A sodium-ion battery sodium supplement, sodium-ion battery
By combining trisodium hypotriacetate with a porous conductive framework and activating it within a specific electrochemical window, combined with a liquid injection and gas extraction process, the problems of low initial coulombic efficiency and safety risks in sodium-ion batteries were solved, achieving efficient and safe sodium replenishment for sodium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-02-11
- Publication Date
- 2026-05-26
AI Technical Summary
Existing sodium-ion batteries irreversibly consume sodium ions during the formation of a solid electrolyte interface film in the first charge cycle, resulting in low initial coulombic efficiency and capacity loss. Furthermore, existing sodium replenishment agents pose safety risks and instability issues.
By using trisodium hyponitrotriacetate and a porous conductive framework nanocomposite, the decomposition path is controlled through a specific electrochemical activation window. Combined with the "liquid injection-gas extraction-liquid replenishment" process, the decomposition is ensured to proceed within a safe range, avoiding the generation of toxic gases.
It achieves efficient sodium replenishment for sodium-ion batteries, with an initial coulombic efficiency of over 91% and a capacity retention rate of over 96% after 500 cycles. The decomposition products are CO2 and stable solids, simplifying storage and processing conditions and facilitating large-scale implementation.
Smart Images
Figure CN122091808A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of sodium-ion battery technology, specifically to a sodium-ion battery sodium replenisher and a sodium-ion battery. Background Technology
[0002] During the initial charge cycle, sodium-ion batteries irreversibly consume sodium ions as a solid electrolyte interphase (SEI) film forms, resulting in low initial coulombic efficiency and capacity loss. Adding sodium replenishment agents is a key method to compensate for this capacity loss and improve battery energy density.
[0003] Currently, mainstream sodium supplements have many drawbacks: The first type (such as sodium aluminate) is strongly alkaline, which is not conducive to electrode processing, and the decomposition products (such as Al(OH)3) are insulators, which thicken the SEI film; The second type (sodium-rich metal oxides) is incompletely decomposed (40-60%), and the residual transition metal oxides will interfere with the battery voltage platform and react with the electrolyte. In addition, the decomposition may produce oxygen, and the price is expensive; The third type (such as sodium nitride and sodium phosphide) is chemically unstable and is easily oxidized or exploded under normal conditions, resulting in poor safety in large-scale processing.
[0004] Trisodium hypotriacetate (NTA-Na3) is an inexpensive, stable, and water-soluble sodium salt of an organic polycarboxylic acid. However, its direct use as a sodium supplement poses significant safety risks due to its poor conductivity and the potential for electrochemical oxidation at higher potentials, which could lead to the breaking of CN bonds and the generation of highly toxic HCN or corrosive NH3 gas. This hinders its practical application.
[0005] Therefore, developing a new type of sodium supplement that is low-cost, environmentally stable, decomposes completely, and is safe and harmless is of great practical significance. Summary of the Invention
[0006] This invention addresses the shortcomings of existing technologies by providing a sodium-ion battery supplement and a sodium-ion battery. It involves uniformly compositing trisodium hypotriacetate (NTA-Na3) with a specific porous conductive framework at the nanoscale, significantly altering its electrochemical oxidation decomposition pathway and potential. Furthermore, it designs a precise electrochemical activation window, far below NTA-Na3's intrinsic CN-bond breakage potential and matching the modified decarboxylation potential. Activation within this specific window ensures that the decomposition of NTA-Na3 is "guided" to a safe decarboxylation pathway, completely avoiding the generation of toxic products, thus achieving safe and efficient sodium supplementation. This invention overcomes the fundamental defect of NTA-Na3 directly used as a sodium supplement, which generates highly toxic gases due to CN-bond breakage, providing a sodium supplement that can safely and efficiently utilize NTA-Na3.
[0007] To address the aforementioned technical problems, the first aspect of this invention provides a sodium-ion battery sodium replenishing agent, comprising a porous conductive framework and trisodium hypotriacetate dispersed within the porous conductive framework, wherein the trisodium hypotriacetate accounts for 90-98% of the total mass of the sodium replenishing agent.
[0008] This invention provides ample confinement space and conductive interfaces through a porous conductive framework, which not only improves the overall conductivity of the material, but also promotes the uniformity of the decomposition reaction of trisodium hypotriacetate through its nanoconfinement effect, avoiding local incomplete decomposition. More importantly, it generates a "nanoconfinement effect" and an "interfacial electronic coupling effect", thereby shifting the effective oxidation and decarboxylation potential of the carboxyl group in NTA-Na3 to a lower potential, while relatively increasing the activation energy barrier for CN bond breaking.
