Positive electrode lithium supplement total battery and preparation and formation method thereof

Abstract

The invention discloses a positive pole lithium supplement total battery and a preparation and formation method, the positive pole lithium supplement total battery is characterized in that a lithium supplement assistant agent is added when a positive pole piece is prepared, then the prepared positive pole piece, a negative pole piece and a diaphragm are subjected to winding or lamination, packaging, drying and electrolyte injection to obtain an initial battery cell, and then the initial battery cell is subjected to formation treatment to obtain the positive pole lithium supplement total battery. And standing, exhausting, grading capacity and testing a K value to obtain the positive pole lithium supplement total battery. The lithium supplement assisting agent in the positive electrode lithium supplement total battery takes dilithium formyl phosphate of cyano, pyridyl and pyrimidyl as a synergistic component. According to the formation method, an initial battery cell is subjected to static treatment for 12-96 hours and then is subjected to formation treatment under the preset formation environment temperature and magnetic field intensity. The preparation method has the beneficial effects that the energy density is improved, the cycling stability is enhanced, the rate capability is improved, the safety is improved, the formation current is improved, and the production efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery processing, and particularly relates to a full cell with cathode lithium supplementation, its preparation method and formation method, especially a full cell with cathode lithium supplementation that can achieve sufficient lithium deintercalation, improve the energy density and shorten the formation time, as well as its preparation method and formation method. Background Art

[0002] During the first charge and discharge stage of a lithium-ion battery, a solid electrolyte interface mainly composed of lithium salt, namely Solid Electrolyte Interface, abbreviated as SEI, will be formed at the interface of the negative electrode material. The formation of the SEI film is an irreversible process, and the permanent loss of active lithium causes the Coulombic efficiency of the first cycle to decrease. Therefore, before the lithium-ion battery works, the pre-lithiation technology route of adding sacrificial additives to the battery cell, that is, the "lithium supplementation" technology, has emerged.

[0003] The most common current lithium supplementation process is the negative electrode lithium supplementation method, that is, using processes such as lithium powder and lithium foil to supplement the irreversible capacity loss of the negative electrode during the first charging process. The negative electrode lithium supplementation process is the most common lithium supplementation method for us, such as lithium powder lithium supplementation and lithium foil lithium supplementation. After the battery is filled with electrolyte, these metallic Li quickly react with the negative electrode and embed into the negative electrode material, thereby improving the first efficiency of the material. However, all of these methods have to face a problem - "the safety problem of metallic lithium". Metallic lithium is a highly reactive alkali metal that can react violently with water, making the environmental requirements for metallic lithium extremely high. This makes it necessary to invest heavily in the transformation of the production line and purchase expensive lithium supplementation equipment for these two negative electrode lithium supplementation processes. At the same time, in order to ensure the lithium supplementation effect, it is also necessary to adjust the existing production process. Compared with the high-difficulty and high-investment negative electrode lithium supplementation process, positive electrode lithium supplementation is relatively simple and easy. That is, adding a small amount of high-capacity lithium-containing oxides to the positive electrode, such as materials like Li2NiO2, Li5FeO4, Li6CoO4, etc., to store extra Li in the positive electrode to supplement the Li loss during the first discharge process. A typical positive electrode lithium supplementation process is to add a small amount of high-capacity positive electrode material during the positive electrode homogenization process. During the charging process, the excess Li element is released from these high-capacity positive electrode materials and embeds into the negative electrode to supplement the irreversible capacity of the first charge and discharge. For example, Su Xin et al. from Argonne National Laboratory in the United States added 7% of Li5FeO4 (LFO) material to the LiCoO2 positive electrode, which increased the first efficiency of the battery by 14% and significantly improved the cycle performance of the battery. Another example is that Chinese Patent 202210254003.2 discloses a positive electrode lithium supplement and its application. Li2NiO2, which also serves as a lithium supplement, is used to coat Li5FeO4 to avoid contact between Li5FeO4 and air, improving the environmental stability of Li5FeO4 and enabling the capacity of Li5FeO4 to be maximally exerted. And Li2NiO2 also has a lithium supplementation effect, and the lithium supplementation effects of both can be utilized simultaneously to improve the energy density and cycle stability of the battery. However, the de-lithiation potential of the lithium-ion battery prepared by the above-mentioned positive electrode lithium supplementation is usually relatively high and needs to be charged to 4.2V - 4.3V. The de-lithiation potential of lithium iron phosphate is relatively low, generally charged to 3.65V. When a positive electrode lithium supplement electrode is added to a lithium iron phosphate battery, due to the large difference in de-lithiation potential between the two, the charging time for battery formation is long, thus affecting production efficiency. The usual solution is to increase the charging current, but increasing the charging current will cause insufficient de-lithiation of the lithium supplement, resulting in a low energy density of the battery, ultimately causing the lithium-ion battery to fail to achieve the expected effect, and even increasing energy consumption and being unfavorable for controlling production costs. In order to fully de-lithiate the lithium supplement, only a small current can be used for charging.As the formation method disclosed in Patent CN 117117106 A, after charging to 3.6V, step charging is adopted. The current range in the first stage is 0.05C to 0.2C, the current range in the second stage is 0.02C to 0.1C, and the current range in the third stage is 0.01C to 0.05C. The current during the charging process is very small. Also, as the formation method disclosed in Patent CN115954453 A, after charging to 3.65V, a current of 0.01C - 0.1C is used to charge the positive electrode pre-lithiated lithium-ion battery, the charging time is controlled to be 1.5 hours - 2 hours, the charging amount is 110% - 120% of the designed capacity of the positive electrode pre-lithiated lithium-ion battery, and the cut-off voltage is 4.3V. The batteries of the above patents also use a small current to de-lithiate the lithium supplement agent during charging. It can be seen from this that in actual production, in order to fully de-lithiate the lithium supplement agent, only a small current can be used for charging, but this will directly lead to a long charging time, reducing the production efficiency and being unfavorable for industrial production. This formation method has the drawback of a long formation time.

