Negative electrode sheet, method for manufacturing the same, and lithium-ion secondary battery
By adding additives such as phosphorus-carbon composite materials to the active material layer of the negative electrode in lithium-ion secondary batteries, the problem of battery performance degradation caused by the migration and deposition of transition metal ions has been solved, and the cycle stability and lifespan of the battery have been extended.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- UNIV OF SCI & TECH OF CHINA
- Filing Date
- 2025-03-06
- Publication Date
- 2026-07-24
AI Technical Summary
In lithium-ion secondary batteries, transition metal ions dissolve from the positive electrode material and migrate to the negative electrode surface to deposit, leading to battery performance degradation, which is particularly severe during high-temperature storage or cycling.
Additives such as phosphorus-carbon composite materials, carbon nanotubes, or polyacrylic acid are added to the active material layer of the negative electrode. These additives interact with transition metal ions, reducing their deposition and accumulation on the surface of the negative electrode.
It effectively reduces the deposition of transition metal ions on the surface of the negative electrode, improves the cycle stability and lifespan of the battery, and does not reduce the energy density.
Smart Images
Figure CN119993987B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of new energy storage materials, and in particular to a negative electrode sheet and its preparation method, and a lithium-ion secondary battery. Background Technology
[0002] With the widespread adoption of lithium-ion rechargeable batteries, they have been widely used in devices such as portable electronic devices, battery packs for hybrid vehicles, electric vehicles, or energy storage devices.
[0003] In lithium-ion rechargeable batteries, the cathode material typically contains transition metal ions (such as cobalt, nickel, and manganese), which are crucial for achieving high energy density. During use, such as high-temperature storage or cycling, these transition metal ions in the cathode material dissolve, enter the electrolyte, and further migrate to the negative electrode, depositing on its surface. This migration and deposition process leads to performance degradation after multiple charge cycles.
[0004] Therefore, how to reduce the deposition of transition metal ions on the negative electrode has become an urgent problem to be solved. Summary of the Invention
[0005] In view of this, in order to at least partially solve at least one of the aforementioned technical problems, the present invention provides a negative electrode sheet and a method for preparing the same, and a lithium-ion secondary battery.
[0006] According to one aspect of the present invention, a negative electrode sheet is provided, comprising: a negative electrode current collector and an active material layer located on the negative electrode current collector; the active material layer comprises: an active material, a conductive agent, a binder, and an additive; wherein the additive comprises at least one of phosphorus-carbon composite material, carbon nanotubes, and polyacrylic acid.
[0007] In some illustrative embodiments, the phosphorus-carbon composite material includes phosphorus and carbon materials, with the phosphorus bonded to the carbon materials via chemical bonds.
[0008] In some illustrative embodiments, the mass content of phosphorus in the phosphorus-carbon composite material is 30-70%.
[0009] In some illustrative embodiments, the mass of the additive accounts for 1 to 20% of the total mass of the negative electrode.
[0010] In some illustrative embodiments, the conductive agent includes conductive carbon, and preferably, the conductive agent includes at least one of carbon black, carbon nanotubes, graphene, carbon fiber, and porous carbon.
[0011] In some illustrative embodiments, the mass ratio of the active material, conductive agent, and binder is 8:1:1.
[0012] In some illustrative embodiments, the active material includes at least one of carbon-based materials and silicon-based materials; the carbon-based materials include at least one of graphite, hard carbon, and soft carbon; the silicon-based materials include at least one of nano-silicon, micron-silicon, silicon-carbon composite materials, and silicon suboxide.
[0013] In some illustrative embodiments, the carbon material includes at least one of graphite, hard carbon, soft carbon, and carbon black; the phosphorus includes at least one of red phosphorus, black phosphorus, white phosphorus, blue phosphorus, and purple phosphorus.
[0014] According to another aspect of the present invention, a method for preparing the above-mentioned negative electrode sheet is provided, comprising: adding active material, additive, binder and conductive agent to a solvent respectively, stirring and coating them onto a negative electrode current collector, and drying them to obtain a negative electrode sheet.
