Preparation method and application of positive electrode lithium supplement agent

Abstract

The invention discloses a preparation method and application of a positive electrode lithium supplement agent, the positive electrode lithium supplement agent is of a core-shell structure, and a core layer comprises lithium-rich metal materials such as lithium-rich lithium ferrite, lithium-rich lithium nickelate and lithium-rich lithium manganate; and a shell layer comprises organic lithium salt materials such as lithium bis (oxalato) borate, lithium bis (fluorosulfonyl) imide, lithium difluorophosphate and lithium difluorobis (oxalato) phosphate. The lithium-rich metal material lithium supplementing agent is coated with the organic lithium salt lithium supplementing agent which is also used as the lithium supplementing agent, so that the lithium-rich metal material is prevented from being in contact with air, and the environmental stability of the lithium-rich metal material is improved; through chelation of specific groups and transition metal ions, the structural stability of the lithium-rich metal material is improved, a lithium ion transmission path is fixed, the capacity of the lithium supplement agent for the lithium-rich metal material can be exerted to the maximum extent, and the organic lithium salt also has a lithium supplement effect, so that the migration rate of lithium ions can be further improved, and the lithium supplement effect is improved. The lithium supplementing effect of the two lithium supplementing agents greatly improves the energy density and the cycling stability of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to a preparation method and application of a positive electrode lithium supplement. Background Art

[0002] Driven by the dual carbon goals, the emergence of portable electronic devices and electric vehicles has created a huge demand for high-energy-density lithium-ion batteries. With the increasing installed capacity, the market has put forward higher safety and economic requirements for lithium-ion batteries. The commonly used positive electrode materials for energy storage lithium-ion batteries currently have the problem of limited theoretical capacity. During the first charge and discharge process of lithium-ion batteries, the electrolyte will undergo irreversible decomposition, and the electrolyte interface (SEI film) formed on the surface of the negative electrode will lead to irreversible loss of active lithium, resulting in battery capacity loss, manifested as lower initial coulombic efficiency and energy density, and affecting the battery's cycle performance. Reducing the impact of irreversible active lithium loss during the first charge and discharge process is the key to improving technical indicators such as battery energy density and cycle life. The pre-lithiation / lithium replenishment strategy based on additional active lithium supplementation compensates for the irreversible loss of active lithium in the battery, helps to maximize the energy density of high-capacity electrodes, and achieves improvements in battery coulombic efficiency and cycle life performance.

[0003] Lithium-ion battery lithium replenishment technologies can be categorized as either negative or positive electrode replenishment, depending on the battery manufacturing process. Compared to negative electrode replenishment, which involves complex processes and safety risks, positive electrode replenishment can compensate for irreversible active lithium loss by directly adding a positive electrode replenisher during the preparation of the positive electrode slurry. The positive electrode replenisher decomposes and releases active lithium, thereby compensating for irreversible active lithium loss. Positive electrode replenishers offer excellent lithium replenishment performance and are highly compatible with existing lithium-ion battery manufacturing processes, providing a novel solution for the commercialization of lithium-ion battery replenishment technology.

[0004] Currently, lithium-rich metal oxide cathode rechargers face the following core issues: 1) Insufficient cycling stability: During long charge and discharge cycles, the material is prone to irreversible phase transitions and lattice oxygen precipitation, leading to structural collapse and capacity decay; 2) Severe interfacial side reactions: Continuous side reactions between the highly active surface and the electrolyte form a thick and uneven CEI film, exacerbating lithium ion transport impedance; and 3) Oxygen release safety hazards: During deep delithiation, lattice oxygen release can trigger thermal runaway, threatening battery safety. Therefore, it is necessary to provide an improved cathode recharger preparation method and application to address these issues. Summary of the Invention

[0005] The purpose of the present invention is to address the deficiencies of the existing technology and provide a preparation method and application technology of a positive electrode lithium replenisher. The positive electrode lithium replenisher prepared by the present invention has high stability and high ionic conductivity, can release sufficient lithium ions to replenish the lithium ions consumed during the cycle, has excellent lithium replenishment effect, and can effectively improve the battery's initial coulombic efficiency and long-cycle performance.

