JP2011146154A - Manufacturing method of anode paste, manufacturing method of anode plate, and manufacturing method of lithium secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of anode paste or the like capable of stabilizing viscosity and improving dispersibility of anode active material particles and a binding material in an anode active material layer. <P>SOLUTION: The manufacturing method of anode paste 129 for a lithium secondary battery 100 comprises an organic acid treatment process of forming acid-treated anode active material particles 127 with organic acid 126 combined or absorbed on a particle surface 125h of the anode active material particles 125 made of a carbon material capable of inserting and removing lithium ion, and a paste preparation process of preparing the anode paste 129 with the acid treatment anode active material particles 127 and the binding material dispersed in a dispersing medium. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a negative electrode paste used for producing a lithium secondary battery, a method for producing a negative electrode plate using the negative electrode paste, and a method for producing a lithium secondary battery using the negative electrode plate.

  Conventionally, in a lithium secondary battery that requires high input / output performance, carbon capable of inserting and releasing lithium ions, such as graphite, carbon black, and carbon fiber, is used as the negative electrode active material particles constituting the negative electrode active material layer of the negative electrode plate. Particles made of material are used. The reason why the carbon material is used is that there is an advantage that it is possible to prevent generation of dentlite in which lithium metal grows in a resinous state while repeating charge and discharge. A method of forming a negative electrode plate using such negative electrode active material particles made of a carbon material is disclosed in, for example, Patent Document 1 (see the claims of Patent Document 1).

  That is, a polyvinylidene fluoride polymer as a binder (binder) is dissolved in an organic solvent, and an acid is further added thereto to prepare a binder solution. Thereafter, a powder electrode material such as negative electrode active material particles is added and dispersed in this binder solution to obtain a negative electrode paste. And after apply | coating this negative electrode paste on a negative electrode collector, it is made to dry and a negative electrode active material layer is formed on a negative electrode collector, and a negative electrode plate is obtained.

  The reason why the acid is added to the binder solution is to prevent a phenomenon in which the viscosity of the binder solution varies depending on the lot of the organic solvent, and the viscosity becomes considerably larger than usual. When the viscosity of the binder solution increases, the paste viscosity of the negative electrode paste also increases, and it may be difficult to obtain a uniform film thickness when the negative electrode paste is applied onto the negative electrode current collector. In some cases, the negative electrode paste gels when the negative electrode active material particles are mixed into the binder solution, and it may be difficult to apply the negative electrode paste to the negative electrode current collector.

JP-A-9-180725

  However, in the manufacturing method of Patent Document 1, the viscosity of the negative electrode paste can be stabilized. However, when the negative electrode active material layer is formed by applying it on the negative electrode current collector and drying it, The binder may segregate. If it does so, the current collection property and reactivity in this negative electrode plate will become non-uniform | heterogenous. And in the lithium secondary battery manufactured using this negative electrode plate, cycling characteristics, especially high-rate cycling characteristics deteriorate.

  The present invention has been made in view of the current situation, and can improve the viscosity stability of the negative electrode paste, and negative electrode active material particles and a binder in a negative electrode active material layer formed by coating the same. It aims at providing the manufacturing method of the negative electrode paste which can improve the dispersibility of this. Further, by using this negative electrode paste, a method for producing a negative electrode plate that can make current collection and reactivity uniform in the negative electrode plate, and a lithium secondary that can improve cycle characteristics by using this negative electrode plate It aims at providing the manufacturing method of a battery.

  One aspect of the present invention for solving the above-described problem is a method for producing a negative electrode paste for a lithium secondary battery, wherein the negative electrode active material particles made of a carbon material capable of inserting and removing lithium ions are provided on the surface of particles. Organic acid treatment step for forming acid-treated negative electrode active material particles to which organic acid is bonded or adsorbed, and paste preparation for preparing the negative electrode paste in which the acid-treated negative electrode active material particles and the binder are dispersed in a dispersion medium A negative electrode paste comprising the steps.

