JP7303084B2 - lithium ion battery - Google Patents

Description

The present disclosure relates to lithium ion batteries.

Japanese Patent Laying-Open No. 2018-152230 (Patent Document 1) discloses a three-dimensional electrode structure.

JP 2018-152230 A

FIG. 1 is a conceptual diagram showing a conventional two-dimensional electrode structure.
Conventionally, lithium-ion batteries (which may be abbreviated as "batteries" hereinafter) have a two-dimensional electrode structure. In the two-dimensional electrode structure, each of positive electrode 210 and negative electrode 220 is sheet-like. A separator 230 is arranged between the positive electrode 210 and the negative electrode 220 . A positive electrode 210 , a negative electrode 220 and a separator 230 constitute a unit cell 200 . The unit cell 200 can also be sheet-like. For example, the strip-shaped unit cell 200 may be spirally wound. For example, multiple unit cells 200 may be stacked. In the unit cell 200, the positive electrode 210 and the negative electrode 220 are planarly adjacent to each other.

One of the problems in the two-dimensional electrode structure is the trade-off between capacity and output. For example, in a two-dimensional electrode structure, in order to increase the capacity, it is required to increase the thickness of the components (the positive electrode 210 and the negative electrode 220) that contribute to the capacity. On the other hand, components that do not contribute to capacity (for example, separator 230, collector foil, etc.) are required to be relatively thin. As a result, ion conduction in the thickness direction of the electrode can be the rate-determining step of the charge-discharge reaction. If the rate-determining step of the charge-discharge reaction becomes ionic conduction, the output may decrease.

Various three-dimensional electrode structures have been proposed to overcome the challenges in two-dimensional electrode structures. A three-dimensional electrode structure indicates an electrode structure in which a positive electrode and a negative electrode are three-dimensionally adjacent to each other. By sterically adjoining the positive electrode and the negative electrode, the electrode facing area (reaction area) per unit volume can be increased. Therefore, it is expected that the trade-off between capacity and output will be resolved.

FIG. 2 is a conceptual diagram showing the three-dimensional electrode structure of the present disclosure.
For example, it is conceivable to form a three-dimensional electrode structure with rod-shaped unit cells 100 . The structural basis (core) in the unit cell 100 is the metal wire 101 . A negative electrode 120 , a separator 130 and a positive electrode 110 are laminated on the surface of the metal wire 101 . A three-dimensional electrode structure can be formed by bundling a plurality of unit cells 100 .

However, in the three-dimensional electrode structure, stress due to expansion and contraction of the electrodes is likely to accumulate. The electrode expands and contracts with charging and discharging. In a two-dimensional electrode structure, stress can be relieved in the thickness direction of the electrode (the z-axis direction in FIG. 1). On the other hand, in the three-dimensional electrode structure, since the entire periphery of the electrode is constrained, it is considered that there is little escape of stress. Therefore, repeated charging and discharging can accumulate stress in the structure. Stress build-up can strain the three-dimensional electrode structure and increase resistance.

An object of the present disclosure is to reduce the increase in resistance associated with repeated charging and discharging in a battery having a three-dimensional electrode structure.

The technical configuration and effects of the present disclosure will be described below. However, the mechanism of action of this disclosure includes speculation. The correctness of the mechanism of action should not limit the scope of the claims.

A lithium ion battery includes a plurality of unit cells. Each of the plurality of unit cells is rod-shaped. A plurality of unit cells are bound together. Each of the plurality of unit cells are arranged parallel to each other. Each of the multiple unit cells includes a metal wire, a negative electrode, a separator, and a positive electrode. The negative electrode covers the surface of the metal wire. The separator covers the surface of the negative electrode. The positive electrode covers the surface of the separator. The negative electrode contains titanium oxide.

A battery in the present disclosure has a three-dimensional electrode structure. Titanium oxide functions as a negative electrode active material. Titanium oxide tends to undergo a small change in volume during charging and discharging. When the negative electrode contains titanium oxide, it is expected that the stress due to the volume change of the electrode is reduced. Furthermore, it is also expected that the adhesion between the negative electrode and the separator is improved.

