Secondary battery, electric device, capacity compensation composite particle and preparation method thereof

Abstract

The invention provides a secondary battery, a power utilization device, a capacity compensation composite particle and a preparation method thereof. The secondary battery comprises a positive pole piece, a negative pole piece, an isolating membrane and an electrolyte; the positive pole piece comprises a positive current collector and a positive film layer arranged on at least one surface of the positive current collector, the positive film layer comprises capacity compensation composite particles, and the capacity compensation composite particles comprise a capacity compensation agent and a catalyst. The catalyst comprises conductive carbon with doped elements and metal nanoparticles loaded on the conductive carbon. According to the invention, the capacity and the first coulombic efficiency of the battery can be improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a secondary battery, an electrical device, capacity-compensating composite particles, and a method for preparing the same. Background Technology

[0002] In recent years, with the increasingly wide application of rechargeable batteries, they have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric cars, aerospace, and many other fields. Due to the significant development of rechargeable batteries, higher requirements have been placed on their capacity.

[0003] During the initial charge and discharge cycle of a rechargeable battery, a solid electrolyte interface membrane (SEI) forms on the negative electrode surface. This process consumes numerous active ions, resulting in unsatisfactory battery capacity and initial coulombic efficiency, thus affecting the full utilization of battery capacity. Capacity compensators are designed to release active ions during the initial charge and discharge cycle to compensate for capacity loss during the first cycle. However, current capacity compensators are difficult to decompose in batteries, limiting their effectiveness. Summary of the Invention

[0004] This application is made in view of the above-mentioned problems, and its purpose is to provide a secondary battery, an electrical device, capacity-compensating composite particles, and a method for preparing the same. The secondary battery exhibits high capacity and initial coulombic efficiency.

[0005] To achieve the above objectives, a first aspect of this application provides a secondary battery, including a positive electrode, a negative electrode, a separator, and an electrolyte; the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including capacity-compensating composite particles; the capacity-compensating composite particles include a capacity compensator and a catalyst, the catalyst including conductive carbon with doped elements and metal nanoparticles loaded on the conductive carbon.

[0006] In this application, by having the capacity compensator and catalyst exist in the positive electrode film in the form of composite particles, the probability of contact between the catalyst and the capacity compensator can be increased. This is beneficial for the catalyst to better exert its role in catalyzing the decomposition of the capacity compensator, thereby improving the battery capacity and initial coulombic efficiency.

[0007] In some embodiments, the catalyst has a porous structure. By employing a catalyst with this porous structure, more reaction sites can be provided, which is more conducive to catalytic activity and thus further promotes the decomposition of the capacity compensator.

[0008] In some embodiments, a coin cell half-cell using the capacity-compensating composite particles as the positive electrode active material and lithium metal or sodium metal as the counter electrode is subjected to charge-discharge tests. When the discharge capacity of the coin cell half-cell decays to half of its initial discharge capacity, the voltage of the coin cell half-cell is between 4.05V and 4.12V. The fact that the voltage of the coin cell half-cell made with the aforementioned capacity-compensating composite particles falls within this range when its discharge capacity decays to half of its initial discharge capacity indicates that the capacity-compensating composite particles decompose relatively easily within the battery. Therefore, using the aforementioned capacity-compensating composite particles is beneficial for further improving the battery capacity and initial coulombic efficiency.

[0009] In some embodiments, the mass ratio of the metal nanoparticles, the conductive carbon, and the dopant element in the catalyst is (2-8):(89.5-96):(2-2.5). In some embodiments, the mass ratio of the metal nanoparticles, the conductive carbon, and the dopant element in the catalyst is (4-5.5):(92-94):(2-2.5). By controlling the mass ratio of the metal nanoparticles, the conductive carbon, and the dopant element in the catalyst within the above ranges, it is beneficial to improve the catalytic activity of the catalyst and reduce the aggregation of metal nanoparticles, thereby further promoting the decomposition of the capacity compensator.

[0010] In some embodiments, the conductive carbon includes one or more of carbon nanotubes, carbon fibers, acetylene black, Ketjen black, conductive carbon black, conductive graphite, C60, or graphene. The aforementioned conductive carbon exhibits high conductivity; by selecting such carbon materials, the conductivity of the capacity-compensating composite particles can be improved, thereby further promoting the decomposition of the capacity compensator.

[0011] In some embodiments, the doping element includes one or more of boron, nitrogen, phosphorus, sulfur, oxygen, fluorine, chlorine, bromine, and iodine. The coordination of these doping elements with the metal portion of the metal nanoparticles promotes the dispersion of the metal nanoparticles, thereby increasing the number of catalytic anchor sites and thus facilitating further decomposition of the capacity compensator.

[0012] In some embodiments, the metal nanoparticles include at least one metal selected from iron, manganese, cobalt, nickel, copper, chromium, vanadium, molybdenum, indium, rhodium, and iridium. These elements possess high catalytic activity, and selecting metal nanoparticles containing these elements facilitates further promotion of the decomposition of the capacity compensator.

[0013] In some embodiments, the volume average particle size Dv50 of the metal nanoparticles is between 50 nm and 500 nm. By controlling the volume average particle size Dv50 of the metal nanoparticles within the above range, it is beneficial to expose more active sites, enhance catalytic activity, and thus further promote the decomposition of the capacity compensator.

[0014] In some embodiments, the capacity compensator includes a sodium supplement or a lithium supplement.

[0015] In some embodiments, the lithium supplement includes at least one of Li2O, Li2O2, Li2CO3, Li2C2O4, Li2C4O4, Li2S, Li2Se, Li2Se2, or LiF; and the sodium supplement includes at least one of Na2O, Na2O2, Na2CO3, Na2C2O4, Na2C4O4, Na2C3O3, Na2C3O5, Na2S, Na2Se, Na2Se2, or NaF.

[0016] In some embodiments, the catalyst comprises 15% to 20% by mass in the capacity-compensating composite particles. By keeping the catalyst within this range, it is advantageous to further increase the probability of contact between the catalyst and the capacity-compensating agent, thereby further promoting the decomposition of the capacity-compensating agent.

[0017] In some embodiments, the capacity compensator comprises 80% to 85% by mass in the capacity-compensating composite particles. Maintaining the mass percentage of the capacity compensator within this range increases the probability of contact between the catalyst and the capacity compensator, thereby further promoting the decomposition of the capacity compensator.

[0018] In some embodiments, the capacity compensation composite particles account for 5%-10% of the mass of the positive electrode film. By keeping the mass ratio of the capacity compensation composite particles within the above range, on the one hand, the loss of active ions can be effectively compensated, thereby improving the battery capacity; on the other hand, it ensures that the addition of the capacity compensation composite particles does not affect the material processing performance.

[0019] In some embodiments, the capacity-compensating composite particles also include a surfactant. This facilitates better dispersion of the metal nanoparticles, thereby providing more catalytic anchoring sites and further promoting the decomposition of the capacity compensator.

[0020] In some embodiments, the volume average particle size Dv50 of the capacity compensation composite particles is 3 μm to 6 μm. By controlling the volume average particle size Dv50 of the capacity compensation composite particles within the above range, it is beneficial to achieve uniform distribution of the compensator in the positive electrode film layer, improve the utilization rate of the capacity compensation composite particles, and thus further promote the decomposition of the capacity compensator.

[0021] In some embodiments, the total pore volume of the capacity-compensating composite particles is 0.1 cm³. 3 / g to 0.5cm 3 / g. By controlling the total pore volume V of the capacity compensation composite particles within the above range, the capacity compensation composite particles can have a larger specific surface area, that is, a larger contact area between the capacity compensation composite particles and the electrolyte, which facilitates ion diffusion and thus helps to improve the battery capacity and initial coulombic efficiency.

[0022] In some embodiments, the average pore size of the capacity-compensating composite particles is between 8 nm and 15 nm. By controlling the average pore size D of the capacity-compensating composite particles within this range, the capacity-compensating composite particles can have a larger specific surface area, resulting in a larger contact area between the electrolyte and the capacity-compensating composite particles, which facilitates ion diffusion and thus helps to improve the battery's capacity and initial coulombic efficiency.

[0023] In some embodiments, the specific surface area of ​​the capacity-compensating composite particles is 30 m². 2 / g to 150m 2 / g. On the one hand, by controlling the specific surface area S of the capacity-compensated composite particles at 30m². 2 A specific surface area (S) of 150 m² / g or higher is beneficial for sufficient contact between the capacity-compensating composite particles and the electrolyte, thereby promoting the decomposition of the capacity compensator. On the other hand, by controlling the specific surface area (S) of the capacity-compensating composite particles to 150 m² / g... 2 Below / g, the absorption of water by the pores inside the volume compensation composite particles can be reduced, thereby reducing the risk of the volume compensation composite particles clogging the pores due to high water content, and thus further promoting the decomposition of the volume compensation agent.

[0024] In some embodiments, the sphericity of the capacity-compensating composite particles is 0.9 to 1. By controlling the sphericity Sw of the capacity-compensating composite particles within the above range, it is beneficial to achieve uniform compounding of the compensator and the catalyst, thereby further promoting the decomposition of the capacity compensator.

[0025] A second aspect of this application provides an electrical device including the secondary battery provided in the first aspect.

[0026] A third aspect of this application provides a capacity-compensating composite particle, comprising a capacity compensator and a catalyst. The catalyst comprises conductive carbon with doped elements and metal nanoparticles supported on the conductive carbon. In this capacity-compensating composite particle, the capacity compensator and catalyst exist in the form of composite particles, which increases the probability of contact between the catalyst and the capacity compensator. This facilitates the catalyst's better performance in catalyzing the decomposition of the capacity compensator, thereby reducing the difficulty of decomposing the capacity compensator. Batteries containing this capacity-compensating composite particle exhibit high capacity and initial coulombic efficiency.