  In this negative electrode paste manufacturing method, first, an organic acid was bonded or adsorbed on the surface of negative electrode active material particles made of a carbon material capable of inserting and releasing lithium ions (organic acid treatment step), and thus obtained. A negative electrode paste in which acid-treated negative electrode active material particles and a binder are dispersed in a dispersion medium is prepared (paste preparation step). This dispersion medium is a dispersion medium to which no acid is added. By doing in this way, it can prevent that the viscosity of a negative electrode paste varies with the lots of a dispersion medium, etc., or gelation of a negative electrode paste can be prevented, and the viscosity stability of a negative electrode paste can be improved. And when this negative electrode paste is apply | coated on a negative electrode electrical power collector and a negative electrode active material layer is formed, it can prevent that a binder segregates in a negative electrode active material layer, and the negative electrode active material in a negative electrode active material layer Dispersibility of the particles and the binder can be improved.

  Examples of the “carbon material capable of inserting and desorbing lithium ions” include natural graphite (scale-like graphite, scale-like graphite, earth-like graphite, etc.), artificial graphite, and the like. It can be used by mixing.

  Examples of the “organic acid” include organic compounds containing at least one carboxylic acid, sulfonic acid, sulfinic acid, sulfenic acid, phosphoric acid, boric acid and the like in the molecule. Specifically, acetoacetic acid, acrylic acid, adipic acid, benzoic acid, formic acid, citric acid, glyoxylic acid, glutaric acid, succinic acid, acetic acid, oxalic acid, stearic acid, trimellitic acid, lactic acid, pyruvic acid, phenylacetic acid, Examples include benzoylpropionic acid, phthalic acid, propionic acid, polyacrylic acid, polymethacrylic acid, maleic acid, malonic acid, methanesulfonic acid, butyric acid, levulinic acid, etc., and these should be used alone or in combination. Can do.

  Examples of the “binder” include resinous polymers such as polyethylene, polypropylene, polyethylene terephthalate, aromatic polyamide, and cellulose, and rubbery polymers such as styrene / butadiene rubber, isoprene rubber, butadiene rubber, and ethylene / propylene rubber. , Styrene / butadiene / styrene block copolymer, hydrogenated product thereof, styrene / ethylene / butadiene / styrene copolymer, styrene / isoprene / styrene block copolymer, thermoplastic elastomeric polymer such as hydrogenated product, Syndiotactic 1,2-polybutadiene, ethylene / vinyl acetate copolymer, propylene / α-olefin (carbon number 2 to 12) copolymer and other soft resinous polymers, polyvinylidene fluoride, polytetrafluoroethylene, poly Tetrafluoroethylene Fluorine polymers such as styrene copolymer, alkali metal ions, include, particularly polymeric compositions having ionic conductivity of lithium ions, and these can be used alone or in more mixed.

As the “dispersion medium”, for example, an organic solvent can be used singly or as a mixture of two or more kinds. Examples of the organic solvent include N-methyl-2-pyrrolidone, dimethylformamide, N, N-dimethylacetamide, N, N-dimethylsulfoxide, hexamethylphosphoamide, dioxane, tetrahydrofuran, tetramethylurea, and triethyl. Examples include phosphate and trimethyl phosphate.
In the “paste preparation step”, in addition to the acid-treated negative electrode active material particles and the binder, for example, a dispersant, a filler, an ionic conductive agent, a pressure enhancer, and the like can be added to the dispersion medium.

  Further, in the above method for producing a negative electrode paste, the organic acid treatment step is a mechanochemical treatment step in which the organic acid is bonded or adsorbed to the particle surface of the negative electrode active material particles by a mechanochemical treatment. A method for producing a certain negative electrode paste is preferable.

  In this negative electrode paste manufacturing method, since the organic acid treatment step is performed by mechanochemical treatment, the organic acid can be easily or reliably bonded or adsorbed on the surface of the negative electrode active material particles.

  Furthermore, in the above method for producing a negative electrode paste, the organic acid mechanochemical treatment step may be a method for producing a negative electrode paste performed by mechanochemical treatment using a ball mill or a bead mill.

  In this negative electrode paste manufacturing method, since the organic acid mechanochemical treatment step described above is performed by mechanochemical treatment using a ball mill or a bead mill, the organic acid is bound to the particle surface of the negative electrode active material particles more easily and reliably. Can be adsorbed.

  Furthermore, in the method for producing the negative electrode paste, the organic acid treatment step is performed by immersing the negative electrode active material particles in a solution containing the organic acid, thereby forming a surface of the negative electrode active material particles on the particle surface. A method for producing a negative electrode paste, which is an organic acid solution dipping step for bonding or adsorbing the organic acid, is preferable.

