JP2015156361A - Negative electrode for lithium primary battery, manufacturing method thereof, lithium primary battery, and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a negative electrode used for a lithium primary battery of low cost in which rising of an internal resistance from unused state to a last stage of discharging is suppressed when compared with a battery in which conventional Li alloy is used for a negative electrode.

SOLUTION: A lithium primary battery includes a positive electrode 5, a negative electrode 10, a separator 4 disposed between the positive electrode 5 and the negative electrode 10, and an electrolyte containing at least a supporting electrolyte and organic solvent. The negative electrode 5 includes at least two layers, or, an Li layer 11 made from lithium (Li) and an LiSi layer 12 containing an alloy of Li and silicon (Si).

COPYRIGHT: (C)2015,JPO&INPIT

Description

  The present invention relates to a lithium primary battery.

  A lithium primary battery using lithium (Li) having the largest ionization tendency among metals as a negative electrode has a high battery voltage because a high potential difference is generated between the positive electrode and the negative electrode. Therefore, this lithium primary battery is widely used for applications such as memory backup of electronic devices and electronic keys.

  In addition, a lithium primary battery does not use a noble metal as an active material, and can be manufactured at a lower cost than other primary batteries, for example, a silver oxide battery using silver which is a noble metal as an active material. Therefore, lithium primary batteries are expected to replace existing primary batteries as low-cost products.

  On the other hand, the lithium primary battery uses Li for the negative electrode, and the electrolyte uses a non-aqueous solvent. Therefore, the internal resistance is larger than that of a silver oxide battery using an alkaline aqueous solution having a high ion conductivity. Moreover, since the Li foil to be used has a small surface area, the internal resistance is further increased. Thus, lithium primary batteries having a low internal resistance have been conventionally used by using a negative electrode obtained by alloying Li and a metal such as aluminum (Al) (for example, Patent Document 1 and Patent Document 2).

Japanese Patent Laid-Open No. 2-144848 JP-A 61-74264

  However, these lithium primary batteries are not sufficient for reducing the internal resistance. In particular, when an unused battery is discharged, the internal resistance increases with the discharge, and the internal resistance increases several times when the battery is used up (hereinafter referred to as the end of discharge). In such a battery having a large internal resistance, the discharge voltage decreases, and the electronic device malfunctions. Therefore, a lithium primary battery using a Li alloy as a negative electrode has been limited in application to a battery having a small initial internal resistance value that is not easily affected by changes in internal resistance.

  The cause of the increase in internal resistance due to the discharge is that the thickness of Li arranged on the negative electrode gradually decreases with the discharge, and the distance between the positive electrode and the negative electrode increases. In the lithium primary battery, Li of the negative electrode is dissolved by the discharge and moves to the positive electrode, so that a reduction in Li thickness is inevitable.

  The present invention has been made in view of the above problems, and can suppress an increase in internal resistance from unused to the end of discharge as compared with a battery using a conventional Li alloy as a negative electrode, and is inexpensive lithium primary. The purpose is to provide batteries.

The inventors of the present invention have made extensive studies to solve the above problems, and have obtained knowledge that the increase in the internal resistance of the battery can be suppressed by making the thickness of the negative electrode constant even when discharged.
That is, the negative electrode for a lithium primary battery according to the present invention has at least two layers of a Li layer made of lithium (Li) and a LiSi layer containing an alloy of Li and silicon (Si).
According to the present invention, even if the amount of Li is reduced by discharge, the volume reduction of the Li layer is compensated by the expansion of the LiSi layer. For this reason, the thickness of the negative electrode becomes constant, and the distance between the positive electrode and the negative electrode can be maintained from unused to the end of discharge. Thereby, an increase in the internal resistance of the battery can be suppressed even at the end of discharge.

In the negative electrode for a lithium primary battery according to the present invention, the molar ratio of Li to Si in the negative electrode is Li / Si> 4.4.
According to the present invention, the negative electrode becomes two layers of the LiSi layer and the Li layer after the alloying of Li and Si of the negative electrode. Thereby, an internal resistance raise can be suppressed and it can be set as a high capacity | capacitance. Further, it is more preferable that the molar ratio of Li and Si in the negative electrode is 15 ≦ Li / Si ≦ 100 because the internal resistance is low and the capacity can be increased.

In the negative electrode for a lithium primary battery according to the present invention, the LiSi layer further includes at least one of carbon and resin.
According to the present invention, when the LiSi layer is formed using a small amount of Si, the amount of Si on the Li layer can be made constant. Thereby, the LiSi layer can be easily formed.

In the negative electrode for a lithium primary battery according to the present invention, the area of the LiSi layer on the surface facing the positive electrode is 50% or more of the area of the Li layer.
According to the present invention, even when the LiSi layer is formed using slurry, the battery has an internal resistance reduction effect. Thereby, formation of a LiSi layer can be made easier.

In the negative electrode for a lithium primary battery according to the present invention, the LiSi layer is formed of metal Li and Si powder having a particle diameter (D ₅₀ ) of 2 μm or more.
In the negative electrode for a lithium primary battery according to the present invention, the LiSi layer has a particle diameter of an alloy of Li and Si of 2 μm or more.
According to the present invention, when metal Li as a starting material and Si powder having a particle diameter of 2 μm or more are used, particle cracking increases due to alloying of Li and Si. At this time, the alloy of Li and Si has a particle diameter of 2 μm or more even when cracked. During such alloying, the LiSi layer tends to expand due to cracking of the particles. However, since the LiSi layer is compressed by the exterior, contact between the particles of the LiSi layer increases. Thereby, the internal resistance of the battery can be lowered.

