Application of sodium ion battery in vehicle safety power supply system

Abstract

The invention relates to an application of a sodium ion battery in a vehicle safety power supply system, and belongs to the technical field of sodium ion batteries. A battery cell of the sodium-ion battery comprises a positive plate, a negative plate and a non-combustible wide-temperature-range electrolyte, an active material of the positive plate and an active material of the negative plate are phosphate-based polyanionic compounds, and the primary particle size D50 of the phosphate-based polyanionic compounds is less than or equal to 1.0 mu m; the non-combustible wide-temperature-range electrolyte is composed of a polycarbonate-polyoxyethylene block copolymer, a functional additive and a sodium salt, the functional additive comprises mesoporous silica and a flame retardant, an ionic liquid is loaded in a mesoporous channel of the mesoporous silica, 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 efficiently run in a long service life under severe working conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium ion batteries, and in particular relates to an application of a sodium ion battery in a safe power supply system for a vehicle. Background Art

[0002] The safety power supply systems of large vehicles such as ships, locomotives, and high-speed trains need to start quickly in emergency situations (such as main power failure, fire, collision, etc.) to power navigation, communication, and escape equipment. Traditional lead-acid batteries are large in size, have low energy density (usually ≤40Wh / kg), have poor high and low temperature performance (capacity decay >50% at -20°C, and severe decay due to water evaporation at high temperatures), and have short cycle lives, making it difficult to meet the lightweight and high reliability requirements of modern transportation equipment. Although ordinary lithium-ion batteries have a high energy density (≥150Wh / kg), they are prone to thermal runaway at high temperatures and are prone to internal structural damage in severe vibration environments, resulting in a 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 uses polyanion materials for both positive and negative electrodes, which can give full play to the advantages of the stable lattice structure of polyanion materials, achieve zero volume effect and long-term application; the non-flammable polymer skeleton in invention patent CN117855614A can ensure that the battery has uneven thermal runaway, which is suitable for high-speed railways, locomotives, ships and other means of transportation with extremely high safety performance requirements, but is far from adapting to the use environment with a wide temperature range of -40°C to 80°C.

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

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

[0006] To solve the above technical problems, the present invention provides an application of a sodium-ion battery in a vehicle safety power supply system. By optimizing the positive and negative active materials and electrolytes, the sodium-ion battery can operate efficiently and for a long life under harsh working conditions.

[0007] The present invention aims to provide an application of a sodium ion battery in a vehicle safety power supply system, wherein the sodium ion battery cell comprises a positive electrode sheet, a negative electrode sheet, and a non-flammable wide-temperature range electrolyte;

[0008] The active material of the positive electrode sheet and the active material of the negative electrode sheet are both phosphate-based polyanionic compounds, and the primary particle size D50 of the phosphate-based polyanionic compound is ≤1.0 μm. The particles under this condition shorten the diffusion path of sodium ions in the active material, especially at low temperatures, where the ion migration speed slows down. The short path can reduce the diffusion time and increase the reaction rate. In addition, small particles have a larger surface area, which can provide more reactive sites, promote contact between the electrode and the electrolyte, and accelerate the charge transfer process. Furthermore, polarization is more significant at low temperatures. Small particle size can reduce polarization caused by limited ion diffusion, thereby improving the charge and discharge efficiency of the battery. If the particle size is too large, the transmission distance of sodium ions in the crystal lattice is long, and the low-temperature performance is seriously degraded.

[0009] The non-flammable wide temperature range electrolyte is composed of a polycarbonate (PC)-polyethylene oxide (PEO) block copolymer, a functional additive, and a sodium salt. The functional additive includes mesoporous silica and a flame retardant. The mesoporous channels of the mesoporous silica are loaded with an ionic liquid. The ionic conductivity of the non-flammable wide temperature range electrolyte is ≥5×10 -3 S / cm.

[0010] In one embodiment of the present invention, the active material of the positive electrode sheet 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 active material of the negative electrode sheet is one or more of NaTi2(PO4)3, Na3Fe2(PO4)3 and Na3MnTi(PO4)3.

