Spinel-type lithium manganese oxide, its production method, and its uses

Abstract

To provide a lithium secondary battery which has excellent charge-discharge cycle characteristics at high temperatures, while having low resistance and excellent output characteristics.SOLUTION: Provided are: spinel-type lithium manganese which contains phosphate and is represented by the chemical formula Li1+XMn2-X-YMYO4 (where 0.02≤X≤0.20, 0.05≤Y≤0.30, and M represents Al or Mg), in which the pore volume of pores having a pore diameter of 0.6 μm or less is from 0.003 cm3 / g to 0.2 cm3 / g inclusive and the relative standard deviation of the secondary particle diameters is from 25% to 45% inclusive; a method for producing the spinel-type lithium manganese; and a use of the spinel-type lithium manganese.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a spinel-type lithium manganese oxide, a method for producing the same, and uses thereof, and more particularly to a spinel-type lithium manganese oxide containing a phosphate, a method for producing the same, and a lithium secondary battery using the same in an electrode. [Background technology]

[0002] Lithium secondary batteries have a higher energy density than other storage batteries, and are therefore widely used as storage batteries for mobile devices. Recently, research has been conducted to further improve their performance, including their application to large-scale applications requiring large capacity and high output, such as stationary and automotive applications.

[0003] The positive electrode material of current lithium secondary batteries is mainly cobalt-based material (LiCoO2) for small consumer batteries such as mobile phones, and nickel-based material (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 However, cobalt and nickel raw materials are scarce and expensive, and the output characteristics are not very high.

[0004] On the other hand, spinel-type lithium manganese oxide, a manganese-based material, is one of the materials suitable for applications requiring large batteries because the raw material manganese is abundant and inexpensive, and it is also highly safe.

[0005] However, spinel-type lithium manganese oxide has problems with high-temperature stability, i.e., problems with charge-discharge characteristics at high temperatures, particularly with the charge-discharge characteristics and storage characteristics of the carbon counter electrode, and a solution to this problem has been desired. For example, Patent Document 1 and Patent Document 2 both propose spinel-type lithium manganese oxide containing phosphate, but there is still room for improvement in the charge-discharge characteristics at high temperatures, particularly with the charge-discharge characteristics of the carbon counter electrode.

[0006] Furthermore, although spinel-type lithium manganese oxide has excellent output characteristics, there is a demand for further improvements in characteristics to produce a battery that has output characteristics equivalent to those of a capacitor and a high energy density. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 5556983 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-31006 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a spinel-type lithium manganese oxide that has excellent charge-discharge characteristics at high temperatures, particularly excellent carbon counter electrode charge-discharge characteristics, as well as low resistance and excellent output characteristics, and further to provide a lithium secondary battery that uses the spinel-type lithium manganese oxide in a positive electrode. [Means for solving the problem]

[0009] The present inventors have conducted extensive research into spinel-type lithium manganese oxide. As a result, they have found that the present invention, which is summarized below, can achieve the above-mentioned object. That is, the present invention provides a lithium manganese oxide containing a phosphate and having the chemical formula Li 1+X Mn 2-X-Y M YSpinel-type lithium manganese oxide represented by the formula O4 (wherein 0.02≦X≦0.20, 0.05≦Y≦0.30, and M is Al or Mg), in which the pore volume of pores with a pore diameter of 0.6 μm or less is 0.003 cm 3 / g or more 0.2cm 3 / g or less, and the relative standard deviation of the secondary particle diameter is 25% or more and 45% or less, a method for producing the same, and uses thereof. [Effects of the Invention]

[0010] When the spinel-type lithium manganese oxide of the present invention is used as a positive electrode material for a lithium secondary battery, it is possible to provide a lithium secondary battery that has superior charge-discharge characteristics, particularly carbon counter electrode charge-discharge characteristics, at high temperatures compared to conventional materials, and also has low resistance and excellent output characteristics. [Brief explanation of the drawings]

[0011] [Figure 1] 1 shows the pore size distribution of the phosphate-containing spinel-type lithium manganese oxide obtained in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below.

