Lithium spinel-type manganese oxide, its manufacturing method, and its uses

Abstract

To provide spinel lithium manganate having improved charge-discharge behavior at high temperature, and a lithium ion secondary battery having improved charge-discharge behavior at high temperature.SOLUTION: A spinel lithium manganate is represented by the chemical formula Li1+XMn2-X-YMYO4 (where 0.02≤X≤0, 35, 0.01≤Y≤0.30, M is Al or Mg). After pressed, the spinel lithium manganate has an average particle size holding rate of 50% or more, with the volume of pores of 0.6 μm or less in pore size being 0.005 cm3 / g or more and 0.050 cm3 / g or less. There are also provided a method for producing the same and applications therefor.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to spinel-type lithium manganate, a method for producing the same, and uses thereof. More specifically, the present invention relates to spinel-type lithium manganate having a particle size retention rate of 50% or more after pressing, a method for producing the same, and a lithium ion secondary battery using the same as an electrode.

Background Art

[0002] Lithium ion secondary batteries are widely used as power storage batteries for portable terminals because of their high energy density compared to other storage batteries. Recently, research has been conducted to further improve performance, such as application to large-scale applications that require high capacity and high output, such as stationary and in-vehicle applications.

[0003] In the positive electrode materials of currently used lithium ion secondary batteries, cobalt-based materials (LiCoO2) are mainly used for small household batteries such as mobile phones, and nickel-based materials (LiNi 0.8 Co 0.15 Al 0.05 O2) and nickel-cobalt-manganese ternary materials (LiNi 0.5 Co 0.2 Mn 0.3 O2, etc.) are used for stationary and in-vehicle applications. However, cobalt-based materials and nickel-based materials are not abundant in resources and are expensive, and their output characteristics are not very high.

[0004] On the other hand, spinel-type lithium manganate, which is one of the manganese-based materials, is suitable for large-scale batteries and applications that require high output because manganese, the raw material, is abundant in resources and inexpensive, and it has excellent output characteristics and safety.

[0005] However, spinel-type lithium manganate has problems with high-temperature stability, that is, charge-discharge characteristics at high temperatures, particularly charge-discharge characteristics with a carbon counter electrode and storage characteristics, and solving this problem has been desired. For example, in Patent Document 1 and Patent Document 2, spinel-type lithium manganate containing phosphate has been proposed in both cases, but there is still room for improvement in the charge-discharge characteristics at high temperatures.

Prior Art Documents

Non-Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to provide a spinel-type lithium manganate that is excellent in charge-discharge characteristics at high temperatures, particularly charge-discharge characteristics with a carbon counter electrode, has a small resistance, and is excellent in output characteristics. Furthermore, the present invention provides a lithium-ion secondary battery using spinel-type lithium manganate as a positive electrode.

Means for Solving the Problems

[0008] As a result of repeated studies on spinel-type lithium manganate, the present inventors have found that the present invention summarized below can achieve the above problems. That is, the present invention is as defined in the claims, and the gist thereof is as follows. [1] A spinel-type lithium manganate represented by the chemical formula Li 1+X Mn 2-X-Y M Y O4 (where 0.02 ≦ X ≦ 0.35, 0.01 ≦ Y ≦ 0.30, and M is Al or Mg), having an average particle size retention rate of 50% or more after pressing, and a pore volume of pores with a pore diameter of 0.6 μm or less of 0.005 cm 3 / g or more and 0.050 cm3 Lithium spinel-type manganese oxide with a content of less than / g. [2] The spinel-type lithium manganate described above [1], which contains a phosphate. [3] The spinel-type lithium manganate described in [1] or [2] above, wherein the phosphorus / manganese molar ratio is 0 or more and 0.1 or less. [4] BET specific surface area is 0.7m 2 / g or more 1.5m 2 Lithium spinel-type manganese oxide described in any one of the above [1] to [3], which is less than or equal to / g. [5] A spinel-type lithium manganate described in any one of the above [1] to [4], wherein the average particle size of the secondary particles is 6 μm or more and 15 μm or less. [6] A spinel-type lithium manganate described in any one of the above [1] to [5], wherein the SO4 content is 0.8 wt% or less. [7] A spinel-type lithium manganate described in any one of the above [1] to [6], wherein the Na content is 500 wt ppm or less. [8] A spinel-type lithium manganate described in any one of the above [1] to [7], having a boron content of 100 wt ppm or more and 1,500 wt ppm or less. [9] A CR2032 type coin cell with a Li counter electrode, wherein the DC resistance in a 50% charged state is 25Ω or less, as described in any one of the above [1] to [8], and is of the spinel type lithium manganese oxide type.

[10] A method for producing spinel-type lithium manganate according to any one of [1] to [9] above, wherein a manganese compound, a lithium compound, a compound containing the element M described in [1] above, and a boron compound are added to a solution to prepare a slurry in which the mixture thereof is dispersed, the average particle size of the mixture is 1 μm or less, the slurry is granulated by spray drying, and then calcined and crushed in air or in a high-concentration oxygen atmosphere (including in a pure oxygen atmosphere) at 750°C to 900°C, and the amount of boron added is 300 wt ppm to 2,500 wt ppm.

[11] A method for producing spinel-type lithium manganate according to

[10] above, wherein after calcination, boron is removed by washing with water to a concentration of 100 wt ppm or more and 1,500 wt ppm or less.

[12] An electrode containing spinel-type lithium manganate as described in any one of [1] to [9] above.

