A method for preparing a hollow tubular lithium battery cathode material based on ion implantation

Abstract

The present application relates to the field of ion implantation preparation of electrode materials, and particularly relates to a method for preparing hollow tubular lithium battery positive electrode materials based on ion implantation method, comprising the following steps: preparing lithium-containing metal-organic composite spinning solution, electrostatically spinning to prepare fiber membrane, processing periodic micropores on the surface of the fiber membrane through laser micropore array, controlling calcination through segmented temperature rise in air atmosphere, performing nano-channel etching and multilayer ion implantation after annealing by using ion implantation device, synchronously applying pulse direct current field, and performing surface functionalization modification on the material, wherein the present application adopts three-stage dynamic rotating ion implantation system, combines with pulse laser assisted opening technology, and realizes gradient element distribution and lattice directional growth of nanoscale thickness.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of ion implantation preparation of electrode materials, and in particular to a method for preparing a hollow tubular lithium battery positive electrode material based on ion implantation. BACKGROUND

[0002] There are three major problems in the preparation of existing lithium battery positive electrode materials: first, uneven element distribution, traditional co-precipitation method leads to insufficient surface active sites and unstable core structure, high nickel surface is easy to cause interface side reaction, low manganese core is easy to cause lattice distortion, resulting in first cycle capacity attenuation and low cycle capacity retention; second, low ion transmission efficiency, the detour path depending on the intergranular space makes the Warburg impedance high, and there is a lack of hierarchical channel design, the electrolyte penetration speed is slow, which is difficult to meet the fast charging demand; third, poor structure stability and interface compatibility, the random lattice is easy to interlayer slip, the proportion of layered phase is low, and the direct contact of electrolyte leads to serious transition metal ion dissolution, which aggravates the interface impedance growth.

[0003] Although the existing technology proposes element gradient doping, hollow structure design, surface functionalization modification and external field assisted crystallization, etc., there are still significant defects: gradient doping technology is limited by wet process, it is difficult to realize nanoscale precise control and has poor industrial repeatability; hollow structure depends on sacrificial template, the process is complex and the internal transmission efficiency is limited; surface modification cannot balance the liquid guiding and transmission demand, and does not solve the lattice distortion; static external field assistance has insufficient uniformity, which is difficult to cooperate with gradient doping. SUMMARY

[0004] In order to solve the problems mentioned in the background art, the present application provides a method for preparing a hollow tubular lithium battery positive electrode material based on ion implantation.

[0005] The method for preparing a hollow tubular lithium battery positive electrode material based on ion implantation provided by the present application adopts the following technical scheme:

[0006] A method for preparing a hollow tubular lithium battery positive electrode material based on ion implantation, comprising the steps of:

[0007] Preparation of lithium-containing metal-organic composite spinning solution, electrospinning to prepare fiber membrane, periodic micropores are formed on the surface of the fiber membrane by laser micropore array, and the periodic micropores are used as positioning marks of the Ar + plasma beam, and then the calcination is controlled by staged heating in air atmosphere to form a porous oxide skeleton;

[0008] Nanochannel etching and multilayer ion implantation are carried out by using an ion implantation device, Ar +Plasma beams are used to etch nanochannels that connect the inside and outside of the fiber at the bottom of the micropores on the surface of the fiber membrane. The diameter of the micropores is larger than the diameter of the nanochannels, forming a hierarchical gradient structure.

[0009] Then, different types of transition metal ions are coaxially implanted in multiple layers, and pulsed lasers are introduced during ion implantation to form crystal nucleus precursors;

[0010] The crystal nucleus precursor is first annealed in an argon atmosphere, and then transferred to a mixed atmosphere of oxygen and nitrogen for annealing, while a pulsed DC electric field is applied simultaneously.

[0011] Surface functionalization modification of materials yields hollow tubular lithium battery cathode materials.

[0012] Furthermore, the lithium-containing metal-organic composite spinning solution includes a polymer and a metal salt. The polymer is a mixture of polyimide and polyvinylpyrrolidone in a mass ratio of (2-4):1. The metal salt includes a lithium source and a transition metal salt. The lithium source is lithium nitrate, and the transition metal salt includes one or more of nickel nitrate, cobalt nitrate, and manganese nitrate.

[0013] Furthermore, calcination is controlled by segmented heating in an air atmosphere. Specifically, the temperature is increased from room temperature to 150°C at a rate of 3°C / min and held for 0.5 hours; the temperature is increased from 150°C to 300°C at a rate of 5°C / min and held for 1 hour; the temperature is increased from 300°C to 450°C at a rate of 5°C / min and held for 2 hours; and the temperature is held at 450°C for 2 hours.

[0014] Furthermore, the initial diameter of the micropores is 200–500 nm, Ar + Plasma beams etch through-hole nanochannels with diameters of 50-100 nm at the bottom of micropores on the fiber surface. + The plasma beam energy injection energy is 70–80 keV, and the current density is 8–12 μA / cm. 2 .

[0015] Furthermore, Ar + During the plasma beam implantation process, machine vision is used to locate micropores, which then become Ar atoms. + The only incident target of the ion beam will be Ar + The plasma beam is uniformly injected along the fiber axis at a tilt angle of 30°, etching through-through nanochannels along the fiber axis.

[0016] Furthermore, different types of transition metal ions are coaxially implanted in multiple layers. Specifically, three independent ion sources are used to generate Ni. 2+ Co 3+ Mn 4+ Ion beam, outer layer implanted with Ni 2+ and Co 3+ Ni implantation in the middle layer2+ Co 3+ Mn 4+ , core layer injects pure Mn 4+ , outer layer Ni 2+ and Co 3+ atomic ratio of Ni 2+ :Co 3+ =(5-7):(1-3), middle layer Ni 2+ , Co 3+ , Mn 4+ atomic ratio of Ni 2+ :Co 3+ :Mn 4+ =(4-6):(1-3):(0.5-1.5).

[0017] Further, the outer layer injection energy is 120-180 keV, the current density is 15-23 μA / cm 2 , the outer layer ions are incident along the nanochannel entrance outer wall at a scattering angle of 60°, and diffuse to the surface layer of the fiber through the nanochannel entrance; the middle layer injection energy is 80-120 keV, the current density is 8-12 μA / cm 2 , the middle layer ion beam is guided by the contraction of the diameter in the middle of the nanochannel, and is refracted and deflected, penetrating into the depth of the fiber along the channel wall, forming a gradient transition zone, and the middle layer ions are distributed in a ring shape on the channel wall surface; the core layer injection energy is 30-70 keV, and the current density is 3-7 μA / cm 2 , the core layer ions are concentrated in the skeleton lattice at the end of the nanochannel.

[0018] Further, the material is surface functionalized and modified, including gradient wettability modification, which includes the steps of:

[0019] The fiber membrane is fixed on the stainless steel sample holder through the edge of the conductive carbon tape, the fiber surface is uniformly bombarded by using a plasma generating device, then atomic layer deposition cycles are performed by using trimethylaluminum and deionized water as precursors, and the cycles are 50-60 times to form an Al2O3 coating layer of 5-10 nm; then a femtosecond laser is used to etch micron-level grooves and nanometer-level protrusions on the surface of the Al2O3 coating layer.

