Method for preparing electrolytic manganese dioxide

Abstract

General formula Li 1+x Mn 2-x-y-z M y M' z Improved cathode materials are disclosed having the general formula LiO4, where x is generally less than 0.25, y is less than about 0.5, z is from about 0.1 to about 0.7, M is a trivalent transition metal, and M' is a divalent transition metal. 1+x Mn 2-x-y-z M y M' z Also disclosed is an improved secondary battery having a cathode material of MnO4. In one embodiment, the method comprises dissolving manganese metal, typically in powder or chip form, in a mineral acid to produce MnO4. ++ preparing a solution of Mn ions in solution; ++ The final concentration of Mn is about 20 g / L to about 254 g / L. Typically, the solution contains about 47 g / L of Mn ++ Contains Mn ++ The final pH of the solution containing may range from about 2 to about 8. However, a typical operating pH is from about 5.5 to about 7.0.

Description

Summary of the Invention

[0001] General formula Li 1+x Mn 2-x-y-z M y M’ z O4 (where x is 0.25 or less, the value of y is 0.5 or less, z is from about 0.1 to about 0.7, M is one or more trivalent transition metals, and M’ is a divalent transition metal, for example, Ni but not limited thereto) is disclosed herein. The lithium manganese oxide has trace metals less than 175 ppm. Specifically, the LMO has less than 30 ppm of Al, less than 130 ppm of Ca, less than 90 ppm of K, less than 75 ppm of Mg, less than 35 ppm of Fe, and less than 50 ppm of Na. As used herein, the term LMO refers to a cathode material suitable for use in secondary batteries.

[0002] In another embodiment, the present disclosure relates to a secondary battery. The secondary battery includes a cathode material using Li 1+x Mn 2-x-y-z M y M’ z O4. The secondary battery has a maximum capacity of at least 115 mAhr / g of cathode active material, and the secondary battery can perform at least 370 charge-discharge cycles before the rechargeable capacity of the battery drops below 80% of the maximum capacity after the secondary battery reaches the maximum capacity.

Mode for Carrying Out the Invention

[0003] This disclosure can be more readily understood by reference to the following description. The following description is not to be regarded as limiting the scope of the embodiments described herein. Also, the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting, except as so indicated. Further, throughout this disclosure, the terms "about," "approximate," and variations thereof are used to indicate a value that includes inherent variations or errors of the device, system, or method being utilized, as will be recognized by those of ordinary skill in the art.

[0004] The disclosed cathode material can be prepared according to the following method that provides for the conversion of metallic manganese to MnO2. Thereafter, the method provides for the conversion of MnO2 (EMD) to Mn2O3.

[0005] In one embodiment, the method comprises preparing a solution of Mn ions by dissolving metallic manganese, typically in the form of powder or chips, in a mineral acid. Typically, the method utilizes sulfuric acid. However, nitric acid and other mineral acids that can dissolve at least 47 g / l of Mn will function adequately. The final concentration of Mn in the solution is from about 20 g / L to about 254 g / L. Typically, the solution contains about 47 g / L of Mn. The final pH of the solution containing Mn can range from about 2 to about 8. However, a typical operating pH is from about 5.5 to about 7.0.

[0006] The mineral acid solution containing Mn flows through a series of electrolytic cells. A current passes through the electrolytic cells at a current density of from about 2.5 Amp / ft 2 to 6 Amp / ft 2 During the application of the current, MnO2 is plated onto the anodes of the electrolytic cells. The plating process is generally carried out at a temperature of from about 93 °C to about 99 °C as the acid solution flows through the cells. The acid solution exiting the cells is substantially Mn​​​​​​​​​​​​++ The ions are depleted. The depleted acid is used to dissolve additional manganese metal and returned to the cell. Typically, the plating process lasts from about 3 days to about 40 days when carried out at the indicated current density.

[0007] After the electrolytic cell is taken offline, i.e., upon completion of the plating process, MnO2 is collected from the anode, ground or crushed to a size suitable for neutralization, neutralized by treatment with a base, filtered, dried, and subjected to further particle reduction steps.

[0008] The collected MnO2 can be ground or crushed using any conventional method, including but not limited to a plate crusher or plate grinder. The grinding process increases the surface area of ​​the particles, thereby improving the subsequent neutralization step. The resulting MnO2 generally has a particle diameter of 2 mm or less.

