A method for directly regenerating a failed positive electrode, and a regenerated positive electrode

Abstract

This application pertains to a cathode regeneration method, specifically addressing the issues in the traditional molten salt method for Li... + The limited transport rate leads to low lithiation efficiency on the surface of failed cathodes. This paper proposes a direct regeneration method for failed cathodes. Compared to the traditional direct regeneration method using lithium hydroxide and lithium nitrate molten salts, this method introduces lithium benzoate containing benzoate groups into the lithium hydroxide / lithium nitrate molten salt system to repair the cathode. The addition of lithium benzoate fundamentally changes the original Li... + Transmission mechanism to implement Li + Stable coupling and decoupling in molten salts to complete Li + The rapid "leap" in Li's development. This transformation facilitated Li's... + The rapid transport of these components ensures sufficient lithiation of the failed cathode surface, thereby guaranteeing efficient reconstruction and repair of the failed cathode structure during the subsequent high-temperature calcination stage. Therefore, the regenerated cathode obtained by the direct regeneration method in this application exhibits excellent electrochemical performance, providing a promising approach for the efficient and sustainable regeneration of spent lithium-ion batteries.

Description

Technical Field

[0001] This application pertains to a positive electrode regeneration method, specifically relating to a direct regeneration method for a failed positive electrode and a regenerated positive electrode. Background Technology

[0002] In recent years, direct regeneration methods for expired LIBs (Lithium-Ion Batteries) have been considered an economical, environmentally friendly, and highly promising recycling technology due to their advantages such as simple process flow, low energy consumption, no damage to the cathode structure, and the ability to reuse the recovered cathode to manufacture new lithium-ion batteries.

[0003] Among numerous direct regeneration methods, the molten salt method leverages its low eutectic point to lower the reaction temperature, allowing the reaction to occur between solid and liquid phases. This results in a faster ion transport rate compared to solid-solid reactions, enabling effective repair of failed cathodes at relatively low temperatures and under normal pressure. Therefore, it has received considerable attention in recent years. Traditional molten salt methods utilize thermally driven processes to regenerate Li... + Rapidly transported to the surface of the cathode particles, completing the lithiation of the failed cathode. However, due to its limited Li... + The transport rate reduces the lithiation efficiency on the surface of the failed cathode, thus affecting the efficient repair effect of the failed cathode. Summary of the Invention

[0004] This application addresses the issue of Li in the traditional molten salt process. + The limited transport rate leads to low lithiation efficiency on the surface of failed cathodes. This paper proposes a direct regeneration method for failed cathodes and a regenerated cathode.

[0005] To achieve the above objectives, this application adopts the following technical solution:

[0006] In a first aspect, this application proposes a direct regeneration method for a failed positive electrode, comprising:

[0007] A first mixture is obtained by mixing positive electrode black powder, lithium hydroxide, lithium nitrate and lithium benzoate;

[0008] The first mixture assembly is pre-lithiated to obtain pre-lithiated cathode powder;

[0009] Pre-lithiated cathode powder and lithium carbonate are mixed to obtain a second mixture;

[0010] The second mixture is sintered to obtain a regenerated positive electrode.

[0011] Furthermore, the addition ratio of positive electrode black powder, lithium hydroxide, lithium nitrate and lithium benzoate is set to 1: (0.2~0.25): (0.25~0.3): 0.5.

[0012] Furthermore, after obtaining the first mixture, the process further includes grinding the first mixture in an infrared environment.

[0013] Furthermore, the conditions for pre-lithiation treatment by assembly include: holding at 300°C for 4-6 hours.

[0014] Furthermore, after the pre-lithiation treatment of the first mixture assembly, the process further includes:

[0015] The pre-lithiated cathode powder was obtained by washing with deionized water and centrifuging multiple times, followed by drying.

[0016] Grind the pre-lithiated cathode powder.

[0017] Furthermore, when mixing the pre-lithiated cathode powder and lithium carbonate, the addition ratio of the pre-lithiated cathode powder and lithium carbonate is 1:(0.25~0.5) molar ratio.