  In this negative electrode paste manufacturing method, since the organic acid treatment step is performed by immersing the negative electrode active material particles in a solution containing an organic acid, the organic acid is easily and reliably bonded to the particle surface of the negative electrode active material particles. Or it can be adsorbed.

  Furthermore, in any of the above-described negative electrode paste manufacturing methods, the binder may be a negative electrode paste manufacturing method including at least a polyvinylidene fluoride polymer.

  In the conventional negative electrode paste manufacturing method described above, when a polyvinylidene fluoride polymer is used as a binder, the viscosity of the negative electrode paste tends to be particularly large, and when the negative electrode paste is applied onto the negative electrode current collector, It is difficult to form a uniform film thickness. Moreover, it is easy to gelatinize at the time of preparation of a negative electrode paste, and application | coating of negative electrode paste itself may become difficult. Furthermore, when a negative electrode active material layer is formed using this negative electrode paste, the binder (polyvinylidene fluoride polymer) is particularly easily segregated in the negative electrode active material layer.

On the other hand, in the manufacturing method described above, since the negative electrode paste is manufactured by the organic acid treatment step and the paste preparation step described above, despite using a binder containing a polyvinylidene fluoride polymer, It is possible to prevent the viscosity of the negative electrode paste from increasing and the negative electrode paste from gelling, and improve the viscosity stability. Further, when the negative electrode paste is applied on the negative electrode current collector to form the negative electrode active material layer, the binder can be prevented from segregating in the negative electrode active material layer, and the negative electrode active material in the negative electrode active material layer can be prevented. Dispersibility of the particles and the binder can be improved.
Examples of the “polyvinylidene fluoride polymer” include, for example, polyvinylidene fluoride (PVDF), vinylidene fluoride-trifluoroethylene polymer (P (VDF-TFE)), vinylidene fluoride-hexafluoropropylene polymer ( P (VDF-HFP)) and the like.

  Furthermore, in the above method for producing a negative electrode paste, the dispersion medium may be a method for producing a negative electrode paste which is an organic solvent capable of dissolving the binder.

  In this negative electrode paste manufacturing method, since the organic solvent capable of dissolving the above-mentioned binder is used as the dispersion medium, the dispersibility of the binder in the negative electrode paste can be improved. Thereby, when this negative electrode paste is apply | coated on a negative electrode electrical power collector and a negative electrode active material layer is formed, it can prevent more reliably that a binder segregates in this negative electrode active material layer.

  Examples of the “organic solvent” include N-methyl-2-pyrrolidone, dimethylformamide, N, N-dimethylacetamide, N, N-dimethylsulfoxide, hexamethylphosphoamide, dioxane, Tetrahydrofuran, tetramethylurea, triethyl phosphate, trimethyl phosphate and the like can be mentioned, and these can be used alone or in combination.

  Another embodiment is a method for producing a negative electrode plate for a lithium secondary battery, comprising a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector, wherein A negative electrode plate manufacturing method comprising a negative electrode active material layer forming step of forming the negative electrode active material layer by applying the negative electrode paste manufactured by the negative electrode paste manufacturing method according to claim 1 onto the negative electrode current collector. .

  In this negative electrode plate manufacturing method, since the negative electrode plate is manufactured using the negative electrode paste manufactured by the negative electrode paste manufacturing method described above, it is possible to prevent the binder from segregating in the negative electrode active material layer. Dispersibility of the particles and the binder can be improved. Thereby, a negative electrode plate with more uniform current collection and reactivity than before can be obtained, and adhesion between the negative electrode active material layer and the negative electrode current collector can be improved.

  Another aspect is a method for manufacturing a lithium secondary battery including a negative electrode plate, wherein the lithium secondary battery is formed using the negative electrode plate manufactured by the negative electrode plate manufacturing method. Is a method for producing a lithium secondary battery.

