Lithium battery preparation method with directional electrolyte permeation and lithium ion battery

Abstract

The invention provides a preparation method of a lithium battery with directional permeation of an electrolyte and the lithium battery, and the preparation method of the lithium battery with directional permeation of the electrolyte comprises the following steps: preparing a silicon carbon electrode with a three-dimensional gradient pore structure, the three-dimensional gradient pore structure consists of a surface-layer straight-through hole, a middle-layer tree-shaped branch hole and a bottom-layer liquid storage cavity which are communicated and have gradually increased radial sizes in a gradient manner; assembling the silicon-carbon electrode and the shell to form a battery cell, and then placing the battery cell in a gradient magnetic field environment with intensity in gradient distribution; adding a magnetic additive into the electrolyte, and injecting the electrolyte into the battery cell; carrying out temperature and pressure synergistic loading circulation on the electrolyte in the battery cell and the silicon carbon electrode; and packaging to obtain the lithium battery. The electrolyte is subjected to three-dimensional cooperation through structure guiding, magnetic force driving of a gradient magnetic field environment and temperature and pressure loading regulation and control, so that the electrolyte directionally permeates in the silicon carbon electrode, the speed of the electrolyte infiltrating the silicon carbon electrode is increased, and then efficient permeation of the electrolyte to the silicon carbon electrode is achieved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of lithium-ion batteries, and in particular to a method for preparing a lithium-ion battery with directional electrolyte infiltration and a lithium-ion battery. Background Art

[0002] With the rapid development of the electric vehicle and energy storage industries, the demand for high-energy-density lithium-ion batteries continues to rise. Silicon-carbon anode materials, with theoretical specific capacities far exceeding those of traditional graphite (approximately 10 times), have become a key option for breaking through the 400Wh / kg energy density bottleneck. The high surface area and porous structure of silicon-carbon anodes present significant challenges to the electrolyte infiltration process. Whether the electrolyte can quickly and evenly penetrate deep into the electrode pores directly determines lithium-ion transmission efficiency, interfacial stability, and battery cycle life.

[0003] The electrolyte infiltration process mostly uses a vacuum immersion method, which relies on a negative pressure environment to promote the slow penetration of the electrolyte into the electrode pores. For graphite anodes, its pore structure is relatively simple and uniform, with a pore diameter of approximately 50-100nm and an infiltration time of approximately 2-4 hours. However, the composite characteristics of the silicon particles and carbon matrix of the silicon-carbon anode make the pore structure of the silicon-carbon anode complex and diverse, with both nano-scale micropores and submicron-scale channels. This coexistence of multi-scale pores leads to significant differences in the electrolyte penetration rate under the traditional vacuum method. The large channels are quickly filled while the micropores have residual air resistance, resulting in a measured pore filling rate of less than 85% (mercury intrusion data), and the proportion of local dry areas exceeds 15%. The silicon particles of the silicon-carbon anode are prone to pre-reaction with the electrolyte during the infiltration process, forming a non-uniform passivation layer, which further hinders the diffusion of the electrolyte and exacerbates the uneven infiltration. The uneven distribution of the electrolyte will cause the local current density to be too high during charging and discharging, accelerating the growth of lithium dendrites and the rupture of the SEI film.

[0004] Furthermore, the contradiction between electrolyte wetting efficiency and uniformity is even more pronounced in industrial production. In mass production of silicon-carbon anode batteries, electrolyte wetting typically takes more than 12 hours, requiring repeated cycles of "wetting-resting-refilling," severely slowing production line performance.

[0005] For example, the comparative document CN202211270882.4 discloses a soft-pack lithium-ion battery electrolyte infiltration method and its application, comprising the following steps: placing a dry battery cell in an aluminum-plastic film, hot-pressing the aluminum-plastic film on three sides, leaving an air bag at one end, and leaving the air bag end open as a liquid injection port; vacuum drying the battery cell and then injecting the electrolyte; after the battery is injected, vacuuming the battery injection port, maintaining the vacuum degree for 0.5 to 10 minutes, and letting it stand at normal pressure for 1 to 10 minutes; clamping the battery cell body, vacuuming the battery injection port, maintaining the vacuum degree for 0.5 to 10 minutes, and letting it stand at normal pressure for 1 to 10 minutes; repeating the injection and vacuum operations several times to complete the infiltration. The electrolyte of this scheme penetrates the silicon-carbon negative electrode slowly, and the "infiltration-standing-replenishment" cycle needs to be repeated, which seriously slows down the production line beat.

[0006] Another example is the electrolyte pre-injection process for battery processing disclosed in the comparative document CN202310187278.3. It uses a high positive pressure and high negative pressure cycle injection method to increase the pressure gradient, promote the liquid flow rate, and improve the electrolyte infiltration efficiency. Although the pressure gradient method can increase the penetration rate, the lack of directional control causes the electrolyte to "bypass" the macropores, resulting in limited improvement in the micropore filling rate. Although the macropores penetrate quickly, the lack of a guide path makes it easy for the electrolyte to accumulate on the surface and difficult to penetrate into the interior of the electrode.

[0007] Another example is the battery electrolyte ultrasonic injection device and method disclosed in the comparative document CN201710694561.X, which includes a base for placing at least one battery to be injected, an injection device corresponding to each battery to be injected, and an ultrasonic generator. The injection device includes a metering pump and an injection needle, and the ultrasonic generator transmits ultrasonic waves to the electrolyte and electrode coils in each battery. However, when ultrasonically assisted infiltration of the silicon-carbon negative electrode is used, the ultrasonic-assisted infiltration accelerates the flow of the electrolyte through high-frequency vibration. The cavitation effect of the ultrasonic wave can cause silicon particles to fall off from the current collector, which in turn reduces the integrity of the electrode structure. Summary of the Invention

[0008] The purpose of the present disclosure is to overcome the deficiencies in the prior art and to provide a lithium battery preparation method and a lithium ion battery with fast and uniform electrolyte directional penetration into silicon-carbon electrodes.

