Additive for new energy battery, preparation method and application thereof

Abstract

The application belongs to the technical field of new energy batteries, and discloses an additive for a new energy battery, a preparation method and application. The additive has a pyridine ring structure, has the advantages of high specific capacity and low decomposition voltage, can realize lithium / sodium supplementation, improves the capacity of a lithium / sodium ion battery, and meets the application requirements of the lithium / sodium ion battery.

Description

Technical Field

[0001] This invention belongs to the field of new energy battery technology, specifically relating to an additive for new energy batteries, its preparation method, and its application. Background Technology

[0002] New energy batteries are the core carriers supporting energy transformation and transportation electrification, with lithium-ion batteries and sodium-ion batteries being the main technological routes in new energy batteries.

[0003] Lithium-ion batteries possess outstanding advantages such as high specific energy, long cycle life, and excellent charge-discharge performance, leading to a continuous expansion of their application scenarios. Their performance directly impacts the upper limit of development for related industries. However, commercial lithium-ion batteries face the challenge of irreversible capacity loss during the first charge-discharge cycle: the formation of the solid electrolyte interphase (SEI) film on the negative electrode consumes active lithium on the positive electrode. Taking conventional graphite negative electrodes as an example, the initial irreversible capacity loss is approximately 10%, while the loss rate for high-capacity negative electrodes made of silicon, tin, and other alloys is as high as 30%, directly resulting in a significant reduction in the actual energy density of the battery.

[0004] Sodium-ion batteries, with their outstanding cost-effectiveness and abundant natural resources, have become one of the most promising energy storage technologies besides lithium-ion batteries. However, improving the energy density of sodium-ion batteries has always faced severe challenges. Among them, the irreversible loss of 20% of active sodium during cycling in the hard carbon anode is the core issue leading to a significant reduction in energy density. The root cause of this problem lies in the large number of irreversible reactions occurring on the surface of the hard carbon anode and the excessive accumulation of the solid electrolyte interphase (SEI) film, resulting in a loss of active capacity similar to that in lithium-ion batteries.

[0005] To overcome the aforementioned challenges, pre-lithiation / sodium addition technology has emerged in existing technologies, mainly including negative electrode lithium / sodium addition, electrolyte lithium / sodium addition, positive electrode lithium / sodium addition, and separator lithium / sodium addition techniques. Among these, the positive electrode lithium / sodium addition additive only requires normal coating after being added together with the positive electrode material, without adding additional process conditions, making it the most likely pre-lithiation / sodium addition technology to achieve commercialization.

[0006] Cathode lithium / sodium supplementation materials include lithium oxalate, sodium oxalate, lithium squartz, sodium squartz, lithium-rich lithium iron phosphate, lithium-rich lithium nickel phosphate, sodium-rich sodium nickel phosphate, etc.; however, currently common lithium / sodium supplementation agents have significant problems. Taking lithium oxalate and sodium oxalate as examples, the decomposition voltage of lithium oxalate is 4.8 V (vs Li). + / Li), the decomposition voltage of sodium oxalate is 4.4 V (vs Na). +The decomposition voltage ( / Na) is higher than the electrochemical window of many electrolytes and far exceeds the operating voltage of many cathode materials, causing significant damage to both the electrolyte and the cathode material. Currently, catalysts are used to reduce the decomposition voltage of lithium oxalate from 4.8V to 4.25V, 4.3V, and 4.12V. While this significantly reduces the decomposition voltage, the catalyst also accelerates the decomposition of the electrolyte. Although the decomposition voltages of lithium squaric acid and sodium squaric acid are relatively low, the high cost of the raw materials currently limits their commercialization.

[0007] Current research on lithium / sodium supplements mainly focuses on reducing the decomposition voltage. Much research has been dedicated to developing catalysts to lower the decomposition voltage of common lithium / sodium supplements, but this inevitably introduces other side reactions. Therefore, developing novel lithium / sodium supplements with low decomposition voltages is essential. Summary of the Invention

[0008] To address the aforementioned technical problems, the present invention aims to provide an additive for new energy batteries, a preparation method thereof, and its application. The additive of the present invention has the advantages of high specific capacity and low decomposition voltage, enabling lithium / sodium replenishment, improving the capacity of lithium / sodium ion batteries, and meeting the application requirements of lithium / sodium ion batteries.

[0009] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides an additive for new energy batteries, wherein the additive is a lithium supplement or a sodium supplement, and the structure is as follows: ; Wherein, R1 is any one of -H, -OR, and -COOR; R2 is any one of -H, -OR, and -COOR; R3 is any one of -H, -OR, and -COOR; R4 is any one of -H, -OR, and -COOR; R5 is any one of -H, -OR, and -COOR; R is Li or Na; and at least one of R1, R2, R3, R4, and R5 contains one -OR and one -COOR. Preferably, in the same additive, all R are Li or Na.

