Powdered lithium oxide, its preparation method and use

Abstract

The present invention relates to a method for producing a polymer having a specific surface area according to the BET method of at least 5 m 2 The present invention relates to a powdered lithium oxide Li2O having a molecular weight of 1.001 g / g and a bulk density of up to 0.3 g / ml, a process for its preparation, and its use in the preparation of perlithiated metal oxides.

Description

[Technical field]

[0001] The present invention relates to a powdered, high surface-rich lithium oxide, an economical method for producing said lithium oxide from lithium peroxide, and the use of said lithium oxide for the production of overlithiated lithium metal oxides, which are used as cathode additives for the prelithiation of lithium ion batteries. [Background technology]

[0002] Lithium oxide is currently used as a raw material for the production of glasses, glass ceramics, ceramics, as well as the positive electrodes of lithium batteries. Furthermore, lithium oxide can also be used to produce lithium hydroxide. Of particular importance is the use of Li2O for the production of perlithiated metal oxides. Perlithiated metal oxides can alternatively be referred to as lithium-rich metal oxides. Perlithiated metal oxides are lithium-containing oxide compounds that have an increased lithium content compared to standard LIB cathode materials, such that this excess content can be utilized during the first charge / discharge cycle to offset the irreversible lithium loss on the anode side. Examples of perlithiated metal compounds are: Li5FeO4, Li2NiO2, Li6CoO4, or perlithiated manganese-containing spinel compounds, especially Li 1+x Mn2O4 or Li 1+x Ni 0.5 Mn 1.5 O4, where x≧0~1.

[0003] Lithium oxide can be produced by burning lithium metal in an oxygen-containing atmosphere, a process that is uneconomical because it uses metallic lithium as a starting material, which is produced by energy-consuming molten salt electrolysis.

[0004] Furthermore, lithium oxide can also be obtained starting from lithium-based chemical lithium carbonate. The method is as follows: Li2CO3 → Li2O + CO2 (1) It requires very high temperatures of about 900-1000°C, preferably under reduced pressure. Due to the intermediate melting point of lithium carbonate, the oxide is usually formed in lumps, which must be crushed before further use (Non-Patent Document 1). The strong corrosive effect of molten lithium salts at such high temperatures inevitably leads to the introduction of undesired impurities into the pyrolysis products and to corrosion-induced destruction of the crucible materials used.

[0005] 10 -5 At extremely low pressures of less than 100 Torr, thermal decomposition can occur even below the melting point of Li2CO3 at 720 °C. (Non-Patent Document 2) However, such low pressures cannot be economically achieved with engineered equipment.

[0006] The admixture of elemental carbon such as carbon black serves to accelerate the decomposition of lithium carbonate (Non-Patent Document 3). This carbon pyrolysis does not require a vacuum but occurs under Ar flow and proceeds rapidly in an alumina crucible at temperatures above about 720° C. (i.e., the melting point temperature of lithium carbonate) according to the following reaction: Li2CO3+C→Li2O+2CO (2).

[0007] A disadvantage is the strong corrosive effect of the carbonate melt on the alumina of the container material used, so that the fired product is contaminated with aluminium.

[0008] Li2O can also be produced by the thermal decomposition of lithium peroxide, Li2O2. : Li2O2 → Li2O+1 / 2O2(3).

[0009] This method has the advantage that there is no intermediate melting or sintering step and Li2O can be obtained directly in powder form. The calcination method starting from lithium peroxide is also characterized by lower energy costs and no corrosion of the container material is expected due to the moderate calcination temperature and the avoidance of melting phenomena.

[0010] Non-Patent Document 4 states that pure white lithium oxide can be obtained by heating lithium peroxide to 300°C in a Pyrex tube. Details such as pyrolysis time are not reported. In the inventors' own experiments, it was found that at least 20 hours are required to achieve a conversion rate of more than 90% to lithium oxide at 300°C.

[0011] Patent document 1 teaches the decomposition of granular porous Li2O2 at temperatures between 225 and 450° C. to obtain granular Li2O suitable for CO2 absorption. In the examples, calcination is performed under argon flow at a temperature of 386° C. for 22 hours and 47 minutes.

