Positive electrode prelithiation material and preparation method thereof, positive electrode sheet and lithium ion battery

Abstract

The application provides a positive electrode pre-lithiation material and a preparation method thereof, a positive electrode sheet and a lithium ion battery. The preparation method comprises the following steps: performing heat treatment on a mixture of lithium powder and a sulfamate salt to obtain a positive electrode pre-lithiation material, wherein the positive electrode pre-lithiation material comprises a metal element, Li2O and Li2S; wherein the sulfamate salt is decomposed during the heat treatment; the metal element in the sulfamate salt and the metal element in the metal element are both Me, and Me is selected from one or more of the elements in the VIIB group and the VIII group. During the heat treatment, the lithium powder is molten, and at the same time, the sulfamate salt is decomposed into a metal oxide and a metal sulfide; the metal oxide and the metal sulfide can undergo a reverse conversion reaction with the lithium element and in-situ generate the metal element, Li2O and Li2S, thereby obtaining the positive electrode pre-lithiation material. The positive electrode pre-lithiation material has a high specific capacity, excellent stability and electrolyte compatibility.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery manufacturing technology, and more specifically, to a positive electrode pre-lithiation material and its preparation method, a positive electrode sheet, and a lithium-ion battery. Background Technology

[0002] Lithium-ion batteries are widely used in 3C electronics and large-scale electric and energy storage applications. Customer demand for high-energy-density lithium-ion batteries is constantly increasing, making improving their energy density a common goal for researchers in the industry. However, during the first charge of a lithium-ion battery, the electrolyte undergoes reduction and decomposition on the surface of the negative electrode, such as graphite, forming a solid electrolyte interphase (SEI) film. The formation of the SEI film permanently consumes a large amount of active lithium from the positive electrode, causing irreversible capacity loss. This results in a low initial coulombic efficiency (ICE) of the lithium-ion battery, further reducing its capacity and energy density. Simultaneously, as charge-discharge cycles continue, side reactions on the electrode surface increase, reducing active lithium and leading to poorer cycle performance. To address these issues, researchers have proposed pre-lithiation technology, which involves adding lithium to the battery before it begins operation to replenish lithium ions. Using this pre-lithiation technology to replenish lithium in the electrode material can offset some of the irreversible lithium loss caused by the formation of the SEI film, thereby improving the battery's total capacity, energy density, and cycle performance.

[0003] Existing lithium replenishment methods mainly include two types: positive electrode lithium replenishment and negative electrode lithium replenishment. Negative electrode lithium replenishment primarily uses lithium metal sheets, lithium metal powder, or lithium-containing compounds (such as Li-Si alloys, Li...). 2.6 Co 0.4 Lithium compensation is achieved through additives such as nitrogen (N). While these methods offer good lithium compensation, the materials used are highly reactive, have poor environmental stability, and are incompatible with existing negative electrode fabrication processes, requiring stringent production conditions. Compared to negative electrode lithium compensation, positive electrode lithium compensation is simpler and less expensive. It involves adding an additional lithium source during the positive electrode slurry preparation process. During battery charging, this source releases a large amount of active lithium, which is then embedded into the negative electrode, compensating for the irreversible loss of active lithium caused by SEI growth. Positive electrode lithium compensation is the most promising method for industrial application due to its high safety and good compatibility with existing lithium-ion battery manufacturing processes.

[0004] Currently, existing cathode lithium replenishment mainly uses lithium-rich materials, such as lithium-rich compounds like Li₂NiO₂ and Li₆CoO₄. However, these materials have relatively low specific capacity. Another type of replenishment material, such as lithium salts like Li₂C₄O₄, LiC₂O₂, Li₂C₃O₅, and Li₂C₄O₆, although having higher specific capacity, decomposes and generates gas during the first charge, which reduces the safety performance of lithium-ion batteries.

[0005] In summary, researching and developing a cathode pre-lithiation material with high specific capacity and good stability is of great significance for improving the energy density and cycle performance of lithium-ion batteries. Summary of the Invention

[0006] The main objective of this invention is to provide a positive electrode pre-lithiation material and its preparation method, a positive electrode sheet, and a lithium-ion battery, so as to solve the problems of low specific capacity and poor stability of the positive electrode pre-lithiation material in the prior art, and the low energy density and poor cycle performance of the lithium-ion battery prepared from it.

[0007] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a positive electrode pre-lithiation material, the method comprising: heating a mixture of lithium powder and aminosulfonate to obtain a positive electrode pre-lithiation material, the positive electrode pre-lithiation material comprising a metal element, Li2O and Li2S; wherein, during the heating process, the aminosulfonate decomposes; the metal element in the aminosulfonate and the metal element in the metal element are both Me, and Me is selected from one or more elements in Group VIIB and Group VIII.

[0008] This application involves heating a mixture of lithium powder and aminosulfonate containing Me element. The lithium powder contains ≥99wt% elemental lithium and the remainder is lithium carbonate. When heated, the lithium powder melts, and the aminosulfonate decomposes into metal oxides and metal sulfides. The generated metal oxides and metal sulfides can undergo a reverse reaction with elemental lithium to generate elemental metal (Me elemental), Li2O and Li2S in situ, thereby obtaining a positive electrode pre-lithiation material.

[0009] The pre-lithiation material for the cathode in this application is obtained based on a reverse lithiation reaction. It possesses high specific capacity, excellent stability, and electrolyte compatibility, while also being well-compatible with existing cathode manufacturing processes. When a cathode containing the aforementioned pre-lithiation material is applied to a lithium-ion battery, the pre-lithiation material releases a large amount of Li during the charging process. + It can compensate for the Li consumed during the first charge. + This can reduce the amount of positive active material in the positive electrode and Li in the negative electrode. +This reduces the consumption of lithium-ion batteries, thereby improving their energy density and cycle performance.

[0010] Compared to other types, the use of the specific type of Me element mentioned above in this application is conducive to the occurrence of the reverse reaction, making it easier to obtain a cathode pre-lithiation material containing elemental Me, Li2O and Li2S, thereby playing its role in lithium replenishment and improving the specific capacity and stability of the cathode pre-lithiation material.

