WO2021128093A1 - 电化学装置及包含其的电子装置 - Google Patents

电化学装置及包含其的电子装置 Download PDF

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Publication number
WO2021128093A1
WO2021128093A1 PCT/CN2019/128445 CN2019128445W WO2021128093A1 WO 2021128093 A1 WO2021128093 A1 WO 2021128093A1 CN 2019128445 W CN2019128445 W CN 2019128445W WO 2021128093 A1 WO2021128093 A1 WO 2021128093A1
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Prior art keywords
negative electrode
mixture layer
electrode mixture
lithium
electrolyte
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PCT/CN2019/128445
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English (en)
French (fr)
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王可飞
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宁德新能源科技有限公司
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Priority to PCT/CN2019/128445 priority Critical patent/WO2021128093A1/zh
Priority to EP19958017.6A priority patent/EP4020651A4/en
Priority to US17/054,207 priority patent/US20230163311A1/en
Priority to KR1020227008657A priority patent/KR20220041935A/ko
Priority to JP2022519794A priority patent/JP7463501B2/ja
Publication of WO2021128093A1 publication Critical patent/WO2021128093A1/zh

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Definitions

  • This application relates to the field of energy storage, in particular to an electrochemical device and an electronic device containing the same, especially a lithium ion battery.
  • Lithium-ion batteries with high energy density and excellent life and cycle characteristics are one of the research directions.
  • the theoretical capacity of a lithium ion battery can vary with the type of negative electrode active material. As the cycle progresses, lithium-ion batteries usually experience a decrease in charge/discharge capacity, which degrades the performance of the lithium-ion battery. In recent years, in the manufacture of lithium-ion batteries, in order to reduce environmental burdens, more and more attention has been paid to aqueous slurry compositions that use aqueous media as dispersion media. However, the presence of air bubbles in the slurry composition This results in multiple pinholes, pits and other defects in the active material layer, thereby affecting the cycle and high-temperature storage performance of the electrochemical device.
  • the embodiments of the present application provide an electrochemical device and an electronic device including the same to at least some extent solve at least one problem in the related field.
  • the present application provides an electrochemical device, including a positive electrode; an electrolyte; and a negative electrode, wherein the electrolyte includes a compound having phosphorus and oxygen, and the negative electrode includes a negative current collector and a After 100 charge and discharge cycles of the negative electrode mixture layer on the negative electrode current collector, based on the total surface area of the negative electrode mixture layer, the lithium-evolving area on the surface of the negative electrode mixture layer is 2% or less.
  • the electrolyte contains at least one of the following compounds:
  • R is a substituted or unsubstituted C 1 -C 10 hydrocarbon group, and when substituted, the substituent is halogen.
  • the electrolyte includes the compound of Formula 1, and the compound of Formula 1 includes at least one of the following structural formulas:
  • the electrolyte includes phosphate ester, and the phosphate ester has formula 2:
  • X is a linear or non-linear alkyl group having 1 to 5 carbon atoms or -SiR 2 R 3 R 4 , wherein R 2 , R 3 and R 4 are each independently having 1 to 5 carbon atoms Alkyl, and
  • R 1 is an alkylene group having 2 to 3 carbon atoms and substituted with a substituent selected from at least one fluorine atom or an alkyl group containing at least one fluorine atom and having 1 to 3 carbon atoms.
  • the content of the compound having phosphorus and oxygen is 0.001 wt% to 10 wt%.
  • the negative electrode mixture layer includes a carbon material, and the carbon material has
  • the surface has amorphous carbon.
  • the negative electrode mixture layer has at least one of the following characteristics:
  • the thickness is not more than 200 ⁇ m
  • the negative electrode mixture layer includes an auxiliary agent, and the auxiliary agent has at least one of the following characteristics:
  • the oxidation potential is not less than 4.5V, and the reduction potential is not more than 0.5V;
  • the surface tension of an aqueous solution containing 0.1 wt% of the auxiliary agent is not more than 30 mN/m.
  • the content of the auxiliary agent is 3000 ppm or less.
  • the present application provides an electronic device including the electrochemical device according to the present application.
  • a list of items connected by the term "at least one of” or other similar terms 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 term "at least one of" has the same meaning as the term "at least one of”.
  • hydrocarbyl encompasses alkyl, alkenyl, and alkynyl groups.
  • alkyl is expected to be a linear saturated hydrocarbon structure having 1 to 20 carbon atoms.
  • Alkyl is also expected to be a branched or cyclic hydrocarbon structure having 3 to 20 carbon atoms.
  • butyl means to include n-butyl, sec-butyl, isobutyl, tert-butyl And cyclobutyl;
  • propyl includes n-propyl, isopropyl and cyclopropyl.
  • alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl, n-pentyl, Isopentyl, neopentyl, cyclopentyl, methylcyclopentyl, ethylcyclopentyl, n-hexyl, isohexyl, cyclohexyl, n-heptyl, octyl, cyclopropyl, cyclobutyl, norbornyl Base and so on.
  • alkenyl refers to a monovalent unsaturated hydrocarbon group that can be straight or branched and has at least one and usually 1, 2, or 3 carbon-carbon double bonds. Unless otherwise defined, the alkenyl group usually contains 2 to 20 carbon atoms and includes, for example, -C 2-4 alkenyl, -C 2-6 alkenyl, and -C 2-10 alkenyl. Representative alkenyl groups include, for example, vinyl, n-propenyl, isopropenyl, n-but-2-enyl, but-3-enyl, n-hex-3-enyl, and the like.
  • alkynyl refers to a monovalent unsaturated hydrocarbon group that can be linear or branched and has at least one and usually 1, 2, or 3 carbon-carbon triple bonds. Unless otherwise defined, the alkynyl group generally contains 2 to 20 carbon atoms and includes, for example, -C 2-4 alkynyl, -C 3-6 alkynyl, and -C 3-10 alkynyl. Representative alkynyl groups include, for example, ethynyl, prop-2-ynyl (n-propynyl), n-but-2-ynyl, n-hex-3-ynyl, and the like.
  • alkylene means a divalent saturated hydrocarbon group that may be linear or branched. Unless otherwise defined, the alkylene group usually contains 2 to 10 carbon atoms, and includes, for example, -C 2-3 alkylene and -C 2-6 alkylene-. Representative alkylene groups include, for example, methylene, ethane-1,2-diyl ("ethylene"), propane-1,2-diyl, propane-1,3-diyl, butane -1,4-diyl, pentane-1,5-diyl, etc.
  • ethylene ethane-1,2-diyl
  • propane-1,3-diyl propane-1,3-diyl
  • butane -1,4-diyl pentane-1,5-diyl, etc.
  • aryl means a monovalent aromatic hydrocarbon having a single ring (for example, phenyl) or a condensed ring.
  • Condensed ring systems include those fully unsaturated ring systems (e.g., naphthalene) as well as those partially unsaturated ring systems (e.g., 1,2,3,4-tetrahydronaphthalene).
  • the aryl group generally contains 6 to 26 carbon ring atoms and includes, for example, a -C 6-10 aryl group.
  • Representative aryl groups include, for example, phenyl, methylphenyl, propylphenyl, isopropylphenyl, benzyl and naphth-1-yl, naphth-2-yl, and the like.
  • halogen refers to a stable atom of Group 17 of the Periodic Table of Elements, such as fluorine, chlorine, bromine or iodine.
  • the theoretical capacity of an electrochemical device may vary with the type of negative electrode active material. As the cycle progresses, electrochemical devices usually experience a decrease in charge/discharge capacity. This is because the electrode interface changes during the charging and/or discharging process of the electrochemical device, causing the electrode active material to fail to perform its function.
  • This application uses a combination of a specific negative electrode material and a specific electrolyte to ensure the interface stability of the electrochemical device during cycling, thereby improving the cycling and high-temperature storage performance of the electrochemical device.
  • the specific anode material in this application is realized by controlling the lithium evolution area on the surface of the anode active material layer.
  • a method for controlling the lithium evolution area you can add additives to the anode slurry or set an additive coating on the surface of the anode active material layer. Layer to control. It is also possible to control the lithium evolution area by adjusting the electrolyte formula, adding special structure additives, or adjusting the compaction density of the positive and negative pole pieces, and adjusting the ratio of the positive electrode active material.
  • the present application provides an electrochemical device, which includes a positive electrode, a negative electrode, and an electrolyte as described below.
  • the negative electrode includes a negative electrode current collector and a negative electrode mixture layer provided on one or both surfaces of the negative electrode current collector.
  • the negative electrode mixture layer contains a negative electrode active material layer, and the negative electrode active material layer contains a negative electrode active material.
  • the negative electrode mixture layer may be one layer or multiple layers, and each layer of the multilayer negative electrode active material may contain the same or different negative electrode active materials.
  • the negative electrode active material is any material that can reversibly insert and extract metal ions such as lithium ions.
  • the chargeable capacity of the negative active material is greater than the discharge capacity of the positive active material to prevent unintentional precipitation of lithium metal on the negative electrode during charging.
  • One of the main characteristics of the electrochemical device of the present application is that after 100 charge-discharge cycles, based on the total surface area of the negative electrode mixture layer, the lithium evolution area on the surface of the negative electrode mixture layer is 2% or less. In some embodiments, after 100 charge-discharge cycles, based on the total surface area of the negative electrode mixture layer, the lithium evolution area on the surface of the negative electrode mixture layer is less than 1%. In some embodiments, after 100 charge-discharge cycles, based on the total surface area of the negative electrode mixture layer, the lithium evolution area on the surface of the negative electrode mixture layer is 0.5% or less.
  • the lithium evolution area of the negative electrode mixture layer can reflect the surface properties of the negative electrode mixture layer, which is one of the physical and chemical parameters that characterize the negative electrode mixture layer. The smaller the area of lithium evolution, the smoother the surface of the negative electrode mixture layer, and the fewer pinholes or pits, which can significantly improve the cycle and high-temperature storage performance of the electrochemical device.
  • the lithium evolution area of the negative electrode mixture layer can be affected by many factors, mainly including the auxiliary agent and the porosity of the negative electrode mixture layer.
  • the negative electrode mixture layer has the lithium evolution area as described above, a stable mixture layer interface can be obtained, so that the lithium ion battery has improved cycle performance, storage performance, and safety performance during charge and discharge cycles.
  • the contact angle of the negative electrode mixture layer with respect to the non-aqueous solvent is not greater than 60° as measured by the contact angle measurement method. In some embodiments, the contact angle of the negative electrode mixture layer with respect to the non-aqueous solvent is not greater than 50° as determined by the contact angle measurement method. In some embodiments, the contact angle of the negative electrode mixture layer with respect to the non-aqueous solvent is not greater than 30° as determined by the contact angle measurement method.
  • the interface of the negative electrode mixture layer has fewer defects, has good stability in the charge and discharge cycle of the electrochemical device, and can ensure the cycle and high-temperature storage performance of the electrochemical device .
  • the contact angle measurement method means that after 3 microliters of diethyl carbonate droplets are dropped on the surface of the negative electrode mixture layer, the droplets are tested on the negative electrode within 100 seconds. The contact angle of the surface of the mixture layer.
  • the droplet diameter of the non-aqueous solvent on the negative electrode mixture layer is not greater than 30 mm as measured by the contact angle measurement method. In some embodiments, the droplet diameter of the non-aqueous solvent on the negative electrode mixture layer is not greater than 20 mm as determined by the contact angle measurement method. In some embodiments, the droplet diameter of the non-aqueous solvent on the negative electrode mixture layer is not greater than 15 mm as determined by the contact angle measurement method. In some embodiments, the droplet diameter of the non-aqueous solvent on the negative electrode mixture layer is not greater than 10 mm as determined by the contact angle measurement method.
  • the contact angle of the negative electrode mixture layer relative to the non-aqueous solvent and the diameter of the non-aqueous solvent droplets can be measured by the following method: drop 3 microliters of diethyl carbonate on the surface of the negative electrode mixture layer, and use the JC2000D3E contact angle measuring instrument within 100 seconds Test the diameter of the droplet, and use the 5-point fitting method (that is, first take 2 points on the left and right planes of the droplet, determine the liquid-solid interface, and then take 3 points on the arc of the droplet) for fitting. The contact angle of the water solvent.
  • Each sample is measured at least 3 times, and at least 3 data with a difference of less than 5° are selected, and the average value is taken to obtain the contact angle of the negative electrode mixture layer with respect to the non-aqueous solvent.
  • the non-aqueous solvent used in the contact angle test can be commonly used electrolyte solvents such as diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate, methyl propyl carbonate, or methyl isopropyl carbonate.
  • the negative electrode mixture layer includes a carbon material.
  • the negative electrode mixture layer includes at least one of artificial graphite, natural graphite, mesocarbon microspheres, soft carbon, hard carbon, and amorphous carbon.
  • the shape of the carbonaceous material includes, but is not limited to, fibrous, spherical, granular, and scaly.
  • the carbon material has at least one of the following characteristics:
  • the surface has amorphous carbon.
  • the carbon material has a specific surface area of less than 5 m 2 /g. In some embodiments, the carbon material has a specific surface area of less than 3 m 2 /g. In some embodiments, the carbon material has a specific surface area of less than 1 m 2 /g. In some embodiments, the carbon material has a specific surface area greater than 0.1 m 2 /g. In some embodiments, the carbon material has a specific surface area of less than 0.7 m 2 /g. In some embodiments, the carbon material has a specific surface area of less than 0.5 m 2 /g. In some embodiments, the specific surface area of the carbon material is within a range composed of any two of the foregoing values. When the specific surface area of the carbon material is within the above range, the precipitation of lithium on the surface of the electrode can be suppressed, and the generation of gas caused by the reaction between the negative electrode and the electrolyte can be suppressed.
  • the specific surface area (BET) of carbon materials can be measured by the following method: using a surface area meter (a fully automatic surface area measuring device manufactured by Okura Riken), pre-drying the sample at 350°C for 15 minutes under nitrogen flow, and then using nitrogen gas The nitrogen-helium mixed gas whose relative pressure value is accurately adjusted to 0.3 at atmospheric pressure is measured by the nitrogen adsorption BET single-point method using the gas flow method.
  • a surface area meter a fully automatic surface area measuring device manufactured by Okura Riken
  • the median particle diameter (D50) of the carbon material refers to a volume-based average particle diameter obtained by a laser diffraction/scattering method. In some embodiments, the carbon material has a median particle diameter (D50) of 5 ⁇ m to 30 ⁇ m. In some embodiments, the carbon material has a median particle diameter (D50) of 10 ⁇ m to 25 ⁇ m. In some embodiments, the carbon material has a median particle diameter (D50) of 15 ⁇ m to 20 ⁇ m.
  • the carbon material has a median particle diameter (D50) of 1 ⁇ m, 3 ⁇ m, 5 ⁇ m, 7 ⁇ m, 10 ⁇ m, 15 ⁇ m, 20 ⁇ m, 25 ⁇ m, 30 ⁇ m, or any two numerical values above.
  • D50 median particle diameter
  • the irreversible capacity of the electrochemical device is small, and it is easy to uniformly coat the negative electrode.
  • the median particle size (D50) of the carbon material can be measured by the following method: the carbon material is dispersed in a 0.2wt% aqueous solution (10 mL) of polyoxyethylene (20) sorbitan monolaurate, and laser diffraction is used. /Scattering particle size distribution meter (LA-700 manufactured by Horiba Manufacturing Co., Ltd.) was tested.
  • the interlayer distance of the lattice plane (002 plane) of the carbon material is in the range of 0.335nm to 0.360nm, 0.335nm to 0.350nm Or in the range of 0.335nm to 0.345nm.
  • the crystallite size (Lc) of the carbon material is greater than 1.0 nm or greater than 1.5 nm.
  • the Raman R value of the carbon material is greater than 0.01, greater than 0.03, or greater than 0.1. In some embodiments, the Raman R value of the carbon material is less than 1.5, less than 1.2, less than 1.0, or less than 0.5. In some embodiments, the Raman R value of the carbon material is within a range composed of any two of the foregoing values.
  • the Raman half-width of the carbon material in the vicinity of 1580 cm -1 is not particularly limited. In some embodiments, the Raman half-width of the carbon material near 1580 cm -1 is greater than 10 cm -1 or greater than 15 cm -1 . In some embodiments, the Raman half-width of the carbon material near 1580 cm -1 is less than 100 cm -1 , less than 80 cm -1 , less than 60 cm -1 or less than 40 cm -1 . In some embodiments, the Raman half-width of the carbon material near 1580 cm ⁇ 1 is within a range composed of any two of the foregoing values.
  • the Raman R value and the Raman half-width are indexes indicating the crystallinity of the surface of the carbon material.
  • the moderate crystallinity can keep the interlayer sites of the carbon material containing lithium during the charge and discharge process and will not disappear, which is beneficial to the chemical stability of the carbon material.
  • the carbon material can form an appropriate film on the surface of the negative electrode, which helps to improve the storage characteristics, cycle characteristics and load characteristics of the electrochemical device At the same time, it is possible to suppress the reduction in efficiency and gas generation caused by the reaction between the carbon material and the electrolyte.
  • Raman R value or Raman half-width can be measured by argon ion laser Raman spectroscopy: use a Raman spectrometer (Raman spectrometer manufactured by JASCO Corporation), let the sample fall naturally and fill it in the measuring cell, right The sample surface in the cell is irradiated with an argon ion laser while rotating the cell in a plane perpendicular to the laser, thereby performing measurement.
  • roundness (the perimeter of an equivalent circle having the same area as the projected shape of the particle)/(the actual perimeter of the projected shape of the particle). When the roundness is 1.0, it is a theoretical sphere.
  • the particle size of the carbon material is 3 ⁇ m to 40 ⁇ m, and the roundness is greater than 0.1, greater than 0.5, greater than 0.8, greater than 0.85, greater than 0.9, or 1.0.
  • the roundness of the carbon material can be measured using a flow particle image analyzer (FPIA manufactured by Sysmex): 0.2 g of a sample is dispersed in a 0.2 wt% aqueous solution of polyoxyethylene (20) sorbitan monolaurate (50 mL In ), after irradiating an ultrasonic wave of 28kHz with an output power of 60W for 1 minute, the specified detection range is 0.6 ⁇ m to 400 ⁇ m, and the particle size is measured in the range of 3 ⁇ m to 40 ⁇ m.
  • FPIA flow particle image analyzer
  • the method of improving the roundness is not particularly limited.
  • the spheroidization treatment can be used to make the shape of the voids between the carbon material particles uniform during the preparation of the electrode.
  • Spheroidization can be performed by mechanical means such as applying shear force or compression force, or mechanical/physical means such as applying a binder or granulating multiple particles through the adhesive force of the particles themselves. , So that the carbon material particles are close to a perfect spherical shape.
  • the tap density of the carbon material is greater than 0.1 g/cm 3 , greater than 0.5 g/cm 3 , greater than 0.7 g/cm 3 or greater than 1 g/cm 3 . In some embodiments, the tap density of the carbon material is less than 2 g/cm 3 , less than 1.8 g/cm 3 or less than 1.6 g/cm 3 . In some embodiments, the tap density of the carbon material is within a range composed of any two of the foregoing values. When the tap density of the carbon material is within the above range, the capacity of the electrochemical device can be ensured, and at the same time, the increase in the resistance between the carbon material particles can be suppressed.
  • the tap density of the carbon material can be tested by the following method: make the sample pass through a 300 ⁇ m mesh and then fall into a 20cm 3 tapped tank until the sample is filled to the upper end of the tank, then use a powder density tester (For example, Tap densor manufactured by Seishin Enterprise Co., Ltd.) 1,000 times of vibration with a stroke length of 10 mm, the tap density is calculated based on the mass at this time and the mass of the sample.
  • a powder density tester Form, Tap densor manufactured by Seishin Enterprise Co., Ltd.
  • the orientation ratio of the carbon material is greater than 0.005, greater than 0.01, or greater than 0.015. In some embodiments, the orientation ratio of the carbon material is less than 0.67. In some embodiments, the orientation ratio of the carbon material is within a range composed of any two of the foregoing values. When the orientation ratio of the carbon material is within the above range, the electrochemical device can have excellent high-density charge and discharge characteristics.
  • the orientation ratio of the carbon material can be measured by X-ray diffraction after the sample is press-molded: 0.47 g of the sample is filled into a molding machine with a diameter of 17 mm and compressed at 58.8 MN ⁇ m -2 to obtain a molded body. The molded body was fixed with clay so that the surface of the molded body and the sample holder for measurement were the same surface, and the X-ray diffraction measurement was performed. The ratio of (110) diffraction peak intensity/(004) diffraction peak intensity was calculated from the peak intensities of the (110) diffraction and (004) diffraction of the obtained carbon.
  • the X-ray diffraction measurement conditions are as follows:
  • ⁇ Target material Cu (K ⁇ ray) graphite monochromator
  • the aspect ratio of the carbon material is greater than 1, greater than 2, or greater than 3. In some embodiments, the aspect ratio of the carbon material is less than 10, less than 8, or less than 5. In some embodiments, the aspect ratio of the carbon material is within a range composed of any two of the foregoing values.
  • the aspect ratio of the carbon material is within the above range, more uniform coating can be performed, and thus the electrochemical device can have excellent high current density charge and discharge characteristics.
  • the porosity of the negative electrode mixture layer is 10% to 60%. In some embodiments, the porosity of the negative electrode mixture layer is 15% to 50%. In some embodiments, the porosity of the negative electrode mixture layer is 20% to 40%. In some embodiments, the porosity of the negative electrode mixture layer is 25% to 30%. In some embodiments, the porosity of the negative electrode mixture layer is 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60% or more. Any two values within the range.
  • the thickness of the negative electrode mixture layer refers to the thickness of the negative electrode mixture layer on either side of the negative electrode current collector. In some embodiments, the thickness of the negative electrode mixture layer is not greater than 200 ⁇ m. In some embodiments, the thickness of the negative electrode mixture layer is not greater than 150 ⁇ m. In some embodiments, the thickness of the negative electrode mixture layer is not greater than 100 ⁇ m. In some embodiments, the thickness of the negative electrode mixture layer is not greater than 50 ⁇ m. In some embodiments, the thickness of the negative electrode mixture layer is not less than 15 ⁇ m. In some embodiments, the thickness of the negative electrode mixture layer is not less than 20 ⁇ m. In some embodiments, the thickness of the negative electrode mixture layer is not less than 30 ⁇ m. In some embodiments, the thickness of the negative electrode mixture layer is within a range composed of any two of the foregoing values.
  • the minimum height of the ball that causes cracks in the negative electrode mixture layer is 50 cm or more. In some embodiments, when a ball with a diameter of 15 mm and a weight of 12 grams falls on the negative electrode mixture layer, the minimum height of the ball that causes cracks in the negative electrode mixture layer is 150 cm or less.
  • the minimum height of the cracked ball in the negative electrode mixture layer is related to the interface of the mixture layer. When the minimum height is 50 cm or more, the interface of the negative electrode mixture layer will not crack in an undesired direction during cutting.
  • the minimum height of the cracked ball in the negative electrode mixture layer is related to the thickness and porosity of the negative electrode mixture layer.
