Battery cell, battery device, energy storage device, energy storage system and charging network

Abstract

The invention relates to the technical field of batteries, in particular to a single battery, a battery device, an energy storage device, an energy storage system and a charging network. The capacity of the provided single battery is larger than or equal to 500 Ah, the single battery comprises a positive pole piece, a negative pole piece and a diaphragm located between the positive pole piece and the negative pole piece, the positive pole piece comprises a positive pole current collector and a positive pole film layer stacked on at least one surface of the positive pole current collector, the positive pole film layer comprises a positive pole active material, and the negative pole film layer comprises a negative pole active material. The positive electrode active material comprises Ti and / or V element doped lithium-containing transition metal phosphate; the diaphragm comprises a base membrane and a coating arranged on at least one surface of the base membrane, and the porosity of the base membrane does not exceed 30%. By optimizing the structural stability of the positive electrode material and cooperatively regulating and controlling the pore structure of the base membrane, the cycling stability and the long-term use safety of the battery are remarkably enhanced while the high capacity of a single battery is maintained, and the comprehensive performance is synchronously improved.

Description

[0001] This application claims priority to PCT patent application No. PCT / CN2025 / 140528, entitled “Battery Cell, Battery Device and Energy Storage Device”, filed on December 5, 2025, with the World Intellectual Property Organization (WIPO) (International Bureau), the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application belongs to the field of battery technology, and in particular relates to a battery cell, battery device, energy storage device, energy storage system and charging network. Background Technology

[0003] Phosphate-based cathode materials have become the mainstream cathode choice in large-scale energy storage due to their high safety, long cycle life, and cost advantages. To meet the demand for larger single-cell capacity in energy storage devices, battery cells are developing towards larger sizes, resulting in a significant increase in structural dimensions. However, large-sized cells present two interconnected technical challenges: internal moisture retention leading to HF corrosion, and subsequent dissolution and diffusion of cathode metal ions to the anode causing a cascading performance degradation. Therefore, there is an urgent need for a cell design that allows batteries containing phosphate cathode materials to maintain a large capacity while simultaneously ensuring excellent cycle stability and long-term safety. Summary of the Invention

[0004] The purpose of this application is to provide a battery cell, a battery device, an energy storage device, an energy storage system, and a charging network, aiming to solve the problems of poor structural stability of large-size battery cells and side reactions caused by the dissolution of positive electrode metal ions in the prior art.

[0005] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows: In a first aspect, embodiments of this application provide a battery cell with a capacity ≥ 500 Ah. The battery cell includes a positive electrode, a negative electrode, and a separator located between the positive and negative electrode. The positive electrode includes a positive current collector and a positive electrode film layer stacked on at least one surface of the positive current collector. The positive electrode film layer includes a positive active material, which includes a lithium-containing transition metal phosphate doped with Ti and / or V. The separator includes a base film and a coating disposed on at least one surface of the base film. The porosity of the base film does not exceed 30%.

[0006] The battery cell provided in this application is a high-capacity cell. The positive electrode active material includes lithium transition metal phosphate doped with Ti and / or V. By introducing Ti / V doping, this material can effectively adjust the lattice strain distribution, reduce local stress concentration, and thus enhance the overall stability of the crystal structure. This characteristic helps to significantly suppress the dissolution of metal ions, reducing the number of metal ions that can migrate from the positive electrode side to the negative electrode side at the source, reducing the side reactions caused by free metal ions at the negative electrode interface, and thus improving the cycle life and long-term operational stability of the cell. At the same time, the battery cell is used with a low-porosity base film. Due to its low porosity, the internal pore structure of this base film is more tortuous and dense, which not only extends the migration path of ions but also significantly increases the resistance of metal ions during trans-electrode transport. It provides a "secondary barrier effect" for metal ions. Even if a small amount of metal ions dissolve from the positive electrode, they will be effectively blocked when passing through the base film, thereby greatly limiting the number of metal ions that finally reach the negative electrode surface, and further suppressing the occurrence of side reactions on the negative electrode side. It can be seen that the structural optimization of the cathode material is aimed at reducing the "generation" of metal ions, while the low porosity base film focuses on weakening their "migration". The two work together to reduce the side reactions caused by metal ions at the anode interface. While maintaining the high capacity of the battery cell, it significantly enhances its cycle stability and long-term safety, and achieves a simultaneous improvement in overall performance.

[0007] In some embodiments, the porosity of the base membrane is 10%-30%.

[0008] With a porosity of 10%-30%, it improves the ability to block metal ions while providing a smoother migration channel for lithium ions, which is conducive to achieving higher charge and discharge rates and improving the long-term cycle life and rate performance of the battery.

[0009] In some embodiments, the lithium-containing transition metal phosphate has components of the following general formula: Li a Fe b M c PO d Where M includes one or more of V, Ti, and Mn, 0.8≤a≤1.15, 0.9≤b<1, 0 <c≤0.1,b+c≤1,3.5≤d≤4。

[0010] Different lithium-containing transition metal phosphates are available to meet specific needs.

[0011] In some embodiments, the content of Ti and / or V elements is 0.05 wt%-0.15 wt% based on the total mass of the lithium-containing transition metal phosphate.

[0012] In some embodiments, the content of Ti and / or V elements is 0.06 wt%-0.12 wt% based on the total mass of the lithium iron phosphate. By limiting the content of titanium elements to 0.05 wt%-0.15 wt%, optionally, the content of titanium elements is limited to 0.06 wt%-0.12 wt%; within this range, titanium doping achieves an optimal balance between high capacity, excellent rate performance, and long cycle life while improving the conductivity of the material.

[0013] In some embodiments, the single-sided coating weight of the positive electrode film is 0.32 g / 1540.25 mm. 2 -0.39 g / 1540.25 mm 2 .

[0014] By increasing the single-sided coating weight of the positive electrode film, the density and mechanical strength of the electrode layer can be effectively increased, reducing the path of electrolyte directly penetrating to the surface of the positive electrode material. This reduces the probability of HF in the electrolyte contacting metal elements, inhibits the dissolution of metal elements, and improves the structural stability and safety of the battery cell during long-term cycling.

[0015] In some embodiments, the negative electrode sheet includes a negative current collector and a negative electrode film layer stacked on at least one surface of the negative current collector, wherein the single-sided coating weight of the negative electrode film layer is 0.15 g / 1540.25 mm. 2 -0.20 g / 1540.25mm 2 .

[0016] Increasing the single-sided coating weight of the negative electrode film can improve its mechanical stability and charge distribution uniformity, which helps to alleviate the volume expansion of the negative electrode material during charging and discharging, reduce microcracks and active material shedding during cycling, thereby reducing the possibility of side reactions between metal ions and the film, and significantly improving the cycle life and safety of the battery cell.

[0017] In some embodiments, the median L of the spheroidal area cumulative distribution curve of particles obtained from a cross-section of the positive electrode film along the electrode thickness direction is... A50 It is 0.70-0.85.

[0018] In some embodiments, the median L of the spheroidal area cumulative distribution curve of particles obtained from a cross-section of the positive electrode film along the electrode thickness direction is... A50 It is 0.70-0.76.

[0019] Median L of the constrained sphericity A50 Within the aforementioned range, the particles are approximately spherical, which helps them maintain excellent slidability during stacking, making it easier to fill the gaps between particles. This further improves the compaction density of the electrode and increases the energy density of the battery.

[0020] In some embodiments, the median roughness R in the cumulative roughness area distribution curve of particles obtained from a cross-section of the positive electrode film along the electrode thickness direction is... A50 It is 0.92-0.96.

[0021] Median roughness R A50 Within the aforementioned range, the particle surface is relatively smooth, and the friction between particles is relatively small. Under the action of external force, it is easy to slip, which can further improve the compaction density of the electrode and increase the energy density of the battery.

[0022] In some embodiments, the roughness concentration (R) is obtained from the cumulative roughness area distribution curve of the particles obtained by slicing the positive electrode film along the thickness direction of the electrode sheet. A90 -R A10 ) / R A50 It is 0.05-0.10.

[0023] The extremely small concentration of roughness indicates that the overall roughness of the particles is highly consistent, which is conducive to the relative sliding between particles and makes it easier to form a high-density stack during rolling, thereby increasing the compaction density of the electrode and the energy density of the battery.

[0024] In some embodiments, the tap density of the lithium transition metal phosphate powder is 1.00 g / cm³. 3 -1.70 g / cm 3 .

[0025] Lithium-containing transition metal phosphate particles not only have a wide particle size distribution, but also have a particle size within a reasonable range, forming an effective gradation. Small particles can fill the gaps between particles, thus resulting in a high tap density.

[0026] In some embodiments, the compaction density of lithium transition metal phosphate powder under 3T pressure is 2.55 g / cm³. 3 -2.70 g / cm 3 .

[0027] Lithium-containing transition metal phosphates form an effective gradation, enabling the material to construct a packing structure with extremely small interparticle gaps under external force, thus achieving higher compaction density. This provides a material basis for improving electrode compaction density and preparing high-energy-density lithium-ion secondary batteries.

[0028] In some embodiments, the positive electrode film layer satisfies one or more of the following characteristics: (1) The single-sided density of the positive electrode film is 20.77 mg / cm³. 2 -25.30 mg / cm 2 ; (2) The compaction density of the positive electrode film is 2.2 g / cm³. 3 -2.75 g / cm 3 ; (3) In the cross section along the thickness direction of the positive electrode film, the porosity of the positive electrode film is 20.4%-38.9%.

[0029] The single-sided density of this positive electrode film allows the film structure to be fully wetted by the electrolyte, providing an efficient bulk transport channel for lithium ions and ensuring the rate performance and capacity utilization of the battery.

[0030] This compaction density optimizes the contact between cathode particles, establishes a robust conductive network, and retains necessary ion transport pores, thereby synergistically improving the battery's coulombic efficiency, cycle stability, and volumetric energy density.

[0031] The porosity of this positive electrode film can increase the rate of rapid migration of lithium ions within the thick film, effectively reducing electrochemical polarization and helping to maintain the voltage stability and capacity of large-size batteries under high-rate charge and discharge.

[0032] In some embodiments, the negative electrode film layer satisfies one or more of the following characteristics: (1) The single-sided density of the negative electrode film is 9.74 mg / cm³. 2 -12.98 mg / cm 2 ; (2) The compaction density of the negative electrode film is 1.4 g / cm³. 3 -1.8 g / cm 3 ; (3) In the cross section along the thickness direction of the electrode, the porosity of the negative electrode film is 35.2%-49.6%.

[0033] Limiting the density of one side of the negative electrode film layer is beneficial to improving the overall energy density of the battery.

[0034] By limiting the compaction density of the negative electrode film, the negative electrode material can have good conductivity while reserving just the right amount of elastic space for the volume expansion of the negative electrode material during charging and discharging, thereby significantly improving the structural integrity and cycle durability of the negative electrode.

[0035] Limiting the porosity of the negative electrode film greatly promotes electrolyte penetration and rapid ion distribution inside the negative electrode, meeting the huge ion flux requirements during high-current charging and suppressing polarization. On the other hand, the abundant pores can better accommodate the continuous growth and thickening of the SEI film during cycling, thus jointly ensuring the battery's excellent fast-charging capability and long-term cycle stability.

[0036] In some embodiments, the coating includes an inorganic coating laminated on one side of the base film and an organic coating laminated on the side of the inorganic coating opposite to the base film; the material of the inorganic coating includes silane compounds and trimethylsilyl ester / alkane.

[0037] In some embodiments, the trimethylsilyl ester / alkane content is 0.03%-0.6% by mass of the total mass of the material based on the inorganic coating.

[0038] The inorganic coating material includes trimethylsilyl ester / alkane, which can effectively reduce the content of residual water and free HF in the electrolyte during cell assembly or operation by taking advantage of its excellent hydrophobicity and acid trapping ability. This inhibits the dissolution of positive electrode metal elements, reduces the side reactions they cause on the negative electrode side, and improves the cycle stability and safety of the cell.

