WO2025000481A1 - 负极材料以及使用该材料的负极、电化学装置和电子装置 - Google Patents

负极材料以及使用该材料的负极、电化学装置和电子装置 Download PDF

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WO2025000481A1
WO2025000481A1 PCT/CN2023/104976 CN2023104976W WO2025000481A1 WO 2025000481 A1 WO2025000481 A1 WO 2025000481A1 CN 2023104976 W CN2023104976 W CN 2023104976W WO 2025000481 A1 WO2025000481 A1 WO 2025000481A1
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Prior art keywords
negative electrode
electrode material
lithium
present application
potential
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English (en)
French (fr)
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陈宇圣
董佳丽
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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Priority to CN202380018127.3A priority Critical patent/CN118633180A/zh
Priority to PCT/CN2023/104976 priority patent/WO2025000481A1/zh
Priority to EP23942982.2A priority patent/EP4738471A1/en
Publication of WO2025000481A1 publication Critical patent/WO2025000481A1/zh
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of energy storage, and in particular to a negative electrode material and a negative electrode, an electrochemical device and an electronic device using the negative electrode material.
  • the present application attempts to solve at least one problem existing in the related art to at least some extent by providing a negative electrode material.
  • the present application provides a negative electrode material comprising graphite, wherein the negative electrode material has an I-stage lithium insertion platform potential P1 of 30 mV to 75 mV and an II-stage lithium insertion platform potential P2 of 90 mV to 110 mV.
  • the I-stage lithium insertion platform potential P1 of the negative electrode material is 30 mV to 60 mV and the II-stage lithium insertion platform potential P2 is 90 mV to 100 mV.
  • the specific surface area of the negative electrode material is S m 2 /g, and the value range of S is 2-8.
  • the value range of S is 4 to 7.
  • the negative electrode material comprises pores having a pore diameter of no greater than 5 nm, the specific surface area of the pores is S1 m 2 /g, and the ratio of S1 to S ranges from 0.05 to 0.3.
  • the ratio of S1 to S ranges from 0.15 to 0.3.
  • the value range of S1 is 0.1 to 1.5.
  • the peak intensity of the negative electrode material at 1350 cm -1 is D
  • the peak intensity of the negative electrode material at 1580 cm -1 is G
  • the ratio of D to G is R
  • thermogravimetric decomposition temperature of the negative electrode material ranges from 650° C. to 850° C.
  • the powder compaction density of the negative electrode material is 1.90 g/cm 3 to 2.10 g/cm 3
  • the powder rebound rate is 15% to 35%.
  • the present application provides a negative electrode, which includes the negative electrode material of the present application, a dispersant and a binder.
  • the porosity of the negative electrode is 17% to 35%.
  • the present application provides an electrochemical device, which includes a positive electrode, a separator, an electrolyte and a negative electrode according to the present application.
  • an electronic device includes the electrochemical device according to the present application.
  • the present application reduces the positive electrode potential to protect the stability of the positive electrode structure under a high voltage system, thereby increasing the gram capacity of the negative electrode material and improving the cycle performance of the electrochemical device under high temperature and high pressure, while taking into account the initial efficiency of the negative electrode material.
  • FIG1 shows the discharge curves of Example 5 and Comparative Example 1 of the present application.
  • FIG. 2 shows the cycle life curves at 45° C. according to Example 10 of the present application and Comparative Example 1.
  • a list of items connected by the term "at least one of” can mean any combination of the listed items. For example, if items A and B are listed, 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, 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 (excluding B); B and C (excluding A); or all of A, B, and C.
  • Item A can include a single element or multiple elements.
  • Item B can include a single element or multiple elements.
  • Item C can include a single element or multiple elements.
  • Electrochemical devices e.g., lithium-ion batteries
  • the voltage system of lithium-ion batteries is constantly improving.
  • the positive electrode is at a high potential for a long time, making it difficult to maintain a high structural stability, thereby shortening the high-temperature cycle life of the lithium-ion battery.
  • the present application solves the above-mentioned problem by lowering the positive electrode potential.
  • the open circuit voltage of the electrochemical device is equal to the positive electrode potential minus the negative electrode potential.
  • the present application introduces a defective lithium insertion mechanism by surface modification of the negative electrode material to make it defective, which will cause the I-order lithium insertion platform potential and the II-order lithium insertion platform potential of the negative electrode material to change.
  • the negative electrode material will undergo phase changes at different potentials as the degree of lithium insertion increases, that is, each phase change will correspond to a lithium insertion platform.
  • the phase transition process of forming LiC1 2 corresponds to the II-order lithium insertion platform
  • the phase transition process of forming LiC 6 corresponds to the I-order lithium insertion platform.
  • the lithium insertion mechanism changes from interlayer lithium insertion to a common lithium insertion mechanism of interlayer lithium insertion and microporous defect adsorption and lithium storage. Therefore, the lithium insertion platform potential corresponding to the interlayer lithium insertion will also change accordingly, that is, the platform potential is reduced, and the degree of potential change is related to the content and proportion of microporous defects.
  • Defective lithium insertion can reduce the negative electrode lithium insertion potential, thereby lowering the positive electrode potential, thereby protecting the stability of the positive electrode structure under high voltage systems, and further improving the cycle performance of electrochemical devices under high temperature and high pressure. At the same time, defective lithium insertion can increase the gram capacity of the negative electrode material while taking into account the initial efficiency of the negative electrode material.
  • the present application provides a negative electrode material, which includes graphite, and the I-stage lithium insertion platform potential P1 of the negative electrode material is 30mV to 75mV and the II-stage lithium insertion platform potential P2 is 90mV to 110mV.
  • P1 is greater than 75mV and P2 is greater than 115mV, the negative electrode lithium insertion potential is too high, and the effect of lowering the positive electrode potential and improving the high-temperature cycle life of the electrochemical device cannot be achieved.
  • P1 is less than 30mV and P2 is less than 90mV, the negative electrode lithium insertion potential is too high.
  • P1 is 30 mV to 60 mV, which can further improve the cycle performance of the electrochemical device under high temperature and high pressure.
  • P2 is 90 mV to 100 mV, which can further improve the cycle performance of the electrochemical device under high temperature and high pressure.
  • the terminal delithiation potential slope S0 of the negative electrode material is 2mAh/g/V to 8mAh/g/V. In some embodiments, S0 is 2mAh/g/V to 5mAh/g/V.
  • the introduction of defect lithium insertion mechanism will increase the terminal delithiation potential slope.
  • the terminal delithiation potential slope can be calculated based on the lithium insertion curve obtained by plotting the discharge gram capacity and voltage of the negative electrode material.
  • the terminal delithiation potential slope of the negative electrode material can reflect the first efficiency of the negative electrode material.
  • the negative electrode material of the present application can still maintain a terminal delithiation potential slope that is basically equivalent to that of graphite without surface defect modification under a high voltage system. Therefore, the negative electrode material can maintain a higher first efficiency.
  • the specific surface area of the negative electrode material is S m 2 /g, and S is in the range of 2 to 8. In some embodiments, S is in the range of 4 to 7. In some embodiments, S is in the range of 5 to 6. In some embodiments, the specific surface area S m 2 /g of the negative electrode material is 2m 2 /g, 3m 2 /g, 4m 2 /g, 5m 2 /g, 6m 2 /g, 7m 2 /g, 8m 2 / g, or a value in the range formed by any two of the above values. Introducing defects on the surface of the negative electrode material will form a porous structure, thereby increasing the specific surface area of the negative electrode material.
