Preparation method of negative electrode material, negative electrode plate containing negative electrode material and battery

Abstract

The invention provides a preparation method of a negative electrode material, a negative electrode plate containing the negative electrode material and a battery. The preparation method comprises the following steps: adding a pretreated high-sulfur coke raw material into an oxidizing solution for oxidation modification desulfurization treatment; the high-sulfur coke raw material obtained after oxidation modification desulfurization treatment is subjected to calcination desulfurization treatment, the negative electrode material is obtained after cooling, calcination desulfurization treatment comprises a first treatment stage and a second treatment stage, the calcination temperature of the first treatment stage is 1450-1550 DEG C, the heat preservation time is 2-7 h, and the calcination temperature of the second treatment stage is higher than that of the first treatment stage.

Description

Technical Field

[0001] The present application relates to the technical field of energy storage, and in particular to a method for preparing a negative electrode material, a negative electrode plate and a battery comprising the negative electrode material. Background Art

[0002] Secondary batteries (such as lithium-ion batteries) have the characteristics of high specific energy, high working voltage, low self-discharge rate, small volume, light weight, etc., and are widely used in various fields such as electric energy storage, portable electronic devices and electric vehicles.

[0003] As the main component in the negative electrode plate, the negative electrode material has a significant impact on the performance of secondary batteries. At present, the raw materials of negative electrode materials are mainly medium and low sulfur coke. Although high sulfur coke (sulfur content greater than or equal to 2.5 wt%) has a lower price, due to the current difficulty in sulfur removal process, on the one hand, the cost of the prepared negative electrode material is relatively high, and on the other hand, the degree of defects of the prepared negative electrode material is relatively high, which in turn leads to poor electrochemical performance of the battery. Summary of the Invention

[0004] In order to solve the above technical problems, the present application discloses a method for preparing a negative electrode material, a negative electrode plate and a battery comprising the negative electrode material, so as to realize the preparation of a negative electrode material with a low degree of defects based on high sulfur coke, thereby improving the electrochemical performance of the battery.

[0005] In the first aspect, the present application provides a method for preparing a negative electrode material, comprising the following steps:

[0006] Adding the pretreated high sulfur coke raw material into an oxidizing solution for oxidative modification desulfurization treatment;

[0007] Performing calcination desulfurization treatment on the high sulfur coke raw material after oxidative modification desulfurization treatment, and cooling to obtain the negative electrode material, wherein,

[0008] The calcination desulfurization treatment includes a first treatment stage and a second treatment stage. The calcination temperature in the first treatment stage is 1450 °C to 1550 °C, and the heat preservation time is 2 h to 7 h. The calcination temperature in the second treatment stage is higher than that in the first treatment stage.

[0009] In some embodiments of the present application, the temperature of the oxidative modification desulfurization treatment is 20 °C to 90 °C, the time of the oxidative modification desulfurization treatment is 5 h to 14 h, and the concentration of the oxidizing solution is 2.5 wt% to 9.5 wt%.

[0010] In some embodiments of the present application, the calcination temperature in the second treatment stage is 2950 °C to 3500 °C, and the heat preservation time is 24 h to 48 h.

[0011] In some embodiments of the present application, the oxidizing solution includes at least one of hydrogen peroxide, nitric acid, sulfuric acid, perchloric acid, and hypochlorous acid.

[0012] In some embodiments of the present application, the sulfur content of the high-sulfur coke raw material is 2.5 wt% to 4 wt%, the sulfur removal rate of the sulfur element in the oxidative modification desulfurization treatment is 20% to 30%, and the sulfur removal rate of the sulfur element in the calcination desulfurization treatment is 75% to 85%.

[0013] In a second aspect, the present application provides a negative electrode material prepared by the method for preparing a negative electrode material described in the first aspect.

[0014] In some embodiments of the present application, the negative electrode material satisfies at least one of the following characteristics:

[0015] a) In the Raman spectrogram of the negative electrode material, there is a first characteristic peak with a peak intensity of I -1 in the range of 1340 cm -1 to 1360 cm D , and there is a second characteristic peak with a peak intensity of I -1 in the range of 1550 cm -1 to 1650 cm G , 0.9 ≤ I D / I G <1;

[0016] b) The sulfur content of the negative electrode material is less than 30 ppm;

[0017] c) The specific surface area of the negative electrode material is BET, 2.0 m 2 / g ≤ BET ≤ 2.8 m 2 / g.

[0018] In a third aspect, the present application provides a negative electrode plate, including a current collector and a negative electrode material layer disposed on at least one surface of the current collector, and the negative electrode material layer includes the negative electrode material described in the second aspect.

[0019] In a fourth aspect, the present application provides a battery, including the positive electrode plate described in the third aspect.

[0020] In a fifth aspect, the present application provides an energy storage device, including a box body and at least one battery described in the fourth aspect, and the battery is housed in the box body.

[0021] In a sixth aspect, the present application provides an electrical equipment, including the energy storage device described in the fifth aspect, and the energy storage device supplies power to the electrical equipment.