[0009] The purpose of this disclosure is achieved through the following technical solutions:

[0010] A method for preparing a lithium battery with directional electrolyte infiltration comprises the following steps:

[0011] A silicon-carbon electrode with a three-dimensional gradient pore structure is prepared, wherein the three-dimensional gradient pore structure is composed of surface straight-through pores, middle-layer tree-like branched pores, and bottom-layer liquid storage cavities that are interconnected and have a radial size gradient;

[0012] Assembling the silicon-carbon electrode and the shell to form a battery core;

[0013] The battery cell is placed in a gradient magnetic field environment with a magnetic field strength gradient distribution of 0.5T-1.2T;

[0014] Adding a magnetic additive to an electrolyte, and then injecting the electrolyte containing the magnetic additive into a battery cell;

[0015] The electrolyte and electrodes in the battery cell are sequentially subjected to a temperature and pressure coordinated loading cycle of low-temperature and low-pressure infiltration, high-temperature and high-pressure filling, and low-temperature negative pressure balance;

[0016] After packaging, a lithium battery is obtained.

[0017] In one embodiment, the magnetic additive is Fe3O4@SiO2 nanoparticles, and the magnetic susceptibility of the Fe3O4@SiO2 nanoparticles is greater than 1.0×10 -3 .

[0018] In one embodiment, the Fe3O4@SiO2 nanoparticles have a core-shell structure consisting of a Fe3O4 core and a SiO2 shell, the Fe3O4 core has a diameter of 17nm-23nm, and the SiO2 shell has a thickness of 4nm-6nm.

[0019] In one embodiment, the concentration of Fe3O4@SiO2 nanoparticles added to the electrolyte is in the range of 0.1wt%-0.3wt%.

[0020] In one embodiment, the magnetic field intensity gradient increment of the gradient magnetic field environment is set to 0.3T / cm-0.5T / cm.

[0021] In one embodiment, the electrolyte and electrodes in the battery cell are subjected to a temperature and pressure coordinated loading cycle of low-temperature and low-pressure infiltration, high-temperature and high-pressure filling, and low-temperature negative pressure balance, including the following steps:

[0022] The electrolyte in the battery cell is loaded with low pressure and the temperature is increased. The loaded low pressure of the low-pressure penetration is 0.5MPa-1.5MPa, and the temperature of the low-pressure penetration is 40℃-45℃. The silicon-carbon electrode is subjected to low-pressure penetration. The electrolyte in the battery cell is then loaded with high pressure and the temperature is increased. The loaded high pressure of the high-pressure filling is 1.5MPa-2.5MPa, and the temperature of the high-pressure filling is 50℃-60℃. The silicon-carbon electrode is subjected to high pressure filling. The electrolyte in the battery cell is then loaded with negative pressure and the temperature is reduced. The silicon-carbon electrode is negatively pressure balanced. The loaded negative pressure of the negative pressure balance is -0.2Mpa to -0.1Mpa, and the temperature of the negative pressure balance cooling is 30℃-40℃.

[0023] In one embodiment, the low-pressure permeation pressure is P1, the low-pressure permeation temperature is T1, the high-pressure permeation pressure is P2, the high-pressure permeation temperature is T2, and the ratio of the temperature and pressure synergistic loading cycle satisfies the following mathematical relationship:

[0024]

[0025] In one embodiment, when the electrode and the electrolyte are subjected to a temperature-pressure coordinated loading cycle, the following steps are further included:

[0026] The penetration depth of the electrolyte is measured in real time by a dielectric sensor.

[0027] In one embodiment, preparing the electrode with the three-dimensional gradient pore structure comprises the following steps:

[0028] PS microspheres and CaCO3 nanoparticles were dispersed in PVDF binder and combined with silicon-carbon composite materials to make composite electrodes;

[0029] The composite electrode was transferred to a tube furnace and filled with N2, and the temperature was raised to 450°C and maintained at the temperature for 1 hour to form through-holes on the surface of the composite electrode;

[0030] A mixture of N2 and H2 was introduced, and the temperature was raised to 550°C and maintained for 2 hours to form tree-like branched pores in the middle layer of the composite electrode;

[0031] Argon gas is introduced and the temperature is raised to 650°C. The temperature is maintained for 1 hour to form a bottom liquid storage cavity in the composite electrode, thereby obtaining a silicon-carbon electrode with a three-dimensional gradient pore structure. A lithium-ion battery is obtained by the lithium battery preparation method of directional electrolyte infiltration described in any of the above embodiments.

[0032] Compared with the prior art, the present disclosure has at least the following advantages:

[0033] In the above-mentioned method for preparing a lithium battery with directional electrolyte penetration, the surface straight-through holes, the middle-layer tree-like branched holes and the bottom-layer liquid storage cavity are connected to form a guide route, so that the electrolyte penetrates and is evenly distributed inside the silicon-carbon electrode, so that the electrolyte fully infiltrates the silicon-carbon electrode; a magnetic adsorption additive is added to the electrolyte, and under the action of a gradient magnetic field environment, the magnetic additive drives the electrolyte to break through the interface impedance of the electrolyte infiltration, thereby accelerating the electrolyte infiltration of the three-dimensional gradient pore structure of the silicon-carbon electrode, thereby significantly improving the electrolyte infiltration efficiency; by sequentially performing low-pressure penetration, high-pressure filling and negative pressure balanced temperature and pressure coordinated loading cycles on the electrolyte in the battery cell, the electrolyte quickly fills the silicon-carbon electrode infiltration micropores and makes the electrolyte evenly distributed, thereby reducing side reactions during the infiltration process of the electrolyte and the silicon-carbon electrode;

[0034] The electrolyte is guided by the three-dimensional gradient pore structure, magnetically driven by the gradient magnetic field environment and magnetic additives, and coordinated loading and cyclic regulation of temperature and pressure to achieve three-dimensional coordination, so that the electrolyte can be directionally penetrated in the three-dimensional gradient pore structure of the silicon-carbon electrode, which accelerates the speed of the electrolyte infiltrating the silicon-carbon electrode and thus realizes the efficient penetration of the electrolyte into the silicon-carbon electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0036] Figure 1 A flowchart of a method for preparing a lithium battery with directional electrolyte infiltration according to an embodiment;

[0037] Figure 2 Graphs of charge and discharge at different rates for Comparative Example 1 and Example 1;

[0038] Figure 3 This is a flow chart of preparing the silicon-carbon electrode with a three-dimensional gradient pore structure according to one embodiment. DETAILED DESCRIPTION

[0039] To facilitate understanding of the present disclosure, a more comprehensive description of the present disclosure will be provided below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present disclosure. However, the present disclosure can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure.