[0006] To achieve the above objectives, the preparation method of the positive electrode lithium supplement agent proposed in the present invention comprises the following steps: (1) dissolving an organic lithium salt lithium supplement in a solvent, wherein the organic lithium salt lithium supplement includes one or more of lithium dioxalatoborate (LiBOB), lithium bis(fluorosulfonyl)imide (LiFSI), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalatophosphate (LiDODFP), and lithium difluorooxalatoborate (LiODFB); the solvent includes diethyl ether (C4H 10 O), anisole (C7H8O), isobutyl isobutyrate (C8H 16 O2), xylene (C8H 10 ), dimethyl carbonate (C3H6O3), diethyl carbonate (C5H 10 O3), one or more of propylene carbonate; (2) Weigh a certain amount of lithium-rich metal material lithium supplement and mix it evenly with the organic lithium salt solvent; (3) Drying the obtained slurry to obtain a positive electrode lithium replenisher with uniform particles, wherein the positive electrode lithium replenisher has a core-shell structure, the core layer is a lithium-rich metal material, and the shell layer is an organic lithium salt.

[0007] In the step (2), the lithium-rich metal material lithium supplement includes lithium-rich lithium ferrite (Li5FeO4)‌, lithium-rich lithium nickelate (Li 1.2 Ni 0.8 O2), lithium-rich lithium manganese oxide (xLi2MnO3·LiNi 0.33 Co 0.33 Mn 0.33 O2, 0<x≤1) one or more. Particle size is in the range of 1-100000 nm.

[0008] The steps (1) to (3) are all carried out in a protective gas atmosphere.

[0009] Preferably, in step (1), the dissolution method of the organic lithium salt lithium supplement includes one or more of stirring, heating, and ultrasound, and the concentration of the solvent is 20-60 mg / ml.

[0010] Preferably, the positive electrode lithium supplement agent obtained in step (3) has a particle size of less than 10 μm and a shell thickness of 25-30 nm.

[0011] Preferably, in step (2), the mass ratio of the lithium-rich metal material lithium replenisher to the organic lithium salt lithium replenisher is 1:0.1-0.5.

[0012] Preferably, 0.01-5 wt% of a conductive agent is added during the mixing process of step (2) to construct an organic lithium salt coating layer with good conductivity, wherein the conductive agent includes one or more of Super P, Ketjen black, acetylene black, graphene, carbon nanotubes, and carbon nanofibers.

[0013] The mixing equipment includes planetary ball mill, high-speed mixer, oblique mixer, vibrator, homogenizer and other mixing equipment.

[0014] Preferably, in step (3), the drying method includes one or more of conventional drying, vacuum drying, freeze drying, and forced air drying, and the drying time is 2-24 h.

[0015] A positive electrode plate, comprising: uniformly mixing a positive electrode lithium replenisher, a positive electrode active material, an electrolyte, and conductive carbon obtained by any of the above methods; adding a binder solution to prepare a slurry; wet coating, and then drying to obtain the positive electrode plate, wherein the positive electrode active material is at least one of lithium iron phosphate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide; the conductive carbon comprises at least one of Super P, Ketjen black, acetylene black, graphene, carbon nanotubes, and carbon nanofibers; the electrolyte comprises one or more of a sulfide electrolyte, a halide electrolyte, a polymer electrolyte, and an oxide electrolyte; the binder comprises one or more of SEBS, SES, SEPS, SBR, PVDF, PIB, EVA, NMP, and CMC; and the mass ratio of the positive electrode lithium replenisher, the positive electrode active material, the electrolyte, and the conductive agent is (1-20):(70-90):(20-30):(1-5).

[0016] Preferably, the concentration of the binder solvent is 20-75 mg / ml, the solid content of the slurry is 40-75 wt %, the wet coating speed of the positive electrode slurry is 0.1-1 cm / s, and the coating thickness is 50-400 μm.

[0017] A lithium-ion battery is provided, which is formed by assembling the positive electrode sheet, electrolyte and negative electrode described in any one of the above items together and finally encapsulating them in a battery casing.

[0018] Among them, the electrolyte is one of a solid electrolyte, a liquid electrolyte, and a semi-solid electrolyte, and the negative electrode is one of negative electrode materials such as lithium indium, lithium, nano-silicon, micron silicon, silicon carbon, etc.

