JP2005032715A - Lithium ion secondary battery and manufacturing method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery with a high output excellent in a charge/discharge cycle property at a high temperature, and a manufacturing method of the same. <P>SOLUTION: The lithium ion secondary battery is composed of a positive electrode having an oxide containing lithium and transition metal or a polyanion group compound as a main component of a positive electrode activator, a negative electrode containing a carbonaceous material as a negative electrode activator, and nonaqueous electrolyte liquid with an electrolyte dissolved in an organic solvent. A compound expressed by a formula (1) is added in the nonaqueous electrolyte liquid as an additive. The negative electrode has a covering substance formed on the surface of the negative electrode and/or the negative electrode activator by decomposing the whole or a part of the additive by charging the lithium ion secondary battery once or more. In the formula, M denotes transition metal, an element of III, IV, or V group of the periodic table, A<SP>a+</SP>denotes a metal ion, proton, or onium ion, a denotes 1 to 3, b denotes 1 to 3, p denotes b/a, m denotes 1 to 4, n denotes 1 to 8, and q denotes 0 or 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a lithium ion secondary battery using insertion / extraction of lithium ions.

  Conventionally, lithium ion secondary batteries that use lithium ion storage / release have high voltage and high energy density. Therefore, in the field of information equipment and communication equipment, mainly personal information terminals such as personal computers and mobile phones. Practical use has progressed and it has become widely popular. In other fields, the development of electric vehicles is urgently required due to environmental problems and resource issues, and the use of lithium ion secondary batteries as power sources for electric vehicles is being studied.

A lithium ion secondary battery has a positive electrode, a negative electrode, and a non-aqueous electrolyte that moves lithium ions between the positive electrode and the negative electrode as main components.
As the negative electrode of the lithium ion secondary battery, for example, one using Li metal, Li alloy or the like as the negative electrode active material has been used. However, a lithium ion secondary battery using Li metal, Li alloy, or the like as the negative electrode active material is likely to generate dendritic precipitates (dendrites) composed of Li by repeatedly performing charge and discharge. For this reason, repeated charge / discharge could reduce the charge / discharge capacity or cause an internal short circuit due to dendrite growth.

Accordingly, lithium ion secondary batteries using a carbon material such as graphite as a negative electrode active material have been developed (see Patent Document 1 and Patent Document 2).
As described above, in a lithium ion secondary battery using a carbon material as the negative electrode active material, lithium ions are inserted into and desorbed from the layered structure of the carbon material, and thus the above-described problems are unlikely to occur.

  However, in the lithium ion secondary battery using a carbon material as the negative electrode active material as described above, when lithium ions enter the carbon layer during charging, carbon and the electrolyte cause a side reaction, and the negative electrode is highly charged. There was a problem of forming a resistive film. In particular, the formation of a film is likely to occur in a high temperature environment of about 60 ° C., and there is a problem that the internal resistance increases with repeated charging and discharging, and the output deteriorates.

Japanese Examined Patent Publication No. 62-23433 JP-A-5-307957

  The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a lithium ion secondary battery having high output and excellent charge / discharge cycle characteristics at high temperature and a method for producing the same.

｛但し，Ｍは，遷移金属，周期律表のIII族，IV族，又はV族元素，Ａ^a+は，金属イオン，プロトン，又はオニウムイオン，ａは１〜３，ｂは１〜３，ｐはｂ／ａ，ｍは１〜４，ｎは１〜８，ｑは０又は１をそれぞれ表し，Ｒ¹は，Ｃ₁〜Ｃ₁₀のアルキレン，Ｃ₁〜Ｃ₁₀のハロゲン化アルキレン，Ｃ₆〜Ｃ₂₀のアリーレン，又はＣ₆〜Ｃ₂₀のハロゲン化アリーレン（これらのアルキレン及びアリーレンはその構造中に置換基，ヘテロ原子を持ってもよく，またｍ個存在するＲ¹はそれぞれが結合してもよい。），Ｒ²は，ハロゲン，Ｃ₁〜Ｃ₁₀のアルキル，Ｃ₁〜Ｃ₁₀のハロゲン化アルキル，Ｃ₆〜Ｃ₂₀のアリール，Ｃ₆〜Ｃ₂₀のハロゲン化アリール，又はＸ³Ｒ³（これらのアルキル及びアリールはその構造中に置換基，ヘテロ原子を持ってもよく，またｎ個存在するＲ²はそれぞれが結合して環を形成してもよい。），Ｘ¹，Ｘ²，Ｘ³は，Ｏ，Ｓ，又はＮＲ⁴，Ｒ³，Ｒ⁴は，それぞれが独立で，水素，Ｃ₁〜Ｃ₁₀のアルキル，Ｃ₁〜Ｃ₁₀のハロゲン化アルキル，Ｃ₆〜Ｃ₂₀のアリール，Ｃ₆〜Ｃ₂₀のハロゲン化アリールをそれぞれ示す（これらのアルキル及びアリールはその構造中に置換基，ヘテロ原子を持ってもよく，また複数個存在するＲ³，Ｒ⁴はそれぞれが結合して環を形成してもよい。）。｝ According to a first invention, a positive electrode containing an oxide or polyanionic compound containing lithium and a transition metal as a main component of a positive electrode active material, a negative electrode containing a carbon material as a negative electrode active material, and an electrolyte in an organic solvent In a lithium ion secondary battery having a non-aqueous electrolyte dissolved therein,
In the non-aqueous electrolyte, a compound represented by the following general formula (1) is added as an additive,
The negative electrode is charged with the lithium ion secondary battery at least once to decompose all or part of the additive to form a coating on the surface of the negative electrode and / or the negative electrode active material. The lithium ion secondary battery is characterized in that (Claim 1).

{Where M is a transition metal, group III, IV or V element of the periodic table, A ^{a +} is a metal ion, proton or onium ion, a is 1 to 3, b is 1 to 3, p Is b / a, m is 1 to 4, n is 1 to 8, q is 0 or 1, R ¹ is C _{1 to} C ₁₀ alkylene, C _{1 to} C ₁₀ halogenated alkylene, C ₆ ~ C ₂₀ arylene or C ₆ -C ₂₀ halogenated arylene (These alkylenes and arylenes may have a substituent or a heteroatom in the structure, and m R ^{1 s} are bonded to each other. R ² may be halogen, C ₁ -C ₁₀ alkyl, C ₁ -C ₁₀ alkyl halide, C ₆ -C ₂₀ aryl, C ₆ -C ₂₀ aryl halide, or X ³ R ³ (the alkyl and aryl substituents in their structures, even with a heteroatom And the n R ² each may combine with each other to form a ring ^{present.), X 1, X 2} , X 3 is O, S, or NR ^4, R ^3, R ⁴ are each Are independent and represent hydrogen, C ₁ -C ₁₀ alkyl, C ₁ -C ₁₀ alkyl halide, C ₆ -C ₂₀ aryl, C ₆ -C ₂₀ aryl halide, respectively (these alkyl and aryl May have a substituent or a hetero atom in the structure, and a plurality of R ³ and R ⁴ may be bonded to each other to form a ring). }

Next, the function and effect of the first invention will be described.
In the lithium ion secondary battery, as described above, a carbon material is used for the negative electrode active material, and the compound represented by the above general formula is added as an additive together with the electrolyte in the non-aqueous electrolyte. . Further, the negative electrode may be charged at least once with the lithium ion secondary battery to decompose all or part of the additive to cover the surface of the negative electrode and / or the negative electrode active material. It has a coating formed.

The coating is low in resistance and stable, and covers the surface of the negative electrode and / or the negative electrode active material as described above. Therefore, in the lithium ion secondary battery, the insertion and extraction of lithium ions is performed smoothly, and the interface between the surface of the positive electrode or / and the negative electrode, the surface of the positive electrode active material or / and the negative electrode active material, and the electrolytic solution. The resistance is reduced and the initial output of the battery can be improved over a wide temperature range. In particular, since the resistance of the electrolytic solution increases at low temperatures, the improvement in output becomes more remarkable.
Moreover, the said covering can suppress formation of the highly resistant film on a negative electrode which occurs by decomposition | disassembly of the electrolyte in a non-aqueous electrolyte, etc. Therefore, an increase in internal resistance of the lithium ion secondary battery can be suppressed, and a decrease in cycle characteristics can be suppressed.
The coating may be formed not only on the surface of the negative electrode and / or the negative electrode active material, but also on the surface of the positive electrode or / and the positive electrode active material.

