JP6065746B2 - Layered rock salt structure active material manufacturing method, layered rock salt structure active material - Google Patents

Description

  The present invention relates to a method for producing an active material having a layered rock salt structure and an active material having a layered rock salt structure.

Conventionally, various materials have been used as active materials for lithium ion secondary batteries. In particular, a lithium complex oxide having a layered rock salt structure is represented by the general formula: Li _a Ni _b Co _c Mn _{d De} O _f (0.2 ≦ a ≦ 1, b + c + d + e = 1, 0 ≦ e <1, D is Li, A material represented by at least one element selected from Fe, Cr, Cu, Zn, Ca, Mg, S, Si, Na, K, and Al, 1.7 ≦ f ≦ 2.1) is a lithium ion secondary battery Widely used as an active material. And in order to provide the active material for lithium ion secondary batteries more excellent, the examination regarding the said material is performed extensively. For example, in Patent Document 1, in the powder X-ray diffraction measurement, the intensity ratio I (003) / of the peak intensity I (003) derived from the (003) plane to the peak intensity I (104) derived from the (104) plane. A lithium composite oxide having I (104) of 0.8 or more is described, and it is described that the lithium composite oxide is produced by various methods. In addition, as disclosed in Patent Documents 2 to 3, many studies have been conducted focusing on the intensity ratio I (003) / I (104) in the powder X-ray diffraction measurement of lithium composite oxide.

Japanese Patent Laid-Open No. 11-25957 JP 2013-073833 A JP 2013-069583 A

  The demand for active materials for lithium ion secondary batteries is still high, and materials that can become active materials with higher performance are eagerly desired.

  The present invention has been made in view of such circumstances, and provides a method for producing an active material having excellent performance using a material that can be an active material as a raw material, and an active material produced by such a production method. The purpose is to do.

As a result of intensive studies by the present inventors, a general formula: Li _a Ni _b Co _c Mn _{d De} O _f (0.2 ≦ a ≦ 1, b + c + d + e = 1, 0 ≦ e) which is a lithium composite oxide having a layered rock salt structure <1, D is represented by at least one element selected from Li, Fe, Cr, Cu, Zn, Ca, Mg, S, Si, Na, K, and Al, 1.7 ≦ f ≦ 2.1) When a specific treatment is performed on the material, the intensity ratio I (003) of the peak intensity I (003) derived from the (003) plane to the peak intensity I (104) derived from the (104) plane in powder X-ray diffraction measurement. ) / I (104) was found to be improved. In addition, when a material having an improved strength ratio is used as an active material for a lithium ion secondary battery, it has been found that the initial capacity of the battery is increased, and the present invention has been completed.

The method for producing an active material of the present invention prepares an aqueous solution for active material modification containing VOSO ₄ and M ₃ PO ₄ (M is independently selected from H, Li, Na, K, and NH ₄ ). Aqueous solution preparation process and general formula of layered rock salt structure: Li _a Ni _b Co _c Mn _{d De} O _f (0.2 ≦ a ≦ 1, b + c + d + e = 1, 0 ≦ e <1, D is Li, Fe, Cr And at least one element selected from Cu, Zn, Ca, Mg, S, Si, Na, K, and Al, 1.7 ≦ f ≦ 2.1). A dipping step of dipping.

Here, the active material having a layered rock salt structure obtained by the production method of the present invention has a general formula: Li _{a ′} Ni _{b ′} Co _{c ′} Mnd _{d De ′} O _{f ′} (0.2 ≦ a ′ ≦ 1, b '+ C' + d '+ e' = 1, 0 ≦ e ′ <1, D ′ is selected from Li, Fe, Cr, Cu, Zn, Ca, Mg, S, Si, Na, K, Al, P, V It is represented by at least one element, 1.7 ≦ f ′ ≦ 2.1).

  The active material obtained by the method for producing an active material of the present invention can improve the initial capacity of a lithium ion secondary battery using the active material.

