阅读说明：本技术 插有锂的二氧化钛、由其制得的钛酸锂颗粒以及相应的方法 (Lithium-inserted titanium dioxide, lithium titanate particles produced therefrom and corresponding method ) 是由 傅国义 于 2015-03-30 设计创作，主要内容包括：本申请涉及插有锂的二氧化钛、由其制得的钛酸锂颗粒以及相应的方法。所述方法包括形成包含二氧化钛前体颗粒和锂化合物水溶液的混合物；以及在密封的压力容器中,在升高了的温度下加热所述混合物,以形成插入了锂的二氧化钛颗粒,其中,选自以下的至少一种粒度特征基本上未被所述加热步骤改变：二氧化钛颗粒的平均一次粒度、粒度分布、平均颗粒内孔径、平均颗粒间孔径、孔径分布和二氧化钛颗粒的颗粒形状。本发明还提供一种电池,所述电池包含第一电极、第二电极和位于所述第一和第二电极之间且包含电解质的分隔件,其中,所述第一和第二电极中的一者包含按照本发明制得的插入了锂的二氧化钛颗粒或钛酸锂尖晶石颗粒。(The present application relates to lithium-intercalated titanium dioxide, lithium titanate particles made therefrom, and corresponding methods. The method includes forming a mixture comprising titanium dioxide precursor particles and an aqueous solution of a lithium compound; and heating the mixture at an elevated temperature in a sealed pressure vessel to form lithium-intercalated titanium dioxide particles, wherein at least one particle size characteristic selected from the group consisting of: the average primary particle size, particle size distribution, average intra-particle pore size, average inter-particle pore size, pore size distribution, and particle shape of the titanium dioxide particles. The present invention also provides a battery comprising a first electrode, a second electrode, and a separator comprising an electrolyte between the first and second electrodes, wherein one of the first and second electrodes comprises lithium-intercalated titanium dioxide particles or lithium titanate spinel particles made according to the present invention.)

1. A method of preparing lithium titanate spinel nanoparticles suitable for use in a battery electrode, the method comprising:

a) forming a mixture comprising titanium dioxide precursor particles and an aqueous solution of a lithium compound, wherein the titanium dioxide precursor particles consist of greater than 95% of an anatase phase; and

b) heating the mixture in a sealed pressure vessel at an elevated temperature of at least 80 ℃ and autogenous pressure for at least three hours to form lithium-intercalated titanium dioxide particles, wherein at least one particle size characteristic of the titanium dioxide particles selected from the group consisting of: average primary particle size, particle size distribution, average intra-particle pore size, average inter-particle pore size, pore size distribution, and particle shape; and

c) calcining the lithium-intercalated titanium dioxide particles at a temperature less than 650 ℃ to form lithium titanate spinel nanoparticles,

wherein the lithium titanate spinel nanoparticles have an average primary particle size of no more than about 80nm and a monodispersity of particle sizes such that the primary particle sizes of all particles are within about 10% of the average primary particle size and are characterized by:

average intra-particle pore size in the mesopore range; and

(ii) a monodisperse intra-particle pore size distribution;

wherein at least one of the average intra-particle pore size in the mesoporous range, the monodisperse particle size distribution, and the monodisperse intra-particle pore size distribution is within about 10% of the same size characteristic of the titanium dioxide precursor particles.

2. Lithium titanate spinel nanoparticles having a monodisperse particle size distribution and characterized by one or more of:

a. average intra-particle pore size in the mesopore range; and

b. (ii) a monodisperse intra-particle pore size distribution;

wherein at least one of the average intra-particle pore size in the mesopore range, the monodisperse particle size distribution, and the monodisperse intra-particle pore size distribution is within about 10% of the same size characteristics of the titanium dioxide precursor particles, and

the titanium dioxide precursor particles have a primary particle size in the range of about 40 to about 60 nm.

3. The lithium titanate spinel nanoparticles of claim 2, wherein the nanoparticles have an average primary particle size of no greater than about 50nm and a monodisperse particle size such that all particles have a primary particle size within about 10% of the average primary particle size.

4. A battery comprising a first electrode, a second electrode, and a separator comprising an electrolyte between the first and second electrodes, wherein one of the first and second electrodes comprises the lithium titanate spinel nanoparticles of claim 2.

5. The lithium titanate spinel nanoparticles of claim 2, wherein the monodisperse particle size distribution is within about 5% of the same size characteristic of the titanium dioxide precursor particles.

6. Lithium titanate spinel nanoparticles according to claim 5, wherein the titanium dioxide precursor particles have a primary particle size in the range of about 40 to about 60 nm.

7. The lithium titanate spinel nanoparticles of claim 2, wherein the monodisperse particle size distribution is within about 2.5% of the same size characteristic of the titanium dioxide precursor particles.

8. The lithium titanate spinel nanoparticles of claim 7, wherein the titanium dioxide precursor particles have a primary particle size in a range from about 40 to about 60 nm.

9. Lithium titanate spinel nanoparticles according to claim 8, wherein the titanium dioxide precursor particles have a primary particle size in the range of about 50 nm.

10. The battery of claim 4, wherein the lithium titanate spinel nanoparticles are characterized by a monodisperse particle size distribution.

11. The battery of claim 10, wherein the monodisperse particle size distribution is within about 5% of the same size characteristic of the titanium dioxide precursor particles.

12. The battery of claim 11, wherein the monodisperse particle size distribution is within about 2.5% of the same size characteristic of the titanium dioxide precursor particles.

Technical Field

The present invention relates to lithium-intercalated titanium dioxide particles and lithium titanate particles suitable for use in the anode of a lithium ion battery, and methods of forming these particles.

