JP6376410B2 - Method for producing positive electrode active material for non-aqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery.

  Non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries (lithium secondary batteries) are lighter and have higher energy density than existing batteries. It is used as a power source. In particular, lithium ion secondary batteries are lightweight and provide high energy density, so they will be used as high-output power sources for driving vehicles such as electric vehicles (EV), hybrid vehicles (HV), and plug-in hybrid vehicles (PHV). It is expected to become increasingly popular.

  One of the factors that determine the performance of the nonaqueous electrolyte secondary battery is a positive electrode active material. The positive electrode active material is a material that reversibly occludes and releases charge carriers such as lithium ions in the positive electrode of the nonaqueous electrolyte secondary battery.

As one of the compounds used for the positive electrode active material, there is a lithium / nickel / cobalt / manganese composite oxide (hereinafter also referred to as “NCM lithium composite oxide”). The positive electrode active material is desired to have high stability. As a highly stable NCM lithium composite oxide, for example, an NCM lithium composite oxide in which a different metal element such as tungsten, molybdenum, zirconium or the like is added and oxygen is partially substituted with fluorine as represented by the following formula Is known (see, for example, Patent Document 1).
(Chemical formula 1)
_{Li (1 + a) Co (} 1-x-y-z) Ni x Mn y M z O (2-b) F c
(In Formula 1, M is at least 1 selected from the group consisting of magnesium, aluminum, boron, titanium, vanadium, chromium, iron, copper, zinc, molybdenum, tin, tungsten, zirconium, yttrium, niobium, calcium, and strontium. X, y, and z are values in the range of 0 <x <1, 0 <y <1, 0 <z ≦ 0.10, and a, b, and c are each −0. (The values are within the range of 10 ≦ a ≦ 0.10, −0.10 ≦ b ≦ 0.20, and 0 <c ≦ 0.10.)

  Such an NCM lithium composite oxide in which a dissimilar metal element is added and a part of oxygen is substituted with fluorine is usually a hydroxide or oxide containing a metal other than lithium and lithium fluoride. Manufactured by firing.

JP 2007-048711 A

  However, as a result of examination by the present inventors, when an NCM lithium composite oxide in which a dissimilar metal element is added and part of oxygen is substituted with fluorine is used as a positive electrode active material for a nonaqueous electrolyte secondary battery, It was found that during use of the non-aqueous electrolyte secondary battery, a foreign metal may be eluted from the positive electrode and deposited on the negative electrode due to a reaction at the interface between the positive electrode active material and the non-aqueous electrolyte. It has been found that when different metals are deposited on the negative electrode, lithium is likely to deposit on the negative electrode, which can lead to a decrease in battery capacity and an increase in internal resistance.

  Therefore, the present invention provides a positive electrode active material for a non-aqueous electrolyte secondary battery, which is an NCM lithium composite oxide in which a dissimilar metal element is added and a part of oxygen is substituted with fluorine. It is an object of the present invention to provide a method capable of producing a positive electrode active material in which the dissimilar metal element is hardly eluted when used.

The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery disclosed herein comprises a compound containing at least one metal X atom selected from the group consisting of molybdenum, zirconium, and tungsten, and lithium fluoride. The metal X atoms and the lithium atoms are mixed in an alkaline aqueous solution so that the ratio of the metal X atoms to the total of the metal X atoms and lithium atoms is 0.1 to 0.5 mol%. A step of obtaining a coprecipitate containing fluorine atoms, and calcining the obtained coprecipitate and a nickel / cobalt / manganese composite hydroxide, whereby lithium atoms containing the metal X atom and the fluorine atom are obtained. And obtaining a nickel-cobalt-manganese composite oxide.
According to such a configuration, in the NCM lithium composite oxide in which the obtained different metal X is added and a part of oxygen is substituted with fluorine, the bond strength between the metal X atom and the fluorine atom or oxygen atom Becomes higher. Therefore, when the NCM lithium composite oxide is used as a positive electrode active material for a non-aqueous electrolyte secondary battery, the different metal X is less likely to elute from the positive electrode active material when the non-aqueous electrolyte secondary battery is used. Therefore, the dissimilar metal X is hardly deposited on the negative electrode, and a decrease in battery capacity and an increase in internal resistance can be suppressed.