[0022] Compared with the prior art, the present application has at least the following beneficial effects:

[0023] The present application provides a method for preparing a negative electrode material, a negative electrode sheet and a battery comprising the negative electrode material. In the preparation method, a high-sulfur coke raw material is first desulfurized by oxidative modification desulfurization treatment, and then further desulfurized by calcination desulfurization treatment. During the calcination desulfurization treatment, some oxygen-containing functional groups generated during the oxidative modification desulfurization treatment can also be removed, reducing the influence of these oxygen-containing functional groups on the performance of the negative electrode material and promoting the transformation of the coke raw material into a graphite structure with a low degree of defects. Through the oxidative modification desulfurization treatment and the calcination desulfurization treatment, the present application can thoroughly remove sulfur elements in the high-sulfur coke raw material, convert the high-sulfur coke raw material into a graphite negative electrode material suitable for secondary batteries, provide a new solution for the utilization of high-sulfur coke raw materials, and is beneficial to reducing the manufacturing cost of enterprises. When the negative electrode material prepared by the present application is applied to a secondary battery, the first Coulomb efficiency and the cycle capacity retention rate of the secondary battery are improved, and it is more suitable for application in the energy storage field with more stringent cost requirements. Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0025] Figure 1 It is a schematic structural diagram of a household energy storage system according to an embodiment of the present application;

[0026] Figure 2 It is a schematic structural diagram of a commercial energy storage system according to an embodiment of the present application.

[0027] Description of the reference numerals: 1 - energy storage device, 2 - power conversion device, 3 - first user load, 4 - second user load, 400 - commercial energy storage system, 410 - high-voltage cable, 420 - first power conversion device, 430 - second power conversion device. Detailed Embodiments

[0028] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, rather than all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0029] In this application, the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal", etc. is based on the orientation or positional relationship shown in the drawings. These terms are mainly used to better describe this application and its embodiments, and are not used to limit that the indicated devices, elements or components must have a specific orientation, or be constructed and operated in a specific orientation.

[0030] Moreover, in addition to being used to represent the orientation or positional relationship, some of the above terms may also be used to represent other meanings. For example, the term "upper" may also be used to represent a certain attachment relationship or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0031] In addition, the terms "install", "set", "provided with", "connect", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or there is internal communication between two devices, elements or components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0032] In addition, terms such as "first", "second", etc. are mainly used to distinguish different devices, elements or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise specified, the meaning of "a plurality" is two or more.

[0033] It should be noted that in the content of this application, a lithium-ion battery is used as an example of a secondary battery to explain this application, but the secondary battery of this application is not limited to lithium-ion batteries.

[0034] This application provides a method for preparing a negative electrode material, including the following steps:

[0035] Step A: Add the pretreated high-sulfur coke raw material to an oxidizing solution for oxidative modification desulfurization treatment;

[0036] Step B: Calcination desulfurization treatment is carried out on the high-sulfur coke raw material after oxidative modification desulfurization treatment, and the negative electrode material is obtained after cooling. The calcination desulfurization treatment includes a first treatment stage and a second treatment stage. The calcination temperature in the first treatment stage is 1450°C to 1550°C, and the heat preservation time is 2h to 7h, preferably 3h to 6h. The calcination temperature in the second treatment stage is higher than that in the first treatment stage. For example, the calcination temperature in the first treatment stage is 1450°C, 1480°C, 1500°C, 1520°C or 1550°C, and the heat preservation time is 2h, 3h, 4h, 5h, 6h or 7h.

[0037] In step A, through oxidative modification desulfurization treatment, the oxidizing solution can oxidize the sulfur element in the high-sulfur coke raw material into sulfur dioxide (SO2) and remove it, achieving the technical effect of preliminary desulfurization. The liquid-solid ratio of the oxidizing solution to the high-sulfur coke raw material can be 10 mL / g to 40 mL / g, which is beneficial to the full immersion of the high-sulfur coke raw material in the oxidizing solution and improves the efficiency of oxidative modification desulfurization treatment.

[0038] After step A, post-treatment such as water washing, filtration, and drying can be carried out on the slurry obtained after oxidative modification desulfurization treatment to remove the impurities generated by the reaction.

[0039] In step B, in the first treatment stage, when the calcination temperature is too low (for example, lower than 1450°C), the sulfur in the high-sulfur coke raw material cannot escape; when the calcination temperature is too high (for example, higher than 1500°C), the temperature is too high, causing a large number of defects on the surface of the negative electrode material; when the heat preservation time is too short (for example, shorter than 2h), the sulfur in the high-sulfur coke raw material cannot escape, and when the heat preservation time is too long (for example, longer than 7h), a large number of defects are caused on the surface of the negative electrode material. By controlling the calcination temperature and heat preservation time in the first treatment stage within the above range, it is beneficial to the overflow of sulfur and maintain the integrity of the negative electrode material structure. And by making the calcination temperature in the second treatment stage higher than that in the first treatment stage, the desulfurized coke raw material can be graphitized, thus transforming into a negative electrode material with a graphite structure.