[0009] The base solution used in the neutralization step has a pH of approximately 8 to 12 and must not introduce contaminants into the solid MnO2. Typically, the neutralization step uses lithium hydroxide, lithium carbonate, lithium bicarbonate, ammonium hydroxide, or a mixture thereof. Bases such as sodium hydroxide, calcium hydroxide, and potassium hydroxide are undesirable because they are likely to contaminate the resulting MnO2 with undesirable calcium, sodium, and potassium. Ammonium hydroxide is particularly advantageous during the neutralization step because it can be removed during heating of the resulting MnO2 particles. The neutralization step produces very high-purity EMD; that is, trace elements such as Ca, Al, K, Mg, and Na are either at extremely low concentrations or not found in the resulting EMD. Specifically, the cathode material has less than 10 ppm Al, less than 50 ppm Ca, less than 50 ppm K, less than 15 ppm Mg, and less than 50 ppm Na.

[0010] The neutralization process can be carried out at temperatures ranging from room temperature to near the boiling point of the slurry or solution, over a period of approximately 20 to 120 minutes. Generally, the neutralization process is considered complete when the pH of the discharge from the particles or particle slurry exceeds 5.5. In this method, neutralization is a diffusion-limited process. As a result, the neutralization solution must contain an excess of base to promote diffusion. To promote the distribution of the base solution and facilitate the washing of anions from the surface of the product, the preferred pH of the neutralization solution is in the range of approximately 8 to 10. The excess liquid generated during the neutralization process is discarded along with the resulting salt.

[0011] Following neutralization, drying, and recovery, the resulting MnO2 particles undergo size reduction and classification. Typically, the size reduction step utilizes a jet mill. However, other equipment can also produce satisfactory particles. The desired resulting particles generally have a particle size in the range of about 100 nm to about 300 micrometers. A typical batch of MnO2 particles can have a median particle size of about 10 micrometers. However, a batch of MnO2 suitable for conversion to Mn2O3 can have a lower median particle size of 3 micrometers, while other batches can have a larger median particle size of 35 micrometers.

[0012] The final EMD produced by the above method is of very high purity. For example, 47.3 g of Mn per liter. ++ Using a sulfuric acid solution containing [the substance], at a temperature of 96°C and a current density of 5.6 Amp / ft, 2 The EMD produced was compared with conventional EMD. The impurity values ​​of high-purity EMD and conventional EMD are shown in Table 1 below. Note: Because the addition of lithium components reduces the final impurity level in the cathode material, the impurity level in the subsequent cathode material differs from the impurity level of the EMD. [Table 1]

[0013] Following the isolation of the desired MnO2 particles, the method converts the MnO2 particles, i.e., high-purity EMD, into Mn2O3 by heating them in an air atmosphere at a temperature of about 700°C to about 850°C for about 1 to about 24 hours. Generally, the heating is carried out at a temperature between about 725°C and about 775°C for about 2 to about 12 hours. Preferably, the heating is carried out at about 700°C for about 12 hours. The resulting Mn2O3 particles are about 0.5 m 2 / g~about 5m 2 It has a surface area of ​​ / g.

[0014] As shown in the following examples, the resulting Mn2O3 particles are suitable for use in the production of lithium manganese oxide (LiMn2O4) cathode materials. The Mn2O3 particles are combined with doping materials such as Li2CO3, LiOH, Li2O, HLiCO3, and additional metal oxides. Preferred metal oxides, but not limited to, include NiCO3, NiO, nickel acetate, nickel nitrate, nickel hydroxide, and other forms of nickel suitable for inclusion in the cathode material.

[0015] The final composition of the cathode material is generally Li 1+x Mn 2-x-y-z M y M' z O4, where x is less than or equal to 0.25, y is less than or equal to approximately 0.5, z is approximately 0.1 to approximately 0.7, M is one or more trivalent transition metals, and M' is a divalent transition metal, such as Ni, but not limited to Ni. More typically, in the final composition, z is 0.2 to 0.7. Thus, the final composition may contain up to approximately 15 wt% of one or more trivalent transition metals and approximately 3 to approximately 24 wt% of divalent transition metals. A preferred divalent transition metal is currently nickel. Typically, the divalent transition metal is present in the range of approximately 6 to approximately 22.4 wt% of the cathode material.