It is a flowchart which shows the outline of the manufacturing method of the positive electrode active material for nonaqueous electrolyte secondary batteries which concerns on one Embodiment of this invention. It is sectional drawing which shows typically the structure of the lithium ion secondary battery constructed | assembled using the positive electrode active material for nonaqueous electrolyte secondary batteries obtained by the manufacturing method which concerns on one Embodiment of this invention. It is a schematic diagram which shows the structure of the winding electrode body of the lithium ion secondary battery constructed | assembled using the positive electrode active material for nonaqueous electrolyte secondary batteries obtained by the manufacturing method which concerns on one Embodiment of this invention.

  Embodiments according to the present invention will be described below with reference to the drawings. Note that matters other than the matters specifically mentioned in the present specification and necessary for the implementation of the present invention (for example, a general configuration of a positive electrode active material for a non-aqueous electrolyte secondary battery that does not characterize the present invention) And manufacturing process) can be understood as a design matter of a person skilled in the art based on the prior art in the field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field. Moreover, in the following drawings, the same code | symbol is attached | subjected and demonstrated to the member and site | part which show | plays the same effect | action. In addition, the dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect actual dimensional relationships.

  In FIG. 1, the outline of the manufacturing method of the positive electrode active material for nonaqueous electrolyte secondary batteries which concerns on this embodiment is shown. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to the present embodiment includes at least one metal X atom selected from the group consisting of molybdenum, zirconium, and tungsten (hereinafter also referred to as “metal atom X”). .) Is mixed with lithium fluoride (LiF) in an alkaline aqueous solution so that the ratio of the metal atom X to the total of the metal atom X and the lithium atom is 0.1 to 0.5 mol%. The step of obtaining a coprecipitate containing metal atom X, lithium atom and fluorine atom (hereinafter also referred to as “first step”), the obtained coprecipitate, and nickel / cobalt / manganese composite water By baking an oxide (hereinafter also referred to as “NCM composite hydroxide”), a lithium / nickel / cobalt / manganese composite oxide containing metal atoms X and fluorine atoms (hereinafter referred to as “F containing”). NCM-X lithium composite oxide "as referred to.) The step of obtaining (hereinafter, also referred to as" second step ".) Including the.

First, the first step will be described. As the compound containing at least one metal X atom selected from the group consisting of molybdenum, zirconium, and tungsten, a water-soluble compound is usually used.
As the compound containing molybdenum, molybdate such as sodium molybdate and potassium molybdate can be preferably used.
As the compound containing zirconium, zirconium sulfate or the like can be preferably used.
As the compound containing tungsten, tungstates such as sodium tungstate and potassium tungstate can be suitably used.

  As a method of mixing a compound containing a metal atom X and lithium fluoride in an alkaline aqueous solution, for example, a mixed aqueous solution containing a compound containing a metal atom X and lithium fluoride is prepared, and the mixed aqueous solution is stirred with pH. Are added to an alkaline aqueous solution of 11 to 14; an aqueous solution of a compound containing a metal atom X and an aqueous solution of lithium fluoride are prepared, and these aqueous solutions are added to an alkaline aqueous solution having a pH of 11 to 14 with stirring. And the like.

  As the alkaline aqueous solution, for example, an aqueous solution containing one or more of lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium carbonate, potassium carbonate, lithium carbonate, ammonium carbonate, ammonium nitrate, ammonia and the like can be used. Of these, it is preferable to use a mixed aqueous solution of sodium hydroxide and ammonia.

  The compound containing metal atom X and lithium fluoride are mixed in an alkaline aqueous solution so that the ratio of metal atom X to the total of metal atom X and lithium atom is 0.1 to 0.5 mol%. When the ratio is less than 0.1 mol%, the effect of stabilizing the positive electrode active material by the metal atom X cannot be sufficiently obtained. On the other hand, when the ratio is more than 0.5 mol%, the stability of the positive electrode active material when lithium is released in the nonaqueous electrolyte secondary battery is impaired.

  By the mixing operation in the alkaline aqueous solution, a coprecipitate containing metal atoms X, lithium atoms, and fluorine atoms is obtained. The coprecipitate can be recovered by filtration after washing with water. The recovered coprecipitate may be dried at a temperature of, for example, about 120 ° C. with a known drying device (eg, hot air dryer).