In this method of manufacturing a lithium secondary battery, a lithium secondary battery is manufactured using the negative electrode plate manufactured by the above-described negative electrode plate manufacturing method. As described above, the negative electrode plate is more uniform in current collection and reactivity than conventional ones, and has improved adhesion between the negative electrode active material layer and the negative electrode current collector. In the lithium secondary battery manufactured in this way, the cycle characteristics of the battery, particularly the high rate cycle characteristics can be improved.
The shape of the lithium ion secondary battery is not particularly limited, and examples thereof include a coin shape, a cylindrical shape, and a square shape.

1 is a cross-sectional view of a lithium secondary battery according to Embodiment 1. FIG. 2 is a cross-sectional view of a negative electrode plate according to Embodiment 1. FIG. It is explanatory drawing which shows typically a mode that negative electrode active material particle is processed with an organic acid according to Embodiment 1, and acid-processed negative electrode active material particle is formed. It is explanatory drawing which shows typically a mode that it concerns on Embodiment 1 and applies a negative electrode paste to a negative electrode collector. It is a graph which shows the relationship between heating temperature and a weight reduction | decrease rate about each of the acid treatment negative electrode active material particle processed with the organic acid, and an untreated negative electrode active material particle. It is a graph which shows about the relationship between the cycle number and a capacity maintenance rate about each of the lithium secondary battery of an Example and a comparative example. It is explanatory drawing which shows the method of measuring the adhesive strength of a negative electrode active material layer and a negative electrode electrical power collector. It is a graph which shows the adhesive strength of a negative electrode active material layer and a negative electrode collector, the IV resistance of a lithium secondary battery, and the paste viscosity of a negative electrode paste about each of an Example and a comparative example.

(Embodiment 1)
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a lithium secondary battery 100 according to the first embodiment. FIG. 2 shows the negative electrode plate 120 according to the first embodiment. The lithium secondary battery 100 is a laminate cell having a substantially rectangular plate shape, and includes a battery case 150, a positive electrode plate 110, a negative electrode plate 120, a separator 130, and the like housed in the battery case 150.

  Among these, the battery case 150 is made of a laminate film, and seals the inside of the battery case 150 while being electrically insulated from the positive electrode plate 110, the negative electrode plate 120, and the like housed in the battery case 150. In the battery case 150, a positive electrode plate 110 and a negative electrode plate 120 are stacked via a separator 130. The battery case 150 is filled with a non-aqueous electrolyte 160.

The positive electrode plate 110 has a rectangular plate shape of 50 cm × 50 cm and a thickness of 100 μm, and includes a positive electrode current collector 113 made of metal foil (aluminum foil in the first embodiment), and a positive electrode formed on the positive electrode current collector 113 The active material layer 111 is included. The positive electrode active material layer 111 is composed of positive electrode active material particles, a conductive material, and a binder. In the first embodiment, particles made of lithium nickel oxide (specifically, LiNiO ₂ ) are used as the positive electrode active material particles, acetylene black is used as the conductive material, and PVDF (polyvinylidene fluoride) is used as the binder. Yes. The weight ratio is positive electrode active material particles: conductive material: binder = 100: 3: 2.

  On the other hand, the negative electrode plate 120 (see also FIG. 2 in addition to FIG. 1) has a rectangular plate shape of 50 cm × 50 cm and a thickness of 100 μm, and a negative electrode current collector 123 made of metal foil (copper foil in the first embodiment) and , And the negative electrode active material layer 121 formed on the negative electrode current collector 123. The negative electrode active material layer 121 is composed of acid-treated negative electrode active material particles 127 (see FIG. 3) composed of negative electrode active material particles 125 and an organic acid 126, and a binder. In the first embodiment, as the negative electrode active material particles 125, particles made of a carbon material (specifically, artificial graphite) capable of inserting and releasing lithium ions are used. In addition, maleic anhydride is used as the organic acid 126, and PVDF (polyvinylidene fluoride) is used as the binder. The weight ratio is negative electrode active material particles: organic acid: binder = 100: 1: 2.

The separator 130 has a rectangular plate shape and is made of a porous film of a polymer compound (in this embodiment, a PP / PE porous film). The non-aqueous electrolyte 160 is made of 1M-LiPF ₆ / EC + DMC + EMC (1: 1: 1).

Next, a manufacturing method of the negative electrode paste 129, a manufacturing method of the negative electrode plate 120, and a manufacturing method of the lithium secondary battery 100 will be described.
First, the manufacturing method of the negative electrode paste 129 for forming the negative electrode active material layer 121 of the negative electrode plate 120 will be described. The manufacturing method of the negative electrode paste 129 includes (1) an organic acid treatment step (organic acid mechanochemical treatment step) and (2) a paste preparation step.

