Modified negative electrode material and preparation method thereof, negative electrode plate, secondary battery and electric device

Abstract

The invention relates to a modified negative electrode material and a preparation method thereof, a negative electrode plate, a secondary battery and an electric device. The modified negative electrode material comprises an inner core and a coating layer coating at least part of the surface of the inner core, the inner core comprises a carbon-based material, the coating layer comprises a silicate material, the framework structure of the silicate material is composed of a three-dimensional network formed by mutually connecting angular top co-oxygen of a silica tetrahedron and a metal oxygen octahedron, and at 25 DEG C, the ionic conductivity of the silicate material is 1 * 10 <-5 > S.cm <-1 >-9 * 10 <-4 > S.cm <-1 >. The coating layer of the modified negative electrode material not only has stable chemical properties, but also can protect the surface of the core material in the circulation process and relieve volume expansion and particle breakage of the core material; meanwhile, the transmission rate of lithium ions on the surface of the core material is increased, battery polarization caused by ion migration is reduced under the condition of high-rate charging and discharging, and the fast charging performance of the battery can be greatly improved.

Description

Technical Field

[0001] The present application relates to the technical field of lithium-ion batteries, and in particular to a modified negative electrode material and a preparation method thereof, a negative electrode plate, a secondary battery, and an electrical device. Background Art

[0002] The statements herein merely provide background information related to the present application and do not necessarily constitute prior art.

[0003] In recent years, the application of lithium-ion batteries has become increasingly widespread. They are widely used in energy storage systems such as hydropower, thermal, wind, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. With the development of today's society, people's demands for the fast-charging performance of lithium-ion batteries are also increasing. However, when carbon-based materials such as graphite are used as negative electrode materials, the fast-charging performance of lithium-ion batteries is poor. Therefore, improving the fast-charging performance of lithium-ion batteries using carbon-based materials such as graphite as negative electrode materials is an urgent problem that needs to be solved. Summary of the Invention

[0004] The present application provides a modified negative electrode material that can effectively improve the fast charging performance of lithium-ion batteries containing carbon-based materials, as well as a preparation method, a negative electrode plate, a secondary battery and an electrical device.

[0005] In order to achieve the above-mentioned object, the first aspect of the present application provides a modified negative electrode material, wherein the modified negative electrode material comprises:

[0006] an inner core comprising a carbon-based material; and

[0007] The coating layer is coated on at least a portion of the surface of the core; the coating layer comprises a silicate material, the silicate material comprises a skeleton structure composed of a three-dimensional network of silicon-oxygen tetrahedra and metal-oxygen octahedra connected to each other at their corners; at 25°C, the ionic conductivity of the silicate material is 1×10 -6 S cm -1 -1×10 -4 S cm -1 .

[0008] Therefore, the modified negative electrode material in this application uses a silicate material as a coating layer, and the silicate material includes a skeleton structure composed of a three-dimensional network of silicon-oxygen tetrahedrons and metal-oxygen octahedrons connected by oxygen at the corners, and its ionic conductivity is 1×10 -6 S cm -1 -1×10 -4 S cm -1The coating layer of the modified negative electrode material not only has stable chemical properties, but can also protect the surface of the core material during the cycle and alleviate the volume expansion and particle breakage of the core material; at the same time, it can increase the rate of lithium ion transmission on the surface of the core material. In the case of high-rate charge and discharge, it can reduce the battery polarization caused by ion migration, thereby greatly improving the fast charging performance of the battery.

[0009] In some embodiments, at 25°C, the ionic conductivity of the silicate material is 5×10 -6 S cm -1 -8×10 -5 S cm -1 .

[0010] In some embodiments, the silicate material has the chemical formula A x B y SiO4, element A includes one or more of Li, Na and K, element B includes one or more of Ca, Fe, Mg, Al, Mn and Ni, 0.4≤x≤2.5, 0.2≤y≤2;

[0011] Optionally, 0.4≤x≤1.6; 0.8≤y≤1.5.

[0012] In some embodiments, the mass ratio of the coating layer to the core is (0.1-5):100, and can be optionally (0.2-1):100.

[0013] In some embodiments, the carbon-based material includes one or more of artificial graphite, natural graphite, hard carbon, soft carbon, and mesophase microspheres.

[0014] The second aspect of the present application provides a method for preparing the modified negative electrode material of the first aspect of the present application, comprising the following steps:

[0015] heating a mixture comprising the silicate material, the core and the gelling agent to prepare a gel-like mixture;

[0016] The gel-like mixture is subjected to a first sintering treatment to prepare the modified negative electrode material.

[0017] In some embodiments, the method for preparing the silicate material comprises:

[0018] The mixture containing silicon dioxide, a salt or oxide containing element A and a salt or oxide containing element B is subjected to a second sintering treatment to prepare a x B y Silicate materials of SiO4;

[0019] Wherein, the A element includes one or more of Li, Na and K, the B element includes one or more of Ca, Fe, Mg, Al, Mn and Ni, 0.4≤x≤2.5, 0.2≤y≤2;

[0020] Optionally, 0.4≤x≤1.6; 0.8≤y≤1.5.

[0021] In some embodiments, the salt containing element A includes one or more of sulfate, sulfite, carbonate, bicarbonate, nitrate, hydrochloride and ammonium salt of element A; and / or

[0022] The salt containing element B includes one or more of sulfate, sulfite, carbonate, bicarbonate, nitrate, hydrochloride and ammonium salt containing element B.

[0023] In some embodiments, the second sintering process includes at least one of the following conditions:

[0024] (1) The temperature of the second sintering treatment is 700°C-1000°C, and can be optionally 800°C-950°C;

[0025] (2) The second sintering treatment time is 3 hours to 12 hours, and can be optionally 5 hours to 10 hours;

[0026] (3) The atmosphere of the second sintering treatment is an inert gas, which may be argon;

[0027] (4) The heating rate of the second sintering treatment is 5°C / min-15°C / min.

[0028] In some embodiments, the mass ratio of the silicate material to the core is (0.1-5):100, optionally (0.2-1):100; and / or

[0029] The mass of the gelling agent accounts for 10%-25% of the mass of the inner core, and can be optionally 15%-20%.

[0030] In some embodiments, the gelling agent comprises one or more of hydrochloric acid, p-toluenesulfonic acid, acetic acid, succinic acid, maleic acid, boric acid, sulfuric acid, nitric acid, aqueous ammonia, sodium hydroxide, EDTA, and citric acid.

