JP2017212175A - Method for resistance evaluation of positive electrode material for nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To evaluate the resistance of a positive electrode material of a nonaqueous electrolyte secondary battery readily in a faster, accurate and low-cost manner.SOLUTION: A method for resistance evaluation of a positive electrode material for a nonaqueous electrolyte secondary battery is arranged to evaluate the resistance of a positive electrode material for a nonaqueous electrolyte secondary battery. The method comprises: a step S12 for stationarily leaving a battery for evaluation which is a nonaqueous electrolyte secondary battery for a given time after production thereof; a step S13 for charging the battery for evaluation which has been stationarily left for the given time with a constant current; a step S15 for discharging the battery for evaluation with a constant current after the constant current charging the battery and a pausing step subsequent thereto; a step S17 for charging the battery for evaluation with a constant current and a constant voltage after the constant current discharging the battery and a pausing step subsequent thereto; and a step S18 for measuring the resistance of the positive electrode material by an AC impedance method after the charging with the constant current and constant voltage.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a resistance evaluation method for a positive electrode material for a non-aqueous electrolyte secondary battery, which evaluates the resistance of the positive electrode material of a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery.

  In recent years, with the widespread use of portable devices such as mobile phones and notebook computers, development of small and lightweight secondary batteries having high energy density is strongly desired. In addition, environmentally friendly vehicles called XEV are also required to have high performance and low cost such as small size, light weight, high capacity, and high output. Furthermore, there is an increasing need for improvement in the travel distance per charge in an environmentally-friendly vehicle and miniaturization, and a further increase in capacity is required.

As such a high capacity secondary battery, there is a non-aqueous electrolyte secondary battery. A typical non-aqueous electrolyte secondary battery is a lithium ion secondary battery, and a lithium metal composite oxide is used as a positive electrode active material for a positive electrode material of the lithium ion secondary battery. The demand for each material used for the lithium ion secondary battery, in particular, the development demand for higher performance for a positive electrode material such as LiCoO ₂ , LiNiO _2, or LiMnO ₄ is increasing. In order to proceed with these developments quickly and at low cost, evaluation means are one of the important factors, and the importance of evaluation methods in the development of positive electrode materials for lithium ion secondary batteries is increasing.

  As a specific evaluation method, a correlation evaluation between the composition of the positive electrode material, the particle size distribution, the particle shape, the crystal structure, the arrangement of constituent elements, etc. and the battery performance by so-called analytical evaluation methods such as composition analysis and XRD, SEM EDX, XPS However, it is indispensable to actually manufacture the battery and evaluate the battery characteristics. In the evaluation of battery characteristics, charge / discharge capacity characteristics and output characteristics are important. In particular, evaluation of output characteristics is indispensable for in-vehicle batteries.

  There are two methods for evaluating the output characteristics of a battery: a direct current method and an alternating current method. In the direct current method, a current is applied for a short time with the fabricated battery in a charged state at a predetermined charging depth, and the voltage drop (V) during that time. The resistance is calculated from the applied current value (A) (see Patent Document 1) and the manufactured battery is subjected to constant current and constant voltage charging, and after a certain period of rest, the battery is discharged at a constant current to a predetermined battery voltage. At this time, from the open circuit voltage (OCV) after a certain period of rest, the closed circuit voltage (CCV) after a certain short period of discharge start, and the discharge current (I) after a certain short period of discharge start, the DC resistance of the battery There is a method for calculating (R) (the calculation formula is R = (OCV−CCV) / I) (see Patent Document 2). On the other hand, the alternating current method uses an alternating current impedance method in which a resistance is separated by applying a minute current to the battery and changing the frequency. The former is a resistance (output) evaluation of the entire battery, and is often used by battery manufacturers and the like. Since the latter can separate resistance components such as a positive electrode and a negative electrode, it is used for analysis of a positive electrode active material and a negative electrode active material, and used by research institutions, manufacturers of positive electrodes, negative electrodes, and electrolytes.

  In the production of batteries for evaluating output characteristics, when carbon is used for the negative electrode, a production method is generally used in which carbon particles are slurried using a solvent together with a binder (also referred to as a binder), kneaded, coated, and dried. However, the process becomes complicated. Further, since uniform dispersion, coating film thickness and void structure are required, a method using a metal lithium sheet cut out to a desired size is simple and economical. However, since the state of dendrite formation on the negative electrode surface changes depending on the pressure applied to the electrodes, the amount of electrolyte between the electrodes, the size of the positive electrode, the size of the negative electrode, the size ratio, etc. Etc., there is a problem that it is difficult to obtain reproducible data.

