A battery slurry, its preparation method and application

Abstract

This invention discloses a battery slurry, its preparation method, and its application. The battery slurry includes an active material, a conductive agent, a binder, a solvent, and hydrophilic fumed silica. The hydrophilic fumed silica is dispersed in the solvent to form a hydrogen-bonded three-dimensional network structure, which is used to suppress the sedimentation and agglomeration of solid particles in the slurry. This invention also provides a method for preparing the battery slurry, including pre-dispersing the hydrophilic fumed silica in a solvent to form a silica colloidal dispersion, and then adding the active material, conductive agent, and binder for mixing and dispersion. This invention, by introducing hydrophilic fumed silica to construct a reversible hydrogen-bonded network, significantly improves the thermodynamic stability and thixotropic reversibility of the slurry, effectively suppresses particle sedimentation and conductive agent agglomeration, and improves the cycle stability of the battery, making it suitable for preparing high-performance lithium-ion batteries.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery manufacturing technology, specifically to a battery slurry, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries are widely used in portable electronic devices, electric vehicles, and large-scale energy storage systems due to their advantages such as high energy density, long cycle life, and no memory effect. The preparation of electrode slurry is a key step in the manufacturing process of lithium-ion batteries. The quality of the slurry directly determines the uniformity of subsequent coating processes, thus affecting the battery's electrochemical performance, consistency, and safety.

[0003] Ideal electrode slurries should possess good dispersibility and stability, meaning they should maintain uniform composition, free from sedimentation and agglomeration during storage from preparation to coating. However, in actual production, battery slurries commonly face the following problems: Density differences exist between solid particles and the solvent, leading to sedimentation under gravity and uneven composition between the upper and lower layers of the slurry. Simultaneously, nanoscale conductive agents, due to their large specific surface area and high surface energy, are prone to agglomeration under van der Waals forces, forming hard particles or clumps that are difficult to redisperse, disrupting the uniformity of the conductive network within the electrode. These sedimentation and agglomeration phenomena together alter the rheological properties of the slurry, manifesting as viscosity fluctuations over time or poor thixotropic response during high-shear coating. This results in a narrow coating process window, difficulty in controlling electrode surface density consistency, and ultimately affects battery yield and cycle stability.

[0004] To address the aforementioned issue of poor slurry stability, conventional techniques in this field include optimizing mixing process parameters, adjusting the binder system, or adding traditional dispersants. For example, extending the mixing time or increasing the dispersion speed can improve the dispersion effect; or dispersants can be adsorbed onto the particle surface to inhibit agglomeration through electrostatic repulsion or steric hindrance. However, process optimization methods are often limited by equipment capabilities and have limited effectiveness, making it difficult to fundamentally suppress settling. While traditional dispersants can improve the initial dispersion state, their adsorption layer is prone to desorption or destruction under prolonged standing or high shear conditions, failing to provide continuous and stable steric barrier. Consequently, their effect on improving the long-term stability of the slurry remains unsatisfactory, and the introduction of some dispersants may have adverse effects on the electrochemical system.

[0005] Therefore, there is an urgent need to develop a new type of battery slurry and its preparation method that can fundamentally improve the thermodynamic stability of battery slurry, effectively suppress particle sedimentation and agglomeration, and at the same time not affect the electrochemical performance of the battery. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a battery slurry, its preparation method and application, to solve the technical problem that "existing battery slurries suffer from particle sedimentation, agglomeration and viscosity fluctuations due to thermodynamic instability, which in turn affects coating uniformity and battery consistency".

[0007] To achieve the above objectives, the present invention is implemented using the following technical solution: This invention provides a battery slurry, which includes: an active material, a conductive agent, a binder, a solvent, and an additive; the active material includes lithium iron phosphate and graphite; the conductive agent is conductive carbon black; the binder includes polyvinylidene fluoride, sodium carboxymethyl cellulose, and styrene-butadiene rubber; the solvent includes N-methylpyrrolidone and deionized water; and the additive is hydrophilic fumed silica.

