Anode material, and anode, electrochemical apparatus and electronic apparatus using the said material

Abstract

This application relates to a negative electrode material, and to a negative electrode, electrochemical apparatus, and electronic apparatus using the material. Specifically, this application provides a negative electrode material comprising graphite, wherein 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. By adopting the negative electrode material of this application, the cycle performance of electrochemical apparatus using it under high voltage and high temperature conditions can be significantly improved, the Coulomb capacity of the negative electrode material can be increased, and the initial efficiency of the negative electrode material can be achieved simultaneously.

Description

[Technical Field]

[0001] This application relates to the field of energy storage, and more specifically to anode materials, as well as anodes, electrochemical devices, and electronic devices using said anode materials. [Background technology]

[0002] As electrochemical devices (such as lithium-ion batteries) become widely used in electronic products such as mobile phones, laptops, tablets, wireless earphones, and wearable watches, people's demands for performance are increasing. Cycle life and energy density of lithium batteries are the most important performance indicators, significantly impacting the lifespan and usage time of electronic products. While increasing voltage helps improve energy density, high-voltage systems degrade the cycle performance of lithium-ion batteries, especially at high temperatures. In light of these circumstances, this application aims to provide an improved anode material that enhances Coulomb capacity, significantly improves the cycle performance of electrochemical equipment at high temperatures and pressures, and simultaneously achieves high initial efficiency of the anode material. [Overview of the Initiative]

[0003] This application provides a negative electrode material to solve, at least to some extent, one problem existing in the related field.

[0004] According to one aspect of this application, the application provides a negative electrode material comprising graphite, wherein 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.

[0005] According to the embodiments of this application, the lithium insertion platform potential P1 of the negative electrode material is 30mV to 60mV, and the lithium insertion platform potential P2 of the negative electrode material is 90mV to 100mV.

[0006] According to the embodiments of the present application, the specific surface area of the negative electrode material is Sm / g, and the numerical range of S is 2 to 8.

[0007] According to the embodiments of the present application, the numerical range of S is 4 to 7.

[0008] According to the embodiments of the present application, the negative electrode material includes pores with a pore diameter of 5 nm or less, and the specific surface area of the pores is S1m 2 / g, and the range of the ratio of S1 to S is 0.05 to 0.3.

[0009] According to the embodiments of the present application, the range of the ratio of S1 to S is 0.15 to 0.3.

[0010] According to the embodiments of the present application, the numerical range of S1 is 0.1 to 1.5.

[0011] According to the embodiments of the present application, by Raman measurement, the peak intensity at 1350 cm -1 of the negative electrode material is D, the peak intensity at 1580 cm -1 of the negative electrode material is G, and when the ratio of D to G is R, 0.025 ≤ R / S ≤ 0.25.

[0012] According to the embodiments of the present application, 0.05 ≤ R / S ≤ 0.15.

[0013] According to the embodiments of the present application, 0.1 ≤ R ≤ 0.7.

[0014] According to the embodiments of the present application, 0.2 ≤ R ≤ 0.55.

[0015] According to the embodiments of the present application, the thermogravimetric decomposition temperature range of the negative electrode material is 650°C to 850°C. ​​​​​​​​​​According to another aspect of this application, the application provides a negative electrode comprising the negative electrode material, dispersant and binder of the application.

[0018] According to the embodiments of this application, the porosity of the negative electrode is 17% to 35%.

[0019] According to another aspect of this application, the application provides an electrochemical apparatus comprising a positive electrode, a separator, an electrolyte, and a negative electrode as described in this application.

[0020] According to another aspect of this application, an electronic device is provided, which includes an electrochemical device as described in this application.

[0021] This application aims to protect the stability of the positive electrode structure in high-voltage systems by lowering the positive electrode potential, thereby improving the Coulomb capacity of the negative electrode material, enhancing the cycle performance of electrochemical equipment at high temperatures and pressures, while simultaneously achieving high initial efficiency of the negative electrode material.

[0022] Further aspects and advantages of this specification are partially described, shown, or understood by the implementation of the examples herein. [Brief explanation of the drawing]

[0023] The following briefly introduces the drawings necessary to illustrate the embodiments of this application or the prior art. Clearly, the drawings in the following description represent only some embodiments of this application. Those skilled in the art can obtain drawings of other embodiments based on the structures shown in these drawings without requiring any creative effort. [Figure 1] The discharge curves of Example 5 and Comparative Example 1 of this application are shown. [Figure 2] The cycle life curves at 45°C for Example 10 and Comparative Example 1 of this application are shown. [Modes for carrying out the invention]

[0024] The embodiments of this application will be described in detail below. The embodiments of this application should not be construed as limiting this application.