[0019] Preferably, the assembly steps of the battery are: pressurizing the positive electrode sheet, electrolyte and negative electrode by 0.5-5 t to obtain a three-layer structure, and finally encapsulating it with a battery shell to form a lithium-ion battery.

[0020] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects: (1) The positive electrode lithium replenisher material prepared by the present invention has uniform particles, improved air stability and structural stability, which greatly improves the positive electrode lithium replenishment effect during the cycle process and improves the first cycle performance and long cycle stability of the battery.

[0021] (2) The preparation method of the battery disclosed in the present invention has a simple process flow and has the advantages of high energy density and high safety.

[0022] (3) The preparation method of the present invention has the advantage of large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the SEM morphology of the positive electrode lithium supplement prepared in Example 1; Figure 2 This is the particle size distribution diagram of the positive electrode lithium supplement prepared in Example 1; Figure 3 This is the impedance diagram of the positive electrode lithium replenisher coated with lithium-rich nickelate prepared in Example 4. DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention.

[0025] Example 1 (1) dissolving the organic lithium salt lithium supplement in a solvent; LiFSI was dissolved in xylene solvent at a concentration of 30 mg / ml and stirred at 80 °C for 6 h.

[0026] (2) Weigh a certain amount of lithium-rich metal material lithium supplement and mix it evenly with the organic lithium salt solvent; Weigh 1 g of lithium-rich ferrite material, 0.1 g of carbon nanotubes, and 6.665 ml of organic lithium salt solvent, using a mass ratio of 1:0.2 for the lithium-rich ferrite supplement: the organic lithium salt supplement. Place the mixture in a ball mill with a ball-to-material ratio of 20:1 and mill for 3 hours at a speed of 400 rpm.

[0027] (3) drying the obtained slurry to obtain a positive electrode lithium supplement with uniform particles; The obtained slurry was placed in a freeze dryer at -60°C for 24 h. The particles of the positive electrode lithium supplement agent were uniform (<10 μm) and the coating layer thickness was 25 nm. Figure 1 and Figure 2 . Figure 2This is the particle size distribution diagram of the prepared positive electrode lithium replenisher. It can be seen that the size of the positive electrode lithium replenisher is uniform, and most of the particles are below 10 μm; (4) The positive electrode lithium supplement, positive electrode active material, electrolyte and conductive carbon are mixed evenly, a binder solvent is added to prepare a slurry, and the slurry is wet-coated and then dried to obtain a positive electrode sheet; According to the mass ratio of the positive electrode lithium supplement (LiFSI + carbon nanotubes + lithium-rich lithium iron oxide), the positive electrode active material (lithium nickel cobalt manganese oxide), the electrolyte (LLZO), and the conductive carbon (VGCF) of 5:70:24:1, a total mass of 2 g of the composite positive electrode was weighed, 4% by mass of the binder solvent was added, and the mixture was mixed in a homogenizer for 10 min. The positive electrode slurry was placed on a wet coater and wet-coated at a speed of 1 cm / s and a coating thickness of 200 μm. After drying for 12 h, the wet positive electrode sheet was obtained.

[0028] (5) Assemble the prepared positive electrode sheet, electrolyte and negative electrode together, and finally encapsulate them in a battery shell to form an all-solid-state ion battery.

[0029] The positive electrode sheet and electrolyte powder are sequentially added to the mold, pressurized to 3.5 tons. A lithium-indium negative electrode is attached to the electrolyte and pressurized to 0.5 tons to obtain a three-layer structure. This is then transferred to the battery case and assembled at a pressure of 1.0 tons to obtain a lithium-ion solid-state battery.

[0030] Example 2 (1) dissolving the organic lithium salt lithium supplement in a solvent; LiFSI was dissolved in xylene solvent at a concentration of 30 mg / ml and stirred at 80 °C for 6 h.

[0031] (2) Weigh a certain amount of lithium-rich metal material lithium supplement and mix it evenly with the organic lithium salt solvent; Weigh 1 g of the lithium-rich ferrite material and 6.665 ml of the organic lithium salt solvent, using a mass ratio of 1:0.2 for the lithium-rich ferrite supplement: the organic lithium salt supplement. Place the mixture in a ball mill with a ball-to-material ratio of 20:1 and mill for 3 hours at a speed of 400 rpm.

