JP3495814B2 - Battery electrode and lithium secondary battery having the electrode - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium secondary battery using lithium as a negative electrode, and particularly to lithium dendrites (resin-like protrusions) generated by repeated charging and discharging.
The present invention relates to a lithium secondary battery capable of suppressing the generation of electricity and suppressing a decrease in current collecting ability.

[0002]

2. Description of the Related Art Recently, it has been pointed out that there is a possibility that global warming may occur due to the greenhouse effect due to an increase in CO ₂ contained in the atmosphere. Thermal power stations convert thermal energy obtained by burning fossil fuels into electric energy, but CO ₂ is emitted along with the combustion, which makes it difficult to construct new thermal power stations. Therefore, as effective use of the generator, it has been proposed to perform so-called load leveling, in which night power, which is surplus power, is stored in a secondary battery installed in a general household to level the load. Also, CO
Demand for the development of lightweight, high energy density secondary batteries for electric vehicles that do not emit substances such as x, NOx, SOx and hydrocarbons that are said to be related to air pollution, book type personal computers, word processors, video cameras, There is an ever-increasing demand for the development of small, lightweight, high-performance secondary batteries used as power sources for portable devices such as mobile phones.

[0003]

As one of the above high performance secondary batteries, a rocking chair type lithium ion battery in which lithium ion is introduced into an intercalation compound as a positive electrode active material and carbon as a negative electrode active material is used. Development is progressing and it is being put to practical use. However, lithium-ion batteries that can be obtained at present do not sufficiently achieve the high energy density, which is an original feature of lithium batteries that use metallic lithium as a negative electrode active material. It cannot be said that a high-capacity lithium storage battery using a lithium metal, which has attracted a great deal of attention as a high energy density secondary battery, as a negative electrode has been sufficiently put into practical use. In a lithium secondary battery, dendritic lithium may be deposited on the negative electrode during charging. This phenomenon may cause a short circuit or self-discharge. One of the reasons why high-capacity lithium storage batteries (secondary batteries) have not been put to practical use is that they occur due to repeated charging and discharging.
This is because we have not succeeded in suppressing the generation of lithium dendrites, which is the main cause of short circuits. When the dendrite of lithium grows and the negative electrode and the positive electrode are short-circuited, the energy of the battery is consumed in that part in a short time,
The battery may generate heat, or the solvent of the electrolytic solution may be decomposed by heat to generate gas and the internal pressure in the battery may increase. In any case, the growth of dendrites tends to damage the battery or shorten the life of the battery due to a short circuit.

A method of using a lithium alloy such as lithium-aluminum for the negative electrode has also been tried in order to suppress the reactivity of lithium and suppress the generation of dendrites. However, under the present circumstances, those having a high energy density and a sufficiently long cycle life have not been put into practical use even though the generation of dendrites can be suppressed.

Examples of using a lithium alloy for the negative electrode include, for example, Japanese Patent Laid-Open Nos. 63-13264 and 5
-47381, Japanese Patent Laid-Open No. 5-190171, and the like. However, even if a lithium alloy is used for the negative electrode, the negative electrode repeatedly expands and contracts during repeated charging and discharging, and the negative electrode may be cracked and maintain sufficient current collecting ability.

Further, Japanese Patent Laid-Open No. 63-114057 discloses a negative electrode based on a mixed sintered body of fibrous aluminum and a metal fiber which is not alloyed with lithium.
However, in this case, due to the expansion and contraction of the fibrous aluminum due to charge and discharge, the binding force between the metal fiber that does not alloy with lithium decreases and cracks occur at the interface with it, maintaining sufficient current collection performance. There were times when you couldn't.

Further, in Japanese Unexamined Patent Publication (Kokai) No. 5-234585, a metal powder that hardly forms an intermetallic compound with lithium metal is uniformly attached to the surface of a base material made of lithium metal to reduce dendrite precipitation. Batteries with high charging efficiency and improved cycle life have been shown. However, the lithium metal, which is also the base material, repeatedly expands and contracts due to charge and discharge, resulting in the falling of the adhered powder and the cracking of the base material. As a result, as described above, maintenance of sufficient current collecting ability of the negative electrode and dendrite In some cases, precipitation cannot be sufficiently suppressed.

In addition, JOURNAL OF APPLI
ED ELECTROCHEMISTRY 22,
620-627, (1992), there is a report of a lithium secondary battery using an aluminum foil whose surface is subjected to etching treatment as a negative electrode. However, when the charging / discharging cycle is repeated up to a practical range, the aluminum foil repeatedly expands and contracts due to repeated charging / discharging, and as a result, the aluminum foil is cracked and the dendrite grows with a decrease in current collecting property. Therefore, in this case as well, a battery having a long cycle life at a practical level has not been obtained. Thus, while the advent of a negative electrode and a lithium secondary battery having a high energy density and a long cycle life has been long awaited, in reality, there are still problems to be solved. .

(Object of the Invention) It is an object of the present invention to provide a lithium secondary battery having a long cycle life and a high energy density, which can solve the above problems.

The present invention also provides a battery electrode having a negative electrode structure and a lithium secondary battery having the electrode, which can suppress deterioration of current collecting ability due to pulverization and cracking due to precipitation and dissolution of lithium during charge and discharge. The purpose is to do.

[0011]

The battery electrode of the present invention, which solves the above problems and achieves the above objects, has at least a metal element that forms an alloy with lithium during charging and does not form an alloy with lithium during charging. The output terminal is drawn out from a metal part that has a metal element as a constituent element and does not form an alloy with lithium during charging, and the roughness of the conductor part on the surface of the negative electrode that is in contact with the electrolyte and faces the positive electrode (from maximum peak to maximum The difference between 1/2 of the maximum height Rmax (up to Fukaya) and the centerline average roughness Ra is 1/10 or less of the distance between the negative electrode surface and the positive electrode surface, and with respect to the roughness of the conductor portion on the negative electrode surface. , L is the measurement length, and n is the number of peaks per measurement length L, 1+ (4n
Ra / L) is 1.05 or more.

Further, the lithium secondary battery of the present invention, a negative electrode, a separator, a positive electrode, at least a lithium secondary battery electrolyte or electrolytic solution, and lithium upon charging and metal element anode make an alloy with lithium at least during charging Having a metal element that does not form an alloy as a constituent element, the output terminal on the negative electrode side is pulled out from the metal part that does not form an alloy with lithium during charging, and is in contact with the electrolytic solution and the conductor part of the negative electrode surface facing the positive electrode. The difference between 1/2 of the maximum height Rmax (from the maximum peak to the deepest valley) of the roughness and the centerline average roughness Ra is 1/1 of the distance between the negative electrode surface and the positive electrode surface.
When the measurement length is L and the number of peaks per measurement length L is n, 1+ (4nRa / L) is 1.05 or more with respect to the roughness of the conductor portion on the negative electrode surface. Is characterized by.

The present inventor has conducted extensive studies in order to solve the above-mentioned problems, and as a result, by appropriately using a composite negative electrode of a metal that alloys with lithium and a metal that does not alloy with lithium, lithium It is based on the finding that a long-life lithium secondary battery can be obtained by suppressing the generation of dendrites.

That is, the above-mentioned problem is that in a secondary battery having at least a negative electrode, a separator, a positive electrode, an electrolyte or an electrolytic solution, and a battery case, the negative electrode is a metal element which forms an alloy with lithium and a metal element which does not form an alloy with lithium. And a lithium secondary battery in which the output terminal on the negative electrode side is drawn from a metal that does not form an alloy with lithium. By disposing a metal that does not form an alloy with lithium in the negative electrode current collecting portion in this manner, it is possible to suppress a decrease in current collecting ability due to pulverization and cracking due to precipitation and dissolution of lithium during charge and discharge.

Further, the negative electrode of the present invention is a current collector which is in contact with the electrolyte and faces the positive electrode, and a current collector connected to the output terminal.
Increasing the content of metallic elements that do not alloy with lithium is preferred.