[0013] The spinel-type lithium manganese oxide of the present invention contains a phosphate. The phosphate contained is not particularly limited, and examples thereof include lithium phosphates such as LiPO and LiPO; 4、Examples include sodium phosphates such as NaH2PO4 and Na2HPO4, and potassium phosphates such as K3PO4, KH2PO4 and K2HPO4. Li3PO4 and LiPO3 are preferred, and Li3PO4 is more preferred. By incorporating a phosphate into spinel-type lithium manganese oxide, it becomes possible to obtain excellent charge-discharge characteristics at high temperatures when used as a positive electrode active material for a lithium secondary battery. The nature of the phosphate to be incorporated is not particularly limited, and examples include crystalline, crystalline and porous, crystalline and dense, amorphous, amorphous and porous, and amorphous and dense, but is not limited to these.

[0014] The spinel-type lithium manganese oxide of the present invention has the chemical formula Li 1+X Mn 2-X-Y M Y O4 (wherein 0.02≦X≦0.20, 0.05≦Y≦0.30, and M is Al or Mg). If the value of X is less than 0.02, capacity loss during charge and discharge at high temperatures is likely to occur, and if it exceeds 0.20, sufficient charge and discharge capacity cannot be obtained. Furthermore, if the value of Y is less than 0.05, capacity loss during charge and discharge at high temperatures is likely to occur, and if it exceeds 0.30, sufficient charge and discharge capacity cannot be obtained. X and Y of the spinel-type lithium manganese oxide can be determined by composition analysis. Examples of methods for this include inductively coupled plasma emission spectrometry and atomic absorption spectrometry.

[0015] The spinel-type lithium manganese oxide of the present invention has a pore volume of 0.003 cm3 for pores with a pore diameter of 0.6 μm or less. 3 / g or more 0.2cm 3 / g or less. The pore volume of pores with a pore diameter of 0.6 μm or less is 0.003 cm 3 / g or more 0.2cm 3 / g or less, when used as a positive electrode for a lithium-ion secondary battery, the electrolyte is contained inside the spinel-type lithium manganese oxide secondary particles, and the contact area between the spinel-type lithium manganese oxide particles and the electrolyte increases, reducing resistance and improving output characteristics. 3If the pore volume of the pores having a diameter of 0.6 μm or less is less than 0.2 cm / g, the amount of electrolyte contained inside the secondary particles of spinel-type lithium manganate becomes insufficient, the contact area between the particles of spinel-type lithium manganate and the electrolyte decreases, and the resistance increases, which is undesirable because the output characteristics tend to decrease. 3 If the pore volume is greater than 0.004 cm3 / g, the density of the positive electrode is likely to decrease, and the amount of electrolyte contained inside the secondary particles of spinel-type lithium manganate increases, which increases the contact area between the spinel-type lithium manganate particles and the electrolyte and makes manganese more likely to leach out. As a result, when used as a positive electrode for a lithium ion secondary battery, durability at high temperatures is likely to decrease, which is undesirable. 3 / g or more 0.15cm 3 / g or less, and 3 / g or more 0.1cm 3 The pore volume of the spinel-type lithium manganese oxide can be measured by mercury intrusion porosimetry.

[0016] The spinel-type lithium manganate of the present invention has a relative standard deviation of secondary particle diameter of 25% to 45%. A relative standard deviation of secondary particle diameter of 25% to 45% results in a sharp particle size distribution of the secondary particles. As a result, when used as a positive electrode for a lithium-ion secondary battery, the spinel-type lithium manganate, conductive agent, and binder are mixed more uniformly, improving charge-discharge cycle characteristics and reducing resistance. The relative standard deviation of secondary particle diameter is preferably 25% to 40%, more preferably 27% to 35%.

[0017] When the spinel-type lithium manganese oxide of the present invention is used as a positive electrode active material for a lithium secondary battery, a reaction in which hydrogen fluoride contained in small amounts in the electrolyte of the lithium secondary battery is captured by the phosphate proceeds quickly, and as a result, manganese elution caused by the reaction between hydrogen fluoride and the spinel-type lithium manganese oxide is further suppressed, and a decrease in capacity during charge and discharge at high temperatures is further suppressed. For this reason, the phosphorus / manganese molar ratio is preferably 0.0015 or more and 0.1 or less, and more preferably 0.002 or more and 0.05 or less.

