KR100550373B1 - Manufacturing method of Li1 + xMn2-xO4 for use as a secondary battery electrode - Google Patents

Abstract

The present invention comprises the steps of sufficiently mixing the lithium hydroxide or lithium salt and manganese oxide or manganese salt; Supplying a sufficiently mixed salt to the reactor; Continuously stirring the mixed salts in the reactor; Heating the stirred mixed salt in the reactor in an oxygen-containing atmosphere at a temperature of about 650 ° C. to about 800 ° C. for a time not exceeding about 4 hours; And cooling the reaction product to less than about 200 ° C. in an oxygen-containing atmosphere for a time period of no greater than about 2 hours. Lithium-doped manganese oxide interlayer having the formula Li _{1 + x} Mn _2-x O ₄ It relates to a continuous process for preparing a compound.

Description

Method for producing Li 1 + XMn 2 -XO 4 for use as a secondary battery electrode

The present invention relates to a continuous process for producing fine powders and / or films of lithium containing ternary oxides. More specifically, the present invention relates to the synthesis of Li _{1 + x} Mn _2-x O _4, an intercalatable compound attracting attention for secondary batteries.

To date, lithium containing ternary hydroxides has been produced by mixing carbonates and oxides of the component compounds and heating the mixture at high temperatures. This method produces a material that is effective for the cell but is not commercially viable due to the long reaction and cooling times.

The present invention relates to secondary, rechargeable lithium and lithium-ion batteries, and more particularly to Li _{1 + x} Mn _2-x O ₄ (x being from about 0 to about 0) for use as a positive electrode of such batteries. About 0.125) to a continuous process for preparing an intercalation compound.

Lithium-cobalt oxide is used as a positive electrode material of a 4V lithium-ion battery currently on the market. Based on low cost, abundant raw materials, incidental safety, environmental water solubility and electrochemical performance, Li _{1 + x} Mn _2-x O ₄ interlayer compounds have been particularly promising as positive electrode materials in such cells. However, in order for Li _{1 + x} Mn _2-x O ₄ to be commercially acclaimed as a cathode material, it is not yet known how to quickly and economically prepare a material with the required electrochemical performance characteristics. . The present invention solves this problem.

LiMn ₂ O ₄ (Li _{1 + x} Mn _2-x O ₄ , where x = 0) was homogeneously mixed in 1958 with Li ₂ CO ₃ and any manganese oxide so that the molar ratio was Li / Mn = 0.50. The mixture was reacted in air at 800-900 ° C. and synthesized by repeatedly grinding and reacting the mixture at this temperature until the sample reached a certain weight (DG Wickham and WJ Croft, J. Phys. Chem. Solids 7 (1958) 351-360). Hunter is described in JC Hunter (Union Carbide), US Pat. No. 4,246,253, January 20, 1981; JC Hunter (Union Carbide), US Pat. No. 4,312,930, January 26, 1982; Hunter JC, J. Solid State Chem 39 (1981) as by 142-147; acid leaching the LiMn ₂ O ₄ for the production of λ-MnO ₂ for holding a crystal structure of LiMn ₂ O ₄ in, then the λ-MnO ₂ has been reported for use as a positive electrode material in lithium batteries. Hunter electrochemically reduced λ-MnO ₂ to LiMn ₂ O ₄ , which occurs at 4V, but they did not cycle in the cell. He also suggested that other lithium and manganese compounds could be used in the synthesis in addition to those proposed by Wickham and Croft, provided that these lithium and manganese compounds decompose into lithium or manganese oxide under the reaction conditions used. Thackeray et al. [M. Thackeray, P. Johnson, L.de Picciotto, P. Bruce and J. Goodenough, Mat. Res.Bull. 19 (1984) 179-187; M. Thackeray, L.de Picciotto, A.de Kock, P.Johnson, V.Nicholas, and K.Adendorff, J. Power Sources 21 (1987) 1-8] have described Li in a LiMn ₂ O ₄ spinel structure. Since intercalation is electrochemically reversible, it provides two voltage plateaus at ˜4.1V and 3.0V for Li, which intercalates / deintercalates of the first and second Li ions into λ-MnO ₂ , respectively. Showed that

Several researchers have studied the synthesis of LiMn ₂ O ₄ by the thermal reaction of lithium and manganese compounds, and found that the synthesis can be carried out over a wide range of temperatures, from 300 to 900 ° C. The ability of the product to intercalate and deintercalate Li was investigated. The so-called “cold materials” produced at temperatures below about 550 ° C. are incomplete crystalline, have a modified spinel structure, and are cycled at about 3V rather than 4V for Li [WJMacklin. RJ Neat and RJ Powell, J. Power Sources 34 (1991) 39-49; T.Nagaura, M.Yokokawa and T.Hashimoto (Sony Corp.), US Pat. No. 4,828,834, May 9, 1989 MMThackery and A. de Kock (CSIR), US Pat. No. 4,980,251, December 25, 1990 Work; V. Manev, A. Momchilov, A. Nassalevska and A. Kozawa, J. Power Sources, 43-44 (1993) 551-559]. These materials are not the material for which this patent application is intended.

The so-called "hot materials" produced at about 600-900 ° C. in the air atmosphere are very crystalline. They exhibit a cycleable output at about 4V for Li, but at 3V the cycleable output is much worse, so they quickly lose capacity. JMTarascon, E. Wang, JKShokoohi, WRMc Kinnon and S. Colson, J. Electrochem. Soc. 138 (1991) 2859-2868]. Even when LiMn ₂ O ₄ is synthesized at low temperatures, such as in the sol-gel process, if it is first calcined / annealed, for example, at a high temperature of 600-800 ° C., it can cycle to 4V regime. Barboux, FKShokoohi and JM Tarascon (Bellcore), US Pat. No. 5,135,732, 4 August 1992]. High temperature LiMn ₂ O ₄ material is another object of the present application.