[0020] Further, the material is surface functionalized and modified, including three-dimensional transport channel strengthening treatment, which includes:

[0021] The edges of the surface micropores are treated by laser chamfering, and the micropore entrance diameter is expanded, an infrared heating plate is used to heat the fiber membrane, and then a carbon nanometer layer is deposited on the outer surface of the Al2O3 coating layer of the fiber membrane.

[0022] The application has the beneficial effects that: the application constructs a three-layer element gradient distribution of "high-activity shell layer-gradient transition layer-stable core layer" from outside to inside in the fiber membrane through three-stage dynamic ion implantation: high-energy implantation of Ni 2+ / Co 3+ forms a high-activity site enrichment area, significantly improves the surface redox activity of the material, and thus improves the specific capacity; low-energy implantation of pure Mn 4+ in the core layer effectively inhibits lattice distortion and transition metal ion dissolution during charging and discharging, reduces the risk of structure degradation, and enhances the cycle stability. In combination with the pulse direct current field assisted in the annealing process, Li + directional migration of transition metal ions is induced, the preferential growth of layered crystal faces is promoted, the transmission path of lithium ions in the interlayer is shortened, the order of the lattice structure is improved, and the capacity retention ability of the material at high rate is further optimized.

[0023] The laser micropore and the nano-channel formed by Ar + plasma beam etching form a hierarchical gradient structure of "macroscopic inlet-microscopic transmission", which shortens the lithium ion transmission path from the traditional micron-level gap of particles to the nanometer-level channel, greatly reduces the ion transmission resistance, and improves the electrolyte permeation speed. Surface functionalization further constructs a gradient wettability interface and a continuous conductive network of "outer repulsion and inner attraction": the Al2O3 coating isolates the electrolyte from the active material, reducing the interface side reaction; the carbon nanometer layer improves the bulk phase conductivity; the micron-level groove and the nanometer-level protrusion adjust the surface wettability, promote the rapid penetration of the electrolyte, and enhance the ion transmission capacity, solving the "ion congestion" problem of traditional materials at high rate from the structural level.

[0024] The pulse laser assisted ion implantation technology promotes the rapid combination of Li + and implanted ions through photo-thermal effect, forms a uniform size layered crystal nucleus precursor, avoids the uneven active sites caused by random ion doping in traditional methods, improves the uniformity of crystal nucleus growth and the surface active site density, and further optimizes the electrochemical activity of the material. The process of staged heating calcination and atmosphere control precisely compensates for the loss of lithium during calcination, ensures the uniform distribution of lithium elements, avoids the capacity attenuation caused by uneven lithium content, and improves the performance stability from the intrinsic composition level of the material.

[0025] Compared with the traditional preparation method, the positive electrode material prepared by the technical scheme of the application presents a significant optimization trend in multiple key performances: the specific capacity is significantly improved due to the design of the surface high-activity layer; the cycle stability is significantly enhanced due to the structural stability of the core layer and the interface modification; the rate performance is greatly improved due to the hierarchical transmission channel and the directional lattice structure; the ion diffusion coefficient and the conductivity are improved by orders of magnitude through the nano-channel network and the conductive coating; the interface side reaction and the transmission resistance are effectively reduced due to the gradient wettability modification and the coating protection, realizing the systematic performance improvement from the material structure to the electrochemical behavior. Attached Figure Description

[0026] Figure 1 This is a flowchart of the method for preparing hollow tubular lithium battery cathode material based on ion implantation in this application;

[0027] Figure 2 This is a cross-sectional SEM image of the hollow tubular lithium battery cathode material prepared in Example 1 of this application. Detailed Implementation

[0028] This invention discloses a method for preparing hollow tubular lithium battery cathode materials based on ion implantation, such as... Figure 1 As shown, a method for preparing hollow tubular lithium battery cathode materials based on ion implantation includes the following steps:

[0029] S1. Prepare a lithium-containing metal-organic composite spinning solution, comprising a polymer and a metal salt, wherein the polymer serves as the main skeleton material, and is composed of polyimide (weight-average molecular weight 50,000–80,000 g / mol) and polyvinylpyrrolidone (K-30 type, molecular weight 30,000–50,000 g / mol) at a mass ratio of (2–4):1, with the total mass accounting for 60–70% of the solid content of the spinning solution, providing the mechanical strength and spinning flowability required for fiber formation. The composite skeleton of polyimide and polyvinylpyrrolidone forms an oxide lattice template after calcination; the metal salt component includes a lithium source and a transition metal salt, wherein the lithium source is one of lithium nitrate, lithium carbonate, lithium hydroxide, or lithium oxalate, and in the examples, lithium nitrate is preferred as the lithium source, providing a lithium-ion precursor; the transition metal salt includes one or more of nickel nitrate, cobalt nitrate, and manganese nitrate, with a total concentration of transition metal salt of 1.2–1.8 mol / L, and a molar ratio of Li:M = 1.2:1 (M is Ni 2+ Co 2+ Mn 4+ (Total), to ensure excess lithium after sintering to compensate for lithium loss during calcination.

[0030] To prepare the lithium-containing metal-organic composite spinning solution, polyimide and polyvinylpyrrolidone are first added to the solvent DMF, with the solvent amount based on a solid content of 15–20% (mass-volume ratio). The solution is stirred in a water bath at 60°C for 12 hours until completely dissolved, forming a transparent and homogeneous polymer solution. Metered lithium nitrate, nickel nitrate, cobalt nitrate, and manganese nitrate are then added to the polymer solution sequentially, and stirring continues for 24 hours (room temperature, protected from light) to ensure uniform dispersion of the metal ions. After stirring, the solution is filtered through a 0.45 μm polytetrafluoroethylene (PTFE) membrane to remove undissolved impurities. Subsequently, it is allowed to stand in a vacuum oven (50°C, pressure <10 mbar) for 2 hours to remove air bubbles, finally obtaining a spinning solution with a viscosity of 80–120 mPa·s suitable for electrospinning.

[0031] Electrospinning was used to prepare the fibers. Specifically, an electrospinning device was configured with a high-voltage power supply (output voltage 15-30 kV), a micro-injection pump (flow rate 0.5-1.5 mL / h), a stainless steel needle (inner diameter 0.8 mm), and a drum-type collector (rotation speed 200-500 rpm). The spinning parameters were controlled as follows: the distance between the needle and the collector was 15-20 cm, the ambient temperature was 25±2℃, the relative humidity was 30-40%, and the solvent was prevented from evaporating too quickly to cause the fibers to break; by adjusting the rotation speed of the drum (200-500 rpm), a continuous and ordered fiber array was formed, the charged fibers were stretched and deposited onto the surface of the drum under the action of the electric field force, and the continuous fibers were stacked on the drum in an interlaced manner, thereby naturally forming a fiber membrane.

[0032] S2. Periodic micropores were formed on the surface of the fibers by laser micropore array, specifically, a femtosecond pulsed laser (wavelength 532 nm, pulse width 50 fs, and repetition frequency 100 kHz) was used, and a galvanometer scanning system (positioning accuracy ±1 μm) was configured to achieve high-precision processing of micrometer-level regions; the output power was controlled to be 5-15 W, the energy density was adjusted to be 0.2-0.5 J / cm 2 (avoiding excessive ablation of the oxide skeleton), the pulse overlap rate was 60-80%, and the edges of the micropores were smooth and free of cracks. During the processing, the fiber membrane obtained by electrospinning was laid on a three-dimensional moving platform (accuracy ±0.1 mm) and fixed by vacuum adsorption to prevent the fibers from moving during processing; a periodic micropore pattern was generated by computer-aided design, for example, the inter-pore distance of the periodic micropore pattern was 1-2 μm (uniformly distributed along the fiber axial direction and the circumferential direction), the diameter of a single micropore was 200-500 nm, the micropores were arranged in a hexagonal or circular array, and the coverage rate was 15-20% (surface area ratio); the processing was carried out in a clean room with a temperature of 20±2℃ and a humidity of ≤40% to avoid dust pollution affecting the processing accuracy.

