Secondary batteries, electrode impregnation methods, and preparation methods of secondary batteries

Abstract

This invention relates to a secondary battery, an electrode wetting method, and a method for preparing the secondary battery. From a product design perspective, this invention reduces the areal density and compaction density of the electrode, increases the number of stacked layers, establishes a correlation between electrode areal density, compaction, and the number of stacked layers and the electrode pore volume, and directionally increases electrode pores to provide channels and storage space for electrolyte penetration. Based on this, the electrolyte formulation is optimized, thereby improving electrolyte wettability and ultimately enhancing the battery's long-term cycle life and high-temperature storage performance.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a secondary battery, an electrode wetting method, and a method for preparing a secondary battery, particularly to a method for improving the wettability of a high-energy-density, large-size soft-pack lithium-ion battery. Background Technology

[0002] Lithium-ion batteries are mainly composed of electrolyte, separator, positive electrode material, and negative electrode material. As one of the four key materials in lithium battery manufacturing, the electrolyte is the medium for lithium-ion migration and charge transfer, often referred to as the "blood" of the battery. As the carrier of lithium ions, the electrolyte transports them during charging and discharging; therefore, it needs to have extremely high ionic conductivity and extremely low electronic conductivity. With vehicle manufacturers demanding increasingly higher energy density from battery systems, the areal density and electrode size of individual cells are also continuously increasing. Ensuring sufficient and uniform wetting of the electrolyte in the center of the cell is therefore crucial. Current methods to improve electrolyte wettability mainly include optimizing the electrolyte injection process, creating porous electrodes to increase electrode porosity, and increasing the settling time after electrolyte injection. Electrolyte filling process optimization generally improves the wetting effect of the electrolyte by adjusting filling conditions, settling time, and filling method. This method significantly improves the wetting effect for batteries with conventional energy densities (200-215Wh / Kg) and sizes (cell length 280-310mm, width 95-115mm), but it is ineffective for improving the wetting effect of high-energy-density, large-size pouch batteries with small aspect ratios. Fabricating porous electrodes increases the porosity of the electrode sheets, creating more penetration channels and storage space for electrolyte wetting to some extent, but it also reduces the feasibility of electrode manufacturing. Increasing the settling time after filling can improve the electrolyte wetting effect of the battery, but it also increases the side reactions generated by the electrolyte, increases the battery's internal resistance, and reduces production efficiency. Summary of the Invention

[0003] The problem the invention aims to solve

[0004] Given that the methods described above, which significantly improve the wetting effect of batteries with conventional energy density and size, are not applicable to large-size, high-energy-density pouch cells with small aspect ratios, it is necessary to develop a secondary battery that can increase the pore volume of the electrode and a method to improve the wetting properties of large-size, high-energy-density pouch cells.

[0005] Solution for solving the problem

[0006] In view of the above, the object of the present invention is to develop a method for increasing the pore volume of the electrode in a secondary battery and improving the wettability of a high-energy-density, large-size pouch lithium-ion battery.

[0007] In the secondary battery of the present invention that increases the pore volume of the electrode, a correlation relationship is established between the electrode surface density, compaction density, and number of stacked layers and the electrode pore volume. This allows for a reduction in the surface density and compaction density of the electrode and an increase in the number of stacked layers from a product design perspective, thereby directionally increasing the electrode pores and providing channels and storage space for electrolyte permeation.

[0008] In addition, in the secondary battery of the present invention, a suitable electrolyte injection amount is determined, and the electrolyte formulation is further optimized based on increasing the pore volume of the electrode, thereby improving the electrolyte wettability and thus improving the long-term cycle and high-temperature storage performance of the battery.

[0009] Specifically, the present invention provides a secondary battery, comprising a positive electrode and a negative electrode, wherein the electrode plates of the positive electrode and / or the negative electrode respectively contain pores to provide space for electrolyte wetting, and the pore volume V of the electrode plates conforms to the following formula:

[0010] Electrode pore volume V (ml) = 9.991a*(b / c / 1000*1.02+0.005)*[1-17.9118 / ((b / c / 1000*1.02+0.005) / 10*9.7*10.3) / a]+10.706d*(e / f / 1000*1.35)*[1-21.9890 / ((e / f / 1000*1.35) / 10*10.1*10.6) / d]

[0011] Where a is the number of positive electrode layers, and b is the areal density of the positive electrode bifacial layer (g / m³). 2 ), where c is the positive electrode compaction density (g / cm³). 3 ), d is the number of negative electrode layers, and e is the areal density of the negative electrode double-sided surface (g / m³). 2 f is the negative electrode compaction density (g / cm³). 3 ), and d = a + 1, e = ab / (1.75a + 0.15).

[0012] Based on the above description of the secondary battery, where a is 12-44; b is 280-400 g / m³ 2 c is 3.2-

[0013] 3.4g / cm 3 d is 13-45; e is 100-300g / m 2 f is 1.45-1.65 g / cm³ 3 The pore volume V of the electrode is 15-37 ml.

[0014] The present invention also provides a secondary battery, comprising a positive electrode, a negative electrode, and an electrolyte, wherein the amount of electrolyte injected satisfies the following formula:

[0015] Electrolyte injection volume = Electrolyte density × Electrode pore volume V × Injection coefficient

[0016] Wherein, the electrode pore volume V (ml) = 9.991a*(b / c / 1000*1.02+0.005)*[1-17.9118 / ((b / c / 1000*1.02+0.005) / 10*9.7*10.3) / a]+10.706d*(e / f / 1000*1.35)*[1-

[0017] 21.9890 / ((e / f / 1000*1.35) / 10*10.1*10.6) / d],

[0018] Wherein, the electrolyte injection volume is taken as g (the value calculated on the right side of the equation), the injection coefficient is 1.4-3.5 g / Ah, a is the number of positive electrode layers, and b is the areal density of the positive electrode (g / m³). 2 ), where c is the positive electrode compaction density (g / cm³). 3 ), d is the number of negative electrode layers, and e is the areal density of the negative electrode double-sided surface (g / m³). 2 f is the negative electrode compaction density (g / cm³). 3 ), and d = a + 1, e = ab / (1.75a + 0.15).

