High-energy-density cylindrical lithium iron phosphate 6.3 Ah battery

Abstract

The invention discloses a high-energy-density cylindrical lithium iron phosphate 6.3 Ah battery. The battery comprises a positive pole piece, a negative pole piece and a positive pole piece, a negative pole piece; an isolating membrane; an electrolyte; a negative electrode active material in the negative electrode diaphragm comprises two-phase mixing of graphite and silicon carbon, the proportion is 95.7%, and the gram volume is 450mAh / g; the surface density of the negative electrode diaphragm is 17.87 mg / cm < 2 >, and the compaction degree is 1.75 g / cc; a positive electrode active material in the positive electrode diaphragm comprises 2-3% of a lithium nickelate lithium supplement agent and 94.2-95.2% of lithium iron phosphate, and the gram capacity of the lithium iron phosphate is 150mAh / g; the surface density of the positive electrode diaphragm is 50mg / cm < 2 >, and the compaction degree is 2.6 g / cc; the high-energy-density cylindrical 26700 lithium iron phosphate 6.3 Ah battery prepared by the invention is a 26700 type product with the highest capacity, the mass energy density of the battery is 200Wh / kg (41.9% higher than 4.0 Ah), the volume energy density of the battery is 542Wh / L, the energy density of the battery is remarkably improved, the performance of lithium iron phosphate is improved, and the energy density and the cycling stability of the battery are enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of cylindrical lithium iron phosphate batteries, and specifically to a high-energy density cylindrical lithium iron phosphate 6.3Ah battery. Background Art

[0002] Lithium-ion batteries can be divided into cylindrical batteries, square batteries and soft-pack batteries due to their different outer packaging forms. Cylindrical batteries are widely popular because of their small volume, simple winding process, high automation degree, high production efficiency and high yield rate. In addition, cylindrical batteries also have advantages such as high battery consistency, flexible arrangement of battery cells during PACK assembly, uniform heat dissipation, strong structural rigidity and low cost, so they are widely used.

[0003] From the perspective of consumers, the main demands for new energy lithium-ion batteries can be summarized into three points: one is the highest possible endurance; the second is the fastest possible charging speed; and the third is the lowest possible price. From the current consumer market, whether it is new energy vehicles or other related application fields, high-energy density batteries are the most practical way to eliminate consumers' electricity consumption anxiety, and at the same time, they are also the most competitive performance indicators in the market.

[0004] The theoretical specific energy of lithium iron phosphate material is 170Wh / kg, and the weight energy density of the batteries usually manufactured by battery manufacturers is between 140 - 165Wh / kg. In order to meet the needs of customers and the requirements of technological development, battery manufacturers are working hard to improve the energy density of lithium-ion batteries. For this purpose, they have adopted a variety of strategies, including:

[0005] 1. Selection of cathode materials: Using ternary materials (such as NCM523, NCM622, NCM811, NCA) or high-voltage system cathode materials, high-nickel materials and lithium-rich materials. However, the thermal stability of these materials themselves is poor, and in terms of safety performance such as short circuit and pinprick, there will be phenomena of explosion and fire.

[0006] 2. Improvement of anode materials: Materials such as lithium metal. However, these materials are prone to form dendrites during charge and discharge, which may lead to internal short circuit, thereby triggering the risk of battery failure or even explosion.

[0007] 3. Research and development of new battery systems: Developing new systems such as semi-solid, all-solid batteries, lithium-sulfur batteries, lithium-air batteries, etc. However, the R & D progress of these new materials and systems in China is slow, with insufficient experience, there are many unsolved problems, the R & D cost is high and the safety is difficult to guarantee, and the use risk is relatively large.

[0008] Currently, the development ideas for high-energy-density lithium iron phosphate batteries mainly include: 1. Developing cathode and anode active materials with higher specific capacities; 2. Increasing the tap density of cathode and anode materials; 3. Increasing the content of main materials in the formulation system, reducing the usage of conductive agents and binders, and developing binders with better adhesiveness and conductive agents with better conductivity; 4. Using thinner copper foils, aluminum foils and separators, and selecting anode materials with less rebound to reduce swelling during cycling.

[0009] Currently, the typical capacities of 26700 cylindrical lithium iron phosphate batteries are 4.0 Ah, 4.6 Ah and 5.0 Ah (as shown in the invention patent applied by the applicant on September 6, 2023, with the application number 202311147035.3), and their weight energy densities are 143 Wh / kg, 156 Wh / kg and 165 Wh / kg respectively. The specific capacities and tap densities of the cathode and anode materials used in these batteries are at conventional levels, and similar materials in the market are relatively common, with relatively low development difficulty.

