JP2005235624A - Manufacturing method for nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To exhibit sufficient performance of a battery using a Ni based compound as a positive active material by removing a residual alkali from the nickel based positive active material. <P>SOLUTION: In the manufacturing method for the nonaqueous electrolyte secondary battery wherein a power generation element comprising a positive electrode using a lithium content stratified nickel oxide represented by a general formula Li<SB>a</SB>Ni<SB>x</SB>M<SB>y</SB>O<SB>2</SB>(0.3≤a≤1.05, 0.7≤x≤1, 0≤y≤0.3, 1≤x+y≤1.02, M is at least one kind of an element selected from B, Al, Mg, Fe, Sn, Cr, Cu, Ti, Zn, Co and Mn.) as an active material, a negative electrode using a carbon material capable of storing and releasing lithium as an active material, a nonaqueous electrolyte and a separator are housed in a battery case, a pulse voltage is applied in a period of 1 to 100 ms so that an open circuit potential of the positive electrode is 3.8-4.2V to the dissolution and deposition potential of lithium and a closed circuit electric potential of the positive electrode is 4.4-4.5V to a dissolution and deposition potential of lithium in a condition that a battery case is opened, then it is sealed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

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

  With the rapid reduction in size and weight of electronic devices, there is an increasing demand for the development of secondary batteries that are small, lightweight, have high energy density, and can be repeatedly charged and discharged with respect to the battery that is the power source. In addition, due to environmental problems such as air pollution and an increase in carbon dioxide, early commercialization of electric vehicles is desired, and an excellent secondary battery having features such as high efficiency, high output, high energy density, and light weight. Development is desired.

  As a secondary battery that satisfies these requirements, a secondary battery using a non-aqueous electrolyte has been put into practical use. This battery has an energy density several times that of a battery using a conventional aqueous electrolyte. For example, a lithium-containing layered cobalt oxide (hereinafter referred to as a Co-based compound), a lithium-containing layered nickel oxide (hereinafter referred to as a Ni-based compound) or a spinel-type lithium manganese composite oxide (hereinafter referred to as a Mn-based) is used as a positive electrode of a nonaqueous electrolyte secondary battery. And a long-life 4V class non-aqueous electrolyte secondary battery using a carbon material capable of inserting and extracting lithium in the negative electrode has been put into practical use.

Among these, the Ni-based compound has a lithium-based amount of lithium that can be inserted and desorbed within the potential range (3.0 to 4.3 V vs. Li / Li ⁺ ) actually used in the nonaqueous electrolyte secondary battery. Since it has more features than Mn-based compounds and is rich in resources, many developments have been made with the aim of developing batteries with high capacity and low cost.

  As shown in Patent Document 1, Ni-based compounds are difficult to synthesize compared to Co-based compounds that have been widely adopted up to now, and initially produce large quantities of homogeneous crystals. However, after that, improvement in crystallinity has been devised by means such as excessive mixing of lithium sources and firing.

  However, as shown in Patent Document 2, when an excess lithium source remains during firing, it reacts with moisture in the air during handling in the furnace or in the air, and an alkali such as lithium hydroxide is present on the surface or inside of the active material. The problem of generating came to happen. This residual alkali content may gradually generate gas in the battery, leading to a decrease in capacity due to an increase in resistance and a liquid leakage due to an increase in internal pressure. Therefore, in order to obtain satisfactory life performance and reliability, It can be said that the smaller the alkali, the better.

  Further, as shown in Example 1 of Patent Document 2, when the molar ratio of the lithium raw material to the metal oxide is set to 1, good crystallinity is often not obtained as described above, and oxygen The process of spending a total of 35 hours on firing using an air current is costly and is not expected to be industrially feasible. In addition, even if the firing process is strictly controlled, depending on the storage conditions after firing and the atmosphere at the time of electrode plate manufacturing and battery assembly, there is a risk that residual alkali may increase rapidly and impair battery performance. An invention of an effective and simple removal method other than the optimization of conditions was also required.

  As shown in Patent Document 3, the decomposition of the residual alkali proceeds promptly in an overcharged state. Therefore, as a method for removing the battery after fabrication, a method of overcharging with the battery case opened can be conceived. However, if overcharge is performed, the crystal structure of the positive electrode active material deteriorates, the electrolytic solution deteriorates due to oxidative decomposition, and many problems such as deposition of metallic lithium on the negative electrode are not appropriate. . Note that the deterioration of the positive electrode crystal structure due to overcharge proceeds rapidly at a potential higher than the potential at which the c-axis length changes from expansion to contraction due to the progress of charging, and there are some fluctuations depending on the composition of the active material. Shrinkage starts when the potential is around 4.3 V with respect to the dissolution precipitation potential of lithium. Also, the oxidative decomposition of the electrolyte proceeds rapidly after the positive electrode is charged to near 4.3V. Therefore, the overcharged state here means a state in which the open circuit potential of the positive electrode is 4.3 V or higher.