[0004] Therefore, how to find a lithium-ion battery, preparation and formation method that can use a large current for charging, ensure sufficient de-lithiation of the battery, and have low energy consumption has become one of the urgent problems to be solved by many front-line researchers and scientific research enterprises in this field. Summary of the Invention

[0005] Aiming at the above problems, the purpose of the present invention is to provide a positive electrode lithium supplement full battery, preparation and formation method with sufficient de-lithiation, high energy density and low energy consumption.

[0006] To achieve the above purpose and other related purposes, the technical solution adopted by the present invention is as follows: The present invention provides a preparation method of a positive electrode lithium supplement full battery, which is characterized by including the following steps: Step 1, preparing a positive electrode sheet: According to mass parts, dissolve 1.5 - 5 parts of a positive electrode binder in 30 - 80 parts of N-methylpyrrolidone, then add 0.5 - 5 parts of a conductive agent, and mix evenly to make a positive electrode conductive adhesive; then add 80 - 97.5 parts of a positive electrode material, 0.5 - 10 parts of a lithium supplement agent, and a lithium supplement assisting agent to the positive electrode conductive adhesive and mix evenly to make a positive electrode slurry. Sieve, coat, dry, roll, cut, and die-cut the positive electrode slurry to make a positive electrode sheet; the addition amount of the lithium supplement assisting agent is 5 - 13% of the lithium supplement agent; Step 2, preparing a negative electrode sheet: According to mass parts, fully dissolve 0.5 - 3 parts of binder A in 78 - 130 parts of deionized water; add 0.5 - 10 parts of a conductive agent, and mix evenly to make a negative electrode conductive adhesive; add 84 - 96 parts of a negative electrode material to the negative electrode conductive adhesive, stir evenly, and then add 0.5 - 3 parts of binder B and mix evenly to make a negative electrode slurry. Sieve, coat, dry, roll, cut, and die-cut the negative electrode slurry to make a negative electrode sheet; Step 3: Wind or stack the positive electrode sheet, negative electrode sheet, and separator, encapsulate, dry, inject electrolyte to obtain an initial battery cell, and then perform formation treatment, static settling, air extraction, capacity grading, and K value testing on the initial battery cell to obtain a full cell with positive electrode lithium supplementation.

[0007] Preferably, the preparation method of the co-lithium supplementing agent in Step 1 is carried out according to the following steps: Step (1): Put 15 - 30 parts by mass of lithium carbamoyl phosphate, 10 - 20 parts of ethyl 2-cyano-3-(3-pyridyl)acrylate, 2 - 5 parts of triethylamine, 0.03 - 0.6 part of 5-allylpyrimidine-4,6-diol, and 200 - 300 parts of N-methylpyrrolidone thiol into a sealed stirring kettle according to the weighed mass parts. Step (2): Introduce an inert gas into the above-mentioned stirring kettle, react at 60 - 74 °C under stirring for 30 - 100 min, and distill the reaction product to obtain the co-lithium supplementing agent.

[0008] Preferably, the positive electrode material is one or a mixture of several of lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium cobalt oxide, and lithium manganese iron phosphate.

