WO2015019481A1 - Positive electrode material for lithium ion secondary batteries, and lithium ion secondary battery - Google Patents

Positive electrode material for lithium ion secondary batteries, and lithium ion secondary battery Download PDF

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WO2015019481A1
WO2015019481A1 PCT/JP2013/071588 JP2013071588W WO2015019481A1 WO 2015019481 A1 WO2015019481 A1 WO 2015019481A1 JP 2013071588 W JP2013071588 W JP 2013071588W WO 2015019481 A1 WO2015019481 A1 WO 2015019481A1
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positive electrode
lithium ion
ion secondary
secondary battery
active material
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PCT/JP2013/071588
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French (fr)
Japanese (ja)
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小西　宏明
章 軍司
孝亮 馮
翔 古月
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株式会社日立製作所
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Priority to PCT/JP2013/071588 priority Critical patent/WO2015019481A1/en
Priority to PCT/JP2014/065834 priority patent/WO2015019709A1/en
Publication of WO2015019481A1 publication Critical patent/WO2015019481A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a positive electrode material for a lithium ion secondary battery, and a positive electrode for a lithium ion secondary battery, a lithium ion secondary battery, and a lithium ion secondary battery system including the same.
  • the problem with electric vehicles is that the energy density of the drive battery is low and the distance traveled by one charge is short. Therefore, there is a need for a secondary battery that is inexpensive and has a high energy density.
  • Lithium ion secondary batteries have a higher energy density per weight than secondary batteries such as nickel metal hydride batteries and lead batteries. Therefore, application to electric vehicles and power storage systems is expected. However, in order to meet the demands of electric vehicles, it is necessary to further increase the energy density. In order to realize high energy density, it is necessary to increase the energy density of the positive electrode and the negative electrode.
  • a layered solid solution represented by Li 2 MO 3 —LiM′O 2 is expected.
  • the layered solid solution uses a highly active property while solidly dissolving electrochemically inactive Li 2 MO 3 and electrochemically active LiM′O 2 to extract a high capacity.
  • the layered solid solution can also be represented by the composition formula Li 1 + x M 1-x ′ O 2 .
  • Patent Document 1 discloses a composition formula Li a Mn b M c O z (M represents Ni, Co, Al, and F) in order to provide a battery having a high capacity, excellent storage performance at high temperature, and excellent cycle performance.
  • One or more elements selected from the group consisting of: a lithium manganese-containing oxide represented by 0 ⁇ a ⁇ 2.5, 0 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 1, 2 ⁇ z ⁇ 3), and an olivine structure
  • a negative electrode containing a titanium-containing metal oxide represented by 0 ⁇ a ⁇ 2.5, 0 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 1, 2 ⁇ z ⁇ 3
  • the layered solid solution positive electrode active material having the composition shown in Patent Document 1 has a high energy density, but has hysteresis in the open circuit voltage (OCV). That is, the OCV differs depending on the charging process and the discharging process, and there are two OCVs in the same SOC. Therefore, there is a problem that it is difficult to detect the state of charge (SOC) of the battery from the voltage. In particular, when the state of charge cannot be accurately grasped in a region where the SOC is low, it is necessary to allow a surplus in the remaining capacity of the battery, and the capacity of the battery that can be used decreases.
  • SOC state of charge
  • an object of the present invention is to provide a lithium ion secondary battery that can obtain a high energy density and improve the SOC detection accuracy from voltage.
  • First positive electrode active material and composition formula LiFe 1-y M ′ y PO 4 (0 ⁇ y ⁇ 0.2, M ′ is Mn, Co, Ni, V, Mg, Mo, W, Al, Nb , At least one element of Ti and Cu), and the content of the second positive electrode active material is 5% by mass or more and 20% by mass or less with respect to the positive electrode material. It is characterized by.
  • the present invention it is possible to provide a lithium ion secondary battery capable of obtaining high energy density and improving the SOC detection accuracy from voltage.
  • ⁇ Positive electrode material> When a lithium ion secondary battery is employed in an electric vehicle, it is expected that the mileage per charge is long and that the SOC can be detected with high accuracy from the battery voltage. In order to increase the travel distance per charge, the battery is required to have a high energy density. A lithium ion secondary battery using a layered solid solution as a positive electrode active material can be expected to have a high energy density, but there is a problem that it is difficult to detect the SOC of the battery from the battery voltage. This is because there is hysteresis in the OCV during the charging process and the OCV during the discharging process.
  • the SOC is detected from the battery voltage.
  • the hysteresis in the OCV in the charging process and the OCV in the discharging process means that the OCV in the charging process is different from the OCV in the discharging process in the same SOC. That is, there are two SOCs corresponding to the same potential.
  • the difference between the two SOCs at the same potential is large, a large error occurs when the SOC is detected from the OCV, so that it is difficult to detect the SOC from the battery voltage. Therefore, in order to detect the SOC with high accuracy, it is necessary to suppress the hysteresis of the OCV.
  • the Fe-containing phosphorus compound having an olivine structure typified by LiFePO 4 has a low reaction potential and is constant. Therefore, by mixing the Fe-containing phosphorus compound having an olivine structure with the layered solid solution, the Fe-containing phosphorus compound having the olivine structure is preferentially reacted over the reaction of the layered solid solution in a region where the SOC is low. Reactions involving oxygen that cause hysteresis in the OCV during the charging process and the OCV during the discharging process are suppressed. As a result, the hysteresis of OCV can be suppressed.
  • the detection accuracy be high, particularly in a region where the SOC is low. This is because in a region where the SOC is low, if the SOC error is large, there is a possibility that the battery will run out and the device will not be able to operate.
  • the Fe-containing phosphorus compound having an olivine structure preferentially reacts in a low SOC region, particularly the hysteresis of OCV at the end of discharge is reduced, and the SOC detection error at the end of discharge is reduced. Can be reduced.
  • a high energy density can be obtained even in a high potential region of 3.4 V or higher.
  • x represents the proportion of Li in Li x Ni a Mn b M c O 2 .
  • x represents the proportion of Li in Li x Ni a Mn b M c O 2 .
  • x represents the proportion of Li in Li x Ni a Mn b M c O 2 .
  • x represents the proportion of Li in Li x Ni a Mn b M c O 2 .
  • x represents the proportion of Li in Li x Ni a Mn b M c O 2 .
  • x represents the proportion of Li in Li x Ni a Mn b M c O 2 .
  • M is an additive or impurity such as V, Mo, W, Zr, Nb, Ti, Al, Fe, Mg, Cu, etc., and does not significantly affect the capacity and OCV of the first positive electrode active material. is there.
  • y represents the content ratio (substance ratio) of M ′.
  • M ′ is an element that is added as appropriate, and the amount added must be kept within the range of 0 ⁇ y ⁇ 0.2 so that the effects of the present invention are not suppressed.
  • the layered solid solution below the reaction potential of the Fe-containing phosphorus compound having an olivine structure cannot be used, when the layered solid solution not included in the above composition range and the Fe-containing phosphorus compound having the olivine structure are mixed, when discharged
  • the wasted capacity will increase.
  • the capacity that is wasted can be reduced by using the layered solid solution having the above composition range, the performance of the layered solid solution can be fully utilized, and a high capacity can be obtained.
  • the content of the second positive electrode active material in the positive electrode material is preferably 5% by mass or more and 20% by mass or less. When the content of the second positive electrode active material exceeds 20% by mass, the ratio of the first positive electrode active material is reduced, so that a high energy density cannot be obtained. As for content of the 2nd positive electrode active material with respect to positive electrode material, it is more preferable that it is 10 mass% or less. From the viewpoint of energy density, the content of the first positive electrode active material is preferably 80% by mass or more.
  • the positive electrode material does not contain Co as a transition metal. Since Co is expensive, the positive electrode material according to the present embodiment has an advantage of low cost in addition to high energy density.
  • the present invention does not depend on the mixed state and particle form of the two types of positive electrode active materials, and it is sufficient that the two types of positive electrode active materials are included in the positive electrode material.
  • the positive electrode material according to the present invention can be produced by a method generally used in the technical field to which the present invention belongs.
  • the first positive electrode active material can be produced, for example, by mixing compounds containing Li, Ni, and Mn at an appropriate ratio and firing.
  • the composition of the positive electrode material can be appropriately adjusted by changing the ratio of the compound to be mixed.
  • the compound containing Li include lithium acetate, lithium nitrate, lithium carbonate, lithium hydroxide, and lithium oxide.
  • the Ni-containing compound include nickel acetate, nickel nitrate, nickel carbonate, nickel sulfate, and nickel hydroxide.
  • the compound containing Mn include manganese acetate, manganese nitrate, manganese carbonate, manganese sulfate, manganese oxide, and the like.
  • the second positive electrode active material is prepared by mixing a compound containing Li, Fe, and P at an appropriate ratio, and then mixing and baking with a carbon source such as polyvinyl alcohol in order to ensure conductivity. can do.
  • Examples of the compound containing Li include lithium acetate, lithium nitrate, lithium carbonate, lithium hydroxide, and lithium oxide.
  • Examples of the compound containing Fe include iron oxalate, iron nitrate, iron sulfide, and iron chloride.
  • Examples of the compound containing P include ammonium dihydrogen phosphate and phosphoric acid.
  • composition of the positive electrode material can be determined by elemental analysis such as by inductively coupled plasma (ICP).
  • ICP inductively coupled plasma
  • a lithium ion secondary battery according to the present invention includes the above positive electrode material.
  • the above positive electrode material for the positive electrode high energy density can be obtained and hysteresis of OCV can be suppressed.
  • the state of charge of the battery can be detected with high accuracy from the battery voltage.
  • the lithium ion secondary battery according to the present invention can be preferably used for an electric vehicle.
  • a lithium ion secondary battery includes a positive electrode including a positive electrode material, a negative electrode including a negative electrode material, a separator, an electrolytic solution, an electrolyte, and the like.
  • the negative electrode material is not particularly limited as long as it is a substance that can occlude and release lithium ions.
  • Substances generally used in lithium ion secondary batteries can be used as the negative electrode material.
  • graphite, a lithium alloy, etc. can be illustrated.
  • separator those generally used in lithium ion secondary batteries can be used.
