CN110380035B

CN110380035B - Slurry for preparing negative electrode material and preparation method of negative electrode material

Info

Publication number: CN110380035B
Application number: CN201910668420.XA
Authority: CN
Inventors: 何伟东; 陈东江; 丁显波; 陈太宝; 袁博韬
Original assignee: Shenzhen Liliu Technology Co ltd
Current assignee: Shenzhen Liliu Technology Co ltd
Priority date: 2019-07-23
Filing date: 2019-07-23
Publication date: 2020-09-08
Anticipated expiration: 2039-07-23
Also published as: CN110380035A

Abstract

The invention discloses slurry for preparing a negative electrode material and a preparation method of the negative electrode material, wherein the slurry comprises the following components in percentage by mass: 90 to 99.98 percent of organic solvent and 0.02 to 10 percent of active substance; the organic solvent comprises a combination of at least two of oleylamine, polyethylene glycol, oleic acid and octadecene; the active substance is ferric oxide, ferric hydroxide, organic substance containing iron source capable of being thermally decomposed into ferric oxide or ferric hydroxide, or mixture of at least two of the inorganic substances. The preparation method of the cathode material provided by the invention is simple in process and easy to implement, is beneficial to improving the production efficiency and saving the production cost, and the comprehensive performance of the cathode material is superior to that of the traditional commercial C material electrode. Thus utilizing Fe₃The battery assembled by the electrode material prepared by the method C has high cycle stability, high rate performance and obviously enhanced battery safety performance.

Description

Slurry for preparing negative electrode material and preparation method of negative electrode material

Technical Field

The invention belongs to the technical field of lithium batteries, and particularly relates to slurry for preparing a negative electrode material and a preparation method of the negative electrode material.

Background

Lithium ion batteries have been widely used in various portable electronic devices and electric vehicles due to their advantages of zero memory effect, low self-discharge, etc., but the electrochemical performance of the batteries is often limited by the performance of the electrodes, so that it is a challenge to find a novel electrode material with high performance, high cycle and high rate. The battery negative electrode material currently in commercial use is carbon. The limited energy density (372mAh g-1) and the poor rate capability, thermal stability and mechanical property of the material can not satisfy the requirement of peopleThere is an increasing quest for high capacity, high full performance batteries. Therefore, the research and development of new materials with high capacity, high thermal stability, strong mechanical properties and low price have very important significance for breaking through the limitation of the existing energy density and further improving the safety performance of the battery. Generally, the charge and discharge mechanism of the negative electrode material of the battery can be classified into the following three mechanisms. Emerging two-dimensional materials, such as graphene, with conductivity (10 ∼ 10)⁶S m^-1) Is more than the traditional graphite (10 to 10)⁵S m^-1) The electrodes are an order of magnitude higher, which leads to significantly improved rate performance, considered to be the best potential electrode in the future. However, one of the serious challenges is the complex and high manufacturing cost, and the inability to mass-produce for large-scale industry limits his industrial/commercial process. Transition metal oxides, including binary transition metal oxides (CuO, Fe)₃O₄NiO, etc.) and ternary transition metal oxides (ZnFe)₂O₄、Zn₂SnO₄、Co₂MnO₄Etc.) has a higher theoretical capacity (500-1000mAh g)^-1) And have received attention from many researchers. However, during charging and discharging, transition metal cations are implanted in Li₂Further reacting in the unit cell of O to generate a metal simple substance. However, the main challenge of transition metal oxides is that the large volume change in their electrochemical reaction does not guarantee the structural integrity of the material. Powdering of the active material is often accompanied during charge and discharge, thereby causing serious capacity fading and safety problems. In addition, the poor electron conductivity also makes its cycle life and charge-discharge capacity very limited. On the other hand, materials such as Si, Sn, and Ge can release a large capacity because they can form an alloy with lithium ions during charging and discharging lithiation. However, the barrier limiting further commercialization of Si electrodes is also the near 400% volume change during their charging and discharging. Its large volume change causes particle powdering and cannot guarantee the structural integrity of the SEI film. Fe₃C and its derivatives are the focus of research due to their better chemical stability, high conductivity (-106S m-1) and mechanical strength. But Fe prepared by the existing method and raw material₃The combination of C and its derivatives is poor, thus limiting Fe₃C and the application of the derivative thereof in lithium batteries.

