Secondary battery and preparation method therefor, positive electrode lithium supplementing agent, positive electrode sheet and electric device

Abstract

The present application relates to a secondary battery and a preparation method therefor, a positive electrode lithium supplementing agent, a positive electrode sheet and an electric device. The secondary battery comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, and the positive electrode film layer comprises a positive electrode lithium supplementing agent. The positive electrode lithium supplementing agent comprises a porous carbon material and a lithium-rich material distributed inside the porous carbon material, wherein the volume-average particle size Dv50 of the lithium-rich material is 0.1-3 μm, and the ratio of the volume-average particle size Dv50 of the lithium-rich material to the volume-average particle size Dv50 of the porous carbon material is denoted as P, where P≤0.35. The mass percentage content of lithium in the positive electrode lithium supplementing agent is 7-11%, and the positive electrode lithium supplementing agent in the secondary battery can improve the discharge capacity of the battery at a relatively low voltage.

Description

Secondary battery and preparation method thereof, positive electrode lithium supplementing agent, positive electrode sheet and electric device

[0001] Cross-reference to related applications

[0002] This application claims priority from Chinese Patent Application No. 202411292873.4, filed on September 14, 2024, entitled "Secondary battery and preparation method thereof, positive electrode lithium supplementing agent, positive electrode sheet and electric device", which is incorporated by reference in its entirety. TECHNICAL FIELD

[0003] The present application relates to the technical field of secondary batteries, and in particular to a secondary battery and a preparation method thereof, a positive electrode lithium supplementing agent, a positive electrode sheet and an electric device. BACKGROUND

[0004] In recent years, with the increasingly wide application of secondary batteries such as lithium ion secondary batteries, lithium ion secondary batteries are widely used in energy storage power supply systems such as hydroelectric, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. Since lithium ion secondary batteries have achieved great development, higher requirements have been put forward for their energy density, cycle performance and safety performance, etc. Pre-adding a lithium supplementing agent that can provide active lithium to the lithium ion secondary battery system is a common measure in the industry.

[0005] The lithium supplementing method in the battery can be mainly divided into positive electrode lithium supplementing and negative electrode lithium supplementing. Among them, the positive electrode lithium supplementing is to add a positive electrode lithium supplementing agent to the positive electrode system of the battery, and the positive electrode lithium supplementing agent is usually a lithium-rich material such as Li2C2O4 (lithium oxalate), Li2C3O5, Li2C4O4, Li2C4O6, etc. However, the lithium-rich material has the problem of high decomposition voltage, which causes the lithium-rich material to be unable to fully release lithium ions under low voltage conditions, thereby affecting the discharge capacity of the battery. SUMMARY

[0006] The present application provides a secondary battery and a preparation method thereof, a positive electrode lithium supplementing agent, a positive electrode sheet and an electric device, which can improve the discharge capacity of the battery at a lower voltage.

[0007] In a first aspect of the present application, a secondary battery is provided, comprising a positive electrode sheet, the positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer comprising a positive electrode lithium supplementing agent, the positive electrode lithium supplementing agent comprising a porous carbon material and a lithium-rich material distributed inside the porous carbon material, the lithium-rich material having a volume average particle size Dv50 of 0.1 μm to 3 μm, a ratio of the volume average particle size Dv50 of the lithium-rich material to the volume average particle size Dv50 of the porous carbon material being denoted as P, P≤0.35, and a mass percentage content of lithium in the positive electrode lithium supplementing agent being 7% to 11%.

[0008] By adsorbing the lithium-rich material through the porous carbon material of the positive electrode lithium supplementing agent in the secondary battery and reducing the Dv50 of the lithium-rich material, and by controlling the ratio of the Dv50 of the lithium-rich material to the Dv50 of the porous carbon material and the mass percentage content of lithium in the positive electrode lithium supplementing agent, the capacity and decomposition potential of the lithium-rich material are balanced, and thus the positive electrode lithium supplementing agent obtained has a lower decomposition voltage and higher lithium supplementing performance, and is capable of supplementing lithium at a low decomposition voltage, thereby improving the discharge capacity of the battery.

[0009] In some embodiments of the present application, the volume average particle size Dv50 of the lithium-rich material is 0.5 μm to 2 μm.

[0010] In some embodiments of the present application, 0.01≤P≤0.35.

[0011] In some embodiments of the present application, 0.05≤P≤0.16.

[0012] In some embodiments of the present application, the volume average particle size Dv50 of the lithium-rich material is 0.5 μm to 1.3 μm.

[0013] In some embodiments of the present application, the volume average particle size Dv50 of the porous carbon material is 2 μm to 30 μm.

[0014] In some embodiments of the present application, the volume average particle size Dv50 of the porous carbon material is 5 μm to 10 μm.

[0015] In some embodiments of the present application, the specific surface area of the porous carbon material is 1700 m 2 / g to 3000 m 2 / g.

[0016] In some embodiments of the present application, the pore volume of the porous carbon material is 0.5 cm 3 / g to 3.5 cm 3 / g.

[0017] In some embodiments of the present application, the lithium-rich material comprises one or more of Li2C2O4, Li2C3O5, Li2C4O4, and Li2C4O6.

[0018] In some embodiments of the present application, the porous carbon material comprises activated carbon.

[0019] In some embodiments of the present application, the positive electrode lithium supplementing agent further comprises a catalyst, the catalyst is distributed on the surface of the porous carbon material, and the catalyst is a non-metallic catalyst. Optionally, the catalyst comprises one or more of polyaniline, nitrogen-doped carbon nanotubes, carboxylated carbon nanotubes, and MNC composite catalysts.

[0020] In some embodiments of the present application, the mass percentage content of the catalyst in the positive electrode lithium supplementing agent is 0.1% to 5%.

[0021] In some embodiments of the present application, the mass percentage content of the catalyst in the positive electrode lithium supplementing agent is 0.5% to 1.5%.

[0022] In some embodiments of the present application, the volume average particle size Dv50 of the catalyst is 1 μm to 10 μm.

[0023] In some embodiments of the present application, the volume average particle size Dv50 of the catalyst is 1 μm to 3 μm.

[0024] In some embodiments of the present application, the positive electrode film layer comprises a positive electrode active material layer, and the mass percentage content of the positive electrode lithium supplementing agent in the positive electrode active material layer is 0.1% to 10%.

[0025] In some embodiments of the present application, the mass percentage content of the positive electrode lithium supplementing agent in the positive electrode active material layer is 0.5% to 4%.

[0026] In some embodiments of the present application, the formation voltage range of the secondary battery is 2.5 V to 4.3 V.