[13] A lithium-ion secondary battery having the electrode described in

[12] above as the positive electrode. [Effects of the Invention]

[0009] When the spinel-type lithium manganese oxide of the present invention is used as a cathode material for lithium-ion secondary batteries, it is possible to provide lithium-ion secondary batteries that have superior charge-discharge characteristics at high temperatures, particularly carbon counter electrode charge-discharge characteristics, compared to conventional materials, as well as low resistance and excellent output characteristics. [Brief explanation of the drawing]

[0010] [Figure 1] This shows the pore distribution of the phosphate-containing spinel-type lithium manganate obtained in Example 3 before and after pressing. [Figure 2] This shows the pore distribution of the phosphate-containing spinel-type lithium manganate obtained in Comparative Example 1, before and after pressing. [Modes for carrying out the invention]

[0011] The present invention will be described in detail below.

[0012] The spinel-type lithium manganate of the present invention has the chemical formula Li 1+X Mn 2-X-Y M YIt is represented by O4 (wherein the formula satisfies 0.02 ≤ X ≤ 0, 35, and 0.01 ≤ Y ≤ 0.30, where M is Al or Mg). If the value of X is less than 0.02, capacity degradation is likely to occur during charging and discharging at high temperatures, and if it exceeds 0.35, sufficient charge and discharge capacity cannot be obtained. Similarly, if the value of Y is less than 0.01, capacity degradation is likely to occur during charging and discharging at high temperatures, and if it exceeds 0.30, sufficient charge and discharge capacity cannot be obtained. X and Y of spinel-type lithium manganese oxide can be determined from compositional analysis. Examples of such methods include inductively coupled plasma emission spectrometry and atomic absorption spectrometry.

[0013] The spinel-type lithium manganate of the present invention is 3 ton / cm³ 2 The average particle size retention rate of secondary particles when uniaxially pressed with this force is 50% or more. This 50% or higher average particle size retention rate suppresses the breakdown of secondary particles of spinel-type lithium manganese oxide when the positive electrode of a lithium-ion secondary battery (a mixture of spinel-type lithium manganese oxide, a conductive agent, and a binder) is manufactured by coating, drying, and pressing. Suppression of secondary particle breakdown maintains the conductive path between the spinel-type lithium manganese oxide and the conductive agent in the positive electrode, resulting in improved charge-discharge cycle characteristics.

[0014] The spinel-type lithium manganese oxide of the present invention has an average particle size retention rate of 50% or more after pressing. If the average particle size retention rate after pressing is less than 50%, secondary particle breakdown and miniaturization are likely to occur when the positive electrode of a lithium-ion secondary battery is manufactured and pressed, making it easier for contact between the spinel-type lithium manganese oxide, the conductive agent, and the binder to be lost, and as a result, the battery characteristics tend to deteriorate. An average particle size retention rate of 60% or more after pressing is preferable, and 70% or more is more preferable. The average particle size retention rate of spinel-type lithium manganese oxide after pressing can be calculated from the average particle size of secondary particles before and after pressing by particle size distribution measurement.

[0015] The spinel-type lithium manganate of the present invention has a pore volume of 0.005 cm³ for pores with a pore diameter of 0.6 μm or less. 3 / g or more 0.050cm 3It is less than / g. The pore volume of pores with a diameter of 0.6 μm or less is 0.005 cm³. 3 / g or more 0.050cm 3 When the concentration is less than / g, the electrolyte is contained within the spinel-type lithium manganese oxide secondary particles when used as the positive electrode of a lithium-ion secondary battery. This increases the contact area between the spinel-type lithium manganese oxide particles and the electrolyte, thus reducing resistance and improving output characteristics. The pore volume of pores with a diameter of 0.6 μm or less is 0.005 cm³. 3 When the value falls below / g, the electrolyte contained within the spinel-type lithium manganate secondary particles becomes insufficient, reducing the contact area between the spinel-type lithium manganate particles and the electrolyte, increasing resistance, and consequently degrading the output characteristics, which is undesirable. The pore volume of pores with a pore diameter of 0.6 μm or less is 0.050 cm³. 3 When the value exceeds / g, the average particle size retention rate during pressing tends to decrease, which is undesirable because it tends to reduce the durability at high temperatures when used as a positive electrode in lithium-ion secondary batteries. The pore volume of pores with a pore diameter of 0.6 μm or less is 0.008 cm³. 3 / g or more 0.047cm 3 It is more preferable that the concentration be less than or equal to / g. The pore volume of spinel-type lithium manganate can be measured by the mercury intrusion method.

[0016] The spinel-type lithium manganate of the present invention does not contain phosphate, but may contain phosphate. By including phosphate, it is possible to obtain excellent charge and discharge characteristics at high temperatures when the spinel-type lithium manganate of the present invention is used as a positive electrode active material in a lithium-ion secondary battery. The phosphate content can be 0% to 13% by mass, and more specifically, 1% to 5% by mass.

[0017] Examples of phosphates include lithium phosphates such as trilithium phosphate (Li3PO4) and LiPO4, sodium phosphates such as Na3PO4, NaH2PO4, and Na2HPO4, and potassium phosphates such as K3PO4, KH2PO4, and K2HPO4. Preferably, it is trilithium phosphate (Li3PO4) or LiPO3, and more preferably trilithium phosphate (Li3PO4). Here, when spinel-type lithium manganate is described as containing phosphate, examples include the phosphate being present as fine particles or as a film on the surface of spinel-type lithium manganate. There are no particular restrictions on the properties of the phosphate, and examples include crystalline, crystalline and porous, crystalline and dense, amorphous, amorphous and porous, and amorphous and dense, but it is not limited to these.

