JP3394484B2 - Lithium secondary battery and design method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery that does not lead to a disaster such as an explosion or a fire even when the battery temperature rises due to a rapid release of battery energy due to an internal short circuit or an external short circuit. The present invention relates to a lithium secondary battery having a limited maximum temperature rise and excellent in safety, and a method for designing the lithium secondary battery.

[0002]

2. Description of the Related Art In recent years, lithium secondary batteries have come to be widely used as power source batteries for portable electronic devices such as mobile phones, VTRs, and notebook computers. In addition, since the lithium secondary battery has a cell voltage of about 4 V, which is higher than that of conventional secondary batteries such as lead storage batteries, and has a large energy density, not only the portable electronic device but also recent environmental problems. Against this background, electric vehicles (E
V) or a hybrid electric vehicle (HEV) as a motor drive power source. Further, application is also being considered as a power source for electric components such as automobile headlights and power windows.

In a lithium secondary battery, generally, a lithium transition metal composite oxide is used as a positive electrode active material, a carbonaceous material is used as a negative electrode active material, and a lithium ion electrolyte is dissolved in an organic solvent as a non-aqueous electrolyte. A liquid is used. There are various forms such as a sandwich type, a wound type, and a laminated type as an electrode body that is a part that performs a battery reaction. In any structure, a positive electrode plate and a negative electrode plate are separated by a separator. There is.

Here, the EV / HEV battery requires a large amount of power for driving a motor and the like, and therefore, a certain amount of capacity is required for each battery. Therefore, it is preferable to use a wound-type or laminated-type electrode body for such an application. To form these electrode bodies, an electrode active material layer is generally formed on the surface of a collector substrate made of metal. Electrode plate formed (referring to positive electrode plate and negative electrode plate)
Is used.

Here, when an internal short circuit, an external short circuit, overcharge, or the like occurs in a lithium secondary battery using a wound type or laminated type electrode body, it is caused by the internal resistance of the electrode body. The battery temperature rises due to the Joule heat generated. At this time, when a large current suddenly flows through the electrode body, the temperature rises naturally, and there is a risk of explosion of the battery or even a disaster.

The temperature rise of the battery is considered to have an internal cause and an external cause. For example, as an internal cause, when there is a damaged portion such as a break in the separator, metal dust which is a good electric conductor is mixed in during the manufacturing of the wound body and penetrates the separator, etc. However, since a short circuit occurs between the electrode plates in the battery, a large current will flow. The Joule heat generated at this time heats and evaporates the non-aqueous electrolyte, so that the internal pressure of the battery rises and there is a risk of ignition and explosion of the battery.

On the other hand, as an external cause, it is conceivable that a good electrical conductor such as a nail penetrates the inside of the battery. In this case, a phenomenon similar to an internal short circuit occurs. Further, it is assumed that the positive and negative terminals of the battery are short-circuited, but in this case, the degree of heat generation varies depending on the magnitude of the load (resistance) at the time of external short circuit. In addition, it is considered that overcharge occurs due to a failure of the charging device, or the device is placed near a heat generating device such as an engine and heated.

The inventors have investigated the causes of temperature rise of such various batteries, and have reported that the Journal of Power Sources
81-82 (1999) 887-890, 2
Regarding the lithium secondary battery having a capacity of 5 Ah, the results of examining the temperature change of the battery when subjected to a nail penetration test, an external short circuit test, an overcharge test, and an external heating test have been published. Among these, the one with the largest temperature rise is the nail penetration test, that is, the case where an internal short circuit occurs, and the temperature rise up to about 400 ° C. is confirmed.

[0009]

A lithium secondary battery having such a large capacity is provided with a pressure relief valve that releases the battery internal pressure to the external pressure at a predetermined pressure when the battery internal pressure rises. , To prevent explosion due to battery temperature rise. However, when the internal pressure of the battery rises rapidly and the release pressure cannot catch up, or when the release valve malfunctions, the battery explosion is inevitable. Further, the closer the battery is to a fully charged state, the more energy is released, so that the temperature rise of the battery due to a short circuit or the like becomes large.