  Below, the best form for implementing the manufacturing method of the active material of this invention is demonstrated. Unless otherwise specified, the numerical range “x to y” described in this specification includes the lower limit x and the upper limit y. The numerical range can be configured by arbitrarily combining these upper limit value and lower limit value and the numerical values listed in the examples. Furthermore, numerical values arbitrarily selected from the numerical value range can be used as upper and lower numerical values.

The method for producing an active material of the present invention prepares an aqueous solution for active material modification containing VOSO ₄ and M ₃ PO ₄ (M is independently selected from H, Li, Na, K, and NH ₄ ). Aqueous solution preparation process and general formula of layered rock salt structure: Li _a Ni _b Co _c Mn _{d De} O _f (0.2 ≦ a ≦ 1, b + c + d + e = 1, 0 ≦ e <1, D is Li, Fe, Cr And at least one element selected from Cu, Zn, Ca, Mg, S, Si, Na, K, and Al, 1.7 ≦ f ≦ 2.1). A dipping step of dipping.

Here, the active material having a layered rock salt structure obtained by the production method of the present invention has a general formula: Li _{a ′} Ni _{b ′} Co _{c ′} Mnd _{d De ′} O _{f ′} (0.2 ≦ a ′ ≦ 1, b '+ C' + d '+ e' = 1, 0 ≦ e ′ <1, D ′ is selected from Li, Fe, Cr, Cu, Zn, Ca, Mg, S, Si, Na, K, Al, P, V It is represented by at least one element, 1.7 ≦ f ′ ≦ 2.1).

The aqueous solution preparation step is a step of preparing an aqueous solution for active material modification containing VOSO ₄ and M ₃ PO ₄ (M is independently selected from H, Li, Na, K, and NH ₄ ). As M ₃ PO ₄ , H ₃ PO ₄ , (NH ₄ ) H ₂ PO ₄ , (NH ₄ ) ₂ HPO ₄ , (NH ₄ ) ₃ PO ₄ , LiH ₂ PO ₄ , Li ₂ HPO ₄ , Li ₃ PO ₄ , NaH ₂ PO ₄ , Na ₂ HPO ₄ , Na ₃ PO ₄ , KH ₂ PO ₄ , K ₂ HPO ₄ , K ₃ PO ₄ can be specifically exemplified. As M ₃ PO ₄ , H ₃ PO ₄ , (NH ₄ ) H ₂ PO ₄ , (NH ₄ ) ₂ HPO ₄ , (NH ₄ ) ₃ PO ₄ , LiH ₂ PO ₄ , Li ₂ HPO ₄ , Li ₃ PO ₄ is preferable, and (NH ₄ ) H ₂ PO ₄ , (NH ₄ ) ₂ HPO ₄ , (NH ₄ ) ₃ PO ₄ , LiH ₂ PO ₄ , and Li ₂ HPO ₄ are particularly preferable. As M ₃ PO _{4 in the} aqueous solution preparation step, the above single compound may be employed, or a plurality of compounds may be used in combination. Also, may be employed anhydride M ₃ PO _4, it may be adopted each hydrates. Similarly, the VOSO ₄ aqueous solution preparation step, may be employed anhydride VOSO _4, may be adopted each hydrates.

The molar ratio of VOSO ₄ and M ₃ PO ₄ used in the aqueous solution preparation step is not particularly limited. Illustrating a preferred molar ratio, VOSO ₄ : M ₃ PO ₄ = 1: 10 to 10: 1 is preferable, 1: 5 to 5: 1 is more preferable, and 1: 2 to 2: 1 Within the range is particularly preferred.

The concentration of VOSO ₄ or M ₃ PO _{4 in} the aqueous solution for active material modification is not particularly limited. When the preferable molar concentration of VOSO ₄ or M ₃ PO ₄ is exemplified, it is preferably within the range of 0.1 mmol / L to 1 mol / L, more preferably within the range of 0.5 mmol / L to 0.5 mol / L. A range of L to 100 mmol / L is particularly preferable.