[0009] Preferably, the lithium supplementing agent is one or several of lithium-rich nickel oxide, lithium-rich iron oxide, lithium-rich cobalt oxide, lithium-rich nickel copper oxide, and squaric acid lithium.

[0010] Preferably, the conductive agent is one or several of conductive carbon black, Ketjen black, multi-walled carbon nanotubes, single-walled carbon nanotubes, and graphene.

[0011] Preferably, the positive electrode binder is at least one of polyvinylidene fluoride, polyimide, and polytetrafluoroethylene.

[0012] Preferably, the binder A is at least one of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, and polyacrylic acid.

[0013] Preferably, the negative electrode binder B is at least one of polyacrylic acid and styrene-butadiene rubber.

[0014] The reaction mechanism of the co-lithium supplementing agent of the present invention is as follows: The amino groups of lithium carbamoyl phosphate respectively carry out addition reactions with ethyl 2-cyano-3-(3-pyridyl)acrylate and 5-allylpyrimidine-4,6-diol to obtain lithium carbamoyl phosphate containing cyano, pyridyl, and pyrimidinyl groups, which is used as an enhancing component of the lithium supplementing agent.

[0015] Preferably, during the mixing of each component in the process of preparing the positive electrode slurry in Step 1, a vacuum is maintained, and the vacuum degree is not lower than -0.085 mPa.

[0016] Preferably, the environmental temperature in step 1 is controlled at 15 - 35°C, and the humidity is controlled below -40°C dew point.

[0017] Preferably, the mesh number of the sieve for screening the positive electrode slurry is not less than 150 meshes, and the coating areal density ranges from 300 g / m 2 - 500 g / m 2 , and the tap density of the positive electrode sheet is 2.0 - 4.0 g / cm 3 .

[0018] Preferably, the negative electrode material is one or a mixture of artificial graphite, natural graphite, hard carbon, and silicon carbon.

[0019] Preferably, the mesh number of the sieve for screening the negative electrode slurry is not less than 120 meshes, and the coating areal density ranges from 150 g / m 2 - 300 g / m 2 , and the tap density of the negative electrode sheet is 0.95 - 1.75 g / cm 3 .

[0020] The present invention also provides a positive electrode lithium - supplemented full cell prepared by the described preparation method.

[0021] The present invention also provides a formation method, which is characterized in that: after the initial cell is static for 12 - 96 hours, formation treatment is carried out under the preset formation environmental temperature and magnetic field strength.

[0022] Preferably, the preset magnetic field strength is 500 mT - 1500 mT, the formation environmental temperature is 30 - 60°C, and the formation treatment includes the following stages: Constant - current charge at a current of 0.01C - 0.2C until 10% - 30% SOC; Constant - current constant - voltage charge at a current of 0.5C - 2.0C until the upper - limit voltage or 100% - 120% SOC; Constant - current discharge at a current of 0.33C - 1.0C until the lower - limit voltage or 0% - 10% SOC; Constant - current constant - voltage charge at a current of 1.0C - 2.0C until 5% - 90% SOC.

[0023] The present invention also provides a positive electrode lithium - supplemented full cell, which is characterized in that it includes the formed cell obtained by the described formation method.

[0024] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in: 1. Improving the energy density: The introduction of functional groups such as cyano, pyridyl, and pyrimidinyl can change the crystal structure of the positive electrode material, thereby affecting its electrochemical performance. These functional groups improve the energy density by increasing the conductivity of the material or improving the ion - transport path.

[0025] 2. Enhance cycle stability: It can form stable chemical bonds with other elements in the cathode material, thereby improving the cycle stability of the material. During charge and discharge processes, these functional groups can reduce the volume change of the material and lower stress concentration, thus extending the service life of the battery.

[0026] 3. Improve rate performance: The introduction of functional groups such as cyano, pyridyl, and pyrimidinyl can improve the electron conductivity of the cathode material, thereby enhancing the rate performance of the battery. This means that the battery can still maintain good electrochemical performance at high current densities and is suitable for application scenarios that require fast charging and discharging.

[0027] 4. Improve safety: The safety of the battery can be improved by reducing the redox potential of the cathode material. In the case of overcharge or overheat, the risk of thermal runaway of the battery can be reduced.

[0028] 5. Increase formation current density: In this application, the lithium-ion battery is formed under a predetermined magnetic field strength. In a magnetic field environment, the formation current density can be increased, the formation time can be shortened to a certain extent, the lithium supplementing agent can better play its role, the capacity of the battery can be effectively increased, the cycle performance of the battery can be improved, and the production efficiency can be improved. Detailed implementation manners

[0029] The following specific examples illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0030] It should be noted that the process equipment or devices not specifically noted in the following examples all adopt conventional equipment or devices in the art.