[0031] In some embodiments, the temperature of the first sintering treatment is 200° C.-500° C., optionally 300° C.-400° C.; and / or

[0032] The time of the first sintering treatment is 1 hour to 2 hours, and can be optionally 1 hour to 1.5 hours.

[0033] In some embodiments, the temperature of the heating treatment is 80°C-120°C, optionally 80°C-90°C; and / or

[0034] The heating treatment time is 1 hour to 2 hours, and can be optionally 1 hour to 1.5 hours.

[0035] The third aspect of the present application provides a negative electrode plate, comprising the modified negative electrode material of the first aspect of the present application or the modified negative electrode material prepared by the preparation method of the second aspect of the present application.

[0036] The fourth aspect of the present application provides a secondary battery comprising the negative electrode sheet of the third aspect of the present application. The secondary battery of the present application comprises the modified negative electrode material of the present application and has excellent fast charging performance.

[0037] The fifth aspect of the present application provides an electric device, comprising the secondary battery of the fourth aspect of the present application. The electric device of the present application comprises the secondary battery provided by the present application, and thus has at least the same advantages as the secondary battery.

[0038] The details of one or more embodiments of the present application are set forth in the following drawings and description. Other features, objects, and advantages of the present application will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the accompanying drawings should not be considered as limiting the scope of the disclosed application, the embodiments or examples currently described, and any of the best modes currently understood for these applications. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the accompanying drawings:

[0040] Figure 1 This is a schematic diagram of a battery cell according to one embodiment of the present application.

[0041] Figure 2 for Figure 1 FIG. 1 is an exploded view of a battery cell according to an embodiment of the present application.

[0042] Figure 3 This is a schematic diagram of a battery module according to one embodiment of the present application.

[0043] Figure 4 Schematic diagram of a battery pack according to one embodiment of the present application.

[0044] Figure 5 for Figure 4 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0045] Figure 6Schematic diagram of an electrical device using a secondary battery as a power source according to one embodiment of the present application.

[0046] Figure 7 This is a cross-sectional SEM image of the modified negative electrode material in Example 1.

[0047] Description of reference numerals:

[0048] 1. Battery pack; 2. Upper box; 3. Lower box; 4. Battery module; 5. Battery cell; 5. Casing; 5. Electrode assembly; 5. Cover; 6. Electrical device. DETAILED DESCRIPTION

[0049] Below, some embodiments of the modified negative electrode material and its preparation method, negative electrode sheet, secondary battery and electric device of the present application are described in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0050] " scope " disclosed in the present application can be limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and any end value can be included or not included independently, and can be arbitrarily combined, that is, any lower limit can form a scope with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3,4 and 5 are also listed, then the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is merely an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to listing the parameter as, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and so on. For example, when a parameter is expressed as an integer selected from "2-10", this is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0051] In this application, "a plurality of" or "a plurality of" refers to a number greater than or equal to 2 unless otherwise specified. For example, "one or more" means one or more than or equal to two.

[0052] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0053] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment or implementation of the present application. The appearance of such phrases in various locations in the specification does not necessarily refer to the same embodiment, nor does it necessarily refer to independent or alternative embodiments that are mutually exclusive with other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments. References to "implementations" herein have a similar understanding.

[0054] It will be appreciated by those skilled in the art that, in the methods of various embodiments or examples, the order in which the steps are written does not imply a strict order of execution and does not constitute any limitation on the implementation process, and the detailed order of execution of each step should be determined by its function and possible inherent logic. Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0055] In this application, open technical features or technical solutions described with words such as "contain," "include," and "include" do not exclude additional members beyond the listed members, unless otherwise specified. This can be considered as providing both closed features or solutions consisting of the listed members and open features or solutions that include additional members beyond the listed members. For example, if A includes a1, a2, and a3, it may or may not include other members unless otherwise specified. This can be considered as providing both the feature or solution that "A consists of a1, a2, and a3," and the feature or solution that "A includes not only a1, a2, and a3, but also other members." In this application, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0056] In this application, the terms "optionally," "optional," and "optional" are optional and refer to either option being present or absent. If a technical solution contains multiple "options," each option is considered independent unless otherwise specified and there are no conflicts or constraints.

[0057] When the negative electrode material contains carbon-based materials such as graphite, the embedding of lithium ions can only be carried out from the end face. However, since it is difficult to prepare graphite products with high isotropy, the fast charging performance of lithium-ion batteries with graphite negative electrodes is poor. In the related art, the methods for improving the fast charging performance of lithium-ion battery negative electrodes mainly include: (1) Modification of the graphite material itself, such as increasing the interlayer spacing of graphite particles, increasing the specific surface area, reducing the particle size, etc.; (2) Coating the graphite surface, mainly with an amorphous carbon or hard carbon coating layer, to enhance the fast charging capability by improving the isotropy of the particle surface; (3) By improving the slurry of the negative electrode material, the graphite slurry has a higher bonding strength with the substrate, avoiding the deterioration of bonding due to the rapid deintercalation of lithium ions, the occurrence of powder loss of the negative electrode, lithium precipitation, gas production, and other deterioration of the cycle performance.

[0058] However, when modifying the graphite particles themselves, the increase in specific surface area and the reduction in particle size can improve the fast charging performance, but it also increases the active sites on the graphite surface, reduces the coulomb efficiency of the negative electrode material, and increases lithium consumption. When coating the graphite surface, such as using amorphous carbon to coat the graphite surface, it only increases the channels for lithium ion embedding on the surface of the graphite particles, but does not increase the rate of lithium ion diffusion on the particle surface. When improving the slurry of the negative electrode material, it only alleviates the capacity attenuation caused by particle breakage caused by fast charging during the cycle, and cannot effectively improve the fast charging capability.

[0059] Based on this, the present application uses silicate materials to coat the negative electrode materials. The skeleton structure of the silicate material is composed of a three-dimensional network formed by the co-oxygenation of silicon oxygen tetrahedrons and metal oxygen octagonal corners. The skeleton structure contains channels and interconnected cavities. The cavities can accommodate cations and water molecules, and the cations can easily move in the channels. Therefore, the rate of lithium ion transmission on the graphite surface can be effectively improved. In the case of high-rate charge and discharge, the battery changes caused by ion migration are reduced, which can greatly improve the fast charging performance of the battery.