(Organic acid treatment process)
FIG. 3 schematically shows the organic acid treatment step. Particles made of natural graphite are prepared as the negative electrode active material particles 125 made of a carbon material capable of inserting and releasing lithium ions, and maleic anhydride is prepared as the organic acid 126. Then, the acid acid negative electrode active material particles 127 are formed by bonding or adsorbing the organic acid 126 to the particle surfaces 125 h of the negative electrode active material particles 125.

  In the first embodiment, the organic acid 126 is bonded or adsorbed to the particle surface 125 h of the negative electrode active material particles 125 by a mechanochemical treatment using a ball mill. Specifically, the negative electrode active material particles 125 and the organic acid 126 are mixed at a weight ratio of 100: 1, put into a desk ball mill machine (not shown), and dry-mixed in dry air at 100 rpm for 24 hours. . As a result, the organic acid 126 is bonded or adsorbed to the particle surface 125 h of the negative electrode active material particles 125, thereby forming acid-treated negative electrode active material particles 127.

  Here, in order to confirm the amount of the organic acid 126 bonded or adsorbed to the negative electrode active material particles 125, the acid-treated negative electrode active material particles 127 were subjected to heat treatment, and the weight change thereof was examined (TG measurement). For comparison, the negative electrode active material particles 125 that were not treated with the organic acid 126 were also heat-treated in the same manner and examined for changes in weight. These results are shown in FIG. FIG. 5 is a graph showing the relationship between the heating temperature and the weight reduction rate.

  As is clear from this graph, when the untreated negative electrode active material particles 125 are heated at about 430 degrees (a temperature at which the organic acid 126 is considered to be completely thermally decomposed), the weight reduction ratio is about 0.1%. Whereas the acid-treated negative electrode active material particles 127 treated with the organic acid 126 were 3%, the weight reduction ratio was about 1.3%. Therefore, it can be seen that about 1.0% of the organic acid 126 is bonded or adsorbed to the acid-treated negative electrode active material particles 127. That is, as described above, in the organic acid treatment step, the negative electrode active material particles 125 and the organic acid 126 are mixed at a weight ratio of 100: 1. All are considered to be bonded or adsorbed to the negative electrode active material particles 125.

(Paste preparation process)
Next, a polyvinylidene fluoride polymer, specifically, PVDF (polyvinylidene fluoride) is prepared as a binder, and an organic solvent capable of dissolving the above binder as a dispersion medium, specifically, Prepare NMP (n-methyl-2-pyrrolidone). Then, the acid-treated negative electrode active material particles 127 obtained by the organic acid treatment step described above and the binder are dispersed in a dispersion medium to prepare a negative electrode paste 129. In Embodiment 1, the acid-treated active material particles 127, the binder, and the dispersion medium are mixed at a weight ratio of 101: 2: 100.

  As described above, in the manufacturing method of the negative electrode paste 129 of the first embodiment, first, the organic acid 126 is bonded or adsorbed on the particle surface 125 h of the negative electrode active material particle 125 made of a carbon material capable of inserting and releasing lithium ions. (Organic acid treatment step) The acid-treated negative electrode active material particles 127 and the binder thus obtained are dispersed in a dispersion medium to prepare a negative electrode paste 129 (paste preparation step). In Embodiment 1, unlike the prior art, no acid is added to the dispersion medium. By doing in this way, it can prevent that the viscosity of the negative electrode paste 129 varies with the lot of a dispersion medium, etc., or the gelling of the negative electrode paste 129 can improve viscosity stability.

In particular, in Embodiment 1, since the organic acid treatment step is performed by mechanochemical treatment using a ball mill (organic acid mechanochemical treatment step), the organic acid 126 is easily and reliably deposited on the particle surface 125h of the negative electrode active material particles 125. Can be bound to or adsorbed to.
In addition, when a polyvinylidene fluoride polymer is used as a binder, the viscosity of the negative electrode paste is increased or the negative electrode paste is easily gelled in the conventional negative electrode paste manufacturing method. On the other hand, in the first embodiment, since the negative electrode paste 129 is manufactured by the organic acid treatment step and the paste preparation step described above, the polyvinylidene fluoride polymer is used as the binder, The viscosity of the negative electrode paste 129 can be prevented from increasing and the negative electrode paste 129 can be prevented from gelling, and the viscosity stability can be improved.
In Embodiment 1, since the organic solvent capable of dissolving the binder is used as the dispersion medium, the dispersibility of the binder in the negative electrode paste 129 can be improved.