The formation of the high-resistance film is particularly likely to occur when the lithium ion secondary battery is used in a high temperature environment of, for example, 60 ° C., and deteriorates cycle characteristics.
In the lithium ion secondary battery according to the first aspect of the invention, since the coating can prevent the formation of a high-resistance film, excellent cycle characteristics can be obtained even when used in a high temperature environment of 60 ° C., for example. It can be demonstrated.
For example, when an electrolytic solution using LiPF ₆ that has already been put into practical use as a supporting salt is used, HF may be generated by hydrolysis. This HF may corrode a current collector made of, for example, Al under an environment of, for example, 60 ° C. and 4.1 V. As a result, the resistance increases and the battery characteristics may be deteriorated.
On the other hand, in the lithium ion secondary battery, since the compound represented by the above general formula is added to the non-aqueous electrolyte, HF is not generated even when hydrolyzed. Therefore, the lithium ion secondary battery can exhibit excellent durability.

  As described above, according to the first aspect of the present invention, it is possible to provide a lithium ion secondary battery having excellent charge / discharge cycle characteristics at high temperatures.

｛但し，Ｍは，遷移金属，周期律表のIII族，IV族，又はV族元素，Ａ^a+は，金属イオン，プロトン，又はオニウムイオン，ａは１〜３，ｂは１〜３，ｐはｂ／ａ，ｍは１〜４，ｎは１〜８，ｑは０又は１をそれぞれ表し，Ｒ¹は，Ｃ₁〜Ｃ₁₀のアルキレン，Ｃ₁〜Ｃ₁₀のハロゲン化アルキレン，Ｃ₆〜Ｃ₂₀のアリーレン，又はＣ₆〜Ｃ₂₀のハロゲン化アリーレン（これらのアルキレン及びアリーレンはその構造中に置換基，ヘテロ原子を持ってもよく，またｍ個存在するＲ¹はそれぞれが結合してもよい。），Ｒ²は，ハロゲン，Ｃ₁〜Ｃ₁₀のアルキル，Ｃ₁〜Ｃ₁₀のハロゲン化アルキル，Ｃ₆〜Ｃ₂₀のアリール，Ｃ₆〜Ｃ₂₀のハロゲン化アリール，又はＸ³Ｒ³（これらのアルキル及びアリールはその構造中に置換基，ヘテロ原子を持ってもよく，またｎ個存在するＲ²はそれぞれが結合して環を形成してもよい。），Ｘ¹，Ｘ²，Ｘ³は，Ｏ，Ｓ，又はＮＲ⁴，Ｒ³，Ｒ⁴は，それぞれが独立で，水素，Ｃ₁〜Ｃ₁₀のアルキル，Ｃ₁〜Ｃ₁₀のハロゲン化アルキル，Ｃ₆〜Ｃ₂₀のアリール，Ｃ₆〜Ｃ₂₀のハロゲン化アリールをそれぞれ示す（これらのアルキル及びアリールはその構造中に置換基，ヘテロ原子を持ってもよく，また複数個存在するＲ³，Ｒ⁴はそれぞれが結合して環を形成してもよい。）。｝ A second invention is a method of manufacturing a lithium ion secondary battery by arranging a positive electrode, a negative electrode, and a non-aqueous electrolyte in a battery case.
An electrolyte solution preparing step for preparing the non-aqueous electrolyte solution by dissolving an electrolyte and a compound represented by the following general formula (1) in an organic solvent;
The battery including the positive electrode containing an oxide or polyanionic compound containing lithium and a transition metal as a main component of a positive electrode active material, the negative electrode containing a carbon material as a negative electrode active material, and the non-aqueous electrolyte. An assembly process to be placed in the case;
A charging step in which the lithium ion secondary battery is charged at least once to decompose all or part of the additive to form a coating covering the surface of the negative electrode and / or the negative electrode active material; The present invention resides in a method for manufacturing a lithium ion secondary battery.

{Where M is a transition metal, group III, IV or V element of the periodic table, A ^{a +} is a metal ion, proton or onium ion, a is 1 to 3, b is 1 to 3, p Is b / a, m is 1 to 4, n is 1 to 8, q is 0 or 1, R ¹ is C _{1 to} C ₁₀ alkylene, C _{1 to} C ₁₀ halogenated alkylene, C ₆ ~ C ₂₀ arylene or C ₆ -C ₂₀ halogenated arylene (These alkylenes and arylenes may have a substituent or a heteroatom in the structure, and m R ^{1 s} are bonded to each other. R ² may be halogen, C ₁ -C ₁₀ alkyl, C ₁ -C ₁₀ alkyl halide, C ₆ -C ₂₀ aryl, C ₆ -C ₂₀ aryl halide, or X ³ R ³ (the alkyl and aryl substituents in their structures, even with a heteroatom And the n R ² each may combine with each other to form a ring ^{present.), X 1, X 2} , X 3 is O, S, or NR ^4, R ^3, R ⁴ are each Are independent and represent hydrogen, C ₁ -C ₁₀ alkyl, C ₁ -C ₁₀ alkyl halide, C ₆ -C ₂₀ aryl, C ₆ -C ₂₀ aryl halide, respectively (these alkyl and aryl May have a substituent or a hetero atom in the structure, and a plurality of R ³ and R ⁴ may be bonded to each other to form a ring). }

Next, the function and effect of the second invention will be described.
The method for manufacturing a lithium ion secondary battery includes the electrolytic solution preparation step, the assembly step, and the charging step. In the charging step, the lithium ion secondary battery is charged at least once, so that all or part of the additive is decomposed, and the coating is made of the negative electrode and / or the negative electrode active material. It is formed on the surface.

The coating thus produced has a low resistance and is stable, and covers the negative electrode or the negative electrode active material as described above. Therefore, in the lithium ion secondary battery, the insertion and extraction of lithium ions is performed smoothly, and the interface between the surface of the positive electrode or / and the negative electrode, the surface of the positive electrode active material or / and the negative electrode active material, and the electrolytic solution. The resistance is reduced and the initial output of the battery can be improved over a wide temperature range. In addition, the coating can suppress the formation of a high-resistance film on the negative electrode caused by decomposition of the electrolyte in the non-aqueous electrolyte. Therefore, it is possible to suppress an increase in internal resistance of the lithium ion secondary battery and suppress a decrease in cycle characteristics.
The coating may be formed not only on the surface of the negative electrode and / or the negative electrode active material, but also on the surface of the positive electrode or / and the positive electrode active material.

The formation of the high-resistance film is particularly likely to occur when the lithium ion secondary battery is used in a high temperature environment of, for example, 60 ° C., and deteriorates cycle characteristics.
In the lithium ion secondary battery obtained by the manufacturing method of the second invention, since the coating can suppress the formation of a high-resistance film, it can be used even in a high temperature environment of, for example, 60 ° C. , Excellent cycle characteristics can be demonstrated.

  Thus, according to the said 2nd invention, the manufacturing method of the lithium ion secondary battery excellent in the charge / discharge cycle characteristic in high output and high temperature can be provided.

In the lithium ion secondary battery of the first invention (invention 1), the compound represented by the general formula (1) is added to the non-aqueous electrolyte as the additive. In the production method of the second invention (invention 9), the compound represented by the general formula (1) is dissolved in an organic solvent as the additive in the electrolytic solution preparation step.
Specific examples of such additives are shown below.

