JP2871077B2 - Manufacturing method of negative electrode for non-aqueous electrolyte secondary battery - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a negative electrode for a non-aqueous electrolyte secondary battery, which has been actively developed recently.

2. Description of the Related Art Non-aqueous electrolyte secondary batteries using lithium or a lithium compound as a negative electrode are expected to have high voltage and high energy density,
Much research has been done.

Until now, the positive electrode active material of non-aqueous electrolyte secondary batteries has been V
Oxides of transition metals such as ₂ O ₅ , Cr ₂ O ₅ , MnO ₂ , TiS ₂ , MoS ₂ and chalcogen compounds are known, and these have a layered or tunnel structure, and have a crystal structure through which lithium ions can enter and leave. Have.

On the other hand, as the negative electrode active material, lithium metal and lithium alloys such as lithium-aluminum capable of inserting and extracting lithium are known. However, when metallic lithium is used for the negative electrode active material, lithium is deposited in a dendritic manner on the lithium surface during charging, and short-circuits due to contact with the positive electrode. When a lithium alloy is used, the dendritic growth of lithium is suppressed when the battery is charged at a potential higher than the potential of lithium. However, when the battery is charged to a potential lower than the potential of lithium, the dendritic growth of lithium occurs as in the case of metallic lithium. In addition, when the charge and discharge are repeated deeply, the electrode becomes finer, and has disadvantages such as poor cycle characteristics. Sufficient characteristics have not yet been obtained.

Problems to be Solved by the Invention As means for solving such a problem, by using a mixture of a metal powder capable of inserting and extracting lithium and a conductive agent for a negative electrode, the metal is dropped or dropped due to pulverization during charge and discharge. Attempts have been made to improve poor current collection. However, simply mixing the metal powder and the conductive agent has the problem that charging and discharging are repeated and the interfacial bonding between the metal powder and the conductive agent becomes insufficient and the capacity is reduced. The present invention solves such a problem,
An object of the present invention is to provide a method for producing a negative electrode for a non-aqueous electrolyte secondary battery having excellent charge / discharge cycle characteristics.

Means for Solving the Problems In order to solve the above problems, the present invention provides a material for a negative electrode for a non-aqueous electrolyte secondary battery comprising a mixture of a metal powder capable of inserting and extracting lithium and a conductive material. The metal powder is immersed in a silane coupling solution, a conductive agent is added thereto, mixed and dried.

The metal powder, which is a constituent material of a negative electrode for a non-aqueous electrolyte secondary battery composed of a mixture of a metal powder capable of occluding and releasing lithium and a conductive agent, is immersed in a silane coupling solution, and this is immersed in a conductive agent Is mixed and dried, the metal powder and the conductive agent are bonded via a chemical bond, and a negative electrode having very strong interfacial bonding can be obtained. As a result, even if charge / discharge is repeated, the interfacial bonding between the metal powder and the conductive agent is sufficiently maintained, the charge / discharge capacity does not decrease with a relatively small number of cycles, and the non-aqueous electrolyte secondary battery having stable battery characteristics. A negative electrode for a battery can be configured.

As the metal powder, aluminum, tin, lead, indium, and bismuth capable of inserting and extracting lithium relatively easily are preferable, and graphite or carbon black is preferable as the conductive agent.

Example Hereinafter, an example will be described in detail.

1% by weight of γ-aminopropyltriethoxysilane was dissolved in a 1: 1 solution of ethanol and distilled water, and 50 g of this solution was added with 1 g of aluminum powder of 70 μm or less,
After immersion for 20 minutes, take out the powder, wash it, add a small amount of 1 g of acetylene black as a conductive agent, a 1: 1 solution of ethanol and distilled water, wet mix thoroughly in a mortar, and dry with a hot air dryer at 100 ° C. I let it. To this is added an emulsion of acrylic resin powder as a binder so that the weight ratio of aluminum, acetylene black and adsorbent is 1: 1: 0.25, and after mixing well, it is dried with a 100 ° C warm air dryer for 10 hours. By doing so, an electrode mixture was obtained.

0.1 g of this electrode mixture was press-formed at a diameter of 17.5 mm at 2 ton / cm ² to obtain an electrode. FIG. 4 shows a cross-sectional view of the manufactured battery. The molded electrode 1 is placed in the case 2. A porous polypropylene film as a separator 3 was placed on the electrode 1. As a counter electrode, a lithium plate 4 having a diameter of 17.5 mm and a thickness of 0.8 mm was pressure-bonded to a sealing plate 5 having a gasket 6 made of polypropylene. As a non-aqueous electrolyte, a mixed solvent of propylene carbonate and dimethoxyethane at a volume ratio of 1: 1 in which 1 mol / 1 of lithium perchlorate was dissolved was used, and this was added on the separator and the counter electrode. Thereafter, the battery was sealed. This battery is designated as A.