[0011] Furthermore, Me is selected from one or more of Ni, Co, Fe and Mn; preferably, Me is Ni and / or Co.

[0012] Compared to other types, using the above-mentioned types of Me elements is beneficial for further improving the specific capacity and stability of cathode pre-lithiation materials.

[0013] Furthermore, the molar ratio of Li element in lithium powder to Me element in aminosulfonate is (10-15):1.

[0014] Compared to other ranges, limiting the molar ratio of Li in lithium powder to Me in aminosulfonate within the above range is beneficial to improving the efficiency of the reversal reaction, thereby improving the stability and lithium replenishment effect of the obtained cathode pre-lithiation material. It also helps to improve the utilization rate of raw materials and reduce production costs.

[0015] Furthermore, the D50 of the lithium powder is 0.1–10 μm.

[0016] Compared to other ranges, limiting the D50 of lithium powder to the above range is beneficial to improving the melting efficiency of lithium powder after heating, thereby further improving the efficiency of the reversal reaction.

[0017] Furthermore, the D50 of elemental metals is 20–200 nm, the D50 of Li₂O is 50–500 nm, and the D50 of Li₂S is 50–500 nm.

[0018] Compared to other ranges, limiting the D50 of elemental metals, Li₂O, and Li₂S to the above-mentioned ranges is beneficial for forming a uniformly mixed positive electrode pre-lithiation material, which in turn facilitates the release of more Li₂ during lithium-ion battery charging. + To compensate for the Li consumed during the first charge. + This will help improve the energy density and cycle performance of lithium-ion batteries.

[0019] Furthermore, the heating process is a laser beam irradiation process, preferably performed using a laser; preferably, the laser is a semiconductor laser; preferably, a galvanometer is used to adjust the exit angle of the laser beam so that the light rays in the laser beam are parallel to each other; more preferably, the power of the laser is 300-360W; more preferably, the longitudinal movement speed of the laser beam is 500-1000mm / s, the lateral movement speed is 10-80mm / s, and the spot diameter is ≥0.5mm; more preferably, the laser beam irradiation process is carried out in a protective gas atmosphere; even more preferably, the protective gas is selected from one or more of the group consisting of helium, argon, a mixture of xenon and radon, neon, and krypton.

[0020] Compared to other methods, the above-mentioned heating treatment method is beneficial to improving the efficiency of heating treatment, improving the efficiency of the reversal reaction, and also improving the purity of the cathode pre-lithiation material, reducing the impurity content, and thus improving the specific capacity and stability of the cathode pre-lithiation material.

[0021] Furthermore, the laser beam irradiation process is a multi-segment intermittent process; preferably, in the multi-segment intermittent process, the time of each laser beam irradiation process is 1 to 15 minutes, and the time interval between two adjacent laser beam irradiation processes is 0.5 to 5 minutes; more preferably, the mixture is stirred during the interval; even more preferably, the stirring rate is 50 to 300 rpm.

[0022] Compared to continuous laser beam irradiation, using multi-segment intermittent processing and limiting the process parameters of the laser beam irradiation process within the aforementioned range is beneficial for controlling the temperature during the heating process, suppressing the occurrence of side reactions caused by local overheating, thereby improving the efficiency of the heating process and, in turn, improving the efficiency of the reversible reaction.

[0023] Furthermore, the preparation method of the positive electrode pre-lithiation material also includes: mixing lithium powder with aminosulfonate to obtain a mixture; preferably, grinding is performed during the mixing process.

[0024] Compared to other methods, the above method is beneficial to improve the dispersibility of lithium powder and aminosulfonate, which in turn improves the melting efficiency of lithium powder and the decomposition efficiency of aminosulfonate, thereby improving the efficiency of the reversal reaction and obtaining positive electrode pre-lithiation materials.

[0025] To achieve the above objectives, a second aspect of this application also provides a positive electrode pre-lithiation material, which is prepared using the preparation method of the positive electrode pre-lithiation material provided in this application.

[0026] The cathode pre-lithiation material in this application includes elemental Me, Li₂O, and Li₂S, which possesses high specific capacity, excellent stability, and electrolyte compatibility, while also being compatible with existing cathode electrode manufacturing processes. When a cathode electrode containing the aforementioned pre-lithiation material is used in a lithium-ion battery, the pre-lithiation material can release a large amount of Li₂S during the lithium-ion battery charging process. + It can compensate for the Li consumed during the first charge. + This can reduce the amount of positive active material in the positive electrode and Li in the negative electrode. + This reduces the consumption of lithium-ion batteries, thereby improving their energy density and cycle performance.

[0027] To achieve the above objectives, a third aspect of this application also provides a positive electrode sheet, comprising a positive electrode active material, a binder, and a conductive agent, wherein the positive electrode active material includes a positive electrode material and the aforementioned positive electrode pre-lithiation material provided in this application.

[0028] When the positive electrode material and the aforementioned positive electrode pre-lithiation material provided in this application are used as positive electrode active materials in lithium-ion batteries, the aforementioned positive electrode pre-lithiation material can release a large amount of Li during the charging process of the lithium-ion battery. + It can compensate for the Li consumed during the first charge. + This can reduce the amount of positive active material in the positive electrode and Li in the negative electrode. + This reduces the consumption of lithium-ion batteries, thereby improving their energy density and cycle performance.

[0029] Furthermore, the cathode material is a ternary cathode material, with the general formula LiNi. x Co y Mn (1-x-y) O2, wherein 0.5≤x<1.0, 0<y≤0.2; preferably, the D50 of the positive electrode material is 2.5~12μm.

[0030] Compared to other types, using the above-mentioned ternary cathode materials and limiting their D50 to the above range is beneficial to improving the electrochemical performance of lithium-ion batteries, such as energy density and cycle performance.

[0031] Furthermore, the weight ratio of the pre-lithiated cathode material to the cathode material is (1-10):100.

[0032] Compared to other ranges, limiting the weight ratio of the cathode pre-lithiation material to the cathode material within the above range is beneficial for the cathode pre-lithiation material to release more Li during lithium-ion battery charging. + To compensate for the Li consumed during the first charge. + This further improves the energy density and cycle stability of lithium-ion batteries.