[0039] In some embodiments, trimethylsilyl ester / alkane includes at least one of tris(trimethylsilane) phosphate, tris(trimethylsilane) borate, and trimethylfluorosilane.

[0040] In some embodiments, based on the total mass of the inorganic coating material being 100%, it further includes: Ceramic matrix 60%-90%; Adhesive content: 9.97%-30%; Additives: 0%-9.4%.

[0041] By adding trimethylsilyl ester to the inorganic coating material, the HF content in the electrolyte can be effectively reduced, while improving the thermal stability and interface protection of the separator, thereby enhancing the cycle life and safety of the battery cell.

[0042] In some embodiments, the ceramic matrix includes at least one of alumina, boehmite, silicon oxide, magnesium oxide, titanium oxide, tin oxide, calcium oxide, zirconium oxide, barium sulfate, yttrium oxide, zinc oxide, silicon carbide, magnesium fluoride, barium titanate, aluminum hydroxide, magnesium hydroxide, or calcium hydroxide.

[0043] In some embodiments, the adhesive includes at least one of polyvinylidene fluoride and its copolymers, polyacrylates, cellulose, and polyurethanes.

[0044] In some embodiments, the additives include at least one of conductive agents, lubricants, and anti-aging agents.

[0045] The ceramic matrix, binder and additives provided include a variety of different types, and the specific type can be selected according to specific needs.

[0046] In some embodiments, the organic coating material includes polymers or copolymers prepared from one or more of the following components: (meth)acrylic acid and its ester monomers, styrene monomers, fluoroolefin monomers, olefin monomers, unsaturated nitrile monomers, epoxy alkane monomers, and polyurethane.

[0047] In some embodiments, (meth)acrylic acid and its ester monomers include at least one of acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, butyl methacrylate, and isooctyl methacrylate; Styrene monomers include at least one of styrene and methylstyrene; Fluoroolefin monomers include at least one of vinylidene fluoride, vinyl fluoride, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, and hexafluoropropylene; Olefin monomers include at least one of ethylene, propylene, butadiene, and isoprene; Unsaturated nitrile monomers include at least one of acrylonitrile and methacrylonitrile; Epoxy alkane monomers include at least one of ethylene oxide and propylene oxide.

[0048] The organic coating materials available include a variety of different types, and the specific type can be selected according to specific needs.

[0049] In some embodiments, the base film material includes at least one of polypropylene and polyethylene.

[0050] In some embodiments, the thickness of the inorganic coating is 1 μm-3 μm.

[0051] In some embodiments, the thickness of the organic coating is 0.5 μm-1 μm.

[0052] In some embodiments, the total thickness of the diaphragm is 7 μm-15 μm.

[0053] In some embodiments, the thickness of the base film is 4 μm-6 μm.

[0054] By controlling the thickness of the inorganic coating to 1 μm-3 μm, the organic coating to 0.5 μm-1 μm, and the base film to 4 μm-6 μm, with a total separator thickness ranging from 7 μm-10 μm, the absorption of free electrolyte by the separator can be effectively reduced, improving the effective utilization rate of the electrolyte, reducing the amount of electrolyte injected, and thus increasing the mass energy density of the battery cell. Simultaneously, this design, while ensuring excellent mechanical strength and thermal safety of the separator, contributes to achieving lightweight and high-performance large-size battery cells.

[0055] In some embodiments, the battery cell further includes an electrolyte, comprising 0.5%-7% by mass of vinylene carbonate, based on 100% of the total mass of the electrolyte.

[0056] Adding an appropriate amount of vinylene carbonate to the electrolyte can optimize the formation and stability of the SEI film on the negative electrode surface, effectively inhibit the decomposition of the electrolyte on the negative electrode side, reduce the side reactions and gas production caused by metal ions, and thus significantly improve the cycle stability, structural integrity and long-term operational safety of the battery cell.

[0057] In some embodiments, the battery cell has a square structure with a height of 210-220 mm and a width of 270-600 mm. In some embodiments, the width is 270-280 mm.

[0058] The battery cells are large-size cells, enabling ultra-large capacity designs of over 500 Ah, laying the physical foundation for high energy density in individual battery cells. Combined with the specific selection of the above-mentioned positive electrode, negative electrode, separator, and electrolyte, the energy density, integration efficiency, and thermal safety performance of the battery system are comprehensively improved.

[0059] Secondly, this application provides a battery device comprising a plurality of the aforementioned battery cells.

[0060] The battery device consists of multiple battery cells as described above. By combining these cells, the voltage and capacity of the battery device can be flexibly adjusted according to actual application needs, meeting the requirements of different equipment. Simultaneously, the coordinated operation of multiple cells improves the overall stability and reliability of the battery device, mitigates the performance fluctuations that may occur in individual battery cells, and enhances the overall performance and lifespan of the battery device.

[0061] Thirdly, this application provides an energy storage device, including a plurality of the above-described battery cells or the above-described battery device.

[0062] The provided energy storage devices include the aforementioned battery cells or battery devices. Energy storage devices using these battery-related components have longer cycle life, more stable operation, and lower safety risks; they are particularly suitable for large-scale energy storage scenarios with stringent requirements for reliability and safety.

[0063] Fourthly, this application provides an energy storage system, including an energy conversion system and the aforementioned energy storage device, wherein the energy conversion system is connected to the energy storage device to convert the current input to the energy storage device or output from the energy storage device into energy.

[0064] The provided energy storage system not only possesses the advantages of large capacity and long lifespan of the energy storage device itself, but also precisely transforms and regulates the charging and discharging current through the energy conversion system, enabling it to efficiently and stably adapt to electrical equipment with different voltage levels or frequency requirements, greatly expanding the application scenarios of the energy storage device.

[0065] Fifthly, this application provides a charging network, including a charging pile and an energy storage device or energy storage system as described above, wherein the energy storage device is used to provide electrical energy to the charging pile.

[0066] The provided charging network utilizes energy storage units to store electrical energy during off-peak hours and provides power to charging piles during peak hours or when charging demand surges, effectively mitigating the instantaneous impact of large-scale charging facilities on the regional power grid. Attached Figure Description

[0067] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0068] Figure 1 This is a schematic diagram of the battery cell structure of one embodiment of the secondary battery cell of this application; Figure 2 for Figure 1 The diagram shows an exploded view of a secondary battery cell. Figure 3 This is a schematic diagram of one embodiment of the battery module of this application; Figure 4 This is a schematic diagram of one embodiment of the energy storage system according to this application. Figure 5 This is a schematic diagram of one embodiment of the charging network of this application. Explanation of reference numerals in the attached figures: 1-Energy storage device; 20-Battery cell; 21-Casing; 22-Top cover assembly; 23-Electrode assembly; 30-Battery Module; 4-Energy conversion system; 5-Power generation equipment; 6-Charging piles; 7-Connector. Detailed Implementation

[0069] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0070] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0071] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means 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.

[0072] To meet the growing demands of large-scale energy storage systems, battery cells containing phosphate-based cathode materials are increasingly being developed towards larger sizes and capacities. Larger cells exhibit significantly increased thickness of the active material coatings on both the positive and negative electrodes, leading to an overall increase in cell size. Because phosphate-based cathode materials are highly hygroscopic, the heat transfer path between the large cells and internal moisture during the baking and dehumidification process is greatly prolonged. This results in the difficulty of evenly and thoroughly removing moisture from deep within the cell, ultimately leaving the finished cell with moisture levels far exceeding safety thresholds.

[0073] These residual moisture particles will undergo a hydrolysis reaction with lithium hexafluorophosphate in the electrolyte after injection, continuously generating highly corrosive hydrofluoric acid (HF). HF attacks the cathode material, specifically through the H+ in HF... + and F - Ions can embed and disrupt the stable olivine crystal structure of LFP; due to the disruption of the crystal lattice, the bonded iron ions are etched out, as Fe²⁺. + In the form of iron ions, these ions dissolve into the electrolyte, leading to irreversible capacity decay and increased internal resistance, thus affecting the cell's capacity. Furthermore, the iron ions dissolved from the positive electrode migrate through the traditional separator to the negative electrode, preferentially undergoing reduction on the negative electrode surface to form elemental iron deposits. These deposits damage the protective solid electrolyte interphase (SEI) film and continuously catalyze the reduction and decomposition of the electrolyte on the negative electrode surface, consuming active lithium and electrolyte. This results in a continuous thickening of the SEI film, a sharp increase in internal resistance, and further accelerated capacity decay. Consequently, the battery's cycle life and capacity retention are severely degraded, posing potential safety risks.

[0074] Based on the above considerations, this application adopts a method of synergistic adjustment of the membrane pore structure by doping the positive electrode active material, aiming to control the dissolution of metal ions from the source and reduce the migration of metal ions from the transport path, so that the battery containing lithium iron phosphate positive electrode material can maintain a large capacity while taking into account excellent cycle stability and long-term safety.

[0075] The specific plan is as follows.

[0076] battery cell In a first aspect, embodiments of this application provide a battery cell with a capacity ≥ 500 Ah. The battery cell includes a positive electrode, a negative electrode, and a separator located between the positive and negative electrode. The positive electrode includes a positive current collector and a positive electrode film layer stacked on at least one surface of the positive current collector. The positive electrode film layer includes a positive active material, which includes a lithium-containing transition metal phosphate doped with Ti and / or V. The separator includes a base film and a coating disposed on at least one surface of the base film. The porosity of the base film does not exceed 30%.

[0077] In some embodiments, lithium-containing transition metal phosphates refer to phosphate materials containing lithium and transition metal elements, which can be detected by any method known in the art. For example, they can be detected by combining X-ray diffraction (XRD) with energy dispersive spectroscopy (EDS).

[0078] Because phosphate-based cathode materials have strong water absorption, they significantly prolong the heat and internal moisture transfer path during the baking and dehydration process of large-sized cells. This makes it difficult for deep-seated moisture in the cell to be uniformly and thoroughly removed, ultimately resulting in residual moisture levels in the finished cell far exceeding safety thresholds. Doping lithium-containing transition metal phosphates with transition metal elements can improve the lattice change rate of the cathode active material during lithium insertion / extraction, reduce oxygen activity on the particle surface, and enhance the structural stability of the material. This, in turn, improves the specific capacity utilization during cycling, further enhancing the cycle stability of the battery cell.

[0079] In this embodiment, the types and contents of elements in the positive electrode active material can be tested using any method known in the art. As an example, inductively coupled plasma atomic emission spectrometry (ICP-AES) is used to test the doping elements and their contents, referring to Appendix C of GB / T 33822-2017.

[0080] In some embodiments, the lithium-containing transition metal phosphate has components of the following general formula: Li a Fe b M c PO dWhere M includes one or more of V, Ti, and Mn, 0.8≤a≤1.15, 0.9≤b<1, 0 <c≤0.1,b+c≤1,3.5≤d≤4。

[0081] Lithium-containing transition metal phosphates can be selected according to specific needs. In some specific embodiments, lithium-containing transition metal phosphates include, but are not limited to, lithium iron aluminum phosphate, lithium iron vanadium phosphate, lithium iron aluminum vanadium phosphate, lithium manganese iron aluminum phosphate, lithium manganese iron vanadium phosphate, and lithium manganese iron aluminum vanadium phosphate.

[0082] In some embodiments, the content of Ti and / or V elements is 0.05 wt%-0.15 wt% based on the total mass of the lithium-containing transition metal phosphate.