[0015] In some illustrative embodiments, the drying temperature is 55-65°C and the processing time is 9-11 hours; the solvent includes at least one of water or N-methylpyrrolidone.
[0016] According to another aspect of the present invention, a lithium-ion secondary battery is provided, comprising the negative electrode sheet as described above.
[0017] According to embodiments of the present invention, by adding at least one of phosphorus-carbon composite materials, carbon nanotubes, and polyacrylic acid as an additive to the active material layer of the negative electrode, the deposition of transition metal ions (e.g., manganese, cobalt, nickel, etc.) on the negative electrode can be reduced during battery cycling. The additive can reduce the migration freedom of transition metal ions through interaction with them, thereby reducing or preventing the deposition and accumulation of transition metal ions on the surface of the negative electrode, thus improving the specific capacity of the battery and extending its service life. Attached Figure Description
[0018] The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the invention with reference to the accompanying drawings, in which:
[0019] Figure 1 A schematic diagram illustrating the mechanism of the continuous adsorption and phagocytosis process of transition metal ions by the phosphorus-carbon composite material according to an embodiment of the present invention is shown.
[0020] Figure 2 The negative electrode of Embodiment 1 and Comparative Example 1 of the present invention is shown in the presence of 20 mM Mn. 2+ Circulating specific capacity and coulombic efficiency in electrolyte;
[0021] Figure 3 This shows a high-resolution transmission electron microscope image of the phosphorus and carbon particles of the negative electrode of Embodiment 1 of the present invention after battery cycling;
[0022] Figure 4 A high-resolution transmission electron microscope image of graphite particles in the negative electrode of Comparative Example 1 of the present invention after battery cycling is shown.
[0023] Figure 5 The negative electrode of Embodiment 2 and Comparative Example 2 of the present invention is shown in the presence of 20 mM Mn 2+ The circulating specific capacity and coulombic efficiency in the electrolyte. Detailed Implementation
[0024] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.
[0025] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "comprising" as used herein indicates the presence of features, steps, or operations, but does not exclude the presence or addition of one or more other features.
[0026] When using expressions such as "at least one of A, B, and C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, and C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.). When using expressions such as "at least one of A, B, or C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, or C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.).
[0027] In related technologies, the cathode materials used in lithium-ion battery systems include LiCoO2, LiMn2O4, and Li(Ni) x Co y Mn 1-x-y Other cathode materials under development include O2, lithium-rich manganese-based materials, and high-voltage spinel materials such as LiNi. 0.5 Mn 1.5O2, etc., indicate that the aforementioned cathode materials all contain transition metal ions, especially manganese. During battery cycling, the dissolution and deposition of transition metal ions is a common and difficult problem to address for these cathodes. This problem can be understood as transition metal ions dissolving from the cathode material and migrating through the electrolyte to deposit on the negative electrode surface. Due to the dissolution and deposition of transition metal ions, the performance of lithium-ion secondary battery systems degrades rapidly in actual use (including storage and cycling), especially during high-temperature storage or cycling, where the dissolution problem is particularly severe.
[0028] Specifically, taking a battery system containing a Mn cathode as an example, Mn ions dissolve and migrate from the cathode to deposit on the surface of the negative electrode in a traditional lithium-ion secondary battery, leading to severe electrolyte decomposition and blockage of lithium-ion transport channels, among other negative effects. The dissolution and deposition process of Mn ions causes a series of phenomena such as increased internal resistance, gas generation, capacity decay, decreased rate performance, and shortened cycle life, thus exacerbating the failure of lithium-ion batteries.
[0029] To overcome the negative impact of transition metal ion crosstalk (i.e. the dissolution and deposition process of transition metal ions) on lithium-ion batteries, related technologies have attempted to solve the crosstalk problem by adding certain reagents to the electrolyte, designing positive electrode coatings, or designing battery separator coatings. However, these methods are relatively complex, and reducing the dissolution process of transition metal ions also affects the energy density and other performance characteristics of lithium-ion batteries.
[0030] In the process of realizing the concept of this invention, it was discovered that by adding additives to the active material layer of the negative electrode, the additives can interact with transition metal ions, thereby reducing the deposition and enrichment of transition metal ions on the surface of the negative electrode.
