Battery cell formation method using lithium squarate material as lithium supplement agent and application

Abstract

The invention discloses a formation method using squaric acid lithium as a lithium supplement agent and application, the formation method comprises the following steps: (1) preparing a to-be-formed battery cell, the positive electrode containing squaric acid lithium; (2) controlling the formation temperature of the battery cell to be 20-35 DEG C, and controlling the internal pressure of the battery cell to be negative pressure; (3) charging the battery cell by stages, and changing the formation current of the battery cell by stages; (3.1) a first stage: charging the battery cell to 3.0 V; (3.2) a second stage: charging the battery cell to be less than or equal to 4.0 V; and (3.3) a third stage: charging the battery cell to 4.2 V or more than 4.2 V, and then stopping charging. The lithium squarate can be used as a lithium supplement agent to be applied to the lithium ion battery, and the problem of application of the lithium squarate is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium batteries, and in particular relates to a method for forming a battery cell using a lithium squarate material as a lithium supplement and its application. Background Art

[0002] Formation is a chemical and electrochemical reaction process in which the electrolyte is converted to a charged state through charging to improve the electrochemical activity of its active substances. Lithium batteries need to go through the formation process before they can be put into use. When a lithium-ion battery is activated during the first cycle of charging, a portion of the lithium ions in the battery will be consumed to form a solid electrolyte membrane (i.e., SEI membrane) on the surface of the negative electrode. In order to make up for this part of the consumed lithium ions, lithium supplement materials are generally required to be added to lithium-ion batteries. For example, lithium-rich lithium iron oxide and lithium-rich lithium nickel oxide are currently common lithium supplements. Lithium squarate is a highly anticipated lithium supplement material. The specific capacity of lithium squarate is as high as 425 milliampere hours per gram (mA·h / g), which is twice the specific capacity of traditional positive electrode materials. It is suitable as a sacrificial lithium salt to supplement the irreversible capacity loss of lithium ions. However, the current battery cell formation process is not suitable for batteries with lithium squarate lithium supplements, which greatly limits the application of lithium squarate in lithium-ion batteries. Summary of the invention

[0003] In order to solve the above technical problems, the purpose of the present invention is to provide a battery cell formation method and application using lithium quartz material as a lithium supplement, so that the lithium quartz material can be used as a lithium supplement in lithium ion batteries, solving the problem of using lithium quartz.

[0004] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:

[0005] In the first aspect of the present invention, the present invention provides a battery cell formation method using a quartzite material as a lithium supplement, using a lower formation temperature and a segmented formation process, so that the quartzite material can be added as a lithium supplement to an existing lithium ion battery. The formation method steps of the present invention are as follows:

[0006] (1) preparing a battery cell to be formed, wherein the lithium quartz material is used as a lithium supplement for the positive electrode;

[0007] (2) Control the battery cell formation temperature to 20-35°C;

[0008] (3) Control the internal pressure of the battery cell to negative pressure and charge the battery cell in stages;

[0009] (3.1) Stage 1: Charge the battery to 3.0V;

[0010] (3.2) Second stage: charge the battery to less than or equal to 4.0V;

[0011] (3.3) The third stage: Charge the battery cell to 4.2V or above, and then stop charging.

[0012] Preferably, the lithium squarate material includes lithium squarate or a lithium squarate composite material, wherein the lithium squarate composite material refers to a composite material formed by mixing lithium squarate with a conductive carbon material.

[0013] Preferably, in step (1), the positive electrode contains 2-10% of lithium squarate in terms of mass percentage, based on the mass of the positive electrode. When a lithium squarate composite material is used, the amount used is calculated based on the lithium squarate in the lithium squarate composite material.

[0014] Preferably, in step (3), the negative pressure condition changes in stages, wherein in step (3.1), the internal pressure of the battery cell is less than or equal to -10 kPa, and in step (3.3), the internal pressure of the battery cell is less than or equal to -10 kPa.

[0015] Preferably, in step (1), the positive electrode of the battery cell to be formed includes one or more of lithium iron phosphate, lithium iron manganese phosphate, lithium cobalt oxide and ternary lithium.

[0016] Preferably, in step (1), the negative electrode of the battery cell to be formed comprises one or both of graphite and silicon carbon.

[0017] In the second aspect of the present invention, the present invention provides an application of a lithium quartz material as a lithium supplement agent, and through the above-mentioned battery cell formation method, the lithium quartz material is used in the production of lithium ion batteries.

[0018] In a third aspect of the present invention, the present invention provides a lithium-ion battery produced by the above-mentioned formation method, such as a lithium iron phosphate battery, a lithium iron manganese phosphate battery, a lithium cobalt oxide battery, and a ternary lithium battery.

[0019] Beneficial effects:

[0020] Compared with the existing battery cell formation process, the present invention adopts a higher formation voltage, which is conducive to the decomposition of lithium quartz and exerts a lithium supplementation effect. Since the battery cell formation process of the present invention is divided into three stages, the formation time is prolonged, and the prolonged time of the battery cell under negative pressure conditions will cause a significant increase in the loss of the battery cell electrolyte. The present invention greatly reduces the battery cell formation temperature and the electrolyte vapor pressure, thereby reducing the loss of the electrolyte, and solves the problem of lithium quartz being used in lithium ion batteries. DETAILED DESCRIPTION

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the specific implementation methods of the present invention will be described below. Obviously, the following descriptions are only some embodiments of the present invention, and for those of ordinary skill in the art, other implementation methods can also be obtained based on these embodiments without creative work.