[0010] Preferably, the additive has a structural formula including one or more of formulas (a) to (e): ; Where R is either Li or Na.

[0011] In a second aspect, the present invention provides a method for preparing an additive for a new energy battery, comprising the following steps: The precursor and the alkaline metal source are dissolved in a solvent, mixed evenly, and reacted to obtain the additive. Among them, alkaline metal source refers to alkaline lithium source or sodium source, or lithium source or sodium source whose solution is alkaline after being dissolved in a solvent; The structural formula of the precursor is: ; R6 is any one of -H, -OH, and -COOH; R7 is any one of -H, -OH, and -COOH; R8 is any one of -H, -OH, and -COOH; R9 is any one of -H, -OH, and -COOH; R 10 It is any one of -H, -OH, or -COOH, and R6, R7, R8, R9, R 10 It contains at least one -OH and one -COOH.

[0012] Preferably, in the alkaline metal source, the lithium source includes one or more of lithium carbonate, lithium bicarbonate, lithium hydroxide, lithium metal, lithium hydride, and organolithium reagents, wherein the organolithium reagents include one or more of tert-butyllithium, n-butyllithium, biphenyl lithium, and naphthalene lithium.

[0013] Preferably, in the alkaline metal source, the sodium source includes one or more of sodium carbonate, sodium hydroxide, metallic sodium, and sodium hydride.

[0014] Preferably, the solvent includes one or more of water, methanol, ethanol, tetrahydrofuran, and N,N-dimethylformamide.

[0015] Preferably, the precursor includes one or more of formulas (I) to (V): .

[0016] Preferably, the reaction time is 0.5 to 20 hours.

[0017] In a third aspect, the present invention proposes the application of an additive for new energy batteries, using the additive in the fields of lithium-ion batteries and / or sodium-ion batteries.

[0018] Preferably, the additive is used in the positive electrode material of a lithium-ion battery or a sodium-ion battery, wherein in the positive electrode material of a lithium-ion battery / sodium-ion battery, the mass of the additive is 1-20% of the total mass of the positive electrode material. More preferably, the mass of the additive is 1-15% of the total mass of the positive electrode material. Beneficial effects: The additive of the present invention contains a pyridine ring with a carboxyl group and a hydroxyl group. After the carboxyl group and the hydroxyl group are replaced by Li / Na, the electron-withdrawing ability decreases, which is beneficial to the decrease of the delithiation potential. In addition, the lithium / sodium content on the pyridine ring increases, which is also beneficial to the decrease of the delithiation / sodium potential. The lithium replenishing agent of the present invention has high specific capacity and low delithiation voltage. The theoretical specific capacity of the lithium replenishing agent of this application is 354-464 mAh / g, and the decomposition voltage is less than 4.4 V. The sodium replenishing agent of the present invention has high specific capacity and low delithiation voltage. The theoretical specific capacity of the sodium replenishing agent of this application is 292-363 mAh / g, and the decomposition voltage is less than 4.0 V.

[0019] The synthesis process of this invention is simple, the reaction yield is high, and the performance is stable. Attached Figure Description

[0020] Figure 1 The figure shows the 1H NMR spectrum of trilithium citrate, an organic lithium supplement in Example 1, where the solvent is D2O, and the chemical shift of 4.79 is the solvent peak.

[0021] Figure 2 The figure shows the 1H NMR spectrum of trisodium citrate, an organic sodium supplement in Example 2, where the solvent is D2O, and the chemical shift of 4.79 is the solvent peak.

[0022] Figure 3 The figure shows the half-cell electrical performance test diagram of the trilithium citriate organic lithium supplement synthesized with methanol as solvent in Example 3, with charge-discharge curves at 2.0-4.7 V.

[0023] Figure 4 The figure shown is a half-cell electrical performance test diagram of the organic lithium supplement 1 lithium citrinate synthesized with water as solvent in Example 3, showing the charge-discharge curves at 2.0-4.7V.

[0024] Appendix Figure 5 The image shows the half-cell electrical performance test results of the organic sodium supplement in Example 4, specifically the charge-discharge curves at 2.0-4.4 V.

[0025] Appendix Figure 6 The image shows the battery test results for the first three charge-discharge cycles of the half-cell with lithium iron phosphate cathode material and organic lithium supplementer in Example 5, at a rate of 0.1C.