In a negative electrode composed of an element that forms an alloy with lithium, lithium is deposited and alloyed and expands during charging, and lithium is discharged into the electrolytic solution and contracts during discharging, resulting in pulverization. This pulverization occurs most actively on the surface of the negative electrode in which a highly reactive element that forms an alloy with lithium is present. At the place where pulverization occurs, the conductivity is reduced and the current collecting ability is significantly reduced. Therefore, by increasing the content of the metal element that does not form an alloy with lithium on the surface of the conductive part that is in contact with the negative electrode electrolyte and faces the positive electrode, the conductivity is maintained through the metal that does not form an alloy with lithium even when pulverized. Since it sags, it is possible to further suppress the decrease in current collecting ability.

The negative electrode of the present invention is formed by binding a powdery member containing a metal element that forms an alloy with lithium to a metal current collecting member that does not form an alloy with lithium with a binder. Alternatively, it may be formed by baking thereafter.

By using such a negative electrode, fatigue fracture caused by repeated expansion and contraction due to alloying with lithium during charging and contraction due to elution of lithium during discharging can be suppressed.
Further, by adopting the powder, the specific surface area of the negative electrode can be increased, the contact area with the electrolytic solution can be increased, and the diffusion of lithium ions into the negative electrode can be facilitated. Further, by performing a treatment such as etching, the specific surface area can be further increased, the dendrite growth of lithium can be suppressed, and the charging and discharging efficiency can be increased.
Further, it becomes easy to control the thickness of the negative electrode, the concentration of the metal element that forms an alloy with lithium and the concentration of the metal element that does not form an alloy with lithium in the negative electrode.

A member containing a metal element that forms an alloy with lithium is molded into the negative electrode with a binder, and when it is not sintered, a conductive additive such as carbon powder or metal powder is mixed in an amount of about 1 to 25 wt%. It is necessary to improve the current collecting property between powders of a member containing a metal element that easily forms an alloy with lithium. As the conductive auxiliary agent, one having a smaller bulk density is more likely to hold the electrolytic solution, and thus the impedance of the electrode can be easily lowered. The more preferable bulk density of the conductive auxiliary material is 0.1 or less.

Further, the particle size of the conductive auxiliary material is preferably as small as possible, but in order to increase the packing density and the current collecting property, a spherical shape, a needle shape, a flake shape (leaf shape) or the like is used. It is preferable to combine the conductive auxiliary agent.

In the case of sintering, the material used for the binder is an inorganic material or an organic material which does not release corrosive gas such as halogen as much as possible at a high temperature, and in the case of an organic material, a polymer which is easily carbonized. preferable. Sintered atmosphere is under reduced pressure,
Alternatively, it is preferably under an inert gas or a reducing gas.

Furthermore, the negative electrode of the present invention may further use an alloy of at least a metal that forms an alloy with lithium and a metal that does not form an alloy with lithium. As a result, the current collecting ability can be increased even inside the negative electrode, and the charge / discharge cycle life can be further extended.

Further, the member of the negative electrode containing a metal element that forms an alloy with lithium may be made of an alloy of two or more kinds of metals which have different etching rates and which can be selectively etched. By further subjecting this negative electrode to etching treatment, the specific surface area of the negative electrode can be dramatically increased.

It is also preferable to selectively etch a metal element that forms an alloy with lithium or a metal element that does not form an alloy with lithium in the negative electrode of the present invention to increase the specific surface area of the negative electrode. By increasing the specific surface area of the negative electrode, the reactivity of the surface of the negative electrode is increased, the actual current density is lowered, the charge / discharge reaction is smoothed, and as a result, the cycle life can be extended.

When protrusions are present on the surface of the negative electrode having an uneven surface and an increased specific surface area, the electric field is concentrated on the protrusions during charging and the current density increases, so that dendrite growth of lithium is likely to occur, causing a short circuit. Easy to do.

Therefore, the difference between 1/2 of the maximum height Rmax (from the maximum peak to the deepest valley) of the conductor portion on the surface of the negative electrode which is in contact with the electrolytic solution and faces the positive electrode and the center line average roughness is It is desirable that the distance is 1/10 or less of the distance between the negative electrode surface and the positive electrode surface.

Further, it is preferable that the ratio of the conductivity of the valley portion to the conductivity of the protruding portion on the surface of the negative electrode is 10 or less. That is, the difference between the height Rmax of the protrusions on the negative electrode surface and the center line average roughness is 1 / the distance between the negative electrode surface and the positive electrode surface.
Even if it is larger than 10, if the electric resistance of the protrusion is larger than the electric resistance of the flat portion, the lines of electric force are not concentrated on the protrusion and the electric field strength does not increase, so that lithium is dendrite-grown on the protrusion during charging. There is no such thing.

When the electric conductivity of the conductor portion on the surface of the negative electrode is uniform or substantially uniform, the negative electrode surface before assembling the battery by the stylus method has a maximum height Rma as shown in FIG.
x and center line average roughness Ra were measured, and then the cycle life of each negative electrode was measured under conditions where lithium dendrite growth in which a battery was formed by using the negative electrode and the charging voltage was increased was likely to occur, and correlation was obtained. . As a result, as shown in FIG. 7, the difference between 1/2 of the maximum height Rmax (from the maximum peak to the deepest valley) of the conductor portion on the surface of the negative electrode facing the positive electrode and the average roughness Ra of the center line. There was some correlation between the negative electrode cycle life and the cycle life of the negative electrode. That is, the difference between 1/2 of the maximum height of the roughness of the conductor portion on the negative electrode surface minus the minimum height and the center line average roughness is 1 of the distance between the negative electrode surface and the positive electrode surface.
It was found that the cycle life becomes longer when the ratio is / 10 or less.

Regarding the roughness of the conductor portion on the surface of the negative electrode of the present invention, when the center line average roughness is Ra, the measurement length is L, and the number of peaks per measurement length L is n, 1+ (4nRa / L)
Is preferably 1.05 or more.

As a result of further intensive studies, it is possible to increase the reactivity of the surface and increase the specific surface area by roughening the surface of the negative electrode by etching or the like, thereby reducing the substantial current density and extending the charge / discharge cycle life. all right. When the correlation between the surface roughness of the negative electrode before charge and discharge and the cycle life is taken, the data as shown in FIG. 8 is obtained. The center line average roughness is Ra, the measurement length is L, and the number of peaks per measurement length L is n. Then, it was found that the cycle life was extended twice or more by setting 1+ (4nRa / L) to 1.05 or more, preferably 1.1 or more, and more preferably 1.2 or more. In FIG. 8, aluminum is used as an element for forming an alloy with lithium of the negative electrode of the present invention, and after roughening the surface by various etching treatments, lithium-nickel oxide is used as the positive electrode active material and ethylene carbonate- is used as the electrolytic solution. It is the result of measuring the charge / discharge cycle life by assembling a battery using an electrolytic solution prepared by dissolving lithium borofluoride in a mixed solvent of dimethyl carbonate (EC-DMC) or propylene carbonate-diethyl carbonate (PC-DEC).

In the present invention, the current collector of the negative electrode may be provided with a conductor layer having a higher elongation at room temperature than that of a metal forming an alloy with lithium. When a lithium-aluminum alloy foil or an aluminum foil is used for the negative electrode, repeated charging and discharging may cause pulverization on the surface of the negative electrode, cracks may occur, and eventually current collection may become impossible. It is speculated that this is mainly due to the expansion and contraction of the negative electrode during charge and discharge.
However, by providing the current collector with a conductor layer having a high elongation at room temperature, cracks in the current collector due to expansion and contraction of the negative electrode can be further suppressed, and the current collecting ability can be secured.

The positive electrode active material forming the positive electrode may contain lithium element. As a result, alloying of the element in the negative electrode with lithium in the negative electrode is not performed until the lithium is deposited during charging. Since the lithium alloy is not prepared and prepared in advance from the time of assembling the battery, the manufacturing process is simplified. In addition, since lithium existing in the positive electrode is discharged and inserted in advance for charge and discharge, expansion and contraction of the positive electrode due to discharge charging is small, and the positive electrode active material does not fall off from the current collector, so cycle life is extended. Become.

Further, the surface of the negative electrode may be covered with an insulating film or a semiconductor film which is permeable to lithium ions but impermeable to lithium metal deposited during charging. This makes it difficult for the lithium deposited during charging to come into direct contact with the electrolytic solution, and prevents the active lithium from reacting with it to form a reactant that cannot contribute to discharging, and it is possible to extend the charge / discharge cycle life. Become. Then, when the negative electrode is made of powder, the surface coating of the negative electrode also has an effect of suppressing the falling of the powder.