[0083] During the charging and discharging process, lithium-containing transition metal phosphates, Li + The insertion / extraction of elements can lead to changes in lattice volume, thereby inducing microcracks and structural pulverization. Doping with titanium is beneficial for Ti... 4+ (Ionic radius approximately 0.60 Å) and Fe 2+ Differences exist in the ionic radius (approximately 0.78 Å). Doping can adjust the lattice strain distribution of lithium phosphate, reducing local stress concentration. Lithium phosphate may undergo a monoclinic to trigonal phase transition during lithium-ion extraction, but titanium-doped lithium phosphate can stabilize the monoclinic phase, lower the phase transition energy barrier, and suppress irreversible phase transitions. Enhanced lattice stability helps reduce the dissolution rate of metals such as Fe and Ti in the HF environment, thereby reducing their migration and side reactions on the negative electrode side. Simultaneously, high amounts of titanium can form fast ions with phosphate and other elements, significantly improving the cycle life and long-term stability of the cell while enhancing the battery's kinetic performance.

[0084] In some embodiments, the content of Ti and / or V elements is 0.06 wt%-0.12 wt% based on the total mass of the lithium iron phosphate.

[0085] In some specific embodiments, based on the total mass of the lithium iron phosphate, the content of titanium element includes, but is not limited to, typical but non-limiting values ​​such as 0.05 wt%, 0.06 wt%, 0.07 wt%, 0.08 wt%, 0.09 wt%, 0.1 wt%, 0.11 wt%, 0.12 wt%, 0.13 wt%, 0.14 wt%, and 0.15 wt%.

[0086] In some embodiments, the tap density of the lithium transition metal phosphate powder is 1.00 g / cm³. 3 -1.70 g / cm 3 .

[0087] In some specific embodiments, the tap density of the lithium transition metal phosphate powder includes, but is not limited to, 1.00 g / cm³. 3 1.10 g / cm 3 1.20 g / cm 3 1.30 g / cm 3 1.40 g / cm 3 1.50 g / cm 3 1.60 g / cm 3 1.70 g / cm 3 Typical but not restrictive values.

[0088] Lithium-containing transition metal phosphate particles not only have a wide particle size distribution, but also have a particle size within a reasonable range, forming an effective gradation. Small particles can fill the gaps between particles, thus resulting in a high tap density.

[0089] The tap density of powder can be tested using any method known in the art. As an example, turn on the electronic balance, place a conical flask as a base on the balance, and zero the balance. Place the tapped graduated cylinder on the conical flask, weigh it, and record the weight. Open the sample bag, use a clean sample spoon to stir the sample in the bag 3-5 times to mix it thoroughly, and then smoothly transfer the sample into the graduated cylinder. Wipe the powder adhering to the surface of the graduated cylinder with lint-free paper, and then place it into the zeroed conical flask and weigh it. Seal the mouth of the graduated cylinder with sealing film, place the tapped graduated cylinder into the matching instrument rubber ring, ensuring the tapped density graduated cylinder fits tightly against the rubber ring and remains perpendicular to the instrument surface. Set the vibration frequency to 250 times / min and the vibration count to 5000 times on the instrument, press the button, and vibrate for 20 seconds. min; then remove the tapped density measuring cylinder, illuminate the surface of the measuring cylinder with a flashlight, and visually read the highest scale V1 and the lowest scale V2, and take the average value V; subtract the mass of the measuring cylinder m0 from the mass of the measuring cylinder and the sample m1 to obtain the mass of the powder m, and obtain the tapped density of the sample by the density formula ρ=m / v.

[0090] In some embodiments, the compaction density of lithium transition metal phosphate powder under 3T pressure is 2.55 g / cm³. 3 -2.70 g / cm 3 .

[0091] In some embodiments, the compaction density of lithium transition metal phosphate powder under 3T pressure includes, but is not limited to, 2.55 g / cm³. 3 2.57 g / cm 3 2.59 g / cm 3 2.60 g / cm 3 2.62 g / cm 3 2.65 g / cm 32.67 g / cm 3 2.69 g / cm 3 2.70 g / cm 3 Typical but not restrictive values.

[0092] This lithium-containing transition metal phosphate forms an effective gradation, which allows it to construct a packing structure with extremely small interparticle gaps under external force, enabling higher compaction density. This provides a material basis for improving electrode compaction density and preparing high-energy-density lithium-ion secondary batteries.

[0093] In this application, the term "powder compaction density" refers to the density of a compacted compact with a certain density and strength, formed during the external force compression process. This density is measured in g / cm³, as the powder moves and deforms, larger voids are filled, the contact area between particles increases, resulting in attractive forces between atoms and enhanced mechanical cohesion between particles. 3 .

[0094] The compaction density of lithium transition metal phosphate powder can be measured using methods and equipment known in the art. For example, it can be measured using a compaction density instrument, referring to GB / T 24533-2009. Specifically, a certain amount of lithium transition metal phosphate is placed on a compaction mold (the mold diameter is known). The mold is hollow in the middle and has a metal disc at the top and bottom. The lithium transition metal phosphate is placed between the metal discs, and a metal cylinder is placed on top. The mold is placed on a compaction density instrument, and the pressure is set to 3T. The thickness of the positive electrode active material under 3T pressure can be read on the instrument. The compaction density of the positive electrode active material powder is ρ=m / v, where v=(S×H), m is the mass of the positive electrode active material, and S is the bottom area of ​​the mold (1.327 cm²). 2 H represents the thickness of the lithium transition metal phosphate after compaction.

[0095] In some embodiments, the single-sided coating weight of the positive electrode film is 0.32 g / 1540.25 mm. 2 -0.39 g / 1540.25 mm 2 .

[0096] For the same capacity, thick coating reduces the number of electrode layers and the contact area between the electrolyte and the positive electrode material. This reduces the path for the electrolyte to directly penetrate to the surface of the positive electrode material, indirectly reducing the probability of HF reacting with metal elements. This is beneficial for improving the structural stability and safety of the cell during long-term cycling.

[0097] In some specific implementations, the single-sided coating weight of the positive electrode film includes, but is not limited to, 0.32 g / 1540.25 mm. 2 0.322 g / 1540.25 mm2 0.325 g / 1540.25 mm 2 0.329 g / 1540.25 mm 2 0.330 g / 1540.25 mm 2 0.332 g / 1540.25 mm 2 0.335 g / 1540.25 mm 2 0.339 g / 1540.25 mm 2 0.340g / 1540.25 mm 2 0.342 g / 1540.25 mm 2 0.345 g / 1540.25 mm 2 0.349 g / 1540.25 mm 2 0.350 g / 1540.25 mm 2 0.352 g / 1540.25 mm 2 0.355 g / 1540.25 mm 2 0.359 g / 1540.25mm 2 0.36 g / 1540.25 mm 2 0.362 g / 1540.25 mm 2 0.365 g / 1540.25 mm 2 0.369 g / 1540.25mm 2 0.370 g / 1540.25 mm 2 0.372 g / 1540.25 mm 2 0.375 g / 1540.25 mm 2 0.379 g / 1540.25 mm 2 0.380 g / 1540.25 mm 2 0.382 g / 1540.25 mm 2 0.385 g / 1540.25 mm 2 0.389g / 1540.25 mm 2 0.39 g / 1540.25 mm 2 Typical but not restrictive values.

[0098] In the embodiments of this application, the term "particle" refers to a particle in the positive electrode film layer that has a recognizable complete boundary in the field of view at a certain magnification, such as 10,000 times. The particle may have defects or scratches inside, but the complete boundary that is sufficient to divide the particle cannot be identified inside the particle.

[0099] The particle identification method is as follows: The positive electrode film layer is cut along the thickness direction of the electrode sheet using an argon ion beam (for example, a Leica EM TIC 3X CP device can be used, operating voltage: 6 kV, operating time: 6 h). After exposing the cut surface, a scanning electron microscope (for example, a Hitachi SU8230 device can be used, operating voltage: 3 kV, beam current: high, probe model: U (LA100), working distance <5 mm) is used to observe the cut surface of the positive electrode film layer along the thickness direction of the electrode sheet. Images are acquired using a field emission scanning electron microscope at a non-edge location in the cut surface of the positive electrode film layer (after observing the electrode edge under the scanning electron microscope, the field of view is adjusted to the center of the sample) in secondary electron mode. Electron micrographs are taken at 10kx magnification, and the particles in the electron micrographs are analyzed using ImageJ software (1.46r, win64 version). The specific usage of ImageJ software is as follows: Load the scanning electron microscope image to be analyzed, use the Cellpose plugin to identify particles, and then perform manual correction; use ImageJ to read and analyze data. The specific method for identifying particles using the Cellpose plugin is as follows: Set the segmentation diameter parameter (diameter in the Segmentation module) to 15 pixels, click "runcyto3" to identify particles; manually mark particles in the image that were not identified by the software, were not fully identified by the software, or had identification errors. Particles that were not identified by the software, were not fully identified by the software, or had identification errors mainly include the following: 1. Particles that are too large or have scratches on their surface, making them unidentifiable or incompletely identifiable; 2. During argon ion beam cutting, scratches may be generated on the particle surface, and the software may misjudge these scratches as particle boundaries, leading to identification errors; 3. Particles that are too small and were not successfully identified; 4. Particles located at the edge of the electron microscope field of view, with the interior of the particle penetrated by the edge, preventing a complete display of the morphology, and resulting in identification errors due to partial identification replacing the whole.For the unidentified or misidentified particles mentioned above, manual calibration is performed as follows: Particles located at the edges of the scanning electron microscope that are not fully displayed are deleted; It is determined whether other unidentified or misidentified particles have internal cracks or scratches. If no cracks or scratches are found, the particle is considered a single particle, and its boundary is manually marked based on observation; If cracks or scratches are found within the particle, it is determined whether the cracks or scratches penetrate the particle. If not, it is considered a single particle and manually marked; If the cracks or scratches penetrate the particle, it is determined whether the cracks or scratches are linear or irregular; If the cracks or scratches are irregular, they are considered the boundary between particles, and particles are divided along this boundary; If the cracks or scratches are linear, contrast is compared; If the contrast is not obvious and there is no crack-like appearance, it is considered a scratch and marked as a single particle; If the contrast is strong and there is a crack-like appearance, it is considered the boundary between particles and marked as two particles. After manual marking, irrelevant information from the automatic image processing is deleted, thus completing the particle identification and marking in the image.

[0100] In some embodiments, the median L of the spheroidal area cumulative distribution curve of particles obtained from a cross-section of the positive electrode film along the electrode thickness direction is... A50 It is 0.70-0.85.

[0101] In some embodiments, the median L of the spheroidal area cumulative distribution curve of particles obtained from a cross-section of the positive electrode film along the electrode thickness direction is... A50 It is 0.70-0.76.

[0102] In some specific embodiments, the median L of the spheroidal area cumulative distribution curve of particles obtained from a cross-section of the positive electrode film along the electrode thickness direction is... A50 Typical but not limited values ​​include, but are not limited to, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, and 0.85.

[0103] Median L of sphericity A50 Within the aforementioned range, the particles are approximately spherical, which helps them maintain good slidability during stacking, making it easier to fill the gaps between particles. This further improves the compaction density of the electrode and increases the energy density of the battery.

[0104] The median sphericity L in a cross-section of the positive electrode film along the electrode thickness direction. A50The specific testing method is as follows: Following the method described above in this application, particles in the cross-section of the positive electrode film were identified. The "Shape Description" and "Area" analysis functions in ImageJ were used to analyze the morphology and area of ​​the particles in the cross-section along the electrode thickness direction. According to the software manual (ImageJ User Guide IJ 1.46r), the "Area" parameter obtained from the analysis represents the pixel area of ​​the particle, and the "Round" parameter represents the ratio of the pixel area of ​​the particle to the area of ​​a circle with the fitted major axis as its diameter. The closer the particle is to a sphere, the closer the ratio of the pixel area to the area of ​​the circle with the fitted major axis as its diameter is to 1. Therefore, the "Round" parameter of the analyzed particles is used to characterize the sphericity of the particles. The sphericity of at least 5000 particles was arranged in ascending order, and the cumulative distribution curve of the sphericity area of ​​the particles in the positive electrode film was obtained with sphericity as the horizontal axis and the cumulative area ratio as the vertical axis. L A50 This is the L-value of sphericity when the cumulative area under the vertical axis of the cumulative distribution curve of L-values ​​accounts for 50%.

