Method for prolonging cycle life of conversion reaction positive electrode battery based on large-current pulse activation

Abstract

The invention provides a method for prolonging the cycle life of a conversion reaction positive electrode battery based on large-current pulse activation. According to the invention, a conventional low-current constant-current activation mode is replaced by a specific charge-discharge system activation method for the conversion reaction positive electrode battery; a conversion reaction positive electrode is repeatedly stimulated, a product is regulated and controlled to be uniformly nucleated, a stable reaction interface is formed, a homogeneous reaction of the product is smoothly realized, a diffusion barrier of a two-phase product reaction is reduced, and a discharge product is promoted to be fully converted into an active substance material; and the volume expansion of the pole piece is effectively inhibited, so that the problems of capacity attenuation and unstable cycle performance of a conversion reaction positive electrode battery caused by inactivation, falling and passivation of active substances are improved. Besides, compared with a traditional low-current activation system, the charging and discharging system provided by the invention shortens the time and can promote the battery to quickly reach the optimal performance state, so that the commercialization value is further improved for the application of the battery.

Description

Technical Field

[0001] The invention belongs to the technical field of metal lithium secondary battery materials, and in particular relates to a method for improving the cycle life of a conversion reaction positive electrode battery based on large current pulse activation. Background Art

[0002] The rapid development of the power energy and energy storage market has put forward higher requirements for the performance indicators of lithium-ion batteries, especially energy density and cycle stability. This trend not only drives the continuous innovation of battery technology, but also prompts researchers to continuously explore and develop new electrode materials to break through the bottleneck of existing technologies. Among them, the energy density of conventional lithium-ion embedding-de-embedding cathodes has gradually approached its theoretical limit, and the research of high-energy-density cathode materials has become a key link, because such materials can significantly improve the overall performance of batteries and meet the growing market demand.

[0003] Among the many candidate materials, conversion reaction cathode materials have attracted much attention due to their unique energy storage mechanism. This type of material achieves an energy density that exceeds that of conventional single electron transfer cathodes through a redox reaction with multiple electron transfer. For example, Fe-based sulfides (such as FeS2, with a theoretical specific capacity and energy density of 894 mAh g -1 、1671Wh kg -1 ) and fluoride (such as FeF3, with a theoretical specific capacity and energy density of 712 mAh g -1 、1947Wh kg -1 ) not only has extremely high theoretical specific capacity and energy density, but also has the advantages of low cost and abundant resources. Therefore, it is regarded as a strong candidate for the next generation of lithium-ion battery positive electrode materials.

[0004] However, although conversion reaction cathode materials show great potential in theoretical performance, they face many challenges in practical applications. First of all, these materials often produce unevenly distributed reaction products during conventional low-current activation, which leads to passivation and inactivation of active substances, and then causes huge capacity attenuation in the early stage. In addition, poor cycle stability is also a major obstacle to its commercialization process. These problems not only reduce the overall performance of the battery, but also increase maintenance costs and risks of use, so there is an urgent need to find effective solutions.

[0005] In response to the above problems, researchers have begun to turn their attention to the innovation of battery activation technology. Traditional lithium-ion battery activation technology mainly optimizes battery performance by changing the charge and discharge system, but this method has limited effect on conversion reaction positive electrode materials. Because the conversion reaction positive electrode will generate two-phase substances after discharge, and traditional activation technology is difficult to effectively promote the subsequent reaction between the two phases of substances, and it is also difficult to overcome the challenge of volume expansion during the charge and discharge process, thus failing to significantly improve the problem of capacity attenuation in the early stage of the battery.

[0006] Therefore, although conversion reaction materials as positive electrode materials for lithium metal batteries are highly adapted to the current market demand due to their high theoretical specific capacity and high energy density, there is still an urgent need to solve the problem of shortened cycle life caused by their huge capacity attenuation in the early stage. Summary of the invention

[0007] In view of the problems in the prior art, the present invention discloses a method for improving the cycle life of a conversion reaction positive electrode battery based on large current pulse activation, wherein the uniform growth of reaction product nucleation is regulated through a specific charge and discharge system, the volume expansion of the pole piece is suppressed, the reaction interface resistance is reduced, a stable reaction interface is formed, and the product phase change reaction process is accelerated; thereby, the discharge product is promoted to be fully converted into an active substance, the deactivation, passivation and shedding of the product are avoided to the greatest extent, the initial capacity attenuation of the battery is reduced, and the cycle stability and energy density of the conversion reaction positive electrode battery can be effectively improved.

[0008] The present invention is achieved through the following technical solutions:

[0009] In a first aspect, the present invention provides a method for improving the cycle life of a positive electrode battery for a conversion reaction based on high current pulse activation, the method comprising the following steps performed sequentially:

[0010] S1: After the conversion reaction cathode battery is assembled, let it stand;

[0011] S2: Perform high current pulse discharge on the conversion reaction positive electrode battery to a specified voltage V1;

[0012] S3: Discharge with a small constant current to a specified voltage V2;

[0013] S4: Perform high current pulse discharge to the specified voltage V3;

[0014] S5: Perform high current pulse charging to a specified voltage V4;

[0015] S6: Perform low current constant current charging to the specified voltage V5;

[0016] S7: Repeat the charge and discharge method of S2-S6 and cycle N1 times to complete the activation of the positive electrode battery for the conversion reaction;

[0017] Among them, V1 ranges from 2.2-3V; V2 ranges from 1.5-2V; V3 ranges from 0.5-1V; V4 ranges from 1.5-2V; V5 ranges from 3-4V; V1>V2>V3, V5>V4>V3; N1≥1 times.

[0018] As a further solution, among V1, V2, V3, V4, and V5, the voltage difference range between V1 and V2 is preferably from 0.2-0.5V; the voltage difference range between V2 and V3 is preferably from 0.5-1V; the voltage difference range between V4 and V3 is preferably from 0.5-1V; and the voltage difference range between V5 and V4 is preferably from 1-1.5V.

[0019] As a further solution, in the S2 and S4 high current pulse discharges, the discharge current C1 ranges from 1-4C, the discharge time T1 ranges from 3s-10s, and the holding time T2 ranges from 5s-50s.

[0020] As a further solution, in the S3 small current constant current discharge, the discharge current C2 is selected from the range of 0.05-0.5C.

[0021] As a further solution, in the S5 high current pulse charging, the charging current C3 is selected from the range of 1-2C, the charging time T3 is 3-7s, and the standby time T4 is 5-10s.

[0022] As a further solution, in the S6 low-current constant-current charging, the charging current C4 range is selected from 0.2-0.33C.

[0023] As a further solution, the standing time in S1 is not less than 8 hours;

[0024] Furthermore, the standing time in S1 is preferably 8-12 hours.

[0025] As a further solution, the number of cycles in S7 is preferably 3-5 times.

[0026] As a further solution, the conversion reaction positive electrode battery in S1 includes a conversion reaction positive electrode material and a lithium-containing negative electrode material.