JP 10-092429 A JP 7-142033 A JP-A-5-242913

General formula Li _a Ni _x M _y O ₂ (0.3 ≦ a ≦ 1.05, 0.7 ≦ x ≦ 1, 0 ≦ y ≦ 0.3, 1 ≦ x + y ≦ 1.02, M is B, Al , Mg, Fe, Sn, Cr, Cu, Ti, Zn, Co, Mn) and a carbon material capable of occluding and releasing lithium, and a positive electrode using a lithium-containing layered nickel oxide as an active material A non-aqueous electrolyte secondary battery in which a power generation element consisting of a negative electrode with an active material and a non-aqueous electrolyte and separator is housed in a battery case generates residual gas on the positive electrode active material gradually decomposes to generate gas However, there has been a problem that the discharge capacity and the life performance are deteriorated or liquid leakage is liable to occur. In addition, since the amount of the residual alkali varies depending on the raw material production lot, storage condition, battery production time, etc., there is a problem that the performance of the produced battery cannot be predicted.

  When the present inventor investigated the cause of the generation of residual alkali, the reaction between the compound and the surrounding water or carbon dioxide gas progresses not only during the raw material firing step but also during raw material storage and battery preparation, and lithium hydroxide and lithium carbonate. Was found to produce. Therefore, in order to prevent the influence of the residual alkali, it has been found that a removal means that can be carried out after the production of the battery is necessary.

  The problem to be solved by the present invention is to propose an effective and simple method for removing residual alkali, other than optimization of the firing conditions of the Ni-based compound. An object of the present invention is to use such a means for removing residual alkali so that the performance of a battery using a Ni-based compound as a positive electrode active material is sufficiently exhibited.

  In view of the above problems, the present inventor has applied a short-period current and induced an overcharged state only in the vicinity of the surface of the positive electrode active material, so that the residual alkali content present on the surface of the active material can be effectively obtained. A non-aqueous electrolyte secondary battery with high capacity, long life and high reliability was obtained.

The invention according to claim 1, the general formula _{Li a Ni x M y O 2} (0.3 ≦ a ≦ 1.05,0.7 ≦ x ≦ 1,0 ≦ y ≦ 0.3,1 ≦ x + y ≦ 1. 02, M is a positive electrode using a lithium-containing layered nickel oxide represented by B, Al, Mg, Fe, Sn, Cr, Cu, Ti, Zn, Co, and Mn) as an active material, lithium In a method for producing a non-aqueous electrolyte secondary battery in which a power generation element comprising a carbon material capable of occluding and releasing carbon, a non-aqueous electrolyte, and a separator is housed in a battery case, the open circuit potential of the positive electrode Is 3.8 to 4.2 V with respect to the dissolution and precipitation potential of lithium, and 1-100 ms so that the closed circuit potential of the positive electrode is 4.4 to 4.5 V with the battery case opened. It is characterized by applying a pulse voltage at a period and then sealing it. .

  According to a second aspect of the present invention, in the method for manufacturing a non-aqueous electrolyte secondary battery, the number of times of voltage application is 100 to 10,000.

  According to the present inventor, by applying a pulse voltage with a short period and inducing a reaction only in the vicinity of the surface of the positive electrode active material, decomposition of residual alkali proceeds without excess or deficiency without deterioration in battery performance, Since the alkaline content remaining on the Ni-based compound can be effectively removed, the performance of the battery using the Ni-based compound as the positive electrode active material is fully exhibited, the original excellent performance is obtained, and the residual alkali is decomposed. Because it is possible to stably supply batteries with superior discharge capacity and life characteristics compared to batteries using conventional Co-based compounds, the discharge capacity and life performance degradation due to the risk of leakage, and the risk of leakage are suppressed. Its industrial value is high.

  Hereinafter, specific embodiments of the non-aqueous electrolyte secondary battery according to the present invention will be described.

In the present invention, the overall composition of lithium-containing layered nickel oxide used as cathode active material, the general formula _{Li a Ni x M y O 2} (0.3 ≦ a ≦ 1.05,0.7 ≦ x ≦ 1,0 ≦ y ≦ 0.3, 1 ≦ x + y ≦ 1.02, and M is represented by at least one selected from B, Al, Mg, Fe, Sn, Cr, Cu, Ti, Zn, Co, and Mn.

Among the lithium-containing layered nickel oxides represented by the general formula Li _a Ni _x M _y O ₂ , the general formula Li _a Ni _x Co _y Al _z O ₂ (0.3 ≦ a ≦ 1.05, 0.7 ≦ x ≦ 0.87, 0.1 ≦ y ≦ 0.27, 0.02 ≦ z ≦ 0.1, 0.98 ≦ x + y + z ≦ 1.02) Things are preferred. In this oxide, since a part of nickel is substituted by cobalt, the change of the crystal structure accompanying charging / discharging is suppressed. Moreover, the crystal structure is further stabilized by adding trivalent and stable aluminum.

  Furthermore, charging to a region where a <0.3 is accompanied by a large change in the c-axis length, which accelerates the collapse of the crystal structure and the increase in plate resistance. Therefore, it is preferable not to charge to such a region. For the same reason, it is preferable that the discharge be within a range of a ≦ 1.05.

