JP2013110037A - Method for manufacturing nonaqueous electrolyte secondary battery, and nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a method for manufacturing a nonaqueous electrolyte secondary battery in which output characteristics can be improved while reduction in a generation amount of gas in overcharge is prevented; and a nonaqueous electrolyte secondary battery.SOLUTION: In one embodiment of the present invention, a method for manufacturing a battery 1 includes: a firing step of producing a tungsten-added fired product obtained by mixing a nickel compound and a lithium compound to be fired; a water washing step of water washing the fired product; and a positive electrode plate preparation step of preparing a positive electrode plate 10 by forming a positive electrode active material layer including a positive electrode active material particle on an aluminum foil, the positive electrode active material particle comprising a tungsten-added lithium transition metal composite oxide obtained after the fired product has been water washed.

Description

  The present invention relates to a method for producing a nonaqueous electrolyte secondary battery having a positive electrode plate including a positive electrode active material layer including positive electrode active material particles made of a lithium transition metal composite oxide, and a nonaqueous electrolyte secondary battery.

  In recent years, a chargeable / dischargeable battery has been used as a driving power source for vehicles such as hybrid vehicles and electric vehicles, and portable electronic devices such as notebook computers and video camcorders. As such a battery, for example, there is a non-aqueous electrolyte secondary battery (sealed battery) that includes a current interruption mechanism (safety mechanism) and includes a gas generating agent such as cyclohexylbenzene in an electrolytic solution. In this nonaqueous electrolyte secondary battery, during overcharging, the current interruption mechanism is activated by increasing the internal pressure of the battery case, starting from the decomposition reaction of the gas generating agent added to the positive electrode or the electrolyte.

  Here, Patent Document 1 discloses a technique for improving output characteristics of a battery by adding tungsten to the surface of positive electrode active material particles in an electrode for a non-aqueous electrolyte secondary battery. .

JP-A-2005-251716

  Here, in a non-aqueous electrolyte secondary battery equipped with a current interruption mechanism, the gas generating agent causes decomposition and polymerization reaction on the positive electrode to release protons, and the released protons diffuse and migrate to move electrons on the negative electrode. By receiving it, gas is generated. Then, when the internal pressure of the battery case rises to a predetermined pressure value or more, the current interrupt mechanism cuts off the current flowing through the electrode body (safety ensuring operation), and stops the battery charging (overcharge).

  Therefore, when the technique of Patent Document 1 is applied to a non-aqueous electrolyte secondary battery having the current interruption mechanism, the concentration of tungsten added to the surface of the positive electrode active material particles is high, so that the reaction field between the gas generating agent and the positive electrode Decreases and gas is hardly generated. Therefore, the amount of gas generated at the time of overcharging is reduced, and the internal pressure of the battery case is difficult to increase. Therefore, the current interruption mechanism may not operate stably during overcharge.

  Accordingly, the present invention has been made to solve the above-described problems, and a method for manufacturing a nonaqueous electrolyte secondary battery capable of improving output characteristics while preventing a decrease in the amount of gas generated during overcharging. It is another object of the present invention to provide a non-aqueous electrolyte secondary battery.

  One aspect of the present invention made to solve the above problems is a battery case comprising a positive electrode plate, a negative electrode plate, an electrolytic solution, a gas generating agent that generates gas during overcharge, and the gas generated during overcharge. In a method for manufacturing a non-aqueous electrolyte secondary battery having a current interruption mechanism that stops charging when the internal pressure of the battery rises, a transition metal compound and a lithium compound are mixed and fired, and tungsten is added. A positive electrode comprising positive electrode active material particles made of a lithium transition metal composite oxide to which tungsten is added, obtained by washing the fired product with water, and a water washing step for washing the fired product with water. A positive electrode plate forming step of forming the positive electrode plate by forming an active material layer on the positive electrode current collector.