Therefore, although the inventors have many causes for the temperature rise of the battery as described above, in most cases, the battery itself is heated by the energy stored in the battery. It was also noted that the battery temperature rises most during an internal short circuit. That is, by satisfying a predetermined condition between the amount of energy that can be stored in the battery and the specific heat ( or heat capacity) of the battery itself, it is considered that the increase in battery temperature can be suppressed below a certain temperature. Reached

[0011]

That is, according to the present invention , a positive electrode active material is provided on a current collecting substrate having a structure for collecting current from a plurality of locations.
Either the material layer or the negative electrode active material layer is formed.
A lithium secondary battery including a positive electrode plate and a negative electrode plate, which are wound or laminated with a separator interposed therebetween, using a non-aqueous electrolyte, and when the battery is fully charged. The energy amount per unit weight at E ₀ (J / g), the specific heat of the battery is Cp (J / ° C · g), the normal operating temperature of the battery is T ₁ (° C), and the maximum temperature rise of the battery is T ₂ (℃),
When the minimum temperature at which the battery is in an unsafe state due to heat is t (° C.), the battery has the following formula, E ₀
There is provided a lithium secondary battery characterized by satisfying a relationship of / Cp + T ₁ = T ₂ <t.

Here, it is preferable that the maximum rise temperature T ₂ be equal to or lower than the boiling point of the non-aqueous electrolyte. Further, the maximum rising temperature T ₂ may be lower than or equal to the lowest temperature among the boiling points of the main components of the non-aqueous electrolyte. Further, it is also preferable that the maximum rise temperature T ₂ is equal to or lower than the highest temperature among the melting points of the main constituent materials of the separator.

The lithium secondary battery of the present invention is suitably used for a battery having a battery capacity of 2 Ah or more when fully charged. Moreover, the lithium secondary battery of the present invention is suitably used as a power source for an electric vehicle or a hybrid electric vehicle. In addition, the positive electrode is placed on the current collecting board, which has a structure to collect current from multiple
Either the active material layer or the active material layer is formed
The positive electrode plate and the negative electrode plate are wound with a separator or
Lithium with non-aqueous electrolyte provided with laminated electrode bodies
A method of designing a secondary battery, comprising the step of including the non-aqueous electrolyte solution.
Of the materials involved in the unsafety of the lithium secondary battery,
Considering thermal characteristics, the lithium secondary battery is
Determine the lowest temperature: t (° C) that will be in an unsafe state, and then
The maximum temperature rise of the lithium secondary battery: T ₂ (℃)
It is determined in consideration of all coefficients and the lithium secondary
Normal operating temperature of battery: T ₁ (° C)
Then, the specific heat of the lithium secondary battery: C
p (J / ° C · g), and then, experimentally, the ratio
Heat: Use a material whose Cp (J / ° C · g) is known,
Also, record the weight of each member, make the first test product, and obtain
Specific heat of the above-mentioned first test product: Cp ₁ (J / ° C · g) and
The energy per unit weight of the first test product when fully charged.
Energy amount: E ₀₁ (J / g) was calculated, and from each obtained value
Calculate E ₀ / Cp ₁ and further consider T ₁
Calculate the theoretical maximum temperature rise of the sample: T ₂₁ '(℃)
T ₂₁ 'is higher or lower than the previously determined T ₂
, T ₂₁ ′ is replaced with T ₂ by using a predetermined method .
The second test product is manufactured so that the difference is within the allowable range.
Then, the specific heat of the obtained second test product: Cp ₂ (J / ° C.
g) and unit weight per full charge of the second test item
Energy amount of sardine: E ₀₂ (J / g) was measured and
Obtain the theoretical maximum temperature rise of the second test product: T ₂₂ '(℃)
Because, as compared to T ₂ in which the previously determined, the second specimen is below
Formula, E ₀₂ / Cp ₂ + T ₁ = T ₂₂ '<t ... Relation of formula
And a step of determining whether or not
A method for designing a lithium secondary battery is provided. This place
If the second test product does not satisfy the relationship of the above formula,
If this is the case, it is preferable to repeat the above steps a predetermined number of times as necessary.
Good Furthermore, the T ₂₁ 'is higher than the previously determined T _2.
Predetermined method when There are, the E ₀₂ is smaller
The area of the positive electrode plate and the negative electrode plate used is small.
And the T ₂₁ 'was decided first.
Predetermined method when less than T ₂ is the temperature of the battery
Increase the heat capacity of the battery so that it will not rise easily
Preferably it is a method.