[0022] At present, the solution of using lithium squarate as a lithium supplement has not been widely promoted. In addition to the difficulty in preparing lithium squarate, more importantly, the existing battery cell formation process is not suitable for lithium-ion batteries with lithium squarate added as a lithium supplement, which limits the application and promotion of lithium squarate in lithium batteries.

[0023] The present invention provides a battery cell formation method using a quartzite material as a lithium supplement agent, using a relatively low formation temperature and a segmented formation process, so that the quartzite material can be added as a lithium supplement agent to an existing lithium ion battery. The formation method steps of the present invention are as follows:

[0024] (1) preparing a battery cell to be formed, wherein the lithium quartz material is used as a lithium supplement for the positive electrode;

[0025] (2) Control the battery cell formation temperature to 20-35°C;

[0026] (3) Control the internal pressure of the battery cell to be negative pressure, and charge the battery cell in three stages;

[0027] (3.1) Stage 1: Charge the battery to 3.0V and then leave it alone;

[0028] (3.2) Second stage: continue charging the battery to less than or equal to 4.0V, then leave it alone;

[0029] (3.3) The third stage: the battery cell is charged to 4.2V or above, the lithium quartz decomposes to replenish lithium, and then the charging is stopped.

[0030] The decomposition voltage of lithium squarate is about 4.0V. Compared with the existing battery cell formation process, the present invention adopts a higher formation voltage. The conventional battery cell formation voltage cannot reach such a high level. The present invention divides the charging process into three stages. In the first stage, a lower constant current is used to charge the battery cell to 3.0V first, for example, the constant current of the first stage is greater than or equal to 0.05C. In the second stage, a higher constant current is used to quickly charge the battery cell to 4.0V, for example, the constant current of the second stage is greater than or equal to 0.2C. Finally, in the third stage, the battery cell is charged to above 4.2V, for example, the constant current of the third stage is greater than or equal to 0.05C, so that the lithium squarate is decomposed to replenish lithium.

[0031] In the present invention, the lithium quartz material is not limited to lithium quartz, but also includes lithium quartz composite materials. For example, the lithium quartz composite material is composed of lithium quartz and a conductive carbon material (such as graphene). Preferably, the lithium quartz composite material is composed of lithium quartz and a conductive carbon material in a mass ratio of (4 to 49):1. For example, the lithium quartz composite material mentioned in the patent previously applied for by the applicant - a graphene composite lithium / sodium quartz material and its preparation method and application (CN115528220A), and the patent - an alkali metal quartz salt composite material and preparation method (CN115911387A).

[0032] The substance that plays the role of lithium replenishment in the lithium squarate composite material is still lithium squarate, and the role of the conductive carbon material is to facilitate the decomposition and lithium replenishment of lithium squarate.

[0033] In addition, the conventional formation process uses a relatively high temperature, which is related to the chemical activity of each component in the formation process. The present invention greatly reduces the formation temperature and can be formed at room temperature. This is because the battery cell formation process of the present invention is divided into three stages. The formation time is prolonged. The prolonged time of the battery cell under negative pressure conditions will cause a significant increase in the loss of the battery cell electrolyte. Formation at room temperature can reduce the loss of electrolyte.

[0034] In step (3), the rest period after each stage of charging is to protect the charging equipment. Generally, the rest period should not be too long, for example, the rest period is 10s to 120s.

[0035] It should be noted that in the conventional battery cell formation process, the formation temperature cannot be too low, and is generally above 45°C. If the temperature drops, the lithium ion activity will decrease accordingly, and the reaction rate of the electrode will also decrease accordingly. In addition, the conventional battery cell formation process is generally carried out under negative pressure conditions, and the formation time cannot be too long, otherwise the electrolyte loss will be too large, and the electrolyte will need to be replenished again, which will lead to a significant increase in battery costs.

[0036] Although the present invention adopts low temperature conditions, it can solve the problems caused by low temperature formation when the formation process is prolonged, and the low temperature conditions effectively solve the problem of excessive electrolyte loss caused by long formation time.

[0037] In the present invention, based on the mass of the positive electrode and calculated by mass percentage, the positive electrode of the battery cell contains 2-10% of lithium squarate, such as 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, and 10%.

[0038] The formation process of the present invention is applicable to different types of existing lithium-ion batteries, for example, a lithium-ion battery whose positive electrode is lithium iron phosphate, a lithium-ion battery whose positive electrode is lithium cobalt oxide, a lithium-ion battery whose positive electrode is lithium iron manganese phosphate, or a lithium-ion battery whose positive electrode is ternary lithium.

[0039] When dealing with different lithium-ion batteries, the voltage reached during the third stage of charging the battery cell also changes to prevent decomposition of other components of the battery cell.

[0040] For example, when the positive electrode of the battery is lithium iron phosphate, the battery cell can be charged to a maximum of 4.4V in the third stage, that is, the battery cell can be charged to 4.2~4.4V in the third stage.

[0041] For example, when the positive electrode of the battery is lithium cobalt oxide, the battery cell can be charged to a maximum of 4.5V in the third stage, that is, the battery cell can be charged to 4.2-4.5V in the third stage.

[0042] For example, when the positive electrode of the battery is ternary lithium, the maximum charging voltage of the battery cell in the third stage can reach 4.3V, that is, in the third stage, the battery cell can be charged to 4.2~4.3V.

