JP2003282139A - Nonaqueous secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous secondary battery with excellent high temperature cycle life and excellent low temperature discharge characteristics. <P>SOLUTION: In the nonaqueous secondary battery formed by housing a positive electrode, a negative electrode, a nonaqueous electrolyte containing a lithium salt in a battery container, (1) a positive active material in the positive electrode is a mixture of a lithium manganese composite oxide and a lithium nickel composite oxide; (2) a negative active material in the negative electrode is graphite; (3) the nonaqueous electrolyte contains a mixed solvent of ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate; (4) the total volume of the ethyl methyl carbonate and diethyl carbonate is 50-90% of the whole solvent volume; and (5) the volume of diethyl carbonate is 10-40% of the whole solvent volume. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a non-aqueous secondary battery.

[0002]

2. Description of the Related Art In recent years, in the field of small secondary batteries for portable devices, nickel hydrogen batteries, lithium secondary batteries, etc. have been rapidly developed in order to meet the conflicting needs of miniaturization and high capacity. Batteries having a volume energy density of 180 Wh / l or more are commercially available. In particular, lithium-ion batteries have the potential to achieve volume energy densities of over 350 Wh / l, and are more reliable in safety and cycle characteristics than lithium secondary batteries that use metallic lithium for the negative electrode. Therefore, the market is expanding dramatically.

As a positive electrode active material for such a lithium ion battery, a lithium cobalt composite oxide, a lithium nickel composite oxide, a lithium manganese composite oxide, etc.
A composite oxide having an electromotive force of more than is used.
In particular, the lithium cobalt composite oxide, which has excellent battery characteristics and is easy to synthesize, is currently used in the largest amount.

However, the raw material cobalt is
There are few recoverable reserves and it is expensive. Therefore, the use of a lithium nickel composite oxide as an alternative substance has been studied so far. The lithium nickel composite oxide is an oxide that has a layered rock salt structure like the lithium cobalt composite oxide and has a high capacity exceeding 200 mAh / g.

However, the lithium-nickel composite oxide has a problem that Ni ⁴⁺ generated during charging is chemically unstable, and that a large amount of lithium is extracted from the structure of the lithium-nickel composite oxide in a highly charged state. There is a problem that the oxygen desorption initiation temperature from the crystal lattice is low due to the instability of the structure. For example, SolidSta
te Ionics, 69, No.3 / 4,265 (1994) reported that the oxygen desorption initiation temperature of lithium nickel composite oxide in a charged state is lower than that of conventional lithium cobalt oxide. .

For this reason, the battery using the lithium nickel composite oxide alone as the positive electrode active material can obtain a high capacity, but has a problem in thermal stability in a high charged state.
Since it cannot secure sufficient safety as a battery, it has not been put to practical use until now.

On the other hand, since the lithium manganese composite oxide has a spinel type crystal structure, it is structurally different from the lithium cobalt composite oxide and the lithium nickel composite oxide having the layered rock salt structure. Due to this difference in structure, the oxygen desorption initiation temperature in a high charge state of the lithium manganese composite oxide is higher than that of the lithium cobalt composite oxide and the lithium nickel composite oxide. That is, the lithium manganese composite oxide is a highly safe positive electrode active material.

However, the lithium secondary battery using the lithium-manganese composite oxide as the positive electrode causes so-called "capacity deterioration" in which the capacity gradually decreases by repeating charging and discharging. Therefore, its practical application has been difficult.

Generally, a lithium ion battery is required to have safety and excellent cycle life. However, a battery using a lithium nickel composite oxide as a positive electrode active material has a problem of low safety because it lacks thermal stability during high charging. In addition, although a battery using a lithium manganese composite oxide has high safety,
There are two problems: (1) it is difficult to realize both high energy density (high charge / discharge capacity) and long cycle life, and (2) storage capacity decreases due to self-discharge.

First, the reason why high capacity cannot be realized in a battery using a lithium manganese composite oxide is as follows.
It is considered that the reaction is non-uniform during the synthesis of complex oxides and the effect of impurities is mixed. In addition, as a cause of capacity deterioration with charge / discharge cycles, the average valence of Mn ions changes between trivalent and tetravalent as charge compensation with Li inflow and outflow. Therefore, Jahn-Teller strain is generated in the crystal, Mn is eluted from the lithium manganese composite oxide, and the eluted Mn
That the impedance is increased due to the precipitation on the negative electrode active material or on the separator, further, the influence of impurities, the inactivation due to the release of the active material particles, the acid generated in the electrolytic solution due to water content This may be due to the influence of oxygen release from the lithium-manganese composite oxide.