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

[0013] The dosage of the sodium salt is 0.5 mol / kg-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 to sodium fluoroborate is (3-5):1, NaTFSI provides a high degree of dissociation (dissociation energy <30 kJ / mol), while NaBF3CF3 remains amorphous at -40°C, 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 greater than 300° C., and PO free radicals are released upon heating to quench the fire source.

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

[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 of ≥90% at -40°C to 80°C, a cycle life of ≥20,000 cycles, and a self-discharge rate of <1% per month. This makes it particularly suitable for applications requiring vibration resistance and wide operating temperature ranges, meeting the stringent requirements of safe power systems for vehicles. Therefore, it can serve as a safe power system for vehicles such as ships, locomotives, and high-speed trains, with remarkable reliability.

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

[0022] In one embodiment of the present invention, the safe power supply system also includes a three-dimensional shock-absorbing platform; the three-dimensional shock-absorbing platform includes a mounting plate, a polyurethane damping layer, a spring steel support layer, a polyurethane honeycomb layer, a polyurethane base and a fixed base arranged in sequence from top to bottom.

[0023] In one embodiment of the present invention, the safety power supply system is capable of monitoring voltage, temperature and vibration status in real time, and switching to power supply mode within 0.5 seconds when a main power failure is detected.

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

[0025] (1) The non-flammable wide temperature range electrolyte in the sodium ion battery of the present invention adopts a polycarbonate (PC)-polyethylene oxide (PEO) block copolymer, and the ether group coordination of the PEO segment provides Na + In the transmission channel, the PC segment can reduce the glass transition temperature Tg to -60°C and greatly enhance low-temperature toughness to achieve low-temperature reliability.

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

[0027] (3) The three-dimensional shock-absorbing platform in the safe power supply system described in the present invention can maintain the overall structural integrity of the battery pack in a complex vibration environment, ensure the relative stability of its center of mass position, avoid interference between internal components due to displacement and deformation, ensure the stable operation of key components and reliable electrical connections, and continuously and efficiently supply reliable electricity for application scenarios with strict stability requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0029] Figure 1 A bottom view of the battery pack of the present invention;

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

[0031] Figure 3 is a schematic diagram of a three-dimensional shock absorbing platform of the present invention;

[0032] Figure 4 is the capacity retention rate of the energy storage system after 20,000 cycles in the test example of the present invention;

[0033] Explanation of the accompanying 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 support layer, 4-polyurethane honeycomb layer, 5-polyurethane substrate, 6-fixed base. DETAILED DESCRIPTION

[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 the present invention and implement it. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. It should be understood that the specific embodiments are only used to illustrate the present invention and are not intended to limit the present invention.

[0035] In the present invention, unless otherwise defined, technical and scientific terms used herein have the same meanings as commonly understood by one skilled in the art to which the present invention belongs.

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

[0037] In the present invention, unless otherwise stated, the experimental methods used in the examples of the present invention are conventional methods unless otherwise stated, and the materials, reagents, etc. used are all commercially available unless otherwise stated.

[0038] In the present invention, unless otherwise specified, the pore size of the mesoporous silica used in the examples of the present invention is 2 nm to 5 nm.

[0039] Example 1

[0040] The safe power supply system and preparation method thereof 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 roller pressing, they are cut into corresponding shapes to obtain positive and negative electrode sheets;

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

[0043] S3. Assembly of battery cells: The positive electrode sheet, negative electrode sheet, and separator are assembled into battery cells by stacking, placed in a battery casing (square shell), injected with non-flammable wide-temperature range electrolyte, and repeatedly vacuumed three times to ensure that the non-flammable wide-temperature range electrolyte completely penetrates the battery cell. After standing at room temperature for 60 minutes, the battery cell is formed and divided into different volumes;

[0044] S4. Assembly of battery pack 111: See Figure 1The battery cells 110 are assembled into a battery pack 111 in a series manner. Silicone rubber shock-absorbing pads 112 are provided between and around the battery 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 safety power supply system: refer to Figure 2 , assemble the battery pack 111 into a 20KWh energy storage system 11, where K1 and K2 are switches, and SA is a dual power switch; and install it in Figure 3 On the three-dimensional shock-absorbing platform shown, the three-dimensional shock-absorbing platform 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, as a 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 method is basically the same as Example 1, except that the non-flammable wide-temperature range electrolyte is prepared as follows:

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

[0049] Example 3

[0050] The method is basically the same as Example 1, except that the non-flammable wide-temperature range electrolyte is prepared as follows:

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

[0052] Comparative Example 1

[0053] The method is basically the same as Example 1, except that the non-flammable wide-temperature range electrolyte is prepared as follows:

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

[0055] Comparative Example 2

[0056] The method is basically the same as Example 1, except that the non-flammable wide-temperature range electrolyte is prepared as follows:

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

[0058] Comparative Example 3

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

[0060] Comparative Example 4

[0061] The method is basically the same as Example 1, except that the non-flammable wide temperature range electrolyte is replaced with a PEO solid electrolyte, that is, solid polyethylene oxide PEO and sodium salt NaClO4 are dissolved in an organic solvent tetrahydrofuran (THF) at a mass ratio of 20:1, and the amount of sodium salt NaClO4 is 1 mol / kg, and stirred to form a mixed solution; then the mixed solution is cast on a polytetrafluoroethylene (PTFE) mold, and the PEO solid electrolyte is obtained after drying and demolding.

[0062] Comparative Example 5

[0063] The process is basically the same as Example 1, except that the positive and negative electrodes are prepared as follows:

[0064] S1. Preparation of positive and negative electrode sheets: The active material of the positive electrode sheet is Na4Fe3(PO4)2(P2O7), and the primary particle size D50 is 1.54μm; the active material of the negative electrode sheet is NaTi2(PO4)3, and the primary particle size D50 is 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 roller pressing, they are cut into corresponding shapes to obtain positive and negative electrode sheets.

[0065] Comparative Example 6

[0066] The process is basically the same as Example 1, except that the positive and negative electrodes are prepared as follows:

[0067] S1. Preparation of positive and negative electrode sheets: The active material of the positive electrode sheet is Na4Fe3(PO4)2(P2O7), and the primary particle size D50 is 0.85μm; the active material of the negative electrode sheet is NaTi2(PO4)3, and the primary particle size D50 is 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 roller pressing, they are cut into corresponding shapes to obtain positive and negative electrode sheets.

[0068] Comparative Example 7

[0069] The process is basically the same as Example 1, except that the positive and negative electrodes are prepared as follows:

[0070] S1. Preparation of positive and negative electrode sheets: The active material of the positive electrode sheet is Na4Fe3(PO4)2(P2O7), and the primary particle size D50 is 1.54μm; the active material of the negative electrode sheet is NaTi2(PO4)3, and the primary particle size D50 is 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 roller pressing, they are cut into corresponding shapes to obtain positive and negative electrode sheets.

[0071] Test Example 1

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

[0073] Self-discharge rate: The self-discharge rate of the battery cells prepared in Examples 1-3 and Comparative Examples 1-6 was tested according to the capacity decay method. The battery was cycled for 3 weeks 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 reached 0.01C; then discharged at a constant current of 0.1C until the voltage dropped to 0.3V) in a 25°C incubator. The discharge capacity in the last week was taken as the initial capacity C0. The battery was fully charged again according to the above charging procedure and stored in a constant temperature environment of 25°C for 30 days. After storage, the battery was 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 embodiment shows significant performance advantages. In terms of electrical conductivity, its ionic conductivity is stably maintained at ≥5×10 -3 S / cm, providing efficient ion transport channels for the battery system. Cells assembled with this electrolyte achieve a self-discharge rate of <1% / month and a charge-discharge energy efficiency of >90%. This exceptional performance is primarily attributed to two key mechanisms: First, the positive and negative electrode active materials utilize an ion-deintercalation design. Under charge, the material lattice structure is thermodynamically stable, resulting in a high ion diffusion barrier, effectively suppressing spontaneous ion deintercalation and deintercalation, thus preventing self-discharge from occurring in the first place. Second, this electrolyte system exhibits high chemical compatibility with the positive and negative electrode active materials. During charge-discharge cycling, side reactions such as abnormal SEI film growth and transition metal dissolution at the electrolyte-electrode interface are absent. In contrast, conventional electrolyte systems are prone to reductive decomposition of solvent molecules 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 at high voltage, leading to increased impedance and capacity fade. These side reactions not only accelerate self-discharge but also cause significant irreversible energy losses, significantly reducing charge-discharge energy efficiency. This shows that the embodiment constructs a stable electrochemical reaction active interface by optimizing the positive and negative electrode active materials and the electrolyte interface chemistry, thereby achieving an overall 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 room-temperature and high-temperature conductivity show a slight increase. This is mainly attributed to the high dissociation characteristics of sodium bis(trifluoromethanesulfonyl)imide (NaTFSI). Its anionic structure reduces the degree of ion association and promotes ion migration at high temperatures. However, at low temperatures, the NaTFSI solvation sheath thickens, increasing the ion diffusion resistance, 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] Comparison of Example 1 and Comparative Example 1 shows that the low-temperature conductivity decreases sharply when sodium fluoroborate is not used. This is because sodium fluoroborate can remain amorphous 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 ionic liquid [EMIM][TFSI] is not loaded into the mesoporous silica mesopores, the overall ionic conductivity decreases by approximately 30%. This is because the ionic liquid within the mesopores forms a fast transport channel, significantly improving the conductivity.