[0027] In some embodiments, the catalyst has a porous structure. Using a catalyst with a porous structure provides abundant catalytic anchor sites, thereby effectively improving the catalytic effect and promoting the decomposition process of the capacitor compensator.

[0028] In some embodiments, a coin cell using the capacity-compensating composite particles as the positive electrode active material and lithium metal or sodium metal as the counter electrode is subjected to charge-discharge tests. When the discharge capacity of the coin cell decays to half of its initial discharge capacity, the voltage of the coin cell is between 4.05V and 4.12V. The fact that the voltage of the coin cell made with the aforementioned capacity-compensating composite particles is within this range when its discharge capacity decays to half of its initial discharge capacity indicates that the capacity-compensating composite particles decompose relatively easily within the battery. Therefore, the battery using the aforementioned capacity-compensating composite particles exhibits improved capacity and initial coulombic efficiency.

[0029] In some embodiments, the mass ratio of the metal nanoparticles, the conductive carbon, and the dopant element in the catalyst is (2-8):(89.5-96):(2-2.5). By controlling the mass ratio of the metal nanoparticles, the conductive carbon, and the dopant element in the catalyst within the above range, it is beneficial to improve the catalytic activity of the catalyst and reduce the aggregation of metal nanoparticles, thereby further promoting the decomposition of the capacity compensator.

[0030] In some embodiments, the conductive carbon includes one or more of carbon nanotubes, carbon fibers, acetylene black, Ketjen black, conductive carbon black, conductive graphite, C60, or graphene. The aforementioned conductive carbon exhibits high conductivity. By selecting these carbon materials, it is beneficial to improve the conductivity of the capacity-compensating composite particles, thereby further promoting the decomposition of the capacity compensator.

[0031] In some embodiments, the doping element includes one or more of boron, nitrogen, phosphorus, sulfur, oxygen, fluorine, chlorine, bromine, and iodine. These doping elements coordinate with the metal portion of the metal nanoparticles, promoting the dispersion of the metal nanoparticles and thereby increasing the number of catalytic anchor sites, which in turn facilitates further decomposition of the capacity compensator.

[0032] In some embodiments, the metal includes at least one selected from iron, manganese, cobalt, nickel, copper, chromium, vanadium, molybdenum, indium, rhodium, and iridium. These elements possess high catalytic activity, and selecting metal nanoparticles containing these elements further facilitates the decomposition of the capacity compensator.

[0033] In some embodiments, the volume average particle size Dv50 of the metal nanoparticles is between 50 nm and 500 nm. By controlling the volume average particle size Dv50 of the metal nanoparticles within the above range, it is beneficial to expose more active sites, enhance catalytic activity, and thus further promote the decomposition of the capacity compensator.

[0034] In some embodiments, the capacity compensator includes a sodium supplement or a lithium supplement.

[0035] In some embodiments, the catalyst comprises 15% to 20% by mass in the capacity-compensating composite particles. By keeping the catalyst within this range, it is advantageous to further increase the probability of contact between the catalyst and the capacity-compensating agent, thereby further promoting the decomposition of the capacity-compensating agent.

[0036] In some embodiments, the capacity compensator comprises 80% to 85% by mass in the capacity-compensating composite particles. Maintaining the mass percentage of the capacity compensator within this range increases the probability of contact between the catalyst and the capacity compensator, thereby further promoting the decomposition of the capacity compensator.

[0037] In some embodiments, the capacity compensation composite particles account for 5% to 10% of the mass of the positive electrode film. By keeping the mass ratio of the capacity compensation composite particles within the above range, on the one hand, the loss of active ions can be effectively compensated, thereby improving the battery capacity; on the other hand, it ensures that the addition of the capacity compensation composite particles does not affect the material processing performance.

[0038] In some embodiments, the capacity-compensating composite particles also include a surfactant. This facilitates better dispersion of the metal nanoparticles, thereby providing more catalytic anchoring sites and further promoting the decomposition of the capacity compensator.

[0039] In some embodiments, the volume average particle size Dv50 of the capacity compensation composite particles is 3 μm to 6 μm. By controlling the volume average particle size Dv50 of the capacity compensation composite particles within the above range, it is beneficial to achieve uniform distribution of the compensator in the positive electrode film layer, improve the utilization rate of the capacity compensation composite particles, and thus further promote the decomposition of the capacity compensator.

[0040] In some embodiments, the total pore volume of the capacity-compensating composite particles is 0.1 cm³. 3 / g to 0.5cm 3 / g. By controlling the total pore volume V of the capacity compensation composite particles within the above range, the capacity compensation composite particles can have a larger specific surface area, that is, a larger contact area between the capacity compensation composite particles and the electrolyte, which facilitates ion diffusion and thus helps to improve the battery capacity and initial coulombic efficiency.

[0041] In some embodiments, the average pore size of the capacity-compensating composite particles is between 8 nm and 15 nm. By controlling the average pore size D of the capacity-compensating composite particles within this range, the capacity-compensating composite particles can have a larger specific surface area, resulting in a larger contact area between the electrolyte and the capacity-compensating composite particles, which facilitates ion diffusion and thus helps to improve the battery's capacity and initial coulombic efficiency.

[0042] In some embodiments, the specific surface area of ​​the capacity-compensating composite particles is 30 m². 2 / g to 150m 2 / g. On the one hand, by controlling the specific surface area S of the capacity-compensated composite particles at 30m². 2 A specific surface area (S) of 150 m² / g or higher is beneficial for sufficient contact between the capacity-compensating composite particles and the electrolyte, thereby promoting the decomposition of the capacity compensator. On the other hand, by controlling the specific surface area (S) of the capacity-compensating composite particles to 150 m² / g... 2 Below / g, the absorption of water by the pores inside the volume compensation composite particles can be reduced, thereby reducing the risk of the volume compensation composite particles clogging the pores due to high water content, and thus further promoting the decomposition of the volume compensation agent.

[0043] In some embodiments, the sphericity of the capacity-compensating composite particles is 0.9 to 1. By controlling the sphericity Sw of the capacity-compensating composite particles within the above range, it is beneficial to achieve uniform compounding of the compensator and the catalyst, thereby further promoting the decomposition of the capacity compensator.

[0044] The fourth aspect of this application provides a method for preparing capacity-compensating composite particles, comprising:

[0045] In the mixing step, the capacity compensator and the catalyst are mixed to obtain a mixed slurry. The catalyst comprises conductive carbon with doped elements and metal nanoparticles supported on the conductive carbon.

[0046] In the composite step, the mixed slurry is treated by spray drying to recrystallize the capacity compensator and thus combine it with the catalyst to obtain capacity compensating composite particles.

[0047] In this application, a spray drying process causes the capacity compensator to recrystallize and grow in situ with the catalyst to form composite particles. The resulting capacity compensator composite particles have an increased contact probability between the catalyst and the capacity compensator, which facilitates the catalyst's better performance in catalyzing the decomposition of the capacity compensator. Batteries containing these capacity compensator composite particles exhibit high capacity.

[0048] In some embodiments, the spray drying satisfies one or more of the following:

[0049] (1) Inlet air temperature 180℃-210℃;

[0050] (2) Air outlet temperature 90℃-100℃;

[0051] (3) The feed rate of the composite slurry is 50 ml / min-150 ml / min. Under the above conditions, capacity-compensating composite particles are formed. The resulting capacity-compensating composite particles have both small average particle size and high sphericity, which is beneficial to the decomposition of the capacity-compensating agent contained in the resulting capacity-compensating composite particles.

[0052] In some embodiments, a catalyst preparation step is included prior to the mixing step.

[0053] The catalyst preparation step includes the following steps:

[0054] The dispersion step involves dispersing the transition metal salt in an organic solvent to obtain a transition metal salt dispersion. The organic solvent includes one or more of dimethylformamide, N-methylpyrrolidone, dimethylacetamide, ethyl acetate, or methyl ethyl ketone.

[0055] The impregnation step involves impregnating conductive carbon in the transition metal salt dispersion.

[0056] The sintering step involves removing the organic solvent and then sintering at 340℃-450℃ to obtain a sintered product.

[0057] The doping step involves reacting the sintered material with a dopant source to perform doping.

[0058] In the above preparation process, on the one hand, a low-volatility organic solvent is used at room temperature, which enables slow drying. This facilitates the uniform distribution of the transition metal salt dispersion on the conductive carbon. During subsequent sintering, it promotes the in-situ formation of uniformly distributed metal nanoparticles on the conductive carbon, thereby enhancing the catalytic anchoring point of the resulting capacity-compensating particles and preparing a catalyst with high catalytic activity. On the other hand, sintering at 340℃-450℃ is beneficial for forming a porous catalyst structure. The porous structure provides more reaction sites for the catalyst, which further enhances the catalytic activity of the obtained catalyst.

[0059] In some embodiments, the solid content of the transition metal salt dispersion in the dispersion step is 10% to 30%. By controlling the solid content of the transition metal salt dispersion within the above range, it is beneficial to obtain capacity-compensating composite particles that combine large total pore volume, large specific surface area, and large average pore size, and it is also beneficial to the decomposition of the capacity compensator inside the capacity-compensating composite particles.

[0060] In some embodiments, the transition metal salt includes one or more of iron, manganese, cobalt, nickel, copper, chromium, vanadium, molybdenum, indium, rhodium, or iridium salts. Selecting the aforementioned soluble transition metal salts facilitates the formation of catalysts with high catalytic activity.

[0061] In some embodiments, the dopant source includes one or more of boron, nitrogen, phosphorus, sulfur, oxygen, fluorine, chlorine, bromine, or iodine. Selecting the above-mentioned dopant sources facilitates the preparation of catalysts with high catalytic activity. Attached Figure Description

[0062] Figure 1 This is a schematic diagram of a battery cell according to one embodiment of this application.

