JP2004259700A - Lithium secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-performance lithium secondary battery which is applicable to a portable equipment or an electric automobile. <P>SOLUTION: A spinel type oxide Li<SB>1+x</SB>Mn<SB>2-x</SB>O<SB>4</SB>(0<x<1.33) is added with at least one kind of xenogenic element other than Li, Mn, or oxygen, which is used as an active material. The xenogenic element includes B, P, Mg, As, Sb, Zr, Na, Be, Y, Si, Al, C, F, Bi, Pb, Ge, Sn, or the like, and the amount of addition is prefered to be 0.01-10 % to the total amount of Mn in mol ratio. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to an active material for a lithium secondary battery using a non-aqueous electrolyte, and a lithium ion secondary battery.

  With the development of the information society, the spread of personal computers, mobile phones, etc. is expected to increase in the future, but with this, the batteries, which are the power sources of portable devices, have been increasing in energy density and capacity. Is required. A lithium secondary battery using a non-aqueous electrolyte has a high battery voltage and a high energy density, and therefore has been actively developed, and some batteries have been put to practical use. However, the Mn-based spinel material currently used as a positive electrode material has some problems in practical use.

  The first is the degradation of cycle life. The spinel-type oxide has a Jahn-Teller instability due to trivalent manganese ions, so that its capacity is significantly deteriorated when charge and discharge are repeated. Secondly, there is a problem of elution, in which Mn starts to dissolve in the electrolytic solution, resulting in deterioration of performance. Third, there is a safety problem that the positive electrode generates heat or ignites in the event of a short circuit or crush.

  These are all problems that can be solved by increasing the structural stability of the positive electrode active material. These problems have been difficult to solve with conventional cathode materials, but some attempts have already been reported.

According to Japanese Patent Application Laid-Open No. Hei 6-187933 by Technology Finance, a spinel oxide Li _{1 + x} Mn _2-x O ₄ (0 ≦ x <1.33) in which the composition ratio of Li and Mn is changed is used as an active material. By using this, the cycle life is improved and elution is prevented. Also, the same thing is attempted by substituting Co for Co instead of Mn. However, such a method has a problem that the initial capacity itself is also reduced.

According to Mori Energy's published patent (Japanese Patent Application No. Hei 9-147767), in a spinel oxide in which the composition ratio of Li to Mn is increased, Li _{1 in} which Mn is further substituted with a transition metal element such as Co or Cr is used. _{+ x M z Mn 2-xz} O 4 (0 ≦ x <0.33, M:. Co, transition metal elements such as Cr), and by using as the positive electrode active material, thereby improving the cycle life characteristics However, a life of 1000 cycles or more required for practical use has not been obtained.

  As described above, conventionally, various methods have been used to stabilize the crystal structure of the positive electrode material, thereby prolonging the life of the battery, preventing elution, and improving safety. However, prolonging the service life reduces the battery capacity, and conversely, increasing the capacity causes a problem in safety, and generates heat or fire when an internal short circuit occurs. was there. The present invention provides a spinel-type oxide positive electrode active material and a method for producing the same to supply a safe, high-capacity battery with a long life.

In order to achieve the object of the present invention, an oxide having a spinel structure defined by a chemical formula of Li _{1 + x} Mn _2-x O ₄ (0 <x <1.33) except for Li, Mn, and oxygen And a positive electrode material to which at least one or more elements are added. The composition ratio of Li and Mn is Li /
If it is called the Mn ratio, increasing the Li / Mn ratio acts to reduce the lattice constant, thereby stabilizing the crystal structure.

  This acts to improve cycle characteristics and prevent elution, and has the effect of improving battery life characteristics. However, increasing the Li / Mn ratio leads to a decrease in the theoretical capacity, and the actual initial capacity cannot be avoided. In an actual battery, the capacity of the battery is determined by the capacity of the positive electrode material, and a decrease in the capacity of the positive electrode material is not preferable.

