Application of a sodium-ion battery in a vehicle safety power supply system

Abstract

The application relates to application of a sodium ion battery in a vehicle safety power supply system and belongs to the technical field of sodium ion batteries. The cell of the sodium ion battery comprises a positive electrode sheet, a negative electrode sheet and a non-combustible wide-temperature-range electrolyte; the active material of the positive electrode sheet and the active material of the negative electrode sheet are both phosphate-based polyanion compounds, and the primary particle size D50 of the phosphate-based polyanion compound is less than or equal to 1.0 mu m; the non-combustible wide-temperature-range electrolyte is composed of polycarbonate-polyethylene oxide block copolymer, a functional additive and a sodium salt, the functional additive comprises mesoporous silicon dioxide and a flame retardant, the mesoporous silicon dioxide is loaded with ionic liquid in mesoporous channels, and the ionic conductivity of the non-combustible wide-temperature-range electrolyte is greater than or equal to 5*10 ‑3 S / cm. By optimizing the positive and negative electrode active materials and the electrolyte, the sodium ion battery can be efficiently and long-livedly operated under harsh working conditions.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery technology, and particularly relates to the application of a sodium-ion battery in a safety power system for vehicles. Background Technology

[0002] Safety power systems for large transportation vehicles such as ships, locomotives, and high-speed trains need to be able to start rapidly in emergencies (such as main power failure, fire, collision, etc.) to power navigation, communication, and escape equipment. Traditional lead-acid batteries are bulky, have low energy density (typically ≤40Wh / kg), poor high and low temperature performance (capacity decay >50% at -20℃, and severe decay due to water evaporation at high temperatures), and short cycle life, making it difficult to meet the lightweight and high reliability requirements of modern transportation equipment. Although ordinary lithium-ion batteries have higher energy density (≥150Wh / kg), they are prone to thermal runaway at high temperatures and internal structural damage under severe vibration, leading to shortened lifespan and even safety hazards, limiting their application in safety power supplies for transportation equipment.

[0003] The electrochemical energy storage battery mentioned in invention patent CN116826039A, which uses polyanion materials for both positive and negative electrodes, can fully leverage the advantages of the stable crystal structure of polyanion materials to achieve zero volume effect and long-term use. The non-flammable polymer skeleton in invention patent CN117855614A can prevent thermal runaway due to uneven battery performance, making it suitable for transportation vehicles such as high-speed trains, locomotives, and ships with extremely high safety requirements. However, it is far from suitable for use in a wide temperature range of -40℃ to 80℃.

[0004] Therefore, it is necessary to develop a new sodium-ion battery that can maintain stable output characteristics under extreme environments (such as high humidity, severe vibration, wide temperature range, and long-term float charging) and serve as a safe power supply system for ships, locomotives, and high-speed trains, significantly improving the reliability of the safe power supply system. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the problems of low energy density, poor high-temperature stability and short cycle life of lead-acid batteries in the prior art.

[0006] To address the aforementioned technical problems, this invention provides an application of sodium-ion batteries in the safety power system of transportation vehicles. By optimizing the positive and negative electrode active materials and electrolyte, sodium-ion batteries can operate efficiently and for a long time under harsh operating conditions.

[0007] The purpose of this invention is to provide an application of sodium-ion batteries in a vehicle safety power system, wherein the cell of the sodium-ion battery includes a positive electrode, a negative electrode, and a non-flammable wide-temperature electrolyte.

[0008] Both the positive and negative electrode active materials are phosphate-based polyanionic compounds with a primary particle size D50 ≤ 1.0 μm. Particles under these conditions result in a shorter diffusion path for sodium ions in the active material, especially at low temperatures where ion migration is slower. A shorter path reduces diffusion time and increases the reaction rate. Furthermore, smaller particles have a larger surface area, providing more reactive sites, promoting contact between the electrode and electrolyte, and accelerating charge transfer. Moreover, polarization is more pronounced at low temperatures; smaller particle sizes reduce polarization caused by limited ion diffusion, thereby improving the battery's charge and discharge efficiency. If the particle size is too large, the sodium ion transport distance in the crystal lattice is long, leading to a significant decrease in low-temperature performance.

