Formation method of battery, battery and electronic equipment

Abstract

The invention provides a formation method of a battery, the battery and electronic equipment. The formation method comprises the following steps: placing the battery in an oven at 25-45 DEG C for primary aging for 24-72 hours after liquid injection and pier sealing; (3) after the primary aging is finished, taking out the battery cell for normal-temperature formation; 4) performing three-step constant-current charging; (5) after secondary aging, charging is carried out for 60-120 min at the constant current and constant voltage of 0.5-0.7 C and the cut-off voltage (3.9-4.1 V) at the cut-off current of 0.025 C; (7) the discharge current is 0.2-0.7 C, and the cut-off voltage is 1.5-2.0 V; the charging current is 0.2 to 1.0 C, the charging cut-off voltage is 3.9 to 4.1 V, and the cut-off current is 0.025 C; the discharge current is 0.2 to 0.7 C, and the cut-off voltage is 1.5 to 2.0 V. According to the formation method provided by the invention, the cycle performance and the capacity of the battery can be ensured while the self-discharge condition of the battery is improved.

Description

Technical Field

[0001] The present invention relates to a battery formation method, a battery, and electronic equipment, belonging to the technical field of batteries. Background Art

[0002] Secondary batteries, also known as rechargeable batteries or storage batteries, are batteries that can be recharged after discharge to reactivate the active materials and continue to be used. Common secondary batteries include lithium-ion batteries, lead-acid batteries, and sodium-ion batteries. Due to their economical, environmentally friendly, and convenient advantages, secondary batteries are widely used in mobile devices, electric vehicles, backup power supplies, and renewable energy storage.

[0003] Currently, the energy density of batteries can be increased through high voltage. However, higher voltage will cause the problem of transition metal ion dissolution, seriously affecting the cycle stability of the battery and causing serious self-discharge.

[0004] Therefore, how to improve the self-discharge situation while ensuring the cycle performance and battery capacity has become a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0005] The present invention provides a battery formation method, which can effectively improve the self-discharge performance and cycle performance of the battery without reducing the battery capacity.

[0006] The present invention also provides a battery, which is prepared by the above-mentioned formation method, so the battery has relatively mild self-discharge and has excellent battery capacity and cycle performance.

[0007] The present invention also provides an electronic device comprising the battery, so that the electronic device has relatively mild self-discharge and has excellent battery capacity and cycle performance.

[0008] One aspect of the present invention provides a battery formation method, comprising the following steps:

[0009] 1) performing a first constant current charging process on the injected battery at a charging current of 0.01-0.05C for 120-180 minutes to obtain a first rechargeable battery;

[0010] 2) performing a second constant current charging process on the first rechargeable battery at a charging current of 0.1-0.2C for a charging time of 90-180 minutes to obtain a second rechargeable battery;

[0011] 3) performing a third constant current charging process on the second rechargeable battery at a charging current of 0.2-0.5C for 30-90 minutes to obtain a formed battery.

[0012] The formation method as described above, further comprising a first aging treatment before the first constant current charging treatment; and / or further comprising a second aging treatment after the third constant current charging treatment;

[0013] Wherein, the temperature of the first aging treatment is 25-45°C and the time is 24-72h;

[0014] The temperature of the second aging treatment is 45-65° C., and the time is 24-72 hours.

[0015] The formation method as described above, after the second aging treatment, further includes performing a constant current and constant voltage charging treatment at a charging current of 0.5-0.7C until the cut-off voltage is reached.

[0016] In the formation method described above, the amount of electricity at the end of the first constant current charging process does not exceed 15% SOC.

[0017] In the formation method described above, the amount of electricity at the end of the second constant current charging process does not exceed 45% SOC.

[0018] In the formation method described above, the amount of electricity at the end of the third constant current charging process does not exceed 80% SOC.

[0019] In the formation method described above, the constant current and constant voltage charging process has a charging current of 0.5 to 0.7C, a charging cut-off voltage of 3.9 to 4.1V, and a cut-off current of 0.025C; after the constant current and constant voltage charging, a discharge-charge-discharge process is also included.

[0020] According to the above-mentioned formation method, the battery after injection is a sodium ion battery.

[0021] The charging end voltage of the first constant current charging process does not exceed 2.1V;

[0022] and / or, the charging end voltage of the second constant current charging process does not exceed 2.9V;

[0023] and / or, the charging end voltage of the third constant current charging process does not exceed 4.1V;

[0024] And / or, the constant current and constant voltage charging process is a charging current of 0.5-0.7C, a charging cut-off voltage of 3.9-4.1V, and a cut-off current of 0.025C;

[0025] And / or, the discharge-charge-discharge process: 1) the discharge current is 0.2-0.7C, and the cut-off voltage is 1.5-2.0V; 2) the charge current is 0.2-1.0C, the charge cut-off voltage is 3.9-4.1V, and the cut-off current is 0.025C; 3) the discharge current is 0.2-0.7C, and the cut-off voltage is 1.5-2.0V.