  The positive electrode is produced by mixing a positive electrode active material with a conductive material, a binder, and a solvent, coating, drying, punching out to a desired size, dry mixing similar members, and using a roll press or the like. The former coating method can reduce the thickness of the coating. Lithium ion rechargeable batteries, which have a rate-determining diffusion rate of lithium ions, can be charged and discharged at a high rate by reducing the coating thickness and shortening the diffusion distance of lithium. Although a secondary battery can be obtained, the process is complicated as in the preparation of the negative electrode, and it is not suitable for the development of a development battery that requires evaluation of a small variety of products such as research and development. The latter dry mixing sheet method has an advantage that the electrode can be quickly produced as compared with the electrode producing method by coating. However, since the electrode becomes thick, it is difficult to evaluate the resistance by the direct current method that applies a high rate.

  In the case of a battery having such a thick electrode, resistance evaluation by an alternating current impedance method with a small applied current is preferable. As a resistance evaluation by the AC impedance method, Patent Document 3 discloses an electrode inspection method for simply and accurately inspecting the resistance of an electrode in which an electrode active material layer is formed on a current collector by an AC impedance method. Yes. Patent Document 4 discloses a method for evaluating the resistance of an electrode by an AC impedance method as an electrode evaluation method that can directly reflect the characteristics of the assembled battery in the electrode state without assembling the battery. Has been.

International Publication No. 2015/182560 JP2015-167118A JP 2014-025850 A JP 2013-110082 A

  In general, a separator of a secondary battery produced for inspection before shipment or the like is made of a polypropylene having a thickness of several tens of microns or a porous film made of polyethylene. These separators are contracted by the heat generated at the time of a short circuit, and the function as a battery can be stopped by closing the pores, thereby improving the safety of the battery. However, these separators have advantages in terms of safety, but the electrolyte retention and wettability are poor, the amount of electrolyte between the electrodes is not stable, and measurement reproducibility becomes unstable. There is also a problem. In particular, in the AC impedance method that reacts sensitively to a small resistance change of the cell, it is difficult to use it as an evaluation cell in terms of measurement reproducibility.

  In addition, in manufacturing each part of the inspection battery before shipping, it is naturally necessary to maintain stable quality and maintain high battery assembly accuracy, but conditioning by temperature control and energization after assembly is necessary. Important for resistance measurements. Among these, it is particularly difficult to uniformly form Li dendrite on the negative electrode, which is a problem. As described above, it is difficult to say that the conventional battery fabrication and measurement methods are excellent in stability, workability, responsiveness, and cost for the purpose of evaluation of development and inspection before shipment of products.

  The present invention has been made in view of the above problems, and is new and improved which can easily and quickly perform resistance evaluation of a positive electrode material of a non-aqueous electrolyte secondary battery at a low cost. It aims at providing the resistance evaluation method of the positive electrode material for non-aqueous electrolyte secondary batteries.

  As a result of intensive studies in order to achieve the above-described object of the present invention, the present inventors have determined a predetermined value after charging and discharging when measuring the AC resistance of the positive electrode material of the non-aqueous electrolyte secondary battery. It is possible to obtain a highly accurate and stable measurement result by performing AC resistance measurement after charging to the charging depth of AC, and to perform initial charge / discharge capacity measurement. As a result, it was found that efficient battery evaluation can be performed, and the present invention has been completed.

  One aspect of the present invention is a method for evaluating resistance of a positive electrode material for a non-aqueous electrolyte secondary battery that evaluates resistance of the positive electrode material of the non-aqueous electrolyte secondary battery, wherein the evaluation battery for the non-aqueous electrolyte secondary battery is A step of allowing the evaluation battery to stand for a predetermined time after fabrication; a step of charging the constant current after leaving the predetermined time; a step of resting the evaluation battery after the constant current charging and discharging a constant current; A step of performing constant-current constant-voltage charging after suspending the evaluation battery after the constant-current discharge, and a step of measuring resistance of the positive electrode material by an alternating current impedance method after the constant-current constant-voltage charging. It is characterized by.

  According to one embodiment of the present invention, variation in the amount of dendrite formed on the negative electrode surface is reduced and the negative electrode surface becomes stable, so that the accuracy of the resistance evaluation value of the positive electrode material is improved by the AC impedance method. .