[0105] In some embodiments, the median roughness R in the cumulative roughness area distribution curve of particles obtained from a cross-section of the positive electrode film along the electrode thickness direction is... A50 It is 0.92-0.96.

[0106] In some specific embodiments, the median roughness R in the cumulative roughness area distribution curve of the particles obtained from the cross-section of the positive electrode film along the electrode thickness direction is... A50 Typical but not limiting values ​​include, but are not limited to, 0.92, 0.93, 0.94, 0.95, and 0.96.

[0107] Median roughness R A50 Within the aforementioned range, the particle surface is relatively smooth, and the friction between particles is relatively small. Under the action of external force, it is easy to slip, which can further improve the compaction density of the electrode and increase the energy density of the battery.

[0108] In the cumulative roughness area distribution curve of particles obtained from a cross-section of the positive electrode film along the electrode thickness direction, the median roughness R is... A50The specific testing method is as follows: Following the method described above in this application, particles in the cross-section of the positive electrode film were identified. The morphology of the particles in the cross-section along the thickness direction of the positive electrode film was analyzed using the "Shape Description" analysis function in ImageJ. According to the software manual (ImageJ User Guide IJ 1.46r), the "Solidity" parameter obtained from the analysis represents the ratio of the pixel area to the convex area of ​​the particle. Therefore, the "Solidity" parameter of the analyzed particles is used to characterize the roughness of the particles. By definition, the closer the roughness is to 1, the smoother the particle. The roughness of at least 5000 particles was arranged in ascending order, and the cumulative area distribution curve of the particles in the positive electrode film was obtained with roughness as the horizontal axis and cumulative area percentage as the vertical axis. A50 This represents the roughness R value when the cumulative area ratio of the vertical axis in the cumulative distribution curve of the roughness R value is 50%.

[0109] In some embodiments, the roughness concentration (R) is obtained from the cumulative roughness area distribution curve of the particles obtained by slicing the positive electrode film along the thickness direction of the electrode sheet. A90 -R A10 ) / R A50 It is 0.05-0.10.

[0110] In some specific implementations, the roughness concentration (R) is shown in the cumulative roughness area distribution curve of the particles obtained from the cross-section of the positive electrode film along the electrode thickness direction. A90 -R A10 ) / R A50 Typical but not limited values ​​include, but are not limited to, 0.05, 0.06, 0.07, 0.08, 0.09, and 0.10.

[0111] The extremely small concentration of roughness indicates that the overall roughness of the particles is highly consistent, which is conducive to the relative sliding between particles and makes it easier to form a high-density stack during rolling, thereby increasing the compaction density of the electrode and the energy density of the battery.

[0112] The roughness concentration test method for the cumulative distribution curve of particles obtained from the cross-section of the positive electrode film along the electrode thickness direction is as follows: Referring to the roughness test method above in this application, and by analogy, R A90 R is the R-value corresponding to the cumulative area ratio on the vertical axis of the cumulative distribution curve of sphericity R-value when it accounts for 90%. A10 This is the R-value corresponding to a cumulative area ratio of 10% on the vertical axis of the roughness R-value area cumulative distribution curve. The roughness concentration is represented by (R... A90 -R A10 ) / R A50 express.

[0113] In some embodiments, the one-sided density of the positive electrode film is 20.77 mg / cm³. 2 -25.30 mg / cm 2 In some specific implementations, the unilateral density of the positive electrode film includes, but is not limited to, 20.77 mg / cm³. 2 21.00 mg / cm 2 21.20 mg / cm 2 21.50 mg / cm 2 21.70 mg / cm 2 21.79 mg / cm 2 22.00 mg / cm 2 22.30 mg / cm 2 22.50 mg / cm 2 22.77 mg / cm 2 22.90 mg / cm 2 23.00 mg / cm 2 23.20 mg / cm 2 23.50 mg / cm 2 23.70 mg / cm 2 23.77 mg / cm 2 23.90 mg / cm 2 24.00 mg / cm 2 24.20 mg / cm 2 24.30 mg / cm 2 24.50 mg / cm 2 24.70 mg / cm 2 24.77 mg / cm 2 25.00 mg / cm 2 25.30 mg / cm 2 Typical but not limiting values.

[0114] The one-sided density of the positive electrode film is 20.77 mg / cm³. 2 -25.30 mg / cm 2 This allows the film structure to be fully wetted by the electrolyte, providing an efficient bulk transport channel for lithium ions and ensuring the rate performance and capacity utilization of the battery.

[0115] In this embodiment, the unilateral density of the positive electrode film layer has a meaning known in the art and can be tested using methods known in the art. For example, take a positive electrode sheet that has been coated on one side and compacted (if it is a double-sided coated positive electrode sheet, the positive electrode film layer on one side can be wiped off first), cut it into a small circular piece with an area of ​​S1, weigh it, and record its weight as M1. Then wipe off the positive electrode film layer of the above-weighed positive electrode sheet, weigh the current collector, and record it as M0. The unilateral density of the positive electrode film layer = (M1-M0) / S1. To make the test results accurate, multiple groups (e.g., 10 groups) of samples can be tested, and the average value can be calculated as the test result.

[0116] In some embodiments, the compaction density of the positive electrode film is 2.2 g / cm³. 3 -2.75 g / cm 3 In some specific embodiments, the compaction density of the positive electrode film is 2.2 g / cm³. 3 2.25 g / cm 3 2.3 g / cm 3 2.35 g / cm 3 2.4 g / cm 3 2.45 g / cm 3 2.5 g / cm 3 2.55 g / cm 3 2.6 g / cm 3 2.65 g / cm 3 2.7 g / cm 3 2.75 g / cm 3 Typical but not restrictive values.

[0117] The compacted density is 2.2 g / cm³. 3 -2.75 g / cm 3 This optimizes the contact between positive electrode particles, establishes a robust conductive network, and retains necessary ion transport pores, thereby synergistically improving the battery's coulombic efficiency, cycle stability, and volumetric energy density.

[0118] The compaction density of the positive electrode film can be tested using methods known in the art. As an example, the battery is placed in a 25°C oven environment and left to stand for 2 hours. After the battery temperature is maintained at 25°C, the battery is discharged at a constant current of 1 / 3C to 2.5V and then discharged at a constant current of 0.1C to 2.0V. The battery is then disassembled to obtain the positive electrode sheet. The residual electrolyte is treated with dimethyl carbonate solvent, the electrode sheet is dried, and it is cut into small circular pieces with an area of ​​S. The mass of the circular pieces is obtained as W1, and the thickness of the positive electrode sheet is measured using a micrometer. Then, the positive electrode film layer of the weighed electrode sheet is wiped off, the mass of the current collector is weighed and recorded as W2, and the thickness of the current collector is measured using a micrometer. Then, the compaction density of the positive electrode film layer PD = (W1-W2) / [(T1-T2)×S].

[0119] In some embodiments, the porosity of the positive electrode film layer in a cross-section along the thickness direction of the electrode sheet is 20.4%-38.9%.

[0120] The porosity of this positive electrode film is 20.4%-38.9%, which can improve the rate of rapid migration of lithium ions in the thick film layer, effectively reduce electrochemical polarization, and help maintain the voltage stability and capacity of large-size batteries under high-rate charge and discharge.

[0121] The porosity of the positive electrode film in a cross-section along the electrode thickness direction can be tested as follows: Import the scanning electron microscope (SEM) image of the positive electrode film obtained as described above into ImageJ software. Select the line tool and use a line to mark the length of the scale bar in the image. Click "Analyze Set Scale" and set the scale parameters in the software according to the scale bar length in the image. Select the rectangle tool and select the part of the image outside the scale bar area. Use "Image Duplicate" to copy the selected area and use "Image Type 8 bit" to adjust the image format. Select "Analyze Set Measurements" and choose the following five options: "Area", "Mean gray value", "Area Fraction", "Limit to threshold", and "Feret's diameter". Select 3 for "Decimal places". Then select "Image" - "Adjust" - "Threshold" and set 0 and 100 respectively in the "Threshold" box. You can then use the Analyze-Measure function to export the porosity data from the SEM image of this cross-section. Export using "Image" - "Overlay" - "Flatten" to obtain a pore image; click "Apply" in "Threshold", then click "Analyze" - "Analyze Particles", check the four columns on the left to obtain pore statistics. It is understood that the "pores" in the cross-section of the positive electrode film layer are identified by image color difference and threshold in the embodiments of this application. These "pores" are not the pore data obtained from the venting test, but are mainly used to characterize the cross-sectional area between particles in the cross-section of the positive electrode film layer. This method is superior to the venting method. The lower the porosity in the cross-section of the positive electrode film layer tested by this method, on the one hand, it means that the gradation of large, medium and small particles in the positive electrode film layer is better and the compaction density is higher. On the other hand, under the same gradation and roller pressure, if the porosity is low, it means that the particles are more likely to slide against each other, thereby reducing the risk of film overpressure and stress concentration, and further reducing the probability of the positive electrode film demolding during long cycle, which is beneficial to improving the long cycle performance of the battery.

[0122] In some embodiments, the positive electrode active layer of the positive electrode sheet may further include a conductive agent and a binder. For example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin. For example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0123] In some embodiments, the positive current collector may be a metal foil, a foamed metal, or a composite current collector. For example, as a metal foil, silver-treated aluminum or stainless steel, stainless steel, copper, aluminum, nickel, carbon electrodes, carbon, nickel, or titanium, etc., may be used. The foamed metal may be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. The composite current collector may include a polymeric material base layer and a metal layer. 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 polymeric material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0124] In some embodiments, the negative electrode sheet includes a negative current collector and a negative electrode film layer stacked on at least one surface of the negative current collector, wherein the single-sided coating weight of the negative electrode film layer is 0.15 g / 1540.25 mm. 2 -0.20 g / 1540.25mm 2 .

[0125] Increase the single-sided coating weight of the negative electrode film to 0.15 g / 1540.25 mm. 2 -0.20 g / 1540.25 mm 2 On the one hand, during high-current charging and discharging, increasing the amount of negative electrode coating can reduce local current density and reduce the risk of lithium dendrite formation, thereby improving safety. On the other hand, it can alleviate volume expansion: the thicker coating layer has higher mechanical strength, which can effectively suppress the volume change of the negative electrode during charging and discharging and extend cycle life.

[0126] In some embodiments, the single-sided coating weight of the negative electrode film includes, but is not limited to, 0.15 g / 1540.25 mm. 2 0.152 g / 1540.25 mm 2 0.153 g / 1540.25 mm 2 0.155 g / 1540.25 mm 2 0.158 g / 1540.25mm 20.160 g / 1540.25 mm 2 0.162 g / 1540.25 mm 2 0.163 g / 1540.25 mm 2 0.165 g / 1540.25 mm 2 0.168 g / 1540.25 mm 2 0.17 g / 1540.25 mm 2 0.172 g / 1540.25 mm 2 0.173g / 1540.25mm 2 0.175 g / 1540.25mm 2 0.178 g / 1540.25mm 2 0.18 g / 1540.25mm 2 0.182 g / 1540.25 mm 2 0.183 g / 1540.25 mm 2 0.185 g / 1540.25 mm 2 0.188 g / 1540.25 mm 2 0.19g / 1540.25 mm 2 Typical but not restrictive values.

[0127] The single-sided coating weight of the negative electrode film can be tested using a method similar to that used for the positive electrode film.

[0128] In some embodiments, the one-sided density of the negative electrode film is 9.74 mg / cm³. 2 -12.98 mg / cm 2 .