Accordingly, the prior art is deficient and needs improvement.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the slurry for preparing the cathode material and the preparation method of the cathode material are provided, so that the assembled battery has high cycle stability, high rate performance and remarkably enhanced battery safety performance.

The technical scheme of the invention is as follows: the slurry for preparing the negative electrode material and the preparation method of the negative electrode material are provided, and the slurry comprises the following components in percentage by mass:

90 to 99.98 percent of organic solvent,

0.02% -10% of active substances.

The organic solvent comprises a combination of at least two of oleylamine, polyethylene glycol, oleic acid and octadecene; the active substance is ferric oxide, ferric hydroxide, organic substance containing iron source capable of being thermally decomposed into ferric oxide or ferric hydroxide, or mixture of at least two of the inorganic substances.

The preparation method comprises the following steps.

S1: weighing the organic solvent and the active substance according to the mass ratio, and filling the organic solvent and the active substance into a container for mixing to obtain slurry for preparing the lithium battery negative electrode material.

S2: and (4) vacuumizing the container containing the slurry for preparing the lithium battery negative electrode material in the step S1 to the negative pressure of 1-10 kpa, stabilizing at room temperature for 10-100 min, and introducing inert gas to obtain first suspension.

S3: and (4) stirring the first suspension prepared in the step (S2) for 10S-60 min at 80-180 ℃ in an inert gas atmosphere to form a stable and uniform second suspension. In this step, still in an inert gas atmosphere; if the organic or inorganic substance containing the iron source is used in step S1, the organic or inorganic substance containing the iron source is decomposed into ferric oxide or ferric hydroxide at 80-180 ℃, and the ferric oxide or ferric hydroxide is uniformly dispersed in the organic solvent through step S2 and step S3. The anhydrous and anaerobic technology can improve the dispersion uniformity of ferric oxide or ferric hydroxide in an organic solvent; and the mixing is carried out in a heating state, so that the mixing uniformity can be effectively improved.

S4: and (4) heating the second suspension in the step S3 to 200-450 ℃ for 0.1-4 h in an inert gas atmosphere to obtain a third suspension. In this step, the high temperature will cause the organic solvent to crack, with the cracked product adhering to the surface of the ferric oxide or ferric hydroxide particles. In this step, it is still in an inert gas atmosphere. The steps S1-S4 are all carried out in the same container, so that the operation steps can be effectively simplified, and the operation is convenient. The steps S2-S4 are all under inert gas, oxygen is isolated, and organic solvent is prevented from being oxidized during pyrolysis.

S5: and (4) carrying out solid-liquid separation on the third suspension prepared in the step S4, separating into a solid component and a liquid component, and drying the solid component at the temperature of 50-130 ℃ for 1-36 h to obtain solid particles.

S6: and (4) carrying out high-temperature heat treatment on the solid particles obtained in the step (S5) under the protection of inert gas, wherein the time of the heat treatment is 0.5-6 h, and the temperature of the heat treatment is 800-1300 ℃, so as to obtain the lithium battery cathode material. Reducing ferric oxide or ferric hydroxide into Fe at high temperature by the pyrolysis product, and further reacting Fe with the pyrolysis product to generate carbon-coated Fe₃C. A carbon nanomaterial.

Further, the organic or inorganic particles containing an iron source are: one or the combination of at least two of ferric perchlorate, ferric acetylacetonate and carbonyl iron, wherein the particle size of the ferric oxide and the ferric hydroxide is 30 nm-90 nm.

Further, the lithium battery cathode material is carbon-coated Fe₃C. A carbon nanomaterial mixture; the particle size of the mixture is not more than 50nm, Fe₃The crystal structure of C is an orthorhombic crystal form, and the coated carbon and carbon nano material are in a hexagonal structure; the carbon-coated Fe₃C is a core-shell structure.

Further, the step S2 is: and (4) vacuumizing the container containing the slurry for preparing the lithium battery negative electrode material in the step S1 to the negative pressure of 2-3 kpa, stabilizing at room temperature for 30-60 min, and introducing inert gas to obtain first suspension.