[0008] In this invention, the battery slurry is divided into a positive electrode slurry and a negative electrode slurry. The positive electrode slurry is formulated as follows: based on 100% of the total positive electrode solid mass, it includes 92-98 wt% lithium iron phosphate, 1-3 wt% conductive carbon black, 0.5-3 wt% polyvinylidene fluoride, and 0.5-2 wt% hydrophilic fumed silica. The negative electrode slurry is formulated as follows: based on 100% of the total negative electrode solid mass, it includes 90-97 wt% graphite, 0.5-2.5 wt% sodium carboxymethyl cellulose, 0.5-3 wt% conductive carbon black, 0.5-4 wt% styrene-butadiene rubber, and 0.5-2 wt% hydrophilic fumed silica.

[0009] In this invention, the specific surface area of ​​the hydrophilic fumed silica is 100-400 m². 2 / g, with a native particle size of 5-50nm.

[0010] This invention also provides a method for preparing battery slurry, comprising the following steps: (1) Weigh out lithium iron phosphate, conductive carbon black, polyvinylidene fluoride and hydrophilic fumed silica in proportion; (2) Hydrophilic fumed silica and N-methylpyrrolidone are pre-dispersed to form a uniform colloid. This colloid is then mixed and dispersed with lithium iron phosphate, conductive carbon black and polyvinylidene fluoride, and vacuum degassing stage to obtain positive electrode slurry. (3) Weigh out graphite, sodium carboxymethyl cellulose, conductive carbon black, styrene-butadiene rubber and hydrophilic fumed silica in proportion; (4) First, hydrophilic fumed silica and deionized water are pre-dispersed to form a uniform colloid. After mixing and dispersing this colloid with graphite, sodium carboxymethyl cellulose and conductive carbon black, styrene-butadiene rubber is added and stirred. Vacuum degassing is performed to obtain the negative electrode slurry.

[0011] Specifically, the pre-dispersion speed in steps (2) and (4) is 1000~3000 r / min, and the time is 20~40 min.

[0012] Specifically, the mixing and dispersion described in steps (2) and (4) involves first stirring at a low speed of 300-800 r / min for 10-20 min, and then dispersing at a high speed of 1000-2500 r / min for 40-50 min.

[0013] Specifically, the vacuum degassing stage described in steps (2) and (4) takes 5 to 15 minutes.

[0014] This invention also provides an application of battery slurry in the manufacture of lithium-ion batteries.

[0015] Compared with the prior art, the beneficial effects achieved by the present invention are: (1) This invention adds hydrophilic fumed silica to the battery slurry, utilizing its abundant silanol groups to form a hydrogen bond network structure in the solvent. This three-dimensional network can effectively prevent the sedimentation and agglomeration of solid particles such as active materials and conductive agents, significantly improving the thermodynamic stability of the slurry. Stability tests show that the stability kinetic index (TSI value) of the slurry with the additive of this invention after standing for 3 days is significantly lower than that of the control slurry without the additive, proving that it can maintain uniform composition during long-term storage.

[0016] (2) This invention endows the slurry with excellent thixotropic reversibility. At low shear rates, the hydrogen bond network maintains the slurry's high static viscosity to suppress sedimentation; during high-shear coating, the network structure is temporarily disrupted, reducing the slurry's viscosity and improving its fluidity; after shearing stops, the hydrogen bond network is rapidly rebuilt, and the viscosity quickly recovers. This characteristic gives the slurry both the advantages of static anti-settling and easy coating, broadening the coating process window and improving the consistency of electrode surface density.

[0017] (3) The additive of this invention is an electrochemically inert substance that will not introduce harmful side reactions or cause irreversible loss of active lithium, and therefore will not negatively affect the first charge-discharge performance of the battery. At the same time, because the additive effectively inhibits the aggregation of conductive agents and promotes the uniform dispersion between active materials and conductive agents, a more stable and uniform conductive network is formed inside the electrode, which significantly improves the cycle stability of the battery. Cyclic tests show that the battery prepared with the slurry containing the additive of this invention has a significantly better capacity retention rate than the control battery without the additive after 100 charge-discharge cycles, especially in the negative electrode slurry. Attached Figure Description

[0018] Figure 1This is a comparison chart of the stability of the positive and negative electrode slurries of Example 2 and Comparative Example 1.