  • the negative electrode When the specific surface area S m 2 /g of the negative electrode material is within the above range, the negative electrode has a low potential defect lithium insertion characteristic, thereby improving the gram capacity of the negative electrode material and the cycle performance of the electrochemical device under high temperature and high pressure, and the reaction area between the negative electrode surface and the electrolyte is appropriate, which can avoid the occurrence of excessive side reactions and excessive consumption of the electrolyte, thereby taking into account the first efficiency of the negative electrode material.
  • the negative electrode material comprises pores having a pore size of no greater than 5 nm, the specific surface area of the pores is S1 m 2 /g, and the ratio of S1 to S is in the range of 0.05 to 0.3. In some embodiments, the ratio of S1 to S is in the range of 0.15 to 0.3. In some embodiments, the ratio of S1 to S is in the range of 0.2 to 0.25. In some embodiments, the ratio of S1 to S is 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, or a value within the range formed by any two of the above values.
  • the specific surface area of pores having a pore size of no greater than 5 nm refers to the sum of the specific surface areas of each pore having a pore size of no greater than 5 nm.
  • the pores having a pore size of no greater than 5 nm may be Providing storage space for lithium ions can increase the gram capacity of the negative electrode material and the cycle performance of the electrochemical device under high temperature and high pressure, while taking into account the initial efficiency of the negative electrode material.
  • S1 has a value range of 0.1 to 1.5, which can further increase the gram capacity of the negative electrode material. In some embodiments, S1 has a value range of 0.5 to 1.2. In some embodiments, S1 m 2 /g is 0.8 m 2 /g to 1 m 2 /g. In some embodiments, S1 m 2 /g is 0.1 m 2 /g, 0.3 m 2 /g, 0.5 m 2 /g, 0.8 m 2 /g, 1.0 m 2 /g, 1.2 m 2 /g, 1.5 m 2 /g, or a value within the range formed by any two of the above values.
  • the peak intensity of the negative electrode material at 1350cm -1 is D
  • the peak intensity of the negative electrode material at 1580cm -1 is G
  • the ratio of D to G is R, 0.025 ⁇ R/S ⁇ 0.25.
  • R/S is 0.025, 0.05, 0.08, 0.1, 0.15, 0.2, 0.25 or a value within the range of any two of the above values.
  • the ratio R of the D peak to the G peak of the Raman spectrum can represent the degree of defects on the surface of the material.
  • the ratio R/S of the R value to the specific surface area S can represent the proportion of defects contained per unit specific surface area.
  • the unit specific surface area of the negative electrode material contains appropriate defects, the negative electrode has low potential defect lithium insertion characteristics, and can avoid excessive consumption of the electrolyte, thereby improving the gram capacity of the negative electrode material and the cycle performance of the electrochemical device under high temperature and high pressure, while taking into account the initial efficiency of the negative electrode material.
  • the negative electrode material has a low potential defect lithium insertion characteristic, thereby improving the cycle performance of the electrochemical device under high temperature and high pressure, and avoiding the occurrence of excessive side reactions and excessive consumption of the electrolyte, thereby taking into account the gram capacity and first efficiency of the negative electrode material and the cycle performance and thermal shock safety performance of the electrochemical device under high temperature and high pressure.
  • the thermogravimetric decomposition temperature of the negative electrode material ranges from 650°C to 850°C. Introducing defects on the surface of the negative electrode material increases the surface reactivity, which causes the negative electrode material to begin to decompose at a lower temperature.
  • the thermogravimetric decomposition temperature of the negative electrode material can reflect the number of surface defects. When the thermogravimetric decomposition temperature of the negative electrode material is within the above range, the surface defects of the negative electrode material are appropriate, the surface has appropriate reactivity, and the increase of side reactions and excessive consumption of the electrolyte can be avoided, thereby improving the gram capacity of the negative electrode material and the cycle performance of the electrochemical device under high temperature and high pressure, while taking into account the initial efficiency of the negative electrode material.
  • the powder compaction density of the negative electrode material is 1.90 g/cm 3 to 2.10 g/cm 3 , and the powder rebound rate is 15% to 35%. In some embodiments, the powder compaction density of the negative electrode material is 1.90 g/cm 3 to 2.00 g/cm 3 , and the powder rebound rate is 20% to 25%. When the negative electrode material is compacted under a certain pressure, powder rebound will occur after the pressure is released.
  • the negative electrode material has the above-mentioned higher powder compaction density, its powder rebound rate is lower, which is beneficial for the negative electrode to maintain a higher compaction density after the electrode sheet is made, thereby improving the volume energy density of the electrochemical device, while not causing a sharp decrease in the pores inside the electrode sheet, which reduces the amount of electrolyte retained, thereby taking into account the cycle performance of the electrochemical device under high temperature and high pressure.
  • the gram capacity of the negative electrode is greater than or equal to 360 mAh/g through a buckle test.
  • the first efficiency of the negative electrode material using the negative electrode material of the present application is 94% to 95%.
  • the present application also provides a negative electrode, which includes the negative electrode material described in the present application, a dispersant and a binder.
  • the porosity of the negative electrode is 17% to 35%. In some embodiments, the porosity of the negative electrode is 20% to 30%. In some embodiments, the porosity of the negative electrode is 25% to 30%. In some embodiments, the porosity of the negative electrode is 17%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, or a value within the range formed by any two of the above values. When the porosity of the negative electrode is within the above range, the cycle performance of the electrochemical device under high temperature and high pressure can be improved.
  • the negative electrode binder includes at least one of styrene-butadiene rubber, polyacrylic acid, polyacrylate, polyimide, polyamide-imide, polyvinylidene fluoride, polyvinylidene fluoride, polytetrafluoroethylene, water-based acrylic resin, polyvinyl formal, or styrene-acrylic copolymer resin.
  • any conductive material can be used as the negative electrode conductive material as long as it does not cause chemical changes.
  • the negative electrode conductive material includes at least one of conductive carbon black, acetylene black, carbon nanotubes, Ketjen black, conductive graphite or graphene.
  • the negative electrode includes a negative electrode current collector, which can be copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or a combination thereof.
  • the present application also provides an electrochemical device, which includes a positive electrode, a separator, an electrolyte and a negative electrode according to the present application.
  • the positive electrode includes a positive electrode active material layer and a positive electrode current collector.
  • the positive electrode active material layer includes a positive electrode active material, a positive electrode binder, and a positive electrode conductor.
  • the positive electrode active material may include at least one of lithium cobalt oxide, lithium nickel manganese cobalt oxide, lithium nickel manganese aluminum oxide, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, spinel lithium manganese oxide, spinel lithium nickel manganese oxide, or lithium titanate.
  • the positive electrode binder may include a binder polymer such as, but not limited to, at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyolefins, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, modified polyvinylidene fluoride, modified SBR rubber, or polyurethane.
  • a binder polymer such as, but not limited to, at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyolefins, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, modified polyvinylidene fluoride, modified SBR rubber, or polyurethane.
  • any conductive material can be used as the positive electrode conductive agent as long as it does not cause chemical changes.
  • positive electrode conductive agents include, but are not limited to, carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.; metal-based materials such as metal powder or metal fiber including copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives, etc.; or mixtures thereof.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • aluminum foil may be used.