In the above example, A ^{a +} in the general formula (1) is ^a lithium ion, but as a cation other than lithium ion, for example, sodium ion, potassium ion, magnesium ion, calcium ion, barium ion, cesium Ion, silver ion, zinc ion, copper ion, cobalt ion, iron ion, nickel ion, manganese ion, titanium ion, lead ion, chromium ion, vanadium ion, ruthenium ion, yttrium ion, lanthanoid ion, actinoid ion, tetrabutylammonium Ion, tetraethylammonium ion, tetramethylammonium ion, triethylmethylammonium ion, triethylammonium ion, pyridinium ion, imidazolium ion, proton Tetraethyl phosphonium ion, tetramethyl phosphonium ion, tetraphenylphosphonium ion, triphenylsulfonium ion, triethylsulfonium ion and the like.

Preferably, A ^{a +} in the general formula (1) is ^a lithium ion, a tetraalkylammonium ion, or a proton.

In the general formula (1), the valence a of A ^{a +} cation is 1-3. When a is larger than 3, the crystal lattice energy of the additive increases, so that it becomes difficult to dissolve in the organic solvent. Therefore, most preferably a = 1. Such cations A ^{a +} include lithium ions, tetraalkylammonium ions, and protons.
Similarly, the valence b of the anion is 1 to 3, and b = 1 is most preferable.
In addition, the constant p representing the ratio of cation to anion is inevitably determined by the valence ratio b / a of both.

The additive has an ionic metal complex structure, and the central M is selected from a transition metal, a group III, group IV, or group V element of the periodic table.
Preferably, M in the general formula (1) is Al, B, V, Ti, Si, Zr, Ge, Sn, Cu, Y, Zn, Ga, Nb, Ta, Bi, P, As, Sc, It may be either Hf or Sb (claims 3 and 11).
In this case, the additive can be easily synthesized.

  More preferably, M in the general formula (1) is Al, B, or P. In this case, in addition to facilitating the synthesis of the additive, it is possible to obtain effects that the toxicity of the additive is reduced and the manufacturing cost is reduced.

  Next, the ligand part of the additive (ionic metal complex) will be described. Hereinafter, in the above general formula (1), an organic or inorganic part bonded to M is referred to as a ligand.

R ¹ in the general formula (1) is selected from C _{1 to} C ₁₀ alkylene, C _{1 to} C ₁₀ halogenated alkylene, C _{6 to} C ₂₀ arylene, or C _{6 to} C ₂₀ halogenated arylene. It consists of things. These alkylene and arylene may have a substituent or a hetero atom in the structure. Specifically, instead of hydrogen on alkylene and arylene, halogen, chain or cyclic alkyl group, aryl group, alkenyl group alkoxy group, aryloxy group, sulfonyl group, amino group, cyano group, carbonyl group, acyl group , An amide group, a hydroxyl group, and a structure in which nitrogen, sulfur, or oxygen is introduced in place of carbon on alkylene and arylene.
Further, when a plurality of R ¹ are present (when q = 1, m = 2 to 4), each may be bonded, and examples thereof include a ligand such as ethylenediaminetetraacetic acid.

R ² is selected from halogen, C ₁ -C ₁₀ alkyl, C ₁ -C ₁₀ alkyl halide, C ₆ -C ₂₀ aryl, C ₆ -C ₂₀ aryl halide, or X ³ R ³ It consists of things. Similarly to R ¹ , alkyl and aryl may have a substituent or a heteroatom in the structure, and when there are a plurality of R ² (when n = 2 to 8), each R ² is They may combine to form a ring.
Preferably, R ² is preferably an electron-withdrawing group, particularly fluorine. In this case, the solubility and dissociation degree of the additive can be improved, and the ion conductivity can be improved accordingly. Furthermore, in this case, the oxidation resistance is improved, thereby preventing the occurrence of side reactions.

X ¹ , X ² , and X ³ are each independently O, S, or NR ⁴ , and the ligand is bonded to M through these heteroatoms. Here, it is not impossible to combine other than O, S, and N, but it becomes very complicated in synthesis. As a feature of the compound represented by the general formula (1), there is binding to M by X ¹ and X ² in the same in the ligand, these ligands form a M and chelate structure . The constant q in this ligand is 0 or 1. When q = 0, the chelate ring becomes a five-membered ring, and the complex structure of the additive is stabilized. Therefore, in this case, it is possible to prevent the additive from causing a side reaction other than the formation of the coating.

R ³ and R ⁴ are each independently hydrogen, C ₁ -C ₁₀ alkyl, C ₁ -C ₁₀ alkyl halide, C ₆ -C ₂₀ aryl, C ₆ -C ₂₀ aryl halide. Yes, these alkyls and aryls may have a substituent or a heteroatom in the structure, and when a plurality of R ³ and R ⁴ are present, they may combine to form a ring. .

The constants m and n related to the number of ligands described above are determined by the type of M at the center, where m is 1 to 4 and n is 1 to 8.
In ^{R 1, R 2, R 3} , R 4 described above, C ₁ -C ₁₀ indicates 1 to 10 carbon atoms, C ₆ -C ₂₀ is 6 to 20 carbon atoms Indicates.

As a method for synthesizing the additive, for example, in the case of a compound having the chemical formula shown in the following formula (2), LiBF ₄ and 2-fold moles of lithium alkoxide are reacted in a non-aqueous solvent, followed by There is a method of replacing an alkoxide bonded to boron with oxalic acid by adding an acid.

Next, in the first aspect of the invention, the lithium ion secondary battery decomposes all or part of the additive by charging the lithium ion secondary battery at least once, and the negative electrode or / And a coating formed by coating the surface of the negative electrode active material.
In the second aspect of the invention, by charging the lithium ion secondary battery at least once, all or part of the additive is decomposed and the surface of the negative electrode and / or the negative electrode active material is decomposed. To form a coating for charging (charging step).

  The coating can be detected by, for example, X-ray photoelectron spectroscopy (XPS) or IR analysis.

  Next, in the first and second inventions, the lithium ion secondary battery includes a positive electrode and a negative electrode, a separator sandwiched between the positive electrode and the negative electrode, and a lithium ion between the positive electrode and the negative electrode. The non-aqueous electrolyte etc. that move can be configured as a main component.

  For example, the positive electrode is made by mixing a conductive material and a binder with the above positive electrode active material and adding a suitable solvent to form a paste-like positive electrode mixture on the surface of a metal foil current collector such as aluminum or stainless steel. It can be applied and dried, and compressed to increase the electrode density as necessary.

  The positive electrode active material is mainly composed of an oxide or polyanionic compound containing lithium and a transition metal.

Examples of the oxide containing lithium and the transition metal M include, for example, LiMO ₂ having a layered rock salt structure, LiM ₂ O ₄ having a spinel structure, and these Li or transition metal M with other metal elements. Some have been partially replaced.

Examples of the polyanionic compound containing lithium and the transition metal M include Li ₃ M ₂ (SO ₄ ) ₃ , Li ₃ M ₂ (WO ₄ ) ₃ , Li ₃ M ₂ (MoO ₄ ) ₃ , In addition, there are olivine-structured phosphorus oxides such as LiMPO ₄ , and other examples include Li ₃ M ₂ (PO ₄ ) ₃ .

Moreover, it is preferable that the said positive electrode active material contains any 1 or more types chosen from Ni, Co, Mn, Fe, and Ti as the said transition metal M (Claim 7 and Claim 14).
In this case, the effect that the potential and charge / discharge capacity of the lithium ion secondary battery are increased can be obtained.

Moreover, the oxide and polyanionic compound which are the main components of the positive electrode active material may contain, for example, Al, Mg and the like in addition to the lithium and the transition metal.
In this case, the effect that the charge / discharge capacity of the lithium ion secondary battery is further improved can be obtained.

Specific examples of oxides and polyanionic compounds containing Al and Mg include, for example, Li (Ni, Co, Al, Mg) O ₂ having a layered rock salt structure.

  Further, the conductive material is for ensuring the electrical conductivity of the positive electrode, and for example, a material obtained by mixing one or more of carbon material powders such as carbon black, acetylene black and graphite is used. Can do.