[0032] (3) drying the obtained slurry to obtain a positive electrode lithium supplement with uniform particles; The obtained slurry was placed in a freeze dryer at -60°C for 24 h. The particles of the positive electrode lithium supplement agent were uniform (<10 μm) and the coating layer thickness was 25 nm.

[0033] (4) The positive electrode lithium supplement, positive electrode active material, electrolyte and conductive carbon are mixed evenly, a binder solvent is added to prepare a slurry, and the slurry is wet-coated and then dried to obtain a positive electrode sheet; According to the mass ratio of the positive electrode lithium supplement (LiFSI + lithium-rich lithium iron oxide), the positive electrode active material (lithium nickel cobalt manganese oxide), the electrolyte (LLZO), and the conductive carbon (VGCF) of 5:70:24:1, a total mass of 2 g of the composite positive electrode was weighed, 4% by mass of the binder solvent was added, and the mixture was mixed in a homogenizer for 10 min. The positive electrode slurry was placed on a wet coater and wet-coated at a speed of 1 cm / s and a coating thickness of 200 μm. After drying for 12 h, the wet positive electrode sheet was obtained.

[0034] (5) Assemble the prepared positive electrode sheet, electrolyte and negative electrode together, and finally encapsulate them in a battery shell to form an all-solid-state ion battery.

[0035] The positive electrode sheet and electrolyte powder are sequentially added to the mold, pressurized to 3.5 tons. A lithium-indium negative electrode is attached to the electrolyte and pressurized to 0.5 tons to obtain a three-layer structure. This is then transferred to the battery case and assembled at a pressure of 1.0 tons to obtain a lithium-ion solid-state battery.

[0036] Example 3 (1) dissolving the organic lithium salt lithium supplement in a solvent; LiPO2F2 was dissolved in diethyl carbonate solvent at a concentration of 40 mg / ml and sonicated for 12 h.

[0037] (2) Weigh a certain amount of lithium-rich metal material lithium supplement and mix it evenly with the organic lithium salt solvent; Weigh 1 g of the lithium-rich ferrite material and 2.5 ml of the organic lithium salt solvent, using a mass ratio of 1:0.1 for the lithium-rich ferrite supplement: the organic lithium salt supplement. Place the mixture in a ball mill with a ball-to-material ratio of 30:1 and mill for 3 hours at a speed of 300 rpm.

[0038] (3) drying the obtained slurry to obtain a positive electrode lithium supplement with uniform particles; The obtained slurry was placed in a vacuum dryer for 24 h. The particles of the positive electrode lithium supplement agent were about 80 μm and the coating layer thickness was 30 nm.

[0039] (4) The positive electrode lithium supplement, positive electrode active material, electrolyte and conductive carbon are mixed evenly, a binder solvent is added to prepare a slurry, and the slurry is wet-coated and then dried to obtain a positive electrode sheet; According to the mass ratio of the positive electrode lithium supplement (LiPO2F2 + lithium-rich lithium iron oxide), the positive electrode active material (lithium iron phosphate), the electrolyte (Li6PS5Cl), and the conductive carbon (VGCF) of 5:70:24:1, a total mass of 2 g of the composite positive electrode was weighed, 4% by mass of the binder solvent was added, and the mixture was mixed in a homogenizer for 10 min. The positive electrode slurry was placed on a wet coater and wet-coated at a speed of 1 cm / s and a coating thickness of 200 μm. After drying for 12 h, the wet positive electrode sheet was obtained.

[0040] (5) Assemble the prepared positive electrode sheet, electrolyte and negative electrode together, and finally encapsulate them in a battery shell to form an all-solid-state ion battery.

[0041] The positive electrode sheet, electrolyte, and nano-silicon negative electrode are sequentially added to the mold and pressurized to 1.0 tons to obtain a three-layer structure. This is then transferred to the battery case and assembled at a pressure of 0.5 tons to obtain a lithium-ion liquid battery.

[0042] Example 4 (1) dissolving the organic lithium salt lithium supplement in a solvent; LiBOB was dissolved in propylene carbonate solvent at a concentration of 35 mg / ml and stirred at 60 °C for 12 h.

