JP6541035B2 - Method of evaluating battery characteristics using non-aqueous electrolyte coin type battery and method of evaluating battery characteristics of positive electrode active material for non-aqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a method of evaluating the characteristics of a non-aqueous electrolyte secondary battery, and more specifically, a method of evaluating battery characteristics using a non-aqueous electrolyte coin type battery and a positive electrode active for a non-aqueous electrolyte secondary battery using the evaluation method The present invention relates to a method for evaluating battery characteristics of a substance.

  Among non-aqueous electrolyte secondary batteries, lithium ion secondary batteries have a high energy density, and are widely used in portable electronic devices such as mobile phones and laptop computers, which are recently required to be smaller and lighter. Also, in automotive applications, development has been brisk as a clean energy source, and high performance and cost reduction such as small size, light weight, high capacity and high output are required.

The requirements for each material used in this lithium ion secondary battery, in particular, for the positive electrode material, for example, high performance for lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ) or lithium manganate (LiMnO ₄ ), etc. The development requirements of are increasingly increasing.
By the way, lithium cobaltate is expensive because it has little reserves, and it has the problem that it contains cobalt as the main component, which is unstable due to supply instability and price fluctuations, so relatively inexpensive nickel or manganese is used. Lithium nickel composite oxide or lithium manganese composite oxide contained as a main component has attracted attention from the viewpoint of cost.

However, although lithium manganate is superior in thermal stability to lithium cobaltate, its charge and discharge capacity is very small compared to other materials, and its charge and discharge cycle characteristics showing a life are also very short. , There are many practical problems as a battery.
On the other hand, lithium nickel oxide is expected as a positive electrode active material which can produce a battery with high energy density at low cost, since lithium nickel oxide exhibits a charge / discharge capacity larger than lithium cobaltate. Such lithium nickelate has the disadvantage that its thermal stability in the charged state is inferior to lithium cobaltate. That is, pure lithium nickel oxide has problems in thermal stability, charge / discharge cycle characteristics and the like, and can not be used as a practical battery. This is because the stability of the crystal structure in the charged state is lower than that of lithium cobaltate.

For this reason, in order to stabilize the crystal structure in a state where lithium is removed by charging, and to obtain a lithium nickel composite oxide having good thermal stability and charge-discharge cycle characteristics as a positive electrode active material, lithium nickel composite oxide It is a common practice to replace some of the nickel in with other substances. For example, part of nickel is replaced with a transition metal element such as cobalt, manganese, or iron, or a different element such as aluminum, vanadium, or tin (see, for example, Patent Document 1).
However, when a part of nickel in the lithium-nickel composite oxide is replaced with another substance, when a large amount of element substitution (in other words, a state in which the nickel ratio is lowered) is performed, the thermal stability increases, but the battery capacity Decrease in

On the other hand, when a small amount of element substitution (in other words, a state in which the nickel ratio is increased) is performed to prevent a decrease in battery capacity, the thermal stability is not sufficiently improved. Furthermore, if the nickel ratio is high, there is also a problem that cation mixing easily occurs at the time of firing and synthesis is difficult.
Therefore, although various lithium-nickel composite oxides in which part of nickel is replaced with another substance have been developed, it is considered that they sufficiently correspond to the demand for higher capacity and higher output in non-aqueous electrolyte secondary batteries. I can not say. Under such circumstances, there is a demand for a positive electrode active material composed of a lithium nickel composite oxide that can sufficiently meet the demand for higher capacity and higher power.

  By adjusting the length of the c-axis obtained from Rietveld analysis of X-ray diffraction in response to the above problems, the thermal stability etc. when used as a positive electrode active material can be maintained, and lithium nickel complex oxide is further obtained. A positive electrode for a non-aqueous electrolyte secondary battery having a high nickel ratio, in which high capacity and high output can be realized by controlling the porosity of particles to enhance the ease of lithium ion removal / insertion. An active material and a method for producing the same have been proposed (see Patent Document 3).

In order to advance the development of a positive electrode active material for a non-aqueous electrolyte secondary battery having a high nickel ratio as exemplified in Patent Document 3 rapidly and at low cost, the evaluation means is one of the important development factors. The need for evaluation methods is increasing.
Specific evaluation methods include so-called analytical evaluation methods such as composition analysis, XRD, SEM-EDX, and XPS, but in order to advance development of a positive electrode active material for a non-aqueous electrolyte secondary battery, the battery should be used. It is essential to actually manufacture and evaluate battery characteristics.

In the battery evaluation, the “charge / discharge capacity characteristics” and the “current output characteristics” are particularly important as the resistance evaluation of the positive electrode active material.
There are two methods for evaluating the output characteristics of a battery: direct current method and alternating current method. Direct current method applies a large current to the battery and determines the resistance from the amount of voltage drop and the applied current at that time. The AC method is a method (AC impedance method) in which a minute current is superimposed and applied, and the resistance is separated by changing the frequency.