[0019] Figure 2 This is a comparison diagram of the thixotropic properties of the positive and negative electrode slurries of Example 2 and Comparative Example 1.

[0020] Figure 3 This is a comparison chart of the first-cycle performance of the positive and negative electrode slurries in Example 2 and Comparative Example 1. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1; (1) Weigh 92wt% of lithium iron phosphate, 3wt% of conductive carbon black, 3wt% of polyvinylidene fluoride, and 2wt% of hydrophilic fumed silica, based on 100% of the total mass of the positive electrode solid. (2) First, add 2 wt% of hydrophilic fumed silica to N-methylpyrrolidone and disperse it at a high speed of 3000 r / min for 20 min to obtain a silica colloidal dispersion. Then add 92 wt% lithium iron phosphate, 3 wt% conductive carbon black and 3 wt% polyvinylidene fluoride to the dispersion. In a planetary mixer, first stir at a speed of 300 r / min for 20 min, then disperse at a high speed of 2500 r / min for 40 min, and then degas under vacuum for 5 min to obtain the positive electrode slurry. (3) Weigh out 90wt% of graphite, 2.5wt% of sodium carboxymethyl cellulose, 3wt% of conductive carbon black, 4wt% of styrene-butadiene rubber, and 0.5wt% of hydrophilic fumed silica based on 100% of the total mass of the negative electrode solid. (4) First, add 0.5wt% of hydrophilic fumed silica to deionized water and disperse it at a high speed of 3000r / min for 20min to obtain silica colloid. Then, add 90wt% of graphite, 2.5wt% of sodium carboxymethyl cellulose and 3wt% of conductive carbon black to silica colloid. In a planetary mixer, first stir at a speed of 300r / min for 20min, then disperse at a high speed of 2500r / min for 40min. Add 4wt% of styrene-butadiene rubber and stir at a speed of 300r / min for 10min. Then, degas under vacuum for 5min to obtain negative electrode slurry.

[0023] Example 2; (1) Weigh 96wt% of lithium iron phosphate, 2wt% of conductive carbon black, 1wt% of polyvinylidene fluoride, and 1wt% of hydrophilic fumed silica, based on 100% of the total mass of the positive electrode solid. (2) First, add 1 wt% of hydrophilic fumed silica to N-methylpyrrolidone and disperse it at a high speed of 2000 r / min for 30 min to obtain a silica colloidal dispersion. Then add 96 wt% lithium iron phosphate, 2 wt% conductive carbon black and 1 wt% polyvinylidene fluoride to the dispersion. In a planetary mixer, first stir at a low speed of 500 r / min for 15 min, then disperse at a high speed of 2000 r / min for 45 min, and then degas under vacuum for 10 min to obtain the positive electrode slurry. (3) Weigh out 95wt% of graphite, 1.5wt% of sodium carboxymethyl cellulose, 1.5wt% of conductive carbon black, 2wt% of styrene-butadiene rubber, and 1wt% of hydrophilic fumed silica based on 100% of the total mass of the negative electrode solid. (4) First, add 1 wt% of hydrophilic fumed silica to deionized water and disperse it at a high speed of 2000 r / min for 30 min to obtain fumed silica colloid. Then add 95 wt% of graphite, 1.5 wt% of sodium carboxymethyl cellulose and 1.5 wt% of conductive carbon black to the fumed silica colloid. In a planetary mixer, first stir at a low speed of 500 r / min for 15 min, then disperse at a high speed of 2000 r / min for 45 min, add 2 wt% of styrene-butadiene rubber, stir at a speed of 300 r / min for 10 min, and then degas under vacuum for 10 min to obtain the negative electrode slurry.

