WO2018024661A1

WO2018024661A1 - Method for producing a cathode material having a low bet surface area and a high tapped density, and a special cathode material

Info

Publication number: WO2018024661A1
Application number: PCT/EP2017/069291
Authority: WO
Inventors: Stipan Katusic; Peter Kress; Armin Wiegand; Harald Alff; Tobias RENGER
Original assignee: Evonik Degussa Gmbh
Priority date: 2016-08-05
Filing date: 2017-07-31
Publication date: 2018-02-08
Also published as: DE102016214590A1; TW201815689A

Abstract

The invention relates to a method for producing a powdered mixed oxide A of general formula Li₁ _+x(Ni_aCo_bMn_c)B_dNa_eO₂, where 0<x≤0.5; 0<a≤1; 0≤b≤1; 0<c≤1; 0.001≤d≤0.1, 0.001<e≤0.2; d+e≥0.0 and d<e, and which mixed oxide has a BET surface area of between 10 and 50 m²/g and a tapped density of 250 to 700 g/l, in which method: a) a solution is provided containing oxidisable and/or hydrolysable metal compounds of lithium, manganese, nickel and sodium and boric acid, each in proportions corresponding to the general formula; b) the solution is atomized by means of an atomizing gas to form an aerosol; c) the aerosol is reacted in a reaction chamber using a flame, wherein the flame is obtained from a mixture of a combustible gas and air, and wherein the total amount of oxygen is at least sufficient in order to completely convert the combustible gas and the metal compounds; d) the reaction chamber is cooled and the solid product is then separated from the reaction flow. The invention also relates to a powdered mixed oxide of general formula Li₁ _+x(Ni_aCo_bMn_c)B_dNa_eO₂, where 0<x≤0.5; 0<a≤1; 0≤b≤1; 0<c≤1; 0.001≤d≤0.1; 0.001<e≤0.2, and which mixed oxide has a BET surface area of 0.1 to 5 m²/g and a tapped density of 1000 to 2500 g/l, the sodium concentration of the mixed oxide particles, determined by means of XPS-ESCA, being highest in a near-surface layer having a depth of approx. 5 nm, and decreases inwardly.

Description

A method of making a cathode material having a low BET surface area and high tapped density and a special cathode material

The invention relates to a method for producing a cathode material with a low BET surface area and high tamped density, as well as a special cathode material itself.

One way to improve the discharge rates and cycle stability of cathode materials is to incorporate certain doping elements into the grid of the cathode material. These are those doping elements which have a similar ion radius as lithium. Although the ionic radius of sodium is greater than that of lithium, positive effects on discharge rate and cycle stability were found.

CN 103915617A describes a process for producing a lithium-rich cathode material of the general formula mLi 2-x Nax MnO 3 -n-Li _y Na _y MO 2 by precipitation, where 0 <x + y <1, m + n = 1 and M = Mn, Ni and Co is.

CN 103606663A discloses a lithium-rich cathode material having the general formula LixNaylv y2, where M = Mn, Ni, Co, 0 <x <1, 5 and 0 <y <0.5. It is obtained by milling a metal oxide precusrsor with a lithium-containing compound in a ball mill, converting it into a precursor at low temperatures by hydrothermal solid-state synthesis, which is converted into the lithium-rich cathode material at high temperatures.

CN 103441265A discloses a cathode material having the general formula Li (i + _a ) NaM (i- _a -b) O (2-c), where M = Mn, Ni, Co, where a = 0-0.3, b = 0-0.2 and c = 0-0.2. The preparation comprises the steps of (1) preparing a metal salt solution, (2) dissolving a dispersing agent and a sodium salt, (3) precipitating the sodium-doped precursor and (4) treating the

Precursor at 400-800 ° C over a period of 1-12 hours to form an oxide precursor and (5) mixing the oxide precursor with lithium salts, milling the mixture in a ball mill and (6) final treatment at 700-1000 ° C a period of 1 -40 hours.