[0027] In a second aspect of the present application, a secondary battery is provided, comprising the steps of preparing a positive electrode sheet; the step of preparing the positive electrode sheet comprises:

[0028] dissolving a lithium salt in a first solvent to obtain a first solution;

[0029] mixing the first solution with a porous carbon material to obtain a second solution;

[0030] crystallization is performed on the second solution by adding a second solvent to form a lithium-rich material inside the porous carbon material, the volume average particle size Dv50 of the lithium-rich material is 0.1-3 μm, a ratio of the volume average particle size Dv50 of the lithium-rich material to the volume average particle size Dv50 of the porous carbon material is denoted as P, P≤0.35, and a positive electrode lithium supplement is obtained, the mass percentage of lithium in the positive electrode lithium supplement is 7-11%.

[0031] A slurry containing the positive electrode lithium supplement is arranged on at least one surface of the positive electrode current collector, a drying process is performed to form a positive electrode film layer, and the positive electrode sheet is obtained.

[0032] In a third aspect of the present application, a positive electrode lithium supplement is provided, which includes a porous carbon material and a lithium-rich material distributed inside the porous carbon material, the volume average particle size Dv50 of the lithium-rich material is 0.1-3 μm, a ratio of the volume average particle size Dv50 of the lithium-rich material to the volume average particle size Dv50 of the porous carbon material is denoted as P, P≤0.35, and the mass percentage of lithium in the positive electrode lithium supplement is 7-11%.

[0033] In a fourth aspect of the present application, a positive electrode sheet is provided, which includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, the positive electrode film layer includes the positive electrode lithium supplement of the third aspect of the present application.

[0034] In a fifth aspect of the present application, an electrical device is provided, which includes at least one of the secondary battery of the first aspect of the present application, the secondary battery prepared by the preparation method of the second aspect of the present application, the positive electrode lithium supplement of the third aspect of the present application, and the positive electrode sheet of the fourth aspect of the present application.

[0035] The details of one or more embodiments of the present application are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the present application will be apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF DRAWINGS

[0036] To better describe and illustrate the embodiments or examples provided by the present application, one or more drawings can be referred to. Additional details or examples used to describe the drawings should not be considered as limiting the scope of the disclosed application, the presently described embodiments or examples, and any one of the best modes of these applications currently understood. Moreover, the same reference numbers are used to represent the same components throughout the drawings. In the drawings:

[0037] FIG. 1 is a schematic diagram of a battery cell according to an embodiment of the present application.

[0038] FIG. 2 is an exploded view of the battery cell according to an embodiment of the present application shown in FIG. 1.

[0039] FIG. 3 is a schematic view of a battery module according to an embodiment of the present application.

[0040] FIG. 4 is a schematic view of a battery pack according to an embodiment of the present application.

[0041] FIG. 5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 4.

[0042] FIG. 6 is a schematic view of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0043] Reference Signs: 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 battery cell; 51 case; 52 electrode assembly; 53 cover plate; 6 electric device. DETAILED DESCRIPTION

[0044] Hereinafter, some embodiments of a secondary battery and a method of manufacturing the same, a positive electrode lithium supplement, a positive electrode tab, and an electric device according to the present application are described in detail with proper reference to the accompanying drawings. However, there can be cases where unnecessary detailed descriptions are omitted. For example, there can be cases where detailed descriptions of matters well known, repetitive descriptions of substantially identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the accompanying drawings and the following description are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0045] "ranges" disclosed herein can be defined, for example, by the lower and upper values. Any lower limit can independently be combined with any upper limit to define a range of any value. For example, if a range of 60-120 and 80-110 is listed as exemplary, it is understood that a range of 60-110 and 80-120 are also contemplated. Furthermore, if a minimum range value of 1 and 2 is listed, and if a maximum range value of 3, 4, and 5 is also listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, the use of "a" and "an" to describe a single item can be taken as equivalent to the use of "one" or "at least one," unless otherwise limited by context. In this application, the use of "or" as a conjunction can be taken as

[0046] In this application, the use of "a" and "an" to describe a single item can be taken as equivalent to the use of "one" or "at least one," unless otherwise limited by context. In this application, the use of "or" as a conjunction can be taken as

[0047] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, if not specifically stated.

[0048] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment or implementation of the application. The appearances of the phrase that the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of other embodiments. It is explicitly stated that the embodiments described herein can be combined with other embodiments. Reference herein to "an implementation" has a similar understanding.

[0049] It is understood by those skilled in the art that the order of writing each step in the method of each embodiment or example does not mean a strict execution order and does not constitute any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. If not specifically stated, all steps of the present application can be performed in sequence or randomly, preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method also comprises step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0050] In the present application, the open technical features or technical solutions described by the words "containing", "including", "comprising" and the like do not exclude additional members other than the listed members, and can be regarded as providing both a closed feature or solution composed of the listed members and an open feature or solution including additional members in addition to the listed members. For example, A includes a1, a2 and a3, and unless otherwise specified, it can also include other members or can not include additional members, and can be regarded as providing both the feature or solution that "A is composed of a1, a2 and a3" and the feature or solution that "A includes a1, a2 and a3, and also includes other members". In the present 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.

[0051] In the present application, "optionally", "optional" and "optional" mean that it can or can not be present, i.e. it can be selected from either of the two parallel solutions "yes" or "no". If there are multiple "optional" in a technical solution, unless otherwise specified, and there is no contradiction or mutual restriction, each "optional" is independent of each other.

[0052] The traditional lithium-rich materials such as Li2C2O4, Li2C3O5, Li2C4O4, Li2C4O6 have poor electrical conductivity, low ion mobility and electrochemical activity, low decomposition efficiency and large particle size, which leads to too large decomposition voltage, and after decomposition is completed in the electrode, large holes are formed in the electrode, causing local stress unevenness to cause collapse, which easily causes problems such as electrode demolding, poor electrode contact, etc. Because the decomposition voltage of the traditional lithium-rich material is too large, when it is applied to the positive electrode tab of the battery for lithium supplementation, the upper limit voltage of the battery formation process usually needs to reach 4.7V or more.

[0053] Based on this, in one aspect, the application provides a secondary battery, comprising a positive electrode sheet, the positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, the positive electrode film layer comprising a positive electrode lithium supplement agent, the positive electrode lithium supplement agent comprising a porous carbon material and a lithium-rich material distributed inside the porous carbon material, the lithium-rich material having a volume average particle size Dv50 of 0.1-3 μm, the ratio of the volume average particle size Dv50 of the lithium-rich material to the volume average particle size Dv50 of the porous carbon material being P, P≤0.35, and the mass percentage of lithium in the positive electrode lithium supplement agent being 7-11%.