Background

Lithium ion batteries are rechargeable batteries that rely on the movement of lithium ions between electrodes. Such batteries are commonly used in various electronic devices due to their high energy density, high power density, and rapid charge-discharge characteristics. The anode is typically composed of graphite, while the cathode is typically composed of a material such as LiCoO₂Such lithium intercalated materials are composed of electrodes formed by, for example, LiPF in a non-aqueous solvent₆Such a liquid electrolyte is connected.

There is a need in the art for improved anode materials for lithium ion batteries to replace conventional carbon-based materials, such as graphite, which in some cases may have the drawbacks of relatively short cycle life and relatively long charge times. Having a spinel crystal structure (i.e., Li)₄Ti₅O₁₂Or LTO) is increasingly being used as an anode material in lithium ion batteries, particularly in electric vehicles and energy storage applications. The lithium titanate is converted into a rock salt crystal structure as lithium ions are intercalated during charging, and is converted back into a spinel crystal structure as lithium ions are dissociated. Lithium titanate undergoes much less lattice volume change due to charge/discharge than a carbon material and generates little heat even when short-circuited with a positive electrode, thereby preventing a fire accident and ensuring high safety. In addition, the use of lithium titanate as the anode material results in longer battery life (more cycles of charging are possible) and shorter charge times (minutes vs hours).

It is highly desirable that lithium titanate be of a cubic spinel structure with highly ordered crystals and high phase purity to achieve a high level of performance in lithium ion batteries. Lithium titanate spinels, like other ceramic materials, can be prepared by conventional solid state reaction processes; that is, the oxide components are mixed together and the mixture is heated or fired to promote the solid state reaction. Due to the kinetic limitations of these solid reactants, it is difficult to achieve high purity phases with uniform particle size and morphology. Also, lithium may be lost during heating or firing due to the volatility of the lithium compound.

To overcome these limitations, wet chemistry techniques have been proposed that involve one or more lithium or titanium compounds dissolved or suspended in a solvent. However, many of these methods have certain drawbacks, such as lack of reaction control, non-uniform reaction, and/or insufficient control of particle morphology, particle size, or crystallinity. There remains a need in the art for a method of forming lithium titanate spinel particles having controlled particle size and morphology for use in lithium ion battery applications.

Disclosure of Invention

The present invention provides a method of forming lithium-containing particles suitable for use in electrodes of lithium ion batteries. For example, the present invention can provide high quality lithium titanate particles that advantageously have small particle sizes (e.g., nanometer size range), narrow particle size distribution, and high crystallinity. In certain embodiments, the use of lithium-containing particles made according to the present invention may result in battery electrodes that provide better safety in terms of explosion and fire, provide longer battery life, and shorter charge times than carbon-based electrodes.

In one aspect, the present invention provides a method of preparing lithium-containing particles suitable for use in a battery electrode, the method comprising:

a) forming a mixture comprising titanium dioxide precursor particles and an aqueous solution of a lithium compound; and

b) heating the mixture at an elevated temperature in a sealed pressure vessel to form lithium-intercalated titanium dioxide particles, wherein at least one particle size characteristic selected from the group consisting of: the average primary particle size, particle size distribution, average intra-particle pore size, average inter-particle pore size, pore size distribution, and particle shape of the titanium dioxide particles.

Typically, at least one of the average primary particle size, the average intra-particle pore size, and the average inter-particle pore size of the lithium-inserted titanium dioxide particles is within about 10% (e.g., within about 5%) of the same size characteristic of the titanium dioxide precursor particles. In certain advantageous embodiments, the titanium dioxide precursor particles and the lithium-inserted titanium dioxide particles are characterized by one or more of: an average primary particle size of less than about 100 nm; the whole body is spherical; average intra-particle pore size in the mesopore range; a monodisperse particle size distribution; and monodisperse intra-particle pore size distribution.

The lithium compound used in the present invention may be various, and examples include lithium hydroxide, lithium oxide, lithium chloride, lithium carbonate, lithium acetate, lithium nitrate, and combinations thereof. The elevated temperature is typically at least about 80 c and the pressure in the heating step is typically autogenous. In certain embodiments, the pH of the mixture is greater than about 9. Typically, the pressure applied to the mixture during the heating step is at least about 20 psig. In one embodiment, the amount of lithium compound in the mixture is between about 2 and about 20 weight percent based on the weight of the titanium dioxide particles.

If desired, the method can further include calcining the lithium-intercalated titanium dioxide particles to form lithium titanate spinel particles (e.g., the calcining step includes heating the lithium-intercalated titanium dioxide particles at a temperature not exceeding about 650 ℃). In certain embodiments, the lithium titanate spinel particles are characterized by one or more of the following: an average primary particle size of less than about 100 nm; average intra-particle pore size in the mesopore range; a monodisperse particle size distribution; and monodisperse intra-particle pore size distribution. Advantageously, at least one of the average primary particle size, average intra-particle pore size, and average inter-particle pore size of the lithium titanate spinel particles is within about 10% of the same size characteristic of the titanium dioxide precursor particles.

In another embodiment, the present invention provides a method of making lithium-containing particles suitable for use in a battery electrode, the method comprising:

a) forming a mixture comprising titanium dioxide precursor nanoparticles and an aqueous solution of a lithium compound;

b) heating the mixture in a sealed pressure vessel at autogenous pressure and at a temperature of at least about 80 ℃ for at least about 2 hours to form lithium-intercalated titanium dioxide nanoparticles, wherein at least one particle size characteristic selected from the group consisting of: the average primary particle size, particle size distribution, average intra-particle pore size, average inter-particle pore size, pore size distribution, and particle shape of the titanium dioxide nanoparticles; and

c) optionally, calcining the lithium-inserted titanium dioxide nanoparticles to form lithium titanate spinel nanoparticles.