[0040] In some embodiments of the present application, the temperature of the oxidative desulfurization treatment is 20°C to 90°C, preferably 25°C to 80°C; the time of the oxidative desulfurization treatment is 5 h to 14 h, preferably 6 h to 12 h; and the concentration of the oxidative solution is 2.5 wt% to 9.5 wt%, preferably 3 wt% to 8 wt%. For example, the temperature of the oxidative desulfurization treatment is 20°C, 25°C, 45°C, 65°C, 80°C or 90°C; the time of the oxidative desulfurization treatment is 5 h, 7 h, 10 h, 12 h or 14 h; and the concentration of the oxidative solution is 2.5 wt%, 3 wt%, 4 wt%, 5 wt%, 7 wt%, 8 wt% or 9.5 wt%. When the temperature of the oxidative desulfurization treatment is too low (e.g., lower than 20°C), the time is too short (e.g., shorter than 5 h), or the concentration of the oxidative solution is too low (e.g., lower than 2.5 wt%), the desulfurization effect on the high-sulfur coke raw material is not obvious; when the temperature of the oxidative desulfurization treatment is too high (e.g., higher than 90°C), the time is too long (e.g., longer than 14 h), or the concentration of the oxidative solution is too high (e.g., higher than 9.5 wt%), although the desulfurization effect is better, it will cause excessive oxidation of the surface of the high-sulfur coke raw material, resulting in an increase in the degree of defects of the prepared anode material. By controlling the temperature of the oxidative desulfurization treatment and the concentration of the oxidative solution within the above ranges, the high-sulfur coke raw material can be effectively desulfurized during the oxidative desulfurization treatment, and the increase in the degree of defects of the anode material can be avoided, thereby achieving a balance between the desulfurization effect and the performance of the anode material.

[0041] In some embodiments of the present application, the calcination temperature in the second treatment stage is 2950°C to 3500°C, and the heat preservation time is 24 h to 48 h. For example, the calcination temperature in the second treatment stage is 2950°C, 2980°C, 3000°C, 3020°C, 3050°C, 3100°C, 3300°C or 3500°C, and the heat preservation time is 24 h, 30 h, 36 h or 48 h. By controlling the calcination temperature and the heat preservation time in the second treatment stage within the above ranges, it is beneficial for the desulfurized coke raw material to transform into an anode material with a graphite structure.

[0042] In some embodiments of the present application, the oxidative solution includes at least one of hydrogen peroxide (H2O2), nitric acid (HNO3), sulfuric acid (H2SO4), perchloric acid (HClO4) and hypochlorous acid (HClO). The solvent in the above oxidative solution includes but is not limited to water, and the present application has no special limitation on the solvent.

[0043] In some embodiments of the present application, the sulfur content of the high-sulfur coke raw material is 2.5 wt% to 4 wt%, the sulfur removal rate of the sulfur element in the oxidative desulfurization treatment is 20% to 30%, and the sulfur removal rate of the sulfur element in the calcination desulfurization treatment is 75% to 85%, indicating that the preparation method of the present application can effectively remove the sulfur element in the high-sulfur coke raw material.

[0044] In this application, the removal rate = (mass percentage of sulfur element in the high-sulfur coke raw material - mass percentage of sulfur element in the coke raw material after desulfurization treatment) / mass percentage of sulfur element in the high-sulfur coke raw material * 100%.

[0045] In some embodiments of this application, the preparation method further includes:

[0046] Crush, grind and size-classify the high-sulfur coke raw material to obtain the pretreated high-sulfur coke raw material. The pretreated high-sulfur coke raw material has a relatively small particle size, which is more conducive to increasing the contact area between the high-sulfur coke raw material and the oxidizing solution and improving the efficiency of the oxidative modification desulfurization treatment.

[0047] The high-sulfur coke raw material of this application can be a commercially available high-sulfur coke raw material, and there is no special limitation in this application as long as the purpose of this application can be achieved.

[0048] This application provides a preparation method for a negative electrode material. First, the high-sulfur coke raw material is desulfurized by oxidative modification desulfurization treatment, and then further desulfurized by calcination desulfurization treatment. During the calcination desulfurization treatment, some oxygen-containing functional groups generated during the oxidative modification desulfurization treatment can also be removed, reducing the influence of these oxygen-containing functional groups on the performance of the negative electrode material and promoting the transformation of the coke raw material into a graphite structure with a low degree of defects. Through the oxidative modification desulfurization treatment and the calcination desulfurization treatment, this application can relatively thoroughly remove the sulfur element in the high-sulfur coke raw material, convert the high-sulfur coke raw material into a graphite negative electrode material suitable for lithium-ion batteries, provide a new solution for the utilization of high-sulfur coke raw materials, and is beneficial to reducing the manufacturing cost of enterprises. When the negative electrode material prepared in this application is applied to a lithium-ion battery, the initial Coulombic efficiency and cycle capacity retention rate of the lithium-ion battery are improved, and it is more suitable for application in the energy storage field with more stringent cost requirements.

[0049] This application also provides a negative electrode material prepared by the preparation method of the negative electrode material described in any of the above embodiments.