The lithium secondary battery of the present invention will be described below with reference to the drawings.

2 and 3 are schematic cross-sectional views of examples of negative electrodes that can be preferably used in the lithium secondary battery of the present invention. Although not shown, in the case of actually constructing a battery, a separator and a positive electrode are provided facing each other above the negative electrode in FIGS. 2 and 3. Note that FIG. 3 (e)
The negative electrodes shown in (g) and (g) are reference examples.

The negative electrode shown in FIG. 2 (a) is a negative electrode composed of a member 102 containing a metal element that forms an alloy with lithium and a current collector 101 made of a metal element that does not form an alloy with lithium. . In the negative electrode shown in FIG. 2A, during charging, lithium ions in the electrolytic solution are alloyed with the member 102 containing a metal element forming an alloy with lithium to be deposited and expanded. Then, in the discharge, lithium ions are released from the member 102 containing a metal element that forms an alloy with lithium into the electrolytic solution and contract. Due to the expansion and contraction due to the charge and discharge, the member 102 containing a metal element that forms an alloy with lithium is pulverized and cracked. However, since the metal element layer 101 that does not form an alloy with lithium is provided in the current collecting portion. A member 1 containing a metal element that forms an alloy with lithium that is finely powdered and cracked, with a small decrease in current collecting ability
The drop of 02 into the electrolytic solution can be suppressed.

The negative electrode shown in FIG. 2 (b) corresponds to that shown in FIG. 2 (a).
This is a case where the metal element 106 that does not form an alloy with lithium is arranged on the surface of the negative electrode having the above constitution. In this case, FIG. 2 (a)
By the metal element 106 which does not form an alloy with lithium, which is arranged on the surface of the negative electrode, more
On the surface of the negative electrode where pulverization is most likely to occur, it is possible to suppress the reduction of the current collecting ability in the surface direction and suppress the promotion of pulverization.

The negative electrode shown in FIG. 2C is a metal which does not form an alloy with lithium by the binder 105 by mixing the conductive auxiliary agent 104 with the powdery member 103 containing a metal element which forms an alloy with lithium. An active layer is formed by binding the current collecting member 101 made of an element. By using a powder from the beginning, instead of using a lump-shaped member containing a metal element that forms an alloy with lithium, stress due to expansion and contraction that occurs during charge and discharge is relaxed and fatigue fracture is prevented, and charge and discharge cycle The life can be further extended. Further, the contact area with the electrolytic solution can be increased, and the reaction during charge / discharge can be carried out more uniformly and smoothly.

In the negative electrode shown in FIG. 2 (c '), active layers similar to those of the negative electrode shown in FIG. 2 (c) are formed on both surfaces of a current collecting member 101 made of a metal element which does not form an alloy with lithium. In this case, the separator and the positive electrode may be arranged to face the upper and lower parts. The electrode configuration of the negative electrode shown in FIG. 2 (c ') in which the current collector is shared and the active layers are provided on both sides is particularly suitable for a spiral cylindrical cell or a rectangular cell with a laminated electrode formation, and the number of manufacturing steps and materials are reduced. , More effective in terms of increasing the electric capacity per unit volume.

The negative electrode shown in FIG. 3 (d) corresponds to that shown in FIG. 1 (a).
In the negative electrode having the above structure, a conductive layer 107 having a high elongation rate is provided between a member 102 containing a metal element that forms an alloy with lithium and a current collecting portion 101 formed of a metal element that does not form an alloy with lithium. Even when a member 102 containing a metal element that forms an alloy with lithium is cracked due to expansion and contraction in a charge / discharge cycle, the conductive layer 107 having a high elongation rate follows expansion and contraction to further reduce the current collecting ability. Can be suppressed. It is also possible to prevent the member 102 containing a metal element that forms an alloy with lithium from dropping into the electrolytic solution.

In the negative electrode shown in FIG. 3 (e), the metal element 106 not forming an alloy with lithium is arranged on the front and back surfaces of the member 102 containing the metal element forming an alloy with lithium.
It is a negative electrode in which a current collecting portion is covered with a conductor layer 107 having a high elongation rate. Due to the repeated charge and discharge cycles, problems on the surface of the negative electrode, a reduction in the current collecting ability of the current collector, and a drop of the member 102 containing a metal element that forms an alloy with lithium into the electrolytic solution are also caused.
Can be prevented.

The negative electrode shown in FIG. 3 (f) corresponds to the negative electrode shown in FIG. 3 (a).
In this example, the current collecting portion of the negative electrode having the structure shown in FIG. A member 10 containing a metal element that suppresses a decrease in current collecting ability of a current collecting portion and forms an alloy with lithium
It is also possible to prevent the drop of 2 into the electrolytic solution.

The negative electrode shown in FIG. 3 (g) employs an alloy 108 of a metal element that forms an alloy with lithium and a metal element that does not form an alloy with lithium. Figure 3
As in the case of the negative electrode shown in (c), it can be applied to the case where the member containing the metal element that forms an alloy with lithium is powder. By using the alloy 108 of a metal element that forms an alloy with lithium and a metal element that does not form an alloy with lithium, a metal element that does not form an alloy with lithium can be arranged to a fine internal portion to maintain the current collecting ability. It is possible to prevent pulverization and cracking of the metal forming the alloy with. Here, the ratio of the metal element forming an alloy with lithium is preferably 50% or more so as not to reduce the utilization efficiency of lithium. In addition, if the etching ratios of the metal element that forms an alloy with lithium and the metal element that does not form an alloy with lithium are different, selective etching is possible, and some metal elements that form an alloy with lithium or that do not form an alloy with lithium can be selected. By etching away, it is possible to obtain a very high specific surface area.

Using a negative electrode as shown in FIGS. 2 and 3 and combining a positive electrode with a separator and an electrolyte,
A secondary battery as shown in can be formed. In FIG. 1, reference numeral 200 is a current collector mainly composed of a metal element that does not form an alloy with lithium, 201 is a layer composed of a member containing a metal element that mainly forms an alloy with lithium, 202 is a negative electrode, 203 is a positive electrode, and 204 Is electrolyte (electrolyte), 205
Is a separator, 206 is a negative electrode terminal, 207 is a positive electrode terminal,
Reference numeral 208 is a battery case. Needless to say, the configuration of the negative electrode 202 can be replaced with the configurations of the negative electrodes shown in FIGS. 2 and 3, respectively.

Since the negative electrode of the present invention is composed of a member containing a metal element that forms an alloy with lithium and a current collecting section made of a metal element that does not form an alloy with lithium, even if charging and discharging are repeated, lithium does not react with lithium. The current collector made of metal elements that do not form alloys does not deteriorate and can maintain the current collecting ability, suppress the rise of charging voltage during constant current charging, suppress the generation of dendrites, and consequently the cycle life. Can be extended.

(Negative Electrode) The negative electrode of the present invention has at least a metal element that forms an alloy with lithium and a metal element that does not form an alloy with lithium as constituent elements, and is composed of a current collecting portion in which a metal that does not form an alloy with lithium is arranged. The output terminal on the negative electrode side is pulled out.

As an actual negative electrode, a metal element that does not form an alloy with lithium is arranged in the current collecting portion of a plate or a foil-shaped member containing a metal element that forms an alloy with lithium, or a metal element that forms an alloy with lithium. A layer made of a powder containing P is formed on a metal current collecting member that does not form an alloy with lithium. Further, a metal element that does not form an alloy with lithium is placed on the surface of the negative electrode facing the positive electrode to enhance the current collecting ability.

For the member containing a metal element that forms an alloy with lithium, an alloy of a metal element that forms an alloy with lithium and a metal element that does not form an alloy with lithium can be used.

Further, the current collector of the negative electrode is covered with a conductive layer having a higher elongation than that of a metal that forms an alloy with lithium at room temperature to prevent fatigue fracture accompanied by expansion and contraction during repeated charging and discharging.