The researchers generally found that several hours or even days of reaction time was required to synthesize a single-phase product in a (stationary) muffle furnace that frequently linked the regrind phase of the heated product to the reheat stage of the regrinded powder. P.Barboux, FKShokoohi and JM Tarascon (Bellcore), US Patent No. 5,135,732, 4 August 1992, WJMacklin, RJNeat and RJPowell, J. Power Sources 34 (1991) 39-49; A. Mosbah, A. Verbaire and M. Tournoux, Mat. Res. Bull. 18 (1983) 1137-1381; T. Ohzuku. M. Kitagawa, and T. Hirai, J. Electrochem. Soc. 137 (1990) 769-775. The omission of the synthetic procedure, which requires this effort, results in various by-products besides LiMn ₂ O ₄ , namely Mn ₂ O ₃ , Mn ₃ O ₄ . Li ₂ MnO ₃ is produced. Such materials are undesirable in lithium batteries and cause low battery capacity and high fade rates.

Apart from the generation of undesirable by-products, synthetic parameters also affect the molecular / crystal structure and physical properties of LiMn ₂ O ₄ , which have a significant impact on the cell capacity of the material and the cycling performance of the material. give. Momchilov, Manev and their researchers [A. Momchilov, V. Manev, and A. Nasslavska, J. Power Sources 14 (1983) 305-314] varied the lithium reactant, MnO ₂ reactant, reaction temperature and reaction time before cooling in air. They found it advantageous to make a spinel from a lithium salt with the lowest melting point possible and the MnO ₂ sample with the largest surface area. The advantage is that a faster reaction time and a more porous product can be obtained, which provides greater capacity and better cycling performance (ie less capacity attenuation over the number of cycles). However, the reaction time takes several days in any case. These researchers [V. Manev, A. Momchilov, A. Nassalevska and A. Kozawa, J. Power Sources, 43-44 (1993) 551-559; A.Momchilov, V.Manev and A.Nassalevska, J. Power Sources 41 (1993) 305-314 found that the optimum reaction temperature was approximately 750 ° C. At higher temperatures, the material loses cell capacity, probably due to a decrease in surface area and a loss of oxygen due to the reduction of some manganese in LiMn ₂ O ₄ . At lower reaction temperatures, longer time is required to synthesize, and apparently traces of spinel deformation have occurred that result in lower doses. The researchers also suggested that it is advantageous to preheat the mixture at a temperature just above the melting point of the lithium reactant before reacting at the final temperature.

Tarascon and the researchers [JMTarascon, WRMc Kinnon, F. Coowar, TNBowmer, G. Amatucci and D. Guyomard, J. Electrochem. Soc. 141 (1994) 1421-1431; JMTarascon (Bellcore), International Patent Application WO 94/26666; U.S. Patent No. 5,425,932, June 20, 1995] discloses (1) Li _{1 + x} Mn ₂ since the molar ratio of Li / Mn is greater than 1/2 (ie, Li / Mn = 1.00 / 2.00 to 1.20 / 2.00). x = 0.0 to 0.125 at _-x o ₄ ) and (2) heat the reaction at 800-900 ° C. for a long time (eg 72 hours), and (3) at a very slow rate, ie preferably The product reacted under an oxygen containing atmosphere at 2-10 ° C./h was cooled to about 500 ° C. and finally (4) the furnace was turned off to rapidly cool the product to room temperature to obtain high capacity and long cycling life. If the atmosphere is rich in oxygen, the cooling rate to 500 ° C. at temperatures above 800 ° C. can be increased to 30 ° C./h. The researchers found that the lattice parameter a。 of the product is an indicator of the product's effectiveness and should be less than about 8.23 kW. In contrast, Li = Mn = 1.00 / 2.00 and a = 8.247 kPa for LiMn ₂ O ₄ prepared under air cooling.

Manev and his team [V.Manev, A.Momchilov, A.Nassalevska and A.Sato. J. Power Sources 54 (1995) 323-328 also found that when the molar ratio of Li / Mn is greater than 1.00 / 2.00, both capacity and cycling performance are advantageous. They chose 1.05 / 2.00 as the optimum ratio. The researchers also found that the dose decreased significantly as the amount of pre-mixture / reactant in the muffle furnace was increased from -10 g to -100 g. They investigated the depletion of air in the furnace and the partial reduction of the resulting product. Flowing air into the furnace could alleviate this problem. If there is too much air flow, the product capacity again decreases, so the air flow must be advantageously optimized. Manev and his team found that the most desirable cooling rate was tens of degrees Celsius per minute, which was more than 100 times faster than the results of Tarascon and its team. After optimizing all conditions, including the use of highly porous chemical manganese dioxide and lithium nitrate as reactants, Manev and his team found that Li _{1 + x} Mn _2-x o ₄ , where x = 0.033 has a very high capacity and long lifetime. ) Product. The use of lithium nitrate negatively affects the manufacturing process because toxic NOx fumes are released during synthesis. Manev has developed a successful synthesis method using lithium carbonate rather than lithium nitrate [V.Manev, paper presented in the 9th IBA Battery Materials Symposium, Cape Town, South Africa, May 20-22, 1955 (summary available) Possible)], this new production process again required several days of reaction time.

Howard [WF Howard, Jr., Proceedings of the 11th Int'l Seminar on Primary and Secondary Battery Technology & Application. February 28-3, 1994, sponsored by Deerfield beach, Fla., SPWolsky & N.Marincic, discussed the possible cost-effective LiMn ₂ O ₄ production equipment. Although no data has been published / presented, Howard suggests that rotary kilns can transfer heat faster than stationary ovens, reducing the reaction time.

The desired slow cooling rate in combination with long thermal reaction times is very difficult to realize in large scale processes such as pilot-plant or commercial operation. Therefore, it is highly desirable to reduce the reaction time and cooling time in order to avoid unwanted by-products and to preserve the necessary Li _{1 + x} Mn _2-x o ₄ stoichiometry and structure (where the structure is demonstrated by smaller lattice parameters ).

Summary of the invention

Lithium manganese oxide represented by the formula Li _{1 + x} Mn _2-x o ₄ (where x is from about 0 to about 0.125) and having a lattice parameter of about 8.235 Pa or less, mixes lithium salt / hydroxide and manganese oxide, The mixture is continuously stirred while heating in an air, oxygen or oxygen rich atmosphere at a temperature of about 650 to about 800 ° C. for up to about 2 hours and then similarly stirred up to about 2 hours in an air, oxygen or oxygen rich atmosphere. By cooling the product.