[0060] The embodiment of the present application provides a modified negative electrode material, which includes a core and a coating layer coated on at least a portion of the surface of the core; the core includes a carbon-based material, and the coating layer includes a silicate material. The silicate material includes a skeleton structure composed of a three-dimensional network of silicon-oxygen tetrahedra and metal-oxygen octahedra connected at their corners. At 25°C, the ionic conductivity of the silicate material is 1×10 -6 S cm -1-1×10 -4 S cm -1 .

[0061] At 25°C, the ionic conductivity of silicate is 1×10 -6 S cm -1 -1×10 -4 S cm -1 When the lithium ion is heated, the transfer rate of lithium ions on the surface of the core material can be effectively improved.

[0062] Silicate materials have a skeleton structure composed of a three-dimensional network of interconnected silicon-oxygen tetrahedra and metal-oxygen octagons, each connected by oxygen. This skeleton structure contains channels and interconnected cavities. The cavities can accommodate cations and water molecules, and the cations can easily move within the channels. Therefore, silicate materials can provide channels for the rapid transport of lithium ions. At the same time, the polyanionic structure of silicate materials has a strong crystal structure and stable chemical properties.

[0063] It can be understood that the coating layer of the modified negative electrode material in the present application not only has stable chemical properties, but can also protect the surface of the core material during the cycle and alleviate the volume expansion and particle breakage of the core material; at the same time, it can increase the rate of lithium ion transmission on the surface of the core material, and in the case of high-rate charge and discharge, it can reduce the battery polarization caused by ion migration, thereby greatly improving the fast charging performance of the battery.

[0064] As an example, the framework structure of the silicate material mentioned above can be determined by X-ray diffraction (XRD).

[0065] As an example, the ionic conductivity of the silicate material mentioned above can be measured using electrochemical impedance spectroscopy (EIS); specifically, it can be measured as follows:

[0066] The test uses a blocked electrode symmetrical cell, and the ionic conductivity σ is calculated as follows: σ=d / Re×S; where d is the thickness of the sample under test (cm); Re is the bulk impedance of the sample under test (ohm), which can be obtained from the intersection of the semicircle and the oblique line in the Nyquist plot of the electrochemical impedance spectroscopy; S is the effective area of ​​the electrode (cm 2 ). Test instrument: Princeton VersaSTAT electrochemical workstation. Test conditions: frequency range 0.1 MHz - 1 MHz, perturbation amplitude 10 mV, test temperature 25°C, after reaching the set temperature, keep the temperature constant for 30 minutes before measurement. In some embodiments, at 25°C, the ionic conductivity of the silicate material is 5×10 -6 S cm -1 -8×10 -5 S cm -1 .

[0067] In some embodiments, the silicate material has the formula A x B y SiO4, element A includes one or more of Li, Na, and K, element B includes one or more of Ca, Fe, Mg, Al, Mn, and Ni, 0.4≤x≤2.5, 0.2≤y≤2. This is conducive to forming a framework structure of silicon oxygen tetrahedrons and metal oxygen octagons, maintaining structural stability, and further improving ionic conductivity.

[0068] In some optional embodiments, 0.4≤x≤1.6; 0.8≤y≤1.5.

[0069] As a possible embodiment, the mass ratio of the coating layer to the core is (0.1-5):100; for example, it can be but not limited to 0.1:100, 0.3:100, 0.5:100, 0.8:100, 1:100, 1.2:100, 1.5:100, 1.8:100, 2:100, 2.3:100, 2.5:100, 2.7:100, 3:100, 3.3:100, 3.5:100, 3.8:100, 4:100, 4.2:100, 4.5:100, 4.8:100, 5:100 or a range between any two of the above ratios. When the mass ratio of the coating layer to the core is within the above range, it is beneficial for the core to perform an electrochemical reaction, and it is also beneficial to improve the transmission rate of lithium ions and improve the fast charging capability.

[0070] In some optional embodiments, the mass ratio of the coating layer to the core is (0.2-1):100.

[0071] As an example, the mass ratio of the coating layer to the core mentioned above can be determined by measuring the mass of silicon and metal elements using ICP, and then deducing the chemical formula of the silicate material based on the measurement results, and then deducing the mass ratio of the coating layer to the core.

[0072] In some embodiments, the carbon-based material includes one or more of artificial graphite, natural graphite, hard carbon, soft carbon, and mesophase microspheres.

[0073] The embodiments of the present application provide a method for preparing a modified negative electrode material, which can be used to prepare the modified negative electrode material provided in the embodiments of the present application. The method for preparing the modified negative electrode material comprises the following steps:

[0074] A mixed solution containing a silicate material, a core and a gelling agent is subjected to a heating treatment to prepare a gel-like mixture; and the gel-like mixture is subjected to a first sintering treatment to prepare a modified negative electrode material.

[0075] It can be understood that by using the gel method to uniformly coat the silicate on the surface of the core material particles to form a coating layer with higher porosity and specific surface area, the transmission rate of lithium ions on the surface of the core material can be further improved, thereby further improving the fast charging performance of the battery.

[0076] In addition, the preparation method is simple to operate, does not require expensive equipment, and can be prepared at a lower temperature into single-component or multi-component mixtures with uniform distribution, high purity, uniform particle size distribution, and high chemical activity.

[0077] It should be noted that the "gel-like mixture" mentioned above refers to a mixture with gel-like properties.

[0078] As a possible implementation manner, the mixed liquid further contains a solvent, and the solvent includes one or more of methanol, ethanol, propanol, butanol, ethylene glycol, ethylene oxide, triethanolamine and xylene.

[0079] In some embodiments, the preparation method of the silicate material comprises: performing a second sintering treatment on a mixture of silicon dioxide, a salt or oxide containing element A, and a salt or oxide containing element B to prepare a silicate material having a chemical formula of A. x B y Silicate material of SiO4; wherein element A includes one or more of Li, Na and K, element B includes one or more of Ca, Fe, Mg, Al, Mn and Ni, 0.4≤x≤2.5, 0.2≤y≤2.

[0080] In some optional embodiments, 0.4≤x≤1.6; 0.8≤y≤1.5.

[0081] As a possible implementation manner, the salt containing element A includes one or more of sulfate, sulfite, carbonate, bicarbonate, nitrate, hydrochloride and ammonium salt containing element A.

[0082] In some exemplary embodiments, the salt containing the B element includes one or more of sulfate, sulfite, carbonate, bicarbonate, nitrate, hydrochloride, and ammonium salt containing the B element.