[0025] In specific embodiments and claims, a list of items connected by “at least one of” means any combination of the enumerated items. For example, if items A and B are enumerated, “at least one of A and B” means A only, B only, or A and B. As another example, if items A, B and C are enumerated, “at least one of A, B and C” means A only, B only, C only, A and B (excluding C), A and C (excluding B), B and C (excluding A), or all of A, B and C. Item A may contain a single element or more elements. Item B may contain a single element or more elements. Item C may contain a single element or more elements.

[0026] Electrochemical devices (such as lithium-ion batteries) are widely used in various fields due to their superior performance, and people's demands for their performance (e.g., energy density, high-temperature cycle performance, service life, charging speed, etc.) are constantly increasing. To improve the energy density of lithium-ion batteries, the voltage systems of lithium-ion batteries continue to improve. However, in high-voltage systems, the positive electrode remains at a high potential for extended periods, making it difficult to maintain high structural stability, which in turn shortens the high-temperature cycle life of lithium-ion batteries.

[0027] This application solves the above problem by lowering the positive electrode potential. The open-circuit voltage of an electrochemical apparatus is equal to the positive electrode potential minus the negative electrode potential. This application introduces a defect mechanism by forming defects in the negative electrode material through surface modification, thereby causing changes in the I-stage lithium insertion platform potential and the II-stage lithium insertion platform potential of the negative electrode material. In the lithium insertion process between layers, the negative electrode material undergoes phase transitions at different potentials as the degree of lithium insertion increases, i.e., each phase transition corresponds to one stage of lithium insertion platform. LiC 12The phase transition process that forms the first stage corresponds to the second-stage lithium insertion platform, and the phase transition process that forms LiC6 corresponds to the first-stage lithium insertion platform. When microporous defect structures are present in the anode material, the lithium insertion mechanism changes, shifting from interlayer lithium insertion to a co-lithium insertion mechanism involving interlayer lithium insertion and lithium storage by adsorption to microporous defects. Consequently, the lithium insertion platform potential corresponding to interlayer lithium insertion also changes accordingly, i.e., the platform potential decreases, and the degree of potential change is related to the content and proportion of microporous defects. By lowering the lithium insertion potential of the anode through defect lithium insertion, the positive electrode potential is reduced, thereby protecting the stability of the positive electrode structure under high-voltage systems and further improving the high-temperature and high-pressure cycle performance of the electrochemical apparatus. At the same time, defect lithium insertion can improve the Coulomb capacity of the anode material while simultaneously achieving high initial efficiency of the anode material.

[0028] Specifically, this application provides a negative electrode material comprising graphite, wherein 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. If P1 exceeds 75mV and P2 exceeds 115mV, the lithium insertion potential of the negative electrode becomes high, and the effect of lowering the positive electrode potential and improving the high-temperature cycle life of the electrochemical apparatus cannot be achieved. If P1 is less than 30mV and P2 is less than 90mV, the potential of the negative electrode is too low when it is close to the lithium insertion saturation state, close to the lithium nucleation potential, which easily induces the formation of lithium dendrites, and poses a safety problem for the electrochemical apparatus. When P1 is 30mV to 75mV and P2 is 90mV to 110mV, not only is the Coulomb capacity of the negative electrode material improved, but the cycle performance of the electrochemical apparatus at high temperature and high pressure can be greatly improved, while simultaneously achieving the initial efficiency of the negative electrode material.

[0029] In some examples, P1 is between 30mV and 60mV, which can further improve the cycling performance of the electrochemical apparatus at high temperature and high pressure.

[0030] In some embodiments, P2 is 90 mV to 100 mV, and the cycle performance of the electrochemical device at high temperature and high pressure can be further improved.

[0031] In some embodiments, the terminal lithium desorption potential gradient S0 of the negative electrode material is 2 mAh / g / V to 8 mAh / g / V. In some embodiments, S0 is 2 mAh / g / V to 5 mAh / g / V. Introducing a defective lithium insertion mechanism increases the terminal lithium desorption potential gradient. The terminal lithium desorption potential gradient can be calculated based on the lithium insertion curve obtained by plotting the discharge Coulomb capacity and voltage of the negative electrode material. The terminal lithium desorption potential gradient of the negative electrode material can reflect the initial efficiency of the negative electrode material. The negative electrode material of the present application can maintain a terminal lithium desorption potential gradient basically equivalent to that of unmodified graphite even in a high-voltage system, so the negative electrode material can maintain a high initial efficiency.

[0032] In some embodiments, the specific surface area of the negative electrode material is Sm 2 / g, and the numerical range of S is 2 to 8. In some embodiments, the numerical range of S is 4 to 7. In some embodiments, the numerical range of S is 5 to 6. In some embodiments, the specific surface area Sm 2 / g of the negative electrode material is 2 m 2 / g, 3 m 2 / g, 4 m 2 / g, 5 m 2 / g, 6 m 2 / g, 7 m 2 / g, 8 m 2 / g, or a value within the range consisting of any two of the above numerical values. Introducing defects on the surface of the negative electrode material forms a porous structure, thereby increasing the specific surface area of the negative electrode material. The specific surface area Sm 2When / g is within the above range, the anode has low-potential defect lithium insertion characteristics, thereby improving the Coulomb capacity of the anode material and the high-temperature, high-pressure cycling performance of the electrochemical apparatus. Furthermore, the reaction area between the anode surface and the electrolyte becomes appropriate, preventing excessive side reactions and excessive electrolyte consumption, thereby achieving both high initial efficiency of the anode material and low initial efficiency.