[0054] The porous carbon material of the positive electrode lithium supplement agent in the secondary battery adsorbs the lithium-rich material and reduces the Dv50 of the lithium-rich material, and the balance between the capacity and decomposition potential of the lithium-rich material is achieved by controlling the ratio of the Dv50 of the lithium-rich material to the Dv50 of the porous carbon material and the mass percentage of lithium in the positive electrode lithium supplement agent, so that the positive electrode lithium supplement agent obtained has a lower decomposition voltage and higher lithium supplement performance, and can supplement lithium at a low decomposition voltage, thereby improving the discharge capacity of the battery.

[0055] The mass percentage of lithium in the positive electrode lithium supplement agent is controlled to be 7-11%, because when the mass percentage of lithium in the positive electrode lithium supplement agent is too high, the conductivity of the positive electrode lithium supplement agent is poor, the polarization is large, the decomposition voltage of the positive electrode lithium supplement agent is still high, and the lithium ions in the positive electrode lithium supplement agent are limited to be released; when the mass percentage of lithium in the positive electrode lithium supplement agent is too low, the lithium supplement performance of the positive electrode lithium supplement agent is affected, and the discharge capacity of the battery is not significantly improved.

[0056] In addition, the above design of the positive electrode lithium supplement agent in the secondary battery can improve the structural stability of the positive electrode lithium supplement agent, thereby improving the problems of demolding and poor electrode contact of the positive electrode sheet into which the positive electrode lithium supplement agent is introduced.

[0057] Understandably, P can include but is not limited to 0.35, 0.33, 0.29, 0.2, 0.21, 0.1, 0.08, 0.05, 0.02, 0.01, 0.008, 0.005, 0.002, 0.001, and optionally, 0.01≤P≤35. Further optionally, 0.05≤P≤0.16. The volume average particle size Dv50 of the lithium-rich material can include but is not limited to 0.1-3 μm and any value therebetween, for example, it can also be 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm. The mass percentage of lithium in the positive electrode lithium supplement agent can include but is not limited to 7-11% and any value therebetween, for example, it can also be 8%, 8.2%, 9%, 9.5%, 10%, 10.1%, 10.2%, 10.3%, 10.4%, 10.5%, 10.6%, 10.7%, 10.8%, 10.9%.

[0058] The mass percentage of lithium in the positive electrode lithium supplement is a well-known concept in the art and can be tested using instruments and methods known in the art, such as inductively coupled plasma atomic emission spectrometry (ICP) to detect the lithium content.

[0059] In some embodiments, the volume average particle size Dv50 of the lithium-rich material is 0.5 μm to 1.3 μm.

[0060] In some embodiments, the volume average particle size Dv50 of the porous carbon material is 2 μm to 30 μm and any value between therewith, for example, it can also be 5 μm, 10 μm, 15 μm, 20 μm, or 25 μm. Optionally, the volume average particle size Dv50 of the porous carbon material is 5 μm to 10 μm. Within this range, the porous carbon material exhibits better kinetic performance and less polarization, which can further reduce the decomposition voltage of the cathode lithium supplement.

[0061] The volume average particle size (Dv50) of lithium-rich materials is a well-known concept in the art. It represents the particle size corresponding to a cumulative volume distribution percentage of 50% for the material. It can be tested using instruments and methods known in the art. For example, a cross-section of the positive electrode lithium supplement is prepared using a cross-section polisher (such as the IB-09010CP argon-ion cross-section polisher from JEOL Corporation), passing through the core of the positive electrode lithium supplement particles. Then, elemental analysis using EDX or EDS combined with TEM or SEM (such as the X-Max EDS from Oxford Instruments combined with the Sigma-02-33 SEM from ZEISS) is performed to obtain the elemental distribution map in the cross-section. The volume average particle size (Dv50) of the lithium-rich material is obtained based on the elemental distribution of the cross-section. More precisely, the volume average particle size (Dv50) of the lithium-rich material at multiple (more than 3, such as 8, 10, 12, etc.) locations on the cross-section can be tested, and the average value is recorded as the volume average particle size (Dv50) of the lithium-rich material.

[0062] The volume average particle size Dv50 of porous carbon materials is a well-known concept in the art. It represents the particle size corresponding to a cumulative volume distribution percentage of 50%. It can be tested using instruments and methods known in the art. For example, it can be conveniently tested using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd. in the UK, in accordance with GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method.

[0063] The porous carbon material is not particularly limited and can be any one or more of biocarbon, mesoporous carbon, activated carbon, hard carbon, soft carbon, and porous carbon black. The porous carbon material can be commercially available, such as Sigma-Aldrich reagent porous carbon or Hunan Shanshan regular porous carbon material, or can be prepared by a method known in the art. The carbon source for preparing the porous carbon material can include, but is not limited to, synthetic carbon-containing polymer materials, activated carbon powder, charcoal powder, coal tar pitch, petroleum pitch, wood powder, cellulose and its derivatives, natural organic materials such as wheat flour, wood powder, corn powder, nut shell powder, starch, coke, coal, and combinations thereof.

[0064] In some embodiments, the porous carbon material includes activated carbon. Activated carbon itself has catalytic effect, and the degree of graphitization of activated carbon is low, has more groups, is more hydrophilic, and the surface of activated carbon can provide a large number of nucleation sites, which can further reduce the decomposition voltage of the positive electrode lithium supplement.

[0065] In some embodiments, the specific surface area of the porous carbon material is 1700 m 2 / g to 3000 m 2 / g, and any value therebetween, for example, can also be 1800 m 2 / g, 1900 m 2 / g, 2000 m 2 / g, 2100 m 2 / g, 2200 m 2 / g, 2300 m 2 / g, 2400 m 2 / g, 2500 m 2 / g, 2600 m 2 / g, 2700 m 2 / g, 2800 m 2 / g, 2900 m 2 / g. Alternatively, the specific surface area of the porous carbon material is 2000 m 2 / g to 2500 m 2 / g.

[0066] The specific surface area of the porous carbon material has a meaning known in the art and can be tested by an instrument and method known in the art, for example, using a specific surface area analyzer (Tristar II 3020M) to test the specific surface area of the porous carbon material by nitrogen adsorption / desorption method. Specifically, the test is performed in accordance with the national standard GB / T 19587-2017.

[0067] In some embodiments, the pore volume of the porous carbon material is 0.5 cm 3 / g to 3.5 cm 3 / g, and any value therebetween, for example, it can also be 0.9 cm 3 / g, 1.5 cm 3 / g, 2 cm 3 / g, 2.5 cm 3 / g, 3 cm 3 / g, 3.4 cm 3 / g. Optionally, the pore volume of the porous carbon material is 2 cm 3 / g~3.5 cm 3 / g.