[0018] The spinel-type lithium manganese oxide of the present invention, when used as a positive electrode active material for a lithium secondary battery, can provide excellent charge-discharge characteristics at high temperatures, and can also reduce resistance and provide better output characteristics. Therefore, the BET specific surface area of ​​the lithium manganese oxide is 0.8 m. 2 / g or more 5.0m 2 / g or less, and 2 / g or more 4.0m 2 It is more preferable that the saturation coefficient is 1 / g or less.

[0019] When the spinel-type lithium manganese oxide of the present invention is used as a positive electrode active material for a lithium secondary battery, the lithium diffusion distance within the spinel-type lithium manganese oxide particles becomes shorter, making it possible to obtain better output characteristics and further improve the packing ability of the positive electrode mixture. Therefore, the average particle size of the secondary particles is preferably 4 μm or more and 20 μm or less, and more preferably 5 μm or more and 10 μm or less.

[0020] The spinel-type lithium manganese oxide of the present invention has a larger charge-discharge capacity when used as a positive electrode active material for a lithium secondary battery, and can also have better charge-discharge characteristics at high temperatures. For this reason, the SO content is preferably 0.8 wt% or less, and more preferably 0.5 wt% or less.

[0021] The spinel-type lithium manganese oxide of the present invention, when used as a positive electrode active material for a lithium secondary battery, can increase the charge-discharge capacity, improve crystallinity, and provide better charge-discharge characteristics at high temperatures. For this reason, the Na content is preferably 3,000 wtppm or less, more preferably 1,500 wtppm or less, and even more preferably 1,000 wtppm or less.

[0022] Next, the method for producing the spinel-type lithium manganese oxide of the present invention will be described.

[0023] The spinel-type lithium manganese oxide of the present invention can be obtained by preparing a slurry in which a mixture of a manganese compound, a lithium compound, a compound containing the element M according to claim 1, a phosphate compound, and a boron compound is dispersed in a solution, and the slurry has an average particle size of 1 μm or less and is then granulated by spray drying. The slurry is then fired at 700°C to 960°C in air or in a high-oxygen atmosphere (including a pure oxygen atmosphere) and crushed. If the average particle size of the mixture exceeds 1 μm, the pore volume of pores with a pore size of 0.6 μm or less will be 0.003 cm. 3 It tends to be smaller than

[0024] The manganese compound, the lithium compound, the compound containing the element M according to claim 1, the phosphate compound, and the boron compound may all be water-soluble substances.

[0025] There is no particular limitation on the manganese compound, and examples thereof include electrolytic manganese dioxide, Mn3O4, Mn2O3, etc., but are not limited to these.

[0026] There is no particular limitation on the lithium compound, and examples thereof include, but are not limited to, lithium carbonate, lithium hydroxide, lithium nitrate, lithium chloride, lithium iodide, and lithium oxalate.

[0027] There are no particular limitations on the phosphate compound, and examples thereof include lithium phosphates such as 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 are not limited to these.

[0028] The compound containing the element M (Al or Mg) described in claim 1 is not particularly limited, and examples thereof include Al(OH)3, AlOOH, Al2O3, Mg(OH)2, MgO, etc., but are not limited to these.

[0029] The boron compound is not particularly limited, and examples thereof include, but are not limited to, H3BO3, B2O3, Li2O·nB2O3 (n=1 to 5), and the like.

[0030] A slurry in which a mixture of a manganese compound, a lithium compound, a compound containing an element M as defined in claim 1, a phosphate compound, and a boron compound is dispersed has an average particle size of 1 μm or less, preferably 0.3 μm to 0.7 μm. Such an average particle size can be obtained by adding the compounds to a solution and grinding and mixing them. Examples of grinding and mixing devices that can be used include a wet medium stirring mill, a ball mill, and a vibration mill. The manganese compound, the lithium compound, the compound containing an element M as defined in claim 1, a phosphate compound, and a boron compound may be partially or completely dissolved in water.

[0031] The solution to which the compound is added is, for example, pure water, water, etc.

[0032] The slurry obtained by wet milling and mixing is granulated by spray drying, which can be performed using a conventional spray dryer in which the slurry is sprayed with a rotating disk or a fluid nozzle and the droplets are dried with hot air.