  The coprecipitate obtained here is an oxide containing a metal atom X, a lithium atom and a fluorine atom, a compound which is converted into an oxide containing a metal atom X, a lithium atom and a fluorine atom by firing, or a metal atom X And a mixture of an oxide containing lithium atom and fluorine atom and a compound converted into an oxide containing metal atom X, lithium atom and fluorine atom by firing.

  Next, the second step will be described. In the second step, the obtained coprecipitate and the NCM composite hydroxide are fired to obtain an F-containing NCM-X lithium composite oxide that is a positive electrode active material for a non-aqueous electrolyte secondary battery.

The content ratio of nickel, cobalt, and manganese contained in the NCM composite hydroxide may be the same as the content ratio of nickel, cobalt, and manganese in the known F-containing NCM-X lithium composite oxide. For _{example, Ni q Co r Mn s (} OH) 2 ( wherein, q, r, and s is an value satisfying q + r + s = 1,0 < q <1,0 <r <1,0 <s <1 NCM composite hydroxide represented by: 0.1 <q <0.9, 0.1 <r <0.4, 0.1 <s <0.4. be able to.

  The NCM composite hydroxide can be produced, for example, by a known crystallization method. Specifically, for example, a mixed aqueous solution in which a water-soluble nickel salt, a water-soluble cobalt salt, and a water-soluble manganese salt are dissolved, or a solution obtained by adding an aqueous solution containing an ammonium ion supplier to this mixed aqueous solution, In order to control the pH value in the reaction tank within a predetermined range while supplying it to the reaction tank with stirring, NCM composite hydroxide is crystallized by supplying a predetermined amount of aqueous sodium hydroxide solution. Can do.

  In the firing, the obtained coprecipitate and the NCM composite hydroxide are mixed. Mixing can be performed according to a known method using a known mixing apparatus (eg, shaker mixer, V blender, ribbon mixer, Julia mixer, Laedige mixer, etc.).

  Firing can be performed using, for example, a batch-type electric furnace or a continuous electric furnace. The firing conditions are not particularly limited as long as the desired F-containing NCM-X lithium composite oxide can be obtained. Usually, firing is performed in an oxidizing atmosphere (particularly in an air atmosphere). The firing temperature is usually 700 ° C to 1000 ° C. The firing time is usually 1 hour to 24 hours. Preferably, the firing is performed at 800 ° C. in the atmosphere.

By the firing, an F-containing NCM-X lithium composite oxide that is a positive electrode active material of the nonaqueous electrolyte secondary battery is obtained. Conventionally, the F-containing NCM-X lithium composite oxide has been manufactured by firing a hydroxide or oxide containing a metal other than lithium and lithium fluoride. When the F-containing NCM-X lithium composite oxide is produced by such a method, the reaction between lithium fluoride and a hydroxide or oxide tends to be uneven. Therefore, the metal X is not easily dissolved, and the metal X is likely to be present at the grain boundary in the F-containing NCM-X lithium composite oxide. In such an F-containing NCM-X lithium composite oxide, the metal X is likely to be eluted and the structure is likely to deteriorate. Therefore, in a non-aqueous electrolyte secondary battery using such an F-containing NCM-X lithium composite oxide as a positive electrode active material, performance such as a decrease in capacity or an increase in internal resistance is likely to occur during use.
However, when the F-containing NCM-X lithium composite oxide is manufactured by the manufacturing method according to the present embodiment, the coprecipitate containing the metal atom X, the lithium atom, and the fluorine atom and the NCM composite hydroxide are fired. By doing so, when lithium diffuses into the solid phase, the metal X also diffuses in the same manner, and the metal X is liable to be dissolved. As a result, in the obtained F-containing NCM-X lithium composite oxide, the bond strength between the metal atom X and the fluorine atom or oxygen atom is increased (for example, 500 to 700 kJ / mol between the metal atom X and the fluorine atom). Bond strength). Therefore, if the F-containing NCM-X lithium composite oxide is used as a positive electrode active material for a non-aqueous electrolyte secondary battery, the metal X is less likely to elute from the positive electrode active material when the non-aqueous electrolyte secondary battery is used. . Therefore, it becomes difficult for the metal X to be deposited on the negative electrode, and a decrease in battery capacity and an increase in internal resistance can be suppressed.