The dipping step is a general formula of a layered rock salt structure: Li _a Ni _b Co _c Mn _{d De} O _f (0.2 ≦ a ≦ 1, b + c + d + e = 1, 0 ≦ e <1, D is Li, Fe, Cr, An active material prepared by an aqueous solution preparation step of a material represented by at least one element selected from Cu, Zn, Ca, Mg, S, Si, Na, K, and Al, 1.7 ≦ f ≦ 2.1) It is a step of immersing in the aqueous solution for reforming. The dipping process is preferably accompanied by stirring.

The layered rock salt structure will be described. General formula: Li _a Ni _b Co _c Mn _{d De} O _f (0.2 ≦ a ≦ 1, b + c + d + e = 1, 0 ≦ e <1, D is Li, Fe, Cr, Cu, Zn, Ca, Mg, The crystal structure of the lithium composite metal oxide represented by at least one element selected from S, Si, Na, K, and Al, 1.7 ≦ f ≦ 2.1) is rhombohedral and inversion symmetric. It has a three-fold axis and a mirror surface, and is represented by a space group R-3m. In “R-3m”, “−3” represents 3 with an overline. Then, the layered rock salt structure of the general formula is a layer having a 3a _{site, Ni b Co c Mn d D} 3b site, _{O f} layers with _e (face) of the layer (surface) having a Li _a the (surface) The 6c site is repeated in the order of the 6c site, 3b site, 6c site, and 3a site. Here, the 3a site, 3b site, and 6c site are descriptions expressed in accordance with the Wyckoff symbol.

General formula: Li _a Ni _b Co _c Mn _{d De} O _f (0.2 ≦ a ≦ 1, b + c + d + e = 1, 0 ≦ e <1, D is Li, Fe, Cr, Cu, Zn, Ca, Mg, In at least one element selected from S, Si, Na, K, and Al, 1.7 ≦ f ≦ 2.1), the values of a, b, c, d, e, and f satisfy the above conditions If there is no particular limitation, at least one of b, c, d is preferably in the range of 0 <b <80/100, 0 <c <50/100, 10/100 <d <1. 30/100 <b <70/100, 10/100 <c <30/100, 20/100 <d <40/100, and more preferably b = 50/100, c = 20/100. , D = 30/100 is particularly preferred. General formula of layered rock salt structure: Li _a Ni _b Co _c Mn _{d De} O _f (0.2 ≦ a ≦ 1, b + c + d + e = 1, 0 ≦ e <1, D is Li, Fe, Cr, Cu, Zn, As the material represented by at least one element selected from Ca, Mg, S, Si, Na, K, and Al, 1.7 ≦ f ≦ 2.1), a commercially available material may be used. You may use what was suitably manufactured with the manufacturing method.

General formula of the layered rock salt structure immersed in the aqueous solution for active material modification: Li _a Ni _b Co _c Mn _{d De} O _f (0.2 ≦ a ≦ 1, b + c + d + e = 1, 0 ≦ e <1, D is Li , Fe, Cr, Cu, Zn, Ca, Mg, S, Si, Na, K, Al, the amount of the material represented by 1.7 ≦ f ≦ 2.1) There is no particular limitation as long as the material can be immersed in the active material modification aqueous solution. If the quantity of the said material with respect to 100 mass parts of aqueous solution for active material modification | reformation is illustrated, the inside of the range of 1-500 mass parts is preferable, The inside of the range of 10-300 mass parts is more preferable, The inside of the range of 50-150 mass parts is preferable. Particularly preferred.

  The time for which the material is immersed in the aqueous solution for active material modification is not particularly limited. When the preferable soaking time is exemplified, it is preferably in the range of 1 to 200 minutes, more preferably in the range of 10 to 150 minutes, and particularly preferably in the range of 30 to 100 minutes.