Further, the step S3 is: and (4) stirring the first suspension prepared in the step S2 at 110-160 ℃ for 20S-30 min to form stable and uniform second suspension.

Further, the step S4 is: and heating the second suspension liquid obtained in the step S3 to 250-350 ℃ for 1-h to obtain a third suspension liquid.

Further, the step S5 is: and (4) carrying out solid-liquid separation on the third suspension prepared in the step S4, separating into a solid component and a liquid component, and drying the solid component at the temperature of 80-100 ℃ for 18-24 h to obtain solid particles.

Further, the step S6 is: and (4) carrying out high-temperature heat treatment on the solid particles obtained in the step (S5) under the protection of inert gas, wherein the heat treatment time is 1.5-2 h, and the heat treatment temperature is 900-1200 ℃, so as to obtain the lithium battery cathode material with the core-shell structure.

Carbon coated Fe₃The C can meet the application in lithium batteries due to good chemical stability and high conductivity, and the high conductivity of the C obviously improves the rate capability of the batteries. Iron element and carbon element rich in earth reserves enable carbon to coat Fe₃The material C is low in price and easy to prepare. In addition, during the formation process, C atoms occupy the gaps of the Fe unit cell and cause electron shrinkage of the d-layer, so that the activation energy of the electrode reaction of the battery can be reduced, and the battery has higher capacity. Due to one Fe₃The C cell can only store 1/6 lithium ions, so Fe₃C can provide energy for mutual conversion of lipids and ethers in SEI film components of electrode part to enable the battery to have higher capacity, so that Fe is coated by carbon₃The battery assembled by the electrode material prepared by the method C has high cycle stability, high rate performance and obviously enhanced battery safety performance.

By adopting the scheme, the invention provides slurry for preparing the cathode material and a preparation method of the cathode material, and the prepared carbon-coated Fe₃The chemical stability and the high conductivity of the C can meet the requirement of application in lithium batteries, and the high conductivity of the C is obviously improved by times of that of the batteriesRate capability. Therefore, the battery assembled by the electrode material prepared by the invention has high cycle stability, high rate performance and obviously enhanced battery safety performance.

Drawings

Fig. 1 is an SEM image of the anode material obtained in example 1 of the present invention;

fig. 2 is a TEM image of an anode material obtained in example 1 of the present invention;

FIG. 3 is an HR-TEM image of the anode material obtained in example 1 of the present invention;

FIG. 4 shows that the material obtained in example 1 of the present invention is a negative electrode, and lithium is a positive electrode in 1M LiPF₆CV diagram of half-cell composed under electrolyte;

FIG. 5 is an EIS diagram of a half cell composed of different electrolytes and obtained in example 1, wherein the material is a negative electrode and lithium is a positive electrode;

fig. 6 is a CV diagram of half-cells composed of different electrolytes with the material negative and the lithium positive obtained in example 1 of the present invention;

FIG. 7 shows that the material obtained in example 1 of the present invention is a negative electrode, and lithium is a positive electrode in 1M LiPF₆Cycle diagram of half cell composed of electrolyte.

Detailed Description

The invention is described in detail below with reference to the figures and the specific embodiments.

Example 1

The invention provides slurry for preparing a negative electrode material and a preparation method of the negative electrode material, wherein the slurry comprises the following components in percentage by mass:

99.91 percent of organic solvent,

0.09% of active substance;

the organic solvent is a combination of 50 wt% oleic acid and 50 wt% octadecene; the active substance is ferric acetylacetonate.

The preparation method of the anode material comprises the following steps:

S2: and (5) vacuumizing the container containing the slurry for preparing the lithium battery negative electrode material in the step S1 to a negative pressure of 3kpa, stabilizing at room temperature for 40min, and introducing argon to obtain first suspension.

S3: the first suspension prepared in step S2 was stirred at 110 ℃ for 25min under an inert gas atmosphere to form a stable and uniform second suspension.

S4: the second suspension in step S3 was heated to 285 ℃ for 1.5 hours under an inert gas atmosphere to obtain a third suspension.