  • examples thereof include polyolefin microporous films and nonwoven fabrics such as polypropylene, polyethylene, and a copolymer of propylene and ethylene.
  • electrolytic solution and the electrolyte those generally used in lithium ion secondary batteries can be used.
  • diethyl carbonate, dimethyl carbonate, ethylene carbonate, propylene carbonate, vinylene carbonate, methyl acetate, ethyl methyl carbonate, methyl propyl carbonate, dimethoxyethane and the like can be exemplified as the electrolytic solution.
  • the lithium ion secondary battery 10 includes an electrode group having a positive electrode 1 in which a positive electrode material is applied on both sides of a current collector, a negative electrode 2 in which a negative electrode material is applied on both sides of the current collector, and a separator 3.
  • the positive electrode 1 and the negative electrode 2 are wound through a separator 3 to form a wound electrode group. This wound body is inserted into the battery can 4.
  • the negative electrode 2 is electrically connected to the battery can 4 via the negative electrode lead piece 6.
  • a sealing lid 7 is attached to the battery can 4 via a packing 8.
  • the positive electrode 1 is electrically connected to the sealing lid 7 through the positive electrode lead piece 5.
  • the wound body is insulated by the insulating plate 9.
  • the electrode group may not be the wound body shown in FIG. 1, but may be a laminated body in which the positive electrode 1 and the negative electrode 2 are laminated via the separator 3.
  • a battery system includes the above lithium ion secondary battery.
  • the lithium ion secondary battery system includes a lithium ion secondary battery, a voltage information acquisition unit that detects a battery voltage, a calculation unit that determines a charging state from the voltage, and a battery control unit that controls charging and discharging based on the charging state. .
  • the battery system it is possible to determine the state of charge from the voltage detected by the voltage information acquisition unit, and to control charge / discharge based on the state of charge.
  • a battery system including a lithium ion battery using a layered solid solution as a positive electrode active material has hysteresis in the OCV during the charging process and the OCV during the discharging process of the lithium ion secondary battery, so the accuracy of the SOC estimated from the battery voltage is low. It is difficult to control charge / discharge based on the estimated SOC.
  • the battery system of the present invention since a lithium ion secondary battery with high SOC detection accuracy is used, control based on voltage is possible. As a result, control stability and reliability are improved. In particular, since a secondary battery with high SOC detection accuracy is used in a region where the SOC is low, the SOC is not overestimated and the reliability of management of the remaining capacity of the battery is improved.
  • the 1st positive electrode active material was produced with the following method. Lithium carbonate, nickel carbonate, and manganese carbonate were mixed with a ball mill to obtain a precursor. The obtained precursor was calcined in the atmosphere at 500 ° C. for 12 hours to obtain a lithium transition metal oxide. The obtained lithium transition metal oxide was pelletized and then fired at 850 to 1050 ° C. for 12 hours in the air. The fired pellets were pulverized in an agate mortar and classified with a 45 ⁇ m sieve to obtain a first positive electrode active material.
  • a second positive electrode active material was produced by the following method. Lithium carbonate, iron oxalate, and ammonium dihydrogen phosphate were mixed with a ball mill to obtain a precursor. The obtained precursor was temporarily calcined at 300 ° C. for 8 hours in argon. Thereafter, the material after provisional baking was mixed with polyvinyl alcohol by a ball mill, and then main baking was performed at 700 ° C. for 8 hours in argon. The fired material was used as the second positive electrode active material.
  • the prepared first and second positive electrode active materials were mixed at an appropriate weight ratio to obtain a positive electrode material.
  • Table 1 shows the composition of the positive electrode material used in each example and comparative example.
  • a positive electrode slurry, a conductive agent, and a binder were mixed uniformly to prepare a positive electrode slurry.
  • the positive electrode slurry was applied onto an aluminum current collector foil having a thickness of 20 ⁇ m, dried at 120 ° C., and compression-molded with a press so that the electrode density was 2.2 g / cm 3 to obtain an electrode plate. Thereafter, the electrode plate was punched into a disk shape having a diameter of 15 mm to produce a positive electrode.
  • the negative electrode was produced using metallic lithium.
  • a solution obtained by dissolving LiPF 6 at a concentration of 1.0 mol / L in a mixed solvent of ethylene carbonate and dimethyl carbonate having a volume ratio of 1: 2 was used.
  • a charge / discharge test was performed on the prototype battery.
  • the charging was constant current constant voltage charging (CC-CV mode), and the upper limit voltage was 4.6V.
  • the discharge was constant current discharge (CC mode), and the lower limit voltage was 2.5V.
  • the charge / discharge current was 0.05 C, and the charge cutoff current was 0.005 C.
  • the energy density obtained by dividing the energy density in the region of 4.6 to 3.4 V where high output is obtained by the energy density in the region of 4.6 to 3.4 V in Comparative Example 1 is used. Ratio. The results are shown in Table 2.
  • a charge / discharge test was performed on the prototype battery. Charging was in CC-CV mode and the upper limit voltage was 4.6V. The discharge was CC mode and the lower limit voltage was 2.5V. The charge / discharge current was 0.05 C, and the charge cutoff current was 0.005 C. The charge / discharge test was performed for two cycles, and the discharge capacity at the second cycle was defined as the rated capacity. Thereafter, the test of charging to 10% of the rated capacity with a current corresponding to 0.05 C and waiting for 5 hours was repeated until the rated capacity was reached. After charging to the rated capacity, the test of discharging 10% of the rated capacity and waiting for 5 hours was repeated until the battery was fully discharged. At this time, the voltage after 5 hours was defined as OCV.
  • the voltage after charging to 20% of the rated capacity (SOC 20%) from the fully discharged state and waiting for 5 hours is the OCV during the charging process, discharged from the fully charged state to 20% of the rated capacity and waiting for 5 hours.
  • the voltage after the discharge was defined as OCV (SOC 20%) in the discharge process.
  • the voltage after charging to 50% of the rated capacity from the fully discharged state and waiting for 5 hours is the OCV (SOC 50%) in the charging process, and after discharging to 50% of the rated capacity from the fully charged state and waiting for 5 hours was defined as OCV (SOC 50%) of the discharging process.
  • FIG. 2 shows the OCV curve of Example 6, and FIG. 3 shows the OCV curve of Comparative Example 1. 2 and 3, the vertical axis represents OCV (V) and the horizontal axis represents SOC (%).
  • the measurement result of the charging process is shown on the upper side, and the measurement result of the discharging process is shown on the lower side. From FIG. 2, in Example 6, the difference between the OCV in the charging process and the OCV in the discharging process at 10% SOC was less than 0.1V, and the difference between the OCV in the charging process and the OCV in the discharging process at 50% SOC was less than 0.3V. It was.
  • Example 6 can reduce the hysteresis of the OCV during the charging process and the OCV during the discharging process as compared with Comparative Example 1, and in particular, can reduce the hysteresis of the OCV of SOC 10% or less.
  • Example 6 the difference in SOC at the same OCV is 15% or less.
  • Comparative Example 1 it can be seen from FIG. 3 that the difference in SOC at the same OCV is about 30%. From the above, by using the positive electrode material of Example 6, a battery with high SOC detection accuracy can be provided.
  • the OCV ratio at SOC 50% and the OCV ratio at SOC 20% are lower.
  • the positive electrode materials of Examples 1 to 14 contain the second positive electrode active material LiFePO 4 . Therefore, it has been found that by mixing Li x Ni a Mn b O 2 and LiFePO 4 , it is possible to suppress the hysteresis of the OCV during the charging process and the OCV during the discharging process, particularly in a low SOC region.
  • the composition of the first positive electrode active material is included in the range of 1 ⁇ x ⁇ 1.2 and 0.2 ⁇ a ⁇ 0.4, but does not include the second positive electrode active material. Therefore, the OCV ratio is high.
  • Examples 1 to 4 have a higher energy density ratio than Comparative Examples 5 and 6. This is because the molar ratio of Li is in the range of 1 ⁇ x ⁇ 1.2. In Examples 1 and 2, the energy density ratio is particularly high. This is because the molar ratio of Li is included in the range of 1 ⁇ x ⁇ 1.15.
  • Comparative Example 4 since the amount of Li in the first positive electrode active material was too small, the amount of Li that can participate in the reaction was small and the energy density was lowered.
  • Comparative Example 6 since the amount of Li in the first positive electrode active material was too large, the crystal structure became unstable and the energy density decreased.
  • FIG. 4 shows the relationship between the Ni content and the OCV ratio in Examples 1, 5, and 8 and Examples 3, 7, and 10.
  • FIG. 4 shows that the OCV ratio decreases as the Ni content increases.
  • filled a ⁇ b it turned out that an energy density ratio becomes high. Therefore, it can be seen that when the Ni content is in the range of 0.2 ⁇ a ⁇ 0.4, the energy density ratio is high and the OCV ratio is small.
  • Examples 1, 11, and 12 have a higher energy density ratio and a lower OCV ratio than Comparative Example 7. This is because the contents of the second positive electrode active materials in Examples 1, 11, and 12 are 5% by mass or more and 20% by mass or less. On the other hand, since the comparative example 7 contained 30 mass% of the second positive electrode active material, the energy density ratio was low. In addition, Example 11 has a lower energy density than Examples 1 and 12. This is because the content of the first positive electrode active material capable of obtaining a high energy density was less than 90% by mass.
  • the energy density ratio is particularly high and the OCV ratio is low. This is because the composition of the first positive electrode active material is in the range of 1 ⁇ x ⁇ 1.15, 0.2 ⁇ y ⁇ 0.4, and the second positive electrode active material is 10% by mass or less of the positive electrode active material. Because it was.
  • a high energy density can be obtained even in a high potential region of 3.4 V or more, and the charging process It is possible to provide a lithium ion secondary battery that can suppress the hysteresis of the OCV and the OCV during the discharge process and can detect the SOC from the voltage with high accuracy. In particular, the detection accuracy in a low SOC region can be improved.