[0043] It is easy to understand that the present invention is aimed at the case where lithium squarate is used as a lithium supplement. When the battery cell is charged, the lithium squarate is decomposed while ensuring that other components of the battery cell do not decompose. In the field of lithium batteries, even if other new positive electrode materials for lithium ion batteries are developed in the future, as long as the decomposition voltage of the positive electrode material is higher than the decomposition voltage of lithium squarate, the formation method of the present invention can also be applied in the same way, and is not limited to the case where the positive electrode material is lithium iron phosphate, lithium iron manganese phosphate, lithium cobalt oxide and ternary lithium.

[0044] In step (3) of the present invention, the negative pressure control is related to the staged charging of step (3). In the first stage, the negative pressure inside the battery cell is controlled to be less than or equal to -10 kPa, for example, the negative pressure is -80 to -10 kPa or below -80 kPa. During this stage, a solid electrolyte interface (SEI) film will be formed on the surface of the negative electrode, and gas will be generated. The generated gas will be extracted from the system in the negative pressure environment.

[0045] In the second stage, the pressure inside the battery cell is not restricted, and the system does not generate gas in this stage. Since the first, second and third stages are continuous and the battery cell is in a negative pressure formation device, in the second stage, the pressure inside the battery cell may be the same as or different from the pressure in the first or third stage. Preferably, the pressure inside the battery cell may be different from the pressure in the first or third stage. More preferably, the negative pressure inside the battery cell is controlled at -40 to 0 kPa, such as -10 to 0 kPa.

[0046] In the third stage, the negative pressure inside the battery cell is controlled to be less than or equal to -10 kPa, for example, the negative pressure is -80 to -10 kPa or below -80 kPa. In this stage, lithium squarate decomposes to produce gas, which is then extracted from the system in the negative pressure environment.

[0047] The technical solution of the present invention is described in detail below with specific embodiments.

[0048] Example 1

[0049] Prepare the battery cell to be formed, the positive electrode is a lithium iron phosphate positive electrode sheet containing 2% lithium quartz lithium supplement, the negative electrode is a graphite negative electrode sheet, the separator is a PP separator, and the electrolyte is 1.0 mol / L LiPF6 / EC+DMC+EMC (weight ratio = 1:1:1) electrolyte.

[0050] The formation temperature is controlled at 25°C, and the internal pressure of the battery cell is controlled by negative pressure formation equipment to change according to different charging stages.

[0051] The internal pressure of the battery cell is -80kPa. The battery cell is charged to 3.0V at a constant current of 0.05C and then left to stand for 1min.

[0052] The internal pressure of the battery cell is -10kPa. The battery cell is charged to 4.0V at a constant current of 0.2C and then left to stand for 1min.

[0053] The internal pressure of the battery cell is -80kPa. The battery cell is charged to 4.4V at a constant current of 0.05C, then left to stand for 1 minute and charging is stopped. The total capacity of the three-step charging is calculated as C0.

[0054] Place the charged battery cells in a 45°C environment for aging and leave them there for 24 hours.

[0055] The battery cells are divided into different capacities. They are charged to 3.65V at 0.2C current, charged to 0.05C at 3.65V constant voltage, and left to stand for 5 minutes. The charging capacity is C1. They are discharged to 2.5V at 0.2C current, left to stand for 5 minutes. The discharge capacity is D1. The specific capacity is calculated based on the mass of the positive electrode main material.

[0056] After the battery cell is manufactured, weigh the battery and calculate the electrolyte loss rate m (%).

[0057] Example 2

[0058] Prepare the battery cell to be formed, the positive electrode is a lithium iron phosphate positive electrode sheet containing 5% lithium quartz lithium supplement, the negative electrode is a graphite negative electrode sheet, the separator is a PP separator, and the electrolyte is 1.0 mol / L LiPF6 / EC+DMC+EMC (weight ratio = 1:1:1) electrolyte.

[0059] The formation temperature is controlled at 25°C, and the internal pressure of the battery cell is controlled by negative pressure formation equipment to change according to different charging stages.

[0060] The internal pressure of the battery cell is -80kPa. The battery cell is charged to 3.0V at a constant current of 0.05C and then left to stand for 1min.

[0061] The internal pressure of the battery cell is -10kPa. The battery cell is charged to 4.0V at a constant current of 0.2C and then left to stand for 1min.

[0062] The internal pressure of the battery cell is -80kPa. The battery cell is charged to 4.4V at a constant current of 0.05C, then left to stand for 1 minute and charging is stopped. The total capacity of the three-step charging is calculated as C0.

[0063] Place the charged battery cells in a 45°C environment for aging and leave them there for 24 hours.

[0064] The battery cells are divided into different capacities. They are charged to 3.65V at 0.2C current, charged to 0.05C at 3.65V constant voltage, and left to stand for 5 minutes. The charging capacity is C1. They are discharged to 2.5V at 0.2C current, left to stand for 5 minutes. The discharge capacity is D1. The specific capacity is calculated based on the mass of the positive electrode main material.

[0065] After the battery cell is manufactured, weigh the battery and calculate the electrolyte loss rate m (%).

[0066] Example 3

[0067] Prepare the battery cell to be formed, the positive electrode is a lithium iron phosphate positive electrode sheet containing 2% lithium quartz lithium supplement, the negative electrode is a graphite negative electrode sheet, the separator is a PP separator, and the electrolyte is 1.0 mol / L LiPF6 / EC+DMC+EMC (weight ratio = 1:1:1) electrolyte.

[0068] The formation temperature is controlled at 25°C, and the internal pressure of the battery cell is controlled by negative pressure formation equipment to change according to different charging stages.