[0026] In another aspect, the present invention provides a battery prepared by the above-mentioned formation method.

[0027] Another aspect of the present invention provides an electronic device comprising the battery as described above.

[0028] The battery formation method provided by the present invention limits the current density and time of the first constant current charging process, the second constant current charging process and the third constant current charging process through a three-step constant current charging process, optimizes the self-discharge of the battery and takes into account the cycle performance and battery capacity of the battery. DETAILED DESCRIPTION

[0029] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0030] On one hand, the present invention provides a battery formation method, comprising the following steps: 1) performing a first constant current charging treatment on a battery after liquid injection at a charging current of 0.01-0.05C for a charging time of 120-180 minutes to obtain a first rechargeable battery; 2) performing a second constant current charging treatment on the first rechargeable battery at a charging current of 0.1-0.2C for a charging time of 90-180 minutes to obtain a second rechargeable battery; and 3) performing a third constant current charging treatment on the second rechargeable battery at a charging current of 0.2-0.5C for a charging time of 30-90 minutes to obtain a formed battery.

[0031] The battery after injection refers to the battery after assembly, injection of electrolyte and sealing. The present invention does not limit the specific process of assembly, injection and sealing.

[0032] In one embodiment, the electrolyte is injected into a sealed device that is dry and filled with an inert gas, wherein the inert gas includes at least one of nitrogen and argon, and the dew point during the injection process does not exceed -50°C.

[0033] It is understood that the battery after injection includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, with the separator being disposed between the positive and negative electrode sheets. The positive electrode sheet includes a positive electrode current collector and a positive electrode active material disposed on the positive electrode current collector, while the negative electrode sheet includes a negative electrode current collector and a negative electrode active material disposed on the negative electrode current collector.

[0034] The first constant current charging process, the second constant current charging process and the third constant current charging process in the present invention are performed at room temperature, for example, 25°C.

[0035] In detail, in step 1), the charging current of the first constant current charging treatment is 0.01-0.05C. For example, the charging current includes but is not limited to 0.01C, 0.02C, 0.03C, 0.04C, 0.05C, or a range consisting of any two thereof; the charging time of the first constant current charging treatment is 120-180min. For example, the charging time includes but is not limited to 120min, 130min, 140min, 150min, 160min, 170min, 180min, or a range consisting of any two thereof.

[0036] In step 2), the charging current of the second constant current charging process is 0.1-0.2C. For example, the charging current includes but is not limited to 0.1C, 0.12C, 0.14C, 0.16C, 0.18C, 0.2C, or a range consisting of any two thereof; the charging time of the second constant current charging process is 90-180min. For example, the charging time includes but is not limited to 90min, 100min, 120min, 140min, 160min, 180min, or a range consisting of any two thereof.

[0037] In step 3), the charging current of the third constant current charging treatment is 0.2-0.5C. For example, the charging current includes but is not limited to 0.2C, 0.25C, 0.3C, 0.35C, 0.4C, 0.45C, 0.5C, or a range consisting of any two thereof; the charging time of the third constant current charging treatment is 60-90min. For example, the charging time includes but is not limited to 30min, 40min, 50min, 60min, 65min, 70min, 75min, 80min, 85min, 90min, or a range consisting of any two thereof.

[0038] There is no idle time between the first constant current charging process, the second constant current charging process and the third constant current charging process in the present invention. It can be understood that there may be a short pause between the first constant current charging process and the second constant current charging process and between the second constant current charging process and the third constant current charging process due to the replacement of the debugging device parameters, and the pause time does not exceed 1 minute.

[0039] The formation method provided by the present invention can effectively improve the self-discharge of the battery while also achieving excellent battery capacity and cycle performance. The inventors have analyzed this and believe that the reason may be that: the first stage adopts a low current of 0.01 to 0.05C, which is conducive to the formation of more dense and stable inorganic sodium salts in the inner layer of the SEI film. At the same time, the gas generated by the low current formation is relatively less, which is conducive to the removal of side reaction gases during film formation; the second stage adopts 0.1 to 0.2C, which is mainly based on loose and porous organic sodium salts. At the same time, the SEI film is properly aged, and some unstable organic sodium salts are further reacted to form more stable inorganic sodium salts, thereby enhancing the stability of the SEI film; the third stage adopts 0.2 to 0.5C, at which time the SEI film structure is relatively stable, and the high current formation shortens the formation process time to meet production needs. When different current densities are adopted and the charging time of each first stage is controlled, a denser SEI film inner layer and SEI film outer layer structure can be formed, thereby optimizing the SEI components and structure, reducing side reactions at the positive and negative electrode / electrolyte interfaces, reducing self-discharge, and improving battery capacity and cycle performance.