S5: and (4) carrying out solid-liquid separation on the third suspension prepared in the step S4, separating into a solid component and a liquid component, and drying the solid component at 90 ℃ for 24h to obtain solid particles.

S6, carrying out high-temperature heat treatment on the solid particles obtained in the step S5 under the protection of argon for 2 hours at 900 ℃, and obtaining the lithium battery cathode material with the particle size of 40nm-50 nm.

Referring to fig. 1, fig. 1 is a Scanning Electron Microscope (SEM) image of the negative electrode material obtained in the present embodiment; fig. 2 is a transmission electron micrograph (TEM image) of the anode material obtained in this example; fig. 3 is a high power transmission electron micrograph (HR-TEM image) and a selected area electron diffraction pattern (sea image) of the anode material obtained in this example. As can be seen from fig. 1, the negative electrode material prepared in this example is spherical particles and strip-shaped particles, the anhydrous and oxygen-free technology can improve the uniformity of iron sesquioxide or iron hydroxide dispersed in an organic solvent, and after thermal reduction treatment, the formed carbon-coated Fe₃The C particles can be uniformly dispersed in the C material substrate, and the shape of the nano particles is kept. The catalytic effect of Fe also catalyzes C to form a nano-carbon layer, further increasing the conductivity of the electrode.

Referring to FIG. 2, it can be seen from the TEM image of FIG. 2 that the nano-carbon layer covers Fe₃C, forming carbon-coated Fe₃C nanometer core-shell structure.

Referring to FIG. 3, FIG. 3 shows HR-TEM test results of the negative electrode material obtained in this example, 0.33nm lattice fringe vs. Fe₃The (020) crystal face of the C particle and the nano carbon layer (004) crystal face which is opposite to the 0.34nm crystal lattice stripe. SAED diffractionThe figure proves Fe₃The C/C particles have good crystallinity. Fe can be seen from the HR-TEM image and the SEAD image₃The crystal structure of C is orthorhombic, and the coated carbon is hexagonal. From the figure, Fe can be seen₃The degree of crystallinity of both the C and nanocarbon layers was very high.

Referring to fig. 4, fig. 4 shows that the material obtained in this embodiment is a negative electrode, and lithium is a positive electrode in 1M LiPF₆CV diagram of half-cell composed under electrolyte; after the stable SEI is formed in the first circle of the half cell, CV curves of 2 nd and 3 rd circles almost coincide, which proves that the anode material obtained in the embodiment has good electrochemical and structural stability.

Referring to fig. 5, fig. 5 is an EIS diagram of a half-cell composed of different electrolytes and made of a negative electrode material and a positive electrode material according to the present embodiment; the negative electrode material obtained in this example was 1M LiPF₆Minimum semi-circle radius under the electrolyte, which demonstrates 1M LiPF₆The interfacial resistance under the electrolyte is minimal. The negative electrode material obtained in this example was 2M LiPF₆With 1M LiClO₄The interfacial transfer resistance under the electrolyte is almost the same.

Referring to fig. 6, fig. 6 is a CV diagram of a half-cell composed of different electrolytes and made of a negative electrode material and a positive electrode material obtained in the present embodiment. As can be seen from the figure, there are significant differences in CV diagrams for different electrolytes. 1M LiPF₆And 2MLiPF₆The oxidation-reduction peaks appeared in the electrolyte at approximately the same positions. While in 1M LiClO₄There is a significant change in the position of the redox peak present in the electrolyte. Description of carbon-coated Fe₃The catalytic performance of the electrode of C has a strong correlation with the F element in the electrolyte.

Referring to fig. 7, fig. 7 shows that the material obtained in this embodiment is a negative electrode, lithium is a positive electrode, and the material is 1M LiPF₆Cycle diagram of half cell composed of electrolyte. Core-shell structure Fe prepared in this example₃The good structure retentivity and conductivity of the C/C nano material are that the battery has the capacity of 480mAh g < -1 > under the high current density of 2A g < -1 >, and the charging and discharging efficiency of 95 percent is still maintained after 1000 cycles. This proves that Fe₃C/C nano electrode material structureStability of (2).

Example 2

99.6 percent of organic solvent,

0.4% of active substance;

the organic solvent is a combination of 40 wt% of polyethylene glycol and 60 wt% of octadecene; the active substance is ferric hydroxide.