[0033] Furthermore, the weight ratio of the positive electrode active material, binder and conductive agent is (80-95):(2.5-10):(2.5-10).

[0034] Compared to other ranges, limiting the weight ratio of the positive electrode active material, binder and conductive agent to the above range is beneficial to exerting the electrochemical performance of the positive electrode material and improving the conductivity of the prepared positive electrode sheet.

[0035] Furthermore, the adhesive is selected from one or more of the group consisting of polyvinylidene fluoride, polytetrafluoroethylene, and polypropylene.

[0036] Compared to other types, using the above-mentioned type of binder is beneficial to improving the stability of the obtained positive electrode sheet.

[0037] Furthermore, the conductive agent is selected from one or more of the group consisting of superconducting carbon black, conductive graphite, carbon nanotubes, graphene, and carbon fibers.

[0038] Compared to other types, using the above-mentioned conductive agents is beneficial to improving the electronic conductivity, thereby improving the electrochemical performance of lithium-ion batteries.

[0039] Furthermore, the compaction density of the positive electrode sheet is 2.9–3.5 g / cm³. 3 .

[0040] Compared to other ranges, limiting the compaction density of the positive electrode sheet to the above range is beneficial to improving the electrochemical capacity and cycle stability of lithium-ion batteries.

[0041] To achieve the above objectives, a fourth aspect of this application also provides a lithium-ion battery, including a positive electrode, a negative electrode, an electrolyte, and a separator disposed between the positive electrode and the negative electrode; wherein the positive electrode includes the positive electrode sheet provided in this application.

[0042] When the above-mentioned positive electrode sheet and positive electrode material provided in this application are used as the positive electrode active material in a lithium-ion battery, the positive electrode pre-lithiation material in the positive electrode sheet can release a large amount of Li during the charging process of the lithium-ion battery. + To compensate for the Li consumed during the first charge. + This can reduce the amount of positive active material in the positive electrode and Li in the negative electrode. + This reduces the consumption of lithium-ion batteries, thereby improving their energy density and cycle performance. Attached Figure Description

[0043] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0044] Figure 1 The rate-cycle curves of the CR2016 coin cells prepared in Example 1 and Comparative Example 1 of this application are shown. Detailed Implementation

[0045] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0046] As described in the background section, existing cathode pre-lithiation materials suffer from low specific capacity and poor stability, resulting in low energy density and poor cycle performance in lithium-ion batteries made from them. To address these technical problems, this application provides a method for preparing a cathode pre-lithiation material. The method includes: heating a mixture of lithium powder and aminosulfonate to obtain the cathode pre-lithiation material, wherein the cathode pre-lithiation material comprises a metallic element, Li₂O, and Li₂S; wherein the aminosulfonate decomposes during the heating process; and both the metallic element in the aminosulfonate and the metallic element in the metallic element are Me, with Me selected from one or more elements in Groups VIIB and VIII.

[0047] This application involves heating a mixture of lithium powder and aminosulfonate containing Me element. The lithium powder contains ≥99wt% elemental lithium and the remainder is lithium carbonate. When heated, the lithium powder melts, and the aminosulfonate decomposes into metal oxides and metal sulfides. The generated metal oxides and metal sulfides can undergo a reverse reaction with elemental lithium to generate elemental metal (Me elemental), Li2O and Li2S in situ, thereby obtaining a positive electrode pre-lithiation material.

[0048] The cathode pre-lithiation material in this application is obtained based on a reverse oxidation reaction and includes elemental Me, Li₂O, and Li₂S. It possesses high specific capacity, excellent stability, and electrolyte compatibility, while also being well-compatible with existing cathode electrode manufacturing processes. When cathode electrodes containing the aforementioned pre-lithiation material are used in lithium-ion batteries, the pre-lithiation material releases a large amount of Li₂ during the charging process. + It can compensate for the Li consumed during the first charge. + This can reduce the amount of positive active material in the positive electrode and Li in the negative electrode. + This reduces the consumption of lithium-ion batteries, thereby improving their energy density and cycle performance.

[0049] Compared to other types, the use of the specific type of Me element in this application is conducive to the occurrence of the reversal reaction, making it easier to obtain a cathode pre-lithiation material with higher specific capacity, thereby playing its role in lithium replenishment and improving the specific capacity and stability of the cathode pre-lithiation material.

[0050] To further improve the specific capacity and stability of the prepared cathode pre-lithiation material, thereby further enhancing its lithium replenishment function, preferably, Me includes, but is not limited to, one or more of Ni, Co, Fe and Mn.

[0051] To further improve the specific capacity and stability of the prepared cathode pre-lithiation material, and thus further enhance its lithium replenishment function, more preferably, Me includes, but is not limited to, Ni and / or Co.

[0052] In a preferred embodiment, the molar ratio of Li in the lithium powder to Me in the aminosulfonate is (10-15):1. The molar ratio of Li in the lithium powder to Me in the aminosulfonate includes, but is not limited to, the range described above. Limiting it to this range is beneficial for improving the efficiency of the reversal reaction, thereby improving the stability and lithium replenishment effect of the obtained cathode pre-lithiation material. It also helps to improve the utilization rate of raw materials and reduce production costs.

[0053] In order to improve the melting efficiency of lithium powder after heating, and thus further improve the efficiency of the reversal reaction, preferably, the D50 of lithium powder is 0.1 to 10 μm.

[0054] In a preferred embodiment, the D50 of the elemental metal is 20–200 nm, the D50 of Li₂O is 50–500 nm, and the D50 of Li₂S is 50–500 nm. The D50 of the elemental metal, Li₂O, and Li₂S includes, but is not limited to, the above ranges. Limiting them to these ranges facilitates the formation of a uniformly mixed cathode pre-lithiation material, improves the specific capacity and stability of the cathode pre-lithiation material, and thus promotes the release of more Li₂ during lithium-ion battery charging. + To compensate for the Li consumed during the first charge. + This helps reduce the amount of positive electrode active material and negative electrode Li in the positive electrode. + This reduces the consumption of lithium-ion batteries, which in turn helps improve their energy density and cycle performance.