In CN 102769136A, a cathode material of the general formula Lii, 3-xNaxCoi-y-zNiyMn _z 02, where x = 0.001-0.5; y = 0, 1 -0.8; z = 0.3-0.8 and y + z = 0.4-0.9. It is obtained by mixing sodium salts, cobalt salts, nickel salts, manganese salts and lithium salts in a molar

Ratio Na / Co / Ni / Mn / Li of 0.8-1, 56: 0.001 -0.05: 0, 1 -0.6: 0, 1 -0.8: 0.3-0.8, under inert gas atmosphere sintered at 250-300 ° C for 3-7 hours, ground and sintered again, at 500-900 ° C for 12-36 hours.

Journal of Alloys and Compounds 618 (2015) 629-634 discloses the synthesis of

Lii, i7 xNaxNio, oiCoo, oi Mno, 630 ₂ (x = 0, 0.02, 0.04, 0.06 and 0.08) were reported by a carbonate co-precipitation method followed by a solid state reaction.

In Materials Chemistry and Physics 95 (2006) 218-221, the synthesis of

Lii, i- _x Na _x [Nio, 2Coo, 3Mno, 4] 02 with x = 0.05, 0, 1 and 0.2 reported via sol-gel method. In WO2016 / 083142 a powdered cathode material in the form of aggregated primary particles comprising a mixed oxide powder is disclosed, which corresponds to a composition

Lii + x (Ni _a CobMn _c ) DdO 2, and H and N as a non-metal component, having a content of H 0.01 - 0, 1 wt .-% and a content of N from 0.002 to 0.05 wt .-% and wherein D may be, inter alia, B and / or Na and 0 <x <0.2; 0 <a <1; 0 <b <1; 0 <c <1, 0 <d <0.2. It is prepared by ammonia and a solution containing a lithium compound, at least one further metal compound selected from the group consisting of Mn, Ni and Co, and at least one doping compound generates an aerosol and this in a

High temperature zone brings to reaction. A particularly preferred doping component is Al. A disadvantage of this method is that the tamped density of the resulting cathode materials is often too low.

A cathode material based on lithium mixed oxides should have a high tamped density in order to keep the volume of the battery small with a given energy capacity. In

US2005 / 106463 discloses an electrode material for a lithium secondary battery containing lithium / transition metal mixed oxides and boron. The electrode material has a specific surface area of 0.1 to 8 m ² / g and a tamped density of 1.6 g to 3.0 g / cm ³ . The electrode material is prepared by mixing a mixture of a lithium, nickel, manganese and cobalt compound and boric acid in the desired stoichiometric ratio with each other, from which produces a dispersion in water, the dispersion milled until a particle diameter of 30 μιτι is reached. This is followed by spray drying. The material thus obtained is thermally treated at elevated temperature. The tamped density varies with the type of thermal treatment. The method mentioned in US2005 / 106463 comprises many steps.

The powders obtained by these processes via flame spray pyrolysis represent useful electrode materials. However, they have a drawback which is too low

Tamping density, which can not be changed later or only by loss of energy capacity.

The object of the present invention was therefore to provide a process which leads to high tamped densities of the powder and which has good electrochemical data.

The invention relates to a process for preparing a powdery mixed oxide A of the general formula Lii + x (NiaCobMnc) BdNa _e 02

with 0 <x <0.5; 0 <a <1; 0 <b <1; 0 <c <1; 0.001 <d <0, 1, 0.001 <e <0.2;

a BET surface area of 10 to 50 m ² / g and a tamped density of 250 to 700 g / l,

in which one

a) providing a solution containing oxidizable and / or hydrolyzable metal compounds of lithium, manganese, nickel and sodium and boric acid, in each case with proportions corresponding to the general formula,

b) atomizing the solution into an aerosol by means of a nebulizer gas,

c) reacting the aerosol in a reaction space with a flame, wherein the

Flame from a mixture of a fuel gas and air is obtained and at the Total amount of oxygen sufficient for at least complete conversion of the fuel gas and the metal compounds,

d) cooling the reaction stream and then separating the solid from the reaction stream.