  • the greater the thickness of the negative electrode mixture layer the greater the minimum height of the ball that causes cracks in the negative electrode mixture layer, but an excessively thick negative electrode mixture layer will reduce the energy density of the electrochemical device.
  • the smaller the porosity of the negative electrode mixture layer the larger the minimum height of the balls that cause cracks in the negative electrode mixture layer, but a too low porosity will reduce the electrochemical performance (for example, rate performance) of the electrochemical device.
  • the negative electrode mixture layer further includes an auxiliary agent.
  • the adjuvant has at least one of the following characteristics:
  • the oxidation potential is not less than 4.5V, and the reduction potential is not more than 0.5V;
  • the surface tension of an aqueous solution containing 0.1 wt% of the auxiliary agent is not more than 30 mN/m.
  • the adjuvant includes polyether siloxane.
  • the polyether siloxane has Si-C and Si-O bonds.
  • the polyether siloxane includes at least one of a composite silicone polyether compound, a polyether modified trisiloxane, or a polyether modified silicone polyether siloxane.
  • polyether siloxanes examples include, but are not limited to, trisiloxane surfactants (CAS No. 3390-61-2; 28855-11-0), silicone surfactants (Sylgard 309), dihydroxy poly Dimethicone ((PMX-0156)) or methyl silicone oil polydimethylsiloxane (CAS No. 63148-62-9).
  • the auxiliary agent contains two or more polyether siloxanes
  • the content of polyether siloxane refers to the total content of two or more polyether siloxanes.
  • the content of the polyether siloxane is 3000 ppm or less, 2000 ppm or less, 1000 ppm or less, 500 ppm or less, 300 ppm or less, or 200 ppm or less.
  • the content of the polyether siloxane is within the above range, it is beneficial to improve the following performance of the electrochemical device: output power characteristics, load characteristics, low temperature characteristics, cycle characteristics, high temperature storage characteristics, and the like.
  • the oxidation potential of the additive is not less than 4.5V, and the reduction potential is not more than 0.5V. In some embodiments, the oxidation potential of the additive is not less than 5V, and the reduction potential is not greater than 0.3V.
  • the electrochemical performance of the auxiliary agent with the above oxidation/reduction potential is stable, which helps to improve the cycle and high-temperature storage performance of the electrochemical device.
  • the surface tension of an aqueous solution containing 0.1 wt% of the auxiliary agent is not greater than 30 mN/m. In some embodiments, the surface tension of an aqueous solution containing 0.1 wt% of the auxiliary agent is not greater than 25 mN/m. In some embodiments, the surface tension of an aqueous solution containing 0.1 wt% of the auxiliary agent is not greater than 20 mN/m. In some embodiments, the surface tension of an aqueous solution containing 0.1 wt% of the auxiliary agent is not greater than 15 mN/m.
  • the surface tension of an aqueous solution containing 0.1 wt% of the auxiliary agent is not greater than 10 mN/m.
  • the auxiliary agent having the above-mentioned surface tension enables the negative electrode mixture layer to have a good interface, which helps to improve the cycle and high-temperature storage performance of the electrochemical device.
  • the surface tension of the additives can be determined by the following method: use the JC2000D3E contact angle measuring instrument to test an aqueous solution of the additive with a solid content of 1%, test each sample at least 3 times, select at least 3 data, and take the average , Get the surface tension of the additive.
  • the negative electrode mixture layer further includes at least one metal of molybdenum, iron, and copper. These metal elements can react with some poorly conductive organic substances in the negative active material, thereby facilitating film formation on the surface of the negative active material.
  • the above-mentioned metal elements are present in the negative electrode mixture layer in trace amounts, and excessive metal elements are likely to form non-conductive by-products and adhere to the surface of the negative electrode.
  • the content of the at least one metal is not more than 0.05 wt%. In some embodiments, the content of the at least one metal is not more than 0.03 wt%. In some embodiments, the content of the at least one metal is not more than 0.01 wt%.
  • the negative electrode mixture layer further includes at least one of a silicon-containing material, a tin-containing material, and an alloy material. According to some embodiments of the present application, the negative electrode mixture layer further includes at least one of a silicon-containing material and a tin-containing material. In some embodiments, the negative electrode mixture layer further includes one or more of a silicon-containing material, a silicon-carbon composite material, a silicon-oxygen material, an alloy material, and a lithium-containing metal composite oxide material. In some embodiments, the negative electrode mixture layer further includes other types of negative electrode active materials, for example, one or more materials containing metal elements and metalloid elements capable of forming alloys with lithium.
  • examples of the metal elements and metalloid elements include, but are not limited to, Mg, B, Al, Ga, In, Si, Ge, Sn, Pb, Bi, Cd, Ag, Zn, Hf, Zr, Y, Pd and Pt.
  • examples of the metal element and metalloid element include Si, Sn, or a combination thereof. Si and Sn have excellent ability to deintercalate lithium ions and can provide high energy density for lithium ion batteries.
  • other types of negative electrode active materials may also include one or more of metal oxides and polymer compounds.
  • the metal oxide includes, but is not limited to, iron oxide, ruthenium oxide, and molybdenum oxide.
  • the polymer compound includes, but is not limited to, polyacetylene, polyaniline, and polypyrrole.
  • the negative electrode mixture layer further includes a negative electrode conductive material
  • the conductive material may include any conductive material as long as it does not cause a chemical change.
  • conductive materials include carbon-based materials (for example, natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), conductive polymers (for example, polyphenylene derivatives) and their mixture.
  • the negative electrode mixture layer further includes a negative electrode binder.
  • the negative electrode binder can improve the bonding between the negative active material particles and the bonding between the negative active material and the current collector.
  • the type of the negative electrode binder is not particularly limited, as long as it is a material that is stable to the electrolyte or the solvent used in the manufacture of the electrode.
  • negative electrode binders include, but are not limited to, polyethylene, polypropylene, polyethylene terephthalate, polymethylmethacrylate, aromatic polyamide, polyimide, cellulose, nitrocellulose Resin polymers such as styrene; styrene-butadiene rubber (SBR), isoprene rubber, polybutadiene rubber, fluororubber, acrylonitrile butadiene rubber (NBR), ethylene and propylene rubber and other rubber-like polymers; styrene ⁇ Butadiene ⁇ styrene block copolymer or its hydrogenated product; ethylene ⁇ propylene ⁇ diene terpolymer (EPDM), styrene ⁇ ethylene ⁇ butadiene ⁇ styrene copolymer, styrene ⁇ isoprene Thermoplastic elastomer-like polymers such as ene ⁇ styrene block copolymer or its hydrogenated products; syndiotact
  • the content of the negative electrode binder is greater than 0.1 wt%, greater than 0.5 wt%, or greater than 0.6 wt%. In some embodiments, based on the total weight of the negative electrode mixture layer, the content of the negative electrode binder is less than 20 wt%, less than 15 wt%, less than 10 wt%, or less than 8 wt%. In some embodiments, the content of the negative electrode binder is within a range composed of any two of the foregoing values. When the content of the negative electrode binder is in the above range, the capacity of the electrochemical device and the strength of the negative electrode can be sufficiently ensured.
  • the content of the negative electrode binder is greater than 0.1 wt% and greater than 0.5 wt% Or greater than 0.6wt%. In some embodiments, based on the total weight of the negative electrode mixture layer, the content of the negative electrode binder is less than 5 wt%, less than 3 wt%, or less than 2 wt%. In some embodiments, based on the total weight of the negative electrode mixture layer, the content of the negative electrode binder is within the range composed of any two of the foregoing values.
  • SBR rubber-like polymer
  • the content of the negative electrode binder is greater than 1 wt%, greater than 2wt% or more than 3wt%. In some embodiments, based on the total weight of the negative electrode mixture layer, the content of the negative electrode binder is less than 15 wt%, less than 10 wt%, or less than 8 wt%. Based on the total weight of the negative electrode mixture layer, the content of the negative electrode binder is within the range composed of any two values mentioned above.
  • the type of solvent used to form the negative electrode slurry is not particularly limited, as long as it can dissolve or disperse the negative electrode active material, the negative electrode binder, and the thickener and conductive material used as needed.
  • the solvent used to form the negative electrode slurry may use any one of an aqueous solvent and an organic solvent.
  • aqueous solvents may include, but are not limited to, water, alcohol, and the like.
  • organic solvents may include, but are not limited to, N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate , Diethyltriamine, N,N-dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, hexamethylphosphoramide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, Methyl naphthalene, hexane, etc.
  • NMP N-methylpyrrolidone
  • dimethylformamide dimethylacetamide
  • methyl ethyl ketone cyclohexanone
  • methyl acetate methyl acrylate
  • Diethyltriamine N,N-dimethylaminopropylamine
  • THF t
  • the thickener is usually used to adjust the viscosity of the negative electrode slurry.
  • the type of thickener is not particularly limited, and examples thereof may include, but are not limited to, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch , Casein and their salts.
  • the above-mentioned thickeners can be used alone or in any combination.
  • the content of the thickener is greater than 0.1 wt%, greater than 0.5 wt%, or greater than 0.6 wt%. In some embodiments, based on the total weight of the negative electrode mixture layer, the content of the thickener is less than 5 wt%, less than 3 wt%, or less than 2 wt%. When the content of the thickener is within the above range, the decrease in the capacity and the increase in the resistance of the electrochemical device can be suppressed, and at the same time, it is possible to ensure that the negative electrode slurry has good coatability.
  • the surface of the negative electrode mixture layer may be attached with a substance having a different composition.
  • the material attached to the surface of the negative electrode mixture layer include, but are not limited to, aluminum oxide, silicon dioxide, titanium dioxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, and other oxides, lithium sulfate, and sodium sulfate.
  • the content of the negative electrode active material is greater than 80% by weight, greater than 82% by weight, or greater than 84% by weight. In some embodiments, based on the total weight of the negative electrode mixture layer, the content of the negative electrode active material is less than 99% by weight or less than 98% by weight. In some embodiments, based on the total weight of the negative electrode mixture layer, the content of the negative electrode active material is within the range composed of any two arrays described above.
  • the density of the negative electrode active material in the negative electrode mixture layer is greater than 1 g/cm 3 , greater than 1.2 g/cm 3 or greater than 1.3 g/cm 3 . In some embodiments, the density of the negative electrode active material in the negative electrode mixture layer is less than 2.2 g/cm 3 , less than 2.1 g/cm 3 , less than 2.0 g/cm 3 or less than 1.9 g/cm 3 . In some embodiments, the density of the negative electrode active material in the negative electrode mixture layer is within the range composed of any two values mentioned above.
  • the density of the negative electrode active material is within the above range, the destruction of the negative electrode active material particles can be prevented, and the increase in the initial irreversible capacity of the electrochemical device or the decrease in the permeability of the electrolyte near the negative electrode current collector/negative electrode active material interface can be suppressed.
  • the high current density charging and discharging characteristics deteriorate, and the capacity decrease and resistance increase of the electrochemical device can be suppressed.
  • any known current collector can be used arbitrarily.
  • the negative electrode current collector include, but are not limited to, metal materials such as aluminum, copper, nickel, stainless steel, and nickel-plated steel. In some embodiments, the negative electrode current collector is copper.
  • the negative electrode current collector may include, but is not limited to, metal foil, metal cylinder, metal coil, metal plate, metal film, metal plate mesh, stamped metal, foamed metal, etc.
  • the negative electrode current collector is a metal thin film.
  • the negative electrode current collector is copper foil.
  • the negative electrode current collector is a rolled copper foil based on a rolling method or an electrolytic copper foil based on an electrolytic method.
  • the thickness of the negative electrode current collector is greater than 1 ⁇ m or greater than 5 ⁇ m. In some embodiments, the thickness of the negative electrode current collector is less than 100 ⁇ m or less than 50 ⁇ m. In some embodiments, the thickness of the negative electrode current collector is within a range composed of any two of the foregoing values.
  • the thickness ratio of the negative electrode current collector to the negative electrode mixture layer refers to the ratio of the thickness of the single-sided negative electrode mixture layer before the electrolyte solution is injected to the thickness of the negative electrode current collector, and the value is not particularly limited. In some embodiments, the thickness ratio of the negative electrode current collector to the negative electrode mixture layer is less than 150, less than 20, or less than 10. In some embodiments, the thickness ratio of the negative electrode current collector to the negative electrode mixture layer is greater than 0.1, greater than 0.4, or greater than 1. In some embodiments, the thickness ratio of the negative electrode current collector to the negative electrode mixture layer is within the range composed of any two of the foregoing values.
  • the thickness ratio of the negative electrode current collector to the negative electrode mixture layer is within the above range, the capacity of the electrochemical device can be ensured, and at the same time, the heat generation of the negative electrode current collector during high current density charging and discharging can be suppressed.
  • the electrolytic solution used in the electrochemical device of the present application includes an electrolyte and a solvent that dissolves the electrolyte.
  • the electrolyte used in the electrochemical device of the present application further includes additives.
  • a main feature of the electrochemical device of the present application is that the electrolyte contains a compound having phosphorus and oxygen.
  • the content of the compound having phosphorus and oxygen is 0.001 wt% to 10 wt%. In some embodiments, the content of the compound having phosphorus and oxygen is 0.005% to 8% by weight based on the total weight of the electrolyte. In some embodiments, based on the total weight of the electrolyte, the content of the compound having phosphorus and oxygen is 0.01 wt% to 5 wt%. In some embodiments, based on the total weight of the electrolyte, the content of the compound having phosphorus and oxygen is 0.05 wt% to 3 wt%.
  • the content of the compound having phosphorus and oxygen is 0.1 wt% to 2 wt%. In some embodiments, based on the total weight of the electrolyte, the content of the compound having phosphorus and oxygen is 0.5 wt% to 1 wt%.
  • the electrolyte includes at least one of the following compounds:
  • R is a substituted or unsubstituted C 1 -C 10 hydrocarbon group, and when substituted, the substituent is halogen.
  • the content of the lithium monofluorophosphate is 0.001 wt% to 10 wt% based on the total weight of the electrolyte. In some embodiments, based on the total weight of the electrolyte, the content of the lithium monofluorophosphate is 0.005% to 8% by weight. In some embodiments, the content of the lithium monofluorophosphate is 0.01 wt% to 5 wt% based on the total weight of the electrolyte. In some embodiments, based on the total weight of the electrolyte, the content of the lithium monofluorophosphate is 0.05 wt% to 3 wt%.
  • the content of the lithium monofluorophosphate is 0.1 wt% to 2 wt%. In some embodiments, the content of the lithium monofluorophosphate is 0.5 wt% to 1 wt% based on the total weight of the electrolyte.
  • the content of the lithium difluorophosphate is 0.001 wt% to 10 wt%. In some embodiments, the content of the lithium difluorophosphate is 0.005% to 8% by weight based on the total weight of the electrolyte. In some embodiments, the content of the lithium difluorophosphate is 0.01 wt% to 5 wt% based on the total weight of the electrolyte. In some embodiments, based on the total weight of the electrolyte, the content of the lithium difluorophosphate is 0.05 wt% to 3 wt%.
  • the content of the lithium difluorophosphate is 0.1 wt% to 2 wt%. In some embodiments, based on the total weight of the electrolyte, the content of the lithium difluorophosphate is 0.5 wt% to 1 wt%.
  • the phosphate ester has formula 2:
  • X is a linear or non-linear alkyl group having 1 to 5 carbon atoms or -SiR 2 R 3 R 4 , wherein R 2 , R 3 and R 4 are each independently having 1 to 5 carbon atoms Alkyl, and
  • R 1 is an alkylene group having 2 to 3 carbon atoms and substituted with a substituent selected from at least one fluorine atom or an alkyl group containing at least one fluorine atom and having 1 to 3 carbon atoms.
  • X is -SiR 2 R 3 R 4
  • R 1 is an alkylene group having 2 carbon atoms and substituted with a substituent selected from: at least one fluorine atom Or an alkyl group containing at least one fluorine atom and having 1 to 3 carbon atoms.
  • the compound of Formula 2 includes at least one of the compounds represented by Formula 2a to Formula 2h:
  • the content of the compound of formula 2 is 0.001 wt% to 10 wt%. In some embodiments, based on the total weight of the electrolyte, the content of the compound of formula 2 is 0.005 wt% to 9 wt%. In some embodiments, based on the total weight of the electrolyte, the content of the compound of formula 2 is 0.01 wt% to 8 wt%. In some embodiments, based on the total weight of the electrolyte, the content of the compound of formula 2 is 0.05 wt% to 7 wt%.
  • the content of the compound of formula 2 is 0.1 wt% to 6 wt%. In some embodiments, based on the total weight of the electrolyte, the content of the compound of formula 2 is 0.5 wt% to 5 wt%. In some embodiments, based on the total weight of the electrolyte, the content of the compound of formula 2 is 1 wt% to 4 wt%. In some embodiments, based on the total weight of the electrolyte, the content of the compound of formula 2 is 2 wt% to 3 wt%.
  • the phosphoric acid cyclic anhydride includes one or more of the compounds of formula 3:
  • R 10 , R 11 and R 12 are each independently a hydrogen atom, a C 1-20 alkyl group (e.g., C 1-15 alkyl group, C 1-10 alkyl group, C 1-5 alkyl group, C 5-20 Alkyl, C 5-15 alkyl, C 5-10 alkyl), C 6-50 aryl (e.g., C 6-30 aryl, C 6-26 aryl, C 6-20 aryl, C 10 -50 aryl, C 10-30 aryl, C 10-26 aryl or C 10-20 aryl), wherein R 10 , R 11 and R 12 may be different from each other, the same as each other, or any two of them are the same .
  • C 1-20 alkyl group e.g., C 1-15 alkyl group, C 1-10 alkyl group, C 1-5 alkyl group, C 5-20 Alkyl, C 5-15 alkyl, C 5-10 alkyl
  • C 6-50 aryl e.g., C 6-30 aryl,
  • the phosphoric acid cyclic anhydride includes, but is not limited to, the following compounds:
  • the content of the phosphoric acid cyclic anhydride is 0.01 wt% to 10 wt%. In some embodiments, based on the total weight of the electrolyte, the content of the phosphoric acid cyclic anhydride is 0.05 wt% to 8 wt%. In some embodiments, based on the total weight of the electrolyte, the content of the phosphoric acid cyclic anhydride is 0.1 wt% to 5 wt%. In some embodiments, based on the total weight of the electrolyte, the content of the phosphoric acid cyclic anhydride is 0.5 wt% to 3 wt%. In some embodiments, based on the total weight of the electrolyte, the content of the phosphoric acid cyclic anhydride is 1 wt% to 2 wt%.
  • the compound of Formula 1 includes at least one of the following structural formulas:
  • the content of the compound of Formula 1 is 0.01 wt% to 15 wt%. In some embodiments, the content of the compound of Formula 1 is 0.05 wt% to 12 wt% based on the total weight of the electrolyte. In some embodiments, based on the total weight of the electrolyte, the content of the compound of Formula 1 is 0.1 wt% to 10 wt%. In some embodiments, based on the total weight of the electrolyte, the content of the compound of Formula 1 is 0.5 wt% to 8 wt%.
  • the content of the compound of Formula 1 is 1 wt% to 5 wt%. In some embodiments, based on the total weight of the electrolyte, the content of the compound of Formula 1 is 2 wt% to 4 wt%.
  • the electrolyte further includes any non-aqueous solvent known in the prior art that can be used as a solvent for the electrolyte.
  • the non-aqueous solvent includes, but is not limited to, one or more of the following: cyclic carbonate, chain carbonate, cyclic carboxylate, chain carboxylate, cyclic Ethers, chain ethers, phosphorus-containing organic solvents, sulfur-containing organic solvents and aromatic fluorine-containing solvents.
  • examples of the cyclic carbonate may include, but are not limited to, one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate.
  • the cyclic carbonate has 3-6 carbon atoms.
  • examples of the chain carbonate may include, but are not limited to, one or more of the following: dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate (DEC), methyl carbonate N-propyl carbonate, ethyl n-propyl carbonate, di-n-propyl carbonate and other chain carbonates.
  • DEC diethyl carbonate
  • chain carbonates substituted by fluorine may include, but are not limited to, one or more of the following: bis(fluoromethyl)carbonate, bis(difluoromethyl)carbonate, bis(trifluoromethyl) Base) 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, 2,2,2-trifluoroethyl methyl carbonate, etc.
  • examples of the cyclic carboxylic acid ester may include, but are not limited to, one or more of the following: one or more of ⁇ -butyrolactone and ⁇ -valerolactone.
  • part of the hydrogen atoms of the cyclic carboxylic acid ester may be substituted by fluorine.
  • examples of the chain carboxylic acid ester may include, but are not limited to, one or more of the following: methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate Ester, sec-butyl acetate, isobutyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate, butyrate Propyl ester, methyl isobutyrate, ethyl isobutyrate, methyl valerate, ethyl valerate, methyl pivalate and ethyl pivalate, etc.
  • part of the hydrogen atoms of the chain carboxylic acid ester may be replaced by fluorine.
  • examples of fluorine-substituted chain carboxylic acid esters may include, but are not limited to, methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, and trifluoroacetic acid 2,2,2-Trifluoroethyl and so on.
  • examples of the cyclic ether may include, but are not limited to, one or more of the following: tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 2-methyl 1,3-dioxolane, 4-methyl 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, and dimethoxypropane.
  • examples of the chain ether may include, but are not limited to, one or more of the following: dimethoxymethane, 1,1-dimethoxyethane, 1,2- Dimethoxyethane, diethoxymethane, 1,1-diethoxyethane, 1,2-diethoxyethane, ethoxymethoxymethane, 1,1-ethoxy Methoxyethane and 1,2-ethoxymethoxyethane, etc.
  • examples of the phosphorus-containing organic solvent may include, but are not limited to, one or more of the following: trimethyl phosphate, triethyl phosphate, dimethyl ethyl phosphate, methyl phosphate Diethyl, Ethylene Methyl Phosphate, Ethylene Ethyl Phosphate, Triphenyl Phosphate, Trimethyl Phosphite, Triethyl Phosphite, Triphenyl Phosphite, Tris(2,2,2- Trifluoroethyl) ester and tris(2,2,3,3,3-pentafluoropropyl) phosphate, etc.
  • examples of the sulfur-containing organic solvent may include, but are not limited to, one or more of the following: sulfolane, 2-methyl sulfolane, 3-methyl sulfolane, dimethyl sulfone, two Ethyl sulfone, ethyl methyl sulfone, methyl propyl sulfone, dimethyl sulfoxide, methyl methanesulfonate, ethyl methanesulfonate, methyl ethanesulfonate, ethyl ethanesulfonate, dimethyl sulfate , Diethyl sulfate and dibutyl sulfate.
  • part of the hydrogen atoms of the sulfur-containing organic solvent may be replaced by fluorine.
  • the aromatic fluorine-containing solvent includes, but is not limited to, one or more of the following: fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene And trifluoromethylbenzene.
  • 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, and combinations thereof .
  • the chain carboxylic acid ester and/or cyclic carboxylic acid ester can form a passivation film on the electrode surface, thereby improving the intermittent charging of the electrochemical device Capacity retention rate after cycling.
  • the electrolyte contains 1 wt% to 60 wt% of chain carboxylic acid esters, cyclic carboxylic acid esters, and combinations thereof.