[0055] During the emission of a laser beam, electrons undergo transitions and fall back, a process accompanied by energy conversion and release, resulting in the instantaneous release of a large amount of heat. In a preferred embodiment, the heat treatment process is a laser beam irradiation process, preferably performed using a laser. Compared to other methods, using the above-described method for heat treatment improves the efficiency of the heat treatment, thereby improving the efficiency of the reversal reaction and facilitating the production of pre-lithiated cathode materials; it also improves the safety of the heat treatment process.

[0056] To further improve the energy utilization rate of the laser beam, further improve the efficiency of the laser beam irradiation process, and thus further improve the efficiency of the reversal reaction, preferably, the laser is a semiconductor laser, and a galvanometer is used to adjust the exit angle of the laser beam in the semiconductor laser so that the light rays in the laser beam are parallel to each other.

[0057] To further improve the efficiency of the laser beam irradiation process, and thus further improve the efficiency of the reversal reaction, preferably, the laser power is 300-360W, the longitudinal movement speed of the laser beam is 500-1000mm / s, the lateral movement speed is 10-80mm / s, and the spot diameter is ≥0.5mm.

[0058] In a preferred embodiment, the laser beam irradiation process is carried out in a protective gas atmosphere. Irradiating the laser beam in a protective gas atmosphere helps suppress side reactions between lithium powder and air during the melting process, thereby improving the purity of the cathode pre-lithiation material, reducing impurity content, and ultimately improving the specific capacity and stability of the cathode pre-lithiation material.

[0059] To further suppress side reactions between lithium powder and air during the melting process and to further improve the purity of the cathode pre-lithiation material, preferably, the protective gas includes, but is not limited to, one or more of the group consisting of helium, argon, a mixture of xenon and radon, neon and krypton.

[0060] In order to carry out the laser beam irradiation process in a protective gas atmosphere, thereby further improving the processing efficiency and the purity of the positive electrode pre-lithiation material, it is more preferable to use a glove box laser integrated instrument for heating treatment, wherein the water content in the glove box is ≤0.01ppm and the oxygen content is ≤0.01ppm.

[0061] In a preferred embodiment, the laser beam irradiation process is a multi-segment intermittent process. Compared to continuous laser beam irradiation, multi-segment intermittent processing facilitates temperature control during the heating process, helps suppress side reactions caused by local overheating, thereby improving the efficiency of the heating process and, consequently, the efficiency of the reversible reaction.

[0062] In order to further control the temperature during the laser beam irradiation process within a more suitable range, thereby further suppressing the occurrence of side reactions caused by local overheating and further improving the efficiency of the reversal reaction, preferably, in the multi-segment intermittent processing, the time of each laser beam irradiation process is 1 to 15 minutes, and the time interval between two adjacent laser beam irradiation processes is 0.5 to 5 minutes.

[0063] In a preferred embodiment, the mixture is stirred during the intervals. Stirring during the intervals between each processing cycle helps to ensure more uniform heating of the lithium powder and aminosulfonate mixture, helps to suppress local overheating that could lead to other side reactions, and thus improves the safety of the reaction; it also helps to improve the dispersibility of lithium powder and aminosulfonate, and improves the melting efficiency of lithium powder and the decomposition efficiency of aminosulfonate, thereby improving the efficiency of the reversal reaction.

[0064] To ensure more uniform heating of the mixture of lithium powder and aminosulfonate, and to further improve the dispersibility of lithium powder and aminosulfonate, further improve the melting efficiency of lithium powder and the decomposition efficiency of aminosulfonate, thereby further improving the efficiency of the reversal reaction, the stirring rate is preferably 50-300 rpm.

[0065] In a preferred embodiment, the preparation method of the cathode pre-lithiation material further includes: mixing lithium powder with aminosulfonate to obtain a mixture. Pre-mixing lithium powder and aminosulfonate before heat treatment is beneficial to improving the dispersibility of lithium powder and aminosulfonate, thereby improving the melting efficiency of lithium powder and the decomposition efficiency of aminosulfonate, which in turn is beneficial to improving the efficiency of the reversal reaction and obtaining the cathode pre-lithiation material.

[0066] To further improve the dispersibility of lithium powder and aminosulfonate, thereby further improving the melting efficiency of lithium powder and the decomposition efficiency of aminosulfonate, and further improving the efficiency of the reversal reaction, grinding is preferably performed during the mixing process.

[0067] The second aspect of this application also provides a positive electrode pre-lithiation material, which is prepared by the preparation method of the positive electrode pre-lithiation material provided in this application.

[0068] The cathode pre-lithiation material in this application includes elemental Me, Li₂O, and Li₂S, which possesses high specific capacity, excellent stability, and electrolyte compatibility, while also being compatible with existing cathode electrode manufacturing processes. When a cathode electrode containing the aforementioned pre-lithiation material is used in a lithium-ion battery, the pre-lithiation material can release a large amount of Li₂S during the lithium-ion battery charging process. + It can compensate for the Li consumed during the first charge. +This can reduce the amount of positive active material in the positive electrode and Li in the negative electrode. + This reduces the consumption of lithium-ion batteries, thereby improving their energy density and cycle performance.

[0069] A third aspect of this application also provides a positive electrode sheet, which includes a positive electrode active material, a binder, and a conductive agent, wherein the positive electrode active material includes a positive electrode material and the aforementioned positive electrode pre-lithiation material provided in this application.

[0070] The positive electrode active material in the positive electrode sheet provided in this application includes the positive electrode material and the aforementioned positive electrode pre-lithiation material. The aforementioned positive electrode pre-lithiation material has high specific capacity, excellent stability, and electrolyte compatibility. It is also well compatible with existing positive electrode sheet manufacturing processes. When used together with the positive electrode material as the positive electrode active material in lithium-ion batteries, the aforementioned positive electrode pre-lithiation material can release a large amount of Li during the charging process of the lithium-ion battery. + It can compensate for the Li consumed during the first charge. + This can reduce the amount of positive active material in the positive electrode and Li in the negative electrode. + This reduces the consumption of lithium-ion batteries, thereby improving their energy density and cycle performance.