When the spinel single phase is formed, the cause of Mn elution is that the trivalent Mn in the spinel structure is partially disproportionated into tetravalent and divalent Mn in the electrolytic solution. It is thought that it may be dissolved easily and may be eluted due to the relative lack of Li ions. As a result, repeated charge and discharge promoted generation of irreversible capacity, disorder of atomic arrangement in the crystal, and dissolution of Mn.
It is assumed that the ions are deposited on the negative electrode or the separator and hinder the movement of Li ions. In addition, the lithium manganese composite oxide is distorted by the Jahn-Teller effect when the Li ions are taken in and out, and the crystal expands and contracts by several percent of the unit lattice length. Therefore, it is presumed that, by repeating the charge / discharge cycle, the particles do not function as an active material due to partial electrical isolation of the particles.

Further, it is considered that the release of oxygen from the lithium-manganese composite oxide is facilitated as Mn is eluted. It is presumed that when the amount of released oxygen increases, the decomposition of the electrolytic solution is promoted, and deterioration of the electrolytic solution also causes deterioration of the charge / discharge cycle.

Suppression of such Mn elution, reduction of lattice distortion,
Achieving reduction of oxygen deficiency is important for improving the cycle characteristics of lithium batteries. Therefore, Japanese Patent Laid-Open No. 2-270268 proposes to improve the cycle characteristics by making the composition of Li sufficiently excess with respect to the stoichiometric ratio. Further, it has been proposed that a part of the Mn element of the lithium-manganese composite oxide is replaced by addition or doping of Co, Ni, Fe, Cr, Al or the like to improve cycle characteristics (Japanese Patent Laid-Open No. 4-141954). JP, JP 4-160758 JP, JP 4-16976 JP, JP 4-237970 JP,
JP-A-4-282560, JP-A-4-289662, etc.).
These methods such as Li-rich composition and addition of metallic elements are effective in improving cycle characteristics, but on the contrary, they reduce charge and discharge capacity, so both high cycle life and high capacity are satisfied. I haven't made it happen.

LiPF6 as an electrolyte for lithium-ion batteries
₆ , a non-aqueous electrolyte solution in which a lithium salt such as LiBF ₄ is dissolved in a mixed solvent of ethylene carbonate and ethyl methyl carbonate, a mixed solvent of ethylene carbonate and diethyl carbonate, etc. is generally used.

However, the electrolytic solution using a mixed solvent of ethylene carbonate and ethyl methyl carbonate is
There is a problem that the cycle life at high temperature is short. Further, the electrolytic solution using a mixed solvent of ethylene carbonate and diethyl carbonate has a problem that the battery capacity becomes small at a low temperature of 0 ° C. or lower. in this way,
It is difficult to achieve both long cycle life at high temperature and high capacity maintenance at low temperature.

[0016]

SUMMARY OF THE INVENTION Accordingly, the main object of the present invention is to provide a non-aqueous secondary battery having excellent high temperature cycle life and low temperature discharge characteristics.

[0017]

Means for Solving the Problems As a result of conducting research while paying attention to the current state of the art as described above, the present inventor has achieved the above object by a non-aqueous secondary battery having a specific configuration. succeeded in.

That is, the present invention provides the following non-aqueous secondary battery. 1. In a non-aqueous secondary battery in which a non-aqueous electrolyte containing a positive electrode, a negative electrode and a lithium salt is housed in a battery container, (1) the positive electrode active material in the positive electrode is composed of a lithium manganese composite oxide and a lithium nickel composite oxide. (2) the negative electrode active material in the negative electrode is graphite, (3) the non-aqueous electrolyte is ethylene carbonate,
Contains a mixed solvent consisting of ethyl methyl carbonate and diethyl carbonate, and (4) the total volume of ethyl methyl carbonate and diethyl carbonate is 50% of the total solvent volume.
A non-aqueous secondary battery characterized in that the volume of (5) diethyl carbonate is 10% to 40% of the total solvent volume. 2. 2. The non-aqueous secondary battery according to 1 above, which contains at least double structure graphite particles as a negative electrode active material.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The positive electrode of the non-aqueous secondary battery according to the present invention uses a mixture of a lithium manganese complex oxide and a lithium manganese complex oxide as a positive electrode active material.