[0033] In some embodiments, the negative electrode material contains pores with a diameter of 5 nm or less, and the specific surface area of ​​these pores is S1 m². 2 The ratio is / g, and the range of the S1 to S ratio is 0.05 to 0.3. In some examples, the range of the S1 to S ratio is 0.15 to 0.3. In some examples, the range of the S1 to S ratio is 0.2 to 0.25. In some examples, the S1 to S ratio is a value within the range of 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, or any two of the above values. The specific surface area having pores with a pore diameter of 5 nm or less refers to the sum of the specific surface areas of each pore with a pore diameter of 5 nm or less. By having pores with a pore diameter of 5 nm or less, a storage space for lithium ions can be provided, thereby improving the Coulomb capacity of the anode material and the cycle performance of the electrochemical device at high temperature and high pressure, while simultaneously achieving the initial efficiency of the anode material.

[0034] In some embodiments, the numerical range of S1 is 0.1 to 1.5, which can further improve the Coulomb capacity of the negative electrode material. In some embodiments, the numerical range of S1 is 0.5 to 1.2. In some embodiments, S1m 2 / g is 0.8m 2 / g~1m 2 / g. In some examples, S1m 2 / g is 0.1m 2 / g, 0.3m 2 / g, 0.5m 2 / g, 0.8m 2 / g, 1.0m 2 / g, 1.2m 2 / g, 1.5m 2 / g, or a value within the range of any two of the above numbers.

[0035] In some examples, Raman measurements revealed that the negative electrode material had a temperature of 1350 cm². -1 D is the peak intensity at 1580 cm² for the negative electrode material. -1 If G is the peak intensity at and R is the ratio of D to G, then 0.025 ≤ R / S ≤ 0.25. In some examples, 0.05 ≤ R / S ≤ 0.15. In some examples, 0.08 ≤ R / S ≤ 0.1. In some examples, R / S is a value within the range of 0.025, 0.05, 0.08, 0.1, 0.15, 0.2, 0.25, or any two of the above values. The ratio R of the D peak to the G peak in the Raman spectrum can represent the degree of defects on the material surface. The ratio R / S of the R value to the specific surface area S value can represent the defect rate per unit specific surface area. When R / S is within the above range, the unit specific surface area of ​​the anode material contains appropriate defects, the anode has low-potential defect lithium insertion characteristics, and at the same time, excessive consumption of the electrolyte can be avoided, thereby improving the Coulomb capacity of the anode material and the high-temperature, high-pressure cycle performance of the electrochemical device, while simultaneously achieving the initial efficiency of the anode material.

[0036] In some embodiments, 0.1 ≤ R ≤ 0.7. In some embodiments, 0.2 ≤ R ≤ 0.55. In some embodiments, 0.2 ≤ R ≤ 0.4. In some embodiments, R is a value within the range of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, or any two of the above values. Introducing defects to the surface of the graphite material increases the ratio R of the D peak to the G peak in the Raman spectrum. When R is within the above range, the anode material has low-potential defect lithium insertion characteristics, thereby improving the high-temperature and high-pressure cycling performance of the electrochemical apparatus, while avoiding the occurrence of excessive side reactions and excessive electrolyte consumption. This makes it possible to achieve both the Coulomb capacity and initial efficiency of the anode material, as well as the high-temperature and high-pressure cycling performance and safety performance such as thermal shock of the electrochemical apparatus. In some embodiments, the thermogravimetric decomposition temperature range of the anode material is 650°C to 850°C. After introducing defects to the surface of the anode material, the surface reaction activity increases, thereby causing the anode material to begin decomposing at a lower temperature. The thermogravimetric decomposition temperature of the anode material can reflect the degree of its surface defects. When the thermogravimetric decomposition temperature of the anode material is within the above range, the surface defects of the anode material become appropriate, the surface has appropriate reaction activity, and at the same time, an increase in side reactions and excessive consumption of the electrolyte can be avoided. This improves the Coulomb capacity of the anode material and the high temperature and high pressure cycling performance of the electrochemical apparatus, while simultaneously achieving the initial efficiency of the anode material.