  After a predetermined dipping time has elapsed, the solid material is taken out from the active material modifying aqueous solution, and the dipping process ends. As the step of taking out the solid from the aqueous solution for active material modification, it is preferable to employ a filtration step. Filtration may be performed under normal pressure conditions, but filtration under reduced pressure conditions, that is, suction filtration is preferred. It is preferable to employ a drying step in which the solid obtained after the filtration step is dried at 100 to 140 ° C. in a drying furnace to remove water adhering to the solid. What is necessary is just to determine the drying time of a drying process suitably, confirming the grade of the removal of a water | moisture content. The dried solid is preferably pulverized in the pulverization step. In the pulverization step, the solid material is pulverized using a mortar and various mixers.

  Next, the solid matter is fired in a firing step to become an active material produced by the production method of the present invention. The firing temperature is preferably in the range of 300 to 1000 ° C, more preferably in the range of 350 to 800 ° C. The firing time may be about 1 to 10 hours. The active material may be pulverized by the same method as in the pulverization step after the firing step so that the active material has a desired particle size.

Through the dipping process and the firing process, the general formula of the material is Li _{a ′} Ni _{b ′} Co _{c ′} Mn _{d ′} D _{e ′} O _{f ′} (0.2 ≦ a ′ ≦ 1, b ′ + c ′ + d ′ + E ′ = 1, 0 ≦ e ′ <1, D ′ is at least one element selected from Li, Fe, Cr, Cu, Zn, Ca, Mg, S, Si, Na, K, Al, P, V, 1.7 ≦ f ′ ≦ 2.1). However, no substantial change is observed in the composition of the material before the dipping process and the composition of the active material after the baking process.

Here, both the material before the dipping process and the active material of the present invention after the baking process were measured with a powder X-ray diffractometer, and derived from the (003) plane with respect to the peak intensity I (104) derived from the (104) plane. When comparing the intensity ratio I (003) / I (104) of the peak intensity I (003), it was confirmed that the active material of the present invention after the firing step was improved. According to the description of the above-mentioned patent document and the like, the strength ratio I increases as the uniformity of the contained elements at each site in the layered rock salt structure of the lithium composite oxide, that is, any one of the 3a site, 3b site, and 6c site, or each of them. It can be said that (003) / I (104) is improved. Then, it is considered that the uniformity of the site-containing elements in the layered rock salt structure of the lithium composite oxide is increased through the immersion process and the firing process of the present invention. In general formula of the layered rock salt _{structure: Li a Ni b Co c Mn} d D e O f (0.2 ≦ a ≦ 1, b + c + d + e = 1,0 ≦ e <1, D is Li, Fe, Cr, Cu, When a material represented by at least one element selected from Zn, Ca, Mg, S, Si, Na, K, and Al, 1.7 ≦ f ≦ 2.1) is measured by a powder X-ray diffractometer, The peak derived from the (003) plane is observed near 2θ = 18 °, and the peak derived from the (104) plane is observed near 2θ = 44 °.

  The method for producing an active material according to the present invention includes a peak derived from the (003) plane relative to the peak intensity I (104) derived from the (104) plane in the active material modification method and powder X-ray diffraction measurement of the active material. It can also be grasped as a method of improving the intensity ratio I (003) / I (104) of the intensity I (003).

The method for modifying an active material of the present invention is to prepare an aqueous solution for modifying an active material containing VOSO ₄ and M ₃ PO ₄ (M is independently selected from H, Li, Na, K, and NH ₄ ). And a general formula of a layered rock salt structure: Li _a Ni _b Co _c Mn _{d De} O _f (0.2 ≦ a ≦ 1, b + c + d + e = 1, 0 ≦ e <1, D is Li, Fe, An active material represented by at least one element selected from Cr, Cu, Zn, Ca, Mg, S, Si, Na, K, and Al, 1.7 ≦ f ≦ 2.1) A dipping step of dipping in an aqueous solution.