  According to this aspect, the concentration of tungsten can be reduced on the surface of the positive electrode active material particles included in the positive electrode active material layer formed on the positive electrode plate. Therefore, it is possible to suppress a decrease in the reaction field between the gas generating agent and the positive electrode plate. Therefore, when the non-aqueous electrolyte secondary battery is overcharged, it is promoted that the gas generating agent decomposes and polymerizes on the positive electrode plate to release protons, and the released protons diffuse and migrate to the negative electrode. The amount of gas generated by receiving electrons on the plate increases. Further, since the positive electrode active material particles are made of a lithium transition metal composite oxide to which tungsten is added, the output characteristics (discharge characteristics and the like) of the nonaqueous electrolyte secondary battery are improved. As described above, the output characteristics of the nonaqueous electrolyte secondary battery are prevented while preventing a decrease in the amount of gas generated from the decomposition reaction between the gas generating agent and the positive electrode plate during overcharge of the nonaqueous electrolyte secondary battery. Can be improved. And when the internal pressure of a battery case rises at the time of overcharge of a nonaqueous electrolyte secondary battery, charge can be stopped stably by a current interruption mechanism.

  In the above aspect of the method for manufacturing a non-aqueous electrolyte secondary battery, the molar fraction of tungsten on the surface of the particle with respect to the total amount of metal of the entire particle in one positive electrode active material particle is 0.8 mol% or less. The mole fraction of tungsten at the surface of the particle with respect to the total metal amount of the whole particle in one positive electrode active material particle, and the surface of the particle with respect to the total metal amount of the whole particle in one positive electrode active material particle The ratio of the molar fraction of tungsten at a depth of 0.2 to 0.2 nm is preferably 0.98 to 1.02.

  According to this aspect, the molar fraction of tungsten with respect to the total metal amount of the entire particle in one positive electrode active material particle has a depth of 0.2 nm from the position of the surface of the positive electrode active material particle and the surface of the positive electrode active material particle. In this position, it is almost the same. Thus, similarly to the surface of the positive electrode active material particles, the concentration of tungsten is low even at a depth of 0.2 nm from the surface of the positive electrode active material particles. As a result, a reaction field between the gas generating agent and the positive electrode plate is sufficiently secured, so that the amount of gas generated increases more reliably during overcharge of the nonaqueous electrolyte secondary battery.

  Another aspect of the present invention made to solve the above-described problems is a battery comprising a positive electrode plate, a negative electrode plate, an electrolyte, a gas generating agent that generates gas during overcharge, and the gas generated during overcharge. A non-aqueous electrolyte secondary battery having a current interruption mechanism that stops charging when the internal pressure of the case increases, wherein the positive electrode plate includes positive electrode active material particles made of lithium transition metal composite oxide to which tungsten is added. The positive electrode active material layer is formed on a positive electrode current collector, and the lithium transition metal composite oxide to which tungsten is added is obtained by mixing and firing a transition metal compound and a lithium compound. It is obtained after washing the fired product to which is added with water.

  According to this aspect, the concentration of tungsten can be reduced on the surface of the positive electrode active material particles included in the positive electrode active material layer formed on the positive electrode plate. Therefore, it is possible to suppress a decrease in the reaction field between the gas generating agent and the positive electrode plate. Therefore, when the non-aqueous electrolyte secondary battery is overcharged, it is promoted that the gas generating agent decomposes and polymerizes on the positive electrode plate to release protons, and the released protons diffuse and migrate to the negative electrode. The amount of gas generated by receiving electrons on the plate increases. Further, since the positive electrode active material particles are made of a lithium transition metal composite oxide to which tungsten is added, the output characteristics (discharge characteristics and the like) of the nonaqueous electrolyte secondary battery are improved. As described above, the output characteristics of the nonaqueous electrolyte secondary battery are prevented while preventing a decrease in the amount of gas generated from the decomposition reaction between the gas generating agent and the positive electrode plate during overcharge of the nonaqueous electrolyte secondary battery. Can be improved. And when the internal pressure of a battery case rises at the time of overcharge of a nonaqueous electrolyte secondary battery, charge can be stopped stably by a current interruption mechanism.

  In the above aspect of the non-aqueous electrolyte secondary battery, the molar fraction of tungsten on the surface of the particle with respect to the total metal amount of the entire particle in one positive electrode active material particle is 0.8 mol% or less, The molar fraction of tungsten at the surface of the particle with respect to the total amount of metal of the whole particle in the positive electrode active material particle, and the surface of the particle with respect to the total amount of metal of the whole particle in one positive electrode active material particle are 0. The ratio of the molar fraction of tungsten at a depth of 2 nm is preferably 0.98 to 1.02.