[0069] The internal pressure of the battery cell is -80kPa. The battery cell is charged to 3.0V at a constant current of 0.05C and then left to stand for 1min.

[0070] The internal pressure of the battery cell is -10kPa. The battery cell is charged to 4.0V at a constant current of 0.2C and then left to stand for 1min.

[0071] The internal pressure of the battery cell is -80kPa. The battery cell is charged to 4.3V at a constant current of 0.05C, then left to stand for 1 minute and charging is stopped. The total capacity of the three-step charging is calculated as C0.

[0072] Place the charged battery cells in a 45°C environment for aging and leave them there for 24 hours.

[0073] The battery cells are divided into different capacities. They are charged to 3.65V at 0.2C current, charged to 0.05C at 3.65V constant voltage, and left to stand for 5 minutes. The charging capacity is C1. They are discharged to 2.5V at 0.2C current, left to stand for 5 minutes. The discharge capacity is D1. The specific capacity is calculated based on the mass of the positive electrode main material.

[0074] After the battery cell is manufactured, weigh the battery and calculate the electrolyte loss rate m (%).

[0075] Example 4

[0076] Prepare the battery cell to be formed, the positive electrode is a lithium cobalt oxide positive electrode sheet containing 2% lithium squarate lithium supplement, the negative electrode is a graphite negative electrode sheet, the diaphragm is a PP diaphragm, and the electrolyte is 1.0 mol / L LiPF6 / EC+DMC+EMC (weight ratio = 1:1:1) electrolyte.

[0077] The formation temperature is controlled at 25°C, and the internal pressure of the battery cell is controlled by negative pressure formation equipment to change according to different charging stages.

[0078] The internal pressure of the battery cell is -80kPa. The battery cell is charged to 3.0V at a constant current of 0.05C and then left to stand for 1min.

[0079] The internal pressure of the battery cell is -10kPa. The battery cell is charged to 4.0V at a constant current of 0.2C and then left to stand for 1min.

[0080] The internal pressure of the battery cell is -80kPa. The battery cell is charged to 4.5V at a constant current of 0.05C, then left to stand for 1 minute and charging is stopped. The total capacity of the three-step charging is calculated as C0.

[0081] Place the charged battery cells in a 45°C environment for aging and leave them there for 24 hours.

[0082] The battery cells are divided into different capacities. Charge to 4.5V with a current of 0.2C, charge to 0.05C with a constant voltage of 4.5V, and let stand for 5 minutes. The charging capacity is C1. Discharge to 3V with a current of 0.2C, let stand for 5 minutes, and the discharge capacity is D1. The specific capacity is calculated based on the mass of the main positive electrode material.

[0083] After the battery cell is manufactured, weigh the battery and calculate the electrolyte loss rate m (%).

[0084] Example 5

[0085] Prepare the battery cell to be formed, the positive electrode is a lithium cobalt oxide positive electrode sheet containing 6% lithium squarate lithium supplement, the negative electrode is a graphite + silicon carbon negative electrode sheet, the diaphragm is a PP diaphragm, and the electrolyte is 1.0 mol / L LiPF6 / EC+DMC+EMC (weight ratio = 1:1:1) electrolyte.

[0086] The formation temperature is controlled at 25°C, and the internal pressure of the battery cell is controlled by negative pressure formation equipment to change according to different charging stages.

[0087] The internal pressure of the battery cell is -80kPa. The battery cell is charged to 3.0V at a constant current of 0.05C and then left to stand for 1min.

[0088] The internal pressure of the battery cell is -10kPa. The battery cell is charged to 4.0V at a constant current of 0.2C and then left to stand for 1min.

[0089] The internal pressure of the battery cell is -80kPa. The battery cell is charged to 4.5V at a constant current of 0.05C, then left to stand for 1 minute and charging is stopped. The total capacity of the three-step charging is calculated as C0.

[0090] Place the charged battery cells in a 45°C environment for aging and leave them there for 24 hours.

[0091] The battery cells are divided into different capacities. Charge to 4.5V with a current of 0.2C, charge to 0.05C with a constant voltage of 4.5V, and let stand for 5 minutes. The charging capacity is C1. Discharge to 3V with a current of 0.2C, let stand for 5 minutes, and the discharge capacity is D1. The specific capacity is calculated based on the mass of the main positive electrode material.

[0092] After the battery cell is manufactured, weigh the battery and calculate the electrolyte loss rate m (%).

[0093] Example 6

[0094] Prepare the battery cell to be formed, the positive electrode is a ternary lithium positive electrode sheet containing 4% lithium squarate lithium supplement, the negative electrode is a graphite negative electrode sheet, the separator is a PP separator, and the electrolyte is 1.0 mol / L LiPF6 / EC+DMC+EMC (weight ratio = 1:1:1) electrolyte.

[0095] The formation temperature is controlled at 25°C, and the internal pressure of the battery cell is controlled by negative pressure formation equipment to change according to different charging stages.

[0096] The internal pressure of the battery cell is -80kPa. The battery cell is charged to 3.0V at a constant current of 0.05C and then left to stand for 1min.

[0097] The internal pressure of the battery cell is -10kPa. The battery cell is charged to 4.0V at a constant current of 0.2C and then left to stand for 1min.

[0098] The internal pressure of the battery cell is -80kPa. The battery cell is charged to 4.3V at a constant current of 0.05C, then left to stand for 1 minute and charging is stopped. The total capacity of the three-step charging is calculated as C0.