  In this measurement by the direct current method, the resistance (output) of the entire battery is evaluated and often used by a battery maker or the like. On the other hand, in the measurement by the alternating current impedance method, since each resistance component can be separated by changing the frequency, it is used for analysis of the positive electrode active material and the negative electrode active material, and it is used in research institutes, positive electrodes, negative electrodes, electrolyte solution manufacturers, etc. It is used.

When carbon is used for the negative electrode in the production of a battery for evaluating output characteristics, the carbon particles are slurried with a binder, using a solvent, kneaded, coated, and dried, but the process is complicated. Further, since uniform dispersion, coating film thickness and void structure are also required, a method using a metal lithium sheet cut out in a desired size is simple and reasonable in speed.
However, since the generation state of dendrite on the negative electrode surface changes depending on the pressure applied to the electrodes, the amount of electrolyte between the electrodes, positive, size of negative electrode, etc., the AC impedance method etc. However, there is also a problem that it is difficult to obtain reproducible data.

Furthermore, in the method of manufacturing the positive electrode, the positive electrode active material is kneaded, coated and dried with a conductive material, a binder, and a solvent, and then coated and dried to a desired size (for example, Patent Document 2 etc.) A sheet method has been proposed in which the dry mixing is performed, a sheet is produced using a roll press or the like, and the sheet is punched into a desired size.
The former coating method is characterized in that the thickness of the coating can be reduced, and the thickness of the coating is reduced and the diffusion distance of lithium is shortened in a lithium ion secondary battery in which the diffusion of lithium ions is limited. Therefore, it is possible to obtain a lithium ion secondary battery that can be charged and discharged at a high rate and that can be evaluated for resistance by the direct current method, but the process is complicated as in the negative electrode production, and a small amount such as research and development It is not suitable for the development of a battery for development that requires evaluation of many varieties.

  The latter dry mixing sheet method has an advantage that the electrode can be prepared quickly compared to the electrode preparation method by coating, but since the electrode becomes thick, it is difficult to evaluate the resistance by the direct current method in which a high rate is applied. In the case of a battery in which such an electrode is thick, resistance evaluation by an alternating current impedance method in which a current to be applied is minute is preferable.

It is common to use a porous film made of polypropylene or polyethylene having a thickness of several tens of microns as the separator. These separators shrink due to heat generated during a short circuit, and the pores can be closed to stop the function as a battery, thereby improving the safety as a battery.
However, although these separators have merits in terms of safety, they have poor liquid retention and wettability of the electrolytic solution, the amount of the electrolytic solution between the electrodes is not stable, and measurement reproducibility becomes unstable. There is also the problem of. In particular, in an AC impedance method sensitively responding to a small resistance change of a cell, it is difficult to use as a member for an evaluation cell in terms of measurement reproducibility.

While maintaining stable quality at all times in the preparation of each part of the battery and keeping the assembly accuracy of the battery high, of course, temperature control after assembly and conditioning by energization are particularly important for resistance measurement.
Among these, the AC impedance in the early stage especially after the end of charging is sensitive to the fluctuation of the condition, and the reliability of the measurement data is an issue. As described above, it is difficult to say that conventional battery preparation and measurement methods are appropriately dealt with in terms of stability, workability, quick response, and cost for the purpose of development evaluation and pre-shipment inspection of products. It was a thing.

Unexamined-Japanese-Patent No. 5-242891 JP, 2014-103107, A International Publication 2015/008582

  Therefore, in view of the above problems, the present invention can control its evaluation conditions in order to accelerate the development of the positive electrode active material for non-aqueous electrolyte secondary batteries having a high nickel ratio at low cost, and be stable and A method for evaluating battery characteristics using a non-aqueous electrolyte coin-type battery capable of simultaneously evaluating AC impedance measurement and initial charge / discharge capacity measurement accurately and a battery of a positive electrode active material for a non-aqueous electrolyte secondary battery using the evaluation method The purpose is to provide a characterization method.

The inventor of the present invention has made it possible to quickly and inexpensively develop a positive electrode active material for a non-aqueous electrolyte secondary battery having a high nickel ratio, which is an important evaluation index, an electric current by initial charge / discharge capacity measurement and AC impedance measurement. As a battery characteristic evaluation method using a non-aqueous electrolyte coin type battery, which can control the evaluation conditions simultaneously and can evaluate the output characteristics stably and accurately.
In particular, when AC impedance measurement is performed, a coin battery is produced and allowed to stand for a predetermined time, then charging and discharging are performed, a constant current charge and discharge cycle is performed, and an initial charge and discharge capacity is measured. The constant current constant voltage charging is performed after the rest time, and after the termination of the constant current constant voltage charging, the resistance measurement by the AC impedance method is performed within a predetermined time, which makes stable resistance measurement possible, and the initial charging is performed. Since discharge capacity measurement can also be continuously performed, it has been found that efficient battery evaluation can be performed in order to shorten the battery characteristic measurement time, and the present invention has been completed.