[0018] Furthermore, the conditions for sintering the second mixture include sintering at 750~850℃ for 6 hours.

[0019] Furthermore, during sintering at 750~850℃, the heating rate is 5~10℃ / min.

[0020] Furthermore, the cathode black powder is LiNi. 0.5 Co 0.2 Mn 0.3 O2 Black Powder

[0021] Secondly, this application proposes a regenerated positive electrode prepared by the direct regeneration method of the above-mentioned failed positive electrode.

[0022] Compared with the prior art, this application has the following beneficial effects:

[0023] This application proposes a direct regeneration method for failed cathodes. Compared to the traditional direct regeneration method using lithium hydroxide and lithium nitrate molten salts, this method involves introducing lithium benzoate containing benzoate groups into the lithium hydroxide / lithium nitrate molten salt system to repair the cathode. The addition of lithium benzoate fundamentally alters the original Li... + Transmission mechanism to implement Li + Stable coupling and decoupling in molten salts to complete Li + The rapid "leap" in Li's development. This transformation facilitated Li's... + The rapid transport of these components ensures sufficient lithiation of the failed cathode surface, thereby guaranteeing efficient reconstruction and repair of the failed cathode structure during the subsequent high-temperature calcination stage. Therefore, the regenerated cathode obtained by the direct regeneration method in this application exhibits excellent electrochemical performance, providing a promising approach for the efficient and sustainable regeneration of spent lithium-ion batteries. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1(a) shows the second charge-discharge curves of the failed NCM523, the regenerated electrode with added lithium benzoate, and the regenerated electrode without added lithium benzoate at a rate of 0.5 C.

[0026] Figure 1(b) shows the long-cycle curves of the failed NCM523, the regenerated electrode with added lithium benzoate, and the regenerated electrode without added lithium benzoate at a rate of 0.5 C.

[0027] Figure 1(c) shows the charge-discharge capacity decay of the regenerated electrode without the addition of lithium benzoate;

[0028] Figure 1(d) shows the charge-discharge capacity decay of the regenerated electrode with added lithium benzoate.

[0029] Figure 2(a) is a schematic diagram of a scanning electron microscope showing a half-cell assembled by RENCM;

[0030] Figure 2(b) is a schematic diagram of a scanning electron microscope showing a half-cell assembled with REBNCM.

[0031] Figure 3 This is a schematic diagram illustrating the principle of the direct regeneration method for the failed positive electrode of this application. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0033] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0034] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0035] In the description of the embodiments of this application, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0036] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0037] In the description of the embodiments of this application, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0038] With the global trend of energy structure transformation and the pursuit of green and sustainable development, lithium-ion batteries (LIBs), as an important component of energy storage, are experiencing a surge in demand in various electronic devices, electric vehicles, and energy storage systems. Typically, lithium-ion batteries have a lifespan of only 5-8 years, and it is predicted that 11 million tons of waste lithium-ion batteries will be generated by 2030. Over 30% of the production cost of LIBs is concentrated in the cathode; therefore, current recycling technologies primarily target commercially available layered cathodes, such as lithium cobalt oxide (LiCoO2) and ternary cathodes (NCM). Currently, traditional methods for recycling spent layered cathodes mainly fall into two categories: pyrometallurgical and hydrometallurgical processes. However, relying on traditional methods for recycling spent LIBs results in excessively high environmental costs and limited economic benefits. In recent years, direct recycling methods for spent LIBs have been considered an economical, environmentally friendly, and promising recycling technology due to their advantages: simple process flow, low energy consumption, no damage to the cathode structure, and the ability to reuse the recovered cathode to manufacture new lithium-ion batteries.