[0099] Place the charged battery cells in a 45°C environment for aging and leave them there for 24 hours.

[0100] The battery cells are divided into different capacities. They are charged to 4.3V at 0.2C current, charged to 0.05C at 4.3V constant voltage, and left to stand for 5 minutes. The charging capacity is C1. They are discharged to 2.8V at 0.2C current, left to stand for 5 minutes. The discharge capacity is D1. The specific capacity is calculated based on the mass of the positive electrode main material.

[0101] After the battery cell is manufactured, weigh the battery and calculate the electrolyte loss rate m (%).

[0102] Example 7

[0103] Prepare the battery cell to be formed, the positive electrode is a lithium iron phosphate positive electrode sheet containing 2% lithium quartz lithium supplement, the negative electrode is a graphite negative electrode sheet, the separator is a PP separator, and the electrolyte is 1.0 mol / L LiPF6 / EC+DMC+EMC (weight ratio = 1:1:1) electrolyte.

[0104] The formation temperature is controlled at 30°C, and the internal pressure of the battery cell is controlled by negative pressure formation equipment to change according to different charging stages.

[0105] The internal pressure of the battery cell is -80kPa. The battery cell is charged to 3.0V at a constant current of 0.05C and then left to stand for 1min.

[0106] The internal pressure of the battery cell is -10kPa. The battery cell is charged to 4.0V at a constant current of 0.2C and then left to stand for 1min.

[0107] The internal pressure of the battery cell is -80kPa. The battery cell is charged to 4.4V at a constant current of 0.05C, then left to stand for 1 minute and charging is stopped. The total capacity of the three-step charging is calculated as C0.

[0108] Place the charged battery cells in a 45°C environment for aging and leave them there for 24 hours.

[0109] The battery cells are divided into different capacities. They are charged to 3.65V at 0.2C current, charged to 0.05C at 3.65V constant voltage, and left to stand for 5 minutes. The charging capacity is C1. They are discharged to 2.5V at 0.2C current, left to stand for 5 minutes. The discharge capacity is D1. The specific capacity is calculated based on the mass of the positive electrode main material.

[0110] After the battery cell is manufactured, weigh the battery and calculate the electrolyte loss rate m (%).

[0111] Example 8

[0112] Prepare the battery cell to be formed, the positive electrode is a lithium iron phosphate positive electrode sheet containing 2% lithium quartz lithium supplement, the negative electrode is a graphite negative electrode sheet, the separator is a PP separator, and the electrolyte is 1.0 mol / L LiPF6 / EC+DMC+EMC (weight ratio = 1:1:1) electrolyte.

[0113] The formation temperature is controlled at 20°C, and the internal pressure of the battery cell is controlled by negative pressure formation equipment to change according to different charging stages.

[0114] The internal pressure of the battery cell is -80kPa. The battery cell is charged to 3.0V at a constant current of 0.05C and then left to stand for 1min.

[0115] The internal pressure of the battery cell is -10kPa. The battery cell is charged to 4.0V at a constant current of 0.2C and then left to stand for 1min.

[0116] The internal pressure of the battery cell is -80kPa. The battery cell is charged to 4.4V at a constant current of 0.05C, then left to stand for 1 minute and charging is stopped. The total capacity of the three-step charging is calculated as C0.

[0117] Place the charged battery cells in a 45°C environment for aging and leave them there for 24 hours.

[0118] The battery cells are divided into different capacities. They are charged to 3.65V at 0.2C current, charged to 0.05C at 3.65V constant voltage, and left to stand for 5 minutes. The charging capacity is C1. They are discharged to 2.5V at 0.2C current, left to stand for 5 minutes. The discharge capacity is D1. The specific capacity is calculated based on the mass of the positive electrode main material.

[0119] After the battery cell is manufactured, weigh the battery and calculate the electrolyte loss rate m (%).

[0120] Example 9

[0121] Prepare the battery cell to be formed, the positive electrode is a lithium iron phosphate positive electrode sheet containing 2% lithium quartz lithium supplement, the negative electrode is a graphite negative electrode sheet, the separator is a PP separator, and the electrolyte is 1.0 mol / L LiPF6 / EC+DMC+EMC (weight ratio = 1:1:1) electrolyte.

[0122] The formation temperature is controlled at 25°C, and the internal pressure of the battery cell is controlled by negative pressure formation equipment to change according to different charging stages.

[0123] The internal pressure of the battery cell is -80kPa. The battery cell is charged to 3.0V at a constant current of 0.05C and then left to stand for 1min.

[0124] The internal pressure of the battery cell is -10kPa. The battery cell is charged to 4.0V at a constant current of 0.5C and then left to stand for 1min.

[0125] The internal pressure of the battery cell is -80kPa. The battery cell is charged to 4.4V at a constant current of 0.05C, then left to stand for 1 minute and charging is stopped. The total capacity of the three-step charging is calculated as C0.

[0126] Place the charged battery cells in a 45°C environment for aging and leave them there for 24 hours.

[0127] The battery cells are divided into different capacities. They are charged to 3.65V at 0.2C current, charged to 0.05C at 3.65V constant voltage, and left to stand for 5 minutes. The charging capacity is C1. They are discharged to 2.5V at 0.2C current, left to stand for 5 minutes. The discharge capacity is D1. The specific capacity is calculated based on the mass of the positive electrode main material.

[0128] After the battery cell is manufactured, weigh the battery and calculate the electrolyte loss rate m (%).