A first invention of the present invention is a battery characteristic evaluation method using a non-aqueous electrolyte coin type battery having an electrode part in which a positive electrode film containing a positive electrode active material and an negative electrode film are disposed opposite to each other with a separator interposed. The positive electrode active material is “general formula: Li _b Ni _C Co _x M _y O ₂ (1)” (wherein, M represents at least one element selected from Al, Ti, Mn and W) , B is 0.95 ≦ b ≦ 1.03, c = 1−x−y, 0.84 ≦ c <1.00, x is 0 <x ≦ 0.15, y is 0 <y ≦ 0.07 And x + y ≦ 0.16), and the positive electrode film containing the positive electrode active material and the negative electrode film have an electrode portion in which the positive electrode film and the negative electrode film face each other with a separator interposed therebetween. Preparation of water-based electrolyte coin type battery, constant current charge, rest, constant current discharge after standing Conduct the current charge and discharge cycle to measure the initial charge and discharge capacity, and after the rest time, perform constant current constant voltage charging, and measure the resistance by the AC impedance method within one hour after the completion of the constant current constant voltage charging. A method of evaluating battery characteristics using a non-aqueous electrolyte coin cell according to claim 1.

  A second invention of the present invention is the non-aqueous electrolyte coin type, wherein the resistance measurement in the first invention is carried out within 0.05 hours or more and within 1 hour after the termination of the constant current constant voltage charging. It is a battery characteristic evaluation method using a battery.

  A third invention of the present invention is the battery characteristic evaluation using a non-aqueous electrolyte coin type battery characterized in that the negative electrode film in the first and second inventions is metal lithium or a metal containing lithium as a main component. It is a method.

  According to a fourth aspect of the present invention, there is provided a non-aqueous electrolyte coin type cell characterized in that the coin type cell of the first to third aspects is a 2032 type or 2016 type coin cell. It is a method.

According to a fifth aspect of the present invention, there is provided a battery according to any one of the first to fourth aspects of the present invention, characterized in that “the general formula: Li _b Ni _C Co” is used. _x M _y O ₂ (1) (wherein, M represents at least one element selected from Al, Ti, Mn and W, and b is 0.95 ≦ b ≦ 1.03, c Nickel content represented by: 1−x−y, 0.84 ≦ c <1.00, x is 0 <x ≦ 0.15, y is 0 <y ≦ 0.07, x + y ≦ 0.16) A method of evaluating battery characteristics of a positive electrode active material for a non-aqueous electrolyte secondary battery, characterized by grasping the characteristics of the positive electrode active material for a non-aqueous electrolyte secondary battery, which is a lithium nickel composite oxide having a high

  According to the present invention, a positive electrode using a positive electrode active material for a non-aqueous electrolyte secondary battery containing lithium having a high nickel content and a negative electrode consisting of metal lithium or a metal containing lithium as a main component face each other with a separator interposed therebetween. In the battery characteristics evaluation method using the 2032 type or 2016 type coin battery in which the electrode portions arranged as described above are immersed in a non-aqueous electrolyte solution, a coin battery is manufactured particularly when AC impedance measurement is performed. Then, after standing for a predetermined time, charge and discharge are performed, a constant current charge / discharge cycle is performed to measure an initial charge / discharge capacity, and then constant current / constant voltage charge is performed after a predetermined rest time. After the termination of the constant current / constant voltage charging, by performing the resistance measurement by the AC impedance method within a predetermined time, stable resistance measurement is made possible.By using the above battery performance evaluation method using the non-aqueous electrolyte coin type battery, the battery performance evaluation of the positive electrode active material for a non-aqueous electrolyte secondary battery using this evaluation method is carried out, development of the positive electrode active material and high performance. It has an industrially significant effect on high-performance battery development.

  Furthermore, the evaluation method of a battery for evaluation using this configuration has the advantage that stable evaluation results with less variation in resistance value among the batteries can be obtained.

It is sectional drawing which shows the 2032 type coin battery for evaluation used in the Example. It is a schematic explanatory drawing of the equivalent circuit used for the measurement example of impedance evaluation, and analysis. It is a battery evaluation flowchart of this invention.

  The present invention relates to a method for evaluating battery characteristics using a non-aqueous electrolyte coin type battery, and a method for evaluating battery characteristics of a positive electrode active material for a non-aqueous electrolyte secondary battery using the evaluation method, including a positive electrode active material A battery characteristic evaluation method using a non-aqueous electrolyte coin type battery having an electrode part in which a positive electrode film and a negative electrode film are disposed opposite to each other with a separator interposed therebetween, the positive electrode active material is lithium nickel composite oxide having a high nickel content Preparation of a non-aqueous electrolyte coin-type battery having an electrode part in which a positive electrode film containing a positive electrode active material and a negative electrode film are disposed opposite to each other with a separator interposed. After standing, constant current charge, pause, constant current discharge Conduct the constant current charge and discharge cycle to measure the initial charge and discharge capacity, and after the rest time, perform constant current constant voltage charging, and within 1 hour of the termination of the constant current constant voltage charging A battery characteristic evaluation method using the non-aqueous electrolyte coin type battery which comprises carrying out the resistance measurement by impedance method.