[0012] US Patent No. 5,399,633 describes a method for producing high purity Li2O by decomposition of Li2O2 in an inert atmosphere at an initial temperature of 350-450°C, followed by a calcination process at 900°C under moderate vacuum.

[0013] Patent document 3 teaches the use of Li2O with a primary particle size D50 of 5 μm or less and a secondary particle size D50 of 10-100 μm for the production of Li2NiO2, where lithium oxide is produced by thermal decomposition of Li2O2 in the temperature range 400-600° C. In the examples, Li2O is obtained by heat treatment at 420° C. for 3 hours.

[0014] US Patent No. 5,399,633 teaches the preparation of finely divided grade lithium peroxide (particle size 1-130 μm, preferably 5-50 μm) and its use for the preparation of lithium oxide. Calcination is carried out at a minimum of 300° C., preferably 350-650° C. In the examples a temperature of 425° C. is mentioned.

[0015] Patent document 5 relates to a method for preparing high purity nanometer lithium oxide, characterized in that lithium peroxide is decomposed at an initial temperature of 350-500 ° C to form lithium oxide, which is then further calcined at 600-800 ° C, and then crushed by a ball mill to the desired fineness.

[0016] The preparation of perlithiated nickel oxide, Li2NiO2, from nickel oxide and Li2O (obtained by thermal decomposition of Li2O2) has been described in a publication by J. Kim et al. (Non-Patent Document 5). The Li2O2 calcination process has been studied in the temperature range of 350-600°C. Li2NiO2 was prepared using the Li2O reaction product calcined at 450°C. According to the cited publication (Non-Patent Document 6), a mixture of NiO and Li2O was ground in a ball mill under argon for 1 day, and then the homogenized mixture was pyrolyzed at 650°C under Ar atmosphere for 24 hours (Kang) or 12 hours (Kim) to obtain the final product Li2NiO2.

[0017] Known methods for producing Li2O from Li2O2 have the disadvantage that they either require long reaction times (at least 20 hours at 300°C) that are not attractive for commercial reasons, or result in granular Li2O and / or require relatively high temperatures of at least 350°C. Temperatures above 350°C are not achievable in classical oil-fired reactors and therefore require furnace technology. Furthermore, pyrolysis temperatures above 350°C are This results in a low surface area of ​​Li2O, which is an obstacle for solid / solid conversions, such as in the preparation of perlithiated metal oxide compounds, e.g., Li2NiO2, from transition metal oxides and Li2O. To achieve complete conversion of transition metal oxides with Li2O in acceptable reaction times (less than 12-24 hours), the material must be thoroughly precoated. This method requires very long meals (24 hours) when using conventional Li2O, e.g., prepared by pyrolysis of Li2O2 at 350°C or higher. This leads to high costs and, in addition, the introduction of impurities due to attrition losses corresponding to the grinding time.

Prior technical literature

[0018]

Patent Document 1

Patent document 2

Patent Document 3

Patent document 4

Patent document 5

Non-licensed literature

[0019]

Non-licensed literature 1

Non-licensed Document 2

Non-licensed Document 4

Non-licensed Document 5

Non-licensed Document 6

[0020] the purpose The present invention is based on the object of providing a method which allows the production of a powdered lithium oxide with a high specific surface area and low density, which can be milled with the lowest possible energy input and which, when mixed with a transition metal oxide, for example nickel oxide, can be advantageously converted into the corresponding lithium metal oxide. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Description of the invention Surprisingly, it has been found that the calcination temperature has a significant effect on the morphology of the lithium oxide formed from the lithium peroxide, as shown in the following table:

[0022] [Table 1]

[0023] Specific surface area is 15 to 20 m 2 Lithium peroxide with a peroxide content of at least 97% (the remainder consisting essentially of LiOH and Li2CO3) was used in the experiments. All experiments were carried out under an inert gas atmosphere consisting of nitrogen, i.e., with the exclusion of air, O2, CO2, and H2O, respectively.

[0024] Up to 325°C, which is in the middle of the range, it has a high specific surface area (10 m 2 It can be seen that product quality with a specific surface area of ​​1000 nm (or more than 1000 nm / g) is obtained. Upon reaching and exceeding about 350° C., the specific surface area drops sharply. At the same time, the bulk density increases.