[0026] Appendix Figure 7 The image shows the first charge-discharge test results of the full battery in Example 6, which uses lithium iron phosphate as the cathode material and lithium iron phosphate with an organic lithium supplement agent. The charge rate is 0.05C.

[0027] Appendix Figure 8 The image shows the first charge-discharge test results of the full battery in Example 7, consisting of sodium iron pyrophosphate as the cathode material and sodium iron pyrophosphate as the cathode material plus an organic sodium supplement agent, at a rate of 0.05C.

[0028] Figure 9 The image shows the XRD data of lithium citriate, lithium citriate 1, and lithium citriate 2 in Example 1.

[0029] Figure 10 The figures shown are the first-cycle performance test graphs of the full cells with lithium iron phosphate as the cathode material, lithium iron phosphate with added lithium thiocyanate as the cathode material, and lithium iron phosphate with added lithium citrinate as the cathode material in Examples 6 and 7, with a rate of 0.05C. Detailed Implementation

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without any creative effort.

[0031] This invention proposes an additive for new energy batteries, which functions as a lithium / sodium supplement. The additive is a lithium supplement or a sodium supplement, and contains a pyridine ring, with the following structure: ; Wherein, R1 is any one of -H, -OR, and -COOR, R2 is any one of -H, -OR, and -COOR, R3 is any one of -H, -OR, and -COOR, R4 is any one of -H, -OR, and -COOR, R5 is any one of -H, -OR, and -COOR, R is Li or Na, and at least one of R1, R2, R3, R4, and R5 contains one -OR and one -COOR.

[0032] It is easy to understand that in the same type of additive, R can only be Li or Na. That is, when the additive is a lithium supplement, R is Li, and when the additive is a sodium supplement, R is Na.

[0033] The additive of this invention contains a carboxyl group. When the hydrogen in the carboxyl group is replaced by Li / Na, the electron-withdrawing ability decreases, which is beneficial for reducing the lithium / sodium desorption potential. Furthermore, the increased lithium / sodium content on the pyridine ring also contributes to the reduction of the lithium / sodium desorption potential. The additive of this invention has the advantages of high specific capacity and low decomposition voltage. When used as a lithium supplement, its theoretical specific capacity reaches 354~464 mAh / g, and its decomposition voltage is no higher than 4.4 V. When used as a sodium supplement, its theoretical specific capacity reaches 292~363 mAh / g, and its decomposition voltage is no higher than 4 V. Specific structural formulas include one or more of formulas (a) to (e): ; Where R is either Li or Na.

[0034] Furthermore, when the additive is a lithium supplement, the additive includes one or more of formulas (1) to (5): .

[0035] Furthermore, when the additive is a sodium supplement, the additive includes one or more of formulas (6) to (10): .

[0036] This invention also proposes a method for preparing additives for new energy batteries, the specific steps of which are as follows: The precursor and the alkaline metal source are dissolved in a solvent, mixed evenly, and reacted. After the reaction, a solid is precipitated, or the solid is concentrated, filtered, and dried to obtain the additive. Among them, alkaline metal source refers to alkaline lithium source or sodium source, or lithium source or sodium source whose solution is alkaline after being dissolved in a solvent; The structural formula of the precursor is: R6 is any one of -H, -OH, or -COOH; R7 is any one of -H, -OH, or -COOH; R8 is any one of -H, -OH, or -COOH; R9 is any one of -H, -OH, or -COOH; R 10 It is any one of -H, -OH, or -COOH, and R6, R7, R8, R9, R 10 It contains at least one -OH and one -COOH.

[0037] The precursor has a structure containing a pyridine ring. The hydroxyl group attached to the pyridine ring is acidic, and the carboxyl group is also acidic. The reaction between the precursor and the alkaline metal source is an acid-base neutralization reaction. Lithium / sodium replaces the hydrogen on the hydroxyl and carboxyl groups, thereby producing a lithium / sodium supplement.

[0038] The precursor and the alkaline metal source are dissolved in a solvent to facilitate subsequent mixing and reaction. Preferably, the solvent is an organic solvent or deionized water. It is easy to understand that the appropriate solvent is selected based on the specific types of the precursor and the alkaline water source. Thorough mixing ensures sufficient contact between the precursor and the alkaline metal source, allowing them to react and generate the product. The alkaline metal source is added based on the complete reaction of the precursor in the solvent; that is, the amount of alkaline metal source used is sufficient or may be excessive relative to the precursor.

[0039] More preferably, the solvent includes one or more of water, methanol, ethanol, tetrahydrofuran, and N,N-dimethylformamide. During the preparation process, if the product is insoluble in the solvent, it is filtered after the reaction to obtain a solid product; if the product is soluble in the solvent, the solvent needs to be concentrated to precipitate the solid before filtration.