  Further, when x is less than 0.7, the discharge capacity is reduced to the same level as that of a conventional non-aqueous electrolyte battery using a cobalt-based compound as a positive electrode active material, and when it is more than 0.87, the thermal stability is extremely reduced. Therefore, x is preferably in the range of 0.7 to 0.87. Further, if y is less than 0.1, the crystal structure becomes unstable. Conversely, even if it exceeds 0.27, the stabilization of the crystal structure reaches its peak, and only leads to a decrease in discharge capacity. A range of .1 to 0.27 is preferred. When z is less than 0.02, the stability of the crystal structure is lowered, and the thermal stability during charging is also lowered. However, when z exceeds 0.1, the discharge capacity is remarkably reduced. Therefore, z is preferably in the range of 0.02 to 0.1.

  By using such a compound as the positive electrode active material, it is possible to design a battery having a higher capacity and a longer life than a battery using a Co-based compound, which is the current mainstream, as the positive electrode active material.

  Next, the open circuit potential of the positive electrode is 3.8 to 4.2 V with respect to the dissolution and precipitation potential of lithium, and the closed circuit potential of the positive electrode is in a cycle of 1 to 100 ms with the battery case opened. The adverse effect of residual alkali can be removed by applying a pulse voltage of 4.4 to 4.5 V and then sealing. When a pulse voltage is applied when the open circuit potential of the positive electrode is 3.8 V or less, the current value increases, and there is a high risk of local overcharge of the positive electrode due to non-uniform charging and lithium electrodeposition on the negative electrode. This is not preferable because it may cause heat generation. In addition, it is not preferable to apply a pulse voltage with an open circuit potential of 4.2 V or higher because the possibility of overcharging not only near the surface but also inside the active material increases.

  The residual alkali begins to decompose at around 4.3 V, but the higher the potential, the better to increase the decomposition rate. However, if the positive electrode potential is raised, that is, if the battery voltage is raised too much, the oxidative decomposition of the electrolyte and the electrodeposition of lithium on the negative electrode proceed rapidly, so the closed circuit potential when the pulse voltage is applied is 4.4-4. It is appropriate to limit the range to 5V.

When the reaction process of Ni-based compounds is analyzed by the AC impedance method, two semicircles generally appear in the Cole-Cole plot, and the semicircle derived from the surface layer impedance at the positive electrode / electrolyte interface is around 10 Hz to 1 kHz. A semi-circle derived from charge transfer impedance is observed in the vicinity of 1 Hz to 10 mHz (Journal of Power Sources 54, 209 (1995)).

  The gist of the present invention is to induce reaction of the compound surface layer to decompose residual alkali, and it is not necessary to charge and discharge the compound. Rather, in order to prevent deterioration of the compound itself due to overcharging, it is necessary to apply a pulse voltage so that the latter does not occur. For this purpose, the period of the applied pulse voltage is preferably 1 ms (corresponding to 1 kHz) to 100 ms (corresponding to 10 Hz).

Note that the pulse voltage pattern to be applied may be a rectangular wave pulse, a triangular wave, a sine wave, or the like as shown in FIG. 2 to FIG. 4 as described in Japanese Patent Laid-Open No. 2002-216850. 2 to 4, the horizontal axis represents time (ms), the vertical axis represents the positive electrode potential (V) with respect to the lithium precipitation potential, CCV represents the maximum positive circuit potential of the positive electrode, and OCV represents the open circuit potential of the positive electrode. Show. 2, T _{1 to} T ₂ are “pulse widths”, T _{2 to} T ₃ are “pulse intervals”, and in FIGS. 2 to 4, T _{1 to} T ₃ are “periods”. is there. In FIG. 3, the time from T _{1 to} T ₂ is equal to the time from T _{2 to} T ₃ .

  When the number of times of application of current is small, the residual alkali is not sufficiently decomposed and it is difficult to obtain the effect of the present invention. On the other hand, when the number of times of application is large, even if the open circuit potential of the positive electrode as a whole is 4.2 V or less, partial overcharge may progress and battery performance may be degraded. Therefore, the number of times of application is preferably about 100 to 10,000.

  In this way, the residual alkali that will gradually decompose when left after charging or when left at high temperature is decomposed in advance when the battery is produced, and the gas generated in the decomposition is degassed and sealed, thereby sealing the battery. It is possible to suppress the expansion of the battery and the increase in internal resistance, so there is little possibility of a decrease in capacity and life, and a non-aqueous electrolyte secondary battery that exhibits the excellent performance inherent in Ni-based compounds can be stabilized. Can be manufactured.

  A cross-sectional structure of the nonaqueous electrolyte secondary battery of the present invention is shown in FIG. In FIG. 1, 1 is a non-aqueous electrolyte secondary battery, 2 is an electrode group, 3 is a negative electrode plate, 4 is a positive electrode plate, 5 is a separator, 6 is a battery container, 7 is a lid, 8 is a safety valve, 9 is a negative electrode terminal, 10 is a negative electrode lead, and 11 is a minute lithium reference electrode.

  This non-aqueous electrolyte secondary battery includes an electrode group 2 in which a positive electrode plate 4 and a negative electrode plate 3 using the above compound as a positive electrode active material are wound into a circular shape or an oval shape via a separator 5. Is stored in the battery container 6 and the electrode group 2 is impregnated with a non-aqueous electrolyte (not shown). The current collector of the positive electrode plate 1 is joined to the battery container 6, and the battery container 6 also serves as a positive electrode terminal. The negative electrode, separator, and electrolytic solution used in this non-aqueous electrolyte secondary battery are not particularly different from those conventionally used, and those that are usually used can be used.