[0129] In some specific embodiments, the unilateral density of the negative electrode film includes, but is not limited to, 9.74 mg / cm³. 2 9.80 mg / cm 2 9.85 mg / cm 2 9.90 mg / cm 2 9.95 mg / cm 2 10.00 mg / cm 2 10.05 mg / cm 2 10.10 mg / cm 2 10.50 mg / cm 2 10.80 mg / cm 2 10.90 mg / cm 2 11.00 mg / cm2 11.20 mg / cm 2 11.50 mg / cm 2 11.70 mg / cm 2 11.90 mg / cm 2 12.00 mg / cm 2 12.10 mg / cm 2 12.30 mg / cm 2 12.50 mg / cm 2 12.70 mg / cm 2 12.80 mg / cm 2 12.90 mg / cm 2 12.98 mg / cm 2 Typical but not restrictive values.

[0130] The single-sided density of the negative electrode film is 9.74 mg / cm³. 2 -12.98 mg / cm 2 It helps to improve the overall energy density of the battery.

[0131] The one-sided density of the negative electrode film can be tested using a method similar to that used for the positive electrode film.

[0132] In some embodiments, the compaction density of the negative electrode film is 1.4 g / cm³. 3 -1.8 g / cm 3 In some specific embodiments, the compaction density of the negative electrode film includes, but is not limited to, 1.4 g / cm³. 3 1.45 g / cm 3 1.5 g / cm 3 1.55 g / cm 3 1.6 g / cm 3 1.65 g / cm 3 1.7 g / cm 3 1.75 g / cm 3 1.8 g / cm 3 Typical but not restrictive values.

[0133] The compaction density of the negative electrode film is 1.4 g / cm³. 3 -1.8 g / cm 3 Within a certain range, the negative electrode material has good conductivity, while reserving just the right amount of elastic space for the volume expansion of the negative electrode material during charging and discharging, thereby significantly improving the structural integrity and cycle durability of the negative electrode.

[0134] The compaction density of the negative electrode film can be tested using a method similar to that used for the positive electrode film.

[0135] In some embodiments, the porosity of the negative electrode film layer in a cross-section along the electrode thickness direction is 35.2%-49.6%. In some specific embodiments, the porosity of the negative electrode film layer in a cross-section along the electrode thickness direction includes, but is not limited to, typical but non-limiting values ​​such as 35.2%, 35.5%, 36%, 36.2%, 36.5%, 36.8%, 37%, 37.2%, 37.5%, 38%, 38.2%, 38.5%, 39%, 39.2%, 39.5%, 40%, 40.5%, 41%, 41.5%, 42%, 42.5%, 43%, 43.5%, 44%, 44.5%, 45%, 45.5%, 46%, 46.5%, 47%, 47.5%, 48%, 48.5%, 49%, and 49.6%.

[0136] The porosity of the negative electrode film is in the range of 35.2%-49.6%. On the one hand, it greatly promotes the penetration of electrolyte and the rapid distribution of ions inside the negative electrode, meeting the huge ion flux requirements during high-current charging and suppressing polarization. On the other hand, the abundant pores can better accommodate the continuous growth and thickening of the SEI film during cycling, thus jointly ensuring the battery's excellent fast charging capability and long-term cycle stability.

[0137] The porosity of the negative electrode film can be tested using a method similar to that used for the positive electrode film.

[0138] The negative electrode current collector can be a metal foil, a foamed metal, or a composite current collector. For example, the metal foil can be silver-treated aluminum or stainless steel, stainless steel, copper, aluminum, nickel, carbon electrodes, carbon, nickel, or titanium, etc. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloys, or foamed carbon, etc. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.). In some embodiments, the positive electrode current collector material can be aluminum foil, and the negative electrode current collector material can be copper foil.

[0139] The negative electrode film contains a negative electrode active material. As an example, the negative electrode active material can be a negative electrode active material known in the art for use in battery cells. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as battery negative electrode active materials may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0140] The negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethyl methacrylate (PMAA), and carboxymethyl chitosan (CMCS). The negative electrode active layer may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the negative electrode active layer may optionally include other additives, such as dispersants, thickeners (e.g., sodium carboxymethyl cellulose), etc.

[0141] In some embodiments, the membrane includes a base membrane and a coating disposed on at least one surface of the base membrane, wherein the porosity of the base membrane does not exceed 30%. Porosity is the percentage of micropore volume in the base membrane relative to the total volume. Compared to conventional base membranes, firstly, low porosity means a higher proportion of solid-state framework within the material and fewer micropores. This structure prevents any ion passing through the base membrane from traveling along a straight or near-straight path, forcing it to navigate through more complex, meandering channels. This significantly prolongs the ion migration path, directly increasing the time required for metal ions to reach the negative electrode from the positive electrode and reducing their flux per unit time. Secondly, the average pore size of a low-porosity base membrane is also narrower, significantly increasing the resistance to metal ion migration. Thirdly, due to its dense structure, a low-porosity base membrane typically has a higher specific surface area, providing more opportunities for contact and interaction between the base membrane material and migrating ions. This allows metal ions to be temporarily bound by the low-porosity membrane through physical adsorption or weak chemical interactions, maximally attenuating the migration flux and rate of metal ions from the positive to the negative electrode.

[0142] In some embodiments, the porosity of the base film is 10%-30%. Controlling the porosity of the base film to 10%-30% improves the barrier ability against metal ions while providing a smoother migration channel for lithium ions, which is beneficial for achieving higher charge and discharge rates and improving the long-term cycle life and rate performance of the battery.

[0143] In some embodiments, the porosity of the base film is 15%-28%. Limiting the porosity to 15%-28% facilitates normal lithium-ion migration, improving charge-discharge performance; and it also allows for the migration of other metal ions (such as Fe²⁺) that are typically larger than lithium ions and migrate more slowly. + It produces a significant "screening" and "blocking" effect, which can effectively intercept most of the metal ions dissolved from the positive electrode, reducing the number of them reaching the negative electrode to an extremely low level.

[0144] In some embodiments, the porosity of the base film is 19%-25%. Within this range, the battery achieves an optimal balance between high capacity retention and low internal resistance growth. This allows the battery to not only exhibit slow capacity decay after multiple cycles but also maintain low internal resistance and a good discharge plateau. Simultaneously, due to the maximal suppression of side reactions, the risks of gas generation and thermal runaway are also reduced, thereby achieving synergistic maximization of cycle life and safety.

[0145] In this embodiment, the porosity of the base membrane can be tested using electrochemical impedance spectroscopy (EIS) combined with an ionic conductivity model. Specifically, the process includes: battery pretreatment: disassembling the battery, removing the cells, and separating the separator from the positive and negative electrodes; scraping off the coating on the separator surface to obtain the base membrane; immediately immersing the removed base membrane in an anhydrous organic solvent to remove impurities, followed by drying; performing electrochemical impedance spectroscopy on the obtained base membrane, recording the corresponding data, and performing analytical calculations to obtain the porosity.

[0146] In some embodiments, the diaphragm includes a base membrane and a coating disposed on at least one surface of the base membrane, wherein the coating includes an inorganic coating laminated on one side of the base membrane and an organic coating laminated on the side of the inorganic coating opposite to the base membrane; the material of the inorganic coating includes silane compounds and trimethylsilyl ester / alkane, and the mass percentage of trimethylsilyl ester / alkane is 0.03%-0.6% based on the total mass of the material of the inorganic coating.

[0147] In some embodiments, the trimethylsilyl ester / alkane includes at least one of tris(trimethylsilane) phosphate, tris(trimethylsilane) borate, and trimethylfluorosilane.

[0148] Because residual moisture in the electrolyte readily reacts with water from lithium salt LiPF6, a large amount of hydrofluoric acid is present in the electrolyte. The inorganic coating of the separator includes trimethylsilyl ester / alkane, which contains highly reactive Si-O groups and preferentially reacts with water compared to LiPF6. Therefore, most of the trace moisture in the electrolyte is preferentially captured by TMSP / TMSB. Furthermore, trimethylsilyl is an excellent Lewis acid acceptor, reacting with hydrofluoric acid (HF) to generate stable trimethylfluorosilane. This reaction converts the highly corrosive, small-molecule HF into volatile, inert TMSF gas. This effectively reduces the content of residual moisture and free HF in the electrolyte during cell assembly or operation, thereby inhibiting the dissolution of positive electrode metal elements, reducing side reactions initiated by them on the negative electrode side, and improving the cycle stability and safety of the cell.

[0149] In some embodiments, the trimethylsilyl ester / alkane content is 0.03%-0.6% by mass of the total mass of the material based on the inorganic coating. In some embodiments, the trimethylsilyl ester / alkane content is 0.04%-0.5% by mass of the total mass of the material based on the inorganic coating.

[0150] In some specific embodiments, the mass percentage of trimethylsilyl ester / alkane, based on the total mass of the inorganic coating material, includes, but is not limited to, typical but non-limiting values ​​such as 0.03%, 0.05%, 0.07%, 0.1%, 0.12%, 0.15%, 0.17%, 0.19%, 0.20%, 0.22%, 0.25%, 0.27%, 0.29%, 0.30%, 0.32%, 0.35%, 0.34%, 0.37%, 0.38%, 0.40%, 0.42%, 0.45%, 0.47%, 0.50%, 0.52%, 0.55%, 0.53%, 0.54%, 0.57%, 0.59%, and 0.60%. Excessive addition of trimethylsilyl ester / alkane will reduce the amount of ceramic matrix added, decrease coating strength, and be detrimental to diaphragm use; insufficient addition will fail to effectively remove water and acid, and will not effectively reduce the hydrofluoric acid content.

[0151] In some specific embodiments, the reaction formulas for the reactions of tris(trimethylsilane)phosphate with water and hydrofluoric acid are as follows: TMSP + H2O → TMSOH + H3PO4; TMSP+HF→TMS-F+PH; It can effectively remove water and acid, and effectively reduce the content of residual water and free HF in the electrolyte.

[0152] In some specific embodiments, the reaction formulas for the reactions of tris(trimethylsilane)borate ester with water and hydrofluoric acid are as follows: TMSB + H₂O → TMSOH + H₃BO₃; TMSB+HF→TMS-F+BH; It can effectively remove water and acid, and effectively reduce the content of residual water and free HF in the electrolyte.

[0153] In some embodiments, based on the total mass of the inorganic coating material being 100%, it further includes: Ceramic matrix 60%-90%; Adhesive content: 9.97%-30%; Additives: 0%-9.4%.

[0154] By adding trimethylsilyl ester to the inorganic coating material, the HF content in the electrolyte can be effectively reduced, while improving the thermal stability and interface protection of the separator, thereby enhancing the cycle life and safety of the battery cell.

[0155] In some specific embodiments, the mass percentage of the ceramic matrix, based on the total mass of the inorganic coating material as 100%, includes, but is not limited to, typical but non-limiting values ​​such as 60%, 65%, 70%, 75%, 80%, 85%, and 90%.

[0156] In some specific embodiments, the mass percentage of the binder, based on the total mass of the inorganic coating material as 100%, includes, but is not limited to, typical but non-limiting values ​​such as 9.97%, 10%, 12%, 15%, 17%, 19%, 20%, 22%, 24%, 26%, and 30%.

[0157] In some specific embodiments, the mass percentage of the additives, based on the total mass of the inorganic coating material as 100%, includes, but is not limited to, typical but non-limiting values ​​such as 0%, 2%, 4%, 6%, 8%, and 9.4%.

[0158] In this embodiment, the method for testing the composition of the composite coating can refer to the aforementioned method for testing the composition of the positive electrode active material.

[0159] In some embodiments, the ceramic matrix includes at least one of alumina, boehmite, silicon oxide, magnesium oxide, titanium oxide, tin oxide, calcium oxide, zirconium oxide, barium sulfate, yttrium oxide, zinc oxide, silicon carbide, magnesium fluoride, barium titanate, aluminum hydroxide, magnesium hydroxide, or calcium hydroxide.