[0129] Example 10

[0130] Prepare the battery cell to be formed, the positive electrode is a lithium iron phosphate positive electrode sheet containing 2% lithium quartz lithium supplement, the negative electrode is a graphite negative electrode sheet, the separator is a PP separator, and the electrolyte is 1.0 mol / L LiPF6 / EC+DMC+EMC (weight ratio = 1:1:1) electrolyte.

[0131] The formation temperature is controlled at 25°C, and the internal pressure of the battery cell is controlled by negative pressure formation equipment to change according to different charging stages.

[0132] The internal pressure of the battery cell is -80kPa. The battery cell is charged to 3.0V at a constant current of 0.1C and then left to stand for 1min.

[0133] The internal pressure of the battery cell is -10kPa. The battery cell is charged to 4.0V at a constant current of 0.5C and then left to stand for 1min.

[0134] The internal pressure of the battery cell is -80kPa. The battery cell is charged to 4.4V at a constant current of 0.15C, and then charged to 0.05C at a constant voltage. Then it is left to stand for 1 minute and the charging is stopped. The total capacity of the three-step charging is calculated as C0.

[0135] Place the charged battery cells in a 45°C environment for aging and leave them there for 24 hours.

[0136] The battery cells are divided into different capacities. They are charged to 3.65V at 0.2C current, charged to 0.05C at 3.65V constant voltage, and left to stand for 5 minutes. The charging capacity is C1. They are discharged to 2.5V at 0.2C current, left to stand for 5 minutes. The discharge capacity is D1. The specific capacity is calculated based on the mass of the positive electrode main material.

[0137] After the battery cell is manufactured, weigh the battery and calculate the electrolyte loss rate m (%).

[0138] Embodiment 11

[0139] Prepare the battery cell to be formed, the positive electrode is a lithium iron phosphate positive electrode sheet containing 2% lithium quartz lithium supplement, the negative electrode is a graphite negative electrode sheet, the separator is a PP separator, and the electrolyte is 1.0 mol / L LiPF6 / EC+DMC+EMC (weight ratio = 1:1:1) electrolyte.

[0140] The formation temperature is controlled at 25°C, and the internal pressure of the battery cell is controlled by negative pressure formation equipment to change according to different charging stages.

[0141] The internal pressure of the battery cell is -80kPa. The battery cell is charged to 3.0V at a constant current of 0.05C and then left to stand for 1min.

[0142] The internal pressure of the battery cell is -40kPa. The battery cell is charged to 4.0V at a constant current of 0.2C and then left to stand for 1min.

[0143] The internal pressure of the battery cell is -80kPa. The battery cell is charged to 4.4V at a constant current of 0.05C, then left to stand for 1 minute and charging is stopped. The total capacity of the three-step charging is calculated as C0.

[0144] Place the charged battery cells in a 45°C environment for aging and leave them there for 24 hours.

[0145] The battery cells are divided into different capacities. They are charged to 3.65V at 0.2C current, charged to 0.05C at 3.65V constant voltage, and left to stand for 5 minutes. The charging capacity is C1. They are discharged to 2.5V at 0.2C current, left to stand for 5 minutes. The discharge capacity is D1. The specific capacity is calculated based on the mass of the positive electrode main material.

[0146] After the battery cell is manufactured, weigh the battery and calculate the electrolyte loss rate m (%).

[0147] Example 12

[0148] Prepare the battery cell to be formed, the positive electrode is a lithium iron phosphate positive electrode sheet containing 2% lithium quartz lithium supplement, the negative electrode is a graphite negative electrode sheet, the separator is a PP separator, and the electrolyte is 1.0 mol / L LiPF6 / EC+DMC+EMC (weight ratio = 1:1:1) electrolyte.

[0149] The formation temperature is controlled at 25°C, and the internal pressure of the battery cell is controlled by negative pressure formation equipment to change according to different charging stages.

[0150] The internal pressure of the battery cell is -60kPa. The battery cell is charged to 3.0V at a constant current of 0.05C and then left to stand for 1min.

[0151] The internal pressure of the battery cell is -10kPa. The battery cell is charged to 4.0V at a constant current of 0.2C and then left to stand for 1min.

[0152] The internal pressure of the battery cell is -60kPa. The battery cell is charged to 4.4V at a constant current of 0.05C, then left to stand for 1 minute and charging is stopped. The total capacity of the three-step charging is calculated as C0.

[0153] Place the charged battery cells in a 45°C environment for aging and leave them there for 24 hours.

[0154] The battery cells are divided into different capacities. They are charged to 3.65V at 0.2C current, charged to 0.05C at 3.65V constant voltage, and left to stand for 5 minutes. The charging capacity is C1. They are discharged to 2.5V at 0.2C current, left to stand for 5 minutes. The discharge capacity is D1. The specific capacity is calculated based on the mass of the positive electrode main material.

[0155] After the battery cell is manufactured, weigh the battery and calculate the electrolyte loss rate m (%).

[0156] Comparative Example 1

[0157] Prepare the battery cell to be formed, the positive electrode is a lithium iron phosphate positive electrode sheet containing 2% lithium quartz lithium supplement, the negative electrode is a graphite negative electrode sheet, the separator is a PP separator, and the electrolyte is 1.0 mol / L LiPF6 / EC+DMC+EMC (weight ratio = 1:1:1) electrolyte.

[0158] The formation temperature is controlled at 45°C, and the internal pressure of the battery cell is controlled at -80KPa through negative pressure formation equipment.

[0159] Charge the cell to 3.0V at a constant current of 0.05C and then let it stand for 1min.