[0043] (2) Weigh a certain amount of lithium-rich metal material lithium supplement and mix it evenly with the organic lithium salt solvent; Weigh 1 g of lithium-rich nickelate and 4.285 ml of organic lithium salt solvent, using a mass ratio of 1:0.15. Place the mixture in a high-speed mixer and mill at 2000 rpm for 3 minutes.

[0044] (3) drying the obtained slurry to obtain a positive electrode lithium supplement with uniform particles; The obtained slurry was placed in a blast dryer for 24 h. The particles of the positive electrode lithium supplement agent were about 20 μm and the coating layer thickness was 8-15 nm. Figure 3 The impedance diagram of the positive electrode lithium supplement coated with lithium nickel oxide is shown in Figure 2. The ionic conductivity is calculated to be 1.26×10 −6 S / cm.

[0045] (4) The positive electrode lithium supplement, positive electrode active material, electrolyte and conductive carbon are mixed evenly, a binder solvent is added to prepare a slurry, and the slurry is wet-coated and then dried to obtain a positive electrode sheet; According to the mass ratio of the positive electrode lithium supplement (LiBOB + lithium-rich nickel oxide), the positive electrode active material (lithium cobalt oxide), the electrolyte (Li6PS5Cl), and the conductive carbon (VGCF) of 5:70:24:1, a total mass of 2 g of the composite positive electrode was weighed, 5% by mass of the binder solvent was added, and the mixture was mixed in a homogenizer for 10 min. The positive electrode slurry was placed on a wet coater and wet-coated at a speed of 1 cm / s and a coating thickness of 200 μm. After drying for 12 h, the wet positive electrode sheet was obtained.

[0046] (5) Assemble the prepared positive electrode sheet, electrolyte and negative electrode together, and finally encapsulate them in a battery shell to form an all-solid-state ion battery.

[0047] The positive electrode sheet, electrolyte powder, and silicon-carbon are sequentially added to the mold and pressurized to 1.0 tons to obtain a three-layer structure. This is then transferred to the battery case and assembled at a pressure of 0.5 tons to obtain a lithium-ion solid-state battery.

[0048] Comparative Example 1 (1) dissolving the organic lithium salt lithium supplement in a solvent; LiFSI was dissolved in xylene solvent at a concentration of 30 mg / ml and stirred at 80 °C for 6 h.

[0049] (2) Weigh a certain amount of lithium-rich metal material lithium supplement and mix it evenly with the organic lithium salt solvent; Weigh 1 g of lithium-rich ferrite material, 0.1 g of carbon nanotubes, and 6.665 ml of organic lithium salt solvent, using a mass ratio of 1:0.2 for the lithium-rich ferrite supplement: the organic lithium salt supplement. Place the mixture in a ball mill with a ball-to-material ratio of 20:1 and mill for 3 hours at a speed of 400 rpm.

[0050] (3) drying the obtained slurry to obtain a positive electrode lithium supplement with uniform particles; The obtained slurry was placed in a dryer at 60°C for 24 h. The particle size of the positive electrode lithium supplement agent was about 50 μm and the coating layer thickness was 20 nm.

[0051] (4) The positive electrode lithium supplement, positive electrode active material, electrolyte and conductive carbon are mixed evenly, a binder solvent is added to prepare a slurry, and the slurry is wet-coated and then dried to obtain a positive electrode sheet; According to the mass ratio of the positive electrode lithium supplement (LiFSI + carbon nanotubes + lithium-rich lithium iron oxide), the positive electrode active material (lithium nickel cobalt manganese oxide), the electrolyte (LLZO), and the conductive carbon (VGCF) of 0.05:0.7:0.24:0.01, a total mass of 2 g of the composite positive electrode was weighed, 4% by mass of the binder solvent was added, and the mixture was mixed in a homogenizer for 10 min. The positive electrode slurry was placed on a wet coater and wet-coated at a speed of 1 cm / s and a coating thickness of 200 μm. After drying for 12 h, the wet positive electrode sheet was obtained.

[0052] (5) Assemble the prepared positive electrode sheet, electrolyte and negative electrode together, and finally encapsulate them in a battery shell to form an all-solid-state ion battery.