  That is, as the negative electrode material used for the nonaqueous electrolyte secondary battery of the present invention, carbon materials such as natural graphite, artificial graphite, cokes, carbon black, pyrolytic carbons, and carbon fibers capable of occluding and releasing lithium ions are available. Can be mentioned.

  In addition, as the separator used in the nonaqueous electrolyte secondary battery of the present invention, a microporous membrane made of a polyolefin resin such as polyethylene is used, and a plurality of microporous membranes having different materials, weight average molecular weights and porosity are laminated. Or those containing a suitable amount of various plasticizers, antioxidants, flame retardants and the like in these microporous membranes.

  There are no particular restrictions on the organic solvent of the electrolyte used in the non-aqueous electrolyte secondary battery of the present invention. For example, ethers, ketones, lactones, nitriles, amines, amides, sulfur compounds, halogenated hydrocarbons. , Esters, carbonates, nitro compounds, phosphate ester compounds, sulfolane hydrocarbons, etc. can be used, among these ethers, ketones, esters, lactones, halogenated hydrocarbons , Carbonates and sulfolane compounds are preferred. Examples of these include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, anisole, monoglyme, 4-methyl-2-pentanone, ethyl acetate, methyl acetate, methyl propionate, ethyl propionate, 1,2-dichloroethane. , Γ-butyrolactone, dimethoxyethane, methyl formate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, propylene carbonate, ethylene carbonate, vinylene carbonate, dimethylformamide, dimethyl sulfoxide, dimethylthioformamide, sulfolane, 3-methyl-sulfolane, phosphorus Examples thereof include trimethyl acid, triethyl phosphate, and mixed solvents thereof, but are not necessarily limited thereto. Cyclic carbonates and cyclic esters are preferred. Most preferably, the organic solvent is a mixture of one or more of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, and diethyl carbonate.

As the electrolyte salt used for the nonaqueous electrolyte secondary battery of the present invention is not particularly _{limited, LiClO 4, LiBF 4, LiAsF} 6, CF 3 SO 3 Li, LiPF 6, LiN (CF 3 SO 2) 2 , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiI, LiAlCl _{4 and the} like and mixtures thereof. Preferably, a lithium salt obtained by mixing one or more of LiBF ₄ and LiPF ₆ is preferable.

  Other battery components include a current collector, a terminal, an insulating plate, a battery case, and the like. However, these components may be used as they are.

  Examples of the present invention will be described below together with comparative examples.

[Synthesis of Ni-based positive electrode active material]
[Synthesis of lithium nickelate]
Nickel hydroxide and lithium hydroxide were mixed uniformly using a ball mill so that the molar ratio of lithium to nickel was 1.05: 1, and this mixture was calcined at 700 ° C. for 20 hours in an oxygen atmosphere. After cooling to room temperature, the mixture was pulverized in dry argon to obtain lithium nickelate (positive electrode active material symbol N0) represented by the composition formula LiNiO ₂ .

[Synthesis of positive electrode active material in which a part of Ni is substituted with Co and Al]
Nickel sulfate and cobalt sulfate were dissolved at a predetermined blending ratio, and a sodium hydroxide solution was added with sufficient stirring to obtain a nickel-cobalt composite coprecipitated hydroxide.

  The produced coprecipitate was washed with water, dried, mixed well with aluminum hydroxide, and then lithium hydroxide monohydrate was added so that the molar ratio of lithium to nickel + cobalt + aluminum was 1.05: 1. The precursor was prepared by adjusting.

Next, this precursor was calcined in an oxygen atmosphere at 700 ° C. for 20 hours, cooled to room temperature, taken out in a dry argon gas and pulverized, and the composition formula: general formula Li _a Ni _x Co _y Al _z O ₂ (0 .3 ≦ a ≦ 1.05, 0.7 ≦ x ≦ 0.87, 0.1 ≦ y ≦ 0.27, 0.02 ≦ z ≦ 0.1, 0.98 ≦ x + y + z ≦ 1.02) Various expressed Ni-based compounds (positive electrode active material symbols N1 to N15) were obtained. In addition, the obtained compound was vacuum-stored in the desiccator.

Subsequently, as a starting material, lithium carbonate and tricobalt tetroxide are mixed, calcined in the atmosphere at 800 ° C. for 20 hours, cooled to room temperature, pulverized in the atmosphere, and expressed by the composition formula LiCoO _2. A Co-based compound (positive electrode active material symbol C1) was obtained. The obtained compound was vacuum-stored in a desiccator.

  A part of the compound was removed from the desiccator and subjected to qualitative analysis. As a result, in powder X-ray diffraction, no peak of impurities such as unreacted hydroxide, lithium aluminate, or lithium carbonate was observed for all compounds. Table 1 shows the average composition of all the compounds analyzed by ICP emission spectroscopy.