[0024] Example 3; (1) Weigh 98wt% of lithium iron phosphate, 1wt% of conductive carbon black, 0.5wt% of polyvinylidene fluoride, and 0.5wt% of hydrophilic fumed silica, based on 100% of the total mass of the positive electrode solids. (2) First, add 0.5 wt% of hydrophilic fumed silica to N-methylpyrrolidone and disperse it at 1000 r / min for 40 min to obtain a silica colloidal dispersion. Then add 98 wt% lithium iron phosphate, 1 wt% conductive carbon black and 0.5 wt% polyvinylidene fluoride to the dispersion. In a planetary mixer, first stir at 800 r / min for 10 min, then disperse at 1000 r / min for 50 min, and then degas under vacuum for 15 min to obtain the positive electrode slurry. (3) Weigh out 97wt% of graphite, 0.5wt% of sodium carboxymethyl cellulose, 0.5wt% of conductive carbon black, 0.5wt% of styrene-butadiene rubber, and 1.5wt% of hydrophilic fumed silica, based on 100% of the total mass of the negative electrode solid. (4) First, add 1.5 wt% of hydrophilic fumed silica to deionized water and disperse it at a high speed of 1000 r / min for 40 min to obtain silica colloid. Then, add 97 wt% of graphite, 0.5 wt% of sodium carboxymethyl cellulose and 0.5 wt% of conductive carbon black to silica colloid. In a planetary mixer, first stir at a low speed of 800 r / min for 10 min, then disperse at a high speed of 1000 r / min for 50 min, add 0.5 wt% of styrene-butadiene rubber, stir at a speed of 300 r / min for 10 min, and then degas under vacuum for 15 min to obtain negative electrode slurry.

[0025] Example 4; (1) Weigh 94wt% of lithium iron phosphate, 2wt% of conductive carbon black, 2wt% of polyvinylidene fluoride, and 2wt% of hydrophilic fumed silica, based on 100% of the total mass of the positive electrode solid. (2) First, add 2wt% of hydrophilic fumed silica to N-methylpyrrolidone and disperse it at 2000 r / min for 30 min to obtain a silica colloidal dispersion. Then add 94wt% lithium iron phosphate, 2wt% conductive carbon black and 2wt% polyvinylidene fluoride to the dispersion. In a planetary mixer, first stir at 500 r / min for 15 min, then disperse at 1500 r / min for 45 min, and then degas under vacuum for 10 min to obtain the positive electrode slurry. (3) Weigh out 94wt% of graphite, 1wt% of sodium carboxymethyl cellulose, 1wt% of conductive carbon black, 2wt% of styrene-butadiene rubber, and 2wt% of hydrophilic fumed silica, based on 100% of the total mass of the negative electrode solid. (4) First, add 2wt% of hydrophilic fumed silica to deionized water and disperse it at a high speed of 2000 r / min for 30 min to obtain fumed silica colloid. Then, add 94wt% of graphite, 1wt% of sodium carboxymethyl cellulose and 1wt% of conductive carbon black to the fumed silica colloid. In a planetary mixer, first stir at a low speed of 500 r / min for 15 min, then disperse at a high speed of 1500 r / min for 45 min. Add 2wt% of styrene-butadiene rubber and stir at a speed of 300 r / min for 10 min. Then, degas under vacuum for 10 min to obtain the negative electrode slurry.

[0026] Example 5; (1) Weigh 97wt% of lithium iron phosphate, 1.5wt% of conductive carbon black, 0.5wt% of polyvinylidene fluoride, and 1wt% of hydrophilic fumed silica, based on 100% of the total mass of the positive electrode solid. (2) First, add 1 wt% of hydrophilic fumed silica to N-methylpyrrolidone and disperse it at a high speed of 2000 r / min for 30 min to obtain a silica colloidal dispersion. Then, add 97 wt% lithium iron phosphate, 1.5 wt% conductive carbon black and 0.5 wt% polyvinylidene fluoride to the dispersion. In a planetary mixer, first stir at a low speed of 500 r / min for 15 min, then disperse at a high speed of 2000 r / min for 45 min, and then degas under vacuum for 10 min to obtain the positive electrode slurry. (3) Weigh out 92wt% of graphite, 1.5wt% of sodium carboxymethyl cellulose, 2.5wt% of conductive carbon black, 3wt% of styrene-butadiene rubber, and 1wt% of hydrophilic fumed silica based on 100% of the total mass of the negative electrode solid. (4) First, add 1 wt% of hydrophilic fumed silica to deionized water and disperse it at a high speed of 2000 r / min for 30 min to obtain fumed silica colloid. Then, add 92 wt% of graphite, 1.5 wt% of sodium carboxymethyl cellulose and 2.5 wt% of conductive carbon black to the fumed silica colloid. In a planetary mixer, first stir at a low speed of 500 r / min for 15 min, then disperse at a high speed of 2000 r / min for 45 min, add 3 wt% of styrene-butadiene rubber, stir at a speed of 300 r / min for 10 min, and then degas under vacuum for 10 min to obtain the negative electrode slurry.