[0010] However, the energy density of lithium iron phosphate batteries in cylindrical batteries (including 18 series, 21 series and 26 series) is basically in the range of 140 - 165 Wh / kg. If we want to further increase the energy density on the basis of the existing structure, we will face great difficulties. Therefore, the main problems of current lithium iron phosphate cylindrical batteries include:

[0011] 1. Low energy density: The capacity of 26 series batteries is basically between 4.0 - 5.0 Ah, and there is almost no capacity reaching above 6.2 Ah. Moreover, there are almost no products with a mass energy density exceeding 200 Wh / kg in the market, lacking market competitiveness;

[0012] 2. Usage cost and safety issues: Some manufacturers use ternary materials or lithium manganate and other cathode materials in order to increase the energy density, resulting in high raw material costs, serious environmental pollution, low battery safety, and poor electrical performance;

[0013] 3. Complex production process: Optimizing the size structure to increase the energy density, such as the 46 series large cylindrical batteries using a full tab design, can increase the weight energy density by about 16%. However, the actual production process is more complex, the production cost is high, there are few mass production manufacturers and mature supporting equipment currently, and there is a lack of experience. Most manufacturers are still in the stage of structural development. Summary of the Invention

[0014] The purpose of the present invention is to provide a high-energy-density cylindrical lithium iron phosphate 6.3 Ah battery to solve the problem of low energy density of existing lithium iron phosphate batteries.

[0015] To achieve the above purpose, the present invention provides the following technical solution: A high-energy-density cylindrical lithium iron phosphate 6.3 Ah battery, comprising:

[0016] The positive electrode sheet, the positive electrode sheet includes a positive electrode current collector and a positive electrode film disposed on the surface of the positive electrode current collector;

[0017] The negative electrode sheet, the negative electrode sheet includes a negative electrode current collector and a negative electrode film disposed on the surface of the negative electrode current collector;

[0018] The separator, the separator is disposed between the positive electrode sheet and the negative electrode sheet;

[0019] The electrolyte, the electrolyte contains an organic solvent, a lithium salt and an electrolyte additive;

[0020] Among them, the negative electrode active material in the negative electrode film includes a mixture of graphite and silicon-carbon, with a proportion of 95.7% and a specific capacity of 450 mAh / g;

[0021] The areal density of the negative electrode film is 17.87 mg / cm 2 , and the compaction degree is 1.75 g / cc;

[0022] The positive electrode active material in the positive electrode film includes 2-3% lithium nickelate as a lithium supplement agent and 94.2-95.2% lithium iron phosphate, and the specific capacity of lithium iron phosphate is 150 mAh / g;

[0023] The areal density of the positive electrode film is 50 mg / cm 2 , and the compaction degree is 2.6 g / cc.

[0024] Among them, the battery is a 26700 model battery, with a mass energy density of 200 Wh / kg and a volume energy density of 542 Wh / L.

[0025] Among them, the negative electrode current collector is copper foil, and the thickness of the negative electrode current collector is 5 μm.

[0026] Among them, the positive electrode current collector is carbon-coated aluminum foil, and the thickness of the positive electrode current collector is 13 μm.

[0027] Among them, the thickness of the separator is 9 μm, and its material is PE.

[0028] Among them, the organic solvent includes a mixed solvent of cyclic carbonate and linear carbonate.

[0029] Among them, the electrolyte additive is a carboxylic acid ester low-temperature electrolyte solvent.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] The high-energy density cylindrical 26700 lithium iron phosphate 6.3Ah battery prepared by the present invention is a 26700 model product with the highest capacity. Its mass energy density is 200 Wh / kg (a 41.9% increase compared to 4.0Ah), and its volume energy density is 542 Wh / L, significantly improving the energy density of the battery, enhancing the performance of lithium iron phosphate, and strengthening the energy density and cycle stability of the battery;

[0032] By optimizing the combination of the positive electrode material, negative electrode material, separator, and electrolyte, the cylindrical lithium iron phosphate 6.3Ah battery has successfully achieved high energy density and excellent safety performance. Specifically, the negative electrode uses a composite material of graphite and silicon carbide, effectively improving the specific capacity of the negative electrode; the positive electrode enhances the performance and specific capacity of the positive electrode active material by adding a lithium supplement agent of lithium nickelate. In addition, the battery uses an ultra-thin PE separator and combines an optimized electrolyte containing an organic solvent, lithium salt, and electrolyte additive to construct a battery system with both high energy density and high safety. Brief Description of the Drawings

[0033] Figure 1 It is a comparison chart of the mass energy density between the high-energy density cylindrical lithium iron phosphate 6.3Ah battery prepared by the present invention and a conventional 4.0Ah battery;

[0034] Figure 2 It is a comparison chart of the volume energy density between the high-energy density cylindrical lithium iron phosphate 6.3Ah battery prepared by the present invention and a conventional 4.0Ah battery;

[0035] Figure 3 It is a comparison chart of the capacity between the high-energy density cylindrical lithium iron phosphate 6.3Ah battery prepared by the present invention and a conventional 4.0Ah battery;