<Arrangement of Metal Element Not Forming Alloy with Lithium> First, a member made of a metal element forming an alloy with lithium is used as a negative electrode base material, and this is treated to arrange the metal element not forming an alloy with lithium. An example of the method of doing will be described below. The surface of the negative electrode of the metal element that does not form an alloy with lithium facing the positive electrode and the current collector, the method of disposing,
There are the following methods.

When the ionization tendency of the metal element that forms an alloy with lithium is higher than that of the metal element that does not form an alloy with lithium, a member made of a metal element that forms an alloy with lithium is used as a salt of a metal element that does not form an alloy with lithium. By immersing in the solution described above, part of the metal element that forms an alloy with lithium can be replaced with the metal element that does not form an alloy with lithium. The substitution amount can be controlled by the time of immersion in the solution, the concentration of salt in the solution, the temperature of the solution, and the like. That is, the longer the time of immersion in the solution, the larger the amount of substitution, and the higher the concentration of salt in the solution or the higher the temperature of the solution, the faster the rate of the substitution reaction.

As another arrangement method, a layer containing a metal element which does not form an alloy with lithium is electroplated, electroless (chemical) plated, laser plated, sputtering, resistance heating vapor deposition, electron beam vapor deposition, cluster ion beam. Vapor deposition, thermal CVD (Chemical Vapor De)
position), low pressure CVD, plasma CVD, laser CVD, or the like. In addition, a coating method of ink or paste containing a metal element that does not form an alloy with lithium, such as screen printing, can be used.

In another method, a base material made of a metal element that does not form an alloy with lithium is used as it is as a current collector, and a layer made of a metal element that forms an alloy with lithium is formed on the base material by sputtering, resistance heating evaporation, electron A method of forming by coating such as beam vapor deposition, cluster ion beam vapor deposition, thermal CVD, reduced pressure CVD, plasma CVD, or screen printing can also be adopted. Various shapes such as a plate, a foil, a punching metal, an expanded metal, and a mesh can be used as the shape of the base material made of a metal element that does not form an alloy with lithium.

<Metallic element that forms an alloy with lithium and metallic element that does not form an alloy with lithium> Examples of the metallic element that forms an alloy with lithium include aluminum, magnesium, potassium, sodium, calcium, strontium, barium, silicon, germanium and tin. , Lead, indium,
Zinc or the like can be used, and aluminum, magnesium, calcium, and lead are particularly preferable.

As the metal element which does not form an alloy with lithium, nickel, titanium, copper, silver, gold, platinum, iron, cobalt, chromium, tungsten, molybdenum, etc. can be used, and particularly nickel, titanium, copper, platinum, Iron is preferred. As the current collecting member, in addition to a single metal of the above elements, an alloy of the above elements can be adopted. Further, stainless steel is also a preferable material as a current collecting member that does not form an alloy with lithium.

<Negative Electrode Containing Powder Containing Metal Element Forming Alloy with Lithium> As a specific method for forming a layer containing the powder containing metal element forming an alloy with lithium on the current collecting member, A powder containing a metal element that forms an alloy with lithium, or an alloy powder of a metal element that forms an alloy with lithium and a metal element that does not form an alloy with lithium,
Resin or low melting point glass is mixed as a binder, an organic solvent or the like is added, and a paste whose viscosity is adjusted is applied on a metal current collecting member that does not form an alloy with lithium,
A method of forming by drying or sintering can be adopted.

When an organic polymer is used as the above-mentioned binder, one which is stable in the electrolytic solution is preferable. For example, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-propylene- Diene terpolymer,
A silicon resin etc. can be mentioned. In addition to these, highly cross-linked polymers are mentioned as preferable materials. When an organic polymer is used as the binder, the active material is less likely to fall off due to expansion and contraction during charge and discharge, but since the current collecting ability is lower than that of metal, carbon black as a conductive auxiliary agent, It is preferable to add carbon powder or metal fine powder such as Ketjen black, acetylene black or graphite to improve the current collecting ability. In particular, if graphite having a shape that is large in the direction parallel to the crystal plane and thin in the direction perpendicular to the surface and has a bulk density of 0.1 or less is used as graphite as a conductive auxiliary material, the conductivity is high and thus the current collecting ability can be improved. At the same time, the amount of the electrolytic solution retained can be increased, so that the impedance of the negative electrode formed of powder can be lowered.

Low melting point glass can be used as the binder, but in this case, the mechanical strength due to expansion / contraction or bending becomes weaker than in the case of using resin.

It is necessary that the current collecting member is a conductive material having at least the surface coated with a metal element that does not form an alloy with lithium. As the shape of the current collecting member, various shapes such as a plate shape, a foil shape, a mesh shape, a sponge shape, a fiber shape, a punching metal, and an expanded metal can be adopted. The material of the current collecting member, nickel, copper,
Examples include titanium, aluminum, silver, gold, platinum, iron, stainless steel, and the like.

<Coating of Current Collecting Section with Conductor Layer with High Elongation Rate> Specific methods for forming the conductor layer with high elongation rate include sputtering, resistance heating vapor deposition, electron beam vapor deposition,
Cluster ion beam deposition, thermal CVD, low pressure CVD,
Methods such as plasma CVD, laser CVD, electrolytic plating, electroless (chemical) plating, and laser plating can be used. In addition, of the ink containing a high elongation conductor,
A coating method represented by screen printing can also be used.

Specific examples of the high-conductivity conductor layer disposed in the current collector of the negative electrode include tin, tin-bismuth alloy, tin-lead alloy, zinc-aluminum alloy, copper-zinc alloy, cadmium-zinc. The conductor layer is composed of one or more kinds of conductors selected from an alloy and a conductive ink in which fine conductor powder is bound with an organic polymer material. In some cases, gold, silver, aluminum and alloys thereof can also be used.

The organic polymer in the conductive ink used for the conductor layer having a high elongation of the negative electrode current collector is a fluororesin, a polyolefin, a silicone resin, or a highly crosslinkable polymer that does not react with the electrolytic solution. Preferably there is. Further, it is desirable that the organic polymer glass transition temperature is equal to or lower than the lowest temperature of the actual use temperature, for example, minus 30.
More preferably, the temperature is not higher than ° C.

<Etching of Negative Electrode> By etching the surface of the negative electrode of the present invention composed of a member containing a metal element that forms an alloy with lithium and a current collecting member containing a metal element that does not form an alloy with lithium, the negative electrode is etched. The specific surface area can be increased.

As the etching method, methods such as chemical etching, electrochemical etching and plasma etching can be adopted.

In the chemical etching, etching is performed by reacting with acid or alkali. The following are specific examples.

As an etching solution for aluminum, which is a metal element that forms an alloy with lithium, phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid, acetic acid, hydrofluoric acid, potassium hydroxide, sodium hydroxide, lithium hydroxide, or a mixed solution thereof is used. Are used.

When magnesium is the metal element forming an alloy with lithium, nitric acid, sulfuric acid,
An alkaline aqueous solution in which hydrochloric acid and ammonium salt are mixed, a mixed solution thereof, and the like are used.

When the metal element which does not form an alloy with lithium is nickel, a dilute acid such as nitric acid is used as an etching solution.

When the metal element that does not form an alloy with lithium is copper, the etchant may be an organic acid such as sulfuric acid, hydrochloric acid, nitric acid, acetic acid, a cupric chloride solution, a ferric chloride solution, or aqueous ammonia. Can be used.

When the metal element which does not form an alloy with lithium is titanium, hydrofluoric acid, phosphoric acid, etc. can be used as the etching solution.

In the case of chemical etching, it is preferable to use an etching solution capable of selective etching because the etching rate ratios of the metal element that forms an alloy with lithium and the metal element that does not form an alloy with lithium are different.

In the electrochemical etching, an electric field is applied between the counter electrodes in an electrolytic solution to electrochemically elute it as metal ions.

A mixed solution of phosphoric acid, sulfuric acid, and chromic acid is used as the electrolytic solution of aluminum, which is a metal element that forms an alloy with lithium.

When the metal element which does not form an alloy with lithium is copper, a phosphoric acid solution or the like can be used as the etching solution.

Plasma etching is a method in which an etching gas is turned into plasma and reactive ions or radicals are reacted to perform etching. As the raw material etching gas, tetrachloromethane, tetrafluoromethane, chlorine, trichloromonofluoromethane, dichlorodifluoromethane, chlorotrifluoromethane, or the like can be used.