[0033] The surface micropores served as “primary channels” for the subsequent step of Ar + plasma beam etching to provide positioning and guidance for the “secondary nanochannels”, forming a “micropore-nanochannel” hierarchical structure and shortening the ion implantation path. The micropores and nanochannels form a size gradient, the initial diameter of the micropores is 200-500 nm, and the diameter of the entrance is expanded to 300-600 nm by laser chamfering after three-dimensional transmission channel strengthening, serving as “primary channels” and being the macroscopic entrance of the electrolyte, having a larger opening size to facilitate the rapid entry of the electrolyte, and the nanochannels are formed by Ar +Etched by plasma beam, these nanochannels, with diameters of 50–100 nm, serve as "secondary channels" connecting the inside and outside of the fiber, providing pathways for transition metal ion implantation and lithium ion micro-transport. This dimensional difference forms a hierarchical gradient structure of "micropores–nanochannels." The larger diameter of the micropores facilitates rapid electrolyte introduction, while the smaller diameter of the nanochannels allows for precise control of ion implantation and gradient element distribution. Simultaneously, the interconnection between the nanochannels and micropores constructs a transport gradient from macroscopic to microscopic, shortening the ion transport path and improving overall transport efficiency.

[0034] S3. Calcination is carried out in an air atmosphere through segmented heating control to form a porous oxide skeleton. Specifically, a programmable box-type high-temperature muffle furnace is used, equipped with a quartz tube furnace chamber to ensure uniform air circulation and avoid local overheating that could lead to structural damage. The air flow rate is precisely controlled at 500–800 mL / min by a mass flow meter to maintain a positive pressure environment (approximately 10 mbar) in the furnace chamber, promoting complete oxidation and decomposition of the polymer. The air source is industrial-grade compressed air with a purity of ≥99.9%, which is filtered through a 0.22 μm filter to remove particulate matter and prevent impurities from contaminating the skeleton material. The muffle furnace is heated in stages. The temperature is increased from room temperature to 150°C at a rate of 3°C / min, and held for 0.5 hours. This stage removes residual DMF solvent from the fibers, preventing sudden solvent evaporation that could cause the fiber membrane to curl. The temperature is then increased from 150°C to 300°C at a rate of 5°C / min, and held for 1 hour. During this stage, polyvinylpyrrolidone (PVP) begins to decompose into CO2 and H2O, and polyimide (PI) partially carbonizes. The temperature is then increased from 300°C to 450°C at a rate of 5°C / min, and held for 2 hours. During this stage, PI is completely oxidized and decomposed into CO2 and N2, and metal salts (LiNO3, Ni(NO3)2, etc.) decompose into Li2O, NiO, CoO, and MnO2, forming the initial oxide framework. Holding at 450°C for 2 hours ensures complete polymer removal and allows the metal oxides to initially crystallize, forming a Li-MO (M = Ni / Co / Mn) porous precursor framework.

[0035] S4. Nanochannel etching and multilayer ion implantation using an ion implantation device.

[0036] In the first stage, Ar is injected obliquely along the fiber axis. + Plasma beams etch nanochannels that connect the inside and outside of fibers at the bottom of micropores on the fiber surface. Specifically, Ar... + The plasma beam energy implantation energy is 70–80 keV, preferably 75 keV. At this energy, Ar can be guaranteed. + Ions etch sufficiently deep nanochannels into the bottom of micropores on the fiber surface while avoiding excessive damage to the fiber structure. The current density is set to 8–12 μA / cm. 2At this current density, the ion implantation efficiency is high, and the uniformity and consistency of the nanochannel can be ensured. According to the size and micropore density of the fiber, the implantation time is accurately calculated and controlled to ensure that each micropore bottom can etch a nanochannel with appropriate depth and through the inside and outside of the fiber. For example, for a fiber with a diameter of 5-10 μm and a micropore spacing of 1-2 μm, the implantation time is controlled at 10-15 minutes. Vacuum adsorption and mechanical clamping are combined to ensure that the fiber is firmly fixed during implantation to avoid vibration or displacement affecting the etching accuracy of the nanochannel. The clamping material is selected from metal materials (such as molybdenum alloy) with good electrical conductivity and thermal stability to reduce interference with the ion implantation process. During implantation, the Ar + plasma beam is uniformly implanted along the fiber axis at an inclination angle of 30°. When the Ar + plasma beam is implanted into the micropore bottom of the fiber surface at an inclination angle of 30°, the ions collide and interact with the fiber material. Due to the high energy of the ions, they can knock out atoms in the fiber material, gradually etching a nanochannel at the micropore bottom. During etching, accurate control of ion implantation energy and angle is crucial, directly affecting the shape, size, and throughness of the nanochannel. At an inclination angle of 30°, the energy of the Ar + plasma beam can effectively act on the micropore bottom of the fiber surface, causing moderate collision and interaction in the fiber material, so that the ions knock out atoms in the fiber material, etching a through nanochannel with a diameter of 50-100 nm. If the angle is too small (e.g., nearly parallel), the ion beam energy is too widely distributed laterally on the fiber surface, the etching depth is insufficient, and it is difficult to form a through channel; if the angle is too large (e.g., nearly vertical), the ion beam energy is too concentrated, which can easily cause excessive damage to the fiber structure, damaging the mechanical strength and integrity of the fiber membrane. At 30°, the inclined implantation of the ion beam along the fiber axis allows the ion beam to be uniformly distributed on the fiber surface, ensuring that each micropore bottom can etch a nanochannel with appropriate depth and throughness. Through the ion implantation process, a through nanochannel with a diameter of 50-100 nm is successfully etched at the micropore bottom of the fiber surface. In this application, the density of the nanochannel is controlled at 5-10 per square micrometer, which can ensure the efficiency of ion transmission and will not cause excessive impact on the mechanical properties of the fiber. The etching of the nanochannel is based on the previously prepared fiber with surface micropores. The surface micropores of the fiber provide a good foundation and guidance for the etching of the nanochannel. The micropores form a regular array on the surface of the fiber membrane and are positioned by a machine vision system, becoming the only incident target of the Ar + ion beam, so that the Ar +The plasma beam can be accurately injected into the bottom of the micropore and etched along the fiber axis to form a through nanochannel. Meanwhile, the previous calcination process makes the fiber form a porous oxide skeleton, which has high porosity and specific surface area, is beneficial to ion transmission and diffusion, and further improves the efficiency and quality of nanochannel etching. The etched nanochannel provides a key transmission channel for the subsequent multi-layer coaxial injection of transition metal ions. Through the nanochannel, transition metal ions can more effectively enter the fiber interior and achieve gradient distribution in different layers, thereby realizing precise control of material performance. In addition, the nanochannel, together with the surface micropore and intergranular gap inside the fiber, forms a three-dimensional transmission network, providing a convenient channel for the rapid transmission of lithium ions in the material, which helps to improve the electrochemical performance of the material.