[0014]

DETAILED DESCRIPTION OF THE INVENTION The lithium secondary battery of the present invention (battery) is Kai wound the positive plate and negative electrode plate via a separator also
Includes an electrode body formed by laminating, in which using a non-aqueous electrolyte. However, although it is a coin-type battery including an electrode body in which a separator is sandwiched between one positive electrode plate and one negative electrode plate, it does not prevent application to a battery having a large battery capacity.

FIG. 1 is a perspective view showing a schematic structure of a wound electrode body (hereinafter referred to as “wound body”) 1. Rolled body 1
Has a structure in which electrode plates 2 and 3 (positive electrode plate 2 and negative electrode plate 3) to which a plurality of current collecting tabs 5 and 6 are attached are wound around the outer periphery of the winding core 13 via a separator 4. ing.

Here, the positive electrode plate 2 is manufactured by applying a positive electrode active material on both surfaces of a current collecting substrate to form a positive electrode active material layer. As the current collector substrate, a metal foil such as an aluminum foil or a titanium foil, which has good corrosion resistance to a positive electrode electrochemical reaction, is preferably used. A punching metal or a mesh can be used instead of the foil. Further, as the positive electrode active material, lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNi
O ₂ ), lithium transition metal composite oxides such as lithium manganate (LiMn ₂ O ₄ ) can be used.

Coating of these various positive electrode active materials on a current collecting substrate (metal foil) is carried out by using a slurry or paste prepared by adding a solvent, a binder or the like to the positive electrode active material powder, a doctor blade method or a roll coater method. It is carried out by applying and drying the current collecting substrate using the above. In forming the positive electrode active material layer, fine carbon powder such as acetylene black or carbon black is usually added to these positive electrode active material powders as a conduction aid.

The negative electrode plate 3 can be manufactured in the same manner as the positive electrode plate 2. A copper foil is used as the current collector substrate of the negative electrode plate 3.
Alternatively, a metal foil such as a nickel foil having good corrosion resistance against the negative electrode electrochemical reaction is preferably used. Of course, punching metal or mesh may be used. As the negative electrode active material,
Amorphous carbonaceous materials such as soft carbon and hard carbon, and highly graphitized carbonaceous powder such as artificial graphite and natural graphite are used.

As the separator 4, a Li ion permeable polyethylene film (PE having micropores) is used.
A film having a three-layer structure in which a porous Li ion permeable polypropylene film (PP film) is sandwiched is preferably used. This is because the PE film is softened at about 130 ° C. and the micropores are crushed when the temperature of the wound body 1 rises, and also serves as a safety mechanism for suppressing the movement of Li ions, that is, the battery reaction. And this PE
By sandwiching the film with the PP film having a higher softening temperature, the PP film retains its shape even when the PE film is softened, and the positive electrode plate 2 and the negative electrode plate 3 are retained.
It is possible to prevent battery contact and short circuit, and to surely suppress battery reaction and ensure safety.

The electrode plates 2 and 3 and the separator 4 are wound around the core 13.
During the work of winding the electrode around the electrode plates 2 and 3, the electrode active material is not coated on the exposed portion of the current collecting substrate.
Electrical members (tabs) 5 and 6 are attached, respectively. This
Like, the current collector substrate has a structure that collects current from multiple locations.
ing. Therefore, the electrode plates 2, 3 is preferably a stripe structure in which an active material layer on at least one end of the width direction of the current Denmoto plate is not formed. The winding core 13 can be made of various materials such as metal, resin, and ceramic. When a conductive material is used, it is necessary to ensure insulation from the electrode plates 2 and 3.

As the tabs 5 and 6, foil-shaped ones made of the same material as the current collecting substrates of the electrode plates 2 and 3 are preferably used. The tabs 5 and 6 can be attached to the electrode plates 2 and 3 by ultrasonic welding, spot welding or the like. At this time, as shown in FIG. 1, the tabs 5 and 6 are arranged so that the tab of one electrode is arranged on one end surface of the wound body 1.
It is preferable to attach each of them so that contact between the tabs 5 and 6 can be prevented.