  Next, test batteries were prepared using the positive electrode active material symbols N0, N1 to N15, and C1. The positive electrode was mixed with 87% by weight of the above compound, 5% by weight of acetylene black, and 8% by weight of polyvinylidene fluoride, and N-methyl-2-pyrrolidone (NMP) having a water content of 50 ppm or less was added to make a paste. It was produced by applying and drying on an aluminum foil to form a positive electrode mixture layer. The negative electrode was prepared by mixing a carbon material (graphite) and polyvinylidene fluoride (PVdF), adding NMP to this to form a paste, and applying and drying on a copper foil to form a negative electrode mixture layer. . After forming the electrode group by winding the belt-like positive electrode and negative electrode thus produced in an oval shape through a separator, this electrode group was inserted into a long cylindrical bottomed aluminum container, After filling the core part of the electrode group with a filler, an electrolytic solution was injected, and the container and the lid were sealed and welded by laser welding. All processes from paste preparation to electrode processing and battery assembly were performed in a dry environment with a dew point of 50 ° C. or lower.

  After charging these test batteries to a voltage of 4.2 V at a current of 800 mA, the discharge capacity when discharging to a voltage of 3.0 V at a current of 800 mA is measured, and the discharge capacity per gram of the positive electrode active material is calculated. did. These values are shown in Table 1.

  Next, these test batteries are charged and discharged for 300 cycles under the same test conditions as the above charge and discharge, the discharge capacity at the 300th cycle is obtained, and this is divided by the discharge capacity at the first cycle. "Retention rate". These values are shown in Table 1.

  Next, the thermal stability test of these test batteries was performed using another battery manufactured simultaneously with the battery subjected to the charge / discharge cycle. In the test batteries of the positive electrode active material symbols N0 and N1 to N15, the battery is charged at a current of 160 mA until the state of Li0.3 is reached, and in the test batteries of the positive electrode active material symbol C1 until the state of Li0.5 is obtained at a current of 160 mA. Charged. After charging, a safety test was conducted in accordance with the nail penetration test method described in “Lithium Secondary Battery Safety Evaluation Standard Guidelines (SBA G101)” issued by Japan Storage Battery Industry Association. These results are shown in Table 1. Compared with the test results of the battery using the positive electrode active material symbol C1, it is marked as ◯ when the safety is equivalent, △ when the safety is slightly lowered, and × when the safety is significantly lowered. It is.

  The storage characteristics of the batteries prepared at the same time as the batteries subjected to the charge / discharge cycle test and the thermal stability test were compared. After charging to a voltage of 4.2 V with a current of 1 CA, charging / discharging of discharging to 3.0 V with a current of 800 mA was repeated three times in the initial stage, and the third discharge capacity was defined as the initial capacity. Next, after charging again to a voltage of 4.2 V at a current of 800 mA, the battery was stored in an environment of 60 ° C. for 10 days, and after the storage, charging and discharging were repeated three times under the same charging and discharging conditions as in the initial stage. The discharge capacity for the second time was defined as the capacity after storage. Then, the capacity after storage was divided by the initial capacity, and this was defined as “capacity retention after storage”. These values are shown in Table 1.

From the results shown in Table 1, compared to conventional non-aqueous electrolyte secondary batteries using Co-based compounds, batteries that are comprehensively superior in terms of discharge capacity, cycle life performance, thermal stability, storage performance, etc. The composition and the composition of the compound surface are the general formulas Li _a Ni _x Co _y Al _z O ₂ (0.3 ≦ a ≦ 1.05, 0.7 ≦ x ≦ 0.87, 0.1 ≦ y ≦ 0.27 , 0.02 ≦ z ≦ 0.1, 0.98 ≦ x + y + z ≦ 1.02), which was found to be a battery using a positive electrode active material.

[Examples 1 to 12 and Comparative Examples 1 to 11]
In Examples 1 to 12 and Comparative Examples 1 to 11, a Ni-based compound in which the overall average composition of the positive electrode active material symbol N1 is represented by Li _1.03 Ni _0.70 Co _0.20 Al _0.10 O ₂ is used. It was. As the positive electrode active material symbol N1, one stored in a desiccator after synthesis was used. The Ni-based compound of the positive electrode active material symbol N1 is a compound analyzed by ICP emission spectroscopy in which no peak of impurities such as unreacted hydroxide and lithium aluminate is observed in the qualitative analysis by powder X-ray diffraction. The overall average composition was also the same as in Example 1.

[Example 1]
A test battery was fabricated using the positive electrode active material symbol N1. For the positive electrode, 87% by weight of the positive electrode active material symbol N1, 5% by weight of acetylene black, and 8% by weight of polyvinylidene fluoride are mixed, and N-methyl-2-pyrrolidone (NMP) having a water content of 50 ppm or less is added to the paste. In addition, it was applied on an aluminum foil and dried to form a positive electrode mixture layer. The negative electrode was prepared by mixing a carbon material (graphite) and polyvinylidene fluoride (PVdF), adding NMP to this to form a paste, and applying and drying on a copper foil to form a negative electrode mixture layer. . After forming the electrode group by winding the belt-like positive electrode and negative electrode thus produced in an oval shape through a separator, this electrode group was inserted into a long cylindrical bottomed aluminum container, After filling the core part of the electrode group with the filler, the electrolyte was injected.