[0009] Furthermore, the conductive framework is selected from one or more of the following materials: active porous carbon, carbon nanotubes, graphene / porous carbon composites, and composites formed by conductive polymers and porous carbon or carbon nanotubes; the conductive polymer is selected from one or more of polyaniline, polypyrrole, polythiophene, and poly(3,4-ethylenedioxythiophene).
[0010] Furthermore, the specific surface area of the porous conductive framework is greater than 1500 m². 2 / g.
[0011] Furthermore, the sodium-ion battery sodium replenishing agent is prepared by mixing an aqueous solution of trisodium hypotriacetate with a porous conductive framework slurry and then evaporating and drying it.
[0012] A second aspect of the present invention provides a sodium-ion battery, comprising a positive electrode and a negative electrode, wherein the positive electrode comprises the sodium replenishing agent described in the first aspect.
[0013] Furthermore, the amount of sodium supplement added is 3-6 wt% of the active material in the positive electrode sheet.
[0014] Furthermore, the activation method of the sodium-ion battery includes the following steps:
[0015] Activation charging: Charge with a small constant current of 0.02C to 0.1C until the voltage is 3.9V to 4.1V, and maintain the voltage constant within this range until the current drops below 0.01C.
[0016] This invention utilizes a porous conductive framework to confine the sodium-replenishing agent, reducing the decarboxylation initiation potential (~3.8V) while simultaneously setting an absolute safe upper limit voltage (4.1V). This creates an "electrochemical potential trap" within the electrode polarization range, allowing only the decarboxylation reaction to occur while effectively suppressing CN bond breakage. A constant current charging process of 0.02C-0.1C is used to reduce polarization overpotential, resulting in a more uniform potential distribution on the electrode surface, closer to the set voltmeter value, and preventing localized high-potential regions due to excessively high current density. The subsequent constant voltage stage (within the 3.9-4.1V range) ensures that all sodium-replenishing agent particles, including those with slightly higher contact resistance, have sufficient time to complete oxidative decomposition at this safe potential.
[0017] Furthermore, before the activation charging, electrolyte is injected into the assembled battery cell to the theoretically required saturation amount of X%, where X = 90-95%.
[0018] Furthermore, the activation and charging process also includes a vacuuming and degassing step. The gas is immediately evacuated after activation to quickly remove the main product CO2 and prevent gas accumulation from causing the electrode to fail to contact the electrolyte ("dry zone") or the internal pressure to rise.
[0019] Furthermore, after the vacuuming and degassing step, Y% of the theoretically saturated electrolyte is injected, Y = (100-X)*1.1; this is used to compensate for the electrolyte consumed during the decomposition process and possible side reactions, as well as the low-pressure volatilization during vacuuming, and to maintain sufficient ion transport channels during long-term circulation.
[0020] The beneficial effects of this invention are:
[0021] The invention provides triple protection through the "trisodium hypotriacetate + porous conductive framework composite", "3.9V-4.1V voltage activation", and "liquid injection-vacuuming-liquid replenishment" activation process, which strictly limits the decomposition of NTA-Na3 to a safe decarboxylation reaction pathway.
[0022] The sodium-ion battery of this invention, with its sodium replenishment agent and specific voltage activation regime, produces almost entirely CO2 gas during decomposition, with no HCN or NH3 detected by gas chromatography. The porous conductive framework not only improves the overall conductivity of the material, but its nano-confinement effect also promotes the uniformity of the decomposition reaction, avoiding localized incomplete decomposition. The NTA-Na3 decomposition rate exceeds 90% in the first cycle, and the contributed sodium ions enable the first coulombic efficiency of the full cell to reach over 91%. The pouch cell retains a capacity retention rate of better than 96% after 500 cycles, proving that the negative impact of decomposition residues on electrode interface stability is minimal.
[0023] The NTA-Na3 raw material of this invention is inexpensive, chemically stable, and not easily hygroscopic or oxidized, which greatly simplifies storage and electrode processing conditions; the preparation and activation process of the composite sodium supplement is highly compatible with existing battery production processes and is easy to implement on a large scale.