At least part of the titanium oxide is reduced by charging and discharging. Titanium oxide in its reduced state exhibits electronic conductivity. Titanium oxides in a reduced state may include Ti ⁴⁺ and Ti ³⁺ . Ti ³⁺ is expected to improve the adhesion between the metal wire and the negative electrode.

A metal wire functions as a negative electrode current collector. A metal wire in the three-dimensional electrode structure of the present disclosure corresponds to a metal foil in a two-dimensional electrode structure. The negative electrode covers the metal wire. Electrons are believed to move in a substantially one-dimensional direction in a metal wire. Since electrons move in one-dimensional direction, it is expected that unevenness in charge/discharge reaction is reduced.

Due to the synergy of the above actions, it is expected that the increase in resistance accompanying repeated charging and discharging will be reduced in a battery having a three-dimensional electrode structure.

FIG. 1 is a conceptual diagram showing a conventional two-dimensional electrode structure. FIG. 2 is a conceptual diagram showing the three-dimensional electrode structure of the present disclosure. 3 is a cross-sectional view parallel to the xy plane of FIG. 2. FIG. FIG. 4 is a conceptual diagram showing the configuration of a unit cell.

Embodiments of the present disclosure (also referred to herein as “present embodiments”) are described below. However, the following description does not limit the scope of the claims.

<Lithium-ion battery>
A “lithium ion battery” of the present embodiment indicates a secondary battery in which lithium (Li) ions are used as carriers (charge carriers) that move between electrodes.

The battery of this embodiment can be applied to any application. Batteries may be used, for example, in mobile terminals, portable devices, stationary power storage devices, electric vehicles, hybrid vehicles, and the like.

The battery of this embodiment can have any shape. The battery may be, for example, coin-shaped, button-shaped, sheet-shaped (paper-shaped), pin-shaped, gum-shaped, pouch-shaped, cylindrical, rectangular, or the like.

Batteries can have any capacity and size. The battery may be, for example, a miniature battery for portable equipment. The battery may be, for example, a large battery for automobiles.

《Unit cell》
As shown in FIG. 2, the battery in this embodiment includes a plurality of unit cells 100. As shown in FIG. A plurality of unit cells 100 may be housed in a predetermined case (not shown), for example. An electrolytic solution may be contained in the case together with the plurality of unit cells 100 . The case may be, for example, a container made of metal, a pouch made of aluminum (Al) laminated film, or the like.

A plurality of unit cells 100 are bound together. "Binding" in the present embodiment indicates that the objects are bundled together. A plurality of unit cells 100 may be integrally and inseparably configured by binding.

Each unit cell 100 is rod-shaped. The “rod-like” in this embodiment means a shape extending in one predetermined direction and having a length to diameter ratio of 2 or more.

Each of the plurality of unit cells 100 are arranged parallel to each other. "Parallel" in this embodiment does not mean only geometrically perfect parallelism. Parallel in this embodiment also includes a relationship considered to be substantially parallel.

3 is a cross-sectional view parallel to the xy plane of FIG. 2. FIG.
The cross section shown in FIG. 3 is a cross section perpendicular to the axial direction (z-axis direction) of the unit cell 100 . In this embodiment, the unit cell 100 may have, for example, a hexagonal cross section. For example, by compressing the plurality of unit cells 100 by isostatic pressing, each of the unit cells 100 can be filled to have a hexagonal cross section. The hexagonal cross section of the unit cell 100 is expected to increase the packing density of the unit cell 100 . Higher packing densities are expected to improve capacity and output. However, the hexagonal shape is an example. A cross-section of the unit cell 100 can have any shape. The cross section of the unit cell 100 may be, for example, circular or rectangular.

FIG. 4 is a conceptual diagram showing the configuration of a unit cell.
Each of the multiple unit cells 100 includes a metal wire 101 , a negative electrode 120 , a separator 130 and a positive electrode 110 .

《Metal wire》
Metal wire 101 is the basis of the structure in unit cell 100 . A negative electrode 120 , a separator 130 and a positive electrode 110 are formed in this order on the surface of the metal wire 101 . Metal wire 101 may have a diameter of, for example, 20 μm to 100 μm. Metal wire 101 may, for example, have a diameter of 20 μm to 50 μm. A reduction in increase in resistance is expected when the metal wire 101 has a diameter of 50 μm or less.