[0037] In some examples, the compressed powder density of the negative electrode material was 1.90 g / cm³. 3 ~2.10 g / cm³ 3 Furthermore, the powder rebound rate is 15% to 35%. In some examples, the powder compression density of the negative electrode material is 1.90 g / cm³. 3 ~2.00g / cm 3 Furthermore, the powder rebound rate is 20% to 25%. When the negative electrode material is compressed at a certain pressure and then the pressure is released, powder rebound occurs. When the negative electrode material has the high powder compression density mentioned above, its powder rebound rate is low, which is advantageous for the negative electrode to maintain a high compression density after being manufactured into an electrode plate. This improves the volumetric energy density of the electrochemical apparatus, while simultaneously preventing a rapid decrease in the void space inside the electrode plate and a reduction in the amount of electrolyte it can hold, thereby achieving both high temperature and high pressure cycle performance for the electrochemical apparatus.

[0038] In some examples, the Coulomb capacity of the negative electrode is 360 mAh / g or higher in coin cell tests.

[0039] In some embodiments, the initial efficiency using the negative electrode material of this application is 94% to 95%.

[0040] This application further provides a negative electrode comprising the negative electrode material, dispersant and binder described in this application.

[0041] In some examples, the porosity of the negative electrode is 17% to 35%. In some examples, the porosity of the negative electrode is 20% to 30%. In some examples, the porosity of the negative electrode is 25% to 30%. In some examples, the porosity of the negative electrode is within the range of 17%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, or any two of the above values. When the porosity of the negative electrode is within the above range, the high-temperature and high-pressure cycle performance of the electrochemical apparatus can be improved.

[0042] In some examples, the negative electrode binder includes at least one of styrene-butadiene rubber, polyacrylic acid, polyacrylate, polyimide, polyamide-imide, polyvinylidene fluoride, polydifluoroethylene, polytetrafluoroethylene, aqueous acrylic resin, polyvinyl formal, or styrene-acrylic copolymer resin.

[0043] In some embodiments, any conductive material can be used as the negative electrode conductive material, as long as it does not cause a chemical change. In some embodiments, the negative electrode conductive material includes at least one of conductive carbon black, acetylene black, carbon nanotubes, Ketjenblack, conductive graphite, or graphene.

[0044] In some embodiments, the negative electrode includes a negative electrode current collector, which can be copper foil, nickel foil, stainless steel foil, titanium foil, foamed nickel, foamed copper, a polymer substrate coated with a conductive metal, or a combination thereof.

[0045] This application further provides an electrochemical apparatus comprising a positive electrode, a separator, an electrolyte, and a negative electrode as described in this application.

[0046] In some embodiments, the positive electrode includes a positive electrode active material layer and a positive electrode current collector.

[0047] In some embodiments, the positive electrode active material layer includes a positive electrode active material, a positive electrode binder, and a positive electrode conductive agent.

[0048] In some embodiments, the positive electrode active material includes at least one of lithium cobalt oxide, lithium nickel manganese cobalt oxide, lithium nickel manganese aluminate, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium iron manganese phosphate, lithium iron phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, spinel-type lithium manganese oxide, spinel-type lithium nickel manganese oxide, or lithium titanate.

[0049] In some embodiments, the positive electrode binder may include, but is not limited to, at least one of the binder polymers, such as polyvinylidene fluoride, polytetrafluoroethylene, polyolefins, sodium carboxymethylcellulose, lithium carboxymethylcellulose, modified polyvinylidene fluoride, modified SBR rubber, or polyurethane. In some embodiments, any conductive material can be used as the positive electrode conductive material, as long as it does not cause a chemical change. Examples of positive electrode conductive materials include, but are not limited to, carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, and carbon fibers; metallic materials such as metal powders or metal fibers containing copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0050] In some embodiments, the positive electrode current collector can be a metal foil sheet or a composite current collector. For example, aluminum foil can be used. Composite current collectors can be manufactured by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer substrate.

[0051] The material and shape of the separator used in the electrochemical apparatus of this application are not particularly limited, and separators manufactured by any technique disclosed in the prior art can be used. In some embodiments, the separator includes a polymer or inorganic material formed from a material stable with respect to the electrolyte of this application. In some embodiments, the separator includes a base layer and a surface treatment layer. In some embodiments, the base layer is a nonwoven fabric, membrane, or composite membrane having a porous structure. In some embodiments, the material of the base layer includes at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. In some embodiments, the material of the base layer includes at least one of a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane.

[0052] In some embodiments, a surface treatment layer is provided on at least one surface of the substrate layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic material.

[0053] In some examples, the inorganic layer comprises inorganic particles and a binder, the inorganic particles being 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 at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl alkoxide, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene.

[0054] In some examples, the polymer layer contains a polymer, and the polymer material is selected from at least one of polyamide, polyacrylonitrile, acrylic acid ester polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl alkoxide, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene).

[0055] The electrochemical apparatus of this application further includes an electrolyte. The electrolyte usable in this application can be an electrolyte known in the prior art.