[0033] The calcination to obtain the spinel-type lithium manganate of the present invention is carried out in air or in a high-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 700°C to 960°C. At temperatures below 700°C, the pore volume of pores with a pore diameter of 0.6 μm or less in the spinel-type lithium manganate becomes too large, which tends to reduce the density when used as a positive electrode. At temperatures above 960°C, oxygen deficiency in the spinel-type lithium manganate increases, which tends to reduce the charge-discharge cycle performance when used as a positive electrode active material in a lithium secondary battery. Calcination is preferably carried out at a temperature of 750°C to 850°C.

[0034] The spinel-type lithium manganese oxide of the present invention is preferably washed with water to remove boron compounds in order to improve charge-discharge cycle characteristics and reduce resistance. Preferably, the boron compounds are removed by washing with water until the concentration is 100 wtppm or less.

[0035] Since secondary particles of spinel-type lithium manganate tend to agglomerate during firing, it is preferable to crush the material to obtain the desired particle size. Crushing by shear force is preferred as the crushing method, as this further suppresses the generation of fine powder.

[0036] After crushing the spinel-type lithium manganese oxide, it is preferable to pass it through a sieve with an opening size of preferably 200 μm or less, more preferably 150 μm or less, in order to remove coarse particles that exceed the thickness of the positive electrode.

[0037] By using the phosphate-containing spinel-type lithium manganese oxide of the present invention in the positive electrode of a lithium secondary battery, it becomes possible to construct a lithium secondary battery that has excellent charge-discharge cycle characteristics at high temperatures, low resistance, and excellent output characteristics, which have not been possible with conventional batteries.

[0038] The structure of the lithium secondary battery other than the positive electrode is not particularly limited. However, the negative electrode may be made of a material that absorbs and releases Li, such as a carbon-based material, a tin oxide-based material, or Li4Ti5O 12, materials 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

[0039] Next, the present invention will be described with specific examples, but the present invention is not construed as being limited to these examples.

[0040] <Measurement of composition analysis, SO4 content, Na content, boron content> The composition, SO4 content, Na content, and boron content of the spinel-type lithium manganate obtained in the examples and comparative examples were analyzed with an inductively coupled plasma optical emission spectrometer (trade name: ICP-AES, manufactured by PerkinElmer Japan) after dissolving the spinel-type lithium manganate in a hydrochloric acid-hydrogen peroxide mixed aqueous solution.

[0041] <Measurement of pore volume> For the spinel-type lithium manganate obtained in the examples and comparative examples, the pore volume was measured with an automatic mercury porosimeter pore size distribution measuring device (trade name: AutoPore V9600, manufactured by Micromeritics). The mercury intrusion pressure was set to 0.48 - 33,000 psia.

[0042] <Measurement of BET specific surface area> 1.0 g of the sample was placed in a glass cell for BET specific surface area measurement, and dehydration treatment was performed at 150 °C for 30 minutes under a nitrogen stream to remove the moisture adhering to the powder particles.

[0043] The treated sample was measured for the BET specific surface area by the one-point method using a BET measuring device (trade name: Micromeritics DeSorbIII, manufactured by Shimadzu Corporation) with a mixed gas of 30% nitrogen - 70% helium as the adsorption gas.

[0044] <Measurement of the average particle size and relative standard deviation of secondary particle size> The average particle diameter (D 50 ) and the standard deviation of particle size were measured.

[0045] From the measured average particle size and standard deviation of the secondary particles, the relative standard deviation of the secondary particle size was calculated according to the following formula.

[0046] Relative standard deviation (%) = (standard deviation of particle size) / (average particle size) x 100 <Initial capacity measurement, DC resistance measurement> The positive electrode was prepared by mixing 1.0 g of the spinel-type lithium manganese oxide obtained in the Examples and Comparative Examples, 0.032 g of acetylene black (trade name: Denka Black, manufactured by Denka), 0.307 mL of a 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 of spinel-type lithium manganese oxide: acetylene black: polyvinylidene fluoride = 94:3:3) in a planetary centrifugal mixer (trade name: AR-100, manufactured by Thinky). The resulting positive electrode slurry was applied to aluminum foil, dried at 150°C for 30 minutes, and then punched out to a diameter of 15.958 mm. The aluminum foil was then subjected to a pressure of 3 ton / cm. 2 The coated amount of spinel-type lithium manganese oxide was 5 mg / cm. 2 It was made to be like this.