[0024] The sodium replenishing agent of this invention mainly consists of CO2 and stable solids as decomposition products. Through the accompanying "vacuuming and liquid replenishment" process, most of the CO2 can be discharged, reducing internal pressure and replenishing electrolyte loss, forming a controllable and clean sodium replenishment process. Attached Figure Description
[0025] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0026] Figure 1 This is a microscopic morphology diagram of the sodium supplement obtained in Example 1 of the present invention;
[0027] Figure 2 This is a voltage-specific capacity curve test of the battery assembled with sodium supplementation agent obtained in Example 1 of the present invention. Detailed Implementation
[0028] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0029] This embodiment relates to a sodium replenishing agent for sodium-ion batteries, comprising a porous conductive framework and trisodium hypotriacetate dispersed within the porous conductive framework, wherein the trisodium hypotriacetate accounts for 90-98% of the total mass of the replenishing agent. This embodiment provides sufficient confinement space and conductive interfaces through the porous conductive framework, which not only improves the overall conductivity of the material, but also promotes the uniformity of the decomposition reaction of trisodium hypotriacetate through its nanoconfinement effect, avoiding localized incomplete decomposition. More importantly, it generates a "nanoconfinement effect" and an "interfacial electronic coupling effect," thereby shifting the effective oxidative decarboxylation potential of the carboxyl groups in NTA-Na3 to a lower potential, while relatively increasing the activation barrier for CN bond breaking.
[0030] In a preferred embodiment, the conductive framework is selected from one or more of the following materials: active porous carbon, carbon nanotubes, graphene / porous carbon composites, and composites formed by conductive polymers and porous carbon or carbon nanotubes; the conductive polymer is selected from one or more of polyaniline, polypyrrole, polythiophene, and poly(3,4-ethylenedioxythiophene); and the specific surface area of the porous conductive framework is greater than 1500 m². 2 / g.
[0031] In a preferred embodiment, the sodium-ion battery sodium replenishing agent is prepared by mixing an aqueous solution of trisodium hypotriacetate with a porous conductive framework slurry and then evaporating and drying it.
[0032] Another embodiment provides a sodium-ion battery, including a positive electrode and a negative electrode, wherein the positive electrode includes the sodium supplement agent described in the above embodiment; the amount of sodium supplement agent added is 3-6 wt% of the active material in the positive electrode.
[0033] In a preferred embodiment, the activation method of the sodium-ion battery includes the following steps:
[0034] Activation charging: A constant current of 0.02C to 0.1C is applied until the voltage reaches 3.9V to 4.1V, and then maintained at a constant voltage within this range until the current drops below 0.01C. This embodiment utilizes a porous conductive framework to confine the sodium-adding agent, reducing the decarboxylation initiation potential (~3.8V), while simultaneously setting an absolute safe upper limit voltage (4.1V). This creates an "electrochemical potential trap" within the electrode polarization range, allowing only the decarboxylation reaction to occur while effectively suppressing CN bond breakage. The constant current charging with a small current of 0.02C-0.1C reduces the polarization overpotential, resulting in a more uniform potential distribution on the electrode surface, closer to the set voltmeter value, and preventing localized high-potential areas due to excessively high current density. The subsequent constant voltage stage (within the 3.9-4.1V range) ensures that all sodium-adding agent particles, including those with slightly higher contact resistance, have sufficient time to complete oxidative decomposition at this safe potential.
[0035] In a preferred embodiment, before activation and charging, electrolyte is injected into the assembled battery cell to the theoretical saturation requirement of X%, where X = 90-95%. After activation and charging, a vacuuming and venting step is also included. The gas is evacuated immediately after activation to quickly remove the main product CO2 and prevent gas accumulation from causing the electrode to fail to contact the electrolyte ("dry zone") or the internal pressure to rise. After the vacuuming and venting step, Y% of the theoretical saturation electrolyte requirement is injected, where Y = (100-X)*1.1. This is used to compensate for the electrolyte consumed during the decomposition process and possible side reactions, as well as the low-pressure volatilization during vacuuming, and to maintain sufficient ion transport channels during long-term cycling.
[0036] Example 1
[0037] This embodiment relates to a method for preparing and testing a sodium-ion battery, including the following steps:
[0038] (1) Preparation of sodium replenishing agent for sodium-ion batteries:
[0039] Weigh 10g of activated porous carbon (specific surface area >1500 m²) ² / g) was dispersed in 200mL of deionized water and ultrasonically treated for 1 hour to form a homogeneous slurry; under vigorous stirring, 90g of trisodium hypotriacetate was dissolved in 100mL of water to form a solution, which was then slowly added dropwise to the porous carbon slurry. After the addition was complete, the mixture was continuously stirred at 60℃ and the solvent was evaporated to dryness. The resulting solid was dried in a vacuum drying oven at 120℃ for 12 hours to obtain a black powdery sodium supplement composite material (microscopic morphology see...). Figure 1 Of which, the NTA-Na3 content is approximately 90 wt%.