[0053] The positive electrode sheet and electrolyte powder are sequentially added to the mold, pressurized to 3.5 tons. A lithium-indium negative electrode is attached to the electrolyte and pressurized to 0.5 tons to obtain a three-layer structure. This is then transferred to the battery case and assembled at a pressure of 1.0 tons to obtain a lithium-ion solid-state battery.

[0054] Comparative Example 2 (1) dissolving the organic lithium salt lithium supplement in a solvent; LiFSI was dissolved in xylene solvent at a concentration of 30 mg / ml and stirred at 80 °C for 6 h.

[0055] (2) Weigh a certain amount of lithium-rich metal material lithium supplement and mix it evenly with the organic lithium salt solvent; Weigh 1 g of the lithium-rich ferrite material and 6.665 ml of the organic lithium salt solvent, using a mass ratio of 1:0.2 for the lithium-rich ferrite supplement: the organic lithium salt supplement. Place the mixture in a ball mill with a ball-to-material ratio of 20:1 and mill for 3 hours at a speed of 400 rpm.

[0056] (3) drying the obtained slurry to obtain a positive electrode lithium supplement with uniform particles; The obtained slurry was placed in a dryer at 60°C for 24 h. The particle size of the positive electrode lithium supplement agent was about 50 μm and the coating layer thickness was 20 nm.

[0057] (4) The positive electrode lithium supplement, positive electrode active material, electrolyte and conductive carbon are mixed evenly, a binder solvent is added to prepare a slurry, and the slurry is wet-coated and then dried to obtain a positive electrode sheet; According to the mass ratio of the positive electrode lithium supplement (LiFSI + lithium-rich lithium iron oxide), the positive electrode active material (lithium nickel cobalt manganese oxide), the electrolyte (LLZO), and the conductive carbon (VGCF) of 0.05:0.7:0.24:0.01, a total mass of 2 g of the composite positive electrode was weighed, 4% by mass of the binder solvent was added, and the mixture was mixed in a homogenizer for 10 min. The positive electrode slurry was placed on a wet coater and wet-coated at a speed of 1 cm / s and a coating thickness of 200 μm. After drying for 12 h, the wet positive electrode sheet was obtained.

[0058] (5) Assemble the prepared positive electrode sheet, electrolyte and negative electrode together, and finally encapsulate them in a battery shell to form an all-solid-state ion battery.

[0059] The positive electrode sheet and electrolyte powder are sequentially added to the mold, pressurized to 3.5 tons. A lithium-indium negative electrode is attached to the electrolyte and pressurized to 0.5 tons to obtain a three-layer structure. This is then transferred to the battery case and assembled at a pressure of 1.0 tons to obtain a lithium-ion solid-state battery.

[0060] Comparative Example 3 (1) dissolving the organic lithium salt lithium supplement in a solvent; LiPO2F2 was dissolved in diethyl carbonate solvent at a concentration of 40 mg / ml and sonicated for 12 h.

[0061] (2) Weigh a certain amount of lithium-rich metal material lithium supplement and mix it evenly with the organic lithium salt solvent; Weigh 1 g of the lithium-rich ferrite material and 2.5 ml of the organic lithium salt solvent, using a mass ratio of 1:0.1 for the lithium-rich ferrite supplement: the organic lithium salt supplement. Place the mixture in a ball mill with a ball-to-material ratio of 30:1 and mill for 1 hour at a speed of 200 rpm.

[0062] (3) drying the obtained slurry to obtain a positive electrode lithium supplement with uniform particles; The obtained slurry was placed in a vacuum dryer for 24 h. The particle size of the positive electrode lithium supplement agent was about 90 μm and the coating layer thickness was 15 nm.

[0063] (4) The positive electrode lithium supplement, positive electrode active material, electrolyte and conductive carbon are mixed evenly, a binder solvent is added to prepare a slurry, and the slurry is wet-coated and then dried to obtain a positive electrode sheet; According to the mass ratio of the positive electrode lithium supplement (LiPO2F2 + lithium-rich lithium iron oxide), the positive electrode active material (lithium iron phosphate), the electrolyte (Li6PS5Cl), and the conductive carbon (VGCF) of 0.05:0.7:0.24:0.01, a total mass of 2 g of the composite positive electrode was weighed, and a 4% mass ratio of the binder solvent was added. The mixture was mixed in a homogenizer for 10 min, and the positive electrode slurry was placed on a wet coater and wet-coated at a speed of 1 cm / s and a coating thickness of 200 μm. After drying for 12 h, the wet positive electrode sheet was obtained.