  • the composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer substrate.
  • the isolation membrane used in the electrochemical device of the present application are not particularly limited, and it can be any technology disclosed in the prior art.
  • the isolation membrane includes a polymer or inorganic substance formed by a material that is stable to the electrolyte of the present application.
  • the isolation membrane may include a substrate layer and a surface treatment layer.
  • the substrate layer is a non-woven fabric, a film or a composite film having a porous structure.
  • the material of the substrate layer includes at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide.
  • the material of the substrate layer includes at least one of a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite film.
  • a surface treatment layer is disposed on at least one surface of the substrate layer.
  • the surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic layer.
  • the inorganic layer includes inorganic particles and a binder, wherein the inorganic particles are selected from at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate.
  • the binder is selected from polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyethylene At least one of alkene oxide, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.
  • the polymer layer comprises a polymer
  • the material of the polymer is selected from at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyethylene alkoxide, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene).
  • the electrochemical device of the present application also includes an electrolyte.
  • the electrolyte that can be used in the present application can be an electrolyte known in the prior art.
  • the electrolyte includes an organic solvent, an electrolyte salt and an optional additive.
  • the organic solvent of the electrolyte according to the present application may be any organic solvent known in the prior art that can be used as a solvent for the electrolyte.
  • the electrolyte used in the electrolyte according to the present application is not limited, and it can be any electrolyte known in the prior art.
  • the additive of the electrolyte according to the present application may be any additive known in the prior art that can be used as an electrolyte additive.
  • the organic solvent includes, but is not limited to: ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate or ethyl propionate.
  • the organic solvent includes an ether solvent, for example, including at least one of 1,3-dioxolane (DOL) and ethylene glycol dimethyl ether (DME).
  • the electrolyte salt may be a lithium salt, a sodium salt, etc.
  • the lithium salt includes at least one of an organic lithium salt or an inorganic lithium salt.
  • the lithium salt includes, but is not limited to, lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium difluorophosphate (LiPO 2 F 2 ), lithium bistrifluoromethanesulfonyl imide LiN(CF 3 SO 2 ) 2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO 2 F) 2 )(LiFSI), lithium bis(oxalatoborate) LiB(C 2 O 4 ) 2 (LiBOB), or lithium difluorooxalatoborate LiBF 2 (C 2 O 4 ) (LiDFOB).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • LiPO 2 F 2 lithium difluorophosphate
  • LiN(CF 3 SO 2 ) 2 LiTFSI
  • LiFSI lithium bis(fluorosulfony
  • the sodium salt includes, but is not limited to, at least one of NaClO 4 , NaPF 6 , NaBF 4 , Na(FSO 2 ) 2 N, Na(CF 3 SO 2 ) 2 N, Na(C 2 F 5 SO 2 ) 2 N, NaCF 3 SO 3 , NaSbF 6 , NaBC 4 O 8 , NaFSI, NaTFSI, sodium salts of lower aliphatic carboxylates, NaAlCl 4 , NaPO 2 F 2 , or Na 2 PO 3 F.
  • the electrochemical device of the present application includes, but is not limited to, all kinds of primary batteries, secondary batteries or capacitors.
  • the electrochemical device is a lithium secondary battery.
  • the lithium secondary battery includes, but is not limited to: a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery or a lithium ion polymer secondary battery.
  • the electrochemical device is a sodium ion battery.
  • the present application further provides an electronic device, which includes the electrochemical device according to the present application.
  • the electronic device or device of the present application is not particularly limited.
  • the electronic device of the present application includes but is not limited to a laptop computer, a pen-type computer, a mobile computer, an e-book player, a portable computer, a Portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.
  • the battery can be prepared by the following method: the positive electrode and the negative electrode are overlapped via a separator, and are wound, folded, and the like as needed to form a bare cell.
  • Stainless steel is selected as the packaging shell, and the bare cell is placed inside the packaging shell.
  • the aluminum tabs of the bare cell and the poles in the sealing assembly are laser welded together to achieve electronic conduction between the poles and the bare cell.
  • the steel shell cover and the shell are connected by laser welding to achieve the sealing of the battery.
  • lithium-ion batteries The preparation of lithium-ion batteries is described below by taking lithium-ion batteries as an example and combining specific embodiments. Those skilled in the art will understand that the preparation method described in this application is only an example, and any other suitable preparation method is within the scope of this application.
  • the negative electrode material sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) are dispersed evenly in an appropriate amount of deionized water at a mass ratio of 97.5:1.2:1.3 to obtain a negative electrode slurry.
  • Copper foil is used as a current collector, and the negative electrode slurry is evenly coated on the current collector. After coating, it is dried and cold pressed to obtain a negative electrode.
  • Lithium cobalt oxide (chemical formula: LiCoO 2 ) is used as the positive electrode active material, and it is fully stirred and mixed with a conductive agent acetylene black and a binder polyvinylidene fluoride (abbreviated as PVDF) in a weight ratio of 96.3:2.2:1.5 in an appropriate amount of N-methylpyrrolidone (abbreviated as NMP) solvent to form a uniform positive electrode slurry.
  • the positive electrode slurry is coated on a current collector aluminum foil, and after coating, it is dried and cold pressed to obtain a positive electrode.
  • the mixture is mixed, and then fluoroethylene carbonate and 1,3-propane sultone are added, dissolved and stirred thoroughly, and then lithium salt LiPF 6 is added, and the mixture is mixed evenly to obtain an electrolyte.
  • the mass percentage of LiPF 6 is 12.5%
  • the mass percentage of fluoroethylene carbonate is 2%
  • the mass percentage of 1,3-propane sultone is 2%.
  • the mass percentage of each substance is calculated based on the mass of the electrolyte.
  • a polyethylene porous polymer film is used as the isolation membrane.
  • the positive electrode, the separator, and the negative electrode are stacked in order, so that the separator is placed between the positive electrode and the negative electrode to play an isolating role, and then they are wound to obtain an electrode assembly; after welding the pole ears, the electrode assembly is placed in an outer packaging foil aluminum-plastic film, and the prepared electrolyte is injected into the dried electrode assembly. After vacuum packaging, standing, formation, shaping, capacity testing and other processes, a soft-pack lithium-ion battery is obtained.
  • the negative electrode material, SBR, CMC and conductive carbon are mixed in a weight ratio of 93:2.5:2.5:2 in an appropriate amount of deionized water solvent and stirred to form a uniform negative electrode slurry.
  • the negative electrode slurry is coated on the current collector copper foil, dried and cold pressed to obtain a negative electrode.
  • the prepared negative electrode was used as the positive electrode of the button battery, and assembled with the lithium sheet, the above-prepared isolation membrane, the above-prepared electrolyte, the steel sheet, the nickel foam and the button battery shell to obtain a button battery, which was left to stand for 6 hours.
  • the assembled button battery was placed on a blue power tester and subjected to two cycles of charge and discharge tests according to the following process:
  • the lithium insertion curve of the material can be obtained by plotting the second cycle discharge capacity and voltage.
  • the I-order lithium insertion platform potential and the II-order lithium insertion platform potential of the negative electrode material can be read out through the lithium insertion curve.
  • the delithiation curve of the material can be obtained by plotting the gram capacity and voltage of the second charge cycle.