[0037] In the second stage, different kinds of transition metal ions are injected in multiple layers, and the atomic percentage of the transition metal ions in each layer decreases from the outer layer to the core layer. Specifically, three independent ion sources are provided to generate Ni 2+ , Co 3 + , Mn 4+ ion beams, Ni 2+ and Co 3+ are injected in the outer layer, the injection energy is 120-180 keV, the current density is 15-23 μA / cm 2 , a high-concentration shell layer is quickly formed, Ni 2+ , Co 3+ , Mn 4+ are injected in the middle layer, the injection energy is 80-120 keV, and the current density is 8-12 μA / cm 2 , so that they are uniformly penetrated, Mn 4+ is injected in the core layer, the energy is 30-70 keV, and the current density is 3-7 μA / cm 2 , to accurately control the deep doping. High-energy injection (120-180 keV) in the outer layer, Ni 2+ / Co 3+ ions quickly penetrate to the surface layer of the fiber to form a high-concentration active layer (total Ni / Co ratio 100%) due to high energy (range 250-300 nm); medium-energy injection (80-120 keV) in the middle layer, the reduced ion energy shortens the range to 400-500 nm, and the penetration ability of Ni / Co ions is weakened (ratio 87.5%→62.5%), Mn 4+ begins to dope (ratio 12.5%), and low-energy injection (30-70 keV) in the core layer: only Mn 4+ ions (range 500-600 nm) can reach the core area, and Ni / Co ions cannot penetrate due to insufficient energy, achieving pure Mn doping in the core layer.

[0038] Outer high activity layer injects Ni 2+ and Co 3+ , ion ratio: Ni 2+ and Co 3+ The atomic ratio of (5-7):(1-3); the outer high activity layer injects Ni 2+ and Co 3+ preferentially occupy the surface active sites of the framework to form a high-capacity outer layer with a thickness of 200-300 nm, the ion beam is incident along the outer sidewall of the nanochannel, and a 60° scattering angle is used to achieve uniform doping of the fiber surface to a depth of 200 nm, and an 808 nm pulsed laser (power density 1.0 J / cm 2 , frequency 10 Hz) is applied synchronously, the laser pulse is triggered synchronously with the ion beam pulse (1 kHz), and the photo-thermal effect (local temperature rise ≤ 150℃) promotes the rapid combination of Li + and Ni 2+ / Co 3+ to form a Li(Ni 0.75 Co 0.25 )O2 crystal nucleus precursor.

[0039] Middle layer transition layer injects Ni 2+ , Co 3+ , Mn 4+ , ternary mixed ratio Ni 2+ :Co 3+ :Mn 4+ =(4-6):(1-3):(0.5-1.5) (achieve Ni / Co content decrease and Mn content increase in the middle layer to balance capacity and structural stability.), penetrate the outer layer with an ion beam of energy 80-120 keV, form a gradient transition zone in the middle layer (300-500 nm deep), and use the diameter contraction effect of the nanochannel (500 nm at the entrance → 200 nm in the middle) to guide the ion beam to deflect towards the inside of the fiber, combined with a platform 360° rotation, to achieve circumferential uniform doping (circumferential concentration deviation <3%).

[0040] Core layer stable layer injects pure Mn 4+ , energy 30-70 keV, only into the core area of the fiber (>500 nm deep), forming a high-Mn-content stable core layer (diameter 500-800 nm) to suppress lattice distortion during charging and discharging.

[0041] Outer high-energy ions (120-180 keV) achieve rapid surface doping, middle layer (80-120 keV) moderate energy balance depth and uniformity, core layer (30-70 keV) low energy to ensure only shallow penetration, forming a gradient distribution of decreasing Ni / Co content and increasing Mn content from the outside to the inside.

[0042] The outer layer ions diffuse rapidly through the channel entrance, the middle layer ions penetrate along the channel wall, and the core layer ions only reach the end of the channel, achieving precise control of "channel-guided-layered injection".

[0043] Multilayer coaxial injection of transition metal ions (Ni 2+ / Co 3+ / Mn 4+ ) completely relies on the pre-etched nanochannel (diameter 50-100 nm) as the only transmission path. The specific mechanism is as follows:

[0044] Outer layer injection (120-180 keV, Ni 2+ / Co 3+ ): A high-energy ion beam is incident along the outer wall of the nanochannel entrance at a scattering angle of 60°, and rapidly diffuses to a depth of 200-300 nm on the surface of the fiber using the channel entrance expansion effect (300-600 nm), forming a high-concentration active layer. The ions are mainly distributed on the outer wall of the channel entrance area and do not touch the core space of the channel;

[0045] Middle layer injection (80-120 keV, Ni 2+ / Co 3+ / Mn 4+ ): A medium-energy ion beam is guided by the nanochannel middle diameter contraction (200 nm) and refracted and deflected, penetrating to a depth of 300-500 nm inside the fiber along the channel wall, forming a gradient transition zone. The ions are distributed in a ring shape on the channel wall, leaving a through space of more than 50 nm in the center of the channel;

[0046] Core layer injection (30-70 keV, Mn 4+ ): A low-energy ion beam can only reach the end of the nanochannel (>500 nm deep), forming a pure Mn 4+ doped layer in the core region of the fiber, with ions concentrated in the skeletal lattice at the end of the channel, and the main structure of the channel remaining intact.

[0047] The penetration depth of each layer of ions is determined by the injection energy (120-180 keV→30-70 keV) and the geometric constraints of the nanochannel, forming an element gradient from the entrance to the end of the channel (outer layer Ni / Co enrichment→middle layer Ni / Co / Mn mixing→core layer Mn enrichment), and completely realizing doping in the inner wall and surrounding skeletal lattice of the nanochannel.

[0048] The nanochannel as the only path for ion implantation ensures the layered penetration of transition metal ions along the preset trajectory, avoiding random doping of the channel-free structure, and forms a transmission-doping synergistic network with the "micropore-nanochannel" hierarchical structure. The gradient distribution of the crystal nucleus precursor is annealed at 600°C, the outer layer of high Ni / Co region preferentially forms a high-activity layered phase, the core layer of high Mn region forms a stable spinel phase, and the axial lattice directional growth is realized by combining with the pulsed direct current electric field, realizing the "lattice directional growth" goal.

[0049] The pulsed laser promotes the combination of Li + and the injected transition metal ions on the channel wall surface to form a crystal nucleus with uniform size, and the crystal nucleus precursor presents a layered α-NaFeO2 type structure. + The diffusion coefficient is improved, which promotes the combination of Li + and the injected transition metal ions on the channel wall surface to form a crystal nucleus with uniform size, and the crystal nucleus precursor presents a layered α-NaFeO2 type structure.

[0050] The crystal nucleus precursor formation process, the injected Ni 2+ / Co 3+ / Mn 4+ ion reacts with Li + in the skeleton under the action of laser to form a [Li(Ni / Co / Mn)O2] coordination intermediate on the nanochannel wall surface, and the local high-concentration Li + environment induced by laser forms a layered crystal nucleus precursor with a thickness of 5-10 nm.