[0047] A Li foil punched to a diameter of 16 mm was used as the negative electrode, and LiPF6 was dissolved at 1 mol / dm in a mixed solvent of ethylene carbonate and dimethyl carbonate (volume ratio 1:2). 3 A CR2032 coin cell was fabricated using the dissolved electrolyte and a separator (product name: Celgard, manufactured by Polypore).

[0048] The fabricated battery was subjected to one cycle of charge and discharge at 24° C. between voltages of 4.3 V and 3.0 V at a current of 0.1 mA, and the discharge capacity was taken as the initial capacity.

[0049] Next, the battery was charged to 50% of the initial capacity, and the DC resistance was measured at 24° C. The DC resistance was measured by charging at a current of 2 mA for 10 seconds, measuring the closed-circuit voltage, then discharging at a current of 0.2 mA for 100 seconds and resting for 1 hour, then charging at a current of 5 mA for 10 seconds, measuring the closed-circuit voltage, then discharging at a current of 0.2 mA for 250 seconds and resting for 1 hour, then charging at a current of 10 mA for 10 seconds, measuring the closed-circuit voltage, then discharging at a current of 0.2 mA for 500 seconds and resting for 1 hour, plotting the closed-circuit voltage against each current value, and the slope was taken as the DC resistance.

[0050] <Charge-discharge cycle test of carbon counter electrode> The positive electrode used was the same as that prepared in the measurement of the initial capacity.

[0051] The negative electrode was prepared by mixing 2.0 g of spherical natural graphite and 2.104 mL of a 10 wt% polyvinylidene fluoride / N-methyl-2-pyrrolidone solution (0.221 g of polyvinylidene fluoride) (weight ratio of graphite to polyvinylidene fluoride = 90:10) in a planetary centrifugal mixer (product name: AR-100, manufactured by Thinky). The resulting negative electrode slurry was applied to copper foil, dried at 150 °C for 30 minutes, and then punched out to a diameter of 16.156 mm. The foil was then subjected to a 3 ton / cm2 punching test. 2 The coated material was uniaxially pressed at 150°C and dried under reduced pressure for 2 hours. The coating amount was 1.8 mg / cm of spherical natural graphite. 2 It was made to be like this.

[0052] The positive and negative electrodes were placed in a mixed solvent of ethylene carbonate and dimethyl carbonate (volume ratio 1:2) with 1 mol / dm LiPF6. 3 A CR2032 coin cell was fabricated using 0.2 mL of the dissolved electrolyte and a separator (product name: Celgard, manufactured by Polypore).

[0053] The fabricated battery was subjected to one cycle of constant-current / constant-voltage charge and discharge at a current of 0.1 mA between cell voltages of 4.25 V and 3.0 V at 24 °C. Next, one cycle of constant-current / constant-voltage charge and discharge at a current of 0.2 mA between cell voltages of 4.25 V and 3.0 V at 24 °C was performed, and the discharge capacity was recorded as the cell capacity. Next, 50 cycles of constant-current / constant-voltage charge and constant-current discharge were performed at a current density of 1 hour discharge rate for the battery capacity between cell voltages of 4.25 V and 3.0 V at 45 °C. The carbon counter electrode charge / discharge cycle retention was calculated from the ratio of the discharge capacity at the 50th cycle to the discharge capacity at the first cycle. The constant-voltage charge was terminated when the charge current decreased to 1 / 10 of that during constant-current charge.

[0054] Example 1 374 g of lithium carbonate, 1533 g of electrolytic manganese dioxide, 73 g of aluminum hydroxide, 15 g of trilithium phosphate, and 3 g of boric acid were added to pure water to prepare 10 L of slurry, which was then ground for 3 hours in a grinder (trade name: Dyno Mill, manufactured by Shinmaru Enterprises). The average particle diameter (D 50 ) was measured using a particle size distribution analyzer (product name: MT3000II series, manufactured by MicrotracBEL) and found to be 0.6 μm. The water in the resulting slurry was evaporated using a spray dryer (manufactured by Okawara Kakoki Co., Ltd.), yielding spherical dried granular particles. Spray drying was carried out at a hot air inlet temperature of 250°C.