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Abstract

The objective of the present invention is to provide a lithium ion secondary battery which has high energy density and is capable of having improved SOC detection accuracy in the final stage of discharge. The objective can be achieved by a positive electrode material for lithium ion secondary batteries, which is characterized by containing a first positive electrode active material that is represented by composition formula LixNiaMnbMcO2 (wherein 1 < x ≤ 1.2, 0.2 < a ≤ 0.4, 0.4 ≤ b < 0.6, 0 ≤ c ≤ 0.02, a + b + c = 0.8, and M represents at least one element selected from among V, Mo, W, Zr, Nb, Ti, Al, Fe, Mg and Cu) and a second positive electrode active material that is represented by composition formula LiFe1-yM'yPO4 (wherein 0 ≤ y ≤ 0.2 and M' represents at least one element selected from among Mn, Co, Ni, V, Mg, Mo, W, Al, Nb, Ti and Cu), and which is also characterized in that the content of the second positive electrode active material is from 5% by mass to 20% by mass (inclusive).

Description

リチウムイオン二次電池用正極材料およびリチウムイオン二次電池Positive electrode material for lithium ion secondary battery and lithium ion secondary battery
　本発明は、リチウムイオン二次電池用の正極材料、及びそれを含むリチウムイオン二次電池用正極、リチウムイオン二次電池、リチウムイオン二次電池システムに関する。 The present invention relates to a positive electrode material for a lithium ion secondary battery, and a positive electrode for a lithium ion secondary battery, a lithium ion secondary battery, and a lithium ion secondary battery system including the same.
　電気自動車の課題は、駆動用電池のエネルギー密度が低く、一充電での走行距離が短いことである。そこで、安価で高エネルギー密度をもつ二次電池が求められている。 The problem with electric vehicles is that the energy density of the drive battery is low and the distance traveled by one charge is short. Therefore, there is a need for a secondary battery that is inexpensive and has a high energy density.
　リチウムイオン二次電池は、ニッケル水素電池や鉛電池等の二次電池に比べて重量当たりのエネルギー密度が高い。そのため、電気自動車や電力貯蔵システムへの応用が期待されている。しかし、電気自動車の要請に応えるためには、さらなる高エネルギー密度化が必要である。高エネルギー密度化を実現するためには、正極及び負極のエネルギー密度を高める必要がある。 Lithium ion secondary batteries have a higher energy density per weight than secondary batteries such as nickel metal hydride batteries and lead batteries. Therefore, application to electric vehicles and power storage systems is expected. However, in order to meet the demands of electric vehicles, it is necessary to further increase the energy density. In order to realize high energy density, it is necessary to increase the energy density of the positive electrode and the negative electrode.
　高エネルギー密度の正極活物質として、Ｌｉ2ＭＯ3－ＬｉＭ′Ｏ2で表される層状固溶体が期待されている。層状固溶体は、電気化学的に不活性なＬｉ2ＭＯ3と、電気化学的に活性なＬｉＭ′Ｏ2とを固溶させ、高容量を引き出しつつ、高活性な性質を利用するものである。層状固溶体は、組成式Ｌｉ1+xＭ1-x’Ｏ2で表すこともできる。 As a high energy density positive electrode active material, a layered solid solution represented by Li 2 MO 3 —LiM′O 2 is expected. The layered solid solution uses a highly active property while solidly dissolving electrochemically inactive Li 2 MO 3 and electrochemically active LiM′O 2 to extract a high capacity. The layered solid solution can also be represented by the composition formula Li 1 + x M 1-x ′ O 2 .
　特許文献１には、高容量で、かつ高温での貯蔵性能、サイクル性能に優れた電池を提供するために、組成式ＬｉaＭｎbＭcＯz（ＭはＮｉ、Ｃｏ、Ａｌ及びＦよりなる群から選択される一種以上の元素、０≦ａ≦２．５、０＜ｂ≦１、０≦ｃ≦１、２≦ｚ≦３）で表されるリチウムマンガン含有酸化物と、オリビン構造を持つＦｅ含有リン化合物とを含む正極、チタン含有金属酸化物を含む負極を用いている。 Patent Document 1 discloses a composition formula Li a Mn b M c O z (M represents Ni, Co, Al, and F) in order to provide a battery having a high capacity, excellent storage performance at high temperature, and excellent cycle performance. One or more elements selected from the group consisting of: a lithium manganese-containing oxide represented by 0 ≦ a ≦ 2.5, 0 <b ≦ 1, 0 ≦ c ≦ 1, 2 ≦ z ≦ 3), and an olivine structure And a negative electrode containing a titanium-containing metal oxide.
特開２０１２－０３３５０７号公報JP 2012-033507 A
　特許文献１に示されている組成の層状固溶体正極活物質は、高いエネルギー密度が得られるが、開回路電圧（ＯＣＶ）にヒステリシスが存在する。つまり、充電過程と放電過程によってＯＣＶが異なり、同一のＳＯＣにおけるＯＣＶが二つ存在する。そのため、電圧から電池の充電状態（ＳＯＣ：Ｓｔａｔｅ　ｏｆ　Ｃｈａｒｇｅ）を検知することが困難であるという課題がある。特に、ＳＯＣが低い領域で、充電状態を正確に把握できないと、電池の残存容量に余裕を見る必要があり、使用できる電池の容量が減少する。 The layered solid solution positive electrode active material having the composition shown in Patent Document 1 has a high energy density, but has hysteresis in the open circuit voltage (OCV). That is, the OCV differs depending on the charging process and the discharging process, and there are two OCVs in the same SOC. Therefore, there is a problem that it is difficult to detect the state of charge (SOC) of the battery from the voltage. In particular, when the state of charge cannot be accurately grasped in a region where the SOC is low, it is necessary to allow a surplus in the remaining capacity of the battery, and the capacity of the battery that can be used decreases.
　そこで、本発明は、高いエネルギー密度が得られ、かつ電圧からのＳＯＣ検知精度を向上できるリチウムイオン二次電池を提供することを目的とする。 Therefore, an object of the present invention is to provide a lithium ion secondary battery that can obtain a high energy density and improve the SOC detection accuracy from voltage.
　本発明に係るリチウムイオン二次電池用正極材料は、組成式ＬｉxＮｉaＭｎbＭcＯ2（１＜ｘ≦１．２、０．２＜ａ≦０．４、０．４≦ｂ＜０．６、０≦ｃ≦０．０２、ａ＋ｂ＋ｃ＝０．８、ＭはＶ、Ｍｏ、Ｗ、Ｚｒ、Ｎｂ、Ｔｉ、Ａｌ、Ｆｅ、Ｍｇ、Ｃｕ等の少なくともいずれかの元素）で表される第一の正極活物質と、組成式ＬｉＦｅ1-yＭ´yＰＯ4（０≦ｙ≦０．２、Ｍ´はＭｎ、Ｃｏ、Ｎｉ、Ｖ、Ｍｇ、Ｍｏ、Ｗ、Ａｌ、Ｎｂ、Ｔｉ、Ｃｕの少なくともいずれかの元素）で表される第二の正極活物質を含み、第二の正極活物質の含有量は、正極材料に対し５質量％以上２０質量％以下であることを特徴とする。 Positive electrode material for a lithium ion secondary battery according to the present invention, the composition formula Li x Ni a Mn b M c O 2 (1 <x ≦ 1.2,0.2 <a ≦ 0.4,0.4 ≦ b <0.6, 0 ≦ c ≦ 0.02, a + b + c = 0.8, M is an element of at least one of V, Mo, W, Zr, Nb, Ti, Al, Fe, Mg, Cu, etc.) First positive electrode active material and composition formula LiFe 1-y M ′ y PO 4 (0 ≦ y ≦ 0.2, M ′ is Mn, Co, Ni, V, Mg, Mo, W, Al, Nb , At least one element of Ti and Cu), and the content of the second positive electrode active material is 5% by mass or more and 20% by mass or less with respect to the positive electrode material. It is characterized by.
　本発明によれば、高エネルギー密度が得られ、かつ電圧からのＳＯＣ検知精度を向上できるリチウムイオン二次電池を提供することができる。 According to the present invention, it is possible to provide a lithium ion secondary battery capable of obtaining high energy density and improving the SOC detection accuracy from voltage.
リチウムイオン二次電池の構造を模式的に示す断面図である。It is sectional drawing which shows the structure of a lithium ion secondary battery typically. 実施例６のＯＣＶ曲線を示す図である。It is a figure which shows the OCV curve of Example 6. 比較例１のＯＣＶ曲線を示す図である。It is a figure which shows the OCV curve of the comparative example 1. 実施例におけるＮｉ含有量とＯＣＶ比との関係を示す図である。It is a figure which shows the relationship between Ni content and OCV ratio in an Example.
　＜正極材料＞
　リチウムイオン二次電池を電気自動車に採用する場合、一充電当たりの走行距離が長いこと、電池電圧からＳＯＣを高い精度で検知できることが期待される。一充電当たりの走行距離を長くするために、電池には、高エネルギー密度であることが要求される。正極活物質として層状固溶体を用いたリチウムイオン二次電池は、高いエネルギー密度が期待できるが、電池電圧から電池のＳＯＣを検知することが困難であるという課題がある。これは、充電過程のＯＣＶ、放電過程のＯＣＶにヒステリシスがあるためである。 <Positive electrode material>
When a lithium ion secondary battery is employed in an electric vehicle, it is expected that the mileage per charge is long and that the SOC can be detected with high accuracy from the battery voltage. In order to increase the travel distance per charge, the battery is required to have a high energy density. A lithium ion secondary battery using a layered solid solution as a positive electrode active material can be expected to have a high energy density, but there is a problem that it is difficult to detect the SOC of the battery from the battery voltage. This is because there is hysteresis in the OCV during the charging process and the OCV during the discharging process.
　リチウムイオン電池では、電池電圧からＳＯＣを検知している。充電過程のＯＣＶ、放電過程のＯＣＶにヒステリシスがあるということは、同一のＳＯＣにおいて、充電過程のＯＣＶと放電過程のＯＣＶが異なるということである。つまり、同一の電位に対応するＳＯＣが二つある。同一の電位における二つのＳＯＣの差が大きい場合、ＯＣＶからＳＯＣを検知する際に大きな誤差が生じてしまうため、電池電圧からＳＯＣを検知することが困難である。したがって、ＳＯＣを高精度で検知するためには、ＯＣＶのヒステリシスを抑制する必要がある。 In the lithium ion battery, the SOC is detected from the battery voltage. The hysteresis in the OCV in the charging process and the OCV in the discharging process means that the OCV in the charging process is different from the OCV in the discharging process in the same SOC. That is, there are two SOCs corresponding to the same potential. When the difference between the two SOCs at the same potential is large, a large error occurs when the SOC is detected from the OCV, so that it is difficult to detect the SOC from the battery voltage. Therefore, in order to detect the SOC with high accuracy, it is necessary to suppress the hysteresis of the OCV.