The preparation method of the anode material comprises the following steps:

S2: and (5) vacuumizing the container containing the slurry for preparing the lithium battery negative electrode material in the step S1 to the negative pressure of 2kpa, stabilizing at room temperature for 40min, and introducing argon to obtain first suspension.

S3: the first suspension prepared in step S2 was stirred at 110 ℃ for 15min under an inert gas atmosphere to form a stable and uniform second suspension.

S4: the second suspension in step S3 is heated to 300 ℃ for 1 hour under an inert gas atmosphere to obtain a third suspension.

S5: and (4) carrying out solid-liquid separation on the third suspension prepared in the step S4, separating into a solid component and a liquid component, and drying the solid component at 80 ℃ for 18h to obtain solid particles.

S6, carrying out high-temperature heat treatment on the solid particles obtained in the step S5 under the protection of argon for 1.5h at 1000 ℃, so as to obtain the lithium battery cathode material with the particle size of 38nm-47 nm.

Example 3

95 percent of organic solvent,

5% of active substance;

the organic solvent is a combination of 60 wt% oleic acid and 40 wt% polyethylene glycol; the active substance is carbonyl iron.

The preparation method of the anode material comprises the following steps:

S2: and (5) vacuumizing the container containing the slurry for preparing the lithium battery negative electrode material in the step S1 to a negative pressure of 3kpa, stabilizing at room temperature for 60min, and introducing argon to obtain first suspension.

S3: the first suspension prepared in step S2 was stirred at 160 ℃ for 30min under an inert gas atmosphere to form a stable and uniform second suspension.

S4: the second suspension in step S3 is heated to 250 ℃ for 2 hours under an inert gas atmosphere to obtain a third suspension.

S5: and (4) performing solid-liquid separation on the third suspension prepared in the step S4 to obtain a solid component and a liquid component, and drying the solid component at 100 ℃ for 23h to obtain solid particles.

Example 4

98 percent of organic solvent,

2% of active substance;

the organic solvent is a combination of 65 wt% oleic acid and 35 wt% polyethylene glycol; the active substance is ferric oxide.

The preparation method of the anode material comprises the following steps:

S2: and (5) vacuumizing the container containing the slurry for preparing the lithium battery negative electrode material in the step S1 to a negative pressure of 3kpa, stabilizing at room temperature for 30min, and introducing argon to obtain first suspension.

S3: the first suspension prepared in step S2 was stirred at 110 ℃ for 20min under an inert gas atmosphere to form a stable and uniform second suspension.

S4: the second suspension in step S3 is heated to 350 ℃ for 1.5 hours under an inert gas atmosphere to obtain a third suspension.

S6, carrying out high-temperature heat treatment on the solid particles obtained in the step S5 under the protection of argon for 2 hours at 1200 ℃, and obtaining the lithium battery cathode material with the particle size of 30-40 nm.

Example 5

99.95 percent of organic solvent,

0.05% of active substance;

the organic solvent is a combination of 55 wt% oleic acid and 45 wt% polyethylene glycol; the active substance is ferric perchlorate.

The preparation method of the anode material comprises the following steps:

S3: the first suspension prepared in step S2 was stirred at 110 ℃ for 2min under an inert gas atmosphere to form a stable and uniform second suspension.

S4: the second suspension in step S3 was heated to 265 ℃ for 1.5 hours under an inert gas atmosphere to obtain a third suspension.

S6, carrying out high-temperature heat treatment on the solid particles obtained in the step S5 under the protection of argon for 2 hours at 1000 ℃, and obtaining the lithium battery cathode material with the particle size of 27nm-40 nm.

Example 6

91 percent of organic solvent,

9% of active substance;

the organic solvent is a combination of 40 wt% oleic acid and 60 wt% octadecene; the active substance is ferric acetylacetonate.

The preparation method of the anode material comprises the following steps:

The following table shows the capacity and charge-discharge efficiency of half-cells composed of the negative electrode materials obtained in examples 1 to 6 and a 1m lipf6 electrolyte in which graphitic carbon is the negative electrode and lithium is the positive electrode.