[0063] Figure 2 yes Figure 1 An exploded view of a battery cell according to one embodiment of this application is shown.

[0064] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application.

[0065] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0066] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0067] Figure 6 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0068] Figure 7 This is an electron microscope (SEM) image of catalyst 1 prepared in Preparation Example 1-1 of this application.

[0069] Figure 8 This is the energy dispersive X-ray spectrum (EDS) of catalyst 1 prepared in Example 1-1 of this application.

[0070] Figure 9 This is an electron microscope (SEM) image of the capacity-compensating composite particles 1 prepared in Preparation Example 2-1 of this application.

[0071] Explanation of reference numerals in the attached figures:

[0072] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0073] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the secondary battery, power-consuming device, capacity-compensating composite particles, and methods for preparing the present application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter of the claims.

[0074] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0075] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0076] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0077] Unless otherwise specified, all steps in this 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 it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0078] Unless otherwise specified, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0079] Unless otherwise specified, the values ​​of the parameters mentioned in this application can be determined using various testing methods commonly used in the art, for example, according to the testing methods given in this application.

[0080] During the first charge and discharge cycle, a secondary battery will form an SEI film on the surface of the negative electrode. The film formation process will consume a large number of active ions (e.g., lithium ions, sodium ions), resulting in low capacity and low initial coulombic efficiency of the secondary battery, which limits the battery's capacity.

[0081] To compensate for the loss of active ions, capacity compensators are typically introduced into the positive electrode. The active ions released by the capacity compensator are used to offset the large amount of active ions consumed during film formation, thereby increasing the capacity of the secondary battery. For example, there are reports of adding sodium-replenishing agents (e.g., sodium acetate, sodium squartzate, and sodium oxalate) to the positive electrode of sodium-ion batteries. This sodium-replenishing agent (active ion source) can release active ions during the first charge of the battery, thus compensating for the irreversible capacity loss during the first charge and discharge process.

[0082] However, the decomposition voltage of current capacity compensators in batteries is relatively high, often exceeding the battery's operating voltage. As a result, the capacity compensators are difficult to decompose in the battery, thus limiting their effectiveness.

[0083] Based on this, this application provides a secondary battery, an electrical device, capacity-compensating composite particles, and a method for preparing the same. The secondary battery exhibits improved capacity and initial coulombic efficiency.

[0084] Secondary batteries

[0085] The first aspect of this application provides a secondary battery. The secondary battery includes a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The positive electrode film layer includes capacity-compensating composite particles. The capacity-compensating composite particles include a capacity compensator and a catalyst. The catalyst includes conductive carbon with doped elements and metal nanoparticles supported on the conductive carbon.

[0086] The capacity-compensating composite particles in this application include a catalyst and a capacity compensator. In the catalyst, the dopant atoms, due to their different size, bond length, and valence electrons compared to carbon atoms, can cause defects at sites near adjacent carbon atoms, disrupting the electroneutrality of carbon atoms and promoting the conductivity of the carbon matrix. Furthermore, metal atoms can be effectively fixed on the doped carbon material through coordination with the dopant atoms. The chelation between the oxygen-containing functional groups on the carbon source surface and the dopant source can more effectively disperse the metal nanoparticles. The addition of dopant atoms can act as anchor points for the high dispersion of metal nanoparticles. This combined effect results in good dispersibility and stability of metal atoms on the carbon material, thereby improving the conductivity of the capacity compensator, and further reducing the decomposition activation energy of the capacity compensator, making it easier to decompose and for active ions to be released.

[0087] In addition, by having the capacity compensator and catalyst exist in the positive electrode film in the form of composite particles, the probability of contact between the catalyst and the capacity compensator can be increased. This is beneficial for the catalyst to better perform its role in catalyzing the decomposition of the capacity compensator, thereby reducing the difficulty of decomposing the capacity compensator and thus improving the battery capacity and initial coulombic efficiency.

[0088] In this application, the morphology of the capacity-compensating composite particles can be determined by acquiring SEM images of the particles.

[0089] In this application, capacity compensators and catalysts can be distinguished using a FEI Talos FS200x transmission electron microscope combined with energy dispersive X-ray spectroscopy (EDS). For example, 0.01 g of capacity compensating composite particles are placed in the transmission electron microscope, and the magnification is adjusted to observe the sample to ensure that the sample is clear and the quantity is distinguishable. Through EDS elemental analysis, capacity compensators and catalysts can be distinguished by specific metal elements in the catalyst.

[0090] In some embodiments, a coin cell using the capacity-compensating composite particles as the positive electrode active material and lithium metal or sodium metal as the counter electrode is subjected to charge-discharge tests. When the discharge capacity of the coin cell decays to half of its initial discharge capacity, the voltage of the coin cell is between 4.05V and 4.12V. The fact that the voltage (i.e., median voltage) of the coin cell made with the aforementioned capacity-compensating composite particles is within the above range when its discharge capacity decays to half of its initial discharge capacity indicates that the capacity-compensating composite particles decompose relatively easily in the battery. Using the aforementioned capacity-compensating composite particles is beneficial for further improving the battery's capacity and initial coulombic efficiency.

[0091] In this application, the median voltage of a coin cell assembled from a test sample (such as a capacity compensator or capacity compensating composite particles) reflects the ease with which the capacity compensator decomposes in the cell. A lower median voltage indicates that the sample decomposes more easily in the cell; conversely, a higher median voltage indicates that the decomposition process is more difficult.

[0092] The median voltage of a coin cell half-cell composed of the test sample can be tested using the following method. The test sample (capacity-compensating composite particles or capacity-compensating agent) is used as the positive electrode material and mixed with conductive additives (e.g., acetylene black) and binders (e.g., polyvinylidene fluoride, PVDF) at a mass ratio of 90:5:5. N-methylpyrrolidone solvent is then added and thoroughly stirred to obtain a homogeneous solution. This solution is then coated onto aluminum foil, dried, and cold-pressed to obtain the positive electrode sheet. A lithium / sodium metal sheet is used as the negative electrode sheet, and the assembly sequence is as follows: negative electrode shell - nickel foam - lithium / sodium sheet - electrolyte - separator - electrolyte - positive electrode sheet - positive electrode shell. The resulting coin cell half-cell is then subjected to constant current charge-discharge testing. The test voltage range is 2V to 4.35V, and the test temperature is room temperature (45℃). The constant current charging and discharging steps are as follows: charge to 4.35V at a current rate of 0.1C, then charge at 4.35V at a constant voltage until the current rate is ≤0.05C, let stand for 5 minutes, and then discharge to 2V at 0.1C. Record the discharge capacity. Repeat the charging and discharging process. The voltage corresponding to the time when the discharge capacity of the coin cell decreases to half of the initial discharge capacity is the median voltage.

[0093] In some embodiments, the catalyst has a porous structure. Using a catalyst with a porous structure provides abundant catalytic anchor sites, thereby effectively improving the catalytic effect and promoting the decomposition process of the capacitor compensator.

[0094] In some embodiments, the mass ratio of the metal nanoparticles, the conductive carbon, and the dopant element in the catalyst is (2-8):(89.5-96):(2-2.5). Optionally, the mass ratio is (4-5.5):(92-94):(2-2.5). By controlling the mass ratio of the metal nanoparticles, the conductive carbon, and the dopant element in the catalyst within the above range, it is beneficial to improve the catalytic activity of the catalyst and reduce the agglomeration of the metal nanoparticles, thereby further promoting the decomposition of the capacity compensator. In some embodiments, the conductive carbon includes one or more of carbon nanotubes, carbon fibers, acetylene black, Ketjen black, conductive carbon black, conductive graphite, C60, or graphene. The above-mentioned conductive carbon has high conductivity. By selecting the above-mentioned carbon materials, it is beneficial to improve the conductivity of the capacity compensating composite particles, thereby further promoting the decomposition of the capacity compensator.

[0095] The mass ratio of the metal nanoparticles, the conductive carbon, and the dopant elements can be determined using methods conventional in the art. In this application, for example, it is determined according to the following method.

[0096] Carbon (conductive carbon) and sulfur (doping element) can be determined according to GB / T 20123-2006. An appropriate amount of sample is weighed into a crucible, a suitable amount of flux is added and mixed evenly. The sample is burned in oxygen to convert carbon and sulfur into CO2 and SO2, respectively, thus obtaining the mass of carbon and sulfur in the sample. The mass of metal elements (metal nanoparticles) and boron (doping element) can be determined according to EPA 6010D-2018. The sample is dissolved using a digestion reagent, and the mass of each element is tested. Nitrogen (doping element) and oxygen (doping element) can be tested according to JY / T 017-1996, wherein nitrogen is tested by combustion in an oxygen atmosphere, and oxygen is tested by pyrolysis in a helium / argon atmosphere. In some embodiments, the doping element includes one or more of boron, nitrogen, phosphorus, sulfur, oxygen, fluorine, chlorine, bromine, and iodine. Optionally, the doping element includes nitrogen. The atomic size, bond length, and valence electron properties of the aforementioned elements differ from those of carbon atoms. Doping with these elements can create defects near carbon atoms, disrupting their original electroneutrality and thus improving the conductivity of conductive carbon. This, in turn, facilitates the further decomposition of the capacity compensator. Furthermore, the dopant elements can form chelates with oxygen-containing functional groups on the surface of conductive carbon, which helps to achieve uniform dispersion of the dopant elements. The coordination of the dopant elements with the metal portions of metal nanoparticles promotes the dispersion of the metal nanoparticles and increases the number of catalytic anchor sites, thereby further promoting the decomposition of the capacity compensator.