[0031] Specifically, according to one embodiment of the present invention, a negative electrode sheet is provided, comprising: a negative electrode current collector and an active material layer located on the negative electrode current collector; the active material layer comprises: an active material, a conductive agent, a binder, and an additive; wherein the additive comprises at least one of phosphorus-carbon composite material, carbon nanotubes, and polyacrylic acid.
[0032] According to embodiments of the present invention, by adding additives to the active material layer, the additives can interact with transition metal ions, reducing the deposition and enrichment of transition metal ions on the surface of the negative electrode, mitigating the damage to the negative electrode caused by transition metal ion crosstalk, and thereby improving the cycle stability and service life of the battery.
[0033] The following will elaborate on the different interactions between several additives and transition metal ions.
[0034] In some illustrative embodiments, the additive is a phosphorus-carbon composite material, in which carbon provides excellent electrical conductivity and mechanical strength, which helps to promote electron transport and reduce internal resistance. Phosphorus can fix transition metal ions on the surface and inside the phosphorus-carbon composite material through continuous adsorption and phagocytosis. Figure 1 A schematic diagram illustrating the mechanism of the continuous adsorption and phagocytosis process of transition metal ions (e.g., manganese ions) by the phosphorus-carbon composite material according to an embodiment of the present invention is shown. Figure 1 As shown, transition metal ions are partially adsorbed on the surface of phosphorus particles, while others are further absorbed into the bulk phase of the phosphorus particles. This helps to reduce deposition on the surface of the negative electrode and mitigate the negative impact on the cycle life of the negative electrode. Simultaneously, the phosphorus-carbon composite material can react with the electrolyte to a certain extent, participating in the formation of the solid electrolyte interphase (SEI) film during battery cycling. This further protects the negative electrode, reduces side reactions between the active material and the electrolyte, and extends the lifespan and cycle stability of the lithium-ion battery.
[0035] In some illustrative embodiments, the additive is polyacrylic acid, which is a good binder that can maintain good contact between active material particles, help increase the adhesion between the active material and the negative electrode current collector, help maintain the integrity of the negative electrode structure, and reduce the shedding of active material during long-term battery cycling, thereby improving the cycle life and safety of the battery.
[0036] In some illustrative embodiments, the additive is carbon nanotubes, which help form a three-dimensional conductive network, improve the overall conductivity of the active material layer, thereby promoting electron transport, reducing internal resistance, and improving the battery's charge and discharge efficiency and power density.
[0037] In some illustrative embodiments, a combination of the above-mentioned materials may also be included, which helps to adapt to different battery application scenarios by adjusting the content of the above-mentioned additives.
[0038] In some illustrative embodiments, the negative electrode current collector can be, for example, copper, copper alloy, or stainless steel, preferably copper, because copper has good stability and is not prone to forming a passivation layer during battery charging and discharging, and therefore can be widely used in lithium-ion batteries.
[0039] In some illustrative embodiments, the phosphorus-carbon composite material includes phosphorus and carbon materials, with the phosphorus bonded to the carbon materials via chemical bonds.
[0040] It is understandable that while phosphorus can adsorb and engulf transition metal ions, the engulfment process and the charge / discharge process both involve significant volume changes in phosphorus. By combining phosphorus with carbon materials to form phosphorus-carbon composites, the carbon materials can effectively buffer the volume expansion caused by phosphorus, helping to maintain the stability of the negative electrode structure, reduce the loss of active materials, and improve battery cycle life. At the same time, the carbon materials can provide high conductivity, which helps to improve the conductivity of the phosphorus-carbon composite.
[0041] In some illustrative embodiments, the mass content of phosphorus in the phosphorus-carbon composite material is 30-70%, for example, 30%, 40%, 50%, 60%, or 70%. If the phosphorus content is too high, it may exacerbate volume expansion during charging and discharging, leading to poor cycle performance of the negative electrode. If the phosphorus content is too low, it is difficult to provide adsorption and phagocytosis of transition metal ions, resulting in limited improvement in the crosstalk effect of transition metal ions. Adjusting the phosphorus content within the above range provides sufficient adsorption and phagocytosis of transition metal ions while maintaining the stability of the negative electrode, further improving the cycle performance and lifespan of the lithium-ion battery.