The present invention may be understood with reference to the following description in conjunction with the accompanying drawings, wherein like elements are denoted by like reference numerals:

1 is a schematic partial cross-sectional view of a preferred embodiment of a continuous reactor used in the process of the present invention.

FIG. 2 is a cross-sectional view of the reactor shell shown in FIG. 1.

3 is a cross-sectional view of a nonaqueous experimental battery.

4- [Sample B] shows Li _{1 + x} prepared from LiOH and EMD heated in a rotary kiln at 725 ° C. in air (2 h) and then slowly cooled (2-1 / 2 h) in a laboratory rotary kiln under oxygen. The X-ray diffraction pattern of Mn _2-x O ₄ spinel is shown.

Figure 5 [Sample C] shows Li _{1 + x} Mn _2- prepared from LiOH and EMD heated in a rotary kiln at 725 ° C. in air (2 h) and then slowly cooled (1-1 / 2 h) in a kiln under air. _x O ₄ is shown the X-ray diffraction pattern of the spinel.

6- [Sample D] is Li _{1 + x} Mn _2-x O ₄ spinel prepared from Li ₂ CO ₃ and EMD heated in a rotary kiln at 725 ° C. under N ₂ (1-1 / 2 h) and then air cooled The X-ray diffraction pattern of is shown.

7- [Sample E] is a control Li _{1 + x} Mn _2-x O ₄ spinel prepared from Li ₂ CO ₃ and EMD which were heated (2 hours) in a static bed at 725 ° C. under air and then air cooled The X-ray diffraction pattern of is shown.

FIG. 8- [Sample I] shows the X-ray diffraction pattern of a control Li _{1 + x} Mn _2-x O ₄ spinel prepared from LiOH and EMD which were heated in air at 725 ° C. stationary phase (2 hours) and then air cooled do.

9- [Sample K] is a control Li _{1 + x} Mn _2-x O ₄ spinel prepared from Li ₂ CO ₃ and EMD heated in a stationary phase at 725 ° C. under air (24 hours) and then slowly cooled (36 hours) The X-ray diffraction pattern of is shown.

10- [Sample C] shows the cycling curves (voltage vs. time) for spinel over two cycles.

FIG. 11- [Sample K] is a typical plot of discharge capacity versus cycle count to show how to obtain the damping rate after 50 cycles (least square method).

Description of Preferred Embodiments

The present invention comprises the steps of homogeneously mixing stoichiometrically lithium hydroxide or degradable Li salt and manganese oxide or degradable Mn salt based on the formula of lithium manganese oxide; Supplying a homogeneously mixed compound to the reactor; Continuously stirring the mixed salts in the reactor; Fluidizing air, oxygen or oxygen rich gas through the reactor; Heating the stirred mixed compound in the reactor at a temperature of about 650 to about 800 ° C. for a time not exceeding about 4 hours; And cooling the reacted product under controlled conditions of less than about 100 ° C., preferably for a time not exceeding 2 hours, to form Li _{1 + x} Mn _2-x O ₄ , wherein 0 ≦ _x ≦ 0.125. Provided is a continuous process for preparing single phase lithium added manganese oxide interlayer compounds. The present invention also relates to a method for synthesizing a nearly single phase lithium manganese oxide having a cubic spinel type crystal structure according to the formula Li _{1 + x} Mn _2-x O ₄ (where 0 ≦ _x ≦ 0.125). In particular, the present invention relates to a method of synthesizing such oxides to produce oxides suitable for use as cathodes in electrochemical cells having an anode comprising Li or a suitable Li-containing alloy. . In addition, the present invention is an oxide produced by this method; And an electrochemical cell comprising the oxide as a cathode.

According to the present invention, a method for synthesizing a lithium manganese oxide having a spinel crystal structure is a finely divided solid form of at least one lithium hydroxide or lithium salt as defined herein and at least one manganese oxide or manganese salt as defined herein. Forming a mixture of the furnace and heating the mixture such that the compound decomposes and reacts with each other at a temperature ranging from about 650 ° C. to about 800 ° C. to form a spinel crystal structure and a cubic densely packed oxygen lattice configuration. Obtaining an oxide.

Lithium salt as defined in the present specification means a lithium compound that decomposes when heated in air to form an oxide of lithium, and as described above, manganese salt is decomposed when heated in air to decompose an oxide of manganese. It means a manganese compound to form.

The lithium compound may be a member selected from the group consisting of LiOH, Li ₂ CO ₃ , LiNO ₃ , and mixtures thereof, the manganese compound being MnO ₂ (prepared by electrolysis or chemically), Mn ₂ O ₃ , MnCO ₃ , Mn ₃ O ₄ , MnO, manganese acetate, and mixtures thereof. The formation of the mixture is stoichiometric, such that the molar ratio of Li: Mn is at least 1: 2, more preferably slightly excess lithium, i.e. 1: 2.0-1: 1.67, more preferably 1: 1.94-1: 1. 1.82. The mixture may be formed by mixing with a rotary drum mixer, vibratory grinder, jet grinder, ball grinder or the like as long as the salts are sufficiently homogeneously mixed.

The homogeneously mixed compound is transferred to the hopper and transferred to the reactor by a screw feeder air conveyor, pulsed air injection, or the like.

The reactor is preferably a horizontal rotary calciner, which is equipped with a rotating screw, a fluidized bed, a heated vacuum conveyor belt, or a cascaded vertical rotary furnace. The reactor type is selected depending on other process parameters and the salt used.

Referring to FIG. 1, in one aspect of the invention, the starting material 1 is poured into a feed hopper 2. This material falls by gravity into the screw conveyor 3 used to regulate the feed rate of starting material to the reactor. The screw conveyor 3 discharges the starting material into the rotary shell reactor 5. The shell 5 can be rotated by conventional rotation drive means. The solid travels the length of the rotating shell 5 and first passes through independently heated zones 6a, 6b, 6c surrounded by an outer shell. The solid is discharged into the product drum 10 through the valve 9 in the rotating shell 5. The reactor is hermetically sealed in the space between the feed screw conveyor 3 and the discharge valve 9, and as shown in the figure, the pressure of the shell 5 is exhausted through the pipe 8 to the bag filter 1. As a result, even if the pressure is substantially equal to atmospheric pressure, it may be somewhat under constant pressure by the atmosphere in contact with the product before the atmosphere is released from the pipe 8. The selectable purge inlet pipe 7 allows the countercurrent of air or oxygen rich gas to flow continuously over the reactants. The purge gas is exhausted from the reactor along with the waste gas through pipe 8. The drive means of the screw conveyor and the rotating shell are known in the art and are not shown.

