Lithium ion battery, preparation method thereof and power utilization device

Abstract

The invention relates to a lithium ion battery and a preparation method thereof. The lithium ion battery comprises a positive pole piece, a diaphragm, a negative pole piece and an electrolyte, the positive pole piece comprises a high-moisture-sensitive positive pole active material, the specific surface area of the positive pole active material is 5m / g-80m / g, and the residual moisture content of the dried positive pole piece is 200ppm-400ppm; the electrolyte comprises a lithium salt, a solvent, a film-forming agent, an auxiliary agent and a hydrogen elimination agent, the film-forming agent is prepared from 1, 3-propane sultone and 0.3 percent to 1.0 percent of ethylene sulfate; the auxiliary agent is tris (trimethylsilane) phosphate; the hydrogen eliminating agent is ammonium p-nitrobenzoate. The lithium ion battery can be compatible with the positive pole piece with relatively high residual moisture, and side reaction caused by the positive pole piece can be effectively inhibited through an electrolyte system with a special formula, so that excellent electrochemical performance and safety are obtained.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a lithium-ion battery, its preparation method, and an electrical device thereof. Background Technology

[0002] Lithium-ion batteries, as crucial energy storage devices, are widely used in portable electronic devices, electric vehicles, and large-scale energy storage systems. To improve energy density, research on cathode materials continues to deepen, with high-voltage, low-cost cathode materials such as lithium iron manganese phosphate (LFMP) and lithium manganese phosphate (LMP) showing great potential. However, these materials typically possess a large specific surface area (e.g., 5...). With a surface area of ​​80 m² / g, it has a large number of active sites and a strong ability to adsorb moisture, resulting in extremely high moisture sensitivity, which poses a severe challenge to battery manufacturing and long-term reliability.

[0003] In current lithium-ion battery manufacturing processes, moisture removal primarily relies on prolonged high-temperature baking of the positive and negative electrode materials and electrode sheets. However, this physical dehumidification method has fundamental drawbacks: firstly, it consumes extremely high energy; secondly, for materials with large specific surface areas, the physically adsorbed trace amounts of moisture (such as 200 kJ / m³) are very limited. Moisture at the 400 ppm level is difficult to remove completely; secondly, and more importantly, this method mainly targets moisture introduced during the initial manufacturing process, but lacks an effective mechanism to deal with the trace amounts of moisture that may continue to be generated during the long-term charge and discharge cycles of the battery and the resulting cumulative damage.

[0004] Residual moisture within the battery system can trigger a series of harmful chain reactions: 1) It reacts with the mainstream electrolyte lithium salt, lithium hexafluorophosphate (LiPF6), to generate highly corrosive hydrofluoric acid (HF), which continuously corrodes the surface of the positive electrode material, leading to the dissolution of transition metal ions, destruction of the crystal structure, irreversible capacity decay, and a sharp increase in interfacial impedance; 2) When charged to a high potential, water molecules undergo electrochemical decomposition on the positive electrode surface, directly producing hydrogen gas. The accumulation of hydrogen gas can cause an increase in internal battery pressure, leading to battery swelling. In extreme cases, it may cause safety valve failure or casing rupture, posing a serious safety hazard.

[0005] Therefore, existing technologies face a key bottleneck: traditional physical dehydration methods cannot dynamically and completely eliminate moisture, and in particular, they lack effective means to suppress the critical hazard of moisture continuously decomposing to produce hydrogen (H2) during electrochemical cycling. This results in batteries using highly moisture-sensitive cathode materials constantly facing performance degradation and safety concerns caused by moisture, limiting their reliability and widespread application. Summary of the Invention

[0006] Therefore, it is necessary to provide a lithium-ion battery, its preparation method, and an electrical device thereof. This lithium-ion battery is compatible with positive electrode sheets with high residual moisture content, and through a specially formulated electrolyte system, it effectively suppresses the side reactions caused by this, thereby obtaining excellent electrochemical performance and safety.

[0007] The first aspect of this application provides a lithium-ion battery, including a positive electrode, a separator, a negative electrode and an electrolyte, wherein the positive electrode comprises a high moisture-sensitive positive electrode active material, the specific surface area of ​​the positive electrode active material is 5m² / g to 80m² / g, and the residual moisture content of the positive electrode after drying is 200ppm to 400ppm. The electrolyte contains lithium salt, solvent, film-forming agent, auxiliary agent and hydrogen scavenger; The film-forming agent comprises 1,3 Propane sulfonate lactone and vinyl sulfate; The auxiliary agent is tris(trimethylsilane) phosphate; The hydrogen scavenger is ammonium p-nitrobenzoate.

[0008] In one embodiment, based on a total mass of 100% for the lithium salt and the solvent, the film-forming agent contains 1,3... The mass percentage of propane sulfonate lactone is 0.5%~1.0%, and the mass percentage of vinyl sulfate is 0.3%~1.0%; the mass percentage of the auxiliary agent tris(trimethylsilane) phosphate is 0.3%~1.0%; and the mass percentage of the hydrogen scavenger ammonium p-nitrobenzene is 0.1%~0.5%.