[0042] In some illustrative embodiments, the mass percentage of the additive to the total mass of the negative electrode sheet is 1-20%, for example, it can be 1%, 5%, 10%, 15% or 20%. During the experiments related to this invention, it was found that by adjusting the mass percentage of the additive, different positive electrode materials can be matched, thereby improving the crosstalk of the appropriate transition metal ions in different positive electrode materials.
[0043] In some illustrative embodiments, the conductive agent includes conductive carbon. Preferably, the conductive agent includes at least one of carbon black, carbon nanotubes, graphene, carbon fibers, and porous carbon, wherein the carbon black can be, for example, Ketjen black. Thus, the addition of the aforementioned conductive agent helps to construct an electron conduction network, reduce the internal resistance of the negative electrode, improve charge and discharge efficiency, and thereby improve battery performance.
[0044] Preferably, the mass ratio of active material, conductive agent, and binder is 8:1:1. This setting helps to control the mass of each material to a better level, resulting in better battery performance.
[0045] More preferably, the mass ratio of the active material, conductive agent, binder, and phosphorus-carbon composite material is 8:1:1:0.5.
[0046] In some illustrative embodiments, the active material includes at least one of carbon-based materials and silicon-based materials. Carbon-based materials exhibit better stability and provide a lower potential plateau or higher specific capacity in lithium-ion batteries. Specifically, carbon-based materials include at least one of graphite, hard carbon, and soft carbon. Graphite provides a lower and more even potential plateau during lithium delithiation and lithium insertion, which improves battery safety. Hard carbon offers higher specific capacity and performs well at low temperatures. Soft carbon has some tunability and higher electronic conductivity, which is beneficial for fast charging and discharging. Silicon-based materials have less volume expansion or are easier to process. Specifically, silicon-based materials include at least one of nano-silicon, micron-silicon, silicon-carbon composites, and silicon suboxide. Nano-silicon has a high theoretical specific capacity (approximately 4200 mAh / g), and its nanoscale size helps alleviate the volume expansion problem of silicon during charging and discharging, reducing the risk of electrode breakage. Micron-silicon has better processing performance, provides electrode forming characteristics, and has a lower cost compared to nano-silicon. Silicon suboxide has a smaller volume expansion rate, which is beneficial for improving the cycle performance of the electrode. Silicon-carbon composite materials can fully utilize the high specific capacity of silicon while taking into account the excellent electrical conductivity and volume stability of carbon.
[0047] In some illustrative embodiments, the carbon material includes at least one of graphite, hard carbon, soft carbon, and carbon black. Graphite helps provide a stable structure, mitigating the volume expansion of phosphorus during charge and discharge, and thus improving electron conduction efficiency. Hard carbon has a disordered structure, providing more active sites for phosphorus dispersion and fixation. Carbon black, such as acetylene black or Ketjen black, has a high specific surface area and conductivity, enabling the formation of an efficient electron transport network and enhancing the conductivity of the negative electrode active material layer. Phosphorus includes at least one of red phosphorus, black phosphorus, white phosphorus, blue phosphorus, and purple phosphorus. Red phosphorus and black phosphorus are preferred. Red phosphorus has high safety and stability, and a high theoretical specific capacity. Black phosphorus has a layered structure, which is beneficial for lithium ion insertion and extraction, exhibiting excellent electrochemical performance.
[0048] According to another aspect of the present invention, a method for preparing the above-mentioned negative electrode sheet is provided, comprising: adding active material, additive, binder and conductive agent to a solvent respectively, stirring and coating them onto a negative electrode current collector, and drying them to obtain a negative electrode sheet.
[0049] According to embodiments of the present invention, the preparation process is relatively simple. By adding additives to the negative electrode components, a negative electrode with reduced transition metal ion crosstalk can be obtained. The method of the present invention can improve the resistance of the negative electrode to transition metal ion crosstalk without reducing the energy density, and has good application prospects.