  After pouring, the lid was not welded and charged so that the positive electrode open circuit potential was 4.1 V, and then the positive electrode closed circuit potential was 4.45 V, and the voltage was applied with the rectangular pulse shown in FIG. . The conditions of the rectangular wave pulse were as follows: CCV was 4.45 V, OCV was 4.1 V, pulse width was 5 ms, pulse interval was 5 ms, cycle was 10 ms, and the number of applications was 1000 times. After the voltage application, the container and the lid were sealed and welded by laser welding. Also in this battery, all processes from paste preparation to electrode processing, battery assembly, and current application were performed in a dry environment with a dew point of 50 ° C. or less. This was designated as the battery of Example 1.

  Note that the open circuit potential and the closed circuit potential of the positive electrode were measured using a small lithium reference electrode 11 inserted in the A part of FIG. The reference electrode was insulated from the positive electrode and the negative electrode, and the potential measurement lead connected to the reference electrode extended to the outside of the battery, and the potential between the potential measurement lead and the positive electrode terminal was measured. The reference electrode does not need to be inserted into every battery, and the charging method according to the present invention performed the condition determination with one battery.

[Example 2]
Before applying the pulse voltage, it is charged so that the positive circuit open circuit potential is 3.9 V, and the rectangular wave pulse conditions are as follows: CCV is 4.45 V, OCV is 3.9 V, pulse width is 5 ms, pulse interval is 5 ms, period Was set to 10 ms, and the battery of Example 2 was fabricated under the same conditions as in Example 1 except that the number of times of application was 1000.

[Example 3]
Before applying the pulse voltage, it is charged so that the positive open circuit potential is 4.2V, and the rectangular wave pulse conditions are as follows: CCV is 4.45V, OCV is 4.2V, pulse width is 5ms, pulse interval is 5ms, period Was set to 10 ms, and the battery of Example 3 was fabricated under the same conditions as Example 1 except that the number of times of application was 1000 times.

[Example 4]
Before applying the pulse voltage, it is charged so that the positive circuit open circuit potential is 3.8V, and the rectangular wave pulse conditions are as follows: CCV is 4.45V, OCV is 3.8V, pulse width is 5ms, pulse interval is 5ms, cycle Was set to 10 ms, and the battery of Example 4 was fabricated under the same conditions as in Example 1 except that the number of times of application was 1000.

[Example 5]
Before applying the pulse voltage, it is charged so that the positive circuit open circuit potential is 4.1V, and the conditions of the rectangular wave pulse are as follows: CCV is 4.4V, OCV is 4.1V, pulse width is 5ms, pulse interval is 5ms, period Was set to 10 ms, and the battery of Example 5 was fabricated under the same conditions as in Example 1 except that the number of times of application was 1000.

[Example 6]
Before applying the pulse voltage, it is charged so that the positive circuit open circuit potential is 4.1V. The conditions of the rectangular wave pulse are as follows: CCV is 4.5V, OCV is 4.1V, pulse width is 5ms, pulse interval is 5ms, period Was set to 10 ms, and the battery of Example 6 was fabricated under the same conditions as Example 1 except that the number of times of application was 1000 times.

[Example 7]
Before applying the pulse voltage, it is charged so that the positive circuit open circuit potential is 4.1 V, and the conditions of the rectangular wave pulse are as follows: CCV is 4.45 V, OCV is 4.1 V, pulse width is 0.5 ms, and pulse interval is 0 A battery of Example 7 was fabricated under the same conditions as in Example 1 except that the period was 0.5 ms, the period was 1 ms, and the number of applications was 1000.

[Example 8]
Before applying the pulse voltage, it is charged so that the positive circuit open circuit potential is 4.1V. The conditions of the rectangular wave pulse are as follows: CCV is 4.45V, OCV is 4.1V, pulse width is 50ms, pulse interval is 50ms, period Was set to 100 ms, and the number of times of application was 1000. A battery of Example 6 was fabricated under the same conditions as in Example 1.

[Example 9]
Before applying the pulse voltage, it is charged so that the positive circuit open circuit potential is 4.1V, and the conditions of the rectangular wave pulse are as follows: CCV is 4.45V, OCV is 4.1V, pulse width is 5ms, pulse interval is 5ms, period Was set to 10 ms, and the battery of Example 9 was fabricated under the same conditions as in Example 1 except that the number of times of application was 100 times.

[Example 10]
Before applying the pulse voltage, it is charged so that the positive circuit open circuit potential is 4.1V, and the conditions of the rectangular wave pulse are as follows: CCV is 4.45V, OCV is 4.1V, pulse width is 5ms, pulse interval is 5ms, period Was 10 ms, and the battery of Example 10 was fabricated under the same conditions as in Example 1 except that the number of times of application was 10,000.

[Example 11]
Before applying the pulse voltage, the positive electrode open circuit potential is charged to 4.1 V, the triangular wave pulse voltage shown in FIG. 3 is applied, and the triangular wave pulse conditions are as follows: CCV is 4.45 V, OCV is 4.1 V, A battery of Example 11 was produced under the same conditions as Example 1 except that the period was 10 ms and the number of times of application was 1000.