[0025] The LiO modified forms with higher surface area are easier to grind and therefore can be brought to the particle size range required for conversion of finely divided metal oxides, i.e., particles less than 20 μm, preferably less than 10 μm, more quickly and with less energy input.

[0026] The lithium peroxide used in the process according to the invention has a Li2O2 content (by weight) of at least 95%, preferably at least 97%, particularly preferably at least 98%, as determined by manganometric titration. The remainder to 100% consists essentially of LiOH and Li2CO3. Although high surface area lithium oxides are formed even from low purity grade lithium peroxide when applying intermediate calcination temperatures, these generally contain undesirable granular components and the residual carbonate and hydroxide content of the Li2O prevents their use in the preparation of perlithiated lithium transition metal oxides.

[0027] According to the BET measurement method, the specific surface area of ​​the lithium peroxide used is 5 to 30 m 2 / g, preferably 10 to 30m 2 / g, more preferably 15 to 20m 2 / g.

[0028] The calcination is carried out under the exclusion of ambient air, in particular under the exclusion of compounds reactive towards lithium oxide and / or lithium peroxide. Such are water (moisture), CO2 and other air trace elements. Therefore, the calcination is preferably carried out either under inert gas (argon, helium, nitrogen) or in vacuum (less than 10 mbar). Furthermore, synthetic, dry and CO2-free air can be used. Due to the moderate reaction temperature, there are no special requirements for the container material; i.e. most heat-resistant materials, metals as well as glasses (e.g. borosilicate glass, quartz glass) and ceramics (aluminum oxide, porcelain, etc.) can be used.

[0029] Calcination can be carried out either statically, i.e., the Li2O2 starting material is placed in a crucible and calcined in a furnace, or under mixed conditions, i.e., in a stirred tank reactor, a rotary tube, or in a heatable mixing unit (e.g., vertical or horizontal dryer, tumble dryer, etc.). A fluidized bed reactor can also be used.

[0030] The calcination temperature is in the range of 280-370°C, preferably 300-350°C, more preferably 310-350°C, particularly preferably 310-340°C. The calcination time to achieve complete conversion depends on the temperature used. Calcination is carried out until the residual amount of lithium peroxide is at most 5, preferably at most 2, particularly preferably at most 1% by weight. This is achieved by a calcination period of 1-30, particularly 1-20, preferably 1-10 hours.

[0031] The specific surface area of ​​the powdered lithium oxide is at least 5m 2 / g, preferably at least 8m 2 / g, particularly preferably at least 10m 2 / g, which is measured by gas adsorption, a method known as the "BET method", named after its creators, Stephen Brunauer, Paul Hugh Emmett, and Edward Teller, according to standard specification ASTM D6556. In this case, the adsorbed gas is nitrogen.

[0032] The powdered lithium oxide has a bulk density of at most 0.3 g / mL, preferably at most 0.2 g / mL, more preferably at most 0.15 g / mL. The bulk density is specified according to the EN ISO 60 standard.

[0033] The high surface area lithium oxide according to the invention is preferably used for the preparation of perlithiated metal compounds, which preferably consist of: LiFeO, LiNiO, LiCoO, or perlithiated manganese-containing spinel compounds, in particular Li 1+x Mn2O4 or Li 1+x Ni0.5 Mn 1.5 O4, where x>0-1. For this purpose, high surface area lithium oxide is reacted with the corresponding transition metal hydroxide or transition metal oxide or a mixture of different transition metal hydroxides or oxides.

[0034] Generally, the high surface area lithium oxide is first thoroughly mixed with and / or ground with a transition metal salt. Preferably, the mixture is ground in a grinding media mill using hard grinding media, such as balls, rods, etc., made of metal (steel or nickel-based alloys) or hard ceramics (metal oxides, metal carbides, metal nitrides, etc.). The Vickers hardness of the grinding vessel and grinding media is at least 400, preferably at least 600. Materials made of stainless steel or metal oxides, such as aluminum oxide or zirconium oxide, are particularly suitable. Ball mills, rod mills, or hammer mills can be used.