  • the electrolyte contains ethyl propionate, propyl propionate, ⁇ -butyrolactone, and combinations thereof.
  • the content of the combination is 1 wt% to 60 wt%, 10 wt% % To 60% by weight, 10% to 50% by weight, and 20% to 50% by weight. In some embodiments, based on the total weight of the electrolyte, the electrolyte contains 1 wt% to 60 wt%, 10 wt% to 60 wt%, 20 wt% to 50 wt%, 20 wt% to 40 wt%, or 30 wt% of propyl propionate. .
  • examples of the additive may include, but are not limited to, one or more of the following: fluorocarbonate, carbon-carbon double bond-containing ethylene carbonate, sulfur-oxygen double bond-containing compound, and acid anhydride .
  • the content of the additive is 0.01 wt% to 15 wt%, 0.1 wt% to 10 wt%, or 1 wt% to 5 wt%.
  • the content of the propionate is 1.5 to 30 times, 1.5 to 20 times, 2 to 20 times, or 5 to 20 times of the additive.
  • the additives include one or more fluorocarbonates.
  • the fluorocarbonate can work with the propionate to form a stable protective film on the surface of the negative electrode, thereby inhibiting the decomposition reaction of the electrolyte.
  • examples of the fluorocarbonate may include, but are not limited to, one or more of the following: fluoroethylene carbonate, cis-4,4-difluoroethylene carbonate, trans-4 ,4-Difluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4-fluoro-4-methylethylene carbonate, 4-fluoro-5-methylethylene carbonate, trifluoromethyl methyl carbonate , Trifluoroethyl methyl carbonate and ethyl trifluoroethyl carbonate, etc.
  • the additives include one or more ethylene carbonates containing carbon-carbon double bonds.
  • the carbon-carbon double bond-containing ethylene carbonate may include, but are not limited to, one or more of the following: vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, carbonic acid-1 ,2-Dimethylvinylene carbonate, -1,2-diethylvinylene carbonate, fluorovinylene carbonate, trifluoromethyl vinylene carbonate; vinyl ethylene carbonate, 1-methyl carbonate 2-vinyl ethylene, 1-ethyl-2-vinyl ethylene carbonate, 1-n-propyl-2-vinyl ethylene carbonate, 1-methyl-2-ethylene carbonate Ethylene carbonate, 1,1-divinyl ethylene carbonate, 1,2-divinyl ethylene carbonate, 1,1-dimethyl-2-methylene ethylene carbonate, and Carbonic acid-1,1-diethyl-2-methylene ethylene and the like.
  • vinylene carbonate
  • the additives include one or more compounds containing sulfur-oxygen double bonds.
  • the sulfur-oxygen double bond-containing compound may include, but are not limited to, one or more of the following: cyclic sulfate, chain sulfate, chain sulfonate, cyclic sulfonate, chain Sulfite and cyclic sulfite, etc.
  • cyclic sulfate may include, but are not limited to, one or more of the following: 1,2-ethylene glycol sulfate, 1,2-propanediol sulfate, 1,3-propanediol sulfate, 1 , 2-butanediol sulfate, 1,3-butanediol sulfate, 1,4-butanediol sulfate, 1,2-pentanediol sulfate, 1,3-pentanediol sulfate, 1 ,4-Pentanediol sulfate and 1,5-Pentanediol sulfate, etc.
  • chain sulfate may include, but are not limited to, one or more of the following: dimethyl sulfate, ethyl methyl sulfate, diethyl sulfate, and the like.
  • chain sulfonate may include, but are not limited to, one or more of the following: fluorosulfonates such as methyl fluorosulfonate and ethyl fluorosulfonate, methyl methanesulfonate, methanesulfonic acid Ethyl ester, butyl dimethanesulfonate, 2-(methanesulfonyloxy) methyl propionate and 2-(methanesulfonyloxy) ethyl propionate, etc.
  • fluorosulfonates such as methyl fluorosulfonate and ethyl fluorosulfonate, methyl methanesulfonate, methanesulfonic acid Ethyl ester, butyl dimethanesulfonate, 2-(methanesulfonyloxy) methyl propionate and 2-(methanesulfonyloxy) ethyl propionate, etc.
  • Examples of the cyclic sulfonate may include, but are not limited to, one or more of the following: 1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2- Fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone, 1-methyl-1,3-propane sultone, 2-methyl-1,3- Propylene sultone, 3-methyl-1,3-propane sultone, 1-propene-1,3-sultone, 2-propene-1,3-sultone, 1-fluoro -1-propene-1,3-sultone, 2-fluoro-1-propene-1,3-sultone, 3-fluoro-1-propene-1,3-sultone, 1- Fluoro-2-propene-1,3-sultone, 2-fluoro-2-propene-1,3-sultone, 3-fluoro-2-propene-1,3-sul
  • chain sulfite may include, but are not limited to, one or more of the following: dimethyl sulfite, ethyl methyl sulfite, diethyl sulfite, and the like.
  • cyclic sulfite may include, but are not limited to, one or more of the following: 1,2-ethylene glycol sulfite, 1,2-propylene glycol sulfite, 1,3-propylene glycol sulfite Sulfate, 1,2-butanediol sulfite, 1,3-butanediol sulfite, 1,4-butanediol sulfite, 1,2-pentanediol sulfite, 1,3 -Pentylene glycol sulfite, 1,4-pentanediol sulfite and 1,5-pentanediol sulfite, etc.
  • the additives include one or more acid anhydrides.
  • the acid anhydride may include, but are not limited to, one or more of carboxylic acid anhydride, disulfonic acid anhydride, and carboxylic acid sulfonic acid anhydride.
  • the carboxylic acid anhydride may include, but are not limited to, one or more of succinic anhydride, glutaric anhydride, and maleic anhydride.
  • the disulfonic acid anhydride may include, but are not limited to, one or more of ethane disulfonic acid anhydride and propane disulfonic acid anhydride.
  • carboxylic acid sulfonic anhydride may include, but are not limited to, one or more of sulfobenzoic anhydride, sulfopropionic anhydride, and sulfobutyric anhydride.
  • the additive is a combination of fluorocarbonate and ethylene carbonate containing carbon-carbon double bonds. In some embodiments, the additive is a combination of a fluorocarbonate and a compound containing a sulfur-oxygen double bond. In some embodiments, the additive is a combination of a fluorocarbonate and a compound having 2-4 cyano groups. In some embodiments, the additive is a combination of fluorocarbonate and cyclic carboxylic acid ester. In some embodiments, the additive is a combination of fluorocarbonate and cyclic phosphoric anhydride. In some embodiments, the additive is a combination of fluorocarbonate and carboxylic anhydride. In some embodiments, the additive is a combination of fluorocarbonate and Huangan anhydride. In some embodiments, the additive is a combination of fluorocarbonate and carboxylic acid anhydride.
  • the electrolyte is not particularly limited, and any known substance as an electrolyte can be used arbitrarily.
  • a lithium salt is generally used.
  • electrolytes may include, but are not limited to, LiPF 6 , LiBF 4 , LiClO 4 , LiAlF 4 , LiSbF 6 , LiTaF 6 , LiWF 7 and other inorganic lithium salts; LiWOF 5 and other lithium tungstates; HCO 2 Li, CH 3 CO 2 Li, CH 2 FCO 2 Li, CHF 2 CO 2 Li, CF 3 CO 2 Li, CF 3 CH 2 CO 2 Li, CF 3 CF 2 CO 2 Li, CF 3 CF 2 CO 2 Li, CF 3 CF 2 CF 2 CO 2 Li, CF 3 CF 2 CF 2 CO 2 Li and other carboxylic acid lithium salts; FSO 3 Li, CH 3 SO 3 Li, CH 2 FSO 3 Li, CHF 2 SO 3 Li, CF 3 SO 3 Li, CF 3 CF 2 SO 3 Li ,
  • the electrolyte is selected from LiPF 6 , LiSbF 6 , LiTaF 6 , FSO 3 Li, CF 3 SO 3 Li, LiN(FSO 2 ) 2 , LiN(FSO 2 )(CF 3 SO 2 ), LiN(CF 3 SO 2 ) 2 , LiN(C 2 F 5 SO 2 ) 2 , cyclic 1,2-perfluoroethane bissulfonimide lithium, cyclic 1,3-perfluoropropane bissulfonimide lithium, LiC(FSO 2 ) 3 , LiC(CF 3 SO 2 ) 3 , LiC(C 2 F 5 SO 2 ) 3 , LiBF 3 CF 3 , LiBF 3 C 2 F 5 , LiPF 3 (CF 3 ) 3 , LiPF 3 ( C 2 F 5 ) 3 , lithium difluorooxalate borate, lithium bis(oxalate) borate or lithium difluorobis(oxalate) phosphate
  • the content of the electrolyte is not particularly limited, as long as it does not impair the effect of the present application.
  • the total molar concentration of lithium in the electrolyte is greater than 0.3 mol/L, greater than 0.4 mol/L, or greater than 0.5 mol/L.
  • the total molar concentration of lithium in the electrolyte is less than 3 mol/L, less than 2.5 mol/L, or less than 2.0 mol/L.
  • the total molar concentration of lithium in the electrolyte is within the range composed of any two of the foregoing values. When the electrolyte concentration is within the above range, the amount of lithium as the charged particles will not be too small, and the viscosity can be in an appropriate range, so it is easy to ensure good electrical conductivity.
  • the electrolyte includes at least one salt selected from the group consisting of borate, oxalate, and fluorosulfonate. In some embodiments, the electrolyte includes a salt selected from the group consisting of oxalate and fluorosulfonate. In some embodiments, the electrolyte includes a lithium salt. In some embodiments, the content of the salt selected from the group consisting of borate, oxalate, and fluorosulfonate is greater than 0.01 wt% or greater than 0.1 wt% based on the total weight of the electrolyte.
  • the content of the salt selected from the group consisting of borate, oxalate, and fluorosulfonate is less than 20 wt% or less than 10 wt% based on the total weight of the electrolyte. In some embodiments, the content of the salt selected from the group consisting of borate, oxalate, and fluorosulfonate is within the range composed of any two of the foregoing values.
  • the electrolyte includes one or more substances selected from the group consisting of borate, oxalate, and fluorosulfonate, and one or more other salts.
  • the lithium salts exemplified above can be cited, and in some embodiments they are LiPF 6 , LiN(FSO 2 )(CF 3 SO 2 ), LiN(CF 3 SO 2 ) 2 , LiN( C 2 F 5 SO 2 ) 2 , cyclic 1,2-perfluoroethane bissulfonimide lithium, cyclic 1,3-perfluoropropane bissulfonimide lithium, LiC(FSO 2 ) 3 , LiC (CF 3 SO 2 ) 3 , LiC (C 2 F 5 SO 2 ) 3 , LiBF 3 CF 3 , LiBF 3 C 2 F 5 , LiPF 3 (CF 3 ) 3 , LiPF 3 (C 2 F 5 ) 3 .
  • the other salt is LiPF 6 , LiN(FSO 2 )(
  • the content of other salts is greater than 0.01 wt% or greater than 0.1 wt%. In some embodiments, based on the total weight of the electrolyte, the content of other salts is less than 20 wt%, less than 15 wt%, or less than 10 wt%. In some embodiments, the content of other salts is within the range composed of any two values mentioned above. Salts other than those having the above content help balance the conductivity and viscosity of the electrolyte.
  • the electrolyte solution may contain additional additives such as a negative electrode coating film forming agent, a positive electrode protective agent, and an overcharge prevention agent as needed.
  • additives generally used in non-aqueous electrolyte secondary batteries can be used, examples of which can include, but are not limited to, vinylene carbonate, succinic anhydride, biphenyl, cyclohexylbenzene, 2,4-difluorobenzyl Ether, propane sultone, propene sultone, etc. These additives can be used alone or in any combination.
  • the content of these additives in the electrolytic solution is not particularly limited, and may be appropriately set according to the type of the additives and the like. In some embodiments, based on the total weight of the electrolyte, the content of the additive is less than 5 wt%, in the range of 0.01 wt% to 5 wt%, or in the range of 0.2 wt% to 5 wt%.
  • the positive electrode includes a positive electrode current collector and a positive electrode mixture layer provided on one or both surfaces of the positive electrode current collector.
  • the positive electrode mixture layer includes a positive electrode active material layer, and the positive electrode active material layer includes a positive electrode active material.
  • the positive active material layer may be one layer or multiple layers. Each layer in the multi-layered positive active material may contain the same or different positive active material.
  • the positive electrode active material is any material that can reversibly insert and extract metal ions such as lithium ions.
  • the type of the positive electrode active material is not particularly limited, as long as it can electrochemically store and release metal ions (for example, lithium ions).
  • the positive active material is a material containing lithium and at least one transition metal.
  • the positive electrode active material may include, but are not limited to, lithium transition metal composite oxides and lithium-containing transition metal phosphate compounds.
  • the transition metal in the lithium transition metal composite oxide includes V, Ti, Cr, Mn, Fe, Co, Ni, Cu, and the like.
  • the lithium transition metal composite oxides include lithium cobalt composite oxides such as LiCoO 2 , lithium nickel composite oxides such as LiNiO 2 , LiMnO 2 , LiMn 2 O 4 , Li 2 MnO 4 and other lithium manganese composite oxides, LiNi 1/3 Mn 1/3 Co 1/3 O 2 , LiNi 0.5 Mn 0.3 Co 0.2 O 2 and other lithium nickel manganese cobalt composite oxides, in which a part of the transition metal atoms as the main body of these lithium transition metal composite oxides is used Replaced by Na, K, B, F, Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, W and other elements .
  • lithium transition metal composite oxides may include, but are not limited to, LiNi 0.5 Mn 0.5 O 2 , LiNi 0.85 Co 0.10 Al 0.05 O 2 , LiNi 0.33 Co 0.33 Mn 0.33 O 2 , LiNi 0.45 Co 0.10 Al 0.45 O 2 , LiMn 1.8 Al 0.2 O 4 and LiMn 1.5 Ni 0.5 O 4 and so on.
  • Examples of combinations of lithium transition metal composite oxides include, but are not limited to, the combination of LiCoO 2 and LiMn 2 O 4 , where a part of Mn in LiMn 2 O 4 may be replaced by a transition metal (for example, LiNi 0.33 Co 0.33 Mn 0.33 O 2 ), a part of Co in LiCoO 2 can be replaced by transition metals.
  • the transition metal in the lithium-containing transition metal phosphate compound includes V, Ti, Cr, Mn, Fe, Co, Ni, Cu, and the like.
  • the lithium-containing transition metal phosphate compounds include iron phosphates such as LiFePO 4 , Li 3 Fe 2 (PO 4 ) 3 , LiFeP 2 O 7 , and cobalt phosphates such as LiCoPO 4 , which are used as these lithium transition metal phosphate compounds Part of the transition metal atoms of the main body is replaced by Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si and other elements.
  • the positive active material includes lithium phosphate, which can improve the continuous charging characteristics of the electrochemical device.
  • the positive active material and lithium phosphate are mixed and used.
  • the content of lithium phosphate is greater than 0.1 wt%, greater than 0.3 wt%, or greater than 0.5 wt%.
  • the content of lithium phosphate is less than 10 wt%, less than 8 wt%, or less than 5 wt% relative to the total weight of the above-mentioned positive active material and lithium phosphate.
  • the content of lithium phosphate is within the range composed of any two of the foregoing values.
  • a substance different from the composition may be attached to the surface of the positive electrode active material.
  • surface attachment substances may include, but are not limited to, oxides such as aluminum oxide, silicon dioxide, titanium dioxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, and bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate , Magnesium sulfate, calcium sulfate, aluminum sulfate and other sulfates, lithium carbonate, calcium carbonate, magnesium carbonate and other carbonates, carbon, etc.
  • These surface attachment materials can be attached to the surface of the positive electrode active material by the following method: the surface attachment material is dissolved or suspended in a solvent, and then infiltrated and added to the positive electrode active material and dried; the surface attachment material precursor is dissolved or suspended In the solvent, after infiltrating and adding to the positive electrode active material, a method of making it react by heating or the like; and a method of adding to the positive electrode active material precursor while firing, and so on.
  • attaching carbon a method of mechanically attaching a carbon material (for example, activated carbon, etc.) can also be used.
  • the content of the surface attachment material is greater than 0.1 ppm, greater than 1 ppm, or greater than 10 ppm. In some embodiments, based on the total weight of the positive electrode mixture layer, the content of the surface attachment material is less than 20%, less than 10%, or less than 10%. In some embodiments, based on the total weight of the positive electrode mixture layer, the content of the surface-attached material is within the range composed of any two of the foregoing values.
  • the oxidation reaction of the electrolyte on the surface of the positive electrode active material can be suppressed, and the life of the electrochemical device can be improved.
  • the amount of the surface-attached substance is too small, its effect cannot be fully expressed; when the amount of the surface-attached substance is too large, it will hinder the ingress and egress of lithium ions, and thus the electrical resistance may sometimes increase.
  • the positive electrode active material to which a substance different from the composition is adhered to the surface of the positive electrode active material is also referred to as a "positive electrode active material”.
  • the shape of the positive electrode active material particles includes, but is not limited to, block shape, polyhedron shape, spherical shape, elliptical spherical shape, plate shape, needle shape, column shape, and the like.
  • the positive active material particles include primary particles, secondary particles, or a combination thereof.
  • the primary particles may agglomerate to form secondary particles.
  • the tap density of the positive active material is greater than 0.5 g/cm 3 , greater than 0.8 g/cm 3 or greater than 1.0 g/cm 3 .
  • the tap density of the positive electrode active material is within the above range, the amount of dispersion medium and the required amount of conductive material and positive electrode binder required for the formation of the positive electrode mixture layer can be suppressed, thereby ensuring the filling rate of the positive electrode active material And the capacity of the electrochemical device.
  • a composite oxide powder with a high tap density a high-density positive electrode mixture layer can be formed.
  • the larger the tap density the better, and there is no particular upper limit.
  • the tap density of the positive active material is less than 4.0 g/cm 3 , less than 3.7 g/cm 3 or less than 3.5 g/cm 3 .
  • the tap density of the positive electrode active material has the upper limit as described above, the decrease in load characteristics can be suppressed.
  • the tap density of the positive electrode active material can be calculated by the following method: Put 5g to 10g of the positive electrode active material powder into a 10mL glass measuring cylinder, and perform 200 strokes of 20mm vibration to obtain the powder packing density (tap density). ).
  • the median diameter (D50) of the positive electrode active material particles refers to the primary particle diameter of the positive electrode active material particles.
  • the median diameter (D50) of the positive electrode active material particles refers to the secondary particle diameter of the positive electrode active material particles.
  • the median diameter (D50) of the positive electrode active material particles is greater than 0.3 ⁇ m, greater than 0.5 ⁇ m, greater than 0.8 ⁇ m, or greater than 1.0 ⁇ m. In some embodiments, the median diameter (D50) of the positive electrode active material particles is less than 30 ⁇ m, less than 27 ⁇ m, less than 25 ⁇ m, or less than 22 ⁇ m. In some embodiments, the median diameter (D50) of the positive electrode active material particles is within the range composed of any two of the foregoing values. When the median diameter (D50) of the positive electrode active material particles is within the above-mentioned range, a high tap density positive electrode active material can be obtained, and degradation of the performance of the electrochemical device can be suppressed.
  • the median diameter (D50) of the positive electrode active material particles can be measured with a laser diffraction/scattering particle size distribution measuring device: when using LA-920 manufactured by HORIBA as the particle size distribution meter, use a 0.1wt% sodium hexametaphosphate aqueous solution As the dispersion medium used in the measurement, the measurement was performed with the measurement refractive index set to 1.24 after 5 minutes of ultrasonic dispersion.
  • the average primary particle size of the positive active material is greater than 0.05 ⁇ m, greater than 0.1 ⁇ m, or greater than 0.5 ⁇ m. In some embodiments, the average primary particle size of the positive active material is less than 5 ⁇ m, less than 4 ⁇ m, less than 3 ⁇ m, or less than 2 ⁇ m. In some embodiments, the average primary particle size of the positive active material is within the range composed of any two of the foregoing values.
  • the average primary particle size of the positive electrode active material is within the above range, the powder filling property and specific surface area can be ensured, the decrease in battery performance can be suppressed, and moderate crystallinity can be obtained, thereby ensuring the reversibility of the electrochemical device's charge and discharge. .
  • the average primary particle size of the positive electrode active material can be obtained by observing the image obtained by the scanning electron microscope (SEM): in the SEM image with a magnification of 10000 times, for any 50 primary particles, the relative The longest value of the slice obtained by the left and right boundary lines of the straight primary particles, and the average value thereof is calculated to obtain the average primary particle size.
  • SEM scanning electron microscope
  • the specific surface area (BET) of the positive active material is greater than 0.1 m 2 /g, greater than 0.2 m 2 /g, or greater than 0.3 m 2 /g. In some embodiments, the specific surface area (BET) of the positive active material is less than 50 m 2 /g, less than 40 m 2 /g, or less than 30 m 2 /g. In some embodiments, the specific surface area (BET) of the positive active material is within the range composed of any two of the foregoing values. When the specific surface area (BET) of the positive electrode active material is within the above range, the performance of the electrochemical device can be ensured, and at the same time, the positive electrode active material can have good coatability.
  • the specific surface area (BET) of the positive electrode active material can be measured by using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken), pre-drying the sample at 150°C for 30 minutes under nitrogen flow, and then A nitrogen-helium mixed gas whose relative pressure value of nitrogen to atmospheric pressure is accurately adjusted to 0.3 is used for measurement by a nitrogen adsorption BET single-point method using a gas flow method.
  • a surface area meter for example, a fully automatic surface area measuring device manufactured by Okura Riken
  • the type of the positive electrode conductive material is not limited, and any known conductive material can be used.
  • the positive electrode conductive material may include, but are not limited to, graphite such as natural graphite and artificial graphite; carbon black such as acetylene black; carbon materials such as amorphous carbon such as needle coke; carbon nanotubes; graphene and the like.
  • the above-mentioned positive electrode conductive materials can be used alone or in any combination.
  • the content of the positive electrode conductive material is greater than 0.01 wt%, greater than 0.1 wt%, or greater than 1 wt%. In some embodiments, based on the total weight of the positive electrode mixture layer, the content of the positive electrode conductive material is less than 50% by weight, less than 30% by weight, or less than 15% by weight. When the content of the positive electrode conductive material is within the above range, sufficient conductivity and the capacity of the electrochemical device can be ensured.
  • the type of the positive electrode binder used in the production of the positive electrode mixture layer is not particularly limited. In the case of the coating method, it may be a material that is soluble or dispersible in the liquid medium used in the electrode production.
  • positive electrode binders may include, but are not limited to, one or more of the following: polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, Aromatic polyamide, cellulose, nitrocellulose and other resin polymers; styrene-butadiene rubber (SBR), nitrile rubber (NBR), fluorine rubber, isoprene rubber, polybutadiene rubber, ethylene-propylene rubber, etc.