[0018] When the spinel-type lithium manganate of the present invention is used as a positive electrode active material for a lithium-ion secondary battery, the reaction in which the phosphate captures hydrogen fluoride, which is present in small amounts in the electrolyte of the lithium-ion secondary battery, proceeds rapidly. As a result, manganese elution due to the reaction between hydrogen fluoride and spinel-type lithium manganate is further suppressed, and the decrease in capacity during charging and discharging at high temperatures is further suppressed. Therefore, a phosphorus / manganese molar ratio of 0 to 0.1 is preferred, 0.0015 to 0.1 is more preferred, 0.016 to 0.08 is even more preferred, and 0.02 to 0.05 is particularly preferred.

[0019] The spinel-type lithium manganate of the present invention, when used as a positive electrode active material in lithium-ion secondary batteries, enables excellent charge-discharge characteristics at high temperatures, reduces resistance, and achieves superior output characteristics, resulting in a BET specific surface area of ​​0.7 m². 2 / g or more 1.5m 2 It is preferable that it be less than or equal to / g, and 0.8m 2 / g or more 1.2m 2 It is more preferable that the value be less than or equal to / g.

[0020] When the spinel-type lithium manganate of the present invention is used as a positive electrode active material for lithium-ion secondary batteries, the lithium diffusion distance within the spinel-type lithium manganate particles is reduced, making it possible to obtain better output characteristics, as well as to improve the packing efficiency of the positive electrode mixture. Furthermore, the average particle size retention rate during pressing is increased, which improves the charge-discharge cycle characteristics. Therefore, the average particle size of the secondary particles is preferably 6 μm to 15 μm, and more preferably 9 μm to 12 μm.

[0021] The spinel-type lithium manganese oxide of the present invention has a higher charge-discharge capacity when used as a positive electrode active material for lithium-ion secondary batteries, and also provides better charge-discharge characteristics at high temperatures. Therefore, the SO4 content is preferably 0.8 wt% or less, and more preferably 0.5 wt% or less.

[0022] The spinel-type lithium manganate of the present invention has a higher charge-discharge capacity when used as a positive electrode active material for lithium-ion secondary batteries, and also has high crystallinity, allowing for better charge-discharge characteristics at high temperatures. Therefore, the Na content is preferably 500 wt ppm or less, and more preferably 400 wt ppm or less.

[0023] The spinel-type lithium manganate of the present invention increases the charge and discharge capacity when used as a positive electrode active material for lithium-ion secondary batteries. Furthermore, when used as a positive electrode active material for lithium-ion secondary batteries, it captures the small amount of hydrogen fluoride contained in the electrolyte of the lithium-ion secondary battery with a boron compound. As a result, manganese elution caused by the reaction between hydrogen fluoride and spinel-type lithium manganate is suppressed, and the capacity decrease during charging and discharging at high temperatures is further suppressed. Therefore, the boron content is preferably 100 wtppm to 1,500 wtppm, and more preferably 120 wtppm to 500 wtppm. The boron content is the content relative to the manganese contained in the spinel-type lithium manganate.

[0024] The spinel-type lithium manganese oxide of the present invention, in order to enhance the output characteristics when used as a lithium-ion secondary battery, preferably has a DC resistance of 25 Ω or less, and more preferably 20 Ω or less, at a 50% charge state in a CR2032 type coin cell with a Li counter electrode. The DC resistance was measured at a 50% charge state in a CR2032 type coin cell using a mixture of spinel-type lithium manganese oxide, acetylene black as a conductive agent, and polyvinylidene fluoride as a binder in a 94:3:3 ratio, applied to aluminum foil for the positive electrode, and Li foil for the negative electrode. The amount of spinel-type lithium manganese oxide applied to the positive electrode was 5 mg / cm². 2 The measurement temperature was set to 24°C.

[0025] Next, the method for producing spinel-type lithium manganate according to the present invention will be described.

[0026] The spinel-type lithium manganate of the present invention is obtained by adding a manganese compound, a lithium compound, a compound containing the element M described in claim 1, and a boron compound to a solution to prepare a slurry in which these mixtures are dispersed, the average particle size of the mixture being 1 μm or less, granulating the slurry by spray drying, and then calcining and crushing it in air or in a high-concentration oxygen atmosphere (including a pure oxygen atmosphere) at 750°C to 900°C, wherein the amount of boron added is 300 wt ppm to 2,500 wt ppm. When producing spinel-type lithium manganate containing phosphate, in the mixing step, a manganese compound, a lithium compound, a compound containing the element M described in claim 1, a phosphoric acid compound, and a boron compound are added to a solution to prepare a slurry in which these mixtures are dispersed.

[0027] The amount of boron added is between 300 wt ppm and 2,500 wt ppm. If the amount is less than 300 wt ppm, the average particle size retention rate after pressing tends to fall below 50%, and if it exceeds 2,500 wt ppm, the oxygen deficiency of spinel-type lithium manganate tends to increase, resulting in a decrease in charge-discharge cycle performance. The amount of boron added is preferably between 1,000 wt ppm and 2,000 wt ppm. The amount of boron added is the amount added relative to the manganese contained in spinel-type lithium manganate.

[0028] When the average particle size of the mixture exceeds 1 μm, the pore volume of pores with a diameter of 0.6 μm or less is 0.005 cm³. 3 It becomes easier to make it smaller.