With reference to FIG. 2, the rotating shell 220 may have four equally spaced lift vanes 210 attached to the interior of the shell. These lift vanes can be welded to the interior of the rotary shell 220 or attached in a suitable manner. Each wing is spaced at equal intervals from an adjacent wing, each extending axially over the entire length of the rotating shell 220. The size and number of these wings can vary considerably as long as they function to continuously mix the solids and provide sufficient contact with the atmosphere in the shell. The wings also assist in moving the solid through the shell 220. In order to further assist the movement of the solid through the shell 220 downstream, the shell is directed to the flow direction at a maximum of 1/4 inch per foot of the reactor length, preferably 1/16 inch per foot, inclination. It is good to lower. The size of the reactor can vary depending on the desired capacity.

The laboratory unit used for illustration consists of a horizontal rotary tube kiln with a 2 "diameter and a 3 'heating zone. The flow rate of the gas is set at 50 to 500 cc / min and the rotation speed is set at 30 RPM.

A similar pilot unit consists of a 6 "diameter reactor with a heating zone of 8 '. The gas flow rate is set to 20-40 SCFH. The rotational speed is 3-10 RPM.

It is important to continue stirring the reaction during the process. This fluidization action can quickly transfer heat and continuously update gas / surface boundary exposures. The combination of these conditions significantly increases the reaction kinetics of the process compared to stationary phase processes.

Heating of the mixture is advantageously heating to a temperature of about 650 ° C. to 800 ° C. under an atmosphere that is continuously purged with a countercurrent of air, oxygen, or an oxygen-rich atmosphere; The mixture is maintained at a maximum temperature, preferably at a temperature of about ± 10 ° C. for less than about 4 hours, preferably less than about 2 hours. This heating step may then be followed by a quenching step in which it is quenched in air or cooled at a natural kiln cooling rate.

The heating step of the present invention is carried out at about 650 ° C to about 800 ° C for a time not exceeding about 4 hours. The temperature of the heating step is preferably about 700 to about 750 ° C. for about 1 and a half to 2 hours.

After the heating step, the reaction product is preferably cooled to less than about 200 ° C. within about 2 hours. Preferably the product is cooled below about 100 ° C. and the cooling step is carried out for less than about an hour and a half. If the cooling step is carried out for a time of 1.5 or less, it is advantageous for the product to absorb oxygen and anneal, thus causing lattice deformation. If the cooling step is carried out for a time of about 1.5 or less, the cooling is advantageously carried out in two or more zones having a gradually cooled temperature. Such cooling is preferably carried out in at least three separate zones, each of which is preferably at least about 90 ° C. cooler than the previous zone. Most preferably, the temperatures in the three cooling zones are about 725 ° C, 625 ° C, and 525 ° C.

The Li _{1 + x} Mn _2-x O ₄ product is characterized by a variety of methods, such as standard chemistry and spectroscopic methods, which provide the Li / Mn ratio and the oxidation number of manganese. This method was applied to the sample to identify the chemical formula used to describe this material.

One of the most useful analytical methods for characterizing these materials is X-ray diffraction (XRD), a technique that uses powder. XRD provides two types of useful data: (1) product purity and (2) lattice parameters. Since all materials have a unique and distinct XRD morphology, the XRD morphology is compared to the standard pattern to determine whether the product is a single phase or not. The researchers found some correlations between XRD patterns and cell performance. For example, spinel has a clear XRD form of LiMn ₂ O ₄ without significant effective peaks derived from Li ₂ MnO ₃ , Mn ₂ O ₃ , and Mn ₃ O ₄ . These materials may leach out of the cathode without being cycled, causing further degradation of the effective material in the cathode.

4, 5, 8 and 9 are clear LiMn ₂ O ₄ XRD patterns for Samples B, C, I and K, respectively. LiMn ₂ O ₄ XRD peaks were identified at known 2θ positions and labeled with integers from 501 to 508. Of course these 2θ values can be converted to well known crystal “d” values by standard methods after recognizing that the X-rays are CuKα radiation. The XRD pattern appears almost the same for the materials, but these four materials may differ depending on the method synthesized, and the methods are described in Tables Ia and Ib.

6 and 7 show XRD patterns for spinel contaminated with by-products. Peaks for the main product Li _{1 + x} Mn _2-x O ₄ are represented by the same integers as the corresponding peaks of pure Li _{i + x} Mn _2-x O ₄ in FIGS. 4, 5, 8 and 9. Peaks represented by integers of 700 belong to Li ₂ MnO ₃ and peaks represented by integers of 600 belong to Mn ₂ O ₃ or Mn ₃ O ₄ (these two compounds are difficult to distinguish from a few small peaks).

The second type of XRD information, ie the lattice parameters, cannot be obtained by inspection of the scan as shown in the figure. Rather, the special technique of "lattice parameter refinement", which is well known to experts in crystallography and XRD technology, allows the precise location of all peaks to be investigated very precisely. The dimensions of the optimal cubic spinel unit grid can be calculated. This is the grid parameter a _o .