[0019] According to the above-described secondary battery, the battery's capacity, thickness, weight, positive and negative electrode dimensions, and N / P ratio are fixed values.

[0020] According to the above-described secondary battery, the electrolyte comprises an electrolyte, a solvent, and an additive, wherein the proportion of the electrolyte is 11.5-15.5% by mass, the proportion of the solvent is 81-85% by mass, the proportion of the additive is 2.4-4.4% by mass, and the total proportion of the electrolyte, the solvent, and the additive is 100% by mass.

[0021] According to the above-described secondary battery, the electrolyte includes a lithium salt;

[0022] Preferably, the lithium salt comprises LiPF6; the solvent comprises one or more of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate; and the additive comprises one or more of vinylene carbonate, 1,3-propanesulfonate lactone, ethylene sulfate, and LiPO2F2.

[0023] According to the above-described secondary battery, the solvent does not include propylene carbonate and diethyl carbonate; the lithium salt does not include lithium difluoro(dioxaate) phosphate.

[0024] According to the above-described secondary battery, when the electrolyte contains LiPO2F2, the content of LiPO2F2 is 0.1-1% by mass.

[0025] According to the secondary battery described above, where a is 12-44; b is 280-400 g / m³ 2 c is 3.2-3.4 g / cm³ 3 d is 13-45; e is 100-300g / m 2 f is 1.45-1.65 g / cm³ 3 The electrolyte density is 1.19-1.22 g / cm³. 3 The injection coefficient is 1.4-3.5 g / Ah; the electrode pore volume V is 15-37 ml; and the N / P ratio is 1.08-1.13.

[0026] According to the above-described secondary battery, the 1C rated capacity of the battery is 15±0.25Ah; the thickness of the battery is 7.9±0.2mm; and the weight of the battery is 2190±10g.

[0027] The dimensions of the positive electrode are: length 103±0.2mm, width 97±0.2mm;

[0028] The dimensions of the negative electrode are: length 106±0.2mm and width 101±0.2mm.

[0029] The present invention also provides an electrode wetting method, which includes the step of injecting electrolyte according to the electrolyte injection amount obtained in the above-described secondary battery to wet the electrode, thereby improving the electrolyte wettability of the electrode.

[0030] The present invention also provides a method for preparing a secondary battery, including the step of impregnating an electrode sheet by the impregnation method described above.

[0031] The effects of the invention

[0032] The above-mentioned technical solution of the present invention has the following beneficial effects:

[0033] (1) In the secondary battery of the present invention, the correlation between the surface density, compaction and number of stacked layers of the electrode and the pore volume of the electrode is established, thereby reducing the surface density and compaction density of the electrode, increasing the number of stacked layers, and directionally increasing the pore volume of the electrode from the product design perspective, providing channels and storage space for electrolyte permeation;

[0034] (2) Based on increasing the pore volume of the electrode, determine the appropriate electrolyte injection amount and adopt an optimized electrolyte formula, thereby improving the electrolyte wettability and thus improving the long-term cycle and high-temperature storage performance of the battery.

[0035] (3) From the perspective of product design and optimization of electrolyte formulation, the wettability of electrolyte is improved, the cost of equipment improvement is saved, the manufacturing feasibility and production efficiency of the product are not reduced, and the long-term cycle and storage performance of the battery is improved, thus extending the service life of the system. Detailed Implementation

[0036] To enable those skilled in the art to better understand the present invention, the invention will be further described in detail below with reference to the accompanying formulas and embodiments, but the invention is not limited thereto. The invention is not limited to the various configurations described below; various modifications can be made within the scope of the claims, and embodiments obtained by appropriately combining different embodiments and the disclosed technical means in appropriate combinations of embodiments are also included within the technical scope of the invention. Furthermore, all documents recorded in this specification are incorporated herein by reference.

[0037] Unless otherwise defined, the technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0038] In this specification, the range of values ​​referred to as "value A to value B" refers to the range including the endpoint values ​​A and B.

[0039] Unless otherwise stated, in this instruction manual, "more" in "multiple", "multi-variety", "multiple", etc., means a value of 2 or more.

[0040] In this specification, the terms "substantially," "largely," or "truly" mean that the error is less than 5%, or less than 3%, or less than 1% compared to the relevant perfect or theoretical standard.

[0041] Unless otherwise specified, "%" in this instruction manual refers to the percentage content by mass.

[0042] In this instruction manual, if terms such as "room temperature" or "normal temperature" appear, the temperature is generally between 10 and 37°C, or between 15 and 35°C.

[0043] In this specification, the meaning of "may" or "can" includes both the existence or non-existence of something, and both the performance of a certain treatment and the non-performance of a certain treatment.

[0044] In this specification, "optional" and "optionally" mean that the event or situation described below may or may not occur, and the description includes both the scenario in which the event occurs and the scenario in which the event does not occur.

[0045] The term "comprising" and any variations thereof in the specification and claims of this invention are intended to cover a non-exclusive inclusion. For example, a process, method, system, product, or apparatus that comprises a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such processes, methods, products, or apparatus.

[0046] In this specification, references to "some / certain / preferred embodiments," "implementation," etc., mean that a specific element (e.g., feature, structure, property, and / or characteristic) related to that embodiment is included in at least one of the embodiments described herein, and may or may not be present in other embodiments. Furthermore, it should be understood that the elements may be combined in any suitable manner in various embodiments.