  Next, the negative electrode plate 120 is manufactured using the negative electrode paste 129. First, a negative electrode current collector 123 made of copper foil is prepared. Then, in the negative electrode active material layer forming step, the above-described negative electrode paste 129 is applied onto the negative electrode current collector 123 as shown in FIG. Thereafter, the negative electrode paste 129 applied on the negative electrode current collector 123 is dried and further pressed to increase the electrode density, whereby the negative electrode active material layer 121 described above is formed. Thus, the negative electrode plate 120 is formed.

  In the first embodiment, since the negative electrode plate 120 is formed using the negative electrode paste 129, the binder can be prevented from segregating in the negative electrode active material layer 121, and the negative electrode active material layer 121 in the negative electrode active material layer 121 can be prevented. The dispersibility of the substance particles 125 and the binder can be improved. In addition, since the above-described negative electrode paste 129 has high viscosity stability, a coating film having a uniform thickness can be easily and reliably formed on the negative electrode current collector 123. In addition, by using the above-described negative electrode paste, the adhesion between the negative electrode current collector 123 and the negative electrode active material layer 121 can be improved. In such a negative electrode plate 120, current collection and reactivity can be made more uniform than in the past.

Next, the lithium secondary battery 100 is manufactured using the negative electrode plate 120 (battery forming step). First, the positive electrode plate 110 is manufactured. Particles made of lithium nickel oxide (specifically, LiNiO ₂ ) as positive electrode active material particles, acetylene black as a conductive material, and PVDF (polypolyvinylidene fluoride) as a binder are prepared. And these are added and disperse | distributed in a dispersion medium, and a positive electrode paste is prepared. In the first embodiment, the positive electrode active material particles, the conductive material, the binder, and the dispersion medium are mixed at a weight ratio of 100: 3: 2: 100.
Thereafter, a positive electrode current collector 113 made of an aluminum foil is prepared, and the positive electrode paste is applied onto the positive electrode current collector 113. Then, if the positive electrode paste applied on the positive electrode current collector 113 is dried and further pressed to increase the electrode density, the positive electrode active material layer 111 described above is formed. Thus, the positive electrode plate 110 is formed.

  Next, a separator 130 and a laminate film for forming the battery case 150 are prepared. A non-aqueous electrolyte 160 is also prepared. And the positive electrode plate 110 and the negative electrode plate 120 are laminated | stacked through the separator 130, and these are enclosed with a laminate film. In addition, a non-aqueous electrolyte 160 is injected into the laminate film. Thereafter, a laminate film is welded to form a battery case 150, and the inside of the battery case 150 is sealed. Thus, the lithium secondary battery 100 is completed.

  In the first embodiment, the lithium secondary battery 100 is manufactured using the negative electrode plate 120 described above. As described above, in the negative electrode plate 120, the segregation of the binder in the negative electrode active material layer 121 is prevented, and the dispersibility of the negative electrode active material particles 125 and the binder is improved. And the current collection property and the reactivity in the negative electrode plate 120 are more uniform than before. For this reason, in the lithium secondary battery 100 manufactured using this, the cycle characteristics of the battery, in particular, the high rate cycle characteristics can be improved.

(Embodiment 2)
Next, a second embodiment will be described. In this Embodiment 2, the organic acid treatment process (organic acid solution immersion process) at the time of manufacturing the negative electrode paste 129 is different from the organic acid treatment process (organic acid mechanochemical treatment process) of Embodiment 1 described above. Other than that, it is basically the same as in the first embodiment, and therefore the description of the same parts as in the first embodiment is omitted or simplified.