  According to this aspect, the molar fraction of tungsten with respect to the total metal amount of the entire particle in one positive electrode active material particle has a depth of 0.2 nm from the position of the surface of the positive electrode active material particle and the surface of the positive electrode active material particle. In this position, it is almost the same. Thus, similarly to the surface of the positive electrode active material particles, the concentration of tungsten is low even at a depth of 0.2 nm from the surface of the positive electrode active material particles. As a result, a reaction field between the gas generating agent and the positive electrode plate is sufficiently secured, so that the amount of gas generated increases more reliably during overcharge of the nonaqueous electrolyte secondary battery.

  According to the method for producing a nonaqueous electrolyte secondary battery and the nonaqueous electrolyte secondary battery according to the present invention, output characteristics can be improved while preventing a decrease in the amount of gas generated during overcharge.

It is a perspective view of the nonaqueous electrolyte secondary battery of a present Example. It is a figure which shows the evaluation result of the molar fraction in each depth of a positive electrode active material particle. It is a figure which shows the surface tungsten ratio in each depth of a positive electrode active material particle. It is a figure which shows the index | exponent calculated by dividing the density | concentration of tungsten in the position of the surface of positive electrode active material particle by the density | concentration of tungsten in the position of depth 0.2nm from the surface of positive electrode active material particle. It is a figure which shows the evaluation result of the discharge characteristic of a nonaqueous electrolyte secondary battery. It is a figure which shows the evaluation result of the discharge characteristic of a nonaqueous electrolyte secondary battery. It is the table | surface which put together the evaluation result regarding the action | operation of the electric current interruption apparatus at the time of overcharge.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings.

[Nonaqueous electrolyte secondary battery]
First, the nonaqueous electrolyte secondary battery (hereinafter, mainly referred to as “battery”) of this example will be described. Initially, the structure of the battery 1 of a present Example is demonstrated. As shown in FIG. 1, the battery 1 of this example includes an electrode body 14 including a positive electrode plate 10 and a negative electrode plate 12, an electrolyte solution 16 containing a gas generating agent composed of cyclohexylbenzene, and the electrode body 14 and electrolysis. This is a sealed lithium ion secondary battery having a battery case 18 containing the liquid 16. In addition, the battery 1 includes a negative electrode terminal structure 20, a positive electrode terminal structure 22, and a current interruption device SD (an electric current interruption device) that interrupts the current flowing through the electrode body 14 (safety ensuring operation) to the positive electrode terminal structure 22. It includes a blocking mechanism (CID: Current Interrupt Device).

  The positive electrode plate 10 includes a positive electrode active material layer (not shown) on both surfaces of a strip-shaped aluminum foil. Then, tungsten is added to positive electrode active material particles made of lithium nickel composite oxide (an example of a lithium transition metal composite oxide) contained in the positive electrode active material layer. Thus, by adding tungsten to the positive electrode active material particles, the battery 1 can maintain good output characteristics. In this example, as described later, the positive electrode active material particles are washed with water. Thereby, the concentration of tungsten on the surface of the positive electrode active material particles (secondary particle surface of the positive electrode active material) is reduced.

  Here, as the concentration of tungsten, the molar fraction of tungsten with respect to the total metal amount of the whole particle in one positive electrode active material particle is taken as an example. Then, in this example, as an example, the molar fraction of tungsten on the surface of the particle with respect to the total metal amount of the entire particle in one positive electrode active material particle is set to 0.8 mol% or less. Then, the tungsten concentration at the position of the surface of the positive electrode active material particles and the tungsten concentration at a position of a depth of 0.2 nm from the surface of the positive electrode active material particles are substantially equal. Specifically, as one example, one positive electrode active material particle with a molar fraction of tungsten at a position of a depth of 0.2 nm from the surface of the particle as a denominator with respect to the total amount of metal of the entire particle in one positive electrode active material particle It is desirable that an index (ratio of mole fraction) obtained by taking the mole fraction of tungsten at the position of the surface of the particle with respect to the total amount of metal in the whole particle in 0.98 to 1.02.