[0009] In one embodiment, the high moisture-sensitive positive electrode active material is lithium manganese iron phosphate or lithium manganese phosphate.

[0010] In one embodiment, the water content of the electrolyte is 5 ppm to 100 ppm.

[0011] In one embodiment, the solvent includes at least one of ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), fluoroethylene carbonate (FEC), propylene carbonate (PC), methyl propyl carbonate (MPC), diethyl carbonate (DEC), methyl formate (MF), methyl acetate (MA), methyl butyrate (MB), and ethyl propionate (EP).

[0012] In one embodiment, the lithium salt includes at least one of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium tetrafluoroborate (LiBF4), lithium dioxolaneborate (LiBOB), and lithium difluorophosphate (LiPO2F2).

[0013] The second aspect provides a method for preparing the lithium-ion battery described in the first aspect, comprising the following steps: The positive electrode, separator, and negative electrode are used to make the battery cell; The lithium salt, solvent, film-forming agent, auxiliary agent, and hydrogen scavenger are mixed evenly to obtain the electrolyte; and The battery cell is placed into a packaging shell and the electrolyte is injected to obtain a lithium-ion battery. The positive electrode sheet contains a high moisture-sensitive positive electrode active material, and the specific surface area of ​​the positive electrode active material is 5m². 2 / g~80m 2 / g, and the residual moisture content of the positive electrode sheet after drying is 200ppm~400ppm; in the electrolyte, the film-forming agent includes 1,3-propanesulfonate lactone and vinyl sulfate, the auxiliary agent is tris(trimethylsilane) phosphate, and the hydrogen scavenging agent is ammonium p-nitrobenzoate.

[0014] In one embodiment, the preparation of the electrolyte includes the following steps: The selected solvents are mixed evenly according to the volume ratio to obtain a mixed solvent; Lithium salt is added to the mixed solvent and mixed evenly to obtain the basic electrolyte; A film-forming agent, an auxiliary agent, and a hydrogen scavenger are added sequentially to the basic electrolyte, mixed evenly, and then degassed under vacuum conditions to obtain the electrolyte.

[0015] In one embodiment, the degassing treatment is carried out at a temperature of 80°C to 100°C and a vacuum degree of not less than 0.05 MPa for 2 to 4 hours.

[0016] The third aspect provides an electrical device including the lithium-ion battery described in the first aspect.

[0017] The present invention has the following beneficial effects: The lithium-ion battery, its preparation method, and the electrical device provided by this invention achieve significant technical effects by applying a synergistic electrolyte system containing specific film-forming agents (PS, DTD), auxiliary agents (TMSP), and hydrogen scavenging agents in a high-moisture positive electrode system (200ppm~400ppm residual water). (1) High efficiency hydrogen elimination and safety improvement: TMSP passivates the electrode surface through Si-O bonds to suppress gas generation; the synergistic hydrogen elimination agent ammonium nitrate can reduce hydrogen evolution reaction, effectively suppress battery swelling, reduce the risk of thermal runaway, and improve safety.

[0018] (2) Significantly reduced interface impedance: PS and DTD synergistically constructed a low-impedance SEI film with "dense inner layer and flexible outer layer". Combined with the HF removal effect of TMSP, the DC internal resistance (DCR) of the battery was reduced from >11.6 mΩ in the comparative example to <8.6 mΩ in the example, thus improving the rate performance.

[0019] (3) Significantly extended cycle life: Thanks to the effective suppression of harmful side reactions caused by moisture and HF, the capacity retention rate of the battery after 1000 cycles at room temperature has been greatly improved from <72.1% in the comparative example to >83.1% in the example (98.7% in the preferred example).

[0020] The synergistic effect of these factors fundamentally resolves the contradiction between "high interfacial impedance" and "high gas production" in the application of high moisture-sensitive cathode materials, providing an effective solution for the development of batteries with high electrochemical performance and high safety. Attached Figure Description

[0021] Figure 1 This is a flowchart of a method for preparing a lithium-ion battery according to an embodiment of the present invention; Figure 2 This is a flowchart of a method for preparing an electrolyte according to an embodiment of the present invention. Detailed Implementation

[0022] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0024] One embodiment of a lithium-ion battery includes a positive electrode, a separator, a negative electrode, and an electrolyte.

[0025] The positive electrode sheet includes a highly moisture-sensitive positive electrode active material with a specific surface area of ​​5 m² / g to 80 m² / g, and a residual moisture content of 200 ppm to 400 ppm after drying. The highly moisture-sensitive positive electrode active material refers to a positive electrode material with a specific surface area in the range of 5 m² / g to 80 m² / g, and which easily retains 200 ppm to 400 ppm of moisture after drying, such as lithium manganese iron phosphate and lithium manganese phosphate. The larger the specific surface area of ​​the material, the more active sites on the surface, and the easier it is to bind with polar water molecules (H₂O) through van der Waals forces or hydrogen bonds.