[0027] As a further embodiment, the conversion reaction cathode material includes metal sulfide (MS x ), metal oxides (MO z ), metal fluoride (MF y ); wherein the metal M is selected from one or more metal elements of Fe, Co, Ni, Cu, Zn, Mo, V, Mn, Ti, Sn, Sb, Te, and W; the values ​​of x, y, and z change accordingly according to the stoichiometric ratio based on the metal element composition.

[0028] Furthermore, the conversion reaction cathode material is preferably selected from iron sulfide (FeS x ), iron oxide (FeO z ), iron fluoride (FeF y ) or more thereof; wherein the values ​​of x, y, and z vary accordingly according to the stoichiometric ratio of the metal element composition.

[0029] As a further solution, the lithium-containing negative electrode material includes metallic lithium negative electrode material; one or more lithium alloy negative electrode materials selected from lithium magnesium alloy negative electrode material, lithium boron alloy negative electrode material, lithium zinc alloy negative electrode material, and lithium aluminum alloy negative electrode material; one or more lithium composite negative electrode materials selected from lithium carbon-based composite negative electrode material and lithium silicon-based composite negative electrode material; as some specific examples: lithium carbon-based composite negative electrode material includes lithiated graphite negative electrode material; lithium silicon-based composite negative electrode material includes lithiated silicon carbon negative electrode material.

[0030] As a further solution, the conversion reaction positive electrode battery in S1 further includes a conversion reaction positive electrode plate, a lithium-containing negative electrode plate, an electrolyte, and a separator.

[0031] As a further solution, the conversion reaction positive electrode plate is made of conversion reaction positive electrode material, a conductive agent, and a binder.

[0032] As a further solution, the lithium-containing negative electrode plate is made of a lithium-containing negative electrode material, a conductive agent, and a binder.

[0033] As a further embodiment, the electrolyte is selected from a solution formed by dissolving one or more lithium salts in an organic solvent; the lithium salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI); the organic solvent includes a mixture of one or more of ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), dimethoxymethane (DMM), and ethylene glycol dimethyl ether (DME).

[0034] As a further embodiment, the diaphragm is selected from one or more of a polypropylene (PP) diaphragm, a polyethylene (PE) diaphragm, and a polysulfone (PS) diaphragm.

[0035] The characteristics and beneficial effects of the present invention are:

[0036] (1) The present invention first activates the conversion reaction positive electrode battery through two large current pulse discharges, which not only provides high-intensity current stimulation, promotes the phase change reaction process, regulates the nucleation and growth of the reaction products, inhibits the volume expansion of the electrode, maintains good bonding performance between particles, forms a complete lithium ion transmission channel, and improves the battery capacity and energy density; it can also avoid side reactions or structural damage that may be caused by constant current discharge.

[0037] (2) The present invention also adds a small constant current discharge between two large current pulse discharges to prevent possible concentration polarization, so that the ions are evenly distributed, the discharge system is maintained stable, and a stable environment is provided for the second large current pulse discharge, while preventing overheating and protecting the battery safety.

[0038] (3) After the present invention is fully discharged to form discharge products with uniform nucleation, growth and distribution, the discharge products are rapidly converted into active substances through high current pulse charging, thereby avoiding the inactivation, shedding and passivation of the active substances, thereby improving the cycle stability and energy density of the battery.

[0039] (4) The present invention also uses a small current constant current charging to a specified voltage after the high current pulse charging is completed, which not only maintains the stability of the internal environment of the battery, but also smoothly realizes the homogeneous reaction of the product, reduces the diffusion barrier of the two-phase product reaction, and ensures the full conversion of the active substance.

[0040] (5) The charge and discharge system provided by the present invention is not only applicable to a variety of conversion reaction positive electrode materials, but also shortens the time compared to the traditional small current activation system, and can promote the battery to quickly reach the optimal performance state, which further enhances the commercial value of the battery application. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0042] Figure 1 This is a comparison diagram of the SEM surface morphology of the cyclic discharge state in the present invention. Figure 1 A is the SEM surface morphology of Example 1 in the discharge state during the 15th charge-discharge cycle after activation; Figure 1 B is the SEM surface morphology of comparative example 1 in the discharged state during the 15th charge and discharge cycle after activation.

[0043] Figure 2 This is a comparison diagram of the cross-sectional morphology of the optical microscope in the present invention. Figure 2 A is an optical microscope cross-sectional morphology image of Example 1 before cycling (i.e., after the battery is assembled and left to stand); Figure 2 B is an optical microscope cross-sectional morphology image of Example 1 after 20 cycles after activation; Figure 2 C is an optical microscope cross-sectional morphology image of comparative example 1 after 20 cycles after activation. DETAILED DESCRIPTION

[0044] In order to facilitate the understanding of the present invention, the present invention will be described in more detail below, and embodiments of the present invention are given, but the scope of the present invention is not limited thereby.

[0045] In a first aspect, the present invention provides a method for improving the cycle life of a positive electrode battery for a conversion reaction based on high current pulse activation, the method comprising the following steps performed sequentially:

[0046] S1: After the conversion reaction cathode battery is assembled, let it stand;

[0047] S2: Perform high current pulse discharge on the conversion reaction positive electrode battery to a specified voltage V1;

[0048] S3: Discharge with a small constant current to a specified voltage V2;

[0049] S4: Perform high current pulse discharge to the specified voltage V3;

[0050] S5: Perform high current pulse charging to a specified voltage V4;

[0051] S6: Perform low current constant current charging to the specified voltage V5;

[0052] S7: Repeat the charge and discharge method of S2-S6 and cycle N1 times to complete the activation of the positive electrode battery for the conversion reaction;

[0053] Among them, V1 ranges from 2.2-3V; V2 ranges from 1.5-2V; V3 ranges from 0.5-1V; V4 ranges from 1.5-2V; V5 ranges from 3-4V; V1>V2>V3, V5>V4>V3; N1≥1 times.

[0054] The present invention provides a new activation method, which mainly regulates the uniform nucleation of reaction products through a specific charge and discharge system, smoothly realizes the homogeneous reaction of products, and reduces the diffusion barrier of two-phase product reactions; it helps the reactants to react more fully on the reaction interface, reduces the reaction resistance on the interface, and thus helps to form a stable reaction interface. The conversion reaction positive electrode battery is avoided to the greatest extent due to the poor kinetic performance of the phase change process, which causes the generation of uneven nucleation of reaction products under the action of current, thereby reducing the deactivation, passivation and uneven passivation layer of the active material, and reducing the initial capacity decay of the battery; effectively improves the cycle stability and energy density of the conversion reaction positive electrode battery. And the charge and discharge system provided by the present invention shortens the time compared with the traditional small current activation system, and can promote the battery to quickly reach the optimal performance state, which further enhances the commercial value of the battery application. In addition, the present invention continues to use the expressions that are usually accustomed to by those skilled in the art. In this article, a large current refers to a current greater than or equal to 1C, and a small current refers to a current less than 1C.