  • the gram capacity corresponding to the potential of 2 V is recorded as Cap2
  • the gram capacity corresponding to the potential of 1 V is recorded as Cap1.
  • the gram capacity of the negative electrode material is obtained by dividing the first cycle charging capacity corresponding to 1.0 V by the weight of the negative electrode material.
  • the initial efficiency of the negative electrode material is calculated by dividing the first cycle charge capacity by the first cycle discharge capacity.
  • the N2 adsorption-desorption curve is obtained by the test software.
  • the obtained N2 adsorption-desorption curve is processed according to the BET model to obtain the specific surface area of the negative electrode material, and then the pore size distribution curve is extracted according to the BJH model.
  • the integral area of the curve in the range of not more than 5nm represents the specific surface area of pores with a pore size of not more than 5nm.
  • the lithium-ion battery is subjected to a charge and discharge cycle test at 45°C according to the following process:
  • Steps 2)-5) are repeated 200 times;
  • Table 1 shows the I-order lithium insertion platform potential and II-order lithium insertion platform potential, gram capacity and first efficiency of the negative electrode material and the cycling performance of lithium-ion batteries under high temperature and high pressure.
  • the negative electrode material surface in Comparative Example 1 is not treated, so its I-stage lithium insertion platform potential and II-stage lithium insertion platform potential are relatively high. Although the negative electrode material has a high initial efficiency, the negative electrode material has a low specific capacity and the cycle life of the lithium ion battery under high temperature and high pressure is short. The platform potential and the II-stage lithium insertion platform potential are too low. Although the cycle life of lithium-ion batteries under high temperature and high pressure is increased, the gram capacity and initial efficiency of the negative electrode material are low.
  • the I-stage lithium insertion platform potential is 30mV to 75mV and the II-stage lithium insertion platform potential is 90mV to 110mV.
  • the negative electrode materials have significantly improved gram capacity, and the cycle life of lithium-ion batteries under high temperature and high pressure is significantly increased, while taking into account the high first efficiency of the negative electrode materials.
  • Figure 1 shows the discharge curves of Example 5 and Comparative Example 1. The results show that Example 5 has lower I-stage and II-stage lithium insertion platform potentials than Comparative Example 1.
  • FIG2 shows the cycle life curves of Example 10 and Comparative Example 1. The results show that the cycle life of Example 10 is significantly longer than that of Comparative Example 1.
  • Table 2 shows the effect of the specific surface area of the negative electrode material on its gram capacity and first efficiency and the cycle performance of the lithium-ion battery under high temperature and high pressure. Except for the parameters listed in Table 2, the other parameters of Examples 11-17 are consistent with those of Example 9.
  • the results show that when the specific surface area S m 2 /g of the negative electrode material is 2 m 2 /g to 8 m 2 /g and/or the ratio of the specific surface area S1 of the pores with a pore size of not more than 5 nm to S is in the range of 0.05 to 0.3, the gram capacity of the negative electrode material can be further improved, the cycle life of the lithium-ion battery under high temperature and high pressure can be increased, and the high initial efficiency of the negative electrode material can be taken into account.