[0160] In some embodiments, the adhesive includes at least one of polyvinylidene fluoride and its copolymers, polyacrylates, cellulose, and polyurethanes.

[0161] In some embodiments, the additives include at least one of conductive agents, lubricants, and anti-aging agents.

[0162] In some embodiments, the organic coating material includes polymers or copolymers prepared from one or more of the following components: (meth)acrylic acid and its ester monomers, styrene monomers, fluoroolefin monomers, olefin monomers, unsaturated nitrile monomers, epoxy alkane monomers, and polyurethane.

[0163] In some embodiments, (meth)acrylic acid and its ester monomers include at least one of acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, butyl methacrylate, and isooctyl methacrylate.

[0164] In some embodiments, styrene monomers include at least one of styrene and methylstyrene.

[0165] In some embodiments, the fluoroolefin monomers include at least one of vinylidene fluoride, vinyl fluoride, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, and hexafluoropropylene.

[0166] In some embodiments, the olefin monomer includes at least one of ethylene, propylene, butadiene, and isoprene.

[0167] In some embodiments, the unsaturated nitrile monomer includes at least one of acrylonitrile and methacrylonitrile.

[0168] In some embodiments, the alkyl oxide monomer includes at least one of ethylene oxide and propylene oxide.

[0169] The organic coating materials available include a variety of different types, and the specific type can be selected according to specific needs.

[0170] In some embodiments, the base film material includes at least one of polypropylene and polyethylene.

[0171] In some embodiments, the thickness of the inorganic coating is 1 μm-3 μm. In some specific embodiments, the thickness of the inorganic coating includes, but is not limited to, typical but non-limiting values ​​such as 1 μm, 1.5 μm, 2 μm, 2.5 μm, and 3 μm.

[0172] In some embodiments, the thickness of the organic coating is 0.5 μm-1 μm. In some specific embodiments, the thickness of the organic coating includes, but is not limited to, typical but non-limiting values ​​such as 0.5 μm, 0.7 μm, 0.9 μm, and 1 μm.

[0173] In some embodiments, the total thickness of the separator is 7 μm-15 μm. In some preferred embodiments, the total thickness of the separator is 7.5 μm-9.5 μm. The internal volume of the battery cell is limited; excessive thickness will occupy the available space for active materials, reduce the volumetric energy density, and increase the absorption of free electrolyte, reducing the effective utilization rate of the electrolyte. Insufficient thickness will affect the separator strength and is detrimental to its use.

[0174] In some embodiments, the thickness of the base film is 4 μm-6 μm. In some specific embodiments, the thickness of the base film is 4.5 μm-5.5 μm. This is beneficial for reducing the absorption of free electrolyte, increasing the effective utilization rate of the electrolyte, thereby reducing the total electrolyte injection volume and improving the cell's mass energy density.

[0175] In some specific embodiments, the separator includes a base membrane and a composite coating disposed on both surfaces of the base membrane. The composite coating comprises an inorganic coating stacked on one side of the base membrane and an organic coating stacked on the side of the inorganic coating facing away from the base membrane. The inorganic coating is made of trimethylsilyl ester, and the total thickness of the composite coating is 4 μm. This effectively reduces the HF content in the electrolyte without significantly increasing the separator thickness.

[0176] In this embodiment, the layer structure of the diaphragm can be determined by analyzing the cross-section of the diaphragm using SEM combined with EDS. The thickness of each layer can be measured using a micrometer or SEM.

[0177] In some embodiments, the battery cell further includes an electrolyte comprising 0.5%-7% vinylene carbonate by mass, based on 100% of the total electrolyte mass. In some specific embodiments, the electrolyte comprises 2.22%-2.52% vinylene carbonate by mass, based on 100% of the total electrolyte mass.

[0178] During the initial charge-discharge process, vinylene carbonate operates at a low potential (≈0.8 V vs. Li / Li). + Preferring electrolyte solvents (such as EC and DEC) to undergo electrochemical reduction and decomposition on the negative electrode surface, a stable SEI film is formed. Ethylene carbonate has a symmetrical molecular structure and tends to form a uniform organic-inorganic composite layer during reduction and decomposition. This helps suppress electrolyte decomposition and side reactions with metal ions, reducing gas production and improving cycle stability.

[0179] In this embodiment, the vinylene carbonate in the electrolyte can be analyzed using a gas chromatography quantitative analysis method for organic components.

[0180] In some embodiments, the electrolyte includes an electrolyte salt and a solvent. The electrolyte salt may be selected from lithium salts, and there are no particular limitations on the specific type; it can be selected according to actual needs. For example, the lithium salt may be selected from one or more of LiPF6, LiClO4, LiBF4, LiClF4, LiAsF6, LiSbF6, LiAlO2, LiAlCl4, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiC(CF3SO2)3, LiCl, LiI, etc.

[0181] In some embodiments, the type of organic solvent in the electrolyte is not particularly limited and can be selected according to actual needs. Specifically, the organic solvent may also include one or more of other types of chain carbonates, cyclic carbonates, and carboxylic acid esters. The types of chain carbonates, cyclic carbonates, and carboxylic acid esters are not specifically limited and can be selected according to actual needs. The organic solvent may also include one or more of diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propionate, ethylene carbonate, propylene carbonate, butenyl carbonate, γ-butyrolactone, methyl formate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, and tetrahydrofuran.

[0182] In some embodiments, the battery cell has a square structure with a height of 210-220 mm and a width of 270-600 mm. In some specific embodiments, the width can be 270-280 mm.

[0183] In some embodiments, the battery cell includes a lithium-ion battery cell. During battery charging and discharging, active lithium ions repeatedly insert and extract between the positive and negative electrode plates. The electrolyte acts as a conductor of ions between the positive and negative electrode plates. A separator is disposed between the positive and negative electrode plates, primarily to prevent short circuits between the positive and negative electrodes, while allowing lithium ions to pass through.

[0184] Furthermore, the lithium-containing transition metal phosphates provided in this application are prepared by co-precipitation or solid-state sintering, and the transition metals are fully reacted with iron and lithium by high-temperature calcination in an inert atmosphere.

[0185] The cathode thick coating provided in this application uses slot coating or spraying processes to uniformly coat the cathode slurry (containing lithium transition metal phosphate, binder, and conductive agent) onto the current collector surface. By optimizing the coating speed, drying temperature, baking time, and rolling pressure, a cathode coating weight of 0.32 g / 1540.25 mm is achieved. 2 -0.39 g / 1540.25 mm 2Within this range, this process can enhance the density and mechanical strength of the positive electrode layer without significantly increasing the electrode thickness, reduce the electrolyte penetration path, and lower the risk of HF corrosion and metal dissolution.

[0186] The negative electrode thick coating method provided in this application employs slot coating or spraying to uniformly coat the negative electrode slurry (containing graphite or silicon-carbon composite materials, binders such as CMC / SBR, and conductive agents such as carbon black) onto the current collector surface. By adjusting the coating speed, drying temperature, and roller pressure parameters, the coating weight is stabilized at 0.15 g / 1540.25 mm. 2 -0.20 g / 1540.25mm². This process can improve the mechanical strength and charge uniformity of the negative electrode layer, alleviate volume expansion during charging and discharging, reduce microcracks and active material shedding during cycling, and suppress side reactions of metal ions on the negative electrode side.

[0187] The low-porosity base membrane provided in this application embodiment is processed using a biaxial stretching process. Specific steps include: selecting PP or PE as the base membrane material, controlling the base membrane thickness to be between 4 μm and 6 μm through a biaxial stretching process, and ensuring the base membrane porosity does not exceed 30%, forming a dense porous structure that effectively blocks the migration path of metal ions to the negative electrode. While possessing a dense porous structure, the thin separator can reduce electrolyte absorption rate, improve electrolyte utilization, and increase the energy density of the battery cell.

[0188] The composite coating provided in this embodiment, applied to both surfaces of the base membrane, employs a double-sided slit coating or spraying process, sequentially coating an inorganic coating and an organic coating onto the base membrane surface. By controlling the coating thickness and drying temperature (100-130℃), the total coating thickness is controlled to approximately 4 μm, with the overall thickness within the range of 7 μm-10 μm, achieving a membrane with acid neutralization, low porosity, and ion conductivity at a low thickness.

[0189] The electrolyte provided in this application embodiment is supplemented with vinylene carbonate (VC) additive, which is uniformly dispersed in the electrolyte by high-speed stirring (500rpm-1000rpm). This process can effectively improve the quality and stability of the SEI film without significantly increasing the electrolyte viscosity, inhibit electrolyte decomposition, reduce metal ion side reactions and gas generation, thereby improving the cycle life and safety of the battery cell.

[0190] Battery device Secondly, embodiments of this application provide a battery device including a plurality of the aforementioned battery cells.

[0191] Here, a battery cell refers to the battery casing and the electrode assembly encapsulated within it. The shape of a battery cell is not particularly limited; it can be cylindrical, square, or any other arbitrary shape. Figure 1 The shown is a square-structured battery cell 20.

[0192] In some embodiments, such as Figure 2 As shown, the outer packaging of the battery cell 20 may include a housing 21 and a top cover assembly 22. The housing 21 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates enclosing a receiving cavity. The housing 21 has an opening communicating with the receiving cavity, and the top cover assembly 22 is used to cover the opening to close the receiving cavity. In the embodiments of this application, the positive electrode sheet, separator, and negative electrode sheet contained in the secondary battery may be formed into an electrode assembly 23 by a winding process. The electrode assembly 23 is encapsulated in the receiving cavity. Electrolyte is immersed in the electrode assembly 23. The number of electrode assemblies 23 contained in the battery cell 20 may be one or more, which can be adjusted according to actual needs.

[0193] The method for preparing the battery cell 20 is well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form the battery cell 20. As an example, the positive electrode, the separator, and the negative electrode can be wound to form an electrode assembly 23, which is then placed in an outer package, dried, injected with electrolyte, and subjected to vacuum sealing, settling, formation, and shaping processes to obtain the battery cell 20.

[0194] A battery module is assembled from the battery cell 20, which means it can contain multiple battery cells 20. The specific number can be adjusted according to the application and capacity of the battery module.

[0195] In some embodiments, Figure 3 This is a schematic diagram of a battery module 30 as an example. In the battery module 30, multiple battery cells 20 can be arranged sequentially along the length of the battery module 30. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 20 can be fixed in place using fasteners.

[0196] Optionally, the battery module 30 may also include a housing with a receiving space in which multiple battery cells 20 are received.

[0197] Energy storage devices Thirdly, this application provides an energy storage device, including a plurality of the above-described battery cells or the above-described battery device.

[0198] The provided energy storage devices include the aforementioned battery cells or battery devices. Energy storage devices using these battery-related components have longer cycle life, more stable operation, and lower safety risks; they are particularly suitable for large-scale energy storage scenarios with stringent requirements for reliability and safety.

[0199] This application provides an energy storage device including one or more battery clusters to improve the voltage and capacity of the energy storage device. A battery cluster may include multiple battery devices, which are connected in series via a busbar to increase the voltage of the energy storage device. When the energy storage device includes multiple battery clusters, the multiple battery clusters are connected in parallel to increase the capacity of the energy storage device. The definition of a battery device is as described above.

[0200] Energy storage devices can be used in energy storage power stations, wind power generation systems, solar power generation systems, mobile power systems, or temporary power supply systems. Energy storage devices can store electrical energy as needed and output it when appropriate. For example, an energy storage device can store electrical energy during off-peak hours and provide power to relevant users or electrical equipment during peak hours. The energy storage system provided in this application embodiment can be any power system that requires energy storage devices.

[0201] In some embodiments, the energy storage device is an energy storage container or an energy storage cabinet.

[0202] In some embodiments, the energy storage device may include a cabinet and one or more battery clusters housed within the cabinet.

[0203] In some embodiments, the energy storage device may include modules such as a thermal management module, a main control module, a central control module, a power distribution module, and a fire protection module.