[0040] Furthermore, in a specific embodiment of the present invention, a first aging treatment is included before the first constant current charging treatment; and / or a second aging treatment is included after the third constant current charging treatment; wherein the temperature of the first aging treatment is 25-45°C and the time is 24-72h; the temperature of the second aging treatment is 45-65°C and the time is 24-72h.

[0041] In detail, the battery after injection is placed in an oven at 25-45°C for a first aging treatment, and the treatment time is 24-74h. For example, the temperature of the first aging treatment is 25°C, 30°C, 35°C, 40°C, 45°C or a range composed of any two thereof, and the time of the first aging treatment is 24h, 30h, 35h, 40h, 45h, 50h, 55h, 60h, 65h, 70h, 72h or a range composed of any two thereof.

[0042] The first aging treatment helps to fix the internal structure of the battery, reduce the internal stress and damage caused by the expansion and contraction of the material, thereby improving the stability and cycle life of the battery. It can also optimize the interaction between the electrode material and the electrolyte and improve the electrochemical performance of the battery.

[0043] The formed battery is subjected to a second aging treatment in an oven at 45-65°C for 24-72 hours. For example, the temperature of the second aging treatment includes, but is not limited to, 45°C, 50°C, 55°C, 60°C, 65°C, or any range therebetween; and the treatment time includes, but is not limited to, 24 hours, 30 hours, 35 hours, 40 hours, 45 hours, 50 hours, 55 hours, 60 hours, 65 hours, 70 hours, 72 hours, or any range therebetween.

[0044] When the temperature and time of the second aging treatment are within the above ranges, the self-discharge of the battery is further improved. This may be because the solubility of sodium salts in the electrolyte solvent is relatively high. Appropriate high-temperature aging can accelerate the dissolution of the highly soluble sodium salts in the SEI film, while forming a more stable sodium salt component, further forming a stable SEI film.

[0045] Furthermore, in a specific embodiment of the present invention, after the second aging treatment, a constant current and constant voltage charging treatment is further performed at a charging current of 0.5-0.7C until the cut-off voltage is reached.

[0046] In detail, in the constant current and constant voltage charging process of the present invention, the charging current includes but is not limited to 0.5C, 0.52C, 0.54C, 0.56C, 0.58C, 0.6C, 0.62C, 0.64C, 0.66C, 0.68C, 0.7C or a range between any two of them.

[0047] It is understandable that different types of secondary batteries have different cut-off voltages, such as 3.9V, 3.95V, 4.0V, and 4.1V.

[0048] When constant current and constant voltage charging is performed according to the above charging current, the charging current is 0.5-0.7C constant current and constant voltage charging to the cut-off voltage (3.9-4.1V), the cut-off current is 0.025C, and the time is set to 60-120min (100% SOC).

[0049] Furthermore, in a specific embodiment of the present invention, the amount of electricity at the end of charging in the first constant current charging process does not exceed 15% SOC.

[0050] Among them, SOC is the reversible capacity of the battery, that is, the state of charge of the battery, which is used to reflect the remaining capacity of the battery. Its value is defined as the ratio of the remaining capacity to the battery capacity, usually expressed as a percentage.

[0051] It is understood that the amount of electricity required to complete charging can be controlled by controlling the charging current, charging voltage, charging time, and charging type.

[0052] When the amount of electricity at the end of the first constant-current charging process is within the above range, possible heat and voltage stress can be reduced, which is helpful for initialization and balancing of the battery.

[0053] Furthermore, in a specific embodiment of the present invention, the amount of electricity at the end of the second constant current charging process does not exceed 45% SOC.

[0054] When the charge at the end of the second constant current charging process is within the above range, the charge capacity of the battery can be further increased, the chemical reaction inside the battery can be promoted, and the instability of the chemical reaction caused by excessive charge can be avoided, thereby affecting the structure of the SEI film.

[0055] Furthermore, in a specific embodiment of the present invention, the amount of electricity at the end of the third constant current charging process does not exceed 80% SOC.

[0056] When the amount of electricity at the end of the first constant current charging process is controlled to be within the above range, the charge state of the battery can be further improved and ensured to reach a certain proportion of the designed capacity.

[0057] Furthermore, in a specific embodiment of the present invention, the constant current and constant voltage charging process is a charging current of 0.5-0.7C, a charging cut-off voltage of 3.9-4.1V, and a cut-off current of 0.025C; after the constant current and constant voltage charging process, it also includes a discharge-charge-discharge process.