In the organic acid treatment step (organic acid solution dipping step) of Embodiment 2, the negative electrode active material particles 125 are immersed in an aqueous solution containing the organic acid 126, so that the organic acid is applied to the particle surface 125h of the negative electrode active material particles 125. 126 is bound or adsorbed. Even with such a technique, the organic acid 126 can be easily or reliably bonded or adsorbed to the particle surface 125 h of the negative electrode active material particle 125.
Thereafter, the paste preparation step is performed in the same manner as in the first embodiment, and the negative electrode paste 129 is manufactured. Then, using this negative electrode paste 129, the negative electrode plate 120 is formed in the same manner as in the first embodiment. Furthermore, the lithium secondary battery 100 is manufactured using the negative electrode plate 120 in the same manner as in the first embodiment.

(Example)
Subsequently, the result of the test conducted in order to verify the effect of this invention is demonstrated. As an example, the negative electrode paste 129, the negative electrode plate 120, and the lithium secondary battery 100 manufactured by the manufacturing method of the first embodiment were prepared.
Moreover, the negative electrode paste manufactured by the conventional manufacturing method, the negative electrode plate, and the lithium secondary battery were prepared as a comparative example. That is, the binder is dispersed in a dispersion medium, and an acid is added thereto to prepare a binder solution. Thereafter, negative electrode active material particles were dispersed in the binder solution to prepare a negative electrode paste. Thereafter, using this negative electrode paste, a negative electrode plate was formed in the same manner as in the first embodiment, and a lithium secondary battery was further produced.

  A cycle characteristic test was performed for each of the lithium secondary batteries of Examples and Comparative Examples. The cycle conditions were a temperature of 60 degrees, a voltage range of 3.0 V to 4.1 V, and a charge / discharge rate of 2C. Moreover, the capacity | capacitance measurement was performed for every 500 cycles, temperature 25 degree | times, charging / discharging rate 0.2C, voltage range 3.0V-4.1V. The results are summarized in the graph of FIG.

As is clear from FIG. 6, in the lithium secondary battery of the comparative example, the capacity retention rate after 500 cycles is sufficiently high at about 99%, but the capacity retention rate after 1000 cycles is greatly reduced to about 95%. The capacity retention rate after 1500 cycles is greatly reduced to about 94%. Furthermore, the capacity maintenance rate after 2000 cycles is greatly reduced to about 88%.
On the other hand, in the lithium secondary battery 100 of the example, the capacity maintenance rate after 500 cycles is sufficiently high as about 99%, and the capacity maintenance rate is about 98% even after 1000 cycles, and the capacity is maintained even after 1500 cycles. The rate is sufficiently high at about 98%, and the battery capacity is reduced only slowly compared to the comparative example. Furthermore, the capacity retention rate after 2000 cycles is about 95%, and the battery capacity is only gradually reduced as compared with the comparative example. From this, it can be seen that if the lithium secondary battery 100 is manufactured by the manufacturing method of Embodiment 1, the high-rate cycle characteristics are improved.

Moreover, the viscosity was investigated about each of the negative electrode paste of an Example and a comparative example. The viscosity was measured with a B-type viscometer. The measurement conditions were room temperature (20 ± 2 degrees) and a rotation speed of 20 rpm. The result is shown in FIG.
As is clear from FIG. 8, the viscosity of the negative electrode paste of the example was lower than that of the negative electrode paste of the comparative example. In addition, even when the example was manufactured by changing the lot of the dispersion medium as compared with the comparative example, there was little variation in viscosity from lot to lot, and the viscosity was stable. From this, if the negative electrode paste 129 is manufactured by the manufacturing method of the first embodiment, it is possible to prevent the viscosity from increasing, to eliminate viscosity variation due to the lot of the dispersion medium, and to improve the viscosity stability. It can be said.

Further, the adhesion between the negative electrode active material layer 121 and the negative electrode current collector 123 was examined for each of the negative electrode plates 120 of Examples and Comparative Examples. Specifically, as shown in FIG. 7, the negative electrode plate 120 was fixed on the sample stage SD with the negative electrode current collector 123 facing the sample stage SD side. Then, a tape TP was attached on the negative electrode active material layer 121 of the negative electrode plate 120, and a part of the negative electrode active material layer 121 was peeled off from the negative electrode current collector 123. Thereafter, the tape TP was pulled vertically (upward in FIG. 7) with respect to the negative electrode current collector 123, and the tensile strength (adhesion strength) at that time was measured. The result is shown in FIG.
As can be seen from FIG. 8, the tensile strength of the negative electrode plate 120 of the example exceeded 1.2 times based on the tensile strength of the negative electrode plate of the comparative example. From this, it can be seen that if the negative electrode plate 120 is manufactured by the manufacturing method of Embodiment 1, the adhesion between the negative electrode active material layer 121 and the negative electrode current collector 123 is improved.