[0071] In a preferred embodiment, the cathode material is a ternary cathode material with the general formula LiNi. x Co y Mn (1-x-y) O2, where 0.5 ≤ x < 1.0, 0 < y ≤ 0.2. Compared to other types of cathode materials, using the above-mentioned ternary cathode material is beneficial for improving the energy density and cycle performance of lithium-ion batteries.

[0072] In order to enable the positive electrode pre-lithiation material to release more Li during the charging process of lithium-ion batteries + To compensate for the Li consumed during the first charge. + This further improves the energy density and cycle stability of lithium-ion batteries. Preferably, the weight ratio of the pre-lithiated cathode material to the cathode material is (1-10):100.

[0073] To increase the specific surface area of ​​the cathode material and to improve the mixing uniformity of the cathode material and the cathode pre-lithiation material, preferably, the D50 of the cathode material is 2.5 to 12 μm.

[0074] In a preferred embodiment, the weight ratio of the positive electrode active material, binder, and conductive agent is (80–95):(2.5–10):(2.5–10). The weight ratio of the positive electrode active material, binder, and conductive agent includes, but is not limited to, the above range. Limiting it to this range is beneficial for improving the conductivity of the prepared positive electrode sheet, for maximizing the electrochemical performance of the positive electrode material, and thus for improving the energy density and cycle performance of the lithium-ion battery.

[0075] In order to improve the stability of the layer formed by the positive electrode active material, thereby improving the stability of the positive electrode sheet, in a preferred embodiment, the binder includes, but is not limited to, one or more of the group consisting of polyvinylidene fluoride, polytetrafluoroethylene and polypropylene.

[0076] In a preferred embodiment, the conductive agent includes, but is not limited to, one or more of the group consisting of superconducting carbon black (Super P), conductive graphite, carbon nanotubes, graphene, and carbon fibers. Compared to other types, using the above-mentioned conductive agents is beneficial for improving electronic conductivity, thereby improving the charge and discharge efficiency of lithium-ion batteries, and further improving the electrochemical performance of lithium-ion batteries. The conductive graphite mentioned in this application can be KS-6 (manufacturer: TMEGO, Switzerland).

[0077] In a preferred embodiment, the compaction density of the positive electrode sheet is 2.9–3.5 g / cm³. 3 The compaction density of the positive electrode sheet includes, but is not limited to, the ranges mentioned above. Limiting it to these ranges is beneficial for improving the electrochemical capacity and cycle stability of lithium-ion batteries.

[0078] The fourth aspect of this application also provides a method for preparing the above-mentioned positive electrode sheet provided in this application. The preparation method includes: step S1, mixing a positive electrode active material, a binder, a conductive agent and a solvent to obtain a positive electrode slurry, wherein the positive electrode active material includes a positive electrode material and the above-mentioned positive electrode pre-lithiation material provided in this application; step S2, coating the positive electrode slurry onto the surface of a current collector to obtain a positive electrode slurry layer; step S3, drying and pressing the positive electrode slurry layer sequentially to obtain a positive electrode sheet.

[0079] In the method for preparing the positive electrode sheet of this application, a positive electrode slurry containing a positive electrode pre-lithiation material is obtained through step S1, coated onto the surface of a current collector in step S2, and then dried and pressed (e.g., roll pressing and slicing) in step S3 to obtain the positive electrode sheet. The positive electrode pre-lithiation material provided in this application has high specific capacity, excellent stability, and electrolyte compatibility. It is also well compatible with the preparation method of the positive electrode sheet described in this application. When used as the positive electrode active material in lithium-ion batteries, the positive electrode pre-lithiation material can release a large amount of Li during the charging process of the lithium-ion battery.+ It can compensate for the Li consumed during the first charge. + This can reduce the amount of positive active material in the positive electrode and Li in the negative electrode. + This reduces the consumption of lithium-ion batteries, thereby improving their energy density and cycle performance.

[0080] The solvents used in this application can be of types commonly used in the art. In a preferred embodiment, the solvent includes, but is not limited to, one or more of the group consisting of N-methylpyrrolidone, N,N-dimethylacetamide, dimethyl sulfoxide, tetramethylurea, and trimethyl phosphate.

[0081] In a preferred embodiment, the solid content of the positive electrode slurry is 30-50 wt%. The solid content of the positive electrode slurry includes, but is not limited to, the above range, and limiting it within the above range facilitates its subsequent coating on the surface of the current collector.

[0082] To improve the uniformity of the positive electrode slurry coating on the current collector surface and to increase the electrochemical capacity of the lithium-ion battery, the coating thickness of the positive electrode slurry is preferably 100–400 μm.

[0083] In a preferred embodiment, the coating amount of the positive electrode slurry per unit area is 70–150 g / cm². 2 The coating amount per unit area of ​​the positive electrode slurry includes, but is not limited to, the range described above. Limiting it to the range described above is beneficial for improving the electrochemical capacity, energy density, and cycle performance of lithium-ion batteries.

[0084] In order to improve the electrochemical performance of lithium-ion batteries, in a preferred embodiment, the current collector is aluminum foil, preferably with a thickness of 6 to 20 μm.

[0085] In a preferred embodiment, the drying in step S3 is vacuum drying, preferably with a vacuum degree ≤500 Pa. Compared to atmospheric pressure drying, vacuum drying is beneficial for improving drying efficiency and solvent removal rate in the positive electrode slurry layer, thus facilitating subsequent pressing and molding.

[0086] To further improve the solvent removal rate in the positive electrode slurry layer, preferably, the drying temperature is 80-120°C and the drying time is 12-24 hours.

[0087] The fifth aspect of this application also provides a lithium-ion battery, including a positive electrode, a negative electrode, an electrolyte, and a separator disposed between the positive electrode and the negative electrode, wherein the positive electrode includes the positive electrode sheet provided in this application.

[0088] The positive electrode active material in the positive electrode sheet provided in this application includes the positive electrode pre-lithiation material provided in this application. The positive electrode pre-lithiation material in this application has high specific capacity, excellent stability, and electrolyte compatibility. It is also well compatible with existing positive electrode sheet manufacturing processes. When used as the positive electrode active material in lithium-ion batteries, along with the positive electrode material, it can release a large amount of Li during the charging process of the lithium-ion battery. + It can compensate for the Li consumed during the first charge. + This can reduce the amount of positive active material in the positive electrode and Li in the negative electrode. + This reduces the consumption of lithium-ion batteries, thereby improving their energy density and cycle performance.