The binder serves to bind the active material particles and the conductive material particles. For example, a fluorine-containing resin such as polytetrafluoroethylene, polyvinylidene fluoride, or fluororubber, or a thermoplastic resin such as polypropylene or polyethylene. Etc. can be used.
For example, an organic solvent such as N-methyl-2-pyrrolidone can be used as a solvent for dispersing the active material, the conductive material, and the binder.

  Next, the negative electrode is prepared by mixing a binder with the carbon material, which is the negative electrode active material, and applying a suitable solvent to form a paste of the negative electrode mixture on the surface of a metal foil current collector such as copper. It can be dried and then formed by pressing. Similarly to the positive electrode, a fluorine-containing resin such as polyvinylidene fluoride can be used as the binder to be mixed with the negative electrode active material, and an organic solvent such as N-methyl-2-pyrrolidone can be used as the solvent.

  Examples of the carbon material of the negative electrode active material include natural or artificial graphite, mesocarbon microbeads (MCMB), mesophase pitch-based carbon fibers and mixed materials thereof, vapor-grown carbonized fibers, and organic compound fired bodies such as phenol resins. And powdery bodies such as coke.

The carbon material as the negative electrode active material preferably has a specific surface area of 0.8 to ⁵ m ² / g (Claim 5 and Claim 12).
In this case, the additive is decomposed, and it becomes easy to form a low-resistance and stable coating on the negative electrode and / or the negative electrode active material, thereby further suppressing an increase in the internal resistance of the lithium ion secondary battery. it can.
When the specific surface area exceeds 5 m ² / g, the coating is not sufficiently formed, and the increase in the internal resistance may not be sufficiently suppressed. On the other hand, if the specific surface area is less than 0.8 m ² / g, the internal resistance may increase even in the initial state.

  The separator to be narrowly attached to the positive electrode and the negative electrode separates the positive electrode and the negative electrode and holds the non-aqueous electrolyte. For example, a thin microporous film such as polyethylene or polypropylene can be used.

  Next, as the non-aqueous electrolyte, a solution obtained by dissolving the additive and the electrolyte in an organic solvent can be used.

The electrolyte may be A ^{a +} (PF ₆ ⁻ ) _a , A ^{a +} (ClO ₄ ⁻ ) _a , A ^{a +} (BF ₄ ⁻ ) _a , A ^{a +} (AsF ₆ ⁻ ) _a , or A ^{a +} (SbF ₆ ⁻ ) _a , (However, A ^{a +} is a metal ion, proton, or onium ion, and a is 1 to 3).

  In this case, it is possible to obtain an effect that the ion conductivity is relatively high and electrochemically stable. In this case, the lithium ion secondary battery can be manufactured at a low cost.

Further, the additive is made of compound A ^{a +} is Li ⁺ in the general formula (1), the _{electrolyte, LiPF 6, LiClO 4, LiBF} 4, LiAsF 6, or one selected from LiSbF ₆ The above is preferable (claims 4 and 11).
In this case, it is possible to obtain an effect that the ion conductivity is relatively high and electrochemically stable, and further, an effect that the lithium ion of the additive can also contribute to the charge / discharge reaction of the battery. be able to. In this case, the lithium ion secondary battery can be produced at low cost.

  As the organic solvent for dissolving the additive and the electrolyte, an aprotic organic solvent can be used. As such an organic solvent, for example, a mixed solvent composed of one or more selected from cyclic carbonate, chain carbonate, cyclic ester, cyclic ether, chain ether, and the like can be used.

  Here, examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate. Examples of the chain carbonate include dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. Examples of the cyclic ester carbonate include gamma butyrolactone and gamma valerolactone. Examples of the cyclic ether include tetrahydrofuran and 2-methyltetrahydrofuran. Examples of the chain ether include dimethoxyethane and ethylene glycol dimethyl ether. As the organic solvent, any one of these may be used alone, or two or more kinds may be mixed and used.

The additive is preferably added so that the molar ratio with the electrolyte is electrolyte: additive = 99.9-50: 0.1-50 (claims 6 and 13). .
When the molar ratio of the additive to the electrolyte is less than 0.1, that is, when the molar ratio of the electrolyte to the additive exceeds 99.9, the coating is not sufficiently formed, and the charge / discharge cycle There is a possibility that the effect of restoring the capacity when repeating the above and the effect of suppressing the increase rate of the internal resistance (IV resistance) are not sufficiently exhibited. On the other hand, when the molar ratio of the additive to the electrolyte exceeds 50, that is, when the molar ratio of the electrolyte to the additive is less than 50, the effect of suppressing an increase in internal resistance may not be sufficiently exhibited. In addition, the initial output may be reduced.

When it is desired to further improve the capacity recovery rate of the lithium ion secondary battery, it is particularly preferable that electrolyte: additive = 95-50: 5-50. More preferably, electrolyte: additive = 80-50: 20-50 is good.
Moreover, when it is desired to further suppress the increase in IV resistance of the lithium ion secondary battery, it is particularly preferable that electrolyte: additive = 99.9-50: 0.1-50. More preferably, electrolyte: additive = 95-60: 5-40.
Moreover, when it is desired to improve the initial output of the lithium ion secondary battery, it is particularly preferable that electrolyte: additive = 99.9 to 90: 0.1 to 10. More preferably, electrolyte: additive = 99 to 93: 1 to 7 is preferable.
Therefore, the mixing ratio of the electrolyte and the additive can be appropriately determined according to the battery characteristics required depending on the use of the lithium ion secondary battery.

(Example 1)
Next, an embodiment of the present invention will be described with reference to FIGS.
As shown in FIGS. 1 and 2, the lithium ion secondary battery 1 of this example includes a positive electrode 2 containing an oxide or polyanionic compound containing lithium and a transition metal as a main component of the positive electrode active material 25, carbon It has the negative electrode 3 which contains a material as the negative electrode active material 35, and the nonaqueous electrolyte solution formed by melt | dissolving the electrolyte 51 in an organic solvent.
The non-aqueous electrolyte is added with the electrolyte 51 and a compound represented by the following formula (2) as an additive 53.

  Further, the negative electrode 3 is charged with the lithium ion secondary battery 1 at least once, so that all or a part of the additive 53 is decomposed to cover the surfaces of the negative electrode and the negative electrode active material. 55 is formed.

Hereinafter, the lithium ion secondary battery 1 of this example will be described in detail with reference to FIGS.
As shown in FIG. 1, the lithium ion secondary battery 1 of this example includes a positive electrode 2, a negative electrode 3, a separator 4, a gasket 59, a battery case 6, and the like. The battery case 6 is an 18650 type cylindrical battery case, and includes a cap 63 and an outer can 65. In the battery case 6, a sheet-like positive electrode 2 and a negative electrode 3 are arranged in a wound state together with a separator 4 sandwiched between the positive electrode 2 and the negative electrode 3.
A gasket 59 is provided inside the cap 63 of the battery case 6, and a non-aqueous electrolyte is injected into the battery case 6.

As shown in FIGS. 1 and 2, the positive electrode 2 contains LiNi _0.80 Co _0.15 Al _0.05 O ₂ as the positive electrode active material 25, and the negative electrode 3 contains a carbon material as the negative electrode active material 35.
The positive electrode 2 and the negative electrode 3 are respectively provided with a positive electrode current collecting lead 23 and a negative electrode current collecting lead 33 by welding. The positive electrode current collecting lead 23 is connected by welding to a positive electrode current collecting tab 235 disposed on the cap 63 side. Further, the negative electrode current collecting lead 33 is connected to the negative electrode current collecting tab 335 disposed on the bottom of the outer can 65 by welding.

In addition, the nonaqueous electrolytic solution is obtained by dissolving LiPF ₆ as the electrolyte 51 in an organic solvent in which ethylene carbonate and diethyl carbonate are mixed at a volume ratio of 30:70 as shown in FIG. Has been injected into. In addition, a compound represented by the above formula (2) (hereinafter appropriately referred to as LBFO) is added as an additive 53 to the non-aqueous electrolyte. And at least one part of an additive decomposes | disassembles by charging a lithium ion secondary battery, and becomes the coating 55 which coat | covers the said negative electrode and negative electrode active material.