[0097] In some embodiments, the metal nanoparticles include one or more of the following elements: iron, manganese, cobalt, nickel, copper, chromium, vanadium, molybdenum, indium, rhodium, and iridium. These elements possess high catalytic activity. By selecting metal nanoparticles containing these elements, it is beneficial to further promote the decomposition of the capacity compensator, thereby enabling the battery to exert more capacity at low voltages.

[0098] In some embodiments, the metal nanoparticles include one or more of the following: ferrous acetate, ferrous nitrate, ferrous chloride, ferric acetate, ferric nitrate, ferric chloride, manganese acetate, manganese nitrate, manganese chloride, cobalt acetate, cobalt nitrate, cobalt chloride, nickel acetate, nickel nitrate, nickel chloride, copper acetate, copper nitrate, copper chloride, chromium acetate, chromium nitrate, chromium chloride, vanadium acetate, vanadium nitrate, vanadium chloride, molybdenum acetate, molybdenum nitrate, molybdenum chloride, indium acetate, indium nitrate, indium chloride, rhodium acetate, rhodium nitrate, rhodium chloride, iridium acetate, iridium nitrate, and iridium chloride.

[0099] In some embodiments, the capacity compensator includes a sodium supplement or a lithium supplement. Exemplarily, sodium supplements include Na₂O, Na₂O₂, Na₂CO₃, Na₂C₂O₄, Na₂C₄O₄, Na₂C₃O₃, and Na₂C₃O₄. 5、 One or more of Na2S, Na2Se, and Na2Se2. For example, the lithium supplement includes one or more of Li2O, Li2O2, Li2CO3, Li2C2O4, Li2C4O4, Li2S, Li2Se, Li2Se2, or LiF.

[0100] In some embodiments, the sodium supplement includes Na2C. x O y Where 1 ≤ x ≤ 4, 3 ≤ y ≤ 6. For example, the sodium replenishing agent includes one or more of Na₂CO₃, Na₂C₂O₄, Na₂C₄O₄, Na₂C₃O₃, and Na₂C₃O₅. Optionally, the sodium replenishing agent includes one or more of Na₂C₄O₄, Na₂C₃O₃, and Na₂C₃O₅. The above-mentioned sodium replenishing agents leave little residue after use, which helps to reduce the proportion of inactive materials inside the battery, thereby increasing the battery's energy density.

[0101] In some embodiments, the mass ratio of the catalyst to the capacity compensator in the capacity-compensating composite particles is (15-20):(80-85). Exemplarily, the mass ratio of the catalyst to the capacity compensator is a value between 15:85, 15:80, 20:85, 20:80, or any two of these values. Maintaining the mass ratio of the catalyst to the capacity compensator within the aforementioned range further increases the probability of contact between the catalyst and the capacity compensator, thereby further promoting the decomposition of the capacity compensator.

[0102] In some embodiments, the catalyst comprises 15%-20% by mass in the capacity-compensating composite particles. Exemplarily, the catalyst comprises 15%, 16%, 17%, 18%, 19%, 20%, or any two of these values. By maintaining the catalyst within this range, it is advantageous to further increase the probability of contact between the catalyst and the capacity-compensating agent, thereby further promoting the decomposition of the capacity-compensating agent.

[0103] In some embodiments, the capacity compensator comprises 80%-85% by mass in the capacity-compensating composite particles. Exemplarily, the capacity compensator comprises 80%, 81%, 82%, 83%, 84%, 85%, or any two of these values. By ensuring the capacity compensator's mass proportion is within the aforementioned range, it is advantageous to further increase the probability of contact between the catalyst and the capacity compensator, and further facilitate the decomposition of the capacity compensator.

[0104] In some embodiments, the capacity compensation composite particles constitute 5%-10% of the positive electrode film layer by mass. Exemplarily, the mass percentage of the capacity compensation composite particles is 5%, 6%, 7%, 8%, 9%, 10%, or a value within a range of any two of these values. Optionally, the mass percentage of the capacity compensation composite particles is 6%-8%. By keeping the mass ratio of the capacity compensation composite particles within the above range, on the one hand, the loss of active ions can be effectively compensated, thereby increasing the battery capacity; on the other hand, it ensures that the addition of the capacity compensation composite particles does not affect the material processing performance.

[0105] In some embodiments, the capacity-compensating composite particles also include surfactants, exemplarily including polyethylene glycol (PEG) and / or polyvinylpyrrolidone (PVP). This facilitates better dispersion of the metal nanoparticles, thereby providing more catalytic anchoring sites, which in turn further promotes the decomposition of the capacity compensator.

[0106] In some embodiments, the volume average particle size (Dv50) of the metal nanoparticles is between 50 nm and 500 nm. Exemplarily, the Dv50 of the metal nanoparticles is a value within the range of 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 150 nm, 200 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, or any two of these values. Optionally, the Dv50 of the metal nanoparticles is 50-150 nm. By controlling the volume average particle size (Dv50) of the metal nanoparticles within the above range, it is beneficial to expose more active sites, enhance catalytic activity, and thereby further facilitate the decomposition of the capacity compensator.

[0107] In some embodiments, the volume average particle size Dv50 of the capacity compensation composite particles is 3 μm to 6 μm. Exemplarily, the volume average particle size Dv50 of the capacity compensation composite particles is a value between 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, or any two of these values. Optionally, the volume average particle size Dv50 of the capacity compensation composite particles is 3.0 μm-5.0 μm, and more preferably 3.5 μm-4.5 μm. By controlling the volume average particle size Dv50 of the capacity compensation composite particles within the above range, it is beneficial to achieve uniform distribution of the compensator in the positive electrode film layer, improve the utilization rate of the capacity compensation composite particles, and thereby further facilitate the decomposition of the capacity compensator.

[0108] In this application, the volumetric particle size distribution (Dv50) of the material is a commonly used definition in the art, representing the particle size corresponding to a cumulative volumetric distribution percentage of 50%, which can be determined using instruments and methods known in the art. For example, it can be determined using a laser particle size analyzer, referring to GB / T 19077-2016. The testing instrument can be the Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0109] In some embodiments, the total pore volume V of the capacity-compensating composite particles is 0.1 cm³. 3 / g to 0.5cm 3 / g. Exemplarily, the total pore volume V of the capacity-compensating composite particles is 0.1 cm³. 3 / g, 0.2cm 3 / g, 0.3cm 3 / g, 0.4cm 3 / g, 0.5cm 3 / g or a value within a range of any two of these values. Optionally, the total pore volume V of the capacity-compensating composite particles is 0.20 cm³. 3 / g-0.40cm3 / g. By controlling the total pore volume V of the capacity compensation composite particles within the above range, the capacity compensation composite particles can have a larger specific surface area, that is, a larger contact area between the capacity compensation composite particles and the electrolyte, which is beneficial to ion diffusion and thus helps to improve the battery capacity.

[0110] In this application, the total pore volume V refers to the total volume of all pores within a material, and it is an important parameter for measuring the pore structure characteristics of porous materials. It can be measured using instruments and methods known in the art. For example, referring to GB / T19587-2017 and GB / T 21650.2-2008, a TriStarⅡ3020 pore size analyzer can be used for testing. By adsorbing gas onto the material under a series of progressively increasing pressures at a constant temperature, the pore size and pore volume distribution of the porous material can be characterized by the curves of the volume of each pore size versus the corresponding partial pressure; the total pore volume V can then be calculated.

[0111] In some embodiments, the average pore size D of the capacity compensation composite particles is between 8 nm and 15 nm. For example, the average pore size D of the capacity compensation composite particles is a value between 8 nm, 8.5 nm, 9 nm, 9.5 nm, 10 nm, 10.5 nm, 11 nm, 11.5 nm, 12 nm, 13 nm, 14 nm, 15 nm, or any two of these values. Optionally, the average pore size D of the capacity compensation composite particles is between 8.5 nm and 11.0 nm. By controlling the average pore size D of the capacity compensation composite particles within the above range, the capacity compensation composite particles can have a larger specific surface area, which is beneficial for increasing the contact area between the electrolyte and the capacity compensation composite particles, thereby facilitating the diffusion of active ions and further improving the battery capacity and initial coulombic efficiency.

[0112] In this application, the average pore size D refers to the average diameter of all pores in the composite particles. It is a key parameter for measuring the pore size of porous materials. The average pore size D can be determined using instruments and methods known in the art. For example, referring to GB / T 19587-2017 and GB / T 21650.2-2008, a TriStarⅡ3020 pore size analyzer can be used for testing. By adsorbing gas onto the test material under a series of progressively increasing pressures at a constant temperature, the pore size and pore volume distribution of the test material can be characterized by the curves of the volume of each pore size versus the corresponding partial pressure. The average pore size D can then be calculated.

[0113] In some embodiments, the specific surface area S of the capacity-compensating composite particles is 30 m². 2 / g to 150m2 / g. For example, the specific surface area S of the capacity-compensating composite particles is 30m². 2 / g、40m 2 / g, 50m 2 / g、60m 2 / g、70m 2 / g、80m 2 / g、90m 2 / g, 100m 2 / g、110m 2 / g、120m 2 / g、130m 2 / g, 140m 2 / g, 150m 2 / g or a value within a range of any two of these values. Optionally, the specific surface area S of the capacity-compensated composite particles is 75m². 2 / g-140m 2 / g, further optionally 95m 2 / g-140m 2 / g. On the one hand, by controlling the specific surface area S of the capacity-compensated composite particles at 30m². 2 A specific surface area (S) of 150 m² / g or higher is beneficial for sufficient contact between the capacity-compensating composite particles and the electrolyte, thereby promoting the decomposition of the capacity compensator. On the other hand, by controlling the specific surface area (S) of the capacity-compensating composite particles to 150 m² / g... 2 Below / g, the absorption of water by the pores inside the volume compensation composite particles can be reduced, thereby reducing the risk of the volume compensation composite particles clogging the pores due to high water content, and thus further promoting the decomposition of the volume compensation agent.