[0055] The present invention first performs two high-current pulse discharges on the assembled conversion reaction positive electrode battery. When the first high-current pulse discharge in step S2 is to 2.2-3V, the voltage range ensures that the conversion reaction inside the battery can be fully carried out, while avoiding battery damage caused by over-discharge; it can effectively activate the active material inside the battery, thereby laying a good foundation for subsequent charge and discharge cycles. When the second high-current pulse discharge in step S4 is to 0.5-1V, the voltage range further promotes the phase change reaction inside the battery, inhibits the volume expansion of the pole piece, and maintains good bonding performance between particles. Through such treatment, the battery can show more stable performance in the subsequent charge and discharge process, reducing the battery performance degradation caused by too low voltage. Through pulsed high-current discharge, high-intensity current stimulation can be accurately provided, generating a strong electrochemical driving force, and a larger nucleation overpotential regulates the uniform nucleation growth of the reaction product, thereby providing a complete and continuous lithium ion transmission channel, which is conducive to the smooth insertion and extraction of lithium ions, and improves the capacity and energy density of the battery; avoids the over-activation of the reaction product that may be caused by the use of high-current constant current discharge, thereby causing unnecessary side reactions or structural damage.

[0056] At the same time, in order to avoid the concentration polarization phenomenon that may be caused by high current pulse discharge, the present invention also adds a small current constant current discharge between two high current pulse discharges. When the first high current pulse discharges to 2.2-3V, the step of discharging to the specified voltage range of 1.5-2V by a small current constant current in step S3 helps to buffer the concentration polarization inside the battery after the first high current pulse discharge, making the ion concentration distribution inside the battery more uniform, and creating good conditions for the second high current pulse discharge to 0.5-1V; and it can effectively avoid the overheating phenomenon that may occur in the battery during the high current discharge process, thereby protecting the safety of the battery. The concentration polarization inside the battery is effectively alleviated by the small current constant current discharge, the discharge system is maintained stable, and the uniform distribution of lithium ions in the electrode material is promoted, laying a good foundation for the subsequent charge and discharge cycle. In addition, the present invention is conducive to the full activation of lithium ions inside the battery by first fully discharging the conversion reaction positive electrode battery, so that in the subsequent charge and discharge process, lithium ions can be more evenly embedded and removed, reducing the situation where the local lithium ion concentration is too high or too low, and further improving the cycle stability and energy density of the battery.

[0057] Secondly, the present invention fully discharges through the discharge system of high current pulse discharge, low current constant current discharge, and high current pulse discharge, and after forming a discharge product with uniform nucleation growth and distribution, step S5 is charged to a specified voltage range (1.5-2V) by a high current pulse. When maintained in this voltage range, it can not only prevent the battery from being damaged by overcharging, but also provide enough energy to quickly convert the discharge product with uniform nucleation after the above-mentioned full discharge into the initial active material state, promote lithium ions to be quickly and evenly embedded in the electrode material, and form a stable lithium ion layer, which helps to reduce the local overcharge phenomenon during the charging process, restore the capacity and performance of the battery, thereby improving the cycle life and safety of the battery. And after fully discharging, the form of high current pulse charging can reduce the heat loss of the battery, improve the charging acceptance of the battery, and thus shorten the charging time to a certain extent. The intermittent power outage and charging method can also avoid the battery plate from crystallizing during the charging process, thereby extending the service life of the battery and preventing the heat accumulation caused by continuous internal charging from causing unsafe risks.

[0058] After being charged to a specified voltage by a high current pulse, in order to avoid the damage to the internal structure of the battery caused by continuous high current pulse charging, the present invention further adopts a small current constant current charging to a specified voltage range (3-4V) in step S6. The charging method at this stage is to further stabilize the electrochemical reaction of the battery by a small current charging method when the battery is close to a fully charged state, and avoid the electrode material damage and rapid decay of battery performance caused by high current charging; it is helpful to achieve the homogeneous reaction of the product, reduce the diffusion barrier of the two-phase product reaction, accelerate the transmission of ions and electrons, and ensure that lithium ions are evenly distributed in the electrode material, reduce the stress concentration inside the battery, and avoid the active material from falling off, inactivation and passivation to the greatest extent, and ensure the thorough conversion of the active material. In this way, a more stable passivation layer can be formed inside the battery, reducing the capacity decay during the cycle, thereby extending the service life of the battery. In addition, the small current constant current charging helps to maintain the temperature stability of the battery, avoiding the impact of the battery performance and safety due to excessive temperature.

[0059] Finally, by repeating the charge and discharge method of S2-S6 and cycling at least once, the electrochemical performance of the battery can be further consolidated to ensure that the battery can maintain good performance after multiple charge and discharge cycles. This cycle process helps to form a stable interaction between the lithium ions and the electrode materials inside the battery, reduce capacity decay, and improve the overall performance of the battery. After the charge and discharge activation method provided by the present invention, it can promote the optimal performance state of the battery, and then perform constant current charge and discharge for subsequent cycles to maintain the long-term stability and reliability of the battery.

[0060] As a further solution, among V1, V2, V3, V4, and V5, the voltage difference range between V1 and V2 is preferably from 0.2-0.5V; the voltage difference range between V2 and V3 is preferably from 0.5-1V; the voltage difference range between V4 and V3 is preferably from 0.5-1V; and the voltage difference range between V5 and V4 is preferably from 1-1.5V.

[0061] As a further solution, in the S2 and S4 high current pulse discharges, the discharge current C1 is in the range of 1-4C, the discharge time T1 is in the range of 3-10s, and the holding time T2 is in the range of 5-50s.

[0062] By selecting the appropriate discharge current and discharge time, it is beneficial to obtain sufficient energy to promote the uniform growth of discharge product nucleation, thereby promoting the insertion and extraction of lithium ions to form a uniform distribution; reduce stress concentration, maintain the stability of the interface reaction, and avoid obstructing the transmission path of lithium ions; and avoid excessive discharge current or long discharge time causing damage to the electrode material and rapid attenuation of battery performance. In addition, by regulating the discharge time and shelf time, it is beneficial to maintain the temperature and chemical stability inside the battery and prevent the battery from being damaged due to overheating. It also effectively balances the uniform growth rate of nucleation and fully restores the microstructure of the material.

[0063] As a further solution, in the S3 small current constant current discharge, the discharge current C2 range is selected from 0.05-0.5 C. By selecting an appropriate small current range for constant current discharge, it is beneficial to maintain a uniform distribution of ion concentrations inside the battery, avoid concentration polarization caused by large current pulse discharge, and reduce the heat generated by the battery during the discharge process caused by excessive current, protect the safety of the battery, and provide a stable discharge environment for the next large current pulse discharge.