　発明者らが鋭意検討した結果、層状固溶体のＮｉ／Ｍｎの組成比を調整し、オリビン構造を有するＦｅ含有リン化合物を混合した正極材料を用いることで、ＯＣＶのヒステリシスを抑制できることを見出した。 As a result of intensive studies by the inventors, it was found that OCV hysteresis can be suppressed by adjusting the Ni / Mn composition ratio of the layered solid solution and using a positive electrode material mixed with an Fe-containing phosphorus compound having an olivine structure.
　正極活物質として層状固溶体を用いると、充電初期に遷移金属がレドックスに関与した反応が起こり、充電末期では、酸素が関与したレドックス反応が起こる。一方、放電初期では、遷移金属がレドックスに関与した反応が起こり、放電末期では、酸素が関与したレドックス反応が起こる。この結果、同様の容量を示す状態においても充電過程と放電過程では反応に寄与する元素種が異なるため、反応電位に差が生じ、充電過程と放電過程のＯＣＶにヒステリシスが生じると考えられる。 When a layered solid solution is used as the positive electrode active material, a reaction in which the transition metal is involved in redox occurs at the beginning of charging, and a redox reaction in which oxygen is involved at the end of charging. On the other hand, at the initial stage of discharge, a reaction involving transition metal in redox occurs, and at the end of discharge, a redox reaction involving oxygen occurs. As a result, even in a state where the capacity is the same, since the element types contributing to the reaction are different between the charging process and the discharging process, a difference occurs in the reaction potential, and it is considered that hysteresis occurs in the OCV in the charging process and the discharging process.
　ＬｉＦｅＰＯ4に代表されるオリビン構造を有するＦｅ含有リン化合物は、反応電位が低く、かつ一定である。そのため、層状固溶体にオリビン構造を有するＦｅ含有リン化合物を混合することで、ＳＯＣが低い領域で、層状固溶体の反応よりも、オリビン構造を有するＦｅ含有リン化合物を優先的に反応し、層状固溶体の充電過程のＯＣＶと放電過程のＯＣＶにヒステリシスが生じる原因となる酸素が関与した反応が抑制される。その結果、ＯＣＶのヒステリシスを抑制できる。 The Fe-containing phosphorus compound having an olivine structure typified by LiFePO 4 has a low reaction potential and is constant. Therefore, by mixing the Fe-containing phosphorus compound having an olivine structure with the layered solid solution, the Fe-containing phosphorus compound having the olivine structure is preferentially reacted over the reaction of the layered solid solution in a region where the SOC is low. Reactions involving oxygen that cause hysteresis in the OCV during the charging process and the OCV during the discharging process are suppressed. As a result, the hysteresis of OCV can be suppressed.
　電池電圧からＳＯＣを検知する際には、特に、ＳＯＣが低い領域で、検知の精度が高いことが求められる。ＳＯＣが低い領域では、ＳＯＣの誤差が大きいと、電池残量がなくなってしまい機器が作動できなくなるおそれがあるためである。本発明に係る正極材料は、ＳＯＣが低い領域で、オリビン構造を有るＦｅ含有リン化合物が優先的に反応するため、特に、放電末期のＯＣＶのヒステリシスが低減し、放電末期におけるＳＯＣ検知の誤差を低減できる。 When detecting the SOC from the battery voltage, it is required that the detection accuracy be high, particularly in a region where the SOC is low. This is because in a region where the SOC is low, if the SOC error is large, there is a possibility that the battery will run out and the device will not be able to operate. In the positive electrode material according to the present invention, since the Fe-containing phosphorus compound having an olivine structure preferentially reacts in a low SOC region, particularly the hysteresis of OCV at the end of discharge is reduced, and the SOC detection error at the end of discharge is reduced. Can be reduced.
　本発明に係るリチウムイオン二次電池用正極材料は、組成式ＬｉxＮｉaＭｎbＭcＯ2（１＜ｘ≦１．２、０．２＜ａ≦０．４、０．４≦ｂ＜０．６、ｃ≦０．０２、ａ＋ｂ＋ｃ＝０．８、ＭはＶ、Ｍｏ、Ｗ、Ｚｒ、Ｎｂ、Ｔｉ、Ａｌ、Ｆｅ、Ｍｇ、Ｃｕ等の元素）で表される第一の正極活物質と、組成式ＬｉＦｅ1-yＭ´yＰＯ4（０≦ｙ≦０．２、Ｍ´はＭｎ、Ｃｏ、Ｎｉ、Ｖ、Ｍｇ、Ｍｏ、Ｗ、Ａｌ、Ｎｂ、Ｔｉ、Ｃｕよりなる群から選択される一種以上の元素）で表される第二の正極活物質を含むことを特徴とする。 Positive electrode material for a lithium ion secondary battery according to the present invention, the composition formula Li x Ni a Mn b M c O 2 (1 <x ≦ 1.2,0.2 <a ≦ 0.4,0.4 ≦ b <0.6, c ≦ 0.02, a + b + c = 0.8, M is an element such as V, Mo, W, Zr, Nb, Ti, Al, Fe, Mg, Cu, etc.) Active material and composition formula LiFe 1-y M ′ y PO 4 (0 ≦ y ≦ 0.2, M ′ is made of Mn, Co, Ni, V, Mg, Mo, W, Al, Nb, Ti, Cu A second positive electrode active material represented by one or more elements selected from the group).
　第一の正極活物質である層状固溶体の組成を、組成式ＬｉxＮｉaＭｎbＭcＯ2（１＜ｘ≦１．２、０．２＜ａ≦０．４、０．４≦ｂ＜０．６、ｃ＜０．０２、ａ＋ｂ＋ｃ＝０．８、ＭはＶ、Ｍｏ、Ｗ、Ｚｒ、Ｎｂ、Ｔｉ、Ａｌ、Ｆｅ、Ｍｇ、Ｃｕ等の元素）で表される組成とすることで、３．４Ｖ以上の高電位の領域においても高いエネルギー密度を得ることができる。 The composition of layered solid solution is the first positive electrode active material, the composition formula Li x Ni a Mn b M c O 2 (1 <x ≦ 1.2,0.2 <a ≦ 0.4,0.4 ≦ b <0.6, c <0.02, a + b + c = 0.8, M is a composition represented by V, Mo, W, Zr, Nb, Ti, Al, Fe, Mg, Cu, etc.) Thus, a high energy density can be obtained even in a high potential region of 3.4 V or higher.
　第一の正極活物質において、ｘは、ＬｉxＮｉaＭｎbＭcＯ2におけるＬｉの割合を示す。ｘが１未満であると、反応に寄与するＬｉの量が減り高容量が得られない。一方、ｘが１．２より大きいと、結晶格子が不安定になり放電容量が低下する。ａは、第一の正極活物質のＮｉの含有比率（物質量比率）を示す。ａが０．２以下であると、充放電容量に占める酸素の寄与が高くなり、充電過程のＯＣＶと放電過程のＯＣＶのヒステリシスが大きくなる。一方、ａが０．４より大きいと、Ｎｉの価数が高くなり、Ｎｉが関与した充放電容量が低減し、高容量が得られない。なお、ＭはＶ、Ｍｏ、Ｗ、Ｚｒ、Ｎｂ、Ｔｉ、Ａｌ、Ｆｅ、Ｍｇ、Ｃｕ等の添加物や不純物であり、第一の正極活物質の容量、ＯＣＶに大きな影響を与えないものである。 In the first positive electrode active material, x represents the proportion of Li in Li x Ni a Mn b M c O 2 . When x is less than 1, the amount of Li contributing to the reaction is reduced, and a high capacity cannot be obtained. On the other hand, if x is larger than 1.2, the crystal lattice becomes unstable, and the discharge capacity decreases. a represents the content ratio (substance ratio) of Ni in the first positive electrode active material. When a is 0.2 or less, the contribution of oxygen to the charge / discharge capacity increases, and the OCV hysteresis during the charge process and the OCV during the discharge process increase. On the other hand, when a is larger than 0.4, the valence of Ni increases, the charge / discharge capacity involving Ni decreases, and a high capacity cannot be obtained. Note that M is an additive or impurity such as V, Mo, W, Zr, Nb, Ti, Al, Fe, Mg, Cu, etc., and does not significantly affect the capacity and OCV of the first positive electrode active material. is there.
　さらに高エネルギー密度を維持し、かつ充電過程のＯＣＶと放電過程のＯＣＶの差を小さくするためには、上記組成式において、１＜ｘ＜１．１５、ａ＜ｂをみたすことが好ましい。 Further, in order to maintain a high energy density and reduce the difference between the OCV in the charging process and the OCV in the discharging process, it is preferable to satisfy 1 <x <1.15 and a <b in the above composition formula.
　第二の正極活物質において、ｙは、Ｍ´の含有比率（物質量比率）を示す。Ｍ´は、適宜加えられる元素であり、添加量は本発明の効果が抑制されないように、０≦ｙ≦０．２の範囲までに抑える必要がある。 In the second positive electrode active material, y represents the content ratio (substance ratio) of M ′. M ′ is an element that is added as appropriate, and the amount added must be kept within the range of 0 ≦ y ≦ 0.2 so that the effects of the present invention are not suppressed.
　なお、オリビン構造を有するＦｅ含有リン化合物の反応電位以下の層状固溶体は使用できないため、上記組成範囲に含まれない層状固溶体とオリビン構造を有するＦｅ含有リン化合物とを混合した場合、放電した際に無駄になる容量が大きくなってしまう。しかし、上記組成範囲の層状固溶体を用いることによって無駄になる容量を少なくできるため、層状固溶体の性能を十分に利用でき、高容量が得られる。 In addition, since the layered solid solution below the reaction potential of the Fe-containing phosphorus compound having an olivine structure cannot be used, when the layered solid solution not included in the above composition range and the Fe-containing phosphorus compound having the olivine structure are mixed, when discharged The wasted capacity will increase. However, since the capacity that is wasted can be reduced by using the layered solid solution having the above composition range, the performance of the layered solid solution can be fully utilized, and a high capacity can be obtained.
