CN-122000323-A - Amorphous iron-based silicon-phosphorus composite anode material and preparation method and application thereof

CN122000323ACN 122000323 ACN122000323 ACN 122000323ACN-122000323-A

Abstract

The invention discloses an amorphous iron-based silicon-phosphorus composite anode material, a preparation method and application thereof, wherein the iron-based silicon-phosphorus composite anode material comprises raw materials of an iron simple substance, a silicon simple substance, a phosphorus simple substance and a carbon material, the molar ratio of silicon element to phosphorus element is 2:1-1:2, the molar ratio of silicon element to iron element is 8:1-1:2, the mass ratio of an iron/silicon/phosphorus mixture to the carbon material is 5:5-8:2, and the iron-based silicon-phosphorus composite anode material is prepared by a one-step or multi-step mechanical ball milling method. According to the iron-based silicon-phosphorus composite anode material, the introduction of the iron simple substance induces disorder of a microstructure, the diffusion energy barrier of lithium ions is reduced, meanwhile, the iron simple substance and lithium phosphide formed in situ respectively provide rich electron and ion transmission paths, and the huge volume deformation of the silicon anode in the lithiation/delithiation process is cooperatively buffered, so that the electrochemical reversibility, the cycling stability and the multiplying power performance of the silicon anode in the lithium storage process are effectively improved.

Inventors

XIAO WEI
ZHANG MENGLIN
LI XIFEI
Lv Mengfei
ZHAO HUIJING
WANG JINGJING

Assignees

西安理工大学

Dates

Publication Date: 20260508
Application Date: 20260202

Claims (10)