In the present invention, the spinel-type Mn oxide cathode material defined by the above composition formula Li _{1 + x} Mn _2-x O ₄ (0 <x <1.33) contains at least one or more types other than Li, Mn, and oxygen. A material to which an element is added is used. As elements to be added, B, P, Mg, As, Sb, Zr,
It is desirable to add at least one element of Na, Be, Y, Si, Al, C, F, Bi, Pb, Ge, and Sn, and the addition amount is based on the total amount of Mn contained in the positive electrode material. The molar ratio is preferably from 0.01% to 10%, but it does not matter if it is added more or less.

In particular, the addition of B, P, and Sb can increase the capacity without changing the crystal structure, that is, maintaining stability and without impairing the life characteristics. Further, from the viewpoint of enhancing safety, substitution of Al, Si, Ga, and Mg is effective. The most suitable composition ratio of the material to be added is 0.02 <x <0.14 in the composition formula of Li _{1 + x} Mn _2-x O ₄ .

The method for producing the positive electrode material according to the present invention is as follows. First, a Mn-based spinel oxide serving as a base material is prepared. For this purpose, Li ₂ CO ₃ , LiOH, LiNO ₃ , LiCOOH, Li ₂ O or the like is used as a lithium raw material, and MnO ₂ (electrolytic manganese dioxide (EMD)) is used as a manganese raw material. Manganese dioxide (CMD) may be used.), Mn ₃ O ₄ , Mn ₂ O ₃ , MnO, MnCO ₃ , MnCOOH, MnOOH, etc. are used.

  These are mixed at a predetermined composition ratio, or mixed in a solution and then precipitated and dried, and used as a raw material. The raw material is calcined for 40 hours in air or an oxygen stream. The firing temperature at this time is preferably in the range of about 600 ° C. to 900 ° C., although it depends on the composition ratio. To add the additive, a predetermined amount is later heat-treated to the obtained base material. The temperature of the heat treatment is preferably from 400 ° C to 900 ° C. Of course, the effect of addition can be obtained without heat treatment, but more preferably, heat treatment is performed.

In order to solve this problem, the following positive electrode material is used. The active _{material, Li 1 + x M y Mn} 2-xy O 4 (0 <x <1.33,0 <y <2, M: differ by at least one or more transition metals and Mn) defined by comprising the formula It is obtained by adding at least one or more elements other than the above-mentioned Li, Mn, oxygen and the transition metal element M to the oxide having a spinel structure. The added element is desirably at least one of B, P, Mg, As, Sb, Zr, Na, Be, Y, Si, Al, C, F, Bi, Pb, Ge, and Sn.

In order to solve the _{problem, Li 1 + x M y Mn} 2-xyz B z O 4 (0 <x <1.33,0 <y + z <2, M: different at least one or more of the Mn An oxide having a spinel structure defined by the chemical formula (transition metal), wherein the element B that substitutes for Mn is at least one or more elements different from Li, Mn, oxygen, and the transition metal M. Active material for a secondary battery, and a lithium secondary battery using the same. B is preferably a transition metal element different from the transition metal element M, for example, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, or Zn, and typical elements Al, Ga, In, Sn, Pb And so on. Further, alkaline earth metals such as Mg, Sr, and Ca may be used.

  In the present invention, in order to solve the problem, at least one element other than Li, Mn, oxygen, a transition metal element M, and a substitution element B is added using the positive electrode material as a base material. . The added element is desirably at least one of B, P, Mg, As, Sb, Zr, Na, Be, Y, Si, Al, C, F, Bi, Pb, Ge, and Sn. In order to use it as a positive electrode material, it is desirable to perform a heat treatment at a temperature between 400 ° C. and 900 ° C. after the addition.