<Negative Electrode Surface Coating> During charging, the negative electrode surface of the battery of the present invention is coated with an insulating film or a semiconductor film that selectively permeates lithium ions and does not permeate precipitated lithium metal. The effect of suppressing the generation of dendrites can be further enhanced.

As the material for coating the surface of the negative electrode of the present invention, one having pores or a molecular structure capable of penetrating lithium ions is used. Examples of those having a molecular structure capable of penetrating lithium ions include polymers having a structure of a large crown ether, a calixarene (a cup-shaped cyclic compound composed of a plurality of phenol units), a structure having an ether bond, and the like. . In addition, a glassy substance in which lithium ions are intercalated can be used. As a method of positively producing pores that can permeate lithium ions, a material such as an electrolyte salt that can be eluted after forming a coating film is mixed in the coating liquid of the coating material, a foaming agent or easily pyrolyzed. A method of preparing the pores by mixing the materials and the like can be adopted.

<Negative Electrode Input / Output Terminal> The negative electrode input / output terminal is drawn out from the current collector in which a metal element that does not form an alloy with lithium of the negative electrode is arranged. A method of connecting a member of a conductor to the current collecting portion by a method such as laser welding, spot welding, or soldering is used to draw out the terminal. Also,
If a negative electrode composed mainly of a metal element that forms an alloy with lithium is formed on a base material that is made of a metal element that does not form an alloy with lithium and is formed on the base material, the current collector must be connected to the input / output terminals beforehand. You may process and provide the drawer part to connect.

The positive electrode of the lithium secondary battery positive electrode is composed of a current collector, a positive electrode active material, a conductive auxiliary agent, a binder and the like. The positive electrode active material, the conductive auxiliary agent and the binder are mixed to form a current collector. It is formed by molding on top. The conductive additive used for the positive electrode is powdery or fibrous aluminum,
Carbon powders and carbon fibers such as copper, nickel, stainless steel, carbon black, Ketjen black and acetylene black can be used. The binder is preferably stable in an electrolytic solution, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-propylene-diene terpolymer,
And so on.

The current collector has a role of supplying a current that is efficiently consumed by the electrode reaction during charging and discharging or collecting a current that is generated. Therefore, a material having high electric conductivity and inert to the battery reaction is desirable. Preferable materials include nickel, titanium, copper, aluminum, stainless steel, platinum, palladium, gold, zinc, various alloys, and composite metals of two or more of the above materials.
As the shape of the current collector, a plate shape, a foil shape, a mesh shape, a sponge shape, a fiber shape, a punching metal, an expanded metal, or the like can be adopted.

As the positive electrode active material, a transition metal oxide or a transition metal sulfide is generally used. The transition metal element of the transition metal oxide or the transition metal sulfide is an element partially having a d-shell or f-shell, and is Sc, Y, a lanthanoid, an actinide, Ti, Zr, Hf, V, Nb, Ta, Cr. , M
o, W, Mn, Tc, Re, Fe, Ru, Os, Co,
Rh, Ir, Ni, Pd, Pt, Cu, Ag and Au are used. Mainly, Ti, V, Cr, M of the first transition series metals
It is preferable to use n, Fe, Co, Ni, Cu.

As the positive electrode active material, it is preferable to use a transition metal oxide or a transition metal sulfide containing lithium. By using a positive electrode made of a positive electrode active material containing lithium, there is no need to prepare a negative electrode containing lithium in advance, which has the advantage of simplifying the battery manufacturing process. As one of the methods for preparing a lithium-containing positive electrode active material, a method for preparing a transition metal oxide or a transition metal sulfide using lithium hydroxide or a salt of lithium can be used. As another method, a method in which a transition metal oxide or a transition metal sulfide is mixed with a lithium compound such as lithium hydroxide, lithium nitrate, or lithium carbonate, which easily causes a thermal decomposition reaction, and heat treatment is also prepared. is there.

Separator The separator is arranged between the negative electrode and the positive electrode and has a role of preventing a short circuit between the negative electrode and the positive electrode. It may also have a role of holding the electrolytic solution. Since the separator has pores through which lithium ions can move and must be insoluble and stable in the electrolytic solution, a nonwoven fabric such as glass, polypropylene, polyethylene, fluororesin, or polyamide, or a material having a micropore structure is used. Further, a metal oxide film having fine pores or a resin film in which a metal oxide is composited can also be used. In particular, when a metal oxide film having a multi-layered structure is used, dendrites are unlikely to penetrate, which is effective in preventing short circuits. When a fluororesin film which is a flame retardant material or a glass or metal oxide film which is a nonflammable material is used, the safety can be further enhanced.

[0084] The electrolyte electrolyte in addition to the case of using as it is, to use those immobilized by adding a gelling agent such as a solution or solution polymer dissolved in a solvent. Generally, an electrolyte solution obtained by dissolving an electrolyte in a solvent is used by holding it in a porous separator.

The higher the conductivity of the electrolyte is, the more preferable. The conductivity at 25 ° C. is preferably 1 × 10 ⁻³ S / cm or more, and more preferably 5 × 10 ⁻³ S / cm or more. preferable.

The electrolyte is an acid such as H ₂ SO ₄ , HCl or HNO ₃ , lithium ion (Li ⁺ ) and Lewis acid ion (BF ₄ ⁻ , PF ₆ ⁻ , ClO ₄ ⁻ , CF ₃ SO ₃ ⁻ , BPh _4). ^-
(Ph: phenyl group)), and mixed salts thereof can be used. In addition to the above supporting electrolyte, a salt of a cation such as sodium ion, potassium ion, tetraalkylammonium ion and Lewis acid ion can be used. It is desirable that the salt be heated under reduced pressure to be sufficiently dehydrated and deoxidized.

As a solvent for the electrolyte, acetonitrile,
Benzonitrile, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, dimethylformamide, tetrahydrofuran, nitrobenzene, dichloroethane, diethoxyethane,
1,2-dimethoxyethane, chlorobenzene, γ-butyrolactone, dioxolane, sulfolane, nitromethane, dimethyl sulfide, dimethylsulfoxide, dimethoxyethane, methyl formate, 3-methyl-2-oxazolidinone, 2-methyltetrahydrofuran, 3-propylsydnone , Sulfur dioxide, phosphoryl chloride, thionyl chloride, sulfuryl chloride, and the like, and mixtures thereof can be used.

The above solvent is dehydrated with activated alumina, molecular sieves, phosphorus pentoxide, calcium chloride or the like, or depending on the solvent, it is distilled in an inert gas in the presence of an alkali metal to remove impurities and dehydrate. Good.

Gelation is preferable in order to prevent leakage of the electrolytic solution. As the gelling agent, it is desirable to use a polymer that absorbs the solvent of the electrolytic solution and swells,
Polymers such as polyethylene oxide, polyvinyl alcohol and polyacrylamide are used.

Shape and Structure of Battery The shape of the actual battery is not particularly limited, and there are flat type, cylindrical type, rectangular type, sheet type and the like. In the spiral cylindrical type, the electrode area can be increased by sandwiching a separator between the negative electrode and the positive electrode, and a large current can be passed during charge / discharge. Further, in the rectangular parallelepiped type, it is possible to effectively use the storage space of the device that stores the secondary battery. As the structure, a single-layer structure or a multi-layer structure can be used.

FIG. 4 and FIG. 5 are examples of schematic cross-sectional views of a single-layer flat type battery and a spiral structure cylindrical battery, respectively. 4 and 5, 300 and 400 are negative electrode current collectors, 301 and 401 are negative electrode active materials, 303 and 403 are positive electrode active materials, 404 is a positive electrode current collector, and 305 and 405 are negative electrode terminals (negative electrode caps). 306 and 406 are positive electrode cans, 30
7 and 407 are electrolytes and separators, 310 and 410 are insulating packings, and 411 is an insulating plate.

As an example of assembling the battery shown in FIGS. 4 and 5,
Negative electrode active material 301, 401 and molded positive electrode active material 30
After sandwiching the separators 307 and 407 with 3,403 and incorporating them into the positive electrode cans 306 and 406 and injecting an electrolyte, the negative electrode caps 305 and 405 and the insulating packings 310 and 41
0 is assembled and caulked to produce a battery. In the figure, the negative electrode current collectors 300 and 400 are connected to a metal that does not form an alloy with lithium of the negative electrode active substances 301 and 401 as shown in FIGS. In some cases, the negative electrode current collector 3
00,400 itself may be a metal that does not form an alloy with lithium.