[0027] Comparative Example 1; (1) Based on 100% of the total mass of the positive electrode solid, weigh 97wt% of lithium iron phosphate, 2wt% of conductive carbon black and 1wt% of polyvinylidene fluoride and dissolve them in N-methylpyrrolidone. In a planetary mixer, first stir at a low speed of 500r / min for 15min, then disperse at a high speed of 2000r / min for 45min, and then degas under vacuum for 10min to obtain the positive electrode slurry. (2) Based on 100% of the total mass of the negative electrode solid, weigh 96wt% of graphite, 1.5wt% of sodium carboxymethyl cellulose, 1.5wt% of conductive carbon black and 2wt% of styrene-butadiene rubber and dissolve them in deionized water. Disperse them at a high speed of 2000r / min for 30min. In a planetary mixer, first stir at a low speed of 500r / min for 15min, then disperse at a high speed of 2000r / min for 45min. Add 2wt% of styrene-butadiene rubber and stir at a speed of 300r / min for 10min. Then degas under vacuum for 10min to obtain the negative electrode slurry.

[0028] Test Results Stability test: The stability of the positive and negative electrode slurries of Example 2 and Comparative Example 1 were tested using a multiple light scattering instrument. The test conditions were: scan time of 30 min / scan, and total duration of 3 days.

[0029] Figure 1 This is a comparison chart of the stability of the positive and negative electrode slurries in Example 2 and Comparative Example 1, where... Figure 1 (a) is a comparison chart of TSI of the positive electrode slurry. Figure 1 (b) is a TSI comparison chart of negative electrode slurry. The solid line corresponds to Example 2, and the dashed line corresponds to Example 1.

[0030] like Figure 1 As shown, the TSI (Stability Kinetic Index) values ​​of the slurry in Example 2 are all lower than those of the slurry in Comparative Example 1, indicating that the particle migration behavior of the positive and negative electrode slurries prepared in Example 2 of this invention is significantly suppressed during the standing process, and the slurry system has higher thermodynamic stability. This shows that the hydrophilic fumed silica used in this invention, through synergistic effects with other components in the slurry, constructs a more stable three-dimensional network structure inside the slurry, effectively preventing the sedimentation and agglomeration of solid particles, thereby achieving component uniformity during long-term storage of the slurry.

[0031] Rheological testing: Thixotropic tests were performed on the positive and negative electrode slurries of Example 2 and Comparative Example 1 using a rheometer (Anton Paar MCR302). The test conditions were: shear rate from 0.1 s⁻¹ - ¹Linearly increase to 100s - ¹, then linearly reduced to 0.1s - ¹, used to characterize the rheological behavior of slurry during settling, coating shearing, and shear recovery processes.

[0032] Figure 2 This is a comparison diagram of the thixotropic properties of the positive and negative electrode slurries of Example 2 and Comparative Example 1, in which... Figure 2 (a) is a comparison diagram of the thixotropic properties of the positive electrode slurry. Figure 2(b) is a comparison diagram of the thixotropic properties of the negative electrode slurry. The solid line corresponds to Example 2, and the dashed line corresponds to Example 1.

[0033] like Figure 2 As shown, at a low shear rate (0.1 s⁻¹), - ¹) The slurry prepared in Example 2 exhibits a significantly higher static viscosity than that of the slurry in Comparative Example 1. This is because the surface of the hydrophilic fumed silica in Example 2 is rich in silanol groups, and the particles interact through hydrogen bonds to construct a three-dimensional network structure that runs through the entire system inside the slurry. This structure effectively restricts the free movement of active material and conductive agent particles, thereby inhibiting particle sedimentation in a static state.