[0050] In some embodiments of this application, in the Raman spectrum of the negative electrode material, there is a first characteristic peak with a peak intensity of I in the range of 1340 cm -1 to 1360 cm -1 , and there is a second characteristic peak with a peak intensity of I in the range of 1550 cm D to 1650 cm -1 , 0.9 ≤ I -1 / I G <1. For example, I D / I G =0.9, I D / I G =0.9, I D / I G= 0.91, I D / I G = 0.92, I D / I G = 0.93 or I D / I G = 0.94. I D / I G That is the R value. The larger the R value, the greater the degree of defect of the negative electrode material. The R value of the negative electrode material of this application is within the above range, indicating that the negative electrode material of this application has a lower degree of defect, which is beneficial to improving the electrochemical performance of the lithium-ion battery.

[0051] In some embodiments of this application, the sulfur content of the negative electrode material is less than 30 ppm. In this way, the influence of too high sulfur content in the negative electrode material on the performance of the negative electrode material can be avoided.

[0052] In some embodiments of this application, the specific surface area of the negative electrode material is BET, 2.0 m 2 / g ≤ BET ≤ 2.8 m 2 / g. For example, BET is 2.0 m 2 / g, 2.1 m 2 / g, 2.3 m 2 / g or 2.8 m 2 / g. In this way, it is beneficial to improve the kinetic performance of the negative electrode material.

[0053] This application also provides a negative electrode plate, which includes a current collector and a negative electrode material layer provided on at least one surface of the current collector. The negative electrode material layer includes the negative electrode material described in any of the above embodiments.

[0054] This application also provides a battery, which includes the negative electrode plate described in any of the above embodiments.

[0055] The battery of this application also includes a positive electrode plate, a separator and an electrolyte. Among them, the separator is located between the positive electrode plate and the negative electrode plate and plays an isolating role.

[0056] In this application, the negative electrode material layer can be disposed on one surface in the thickness direction of the negative electrode current collector, or can be disposed on two surfaces in the thickness direction of the negative electrode current collector. In this application, the negative electrode material layer is disposed on the surface of the negative electrode current collector, that is, the negative electrode material layer can be disposed on a partial area of one surface of the negative electrode current collector, or can be disposed on the entire area of one surface of the negative electrode current collector. There is no particular limitation on the negative electrode current collector in this application, as long as the object of this application can be achieved. For example, it can include, but is not limited to, copper foil, copper alloy foil, nickel foil, or composite current collector, etc. In this application, there is no particular limitation on the thickness of the negative electrode current collector, as long as the object of this application can be achieved. For example, the thickness is 4 μm to 12 μm. The single-sided thickness of the negative electrode material layer in this application can be 70 μm to 200 μm.

[0057] In this application, the negative electrode material layer may further include a negative electrode binder. There is no particular limitation on the negative electrode binder in this application, as long as the object of this application can be achieved. For example, it can include, but is not limited to, at least one of acrylate, polyamide, polyimide, polyamideimide, polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethyl cellulose, and potassium carboxymethyl cellulose.

[0058] There is no particular limitation on the positive electrode sheet in this application, as long as the object of this application can be achieved. For example, the positive electrode sheet generally includes a positive electrode current collector and a positive electrode material layer. The positive electrode material layer can be disposed on one surface or two surfaces in the thickness direction of the positive electrode current collector. In this application, the positive electrode material layer is disposed on the surface of the positive electrode current collector, that is, the positive electrode material layer can be disposed on a partial area of one surface of the positive electrode current collector, or can be disposed on the entire area of one surface of the positive electrode current collector. In this application, there is no particular limitation on the positive electrode current collector, as long as the object of this application can be achieved. For example, it can include, but is not limited to, aluminum foil, aluminum alloy foil, or composite current collector, etc. In this application, there is no particular limitation on the thickness of the positive electrode current collector, as long as the object of this application can be achieved. For example, the thickness is 4 μm to 12 μm. The single-sided thickness of the positive electrode material layer in this application can be 100 μm to 200 μm.

[0059] In this application, the positive electrode material layer includes a positive electrode material. There is no particular limitation on the positive electrode material in this application, as long as the object of this application can be achieved. For example, it can include at least one of lithium iron phosphate, lithium-rich manganese-based material, lithium cobaltate, lithium manganate, and lithium manganese iron phosphate.

[0060] In the present application, the positive electrode material layer may further include a positive electrode conductive agent. There is no particular limitation on the positive electrode conductive agent in the present application, as long as the purpose of the present application can be achieved. For example, it may include but is not limited to at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fibers, acetylene black, and graphene. The above-mentioned carbon nanotubes may include but are not limited to single-walled carbon nanotubes and / or multi-walled carbon nanotubes. In the present application, the positive electrode material layer may further include a positive electrode binder. There is no particular limitation on the positive electrode binder in the present application, as long as the purpose of the present application can be achieved. For example, it may include but is not limited to at least one of fluororesins, polypropylene resins, fiber-type binders, rubber-type binders, or polyimide-type binders.