[0035] The subsequent reaction of the mixture of high surface area lithium oxide and transition metal oxide or hydroxide to perlithiated metal oxide is usually carried out in the absence of oxygen, i.e. in a reducing atmosphere or in vacuum at a pressure of 0.01 to 50 mbar, at temperatures between 400 and 900° C. The reducing atmosphere consists of nitrogen or nitrogen compounds. The reducing atmosphere consists of nitrogen or a noble gas, preferably argon or helium. However, there are exceptions to the atmosphere, i.e. when the oxidation state of the transition metal in the starting oxide or hydroxide is lower than that of the final product produced. In this case, an oxidizing atmosphere is necessary, at least temporarily. This will be explained with reference to some characteristic transformations.

[0036] For example, perlithiated lithium nickel oxide (LiNiO) is produced according to the prior art by reacting lithium oxide with nickel oxide in an inert (i.e. reducing, oxygen-free) atmosphere (G. Cedar, Chem. Mater. 2004, 2685): TIFF2025501782000002.tif29163

[0037] For this purpose, nickel oxide is first ground in a ball mill together with high surface area lithium oxide and calcined at about 650 °C for 1-24 h under an inert argon atmosphere. Perlithiated lithium cobalt oxide Li6CoO4 is prepared by solid / solid reaction by reacting CoO with Li2O at 900 °C under a nitrogen atmosphere (Yingying Zhou, dissertation 2021, https: / / doi.org / 10.14989 / doctor.k22548). Li5FeO4 is prepared from Li2O and Fe3O4 at 500 or 800 °C under an air atmosphere according to the following (MV Blanco et al., Chem. Eng. J. 354, 2018, 370-7): Fe3O4+7.5Li2O+0.5O2→3Li5FeO4

[0038] Fe3O4 contains two iron species, one with a +2 oxidation state and the other with a +3 oxidation state. To convert from the +2 state to +3, the reaction is carried out, at least temporarily, under oxidizing conditions. In contrast, the same perlithiated metal compounds are synthesized from a ground mixture of Fe2O3 (iron oxidation state +3) and Li2O by heating first at 450 °C and then at 750 °C under inert conditions (WM Dose et al., J. Electrochem. Soc. 2020, 167 160543): Fe2O3+5Li2O→2Li5FeO4

[0039] Perlithiated spinels, e.g., Li 1+x Ni 0.5 Mn 1.5 O4 etc. are the equivalent normal cathode material LiNi 0.5 Mn 1.5 It is prepared by reacting O4 with lithium oxide under reducing conditions at 600 °C (G. Gabrielli et al., J. Power Sources, 351, 2017, 35). EXAMPLES

[0040] Example 1. Preparation of high surface area Li2O from Li2O2 according to the present invention. In an Ar-filled glove box, 15.0 g of lithium peroxide (peroxide content 97.9%) was loaded into a ceramic container made of alumina ceramic and placed in a hinged tube furnace equipped with a borosilicate reaction tube under the exclusion of air. The furnace temperature was set to 325° C. under a slight nitrogen overflow and maintained at this temperature for 5 hours.

[0041] Yield: 9.5 g (97% of theory) of a fine white powder. Specific surface area: 13.5m 2 / g Bulk density: 0.12g / mL Li2O content: 98.6% by weight (acid titration) Peroxide content: Not detectable (less than 0.5% by weight)

[0042] Example 2. Preparation of Li2NiO2 from high surface area Li2O and NiO according to the present invention. In an Ar-filled glove box, 1.49 g (50 mmol) of lithium oxide (from Example 1) and 3.73 g (50 mmol) of nickel(II) oxide (nano powder from Sigma-Aldrich, 99.8% purity based on trace metal impurities) were mixed in an agate mortar and ground with a pestle.

[0043] This mixture was then loaded into an alumina crucible and placed in a hinged tube furnace from which the air was largely excluded. The heated, nitrogen permeable furnace tube was made of Inconell 601.

[0044] The ground mixture was calcined at a furnace temperature of 650° C. for 10 hours.

[0045] After cooling to RT, the crucible was introduced into an Ar-filled glove box under the exclusion of air.

[0046] Yield: 5.1 g (98% of theory). XRD: Nearly phase pure Li2NiO2 (Immm structure); traces (<1%) of NiO.