[0160] The cell was charged to 60% SOC (3.3 V) at a constant current of 0.2 C, and the charging was stopped. The total capacity of the two-step charging was calculated as C0.

[0161] Place the charged battery cells in a 45°C environment for aging and leave them there for 24 hours.

[0162] The battery cells are divided into different capacities. They are charged to 3.65V at 0.2C current, charged to 0.05C at 3.65V constant voltage, and left to stand for 5 minutes. The charging capacity is C1. They are discharged to 2.5V at 0.2C current, left to stand for 5 minutes. The discharge capacity is D1. The specific capacity is calculated based on the mass of the positive electrode main material.

[0163] After the battery cell is manufactured, weigh the battery and calculate the electrolyte loss rate m (%).

[0164] Comparative Example 2

[0165] Prepare the battery cell to be formed, the positive electrode is a lithium iron phosphate positive electrode sheet containing 2% lithium quartz lithium supplement, the negative electrode is a graphite negative electrode sheet, the separator is a PP separator, and the electrolyte is 1.0 mol / L LiPF6 / EC+DMC+EMC (weight ratio = 1:1:1) electrolyte.

[0166] The formation temperature is controlled at 45°C, and the internal pressure of the battery cell is controlled at -80KPa through negative pressure formation equipment.

[0167] Charge the cell to 3.0V at a constant current of 0.05C and then let it stand for 1min.

[0168] Charge the cell to 4.0V at a constant current of 0.2C, then let it sit for 1 minute;

[0169] The battery cell was charged to 4.4V at a constant current of 0.05C, then left to stand for 1min and charging was stopped. The total capacity of the three-step charging was calculated as C0.

[0170] Place the charged battery cells in a 45°C environment for aging and leave them there for 24 hours.

[0171] The battery cells are divided into different capacities. They are charged to 3.65V at 0.2C current, charged to 0.05C at 3.65V constant voltage, and left to stand for 5 minutes. The charging capacity is C1. They are discharged to 2.5V at 0.2C current, left to stand for 5 minutes. The discharge capacity is D1. The specific capacity is calculated based on the mass of the positive electrode main material.

[0172] After the battery cell is manufactured, weigh the battery and calculate the electrolyte loss rate m (%).

[0173] Comparative Example 3

[0174] Prepare the battery cell to be formed, the positive electrode is a lithium iron phosphate positive electrode sheet containing 2% lithium quartz lithium supplement, the negative electrode is a graphite negative electrode sheet, the separator is a PP separator, and the electrolyte is 1.0 mol / L LiPF6 / EC+DMC+EMC (weight ratio = 1:1:1) electrolyte.

[0175] The formation temperature is controlled at 25°C, and the internal pressure of the battery cell is controlled at -80KPa through negative pressure formation equipment.

[0176] The internal pressure of the battery cell is -80kPa. The battery cell is charged to 3.0V at a constant current of 0.05C and then left to stand for 1min.

[0177] The internal pressure of the battery cell is -10kPa. The battery cell is charged to 4.0V at a constant current of 0.2C and then left to stand for 1min.

[0178] The internal pressure of the battery cell is -80kPa. The battery cell is charged to 4.4V at a constant current of 0.05C, then left to stand for 1 minute and charging is stopped. The total capacity of the three-step charging is calculated as C0.

[0179] Place the charged battery cells in a 45°C environment for aging and leave them there for 24 hours.

[0180] The battery cells are divided into different capacities. They are charged to 3.65V at 0.2C current, charged to 0.05C at 3.65V constant voltage, and left to stand for 5 minutes. The charging capacity is C1. They are discharged to 3.5V at 0.2C current, and left to stand for 5 minutes. The discharge capacity is D1. The specific capacity is calculated based on the mass of the positive electrode main material.

[0181] After the battery cell is manufactured, weigh the battery and calculate the electrolyte loss rate m (%).

[0182] Comparative Example 4

[0183] Prepare the battery cell to be formed, the positive electrode is a lithium iron phosphate positive electrode sheet containing 2% lithium quartz lithium supplement, the negative electrode is a graphite negative electrode sheet, the separator is a PP separator, and the electrolyte is 1.0 mol / L LiPF6 / EC+DMC+EMC (weight ratio = 1:1:1) electrolyte.

[0184] The formation temperature is controlled at 25°C, and the internal pressure of the battery cell is controlled at -80KPa through negative pressure formation equipment.

[0185] Charge the cell to 3.0V at a constant current of 0.05C and then let it stand for 1min.

[0186] Charge the cell to 4.0V at a constant current of 0.2C, then let it sit for 1 minute;

[0187] The battery cell was charged to 4.1V at a constant current of 0.05C, then left to stand for 1min and charging was stopped. The total capacity of the three-step charging was calculated as C0.

[0188] Place the charged battery cells in a 45°C environment for aging and leave them there for 24 hours.

[0189] The battery cells are divided into different capacities. They are charged to 3.65V at 0.2C current, charged to 0.05C at 3.65V constant voltage, and left to stand for 5 minutes. The charging capacity is C1. They are discharged to 2.5V at 0.2C current, left to stand for 5 minutes. The discharge capacity is D1. The specific capacity is calculated based on the mass of the positive electrode main material.

[0190] After the battery cell is manufactured, weigh the battery and calculate the electrolyte loss rate m (%).