Next, the manufacturing method of the lithium ion secondary battery of this example will be described with reference to FIGS.
As shown in FIG. 1, the manufacturing method of this example is a method of manufacturing the lithium ion secondary battery 1 by arranging the positive electrode 2, the negative electrode 3, and the nonaqueous electrolytic solution in the battery case 6.
In the manufacturing method of this example, an electrolyte solution preparation process, an assembly process, and a charging process described later are performed.

  In the electrolytic solution preparation step, an electrolyte and a compound represented by the following formula (2) are dissolved in an organic solvent to prepare the nonaqueous electrolytic solution.

Further, in the assembly process, as shown in FIGS. 1 and 2, the positive electrode 2 containing an oxide containing lithium and a transition metal as a main component of the positive electrode active material 25 and the carbon material as a negative electrode active material 35 are contained. The negative electrode 3 and the non-aqueous electrolyte are disposed in the battery case 6.
In the charging step, as shown in FIG. 2, the lithium ion secondary battery 1 is charged at least once, so that all or part of the additive 53 is decomposed, and the negative electrode 3 and / or the negative electrode active material. A coating 55 covering the surface of 35 is formed.

Hereinafter, the manufacturing method of the lithium ion secondary battery of this example will be described in detail.
First, the non-aqueous electrolyte was prepared as follows.
That is, first, LiPF ₆ as an electrolyte was added to an organic solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio of 3: 7 so that the final concentration was 1M. Furthermore, the compound (LBFO) represented by the above formula (2) was added as an additive to produce a non-aqueous electrolyte (electrolyte preparation step). The additive amount was such that the molar ratio with the electrolyte was electrolyte: additive = 90: 10.

Next, a positive electrode and a negative electrode were prepared as follows.
In the positive electrode, first, LiNi _0.80 Co _0.15 Al _0.05 O ₂ is prepared as a positive electrode active material, the positive electrode active material, carbon black as a conductive material, and polyvinylidene fluoride as a binder are mixed, and a dispersing agent is prepared. An appropriate amount of n-methyl-2-pyrrolidone was added and kneaded to obtain a paste material for a positive electrode. The mixing ratio of the positive electrode active material, the conductive material, and the binder was a weight ratio of positive electrode active material: conductive material: binder = 85: 10: 5.

Next, the positive electrode paste material obtained as described above was applied to both sides of an aluminum foil current collector having a thickness of 20 μm and dried. Thereafter, the sheet was densified with a roll press and cut into a shape having a width of 52 mm and a length of 450 mm to produce a sheet-like positive electrode. The amount of positive electrode active material deposited was about 7 mg / cm ² per side.

On the other hand, in the negative electrode, MCMB (manufactured by Osaka Gas Chemical Co., Ltd., graphitized mesocarbon microbeads, specific surface area 1.0 m ² / g) is prepared as the negative electrode active material. Polyvinylidene fluoride was mixed, an appropriate amount of n-methyl-2-pyrrolidone was added as a dispersant, and kneaded to obtain a paste material for a negative electrode. The mixing ratio of the negative electrode active material and the binder was a weight ratio of negative electrode active material: binder = 95: 5.

Next, the negative electrode paste material obtained as described above was applied to both sides of a 10 μm thick copper foil current collector and dried. Thereafter, the sheet was densified with a roll press and cut into a shape having a width of 54 mm and a length of 500 mm to produce a sheet-like negative electrode. In addition, the adhesion amount of the negative electrode active material was about 5 mg / cm ² per side.

  Next, as shown in FIG. 1, a positive electrode current collecting lead 23 and a negative electrode current collecting lead 33 were welded to the sheet-like positive electrode 2 and negative electrode 3 obtained as described above, respectively. The positive electrode 2 and the negative electrode 3 were wound together with a polyethylene separator 4 having a width of 56 mm and a thickness of 25 μm to produce a spiral wound electrode.

  Subsequently, the wound electrode was inserted into an 18650-type cylindrical battery case 6 including an outer can 65 and a cap 63. At this time, the positive electrode current collecting lead 25 is connected to the positive electrode current collecting tab 235 disposed on the cap 63 side of the battery case 6 by welding, and the negative electrode current collecting lead is disposed on the negative electrode current collecting tab 335 disposed on the bottom of the outer can 6. 33 was connected by welding.

  Next, the battery case 6 was impregnated with the non-aqueous electrolyte prepared as described above. A gasket 59 is disposed inside the cap 63, and the cap 63 is disposed in the opening of the outer can 65. Subsequently, the battery case 6 was sealed by caulking the cap 63 to produce the lithium ion secondary battery 1 (assembly process).

Next, the lithium ion secondary battery 1 was charged at least once. As a result, as shown in FIG. 2, all or part of the additive 53 was decomposed, and the negative electrode 3 and the negative electrode active material 35 were coated to form a covering 55. (Charging process)
The lithium ion secondary battery 1 thus obtained is designated as sample E1.

Further, in this example, lithium ion secondary batteries were produced by changing the type of the negative electrode active material.
That is, in the lithium ion secondary battery of the sample E1, as described above, MCMB was used as the negative electrode active material. Instead of MCMB, MCF (manufactured by Petka Materials Co., Ltd., graphitized mesophase pitch system) was used. Carbon fiber, specific surface area S = 1.1 m ² / g), BMCF (manufactured by Petka Materials Co., Ltd., B doped graphitized mesophase pitch-based carbon fiber, specific surface area S = 1.3 m ² / g), GMCF (stock) Company Petka Materials, graphitized mesophase pitch-based carbon fiber-based mixture, specific surface area S = 1.2.8 m ² / g), and VGCF (manufactured by Showa Denko KK, vapor-phase carbonized fiber, specific surface area S = 25 m ² / g) was used to fabricate lithium ion secondary batteries, which were designated as samples E2 to E5, respectively. Samples E2 to E5 are the same as the sample E1 except that the type of the negative electrode active material is changed. The types of negative electrode active materials of Samples E1 to E5 are shown in Table 1 described later.

(Comparative example)
This example is an example in which a comparative lithium ion secondary battery was manufactured in order to clarify the excellent characteristics of the lithium ion secondary batteries (sample E1 to sample E5) manufactured in Example 1.
First, a lithium ion secondary battery not containing the additive and not having the coating was produced.

Specifically, first, LiPF ₆ as an electrolyte is added to an organic solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed at a volume ratio of 3: 7 so as to have a final concentration of 1M. An aqueous electrolyte was prepared.
Using this non-aqueous electrolyte, five other types of comparative lithium ion secondary batteries were produced in the same manner as in Example 1. These are designated as Samples C1 to C5.

Samples C1 to C5 contain different carbon materials as negative electrode active materials, and Samples C1 to C5 contain negative electrode active materials similar to Samples E1 to E5, respectively. The types of negative electrode active materials in Samples C1 to C5 are shown in Table 1 described later.
As is known from Table 1 described later, Samples C1 to C5 are each Sample E1 except that the additive is not added to the non-aqueous electrolyte and the coating is not included. To E5.

In this example, a comparative lithium ion secondary battery containing a lithium compound instead of a carbon material as a negative electrode active material was produced.
Specifically, Li ₄ Ti ₅ O ₁₂ is first prepared as a negative electrode active material, and the negative electrode active material, carbon black as a conductive material, and polyvinylidene fluoride as a binder are mixed and dispersed. An appropriate amount of n-methyl-2-pyrrolidone was added as a material and kneaded to obtain a paste material for a negative electrode. The mixing ratio of the negative electrode active material, the conductive material, and the binder was a weight ratio of negative electrode active material: conductive material: binder = 85: 10: 5.

Next, the negative electrode paste material obtained as described above was applied to both surfaces of a 20 μm thick aluminum foil current collector and dried. Thereafter, the sheet was densified with a roll press and cut into a shape having a width of 54 mm and a length of 500 mm to produce a sheet-like negative electrode. In addition, the adhesion amount of the negative electrode active material was about 8 mg / cm ² per side.