[0055] 300 g of the dried granular particles were calcined in a box furnace at 750°C for 6 hours while air was circulated at a rate of 5 L / min, and then cooled to room temperature. The temperature was increased at a rate of 100°C / hr, and decreased at a rate of 20°C / hr from 800°C to 600°C, and 100°C / hr from 600°C to room temperature. Next, pure water was added and the mixture was stirred for 1 hour. After filtration and drying at 150°C, the mixture was crushed in a powerful small crusher (product name: Rotary Crusher, manufactured by Osaka Chemical Co., Ltd.) and passed through a sieve with 150 μm openings to obtain phosphate-containing spinel-type lithium manganese oxide.

[0056] The composition of the obtained phosphate-containing spinel-type lithium manganese oxide was Li 1.10 Mn 1.80 Al 0.10 O4. XRD measurement also revealed that the obtained phosphate-containing spinel-type lithium manganese oxide was a mixed phase of JCPDS No. 35-782 (LiMn2O4) and No. 25-1030 (Li3PO4). The measurement results for the phosphorus / manganese molar ratio, pore volume of pores with a pore diameter of 0.6 μm or less, BET specific surface area, average particle diameter of lithium manganese oxide secondary particles, relative standard deviation of lithium manganese oxide secondary particle diameter, SO4 content, Na content, and B content (hereinafter referred to as "measurement results") are shown in Table 1, and the battery performance is shown in Table 2.

[0057] [Table 1]

[0058] [Table 2]

[0059] The pore size distribution of the phosphate-containing spinel-type lithium manganese oxide is shown in Figure 1.

[0060] Example 2 A phosphate-containing spinel-type lithium manganese oxide was obtained in the same manner as in Example 1, except that the amount of boric acid was 0.6 g and the firing temperature was 900°C.

[0061] The composition of the obtained phosphate-containing spinel-type lithium manganese oxide was Li 1.09 Mn 1.81 Al 0.10 XRD measurements also showed that the resulting phosphate-containing spinel-type lithium manganese oxide was a mixture of JCPDS No. 35-782 (LiMn2O4) and No. 25-1030 (Li3PO4). The measurement results are shown in Table 1, and the battery performance is shown in Table 2.

[0062] Example 3 A phosphate-containing spinel-type lithium manganese oxide was obtained in the same manner as in Example 1, except that the firing temperature was set to 800°C.

[0063] The composition of the obtained phosphate-containing spinel-type lithium manganese oxide was Li 1.10 Mn 1.80 Al 0.10 XRD measurements also showed that the resulting phosphate-containing spinel-type lithium manganese oxide was a mixture of JCPDS No. 35-782 (LiMn2O4) and No. 25-1030 (Li3PO4). The measurement results are shown in Table 1, and the battery performance is shown in Table 2.

[0064] Example 4 A phosphate-containing spinel-type lithium manganese oxide was obtained in the same manner as in Example 1, except that the firing temperature was set to 900°C.

[0065] The composition of the obtained phosphate-containing spinel-type lithium manganese oxide was Li 1.11 Mn 1.79 Al 0.10 XRD measurements also showed that the resulting phosphate-containing spinel-type lithium manganese oxide was a mixture of JCPDS No. 35-782 (LiMn2O4) and No. 25-1030 (Li3PO4). The measurement results are shown in Table 1, and the battery performance is shown in Table 2.

[0066] Example 5 A phosphate-containing spinel-type lithium manganese oxide was obtained in the same manner as in Example 1, except that the amount of trilithium phosphate was 31 g, the amount of boric acid was 1 g, and the firing temperature was 810°C.

[0067] The composition of the obtained phosphate-containing spinel-type lithium manganese oxide was Li 1.09 Mn 1.81 Al 0.10 XRD measurements also showed that the resulting phosphate-containing spinel-type lithium manganese oxide was a mixture of JCPDS No. 35-782 (LiMn2O4) and No. 25-1030 (Li3PO4). The measurement results are shown in Table 1, and the battery performance is shown in Table 2.

[0068] Example 6 A phosphate-containing spinel-type lithium manganate was obtained in the same manner as in Example 5, except that the amount of trilithium phosphate was 46 g.

[0069] The composition of the obtained phosphate-containing spinel-type lithium manganese oxide was Li 1.09 Mn 1.81 Al 0.10 XRD measurements also showed that the resulting phosphate-containing spinel-type lithium manganese oxide was a mixture of JCPDS No. 35-782 (LiMn2O4) and No. 25-1030 (Li3PO4). The measurement results are shown in Table 1, and the battery performance is shown in Table 2.