[0061] The lithium-ion battery of the present application further includes a separator. There is no particular limitation on the separator in the present application, and those skilled in the art can select it according to actual needs, as long as the purpose of the present application can be achieved. For example, the separator may include a base material layer and a surface treatment layer. The base material layer is a non-woven fabric, film, or composite film with a porous structure, and the material of the base material layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Specifically, a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be selected.

[0062] The battery of the present application further includes an electrolyte. There is no particular limitation on the electrolyte in the present application, and those skilled in the art can select it according to actual needs, as long as the purpose of the present application can be achieved. For example, after mixing at least one of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl propionate (EP), propyl propionate (PP), ethylene methyl carbonate (EMC), dimethyl carbonate (DMC), vinylene carbonate (VC), or fluoroethylene carbonate (FEC) in a certain mass ratio or volume ratio to obtain a non-aqueous organic solvent, a lithium salt is added and dissolved and mixed evenly. There is no limitation on the type of lithium salt in the present application, as long as the purpose of the present application can be achieved. For example, the lithium salt may include at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, lithium bis(oxalato)borate (LiBOB), or lithium difluoroborate.

[0063] There is no particular limitation on the concentration of the lithium salt in the electrolyte in the present application, as long as the purpose of the present application can be achieved. Taking LiPF6 as an example, the concentration of LiPF6 in the electrolyte is 1 mol / L to 2 mol / L. For example, the concentration of LiPF6 is 1 mol / L, 1.3 mol / L, 1.5 mol / L, 1.8 mol / L, or 2 mol / L.

[0064] The battery of the present application further includes a housing, and there is no particular limitation on the housing. Those skilled in the art can select according to actual needs as long as the purpose of the present application can be achieved. For example, the housing may include an aluminum-plastic film.

[0065] There is no particular limitation on the manufacturing method of the battery of the present application. The manufacturing methods well-known in the art can be selected as long as the purpose of the present application can be achieved. For example, the manufacturing method of the battery includes but is not limited to the following steps: stacking the positive electrode sheet, the separator, and the negative electrode sheet in sequence, and performing operations such as winding and folding according to needs to obtain a wound bare battery cell. Then, the bare battery cell is placed in a packaging bag, and the electrolyte is injected into the packaging bag and sealed to obtain the battery.

[0066] The present application also provides an energy storage device, which includes a box body and at least one battery in any of the above embodiments. The battery is housed in the box body. The energy storage device with this battery has excellent performance, which is beneficial to the use of the energy storage device. By housing the battery in the box body, the fixation and protection of the battery can be increased, and the service life of the energy storage device can be improved. It can be understood that there may be one or more batteries in the energy storage device. When the energy storage device contains multiple batteries, the multiple batteries can be connected in at least one of parallel and series manners.

[0067] The present application also provides an electrical device, which includes the energy storage device in the above embodiments, which is beneficial to improving the product competitiveness and service performance of the electrical device. In an optional embodiment, the electrical device includes an electrical device body, and the energy storage device is used to supply power to the electrical device body. In an optional embodiment, the electrical device body includes a device positive electrode and a device negative electrode. The positive electrode sheet of the battery in the energy storage device is used to electrically connect to the device positive electrode of the electrical device body, and the negative electrode sheet of the battery in the energy storage device is used to electrically connect to the device negative electrode of the electrical device body to supply power to the electrical device.

[0068] The electrical devices of the present application may include but are not limited to: containers, battery cars, electric vehicles, ships, spacecrafts, electric toys, and electric tools, etc. Among them, the spacecrafts are, for example, airplanes, rockets, space shuttles, and spaceships, etc. The electric toys include, for example, fixed or mobile electric toys. Specifically, for example, electric vehicle toys, electric ship toys, and electric airplane toys, etc. The electric tools include, for example, metal cutting electric tools, grinding electric tools, assembly electric tools, and railway electric tools. Specifically, for example, electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact electric drills, concrete vibrators, and electric planers.

[0069] Please refer to Figure 1 , Figure 1 which is a schematic structural diagram of a household energy storage system according to an embodiment of the present application, and the present application Figure 1The embodiments are described by taking the household energy storage scenario in user-side energy storage as an example. The energy storage device of the present application is not limited to the household energy storage scenario.

[0070] The present application provides a household energy storage system, which includes an electric energy conversion device 2 (photovoltaic panel), a first user load 3 (street lamp), a second user load 4 (such as household appliances like air conditioners), etc., and an energy storage device 1. The energy storage device 1 is a small energy storage box and can be installed on an outdoor wall in a wall-mounted manner. Specifically, the photovoltaic panel can convert solar energy into electric energy during the low electricity price period. The energy storage device 1 is used to store this electric energy and supply it to the street lamp and household appliances for use during the high electricity price period, or to supply power when the power grid is powered off / out of power.

[0071] Please refer to Figure 2 , Figure 2 which is a schematic structural diagram of a commercial energy storage system 400 according to an embodiment of the present application, and the embodiments of the present application Figure 2 are described by taking the shared energy storage scenario on the power generation / distribution side as an example. The energy storage device 1 of the present application is not limited to its energy storage scenario on the power generation / distribution side.