[0051] S5. The crystal nucleus precursor is annealed at 200°C for 1h in an argon environment, and then transferred to an oxygen and nitrogen mixed gas atmosphere at 600°C for 2h, and a pulsed direct current electric field is applied at the same time. Specifically, a tubular annealing furnace is used, high-purity argon is introduced, the flow rate is 50mL / min, the positive pressure in the furnace (10mbar) is maintained to avoid air infiltration. The heating rate is controlled at 10°C / min, and the temperature is kept at 200°C for 1h after being raised from room temperature. The temperature is monitored in real time by a thermocouple to ensure uniform heating of the crystal nucleus precursor. The effect is to eliminate the lattice distortion (such as vacancies, interstitial atoms and other defects) generated during the ion implantation process, rearrange the atoms through low-energy vibration, stabilize the layered structure of the crystal nucleus precursor, and inhibit the disordered migration of Li + at low temperature to provide an ordered lattice template for subsequent high-temperature annealing.

[0052] High-temperature annealing was performed in an oxygen-nitrogen mixed atmosphere, with oxygen volume fraction of 5–15% and nitrogen as the carrier gas at a total flow rate of 200 mL / min. The temperature was increased from 200 °C to 600 °C at a rate of 20 °C / min and held for 2 hours. During this period, the O2 concentration in the atmosphere was monitored online using a mass spectrometer to ensure the oxidation environment required for the formation of the layered phase. The phase transformation mechanism was that high oxygen partial pressure promoted the stabilization of the high valence state of transition metal ions (Ni). 2+ / Co 3 + / Mn 4+ ), with Li + It forms a stable layered α-NaFeO2-type structure, suppressing the formation of spinel phase.

[0053] The pulsed DC electric field uses parallel plate electrodes with a fiber membrane laid flat in the middle. The electric field direction is consistent with the fiber axis, the electric field strength is 10 V / cm, the pulse frequency is 1 Hz, and the duty cycle is 50% (1 s on, 1 s off). The pulsed electric field induces Li + With the directional migration of transition metal ions along the fiber axis, and under the assistance of an electric field, the interlayer distance of the nucleation precursor shrinks, enhancing the stability of the layered structure and suppressing lattice slip during cycling. High-temperature activation of ion diffusion at 600℃ and the pulsed electric field provide the directional driving force, forming a dual effect of "thermal activation + electric field guidance," enabling Li... + The diffusion coefficient inside the crystal nucleus is increased, and the electric field-induced ion migration reduces the stress concentration at the grain boundaries. Combined with the temperature gradient of graded annealing, the axial residual stress of the material is reduced, thereby improving the structural stability.

[0054] S6. Surface functionalization modification of the material is performed to obtain a hollow tubular lithium battery cathode material. Specifically, surface functionalization modification includes gradient wettability modification and three-dimensional transport channel enhancement treatment;

[0055] The gradient wettability modification includes the following steps:

[0056] Plasma pretreatment specifically involves fixing the fiber membrane to a stainless steel sample holder using conductive carbon tape along its edges. A plasma generator, equipped with an RF plasma source and a gas mass flow controller, is used to uniformly bombard the fiber surface. The Ar gas purity is ≥99.999%, and the flow rate is 50 sccm (standard cubic centimeters per minute). During the pretreatment process, Ar... + Ions with kinetic energy of 10–20 eV bombard and remove organic matter (such as residual DMF solvent and calcined residual carbon) adsorbed on the fiber surface. Plasma induces surface hydroxylation to generate -OH groups, providing chemisorption sites for TMA precursors.

[0057] Then, using trimethylaluminum (TMA) and deionized water as precursors, atomic layer deposition cycles are performed for 50-60 times to form a 5-10 nm uniform coating layer, with a deposition rate of 0.1 nm / cycle and a surface coverage of ≥99%. Specifically, a single cycle process is as follows: the TMA tank is heated to 50°C (saturated vapor pressure of 12 Torr), gaseous TMA is pulsed into the reaction chamber through N2 carrier gas (flow rate of 20 sccm) with a pulse width of 0.1 s to ensure only surface chemical adsorption (physical adsorption <5%), TMA molecules undergo monolayer chemical adsorption (self-limiting reaction) with the fiber surface hydroxyl groups to form -Al(CH3)2 active sites, with a theoretical monolayer thickness of 0.16 nm; then, using high-purity N2 (purity ≥99.999%) at a flow rate of 100 sccm, the residual TMA and byproducts (CH4, C2H6) in the reaction chamber are removed by purging for 5 s to avoid cross-cycle contamination; the reaction chamber pressure is suddenly increased from 200 mTorr to 300 mTorr and then rapidly decreased to 200 mTorr by a molecular pump to ensure that no residual gas is retained; then, by starting the deionized water ultrasonic atomizer, the deionized water is converted into droplets with an average particle size of 30 nm, which are pulsed into the reaction chamber through N2 carrier gas (flow rate of 10 sccm) with a pulse width of 0.1 s, and the atomized water undergoes a hydrolysis reaction with the adsorbed TMA (-Al(CH3)2 + H2O → -Al(OH)(CH3) + CH4↑) to generate Al-O bonds and release methane, completing the deposition of a monolayer of Al2O3, and finally, N2 is used for purging for 5 s to remove residual water mist and reaction byproducts, providing a clean surface for the next TMA adsorption cycle and ensuring a clear interlayer interface (without mixed layers).

[0058] The Al2O3 coating layer prevents direct contact between the electrolyte and the active material, reduces interfacial side reactions, and lowers the surface roughness of the coating layer, thereby reducing the adsorption resistance of the electrolyte.

[0059] Then, a secondary laser treatment is performed, which uses a femtosecond laser (wavelength of 532 nm, energy density of 0.3-0.4 J / cm 2 ), combined with a galvanometer scanning system, to etch micron-scale grooves (pitch of 5-10 μm, depth of 200-300 nm) and nanoscale protrusions (diameter of 50-100 nm, height of 80-120 nm) on the coating surface. Specifically, the surface pattern is designed with lower-density grooves (pitch of 10 μm) etched on the outer layer region (fiber outer surface) to adjust the contact angle to 120°±5° (hydrophobic); the inner layer region (nanochannel inner wall) retains the original coating, with a contact angle of 60°±3° (hydrophilic), forming a "hydrophobic outer layer and hydrophilic inner layer" gradient. The outer layer hydrophobic structure reduces the ineffective retention of electrolyte on the fiber surface, promoting rapid penetration; the inner layer hydrophilic channel wall enhances the transport capacity of the solvated ions, improving the electrolyte penetration speed. + The transport capacity of the solvated ions improves the electrolyte penetration speed.

[0060] wherein the three-dimensional transmission channel reinforcing treatment comprises the steps of:

[0061] The surface micro-hole edges are laser chamfered (chamfer angle 45°) to eliminate stress concentration caused by sharp edges, while expanding the micro-hole entrance diameter to 300-600 nm to improve the efficiency of electrolyte entering the nanochannel. The fiber membrane is heated to 150°C by an infrared heating plate and kept for 10 min, and a thermocouple is used to monitor the surface temperature of the fiber membrane in real time, so that the intercrystalline gap connectivity rate of the skeleton is improved. Then a 5 nm thick carbon nanolayer is deposited on the outer surface of the Al2O3 coating of the fiber membrane to form a continuous conductive coating, which improves the bulk phase conductivity and reduces the charge transfer resistance.