[0031] In addition, it should be understood that one or more method steps mentioned in the present invention do not exclude the existence of other method steps before and after the combined steps or the insertion of other method steps between these clearly mentioned steps, unless otherwise stated; it should also be understood that the combined connection relationship between one or more devices / devices mentioned in the present invention does not exclude the existence of other devices / devices before and after the combined devices / devices or the insertion of other devices / devices between these two clearly mentioned devices / devices, unless otherwise stated. Moreover, unless otherwise stated, the numbers of the method steps are only convenient tools for identifying the method steps, rather than limiting the arrangement order of the method steps or the scope in which the present invention can be implemented. The change or adjustment of their relative relationships, without substantial change in technical content, should also be regarded as the scope in which the present invention can be implemented.

[0032] Example 1 Preparation of dispersing aids with different ratios Step (1): Weigh 15 - 30 parts by mass of lithium carbamoyl phosphate, 10 - 20 parts of ethyl 2 - cyano - 3 - (3 - pyridyl) acrylate, 2 - 5 parts of triethylamine, 0.03 - 0.6 part of 5 - allylpyrimidine - 4,6 - diol, and 200 - 300 parts of N - methylpyrrolidone sulfide and put them into a closed stirring kettle; Step (2): Introduce an inert gas into the above - mentioned stirring kettle, stir and react at 60 - 74 °C for 30 - 100 min, and distill the reaction product to obtain a lithium - supplementing agent. The component ratios of the lithium - supplementing agent are shown in Table 1.

[0033] Table 1 Component ratios and reaction conditions of the lithium - supplementing agent Example 2 A preparation method for a positive - electrode lithium - supplementing full battery, comprising the following steps: Step 1: Prepare the positive - electrode sheet: Dissolve 1.5 g of binder in 80 g of N - methylpyrrolidone by mass, then add 0.5 g of conductive agent, and stir well to form a conductive adhesive; Add 97.5 g of positive - electrode material, 0.5 g of lithium - supplementing agent, and the lithium - supplementing aid in Formula 1 into the conductive adhesive and mix well. Keep the vacuum during the mixing process, and the vacuum degree is not less than - 0.085 mPa. After the prepared positive - electrode slurry is sieved, it is coated on carbon - coated aluminum foil or aluminum foil, dried, rolled, slit, and die - cut to make a positive - electrode sheet; The addition amount of the lithium - supplementing aid is 5% of the lithium - supplementing agent; Step 2: Prepare the negative - electrode sheet: Dissolve 1.2 g of binder A in 70 g of deionized water by mass; Add 1 g of conductive agent and stir well; Add 96 g of negative - electrode material into the conductive adhesive and stir well; Then add 1.8 g of binder B and stir well. The negative - electrode slurry is sieved and coated on copper foil, dried, rolled, slit, and die - cut to make a negative - electrode sheet; Step 3: Wind or stack the prepared positive - electrode sheet, negative - electrode sheet, and separator, then encapsulate and dry them; When the moisture content of the electrode sheet is lower than 300 ppm, inject the electrolyte. After standing for 12 hours, carry out formation at a formation ambient temperature of 30 °C. After the formation of the battery cell is completed, after standing, degassing, grading, and K - value testing, the battery cell is prepared.

[0034] The positive - electrode material is lithium iron phosphate.

[0035] The lithium - supplementing agent is lithium - rich lithium nickelate.

[0036] The conductive agent is conductive carbon black.

[0037] The positive electrode binder is polyvinylidene fluoride, binder A is sodium carboxymethyl cellulose, and binder B is styrene-butadiene rubber.

[0038] The ambient temperature in step 1 is controlled at 15°C, and the humidity is controlled below -40°C dew point.

[0039] The mesh number of the sieve for screening the positive electrode slurry is not less than 150 mesh, and the coating surface density ranges from 300 g / m 2 , and the compaction density of the positive electrode sheet is 2.0 g / cm 3 .

[0040] The negative electrode material is artificial graphite.

[0041] The mesh number of the sieve for screening the negative electrode slurry is not less than 120 mesh, and the coating surface density ranges from 150 g / m 2 , and the compaction density of the negative electrode sheet is 1.5 g / cm 3 .

[0042] The magnetic field strength during formation is 500 mT, including the following stages: Constant current charging at 0.01C to 10% SOC; Constant current and constant voltage charging at 0.5C to the upper limit voltage; Constant current discharging at 0.33C to the lower limit voltage; Constant current and constant voltage charging at 1.0C to 5% SOC.