[0029] The manganese compound, lithium compound, the compound containing M described in claim 1, the phosphoric acid compound, and the boron compound may all be water-soluble substances.

[0030] There are no particular restrictions on the manganese compounds used; for example, electrolytic manganese dioxide, Mn3O4, Mn2O3, etc., are examples, but the work is not limited to these.

[0031] There are no particular restrictions on lithium compounds; for example, lithium carbonate, lithium hydroxide, lithium nitrate, lithium chloride, lithium iodide, lithium oxalate, etc., are examples, but the invention is not limited to these.

[0032] There are no particular restrictions on the phosphate compounds used. Examples include lithium phosphates such as trilithium phosphate (Li3PO4) and LiPO3, sodium phosphates such as Na3PO4, NaH2PO4, and Na2HPO4, potassium phosphates such as K3PO4, KH2PO4, and K2HPO4, magnesium phosphates such as Mg3(PO4)2, MgHPO4, and Mg(H2PO4)2, ammonium phosphates such as NH4H2PO4 and (NH4)2HPO4, and hydrogen phosphates such as H3PO4, but the phosphate compounds are not limited to these.

[0033] The compound containing the element M (Al or Mg) described in claim 1 is not particularly limited, and examples include, but is not limited to, Al(OH)3, AlOOH, Al2O3, Mg(OH)2, MgO, etc.

[0034] There are no particular restrictions on the boron compounds used; for example, boric acid (H3BO3), B2O3, Li2O·nB2O3 (n=1~5), etc., are given as examples, but the text is not limited to these.

[0035] A slurry in which a mixture containing a manganese compound, a lithium compound, a compound containing the element M described in claim 1, and a boron compound is dispersed, or a slurry in which a mixture containing a manganese compound, a lithium compound, a compound containing the element M described in claim 1, a phosphate compound, and a boron compound is dispersed, has an average particle size of 1 μm or less, but preferably 0.3 μm or more and 0.8 μm or less. Such an average particle size can be obtained by adding the compounds to a solution and grinding and mixing them. As grinding and mixing equipment, for example, a wet media stirring mill, a ball mill, a vibrating mill, etc., can be used. The manganese compound, lithium compound, compound containing the element M described in claim 1, phosphate compound, and boron compound may be partially or completely dissolved in water.

[0036] Examples of solutions to which the compound is added include pure water and water.

[0037] The slurry obtained by wet grinding and mixing is granulated by spray drying. For spray drying, a conventional spray dryer can be used, in which the slurry is sprayed with a rotating disc or fluid nozzle and the droplets are dried with hot air.

[0038] The calcination process for obtaining spinel-type lithium manganate of the present invention is carried out in air or in a high-concentration oxygen atmosphere (including a pure oxygen atmosphere), i.e., in an oxygen atmosphere with an oxygen content of 18 to 100 vol%, at a temperature of 750°C to 900°C. Below 750°C, crystallinity decreases and the average secondary particle size retention rate during pressing tends to decrease, leading to deterioration of charge-discharge cycle characteristics. Above 900°C, the pore volume of pores with a diameter of 0.6 μm or less decreases, and the output characteristics tend to deteriorate. It is preferable to carry out the calcination at a temperature of 800°C to 850°C.

[0039] In order to improve charge-discharge cycle characteristics and reduce resistance, it is preferable to wash the spinel-type lithium manganate of the present invention with water to remove boron. It is preferable to remove boron by washing with water until the concentration is between 100 wtppm and 1,500 wtppm.

[0040] Since spinel-type lithium manganate tends to solidify with other secondary particles during calcination, it is preferable to crush it to obtain the desired particle size. For crushing, shearing force is preferred to further suppress the generation of fine powder.

[0041] After crushing the spinel-type lithium manganate, it is preferable to pass it through a sieve to remove coarse particles that exceed the thickness of the positive electrode. The sieve opening is preferably 200 μm or less, and more preferably 150 μm or less.

[0042] By using the spinel-type lithium manganese oxide of the present invention as the positive electrode of a lithium-ion secondary battery, it becomes possible to construct a lithium-ion secondary battery with excellent charge-discharge cycle characteristics at high temperatures, which was not possible with conventional methods.

[0043] There are no particular restrictions on the composition of lithium-ion secondary batteries other than the positive electrode, but the negative electrode should be made of a material that absorbs and desorbs Li, such as carbon-based materials, tin oxide-based materials, or Li4Ti5O 12Materials such as those that form an alloy with SiO, Li, etc. are exemplified. Examples of materials that form an alloy with Li include, for example, silicon-based materials and aluminum-based materials. Examples of electrolytes include, for example, organic electrolytic solutions in which Li salts and various additives are dissolved in an organic solvent, Li-ion conductive solid electrolytes, combinations thereof, and the like.

Examples

[0044] Although the specific examples of the present invention will be described, the present invention is not to be construed as being limited to these examples.

[0045] <Composition analysis, measurement of SO4 content, Na content, boron content, phosphate content> For the composition, SO4 content, Na content, boron content, and phosphate content of the spinel-type lithium manganate obtained in the examples and comparative examples, after dissolving the spinel-type lithium manganate in a hydrochloric acid-hydrogen peroxide mixed aqueous solution, it was analyzed using an inductively coupled plasma optical emission spectrometer (trade name: ICP-AES, manufactured by PerkinElmer Japan). Also, the Al content was subjected to pressure acid decomposition on the sample dissolved in a hydrochloric acid-hydrogen peroxide mixed aqueous solution and analyzed using the above device.