[0026] The specific surface area of ​​the positive electrode active material was determined by the Brunauer-Emmett-Teller (BET) method using nitrogen adsorption-desorption, and the testing standard can be found in GB / T 19587-2017. The residual moisture content of the dried positive electrode sheet was determined by the Karl Fischer coulommetric titration method, and the testing standard can be found in GB / T45330—2025. During the test, the ambient dew point temperature should not exceed -20℃, the ambient temperature should be 15℃~30℃, and 0.1g~0.2g of sample should be taken. The electrode sample should be quickly transferred to a glass bottle, and the sample bottle should be placed on a Karl Fischer coulommetric moisture analyzer for measurement. The heating temperature should be 120~150℃, and the moisture content in the sample bottle should be recorded after the test.

[0027] Furthermore, the specific surface area of ​​the positive electrode active material may be, but is not limited to, 5 m² / g, 10 m² / g, 15 m² / g, 20 m² / g, 25 m² / g, 30 m² / g, 35 m² / g, 40 m² / g, 45 m² / g, 50 m² / g, 55 m² / g, 60 m² / g, 65 m² / g, 70 m² / g, 75 m² / g, or 80 m² / g, and the residual moisture content of the positive electrode sheet after drying may be, but is not limited to, 200 ppm, 250 ppm, 300 ppm, 350 ppm, or 400 ppm.

[0028] The electrolyte contains lithium salt, solvent, film-forming agent, auxiliary agent and hydrogen scavenger.

[0029] Among them, the film-forming agent includes 1,3 Propane sulfonate lactone (PS) and vinyl sulfate (DTD); the auxiliary agent is tris(trimethylsilane) phosphate (TMSP); the hydrogen scavenger is ammonium p-nitrobenzoate.

[0030] In this embodiment, PS and DTD jointly construct an SEI film with a "dense inner layer and flexible outer layer." The film-forming effect reduces the direct contact between the electrolyte and the electrode, lowering the rate of side reactions. TMSP further optimizes the ion conductivity and structural stability of the film. The three work synergistically to reduce the impedance of the SEI film. At the same time, TMSP further inhibits LiPF6 hydrolysis by removing HF and H2O, and the hydrogen scavenger can consume H2O. + TMSP works synergistically with hydrogen scavengers to eliminate hydrogen, suppress hydrogen evolution reaction, inhibit gas generation and reduce interfacial side reactions, improve the rate performance and cycle life of the battery, and solve the contradiction of "high impedance + high gas production" in traditional electrolytes.

[0031] In this embodiment, the hydrogen scavenger is ammonium p-nitrobenzoate. Ammonium p-nitrobenzoate can preferentially bind H+ through the electron-withdrawing effect of the nitro group. + It inhibits hydrogen evolution and neutralizes corrosive HF through alkaline ammonium ions, thereby synergizing with the auxiliary agent TMSP to achieve hydrogen removal and acid scavenging effects far exceeding those of ordinary hydrogen scavengers or single-mechanism agents, precisely curbing gas generation and interface corrosion from the source.

[0032] In this embodiment, the hydrogen scavenger is ammonium p-nitrobenzoate, and its core mechanism of action is as follows: The specific chemical reactions that lead to hydrogen production include the hydrolysis of water from the electrode itself, the electrolyte, and water impurities generated by side reactions during battery cycling. 2H2O+2e →H₂↑+2OH⁻ Ammonium p-nitrobenzoate, as a hydrogen scavenger in lithium battery electrolytes, has a core mechanism of action revolving around the electron-withdrawing effect of the nitro group, the alkaline neutralization of the ammonium group, and the regulation of the interfacial film.

[0033] 1. Electron-withdrawing effect of nitro groups: inhibits hydrogen evolution reaction. The nitro group (-NO2) in ammonium p-nitrobenzoate is a strong electron-withdrawing group, which adsorbs free H+. + It can preferentially adsorb free hydrogen ions in the electrolyte, reducing H+ ions. + The reduction reaction (2H) on the negative electrode surface + +2e - →H2↑), thereby reducing the amount of hydrogen produced.

[0034] 2. Ammonium ion neutralization: removal of harmful acid (HF) The ammonium ion (NH4+) generated by the dissociation of ammonium p-nitrobenzoate + It has a certain alkalinity and can undergo a neutralization reaction with hydrofluoric acid (HF) in the electrolyte: NH4 + + HF →NH3·H2O+F This reaction not only directly consumes HF (HF is the most corrosive impurity in the electrolyte, which can damage the SEI film and corrode the electrode), but also can complex F - (e.g., forming NH4F) reduces F - Concentration, to inhibit the excessive formation of LiF (LiF is a high-impedance product, which will increase the interfacial impedance).

[0035] Meanwhile, the synergistic effect of ammonium p-nitrobenzene and TMSP further enhances the hydrogen removal effect: TMSP adsorbs H through Si-O bonds + It catalyzes the recombination of H2 and O2 (2H2 + O2 → 2H2O), adsorbs moisture to reduce hydrogen production, and uses the hydrogen scavenger ammonium p-nitrobenzene to consume H2 through nitro reduction. + The two work together to inhibit the hydrogen evolution reaction, reducing the concentration of H2 produced to 50 ppm.