  That is, the method for evaluating the battery characteristics using the non-aqueous electrolyte coin battery according to the present invention is as shown in the flow of FIG. 3, and the above non-aqueous electrolyte coin battery is manufactured. Conduct a constant current charge / discharge cycle to conduct current discharge to measure the initial charge / discharge capacity, and then perform constant current constant voltage charging after a rest time, then perform resistance measurement by AC impedance method after a rest time However, it was invented as a result of finding that the rest time from the constant current constant voltage charging to the resistance measurement affects the resistance measurement result of the positive electrode active material having a high nickel content by the above-mentioned AC impedance method. .

By setting the rest time to the resistance measurement by the AC impedance method within one hour, the resistance value obtained by the AC impedance measurement (hereinafter also referred to as impedance measurement) can be accurately and stably obtained.
The reason for this is that, as shown in FIG. 3, the battery is left in the high voltage charging state as the rest time until the resistance measurement by the AC impedance method is performed.
Since the positive electrode active material evaluated in the present invention is a lithium nickel composite oxide having a high nickel content, the cobalt content decreases as the nickel content increases. The above cobalt has the effect of suppressing cycle deterioration and stabilizes the crystal structure. Therefore, the higher the nickel content, the more unstable the crystal structure becomes, and the crystal structure becomes stable by being left at high potential. It is thought that the phenomenon of mutation is likely to occur, and the resistance obtained in the AC impedance measurement increases with the elapse of the pause time.

Furthermore, since the tendency becomes more remarkable as the nickel content is higher, it is preferable that the shorter the pause time, the more accurate and stable measurement result can be obtained.
On the other hand, when the nickel content decreases, the variation in resistance obtained in impedance measurement decreases even if the rest time exceeds one hour.

1. Cathode Active Material Next, in the non-aqueous electrolyte coin-type battery used for the battery characteristics evaluation method of the present invention, the cathode active material used for evaluation has a general formula: Li _b Ni _C Co _x M _y O ₂ (M is Al, At least one element selected from Ti, Mn and W, b is 0.95 ≦ b ≦ 1.03, c = 1−x−y, 0.84 ≦ c <1.00, x is 0 < It is a lithium nickel composite oxide represented by x ≦ 0.15, y is 0 <y ≦ 0.07, x + y ≦ 0.16).

[Ni content]
The positive electrode active material of the present invention is a hexagonal lithium nickel complex oxide, and the subscript "c" indicating the content of nickel (Ni) in the above general formula is 0.84 or more.
The upper limit of the content of nickel in the positive electrode active material of the present invention can be high capacity when it is used as a positive electrode active material as the nickel content is large, but when it is too large, sufficient thermal stability is obtained It is less than 1.0 in order to eliminate or to make cation mixing more likely to occur during firing.
On the other hand, when the content of nickel decreases, the capacity decreases, and when the content is less than 0.84, problems such as a sufficient capacity per battery volume can not be obtained even if the chargeability of the positive electrode is increased.
Therefore, in the positive electrode active material of the present invention, the content of nickel is preferably 0.84 or more and less than 1.00, more preferably 0.84 or more and 0.98 or less, and more preferably 0.845 or more and 0.950 or less. Preferably, 0.85 or more and 0.95 or less are more preferable.

[Co content]
The positive electrode active material of the present invention contains cobalt (Co). By including this cobalt, the cycle characteristics of the positive electrode active material can be improved.
In the positive electrode active material of the present invention, the cycle characteristics of the positive electrode active material can be improved by increasing the content of cobalt, while when the content of cobalt exceeds 0.15, the capacity of the positive electrode active material is increased. It will be difficult.

Therefore, in order to increase the capacity while improving the cycle characteristics of the positive electrode active material of the present invention, the cobalt content (x in the above general formula) is set to 0 <x ≦ 0.15.
On the other hand, when the content of cobalt is too small, the cycle characteristics may not be sufficiently improved even when cobalt is contained, so the content x of cobalt in the positive electrode active material of the present invention is 0.03 ≦ x ≦ 0.15 or more are more preferable, and 0.05 <= x <= 0.12 are more preferable.

[Containment of additional elements]
The positive electrode active material of the present invention may contain other elements in addition to cobalt in order to obtain the effect of improving the battery characteristics.
For example, when at least one additive element selected from Al, Ti, Mn and W is added as an additive element (M in the above general formula), battery characteristics such as thermal stability can be improved.

When the content of the additive element in the positive electrode active material of the present invention (y in the above general formula) exceeds 0.07, it is difficult to increase the capacity of the positive electrode active material. In order to obtain a sufficient improvement effect on battery characteristics by the addition of the additive element, it is preferable to set the content of the additive element to 0.01 or more.
Therefore, in order to achieve high capacity while improving the battery characteristics of the positive electrode active material of the present invention, 0 <y ≦ 0.07, and 0.01 ≦ y ≦ 0.05 is more preferable.