[Example 12]
Before applying the pulse voltage, the positive electrode open circuit potential is charged to 4.1 V, the sine wave pulse voltage shown in FIG. 4 is applied, and the conditions of the sine wave pulse are 4.45 V for CCV and 4. V for OCV. A battery of Example 12 was fabricated under the same conditions as Example 1 except that the voltage was 1 V, the period was 10 ms, and the number of times of application was 1000.

[Comparative Example 1]
Before applying the pulse voltage, it is charged so that the positive circuit open circuit potential is 4.1V, and the conditions of the rectangular wave pulse are as follows: CCV is 4.6V, OCV is 4.1V, pulse width is 5ms, pulse interval is 5ms, period Was set to 10 ms, and the battery of Comparative Example 1 was fabricated under the same conditions as in Example 1 except that the number of times of application was 1000.

[Comparative Example 2]
Before applying the pulse voltage, it is charged so that the positive circuit open circuit potential is 4.1V, and the conditions of the rectangular wave pulse are as follows: CCV is 4.3V, OCV is 4.1V, pulse width is 5ms, pulse interval is 5ms, period Was set to 10 ms, and the battery of Comparative Example 2 was fabricated under the same conditions as in Example 1 except that the number of times of application was 1000.

[Comparative Example 3]
Before applying the pulse voltage, it is charged so that the positive circuit open circuit potential is 4.1 V, and the conditions of the rectangular wave pulse are as follows: CCV is 4.45 V, OCV is 4.1 V, pulse width is 0.05 ms, and pulse interval is 0 A battery of Comparative Example 3 was manufactured under the same conditions as in Example 1 except that the period was set to 0.05 ms, the period was 0.1 ms, and the number of times of application was 1000 times.

[Comparative Example 4]
Before applying the pulse voltage, it is charged so that the positive circuit open circuit potential is 4.1V, and the conditions of the rectangular wave pulse are as follows: CCV is 4.45V, OCV is 4.1V, pulse width is 500ms, pulse interval is 500ms, period Was set to 1000 ms, and the battery of Comparative Example 4 was produced under the same conditions as in Example 1 except that the number of times of application was 1000 times.

[Comparative Example 5]
Before applying the pulse voltage, it is charged so that the positive circuit open circuit potential is 4.1V, and the conditions of the rectangular wave pulse are as follows: CCV is 4.45V, OCV is 4.1V, pulse width is 5ms, pulse interval is 5ms, period Was set to 10 ms, and the battery of Comparative Example 5 was fabricated under the same conditions as in Example 1 except that the number of times of application was 10.

[Comparative Example 6]
Before applying the pulse voltage, it is charged so that the positive circuit open circuit potential is 4.1V, and the conditions of the rectangular wave pulse are as follows: CCV is 4.45V, OCV is 4.1V, pulse width is 5ms, pulse interval is 5ms, period Was 10 ms, and the number of times of application was 100,000. A battery of Comparative Example 6 was produced under the same conditions as in Example 1.

[Comparative Example 7]
Immediately after injecting the electrolyte, the container and the lid are sealed and welded by laser welding, and then charged so that the positive electrode open circuit potential is 4.1 V. A rectangular wave pulse voltage under the same conditions as in Comparative Example 6 A battery of Comparative Example 7 was produced under the same conditions as in Example 1 except that was applied.

[Comparative Example 8]
Before applying the pulse voltage, it is charged so that the positive circuit open circuit potential is 4.4V, and the conditions of the rectangular wave pulse are as follows: CCV is 4.45V, OCV is 4.4V, pulse width is 5ms, pulse interval is 5ms, period Was 10 ms, and the battery of Comparative Example 8 was fabricated under the same conditions as in Example 1 except that the number of times of application was 1000.

[Comparative Example 9]
Before applying the pulse voltage, it is charged so that the positive circuit open circuit potential is 3.7V, and the conditions of the rectangular wave pulse are as follows: CCV is 4.45V, OCV is 3.7V, pulse width is 5ms, pulse interval is 5ms, period Was 10 ms, and the battery of Comparative Example 9 was produced under the same conditions as in Example 1 except that the number of times of application was 1000.

[Comparative Example 10]
Before applying the pulse voltage, it is charged so that the positive circuit open circuit potential is 4.3V, and the conditions of the rectangular wave pulse are as follows: CCV is 4.45V, OCV is 4.3V, pulse width is 5ms, pulse interval is 5ms, period Was set to 10 ms, and the battery of Comparative Example 10 was produced under the same conditions as in Example 1 except that the number of times of application was 1000 times.

[Comparative Example 11]
Immediately after injecting the electrolyte, the container and the lid were sealed by laser welding, and a battery of Comparative Example 11 was produced under the same conditions as in Example 1 except that no pulse voltage was applied.

  The positive open circuit potential and the pulse conditions during charging before applying the pulse voltage of Examples 1 to 12 are shown in Table 2, and the same conditions of Comparative Examples 1 to 11 are shown in Table 3.

  About the test battery of Examples 1-12 and Comparative Examples 1-11, the discharge capacity measurement test, the charging / discharging cycle test, and the storage test were done.