[0036] The SEI film formed by 1,3-propanesulfonyl lactone (PS) and vinyl sulfate (DTD) can reduce the contact area between the electrolyte and the electrode, reduce the side reaction rate, and provide interfacial environment support for the hydrogen removal effect of ammonium p-nitrobenzoate.

[0037] Based on the foregoing embodiments, and assuming the total mass of the lithium salt and the solvent is 100%, the film-forming agent contains 0.5%~1.0% 1,3-propanesulfonate lactone (PS) and 0.3%~1.0% ethylene sulfate (DTD); the auxiliary agent tris(trimethylsilane) phosphate (TMSP) contains 0.3%~1.0% 1,3-propanesulfonate lactone (PS) by mass. Propane sulfonate lactone (PS) accounts for 0.5% to 1.0% of the total mass of the solvent and lithium salt, and vinyl sulfate (DTD) accounts for 0.3% to 1.0% of the total mass of the solvent and lithium salt. Further, 1,3 The mass fraction of propane sulfonate lactone may be, but is not limited to, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1.0%, and the mass fraction of vinyl sulfate may be, but is not limited to, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1.0%.

[0038] Similarly, tris(trimethylsilane) phosphate (TMSP) accounts for 0.3% to 1.0% of the total mass of the solvent and lithium salt. Further, the mass fraction of tris(trimethylsilane) phosphate may be, but is not limited to, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1.0%.

[0039] The hydrogen scavenger, ammonium p-nitrobenzene, comprises 0.1% to 0.5% of the total mass of the solvent and lithium salt. Similarly, the hydrogen scavenger, ammonium p-nitrobenzene, comprises 0.1% to 0.5% of the total mass of the solvent and lithium salt. Further, the mass percentage of the hydrogen scavenger, ammonium p-nitrobenzene, may be, but is not limited to, 0.1%, 0.2%, 0.3%, 0.4%, or 0.5%.

[0040] Based on the aforementioned embodiments, the high moisture-sensitive cathode active material is lithium iron manganese phosphate (LFMP) or lithium manganese phosphate (LMP). The solution of this invention best addresses the extreme moisture management and gas generation challenges posed by high-voltage, high-specific-surface-area cathode materials such as LFMP / LMP, demonstrating the outstanding value and targeted application of this invention in improving the reliability of specific high-performance material batteries.

[0041] Based on the aforementioned implementation method, the water content of the electrolyte is 5ppm to 100ppm. The water content of the electrolyte is determined using the Karl Fischer coulometric method. Appropriate amounts of Karl Fischer reagent are added to the titration cell and cathode chamber, respectively. The electrolyte sample to be analyzed is repeatedly drawn using a 2.50mL syringe, and the syringe is rinsed 5-8 times. Then, 1-2mL of the electrolyte sample to be tested is drawn and rapidly added to the titration cell through the injection port. The instrument automatically performs the titration. At the endpoint, the instrument display shows the water content of the sample. This ensures that the electrolyte injected into the battery itself introduces very little water, reducing the overall water load of the system from the source. This allows the additive system to focus more on treating the limited water remaining on the electrodes and generated during circulation, thus providing more efficient and stable synergistic protection and improving the feasibility of the entire technical solution.

[0042] Based on the foregoing embodiments, the solvent includes at least one of ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), fluoroethylene carbonate (FEC), propylene carbonate (PC), methyl propyl carbonate (MPC), diethyl carbonate (DEC), methyl formate (MF), methyl acetate (MA), methyl butyrate (MB), and ethyl propionate (EP).

[0043] Preferably, the solvent comprises ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and fluoroethylene carbonate (FEC), wherein the volume ratio of ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and fluoroethylene carbonate (FEC) is (30... 35): (35) 40): (20 25): (5 10) The solvent accounts for 85%~90% of the total mass of the solvent and lithium salt. This embodiment constructs an optimized solvent environment that balances high dielectric constant (facilitating lithium salt dissociation), suitable viscosity (facilitating wetting and ion migration), and low freezing point (non-freezing at -40℃). This specific solvent system provides an ideal platform for the interaction of lithium salt and various additives, ensuring the normal operation of the battery over a wide temperature range, especially at low temperatures, and is an important prerequisite for obtaining excellent overall performance.

[0044] Based on the aforementioned embodiments, the lithium salt includes at least one of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium tetrafluoroborate (LiBF4), lithium dioxolaneborate (LiBOB), and lithium difluorophosphate (LiPO2F2).

[0045] Preferably, the lithium salt comprises lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, wherein the concentration of lithium hexafluorophosphate is 1.0 mol / L to 1.5 mol / L, and the concentration of lithium bis(fluorosulfonyl)imide is 0.3 mol / L to 0.5 mol / L; the mass fraction of the lithium salt in the total mass of the solvent and lithium salt is 10% to 15%. In this embodiment, lithium hexafluorophosphate is the main salt and lithium bis(fluorosulfonyl)imide is the auxiliary salt. By limiting the use of a double lithium salt system of LiPF6 and LiFSI and a specific concentration, the high-temperature stability of LiPF6 and the excellent ionic conductivity and low-temperature performance of LiFSI are combined. This compounding scheme not only ensures the basic electrochemical stability window of the electrolyte, but also significantly improves the ion migration rate at low temperatures, thereby effectively reducing the overall impedance of the battery. It is particularly helpful in improving high-power output and low-temperature discharge performance, and together with functional additives, achieves the goal of low impedance.