[0062] The Al2O3 coating effectively inhibits the dissolution of transition metal ions, and the gradient wettability shortens the penetration time of the electrolyte on the surface of the fiber membrane and improves the transmission speed in the nanochannel. After surface modification, the tensile strength of the fiber membrane is improved.

[0063] Example 1: Preparation of hollow tubular lithium battery positive electrode material based on ion implantation method

[0064] S1. Preparation of lithium metal-organic composite spinning solution and fiber preparation;

[0065] The raw materials are configured as shown in Table 1 (based on 100 mL of spinning solution):

[0066]

[0067]

[0068] Table 1 Preparation of lithium metal-organic composite spinning solution in Example 1

[0069] PI and PVP are added to DMF, stirred in a 60°C water bath for 12 hours (speed 200 rpm), until a transparent and uniform solution (viscosity 100 mPa·s) is formed. Lithium nitrate, nickel nitrate, cobalt nitrate, and manganese nitrate are added in sequence, and stirred at room temperature for 24 hours (speed 150 rpm) in the dark to ensure uniform dispersion of metal ions. The undissolved impurities are filtered through a 0.45 μm polytetrafluoroethylene filter membrane, and transferred to a vacuum oven (50°C, pressure <10 mbar) for 2 hours to remove bubbles, obtaining a spinning solution suitable for electrospinning.

[0070] The electrospinning equipment parameters are configured as a high-voltage power supply of 20 kV, a needle inner diameter of 0.8 mm, a pushing rate of 1.0 mL / h, a drum collector rotating speed of 300 rpm, a needle-to-collector distance of 18 cm, an ambient temperature of 25±2 ℃, a humidity of 35%, the electrospinning equipment is started, charged spinning liquid droplets are stretched to form fibers, the charged fibers are stretched and deposited on the drum surface under the action of electric field force, and the continuous fibers are staggered and stacked on the drum to naturally form a fiber membrane with a thickness of 50-100 μm.

[0071] S2. Laser micropore processing, a femtosecond laser is used, the wavelength is 532 nm, the pulse width is 50 fs, the repetition frequency is 100 kHz, and the energy density is 0.3 J / cm 2 ; the micropores are designed as a hexagonal array with a pore spacing of 1.5 μm and a diameter of 300 nm, the surface area coverage rate is 18%, the fiber membrane is fixed by vacuum adsorption, the processing is performed in a clean room (temperature 20±2 ℃, humidity ≤40%), the preset pattern is scanned through a galvanometer scanning system, the pulse overlap rate is 70%, and periodic micropores (density 5×10 5 cm 2 ) with smooth edges are processed.

[0072] S3. The muffle furnace is controlled to be heated in sections, the temperature is increased from room temperature to 150 ℃ at a rate of 3 ℃ / min, and the temperature is kept for 0.5 h to remove residual DMF solvent in the fiber and avoid fiber membrane curling caused by sudden solvent volatilization; the temperature is increased from 150 ℃ to 300 ℃ at a rate of 5 ℃ / min, and the temperature is kept for 1 h, polyvinylpyrrolidone (PVP) starts to decompose into CO2 and H2O, and polyimide (PI) is partially carbonized; the temperature is increased from 300 ℃ to 450 ℃ at a rate of 5 ℃ / min, and the temperature is kept for 2 h, the PI is completely oxidized and decomposed into CO2 and N2, and metal salts (LiNO3, Ni(NO3)2, etc.) are decomposed into Li2O, NiO, CoO and MnO2 to form an initial oxide skeleton. The temperature is kept at 450 ℃ for 2 h to ensure that the polymer is completely removed and the metal oxide is preliminarily crystallized to form a Li-M-O (M=Ni / Co / Mn) porous precursor skeleton.

[0073] S4. Nano-channel etching and multi-layer ion implantation

[0074] First, Ar + plasma beams are injected along the fiber axis at an angle, and the ion implantation device is etched with the parameters configured as an ion energy of 75 keV, a current density of 10 μA / cm 2 , and an injection angle of 30° along the fiber axis, the fiber membrane is adsorbed and clamped by vacuum and machinery, the etching time is 12 minutes, the micropores are positioned by a machine vision system to ensure that the Ar + ion beam is only incident on the bottom of the micropore, and a through nano-channel is etched to form a trapezoidal hierarchical structure with the micropore.

[0075] Multilayer coaxial ion implantation, outer layer high activity layer (Ni 2+ : Co 3+ = 6:2), ion energy 150 keV, current density 20 μA / cm 2 , incident angle 60° scattering angle, synchronous trigger 808 nm pulsed laser (power density 1.0 J / cm 2 , frequency 10 Hz), incident along the outside wall of the nanochannel entrance, forming a high concentration of active layer (Ni / Co total proportion of 100%) of 250 nm depth.

[0076] Middle layer gradient transition layer (Ni 2+ : Co 3+ : Mn 4+ = 5:2:1), ion energy 100 keV, current density 10 μA / cm 2 , using the middle shrinkage of the nanochannel to guide the ion deflection, 360° rotation platform to ensure the circumferential concentration deviation <3%, penetration depth 400 nm.

[0077] Core layer stable layer (pure Mn 4+ ), ion energy 50 keV, current density 5 μA / cm 2 , only into > 500 nm depth, forming a diameter of 500-800 nm of pure Mn 4+ doped layer.

[0078] S5. Subsection annealing and electric field assisted crystallization;

[0079] Tubular furnace into high purity argon (flow 50 mL / min), to 200 ℃ at 10 ℃ / min, 1 hour, eliminate ion implantation caused by lattice vacancies and interstitial atoms, stable crystal nucleus precursor layer structure. Oxygen nitrogen annealing and pulse electric field assisted, O2 volume fraction 10%, N2 carrier gas (total flow 200 mL / min), to 600 ℃ at 20 ℃ / min, 2 hours, parallel plate electrode to apply pulse direct current electric field (electric field strength 10 V / cm, pulse frequency 1 Hz, duty cycle 50%), along the fiber axis to induce Li + directional migration, promote (003) crystal face preferential growth, layered phase ratio to 92%.

[0080] S6. Surface functional modification;

[0081] Gradient wettability modification, Ar flow 50 sccm, ion kinetic energy 10-20 eV, bombard the fiber surface for 30 seconds, remove organic matter and induce surface hydroxylation (-OH group density ≥ 1 × 1015 / cm 2 ), precursor trimethylaluminum (TMA) and deionized water, 150 ℃ for 55 times.

[0082] Secondary laser etching, femtosecond laser energy density 0.3 J / cm 2 , etching micron-level grooves (pitch 8 μm, depth 250 nm) and nanometer-level protrusions (diameter 80 nm, height 100 nm), adjusting the contact angle of the outer surface of the fiber to 120°±5° (hydrophobic), and the contact angle of the inner wall of the nanochannel to 60°±3° (hydrophilic).

[0083] Three-dimensional transmission channel reinforcement, laser chamfering 45° processing of the micro-hole edge, expanding the inlet diameter to 500 nm, improving the electrolyte import efficiency, heating to 150℃ by an infrared heating plate, and keeping warm for 10 minutes (temperature fluctuation ±2℃), so that the intercrystalline gap connectivity rate of the skeleton is improved from 75% to 92%, and a 5 nm thick carbon nanolayer is deposited on the outer surface of the Al2O3 coating layer by chemical vapor deposition (CVD).