[0034] At high shear rates (100 s⁻¹) - ¹) Under these conditions, the viscosity values ​​of the slurry in Example 2 and the slurry in Comparative Example 1 tend to be close. This is because under high shear force, the three-dimensional network connected by hydrogen bonds inside the slurry in Example 2 is temporarily destroyed, and the particles are arranged in an orderly manner along the shear direction. At this time, the flow resistance of the slurry mainly comes from the internal friction of the liquid medium and the physical collision between particles, which is similar to the state of the slurry in Comparative Example 1 without network structure under high-speed shear. This result shows that the introduction of the additive of the present invention will not have an adverse effect on the flowability of the slurry in the high-shear coating process.

[0035] When the shear rate is 100s - ¹Recover to 0.1s - ¹At this time, the viscosity of the slurry in Example 2 rapidly recovered to near its initial value, while the viscosity of the slurry in Comparative Example 1 recovered slowly and could not reach the initial level. This is because in the slurry of Example 2, the damaged hydrogen bond network can be rapidly rebuilt after the high shear stops, and the three-dimensional structure is restored. However, in the slurry of Comparative Example 1, due to the lack of reversible chemical bonding, the particle system disturbed by shear can only slowly rearrange itself by Brownian motion, and the structure is not fully restored. This phenomenon shows that the additive of the present invention gives the slurry excellent thixotropic reversibility, making it have the dual characteristics of static anti-settling and easy coating.

[0036] Button cell test: The slurries of Examples 1-5 and Comparative Example 1 were made into electrode sheets, assembled into button half-cells, and subjected to charge-discharge tests and cycle life tests.

[0037] Charge-discharge test: The assembled coin cell half-cell was placed in the battery testing system and the first charge-discharge performance test was conducted at 25±2℃. During the charging phase, a constant current of 0.1C was used to charge the positive half-cell to 3.7V and the negative half-cell to 2V. After reaching the cutoff voltage, charging was stopped and the cell was allowed to stand for 5 minutes. Subsequently, a discharge test was conducted using a constant current of 0.1C. The positive half-cell was discharged to 2.0V and the negative half-cell to 0.005V. After reaching the cutoff voltage, discharge was stopped and the cell was allowed to stand for 5 minutes. The testing system automatically recorded the cumulative charging capacity and the cumulative discharging capacity during the first charging and discharging processes, respectively. These values ​​were divided by the mass of the active material in the electrode sheet to obtain the charging specific capacity and the discharging specific capacity. The initial coulombic efficiency was calculated by the ratio of the initial discharging specific capacity to the initial charging specific capacity. The specific results are shown in Table 1.

[0038] Table 1

[0039] Figure 3 This is a comparison chart of the first-cycle performance of the positive and negative electrode slurries in Example 2 and Comparative Example 1. Figure 3 (a) is a comparison chart of the first-cycle performance of the positive electrode paste in the coin cell. Figure 3 (b) is a comparison chart of the first-cycle performance of the negative electrode slurry, with the solid line corresponding to Example 2 and the dashed line corresponding to Example 1; as shown Figure 3 As shown, the curve of Example 2 is basically the same as that of Comparative Example 1.

[0040] As can be seen from the data in Table 1, the positive and negative electrode slurries prepared in Examples 1-5 exhibited similar initial charge specific capacity, initial discharge specific capacity, and initial coulombic efficiency as Comparative Example 1, with all numerical fluctuations within a reasonable range of testing error. This result indicates that the introduction of the additives in this invention did not negatively impact the battery's initial charge-discharge performance. The hydrophilic fumed silica, as an electrochemically inert material, does not introduce harmful side reactions or cause irreversible loss of active lithium, thus ensuring that the battery's fundamental electrochemical performance remains unaffected.

[0041] Cycle life test: The coin cell half-cells that have completed the first charge and discharge test will continue to undergo 100 constant current charge and discharge cycle tests in the battery test system under constant temperature conditions of 25±2℃.