In order to solve this _{problem, (Li, A) 1 +} x M y Mn 2-xyz B z O 4 (0 <x <1.33,0 <y + z <2, M: at least one different from the Mn The positive electrode active material having a spinel structure defined by the chemical formula of the above transition metal and at least one or more elements different from A: Li) is used. Here, (Li, A) indicates that both Li and the element A are included. The element B for substituting Mn is at least one or more elements different from Li, Mn and the transition metal M, and the substituting element A is desirably Mg, Zn, Fe, Cu, Ni. Further, a positive electrode material can be obtained by adding another element to the active material.

  In order to solve the problem, the lattice constant of these spinel oxides is set to be larger than 8.10 angstroms and smaller than 8.25 angstroms. As described above, by selecting a substance having a small lattice constant as the positive electrode material, the cycle characteristics can be improved. This can be achieved by selecting an element having a small ionic radius as a substitution element, or by reducing the cooling rate after firing as much as possible. The cooling rate is desirably 3 ° C./min or less. Also, firing in an oxygen stream has the same effect.

  The following method is used to form a positive electrode for a secondary battery using the positive electrode active material according to the present invention. First, the positive electrode active material is kneaded with carbon as a conductive material. Next, a resin binder is added as a binder to the mixture, and the mixture is further kneaded, applied to an electrode substrate, and press-dried. As the negative electrode, an amorphous carbon material, a graphite carbon material, or the like is preferable.

Even if these negative electrode materials are electrode active materials other than those described above, they do not affect the object of the invention. For example, tin oxide can be used. In addition, as the electrode material, an organic electrolyte in which a lithium salt selected from, for example, LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiPF _6, or the like is dissolved in a nonaqueous solvent such as propylene carbonate, a propylene carbonate derivative, ethylene carbonate, or the like. An electrolyte such as a liquid electrolyte or a solid electrolyte having lithium ion conductivity or a gel electrolyte can be used.

  Further, even if a microporous separator is used according to the necessity in the structure of the battery, the effect of the present invention is not impaired at all. The produced positive electrode, negative electrode and separator are wound around a center pin and inserted into a cylindrical or rectangular container, and then sealed by injecting an electrolytic solution.

  The use of the battery of the present invention is not particularly limited. The use described in claim 11 is a typical one, but other examples include a notebook personal computer, a pen input personal computer, a pocket personal computer, a notebook type word processor, a pocket word processor, an electronic book player, a mobile phone, and a cordless phone handset. , Pager, handy terminal, portable copy, electronic organizer, calculator, LCD TV, electric shaver, power tool, electronic translator, car phone, transceiver, voice input device, memory card, backup power supply, tape recorder, radio, headphone stereo, Power supplies for devices such as portable printers, handy cleaners, portable CDs, video movies, and navigation systems, as well as refrigerators, air conditioners, televisions, stereos, water heaters, oven microwaves, dishwashers, washing machines, dryers, game machines, and lighting. Equipment, toys , It can be used for load conditioner, medical equipment, electric vehicles, golf cart, as a power source for electric carts. In addition to these consumer products, it can also be used for large power storage systems, munitions, and space.

  That is, it functions as a positive electrode active material.

  According to the present invention, a high-capacity, long-life active material for a secondary battery can be obtained, and thereby a high-capacity, high-safety, long-life battery and assembled battery applicable to a portable device or an electric vehicle can be provided.

  Hereinafter, the present invention will be described with reference to examples. Note that the present invention is not limited to the embodiments described below.

(Example 1)
First, Li _{1 + x} Mn _2-x O ₄ as a base material was produced. The manufacturing method is as follows. First, lithium carbonate and electrolytic manganese dioxide (EMD) are mixed at a predetermined molar ratio. After that, firing is performed at a firing temperature of 650 to 900 ° C. for about 10 to 40 hours. The atmosphere does this in a stream of air or oxygen. An additive element was added to the obtained base material (x = 0.08 in this example). As a raw material for adding the additional element, boric acid, a phosphate, and other oxides are used. The ratio of addition was 0.25% with respect to the number of moles of Mn in the active material.