[0089] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0090] It should be noted that the positive electrode pre-lithiation materials in all embodiments of this application were prepared using a glove box laser integrated instrument (Wuhan Zhonggu Lianchuang Optoelectronic Technology Co., Ltd., ZG-1GY-500 / 700B). The glove box was in an argon atmosphere with a water content ≤0.01ppm and an oxygen content ≤0.01ppm.

[0091] Example 1

[0092] A method for preparing a positive electrode sheet specifically includes the following steps:

[0093] (1) Weigh 2g of cobalt aminosulfonate (CAS No.: 14017-41-5) and 0.6g of lithium powder (D50 is 5μm, purity is 99.8wt%) in a glove box and grind them in a mortar to obtain a mixture;

[0094] (2) Transfer all of the above mixture to a quartz crucible and use a semiconductor laser in a glove box to perform three-stage intermittent heating treatment on the mixture. The power of the semiconductor laser is 350W, the longitudinal movement speed of the laser beam is 1000mm / s, the lateral movement speed is 50mm / s, and the spot diameter is 0.5mm. After the first stage of heating treatment lasts for 10min, heating is stopped and the mixture is stirred at 300rpm for 1min before starting the second stage of heating treatment. After the second stage of heating treatment lasts for 5min, heating is stopped and the mixture is stirred at 150rpm for 1min before starting the third stage of heating treatment. After the third stage of heating treatment lasts for 3min, heating is stopped and the mixture is stirred at 50rpm for 1min before ending the reaction, and a positive electrode pre-lithiation material including elemental Co, Li2O and Li2S is obtained.

[0095] In the positive electrode pre-lithiation material obtained in step (2), the D50 of elemental Co is 50 nm, the D50 of Li2O is 200 nm, and the D50 of Li2S is 200 nm.

[0096] (3) Weigh out 0.1g of the pre-lithiated cathode material obtained in step (2) and 4.9g of the ternary cathode material LiNi. 0.7 Co 0.1 Mn 0.2 O2 (the preparation method of this ternary cathode material can be found in patent CN111777104A), and the two are mixed evenly to obtain the cathode active material;

[0097] (4) The above positive electrode active material, superconducting carbon black (Swiss Temiko, SUPER PLI) and polyvinylidene fluoride (PVDF) were mixed with N-methylpyrrolidone (NMP) solution in a weight ratio of 90:5:5. After stirring at 25°C for 2 hours, a positive electrode slurry with a solid content of 45wt% was obtained.

[0098] (5) The above positive electrode slurry is coated on one side surface of a 20μm thick aluminum foil to obtain a positive electrode slurry layer, wherein the coating thickness of the slurry is 400μm;

[0099] (6) The above-mentioned positive electrode slurry layer was dried in a vacuum oven at 110°C for 20 hours, and then rolled and sliced ​​to obtain a positive electrode sheet with a compaction density of 3.5 g / cm³. 3 .

[0100] Example 2

[0101] The difference from Example 1 is that in step (1), 1.5g of nickel aminosulfonate (CAS No.: 13770-89-3) and 1.0g of lithium powder are weighed in a glove box and ground in a mortar to obtain a mixture. The remaining steps are the same as in Example 1.

[0102] The cathode pre-lithiation material prepared in Example 2 includes elemental Ni, Li2O and Li2S, wherein the D50 of elemental Ni is 100 nm, the D50 of Li2O is 200 nm and the D50 of Li2S is 200 nm.

[0103] Example 3

[0104] The difference from Example 1 is that in step (1), 3.3g of cobalt aminosulfonate, 1.5g of nickel aminosulfonate and 2g of lithium powder are weighed in a glove box and ground in a mortar to obtain a mixture. The remaining steps are the same as in Example 1.

[0105] The cathode pre-lithiation material prepared in Example 3 includes elemental Co, elemental Ni, Li2O and Li2S, wherein the D50 of elemental Co is 50 nm, the D50 of elemental Ni is 100 nm, the D50 of Li2O is 200 nm and the D50 of Li2S is 200 nm.

[0106] Example 4

[0107] The difference from Example 1 is that in step (1), an equimolar amount of ferrous aminosulfonate (CAS No.: 14017-39-1) is used to replace cobalt aminosulfonate, and the remaining steps are the same as in Example 1.

[0108] The cathode pre-lithiation material prepared in Example 4 includes elemental Fe, Li2O and Li2S, wherein the D50 of elemental Fe is 20 nm, the D50 of Li2O is 50 nm and the D50 of Li2S is 50 nm.

[0109] Example 5

[0110] The difference from Example 1 is that the molar ratio of Co in cobalt sulfamate to Li in lithium powder in step (1) is 1:10, and the rest of the steps are the same as in Example 1.

[0111] Example 6

[0112] The difference from Example 1 is that the molar ratio of Co in cobalt aminosulfonate to Li in lithium powder in step (1) is 1:15, and the rest of the steps are the same as in Example 1.

[0113] Example 7

[0114] The difference from Example 1 is that the molar ratio of Co in cobalt sulfamate to Li in lithium powder in step (1) is 1:20, and the rest of the steps are the same as in Example 1.

[0115] Example 8

[0116] The difference from Example 1 is that in step (2), a semiconductor laser in the glove box is used to perform two-stage intermittent heating treatment on the mixture. The power of the semiconductor laser is 300W, the longitudinal movement speed of the laser beam is 500mm / s, the lateral movement speed is 10mm / s, and the spot diameter is 0.8mm. The heating is stopped after the first stage of heating treatment lasts for 15 minutes, and the second stage of heating treatment is started after stirring at a rate of 200rpm for 1 minute. The heating is stopped after the second stage of heating treatment lasts for 5 minutes, and the reaction is ended after stirring at a rate of 100rpm for 1 minute. The remaining steps are the same as in Example 1.