[0064] (5) Assemble the prepared positive electrode sheet, electrolyte and negative electrode together, and finally encapsulate them in a battery shell to form an all-solid-state ion battery.

[0065] The positive electrode sheet, electrolyte, and nano-silicon negative electrode are sequentially added to the mold and pressurized to 1.0 tons to obtain a three-layer structure. This is then transferred to the battery case and assembled at a pressure of 0.5 tons to obtain a lithium-ion liquid battery.

[0066] Comparative Example 4 (1) dissolving the organic lithium salt lithium supplement in a solvent; LiBOB was dissolved in propylene carbonate solvent at a concentration of 35 mg / ml and stirred at 60 °C for 12 h.

[0067] (2) Weigh a certain amount of lithium-rich metal material lithium supplement and mix it evenly with the organic lithium salt solvent; Weigh 1 g of lithium-rich nickelate and 4.285 ml of organic lithium salt solvent, using a mass ratio of 1:0.15. Place the mixture in a high-speed mixer and mill at 1000 rpm for 3 minutes.

[0068] (3) drying the obtained slurry to obtain a positive electrode lithium supplement with uniform particles; The obtained slurry was placed in a blast dryer for 24 h. The particle size of the positive electrode lithium supplement agent was about 100 μm, and the coating layer thickness was 1-5 nm.

[0069] (4) The positive electrode lithium supplement, positive electrode active material, electrolyte and conductive carbon are mixed evenly, a binder solvent is added to prepare a slurry, and the slurry is wet-coated and then dried to obtain a positive electrode sheet; According to the mass ratio of the positive electrode lithium supplement (LiBOB + lithium-rich lithium nickel oxide), the positive electrode active material (lithium cobalt oxide), the electrolyte (Li6PS5Cl), and the conductive carbon (VGCF) of 0.05:0.7:0.24:0.01, a total mass of 2 g of the composite positive electrode was weighed, 5% by mass of the binder solvent was added, and the mixture was mixed in a homogenizer for 10 min. The positive electrode slurry was placed on a wet coater and wet-coated at a speed of 1 cm / s and a coating thickness of 200 μm. After drying for 12 h, the wet positive electrode sheet was obtained.

[0070] (5) Assemble the prepared positive electrode sheet, electrolyte and negative electrode together, and finally encapsulate them in a battery shell to form an all-solid-state ion battery.

[0071] The positive electrode sheet, electrolyte powder, and silicon-carbon are sequentially added to the mold and pressurized to 1.0 tons to obtain a three-layer structure. This is then transferred to the battery case and assembled at a pressure of 0.5 tons to obtain a lithium-ion solid-state battery.

[0072] Performance test: Table 1 below shows the positive electrode lithium supplement and battery performance data of these examples and comparative examples.

[0073] Table 1 Performance diagram of examples and comparative examples In summary, by comparing Example 1 and Example 2, and Comparative Example 1 and Comparative Example 2, it can be seen that introducing an appropriate amount of conductive agent into the organic lithium supplement coating layer helps to improve the first cycle performance and cycle stability of the battery, because a good conductive transmission network is constructed.

[0074] Comparing Example 2 with Comparative Example 2 shows that the freeze-drying technique significantly reduces the size of the positive electrode lithium replenisher compared to Comparative Example 2, resulting in a better coating effect and an 8.6% increase in the 200-cycle retention rate. This is because the reduced size of the positive electrode lithium replenisher (<10 μm) improves the positive electrode interface contact and facilitates lithium ion release, facilitating positive electrode lithium replenishment. Furthermore, the effective control of the shell thickness (25-30 nm) improves the stability of the positive electrode lithium replenisher and further enhances the long-cycle performance of the battery.