[0009] The non-flammable wide-temperature-range electrolyte is composed of polycarbonate (PC)-polyethylene oxide (PEO) block copolymer, functional additives, and sodium salt. The functional additives include mesoporous silica and flame retardants. Ionic liquids are loaded within the mesoporous channels of the mesoporous silica. The ionic conductivity of the non-flammable wide-temperature-range electrolyte is ≥5×10⁻⁶. -3 S / cm.

[0010] In one embodiment of the present invention, the active material of the positive electrode is selected from Na4Fe3(PO4)2(P2O7), Na4Fe 2.5 Ti 0.5 (PO4)2(P2O7), Na4Fe 3-x Mn x One or more of (PO4)2(P2O7), Na4Mn3(PO4)2(P2O7) and Na3MnTi(PO4)3, wherein 0 < X ​​< 3;

[0011] The negative electrode is made of one or more of the active materials NaTi2(PO4)3, Na3Fe2(PO4)3 and Na3MnTi(PO4)3.

[0012] In one embodiment of the present invention, the non-flammable wide-temperature-range electrolyte contains 80%-98% polycarbonate-polyoxyethylene block copolymer, 1%-10% mesoporous silica, and 1%-10% flame retardant by weight.

[0013] The amount of sodium salt used is 0.5 mol / kg to 2 mol / kg.

[0014] In one embodiment of the present invention, the sodium salt is composed of sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) and sodium fluoroborate (NaBF3CF3);

[0015] The flame retardant is a phosphazene compound.

[0016] In one embodiment of the present invention, the molar ratio of sodium bis(trifluoromethanesulfonyl)imide and sodium fluoroborate is (3-5):1. NaTFSI provides a high degree of dissociation (dissociation energy <30kJ / mol), while NaBF3CF3 remains amorphous at -40℃, inhibiting crystallization and improving low-temperature conductivity.

[0017] In one embodiment of the present invention, the phosphazene compound is selected from one or more of hexaphenoxycyclotriphosphazene, hexaaminocyclotriphosphazene, and hexa(p-tolyloxy)cyclotriphosphazene; the thermal decomposition temperature of the phosphazene compound is >300°C, and it releases PO free radicals to quench the fire source when heated.

[0018] In one embodiment of the present invention, the pore size of the mesoporous silica is 2nm-5nm.

[0019] In one embodiment of the present invention, the ionic liquid is selected from one or more of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([EMIM][TFSI]), 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), and 1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim][BF4]).

[0020] In one embodiment of the present invention, the sodium-ion battery exhibits a charge-discharge energy efficiency ≥90% under conditions ranging from -40°C to 80°C, a cycle life ≥20,000 cycles, and a self-discharge rate <1% / month. It is particularly suitable for applications requiring vibration resistance and adaptability to a wide temperature range, meeting the stringent requirements of safety power systems for transportation vehicles. Therefore, it can serve as a safety power system for ships, locomotives, high-speed trains, and other transportation vehicles, demonstrating significant reliability.

[0021] In one embodiment of the present invention, the number of battery cells in the battery pack of the safe power system is 6-48, and shock-absorbing pads are provided between the battery cells.

[0022] In one embodiment of the present invention, the safe power supply system further includes a three-dimensional vibration damping platform; the three-dimensional vibration damping platform includes, from top to bottom, a mounting plate, a polyurethane damping layer, a spring steel support layer, a polyurethane honeycomb layer, a polyurethane substrate, and a fixing base.

[0023] In one embodiment of the present invention, the safe power supply system can monitor voltage, temperature and vibration status in real time, and switch to power supply mode within 0.5s when a main power supply failure is detected.

[0024] The technical solution of the present invention has the following advantages compared with the prior art:

[0025] (1) The non-flammable wide-temperature-range electrolyte in the sodium-ion battery of the present invention uses a polycarbonate (PC)-polyethylene oxide (PEO) block copolymer, and the ether oxygen groups of the PEO segments provide Na + The transmission channel, PC chain segment can reduce the glass transition temperature Tg to -60℃ and greatly enhance low-temperature flexibility, achieving low-temperature reliability.