[0047] Secondary batteries

[0048] In the secondary battery of the present invention, a correlation relationship is established between the electrode surface density, compaction density, and number of stacked layers and the electrode pore volume. From the product design perspective, the surface density and compaction density of the electrode are reduced and the number of stacked layers is increased, thereby directionally increasing the electrode pores and providing channels and storage space for electrolyte permeation.

[0049] The secondary battery of the present invention includes a positive electrode and a negative electrode, wherein the electrode plates of the positive electrode and / or the negative electrode respectively contain pores to provide space for electrolyte wetting. The pore volume V of the electrode plate conforms to the following formula (1):

[0050] Electrode pore volume V (ml) = 9.991a*(b / c / 1000*1.02+0.005)*[1-17.9118 / ((b / c / 1000*1.02+0.005) / 10*9.7*10.3) / a]+10.706d*(e / f / 1000*1.35)*[1-

[0051] 21.9890 / ((e / f / 1000*1.35) / 10*10.1*10.6) / d],

[0052] Where a is the number of positive electrode layers, and b is the areal density of the positive electrode bifacial layer (g / m³). 2 ), where c is the positive electrode compaction density (g / cm³). 3 ), d is the number of negative electrode layers, and e is the areal density of the negative electrode double-sided surface (g / m³). 2 f is the negative electrode compaction density (g / cm³). 3 ), and d = a + 1, e = ab / (1.75a + 0.15).

[0053] In some specific implementation schemes, 'a' can be 12-44, for example, 12, 15, 20, 25, 30, 35, 40, 44, etc. 'b' can be 280-400 g / m³. 2 For example, it can be 280g / m 2 300g / m 2 320g / m 2 350g / m 2 380g / m 2 400g / m 2 etc. c can be 3.2-3.4 g / cm³. 3 For example, it could be 3.2 g / cm³. 3 3.3g / cm 3 3.4g / cm 3 etc. d can be 13-45, for example, 13, 15, 20, 25, 30, 35, 40, 45. e can be 100-300 g / m³. 2 For example, it can be 100g / m 2 150g / m 2 200g / m 2 250g / m 2 300g / m 2 etc. f can be 1.45-1.65 g / cm³. 3 For example, it could be 1.45 g / cm³. 3 1.50g / cm 3 1.55g / cm 3 1.60g / cm 3 1.65g / cm 3 wait.

[0054] In the secondary battery of the present invention, the electrolyte injection volume satisfies the following formula:

[0055] Electrolyte injection volume = electrolyte density × electrode pore volume V × injection coefficient.

[0056] In this invention, the electrolyte injection volume is taken as g, calculated using the value on the right side of the equal sign.

[0057] In this invention, the electrolyte density can be 1.19-1.22 g / cm³. 3 For example, it could be 1.19 g / cm³. 3 1.20g / cm 3 1.21 g / cm 3 1.22g / cm 3 wait.

[0058] In this invention, the electrode pore volume V is determined as per formula (1) above. Formula (1) is the same as above and will not be repeated here.

[0059] In this invention, the injection coefficient can be 1.4-3.5 g / Ah, more specifically 1.4-3.0 g / Ah, for example, 1.4 g / Ah, 1.5 g / Ah, 1.6 g / Ah, 1.8 g / Ah, 2.0 g / Ah, 2.2 g / Ah, 2.5 g / Ah, 2.6 g / Ah, 2.7 g / Ah, 2.8 g / Ah, 2.9 g / Ah, 3.0 g / Ah, 3.5 g / Ah, etc.

[0060] In the secondary battery of the present invention, the battery capacity, thickness, weight, positive and negative electrode size, and N / P ratio are fixed values.

[0061] In some specific implementations, the 1C rated capacity of the battery is 15±0.25Ah; the battery thickness is 7.9±0.2mm; the battery weight is 2190±10g; the positive electrode dimensions are: length 103±0.2mm, width 97±0.2mm; the negative electrode dimensions are: length 106±0.2mm, width 101±0.2mm. The N / P ratio can be 1.08-1.13, for example, 1.08, 1.09, 1.10, 1.11, 1.12, 1.13, etc. The pore volume of the electrode can be 15-37ml, for example, 15ml, 20ml, 25ml, 30ml, 35ml, 37ml, etc.

[0062] In the secondary battery of the present invention, apart from the electrolyte, the structural design of the battery and all raw materials are known fixed values, such as the battery capacity, thickness, weight, positive and negative electrode size, and N / P ratio. The present invention provides guidance from the product design perspective by establishing a correlation formula between the electrode surface density, compaction density, and number of electrode layers (for stacked batteries, this refers to the number of stacked layers; for wound batteries, it refers to the number of layers observed from the side after winding) and the electrode pore volume (i.e., the above formula (1)). This reduces the electrode surface density and compaction density, increases the number of stacked layers, and directionally increases the electrode pore volume V (ml), providing channels and storage space for electrolyte penetration, thereby improving the electrolyte wettability of the electrode.

[0063] For example, guided by equation (1), to increase the pore volume of the electrode, the areal density of the positive electrode bifacial layer can be increased from the conventionally used median of 366.2 g / m³. 2 It becomes 290g / m² in Example 1. 2 The areal density of the negative electrode bifacial layer can be increased from the commonly used median of 214 g / m³. 2 It becomes 165.7 g / m³ as in Example 1. 2 The positive electrode compaction density is increased from the commonly used median of 3.4 g / cm³. 3 It becomes 3.2 g / cm³ as in Example 1. 3The negative electrode compaction density is higher than the commonly used median of 1.55 g / cm³. 3 It becomes 1.5 g / cm³ as in Example 1. 3 The number of positive electrode layers can be increased from 19 to 29 in Example 1, and the number of negative electrode layers can be increased from 20 to 30 in Example 1. This allows for a directional increase in the electrode pore volume V (ml), providing channels and storage space for electrolyte permeation, thereby improving the electrolyte wettability of the electrode.