When assembling a battery using the wound body 1 manufactured as described above, first, while ensuring electrical connection between the positive and negative terminals for taking out a current and the tabs 5 and 6, respectively. The prepared wound body 1 is inserted into a battery case and held at a stable position. After that, the wound body 1 is impregnated with the non-aqueous electrolytic solution, and then the battery case is sealed to manufacture a battery. In the present invention, it goes without saying that there is no limitation on the shape or structure of the battery case or the form of connection between the tabs 5 and 6 of the wound body 1 and the positive and negative electrode terminals.

As the non-aqueous electrolyte, lithium hexafluorophosphate (LiPF ₆ ) or lithium borofluoride (L
A lithium complex fluorine compound such as iBF ₄ ), or one or more electrolytes selected from lithium halides such as lithium perchlorate (LiClO ₄ ), ethylene carbonate (EC), diethyl carbonate (DEC), Those dissolved in a carbonate ester solvent such as dimethyl carbonate (DMC) or propylene carbonate (PC) or a single solvent such as γ-butyrolactone, tetrahydrofuran or acetonitrile, or a mixed solvent are preferably used.

Next, FIG. 2 shows a perspective view of the laminated electrode body (hereinafter referred to as “laminated body”) 7. The laminated body 7 has a structure in which the positive electrode plates 8 and the negative electrode plates 9 are alternately laminated with the separators 10 interposed therebetween, and the tabs 11 and 12 are attached to the electrode plates 8 and 9 one by one. There is. Thus,
The electrode plates 8 and 9 have a structure in which current is collected from a plurality of locations.
The surface shape of the electrode plate 8, 9, etc. in FIG. 2 is a quadrangle, it can be circular, elliptical or the like various shapes.

For manufacturing the electrode plates 8 and 9, it is possible to use the same method as the electrode plates 2 and 3 used for the wound body 1 described above. Needless to say, there is no limitation on the shape of the battery case accommodating the laminated body 7, the terminal position of the battery, and the outer shape of the battery, as well as the case where the wound body 1 is used for the separator and the non-aqueous electrolyte. The same can be used.

In the present invention, by using the above-described wound body 1 or laminated body 7, the following equation, E ₀ / Cp + T ₁ = T ₂ <t, where E ₀ (J / g) : Energy amount per unit weight when the battery is fully charged, Cp (J / ° C · g): Specific heat of battery, T ₁ (° C): Normal operating temperature of battery, T ₂ (° C): Maximum rising temperature of battery , T (° C.): the minimum temperature at which the battery is in an unsafe state due to heat, and the battery is configured so that the relationship:

Here, when the energy amount per unit weight actually filled in the battery is E (J / g), E ≦
Since the relationship of E ₀ is established, the equation is established regardless of the state of charge. Specific heat of battery Cp (J / ℃ ・
g) refers to the specific heat of the entire battery, not the specific heat of only the electrode body. Incidentally, the amount of energy E ₀ of the entire battery '(J) instead of E _0, even by using a heat capacity of the entire battery in place of Cp C (J / ℃), wherein it is clear that similarly valid . The amount of energy stored in the battery is
It can be calculated from the charge capacity (dischargeable capacity) of the battery.

The specific heat Cp of the battery is determined by placing the battery, which is kept in a constant temperature inside the battery by placing it in a constant temperature dryer, into the water stored in the Dewar bottle, It can be determined by a method of measuring the rising water temperature. In addition, if the heat loss due to heat dissipation from the Dewar bottle is obtained in advance using a material block having a known specific heat, the specific heat of the battery can be measured more accurately.

The normal operating temperature T ₁ (° C.) is usually room temperature in many cases, but when it is used as a power source for electric components such as headlights of automobiles and power windows, for example, an engine is mounted. Since it is often placed inside the hood, it can be defined as the temperature at the portion to be placed inside the bonnet.