[0083] In some embodiments, when preparing the cobaltate material, the second sintering temperature is 700°C-1000°C. For example, the temperature may be, but is not limited to, 700°C, 730°C, 750°C, 77°C, 800°C, 820°C, 850°C, 870°C, 900°C, 930°C, 950°C, 970°C, 1000°C, or a range between any two of the foregoing temperatures. Optionally, the second sintering temperature is 800°C-950°C.

[0084] In some optional embodiments, when preparing a silicate material, the second sintering treatment time is 3 hours to 12 hours; for example, it can be, but is not limited to, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, or a range between any two of the above times. Optionally, the second sintering treatment time is 5 hours to 10 hours.

[0085] As a possible implementation, when preparing the silicate material, the atmosphere of the second sintering treatment is an inert gas, which may be argon.

[0086] In some possible embodiments, the heating rate of the second sintering treatment is 5°C / min-15°C / min; for example, it can be but not limited to 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, 11°C / min, 12°C / min, 13°C / min, 14°C / min, 15°C / min or a range between any two of the above heating rates.

[0087] It should be noted that the temperature, time, atmosphere and heating rate of the second sintering treatment can be combined in any appropriate manner, and the four can be selected from any temperature, time, atmosphere and heating rate of the second sintering treatment described in this article.

[0088] As a possible embodiment, when preparing the silicate material, a mixture containing silicon dioxide, a salt or oxide containing element A, and a salt or oxide containing element B is ball milled in a ball mill at a speed of 200 rpm to 500 rpm for 10 h to 20 h. After taking out the mixture, it is subjected to a second sintering treatment in an inert atmosphere in a sealed crucible.

[0089] The rotation speed of the mixed material in the ball mill can be, but is not limited to, 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, or a range between any two of the above rotation speeds. The ball milling time can be, but is not limited to, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, 20 h, or a range between any two of the above times.

[0090] In some embodiments, the mass ratio of the silicate material to the core is (0.1-5):100; for example, it can be, but is not limited to, 0.1:100, 0.3:100, 0.5:100, 0.8:100, 1:100, 1.2:100, 1.5:100, 1.8:100, 2:100, 2.3:100, 2.5:100, 2.7:100, 3:100, 3.3:100, 3.5:100, 3.8:100, 4:100, 4.2:100, 4.5:100, 4.8:100, 5:100, or a range between any two of the above ratios. When the mass ratio of the silicate material to the core is within the above range, it is beneficial for the electrochemical reaction of the core to also improve the transmission rate of lithium ions and enhance the fast charging capability.

[0091] Optionally, the mass ratio of the silicate material to the inner core is (0.2-1):100.

[0092] As one possible embodiment, the mass of the gelling agent accounts for 10%-25% of the mass of the inner core; for example, it can be, but is not limited to, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, or a range between any two of the foregoing values. When the mass of the gelling agent accounts for the mass of the inner core within the above range, it is beneficial to evenly coat the silicate material on the surface of the inner core.

[0093] In some embodiments, the gelling agent comprises one or more of hydrochloric acid, p-toluenesulfonic acid, acetic acid, succinic acid, maleic acid, boric acid, sulfuric acid, nitric acid, aqueous ammonia, sodium hydroxide, EDTA, and citric acid.

[0094] In some optional embodiments, the temperature of the first sintering process is 200°C-500°C; for example, it can be, but is not limited to, 200°C, 220°C, 250°C, 280°C, 300°C, 320°C, 350°C, 380°C, 400°C, 430°C, 450°C, 470°C, 500°C, or a range between any two of the above temperatures. Optionally, the temperature of the first sintering process is 300°C-400°C.

[0095] As a possible embodiment, the first sintering treatment time is 1 hour to 2 hours; for example, it can be but not limited to 1 hour, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours, 2 hours, or a range between any two of the above times. Optionally, the first sintering treatment time is 1 hour to 1.5 hours.

[0096] It should be noted that the temperature and time of the first sintering treatment can be combined in any appropriate manner, and both can be selected from any temperature and time of the first sintering treatment described herein.

[0097] In some embodiments, the temperature of the heating treatment is 80°C-120°C; for example, it can be but not limited to 80°C, 90°C, 100°C, 110°C, 120°C or a range between any two of the above temperatures.

[0098] As a possible embodiment, the heating treatment time is 1 hour to 2 hours; for example, it can be but not limited to 1 hour, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours, 2 hours, or a range between any two of the above times. Optionally, the heating treatment time is 1 hour to 1.5 hours.

[0099] It should be noted that the temperature and time of the heating treatment can be combined in any appropriate manner, and both can be selected from any heating treatment temperature and time described in this document.

[0100] In some embodiments, the method for preparing the modified negative electrode material comprises the following steps:

[0101] A mixture of silicon dioxide, a salt or oxide containing element A, and a salt or oxide containing element B is ball-milled at a speed of 200-500 rpm for 10-20 hours. The mixture is taken out and heated to 700-1000°C in a sealed crucible in an inert atmosphere at a heating rate of 5-15°C / min for a second sintering treatment. The second sintering treatment time is 3-12 hours to obtain silicate material A. x B y SiO4; element A includes one or more of Li, Na, and K; element B includes one or more of Ca, Fe, Mg, Al, Mn, and Ni; 0.4≤x≤2.5, 0.2≤y≤2. The salt contains one or more of the following: sulfates, sulfites, carbonates, bicarbonates, nitrates, hydrochlorides, and ammonium salts of element A. Salts containing element B include one or more of the following: sulfates, sulfites, carbonates, bicarbonates, nitrates, hydrochlorides, and ammonium salts of element B.

[0102] A silicate material and a core are dispersed in a solvent, and a gelling agent is added to prepare a mixed solution. The mixed solution containing the silicate material, core, and gelling agent is stirred and heated to prepare a gel-like mixture. The mass ratio of the silicate material to the core is (0.1-5):100. The mass of the gelling agent accounts for 10%-25% of the mass of the core. The gelling agent includes one or more of hydrochloric acid, p-toluenesulfonic acid, acetic acid, succinic acid, maleic acid, boric acid, sulfuric acid, nitric acid, aqueous ammonia, sodium hydroxide, EDTA, and citric acid. The heating temperature is 80°C-120°C and the time is 1-2 hours. The solvent includes one or more of methanol, ethanol, propanol, butanol, ethylene glycol, ethylene oxide, triethanolamine, and xylene.