[0046] The lithium-ion battery provided by this invention achieves significant technical effects by applying a synergistic electrolyte system containing specific film-forming agents (PS, DTD), auxiliary agents (TMSP), and hydrogen scavenging agents in a high-moisture positive electrode system (200ppm~400ppm residual water). (1) High efficiency hydrogen elimination and safety improvement: TMSP passivates the electrode surface through Si-O bonds to suppress gas generation; the synergistic hydrogen elimination agent ammonium nitrate can reduce hydrogen evolution reaction, effectively suppress battery swelling, reduce the risk of thermal runaway, and improve safety.

[0047] (2) Significantly reduced interface impedance: PS and DTD synergistically constructed a low-impedance SEI film with "dense inner layer and flexible outer layer". Combined with the HF removal effect of TMSP, the DC internal resistance (DCR) of the battery was reduced from >11.6 mΩ in the comparative example to <8.6 mΩ in the example, thus improving the rate performance.

[0048] (3) Significantly extended cycle life: Thanks to the effective suppression of harmful side reactions caused by moisture and HF, the capacity retention rate of the battery after 1000 cycles at room temperature has been greatly improved from <72.1% in the comparative example to >83.1% in the example (98.7% in the preferred example).

[0049] The synergistic effect of these factors fundamentally resolves the contradiction between "high interfacial impedance" and "high gas production" in the application of high moisture-sensitive cathode materials, providing an effective solution for the development of batteries with high electrochemical performance and high safety.

[0050] Please see Figure 1 The method for preparing the lithium-ion battery according to one embodiment of the present invention includes the following steps: S10. The positive electrode, separator, and negative electrode are made into a battery cell.

[0051] In step S10, the positive electrode, separator, and negative electrode can be stacked or wound to form a battery cell.

[0052] In one embodiment, the preparation of the positive electrode sheet includes: mixing the positive active material, conductive agent, and binder in a mass ratio of (96%). 98): (1 3): (1 2) The materials are mixed in a specific ratio to form a slurry, which is then coated, dried, and rolled to obtain a positive electrode sheet. The drying temperature is 80℃~90℃, and the time is 36 hours~50 hours, so that the residual moisture content of the positive electrode sheet after drying is 200ppm~400ppm. This embodiment clarifies a practical method for stably controlling the residual moisture content of high specific surface area positive electrode materials within the target range of 200ppm~400ppm. This process achieves a balance between moisture control and production energy consumption and efficiency without excessively damaging the material structure, making the technical solution feasible for industrial implementation.

[0053] S20. Mix lithium salt, solvent, film-forming agent, auxiliary agent and hydrogen scavenger evenly to obtain electrolyte.

[0054] In step S20, the selection of lithium salt, solvent, film-forming agent, auxiliary agent and hydrogen scavenger is as described above.

[0055] Please see Figure 2 In one embodiment, the preparation of the electrolyte includes the following steps: S21. Mix the selected solvents evenly according to the volume ratio to obtain a mixed solvent; S22. Add lithium salt to the mixed solvent obtained in step S21, and mix evenly to obtain the basic electrolyte. S23. Add film-forming agent, auxiliary agent and hydrogen scavenger to the basic electrolyte obtained in step S22 in sequence, mix evenly and then degas under vacuum to obtain electrolyte.

[0056] Further, step S21 can be performed by mixing ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and fluoroethylene carbonate in a volume ratio of (30...) 35): (35) 40): (20 25): (5 10) Mix thoroughly to obtain a mixed solvent.

[0057] Further, step S22 can be performed by adding lithium hexafluorophosphate and lithium difluorosulfonylimide to the mixed solvent obtained in step S21, mixing them evenly to obtain a basic electrolyte; wherein the concentration of lithium hexafluorophosphate is 1.0 mol / L to 1.5 mol / L, and the concentration of lithium difluorosulfonylimide is 0.3 mol / L to 0.5 mol / L.

[0058] Furthermore, the mixing process in steps S21 and S22 can be, but is not limited to, stirring at 200 rpm to 500 rpm for 1 h to 4 h at 25℃ to 50℃; the vacuum degassing process in step S23 can be, but is not limited to, vacuum degassing at 80℃ to 100℃ and -0.2 MPa to -0.05 MPa for 2 h to 4 h.

[0059] The electrolyte preparation method described above ensures that all components, especially water- and oxygen-sensitive lithium salts and additives, can form a homogeneous solution uniformly and stably in a controlled environment. This process avoids localized failures or decompositions that may result from improper mixing, and is crucial for ensuring the consistency and reproducibility of the final electrolyte performance, providing a reliable process foundation for the large-scale production of batteries.