  The nonaqueous electrolyte secondary battery using the positive electrode active material obtained by the manufacturing method according to the present embodiment can be constructed according to a conventional method. In the present specification, the “secondary battery” refers to a general power storage device that can be repeatedly charged and discharged, and is a term including a power storage element such as a so-called storage battery and an electric double layer capacitor.

  As a specific example, a nonaqueous electrolyte secondary battery (lithium ion secondary battery) 100 constructed using a positive electrode active material obtained by the manufacturing method according to the present embodiment will be described with reference to the drawings. In the present specification, the “lithium ion secondary battery” refers to a secondary battery that uses lithium ions as a charge carrier and is charged / discharged by movement of charges accompanying the lithium ions between the positive and negative electrodes.

  A lithium ion secondary battery 100 shown in FIG. 2 is constructed by accommodating a flat wound electrode body 20 and a nonaqueous electrolyte (not shown) in a flat rectangular battery case (that is, an exterior container) 30. Is a sealed battery 100. The battery case 30 is provided with a positive terminal 42 and a negative terminal 44 for external connection, and a thin safety valve 36 set to release the internal pressure when the internal pressure of the battery case 30 rises to a predetermined level or more. It has been. The positive and negative terminals 42 and 44 are electrically connected to the positive and negative current collectors 42a and 44a, respectively. As the material of the battery case 30, for example, a light metal material having good thermal conductivity such as aluminum is used.

  As shown in FIGS. 2 and 3, the wound electrode body 20 has a positive electrode active material layer 54 formed along the longitudinal direction on one side or both sides (here, both sides) of an elongated positive electrode current collector 52. The positive electrode sheet 50 and the negative electrode sheet 60 in which the negative electrode active material layer 64 is formed along the longitudinal direction on one side or both sides (here, both sides) of the long negative electrode current collector 62 are two long shapes. The separator sheet 70 is overlapped and wound in the longitudinal direction. It should be noted that the positive electrode active material non-forming portion 52a (that is, the positive electrode active material) formed so as to protrude outward from both ends in the winding axis direction of the wound electrode body 20 (referred to as the sheet width direction perpendicular to the longitudinal direction). The portion where the positive electrode current collector 52 is exposed without forming the material layer 54) and the negative electrode active material layer non-forming portion 62a (that is, the portion where the negative electrode current collector 62 is exposed without forming the negative electrode active material layer 64). The positive electrode current collector plate 42a and the negative electrode current collector plate 44a are joined to each other.

  Examples of the positive electrode current collector 52 constituting the positive electrode sheet 50 include aluminum foil. The positive electrode active material layer 54 includes a positive electrode active material obtained by the manufacturing method according to the above-described embodiment. The positive electrode active material layer 54 may further include a conductive material, a binder, and the like. As the conductive material, carbon black such as acetylene black (AB) and other (such as graphite) carbon materials can be suitably used. As the binder, polyvinylidene fluoride (PVDF) or the like can be used.

  Examples of the negative electrode current collector 62 constituting the negative electrode sheet 60 include copper foil. The negative electrode active material layer 64 includes a negative electrode active material. As the negative electrode active material, for example, a carbon material such as graphite, hard carbon, or soft carbon can be used. The negative electrode active material layer 64 can further include a binder, a thickener, and the like. As the binder, styrene butadiene rubber (SBR) or the like can be used. As the thickener, for example, carboxymethyl cellulose (CMC) can be used.

  As the separator 70, various microporous sheets similar to those conventionally used in lithium ion secondary batteries can be used. For example, a microporous resin made of a resin such as polyethylene (PE) or polypropylene (PP). Sheet. Such a microporous resin sheet may have a single-layer structure or a multilayer structure of two or more layers (for example, a three-layer structure in which PP layers are laminated on both sides of a PE layer). The separator 70 may include a heat resistant layer (HRL).