[0070] Example 7 356 g of lithium carbonate, 1577 g of electrolytic manganese dioxide, 53 g of magnesium hydroxide, 47 g of trilithium phosphate, and 1.7 g of boric acid were added to pure water to prepare 10 L of slurry, which was then pulverized for 3 hours using a pulverizer (trade name: Dyno Mill, manufactured by Shinmaru Enterprises). The average particle diameter (D 50 ) was measured using a particle size distribution analyzer (product name: MT3000II series, manufactured by MicrotracBEL) and found to be 0.6 μm. The water in the resulting slurry was evaporated using a spray dryer (manufactured by Okawara Kakoki Co., Ltd.), yielding spherical dried granular particles. Spray drying was carried out at a hot air inlet temperature of 250°C.

[0071] 300 g of the dried granular particles were fired in a box furnace at 775°C for 6 hours while air was circulated at a rate of 5 L / min, and then cooled to room temperature. The heating rate was 100°C / hr, and the cooling rate was 20°C / hr from 7750°C to 600°C, and 100°C / hr from 600°C to room temperature. Next, pure water was added and stirred for 1 hour. After filtration and drying at 150°C, the mixture was crushed in a powerful small crusher (product name: Rotary Crusher, manufactured by Osaka Chemical Co., Ltd.) and passed through a sieve with 150 μm openings to obtain phosphate-containing spinel-type lithium manganese oxide.

[0072] The composition of the obtained phosphate-containing spinel-type lithium manganese oxide was Li 1.07 Mn 1.83 Mg 0.10 XRD measurements also showed that the resulting phosphate-containing spinel-type lithium manganese oxide was a mixture of JCPDS No. 35-782 (LiMn2O4) and No. 25-1030 (Li3PO4). The measurement results are shown in Table 1, and the battery performance is shown in Table 2.

[0073] Example 8 A phosphate-containing spinel-type lithium manganese oxide was obtained in the same manner as in Example 7, except that the amount of trilithium phosphate was 63 g and the firing temperature was 800°C.

[0074] The composition of the obtained phosphate-containing spinel-type lithium manganese oxide was Li 1.07 Mn 1.83 Mg 0.10 XRD measurements also showed that the resulting phosphate-containing spinel-type lithium manganese oxide was a mixture of JCPDS No. 35-782 (LiMn2O4) and No. 25-1030 (Li3PO4). The measurement results are shown in Table 1, and the battery performance is shown in Table 2.

[0075] Example 9 A phosphate-containing spinel-type lithium manganate was obtained in the same manner as in Example 7, except that the amount of trilithium phosphate was 31 g and the firing temperature was 800°C.

[0076] The composition of the obtained phosphate-containing spinel-type lithium manganese oxide was Li 1.06 Mn 1.84 Mg 0.10 XRD measurements also showed that the resulting phosphate-containing spinel-type lithium manganese oxide was a mixture of JCPDS No. 35-782 (LiMn2O4) and No. 25-1030 (Li3PO4). The measurement results are shown in Table 1, and the battery performance is shown in Table 2.

[0077] Example 10 A phosphate-containing spinel-type lithium manganate was obtained in the same manner as in Example 7, except that the amount of trilithium phosphate was 62 g and the firing temperature was 850°C.

[0078] The composition of the obtained phosphate-containing spinel-type lithium manganese oxide was Li 1.07 Mn 1.80 Mg 0.10 XRD measurements also showed that the resulting phosphate-containing spinel-type lithium manganese oxide was a mixture of JCPDS No. 35-782 (LiMn2O4) and No. 25-1030 (Li3PO4). The measurement results are shown in Table 1, and the battery performance is shown in Table 2.

[0079] Example 11 A phosphate-containing spinel-type lithium manganese oxide was obtained in the same manner as in Example 7, except that the amount of trilithium phosphate was 62 g, the amount of boric acid was 2.8 g, and the firing temperature was 850°C.

[0080] The composition of the obtained phosphate-containing spinel-type lithium manganese oxide was Li 1.06 Mn 1.84 Mg 0.10 XRD measurements also showed that the resulting phosphate-containing spinel-type lithium manganese oxide was a mixture of JCPDS No. 35-782 (LiMn2O4) and No. 25-1030 (Li3PO4). The measurement results are shown in Table 1, and the battery performance is shown in Table 2.