[0039] Among numerous direct regeneration methods, the molten salt method leverages the advantage of a low eutectic point to lower the reaction temperature. The reaction can occur between solid and liquid phases, and the ion transport rate is faster than in solid-solid reactions. It can achieve good repair results for failed cathodes at relatively low temperatures under normal pressure, thus attracting significant attention in recent years. Generally, the molten salt method for repairing failed cathodes mainly includes two stages (surface lithiation and subsequent high-temperature calcination). The first stage involves selecting a suitable molten salt system and heating it at a certain temperature to form a molten state with a low eutectic point, thereby achieving lithiation of the failed cathode surface, i.e., Lithium. + The formation of a lithium-containing complex on the surface of the failed cathode provides a sufficient lithium source for the second-stage repair of the defective structure of the failed cathode. The second stage involves reconstructing the surface structure of the failed cathode through high-temperature calcination, restoring it to a perfect layered structure. In the process of repairing the failed cathode using molten salt, surface lithiation of the failed cathode is crucial for subsequent structural recovery.

[0040] Current traditional molten salts are produced by thermally driven processes to ignite Li. + Rapid transport to the surface of the cathode particles completes the lithiation of the failed cathode. However, due to its limited Li... + The reduced transport rate decreases the lithiation efficiency on the surface of the failed cathode, thus affecting its efficient repair. Only by improving the lithiation effect on the failed cathode surface can efficient repair be achieved. However, Li in the molten salt system... + Transport efficiency is a crucial factor affecting lithiation on the surface of a failed cathode. Therefore, improving Lithium transport efficiency during the lithiation stage of molten salt repair is essential. + Transport efficiency is the key to achieving efficient repair of failed positive electrodes.

[0041] The Grotthuss mechanism, first proposed by Theodore von Grotthuss in 1804, demonstrates that the transport efficiency of hydrogen ions in liquids via hydrogen bonding is far higher than that via diffusion solely due to concentration gradients. This mechanism provides a method for improving cation transport efficiency. The objective of this application is to introduce lithium benzoate containing benzoate groups into a lithium hydroxide / lithium nitrate molten salt system, utilizing the benzoate group to achieve Li... + Stable coupling and decoupling in molten salts to complete Li + The rapid "leap" of the cathode enables full lithiation of the failed cathode surface, providing a guarantee for efficient structural reconstruction and repair of the failed cathode during the subsequent high-temperature calcination stage, thereby achieving efficient repair of the failed cathode.

[0042] Based on the above, this application proposes a direct regeneration method for a failed positive electrode and a regenerated positive electrode. The following is a detailed description of this application in conjunction with embodiments and accompanying drawings.

[0043] This application proposes a direct regeneration method for a failed positive electrode, which may include:

[0044] A first mixture is obtained by mixing positive electrode black powder, lithium hydroxide, lithium nitrate and lithium benzoate;

[0045] The first mixture assembly is pre-lithiated to obtain pre-lithiated cathode powder;

[0046] Pre-lithiated cathode powder and lithium carbonate are mixed to obtain a second mixture;

[0047] The second mixture is sintered to obtain a regenerated positive electrode.

[0048] In some embodiments of this application, the molar ratio of the positive electrode black powder, lithium hydroxide, lithium nitrate and lithium benzoate is set to 1:(0.2~0.25):(0.3~0.25):0.5, which can control the molar ratio of the first two to the molar ratio of lithium benzoate to be 1:1. The molar ratio range of lithium hydroxide and lithium nitrate takes into account their molten salt phase diagrams. When the ratio range is 0.4~0.5, they can all become molten at a melting temperature of 300 degrees Celsius.

[0049] In some embodiments of this application, the conditions for pre-lithiation treatment by assembly include: holding at 300°C for 4-6 hours. Too short a holding time results in insufficient pre-lithiation, and lithium ions cannot completely lithiate the failed cathode, resulting in poor electrochemical performance. When the lithiation time is extended to more than 6 hours, the electrochemical performance is not completely improved. On the contrary, long-term treatment may lead to slight degradation of the material structure.

[0050] In some embodiments of this application, when mixing the second grinding material and lithium carbonate, the addition ratio of the second grinding material to lithium carbonate is 1:0.25~0.5 molar ratio. When the addition range is 0.25~0.5, the lithium loss during the high-temperature calcination stage can be compensated. The electrochemical performance is almost identical. Currently reported lithium carbonate addition amounts are all 0.5, and experiments in this application have demonstrated that a lower molar ratio of 0.25 does not cause a significant difference in electrochemical performance.