[0040] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly attached to the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this disclosure pertains. The terms used herein in the specification of this disclosure are intended only to describe specific embodiments and are not intended to limit this disclosure. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0042] In order to better understand the technical solutions and beneficial effects of the present disclosure, the present disclosure is further described in detail below with reference to specific embodiments:

[0043] The present invention relates to a method for preparing a lithium battery with directional electrolyte infiltration, comprising the following steps: preparing a silicon-carbon electrode with a three-dimensional gradient pore structure, wherein the three-dimensional gradient pore structure comprises a surface layer of interconnected straight-through pores, a middle layer of tree-like branched pores, and a bottom layer of liquid storage cavities, each of which has a radially increasing gradient. In this embodiment, the pore structure of the three-dimensional gradient pore structure of the silicon-carbon electrode, comprising the surface layer of straight-through pores, the middle layer of tree-like branched pores, and the bottom layer of liquid storage cavities, with different gradient sizes, facilitates electrolyte infiltration. The silicon-carbon electrode and a shell are assembled into a battery cell. The battery cell is placed in a gradient magnetic field environment with a magnetic field strength gradient distribution of 0.5T to 1.2T; a magnetic additive is added to the electrolyte, and the electrolyte containing the magnetic additive is then injected into the battery cell; the electrolyte and electrode in the battery cell are subjected to a temperature and pressure coordinated loading cycle of low-temperature and low-pressure infiltration, high-temperature and high-pressure filling, and low-temperature negative pressure balance in sequence; and a lithium battery is obtained after packaging.

[0044] See also Figure 1 , which is a method for preparing a lithium battery with directional electrolyte infiltration according to an embodiment of the present invention, comprising the following steps:

[0045] S101 prepares a silicon-carbon electrode with a three-dimensional gradient pore structure, wherein the three-dimensional gradient pore structure comprises a surface layer of straight through pores, a middle layer of dendritic branched pores, and a bottom layer of liquid storage cavities, which are interconnected and have increasing radial size gradients. In this embodiment, the three-dimensional gradient pore structure of the silicon-carbon electrode, comprising the surface layer of straight through pores, the middle layer of dendritic branched pores, and the bottom layer of liquid storage cavities, has pore structures of different gradient sizes, which facilitates the infiltration of the electrolyte.

[0046] S103 assembles the silicon-carbon electrode and the shell into a battery cell.

[0047] S105: placing the battery cell in a gradient magnetic field environment with a magnetic field strength gradient distribution of 0.5T-1.2T;

[0048] S107 adds a magnetic additive to the electrolyte, and then injects the electrolyte containing the magnetic additive into the battery cell;

[0049] S109 sequentially performs temperature and pressure coordinated loading cycles of low-temperature and low-pressure infiltration, high-temperature and high-pressure filling, and low-temperature negative pressure balance on the electrolyte and silicon-carbon electrode in the battery cell;

[0050] The lithium battery is obtained after S111 packaging.

[0051] In this embodiment, the three-dimensional gradient pore structure of the silicon-carbon electrode has pore structures of different gradient sizes, including the surface straight-through pores, the middle-layer tree-like branched pores, and the bottom-layer liquid storage cavity. The surface straight-through pores form a pore network to accelerate the penetration rate of the electrolyte, and the pore branching structure of the middle-layer tree-like branched pores enhances the capillary force and improves the infiltration of the electrolyte. The larger pore size of the bottom-layer liquid storage cavity increases the absorption of the electrolyte, which is beneficial to the infiltration of the electrolyte into the silicon-carbon electrode.

[0052] It can be understood that after the magnetic additive is added to the electrolyte, under the control of the external magnetic field, the magnetic additive moves in the direction of decreasing magnetic field intensity. The magnetic additive drives the electrolyte to penetrate directionally in the three-dimensional gradient pore structure of the silicon-carbon electrode, which greatly reduces the interfacial impedance of the electrolyte infiltration. The electrolyte can quickly migrate and penetrate along the straight-through holes to the deep middle-layer tree-like branch pores and the bottom liquid storage cavity, thereby significantly improving the infiltration efficiency of the electrolyte.

[0053] It can be understood that when the silicon-carbon electrode is infiltrated at low pressure, the temperature increase reduces the viscosity of the electrolyte, and the electrolyte quickly fills the larger pores of the silicon-carbon electrode; when the silicon-carbon electrode is filled at high pressure, the temperature increase further reduces the viscosity of the electrolyte, and the increased pressure allows the electrolyte to further penetrate into the micropores, increasing the absorption amount; when the silicon-carbon electrode is negatively balanced, residual bubbles and excess electrolyte can be extracted, and the electrolyte is evenly distributed. Cooling causes the electrolyte viscosity to rise, so that the infiltration of the electrolyte and the silicon-carbon electrode remains stable, and the electrolyte is evenly distributed in the silicon-carbon electrode with a three-dimensional gradient pore structure, reducing the side reactions between the electrolyte and the silicon-carbon motor.

[0054] In the above-mentioned method for preparing lithium batteries with directional electrolyte penetration, the surface straight-through holes, the middle-layer tree-like branch holes and the bottom-layer liquid storage cavity are connected to form a guide route, so that the electrolyte penetrates and is evenly distributed inside the silicon-carbon electrode, so that the electrolyte fully infiltrates the silicon-carbon electrode; a magnetic adsorption additive is added to the electrolyte, and under the action of a gradient magnetic field environment, the magnetic additive drives the electrolyte to break through the interface impedance of the electrolyte infiltration, accelerates the electrolyte infiltration of the three-dimensional gradient pore structure of the silicon-carbon electrode, thereby significantly improving the electrolyte infiltration efficiency; by sequentially performing low-pressure penetration of the electrolyte in the battery cell The temperature and pressure coordinated loading cycle of high-pressure filling and negative pressure balance allows the electrolyte to quickly fill the silicon-carbon electrode infiltration micropores and evenly distribute the electrolyte, thereby reducing side reactions during the infiltration process of the electrolyte and the silicon-carbon electrode; the electrolyte is guided by the three-dimensional gradient pore structure, the magnetic drive of the gradient magnetic field environment and the magnetic additives, and the temperature and pressure coordinated loading cycle regulation to perform three-dimensional coordination, so that the electrolyte can be directionally penetrated in the three-dimensional gradient pore structure of the silicon-carbon electrode, which accelerates the speed of the electrolyte infiltrating the silicon-carbon electrode, thereby realizing efficient penetration of the electrolyte into the silicon-carbon electrode.