[0068] The pore volume of the porous carbon material is the meaning known in the art, which can be tested by using the instruments and methods known in the art, and the testing method can refer to the above-mentioned specific surface area testing method, and the pore volume is calculated.

[0069] In some embodiments, the pore diameter of the pores accounting for 90% of the total pore volume in the porous carbon material is 20 nm~500 nm and any value therebetween, for example, it can also be 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm. Optionally, the pore diameter of the pores accounting for 90% of the total pore volume in the porous carbon material is 50 nm~300 nm.

[0070] The pore size distribution of the porous carbon material is the meaning known in the art, which can be tested by using the instruments and methods known in the art, and the testing method can refer to the above-mentioned specific surface area testing method, and the pore size distribution is calculated according to the BJH (pore volume and pore size distribution) theory.

[0071] When any one or more of the specific surface area, pore volume and pore size distribution of the porous carbon material is within the above-mentioned range, it is more beneficial to reduce the decomposition voltage of the positive electrode lithium supplement agent and improve the lithium supplement capacity of the positive electrode lithium supplement agent.

[0072] In some embodiments, the lithium-rich material includes one or more of Li2C2O4, Li2C3O5, Li2C4O4 and Li2C4O6.

[0073] In some embodiments, the positive electrode lithium supplement agent further includes a catalyst. The use of a catalyst can further reduce the decomposition voltage. Optionally, the catalyst is a non-metal catalyst. Metal or metal oxide catalysts can cause metal ions to dissolve, deposit on the anode, accelerate the formation of SEI film, and thus accelerate the aging of the battery. The use of a non-metal catalyst can avoid these problems. Further optionally, the non-metal catalyst includes one or more of polyaniline, nitrogen-doped carbon nanotubes, carboxylated carbon nanotubes and MNC composite catalysts.

[0074] It should be noted that the MNC composite catalyst is a kind of catalyst in which non-noble metal ions are loaded in a nitrogen-doped carbon carrier. The MNC composite catalyst comprises a nitrogen-doped carbon carrier and a loading component, which optionally comprises a metal M oxide or a metal M complex, the metal M comprising one or more of Ni, Co, Mn, Fe, Cu, Ti, and V; optionally, the ratio of the metal M to nitrogen is 1:(1-10); further optionally, the loading component accounts for 0.1%-5% of the mass percentage of the MNC composite catalyst, preferably 0.5%-1%.

[0075] In some embodiments, the mass percentage of the catalyst in the positive electrode lithium supplementing agent is 0.1%-5% and any value therebetween, for example, it can also be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, or 4.5%.

[0076] The mass percentage of the catalyst in the positive electrode lithium supplementing agent in the above range can further reduce the decomposition voltage of the positive electrode lithium supplementing agent while ensuring good lithium supplementing performance.

[0077] The test method for the mass percentage of the catalyst in the positive electrode lithium supplementing agent can refer to the test method for the mass percentage of lithium in the positive electrode lithium supplementing agent, and the content of a specific element in the catalyst, such as N or hydrogen, is obtained by integrating the distribution of the element.

[0078] In some embodiments, the volume average particle size Dv50 of the catalyst is 1-10 μm and any value therebetween, for example, it can also be 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, or 9 μm. Optionally, the volume average particle size Dv50 of the catalyst is 1-3 μm.

[0079] The volume average particle size Dv50 of the catalyst is a meaning known in the art, which represents the particle size corresponding to the cumulative volume distribution percentage of 50%, and can be tested by using instruments and methods known in the art, for example, it can be conveniently tested by using a laser particle size analyzer according to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method, such as a Mastersizer 2000E laser particle size analyzer of Malvern Instruments Limited, UK.

[0080] In some embodiments, the positive electrode film layer comprises a positive electrode active material layer, and the mass percentage of the positive electrode lithium supplementing agent in the positive electrode active material layer is 0.1%-10% and any value therebetween, for example, it can also be 0.5%, 1%, 1.3%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, or 9%. Optionally, the mass percentage of the positive electrode lithium supplementing agent in the positive electrode active material layer is 0.1%-1.3%.

[0081] It should be noted that the positive electrode lithium supplementing agent provided in the present application takes into account the effects of the lithium supplementing agent and the conductive agent. In some embodiments, the positive electrode active material layer can not contain the conductive agent. In other embodiments, the positive electrode active material layer can further comprise the conductive agent, and optionally, the mass percentage content of the conductive agent in the positive electrode active material layer is 0.5% to 2%.

[0082] In another aspect of the present application, a preparation method of a secondary battery is provided, which comprises a step of preparing a positive electrode sheet; the step of preparing the positive electrode sheet comprises:

[0083] dissolving the lithium salt in a first solvent to obtain a first solution;

[0084] mixing the first solution with the porous carbon material to obtain a second solution;

[0085] adding a second solvent to the second solution to perform crystallization, so as to form the lithium-rich material inside the porous carbon material, the volume average particle size Dv50 of the lithium-rich material is 0.1 μm to 3 μm, the ratio of the volume average particle size Dv50 of the lithium-rich material to the volume average particle size Dv50 of the porous carbon material is P, P≤0.35, to obtain the positive electrode lithium supplementing agent, and the mass percentage content of lithium in the positive electrode lithium supplementing agent is 7% to 11%;

[0086] arranging a slurry containing the positive electrode lithium supplementing agent on at least one surface of the positive electrode current collector, performing a drying treatment to form a positive electrode film layer, and obtaining the positive electrode sheet.

[0087] By using the porous carbon material of the positive electrode lithium supplementing agent in the secondary battery to adsorb the lithium-rich material and reduce the Dv50 of the lithium-rich material, and by controlling the ratio of the Dv50 of the lithium-rich material to the Dv50 of the porous carbon material and the mass percentage content of lithium in the positive electrode lithium supplementing agent, the capacity and the decomposition potential of the lithium-rich material are balanced, so that the obtained positive electrode lithium supplementing agent has a lower decomposition voltage and a higher lithium supplementing performance, and can play a role in supplementing lithium at a low decomposition voltage, thereby improving the discharge capacity of the battery. It should be noted that the lithium salt is a lithium salt corresponding to the lithium-rich material, and the lithium-rich material is a product obtained by recrystallization of the lithium salt inside the porous carbon material.

[0088] In some embodiments, the first solvent can be water, and the second solvent can be ethanol and / or ethylene glycol.

[0089] In some embodiments, the porous carbon material comprises activated carbon. The activated carbon has a low degree of graphitization, more groups, and is more hydrophilic. The surface of the activated carbon provides a large number of nucleation sites, which can further reduce the particle size of the lithium-rich material crystals formed inside the activated carbon.