[0204] As an example, the thermal management module may include a liquid cooling unit that supplies coolant to each battery device via piping to regulate the temperature of the individual battery cells.

[0205] As an example, the main control module can serve as the battery management unit for the battery cluster, used to monitor and manage the battery cluster. The main control module can monitor information such as the current, voltage, power, or temperature of the battery cluster. For instance, it can control the charging and discharging current and voltage of the battery cluster. The main control module includes modules such as an auxiliary battery management unit (SBMU) and a fusion switch.

[0206] As an example, the central control module can serve as the battery management unit for an energy storage device, used to monitor and manage the device. The central control module can monitor information such as the energy storage device's current, voltage, power, state of charge, or temperature. For instance, it can control the charging and discharging current and voltage of the energy storage device. As an example, the central control module includes modules such as an Insulation Monitoring Module (IMM), a Master Battery Management Unit (MBMU), an Ethernet (ETH) module, and a fiber optic conversion module.

[0207] As an example, a fire protection system includes control panels, detectors, alarm devices, etc., used to detect, alarm, or extinguish fires in energy storage systems. As an example, the power distribution unit can be used to distribute power to the power modules of the energy storage device.

[0208] Energy storage system Fourthly, embodiments of this application provide an energy storage system, including an energy conversion system and the aforementioned energy storage device, wherein the energy conversion system is connected to the energy storage device to perform energy conversion on the current input to the energy storage device or output from the energy storage device.

[0209] The provided energy storage system not only possesses the advantages of large capacity and long lifespan of the energy storage device itself, but also precisely transforms and regulates the charging and discharging current through the energy conversion system, enabling it to efficiently and stably adapt to electrical equipment with different voltage levels or frequency requirements, greatly expanding the application scenarios of the energy storage device.

[0210] In some embodiments, such as Figure 4 As shown, the energy storage system may include one or more energy storage devices 1 and a power conversion system 4 (PCS). The power conversion system 4 is used to connect the power generation equipment 5, the power grid, or the load to the energy storage device 1. The power generation equipment 5 generates electrical energy, the energy storage device 1 stores electrical energy, and the power conversion system 4 converts the current input to the energy storage device 1 or the current output from the energy storage device 1 into energy. The electrical energy generated by the power generation equipment 5 can be stored in the energy storage device 1 through the power conversion system 4, and the electrical energy stored in the energy storage device 1 can also be output to the load or the power grid through the power conversion system 4. As an example, the power generation equipment 5 may specifically be a solar panel, a hydroelectric power generation device, a thermal power generation device, a wind power generation device, etc. The specific type of the power generation equipment 5 is not limited in this application.

[0211] Charging Network Fifthly, embodiments of this application provide a charging network, including charging piles and an energy storage device or energy storage system as described above, wherein the energy storage device is used to provide electrical energy to the charging piles.

[0212] The provided charging network utilizes energy storage units to store electrical energy during off-peak hours and provides power to charging piles during peak hours or when charging demand surges, effectively mitigating the instantaneous impact of large-scale charging facilities on the regional power grid.

[0213] This application provides a charging network, such as... Figure 5 The system includes a charging pile 6 and an energy storage device 1. The charging pile 6 is electrically connected to the energy storage device 1, which provides power to the charging pile 6. The charging pile 6 is electrically connected to a battery device in the energy storage device 1 via a cable, allowing the battery device to supply its stored energy to the charging pile 6. The charging pile 6 has one or more connectors 7 for connecting to electrical equipment (such as vehicles) to replenish power to the equipment. The energy storage device can be located inside the charging pile (e.g., an integrated charging and energy storage unit) or outside the charging pile.

[0214] Example The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain the embodiments of this application, and should not be construed as limiting the embodiments of 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 the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0215] Example 1 battery cell (1) Preparation of positive electrode active material Step S1: Add lithium carbonate, iron phosphate and titanium dioxide to water and mix in a premix tank at 1800 rpm. The ratio of lithium carbonate to iron phosphate is such that the molar ratio of iron to phosphorus is 0.975, and the titanium dioxide doping amount is such that the titanium content in the positive electrode active material product is 600 ppm. Step S2: The mixed raw materials are ground twice in a sand mill. The first grinding is carried out using zirconia balls with a diameter of 0.6 mm and a speed of 500 rpm for 1 hour. The grinding chamber pressure is less than 0.3 MPa. The second grinding is then carried out to obtain a mixed slurry with a particle size DV50 of 0.40 μm. Step S3: Spray dry the mixed slurry to obtain precursor powder. Step S4: Sinter the precursor powder to obtain lithium iron phosphate cathode material. The sintering process includes: First sintering: Sinter the precursor powder in a nitrogen atmosphere, heating from 25 ℃ to 760 ℃ at a heating rate of 5 ℃ / min, and holding at that temperature for 10 h. After cooling, the first sintered product is obtained. Second sintering: The first sintering product is sintered in a nitrogen atmosphere, heated from 25℃ to 800℃ at a heating rate of 5℃ / min, and held at that temperature for 10 h. After cooling, the second sintering product is obtained. Step S5: After sintering, cool to below 100 ℃ and crush the second sintering product using air jet milling to obtain titanium-containing lithium iron phosphate cathode active material. The air jet milling stage frequency is 25 Hz and the milling pressure is 0.55 MPa.

[0216] (2) Preparation of the positive electrode sheet: 2.2 wt% PVDF, 0.8 wt% conductive carbon black, and 97.0 wt% of the positive electrode active material prepared in step (1) above were added sequentially and dry-mixed. N-methylpyrrolidone was then added, and the mixture was stirred and the viscosity adjusted to obtain a positive electrode active slurry. The positive electrode active slurry was then transferred and coated onto a current collector aluminum foil for double-sided coating. The drying temperature was 130 ℃, the coating speed was 2.0 m / min, and the weight of the coating on one side was 0.32 g / 1540.25 cm. 2 The positive electrode film layer.

[0217] (3) Preparation of negative electrode sheet: A mixture of 95.5 wt% conductive carbon black, 1.0 wt% styrene-butadiene rubber (SBR), and 1.5 wt% sodium carboxymethyl cellulose was prepared by mixing, adding deionized water, and stirring to disperse the mixture into a negative electrode active slurry. The negative electrode active slurry was then transferred and coated onto a current collector copper foil for double-sided coating. The drying temperature was 130 ℃, and the coating speed was 2.0 m / min, resulting in a single-sided coating weight of 0.15 g / 1540.25 cm⁻¹. 2 The negative electrode film layer. (4) Preparation of the diaphragm Step Q1: Mix 90% alumina ceramic material, 0.03% TMSP powder, and 9.97% PVDF binder with deionized water to adjust the solid content of the slurry to 40% and prepare an inorganic coating slurry; prepare an organic coating slurry by mixing PVDF and NMP in a mass ratio of 15:85. Step Q2: PP is selected as the base membrane material for the separator. The base membrane is processed by biaxial stretching to obtain a base membrane thickness of 4 μm and a porosity of 10%. Step Q3: A double-sided slit coating process is used to coat the base film surface with inorganic and organic coating slurries sequentially on both surfaces. The coating thickness and drying temperature are controlled at 120 ℃ to prepare the coating. The total coating thickness is controlled to be 4 μm, and the total thickness is controlled to be 8 μm.

[0218] (5) Preparation of electrolyte In an argon-atmospheric glove box, ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed uniformly at a volume ratio of 1:1. Lithium salt LiPF6 was then added and dissolved in the organic solvent. The concentration of LiPF6 in the electrolyte was 1 mol / L, thus obtaining the electrolyte. (6) Battery fabrication: The positive electrode, separator, and negative electrode are stacked in sequence. The separator should be able to isolate the anode and cathode. The bare cell is obtained by winding. The bare cell is placed in the outer packaging, electrolyte is injected, and it goes through processes such as encapsulation, formation, and venting to finally obtain a battery cell.

[0219] Example 2-22 The specific difference from Example 1 is shown in Table 1; everything else is the same as Example 1.

[0220] Comparative Examples 1-4 The specific difference from Example 1 is shown in Table 1; everything else is the same as Example 1.

[0221] Table 1

[0222] Performance testing 1. Battery cell expansion rate test The test method is as follows: The battery cell is clamped in three steel clamps, restricting its lateral displacement and allowing free expansion only in the thickness direction. Dimensional changes in the battery thickness direction are monitored in real time using high-precision sensors. During the thermal runaway test, the thickness value is continuously recorded, and the expansion rate is calculated (expansion rate = (test thickness - initial thickness) / initial thickness × 100%).

[0223] 2. Battery cell capacity retention test at room temperature (25℃): The test method is as follows: Under a constant temperature environment of 25℃, charge-discharge cycles are performed at a constant current rate of 1C. The test endpoint is set at 3000 cycles. After the cycle test, a capacity calibration test is performed: the battery cell is charged at a constant current rate of 1C to the upper limit voltage, then switched to constant voltage charging until the current drops to 0.05C. After resting, it is discharged at a constant current rate of 1C to the cutoff voltage. The current actual capacity is then measured. The capacity retention rate is calculated using the following formula: Capacity retention rate (%) = (Actual discharge capacity after cycle test / Initial rated capacity of battery cell) × 100%.

[0224] 3. Battery cell capacity retention test at high temperature (60℃): The test method is as follows: Select battery cells with a rated capacity ranging from 500 to 1200 Ah, and conduct continuous charge-discharge cycles at a constant current rate of 1C under a constant temperature environment of 60°C. The test will be conducted for 3000 cycles; a complete charge-discharge cycle is completed at a 1C rate (constant current charging to the cutoff voltage, then switching to constant voltage to the current cutoff, allowing sufficient rest, and then constant current discharging to the cutoff voltage) to accurately measure the current actual capacity. The capacity retention rate is calculated using the following formula: Capacity retention rate (%) = (actual discharge capacity after the current cycle / initial rated capacity of the battery) × 100%.

[0225] 4. Battery cell gas production test: The testing method is as follows: A single battery cell is placed in a sealed container, and the volume and composition of the gas produced are monitored in real time under overcharge conditions. During the test, the gas production rate is measured using a gas collection device (such as a water-sealed gas flow meter or pressure sensor), and the gas composition (such as H2, CO2, CO, etc.) is analyzed using gas chromatography (GC). Finally, the gas production rate (mL / h) and component percentage are calculated to evaluate the battery's gas generation capacity and safety under abnormal operating conditions.

[0226] 5. Battery cell thermal runaway temperature test: The test method is as follows: A metal heating plate (with an outer insulating material) with a power range of 800 W-1001 W is placed in the center of the large surface of the battery cell, and a steel plate clamp is installed (completely covering the large surface of the battery cell); the temperature of the center of the two large surfaces of the battery cell, the two sides, the positive and negative terminals, and the edge of the large surface not covered by the heating plate is monitored by thermocouples; constant current charging at 0.5 C is started simultaneously and heating is started, which continues until the battery cell triggers thermal runaway or the experiment reaches 4 hours, at which point the overcharging and heating operations are automatically stopped.

[0227] Results Analysis As shown in Table 2, when comparing Example 1 and Comparative Example 1, the cell expansion rate of Example 1 (the positive electrode active material is selected from titanium-containing lithium iron phosphate) is lower than that of ternary positive electrode active materials. At the same time, the capacity retention rate is better at room temperature and high temperature, the gas production is also lower, and the thermal runaway temperature is higher, indicating better thermal stability.

[0228] Comparing Example 1 and Example 2, the positive electrode active materials were selected from titanium-containing lithium iron phosphate or vanadium-containing lithium iron phosphate, respectively. It can be seen that the cell expansion rate and gas production of Example 1 (containing titanium dopant) are both lower. Moreover, the capacity retention rate is better at room temperature and high temperature, and the thermal runaway temperature is higher, indicating better thermal stability.