  • S m 2 /g is 4 m 2 /g to 7 m 2 /g and/or the ratio of S1 to S is in the range of 0.15 to 0.3, a more excellent effect can be obtained.
  • Table 3 shows the influence of the ratio R of the D peak to the G peak and the ratio R/S of the D peak to the G peak obtained by Raman test on the gram capacity and the first efficiency of the negative electrode material and the cycle performance of the lithium-ion battery under high temperature and high pressure. Except for the parameters listed in Table 3, the other parameters of Examples 18-22 are consistent with those of Example 12.
  • R is in the range of 0.1 to 0.7, the gram capacity of the negative electrode material can be further increased, the cycle life of the lithium-ion battery under high temperature and high pressure can be increased, and the high initial efficiency of the negative electrode material can be taken into account.
  • R is in the range of 0.2 to 0.55, a more excellent effect can be obtained.
  • Table 4 shows the effect of the powder compaction density and powder rebound rate of the negative electrode material and the porosity of the negative electrode on the cycle performance of the lithium-ion battery under high temperature and high pressure. Except for the parameters listed in Table 4, the other parameters of Examples 23-29 are consistent with those of Example 21.
  • the porosity of the negative electrode is 17% to 35%, the cycle life of the lithium-ion battery under high temperature and high pressure can be further improved.
  • references to "embodiment”, “part of the embodiment”, “one embodiment”, “another example”, “example”, “specific example” or “part of the example” throughout the specification mean that at least one embodiment or example in the present application includes the specific features, structures, materials or characteristics described in the embodiment or example. Therefore, descriptions appearing in various places throughout the specification, such as “in some In the embodiments, “in an embodiment”, “in one embodiment”, “in another example”, “in one example”, “in a particular example” or “example”, it is not necessarily referring to the same embodiment or example in the present application.
  • the specific features, structures, materials or characteristics described herein can be combined in any suitable manner in one or more embodiments or examples.

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Abstract

本申请涉及负极材料以及使用该材料的负极、电化学装置和电子装置。具体地，本申请提供一种负极材料，其包括石墨，负极材料的I阶嵌锂平台电位P1为30mV至75mV并且II阶嵌锂平台电位P2为90mV至110mV。采用本申请的负极材料可以显著改善使用其的电化学装置在高电压和高温下的循环性能，提升负极材料的克容量，同时兼顾负极材料的首次效率。

Description

负极材料以及使用该材料的负极、电化学装置和电子装置 技术领域
本申请涉及储能领域，具体涉及一种负极材料以及使用该负极材料的负极、电化学装置和电子装置。
背景技术
随着电化学装置(例如，锂离子电池)在手机、笔记本电脑、平板电脑、蓝牙耳机、穿戴手表等电子产品中的广泛应用，人们对其性能的要求越来越高。锂电池的循环寿命和能量密度是其最为重要的性能指标，对电子产品的使用寿命和时间有着重要影响。提高电压有助于提高能量密度，但在高电压体系下锂离子电池的循环性能，尤其是高温下的循环性能，会发生恶化。
有鉴于此，确有必要提供一种改进的负极材料，其具有提升的克容量并能够显著改善电化学装置在高温高压下循环性能，同时兼顾负极材料的首次效率。
发明内容
本申请通过提供一种负极材料以试图在至少某种程度上解决至少一种存在于相关领域中的问题。
根据本申请的一个方面，本申请提供了一种负极材料，其包括石墨，负极材料的I阶嵌锂平台电位P1为30mV至75mV并且II阶嵌锂平台电位P2为90mV至110mV。
根据本申请的实施例，负极材料的I阶嵌锂平台电位P1为30mV至60mV并且II阶嵌锂平台电位P2为90mV至100mV。
根据本申请的实施例，负极材料的比表面积为S m2/g，S的取值范围为2至8。
根据本申请的实施例，S的取值范围为4至7。
根据本申请的实施例，负极材料包含具有不大于5nm的孔径的孔，孔的比表面积为S1 m2/g，S1与S的比值范围为0.05至0.3。
根据本申请的实施例，S1与S的比值范围为0.15至0.3。
根据本申请的实施例，S1的取值范围为0.1至1.5。
根据本申请的实施例，通过Raman测试，负极材料在1350cm-1处的峰值强度为D，负极材料在1580cm-1处的峰值强度为G，D与G的比值为R，0.025≤R/S≤0.25。
根据本申请的实施例，0.05≤R/S≤0.15。
根据本申请的实施例，0.1≤R≤0.7。
根据本申请的实施例，0.2≤R≤0.55。
根据本申请的实施例，负极材料的热重分解温度范围为650℃至850℃；
根据本申请的实施例，负极材料的粉末压实密度为1.90g/cm3至2.10g/cm3，且粉末反弹率为15％至35％。
根据本申请的另一个方面，本申请提供了一种负极，其包括本申请的负极材料、分散剂和粘结剂。
根据本申请的实施例，负极的孔隙率为17％至35％。
根据本申请的另一个方面，本申请提供了一种电化学装置，其包括正极、隔离膜、电解液和根据本申请所述的负极。
根据本申请的另一个方面，一种电子装置，其包括根据本申请所述的电化学装置。