[Li content]
The content (b in the above general formula) of lithium (Li) in the positive electrode active material of the present invention is 0.95 or more and 1.03 or less.
When the lithium content is less than 0.95, a metal element such as Ni is mixed in the lithium layer in the layered compound to lower the lithium insertion / removal property, so the battery capacity is lowered and the output characteristics are deteriorated. On the other hand, even if the lithium content exceeds 1.03, Li is mixed in the metal layer in the layered compound, so the battery capacity is reduced.
Therefore, the content of lithium in the positive electrode active material of the present invention is 0.95 ≦ b ≦ 1.03, and more preferably 0.95 ≦ b ≦ 1.01, in order to maintain the battery capacity and the output characteristics. .

As described above, using a known technique, a positive electrode active material manufactured in consideration of each factor affecting the characteristics of the positive electrode active material such as the component composition, the particle size, and the surface is used.
Furthermore, the positive electrode is used by forming a positive electrode mixture in which auxiliary agents such as a conductive material and a binder (binder) are mixed in addition to the positive electrode active material.
For the evaluation of the battery, a battery for evaluation is manufactured using an appropriate one because it is affected by these additives.

  The conductive material is for enhancing the electrical conductivity between the positive electrode active material particles and efficiently performing the charge / discharge reaction of the positive electrode, and may be a conductive material used in general non-aqueous electrolyte secondary batteries. For example, carbon materials such as graphite (natural graphite, artificial graphite, expanded graphite and the like) and carbon black materials such as acetylene black and ketjen black (registered trademark) can be used alone or in combination.

  The binder (binding material) plays the role of connecting and keeping the positive electrode active material particles, and may be one used in a general non-aqueous electrolyte secondary battery, for example, polytetrafluoroethylene, polyvinylidene fluoride A fluorine-containing resin such as fluorine rubber, a heat plasticity resin such as polypropylene and polyethylene, ethylene propylene rubber, styrene butadiene, a cellulose resin, polyacrylic acid and the like can be used.

Furthermore, the preparation of the positive electrode film involves dry mixing treatment, which may adversely affect the characteristics of the positive electrode film depending on the degree of mixing, and devices used for dry mixing there are dry ball mills, dry bead mills, blades. A planetary motion type mixer, a container rotational type planetary motion mixer, a stirrer, a homogenizer, etc. may be mentioned, but a container rotational type planetary motion mixer is preferable.
The planetary motion mixer can perform uniform mixing in a short time, and can obtain a high productivity and a uniform mixture.

The positive electrode thus obtained is simple and quick in its production, and is suitable for producing a battery for evaluation in which rapid battery production is required. In that case, it is preferable to control the positive electrode active material contained in the positive electrode in the range of 50 to 60 mg / cm ² per positive electrode area facing the negative electrode.

2. Negative Electrode Furthermore, when configuring the non-aqueous electrolyte coin-type battery used in the battery characteristics evaluation method of the present invention, it is preferable to use metallic lithium, an alloy containing lithium as a main component, or the like for the negative electrode. The negative electrode can be obtained by punching out the metal lithium foil or an alloy foil containing lithium as a main component.

3. Separator Further, when configuring a non-aqueous electrolyte coin-type battery used in the battery characteristics evaluation method of the present invention, a separator is interposed between a positive electrode and a negative electrode.
The separator separates the positive electrode and the negative electrode and holds the electrolyte, and may be a thin resin film of polyethylene, polypropylene or the like, and a resin film having many fine holes can be used. However, since these resin films have high oil repellency, they cause dispersion of the resistance evaluation results.

Although the thickness is thicker than the resin film, by using the glass fiber having high liquid absorbability of the electrolyte, sufficient electrolyte can be supplied in the electrode or between the electrodes in a short time, and stable battery evaluation can be performed. It is preferable because it can be done.
When the thickness of the separator is increased, the distance between the positive electrode and the negative electrode is increased. Therefore, the thickness is preferably 20 to 1000 μm, and more preferably 50 to 800 μm.

4. Nonaqueous Electrolyte Furthermore, when constructing the nonaqueous electrolyte coin type battery used for the battery characteristic evaluation method of the present invention, as nonaqueous electrolyte, what used lithium salt as a supporting salt dissolved in organic solvent is used. Is preferred.
As the organic solvent, cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate and trifluoropropylene carbonate, linear carbonates such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate and dipropyl carbonate, and further tetrahydrofuran, 2-methyl Use one or a mixture of two or more selected from ether compounds such as tetrahydrofuran and dimethoxyethane, sulfur compounds such as ethyl methyl sulfone and butanesultone, and phosphorus compounds such as triethyl phosphate and trioctyl phosphate it can.

As the supporting salt, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) _{2 and the} like, and complex salts thereof can be used. Furthermore, the non-aqueous electrolyte solution may contain a radical scavenger, a surfactant, a flame retardant, and the like.