[0050] It should be noted that the types and quality of the negative electrode current collector, active material, additives, binder, conductive agent and other materials of the present invention are the same as those described above, and will not be repeated here.
[0051] It is understood that this invention rationally designs the negative electrode components, introduces additional additives, and produces a negative electrode capable of resisting transition metal ion crosstalk through a simple manufacturing method. Compared with related technologies such as membrane coating, electrolyte modification, and positive electrode modification, this invention simplifies the production process, offers better economic benefits, does not reduce energy density, and enhances the negative electrode's resistance to transition metal ion crosstalk.
[0052] In some illustrative embodiments, the drying temperature is 55~65℃, for example, 55℃, 60℃, or 65℃, preferably 60℃, and the processing time is 9~11 hours, for example, 9h, 10h, or 11h, preferably 10h; the solvent includes at least one of water or N-methylpyrrolidone. It is understood that the preparation process of the negative electrode sheet of the present invention is adaptable to both aqueous solvents and organic solvents, and has good application prospects.
[0053] According to another aspect of the present invention, a lithium-ion secondary battery is provided, comprising the negative electrode sheet as described above.
[0054] According to embodiments of the present invention, the active material can improve the energy density of the negative electrode material, thereby increasing the specific capacity of the negative electrode and the energy density of the battery. The introduction of additives helps to form interactions with transition metal ions; in particular, phosphorus-carbon composite materials can reduce crosstalk of transition metal ions through continuous adsorption and phagocytosis, thereby improving the cycle stability and lifespan of the battery. The introduction of conductive agents helps to reduce the internal resistance of the negative electrode and improve the rate performance of the battery. Through the synergistic use of the above materials, various performance characteristics of lithium-ion secondary batteries can be improved.
[0055] The present invention will be further illustrated below through embodiments and related test experiments and results. In the following detailed description, numerous specific details are set forth for ease of explanation to provide a comprehensive understanding of the embodiments of the present invention. However, it will be apparent that one or more embodiments may be practiced without these specific details. Moreover, the details in the following embodiments can be arbitrarily combined to form other feasible embodiments without conflict.
[0056] It should be noted that the specific embodiments described below are merely illustrative examples, and the scope of protection of the present invention is not limited thereto. The chemicals and raw materials used in the following embodiments are all commercially available or prepared using recognized processing methods.
[0057] Example 1:
[0058] Preparation of phosphorus-carbon particles:
[0059] Phosphorus-carbon particles were prepared by ball milling red phosphorus, graphite, and carbon nanotubes at a mass ratio of 7:2:1 in a star-shaped ball mill at 600 rpm for 10 hours.
[0060] Artificial graphite powder AML350 powder, Ketjen Black conductive agent, polyvinylidene fluoride (PVDF) binder, and phosphorus carbon particles were mixed in N-methylpyrrolidone at a mass ratio of 8:1:1:0.5 and stirred evenly. The mixture was then coated onto copper foil with a scraper and dried in a vacuum oven at 60°C for 10 hours to obtain a complete negative electrode sheet.
[0061] After cutting the entire negative electrode sheet into wafers, it was assembled into a full cell with a ternary composite positive electrode (NCM523) made of lithium nickel cobalt manganese oxide purchased from a certain company (the capacity ratio of the negative electrode to the positive electrode was 1~1.1). The electrolyte for the full cell used 1M lithium hexafluorophosphate (LiPF6) and ethylene carbonate and diethyl carbonate in a 1:1 volume ratio, with 10% by volume of fluoroethylene carbonate added to the total electrolyte. Then, 20 mM / L of Mn(TFSI)2 salt, a compound formed by manganese and bis(trifluoromethanesulfonyl)imide (TFSI), was added to simulate the transition metal manganese ions overflowing from the positive electrode material. The mixture was stirred for 6 hours before use. A commercial PP separator purchased from a certain company was used as the separator. The assembled full cell underwent long-cycle testing.
[0062] Comparative Example 1:
[0063] The assembly process of Comparative Example 1 is largely the same as that of Example 1, except that no phosphorus carbon particles were added to Comparative Example 1.