[0064] As a further solution, in the S5 high-current pulse charging, the charging current C3 range is selected from 1-2C, the charging time T3 is 3-7s, and the standby time T4 is 5-10s. When the battery is fully discharged and high-current pulse charging is performed, regulating the charging current range and charging time is conducive to providing sufficient energy to prompt the discharge reaction products to be quickly converted into the initial active material state, avoiding the incomplete conversion of the discharge products due to too small current or too short time, resulting in uneven deposition inside the battery, thereby affecting the capacity and cycle life of the battery. And by regulating the high-current pulse charging time and the standby time, it is conducive to effectively balancing the uniform distribution of active materials inside the battery, eliminating the potential difference and concentration difference that may exist inside the battery to the greatest extent, preventing crystallization on the surface of the battery plate, and further improving the cycle stability and energy density of the battery. In addition, suitable charging current, charging time and standby time are conducive to preventing battery overcharging, reducing heat accumulation inside the battery, and maintaining the cycle stability of the battery pole piece.

[0065] As a further solution, in the S6 low-current constant-current charging, the charging current C4 range is selected from 0.2-0.33C. After the battery is charged with a high-current pulse, the specified voltage is reached by selecting a suitable range of low-current constant-current charging range, which is conducive to further stabilizing the electrochemical reaction of the battery, avoiding damage to the electrode material and rapid attenuation of battery performance caused by high-current charging, and maintaining the temperature of the battery stable by a small current to avoid affecting the battery performance and safety due to excessive temperature.

[0066] As a further solution, the standing time in S1 is not less than 8 hours; standing the installed conversion reaction lithium secondary for not less than 8 hours is conducive to reducing the initial stress inside the battery, so that the electrode material has enough time to adjust its structure, thereby improving the initial capacity and cycle performance of the conversion reaction positive electrode battery. In addition, long-term standing can simulate the long-term storage state of the battery before actual use, ensuring that the battery can still maintain good performance after long-term storage. Through such a standing treatment, the electrochemical performance of the battery is optimized, providing a guarantee for the long-term stability and reliability of the battery.

[0067] Furthermore, the standing time in S1 is preferably 8-12 hours.

[0068] As a further solution, the number of cycles in S7 is preferably 3-5 times. Repeating the charge-discharge system of the present invention for 3-5 times can achieve a good consolidation effect on the electrochemical performance of the battery, promote the battery to achieve the optimal performance state, and ensure that the battery can still maintain good performance after multiple charge-discharge cycles.

[0069] As a further solution, the conversion reaction positive electrode battery in S1 includes a conversion reaction positive electrode material and a lithium-containing negative electrode material.

[0070] As a further embodiment, the conversion reaction cathode material includes metal sulfide (MS x ), metal oxides (MO z ), metal fluoride (MF y ) or more; wherein the metal M is selected from one or more metal elements of Fe, Co, Ni, Cu, Zn, Mo, V, Mn, Ti, Sn, Sb, Te, and W; the values ​​of x, y, and z are changed accordingly according to the stoichiometric ratio according to the metal element composition. Compounds within this range are beneficial for providing higher energy density and more stable cycle performance as positive electrode materials for conversion reactions. Good structural stability helps to reduce the damage to electrode materials caused by volume changes during the cycle, thereby extending the service life of the battery. Metal sulfides, metal oxides, and metal fluorides can achieve good electrochemical reactions during the battery charging and discharging process, thereby improving the battery charging and discharging efficiency.

[0071] Furthermore, the conversion reaction cathode material is preferably selected from iron sulfide (FeS x ), iron oxide (FeO z ), iron fluoride (FeF y ) or more; wherein the values ​​of x, y, and z are changed accordingly according to the stoichiometric ratio according to the metal element composition. The iron compound within the optimized range not only has a high energy density and good structural stability; it also has a high activity during the conversion reaction, can effectively promote the conversion of active substances, thereby promoting uniform nucleation growth, and further promotes the insertion and extraction of lithium ions under the specially selected charge and discharge system of the present invention to form a uniform distribution; it helps to reduce the capacity decay of the battery during the cycle, thereby improving the capacity retention rate and cycle stability of the battery.

[0072] As a further solution, the lithium-containing negative electrode material includes metallic lithium negative electrode material; one or more lithium alloy negative electrode materials selected from lithium magnesium alloy negative electrode material, lithium boron alloy negative electrode material, lithium zinc alloy negative electrode material, and lithium aluminum alloy negative electrode material; one or more lithium composite negative electrode materials selected from lithium carbon-based composite negative electrode material and lithium silicon-based composite negative electrode material; as some specific examples: lithium carbon-based composite negative electrode material includes lithiated graphite negative electrode material; lithium silicon-based composite negative electrode material includes lithiated silicon carbon negative electrode material.

[0073] As a further solution, the conversion reaction positive electrode battery in S1 further includes a conversion reaction positive electrode plate, a lithium-containing negative electrode plate, an electrolyte, and a separator.

[0074] As a further solution, the conversion reaction positive electrode plate is made of conversion reaction positive electrode material, conductive agent and binder;

[0075] As a further solution, the lithium-containing negative electrode plate is made of a lithium-containing negative electrode material, a conductive agent, and a binder;

[0076] The present invention has no particular restrictions on the type of conductive agent, as long as it has the function of enhancing the conductivity of the positive electrode or negative electrode and does not adversely affect the performance of the positive electrode battery of the conversion reaction. Those skilled in the art can select the conductive agent commonly used in the art according to actual needs. As some specific examples, the conductive agent used to prepare the positive or negative electrode plate can be selected from carbon blacks such as acetylene black and conductive carbon black; conductive polymers such as polyaniline, polypyrrole, and polythiophene; metal oxide conductive agents such as tin oxide and zinc oxide, and carbon nanofiber conductive agents, etc.

[0077] The present invention does not particularly limit the type of binder, as long as it has the function of enhancing the conductivity of the positive electrode or the negative electrode and does not adversely affect the performance of the conversion reaction positive electrode battery. Those skilled in the art can make a selection according to actual needs. As some specific examples, the binder for preparing the positive or negative electrode sheet can be selected from polyvinylidene fluoride, polyvinyl alcohol, polyimide, sodium carboxymethyl cellulose, polyvinylidene fluoride, polytetrafluoroethylene, polystyrene sulfonic acid, polyacrylonitrile, polycarbonate or polyacrylamide, etc.

[0078] As a further embodiment, the electrolyte is selected from a solution formed by dissolving one or more lithium salts in an organic solvent; the lithium salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI); the organic solvent includes a mixture of one or more of ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), dimethoxymethane (DMM), and ethylene glycol dimethyl ether (DME).

[0079] As a further embodiment, the diaphragm is selected from one or more of a polypropylene (PP) diaphragm, a polyethylene (PE) diaphragm, and a polysulfone (PS) diaphragm.

[0080] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0081] Example 1

[0082] FeS2 is used as the positive electrode of the conversion reaction battery, and metallic lithium is used as the negative electrode of the conversion reaction battery. After the conversion reaction positive electrode battery is assembled according to the above formula, it is allowed to stand at room temperature for 12 hours.