　正極材料における、第二の正極活物質の含有量は５質量％以上２０質量％以下であることが好ましい。第二の正極活物質の含有量が２０質量％を超えると、第一の正極活物質の割合が減るため、高エネルギー密度が得られない。正極材料に対する第二の正極活物質の含有量は１０質量％以下であることがより好ましい。エネルギー密度の観点から、第一の正極活物質の含有量は８０質量％以上であることが好ましい。 The content of the second positive electrode active material in the positive electrode material is preferably 5% by mass or more and 20% by mass or less. When the content of the second positive electrode active material exceeds 20% by mass, the ratio of the first positive electrode active material is reduced, so that a high energy density cannot be obtained. As for content of the 2nd positive electrode active material with respect to positive electrode material, it is more preferable that it is 10 mass% or less. From the viewpoint of energy density, the content of the first positive electrode active material is preferably 80% by mass or more.
　本発明の一実施形態において、正極材料は遷移金属としてＣｏを含んでいない。Ｃｏは高価であるため、本実施形態における正極材料は、高エネルギー密度に加えて、低コストであるという利点を有する。 In one embodiment of the present invention, the positive electrode material does not contain Co as a transition metal. Since Co is expensive, the positive electrode material according to the present embodiment has an advantage of low cost in addition to high energy density.
　また、本発明は、二種類の正極活物質の混合状態、粒子形態には依存せず、二種類の正極活物質が正極材料に含まれていればよい。 Further, the present invention does not depend on the mixed state and particle form of the two types of positive electrode active materials, and it is sufficient that the two types of positive electrode active materials are included in the positive electrode material.
　本発明に係る正極材料は、本発明の属する技術分野において一般的に使用されている方法で作製することができる。 The positive electrode material according to the present invention can be produced by a method generally used in the technical field to which the present invention belongs.
　第一の正極活物質は、例えば、Ｌｉ、Ｎｉ、及びＭｎをそれぞれ含む化合物を適当な比率で混合し、焼成することにより作製することができる。混合する化合物の比率を変化させることにより、正極材料の組成を適宜調節することができる。Ｌｉを含有する化合物としては、例えば、酢酸リチウム、硝酸リチウム、炭酸リチウム、水酸化リチウム、酸化リチウム等を挙げることができる。Ｎｉを含有する化合物としては、例えば、酢酸ニッケル、硝酸ニッケル、炭酸ニッケル、硫酸ニッケル、水酸化ニッケル等を挙げることができる。Ｍｎを含有する化合物としては、例えば、酢酸マンガン、硝酸マンガン、炭酸マンガン、硫酸マンガン、酸化マンガン等を挙げることができる。 The first positive electrode active material can be produced, for example, by mixing compounds containing Li, Ni, and Mn at an appropriate ratio and firing. The composition of the positive electrode material can be appropriately adjusted by changing the ratio of the compound to be mixed. Examples of the compound containing Li include lithium acetate, lithium nitrate, lithium carbonate, lithium hydroxide, and lithium oxide. Examples of the Ni-containing compound include nickel acetate, nickel nitrate, nickel carbonate, nickel sulfate, and nickel hydroxide. Examples of the compound containing Mn include manganese acetate, manganese nitrate, manganese carbonate, manganese sulfate, manganese oxide, and the like.
　第二の正極活物質は、Ｌｉ、Ｆｅ、及びＰをそれぞれ含む化合物を適当な比率で混合した後、導電性を確保するために、ポリビニルアルコールなどの炭素源と混合し、焼成することにより作製することができる。 The second positive electrode active material is prepared by mixing a compound containing Li, Fe, and P at an appropriate ratio, and then mixing and baking with a carbon source such as polyvinyl alcohol in order to ensure conductivity. can do.
　Ｌｉを含有する化合物としては、例えば、酢酸リチウム、硝酸リチウム、炭酸リチウム、水酸化リチウム、酸化リチウム等を挙げることができる。Ｆｅを含有する化合物としては、例えば、シュウ酸鉄、硝酸鉄、硫化鉄、塩化鉄を挙げることができる。Ｐを含有する化合物としては、例えば、リン酸二水素アンモニウム、リン酸等を挙げることができる。 Examples of the compound containing Li include lithium acetate, lithium nitrate, lithium carbonate, lithium hydroxide, and lithium oxide. Examples of the compound containing Fe include iron oxalate, iron nitrate, iron sulfide, and iron chloride. Examples of the compound containing P include ammonium dihydrogen phosphate and phosphoric acid.
　正極材料の組成は、例えば誘導結合プラズマ法（ＩＣＰ）等による元素分析により決定することができる。 The composition of the positive electrode material can be determined by elemental analysis such as by inductively coupled plasma (ICP).
　＜リチウムイオン二次電池＞
　本発明に係るリチウムイオン二次電池は、上記の正極材料を含むことを特徴とする。上記の正極材料を正極に使用することにより、高エネルギー密度が得られ、かつＯＣＶのヒステリシス抑制できる。その結果、電池電圧から電池の充電状態を高い精度で検知できる。特に、ＳＯＣが低い領域で電池残量の検知の精度を向上できる。本発明に係るリチウムイオン二次電池は、電気自動車に対して好ましく使用することができる。 <Lithium ion secondary battery>
A lithium ion secondary battery according to the present invention includes the above positive electrode material. By using the above positive electrode material for the positive electrode, high energy density can be obtained and hysteresis of OCV can be suppressed. As a result, the state of charge of the battery can be detected with high accuracy from the battery voltage. In particular, it is possible to improve the accuracy of detection of the remaining battery level in a low SOC region. The lithium ion secondary battery according to the present invention can be preferably used for an electric vehicle.
　リチウムイオン二次電池は、正極材料を含む正極、負極材料を含む負極、セパレータ、電解液、電解質等から構成される。 A lithium ion secondary battery includes a positive electrode including a positive electrode material, a negative electrode including a negative electrode material, a separator, an electrolytic solution, an electrolyte, and the like.
　負極材料は、リチウムイオンを吸蔵放出することができる物質であれば特に限定されない。リチウムイオン二次電池において一般的に使用されている物質を負極材料として使用することができる。例えば、黒鉛、リチウム合金等を例示することができる。 The negative electrode material is not particularly limited as long as it is a substance that can occlude and release lithium ions. Substances generally used in lithium ion secondary batteries can be used as the negative electrode material. For example, graphite, a lithium alloy, etc. can be illustrated.
　セパレータとしては、リチウムイオン二次電池において一般的に使用されているものを使用することができる。例えば、ポリプロピレン、ポリエチレン、プロピレンとエチレンとの共重合体等のポリオレフィン製の微孔性フィルムや不織布等を例示することができる。 As the separator, those generally used in lithium ion secondary batteries can be used. Examples thereof include polyolefin microporous films and nonwoven fabrics such as polypropylene, polyethylene, and a copolymer of propylene and ethylene.
　電解液及び電解質としては、リチウムイオン二次電池において一般的に使用されているものを使用することができる。例えば、電解液として、ジエチルカーボネート、ジメチルカーボネート、エチレンカーボネート、プロピレンカーボネート、ビニレンカーボネート、メチルアセテート、エチルメチルカーボネート、メチルプロピルカーボネート、ジメトキシエタン等を例示することができる。また、電解質として、ＬｉＣｌＯ4、ＬｉＰＦ6、ＬｉＢＦ4、ＬｉＡｓＦ6、ＬｉＳｂＦ6、ＬｉＣＦ3ＳＯ3、ＬｉＣ4Ｆ9ＳＯ3、ＬｉＣＦ3ＣＯ2、Ｌｉ2Ｃ2Ｆ4（ＳＯ3）2、ＬｉＮ（ＣＦ3ＳＯ2）2、ＬｉＣ（ＣＦ3ＳＯ2）3等を例示することができる。 As the electrolytic solution and the electrolyte, those generally used in lithium ion secondary batteries can be used. For example, diethyl carbonate, dimethyl carbonate, ethylene carbonate, propylene carbonate, vinylene carbonate, methyl acetate, ethyl methyl carbonate, methyl propyl carbonate, dimethoxyethane and the like can be exemplified as the electrolytic solution. Further, as the electrolyte, LiClO 4 , LiPF 6 , LiBF 4 , LiAsF 6 , LiSbF 6 , LiCF 3 SO 3 , LiC 4 F 9 SO 3 , LiCF 3 CO 2 , Li 2 C 2 F 4 (SO 3 ) 2 , LiN Examples thereof include (CF 3 SO 2 ) 2 and LiC (CF 3 SO 2 ) 3 .
　本発明に係るリチウムイオン二次電池の構造の一実施形態を、図１を用いて説明する。リチウムイオン二次電池１０は、集電体の両面に正極材料を塗布した正極１と、集電体の両面に負極材料を塗布した負極２と、セパレータ３とを有する電極群を備える。正極１及び負極２は、セパレータ３を介して捲回され、捲回体の電極群を形成している。この捲回体は電池缶４に挿入される。 An embodiment of the structure of a lithium ion secondary battery according to the present invention will be described with reference to FIG. The lithium ion secondary battery 10 includes an electrode group having a positive electrode 1 in which a positive electrode material is applied on both sides of a current collector, a negative electrode 2 in which a negative electrode material is applied on both sides of the current collector, and a separator 3. The positive electrode 1 and the negative electrode 2 are wound through a separator 3 to form a wound electrode group. This wound body is inserted into the battery can 4.
　負極２は、負極リード片６を介して、電池缶４に電気的に接続される。電池缶４には、パッキン８を介して、密閉蓋７が取り付けられる。正極１は、正極リード片５を介して、密閉蓋７に電気的に接続される。捲回体は、絶縁板９によって絶縁される。 The negative electrode 2 is electrically connected to the battery can 4 via the negative electrode lead piece 6. A sealing lid 7 is attached to the battery can 4 via a packing 8. The positive electrode 1 is electrically connected to the sealing lid 7 through the positive electrode lead piece 5. The wound body is insulated by the insulating plate 9.