[0046] <Measurement of pore volume> For the spinel-type lithium manganate obtained in the examples and comparative examples, the measurement of the pore volume of pores with a pore diameter of 0.6 μm or less was carried out using an automatic mercury porosimeter pore distribution measuring device (trade name: AutoPore V9600, manufactured by Micromeritics). The mercury intrusion pressure was set to 0.48 to 33,000 psia.

[0047] <Measurement of BET specific surface area> 0.5 g of the sample was placed in a glass cell for BET specific surface area measurement, and dehydration treatment was carried out at 150 °C for at least 20 minutes under a nitrogen stream to remove the moisture adhering to the powder particles.

[0048] The treated samples were subjected to BET specific surface area measurement using a single-point method with a BET measuring device (product name: MICROMETRITICS DeSorbIII, manufactured by Shimadzu Corporation), employing a mixed gas of 30% nitrogen and 70% helium as the adsorption gas.

[0049] <Measurement of the average particle size of secondary particles of spinel-type lithium manganate> Using a particle size distribution analyzer (product name: MT3000II series, manufactured by MicrotracBEL), the average particle size (D) of secondary particles of spinel-type lithium manganese oxide was measured. 50 The following measurements were taken: 1 g of powder was pressed using a 13 mm diameter mold at a rate of 3 tons / cm². 2 Uniaxial pressing was performed, and the average particle diameter of the secondary particles was measured using the above-mentioned apparatus. The retention rate of the average particle diameter after pressing was calculated from the ratio of the average particle diameter of the secondary particles after pressing to the average particle diameter of the secondary particles before pressing ((average particle diameter of secondary particles after pressing / average particle diameter of secondary particles before pressing) × 100).

[0050] <Measurement of initial capacitance, measurement of DC resistance> For the positive electrode, 1.0 g of spinel-type lithium manganate obtained in the examples and comparative examples, 0.032 g of acetylene black (product name: Denka Black, manufactured by Denka), 0.307 mL of 10 wt% polyvinylidene fluoride / N-methyl-2-pyrrolidone solution (0.032 g of polyvinylidene fluoride), and 0.751 mL of N-methyl-2-pyrrolidone (weight ratio: lithium spinel-type lithium manganate: acetylene black: polyvinylidene fluoride = 94:3:3) were mixed in a rotation-orbit mixer (product name: AR-100, manufactured by Thinky) to prepare a positive electrode material slurry. The obtained positive electrode material slurry was applied to aluminum foil, dried at 150°C for 30 minutes, and then punched out to a diameter of 15.958 mm at a rate of 3 tons / cm². 2 It was uniaxially pressed and dried under reduced pressure at 150°C for 2 hours before use. The coating amount was 5 mg / cm³ of spinel-type lithium manganate. 2 I made it so that it would be like that.

[0051] A 16mm diameter die-cut piece of Li foil was used as the negative electrode, and 1 mol / dm³ of LiPF6 was added to a mixed solvent of ethylene carbonate and dimethyl carbonate (volume ratio 1:2). 3 A CR2032 type coin cell was fabricated using the dissolved electrolyte and a separator (product name: Cellguard, manufactured by Polypore).

[0052] Using the fabricated battery, a charge-discharge cycle was performed at 24°C with a voltage of 4.3V and a current of 0.1mA, and the discharge capacity was defined as the initial capacity.

[0053] Next, the battery was charged to 50% of its initial capacity, and the DC resistance was measured at 24°C. The DC resistance was measured by first charging with a current of 2mA for 10 seconds and measuring the closed-circuit voltage, then discharging with a current of 0.2mA for 100 seconds and resting for 1 hour, then charging with a current of 5mA for 10 seconds and measuring the closed-circuit voltage, then discharging with a current of 0.2mA for 250 seconds and resting for 1 hour, then charging with a current of 10mA for 10 seconds and measuring the closed-circuit voltage, then discharging with a current of 0.2mA for 500 seconds and resting for 1 hour, and the closed-circuit voltage for each current value was plotted, with the slope representing the DC resistance.

[0054] <Carbon Counter Electrode Charge-Discharge Cycle Test> The same cathode used was the one prepared for the initial capacity measurement.

[0055] The negative electrode was prepared by mixing 2.0 g of spheroidized natural graphite and 2.104 mL of 10 wt% polyvinylidene fluoride / N-methyl-2-pyrrolidone solution (0.221 g of polyvinylidene fluoride) (weight ratio of graphite:polyvinylidene fluoride = 90:10) in a rotation-orbit mixer (product name: AR-100, manufactured by Sinky) to prepare a negative electrode material slurry. The obtained negative electrode material slurry was applied to copper foil, dried at 150°C for 30 minutes, and then punched out to a diameter of 16.156 mm at a rate of 3 tons / cm². 2 It was pressed using a single-axis press and dried under reduced pressure at 150°C for 2 hours before use. The coating amount was 1.8 mg / cm² of spheroidized natural graphite. 2 I made it so that it would be like that.

[0056] The positive electrode, negative electrode, and a mixed solvent of ethylene carbonate and dimethyl carbonate (volume ratio 1:2) are combined with 1 mol / dm³ of LiPF6. 3 A CR2032 coin cell was prepared using 0.2 mL of dissolved electrolyte and a separator (product name: Cellguard, manufactured by Polypore).