In summary, the invention provides a slurry for preparing a negative electrode material and a preparation method of the negative electrode material, and the prepared carbon-coated Fe₃The chemical stability and the high conductivity of the C can meet the requirement of application in a lithium battery, and the high conductivity of the C obviously improves the rate capability of the battery. Therefore, the battery assembled by the electrode material prepared by the invention has high cycle stability, high rate performance and obviously enhanced battery safety performance.

The present invention is not limited to the above preferred embodiments, and any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A preparation method of a negative electrode material is characterized by comprising the following steps:

s1: weighing an organic solvent and an active substance according to a mass ratio, and filling the organic solvent and the active substance into a container for mixing to obtain slurry for preparing the lithium battery cathode material; the slurry comprises the following components in percentage by mass: 90 to 99.98 percent of organic solvent and 0.02 to 10 percent of active substance; the organic solvent comprises a combination of at least two of oleylamine, polyethylene glycol, oleic acid and octadecene; the active substance is ferric oxide, ferric hydroxide, organic matter containing iron source capable of being thermally decomposed into ferric oxide or ferric hydroxide, or mixture of at least two of the inorganic matters;

s2: vacuumizing the container containing the slurry for preparing the lithium battery negative electrode material in the step S1 to a negative pressure of 1-10 kpa, stabilizing at room temperature for 10-100 min, and introducing inert gas to obtain a first suspension;

s3: stirring the first suspension prepared in the step S2 for 10S-60 min at 80-180 ℃ in an inert gas atmosphere to form stable and uniform second suspension;

s4: heating the second suspension in the step S3 to 200-450 ℃ for 0.1-4 h in an inert gas atmosphere to obtain a third suspension;

s5: carrying out solid-liquid separation on the third suspension prepared in the step S4 to obtain a solid component and a liquid component, and drying the solid component at the temperature of 50-130 ℃ for 1-36 h to obtain solid particles;

s6: and (4) carrying out high-temperature heat treatment on the solid particles obtained in the step (S5) under the protection of inert gas, wherein the time of the heat treatment is 0.5-6 h, and the temperature of the heat treatment is 800-1300 ℃, so as to obtain the lithium battery cathode material.

2. The method for producing the anode material according to claim 1, wherein the organic or inorganic substance containing the iron source is: one or the combination of at least two of ferric perchlorate, ferric acetylacetonate and carbonyl iron, wherein the particle size of the ferric oxide and the ferric hydroxide is 30 nm-90 nm.

3. The method for preparing the negative electrode material of claim 1, wherein the negative electrode material for lithium battery is carbon-coated Fe₃C. A carbon nanomaterial mixture; the particle size of the mixture is not more than 50nm, Fe₃The crystal structure of C is an orthorhombic crystal form, and the coated carbon and carbon nano material are in a hexagonal structure; the carbon-coated Fe₃C is a core-shell structure.

4. The method for preparing the anode material according to claim 1, wherein the step S2 is: and (4) vacuumizing the container containing the slurry for preparing the lithium battery negative electrode material in the step S1 to the negative pressure of 2-3 kpa, stabilizing at room temperature for 30-60 min, and introducing inert gas to obtain first suspension.

5. The method for preparing the anode material according to claim 1, wherein the step S3 is: and (4) stirring the first suspension prepared in the step S2 at 110-160 ℃ for 20S-30 min to form stable and uniform second suspension.

6. The method for preparing the anode material according to claim 1, wherein the step S4 is: and heating the second suspension liquid obtained in the step S3 to 250-350 ℃ for 1-2 h to obtain a third suspension liquid.

7. The method for preparing the anode material according to claim 1, wherein the step S5 is: and (4) carrying out solid-liquid separation on the third suspension prepared in the step S4, separating into a solid component and a liquid component, and drying the solid component at the temperature of 80-100 ℃ for 18-24 h to obtain solid particles.

8. The method for preparing the anode material according to claim 1, wherein the step S6 is: and (4) carrying out high-temperature heat treatment on the solid particles obtained in the step (S5) under the protection of inert gas, wherein the heat treatment time is 1.5-2 h, and the heat treatment temperature is 900-1200 ℃, so as to obtain the lithium battery cathode material with the core-shell structure.