[0026] (2) The mesoporous silica in the sodium-ion battery of the present invention is loaded with ionic liquid in the mesoporous channels. The ionic liquid in the mesoporous channels forms a fast transport channel, which can increase the conductivity by two orders of magnitude. At the same time, the surface hydroxyl groups form hydrogen bonds with the polymer, which enhances the mechanical strength.

[0027] (3) The three-dimensional vibration reduction platform in the safe power system described in this invention can maintain the overall structural integrity of the battery pack under complex vibration environment, ensure the relative stability of its center of mass, avoid interference caused by displacement and deformation of internal components, ensure the stable operation of key components and reliable electrical connection, and provide reliable power supply for application scenarios with strict stability requirements. Attached Figure Description

[0028] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein:

[0029] Figure 1 This is a bottom view of the battery pack of the present invention;

[0030] Figure 2 This is a wiring diagram of the safe power supply system of the present invention;

[0031] Figure 3 This is a schematic diagram of the three-dimensional vibration reduction platform of the present invention;

[0032] Figure 4 This refers to the capacity retention rate of the energy storage system after 20,000 cycles in the test example of this invention.

[0033] Explanation of reference numerals in the attached drawings: 111-Battery pack, 110-Battery cell, 112-Silicone rubber shock-absorbing pad, 11-Energy storage system, 1-Mounting plate, 2-Polyurethane damping layer, 3-Spring steel bracket layer, 4-Polyurethane honeycomb layer, 5-Polyurethane substrate, 6-Fixing base. Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. It should be understood that the specific embodiments are only used to explain the present invention, but the embodiments are not intended to limit the present invention.

[0035] In this invention, unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0036] In this invention, unless otherwise stated, the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0037] In this invention, unless otherwise specified, the experimental methods used in the embodiments of this invention are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0038] In this invention, unless otherwise stated, the pore size of the mesoporous silica used in the embodiments of this invention is 2nm-5nm.

[0039] Example 1

[0040] The safe power supply system and its preparation method of the present invention specifically include the following steps:

[0041] S1. Preparation of positive and negative electrode sheets: The active material of the positive electrode sheet is Na4Fe3(PO4)2(P2O7) with a primary particle size D50 of 0.85μm; the active material of the negative electrode sheet is NaTi2(PO4)3 with a primary particle size D50 of 0.69μm; the active material, conductive carbon black and polyvinylidene fluoride are prepared into positive and negative electrode slurries in a mass ratio of 8:1:1, and then the positive and negative electrode slurries are coated on aluminum foil with a wet coating thickness of 500μm. After drying and rolling, they are cut into the corresponding shapes to obtain the positive and negative electrode sheets.

[0042] S2. Preparation of non-flammable wide-temperature-range electrolyte: First, polycarbonate-polyoxyethylene block copolymer, mesoporous silica and flame retardant are mixed evenly in a mass ratio of 92.5:4:3.5. Then, sodium salt is added and stirred evenly to obtain non-flammable wide-temperature-range electrolyte. The sodium salt is obtained by mixing sodium bis(trifluoromethanesulfonyl)imide and sodium fluoroborate in a molar ratio of 3:1. The total sodium ion content is 1 mol / kg. The mesoporous silica channels are loaded with ionic liquid [EMIM][TFSI]. The flame retardant is hexaphenoxycyclotriphosphazene.

[0043] S3. Assembly of the battery cell: The positive electrode, negative electrode and separator are assembled into a battery cell by stacking. The cell is placed in the battery shell (square shell), and a non-flammable wide-temperature-range electrolyte is injected. The cell is repeatedly vacuumed 3 times to ensure that the non-flammable wide-temperature-range electrolyte completely wets the cell. After standing at room temperature for 60 minutes, the cell is formed and capacity tested to obtain the battery cell.