  In the discharge capacity measurement test, the test battery is charged to a voltage of 4.2 V at a current of 800 mA in a 25 ° C. environment, and then discharged to a voltage of 3.0 V at a current of 1 CA. This capacity is defined as an “initial discharge capacity”. Further, after the discharge, the AC internal resistance and the battery thickness at 1 kHz were measured to obtain “initial internal resistance” and “initial battery thickness”.

  In the charge / discharge cycle test, the test battery is charged / discharged for 300 cycles under the same conditions as the discharge capacity measurement test, the discharge capacity at the 300th cycle is defined as “post-cycle discharge capacity”, and the post-cycle discharge capacity is divided by the initial discharge capacity. The “capacity retention after cycle” was calculated. Further, even after 300 cycles of charge and discharge, the AC internal resistance and battery thickness at 1 kHz were measured, and were defined as “post-cycle internal resistance” and “post-cycle battery thickness”.

  The storage test was performed by comparing the storage characteristics of another battery produced at the same time as the battery subjected to the charge / discharge cycle test. After charging to a voltage of 4.2 V with an ICA current, charging / discharging to discharge to 3.0 V with a current of 1 CA was repeated three times in the initial stage, and the third discharge capacity was defined as “discharge capacity before storage”. Next, after charging again to a voltage of 4.2 V with a current of 1 CA, the battery was stored in an environment of 60 ° C. for 10 days, and after the storage, the battery was repeatedly charged and discharged three times under the same charge / discharge conditions as in the initial stage. The discharge capacity at the second time was defined as “discharge capacity after storage”. Then, the “discharge capacity after storage” was calculated by dividing the discharge capacity after storage by the discharge capacity before storage. Moreover, the AC internal resistance and battery thickness at 1 kHz were measured after storage, and were set as “internal resistance after storage” and “battery thickness after storage”.

  These measurement results are shown in Tables 4-7.

  From the results shown in Tables 4 to 7, as in the batteries of Examples 1 to 12, the positive electrode was in a state where the open circuit potential of the positive electrode was 3.8 to 4.2 V and the battery case was opened. By applying a pulse current having a period of 1 to 100 ms so that the closed circuit potential of the battery becomes 4.4 to 4.5 V, the residual alkali can be effectively removed even after the battery is assembled. It was found that the discharge capacity of the battery using the compound as the positive electrode active material was improved, and both the life performance and the standing performance could be improved without sacrificing safety. In addition, it was found that there is almost no effect when the number of application of the pulse current is small or too large, and the current application of 100 to 10,000 times is optimal.

  In addition, like the batteries of Comparative Examples 1 to 11, when the pulse current application conditions deviate from the scope of the present invention, compared with the batteries of Examples 1 to 12, the capacity retention rate after cycling and after storage It was found that the capacity retention ratio decreased, the internal resistance after cycling and the battery thickness after cycling increased, and the internal resistance after storage and the battery thickness after storage increased.

In Examples 1 to 12 and Comparative Examples 1 to 11, a Ni-based compound in which the overall average composition of the positive electrode active material symbol N1 is represented by Li _1.03 Ni _0.70 Co _0.20 Al _0.10 O ₂ is used as the positive electrode. Although used as an active material, even when the positive electrode active material symbols N0 and N2 to N15 shown in Table 1 other than the positive electrode active material symbol N1 are used, the pulse current application conditions are within the scope of the present invention. It has been confirmed that residual alkali can be effectively removed even after the battery is assembled, the discharge capacity of the battery is improved, and both the life performance and the leaving performance can be improved without sacrificing safety.

The figure which shows the cross-section of a nonaqueous electrolyte secondary battery. The figure which shows a rectangular wave pulse voltage pattern. The figure which shows a triangular wave pulse voltage pattern. The figure which shows a sine wave pulse voltage pattern.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Nonaqueous electrolyte secondary battery 2 Electrode group 3 Negative electrode plate 4 Positive electrode plate 5 Separator 6 Battery container 7 Lid 8 Safety valve 9 Negative electrode terminal 10 Negative electrode lead 11 Minute lithium reference electrode

Claims (2)

General formula Li _a Ni _x M _y O ₂ (0.3 ≦ a ≦ 1.05, 0.7 ≦ x ≦ 1, 0 ≦ y ≦ 0.3, 1 ≦ x + y ≦ 1.02, M is B, Al , Mg, Fe, Sn, Cr, Cu, Ti, Zn, Co, Mn) and a carbon material capable of occluding and releasing lithium, and a positive electrode using a lithium-containing layered nickel oxide as an active material In the method of manufacturing a non-aqueous electrolyte secondary battery in which a power generation element comprising a negative electrode made of an active material, a non-aqueous electrolyte, and a separator is housed in a battery case, the open circuit potential of the positive electrode is changed to a lithium dissolution precipitation potential. On the other hand, it is 3.8 to 4.2 V, and in the state where the battery case is opened, the closed circuit potential of the positive electrode is 4.4 to 4.5 V with respect to the lithium dissolution precipitation potential. A pulse voltage was applied at a period of 100 ms and then sealed. Non-aqueous method for producing a liquid electrolyte secondary battery characterized by and. 2. The method for producing a non-aqueous electrolyte secondary battery according to claim 1, wherein the voltage is applied 100 to 10,000 times.

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