[0060] S30. Place the battery cell obtained in step S10 into a packaging shell and inject the electrolyte obtained in step S20 to obtain a lithium-ion battery; wherein, the positive electrode sheet contains a highly moisture-sensitive positive electrode active material, and the specific surface area of ​​the positive electrode active material is 5m². 2 / g~80m 2 / g, and the residual moisture content of the positive electrode sheet after drying is 200ppm~400ppm; in the electrolyte, the film-forming agent includes 1,3-propanesulfonate lactone and vinyl sulfate, the auxiliary agent is tris(trimethylsilane) phosphate, and the hydrogen scavenging agent is ammonium p-nitrobenzene.

[0061] In step S30, conventional methods in the art can be used to place the battery cell into the packaging shell and inject electrolyte to obtain a lithium-ion battery.

[0062] In some embodiments, the packaging shell of the lithium-ion battery involved in this invention can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The packaging shell of the secondary battery can also be a soft pack, such as a pouch-type soft pack. The material of the soft pack can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

[0063] In one embodiment, the active material of the negative electrode is graphite, the separator is a polyolefin porous separator, and the lithium-ion battery is a pouch battery. In other words, the synergistic electrolyte system of this invention can be seamlessly adapted to existing mature battery material systems and manufacturing platforms. It can significantly improve the performance of batteries using high-moisture-sensitive positive electrode materials without changing core raw materials or disrupting existing production lines, greatly reducing the barriers to technological upgrades and industrialization.

[0064] It should be noted that the order of steps S10 and S20 in the preparation method of the lithium-ion battery of the present invention is not limited.

[0065] One embodiment of the electrical device includes any of the lithium-ion batteries described above.

[0066] Wherein, "electrical device" refers to any device or system that uses any of the aforementioned lithium-ion batteries as its power source or a component of its power source. Electrical devices may include, but are not limited to: portable electronic devices, such as mobile phones, laptops, tablets, digital cameras, and wearable devices; electric vehicles, such as electric cars, electric bicycles, electric scooters, and power utility vehicles; energy storage systems, such as home energy storage units, grid-side energy storage power stations, and backup power supplies for communication base stations; and other power or backup power equipment.

[0067] Because the lithium-ion battery of the present invention has advantages such as low impedance, long cycle life, high safety and low gas production, and is particularly compatible with high moisture-sensitive cathode materials, it can significantly improve the overall performance of the electrical device, including but not limited to: longer battery life, faster charging capability, wider operating temperature range, higher safety and longer service life.

[0068] Referring to the above embodiments, in order to make the technical solution of the present invention more specific, clear and easy to understand, examples of the technical solution of the present invention are given below. However, it should be noted that the content to be protected by the present invention is not limited to the following embodiments.

[0069] Example 1 (1) Preparation of electrolyte: 1. Solvent mixing: EC, DMC, EMC and FEC are added in sequence at a volume ratio of 30:40:20:10. Stir at 300 rpm for 2 hours at 25°C until transparent. The mass fraction of the mixed solvent is 85% of the total mass of the solvent and lithium salt.

[0070] 2. Lithium salt dissolution: Slowly add LiPF6 and LiFSI to the above solvent, controlling the final concentration of LiPF6 to be 1.2 mol / L and the final concentration of LiFSI to be 0.3 mol / L. Stir at 40℃ and 500 rpm for 2 hours until completely dissolved to obtain the basic electrolyte. The mass fraction of lithium salt is approximately 15% of the total mass of solvent and lithium salt.

[0071] 3. Additive addition: Film-forming agent PS (addition amount is 0.8%), DTD (0.5%), auxiliary agent TMSP (0.5%) and hydrogen scavenging agent ammonium p-nitrobenzoate (0.2%) were added to the above basic electrolyte in sequence (the addition amount is calculated based on the total mass of solvent and lithium salt in the system after steps 1 and 2 being 100%), and ultrasonic treatment was carried out at room temperature for 45 min.

[0072] 4. Vacuum degassing: Vacuum degassing at 80℃ and -0.095MPa for 2 hours, followed by cooling to obtain the electrolyte.

[0073] (2) Preparation of positive electrode sheet: LMFP, conductive agent, and binder polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 97:2:1, and N-methylpyrrolidone (NMP) was added. The mixture was stirred to prepare a uniform slurry with a viscosity of approximately 6500 mPa·s. The slurry was coated onto an aluminum foil current collector, and after coating and staged drying, an electrode sheet with a dry film thickness of approximately 150 μm was obtained. The electrode sheet was then compacted by roller pressing to a density of 2.3 g / cm³, and then dried at 85°C for 48 hours. The final positive electrode sheet had a residual moisture content of approximately 300 ppm.

[0074] (3) Preparation of negative electrode sheet: Graphite, sodium carboxymethyl cellulose (CMC) binder, styrene-butadiene rubber (SBR) (with a CMC to SBR mass ratio of 1:1), and conductive agent Super P were mixed at a mass ratio of 96:3:1, and deionized water was added to prepare a slurry with a viscosity of approximately 4000 mPa·s. The slurry was coated onto copper foil, and after coating and drying, an electrode sheet with a dry film thickness of 93 μm was obtained. The electrode sheet was then rolled and compacted to a density of 1.6 g / cm³.

[0075] (4) Battery assembly: The positive electrode, separator, and negative electrode prepared above are stacked to form a battery cell. There are 29 positive electrode sheets in total. The stacked body is placed in an aluminum-plastic film for encapsulation, and finally the electrolyte is added to form a soft-pack battery.