Next, in the same manner as in Example 1, a positive electrode containing LiNi _0.80 Co _0.15 Al _0.05 O ₂ as a positive electrode active material, and a nonaqueous electrolytic solution containing LiPF ₆ as an electrolyte and LBFO as an additive were prepared. In the same manner as in Example 1, a lithium ion secondary battery was prepared. This was designated as Sample C6.
Sample C6 is the same as Samples E1 to E5 except that Li ₄ Ti ₅ O ₁₂ was used as the negative electrode active material.

In the lithium ion secondary battery of the sample C6, an additive is added to the nonaqueous electrolyte solution. In this example, the additive is not added, and the other is the same as the sample C6. A secondary battery was produced. This was designated as Sample C7.
That is, the lithium ion secondary battery of Sample C7 is the same as Samples E1 to E5, except that Li ₄ Ti ₅ O ₁₂ is used as the negative electrode active material and no additive is added to the non-aqueous electrolyte. Is.
Table 1 to be described later shows the types of negative electrode active materials and the presence or absence of additives in Samples C6 and C7.

(Experimental example)
Next, for the lithium ion secondary batteries of Sample E1 to Sample E5 and Sample C1 to Sample C7 prepared in Example 1 and the comparative example, 500 charge / discharge cycle tests were performed, and the capacity recovery rate at that time and The resistance increase rate was examined.

"Charge / discharge cycle test"
The charge / discharge cycle test was conducted at a constant current of ² mA / cm ² under a temperature condition of 60 ° C., which is regarded as the upper limit of the actual use temperature range of the battery. For samples E1 to E5 and samples C1 to C5, the charge upper limit voltage is 4.1 V and the discharge lower limit voltage is 3.0 V, and for samples C6 and C7, the charge upper limit voltage is 2.7 V and the discharge lower limit voltage is 1 The total charge / discharge cycle was 500 cycles at .6V. The difference in the end voltage of charge / discharge between Samples E1 to E5 and Samples C1 to C5 and Sample C6 and Sample C7 is due to the difference in charge / discharge potential of the negative electrode active material.

"Evaluation of capacity recovery rate"
The capacity recovery rate was measured before and after the charge / discharge cycle test at 20 ° C. with a current density of 100 mA. The discharge capacity before the charge / discharge cycle test was discharge capacity A, and the discharge capacity after the charge / discharge cycle test was discharged. When the capacity was B, it was calculated by the following formula (a).
Capacity recovery rate (%) = discharge capacity B / discharge capacity A × 100 (a)

"Evaluation of resistance increase rate"
First, for each sample before and after the charge / discharge cycle test, the battery capacity was adjusted to 50% (SOC = 50%). Thereafter, currents of 0.5A, 1A, 2A, 3A, and 5A were passed, the battery voltage after 10 seconds was measured, and the IV resistance was obtained from the slope by linearly approximating the passed current and voltage. The rate of increase in resistance was calculated by the following equation (b), where IV resistance before the charge / discharge cycle test was resistance A and IV resistance after the charge / discharge cycle test was resistance B.
Resistance increase rate (%) = (resistance B−resistance A) / resistance A × 100 (b)

Table 1 shows the results of the capacity recovery rate and the resistance increase rate in Sample E1 to Sample E5 and Sample C1 to Sample C7.
In addition to the above results, Table 1 shows the characteristics of each sample, the types of positive electrode active material and negative electrode active material, and the presence or absence of additives.

  As can be seen from Table 1, when sample E1 to sample E5 and sample C1 to sample C5 were respectively compared, sample E1 had a higher IV resistance after the cycle test than sample C1 having the same negative electrode active material. . Similarly, in the samples E2 to E5, the increase in IV resistance was suppressed more than in the samples C2 to C5 having the same negative electrode active material.

In particular, the increase in IV resistance is significantly suppressed in the samples E1 to E4 compared to the samples C1 to C4, respectively. In the sample E5, the reason why the effect of suppressing the increase in the IV resistance is small is that the specific surface area of the VGCF used as the negative electrode active material is large. This is probably because the film could not be formed uniformly on the surface of the film. From this, it is considered that the negative electrode active material preferably has a specific surface area of 20 m ² / g or less, more preferably 5 m ² / g or less.
Samples E1 to E5 showed the same excellent capacity recovery rate as Samples C1 to C5, respectively.

  On the other hand, when comparing the sample C6 using the lithium compound as the negative electrode active material and the sample C7, the sample C6 having the non-aqueous electrolyte to which the additive is added has an increased IV resistance than the C7 to which the additive is not added. The rate was large, and the suppression effect like the said samples E1-E5 was not able to be acquired.

  This shows that it is necessary to use a carbon material as the negative electrode active material. This is considered to be because, in carbon materials, the charge / discharge potential is sufficiently lower than the potential for decomposition of the above additives and the formation of the coating, so that a good coating is sufficiently formed. .

  As described above, the lithium ion secondary batteries of Sample E1 to Sample E5 were excellent in charge / discharge cycle characteristics at high temperatures.

(Example 2)
In this example, a lithium ion secondary battery was produced by changing the amount of the additive, and the capacity recovery rate and the IV resistance increase rate after the cycle test of the lithium ion secondary battery were examined.
First, in the same manner as in Example 1, an organic solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed at a volume ratio of 3: 7 is mixed with LiPF ₆ as an electrolyte so that the final concentration becomes 1M. added. Furthermore, LBFO was added as an additive to produce a non-aqueous electrolyte. At this time, in this example, the additive is added so that the molar ratio with the electrolyte is electrolyte: additive = 80: 20, or electrolyte: additive = 50: 50, and two types of non-aqueous electrolytes are used. Was made.

Next, two types of lithium ion secondary batteries were produced using the two types of non-aqueous electrolytes (sample E6 and sample E7).
Sample E6 and Sample E7 were prepared in the same manner as Sample E1 of Example 1 except that the mixing ratio of the electrolyte and additive in the non-aqueous electrolyte was changed. That is, Sample E6 and Sample E7 contain LiNi _0.80 Co _0.15 Al _0.05 O ₂ as the positive electrode active material and MCMB as the negative electrode active material, as in Sample E1.

Subsequently, for the lithium ion secondary batteries of Sample E6 and Sample E7, the capacity recovery rate and the IV resistance increase rate after the cycle test were examined in the same manner as in the experimental example. The results are shown in Table 2.
For comparison, Table 2 also shows the results of the sample C1 to which no additive is added and the results of the sample E1 to which the additive is added so that electrolyte: additive = 90: 10. It is.

  As is known from Table 2, the sample E1, sample E6 and sample E7 in which the additive is added to the non-aqueous electrolyte are increased in IV resistance after the cycle test compared to the sample C1 in which the additive is not added. The rate was small and excellent. On the other hand, the capacity recovery rate is similar in each sample. That is, it can be seen that by adding the above-mentioned additive, the increase in IV resistance after the cycle test can be suppressed without affecting the capacity recovery rate.

Here, FIG. 3 shows voltage-charge capacity curves at the time of initial charge of the sample E1, the sample E6, the sample E7, and the sample C1. In FIG. 3, the horizontal axis indicates the charge capacity (mAh · g ⁻¹ ), and the vertical axis indicates the voltage (V).
As can be seen from FIG. 3, in sample samples E1, E6, and E7 in which an additive is added to the nonaqueous electrolyte together with the electrolyte, the additive is considered to decompose to form a coating on the negative electrode. Is observed near 1.8V.
On the other hand, in the sample C1 to which no additive is added, there is no capacity component near 1.8V as described above, and it is considered that no coating is formed on the negative electrode.