  • styrene ⁇ butadiene ⁇ styrene block copolymer or its hydrogenated product ethylene ⁇ propylene ⁇ diene terpolymer (EPDM), styrene ⁇ ethylene ⁇ butadiene ⁇ ethylene copolymer, benzene Thermoplastic elastomer-like polymers such as ethylene ⁇ isoprene ⁇ styrene block copolymer or its hydrogenated products; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene ⁇ vinyl acetate copolymer, Soft resin-like polymers such as propylene ⁇ -olefin copolymers; fluorine-based polymers such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene ⁇ ethylene copolymers, etc. ; Polymer composition with alkali metal i
  • the content of the positive electrode binder is greater than 0.1 wt%, greater than 1 wt%, or greater than 1.5 wt%. In some embodiments, based on the total weight of the positive electrode mixture layer, the content of the positive electrode binder is less than 80% by weight, less than 60% by weight, less than 40% by weight, or less than 10% by weight. When the content of the positive electrode binder is within the above range, the positive electrode can have good conductivity and sufficient mechanical strength, and ensure the capacity of the electrochemical device.
  • the type of solvent used to form the positive electrode slurry is not limited, as long as it can dissolve or disperse the positive electrode active material, the conductive material, the positive electrode binder, and the thickener used as needed.
  • the solvent used to form the positive electrode slurry may include any one of an aqueous solvent and an organic solvent.
  • Examples of the aqueous medium may include, but are not limited to, water and a mixed medium of alcohol and water, and the like.
  • organic media include, but are not limited to, aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, methyl naphthalene; heterocyclic compounds such as quinoline and pyridine; acetone, methyl ethyl Ketones such as methyl ketone and cyclohexanone; esters such as methyl acetate and methyl acrylate; amines such as diethylene triamine and N,N-dimethylaminopropylamine; diethyl ether, propylene oxide, tetrahydrofuran (THF) ) And other ethers; N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide and other amides; hexamethylphosphoramide, dimethylsulfoxide and other aprotic polar solvents.
  • aliphatic hydrocarbons such as hexane
  • aromatic hydrocarbons such as benzen
  • Thickeners are usually used to adjust the viscosity of the slurry.
  • a thickener and styrene butadiene rubber (SBR) emulsion can be used for slurrying.
  • SBR styrene butadiene rubber
  • the type of thickener is not particularly limited, and examples thereof may include, but are not limited to, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch , Casein and their salts.
  • the above-mentioned thickeners can be used alone or in any combination.
  • the content of the thickener is greater than 0.1 wt%, greater than 0.2 wt%, or greater than 0.3 wt%. In some embodiments, based on the total weight of the positive electrode mixture layer, the content of the thickener is less than 5 wt%, less than 3 wt%, or less than 2 wt%. In some embodiments, based on the total weight of the positive electrode mixture layer, the content of the thickener is within the range composed of any two of the foregoing values. When the content of the thickener is within the above-mentioned range, the positive electrode slurry can be made to have good coatability, and at the same time, the capacity decrease and the resistance increase of the electrochemical device can be suppressed.
  • the content of the positive electrode active material is greater than 80% by weight, greater than 82% by weight, or greater than 84% by weight. In some embodiments, based on the total weight of the positive electrode mixture layer, the content of the positive electrode active material is less than 99% by weight or less than 98% by weight. In some embodiments, based on the total weight of the positive electrode mixture layer, the content of the positive electrode active material is within the range composed of any two arrays described above. When the content of the positive electrode active material is within the above range, the electric capacity of the positive electrode active material in the positive electrode mixture layer can be ensured while maintaining the strength of the positive electrode.
  • the density of the positive electrode mixture layer is greater than 1.5 g/cm 3 , greater than 2 g/cm 3 or greater than 2.2 g/cm 3 . In some embodiments, the density of the positive electrode mixture layer is less than 5 g/cm 3 , less than 4.5 g/cm 3 or less than 4 g/cm 3 . In some embodiments, the density of the positive electrode mixture layer is within the range composed of any two of the foregoing values. When the density of the positive electrode mixture layer is within the above range, the electrochemical device can have good charge and discharge characteristics, and at the same time, the increase in resistance can be suppressed.
  • the thickness of the positive electrode mixture layer refers to the thickness of the positive electrode mixture layer on either side of the positive electrode current collector. In some embodiments, the thickness of the positive electrode mixture layer is greater than 10 ⁇ m or greater than 20 ⁇ m. In some embodiments, the thickness of the positive electrode mixture layer is less than 500 ⁇ m or less than 450 ⁇ m.
  • the positive electrode active material can be produced using a common method for producing inorganic compounds.
  • the following manufacturing method can be used: dissolve or pulverize the transition metal raw materials in a solvent such as water, adjust the pH while stirring, make spherical precursors and recover them, as needed After it is dried, a Li source such as LiOH, Li 2 CO 3 , LiNO 3 is added, and it is fired at a high temperature to obtain a positive electrode active material.
  • the type of the positive electrode current collector is not particularly limited, and it can be any material known to be suitable for use as a positive electrode current collector.
  • Examples of the positive electrode current collector may include, but are not limited to, metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; and carbon materials such as carbon cloth and carbon paper.
  • the positive electrode current collector is a metal material.
  • the positive current collector is aluminum.
  • the form of the positive electrode current collector is not particularly limited.
  • the form of the positive electrode current collector may include, but is not limited to, metal foil, metal cylinder, metal coil, metal plate, metal film, metal plate mesh, stamped metal, foamed metal, etc.
  • the positive electrode current collector is a carbon material
  • the form of the positive electrode current collector may include, but is not limited to, a carbon plate, a carbon film, a carbon cylinder, and the like.
  • the positive electrode current collector is a metal thin film.
  • the metal film is mesh-shaped. The thickness of the metal thin film is not particularly limited.
  • the thickness of the metal film is greater than 1 ⁇ m, greater than 3 ⁇ m, or greater than 5 ⁇ m. In some embodiments, the thickness of the metal film is less than 1 mm, less than 100 ⁇ m, or less than 50 ⁇ m. In some embodiments, the thickness of the metal thin film is within a range composed of any two of the foregoing values.
  • the surface of the positive electrode current collector may include a conductive auxiliary agent.
  • the conductive assistant may include, but are not limited to, carbon and noble metals such as gold, platinum, and silver.
  • the thickness ratio of the positive electrode current collector to the positive electrode mixture layer refers to the ratio of the thickness of the positive electrode mixture layer on one side before the electrolyte solution is injected to the thickness of the positive electrode current collector, and the value is not particularly limited. In some embodiments, the thickness ratio of the positive electrode current collector to the positive electrode mixture layer is less than 20, less than 15, or less than 10. In some embodiments, the thickness ratio of the positive electrode current collector to the positive electrode mixture layer is greater than 0.5, greater than 0.8, or greater than 1. In some embodiments, the ratio of the thickness of the positive electrode current collector to the positive electrode mixture layer is within the range composed of any two values mentioned above. When the thickness ratio of the positive electrode current collector to the positive electrode mixture layer is within the above range, the heat generation of the positive electrode current collector during high current density charging and discharging can be suppressed, and the capacity of the electrochemical device can be ensured.
  • the positive electrode can be produced by forming a positive electrode mixture layer containing a positive electrode active material and a viscous active material on a current collector.
  • the manufacture of a positive electrode using a positive electrode active material can be carried out by a conventional method, that is, the positive electrode active material and the viscous active material, as well as the conductive material and thickener as required, are dry-mixed to form a sheet, and the obtained The sheet material is pressed onto the positive electrode current collector; or these materials are dissolved or dispersed in a liquid medium to form a slurry, and the slurry is coated on the positive electrode current collector and dried to form on the current collector A positive electrode mixture layer is used to obtain a positive electrode.
  • a separator is usually provided between the positive electrode and the negative electrode.
  • the electrolyte solution of the present application is usually used by infiltrating the separator.
  • the material and shape of the isolation film are not particularly limited, as long as the effect of the present application is not significantly impaired.
  • the isolation film may be resin, glass fiber, inorganic substance, etc. formed of a material that is stable to the electrolyte of the present application.
  • the isolation membrane includes a porous sheet or a non-woven fabric-like material with excellent liquid retention properties.
  • the material of the resin or glass fiber isolation membrane may include, but are not limited to, polyolefin, aromatic polyamide, polytetrafluoroethylene, polyethersulfone, glass filter, and the like.
  • the material of the isolation membrane is a glass filter.
  • the polyolefin is polyethylene or polypropylene.
  • the polyolefin is polypropylene.
  • the isolation film may also be a material formed by laminating the above-mentioned materials, and examples thereof include, but are not limited to, a three-layer isolation film formed by laminating polypropylene, polyethylene, and polypropylene in the order.
  • inorganic materials may include, but are not limited to, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates (for example, barium sulfate, calcium sulfate, etc.).
  • the form of the inorganic substance may include, but is not limited to, granular or fibrous.
  • the form of the isolation membrane may be a thin film form, and examples thereof include, but are not limited to, non-woven fabrics, woven fabrics, microporous membranes, and the like.
  • the pore diameter of the isolation membrane is 0.01 ⁇ m to 1 ⁇ m, and the thickness is 5 ⁇ m to 50 ⁇ m.
  • separators can also be used: a separator formed by forming a composite porous layer containing the above-mentioned inorganic particles on the surface of the positive electrode and/or the negative electrode using a resin-based binder, For example, a separator formed by using a fluororesin as a binder to form a porous layer on both sides of the positive electrode with 90% of alumina particles having a particle diameter of less than 1 ⁇ m.
  • the thickness of the isolation film is arbitrary. In some embodiments, the thickness of the isolation film is greater than 1 ⁇ m, greater than 5 ⁇ m, or greater than 8 ⁇ m. In some embodiments, the thickness of the isolation film is less than 50 ⁇ m, less than 40 ⁇ m, or less than 30 ⁇ m. In some embodiments, the thickness of the isolation film is within a range composed of any two of the foregoing values. When the thickness of the isolation film is within the above range, insulation and mechanical strength can be ensured, and the rate characteristics and energy density of the electrochemical device can be ensured.
  • the porosity of the separator is arbitrary. In some embodiments, the porosity of the isolation membrane is greater than 20%, greater than 35%, or greater than 45%. In some embodiments, the porosity of the isolation membrane is less than 90%, less than 85%, or less than 75%. In some embodiments, the porosity of the isolation membrane is within a range composed of any two values mentioned above. When the porosity of the isolation membrane is within the above range, insulation and mechanical strength can be ensured, and membrane resistance can be suppressed, so that the electrochemical device has good rate characteristics.
  • the average pore diameter of the separation membrane is also arbitrary. In some embodiments, the average pore diameter of the isolation membrane is less than 0.5 ⁇ m or less than 0.2 ⁇ m. In some embodiments, the average pore diameter of the isolation membrane is greater than 0.05 ⁇ m. In some embodiments, the average pore size of the isolation membrane is within a range composed of any two of the foregoing values. If the average pore diameter of the isolation membrane exceeds the above range, a short circuit is likely to occur. When the average pore diameter of the isolation membrane is within the above range, the membrane resistance can be suppressed while preventing short circuits, so that the electrochemical device has good rate characteristics.
  • the electrochemical device assembly includes an electrode group, a current collection structure, an outer casing and a protection element.
  • the electrode group may have a layered structure in which the positive electrode and the negative electrode are laminated with the separator film interposed therebetween, and a structure in which the positive electrode and the negative electrode are wound in a spiral shape with the separator film interposed therebetween.
  • the proportion of the mass of the electrode group in the internal volume of the battery is greater than 40% or greater than 50%.
  • the electrode group occupancy rate is less than 90% or less than 80%.
  • the occupancy rate of the electrode group is within a range composed of any two of the foregoing values.
  • the capacity of the electrochemical device can be ensured, and the decrease in characteristics such as repeated charge and discharge performance and high-temperature storage associated with the increase in internal pressure can be suppressed, and the operation of the gas release valve can be prevented.
  • the current collection structure is not particularly limited.
  • the current collection structure is a structure that reduces the resistance of the wiring part and the junction part.
  • the electrode group has the above-mentioned laminated structure, it is suitable to use a structure formed by bundling the metal core portions of the electrode layers and welding them to the terminals.
  • the electrode area of a sheet increases, the internal resistance increases. Therefore, it is also suitable to provide two or more terminals in the electrode to reduce the resistance.
  • the electrode group has the above-mentioned winding structure, by providing two or more lead structures on the positive electrode and the negative electrode, and bunching them on the terminals, the internal resistance can be reduced.
  • the material of the outer casing is not particularly limited, as long as it is stable with respect to the electrolyte used.
  • the outer casing can be used, but is not limited to nickel-plated steel plate, stainless steel, metal such as aluminum or aluminum alloy, magnesium alloy, or a laminated film of resin and aluminum foil.
  • the outer casing is a metal or laminated film of aluminum or aluminum alloy.
  • the metal-based exterior casing includes, but is not limited to, a packaged hermetic structure formed by welding metals by laser welding, resistance welding, or ultrasonic welding; or a riveted structure formed by using the above-mentioned metals via a resin gasket.
  • the exterior case using the above-mentioned laminated film includes, but is not limited to, a sealing structure formed by thermally bonding resin layers to each other, and the like. In order to improve sealing properties, a resin different from the resin used in the laminated film may be sandwiched between the above-mentioned resin layers.
  • the resin layer When the resin layer is thermally bonded through the current collector terminal to form a hermetic structure, due to the bonding of the metal and the resin, a resin having a polar group or a modified resin into which a polar group is introduced can be used as the resin to be sandwiched.
  • the shape of the exterior body is also arbitrary, and for example, it may be any of a cylindrical shape, a square shape, a laminated type, a button type, and a large size.
  • the protection element can be used as a positive temperature coefficient (PTC), temperature fuse, thermistor, which increases resistance when abnormal heat is released or excessive current flows, and it is cut off by a sharp rise in the internal pressure or internal temperature of the battery when abnormal heat is released. Valves (current cutoff valves) for the current flowing in the circuit, etc.
  • the above-mentioned protection element can be selected to be an element that does not work in the normal use of high current, and can also be designed in a form that does not cause abnormal heat release or thermal runaway even if there is no protection element.
  • 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, cars, motorcycles, power assistance Bicycles, bicycles, lighting equipment, toys, game consoles, clocks, power tools, flashlights, cameras, large household storage batteries and lithium-ion capacitors, etc.
  • the artificial graphite, styrene-butadiene rubber and sodium carboxymethyl cellulose are mixed with deionized water in a mass ratio of 96%: 2%: 2%, and 2000 ppm auxiliary agent is added, and the mixture is stirred uniformly to obtain a negative electrode slurry.
  • This negative electrode slurry was coated on a 12 m copper foil. After drying, cold pressing, cutting and welding the tabs, the negative electrode is obtained.
  • the negative electrode was set according to the conditions of the following examples and comparative examples to have corresponding parameters.
  • auxiliary agents used in the following examples are as follows:
  • LiCoO 2 lithium cobaltate
  • Super-P conductive material
  • PVDF polyvinylidene fluoride
  • NMP N-methylpyrrolidone
  • a polyethylene (PE) porous polymer film is used as the isolation membrane.
  • the obtained positive electrode, separator film and negative electrode are wound in order and placed in the outer packaging foil, leaving a liquid injection port.
  • the electrolyte is poured from the injection port, encapsulated, and then undergoes processes such as chemical conversion and capacity to prepare a lithium-ion battery.
  • the lithium-ion battery is charged to 4.45V at a constant current of 1C, then charged at a constant voltage to a current of 0.05C, and then discharged at a constant current of 1C to 3.0V, which is the first cycle.
  • the lithium-ion battery was cycled 100 times.
  • Obtain the lithium-extraction area of the negative electrode mixture layer by the following method: get the fully charged battery, and then disassemble the negative electrode piece.
  • the golden yellow is the normal area and the white is the lithium-exhaustion area.
  • Analyze different areas abstract the white area into a circle, and use the gray difference to count the lithium-extracted areas to obtain the lithium-extracted area.
  • the lithium-ion battery is charged to 4.45V at a constant current of 1C, then charged at a constant voltage to a current of 0.05C, and then discharged at a constant current of 1C to 3.0V, which is the first cycle.
  • the lithium ion battery was cycled 20 times under the above conditions. Use a micrometer to test the thickness of the pole piece before and after the cycle. Calculate the thickness expansion rate of the pole piece by the following formula:
  • Pole piece thickness expansion ratio [(thickness after cycle-thickness before cycle)/thickness before cycle] ⁇ 100%.
  • the lithium-ion battery is charged to 4.45V at a constant current of 1C, then charged at a constant voltage to a current of 0.05C, and then discharged at a constant current of 1C to 3.0V, which is the first cycle.
  • the lithium ion battery was cycled 20 times under the above conditions.
  • the height gauge is used to test the battery thickness before and after the cycle.
  • the thickness expansion rate is calculated by the following formula:
  • Thickness expansion ratio [(thickness after cycle-thickness before cycle)/thickness before cycle] ⁇ 100%.
  • the lithium-ion battery At 0°C, the lithium-ion battery is charged to 4.45V at a constant current of 1C, then charged at a constant voltage to a current of 0.05C, and then discharged at a constant current of 1C to 3.0V, which is the first cycle.
  • the lithium ion battery was cycled 20 times under the above conditions. Calculate the low-temperature capacity retention rate of lithium-ion batteries by the following formula:
  • Low-temperature capacity retention rate [(capacity after cycle-capacity before cycle) capacity before cycle] ⁇ 100%.
  • the lithium-ion battery was allowed to stand for 30 minutes, then charged to 4.45V at a constant current rate of 0.5C, then charged to 0.05C at a constant voltage at 4.45V, and allowed to stand for 5 minutes to measure the thickness.
  • the thickness of the battery was measured after 21 days of storage at 60°C.
  • the high-temperature storage thickness expansion rate of lithium-ion batteries is calculated by the following formula:
  • High temperature storage thickness expansion ratio [(thickness after storage-thickness before storage)/thickness before storage] ⁇ 100%.
  • Table 1 shows the lithium evolution area of the negative electrode mixture layer of each example and the comparative example and the components in the electrolyte, as well as the plate thickness expansion rate and battery thickness expansion rate of the lithium ion battery.
  • Table 1 Examples use Auxiliary 1.
  • Comparative Example 1 when the lithium-evolving area of the negative electrode mixture layer is greater than 2% and the electrolyte does not contain a compound with phosphorus and oxygen, the thickness expansion rate of the pole piece and the battery thickness expansion rate of the lithium ion battery are relatively high. As shown in Comparative Example 2, when the lithium-evolving area of the negative electrode mixture layer is 2% but the electrolyte does not contain compounds with phosphorus and oxygen, the thickness expansion rate of the pole piece and the battery thickness expansion rate of the lithium ion battery are still relatively high.
  • the compound having phosphorus and oxygen can effectively improve the interface stability of the negative electrode mixture layer.
  • the thickness expansion rate of the pole piece of the lithium ion battery and the battery thickness expansion rate are significantly reduced, and the safety performance of the lithium ion battery is improved.
  • Table 2 shows the influence of the characteristics of the carbon material in the negative electrode mixture layer on the thickness expansion rate of the pole piece and the battery thickness expansion rate of the lithium ion battery. Except for the parameters listed in Table 2, the other settings of Examples 10-20 are the same as those of Example 9, and additive 1 is used.
  • the carbon material in the negative electrode mixture layer has the following characteristics: the specific surface area is less than 5 m 2 /g; the median particle size is 5 ⁇ m to 30 ⁇ m; and/or the surface has amorphous carbon.
  • the carbon material in the negative electrode mixture layer has the above characteristics, the plate thickness expansion rate and the battery thickness expansion rate of the lithium ion battery are further significantly reduced.
  • Table 3 shows the influence of the characteristics of the negative electrode mixture layer on the thickness expansion rate of the pole piece and the battery thickness expansion rate of the lithium ion battery. Except for the parameters listed in Table 3, the other settings of Examples 21-32 are the same as those of Example 8, and additive 1 is used.
  • the negative electrode mixture layer has the following characteristics: the thickness is not more than 200 ⁇ m; the porosity is 10% to 60%; and/or the smash height (that is, when the diameter is 15 mm and the weight is 12 grams)
  • the minimum height of the ball that causes cracks in the negative electrode mixture layer is 50 cm or more.
  • Table 4 shows the influence of the additives in the negative electrode mixture layer on the low-temperature capacity retention rate and the high-temperature storage thickness expansion rate of the lithium-ion battery.
  • the difference between Examples 33-40 in Table 4 and Example 9 is only in the type and content of the auxiliary agent.
  • the kind of auxiliary agent used should only be capable of reducing the lithium-evolving area on the surface of the negative electrode mixture layer to 2% or less.