[0044] S4, Assembly of Battery Pack 111: Refer to Figure 1The cells 110 are assembled into a battery pack 111 by connecting them in series. Silicone rubber shock-absorbing pads 112 are provided between and around the cells 110. The outer shell of the battery pack is made of ABS / PP composite material and is sealed by laser welding.

[0045] S5. Assembly of the safety power system: Refer to... Figure 2 The battery pack 111 is assembled into a 20kWh energy storage system 11, where K1 and K2 are switches, and SA is a dual power supply switching switch; and installed on Figure 3 The three-dimensional vibration damping platform shown includes, from top to bottom, a mounting plate 1 (made of aluminum alloy 6061), a 3mm thick polyurethane damping layer 2 (for absorbing axial vibration), a spring steel support layer 3 (Z-direction truss, serving as three-dimensional rigid support), a 5mm thick polyurethane honeycomb layer 4 (for absorbing radial vibration dissipation), a 2mm thick polyurethane base 5 (for interface stress buffering), and a fixed base (made of Q235 steel).

[0046] Example 2

[0047] The process is basically the same as in Example 1, except for the preparation of the non-flammable wide-temperature-range electrolyte, as detailed below:

[0048] S2. Preparation of non-flammable wide-temperature-range electrolyte: First, polycarbonate-polyoxyethylene block copolymer, mesoporous silica and flame retardant are mixed evenly in a mass ratio of 92.5:4:3.5. Then, sodium salt is added and stirred evenly to obtain non-flammable wide-temperature-range electrolyte. The sodium salt is obtained by mixing sodium bis(trifluoromethanesulfonyl)imide and sodium fluoroborate in a molar ratio of 5:1. The total sodium ion content is 1 mol / kg. The mesoporous silica channels are loaded with ionic liquid [EMIM][TFSI]. The flame retardant is hexaphenoxycyclotriphosphazene.

[0049] Example 3

[0050] The process is basically the same as in Example 1, except for the preparation of the non-flammable wide-temperature-range electrolyte, as detailed below:

[0051] S2. Preparation of non-flammable wide-temperature-range electrolyte: First, polycarbonate-polyoxyethylene block copolymer, mesoporous silica and flame retardant are mixed evenly in a mass ratio of 92.5:4:3.5. Then, sodium salt is added and stirred evenly to obtain non-flammable wide-temperature-range electrolyte. The sodium salt is obtained by mixing sodium bis(trifluoromethanesulfonyl)imide and sodium fluoroborate in a molar ratio of 3:1. The total sodium ion content is 1 mol / kg. The mesoporous silica channels are loaded with ionic liquids [EMIM][TFSI]. The flame retardant is hexaaminocyclotriphosphazene.

[0052] Comparative Example 1

[0053] The process is basically the same as in Example 1, except for the preparation of the non-flammable wide-temperature-range electrolyte, as detailed below:

[0054] S2. Preparation of non-flammable wide-temperature-range electrolyte: First, polycarbonate-polyoxyethylene block copolymer, mesoporous silica and flame retardant are mixed evenly at a mass ratio of 92.5:4:3.5. Then, sodium salt is added and stirred evenly to obtain non-flammable wide-temperature-range electrolyte. Among them, sodium salt is sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), the total sodium ion content is 1 mol / kg, the mesoporous silica channels are loaded with ionic liquid [EMIM][TFSI], and the flame retardant is hexaphenoxycyclotriphosphazene.

[0055] Comparative Example 2

[0056] The process is basically the same as in Example 1, except for the preparation of the non-flammable wide-temperature-range electrolyte, as detailed below:

[0057] S2. Preparation of non-flammable wide-temperature-range electrolyte: First, polycarbonate-polyoxyethylene block copolymer, mesoporous silica and flame retardant are mixed evenly in a mass ratio of 92.5:4:3.5. Then, sodium salt is added and stirred evenly to obtain non-flammable wide-temperature-range electrolyte. The sodium salt is obtained by mixing sodium bis(trifluoromethanesulfonyl)imide and sodium fluoroborate in a molar ratio of 3:1. The total sodium ion content is 1 mol / kg. The mesoporous silica does not contain ionic liquids [EMIM][TFSI]. The flame retardant is hexaphenoxycyclotriphosphazene.