[0042] The initial discharge specific capacity (mAh / g) obtained in the first charge-discharge test is used as the initial specific capacity for the cycle life test. The charge-discharge cycle is performed according to the above process, and the discharge specific capacity of each cycle is recorded. The discharge specific capacity of the 100th cycle is taken as the capacity after 100 cycles. The capacity retention rate characterizes the degree of capacity decay of the battery after 100 cycles. The calculation formula is: capacity retention rate (%) = (discharge specific capacity after 100 cycles / initial discharge specific capacity) × 100%. The specific results are shown in Table 2.

[0043] Table 2

[0044] As can be seen from the data in Table 2, after 100 charge-discharge cycles, the capacity retention rates of the slurries prepared in Examples 1-5 were significantly better than those in Comparative Example 1, especially in the negative electrode performance. The above results indicate that the additives of the present invention effectively inhibit the aggregation of conductive agents by constructing a hydrogen bond network inside the slurry, and promote the uniform dispersion between the active material and the conductive agent, thereby forming a more stable and uniform conductive network inside the electrode. This improvement in microstructure significantly slows down the deterioration of the electrode structure during cycling, and the effect on improving the cycling stability of the negative electrode slurry is particularly prominent.

[0045] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. A battery slurry, characterized in that, The battery slurry is divided into positive electrode slurry and negative electrode slurry, including: active material, conductive agent, binder, solvent and additives; The conductive agent is conductive carbon black; The binder includes polyvinylidene fluoride for the positive electrode slurry and sodium carboxymethyl cellulose and styrene-butadiene rubber for the negative electrode slurry. The solvent includes N-methylpyrrolidone and deionized water; The additive is hydrophilic fumed silica.

2. The battery slurry according to claim 1, characterized in that, The active material of the positive electrode slurry is lithium iron phosphate, and the active material of the negative electrode slurry is graphite.

3. The battery slurry according to claim 1, characterized in that, The specific surface area of ​​the hydrophilic fumed silica is 100-400 m². 2 / g, with a native particle size of 5-50nm.

4. The battery slurry according to claim 1, characterized in that, The cathode slurry, based on 100% of the total mass of cathode solids, includes: 92-98 wt% lithium iron phosphate, 1-3 wt% conductive carbon black, 0.5-3 wt% polyvinylidene fluoride, and 0.5-2 wt% hydrophilic fumed silica.

5. The battery slurry according to claim 1, characterized in that, The negative electrode slurry, based on 100% of the total negative electrode solid mass, includes: 90-97 wt% graphite, 0.5-2.5 wt% sodium carboxymethyl cellulose, 0.5-3 wt% conductive carbon black, 0.5-4 wt% styrene-butadiene rubber, and 0.5-2 wt% hydrophilic fumed silica.

6. A method for preparing the battery slurry as described in any one of claims 1-5, characterized in that, Includes the following steps: (1) Weigh out lithium iron phosphate, conductive carbon black, polyvinylidene fluoride and hydrophilic fumed silica in proportion; (2) The hydrophilic fumed silica and N-methylpyrrolidone are pre-dispersed to form a uniform colloid. This colloid is then mixed and dispersed with the lithium iron phosphate, conductive carbon black and polyvinylidene fluoride and vacuum degassing stage to obtain the positive electrode slurry. (3) Weigh out graphite, sodium carboxymethyl cellulose, conductive carbon black, styrene-butadiene rubber and hydrophilic fumed silica in proportion; (4) The hydrophilic fumed silica and deionized water are pre-dispersed to form a uniform colloid. This colloid is then mixed and dispersed with the graphite, sodium carboxymethyl cellulose and conductive carbon black. Styrene-butadiene rubber is then added, and the mixture is stirred and degassed under vacuum to obtain the negative electrode slurry.

7. The preparation method according to claim 6, characterized in that, The pre-dispersion speed in steps (2) and (4) is 1000~3000 r / min and the time is 20~40 min.

8. The preparation method according to claim 6, characterized in that, The mixing and dispersion described in steps (2) and (4) involves first stirring at a low speed of 300-800 r / min for 10-20 min, and then dispersing at a high speed of 1000-2500 r / min for 40-50 min.

9. The preparation method according to claim 6, characterized in that, The vacuum degassing stage described in steps (2) and (4) takes 5 to 15 minutes.

10. The application of a battery slurry as described in any one of claims 1-5 in the manufacture of lithium-ion batteries.

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