[0103] The gel-like mixture is subjected to a first sintering treatment to prepare a modified negative electrode material. The first sintering treatment is performed at a temperature of 200° C. to 500° C. and for a time of 1 hour to 2 hours.

[0104] In addition, the secondary battery and the electric device of the present application will be described below with reference to the drawings as appropriate.

[0105] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0106] The secondary battery of the present application includes the modified negative electrode material of the present application and has excellent fast charging performance.

[0107] Negative electrode

[0108] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode current collector. The negative electrode active material layer includes the modified negative electrode material of the first aspect of the present application or the modified negative electrode material prepared by the preparation method of the second aspect of the present application.

[0109] As a non-limiting example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material layer is provided on either or both of the two facing surfaces of the negative electrode current collector.

[0110] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be obtained by forming a metal material on a polymer substrate. Non-limiting examples of the metal material in the negative electrode current collector may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymer substrate in the negative electrode current collector may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0111] In some embodiments, the negative electrode active material layer may further include other negative electrode active materials for batteries known in the art. As non-limiting examples, the negative electrode active material may further include one or more of the following materials: tin-based materials and lithium titanate. Tin-based materials may include one or more of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0112] In some embodiments, the negative electrode active material layer optionally further includes a binder. Optionally, the binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyacrylic acid, polyimide, and polyacrylonitrile. The binder also optionally includes one or more of sodium polyacrylate (PAAS), polyacrylamide (PAM), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0113] In some embodiments, the negative electrode active material layer may further include a conductive agent. Optionally, the conductive agent may include one or more of conductive carbon black, superconducting carbon black, conductive graphite, acetylene black, Ketjen black, graphene, and carbon nanotubes.

[0114] In some embodiments, the negative electrode active material layer may optionally further include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0115] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the modified negative electrode material, the conductive agent, the binder and any other components, are dispersed in a solvent (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on at least one side of the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or two surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 40wt%-60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000mPa·s-10000mPa·s. When coating the negative electrode slurry, the coating unit surface density based on dry weight (excluding solvent) can be 0.05-0.18g / 1540.25mm 2 The compaction density of the negative electrode can be 1.0g / cm 3 -1.8g / cm 3 .

[0116] In some embodiments, after the negative electrode active material, conductive agent, binder and any other components are dispersed in a solvent, a turbine, paddle, propeller, screw or planetary agitator may be used for stirring to form a negative electrode slurry.

[0117] Positive electrode

[0118] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material.

[0119] As a non-limiting example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is disposed on either or both of the two facing surfaces of the positive electrode current collector.

[0120] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be obtained by forming a metal material on a polymer material substrate. In the positive electrode current collector, non-limiting examples of the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. In the positive electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0121] In some embodiments, the positive electrode active material may further include one or more of a ternary material and a lithium manganese iron phosphate material; wherein the ternary material includes Li x (Ni a Co b Mn c )1-dM d O2-yA y (x is 0.2-1.2) and / or Li x A a (Ni a Co b Mn c )1-dM d O2-yA y (x+a is 0.2-1.2); lithium manganese iron phosphate materials include Li a Mn 1-y B y P 1-z C z O 4-n D n (a is 0-1.1) and / or Li a A x Mn 1-y B y P 1-z C z O 4-n D n (a+x is 0-1.1).

[0122] It should be noted that the above limitation on x includes the molar content of Li in different charge and discharge states of the battery (usually the battery voltage is between 2-5V).

[0123] It is understandable that the battery will be accompanied by lithium (Li) deintercalation and consumption during the charge and discharge process, and the content of Li in the positive electrode plate is different when the battery is discharged to different states. In the list of positive electrode materials in this application, unless otherwise specified, the Li content is the initial state of the material. The positive electrode material is applied to the positive electrode plate in the battery system, and after the charge and discharge cycle, the Li content in the positive electrode material contained in the plate will usually change. Among them, the Li content can be measured by molar content, but is not limited to this. Regarding "the Li content is the initial state of the material", the initial state of the material refers to the state before the material is added to the positive electrode slurry. It is understandable that new materials obtained by appropriate modification on the basis of the listed positive electrode materials are also within the scope of positive electrode materials. The aforementioned appropriate modification refers to acceptable modification methods for positive electrode materials, and non-limiting examples include coating modification.

[0124] In the examples of positive electrode materials in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual O content will fluctuate. The O content can be measured by molar content, but is not limited to this.

[0125] In some embodiments, the positive electrode active material may also utilize other battery positive electrode active materials known in the art. As non-limiting examples, the positive electrode active material may include one or more of the following materials: olivine-structured lithium-containing phosphates, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials; other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, one or more of lithium cobalt oxide (such as LiCoO2), lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds. Non-limiting examples of olivine-structured lithium-containing phosphates include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ) etc. Non-limiting examples of lithium nickel cobalt aluminum oxide may include LiNi 0.80 Co 0.15 Al 0.05O2.

[0126] In some embodiments, the positive electrode active material layer may further optionally include a binder. As non-limiting examples, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0127] In some embodiments, the positive electrode active material layer may further include a conductive agent. As non-limiting examples, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0128] In some embodiments, a positive electrode sheet can be prepared by dispersing the components for preparing a positive electrode sheet, such as a positive electrode active material, a conductive agent, a binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry on at least one surface of a positive electrode current collector; and performing drying, cold pressing, and other processes to obtain a positive electrode sheet. The solvent can be selected from, but is not limited to, any of the aforementioned embodiments, such as N-methylpyrrolidone (NMP). The positive electrode slurry can be applied to a single surface of the positive electrode current collector or to both surfaces of the positive electrode current collector. The positive electrode slurry can be applied to a single surface of the positive electrode current collector or to both surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40 wt% to 80 wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000 mPa·s to 25000 mPa·s. When applying the positive electrode slurry, the coating unit area density based on dry weight (excluding solvent) can be 0.2-0.45g / 1540.25mm 2 The compaction density of the positive electrode can be 2.4g / cm 3 -2.8g / cm 3 , optional 2.4g / cm 3 -2.7g / cm 3 .

[0129] electrolytes

[0130] The electrolyte conducts ions between the positive and negative electrodes. This application does not specifically limit the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0131] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0132] In some embodiments, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorobis(oxalatophosphate) (LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP).

[0133] In some embodiments, the solvent may include ethylene carbonate (EC, ), propylene carbonate (PC, ), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate ( ), one or more of fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0134] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0135] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethylethylene carbonate (TFPC), and the like.