[0043] Example 3 A preparation method of a positive electrode lithium supplementation full cell, comprising the following steps: Step 1: According to mass parts, dissolve 2.5 g of binder in 30 g of N-methylpyrrolidone, then add 2.5 g of conductive agent, and stir evenly to form conductive glue; add 90 g of positive electrode material, 5 g of lithium supplementation agent, and the auxiliary lithium supplementation agent in formula 2 into the conductive glue and mix evenly. Keep vacuum during the mixing process, and the vacuum degree is not less than -0.085 mPa. After screening the prepared positive electrode slurry, coat it on carbon-coated aluminum foil or aluminum foil, dry, roll, slit, and die-cut to make a positive electrode sheet; the addition amount of the auxiliary lithium supplementation agent is 10% of the lithium supplementation agent; Step 2: According to mass parts, fully dissolve 2 g of binder A in 80 g of deionized water; add 5 g of conductive agent and stir evenly; add 90 g of negative electrode material into the conductive glue and stir evenly; then add 3 g of binder B and stir evenly. After screening the negative electrode slurry, coat it on copper foil, dry, roll, slit, and die-cut to make a negative electrode sheet; Step 3: Wind or stack the prepared positive electrode sheet, negative electrode sheet, and separator, then encapsulate and dry them. When the moisture content of the electrode sheet is lower than 300 ppm, inject the electrolyte. After standing for 54 hours, carry out formation at an ambient temperature of 45°C. After the formation of the battery cell is completed, through standing, air extraction, grading, and K value testing, the preparation of the battery cell is completed.

[0044] The positive electrode material is lithium nickel cobalt manganese oxide.

[0045] The lithium supplement agent is lithium-rich iron oxide.

[0046] The conductive agent is multi-walled carbon nanotubes.

[0047] The positive electrode binder is polyvinylidene fluoride, binder A is sodium carboxymethyl cellulose, and binder B is styrene-butadiene rubber.

[0048] The ambient temperature in Step 1 is controlled at 25°C, and the humidity is controlled below the dew point of -40°C.

[0049] The mesh number of the sieve for screening the positive electrode slurry is not less than 150 meshes, and the coating surface density range is 400 g / m 2 , and the compaction density of the positive electrode sheet is 3.6 g / cm 3 .

[0050] The negative electrode material is hard carbon.

[0051] The mesh number of the sieve for screening the negative electrode slurry is not less than 120 meshes, and the coating surface density range is 230 g / m 2 , and the compaction density of the negative electrode sheet is 0.95 g / cm 3 .

[0052] The magnetic field strength during formation treatment is 1000 mT, including the following stages: Constant current charge at 0.1C until 20% SOC; Constant current and constant voltage charge at 1C until 100% SOC; Constant current discharge at 0.6C until 10% SOC; Constant current and constant voltage charge at 1.5C until 50% SOC.

[0053] Example 4 A preparation method for a positive electrode lithium-supplemented full battery, comprising the following steps: Step 1: According to the parts by mass, dissolve 5 g of binder in N-methylpyrrolidone, then add 5 g of conductive agent, and stir well to form conductive paste; add 80 g of cathode material, 10 g of lithium supplement agent, and the co-lithium supplement agent in Formula 3 into the conductive paste and mix well. Keep the vacuum during the mixing process, and the vacuum degree is not lower than -0.085 mPa. After the prepared cathode slurry is sieved, coat it on carbon-coated aluminum foil or aluminum foil, dry it, roll it, slit it, and die-cut it to make a cathode plate; the addition amount of the co-lithium supplement agent is 13% of the lithium supplement agent; Step 2: According to the parts by mass, dissolve 3 g of binder A in 130 g of deionized water; add 10 g of conductive agent and stir well; add 84 g of anode material into the conductive paste and stir well; then add 3 g of binder B and stir well. After the anode slurry is sieved, coat it on copper foil, dry it, roll it, slit it, and die-cut it to make an anode plate; Step 3: Wind or stack the prepared cathode plate, anode plate, and separator, then encapsulate and dry them; when the moisture content of the electrode plate is lower than 300 ppm, inject the electrolyte. After standing for 96 hours, carry out formation at an ambient temperature of 60 °C. After the formation of the battery cell is completed, then through standing, air extraction, grading, and K value testing, the battery cell preparation is completed.

[0054] The cathode material is lithium iron manganese phosphate.

[0055] The lithium supplement agent is lithium-rich nickel copper oxide.

[0056] The conductive agent is graphene.