5. Nonaqueous Electrolyte Coin Type Battery The nonaqueous electrolyte coin type battery according to the present invention, which is composed of the positive electrode, the negative electrode, the separator, and the nonaqueous electrolytic solution described above, is a 2032 type or 2016 type coin battery However, it is desirable from the easiness of preparation, the reproducibility of evaluation, etc. FIG. 1 shows a cross-sectional view of a 2032 type coin battery.
The positive electrode 1 and the negative electrode 2 are made into the electrode part 8 through the separator 3, and the above-mentioned electrode body is impregnated with the above-mentioned predetermined non-aqueous electrolytic solution. The non-aqueous electrolyte coin-type battery used in the present invention can be completed by sealing the above configuration into a coin battery.

The manufacturing method of the coin-type battery for characteristic evaluation of the positive electrode active material for non-aqueous electrolyte secondary batteries demonstrated so far is demonstrated in more detail.
The manufacturing method in the present invention includes at least a positive electrode manufacturing step, a negative electrode manufacturing step, an electrode portion forming step, and a battery assembling step, and is performed based on other known nonaqueous electrolyte coin type secondary battery manufacturing steps. .

[Positive electrode preparation process and negative electrode preparation process]
In the positive electrode preparation step, the positive electrode mixture in a state in which the positive electrode active material and the auxiliary material as the base material of the positive electrode film are uniformly dispersed by uniformly mixing the positive electrode active material and the auxiliary material such as the conductive material and the binder. Perform mixed processing to make.
For this mixing process, a dry ball mill, a dry bead mill, a blade planetary motion type mixer, a container rotation type planetary motion mixer, a stirrer, a homogenizer, etc. can be used if it is a dry mixing method. It is easy to obtain a homogeneous positive electrode mixture by using a motion mixer. Furthermore, after producing a positive electrode mixture, it is preferable to produce a positive electrode film by a sheet method using a roll press or the like and to punch it into a desired size.
In the negative electrode production step, it is preferable to obtain a negative electrode obtained by punching out a metal lithium foil or an alloy foil containing lithium as a main component, which is used in the present invention in the present invention.

The positive electrode film and the negative electrode film produced in the positive electrode production step and the negative electrode production step have a circular shape or a plane shape having an axis of rotational symmetry, and the positive electrode film has a circular shape or a plane shape having a rotational symmetry axis. It is preferable that the dimensional ratio (φ _C / φ _A ) of the diameter (φ _C ) to the diameter of the negative electrode film (φ _A ) be related so as to be in the range of 0.80 to 0.90.
By controlling the electrode size ratio between the positive electrode film and the negative electrode film within the range of 0.80 to 0.90, it is possible to separate the arc of positive electrode reaction resistance and the arc of negative electrode reaction resistance obtained by AC impedance measurement. The reaction resistance value of only the positive electrode can be obtained. Further, the smaller the size of the positive electrode film, the more the positional deviation of the assembly can be suppressed.

When the electrode size ratio between the positive electrode film and the negative electrode film is less than 0.80, the size of the positive electrode film is reduced, so assembly displacement is less likely to occur, but the positive electrode reaction resistance and the negative electrode reaction resistance obtained by impedance measurement are 1 As a result, the problem arises that the reaction resistance value of only the positive electrode can not be separated.
When the electrode size ratio between the positive electrode film and the negative electrode film exceeds 0.90, the reaction resistance obtained by impedance measurement can be separated, but the sizes of the positive electrode film and the negative electrode film become almost the same diameter, resulting in misalignment of assembly. It becomes easy, and the variance of resistance becomes large.

Also, in order to sufficiently obtain the effect due to the electrode size ratio, the shapes of the opposite surfaces of the positive electrode film and the negative electrode film, which are disposed opposite to each other via the separator, also affect when incorporated as an electrode portion of the battery. I'm heading. That is, each opposing surface is similar, preferably circular, and may be planar having an axis of rotational symmetry.
By limiting the shape of each opposing surface in this manner, when the electrode portion (FIG. 1, reference numeral 8) is formed, positional deviation of the opposing surfaces of the positive and negative electrode films can be suppressed, and the positive electrode film is a negative electrode. It becomes easy to arrange so as not to go out of the film, and shows an effect of suppressing the variation of reaction resistance.
Furthermore, it is desirable to arrange the positive electrode film so as not to protrude from the negative electrode film. Although it is easy and preferable for the preparation of the electrode portion that the facing surfaces have similar shapes, it may be a different shape as long as the condition that the positive electrode film does not protrude from the outer periphery of the negative electrode film is satisfied.

[Electrode part preparation process]
In this step, the positive electrode film and the negative electrode film are disposed opposite to each other through the separator so that the positive electrode film does not protrude from the outer periphery of the negative electrode film to form an electrode portion.