[0058] Comparative Example 3

[0059] The process is basically the same as in Example 1, except that the non-flammable wide-temperature-range electrolyte is replaced with a liquid electrolyte, namely a NaPF6 solution with a concentration of 1.15 mol / L. The solvent is obtained by mixing EC, PC and DMC in a volume ratio of 1:1:1.

[0060] Comparative Example 4

[0061] The process is basically the same as in Example 1, except that the non-flammable wide-temperature-range electrolyte is replaced with a PEO solid electrolyte. Specifically, solid polyethylene oxide (PEO) and sodium salt NaClO4 are dissolved in the organic solvent tetrahydrofuran (THF) at a mass ratio of 20:1, with the amount of sodium salt NaClO4 being 1 mol / kg. The mixture is stirred to form a solution. The solution is then cast onto a polytetrafluoroethylene (PTFE) mold, dried, and demolded to obtain the PEO solid electrolyte.

[0062] Comparative Example 5

[0063] The process is basically the same as in Example 1, except for the preparation of the positive and negative electrodes, as detailed below:

[0064] S1. Preparation of positive and negative electrode sheets: The active material of the positive electrode sheet is Na4Fe3(PO4)2(P2O7) with a primary particle size D50 of 1.54μm; the active material of the negative electrode sheet is NaTi2(PO4)3 with a primary particle size D50 of 0.69μm; the active material, conductive carbon black and polyvinylidene fluoride are prepared into positive and negative electrode slurries in a mass ratio of 8:1:1, and then the positive and negative electrode slurries are coated on aluminum foil with a wet coating thickness of 500μm. After drying and rolling, they are cut into the corresponding shapes to obtain the positive and negative electrode sheets.

[0065] Comparative Example 6

[0066] The process is basically the same as in Example 1, except for the preparation of the positive and negative electrodes, as detailed below:

[0067] S1. Preparation of positive and negative electrode sheets: The active material of the positive electrode sheet is Na4Fe3(PO4)2(P2O7) with a primary particle size D50 of 0.85μm; the active material of the negative electrode sheet is NaTi2(PO4)3 with a primary particle size D50 of 2.48μm; the active material, conductive carbon black and polyvinylidene fluoride are prepared into positive and negative electrode slurries in a mass ratio of 8:1:1, and then the positive and negative electrode slurries are coated on aluminum foil with a wet coating thickness of 500μm. After drying and rolling, they are cut into the corresponding shapes to obtain the positive and negative electrode sheets.

[0068] Comparative Example 7

[0069] The process is basically the same as in Example 1, except for the preparation of the positive and negative electrodes, as detailed below:

[0070] S1. Preparation of positive and negative electrode sheets: The active material of the positive electrode sheet is Na4Fe3(PO4)2(P2O7) with a primary particle size D50 of 1.54μm; the active material of the negative electrode sheet is NaTi2(PO4)3 with a primary particle size D50 of 2.48μm; the active material, conductive carbon black and polyvinylidene fluoride are prepared into positive and negative electrode slurries in a mass ratio of 8:1:1, and then the positive and negative electrode slurries are coated on aluminum foil with a wet coating thickness of 500μm. After drying and rolling, they are cut into the corresponding shapes to obtain the positive and negative electrode sheets.

[0071] Test Example 1

[0072] Conductivity: The conductivity of the electrolytes prepared in Examples 1-3 and Comparative Examples 1-4 was tested using a Mettler Toledo conductivity meter in accordance with GB / T 26521-2011.

[0073] Self-discharge rate: The self-discharge rate of the cells prepared in Examples 1-3 and Comparative Examples 1-6 was tested according to the capacity decay method. The cells were cycled for 3 weeks in a 25°C chamber at a rate of 0.1C / 0.1C (charged at a constant current of 0.1C to 1.6V, then charged at a constant voltage of 1.6V until the current reaches 0.01C; then discharged at a constant current of 0.1C until the voltage drops to 0.3V). The discharge capacity of the last week was taken as the initial capacity C0. The cells were then fully charged again according to the above charging procedure and stored at a constant temperature of 25°C for 30 days. After storage, the cells were discharged and the remaining capacity C1 was recorded. The self-discharge rate was calculated according to the formula: Self-discharge rate = (C0-C1) / C0×100%.