　なお、電極群は、図１に示す捲回体でなくてもよく、セパレータ３を介して正極１と負極２とを積層した積層体でもよい。 The electrode group may not be the wound body shown in FIG. 1, but may be a laminated body in which the positive electrode 1 and the negative electrode 2 are laminated via the separator 3.
　＜電池システム＞
　本発明に係る電池システムは、上記のリチウムイオン二次電池を備えることを特徴とする。リチウムイオン二次電池システムは、リチウムイオン二次電池と、電池電圧を検知する電圧情報取得部と、電圧から充電状態を判断する演算部と、充電状態に基づき充放電を制御する電池制御手段と、を備える。上記電池システムによれば、電圧情報取得部で検知した電圧から充電状態を判断し、充電状態に基づき充放電を制御できる。 <Battery system>
A battery system according to the present invention includes the above lithium ion secondary battery. The lithium ion secondary battery system includes a lithium ion secondary battery, a voltage information acquisition unit that detects a battery voltage, a calculation unit that determines a charging state from the voltage, and a battery control unit that controls charging and discharging based on the charging state. . According to the battery system, it is possible to determine the state of charge from the voltage detected by the voltage information acquisition unit, and to control charge / discharge based on the state of charge.
　正極活物質として層状固溶体を用いたリチウムイオン電池を備える電池システムは、リチウムイオン二次電池の充電過程のＯＣＶと放電過程のＯＣＶにヒステリシスがあるため、電池電圧から推定されるＳＯＣの精度が低く、推定されたＳＯＣに基づく充放電の制御が困難である。これに対し、本発明に係る電池システムによれば、ＳＯＣの検知精度の高いリチウムイオン二次電池を用いるため、電圧に基づく制御が可能となる。その結果、制御の安定性、信頼性が向上する。特に、ＳＯＣが低い領域において、ＳＯＣの検知精度が高い二次電池を用いているため、ＳＯＣを過大に見積もることがなく、電池の残存容量の管理の信頼性が向上する。 A battery system including a lithium ion battery using a layered solid solution as a positive electrode active material has hysteresis in the OCV during the charging process and the OCV during the discharging process of the lithium ion secondary battery, so the accuracy of the SOC estimated from the battery voltage is low. It is difficult to control charge / discharge based on the estimated SOC. In contrast, according to the battery system of the present invention, since a lithium ion secondary battery with high SOC detection accuracy is used, control based on voltage is possible. As a result, control stability and reliability are improved. In particular, since a secondary battery with high SOC detection accuracy is used in a region where the SOC is low, the SOC is not overestimated and the reliability of management of the remaining capacity of the battery is improved.
　以下、実施例及び比較例を用いて本発明をより詳細に説明するが、本発明の技術的範囲はこれに限定されるものではない。 Hereinafter, the present invention will be described in more detail using examples and comparative examples, but the technical scope of the present invention is not limited thereto.
　＜正極材料の作製＞
　第一の正極活物質を以下の方法で作製した。炭酸リチウム、炭酸ニッケル、及び炭酸マンガンをボールミルで混合し、前駆体を得た。得られた前駆体を大気中において５００℃で１２時間焼成し、リチウム遷移金属酸化物を得た。得られたリチウム遷移金属酸化物をペレット化した後、大気中において８５０～１０５０℃で１２時間焼成した。焼成したペレットをメノウ乳鉢で粉砕し、４５μｍのふるいで分級し、第一の正極活物質とした。 <Preparation of positive electrode material>
The 1st positive electrode active material was produced with the following method. Lithium carbonate, nickel carbonate, and manganese carbonate were mixed with a ball mill to obtain a precursor. The obtained precursor was calcined in the atmosphere at 500 ° C. for 12 hours to obtain a lithium transition metal oxide. The obtained lithium transition metal oxide was pelletized and then fired at 850 to 1050 ° C. for 12 hours in the air. The fired pellets were pulverized in an agate mortar and classified with a 45 μm sieve to obtain a first positive electrode active material.
　第二の正極活物質を以下の方法で作製した。炭酸リチウム、シュウ酸鉄、及びリン酸二水素アンモニウムをボールミルで混合し、前駆体を得た。得られた前駆体をアルゴン中、３００℃で８時間仮焼成した。その後、仮焼成後の材料をポリビニルアルコールとともにボールミルで混合した後、アルゴン中、７００℃で８時間本焼成した。焼成した材料を、第二の正極活物質とした。 A second positive electrode active material was produced by the following method. Lithium carbonate, iron oxalate, and ammonium dihydrogen phosphate were mixed with a ball mill to obtain a precursor. The obtained precursor was temporarily calcined at 300 ° C. for 8 hours in argon. Thereafter, the material after provisional baking was mixed with polyvinyl alcohol by a ball mill, and then main baking was performed at 700 ° C. for 8 hours in argon. The fired material was used as the second positive electrode active material.
　作製した第一、第二の正極活物質を適当な重量比で混合し、正極材料とした。各実施例及び比較例において使用した正極材料の組成を表１に示す。 The prepared first and second positive electrode active materials were mixed at an appropriate weight ratio to obtain a positive electrode material. Table 1 shows the composition of the positive electrode material used in each example and comparative example.
　＜試作電池の作製＞
　各実施例及び比較例では、上述のように作製した２１種類の正極材料を用いて正極を作製し、２１種類の試作電池を作製した。 <Production of prototype battery>
In each example and comparative example, positive electrodes were manufactured using 21 types of positive electrode materials manufactured as described above, and 21 types of prototype batteries were manufactured.
　正極材料と導電剤とバインダとを均一に混合して正極スラリーを作製した。正極スラリーを厚み２０μｍのアルミ集電体箔上に塗布し、１２０℃で乾燥し、プレスにて電極密度が２．２ｇ／ｃｍ3になるように圧縮成形して電極板を得た。その後、電極板を直径１５ｍｍの円盤状に打ち抜き、正極を作製した。 A positive electrode slurry, a conductive agent, and a binder were mixed uniformly to prepare a positive electrode slurry. The positive electrode slurry was applied onto an aluminum current collector foil having a thickness of 20 μm, dried at 120 ° C., and compression-molded with a press so that the electrode density was 2.2 g / cm 3 to obtain an electrode plate. Thereafter, the electrode plate was punched into a disk shape having a diameter of 15 mm to produce a positive electrode.
　負極は金属リチウムを用いて作製した。非水電解液としては、体積比１：２のエチレンカーボネートとジメチルカーボネートとの混合溶媒に、ＬｉＰＦ6を１．０ｍｏｌ／Ｌの濃度で溶解させたものを用いた。 The negative electrode was produced using metallic lithium. As the non-aqueous electrolyte, a solution obtained by dissolving LiPF 6 at a concentration of 1.0 mol / L in a mixed solvent of ethylene carbonate and dimethyl carbonate having a volume ratio of 1: 2 was used.
　＜充放電試験＞
　各実施例及び比較例では、上述のように作製した２１種類の試作電池に対して、充放電試験を行った。 <Charge / discharge test>
In each example and comparative example, a charge / discharge test was performed on 21 types of prototype batteries produced as described above.
　試作電池に対し、充放電試験をした。充電は定電流定電圧充電（ＣＣ－ＣＶモード）とし、上限電圧は４．６Ｖとした。放電は定電流放電（ＣＣモード）とし、下限電圧は２．５Ｖとした。充放電の電流は０．０５Ｃ相当とし、充電のカットオフ電流は０．００５Ｃ相当とした。各実施例及び比較例において、高出力が得られる４．６～３．４Ｖの領域におけるエネルギー密度を、比較例１において４．６～３．４Ｖの領域におけるエネルギー密度で除した値をエネルギー密度比とした。結果を表２に示す。 A charge / discharge test was performed on the prototype battery. The charging was constant current constant voltage charging (CC-CV mode), and the upper limit voltage was 4.6V. The discharge was constant current discharge (CC mode), and the lower limit voltage was 2.5V. The charge / discharge current was 0.05 C, and the charge cutoff current was 0.005 C. In each of Examples and Comparative Examples, the energy density obtained by dividing the energy density in the region of 4.6 to 3.4 V where high output is obtained by the energy density in the region of 4.6 to 3.4 V in Comparative Example 1 is used. Ratio. The results are shown in Table 2.
　＜ＯＣＶの測定＞
　各実施例及び比較例では、上述のように作製した２０種類の試作電池に対して、充電過程のＯＣＶと放電過程のＯＣＶの差を求めた。 <Measurement of OCV>
In each of the examples and comparative examples, the difference between the OCV in the charging process and the OCV in the discharging process was determined for the 20 prototype batteries manufactured as described above.