[0083] (1) Using 3C (1C = 894mAg -1 ) The current is discharged for 6 seconds and then placed for 30 seconds, and the pulse discharge cycle is repeated 600 times until the voltage reaches 2.2V;

[0084] (2) Then discharge at 0.5C to 1.5V;

[0085] (3) Continue to discharge with 3C current for 6 seconds and then rest for 30 seconds, repeating the pulse discharge cycle for 600 times until the voltage reaches 1V;

[0086] (4) Charge with 1.5C current for 3 seconds and then leave for 6 seconds, repeating the pulse discharge cycle for 600 times until the voltage reaches 1.5V;

[0087] (5) Charge to 3V with 0.2C constant current;

[0088] (6) Finally, repeat steps (1) to (5) and cycle three times to complete the activation of the conversion reaction positive electrode battery.

[0089] Example 2

[0090] The specific steps and methods are the same as those in Example 1, except that Fe7S8 is used as the positive electrode of the conversion reaction battery, metallic lithium is used as the negative electrode of the conversion reaction battery, and the conversion reaction positive electrode battery is assembled according to the above formula and left to stand at room temperature for 10 hours.

[0091] Example 3

[0092] The specific steps and methods are the same as those in Example 1, except that FeF3 is used as the positive electrode of the conversion reaction battery, metallic lithium is used as the negative electrode of the conversion reaction battery, and the conversion reaction positive electrode battery is assembled according to the above formula and allowed to stand at room temperature for 10 hours.

[0093] Example 4

[0094] The specific steps and methods are the same as those in Example 1, except that Fe2O3 is used as the positive electrode of the conversion reaction battery, metallic lithium is used as the negative electrode of the conversion reaction battery, and the conversion reaction positive electrode battery is assembled according to the above formula and left to stand at room temperature for 8 hours.

[0095] Example 5

[0096] The specific steps and methods are the same as those in Example 1, except that CoS2 is used as the positive electrode of the conversion reaction battery, metallic lithium is used as the negative electrode of the conversion reaction battery, and the conversion reaction positive electrode battery is assembled according to the above formula and allowed to stand at room temperature for 16 hours.

[0097] Example 6

[0098] The specific steps and methods are the same as those in Example 1, except that: VS4 is used as the positive electrode of the conversion reaction battery, metallic lithium is used as the negative electrode of the conversion reaction battery, and the conversion reaction positive electrode battery is assembled according to the above formula and allowed to stand at room temperature for 16 hours.

[0099] Example 7

[0100] The specific steps and methods are the same as those in Example 1, except that:

[0101] (1) Using 3C (1C = 894mAg -1 ) The current is discharged for 6 seconds and then placed for 30 seconds, and the pulse discharge cycle is repeated 600 times until the voltage reaches 2.5V;

[0102] (2) Then discharge at 0.5C to 2V;

[0103] (3) Continue to discharge with 3C current for 6 seconds and then rest for 30 seconds, repeating the pulse discharge cycle for 600 times until the voltage reaches 1V;

[0104] (4) Charge with 1C current for 3 seconds and then leave for 6 seconds, repeating the pulse discharge cycle 600 times until the voltage reaches 2V;

[0105] (5) Charge to 4V with 0.2C constant current;

[0106] (6) Finally, repeat steps (1) to (5) and cycle three times to complete the activation of the conversion reaction positive electrode battery.

[0107] Example 8

[0108] The specific steps and methods are the same as those in Example 1, except that:

[0109] (1) Use 2C (1C = 894mAg -1 ) The current is discharged for 8 seconds and then placed for 25 seconds, and the pulse discharge cycle is repeated 600 times until the voltage reaches 2.6V;

[0110] (2) Then discharge at 0.5C to 1.5V;

[0111] (3) Continue to discharge with 3C current for 6 seconds and then rest for 25 seconds, repeating the pulse discharge cycle for 600 times until the voltage reaches 0.8V;

[0112] (4) Charge with 2C current for 4 seconds and then leave for 8 seconds, repeating the pulse discharge cycle for 600 times until the voltage reaches 1.5V;

[0113] (5) Charge to 4V with 0.3C constant current;

[0114] (6) Finally, repeat steps (1) to (5) and cycle 5 times to complete the activation of the conversion reaction positive electrode battery.

[0115] Example 9

[0116] The specific steps and methods are the same as those in Example 1, except that:

[0117] (1) Using 3C (1C = 894mAg -1 ) The current is discharged for 6 seconds and then placed for 30 seconds, and the pulse discharge cycle is repeated 600 times until the voltage reaches 1.8V;

[0118] (2) Then discharge at 0.3C to 2.3V;

[0119] (3) Continue to discharge with 2C current for 6 seconds and then rest for 40 seconds, repeating the pulse discharge cycle for 600 times until the voltage reaches 1V;

[0120] (4) Charge with 1.5C current for 4 seconds and then leave for 10 seconds. Repeat the pulse discharge cycle 600 times until the voltage reaches 2V.

[0121] (5) Charge to 3V with 0.3C constant current;

[0122] (6) Finally, repeat steps (1) to (5) and cycle 4 times to complete the activation of the conversion reaction positive electrode battery.

[0123] Example 10

[0124] The specific steps and methods are the same as those in Example 1, except that:

[0125] (1) Use 1.5C (1C = 894mA) -1 ) The current is discharged for 10 seconds and then placed for 40 seconds, and the pulse discharge cycle is repeated 600 times until the voltage reaches 2.8V;

[0126] (2) Then discharge at 0.1C to 1.5V;

[0127] (3) Continue to discharge with 4C current for 5 seconds and then rest for 30 seconds, repeating the pulse discharge cycle for 600 times until the voltage reaches 0.5V;

[0128] (4) Charge with 1.5C current for 4 seconds and then leave for 5 seconds, repeating the pulse discharge cycle for 600 times until the voltage reaches 1.5V;

[0129] (5) Charge to 3.5V with 0.33C constant current;

[0130] (6) Finally, repeat steps (1) to (5) and cycle 6 times to complete the activation of the conversion reaction positive electrode battery.

[0131] Comparative Example 1

[0132] The specific steps and methods are the same as those in Example 1, except that:

[0133] (1) Directly discharge to 1V using 0.05C constant current;

[0134] (2) Charge with 1.5C current for 3 seconds and then leave for 6 seconds, repeating the pulse discharge cycle 600 times until the voltage reaches 1.5V;

[0135] (3) Charge to 3V with 0.2C constant current;

[0136] (4) Finally, repeat steps (1) to (3) and cycle three times to complete the activation of the conversion reaction positive electrode battery.

[0137] Comparative Example 2

[0138] The specific steps and methods are the same as those in Example 1, except that:

[0139] (1) Discharge with 3C current for 6 seconds and then leave for 30 seconds. Repeat the pulse discharge cycle 600 times until the voltage reaches 2.2V.