[0051] In some embodiments of this application, the sintering conditions for the second mixture include sintering at 750~850 °C for 6 hours. Holding at 750~850 °C for 6 hours is crucial. At lower temperatures (below 750 °C), the transformation from rock salt phase to layered phase is incomplete, leading to insufficient crystallization. When the temperature exceeds 850 °C, the excessively high temperature can damage the material's structure, resulting in poor electrochemical performance.

[0052] In some embodiments of this application, the heating rate is 5-10 °C / min during sintering at 750-850 °C. Rapid heating may lead to uneven temperature distribution inside and on the surface of the material, causing thermal stress concentration, which may trigger cracks or other structural defects. Furthermore, rapid heating is not conducive to the transformation of the rock salt phase to the layered phase in the failed cathode. When the heating rate is below 5 °C / min, slow heating may lead to uneven energy distribution, and an excessively slow heating rate will increase the production cycle, reduce production efficiency, and increase costs.

[0053] It should be noted that, in order to make the mixing more uniform, after obtaining the first mixture and the pre-lithiated cathode powder, the uniformity of the mixing can be improved by grinding. Additionally, when performing pre-lithiation treatment on the first mixture assembly, the first mixture can be dispersed in an alumina ceramic boat, using the alumina ceramic boat as a carrier; other carriers can also be used depending on the actual situation.

[0054] Example 1

[0055] (1) Using LiNi 0.5 Co 0.2 Mn 0.3 O2 is used as the cathode black powder (denoted as SNCM523). In this embodiment, the cathode black powder SNCM523 comes from waste lithium-ion batteries of 3C digital products or electric vehicles, and is processed into cathode black powder by a battery recycling company. The cathode black powder SNCM523 is a commercially recycled ternary NCM523 cathode black powder with a lithium molar content between 0.6 and 1.

[0056] (2) SNCM523, lithium hydroxide (LiOH), lithium nitrate (LiNO3) and lithium benzoate (LiC7H5O2) are mixed in a molar ratio of 1:0.2:0.3:0.5 and ground in a mortar for 10 min. Due to the strong water absorption of lithium nitrate (LiNO3), the grinding process can be carried out under an infrared lamp to obtain the first ground material.

[0057] (3) The first grinding material is evenly dispersed in an alumina ceramic boat and assembled at 300 °C for pre-lithiation treatment for 4 hours.

[0058] (4) Wash the powder treated in the previous step with deionized water and centrifuge 6 times, 3 min each time, at a speed of 6000 rpm. In actual application, the number of washing and centrifugation times and centrifugation parameters can be adjusted according to the actual situation. Dry the centrifuged powder in an oven at 60 ℃ for 12 h to obtain the pre-lithiated cathode powder, named SEBNCM.

[0059] (5) After SEBNCM is thoroughly ground in a mortar, SEBNCM is mixed with lithium carbonate (Li2CO3) at a molar ratio of 1:0.25 and ground for 10 min. Then, it is sintered in a muffle furnace at 850℃ for 6 h with a heating rate of 5℃ / min. Finally, the regenerated positive electrode is obtained, which is denoted as REBNCM.

[0060] Example 2

[0061] (1) Using LiNi 0.5 Co 0.2 Mn 0.3 O2 is used as the positive electrode black powder (denoted as SNCM523). In this embodiment, the positive electrode black powder SNCM523 comes from waste lithium-ion batteries of 3C digital products or electric vehicles, and is processed into positive electrode black powder by a battery recycling company.

[0062] (2) SNCM523, lithium hydroxide (LiOH), lithium nitrate (LiNO3) and lithium benzoate (LiC7H5O2) are mixed in a molar ratio of 1:0.3:0.2:0.5 and ground in a mortar for 10 min. Due to the strong water absorption of lithium nitrate (LiNO3), the grinding process can be carried out under an infrared lamp to obtain the first ground material.