[0082] Comparing Example 1 and Comparative Example 3 reveals that the thermodynamic properties of the conventional liquid electrolyte solvents EC (ethylene carbonate, freezing point 36.4°C), PC (propylene carbonate, freezing point -48.8°C), and DMC (dimethyl carbonate, boiling point 90°C) have limitations. EC readily crystallizes at low temperatures, while DMC volatilizes more rapidly at high temperatures, leading to a sudden change in electrolyte viscosity and impeded ion conduction. This indicates that the electrolyte cannot meet the requirements for stable electrochemical performance over a wide temperature range of -40°C to 80°C.

[0083] Comparing Example 1 and Comparative Example 4, it can be seen that at low temperatures, the ionic conductivity of conventional PEO solid electrolytes plummets due to restricted molecular segment mobility, which blocks ion migration pathways. Simultaneously, interfacial charge recombination intensifies, significantly increasing the self-discharge rate and 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 of Example 1 and Comparative Examples 3-4 were tested; wherein the operating temperature range is to test the conductivity at different temperatures until the conductivity is less than 1×10 -4 If the electrolyte shows no S / cm or undergoes physical changes (such as volatilization), it is confirmed to be unusable. This temperature is the end point of the operating temperature range. The flame retardancy is tested according to the UL94HB test standard. The electrolyte is ignited or immersed in the diaphragm and then ignited to observe the combustion situation. The specific test results are shown in Table 2:

[0086] Table 2

[0087] Sample Ionic conductivity at 25°C (S / cm) Operating temperature range (℃) Flame retardant properties 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 Burn

[0088] As can be seen from Table 2, the electrolyte of Example 1 maintains an ionic conductivity of >1×10- -4 S / cm, and exhibits excellent non-flammable properties; although the conventional liquid electrolyte of Comparative Example 3 has a high conductivity at 25°C, the 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 flammable properties significantly increase safety hazards; although the PEO-based solid electrolyte of Comparative Example 4 has a wide high-temperature adaptability, its crystal phase structure causes the failure of low-temperature ion transmission. At the same time, a slow spread phenomenon occurs in the combustion test, which makes it difficult to meet the needs 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. The battery cells were placed at the test temperature for 24 hours. After reaching 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] Sample Discharge capacity at -40℃ (Ah) Discharge capacity at 25℃ (Ah) Discharge capacity at 80℃ (Ah) 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 can be seen in Table 3, particle size is key to improving the low-temperature performance of battery cells. Active materials with larger particle sizes experience a significant decrease in ion activity and migration at low temperatures. Smaller particles mean a shorter diffusion path for sodium ions in the active material. Ion migration is particularly slow at low temperatures, and a shorter path can reduce diffusion time and increase reaction rates. Small particles have a larger surface area, providing more reactive sites, promoting contact between the electrode and the electrolyte, and accelerating the charge transfer process. More importantly, polarization is more pronounced at low temperatures, and a small particle size can reduce polarization caused by restricted ion diffusion, thereby improving battery performance at low temperatures.