1. The amorphous iron-based silicon-phosphorus composite anode material is characterized by comprising an iron simple substance, a silicon simple substance, a phosphorus simple substance and a carbon material, wherein the molar ratio of silicon element to phosphorus element is 2:1-1:2, the molar ratio of silicon element to iron element is 8:1-1:2, the mass ratio of a mixture of the iron simple substance, the silicon simple substance and the phosphorus simple substance to the carbon material is 5:5-8:2, and the iron-based silicon-phosphorus composite anode material is prepared by a one-step or multi-step mechanical ball milling method.
2. The amorphous iron-based silicon-phosphorus composite anode material according to claim 1, wherein the elemental iron source is elemental iron powder or nano iron powder, the elemental silicon source is elemental silicon powder or nano silicon powder, the elemental phosphorus source is elemental phosphorus powder or nano phosphorus powder, and the carbon material is conductive carbon black or carbon nano material.
3. The amorphous iron-based silicon-phosphorus composite anode material according to claim 1, wherein the mass ratio of the mixture of elemental silicon, elemental phosphorus and elemental iron to the carbon material is 5:5 or 6:4 or 7:3 or 8:2, the purity of elemental silicon is 99.9%, the particle size is 50-500 nm, and the purity of elemental phosphorus is 98-99.99%.
4. A method for preparing the amorphous iron-based silicon-phosphorus composite anode material according to any one of claims 1 to 3, comprising the steps of: (1) Weighing a simple substance of silicon, a simple substance of phosphorus, a simple substance of iron and a carbon material; (2) Weighing grinding balls; (3) The iron-based silicon-phosphorus composite anode material is prepared by a one-step or multi-step mechanical ball milling method.
5. The method for preparing the amorphous iron-based silicon-phosphorus composite anode material according to claim 4, wherein the one-step mechanical ball milling method of the step (3) is characterized in that firstly, the raw materials weighed in the step (1) and the grinding balls weighed in the step (2) are transferred into a ball milling tank, then, the ball milling tank is assembled in argon, and the iron simple substance, the silicon simple substance, the phosphorus simple substance and the carbon material in the step (1) are mixed and milled by utilizing a ball mill, firstly, preliminary physical mixing is carried out for 8-24 hours at 100-200 rpm and 200-300 rpm respectively, then, high-energy ball milling is carried out for 12-48 hours at 300-600 rpm, and the preliminary physical mixing and the high-energy ball milling are repeated for at least 2 times to obtain the material.
6. The method for preparing an amorphous iron-based silicon-phosphorus composite anode material according to claim 4, wherein the multi-step mechanical ball milling method of step (3) is as follows: Firstly, transferring the iron simple substance, the silicon simple substance and the phosphorus simple substance weighed in the step (1) and the grinding balls weighed in the step (2) into a ball milling tank, and sealing and assembling in an argon atmosphere, and further adopting a gradient ball milling technology, firstly respectively performing primary physical mixing for 8-24 hours at 100-200 rpm and 200-300 rpm in sequence, then performing high-energy ball milling for 12-48 hours at 300-600 rpm, and repeating the ball milling step for at least 2 times to obtain an iron/silicon/phosphorus composite anode material; And (2) adding the carbon material weighed in the step (1) and the prepared iron/silicon/phosphorus composite anode material into a ball milling tank, sealing and assembling in an argon atmosphere, and finally adopting a gradient ball milling technology to perform primary physical mixing for 8-24 hours at 100-200 rpm and 200-300 rpm respectively, performing high-energy ball milling for 12-48 hours at 300-600 rpm rpm, and repeating the primary physical mixing and the high-energy ball milling for at least 2 times to obtain the amorphous iron-based silicon-phosphorus composite anode material.
7. The method for preparing the amorphous iron-based silicon-phosphorus composite anode material according to claim 5 or 6, wherein the mass ratio of the grinding balls to the raw materials is 20:1-50:1, the grinding balls are composed of stainless steel balls with different diameters of 2-10 mm, the protective atmosphere is one or more gas mixtures of argon, nitrogen, helium, argon and hydrogen or a gas mixture of nitrogen and hydrogen, the high-energy ball milling is performed for 8-24 hours at a rotating speed of 100-200 rpm, the high-energy ball milling is performed for 12-18 hours at a rotating speed of 100, 150 or 200 rpm, the high-energy ball milling is performed for 8-24 hours at a rotating speed of 200-300 rpm, the high-energy ball milling is performed for 12-18 hours at a rotating speed of 200-250 or 300 rpm, and the high-energy ball milling is performed for 24-36 hours at a rotating speed of 350, 400, 450 or 500 rpm.
8. The method for preparing the amorphous iron-based silicon-phosphorus composite anode material according to claim 7, wherein the mass ratio of the grinding balls to the raw materials is 20:1 or 30:1 or 40:1, three stainless steel balls with the dimensions of 2mm, 3mm and 5 mm are selected and mixed, and the mass ratio of the three stainless steel balls is 1:1:1.
9. The preparation method of the lithium ion half-cell is characterized by comprising the following steps: S1, weighing the iron-based silicon-phosphorus composite material, conductive carbon black and a binder according to the mass ratio of m to n to l to obtain a mixture, wherein m is 60-80 wt%, n is 10-30 wt%, and l is 10-30 wt%, and uniformly dispersing the mixture in deionized water to prepare electrode slurry; S2, uniformly coating the slurry obtained in the step S1 on a copper foil, vacuum drying at 60-70 ℃ for 10-15 hours, and then cutting the copper foil into round pole pieces for later use; S3, taking the pole piece obtained in the step S2 as a negative electrode, taking a lithium metal piece as a counter electrode, and assembling the half-cell after dropwise adding electrolyte; The electrolyte was 1.0M LiPF 6 in DMC: EC: EMC=1:1:1 Vol% with 10% FEC,2% VC.
10. The lithium ion full battery is characterized in that the preparation method comprises the following steps: S'1, weighing the iron-based silicon-phosphorus composite material, conductive carbon black and a binder according to the mass ratio of m to n, wherein m is 60-80 wt%, n is 10-30 wt%, and l is 10-30 wt%, uniformly dispersing the mixture in deionized water to prepare electrode slurry with stable property and uniform dispersion; S '2, uniformly coating the slurry obtained in the step S'1 on a copper foil, vacuum drying at 60-70 ℃ for 10-15 hours, and then cutting the copper foil into round pole pieces for later use; S'3, weighing an anode active material, conductive carbon black and a binder according to the mass ratio of m to N, wherein m is 60-80 wt%, N is 10-30 wt%, and l is 10-30 wt%, and uniformly dispersing the mixture in an N-methylpyrrolidone solvent to prepare electrode slurry; S '4, uniformly coating the slurry obtained in the step S'3 on an aluminum foil, drying for 10-15 hours at 90-120 ℃, and cutting the aluminum foil into round pole pieces for later use; S '5, carrying out physical prelithiation on the pole piece obtained in the step S'2, wherein the physical prelithiation is to physically attach the negative pole piece to lithium metal in a proper amount of electrolyte, and simultaneously, externally applying a pressure of 0.2-1.0 MPa, wherein the prelithiation time is 10-30 minutes; S '6, taking the pole piece obtained in the step S '5 as a negative electrode, taking the pole piece obtained in the step S '4 as a counter electrode, and assembling the full battery after dropwise adding electrolyte; The electrolyte was 1.0M LiPF 6 in EC: DMC: emc=3:4:3 vol% with 10% FEC,2% VC, or 1.0M LiPF 6 in DMC: emc=1:1:1 vol% with 10% FEC,2% VC, or 1.0M LiPF 6 in EC: emc=3:7 vol% with 5% FEC,2% VC,3% TEOSCN, or 1.0M LiPF 6 in EC: DMC: emc=1:1:1 vol% with 10% FEC,1-2% MBA, or 1.2M LiFSI with 0.05M LiDFOB in DME:HFE:FEC =3:6:1 vol%.