[0055] In one embodiment, the magnetic additive is Fe3O4@SiO2 nanoparticles, and the magnetic susceptibility of the Fe3O4@SiO2 nanoparticles is greater than 1.0×10 -3 In this embodiment, the magnetic susceptibility of Fe3O4@SiO2 is greater than 1.0×10 -3 When the Fe3O4@SiO2 nanoparticles are exposed to a weak magnetic field, they can exhibit significant magnetism. This makes the Fe3O4@SiO2 nanoparticles have a strong magnetic response. The Fe3O4@SiO2 nanoparticles can drive the electrolyte to break through the interface impedance of the infiltrated silicon-carbon electrode, thereby improving the infiltration effect of the electrolyte on the silicon-carbon electrode.

[0056] In one embodiment, the concentration of Fe3O4@SiO2 nanoparticles added to the electrolyte is in the range of 0.1wt% to 0.3wt%. In this embodiment, when the amount of Fe3O4@SiO2 nanoparticles added is less than 0.1wt%, the magnetic field gradient acts on the Fe3O4@SiO2 nanoparticles, reducing the efficiency of the electrolyte in filling micropores with the Fe3O4@SiO2 nanoparticles, thereby slowing the electrolyte's infiltration of the silicon-carbon electrode, thereby restricting the production efficiency of the lithium battery. When the amount of Fe3O4@SiO2 nanoparticles added is greater than 0.3wt%, the excessive amount of nanoparticles causes an increase in the viscosity of the electrolyte. At the same time, excessive aggregation of the Fe3O4@SiO2 nanoparticles easily blocks smaller pores, resulting in uneven infiltration.

[0057] In one embodiment, the Fe3O4@SiO2 nanoparticles have a core-shell structure consisting of an Fe3O4 core and a SiO2 shell. The Fe3O4 core has a diameter of 17nm-23nm and the SiO2 shell is 4-6nm thick. In this embodiment, the Fe3O4 core diameter of 17nm-23nm and the SiO2 shell thickness of 4-6nm result in a smaller radius of the Fe3O4@SiO2 nanoparticles, reducing the risk of Fe3O4@SiO2 nanoparticles clogging the pores of the silicon-carbon electrode. The Fe3O4@SiO2 nanoparticles use Fe3O4 as a magnetic core, while the SiO2 shell protects the Fe3O4 core from oxidation and corrosion, improving the chemical stability of the Fe3O4@SiO2 nanoparticles.

[0058] In one embodiment, the magnetic field intensity gradient increment of the gradient magnetic field environment is set to 0.3T / cm-0.5T / cm. In this embodiment, the gradient magnetic field environment is a Halbach permanent magnet array, and the magnetic field gradient in the Z-axis direction is ΔB / Δz = 0.3T / cm-0.5T / cm. The Halbach permanent magnet array significantly increases the magnetic field intensity on one side while weakening the magnetic field on the other side by superimposing the parallel magnetic field and the radial magnetic field. By adjusting the arrangement and size of the magnets, the magnetic field intensity gradient increment in the Z-axis direction can be precisely controlled to be 0.3T / cm-0.5T / cm, thereby affecting the gradient change of the magnetic field intensity layer of the magnetic additive in the electrolyte along the Z-axis direction, so that the direction of the gradient change of the electrolyte magnetic field intensity layer penetrates the silicon-carbon electrode.

[0059] In one embodiment, the electrolyte and electrodes in the battery cell are subjected to a temperature and pressure coordinated loading cycle of low-temperature and low-pressure infiltration, high-temperature and high-pressure filling, and low-temperature negative pressure balance, including the following steps:

[0060] The electrolyte in the battery cell is loaded with low pressure and the temperature is increased. The loaded low pressure of the low-pressure penetration is 0.5MPa-1.5MPa, and the temperature of the low-pressure penetration is 40℃-45℃. The silicon-carbon electrode is subjected to low-pressure penetration. The electrolyte in the battery cell is then loaded with high pressure and the temperature is increased. The loaded high pressure of the high-pressure filling is 1.5MPa-2.5MPa, and the temperature of the high-pressure filling is 50℃-60℃. The silicon-carbon electrode is subjected to high pressure filling. The electrolyte in the battery cell is then loaded with negative pressure and the temperature is reduced. The silicon-carbon electrode is negatively pressure balanced. The loaded negative pressure of the negative pressure balance is -0.2Mpa to -0.1Mpa, and the temperature of the negative pressure balance cooling is 30℃-40℃. In this embodiment, the temperature rise reduces the viscosity of the electrolyte, and the electrolyte quickly fills the larger pores of the silicon-carbon electrode; when the silicon-carbon electrode is filled with high pressure, the temperature rise further reduces the viscosity of the electrolyte, and the pressure increase allows the electrolyte to further penetrate into the micropores, thereby increasing the absorption amount; when the silicon-carbon electrode is negatively balanced, the residual bubbles and excess electrolyte can be extracted, and the electrolyte is evenly distributed. The temperature drop causes the electrolyte viscosity to rise, so that the infiltration of the electrolyte and the silicon-carbon electrode remains stable; the temperature range of the low-pressure infiltration heating is 40°C-45°C, which reduces the viscosity of the electrolyte and promotes the infiltration of the electrolyte. The loaded low pressure is 0.5MPa-1.5MPa, and the loaded low pressure is greater than 0.5Mpa, so that the electrolyte quickly fills the larger pores of the silicon-carbon electrode, and the pressurized low pressure The pressure is less than 1.5Mpa, forming a gradient pressurization with the loaded high pressure, reducing the deep penetration effect of the loaded high pressure and improving the uniformity of the infiltration; the loaded high pressure is 1.5MPa-2.5MPa, and the loaded high pressure is less than 2.5MPa to reduce the force on the battery shell and avoid deformation of the battery shell. The loaded high pressure is greater than 1.5MPa, so that the electrolyte has a better penetration effect on the micropores of the silicon-carbon electrode; the loaded negative pressure is -0.2Mpa to -0.1MPa. When the loaded negative pressure is small, the loaded negative pressure is conducive to extracting residual bubbles and excess electrolyte to achieve uniform distribution of the electrolyte. When the loaded negative pressure is large, more electrolyte is extracted, resulting in insufficient infiltration of the motor. When the loaded negative pressure is small, the excess bubbles and excess electrolyte cannot be effectively extracted.