A lithium primary battery according to the present invention includes the negative electrode for a lithium primary battery according to the present invention, a positive electrode, and a nonaqueous electrolyte.
According to the present invention, by using a lithium primary battery having these configurations, an increase in internal resistance from unused to the end of discharge can be suppressed, and an inexpensive lithium primary battery can be obtained.

In the lithium primary battery according to the present invention, the LiSi layer is formed on a surface of the negative electrode facing the positive electrode.
According to the present invention, the LiSi layer that has a large surface area and easily contains an electrolyte solution is opposed to the positive electrode. Thereby, the internal resistance of the battery can be lowered.

The lithium primary battery according to the present invention is characterized in that the positive electrode contains copper (II) oxide.
According to the present invention, the density of the LiSi layer can be increased by expansion of the positive electrode due to discharge. Thereby, the internal resistance of the battery can be further reduced.

A lithium primary battery according to the present invention includes the positive electrode, the negative electrode, a non-aqueous electrolyte, and a positive electrode can, a negative electrode can, and a gasket that house them, and the LiSi layer is compressed by a caulking seal. It is characterized by that.
According to the present invention, the LiSi layer is compressed by the caulking force in the battery, so that the expansion is suppressed. Thereby, an increase in internal resistance can be suppressed even at the end of discharge.

The method for producing a negative electrode for a lithium primary battery according to the present invention includes a step of forming a Li layer made of lithium (Li) and a step of forming a Si layer made of silicon (Si) or a mixture containing Si on the Li layer. And an alloying step in which Li in the Li layer and Si in the Si layer are alloyed to form at least two layers of the Li layer and the LiSi layer.
According to the present invention, the LiSi layer can be formed by alloying Li and Si inside the battery. Thereby, a LiSi layer can be easily produced.

In the method for manufacturing a negative electrode for a lithium primary battery according to the present invention, Li and Si in the negative electrode have a molar ratio of Li / Si> 4.4.
According to the present invention, after the alloying of Li and Si in the negative electrode, a negative electrode composed of two layers of a LiSi layer and a Li layer can be formed. Thereby, an increase in the internal resistance of the battery can be suppressed and the capacity can be increased.

In the method for manufacturing a negative electrode for a lithium primary battery according to the present invention, the alloying step is performed by compressing the Li layer and the Si layer in a stacking direction and alloying Li and Si. It is characterized by.
According to the present invention, the reaction between Li and Si can be facilitated by compressing the Li layer and the Si layer from above and below (stacking direction), and a high-density LiSi layer can be formed. Further, since the expansion of the LiSi layer is suppressed by the compression, a substantial distance between the positive electrode and the negative electrode can be maintained even when the discharge proceeds. Thereby, reduction of the internal resistance of a battery and the raise of the internal resistance by discharge can be suppressed.

A method for manufacturing a lithium primary battery according to the present invention is a method for manufacturing a lithium primary battery including the positive electrode, the negative electrode, the nonaqueous electrolyte, a positive electrode can, a negative electrode can, and a gasket that house them. The alloying step compresses the Li layer and the Si layer in the stacking direction by caulking and sealing the positive electrode can and the negative electrode can.
According to the present invention, the Li layer and the Si layer can be sufficiently compressed by the caulking sealing between the positive electrode can and the negative electrode can of the battery. Thereby, a coin-type lithium primary battery with low internal resistance can be easily manufactured even at the end of discharge.

  ADVANTAGE OF THE INVENTION According to this invention, the lithium primary battery which can suppress a raise of internal resistance from unused to the last stage of discharge can be provided.

It is sectional drawing which shows the lithium primary battery of embodiment of this invention. It is sectional drawing which shows the lithium primary battery of embodiment of this invention, Comprising: The state before alloying is shown. It is sectional drawing which shows the lithium primary battery of embodiment of this invention, Comprising: The state of the end stage of discharge is shown. It is sectional drawing which shows the conventional lithium primary battery. It is sectional drawing which shows the conventional lithium primary battery, Comprising: The state at the end of discharge is shown. It is sectional drawing of the lithium primary battery of embodiment of this invention, Comprising: The state of the end stage of discharge in case the expansion | swelling of a positive electrode is large is shown. It is sectional drawing which shows the lithium primary battery of embodiment of this invention. It is sectional drawing which shows the lithium primary battery of embodiment of this invention. It is a graph which shows the difference in internal resistance by the negative electrode material shown in Example 1 and Comparative Examples 1-5. It is a graph which shows the change of the internal resistance accompanying discharge when changing the molar ratio of Li of a negative electrode in Example 2, and Si. It is a graph which shows the particle size distribution at the time of the un-sized particle of raw material Si powder in Example 3, and after crushing. In Example 3, when changing the particle diameter of Si (D _50), it is a graph showing changes in the internal resistance due to discharge. It is an observation image by the scanning electron microscope (SEM) of Si particle | grains before and after Li and Si alloying in Example 3. FIG.

  Hereinafter, as an embodiment of a lithium primary battery according to the present invention, an embodiment of a coin (button) type lithium primary battery will be described, and each configuration will be described with reference to the drawings. The configuration of the present invention is not limited to the coin (button) shape, but can be applied to other container forms such as an aluminum laminate shape, a square shape, and a cylindrical shape.