In another embodiment, the present invention provides a method of making lithium-containing particles suitable for use in a battery electrode, the method comprising:

a) the titania precursor particles are prepared by: forming an aqueous solution of a titanium salt and an organic acid, which aqueous solution is thermally hydrolyzed at an elevated temperature and optionally in the presence of a titanium dioxide seed material to produce titanium dioxide precursor particles in a mother liquor;

b) separating the resulting titanium dioxide precursor particles from the mother liquor;

c) optionally, drying the separated titanium dioxide precursor particles;

d) forming a mixture comprising the titanium dioxide precursor particles and an aqueous solution of a lithium compound;

e) heating the mixture in a sealed pressure vessel at autogenous pressure and at a temperature of at least about 80 ℃ for at least about 2 hours to form lithium-intercalated titanium dioxide particles, wherein at least one particle size characteristic selected from the group consisting of: an average primary particle size, a particle size distribution, an average intra-particle pore size, an average inter-particle pore size, a pore size distribution, and a particle shape of the precursor titania precursor particles of the precursor titania; and

f) optionally, calcining the lithium-inserted titanium dioxide particles to form lithium titanate spinel particles.

In another aspect, the invention provides a battery (e.g., a lithium ion battery) comprising a first electrode, a second electrode, and a separator comprising an electrolyte between the first and second electrodes, wherein one of the first and second electrodes comprises lithium-inserted titanium dioxide particles or lithium titanate spinel particles made according to any of the above methods.

In another aspect, the invention provides a battery (e.g., a lithium ion battery) comprising a first electrode, a second electrode, and a separator comprising an electrolyte between the first and second electrodes, wherein one of the first and second electrodes comprises lithium-intercalated titanium dioxide particles. These lithium-inserted titanium dioxide particles can be characterized by, for example, one or more of the following: an average primary particle size of less than about 100 nm; the whole body is spherical; average intra-particle pore size in the mesopore range; a monodisperse particle size distribution; and monodisperse intra-particle pore size distribution.

In another aspect, the present invention provides lithium-intercalated titanium dioxide nanoparticles comprising from about 1 to about 12 weight percent lithium based on the total weight of the lithium-intercalated titanium dioxide nanoparticles, wherein the lithium-intercalated titanium dioxide nanoparticles are characterized by one or more of: the whole body is spherical; average intra-particle pore size in the mesopore range; a monodisperse particle size distribution; and monodisperse intra-particle pore size distribution. In one embodiment, the lithium-inserted titanium dioxide nanoparticles are characterized by an overall spherical shape and a monodisperse particle size distribution, wherein the nanoparticles have an average primary particle size of no more than about 80nm and a monodispersity of particle sizes such that the primary particle size of all particles is within about 10% of the average primary particle size.

Additionally, the present invention provides lithium titanate spinel nanoparticles characterized by one or more of the following: average intra-particle pore size in the mesopore range; a monodisperse particle size distribution; and monodisperse intra-particle pore size distribution. In certain embodiments, the lithium titanate spinel nanoparticles have an average particle size of no more than about 80nm and a monodispersity of particle sizes such that the primary particle size of all particles is within about 10% of the average primary particle size. Such lithium titanate spinel nanoparticles can be used in a battery, such as a lithium battery, comprising a first electrode, a second electrode, and a separator positioned between the first and second electrodes and comprising an electrolyte, wherein one of the first and second electrodes comprises lithium titanate spinel nanoparticles.

The present invention includes, but is not limited to, the following embodiments.

Embodiment 1: a method of making lithium-containing particles suitable for use in a battery electrode, the method comprising:

a) forming a mixture comprising titanium dioxide precursor particles and an aqueous solution of a lithium compound; and

b) heating the mixture at an elevated temperature in a sealed pressure vessel to form lithium-intercalated titanium dioxide particles, wherein at least one particle size characteristic selected from the group consisting of: the average primary particle size, particle size distribution, average intra-particle pore size, average inter-particle pore size, pore size distribution, and particle shape of the titanium dioxide particles.

Embodiment 2: the method of any preceding or subsequent embodiment, wherein at least one of the average primary particle size, the average intra-particle pore size, and the average inter-particle pore size of the lithium-inserted titanium dioxide particles is within about 10% of the same size characteristic of the titanium dioxide precursor particles.

Embodiment 3: the method of any preceding or subsequent embodiment, wherein at least one of the average primary particle size, the average intra-particle pore size, and the average inter-particle pore size of the lithium-inserted titanium dioxide particles is within about 5% of the same size characteristic of the titanium dioxide precursor particles.

Embodiment 4: the method of any preceding or subsequent embodiment, wherein the titanium dioxide precursor particles and the lithium-inserted titanium dioxide particles are characterized by one or more of:

a) an average primary particle size of less than about 100 nm;

b) the whole body is spherical;

c) average intra-particle pore size in the mesopore range;

d) a monodisperse particle size distribution;

e) a bimodal particle size distribution; and

f) monodisperse intra-particle pore size distribution.

Embodiment 5: the method of any preceding or subsequent embodiment, wherein the lithium compound is selected from the group consisting of lithium hydroxide, lithium oxide, lithium chloride, lithium carbonate, lithium acetate, lithium nitrate, and combinations thereof.

Embodiment 6: the method of any preceding or subsequent embodiment, wherein the elevated temperature is at least about 80 ℃, and the pressure in the heating step is autogenous.

Embodiment 7: the method of any preceding or subsequent embodiment, wherein the pH of the mixture is greater than about 9.

Embodiment 8: the method of any preceding or subsequent embodiment, wherein the pressure applied to the mixture in the heating step is at least about 20 psig.