[0081] Comparative Example 1 A spinel-type lithium manganese oxide was obtained in the same manner as in Example 3, except that trilithium phosphate was not added.

[0082] The composition of the obtained spinel-type lithium manganese oxide was Li 1.10 Mn 1.80 Al 0.10 XRD measurements also showed that the resulting spinel-type lithium manganese oxide was a single phase JCPDS No. 35-782 (LiMn2O4). The measurement results are shown in Table 1, and the battery performance is shown in Table 2.

[0083] Comparative Example 2 300 g of electrolytic manganese dioxide (average particle size: 3 μm), 71 g of lithium carbonate (average particle size: 3 μm), 6 g of magnesium hydroxide (average particle size: 2 μm), and 3 g of trilithium phosphate (average particle size: 3 μm) were dry-mixed, and then fired in a box furnace at 930°C for 6 hours while circulating air at a rate of 5 L / min. The mixture was 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. The mixture was then crushed in a powerful small crusher (product name: Rotary Crusher, manufactured by Osaka Chemical Co., Ltd.) and passed through a 32 μm mesh sieve to obtain a phosphate-containing spinel-type lithium manganese oxide.

[0084] The composition of the obtained phosphate-containing spinel-type lithium manganese oxide was Li 1.12 Mn 1.82 Mg 0.06 XRD measurements also showed that the resulting phosphate-containing spinel-type lithium manganese oxide was a mixture of JCPDS No. 35-782 (LiMn2O4) and No. 25-1030 (Li3PO4). The measurement results are shown in Table 1, and the battery performance is shown in Table 2. [Industrial Applicability]

[0085] The phosphate-containing spinel-type lithium manganese oxide of the present invention has pores with a certain pore volume and a secondary particle size, and therefore has excellent charge-discharge characteristics at high temperatures, particularly carbon counter electrode charge-discharge characteristics, and can be used as a positive electrode active material for lithium secondary batteries with excellent output characteristics.

Claims

1. Contains phosphate and has the chemical formula Li １＋Ｘ Mn ２－Ｘ－Ｙ M Ｙ O ４ (wherein 0.02≦X≦0.20, 0.05≦Y≦0.30, and M is Al or Mg), and the pore volume of pores with a pore diameter of 0.6 μm or less is 0.003 cm ３ / g or more 0.2cm ３ / g or less, and the relative standard deviation of the secondary particle diameter is 25% or more and 45% or less.

2. 2. The spinel-type lithium manganate according to claim 1, wherein the phosphorus / manganese molar ratio is 0.0015 or more and 0.1 or less.

3. BET specific surface area is 0.8m ２ / g or more 5.0m ２ 3. The spinel-type lithium manganese oxide according to claim 1, wherein the SiO2 content is 0.15 / g or less.

4. 4. The spinel-type lithium manganese oxide according to claim 1, wherein the average particle size of the secondary particles is 4 μm or more and 20 μm or less.

5. SO ４ 5. The spinel-type lithium manganese oxide according to claim 1, wherein the content of

6. 6. The spinel-type lithium manganese oxide according to claim 1, wherein the Na content is 3,000 wtppm or less.

7. 7. The spinel-type lithium manganese oxide according to claim 1, wherein the boron content is 100 wtppm or less.

8. 8. The spinel-type lithium manganese oxide according to claim 1, wherein a direct current resistance in a 50% charged state is 25 Ω or less when used in a CR2032 coin cell with a Li counter electrode.

9. 9. The method for producing a spinel-type lithium manganate according to claim 1, comprising the steps of: adding a manganese compound, a lithium compound, a compound containing the element M according to claim 1, a phosphate compound, and a boron compound to a solution to prepare a slurry in which a mixture of these is dispersed; granulating the slurry by spray drying, the slurry having an average particle size of 1 μm or less, and then firing the slurry at 700° C. or higher and 960° C. or lower in the air or in a high-oxygen atmosphere (including a pure oxygen atmosphere), followed by pulverizing the granulated slurry.

10. 10. The method for producing a spinel-type lithium manganese oxide according to claim 9, wherein after the calcination, boron is removed by washing with water to a concentration of 100 wtppm or less.

11. An electrode comprising the spinel-type lithium manganese oxide according to any one of claims 1 to 8.

12. A lithium secondary battery using the electrode according to claim 11 as a positive electrode.

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