[0090] In some embodiments, the volume of pores with a pore size of 20-500 nm accounts for 90% of the total pore volume in the porous carbon material, and the volume of pores with a pore size of 50-300 nm accounts for 90% of the total pore volume. The capillary action of the liquid is the driving force for the first solution to enter the pores inside the porous carbon material, while the surface tension of the liquid is the resistance for the first solution to enter the pores inside the porous carbon material, and the pore size is an important factor in balancing the capillary action and the surface tension of the liquid, which determines the amount of the first solution entering the pores inside the porous carbon material. Therefore, when the pore size distribution of the porous carbon material is within the above range, it is more conducive to reducing the decomposition voltage of the positive electrode lithium supplement and improving the lithium supplement capacity of the positive electrode lithium supplement.

[0091] Further, the crystallization can be performed by heating evaporation crystallization or spray drying. In some embodiments, the temperature of the evaporation crystallization is 70-100°C, and optionally 80-90°C. The temperature of the evaporation crystallization within the range can further reduce the particle size of the lithium-rich material in the positive electrode lithium supplement.

[0092] It should be noted that the above-mentioned secondary battery can be obtained by adjusting the process parameters or process conditions in the preparation method of the secondary battery.

[0093] In another aspect, the application provides a positive electrode lithium supplement, which comprises a porous carbon material and a lithium-rich material distributed inside the porous carbon material, the volume average particle size Dv50 of the lithium-rich material is 0.1-3 μm, the ratio of the volume average particle size Dv50 of the lithium-rich material to the volume average particle size Dv50 of the porous carbon material is P, P≤0.35, and the mass percentage of lithium in the positive electrode lithium supplement is 7-11%.

[0094] The porous carbon material of the positive electrode lithium supplement is used to adsorb the lithium-rich material and reduce the Dv50 of the lithium-rich material, and the balance between the capacity and the decomposition potential of the lithium-rich material is achieved by controlling the ratio of the Dv50 of the lithium-rich material to the Dv50 of the porous carbon material and the mass percentage of lithium in the positive electrode lithium supplement, so that the obtained positive electrode lithium supplement has a lower decomposition voltage and a higher lithium supplement performance, and can play a lithium supplement role at a low decomposition voltage, thereby improving the discharge capacity of the battery.

[0095] In some embodiments, the positive electrode lithium supplement is the positive electrode lithium supplement in the above-mentioned secondary battery.

[0096] In another aspect, the application provides a positive electrode tab, which comprises a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, and the positive electrode film layer comprises the positive electrode lithium supplement of any of the above-mentioned embodiments.

[0097] In another aspect of the present application, a power consuming device is provided, which comprises at least one of the secondary battery, the secondary battery prepared by the preparation method, the positive electrode lithium supplement, and the positive electrode tab as described above.

[0098] In addition, the secondary battery and the power consuming device of the present application are described below with appropriate reference to the accompanying drawings.

[0099] Generally, the secondary battery comprises a positive electrode tab, a negative electrode tab, an electrolyte, and a separator. During the charging and discharging of the battery, active ions are inserted into and extracted from the positive electrode tab and the negative electrode tab. The electrolyte serves to conduct ions between the positive electrode tab and the negative electrode tab. The separator is disposed between the positive electrode tab and the negative electrode tab, and mainly serves to prevent the short circuit of the positive electrode and the negative electrode, while allowing ions to pass through.

[0100] Positive electrode tab

[0101] The positive electrode tab comprises a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector. The positive electrode film layer comprises a positive electrode active material layer. The positive electrode active material layer comprises a positive electrode active material and a positive electrode lithium supplement.

[0102] As a non-limiting example, the positive electrode current collector has two opposite surfaces in the thickness direction thereof, and the positive electrode active material layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0103] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, an aluminum foil can be used. The composite current collector can comprise 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 can be obtained by forming a metal material on a polymer material base material. In the positive electrode current collector, non-limiting examples of the metal material can include one or more of aluminum, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, a silver alloy, and the like. In the positive electrode current collector, non-limiting examples of the polymer material base material can include one or more of a polypropylene (PP) base material, a polyethylene terephthalate (PET) base material, a polybutylene terephthalate (PBT) base material, a polystyrene (PS) base material, a polyethylene (PE) base material, and the like.

[0104] In some embodiments, the positive electrode active material may be a known positive electrode active material for batteries. As a non-limiting example, the positive electrode active material may include one or more of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries 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 oxides (such as LiCoO2), lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, and their modified compounds. Non-limiting examples of lithium-containing phosphates with an olivine structure 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 manganese iron 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 known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 Examples of lithium nickel cobalt aluminum oxides include LiNi, etc. 0.8 Co 0.15 Al 0.05 O2.

[0105] In some embodiments, the positive electrode active material layer can also optionally include a binder. As non-limiting examples, the binder can 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.

[0106] In some embodiments, the positive electrode active material layer can also optionally include a conductive agent. As non-limiting examples, the conductive agent can include one or more of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0107] In some embodiments, the positive electrode tab can be prepared by dispersing the above-mentioned components for preparing the positive electrode tab, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry on at least one side surface of the positive electrode current collector; and subjecting the positive electrode current collector to a drying, cold-pressing, or other process to obtain the positive electrode tab. The solvent can be selected from, but is not limited to, any of the above-mentioned embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector on which the positive electrode slurry is coated can be a single surface of the positive electrode current collector or both surfaces of the positive electrode current collector. The surface of the positive electrode current collector on which the positive electrode slurry is coated can be a single surface of the positive electrode current collector or 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 5,000 mPa s to 25,000 mPa s. When coating the positive electrode slurry, the coating unit area density, in terms of dry weight (excluding the solvent), can be 15 mg / cm 2 to 35 mg / cm 2 . The positive electrode tab can have a compacted density of 3.0 g / cm 3 to 3.6 g / cm 3 , optionally 3.3 g / cm 3 to 3.5 g / cm 3 .

[0108] Negative electrode tab

[0109] The negative electrode tab includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, the negative electrode active material layer including a negative electrode active material.

[0110] As non-limiting examples, the negative electrode current collector has two opposite surfaces in the thickness direction of the negative electrode current collector itself, and the negative electrode active material layer is disposed on either one or both of the two opposite surfaces of the negative electrode current collector.

[0111] In some embodiments, the negative current collector can employ a metal foil or a composite current collector. For example, as a metal foil, a copper foil can be employed. The composite current collector can 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 can be obtained by forming a metal material on a polymer material base layer. Non-limiting examples of the metal material in the negative current collector can include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, and the like. Non-limiting examples of the polymer material base layer in the negative current collector can include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), and the like.