[0057] Using the fabricated battery, one cycle of constant current / constant voltage charging and discharging was performed at 24°C with a current of 0.1mA between cell voltages of 4.25V and 3.0V. Next, at 24°C, one cycle of constant current / constant voltage charging and discharging was performed with a current of 0.2mA between cell voltages of 4.25V and 3.0V, and the discharge capacity was defined as the cell capacity. Then, at 45°C, 50 cycles of constant current / constant voltage charging and discharging were performed at a current density equal to the 1-hour discharge rate relative to the battery capacity. The carbon counter electrode charge / discharge cycle retention rate was determined from the ratio of the discharge capacity at the 50th cycle to that at the 1st cycle. The termination condition for constant voltage charging was defined as when the charging current decreased to 1 / 10 of that during constant current charging.

[0058] Example 1 A slurry with a solid content of 20 wt% was prepared by adding 766 g of electrolytic manganese dioxide, 182 g of lithium carbonate, 37 g of aluminum hydroxide, 31 g of trilithium phosphate, and 4 g of boric acid (boron added relative to manganese: 1,500 wt ppm) to pure water, and then grinding it in a grinder (product name: Dynomill, manufactured by Shinmaru Enterprise) for 3 hours. The average particle size (D) of the mixture of electrolytic manganese dioxide, lithium carbonate, aluminum hydroxide, trilithium phosphate, and boric acid was determined. 50 The particle size distribution was measured using a particle size analyzer (product name: MT3000II series, manufactured by MicrotracBEL) and found to be 0.6 μm. The obtained slurry was dried using a spray dryer (manufactured by Pris Co., Ltd.) and D 50 Spherical granular dried particles with a diameter of 5 μm were obtained.

[0059] Six g of dried granular particles were calcined in a box-type furnace at 900°C for 6 hours while air was circulated at a rate of 8 L / min, and then cooled to room temperature. The heating rate was 100°C / hr, and the cooling rate was 20°C / hr from 900°C to 600°C, and 100°C / hr from 600°C to room temperature. Next, pure water was added and stirred for 1 hour, filtered, dried at 110°C, then crushed in a small pulverizer, and passed through a sieve with a mesh size of 32 μm to obtain phosphate-containing spinel-type lithium manganate.

[0060] The composition of the obtained phosphate-containing spinel-type lithium manganate is Li 1.09 Mn 1.81 Al 0.10 The material was O4, and the trilithium phosphate content was 2.9% by mass. XRD measurements revealed that the obtained phosphate-containing spinel-type lithium manganate was a mixed phase of JCPDS No. 35-782 (LiMn2O4) and No. 25-1030 (Li3PO4). Table 1 shows the average particle size, BET specific surface area, and average particle size retention rate after pressing. Table 2 shows the measured results for SO4 content, Na content, phosphorus / manganese molar ratio, boron (B) content, and pore volume of pores with a diameter of 0.6 μm or less. Table 3 shows the battery performance.

[0061] [Table 1]

[0062] [Table 2]

[0063] [Table 3]

[0064] Example 2 Average particle size D of dried granular particles 50 A phosphate-containing spinel-type lithium manganate was obtained using the same method as in Example 1, except that the particle size was 7 μm and the calcination temperature was 800°C.

[0065] The composition of the obtained phosphate-containing spinel-type lithium manganate is Li 1.08 Mn 1.82 Al 0.10 The material was O4, and the trilithium phosphate content was 2.7% by mass. XRD measurements revealed that the obtained phosphate-containing spinel-type lithium manganate was a mixed phase of JCPDS No. 35-782 (LiMn2O4) and No. 25-1030 (Li3PO4). Table 1 shows the average particle size, BET specific surface area, and average particle size retention rate after pressing. Table 2 shows the measured results for SO4 content, Na content, phosphorus / manganese molar ratio, boron (B) content, and pore volume of pores with a diameter of 0.6 μm or less. Table 3 shows the battery performance.

[0066] Example 3 A phosphate-containing spinel-type lithium manganate was obtained using the same method as in Example 2, except that the average particle size of the dried granules was 9 μm.

[0067] The composition of the obtained phosphate-containing spinel-type lithium manganate is Li 1.09 Mn 1.81 Al 0.10 The material was O4, and the trilithium phosphate content was 3.0% by mass. XRD measurements revealed that the obtained phosphate-containing spinel-type lithium manganate was a mixed phase of JCPDS No. 35-782 (LiMn2O4) and No. 25-1030 (Li3PO4). Table 1 shows the average particle size, BET specific surface area, and average particle size retention rate after pressing. Table 2 shows the measured results for SO4 content, Na content, phosphorus / manganese molar ratio, boron (B) content, and pore volume of pores with a diameter of 0.6 μm or less. Table 3 shows the battery performance. Figure 1 shows the particle pore distribution before and after pressing.

[0068] Example 4 Average particle size D of dried granular particles 50 A phosphate-containing spinel-type lithium manganate was obtained by the same method as in Example 1, except that the particle size was 12 μm and the calcination temperature was 750°C.

[0069] The composition of the obtained phosphate-containing spinel-type lithium manganate is Li 1.09 Mn 1.81Al 0.10 The material was O4, and the trilithium phosphate content was 3.2% by mass. XRD measurements revealed that the obtained phosphate-containing spinel-type lithium manganate was a mixed phase of JCPDS No. 35-782 (LiMn2O4) and No. 25-1030 (Li3PO4). Table 1 shows the average particle size, BET specific surface area, and average particle size retention rate after pressing. Table 2 shows the measured results for SO4 content, Na content, phosphorus / manganese molar ratio, boron (B) content, and pore volume of pores with a diameter of 0.6 μm or less. Table 3 shows the battery performance.