[0114] In this application, the specific surface area of ​​the material has a meaning known in the art and can be determined using instruments and methods known in the art. For example, it can be tested using the nitrogen adsorption specific surface area analysis method according to GB / T 19587-2017 and calculated using the BET (Brunauer Emmett Teller) method. The testing instrument can be the Tri-Star 3020 specific surface area and pore size analyzer from Micromeritics, USA.

[0115] In some embodiments, the sphericity Sw of the capacity-compensating composite particles is between 0.9 and 1. Exemplarily, the sphericity Sw of the capacity-compensating composite particles is a value between 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1, or any two of these values. Optionally, the sphericity Sw of the capacity-compensating composite particles is between 0.90 and 0.95. By controlling the sphericity Sw of the capacity-compensating composite particles within the above range, it is beneficial to achieve uniform compounding of the compensator and the catalyst, thereby further promoting the decomposition of the capacity compensator.

[0116] In this application, sphericity is a generally accepted definition in the art, a parameter used to describe how closely a particle's shape approximates an ideal sphere. It can be measured using instruments and methods known in the art. For example, according to the national standard GB / T38887-2020, the sphericity Sw of the particles is obtained using a ZEIS-SEM (Sigma-02-33) scanning electron microscope and image analysis software.

[0117] In the positive electrode sheet, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0118] In some embodiments, the positive 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 substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0119] In addition to the capacity-compensating composite particles mentioned above, the positive electrode film also includes positive electrode active materials.

[0120] In some embodiments, when the battery cell is a lithium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for lithium-ion batteries. As an 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 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.

[0121] During the charging and discharging process of a battery, Li undergoes insertion / extraction and consumption, resulting in varying molar Li content at different discharge states. In the examples of positive electrode active materials in this application, the molar Li content refers to the initial state of the material, i.e., before feeding. When the positive electrode active material is applied to the battery system, the molar Li content changes after charge-discharge cycles.

[0122] In some embodiments, when the battery cell is a sodium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for use in sodium-ion batteries. As an example, the positive electrode active material may include one or more of sodium-containing layered oxides, polyanionic sodium compounds, and Prussian blue sodium compounds.

[0123] As an example, sodium-containing layered oxides can be iron-manganese layered oxides. Iron-manganese layered oxides include one or more of nickel-iron-manganese layered oxides and copper-iron-manganese layered oxides. Polyanionic sodium compounds can have sodium ions, transition metal ions, and a tetrahedral (YO4) structure. n- A class of compounds with anionic units. The transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be one or more of P, S, and Si; n represents (YO4). n- The valence state. Polyanionic sodium compounds can also have sodium ions, transition metal ions, or tetrahedral (YO4) forms. n- A class of compounds containing anionic units and halide anions. The transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be one or more of P, S, and Si, and n represents (YO4). n- The valence state; halogens can be one or more of F, Cl and Br.

[0124] Prussian blue compounds can be a class of compounds containing sodium ions, transition metal ions, and cyanide ions (CN-). The transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Examples of Prussian blue compounds include Na. a Me b Me' c (CN)6, wherein Me and Me' each independently include one or more of Ni, Cu, Fe, Mn, Co, and Zn, 0 <a≤2,0<b<1,0<c<1。

[0125] In the examples of positive electrode active materials in this application, the molar content of O is only a theoretical value. Oxygen release from the crystal lattice will cause changes in the molar content of oxygen, and the actual molar content of O will fluctuate.

[0126] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0127] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, 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, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0129] Negative electrode sheet

[0130] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0131] 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 material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0132] In some embodiments, the negative electrode active material may be one or more of those known in the art for use in batteries. For example, the negative electrode active material may include one or more of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. Silicon-based materials may be selected from one or more of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from one or more of elemental tin, tin oxides, and tin alloys. However, this 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.

[0133] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, first binder, second binder and dispersant, in a solvent (e.g. deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0134] electrolytes

[0135] In some embodiments, the secondary battery cell also includes an electrolyte. During battery charging and discharging, active ions move back and forth between the positive and negative electrode plates, inserting and extracting. The electrolyte acts as a conductor of ions between the positive and negative electrode plates. This application does not impose specific limitations on the type of electrolyte, which can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or entirely solid.

[0136] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0137] In some embodiments, the electrolyte salt may be selected from one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium perchlorate, sodium hexafluoroarsenate, sodium difluorosulfonamide, sodium ditrifluoromethanesulfonamide, sodium trifluoromethanesulfonate, sodium difluorophosphate, sodium difluorooxalate borate, sodium dioxalate borate, sodium difluorodioxalate phosphate, and sodium tetrafluorooxalate phosphate.

[0138] In some embodiments, the solvent may be selected from one or more of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0139] In some embodiments, the electrolyte may optionally include capacity-compensating composite particles. For example, the capacity-compensating composite particles may include negative electrode film-forming capacity-compensating composite particles, positive electrode film-forming capacity-compensating composite particles, and may also include capacity-compensating composite particles that can improve certain battery performance, such as capacity-compensating composite particles that improve battery overcharge performance, or capacity-compensating composite particles that improve battery high-temperature or low-temperature performance.

[0140] Separating membrane

[0141] In some embodiments, the battery cell also includes a separator. The separator is disposed between the positive and negative electrodes, primarily serving to prevent short circuits between the positive and negative electrodes while allowing ions to pass through. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0142] In some embodiments, the material of the separator can be selected from one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can 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 can be the same or different, without particular limitation.

[0143] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0144] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0145] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0146] The term "secondary battery" used in this article refers to a single battery cell, a battery module, or a battery pack. These will be explained separately below.

[0147] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 The example shown is a square-structured battery cell 5.

[0148] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a top cover assembly 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the top cover assembly 53 can be placed over the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0149] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0150] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3 In battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0151] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0152] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0153] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0154] Electrical appliances

[0155] The second aspect of this application provides an electrical device, which includes the secondary battery provided in the first aspect of this application. The secondary battery can be used as a power source for the electrical device or as an energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0156] As an electrical device, you can choose individual battery cells, battery modules, or battery packs according to your usage requirements.

[0157] Figure 6This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0158] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0159] Preparation method of capacity-compensating composite particles

[0160] The capacity-compensating composite particles of this application can be prepared by the following method, including the following steps:

[0161] The mixing step involves mixing the capacity compensator and the catalyst to obtain a mixed slurry, wherein the catalyst comprises conductive carbon with doped elements and metal nanoparticles supported on the conductive carbon; and

[0162] In the composite step, the mixed slurry is treated by spray drying to recrystallize the capacity compensator and thus combine it with the catalyst to obtain capacity compensating composite particles.

[0163] In this application, the capacity compensator is recrystallized by spray drying and grown in situ with the catalyst to form composite particles. The contact probability between the catalyst and the capacity compensator in the obtained capacity compensator composite particles is increased, which is conducive to the catalyst playing a better role in catalyzing the decomposition of the capacity compensator. The battery using the capacity compensator composite particles has high capacity and first coulombic efficiency.

[0164] In some embodiments, the spray drying satisfies one or more of the following: (1) inlet air temperature 180℃-210℃; (2) outlet air temperature 90℃-100℃; (3) the feed rate of the composite slurry is 50ml / min-150ml / min. Under the above conditions, capacity-compensating composite particles are formed, resulting in particles with both small average particle size and high sphericity, which facilitates the decomposition of the capacity-compensating agent contained in the resulting capacity-compensating composite particles.

[0165] In addition, the catalyst described above in this application is prepared by the following method, including the following steps:

[0166] The dispersion step involves dispersing the transition metal salt in an organic solvent to obtain a transition metal salt dispersion, wherein the organic solvent includes one or more of dimethylformamide (DMF), N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), ethyl acetate (EA), or methyl ethyl ketone.

[0167] The impregnation step involves impregnating conductive carbon in the transition metal salt dispersion.

[0168] The sintering step involves removing the organic solvent and then sintering at 340°C-450°C to obtain a sintered product;

[0169] The doping step involves reacting the sintered material with a dopant source to obtain the catalyst.

[0170] In the above preparation process, on the one hand, a low-volatility organic solvent is used at room temperature, which enables slow drying. This facilitates the uniform distribution of the transition metal salt dispersion on the conductive carbon. During subsequent sintering, it promotes the in-situ formation of uniformly distributed metal nanoparticles on the conductive carbon, thereby enhancing the catalytic anchoring point of the resulting capacity-compensating particles and preparing a catalyst with high catalytic activity. On the other hand, sintering at 340℃-450℃ is beneficial for forming a porous catalyst structure. The porous structure provides more reaction sites for the catalyst, which further enhances the catalytic activity of the obtained catalyst.

[0171] In some embodiments, during the dispersion step, the solid content of the transition metal salt dispersion is 3%-15%. By controlling the solid content of the transition metal salt dispersion within the above range, it is beneficial to obtain capacity-compensating composite particles that combine large total pore volume, large specific surface area, and large average pore size, and it is also beneficial to the decomposition of the capacity compensator inside the capacity-compensating composite particles.

[0172] In some embodiments, the transition metal salt includes one or more of iron, manganese, cobalt, nickel, copper, chromium, vanadium, molybdenum, indium, rhodium, or iridium salts. Optionally, the transition metal salt includes acetates, nitrates, or chlorides of elements such as iron, manganese, cobalt, nickel, copper, chromium, vanadium, molybdenum, indium, rhodium, and iridium. Using the above-mentioned soluble transition metal salts is beneficial for forming catalysts with high catalytic activity.