[0191] Comparative Example 5

[0192] Prepare the battery cell to be formed, the positive electrode is a lithium iron phosphate positive electrode sheet containing 2% lithium iron-rich lithium supplement, the negative electrode is a graphite negative electrode sheet, the diaphragm is a PP diaphragm, and the electrolyte is 1.0 mol / L LiPF6 / EC+DMC+EMC (weight ratio = 1:1:1) electrolyte.

[0193] The formation temperature is controlled at 45°C, and the internal pressure of the battery cell is controlled at -80KPa through negative pressure formation equipment.

[0194] Charge the cell to 3.0V at a constant current of 0.05C and then let it stand for 1min.

[0195] The cell was charged to 60% SOC (3.3 V) at a constant current of 0.2 C, and the charging was stopped. The total capacity of the two-step charging was calculated as C0.

[0196] Place the charged battery cells in a 45°C environment for aging and leave them there for 24 hours.

[0197] The battery cells are divided into different capacities. They are charged to 3.65V at 0.2C current, charged to 0.05C at 3.65V constant voltage, and left to stand for 5 minutes. The charging capacity is C1. They are discharged to 2.5V at 0.2C current, left to stand for 5 minutes. The discharge capacity is D1. The specific capacity is calculated based on the mass of the positive electrode main material.

[0198] After the battery cell is manufactured, weigh the battery and calculate the electrolyte loss rate m (%).

[0199] The data and measurement results of Examples 1-12 and Comparative Examples 1-5 are shown in Table 1 below.

[0200] Table 1 Comparison of various data of Examples 1-12 and Comparative Examples 1-5

[0201]

[0202]

[0203] According to the data in Table 1, Examples 1-6 have a higher discharge specific capacity, indicating that the formation method of the present invention is feasible for different lithium-ion batteries. Comparative Example 5 is an existing conventional battery cell formation process. It can be seen from the comparison between Examples 1-12 and Comparative Example 5 that the formation process of the present invention is better than the existing formation process. It can be seen from the comparison between Examples 1-3 and 7-12 and Comparative Examples 2-4 that the formation method of the present invention can effectively reduce the loss of electrolyte. It can be seen from the comparison between Example 1 and Comparative Example 1 that the discharge specific capacity of Example 1 is significantly better than the discharge specific capacity of Comparative Example 1, and the three-stage charging effect of the present invention is better.

[0204] According to the comparison between Comparative Example 4 and Example 1, when the third stage is only charged to 4.1V, its final discharge specific capacity is lower than the discharge specific capacity of Example 1. This is because under the condition of 4.1V, the lithium quartz cannot be completely decomposed to replenish lithium. In addition, Comparative Example 4 adopts negative pressure conditions without segmented control. Under the condition of -80kPa throughout the process, its electrolyte loss is relatively large. The negative pressure of the second stage of Example 1 is increased, which reduces the electrolyte loss in this stage, which is beneficial to reducing costs.

[0205] The formation method of the present invention is applicable to the existing lithium ion battery production. Compared with the existing battery cell formation process, the present invention adopts a higher formation voltage. Since the battery cell formation process of the present invention is divided into three stages, the formation time is prolonged, and the prolonged time of the battery cell under negative pressure conditions will lead to a significant increase in the loss of the battery cell electrolyte. The present invention greatly reduces the battery cell formation temperature and the electrolyte vapor pressure, thereby reducing the electrolyte loss and solving the problem of lithium quartz being applied to lithium ion batteries.

[0206] The embodiments provided by the present invention are described in detail above. Specific examples are used herein to describe the principles and implementation methods of the present invention, and the description of the above embodiments is only used to help understand the core idea of ​​the present invention. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, the present invention can also be improved and modified in a number of ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for forming a battery cell using a lithium quartz material as a lithium supplement, characterized in that: Here are the steps: (1) preparing a battery cell to be formed, wherein the lithium quartz material is used as a lithium supplement for the positive electrode; (2) Control the battery cell formation temperature to 20-35°C; (3) Control the internal pressure of the battery cell to negative pressure and charge the battery cell in stages; (3.1) Stage 1: Charge the battery to 3.0V; (3.2) Second stage: charge the battery to less than or equal to 4.0V; (3.3) The third stage: Charge the battery cell to 4.2V or above, and then stop charging.

2. The battery cell formation method according to claim 1, characterized in that: The lithium squarate material includes lithium squarate or a lithium squarate composite material, wherein the lithium squarate composite material refers to a composite material formed by mixing lithium squarate with a conductive carbon material.

3. The chemical formation method according to claim 2, characterized in that: In step (1), based on the mass of the positive electrode, the positive electrode contains 2-10% of lithium squarate in terms of mass percentage.

4. The battery cell formation method according to claim 1, characterized in that: In step (3), the negative pressure condition changes in stages, wherein in step (3.1), the internal pressure of the battery cell is less than or equal to -10 kPa, and in step (3.3), the internal pressure of the battery cell is less than or equal to -10 kPa.

5. The battery cell formation method according to claim 1, characterized in that: In step (1), the positive electrode of the battery cell to be formed includes one or more of lithium iron phosphate, lithium iron manganese phosphate, lithium cobalt oxide and ternary lithium.

6. The chemical formation method according to claim 1, characterized in that: In step (1), the negative electrode of the battery cell to be formed includes one or both of graphite and silicon carbon.

7. An application of a lithium quarate material as a lithium supplement, characterized in that: By using the battery cell formation method as described in any one of claims 1 to 6, the lithium quartz material is used in the production of lithium ion batteries.

8. A lithium ion battery, characterized in that: The battery is prepared by the battery cell formation method as described in any one of claims 1 to 6.

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