[0076] Example 2 The difference from Example 1 is that the film-forming agent PS (0.5%) and DTD (0.3%) are used.

[0077] Example 3 The difference from Example 1 is the addition of the adjuvant TMSP (0.3%).

[0078] Example 4 The difference from Example 1 is that the hydrogen scavenger is ammonium p-nitrobenzoate (0.1%).

[0079] Example 5 The difference from Example 1 is that film-forming agent PS (0.8%), DTD (0.7%), auxiliary agent TMSP (0.6%), and hydrogen scavenger ammonium p-nitrobenzene (0.3%) were added sequentially.

[0080] Example 6 The difference from Example 1 is that film-forming agent PS (0.5%), DTD (0.3%), auxiliary agent TMSP (0.3%), and hydrogen scavenger ammonium p-nitrobenzene (0.1%) were added in sequence.

[0081] Example 7 The difference from Example 1 is that film-forming agent PS (1%), DTD (1%), auxiliary agent TMSP (1%), and hydrogen scavenger ammonium p-nitrobenzene (0.5%) were added in sequence.

[0082] Example 8 The difference from Example 1 is that film-forming agent PS (0.2%), DTD (0.2%), auxiliary agent TMSP (0.2%), and hydrogen scavenger ammonium p-nitrobenzoate (0.05%) were added in sequence.

[0083] Example 9 The difference from Example 1 is that film-forming agent PS (1.3%), DTD (1.2%), auxiliary agent TMSP (1%), and hydrogen scavenger ammonium p-nitrobenzene (1%) were added in sequence.

[0084] Comparative Example 1 Compared with Example 1, the difference is that a conventional electrolyte is used, without the addition of any PS, DTD, TMSP and hydrogen scavenging agent, containing only solvent and lithium salt (LiPF6 1.2 mol / L, LiFSI 0.3 mol / L).

[0085] Comparative Example 2 Compared with Example 1, the difference is that PS (0.8%), DTD (0.5%), and ammonium p-nitrobenzoate (0.2%) were added, but the auxiliary agent TMSP was not added.

[0086] Comparative Example 3 Compared with Example 1, the difference is that PS (0.8%), DTD (0.5%), and TMSP (0.5%) were added, but the hydrogen scavenger ammonium p-nitrobenzene was not added.

[0087] Performance testing: The performance of the lithium-ion batteries of Examples 1-9 and Comparative Examples 1-5 was tested. The test methods are as follows, and the test results are shown in Table 1.

[0088] Low-temperature capacity retention: At 25℃, constant volume at 1C; after temperature equalization at -20℃ for 6 hours, discharge at 1C to 2.5V, and let stand for 30 minutes; record the discharge capacity.

[0089] DC impedance DCR: At an ambient temperature of 25±2℃, charge at 1C constant current to the upper limit voltage of 4.3V, cut off current to 0.05C, and let stand for 1h; discharge at 1Cn constant current to 50% SOC and let stand for 1h; discharge at 3C0 for 10s and let stand for 10min. Calculate the discharge DCR at 50% SOC.

[0090] Moisture content test: The Karl Fischer coulometric method was used to test the electrolyte in the battery after the low-temperature test.

[0091] Cycle life: At an ambient temperature of 25±2℃, the system is charged at 0.33C constant current and constant voltage to the upper limit voltage of 4.4V, and the cutoff current is reduced to 0.05C; then left to stand for 30 minutes; discharged at 1C constant current to 2.5V; left to stand for 30 minutes; and the charge-discharge cycle is repeated 1000 times while the data is recorded and the capacity retention rate is calculated.

[0092] Gas chromatography-mass spectrometry: Collect gas samples after battery cycling (10 mL of gas is drawn with a syringe); inject into the GC-MS instrument and test the H2 concentration.

[0093] Table 1 Performance test results of lithium-ion batteries in the examples and comparative examples As can be seen from the data in Table 1: The key performance indicators (DCR < 6.1 mΩ, H2 concentration < 63 ppm, cycle retention > 86.2%) of the lithium-ion batteries in Examples 1 to 7 of this invention are all maintained at an excellent level. Among them, Example 1 represents the complete additive system under the preferred ratio of this invention, and its performance indicators are all optimal: the lowest residual water content in the electrolyte (20 ppm), the lowest interfacial impedance (DCR 2.6 mΩ), the highest low temperature performance (capacity retention of 86.5% at -20℃) and cycle life (capacity retention of 98.7% after 1000 cycles), and extremely low gas production (H2 concentration 50 ppm).

[0094] Example 8 shows that the dosage was insufficient, indicating that when the dosage of each additive is close to or lower than the lower limit of the preferred range of the claims, the battery performance is better than the comparison of no / missing components, but significantly inferior to the preferred embodiment, indicating that insufficient dosage will not have a good effect.

[0095] Example 9 showed an excessive dosage, indicating that when the additive dosage exceeded the upper limit of the preferred range, the performance (especially the DCR increased to 8.6 mΩ, and the cycle retention decreased to 83.1%) was worse than that of Examples 1-7. This suggests that excessive addition may introduce new side reactions or have a negative impact on the electrode interface, and more is not necessarily better.