[0056] In some examples, the electrolyte comprises an organic solvent, an electrolyte salt, and an optional additive. The organic solvent of the electrolyte of this application may be any organic solvent that is known in the prior art and usable as a solvent for electrolytes. The electrolyte used in the electrolyte of this application is not limited and may be any electrolyte known in the prior art. The additives of the electrolyte of this application may be any additive that is known in the prior art and usable as an electrolyte additive. In some examples, 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. In some examples, the organic solvent includes an ether-based solvent, for example, at least one of 1,3-dioxolane (DOL) and ethylene glycol dimethyl ether (DME). In some examples, the electrolyte salt may be a lithium salt, a sodium salt, etc. In some examples, the lithium salt includes at least one of an organolithium salt or an inorganic lithium salt. In some examples, the lithium salt includes, but is not limited to, lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium bistrifluoromethanesulfonylimide (LiN(CF3SO2)2,LiTFSI), lithium bis(fluorosulfonyl)imide (Li(N(SO2F)2),LiFSI), lithium bisoxalate borate (LiB(C2O4)2,LiBOB), and lithium difluoride oxalate borate (LiBF2(C2O4),LiDFOB). In some examples, the sodium salt includes, but is not limited to, at least one of NaClO4, NaPF6, NaBF4, Na(FSO2)2N, Na(CF3SO2)2N, Na(C2F5SO2)2N, NaCF3SO3, NaSbF6, NaBC4O8, LiFSI, LiTFSI, sodium lower aliphatic carboxylate, NaAlCl4, NaPO2F2, or Na2PO3F.

[0057] In some embodiments, the electrochemical apparatus of this application includes, but is not limited to, all types of primary batteries, secondary batteries, or capacitors. In some embodiments, the electrochemical apparatus is a lithium secondary battery. In some embodiments, the lithium secondary battery includes, but is not limited to, lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries. In some embodiments, the electrochemical apparatus is a sodium-ion battery.

[0058] This application further provides an electronic device, which includes the electrochemical device described in this application.

[0059] The electronic devices or apparatus of this application are not particularly limited. In some embodiments, the electronic devices of this application include, but are not limited to, notebook computers, pen-input computers, mobile computers, e-readers, mobile phones, portable facsimile machines, portable copiers, portable printers, headphone stereos, video recorders, LCD televisions, portable cleaners, portable CD players, MiniDisc players, transceivers, electronic organizers, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric-assist bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, strobes, cameras, large household storage batteries, and lithium-ion capacitors.

[0060] The manufacturing processes for electrochemical and electronic devices are well known to those skilled in the art, and this application does not particularly limit them. For example, a battery can be manufactured by the following method: A bare battery cell is manufactured by stacking a positive electrode and a negative electrode with a separator in between, and performing operations such as winding and folding as necessary. Stainless steel is selected as the sealing casing, and the bare battery cell is placed inside the sealing case. The aluminum tabs of the bare battery cell and the electrode posts of the sealing assembly are connected by laser welding to achieve electrical conductivity between the electrode posts and the bare battery cell. The lid and body of the steel case are connected by laser welding to achieve sealing of the battery. Through holes exist on the surface of the steel case, and electrolyte is injected into the battery cell through these through holes. After sufficient impregnation, the battery cell is activated under certain current and voltage conditions, thereby completing the manufacturing of the battery.

[0061] The manufacturing of lithium-ion batteries will be described below using lithium-ion batteries as an example, combining specific embodiments. Those skilled in the art will understand that the manufacturing methods described in this application are merely examples, and that any other suitable manufacturing methods are also included within the scope of this application.

[0062] Examples The following describes the performance evaluation of the examples and comparative examples of the lithium-ion battery of this application.

[0063] 1. Manufacturing of lithium-ion batteries 1. Manufacturing of negative electrode materials Artificial graphite is used as the raw material. It is placed in an atmospheric furnace, a mixture of water vapor and air is introduced, and the gas flow rate is set to F. A three-stage constant temperature reaction is carried out in this atmosphere. In the first stage, the reaction is carried out at temperature T1 for H1 hours. In the second stage, the reaction is carried out at temperature T2 for H2 hours. In the third stage, the reaction is carried out at temperature T3 for H3 hours. After the reaction is complete, it is allowed to cool naturally to room temperature to obtain the negative electrode material. The reaction conditions for each example and comparative example are shown in the table below, with Comparative Example 1 being graphite that has not undergone the reaction.

[0064] [Table 1] JPEG2026521961000003.jpg71166

[0065] 2. Manufacturing of the negative electrode The negative electrode material, sodium carboxymethylcellulose (CMC), and styrene-butadiene rubber (SBR) are uniformly dispersed in an appropriate amount of deionized water in a mass ratio of 97.5:1.2:1.3 to obtain a negative electrode slurry. Copper foil is used as the current collector, and the negative electrode slurry is uniformly applied onto the current collector. After application, drying and cold pressing are performed to manufacture the negative electrode.