Mixed oxide is the intimate mixing of all mixed oxide components to understand. It is therefore largely a mixture at the atomic level, not a physical mixture of oxides. The mixed oxide particles are usually present in the form of aggregated primary particles.

Furthermore, the method is particularly suitable for the preparation of mixed oxides A, in which at least one of the conditions 1 <a / b <2; 0.1 <a / c <0.5; 0.1 <b / c <0.5; 0.7 <a + b + c <0.8 and x + a + b + c + d + e = 1 is satisfied.

Furthermore, the process is particularly suitable for the preparation of mixed oxides A, in which at least one of the conditions d + e> 0.05 and d <e is met.

It has also proved to be advantageous to introduce ammonia into the reaction space. This is most easily done when ammonia is part of the nebulizer gas. It appears that the addition of ammonia has an influence on the aggregate structure of the primary particles of mixed oxide A during particle genesis during flame spray pyrolysis and thus leads to particularly high values for the tamped density and particularly low values for the BET surface area during the subsequent thermal treatment. The concentration of ammonia in the

Atomizing gas is preferably 0.01 to 0.5 kg / Nm ³ .

A further preferred embodiment provides that within the reaction space, the flame and the aerosol are partially spatially separated from each other. The spatial separation can be done for example by a bell that surrounds the introduced into the reaction space aerosol. Only at a later time are the products resulting from the ignition of the flame essentially water, and the particles formed from the aerosol, the reaction product, brought together. The particles thus obtained have favorable sintering properties in the subsequent thermal treatment.

The solution used should have the highest possible concentration. An optimum should be aimed at between the production quantity and the material properties of the powder. For the process according to the invention, these requirements are best satisfied in a range from 5 to 20% by weight, based on the sum of Li, Ni, Mn, and Co. The concentration of the solution in the atomizing gas is preferably 0.1 to 1 kg / Nm ³ and more preferably 0.3 to 0.7 kg / Nm ³ .

As the fuel gas, hydrogen, methane, ethane, propane, butane and mixtures thereof can be used. Preference is given to using hydrogen.

The oxygen-containing gas is usually air. The amount of oxygen is to be selected in the inventive method so that it is sufficient at least for complete conversion of the fuel gas and all metal compounds. It is usually beneficial one Use excess oxygen. This excess is conveniently expressed as the ratio of oxygen present / combustion of the fuel gas necessary oxygen and referred to as lambda. Lambda is preferably 1, 1 to 6.0, particularly preferably 2.0 to 4.0.

It is advantageous for the present invention if the metal compounds and the boric acid are present in a solution. In order to achieve solubility and to achieve a suitable viscosity for sputtering the solution, the solution can be heated. In principle, all soluble metal compounds which are oxidizable can be used. These may be inorganic metal compounds, such as nitrates, chlorides, bromides, or organic metal compounds, such as alkoxides or carboxylates, inorganic and / or organic metal compounds. The alkoxides used may preferably be ethylates, n-propylates, isopropylates, n-butylates and / or tert-butylates. The carboxylates which can be used are the compounds based on acetic acid, propionic acid, butanoic acid, hexanoic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, octanoic acid, 2-ethylhexanoic acid, valeric acid, capric acid and / or lauric acid. In a preferred embodiment, at least one metal nitrate is used.

The solvent may preferably be selected from the group consisting of water, Cs-C2o alkanes, Ci-Ci5-alkanecarboxylic acids and / or Ci-Cis alkanols. Particular preference may be given to using water or a mixture of water and an organic solvent. As organic solvents, or as a component of mixtures of organic solvents, alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol or tert-butanol, diols such as ethanediol, pentanediol, 2-methyl-2, 4-pentanediol, Ci-Ci2-carboxylic acids such as acetic acid, propionic acid, butanoic acid, hexanoic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, octanoic acid, 2-ethylhexanoic acid, valeric acid, capric acid, lauric acid. Furthermore, benzene, toluene, naphtha and / or gasoline can be used. Preferably, an aqueous solvent is used.