In the powder X-ray diffraction measurement of the present invention, the intensity ratio I (003) / I of the peak intensity I (003) derived from the (003) plane to the peak intensity I (104) derived from the (104) plane of the active material. (104) The improvement method is an aqueous solution preparation step of preparing an aqueous solution for active material modification containing VOSO ₄ and M ₃ PO ₄ (M is independently selected from H, Li, Na, K, and NH ₄ ). And a general formula of a layered rock salt structure: Li _a Ni _b Co _c Mn _{d De} O _f (0.2 ≦ a ≦ 1, b + c + d + e = 1, 0 ≦ e <1, D is Li, Fe, Cr, Cu, An active material represented by at least one element selected from Zn, Ca, Mg, S, Si, Na, K, and Al, 1.7 ≦ f ≦ 2.1) is immersed in the aqueous solution for active material modification. An immersion step.

For example, the intensity ratio I (003) / I (104 ) is the general formula of the layered rock salt structure of less than _{1.20: Li a Ni b Co c} Mn d D e O f (0.2 ≦ a ≦ 1, b + c + d + e = 1 , 0 ≦ e <1, D is at least one element selected from Li, Fe, Cr, Cu, Zn, Ca, Mg, S, Si, Na, K, Al, 1.7 ≦ f ≦ 2.1) By applying the modification method of the present invention to the active material represented by the following formula, an active material having an intensity ratio I (003) / I (104) of 1.20 or more can be obtained. General formula of a layered rock salt structure with an intensity ratio I (003) / I (104) of 1.20 or more: Li _{a ′} Ni _{b ′} Co _{c ′} Mnd _{d De ′} O _{f ′} (0.2 ≦ a ′ ≦ 1, b ′ + c ′ + d ′ + e ′ = 1, 0 ≦ e ′ <1, D ′ is Li, Fe, Cr, Cu, Zn, Ca, Mg, S, Si, Na, K, Al, P, V A lithium ion secondary battery using an active material represented by at least one element selected from: 1.7 ≦ f ′ ≦ 2.1) exhibits improved initial capacity. Although there is no restriction | limiting in particular in the upper limit of intensity ratio I (003) / I (104), 2.0 and 1. 5, 1.3 can be shown.

  A lithium ion secondary battery can be manufactured using the active material of the present invention. The lithium ion secondary battery includes a negative electrode, a separator, and an electrolyte solution as a battery component in addition to an electrode (for example, a positive electrode) having the active material of the present invention.

  The positive electrode includes a current collector and an active material layer containing the active material of the present invention.

  The current collector refers to a chemically inert electronic high conductor that keeps a current flowing through an electrode during discharge or charging of a lithium ion secondary battery. As the current collector, at least one selected from silver, copper, gold, aluminum, magnesium, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, and stainless steel Examples of such a metal material can be given. The current collector may be covered with a known protective layer.

  The current collector can take the form of a foil, a sheet, a film, a line, a bar, and the like. Therefore, metal foils, such as copper foil, nickel foil, aluminum foil, stainless steel foil, can be used suitably as a collector. When the current collector is in the form of foil, sheet or film, the thickness is preferably in the range of 10 μm to 100 μm.

  A positive electrode can be obtained by forming an active material layer on the surface of the current collector.

  The active material layer may contain a conductive additive. The conductive assistant is added to increase the conductivity of the electrode. Examples of the conductive assistant include carbon black, natural graphite, acetylene black, ketjen black (registered trademark), and vapor grown carbon fiber (VGCF) which are carbonaceous fine particles. These conductive assistants can be added to the active material layer alone or in combination of two or more. Although there is no restriction | limiting in particular about the usage-amount of a conductive support agent, For example, it can be set as 0.5-30 mass parts with respect to 100 mass parts of active materials of this invention.

  The active material layer may contain a binder. The binder serves to bind the active material and the conductive additive of the present invention to the surface of the current collector. Binders include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, alkoxysilyl group-containing resins, and styrene. Examples thereof include copolymers such as butadiene rubber and cellulose derivatives such as carboxymethylcellulose. These binders can be added to the active material layer alone or in combination of two or more. Although there is no restriction | limiting in particular about the usage-amount of a binder, For example, it can be set as 0.5-30 mass parts with respect to 100 mass parts of active materials.