[0036] Figure 4 It is a physical picture of the high-energy density cylindrical lithium iron phosphate 6.3Ah battery prepared by the present invention during a nail penetration test. Detailed Embodiments

[0037] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0038] Embodiment

[0039] Refer to Figures 1-4 , the present invention provides a high-energy density cylindrical lithium iron phosphate 6.3Ah battery, including:

[0040] Positive electrode sheet, the positive electrode sheet includes a positive current collector and a positive electrode film disposed on the surface of the positive current collector. The positive active material in the positive electrode film includes 2-3% lithium nickelate lithium supplement agent and 94.2-95.2% lithium iron phosphate, and the specific capacity of lithium iron phosphate is 150 mAh / g; the areal density of the positive electrode film is 50 mg / cm 2 , and the compaction density is 2.6 g / cc; the positive current collector is carbon-coated aluminum foil, and the thickness of the positive current collector is 13 μm.

[0041] Negative electrode sheet, the negative electrode sheet includes a negative current collector and a negative electrode film disposed on the surface of the negative current collector; the negative active material in the negative electrode film includes a mixture of graphite and silicon-carbon two phases, accounting for 95.7%, and the specific capacity is 450 mAh / g; the areal density of the negative electrode film is 17.87 mg / cm 2 , and the compaction density is 1.75 g / cc; the negative current collector is copper foil, and the thickness of the negative current collector is 5 μm.

[0042] Separator, the separator is disposed between the positive electrode sheet and the negative electrode sheet; the thickness of the separator is 9 μm, and its material is PE.

[0043] Electrolyte, the electrolyte contains an organic solvent, a lithium salt and an electrolyte additive; the organic solvent includes a mixed solvent of a cyclic carbonate and a linear carbonate, and the electrolyte additive is a carboxylate low-temperature electrolyte solvent.

[0044] Among them, the cylindrical lithium iron phosphate 6.3 Ah battery is a 26700 model battery, and its mass energy density is 200 Wh / kg, and the volume energy density is 542 Wh / L.

[0045] Among them, by optimizing the positive electrode material, especially introducing 2-3% lithium nickelate lithium supplement agent, and improving the material properties of the positive electrode and the negative electrode, such as the specific capacity of the positive electrode reaching 150 mAh / g, and the negative electrode being doped with graphite and silicon-carbon materials, with a specific capacity of 450 mAh / g, thus significantly improving the mass energy density and volume energy density of the battery.

[0046] Among them, by optimizing the areal density, compaction density and material ratio of the electrode, the capacity of the battery is successfully increased to 6.3 Ah, which is 41.9% higher than that of the traditional 4.0 Ah battery, making it a high-capacity product in the 26700 model.

[0047] Among them, by introducing lithium nickelate as a lithium supplement agent and optimizing the silicon-carbon doped negative electrode material, the present invention ensures the stability of the battery while increasing the energy density, enabling the battery to pass severe safety tests such as needle puncture, and ensuring the safety performance under extreme conditions.

[0048] Among them, the compaction degree and surface density of the positive electrode and the negative electrode are reasonably optimized. The compaction degree of the positive electrode film is 2.6 g / cc, and the surface density is 50 mg / cm 2 ; the compaction degree of the negative electrode film is 1.75 g / cc, and the surface density is 17.87 mg / cm 2 . Such a design ensures high energy density while maintaining the long cycle life and stability of the battery.

[0049] Among them, by improving the energy density of the battery (the mass energy density reaches 200 Wh / kg, and the volume energy density reaches 542 Wh / L) and capacity, it is applicable to application scenarios such as new energy vehicles and energy storage devices with higher requirements for battery performance.

[0050] A preparation method of a high energy density cylindrical lithium iron phosphate 6.3 Ah battery includes the following steps:

[0051] Step 1, Prepare positive and negative active materials: Mix graphite and silicon-carbon materials in proportion as the negative active material to ensure that the specific capacity reaches 450 mAh / g; Mix lithium nickelate lithium supplement agent and lithium iron phosphate to obtain the positive active material, and control the specific capacity of lithium iron phosphate at 150 mAh / g.

[0052] Step 2, Prepare positive and negative electrode sheets: Coat the negative active material on a 5 μm copper foil to form a negative electrode sheet, and control its surface density to be 17.87 mg / cm 2 , and the compaction degree is 1.75 g / cc; Similarly, coat the positive active material on a 13 μm carbon-coated aluminum foil to form a positive electrode sheet, and control its surface density to be 50 mg / cm 2 , and the compaction degree is 2.6 g / cc.

[0053] Step 3, Selection and treatment of the separator: Select a separator with a thickness of 9 μm to ensure its good insulation and thermal stability.