[0057] The cathode binder is polyvinylidene fluoride, binder A is sodium carboxymethyl cellulose, and binder B is polyacrylic acid (PAA).

[0058] The ambient temperature in Step 1 is controlled at 35 °C, and the humidity is controlled below the dew point of -40 °C.

[0059] The mesh number of the sieve for sieving the cathode slurry is not lower than 150 meshes, and the coating surface density range is 500 g / m 2 , and the compaction density of the cathode plate is 2.4 g / cm 3 .

[0060] The anode material is silicon-carbon.

[0061] The mesh number of the sieve for sieving the anode slurry is not lower than 120 meshes, and the coating surface density range is 300 g / m 2 , and the compaction density of the anode plate is 1.75 g / cm 3 .

[0062] The magnetic field strength of the formation is 1500 mT, including the following stages: Constant current charge at 0.2C until 30% SOC; Constant current and constant voltage charge at 2.0C until 120% SOC; Constant current discharge at 1.0C until 0%; Constant current and constant voltage charge at 2.0C until 90% SOC.

[0063] Example 5 The difference between this example and Example 3 is that the co-dispersant is prepared according to the ratio in Formula 1, and the rest of the processes are exactly the same.

[0064] Example 6 The difference between this example and Example 3 is that the co-dispersant is prepared according to the ratio in Formula 3, and the rest of the processes are exactly the same.

[0065] Example 7 The difference between this example and Example 3 is that the amounts of each component of the positive electrode sheet and the negative electrode sheet are different. The amounts of each component of the positive electrode sheet are as follows: 1.5 g of binder, 35 g of N-methylpyrrolidone, 0.5 g of conductive agent, 97.5 g of positive electrode material, 0.5 g of lithium supplement agent, and the co-lithium supplement agent in Formula 2; the addition amount of the co-lithium supplement agent is 10% of the lithium supplement agent; the amounts of each component of the negative electrode sheet are as follows: 0.5 g of binder A, 78 g of deionized water, 0.5 g of conductive agent, 96 g of negative electrode material, 0.5 g of binder B, and the rest of the processes are exactly the same.

[0066] Example 8 The difference between this example and Example 3 is that the amounts of each component of the positive electrode sheet and the negative electrode sheet are different. The amounts of each component of the positive electrode sheet are as follows: 5 g of binder, 40 g of N-methylpyrrolidone, 5 g of conductive agent, 80 g of positive electrode material, 10 g of lithium supplement agent, and the co-lithium supplement agent in Formula 2; the addition amount of the co-lithium supplement agent is 10% of the lithium supplement agent; the amounts of each component of the negative electrode sheet are as follows: 3 g of binder A, 130 g of deionized water, 10 g of conductive agent, 84 g of negative electrode material, 3 g of binder B, and the rest of the processes are exactly the same.

[0067] Example 9 The difference between this example and Example 3 is that the addition amount of the co-dispersant is different. The addition amount of the co-dispersant is 5%, and the rest of the processes are exactly the same.

[0068] Example 10 The difference between this example and Example 3 is that the addition amount of the co-dispersant is different. The addition amount of the co-dispersant is 13%, and the rest of the processes are exactly the same.

[0069] Example 11 The difference between this embodiment and Embodiment 3 lies in the formation method, and the remaining processes are exactly the same. In this embodiment, the magnetic field strength in the formation method is 500 mT, and it includes the following stages: Constant current charge at 0.01C until 10% SOC; Constant current and constant voltage charge at 0.5C until the upper limit voltage; Constant current discharge at 0.33C until the lower limit voltage; Constant current and constant voltage charge at 1.0C until 5% SOC.

[0070] Embodiment 12 The difference between this embodiment and Embodiment 3 lies in the formation method, and the remaining processes are exactly the same. In this embodiment, the magnetic field strength in the formation method is 1500 mT, and it includes the following stages: Constant current charge at 0.2C until 30% SOC; Constant current and constant voltage charge at 2.0C until 120% SOC; Constant current discharge at 1.0C until the lower limit voltage; Constant current and constant voltage charge at 2.0C until 90% SOC.

[0071] Comparative Example 1 In this comparative example, no lithium supplementing agent is added, and the remaining technical solutions are the same as those in Embodiment 3.

[0072] Comparative Example 2 In this comparative example, lithium carbamoyl phosphate is not added during the preparation of the lithium supplementing agent, and the remaining technical solutions are the same as those in Embodiment 3.

[0073] Comparative Example 3 In this comparative example, ethyl 2-cyano-3-(3-pyridyl)acrylate is not added during the preparation of the lithium supplementing agent, and the remaining technical solutions are the same as those in Embodiment 3.