[0040] (2) Preparation of sodium-ion batteries:
[0041] Positive electrode preparation: The positive electrode active material (NFPP), conductive agent (Super P), binder (PVDF) and sodium supplementation agent composite material prepared in Example 1 are mixed in a mass ratio of 92:2:2:4. N-methylpyrrolidone (NMP) is added to prepare a slurry, which is then coated on aluminum foil and dried, rolled, and cut into sheets to form a positive electrode sheet.
[0042] Preparation of negative electrode sheet: Hard carbon, acetylene black and polyvinylidene fluoride are mixed in a mass ratio of 8:1:1, water is added and stirred to form a uniform and stable negative electrode slurry. The negative electrode slurry is then uniformly coated on the surface of the negative electrode current collector, coated with a 200 μm doctor blade, dried and cold pressed to obtain the negative electrode sheet.
[0043] The negative electrode, separator, and positive electrode are stacked to obtain the battery cell, which is then packaged into a pouch battery using an aluminum-plastic casing.
[0044] (3) First activation
[0045] Inject electrolyte to completely wet the electrode (approximately 90 ml, corresponding to 92% of the theoretical required amount).
[0046] The battery was placed on a tester and charged to 4.1V at a constant current of 0.05C (based on the theoretical capacity of the positive electrode). Then, the voltage was kept constant at 4.1V until the current dropped below 0.01C, completing the initial activation. The discharge current was 0.1C. The initial coulombic efficiency was calculated according to the formula: Initial coulombic efficiency = the ratio of the initial discharge capacity to the initial charge capacity.
[0047] The battery was moved into the glove box, opened and quickly evacuated, and then replenished with 8.8% of the theoretically required amount of electrolyte before being resealed.
[0048] (4) Normal charge-discharge cycle test:
[0049] First, a 0.5 C capacity calibration was performed, and the discharge capacity was recorded as C0. Then, a 2 C charge-discharge cycle was used (charged to 3.5 V, discharged to 1.5 V). A 0.1 C capacity calibration was performed every 100 cycles, and the capacity retention rate after the 100th cycle was recorded. The cycle stability of the sodium-ion battery over 500 cycles was evaluated using the discharge capacity C5 from the 5th 0.1 C capacity calibration, and the capacity retention rate R = C5 / C0 × 100%.
[0050] Sodium supplementation effect test:
[0051] The sodium-supplementing composite material prepared in Example 1 was mixed with N-methylpyrrolidone (NMP) to form a slurry, which was then coated onto aluminum foil and dried, rolled, and cut into sheets to form a positive electrode.
[0052] In an argon-filled glove box, a CR2032 coin cell was assembled using a sodium metal sheet as the negative electrode, a glass fiber membrane as the separator, and 1M NaPF6 in EC / DEC (1:1 vol%) as the electrolyte. Voltage-specific capacity curves were then tested, and the results are shown below. Figure 2 It is evident that the sodium-supplemented composite material can release approximately 80% of its capacity at a decomposition voltage of 3.8-4.1V; above 4.1V, CN bonds may break, leading to the generation of harmful gases. The charge-discharge curves also show only charging capacity, while the discharging capacity is almost zero, indicating that the material exhibits irreversible properties.
[0053] Comparative Example 1
[0054] The difference between this comparative example and Example 1 is that step (1) is omitted, and in step (2), the sodium supplement is directly trisodium hypotriacetate. Other steps and parameters remain unchanged.
[0055] Comparative Example 2
[0056] The difference between this comparative example and Example 1 is that in step (3), the constant current is first activated and charged to 4.3V, while the other steps and parameters remain unchanged.
[0057] Comparative Example 3
[0058] The difference between this comparative example and Example 1 is that the amount of electrolyte injected in step (3) is 100% of the theoretically required amount. Other steps and parameters remain unchanged.
[0059] The performance test results of the batteries obtained in Example 1 and Comparative Examples 1-3 are shown in Table 1.
[0060] Table 1
[0061]
[0062] As shown in Table 1, Example 1 exhibits excellent first-efficiency and cycle performance. This is attributed to the uniform dispersion of trisodium hypotriacetate within the porous conductive framework and the strict control of its decomposition within the safe voltage window (3.9-4.1V), primarily resulting in a decarboxylation reaction that produces CO2 and Na. + It effectively replenishes sodium without producing toxic gases.