[0061] Furthermore, the heating rate of the low-pressure infiltration is 2°C / min, the heating rate of the high-pressure filling is 2°C / min, and the cooling rate of the negative pressure balance is 2°C / min. It can be understood that before low-pressure infiltration and high-pressure filling, the electrolyte needs to be heated. The slow heating rate avoids sudden changes in the electrolyte temperature and reduces the damage to the silicon-carbon electrode structure caused by thermal stress. After the electrolyte is heated, the viscosity decreases and the fluidity increases. Before negative pressure leveling, the electrolyte needs to be cooled. The slow cooling rate reduces the change in the interfacial tension of the electrolyte and maintains good contact between the silicon-carbon electrode and the electrolyte. After the electrolyte is cooled, the viscosity increases, and the infiltration of the electrolyte and the silicon-carbon electrode remains stable.

[0062] In one embodiment, the low-pressure permeation pressure is P1, the low-pressure permeation temperature is T1, the high-pressure permeation pressure is P2, the high-pressure permeation temperature is T2, and the ratio of the temperature to pressure synergistic loading cycle satisfies the following mathematical relationship:

[0063]

[0064] In this embodiment, for every 1 MPa increase in pressure, the temperature needs to be increased by 10.0°C to maintain the infiltration efficiency, with an allowable error in the range of 9.5°C / MPa-10.5°C / MPa to adapt to different electrolytes. The pressure increase can promote the flow of the electrolyte and enhance the capillary force to drive the electrolyte into deep pores. The temperature increase reduces the viscosity of the electrolyte, thereby increasing the infiltration rate of the electrolyte. When the temperature-pressure synergy ratio is high, the infiltration time is shortened. When the ratio of the temperature-pressure synergy loading cycle is greater than 10.0±0.5°C / MPa, a short infiltration time will affect the uniformity of the electrolyte distribution. When the temperature-pressure synergy ratio is less than 10.0±0.5°C / MPa, the infiltration time is longer, thereby reducing the infiltration efficiency. When the temperature-pressure synergy loading cycle ratio is 10.0±0.5°C / MPa, the electrolyte infiltration efficiency is high, the electrolyte distribution is better, and the pore filling rate is improved. By quantifying the temperature and pressure for coordinated loading, the electrolyte maintains the optimal wetting efficiency, thereby improving the wetting effect of the electrolyte on the silicon-carbon electrode.

[0065] Furthermore, the direction of the magnetic field increment of the gradient magnetic field is parallel to the direction of the battery cell injection port. In this embodiment, the battery cell injection port is located above the battery cell, and the electrolyte infiltrates the silicon-carbon electrode in the battery cell from top to bottom. The magnetic field strength increases from bottom to top, generating a magnetic field gradient, which drives the Fe3O4@SiO2 nanoparticles to guide the electrolyte to penetrate deep into the pores of the silicon-carbon electrode in the direction of decreasing magnetic field, thereby accelerating the electrolyte infiltration process.

[0066] In one embodiment, it is characterized in that when the electrode and the electrolyte are subjected to temperature and pressure coordinated loading cycle, the following steps are further included:

[0067] The dielectric sensor measures the electrolyte penetration depth in real time. In this embodiment, when the electrolyte penetrates the silicon-carbon electrode, the capacitance of the dielectric sensor changes because the dielectric constant of the electrolyte is greater than that of air or other non-conductive materials. This allows the dielectric sensor to measure the electrolyte penetration depth in real time, thereby promptly monitoring the penetration effect of the silicon-carbon electrode.

[0068] Furthermore, in one embodiment, the operating frequency of the dielectric sensor is 1 MHz-10 MHz, and the dielectric constant change rate Δε / Δt and the penetration depth satisfy d=0.25×(Δε / Δt)0.67 , d is the penetration depth. The measured rate of change of the dielectric constant, Δε / Δt, allows for feedback on the penetration depth. By controlling the penetration depth and immersion time through feedback, the pressure and temperature during the temperature-pressure co-loading cycle can be optimized, and thus adjusted.

[0069] like Figure 3 As shown, in one embodiment, preparing the electrode with the three-dimensional gradient pore structure includes the following steps:

[0070] S1011 dispersed PS microspheres and CaCO3 nanoparticles in PVDF binder and made composite electrodes with silicon-carbon composite materials;

[0071] S1013: Transfer the composite electrode to a tube furnace, introduce N2, raise the temperature to 450°C, and maintain the temperature for 1 hour to form through-holes on the surface of the composite electrode;

[0072] In step S1015, a mixture of N2 and H2 is introduced, and the temperature is raised to 550°C and maintained at this temperature for 2 hours to form tree-like branched pores in the middle layer of the composite electrode;

[0073] In step S1017, argon gas is introduced and the temperature is raised to 650°C. The temperature is maintained for 1 hour to form a solid structure, thereby forming a bottom liquid storage cavity in the composite electrode, thereby obtaining a silicon-carbon electrode with a three-dimensional gradient pore structure. In this embodiment, N2 is introduced at a flow rate of 5 L / min. When N2 is introduced at 450°C, only PS decomposes in the composite electrode to form surface through-holes with high porosity. When N2 and H2 are introduced at 550°C, CaCO3 in the composite electrode partially decomposes, and CO2 gas escapes to form middle-layer dendritic branched pores that interweave with the residual PS carbon skeleton, enhancing capillary action. When argon is introduced at 650°C, CaCO3 completely decomposes, and the diffused gas escapes to form a large-aperture liquid storage cavity, thereby forming a three-dimensional gradient pore structure in the silicon-carbon electrode. The surface through-holes, middle-layer dendritic branched pores, and bottom liquid storage cavity are connected by gas overflow channels, allowing the electrolyte to smoothly permeate the surface through-holes, middle-layer dendritic branched pores, and bottom liquid storage cavity.

[0074] Furthermore, the heating rate for introducing N2 to 450°C is 5°C / min, the heating rate for introducing mixed hydrogen to 550°C is 5°C / min, and the heating rate for introducing argon to 650°C is 5°C / min. In this embodiment, by controlling the heating rate to 5°C / min, the PS microspheres are synchronously decomposed to form a network of surface straight-through holes, avoiding local overheating and excessive expansion, so that the formed surface straight-through holes are evenly distributed; the decomposition rate of CaCO3 in the composite electrode is affected by temperature. Excessive heating will lead to local temperature unevenness, resulting in differences in decomposition rates in different regions. By slowly heating, the decomposition rate of CaCO3 tends to be consistent, thereby forming a middle-layer tree-like branched pore structure with uniform porosity and a bottom-layer liquid storage cavity, thereby improving the uniformity of electrolyte infiltration.