  Moreover, the negative electrode plate 12 is equipped with the negative electrode active material layer (not shown) on both surfaces of a strip | belt-shaped copper foil. Moreover, the electrolyte solution 16 adds LiPF6 as a solute to a mixed organic solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are adjusted to a volume ratio of EC: EMC = 3: 7, and lithium ions are added. It is an organic electrolyte having a concentration of 1.0 mol / l. In addition, cyclohexylbenzene, which is a gas generating agent, is added to the electrolytic solution 16. In this embodiment, as an example, 3 wt% of cyclohexylbenzene is added to the electrolytic solution 16. Cyclohexylbenzene undergoes a decomposition / polymerization reaction on the positive electrode plate 10 when the battery 1 is overcharged to release protons. The released protons diffuse and migrate, receive electrons on the negative electrode plate 12, and generate hydrogen gas. Thereby, the internal pressure of the battery case 18 rises.

  The electrode body 14 is formed by winding a belt-like positive electrode plate 10 and a negative electrode plate 12 into a flat shape via a belt-like porous separator (not shown) made of polyethylene. The positive electrode plate 10 is bonded to the positive electrode terminal structure 22, and the negative electrode plate 12 is bonded to the negative electrode terminal structure 20.

  The battery case 18 has a case body member 24 including an opening and a sealing lid 26. Among these, the sealing lid 26 has a rectangular plate shape, closes the opening of the case body member 24, and is welded to the case body member 24.

  In addition, the current interrupting device SD performs the interruption of the current flowing through the electrode body 14 (safety ensuring operation) when the internal pressure of the battery case 18 rises to a predetermined pressure value or more when the battery 1 is overcharged. Stop charging (overcharge).

[Method for producing non-aqueous electrolyte secondary battery]
Next, a method for manufacturing the battery 1 of this example will be described. First, a method for producing positive electrode active material particles made of a lithium nickel composite oxide contained in a positive electrode active material layer (not shown) provided in the positive electrode plate 10 will be described. The method for producing positive electrode active material particles of this example includes a nickel compound preparation step, a firing step, a water washing step, and a drying step.

(Nickel compound preparation process)
First, in the nickel compound preparation step, nickel hydroxide or nickel oxy which contains nickel as a main component and at least one element selected from other transition metal elements, group 2 elements, or group 13 elements as subcomponents. Prepare the hydroxide. Alternatively, the obtained nickel hydroxide or nickel oxyhydroxide is subsequently roasted to prepare nickel oxide. In this way, a nickel compound selected from nickel hydroxide, nickel oxyhydroxide or nickel oxide is prepared.

  Here, as the nickel hydroxide or nickel oxyhydroxide, those obtained via a crystallization method are preferable. The nickel oxide is particularly preferably a nickel oxide obtained by roasting nickel hydroxide or nickel oxyhydroxide obtained by crystallization.

  In order to obtain nickel hydroxide by a crystallization method, for example, in a reaction vessel heated to 40 to 60 ° C., nickel as a main component and other transition metal elements, group 2 elements as subcomponents, Alternatively, an aqueous solution of a metal compound containing at least one element selected from Group 13 elements and an aqueous solution containing an ammonium ion supplier are dropped, and at that time, the reaction solution is kept alkaline, preferably at a pH of 10 to 14. A sufficient amount of an aqueous solution of an alkali metal hydroxide is appropriately dropped as required. On the other hand, in order to obtain nickel oxyhydroxide by a crystallization method, it is prepared by further adding an oxidizing agent such as sodium hypochlorite or hydrogen peroxide to the aqueous solution in which the nickel hydroxide is formed.

  Moreover, it does not specifically limit as roasting conditions for obtaining nickel oxide, For example, it roasts in the air atmosphere, Preferably it is 500-1100 degreeC, More preferably, it is 600-900 degreeC. It is desirable.

(Baking process)
Next, in the firing step, the nickel compound and the lithium compound are adjusted so that the molar amount of lithium in the lithium compound is 1.00 to 1.15 with respect to the total amount of nickel and subcomponents in the nickel compound. Are then fired in an oxygen atmosphere at a maximum temperature of 650 to 850 ° C.