[0063] Compared to Example 1, in Comparative Example 1, trisodium hypotriacetate does not combine with the porous conductive framework. Pure trisodium hypotriacetate has poor conductivity and uneven distribution in the electrode, easily causing local overpotential. Local areas may be charged to high voltages, potentially triggering CN bond breakage and generating toxic gases such as HCN / NH3. This poisons the electrolyte and damages the electrode interface, leading to low sodium replenishment efficiency and rapid degradation of cycle performance. In Comparative Example 2, the activation voltage is higher, reaching 4.3V, which is close to or even exceeds the critical point for CN bond breakage. HCN and NH3 were detected in the gas. Although a composite sodium replenishment agent improves conductivity, it is still difficult to completely suppress harmful side reaction pathways at this high voltage. The generated toxic gases will continue to damage the internal chemical environment of the battery in subsequent cycles, severely impairing long-term cycle stability. In Comparative Example 3, the electrolyte was filled to the brim, but the CO2 gas generated by activation and decomposition could not be effectively discharged, forming a gas chamber inside the battery. This could lead to poor contact between the electrodes and the electrolyte and increased interfacial impedance. The lack of a "replenishment" step also meant that the electrolyte consumed by gas generation and side reactions could not be replenished, thus affecting ion conduction and long-term cycle performance.
[0064] In summary, the triple safeguards of this invention—"trisodium hypotriacetate + porous conductive framework composite," "3.9V-4.1V voltage activation," and the "liquid injection-vacuuming-liquid replenishment" activation process—strictly limit the decomposition of NTA-Na3 to a safe decarboxylation reaction pathway. With the sodium replenishment agent in the sodium-ion battery combined with the specific voltage activation regime, the gases produced by decomposition are almost entirely CO2, with no HCN or NH3 detected by gas chromatography. The porous conductive framework not only improves the overall conductivity of the material, but its nano-confinement effect further promotes the uniformity of the decomposition reaction, avoiding localized incomplete decomposition. The initial decomposition rate of NTA-Na3 exceeds 90%, and the contributed sodium ions enable the initial coulombic efficiency of the full cell to reach over 91%. The capacity retention rate of the pouch cell after 500 cycles is still better than 96%, proving that the negative impact of decomposition residues on electrode interface stability is minimal. NTA-Na3 raw material is inexpensive, chemically stable, and not easily hygroscopic or oxidized, greatly simplifying storage and electrode processing conditions. The preparation and activation process of the composite sodium replenisher is highly compatible with existing battery manufacturing processes and is easy to scale up. The decomposition products of the sodium replenisher are mainly CO2 and stable solids. Through a complementary "vacuuming and electrolyte replenishment" process, most of the CO2 can be discharged, reducing internal pressure and simultaneously replenishing electrolyte losses, forming a controllable and clean sodium replenishment process.
[0065] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.
Claims
1. A sodium replenishing agent for sodium-ion batteries, characterized in that, It includes a porous conductive framework and trisodium hypotriacetate dispersed within the porous conductive framework, wherein the trisodium hypotriacetate accounts for 90-98% of the total mass of the sodium supplement.
2. The sodium-ion battery sodium replenishing agent as described in claim 1, characterized in that, The conductive framework is selected from one or more of the following materials: active porous carbon, carbon nanotubes, graphene / porous carbon composites, and composites formed by conductive polymers and porous carbon or carbon nanotubes. The conductive polymer is selected from one or more of polyaniline, polypyrrole, polythiophene, and poly(3,4-ethylenedioxythiophene).
3. The sodium-ion battery sodium replenishing agent as described in claim 1, characterized in that, The specific surface area of the porous conductive framework is greater than 1500 m². 2 / g.
4. The sodium-ion battery sodium replenishing agent as described in claim 1, characterized in that, The sodium-ion battery sodium replenishing agent is prepared by mixing an aqueous solution of trisodium hypotriacetate with a porous conductive framework slurry and then evaporating and drying it.
5. A sodium-ion battery, characterized in that, It includes a positive electrode and a negative electrode, wherein the positive electrode includes the sodium supplement as described in any one of claims 1-4.
6. The sodium-ion battery as described in claim 5, characterized in that, The amount of sodium supplement added is 3-6 wt% of the active material in the positive electrode.
7. The sodium-ion battery as described in claim 5, characterized in that, The activation method of the sodium-ion battery includes the following steps: Activation charging: Charge with a small constant current of 0.02C to 0.1C until the voltage is 3.9V to 4.1V, and maintain the voltage constant within this range until the current drops below 0.01C.
8. The sodium-ion battery as described in claim 7, characterized in that, Before activation and charging, electrolyte is injected into the assembled battery cell to the theoretical saturation requirement of X%, where X = 90-95%.
9. The sodium-ion battery as described in claim 8, characterized in that, The activation and charging process also includes a vacuuming and exhausting step.
10. The sodium-ion battery as described in claim 9, characterized in that, After the vacuuming and venting step, replenish the theoretically saturated electrolyte by Y%, Y = (100-X)*1.1.