(Outline of lithium primary battery)
The coin-type lithium primary battery shown in FIG. 1 includes a positive electrode can 2 that is a bottomed cylindrical main body and a negative electrode can 1 that is a covered cylindrical lid that closes the opening of the positive electrode can 2. Moreover, the gasket 3 is provided along the inner peripheral surface of the opening part of the positive electrode can 2, and the opening part periphery of the positive electrode can 2 is being fixed by crimping inside.

  The inside of the battery formed by the positive electrode can 2 and the negative electrode can 1 includes a positive electrode 5, a negative electrode 10, a separator 4 disposed between the positive electrode 5 and the negative electrode 10, and an electrolytic solution containing at least a supporting salt and an organic solvent ( (Not shown). The positive electrode 5 is electrically connected to the inner surface of the positive electrode can 2, and the negative electrode 10 is electrically connected to the inner surface of the negative electrode can 1. The positive electrode can 2 functions as a current collector for the positive electrode 5, and the negative electrode can 1 functions as a current collector for the negative electrode 10.

  As materials for the positive electrode can 2 and the negative electrode can 1, conventionally known materials such as austenitic stainless steel, ferritic stainless steel, and austenitic / ferrite duplex stainless steel can be used.

(Negative electrode)
As shown in FIG. 1, the negative electrode 10 in this embodiment includes a Li layer 11 connected to the inner surface of the negative electrode can 1 and a LiSi layer 12 formed on the surface of the Li layer 11 facing the positive electrode. The Li layer 11 is made of Li, and the LiSi layer 12 is a layer containing an alloy of Li and Si.

The theoretical capacity of Si used as the material of the negative electrode 10 is 4198 mAh / g (Li _4.4 Si), which is the highest capacity negative electrode active material currently known. This theoretical capacity is larger than carbon (LiC ₆ 372 mAh / g) used in the negative electrode of the lithium ion secondary battery and aluminum (LiAl 993 mAh / g) used in the negative electrode of the lithium primary battery.

  On the other hand, when Si reacts with Li, it expands more violently than when carbon or aluminum reacts with Li. In the present invention, the inventors have found that when a lithium primary battery is manufactured using such a property that Si violently expands when reacting with Li, an increase in internal resistance can be suppressed. This will be described below with an example.

  The state before alloying of the lithium primary battery of this embodiment is shown in FIG. This is the state immediately after the lithium primary battery is assembled. An Li layer 11 made of Li is formed on the negative electrode can 1, and an Si layer 13 made of powdered Si is formed on the Li layer 11. The battery is filled with an electrolytic solution.

Thereafter, Li and Si gradually react in the negative electrode 10 to form the LiSi layer 12 shown in FIG. The composition of the LiSi alloy generated by this reaction is Li _x Si (0 ≦ x ≦ 4.4). When Li and Si react to the maximum, Li _4.4 Si is obtained. Therefore, when the molar ratio of Li and Si is Li / Si> 4.4, two layers of the Li layer 11 made of unreacted Li and the LiSi layer 12 made of the alloy after the reaction are formed in the negative electrode 10.

When the battery is discharged, in the negative electrode 10, Li is released from the LiSi layer 12 to the positive electrode 5, and at the same time, Li is supplemented from the Li layer 11 to the LiSi layer 12. For this reason, the composition of the LiSi layer 12 is always Li _4.4 Si. In particular, if the amount of Li in the Li layer 11 before alloying is set to an amount that exceeds the total of the positive electrode capacity and the irreversible capacity of Si, the supply of Li from the Li layer 11 to the LiSi layer 12 is continued until the end of discharge. Can do. Therefore, the composition of the LiSi layer 12 is always Li _4.4 Si from the unused battery to the end of discharge.

Further, the Si layer 13 has a larger expansion due to alloying as the amount of Li to be reacted is larger, and the expansion is maximized when the alloy composition is Li _4.4 Si. Therefore, the Si layer 13 to which a sufficient amount of Li is supplied to the negative electrode always obtains the maximum expansion from the unused battery to the end of discharge.

  In the lithium primary battery before alloying shown in FIG. 2, the Si layer 13 is compressed by the caulking force of the positive electrode can 2, the negative electrode can 1, and the gasket 3. When the Si layer 13 reacts with Li, it forms a LiSi alloy and tries to expand. However, since the Si layer 13 is compressed by the caulking force, the expansion is suppressed. Thereby, a high-density LiSi layer 12 as shown in FIG. 1 is formed.

  FIG. 3 shows a cross section when the battery is discharged. As Li is consumed by the discharge, the Li layer 11 decreases. On the other hand, the LiSi layer 12 that has been compressed by caulking is expanded by the amount of decrease of the Li layer 11 and the density is lowered. The lithium primary battery has a slight increase in internal resistance as much as the density of the LiSi layer 12 is lowered, but the conductivity is maintained because the electrolyte solution is contained between the particles of the LiSi layer 12. Therefore, since a substantial gap does not occur between the positive electrode 5 and the negative electrode 10 and the distance between the positive electrode and the negative electrode is maintained throughout the state from the unused period of the battery to the end of discharge, the increase in the internal resistance of the battery is suppressed. Can do.

  On the other hand, when the molar ratio of Li and Si in the negative electrode 10 is Li / Si ≦ 4.4, the negative electrode 10 has only one LiSi layer 12 and does not have two layers. Thus, when the amount of Li is small, the expansion of the LiSi layer 12 during discharge is small, so that it is difficult to fill the gap between the positive electrode 5 and the negative electrode 10 with the LiSi layer 12, and the internal resistance increases. Further, since the amount of Li is small, the battery capacity is also small.