The non-aqueous electrolyte can be the same as that of a conventional lithium ion secondary battery, and typically, an organic solvent (non-aqueous solvent) containing a supporting salt can be used. As the non-aqueous solvent, various organic solvents such as carbonates, ethers, esters, nitriles, sulfones, lactones and the like used in electrolytes of general lithium ion secondary batteries are used without particular limitation. Can do. Specific examples include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and the like. Such a non-aqueous solvent can be used individually by 1 type or in combination of 2 or more types as appropriate. As the supporting salt, for example, a lithium salt such as LiPF ₆ , LiBF ₄ , or LiClO ₄ can be suitably used. The concentration of the supporting salt is preferably 0.7 mol / L or more and 1.3 mol / L or less.
In the non-aqueous electrolyte, components other than the non-aqueous solvent and the supporting salt described above, for example, a gas generating agent, a film forming agent, a dispersing agent, and a thickening agent, unless the effects of the present invention are significantly impaired. And various other additives.

  The lithium ion secondary battery 100 can be used for various applications. Suitable applications include drive power sources mounted on vehicles such as plug-in hybrid vehicles (PHV), hybrid vehicles (HV), and electric vehicles (EV). The lithium ion secondary battery 100 can also be used in the form of an assembled battery in which a plurality of lithium ion secondary batteries are electrically connected.

  EXAMPLES Examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the examples.

<Example 1>
A mixed aqueous solution of lithium fluoride and sodium tungstate was prepared. In this mixed aqueous solution, the ratio of tungsten atoms to the total of lithium atoms and tungsten atoms was 0.1 mol%. The mixed aqueous solution was added to the alkaline aqueous solution with stirring to produce a coprecipitate. The obtained coprecipitate was washed with water, collected by filtration, and dried at 120 ° C. with a hot air dryer.
Moreover, the mixed aqueous solution of nickel sulfate, cobalt sulfate, and manganese sulfate was prepared. The mixed solution is added to an alkaline aqueous solution with stirring, and the precipitate is washed with water, filtered and dried to obtain an NCM composite hydroxide (Ni _1/3 Co _1/3 Mn _1/3 (OH) ₂ ). It was.
The coprecipitate and the NCM composite hydroxide are mixed at a molar ratio of approximately 1: 1, fired at 800 ° C. in the atmosphere, and F-containing NCM-X lithium as a positive electrode active material for a nonaqueous electrolyte secondary battery. A composite oxide was obtained. The tap density of the positive electrode active material was 1.5 / cm ³ .

The produced positive electrode active material, acetylene black (AB) as a conductive material, and polyvinylidene fluoride (PVDF) as a binder are mixed with NMP at a mass ratio of positive electrode active material: AB: PVDF = 90: 8: 2. Then, a positive electrode active material layer forming paste was prepared. This paste was applied to both sides of a long aluminum foil (material: 8021, thickness: 15 μm) and then dried to prepare a positive electrode sheet.
Further, graphite (C) as a negative electrode active material, styrene butadiene rubber (SBR) as a binder, and carboxymethyl cellulose (CMC) as a thickener have a mass of C: SBR: CMC = 98: 1: 1. A negative electrode active material layer forming paste was prepared by mixing with ion exchange water at a ratio. This paste was applied to both sides of a long copper foil, dried, pressed, processed into a predetermined size, and a negative electrode sheet was produced.
In addition, two long separator sheets (porous polyolefin sheets) were prepared.

The prepared positive electrode sheet, the negative electrode sheet, and the two prepared separator sheets were overlapped and wound to prepare a wound electrode body.
A current collector was attached to the produced wound electrode body and housed in a battery case. Subsequently, a non-aqueous electrolyte was injected from the injection port of the battery case, and the injection port was hermetically sealed to produce a lithium ion secondary battery (capacity 4 Ah) according to Example 1. The nonaqueous electrolyte is supported by a mixed solvent containing ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of EC: DMC: EMC = 3: 4: 3. of LiPF ₆ as a salt were used as dissolved at a concentration of 1.0 mol / L.

<Example 2>
In the mixed aqueous solution of lithium fluoride and sodium tungstate, the lithium ion secondary battery according to Example 2 is performed in the same manner as in Example 1 except that the ratio of tungsten atoms to the total of lithium atoms and tungsten atoms is 0.3 mol%. Was made.

<Example 3>
A lithium ion secondary battery according to Example 3 in the same manner as in Example 1 except that in the mixed aqueous solution of lithium fluoride and sodium tungstate, the ratio of tungsten atoms to the total of lithium atoms and tungsten atoms was 0.5 mol% Was made.