[0064] In this invention, the electrolyte comprises an electrolyte, a solvent, and additives. There are no particular limitations on the types and proportions of the electrolyte, solvent, and additives; commonly used types and proportions in the art can be used. However, from the perspective of optimizing the electrolyte formulation, the proportions between the electrolyte, solvent, and additive components can be adjusted, and the types of solvent and additives can also be adjusted to further improve the wettability of the electrolyte, thereby improving the long-term cycle life and high-temperature storage performance of the battery.

[0065] In some specific embodiments, the electrolyte includes a lithium salt, such as LiPF6. The solvent includes one or more of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate. The additives include one or more of vinylene carbonate (VC), 1,3-propanesulfonate lactone (PS), vinyl sulfate (DTD), and LiPO2F2.

[0066] In some preferred embodiments, the solvents do not include propylene carbonate (PC) and diethyl carbonate (DEC). The lithium salts do not include lithium difluoro(dioxadic) phosphate (LiDFOP).

[0067] In some specific embodiments, the proportion of electrolyte can be 11.5 to 15.5% by mass, the proportion of solvent can be 81 to 85% by mass, the proportion of additive can be 2.4 to 4.4% by mass, and the total proportion of electrolyte, solvent and additive is 100% by mass. In this invention, the above-mentioned proportional relationship between electrolyte and each component solvent and additive is referred to as "Formula (2)".

[0068] More specifically, the proportion of electrolyte can be 11.5% by mass, 12.0% by mass, 12.5% ​​by mass, 13.0% by mass, 13.5% by mass, 14.0% by mass, 14.5% by mass, 15.0% by mass, 15.5% by mass, etc. The proportion of solvent can be 81% by mass, 82% by mass, 83% by mass, 84% by mass, 85% by mass, etc. The proportion of additives can be 2.4% by mass, 2.5% by mass, 2.8% by mass, 3.0% by mass, 3.2% by mass, 3.5% by mass, 3.8% by mass, 4.0% by mass, 4.4% by mass, etc.

[0069] When the electrolyte contains two or more solvents, there is no particular limitation on their ratio; it can be adjusted according to the actual situation. Similarly, when the electrolyte contains two or more additives, there is no particular limitation on their ratio; it can be adjusted according to the actual situation.

[0070] In some preferred embodiments, the content of fluorine-containing additives in the electrolyte can be reduced. For example, when the electrolyte contains LiPO2F2, the content of LiPO2F2 can be 0.1-1% by mass, such as 0.1%, 0.3%, 0.5%, 0.8%, 1.0%, etc.

[0071] In this invention, an optimized electrolyte formulation is used to establish a correlation formula between the electrolyte and each solvent component (see formula (2)). The ratio between the electrolyte and each solvent component is adjusted according to the formula, and the types of solvent and lithium salt and the content of fluorine additives are optimized, thereby improving the wettability of the electrolyte, improving the long-term cycle and high-temperature storage performance of the battery, and thus developing a high-energy-density large-size soft-pack lithium-ion battery with good electrolyte wettability.

[0072] In some preferred embodiments, when optimizing the electrolyte formulation, solvents PC and DEC can be removed, lithium salt LiDFOP can be removed, VC, PS, and DTD can be added, and the content of fluorine-containing additive LiPO2F2 can be reduced, thereby further improving the wettability of the electrolyte.

[0073] Compared with existing technologies, this invention provides a method for improving the wettability of high-energy-density, large-size soft-pack lithium-ion batteries. Under the premise that the battery's capacity, thickness, weight, positive and negative electrode sizes, and N / P ratio are known fixed values, and that the battery's structural design and all raw materials (except the electrolyte) are also known fixed values, the method first reduces the areal density and compaction of the electrodes and increases the number of stacked layers from a product design perspective. It establishes a correlation between electrode areal density, compaction, and the number of stacked layers and the electrode pore volume, directionally increasing electrode pores to provide channels and storage space for electrolyte penetration. Based on this, the electrolyte formulation is optimized, thereby improving the electrolyte wettability of the electrodes, and consequently improving the battery's long-term cycle and high-temperature storage performance, thus achieving improved wettability of high-energy-density, large-size soft-pack lithium-ion batteries. This invention uses a combination of adjusting product design and optimizing electrolyte formulation to improve electrolyte wettability, saving equipment improvement costs, without reducing the product's manufacturing feasibility and production efficiency, while simultaneously improving the battery's long-term cycle and storage performance and extending the system's lifespan.

[0074] Based on the above-described design, this invention provides a method for improving the wettability of secondary batteries and high-energy-density large-size soft-pack lithium-ion batteries. The method of this invention is conducive to large-scale application and has significant practical significance for production.

[0075] <Methods for wetting electrode sheets>

[0076] The present invention also provides an electrode wetting method, which includes the step of injecting electrolyte according to the electrolyte injection amount obtained in the above-described secondary battery to wet the electrode, thereby improving the electrolyte wettability of the electrode.

[0077] <Preparation Methods of Secondary Batteries>

[0078] The present invention also provides a method for preparing a secondary battery, including the step of wetting the electrode sheet by the electrode sheet wetting method described above.

[0079] In some specific implementation schemes, based on the product design of the above formula (1), the positive and negative electrode sheets are produced by homogenization, coating, rolling, slitting and die cutting; the positive and negative electrode sheets are baked separately, and after baking, the positive and negative electrode sheets and the separator are stacked in a Z-shape using a stacking machine, and then welded and packaged to obtain the packaged battery cell; the packaged battery cell is baked, and after baking, electrolyte with optimized electrolyte formula is injected; after injection, it is aged at high temperature and charged and discharged using a charge and discharge device to obtain a high energy density large-size soft-pack lithium-ion battery with improved wettability.