[0074] Comparative Example 4 In this comparative example, no lithium supplementing agent and lithium supplementing aid are added, and the remaining technical solutions are the same as those in Embodiment 3.

[0075] Comparative Example 5 In this comparative example, the formation is carried out in a magnetic field-free environment, and the remaining technical solutions are the same as those in Embodiment 3.

[0076] Comparative Document 6 In this comparative example, the traditional formation method is adopted, and the remaining technical solutions are the same as those in Embodiment 3. The traditional formation method includes the following stages Constant current charge at 0.05C until 10% SOC; Constant current and constant voltage charging is carried out at a current of 0.2C until 100% SOC; Constant current and constant voltage charging is carried out at a current of 0.05C until 120% SOC; Constant current discharge is carried out at a current of 0.5C until the lower limit voltage; Constant current and constant voltage charging is carried out at 0.5C until 90% SOC.

[0077] Comparative Example 7 In this comparative example, a lithium supplement agent is used to replace the co-lithium supplement agent, and the rest of the technical solutions are the same as those in Example 3.

[0078] The first charge and discharge capacity of the above-mentioned battery cells is tested at 0.2C, and the discharge capacity is tested at 1C and 2C in turn. Under the condition of 1C charge and discharge, the capacity retention rate after 1000 tests is tested, and the test results are shown in Table 2.

[0079] Table 2 Battery cell performance test table It can be seen from Examples 2 to 10, Comparative Examples 1 to 4 and Comparative Example 7 that when preparing the cathode lithium-supplemented full battery, adding the lithium-supplementing agent protected by the present application, when the addition amount of the lithium-supplementing agent is 5-13% of the lithium-supplementing agent, the energy density of the battery can be significantly improved. Comparing Example 3 with Comparative Example 1 and Comparative Example 7, it can be seen that when preparing the battery, only the lithium-supplementing agent is added without adding the lithium-supplementing agent. Although the energy density of the battery can be improved to a certain extent, it is far less obvious than adding the lithium-supplementing agent. If all the lithium-supplementing agent is used, although the effect is good, the cost is significantly increased; comparing Example 3 with Examples 2 and 3, it can be seen that when the lithium-supplementing agent does not contain lithium carbamoyl phosphate and ethyl 2-cyano-3-(3-pyridyl)acrylate, the effect of the present application cannot be achieved either. The reason is that the lithium carbamoyl phosphate obtained by the addition reaction of the amino group of lithium carbamoyl phosphate with ethyl 2-cyano-3-(3-pyridyl)acrylate and 5-allylpyrimidine-4,6-diol respectively, and the lithium carbamoyl phosphate containing cyano group, pyridyl group and pyrimidine group can be used as the synergistic component of the lithium-supplementing agent. The introduction of functional groups such as cyano group, pyridyl group and pyrimidine group can not only change the crystal structure of the cathode material, thus affecting its electrochemical performance, but also increase the conductivity of the material or improve the ion transport path through these functional groups, and at the same time can synergistically enhance the effect with the lithium-supplementing agent to jointly improve the energy density of the battery; the lithium-supplementing agent prepared by the present application can also form stable chemical bonds with other elements in the cathode material, thereby improving the cycle stability of the material. During the charge and discharge process, these functional groups can reduce the volume change of the material and reduce the stress concentration, thereby prolonging the service life of the battery, and the introduction of functional groups such as cyano group, pyridyl group and pyrimidine group in the lithium-supplementing agent can improve the electron conductivity of the cathode material, thereby improving the rate performance of the battery. This means that the battery can still maintain good electrochemical performance at high current density and is suitable for application scenarios that require fast charge and discharge.

[0080] It can be seen from the comparison between Example 3 and Comparative Examples 5 and 6 that increasing the magnetic field during formation can significantly increase the battery capacity, that is, increase the energy density, and can shorten the formation time to a certain extent, or can greatly increase the battery capacity within approximately the same formation time. Using the formation method of the present application to perform formation treatment on the lithium-supplemented full battery protected by the present application can reduce the risk of thermal runaway of the battery in the case of overcharge or overheat, and improve the production efficiency.

[0081] The above embodiments are intended to illustrate the embodiments disclosed in the present invention and should not be construed as limiting the present invention. In addition, various modifications listed herein and changes in the methods and compositions of the invention will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. Although the present invention has been specifically described in connection with various specific preferred embodiments of the present invention, it should be understood that the present invention should not be limited to these specific embodiments. In fact, all modifications that are obvious to those skilled in the art as described above to obtain the invention should be included within the scope of the present invention.