As the lithium manganese-based composite oxide, for example, a lithium manganese composite oxide (LiMn ₂ O ₄ ), a composite oxide (Li _{1 + a} Mn) in which at least one kind of a different metal element is added to the lithium manganese composite oxide is used. _2-ab MA _b O ₄ ), lithium-manganese composite oxide containing lithium in excess of stoichiometric ratio
(Li _{1 + x} Mn _2-x O ₄ ) and the like can be exemplified.

A composite oxide (Li _{1 + a} Mn) obtained by adding at least one kind of a different metal element to a lithium manganese composite oxide.
_{In 2-ab} MA _b O ₄ ), MA in the formula represents a different metal element. Examples of MA include Al, Mg, Cr, Fe, Co, Ni and the like, and among these, Al, Mg, Cr and the like are preferable. The value of a in the above formula is usually about 0.01 to 0.2, preferably about 0.03 to 0.15. In the formula
The value of b is usually about 0.01 to 0.2, preferably 0.03 to
It is about 0.15.

In the lithium manganese composite oxide Li _{1 + x} Mn _2-x O ₄ containing lithium in an excess amount over the stoichiometric ratio, x in the formula
Is usually about 0.01 to 0.2, preferably 0.03 to 0.15
It is a degree.

As the lithium nickel-based composite oxide,
For example, a composite oxide (LiNi _1-c MB _c O ₂ ) in which at least one kind of different metal element is added to a lithium nickel composite oxide can be exemplified.

[0024] A composite oxide (LiNi _1-c MB _c O
_{In 2} ), MB represents a different metal element. Examples of MB include Co, Al, and Mn. C in the above formula is usually about 0.01 to 0.5, preferably about 0.1 to 0.3.

The proportion of the lithium manganese-based composite oxide in the mixture used as the positive electrode active material in the present invention is 70 when the total amount of the lithium-manganese-based composite oxide and the lithium-nickel-based composite oxide is 100 parts by weight. To about 95 parts by weight, preferably about 70 to 85 parts by weight. The proportion of the lithium-nickel-based composite oxide is about 5 to 30 parts by weight, preferably 15 to 30 parts by weight, when the total of the lithium-manganese-based composite oxide and the lithium-nickel-based composite oxide is 100 parts by weight. It is a degree. Within the above range, it is possible to more reliably obtain the effect of improving the capacity and improving the cycle characteristics.

The average particle size of the positive electrode active material is not particularly limited and can be made to be approximately the same as the particle size of conventional active materials.
The average particle size of the positive electrode active material is usually about 1 to 60 μm, preferably about 5 to 40 μm, more preferably about 10 to 30 μm. In the present specification, the “average particle size” means the central particle size in the volume particle size distribution obtained by the dry laser diffraction measurement method.

The specific surface area of the positive electrode active material is not particularly limited, but is usually about 1 m ² / g or less, more preferably 0.2 to
It is about 0.7 m ² / g. In the present specification, “specific surface area” refers to a value measured by the BET method using nitrogen gas.

The negative electrode of the present invention uses graphite as a negative electrode active material. Examples of graphite include natural graphite, artificial graphite, graphitized mesocarbon microbeads, graphitized carbon fiber, and double-structured graphite particles in which the core surface of graphite particles is coated with amorphous carbon. it can.
Among these, the above-mentioned double structure graphite particles are preferable from the viewpoints of battery capacity, cost and the like.

The double-structured graphite particles are not particularly limited as long as the core surface of the graphite particles is covered with amorphous carbon. The graphite particles that are the core portion have an interplanar spacing (d002) of (002) plane by X-ray wide-angle diffraction method of usually 0.34 nm or less, preferably 0.3354 to 0.338 nm, and more preferably 0.3354 to 0.336 nm. Is. When the above range is set, the effective capacity that can be used as a battery can be increased more reliably. The interplanar spacing of the amorphous carbon layer coating the core portion of the graphite-based particles is such that the interplanar spacing (d002) of the (002) plane by X-ray wide angle diffraction exceeds 0.34 nm, and more preferably 0.34 nm. To 0.38 nm or less, more preferably 0.34 nm or more and 0.36 nm or less. By setting the content in the above range, excellent charge / discharge efficiency can be obtained more reliably. The method for producing such double-structured graphite particles is not particularly limited, and, for example, a known method described in WO97 / 18160 can be used.