  At this time, in one embodiment of the present invention, the predetermined time for allowing the evaluation battery to stand after production may be at least 4 hours or longer.

  In this way, since the electrolyte solution completely penetrates into the positive electrode membrane of the evaluation battery, the accuracy of the resistance evaluation value of the positive electrode material by the subsequent AC impedance method is improved.

In one embodiment of the present invention, the non-aqueous electrolyte secondary battery is configured such that a positive electrode of a transition metal oxide containing lithium and a negative electrode made of metal lithium or a metal containing lithium as a main component face each other with a separator interposed therebetween. In particular, the separator may be made of glass fiber whose main component is SiO ₂ .

  In this way, in particular, the accuracy of the resistance evaluation value of the positive electrode material by the AC impedance method in the lithium ion secondary battery is improved.

  In one embodiment of the present invention, the positive electrode may be composed of a porous positive electrode film.

  In this way, since the electrolyte solution completely penetrates into the hole of the positive electrode film, the accuracy of the resistance evaluation value of the positive electrode material by the subsequent AC impedance method is improved.

  In one embodiment of the present invention, the positive electrode film may be formed by dry mixing or wet mixing.

  In this way, a positive electrode film suitable as a positive electrode material for a lithium ion secondary battery can be efficiently formed.

  As described above, according to the present invention, from the viewpoint of resistance evaluation in battery material development of a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery and pre-shipment inspection of a product, the positive electrode of the non-aqueous electrolyte secondary battery The resistance evaluation of the active material can be easily performed quickly, with high accuracy and at low cost.

It is sectional drawing which shows the structure of the nonaqueous electrolyte secondary battery for evaluation applied with the resistance evaluation method of the positive electrode material for nonaqueous electrolyte secondary batteries which concerns on one Embodiment of this invention. It is a flowchart which shows the outline of the resistance evaluation method of the positive electrode active material for non-aqueous electrolyte secondary batteries which concerns on one Embodiment of this invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail. The present embodiment described below does not unduly limit the contents of the present invention described in the claims, and all the configurations described in the present embodiment are essential as means for solving the present invention. Not necessarily.

  A non-aqueous electrolyte secondary battery applied in the capacity evaluation method for a positive electrode material for a non-aqueous electrolyte secondary battery according to an embodiment of the present invention includes a positive electrode, a negative electrode, a non-aqueous electrolyte, and the like, and is a general non-aqueous electrolyte. It is comprised by the component similar to a secondary battery. An example in which a non-aqueous electrolyte secondary battery according to an embodiment of the present invention is applied to a 2032 type coin battery will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a configuration of a nonaqueous electrolyte secondary battery for evaluation applied in a capacity evaluation method for a positive electrode material for a nonaqueous electrolyte secondary battery according to an embodiment of the present invention.

  A nonaqueous electrolyte secondary battery 1 according to an embodiment of the present invention is a 2032 type coin battery, and includes a case 2 and an electrode 3 accommodated in the case 2. As shown in FIG. 1B, the case 2 has a positive electrode can 2a that is hollow and open at one end, and a negative electrode can 2b that is disposed in the opening of the positive electrode can 2a. Is disposed in the opening of the positive electrode can 2a, a space for accommodating the electrode 3 is formed between the negative electrode can 2b and the positive electrode can 2a. The electrode 3 includes a positive electrode 3a, a separator 3c, and a negative electrode 3b, which are stacked in this order, the positive electrode 3a is in contact with the inner surface of the positive electrode can 2a, and the negative electrode 3b is interposed through a wave washer 4. The case 2 is accommodated so as to be in contact with the inner surface of the negative electrode can 2b.

  As shown in FIG. 1, the case 2 includes a gasket 2c, and the gasket 2c is fixed so that the positive electrode can 2a and the negative electrode can 2b are electrically insulated. Further, the gasket 2c also has a function of sealing a gap between the positive electrode can 2a and the negative electrode can 2b and blocking between the inside of the case 2 and the outside in an airtight and liquid tight manner.

  Next, the flow of the resistance evaluation method for the positive electrode active material for a non-aqueous electrolyte secondary battery according to an embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a flowchart showing an outline of a resistance evaluation method for a positive electrode active material for a non-aqueous electrolyte secondary battery according to an embodiment of the present invention.