The preparation of the lithium battery material and the assembly of the battery are preferably carried out in dry air from which water is sufficiently removed or in dry inert gas.

[0094] As the material for the insulating packing insulating packing 310, 410, may be used fluororesin, polyamide resin, polysulfone resin, and various rubbers. As a sealing method, in addition to caulking using a gasket such as an insulating packing as shown in FIGS. 4 and 5, a method such as a glass sealing tube, an adhesive, welding, and soldering can be preferably used.

Various organic resin materials and ceramics can be preferably used as the material of the insulating plate 411 of FIG.

Outer can Positive electrode cans 306, 406 and negative electrode cap 30 of actual battery
As the material of 5,405, stainless steel, particularly titanium clad stainless steel, copper clad stainless steel, nickel-plated steel plate and the like can be preferably used.

In FIGS. 4 and 5, the positive electrode cans 306 and 406 also serve as the battery case.
Other than stainless steel, a metal such as zinc, a plastic such as polypropylene, or a composite material of metal or glass fiber and plastic can be used.

Safety valve Although not shown in FIG. 4 and FIG. 5, it is preferable to provide a safety valve such as rubber, spring, metal ball, or rupture foil as a safety measure when the internal pressure of the battery increases.

[0099]

EXAMPLES The present invention will be described in detail below based on examples. The present invention is not limited to these examples.

(Example 1) A lithium secondary battery having a schematic sectional structure shown in FIG. 50% -50% titanium-aluminum alloy foil polished to a thickness of 50 microns is added to a 5 wt% potassium hydroxide aqueous solution.
It was immersed for a minute to etch aluminum on the surface, washed with water and dried to be used as the negative electrode 301 (titanium is a metal element which does not form an alloy with lithium). The surface roughness of the surface of the negative electrode facing the positive electrode measured by the stylus method by the surface polishing and etching treatment of the titanium-aluminum alloy plate before the production of the negative electrode was 0.6 μm or less in terms of center line average roughness. The maximum height was adjusted to be 3.8 microns or less. At this time, the measured length is 80 microns, but the number of rough mountains is 7.
Met.

As the positive electrode active material, electrolytic manganese dioxide and lithium carbonate were mixed in a ratio of 1: 0.4, and then 80
A lithium-manganese oxide was prepared by heating at 0 ° C.
3 wt% carbon powder of acetylene black and 5 wt% polyvinylidene fluoride powder were mixed with the prepared lithium-manganese oxide, N-methyl-2-pyrrolidone was added to prepare a paste, and the mixture was applied to an aluminum foil and dried. To form a positive electrode.

The electrolytic solution contained ethylene carbonate (EC) and dimethocarbonate (D
1M (mol / l) of tetrafluoroboric acid lithium salt was dissolved in an equivalent mixed solvent of MC).

As the separator, a polypropylene non-woven fabric and a microporous film sandwiched and adjusted to a thickness of 50 μm was used.

Assembly was carried out in a dry argon gas atmosphere,
Insert a separator between the negative and positive electrodes, insert it into a titanium-clad stainless steel positive electrode can, inject the electrolyte, and then seal with a titanium-clad stainless steel negative electrode cap and fluororubber insulating packing, A secondary battery was produced.

(Example 2) A lithium secondary battery having a schematic sectional structure shown in FIG.

First, the negative electrode was manufactured by the following procedure.
A 30-micron-thick aluminum foil was immersed in a 5% aqueous potassium hydroxide solution for 5 minutes to etch the surface, and then washed and dried. Next, it was immersed in a 20 wt% nickel chloride aqueous solution at 50 ° C for 5 minutes, part of the aluminum on both surfaces was replaced with nickel, washed with water, and dried under reduced pressure at 150 ° C (nickel does not form an alloy with lithium). element). By the surface polishing and etching treatment, the surface roughness of the negative electrode surface facing the positive electrode measured by the stylus method is 0.4 μm or less in the center line average roughness and 2.0 μm or less in the maximum height. Was adjusted. At this time, the number of rough peaks was 8 for the measurement length of 80 μm.

A 25-micron-thick polypropylene microporous film was used as the separator.

A battery was assembled in the same manner as in Example 1 below.

Example 3 A lithium secondary battery having a schematic cross-sectional structure shown in FIG. 4 having a simple structure and easy assembly was produced.

A conductive ink in which fine silver powder was dispersed in an epoxy resin having a glass transition temperature of -30 ° C. was applied to the surface of the negative electrode prepared in the same manner as in Example 2 on the current collecting side by screen printing to a thickness of 10 μm. A negative electrode was prepared by forming the conductive film with a thickness and crosslinking and curing at 150 ° C. under reduced pressure.

A battery was assembled in the same manner as in Example 1 below.

(Example 4) A lithium secondary battery having a schematic sectional structure shown in FIG.

First, the negative electrode was manufactured by the following procedure.
A 30-micron-thick aluminum foil was immersed in a 5% aqueous solution of hydrofluoric acid to etch the surface, and then washed and dried. Next, in a mixed solution of copper sulfate and sulfuric acid, both surfaces are plated with copper with a thickness of 50 nanometers and dried under reduced pressure at 150 ° C. Then, tin-bismuth alloy is sputtered on the surface of the current collecting side to a thickness of 500 nanometers. To form a negative electrode (copper is a metal element that does not form an alloy with lithium, and tin-bismuth alloy is an alloy that forms a conductor layer having a high elongation). The surface roughness of the negative electrode surface facing the positive electrode measured by the stylus method by the surface polishing and etching treatment was 0.3 μm or less in the center line average roughness and 1.7 in the maximum height.
It was adjusted to be less than or equal to micron. Measurement length 8 at this time
The number of rough peaks was 8 for 0 micron.

A battery was assembled in the same manner as in Example 1 below.

(Embodiment 5) A lithium secondary battery having a schematic sectional structure shown in FIG.

First, the negative electrode was manufactured by the following procedure.
300 mesh aluminum powder: binder polyvinylidene fluoride powder: acetylene black: flake graphite were mixed in a weight ratio of 89: 5: 3: 3, and N-methyl-2-
Pyrrolidone was added to prepare a paste, which was applied to a tin-plated copper foil having a thickness of 35 μm, the coating thickness was adjusted uniformly with a roll press, and dried under reduced pressure at 150 ° C. to prepare a 70 μm-thick negative electrode.

A battery was assembled in the same manner as in Example 1 below.

(Embodiment 6) A lithium secondary battery having a schematic sectional structure shown in FIG. 4 having a simple structure and assembly was produced.

First, the negative electrode was manufactured by the following procedure.
Nickel-plated iron punching metal foil, 300
Aluminum powder of mesh: Nickel ultrafine powder having a particle size of 0.1 micron or less: 90% of methylcellulose as a binder
Mix in a weight ratio of 5: 5, add xylene to form a paste and coat it on a 35 micron thick nickel foil with a coater.
It was dried at ° C. Then, it was sintered under a reduced pressure of 700 ° C.

Next, 5 wt.
It was immersed at 0 ° C. for 5 minutes, a part of aluminum in the aluminum powder was replaced with nickel, washed, dried, and dried under reduced pressure at 150 ° C. to prepare a 60-micron-thick negative electrode.

A battery was assembled in the same manner as in Example 1 below.

(Example 7) A lithium secondary battery having a schematic sectional structure shown in FIG.

First, the negative electrode was manufactured by the following procedure.
250-mesh 40% -60% nickel-aluminum alloy powder: 90% by weight of a binder methylcellulose are mixed, and xylene is added to form a paste, and a 35 micron-thick nickel expanded metal foil is coated with a coater. The coating thickness was uniformly adjusted with a roll press and dried at 100 ° C. Then, it was sintered under a reduced pressure of 700 ° C. Next, the surface was etched by immersing it in a 5 wt% potassium hydroxide aqueous solution for 5 minutes to prepare a 50-micron-thick negative electrode.

A battery was assembled in the same manner as in Example 1 below.