　試作電池に対し、充放電試験をした。充電はＣＣ－ＣＶモードとし、上限電圧は４．６Ｖとした。放電はＣＣモードとし、下限電圧は２．５Ｖとした。充放電の電流は０．０５Ｃ相当とし、充電のカットオフ電流は０．００５Ｃ相当とした。充放電試験を２サイクルし、２サイクル目の放電容量を定格容量とした。その後、０．０５Ｃ相当の電流で定格容量の１０％まで充電し、５時間待機するという試験を定格容量になるまで繰り返した。定格容量まで充電した後、定格容量の１０％を放電し、５時間待機するという試験を満放電状態まで繰り返した。このとき、５時間後の電圧をＯＣＶと定義した。本試験において、満放電状態から定格容量の２０％（ＳＯＣ２０％）まで充電して５時間待機した後の電圧を充電過程のＯＣＶ、満充電状態から定格容量の２０％まで放電して５時間待機した後の電圧を放電過程のＯＣＶ（ＳＯＣ２０％）と定義した。また、満放電状態から定格容量の５０％まで充電して５時間待機した後の電圧を充電過程のＯＣＶ（ＳＯＣ５０％）、満充電状態から定格容量の５０％まで放電して５時間待機した後の電圧を放電過程のＯＣＶ（ＳＯＣ５０％）と定義した。各実施例及び比較例において、充電過程のＯＣＶと放電過程のＯＣＶの差を、比較例１の充電過程のＯＣＶと放電過程のＯＣＶの差で除した値をＯＣＶ比とした。結果を表１に示す。 A charge / discharge test was performed on the prototype battery. Charging was in CC-CV mode and the upper limit voltage was 4.6V. The discharge was CC mode and the lower limit voltage was 2.5V. The charge / discharge current was 0.05 C, and the charge cutoff current was 0.005 C. The charge / discharge test was performed for two cycles, and the discharge capacity at the second cycle was defined as the rated capacity. Thereafter, the test of charging to 10% of the rated capacity with a current corresponding to 0.05 C and waiting for 5 hours was repeated until the rated capacity was reached. After charging to the rated capacity, the test of discharging 10% of the rated capacity and waiting for 5 hours was repeated until the battery was fully discharged. At this time, the voltage after 5 hours was defined as OCV. In this test, the voltage after charging to 20% of the rated capacity (SOC 20%) from the fully discharged state and waiting for 5 hours is the OCV during the charging process, discharged from the fully charged state to 20% of the rated capacity and waiting for 5 hours. The voltage after the discharge was defined as OCV (SOC 20%) in the discharge process. In addition, the voltage after charging to 50% of the rated capacity from the fully discharged state and waiting for 5 hours is the OCV (SOC 50%) in the charging process, and after discharging to 50% of the rated capacity from the fully charged state and waiting for 5 hours Was defined as OCV (SOC 50%) of the discharging process. In each example and comparative example, a value obtained by dividing the difference between the OCV in the charging process and the OCV in the discharging process by the difference between the OCV in the charging process and the OCV in the discharging process in Comparative Example 1 was defined as the OCV ratio. The results are shown in Table 1.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　図２に実施例６のＯＣＶ曲線を、図３に比較例１のＯＣＶ曲線を示す。図２、３において、縦軸はＯＣＶ（Ｖ）、横軸はＳＯＣ（％）を表しており、充電過程の測定結果は上側、放電過程の測定結果は下側に示される。図２より、実施例６では、ＳＯＣ１０％における充電過程のＯＣＶと放電過程のＯＣＶの差が０．１Ｖ未満、ＳＯＣ５０％における充電過程のＯＣＶと放電過程のＯＣＶの差は０．３Ｖ未満であった。一方、比較例１では、図３よりＳＯＣ１０％における充電過程のＯＣＶと放電過程のＯＣＶの差が０．２Ｖ程度、ＳＯＣ５０％における充電過程のＯＣＶと放電過程のＯＣＶの差は０．３Ｖ程度であった。したがって、実施例６は比較例１と比して、充電過程のＯＣＶと放電過程のＯＣＶのヒステリシスを低減でき、特に、ＳＯＣ１０％以下のＯＣＶのヒステリシスを低減できることが分かった。 FIG. 2 shows the OCV curve of Example 6, and FIG. 3 shows the OCV curve of Comparative Example 1. 2 and 3, the vertical axis represents OCV (V) and the horizontal axis represents SOC (%). The measurement result of the charging process is shown on the upper side, and the measurement result of the discharging process is shown on the lower side. From FIG. 2, in Example 6, the difference between the OCV in the charging process and the OCV in the discharging process at 10% SOC was less than 0.1V, and the difference between the OCV in the charging process and the OCV in the discharging process at 50% SOC was less than 0.3V. It was. On the other hand, in Comparative Example 1, the difference between the OCV during the charging process and the OCV during the discharging process at 10% SOC is about 0.2V, and the difference between the OCV during the charging process and the OCV during the discharging process at 50% SOC is about 0.3V. there were. Therefore, it was found that Example 6 can reduce the hysteresis of the OCV during the charging process and the OCV during the discharging process as compared with Comparative Example 1, and in particular, can reduce the hysteresis of the OCV of SOC 10% or less.
　また、図２より実施例６では、同一のＯＣＶにおけるＳＯＣの差が１５％以下であることが分かる。一方、比較例１では、図３より同一のＯＣＶにおけるＳＯＣの差が３０％程度であることが分かる。以上のことから、実施例６の正極材料を用いることにより、ＳＯＣ検知の精度が高い電池を提供できる。 Further, it can be seen from FIG. 2 that in Example 6, the difference in SOC at the same OCV is 15% or less. On the other hand, in Comparative Example 1, it can be seen from FIG. 3 that the difference in SOC at the same OCV is about 30%. From the above, by using the positive electrode material of Example 6, a battery with high SOC detection accuracy can be provided.
　表１に示すように、比較例１、２と比較して、実施例１～１４では、ＳＯＣ５０％におけるＯＣＶ比及び、ＳＯＣ２０％におけるＯＣＶ比が低い。これは、実施例１から１４の正極材料が、第二の正極活物質ＬｉＦｅＰＯ4を含んでいるためである。したがって、ＬｉxＮｉaＭｎbＯ2とＬｉＦｅＰＯ4とを混合することによって、特にＳＯＣが低い領域での充電過程のＯＣＶと放電過程のＯＣＶのヒステリシスを抑制できることが分かった。一方、比較例２では、第一の正極活物質の組成が１＜ｘ≦１．２、０．２＜ａ≦０．４の範囲に含まれるが、第二の正極活物質を含んでいないため、ＯＣＶ比が高い。 As shown in Table 1, compared with Comparative Examples 1 and 2, in Examples 1 to 14, the OCV ratio at SOC 50% and the OCV ratio at SOC 20% are lower. This is because the positive electrode materials of Examples 1 to 14 contain the second positive electrode active material LiFePO 4 . Therefore, it has been found that by mixing Li x Ni a Mn b O 2 and LiFePO 4 , it is possible to suppress the hysteresis of the OCV during the charging process and the OCV during the discharging process, particularly in a low SOC region. On the other hand, in Comparative Example 2, the composition of the first positive electrode active material is included in the range of 1 <x ≦ 1.2 and 0.2 <a ≦ 0.4, but does not include the second positive electrode active material. Therefore, the OCV ratio is high.
　実施例１～４は、比較例５、６と比して、エネルギー密度比が高い。これは、Ｌｉのモル比が１＜ｘ≦１．２の範囲に入っているためである。また、実施例１、２は、特にエネルギー密度比が高い。これは、Ｌｉのモル比が１＜ｘ＜１．１５の範囲に含まれるためである。比較例４では、第一の正極活物質のＬｉ量が少なすぎたため、反応に関与できるＬｉが少なくエネルギー密度が低下した。比較例６では、第一の正極活物質のＬｉ量が多すぎたため、結晶構造が不安定になりエネルギー密度が低下した。 Examples 1 to 4 have a higher energy density ratio than Comparative Examples 5 and 6. This is because the molar ratio of Li is in the range of 1 <x ≦ 1.2. In Examples 1 and 2, the energy density ratio is particularly high. This is because the molar ratio of Li is included in the range of 1 <x <1.15. In Comparative Example 4, since the amount of Li in the first positive electrode active material was too small, the amount of Li that can participate in the reaction was small and the energy density was lowered. In Comparative Example 6, since the amount of Li in the first positive electrode active material was too large, the crystal structure became unstable and the energy density decreased.
　実施例１、５、８と、実施例２、４、６と、実施例３、７、１０より、Ｎｉ含有率とＭｎの含有量の関係がＯＣＶ比に影響することが分かる。図４に実施例１、５、８と、実施例３、７、１０のＮｉ含有量とＯＣＶ比の関係を示す。図４から、Ｎｉ含有率が高くなるにつれてＯＣＶ比が小さくなることが分った。また、Ｎｉ含有量とＭｎ含有量がａ＜ｂを満たすと、エネルギー密度比が高くなることが分かった。したがって、Ｎｉ含有量が０．２＜ａ＜０．４の範囲とすることにより、エネルギー密度比は高く、ＯＣＶ比は小さくなることが分かる。 From Examples 1, 5, 8 and Examples 2, 4, 6, and Examples 3, 7, and 10, it can be seen that the relationship between the Ni content and the content of Mn affects the OCV ratio. FIG. 4 shows the relationship between the Ni content and the OCV ratio in Examples 1, 5, and 8 and Examples 3, 7, and 10. FIG. 4 shows that the OCV ratio decreases as the Ni content increases. Moreover, when Ni content and Mn content satisfy | filled a <b, it turned out that an energy density ratio becomes high. Therefore, it can be seen that when the Ni content is in the range of 0.2 <a <0.4, the energy density ratio is high and the OCV ratio is small.
　実施例１、１１、１２は、比較例７と比してエネルギー密度比が高く、ＯＣＶ比が小さい。これは、実施例１、１１、１２第二の正極活物質の含有量が５質量％以上２０質量％以下であるためである。一方、比較例７は第二の正極活物質が３０質量％含まれているために、エネルギー密度比が低くなった。また、実施例１１は実施例１、１２と比して、エネルギー密度が低い。これは、高エネルギー密度が得られる第一の正極活物質の含有量が９０質量％未満であったためである。 Examples 1, 11, and 12 have a higher energy density ratio and a lower OCV ratio than Comparative Example 7. This is because the contents of the second positive electrode active materials in Examples 1, 11, and 12 are 5% by mass or more and 20% by mass or less. On the other hand, since the comparative example 7 contained 30 mass% of the second positive electrode active material, the energy density ratio was low. In addition, Example 11 has a lower energy density than Examples 1 and 12. This is because the content of the first positive electrode active material capable of obtaining a high energy density was less than 90% by mass.
　実施例１、２、５、６、１２、１４では、特に、エネルギー密度比が高く、ＯＣＶ比が低い。これは第一の正極活物質の組成が１＜ｘ＜１．１５、０．２＜ｙ＜０．４の範囲に入っており、第二の正極活物質が正極活物質の１０質量％以下であったためである。 In Examples 1, 2, 5, 6, 12, and 14, the energy density ratio is particularly high and the OCV ratio is low. This is because the composition of the first positive electrode active material is in the range of 1 <x <1.15, 0.2 <y <0.4, and the second positive electrode active material is 10% by mass or less of the positive electrode active material. Because it was.
　以上の通り、層状固溶体とオリビン構造を有するＦｅ含有リン化合物とを混合した正極材料を用いることで、３．４Ｖ以上の高電位の領域においても高いエネルギー密度を得ることができ、かつ充電過程のＯＣＶと放電過程のＯＣＶのヒステリシスを抑制し、電圧からＳＯＣを高精度で検知できるリチウムイオン二次電池を提供することができる。特に、ＳＯＣが低い領域での検知精度を向上できる。 As described above, by using a positive electrode material in which a layered solid solution and an Fe-containing phosphorus compound having an olivine structure are used, a high energy density can be obtained even in a high potential region of 3.4 V or more, and the charging process It is possible to provide a lithium ion secondary battery that can suppress the hysteresis of the OCV and the OCV during the discharge process and can detect the SOC from the voltage with high accuracy. In particular, the detection accuracy in a low SOC region can be improved.