[0080] Example

[0081] The present invention will be described in detail below through embodiments. These embodiments are intended to explain the invention and should not be construed as limiting it. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0082] Example 1

[0083] The battery's capacity (1C rated capacity 15Ah), thickness (7.9±0.2mm), weight (2190±10g), positive and negative electrode dimensions (positive electrode (103±0.2)mm×(97±0.2)mm, negative electrode (106±0.2)mm×(101±0.2)mm), and N / P ratio (1.09) are known fixed values. Apart from these, the battery's structural design and all raw materials are known fixed values ​​(except for the electrolyte formulation). Assume the number of positive electrode layers a = 29, and the positive electrode bifacial density b = 290g / m³. 2 (area density through area 20cm²) 2 (Obtained by sampling device punching and weighing measurement), the positive electrode compaction density c = 3.2 g / cm³. 3(The compaction density is calculated by measuring the thickness of the rolled electrode sheet using a micrometer), the number of negative electrode layers d = a + 1 = 30, and the double-sided areal density of the negative electrode e = ab / (1.75a + 0.15) = 165.7 g / m³ 2 The negative electrode compaction density f = 1.5 g / cm³ 3 Electrolyte density 1.22 g / cm³ 3 The injection coefficient g = 1.52 g / Ah. Using the correlation formula (1) between electrode surface density, compaction density and number of stacked layers and electrode pore volume, the electrode pore volume V (ml) is calculated.

[0084] V=9.991a*(b / c / 1000*1.02+0.005)*[1-17.9118 / ((b / c / 1000*1.02+0.005) / 10*9.7*10.3) / a]+10.706d*(e / f / 1000*1.35)*[1-

[0085] 21.9890 / ((e / f / 1000*1.35) / 10*10.1*10.6) / d]=36.22ml, thus the electrolyte injection volume = electrolyte density × electrode pore volume × injection coefficient = 1.22×36.22×1.52=67.17g.

[0086] Using the above formula relating electrode areal density, compaction density, number of stacked layers, and electrode pore volume, the product design is adjusted. Compared with Examples 2-4 and Comparative Example 1, this example reduces areal density, increases the number of stacked layers, and increases electrode pore volume, thereby obtaining a high-energy-density, large-size soft-pack lithium-ion battery product design with increased electrode pore volume.

[0087] The electrolyte formulation was optimized using the ratio formula (2) between the electrolyte and the solvents and additives of each component. Based on the conventional electrolyte formulation, the solvents PC and DEC were removed, and the additives VC, PS, and DTD were added. The content of fluorine-containing additives in LiPO2F2 was reduced to 0.7%, thereby improving the wettability of the electrolyte and thus improving the long-term cycle and high-temperature storage performance of the battery. The electrolyte ratio was LiPF6 = 13.5% by mass, the solvent ratio was EC + EMC = 83.1% by mass (EC:EMC = 1:2.33), and the additive ratio was VC + PS + LiPO2F2 + DTD = 3.4% by mass (VC:PS:LiPO2F2). 2: DTD = 2.4:1:1.4:2), with the total ratio of electrolyte, solvent, and additives being 100% by mass.

[0088] Based on the product design of formula (1), the positive and negative electrode sheets are produced by homogenization, coating, rolling, slitting and die cutting; the positive and negative electrode sheets are baked separately, and after baking, the positive and negative electrode sheets and the separator are stacked in a Z-shape using a stacking machine, and then welded and packaged to obtain the packaged battery cell; the packaged battery cell is baked, and after baking, electrolyte with optimized electrolyte formula is injected; after injection, it is aged at high temperature and charged and discharged using a charge and discharge device to obtain a high energy density large-size soft-pack lithium-ion battery with improved wettability.

[0089] Example 2

[0090] The battery's capacity (1C rated capacity 15Ah), thickness (7.9±0.2mm), weight (2190±10g), positive and negative electrode dimensions (positive electrode (103±0.2)mm×(97±0.2)mm, negative electrode (106±0.2)mm×(101±0.2)mm), and N / P ratio (1.09) are known fixed values. Apart from these, the battery's structural design and all raw materials are known fixed values ​​(except for the electrolyte formulation). Assume the number of positive electrode layers a = 20, and the positive electrode double-sided areal density b = 326.9g / m³. 2 The positive electrode compaction density c = 3.2 g / cm³ 3 The number of negative electrode layers d = a + 1 = 21, and the double-sided areal density of the negative electrode e = ab / (1.75a + 0.15) = 186 g / m³ 2 The negative electrode compaction density f = 1.5 g / cm³ 3 Electrolyte density 1.22 g / cm³ 3 The injection coefficient g = 1.52 g / Ah. Using the correlation formula (1) between electrode surface density, compaction density, and number of stacked layers and electrode pore volume, the electrode pore volume V (ml) is calculated.

[0091] V=9.991a*(b / c / 1000*1.02+0.005)*[1-17.9118 / ((b / c / 1000*1.02+0.005) / 10*9.7*10.3) / a]+10.706d*(e / f / 1000*1.35)*[1-

[0092] 21.9890 / ((e / f / 1000*1.35) / 10*10.1*10.6) / d]=19.56ml, thus the injection volume=1.22×19.56×1.52=36.27g.

[0093] The electrolyte formulation was optimized using the ratio formula (2) between the electrolyte and the solvents and additives of each component. Based on the conventional electrolyte formulation, the solvents PC and DEC were removed, and the additives VC, PS, and DTD were added. The content of fluorine-containing additives in LiPO2F2 was reduced to 0.7%, thereby improving the wettability of the electrolyte and thus improving the long-term cycle and high-temperature storage performance of the battery. The electrolyte ratio was LiPF6 = 13.5% by mass, the solvent ratio was EC + EMC = 83.1% by mass (EC:EMC = 1:2.33), and the additive ratio was VC + PS + LiPO2F2 + DTD = 3.4% by mass (VC:PS:LiPO2F2). 2: DTD = 2.4:1:1.4:2), with the total ratio of electrolyte, solvent, and additives being 100% by mass.