[0075] By comparing Example 3 and Comparative Example 3, and Example 4 and Comparative Example 4, it can be seen that the time and rotation speed of mechanical mixing have a significant effect on the particle size. The less energy input for mechanical activation leads to larger particle size, which further affects the speed of lithium removal, resulting in a significant decrease in the first charge gram capacity and coulombic efficiency compared to the corresponding examples.

[0076] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a positive electrode lithium supplement, characterized in that: The method comprises the following steps: (1) dissolving an organic lithium salt lithium supplement in a solvent, wherein the organic lithium salt lithium supplement includes one or more of lithium dioxalatoborate, lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, lithium difluorodioxalatophosphate, and lithium difluorooxalatoborate; and the solvent includes one or more of ethyl ether, anisole, isobutyl isobutyrate, xylene, dimethyl carbonate, diethyl carbonate, and propylene carbonate; (2) Weighing a certain amount of a lithium-rich metal material lithium replenisher and mixing it evenly with an organic lithium salt solvent, wherein the lithium-rich metal material lithium replenisher includes one or more of lithium-rich lithium ferrite, lithium-rich lithium nickelate, and lithium-rich lithium manganate; (3) Drying the obtained slurry to obtain a positive electrode lithium replenisher with uniform particles, wherein the positive electrode lithium replenisher has a core-shell structure, the core layer is a lithium-rich metal material, and the shell layer is an organic lithium salt.

2. The method for preparing a positive electrode lithium supplement according to claim 1, wherein: In the step (1), the dissolution method of the organic lithium salt lithium supplement includes one or more of stirring, heating, and ultrasound, and the concentration of the solvent is 20-60 mg / ml.

3. The method for preparing a positive electrode lithium supplement according to claim 1, wherein: The positive electrode lithium supplement agent obtained in step (3) has a particle size of <10 μm and a shell thickness of 25-30 nm.

4. The method for preparing a positive electrode lithium supplement according to claim 1, wherein: In the step (2), the mass ratio of the lithium-rich metal material lithium replenisher to the organic lithium salt lithium replenisher is 1:0.1-0.

5.

5. The method for preparing a positive electrode lithium supplement according to claim 1, wherein: A conductive agent is added during the mixing process of step (2) to construct an organic lithium salt coating layer with good conductivity, wherein the conductive agent includes one or more of Super P, Ketjen black, acetylene black, graphene, carbon nanotubes, and carbon nanofibers.

6. The method for preparing a positive electrode lithium supplement according to claim 1, wherein: In step (3), the drying method includes one or more of conventional drying, vacuum drying, freeze drying, and forced air drying, and the drying time is 2-24 h.

7. A positive electrode plate, characterized in that: The positive electrode lithium replenisher, positive electrode active material, electrolyte and conductive carbon prepared by the method according to any one of claims 1 to 6 are uniformly mixed, a binder solution is added to prepare a slurry, wet-coated and then dried to obtain the positive electrode sheet, wherein the positive electrode active material is at least one of lithium iron phosphate, lithium cobalt oxide, lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide; the conductive carbon includes at least one of Super P, Ketjen black, acetylene black, graphene, carbon nanotubes and carbon nanofibers; the electrolyte includes one or more of a sulfide electrolyte, a halide electrolyte, a polymer electrolyte and an oxide electrolyte; the binder includes one or more of SEBS, SES, SEPS, SBR, PVDF, PIB, EVA, NMP and CMC; the mass ratio of the positive electrode lithium replenisher, the positive electrode active material, the electrolyte and the conductive agent is (1-20): (70-90): (20-30): (1-5).

8. The positive electrode sheet according to claim 7, characterized in that: The concentration of the binder solvent is 20-75 mg / ml, the solid content of the slurry is 40-75 wt%, the wet coating speed of the positive electrode slurry is 0.1-1 cm / s, and the coating thickness is 50-400 μm.

9. A lithium-ion battery, characterized in that: The positive electrode sheet, electrolyte and negative electrode according to claim 7 or 8 are assembled together, and finally packaged with a battery shell to form the lithium-ion battery.

10. The lithium-ion battery according to claim 9, characterized in that The battery assembly steps are: pressurize the positive electrode, electrolyte and negative electrode by 0.5-5 tons to obtain a three-layer structure, and finally encapsulate it in a battery shell to form a lithium-ion battery.

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