[0016] Furthermore, the cathode material used contains trace metals in amounts less than 175 ppm. Specifically, the cathode material has less than 30 ppm of Al, less than 130 ppm of Ca, less than 90 ppm of K, less than 75 ppm of Mg, and less than 35 ppm of Fe. More typically, the cathode material has less than 20 ppm of Al, less than 110 ppm of Ca, less than 80 ppm of K, less than 65 ppm of Mg, and less than 25 ppm of Fe. Note: In another embodiment, the improved cathode material does not contain trivalent metals. In this embodiment, the general formula for the improved cathode material is Li 1+x Mn 2-x-z M' z The composition is O4, x is less than or equal to 0.25, and z is approximately 0.1 to 0.7. More typically, in the final composition, z is 0.2 to 0.7.

[0017] In this example, 1648.6 grams of Mn2O3 particles (median particle size of 10 micrometers) prepared according to the method outlined above were mixed with 826.4 grams of NiCO3 to obtain a homogeneous mixture. The resulting mixture was heated in air at 925°C for 24 hours and then cooled to room temperature. After cooling, the product was decomposed and mixed with 514.5 grams of Li2CO3 to obtain a homogeneous mixture. The resulting mixture was heated at 750°C for 10 hours and then cooled to room temperature at 1°C / min. Then, the formula LiMn 1.5 Ni 0.5 The final product containing O4 was ground and screened to remove particles larger than 45 micrometers. 1+x Mn 2-x-y-z M y M' z If the final composition of the cathode material represented by O4 has values ​​of 0 for x and y, one suitable composition is LiMn 1.5 Ni 0.5 O4, x=0, y=0 and z=0.5 are possible. Table 2 shows the formula LiMn used in improved secondary batteries. 1.5 Ni 0.5 This shows the trace metal concentrations in cathode materials with an O4 formulation.

[0018] The cathode prepared from the final product was tested as part of an improved secondary battery having a carbon anode. That is, the improved secondary battery was a full cell, not a half cell. The improved secondary battery was repeatedly cycled at room temperature, i.e., approximately 25°C, with a single complete discharge completed in 3 hours, followed by charging to a level of 4.9V in 3 hours to obtain an average operating discharge value of 4.7V. The improved secondary battery had an average fade rate of 0.054% / cycle and a maximum capacity of at least 115mAhr / g. Formula: LiNi 0.5 Mn 1.5 The theoretical capacity of a secondary battery manufactured using an O4 cathode is 146.2 mAhr / g, as determined by the available lithium in the cathode material. Therefore, the final maximum capacity of the secondary battery is 78.7% of the theoretical value.

[0019] As is known to those skilled in the art, secondary batteries do not necessarily reach their full capacity upon initial charging. Therefore, the lifespan and fade rate of a rechargeable battery, i.e., a secondary battery, are determined based on the battery's maximum capacity. Typically, after achieving maximum capacity, the final charge capacity of the secondary battery decreases with each recharge. A battery is considered to be at the “end of its life” when it can no longer be charged to 80% of its maximum capacity. Rechargeable batteries prepared from the improved materials described provide at least 370 charge-discharge cycles. Note: Li 1+x Mn 2-x-y-z M y M' z The secondary battery used to determine the improvements provided by the cathode composition of O4 used graphite as the anode, but other anode materials can be substituted for graphite.

[0020] To provide a direct comparative example, conventional lithium neutralization alkaline battery grade electrolytic manganese dioxide (EMD) is converted to Mn2O3 and processed according to the steps described in the above example to obtain LiMn 1.5 Ni0.5 A cathode material having the composition of O4 was prepared. This conventional cathode material contains nickel, but differs from the nickel-containing cathode material described above in that the main impurities (Al, Ca, Fe, K, Mg) are present at considerably higher concentrations than those typically found in currently available cathode materials (see Table 2 below) compared to the improved composition of LiMn5Ni5O4 used in improved secondary battery cathode materials. Conventional alkaline battery-grade EMD is prepared from manganese sulfate and purified according to conventional methods. A secondary battery with a cathode prepared from conventional lithium manganese oxide material had a fade rate of 0.067% / cycle and a maximum discharge capacity of 110 mAhr / g. Batteries prepared from this material are expected to retain less than 80% of their capacity after approximately 300 charge-discharge cycles. Furthermore, the battery has a maximum discharge capacity of only 75% of its theoretical capacity. [Table 2]

[0021] Therefore, the improved secondary battery using a cathode prepared from the nickel-containing lithium manganese oxide cathode described above has an improved average fade rate compared to batteries prepared from lithium manganese oxide synthesized with conventional alkaline battery grade EMD. The improved cathode material disclosed herein resulted in an average fade rate of only 0.054% per recharge cycle, while the conventional cathode material showed an average fade rate of 0.067% per recharge cycle. The improved cathode material has a useful life of at least 370 charge-discharge cycles. In contrast, the conventional cathode material fell below 80% of its maximum capacity after only 300 charge-discharge cycles. Therefore, Li 1+x Mn 2-x-y-z M y M' z Secondary batteries using a cathode with an O4 composition showed a 23% improvement in charge-discharge cycles and a 23% improvement in fade rate compared to conventional cathode materials containing nickel.