[0058] Specifically, the battery reaches the cutoff voltage during constant current constant voltage charging, and then performs a discharge process. After all the battery power is discharged, the battery is charged again to the cutoff voltage, and then performs a discharge process again to 1.5-2.0V (0% SOC).

[0059] When the discharge-charge-discharge treatment is performed, the stability and capacity retention of the battery can be further evaluated, and then the cycle stability and battery capacity of the battery in actual application can be evaluated.

[0060] Furthermore, in a specific embodiment of the present invention, the battery after injection is a sodium ion battery, and the charging end voltage of the first constant current charging process does not exceed 2.1V;

[0061] and / or, the charging end voltage of the second constant current charging process does not exceed 2.9V;

[0062] and / or, the charging end voltage of the third constant current charging process does not exceed 4.1V;

[0063] And / or, the constant current and constant voltage charging process is a charging current of 0.5-0.7C, a charging cut-off voltage of 3.9-4.1V, and a cut-off current of 0.025C;

[0064] And / or, discharge-charge-discharge treatment: 1) discharge current is 0.2~0.7C, cut-off voltage is 1.5-2.0V; 2) charge current is 0.2~1.0C, charge cut-off voltage is 3.9-4.1V, cut-off current is 0.025C; 3) discharge current is 0.2~0.7C, cut-off voltage is 1.5-2.0V.

[0065] In detail, the battery after injection is a sodium ion battery, which includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte.

[0066] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material, and the positive electrode active material is not limited to a layered oxide (L x Na y M z Cu α Fe β Mn γ O 2+δ-0.5η X η , wherein L is an alkali metal doping substitution element, M is a transition metal doping substitution element, X is an oxygen doping substitution element, 0≤x<0.35, 0.65≤y≤1, 0<α≤0.3, 0<β≤0.5, 0<γ≤0.5, -0.03≤δ≤0.03, 0≤η≤0.1, z+α+β+γ=1, and mx+y+nz+2α+3β+4γ=2(2+δ)), polyanion (A a M b (PO4) c O x X 3-x active material, wherein A is one or more of H, Li, Na, K and NH4, M is one or more of Ti, Cr, Mn, Fe, Co, Ni, V, Cu and Zn, X is one or more of F, Cl and Br, 0<a≤4, 0<b≤2, 1≤c≤3, 0≤x≤2), Prussian blue / white (A x M[M′(CN)6] y ·zH2O, wherein A is one or more of alkali metal ions and alkaline earth metal ions, M and M' are transition metals, 0 <x≤2,0.8≤y<1,0<z≤20)。

[0067] The positive electrode current collector includes but is not limited to at least one of a metal foil, a carbon-coated metal foil or a porous metal plate, such as aluminum foil.

[0068] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer containing a negative electrode active material. The negative electrode active material includes but is not limited to hard carbon (resin-based / biomass-based / asphalt / coal-based, etc.), soft carbon (coal / asphalt, etc.), etc.

[0069] The negative electrode current collector includes but is not limited to at least one of a metal foil, a carbon-coated metal foil or a porous metal plate, such as aluminum foil.

[0070] The positive electrode active material layer also includes a conductive agent, a binder, and a liquid dispersant. The conductive agent improves the conductivity of the positive electrode active material layer, and the binder serves to firmly bond the positive electrode active material to the positive electrode current collector through the binder. The present invention does not specifically limit the types of conductive agent and binder, and they can be selected according to actual needs. In one embodiment, the conductive agent includes, but is not limited to, one or more combinations of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In one embodiment, the binder includes, but is not limited to, one or more combinations of polyvinylidene fluoride, polyacrylic acid, lithium polyacrylate, sodium polyacrylate, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, and styrene-butadiene rubber. The liquid dispersant includes, but is not limited to, one or more of N-methyl-2-pyrrolidone, tetrahydrofuran, dimethylformamide, and ethanol.

[0071] The negative electrode active material layer also includes a conductive agent, a binder, a thickener, and a liquid dispersant. The conductive agent improves the conductivity of the negative electrode active material layer, while the binder securely bonds the negative electrode active material to the negative electrode current collector. The present invention does not impose specific restrictions on the types of conductive agent, binder, and thickener; they can be selected based on actual needs.

[0072] In one embodiment, the conductive agent includes, but is not limited to, one or more combinations of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The binder includes, but is not limited to, one or more combinations of polyvinylidene fluoride, polyacrylic acid, lithium polyacrylate, sodium polyacrylate, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, and styrene-butadiene rubber. The thickener includes, but is not limited to, one or more combinations of carboxymethyl cellulose, sodium carboxymethyl cellulose, and lithium carboxymethyl cellulose. The liquid dispersant includes, but is not limited to, one or more combinations of water, N-methyl-2-pyrrolidone, tetrahydrofuran, dimethylformamide, and ethanol.