[0040] Preferably, in the alkaline metal source, the lithium source includes one or more of lithium carbonate, lithium bicarbonate, lithium hydroxide, lithium metal, lithium hydride, and organolithium reagents, wherein the organolithium reagents include tert-butyllithium, n-butyllithium, biphenyl lithium, naphthalene lithium, etc.

[0041] Preferably, in the alkaline metal source, the sodium source includes one or more of sodium carbonate, sodium hydroxide, metallic sodium, and sodium hydride.

[0042] More preferably, a corresponding precursor is selected based on the structural formula of the pre-synthesized additive, the precursor including one or more of formulas (I) to (V): .

[0043] Preferably, the reaction time is 0.5 to 20 h; the drying conditions are vacuum drying for 10 to 24 h and drying temperature for 80 to 120 °C.

[0044] The preparation process of this invention is simple, with the advantages of high reaction yield and stable product performance, making it suitable for industrial production.

[0045] When the additive of the present invention is used in the cathode material of lithium-ion / sodium-ion batteries, the additive has the advantages of high specific capacity and low delithiation / sodium voltage. The decomposition products are partially soluble in the electrolyte, the degree of irreversible delithiation / sodium is high, and some gaseous products are discharged at once during the formation process, so there will be no continuous gas production that would cause battery safety problems.

[0046] Positive electrode materials generally include positive electrode active materials, conductive agents, and binders. This invention further incorporates additives into the positive electrode material to achieve lithium / sodium supplementation. This invention innovatively proposes a new lithium / sodium supplementation material for application in the fields of lithium-ion batteries or sodium-ion batteries.

[0047] When the additive is a lithium replenisher, its application in the field of lithium-ion batteries can be as follows: the additive is added to the positive electrode of the lithium-ion battery. For example, the positive electrode material of a lithium-ion battery includes positive electrode active material, conductive agent, binder and additive.

[0048] More preferably, in the positive electrode material, the mass percentage of the positive electrode active material is 80% to 90% of the total mass of the positive electrode material; the mass of the conductive agent is 2% to 10% of the total mass of the positive electrode material; the mass of the binder is 2% to 10% of the total mass of the positive electrode material; and the mass of the additive is 1% to 15% of the total mass of the positive electrode material.

[0049] More preferably, the preparation method of the positive electrode material of lithium-ion battery is as follows: positive electrode active material, conductive agent, binder and additive are added to a grinding tank according to the above dosage range, and solvent NMP (N-methylpyrrolidone) is added to make a slurry, wherein the solid content of the slurry is 15%~30%, and then the slurry is ground for 1 hour. The ground slurry is then coated on a current collector such as aluminum foil and dried to obtain the positive electrode material of lithium-ion battery.

[0050] Preferably, in the positive electrode material of the lithium-ion battery, the positive electrode active material is a conventional material, such as one or more of lithium iron phosphate materials, carbon-coated lithium iron phosphate materials, lithium nickel cobalt manganese oxide ternary materials, doped and modified lithium nickel cobalt manganese oxide ternary materials, lithium manganese iron phosphate materials, lithium cobalt oxide materials, and lithium manganese oxide materials. More preferably, the positive electrode active material of the lithium-ion battery is lithium iron phosphate material or carbon-coated lithium iron phosphate material.

[0051] When the additive is a sodium replenisher, its application in the sodium-ion battery field can be: the additive can be directly added to the positive electrode material, or the additive can be combined with a PE separator to form a composite sodium replenisher PE separator. The following explains both scenarios.

[0052] When additives are added directly to the cathode material, the cathode material of a sodium-ion battery includes the cathode active material, conductive agent, binder, and additives.

[0053] In the cathode material, the mass percentage of the positive electrode active material is 80% to 90% of the total mass of the cathode material; the mass of the conductive agent is 2% to 10% of the total mass of the cathode material; the mass of the binder is 2% to 10% of the total mass of the cathode material; and the mass of the additive is 1% to 15% of the total mass of the cathode material.

[0054] Furthermore, the preparation method of the positive electrode material of sodium-ion battery is as follows: positive electrode active material, conductive agent, binder and additive are added to a grinding jar in the proportions provided above, and solvent NMP (N-methylpyrrolidone) is added to make the solid content of the slurry 15%~30%. Then, the slurry is ground for 1 hour, coated on aluminum foil, and dried to obtain sodium-ion positive electrode material.