[0066] 3. Manufacturing of the positive electrode Lithium cobalt oxide (chemical formula: LiCoO2) is used as the positive electrode active material. This is thoroughly mixed with acetylene black, a conductive agent, and polyvinylidene fluoride (PVDF), a binder, in an appropriate amount of N-methylpyrrolidone (NMP) solvent in a mass ratio of 96.3:2.2:1.5 to form a uniform positive electrode slurry. This slurry is then applied to aluminum foil, which serves as the current collector. After application, the material is dried and cold-pressed to manufacture the positive electrode.

[0067] 4. Manufacturing of electrolyte In a glove box under a dry argon atmosphere, ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of EC:PC:EMC:DEC = 1:3:3:3. Then, fluoroethylene carbonate and 1,3-propanesultone are added and dissolved, and the mixture is thoroughly stirred. Finally, the lithium salt LiPF6 is added and mixed uniformly to obtain the electrolyte. Here, the mass percentage of LiPF6 is 12.5%, the mass percentage of fluoroethylene carbonate is 2%, and the mass percentage of 1,3-propanesultone is 2%. The mass percentages of each substance are calculated based on the mass of the electrolyte.

[0068] 5. Manufacturing of separators A porous polyethylene polymer thin film is used as the separator.

[0069] 6. Manufacturing of lithium-ion batteries The positive electrode, separator, and negative electrode are stacked in order, with the separator positioned between the positive and negative electrodes to provide isolation, and then wound to obtain an electrode assembly. After welding tabs, the electrode assembly is placed in an outer foil aluminum plastic film, the electrolyte prepared above is injected into the dried electrode assembly, and after processes such as vacuum sealing, standing, chemical molding, shaping, and capacity testing, a soft pack lithium-ion battery is obtained.

[0070] 2. Test Method 1. Testing of negative electrode materials A completely discharged lithium-ion battery is disassembled to remove the negative electrode, which is then immersed in dimethyl carbonate (DMC) for 20 minutes. After that, it is rinsed once each with DMC and acetone to remove the electrolyte and surface SEI film. The negative electrode is then placed in an oven and baked at 80°C for 12 hours to obtain the treated negative electrode. Next, the powder on the negative electrode is scraped off with a scraper and roasted in an air atmosphere at 500°C for 3 hours to remove the CMC and SBR contained in the powder to obtain the negative electrode material. The following tests are performed on the obtained negative electrode material.

[0071] (1) Lithium insertion platform potential test The negative electrode material, SBR, CMC, and conductive carbon are thoroughly stirred and mixed in an appropriate amount of deionized water solvent in a mass ratio of 93:2.5:2.5:2 to form a uniform negative electrode slurry. This negative electrode slurry is then applied to the copper foil of the current collector, dried, and cold-pressed to manufacture the negative electrode. 1. The manufactured negative electrode is used as the positive electrode of the coin cell. It is assembled with lithium foil, the separator manufactured above, the electrolyte manufactured above, steel plate, foamed nickel, and a coin cell case to create a coin cell, and left to stand for 6 hours. The assembled coin cell is placed on a battery characteristic evaluation device (Aiden Tester) manufactured by Aiden, and a 2-cycle charge-discharge test is performed using the following process: 5 minutes of standing; 2. Discharge to 5mV at 0.05C; 3. Let it stand for 5 minutes; 4. Discharge to 5mV at 0.05mA; 5. Let it stand for 5 minutes; 6. Discharge to 5mV at 0.01mA; 7. Let stand for 5 minutes; 8. Charge to 2V at 0.1C; 9. Let it stand for 5 minutes. After the test is complete, the discharge Coulomb capacity and voltage of the second cycle can be plotted to obtain the lithium insertion curve of the material, and the I-stage lithium insertion platform potential and II-stage lithium insertion platform potential of the negative electrode material can be read from the lithium insertion curve.

[0072] (2) Terminal lithium desorption potential gradient test Using the same method as in "(1) Lithium Insertion Platform Potential Test," the lithium desorption curve of the material can be obtained by plotting the charging Coulomb capacity and voltage during the second cycle. Let Cap2 be the Coulomb capacity corresponding to a 2V potential and Cap1 be the Coulomb capacity corresponding to a 1V potential, and calculate the terminal lithium desorption potential gradient S0 (unit: mAh / g / V) using the following formula: S0 = (Cap2 - Cap1) / (2V - 1V) mAh / g / V.

[0073] (3) Coulomb capacity test Using the same method as in "(1) Lithium Insertion Platform Potential Test," the Coulomb capacity of the negative electrode material can be obtained by dividing the charging capacity of the first cycle corresponding to 1.0V by the mass of the negative electrode material.

[0074] (4) Initial efficiency test The initial efficiency of the negative electrode material is calculated by dividing the charging coulomb capacity in the first cycle by the discharging coulomb capacity in the first cycle, using the same method as in "(1) Lithium Insertion Platform Potential Test".