[0022] Furthermore, when incorporated into a secondary battery, the general formula Li 1+x Mn 2-x-y-z M y M' z Cathode materials containing O4 provide a higher voltage than conventional nickel-free cathode materials. 1+x Mn 2-x-y-z M y M' z A secondary battery containing a cathode prepared using the O4 composition has an operating voltage greater than 4.0. For example, LiNi 0.5 Mn 1.5 Batteries containing O4 、 It provides an operating voltage of 4.7 volts. In contrast, a battery containing a cathode with a LiMnO4 composition has an operating voltage of 4 volts.

[0023] A further unexpected property of the improved nickel-containing cathode material is the stability of the cathode. Specifically, the degree of degradation due to the presence of nickel in the improved cathode material is less than expected, thereby enabling the use of nickel in the cathode material, which provides improvements in operating voltage, fade rate, and charge / recharge cycles. As is known to those skilled in the art, the presence of nickel in the cathode material stresses the structure of the cathode material during recharge cycles. This stress generally leads to rapid degradation of the cathode. The resulting degradation significantly reduces the number of charge / discharge cycles before the secondary battery drops to less than 80% of its maximum capacity. Therefore, those skilled in the art know that the general formula -Li 1+x Mn 2-x-y-z M y M' z One would expect the O4- cathode material to perform similarly to the comparative example in terms of fade rate and charge / discharge cycle count. However, when used in secondary batteries, the disclosed composition not only increases the maximum capacity but also increases the number of charge / discharge cycles before the secondary battery reaches the end of its life, as described above. Furthermore, the improved cathode material reduces electrolyte degradation in secondary batteries, as evidenced by the improved fade rate and increased cycle life.

[0024] Additional notes (sections 1 to 20) Item 1 A secondary battery comprising a cathode material containing lithium manganese oxide, The lithium manganese The oxide is Li 1+x Mn 2-x-y-z M y M' z O4( In the equation, x is generally less than 0.25, y is approximately less than 0.5, and z is approximately 0.1 to approximately 0. (where M is a trivalent transition metal and M' is a divalent transition metal), Secondary battery. Section 2 The aforementioned secondary battery has at least 115 mAhr / g of Li 1+x Mn 2-x-y-z M y M' z A secondary battery as described in item 1, having the maximum capacity of O4. Section 3 The secondary battery shall, before its capacity falls below 80% of its maximum capacity, A secondary battery as described in item 1, capable of performing 370 charge-discharge cycles. Section 4 A secondary battery as described in item 1, wherein M' is nickel. Section 5 The secondary battery according to item 1, wherein M is up to 15% by weight of the cathode material. Section 6 The secondary battery described in item 1, wherein M' is approximately 3% to approximately 24% by weight of the cathode material. . Section 7 The cathode material contains less than 30 ppm of Al, less than 130 ppm of Ca, and less than 90 ppm of The secondary electric charge described in item 1, containing less than 75 ppm of K, less than 75 ppm of Mg, and less than 35 ppm of Fe. pond. Section 8 The Mn2O3 particles in the lithium manganese oxide are approximately 0.5 m 2 / g~about 5m 2 A secondary battery as described in item 1, having a surface area of ​​ / g. Section 9 The secondary battery according to item 1, wherein the cathode material does not contain a trivalent metal. Section 10 The cathode material does not contain a trivalent metal, and the cathode material is Li 1+x Mn 2- x-z M' z It is represented as O4, x is less than or equal to 0.25, and z is approximately between 0.1 and 0.7. The secondary battery described in item 1. Section 11 A secondary battery as described in item 1, where z is approximately 0.2 to approximately 0.7. Section 12 A cathode material containing lithium manganese oxide, The lithium manganese The oxide is Li 1+x Mn 2-x-y-z M y M' z O4( In the equation, x is generally less than 0.25, y is approximately less than 0.5, and z is approximately 0.1 to approximately 0. (where M is a trivalent transition metal and M' is a divalent transition metal), represented as Casso Material. Section 13 The cathode material described in item 12, wherein M' is nickel. Section 14 The cathode material according to item 12, wherein M is up to 15% by weight of the cathode material. Section 15 The cathode according to item 12, wherein M' is about 3% to about 24% by weight of the cathode material Materials. Section 16 The cathode material contains less than 30 ppm of Al, less than 130 ppm of Ca, and less than 90 ppm of Cassate as described in item 12, containing less than 75 ppm of K, less than 75 ppm of Mg, and less than 35 ppm of Fe. Material. Item 17 The Mn2O3 particles in the lithium manganese oxide are approximately 0.5 m 2 / g~about 5m 2 A cathode material according to item 12, having a surface area of ​​ / g. Section 18 The cathode material according to item 12, wherein the cathode material does not contain a trivalent metal. Item 19 The cathode material does not contain a trivalent metal, and the cathode material is Li 1+x Mn 2- x-z M' z It is represented as O4, where x is less than or equal to 0.25, and z is approximately 0.1 to approximately 0.7. As described in item 12 Cathode material . Section 20 z is approximately 0.2 to approximately 0.7, as described in item 19. Cathode material . Other embodiments of the present invention will be apparent to those skilled in the art, and therefore the foregoing description is not relevant to the present invention. This merely enables and describes the general use and methods of the invention. Therefore, the following claims This defines the true scope of the present invention.