  • the interface stability of the negative electrode mixture layer can be further improved, thereby improving the low-temperature capacity retention rate and/or high-temperature storage thickness expansion rate of the lithium ion battery, thereby improving lithium Storage performance of 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 embodiments”, “in one embodiment”, “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

一种电化学装置及包含其的电子装置，电化学装置包括正极；电解液；和负极，其中：所述电解液包含具有磷和氧的化合物，并且所述负极包括负极集流体和形成在所述负极集流体上的负极合剂层，在100次充放电循环后，基于所述负极合剂层的总表面积，所述负极合剂层表面的析锂面积为2％以下。电化学装置具有改进的循环性能、存储性能和安全性能。

Description

电化学装置及包含其的电子装置 技术领域
本申请涉及储能领域，具体涉及一种电化学装置及包含其的电子装置，特别是锂离子电池。
背景技术
随着技术的发展和对移动装置的需求的增加，人们对电化学装置(例如，锂离子电池)的需求显著增加。同时具有高能量密度以及优异的寿命和循环特性的锂离子电池是研究方向之一。
锂离子电池的理论容量可随着负极活性物质的种类而变化。随着循环的进行，锂离子电池通常会产生充电/放电容量降低的现象，使锂离子电池的性能劣化。近年来，在锂离子电池制造中，为了降低环境负担等，使用水性介质作为分散介质的水性浆料组合物得到越来越多的关注，但水性浆料会因为浆料组合物中气泡的存在导致活性物质层中产生多个针孔、凹坑等缺陷，从而影响电化学装置的循环和高温存储性能。
有鉴于此，确有必要提供一种具有改进的循环性能、存储性能和安全性能的电化学装置及包含其的电子装置。
发明内容
本申请实施例通过提供一种电化学装置及包含其的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。
在本申请的一方面，本申请提供了一种电化学装置，包括正极；电解液；和负极，其中所述电解液包含具有磷和氧的化合物，并且所述负极包括负极集流体和形成在所述负极集流体上的负极合剂层，在100次充放电循环后，基于所述负极合剂层的总表面积，所述负极合剂层表面的析锂面积为2％以下。
根据本申请的一些实施例，所述电解液包含以下化合物中的至少一种：
(a)单氟磷酸锂；
(b)二氟磷酸锂；
(c)磷酸酯；
(d)磷酸环酐；或
(e)式1化合物：
Figure PCTCN2019128445-appb-000001
其中R为取代或未取代的C 1-C 10烃基，且当取代时，取代基为卤素。
根据本申请的一些实施例，所述电解液包含所述式1化合物，且所述式1化合物包含以下结构式中的至少一种：
Figure PCTCN2019128445-appb-000002
根据本申请的一些实施例，所述电解液包含磷酸酯，且所述磷酸酯具有式2：
Figure PCTCN2019128445-appb-000003
其中，X是具有1至5个碳原子的直链或非直链烷基或者-SiR 2R 3R 4，其中R 2、R 3和R 4各自独立地是具有1至5个碳原子的烷基，并且
R 1是具有2至3个碳原子且被选自以下的取代基取代的亚烷基：至少一个氟原子或含至少一个氟原子且具有1至3个碳原子的烷基。
根据本申请的一些实施例，基于所述电解液的总重量，所述具有磷和氧的化合物的含量为0.001wt％至10wt％。
根据本申请的一些实施例，所述负极合剂层包括碳材料，所述碳材料具有以
下特征中的至少一者：
(a)小于5m 2/g的比表面积；
(b)5μm至30μm的中值粒径；
(c)表面具有无定形碳。
根据本申请的一些实施例，所述负极合剂层具有以下特征中的至少一者：
(a)厚度不大于200μm；
(b)具有10％至60％的孔隙率；
(c)当直径15mm、重量12克的球落到所述负极合剂层上时，使所述负极合剂层产生裂纹的球的最小高度为50cm以上。
根据本申请的一些实施例，所述负极合剂层包括助剂，所述助剂具有以下特征中的至少一者：
(a)包括聚醚硅氧烷；
(b)氧化电位不小于4.5V，且还原电位不大于0.5V；
(c)含0.1wt％所述助剂的水溶液的表面张力不大于30mN/m。
根据本申请的一些实施例，基于所述负极合剂层的总重量，所述助剂的含量为3000ppm以下。
在本申请的另一方面，本申请提供一种电子装置，其包括根据本申请的电化学装置。
本申请实施例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。
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。本申请的实施例不应该被解释为对本申请的限制。
除非另外明确指明，本文使用的下述术语具有下文指出的含义。
在具体实施方式及权利要求书中，由术语“中的至少一者”或其他相似术语所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。术语“中的至少一种”具有与术语“中的 至少一者”相同的含义。
如本文中所使用，术语“烃基”涵盖烷基、烯基、炔基。
如本文中所使用，术语“烷基”预期是具有1至20个碳原子的直链饱和烃结构。“烷基”还预期是具有3至20个碳原子的支链或环状烃结构。当指定具有具体碳数的烷基时，预期涵盖具有该碳数的所有几何异构体；因此，例如，“丁基”意思是包括正丁基、仲丁基、异丁基、叔丁基和环丁基；“丙基”包括正丙基、异丙基和环丙基。烷基实例包括，但不限于甲基、乙基、正丙基、异丙基、环丙基、正丁基、异丁基、仲丁基、叔丁基、环丁基、正戊基、异戊基、新戊基、环戊基、甲基环戊基、乙基环戊基、正己基、异己基、环己基、正庚基、辛基、环丙基、环丁基、降冰片基等。
如本文中所使用，术语“烯基”是指可为直链或具支链且具有至少一个且通常1个、2个或3个碳碳双键的单价不饱和烃基团。除非另有定义，否则所述烯基通常含有2个到20个碳原子且包括(例如)-C 2-4烯基、-C 2-6烯基及-C 2-10烯基。代表性烯基包括(例如)乙烯基、正丙烯基、异丙烯基、正-丁-2-烯基、丁-3-烯基、正-己-3-烯基等。
如本文中所使用，术语“炔基”是指可为直链或具支链且具有至少一个且通常具有1个、2个或3个碳碳三键的单价不饱和烃基团。除非另有定义，否则所述炔基通常含有2个到20个碳原子且包括(例如)-C 2-4炔基、-C 3-6炔基及-C 3-10炔基。代表性炔基包括(例如)乙炔基、丙-2-炔基(正-丙炔基)、正-丁-2-炔基、正-己-3-炔基等。
如本文中所使用，术语“亚烷基”意指可为直链或具支链的二价饱和烃基。除非另有定义，否则所述亚烷基通常含有2到10个碳原子，且包括(例如)-C 2-3亚烷基和-C 2-6亚烷基-。代表性亚烷基包括(例如)亚甲基、乙烷-1,2-二基(“亚乙基”)、丙烷-1,2-二基、丙烷-1,3-二基、丁烷-1,4-二基、戊烷-1,5-二基等。
术语“芳基”意指具有单环(例如，苯基)或稠合环的单价芳香族烃。稠合环系统包括那些完全不饱和的环系统(例如，萘)以及那些部分不饱和的环系统(例如，1,2,3,4-四氢萘)。除非另有定义，否则所述芳基通常含有6个到26个碳环原子且包括(例如)-C 6-10芳基。代表性芳基包括(例如)苯基、甲基苯基、丙基苯基、异丙基苯基、苯甲基和萘-1-基、萘-2-基等等。
如本文中所使用，术语“卤素”是指元素周期表的第17族的稳定原子，例如 氟、氯、溴或碘。
电化学装置(例如，锂离子电池)的理论容量可随着负极活性物质的种类而变化。随着循环的进行，电化学装置通常会产生充电/放电容量降低的现象。这是因为电化学装置在充电和/或放电过程中电极界面会发生变化，导致电极活性物质不能发挥其功能。
本申请通过使用特定的负极材料与特定的电解液的组合保证了电化学装置在循环过程中的界面稳定性，从而提高了电化学装置的循环和高温存储性能。
本申请特定的负极材料是通过控制负极活性物质层表面的析锂面积来实现，作为析锂面积的控制方法，可以通过在负极浆料中添加助剂或在负极活性物质层表面设置助剂涂层来控制。还可以通过调整电解液配方、添加特殊结构的添加剂，或是正负极极片的压实密度、正极活性材料比例调整等来实现析锂面积的控制。
在一个实施例中，本申请提供了一种电化学装置，其包括如下所述的正极、负极和电解液。
I、负极
负极包括负极集流体和设置在所述负极集流体的一个或两个表面上的负极合剂层。
1、负极合剂层
负极合剂层包含负极活性物质层，负极活性物质层包含负极活性物质。负极合剂层可以是一层或多层，多层负极活性物质中的每层可以包含相同或不同的负极活性物质。负极活性物质为任何能够可逆地嵌入和脱嵌锂离子等金属离子的物质。在一些实施例中，负极活性物质的可充电容量大于正极活性物质的放电容量，以防止在充电期间锂金属无意地析出在负极上。
(1)析锂面积
本申请的电化学装置的一个主要特征在于在100次充放电循环后，基于所述负极合剂层的总表面积，所述负极合剂层表面的析锂面积为2％以下。在一些实施例中，在100次充放电循环后，基于所述负极合剂层的总表面积，所述负极合剂层表面的析锂面积为1％以下。在一些实施例中，在100次充放电循环后，基于所述负极合剂层的总表面积，所述负极合剂层表面的析锂面积为0.5％以下。
负极合剂层的析锂面积可反映出负极合剂层的表面性质，其是表征负极合剂层的物理化学参数之一。析锂面积越小，负极合剂层的表面越平整，具有越少的 针孔或凹坑缺陷，可显著改善电化学装置的循环和高温存储性能。负极合剂层的析锂面积可受多种因素影响，主要包括助剂和负极合剂层的孔隙率等。
当负极合剂层具有如上所述的析锂面积时，可获得稳定性良好的合剂层界面，使得锂离子电池在充放电循环中具有改进的循环性能、存储性能和安全性能。
(2)接触角
根据本申请的一些实施例，经接触角测定法测定，所述负极合剂层相对非水溶剂的接触角不大于60°。在一些实施例中，经接触角测定法测定，所述负极合剂层相对非水溶剂的接触角不大于50°。在一些实施例中，经接触角测定法测定，所述负极合剂层相对非水溶剂的接触角不大于30°。当负极合剂层相对非水溶剂具有如上所述的接触角时，负极合剂层界面具有较少缺陷，在电化学装置的充放电循环中稳定性良好，可保证电化学装置的循环和高温存储性能。
根据本申请的一些实施例，所述接触角测定法是指在所述负极合剂层表面滴加3微升碳酸二乙酯的液滴后，在100秒内测试所述液滴在所述负极合剂层的表面的接触角。
根据本申请的一些实施例，经接触角测定法测定，所述非水溶剂在所述负极合剂层上的液滴直径不大于30mm。在一些实施例中，经接触角测定法测定，所述非水溶剂在所述负极合剂层上的液滴直径不大于20mm。在一些实施例中，经接触角测定法测定，所述非水溶剂在所述负极合剂层上的液滴直径不大于15mm。在一些实施例中，经接触角测定法测定，所述非水溶剂在所述负极合剂层上的液滴直径不大于10mm。在负极合剂层相对非水溶剂具有上述接触角且同时所述非水溶剂具有上述液滴直径时，电化学装置的循环和高温存储性能得到进一步提升。
负极合剂层相对非水溶剂的接触角和非水溶剂液滴的直径可通过以下方法测定：在负极合剂层表面滴加3微升碳酸二乙酯，在100秒内使用JC2000D3E型接触角测量仪进行测试液滴直径，并选用5点拟合法(即，先取液滴左右平面2点，确定液固交接面，然后在液滴圆弧上取3点)进行拟合，得到负极合剂层相对非水溶剂的接触角。每个样品至少测量3次，选取至少3个差值小于5°的数据，取平均值，得到负极合剂层相对非水溶剂的接触角。接触角测试使用的非水溶剂可以选用碳酸二乙酯、碳酸甲乙酯、碳酸二甲酯、碳酸甲丙酯或碳酸甲异丙酯等常用电解液溶剂。
(3)碳材料
根据本申请的一些实施例，所述负极合剂层包括碳材料。
根据本申请的一些实施例，所述负极合剂层包括人造石墨、天然石墨、中间相碳微球、软碳、硬碳和无定形碳中的至少一种。
根据本申请的一些实施例，所述碳质材料的形状包括，但不限于，纤维状、球状、粒状和鳞片状。
根据本申请的一些实施例，所述碳材料具有以下特征中的至少一者：
(a)小于5m 2/g的比表面积(BET)；
(b)5μm至30μm的中值粒径(D50)；或
(c)表面具有无定形碳。
比表面积(BET)
在一些实施例中，所述碳材料具有小于5m 2/g的比表面积。在一些实施例中，所述碳材料具有小于3m 2/g的比表面积。在一些实施例中，所述碳材料具有小于1m 2/g的比表面积。在一些实施例中，所述碳材料具有大于0.1m 2/g的比表面积。在一些实施例中，所述碳材料具有小于0.7m 2/g的比表面积。在一些实施例中，所述碳材料具有小于0.5m 2/g的比表面积。在一些实施例中，所述碳材料的比表面积在上述任意两个数值所组成的范围内。当所述碳材料的比表面积在上述范围内时，可以抑制锂在电极表面的析出，并可以抑制负极与电解液反应所导致的气体产生。
碳材料的比表面积(BET)可通过如下方法测定：使用表面积计(大仓理研制造的全自动表面积测定装置)，在氮气流通下于350℃对试样进行15分钟预干燥，然后使用氮气相对于大气压的相对压力值准确调节为0.3的氮氦混合气体，通过采用气体流动法的氮吸附BET单点法进行测定。
中值粒径(D50)
所述碳材料的中值粒径(D50)是指通过激光衍射/散射法得到的体积基准的平均粒径。在一些实施例中，所述碳材料具有5μm至30μm的中值粒径(D50)。在一些实施例中，所述碳材料具有10μm至25μm的中值粒径(D50)。在一些实施例中，所述碳材料具有15μm至20μm的中值粒径(D50)。在一些实施例中，所述碳材料具有1μm、3μm、5μm、7μm、10μm、15μm、20μm、25μm、30μm或在以上任意两个数值的范围内的中值粒径(D50)。当所述碳材料的中值 粒径在上述范围内时，电化学装置的不可逆容量较小，且易于均匀地涂布负极。
所述碳材料的中值粒径(D50)可通过如下方法测定：将碳材料分散于聚氧乙烯(20)山梨糖醇酐单月桂酸酯的0.2wt％水溶液(10mL)中，利用激光衍射/散射式粒度分布计(堀场制作所社制造LA-700)进行测试。
X射线衍射图谱参数
根据本申请的一些实施例，基于学振法的X射线衍射图谱，所述碳材料的晶格面(002面)的层间距离在0.335nm至0.360nm的范围内、在0.335nm至0.350nm的范围内或在0.335nm至0.345nm的范围内。
根据本申请的一些实施例，基于学振法的X射线衍射图谱，所述碳材料的微晶尺寸(Lc)大于1.0nm或大于1.5nm。
拉曼光谱参数
在一些实施例中，所述碳材料的拉曼R值为大于0.01、大于0.03或大于0.1。在一些实施例中，所述碳材料的拉曼R值为小于1.5、小于1.2、小于1.0或小于0.5。在一些实施例中，所述碳材料的拉曼R值在上述任意两个数值所组成的范围内。
所述碳材料在1580cm -1附近的拉曼半峰宽没有特别限制。在一些实施例中，所述碳材料在1580cm -1附近的拉曼半峰宽为大于10cm -1或大于15cm -1。在一些实施例中，所述碳材料在1580cm -1附近的拉曼半峰宽为小于100cm -1、小于80cm -1、小于60cm -1或小于40cm -1。在一些实施例中，所述碳材料在1580cm -1附近的拉曼半峰宽在上述任意两个数值所组成的范围内。
拉曼R值和拉曼半峰宽是表示碳材料表面的结晶性的指标。适度的结晶性可使碳材料在充放电过程中容纳锂的层间位点得以保持，不会消失，从而有利于碳材料的化学稳定性。
当拉曼R值和/或拉曼半峰宽在如上所述的范围内时，碳材料可在负极表面形成适当的覆膜，有助于改善电化学装置的保存特性、循环特性以及负荷特性等，同时可以抑制碳材料与电解液的反应导致的效率降低及气体产生。
拉曼R值或拉曼半峰宽可通过氩离子激光拉曼光谱法测定：使用拉曼分光器(日本分光社制造的拉曼分光器)，使试样自然落下并填充于测定池内，对池内的样品表面照射氩离子激光，同时使池在与激光垂直的面内旋转，由此进行测定。对于所得到的拉曼光谱，测定在1580cm -1附近的峰PA的强度IA和在1360cm -1 附近的峰PB的强度IB，计算出其强度比R(R＝IB/IA)。
上述拉曼光谱法的测定条件如下：
·氩离子激光波长：514.5nm
·试样上的激光功率：15-25mW
·分辨率：10-20cm -1
·测定范围：1100cm -1-1730cm -1
·拉曼R值、拉曼半峰宽分析：背景处理
·平滑处理：简单平均、卷积5点
圆度
“圆度”的定义如下：圆度＝(具有与颗粒投影形状相同面积的等效圆的周长)/(颗粒投影形状的实际周长)。当圆度为1.0时，即为理论上的正球。
在一些实施例中，所述碳材料的粒径为3μm至40μm，且圆度为大于0.1、大于0.5、大于0.8、大于0.85、大于0.9或为1.0。
对于高电流密度充放电特性来说，碳材料的圆度越大，填充性越高，这有助于抑制颗粒间的电阻，从而改善电化学装置在高电流密度下的充放电特性。
碳材料的圆度可使用流式颗粒图像分析装置(Sysmex社制造FPIA)进行测量：将0.2g试样分散于聚氧乙烯(20)山梨糖醇酐单月桂酸酯的0.2wt％水溶液(50mL)中，以输出功率60W照射1分钟28kHz的超声波后，指定检测范围为0.6μm至400μm，对粒径为3μm至40μm范围的颗粒进行测定。
提高圆度的方法没有特别限制。可采用球形化处理，使得在制备电极时碳材料颗粒间的空隙形状统一。可通过施加剪切力或压缩力等机械手段来实施球形化处理，亦可通过施用粘结剂或者通过颗粒自身所具有的附着力将多个微粒造粒等机械/物理手段来实施球形化处理，从而使碳材料颗粒接近正球形。
振实密度
在一些实施例中，所述碳材料的振实密度为大于0.1g/cm 3、大于0.5g/cm 3、大于0.7g/cm 3或大于1g/cm 3。在一些实施例中，所述碳材料的振实密度为小于2g/cm 3、小于1.8g/cm 3或小于1.6g/cm 3。在一些实施例中，所述碳材料的振实密度在上述任意两个数值所组成的范围内。当碳材料的振实密度在上述范围内时，可以确保电化学装置的容量，同时可以抑制碳材料颗粒间的电阻增大。
碳材料的振实密度可通过如下方法测试：使试样通过网孔为300μm的筛后 落入20cm 3的振实槽中，直到试样充满至槽的上端面后，利用粉体密度测定器(例如，Seishin企业社制造的Tap densor)进行1000次冲程长度为10mm的振动，根据此时的质量和试样的质量计算出振实密度。
取向比
在一些实施例中，所述碳材料的取向比为大于0.005、大于0.01或大于0.015。在一些实施例中，所述碳材料的取向比为小于0.67。在一些实施例中，所述碳材料的取向比在上述任意两个数值所组成的范围内。当碳材料的取向比在上述范围内时，可使电化学装置具有优异的高密度充放电特性。
碳材料的取向比可在对试样进行加压成型后利用X射线衍射进行测定：将试样0.47g填充至直径为17mm的成型机中，在58.8MN·m -2下压缩得到成型体，用粘土固定该成型体，使该成型体与测定用试样架的面为同一面，从而进行X射线衍射测定。由所得到的碳的(110)衍射和(004)衍射的峰强度计算出(110)衍射峰强度/(004)衍射峰强度所表示的比。
X射线衍射测定条件如下：
·靶材：Cu(Kα射线)石墨单色器
·狭缝：发散狭缝＝0.5度；受光狭缝＝0.15mm；散射狭缝＝0.5度
·测定范围和步进角/计测时间(“2θ”表示衍射角)：
(110)面：75度≤2θ≤80度1度/60秒
(004)面：52度≤2θ≤57度1度/60秒
长厚比
在一些实施例中，所述碳材料的长厚比为大于1、大于2或大于3。在一些实施例中，所述碳材料的长厚比为小于10、小于8或小于5。在一些实施例中，所述碳材料的长厚比在上述任意两个数值所组成的范围内。
当碳材料的长厚比在上述范围内时，可进行更均匀的涂布，因而可以使电化学装置具有优异的高电流密度充放电特性。
(4)孔隙率
根据本申请的一些实施例，所述负极合剂层的孔隙率为10％至60％。在一些实施例中，所述负极合剂层的孔隙率为15％至50％。在一些实施例中，所述负极合剂层的孔隙率为20％至40％。在一些实施例中，所述负极合剂层的孔隙率为25％至30％。在一些实施例中，所述负极合剂层的孔隙率为10％、15％、20％、 25％、30％、35％、40％、45％、50％、55％、60％或在以上任意两个数值所组成的范围内。
所述负极合剂层的孔隙率可通过以下方法测定：使用真密度测试仪AccuPyc II 1340进行测试，每个样品至少进行3次测量，选取至少3个数据取平均值。根据下式计算负极合剂层的孔隙率：孔隙率＝(V1-V2)/V1×100％，其中，V1为表观体积，V1＝样品表面积×样品厚度×样品数量；V2为真实体积。
(5)厚度
负极合剂层的厚度是指负极合剂层在负极集流体的任意一侧上的厚度。在一些实施例中，所述负极合剂层的厚度为不大于200μm。在一些实施例中，所述负极合剂层的厚度为不大于150μm。在一些实施例中，所述负极合剂层的厚度为不大于100μm。在一些实施例中，所述负极合剂层的厚度为不大于50μm。在一些实施例中，所述负极合剂层的厚度为不小于15μm。在一些实施例中，所述负极合剂层的厚度为不小于20μm。在一些实施例中，所述负极合剂层的厚度为不小于30μm。在一些实施例中，负极合剂层的厚度在上述任意两个数值所组成的范围内。
(6)负极合剂层的砸球测试
根据本申请的一些实施例，当直径15mm、重量12克的球落到所述负极合剂层上时，使所述负极合剂层产生裂纹的球的最小高度为50cm以上。在一些实施例中，当直径15mm、重量12克的球落到所述负极合剂层上时，使所述负极合剂层产生裂纹的球的最小高度为150cm以下。