[0055] When the additive forms a PE separator with a composite sodium-replenishing agent, the PE separator with the composite sodium-replenishing agent includes the additive, a conductive agent, and a binder. Specifically, in the PE separator with the composite sodium-replenishing agent, the mass of the sodium-replenishing agent is 50%–80% of the total mass of the PE separator; the mass of the binder is 10%–20% of the total mass of the PE separator; and the mass of the conductive agent is 10%–30% of the total mass of the PE separator. At this point, the positive electrode material of the sodium-ion battery is a conventional positive electrode, which includes positive electrode active material, conductive agent, and binder. For example, the positive electrode active material of the sodium-ion battery accounts for 80% to 90% of the total positive electrode mass; the conductive agent accounts for 4% to 10% of the total positive electrode mass; and the binder accounts for 4% to 10% of the total positive electrode mass.

[0056] Furthermore, the preparation method of the PE diaphragm with composite sodium supplement is as follows: additives, conductive agents and binders are added to a grinding tank in the proportions provided above, and solvent NMP (N-methylpyrrolidone) is added to make the slurry solid content 15%~30%. Then, the mixture is ground for 1 hour, the slurry is coated on the PE diaphragm, and after drying, the PE diaphragm with composite sodium supplement is obtained.

[0057] Correspondingly, the preparation method of the positive electrode material of sodium-ion battery is as follows: add positive electrode active material, conductive agent and binder into a grinding jar according to the proportion provided above, add solvent NMP (N-methylpyrrolidone) to make the solid content of slurry 15%~30%, then grind for 1 hour, coat the slurry on aluminum foil, and dry to obtain sodium-ion positive electrode material.

[0058] In the positive electrode materials of sodium-ion batteries, the positive electrode active material is a conventional material, such as one or more of polyanionic materials, layered metal oxide materials, and Prussian blue materials. Polyanionic materials include one or more of sodium iron pyrophosphate, sodium iron phosphate, sodium vanadium phosphate, sodium manganese phosphate, and sodium iron sulfate; layered metal oxide materials include one or both of sodium iron manganate and sodium nickel manganese titanate; and Prussian blue materials include sodium ferricyanide. More preferably, the positive electrode active material of sodium-ion batteries is sodium iron pyrophosphate.

[0059] Preferably, in the positive electrode material of lithium-ion / sodium-ion batteries, the conductive agent is a conventional material, such as one or more of Super P, Ketjen Black, acetylene black, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, and graphene oxide.

[0060] Preferably, in the positive electrode material of lithium-ion / sodium-ion batteries, the binder is a conventional material, such as one or more of polyvinylpyrrolidone, polyvinylidene fluoride, polyethylene oxide, polytetrafluoroethylene, sodium carboxymethyl cellulose, and copolymers of styrene and butadiene.

[0061] The technical solution of the present invention will be described in detail below with specific embodiments.

[0062] Example 1 The method for preparing lithium citrinate is as follows: (1) When methanol is used as solvent: 2,6-dihydroxypyridinecarboxylic acid (citric acid) (purity ≥98.5%) and lithium hydroxide monohydrate (purity ≥99.0%) are used as reaction raw materials. The molar ratio of 2,6-dihydroxypyridinecarboxylic acid to lithium hydroxide monohydrate is 1:3. The above raw materials are added to 200 mL of methanol, and then stirred at 70 °C for 3 h. After the solid in the solution turns yellow, the solid is filtered and dried in an oven at 100 °C to obtain trilithium citric acid.

[0063] (2) When water is used as a solvent: 2,6-dihydroxypyridinecarboxylic acid (citric acid) (purity ≥98.5%) and lithium hydroxide monohydrate (purity ≥99.0%) are used as reaction raw materials. 2,6-dihydroxypyridinecarboxylic acid and lithium hydroxide monohydrate are dissolved in deionized water at a molar ratio of 1:3 as combination one. 2,6-dihydroxypyridinecarboxylic acid and lithium hydroxide monohydrate are dissolved in deionized water at a molar ratio of 1:2 as combination two. After the raw materials have completely dissolved and reacted, the solution is evaporated and concentrated. After solids appear, the solids obtained from combination one and combination two are filtered separately. Then, the solids are dried in an oven at 100 °C to obtain lithium citrinate 1 (i.e., the product of combination one) and lithium citrinate 2 (i.e., the product of combination two).

[0064] The XRD patterns of lithium citriate, lithium citriate 1, and lithium citriate 2 are shown below. Figure 9 As shown.

[0065] Example 2 Preparation of trisodium citrate: The preparation steps are the same as those for trilithium citrate in Example 1, except that lithium hydroxide monohydrate in Example 1 is replaced with sodium hydroxide, and the other steps remain unchanged.