[0063] (3) The first grinding material is evenly dispersed in an alumina ceramic boat and assembled at 300°C for pre-lithiation treatment for 6 hours.

[0064] (4) Wash the powder treated in the previous step with deionized water and centrifuge 6 times, 3 min each time, at a speed of 6000 rpm. In actual applications, the number of washing and centrifugation times and centrifugation parameters can be adjusted according to the actual situation. Dry the centrifuged powder in an oven at 60℃ for 12 h to obtain pre-lithiated cathode powder, named SEBNCM.

[0065] (5) After SEBNCM is thoroughly ground in a mortar, SEBNCM is mixed with lithium carbonate (Li2CO3) at a molar ratio of 1:0.5 and ground for 10 min. Then, it is sintered in a muffle furnace at 750 °C for 6 h with a heating rate of 10 °C / min. Finally, the regenerated positive electrode is obtained, which is denoted as REBNCM.

[0066] Example 3

[0067] (1) Using LiNi 0.5 Co 0.2 Mn 0.3 O2 is used as the positive electrode black powder (denoted as SNCM523). In this embodiment, the positive electrode black powder SNCM523 comes from waste lithium-ion batteries of 3C digital products or electric vehicles, and is processed into positive electrode black powder by a battery recycling company.

[0068] (2) SNCM523, lithium hydroxide (LiOH), lithium nitrate (LiNO3) and lithium benzoate (LiC7H5O2) are mixed in a molar ratio of 1:0.25:0.25:0.5 and ground in a mortar for 10 min. Due to the strong water absorption of lithium nitrate (LiNO3), the grinding process can be carried out under an infrared lamp to obtain the first ground material.

[0069] (3) The first grinding material is evenly dispersed in an alumina ceramic boat and assembled at 300°C for pre-lithiation treatment for 5 hours.

[0070] (4) Wash the powder treated in the previous step with deionized water and centrifuge 6 times, 3 min each time, at a speed of 6000 rpm. In actual applications, the number of washing and centrifugation times and centrifugation parameters can be adjusted according to the actual situation. Dry the centrifuged powder in an oven at 60℃ for 12 h to obtain pre-lithiated cathode powder, named SEBNCM.

[0071] (5) After SEBNCM is thoroughly ground in a mortar, SEBNCM is mixed with lithium carbonate (Li2CO3) at a molar ratio of 1:0.3 and ground for 10 min. Then, it is sintered in a muffle furnace at 800℃ for 6 h with a heating rate of 8℃ / min. Finally, the regenerated positive electrode is obtained, which is denoted as REBNCM.

[0072] Example 4

[0073] (1) Using LiNi 0.5 Co 0.2 Mn 0.3 O2 is used as the positive electrode black powder (denoted as SNCM523). In this embodiment, the positive electrode black powder SNCM523 comes from waste lithium-ion batteries of 3C digital products or electric vehicles, and is processed into positive electrode black powder by a battery recycling company.

[0074] (2) SNCM523, lithium hydroxide (LiOH), lithium nitrate (LiNO3) and lithium benzoate (LiC7H5O2) are mixed in a molar ratio of 1:0.22:0.28:0.5 and ground in a mortar for 10 min. Due to the strong water absorption of lithium nitrate (LiNO3), the grinding process can be carried out under an infrared lamp to obtain the first ground material.

[0075] (3) The first grinding material is evenly dispersed in an alumina ceramic boat and assembled at 300 °C for pre-lithiation treatment for 4 hours.

[0076] (4) Wash the powder treated in the previous step with deionized water and centrifuge 6 times, 3 min each time, at a speed of 6000 rpm. In actual application, the number of washing and centrifugation times and centrifugation parameters can be adjusted according to the actual situation. Dry the centrifuged powder in an oven at 60 ℃ for 12 h to obtain the pre-lithiated cathode powder, named SEBNCM.