Several researchers have shown that the lattice parameter itself can be a diagnostic tool because the lattice parameter is frequently directly related to the capacity decay rate, which indicates a decrease in discharge capacity with a cycle number. The lattice parameters depend on the formula weight of the cubic Li—Mn spinel (ie, depending on the _{x in} Li _{1 + x} Mn ₂ O ₄ ) and the degree of oxidation of the spinel. The lattice parameter of Li _1.00 Mn _2.00 O ₄ is a ₀ = 8.2476 ((Standard X-ray Diffraction Powder Patterns, Chapter 21—Data for 92 Substances MCMoris, HFMcMurdie, EHEvans, B.Paretzkin HSParker, W.Wong-Ng, DMGladhill and CRHubbard, National Bureau of Standards, US, Monograph 25, 21 78 (1984)). The a ₀ value decreases upon Li removal (oxidation) and represents a value of 8.03 kPa for the cubic Mn ₂ O ₄ (λ-MnO ₂ ) phase. When lithium is added to LiMn ₂ O ₄ (x> 0 in Li _{1 + x} Mn _2-x O ₄ ), manganese is further oxidized and a ₀ is reduced to about 8.2 kPa [JMTarascon, WRMcKinnon, F. Coowar, TNBowmer , G.Amaticci and D.Guyomard, J.Electrochem. Soc. 141 (1994) 1421-1431, which also reduces the rate of decay of the spinel. Additional lithium and manganese oxidation reduces the discharge capacity so that the theoretical 4V maximum discharge capacity is measured as Li _{1 + x} Mn _2-x O ₄ (1-3x) lithium per molecular unit as measured by the theoretical maximum Mn oxide of 4.00 Ion / electron.

Samples of lithium manganese oxide prepared in accordance with the disclosed technique may comprise the steps of homogeneously mixing a small amount of graphite (10 to 40% by weight) and the binder (to 5% by weight) to form a cathode mixture; Pressing the cathode mixture onto a conductive backing; The cathode-mixture / backing assembly (so-called positive electrode) is heated and dried under anhydrous gas stream to form a positive secondary battery electrode. These electrodes were then tested in a conventional manner in flat electrochemical test cells. One type of such battery is the removable battery shown in FIG. The cell is assembled under anhydrous argon atmosphere using a Li _{1 + x} Mn _2-x O ₄ -containing anode 301 with a conductive backing 302, wherein the conductive backing 302 is made of porous glass fibers and / or Or polypropylene and / or polyethylene separators 305 and 306, separated from the lithium foil negative electrode 303 with stainless steel conductive backing 304, wherein the separators 305 and 306 are ethylene. Saturated with an electrolyte containing a mixture of 1 mole of lithium hexafluorophosphate (LiPF ₆ ) in a 50/50 wt / wt solution of carbonate (EC) and dimethyl carbonate (DMC). These active cell components are pressurized, for example, in a state of being cut off from the atmosphere. In the removable battery of FIG. 3, the two bottom bottom flat cylindrical cells 307 and 308 constituting the battery body were implemented. The two pieces of polypropylene in which the active cell sandwich is located are processed with a bolt (not shown in FIG. 3) to squeeze the cell components together. A polypropylene-polyethylene “0” ring 309 around the cell between two cylindrical halves 307 and 308 is used to seal leakage of electrolyte from the cell or the inflow of air into the cell when the cell components are processed together. Not only does it work, but it also removes excess pressure from the bolt. The two half cells consist of a metal bolt sealed to the central portions 310 and 311, which causes the bolt to flow current into and out of the active cell component. The 0-ring is also used to tightly seal around the current collecting bolts 312 and 313. The bolt is secured to the "0" ring by nut 314 and washer 315.

The test cell was then evaluated to determine the aspect of the cell voltage during the charge-discharge cycle as a function of the change in lithium content per formula unit during the reversible modification of Li _{1 + x} Mn _2-x O ₄ . When charging is initiated (ie, battery voltage about 3.1 to 3.5 volts), manganese begins to oxidize and lithium ions migrate through the electrolyte from Li _{1 + x} Mn _2-x O ₄ to the lithium foil. This process proceeds until a voltage of 4.3 V, which is the potential for most lithium atoms to move to the lithium anode. The cell is then discharged to 3.0 V and recharged several times at a rate of 0.5 mA / cathode region 1 cm 2. This two stage charge and discharge cycle is shown in FIG. 10.

The cells each passed about 120 mAh of charge per 1 g of active cathode material, ie Li _{1 + x} Mn _2-x O ₄ . This amount of charge decreases with the number of cycles, which is common in any cell system. This charge reduction, called cycle attenuation, together with the initial discharge capacity, is one of the most important cell performance characteristics of the cathode material. Record the maximum discharge capacity of the battery. This is usually the discharge capacity in the first cycle, but in some cells, the capacity was maximum in the second or third cycle. The attenuation rate for the cell is calculated as the linear slope of the least squares method by the graph of discharge capacity versus cycle number after 30 and 50 cycles (see FIG. 11). The slope, which is mAh per 1 g of Li _{1 + x} Mn _2-x O ₄ , is divided by the initial discharge capacity and multiplied by 100 to convert it to attenuation rate of% capacity loss per cycle.

Spinel was synthesized by the proposed process in a pilot-scale rotary kiln (reactor). Spinels were also synthesized by various other published or patented processes to compare with those produced by the proposed process. These methods include (a) standard laboratory procedures, i.e., cooling under ambient atmosphere after a heating reaction in a muffle furnace, (b) slowly cooling standard laboratory procedures (using a computerized controller in the kiln), and (c) Specially annealed at 850 ° C. after air cooling and then very slowly cooling (10 ° C./h) to 500 ° C. or room temperature. The synthesis was also carried out in a pilot reactor with various modifications to evaluate various process parameters.

During the “very gentle cooling / annealing” step in air or oxygen rich atmospheres, spinels are known to absorb oxygen into the crystal lattice. This phenomenon can be observed by examining the weight gain using thermal gravimetric analysis (TGA).

Using a gentle cooling process in accordance with the present invention, the spinel material can be continuously stirred to significantly increase the cooling rate. This greatly increases the exposure of the solid / gas interface. In addition, continuous purging of air or oxygen allows for rapid absorption into the lattice using oxygen continuously at the surface interface.

As exemplified in the Examples below, the capacity and cycle attenuation rates for spinels made with the processes presented herein are determined by the optimal laboratory process described above, which includes many hours or even days of heating and cooling. It's almost the same as for spinel made. On the other hand, when compared to the time taken using the proposed method, when the laboratory process is carried out for only a few hours, the capacity is much lower and in some cases the attenuation rate is high.

Several samples were examined to provide confidence in the correlation. Batteries that were cycled through duplicate tests were used so that each test could not be predicted. Therefore, the difference between the capacity and the attenuation rate was statistically investigated. A description of how the material is made is given in Tables Ia and Ib and all mean values and standard deviations (σ) are given in Table II.