[0140] (2) Then discharge at 0.5C to 1V;

[0141] (3) Charge with 1.5C current for 3 seconds and then leave for 6 seconds, repeating the pulse discharge cycle for 600 times until the voltage reaches 1.5V;

[0142] (4) Charge to 3V with 0.2C constant current;

[0143] (5) Finally, repeat steps (1) to (4) and cycle for 3 times to complete the activation of the conversion reaction positive electrode battery.

[0144] Comparative Example 3

[0145] The specific steps and methods are the same as those in Example 1, except that:

[0146] (1) Discharge directly at 0.5C to 2V;

[0147] (2) Continue to discharge with 3C current for 6 seconds and then rest for 30 seconds, repeating the pulse discharge cycle for 600 times until the voltage reaches 1V;

[0148] (3) Charge with 1C current for 3 seconds and then leave for 6 seconds, repeating the pulse discharge cycle 600 times until the voltage reaches 2V;

[0149] (4) Charge to 4V with 0.2C constant current;

[0150] (5) Finally, repeat steps (1) to (4) and cycle for 3 times to complete the activation of the conversion reaction positive electrode battery.

[0151] Comparative Example 4

[0152] The specific steps and methods are the same as those in Example 1, except that:

[0153] (1) Discharge directly to 1V with 0.05C current;

[0154] (2) Charge to 4V with 0.2C constant current;

[0155] (3) Finally, repeat steps (1)-(2) and cycle for 3 times to complete the activation of the conversion reaction positive electrode battery.

[0156] Comparative Example 5

[0157] The specific steps and methods are the same as those in Example 5, except that:

[0158] (1) Use 3C (1C = 870mAg -1) The current is discharged for 6 seconds and then placed for 30 seconds. This pulse discharge cycle is repeated 600 times until the voltage reaches 1V;

[0159] (2) Then directly charge with 1.5C current for 3 seconds and then leave for 6 seconds, repeating the pulse discharge cycle 600 times until the voltage reaches 3V;

[0160] (3) Finally, repeat steps (1)-(2) and cycle for 3 times to complete the activation of the conversion reaction positive electrode battery.

[0161] Comparative Example 6

[0162] The specific steps and methods are the same as those in Example 6, except that:

[0163] (1) Use 3C (1C = 1195mAg -1 ) The current is discharged for 6 seconds and then placed for 30 seconds, and the pulse discharge cycle is repeated 600 times until the voltage reaches 2.2V;

[0164] (2) Then discharge at 0.5C to 1.5V;

[0165] (3) Continue to discharge with 3C current for 6 seconds and then rest for 30 seconds, repeating the pulse discharge cycle for 600 times until the voltage reaches 1V;

[0166] (4) Charge to 1.5V with 0.2C constant current;

[0167] (5) Charge with 1.5C current for 3 seconds and then leave for 6 seconds. Repeat the pulse discharge cycle 600 times until the voltage reaches 3V.

[0168] (6) Finally, repeat steps (1) to (5) and cycle three times to complete the activation of the conversion reaction positive electrode battery.

[0169] Comparative Example 7

[0170] The specific steps and methods are the same as those in Example 1, except that:

[0171] (1) Use 6C (1C = 894mAg -1 ) The current is discharged for 20 seconds and then placed for 2 seconds. This pulse discharge cycle is repeated 600 times until the voltage reaches 2.2V;

[0172] (2) Then discharge at 0.5C to 1.5V;

[0173] (3) Continue to discharge with 6C current for 20 seconds and then rest for 2 seconds, repeating the pulse discharge cycle for 600 times until the voltage reaches 1V;

[0174] (4) Charge with 4C current for 10 seconds and then leave for 2 seconds, repeating the pulse discharge cycle for 600 times until the voltage reaches 1.5V;

[0175] (5) Charge to 3V with 0.2C constant current;

[0176] (6) Finally, repeat steps (1) to (5) and cycle three times to complete the activation of the conversion reaction positive electrode battery.

[0177] Comparative Example 8

[0178] The specific steps and methods are the same as those in Example 1, except that:

[0179] (1) Using 3C (1C = 894mAg -1 ) The current is discharged for 1 second and then left for 100 seconds. This pulse discharge cycle is repeated 600 times until the voltage reaches 2.2V;

[0180] (2) Then discharge at 0.5C to 1.5V;

[0181] (3) Continue to discharge with 3C current for 1 second and then rest for 100 seconds, and repeat the pulse discharge cycle 600 times until the voltage reaches 1V;

[0182] (4) Charge with 1.5C current for 3 seconds and then leave for 30 seconds. Repeat the pulse discharge cycle 600 times until the voltage reaches 1.5V.

[0183] (5) Charge to 3V with 0.2C constant current;

[0184] (6) Finally, repeat steps (1) to (5) and cycle three times to complete the activation of the conversion reaction positive electrode battery.

[0185] Specific test methods and conditions:

[0186] (1) The positive electrode active material, conductive agent Super P, and binder CMC are dissolved in deionized water at a mass ratio of 8:1:1 to prepare a positive electrode material slurry; the positive electrode sheet for the conversion reaction is prepared by coating and drying; the electrolyte is composed of 1.5M LiFSI&DME / OFE / TTE (v:v:v=1:1:1), the negative electrode is a metal lithium sheet; the diaphragm is a polyethylene (PE) diaphragm; and the conversion reaction positive electrode battery is assembled.

[0187] (2) Voltage window 1-3V, constant current charge and discharge mode for cycle test, battery test system model CT-4008Tn, NEWARE. Specific test method: After completing the activation of the conversion reaction positive electrode battery in the manner of Examples 1-10; within the voltage range of 1-3V, 1) stand for 30 minutes; 2) rate discharge (0.33C, 1.0V); 3) rate charge (0.33C, 3.0V), record the initial discharge specific capacity C1 and the cycle discharge specific capacity C2 after N cycles. The capacity retention rate is calculated by the formula C2 / C1×100%.

[0188] The test results of Examples 1-10 and Comparative Examples 1-8 are shown in Table 1.

[0189] Table 1

[0190]

[0191] It can be seen from the data of Examples 1-10, Comparative Examples 1-8 and Table 1 that the electrochemical performance of the conversion reaction positive electrode battery obtained in Examples 1-10 is better than that of Comparative Examples 1-8. It can be seen that the method of high current pulse regulation of uniform nucleation of the conversion reaction proposed in the present invention can significantly reduce the huge capacity loss of the conversion reaction positive electrode material in the early stage of the cycle, which is beneficial to improve the discharge specific capacity and cycle life of the conversion reaction positive electrode battery. More excellent electrochemical performance can be achieved through simple current regulation, and it can also be applied to improve the cycle life and capacity retention rate of multiple types of conversion reaction positive electrode material system batteries, showing good economic benefits.