[0096] Comparative Example 1 (without any additives) had the worst performance in all aspects, especially with a DCR as high as 15.6 mΩ, an H2 concentration of 90 ppm, and a cycle retention rate of only 65%.

[0097] For Comparative Examples 2 (lacking TMSP) and 3 (lacking hydrogen scavenger), although the performance was better than Comparative Example 1, the DCR, H2 concentration, and cycle retention were significantly worse than in Example 1. This strongly demonstrates that PS, DTD, TMSP, and the hydrogen scavenger ammonium p-nitrobenzene constitute a synergistic whole, and the absence of any core component will lead to a significant decline in overall performance. Therefore, although single or partial additive combinations may bring certain improvements, only when the specific types and proportions of film-forming agents, auxiliary agents, and hydrogen scavengers described in this invention work together can the optimal balance between low impedance, high cycle retention, and extremely low gas production, as shown in Example 1, be achieved, thereby systematically solving the fundamental contradiction in the application of high-moisture cathode materials.

[0098] In summary, this invention, through the synergistic effect of specific types and ratios of film-forming agents (PS, DTD), auxiliary agents (TMSP), and hydrogen scavengers, can be compatible with positive electrode sheets with high residual moisture content, effectively suppressing the side reactions caused by this, thereby obtaining excellent electrochemical performance and safety.

[0099] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0100] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A lithium-ion battery, comprising a positive electrode, a separator, a negative electrode, and an electrolyte, characterized in that, The positive electrode sheet contains a high moisture-sensitive positive electrode active material, the specific surface area of ​​which is 5m² / g to 80m² / g, and the residual moisture content of the positive electrode sheet after drying is 200ppm to 400ppm. The electrolyte contains lithium salt, solvent, film-forming agent, auxiliary agent and hydrogen scavenger; The film-forming agent comprises 1,3 Propane sulfonate lactone and vinyl sulfate; The auxiliary agent is tris(trimethylsilane) phosphate; The hydrogen scavenger is ammonium p-nitrobenzoate.

2. The lithium-ion battery according to claim 1, characterized in that, Based on a total mass of 100% for the lithium salt and the solvent, the film-forming agent contains 1,3... The mass percentage of propane sulfonate lactone is 0.5%~1.0%, and the mass percentage of vinyl sulfate is 0.3%~1.0%; the mass percentage of the auxiliary agent tris(trimethylsilane) phosphate is 0.3%~1.0%; and the mass percentage of the hydrogen scavenger ammonium p-nitrobenzene is 0.1%~0.5%.

3. The lithium-ion battery according to claim 1, characterized in that, The high moisture-sensitive positive electrode active material is lithium manganese iron phosphate or lithium manganese phosphate.

4. The lithium-ion battery according to claim 1, characterized in that, The electrolyte has a water content of 5ppm to 100ppm.

5. The lithium-ion battery according to any one of claims 1 to 4, characterized in that, The solvent includes at least one of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, fluoroethylene carbonate, propylene carbonate, methyl propyl carbonate, diethyl carbonate, methyl formate, methyl acetate, methyl butyrate, and ethyl propionate.

6. The lithium-ion battery according to any one of claims 1 to 4, characterized in that, The lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, lithium dioxaborate, and lithium difluorophosphate.

7. A method for preparing a lithium-ion battery as described in any one of claims 1 to 6, characterized in that, Includes the following steps: The positive electrode, separator, and negative electrode are used to make the battery cell; The lithium salt, solvent, film-forming agent, auxiliary agent and hydrogen scavenger are mixed evenly to obtain the electrolyte; as well as The battery cell is placed into a casing, and the electrolyte is injected to obtain a lithium-ion battery. The positive electrode sheet contains a high moisture-sensitive positive electrode active material, and the specific surface area of ​​the positive electrode active material is 5 m². 2 / g~80m 2 / g, and the residual moisture content of the positive electrode sheet after drying is 200ppm~400ppm; in the electrolyte, the film-forming agent includes 1,3-propanesulfonate lactone and vinyl sulfate, the auxiliary agent is tris(trimethylsilane) phosphate, and the hydrogen scavenging agent is ammonium p-nitrobenzoate.

8. The method for preparing a lithium-ion battery according to claim 7, characterized in that, The preparation of the electrolyte includes the following steps: The selected solvents are mixed evenly according to the volume ratio to obtain a mixed solvent; Lithium salt is added to the mixed solvent and mixed evenly to obtain the basic electrolyte; A film-forming agent, an auxiliary agent, and a hydrogen scavenger are added sequentially to the basic electrolyte, mixed evenly, and then degassed under vacuum conditions to obtain the electrolyte.

9. The method for preparing a lithium-ion battery according to claim 8, characterized in that, The degassing treatment is carried out at a temperature of 80℃~100℃ and a vacuum degree of not less than 0.05MPa for 2h~4h.

10. An electrical device, characterized in that, Including the lithium-ion battery as described in any one of claims 1 to 6.

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