[0066] Example 3 Half-cell test with pure lithium supplement: The lithium citrinate obtained in Example 1 was ground and mixed evenly with conductive agent SP carbon black and binder PVDF at a mass ratio of 5:3:2. NMP (N-methylpyrrolidone) was added to form a slurry with a solid content of 15%. The slurry was then ground in a grinding jar for 1 hour. The ground slurry was uniformly coated onto the positive current collector aluminum foil and dried to obtain a positive electrode sheet with pure lithium supplementation. The lithium citrinate 1 obtained in Example 1 was used to prepare a positive electrode sheet with pure lithium supplementation following the same steps.

[0067] The pure lithium-added positive electrode sheet and lithium sheet were assembled into a coin cell. The coin cell was installed on the fixture of the battery testing system and charged at a constant current of 0.1C to 4.7 / 4.4 V. Then it was charged at a constant voltage of 4.7 / 4.4 V until the current was less than 0.05C. After standing for 1 min, it was discharged at a constant current of 0.1C to 2.0V. The charge / discharge specific capacity was recorded.

[0068] Example 4 Half-cell test of pure sodium supplement: The trisodium citrinate obtained in Example 2 was ground and mixed evenly with conductive agent SP carbon black and binder PVDF at a mass ratio of 5:3:2. NMP (N-methylpyrrolidone) was added to form a slurry with a solid content of 15%. The slurry was then ground in a grinding jar for 1 hour. The ground slurry was uniformly coated onto the positive electrode current collector aluminum foil and dried to obtain a positive electrode sheet with pure sodium supplementation.

[0069] The positive electrode and sodium electrode were assembled into a coin cell. The coin cell was mounted on the fixture of the battery testing system and charged at a constant current of 0.1C to 4.4V. Then it was charged at a constant voltage of 4.4V until the current was less than 0.05C. After standing for 1 minute, it was discharged at a constant current of 0.1C to 2.0V. The charge / discharge specific capacity was recorded.

[0070] Example 5 Half-cell test of lithium iron phosphate with added lithium supplement: The lithium citriene tartarate prepared in Example 1 was ground and mixed evenly with lithium iron phosphate (positive electrode active material), SP carbon black (conductive agent), and PVDF (binder) at a mass ratio of 75:5:10:10. NMP (N-methylpyrrolidone) was added to form a slurry with a solid content of 30%. The slurry was then ground in a grinding jar for 1 hour. The ground slurry was uniformly coated onto the aluminum foil of the positive electrode current collector and dried to obtain the positive electrode sheet.

[0071] The positive electrode and lithium sheet were assembled into a coin cell. The coin cell was mounted on the fixture of the battery testing system and charged to 4.7V under constant current at a charging current of 0.1C. After standing for 1 minute, it was discharged to 2.0V under constant current at a discharging current of 0.1C. The charge / discharge specific capacity was recorded.

[0072] Example 6 Full-cell test of lithium iron phosphate batteries with added lithium supplementation agent: 1. Preparation of negative electrode sheet: Negative electrode graphite, conductive agent SP carbon black and PVDF are mixed and ground in a mass ratio of 9:0.5:0.5. NMP is added to form a slurry with a solid content of 30%. The slurry is placed in a grinding jar and ground for 1 h. Then the slurry is evenly coated on the negative electrode current collector copper foil and dried to obtain the negative electrode sheet.

[0073] 2. Preparation of positive electrode sheet: The positive electrode sheet was prepared according to the steps of Example 5. In the positive electrode sheet, the ratio of lithium iron phosphate, lithium supplementer trilithium citrate, conductive agent SP carbon black and binder PVDF was 75:5:10:10.

[0074] 3. Assembly of coin cell: The prepared positive and negative electrode sheets and the separator are assembled into a coin cell. The capacity ratio of the positive and negative electrodes is controlled to be between 1 and 1.2. Then, the cell is charged to 4.7 V at a constant current of 0.05 C, and after standing for 1 min, it is discharged to 2.5 V at a constant current of 0.1 C. The charge / discharge specific capacity is recorded.

[0075] Example 7 1. Preparation of negative electrode sheet: Negative electrode hard carbon, conductive agent SP carbon black and PVDF are mixed and ground in a mass ratio of 9:0.5:0.5. Then NMP is added to make the solid content of the slurry 30%. The slurry is placed in a grinding tank and ground for 1 h. Then the slurry is evenly coated on the negative electrode current collector aluminum foil and dried to obtain the negative electrode sheet.