[0094] Based on the product design of formula (1), the positive and negative electrode sheets are produced by homogenization, coating, rolling, slitting and die cutting; the positive and negative electrode sheets are baked separately, and after baking, the positive and negative electrode sheets and the separator are stacked in a Z-shape using a stacking machine, and then welded and packaged to obtain the packaged battery cell; the packaged battery cell is baked, and after baking, electrolyte with optimized electrolyte formula is injected; after injection, it is aged at high temperature and charged and discharged using a charge and discharge device to obtain a high energy density large-size soft-pack lithium-ion battery with improved wettability.

[0095] Example 3

[0096] The battery's capacity (1C rated capacity 15Ah), thickness (7.9±0.2mm), weight (2190±10g), positive and negative electrode dimensions (positive electrode (103±0.2)mm×(97±0.2)mm, negative electrode (106±0.2)mm×(101±0.2)mm), and N / P ratio (1.09) are known fixed values. Apart from these, the battery's structural design and all raw materials are known fixed values ​​(except for the electrolyte formulation). Assume the number of positive electrode layers a = 20, and the positive electrode double-sided areal density b = 326.9g / m³. 2 The positive electrode compaction density c = 3.2 g / cm³ 3 The number of negative electrode layers d = a + 1 = 21, and the double-sided areal density of the negative electrode e = ab / (1.75a + 0.15) = 186 g / m³ 2 The negative electrode compaction density f = 1.5 g / cm³ 3 Electrolyte density 1.22 g / cm³ 3 The injection coefficient g = 1.52 g / Ah. Using the correlation formula (1) between electrode surface density, compaction density and number of stacked layers and electrode pore volume, the electrode pore volume V (ml) is calculated.

[0097] V = 9.991a*(b / c / 1000*1.02+0.005)*[1-17.9118 / ((b / c / 1000*1.02+0.005) / 10*9.7*10.3) / a]+10.706d*(e / f / 1000*1.35)*[1-21.9890 / ((e / f / 1000*1.35) / 10*10.1*10.6) / d] = 19.56ml, thus the injection volume = 1.22×19.56×1.52 = 36.27g.

[0098] The electrolyte formulation was optimized using the ratio formula (2) between the electrolyte and the solvents and additives of each component. Based on the conventional electrolyte formulation, the solvents PC and DEC were removed, and the additives VC, PS, and DTD were added. The content of fluorine-containing additives in LiPO2F2 was reduced to 0.7%, thereby improving the wettability of the electrolyte and thus improving the long-term cycle and high-temperature storage performance of the battery. The electrolyte ratio was LiPF6 = 13.5% by mass, the solvent ratio was EC + EMC = 83.3% by mass (EC:EMC = 1:2.34), the VC additive ratio was adjusted to 1.0% by mass, and the additive ratio was VC + PS + LiPO2F2 + DTD = 3.2% by mass (VC:PS:LiPO2F2). 2: DTD = 2.0:1:1.4:2), with the total ratio of electrolyte, solvent, and additives being 100% by mass.

[0099] Based on the product design of formula (1), the positive and negative electrode sheets are produced by homogenization, coating, rolling, slitting and die cutting; the positive and negative electrode sheets are baked separately, and after baking, the positive and negative electrode sheets and the separator are stacked in a Z-shape using a stacking machine, and then welded and packaged to obtain the packaged battery cell; the packaged battery cell is baked, and after baking, electrolyte with optimized electrolyte formula is injected; after injection, it is aged at high temperature and charged and discharged using a charge and discharge device to obtain a high energy density large-size soft-pack lithium-ion battery with improved wettability.

[0100] Example 4

[0101] The battery's capacity (1C rated capacity 15Ah), thickness (7.9±0.2mm), weight (2190±10g), positive and negative electrode dimensions (positive electrode (103±0.2)mm×(97±0.2)mm, negative electrode (106±0.2)mm×(101±0.2)mm), and N / P ratio (1.09) are known fixed values. Apart from these, the battery's structural design and all raw materials are known fixed values ​​(except for the electrolyte formulation). Assume the number of positive electrode layers a = 20, and the positive electrode double-sided areal density b = 326.9g / m³. 2 The positive electrode compaction density c = 3.2 (3.2-3.4 g / cm³)3 The number of negative electrode layers d = a + 1 = 21, and the double-sided areal density of the negative electrode e = ab / (1.75a + 0.15) = 186 g / m³ 2 The negative electrode compaction density f = 1.5 g / cm³ 3 Electrolyte density 1.22 g / cm³ 3 The injection coefficient g = 1.52 g / Ah. Using the correlation formula (1) between electrode surface density, compaction density, and number of stacked layers and electrode pore volume, the electrode pore volume V (cm³) is calculated. 3 ),

[0102] V=9.991a*(b / c / 1000*1.02+0.005)*[1-17.9118 / ((b / c / 1000*1.02+0.005) / 10*9.7*10.3) / a]+10.706d*(e / f / 1000*1.35)*[1-

[0103] 21.9890 / ((e / f / 1000*1.35) / 10*10.1*10.6) / d]=19.56ml, thus the injection volume=1.22×19.56×1.52=36.27g.

[0104] By utilizing the correlation formulas between electrode areal density, compaction density, number of stacked layers, and electrode pore volume, the product design can be adjusted to reduce areal density and compaction density, increase the number of stacked layers, and increase electrode pore volume, thereby obtaining a high-energy-density, large-size soft-pack lithium-ion battery product design with increased electrode pore volume.