  The method for evaluating the resistance of a positive electrode active material for a non-aqueous electrolyte secondary battery according to an embodiment of the present invention includes a development evaluation of a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery and a positive electrode in a pre-shipment inspection of a product. This is applied when evaluating the resistance of materials. As shown in FIG. 2, the resistance evaluation method for the positive electrode active material for a non-aqueous electrolyte secondary battery according to an embodiment of the present invention includes an evaluation battery preparation step S11, a stationary step S12, a constant current charging step S13, and a pause. The process S14, the constant current discharge process S15, the rest process S16, the constant current constant voltage charge process S17, and the alternating current impedance measurement process S18 are included.

  In the evaluation battery preparation step S11, a non-aqueous electrolyte secondary battery evaluation battery is prepared. In this embodiment, as a lithium ion secondary battery as shown in FIGS. 1A and 1B described above, a 2032 type coin battery is used as an evaluation battery in a glove box or dry room having a dew point of less than −30 ° C. create. Specifically, a lithium ion secondary battery in which a positive electrode of a transition metal oxide containing lithium and a negative electrode made of metal lithium or a metal containing lithium as a main component face each other with a separator interposed therebetween is an evaluation battery. To make.

  In the present embodiment, the negative electrode plate constituting the negative electrode is produced by punching out a metal having a diameter of 14 mm and a thickness of 1.0 mm made of metal lithium or an alloy containing lithium as a main component. The positive electrode film constituting the positive electrode is produced by uniformly mixing a positive electrode active material, a conductive material, and a powder binder at an arbitrary ratio, weighing them, pouring them into a mold, and pressure molding. Specifically, for example, 75 wt% of lithium nickel composite oxide powder and 25 wt% of a mixture of carbon powder as a conductive material and polytetrafluoroethylene as a binder, for example, 2 to 1 are mixed. A porous positive electrode film having a diameter of 11 mm, a thickness of about 0.5 mm, and a weight of about 10 mg is efficiently produced. The porous positive electrode film can also be efficiently formed by wet mixing in which slurry is mixed and applied to a current collector.

The separator is preferably made of glass fiber having a high liquid-absorbing property of the electrolytic solution because a sufficient amount of electrolyte can be supplied inside or between the electrodes in a short time and stable battery evaluation can be performed. Moreover, since the distance between a positive electrode and a negative electrode will become large when the thickness of a separator becomes thick, it is preferable that it is 20-1000 micrometers, and it is more preferable that it is 50-800 micrometers. Further, preferably one that the main component of glass fibers and SiO _2. If an alkali component is contained, it may be dissolved in the electrolytic solution depending on conditions, which may affect the durability of the battery.

As the nonaqueous electrolytic solution, it is preferable to use a solution obtained by dissolving a lithium salt as a supporting salt in an organic solvent. Examples of the organic solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and trifluoropropylene carbonate; chain carbonates such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, and dipropyl carbonate; and tetrahydrofuran, 2- One kind selected from ether compounds such as methyltetrahydrofuran and dimethoxyethane, sulfur compounds such as ethylmethylsulfone and butanesultone, phosphorus compounds such as triethyl phosphate and trioctyl phosphate, etc. may be used alone or in admixture of two or more. Can do. As the supporting salt, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , 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.

  After the evaluation battery is produced, the evaluation battery is allowed to stand for a predetermined time (stationary step S12). In the present embodiment, the accuracy of the resistance evaluation value of the positive electrode material by the AC impedance method is improved by allowing the electrolyte solution to completely penetrate into the positive electrode film of the evaluation battery as a predetermined time for standing after the evaluation battery is manufactured. Therefore, it is characterized by standing for at least 4 hours.

  As described above, since the positive electrode film is porous, if the degree of penetration into the positive electrode film varies, the impedance measurement result of the positive electrode material also varies, so that it is necessary for the electrolyte to completely enter the pores. Further, when the standing time in the standing step S12 is less than 4 hours, the penetration of the electrolyte into the positive electrode film is not stable. On the other hand, when the standing time is 18 hours or more, there is a problem from the viewpoint of operation efficiency. The longer the standing time, the more reliably the electrolyte can permeate, so that it is more preferably 8 hours or longer, and still more preferably 12 hours or longer. For this reason, in this embodiment, in order to increase the accuracy of the resistance evaluation value of the positive electrode material by the AC impedance method, in view of the operation efficiency of the evaluation method after more completely infiltrating the electrolyte into the positive electrode film, The standing time in the standing step S12 after completion of the evaluation battery production step S11 is at least 4 hours.