Embodiment 9: the method of any preceding or subsequent embodiment, wherein the amount of the lithium compound in the mixture is between about 2 to about 20 wt% based on the weight of the titanium dioxide particles.

Embodiment 10: the method of any preceding or subsequent embodiment, further comprising calcining the lithium-inserted titanium dioxide particles to form lithium titanate spinel particles.

Embodiment 11: the method of any preceding or subsequent embodiment, wherein the calcining step comprises heating the lithium-inserted titanium dioxide particles at a temperature of no more than about 650 ℃.

Embodiment 12: the method of any preceding or subsequent embodiment, wherein the lithium titanate spinel particles are characterized by one or more of:

a) an average primary particle size of less than about 100 nm;

b) average intra-particle pore size in the mesopore range;

c) a monodisperse particle size distribution;

d) a bimodal particle size distribution; and

e) monodisperse intra-particle pore size distribution.

Embodiment 13: the method of any preceding or subsequent embodiment, wherein at least one of the average primary particle size, the average intra-particle pore size, and the average inter-particle pore size of the lithium titanate spinel particles is within about 10% of the same size characteristic of the titanium dioxide precursor particles.

Embodiment 14: the method of any preceding or subsequent embodiment, comprising:

a) forming a mixture comprising titanium dioxide precursor nanoparticles and an aqueous solution of a lithium compound;

b) heating the mixture in a sealed pressure vessel at autogenous pressure and at a temperature of at least about 80 ℃ for at least about 2 hours to form lithium-intercalated titanium dioxide nanoparticles, wherein at least one particle size characteristic selected from the group consisting of: the average primary particle size, particle size distribution, average intra-particle pore size, average inter-particle pore size, pore size distribution, and particle shape of the titanium dioxide nanoparticles; and

c) optionally, calcining the lithium-inserted titanium dioxide nanoparticles to form lithium titanate spinel nanoparticles.

Embodiment 15: the method of any preceding or subsequent embodiment, wherein the titanium dioxide precursor nanoparticles, the lithium-inserted titanium dioxide nanoparticles, and the lithium titanate spinel nanoparticles are characterized by one or more of:

a) average intra-particle pore size in the mesopore range;

b) a monodisperse particle size distribution;

c) a bimodal particle size distribution; and

d) monodisperse intra-particle pore size distribution.

Embodiment 16: the method of any preceding or subsequent embodiment, comprising:

a) the titania precursor particles are prepared by: forming an aqueous solution of a titanium salt and an organic acid, which aqueous solution is thermally hydrolyzed at an elevated temperature and optionally in the presence of a titanium dioxide seed material to produce titanium dioxide precursor particles in a mother liquor;

b) separating the resulting titanium dioxide precursor particles from the mother liquor;

c) optionally, drying the separated titanium dioxide precursor particles;

d) forming a mixture comprising the titanium dioxide precursor particles and an aqueous solution of a lithium compound;

e) heating the mixture in a sealed pressure vessel at autogenous pressure and at a temperature of at least about 80 ℃ for at least about 2 hours to form lithium-intercalated titanium dioxide particles, wherein at least one particle size characteristic selected from the group consisting of: an average primary particle size, a particle size distribution, an average intra-particle pore size, an average inter-particle pore size, a pore size distribution, and a particle shape of the precursor titania precursor particles; and

f) optionally, calcining the lithium-inserted titanium dioxide particles to form lithium titanate spinel particles.

Embodiment 17: a battery comprising a first electrode, a second electrode, and a separator comprising an electrolyte between the first and second electrodes, wherein one of the first and second electrodes comprises lithium-intercalated titanium dioxide particles or lithium titanate spinel particles made according to any of the methods set forth herein, including any of the embodiments described above.

Embodiment 18: a lithium-containing particle suitable for use in a lithium ion battery electrode, comprising:

a) a plurality of lithium-inserted titanium dioxide particles characterized by one or more of:

i. an average primary particle size of less than about 100 nm;

overall spherical;

average intra-particle pore size in the mesopore range;

monodisperse particle size distribution;

v. bimodal particle size distribution; and

monodisperse intra-particle pore size distribution; or

b) A plurality of lithium titanate spinel nanoparticles characterized by one or more of:

i. average intra-particle pore size in the mesopore range;

a monodisperse particle size distribution;

bimodal particle size distribution; and

monodisperse intra-particle pore size distribution.

Embodiment 19: the particle of any preceding or subsequent embodiment, wherein the lithium-inserted titanium dioxide particle is nanoparticulate and comprises from about 1 to about 12 wt% lithium, based on the total weight of the lithium-inserted titanium dioxide nanoparticle, wherein the lithium-inserted titanium dioxide nanoparticle is characterized by one or more of:

a) the whole body is spherical;

b) average intra-particle pore size in the mesopore range;

c) a monodisperse particle size distribution;

d) a bimodal particle size distribution; and

e) monodisperse intra-particle pore size distribution.

Embodiment 20: the particle of any preceding or subsequent embodiment, wherein the lithium-inserted titanium dioxide nanoparticles are characterized by an overall spherical shape and a monodisperse particle size distribution, wherein the nanoparticles have an average primary particle size of no more than about 80nm and a monodispersity of particle sizes such that the primary particle sizes of all particles are within about 10% of the average primary particle size.

Embodiment 21: the particle of any preceding or subsequent embodiment, wherein the lithium-inserted titanium dioxide nanoparticles are characterized by an XRD diffraction pattern substantially as shown in figure 6.

Embodiment 22: the particles of any preceding or subsequent embodiment, wherein the lithium titanate spinel nanoparticles have an average primary particle size of no more than about 80nm and a monodispersity of particle sizes such that the primary particle size of all particles is within about 10% of the average primary particle size.