Most important features of the claimed process are explained by pairwise camparision (as opposed to linear multiple regression of all data). In the case of a comparative comparison, it is desirable to keep all parameters except the one under investigation constant. For example, it is desirable to compare the same materials when comparing different heating / cooling treatments. In addition, when comparing different materials for a given compositional difference (eg, lithium to manganese ratio), the materials are preferably made from the same precursor EMDs and lithium compounds. This is done to the extent possible. All sample spinels are synthesized from alkaline cell grade EMD from Kerr-McGee Chemical, which has repeatability specifications. If possible, a material synthesized from the same lithium compound, i.e., lithium hydroxide or lithium carbonate, is compared.

Example 1

Embodiments of the invention are equally or better than any other material tested. The process used in the embodiment of the present invention includes a reaction step in a rotary kiln under air for about 2 hours and a cooling step in a rotary kiln under air for about 2 hours, with excess lithium, i.e. Li / Mn ₂ = 1.05 (Li / Mn ₂ = 1.00 or more). Examples of the invention are Samples B and C. For sample B, the sample is cooled under an atmosphere of oxygen in a small laboratory rotary kiln (after reheating the sample to 725 ° C. first), but for sample C, the sample is band cooled in a pilot kiln under air. These two samples were processed in the same process. Table II shows that Samples B and C exhibit appropriate discharge capacities and minimum attenuation (or equivalent) in the table. In addition, their XRD pattern (FIGS. 4 and 5) are clear and the lattice parameter belongs to the lowest lattice parameter.

In particular, the embodiment of the present invention is superior to the material produced by the laboratory long path (still kiln), which has a reaction time of 20 hours and (a) a cooling time of 12 hours ( 60 ° C./h) [called “laboratory-slow-cooling”] or (b) annealing the sample above 800 ° C. and then cooling it very slowly, ie 10 ° C./h [“annealing / very Gentle cooling ". The comparison shown in Table II is described in detail below.

a. Compared to B and C (invention), H ("same" pilot material but after annealing [annealed / very gentle cooling]), the material of the invention is not better than [annealed / very gentle cooling] treated material. Even the same degree of excellence.

b. Sample I was a sample prepared experimentally using the same composition and precursor as that of the present invention, except that Sample I was subjected to annealing / very gentle cooling. Material I is on average worse than B and C. The 50-cycle attenuation rate and capacity of I are statistically identical to that of B and C because the standard deviation of the "I" value is very large. Sample I formed a clear XRD pattern (FIG. 8).

c. Sample K had the same precursor and composition as those of B and C, but K was reacted for 20 hours in a laboratory stationary kiln and then treated as "lab-cooled" rather than [annealed / very gentle cooling]. Sample K is one of the best materials, but not better than B and C in capacity and attenuation rate. The XRD pattern for K is clear (FIG. 9).

d. Sample L 'is a pilot material made of Li ₂ CO ₃ and subjected to [annealing / very gentle cooling] treatment (similar [annealing / very gentle cooling] treatment sample, H was made of LiOH). There is no embodiment of the invention made from Li ₂ CO ₃ . However, sample O, except that it was laboratory-cold treated. It is a sample prepared for the laboratory like sample L '. Sample O is as good as Sample L ', indicating that the [annealing / very gentle cooling] treatment has not improved compared to the laboratory-cold treatment after reaction at 725 ° C.

e. Sample G was a pilot material synthesized the same as L ', but was reheated and lab-cold treated. Sample G has a lower damping rate than L ', suggesting that, as in (d), the [annealing / very gentle cooling] treatment may be worse than the laboratory-cold treatment after treatment at 725 ° C.

g. Samples I vs. I 'and J vs. J' show that [annealing / very gentle cooling] treatment of the material produced at 725 ° C. improves performance.

Example 2

The present invention provides that (1) the reaction time in a rotary kiln using air flow is only about 2 hours, but the reaction for 2 hours in a stationary kiln provides a completely inappropriate product, and (2) a rotary kiln using air. It is shown in Table II that a reaction time of about 20 hours is required in a stationary laboratory kiln to yield the same effect as the reaction for about 2 hours at. In this example, air-cooling was used, because lab-wand cooling actually confounded the test by extending the reaction time by 2 hours or more.

a. Sample M was synthesized in a stationary kiln for only 2 hours and then air cooled. This process contaminated the material with harmful by-products, as the XRD scan shows. The initial capacity was only 76.8 mAh / g and two of the four cells combined did not cycle even 10 times. This problem is due to the high concentration of impurities. Such materials are completely inappropriate as battery cathodes. Sample N, a comparative starting material prepared from LiOH with Li / Mn ₂ = 1.00, was reacted for 20 hours in a stationary kiln. This material showed good XRD patterns and initial capacity, but the attenuation rate is moderate compared to the standard value of good materials. There was no material with Li / Mn ₂ = 1.00 made in a rotary kiln.

b. Samples A and F are two materials starting from the same premix, reacted in a rotary kiln under air flow and then air cooled. Sample I 'having the same precursor and composition as A and F was prepared in a stationary / laboratory kiln with a reaction time of 20 h. The rotary samples A and F were similar in terms of discharge capacity and attenuation rate with the material I 'reacted for 20 hours in a laboratory kiln. From this Example and 2.a, it was confirmed that the reaction of 2 hours in the rotary kiln was almost the same effect as the reaction of 20 hours in the stationary kiln, thus being substantially more effective than the reaction of 2 hours in the stationary kiln. .

c. Three samples of the same precursor (Li ₂ CO ₃ ) and the same composition, E (prepared by air cooling after 2 hours in a stationary laboratory kiln), L (prepared by air cooling after 2 hours in a pilot rotary kiln) And J '(prepared by reacting for 20 hours in a stationary laboratory kiln and air cooled). The E process resulted in contaminated material (see XRD pattern in FIG. 7) and showed somewhat lower discharge capacity (112 mAh / g). J 'exhibited a somewhat lower capacity although the XRD pattern was clear. The pilot sample L showed the best capacity among the three samples and the pattern was clear. In all cases the attenuation was medium to poor, but surprisingly the 2 hour laboratory sample had the best attenuation.