负极合剂层产生裂纹的球的最小高度与合剂层的界面相关。当所述最小高度为50cm以上时，负极合剂层的界面在切割时不会在不希望的方向上产生裂纹。
在取得纵向(Machine Direction，MD)和横向(Transverse Direction，TD)的平衡的基础上，使所述负极合剂层产生裂纹的球的最小高度与负极合剂层的厚度和孔隙率有关。负极合剂层的厚度越大，使负极合剂层产生裂纹的球的最小高度越大，但过厚的负极合剂层会使电化学装置的能量密度下降。负极合剂层的孔隙率越小，使所述负极合剂层产生裂纹的球的最小高度越大，但过低的孔隙率会使电化学装置的电化学性能(例如，倍率性能)降低。
(7)助剂
根据本申请的一些实施例，所述负极合剂层进一步包括助剂。
根据本申请的一些实施例，所述助剂具有以下特征中的至少一者：
(a)包括聚醚硅氧烷；
(b)氧化电位不小于4.5V，且还原电位不大于0.5V；或
(c)含0.1wt％所述助剂的水溶液的表面张力不大于30mN/m。
聚醚硅氧烷
在一些实施例中，所述助剂包括聚醚硅氧烷。在一些实施例中，所述聚醚硅氧烷具有Si-C和Si-O键。在一些实施例中，所述聚醚硅氧烷包括复合硅酮聚醚复合物、聚醚改性三硅氧烷或聚醚改性有机硅聚醚硅氧烷中的至少一种。
聚醚硅氧烷的实例包括，但不限于，三硅氧烷表面活性剂(CAS No.3390-61-2；28855-11-0)、有机硅表面活性剂(Sylgard 309)、二羟基聚二甲基硅氧烷((PMX-0156))或甲基硅油聚二甲基硅氧烷(CAS No.63148-62-9)。
上述聚醚硅氧烷可单独使用或任意组合使用。若所述助剂含两种或多种聚醚硅氧烷时，聚醚硅氧烷的含量是指两种或多种聚醚硅氧烷的总含量。在一些实施例中，基于所述负极合剂层的总重量，所述聚醚硅氧烷的含量为3000ppm以下、2000ppm以下、1000ppm以下、500ppm以下、300ppm以下或200ppm以下。当聚醚硅氧烷的含量在上述范围内时，有利于改善电化学装置的以下性能：输出功率特性、负荷特性、低温特性、循环特性和高温保存特性等。
氧化/还原电位
在一些实施例中，所述助剂的氧化电位不小于4.5V，且还原电位不大于0.5V。在一些实施例中，所述助剂的氧化电位不小于5V，且还原电位不大于0.3V。具有上述氧化/还原电位的助剂电化学性能稳定，有助于改善电化学装置的循环和高温存储性能。
表面张力
在一些实施例中，含0.1wt％所述助剂的水溶液的表面张力不大于30mN/m。在一些实施例中，含0.1wt％所述助剂的水溶液的表面张力为不大于25mN/m。在一些实施例中，含0.1wt％所述助剂的水溶液的表面张力为不大于20mN/m。在一些实施例中，含0.1wt％所述助剂的水溶液的表面张力为不大于15mN/m。在一些实施例中，含0.1wt％所述助剂的水溶液的表面张力为不大于10mN/m。具有如上所述的表面张力的助剂使得负极合剂层具有良好的界面，有助于改善电化学装置的循环和高温存储性能。
所述助剂的表面张力可通过如下方法测定：使用JC2000D3E型接触角测量仪对固含量为1％的助剂水溶液进行测试，每个样品至少测试3次，选取至少3个数据，取平均值，得到助剂的表面张力。
(8)其它组分
微量元素
根据本申请的一些实施例，所述负极合剂层进一步包括钼、铁和铜中的至少一种金属。这些金属元素可以与负极活性物质中一些导电能力差的有机物反应，从而有利于负极活性物质表面成膜。
根据本申请的一些实施例，上述金属元素以微量存在于所述负极合剂层中，过多的金属元素容易形成不导电的副产物并附着于负极的表面。在一些实施例中，基于所述负极合剂层的总重量计，所述至少一种金属的含量为不大于0.05wt％。在一些实施例中，所述至少一种金属的含量为不大于0.03wt％。在一些实施例中，所述至少一种金属的含量为不大于0.01wt％。
含硅和/或锡元素的材料
根据本申请的一些实施例，所述负极合剂层进一步包括含硅材料、含锡材料、合金材料中的至少一种。根据本申请的一些实施例，所述负极合剂层进一步包括含硅材料和含锡材料中的至少一种。在一些实施例中，所述负极合剂层进一步包括含硅材料、硅碳复合材料、硅氧材料、合金材料和含锂金属复合氧化物材料中的一种或多种。在一些实施例中，所述负极合剂层进一步包含其它种类的负极活性物质，例如，一种或多种包含能够与锂形成合金的金属元素和准金属元素的材料。在一些实施例中，所述金属元素和准金属元素的实例包括，但不限于，Mg、B、Al、Ga、In、Si、Ge、Sn、Pb、Bi、Cd、Ag、Zn、Hf、Zr、Y、Pd和Pt。在一些实施例中，所述金属元素和准金属元素的实例包括Si、Sn或其组合。Si和Sn具有优异的脱嵌锂离子的能力，可为锂离子电池提供高能量密度。在一些实施例中，其它种类的负极活性物质还可以包括金属氧化物和高分子化合物中的一种或多种。在一些实施例中，所述金属氧化物包括，但不限于，氧化铁、氧化钌和氧化钼。在一些实施例中，所述高分子化合物包括，但不限于，聚乙炔、聚苯胺和聚吡咯。
负极导电材料
在一些实施例中，所述负极合剂层进一步包含负极导电材料，该导电材料可 以包括任何导电材料，只要它不引起化学变化即可。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)、导电聚合物(例如，聚亚苯基衍生物)和它们的混合物。
负极粘结剂
在一些实施例中，所述负极合剂层还包括负极粘合剂。负极粘合剂可提高负极活性物质颗粒彼此间的结合和负极活性物质与集流体的结合。负极粘合剂的种类没有特别限制，只要是对于电解液或电极制造时使用的溶剂稳定的材料即可。
负极粘合剂的实例包括，但不限于，聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯、聚甲基丙烯酸甲酯、芳香族聚酰胺、聚酰亚胺、纤维素、硝酸纤维素等树脂系高分子；丁苯橡胶(SBR)、异戊二烯橡胶、聚丁橡胶、氟橡胶、丙烯腈·丁二烯橡胶(NBR)、乙烯·丙烯橡胶等橡胶状高分子；苯乙烯·丁二烯·苯乙烯嵌段共聚物或其氢化物；乙烯·丙烯·二烯三元共聚物(EPDM)、苯乙烯·乙烯·丁二烯·苯乙烯共聚物、苯乙烯·异戊二烯·苯乙烯嵌段共聚物或其氢化物等热塑性弹性体状高分子；间规-1,2-聚丁二烯、聚乙酸乙烯酯、乙烯·乙酸乙烯酯共聚物、丙烯·α-烯烃共聚物等软质树脂状高分子；聚偏二氟乙烯、聚四氟乙烯、氟化聚偏二氟乙烯、聚四氟乙烯·乙烯共聚物等氟系高分子；具有碱金属离子(例如，锂离子)的离子传导性的高分子组合物等。上述负极粘合剂可以单独使用，也可以任意组合使用。
在一些实施例中，基于负极合剂层的总重量，所述负极粘结剂的含量大于0.1wt％、大于0.5wt％或大于0.6wt％。在一些实施例中，基于负极合剂层的总重量，所述负极粘结剂的含量小于20wt％、小于15wt％、小于10wt％或小于8wt％。在一些实施例中，所述负极粘结剂的含量在上述任意两个数值所组成的范围内。当负极粘结剂的含量在上述范围时，可以充分确保电化学装置的容量和负极的强度。
在负极合剂层含有橡胶状高分子(例如，SBR)的情况下，在一些实施例中，基于负极合剂层的总重量，所述负极粘结剂的含量为大于0.1wt％、大于0.5wt％或大于0.6wt％。在一些实施例中，基于负极合剂层的总重量，所述负极粘结剂的含量为小于5wt％、小于3wt％或小于2wt％。在一些实施例中，基于负极合剂层的总重量，所述负极粘结剂的含量在上述任意两个数值所组成的范围内。
在负极合剂层含有氟系高分子(例如，聚偏二氟乙烯)的情况下，在一些实 施例中，基于负极合剂层的总重量，所述负极粘结剂的含量为大于1wt％、大于2wt％或大于3wt％。在一些实施例中，基于负极合剂层的总重量，所述负极粘结剂的含量为小于15wt％、小于10wt％或小于8wt％。基于负极合剂层的总重量，所述负极粘结剂的含量在上述任意两个数值所组成的范围内。
溶剂
用于形成负极浆料的溶剂的种类没有特别限制，只要是能够溶解或分散负极活性物质、负极粘结剂、以及根据需要使用的增稠剂和导电材料的溶剂即可。在一些实施例中，用于形成负极浆料的溶剂可以使用水系溶剂和有机系溶剂中的任一种。水系溶剂的实例可包括，但不限于，水、醇等。有机系溶剂的实例可包括，但不限于，N-甲基吡咯烷酮(NMP)、二甲基甲酰胺、二甲基乙酰胺、甲基乙基酮、环己酮、乙酸甲酯、丙烯酸甲酯、二乙基三胺、N,N-二甲氨基丙胺、四氢呋喃(THF)、甲苯、丙酮、二乙醚、六甲基磷酰胺、二甲基亚砜、苯、二甲苯、喹啉、吡啶、甲基萘、己烷等。上述溶剂可以单独使用或任意组合使用。
增稠剂
增稠剂通常是为了调节负极浆料的粘度而使用的。增稠剂的种类没有特别限制，其实例可包括，但不限于，羧甲基纤维素、甲基纤维素、羟甲基纤维素、乙基纤维素、聚乙烯醇、氧化淀粉、磷酸化淀粉、酪蛋白和它们的盐等。上述增稠剂可以单独使用，也可以任意组合使用。
在一些实施例中，基于负极合剂层的总重量，所述增稠剂的含量为大于0.1wt％、大于0.5wt％或大于0.6wt％。在一些实施例中，基于负极合剂层的总重量，所述增稠剂的含量为小于5wt％、小于3wt％或小于2wt％。当增稠剂的含量在上述范围没时，可以抑制电化学装置的容量降低及电阻的增大，同时可以确保负极浆料具有良好的涂布性。
(9)表面被覆
在一些实施例中，负极合剂层的表面可附着有与其组成不同的物质。负极合剂层的表面附着物质的实例包括，但不限于，氧化铝、二氧化硅、二氧化钛、氧化锆、氧化镁、氧化钙、氧化硼、氧化锑、氧化铋等氧化物、硫酸锂、硫酸钠、硫酸钾、硫酸镁、硫酸钙、硫酸铝等硫酸盐、碳酸锂、碳酸钙、碳酸镁等碳酸盐等。
(10)负极活性物质的含量
在一些实施例中，基于负极合剂层的总重量，负极活性物质的含量为大于80wt％、大于82wt％或大于84wt％。在一些实施例中，基于负极合剂层的总重量，负极活性物质的含量为小于99wt％或小于98wt％。在一些实施例中，基于负极合剂层的总重量，负极活性物质的含量在上述任意两个数组所组成的范围内。
(11)负极活性物质的密度
在一些实施例中，负极合剂层中的负极活性物质的密度为大于1g/cm 3、大于1.2g/cm 3或大于1.3g/cm 3。在一些实施例中，负极合剂层中的负极活性物质的密度为小于2.2g/cm 3、小于2.1g/cm 3、小于2.0g/cm 3或小于1.9g/cm 3。在一些实施例中，负极合剂层中的负极活性物质的密度在上述任意两个数值所组成的范围内。
当负极活性物质的密度在上述范围内时，可防止负极活性物质颗粒的破坏，可以抑制电化学装置初期不可逆容量的增加或电解液在负极集流体/负极活性物质界面附近的渗透性降低所导致的高电流密度充放电特性恶化，还可以抑制电化学装置的容量降低及电阻增大。
2、负极集流体
作为保持负极活性物质的集流体，可以任意使用公知的集流体。负极集流体的实例包括，但不限于，铝、铜、镍、不锈钢、镀镍钢等金属材料。在一些实施例中，负极集流体为铜。
在负极集流体为金属材料的情况下，负极集流体形式可包括，但不限于，金属箔、金属圆柱、金属带卷、金属板、金属薄膜、金属板网、冲压金属、发泡金属等。在一些实施例中，负极集流体为金属薄膜。在一些实施例中，负极集流体为铜箔。在一些实施例中，负极集流体为基于压延法的压延铜箔或基于电解法的电解铜箔。
在一些实施例中，负极集流体的厚度为大于1μm或大于5μm。在一些实施例中，负极集流体的厚度为小于100μm或小于50μm。在一些实施例中，负极集流体的厚度在上述任意两个数值所组成的范围内。
负极集流体与负极合剂层的厚度比是指注入电解液前的单面负极合剂层厚度与负极集流体的厚度的比率，其数值没有特别限制。在一些实施例中，负极集流体与负极合剂层的厚度比为小于150、小于20或小于10。在一些实施例中，负极集流体与负极合剂层的厚度比为大于0.1、大于0.4或大于1。在一些实施例 中，负极集流体与负极合剂层的厚度比在上述任意两个数值所组成的范围内。当负极集流体与负极合剂层的厚度比在上述范围内时，可以确保电化学装置的容量，同时可以抑制高电流密度充放电时的负极集流体的放热。
II、电解液
本申请的电化学装置中的使用的电解液包括电解质和溶解该电解质的溶剂。在一些实施例中，本申请的电化学装置中的使用的电解液进一步包括添加剂。
本申请的电化学装置的一个主要特征在于所述电解液包含具有磷和氧的化合物。
根据本申请的一些实施例，基于所述电解液的总重量，所述具有磷和氧的化合物的含量为0.001wt％至10wt％。在一些实施例中，基于所述电解液的总重量，所述具有磷和氧的化合物的含量为0.005wt％至8wt％。在一些实施例中，基于所述电解液的总重量，所述具有磷和氧的化合物的含量为0.01wt％至5wt％。在一些实施例中，基于所述电解液的总重量，所述具有磷和氧的化合物的含量为0.05wt％至3wt％。在一些实施例中，基于所述电解液的总重量，所述具有磷和氧的化合物的含量为0.1wt％至2wt％。在一些实施例中，基于所述电解液的总重量，所述具有磷和氧的化合物的含量为0.5wt％至1wt％。
根据本申请的一些实施例，所述电解液包括以下化合物中的至少一种：
(a)单氟磷酸锂；
(b)二氟磷酸锂；
(c)磷酸酯；
(d)磷酸环酐；或
(e)式1化合物：
Figure PCTCN2019128445-appb-000004
其中R为取代或未取代的C 1-C 10烃基，且当取代时，取代基为卤素。
(a)单氟磷酸锂
在一些实施例中，基于所述电解液的总重量，所述单氟磷酸锂的含量为0.001wt％至10wt％。在一些实施例中，基于所述电解液的总重量，所述单氟磷酸锂的含量为0.005wt％至8wt％。在一些实施例中，基于所述电解液的总重量，所 述单氟磷酸锂的含量为0.01wt％至5wt％。在一些实施例中，基于所述电解液的总重量，所述单氟磷酸锂的含量为0.05wt％至3wt％。在一些实施例中，基于所述电解液的总重量，所述单氟磷酸锂的含量为0.1wt％至2wt％。在一些实施例中，基于所述电解液的总重量，所述单氟磷酸锂的含量为0.5wt％至1wt％。
(b)二氟磷酸锂
在一些实施例中，基于所述电解液的总重量，所述二氟磷酸锂的含量为0.001wt％至10wt％。在一些实施例中，基于所述电解液的总重量，所述二氟磷酸锂的含量为0.005wt％至8wt％。在一些实施例中，基于所述电解液的总重量，所述二氟磷酸锂的含量为0.01wt％至5wt％。在一些实施例中，基于所述电解液的总重量，所述二氟磷酸锂的含量为0.05wt％至3wt％。在一些实施例中，基于所述电解液的总重量，所述二氟磷酸锂的含量为0.1wt％至2wt％。在一些实施例中，基于所述电解液的总重量，所述二氟磷酸锂的含量为0.5wt％至1wt％。
(c)磷酸酯
根据本申请的一些实施例，所述磷酸酯具有式2：
Figure PCTCN2019128445-appb-000005
其中，X是具有1至5个碳原子的直链或非直链烷基或者-SiR 2R 3R 4，其中R 2、R 3和R 4各自独立地是具有1至5个碳原子的烷基，并且
R 1是具有2至3个碳原子且被选自以下的取代基取代的亚烷基：至少一个氟原子或含至少一个氟原子且具有1至3个碳原子的烷基。
根据本申请的一些实施例，在式2中，X是-SiR 2R 3R 4，并且R 1是具有2个碳原子且被选自以下的取代基取代的亚烷基：至少一个氟原子或含至少一个氟原子且具有1至3个碳原子的烷基。
根据本申请的一些实施例，所述式2化合物包括式2a至式2h表示的化合物中的至少一种：
Figure PCTCN2019128445-appb-000006
根据本申请的一些实施例，基于所述电解液的总重量，所述式2化合物的含量为0.001wt％至10wt％。在一些实施例中，基于所述电解液的总重量，所述式2化合物的含量为0.005wt％至9wt％。在一些实施例中，基于所述电解液的总重量，所述式2化合物的含量为0.01wt％至8wt％。在一些实施例中，基于所述电解液的总重量，所述式2化合物的含量为0.05wt％至7wt％。在一些实施例中，基于所述电解液的总重量，所述式2化合物的含量为0.1wt％至6wt％。在一些实施例中，基于所述电解液的总重量，所述式2化合物的含量为0.5wt％至5wt％。在一些实施例中，基于所述电解液的总重量，所述式2化合物的含量为1wt％至4wt％。在一些实施例中，基于所述电解液的总重量，所述式2化合物的含量为2wt％至3wt％。
(d)磷酸环酐
在一些实施例中，所述磷酸环酐包括式3化合物中的一种或多种：
Figure PCTCN2019128445-appb-000007
其中R 10、R 11和R 12各自独立地为氢原子、C 1-20烷基(例如，C 1-15烷基、C 1-10烷基、C 1-5烷基、C 5-20烷基、C 5-15烷基、C 5-10烷基)、C 6-50芳基(例如，C 6-30芳基、C 6-26芳基、C 6-20芳基、C 10-50芳基、C 10-30芳基、C 10-26芳基或C 10-20芳基)，其中R 10、R 11和R 12可以互不相同、彼此相同或者是其中任意两者相同。
在一些实施例中，所述磷酸环酐包括，但不限于，以下化合物：
Figure PCTCN2019128445-appb-000008
Figure PCTCN2019128445-appb-000009
在一些实施例中，基于所述电解液的总重量，所述磷酸环酐的含量为0.01wt％至10wt％。在一些实施例中，基于所述电解液的总重量，所述磷酸环酐的含量为0.05wt％至8wt％。在一些实施例中，基于所述电解液的总重量，所述磷酸环酐的含量为0.1wt％至5wt％。在一些实施例中，基于所述电解液的总重量，所述磷酸环酐的含量为0.5wt％至3wt％。在一些实施例中，基于所述电解液的总重量，所述磷酸环酐的含量为1wt％至2wt％。
(e)式1化合物
根据本申请的一些实施例，所述式1化合物包含以下结构式中的至少一种：
式1a：
Figure PCTCN2019128445-appb-000010
(1,2-双(二氟磷氧)乙烷)；
式1b：
Figure PCTCN2019128445-appb-000011
(1,2-双(二氟磷氧)丙烷)；或
式1c：
Figure PCTCN2019128445-appb-000012
(1,2-双(二氟磷氧)丁烷)。
在一些实施例中，基于所述电解液的总重量，所述式1化合物的含量为0.01wt％至15wt％。在一些实施例中，基于所述电解液的总重量，所述式1化合 物的含量为0.05wt％至12wt％。在一些实施例中，基于所述电解液的总重量，所述式1化合物的含量为0.1wt％至10wt％。在一些实施例中，基于所述电解液的总重量，所述式1化合物的含量为0.5wt％至8wt％。在一些实施例中，基于所述电解液的总重量，所述式1化合物的含量为1wt％至5wt％。在一些实施例中，基于所述电解液的总重量，所述式1化合物的含量为2wt％至4wt％。
溶剂
在一些实施例中，所述电解液进一步包含现有技术中已知的任何可作为电解液的溶剂的非水溶剂。
在一些实施例中，所述非水溶剂包括，但不限于，以下中的一种或多种：环状碳酸酯、链状碳酸酯、环状羧酸酯、链状羧酸酯、环状醚、链状醚、含磷有机溶剂、含硫有机溶剂和芳香族含氟溶剂。
在一些实施例中，所述环状碳酸酯的实例可包括，但不限于，以下中的一种或多种：碳酸亚乙酯(EC)、碳酸亚丙酯(PC)和碳酸亚丁酯。在一些实施例中，所述环状碳酸酯具有3-6个碳原子。
在一些实施例中，所述链状碳酸酯的实例可包括，但不限于，以下中的一种或多种：碳酸二甲酯、碳酸甲乙酯、碳酸二乙酯(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等。被氟取代的链状碳酸酯的实例可包括，但不限于，以下中的一种或多种：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等。
在一些实施例中，所述环状羧酸酯的实例可包括，但不限于，以下中的一种或多种：γ-丁内酯和γ-戊内酯中的一种或多种。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，所述链状羧酸酯的实例可包括，但不限于，以下中的一种或多种：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等。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的实例可包括，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2,2,2-三氟乙酯等。
在一些实施例中，所述环状醚的实例可包括，但不限于，以下中的一种或多种：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，所述链状醚的实例可包括，但不限于，以下中的一种或多种：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-乙氧基甲氧基乙烷等。
在一些实施例中，所述含磷有机溶剂的实例可包括，但不限于，以下中的一种或多种：磷酸三甲酯、磷酸三乙酯、磷酸二甲基乙酯、磷酸甲基二乙酯、磷酸亚乙基甲酯、磷酸亚乙基乙酯、磷酸三苯酯、亚磷酸三甲酯、亚磷酸三乙酯、亚磷酸三苯酯、磷酸三(2,2,2-三氟乙基)酯和磷酸三(2,2,3,3,3-五氟丙基)酯等。
在一些实施例中，所述含硫有机溶剂的实例可包括，但不限于，以下中的一种或多种：环丁砜、2-甲基环丁砜、3-甲基环丁砜、二甲基砜、二乙基砜、乙基甲基砜、甲基丙基砜、二甲基亚砜、甲磺酸甲酯、甲磺酸乙酯、乙磺酸甲酯、乙磺酸乙酯、硫酸二甲酯、硫酸二乙酯和硫酸二丁酯。在一些实施例中，含硫有机溶剂的部分氢原子可被氟取代。
在一些实施例中，所述芳香族含氟溶剂包括，但不限于，以下中的一种或多种：氟苯、二氟苯、三氟苯、四氟苯、五氟苯、六氟苯和三氟甲基苯。
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-丁内酯及其组合。