Embodiment 23: a battery comprising a first electrode, a second electrode, and a separator comprising an electrolyte between the first and second electrodes, wherein one of the first and second electrodes comprises any of the lithium-containing particles set forth herein, including any of the above particle embodiments.

These and other features, aspects, and advantages of the present invention will become apparent from the following detailed description, which is to be read in connection with the accompanying drawings, which are briefly described below. The present invention includes combinations of two, three, four or more of the above-described embodiments, and combinations of two, three, four or more of the features or elements set forth herein, whether or not such features or elements are expressly combined in a particular embodiment described herein. Any divisible feature or element of the disclosed methods in any of its various aspects and embodiments should be considered as being intended to be combinable features or elements unless the context clearly dictates otherwise.

Brief description of the drawings

Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

FIG. 1 is an SEM photograph of precursor titanium dioxide nanoparticles according to one embodiment of the present invention;

FIG. 2 is an SEM photograph of lithium-inserted titanium dioxide nanoparticles according to one embodiment of the present invention;

fig. 3 is an SEM photograph of lithium titanate nanoparticles according to an embodiment of the present invention;

FIGS. 4A and 4B are TEM photographs of lithium titanate nanoparticles according to an embodiment of the present invention at different magnifications;

FIG. 5 is an X-ray diffraction (XRD) pattern of precursor titanium dioxide nanoparticles according to one embodiment of the present invention, referenced to a standard anatase titanium dioxide pattern bar (patterrn bar);

FIG. 6 is an XRD pattern of lithium-inserted titanium dioxide nanoparticles according to an embodiment of the present invention, referenced to standard anatase titanium dioxide pattern bars;

FIG. 7 is an XRD pattern of lithium titanate nanoparticles according to an embodiment of the present invention, referenced to a standard lithium titanate spinel pattern bar; and

fig. 8 is a schematic diagram of an exemplary lithium ion battery in which lithium-intercalated titanium dioxide nanoparticles or lithium titanate nanoparticles of the present invention may be used as part of an electrode material.

Detailed Description

The present invention will be described in more detail below by various embodiments. These embodiments, therefore, are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Indeed, this invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Herein, like reference numerals refer to like elements. As used in this specification and the appended claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise.

I. Titanium dioxide precursor particles

Titanium dioxide (TiO) for use in the present invention₂) The precursor particles can be of a wide variety, and in particular, particle size, particle morphology, polymorphic crystals, grain size, pore size, and the like can be found in certain embodiments of the inventionThe embodiments are different. TiO 2₂Both the anatase and rutile polymorphs of (a) can be used to practice the inventive process described herein, but the anatase crystal structure is preferred. In certain embodiments, these precursor particles can be characterized as having a completely or substantially pure anatase crystalline structure, e.g., TiO consisting of greater than about 95% anatase phase₂And (3) granules.

The present invention is not particularly limited to the precursor TiO₂The size of the particles. It is generally preferred to use ultra-fine particles with a narrow particle size distribution in electrode applications. Thus, in certain embodiments, the precursor TiO used in the present invention₂The particles may be characterized as ultrafine particles or nanoparticles. As used herein, the term "ultrafine particle" or "nanoparticle" refers to a particle having at least one dimension less than 100 nm. The ultrafine particles used in the present invention will generally have an average primary particle size of no more than about 100nm, more typically no more than about 80nm, and in some embodiments no more than about 50nm, as determined by the following method: a transmission electron microscope ("TEM") image or a micrograph of a scanning electron microscope ("SEM") image is visually inspected, the diameter of the particles in the image is measured, and the average primary particle size of the measured particles is calculated based on the magnification of the TEM or SEM image. The primary particle size of a particle refers to the smallest diameter sphere that completely surrounds the particle. The above size range refers to the average value of the particles having the size distribution.

In certain embodiments, the precursor TiO₂The particles may be characterized by a particle size distribution. In certain embodiments, the particles may be considered monodisperse, meaning that the population of particles is highly uniform in size. Certain monodisperse particle populations useful in the present invention can be characterized as consisting of particles having a primary particle size within 20%, or within 15%, or within 10% of the average primary particle size of the particle population (i.e., all particles in the population have a primary particle size within a given percentage range around the average primary particle size). In an exemplary embodiment, the average primary particle size is about 50nm and the primary particle size of all particles in the population is in the range of about 40 to about 60nm(i.e., within 20% of the average primary particle size).

Other particle size ranges may be used without departing from the invention, such as microparticles having at least one dimension less than 1000 μm (e.g., from about 50 μm to about 1000 μm). Mixtures of particles having different average particle sizes (e.g., bimodal particle distributions) within the ranges described herein can also be used.

TiO₂The particle morphology (i.e., shape) of the precursor particles may also vary without departing from the invention. In certain embodiments, the precursor particles are spherical in shape throughout. Preferably, the precursor particles exhibit a highly uniform particle morphology, meaning that there are relatively small differences in particle shape within the population.

TiO suitable for use in the present invention₂The particles may also be characterized by different grain sizes, with advantageous size ranges of less than about 20nm, such as less than about 15nm, or less than about 12nm (e.g., about 4nm to about 12 nm).

These precursor particles can also be characterized by different pore size distributions (intra-particle pores and inter-particle pores), as well as by different surface areas. Exemplary intra-particle pore sizes include average pore sizes in the mesopore size range, e.g., from about 2nm to about 12nm, while exemplary inter-particle pore sizes include average pore sizes in the range of from about 15nm to about 80 nm. Exemplary average BET specific surface areas of precursor particles for use in the present invention include about 50m²G to about 400m²Per g (e.g., about 100 to about 300 m)²In the range of/g or from about 120 to about 250m²In terms of/g). It will be understood by those of ordinary skill in The art that BET specific surface area refers to The specific surface area as measured by nitrogen adsorption according to ASTM D3663-78, based on The method of Brunauer-Emmett-Teller, published in The Journal of The American Chemical Society, 60, 309(1938), in The Journal of The American Chemical Society. Pore size measurements can also be made using the BET method.