[0084] Figure 2 is a cross-sectional SEM image of the hollow tubular lithium battery cathode material based on ion implantation prepared in Example 1.

[0085] Comparative Example 1

[0086] Lithium battery cathode material prepared by traditional coprecipitation method

[0087] Li(Ni 0.8 Co 0.15 Mn 0.05 )O2 particles without nanochannels and gradient doping, ion transmission depends on the intergranular gap, the specific steps are as follows:

[0088] Dissolve nickel nitrate, cobalt nitrate, and manganese nitrate in deionized water according to the stoichiometric ratio to form a mixed solution;

[0089] Dissolve lithium carbonate in deionized water to form a lithium carbonate solution;

[0090] Under stirring conditions, slowly add the lithium carbonate solution to the mixed solution to form a precipitate;

[0091] After filtering, washing, and drying the precipitate, calcine it at high temperature to obtain Li(Ni 0.8 Co 0.15 Mn 0.05 )O2 particles.

[0092] Test Example:

[0093] Evaluate the specific capacity (mAh / g), cycle stability (capacity retention rate), rate performance (specific capacity under different current densities), ion diffusion coefficient (cm 2 / s), and electrical conductivity (S / cm) of the cathode materials prepared in Example 1 and Comparative Example 1;

[0094] The specific capacity test adopts constant current charge and discharge test. The positive electrode material is charged and discharged at a certain current density, and the charge and discharge capacity is recorded. The cycle stability test is carried out by multiple charge and discharge cycles at a certain current density, and the capacity retention rate after each cycle is calculated. The rate performance test is carried out by charge and discharge test at different current densities, and the specific capacity at different current densities is recorded. The ion diffusion coefficient test adopts electrochemical impedance spectroscopy (EIS) test, and the ion diffusion coefficient is obtained by fitting. The conductivity test adopts four-probe method to test the conductivity of the positive electrode material.

[0095] The performance test data of Example 1 is as follows:

[0096] Specific capacity: at 0.1C current density, the first charge specific capacity is 200 mAh / g, and the first discharge specific capacity is 180 mAh / g.

[0097] Cycle stability: at 0.5C current density, after 100 cycles, the capacity retention rate is 90%.

[0098] Rate performance: at 0.1C, 0.2C, 0.5C, 1C, 2C current density, the specific capacity is 180 mAh / g, 160 mAh / g, 140 mAh / g, 120 mAh / g, 100 mAh / g, respectively.

[0099] Ion diffusion coefficient: obtained by EIS test, the ion diffusion coefficient is 1.0×10 -10 cm 2 / s.

[0100] Conductivity: obtained by four-probe method, the conductivity is 1.0×10 -3 S / cm.

[0101] The performance test data of Comparative Example 1 is as follows:

[0102] Specific capacity: at 0.1C current density, the first charge specific capacity is 160 mAh / g, and the first discharge specific capacity is 140 mAh / g.

[0103] Cycle stability: at 0.5C current density, after 100 cycles, the capacity retention rate is 80%.

[0104] Rate performance: at 0.1C, 0.2C, 0.5C, 1C, 2C current density, the specific capacity is 140 mAh / g, 120 mAh / g, 100 mAh / g, 80 mAh / g, 60 mAh / g, respectively.

[0105] Ion diffusion coefficient: obtained by EIS test, the ion diffusion coefficient is 1.0×10 -11 cm 2 / s.

[0106] The conductivity is 1.0 x 10 -4 S / cm.

[0107] It can be seen from the performance test data of Comparative Example 1 and Example 1 that the positive electrode material prepared in Example 1 is superior to the positive electrode material prepared in Comparative Example 1 in specific capacity, cycle stability, rate performance, ion diffusion coefficient and conductivity, etc., which indicates that the technical scheme of the present application can effectively improve the performance of the positive electrode material of the lithium battery.

[0108] Example 2: Preparation of hollow tubular lithium battery positive electrode material based on ion implantation method

[0109] S1. Preparation of lithium metal-organic composite spinning solution and fiber

[0110] The raw materials are configured as shown in Table 2 (based on 100 mL of spinning solution):

[0111]

[0112] The other components and preparation process are the same as in Example 1 (the volume of solvent DMF is adjusted to a solid content of 18%, the viscosity of the spinning solution is 80 mPa·s, and the magnetic field assisted electrospinning parameters are the same, forming a fiber membrane with a diameter of 5 μm and a pitch of 5 μm).

[0113] The micropore processing and calcination process of S2 and S3 are the same as in Example 1.

[0114] S4. Nano-channel etching and multi-layer ion implantation

[0115] Ar + Plasma beam etching: ion energy 70 keV, current density 8 μA / cm 2 , etching time 15 minutes, nano-channel diameter 70 nm.

[0116] Multi-layer coaxial ion implantation: outer layer high activity layer (Ni 2+ : Co 3+ = 7:1), ion energy 120 keV, current density 15 μA / cm 2 , incident angle 55° scattering angle, active layer thickness 200 nm.

[0117] Middle layer gradient transition layer (Ni 2+ : Co 3+ : Mn 4+ = 6:1:0.5), ion energy 80 keV, current density 8 μA / cm 2 , penetration depth 300 nm.

[0118] Core layer stable layer (pure Mn4+ ), ion energy 30keV, current density 3μA / cm² 2 The diameter of the doped layer is 500 nm.

[0119] S5 segmented annealing is the same as in Example 1;

[0120] S6. Surface functionalization modification;

[0121] Gradient wettability modification: Atomic layer deposition (ALD) cycles of 50 times to form a 5 nm Al2O3 coating.

[0122] Secondary laser etching: micron groove spacing 10μm, depth 200nm, nano protrusion diameter 50nm, contact angle outer layer 115°±5° (hydrophobic), inner layer 65°±3° (hydrophilic).

[0123] Enhanced three-dimensional transport channels: the diameter of the micropore inlet is increased to 300 nm, and the thickness of the carbon nanolayer is 5 nm.

[0124] Experimental example:

[0125] The specific capacity (mAh / g), cycle stability (capacity retention), rate performance (specific capacity at different current densities), and ion diffusion coefficient (cm²) of the cathode materials prepared in Examples 2, 1, and 1 were evaluated. 2 / s), conductivity (S / cm);

[0126] Specific capacity testing employed constant current charge-discharge testing, where the cathode material was charged and discharged at a specific current density, and the charge-discharge capacity was recorded. Cycle stability testing involved multiple charge-discharge cycles at a specific current density, and the capacity retention rate after each cycle was calculated. Rate performance testing involved charge-discharge tests at different current densities, and the specific capacity at each current density was recorded. Ion diffusion coefficient testing utilized electrochemical impedance spectroscopy (EIS), and the ion diffusion coefficient was obtained through fitting. Conductivity testing employed the four-probe method to measure the conductivity of the cathode material.

[0127] The performance test data is shown in Table 3 below:

[0128]

[0129] Table 3 Performance Comparison of Examples and Comparative Examples

[0130] Example 2 Outer Ni 2+ ∶Co 3+ =7:1 (higher than 6:2 in Example 1), the high Ni content increased the active sites, and the first discharge specific capacity was increased to 185 mAh / g (180 mAh / g in Example 1), which is 32% higher than Comparative Example 1 (140 mAh / g).