[0136] Isolation film

[0137] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0138] In some embodiments, the material of the separator may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0139] In some embodiments, the isolation film has a thickness of 6-40 μm, and optionally 10-16 μm.

[0140] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0141] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0142] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery can also be a soft shell, such as a pouch-type soft shell. The material of the soft shell can be plastic. Further, non-limiting examples of plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0143] A secondary battery includes at least one battery cell. A secondary battery may include one or more battery cells.

[0144] In this application, unless otherwise specified, a "battery cell" refers to a basic unit that can achieve the mutual conversion of chemical energy and electrical energy. Further, generally speaking, it includes at least a positive electrode plate, a negative electrode plate, and an electrolyte. During the battery's charge and discharge process, active ions are embedded in and out of the positive and negative electrode plates. The electrolyte plays the role of conducting active ions between the positive and negative electrode plates.

[0145] The present application has no particular restrictions on the shape of the battery cell, which can be cylindrical, square or any other shape. For example, Figure 1 The battery cell 5 is a square structure as an example.

[0146] In some of these embodiments, reference Figure 2 The outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to actual needs.

[0147] The secondary battery may be a battery module 4 or a battery pack 1 .

[0148] A battery module includes at least one battery cell. The number of battery cells contained in a battery module can be one or more, and those skilled in the art can select an appropriate number based on the application and capacity of the battery module.

[0149] Figure 3 4 is an example of a battery module. Figure 3 In the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. The plurality of battery cells 5 may further be fixed by fasteners.

[0150] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0151] In some embodiments, the battery modules may be assembled into a battery pack. The battery pack may contain one or more battery modules. Those skilled in the art may select an appropriate number based on the application and capacity of the battery pack.

[0152] Figure 4 and Figure 5 The battery pack 1 is used as an example. Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner in the battery box.

[0153] In addition, the present application also provides an electrical device, which includes the secondary battery provided in the present application. The secondary battery can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device can include, but is not limited to, mobile devices, electric vehicles, electric trains, ships, satellites, energy storage systems, etc. Among them, mobile devices can be, for example, mobile phones, laptops, etc.; electric vehicles can be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to these.

[0154] As an electrical device, a secondary battery can be selected according to its usage requirements.

[0155] Figure 6 The power consumption device 6 is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the power consumption device's requirements for high power and high energy density of secondary batteries, a battery pack or battery module can be used.

[0156] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0157] Example

[0158] Below, the embodiment of the present application is described. The embodiment described below is exemplary, is only used to explain the present application, and is not to be construed as limiting the present application. Where the technology or conditions are not specified in the embodiment, the technology or conditions described in the literature in this area or the product instructions are used. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be obtained commercially.

[0159] 1. Preparation of modified negative electrode materials

[0160] Example 1

[0161] (1) 1 mol SiO2, 0.5 mol Al2O3, and 0.5 mol Li2O were ball milled at 500 rpm for 10 h and then sintered at 900°C in a muffle furnace for 8 h to prepare LiAlSiO4 material (as a silicate material).

[0162] (2) Add 15 g of citric acid (as a gelling agent), 0.5 g of LiAlSiO4, and 100 g of artificial graphite (as a core) to 1 L of deionized water, stir thoroughly, and heat at 80 °C until a gel-like mixture is formed.

[0163] (3) The gel-like mixture was placed in a muffle furnace and sintered at 350°C for 1 hour to obtain a modified negative electrode material.

[0164] The cross-sectional SEM image of the modified negative electrode material prepared in Example 1 is as follows: Figure 7 As shown by Figure 7 It can be seen that the modified negative electrode material prepared in Example 1 is a core-shell structure, in which the LiAlSiO4 material (coating layer) is coated on the surface of the artificial graphite (core).

[0165] Example 2-22

[0166] The preparation methods of Examples 2-22 are similar to those of Example 1, and the differences are detailed in Table 1. The preparation methods of the silicate materials in Examples 5-13 are as follows:

[0167] In Example 5, the silicate material Li 1.6 Al 0.8The preparation method of SiO4 is as follows: 1 mol SiO2, 0.4 mol Al2O3 and 0.8 mol Li2O are ball milled at 500 rpm for 10 h, and then sintered at 900 ° C in a muffle furnace for 8 h to obtain Li 1.6 Al 0.8 SiO4 material (as silicate material).

[0168] In Example 6, the silicate material Li 0.4 Al 1.2 The preparation method of SiO4 is as follows: 1 mol SiO2, 0.6 mol Al2O3 and 0.2 mol Li2O are ball milled at 500 rpm for 10 h, and then sintered at 900 ° C in a muffle furnace for 8 h to obtain Li 0.4 Al 1.2 SiO4 material (as silicate material).

[0169] The silicate material LiMg in Example 7 1.5 The preparation method of SiO4 is as follows: 2 mol SiO2, 3 mol MgO and 1 mol Li2O are ball milled at 500 rpm for 10 h, and then sintered at 900 ° C in a muffle furnace for 8 h to obtain LiMg 1.5 SiO4 material (as silicate material).

[0170] In Example 8, the silicate material LiMn 1.5 The preparation method of SiO4 is as follows: 2 mol SiO2, 3 mol MnO and 1 mol Li2O are ball milled at 500 rpm for 10 h, and then sintered at 900 ° C in a muffle furnace for 8 h to obtain LiMn 1.5 SiO4 material (as silicate material).

[0171] In Example 9, the silicate material LiCa 1.5 The preparation method of SiO4 is as follows: 2 mol SiO2, 3 mol CaO and 1 mol Li2O are ball milled at 500 rpm for 10 h, and then sintered at 900 ° C in a muffle furnace for 8 h to obtain LiCa 1.5 SiO4 material (as silicate material).

[0172] In Example 10, the silicate material LiNi 1.5 The preparation method of SiO4 is as follows: 2 mol SiO2, 3 mol NiO and 1 mol Li2O are ball milled at 500 rpm for 10 h, and then sintered at 900 ° C in a muffle furnace for 8 h to obtain LiNi 1.5SiO4 material (as silicate material).

[0173] The preparation method of the silicate material LiFeSiO4 in Example 11 is as follows: 1 mol SiO2, 0.5 mol Fe2O3 and 0.5 mol Li2O are ball-milled at a speed of 500 rpm for 10 hours, and then sintered at a high temperature of 900°C in a muffle furnace for 8 hours to obtain LiFeSiO4 material (as a silicate material).