[0112] In some embodiments, the negative active material can employ a negative active material for a battery known in the art. As non-limiting examples, the negative active material can include one or more of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate, and the like. The silicon-based material can include one or more of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material can include one or more of elemental tin, tin oxide compound, and tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative active material for a battery can also be used. The negative active material can be used alone or in combination of two or more.

[0113] In some embodiments, the negative active material layer can further optionally include a binder. The binder can include one or more of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0114] In some embodiments, the negative active material layer can further optionally include a conductive agent. The conductive agent can include one or more of super P, acetylene black, carbon black, ketjen black, carbon dot, carbon nanotube, graphene, and carbon nanofiber.

[0115] In some embodiments, the negative active material layer can further optionally include other auxiliary agents, such as a thickening agent (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like.

[0116] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder, and any other components, in a solvent (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry; coating the negative electrode slurry on at least one side surface of the negative electrode current collector, and after processes such as drying, cold pressing, etc., the negative electrode sheet can be obtained. The surface of the negative electrode current collector to which the negative electrode slurry is coated can be on a single surface of the negative electrode current collector, or on both surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 40 wt% to 60 wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000 mPa·s to 10000 mPa·s. When coating the negative electrode slurry, the coating unit area density (excluding the solvent) can be 75 g / m 2 to 220 g / m 2 . The compaction density of the negative electrode sheet can be 1.0 g / cm 3 to 1.8 g / cm 3 .

[0117] Electrolyte

[0118] The electrolyte has the function of conducting ions between the positive electrode sheet and the negative electrode sheet. The type of the electrolyte is not particularly limited in the present application, and can be selected as needed. For example, the electrolyte can be liquid, gel, or all-solid.

[0119] In some embodiments, the electrolyte uses an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0120] In some embodiments, the electrolyte salt can include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bis-trifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluoro-oxalato-borate (LiDFOB), lithium bis-oxalato-borate (LiBOB), lithium difluoro-bis-oxalato-phosphate (LiDFOP), and lithium tetrafluoro-oxalato-phosphate (LiTFOP).

[0121] In some embodiments, the solvent can include ethylene carbonate (EC, ), propylene carbonate (PC, ), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethylene carbonate one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl ethylene carbonate (TFPC), and the like.

[0122] In some embodiments, the electrolyte solution can further optionally include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can further include an additive capable of improving certain performance of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature or low-temperature performance of the battery, and the like.

[0123] In some embodiments, the additive in the electrolyte solution can include, but is not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl ethylene carbonate (TFPC), and the like.

[0124] Separator film

[0125] In some embodiments, the secondary battery further includes a separator film. The type of the separator film is not particularly limited in the present application, and any publicly known porous structure separator film having good chemical stability and mechanical stability can be used.

[0126] In some embodiments, the material of the separator film can include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator film can be a single layer film or a multi-layer composite film, and is not particularly limited. When the separator film is a multi-layer composite film, the materials of the respective layers can be the same or different, and are not particularly limited.

[0127] In some embodiments, the thickness of the separator film is 6 μm to 40 μm, and can be optionally 12 μm to 20 μm.

[0128] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator film can be used to make an electrode assembly through a winding process or a stacking process.

[0129] In some embodiments, the secondary battery can include an outer package. The outer package can be used to package the electrode assembly and the electrolyte solution described above.

[0130] In some embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, and the like. The outer package of the secondary battery can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, and further, non-limiting examples of the plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate, and the like.

[0131] The secondary battery includes at least one battery cell. The secondary battery can include one or more battery cells.

[0132] In the present application, a "battery cell" refers to a basic unit capable of converting chemical energy and electrical energy to each other, and further, generally includes at least a positive electrode sheet, a negative electrode sheet, and an electrolyte. During the charging and discharging of the battery, active ions are inserted and extracted between the positive electrode sheet and the negative electrode sheet. The electrolyte functions to conduct the active ions between the positive electrode sheet and the negative electrode sheet.

[0133] The shape of the battery cell is not particularly limited in the present application, and can be cylindrical, square, or any other shape. For example, FIG. 1 is a battery cell 5 of a square structure as an example.

[0134] In some embodiments, referring to FIG. 2, the outer package can include a housing 51 and a cover plate 53. The housing 51 can 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 housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be provided on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator can form an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is packaged 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 a person skilled in the art can select according to actual needs.

[0135] The secondary battery can be a battery module 4 or a battery pack 1.

[0136] The battery module includes at least one battery cell. The number of battery cells contained in the battery module can be one or more, and a person skilled in the art can select a suitable number according to the application and capacity of the battery module.

[0137] FIG. 3 is a battery module 4 as an example. Referring to FIG. 3, in the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, other arbitrary arrangements can also be used. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0138] Optionally, the battery module 4 can further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0139] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and a person skilled in the art can select a suitable number according to the application and capacity of the battery pack.

[0140] FIGS. 4 and 5 are a battery pack 1 as an example. Referring to FIGS. 4 and 5, a battery case and a plurality of battery modules 4 disposed in the battery case can be included in the battery pack 1. The battery case includes an upper case 2 and a lower case 3, and the upper case 2 can be disposed to cover the lower case 3 and form an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery case in any manner.

[0141] In addition, the application also provides a power consuming device including the secondary battery provided by the application. The secondary battery can be used as a power source of the power consuming device, or can be used as an energy storage unit of the power consuming device. The power consuming device can include a mobile device, an electric vehicle, an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto. Among them, the mobile device can be a mobile phone, a notebook computer, etc.; the electric vehicle can be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc., but is not limited thereto.

[0142] As the power consuming device, the secondary battery can be selected according to the use requirements thereof.

[0143] FIG. 6 is a power consuming device 6 as an example. The power consuming device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the secondary battery for the power consuming device, a battery pack or a battery module can be used.

[0144] As another example of the device, it can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thin and light, and the secondary battery can be used as a power source.

[0145] Hereinafter, the embodiments of the application are described. The embodiments described below are exemplary and are only used to explain the application, and cannot be understood as a limitation of the application. If the technology or conditions are not specified in the embodiments, the technology or conditions described in the literature in the art or according to the product manual are used. If the reagents or instruments are not specified by the manufacturer, they are all conventional products that can be obtained by purchase.

[0146] I. Preparation of Embodiments

[0147] Preparation of Embodiments

[0148] 5 kg of lithium salt (lithium oxalate Li2C2O4) and 100 L of deionized water (first solvent) were mixed, heated and stirred until the lithium salt was dissolved to obtain a lithium oxalate aqueous solution. 1 kg of porous carbon material activated carbon was added to the lithium oxalate aqueous solution, and the specific surface area of the activated carbon material was 2800 m 2 / g, and the pore volume was 2.5 cm 3 / g, the volume average particle size Dv50 was 2 μm, 10 L of ethanol (second solvent) was added during the ultrasonic process. After ultrasonic treatment for 30 min, the mixture was placed in an oil bath (heating temperature was 80 °C) to dry, and the positive electrode lithium supplement agent was obtained by grinding.