[0117] Example 9

[0118] The difference from Example 1 is that in step (2), the mixture is continuously irradiated with a semiconductor laser in the glove box, the irradiation is stopped after 18 minutes, and the reaction is ended after stirring at a rate of 300 rpm for 1 minute. The remaining steps are the same as in Example 1.

[0119] Example 10

[0120] The difference from Example 1 is that in step (2), the power of the semiconductor laser is 250W, the longitudinal movement speed of the laser beam is 300mm / s, the lateral movement speed is 5mm / s, and the spot diameter is 0.4mm. The remaining steps are the same as in Example 1.

[0121] Example 11

[0122] The difference from Example 1 is that in step (3), 0.25g of the pre-lithiation material of the cathode obtained in step (2) and 4.75g of the ternary cathode material LiNi are weighed. 0.7 Co 0.1 Mn 0.2 After O2 is mixed evenly, the positive electrode active material is obtained, and the remaining steps are the same as in Example 1.

[0123] Example 12

[0124] The difference from Example 1 is that in step (3), 0.45g of the pre-lithiation material of the cathode obtained in step (2) and 4.55g of the ternary cathode material LiNi are weighed. 0.7 Co 0.1 Mn 0.2 After O2 is mixed evenly, the positive electrode active material is obtained, and the remaining steps are the same as in Example 1.

[0125] Example 13

[0126] The difference from Example 1 is that in step (3), 1g of the positive electrode pre-lithiation material obtained in step (2) and 4g of the ternary positive electrode material LiNi are weighed. 0.7 Co 0.1 Mn 0.2 After O2 is mixed evenly, the positive electrode active material is obtained, and the remaining steps are the same as in Example 1.

[0127] Comparative Example 1

[0128] The difference from Example 1 is that steps (1) and (2) are omitted, and in step (3) 5g of ternary cathode material LiNi is used. 0.7 Co 0.1 Mn 0.2 O2 is used as the positive electrode active material, meaning that no positive electrode pre-lithiation material is added to the positive electrode active material, and the remaining steps are the same as in Example 1.

[0129] Comparative Example 2

[0130] The difference from Example 1 is that steps (1) and (2) are omitted, and in step (3) an equal amount of Co / Li2O is used to replace the positive electrode pre-lithiation material. The remaining steps are the same as in Example 1.

[0131] Comparative Example 3

[0132] The difference from Example 1 is that steps (1) and (2) are omitted, and an equal amount of Co / Li2S is used to replace the positive electrode pre-lithiation material in step (3). The remaining steps are the same as in Example 1.

[0133] Using the positive electrode sheets prepared in Examples 1 to 13 and Comparative Examples 1 to 3 of this application as positive electrodes, lithium metal sheets as negative electrodes, 1.0 mol / L LiPF6 / EC+DEC+EMC as electrolyte, and a separator prepared by a wet process as a separator, CR2016 coin cells were assembled and their electrochemical performance was tested after standing for 4 hours.

[0134] The following performance tests were performed on the CR2016 coin cells prepared in all embodiments and comparative examples of this application:

[0135] (1) The test conditions for the first charge specific capacity and the first coulombic efficiency are as follows: constant current charging at a rate of 0.2C, with a voltage range of 2.8 to 4.5V;

[0136] (2) The test conditions for the first discharge specific capacity and the 0.2C return test specific capacity are as follows: constant current discharge at 0.2C rate, voltage range of 2.8 to 4.5V;

[0137] (3) The test conditions for 1C discharge specific capacity are as follows: constant current discharge at 1C rate, voltage range of 2.8 to 4.5V;

[0138] (4) The test conditions for capacity retention are as follows: 1C rate, 25℃, voltage range of 2.8~4.5V, 50 cycles.

[0139] The test results are shown in Table 1. The rate-cycle curves of the CR2016 coin cells prepared in Example 1 and Comparative Example 1 are shown in the figure below. Figure 1 As shown, by Figure 1 It can be seen that the CR2016 coin cell prepared in Example 1 has better cycle performance.

[0140] Table 1

[0141]

[0142] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0143] Compared to existing cathode materials, the pre-lithiation cathode material provided in this application has a higher mass energy density and volumetric energy density, which are more than four times that of existing cathode materials. Furthermore, it exhibits a significant charge / discharge voltage hysteresis; when the voltage reaches 3V during charging, Li… + It can almost completely decouple at this voltage, which is within the upper limit voltage range of the ternary cathode material, while the discharge voltage range is 1.2–0.01V. This voltage is lower than the lower limit voltage of the ternary cathode material, thus the large voltage hysteresis provides a large amount of Li to the ternary cathode material. + Used to compensate for the Li consumed in the formation of the SEI film. + When used in lithium-ion batteries, along with the cathode material, as the positive electrode active material, only 1-10 wt% of the above-mentioned pre-lithiation material is needed to offset the initial Li loss. Correspondingly, the mass energy density and volumetric energy density of the lithium-ion battery can be increased by 8-13% and 11-14%, respectively.

[0144] Comparing Example 1 and Comparative Example 1, it can be seen that, compared to Comparative Example 1, the CR2016 coin cell prepared in Example 1 has an increased initial charge capacity (0.2C) of 9.6 mAh / g, while the discharge capacity remains basically the same, and the capacity retention rate is improved by 9%. This demonstrates that when the positive electrode pre-lithiation material and positive electrode material of this application are used as positive electrode active materials in lithium-ion batteries, the positive electrode pre-lithiation material can release a large amount of Li during the charging process of the lithium-ion battery. + It can compensate for the Li consumed during the first charge. + This can reduce the amount of positive active material in the positive electrode and Li in the negative electrode. + This reduces energy consumption, thereby improving the energy density and cycle performance of lithium-ion batteries.

[0145] Comparing Example 1 with Comparative Examples 2 and 3, it can be seen that, compared to cathode pre-lithiation materials containing only elemental Co and Li₂O or elemental Co and Li₂S, the cathode pre-lithiation material prepared in Example 1, which includes elemental Co, Li₂O, and Li₂S, exhibits higher initial charge capacity and capacity retention. This demonstrates that the cathode pre-lithiation material described in this application possesses higher specific capacity, better stability, and electrolyte compatibility. When applied to lithium-ion batteries, it can release more Li₂S during the lithium-ion battery charging process. + To compensate for the Li consumed during the first charge. + This can reduce the amount of positive active material in the positive electrode and Li in the negative electrode. + This reduces the consumption of lithium-ion batteries, thereby improving their energy density and cycle performance.