As is clear from the equation, the maximum temperature rise T ₂ (° C.) depends on the energy stored in the battery,
It refers to the battery temperature reached when the battery itself is heated.
Also, the minimum temperature t at which the battery becomes unsafe due to heat
(° C.) means, for example, the temperature at which the non-aqueous electrolyte solution evaporates, the temperature at which the positive electrode plate and the negative electrode plate are short-circuited due to the melting of the separator, the temperature at which the reaction rapidly starts due to the exothermic reaction of the battery constituents, etc. . Here, the boiling point of the non-aqueous electrolytic solution varies depending on the type and mixing ratio of the solvent forming the non-aqueous electrolytic solution, and the melting temperature also varies depending on the material of the separator used, so t is the value of the battery It depends on the design (structure, materials used, etc.).

Next, a method of designing a battery so as to satisfy the formula will be described below. First, t is determined in consideration of the thermal characteristics of the materials such as the non-aqueous electrolyte used that are involved in the unsafety of the battery. Next, T ₂ is arbitrarily set in consideration of the safety factor and the like. T ₁ is determined by the method of use and the position of arrangement.

In determining Cp, first, the specific heat of only the other parts excluding the electrode body such as the battery case and the battery terminal is obtained by the above-mentioned method using the Dewar bottle, and then the electrode. The specific heat of the body alone is determined by the same method. Further, when the electrode body is a wound body, it is preferable to determine the specific heat of the winding core alone, whereby the specific heat of the portion composed of the positive electrode plate, the negative electrode plate and the separator can be determined.

Next, as a test, a material whose specific heat is known as described above was used, and the weight of each member was recorded to prepare a battery, and the actually completed battery (first test product)
Cp ₁ and E ₀₁ of From each value obtained, E ₀₁ /
When Cp ₁ is calculated and T ₁ is further taken into consideration, the theoretical maximum battery temperature rise of the first test product (hereinafter referred to as “ T ₂₁ ′ ”) can be obtained. The T ₂₁ 'when a higher than T ₂ which defines first, large by using at least one of two ways:, T _21' to within an acceptable range the difference between T ₂ You can pay.

One method at this time is that E ₀₁ can be considered to be proportional to the area of the positive electrode plate in the electrode body, so that the area of the electrode plate to be used is made smaller so that E ₀₁ becomes smaller, that is, the electrode It is a method to make the body smaller.
For example, regarding parts other than the electrode body such as a battery case,
If the same test product is used, the weight of the electrode body will decrease, the amount of non-aqueous electrolyte that will be filled will decrease as the weight of the electrode body decreases, and the electrode body will be stable in the battery case. In the case of increasing the diameter of the winding core in order to hold the core, considering that the heat capacity changes as the weight of the winding core increases,
A suitable area of the positive electrode plate is calculated in advance, and a battery (second test product) is manufactured again.

The average Cp obtained from the members used for producing the first test product and the actual battery Cp ₁ obtained from the first test product produced were compared and the above-mentioned It is also preferable to correct the calculation performed in producing the two test products.

Another method is to increase the heat capacity of the battery so that the temperature rise of the battery is less likely to occur. Specifically, the battery case is made larger, and the member (material) used.
And a method of adding a material having an appropriate thermal conductivity to the space inside the battery or the outer periphery of the battery. However, such a method often leads to an increase in the weight of the battery itself, that is, a decrease in the weight energy density. Therefore, it is preferable to use it only when the difference between T ₂₁ ′ and T ₂ of the test product is small. Of course, it is also possible to use the above two methods together.

Cp ₂ and E ₀₂ of the battery (second test product) manufactured again by such a method are measured to obtain T ₂₂ ′ ,
Compared with a predetermined T ₂ , the condition (E ₀₂ / Cp ₂ + T ₁
= T ₂₂ '<t ... Relation of formula) is determined. Although such work varies depending on the accuracy of calculation etc. at the time of reviewing the area of the positive electrode plate, accurate work conditions for the battery can be obtained by performing the work at least several times. In addition, when changing the size of the battery case etc.,
It is preferable to consider the change in heat capacity due to the size change.

By the way, when T ₂₁ ′ in the first test product is lower than T ₂ set, it is possible to increase the size of the electrode body. At this time, it is necessary to increase the size of the battery case or the like. In some cases, it is sufficient to consider the change in heat capacity that accompanies the increase in size of the battery case or the like.