(Example 8) A lithium secondary battery having a schematic cross-sectional structure shown in Fig. 4 was manufactured, which is easy in structure and assembly.

First, the negative electrode was manufactured by the following procedure.
300 mesh of 50% -50% lithium-aluminum alloy powder: 150 mesh of magnesium powder: acetyl cellulose as a binder are mixed in a weight ratio of 45:45:10, and xylene is added to form a paste. Three
Apply to a 5 micron thick expanded metal foil of nickel and adjust the coating thickness evenly with a roll press machine to 100
It was dried at ° C. Then, it was sintered under a reduced pressure of 700 ° C. Next, the surface was etched by immersing it in a 5 wt% potassium hydroxide aqueous solution for 5 minutes to prepare a 60-micron-thick negative electrode.

A battery was assembled in the same manner as in Example 1 below.

Example 9 A lithium secondary battery having the schematic sectional structure shown in FIG.

First, a xylene solution of a copolymer of tetrafluoroethylene and vinyl ether (trade name: Super Konak F) manufactured by NOF CORPORATION and a dimethyl carbonate solution of lithium borofluoride were mixed to prepare a solution for surface coating. . Note that lithium borofluoride was mixed in an amount of 1 wt% with respect to the entire mixed solution. Next, the surface coating solution previously prepared with a spinner was applied to the surface of the negative electrode prepared in the same manner as in Example 4 facing the positive electrode, dried and cured at 170 ° C. under reduced pressure, and further irradiated with ultraviolet rays. Then, a negative electrode having a surface coated with a lithium ion permeable film having a film thickness of about 100 nanometers was produced.

A battery was assembled in the same manner as in Example 1 below.

The positive electrode active materials of Examples 1 to 9 used one type of lithium-manganese oxide in order to evaluate the performance of the negative electrode. However, the present invention is not limited to this, and lithium-nickel oxide is used. Thing, lithium-cobalt oxide,
Various positive electrode active materials can also be adopted.

Further, regarding the electrolytic solution, Examples 1 to 9 were used.
Although the same has been used up to now, the present invention is not limited thereto.

(Comparative Example 1) A battery having a schematic sectional structure shown in FIG. 4 was prepared in the same procedure as in Example 1, except that the negative electrode of Example 1 was replaced with an aluminum foil having a thickness of 30 μm. did. The surface roughness of the surface of the negative electrode facing the positive electrode measured by the stylus method was 0.15 μm or less in center line average roughness and 0.7 in maximum height.
It was less than micron. At this time, the number of rough peaks was 6 for the measurement length of 80 μm.

Comparative Example 2 A battery having a schematic sectional structure shown in FIG. 4 was used in the same manner as in Example 1 except that the negative electrode of Example 1 was replaced by a 100 μm thick aluminum foil manufactured by Nihon Denki Kogyo Kogyo Co., Ltd. Was manufactured in the same procedure as in Example 1.

(Comparative Example 3) A battery having the schematic cross-sectional structure shown in FIG. 4 was prepared in the same procedure as in Example 2 in the same manner as in Example 2 except that the graphite anode prepared in the following procedure was used instead of the anode in Example 2. It was made. The graphite negative electrode was prepared by heat treating natural graphite powder at 2000 ° C. under argon gas, mixing natural graphite powder: acetylene black: polyvinylidene fluoride powder at a weight ratio of 82: 3: 5, and adding N-methyl-2-pyrrolidone. After preparing into a paste,
A 35-micron-thick copper foil was coated, the coating thickness was adjusted uniformly with a roll press, and dried under reduced pressure at 150 ° C. to prepare a 110-micron-thick negative electrode.

Performance Evaluation of Lithium Secondary Battery A charge / discharge cycle test was performed under the following conditions to evaluate the performance of the lithium secondary batteries manufactured in Examples and Comparative Examples, and the performance was evaluated in comparison with the batteries of Comparative Examples.

The conditions of the cycle test are: charge and discharge of 0.5 C (0.5 times the capacity / hour of current) based on the electric capacity calculated from the amount of the positive electrode active material;
5V, 30 minutes rest time, discharge cut-off voltage 2.5
V. The charge cut-off voltage was determined so that decomposition of the solvent in the electrolytic solution would not proceed. Hokuto Denko HJ-106M was used for the battery charging / discharging device. The charge / discharge test was started from charging, the battery capacity was the third discharge amount, and the cycle life was the number of cycles at which the charge potential reached 4.5V.

The performance evaluation results of the lithium battery manufactured by using the negative electrode of the present invention, that is, the discharge energy density per unit volume and the cycle life of the batteries of Examples and Comparative Examples are shown as the performance (discharge) of the battery of Comparative Example 1. Capacity and cycle life) were standardized as 1.0 and summarized in Table 1.

As can be seen from Table 1, Examples 1 to 9
From the comparison between Comparative Examples 1 and 2, it was found that the cycle life was extended by adopting the secondary battery using the negative electrode of the present invention, activating the surface of the negative electrode, and improving the current collecting ability. Further, from the comparison between Examples 1 to 9 and Comparative Example 3, it was found that it is possible to manufacture a secondary battery having substantially the same life as the carbon negative electrode but a high energy density.

[0140]

[Table 1]

[0141]

According to the present invention described above, it is possible to provide a high energy density lithium secondary battery having a long charge / discharge cycle life.

Further, according to the present invention, a battery electrode having a negative electrode structure and a lithium battery having the electrode, which can suppress deterioration of current collecting ability due to pulverization and cracking due to precipitation and dissolution of lithium during charge and discharge, A secondary battery can be provided.

[Brief description of drawings]

FIG. 1 is a conceptual configuration diagram for explaining a preferred example of a secondary battery of the present invention.

2 (a), (b), (c) and (c ') are schematic cross-sectional views for explaining a preferred example of the negative electrode of the present invention.

3 (d), (e), (f) and (g) are schematic cross-sectional views for explaining a preferred example of the negative electrode of the present invention.

FIG. 4 is a schematic cross-sectional view for explaining an example of a single-layer flat type battery.

FIG. 5 is a schematic cross-sectional view for explaining an example of a spiral structure cylindrical battery.

FIG. 6 is a diagram for explaining an example of a measurement result of a negative electrode surface by a stylus method.

FIG. 7 is the maximum height Rm of the surface roughness of the conductor portion on the negative electrode surface.
It is a figure showing an example of the relation between the cycle life of a negative electrode and the difference of 1/2 of ax and center line average roughness Ra.

FIG. 8 is a diagram showing an example of the relationship between the centerline average roughness Ra of the conductor portion on the negative electrode surface, the measurement length L, the number n of peaks per measurement length L, and the cycle life of the negative electrode.

[Explanation of symbols]

Reference numeral 101 is a current collector made of a metal element that does not form an alloy with lithium 102 is a member that contains a metal element that forms an alloy with lithium 103 is a powdery member that contains a metal element that forms an alloy with lithium 104 Conductive auxiliary agent 105 Binder 106 Metal element that does not form an alloy with lithium 107 Conductive layer 108 having a high elongation rate 108 Alloy of a metal element that forms an alloy with lithium and a metal element that does not form an alloy with lithium 200 Current collecting portion 201 Member that contains a metal element that forms an alloy with lithium Layer 202 made of negative electrode 203 positive electrode 204 electrolyte (electrolyte) 205 separator 206 negative electrode terminal 207 positive electrode terminal 208 battery case 300 negative electrode current collector 301 negative electrode active material (or negative electrode) 303 positive electrode active material (or positive electrode) 305 negative electrode terminal 306 positive electrode Can 307 Electrolyte and separator 310 Insulating packing 400 Negative electrode current collector 401 negative electrode active material (or negative electrode) 403 positive electrode active material (or positive electrode) 404 positive electrode current collector 405 negative electrode terminal 406 positive electrode can 407 electrolyte and separator 410 insulating packing 411 insulating plate