  In this firing step, the nickel compound and the lithium compound are mixed, and the resulting mixture is fired in an oxygen atmosphere. When mixing the nickel compound and the lithium compound, a dry mixer such as a V blender or a mixing granulator is used. Further, when the obtained mixture is baked in an oxygen atmosphere, an electric furnace, kiln, adjusted to a gas atmosphere having an oxygen concentration of 20% by weight or more such as an oxygen atmosphere, a dry air atmosphere subjected to dehumidification and carbonation treatment, A firing furnace such as a tubular furnace or a pusher furnace is used.

  In this embodiment, in this firing step, tungsten is added as a salt and fired to produce a fired product to which tungsten is added. Alternatively, in this firing step, by solid-phase mixing a fired product obtained by mixing and firing a nickel compound and a lithium compound and an adherend containing tungsten, and baking the resulting mixture, A fired product to which tungsten is added is generated.

(Washing process)
Next, in the washing step, the fired product obtained in the firing step is washed with water. In this water washing step, as an example, for the positive electrode active material particles obtained after water washing, the molar fraction of tungsten on the surface of the particles with respect to the total metal amount of the whole particles in one positive electrode active material particle is 0.8 mol% or less. Select the washing conditions so that For example, the slurry concentration at the time of washing the fired product with water is 1000 g / L, and is maintained for 1 hour under stirring.

(Drying process)
Next, in the drying step, the fired product washed in the water washing step is filtered and dried to obtain a lithium nickel composite oxide powder. For example, vacuum-drying is performed while holding the powder obtained by filtering the fired product washed with water at 80 ° C. for 10 hours. Here, since tungsten is added to the fired product generated in the firing step as described above, tungsten is added to the lithium nickel composite oxide obtained through the water washing step and the drying step.

  In the lithium nickel composite oxide thus obtained, the tungsten concentration at the surface position and the tungsten concentration at a depth of 0.2 nm from the surface are substantially equal. Specifically, as one example, one positive electrode active material particle with a molar fraction of tungsten at a position of a depth of 0.2 nm from the surface of the particle as a denominator with respect to the total amount of metal of the entire particle in one positive electrode active material particle It is desirable that an index (ratio of mole fraction) obtained by taking the mole fraction of tungsten at the position of the surface of the particle with respect to the total amount of metal in the whole particle in 0.98 to 1.02.

  This is the description of the method for producing the positive electrode active material particles. As described above, positive electrode active material particles made of a lithium nickel composite oxide are produced.

  Then, the positive electrode paste including the positive electrode active material particles made of the lithium nickel composite oxide, the conductive material, and the binder prepared as described above is applied to both surfaces of the aluminum foil, and then dried and pressed. (Positive electrode plate making process). Thus, the positive electrode plate 10 is formed by forming the positive electrode active material layer which consists of said positive electrode paste in aluminum foil. The aluminum foil is an example of the “positive electrode current collector” in the present invention.

  In this embodiment, when the positive electrode plate 10 is formed, acetylene black is adopted as a conductive material contained in the positive electrode paste, and polyvinylidene fluoride (PVDF) is adopted as a binder contained in the positive electrode paste. Then, the positive electrode active material particles, acetylene black, and polyvinylidene fluoride are charged into a planetary mixer and mixed, and the viscosity is adjusted with NMP (N-methyl-2-pyrrolidone) to prepare a positive electrode paste. Here, as an example, the mixing ratio is 91 wt% for the positive electrode active material particles, 6 wt% for acetylene black, and 3 wt% for PVDF. Moreover, the density of a positive electrode paste is adjusted to 3.0 g / cc with a roll press as an example.

  On the other hand, a negative electrode paste containing negative electrode active material particles made of natural graphite, a conductive material, and a binder is applied to both surfaces of the copper foil, and then dried and pressed to form the negative electrode plate 12.