[0173] In some embodiments, the sintering step further includes a step of removing the organic solvent by drying, wherein the drying step satisfies one or more of the following: (1) the drying temperature is 60°C to 80°C, and (2) the drying time is 8h to 12h. Drying the transition metal salt dispersion under the above conditions can limit the rate of nucleation and / or growth of the transition metal salt, thereby facilitating the preparation of catalysts with small particle sizes. This is beneficial for preparing capacity-compensated composite particles that combine large total pore volume, large specific surface area, and large average pore size.

[0174] In some embodiments, the sintering step satisfies one or more of the following: (1) the heating rate is 5℃ / min-20℃ / min; (2) the sintering time is 0.5h to 1h; and (3) the sintering atmosphere is Ar. Performing the sintering step under the above conditions is beneficial to ensure complete pyrolysis of the transition metal salt and appropriate metal particle size.

[0175] In some embodiments, the dopant source includes one or more of boron, nitrogen, phosphorus, sulfur, oxygen, fluorine, chlorine, bromine, or iodine. Selecting the above-mentioned dopant source facilitates the preparation of a catalyst with high catalytic activity, thereby further reducing the decomposition voltage of the prepared capacity-compensated composite particles. In some embodiments, the dopant source in the doping step includes NH3 or melamine. For example, NH3 / Ar gas is introduced at a flow rate of 3-5 L / min for 1-2 hours. Alternatively, the sintered material can be mixed with melamine at a mass ratio of 1:12 to 1:20 and then heat-treated at 800-950°C for 1-2 hours. Forming a catalyst under these conditions facilitates the full incorporation of nitrogen atoms into the carbon material, improving the conductivity of the conductive carbon.

[0176] Example

[0177] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0178] Catalyst preparation

[0179] Preparation Example 1-1

[0180] In the dispersion step, 25g (M1) transition metal salt (Ni(NO3)2·6H2O) and 0.5g surfactant (polyvinylpyrrolidone, PVP) were dispersed in 100ml organic solvent (dimethylformamide, DMF) to obtain a transition metal salt dispersion (nickel salt dispersion) with a solid content of 15%.

[0181] In the impregnation step, 90g (M2) of carbon material (conductive graphite) is impregnated in the above nickel salt dispersion.

[0182] The sintering process involves slow drying at a drying temperature of 60℃ (t2) for 8 hours (T2) to remove the organic solvent. Then, the temperature is increased to 400℃ (t3) in an Ar atmosphere at a heating rate of 20℃ / min (V3), followed by sintering for 30 minutes (T3).

[0183] In the doping step, a dopant source (NH3) is introduced into the above sintered product at a gas flow rate of 8 L / min (V4) to carry out a nitriding reaction, and the reaction is carried out for 1.5 h (T4-1) to obtain catalyst 1.

[0184] Preparation Examples 1-2 to 1-5

[0185] The catalyst was prepared according to the method of Preparation Example 1-1, with the difference being:

[0186] Adjust the preparation conditions in the dispersion, sintering and doping steps according to the records in Table 1-1.

[0187] Preparation Examples 1-6

[0188] The catalyst was prepared using a method similar to that used in the preparation example, with the following differences:

[0189] After removing the organic solvent, the mixture was mixed with 1725g of melamine (M4) and then heat-treated at 800℃ (t4) for 1h (T4-2).

[0190] Preparation Example 1-1'

[0191] The catalyst was prepared according to the method of Preparation Example 1-1, except that no transition metal salt was added in the dispersion step.

[0192] Preparation Examples 1-2'

[0193] The catalyst was prepared according to the method of Preparation Example 1-1, except that no doping step was performed.

[0194] Table 1-1

[0195]

[0196]

[0197] In Table 1-1, " / " indicates that no related items have been set, M 1 Salt represents a transition metal salt, M 2 The source indicates the dopant element source.

[0198] Catalyst testing

[0199] (1) Test of catalyst morphology

[0200] SEM images of catalyst 1 were acquired using a scanning electron microscope (HR-TEM Talos F200), such as... Figure 7 As shown. By Figure 7 It can be seen that the catalyst 1 has a porous structure.

[0201] EDS images of catalyst 1 were acquired using energy-dispersive X-ray spectroscopy (EDS), with carbon and nickel elemental images as shown below. Figure 8 As shown, nickel (metal nanoparticles) is uniformly distributed.

[0202] (2) Test of volume average particle size Dv50:

[0203] According to GB / T 19077-2016, the volume average particle size Dv50 of each catalyst was determined using a laser particle size analyzer, and the test results are recorded in Table 1-2.

[0204] (3) Testing of the mass ratio of metal nanoparticles, conductive carbon, and doping elements:

[0205] The mass of each element was tested according to the following method:

[0206] ① Mass of carbon (conductive carbon) and sulfur (doped element): According to GB / T 20123-2006, weigh an appropriate amount of sample into a crucible, add an appropriate amount of flux and mix evenly. The sample is burned in oxygen to convert carbon and sulfur into CO2 and SO2, and the mass of carbon and sulfur in the sample can be obtained.

[0207] ② Mass of metal elements (metal nanoparticles) and element B (doping element): Inductively coupled plasma atomic emission spectrometry was used, in accordance with EPA 6010D-2018, to dissolve the sample with a digestion reagent and test the mass of each element.

[0208] ③ The quality of N (doped element) and O (doped element) elements: tested according to JY / T 017-1996, wherein N element is tested by combustion method in oxygen atmosphere and O element is tested by pyrolysis method in helium / argon atmosphere.

[0209] Based on the above test results, the mass ratios of metal nanoparticles, conductive carbon, and doping elements in each catalyst were calculated, and the test results are recorded in Table 1-2.

[0210] Table 1-2

[0211] Catalyst number DV50(nm) The mass ratio of metal nanoparticles, conductive carbon, and doping elements Catalyst 1 212 Ni:C:N = 5.2:92.5:2.3 Catalyst 2 245 Ni:C:N = 4.3:93.6:2.1 Catalyst 3 50 Ni:C:B = 4.6:93:2.4 Catalyst 4 500 Ni:C:S = 5:92.9:2.1 Catalyst 5 232 Ni:C:O = 4.1:93.6:2.3 Catalyst 6 216 Ni:C:N = 4.8:93:2.2 Catalyst 1' 320 C:N = 95.7:4.3 Catalyst 2' 212 Ni:C = 8.2:91.8

[0212] Preparation of capacity-compensating composite particles

[0213] Preparation Example 2-1

[0214] Mixing steps: Add 85g of capacity compensator (Na2C2O4) and 15g of catalyst (catalyst 1) to 2L of deionized water solvent to prepare a composite slurry with a solid content of 5%, and mill the composite slurry for 1 hour.

[0215] Composite step: Set the inlet air temperature of the spray drying equipment to 180℃, the outlet air temperature to 90℃, and the feeding speed to 100ml / min. Add the composite slurry formed in step S1 to the inlet of the spray drying equipment to obtain volume-compensated composite particles 1.

[0216] Preparation Example 2-2

[0217] Capacity-compensating composite particles 2 were prepared according to the method of preparation example 2-1, with the difference being:

[0218] In the mixing step: 80g of capacity compensator (Na2C2O4) and 20g of catalyst 1 were added to 2L of deionized water solvent to prepare a composite slurry with a solid content of 5%, and the composite slurry was sand-milled for 1h.

[0219] Preparation Examples 2-3

[0220] Capacity-compensating composite particles 3 were prepared according to the method of preparation example 2-1, with the difference being:

[0221] In the mixing step: 85g of capacity compensator (Na2C2O4) and 15g of catalyst 2 are added to 2L of deionized water solvent to prepare a composite slurry with a solid content of 5%. The composite slurry is then milled for 1 hour. In the compounding step (spray drying): The inlet air temperature of the spray drying equipment is set to 180℃, the outlet air temperature to 90℃, and the feed rate to 100ml / min. The resulting composite slurry is then added to the inlet of the spray drying equipment.

[0222] Preparation Examples 2-4

[0223] Capacity-compensating composite particles 4 were prepared according to the method of Preparation Example 2-1, with the difference being:

[0224] In the mixing step: 82g of Na2C3O3 and 18g of catalyst 3 were added to 2L of deionized water solvent to prepare a composite slurry with a solid content of 5%, and the composite slurry was milled for 1 hour. In the compounding step (spray drying): the inlet air temperature of the spray drying equipment was set to 210℃, the outlet air temperature to 100℃, and the feed rate to 150ml / min. The formed composite slurry was added to the feed port of the spray drying equipment.

[0225] Preparation Examples 2-5

[0226] Capacity-compensating composite particles 5 were prepared according to the method of Preparation Example 2-1, with the difference being:

[0227] In the mixing step: 84g of capacity compensator (Na2C4O4) and 16g of catalyst 4 were added to 2L of deionized water solvent to prepare a composite slurry with a solid content of 5%, and the composite slurry was sand-milled for 1 hour.

[0228] In the compounding step: set the inlet air temperature of the spray drying equipment to 180℃, the outlet air temperature to 90℃, and the feeding speed to 100ml / min, and add the formed compound slurry to the inlet of the spray drying equipment.

[0229] Preparation Examples 2-6

[0230] Capacity-compensating composite particles 6 were prepared according to the method of Preparation Example 2-1, with the difference being:

[0231] In the mixing step: 85g of capacity compensator (Na2CO3) and 15g of catalyst 5 were added to 2L of deionized water solvent to prepare a composite slurry with a solid content of 5%, and the composite slurry was sand-milled for 1 hour.

[0232] In the compounding step: set the inlet air temperature of the spray drying equipment to 180℃, the outlet air temperature to 90℃, and the feeding speed to 100ml / min, and add the formed compound slurry to the inlet of the spray drying equipment.