The average particle size of the negative electrode active material is not particularly limited, and may be the same as the particle size of conventional active materials, for example. The average particle size is usually about 1 to 60 μm, preferably 5 to 40
It is about μm, more preferably about 10 to 30 μm.

The specific surface area of the negative electrode active material is not particularly limited, but is usually about 0.2 to ³ m ² / g, preferably about 0.2 to ^2.5 m ² / g.

The non-aqueous secondary battery of the present invention may include a separator. The separator is not particularly limited, and a known separator can be used, and can be appropriately determined according to the heat resistance of the battery, desired safety, and the like. Examples of the material of the separator include microporous membranes such as polyolefin-based materials (polyethylene, polypropylene, etc.); nonwoven fabrics such as polyamide, kraft paper, glass, and cellulose-based materials (rayon, etc.).

The constitution of the separator is not particularly limited, and for example, a single-layer or multi-layer separator can be used. When forming a multilayer, it is preferable to use at least one nonwoven fabric. When at least one non-woven fabric is used, cycle characteristics are improved.

The secondary battery of the present invention uses a non-aqueous electrolyte containing a lithium salt. The lithium salt contained in the non-aqueous electrolyte is not particularly limited, and comprehensively considering the types of positive electrode material, negative electrode material, and usage conditions such as charging voltage,
It can be appropriately determined from known lithium salts according to a conventional method. For example, LiPF ₆ , LiClO ₄ , LiBF ₄ , LiAsF ₆ ,
Examples thereof include LiSbF ₆ , and LiPF ₆ and LiBF ₄ are preferable.

The non-aqueous electrolyte used in the present invention includes ethylene carbonate (EC) and ethyl methyl carbonate (E).
It contains a mixed solvent consisting of MC) and diethyl carbonate (DEC). EM in a mixed solvent consisting of EC, EMC and DEC
The total volume of C and DEC is usually about 50 to 90% of the total solvent volume, preferably about 55 to 85%, more preferably 6
It is about 0 to 80%. If the total volume of EMC and DEC is too small, the proportion of EC having a relatively high freezing point (39 ° C) becomes too large, and the EC easily separates and solidifies at a low temperature. When separated and solidified, the discharge capacity of the battery at a low temperature of -10 ° C or lower remarkably decreases.

The volume of DEC is usually 10% to 40% of the total solvent volume.
%. If the volume of DEC is too low, 50 ° C
The cycle life at the above high temperatures may be shortened. On the other hand, if it exceeds 50%, the discharge capacity of the battery at a low temperature of -10 ° C or lower may be significantly reduced.

The volume of ethylene carbonate is usually about 10% or more of the total solvent volume.

The concentration of the lithium salt in the non-aqueous electrolyte is not particularly limited, but is generally about 0.5 to 2 mol per liter of the mixed solvent. As a matter of course, the non-aqueous electrolyte preferably has a water content as low as possible, specifically, a water content of about 100 ppm or less.

The term "non-aqueous electrolyte" used in the present specification includes non-aqueous electrolyte solutions and organic electrolyte solutions. The term "non-aqueous electrolyte" also includes a gel or solid electrolyte.

The non-aqueous electrolyte used in the present invention may optionally contain a known additive such as a disulfide derivative. The blending amount of these additives is not particularly limited as long as the effects of the present invention are exhibited, but is usually about 0.01 to 5% by weight based on the whole non-aqueous electrolyte.

The positive electrode and the negative electrode of the present invention can be prepared by a known method (for example, molding) in consideration of the shape and characteristics of the desired non-aqueous secondary battery. More specifically, a method of applying a mixture containing an active material, a binder and, if necessary, a conductive material and an organic solvent to a current collector, followed by drying and molding, can be exemplified.