Example 3

Gases containing oxygen in the rotor are essential in the process of the invention. This is shown in Table II using sample D made by passing nitrogen streams through the reaction and cooling process. The capacity was lower than acceptable (101 mAh / g). This corresponds to a contaminated XRD scan (FIG. 6). The attenuation rate was also moderate to poor. Comparative sample L under air in a rotary kiln showed acceptable capacity and clear XRD scan, proving superior to D. The decay rate of L is comparable to D, but the decay rate of L proceeds from higher capacity. The results for Examples B and C of the present invention show that the oxygen or air atmosphere provides satisfactory results.

Example 4

The process (2h) of the present invention to slow / band cool in a rotary kiln is advantageous. This is demonstrated by comparing Samples B and C, cooled as above, with Sample A, which is the same premix and reaction product, except that air cooled, as shown in Table II. Samples B and C show significantly better capacity and particularly attenuation rate than sample A.

Example 5

Table II shows that the Li / Mn ₂ ratio in the process of the present invention is preferably greater than 1.00. There was no sample with Li / Mn ₂ = 1.00 cooled in a rotary kiln; That is, there was no direct comparison with Samples B and C. The reason for this was that it was previously confirmed that the use of laboratory synthesized materials resulted in limited benefits from excess lithium. Therefore, it was not necessary to produce worse materials in the pilot plant. In (1. c) above, the synthesis method of the "invention" was found to be as good as the laboratory synthesis method with the 20 hour reaction and the laboratory-cold cooling (ie 60 ° C / h or 12 hour cooling). Therefore, the best laboratory material is Li / Mn ₂ = with the exception that the 1.00 cases were identified as better than the same materials, Li / Mn _2> 1.00 pilot (the process of the present invention), the material is Li / Mn ₂ = 1.00 It can be estimated that it is superior to the material of the process of this invention.

The same sample K as the process materials B and C of the present invention is compared to the same K 'except that Li / Mn ₂ = 1.00. Sample K 'shows a larger capacity than K, which is theoretically expected. However, the capacity of K is large enough to be moderate. At the necessary decay rate, sample K is much better than sample K '. Inferred, the material of the process of the present invention should be better than the material produced in a rotary kiln with Li / Mn ₂ = 1.00.

Claims (61)