[0076] 2. Preparation of the positive electrode sheet: The positive electrode active material sodium iron pyrophosphate, conductive agent SP carbon black, and binder PVDF are mixed and ground at a mass ratio of 92:4:4. Then NMP is added to make the solid content of the slurry 30%. The slurry is ground in a grinding jar for 1 hour. Then the slurry is uniformly coated on the positive electrode current collector aluminum foil and dried to obtain the positive electrode sheet. The surface density of the active material in the positive electrode sheet is 10.1 mg / cm³. 2 .

[0077] 3. PE diaphragm coating with composite sodium supplement: The sodium supplement trisodium citrinate, conductive agent SP carbon black, and PVDF were ground and mixed together at a mass ratio of 8:1:1. NMP was then added to achieve a slurry solid content of 30%, and the mixture was ground in a grinding jar for 1 hour. The slurry was then evenly coated onto one side of a PE membrane to obtain a PE membrane with a composite sodium supplement. The areal density of the active sodium supplement on the membrane was 1.7 mg / cm³. 2 .

[0078] 4. Assembly of coin cell: Cut the prepared positive electrode sheet into a 12mm diameter disc and the PE separator with sodium-supplementing agent into a 16mm diameter disc. Attach the positive electrode active material side of the positive electrode sheet to the PE separator side with sodium-supplementing agent, then place a glass fiber separator on top, and finally place a hard carbon negative electrode sheet to assemble the coin cell. Control the N / P ratio between 1 and 1.2. Then, charge the cell to 4.4V at a constant current of 0.05C, let it stand for 1 minute, and then discharge it to 1.5V at a constant current of 0.1C. Record the charge / discharge specific capacity.

[0079] Comparative Example 1 Lithium iron phosphate full battery test: 1. Preparation of negative electrode: The preparation method is the same as that of the negative electrode in Example 6.

[0080] 2. Preparation of positive electrode sheet: Similar to the preparation method of positive electrode sheet in Example 5, except that lithium citriene supplementation agent is not added in this comparative example, and the ratio of positive electrode material lithium iron phosphate, conductive agent sp carbon black and binder PVDF is 80:10:10.

[0081] 3. Assembly of button cell full battery: Assembly and testing were carried out according to the button cell full battery installation and testing conditions in Example 6.

[0082] Comparative Example 2 Full cell test of sodium iron pyrophosphate: 1. Preparation of negative electrode: The preparation steps are the same as those for the negative electrode in Example 7.

[0083] 2. Preparation of the positive electrode: Similar to the preparation of the positive electrode in Example 7.

[0084] The difference lies in the fact that the composite PE separator does not contain the sodium supplement trisodium citrate, and the positive electrode material sodium iron pyrophosphate, conductive agent SP carbon black and binder PVDF have a mass ratio of 92:4:4.

[0085] 3. Assembly of button cells: The assembly and testing conditions of button cells in this comparative example are basically the same as those in Example 7, except that a layer of composite sodium supplementation agent PE membrane is not added.

[0086] The battery performance test results of the above embodiments and comparative examples are shown in Table 1.

[0087] Table 1 shows the battery performance test results of Examples 3-7 and Comparative Examples 1-2. .

[0088] Data from Examples 3 and 4 in Table 1 show that the irreversible capacities of the organic lithium supplement and organic sodium supplement synthesized from 2,6-dihydroxypyridinecarboxylic acid (citric acid) reached 422 mAh / g and 324 mAh / g, respectively. Their decomposition voltage is lower than the upper limit voltage of the positive electrode active material, proving that the organic lithium supplement and organic sodium supplement of this invention have feasible lithium / sodium compensation effects.

[0089] From Example 5 and its appendices Figure 6 It can be seen that after adding an organic lithium replenishing agent to the cathode material lithium iron phosphate, the specific capacity of the first charge at a cutoff of 4.7V reached 196 mAh / g, and the specific capacity of the first discharge was 160 mAh / g. This shows that the organic lithium replenishing agent does not have an adverse effect on the cathode material.

[0090] Examples 6 and 7, along with Comparative Examples 1 and 2, demonstrate that the lithium and sodium supplements, when used in a full-cell system, improve the specific capacity of the battery, as shown in the attached figures.Figure 7 and 8 As shown, adding 6.25% lithium replenisher (i.e., the lithium replenisher replaces 6.25% of the cathode material lithium iron phosphate, calculated by mass of lithium iron phosphate) increased the first-cycle discharge from 132 mAh / g to 158 mAh / g; adding sodium replenisher increased the first-cycle discharge from 60 mAh / g to 82 mAh / g. This demonstrates that the lithium and sodium replenishers successfully compensated for the loss of active lithium and sodium ions due to the formation of the SEI film.