本申请通过拉低正极电位以保护正极结构在高电压体系下的稳定性，从而提升负极材料的克容量，改进电化学装置在高温高压下的循环性能，同时兼顾负极材料的首次效率。
本申请的额外层面及优点将部分地在后续说明中描述、显示、或是经由本申请实施例的实施而阐释。
附图说明
在下文中将简要地说明为了描述本申请实施例或现有技术所必要的附图以便于描述本申请的实施例。显而易见地，下文描述中的附图仅只是本申请中的部分实施例。对本领域技术人员而言，在不需要创造性劳动的前提下，依然可以根据这些附图中所例示的结构来获得其他实施例的附图。
图1展示了本申请实施例5和对比例1的放电曲线。
图2展示了根据本申请实施例10和对比例1在45℃下的循环寿命曲线。
具体实施方式
本申请的实施例将会被详细的描示在下文中。本申请的实施例不应该被解释为对本申请的限制。
在具体实施方式及权利要求书中，由术语“中的至少一种”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中的至少一种”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中的至少一种”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。
电化学装置(例如，锂离子电池)因其优越的性能已广泛应用于各个领域，人们对其性能的要求越来越高，例如，能量密度、高温循环性能、使用寿命、充电速度等。为了提高锂离子电池的能量密度，锂离子电池的电压体系在不断提高。然而，在高电压体系下，正极长期处于高电位，使得其难以保持较高的结构稳定性，由此会缩短锂离子电池的高温循环寿命。
本申请通过拉低正极电位解决了上述问题。电化学装置的开路电压等于正极电位减负极电位。本申请通过对负极材料进行表面修饰使其具有缺陷，从而引入缺陷嵌锂机制，由此会导致负极材料的I阶嵌锂平台电位和II阶嵌锂平台电位发生变化。负极材料在层间嵌锂过程中随着嵌锂度的提高会在不同电位下发生相变，即每段相变会对应一段嵌锂平台。形成LiC12的相转变过程对应II阶嵌锂平台，形成LiC6的相转变过程对应I阶嵌锂平台。当负极材料存在微孔缺陷结构时，嵌锂机制发生变化，由层间嵌锂变为层间嵌锂和微孔缺陷吸附储锂的共同嵌锂机制。因此，层间嵌锂对应的嵌锂平台电位也会发生相应改变，即平台电位降低，而电位改变的程度与微孔缺陷的含量和占比有关。缺陷嵌锂可使负极嵌锂电位降低，从而拉低正极电位，由此可以保护正极结构在高电压体系下的稳定性，进而改进电化学装置在高温高压下的循环性能。同时，缺陷嵌锂可提高负极材料的克容量，同时可兼顾负极材料的首次效率。
具体而言，本申请提供了一种负极材料，其包括石墨，负极材料的I阶嵌锂平台电位P1为30mV至75mV并且II阶嵌锂平台电位P2为90mV至110mV。当P1大于75mV、P2大于115mV时，负极嵌锂电位偏高，无法达到拉低正极电位和改善电化学装置的高温循环寿命的效果。当P1小于30mV、P2小于90mV 时，负极在接近满嵌时电位过低，接近锂的成核电位，容易诱导锂枝晶生成，导致电化学装置存在安全隐患。当P1为30mV至75mV并且P2为90mV至110mV时，不仅可以提升的负极材料克容量，还能够显著改善电化学装置在高温高压下循环性能，同时可以兼顾负极材料的首次效率。
在一些实施例中，P1为30mV至60mV，可进一步改善电化学装置在高温高压下的循环性能。
在一些实施例中，P2为90mV至100mV，可进一步改善电化学装置在高温高压下的循环性能。
在一些实施例中，负极材料的末端脱锂电位斜率S0为2mAh/g/V至8mAh/g/V。在一些实施例中，S0为2mAh/g/V至5mAh/g/V。在引入缺陷嵌锂机制会使末端脱锂电位斜率增大。末端脱锂电位斜率可根据负极材料的放电克容量和电压作图得到嵌锂曲线计算得到。负极材料的末端脱锂电位斜率可反映出负极材料的首次效率。本申请的负极材料在高电压体系下依然可以保持与未表面缺陷改性的石墨基本相当的末端脱锂电位斜率，因此，负极材料可维持较高的首次效率。
在一些实施例中，负极材料的比表面积为S m2/g，S的取值范围为2至8。在一些实施例中，S的取值范围为4至7。在一些实施例中，S的取值范围为5至6。在一些实施例中，负极材料的比表面积S m2/g为2m2/g、3m2/g、4m2/g、5m2/g、6m2/g、7m2/g、8m2/g或在上述任意两个数值所组成的范围内的值。在负极材料表面引入缺陷会形成多孔结构，由此会使负极材料的比表面积增加。当负极材料的比表面积S m2/g在上述范围内时，负极具有低电位缺陷嵌锂特性，由此可改善负极材料的克容量以及电化学装置在高温高压下的循环性能，并且负极表面与电解液的反应面积恰当，可避免过多的副反应的发生以及电解液的过度消耗，从而可兼顾负极材料的首次效率。
在一些实施例中，负极材料包含具有不大于5nm的孔径的孔，孔的比表面积为S1 m2/g，S1与S的比值范围为0.05至0.3。在一些实施例中，S1与S的比值范围为0.15至0.3。在一些实施例中，S1与S的比值范围为0.2至0.25。在一些实施例中，S1与S的比值为0.05、0.1、0.15、0.2、0.25、0.3或在上述任意两个数值所组成的范围内的值。具有不大于5nm的孔径的孔的比表面积指的是具有不大于5nm的孔径的每一孔的比表面积之和。具有不大于5nm的孔径的孔可 为锂离子提供储存空间，从而可提高负极材料的克容量以及电化学装置在高温高压下的循环性能，同时可兼顾负极材料的首次效率。
在一些实施例中，S1的取值范围为0.1至1.5，可进一步提高负极材料的克容量。在一些实施例中，S1的取值范围为0.5至1.2。在一些实施例中，S1m2/g为0.8m2/g至1m2/g。在一些实施例中，S1m2/g为0.1m2/g、0.3m2/g、0.5m2/g、0.8m2/g、1.0m2/g、1.2m2/g、1.5m2/g或在上述任意两个数值所组成的范围内的值。
在一些实施例中，通过Raman测试，负极材料在1350cm-1处的峰值强度为D，负极材料在1580cm-1处的峰值强度为G，D与G的比值为R，0.025≤R/S≤0.25。在一些实施例中，0.05≤R/S≤0.15。在一些实施例中，0.08≤R/S≤0.1。在一些实施例中，R/S为0.025、0.05、0.08、0.1、0.15、0.2、0.25或在上述任意两个数值所组成的范围内的值。Raman光谱的D峰与G峰的比值R可表示材料表面的缺陷程度。R值与比表面积S的值的比值R/S可表示单位比表面积所含的缺陷比例。当R/S在上述范围内时，负极材料的单位比表面积含有恰当的缺陷，负极具有低电位缺陷嵌锂特性，同时可避免电解液的过度消耗，由此可改善负极材料的克容量以及电化学装置在高温高压下的循环性能，同时可兼顾负极材料的首次效率。。
在一些实施例中，0.1≤R≤0.7。在一些实施例中，0.2≤R≤0.55。在一些实施例中，0.2≤R≤0.4。在一些实施例中，R为0.1、0.2、0.3、0.4、0.5、0.6、0.7或在上述任意两个数值所组成的范围内的值。在石墨材料表面引入缺陷会使Raman光谱的D峰与G峰的比值R增大。当R在上述范围内时，负极材料具有低电位缺陷嵌锂特性，由此可改善电化学装置在高温高压下的循环性能，并且可避免过多的副反应的发生以及电解液的过度消耗，从而可兼顾负极材料的克容量和首次效率以及电化学装置在高温高压下的循环性能和热冲击等安全性能。
在一些实施例中，负极材料的热重分解温度范围为650℃至850℃。在负极材料表面引入缺陷后会使表面反应活性增大，由此会导致负极材料在较低的温度下开始分解。负极材料的热重分解温度可反映出其表面缺陷的多少。当负极材料的热重分解温度在上述范围内时，负极材料表面缺陷恰当，表面具有恰当的反应活性，同时可避免副反应的增加以及电解液的过度消耗，从而可改善负极材料的克容量和电化学装置在高温高压下的循环性能，同时兼顾负极材料的首次效率。
在一些实施例中，负极材料的粉末压实密度为1.90g/cm3至2.10g/cm3，且粉末反弹率为15％至35％。在一些实施例中，负极材料的粉末压实密度为1.90g/cm3至2.00g/cm3，且粉末反弹率为20％至25％。当负极材料在一定压力下压实后，卸掉压力后会出现粉末反弹。当负极材料具有上述较高的粉末压实密度时，其粉末反弹率较低，在制成极片后有利于负极维持较高的压实密度，从而可改善电化学装置的体积能量密度，同时不会导致极片内部孔隙急剧减少使得电解液保有量减少，由此兼顾电化学装置在高温高压下的循环性能。
在一些实施例中，通过扣电测试，负极的克容量大于或等于360mAh/g。
在一些实施例中，使用本申请的负极材料的负极材料的首次效率为94％至95％。
本申请还提供了一种负极，其包括根据本申请所述的负极材料、分散剂和粘结剂。