The binder is not particularly limited, and specific examples thereof include fluorine-based resins such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene; rubber-based materials such as fluororubber and SBR; polyolefins such as polyethylene and polypropylene; An acrylic resin etc. can be illustrated. When the negative electrode active material contains at least double structure graphite particles (for example,
If the negative electrode active material is only double-structured graphite particles, such as a mixture of doublet graphite particles and graphitized mesocarbon microbeads), as a binder, polyvinylidene fluoride (PVDF) -based material is preferred. , Especially in the PVDF structure
Modified PVDF having a —COOH group or the like introduced therein is more preferable.

The amount of the binder blended may be appropriately determined according to the type, particle size, shape, intended electrode thickness, strength, etc. of the positive electrode or negative electrode active material of the present invention, and is not particularly limited. But the positive electrode active material or negative electrode active material
When it is 0 parts by weight, it is usually about 1 to 30 parts by weight.

As the conductive material, a conductive material known in the art can be used, and examples thereof include acetylene black, natural graphite, artificial graphite and Ketjen black.

The amount of the conductive material used in the positive electrode is not particularly limited and can be appropriately set according to the type of active material. The amount of conductive material used in the positive electrode depends on the positive electrode active material.
When it is 100 parts by weight, it is usually about 20 parts by weight or less. In the negative electrode, even if the conductive material is unnecessary or mixed, it is easier to obtain the effects of the present invention by reducing the amount to about 0.1 to 10 parts by weight with respect to 100 parts by weight of the negative electrode active material.

Examples of the organic solvent include N-methyl-2-
Examples include pyrrolidone (NMP) and N, N-dimethylformamide (DMF).

The current collector is not particularly limited, and examples of the current collector for the positive electrode include aluminum foil, and examples of the current collector for the negative electrode include copper foil and stainless steel foil. further,
A material on which an electrode can be formed on a metal foil or in a gap between metals, such as expanded metal or mesh, can be used as the current collector for the positive electrode and the negative electrode.

The shape, size, etc. of the non-aqueous secondary battery of the present invention are not particularly limited, and may be any of cylindrical, rectangular, thin, box-shaped, flat, etc. depending on each application. The shape of can be selected. Also, the size can be appropriately selected according to the application.

[0049]

According to the present invention, it is possible to provide a non-aqueous secondary battery having an excellent cycle life at high temperature.
That is, it is possible to provide a non-aqueous secondary battery that can maintain a high discharge capacity when repeatedly used at high temperatures.

According to the present invention, it is possible to provide a non-aqueous secondary battery having excellent discharge characteristics at low temperatures. That is,
A non-aqueous secondary battery having a sufficient discharge capacity even at a low temperature can be provided.

[0051]

EXAMPLES The present invention will now be described more specifically by showing examples of the present invention. The invention is not limited by the description of these examples.

Example 1 (1) Li _1.1 Mn _1.8 as a lithium manganese-based composite oxide
Al _0.1 O ₄ , LiNi as lithium-nickel composite oxide
_0.82 Co _0.18 O ₂ and acetylene black which is a conductive material are dry mixed, and the resulting mixture is uniformly dissolved in N-methyl-2-pyrrolidone (NMP) in which polyvinylidene fluoride (PVDF) which is a binder is dissolved. Slurry 1 was prepared by dispersing.
Next, the slurry 1 was applied on both sides of an aluminum foil serving as a current collector, dried and then pressed to obtain a positive electrode. The solid content ratio (weight ratio) in the positive electrode was set to lithium manganese composite oxide: lithium nickel composite oxide: acetylene black: PVDF = 72: 18: 4: 6. The coating area (W1 × W2) of the positive electrode in this example was 50 × 30 mm ² . Also,
The electrode is provided with a current collector which is not coated with the slurry 1.

(2) Double structure graphite particles (of graphite particle core
(002) face spacing (d002) is less than 0.34 nm, (002) face spacing of the coating layer (d002) is greater than 0.34 nm), and is a binder after dry-mixing acetylene black as a conductive material. PV
Slurry 2 was prepared by uniformly dispersing DF in dissolved NMP. Next, the slurry 2 was applied onto both sides of a copper foil serving as a current collector, dried and then pressed to obtain a negative electrode. The solid content ratio (weight ratio) in the negative electrode was double structure graphite particles: acetylene black: PVDF = 93: 2: 6. Negative electrode coating area (W1
× W2) was set to 52 × 32 mm ² . In addition, the slurry 2
Is provided with a current collector not coated with.