[0074] Table 1 shows the conductivity and self-discharge rate:

[0075] Table 1

[0076]

[0077]

[0078] As can be seen from Table 1, the non-flammable wide-temperature-range electrolyte prepared in the examples exhibits significant performance advantages. In terms of conductivity, its ionic conductivity remains stably maintained at ≥5×10⁻⁶. -3 The electrolyte's S / cm provides a highly efficient ion transport channel for the battery system. Cells assembled using this electrolyte exhibit a self-discharge rate of <1% / month and a charge-discharge energy efficiency of >90%. This superior performance is primarily attributed to two core mechanisms: First, the positive and negative electrode active materials employ an ion-deintercalation / deintercalation design. In the charging state, the material's lattice structure is thermodynamically stable, with a high ion diffusion barrier, effectively suppressing spontaneous ion deintercalation / deintercalation and preventing self-discharge at its source. Second, this electrolyte system exhibits high chemical compatibility with the positive and negative electrode active materials. During charge-discharge cycles, there are no side reactions such as abnormal SEI film growth or transition metal dissolution at the electrolyte-electrode interface. In contrast, traditional electrolyte systems are prone to solvent molecule reduction and decomposition on the negative electrode surface, forming an unstable SEI film that continuously consumes the active sodium source. On the positive electrode side, the electrolyte undergoes oxidative decomposition under high voltage, leading to increased impedance and capacity decay. These side reactions not only accelerate the self-discharge process but also cause significant irreversible energy loss, resulting in a substantial reduction in charge-discharge energy efficiency. This demonstrates that by optimizing the chemical design of the positive and negative electrode active materials and the electrolyte interface, the embodiments constructed a stable electrochemical reaction active interface, thereby achieving a comprehensive improvement in battery performance.

[0079] Comparing Examples 1 and 2, it can be seen that when the amount of sodium fluoroborate (NaBF4) is reduced, the low-temperature conductivity of the system decreases significantly, while the conductivity at room temperature and high temperature shows a slight increase. This is mainly attributed to the high dissociation characteristics of sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), whose anionic structure reduces the degree of ion association and promotes ion migration at high temperatures; however, at low temperatures, the solubilized sheath of NaTFSI thickens, increasing the resistance to ion diffusion and leading to a deterioration in low-temperature conductivity. The high solubility of NaBF4 at low temperatures can compensate for this, highlighting the synergistic and competitive effects of the two salts at different temperatures.

[0080] Comparing Example 1 and Comparative Example 1, it can be seen that the low-temperature conductivity decreases sharply without the use of sodium fluoroborate. This is because sodium fluoroborate can remain in an amorphous state at -40°C, inhibiting crystallization and improving low-temperature conductivity.

[0081] Comparing Example 1 and Comparative Example 2, it can be seen that when the mesoporous silica channels are not loaded with ionic liquids [EMIM][TFSI], the overall ionic conductivity decreases by about 30%. This is because the ionic liquids within the mesoporous channels can form rapid transport channels, which can significantly improve conductivity.

[0082] Comparing Example 1 and Comparative Example 3, it can be seen that the thermodynamic properties of the solvents EC (ethylene carbonate, freezing point 36.4℃), PC (propylene carbonate, freezing point -48.8℃), and DMC (dimethyl carbonate, boiling point 90℃) in conventional liquid electrolytes are limited. EC easily crystallizes and precipitates at low temperatures, while DMC volatilizes more rapidly at high temperatures, leading to a sudden change in electrolyte viscosity and impaired ion conduction. This indicates that they cannot meet the requirements for stable electrochemical performance over a wide temperature range of -40℃ to 80℃.