[0070] Example 5 A slurry with a solid content of 20 wt% was prepared by adding 1577 g of electrolytic manganese dioxide, 369 g of lithium carbonate, 53 g of magnesium hydroxide, 63 g of trilithium phosphate, and 5.7 g of boric acid (boron added relative to manganese: 1,000 wt ppm) to pure water, and then grinding it in a grinder (product name: Dinomill, manufactured by Shinmaru Enterprise) for 3 hours. The average particle size (D) of the mixture of electrolytic manganese dioxide, lithium carbonate, magnesium hydroxide, trilithium phosphate, and boric acid was determined. 50 The particle size distribution was measured using a particle size analyzer (product name: MT3000II series, manufactured by MicrotracBEL) and found to be 0.6 μm. The obtained slurry was dried using a spray dryer (manufactured by Pris Co., Ltd.) and D 50 Spherical granular dried particles with a diameter of 9 μm were obtained.

[0071] Six g of dried granular particles were calcined in a box-type furnace at 800°C for 6 hours while air was circulated at a rate of 8 L / min, and then cooled to room temperature. The heating rate was 100°C / hr, and the cooling rate was 20°C / hr from 900°C to 600°C, and 100°C / hr from 600°C to room temperature. Next, pure water was added and stirred for 1 hour, filtered, dried at 110°C, then crushed in a small pulverizer, and passed through a sieve with a mesh size of 32 μm to obtain phosphate-containing spinel-type lithium manganate.

[0072] The composition of the obtained phosphate-containing spinel-type lithium manganate is Li 1.14 Mn 1.81 Mg 0.05The material was O4, and the trilithium phosphate content was 2.7% by mass. XRD measurements revealed that the obtained phosphate-containing spinel-type lithium manganate was a mixed phase of JCPDS No. 35-782 (LiMn2O4) and No. 25-1030 (Li3PO4). Table 1 shows the average particle size, BET specific surface area, and particle size retention rate after pressing. Table 2 shows the results for SO4 content, Na content, phosphorus / manganese molar ratio, boron (B) content, and pore volume of pores with a diameter of 0.6 μm or less. Table 3 shows the battery performance.

[0073] Example 6 A phosphate-containing spinel-type lithium manganate was obtained using the same method as in Example 5, except that 1.7 g of boric acid was used (boron added relative to manganese: 300 wt ppm) and the calcination temperature was set to 850°C.

[0074] The composition of the obtained phosphate-containing spinel-type lithium manganate is Li 1.16 Mn 1.79 Mg 0.05 The material was O4, and the trilithium phosphate content was 2.6% by mass. XRD measurements revealed that the obtained phosphate-containing spinel-type lithium manganate was a mixed phase of JCPDS No. 35-782 (LiMn2O4) and No. 25-1030 (Li3PO4). Table 1 shows the average particle size, BET specific surface area, and particle size retention rate after pressing. Table 2 shows the results for SO4 content, Na content, phosphorus / manganese molar ratio, boron (B) content, and pore volume of pores with a diameter of 0.6 μm or less. Table 3 shows the battery performance.

[0075] Example 7 A phosphate-containing spinel-type lithium manganate was obtained in the same manner as in Example 6, except that 2.8 g of boric acid was used (amount of boron added relative to manganese: 500 wt ppm).

[0076] The composition of the obtained phosphate-containing spinel-type lithium manganate is Li 1.19 Mn 1.76 Mg 0.05The material was O4, and the trilithium phosphate content was 2.5% by mass. XRD measurements revealed that the obtained phosphate-containing spinel-type lithium manganate was a mixed phase of JCPDS No. 35-782 (LiMn2O4) and No. 25-1030 (Li3PO4). Table 1 shows the average particle size, BET specific surface area, and particle size retention rate after pressing. Table 2 shows the results for SO4 content, Na content, phosphorus / manganese molar ratio, boron (B) content, and pore volume of pores with a diameter of 0.6 μm or less. Table 3 shows the battery performance.

[0077] Example 8 Lithium spinel-type manganese oxide was obtained using the same method as in Example 3, except that trilithium phosphate was not added and the calcination temperature was set to 780°C.

[0078] The composition of the obtained spinel-type lithium manganate is Li 1.02 Mn 1.88 Al 0.10 The material was O4. Furthermore, XRD measurements revealed that the obtained spinel-type lithium manganate was single-phase, JCPDS No. 35-782 (LiMn2O4). Table 1 shows the average particle size, BET specific surface area, and particle size retention rate after pressing. Table 2 shows the results for SO4 content, Na content, phosphorus / manganese molar ratio, boron (B) content, and pore volume of pores with a diameter of 0.6 μm or less. Table 3 shows the battery performance.

[0079] Comparative Example 1 A slurry with a solid content of 20 wt% was prepared by adding 1916 g of electrolytic manganese dioxide, 455 g of lithium carbonate, 91 g of aluminum hydroxide, 57 g of trilithium phosphate, and 2 g of boric acid (boron added relative to manganese: 250 wt ppm) to pure water, and then grinding it in a grinder (product name: Dinomill, manufactured by Shinmaru Enterprise) for 3 hours. The average particle size (D) of the mixture of electrolytic manganese dioxide, lithium carbonate, aluminum hydroxide, trilithium phosphate, and boric acid was measured. 50 The particle size distribution was measured using a particle size analyzer (product name: MT3000II series, manufactured by MicrotracBEL) and found to be 0.6 μm. The obtained slurry was dried using a spray dryer (manufactured by Okawara Chemical Machinery Co., Ltd.) and D 50Spherical granular dried particles with a diameter of 5 μm were obtained.

