，所述负极活性材料层的热分解温度不小于280℃。
  11. 根据权利要求5所述的电化学装置，其中在所述电化学装置满放状态下，所述负极活性材料层的热分解温度不小于130℃。
  12. 一种电子装置，其包括根据权利要求5-11中任一权利要求所述的电化学装置。
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