Claims

1. The specific surface area by BET method is at least 5 m ２ / g and a bulk density of up to 0.3 g / ml. ２ A method for preparing O, comprising the steps of: Li ２ O ２ Powdered lithium peroxide Li with a minimum content of 95% by weight ２ O ２ However, under inert gas conditions or in vacuum, at a pressure of less than 10 mbar, at a temperature of 280 to 370° C., Li ２ Oh ２ →Li ２ O+1 / 2O ２ Lithium oxide Li ２ calcining until reaction to O has occurred to at least 95%, based on the weight of the calcined reaction product; The method according to claim 1,

2. The Li after firing ２ O ２ 2. The method according to claim 1, characterized in that the residual amount is at most 2% by weight, preferably at most 1% by weight, based on the weight of the calcined reaction product.

3. The inert gas may be nitrogen, argon, helium, or dry CO ２ 3. The method according to claim 1 or 2, characterized in that the mixture is selected from air-free mixtures.

4. The method according to any one of claims 1 to 3, characterized in that the calcination period is between 1 and 30, in particular between 1 and 20, preferably between 1 and 10 hours.

5. The powdered lithium peroxide is Li ２ O ２ A method according to any one of claims 1 to 4, characterised in that the content is at least 97% by weight, preferably at least 98% by weight.

6. The method according to any one of claims 1 to 5, characterized in that the calcination temperature is between 300 and 350°C, preferably between 310 and 350°C, in particular between 310 and 340°C.

7. The specific surface area of ​​the lithium peroxide used, as measured by the BET method, is 5 to 30 m ２ / g, preferably 10 to 30 m ２ / g, more preferably 15 to 20m ２ The method according to any one of claims 1 to 6, characterized in that:

8. BET specific surface area of ​​at least 5 m ２ / g and a bulk density of up to 0.3 g / ml. ２ O.

9. A specific surface area according to BET is at least 8, preferably at least 10 m ２ / g, more preferably at least 12m ２ / g, and even more preferably at least 15m ２ The powdered lithium oxide according to claim 8, wherein the lithium oxide content is 1 / g.

10. 10. Powdered lithium oxide according to claim 8 or 9, characterized in that it has a bulk density of at most 0.2 g / mL, preferably at most 0.12 g / mL.

11. A method for preparing a perlithiated metal oxide, comprising the steps of: mixing one or more transition metal oxide salts (several) with a powdered lithium oxide Li ２ O and then reacting in a calcination process at a temperature ranging from 400 to 900° C. under inert gas or in vacuum below 50 mbar to obtain said perlithiated metal oxide.

12. 12. The method of claim 11, wherein the oxidized transition metal salt(s) is selected from the group of substances transition metal oxides or transition metal hydroxides.

13. The transition metal oxide salt is selected from nickel oxide, manganese oxide, cobalt oxide, and iron oxide, preferably NiO, CoO, FeO ２ O ３ , Fe ３ O ４ , and FeO, particularly preferably NiO, CoO, and Fe ２ O ３ 13. The method according to claim 11 or 12, characterized in that it is selected from the group consisting of: or the corresponding hydroxide compounds.

14. 14. The method according to claim 11, characterized in that the calcination is carried out under reducing conditions, in particular in an oxygen-free atmosphere or in vacuum, at 0.01 to 50 mbar, when the raw materials are in the ideal transition metal oxidation state as in the final product.

15. The method according to any one of claims 11 to 14, characterized in that the reducing atmosphere is selected from nitrogen, argon and helium.

16. The perlithiated metal oxide is Li ５ FeO ４ , Li ２ NiO ２ , Li ６ CoO ４ or perlithiated manganese-containing spinel compounds, particularly Li １＋ｘ Mn ２ O ４ Or Li １＋ｘ Ni ０．５ Mn １．５ O ４ The method according to any one of claims 11 to 15, characterized in that the compound is selected from the group consisting of:

17. Perlithiated metal oxides, especially Li ５ FeO ４ , Li ２ NiO ２ , Li ６ CoO ４ or a perlithiated manganese-containing spinel compound, preferably Li １＋ｘ Mn ２ O ４ Or Li １＋ｘ Ni ０．５ Mn １．５ O ４ 11. Use of lithium oxide according to any one of claims 8 to 10 or prepared by the method according to any one of claims 1 to 7 for the preparation of a perlithiated metal oxide selected from the group consisting of:

Images