[0229] Comparing Examples 1 and 3-4, it can be seen that as the content of doping elements increases, the cell expansion rate decreases, the capacity retention rate slightly improves, and the thermal stability slightly increases; indicating that appropriately increasing the content of doping elements is beneficial to improving the overall electrochemical performance and thermal stability of the battery.

[0230] Comparing Examples 1 and 5-7, it can be seen that as the weight of the positive electrode coating increases, the cell expansion rate does not change significantly, the capacity retention rate decreases slightly, the gas production decreases significantly, and the thermal runaway temperature decreases slightly. This indicates that increasing the weight of the positive electrode coating may suppress gas production, but it may have some impact on capacity and thermal stability.

[0231] Comparing Examples 1 and 8-9, it can be seen that improving the sphericity / roughness of the positive electrode particles is beneficial to reducing the cell expansion rate and gas production.

[0232] Comparing Examples 1 and 10-12, it can be seen that as the negative electrode coating weight increases, the cell expansion rate increases significantly, the capacity retention rate at high temperatures decreases, gas production increases, and the thermal runaway temperature decreases. This indicates that increasing the negative electrode coating weight is detrimental to expansion control, capacity retention, and thermal stability.

[0233] Comparing Examples 1 and 13-14, it can be seen that as the porosity of the base film increases, the cell expansion rate increases significantly; the capacity retention rate at room temperature slightly improves; and the thermal runaway temperature decreases. This indicates that the porosity of the base film should be appropriately controlled to be relatively small.

[0234] Comparing Example 1 and Example 15, it can be seen that as the thickness of the base film increases, it is beneficial to reduce the expansion rate of the battery cell.

[0235] Comparing Examples 1 and 16-19, it can be seen that as the content of TMSP material in the inorganic coating increases, the cell expansion rate decreases, the high-temperature capacity retention rate increases, the gas production decreases, and the thermal stability is better.

[0236] Compared to Example 20, with the increase of the inorganic coating / composite coating thickness, the cell expansion rate and gas production decreased, and the thermal stability was better. This indicates that increasing the coating thickness is beneficial for suppressing gas production and improving thermal stability.

[0237] Compared with Example 1, increasing the vinylene carbonate content in Example 21 helps reduce cell expansion rate, improve capacity retention, significantly reduce gas production, and improve thermal stability. It can be seen that appropriate addition of vinylene carbonate helps improve overall performance.

[0238] In Examples 1 and Comparative Examples 2-3, excessively high base film porosity leads to increased cell expansion rate, decreased high-temperature capacity retention rate, and increased gas production; conversely, excessively low base film porosity affects gas production. Compared to Comparative Example 4, the overall battery performance is poor.

[0239] Table 2

[0240] In summary, the battery cell provided in this application is a high-capacity cell, and the positive electrode active material of the battery cell uses lithium-containing transition metal phosphate. By introducing Ti element doping, this material can effectively adjust the lattice strain distribution, reduce local stress concentration, and thus enhance the overall stability of the crystal structure. This characteristic helps to significantly suppress the dissolution of metal ions, reduce the number of metal ions that can migrate from the positive electrode side to the negative electrode side from the source, reduce the side reactions caused by free metal ions at the negative electrode interface, and thus improve the cycle life and long-term operational stability of the cell. At the same time, the battery cell is used in conjunction with a low-porosity base film. Due to its low porosity, the internal pore structure of this base film is more tortuous and dense, which not only extends the migration path of ions, but also significantly increases the resistance of metal ions in the trans-electrode transport process, providing a "secondary barrier effect" for metal ions. Even if a small amount of metal ions dissolve from the positive electrode, they will be effectively blocked when passing through the base film, thereby greatly limiting the number of metal ions that finally reach the negative electrode surface, and further suppressing the occurrence of side reactions on the negative electrode side. It can be seen that the structural optimization of the cathode material is aimed at reducing the "generation" of metal ions, while the low porosity base film focuses on weakening their "migration". The two work together to reduce the side reactions caused by metal ions at the anode interface. While maintaining the high capacity of the battery cell, it significantly enhances its cycle stability and long-term safety, and achieves a simultaneous improvement in overall performance.

[0241] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included within the protection scope of the present application.

Claims

1. A battery cell, characterized in that, The battery cell has a capacity of ≥500 Ah. The battery cell includes a positive electrode, a negative electrode, and a separator located between the positive electrode and the negative electrode. The positive electrode includes a positive current collector and a positive electrode film layer stacked on at least one surface of the positive current collector. The positive electrode film layer includes a positive electrode active material, which includes a lithium-containing transition metal phosphate doped with Ti and / or V. The separator includes a base film and a coating disposed on at least one surface of the base film. The porosity of the base film does not exceed 30%.

2. The battery cell according to claim 1, characterized in that, The porosity of the base membrane is 10%-30%.

3. The battery cell according to claim 1 or 2, characterized in that, The lithium-containing transition metal phosphate has the following general formula: Li a Fe b M c PO d Where M includes one or more of V, Ti, and Mn, 0.8≤a≤1.15, 0.9≤b<1, 0 <c≤0.1,b+c≤1,3.5≤d≤4。 4. The battery cell according to claim 3, characterized in that, Based on the total mass of the lithium-containing transition metal phosphate, the content of Ti and / or V is 0.05wt%-0.15wt%.

5. The battery cell according to claim 4, characterized in that, Based on the total mass of the lithium iron phosphate, the content of Ti and / or V is 0.06 wt%-0.12 wt%.

6. The battery cell according to claim 1, characterized in that, The single-sided coating weight of the positive electrode film is 0.32 g / 1540.25 mm. 2 -0.39 g / 1540.25 mm 2 ; and / or, The negative electrode sheet includes a negative current collector and a negative electrode film layer stacked on at least one surface of the negative current collector, wherein the single-sided coating weight of the negative electrode film layer is 0.15 g / 1540.25 mm. 2 -0.20 g / 1540.25 mm 2 .

7. The battery cell according to claim 6, characterized in that, In the cumulative distribution curve of the spheroidal area of ​​the particles obtained from the cross-section of the positive electrode film along the thickness direction of the electrode sheet, the median L of the spheroidality is... A50 It is 0.70-0.

85.

8. The battery cell according to claim 7, characterized in that, In the cumulative distribution curve of the spheroidal area of ​​the particles obtained from the cross-section of the positive electrode film along the thickness direction of the electrode sheet, the median L of the spheroidality is... A50 It is 0.70-0.

76.

9. The battery cell according to claim 8, characterized in that, In the cumulative roughness area distribution curve of the particles obtained from the cross-section of the positive electrode film along the thickness direction of the electrode sheet, the median roughness R A50 It is 0.92-0.

96.

10. The battery cell according to claim 9, characterized in that, In the cumulative roughness area distribution curve of the particles obtained from the cross-section of the positive electrode film along the thickness direction of the electrode sheet, the roughness concentration (R) is... A90 -R A10 ) / R A50 It is 0.05-0.

10.

11. The battery cell according to claim 10, characterized in that, The tap density of the lithium-containing transition metal phosphate powder is 1.00 g / cm³. 3 -1.70 g / cm 3 ; and / or, The lithium-containing transition metal phosphate powder has a compacted density of 2.55 g / cm³ under 3T pressure. 3 -2.70 g / cm 3 .

12. The battery cell according to claim 11, characterized in that, The positive electrode film layer satisfies one or more of the following characteristics: (1) The single-sided density of the positive electrode film is 20.77 mg / cm³. 2 -25.30 mg / cm 2 ; (2) The compaction density of the positive electrode film is 2.2 mg / cm³. 3 -2.75 g / cm 3 ; (3) In the cross section along the thickness direction of the positive electrode film, the porosity of the positive electrode film is 20.4%-38.9%.

13. The battery cell according to claim 6, characterized in that, The negative electrode film layer satisfies one or more of the following characteristics: (1) The one-sided density of the negative electrode film is 9.74 mg / cm³. 2 -12.98 mg / cm 2 ; (2) The compaction density of the negative electrode film is 1.4 g / cm³. 3 -1.8 g / cm 3 ; (3) In the cross section along the thickness direction of the electrode sheet, the porosity of the negative electrode film layer is 35.2%-49.6%.

14. The battery cell according to claim 1, characterized in that, The coating comprises an inorganic coating layered on one side of the base film and an organic coating layered on the side of the inorganic coating opposite to the base film; The materials of the inorganic coating include silane compounds and trimethylsilyl esters / alkanes; Based on the total mass of the material of the inorganic coating, the mass percentage of trimethylsilyl ester / alkane is 0.03%-0.6%.

15. The battery cell according to claim 14, characterized in that, The trimethylsilyl ester / alkane includes at least one of tris(trimethylsilane) phosphate, tris(trimethylsilane) borate, and trimethylfluorosilane.

16. The battery cell according to claim 14 or 15, characterized in that, Based on the total mass of the inorganic coating material being 100%, it also includes: Ceramic matrix 60%-90%; Adhesive content: 9.97%-30%; Additives: 0%-9.4%.

17. The battery cell according to claim 16, characterized in that, The ceramic matrix includes at least one of alumina, boehmite, silicon oxide, magnesium oxide, titanium oxide, tin oxide, calcium oxide, zirconium oxide, barium sulfate, yttrium oxide, zinc oxide, silicon carbide, magnesium fluoride, barium titanate, aluminum hydroxide, magnesium hydroxide, or calcium hydroxide. The adhesive includes at least one of polyvinylidene fluoride and its copolymers, polyacrylates, cellulose, and polyurethanes; The additives include at least one of conductive agents, lubricants, and anti-aging agents.

18. The battery cell according to claim 14, characterized in that, The organic coating material includes polymers or copolymers prepared from one or more of the following components: (meth)acrylic acid and its ester monomers, styrene monomers, fluoroolefin monomers, olefin monomers, unsaturated nitrile monomers, epoxy alkane monomers, and polyurethane.

19. The battery cell according to claim 18, characterized in that, The (meth)acrylic acid and its ester monomers include at least one of acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, butyl methacrylate, and isooctyl methacrylate; The styrene monomers include at least one of styrene and methylstyrene; The fluoroolefin monomers include at least one of vinylidene fluoride, vinyl fluoride, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, and hexafluoropropylene; The olefin monomers include at least one of ethylene, propylene, butadiene, and isoprene; The unsaturated nitrile monomers include at least one of acrylonitrile and methacrylonitrile; The epoxide monomers include at least one of ethylene oxide and propylene oxide.

20. The battery cell according to claim 14, characterized in that, The base film is made of at least one of polypropylene and polyethylene.

21. The battery cell according to claim 14, characterized in that, The thickness of the inorganic coating is 1 μm-3 μm; and / or, The thickness of the organic coating is 0.5 μm-1 μm; and / or, The total thickness of the diaphragm is 7 μm-15 μm; and / or, The thickness of the base film is 4 μm-6 μm.

22. The battery cell according to claim 1, characterized in that, The battery cell also includes an electrolyte, which, based on the total mass of the electrolyte (100%), includes 0.5%-7% vinylene carbonate by mass.

23. The battery cell according to claim 1, characterized in that, The battery cell has a square structure with a height of 210 mm-220 mm and a width of 270 mm-600 mm.

24. The battery cell according to claim 23, characterized in that, The width is 270 mm-280 mm.

25. A battery device, characterized in that, It includes multiple battery cells according to any one of claims 1-24.

26. An energy storage device, characterized in that, It includes multiple battery cells according to any one of claims 1-24 or battery devices according to claim 25.

27. An energy storage system, characterized in that, It includes an energy conversion system and an energy storage device as described in claim 26, wherein the energy conversion system is connected to the energy storage device to convert the current input to or output from the energy storage device.

28. A charging network, characterized in that, It includes a charging pile and an energy storage device as described in claim 26 or an energy storage system as described in claim 27, wherein the energy storage device is used to provide electrical energy to the charging pile.

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