[0073] The isolation membrane includes a single-layer or multi-layer film of one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.

[0074] The electrolyte includes an organic solvent and a sodium salt, wherein the organic solvent includes but is not limited to one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC) and corresponding ether substances (such as ethylene glycol monomethyl ether series - EM / DEM / TEM, etc.); the sodium salt includes but is not limited to one or more combinations of NaPF6, NaFSI, NaClO4, NaBCl4, NaSO3CF3 and Na(CH3)C6H4SO3.

[0075] In detail, when the battery in the present invention refers to a sodium ion battery, the charging end voltage of the first constant current charging treatment does not exceed 2.1V; and / or, the charging end voltage of the second constant current charging treatment does not exceed 2.9V; and / or, the charging end voltage of the third constant current charging treatment does not exceed 4.1V; and / or, the charging cut-off voltage of the discharge-charge-discharge treatment is 3.9-4.1V, and the cut-off current is 0.025C; the discharge cut-off voltage is 1.5-2.0V.

[0076] When the battery of the present invention is a sodium-ion battery and falls within the aforementioned voltage range, the aforementioned formation method can produce a high-capacity sodium-ion battery with excellent self-discharge and cycling performance. This is because the use of different current densities and step-by-step charging creates a denser inner SEI layer and a looser outer SEI layer. Furthermore, the overall SEI film is regulated by the temperature and time of the secondary aging process, achieving dissolution and reconstruction of the entire SEI film. This optimizes the SEI film composition and structure, reduces side reactions at the positive and negative electrode / electrolyte interfaces, and thus reduces self-discharge and achieves superior cycling performance.

[0077] Another aspect of the present invention provides a battery prepared by the above-mentioned formation method.

[0078] The present invention does not limit the specific selection of the positive electrode sheet and the electrolyte in the battery. Optionally, the positive electrode sheet includes a layered oxide (L x Na y M z Cu α Fe β Mn γ O 2+δ-0.5η X η ), polyanion (A a M b (PO4) c O x X 3-x ), Prussian Blue / White(A x M[M′(CN)6] y At least one of:

[0079] The electrolyte includes sodium salt, solvent and additives; wherein the sodium salt is at least one of NaPF6, NaFSI, NaClO4, NaBCl4, NaSO3CF3 and Na(CH3)C6H4SO3; the solvent is one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC) and corresponding ether substances (such as ethylene glycol monomethyl ether series - EM / DEM / TEM, etc.); the additive is VC, FEC, DFEC or other film-forming additives.

[0080] The battery provided by the present invention is prepared by the above-mentioned formation method, so the self-discharge situation is effectively improved, and at the same time, the battery has excellent battery capacity and cycle performance.

[0081] Another aspect of the present invention provides an electronic device comprising the battery as described above.

[0082] The present invention is not limited to the specific type of electronic equipment and can include electric vehicles, mobile phones, smart homes, robots, drones, electronic cigarettes, speakers, and any other device that requires battery power.

[0083] The electronic device provided by the present invention includes the battery of the second aspect, so the self-discharge situation is effectively improved, and at the same time, the battery has excellent capacity and cycle performance.

[0084] Hereinafter, the formation method provided by the present invention will be described in detail through specific examples.

[0085] Example 1

[0086] The formation method provided in this embodiment comprises the following steps:

[0087] 1. Wind the positive electrode sheet, separator, and negative electrode sheet to obtain a battery cell, inject the electrolyte into a dry sealing device filled with nitrogen atmosphere, remove the battery from the sealing device, seal it, and pre-charge it to 1% SOC to obtain a battery after injection.

[0088] Among them, the positive electrode: layered oxide (NaNi 0.33 Fe 0.33 Mn 0.33 O2): conductive agent (conductive carbon black SP / carbon nanotube CNT): binder (PVDF) = 96:2:2 (weight ratio);

[0089] Negative electrode: hard carbon: conductive agent (conductive carbon black SP / carbon nanotube CNT): binder (SBR): dispersant (CMC) = 94:2:2.5:1.5 (weight ratio);

[0090] The electrolyte is composed of sodium salt (NaPF6 / NaFSI=11:2 (weight ratio)), solvent (PC / EMC / DEM=45:45:10 (weight ratio)) and additives (VC / FEC / PS / NaPF2O2 / NaDFOB=1:0.5:2:0.5:0.5 (weight ratio)).

[0091] 2. The battery after injection was placed in an oven at 25°C for the first aging treatment for 72 hours, and then the first constant current charging treatment was performed at a charging current of 0.04C for 150 minutes. The charging end voltage was 2.0V, and the charging end capacity was 10% SOC, thereby obtaining a first rechargeable battery.

[0092] 3. Perform a second constant current charging process at a charging current of 0.1 C for 180 min, with a charging end voltage of 2.8 V and a charging end capacity of 40% SOC, to obtain a second rechargeable battery.