[0054] Step 4, Preparation of the electrolyte: Mix organic solvents, lithium salts and electrolyte additives in a certain proportion to obtain an electrolyte with excellent performance.

[0055] Step 5, Battery assembly and formation: Wind the positive and negative electrode sheets and the separator to form an electric core; then place the electric core in a battery case, inject the prepared electrolyte, and perform formation treatment.

[0056] Step 6, Performance testing and optimization: Perform various performance tests on the assembled battery, including energy density test and safety performance test, and optimize and adjust the battery according to the test results.

[0057] The test results are as shown in the appendix of the specification Figures 1-4 as shown, Figure 1Comparison chart of the mass energy density between the high-energy density cylindrical lithium iron phosphate 6.3Ah battery prepared according to the present invention and the conventional 4.0Ah battery; the mass energy density of this battery is 201 Wh / kg, which is about 41.92% higher than the mass energy density of the conventional 4.0Ah battery of the same volume (see details in Figure 1 ).

[0058] Figure 2 Comparison chart of the volume energy density between the high-energy density cylindrical lithium iron phosphate 6.3Ah battery prepared according to the present invention and the conventional 4.0Ah battery; the volume energy density of this battery is 542 Wh / L, which is about 57.5% higher than the volume energy density of the conventional 4.0Ah battery of the same volume (see details in Figure 2 ).

[0059] Figure 3 Comparison chart of the capacity between the high-energy density cylindrical lithium iron phosphate 6.3Ah battery prepared according to the present invention and the conventional 4.0Ah battery; the capacity of this battery is 6377 mAh, which is 57.5% higher than the capacity of the conventional 4.0Ah battery of the same volume (see details in Figure 3 ).

[0060] Figure 4 Physical diagram of the acupuncture experiment on the high-energy density cylindrical lithium iron phosphate 6.3Ah battery prepared according to the present invention; this battery does not catch fire or explode after acupuncture and heavy object impact, and has high safety (see details in Figure 4 ).

[0061] In summary, the present invention has successfully achieved high energy density and excellent safety performance by optimizing the combination of the positive electrode material, negative electrode material, separator and electrolyte. Specifically, the negative electrode uses a graphite and silicon-carbon composite material, effectively improving the specific capacity of the negative electrode; the positive electrode enhances the performance and specific capacity of the positive electrode active material by adding a lithium nickelate lithium supplement agent. In addition, the battery uses an ultra-thin PE separator and combines an optimized electrolyte containing an organic solvent, a lithium salt and an electrolyte additive to construct a battery system with both high energy density and high safety.

[0062] Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Claims

1. A high energy density cylindrical lithium iron phosphate 6.3Ah battery, comprising: A positive electrode sheet, the positive electrode sheet comprising a positive electrode current collector and a positive electrode membrane arranged on the surface of the positive electrode current collector; A negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a negative electrode membrane sheet disposed on the surface of the negative electrode current collector; A separator, the separator being disposed between the positive electrode sheet and the negative electrode sheet; An electrolyte, wherein the electrolyte comprises an organic solvent, a lithium salt and an electrolyte additive; It is characterized in that The negative electrode active material in the negative electrode membrane includes a mixture of graphite and silicon-carbon, accounting for 95.7% and having a gram capacity of 450 mAh / g; The surface density of the negative electrode membrane is 17.87 mg / cm 2 , compaction degree is 1.75g / cc; The positive electrode active material in the positive electrode film includes 2-3% lithium nickelate lithium supplement and 94.2-95.2% lithium iron phosphate, and the lithium iron phosphate has a gram capacity of 150 mAh / g; The surface density of the positive electrode film is 50 mg / cm 2 , compaction degree is 2.6g / cc.

2. A high energy density cylindrical lithium iron phosphate 6.3Ah battery according to claim 1, characterized in that: The battery is a 26700 model battery, with a mass energy density of 200Wh / kg and a volume energy density of 542Wh / L.

3. A high energy density cylindrical lithium iron phosphate 6.3Ah battery according to claim 1, characterized in that: The negative electrode current collector is copper foil, and the thickness of the negative electrode current collector is 5 μm.

4. A high energy density cylindrical lithium iron phosphate 6.3Ah battery according to claim 1, characterized in that: The positive electrode current collector is a carbon-coated aluminum foil, and the thickness of the positive electrode current collector is 13 μm.

5. A high energy density cylindrical lithium iron phosphate 6.3Ah battery according to claim 1, characterized in that: The thickness of the isolation film is 9 μm and the material thereof is PE.

6. A high energy density cylindrical lithium iron phosphate 6.3Ah battery according to claim 1, characterized in that: The organic solvent includes a mixed solvent of cyclic carbonate and chain carbonate.

7. A high energy density cylindrical lithium iron phosphate 6.3Ah battery according to claim 1, characterized in that: The electrolyte additive is a carboxylate low-temperature electrolyte solvent.

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