[0233] Preparation Examples 2-7

[0234] The capacity-compensating composite particles 7 were prepared according to the method of Preparation Example 2-1, except that in the mixing step: 85g of capacity-compensating agent (Na2C2O4) and 15g of catalyst 6 were added to 2L of deionized water solvent to prepare a composite slurry with a solid content of 5%, and the composite slurry was sand-milled for 1h.

[0235] In the compounding step: set the inlet air temperature of the spray drying equipment to 180℃, the outlet air temperature to 90℃, and the feeding speed to 100ml / min, and add the formed compound slurry to the inlet of the spray drying equipment.

[0236] Preparation Examples 2-8

[0237] Capacity-compensating composite particles 8 were prepared according to the method of Preparation Example 2-1, except that in the mixing step: 85g of capacity compensator (Li2C2O4) and 15g of catalyst 8 were added to 2L of deionized water solvent to prepare a composite slurry with a solid content of 5%, and the composite slurry was sand-milled for 1h.

[0238] In the compounding step: set the inlet air temperature of the spray drying equipment to 180℃, the outlet air temperature to 90℃, and the feeding speed to 100ml / min, and add the formed compound slurry to the inlet of the spray drying equipment.

[0239] Preparation Example 2-1'

[0240] Capacity supplement particles 1' were prepared according to the method of Preparation Example 2-1, except that catalyst 1 was replaced with catalyst 1'.

[0241] Preparation Example 2-2'

[0242] Capacity supplement particles 2' were prepared according to the method of Preparation Example 2-1, except that catalyst 1 was replaced with catalyst 2'.

[0243] Preparation Examples 2-3'

[0244] The capacity-supplementing particles 3' were prepared according to the method of Preparation Example 2-1, with the difference being:

[0245] The following steps were performed after the mixing step: the capacity compensator (Na2C2O4) was ball-milled with catalyst 1 at a speed of 300 r / min for 3 h.

[0246] Testing of parameters of capacity-compensated composite particles

[0247] (1) Morphological testing:

[0248] SEM images of volume-compensated composite particles 1 were acquired using a scanning electron microscope (HR-TEM Talos F200), such as... Figure 9 As shown in the figure, composite particle 1 is spherical.

[0249] (2) Test of volume average particle size Dv50:

[0250] Referring to GB / T 19077-2016, the volume average particle size Dv50 of each capacity-compensated composite particle was determined using a laser particle size analyzer, and the test results are recorded in Table 2.

[0251] (3) Testing of total pore volume V and average pore diameter D:

[0252] According to GB / T 19587-2017 and GB / T 21650.2-2008, the total pore volume V and average pore diameter D of each capacity-compensated composite particle were tested using a TriStarⅡ3020 pore size analyzer. The test results are recorded in Table 2.

[0253] (4) Test of specific surface area S:

[0254] The specific surface area S of each capacity-compensated composite particle can be tested using the nitrogen adsorption specific surface area analysis test method according to GB / T 19587-2017. The test results are recorded in Table 2.

[0255] (5) Test of sphericity Sw:

[0256] In accordance with the national standard GB / T 38887-2020, a scanning electron microscope of model ZEIS-SEM (Sigma-02-33) was used to attach the ethanol-dispersed material to the sample stage with conductive adhesive, install the sample stage into the sample chamber and ensure it is fixed, and test the sphericity Sw of each capacity-compensated composite particle. The test results are recorded in Table 2.

[0257] (6) Testing of median voltage:

[0258] Capacity-compensating composite particles, used as the positive electrode material, were mixed with conductive additives (e.g., acetylene black) and binders (e.g., polyvinylidene fluoride, PVDF) at a mass ratio of 90:5:5. The mixture was then added to N-methylpyrrolidone solvent and stirred thoroughly to obtain a homogeneous solution. This solution was then coated onto aluminum foil, dried, and cold-pressed to obtain the positive electrode sheet. Lithium / sodium metal sheets were used as the negative electrode sheets, and the assembly sequence was as follows: negative electrode shell - nickel foam - lithium / sodium sheet - electrolyte - separator - electrolyte - positive electrode sheet - positive electrode shell. A coin cell half-cell was obtained and subjected to constant current charge-discharge testing. The test voltage range was 2V to 4.35V, and the test temperature was room temperature (45℃). The constant current charge-discharge procedure was as follows: charge at a current rate of 0.1C to 4.35V, then charge at a constant voltage of 4.35V until the current rate ≤ 0.05C, let stand for 5 minutes, and then discharge at 0.1C to 2V. The discharge capacity was recorded, and the charge-discharge cycle was repeated. The median voltage is the voltage at which the capacity of a coin cell decays to half of its initial discharge capacity. The test results are recorded in Table 2.

[0259] Table 2

[0260]

[0261]

[0262] Example 1

[0263] Preparation of positive electrode sheet

[0264] The positive electrode active material (P2-Na) 2 / 3 Ni 1 / 3 Mn 1 / 3 Ti 1 / 3 O2), capacity-compensating composite particles 1, conductive agent (acetylene black), and binder (polyvinylidene fluoride) are added to N-methylpyrrolidone solvent in a mass ratio of 82:8:5:5 and stirred thoroughly to obtain a uniformly mixed solution. The solution is then coated on both sides of aluminum foil, dried, and cold-pressed to obtain a positive electrode sheet.

[0265] Negative electrode sheet

[0266] The negative electrode active material, artificial graphite, hard carbon, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are added to a deionized water solvent in a mass ratio of 90:5:2:2:1 and thoroughly mixed. The mixture is then coated onto both sides of a copper foil, dried, and cold-pressed to obtain the negative electrode sheet.

[0267] Separating membrane

[0268] A polyethylene film (PE) with a thickness of 13 μm.

[0269] Electrolyte preparation

[0270] NaPF6 was dissolved in a mixed solvent of ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) in a volume ratio of 1:1:1 to obtain a NaPF6 solution with a molar concentration of 1 mol / L, which was used as the electrolyte.

[0271] Battery assembly

[0272] Assemble the button cell (secondary battery) in the following order: negative electrode shell → high elastic sheet → steel sheet → negative electrode plate → separator → positive electrode plate → positive electrode shell.

[0273] Examples 2 to 7

[0274] The secondary battery was prepared according to the preparation method of Example 1, except that the type of capacity compensation composite particles was adjusted according to Table 3.

[0275] Comparative Examples 1 to 3

[0276] The secondary battery was prepared according to the preparation method of Example 1, except that the type of capacity compensation composite particles was adjusted according to Table 3.

[0277] Comparative Example 4

[0278] The secondary battery was prepared according to the preparation method of Example 1, except that no capacity compensation composite particles were added when preparing the positive electrode sheet.

[0279] Testing the capacity of secondary batteries

[0280] The full battery was subjected to constant current charge-discharge testing using the Blue Battery Testing System (CT2001A), and the cycle charge-discharge capacity curves were recorded. The test voltage range was 2V to 4.5V, and the test temperature was room temperature (45℃). The constant current charge-discharge steps were as follows:

[0281] ① Charge to 4.5V at a current rate of 0.1C.

[0282] ② Charge at a constant voltage of 4.5V until the current ratio is ≤0.05C, and record the charging capacity C0.

[0283] ③ Let it stand for 5 minutes, then discharge it to 2V at 0.1C and record the discharge capacity D0.

[0284] First charge specific capacity = first charge capacity C0 / mass of positive electrode active material.

[0285] First discharge specific capacity = First discharge capacity D0 / Mass of positive electrode active material.

[0286] Initial coulombic efficiency = initial discharge specific capacity / initial charge specific capacity.

[0287] The test results are recorded in Table 3.

[0288] Table 3 (Sodium-ion batteries)

[0289]

[0290] As can be seen from the data in Table 3, compared with Comparative Example 1 (capacity compensation composite particles do not include metal nanoparticles), Comparative Example 2 (conductive carbon in capacity compensation composite particles does not contain doping elements), Comparative Example 3 (capacity compensator and catalyst are not composited) and Comparative Example 4 (no capacity compensation composite particles are added), the sodium-ion secondary batteries obtained in Examples 1 to 7 have improved capacity and initial coulombic efficiency.

[0291] Example 8

[0292] The secondary battery was prepared according to the preparation method of Example 1, except that the positive electrode was prepared and the electrolyte was prepared.

[0293] Preparation of positive electrode sheet

[0294] The positive electrode active material (lithium iron phosphate), capacity compensation composite particles 8, conductive agent (acetylene black), and binder (polyvinylidene fluoride) are added to N-methylpyrrolidone solvent in a mass ratio of 82:8:5:5 and stirred thoroughly to obtain a uniformly mixed solution. The solution is then coated on both sides of aluminum foil, dried, and cold-pressed to obtain the positive electrode sheet.

[0295] Electrolyte preparation

[0296] LiPF6 was dissolved in a mixed solvent of ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) in a volume ratio of 1:1:1 to obtain a LiPF6 solution with a molar concentration of 1 mol / L, which was used as the electrolyte.

[0297] Comparative Example 5

[0298] The secondary battery was prepared according to the preparation method of Example 8, except that no capacity compensation composite particles were added when preparing the positive electrode sheet.

[0299] The same test methods as those used in the examples were applied to Example 8 and Comparative Example 5, and the results are shown in Table 4.

[0300] Table 4 (Lithium-ion Batteries)

[0301]

[0302] As shown in Table 4, compared with Comparative Example 5 (without capacity compensation composite particles), the lithium-ion secondary battery obtained in Example 8 has improved capacity and initial coulombic efficiency.

[0303] Examples 9 and 10

[0304] The battery was assembled in the same manner as in Example 1, except that the amount of capacity compensation composite particles 1 added was adjusted according to Table 4.