[0072] The present application provides a commercial energy storage system 400, which includes: a high-voltage cable 410, a first electric energy conversion device 420, a second electric energy conversion device 430, and the energy storage device 1 provided by the present application. In the case of power generation, the first electric energy conversion device 420 and the second electric energy conversion device 430 are used to convert other forms of energy into electric energy, connect with the high-voltage cable 410 and supply it for use on the power distribution side of the power grid. When the power consumption load is low and the first electric energy conversion device 420 and the second electric energy conversion device 430 generate an excess of electricity, the excess electricity is stored in the energy storage device 1 to reduce the curtailment rate of wind and light and improve the problem of new energy power generation accommodation; when the power consumption load is high, the power grid issues an instruction, and the electricity stored in the energy storage device 1 is transmitted in a grid-connected mode in cooperation with the high-voltage cable 410 to supply power for use on the power consumption side, providing various services such as peak shaving, frequency modulation, and standby for the power grid operation, giving full play to the role of the power grid in peak shaving, promoting peak shaving and valley filling of the power grid, and alleviating the power supply pressure of the power grid.

[0073] Optionally, the first electric energy conversion device 420 and the second electric energy conversion device 430 can convert at least one of solar energy, light energy, wind energy, thermal energy, tidal energy, biomass energy, and mechanical energy into electric energy.

[0074] The number of the energy storage devices 1 can be multiple. The multiple energy storage devices 1 are connected in series or in parallel with each other, and the multiple energy storage devices 1 are supported and electrically connected by a partition board (not shown in the figure). In this embodiment, "multiple" means two or more. An energy storage box can also be provided outside the energy storage device 1 for accommodating the energy storage device 1.

[0075] Optionally, the energy storage device 1 may include, but is not limited to, battery modules, battery packs, battery systems, etc. Among them, the battery module may be a battery module formed by connecting multiple batteries of the present application in series / parallel, the battery pack may include multiple batteries of the present application, and the battery system may be a charge-discharge system including the batteries or battery packs of the present application.

[0076] The actual application forms of the energy storage device 1 provided in the embodiments of the present application may be, but are not limited to, the listed products, and may also be other application forms. The embodiments of the present application do not strictly limit the application forms of the energy storage device 1. The embodiments of the present application only take the energy storage device 1 as a multi-core battery as an example for illustration. When the energy storage device 1 includes single cells, the single cells may be at least one of cylindrical batteries, square batteries, etc.

[0077] Embodiment

[0078] Hereinafter, preparation examples, examples, and comparative examples are given to more specifically illustrate the embodiments of the present application. Various tests and evaluations are carried out according to the following methods.

[0079] Example 1

[0080] <Preparation of negative electrode material>

[0081] Select a high-sulfur coke raw material with a sulfur content of 2.8 wt%, and perform pretreatment such as coarse crushing, grinding, and particle size classification on it to obtain a pretreated high-sulfur coke raw material (average particle size is 12 μm); take 1 kg of the pretreated high-sulfur coke raw material and add it to 10 L of nitric acid (concentration is 7 wt%), stir at 34 °C for 7 h for oxidative modification desulfurization treatment, and then perform post-treatment on the obtained slurry such as washing, filtering, and drying. The obtained product is subjected to calcination desulfurization treatment: first, a first treatment stage with a calcination temperature of 1500 °C and a holding time of 3 h is carried out, and then a second treatment stage with a calcination temperature of 3000 °C and a holding time of 27 h is carried out. After natural cooling, the negative electrode material is obtained.

[0082] <Preparation of negative electrode sheet>

[0083] Dissolve 0.5% carboxymethyl cellulose and 1.7% binder PVDF by mass in water, add 0.8% carbon black conductive agent by mass and 97% active material by mass to prepare a negative electrode slurry with a solid content of 60 wt%, and stir evenly; uniformly coat the negative electrode slurry on one surface of a negative electrode current collector copper foil with a thickness of 10 μm, with a coating thickness of 130 μm, and then vacuum dry at 110 °C for 12 h, and obtain a negative electrode sheet after rolling.

[0084] <Preparation of positive electrode sheet>

[0085] The cathode active material lithium iron phosphate, the conductive agent conductive carbon black (SP), and the binder polyvinylidene fluoride (PVDF) were dispersed in the solvent N-methylpyrrolidone (NMP) according to a mass ratio of 97:0.5:2.5 to prepare a cathode slurry with a solid content of 50 wt%. The cathode slurry was uniformly coated on one surface of a cathode current collector aluminum foil with a thickness of 10 μm, and the coating thickness was 100 μm. Then, it was vacuum dried at 110 °C for 12 h, and a cathode plate was obtained after rolling.

[0086] <Preparation of electrolyte>

[0087] In an argon atmosphere glove box with a water content ≤ 1 ppm, ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) were mixed according to a mass ratio of 1:1:1. After that, the dried lithium salt lithium hexafluorophosphate was dissolved in the solvent and stirred until completely dissolved and uniform. Then, the lithium salt LiPF6 was added and dissolved in the above solvent. After mixing evenly, an electrolyte was obtained. Among them, the molar concentration of LiPF6 in the electrolyte was 1 mol / L.