[0149] The lithium-rich material described below refers to recrystallized lithium oxalate or other lithium salt. The volume average particle size Dv50 of the lithium-rich material can be obtained by further testing.

[0150] Preparation Examples 2-12 and Preparation Comparative Example 1

[0151] The preparation method of Preparation Examples 2-12 and Preparation Comparative Example 1 was similar to that of Preparation Example 1, except that the type of lithium salt, the type of porous carbon material, the specific surface area, the pore volume and Dv50, the type and amount of catalyst, and the heating temperature were adjusted. The specific parameters are shown in Table 1 below. In Preparation Example 12, 1 kg of porous carbon material activated carbon and 0.05 kg of nitrogen-doped carbon nanotubes (catalyst) were added to the lithium oxalate aqueous solution at the same time, the Dv50 of the nitrogen-doped carbon nanotubes was 3 μm, and the mass percentage of the catalyst in the positive electrode lithium supplement agent prepared in Preparation Example 12 was about 0.83%.

[0152] II. Application Examples

[0153] Example 1

[0154] Preparation of lithium ion secondary battery:

[0155] 1) Preparation of positive electrode sheet

[0156] The positive electrode lithium supplement agent of Preparation Example 1, the positive electrode active material LiFePO4, the conductive carbon black, and the polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 1.3:95.7:2:1, deionized water was added, and the positive electrode slurry was obtained under the action of a vacuum stirrer; the positive electrode slurry was uniformly coated on the double-sided surface of an aluminum foil; the aluminum foil was transferred to a 120 °C oven after air drying at room temperature for 1 h, and then cold-pressed and cut to obtain the positive electrode sheet.

[0157] 2) Preparation of negative electrode sheet

[0158] The negative electrode active material artificial graphite, the conductive agent acetylene black, the binder styrene butadiene rubber (SBR), and the thickening agent sodium carboxymethyl cellulose (CMC-Na) were mixed in a mass ratio of 96.5:0.7:1.8:1 in a deionized water solvent system, and the negative electrode slurry was obtained after sufficient stirring and mixing. The negative electrode slurry was coated on the double-sided surface of a copper foil, dried, and cold-pressed to obtain the negative electrode sheet.

[0159] 3) Assembly of battery

[0160] A porous PP (polypropylene) film with a thickness of 12 μm was used as a separator. EC, DEC, and DMC were mixed in a volume ratio of 1:1:1, and 1.1 M LiPF6 lithium salt was dissolved to form an electrolyte. The positive electrode sheet, the separator, and the negative electrode sheet were stacked in order, with the separator between the positive electrode sheet and the negative electrode sheet to play a role of separation, and were wound to obtain a bare battery cell. The bare battery cell was placed in an outer package, the above-mentioned electrolyte was injected, and the opening was sealed. After standing, hot and cold pressing, and formation, a lithium ion secondary battery was obtained. The formation voltage was in the range of 2.5 V to 4.3 V. That is, the upper limit voltage of the formation process of the battery of Example 1 was 4.3 V.

[0161] The batteries of Examples 2 to 14 and Comparative Example 1 were prepared in a similar manner to the battery of Example 1, but the positive electrode lithium supplementing agent of the corresponding preparation example or preparation comparative example was used. In addition, the mass percentage content of the positive electrode lithium supplementing agent and the positive electrode active material in the positive electrode active material layer of Examples 2 to 14 was 97%.

[0162] The battery of Comparative Example 2 was prepared in a similar manner to the battery of Example 1, but the positive electrode lithium supplementing agent of Preparation Example 1 was replaced by a lithium salt (lithium oxalate Li2C2O4) in Preparation Example 1 in the preparation of the positive electrode sheet in step 1).

[0163] The battery of Comparative Example 3 was prepared in a similar manner to the battery of Example 1, but the positive electrode lithium supplementing agent of Preparation Example 1 was replaced by a lithium salt (lithium oxalate Li2C2O4) in Preparation Example 1 in the preparation of the positive electrode sheet in step 1), and the range of the formation voltage of the battery in step 3) was adjusted to 2.5 V to 4.7 V, that is, the upper limit voltage of the formation process of the battery of Comparative Example 3 was 4.7 V.

[0164] III. Test Methods

[0165] 1. Specific surface area, pore volume, and pore size distribution test

[0166] A specific surface area analyzer (Tristar II 3020M) was used to measure the specific surface area and pore volume of the porous carbon materials in the preparation examples and the preparation comparative examples by nitrogen adsorption / desorption method. The specific test was carried out in accordance with the national standard GB / T 19587-2017.

[0167] 2. Particle size distribution test

[0168] A Malvern particle size tester was used to test the particle size distribution of the porous carbon materials and the lithium-rich materials in the preparation examples and the preparation comparative examples, and the volume average particle size Dv50 of the porous carbon materials and the lithium-rich materials was obtained. The specific test was carried out in accordance with the national standard GB / T 19077-2016.

[0169] 3. Test of mass percentage of lithium element in positive electrode lithium supplement agent

[0170] A cross-section of the positive electrode lithium supplement agent particle is prepared by a cross-section polisher (e.g. IB-09010CP argon ion cross-section polisher of JEOL), which passes through the core of the positive electrode lithium supplement agent particle. Then, the element distribution map in the cross-section is obtained by X-Max EDS of Oxford Instruments combined with SEM surface scanning test of Sigma-02-33 of ZEISS. In a region in the cross-section, the lithium element content (mass percentage) in the region is obtained by integrating the lithium element distribution. Ten regions are tested in total, and the average value is taken as the test result.

[0171] 4. Discharge specific capacity and discharge capacity

[0172] The battery is charged at 0.33C rate to the charge termination voltage 3.65V at room temperature (25℃), and then charged at constant voltage to 0.05C. The battery which has completed the above charging is discharged at 0.33C rate to the discharge termination voltage 2.5V, and the discharge capacity E is measured. d0 The discharge capacity E is divided by the average active material weight of the battery, and the discharge specific capacity is obtained. d0

[0173] Discharge specific capacity (mAh / g) = discharge capacity of the first cycle / mass of positive electrode active material, wherein the positive electrode active material refers to the total mass of the positive electrode lithium supplement agent and the positive electrode active material.

[0174] The test results of the positive electrode lithium supplement agent and the battery performance of Examples 1-14 and Comparative Examples 1-3 are shown in Table 2. " / " represents that the substance or the parameter does not exist.