Another object of the invention is a process for preparing a powdery mixed oxide B of the general formula A of the general formula Lii + x (NiaCobMnc) BdNa _e 02 with 0 <x <0.5; 0 <a <1; 0 <b <1; 0 <c <1; 0.001 <d <0, 1, 0.001 <e <0.2;

a BET surface area of 0.1 to 5 m ² / g, preferably 0.3 to 2 m ² / g, and a tamped density of 1000 to 2500 g / l, preferably 1 100 to 2000 g / l,

in which the powdered mixed oxide A at 700 to 1 100 ° C, preferably 800 to 1000 ° C, over a period of 2 to 36 hours, preferably 1 to 10 hours, thermally treated. Thus, the preparation of the mixed oxide B comprises the process steps for the preparation of the mixed oxide A. Overall, the preparation of the powdery mixed oxide B of the general formula Lii + x (NiaCobMnc) BdNa _e 02

with 0 <x <0.5; 0 <a <1; 0 <b <1; 0 <c <1; 0.001 <d <0, 1, 0.001 <e <0.2; a BET surface area of 0, 1 to 5 m ² / g, preferably 0.3 to 3 m ² / g, and a tamped density of 1000 to 2500 g / l, preferably 1 100 to 2000 g / l, a method in which you

a) providing a solution, the oxidizable and / or hydrolyzable metal compounds of lithium, manganese and / or nickel and boric acid, in each case with proportions corresponding to the general formula,

b) atomizing the solution into an aerosol by means of a nebulizer gas,

c) brings the aerosol in a reaction chamber with a flame to react, wherein the flame is obtained from a mixture of a fuel gas and air and in which the total amount of oxygen at least for the complete conversion of the fuel gas and the

Sufficient metal compounds,

d) cooling the reaction stream and then separating the solid from the reaction stream and

e) the solid at 700 to 1 100 ° C, preferably 800 to 1000 ° C, over a period of 2 to 36 hours, preferably 1 to 10 hours, thermally treated.

Mixed oxide B has a higher crystallinity than mixed oxide A.

Another object of the invention is a special powdery mixed oxide B of the general formula Lii ₊ x (Ni _a CobMnc) BdNa _e 02 with 0 <x <0.5; 0 <a <1; 0 <b <1; 0 <c <1; 0.001 <d <0, 1; 0.001 <e <0.2, which has a BET surface area of 0, 1 to 5 m ² / g and a tamped density of 1000 to 2500 g / l and in which the XPS-ESCA in a near-surface layer with a depth of 5 nm certain sodium concentration of the mixed oxide particles is highest and decreases inwards. The higher level of sodium on the surface can be beneficial in the use of the mixed oxide in lithium-ion batteries.

For the detection of sodium in the near-surface layer, a large area (1 cm ² ) XPS / ESCA analysis (XPS = X-ray photoelectron spectroscopy, ESCA = Electron

Spectroscopy for Chemical Analysis).

The evaluation is based on the general recommendations according to DIN Technical Report no. 39, DMA (A) 97 of the National Physics Laboratory, Teddington, U.K., and the previous findings on the development-accompanying standardization of the working committee "Surface and

Microscope analyzes "NMP816 (DIN)

Comparison spectra from the literature considered. The values are through

Substrate subtraction, calculated taking into account the relative sensitivity factors of the respective specified electron levels. The information is given in area percent. The accuracy is relative to +/- 5% relative.

Another object of the invention is the use of special, powdery mixed oxide as a cathode material in lithium-ion batteries.

Examples For each of Examples 1 to 3, a solution containing the salts and boric acid mentioned in Table 1 is prepared with water as the solvent.

From the solution and atomizing air, an aerosol is generated by means of a nozzle, which is atomized into a reaction space. Here a blast gas flame burns out of hydrogen and air, in which the aerosol is brought to the reaction. After cooling, the solid is separated on a filter of gaseous substances.

The solid is heated to a temperature of 800 to 960 ° C over 3 to 10 hours in a rotary kiln over a period of 4 to 6 hours.

Table 1 lists all relevant parameters for the preparation of the cathode material.

Table 2 shows BET surface areas and tamped densities of the mixed oxides produced.