The mixed base material and the added material were heat-treated in air at a temperature of 300 ° C. to 600 ° C. for 10 hours. In the present embodiment, the positive electrode was classified by a sieve having a mesh diameter of 45 microns, kneaded together with a binder and a conductive material, applied on an aluminum foil, pressed and dried. A charge / discharge test was performed using a non-aqueous electrolyte containing LiPF ₆ . Table 1 shows the effects of the initial capacity, the capacity retention rate after 100 cycles, and the added elements.

  It can be seen that these additional elements act to stabilize the crystal structure, which is effective for improving cycle characteristics, suppressing elution, and improving safety for preventing exothermic ignition.

(Example 2)
Another embodiment of the present invention will be described below. As a base material,
Li _{1 + x} Co _y Mn _2-xyz Mg _z O ₄ (x = 0.10, y = 0.10, z = 0.15) was produced. Further, B, P, Bi, and Pb were added thereto. The proportion of addition was 0.25% with respect to the number of moles of Mn in the active material as in Example 1. The heat treatment temperature after addition is
Heat treatment was performed at 400 ° C. for 10 hours. FIG. 1 shows the cycle characteristics. In each of these cases, an improvement in capacity has been observed. Also, no deterioration in cycle characteristics is observed as compared with the non-added material.

(Example 3)
Further, FIG. 2 shows the result of examining the rate dependence of discharge characteristics using the positive electrode material according to the present invention as an active material. As a comparative example, a case where an unadded positive electrode material is used is shown. The composition formula of the additive-free material is Li _{1 + x} Mn _2-x O ₄ (x = 0.08). In the case of a spinel-type positive electrode material to which no additive is added, the capacity increases as the discharge rate (1C means charging in one hour; 2C means 0.5 hours until fully charged). It can be seen that the material deteriorates, but the material to which Sn and In are added shows little deterioration of the capacity. The addition ratio was 0.25% based on the number of moles of Mn in the active material as in Example 1. The effect of these additives is to enhance the electron conductivity of the positive electrode active material, thereby preventing the particles of the active material from being charged up during high-speed charging and discharging.

FIG. 4 is a cycle characteristic diagram of a secondary battery according to the present invention. FIG. 4 is a characteristic diagram showing a relationship between a discharge capacity and a discharge rate of the secondary battery according to the present invention.

Explanation of reference numerals

1: Cycle characteristics when boron is added to active Li _{1 + x} Co _y Mn _2-xyz Mg _z O ₄ (x = 0.10, y = 0.10, z = 0.15), 2 ... Li _{1 + x} Co _y Mn _2-xyz Mg _z O ₄ (x =
0.10, y = 0.10, z = 0.15) and the cycle characteristics when phosphorus is added, 3 ...
Li _{1 + x} Co _y Mn _2-xyz Mg _z O ₄ (x = 0.10, y = 0.10, z = 0.15) cycle characteristics when bismuth is added, 4 ... Li _{1 + x} Co _{y Mn 2-xyz Mg z O} 4 (x = 0.10, y = 0.10, z = 0.15) cycle characteristics when added _{lead, 5 ... Li 1 + x Mn} 2-x O 4 (X = 0.08, y = 0.10, z = 0.15) rate characteristics when tin is added, 6... Li _{1 + x} Mn _2-x O ₄ (x = 0.08, y = Rate characteristics when indium is added to 0.10, z = 0.15), 7: Rate characteristics of active Li _{1 + x} Mn _2-x O ₄ (x = 0.08) without addition of additives.