[0093] 4. A third constant current charging process was performed at a charging current of 0.25 C for 60 min, with a charging end voltage of 3.1 V and a charging end capacity of 65% SOC, to obtain a formed battery.

[0094] 5. The formed battery was placed in an oven at 45°C for a second aging treatment for 72 hours. The battery was then subjected to a constant current and constant voltage charging treatment at a charging current of 0.5C until the cutoff voltage was reached and the cutoff current was 0.025C. Finally, a discharge-charge-discharge treatment was performed, wherein the discharge cutoff voltage was 1.5V, the charge cutoff voltage was 4.1V, and the cutoff current was 0.025C, to obtain a battery.

[0095] Example 2

[0096] The formation method provided in this embodiment comprises the following steps:

[0097] 1. Wind the positive electrode sheet, separator, and negative electrode sheet to obtain a battery cell, inject the electrolyte into a dry sealing device filled with nitrogen atmosphere, remove the battery from the sealing device, seal it, and pre-charge it to 1% SOC to obtain a battery after injection.

[0098] Among them, the positive electrode: layered oxide (NaNi 0.33 Fe 0.33 Mn 0.33 O2): conductive agent (conductive carbon black SP / carbon nanotube CNT): binder (PVDF) = 96:2:2 (weight ratio);

[0099] Negative electrode: hard carbon: conductive agent (conductive carbon black SP / carbon nanotube CNT): binder (SBR): dispersant (CMC) = 94:2:2.5:1.5 (weight ratio);

[0100] The electrolyte is composed of sodium salt (NaPF6 / NaFSI=11:2 (weight ratio)), solvent (PC / EMC / DEM=45:45:10 (weight ratio)) and additives (VC / FEC / PS / NaPF2O2 / NaDFOB=1:0.5:2:0.5:0.5 (weight ratio)).

[0101] 2. The battery after injection was placed in an oven at 45°C for the first aging treatment for 24 hours, and then the first constant current charging treatment was performed at a charging current of 0.01C for 180 minutes. The charging end voltage was 1.65V, and the charging end capacity was 3% SOC, thereby obtaining a first rechargeable battery.

[0102] 3. Perform a second constant current charging process at a charging current of 0.2C for 90 minutes, with a charging end voltage of 2.6V and a charging end capacity of 33% SOC, to obtain a second rechargeable battery.

[0103] 4. A third constant current charging process was performed at a charging current of 0.5 C for 30 min, with a charging end voltage of 3.0 V and a charging end capacity of 58% SOC, to obtain a formed battery.

[0104] 5. The formed battery was placed in an oven at 60°C for a second aging treatment for 72 hours. The battery was then subjected to a constant current and constant voltage charging treatment at a charging current of 0.7C until the cutoff voltage was reached and the cutoff current was 0.025C. Finally, a discharge-charge-discharge treatment was performed, wherein the discharge cutoff voltage was 2.0V, the charge cutoff voltage was 3.9V, and the cutoff current was 0.025C, to obtain a battery.

[0105] Example 3

[0106] The formation method provided in this embodiment comprises the following steps:

[0107] 1. Wind the positive electrode sheet, separator, and negative electrode sheet to obtain a battery cell, inject the electrolyte into a dry sealing device filled with nitrogen atmosphere, remove the battery from the sealing device, seal it, and pre-charge it to 1% SOC to obtain a battery after injection.

[0108] Among them, according to the weight ratio of positive electrode: layered oxide (NaNi 0.33 Fe 0.33 Mn 0.33O2): conductive agent (conductive carbon black SP / carbon nanotubes CNT): binder (PVDF) = 96:2:2; negative electrode: hard carbon: conductive agent (conductive carbon black SP / carbon nanotubes CNT): binder (SBR): dispersant (CMC) = 94:2:2.5:1.5; the electrolyte is composed of sodium salt (NaPF6 / NaFSI = 11:2 (weight ratio)), solvent (PC / EMC / DEM = 45:45:10 (weight ratio)) and additives (VC / FEC / PS / NaPF2O2 / NaDFOB = 1:0.5:2:0.5:0.5 (weight ratio)).

[0109] 2. The battery after injection was placed in an oven at 30°C for the first aging treatment for 48 hours, and then the first constant current charging treatment was performed at a charging current of 0.03C for 150 minutes. The charging end voltage was 1.8V, and the charging end capacity was 7.5% SOC, thereby obtaining a first rechargeable battery.

[0110] 3. Perform a second constant current charging process at a charging current of 0.15C for 120 minutes, with a charging end voltage of 2.7V and a charging end capacity of 37.5% SOC, to obtain a second rechargeable battery.