[0192] It can be seen from Examples 1-10 and Comparative Example 1 that Comparative Example 1 did not undergo two high-current pulse discharges, but only discharged to a specified voltage through a small current constant current. The capacity retention rate and discharge specific capacity of the conversion reaction positive electrode battery are relatively low compared to Examples 1-10. This is because the lack of precise stimulation of two high-current pulses is not conducive to reducing the nucleation difference, thereby forming a scattered distribution of discharge products. Although a good subsequent charging system can promote the full conversion of the discharge products, the early nucleation difference will cause the inactivation, shedding and passivation of the discharge products, which is not conducive to the formation of a stable reaction interface, reducing the convertible discharge products and leading to irreversible capacity loss. In contrast, in Examples 1-10, two high-current pulse discharges effectively promoted the uniformity of nucleation and reduced the nucleation difference, thereby making the distribution of the discharge products more concentrated and orderly. This orderly distribution of discharge products is conducive to maintaining a high capacity retention rate and discharge specific capacity during the cycle.

[0193] It can be seen from Examples 1-10 and Comparative Example 2 that Comparative Example 2 did not perform a second high-current pulse discharge. During discharge, it only underwent a high-current pulse discharge and a low-current constant-current discharge. It can be seen that the battery performance of its conversion reaction positive electrode battery in the subsequent cycle process is better than that of other comparative examples, but it is still lower than that of Example 1-10; we believe that this is because the lack of a second high-current pulse discharge will reduce the phase change reaction inside the battery, which is not conducive to the battery suppressing the volume expansion of the pole piece after discharge, maintaining good bonding performance between particles, and maintaining more stable performance. Therefore, Example 1-10 is balanced by two high-current pulse discharge stimulations and a low-current constant-current discharge, which is conducive to promoting the progress of the phase change reaction, fully promoting the changes in the chemical reaction, generating uniformly grown nuclei, and providing a good stable foundation for the subsequent transformation of active substances.

[0194] It can be seen from Examples 1-10 and Comparative Example 3 that Comparative Example 3 first performs a small current constant current discharge, and then performs a large current pulse discharge. Compared with the discharge system of Example 1-10, which first performs a large current pulse discharge, then performs a small current constant current discharge, and the second large current pulse discharge, the battery discharge specific capacity, capacity retention rate, and cycle stability of the final battery under the constant current charge and discharge cycle are all poor; we can think that this phenomenon is due to the fact that Comparative Example 3 first performs a small current constant current discharge, which will cause the generation of uneven nucleation of discharge products, resulting in an increase in the internal impedance of the battery, which is not conducive to the uniform insertion and extraction of lithium ions, thereby affecting the interface stability and ion transmission efficiency, causing a decrease in battery performance. In Examples 1-10, by first performing a large current pulse discharge, then a small current constant current discharge, and a specific discharge system of a second large current pulse discharge, it is possible to effectively promote the uniform nucleation of discharge products, provide a complete and connected lithium ion transmission channel, and thus enhance the cycle stability and capacity retention rate of the battery.

[0195] Through Examples 1-10 and Comparative Example 4, it can be found that Comparative Example 4 only uses small current constant current charge and discharge to activate the battery, and does not undergo a large current pulse charge and discharge system. The capacity of the battery decays severely during subsequent cycles, and the cycle stability performance is also poor; this is because small current constant current discharge is not conducive to uniform nucleation of the product. The absence of large current pulse stimulation will reduce the rate of phase change reaction, resulting in the phase change process being too slow, so that some products fail to fully participate in the reaction, and the nucleation rate is reduced, and the particle structure is uneven, thereby affecting the capacity and performance of the battery. The charge and discharge system adopted in Examples 1-10 can not only fully promote the homogeneous reaction process and increase the rate of uniform nucleation, but also prevent the accumulation of heat inside the battery caused by long-term constant current charge and discharge, causing safety hazards. Furthermore, the conversion reaction positive electrode battery prepared in Examples 1-10 has high capacity retention and cycle stability in subsequent cycles.

[0196] Through Examples 1-10 and Comparative Example 5, it can be found that Comparative Example 5 only uses large current pulses for charging and discharging. Compared with Examples 1-10, the capacity and cycle performance of the conversion reaction positive electrode battery prepared by it in the subsequent cycle process are worse than those of Examples 1-10. We believe that this is because although high-current pulse discharge to a specified voltage can provide sufficient energy to promote uniform nucleation of products and promote the phase change reaction process, long-term high-current pulse discharge will bring about concentration polarization, causing the internal temperature of the battery to rise, thereby accelerating the degradation of battery materials and the decline in battery performance. In addition, long-term high-current pulse discharge may also cause damage to the internal structure of the battery, affect the transmission channel of lithium ions, and further affect the cycle stability and capacity retention rate of the battery. Although charging only with high-current pulses during the charging process promotes the full conversion of the discharge products, due to the damage to the internal structure of the battery that may be caused by only high-current pulse discharge, the internal structure of the battery will be further damaged due to heat accumulation and unstable reaction interface, resulting in a further decline in the performance of the prepared conversion reaction positive electrode battery.

[0197] It can be seen from Examples 1-10 and Comparative Example 6 that when charging, Comparative Example 6 first performs a small current constant current charge to a specified voltage and then performs a large current pulse charge. Compared with the method of first performing a small current constant current charge and then a large current pulse charge in Example 1-10, the discharge specific capacity, capacity retention rate and cycle stability performance in the subsequent cycle process are poorer than those in Example 1-10. We can think that this is because when the conversion reaction positive electrode battery after full discharge is charged by a small current constant current system, it is not easy to achieve rapid and full conversion of the discharge product relative to the stimulation of a large current pulse, resulting in the generation of phenomena such as inactivation, passivation and uneven deposition of active substances, thereby causing the capacity of the conversion reaction positive electrode battery to decay and reduce the cycle life of the battery; and finally performing a large current pulse charge is not conducive to maintaining the stability of the internal environment of the battery, and has a certain impact on the long-term cycle performance of the battery. However, in Example 1-10, first performing a large current pulse charge can provide sufficient energy to promote the full conversion of the discharge product and increase the content of the active substance. Secondly, the internal environment of the battery is stabilized by a small current constant current charge to avoid damage to the internal structure of the battery, thereby improving the battery capacity and cycle performance.

[0198] It can be seen from Examples 1-10, Comparative Examples 7 and 8 that the appropriate range of charging and discharging parameters helps to better promote uniform nucleation of products, realize homogeneous reactions of products, reduce the diffusion barriers of two-phase products, thereby accelerating the uniform insertion and extraction of lithium ions, and obtaining a good conversion reaction positive electrode battery capacity retention rate. However, when the pulse discharge current and discharge time selected in Comparative Example 7 are relatively long and the shelf time is relatively short, it is not conducive to maintaining the temperature and chemical stability inside the battery; it will bring certain obstacles to the transmission path of lithium ions, affect the nucleation growth rate, and thus lead to the conversion reaction positive electrode battery capacity retention rate and cycle stability performance of Comparative Example 7. The pulse charging time used in Comparative Example 8 is too short, and the shelf time is long, which will lead to the generation of uneven deposition of active substances, and the short charging time will also cause incomplete conversion of discharge products, resulting in inactivation, shedding and passivation of active substances, thereby causing the battery capacity to decay, making the conversion reaction positive electrode battery discharge specific capacity and cycle performance of Comparative Example 8 worse than those of Examples 1-10.