[0094] Test Example 4

[0095] Based on Example 1, the energy storage system (Group A) placed on the three-dimensional shockproof platform and the energy storage system (Group B) placed on the conventional platform were subjected to cyclic performance tests under xyz three-cycle random vibration conditions in accordance with GB / T38031-2020. Both groups adopted the 10C charge and discharge acceleration test method, with capacity calibration at 1C every 1000 cycles. The capacity retention rate after 20,000 cycles was tested, and the results are as follows: Figure 4 As shown. Figure 4As can be seen, the energy storage systems in Groups A and B achieved capacity retention rates of 85.7% and 28.4%, respectively, after 20,000 cycles. This difference is primarily due to the protection provided by the three-dimensional vibration-proof platform for the backup power system. The three-dimensional vibration-proof structure, composed of components such as a mounting plate, a polyurethane damping layer, a spring steel support layer, a polyurethane honeycomb layer, and a polyurethane base, provides comprehensive and efficient vibration protection for the energy storage system. This design leverages the properties of various materials and the principles of structural mechanics to comprehensively absorb, dissipate, and disperse vibration energy from various directions, including axial and radial directions. This effectively suppresses vibration transmission to the energy storage system, reduces vibration amplitude, and ensures stable operation. Energy storage systems placed on conventional platforms, however, face significant challenges in the connections between their internal electrical components due to long-term, irregular vibrations (common in construction equipment, such as rail joints in locomotives and the turbulence of ships). These irregular vibrations repeatedly subject the connections within the backup power system to alternating stresses. According to material fatigue theory, this alternating stress can gradually cause microscopic cracks in the metal at these connections. Over time and with the accumulation of vibrations, microscopic cracks continue to expand and converge, eventually leading to fatigue fracture or loose connections. Once fatigue fracture or loosening occurs between electrical components, the integrity of the circuit is compromised, and electrons encounter additional resistance during transmission, or even short circuits. This directly reduces the energy output efficiency of the backup power system.

[0096] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. Application of a sodium ion battery in a vehicle safety power supply system, characterized in that: The sodium ion battery cell comprises a positive electrode sheet, a negative electrode sheet and a non-flammable 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 polyanionic compounds, and the primary particle size D50 of the phosphate-based polyanionic compound is ≤1.0 μm; The non-flammable wide temperature range electrolyte is composed of a polycarbonate-polyethylene oxide block copolymer, a functional additive, and a sodium salt. The functional additive includes mesoporous silica and a flame retardant. The mesoporous channels of the mesoporous silica are loaded with an ionic liquid. The ionic conductivity of the non-flammable wide temperature range electrolyte is ≥5×10 -3 S / cm.

2. The use 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 sheet is one or more of NaTi2(PO4)3, Na3Fe2(PO4)3 and Na3MnTi(PO4)3.

3. The use according to claim 1, characterized in that The non-flammable wide temperature range electrolyte comprises 80% to 98% by weight of a polycarbonate-polyethylene oxide block copolymer, 1% to 10% by weight of mesoporous silica, and 1% to 10% by weight of a flame retardant. The dosage of the sodium salt is 0.5 mol / kg-2 mol / kg.

4. The use according to claim 1, characterized in that The sodium salt consists of sodium bis(trifluoromethanesulfonyl)imide and sodium fluoroborate; The flame retardant is a phosphazene compound.

5. The use according to claim 4, characterized in that The molar ratio of the sodium bis(trifluoromethanesulfonyl)imide to sodium fluoroborate is (3-5):

1.

6. The use according to claim 4, characterized in that The phosphazene compound is selected from one or more of hexaphenoxy cyclotriphosphazene, hexaamino cyclotriphosphazene and hexa(p-tolyloxy)cyclotriphosphazene.

7. The use according to claim 1, characterized in that The pore size of the mesoporous silica is 2nm-5nm.

8. The use 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 use according to claim 1, characterized in that The sodium ion battery has a charge and discharge energy efficiency of ≥90% under the conditions of -40°C to 80°C, a cycle life of ≥20,000 times, and a self-discharge rate of <1% / month.

10. The use according to claim 1, characterized in that The safe power supply system also includes a three-dimensional shock-absorbing platform; the three-dimensional shock-absorbing platform includes a mounting plate, a polyurethane damping layer, a spring steel support layer, a polyurethane honeycomb layer, a polyurethane substrate and a fixed base arranged in sequence from top to bottom.

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