  Further, as can be seen from Table 2, it can be seen that when the amount of the additive is not more than the same amount as the electrolyte in terms of molar ratio, the increase in IV resistance can be suppressed remarkably. Although not shown in the table, when the above additive is added in a molar ratio more than the electrolyte, the effect of suppressing the increase in IV resistance after the cycle test cannot be obtained sufficiently, and the additive is added. It became the same thing as IV resistance increase rate of the lithium ion secondary battery (sample C1) which has not added the agent.

(Example 3)
In this example, a lithium ion secondary battery was manufactured using an additive different from that in Example 1 and Example 2, and the initial output at low temperature was evaluated.
In the lithium ion secondary battery of this example, a compound represented by the following formula (6) (LiPF ₂ (C ₂ O ₄ ) ₂ , hereinafter referred to as “LPFO” as appropriate) is added as an additive in the non-aqueous electrolyte. It has been added.

Like the sample E1 of Example 1, the lithium ion secondary battery of this example contains LiNi _0.80 Co _0.15 Al _0.05 O ₂ as the positive electrode active material and MCMB that is artificial graphite as the negative electrode active material. . Other configurations are the same as the sample E1 of Example 1 except that the type and amount of the additive are changed.

Next, the manufacturing method of the lithium ion secondary battery of this example will be described.
First, an electrolyte solution preparation step is performed as follows to produce a non-aqueous electrolyte solution.
That is, first, an electrolyte solution is prepared by adding LiPF ₆ as an electrolyte to an organic solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed at a volume ratio of 3: 7 to a final concentration of 1M. did. In addition, the final concentration of the compound (LPFO) represented by the above formula (6) is 1M in an organic solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed at a volume ratio of 3: 7. In addition to the above, an additive solution was prepared.

Next, the electrolyte solution and the additive solution were mixed to prepare a non-aqueous electrolyte. At this time, the electrolyte (LiPF ₆ ) in the electrolyte solution and the additive (LiPF ₂ (C ₂ O ₄ ) ₂ ) in the additive solution are in an additive (mol) / (electrolyte) molar ratio. (Mole) + Additive (Mole)) = 0.03.
That is, in the non-aqueous electrolyte, the molar ratio of the electrolyte to the additive is electrolyte: additive = 97: 3.

Next, an assembly process was performed in the same manner as in Example 1 to produce a lithium ion secondary battery. In this example, LiNi _0.80 Co _0.15 Al _0.05 O ₂ was used as the positive electrode active material as in the sample E1 of Example 1, and MCMB as in the sample E1 was used as the negative electrode active material.

Next, the charging process was performed in the same manner as in Example 1 to charge the lithium ion secondary battery at least once. As a result, all or part of the additive was decomposed, and the negative electrode and the negative electrode active material were coated to form a coating.
The lithium ion secondary battery thus obtained is designated as sample E8.
That is, sample E8 contains LPFO as an additive, and contains the electrolyte and the additive in a nonaqueous electrolytic solution in a ratio of electrolyte: additive = 97: 3. This is the same as the sample E1.

  Further, in this example, five types of lithium ion secondary batteries having different mixing ratios of the electrolyte and the additive in the non-aqueous electrolyte are prepared in the same manner as the sample E8, and the samples E8 are respectively prepared. Sample E9 to sample E13. The lithium ion secondary batteries of Sample E9 to Sample E13 were produced in the same manner as Sample E8 except that the mixing ratio of the electrolyte and additive in the non-aqueous electrolyte was changed.

Specifically, in the sample E9, the electrolyte (LiPF ₆ ) and the additive (LPFO) are in a molar ratio of additive (mol) / (electrolyte (mol) + additive (mol)) = 0.05. Thus, the electrolyte solution and the additive solution were mixed to prepare a nonaqueous electrolyte solution, and a lithium ion secondary battery (sample E9) was prepared using the nonaqueous electrolyte solution.
That is, in the non-aqueous electrolyte of sample E9, the molar ratio of electrolyte to additive is electrolyte: additive = 95: 5.

In sample E10, the electrolyte (LiPF ₆ ) and the additive (LPFO) have a molar ratio of additive (mol) / (electrolyte (mol) + additive (mol)) = 0.07. Then, the electrolyte solution and the additive solution were mixed to prepare a non-aqueous electrolyte, and a lithium ion secondary battery (sample E10) was prepared using the non-aqueous electrolyte.
That is, in the non-aqueous electrolyte of sample E10, the molar ratio of electrolyte to additive is electrolyte: additive = 93: 7.

In the sample E11, the electrolyte (LiPF ₆ ) and the additive (LPFO) have a molar ratio of additive (mol) / (electrolyte (mol) + additive (mol)) = 0.1. Then, the electrolyte solution and the additive solution were mixed to prepare a non-aqueous electrolyte, and a lithium ion secondary battery (sample E11) was prepared using the non-aqueous electrolyte.
That is, in the nonaqueous electrolytic solution of sample E11, the molar ratio of the electrolyte and the additive is electrolyte: additive = 90: 10.

In sample E12, the electrolyte (LiPF ₆ ) and the additive (LPFO) have a molar ratio of additive (mol) / (electrolyte (mol) + additive (mol)) = 0.15. In addition, the electrolyte solution and the additive solution were mixed to prepare a non-aqueous electrolyte, and a lithium ion secondary battery (sample E12) was prepared using the non-aqueous electrolyte.
That is, in the non-aqueous electrolyte of sample E12, the molar ratio of electrolyte to additive is electrolyte: additive = 85: 15.

In sample E13, the electrolyte (LiPF ₆ ) and the additive (LPFO) have a molar ratio of additive (mol) / (electrolyte (mol) + additive (mol)) = 0.20. In addition, the electrolyte solution and the additive solution were mixed to prepare a non-aqueous electrolyte, and a lithium ion secondary battery (sample E13) was prepared using the non-aqueous electrolyte.
That is, in the non-aqueous electrolyte of sample E13, the molar ratio of electrolyte to additive is electrolyte: additive = 80: 20.

  Next, in this example, the initial output at low temperature (−30 ° C.) was measured for the samples E8 to E13. Further, the initial output was measured in the same manner for the sample C1 produced in the comparative example for comparison. The measurement was performed by the following initial output test.

"Initial output test"
Each sample (Sample E8 to Sample E13 and Sample C1) was kept at −30 ° C. After that, the battery capacity is adjusted to 50% (SOC = 50%), and 0.12A, 0.4A, 1.2A, 2.4A, 4.8A current is applied and the battery voltage after 10 seconds is measured. The output value was calculated. The measurement was performed by preparing three samples similar to each sample, and obtaining the average. The output value of each sample was expressed as a relative value when the value of the sample C1 was 1, that is, a value normalized based on the value of the sample C1.
The results are shown in Table 3.

  As is known from Table 3, at a low temperature of −30 ° C., the sample E9 showed the highest initial output value, and the output was 1.38 times larger than that of the sample C1. Sample E8 and Sample E10 also showed a large output of 1.22 times that of Sample C1, and Sample E11 showed the same output as Sample C1. Samples E12 and E13 showed a smaller output than sample C1.

  That is, as is known from Table 3, there is an optimum ratio of the electrolyte and additive for improving the output at low temperature, and in this example, 0 <{additive (mol) / (electrolyte ( It can be seen that a good initial output can be obtained if the mixing ratio is such that (mol) + additive (mol)) <0.1. Further, in view of balance with durability, it is more preferable that 0.03 ≦ {additive (mol) / (electrolyte (mol) + additive (mol)) ≦≦ 0.07.

  Thus, it can be seen that the output performance at low temperature is remarkably improved by adding an appropriate amount of the additive (LPFO). This is thought to be because at least part of the additive (LPFO) is decomposed during the initial charge, and a stable film is formed on the surface of the positive electrode or / and the negative electrode, or the positive electrode active material or / and the negative electrode active material. It is done. This film activates the interface between the active material and the electrolytic solution (the interface between the electrode and the electrolytic solution), so that lithium ions can be smoothly inserted and desorbed. As a result, the resistance at the interface is reduced. It is thought that the initial output of the battery could be improved.

BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which shows the structure of the lithium ion secondary battery concerning Example 1. FIG. The elements on larger scale of the positive electrode of the lithium ion secondary battery concerning Example 1, and a negative electrode. Explanatory drawing which shows the voltage-charge capacity curve at the time of the first charge of the lithium ion secondary battery of Example E1, Sample E6, Sample E7, and Sample C1 concerning Example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lithium ion secondary battery 2 Positive electrode 25 Positive electrode active material 3 Negative electrode 35 Negative electrode active material 51 Electrolyte 53 Additive 55 Covering material

Claims (14)

A non-aqueous solution comprising a positive electrode containing an oxide or polyanionic compound containing lithium and a transition metal as a main component of a positive electrode active material, a negative electrode containing a carbon material as a negative electrode active material, and an electrolyte dissolved in an organic solvent In a lithium ion secondary battery having an electrolyte solution,
In the non-aqueous electrolyte, a compound represented by the following general formula (1) is added as an additive,
The negative electrode is charged with the lithium ion secondary battery at least once to decompose all or part of the additive to form a coating on the surface of the negative electrode and / or the negative electrode active material. A lithium ion secondary battery characterized by comprising:

{Where M is a transition metal, group III, IV or V element of the periodic table, A ^{a +} is a metal ion, proton or onium ion, a is 1 to 3, b is 1 to 3, p Is b / a, m is 1 to 4, n is 1 to 8, q is 0 or 1, R ¹ is C _{1 to} C ₁₀ alkylene, C _{1 to} C ₁₀ halogenated alkylene, C ₆ ~ C ₂₀ arylene or C ₆ -C ₂₀ halogenated arylene (These alkylenes and arylenes may have a substituent or a heteroatom in the structure, and m R ^{1 s} are bonded to each other. R ² may be halogen, C ₁ -C ₁₀ alkyl, C ₁ -C ₁₀ alkyl halide, C ₆ -C ₂₀ aryl, C ₆ -C ₂₀ aryl halide, or X ³ R ³ (the alkyl and aryl substituents in their structures, even with a heteroatom And the n R ² each may combine with each other to form a ring ^{present.), X 1, X 2} , X 3 is O, S, or NR ^4, R ^3, R ⁴ are each Are independent and represent hydrogen, C ₁ -C ₁₀ alkyl, C ₁ -C ₁₀ alkyl halide, C ₆ -C ₂₀ aryl, C ₆ -C ₂₀ aryl halide, respectively (these alkyl and aryl May have a substituent or a hetero atom in the structure, and a plurality of R ³ and R ⁴ may be bonded to each other to form a ring). }   In claim 1, M in the general formula (1) is Al, B, V, Ti, Si, Zr, Ge, Sn, Cu, Y, Zn, Ga, Nb, Ta, Bi, P, As, A lithium ion secondary battery, which is any one of Sc, Hf, and Sb. 3. The electrolyte according to claim 1, wherein the electrolyte includes A ^{a +} (PF ₆ ⁻ ) _a , A ^{a +} (ClO ₄ ⁻ ) _a , A ^{a +} (BF ₄ ⁻ ) _a , A ^{a +} (AsF ₆ ⁻ ) _a , or A ^{a +.} A lithium ion secondary battery characterized by being one or more selected from (SbF ₆ ⁻ ) _a , wherein A ^{a +} is a metal ion, proton, or onium ion, and a is 1 to 3. _4. The additive according to claim 1, wherein the additive is a compound in which A ^{a +} in the general formula (1) is Li ⁺ , and the electrolyte is LiPF ₆ , LiClO ₄ , LiBF ₄ , LiAsF. ₆ or a lithium ion secondary battery characterized by being at least one selected from LiSbF ₆ . 5. The lithium ion secondary battery according to claim 1, wherein the carbon material as the negative electrode active material has a specific surface area of 0.8 to ⁵ m ² / g.   The additive according to any one of claims 1 to 5, wherein the additive is added so that a molar ratio with the electrolyte is electrolyte: additive = 99.9-50: 0.1-50. A featured lithium ion secondary battery.   7. The lithium ion secondary material according to claim 1, wherein the positive electrode active material contains at least one selected from Ni, Co, Mn, Fe, and Ti as the transition metal. Next battery. In a method of manufacturing a lithium ion secondary battery by arranging a positive electrode, a negative electrode, and a non-aqueous electrolyte in a battery case,
An electrolyte solution preparing step for preparing the non-aqueous electrolyte solution by dissolving an electrolyte and a compound represented by the following general formula (1) in an organic solvent;
The battery including the positive electrode containing an oxide or polyanionic compound containing lithium and a transition metal as a main component of a positive electrode active material, the negative electrode containing a carbon material as a negative electrode active material, and the non-aqueous electrolyte. An assembly process to be placed in the case;
A charging step in which the lithium ion secondary battery is charged at least once to decompose all or part of the additive to form a coating covering the surface of the negative electrode and / or the negative electrode active material; A method for producing a lithium ion secondary battery, comprising:

{Where M is a transition metal, group III, IV or V element of the periodic table, A ^{a +} is a metal ion, proton or onium ion, a is 1 to 3, b is 1 to 3, p Is b / a, m is 1 to 4, n is 1 to 8, q is 0 or 1, R ¹ is C _{1 to} C ₁₀ alkylene, C _{1 to} C ₁₀ halogenated alkylene, C ₆ ~ C ₂₀ arylene or C ₆ -C ₂₀ halogenated arylene (These alkylenes and arylenes may have a substituent or a heteroatom in the structure, and m R ^{1 s} are bonded to each other. R ² may be halogen, C ₁ -C ₁₀ alkyl, C ₁ -C ₁₀ alkyl halide, C ₆ -C ₂₀ aryl, C ₆ -C ₂₀ aryl halide, or X ³ R ³ (the alkyl and aryl substituents in their structures, even with a heteroatom And the n R ² each may combine with each other to form a ring ^{present.), X 1, X 2} , X 3 is O, S, or NR ^4, R ^3, R ⁴ are each Are independent and represent hydrogen, C ₁ -C ₁₀ alkyl, C ₁ -C ₁₀ alkyl halide, C ₆ -C ₂₀ aryl, C ₆ -C ₂₀ aryl halide, respectively (these alkyl and aryl May have a substituent or a hetero atom in the structure, and a plurality of R ³ and R ⁴ may be bonded to each other to form a ring). }   In Claim 8, M in the said General formula (1) is Al, B, V, Ti, Si, Zr, Ge, Sn, Cu, Y, Zn, Ga, Nb, Ta, Bi, P, As, A method of manufacturing a lithium ion secondary battery, wherein the method is any one of Sc, Hf, and Sb. 10. The electrolyte according to claim 8, wherein the electrolyte is A ^{a +} (PF ₆ ⁻ ) _a , A ^{a +} (ClO ₄ ⁻ ) _a , A ^{a +} (BF ₄ ⁻ ) _a , A ^{a +} (AsF ₆ ⁻ ) _a , or A ^{a +.} (SbF ₆ ⁻ ) _a , wherein A ^{a +} is a metal ion, proton, or onium ion, and a is 1 to 3; Method. The additive according to any one of claims 8 to 10, wherein the additive is composed of a compound in which A ^{a +} in the general formula (1) is Li ⁺ , and the electrolyte is LiPF ₆ , LiClO ₄ , LiBF ₄ , LiAsF. ₆ or a method selected from the group consisting of LiSbF ₆ and a method for producing a lithium ion secondary battery. The method of manufacturing a lithium ion secondary battery according to any one of claims 8 to 11, wherein the carbon material as the negative electrode active material has a specific surface area of 0.8 to ⁵ m ² / g. .   The additive according to any one of claims 8 to 12, wherein the additive is added so that a molar ratio with the electrolyte is electrolyte: additive = 99.9-50: 0.1-50. A method for producing a lithium ion secondary battery.   The lithium ion secondary material according to any one of claims 8 to 13, wherein the positive electrode active material contains at least one selected from Ni, Co, Mn, Fe, and Ti as the transition metal. A method for manufacturing a secondary battery.

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