  Thus, if Si is provided on Li of the negative electrode 10 and the molar ratio is Li / Si> 4.4, an increase in internal resistance from unused to the end of discharge can be suppressed, and high capacity lithium primary It can be a battery.

  When the Li / Si molar ratio Li / Si in the negative electrode 10 is Li / Si> 4.4 as described above, two layers of the Li layer 11 and the LiSi layer 12 are formed, and the effects of the present application are achieved. is there. In particular, if the molar ratio of Li to Si is Li / Si ≧ 15, a lithium primary battery having a high capacity and a low internal resistance can be produced. Further, when Li / Si increases, sufficient expansion of the LiSi layer 12 cannot be obtained, and the internal resistance increases. Therefore, the molar ratio of Li to Si is preferably Li / Si ≦ 100, and more preferably Li / Si ≦ 50. The optimum Li / Si value depends on the thickness of the negative electrode. For this reason, if the Li / Si ratio is optimized with a predetermined battery size, a battery having a high capacity and a low internal resistance can be produced.

As a comparison, FIGS. 4 and 5 show the structure of the battery when the LiSi layer is not formed. FIG. 4 is a diagram showing a battery in an unused state. The negative electrode 10 is composed of only the Li layer 11.
FIG. 5 shows the state of the battery at the end of discharge when the discharge has progressed. When the battery is discharged, Li of the negative electrode 10 melts from the surface facing the positive electrode and reduces the positive electrode. The distance between the positive electrode 5 and the negative electrode 10 (Li layer 11) is only the thickness of the separator 4 when the battery is not used. As the discharge progresses, the volume of Li decreases with the discharge, and a gap 20 is generated between the positive electrode 5 and the negative electrode 10. As a result, the distance between the positive electrode 5 and the negative electrode 10 gradually increases, and the internal resistance of the battery increases. Since the Li layer 11 disappears at the end of discharge, the gap 20 between the positive electrode 5 and the negative electrode 10 is maximized and the internal resistance is also maximized. This effect becomes more prominent as the thickness of the negative electrode 10 increases.

  The negative electrode 10 in the present invention has at least two layers of a Li layer 11 and a LiSi layer 12. For example, since Li easily reacts with components in the atmosphere such as oxygen, nitrogen, carbon dioxide, and moisture, a thin layer may be formed on the Li surface by handling. Moreover, it reacts with Li and an electrolyte component, and a thin layer may be formed on the surface of the Li layer 11 or the LiSi layer 13 in some cases.

  In addition, the negative electrode 10 in this embodiment may have another layer in addition to the two layers of the Li layer 11 and the LiSi layer 12. For example, a third layer 14 may be provided as shown in FIG. The third layer 14 includes an adhesive layer containing carbon particles and a binder for fixing the Li layer 11 and the negative electrode can 1, Li, Al, Pb, Zn, Sn, Bi, In, Ga, Mg, and the like. It can be set as an alloy layer.

  As shown in FIG. 1, the LiSi layer 12 in the present embodiment is formed on the surface facing the positive electrode 5. What is necessary for reducing the internal resistance of the battery is that the facing area between the positive electrode 5 and the negative electrode 10 is large, the distance between the positive electrode 5 and the negative electrode 10 is short, and a sufficient amount of electrolyte is provided between the positive electrode 5 and the negative electrode 10. It is to include. By forming the powdered LiSi layer 12 on the surface facing the positive electrode 5, the surface area of the negative electrode 10 can be increased, and it is easy to contain an electrolytic solution, which is advantageous for reducing internal resistance.

FIG. 13 shows images observed with a scanning electron microscope (SEM) of Li and Si particles before alloying and Li _x Si particles after alloying. The pre-alloyed Si particles with a median diameter (D ₅₀ ) of 11.6 μm in the particle size distribution measured by the laser diffraction / scattering method are finely cracked by alloying and change greatly before and after alloying. was there. On the other hand, when the particle size was small (1.6 μm and 0.2 μm), the particle size change before and after alloying was small. In particular, Si particles having a particle diameter of 0.2 μm hardly changed. FIG. 12 shows changes in internal resistance during discharge of a battery using these Si particles. A battery in which a LiSi layer was formed using a Si particle diameter of 11.6 μm had a low internal resistance. On the other hand, the internal resistance of the battery using powder Si having particle diameters of 1.6 μm and 0.2 μm was larger than that of 11.6 μm.

  That is, Si particles having a large particle diameter are often cracked due to an alloying reaction with Li, and a LiSi layer having a large expansion can be obtained. For this reason, the internal resistance of a battery can be made low. On the other hand, the smaller the particles, the smaller the particle cracking due to alloying, and the smaller the expansion of the LiSi layer, the higher the internal resistance of the battery.

  Here, as shown in FIG. 13, when the Si particle diameter is 11.6 μm, the particle diameter of LiSi after alloying is 2 μm or more. On the other hand, when the Si particle diameter is 1.6 μm, the change in the particle diameter after alloying is small. Therefore, it is preferable to use Si having a particle diameter such that the LiSi particle diameter in the LiSi layer 12 is 2 μm for the Si layer 13.

  The Si powder used for the Si layer 13 has a particle diameter of about several tens of μm when the powder before pulverization is used as it is, and can be used by appropriately adjusting the particle diameter by a ball mill or the like. If it is a powder form, the Si particle diameter is preferably as large as possible within the range of the thickness of the Si layer 13.