[0083] Comparing Example 1 and Comparative Example 4, it can be seen that at low temperatures, the ionic conductivity of conventional PEO solid electrolytes drops sharply due to restricted molecular chain activity and obstructed ion migration channels. Simultaneously, increased interfacial charge recombination leads to a significant increase in self-discharge rate, making it difficult to meet the requirements of complex operating conditions.

[0084] Test Example 2

[0085] Based on Test Example 1, the operating temperature range and flame retardant properties of the electrolytes in Example 1 and Comparative Examples 3-4 were tested; wherein, the operating temperature range was determined by testing the conductivity at different temperatures until the conductivity was less than 1×10⁻⁶. -4 If the electrolyte temperature drops to S / cm or undergoes a physical change (such as volatilization), it is deemed unusable; this temperature marks the end of the operating temperature range. Flame retardancy is tested according to the UL94HB standard, by igniting the electrolyte or immersing it in the diaphragm and then igniting it, observing the combustion. Specific test results are shown in Table 2.

[0086] Table 2

[0087] Example 1 <![CDATA[7.6×10 -3 ]]> -40 to 80 non-flammable Comparative Example 3 <![CDATA[2×10 -2 ]]> -20 to 60 Flammable Comparative Example 4 <![CDATA[1×10 -4 ]]> 0 to 80 Slow burning

[0088] As can be seen from Table 2, the electrolyte of Example 1, thanks to its unique solvent and sodium salt ratio, maintains an ionic conductivity >1×10⁻⁶ over a wide temperature range from -40°C to 80°C. -4 The S / cm of the electrolyte in Comparative Example 3 exhibits excellent non-flammable properties. Although the conventional liquid electrolyte in Comparative Example 3 has a high conductivity at 25°C, its operating temperature range is narrowed to -20°C to 60°C due to the low-temperature crystallization and high-temperature volatilization of the EC / DMC system, and its flammability significantly increases safety hazards. Although the PEO-based solid electrolyte in Comparative Example 4 has a wide range of high-temperature adaptability, its crystal structure leads to the failure of low-temperature ion transport, and it also exhibits slow propagation in combustion tests, making it difficult to meet the requirements of high-safety energy storage scenarios.

[0089] Test Example 3

[0090] The electrochemical performance of the battery cells prepared in Example 1 and Comparative Examples 5-7 was tested at different temperatures. After the battery cells were placed at the test temperature for 24 hours to reach temperature equilibrium, they were charged and discharged at a rate of 1C to obtain the discharge capacity, as shown in Table 3.

[0091] Table 3

[0092] Example 1 84 125 130 Comparative Example 5 45 125 128 Comparative Example 6 38 125 127 Comparative Example 7 17 125 125

[0093] As shown in Table 3, particle size is key to improving the low-temperature performance of battery cells. Larger particle sizes in active materials significantly reduce ion activity and migration capacity at low temperatures. Smaller particles mean shorter diffusion paths for sodium ions within the active material, especially at low temperatures where ion migration is slower. Shorter paths reduce diffusion time and increase reaction rates. Smaller particles also have a larger surface area, providing more reactive sites, promoting contact between the electrode and electrolyte, and accelerating charge transfer. More importantly, polarization is more pronounced at low temperatures, and smaller particle sizes can reduce polarization caused by limited ion diffusion, thereby improving battery performance at low temperatures.