[0064] The full cells assembled in Example 1 and Comparative Example 1 were tested. Figure 2 The negative electrode of Embodiment 1 and Comparative Example 1 of the present invention is shown in the presence of 20 mM Mn. 2+ The diagram shows the cyclic specific capacity and coulombic efficiency in the electrolyte. In Example 1, the battery is labeled Gr / PIINCM523, corresponding to the color purple, and the coulombic efficiency is represented by a hollow circle with a purple outline. In Comparative Example 1, the battery is labeled GrIINCM523, corresponding to the color red, and the coulombic efficiency is represented by a hollow circle with a red outline. Figure 2 As shown, the coulombic efficiency of the two is basically the same, but in terms of specific capacity, Example 1 still maintains the same specific capacity even after 50 cycles, showing better cycle performance; while in Comparative Example 1, the specific capacity continues to decrease during the cycle, indicating that the cycle stability and lifespan of the battery assembled thereis relatively poor.
[0065] To verify the mechanism of action of the additive, the negative electrodes of the full cells of Example 1 and Comparative Example 1 after cycling were removed and subjected to high-resolution tests. Figure 3 A high-resolution transmission microscope image of phosphorus and carbon particles in the negative electrode of Embodiment 1 of the present invention after battery cycling is shown. Figure 3 As shown, after cycling, manganese ions are uniformly distributed within the bulk phase of the phosphorus-carbon particles. This indicates that some manganese ions are absorbed by phosphorus and enter the bulk phase of the phosphorus particles (phosphorus particles in the phosphorus-carbon particles), and the remaining ions are adsorbed by the phosphorus particles. This reduces the crosstalk phenomenon of manganese ions in the positive electrode, mitigates the negative impact on the graphite negative electrode, and improves the cycle stability and lifespan of the lithium-ion battery. Figure 4 A high-resolution transmission electron microscope (TEM) image of the graphite particles in the negative electrode of Comparative Example 1 of the present invention after battery cycling is shown. Figure 4 As shown, manganese ions deposit on the surface of graphite particles without penetrating the bulk phase. This surface deposition catalyzes electrolyte decomposition, leading to a series of side reactions and deterioration of battery performance.
[0066] Further calculations were performed, specifically, the energy changes in the red phosphorus system under electron injection conditions, including the adsorption and phagocytosis of manganese ions. Figure 1 As shown, the energy of the system is decreasing continuously, indicating that the transition metal ions tend to be stably adsorbed and fixed on the surface of phosphorus particles, and the process of being further absorbed into the bulk phase of phosphorus particles is thermodynamically stable.
[0067] Example 2:
[0068] The additive used in Example 2 is the phosphorus carbon particles prepared in Example 1.
[0069] Commercial silicon-carbon powder (Si content of 48%), Ketjen Black conductive agent, lithium polyacrylate (PAA-Li) binder and phosphorus-carbon particles were mixed in water at a mass ratio of 8:1:1:0.5 and stirred evenly. The mixture was then coated onto copper foil with a scraper and dried in a vacuum oven at 60°C for 10 hours to obtain a complete negative electrode sheet.
[0070] After cutting the entire negative electrode sheet into wafers, it was assembled into a full cell with a ternary composite positive electrode (NCM523) made of lithium nickel cobalt manganese oxide purchased from a certain company (the capacity ratio of the negative electrode to the positive electrode was 1~1.1). The electrolyte for the full cell used 1M lithium hexafluorophosphate (LiPF6) and ethylene carbonate and diethyl carbonate in a 1:1 volume ratio, with 10% by volume of fluoroethylene carbonate added to the total electrolyte. Then, 20 mM / L of Mn(TFSI)2 salt, a compound formed by manganese and bis(trifluoromethanesulfonyl)imide (TFSI), was added to simulate the transition metal manganese ions overflowing from the positive electrode material. The mixture was stirred for 6 hours before use. A commercial PP separator purchased from a certain company was used as the separator. The assembled full cell underwent long-cycle testing.