[0146] Comparing Examples 1 to 4 and Comparative Examples 1 to 3, it can be seen that, compared with other types, the use of the specific type of Me element in this application is conducive to the occurrence of the reversal reaction, and it is easier to obtain a positive electrode pre-lithiation material containing elemental Me, Li2O and Li2S, which is conducive to exerting its lithium replenishment function, and thus conducive to improving the energy density and cycle performance of lithium-ion batteries.

[0147] Comparing Examples 1, 5 to 7, it can be seen that, compared with other ranges, limiting the molar ratio of Li element in lithium powder to Me element in aminosulfonate within the range described above in this application is beneficial to improving the efficiency of the reversal reaction, thereby improving the lithium replenishment effect of the obtained positive electrode pre-lithiation material, and further improving the cycle performance of lithium-ion batteries.

[0148] Comparing Examples 1, 8 to 10, it can be seen that, compared with continuous laser beam irradiation, using multi-segment intermittent processing and limiting the process parameters of each segment to the range described above in this application is beneficial for controlling the temperature during the heating process, suppressing the occurrence of side reactions caused by local overheating, improving the efficiency of the heating process, thereby improving the efficiency of the reversal reaction, and further improving the lithium replenishment effect of the obtained cathode pre-lithiation material.

[0149] Comparing Examples 1, 11 to 13, it can be seen that the weight ratio of the cathode pre-lithiation material to the ternary cathode material includes, but is not limited to, the range described above. Limiting it to the range described above is beneficial for the cathode pre-lithiation material to release more Li during the lithium-ion battery charging process. + To compensate for the Li consumed during the first charge. + This helps improve the cycle performance of lithium-ion batteries.

[0150] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0151] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a positive electrode pre-lithiation material, characterized in that, The method for preparing the cathode pre-lithiation material includes: heating a mixture of lithium powder and metal aminosulfonate to obtain the cathode pre-lithiation material, wherein the cathode pre-lithiation material includes elemental metals, Li2O, and Li2S; wherein the metal aminosulfonate decomposes during the heating process; the metal element in the metal aminosulfonate and the metal element in the elemental metal are both Me, and the Me is selected from one or more of Ni, Co, Fe, and Mn.

2. The method for preparing the positive electrode pre-lithiation material according to claim 1, characterized in that, The molar ratio of Li element in the lithium powder to Me element in the metal aminosulfonate is (10-15):1; The lithium powder has a D50 of 0.1–10 μm; The D50 of the metallic element is 20-200 nm, the D50 of Li2O is 50-500 nm, and the D50 of Li2S is 50-500 nm.

3. The method for preparing the positive electrode pre-lithiation material according to claim 2, characterized in that, The Me is selected from Ni and / or Co.

4. The method for preparing the positive electrode pre-lithiation material according to claim 1, characterized in that, The heat treatment process is a laser beam irradiation process, and the laser beam irradiation is performed using a laser. The laser is a semiconductor laser; a galvanometer is used to adjust the exit angle of the laser beam so that the light rays in the laser beam are parallel to each other.

5. The method for preparing the positive electrode pre-lithiation material according to claim 4, characterized in that, The power of the laser is 300-360W; the longitudinal movement speed of the laser beam is 500-1000mm / s, the lateral movement speed is 10-80mm / s, and the spot diameter is ≥0.5mm. The laser beam irradiation process is carried out in a protective gas atmosphere; the protective gas is selected from one or more of the group consisting of helium, argon, a mixture of xenon and radon, neon and krypton.

6. The method for preparing the positive electrode pre-lithiation material according to claim 4, characterized in that, The laser beam irradiation process is a multi-segment intermittent process; In the multi-segment intermittent processing, the duration of each laser beam irradiation process is 1 to 15 minutes, and the interval between two adjacent laser beam irradiation processes is 0.5 to 5 minutes. The mixture is stirred during the interval; the stirring rate is 50 to 300 rpm.

7. The method for preparing the positive electrode pre-lithiation material according to any one of claims 1 to 6, characterized in that, The preparation method of the positive electrode pre-lithiation material further includes: mixing the lithium powder with the metal aminosulfonate to obtain the mixture; and grinding is performed during the mixing process.

8. A positive electrode pre-lithiation material, characterized in that, The positive electrode pre-lithiation material is prepared by the method for preparing the positive electrode pre-lithiation material according to any one of claims 1 to 7.

9. A positive electrode sheet, characterized in that, The positive electrode sheet includes a positive electrode active material, a binder, and a conductive agent. The positive electrode active material includes a positive electrode material and the positive electrode pre-lithiation material as described in claim 8.

10. The positive electrode sheet according to claim 9, characterized in that, The cathode material is a ternary cathode material with the general formula LiNi. x Co y Mn (1-x-y) O2, where 0.5 ≤ x < 1.0, 0 < y ≤ 0.2; The weight ratio of the pre-lithiation material to the cathode material is (1-10):100; The D50 of the cathode material is 2.5–12 μm.

11. The positive electrode sheet according to claim 9 or 10, characterized in that, The weight ratio of the positive electrode active material, the binder, and the conductive agent is (80-95):(2.5-10):(2.5-10). The adhesive is selected from one or more of the group consisting of polyvinylidene fluoride, polytetrafluoroethylene and polypropylene; The conductive agent is selected from one or more of the group consisting of superconducting carbon black, conductive graphite, carbon nanotubes, graphene, and carbon fibers.

12. The positive electrode sheet according to claim 11, characterized in that, The compaction density of the positive electrode sheet is 2.9–3.5 g / cm³. 3 .

13. A lithium-ion battery, comprising a positive electrode, a negative electrode, an electrolyte, and a separator disposed between the positive electrode and the negative electrode, characterized in that, The positive electrode comprises the positive electrode sheet according to any one of claims 9 to 12.

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