  In this embodiment, when the negative electrode plate 12 is formed, carboxymethyl cellulose (CMC) is adopted as a thickener contained in the negative electrode paste, and styrene butadiene rubber (SBR) is adopted as a binder contained in the negative electrode paste. Then, negative electrode active material particles, carboxymethyl cellulose, and styrene butadiene rubber are mixed, and the viscosity is adjusted with water to prepare a negative electrode paste. Here, as an example, the mixing ratio is such that the positive and negative electrode active material particles are 98 wt%, the carboxymethyl cellulose is 1 wt%, and the styrene butadiene rubber is 1 wt%. Moreover, the density of negative electrode paste is adjusted to 1.6 g / cc with a roll press as an example.

  And it rolls by interposing the strip | belt-shaped porous separator (not shown) which consists of polyethylene between the positive electrode plate 10 and the negative electrode plate 12 which were produced in this way, and the electrode body 14 is produced.

  Next, the electrode body 14 thus created is connected to the sealing lid 26. At this time, the positive electrode plate 10 is bonded to the positive electrode terminal structure 22, and the negative electrode plate 12 is bonded to the negative electrode terminal structure 20. Next, the electrode body 14 is accommodated in the case body member 24, and the case body member 24 is sealed with the sealing lid 26. Next, the electrolytic solution 16 is injected from a liquid injection hole (not shown) of the sealing lid 26, and the liquid injection hole is sealed to complete the battery 1 (see FIG. 1). The above is the description of the method for manufacturing the battery 1 of this example.

[Evaluation of change in concentration of tungsten in positive electrode active material particles by washing with water]
Here, the change in the concentration of tungsten in the positive electrode active material particles by washing with water was evaluated. In the evaluation, positive electrode active material particles that were washed with water and positive electrode active material particles that were not washed with water were prepared. Then, the concentration of tungsten distributed in the depth direction from the surface of each positive electrode active material particle was evaluated by X-ray photoelectron spectroscopy (XPS). The evaluation results are shown in FIG. In FIG. 2, the horizontal axis represents the depth (unit: nm) from the surface of the positive electrode active material particles, and the vertical axis represents the mole fraction (specifically, the mole fraction of tungsten with respect to the total metal amount of one positive electrode active material particle as a whole. ). Then, as shown in FIG. 2, it was revealed that the positive electrode active material particles that had been washed with water had a lower tungsten concentration than the positive electrode active material particles that had not been washed with water. In the evaluation results shown in FIG. 2 and subsequent FIGS. 3 to 7, the case where water washing is performed is represented as “with water washing”, and the case where water washing is not performed is represented as “no water washing”.

  Therefore, FIG. 3 shows the surface tungsten ratio for each depth from the surface of the positive electrode active material particles. Here, the surface tungsten ratio is the concentration of tungsten at each depth position from the surface of the positive electrode active material particles (molar fraction of tungsten with respect to the total metal amount of one positive electrode active material particle), and the positive electrode active material. It is a value divided by the tungsten concentration at the position of the particle surface (molar fraction of tungsten with respect to the total amount of metal of one positive electrode active material particle as a whole). In FIG. 3, the horizontal axis represents the depth (unit: nm) from the surface of the positive electrode active material particles, and the vertical axis represents the surface tungsten ratio. Moreover, in FIG. 3, it has shown about the range whose depth from the surface of positive electrode active material particle is 0-0.6 nm. In FIG. 3, two evaluation results are shown for each of the case where the washing is not performed and the case where the washing is performed.

  Then, as shown in FIG. 3, the positive electrode active material particles that were not washed with water had a tungsten concentration at a position of 0.2 nm deep from the surface of the positive electrode active material particles. The concentration of tungsten is increased. In contrast, the positive electrode active material particles that have been washed with water have a tungsten concentration at a position where the depth from the surface of the positive electrode active material particles is 0.2 nm and a tungsten concentration at the position of the surface of the positive electrode active material particles. It became equivalent.

  Further, the concentration of tungsten at the position where the depth from the surface of the positive electrode active material particles is 0.2 nm (molar fraction of tungsten with respect to the total amount of metal of one positive electrode active material particle) is used as the denominator. FIG. 4 shows an index calculated using the concentration of tungsten at the surface position (molar fraction of tungsten with respect to the total amount of metal in one positive electrode active material particle) as a molecule. In FIG. 4, two evaluation results are shown for each of the case where the washing is not performed and the case where the washing is performed. Then, as shown in FIG. 4, it was found that the positive active material particles that were washed with water had a significantly higher index than the positive active material particles that were not washed with water.