<Example 4>
An example except that a mixed aqueous solution of lithium fluoride and sodium molybdate (the ratio of molybdenum atoms to the total of lithium atoms and molybdenum atoms is 0.3 mol%) was used instead of the mixed aqueous solution of lithium fluoride and sodium tungstate. In the same manner as in Example 1, a lithium ion secondary battery according to Example 4 was produced.

<Example 5>
Example 1 except that instead of the mixed aqueous solution of lithium fluoride and sodium tungstate, a mixed aqueous solution of lithium fluoride and zirconium sulfate (the ratio of zirconium atoms to the total of lithium atoms and zirconium atoms was 0.3 mol%) was used. In the same manner, a lithium ion secondary battery according to Example 5 was produced.

<Example 6>
NCM composite hydroxide was prepared in the same manner as in Example 1. The produced NCM composite hydroxide, tungsten oxide (WO ₃ ), and lithium fluoride were mixed and fired at 800 ° C. in the atmosphere to obtain a positive electrode active material. Tungsten oxide was mixed so that the ratio of tungsten atoms to the total of lithium atoms and tungsten atoms was 0.3 mol%.
Using this positive electrode active material, a lithium ion secondary battery according to Example 6 was produced in the same manner as in Example 1.

<Example 7>
NCM composite hydroxide was prepared in the same manner as in Example 1. The produced NCM composite hydroxide, molybdenum oxide (MO _α ), and lithium fluoride were mixed and fired at 800 ° C. in the atmosphere to obtain a positive electrode active material. Molybdenum oxide was mixed so that the ratio of molybdenum atoms to the total of lithium atoms and molybdenum atoms was 0.3 mol%.
Using this positive electrode active material, a lithium ion secondary battery according to Example 7 was produced in the same manner as in Example 1.

<Example 8>
NCM composite hydroxide was prepared in the same manner as in Example 1. The produced NCM composite hydroxide, zirconium oxide (ZrO ₂ ), and lithium fluoride were mixed and fired at 800 ° C. in the atmosphere to obtain a positive electrode active material. Zirconium oxide was mixed so that the ratio of zirconium atoms to the total of lithium atoms and zirconium atoms was 0.3 mol%.
Using this positive electrode active material, a lithium ion secondary battery according to Example 8 was produced in the same manner as in Example 1.

<Example 9>
NCM composite hydroxide was prepared in the same manner as in Example 1. The produced NCM composite hydroxide and lithium fluoride were mixed and fired at 800 ° C. in the atmosphere to obtain a positive electrode active material.
Using this positive electrode active material, a lithium ion secondary battery according to Example 9 was produced in the same manner as in Example 1.

<Example 10>
In the mixed aqueous solution of lithium fluoride and sodium tungstate, the lithium ion secondary battery according to Example 10 was performed in the same manner as in Example 1 except that the ratio of tungsten atoms to the total of lithium atoms and tungsten atoms was 0.6 mol%. Was made.

[Bonding strength measurement]
The bond strength between the metal atom X and the fluorine atom in the positive electrode active materials produced in Examples 1 to 10 was determined by Rietveld analysis. The results are shown in Table 1.

[Initial capacity measurement]
Initial charging was performed on the lithium ion secondary batteries according to Examples 1 to 10 prepared above. That is, charging was performed at a constant current up to 4.1 V at 4 A. Thereafter, discharging was performed at a constant current up to 3.0 V at 4 A. The discharge capacity at this time was measured, and the discharge capacity (initial capacity) per 1 g of the positive electrode active material was determined.

[Measurement of IV resistance and capacity retention after charge / discharge cycle]
About the lithium ion secondary battery which concerns on Examples 1-10 after the said initial stage capacity | capacitance measurement, after charging / discharging 500 cycles, IV resistance and a capacity | capacitance maintenance factor were calculated | required. Charge / discharge is a charge / discharge in which constant current charge is performed up to 100% SOC (State Of Charge) at a charge rate of 2C under a temperature condition of 60 ° C. and then constant current discharge is performed up to SOC 0% at a discharge rate of 2C Cycle. The IV resistance was calculated by adjusting the battery to SOC 60%, discharging at a current value of 10 C for 10 seconds in an environmental atmosphere of 25 ° C., and measuring the voltage value 10 seconds after the start of discharge. Further, the battery capacity was measured in the same procedure as the above initial capacity measurement, and the capacity maintenance rate was calculated as battery capacity after charge / discharge cycle / initial capacity × 100.
The evaluation results are shown in Table 1.