[0088] <Assembly of lithium-ion battery>

[0089] The prepared cathode plate, separator, and anode plate were stacked in sequence, with the separator in the middle of the cathode plate and the anode plate. After winding, a bare battery cell was obtained. After welding the tabs, the bare battery cell was assembled into the outer package. After injecting the prepared electrolyte, the battery cell was encapsulated, left standing, formed, shaped, capacity tested, etc., to prepare a lithium-ion battery.

[0090] Examples 2 to 6

[0091] Except that in <Preparation of anode material>, the relevant preparation parameters in the calcination desulfurization treatment process were adjusted according to Table 1, the rest were the same as in Example 1.

[0092] Examples 7 to 19

[0093] Except that in <Preparation of anode material>, the relevant preparation parameters in the oxidation modification desulfurization treatment process were adjusted according to Table 2, the rest were the same as in Example 1.

[0094] Comparative Example 1

[0095] Except that in <Preparation of anode material>, only the calcination desulfurization treatment was carried out without the oxidation modification desulfurization treatment, the rest were the same as in Example 1.

[0096] Comparative Example 2

[0097] Except that in <Preparation of anode material>, only the oxidation modification desulfurization treatment was carried out without the calcination desulfurization treatment, the rest were the same as in Example 1.

[0098] Comparative Example 3 to Comparative Example 6

[0099] Except in the <preparation of the negative electrode material>, the relevant preparation parameters in the calcination desulfurization treatment process were adjusted according to Table 1, and the rest was the same as in Example 1.

[0100] Table 1: Preparation parameters of Examples 1 to 6, Comparative Examples 3 to 6

[0101]

[0102] Table 2: Preparation parameters of Example 1, Examples 7 to 19

[0103]

[0104]

[0105] Testing methods and equipment:

[0106] Specific surface area test of the negative electrode material:

[0107] The specific surface area of the negative electrode material was tested using a carbon black specific surface area analyzer (model: TriStar II 3030).

[0108] Sulfur content test of the negative electrode material:

[0109] The content of sulfur element in the negative electrode material was tested using an inductively coupled plasma (ICP) spectrometer (model: Thermo Fisher L-21-0398).

[0110] Raman spectroscopy test:

[0111] The Raman spectrum of the negative electrode material was tested using a Raman spectrometer (model: LabRAM HR Evolution). The peak intensity of the negative electrode material at 1340 cm -1 to 1360 cm -1 (i.e., around 1350 cm -1 ) is I D , and the peak intensity at 1550 cm -1 to 1650 cm -1 (i.e., around 1580 cm -1 ) is I G . Based on this, I D / I G was calculated.

[0112] Cycling performance test:

[0113] At 25 °C, the lithium-ion battery was subjected to a constant-power charge-discharge cycle test on a charge-discharge instrument (model: Nebula Charge-Discharge Test System BAT-NEEFLCT-05300-V010). The charge-discharge rate was 0.5C, the charge-discharge voltage window was 2.5V to 3.65V, and the battery was cycled until the capacity of the lithium-ion battery was less than 80% of the initial capacity. The number of cycles was recorded.

[0114] Calculate the capacity retention rate after 200 cycles. The calculation formula is: Capacity retention rate after the Nth cycle = (Discharge capacity after the Nth cycle / Discharge capacity of the first cycle) × 100%.

[0115] Among them, a complete charge-discharge is usually called a charge-discharge cycle, and cycling N times means repeating the above process N times.

[0116] Table 3: Performance data of each example and comparative example

[0117]

[0118]

[0119] Combined with Table 3, it can be seen from Examples 1 to 19 and Comparative Examples 1 to 2 that when only calcination desulfurization treatment is carried out without oxidation modification desulfurization treatment (such as Comparative Example 1), the R value of the negative electrode material is relatively large, indicating a higher degree of defects in the negative electrode material, and both the first Coulomb efficiency of the lithium-ion battery and the capacity retention rate after 200 cycles are relatively low. In addition, since only calcination desulfurization treatment was carried out in Comparative Example 1, its specific surface area is relatively large; when only oxidation modification desulfurization treatment is carried out without calcination desulfurization treatment (such as Comparative Example 2), the R value of the negative electrode material is also relatively large, indicating a higher degree of defects in the negative electrode material, and both the first Coulomb efficiency of the lithium-ion battery and the capacity retention rate after 200 cycles are also relatively low. In addition, since only oxidation modification desulfurization treatment was carried out in Comparative Example 2, its specific surface area is relatively large; while in this application, the high-sulfur coke raw material is subjected to two-step treatment of oxidation modification desulfurization treatment and calcination desulfurization treatment, and the R value of the prepared negative electrode material is small, indicating a low degree of defects in the negative electrode material, and the first Coulomb efficiency of the lithium-ion battery and the capacity retention rate after 200 cycles are improved.