[0071] Comparative Example 2:
[0072] The assembly process of Comparative Example 2 is largely the same as that of Example 2, except that no phosphorus carbon particles were added to Comparative Example 2.
[0073] The full cells assembled in Example 2 and Comparative Example 2 were tested. Figure 5 The negative electrode of Embodiment 2 and Comparative Example 2 of the present invention is shown in the presence of 20 mM Mn 2+ The diagram shows the cycling specific capacity and coulombic efficiency in the electrolyte. In Example 2, the battery is labeled Si / PIINCM523, corresponding to the blue color, and the coulombic efficiency is represented by a hollow circle with a blue outline. In Comparative Example 2, the battery is labeled SiIINCM523, corresponding to the red color, and the coulombic efficiency is represented by a hollow circle with a red outline. Figure 5 As shown, the coulombic efficiency of the two is basically the same, but in terms of specific capacity, Example 2 still maintains the same specific capacity even after 50 cycles, showing better cycle performance; while in Comparative Example 2, the specific capacity continues to decrease during the cycle, indicating that the cycle stability and lifespan of the battery assembled there is relatively poor.
[0074] The cyclic performance test results of Examples 1-2 and Comparative Examples 1-2 are shown in Table 1 below.
[0075] Table 1. Cyclic performance test results of Examples 1-2 and Comparative Examples 1-2
[0076]
[0077] As shown in Table 1, the full-cell systems of Examples 1 and 2 with additive-containing negative electrodes exhibit good tolerance to transition metal ions in the electrolyte. Their initial coulombic efficiency and specific capacity remain normal, and their reversible capacity remains high after 50 cycles, showing little impact. In contrast, the electrochemical performance of the full-cell systems of Comparative Examples 1 and 2 without additives is significantly affected by the presence of transition metal ions (Mn).2+ The crosstalk has a significant impact, and the specific capacity has a large attenuation.
[0078] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A lithium-ion secondary battery, comprising a positive electrode and a negative electrode, wherein, The positive electrode includes transition metal ions, and the negative electrode includes: a negative current collector and an active material layer located on the negative current collector; The active material layer includes: active material, conductive agent, binder and additive; The additive is a phosphorus-carbon composite material; The additive accounts for 1 to 10% of the total mass of the negative electrode, and the active material is selected from carbon-based or silicon-based materials.
2. The lithium-ion secondary battery according to claim 1, wherein, The phosphorus-carbon composite material includes phosphorus and carbon materials, with phosphorus connected to the carbon materials by chemical bonds.
3. The lithium-ion secondary battery according to claim 1 or 2, wherein, The phosphorus content in the phosphorus-carbon composite material is 30-70% by mass.
4. The lithium-ion secondary battery according to claim 1 or 2, wherein, The conductive agent includes conductive carbon.
5. The lithium-ion secondary battery according to claim 4, wherein, The conductive agent includes at least one of the following: carbon black, carbon nanotubes, graphene, carbon fiber, and porous carbon.
6. The lithium-ion secondary battery according to claim 1, wherein, The mass ratio of the active material, the conductive agent, and the binder is 8:1:
1.
7. The lithium-ion secondary battery according to claim 1 or 2, wherein, The carbon-based material includes at least one of graphite, hard carbon, and soft carbon; The silicon-based material includes at least one of nano-silicon, micro-silicon, silicon-carbon composite material, and silicon suboxide.
8. The lithium-ion secondary battery according to claim 2, wherein, The carbon material includes at least one of graphite, hard carbon, soft carbon, and carbon black; The phosphorus includes at least one of red phosphorus, black phosphorus, white phosphorus, blue phosphorus, and purple phosphorus.
9. The lithium-ion secondary battery according to claim 1, wherein, The negative electrode sheet is prepared by the following method: The active material, additives, binder, and conductive agent are added to a solvent, stirred, and coated onto the negative electrode current collector. After drying, the negative electrode sheet is obtained.
10. The lithium-ion secondary battery according to claim 9, wherein, The drying process is carried out at a temperature of 55-65°C for 9-11 hours. The solvent includes at least one of water or N-methylpyrrolidone.