  The LiSi layer 12 in this embodiment may contain carbon or resin in addition to the LiSi alloy. When the size of the battery is small, the amount of Si used to form the LiSi layer 12 becomes a very small amount, so it is difficult to keep the amount of Si added on the Li layer 11 constant in the process. Further, since Si is a powder, it is difficult to handle. Therefore, the Si layer 13 can be easily mass-produced by using a carbon powder or resin added to the Si powder to increase the amount or thickness.

  As the carbon material, graphite, acetylene black, ketjen black, or the like used as a conductive aid for battery electrodes can be used. In addition, as a resin, various materials other than polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), carboxyvinyl polymer, sodium polyacrylate, carboxymethylcellulose (CMC) used as a binder for battery electrodes can be used. Can be used.

  Such a LiSi layer 12 containing carbon or resin is formed by reacting Si powder and Si layer 13 containing carbon or resin with Li in the battery. For example, Si powder, carbon powder, and resin can be mixed, and the pellet formed by compression molding can be used as the Si layer 13. The pellets are sufficiently dried and then placed on the Li layer 11 to form the LiSi layer 12 by assembling the battery.

  Alternatively, a slurry in which Si powder, carbon powder, resin, and solvent are mixed is prepared, and dropped onto the Li layer 11 and dried to remove the solvent, thereby forming the Si layer 13. As the solvent at this time, a non-aqueous solvent that does not react with Li is used. The resin is preferably soluble in this solvent. For example, N-methyl-2-pyrrolidone (NMP) can be used as the non-aqueous solvent, and PVDF can be used as the resin.

  In the method of forming the LiSi layer 12 using such a slurry, the LiSi layer 12 may not spread over the entire surface of the Li layer 11 as shown in FIG. Even in such a case, in the negative electrode 10, if the area of the LiSi layer 12 is 50% or more of the area of the Li layer 11, the internal resistance due to the negative electrode 10 including two layers of the Li layer 11 and the LiSi layer 12. A reduction effect is obtained. On the other hand, when the area of the LiSi layer 12 is less than 50% of the area of the Li layer 11, such an internal resistance reduction effect is almost lost.

(Positive electrode)
As the positive electrode 5, a positive electrode active material used as a material for a lithium primary battery can be used. In particular, it is preferable to use manganese dioxide, graphite fluoride, iron sulfide, copper (II) oxide, or the like. Since these positive electrode active materials have poor electrical conductivity, a conductive additive such as carbon and a binder are added to the positive electrode 5. These positive electrode materials can be used as the positive electrode 5 by granulating and granulating them into pellets. Further, a material in which these materials are dispersed in a solvent to form a slurry and applied to a metal foil such as aluminum can be used as the positive electrode 5.

  As the conductive assistant, graphite, acetylene black, ketjen black, or the like can be used. As the binder, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), carboxyvinyl polymer, sodium polyacrylate, carboxymethyl cellulose (CMC), or the like can be used.

  Also, the positive electrode may swell when discharged. In the configuration of the lithium primary battery shown in FIG. 1, a comparison was made between the case where manganese dioxide was used as the positive electrode active material and the case where copper (II) oxide was used. After the battery was produced and completely discharged, the positive electrode was observed by transmission X-ray. As a result, the battery using manganese dioxide had a structure with almost no positive electrode swelling as shown in FIG. On the other hand, in the battery using copper (II) oxide, a structure in which the positive electrode swells violently as shown in FIG. 6 was observed. Thus, when the positive electrode active material in which the positive electrode is easy to expand is used, the density of the LiSi layer 12 is not easily lowered even when discharged, and thus the internal resistance is reduced.

(Separator)
For the separator 4, an insulating film having high ion permeability and mechanical strength can be used. For example, polyphenylene sulfide, polyamide, polyimide, polytetrafluoroethylene, glass fiber, cellulose, polyolefin, and the like can be given.

(gasket)
As shown in FIG. 1, the gasket 3 is formed in an annular shape along the inner peripheral surface of the positive electrode can 2, and the end of the negative electrode can 1 is disposed inside the annular groove. Examples of the material of the gasket 3 include polypropylene resin, polyethylene terephthalate, polyamide, liquid crystal polymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA), polyether ether ketone resin (PEEK), polyphenylene sulfide (PPS), Polyether nitrile resin (PEN), polyether ketone resin (PEK), polyarylate resin, polybutylene terephthalate resin (PBT), polycyclohexanedimethylene terephthalate resin, polyether sulfone resin (PES), polyamino bismaleimide resin, polyether Resins such as imide resins and fluororesins can be used.

(Nonaqueous electrolyte)
Examples of the non-aqueous electrolyte include acetonitrile, diethyl ether, diethyl carbonate, dimethyl carbonate, 1,2-dimethoxyethane, tetrahydrofuran, propylene carbonate, ethylene carbonate, γ-butyrolactone, and the like, or a non-aqueous solvent in which a plurality of them are mixed. In addition, lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium borofluoride (LiBF ₄ ), lithium hexafluoroarsenide (LiAsF ₆ ), lithium trifluorometasulfonate (LiCF ₃ SO) ₃ ) A nonaqueous electrolytic solution in which a supporting salt such as bistrifluoromethylsulfonylimide lithium [LiN (CF ₃ SO ₂ ) ₂ ] is dissolved can be used. Moreover, what is known conventionally and does not contain water substantially, such as a liquid, a gel form, an ionic liquid, and a solid electrolyte, can be used as a non-aqueous electrolyte.