Thus, the BET surface area and the tamped density of the mixed oxide A, ie from the

Flammenspraypyrolyse, similar to Example 1 and Comparative Examples 2 and 3 according to the invention. Sodium as the only doping element (Example 3) does not give sufficiently high

Tamped density and no sufficiently low BET surface area. Boron as the only doping element (Example 2) gives similar values in terms of BET surface area and tapped density for the mixed oxides A and B, such as the mixed oxides prepared by the process according to the invention. The positive electrochemical properties of a sodium doping, the mixed oxide of Example B, however, not on.

Table 3 shows the determined by XPS-ESCA sodium concentration of a mixed oxide powder according to the invention and a comparative example. In contrast to the comparative example, the mixed oxide powder according to the invention has the highest sodium concentration at the surface.

Table 1: Starting materials and reaction conditions

a) flame temperature; measured 10 cm below the feed point of H2 and air into the reaction space; TABLE 2 BET surface area, tamped density of mixed oxides A and B

According to

Comparative Example Invention

Example 1 2 3

BET mixed oxide A ^a > m ² / g 33 33 32

BET mixed oxide B ^a > m ² / g 2,4 2,2 12

Decrease BET% 93 93 63

Tamped density mixed oxide A ^b) g / i 440 515 590

Tamped density mixed oxide B ^b) g / i 1278 1237 859

Increase stock density% 290 240 145 a) BET surface area according to DIN ISO 9277; b) tamped density according to DIN EN ISO 787/1 1;

Table 3: Sodium concentration in mixed oxides B

According to the comparative invention, for example

Example 1 3

near surface atomic% 0.9 0.7

sputtered atom% <0, 1 0.7

Claims

claims

1. A process for the preparation of a powdery mixed oxide A of the general formula

Lii + x (NiaCobMnc) BdNa _e 02,

with 0 <x <0.5; 0 <a <1; 0 <b <1; 0 <c <1; 0.001 <d <0, 1, 0.001 <e <0.2;

a BET surface area of 10 to 50 m ² / g and a tamped density of 250 to 700 g / l, in which

b) atomizing the solution into an aerosol by means of a nebulizer gas,

c) reacting the aerosol in a reaction space with a flame, wherein the

Flame is obtained from a mixture of a fuel gas and air and in which the total amount of oxygen sufficient at least for the complete implementation of the fuel gas and the metal compounds,

2. The method according to claim 1, characterized in that

the concentration of the solution in the atomizing gas is preferably 0.1 to 1 kg / Nm ³ .

3. Process according to claims 1 or 2, characterized in that

ammonia is introduced into the reaction space.

4. Process according to claims 1 to 3, characterized in that

within the reaction space, the flame and the mixture are at least partially spatially separated from each other.

5. Process according to claims 1 to 4, characterized in that

the ratio of existing oxygen / combustion of the fuel gas necessary

Oxygen is 1, 1 to 6.

6. A process for the preparation of a powdery mixed oxide B of the general formula

Lii + x (NiaCobMnc) BdNa _e 02,

with 0 <x <0.5; 0 <a <1; 0 <b <1; 0 <c <1; 0.001 <d <0.1; 0.001 <e <0.2;

a BET surface area of 0.1 to 5 m ² / g and

a tamped density of 1000 to 2500 g / l,

in which the powdered mixed oxide A is thermally treated at temperatures of 700 to 1100 ° C over a period of 2 to 36 hours.

7. Powdered mixed oxide B of the general formula

Lii + x (NiaCobMnc) BdNa _e 02

with 0 <x <0.5; 0 <a <1; 0 <b <1; 0 <c <1; 0.001 <d <0.1; 0.001 <e <0.2,

which has a BET surface area of 0, 1 to 5 m ² / g and a tamped density of 1000 to 2500 g / l owns and

in which the sodium concentration of the mixed oxide particles determined by means of XPS-ESCA in a near-surface layer with a depth of approximately 5 nm is highest and decreases inwardly.

Use of the powdery mixed oxide B according to claim 7 as cathode material in lithium-ion batteries.