[0105] The electrolyte formulation was optimized using the ratio formula (2) between the electrolyte and the solvents and additives of each component. Based on the conventional electrolyte formulation, the solvents PC and DEC were removed, and the additives VC, PS, and DTD were added. The content of fluorine-containing additives in LiPO2F2 was reduced to improve the wettability of the electrolyte, thereby improving the long-term cycle and high-temperature storage performance of the battery. The electrolyte ratio was LiPF6 = 13.5% by mass, the solvent ratio was EC + EMC = 83.4% by mass (EC:EMC = 1:2.35), the DTD additive ratio was adjusted to 0.7% by mass, and the additive ratio was VC + PS + LiPO2F2 + DTD = 3.1% by mass (VC:PS:LiPO2F2). 2: DTD = 2.0:1:1.4:1.4), with the total ratio of electrolyte, solvent, and additives being 100% by mass.

[0106] Based on the product design of formula (1), the positive and negative electrode sheets are produced by homogenization, coating, rolling, slitting and die cutting; the positive and negative electrode sheets are baked separately, and after baking, the positive and negative electrode sheets and the separator are stacked in a Z-shape using a stacking machine, and then welded and packaged to obtain the packaged battery cell; the packaged battery cell is baked, and after baking, electrolyte with optimized electrolyte formula is injected; after injection, it is aged at high temperature and charged and discharged using a charge and discharge device to obtain a high energy density large-size soft-pack lithium-ion battery with improved wettability.

[0107] Comparative Example 1

[0108] The battery's capacity (1C rated capacity 15Ah), thickness (7.9±0.2mm), weight (2190±10g), positive and negative electrode dimensions (positive electrode: length (103±0.2)mm, width (97±0.2)mm; negative electrode: length (106±0.2)mm, width (101±0.2)mm), and N / P ratio (1.09) are known fixed values. Apart from these, the battery's structural design and all raw materials are known fixed values ​​(the electrolyte is a conventional formulation). Assume the number of positive electrode layers a = 19, and the positive electrode double-sided areal density b = 344.6g / m³. 2 The positive electrode compaction density c = 3.2 g / cm³ 3 The number of negative electrode layers d = a + 1 = 20, and the double-sided areal density of the negative electrode e = ab / (1.75a + 0.15) = 196 g / m³ 2 The negative electrode compaction density f = 1.48 g / cm³ 3 Electrolyte density 1.22 g / cm³ 3 Given an electrolyte injection coefficient g = 1.52 g / Ah, and utilizing the relationship between electrode areal density, compaction density, number of stacked layers, and battery capacity, weight, and thickness, the electrode pore volume V (ml) is calculated to be 20.26, thus yielding an electrolyte injection amount of 1.22 × 20.26 × 1.52 = 37.57 g. Based on this relationship between electrode areal density, compaction density, number of stacked layers, and battery capacity, weight, and thickness, a conventional high-energy-density, large-size soft-pack lithium-ion battery product design is obtained.

[0109] A standard electrolyte formulation is used for battery filling after encapsulation. The electrolyte ratio is LiPF6 = 14% by mass, the solvent ratio is EC + EMC + PC + DEC = 84% by mass, and the additive ratio is LiPO2F2 + LiDFOP = 2% by mass. The total ratio of electrolyte, solvent and additive is 100% by mass.

[0110] Based on the above product design, the positive and negative electrode sheets are produced by homogenization, coating, rolling, slitting, and die-cutting. The positive and negative electrode sheets are baked separately. After baking, the positive and negative electrode sheets and the separator are stacked in a Z-shape using a stacking machine, and then welded and packaged to obtain the packaged battery cell. The packaged battery cell is baked, and after baking, it is injected with electrolyte of a conventional formula. After electrolyte injection, it is aged at high temperature and charged and discharged using charge and discharge equipment to obtain a conventional high energy density large-size soft-pack lithium-ion battery.

[0111] Performance testing

[0112] The capacity retention and recovery rates of the batteries from Examples 1-4 and Comparative Example 1 after 7 days of storage at 55 degrees Celsius, as well as the capacity retention rates after cycling at room temperature and high temperature, were compared. The specific results are shown in Table 1.

[0113] Table 1 Comparison of battery electrical performance data

[0114]

[0115] As can be seen from the data in Table 1, compared with conventional methods for improving the wettability of high-energy-density large-size soft-pack lithium-ion batteries, the wettability improvement methods of Examples 1-4 for high-energy-density large-size soft-pack lithium-ion batteries resulted in the following improvements: 7-day storage capacity retention at 55 degrees Celsius increased by 1.74%, 0.86%, 0.59%, and 0.42%, respectively; 7-day storage capacity recovery at 55 degrees Celsius increased by 1.00%, 0.85%, 0.53%, and 0.42%, respectively; 600-cycle capacity retention at high temperature (45±2℃) increased by 5.15%, 4.09%, 3.42%, and 2.5%, respectively; and 600-cycle capacity retention at room temperature (25±2℃) increased by 2.53%, 1.98%, 1.66%, and 1.38%, respectively.

[0116] Comparing the capacity retention and recovery rates of the batteries in Examples 1-4 and Comparative Example 1 after 7 days of storage at 55 degrees Celsius, and the capacity retention rates after cycling at room temperature and high temperature, the wettability improvement method for high-energy-density large-size soft-pack lithium-ion batteries provided by this invention, under the premise that the battery's capacity, thickness, weight, positive and negative electrode sizes, and N / P ratio are known fixed values, and that the battery's structural design and all raw materials (except the electrolyte) are also known fixed values, firstly, from a product design perspective, the areal density and compaction density of the electrode sheets are reduced, and the number of stacked layers is increased. This establishes a relationship between the areal density, compaction density, and number of stacked layers and the pore volume of the electrode sheets. The correlation between the product design and the directional increase in electrode porosity provides channels and storage space for electrolyte penetration. Therefore, compared to Examples 2-4 and Comparative Example 1, the optimized product design of Example 1 exhibits higher capacity retention, high-temperature performance, and storage performance. Based on this, the electrolyte formulation is optimized to improve electrolyte wettability, thereby enhancing the battery's long-term cycle and high-temperature storage performance. Examples 1-4, employing optimized electrolyte formulations, show significantly improved performance compared to Comparative Example 1 with a conventional electrolyte. Examples 1-2 further optimize the electrolyte formulation based on Examples 3-4, achieving improved wettability for high-energy-density, large-size soft-pack lithium-ion batteries. By combining product design adjustments with electrolyte formulation optimization, electrolyte wettability is improved, saving equipment modification costs without reducing product manufacturing feasibility and production efficiency. Simultaneously, it enhances the battery's long-term cycle and storage performance, extending the system's lifespan.