[0111] 4. A third constant current charging process was performed at a charging current of 0.3C for 80 minutes. The charging end voltage was 3.2V, and the charging end capacity was 77.5% SOC, thereby obtaining a formed battery.

[0112] 5. The formed battery was placed in an oven at 65°C for a second aging treatment for 24 hours. The battery was then charged at a constant current and constant voltage at a charging current of 0.6C until the cutoff voltage was reached, with a cutoff current of 0.025C. Finally, a discharge-charge-discharge treatment was performed, with the discharge cutoff voltage being 1.7V and the charge cutoff voltage being 4.0V, to obtain a battery.

[0113] Example 4

[0114] The formation method provided in this embodiment is basically the same as that in Example 1, except that:

[0115] In step 2), the temperature of the first aging treatment is 20° C. and the time is 74 h.

[0116] Example 5

[0117] The formation method provided in this embodiment is basically the same as that in Example 1, except that:

[0118] In step 5), the temperature of the second aging treatment is 40° C. and the time is 74 h.

[0119] Example 6

[0120] The formation method provided in this embodiment is basically the same as that in Example 1, except that:

[0121] In step 5), the charging current of the constant current constant voltage charging process is 0.4C.

[0122] Example 7

[0123] The formation method provided in this embodiment is basically the same as that in Example 1, except that:

[0124] In step 2), the charging ends at 20% SOC.

[0125] Example 8

[0126] The formation method provided in this embodiment is basically the same as that in Example 1, except that:

[0127] In step 3), the charging ends at 50% SOC.

[0128] Example 9

[0129] The formation method provided in this embodiment is basically the same as that in Example 1, except that:

[0130] In step 4), the charging ends at 90% SOC.

[0131] Comparative Example 1

[0132] The formation method provided in this comparative example is basically the same as that in Example 1, except that:

[0133] No step 2)

[0134] In step 3), the current of the second constant current charging treatment is 0.2C and the time is 120 minutes;

[0135] In step 4), the third constant current charging process has a current of 0.5C and a time of 30 minutes.

[0136] Comparative Example 2

[0137] The formation method provided in this comparative example is basically the same as that in Example 1, except that:

[0138] In step 3), the current of the second constant current charging process is 0.6C;

[0139] In step 4), the current of the third constant current charging process is 1.0C.

[0140] Comparative Example 3

[0141] The formation method provided in this comparative example is basically the same as that in Example 1, except that:

[0142] In step 2), the first constant current charging treatment lasts for 100 minutes, and the final charge capacity is 6.67% SOC;

[0143] In step 3), the second constant current charging process lasts for 80 minutes, and the charging ends at a state of charge of 20%;

[0144] In step 4), the third constant current charging process lasts for 100 minutes, and the final charge level is 61.67% SOC.

[0145] Test Case

[0146] 1. Self-discharge test

[0147] At 23±2°C and normal pressure (0.1MPa), the batteries prepared in the examples and comparative examples were charged at a constant current rate of 0.2C to the charge and discharge cut-off voltage, then charged at a constant voltage to a cut-off current of 0.05C, then allowed to stand for 5 minutes, and then discharged at a constant current rate of 0.2C to the lower limit of the charge and discharge cut-off voltage. After standing for 5 minutes, they were then charged at a constant current and constant voltage rate of 0.2C to 3.2V. After the cells were removed from the cabinet, the voltage was sorted between 3.10V and 3.20V, and low-voltage recharge was performed. After being removed from the cabinet, the cells were stored at room temperature for 24 hours, and the voltage (OCV1) was measured. The voltage (OCV2) was then measured at 23±5°C for 120 hours. The calculation was performed according to the following formula. The specific results are shown in Table 1.

[0148]

[0149] 2. Cycle performance test

[0150] At 25±3℃, charge to 3.95V at a constant current of 1.0C, charge to 0.025C, and then discharge to 1.5V at a discharge rate of 2.0C. Repeat this charge and discharge cycle 100 times and measure the discharge capacity Q1 at the first cycle and the discharge capacity Q at the 100th cycle. 100 .

[0151] The capacity retention rate Q after 100 cycles was calculated according to the following formula:

[0152] Capacity retention rate Q = Q 100 / Q1*100%

[0153] See Table 1 for specific results.