[0075] (5) Specific surface area test Weigh 20g to 30g of negative electrode material and compress it into tablets. After compression, weigh 1.5g to 3.5g and load it into a test sample tube. Degas the sample under 200°C conditions for 2 hours, then introduce high-purity nitrogen and set the sample to liquid nitrogen temperature and relative pressure 10°C. -6Nitrogen is adsorbed under torr conditions until adsorption saturates. An N2 adsorption / desorption curve is obtained using test software. The obtained N2 adsorption / desorption curve is processed using the BET model to obtain the specific surface area of ​​the negative electrode material. Then, a pore size distribution curve is extracted using the BJH model, and the integrated area of ​​the curve in the range of 5 nm or less represents the specific surface area of ​​pores with a diameter of 5 nm or less.

[0076] (6) Powder compression density and powder rebound rate test m grams of negative electrode material are weighed and placed in a test mold. The mold bottom area is denoted as S, and the material is compressed with a pressure of 5 tons. The filling height after the material is pressurized is recorded as H1, and then the filling height after the pressure is released and the material rebounds is recorded as H2. The powder compression density = m / (S × H1) and the powder rebound rate = (1 - H1 / H2) × 100% are calculated using the following formulas.

[0077] 2. Cycle performance testing of lithium-ion batteries under high temperature and high pressure. The lithium-ion battery will undergo charge-discharge cycle testing in a 45°C environment using the following process. 1) Let stand for 30 minutes; 2) Charge at 1C up to 4.48V, then steer at a constant voltage of 0.05C; 3) Let stand for 10 hours; 4) Discharge to 3.0V at 1C; 5) Let stand for 30 minutes; 6) Repeat steps 2) through 5) 200 times; 7) Charge at 1C up to 4.45V, then steer at a constant voltage of 0.05C; 8) Let stand for 10 hours; 9) Discharge to 3.0V at 1C; 10) Let stand for 30 minutes; 11) Repeat steps 7) to 10) until the battery capacity retention rate drops to 80%, and the recorded number of cycles is defined as the cycle life of the lithium-ion battery under high temperature and pressure.

[0078] 3. Test Results Table 1 shows the I-stage lithium insertion platform potential, II-stage lithium insertion platform potential, Coulomb capacity, and initial efficiency of the negative electrode material, as well as the cycle performance of the lithium-ion battery at high temperature and high pressure.

[0079] [Table 2]

[0080] In Comparative Example 1, the negative electrode material was not surface-treated, resulting in high lithium insertion platform potentials for both the first and second stages. Although the negative electrode material exhibited high initial efficiency, its Coulomb capacity was low, leading to a short cycle life for the lithium-ion battery at high temperature and pressure. In Comparative Example 2, after surface modification, the lithium insertion platform potentials for both the first and second stages were too low. While this extended the cycle life for the lithium-ion battery at high temperature and pressure, the Coulomb capacity and initial efficiency of the negative electrode material were low.

[0081] After surface modification, the negative electrode materials of Examples 1 to 10 exhibited a stage I lithium insertion platform potential of 30 mV to 75 mV and a stage II lithium insertion platform potential of 90 mV to 110 mV. This significantly improved the Coulomb capacity of the negative electrode material, greatly extending the cycle life of the lithium-ion battery at high temperature and high pressure, while simultaneously achieving high initial efficiency of the negative electrode material. Figure 1 shows the discharge curves of Example 5 and Comparative Example 1, showing that Example 5 has lower stage I and stage II lithium insertion platform potentials compared to Comparative Example 1.

[0082] Figure 2 shows the cycle life curves for Example 10 and Comparative Example 1, demonstrating that the cycle life of Example 10 is significantly extended compared to Comparative Example 1.

[0083] Table 2 shows the effect of the specific surface area of ​​the negative electrode material on its Coulomb capacity, initial efficiency, and the cycle performance of the lithium-ion battery at high temperature and pressure. Except for the parameters listed in Table 2, the other parameters of Examples 11 to 17 are the same as those of Example 9.

[0084] [Table 3]

[0085] As can be seen from the results, the specific surface area Sm of the negative electrode material 2 / g is 2m 2 / g~8m 2 If the ratio of the specific surface area S1 to S of pores with a pore diameter of 5 nm or less is in the range of 0.05 to 0.3, the Coulomb capacity of the negative electrode material can be further improved, extending the cycle life of lithium-ion batteries at high temperature and high pressure, while simultaneously achieving high initial efficiency of the negative electrode material. 2 / g is 4m 2 / g~7m 2 Even better results can be obtained if the ratio is / g and / or if the ratio of S1 to S is in the range of 0.15 to 0.3.

[0086] Table 3 shows the influence of the ratio R of the D peak to the G peak and its ratio R / S of S obtained by Raman measurement on the Coulomb capacity and initial efficiency of the negative electrode material, as well as the cycle performance of the lithium-ion battery at high temperature and high pressure. Except for the parameters listed in Table 3, the other parameters of Examples 18 to 22 are the same as those of Example 12.