Claims

1. A secondary battery comprising a cathode material containing lithium manganese oxide, The lithium manganese oxide is Li １＋ｘ Mn ２－ｘ－ｙ－ｚ M ｙ M' ｚ O ４ (In the ceremony x is less than 0.25, y is less than 0.5, z is between 0.1 and 0.7, and M is three It is represented as a valence transition metal, where M' is a divalent transition metal. The cathode material contains less than 30 ppm of Al, less than 130 ppm of Ca, and less than 90 ppm of Contains a full amount of K, less than 75 ppm of Mg, and less than 35 ppm of Fe. Secondary battery.

2. The aforementioned secondary battery contains at least 115 mAhr / g of Li １＋ｘ Mn ２－ｘ－ｙ－ｚ M ｙ M' ｚ O ４ The secondary battery according to claim 1, having a maximum capacity of

3. The secondary battery shall, before the capacity of the battery falls to less than 80% of its maximum capacity, The secondary battery according to claim 1, which can perform 370 charge-discharge cycles.

4. The secondary battery according to claim 1, wherein M' is nickel.

5. The secondary battery according to claim 1, wherein M is up to 15% by weight of the cathode material.

6. The secondary battery according to claim 1, wherein M' is 3% to 24% by weight of the cathode material. 。

7. The secondary battery according to claim 1, wherein the cathode material does not contain a trivalent metal.

8. The cathode material does not contain a trivalent metal, and the cathode material is Li １＋ｘ Mn ２－ ｘ－ｚ M' ｚ O ４ The expression is given by where x is less than or equal to 0.25 and z is between 0.1 and 0.7, claim The secondary battery described in item 1.

9. The secondary battery according to claim 1, wherein z is 0.2 to 0.

7.

10. A cathode material containing lithium manganese oxide, The lithium manganese oxide is Li １＋ｘ Mn ２－ｘ－ｙ－ｚ M ｙ M' ｚ O ４ (In the ceremony x is less than 0.25, y is less than 0.5, z is between 0.1 and 0.7, and M is three It is represented as a valence transition metal, where M' is a divalent transition metal. The cathode material contains less than 30 ppm of Al, less than 130 ppm of Ca, and less than 90 ppm of Contains a full amount of K, less than 75 ppm of Mg, and less than 35 ppm of Fe. Cathode material.

11. The cathode material according to claim 10, wherein M' is nickel.

12. The cathode material according to claim 10, wherein M is up to 15% by weight of the cathode material.

13. The cathode according to claim 10, wherein M' is 3% to 24% by weight of the cathode material Materials.

14. The cathode material according to claim 10, wherein the cathode material does not contain a trivalent metal.

15. The cathode material does not contain a trivalent metal, and the cathode material is Li １＋ｘ Mn ２－ ｘ－ｚ M' ｚ O ４ The claim is expressed as follows, where x is 0.25 or less and z is between 0.1 and 0.

7. The cathode material described in item 10.

16. The cathode material according to claim 15, wherein z is 0.2 to 0.7.

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