Battery assembly process
The battery assembly process has an electrode part installation process in which an electrode part is disposed on the concave bottom of the positive electrode can 4 having a concave cross section which constitutes a battery housing.
This electrode portion setting process satisfies the characteristics of the coin-type battery for characteristic evaluation of the present invention together with the dimensional ratio (φ _C / φ _A ) of the positive electrode membrane diameter (φ _C ) and the negative electrode membrane diameter (φ _A ). The above is an important condition.
In the present invention, the ratio (φ _C / B) of the positive electrode membrane diameter (φ _C ) to the specific amount of the gap between the positive electrode membrane and the wall of the gasket 4 (electrode / casing void amount: B _S ) _{If S 2} ) is in the range of 1.5 to 2.3, it has the effect of suppressing the variation among the batteries in combination with the above other features. From the above relationship, the space shape inside the positive electrode can desirably has a shape similar to the facing surface shape of the positive electrode film and the negative electrode film, but may be circular (that is, the space shape is cylindrical).

6. Battery Characteristic Evaluation Method Using Non-Aqueous Electrolyte Coin-Type Battery Although battery characteristic evaluation can be performed by the following method, measurement conditions are not limited.
[Initial charge and discharge capacity]
For measurement of the initial discharge capacity, a multi-channel voltage / current generator (manufactured by ADVANTEST CORPORATION, R6741A) is used.
First, a coin-type battery is produced and left for 12 hours or more. After the open circuit voltage OCV (Open Circuit Voltage) is stabilized, it is charged to a cutoff voltage of 4.3 V with a current density to the positive electrode of 0.4 mA / cm ² , and after rest for 1 hour, the cutoff voltage is fixed to 3.0 V Discharge current. Then, the capacity when discharged to a cutoff voltage of 3.0 V is taken as an initial discharge capacity.

[AC impedance measurement]
The positive electrode resistance can be calculated by the following method.
First, a coin-type battery was charged at a charge potential of 4.0 V, and constant current constant voltage charging was performed at a current of 1.6 mA-0.2 mA.
Thereafter, a frequency response analyzer and a potentiogalvanostat (manufactured by Solartron, 1255B) are used to measure by an AC impedance method. Then, the Nyquist plot shown in FIG. 2 is obtained. Since this Nyquist plot represents the solution resistance, the negative electrode resistance and its capacity, and the sum of the positive electrode resistance and its characteristic curve, the fitting calculation is performed using an equivalent circuit based on this Nyquist plot, and the positive electrode reaction is performed. Calculate the resistance value. In addition, let positive value resistance be a relative value which set the alternating current resistance value immediately after charge to 1.00 as an evaluation value.

  Hereinafter, the present invention will be specifically described based on examples. The present invention is not limited to the following examples.

  As a negative electrode used for battery evaluation, a 1.0 mm-thick metal lithium was used as a negative electrode material, and a material punched to a diameter of 13 mm was used as a negative electrode film. As the positive electrode material, 75 wt% of lithium nickelate powder, which is a nickel composite oxide with a Ni: Co: Al molar ratio (%) of 91: 6: 3, and acetylene black powder as a carbon powder to be a conductive material A mixture of 25 wt% of polytetrafluoroethylene as a binder and a mixture of 2 to 1 was used as a positive electrode film having a diameter of 11 mm and a weight of 75 mg. The weight of the active material of this positive electrode film is equivalent to 52.5 mg.

The separator used was a glass fiber filter having a thickness of 0.20 mm and having a diameter of 19 mm, which was 0.3 mμ of the retention particle system of JIS P 3801.
The electrolyte used was an equivalent mixed solution of ethylene carbonate (EC) and diethyl methyl carbonate (DEC) containing 1 mol / L of electrolyte LiClO ₄ .
These materials were used to make a 2032 coin cell in a glove box or dry room with a dew point below -30 ° C.

In the resistance evaluation, as shown in the flow of FIG. 3, first, the prepared battery is allowed to stand for 12 hours, constant voltage charging is performed to 4.3 V at 0.4 mA, and discharging to 3.0 V after 1 hour of rest One cycle of the above was performed to determine the "initial discharge capacity".
The battery was rested for 1 hour and then subjected to constant current constant voltage charging at a current of 1.6 mA to 0.2 mA up to 4.0 V.
After charging to 4.0 V, measurement was performed by an alternating current impedance method after one hour, and an alternating current resistance measurement value of a positive electrode was calculated using an equivalent circuit with respect to a curve obtained by Cole-Cole plot.

The results are summarized and shown in Table 1.
In Table 1, the case where the calculated alternating current resistance measurement value of the positive electrode is within 1.1 times of the alternating current resistance measurement value of the positive electrode immediately after charging to 4.0 V is determined as “o”, 1.1 times or more The case was evaluated as "x".

After charging to 4.0 V, an evaluation battery was manufactured and evaluated under the same conditions as in Example 1 except that measurement was performed by an AC impedance method after 0.2 hours had elapsed.
The results are summarized and shown in Table 1.

A battery for evaluation was produced and evaluated under the same conditions as in Example 1 except that the battery was charged to 4.0 V and then measured by an alternating current impedance method after 0.5 hours.
The results are summarized and shown in Table 1.