Claims

1. A preparation method of a positive electrode lithium-supplemented full battery, characterized in that, It includes the following steps: Step 1, preparing a positive electrode sheet: By mass parts, dissolve 1.5 - 5 parts of a positive electrode binder in 30 - 80 parts of N-methylpyrrolidone, then add 0.5 - 5 parts of a conductive agent, and mix evenly to form a positive electrode conductive paste; then add 80 - 97.5 parts of a positive electrode material, 0.5 - 10 parts of a lithium supplement agent, and a lithium supplement assisting agent into the positive electrode conductive paste and mix evenly to form a positive electrode slurry. Screen, coat, dry, roll, slit, and die-cut the positive electrode slurry to make a positive electrode sheet; the addition amount of the lithium supplement assisting agent is 5 - 13% of the lithium supplement agent; Step 2, preparing a negative electrode sheet: By mass parts, fully dissolve 0.5 - 3 parts of binder A in 78 - 130 parts of deionized water; add 0.5 - 10 parts of a conductive agent, and mix evenly to form a negative electrode conductive paste; add 84 - 96 parts of a negative electrode material into the negative electrode conductive paste, stir evenly, and then add 0.5 - 3 parts of binder B and mix evenly to form a negative electrode slurry. Screen, coat, dry, roll, slit, and die-cut the negative electrode slurry to make a negative electrode sheet; Step 3, winding or laminating, encapsulating, and drying the positive electrode sheet, negative electrode sheet, and separator, injecting an electrolyte to obtain an initial battery cell, and then performing formation treatment, standing, degassing, grading, and K value testing on the initial battery cell to obtain a positive electrode lithium-supplemented full battery.

2. The preparation method of a cathode lithium-supplemented full cell according to claim 1, characterized in that, The lithium supplement assisting agent in Step 1 is prepared by the following method: Step (1), put 15 - 30 parts of lithium carbamoyl phosphate, 10 - 20 parts of ethyl 2-cyano-3-(3-pyridyl)acrylate, 2 - 5 parts of triethylamine, 0.03 - 0.6 parts of 5-allylpyrimidine-4,6-diol, and 200 - 300 parts of N-methylpyrrolthione weighed by mass parts into a sealed stirring kettle; Step (2), introduce an inert gas into the above stirring kettle, stir and react at 60 - 74 °C for 30 - 100 min, and distill the reaction product to obtain the lithium supplement assisting agent.

3. The preparation method of a cathode lithium-supplemented full cell according to claim 1, characterized in that: The environmental temperature during the preparation of the positive electrode sheet in Step 1 is controlled at 15 - 35 °C, the humidity is controlled below the dew point of -40 °C, and a vacuum is maintained during the mixing of each component, and the vacuum degree is not lower than -0.085 mPa.

4. The preparation method of the positive electrode lithium - supplemented full battery according to claim 1, wherein: The positive electrode material is one or a mixture of several of lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium cobalt oxide, and lithium manganese iron phosphate.

5. The preparation method of a cathode lithium-supplemented full cell according to claim 1, characterized in that: The lithium supplement agent is one or several of lithium-rich nickelate, lithium-rich ferrate, lithium-rich cobaltate, lithium-rich nickel copperate, and squaric acid lithium.

6. The preparation method of a cathode lithium-supplemented full cell according to claim 1, characterized in that: The conductive agent is one or a mixture of several of conductive carbon black, Ketjen black, multi-walled carbon nanotubes, single-walled carbon nanotubes, and graphene.

7. The preparation method of a cathode lithium-supplemented full battery according to claim 1, characterized in that: The negative electrode material is one or a mixture of several of artificial graphite, natural graphite, hard carbon, and silicon carbon.

8. A positive electrode lithium-supplemented full battery prepared by the preparation method described in any one of claims 1 - 7.

9. A forming method, characterized in that: The initial battery cell is left standing for 12 - 96 hours and then subjected to formation treatment at a preset formation environmental temperature and magnetic field intensity.

10. The forming method according to claim 9, characterized in that: The preset magnetic field intensity is 500 mT - 1500 mT, the formation environmental temperature is 30 - 60 °C, and the formation treatment includes the following stages: Constant current charge at a current of 0.01C - 0.2C until 10% - 30% SOC; Constant current and constant voltage charging is carried out at a current of 0.5C to 2.0C until the upper limit voltage or 100% to 120% SOC; Constant current discharging is carried out at a current of 0.33C to 1.0C until the lower limit voltage or 0% to 10% SOC; Constant current and constant voltage charging is carried out at 1.0C to 2.0C until 5% to 90% SOC.

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