[0075] Furthermore, the volume ratio of the PS microspheres to the CaCO3 nanoparticles is 3:6.8-7.2. In this embodiment, the PS microspheres decompose to form an initial microporous network, while the CaCO3 nanoparticles decompose to form a macroporous structure. When the volume of the CaCO3 nanoparticles is small, the silicon-carbon electrode absorbs less electrolyte. By adjusting the ratio of the PS microspheres to the CaCO3 nanoparticles, the silicon-carbon electrode forms a stable, interconnected structure with surface straight-through pores, middle-layer tree-like branching pores, and bottom-layer liquid storage cavities with increasing radial size gradients, thereby maintaining the electrolyte's infiltration effect on the silicon-carbon electrode.

[0076] Furthermore, in one embodiment, the radius of the through hole is 50nm-80nm, the radius of the tree-like branched hole is 100nm-150nm, and the radius of the bottom liquid storage cavity is 200nm-300nm. In this embodiment, the small-diameter through hole and the size of the Fe3O4@SiO2 nanoparticles form a capillary action gradient, which promotes the electrolyte to penetrate along the low-resistance path; the tree-like branched hole enhances the uniformity of electrolyte distribution by expanding the specific surface area; the bottom liquid storage cavity accelerates the nanoparticles to drive the directional flow of electrolyte under the drive of the magnetic field; the Fe3O4@SiO2 nanoparticles are significantly smaller than the through hole, tree-like branched hole and bottom liquid storage cavity of the silicon-carbon electrode, allowing the Fe3O4@SiO2 nanoparticles to effectively penetrate the interface barrier formed by gas retention during the electrolyte infiltration process, overcome the gas-liquid interfacial tension through magnetic force, and thus increase the electrolyte infiltration speed.

[0077] The present application also provides a lithium battery obtained by the method for preparing a lithium battery using directional electrolyte infiltration as described in any of the above embodiments. In this embodiment, the lithium battery obtained by the method for preparing a lithium battery using directional electrolyte infiltration has a shorter infiltration time, thereby improving the production efficiency of the lithium battery. The electrolyte has a better infiltration effect on the silicon-carbon electrode with a three-dimensional gradient pore structure, a high electrolyte filling rate of the electrode micropores, and a uniform electrolyte distribution, which reduces side reactions during the infiltration process, thereby improving the lithium ion transmission efficiency, interface stability, and battery cycle life in the lithium battery.

[0078] Compared with the prior art, the present disclosure has at least the following advantages:

[0079] In the above-mentioned method for preparing a lithium battery with directional electrolyte penetration, the surface straight-through holes, the middle-layer tree-like branched holes and the bottom-layer liquid storage cavity are connected to form a guide route, so that the electrolyte penetrates into the interior of the silicon-carbon electrode, which is conducive to the full infiltration of the electrolyte into the silicon-carbon electrode; a magnetic adsorption additive is added to the electrolyte, and under the action of a gradient magnetic field environment, the magnetic additive drives the electrolyte to break through the interface impedance of the electrolyte infiltration, thereby accelerating the electrolyte infiltration into the three-dimensional gradient pore structure of the silicon-carbon electrode, thereby significantly improving the infiltration efficiency of the electrolyte; by coordinating the loading cycle of the electrolyte temperature and pressure in the battery cell and performing low-pressure penetration, high-pressure filling and negative pressure balance in sequence, the electrolyte can quickly fill the silicon-carbon electrode infiltration micropores and make the electrolyte evenly distributed, thereby reducing side reactions during the infiltration process of the electrolyte and the silicon-carbon electrode;

[0080] The electrolyte is guided by the three-dimensional gradient pore structure, magnetically driven by the gradient magnetic field environment and magnetic additives, and coordinated loading and cyclic regulation of temperature and pressure to achieve three-dimensional coordination, so that the electrolyte can be directionally penetrated in the three-dimensional gradient pore structure of the silicon-carbon electrode, which accelerates the speed of the electrolyte infiltrating the silicon-carbon electrode and thus realizes the efficient penetration of the electrolyte into the silicon-carbon electrode.

[0081] The following are some specific examples, where "%" refers to percentages by weight. It should be noted that the following examples are not exhaustive and that the materials used in the following examples are all commercially available unless otherwise specified.

[0082] Comparative Example 1

[0083] An electrode was made of silicon carbon with a specific capacity of 700mAh / g; the composite electrode was transferred to a tube furnace and N2 was introduced at a flow rate of 5L / min, and the temperature was increased to 450℃ at a heating rate of 5℃ / min, and the temperature was maintained for 1h to form surface straight-through holes in the composite electrode; then a mixed gas of N2 and H2 (N2 / H2=95:5) was introduced and the temperature was increased to 550℃ at a heating rate of 5℃ / min, and the temperature was maintained for 2h to form middle-layer tree-like branched pores in the composite electrode; finally, the temperature was increased to 650℃ and argon (Ar) was introduced, and the temperature was maintained for 1h to fix the shape, so that the composite electrode formed a bottom liquid storage cavity, thereby obtaining a silicon carbon electrode with a three-dimensional gradient pore structure.

[0084] Inject the electrolyte into the battery cell, use the vacuum immersion method to vacuum the battery filling port, reduce the pressure to -0.1MPa, maintain the vacuum degree for 0.5min-10min, let it stand at normal pressure for 110min, and repeat the injection and vacuum operation several times until the immersion is completed.

[0085] Furthermore, a customized high-pressure autoclave was used to heat the battery cell to 45°C at a heating rate of 2°C / min, and pressurized to 0.5MPa at 0.4MPa / s and maintained for 3min, so as to perform low-pressure infiltration on the silicon-carbon electrode; then, the battery cell was heated to 60°C at a heating rate of 2°C / min, and pressurized to 2MPa at 0.4MPa / s and maintained for 5min, so as to perform high-pressure filling on the silicon-carbon electrode; finally, the battery cell was cooled to 35°C at a cooling rate of 2°C / min, and the pressure was reduced to -0.1MPa and maintained for 2min, so as to perform negative pressure balance on the silicon-carbon electrode; and a lithium battery was obtained after packaging.