In certain embodiments, the precursor TiO₂The particles may be characterized by a pore size distribution. In certain embodiments, the particles can be considered to be monodisperse across the pore size, meaning that the population of particles is highly uniform across the pore sizeAnd (4) homogenizing. Certain monodisperse particle populations useful in the present invention can be characterized as consisting of particles having a pore size within 20%, or within 15%, or within 10% of the mean intra-particle pore size (or inter-particle pore size) of the particle population (i.e., the pore size of all particles in the population is within a given percentage range around the mean pore size). In an exemplary embodiment, the average intra-particle pore size is about 10nm, and the particle size of all particles in the population is in the range of about 8 to about 12nm (i.e., within 20% of the average pore size).

Suitable TiO for use in the present invention₂The precursor particles are available from Cowster corporation (Cristal Global) under the trade nameAT1 and CristalcatiV^TMThe product of (1). With respect to TiO₂Reference is also made to u rwin, U.S. patent No. 4012338, Fu et al, U.S. patent publication No. 2005/0175525, Fu et al, 2009/0062111, and Fu et al, 2009/0324472, which are incorporated herein by reference.

In one embodiment, the TiO is₂The precursor particles are provided in the form described in U.S. patent publication No. 2013/0122298 to Fu et al, which is incorporated herein by reference. TiO as generally described herein₂Nanoparticles can be prepared by: an aqueous solution of a titanium salt and an organic acid is prepared, and the organic acid functions as a morphology controlling agent. TiO 2₂The nanoparticles are formed by thermal hydrolysis of a titanium salt solution at a temperature in the vicinity of 100 ℃ for several hours. The nanoparticles can be separated from the mother liquor and used as a precursor material for insertion of lithium without first drying the particles. Alternatively, the particles may be dried prior to the insertion step of lithium as described in the publications cited above. Example 1 described below TiO was prepared according to this general procedure₂And (3) nanoparticles.

Albeit TiO₂It is preferred that other metal oxides be used to practice the invention. Exemplary alternative metal oxides include silicon oxide (e.g., SiO or SiO)₂) Copper oxide (e.g., CuO or Cu)₂O), tin oxide, magnesium oxide (MgO)₂) Manganese oxide (e.g., MnO or Mn)₂O₃) Iron oxide (e.g., FeO, Fe)₂O₃Or Fe₃O₄) Zirconium oxide, aluminum oxide, vanadium oxide (e.g. VO or V)₂O₃) Molybdenum oxide, cerium oxide, tungsten oxide, zinc oxide, thorium oxide, and the like.

II.Lithium-inserted titanium dioxide nanoparticles

Lithium-intercalated titanium dioxide nanoparticles by reacting with the above TiO₂The precursor particles are formed using a treatment process. As used herein, reference to "lithium-inserted" or "lithium-inserted" particles refers to particles having lithium ions inserted into the crystal structure of the particle. In the process of the invention, the particle size and morphology of the precursor particles is advantageously maintained, which means that the method of introducing lithium does not significantly affect the particle size and morphology, thereby providing better control over these important particle characteristics. Once formed, the precursor particles having the desired size and morphology characteristics, the present invention allows for the formation of lithium-containing particles that are substantially similar in size and shape to the original particles.

The lithium intercalation process involves reacting TiO in the presence of an aqueous solution of a lithium compound₂The particles are subjected to a hydrothermal treatment. The aqueous solvent is preferably pure water (e.g., deionized water), but mixtures with other polar co-solvents such as alcohols, with water as the predominant solvent (e.g., greater than 50% by weight of the total solvent, more typically greater than about 75% or greater than about 95%) may be used without departing from the invention. The amount of water used in the mixture is not particularly limited, although it is advantageous to use sufficient water to maintain the lithium compound in a dissolved form.

Any lithium compound that is generally soluble and dissociable in water can be used in the solution. Exemplary lithium salts include lithium hydroxide, lithium oxide, lithium chloride, lithium carbonate, lithium acetate, lithium nitrate, and the like. Strongly basic lithium compounds, such as lithium hydroxide, are preferred. A less basic lithium compound is typically used in combination with a strong base, such as sodium hydroxide or ammonia, to increase the pH of the solution. The pH of the reaction mixture is typically greater than about 9, for example greater than about 10.

Subjecting an aqueous solution of a lithium compound and TiO to hydrothermal treatment at an elevated temperature (i.e., above room temperature)₂The mixture of precursor particles is heat treated. The heating step is typically carried out in a sealed pressure vessel (e.g., autoclave) to enable these processes to be carried out at elevated temperatures and autogenous pressures. Exemplary autoclave apparatus useful in the present invention are those available from Berghof/U.S. company (Berghof/America Inc) and Parr instruments company (Parr Instrument Co.), and are described in Hukvari et al, U.S. patent No. 4882128, which is incorporated herein by reference. The operation of these exemplary containers will be apparent to those skilled in the art.

The temperature applied to the mixture in the hydrothermal treatment may be various. In certain embodiments, the temperature is at least about 80 ℃, at least about 90 ℃, at least about 100 ℃, or at least about 110 ℃. The temperature typically does not exceed about 160 deg.C, and in some embodiments does not exceed about 150 deg.C. Typical temperatures range from about 80 deg.C to about 150 deg.C (e.g., from about 100 deg.C to about 130 deg.C). As mentioned above, the pressure during hydrothermal treatment is generally autogenous, which means that the pressure inside the sealed chamber is not controlled externally, but is only caused by the heat treatment applied to the chamber. Typical pressures for the hydrothermal treatment range from about 5 to about 200 psig. More typically the pressure ranges from about 30 to about 120 psig. In certain embodiments, the pressure applied to the mixture can be characterized as at least about 20psig, at least about 30psig, or at least about 40 psig. The elevated pressure experienced by the reaction mixture is important to achieve the desired level of lithium loading in the particles.