Further, the slurry 2 was applied to only one surface by the same method as above to prepare a single-sided electrode. The single-sided electrode was arranged outside in the electrode laminate described later.

(3) A separator (polyethylene microporous membrane; basis weight 13.3) was prepared by using 8 positive electrodes obtained in (1) above and 9 negative electrodes (2 inside one side) obtained in (2) above. g / m ² ) and were laminated alternately to prepare an electrode laminate.

(4) After attaching a positive electrode terminal made of aluminum to the positive electrode current collecting portion of the electrode laminate obtained in the above item (3) and a negative electrode terminal made of nickel to the negative electrode current collecting portion by spot welding, The aluminum-resin laminate film (aluminum layer 0.02 mm) having a thickness of 0.11 mm was housed in a container having an exterior body. In advance, the volume ratio of ethylene carbonate: ethyl methyl carbonate: diethyl carbonate is 30:35:
LiPF ₆ to 1 mol / l in the solvent mixed to be 35
An electrolytic solution in which was dissolved was prepared, and the electrolytic solution was poured into and impregnated in the container. Then, the liquid injection part was sealed so that the internal pressure of the container was 0.1 atm or less, and a battery was obtained.

(5) The characteristics of the obtained battery were evaluated.
`` After charging to 4.2V with a current of 120mA, constant-current constant-voltage charging in which a constant voltage of 4.2V is applied is performed for a total of 8 hours.
The step of "discharging to 2.5 V with a constant current of mA" was set as one cycle, and this test was performed at 25 ° C for 3 cycles and then at 50 ° C for 100 cycles.

Further, in order to evaluate the cycle characteristics, 1
The capacity retention rate was calculated from the discharge capacity after 100 cycles and 100 cycles. The results are shown in Table 2.

Further, as a test for evaluating the discharge capacity at low temperature, the battery was charged to 4.2 V with a current of 120 mA, and then 4.2
After constant-current constant-voltage charging applying a constant voltage of V was carried out for a total of 8 hours to bring the battery to a fully charged state, it was discharged to 3.0 V at 0.2 C current at -10 ° C. The results are shown in Table 2.

Comparative Examples 1 to 5 A battery was prepared in the same manner as in Example 1 except that the mixed solvent of the electrolytic solution in (4) of Example 1 was used as shown in Table 1 below. The high temperature cycle characteristics and the capacity retention rate were measured by the same method as described in (1) and the low temperature discharge characteristics were evaluated. The results are shown in Table 2.

[0061]

[Table 1]

[0062]

[Table 2]

As is clear from the results shown in Table 2, when the electrolytic solution within the scope of the present invention is used, remarkable effects are achieved in high temperature cycle characteristics and low temperature discharge characteristics.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shizukuni Yada             4-1-2 Hirano-cho, Chuo-ku, Osaka-shi, Osaka Prefecture               Kansai Research Institute of Technology (72) Inventor Hiroyuki Tajiri             4-1-2 Hirano-cho, Chuo-ku, Osaka-shi, Osaka Prefecture               Within Osaka Gas Co., Ltd. F-term (reference) 5H029 AJ02 AJ05 AK03 AL07 AM03                       AM05 AM07 BJ04 DJ16 DJ17                       DJ18 HJ07                 5H050 AA06 AA07 BA17 CA08 CA09                       CB08 FA17 FA18 FA19 FA20                       HA07

Claims (2)

[Claims] 1. A non-aqueous secondary battery in which a non-aqueous electrolyte containing a positive electrode, a negative electrode and a lithium salt is housed in a battery container,
(1) The positive electrode active material in the positive electrode is a mixture of a lithium manganese composite oxide and a lithium nickel composite oxide, (2) the negative electrode active material in the negative electrode is graphite, and (3) non- The aqueous electrolyte contains a mixed solvent consisting of ethylene carbonate, ethyl methyl carbonate and diethyl carbonate, (4) the total volume of ethyl methyl carbonate and diethyl carbonate is 50 to 90% of the total solvent volume, and (5) diethyl carbonate A non-aqueous secondary battery having a volume of 10% to 40% of the total solvent volume. 2. The non-aqueous secondary battery according to claim 1, wherein the negative electrode active material contains at least double structure graphite particles.