在电解液中加入链状羧酸酯及/或环状羧酸酯后，链状羧酸酯及/或环状羧酸酯可在电极表面形成钝化膜，从而提高电化学装置的间歇充电循环后的容量保持率。在一些实施例中，所述电解液中含有1wt％至60wt％的链状羧酸酯、环状羧酸酯及其组合。在一些实施例中，所述电解液中含有丙酸乙酯、丙酸丙酯、γ-丁 内酯及其组合，基于电解液的总重量，该组合的含量为1wt％至60wt％、10wt％至60wt％、10wt％至50wt％、20wt％至50wt％。在一些实施例中，基于电解液的总重量，所述电解液中含有1wt％至60wt％、10wt％至60wt％、20wt％至50wt％、20wt％至40wt％或30wt％的丙酸丙酯。
添加剂
在一些实施例中，所述添加剂的实例可包括，但不限于，以下的一种或多种：氟代碳酸酯、含碳碳双键的碳酸乙烯酯、含硫氧双键的化合物和酸酐。
在一些实施例中，基于所述电解液的总重量，所述添加剂的含量为0.01wt％至15wt％、0.1wt％至10wt％或1wt％至5wt％。
根据本申请的实施例，基于所述电解液的总重量，所述丙酸酯的含量为所述添加剂的1.5至30倍、1.5至20倍、2至20倍或5-20倍。
在一些实施例中，所述添加剂包含一种或多种氟代碳酸酯。在锂离子电池充电/放电时，氟代碳酸酯可与丙酸酯共同作用以在负极的表面上形成稳定的保护膜，从而抑制电解液的分解反应。
在一些实施例中，所述氟代碳酸酯具有式C＝O(OR 1)(OR 2)，其中R 1和R 2各自选自具有1-6个碳原子的烷基或卤代烷基，其中R 1和R 2中的至少一者选自具有1-6个碳原子的氟代烷基，且R 1和R 2任选地连同其所连接的原子形成5元至7元环。
在一些实施例中，所述氟代碳酸酯的实例可包括，但不限于，以下的一种或多种：氟代碳酸乙烯酯、顺式4,4-二氟碳酸乙烯酯、反式4,4-二氟碳酸乙烯酯、4,5-二氟碳酸乙烯酯、4-氟-4-甲基碳酸乙烯酯、4-氟-5-甲基碳酸乙烯酯、碳酸三氟甲基甲酯、碳酸三氟乙基甲酯和碳酸乙基三氟乙酯等。
在一些实施例中，所述添加剂包含一种或多种含碳碳双键的碳酸乙烯酯。所述含碳碳双键的碳酸乙烯酯的实例可包括，但不限于，以下的一种或多种：碳酸亚乙烯酯、碳酸甲基亚乙烯酯、碳酸乙基亚乙烯酯、碳酸-1,2-二甲基亚乙烯酯、碳酸-1,2-二乙基亚乙烯酯、碳酸氟亚乙烯酯、碳酸三氟甲基亚乙烯酯；碳酸乙烯基亚乙酯、碳酸-1-甲基-2-乙烯基亚乙酯、碳酸-1-乙基-2-乙烯基亚乙酯、碳酸-1-正丙基-2-乙烯基亚乙酯、碳酸1-甲基-2-乙烯基亚乙酯、碳酸-1,1-二乙烯基亚乙酯、碳酸-1,2-二乙烯基亚乙酯、碳酸-1,1-二甲基-2-亚甲基亚乙酯和碳酸-1,1-二乙基-2-亚甲基亚乙酯等。在一些实施例中，所述含碳碳双键的碳酸乙烯酯包括碳 酸亚乙烯酯，其易于获得并可实现更为优异的效果。
在一些实施例中，所述添加剂包含一种或多种含硫氧双键的化合物。所述含硫氧双键的化合物的实例可包括，但不限于，以下的一种或多种：环状硫酸酯、链状硫酸酯、链状磺酸酯、环状磺酸酯、链状亚硫酸酯和环状亚硫酸酯等。
所述环状硫酸酯的实例可包括，但不限于，以下的一种或多种：1,2-乙二醇硫酸酯、1,2-丙二醇硫酸酯、1,3-丙二醇硫酸酯、1,2-丁二醇硫酸酯、1,3-丁二醇硫酸酯、1,4-丁二醇硫酸酯、1,2-戊二醇硫酸酯、1,3-戊二醇硫酸酯、1,4-戊二醇硫酸酯和1,5-戊二醇硫酸酯等。
所述链状硫酸酯的实例可包括，但不限于，以下的一种或多种：硫酸二甲酯、硫酸甲乙酯和硫酸二乙酯等。
所述链状磺酸酯的实例可包括，但不限于，以下的一种或多种：氟磺酸甲酯和氟磺酸乙酯等氟磺酸酯、甲磺酸甲酯、甲磺酸乙酯、二甲磺酸丁酯、2-(甲磺酰氧基)丙酸甲酯和2-(甲磺酰氧基)丙酸乙酯等。
所述环状磺酸酯的实例可包括，但不限于，以下的一种或多种：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、3-氟-1,3-丙磺酸内酯、1-甲基-1,3-丙磺酸内酯、2-甲基-1,3-丙磺酸内酯、3-甲基-1,3-丙磺酸内酯、1-丙烯-1,3-磺酸内酯、2-丙烯-1,3-磺酸内酯、1-氟-1-丙烯-1,3-磺酸内酯、2-氟-1-丙烯-1,3-磺酸内酯、3-氟-1-丙烯-1,3-磺酸内酯、1-氟-2-丙烯-1,3-磺酸内酯、2-氟-2-丙烯-1,3-磺酸内酯、3-氟-2-丙烯-1,3-磺酸内酯、1-甲基-1-丙烯-1,3-磺酸内酯、2-甲基-1-丙烯-1,3-磺酸内酯、3-甲基-1-丙烯-1,3-磺酸内酯、1-甲基-2-丙烯-1,3-磺酸内酯、2-甲基-2-丙烯-1,3-磺酸内酯、3-甲基-2-丙烯-1,3-磺酸内酯、1,4-丁磺酸内酯、1,5-戊磺酸内酯、甲烷二磺酸亚甲酯和甲烷二磺酸亚乙酯等。
所述链状亚硫酸酯的实例可包括，但不限于，以下的一种或多种：亚硫酸二甲酯、亚硫酸甲乙酯和亚硫酸二乙酯等。
所述环状亚硫酸酯的实例可包括，但不限于，以下的一种或多种：1,2-乙二醇亚硫酸酯、1,2-丙二醇亚硫酸酯、1,3-丙二醇亚硫酸酯、1,2-丁二醇亚硫酸酯、1,3-丁二醇亚硫酸酯、1,4-丁二醇亚硫酸酯、1,2-戊二醇亚硫酸酯、1,3-戊二醇亚硫酸酯、1,4-戊二醇亚硫酸酯和1,5-戊二醇亚硫酸酯等。
在一些实施例中，所述添加剂包含一种或多种酸酐。所述酸酐的实例可包括，但不限于，羧酸酐、二磺酸酐和羧酸磺酸酐中的一种或多种。所述羧酸酐的实例 可包括，但不限于，琥珀酸酐、戊二酸酐和马来酸酐中的一种或多种。所述二磺酸酐的实例可包括，但不限于，乙烷二磺酸酐和丙烷二磺酸酐中的一种或多种。所述羧酸磺酸酐的实例可包括，但不限于，磺基苯甲酸酐、磺基丙酸酐和磺基丁酸酐中的一种或多种。
在一些实施例中，所述添加剂为氟代碳酸酯与含碳碳双键的碳酸乙烯酯的组合。在一些实施例中，所述添加剂为氟代碳酸酯与含硫氧双键的化合物的组合。在一些实施例中，所述添加剂为氟代碳酸酯与具有2-4个氰基的化合物的组合。在一些实施例中，所述添加剂为氟代碳酸酯与环状羧酸酯的组合。在一些实施例中，所述添加剂为氟代碳酸酯与环状磷酸酐的组合。在一些实施例中，所述添加剂为氟代碳酸酯与羧酸酐的组合。在一些实施例中，所述添加剂为氟代碳酸酯与璜酸酐的组合。在一些实施例中，所述添加剂为氟代碳酸酯与羧酸璜酸酐的组合。
电解质
电解质没有特别限制，可以任意地使用作为电解质公知的物质。在锂二次电池的情况下，通常使用锂盐。电解质的实例可包括，但不限于，LiPF 6、LiBF 4、LiClO 4、LiAlF 4、LiSbF 6、LiTaF 6、LiWF 7等无机锂盐；LiWOF 5等钨酸锂类；HCO 2Li、CH 3CO 2Li、CH 2FCO 2Li、CHF 2CO 2Li、CF 3CO 2Li、CF 3CH 2CO 2Li、CF 3CF 2CO 2Li、CF 3CF 2CF 2CO 2Li、CF 3CF 2CF 2CF 2CO 2Li等羧酸锂盐类；FSO 3Li、CH 3SO 3Li、CH 2FSO 3Li、CHF 2SO 3Li、CF 3SO 3Li、CF 3CF 2SO 3Li、CF 3CF 2CF 2SO 3Li、CF 3CF 2CF 2CF 2SO 3Li等磺酸锂盐类；LiN(FCO) 2、LiN(FCO)(FSO 2)、LiN(FSO 2) 2、LiN(FSO 2)(CF 3SO 2)、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2、环状1,2-全氟乙烷双磺酰亚胺锂、环状1,3-全氟丙烷双磺酰亚胺锂、LiN(CF 3SO 2)(C 4F 9SO 2)等酰亚胺锂盐类；LiC(FSO 2) 3、LiC(CF 3SO 2) 3、LiC(C 2F 5SO 2) 3等甲基化锂盐类；双(丙二酸根合)硼酸锂盐、二氟(丙二酸根合)硼酸锂盐等(丙二酸根合)硼酸锂盐类；三(丙二酸根合)磷酸锂、二氟双(丙二酸根合)磷酸锂、四氟(丙二酸根合)磷酸锂等(丙二酸根合)磷酸锂盐类；以及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 3CF 3、LiBF 3C 2F 5、LiBF 3C 3F 7、LiBF 2(CF 3) 2、LiBF 2(C 2F 5) 2、LiBF 2(CF 3SO 2) 2、LiBF 2(C 2F 5SO 2) 2等含氟有机锂盐类；二氟草酸硼酸锂、双(草酸)硼酸锂等草酸硼酸锂盐类；四氟草酸根合磷酸锂、二氟双(草酸根合)磷酸锂、三(草酸根合)磷酸锂等草酸根合磷酸锂盐类等。
在一些实施例中，电解质选自LiPF 6、LiSbF 6、LiTaF 6、FSO 3Li、CF 3SO 3Li、 LiN(FSO 2) 2、LiN(FSO 2)(CF 3SO 2)、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2、环状1,2-全氟乙烷双磺酰亚胺锂、环状1,3-全氟丙烷双磺酰亚胺锂、LiC(FSO 2) 3、LiC(CF 3SO 2) 3、LiC(C 2F 5SO 2) 3、LiBF 3CF 3、LiBF 3C 2F 5、LiPF 3(CF 3) 3、LiPF 3(C 2F 5) 3、二氟草酸硼酸锂、双(草酸)硼酸锂或二氟双(草酸根合)磷酸锂，其有助于改善电化学装置的输出功率特性、高倍率充放电特性、高温保存特性和循环特性等。
电解质的含量没有特别限制，只要不损害本申请的效果即可。在一些实施例中，电解液中的锂的总摩尔浓度为大于0.3mol/L以上、大于0.4mol/L或大于0.5mol/L。在一些实施例中，电解液中的锂的总摩尔浓度为小于3mol/L、小于2.5mol/L或小于2.0mol/L以下。在一些实施例中，电解液中的锂的总摩尔浓度在上述任意两个数值所组成的范围内。当电解质浓度在上述范围内时，作为带电粒子的锂不会过少，并且可以使粘度处于适当的范围，因而容易确保良好的电导率。
当使用两种以上的电解质的情况下，电解质包括至少一种为选自由硼酸盐、草酸盐和氟磺酸盐组成的组中的盐。在一些实施例中，电解质包括选自由草酸盐和氟磺酸盐组成的组中的盐。在一些实施例中，电解质包括锂盐。在一些实施例中，基于电解质的总重量，选自由硼酸盐、草酸盐和氟磺酸盐组成的组中的盐的含量为大于0.01wt％或大于0.1wt％。在一些实施例中，基于电解质的总重量，选自由硼酸盐、草酸盐和氟磺酸盐组成的组中的盐的含量为小于20wt％或小于10wt％。在一些实施例中，选自由硼酸盐、草酸盐和氟磺酸盐组成的组中的盐的含量在上述任意两个数值所组成的范围内。
在一些实施例中，电解质包含选自由硼酸盐、草酸盐和氟磺酸盐组成的组中的一种以上物质和除此以外的一种以上的盐。作为除此以外的盐，可以举出在上文中例示的锂盐，在一些实施例中为LiPF 6、LiN(FSO 2)(CF 3SO 2)、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2、环状1,2-全氟乙烷双磺酰亚胺锂、环状1,3-全氟丙烷双磺酰亚胺锂、LiC(FSO 2) 3、LiC(CF 3SO 2) 3、LiC(C 2F 5SO 2) 3、LiBF 3CF 3、LiBF 3C 2F 5、LiPF 3(CF 3) 3、LiPF 3(C 2F 5) 3。在一些实施例中，除此以外的盐为LiPF 6。
在一些实施例中，基于电解质的总重量，除此以外的盐的含量为大于0.01wt％或大于0.1wt％。在一些实施例中，基于电解质的总重量，除此以外的盐的含量为小于20wt％、小于15wt％或小于10wt％。在一些实施例中，除此以外的盐的含量在上述任意两个数值所组成的范围内。具有上述含量的除此以外的盐 有助于平衡电解液的电导率和粘度。
在电解液中，除了含有上述溶剂、添加剂和电解质盐以外，可以根据需要含有负极被膜形成剂、正极保护剂、防过充电剂等额外添加剂。作为添加剂，可使用一般在非水电解质二次电池中使用的添加剂，其实例可包括，但不限于，碳酸亚乙烯酯、琥珀酸酐、联苯、环己基苯、2,4-二氟苯甲醚、丙烷磺内酯、丙烯磺内酯等。这些添加剂可以单独使用或任意组合使用。另外，电解液中的这些添加剂的含量没有特别限制，可以根据该添加剂的种类等适当地设定即可。在一些实施例中，基于电解液的总重量，添加剂的含量为小于5wt％、在0.01wt％至5wt％的范围内或在0.2wt％至5wt％的范围内。
III、正极
正极包括正极集流体和设置在所述正极集流体的一个或两个表面上的正极合剂层。
1、正极合剂层
正极合剂层包含正极活性物质层，所述正极活性物质层包含正极活性物质。所述正极活性物质层可以是一层或多层。多层正极活性物质中的每层可以包含相同或不同的正极活性物质。正极活性物质为任何能够可逆地嵌入和脱嵌锂离子等金属离子的物质。
正极活性物质的种类没有特别限制，只要是能够以电化学方式吸藏和释放金属离子(例如，锂离子)即可。在一些实施例中，正极活性物质为含有锂和至少一种过渡金属的物质。正极活性物质的实例可包括，但不限于，锂过渡金属复合氧化物和含锂过渡金属磷酸化合物。
在一些实施例中，锂过渡金属复合氧化物中的过渡金属包括V、Ti、Cr、Mn、Fe、Co、Ni、Cu等。在一些实施例中，锂过渡金属复合氧化物包括LiCoO 2等锂钴复合氧化物、LiNiO 2等锂镍复合氧化物、LiMnO 2、LiMn 2O 4、Li 2MnO 4等锂锰复合氧化物、LiNi 1/3Mn 1/3Co 1/3O 2、LiNi 0.5Mn 0.3Co 0.2O 2等锂镍锰钴复合氧化物，其中作为这些锂过渡金属复合氧化物的主体的过渡金属原子的一部分被Na、K、B、F、Al、Ti、V、Cr、Mn、Fe、Co、Li、Ni、Cu、Zn、Mg、Ga、Zr、Si、Nb、Mo、Sn、W等其它元素所取代。锂过渡金属复合氧化物的实例可包括，但不限于，LiNi 0.5Mn 0.5O 2、LiNi 0.85Co 0.10Al 0.05O 2、LiNi 0.33Co 0.33Mn 0.33O 2、LiNi 0.45Co 0.10Al 0.45O 2、LiMn 1.8Al 0.2O 4和LiMn 1.5Ni 0.5O 4等。锂过渡金属复合氧化 物的组合的实例包括，但不限于，LiCoO 2与LiMn 2O 4的组合，其中LiMn 2O 4中的一部分Mn可被过渡金属所取代(例如，LiNi 0.33Co 0.33Mn 0.33O 2)，LiCoO 2中的一部分Co可被过渡金属所取代。
在一些实施例中，含锂过渡金属磷酸化合物中的过渡金属包括V、Ti、Cr、Mn、Fe、Co、Ni、Cu等。在一些实施例中，含锂过渡金属磷酸化合物包括LiFePO 4、Li 3Fe 2(PO 4) 3、LiFeP 2O 7等磷酸铁类、LiCoPO 4等磷酸钴类，其中作为这些锂过渡金属磷酸化合物的主体的过渡金属原子的一部分被Al、Ti、V、Cr、Mn、Fe、Co、Li、Ni、Cu、Zn、Mg、Ga、Zr、Nb、Si等其它元素所取代。
在一些实施例中，正极活性物质中包含磷酸锂，其可提高电化学装置的连续充电特性。磷酸锂的使用没有限制。在一些实施例中，正极活性物质和磷酸锂混合使用。在一些实施例中，相对于上述正极活性物质与磷酸锂的总重量，磷酸锂的含量为大于0.1wt％、大于0.3wt％或大于0.5wt％。在一些实施例中，相对于上述正极活性物质与磷酸锂的总重量，磷酸锂的含量为小于10wt％、小于8wt％或小于5wt％。在一些实施例中，磷酸锂的含量在上述任意两个数值所组成的范围内。
表面被覆
在上述正极活性物质的表面可附着有与其组成不同的物质。表面附着物质的实例可包括，但不限于，氧化铝、二氧化硅、二氧化钛、氧化锆、氧化镁、氧化钙、氧化硼、氧化锑、氧化铋等氧化物、硫酸锂、硫酸钠、硫酸钾、硫酸镁、硫酸钙、硫酸铝等硫酸盐、碳酸锂、碳酸钙、碳酸镁等碳酸盐、碳等。
这些表面附着物质可以通过下述方法附着于正极活性物质表面：使表面附着物质溶解或悬浮于溶剂中而渗入添加到该正极活性物质中并进行干燥的方法；使表面附着物质前体溶解或悬浮于溶剂中，在渗入添加到该正极活性物质中后，利用加热等使其反应的方法；以及添加到正极活性物质前体中同时进行烧制的方法等等。在附着碳的情况下，还可以使用将碳材料(例如，活性炭等)进行机械附着的方法。
在一些实施例中，基于正极合剂层的总重量，表面附着物质的含量为大于0.1ppm、大于1ppm或大于10ppm。在一些实施例中，基于正极合剂层的总重量，表面附着物质的含量为小于20％、小于10％或小于10％。在一些实施例中，基于正极合剂层的总重量，表面附着物质的含量在上述任意两个数值所组成的范 围内。
通过在正极活性物质表面附着物质，可以抑制正极活性物质表面的电解液的氧化反应，可以提高电化学装置的寿命。当表面附着物质的量过少时，其效果无法充分表现；当表面附着物质的量过多时，会阻碍锂离子的出入，因而电阻有时会增加。
本申请中，将在正极活性物质的表面附着有与其组成不同的物质的正极活性物质也称为“正极活性物质”。
形状
在一些实施例中，正极活性物质颗粒的形状包括，但不限于，块状、多面体状、球状、椭圆球状、板状、针状和柱状等。在一些实施例中，正极活性物质颗粒包括一次颗粒、二次颗粒或其组合。在一些实施例中，一次颗粒可以凝集而形成二次颗粒。
振实密度
在一些实施例中，正极活性物质的振实密度为大于0.5g/cm 3、大于0.8g/cm 3或大于1.0g/cm 3。当正极活性物质的振实密度在上述范围内时，可以抑制正极合剂层形成时所需要的分散介质量及导电材料和正极粘合剂的所需量，由此可以确保正极活性物质的填充率和电化学装置的容量。通过使用振实密度高的复合氧化物粉体，可以形成高密度的正极合剂层。振实密度通常越大越优选，没有特别的上限。在一些实施例中，正极活性物质的振实密度为小于4.0g/cm 3、小于3.7g/cm 3或小于3.5g/cm 3。当正极活性物质的振实密度的具有如上所述的上限时，可以抑制负荷特性的降低。
正极活性物质的振实密度可通过以下方式计算：将5g至10g的正极活性物质粉体放入10mL的玻璃制量筒中，进行200次冲程20mm的振动，得出粉体填充密度(振实密度)。
中值粒径(D50)
当正极活性物质颗粒为一次颗粒时，正极活性物质颗粒的中值粒径(D50)指的是正极活性物质颗粒一次粒径。当正极活性物质颗粒的一次颗粒凝集而形成二次颗粒时，正极活性物质颗粒的中值粒径(D50)指的是正极活性物质颗粒二次粒径。
在一些实施例中，正极活性物质颗粒的中值粒径(D50)为大于0.3μm、大 于0.5μm、大于0.8μm或大于1.0μm。在一些实施例中，正极活性物质颗粒的中值粒径(D50)为小于30μm、小于27μm、小于25μm或小于22μm。在一些实施例中，正极活性物质颗粒的中值粒径(D50)在上述任意两个数值所组成的范围内。当正极活性物质颗粒的中值粒径(D50)在上述范围内时，可得到高振实密度的正极活性物质，可以抑制电化学装置性能的降低。另一方面，在电化学装置的正极的制备过程中(即，将正极活性物质、导电材料和粘结剂等用溶剂浆料化而以薄膜状涂布时)，可以防止条纹产生等问题。此处，通过将具有不同中值粒径的两种以上的正极活性物质进行混合，可以进一步提高正极制备时的填充性。
正极活性物质颗粒中值粒径(D50)可利用激光衍射/散射式粒度分布测定装置测定：在使用HORIBA社制造的LA-920作为粒度分布计的情况下，使用0.1wt％六偏磷酸钠水溶液作为测定时使用的分散介质，在5分钟的超声波分散后将测定折射率设定为1.24而进行测定。
平均一次粒径
在正极活性物质颗粒的一次颗粒凝集而形成二次颗粒的情况下，在一些实施例中，正极活性物质的平均一次粒径为大于0.05μm、大于0.1μm或大于0.5μm。在一些实施例中，正极活性物质的平均一次粒径为小于5μm、小于4μm、小于3μm或小于2μm。在一些实施例中，正极活性物质的平均一次粒径在上述任意两个数值所组成的范围内。当正极活性物质的平均一次粒径在上述范围内时，可以确保粉体填充性和比表面积、抑制电池性能的降低、并得到适度的结晶性，由此可以确保电化学装置充放电的可逆性。
正极活性物质的平均一次粒径可通过对扫描电子显微镜(SEM)得到的图像进行观察而得出：在倍率为10000倍的SEM图像中，对于任意50个一次颗粒，求出由相对于水平方向直线的一次颗粒的左右边界线所得到的切片的最长值，求出其平均值，由此得到平均一次粒径。
比表面积(BET)
在一些实施例中，正极活性物质的比表面积(BET)为大于0.1m 2/g、大于0.2m 2/g或大于0.3m 2/g。在一些实施例中，正极活性物质的比表面积(BET)为小于50m 2/g、小于40m 2/g或小于30m 2/g。在一些实施例中，正极活性物质的比表面积(BET)在上述任意两个数值所组成的范围内。当正极活性物质的比表面 积(BET)在上述范围内时，可以确保电化学装置的性能，同时可以使正极活性物质具有良好的涂布性。
正极活性物质的比表面积(BET)可通过如下方法测量：使用表面积计(例如，大仓理研制造的全自动表面积测定装置)，在氮气流通下于150℃对试样进行30分钟预干燥，然后使用氮气相对于大气压的相对压力值准确调节为0.3的氮氦混合气体，通过采用气体流动法的氮吸附BET单点法进行测定。
正极导电材料
正极导电材料的种类没有限制，可以使用任何已知的导电材料。正极导电材料的实例可包括，但不限于，天然石墨、人造石墨等石墨；乙炔黑等炭黑；针状焦等无定形碳等碳材料；碳纳米管；石墨烯等。上述正极导电材料可单独使用或任意组合使用。
在一些实施例中，基于正极合剂层的总重量，正极导电材料的含量为大于0.01wt％、大于0.1wt％或大于1wt％。在一些实施例中，基于正极合剂层的总重量，正极导电材料的含量为小于50wt％、小于30wt％以下或小于15wt％。当正极导电材料的含量在上述范围内时，可以确保充分的导电性和电化学装置的容量。
正极粘结剂
正极合剂层的制造中使用的正极粘结剂的种类没有特别限制，在涂布法的情况下，只要是在电极制造时使用的液体介质中可溶解或分散的材料即可。正极粘结剂的实例可包括，但不限于，以下中的一种或多种：聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯、聚甲基丙烯酸甲酯、聚酰亚胺、芳香族聚酰胺、纤维素、硝酸纤维素等树脂系高分子；丁苯橡胶(SBR)、丁腈橡胶(NBR)、氟橡胶、异戊二烯橡胶、聚丁橡胶、乙烯-丙烯橡胶等橡胶状高分子；苯乙烯·丁二烯·苯乙烯嵌段共聚物或其氢化物、乙烯·丙烯·二烯三元共聚物(EPDM)、苯乙烯·乙烯·丁二烯·乙烯共聚物、苯乙烯·异戊二烯·苯乙烯嵌段共聚物或其氢化物等热塑性弹性体状高分子；间规-1,2-聚丁二烯、聚乙酸乙烯酯、乙烯·乙酸乙烯酯共聚物、丙烯·α-烯烃共聚物等软质树脂状高分子；聚偏二氟乙烯(PVDF)、聚四氟乙烯、氟化聚偏二氟乙烯、聚四氟乙烯·乙烯共聚物等氟系高分子；具有碱金属离子(特别是锂离子)的离子传导性的高分子组合物等。上述正极粘结剂可单独使用或任意组合使用。