[0199] It can be seen from Examples 1, 2, 3, 4 and Examples 5 and 6 that for different conversion reaction cathode materials optimized by the present invention, the charge and discharge regime can obtain good battery capacity retention and cycle stability; and the iron compound conversion reaction cathode material optimized by the present invention can achieve a better range of battery performance. This is because the iron compound conversion reaction cathode material has a high electrochemical activity, which can effectively promote the conversion of active substances, thereby promoting the insertion and extraction of lithium ions. In addition, the iron compound has good stability, can maintain the integrity of the structure during the battery charge and discharge process, promote uniform nucleation growth, and reduce the reduction in capacity retention due to material structure damage.

[0200] pass Figure 1 As shown, Figure 1 ACompared to Figure 1 B shows discharge product particles with smaller size and more uniform distribution, indicating that the activation method of the present invention is conducive to the formation of more uniform nucleation of the conversion reaction positive electrode battery, which provides an effective reaction pathway for the subsequent full conversion of the discharge product into active substances.

[0201] observe Figure 2 middle Figure 2 A is not cycled with Figure 2 B. Figure 2Comparison of the morphology of the optical cross-section after 20 C cycles; based on the size change, it can be found that the cross-sectional dimensions of Example 1 and Comparative Example 1 after cycling increased from 32.3μm in the original uncycled state to 50.6μm and 65.8μm, respectively, and the volume expansion ratios were 56.7% and 103.7%, respectively. The results indirectly prove that after the 3C pulse improves the nucleation, the distribution of the discharge products is more uniform, which is more conducive to inhibiting the loss of active materials and promoting the subsequent high reversible capacity.

[0202] It should be noted that the above description is only a preferred embodiment of the present invention and is 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 in the protection scope of the present invention.

Claims

1. A method for improving the cycle life of a conversion reaction positive electrode battery based on high current pulse activation, the method comprising the following steps performed in sequence: S1: After the conversion reaction cathode battery is assembled, let it stand; S2: Perform high current pulse discharge on the conversion reaction positive electrode battery to a specified voltage V1; S3: Discharge with a small constant current to a specified voltage V2; S4: Perform high current pulse discharge to the specified voltage V3; S5: Perform high current pulse charging to a specified voltage V4; S6: Perform low current constant current charging to the specified voltage V5; S7: Repeat the charge and discharge method of S2-S6 and cycle N1 times to complete the activation of the positive electrode battery for the conversion reaction; in, The range of V1 is 2.2-3V; the range of V2 is 1.5-2V; the range of V3 is 0.5-1V; the range of V4 is 1.5-2V; the range of V5 is 3-4V; V1>V2>V3, V5>V4>V3; N1≥1 times.

2. The method for improving the cycle life of a positive electrode battery for a conversion reaction based on high current pulse activation according to claim 1, characterized in that: Among the V1, V2, V3, V4 and V5, the voltage difference between V1 and V2 is preferably in the range of 0.2-0.5V; the voltage difference between V2 and V3 is preferably in the range of 0.5-1V; the voltage difference between V4 and V3 is preferably in the range of 0.5-1V; the voltage difference between V5 and V4 is preferably in the range of 1-1.5V.

3. The method for improving the cycle life of a positive electrode battery for a conversion reaction based on high current pulse activation according to claim 1, characterized in that: In the S2 and S4 high current pulse discharges, the discharge current C1 ranges from 1 to 4 C, the discharge time T1 ranges from 3 s to 10 s, and the standby time T2 ranges from 5 s to 50 s.

4. The method for improving the cycle life of a positive electrode battery for a conversion reaction based on high current pulse activation according to claim 1, characterized in that: In the S3 small current constant current discharge, the discharge current C2 is selected from the range of 0.05-0.5C.

5. The method for improving the cycle life of a positive electrode battery of a conversion reaction based on high current pulse activation according to claim 1, characterized in that: In the S5 high current pulse charging, the charging current C3 is selected from the range of 1-2C, the charging time T3 is 3-7s, and the standby time T4 is 5-10s; In the S6 low-current constant-current charging, the charging current C4 range is selected from 0.2-0.33C.

6. The method for improving the cycle life of a positive electrode battery of a conversion reaction based on high current pulse activation according to claim 1, characterized in that: The number of cycles in S7 is preferably 3-5 times; the standing time in S1 is not less than 8 hours; Furthermore, the standing time in S1 is preferably 8-12 hours.

7. The method for improving the cycle life of a positive electrode battery of a conversion reaction based on high current pulse activation according to claim 1, characterized in that: The conversion reaction positive electrode battery in S1 includes a conversion reaction positive electrode material and a lithium-containing negative electrode material.

8. The method for increasing the cycle life of a positive electrode battery for a conversion reaction based on high current pulse activation according to claim 7, characterized in that: The conversion reaction positive electrode material includes metal sulfide (MS x ), metal oxides (MO z ), metal fluoride (MF y ) or more thereof; wherein the metal M is selected from one or more metal elements of Fe, Co, Ni, Cu, Zn, Mo, V, Mn, Ti, Sn, Sb, Te, and W; Furthermore, the conversion reaction cathode material is preferably selected from iron sulfide (FeS x ), iron oxide (FeO z ), iron fluoride (FeF y ) or more thereof; wherein the values ​​of x, y, and z vary accordingly according to the stoichiometric ratio of the metal element composition.

9. The method for increasing the cycle life of a positive electrode battery for a conversion reaction based on high current pulse activation according to claim 7, characterized in that: The lithium-containing negative electrode material includes a metallic lithium negative electrode material; one or more lithium alloy negative electrode materials selected from the group consisting of a lithium-magnesium alloy negative electrode material, a lithium-boron alloy negative electrode material, a lithium-zinc alloy negative electrode material, and a lithium-aluminum alloy negative electrode material; and one or more lithium composite negative electrode materials selected from the group consisting of a lithium-carbon-based composite negative electrode material and a lithium-silicon-based composite negative electrode material.

10. The method for increasing the cycle life of a positive electrode battery for a conversion reaction based on high current pulse activation according to claim 1, characterized in that: The conversion reaction positive electrode battery in S1 further includes a conversion reaction positive electrode plate, a lithium-containing negative electrode plate, an electrolyte, and a separator; Furthermore, the conversion reaction positive electrode plate is made of the conversion reaction positive electrode material, conductive agent and binder according to claim 8; Furthermore, the lithium-containing negative electrode plate is made of the lithium-containing negative electrode material, conductive agent, and binder according to claim 9; Further, the electrolyte is selected from a solution formed by dissolving one or more lithium salts in an organic solvent; Furthermore, the diaphragm is selected from one or more of a polypropylene (PP) diaphragm, a polyethylene (PE) diaphragm, and a polysulfone (PS) diaphragm.

Images