[0086] Example 1

[0087] PS microspheres and CaCO3 nanoparticles are dispersed in PVDF binder in a volume ratio of 3:7, and a composite electrode is made with a silicon-carbon composite material with a specific capacity of 700mAh / g; the composite electrode is transferred to a tube furnace and N2 is introduced at a flow rate of 5L / min, and the temperature is increased to 450℃ at a heating rate of 5℃ / min, and the temperature is maintained for 1h to form surface straight-through holes in the composite electrode; then a mixed gas of N2 and H2 (N2 / H2=95:5) is introduced and the temperature is increased to 550℃ at a heating rate of 5℃ / min, and the temperature is maintained for 2h to form middle-layer tree-like branched pores in the composite electrode; finally, the temperature is increased to 650℃ and argon (Ar) is introduced, and the temperature is maintained for 1h to fix the shape, so that the composite electrode forms a bottom liquid storage cavity, thereby obtaining a silicon-carbon electrode with a three-dimensional gradient pore structure.

[0088] Furthermore, the silicon-carbon electrode and the shell were assembled to form a battery cell; a 300mm×200mm×50mm (length×width×height) Halbach magnetic field array was used, and the Z-axis gradient ΔB / Δz was adjusted to 0.402T / cm using a Hall probe to form a suitable gradient magnetic field environment; 0.2wt% Fe3O4@SiO2 was added to the electrolyte, and then the electrolyte containing Fe3O4@SiO2 was injected into the battery cell.

[0089] Furthermore, a customized high-pressure autoclave was used to heat the battery cell to 45°C at a heating rate of 2°C / min, and pressurized to 0.5MPa at 0.4MPa / s and maintained for 3min, so as to perform low-pressure infiltration on the silicon-carbon electrode; then, the battery cell was heated to 60°C at a heating rate of 2°C / min, and pressurized to 2MPa at 0.4MPa / s and maintained for 5min, so as to perform high-pressure filling on the silicon-carbon electrode; finally, the battery cell was cooled to 35°C at a cooling rate of 2°C / min, and the pressure was reduced to -0.1MPa and maintained for 2min, so as to perform negative pressure balance on the silicon-carbon electrode; and a lithium battery was obtained after packaging.

[0090] Example 2

[0091] PS microspheres and CaCO3 nanoparticles are dispersed in PVDF binder in a volume ratio of 3:7, and a composite electrode is made with a silicon-carbon composite material with a specific capacity of 700mAh / g; the composite electrode is transferred to a tube furnace and N2 is introduced at a flow rate of 5L / min, and the temperature is increased to 450℃ at a heating rate of 5℃ / min, and the temperature is maintained for 1h to form surface straight-through holes in the composite electrode; then a mixed gas of N2 and H2 (N2 / H2=95:5) is introduced and the temperature is increased to 550℃ at a heating rate of 5℃ / min, and the temperature is maintained for 2h to form middle-layer tree-like branched pores in the composite electrode; finally, the temperature is increased to 650℃ and argon (Ar) is introduced, and the temperature is maintained for 1h to fix the shape, so that the composite electrode forms a bottom liquid storage cavity, thereby obtaining a silicon-carbon electrode with a three-dimensional gradient pore structure.

[0092] Furthermore, the silicon-carbon electrode and the shell were assembled to form a battery cell; a 300mm×200mm×50mm (length×width×height) Halbach magnetic field array was used, and the Z-axis gradient ΔB / Δz was adjusted to 0.402T / cm using a Hall probe to form a suitable gradient magnetic field environment; 0.2wt% Fe3O4@SiO2 was added to the electrolyte, and then the electrolyte containing Fe3O4@SiO2 was injected into the battery cell.

[0093] Furthermore, a customized high-pressure autoclave was used to heat the battery cell to 40°C at a heating rate of 2°C / min, and pressurized to 0.5MPa at 0.4MPa / s and maintained for 3min, so as to perform low-pressure infiltration on the silicon-carbon electrode; then, the battery cell was heated to 60°C at a heating rate of 2°C / min, and pressurized to 1.5MPa at 0.4MPa / s and maintained for 5min, so as to perform high-pressure filling on the silicon-carbon electrode; finally, the battery cell was cooled to 35°C at a cooling rate of 2°C / min, and the pressure was reduced to -0.1MPa and maintained for 2min, so as to perform negative pressure balance on the silicon-carbon electrode; and a lithium battery was obtained after packaging.

[0094] Example 3

[0095] PS microspheres and CaCO3 nanoparticles are dispersed in PVDF binder in a volume ratio of 3:7, and a composite electrode is made with a silicon-carbon composite material with a specific capacity of 700mAh / g; the composite electrode is transferred to a tube furnace and N2 is introduced at a flow rate of 5L / min, and the temperature is increased to 450℃ at a heating rate of 5℃ / min, and the temperature is maintained for 1h to form surface straight-through holes in the composite electrode; then a mixed gas of N2 and H2 (N2 / H2=95:5) is introduced and the temperature is increased to 550℃ at a heating rate of 5℃ / min, and the temperature is maintained for 2h to form middle-layer tree-like branched pores in the composite electrode; finally, the temperature is increased to 650℃ and argon (Ar) is introduced, and the temperature is maintained for 1h to fix the shape, so that the composite electrode forms a bottom liquid storage cavity, thereby obtaining a silicon-carbon electrode with a three-dimensional gradient pore structure.

[0096] Furthermore, the silicon-carbon electrode and the shell were assembled to form a battery cell; a 300mm×200mm×50mm (length×width×height) Halbach magnetic field array was used, and the Z-axis gradient ΔB / Δz was adjusted to 0.402T / cm using a Hall probe to form a suitable gradient magnetic field environment; 0.2wt% Fe3O4@SiO2 was added to the electrolyte, and then the electrolyte containing Fe3O4@SiO2 was injected into the battery cell.

[0097] Furthermore, a customized high-pressure autoclave was used to heat the battery cell to 46.5°C at a heating rate of 2°C / min, and pressurized to 0.5MPa at 0.4MPa / s and maintained for 3min, so as to perform low-pressure infiltration on the silicon-carbon electrode; then, the battery cell was heated to 60°C at a heating rate of 2°C / min, and pressurized to 2MPa at 0.4MPa / s and maintained for 5min, so as to perform high-pressure filling on the silicon-carbon electrode; finally, the battery cell was cooled to 35°C at a cooling rate of 2°C / min, and the pressure was reduced to -0.1MPa and maintained for 2min, so as to perform negative pressure balance on the silicon-carbon electrode; and a lithium battery was obtained after packaging.