在一些实施例中，基于正极合剂层的总重量，正极粘结剂的含量为大于0.1wt％、大于1wt％或大于1.5wt％。在一些实施例中，基于正极合剂层的总重量，正极粘结剂的含量为小于80wt％、小于60wt％、小于40wt％或小于10wt％。当正极粘结剂的含量在上述范围内时，可使正极具有良好的导电性和足够的机械强度，并保证电化学装置的容量。
溶剂
用于形成正极浆料的溶剂的种类没有限制，只要是能够溶解或分散正极活性物质、导电材料、正极粘合剂和根据需要使用的增稠剂的溶剂即可。用于形成正极浆料的溶剂的实例可包括水系溶剂和有机系溶剂中的任一种。水系介质的实例可包括，但不限于，水和醇与水的混合介质等。有机系介质的实例可包括，但不限于，己烷等脂肪族烃类；苯、甲苯、二甲苯、甲基萘等芳香族烃类；喹啉、吡啶等杂环化合物；丙酮、甲基乙基酮、环己酮等酮类；乙酸甲酯、丙烯酸甲酯等酯类；二亚乙基三胺、N,N-二甲氨基丙胺等胺类；二乙醚、环氧丙烷、四氢呋喃(THF)等醚类；N-甲基吡咯烷酮(NMP)、二甲基甲酰胺、二甲基乙酰胺等酰胺类；六甲基磷酰胺、二甲基亚砜等非质子性极性溶剂等。
增稠剂
增稠剂通常是为了调节浆料的粘度而使用的。在使用水系介质的情况下，可使用增稠剂和丁苯橡胶(SBR)乳液进行浆料化。增稠剂的种类没有特别限制，其实例可包括，但不限于，羧甲基纤维素、甲基纤维素、羟甲基纤维素、乙基纤维素、聚乙烯醇、氧化淀粉、磷酸化淀粉、酪蛋白和它们的盐等。上述增稠剂可单独使用或任意组合使用。
在一些实施例中，基于正极合剂层的总重量，增稠剂的含量为大于0.1wt％、大于0.2wt％或大于0.3wt％。在一些实施例中，基于正极合剂层的总重量，增稠剂的含量为小于5wt％、小于3wt％或小于2wt％。在一些实施例中，基于正极合剂层的总重量，增稠剂的含量在上述任意两个数值所组成的范围内。当增稠剂的含量在上述范围内时，可使正极浆料具有良好的涂布性，同时可以抑制电化学装置的容量降低及电阻增大。
正极活性物质的含量
在一些实施例中，基于正极合剂层的总重量，正极活性物质的含量为大于80wt％、大于82wt％或大于84wt％。在一些实施例中，基于正极合剂层的总重量， 正极活性物质的含量为小于99wt％或小于98wt％。在一些实施例中，基于正极合剂层的总重量，正极活性物质的含量在上述任意两个数组所组成的范围内。当正极活性物质的含量在上述范围内时，可以确保正极合剂层中的正极活性物质的电容量，同时可以保持正极的强度。
正极活性物质的密度
对于通过涂布、干燥而得到的正极合剂层，为了提高正极活性物质的填充密度，可通过手动压机或辊压机等进行压紧处理。在一些实施例中，正极合剂层的密度为大于1.5g/cm 3、大于2g/cm 3或大于2.2g/cm 3。在一些实施例中，正极合剂层的密度为小于5g/cm 3、小于4.5g/cm 3或小于4g/cm 3。在一些实施例中，正极合剂层的密度在上述任意两个数值所组成的范围内。当正极合剂层的密度在上述范围内时，可使电化学装置具有良好的充放电特性，同时可以抑制电阻的增大。
正极合剂层的厚度
正极合剂层的厚度是指正极合剂层在正极集流体的任意一侧上的厚度。在一些实施例中，正极合剂层的厚度为大于10μm或大于20μm。在一些实施例中，正极合剂层的厚度为小于500μm或小于450μm。
正极活性物质的制造法
正极活性物质可使用制造无机化合物的常用方法来制造。为了制作球状或椭圆球状的正极活性物质，可采用以下制造方法：将过渡金属的原料物质溶解或粉碎分散于水等溶剂中，边搅拌边调节pH，制作球状的前体并回收，根据需要对其进行干燥后，加入LiOH、Li 2CO 3、LiNO 3等Li源，在高温下进行烧制，得到正极活性物质。
2、正极集流体
正极集流体的种类没有特别限制，其可为任何已知适于用作正极集流体的材质。正极集流体的实例可包括，但不限于，铝、不锈钢、镍镀层、钛、钽等金属材料；碳布、碳纸等碳材料。在一些实施例中，正极集流体为金属材料。在一些实施例中，正极集流体为铝。
正极集流体的形式没有特别限制。当正极集流体为金属材料时，正极集流体的形式可包括，但不限于，金属箔、金属圆柱、金属带卷、金属板、金属薄膜、金属板网、冲压金属、发泡金属等。当正极集流体为碳材料时，正极集流体的形式可包括，但不限于，碳板、碳薄膜、碳圆柱等。在一些实施例中，正极集流体 为金属薄膜。在一些实施例中，所述金属薄膜为网状。所述金属薄膜的厚度没有特别限制。在一些实施例中，所述金属薄膜的厚度为大于1μm、大于3μm或大于5μm。在一些实施例中，所述金属薄膜的厚度为小于1mm、小于100μm或小于50μm。在一些实施例中，所述金属薄膜的厚度在上述任意两个数值所组成的范围内。
为了降低正极集流体和正极合剂层的电子接触电阻，正极集流体的表面可包括导电助剂。导电助剂的实例可包括，但不限于，碳和金、铂、银等贵金属类。
正极集流体与正极合剂层的厚度比是指注入电解液前的单面的正极合剂层的厚度与正极集流体的厚度的比率，其数值没有特别限制。在一些实施例中，正极集流体与正极合剂层的厚度比为小于20、小于15或小于10。在一些实施例中，正极集流体与正极合剂层的厚度比为大于0.5、大于0.8或大于1。在一些实施例中，正极集流体与正极合剂层的厚度比在上述任意两个数值所组成的范围内。当正极集流体与正极合剂层的厚度比在上述范围内时，可以抑制高电流密度充放电时的正极集流体的放热，可以确保电化学装置的容量。
3、正极的构成和制作法
正极可以通过在集流体上形成含有正极活性物质和粘活性物质的正极合剂层来制作。使用正极活性物质的正极的制造可以通过常规方法来进行，即，将正极活性物质和粘活性物质、以及根据需要的导电材料和增稠剂等进行干式混合，制成片状，将所得到的片状物压接至正极集流体上；或者将这些材料溶解或分散于液体介质中而制成浆料，将该浆料涂布到正极集流体上并进行干燥，从而在集流体上形成正极合剂层，由此可以得到正极。
IV、隔离膜
为了防止短路，在正极与负极之间通常设置有隔离膜。这种情况下，本申请的电解液通常渗入该隔离膜而使用。
对隔离膜的材料及形状没有特别限制，只要不显著损害本申请的效果即可。所述隔离膜可为由对本申请的电解液稳定的材料所形成的树脂、玻璃纤维、无机物等。在一些实施例中，所述隔离膜包括保液性优异的多孔性片或无纺布状形态的物质等。树脂或玻璃纤维隔离膜的材料的实例可包括，但不限于，聚烯烃、芳香族聚酰胺、聚四氟乙烯、聚醚砜、玻璃过滤器等。在一些实施例中，所述隔离膜的材料为玻璃过滤器。在一些实施例中，所述聚烯烃为聚乙烯或聚丙烯。在一 些实施例中，所述聚烯烃为聚丙烯。上述隔离膜的材料可以单独使用或任意组合使用。
所述隔离膜还可为上述材料层积而成的材料，其实例包括，但不限于，按照聚丙烯、聚乙烯、聚丙烯的顺序层积而成的三层隔离膜等。
无机物的材料的实例可包括，但不限于，氧化铝、二氧化硅等氧化物、氮化铝、氮化硅等氮化物、硫酸盐(例如，硫酸钡、硫酸钙等)。无机物的形式可包括，但不限于，颗粒状或纤维状。
所述隔离膜的形态可为薄膜形态，其实例包括，但不限于，无纺布、织布、微多孔性膜等。在薄膜形态中，所述隔离膜的孔径为0.01μm至1μm，厚度为5μm至50μm。除了上述独立的薄膜状隔离膜以外，还可以使用下述隔离膜：通过使用树脂类的粘合剂在正极和/或负极的表面形成含有上述无机物颗粒的复合多孔层而形成的隔离膜，例如，将氟树脂作为粘合剂使90％粒径小于1μm的氧化铝颗粒在正极的两面形成多孔层而形成的隔离膜。
所述隔离膜的厚度是任意的。在一些实施例中，所述隔离膜的厚度为大于1μm、大于5μm或大于8μm。在一些实施例中，所述隔离膜的厚度为小于50μm、小于40μm或小于30μm。在一些实施例中，所述隔离膜的厚度在上述任意两个数值所组成的范围内。当所述隔离膜的厚度在上述范围内时，则可以确保绝缘性和机械强度，并可以确保电化学装置的倍率特性和能量密度。
在使用多孔性片或无纺布等多孔质材料作为隔离膜时，隔离膜的孔隙率是任意的。在一些实施例中，所述隔离膜的孔隙率为大于20％、大于35％或大于45％。在一些实施例中，所述隔离膜的孔隙率为小于90％、小于85％或小于75％。在一些实施例中，所述隔离膜的孔隙率在上述任意两个数值所组成的范围内。当所述隔离膜的孔隙率在上述范围内时，可以确保绝缘性和机械强度，并可以抑制膜电阻，使电化学装置具有良好的倍率特性。
所述隔离膜的平均孔径也是任意的。在一些实施例中，所述隔离膜的平均孔径为小于0.5μm或小于0.2μm。在一些实施例中，所述隔离膜的平均孔径为大于0.05μm。在一些实施例中，所述隔离膜的平均孔径在上述任意两个数值所组成的范围内。若所述隔离膜的平均孔径超过上述范围，则容易发生短路。当隔离膜的平均孔径在上述范围内时，在防止短路的同时可抑制了膜电阻，使电化学装置具有良好的倍率特性。
V、电化学装置组件
电化学装置组件包括电极组、集电结构、外装壳体和保护元件。
电极组
电极组可以是由上述正极和负极隔着上述隔离膜层积而成的层积结构、以及上述正极和负极隔着上述隔离膜以漩涡状卷绕而成的结构中的任一种。在一些实施例中，电极组的质量在电池内容积中所占的比例(电极组占有率)为大于40％或大于50％。在一些实施例中，电极组占有率为小于90％或小于80％。在一些实施例中，电极组占有率在上述任意两个数值所组成的范围内。当电极组占有率在上述范围内时，可以确保电化学装置的容量，同时可以抑制与内部压力上升相伴的反复充放电性能及高温保存等特性的降低，进而可以防止气体释放阀的工作。
集电结构
集电结构没有特别限制。在一些实施例中，集电结构为降低配线部分及接合部分的电阻的结构。当电极组为上述层积结构时，适合使用将各电极层的金属芯部分捆成束而焊接至端子上所形成的结构。一片的电极面积增大时，内部电阻增大，因而在电极内设置2个以上的端子而降低电阻也是适合使用的。当电极组为上述卷绕结构时，通过在正极和负极分别设置2个以上的引线结构，并在端子上捆成束，从而可以降低内部电阻。
外装壳体
外装壳体的材质没有特别限制，只要是对于所使用的电解液稳定的物质即可。外装壳体可使用，但不限于，镀镍钢板、不锈钢、铝或铝合金、镁合金等金属类、或者树脂与铝箔的层积膜。在一些实施例中，外装壳体为铝或铝合金的金属或层积膜。
金属类的外装壳体包括，但不限于，通过激光焊接、电阻焊接、超声波焊接将金属彼此熔敷而形成的封装密闭结构；或者隔着树脂制垫片使用上述金属类形成的铆接结构。使用上述层积膜的外装壳体包括，但不限于，通过将树脂层彼此热粘而形成的封装密闭结构等。为了提高密封性，还可以在上述树脂层之间夹入与层积膜中所用的树脂不同的树脂。在通过集电端子将树脂层热粘而形成密闭结构时，由于金属与树脂的接合，可使用具有极性基团的树脂或导入了极性基团的改性树脂作为夹入的树脂。另外，外装体的形状也是任意的，例如可以为圆筒形、 方形、层积型、纽扣型、大型等中的任一种。
保护元件
保护元件可以使用在异常放热或过大电流流过时电阻增大的正温度系数(PTC)、温度熔断器、热敏电阻、在异常放热时通过使电池内部压力或内部温度急剧上升而切断在电路中流过的电流的阀(电流切断阀)等。上述保护元件可选择在高电流的常规使用中不工作的条件的元件，亦可设计成即使不存在保护元件也不至于发生异常放热或热失控的形式。
VI、应用
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。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。
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。在一些实施例中，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、丁苯橡胶和羧甲基纤维素钠按照96％:2％:2％的质量比例与去离子水混合、再加入2000ppm助剂，搅拌均匀，得到负极浆料。将该负极浆料 涂布在12μm的铜箔上。干燥，冷压，再经过裁片、焊接极耳，得到负极。根据以下实施例和对比例的条件设置负极，使其具有相应参数。
以下实施例中所使用的助剂如下所示：
  名称(商品名)
助剂1 三硅氧烷表面活性剂(CAS No.3390-61-2；28855-11-0)
助剂2 有机硅表面活性剂(Sylgard 309)
助剂3 二羟基聚二甲基硅氧烷(PMX-0156)
助剂4 N-β-氨乙基-Y-氨丙基二甲氧基甲基硅烷(KH-602)
助剂5 甲基硅油聚二甲基硅氧烷(CAS No.63148-62-9)
2、正极的制备
将钴酸锂(LiCoO 2)、导电材料(Super-P)和聚偏氟乙烯(PVDF)按照95％:2％:3％的质量比例与N-甲基吡咯烷酮(NMP)混合，搅拌均匀，得到正极浆料。将该正极浆料涂布在12μm的铝箔上，干燥，冷压，再经过裁片、焊接极耳，得到正极。
3、电解液的制备
在干燥氩气环境下，将EC、PC和DEC(重量比1：1：1)混合，加入LiPF 6混合均匀，形成基础电解液，其中LiPF 6的浓度为1.15mol/L。在基础电解液中加入不同含量添加剂得到不同实施例和对比例的电解液。
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
将得到的正极、隔离膜和负极按次序卷绕，置于外包装箔中，留下注液口。从注液口灌注电解液，封装，再经过化成、容量等工序制得锂离子电池。
二、测试方法
1、负极合剂层的析锂面积的测试方法
在12℃下，将锂离子电池以1C恒流充电至4.45V，然后恒压充电至电流为0.05C，再以1C恒流放电至3.0V，此为首次循环。按照上述条件对锂离子电池进行100次循环。通过以下方法获得负极合剂层的析锂面积：拿到满充电池，拆解后获得负极极片，金黄色为正常区域，白色为析锂区域，利用高倍(20倍以上)显微镜拍照后，对不同区域进行分析，把白色区域抽象为圆形，利用灰度差对析锂区域进行统计，获得析锂面积。
2、锂离子电池的极片厚度膨胀率的测试方法
在12℃下，将锂离子电池以1C恒流充电至4.45V，然后恒压充电至电流为0.05C，再以1C恒流放电至3.0V，此为首次循环。按照上述条件对锂离子电池进行20次循环。用千分尺测试循环前和循环后的极片厚度。通过下式计算极片厚度膨胀率：
极片厚度膨胀率＝[(循环后厚度-循环前厚度)/循环前厚度]×100％。
3、锂离子电池的厚度膨胀率的测试方法
在12℃下，将锂离子电池以1C恒流充电至4.45V，然后恒压充电至电流为0.05C，再以1C恒流放电至3.0V，此为首次循环。按照上述条件对锂离子电池进行20次循环。用高度规测试循环前和循环后的电池厚度。通过下式计算厚度膨胀率：
厚度膨胀率＝[(循环后厚度-循环前厚度)/循环前厚度]×100％。
4、锂离子电池的低温存储性能的测试方法
在0℃下，将锂离子电池以1C恒流充电至4.45V，然后恒压充电至电流为0.05C，再以1C恒流放电至3.0V，此为首次循环。按照上述条件对锂离子电池进行20次循环。通过下式计算锂离子电池的低温容量保持率：
低温容量保持率＝[(循环后容量-循环前容量)循环前容量]×100％。
5、锂离子电池高温存储厚度膨胀率的测试方法
在25℃下，将锂离子电池静置30分钟，然后以0.5C倍率恒流充电至4.45V，再在4.45V下恒压充电至0.05C，静置5分钟，测量厚度。在60℃下存储21天后测量电池的厚度。通过下式计算锂离子电池的高温存储厚度膨胀率：
高温存储厚度膨胀率＝[(存储后厚度-存储前厚度)/存储前厚度]×100％。
三、测试结果
表1展示了各实施例和对比例的负极合剂层的析锂面积及电解液中的组分，以及锂离子电池的极片厚度膨胀率和电池厚度膨胀率。表1实施例使用助剂1。
表1
Figure PCTCN2019128445-appb-000013
Figure PCTCN2019128445-appb-000014
如对比例1所示，当负极合剂层的析锂面积大于2％且电解液不含具有磷和氧的化合物时，锂离子电池的极片厚度膨胀率和电池厚度膨胀率较高。如对比例2所示，当负极合剂层的析锂面积为2％但电解液不含具有磷和氧的化合物时，锂离子电池的极片厚度膨胀率和电池厚度膨胀率依然较高。如实施例1-9所示，当负极合剂层的析锂面积为2％以下且电解液含具有磷和氧的化合物时，具有磷和氧的化合物可有效改善负极合剂层的界面稳定性，从而使锂离子电池的极片厚度膨胀率和电池厚度膨胀率显著下降，提高锂离子电池的安全性能。
表2展示了负极合剂层中碳材料的特性对锂离子电池的极片厚度膨胀率和电池厚度膨胀率的影响。除表2中所列参数，实施例10-20的其他设置与实施例9相同，都使用助剂1。
表2
Figure PCTCN2019128445-appb-000015
如表2所示，负极合剂层中的碳材料具有以下特性：比表面积小于5m 2/g；中值粒径为5μm至30μm；和/或表面具有无定形碳。当负极合剂层中的碳材料具有以上特性时，锂离子电池的极片厚度膨胀率和电池厚度膨胀率进一步显著降 低。
表3展示了负极合剂层的特性对锂离子电池的极片厚度膨胀率和电池厚度膨胀率的影响。除表3中所列参数，实施例21-32的其他设置与实施例8相同，都使用助剂1。
表3
Figure PCTCN2019128445-appb-000016
如实施例8和21-32所示，负极合剂层具有以下特性：厚度不大于200μm；具有10％至60％的孔隙率；和/或砸球高度(即，当直径15mm、重量12克的球落到所述负极合剂层上时，使所述负极合剂层产生裂纹的球的最小高度)为50cm以上。当负极合剂层具有以上特性时，锂离子电池的极片厚度膨胀率和电池厚度膨胀率显著降低。
表4展示了负极合剂层中的助剂对锂离子电池的低温容量保持率和高温存储厚度膨胀率的影响。表4中的实施例33-40与实施例9的区别仅在于助剂种类及含量不同。
表4
Figure PCTCN2019128445-appb-000017
Figure PCTCN2019128445-appb-000018
结果表明，所使用的助剂种类只要能够使负极合剂层表面的析锂面积为2％以下即可。当助剂的含量占负极合剂层的总重量的3000ppm以下，可进一步提高负极合剂层的界面稳定性，由此改善锂离子电池的低温容量保持率和/或高温存储厚度膨胀率，从而改善锂离子电池的存储性能。
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：“在一些实施例中”、“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。

Claims (10)

  1. 一种电化学装置，包括：
    正极；
    电解液；和
    负极，
    其中：
    所述电解液包含具有磷和氧的化合物，并且
    所述负极包括负极集流体和形成在所述负极集流体上的负极合剂层，在100次充放电循环后，基于所述负极合剂层的总表面积，所述负极合剂层表面的析锂面积为2％以下。
  2. 根据权利要求1所述的电化学装置，其中所述电解液包含以下化合物中的至少一种：
    (a)单氟磷酸锂；
    (b)二氟磷酸锂；
    (c)磷酸酯；
    (d)磷酸环酐；或
    (e)式1化合物：
    Figure PCTCN2019128445-appb-100001
    其中R为取代或未取代的C 1-C 10烃基，且当取代时，取代基为卤素。
  3. 根据权利要求2所述的电化学装置，其中所述电解液包含所述式1化合物，且所述式1化合物包含以下结构式中的至少一种：
    Figure PCTCN2019128445-appb-100002
    Figure PCTCN2019128445-appb-100003
  4. 根据权利要求2所述的电化学装置，其中所述电解液包含磷酸酯，且所述磷酸酯具有式2：
    Figure PCTCN2019128445-appb-100004
    其中，X是具有1至5个碳原子的直链或非直链烷基或者-SiR 2R 3R 4，其中R 2、R 3和R 4各自独立地是具有1至5个碳原子的烷基，并且
    R 1是具有2至3个碳原子且被选自以下的取代基取代的亚烷基：至少一个氟原子或含至少一个氟原子且具有1至3个碳原子的烷基。
  5. 根据权利要求1所述的电化学装置，其中基于所述电解液的总重量，所述具有磷和氧的化合物的含量为0.001wt％至10wt％。
  6. 根据权利要求1所述的电化学装置，其中所述负极合剂层包括碳材料，所述碳材料具有以下特征中的至少一者：
    (a)小于5m 2/g的比表面积；
    (b)5μm至30μm的中值粒径；
    (c)表面具有无定形碳。
  7. 根据权利要求1所述的电化学装置，其中所述负极合剂层具有以下特征中的至少一者：
    (a)厚度不大于200μm；
    (b)具有10％至60％的孔隙率；
    (c)当直径15mm、重量12克的球落到所述负极合剂层上时，使所述负极合剂层产生裂纹的球的最小高度为50cm以上。
  8. 根据权利要求1所述的电化学装置，其中所述负极合剂层包括助剂，所述助剂具有以下特征中的至少一者：
    (a)包括聚醚硅氧烷；
    (b)氧化电位不小于4.5V，且还原电位不大于0.5V；
    (c)含0.1wt％所述助剂的水溶液的表面张力不大于30mN/m。
  9. 根据权利要求1所述的电化学装置，其中基于所述负极合剂层的总重量，所述助剂的含量为3000ppm以下。
  10. 一种电子装置，其包括根据权利要求1-9中任一项所述的电化学装置。
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