[0131] The nanochannels have a diameter of 70 nm (50-100 nm in Example 1), a moderate pore size that ensures efficient ion transport while enhancing redox reactivity through the high Ni outer layer. Example 2 uses a Ni layer... 2+ ∶Co 3+ ∶Mn 4+ = 6∶1∶0.5 (Mn content is lower than 5∶2∶1 in Example 1), core layer pure Mn 4+ The thickness of the doped region remained unchanged, but the reduction in the Mn content in the middle layer may have slightly decreased the lattice stability. The cycle retention rate was 88% (90% in Example 1), which is still significantly better than Comparative Example 1 (80%). The ion diffusion coefficient in Example 2 reached 1.2 × 10⁻⁶. -10 cm 2 / s (Example 1 is 1.0 × 10 -10 Thanks to the nanochannel diameter contraction effect (70 nm) and high-energy ion implantation (120 keV) in the outer layer, the specific capacity remained at 105 mAh / g at a high rate of 2C (100 mAh / g in Example 1), compared to only 60 mAh / g in Comparative Example 1. In Example 2, the surface carbon nanolayer (5 nm) and gradient wettability modification synergistically achieved a conductivity of 1.5 × 10⁻⁶. -3 S / cm (Example 1: 1.0 × 10⁻⁶) -3 This reduces charge transport resistance and further improves high-rate performance.

[0132] Example 2 shows a slight improvement in specific capacity and rate performance compared to Example 1, while maintaining excellent cycle stability. Its overall performance is significantly better than that of the traditional co-precipitation method (Comparative Example 1), verifying the synergistic optimization effect of ion implantation combined with gradient structure design on the electrochemical performance of cathode materials.

[0133] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0134] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a hollow tubular lithium battery cathode material based on ion implantation, characterized in that, Comprising the steps of: A lithium-containing metal-organic composite spinning solution is prepared, a fiber membrane is prepared by electrospinning, periodic micropores are formed on the surface of the fiber membrane by laser micropore array processing, and the periodic micropores are used as Positioning marks of the plasma beam, and then calcination is controlled by staged temperature rise in an air atmosphere to form a porous oxide skeleton; The nanochannel etching and multilayer ion implantation are carried out by using an ion implantation device The nanochannel is etched at the bottom of the micro-pore on the surface of the fiber membrane by using a plasma beam, and the nanochannel penetrates the inside and outside of the fiber, the diameter of the micro-pore is greater than that of the nanochannel, and a hierarchical gradient structure is formed. Then multi-layer coaxial injection of different kinds of transition metal ions, ion implantation when introducing pulsed laser, forming crystal nucleus precursor; The crystal nucleus precursor is annealed in an argon environment first, and then transferred into an oxygen and nitrogen mixed atmosphere for annealing, and a pulsed direct current electric field is applied synchronously; Surface functional modification is performed on the material to obtain a hollow tubular lithium battery positive electrode material; The lithium-containing metal-organic composite spinning solution comprises a polymer and a metal salt, the polymer is a mixture of polyimide and polyvinylpyrrolidone in a mass ratio of (2-4) : 1, the metal salt comprises a lithium source and a transition metal salt, the lithium source is lithium nitrate, and the transition metal salt comprises one or more of nickel nitrate, cobalt nitrate and manganese nitrate; The calcination is controlled by staged temperature rising in an air atmosphere, specifically, the temperature is raised from room temperature to 150 DEG C at a controlled temperature rising rate of 3 DEG C / min, the temperature is kept for 0.5 h, the temperature is raised from 150 DEG C to 300 DEG C at a controlled temperature rising rate of 5 DEG C / min, the temperature is kept for 1 h, the temperature is raised from 300 DEG C to 450 DEG C at a controlled temperature rising rate of 5 DEG C / min, the temperature is kept for 2 h, and the temperature is kept for 2 h at 450 DEG C; Multi-layer coaxial injection of different kinds of transition metal ions, specifically, equipped with three groups of independent ion sources, respectively generating Ni 2+ , Co 3+ , Mn 4+ ion beams, outer layer injection of Ni 2+ and Co 3+ , middle layer injection of Ni 2+ , Co 3+ , Mn 4+ , core layer injection of pure Mn 4+ , the atomic ratio of outer layer Ni 2+ and Co 3+ is Ni 2+ ∶Co 3+ =(5~7)∶(1~3), the atomic ratio of middle layer Ni 2+ , Co 3+ , Mn 4+ is Ni 2+ ∶Co 3+ ∶Mn 4+ =(4~6)∶(1~3)∶(0.5~1.5).

2. The method for preparing a hollow tubular cathode material for lithium batteries based on ion implantation according to claim 1, characterized in that, micro-holes with initial diameter of 200-500 nm, plasma beam etching through nano-channels with diameter of 50-100 nm at the bottom of the micro-holes on the fiber surface, plasma beam energy injection energy of 70-80 keV, current density of 8-12 μΑ / cm².

3. The method for preparing a hollow tubular cathode material for lithium batteries based on ion implantation according to claim 1, characterized in that, The plasma beam, in the implantation process, locates the micro-holes by machine vision, and the micro-holes become The only incident target point of the ion beam, will The plasma beam is uniformly implanted along the fiber axis at an inclination angle of 30°, and a through nano-channel is etched along the fiber axis.

4. The method for preparing a hollow tubular cathode material for lithium batteries based on ion implantation according to claim 1, characterized in that, The outer layer injection energy is 120-180 keV, the current density is 15-23 mu A / cm2, the outer layer ions are incident along the nanochannel entrance outer wall at a scattering angle of 60 DEG, and diffuse to the fiber surface layer through the nanochannel entrance; the middle layer injection energy is 80-120 keV, the current density is 8-12 mu A / cm2, the middle layer ion beam is guided under the diameter contraction of the middle part of the nanochannel, and refraction deflection occurs, penetrates into the depth of the fiber interior along the channel wall, forms a gradient transition zone, and the middle layer ions are distributed in a ring shape on the channel wall surface; the core layer injection energy is 30-70 keV, the current density is 3-7 mu A / cm2, and the core layer ions are concentrated in the skeleton lattice at the end of the nanochannel.

5. The method for preparing a hollow tubular cathode material for lithium batteries based on ion implantation according to claim 1, characterized in that, Surface functional modification is performed on the material, including gradient wettability modification, and the gradient wettability modification comprises the steps of: The fiber membrane is fixed on the stainless steel sample holder by the edge of the conductive carbon tape, the surface of the fiber is uniformly bombarded by the plasma generating device, then the atomic layer deposition cycle is carried out by using trimethylaluminum and deionized water as the precursor, the cycle is 50-60 times, and the 5-10 nm coating layer; then the micron-level groove and nanometer-level convex are etched on the surface of the coating layer by using a femtosecond laser.

6. The method for preparing a hollow tubular cathode material for lithium batteries based on ion implantation according to claim 1, characterized in that, Surface functional modification is performed on the material, including three-dimensional transmission channel strengthening treatment, and the three-dimensional transmission channel strengthening treatment comprises: Surface functional modification is performed on the material, including three-dimensional transmission channel strengthening treatment, and the three-dimensional transmission channel strengthening treatment comprises: The laser chamfering treatment is performed on the edge of the surface micropore, and the diameter of the micropore entrance is expanded. An infrared heating plate is used to heat the fiber membrane, and then a carbon nanolayer is deposited on the outer surface of the coating layer of the fiber membrane. The coating outer surface deposits a carbon nanolayer.

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