[0154] Table 1

[0155]

[0156] Comparing Examples 1 to 9 with Comparative Example 1, it can be seen that, within a certain range, increasing the first-stage low-current formation temperature can help increase the capacity of the sodium-ion battery and improve the self-discharge effect, while also significantly improving the cycle retention rate: this indicates that low-current formation can form a more dense and stable SEI film inner layer structure. Comparing Examples 1 and 4, it can be seen that, within a certain range, a suitable primary aging temperature can enhance the electrolyte infiltration effect, ensure the uniformity of film formation, and obtain a more stable SEI film, thereby obtaining a sodium-ion battery with better performance. Comparing Examples 1 and 5, it can be seen that, within a certain range, lowering the secondary aging temperature may not effectively achieve the dissolution and reconstruction of the SEI film, resulting in no significant improvement in its self-discharge. Comparing Examples 1 and 6, it can be seen that there is no significant difference. Simply increasing the constant current and constant voltage time increases the time required for the formation process. Comparing Examples 1 and 7, it can be seen that the increase in the first-stage charging SOC and the thicker SEI film inner layer are beneficial to improving the self-discharge effect. However, the thicker SEI film inner layer structure leads to greater transmission impedance, which is not conducive to the battery's capacity utilization and cycle performance. Comparing Example 1 and Example 8, it can be seen that the charging SOC in the second stage increases, and the outer layer of the SEI film is thicker, which is beneficial to improving the self-discharge effect, but is not conducive to the capacity and cycle performance of the battery. Comparing Example 1 and Example 9, it can be seen that the charging SOC in the third stage increases, and the final SEI film is thicker, which is beneficial to improving the self-discharge effect, but is not conducive to the capacity and cycle performance of the battery. Comparing Example 1 and Comparative Example 2, it can be seen that the constant current in the second and third stages is too large, which is not conducive to the dissolution and reconstruction of the SEI film, and the effect of improving the self-discharge is not significant, and the capacity and cycle performance of the battery are poor. Comparing Example 1 and Comparative Example 3, it can be seen that when the constant current SOC in the second stage is too low, the SEI film formation may not be sufficient and uniform, and the self-discharge cannot be significantly improved, and the capacity and cycle performance of the battery are slightly poor.

[0157] In summary, the formation method provided by the present invention effectively improves the self-discharge performance of the sodium ion battery without reducing the capacity of the sodium ion battery, and at the same time has excellent cycle performance.

[0158] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A battery formation method, characterized in that: The following steps are involved: 1) performing a first constant current charging process on the injected battery at a charging current of 0.01-0.05C for 120-180 minutes to obtain a first rechargeable battery; 2) performing a second constant current charging process on the first rechargeable battery at a charging current of 0.1-0.2C for a charging time of 90-180 minutes to obtain a second rechargeable battery; 3) performing a third constant current charging process on the second rechargeable battery at a charging current of 0.2-0.5C for 30-90 minutes to obtain a formed battery.

2. The chemical formation method according to claim 1, characterized in that The first constant current charging treatment further includes a first aging treatment before the first constant current charging treatment; and / or the third constant current charging treatment further includes a second aging treatment; Wherein, the temperature of the first aging treatment is 25-45°C and the time is 24-72h; The temperature of the second aging treatment is 45-65° C., and the time is 24-72 hours.

3. The chemical formation method according to claim 2, characterized in that After the second aging treatment, a constant current and constant voltage charging treatment is performed at a charging current of 0.5-0.7C until the cut-off voltage is reached.

4. The chemical formation method according to claim 3, characterized in that The amount of electricity at the end of the first constant current charging process does not exceed 15% SOC.

5. The chemical formation method according to claim 3 or 4, characterized in that: The amount of electricity at the end of the second constant current charging process does not exceed 45% SOC.

6. The chemical formation method according to any one of claims 3 to 5, characterized in that: The amount of electricity at the end of the third constant current charging process does not exceed 80% SOC.

7. The chemical formation method according to any one of claims 3 to 6, characterized in that: The constant current and constant voltage charging process is a charging current of 0.5-0.7C, a charging cut-off voltage of 3.9-4.1V, and a cut-off current of 0.025C; after the constant current and constant voltage charging, it also includes a discharge-charge-discharge process.

8. The chemical formation method according to claim 7, characterized in that The battery after injection is a sodium ion battery, The charging end voltage of the first constant current charging process does not exceed 2.1V; and / or, the charging end voltage of the second constant current charging process does not exceed 2.9V; and / or, the charging end voltage of the third constant current charging process does not exceed 4.1V; And / or, the constant current and constant voltage charging process is a charging current of 0.5-0.7C, a charging cut-off voltage of 3.9-4.1V, and a cut-off current of 0.025C; And / or, the discharge-charge-discharge process: 1) the discharge current is 0.2-0.7C, and the cut-off voltage is 1.5-2.0V; 2) the charge current is 0.2-1.0C, the charge cut-off voltage is 3.9-4.1V, and the cut-off current is 0.025C; 3) the discharge current is 0.2-0.7C, and the cut-off voltage is 1.5-2.0V.

9. A battery, characterized in that: The compound is prepared by the chemical formation method according to any one of claims 1 to 8.

10. An electronic device, characterized in that: A battery comprising the battery of claim 9.

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