  As a method of forming an active material layer on the surface of the current collector, a conventionally known method such as a roll coating method, a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method is used. What is necessary is just to apply | coat the active material of this invention to the surface. Specifically, an active material layer-forming composition containing the active material of the present invention and, if necessary, a binder and a conductive aid is prepared, and an appropriate solvent is added to the composition to make a paste. Then, after applying to the surface of the current collector, it is dried. If necessary, the dried product may be compressed to increase the electrode density. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, ethanol, methyl isobutyl ketone, and water.

  The negative electrode has a current collector and a negative electrode active material layer bound to the surface of the current collector. The negative electrode active material layer includes a negative electrode active material and, if necessary, a binder and / or a conductive aid. The current collector, binder and conductive additive are the same as those described for the positive electrode.

  Examples of the negative electrode active material include a carbon-based material capable of inserting and extracting lithium, an element capable of being alloyed with lithium, an elemental compound having an element capable of being alloyed with lithium, or a polymer material.

  Examples of the carbon-based material include non-graphitizable carbon, artificial graphite, coke, graphite, glassy carbon, organic polymer compound fired body, carbon fiber, activated carbon, or carbon black. Here, the organic polymer compound fired body refers to a material obtained by firing and carbonizing a polymer material such as phenols and furans at an appropriate temperature.

  Specifically, elements that can be alloyed with lithium include Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Ti, Ag, Zn, Cd, Al, Ga, In, Si. Ge, Sn, Pb, Sb, Bi can be exemplified, and silicon (Si) or tin (Sn) is particularly preferable.

Specific examples of elemental compounds having elements that can be alloyed with lithium include ZnLiAl, AlSb, SiB ₄ , SiB ₆ , Mg ₂ Si, Mg ₂ Sn, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , and NiSi _{2. , CaSi 2, CrSi 2, Cu} 5 Si, FeSi 2, MnSi 2, NbSi 2, TaSi 2, VSi 2, WSi 2, ZnSi 2, SiC, Si 3 N 4, Si 2 N 2 O, SiO v (0 < v ≦ 2), SnO _w (0 <w ≦ 2), SnSiO ₃ , LiSiO 2 or LiSnO can be exemplified, and SiO _x (0.5 ≦ x ≦ 1.5) is particularly preferable. In addition, as an elemental compound having an element capable of alloying with lithium, a tin compound such as a tin alloy (Cu—Sn alloy, Co—Sn alloy, etc.) can be exemplified.

  Specific examples of the polymer material include polyacetylene and polypyrrole.

  The separator separates the positive electrode and the negative electrode and allows lithium ions to pass while preventing a short circuit of current due to contact between the two electrodes. Examples of the separator include a porous film using one or more synthetic resins such as polytetrafluoroethylene, polypropylene, and polyethylene, or a ceramic porous film.

  The electrolytic solution includes a solvent and an electrolyte dissolved in the solvent.

  As the solvent, cyclic esters, chain esters, ethers and the like can be used. Examples of cyclic esters include ethylene carbonate, propylene carbonate, butylene carbonate, gamma butyrolactone, vinylene carbonate, 2-methyl-gamma butyrolactone, acetyl-gamma butyrolactone, and gamma valerolactone. Examples of chain esters include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, methyl ethyl carbonate, propionic acid alkyl ester, malonic acid dialkyl ester, and acetic acid alkyl ester. Examples of ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, and 1,2-dibutoxyethane. These solvents may be used alone or in combination.

Examples of the electrolyte include lithium salts such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , and LiN (CF ₃ SO ₂ ) ₂ .

As an electrolytic solution, a lithium salt such as LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ or the like in a solvent such as ethylene carbonate, diethyl carbonate, propylene carbonate, dimethyl carbonate or the like is used in an amount of 0.5 mol / l to 1.7 mol / l. A solution dissolved at a concentration of about can be exemplified.