[0091] In Examples 1 and 2, methanol was used as the solvent for synthesizing trilithium citrate and trisodium citrate. The synthesized trilithium citrate and trisodium citrate salts are insoluble in methanol, and the solids can be separated by simple filtration. Moreover, methanol can be reused, and there is no need to use reagents such as lithium hydride and sodium hydride. This synthesis method is more environmentally friendly and cost-effective. Figure 1 and 2 The nuclear magnetic resonance hydrogen spectrum proved that the hydrogen substitution reaction on all hydroxyl groups was successful.

[0092] The XRD results of the product obtained in Example 1 are as follows: Figure 9 As shown, it can be seen that lithium citrate can only be synthesized in water to form dilithium citrate, and trilithium citrate cannot be synthesized directly in water. Figure 3 and Figure 4 The results show that their specific capacities all exceed 460 mAh / g, among which... Figure 4 There was a false capacity utilization, presumably due to the oxidation of a hydroxyl group on the lithium citrinate dilithium salt. For example... Figure 10 As shown, adding the same proportion of lithium citrate resulted in a higher first-cycle discharge specific capacity when synthesized from methanol, further confirming that the lithium salt synthesized in water is dilithium citrate. According to the data in Table 1 and the attached figures, dilithium citrate, when used as an additive, also exhibits good lithium replenishment effects.

[0093] In summary, the additive of this invention has the advantages of high specific capacity and low decomposition voltage, enabling lithium / sodium compensation, improving the capacity of lithium / sodium ion batteries, and meeting the application requirements of lithium / sodium ion batteries. Electrochemical performance tests show that this lithium / sodium compensation additive has a feasible compensation effect, and the products generated after the first decomposition do not affect the positive electrode active material. Its application in lithium / sodium ion batteries is beneficial to improving the electrochemical performance of the battery.

[0094] The embodiments provided by the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention, and the descriptions of the embodiments above are only for the purpose of helping to understand the core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. An additive for new energy batteries, characterized in that, The additive is a lithium supplement or sodium supplement, with the following structure: ； Wherein, R1 is any one of -H, -OR, and -COOR, R2 is any one of -H, -OR, and -COOR, R3 is any one of -H, -OR, and -COOR, R4 is any one of -H, -OR, and -COOR, R5 is any one of -H, -OR, and -COOR, R is Li or Na, and at least one of R1, R2, R3, R4, and R5 contains one -OR and one -COOR.

2. The additive according to claim 1, characterized in that, The structural formula of the additive includes one or more of formulas (a) to (e): ； Where R is either Li or Na.

3. A method for preparing an additive for new energy batteries, characterized in that, The additive as described in claim 1 or 2 is prepared by the following steps: The precursor and the alkaline metal source are dissolved in a solvent, mixed evenly, and reacted to obtain the additive. Among them, alkaline metal source refers to alkaline lithium source or sodium source, or lithium source or sodium source whose solution is alkaline after being dissolved in a solvent; The structural formula of the precursor is: ; R6 is any one of -H, -OH, and -COOH; R7 is any one of -H, -OH, and -COOH; R8 is any one of -H, -OH, and -COOH; R9 is any one of -H, -OH, and -COOH; R 10 It is any one of -H, -OH, or -COOH, and R6, R7, R8, R9, R 10 It contains at least one -OH and one -COOH.

4. The preparation method according to claim 3, characterized in that, In alkaline metal sources, lithium sources include one or more of lithium carbonate, lithium bicarbonate, lithium hydroxide, lithium metal, lithium hydride, and organolithium reagents, wherein organolithium reagents include one or more of tert-butyllithium, n-butyllithium, biphenyl lithium, and naphthalene lithium.

5. The preparation method according to claim 3, characterized in that, Among alkaline metal sources, sodium sources include one or more of sodium carbonate, sodium hydroxide, metallic sodium, and sodium hydride.

6. The preparation method according to claim 3, characterized in that, Precursors include one or more of formulas (I) to (V): 。 7. The preparation method according to any one of claims 3-6, characterized in that, Solvents include one or more of water, methanol, ethanol, tetrahydrofuran, and N,N-dimethylformamide.

8. The preparation method according to claim 3, characterized in that, The reaction time is 0.5~20 h.

9. The application of an additive in a new energy battery, characterized in that, The additives described in claim 1 or 2 are used in the fields of lithium-ion batteries and / or sodium-ion batteries.

10. The application according to claim 9, characterized in that, The additive is used in the cathode material of lithium-ion batteries or sodium-ion batteries, wherein the mass of the additive in the cathode material of lithium-ion batteries or sodium-ion batteries is 1 to 15% of the total mass of the cathode material.

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