[0080] Six g of dried granular particles were calcined in a box-type furnace at 810°C for 6 hours while air was circulated at a rate of 8 L / min, and then cooled to room temperature. The heating rate was 100°C / hr, and the cooling rate was 20°C / hr from 810°C to 600°C, and 100°C / hr from 600°C to room temperature. Next, pure water was added and stirred for 1 hour, filtered, dried at 110°C, then crushed in a small pulverizer, and passed through a sieve with a mesh size of 32 μm to obtain phosphate-containing spinel-type lithium manganate.

[0081] The composition of the obtained phosphate-containing spinel-type lithium manganate is Li 1.09 Mn 1.81 Al 0.10 The material was O4, and the trilithium phosphate content was 2.6% by mass. XRD measurements revealed that the obtained phosphate-containing spinel-type lithium manganate was a mixed phase of JCPDS No. 35-782 (LiMn2O4) and No. 25-1030 (Li3PO4). Table 1 shows the average particle size, BET specific surface area, and average particle size retention rate after pressing. Table 2 shows the measured results for SO4 content, Na content, phosphorus / manganese molar ratio, boron (B) content, and pore volume of pores with a diameter of 0.6 μm or less. Table 3 shows the battery performance. Figure 2 shows the pore distribution of the phosphate-containing spinel-type lithium manganate before and after pressing.

[0082] Comparative Example 2 A phosphate-containing spinel-type lithium manganate was obtained using the same method as in Example 1, except that boric acid was not added.

[0083] The composition of the obtained phosphate-containing spinel-type lithium manganate is Li 1.09 Mn 1.81 Al 0.10The material was O4, and the trilithium phosphate content was 2.8% by mass. XRD measurements revealed that the obtained phosphate-containing spinel-type lithium manganate was a mixed phase of JCPDS No. 35-782 (LiMn2O4) and No. 25-1030 (Li3PO4). Table 1 shows the average particle size, BET specific surface area, and average particle size retention rate after pressing. Table 2 shows the measured results for SO4 content, Na content, phosphorus / manganese molar ratio, boron (B) content, and pore volume of pores with a diameter of 0.6 μm or less. Table 3 shows the battery performance. Figure 2 shows the pore distribution of the phosphate-containing spinel-type lithium manganate before and after pressing. [Industrial applicability]

[0084] The spinel-type lithium manganate of the present invention has pores with a unique pore volume and a high average particle size retention rate after pressing. Therefore, it can be used as a positive electrode active material for lithium secondary batteries, exhibiting excellent charge-discharge characteristics at high temperatures, particularly for carbon counter electrodes, as well as superior output characteristics.

Claims

1. A chemical formula Li containing a phosphate, wherein the phosphorus / manganese molar ratio is 0.02 or more and 0.05 or less. １＋Ｘ Mn ２－Ｘ－Ｙ M Ｙ O ４ A spinel-type lithium manganate represented by the formula (wherein 0.02 ≤ X ≤ 0.35, 0.01 ≤ Y ≤ 0.30, and M is Al or Mg), wherein the average particle size retention rate after pressing is 60% or more and 67% or less, and the pore volume of pores with a pore diameter of 0.6 μm or less is 0.005 cm³. ３ / g or more 0.050cm ３ Lithium spinel-type manganese oxide with a concentration of less than / g.

2. BET specific surface area is 0.7 m² ２ / g or more 1.5m ２ The spinel-type lithium manganate according to claim 1, wherein the amount is less than or equal to / g.

3. The spinel-type lithium manganate according to claim 1 or claim 2, wherein the average particle diameter of the secondary particles is 6 μm or more and 15 μm or less.

4. SO ４ The spinel-type lithium manganate according to claim 1 or claim 2, wherein the content of

5. The spinel-type lithium manganate according to claim 1 or claim 2, wherein the Na content is 500 wt ppm or less.

6. The spinel-type lithium manganate according to claim 1 or claim 2, wherein the boron content is 100 wt ppm or more and 1,500 wt ppm or less.

7. A spinel-type lithium manganese oxide according to claim 1 or claim 2, wherein the CR2032 type coin cell with a Li counter electrode has a DC resistance of 19.1 Ω or less when charged to 50%.

8. A method for producing spinel-type lithium manganate according to claim 1 or claim 2, comprising adding a manganese compound, a lithium compound, a compound containing element M as described in claim 1, and a boron compound to a solution to prepare a slurry in which the mixture thereof is dispersed, the average particle size of the mixture being 1 μm or less, granulating the slurry by spray drying, and then calcining and crushing it in the air or in a high-concentration oxygen atmosphere (including a pure oxygen atmosphere) at 750°C to 900°C, wherein the amount of boron added is 1,400 wt ppm to 1,600 wt ppm.

9. A method for producing spinel-type lithium manganate according to claim 8, wherein after calcination, boron is removed to a level of 100 wt ppm or more and 1,500 wt ppm or less by washing with water.

10. An electrode comprising spinel-type lithium manganate according to claim 1 or claim 2.

11. Lithium-ion secondary battery having the electrode described in claim 10 as the positive electrode

Images