(a) homogeneously mixing a predetermined amount of lithium hydroxide or lithium salt with manganese oxide or manganese salt based on the lithium-manganese oxide compound added; (b) feeding the homogeneously mixed compound to the reactor; (c) continuously stirring the mixed compounds in the reactor; (d) Li _{1 + x} Mn _2-x O ₄ spinel by heating the stirred mixed compound at a temperature of from about 650 ° C. to about 80 ° C. in a reactor under air or oxygen rich atmosphere for a time not exceeding about 4 hours. Forming a structural intercalation compound; And (e) cooling the reacted product to a temperature below about 200 ° C. for less than about 2 hours, wherein the formula Li _{1 + x} Mn _2-x O ₄ with a spinel-like structure, wherein x is from 0.0328 to about 0.125 and the a-axis lattice parameter is about 8.235 GPa or less]. The method of claim 1, further comprising cooling the reacted product to a temperature below about 100 ° C. 5. The method of claim 1, further comprising the step of separating the cooled product from the reactor after the cooling step. A process for the continuous production of a single phase lithium-manganese oxide interlayer compound according to claim 1, wherein step (a) is carried out with a rotary drum mixer. A process for the continuous preparation of a single phase lithium added manganese oxide interlayer compound according to claim 1, wherein step (a) is carried out with a ball mill. A process for the continuous production of a single phase lithium-added manganese oxide interlayer compound according to claim 1, wherein step (a) is performed with a vibratory mill. A process for the continuous production of a single phase lithium-added manganese oxide interlayer compound according to claim 1, wherein step (a) is carried out with a jet mill. A process for the continuous preparation of a single phase lithium added manganese oxide interlayer compound according to claim 1, wherein the feeding step (b) is performed with a threaded feeder. A process for the continuous production of a single phase lithium added manganese oxide interlayer compound according to claim 1, wherein the feeding step (b) is performed with a pneumatic conveyor. A process for the continuous preparation of a single phase lithium added manganese oxide interlayer compound according to claim 1, wherein the feeding step (b) is performed by pulsed air injection. The method of claim 1, wherein the atmosphere in step (c) is continuously purged with an air stream of air, oxygen, or oxygen enriched air. The method of claim 1, wherein the atmosphere in step (c) is continuously purged with a countercurrent to an oxygen enriched atmosphere. The method of claim 1 wherein the reactor is a horizontal rotary tube whose outlet end is slightly lower than the inlet end. The method of claim 1 wherein the reactor is a horizontal calciner equipped with a rotating screw. The process for the continuous production of a single phase lithium-manganese oxide interlayer compound of claim 1, wherein the reactor is a fluidized bed. The method of claim 1, wherein the reactor is a heated vibratory conveyor belt. The process for the continuous production of a single phase lithium-added manganese oxide interlayer compound according to claim 1, wherein the reactor is a cascaded vertical rotary furnace. The method of claim 1, wherein the heating step is performed for about 2 hours or less. The method of claim 1, wherein the heating step is performed for about 1 hour 30 minutes or less. 20. The method of claim 19, wherein the temperature of the heating step is from about 700 ° C to about 800 ° C. The method of claim 1, comprising continuously purging with air, oxygen, or an oxygen-enriched atmosphere in step (d). 22. The method of claim 21, wherein the continuous purging step uses countercurrent of air. The method of claim 1, wherein the cooling step is performed in a horizontal calciner equipped with a rotating screw. The process of claim 1 wherein the cooling step is carried out in a fluidized bed. The process for the continuous production of a single phase lithium-added manganese oxide interlayer compound according to claim 1, wherein the cooling step is performed in a rotary kiln. The method of claim 1, wherein the cooling step is carried out in a heated vibratory conveyor belt. The process for the continuous production of a single phase lithium-added manganese oxide interlayer compound according to claim 1, wherein the cooling step is performed in a cascaded vertical rotary furnace. The method of claim 1, wherein the cooling step is performed for about 1 hour 30 minutes or less. The process of claim 1, wherein the cooling step is performed for less than about 1 hour 30 minutes. A process for the continuous preparation of a single phase lithium-doped manganese oxide interlayer compound according to claim 1, wherein the cooling step is carried out in a zone of temperature at which it is gradually cooled. 31. The method of claim 30, wherein the cooling step is performed in at least two zones. 32. The method of claim 31 wherein the temperature in each of the progressively cooled zones is at least about 90 [deg.] C. below the temperature in the zone immediately preceding. 33. The method of claim 32, wherein the temperatures in the progressively cooled zone are about 725 ° C, 625 ° C, and 525 ° C. 33. The method of claim 32, wherein the temperatures in the zone to be gradually cooled are about 800 ° C, 650 ° C, and 500 ° C. 33. The method of claim 32, wherein the temperatures in the gradually cooled zone are about 750 ° C, 600 ° C, and 450 ° C. 33. A single phase lithium added manganese oxide according to claim 32, characterized in that a spinel-structured lithium added interlayer compound of formula Li _{1 + x} Mn _2-x O ₄ is prepared, wherein the cooled product is annealed by absorbing oxygen. Process for the continuous preparation of interlayer compounds. 37. The method of claim 36, wherein the cooled product is annealed by absorbing the maximum amount of oxygen. The method of claim 1, wherein in the cooling step the atmosphere is continuously purged with a stream of air, oxygen, or oxygen enriched atmosphere. 39. The method of claim 38 wherein in the cooling step the atmosphere is continuously purged with countercurrent of air. The single-phase lithium addition of claim 1, wherein the manganese oxide or manganese salt is selected from the group consisting of MnO ₂ , MnCo ₃ , Mn ₂ O ₃ , Mn ₃ O ₄ , MnO, manganese acetate, and mixtures thereof. Process for the continuous preparation of manganese oxide interlayer compounds. A process for the continuous preparation of a single phase lithium added manganese oxide interlayer compound according to claim 1, wherein the manganese oxide is heat treated before performing step (a). _2. The continuous preparation of a single phase lithium added manganese oxide interlayer compound according to claim 1, wherein the lithium hydroxide or lithium salt is selected from the group consisting of LiOH, Li ₂ CO ₃ , LiNO ₃ and mixtures thereof and hydrates thereof. Way. 42. A process for the continuous production of a single phase lithium-added manganese oxide interlayer compound according to claim 41, wherein MnO ₂ is produced by an electrolytic method and neutralized with LiOH or NH ₄ OH during the synthesis. At least one lithium hydroxide or lithium salt reactant selected from the group consisting of LiOH, Li ₂ CO ₃ , LiNO ₃ and mixtures thereof with MnO ₂ , Mn ₂ O ₃ , MnCO ₃ , Mn ₃ O ₄ , MNO, acetane and these Forming a homogeneous mixture of at least one manganese oxide or manganese salt selected from the group consisting of mixtures in the form of fine solids, and at a temperature ranging from about 650 ° C. to about 800 ° C. in the reactor under continuous purge of countercurrent air. Formula Li ₁₊ having a spinel crystal structure with a a-axis lattice parameter of about 8.235 Pa or less, including the step of continuously stirring and heating the mixture for a time not exceeding time to react the reactants to form lithium manganese oxide _x Mn _2-x O _4, wherein x is from about 0.0328 to about 0.125. The method of claim 44, wherein the heating step of the mixture is performed under air at a temperature of about 700 ° C. to about 800 ° C., and the mixture is maintained at maximum temperature for less than about 2 hours. 45. The method of claim 44, wherein the manganese oxide is heat treated prior to forming the mixture. A lithium manganese oxide having a spinel crystal structure synthesized by the method according to claim 44. 45. The method of claim 44, wherein Li _{1 + x} Mn _2-x O ₄ has a (Mn ₂ ) O ₄ (Mn ₂ ) O ₄ ^n-1 framework structure that varies with the stoichiometry of the amount of Mn cation. Synthesis method of lithium manganese oxide. The method of claim 1, wherein before the cooling step (i) separating the product from the reactor; (ii) a process for the continuous preparation of a single phase lithium added manganese oxide interlayer compound, characterized by the additional step of transferring the reacted product to a separate vessel. (a) homogeneously mixing a stoichiometric amount of lithium hydroxide or lithium salt with manganese oxide or manganese salt based on the lithium added manganese oxide compound; (b) feeding the homogeneously mixed compound to the reactor; (c) stirring the mixed compounds in a reactor; (d) heating the stirred mixed compound at a temperature of about 650 ° C. to about 80 ° C. in a reactor in the presence of air or an oxygen enriched atmosphere for a time not exceeding 4 hours; (e) forming an oxygen deficient spinel structure interlayer compound; And (f) cooling the oxygen depleted product to less than about 100 ° C. for less than about 2 hours to form Li _{1 + x} Mn _2-x O ₄ with about 0.0328 to about 0.125 and an a-axis lattice parameter of about 8.235 Pa or less. A method for producing a single-phase lithium-added manganese oxide interlayer compound of formula Li _{1 + x} Mn _2-x O ₄ having a spinel structure, comprising a batch process. 51. The method of claim 50, wherein the cooling vessel is a horizontal calciner with a rotating screw. 51. The method of claim 50, wherein the cooling vessel is a fluidized bed. 51. The process of claim 50, wherein the cooling vessel is a heated vibratory conveyor belt. 51. The method of claim 50, wherein the cooling vessel is a cascaded vertical rotary furnace. 51. The method of claim 50, wherein the cooling vessel is a rotary kiln. 51. The method of claim 50, wherein the cooling step is performed for about 1 hour and 30 minutes or less. 51. The method of claim 50, wherein said cooling step is performed for less than about 1 hour. A process for the continuous preparation of a single phase lithium added manganese oxide interlayer compound according to claim 1, wherein the heating step (d) is carried out in a zone of temperature which is gradually elevated. 59. The method of claim 58, wherein the heating step is performed in at least four zones. 60. The method of claim 59, wherein the temperature in each of the gradually elevated zones is at least 25 [deg.] C. higher than the temperature in the immediately preceding zone. 59. The method of claim 58, wherein the stirred mixed compound is left in each zone for at least about 30 minutes.

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