Next, as a comparative example, without performing silane coupling treatment, an electrode mixture was prepared such that the weight ratio of aluminum, acetylene black, and binder was 1: 1: 0.25, and 0.1 g of the electrode mixture was prepared. A battery was formed in a similar manner using the constituent materials used in the above example by pressing the electrode at a pressure of 2 ton / cm ² to a diameter of 17.5 mm to obtain a comparative battery. This battery is designated as B.

As described above, comparison of the charge / discharge cycle characteristics was performed using the two batteries A and B. The charge and discharge conditions used were a capacity regulation for charging and discharging at a constant current of 2 mA for 8 hours and a voltage regulation with a voltage range of 0 to 1.5 V. In other words, charging and discharging are switched every 8 hours, and when the voltage rises to 1.5V within 8 hours of discharging, discharging is stopped and charging starts, and conversely, the voltage drops to 0V within 8 hours of charging In this case, the charging and discharging conditions were set so that charging was stopped and discharging started. The voltage range is 0
The reason for setting the voltage to 1.5 V is to prevent the decomposition of the solvent on the electrode and the dendritic growth of lithium when the voltage is exceeded.

FIG. 1 shows the charging curves of the battery A at the second and 100th cycles, and FIG. 2 shows the charging curves of the battery B at the second, 40th and 100th cycles. FIG. 3 shows the cycle characteristics of Battery A and Battery B.

The battery A of this example using the silane-coupled electrode had a charging voltage of 210 mV with respect to the lithium electrode, and there was almost no change in the charging curves at the second cycle and the 100th cycle. Comparative battery B using an electrode that has not been subjected to silane coupling treatment, while showing stable cycle characteristics regardless of regulations,
When the charging voltage in the second cycle is 150 mV and is compared with that of the battery A, the polarization is large as low as 60 mV. In addition, charge and discharge will be repeated by voltage regulation from the 40th cycle,
By the 100th cycle, the capacity was reduced to 50% of the initial capacity, and the battery A of this example was superior.

As described above, in the present embodiment, in a negative electrode of a nonaqueous electrolyte secondary battery composed of a mixture of aluminum powder capable of inserting and extracting lithium and acetylene black as a conductive agent, the negative electrode is a constituent material of the negative electrode. By immersing the aluminum powder in a silane coupling solution, adding and mixing acetylene black as a conductive agent, and drying it, a negative electrode for a non-aqueous electrolyte secondary battery having excellent cycle characteristics was realized. .

In this example, γ-aminopropyltriethoxysilane was used as the silane coupling agent, but γ-aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane When using any of N-phenyl-γ-aminopropyltrimethoxysilane and the like, it was confirmed that a negative electrode for a non-aqueous electrolyte secondary battery having excellent cycle characteristics was obtained in substantially the same manner as described above. ing.

Further, in the examples, the combination of aluminum as the metal powder and acetylene black as the conductive agent was described.
Similarly, it was confirmed that almost the same effect was obtained with any combination of tin, lead, indium, bismuth powder capable of absorbing and releasing lithium to form an alloy with lithium and graphite and carbon black as a conductive agent. .

Effect of the Invention As described above, a negative electrode for a non-aqueous electrolyte secondary battery having excellent charge / discharge cycle characteristics can be obtained by the production method of the present invention.

[Brief description of the drawings]

FIG. 1 is a charge curve diagram of a battery including an electrode according to an embodiment of the present invention as a component, FIG. 2 is a charge curve diagram of a comparative battery, and FIG. 3 is a charge / discharge of the battery of the present embodiment and the comparative battery. FIG. 4 is a cross-sectional view of the batteries of Examples and Comparative Examples. 1 ... electrode 2 ... case 3 ... separator 4 ...
Lithium, 5 ... sealing plate, 6 ... gasket.

Continuing on the front page (72) Inventor Yasuhiko Mito 1006 Kazuma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. In-company (56) References JP-A-3-167766 (JP, A) JP-A-2-75158 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01M 4/02, 4/04 H01M 4/62 H01M 10/40

Claims (2)

(57) [Claims] In a negative electrode of a non-aqueous electrolyte secondary battery comprising a mixture of a metal powder capable of inserting and extracting lithium and a conductive agent, the metal powder is immersed in a silane coupling solution. A method for producing a negative electrode for a non-aqueous electrolyte secondary battery, comprising adding, mixing and drying the conductive agent. 2. The metal powder capable of inserting and extracting lithium is aluminum, tin, lead, indium or bismuth, and is selected from at least one of them.
A method for producing a negative electrode for a nonaqueous electrolyte secondary battery according to the above.