Next, a mode of determining the maximum temperature rise T ₂ will be described. One method is to set the maximum rising temperature T ₂ to be equal to or lower than the boiling point of the non-aqueous electrolyte. For example, the boiling point of the solvent used for the non-aqueous electrolyte is 2 in PC.
41 ° C., 248 ° C. by EC, 127 ° C. by DEC, 90 ° C. by DMC. When such a solvent is mixed, the boiling point may increase due to intermolecular interaction, but it may occur that each component starts to evaporate at the boiling point.

Therefore, the boiling point of the non-aqueous electrolytic solution defined in the present invention refers to the temperature at which at least one component constituting the non-aqueous electrolytic solution starts to evaporate from the non-aqueous electrolytic solution. Although the boiling point changes depending on the external pressure, it goes without saying that the external pressure applied to the non-aqueous electrolyte in the battery is the internal pressure of the battery, and is usually 1
Atmospheric pressure. However, it may change depending on the temperature outside the battery, the pressure of the inert gas at the time of sealing the battery, and the like.

Another form is a method of setting the maximum rise temperature T ₂ to be equal to or lower than the lowest temperature among the boiling points of the main components of the non-aqueous electrolyte. This is because it is unlikely that the vaporization of the trace components causes an increase in internal pressure that immediately causes the battery to burst. In addition, the main component of the non-aqueous electrolyte does not specifically mean a component that is contained in an amount of several percent or more.
For example, in an equivalent mixture of solvent A and solvent B, both solvents A and B
Needless to say that is the main component, solvent A is 20
%, And the solvent B is 80%, the solvent A can be considered as the main component. On the other hand, in a mixed solvent in which the solvent A is 98% and the solvent B is 2%, the main component can be considered to be only the solvent A. Whether or not it is a major component is 1/20 relative to any other component.
A component containing only the following contents is not a main component, and this condition can be used as a criterion.

By the way, yet another form is the maximum temperature rise T
_{The second} criterion is a method in which the temperature is not higher than the highest temperature among the melting points of the main constituent materials of the separator. For example, the above-mentioned separator made of a PP / PE / PP film having a three-layer structure has a high melting point, and when the PP film forming the skeleton of the separator is melted, the risk of direct contact between the positive electrode plate and the negative electrode plate increases. From the above, it is preferable to set T ₂ to be equal to or lower than the melting temperature of the PP film because the safety of the battery is secured.

By the way, the above equation is based on the assumption that the battery is in a heat insulating state with respect to the external environment.
In reality, when the temperature of the battery rises, heat is released from the surface of the battery to the outside. Therefore, even if the battery itself is heated by the energy stored in the battery, the temperature of the battery set at T ₂ It can be said that reaching to is impossible in reality. In other words, this means that the temperature rise of the battery can be suppressed to a temperature lower than T ₂ , so that the battery satisfying the formula is
It shows that the safety is improved.

The structure of the lithium secondary battery of the present invention satisfying the above formula is suitably used for a large capacity battery having a battery capacity of 2 Ah or more, particularly 5 Ah or more when fully charged.
Of course, it can be used for a battery having a capacity of Ah or less. Needless to say, the use of the battery is not limited, but particularly as a power source for driving a motor or a power source for electric components for an electric vehicle or a hybrid electric vehicle that is required to ensure safety. It is preferably used.

[0045]

As described above, according to the lithium secondary battery of the present invention, even when the battery self-heats due to a short circuit accident or the like, the stored energy is limited in relation to the specific heat of the battery, The battery temperature never rises above a predetermined temperature. Therefore, it is possible to obtain an excellent effect that the explosion and the ignition of the battery are avoided and the safety is secured.

[Brief description of drawings]

FIG. 1 is a perspective view showing a schematic structure of a wound electrode body.

FIG. 2 is a perspective view showing a schematic structure of a laminated electrode body.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Wound type electrode body, 2 ... Positive electrode plate, 3 ... Negative electrode plate, 4 ... Separator, 5 , 6 ... Collection member (tab) , 7 ... Laminated electrode body, 8 ... Positive electrode plate, 9 ... Negative electrode plate 10 ... Separator, 1
1 , 12 ... Current collecting member (tab) , 13 ... Core.