[0077] (5) After SEBNCM is thoroughly ground in a mortar, SEBNCM is mixed with lithium carbonate (Li2CO3) at a molar ratio of 1:0.4 and ground for 10 min. Then, it is sintered in a muffle furnace at 820℃ for 6 h with a heating rate of 6℃ / min. Finally, the regenerated positive electrode is obtained, which is denoted as REBNCM.

[0078] Comparative example:

[0079] SNCM523, lithium hydroxide (LiOH), and lithium nitrate (LiNO3) were mixed at a molar ratio of 1:0.4:0.6 and ground in a mortar for 10 min. Due to the strong hygroscopicity of lithium nitrate, this grinding process could be carried out under an infrared lamp. The ground sample was uniformly dispersed in an alumina ceramic boat and pre-lithiated at 300 °C for 4 h. The powder treated in the previous step was washed with deionized water and centrifuged 6 times, 3 min each time, at a speed of 6000 rpm. The centrifuged powder was then dried in an oven at 60 °C for 12 h to obtain the pre-lithiated cathode powder, named SENCM. After SENCM was thoroughly ground in an agate mortar, SEBNCM was mixed with lithium carbonate (Li2CO3) at a molar ratio of 1:0.25 and ground in a mortar for 10 min. The mixture was then sintered in a muffle furnace at 850 °C for 6 h at a heating rate of 5 °C / min. The final regenerated positive electrode is abbreviated as RENCM.

[0080] To verify the effectiveness of this application, REBNCM obtained in Example 1 and RENCM obtained in the comparative example were assembled into button cells for electrochemical performance testing: First, RENCM or REBNCM, carbon black, and polyvinylidene fluoride were dissolved in N-methylpyrrolidone at a weight ratio of 8:1:1 to obtain a slurry; then, the slurry was coated onto aluminum foil, dried at 80°C for 6 hours, and then transferred to a vacuum drying oven and vacuum dried at 120°C for 12 hours to obtain a dried electrode; then, the dried electrode was punched into a circle with a diameter of 12 mm as the positive electrode, with an active material loading of 3-5 mg·cm³. -2 Commercial PP2500 separators were used, with a diameter of 19 mm. The battery casing was CR2032. Button cells were assembled in an argon-filled glove box, and half-cells were assembled using Li negative electrodes.

[0081] Electrochemical performance and scanning electron microscopy tests were conducted: long-cycle tests were performed at 2.5-4.3 V at a magnification of 0.5 C, and the microstructure of the regenerated cathode was observed using SEM.

[0082] Figure 1(a) shows the second charge-discharge curves of the degraded NCM523, the regenerated electrode with added lithium benzoate, and the regenerated electrode without added lithium benzoate at a 0.5 C rate. The discharge capacity of the degraded NCM523 at a 0.5 C rate is only 108.5 mAh / g. The discharge capacity of the regenerated cathode with added lithium benzoate at a 0.5 C rate can reach 148.7 mAh / g, while the regenerated cathode without added lithium benzoate only shows 136.2 mAh / g. This proves that the rapid Li-ionization process after adding lithium benzoate... + Transport kinetics enabled successful repair of the failed cathode. Figure 1(b) shows the long-cycle curves of the failed NCM523, the regenerated electrode with added lithium benzoate, and the regenerated electrode without added lithium benzoate at a rate of 0.5 C. The results show that the regenerated cathode of the lithium hydroxide-lithium nitrate molten salt system with added lithium benzoate exhibits good cycle stability in the voltage range of 2.5-4.3V, with capacity retention rates of 93.4%, 83.9%, and 70.1% after 100, 200, and 300 cycles, respectively, which are far superior to the regenerated cathode of the lithium hydroxide-lithium nitrate molten salt system without added lithium benzoate. Figure 1(c) shows the charge-discharge capacity decay of the regenerated electrode without added lithium benzoate. The regenerated cathode of the lithium hydroxide-lithium nitrate system without added lithium benzoate exhibits rapid capacity decay. Figure 1(d) shows the charge-discharge capacity decay of the regenerated electrode with added lithium benzoate. The regenerated cathode of the lithium hydroxide-lithium nitrate molten salt system with added lithium benzoate exhibited slow capacity decay after 200 cycles in the voltage range of 2.5-4.3V.