  After the produced evaluation battery is allowed to stand for 4 hours, the evaluation battery is charged with a constant current (constant current charging step S13). In this embodiment, constant current charging is performed up to 4.3 V at 0.4 mA. Thereafter, the evaluation battery is subjected to a constant current discharge after a one-hour pause (pause step S14) (constant current discharge step S15). In this embodiment, constant current discharge is performed up to 3.0V. In this way, in the present embodiment, one cycle of the constant current charging step S13, the pause step S14, and the constant current discharging step S15 is performed.

  Thereafter, the evaluation battery is paused for 1 hour (step S16), and then constant current and constant voltage charging is performed (constant current and constant voltage charging step S17). In the present embodiment, constant current and constant voltage charging is performed at a current of 1.6 mA to 0.2 mA up to 4.0 V. Then, the resistance measurement of the positive electrode material of the evaluation battery charged to 4.0 V in the constant current constant voltage charging step S17 is performed by the AC impedance method (AC impedance measuring step S18).

Thus, in this embodiment, first, after assembling the evaluation battery, the electrolyte solution is allowed to permeate into the electrode film of the positive electrode that is porous by allowing it to stand for 4 hours or more. Thereafter, when impedance measurement is performed after charging to a state where impedance measurement is performed, Li reaches the Li metal surface of the negative electrode from the positive electrode active material LiNi ₂ O. At this time, Li dendrite is formed in spots on the surface of the negative electrode, but since the amount of formation varies, the state of the negative electrode surface becomes unstable.

  For this reason, in this embodiment, as an initial evaluation of the positive electrode material, the charge / discharge capacity and impedance are measured, but after charging / discharging is performed for one cycle, when charging is performed until the impedance is measured, Li is extracted from the positive electrode. When the amount of Li reaching the Li metal surface of the negative electrode is charged twice, the amount becomes twice or more as described above, and the Li dendrite formed on the surface of the Li metal is made uniform. If the number of charge / discharge cycles is increased once to 2 times, it takes time and cost, and the amount of Li reaching the Li metal surface of the negative electrode further increases, Li dendrite crystals grow, and the separator is removed. Increased risk of short-circuit due to penetration.

  Usually, the accuracy of the evaluation results can be improved by performing one cycle, but the optimum number of cycles can be appropriately determined by experiments or the like in consideration of the charge / discharge conditions and the size of the negative electrode plate. it can. As a result, the impedance can be stably measured. In this way, in this embodiment, variation in the amount of dendrite formed on the negative electrode surface is reduced and the negative electrode surface becomes stable, so the accuracy of the resistance evaluation value of the positive electrode material is improved by the AC impedance method. To come.

  Next, the resistance evaluation method for the positive electrode material for a lithium ion secondary battery according to an embodiment of the present invention will be described in detail with reference to examples. The present invention is not limited to these examples.

Example 1
As a negative electrode plate used for battery evaluation, a metal plate having a thickness of 1.0 mm punched out to a diameter of 14 mm was used. As the positive electrode material, 75 wt% lithium nickelate powder and acetylene black powder as a carbon powder serving as a conductive material were used. In addition, 75 mg of 11 mm in diameter, which is a mixture of 25 wt% of 2: 1 mixed with polytetrafluoroethylene as a binder, is used. The active material weight of this positive electrode film is equivalent to 52.5 mg. The separator used was a JIS P 3801 retained particle system of 0.3 m and a glass fiber filter having a thickness of 0.20 mm cut to a diameter of 16 mm.

As the electrolytic solution, an equivalent mixed solution of ethylene carbonate (EC) and diethyl methyl carbonate (DEC) containing 1 mol / L of electrolyte LiClO ₄ was used. Using these materials, two 2032 type coin batteries were produced in a glove box or a dry room having a dew point of less than −30 ° C.

  For resistance evaluation, the produced battery was left to stand for 4 hours, charged at a constant current to 4.3 V at 0.4 mA, and after one hour of rest, one cycle of discharging to 3.0 V was performed, followed by one hour of rest. Later, constant current and constant voltage charging was performed at a current of 1.6 mA to 0.2 mA up to 4.0 V. The battery charged to 4.0 V was measured by the AC impedance method, and the interface resistance of the positive electrode was calculated using an equivalent circuit for the curve obtained by the Cole-Cole plot.