[Metal deposition on the negative electrode]
The lithium ion secondary batteries according to Examples 1 to 10 after the charge / discharge cycle were disassembled, and the amount of metal deposited on the negative electrode was determined by ICP-MS measurement.

  Examples 1 to 5 are examples in which a positive electrode active material was produced by the production method according to this embodiment, and a lithium ion secondary battery was produced using the positive electrode active material. From Table 1, in Examples 1-5, the bond strength between the metal atom X-fluorine atoms in the positive electrode active material is high, the amount of metal deposited on the negative electrode after the charge / discharge cycle of the lithium ion secondary battery is small, and the charge / discharge cycle. It can be seen that the later IV resistance was low and the capacity retention rate was high. From this, according to the manufacturing method according to the present embodiment, the metal X is less likely to elute from the positive electrode active material, and as a result, the IV resistance of the lithium ion secondary battery after the charge / discharge cycle is kept low, It can also be seen that the capacity is kept high.

  On the other hand, in Examples 6 to 8 in which the metal atom X was introduced as an oxide at the time of firing, the bond strength between the metal atom X and the fluorine atom in the positive electrode active material was low, and on the negative electrode after the charge / discharge cycle of the lithium ion secondary battery The amount of deposited metal was large and the capacity retention rate was low. This is because in the positive electrode active material in which the metal atom X is introduced as an oxide at the time of firing, the metal X not dissolved in the positive electrode active material (composite oxide) is present at the grain boundary, and this metal X is the electrolyte. This is considered to be due to elution into the electrode and deposition on the negative electrode. In Example 7 using molybdenum oxide as the metal X source, it is considered that the metal X further dissolved in the positive electrode active material (composite oxide) was also eluted into the electrolytic solution and deposited on the negative electrode. In Example 8 using zirconium oxide as the metal X source, the IV resistance after the charge / discharge cycle was further high. From this, it is considered that the battery reaction is inhibited. In the lithium ion secondary battery according to Example 9 in which the metal atom X was not introduced into the positive electrode active material, the amount of metal deposited on the negative electrode after the charge / discharge cycle was large, the IV resistance was high, and the capacity retention rate was low. This is presumably because metals other than metal X were eluted from the positive electrode active material and deposited on the negative electrode, which caused an increase in IV resistance and a decrease in battery capacity. In Example 10 in which the addition amount of the metal atom X is too large, the bond strength between the metal atom X and the fluorine atom was high, but the amount of metal deposited on the negative electrode after the discharge cycle of the lithium ion secondary battery was increased, The capacity maintenance rate was low. This is presumably because metal elution occurred due to destabilization of the structure of the positive electrode active material that released lithium during the battery reaction.

  As mentioned above, although the specific example of this invention was demonstrated in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

20 wound electrode body 30 battery case 36 safety valve 42 positive electrode terminal 42a positive electrode current collector plate 44 negative electrode terminal 44a negative electrode current collector plate 50 positive electrode sheet (positive electrode)
52 Positive Current Collector 52a Positive Electrode Active Material Layer Non-Forming Portion 54 Positive Electrode Active Material Layer 60 Negative Electrode Sheet (Negative Electrode)
62 Negative electrode current collector 62a Negative electrode active material layer non-formed portion 64 Negative electrode active material layer 70 Separator sheet (separator)
100 Lithium ion secondary battery

Claims (1)

A compound containing at least one metal X atom selected from the group consisting of molybdenum, zirconium, and tungsten, and lithium fluoride, wherein the ratio of the metal X atom to the total of the metal X atom and lithium atom is Mixing in an alkaline aqueous solution so as to be 0.1 to 0.5 mol% to obtain a coprecipitate containing the metal X atom, lithium atom and fluorine atom;
Firing the obtained coprecipitate and the nickel / cobalt / manganese composite hydroxide to obtain a lithium / nickel / cobalt / manganese composite oxide containing the metal X atom and the fluorine atom; A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery.

Images