  The manufacturing method of the lithium ion secondary battery is as follows. A separator is sandwiched between the positive electrode and the negative electrode to form an electrode body. After connecting the current collector of the positive electrode and the current collector of the negative electrode to the positive electrode terminal and the negative electrode terminal connected to the outside with a current collecting lead or the like, an electrolyte is added to the electrode body to obtain a lithium ion secondary battery. . The shape of the lithium ion secondary battery is not particularly limited, and various shapes such as a cylindrical shape, a laminated shape, a coin shape, and a laminated shape can be employed.

  The lithium ion secondary battery using the active material of the present invention shows an improvement in initial capacity.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. The present invention can be implemented in various forms without departing from the gist of the present invention, with modifications and improvements that can be made by those skilled in the art.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In addition, this invention is not limited by these Examples. In the following, unless otherwise specified, “part” means part by mass, and “%” means mass%.

Example 1
VOSO ₄ dihydrate 0.06 g and (NH ₄ ) ₂ HPO ₄ anhydrous 0.04 g were dissolved in 50 mL of pure water to obtain an aqueous solution for active material modification. 50 g of a material represented by a commercially available layered rock salt structure LiNi _5/10 Co _2/10 Mn _3/10 O ₂ was added to the aqueous solution for active material modification, and immersed for 1 hour. After stirring, the liquid was filtered with suction to separate a solid. The solid was dried at 120 ° C. in a drying furnace to remove moisture from the solid. The solid matter after drying was pulverized using a mixer. Next, the pulverized solid was fired at 400 ° C. for 5 hours to obtain an active material. The active material after firing was pulverized using a mixer to obtain an active material of Example 1.

  Using the active material of Example 1, a lithium ion secondary battery was produced as follows.

88 parts by mass of the active material of Example 1, 6 parts by mass of acetylene black as a conductive auxiliary agent, and 6 parts by mass of polyvinylidene fluoride as a binder were mixed, and this mixture was then mixed with N-methyl-2- A slurry was prepared by dispersing in pyrrolidone. The slurry was placed on an aluminum foil having a thickness of 20 μm, which was a current collector, and applied to the current collector using a doctor blade so that the slurry became a film shape to obtain a sheet. The obtained sheet was dried at 80 ° C. for 20 minutes to remove N-methyl-2-pyrrolidone. Thereafter, using a roll press machine, the current collector and the coated material were firmly bonded so that the electrode density was 2.3 g / cm ² . The bonded article was heated at 120 ° C. for 6 hours under reduced pressure using a vacuum dryer, and then the bonded article was cut into a 25 mm × 30 mm rectangular shape to obtain a positive electrode having a thickness of about 50 μm.

  The negative electrode was produced as follows. 97 parts by mass of graphite powder as an active material, 1 part by mass of acetylene black as a conductive additive, 1 part by mass of styrene-butadiene rubber as a binder and 1 part by mass of carboxymethylcellulose are mixed, and this mixture is ionized. A slurry was prepared by dispersing in exchange water. The slurry was placed on a copper foil having a thickness of 20 μm, which is a negative electrode current collector, and applied to the current collector using a doctor blade so that the slurry was formed into a film, to obtain a sheet. The obtained sheet was dried to remove moisture. Thereafter, the current collector and the coated material were firmly bonded using a roll press. The joined product was heated at 120 ° C. for 6 hours under reduced pressure using a vacuum dryer, and then the joined product was cut into a 25 mm × 30 mm rectangular shape to obtain a negative electrode having a thickness of about 45 μm.

Using the above positive electrode and negative electrode, a laminate type lithium ion secondary battery was manufactured as follows. A rectangular sheet (27 × 32 mm, thickness 25 μm) made of polypropylene resin was sandwiched between the positive electrode and the negative electrode to form an electrode body. This electrode body was covered with a laminate film, and then the three sides of the laminate film were sealed to form a bag. An electrolyte solution was injected into the bag-shaped laminate film. As the electrolytic solution, a solution in which LiBF ₄ was dissolved at a concentration of 1 mol / L in a mixed solvent of 3 parts by volume of ethylene carbonate and 7 parts by volume of diethyl carbonate was used. After injecting the electrolyte, the remaining one side of the bag-like laminate film was sealed to obtain a laminated lithium ion secondary battery. Each of the current collectors of the laminated lithium ion secondary battery includes a tab that can be electrically connected to the outside, and a part of the tab extends to the outside of the laminated lithium ion secondary battery.