(Comparative Example 1)
A battery produced with a battery configuration equivalent to that of Example 1 was allowed to stand for 1 hour, and then charged with constant current and constant voltage up to 4.0 V at a current of 1.6 mA to 0.2 mA. The same operation as in Example 1 was performed except that the battery charged at 4.0 V was measured by the AC impedance method.

(Comparative Example 2)
A battery produced with a battery configuration equivalent to that of Example 1 was allowed to stand for 12 hours, and then charged with constant current and constant voltage up to 4.0 V at a current of 1.6 mA to 0.2 mA. The same operation as in Example 1 was performed except that the battery charged at 4.0 V was measured by the AC impedance method.

  The resistance evaluation results of Example 1, Comparative Example 1, and Comparative Example 2 are shown in Table 1 below.

  In the resistance evaluation result of Example 1, the variation in the value of the positive electrode interface resistance of the two batteries (the difference in the positive electrode interface resistance value of the two cells) is about 2.0% of the first measured value, and the variation It was found that a small and stable resistance evaluation result can be obtained. On the other hand, in Comparative Example 1, the variation in the positive electrode interface resistance of the two batteries is about 40% of the first measured value. In Comparative Example 2, the variation in the positive electrode interface resistance of the two batteries is the first measurement. 25% of the value. From the above results, by using the resistance evaluation method for the positive electrode material for a lithium ion secondary battery according to one embodiment of the present invention, the variation in the resistance evaluation results of the lithium ion secondary battery is reduced and the accuracy is improved. I found out that I could do it.

  Although the embodiments and examples of the present invention have been described in detail as described above, it will be understood by those skilled in the art that many modifications can be made without departing from the novel matters and effects of the present invention. It will be easy to understand. Therefore, all such modifications are included in the scope of the present invention.

  For example, a term described with a different term having a broader meaning or the same meaning at least once in the specification or the drawings can be replaced with the different term in any part of the specification or the drawings. Further, the configuration of the non-aqueous electrolyte secondary battery and the operation of the resistance evaluation method of the positive electrode material for the non-aqueous electrolyte secondary battery are not limited to those described in each embodiment and each example of the present invention, and various modifications are made. Is possible.

1 Nonaqueous electrolyte secondary battery (lithium ion secondary battery), 2 case, 2a positive electrode can, 2b negative electrode can, 2c gasket, 3 electrode, 3a positive electrode (positive electrode film), 3b negative electrode, 3c separator, 4 wave washer, S11 Battery production process for evaluation, S12 stationary process, S13 constant current charging process, S14 pause process, S15 constant current discharge process, S16 pause process, S17 constant current constant voltage charging process, S18 AC impedance measurement process

Claims (6)

A method for evaluating the resistance of a positive electrode material for a non-aqueous electrolyte secondary battery, wherein the resistance of the positive electrode material for the non-aqueous electrolyte secondary battery is evaluated.
A step of standing the evaluation battery for a predetermined time after producing the evaluation battery of the non-aqueous electrolyte secondary battery;
Charging with a constant current after standing the predetermined time;
A step of suspending the evaluation battery after the constant current charge and then performing a constant current discharge;
Performing constant current constant voltage charging after suspending the evaluation battery after the constant current discharge;
And a step of measuring resistance of the positive electrode material by an AC impedance method after the constant current and constant voltage charging, and a resistance evaluation method for the positive electrode material for a non-aqueous electrolyte secondary battery.   2. The method for evaluating resistance of a positive electrode material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the predetermined time of standing after the battery for evaluation is at least 4 hours or longer.   The non-aqueous electrolyte secondary battery is a lithium ion secondary battery in which a positive electrode of a transition metal oxide containing lithium and a negative electrode made of metal lithium or a metal containing lithium as a main component face each other with a separator interposed therebetween. The resistance evaluation method for a positive electrode material for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein: The separator resistance evaluation method of the non-aqueous electrolyte secondary battery positive electrode material according to claim 3, characterized in that it consists of glass fibers the major component and SiO _2.   The method for evaluating resistance of a positive electrode material for a non-aqueous electrolyte secondary battery according to claim 3 or 4, wherein the positive electrode is composed of a porous positive electrode film.   The resistance evaluation method for a positive electrode material for a non-aqueous electrolyte secondary battery according to claim 5, wherein the positive electrode film is formed by dry mixing or wet mixing.