[0083] Figure 2(a) shows a schematic diagram of a scanning electron microscope (SEM) image of a half-cell assembled with RENCM, and Figure 2(b) shows a schematic diagram of a scanning electron microscope (SEM) image of a half-cell assembled with REBNCM. In the SEM images, the regenerated cathode particles of the lithium hydroxide-lithium nitrate molten salt system after adding lithium benzoate are intact and free of microcracks, while the regenerated cathode particles of the lithium hydroxide-lithium nitrate molten salt system without added lithium benzoate still show some microcracks, indicating that the repair is not complete.

[0084] like Figure 3 The diagram shown illustrates the principle of the direct regeneration method for the failed positive electrode in this application. Compared to the traditional direct regeneration method using lithium hydroxide and lithium nitrate molten salt, this method repairs the SNCM523 positive electrode by introducing lithium benzoate containing benzoate into the lithium hydroxide / lithium nitrate molten salt system. The addition of lithium benzoate fundamentally alters the original Li... +The transport mechanism transforms it from thermally driven disordered transport to a quasi-Grotthussian topological chemical transport mechanism facilitated by the benzoate ion in lithium benzoate, thereby realizing Li + Stable coupling and decoupling in molten salts to complete Li + The rapid "leap" in Li's development. This transformation facilitated Li's... + The rapid transport of these materials ensures sufficient lithiation of the failed cathode surface, thereby guaranteeing efficient reconstruction and repair of the failed cathode structure during the subsequent high-temperature calcination stage. Therefore, the cathode material synthesized using our proposed method exhibits excellent electrochemical performance, comparable to commercially available LiNi. 0.5 Co 0.2 Mn 0.3 Comparable to O2 (CNCM) cathodes, it provides a promising approach for the efficient and sustainable recycling of spent lithium-ion batteries.

[0085] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for direct regeneration of a failed positive electrode, characterized in that, include: A first mixture is obtained by mixing cathode black powder, lithium hydroxide, lithium nitrate and lithium benzoate; the addition ratio of cathode black powder, lithium hydroxide, lithium nitrate and lithium benzoate is set to 1: (0.2~0.25): (0.25~0.3): 0.5; The first mixture assembly is subjected to pre-lithiation treatment to obtain pre-lithiated cathode powder; the conditions for the pre-lithiation treatment by assembly include: holding at 300°C for 4~6 hours; The pre-lithiated cathode powder and lithium carbonate are mixed to obtain a second mixture; The second mixture is sintered to obtain a regenerated positive electrode.

2. The direct regeneration method for the failed positive electrode according to claim 1, characterized in that, After obtaining the first mixture, the process further includes: The first mixture was ground in an infrared environment.

3. The direct regeneration method for the failed positive electrode according to claim 1, characterized in that, Following the pre-lithiation treatment of the first mixture assembly, the process further includes: The pre-lithiated cathode powder was obtained by washing with deionized water and centrifuging multiple times, followed by drying. Grind the pre-lithiated cathode powder.

4. The direct regeneration method for the failed positive electrode according to claim 1, characterized in that, When mixing the pre-lithiated cathode powder and lithium carbonate, the ratio of the pre-lithiated cathode powder to lithium carbonate is 1:(0.25~0.5) molar ratio.

5. The direct regeneration method for the failed positive electrode according to claim 1, characterized in that, The conditions for sintering the second mixture include sintering at 750~850℃ for 6 hours.

6. The direct regeneration method for the failed positive electrode according to claim 5, characterized in that, During sintering at 750~850℃, the heating rate is 5~10℃ / min.

7. The direct regeneration method for the failed positive electrode according to claim 1, characterized in that, The cathode black powder is LiNi 0.5 Co 0.2 Mn 0.3 O2 Black Powder 8. A regenerated positive electrode prepared by a direct regeneration method of the failed positive electrode according to any one of claims 1 to 7.

Images