[0087] [Table 4]

[0088] As the results show, when the R / S range is 0.025 to 0.25, the Coulomb capacity of the negative electrode material can be further improved, extending the cycle life of lithium-ion batteries at high temperature and pressure, while simultaneously achieving high initial efficiency of the negative electrode material. When the R / S range is 0.05 to 0.15, even better effects can be obtained.

[0089] When R is in the range of 0.1 to 0.7, the Coulomb capacity of the negative electrode material can be further improved, extending the cycle life of lithium-ion batteries at high temperatures and pressures, while simultaneously achieving high initial efficiency of the negative electrode material. When R is in the range of 0.2 to 0.55, even better effects can be obtained.

[0090] Table 4 shows the effect of the powder compressibility and powder rebound coefficient of the anode material, as well as the porosity of the anode, on the cycle performance of the lithium-ion battery at high temperature and high pressure. Except for the parameters listed in Table 4, the other parameters of Examples 23 to 29 are the same as those of Example 21.

[0091] [Table 5]

[0092] As the results show, the compressed density of the anode material powder was 1.90 g / cm³. 3 ~2.10 g / cm³ 3 Furthermore, if the powder rebound rate is between 15% and 35%, the cycle life of lithium-ion batteries at high temperatures and pressures can be further extended.

[0093] When the negative electrode porosity is between 17% and 35%, the cycle life of lithium-ion batteries at high temperatures and pressures can be further extended.

[0094] Any reference to “Examples,” “Some Examples,” “One Example,” “Another Example,” “Example,” “Specific Example,” or “Some Examples” throughout the specification means that at least one example or example of this application includes the specific features, structures, materials, or properties described in that example or example. Therefore, any mention of “In Some Examples,” “In Examples,” “In One Example,” “In Another Example,” “In One Example,” “Specific Example,” or “Example” throughout the specification does not necessarily refer to the same example or example of this application. Furthermore, any specific features, structures, materials, or properties described herein may be combined in any suitable manner in one or more examples or examples.

[0095] While explanatory embodiments have been shown and described, those skilled in the art will understand that the above embodiments should not be construed as limiting this application, and that modifications, substitutions, and alterations can be made to the embodiments without departing from the spirit, principles, and scope of this application.

Claims

1. A negative electrode material comprising graphite, characterized in that the I-stage lithium insertion platform potential P1 of the negative electrode material is 30 mV to 75 mV, and the II-stage lithium insertion platform potential P2 is 90 mV to 110 mV.

2. The specific surface area of ​​the negative electrode material is Sm ２ The negative electrode material according to claim 1, characterized in that it is / g and the numerical range of S is 2 to 8.

3. The negative electrode material has pores with a diameter of 5 nm or less, and the specific surface area of ​​the pores is S1 m². ２ The negative electrode material according to claim 2, characterized in that it is / g and the ratio of S1 to S is in the range of 0.05 to 0.

3.

4. The aforementioned negative electrode material is subject to the following conditions (1) to (3): (1) The numerical range of S is 4 to 7; (2) The numerical range of S1 is 0.1 to 1.5; (3) The ratio of S1 to S is in the range of 0.15 to 0.

3. The negative electrode material according to claim 3, characterized in that it satisfies at least one of the following conditions.

5. The negative electrode material according to claim 1, characterized in that the I-stage lithium insertion platform potential P1 is 30 mV to 60 mV, and the II-stage lithium insertion platform potential P2 is 90 mV to 100 mV.

6. Raman measurement revealed that the negative electrode material had a temperature of 1350 cm⁻¹. －１ D is the peak intensity at 1580 cm² of the negative electrode material. －１ The negative electrode material according to claim 2, characterized in that, if G is the peak intensity at and R is the ratio of D to G, then 0.025 ≤ R / S ≤ 0.

25.

7. The aforementioned negative electrode material is subject to the following conditions (1) to (2) (1) 0.1 ≤ R ≤ 0.7; (2) 0.05 ≤ R / S ≤ 0.15 The negative electrode material according to claim 6, characterized in that it satisfies at least one of the following conditions.

8. The negative electrode material according to claim 6, characterized in that 0.2 ≤ R ≤ 0.

55.

9. The aforementioned negative electrode material is subject to the following conditions (1) to (2) (1) The thermogravimetric decomposition temperature range of the negative electrode material is 650°C to 850°C; (2) The powder compression density of the negative electrode material is 1.90 g / cm³. ３ ~2.10 g / cm ３ Furthermore, the powder rebound rate is 15% to 35%. The negative electrode material according to claim 1, characterized in that it satisfies at least one of the following conditions.

10. A negative electrode characterized by comprising a negative electrode material, a dispersant, and a binder as described in any one of claims 1 to 9.

11. The negative electrode according to claim 10, characterized in that the porosity of the negative electrode is 17% to 35%.

12. An electrochemical apparatus characterized by comprising a positive electrode, a separator, an electrolyte, and the negative electrode described in claim 10 or 11.

13. An electronic apparatus characterized by including the electrochemical apparatus described in claim 12.

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