The time for the hydrothermal treatment of the compound may be various. Typically, the hydrothermal treatment is carried out for at least about 2 hours or at least about 3 hours. The maximum treatment time is not particularly limited, although treatment over about 48 hours is generally unnecessary.

The amount of lithium compound used in the mixture can vary and depends in part on the desired level of lithium loading within the particles. The amount of lithium that can be inserted into the precursor particles can vary widely, with a typical range being from about 1 to about 12 weight percent lithium based on the total weight of the lithium-inserted particles. A more typical range for insertion of lithium is from about 3% to about 8%. If it is desired to calcine the lithium-intercalated particles to form LTO as described more fully below, the lithium loading of the particles should be in the range of about 5 to about 7 weight percent. The amount of lithium compound used in the mixture to achieve the desired lithium loading is from about 2% to about 20% by weight of lithium relative to the weight of titanium dioxide.

As described above, the hydrothermal treatment used to insert lithium into the precursor particles leaves the primary particle size and morphology generally unaffected. Thus, lithium-inserted particles can be characterized as having substantially the same particle size and morphology characteristics as the precursor particles, as described above. For example, the characteristics of average particle size, particle size distribution (e.g., monodispersity), intra-and inter-particle pore size, pore size distribution (e.g., monodispersity), and particle shape are not significantly altered by hydrothermal treatment. In certain embodiments, any or all of the above features can be considered relatively unchanged, meaning that one or more of the average particle size, particle size distribution (e.g., monodispersity), intra-and inter-particle pore sizes, pore size distribution (e.g., monodispersity), and particle shape of the lithium-inserted particles will be within about 10% (e.g., within about 5% or within about 2.5%) of the value of the same feature of the precursor particles.

The lithium-inserted titanium dioxide nanoparticles can be characterized by an X-ray diffraction (XRD) pattern distinct from the precursor titanium dioxide nanoparticles, which clearly shows that the method of the invention results in the diffusion of lithium into TiO₂In the crystal structure. In one embodiment, the lithium-inserted titanium dioxide nanoparticles are characterized by an XRD diffraction pattern substantially as shown in figure 6. As shown, the lithium-inserted titanium dioxide nanoparticles of the present invention will generally exhibit an XRD pattern with peaks at one or more of the following 2-theta diffraction angles: between about 39 ° and about 40 ° (e.g., about 39.5 °), between about 45 ° and about 47 ° (e.g., about 46 °), and about 81 °.

It will be understood by those skilled in the art that the diffraction pattern data should not be considered absolute, and therefore the lithium-inserted titanium dioxide nanoparticles of the present invention are not limited to particles having the same XRD pattern as that of fig. 6. Any lithium-intercalated titanium dioxide nanoparticles having an XRD pattern substantially the same as that of fig. 6 fall within the scope of the present invention. One skilled in the art of X-ray powder diffraction can make a determination as to whether the X-ray powder diffraction patterns are substantially the same. In general, the measurement error of the diffraction angle in the X-ray powder diffraction pattern is about 2 θ 0.5 ° or less (more suitably about 2 θ 0.2 ° or less), and such a degree of measurement error should be taken into consideration when considering the X-ray powder diffraction pattern in fig. 6 or the peak values provided above. In other words, the values for the peaks in FIG. 6 and the peaks given above may be considered +/-0.5 or +/-0.2 in certain embodiments. See Pecharsky and Zavialij for Powder Diffraction and Structural Characterization basis (Fundamentals of Powder Diffraction and Structural Characterization, Kluyveromyces Publishers, 2003).

Lithium titanate nanoparticles

Although the lithium-intercalated nanoparticles prepared according to the above-described method may be used as electrode materials without further modification, in certain embodiments of the present invention, the lithium-intercalated nanoparticles are further processed to form Lithium Titanate (LTO) particles. The conversion to LTO includes calcining the lithium-inserted nanoparticles at an elevated temperature, for example at a temperature of about 400 ℃ to about 800 ℃. In certain embodiments, the calcination temperature may be characterized as less than about 650 ℃, less than about 600 ℃, or less than about 550 ℃. Calcination conditions of at least about 1 hour or at least about 2 hours (e.g., from about 2 to about 8 hours) are generally applied. The maximum treatment time is not particularly limited, although treatment over about 12 hours is generally unnecessary.

The calcination process does not significantly change the original particle size and morphology of the lithium-inserted nanoparticles, although the shape of the particles becomes more cubic to conform to the cubic LTO spinel structure. Thus, LTO particles may be characterized as having substantially the same particle size and morphology characteristics as the precursor and lithium-intercalated particles, as described above. For example, the characteristics of the average particle size, particle size distribution (e.g., monodispersity), intra-and inter-particle pore sizes, and pore size distribution (e.g., monodispersity) are not significantly altered by the calcination treatment. In certain embodiments, any or all of the above features may be considered relatively unchanged, meaning that one or more of the average particle size, particle size distribution (e.g., monodispersity), intra-and inter-particle pore sizes, and pore size distribution (e.g., monodispersity) of the LTO particles will be within about 10% (e.g., within about 5% or within about 2.5%) of the same feature of the precursor particles and/or the lithium-inserted particles.