在一些实施例中，负极的孔隙率为17％至35％。在一些实施例中，负极的孔隙率为20％至30％。在一些实施例中，负极的孔隙率为25％至30％。在一些实施例中，负极的孔隙率为17％、20％、22％、25％、28％、30％、32％、35％或在上述任意两个数值所组成的范围内的值。当负极的孔隙率在上述范围内时，可改善电化学装置在高温高压下的循环性能。
在一些实施例中，负极粘结剂包括丁苯橡胶、聚丙烯酸、聚丙烯酸盐、聚酰亚胺、聚酰胺酰亚胺、聚偏氟乙烯、聚二氟乙烯、聚四氟乙烯、水性丙烯酸树脂、聚乙烯醇缩甲醛或苯乙烯-丙烯酸共聚树脂中的至少一种。
在一些实施例中，可以使用任何导电的材料作为该负极导电材料，只要它不引起化学变化即可。在一些实施例中，负极导电材料包括导电炭黑、乙炔黑、碳纳米管、科琴黑、导电石墨或石墨烯中的至少一种。
在一些实施例中，负极包括负极集流体，负极集流体可以为铜箔、镍箔、不锈钢箔、钛箔、泡沫镍、泡沫铜、包覆有导电金属的聚合物基板或它们的组合。
本申请还提供了一种电化学装置，其包括正极、隔离膜、电解液和根据本申请所述的负极。
在一些实施例中，正极包括正极活性材料层和正极集流体。
在一些实施例中，正极活性材料层包括正极活性材料、正极粘结剂和正极导电剂。
在一些实施例中，正极活性材料可以包括钴酸锂、镍锰钴酸锂、镍锰铝酸锂、磷酸铁锂、磷酸钒锂、磷酸钴锂、磷酸锰锂、磷酸锰铁锂、硅酸铁锂、硅酸钒锂、硅酸钴锂、硅酸锰锂、尖晶石型锰酸锂、尖晶石型镍锰酸锂或钛酸锂中的至少一种。
在一些实施例中，正极粘结剂可以包括粘合剂聚合物，例如，但不限于，聚偏氟乙烯、聚四氟乙烯、聚烯烃类、羧甲基纤维素钠、羧甲基纤维素锂、改性聚偏氟乙烯、改性SBR橡胶或聚氨酯中的至少一种。
在一些实施例中，可以使用任何导电的材料作为正极导电剂，只要它不引起化学变化即可。正极导电剂的实例包括，但不限于，碳基材料，例如天然石墨、人造石墨、炭黑、乙炔黑、科琴黑、碳纤维等；金属基材料，例如包括铜、镍、铝、银等的金属粉或金属纤维；导电聚合物，例如聚亚苯基衍生物等；或它们的混合物。
在一些实施例中，正极集流体可以采用金属箔片或复合集流体。例如，可以使用铝箔。复合集流体可以通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子基材上而形成。
本申请的电化学装置中使用的隔离膜的材料和形状没有特别限制，其可为任何现有技术中公开的技术。在一些实施例中，隔离膜包括由对本申请的电解液稳定的材料形成的聚合物或无机物等。在一些实施例中，隔离膜可包括基材层和表面处理层。在一些实施例中，基材层为具有多孔结构的无纺布、膜或复合膜。在一些实施例中，基材层的材料包括聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯和聚酰亚胺中的至少一种。在一些实施例中，基材层的材料包括聚丙烯多孔膜、聚乙烯多孔膜、聚丙烯无纺布、聚乙烯无纺布或聚丙烯-聚乙烯-聚丙烯多孔复合膜中的至少一种。
在一些实施例中，基材层的至少一个表面上设置有表面处理层，表面处理层可以是聚合物层或无机物层，也可以是混合聚合物与无机物所形成的层。
在一些实施例中，无机物层包括无机颗粒和粘结剂，无机颗粒选自氧化铝、氧化硅、氧化镁、氧化钛、二氧化铪、氧化锡、二氧化铈、氧化镍、氧化锌、氧化钙、氧化锆、氧化钇、碳化硅、勃姆石、氢氧化铝、氢氧化镁、氢氧化钙和硫酸钡中的至少一种。粘结剂选自聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙 烯烷氧、聚甲基丙烯酸甲酯、聚四氟乙烯和聚六氟丙烯中的至少一种。
在一些实施例中，聚合物层中包含聚合物，聚合物的材料选自聚酰胺、聚丙烯腈、丙烯酸酯聚合物、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯烷氧、聚偏氟乙烯、聚(偏氟乙烯-六氟丙烯)中的至少一种。
本申请的电化学装置还包括电解液。可用于本申请的电解液可以为现有技术中已知的电解液。
在一些实施例中，电解液包括有机溶剂、电解质盐和可选的添加剂。根据本申请的电解液的有机溶剂可为现有技术中已知的任何可作为电解液的溶剂的有机溶剂。根据本申请的电解液中使用的电解质没有限制，其可为现有技术中已知的任何电解质。根据本申请的电解液的添加剂可为现有技术中已知的任何可作为电解液添加剂的添加剂。在一些实施例中，有机溶剂包括，但不限于：碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)、碳酸二甲酯(DMC)、碳酸亚丙酯或丙酸乙酯。在一些实施例中，有机溶剂包括醚类溶剂，例如包括1，3-二氧五环(DOL)和乙二醇二甲醚(DME)中的至少一种。在一些实施例中，电解质盐可以是锂盐、钠盐等。在一些实施例中，锂盐包括有机锂盐或无机锂盐中的至少一种。在一些实施例中，锂盐包括，但不限于：六氟磷酸锂(LiPF6)、四氟硼酸锂(LiBF4)、二氟磷酸锂(LiPO2F2)、双三氟甲烷磺酰亚胺锂LiN(CF3SO2)2(LiTFSI)、双(氟磺酰)亚胺锂Li(N(SO2F)2)(LiFSI)、双草酸硼酸锂LiB(C2O4)2(LiBOB)或二氟草酸硼酸锂LiBF2(C2O4)(LiDFOB)。在一些实施例中，钠盐包括，但不限于：NaClO4、NaPF6、NaBF4、Na(FSO2)2N、Na(CF3SO2)2N、Na(C2F5SO2)2N、NaCF3SO3、NaSbF6、NaBC4O8、NaFSI、NaTFSI、低级脂肪族羧酸钠盐、NaAlCl4、NaPO2F2或Na2PO3F中的至少一种。
在一些实施例中，本申请的电化学装置包括，但不限于，所有种类的一次电池、二次电池或电容。在一些实施例中，电化学装置是锂二次电池。在一些实施例中，锂二次电池包括，但不限于：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。在一些实施例中，电化学装置是钠离子电池。
本申请还进一步提供了一种电子装置，其包括根据本申请所述电化学装置。
本申请的电子设备或装置没有特别限定。在一些实施例中，本申请的电子设备包括但不限于，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。
电化学装置和电子装置的制备过程为本领域技术人员所熟知的，本申请没有特别的限制。例如，电池可通过以下方法制备：将正极和负极经由隔离膜重叠，并根据需要将其卷绕、折叠等操作后制成裸电芯。选取不锈钢作为封装外壳，裸电芯置于封装壳内部，裸电芯的铝极耳和密封组件中的极柱通过激光焊接在一起，实现极柱和裸电芯之间的电子导通。通过激光焊接连接钢壳壳盖和壳体，实现电池的密封。钢壳表面存在通孔，将电解液通过该通孔注射进入电芯内部。充分浸润后，在一定电流电压条件下对电芯活化，至此完成电池的制备。
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、负极材料的制备
以人造石墨作为原料，将其放入气氛炉中，通入水气/空气的混合气，气流量为F，在该气氛下进行3段恒温反应：第一段为在T1温度下反应H1小时，第二段为在T2温度下反应H2小时，第三段为在T3温度下反应H3小时，待反应结束后自然冷却到室温，得到负极材料。各实施例和对比例的反应条件如下表所示，其中对比例1为未反应的石墨：

2、负极的制备
将负极材料、羧甲基纤维素钠(CMC)及丁苯橡胶(SBR)按质量比97.5:1.2:1.3在适量的去离子水中分散均匀，得到负极浆料。以铜箔作为集流体，将负极浆料均匀涂覆在集流体上，涂布后烘干、冷压，即制得负极。
3、正极的制备
以钴酸锂(化学式：LiCoO2)作为正极活性材料，将其与导电剂乙炔黑、粘结剂聚偏二氟乙烯(简写为PVDF)按重量比96.3:2.2:1.5在适量的N-甲基吡咯烷酮(简写为NMP)溶剂中充分搅拌混合，使其形成均匀的正极浆料，将正极浆料涂覆于集流体铝箔上，涂布后烘干、冷压，即制得到正极。
4、电解液的制备
在干燥的氩气气氛手套箱中，将碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按照质量比为EC:PC:EMC:DEC＝1:3:3:3 进行混合，接着加入氟代碳酸乙烯酯和1,3-丙烷磺内酯，溶解并充分搅拌后加入锂盐LiPF6，混合均匀后得到电解液。其中，LiPF6的质量百分含量为12.5％，氟代碳酸乙烯酯的质量百分含量为2％，1,3-丙烷磺内酯的质量百分含量为2％，各物质的质量百分含量为基于电解液的质量计算得到。
5、隔离膜的制备
以聚乙烯多孔聚合物薄膜作为隔离膜。
6、锂离子电池的制备
将正极、隔离膜、负极按顺序叠好，使隔离膜处于正极和负极之间起到隔离的作用，然后卷绕得到电极组件；焊接极耳后将电极组件置于外包装箔铝塑膜中，将上述制备好的电解液注入到干燥后的电极组件中，经过真空封装、静置、化成、整形、容量测试等工序，获得软包锂离子电池。