[Evaluation of battery performance]
Next, the influence on the battery performance by the presence or absence of washing with water was evaluated. Then, the evaluation result of the discharge characteristic of the battery 1 in the case where it washed with water and the case where it did not wash is shown in FIG. 5 and FIG. 5 and 6, the horizontal axis represents time (unit: sec), and the vertical axis represents voltage (unit: V). Here, two batteries 1 were evaluated for each of the case where water was washed and the case where water was not washed.

  Then, as shown in FIGS. 5 and 6, it was found that the output characteristics of the battery 1 were not deteriorated due to the washing with water. 5 shows the discharge characteristics under condition 1 (discharge characteristics when the SOC of the battery is 20% and the discharge current value is 20 C under the conditions of 25 ° C.), and FIG. 6 shows the discharge characteristics under condition 2 (25 ° C. Shows the discharge characteristics when the SOC of the battery is 60% and the discharge current value is 20 C. FIG. 6 shows that almost the same evaluation results were obtained when washing was performed and when washing was not performed. Also, SOC is an abbreviation for State Of Charge (charging state, charging rate). Furthermore, the discharge current value of “20C” corresponds to a current value of a magnitude that allows a constant current discharge (pulse discharge) of the SOC 100% battery to SOC 0% in 0.05 hours.

[Overcharge evaluation]
Next, when the discharge current value was 1 C under the condition of room temperature (25 ° C.), the amount of gas generated when the battery 1 was overcharged with or without washing was evaluated. Therefore, the evaluation result is shown in FIG. Then, as shown in FIG. 7, when water washing was not performed, the amount of gas generated when the battery 1 was overcharged did not reach a predetermined value, so that the current interrupt device (CID) SD did not operate. On the other hand, when washing was performed with water, since the amount of gas generated when the battery 1 was overcharged reached a predetermined value, the current interrupting device (CID) SD was activated.

  The reason why the amount of gas generated when the battery 1 is overcharged by washing with water as described above is estimated as follows. It is considered that the tungsten was removed on the interface of the positive electrode active material particles by washing with water, the diffusibility of the gas generating agent was improved, and the reactivity was improved. Alternatively, it is considered that by performing washing with water, the form of tungsten on the surface of the positive electrode active material particles was changed (for example, changed from a film shape to a particle shape), and the reactivity was improved. Alternatively, it is considered that the reactivity was improved by increasing the surface area of the transition metal of the positive electrode active material particles by washing with water.

  According to the present embodiment as described above, in the firing step, a nickel compound and a lithium compound are mixed and fired to produce a fired product to which tungsten is added. Then, the fired product is washed with water in a washing step, and then a lithium transition metal composite oxide to which tungsten is added is obtained. Then, in the positive electrode plate forming step, the positive electrode active material layer including the positive electrode active material particles made of the lithium transition metal composite oxide to which tungsten is added is formed on the aluminum foil, and the positive electrode plate 10 is formed. Thereby, the density | concentration of tungsten can be reduced in the surface of the positive electrode active material particle contained in the positive electrode active material layer formed in the positive electrode plate 10. FIG. Therefore, a reduction in the reaction field between cyclohexylbenzene (gas generating agent) and the positive electrode plate 10 can be suppressed. Therefore, when the battery 1 is overcharged, cyclohexylbenzene is decomposed and polymerized on the positive electrode plate 10 to promote the release of protons, and the released protons diffuse and migrate to move on the negative electrode plate 12. The amount of hydrogen gas generated by receiving electrons increases. Further, since the positive electrode active material particles are made of a lithium transition metal composite oxide to which tungsten is added, the output characteristics (discharge characteristics and the like) of the battery 1 are improved. As described above, the output characteristics of the battery 1 can be improved while preventing a decrease in the amount of hydrogen gas generated from the reaction between the gas generating agent and the positive electrode plate when the battery 1 is overcharged. Then, when the internal pressure of the battery case 18 rises when the battery 1 is overcharged, charging can be stably stopped by the current interrupt device SD.