[0098] Table 1

[0099]

[0100] From Table 1 and Figure 2 It can be seen that compared with Comparative Example 1, the infiltration time of Examples 1-3 is greatly shortened during the infiltration process, the electrolyte distribution is more uniform, the filling rate of the pores is improved, and the interface impedance of the electrolyte is reduced; the retention rate of the cycle capacity of the lithium battery prepared in Example 1 through charge and discharge at different rates is better than that of Comparative Example 1, indicating that the lithium battery prepared in Example 1 has better lithium ion transmission efficiency, interface stability and battery cycle life.

[0101] The temperature-pressure synergy ratio for Example 1 satisfies 10.0±0.5°C / MPa, the temperature-pressure synergy ratio for Example 2 is greater than 10.0±0.5°C / MPa, and the temperature-pressure synergy ratio for Example 3 is less than 10.0±0.5°C / MPa. The infiltration times for both Examples 1 and 2 are relatively short, and the electrolyte distribution uniformity for Example 1 is superior to that for Example 2, indicating that a higher temperature-pressure synergy ratio is beneficial for improving electrolyte distribution uniformity. The pore filling rates for both Examples 1 and 3 are relatively good, and the electrolyte infiltration time for Example 1 is superior to that for Example 3, indicating that a temperature-pressure synergy ratio of 10.0±0.5°C / MPa is beneficial for improving electrolyte infiltration efficiency.

[0102] The above-described embodiments merely represent several implementation methods of the present disclosure. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the disclosed patent. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the scope of the present disclosure, all of which fall within the scope of protection of the present disclosure. Therefore, the scope of protection of the disclosed patent shall be determined by the appended claims.

Claims

1. A method for preparing a lithium battery with directional electrolyte infiltration, characterized in that: The steps include: A silicon-carbon electrode with a three-dimensional gradient pore structure is prepared, wherein the three-dimensional gradient pore structure is composed of surface straight-through pores, middle-layer tree-like branched pores, and bottom-layer liquid storage cavities that are interconnected and have a radial size gradient; Assembling the silicon-carbon electrode and the shell to form a battery core; The battery cell is placed in a gradient magnetic field environment with a magnetic field strength gradient distribution of 0.5T-1.2T; Adding a magnetic additive to an electrolyte, and then injecting the electrolyte containing the magnetic additive into a battery cell; The electrolyte and the silicon-carbon electrode in the battery cell are subjected to a temperature and pressure coordinated loading cycle of low-temperature and low-pressure infiltration, high-temperature and high-pressure filling, and low-temperature negative pressure balance in sequence; After packaging, a lithium battery is obtained.

2. The method for preparing a lithium battery by directional electrolyte infiltration according to claim 1, characterized in that: The magnetic additive is Fe3O4@SiO2 nanoparticles, and the magnetic susceptibility of the Fe3O4@SiO2 nanoparticles is greater than 1.0×10 -3 .

3. The method for preparing a lithium battery by directional electrolyte infiltration according to claim 2, characterized in that: Fe3O4@SiO2 nanoparticles have a core-shell structure consisting of a Fe3O4 core and a SiO2 shell. The diameter of the Fe3O4 core is 17nm-23nm, and the thickness of the SiO2 shell is 4nm-6nm.

4. The method for preparing a lithium battery by directional electrolyte infiltration according to claim 2, characterized in that: The concentration of the Fe3O4@SiO2 nanoparticles added to the electrolyte is in the range of 0.1 wt% to 0.3 wt%.

5. The method for preparing a lithium battery by directional electrolyte infiltration according to claim 1, characterized in that: The magnetic field intensity gradient increment of the gradient magnetic field environment is set to 0.3T / cm-0.5T / cm.

6. The method for preparing a lithium battery with directional electrolyte infiltration according to claim 1, characterized in that: The electrolyte and electrodes in the battery cell are subjected to a temperature and pressure coordinated loading cycle of low-temperature and low-pressure infiltration, high-temperature and high-pressure filling, and low-temperature negative pressure balance, including the following steps: The electrolyte in the battery cell is loaded with low pressure and the temperature is increased. The loaded low pressure of the low-pressure penetration is 0.5MPa-1.5MPa, and the temperature of the low-pressure penetration is 40℃-45℃. The silicon-carbon electrode is subjected to low-pressure penetration. The electrolyte in the battery cell is then loaded with high pressure and the temperature is increased. The loaded high pressure of the high-pressure filling is 1.5MPa-2.5MPa, and the temperature of the high-pressure filling is 50℃-60℃. The silicon-carbon electrode is subjected to high pressure filling. The electrolyte in the battery cell is then loaded with negative pressure and the temperature is reduced. The silicon-carbon electrode is negatively pressure balanced. The loaded negative pressure of the negative pressure balance is -0.2Mpa to -0.1Mpa, and the temperature of the negative pressure balance cooling is 30℃-40℃.

7. The method for preparing a lithium battery with directional electrolyte infiltration according to claim 6, characterized in that: The low-pressure penetration pressure is P1, the low-pressure penetration temperature is T1, the high-pressure penetration pressure is P2, the high-pressure penetration temperature is T2, and the ratio of the temperature and pressure in the collaborative loading cycle satisfies the following mathematical relationship:

8. The method for preparing a lithium battery with directional electrolyte infiltration according to claim 1, wherein: When the electrode and the electrolyte are subjected to temperature and pressure coordinated loading cycles, the following steps are also included: The penetration depth of the electrolyte is measured in real time by a dielectric sensor.

9. The method for preparing a lithium battery by directional electrolyte infiltration according to claim 1, characterized in that: The preparation of the electrode with the three-dimensional gradient pore structure comprises the following steps: PS microspheres and CaCO3 nanoparticles were dispersed in PVDF binder and combined with silicon-carbon composite materials to make composite electrodes; The composite electrode was transferred to a tube furnace and filled with N2, and the temperature was raised to 450°C and maintained at the temperature for 1 hour to form through-holes on the surface of the composite electrode; A mixture of N2 and H2 was introduced, and the temperature was raised to 550°C and maintained for 2 hours to form tree-like branched pores in the middle layer of the composite electrode; Argon gas was introduced and the temperature was raised to 650°C, and the temperature was maintained for 1 hour to form a bottom liquid storage cavity in the composite electrode, thereby obtaining a silicon-carbon electrode with a three-dimensional gradient pore structure.

10. A lithium ion battery, characterized in that: The method is obtained by the lithium battery preparation method of directional electrolyte infiltration according to any one of claims 1 to 9.

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