[0094] Test Example 4

[0095] Based on Example 1, energy storage systems placed on a three-dimensional anti-vibration platform (Group A) and energy storage systems placed on a conventional platform (Group B) were subjected to cyclic performance tests under three-cycle random vibration (x, y, z) according to GB / T38031-2020. Both groups used a 10C charge-discharge acceleration test method, with capacity calibration performed at 1C every 1000 cycles. The capacity retention rate was tested after 20,000 cycles. The results are as follows: Figure 4 As shown. From Figure 4It can be seen that the capacity retention rates of the energy storage systems in Group A and Group B after 20,000 cycles were 85.7% and 28.4%, respectively. This difference mainly stems from the protection of the backup power system provided by the three-dimensional vibration isolation platform. The three-dimensional vibration reduction structure, composed of components such as mounting plates, polyurethane damping layers, spring steel support layers, polyurethane honeycomb layers, and a polyurethane substrate, provides comprehensive and efficient vibration isolation for the energy storage system. This design, leveraging the properties of various materials and structural mechanics principles, comprehensively absorbs, dissipates, and disperses vibration energy from different directions, including axial and radial directions, effectively suppressing the transmission of vibration to the energy storage system body, reducing vibration amplitude, and ensuring the stability of equipment operation. In contrast, when the energy storage system is placed on a conventional platform, under long-term irregular vibration (which is common in construction tools, such as rail joints in locomotives and the turbulence of ships), the connections between its internal electrical components face severe challenges. Under the continuous action of these irregular vibrations, the connection points of the internal electrical components of the backup power system repeatedly endure alternating stress. According to the theory of material fatigue, this alternating stress will gradually cause micro-cracks to form in the metal material at the connection points. Over time and with the accumulation of vibrations, micro-cracks propagate and converge, eventually leading to fatigue fracture at the connection points or loosening of the connection. Once fatigue fracture or loosening occurs in the connection between electrical components, the integrity of the circuit is compromised, electrons encounter additional resistance during transmission, and even open circuits may occur. This directly results in a significant reduction in the energy output efficiency of the backup power system.

[0096] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An application of a sodium-ion battery in a vehicle safety power system, characterized in that, The sodium-ion battery cell includes a positive electrode, a negative electrode, and a non-flammable wide-temperature-range electrolyte. The active material of the positive electrode and the active material of the negative electrode are both phosphate-based polyanionic compounds, and the primary particle size D50 of the phosphate-based polyanionic compounds is ≤1.0 μm. The non-flammable, wide-temperature-range electrolyte is composed of a polycarbonate-polyethylene block copolymer, functional additives, and a sodium salt. The functional additives include mesoporous silica and a flame retardant, with ionic liquids loaded within the mesoporous channels of the silica. The sodium salt is composed of sodium bis(trifluoromethanesulfonyl)imide and sodium fluoroborate. The ionic conductivity of the non-flammable, wide-temperature-range electrolyte is ≥5×10⁻⁶. -3 S / cm.

2. The application according to claim 1, characterized in that, The active material of the positive electrode is selected from Na4Fe3(PO4)2(P2O7), Na4Fe 2.5 Ti 0.5 (PO4)2(P2O7), Na4Fe 3-x Mn x One or more of (PO4)2(P2O7), Na4Mn3(PO4)2(P2O7) and Na3MnTi(PO4)3, wherein 0 < X ​​< 3; The active material of the negative electrode is selected from one or more of NaTi2(PO4)3, Na3Fe2(PO4)3 and Na3MnTi(PO4)3.

3. The application according to claim 1, characterized in that, The non-flammable wide-temperature-range electrolyte contains 80%-98% polycarbonate-polyoxyethylene block copolymer, 1%-10% mesoporous silica, and 1%-10% flame retardant by weight. The amount of sodium salt used is 0.5 mol / kg to 2 mol / kg.

4. The application according to claim 1, characterized in that, The flame retardant is a phosphazene compound.

5. The application according to claim 4, characterized in that, The phosphazene compounds are selected from one or more of hexaphenoxycyclotriphosphazene, hexaaminocyclotriphosphazene, and hexa(p-tolyloxy)cyclotriphosphazene.

6. The application according to claim 1, characterized in that, The molar ratio of sodium bis(trifluoromethanesulfonyl)imide and sodium fluoroborate is (3-5):

1.

7. The application according to claim 1, characterized in that, The mesoporous silica has a pore size of 2nm-5nm.

8. The application according to claim 1, characterized in that, The ionic liquid is selected from one or more of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium hexafluorophosphate, and 1-butyl-3-methylimidazolium tetrafluoroborate.

9. The application according to claim 1, characterized in that, The safety power system also includes a three-dimensional vibration damping platform; the three-dimensional vibration damping platform includes, from top to bottom, a mounting plate, a polyurethane damping layer, a spring steel support layer, a polyurethane honeycomb layer, a polyurethane substrate, and a fixing base.

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