[0175] Table 1

[0176] Table 2

[0177] In Table 2, P represents the ratio of the volume average particle size Dv50 of the lithium-rich material to the volume average particle size Dv50 of the porous carbon material.

[0178] ​The upper limit voltage of the formation process of the batteries of Examples 1-14 and Comparative Examples 1-2 is 4.3 V, and the upper limit voltage of the formation process of the battery of Comparative Example 3 is 4.7 V. As can be seen from Table 1 and Table 2, the batteries of Examples 1-14 have higher discharge specific capacity and discharge capacity compared to Comparative Examples 1-3, which indicates that the lithium supplement agent in the positive electrode of the batteries of Examples 1-14 can be decomposed at 4.3 V, i.e., the lithium supplement agent in the positive electrode of the batteries of Examples 1-14 has a relatively low decomposition voltage. Therefore, compared to Comparative Examples 1-3, the lithium supplement agent in the positive electrode of the batteries of Examples 1-14 can improve the discharge specific capacity and discharge capacity of the batteries at a lower voltage.

[0179] The above description of various embodiments tends to emphasize differences between various embodiments, and the same or similar parts can be referred to each other, which will not be repeated herein for the sake of brevity.

[0180] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration and playing the same role and effect as the technical idea within the scope of the technical solutions of the present application are all included in the technical scope of the present application. In addition, within the scope of the gist of the present application, various modifications that can be thought of by those skilled in the art, other modes constructed by combining part of the configuration elements of the embodiments are also included in the scope of the present application.

Claims

1. A secondary battery, comprising a positive electrode sheet, the positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, the positive electrode film layer comprising a positive electrode lithium supplement agent, the positive electrode lithium supplement agent comprising a porous carbon material and a lithium-rich material distributed inside the porous carbon material, a volume average particle size Dv50 of the lithium-rich material being 0.1 μm to 3 μm, a ratio of the volume average particle size Dv50 of the lithium-rich material to the volume average particle size Dv50 of the porous carbon material being P, P≤0.35, and a mass percentage of lithium in the positive electrode lithium supplement agent being 7% to 11%.

2. The secondary battery according to claim 1, wherein The volume average particle size Dv50 of the lithium-rich material is 0.5 μm to 2 μm.

3. The secondary battery according to claim 1, wherein 0.01≤P≤0.35。 4. The secondary battery according to claim 3, wherein 0.05≤P≤0.16。 5. The secondary battery according to any one of claims 1 to 4, wherein The volume average particle size Dv50 of the porous carbon material is 2 μm to 30 μm.

6. The secondary battery according to claim 5, wherein The volume average particle size Dv50 of the porous carbon material is 5 μm to 10 μm.

7. The secondary battery according to any one of claims 1 to 6, wherein The volume average particle size Dv50 of the lithium-rich material is 0.5 μm to 1.3 μm.

8. The secondary battery according to any one of claims 1 to 7, wherein The specific surface area of the porous carbon material is 1700 m 2 / g ~ 3000 m 2 / g.

9. The secondary battery according to any one of claims 1 to 8, wherein The porous carbon material has a pore volume of 0.5 cm 3 / g ~ 3.5 cm 3 / g.

10. The secondary battery according to any one of claims 1 to 9, wherein The lithium-rich material comprises one or more of Li 2 C 2 O 4, Li 2 C 3 O 5, Li 2 C 4 O 4 and Li 2 C 4 O 6.

11. The secondary battery according to any one of claims 1 to 10, wherein The porous carbon material comprises activated carbon.

12. The secondary battery according to any one of claims 1 to 11, wherein The positive electrode lithium supplement agent further comprises a catalyst, the catalyst being distributed on the surface of the porous carbon material, and the catalyst being a non-metallic catalyst.

13. The secondary battery according to claim 12, wherein The catalyst comprises one or more of polyaniline, nitrogen-doped carbon nanotubes, carboxylated carbon nanotubes and MNC composite catalysts.

14. The secondary battery according to any one of claims 12 to 13, wherein The mass percentage of the catalyst in the positive electrode lithium supplement agent is 0.1% to 5%.

15. The secondary battery according to claim 14, wherein The mass percentage of the catalyst in the positive electrode lithium supplement agent is 0.5% to 1.5%.

16. The secondary battery according to any one of claims 12 to 15, wherein The volume average particle size Dv50 of the catalyst is 1 μm to 10 μm.

17. The secondary battery according to claim 16, wherein The volume average particle size Dv50 of the catalyst is 1 μm to 3 μm.

18. The secondary battery according to any one of claims 1 to 17, wherein The positive electrode film layer comprises a positive electrode active material layer, and the mass percentage of the positive electrode lithium supplement agent in the positive electrode active material layer is 0.1% to 10%.

19. The secondary battery according to claim 18, wherein The mass percentage of the positive electrode lithium supplement agent in the positive electrode active material layer is 0.5% to 4%.

20. The secondary battery according to any one of claims 1 to 19, wherein The formation voltage range of the secondary battery is 2.5 V to 4.3 V.

21. A method of producing a secondary battery, wherein The method comprises a step of preparing a positive electrode sheet; The step of preparing the positive electrode sheet comprises: dissolving a lithium salt in a first solvent to obtain a first solution; mixing the first solution with a porous carbon material to obtain a second solution; adding a second solvent to the second solution to perform crystallization, so as to form a lithium-rich material inside the porous carbon material, a volume average particle size Dv50 of the lithium-rich material being 0.1 μm to 3 μm, a ratio of the volume average particle size Dv50 of the lithium-rich material to the volume average particle size Dv50 of the porous carbon material being P, P≤0.35, to obtain a positive electrode lithium supplement agent, and a mass percentage of lithium in the positive electrode lithium supplement agent being 7% to 11%; providing a slurry containing the positive electrode lithium supplement agent on at least one surface of a positive electrode current collector, and performing a drying process to form a positive electrode film layer, so as to obtain the positive electrode sheet. 22.A positive electrode lithium supplement agent, comprising a porous carbon material and a lithium-rich material distributed inside the porous carbon material, wherein the lithium-rich material has a volume average particle size Dv50 of 0.1 μm to 3 μm, a ratio of the volume average particle size Dv50 of the lithium-rich material to the volume average particle size Dv50 of the porous carbon material is P, and P≤0.35, and the mass percentage of lithium in the positive electrode lithium supplement agent is 7%to 11%. 23.A positive electrode sheet, comprising a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode film layer comprises the positive electrode lithium supplement agent of claim 22. 24.An electric device, comprising at least one of the secondary battery of any one of claims 1 to 20, the secondary battery prepared by the preparation method of claim 21, the positive electrode lithium supplement agent of claim 22, and the positive electrode sheet of claim 23.

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