二、测试方法
1、负极材料的测试
取完全放电的锂离子电池，拆解后取出负极，用乙烯碳酸酯(DMC)浸泡20分钟后，再依次用DMC和丙酮各淋洗一遍，以去除电解液及表层SEI膜，之后将其置于烘箱内，在80℃下烘烤12小时，获得处理后的负极。然后，用刮刀刮下负极上的粉末，在500℃空气气氛下焙烧3小时，以去除粉料中所含的CMC和SBR，获得负极材料。对所得负极材料进行如下测试：
(1)嵌锂平台电位测试
将负极材料、SBR、CMC和导电碳按照重量比93:2.5:2.5:2配比，在适量的去离子水溶剂中充分搅拌混合，使其形成均匀的负极浆料。将此负极浆料涂覆于集流体铜箔上，烘干、冷压，制得负极。
将制备的负极作为扣式电池的正极，与锂片、上述制备的隔离膜、上述制备的电解液、钢片、泡沫镍以及扣式电池壳组装在一起得到扣式电池，静置6小时。将组装后的扣式电池置于蓝电测试仪上按照以下流程进行两圈充放电测试：
1)搁置5分钟；
2)0.05C放电至5mV；
3)搁置5分钟；
4)0.05mA放电至5mV；
5)搁置5分钟；
6)0.01mA放电至5mV；
7)搁置5分钟；
8)0.1C充电至2V；
9)搁置5分钟。
测试结束后，以第二圈放电克容量和电压作图可得材料的嵌锂曲线，通过嵌锂曲线可读出负极材料的I阶嵌锂平台电位和II阶嵌锂平台电位。
(2)末端脱锂电位斜率测试
根据“(1)嵌锂平台电位测试”相同的方法，以第二圈充电克容量和电压作图可得材料的脱锂曲线，记录2V电位下对应的克容量为Cap2，1V电位下对应的克容量为Cap1，通过下式计算脱锂末端电位斜率S0(单位为mAh/g/V)：
S0＝(Cap2-Cap1)/(2V-1V)mAh/g/V。
(3)克容量测试
根据“(1)嵌锂平台电位测试”相同的方法，以1.0V对应的首圈充电容量除以负极材料的重量得到负极材料的克容量。
(4)首次效率测试
根据“(1)嵌锂平台电位测试”相同的方法，以首圈充电克容量除以首圈放电克容量计算得到负极材料的首次效率。
(5)比表面积测试
称取20g至30g负极材料进行压片，压片后称取1.5g至3.5g装入测试样品管中。将样品在200℃条件下脱气处理2小时，然后通入高纯氮气，使样品在液氮温度和相对压强10-6torr的条件下吸附氮气直至吸附饱和。通过测试软件得到N2吸脱附曲线。将所得N2吸脱附曲线按照BET模型进行数据处理，得到负极材料的比表面积，然后按照BJH模型提取孔径分布曲线，曲线在不大于5nm范围的积分面积即表示具有不大于5nm的孔径的孔的比表面积。
(6)粉末压实密度和粉末反弹率测试
称取m克负极材料，装入测试模具中，模具底面积记为S，以5吨压力将材料压实，记录材料受压后的装填高度为H1，然后卸掉压力记录材料反弹后的装填高度为H2。通过下式计算：粉末压实密度＝m/(S×H1)，粉末反弹率＝(1-H1/H2)×100％。
2、锂离子电池在高温高压下的循环性能的测试
将锂离子电池在45℃环境下按以下流程进行充放电循环测试：
1)搁置30分钟；
2)1C充电到4.48V，恒压到0.05C；
3)搁置10小时；
4)1C放电到3.0V；
5)搁置30分钟；
6)第2)-5)步循环200圈；
7)1C充电到4.45V，恒压到0.05C；
8)搁置10小时；
9)1C放电到3.0V；
10)搁置30分钟；
11)循环第7)-10)步直到电池容量保持率衰减到80％，记录循环圈数即为锂离子电池在高温高压下的循环寿命。
三、测试结果
表1展示了负极材料的I阶嵌锂平台电位和II阶嵌锂平台电位、克容量和首次效率以及锂离子电池在高温高压下的循环性能。
表1
对比例1中的负极材料表面未进行处理，因此其I阶嵌锂平台电位和II阶嵌锂平台电位较高，负极材料虽然具有高首次效率，但负极材料克容量低且锂离子电池在高温高压下的循环寿命短。对比例2中的负极材料表面经改性后I阶嵌锂 平台电位和II阶嵌锂平台电位过低，虽然锂离子电池在高温高压下的循环寿命增长，但负极材料的克容量和首次效率较低。
实施例1-10负极材料表面经改性后I阶嵌锂平台电位为30mV至75mV且II阶嵌锂平台电位为90mV至110mV，负极材料具有显著改善的克容量，锂离子电池在高温高压下的循环寿命显著增长，同时可兼顾负极材料的高首次效率。图1展示了实施例5与对比例1的放电曲线，结果显示实施例5具有较对比例1更低的I阶和II阶嵌锂平台电位。
图2展示了实施例10与对比例1的循环寿命曲线，结果表明，实施例10的循环寿命比对比例1显著增长。
表2展示了负极材料的比表面积对其克容量和首次效率以及锂离子电池在高温高压下的循环性能的影响。除表2中所列参数以外，实施例11-17的其它参数与实施例9一致。
表2
结果表明，当负极材料的比表面积S m2/g为2m2/g至8m2/g和/或具有不大于5nm的孔径的孔的比表面积S1与S的比值范围为0.05至0.3时，可进一步提升负极材料的克容量，增长锂离子电池在高温高压下的循环寿命，同时可兼顾负极材料的高首次效率。当S m2/g为4m2/g至7m2/g和/或S1与S的比值范围为0.15至0.3时，可获得更为优异的效果。
表3展示了Raman测试得到的D峰与G峰的比值R及其与S的比值R/S对负极材料的克容量和首次效率以及锂离子电池在高温高压下的循环性能的影响。除表3中所列参数以外，实施例18-22的其它参数与实施例12一致。
表3

结果表明，当R/S的范围为0.025至0.25时，可进一步提升负极材料的克容量，增长锂离子电池在高温高压下的循环寿命，同时可兼顾负极材料的高首次效率。当R/S的范围为0.05至0.15时，可获得更为优异的效果。
当R的范围为0.1至0.7时，可进一步提升负极材料的克容量，增长锂离子电池在高温高压下的循环寿命，同时可兼顾负极材料的高首次效率。当R的范围为0.2至0.55时，可获得更为优异的效果。
表4展示了负极材料的粉末压实密度和粉末反弹率以及负极的孔隙率对锂离子电池在高温高压下的循环性能的影响。除表4中所列参数以外，实施例23-29的其它参数与实施例21一致。
表4
结果表明，当负极材料的粉末压实密度为1.90g/cm3至2.10g/cm3且粉末反弹率为15％至35％时，可进一步提升锂离子电池在高温高压下的循环寿命。
当负极的孔隙率为17％至35％时，可进一步提升锂离子电池在高温高压下的循环寿命。
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 (13)

  1. 一种负极材料，其包括石墨，所述负极材料的I阶嵌锂平台电位P1为30mV至75mV并且II阶嵌锂平台电位P2为90mV至110mV。
  2. 根据权利要求1所述的负极材料，其中所述负极材料的比表面积为S m2/g，S的取值范围为2至8。
  3. 根据权利要求2所述的负极材料，其中所述负极材料具有不大于5nm的孔径的孔，所述孔的比表面积为S1 m2/g，S1与S的比值范围为0.05至0.3。
  4. 根据权利要求3所述的负极材料，其中所述负极材料满足以下至少一者：
    (1)S的取值范围为4至7；
    (2)S1的取值范围为0.1至1.5；
    (3)S1与S的比值范围为0.15至0.3。
  5. 根据权利要求1所述的负极材料，其中所述I阶嵌锂平台电位P1为30mV至60mV并且所述II阶嵌锂平台电位P2为90mV至100mV。
  6. 根据权利要求2所述的负极材料，其中通过Raman测试，所述负极材料在1350cm-1处的峰值强度为D，所述负极材料在1580cm-1处的峰值强度为G，D与G的比值为R，0.025≤R/S≤0.25。
  7. 根据权利要求6所述的负极材料，其中所述负极材料满足如下条件中的至少一者：
    (1)0.1≤R≤0.7；
    (2)0.05≤R/S≤0.15。
  8. 根据权利要求6所述的负极材料，其中0.2≤R≤0.55。
  9. 根据权利要求1所述的负极材料，其中所述负极材料满足以下条件中的至少一者：
    (1)所述负极材料的热重分解温度范围为650℃至850℃；
    (2)所述负极材料的粉末压实密度为1.90g/cm3至2.10g/cm3，且粉末反弹率为15％至35％。
  10. 一种负极，其包括根据权利要求1-9中任一项所述的负极材料、分散剂和粘结剂。
  11. 根据权利要求10所述的负极，其中所述负极的孔隙率为17％至35％。
  12. 一种电化学装置，其包括正极、隔离膜、电解液和根据权利要求10或11所述的负极。
  13. 一种电子装置，其包括根据权利要求12所述的电化学装置。
PCT/CN2023/104976 2023-06-30 2023-06-30 负极材料以及使用该材料的负极、电化学装置和电子装置 Ceased WO2025000481A1 (zh)

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