(Manufacture of batteries)
Next, the manufacturing method of the lithium primary battery in this embodiment is shown. The coin-type lithium primary battery shown in FIG. 1 includes a step of forming the positive electrode 5 on the positive electrode can 2, a step of forming the negative electrode 10 on the negative electrode can 1, and a separator 4 placed on the positive electrode 5. The positive electrode 5 and the negative electrode 10 can be manufactured by injecting an electrolyte solution and impregnating the positive electrode can 2 and the negative electrode can 1 through the gasket 3 and assembling the battery by caulking.

Here, in the present embodiment, the step of forming the negative electrode 10 includes the step of forming the Li layer 11 on the negative electrode can 1, the step of forming the Si layer 13 on the Li layer 11, and Li and Si inside the battery. And forming a LiSi layer 12. In this way, by alloying Li and Si inside the battery, the LiSi layer 12 is compressed inside the battery and the expansion is suppressed immediately after assembly. Further, as shown in FIG. 3, at the end of discharge, the LiSi layer 12 expands by the amount of decrease of the Li layer 11, and no substantial gap is generated between the positive electrode and the negative electrode. Thereby, an increase in internal resistance can be suppressed even at the end of discharge.
In addition, the LiSi layer 12 shown in FIG. 1 can be formed by preparing an alloy of Li and Si in advance, placing this on the Li layer 11, and then assembling the battery.

  In the lithium primary battery according to this embodiment, when copper (II) oxide is used as the positive electrode active material, the positive electrode is reduced and used at a predetermined nominal voltage when the battery is manufactured. In this lithium primary battery, the open circuit voltage after assembly is about 3V, whereas the nominal voltage specified in JISC8500 is 1.5V, so the voltage needs to be lowered. As a method for lowering the voltage, for example, a predischarge is performed through an external circuit after the battery is assembled, and the positive electrode is reduced with a part of the negative electrode lithium. There is a way to keep it. A predetermined voltage can be obtained by these methods.

(Battery shape)
In the present embodiment, a coin (button) type lithium primary battery has been described as an example. In the coin (button) lithium primary battery, the positive electrode can 2 and the negative electrode can 1 are caulked and sealed, thereby suppressing the expansion of the LiSi layer 12 and forming a high-density LiSi layer.

  Further, in the present embodiment, other battery shapes can be used as long as a force can be applied to the LiSi layer 12 to suppress expansion. Examples of the battery shape include an aluminum laminate shape, a square shape, and a cylindrical shape.

  The aluminum laminate type consists of a metal foil coated with an electrode material as a positive electrode and a negative electrode, with a separator sandwiched between them to form a laminated electrode, which is placed in an aluminum laminate bag, and the bag is decompressed to produce a positive electrode and a negative electrode The force which crushes a separator can be obtained. In addition, the square can obtain a force by making the thickness of the laminated electrode larger than the inner diameter of the outer can. The cylindrical type can obtain force by winding a metal foil coated with an electrode material as a positive electrode and a negative electrode and sandwiching a separator between them. At this time, various electrode shapes such as a pellet electrode, a wound electrode, and a laminated electrode can be used in accordance with the battery shape.

  As described above, in any shape of the battery, the positive and negative electrodes can apply force to the negative electrode side and the negative electrode can apply force to the negative electrode side and the negative electrode to the positive electrode side in order to reduce internal resistance. For this reason, even if lithium in the negative electrode decreases due to discharge, the density of the LiSi layer only decreases, so that a gap between the positive electrode and the negative electrode is not substantially generated, and a lithium primary battery with low internal resistance can be manufactured.

Next, an Example and a comparative example are shown and this invention is demonstrated further more concretely.
Example 1
In Example 1, a coin-type lithium primary battery as shown in FIG. 1 was produced. The positive electrode was prepared by mixing and granulating copper (II) oxide, graphite, and carboxymethyl cellulose into a pellet by compression molding, drying, and placing on a stainless steel positive electrode can.

As the negative electrode, a Li foil was punched out to form a Li layer, which was attached onto a stainless steel negative electrode can. Si having a purity of 96% or more was used. When the particle diameter of this Si was measured by a laser diffraction / scattering method, it was D ₅₀ = 11.6 μm. As the Si layer, a mixture of 95% by weight of Si and 5% by weight of carboxymethyl cellulose was compression-molded to obtain a pellet-shaped Si layer having a thickness of 100 μm, dried, and pasted on the Li layer. At this time, the molar ratio between Li and Si in the negative electrode was Li / Si = 17.

The electrolytic solution used was a solution of LiPF _{6 in} a mixed solvent of ethylene carbonate and 1,2-dimethoxyethane. The separator used was a polyolefin microporous membrane. The separator, the positive electrode, and the Si layer are impregnated with an electrolytic solution, and a force is applied from above the negative electrode can, and it is sealed with a polypropylene gasket and a stainless steel positive electrode can, and a coin having an outer diameter of 6.8 mm and a thickness of 2.6 mm Type lithium primary battery was produced.

  After 7 days had passed since the battery was sealed, the thickness of the battery was measured to be 2.7 mm, which was 0.1 mm larger than immediately after the battery was sealed. This is because the negative electrode expanded due to the reaction between Li and Si. Therefore, force was again applied from above the negative electrode can to perform caulking sealing, and the battery thickness was returned to 2.6 mm. Thereafter, the battery was disassembled and the thickness of the LiSi layer was measured. The internal resistance of the battery was measured at −10 ° C. after discharging to each discharge depth. The measurement method was determined from the difference between the open circuit voltage and the closed circuit voltage after connecting a load resistance of 2 kΩ to 7.8 mS, as defined in IEC 60086-3.