[0120] It can be seen from Examples 1 to 6 and Comparative Examples 3 to 6 that when the calcination temperature in the first treatment stage is too low or too high (such as Comparative Example 3 or Comparative Example 4), the R value of the negative electrode material is relatively large, indicating a relatively high degree of defects in the negative electrode material, and both the first Coulombic efficiency of the lithium-ion battery and the capacity retention rate after 200 cycles are relatively low; when the heat preservation time in the first treatment stage is too short or too long (such as Comparative Example 5 or Comparative Example 6), the R value of the negative electrode material is also relatively large, indicating a relatively high degree of defects in the negative electrode material, and both the first Coulombic efficiency of the lithium-ion battery and the capacity retention rate after 200 cycles are also relatively low; based on the two-step treatment of oxidative modification desulfurization treatment and calcination desulfurization treatment of the high-sulfur coke raw material in this application, by regulating the calcination temperature and heat preservation time in the first treatment stage of the calcination desulfurization treatment, it is beneficial to obtain a negative electrode material with a low degree of defects, thereby being beneficial to the improvement of the electrochemical performance of the lithium-ion battery.

[0121] Process parameters such as the type of oxidizing solution, the concentration of the oxidizing solution, the temperature of the oxidative modification desulfurization treatment, and the time of the oxidative modification desulfurization treatment usually also affect the performance of the negative electrode material. It can be seen from Example 1, Examples 7 to 19 that based on the two-step treatment of oxidative modification desulfurization treatment and calcination desulfurization treatment of the high-sulfur coke raw material in this application, by regulating the above process parameters within the scope of this application, it is beneficial to obtain a negative electrode material with a low degree of defects, thereby being beneficial to the improvement of the electrochemical performance of the lithium-ion battery.

[0122] The above has introduced in detail a method for preparing a negative electrode material, a negative electrode sheet and a battery including the negative electrode material disclosed in this application. Specific examples are used in this article to elaborate on the principle and implementation manner of this application. The description of the above examples is only used to help understand the technical solution and the core invention point of the embodiments of this application; at the same time, for those of ordinary skill in the art, according to the idea of this application, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to this application.

Claims

1. A method for preparing a negative electrode material, characterized in that, It includes the following steps: Adding the pretreated high-sulfur coke raw material into an oxidizing solution for oxidative modification desulfurization treatment; Performing calcination desulfurization treatment on the high-sulfur coke raw material after oxidative modification desulfurization treatment, and obtaining the negative electrode material after cooling, wherein, The calcination desulfurization treatment includes a first treatment stage and a second treatment stage. The calcination temperature in the first treatment stage is 1450°C to 1550°C, and the heat preservation time is 2h to 7h. The calcination temperature in the second treatment stage is higher than that in the first treatment stage.

2. The preparation method according to claim 1, characterized in that, The temperature of the oxidative modification desulfurization treatment is 20°C to 90°C, the time of the oxidative modification desulfurization treatment is 5h to 14h, and the concentration of the oxidizing solution is 2.5wt% to 9.5wt%.

3. The preparation method according to claim 1, wherein The calcination temperature in the second treatment stage is 2950°C to 3500°C, and the heat preservation time is 24h to 48h.

4. The preparation method according to claim 1, characterized in that, The oxidizing solution includes at least one of hydrogen peroxide, nitric acid, sulfuric acid, perchloric acid, and hypochlorous acid.

5. The preparation method according to claim 1, characterized in that, The sulfur content of the high-sulfur coke raw material is 2.5wt% to 4wt%. The sulfur removal rate of the sulfur element in the oxidative modification desulfurization treatment is 20% to 30%. The sulfur removal rate of the sulfur element in the calcination desulfurization treatment is 75% to 85%.

6. The preparation method according to claim 1, characterized in that, The preparation method further includes: Performing crushing, grinding, and particle size classification treatment on the high-sulfur coke raw material to obtain the pretreated high-sulfur coke raw material.

7. A negative electrode material, characterized in that, It is prepared by the preparation method of the negative electrode material according to any one of claims 1 to 6.

8. The negative electrode material according to claim 7, characterized in that, The negative electrode material satisfies at least one of the following characteristics: a) In the Raman spectrum of the negative electrode material, there is a first characteristic peak with peak intensity I -1 in the range of 1340 cm -1 to 1360 cm D , and a second characteristic peak with peak intensity I -1 in the range of 1550 cm -1 to 1650 cm G . 0.9 ≤ I D / I G <1; b) The sulfur content of the negative electrode material is lower than 30 ppm; c) The specific surface area of the negative electrode material is BET, 2.0 m 2 / g ≤ BET ≤ 2.8 m 2 / g.

9. A negative electrode plate, characterized in that, It includes a current collector and a negative electrode material layer provided on at least one surface of the current collector. The negative electrode material layer includes the negative electrode material according to claim 7 or 8.

10. A battery, characterized in that, It includes the negative electrode plate according to claim 9.

11. An energy storage device, characterized in that, It includes a box body and at least one battery according to claim 10. The battery is housed in the box body.

12. An electrical device, characterized in that, It includes the energy storage device according to claim 11. The energy storage device supplies power to the electrical equipment.

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