(Example 2)
The active material and lithium ion of Example 2 were the same as Example 1 except that VOSO ₄ dihydrate was changed to 0.301 g and (NH ₄ ) ₂ HPO ₄ anhydride was changed to 0.2 g. A secondary battery was produced.

(Example 3)
The active material and lithium ion of Example 3 were the same as Example 1 except that VOSO ₄ dihydrate was changed to 0.603 g and (NH ₄ ) ₂ HPO ₄ anhydride was changed to 0.4 g. A secondary battery was produced.

(Comparative Example 1)
A commercially available material represented by LiNi _5/10 Co _2/10 Mn _3/10 O ₂ having a layered rock salt structure was used as the active material of Comparative Example 1. Otherwise, a lithium ion secondary battery was produced in the same manner as in Example 1.

<Powder X-ray diffraction measurement>
For the active materials of Example 1, Example 2, Example 3, and Comparative Example 1, powder X-ray diffraction measurement was performed under the following conditions.
X-ray: CuKα ray, tube voltage: 45 kV, tube current: 200 mA,
Scanning axis: 2θ / θ, scanning mode: continuous, scanning step: 0.01 °
A peak intensity I (003) derived from the (003) plane observed near 2θ = 18 °, a peak intensity I (104) derived from the (104) plane observed near 2θ = 44 °, and an intensity ratio I ( 003) / I (104). The results are shown in Table 1.

<Initial capacity measurement>
The initial capacities of lithium ion secondary batteries using the active materials of Example 1, Example 2, Example 3, and Comparative Example 1 were measured. First, CCCV charge (constant current constant voltage charge) was performed on the battery at 25 ° C., a 1C rate, and a voltage of 4.5V. The voltage was held for 1 hour. Subsequently, CCCV discharge (constant current constant voltage discharge) was performed from the battery at a voltage of 3.0 V and a 1 C rate. The capacity in CCCV discharge was measured and used as the initial capacity. The results are shown in Table 1.

From the results of I (003) / I (104) in Table 1, compared with the active material of Comparative Example 1, all of the active materials of Examples 1 to 3 have the intensity ratio I (003) / I (104). It became high. In Examples 1 to 3, VOSO ₄ and _{(NH 4)} in the active material for modification solution used in the immersing step 2 despite the concentration of HPO ₄ are different, one of the active substances uniformly It can be seen that the intensity ratio I (003) / I (104) has increased. And from the result of the initial capacity of Table 1, compared with the battery using the active material of Comparative Example 1, all the batteries using the active material of Examples 1 to 3 showed the improvement of the initial capacity. I understand.

Claims (1)

An aqueous solution preparation step of preparing an aqueous solution for active material modification containing VOSO ₄ and M ₃ PO ₄ (M is independently selected from H, Li, Na, K, and NH ₄ );
General formula of layered rock salt structure: Li _a Ni _b Co _c Mn _{d De} O _f (0.2 ≦ a ≦ 1, b + c + d + e = 1, 0 ≦ e <1, D is Li, Fe, Cr, Cu, Zn, An immersion step of immersing a material represented by at least one element selected from Ca, Mg, S, Si, Na, K, and Al, 1.7 ≦ f ≦ 2.1) in the aqueous solution for active material modification; ,
A firing step of firing the material that has undergone the immersion step;
General formula of layered rock salt structure characterized by containing: Li _{a ′} Ni _{b ′} Co _{c ′} Mn _{d ′} D _{e ′} O _{f ′} (0.2 ≦ a ′ ≦ 1, b ′ + c ′ + d ′ + e ′ = 1, 0 ≦ e ′ <1, D ′ is at least one element selected from Li, Fe, Cr, Cu, Zn, Ca, Mg, S, Si, Na, K, Al, P, V. The manufacturing method of the active material represented by 7 <= f '<= 2.1).