(Comparative Example 1)
For comparison, a battery was manufactured in the same manner as in Example 1 except that the negative electrode was composed only of Li as shown in FIG.
(Comparative Example 2)
For comparison, a battery was manufactured in the same manner as in Example 1 except that the negative electrode was changed to an Al foil having a thickness of 100 μm on Li.
(Comparative Example 3)
For comparison, a battery was manufactured in the same manner as in Example 1 except that the anode was compression-molded with 95% by weight of graphite and 5% by weight of carboxymethylcellulose mixed on Li and changed to a graphite layer with a thickness of 100 μm. did.
(Comparative Example 4)
For comparison, a battery was manufactured in the same manner as in Example 1 except that the negative electrode was a mixture of 95% by weight of SiO and 5% by weight of carboxymethylcellulose formed on Li by compression molding and changing to a 100 μm thick SiO layer. .
(Comparative Example 5)
For comparison, the negative electrode was compression-molded with a mixture of 95% by weight of Li ₄ Ti ₅ O ₁₂ and 5% by weight of carboxymethyl cellulose on Li, and changed to a Li ₄ Ti ₅ O ₁₂ layer having a thickness of 100 μm. Produced the same battery as in Example 1.

  The measurement results of Example 1 and Comparative Examples 1 to 5 are shown in Table 1 and FIG. As shown in Table 1, only the layer using Si (Example 1) among these expanded violently and battery swelling occurred. The internal resistance when not discharged was lowest in Example 1. Furthermore, as shown in FIG. 9, Example 1 had the lowest internal resistance at each discharge depth. After discharging, the battery of Example 1 was disassembled. As shown in FIG. 6, the positive electrode expanded and Li decreased.

(Example 2)
In Example 2, the optimal composition ratio of Li and Si was examined. Batteries of Examples 2-1 to 2-7 were produced under the same conditions as in Example 1 except that the amounts of Li and Si were changed to those shown in Table 2. Moreover, the thickness of the negative electrode was adjusted to be the same. The battery thickness after battery sealing and 7 days after sealing was measured, and the difference was defined as battery swelling. In the same manner as in Example 1, a force was applied from above the negative electrode can, and caulking was performed again to return the battery thickness to 2.6 mm.

  When these batteries were disassembled after production, in Example 2-7 (Li / Si = 4.4), the Li layer disappeared and all became LiSi layers. On the other hand, in each of Examples 2-1 to 2-6 (Li / Si> 4.4), two layers of a Li layer and a LiSi layer were observed. The battery swelled as Li / Si was small. That is, it was found that the thicker the LiSi layer, the larger the expansion of the negative electrode.

  The internal resistance of the produced battery was measured at −10 ° C. as in Example 1. FIG. 10 shows the change in internal resistance with respect to the discharge capacity during discharge in each example. In Example 2-4 (Li / Si = 15.0), the internal resistance was low with a high capacity. Further, in Examples 2-1 to 2-3 in which Li / Si is larger, that is, the LiSi layer is thin, the internal resistance is increased. This is because the amount of the LiSi layer that fills the gap between the positive electrode and the negative electrode is insufficient. On the other hand, in Examples 2-5 and 2-6 in which Li / Si was smaller, that is, the LiSi layer was thicker, the capacity was small as shown in FIG. This is because the amount of the LiSi layer that fills the gap between the positive electrode and the negative electrode is sufficient, but the capacity is reduced due to an increase in the irreversible capacity of Si and an insufficient amount of Li.

(Example 3)
In Example 3, it was examined whether the internal resistance of the battery was changed by changing the particle size of Si used for the negative electrode of the battery.
The raw material Si powder used was an unadjusted powder (Example 3-1) and a powder obtained by pulverizing the Si powder of Example 3-1 with a ball mill (Example 3-2 and Example 3-). 3). The particle size distribution obtained by measuring the particle size of the Si powders of Examples 3-1 to 3-3 by the laser diffraction / scattering method is shown in FIG. FIG. 11A, FIG. 11B, and FIG. 11C correspond to the particle size distributions in Examples 3-1, 3-2, and 3-3, respectively.

11 (a), 11 (b), and 11 (c), the median diameter (D ₅₀ ) is D ₅₀ = 11.6 μm, D ₅₀ = 1.6 μm, and D ₅₀ = 0. It was 2 μm. Further, the proportions of particle diameters of 2 μm or more were 92%, 60%, and 0%, respectively.

  To this Si powder, polyvinylidene fluoride (PVDF) as a resin and N-methyl-2-pyrrolidone (NMP) as a solvent were added and mixed to obtain a slurry. And this slurry was dripped on Li layer of the negative electrode of a battery, and it was made to dry and produced Si layer. At this time, the molar ratio of Li and Si in the negative electrode was Li / Si = 15. Others were manufactured in the same manner as in Example 1, and a coin-type lithium primary battery using the Si powder of Examples 3-1 to 3-3 as a raw material, in which a LiSi layer was formed by alloying Li and Si. Produced. The lithium primary battery was measured for battery swelling and internal resistance at −10 ° C. in the same manner as in Example 1. The results are shown in Table 3 and FIG.