Moreover, IV resistance was measured about each of the lithium secondary battery 100 of an Example and a comparative example. The measurement conditions were a temperature of 25 degrees, a voltage drop (or rise) when charging and discharging at constant current for 10 seconds at each rate of 0.2C, 1C, and 2C, and resistance from the plot of applied current and voltage change. The value was calculated. The result is shown in FIG.
As is apparent from FIG. 8, the IV resistance in the lithium secondary battery 100 of the example was smaller than the IV resistance in the lithium secondary battery of the comparative example. From this, it can be seen that the IV resistance can be reduced in the lithium secondary battery 100 manufactured by the manufacturing method of the first embodiment.

In the above, the present invention has been described with reference to the embodiments. However, the present invention is not limited to the above-described first and second embodiments, and it is needless to say that the present invention can be appropriately modified and applied without departing from the gist thereof. Yes.
For example, in the first and second embodiments, the lithium secondary battery 100 in which one positive electrode plate 110 and one negative electrode plate 120 are stacked via the separator 130 is illustrated, but the form of the electrode body is not limited to this. . For example, a stacked electrode body in which a plurality of positive electrode plates 110 and a plurality of negative electrode plates 120 are alternately stacked via separators 130 may be used, or a positive electrode plate and a negative electrode plate stacked via separators may be wound. A round electrode body may be used.

100 lithium secondary battery 110 positive electrode plate 111 positive electrode active material layer 113 positive electrode current collector 120 negative electrode plate 121 negative electrode active material layer 123 negative electrode current collector 125 negative electrode active material particle 126 organic acid 127 acid-treated negative electrode active material particle 129 negative electrode paste 130 Separator 150 Battery case

Claims (8)

A method for producing a negative electrode paste for a lithium secondary battery, comprising:
An organic acid treatment step of forming acid-treated negative electrode active material particles in which an organic acid is bonded or adsorbed on the surface of the negative electrode active material particles made of a carbon material capable of inserting and releasing lithium ions;
And a paste preparation step of preparing the negative electrode paste in which the acid-treated negative electrode active material particles and the binder are dispersed in a dispersion medium. It is a manufacturing method of the negative electrode paste according to claim 1,
The organic acid treatment step
A method for producing a negative electrode paste, which is an organic acid mechanochemical treatment step in which the organic acid is bound or adsorbed on the surface of the negative electrode active material particles by mechanochemical treatment. It is a manufacturing method of the negative electrode paste according to claim 2,
The organic acid mechanochemical treatment step is:
A method for producing a negative electrode paste by mechanochemical treatment using a ball mill or a bead mill. It is a manufacturing method of the negative electrode paste according to claim 1,
The organic acid treatment step
A method for producing a negative electrode paste, which is a step of immersing the negative electrode active material particles in a solution containing the organic acid to bond or adsorb the organic acid to the particle surfaces of the negative electrode active material particles. . A method for producing a negative electrode paste according to any one of claims 1 to 4,
The said binder is a manufacturing method of the negative electrode paste containing a polyvinylidene fluoride type polymer at least. It is a manufacturing method of the negative electrode paste according to claim 5,
The said dispersion medium is a manufacturing method of the negative electrode paste which is an organic solvent which can melt | dissolve the said binder. A method for producing a negative electrode plate for a lithium secondary battery comprising a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector,
The negative electrode active material which forms the said negative electrode active material layer by apply | coating the said negative electrode paste manufactured with the manufacturing method of the negative electrode paste as described in any one of Claims 1-6 on the said negative electrode collector. A manufacturing method of a negative electrode plate provided with a layer formation process. A method for producing a lithium secondary battery comprising a negative electrode plate,
The manufacturing method of a lithium secondary battery provided with the battery formation process which forms the said lithium secondary battery using the said negative electrode plate manufactured with the manufacturing method of the negative electrode plate of Claim 7.

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