　１　正極
　２　負極
　３　セパレータ
　４　電池缶
　５　正極リード片
　６　負極リード片
　７　密閉蓋
　８　パッキン
　９　絶縁板
　１０　リチウムイオン二次電池 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Battery can 5 Positive electrode lead piece 6 Negative electrode lead piece 7 Sealing lid 8 Packing 9 Insulating plate 10 Lithium ion secondary battery

Claims (14)

  1. 　リチウムイオンを吸蔵、放出する正極活物質を備えるリチウムイオン二次電池用正極材料であって、
    　組成式ＬｉxＮｉaＭｎbＭcＯ2（１＜ｘ≦１．２、０．２＜ａ≦０．４、０．４≦ｂ＜０．６、ｃ≦０．０２、ａ＋ｂ＋ｃ＝０．８、ＭはＶ、Ｍｏ、Ｗ、Ｚｒ、Ｎｂ、Ｔｉ、Ａｌ、Ｆｅ、Ｍｇ、Ｃｕから選択される少なくともいずれかの元素）で表される第一の正極活物質と、組成式ＬｉＦｅ1-yＭ´yＰＯ4（０≦ｙ≦０．２、Ｍ´はＭｎ、Ｃｏ、Ｎｉ、Ｖ、Ｍｇ、Ｍｏ、Ｗ、Ａｌ、Ｎｂ、Ｔｉ、Ｃｕから選択される少なくともいずれかの元素）で表される第二の正極活物質とを含み、
    　前記第二の正極活物質の含有量は、前記正極材料に対し５質量％以上２０質量％以下であることを特徴とするリチウムイオン二次電池用正極材料。     A positive electrode material for a lithium ion secondary battery comprising a positive electrode active material that occludes and releases lithium ions,
    The composition formula Li x Ni a Mn b M c O 2 (1 <x ≦ 1.2,0.2 <a ≦ 0.4,0.4 ≦ b <0.6, c ≦ 0.02, a + b + c = 0 .8, M is at least one element selected from V, Mo, W, Zr, Nb, Ti, Al, Fe, Mg, and Cu), and a composition formula LiFe 1 -y M ′ y PO 4 (0 ≦ y ≦ 0.2, M ′ is at least one element selected from Mn, Co, Ni, V, Mg, Mo, W, Al, Nb, Ti, Cu) A second positive electrode active material represented by
    Content of said 2nd positive electrode active material is 5 mass% or more and 20 mass% or less with respect to the said positive electrode material, The positive electrode material for lithium ion secondary batteries characterized by the above-mentioned.
  2. 　請求項１に記載のリチウムイオン二次電池用正極材料であって、
    　前記第二の正極活物質の含有量は、前記正極材料に対し１０質量％以下であることを特徴とするリチウムイオン二次電池用正極材料。     The positive electrode material for a lithium ion secondary battery according to claim 1,
    Content of said 2nd positive electrode active material is 10 mass% or less with respect to the said positive electrode material, The positive electrode material for lithium ion secondary batteries characterized by the above-mentioned.
  3. 　請求項１に記載のリチウムイオン二次電池用正極材料であって、
    　前記第一の正極活物質の組成は、１＜ｘ＜１．１５を満たすことを特徴とするリチウムイオン二次電池用正極材料。     The positive electrode material for a lithium ion secondary battery according to claim 1,
    The positive electrode material for a lithium ion secondary battery, wherein the composition of the first positive electrode active material satisfies 1 <x <1.15.
  4. 　請求項３に記載のリチウムイオン二次電池用正極材料であって、
    　前記第一の正極活物質の組成は、ａ＜ｂを満たすことを特徴とするリチウムイオン二次電池用正極材料。     The positive electrode material for a lithium ion secondary battery according to claim 3,
    The positive electrode material for a lithium ion secondary battery, wherein the composition of the first positive electrode active material satisfies a <b.
  5. 　請求項１から４のいずれかに記載のリチウムイオン二次電池用正極材料を含むことを特徴とするリチウムイオン二次電池用正極。 A positive electrode for a lithium ion secondary battery comprising the positive electrode material for a lithium ion secondary battery according to any one of claims 1 to 4.
  6. 　正極材料を含む正極と、負極材料を含む負極とを備えるリチウムイオン二次電池であって、
    　前記正極材料は、組成式ＬｉxＮｉaＭｎbＭcＯ2（１＜ｘ≦１．２、０．２＜ａ≦０．４、０．４≦ｂ＜０．６、ｃ≦０．０２、ａ＋ｂ＋ｃ＝０．８、ＭはＶ、Ｍｏ、Ｗ、Ｚｒ、Ｎｂ、Ｔｉ、Ａｌ、Ｆｅ、Ｍｇ、Ｃｕから選択される少なくともいずれかの元素）で表される第一の正極活物質と、組成式ＬｉＦｅ1-yＭ´yＰＯ4（０≦ｙ≦０．２、Ｍ´はＭｎ、Ｃｏ、Ｎｉ、Ｖ、Ｍｇ、Ｍｏ、Ｗ、Ａｌ、Ｎｂ、Ｔｉ、Ｃｕから選択される少なくともいずれかの元素）で表される第二の正極活物質とを含み、
    　前記第二の正極活物質の含有量は、前記正極材料に対し５質量％以上２０質量％以下であることを特徴とするリチウムイオン二次電池。     A lithium ion secondary battery comprising a positive electrode including a positive electrode material and a negative electrode including a negative electrode material,
    The positive electrode material has a composition formula Li x Ni a Mn b M c O 2 (1 <x ≦ 1.2, 0.2 <a ≦ 0.4, 0.4 ≦ b <0.6, c ≦ 0. 02, a + b + c = 0.8, M is at least one element selected from V, Mo, W, Zr, Nb, Ti, Al, Fe, Mg, Cu) , Composition formula LiFe 1-y M ′ y PO 4 (0 ≦ y ≦ 0.2, M ′ is at least selected from Mn, Co, Ni, V, Mg, Mo, W, Al, Nb, Ti, Cu) A second positive electrode active material represented by any element),
    Content of said 2nd positive electrode active material is 5 to 20 mass% with respect to the said positive electrode material, The lithium ion secondary battery characterized by the above-mentioned.
  7. 　請求項６に記載のリチウムイオン二次電池であって、
    　前記第二の正極活物質の含有量は、前記正極材料に対し１０質量％以下であることを特徴とするリチウムイオン二次電池。     The lithium ion secondary battery according to claim 6,
    Content of said 2nd positive electrode active material is 10 mass% or less with respect to the said positive electrode material, The lithium ion secondary battery characterized by the above-mentioned.
  8. 　請求項６に記載のリチウムイオン二次電池であって、
    　前記第一の正極活物質の組成は、１＜ｘ＜１．１５を満たすことを特徴とするリチウムイオン二次電池。     The lithium ion secondary battery according to claim 6,
    The composition of the first positive electrode active material satisfies 1 <x <1.15, and is a lithium ion secondary battery.
  9. 　請求項８に記載のリチウムイオン二次電池であって、
    　前記第一の正極活物質の組成は、ａ＜ｂを満たすことを特徴とするリチウムイオン二次電池。     The lithium ion secondary battery according to claim 8,
    The lithium ion secondary battery, wherein the composition of the first positive electrode active material satisfies a <b.
  10. 　請求項６ないし９のいずれかに記載のリチウムイオン二次電池であって、
    　３．４Ｖ～４．６Ｖの電位範囲で使用されるリチウムイオン二次電池。     The lithium ion secondary battery according to any one of claims 6 to 9,
    A lithium ion secondary battery used in a potential range of 3.4V to 4.6V.
  11. 　請求項１０に記載のリチウムイオン二次電池であって、
    　充電過程で定格容量の１０％となるときの開回路電圧と、放電過程で定格容量の１０％となるときの開回路電圧と、の差が０．１Ｖ以下であることを特徴とするリチウムイオン二次電池。     The lithium ion secondary battery according to claim 10,
    Lithium ion, characterized in that the difference between the open circuit voltage at 10% of the rated capacity during charging and the open circuit voltage at 10% of the rated capacity during discharging is 0.1 V or less Secondary battery.
  12. 　請求項１０に記載のリチウムイオン二次電池であって、
    　充電過程で定格容量の５０％となるときの開回路電圧と、放電過程で定格容量の５０％となるときの開回路電圧と、の差が０．３Ｖ以下であることを特徴とするリチウムイオン二次電池。     The lithium ion secondary battery according to claim 10,
    Lithium ion characterized in that the difference between the open circuit voltage at 50% of the rated capacity in the charging process and the open circuit voltage at 50% of the rated capacity in the discharging process is 0.3 V or less Secondary battery.
  13. 　請求項１０に記載のリチウムイオン二次電池であって、
    　充電過程の開回路電圧と放電過程の開回路電圧が同一であるときの、充電過程のＳＯＣと放電過程のＳＯＣの差が１５％以下であることを特徴とするリチウムイオン二次電池。     The lithium ion secondary battery according to claim 10,
    A lithium ion secondary battery, wherein a difference between an SOC in a charging process and an SOC in a discharging process is 15% or less when an open circuit voltage in a charging process and an open circuit voltage in a discharging process are the same.
  14. 　電池電圧を検知する電圧情報取得部と、前記電池電圧から充電状態を判断する演算部と、前記充電状態に基づき充放電を制御する電池制御手段と、請求項６ないし９のいずれかに記載のリチウムイオン二次電池と、を備えるリチウムイオン電池システム。 The voltage information acquisition part which detects battery voltage, the calculating part which judges a charge condition from the said battery voltage, the battery control means which controls charging / discharging based on the said charge condition, The any one of Claim 6 thru | or 9 A lithium ion battery system comprising: a lithium ion secondary battery.
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CN116525815B (en) * 2023-06-30 2023-11-17 宜宾锂宝新材料有限公司 Spherical lithium nickel manganese oxide positive electrode material, preparation method thereof and composite positive electrode material

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