Regarding Examples 3-1 to 3-3, Table 3 shows the battery swelling after sealing and the internal resistance at the time of non-discharge in each particle diameter (D ₅₀ ) of Si. FIG. 12 shows the change in internal resistance with respect to the discharge capacity during discharge. From these Table 3 and FIG. 12, it was found that the larger the particle size of Si as the starting material, the smaller the internal resistance of the battery and the larger the battery swelling due to negative electrode expansion. In particular, in Example 3-1, the internal resistance of the battery was significantly smaller than in the other examples, while battery swelling was also observed.

Here, what dried the slurry used for each example of Examples 3-1 to 3-3 (Si particles before alloying), and Li after the alloying obtained by disassembling the battery of each example A scanning electron microscope (SEM) observation image of _x Si particles is shown in FIG. In FIG. 13, the SEM observation image of Example 3-1 was observed at a magnification of 1000 times, and the photographs obtained by observing the SEM observation images of Examples 3-2 and 3-3 at a magnification of 10000 times were reduced and displayed. Yes. Hereinafter, the maximum size of each individual Si particle and Li _x Si particle obtained from the SEM observation image will be considered as the particle diameter.

In Example 3-1 (Si D ₅₀ = 11.6 μm condition), Si particles before alloying are observed. There are also Si particles as large as several tens of μm. This is because it is Si before pulverization. When the Si particles were alloyed, most of the Li _x Si particles with a size exceeding 2 μm were occupied. This is because the particles were cracked after alloying.

On the other hand, even in Example 3-2 (Si D ₅₀ = 1.6 μm condition), Si particles before alloying are cracked after alloying, so that most of them become Li _x Si particles having a particle diameter of about 1 μm, which is slightly smaller. It was. However, the degree of change was smaller than in Example 3-1.
Furthermore, in Example 3-3 (Si D ₅₀ = 0.2 μm condition), no change in particle diameter was observed between the Si particles before alloying and the Li _x Si particles after alloying.

As shown in Table 3, the battery of Example 3-1 (Si D ₅₀ = 11.6 μm condition) had the battery expanded after sealing and the negative electrode expanded. On the other hand, in the batteries of Example 3-2 (Si D ₅₀ = 1.6 μm condition) and Example 3-3 (Si D ₅₀ = 0.2 μm condition), there was no swelling after sealing and there was little expansion of the negative electrode. .
From the above results, the larger the Si particles, the larger the expansion of the Si layer due to alloying, and a battery with low internal resistance can be obtained.

DESCRIPTION OF SYMBOLS 1 ... Negative electrode can 2 ... Positive electrode can 3 ... Gasket 4 ... Separator 5 ... Positive electrode 10 ... Negative electrode 11 ... Li layer 12 ... LiSi layer 13 ... Si layer 14 ... 3rd layer 20 ... Gap

Claims (15)

  A negative electrode for a lithium primary battery, comprising at least two layers of a Li layer made of lithium (Li) and a LiSi layer containing an alloy of Li and silicon (Si).   2. The negative electrode for a lithium primary battery according to claim 1, wherein the molar ratio of Li and Si in the negative electrode is Li / Si> 4.4.   3. The negative electrode for a lithium primary battery according to claim 2, wherein the molar ratio of Li and Si in the negative electrode is 15 ≦ Li / Si ≦ 100.   The said LiSi layer further contains at least 1 type of carbon and resin, The negative electrode for lithium primary batteries as described in any one of Claim 1 to 3 characterized by the above-mentioned.   The negative electrode for a lithium primary battery according to any one of claims 1 to 4, wherein the LiSi layer is formed with an area of 50% or more with respect to the Li layer. The LiSi layer, Li and, particle diameter (D ₅₀₎ a negative electrode for a lithium primary battery according to claim 1, any one of 5, characterized in that it is formed from Si powder is 2μm or more.   The negative electrode for a lithium primary battery according to any one of claims 1 to 6, wherein the LiSi layer has a particle diameter of an alloy of Li and Si of 2 µm or more.   A lithium primary battery comprising the negative electrode for a lithium primary battery according to any one of claims 1 to 7, a positive electrode, and a nonaqueous electrolyte.   The lithium primary battery according to claim 8, wherein the LiSi layer is formed on a surface of the negative electrode facing the positive electrode.   The lithium primary battery according to claim 8 or 9, wherein the positive electrode contains copper (II) oxide.   The positive electrode, the negative electrode, the non-aqueous electrolyte, and a positive electrode can, a negative electrode can, and a gasket that house them, and the LiSi layer is compressed by a caulking seal. The lithium primary battery according to any one of 10. Forming a Li layer made of lithium (Li);
Forming a Si layer made of silicon (Si) or a mixture containing Si on the Li layer;
An alloying step of alloying Li in the Li layer and Si in the Si layer to form at least two layers including the Li layer and the LiSi layer;
The manufacturing method of the negative electrode for lithium primary batteries provided with.   The method for producing a negative electrode for a lithium primary battery according to claim 12, wherein the molar ratio of Li and Si in the negative electrode is Li / Si> 4.4.   14. The negative electrode for a lithium primary battery according to claim 12, wherein the alloying step is performed by compressing the Li layer and the Si layer in a stacking direction and alloying Li and Si. Manufacturing method. A method for producing a lithium primary battery comprising the positive electrode, the negative electrode, the non-aqueous electrolyte, a positive electrode can that accommodates these, a negative electrode can, and a gasket,
The said alloying process compresses the said Li layer and the said Si layer in the lamination direction by crimping the said positive electrode can and the said negative electrode can, The any one of Claims 12-14 characterized by the above-mentioned. The manufacturing method of the lithium primary battery as described in any one of.