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01M 10/40

Claims (10)

(57) [Claims] 1. A current collecting substrate having a structure for collecting current from a plurality of locations.
Either the positive electrode active material layer or the negative electrode active material layer, respectively.
A positive electrode plate and a negative electrode plate thus formed are wound or laminated with a separator interposed therebetween, and a lithium secondary battery using a non-aqueous electrolyte, which is a unit when the battery is fully charged. The amount of energy per weight is E ₀ (J / g) and the specific heat of the battery is Cp (J / ° C).
-G), the normal operating temperature of the battery is T ₁ (° C), the maximum temperature rise of the battery is T ₂ (° C), and the minimum temperature at which the battery becomes unsafe due to heat is t (° C) ), The battery satisfies the following equation: E ₀ / Cp + T ₁ = T ₂ <t. 2. The lithium secondary battery according to claim 1, wherein the maximum rise temperature T ₂ is not higher than the boiling point of the non-aqueous electrolyte. 3. The lithium secondary battery according to claim 1, wherein the maximum rising temperature T ₂ is equal to or lower than the lowest temperature among the boiling points of the main components of the non-aqueous electrolyte. 4. The lithium secondary according to claim 1, wherein the maximum rise temperature T ₂ is equal to or lower than the highest temperature among melting points of main constituent materials of the separator. battery. 5. The lithium secondary battery according to claim 1, wherein the battery capacity when fully charged is 2 Ah or more. 6. Use as a power source for an electric vehicle or a hybrid electric vehicle.
5. The lithium secondary battery according to any one of 5 above. 7. A current collecting substrate having a structure for collecting current from a plurality of locations
Either the positive electrode active material layer or the negative electrode active material layer is
Winding the formed positive electrode plate and negative electrode plate through the separator
Alternatively, a lithium battery using a non-aqueous electrolyte with an electrode body formed by stacking
A method of designing a secondary battery, Unsafety of the lithium secondary battery including the non-aqueous electrolyte
In consideration of the thermal characteristics of the material involved in the
Minimum temperature at which the secondary battery becomes unsafe due to heat Degree: t
(℃), Next, the maximum temperature rise of the lithium secondary battery: T
₂ (℃) is determined in consideration of the safety factor and
Normal operating temperature of lithium secondary battery: T ₁ How to use (℃)
Determined by the method and placement position, Next, the specific heat of the lithium secondary battery: Cp (J / ° C.
g), Next, as a test, the specific heat: Cp (J / ° C · g) is known.
Use the material that is
A specific heat of the first test product obtained by making a test product: Cp
₁ (J / ° C · g) and when the first test product is fully charged
Energy amount per unit weight: E ₀₁ Find (J / g)
Therefore, from each obtained value E ₀ / Cp ₁ And then T ₁ To
Considering the above, the theoretical maximum temperature rise of the first test product: T
_{twenty one} '(℃), This T _{twenty one} 'That was decided earlier ₂ Higher or lower than
In this case, by using a predetermined method, T _{twenty one} 'To T ₂ When
The second test product is manufactured so that the difference between
Made, Specific heat of the obtained second test product: Cp ₂ (J / ℃ ・ g)
And per unit weight when the second test product is fully charged
Energy amount: E ₀₂ (J / g) and measure the second
Theoretical maximum temperature rise of test product: T _{twenty two} '(℃),
T decided earlier ₂ Compared to The second test product is the following formula, E ₀₂ / Cp ₂ + T ₁ = T _{twenty two} '<T ... expression It includes a step of determining whether or not the relationship of
The method of designing a lithium secondary battery. 8. The second test product satisfies the relation of the above formula
If not, repeat the above steps as many times as necessary
The lithium secondary battery according to claim 7, wherein
Design method. 9. The T _{twenty one} 'That was decided earlier ₂ Higher than
The predetermined method in the case is the above-mentioned E ₀₂ So that
In addition, the area of the positive electrode plate and the negative electrode plate used is reduced.
9. The method according to claim 7, wherein the method is
Design method for lithium secondary battery. 10. The T _{twenty one} 'That was decided earlier ₂ Lower than
If the temperature rises in the battery,
It is a way to increase the heat capacity of the battery so that it becomes difficult.
The lithium secondary battery according to claim 7 or 8,
How to design a pond.