Claims (11)

An active material for producing a chargeable / dischargeable secondary battery by insertion of lithium ions, defined by a chemical formula of Li _{1 + x} Mn _2-x O ₄ (0 <x <1.33). Characterized in that at least one element other than Li, Mn and oxygen is added to the oxide having a spinel structure in a molar ratio of 0.01% to 10% with respect to the total amount of Mn. A rechargeable lithium battery using a substance material and the substance as a positive electrode material. An active material for producing a chargeable / dischargeable secondary battery by insertion of lithium ions, defined by a chemical formula of Li _{1 + x} Mn _2-x O ₄ (0 <x <1.33). B, P, Mg, As, Sb, Zr, Na, Be, Y, Si, Al, from 0.01% to 10% by mole ratio based on the total amount of Mn in the oxide having a spinel structure. An active material, wherein at least one of C, F, Bi, Pb, Ge, and Sn is added, and a lithium secondary battery using the material as a positive electrode material. An active material for producing a chargeable / dischargeable secondary battery by insertion of lithium ions, defined by a chemical formula of Li _{1 + x} Mn _2-x O ₄ (0 <x <1.33). At least one element other than Li, Mn, and oxygen is added to the oxide having a spinel structure from 0.01% to 10% by mole ratio based on the total amount of Mn. An active material for a secondary battery, which is obtained by heat treatment at a temperature of ° C., and a method for producing the same. By lithium ions insertion, and an active material for making a rechargeable secondary _{battery, Li 1 + x M y Mn} 2-xy O 4 (0 <x <1.33,0 < y <2, M:
At least one or more elements other than Li, Mn, oxygen and the transition metal element M are added to an oxide having a spinel structure defined by a chemical formula of at least one or more transition metals different from Mn. An active material for a secondary battery, which is obtained by adding from 0.01% to 10% by mole ratio to a lithium secondary battery and a lithium secondary battery using the same.   In claim 4, the at least one additional element different from Li and the metal element M is B, P, Mg, As, Sb, Zr, Na, Be, Y, Si, Al, C, F. , Bi, Pb, Ge, Sn, and at least one active material for a secondary battery and a lithium secondary battery using the same. By lithium ions insertion, and an active material for making a rechargeable secondary _{battery, Li 1 + x M y Mn} 2-xyz B z O 4 (0 <x <1.33,0 < y + z <2, M: at least one transition metal different from Mn) is an oxide having a spinel structure defined by a chemical formula, wherein the element B that substitutes for Mn is Li, Mn, oxygen, and a transition metal. A secondary battery active material comprising at least one element different from M and a lithium secondary battery using the same.   At least one element other than Li, Mn, oxygen, transition metal element M, and substitution element B is added to the active material of claim 6 in a molar ratio of 0.01% to 10% based on the total amount of Mn. % Of the active material for a secondary battery, and a lithium secondary battery using the same. By lithium ions insertion, and an active material for making a rechargeable secondary _{battery, (Li, A) 1 +} x M y Mn 2-xyz B z O 4 (0 <x < 1.33, 0 <y + z <2, M: at least one or more transition metals different from Mn, A: at least one or more elements different from Li. (Li, A) means that Li and element A are An oxide having a spinel structure defined by the chemical formula: wherein the element B for substituting Mn is at least one or more elements different from Li, Mn and the transition metal M; An active material for a secondary battery, wherein the substitution element A is Mg, Zn, Fe, Cu, Ni, and a lithium secondary battery using the same.   The active material according to claim 6, wherein at least one element different from Li, Mn, oxygen, transition metal element M, and substitution elements A and B is used in a molar ratio of 0.01% to 10% with respect to the total amount of Mn. % Of the active material for a secondary battery, and a lithium secondary battery using the same. 10. A spinel-type oxide as defined in claim 1 for producing a secondary battery capable of being charged and discharged by insertion of lithium ions, wherein the lattice constant is larger than 8.10 angstroms. An active material for a secondary battery, which is smaller than 25 angstroms, and a lithium secondary battery using the same. 10. A portable information communication device, a portable video, a personal computer household appliance, a power source, wherein a lithium secondary battery using the active material for a secondary battery according to claim 1 is used as a power source. Power storage system and electric vehicle.

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