An evaluation battery was prepared and evaluated under the same conditions as in Example 3 except that the molar ratio of Ni: Co: Al in the positive electrode material was changed to 94: 3: 3.
The results are summarized and shown in Table 1.

  After charging to 4.0 V, an evaluation battery was manufactured and evaluated under the same conditions as in Example 4 except that measurement was performed by an alternating current impedance method after 1.0 hour has elapsed. The results are summarized and shown in Table 1.

(Comparative example 1)
After charging to 4.0 V, an evaluation battery was manufactured and evaluated under the same conditions as in Example 1 except that measurement was performed by an AC impedance method after 1.2 hours. The results are summarized and shown in Table 1.

(Comparative example 2)
After charging to 4.0 V, an evaluation battery was manufactured and evaluated under the same conditions as in Example 1 except that measurement was performed by an alternating current impedance method after 2 hours.
The results are summarized and shown in Table 1.

(Comparative example 3)
After charging to 4.0 V, an evaluation battery was produced and evaluated under the same conditions as in Example 1 except that measurement was performed by an AC impedance method after 3 hours.
The results are summarized and shown in Table 1.

(Comparative example 4)
An evaluation battery was prepared and evaluated under the same conditions as in Example 3 except that the molar ratio of Ni: Co: Al was 82: 15: 3 and the nickel content of the positive electrode material was changed.
The results are summarized and shown in Table 1.

(Comparative example 5)
After charging to 4.0 V, an evaluation battery was manufactured and evaluated under the same conditions as in Comparative Example 4 except that measurement was performed by an AC impedance method after 3 hours. The results are summarized and shown in Table 1.

As is apparent from Table 1, in Examples 1 to 5 in which the Ni content is high according to the present invention, the positive electrode reaction resistance measured by performing AC impedance measurement after a rest time within one hour is It can be seen that the amount of change is small relative to the reaction resistance immediately after charging, and the variation is also small.
On the other hand, in Comparative Examples 1 and 2 with a high Ni content and Comparative Example 3, when the rest time exceeds 1 hour, it can be seen that the measured reaction resistance is greatly increased, and a comparative example with a low Ni content. In 4 and 5, it was possible to measure the reaction resistance without being influenced by the length of the pause time.

1 positive electrode 2 Li metal negative electrode 3 separator 4 gasket 5 wave washer 6 positive electrode can 7 negative electrode can 8 electrode part

Claims (5)

A battery characteristics evaluation method using a non-aqueous electrolyte coin type battery having an electrode part in which a positive electrode film containing a positive electrode active material and a negative electrode film are disposed opposite to each other with a separator interposed,
The positive electrode active material is “general formula: Li _b Ni _C Co _x M _y O ₂ (1)” (wherein, M represents at least one element selected from Al, Ti, Mn and W) B is 0.95 ≦ b ≦ 1.03, c = 1−x−y, 0.84 ≦ c <1.00, x is 0 <x ≦ 0.15, y is 0 <y ≦ 0. Lithium nickel composite oxide having a high nickel content represented by 07, x + y ≦ 0.16),
Production of a non-aqueous electrolyte coin-type battery having an electrode part in which a positive electrode film containing the positive electrode active material and a negative electrode film are disposed opposite to each other with a separator interposed, constant current charge, rest, constant current discharge after standing Conduct the current charge and discharge cycle to measure the initial charge and discharge capacity,
After that, through a rest time, constant current constant voltage charging is performed, and resistance measurement by an AC impedance method is performed within one hour after the completion of the constant current constant voltage charging. How to evaluate battery characteristics.   The battery characteristic evaluation using the non-aqueous electrolyte coin-type battery according to claim 1, wherein the resistance measurement is performed within 0.05 hours or more and within 1 hour after the termination of the constant current constant voltage charging. Method.   The said negative electrode film is a metal which has metal lithium or lithium as a main component, The battery characteristics evaluation method using the non-aqueous electrolyte coin-type battery of Claim 1 or 2 characterized by the above-mentioned.   The battery characteristic evaluation method using the non-aqueous electrolyte coin battery according to any one of claims 1 to 3, wherein the coin battery is a 2032 type or 2016 type coin battery. A battery characteristic evaluation method using the non-aqueous electrolyte coin battery according to any one of claims 1 to 4,
_In: "general formula _{Li b Ni C Co x M y} O 2 ··· (1) " (wherein, M is, Al, Ti, represents at least one element selected from Mn and W, b is 0. 95 ≦ b ≦ 1.03, c = 1−x−y, 0.84 ≦ c <1.00, x is 0 <x ≦ 0.15, y is 0 <y ≦ 0.07, x + y ≦ 0. 16) A battery of a positive electrode active material for a non-aqueous electrolyte secondary battery characterized by grasping characteristics of the positive electrode active material for a non-aqueous electrolyte secondary battery which is a lithium nickel composite oxide having a high nickel content represented by 16). Characterization method.

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