[0174] The preparation method of the silicate material NaAlSiO4 in Example 12 is as follows: 1 mol SiO2, 0.5 mol Al2O3 and 0.5 mol Na2O are ball-milled at a speed of 500 rpm for 10 hours, and then sintered at a high temperature of 900°C in a muffle furnace for 8 hours to obtain NaAlSiO4 material (as a silicate material).

[0175] The silicate material KAlSiO4 in Example 13 was prepared by ball milling 1 mol SiO2, 0.5 mol Al2O3, and 0.5 mol K2O at 500 rpm for 10 h in a ball mill, and then sintering the mixture at 900°C in a muffle furnace for 8 h to obtain KAlSiO4 material (as a silicate material).

[0176] Comparative Example 1

[0177] The preparation methods of Comparative Example 1 are similar to those of Example 1, except that artificial graphite is used as the negative electrode material in Comparative Example 1 without modification; see Table 1 for details.

[0178] Comparative Example 2

[0179] The preparation methods of Comparative Example 2 are similar to those of Example 2, except that natural graphite is used as the negative electrode material in Comparative Example 2 without modification; see Table 1 for details.

[0180] Comparative Example 3

[0181] The preparation methods of Comparative Example 3 are similar to those of Example 3, except that soft carbon is used as the negative electrode material in Comparative Example 3 without modification. See Table 1 for details.

[0182] Comparative Example 4

[0183] The preparation methods of Comparative Example 4 are similar to those of Example 4, except that hard carbon is used as the negative electrode material in Comparative Example 4 without modification; see Table 1 for details.

[0184] Comparative Example 5

[0185] The preparation method of Comparative Example 5 is similar to that of Example 1, except that the silicate material used in Comparative Example 5 is different in type. The silicate material used in Comparative Example 5 is Li 2.8 Al 0.4 SiO4, its ionic conductivity is 1.1×10 -4 .

[0186] The silicate material Li2Al in Comparative Example 5 0.66 The preparation method of SiO4 is as follows: 1.4 mol SiO2, 0.2 mol Al2O3 and 1 mol Li2O are ball milled at 500 rpm for 10 h, and then sintered at 900 ° C in a muffle furnace for 8 h to obtain Li 2.8 Al 0.4 SiO4 material (as silicate material).

[0187] Comparative Example 6

[0188] The preparation method of Comparative Example 6 is similar to that of Example 1, except that the silicate material used in Comparative Example 6 is different in type. The silicate material used in Comparative Example 6 is Li 0.1 Al 1.3 SiO4, its ionic conductivity is 8.2×10 -7 .

[0189] In Comparative Example 6, the silicate material Li 0.1 Al 1.3 The preparation method of SiO4 is as follows: 1 mol SiO2, 0.65 mol Al2O3 and 0.05 mol Li2O are ball milled at 500 rpm for 10 h, and then sintered at 900 ° C in a muffle furnace for 8 h to obtain Li 0.1 Al 1.3 SiO4 material (as silicate material).

[0190] The preparation parameters of the above embodiments and comparative examples are shown in Table 1.

[0191] Table 1

[0192]

[0193] Wherein, n in Table 1 represents the mass percentage of silicate material in the inner core.

[0194] The ionic conductivity of the silicate materials mentioned above was measured using electrochemical impedance spectroscopy (EIS), as follows:

[0195] The test uses a blocked electrode symmetrical cell, and the ionic conductivity σ is calculated as follows: σ=d / Re×S; where d is the thickness of the sample under test (cm); Re is the bulk impedance of the sample under test (ohm), which can be obtained from the intersection of the semicircle and the oblique line in the Nyquist plot of the electrochemical impedance spectroscopy; S is the effective area of ​​the electrode (cm 2 ). Test instrument: Princeton VersaSTAT electrochemical workstation. Test conditions: frequency range: 0.1 MHz to 1 MHz, perturbation amplitude: 10 mV, test temperature: 25°C. After reaching the set temperature, the temperature was maintained for 30 minutes before measurement.

[0196] 2. Preparation of Secondary Batteries

[0197] 1. Preparation of positive electrode sheet

[0198] Lithium iron phosphate, conductive carbon black SP, and binder PVDF were dispersed in a solvent N-methylpyrrolidone at a weight ratio of 96:2:2 and mixed evenly to obtain a positive electrode slurry. The positive electrode slurry was evenly coated on both sides of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet was obtained. The coating amount per unit area on both sides was 0.25 g / 1540.25 mm 2 .

[0199] 2. Preparation of negative electrode sheet

[0200] The modified negative electrode material, the binder polyvinylidene fluoride, and the conductive agent acetylene black were mixed in a mass ratio of 98:1:1, and deionized water was added to obtain a negative electrode slurry under the action of a vacuum mixer; the negative electrode slurry was evenly coated on both sides of the copper foil; the copper foil was dried at room temperature and then transferred to a 120°C oven for drying for 1 hour, and then cold pressed and cut to obtain a negative electrode sheet, wherein the coating amount per unit area on both sides was 0.15g / 1540.25mm 2 .

[0201] 3. Isolation film

[0202] A 12μm thick polyethylene isolation film was selected.

[0203] 4. Preparation of Electrolyte

[0204] The organic solvent is a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC), with a volume ratio of 3:7. In an argon atmosphere glove box with a water content of <10 ppm, fully dried lithium salt LiPF6 is dissolved in the organic solvent. 2 wt% fluoroethylene carbonate (FEC) is added and mixed thoroughly to obtain an electrolyte solution. The lithium salt concentration is 1 mol / L.

[0205] 5. Preparation of Batteries

[0206] The positive electrode sheet, separator, and negative electrode sheet are stacked in this order to form a cell. The bare cell is then placed in an outer package, injected with the aforementioned electrolyte, and sealed. After a series of steps, such as resting, hot and cold pressing, formation, clamping, and capacity separation, a secondary battery is obtained. The formation process involves charging at 0.04C to 30% remaining capacity (SOC).