Application of the Battery

In general, lithium-intercalated nanoparticles and LTO nanoparticles are ion conductors and therefore can be used in any application that utilizes materials with ionic conductivity. In one embodiment, lithium-intercalated nanoparticles and LTO nanoparticles may be used as electrode materials in lithium ion batteries. For example, these materials may be used as part of a battery 100 as schematically depicted in fig. 8, although the figure is merely illustrative and is not intended to limit the scope of the invention to one particular lithium ion battery configuration. The battery 100 includes an anode 102, a cathode 104, and a separator 106 containing an electrolyte. Exemplary lithium ion batteries suitable for use with the present invention are set forth, for example, in U.S. patent publication No. 2013/0343983 to Ito et al and 2013/0337302 to Inagaki et al, both of which are incorporated herein by reference.

In certain embodiments, the lithium-intercalated nanoparticles and LTO nanoparticles of the present invention are used in the anode of a lithium ion battery. The anode material for a battery may further include additives such as a conductive agent to adjust the conductivity of the anode (e.g., graphite, carbon black, or metal powder), and a binder or filler (e.g., polysaccharide, thermoplastic resin, or elastic polymer). The material used in the cathode may be various, and examples include lithium manganate, lithium cobaltate, lithium nickelate, vanadium pentoxide, and the like. The electrolyte typically comprises a lithium salt and a solvent. Exemplary solvents include propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-Butyrolactone, methyl formate, methyl acetate, tetrahydrofuran, dimethyl sulfoxide, formamide, dioxolane and acetonitrile. Exemplary lithium salts include LiPF₆、LiClO₄、LiCF₃SO₃、LiN(CF₃SO₂)₂And LiBF₄。

It should be noted that the lithium-intercalated nanoparticles and LTO nanoparticles of the present invention may also be used as cathode matrix materials in certain battery embodiments, such as lithium-sulfur (Li-S) batteries with sulfur inserted in the cathode matrix material.

Aspects of the present invention will be more fully described by the following examples, which are set forth to illustrate certain aspects of the present invention and are not to be construed as limiting the invention.

Examples

Example 1 lithium intercalated TiO₂Preparation of nanospheres

In a heated reactor equipped with a glass condenser and an overhead stirrer, 1195g of deionized water, 79g of hydrochloric acid solution (37% from Fisher Scientific), 7.9g of citric acid monohydrate (Alfa Aesar), and 398g of titanium oxychloride solution (as TiO) were charged₂25.1% by weight, costt) were mixed together. The mixture was heated to 75 ℃ with constant stirring and a small amount of anatase TiO was added rapidly₂Seed crystal (relative to TiO)₂0.1 percent; anatase seed crystals are produced by costt). The reaction was held at 75 ℃ for 2 hours. During this time, TiO₂The particles begin to form by hydrolysis of the titanium oxychloride. The reaction temperature was then raised to 85 ℃ and held at that temperature for 3 hours. Hydrolysis is substantially complete at this stage.

The reaction mixture was cooled to room temperature and the stirring was stopped. Allowing the TiO formed₂The slurry was allowed to settle for about 3 hours. Thereafter, as substantially all of the particles settled to the bottom of the vessel, the mother liquor was removed and an approximately equal amount of deionized water was added. A small sample was taken and examined under SEM. SEM image shows TiO₂The particles were uniform, spherical in shape overall and approximately 40nm in size, as compared to FIG. 1Shown substantially the same. Measurement of a small amount of sample dried in an oven by XRD showed TiO₂In anatase form (as shown in FIG. 5). Can be usedCu K alpha of₁XRD measurements were performed on a irradiated PANALYTICAL X' Pert Pro diffractometer. The diffractometer was equipped with a sealed Cu X-ray tube and an X-Celerator position sensitive detector. The instrument conditions were set to 45kV, 40mA, 0.016 ° 2 θ/step and 50 second dwell time.

After sampling, stirring was resumed and 78.8g of lithium hydroxide monohydrate (alfa aesar) were added in small portions. After stirring for about 15 minutes, the mixture was transferred to a hydrothermal reactor (Parr apparatus) and treated at 120 ℃ and autogenous pressure for 24 hours. The reaction was then allowed to cool to room temperature, the product was isolated by filtration and washed several times with deionized water until the conductivity of the filtrate was less than 500. mu.S/cm. The washed samples were dried in an oven at 90 ℃. SEM measurements showed that the particles were still rather uniformly nanospherical (as shown in figure 2). Compared to SEM images of precursor nanoparticles for insertion (e.g., fig. 1), the following conclusions can be drawn: the nanoparticles remained intact after insertion and the particle morphology did not change during the treatment. XRD measurement showed TiO₂Still in the anatase form, although most of the peaks are clearly shifted (as shown in fig. 6). Lithium analysis using ICP-OES (inductively coupled plasma-emission Spectroscopy) analysis (iCAP 6000 of Semmerfell's science) showed that a product containing about 6 wt% Li was produced, confirming that the shift of XRD peak was due to insertion of lithium into TiO₂Caused by the crystal lattice. Measurement of lithium-inserted TiO₂The samples were dissolved in hydrofluoric acid solution prior to use. Lithium standard solutions were purchased from High-Purity Standards, Inc.

Example 2 lithium intercalated TiO₂Conversion to lithium titanate spinel (LTO).

Lithium-intercalated TiO from example 1 was heated at 600 ℃ in a furnace₂The nanospheres were treated for 6 hours. SEM image displayThe transformed nanoparticles remain predominantly spherical and the original morphological characteristics are substantially preserved (as shown in figure 3). High magnification TEM images show that the shape of the nanoparticles is cubic, consistent with a cubic spinel structure (as shown in fig. 4A and 4B). The XRD pattern of the nanoparticles (as shown in FIG. 7) completely matched that of standard cubic spinel lithium titanate (Li)₄Ti₅O₁₂)。

Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.