[0305] The performance of the batteries of Example 9 and Example 10 was tested according to the test method of Example 1, and the test results are recorded in Table 5.

[0306] Table 5

[0307]

[0308] The data in Table 5 show that when the mass percentage of capacity-compensating composite particles is 5%-10%, the secondary battery exhibits improved capacity and initial coulombic efficiency.

[0309] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A secondary battery, characterized in that, It includes the positive electrode, negative electrode, separator, and electrolyte. The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including capacity-compensating composite particles. The capacity-compensating composite particles include a capacity compensator and a catalyst. The catalyst comprises conductive carbon with doped elements and metal nanoparticles supported on the conductive carbon.

2. The secondary battery according to claim 1, characterized in that, The catalyst has a porous structure.

3. The secondary battery according to claim 1 or 2, characterized in that, A coin cell half-cell using the capacity-compensating composite particles as the positive electrode active material and lithium metal or sodium metal as the counter electrode was subjected to charge-discharge tests. When the discharge capacity of the coin cell half-cell decayed to half of the initial discharge capacity, the voltage of the coin cell half-cell was 4.05V to 4.12V.

4. The secondary battery according to any one of claims 1 to 3, characterized in that, In the catalyst, the mass ratio of the metal nanoparticles, the conductive carbon, and the dopant element is (2-8):(89.5-96):(2-2.5).

5. The secondary battery according to any one of claims 1 to 4, characterized in that, In the catalyst, the mass ratio of the metal nanoparticles, the conductive carbon, and the dopant element is (4-5.5):(92-94):(2-2.5).

6. The secondary battery according to any one of claims 1 to 5, characterized in that, The conductive carbon includes one or more of carbon nanotubes, carbon fibers, acetylene black, Ketjen black, conductive carbon black, conductive graphite, C60, or graphene.

7. The secondary battery according to any one of claims 1 to 6, characterized in that, The doping elements include one or more of the following: boron, nitrogen, phosphorus, sulfur, oxygen, fluorine, chlorine, bromine, and iodine.

8. The secondary battery according to any one of claims 1 to 7, characterized in that, The metal nanoparticles include at least one of iron, manganese, cobalt, nickel, copper, chromium, vanadium, molybdenum, indium, rhodium, and iridium.

9. The secondary battery according to any one of claims 1 to 8, characterized in that, The volume average particle size Dv50 of the metal nanoparticles is 50 nm to 500 nm.

10. The secondary battery according to any one of claims 1 to 9, characterized in that, The capacity compensator includes a sodium supplement or a lithium supplement.

11. The secondary battery according to claim 10, characterized in that, The lithium supplement includes at least one of Li2O, Li2O2, Li2CO3, Li2C2O4, Li2C4O4, Li2S, Li2Se, Li2Se2, or LiF; the sodium supplement includes at least one of Na2O, Na2O2, Na2CO3, Na2C2O4, Na2C4O4, Na2C3O3, Na2C3O5, Na2S, Na2Se, Na2Se2, or NaF.

12. The secondary battery according to any one of claims 1 to 11, characterized in that, In the capacity-compensating composite particles, the mass percentage of the catalyst is 15% to 20%.

13. The secondary battery according to any one of claims 1 to 12, characterized in that, In the capacity-compensating composite particles, the capacity compensator accounts for 80% to 85% of the mass.

14. The secondary battery according to any one of claims 1 to 13, characterized in that, The capacity-compensating composite particles also include surfactants.

15. The secondary battery according to any one of claims 1 to 14, characterized in that, In the positive electrode film layer, the mass percentage of the capacity compensation composite particles is 5% to 10%.

16. The secondary battery according to any one of claims 1 to 15, characterized in that, The volume average particle size Dv50 of the capacity-compensating composite particles is 3 μm to 6 μm.

17. The secondary battery according to any one of claims 1 to 16, characterized in that, The total pore volume of the capacity-compensating composite particles is 0.1 cm³. 3 / g to 0.5cm 3 / g.

18. The secondary battery according to any one of claims 1 to 17, characterized in that, The average pore size of the capacity-compensating composite particles is 8 nm to 15 nm.

19. The secondary battery according to any one of claims 1 to 18, characterized in that, The specific surface area of ​​the capacity-compensating composite particles is 30 m². 2 / g to 150m 2 / g.

20. The secondary battery according to any one of claims 1 to 19, characterized in that, The sphericity of the capacity-compensating composite particles is 0.9 to 1.

21. An electrical appliance, characterized in that, The secondary battery includes any one of claims 1 to 20.

22. A capacity-compensating composite particle, characterized in that, It includes a capacity compensator and a catalyst, wherein the catalyst comprises conductive carbon with doped elements and metal nanoparticles supported on the conductive carbon.

23. The capacity-compensating composite particles according to claim 22, characterized in that, The catalyst has a porous structure.

24. The capacity-compensating composite particles according to claim 22 or 23, characterized in that, A coin cell half-cell using the capacity-compensating composite particles as the positive electrode active material and lithium metal or sodium metal as the counter electrode was subjected to charge-discharge tests. When the discharge capacity of the coin cell half-cell decayed to half of the initial discharge capacity, the voltage of the coin cell half-cell was 4.05V to 4.12V.

25. The capacity-compensating composite particles according to any one of claims 22 to 24, characterized in that, In the catalyst, the mass ratio of the metal nanoparticles, the conductive carbon, and the dopant element is (2-8):(89.5-96):(2-2.5).

26. The capacity-compensating composite particles according to any one of claims 22 to 25, characterized in that, The conductive carbon includes one or more of carbon nanotubes, carbon fibers, acetylene black, Ketjen black, conductive carbon black, conductive graphite, C60, or graphene.

27. The capacity-compensating composite particles according to any one of claims 22 to 26, characterized in that, The doping elements include one or more of the following: boron, nitrogen, phosphorus, sulfur, oxygen, fluorine, chlorine, bromine, and iodine.

28. The capacity-compensating composite particles according to any one of claims 22 to 27, characterized in that, The metal nanoparticles include at least one metal selected from iron, manganese, cobalt, nickel, copper, chromium, vanadium, molybdenum, indium, rhodium, and iridium.

29. The capacity-compensating composite particles according to any one of claims 22 to 28, characterized in that, The volume average particle size Dv50 of the metal nanoparticles is 50 nm to 500 nm.

30. The capacity-compensating composite particles according to any one of claims 22 to 29, characterized in that, The capacity compensator includes a sodium supplement or a lithium supplement.

31. The capacity-compensating composite particles according to any one of claims 22 to 30, characterized in that, In the capacity-compensating composite particles, the mass percentage of the catalyst is 15% to 20%.

32. The capacity-compensating composite particles according to any one of claims 22 to 31, characterized in that, In the capacity-compensating composite particles, the capacity compensator accounts for 80% to 85% of the mass.

33. The capacity-compensating composite particles according to any one of claims 22 to 32, characterized in that, The volume average particle size Dv50 of the capacity-compensating composite particles is 3 μm to 6 μm.

34. The capacity-compensating composite particles according to any one of claims 22 to 33, characterized in that, The total pore volume of the capacity-compensating composite particles is 0.1 cm³. 3 / g to 0.5cm 3 / g.

35. The capacity-compensating composite particles according to any one of claims 22 to 34, characterized in that, The average pore size of the capacity-compensating composite particles is 8 nm to 15 nm.

36. The capacity-compensating composite particles according to any one of claims 22 to 35, characterized in that, The specific surface area of ​​the capacity-compensating composite particles is 30 m². 2 / g to 150m 2 / g.

37. The capacity-compensating composite particles according to any one of claims 22 to 36, characterized in that, The sphericity of the capacity-compensating composite particles is 0.9 to 1.

38. A method for preparing capacity-compensating composite particles, characterized in that, include: In the mixing step, the capacity compensator and the catalyst are mixed to obtain a mixed slurry. The catalyst comprises conductive carbon with doped elements and metal nanoparticles supported on the conductive carbon. In the composite step, the mixed slurry is treated by spray drying to recrystallize the capacity compensator and thus combine it with the catalyst to obtain capacity compensating composite particles.

39. The preparation method according to claim 38, characterized in that, The spray drying satisfies one or more of the following: (1) Inlet air temperature 180℃-210℃; (2) Air outlet temperature 90℃-100℃; (3) The feeding rate of the composite slurry is 50ml / min-150ml / min.

40. The preparation method according to claim 38 or 39, characterized in that, Prior to the mixing step, a catalyst preparation step is also included. The catalyst preparation step includes the following steps: The dispersion step involves dispersing the transition metal salt in an organic solvent to obtain a transition metal salt dispersion. The organic solvent includes one or more of dimethylformamide, N-methylpyrrolidone, dimethylacetamide, ethyl acetate, or methyl ethyl ketone. The impregnation step involves impregnating conductive carbon in the transition metal salt dispersion. The sintering step involves removing the organic solvent and then sintering at 340℃-450℃ to obtain a sintered product. The doping step involves reacting the sintered material with a dopant source to perform doping.

41. The preparation method according to claim 40, characterized in that, In the dispersion step, the solid content of the transition metal salt dispersion is 10% to 30%.

42. The preparation method according to claim 40 or 41, characterized in that, The transition metal salts include one or more of the following: iron salts, manganese salts, cobalt salts, nickel salts, copper salts, chromium salts, vanadium salts, molybdenum salts, indium salts, rhodium salts, or iridium salts.

43. The preparation method according to any one of claims 40 to 42, characterized in that, The doping element source includes one or more of the following: boron source, nitrogen source, phosphorus source, sulfur source, oxygen source, fluorine source, chlorine source, bromine source, or iodine source.

Images