  In addition, the molar fraction of tungsten on the surface of the particle with respect to the total metal amount of the entire particle in one positive electrode active material particle is 0.8 mol% or less. Further, the molar fraction of tungsten at the surface of the particle with respect to the total metal amount of the whole particle in one positive electrode active material particle, and the surface of the particle with respect to the total metal amount of the whole particle in one positive electrode active material particle The ratio to the molar fraction of tungsten at a depth of 0.2 nm is 0.98 to 1.02. Thereby, similarly to the surface of the positive electrode active material particles, the tungsten concentration is low even at a depth of 0.2 nm from the surface of the positive electrode active material particles. Therefore, a sufficient reaction field between cyclohexylbenzene and the positive electrode plate 10 is secured, so that the amount of hydrogen gas generated increases more reliably when the battery 1 is overcharged.

  It should be noted that the above-described embodiment is merely an example and does not limit the present invention in any way, and various improvements and modifications can be made without departing from the scope of the invention.

For example, instead of positive electrode active material particles made of lithium nickel composite oxide, positive electrode active material particles made of other lithium transition metal composite oxides may be used. Other lithium transition metal composite oxide, _such as LiCoO _2, LiMnO _4, LiFeO 4 can be cited as a candidate.

DESCRIPTION OF SYMBOLS 1 Battery 10 Positive electrode plate 12 Negative electrode plate 14 Electrode body 16 Electrolyte 18 Battery case 20 Negative electrode terminal structure 22 Positive electrode terminal structure 24 Case main body member 26 Sealing lid SD Current interruption device

Claims (4)

A positive electrode plate, a negative electrode plate, an electrolyte, a gas generating agent that generates a gas when overcharged, and a current interruption mechanism that stops charging when the internal pressure of the battery case increases due to the gas generated during overcharging, In a method for producing a non-aqueous electrolyte secondary battery having
A firing step for producing a fired product to which tungsten is added, wherein the transition metal compound and the lithium compound are mixed and fired;
A water washing step of washing the fired product;
A positive electrode for forming the positive electrode plate by forming, on a positive electrode current collector, a positive electrode active material layer containing positive electrode active material particles made of lithium transition metal composite oxide to which the tungsten is added, obtained after washing the fired product with water Plate making process,
A method for producing a nonaqueous electrolyte secondary battery, comprising: In the manufacturing method of the nonaqueous electrolyte secondary battery of Claim 1,
The molar fraction of tungsten on the surface of the particle with respect to the total metal amount of the entire particle in one positive electrode active material particle is 0.8 mol% or less,
The molar fraction of tungsten at the surface of the particle with respect to the total metal amount of the whole particle in one positive electrode active material particle, and the surface of the particle with respect to the total metal amount of the whole particle in one positive electrode active material particle The ratio to the molar fraction of tungsten at a depth of 0.2 nm is 0.98 to 1.02.
A method for producing a nonaqueous electrolyte secondary battery. A positive electrode plate, a negative electrode plate, an electrolyte, a gas generating agent that generates a gas when overcharged, and a current interruption mechanism that stops charging when the internal pressure of the battery case increases due to the gas generated during overcharging, In a non-aqueous electrolyte secondary battery having
The positive electrode plate is formed by forming a positive electrode active material layer including positive electrode active material particles made of lithium transition metal composite oxide added with tungsten on a positive electrode current collector,
The lithium-transition metal composite oxide to which tungsten is added is obtained by mixing and firing a transition metal compound and a lithium compound, and obtained after washing the fired product to which tungsten is added,
A non-aqueous electrolyte secondary battery. The nonaqueous electrolyte secondary battery according to claim 3,
The molar fraction of tungsten on the surface of the particle with respect to the total metal amount of the entire particle in one positive electrode active material particle is 0.8 mol% or less,
The molar fraction of tungsten at the surface of the particle with respect to the total metal amount of the whole particle in one positive electrode active material particle, and the surface of the particle with respect to the total metal amount of the whole particle in one positive electrode active material particle The ratio to the molar fraction of tungsten at a depth of 0.2 nm is 0.98 to 1.02.
A non-aqueous electrolyte secondary battery.

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