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI H01M 4/66 H01M 4/66 A 10/40 10/40 Z (72) Inventor Masaya Asao 3-30 Shimomaruko, Ota-ku, Tokyo No. 2 within Canon Inc. (56) Reference JP 62-243247 (JP, A) JP 61-8849 (JP, A) JP 3-167762 (JP, A) JP 4- 179069 (JP, A) JP 4-129177 (JP, A) JP 3-291852 (JP, A) JP 63-285865 (JP, A) JP 60-175375 (JP, A) JP-A-4-259764 (JP, A) JP-A-63-126157 (JP, A) JP-A-6-84512 (JP, A) JP-A-4-149959 (JP, A) JP-A-5-144475 (JP, A) JP-A-4-206258 (JP, A) JP-A-4-249862 (JP, A) JP-A-6-36800 JP, A) (58) investigated the field (Int.Cl. ^7, DB name) H01M 10/36 - 10/40 H01M 4/02 - 4/04 H01M 4/36 - 4/62 H01M 4/66

Claims (26)

(57) [Claims] 1. A negative electrode, a separator, a positive electrode, at least a lithium secondary battery electrolyte or electrolytic solution, component a metal element anode is not made of an alloy with lithium during charging and the metal element to make an alloy with lithium at least during charging as a, an output terminal of the negative electrode side of a metal portion which is not made of an alloy with lithium is drawn during charging, the electric
The roughness of the conductor part on the surface of the negative electrode that is in contact with the solution and faces the positive electrode
1/2 of maximum height Rmax (from maximum mountain to deepest valley)
And the centerline average roughness Ra is the difference between the negative electrode surface and the positive electrode surface.
It is 1/10 or less of the distance, and
Regarding roughness, the measurement length is L and the number of peaks per measurement length L is
When n, 1+ (4nRa / L) is 1.05 or more
Lithium secondary battery, characterized by that. 2. The content of a metal element which does not form an alloy with lithium at the time of charging is high in a portion of the surface of the negative electrode which is in contact with the electrolytic solution and faces the positive electrode and a portion which is connected to the output terminal. The lithium secondary battery according to claim 1. Wherein the member to which the anode contains a metal element to make an alloy with lithium during charging of the powdery, in a binder, charge
Can any of claims 1 to 2, characterized in that is bound to at lithium alloy metallic current collecting member not to make 1
The lithium secondary battery according to the item. Wherein said negative electrode comprises a metal making lithium <br/> arm and alloys least during charging, the metal does not form an alloy with lithium during charge, claim 1, characterized by being composed of an alloy 4. The lithium secondary battery according to any one of items 1 to 3. 5. The member containing a metal element that forms an alloy with lithium upon charging is made of an alloy of two or more kinds of metals having different etching rates and capable of being selectively etched. The lithium secondary battery according to any one of 1. 6. The specific surface area is increased by selectively etching at least one of a metal element that forms an alloy with lithium during charging or a metal element that does not form an alloy with lithium during charging in the negative electrode. It has a negative electrode, The lithium secondary battery of any one of Claim 1 thru | or 5 characterized by the above-mentioned. 7. The current collecting portion of the negative electrode has an elongation percentage at room temperature.
The lithium secondary battery according to any one of claims 1 to 6, characterized in that a high conductive layer of a metal to make an alloy with lithium during the charging. 8. The metal element which forms an alloy with lithium upon charging is one or more elements selected from aluminum, magnesium, potassium, sodium, calcium, strontium, barium, silicon, germanium, tin, lead, indium and zinc. It exists, The lithium secondary battery of any one of Claims 1 thru | or 6 characterized by the above-mentioned. 9. The current collecting member made of a metal element that does not form an alloy with lithium during charging is nickel, titanium, copper,
Silver, gold, platinum, iron, cobalt, chromium, tungsten,
The lithium secondary battery according to any one of claims 1 to 6, wherein the lithium secondary battery is one or more members selected from molybdenum. 10. The high-elongation conductor layer disposed in the current collector of the negative electrode comprises tin, tin-bismuth alloy, tin-lead alloy, zinc-aluminum alloy, copper-zinc alloy, cadmium-zinc alloy, The lithium secondary battery according to claim 7 , wherein the lithium secondary battery is composed of one or more kinds of conductors selected from a conductive ink in which fine conductor powder is bound with an organic polymer material. 11. A fluororesin, a polyolefin, a silicone resin, in which an organic polymer in a conductive ink used for a conductor layer having a high elongation of the negative electrode current collector does not react with an electrolytic solution,
Claim, characterized in that a polymer that highly crosslinked 1
The lithium secondary battery according to 0 . 12. The lithium secondary battery according to claim 1, wherein the positive electrode active material forming the positive electrode contains a lithium element. 13. The negative electrode surface is covered with an insulating film or a semiconductor film which is insoluble in an electrolytic solution and is permeable to lithium ions but impermeable to lithium metal deposited by charging. 1 to 6
The lithium secondary battery according to the item. Has a 14. A metal element does not form an alloy with lithium at least during charging and the metal element to make an alloy with lithium during charging as a component, an output terminal from the metal portion does not form an alloy with lithium during charging withdrawn, As the negative electrode
An electrode for a battery that is used as a positive electrode
The roughness of the conductor part on the surface of the facing negative electrode
1/2 of maximum height Rmax (to valley) and center line average roughness
The difference from Ra is 1/10 or less of the distance between the negative electrode surface and the positive electrode surface.
Below, the roughness of the conductor portion on the surface of the negative electrode was measured.
When the fixed length is L and the number of peaks per measured length L is n, 1+
(4nRa / L) is 1.05 or more, The electrode for batteries characterized by the above-mentioned . 15. The content of a metal element that does not form an alloy with lithium at the time of charging is high in the surface of the negative electrode that is in contact with the electrolytic solution and faces the positive electrode, and the portion that is connected to the output terminal. 15. The battery electrode according to claim 14 . The member of claim 16 wherein said negative electrode contains a metal element to make an alloy with lithium during charging of the powdery, in a binder, charge
The battery electrode according to claim 14 or 15 , which is bound to a metal current collecting member that does not form an alloy with lithium when electricity is applied. 17. The negative electrode includes a metal making lithium <br/> um alloy at least during charging, the metal does not form an alloy with lithium during charge, claim 14, characterized by being composed of an alloy 17. The battery electrode according to any one of items 1 to 16 . 18. member containing the metal element to make an alloy with lithium during the charging, claims 14 to 17, characterized in that it consists of selectively etchable two or more metal alloy different from the etching rate The battery electrode according to any one of 1 . 19. The specific surface area is increased by selectively etching at least one of a metal element that forms an alloy with lithium during charging or a metal element that does not form an alloy with lithium during charging in the negative electrode. The battery electrode according to any one of claims 14 to 18, which has a negative electrode. To 20. collector portion of the negative electrode, Neu claims 14 to 19 elongation, characterized in that a high conductive layer of a metal to make an alloy with lithium during the charging at room temperature
The battery electrode according to item 1 . 21. The metal element which forms an alloy with lithium upon charging is one or more elements selected from aluminum, magnesium, potassium, sodium, calcium, strontium, barium, silicon, germanium, tin, lead, indium and zinc. Claims characterized by
Item 20. The battery electrode according to any one of items 14 to 19 . 22. The current collecting member made of a metal element that does not form an alloy with lithium during charging is nickel, titanium, copper,
Silver, gold, platinum, iron, cobalt, chromium, tungsten,
The battery electrode according to any one of claims 14 to 19, which is one or more members selected from molybdenum. 23. The high-elongation conductor layer disposed in the current collector of the negative electrode comprises tin, tin-bismuth alloy, tin-lead alloy, zinc-aluminum alloy, copper-zinc alloy, cadmium-zinc alloy, 21. The battery electrode according to claim 20 , comprising one or more kinds of conductors selected from a conductive ink in which fine conductor powder is bound with an organic polymer material. 24. A fluororesin, a polyolefin, a silicone resin, in which an organic polymer in a conductive ink used for a conductive layer having a high elongation of the negative electrode current collector does not react with an electrolytic solution,
3. A highly cross-linked polymer.
3. The battery electrode according to item 3 . 25. The battery electrode according to claim 14 , wherein the positive electrode active material forming the positive electrode contains a lithium element. 26. The method of claim 25, wherein the surface of the negative electrode does not dissolve in the electrolytic solution, claim 14, characterized in that it can pass through the lithium ion of lithium metal precipitated at a charge is covered with an insulating film or a semiconductor film does not transmit Any of through 19
2. The battery electrode according to item 1 .