[0207] 3. Performance Testing

[0208] 1. Lithium deposition window test

[0209] The lithium deposition window is used to characterize the rate limit of the negative electrode. A 200-micron-diameter copper wire is placed on the anode surface. The copper wire is then connected to an electrode and a nickel sheet is welded to serve as the third electrode (reference electrode). This creates a three-electrode battery. The lithium deposition window at different rates is verified at room temperature using the following methods:

[0210] (1) Lithium plating on the copper wire surface: Connect the positive electrode of the charge and discharge tester to the cathode of the battery and the negative electrode of the charge and discharge tester to the copper wire. Charge at a current of 20 microamperes for two hours to allow the lithium ions in the cathode to be deposited on the copper wire. Then connect the positive electrode of the charge and discharge tester to the anode of the battery and the negative electrode to the copper wire. Charge at a current of 20 microamperes for two hours to allow the lithium ions in the anode to be deposited on the copper wire.

[0211] (2) Charging and discharging at different rates: Different rates are selected for charging at room temperature, while monitoring the potential of the third electrode (copper wire) and the anode potential, so that the potential difference (potential) between the two is 0 volts and the SOC (state of charge, SOC = charging capacity / total capacity of the battery cell) at different rates is monitored to characterize the lithium plating window on the surface of the anode electrode in the battery.

[0212] 2. Rate performance test

[0213] At 25°C, discharge at 3C to 2.0V. Then perform a charge-discharge cycle as follows: let it rest for 5 minutes, charge at 3C to 3.65V, and charge at 3.65V to 0.05C. Record the number of cycles required to decay to 80% SOH.

[0214] The test results of the above embodiments and comparative examples are shown in Table 2.

[0215] Table 2

[0216]

[0217] From the comparison of the results in Table 2, it can be seen that compared with Comparative Examples 1-6, the charging window of Example 1-22 is increased, and the number of cycles required to decay to 80% SOH is significantly increased, indicating that the modified negative electrode material provided in this application has excellent fast charging performance and cycle performance.

[0218] The above description of the various embodiments tends to emphasize the differences between the various embodiments. The same or similar aspects can be referenced with each other and will not be repeated herein for the sake of brevity.

[0219] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A modified negative electrode material, characterized in that The modified negative electrode material comprises: an inner core comprising a carbon-based material; and The coating layer is coated on at least a portion of the surface of the core; the coating layer comprises a silicate material, the silicate material comprises a skeleton structure composed of a three-dimensional network of silicon-oxygen tetrahedra and metal-oxygen octahedra connected to each other at their corners; at 25°C, the ionic conductivity of the silicate material is 1×10 -6 S cm -1 -1×10 -4 S cm -1 .

2. The modified negative electrode material according to claim 1, wherein At 25°C, the ionic conductivity of the silicate material is 5×10 -6 S cm -1 -8×10 -5 S cm -1 .

3. The modified negative electrode material according to any one of claims 1 to 2, characterized in that The chemical formula of the silicate material is A x B y SiO4, element A includes one or more of Li, Na and K, element B includes one or more of Ca, Fe, Mg, Al, Mn and Ni, 0.4≤x≤2.5, 0.2≤y≤2; Optionally, 0.4≤x≤1.6; 0.8≤y≤1.

5.

4. The modified negative electrode material according to any one of claims 1 to 3, characterized in that The mass ratio of the coating layer to the core is (0.1-5):100, and can be optionally (0.2-1):

100.

5. The modified negative electrode material according to any one of claims 1 to 4, characterized in that The carbon-based material includes one or more of artificial graphite, natural graphite, hard carbon, soft carbon and mesophase microspheres.

6. A method for preparing a modified negative electrode material according to any one of claims 1 to 5, characterized in that: The method comprises the following steps: heating a mixed solution containing the silicate material, the core and the gelling agent to prepare a gel-like mixture; The gel-like mixture is subjected to a first sintering treatment to prepare the modified negative electrode material.

7. The preparation method according to claim 6, wherein The preparation method of the silicate material comprises: The mixture containing silicon dioxide, a salt or oxide containing element A and a salt or oxide containing element B is subjected to a second sintering treatment to prepare a x B y Silicate materials of SiO4; Wherein, the A element includes one or more of Li, Na and K, the B element includes one or more of Ca, Fe, Mg, Al, Mn and Ni, 0.4≤x≤2.5, 0.2≤y≤2; Optionally, 0.4≤x≤1.6; 0.8≤y≤1.

5.

8. The preparation method according to claim 7, wherein The salt containing element A includes one or more of sulfate, sulfite, carbonate, bicarbonate, nitrate, hydrochloride and ammonium salt containing element A; and / or The salt containing element B includes one or more of sulfate, sulfite, carbonate, bicarbonate, nitrate, hydrochloride and ammonium salt containing element B.

9. The preparation method according to any one of claims 7 to 8, characterized in that The second sintering process includes at least one of the following conditions: (1) The temperature of the second sintering treatment is 700°C-1000°C, and can be optionally 800°C-950°C; (2) The second sintering treatment time is 3 hours to 12 hours, and can be optionally 5 hours to 10 hours; (3) The atmosphere of the second sintering treatment is an inert gas, which may be argon; (4) The heating rate of the second sintering treatment is 5°C / min-15°C / min.

10. The preparation method according to any one of claims 6 to 9, characterized in that: The mass ratio of the silicate material to the core is (0.1-5):100, optionally (0.2-1):100; and / or The mass of the gelling agent accounts for 10%-25% of the mass of the inner core, and can be optionally 15%-20%.

11. The preparation method according to any one of claims 6 to 10, characterized in that: The gelling agent includes one or more of hydrochloric acid, p-toluenesulfonic acid, acetic acid, succinic acid, maleic acid, boric acid, sulfuric acid, nitric acid, ammonia water, sodium hydroxide, EDTA and citric acid.

12. The preparation method according to any one of claims 6 to 11, characterized in that: The temperature of the first sintering treatment is 200° C.-500° C., optionally 300° C.-400° C.; and / or The time of the first sintering treatment is 1 hour to 2 hours, and can be optionally 1 hour to 1.5 hours.

13. The preparation method according to any one of claims 6 to 12, characterized in that: The temperature of the heating treatment is 80°C-120°C, optionally 80°C-90°C; and / or The heating treatment time is 1 hour to 2 hours, and can be optionally 1 hour to 1.5 hours.

14. A negative electrode plate, characterized in that: The modified negative electrode material comprises the modified negative electrode material according to any one of claims 1 to 5 or the modified negative electrode material prepared by the preparation method according to any one of claims 6 to 13.

15. A secondary battery, characterized in that: Including the negative electrode sheet according to claim 14.

16. An electrical device, characterized in that: The secondary battery according to claim 15 is included.

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