[0117] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

[0118] Industrial availability

[0119] This invention reduces the areal density and compaction density of the electrode from a product design perspective, increases the number of stacked layers, establishes the correlation between the areal density, compaction density, and number of stacked layers of the electrode and the pore volume of the electrode, and directionally increases the pore size of the electrode to provide channels and storage space for electrolyte penetration; based on this, the electrolyte formulation is optimized to improve electrolyte wettability, thereby improving the long-term cycle and high-temperature storage performance of the battery.

Claims

1. A secondary battery comprising a positive electrode and a negative electrode, wherein the electrode plates of the positive electrode and / or the negative electrode respectively contain pores to provide space for electrolyte wetting, characterized in that, The pore volume V of the electrode conforms to the following formula: The electrode pore volume V = 9.991a*(b / c / 1000*1.02+0.005)*[1-17.9118 / ((b / c / 1000*1.02+0.005) / 10*9.7*10.3) / a]+10.706d*(e / f / 1000*1.35)*[1-21.9890 / ((e / f / 1000*1.35) / 10*10.1*10.6) / d] Where a is the number of positive electrode layers, b is the areal density of the positive electrode bifacial layer, c is the compaction density of the positive electrode, d is the number of negative electrode layers, e is the areal density of the negative electrode bifacial layer, and f is the compaction density of the negative electrode, and d = a + 1, e = ab / (1.75a + 0.15). The units for b and e are g / m³. 2 The units for c and f are g / cm³. 3 The unit of electrode pore volume V is ml. Where a is 12-44; b is 280-400; c is 3.2-3.4; d is 13-45; e is 100-300; f is 1.45-1.65, and the electrode pore volume V is 15-37. The battery has a 1C rated capacity of 15±0.25Ah; a thickness of 7.9±0.2mm; a weight of 2190±10g; the dimensions of the positive electrode are: length 103±0.2mm, width 97±0.2mm; the dimensions of the negative electrode are: length 106±0.2mm, width 101±0.2mm; and an N / P ratio of 1.08-1.

13.

2. A secondary battery, comprising a positive electrode, a negative electrode, and an electrolyte, characterized in that, The injection volume of the electrolyte satisfies the following formula: Electrolyte injection volume = electrolyte density × electrode pore volume V × injection coefficient Wherein, the electrode pore volume V = 9.991a*(b / c / 1000*1.02+0.005)*[1-17.9118 / ((b / c / 1000*1.02+0.005) / 10*9.7*10.3) / a]+10.706d*(e / f / 1000*1.35)*[1-21.9890 / ((e / f / 1000*1.35) / 10*10.1*10.6) / d], The electrolyte injection volume is calculated using the value on the right side of the equation in grams (g), the injection coefficient is 1.4-3.5 g / Ah, and the electrolyte density is 1.19-1.22 g / cm³. 3 ; a represents the number of positive electrode layers, b represents the areal density of the positive electrode on both sides, c represents the compaction density of the positive electrode, d represents the number of negative electrode layers, e represents the areal density of the negative electrode on both sides, f represents the compaction density of the negative electrode, and d = a + 1, e = ab / (1.75a + 0.15). The units for b and e are g / m³. 2 The units for c and f are g / cm³. 3 The unit of electrode pore volume V is ml. Wherein a is 12-44; b is 280-400; c is 3.2-3.4; d is 13-45; e is 100-300; f is 1.45-1.65; and the electrode pore volume V is 15-37. The electrolyte comprises an electrolyte, a solvent, and an additive, wherein the electrolyte comprises 11.5-15.5% by mass, the solvent comprises 81-85% by mass, the additive comprises 2.4-4.4% by mass, and the total proportion of the electrolyte, the solvent, and the additive is 100% by mass. The electrolyte includes lithium salt, The solvents mentioned herein do not include propylene carbonate and diethyl carbonate; the lithium salts mentioned herein do not include lithium difluoro(dioxaate) phosphate. The battery has a 1C rated capacity of 15±0.25Ah; a thickness of 7.9±0.2mm; a weight of 2190±10g; the dimensions of the positive electrode are: length 103±0.2mm, width 97±0.2mm; the dimensions of the negative electrode are: length 106±0.2mm, width 101±0.2mm; and an N / P ratio of 1.08-1.

13.

3. The secondary battery according to claim 2, wherein the lithium salt comprises LiPF6; the solvent comprises one or more of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate; and the additive comprises one or more of vinylene carbonate, 1,3-propanesulfonate lactone, ethylene sulfate, and LiPO2F2.

4. The secondary battery according to claim 2, wherein when the electrolyte contains LiPO2F2, the content of LiPO2F2 is 0.1-1 by mass.

5. A method for impregnating an electrode sheet, characterized in that, It includes the step of injecting the electrolyte obtained in the secondary battery according to claim 2 into the electrolyte to wet the electrode, thereby improving the electrolyte wettability of the electrode.

6. A method for preparing a secondary battery, comprising the step of impregnating an electrode sheet by the impregnation method described in claim 5.

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