Description

Amorphous iron-based silicon-phosphorus composite anode material and preparation method and application thereof Technical Field The invention relates to the technical field of lithium ion battery anode materials, in particular to an amorphous iron-based silicon-phosphorus composite anode material, and a preparation method and application thereof. Background The lithium ion battery has the advantages of high energy density, long cycle life, no memory effect, mature manufacturing process and the like, is widely applied in the field of portable consumer electronics, and continuously promotes the rapid development of the electric automobile industry and the large-scale energy storage industry. However, current commercial lithium ion batteries are limited by the limited specific capacity and working voltage of the traditional electrode materials, the energy density reaches the limit, the multiplying power performance is poor, and the practical requirements of long endurance and quick charging of the electric automobile are difficult to meet, so that the basic electrochemical performance of the lithium ion batteries is urgently improved by updating an electrode material system. As a commercial lithium ion battery negative electrode material, graphite has a low and stable working voltage, but the theoretical capacity is 372 mAh g -1 only, and the design requirement of a high specific energy lithium ion battery is difficult to meet. Silicon, which is abundant in resource reserve and low in price, can undergo multi-electron reversible alloying/dealloying reaction with Li + at a lower potential, thus exhibiting extremely high theoretical capacity and lower operating voltage and ultra-high energy density, is considered as a key negative electrode material in next-generation lithium ion batteries, but silicon is significantly reduced in electrochemical performance due to poor structural stability and poor electron/ion conductivity during discharge/charge. Firstly, the huge volume expansion/contraction (400%) of the silicon anode material in the lithiation/delithiation process directly causes the structural collapse, electrode pulverization and the rapid attenuation of reversible capacity and working voltage. And secondly, the larger volume change can not only directly destroy the solid electrolyte interface layer of the silicon negative electrode and reduce the structural stability of the electrode, but also accelerate the interface side reaction of fresh exposed silicon particles and active electrolyte, promote the disordered growth of the non-uniform solid electrolyte interface layer, seriously consume active Li + for migration in the lithium ion battery, and further obviously reduce the coulomb efficiency and the cycle life of the active Li +. Worse still, the poor electron conductivity (10 -5~10-3 S cm-1) and ion conductivity (10 -14~10-13 cm2 s-1) of silicon itself will severely hinder the rapid migration of Li +/electrons in the active material during the electrochemical reaction, resulting in its large electrochemical polarization and poor rate capability at high currents. In the mainstream silicon negative electrode research route, the composite with carbon can improve the problems related to unstable structure and slow reaction kinetics in the lithium storage process of the silicon negative electrode material to a certain extent. However, in the silicon/carbon anode material prepared by the conventional chemical vapor deposition method and the mechanical ball milling method, the carbon material with low electrochemical activity occupies a relatively high proportion, so that the overall reversible capacity and energy density of the silicon/carbon anode material are directly weakened, and meanwhile, the lithium ion conduction capacity of the carbon material is poor, so that the lithium storage reaction kinetics and rate capability of the silicon/carbon anode material are further limited. Meanwhile, the currently reported porous silicon/carbon anode material has complex synthesis process, higher manufacturing cost and difficult industrial application. As a typical alloy type negative electrode material-phosphorus, the material is rich in reserves and low in cost, can perform reversible alloying/dealloying reaction with a plurality of Li +, and has extremely high theoretical specific capacity (2596 mAh g -1), excellent rate performance and outstanding volumetric energy density. Although the higher lithium storage potential of phosphorus (> 0.7V vs. Li/Li +) inevitably weakens the energy density, the safe working voltage of the negative electrode in the actual full battery (> 0V vs. Li/Li +) can effectively avoid the precipitation of the negative electrode lithium dendrite under high-rate charging and improve the safety of the lithium ion battery under working conditions. Meanwhile, phosphorus has a relatively low solid-phase lithium ion diffusion energy barrier and can spontaneously form lithium phosphide (Li 3 P)