Metal wire 101 exhibits electronic conductivity. Metal wire 101 functions as a negative electrode current collector. The metal wire 101 contains metal. The metal wire 101 may consist essentially of metal. Metal wire 101 may contain one kind of metal alone. The metal wire 101 may be, for example, copper (Cu) wire, Al wire, or the like. Since the metal wire 101 is an Al wire, it is expected that the increase in resistance will be reduced.

Metal wire 101 may contain two or more metals. For example, the metal wire 101 may have a core-sheath structure. The core and the sheath may contain different metals. Metal wire 101 may contain, for example, at least one selected from the group consisting of Cu and Al.

《Negative electrode》
The negative electrode 120 covers the surface of the metal wire 101 . At one end in the z-axis direction in FIG. 2, the negative electrode 120 is electrically connected to the negative electrode collector 152 . The negative collector member 152 is electrically connected to a negative terminal (not shown). The negative electrode current collecting member 152 may be, for example, a porous metal sheet, a thin metal plate, or the like.

The negative electrode 120 is cylindrical. The inner diameter of negative electrode 120 may be substantially equal to the diameter of metal wire 101 . The negative electrode 120 may have an outer diameter of, for example, 100 μm to 300 μm. The negative electrode 120 may have an outer diameter of, for example, 100 μm to 200 μm. The negative electrode 120 may have an outer diameter of, for example, 200 μm to 300 μm.

Negative electrode 120 includes a negative electrode active material. The negative electrode 120 may consist essentially of the negative electrode active material. The negative electrode 120 may further contain, for example, a conductive material, a binder, etc. in addition to the negative electrode active material. The negative electrode 120 may be composed of, for example, 0.1% to 10% by mass of a conductive material, 0.1% to 10% by mass of a binder, and the balance of the negative electrode active material. The conductive material can contain any component. The conductive material may contain, for example, carbon black. The binder can contain optional ingredients. The binder may contain, for example, polyvinylidene fluoride (PVdF).

The negative electrode active material contains titanium oxide. That is, the negative electrode 120 contains titanium oxide. The negative electrode active material may consist essentially of titanium oxide.

"Titanium oxide" in the present embodiment indicates a compound containing at least titanium (Ti) and oxygen (O). Titanium oxide may be, for example, titanium oxide (TiO ₂ ). Titanium oxide can have any crystal structure. Titanium oxide may have, for example, an anatase structure, a rutile structure, or the like.

Titanium oxide may further contain Li and the like in addition to Ti and O, for example. That is, the titanium oxide may be a lithium-titanium composite oxide or the like. A lithium-titanium composite oxide can have any crystal structure. The lithium-titanium composite oxide may have, for example, a ramsdellite structure, a spinel structure, or the like. Lithium-titanium composite oxides with a spinel structure tend to undergo a small volume change (change in lattice constant) during charging and discharging. The use of the lithium-titanium composite oxide with a spinel structure is expected to reduce the increase in resistance.

Lithium-titanium composite oxide, for example, the following formula (1):
Li4 _{+xTi5O12 ( 1} )
may be represented by x in formula (1) satisfies the relationship of -1≤x≤3.

Li _4+x Ti ₅ O ₁₂ represented by the above formula (1) has a spinel structure. In one embodiment, Li _4+x Ti ₅ O ₁₂ has a negligible change in lattice constant with charging and discharging. Lithium-titanium composite oxide WHEREIN: A part of Li and Ti may be substituted by the other element. Other elements (substitution elements) may be, for example, Al, magnesium (Mg), and the like. Partial replacement may reduce the change in lattice constant due to charging and discharging.

The negative electrode active material includes, for example, TiO ₂ (anatase structure), TiO ₂ (rutile structure), Li ₂ Ti ₃ O ₇ (ramsdellite structure), and Li ₄ Ti ₅ O ₁₂ (spinel structure). It may contain at least one selected from the group consisting of:

《Separator》
A separator 130 covers the surface of the negative electrode 120 . A separator 130 separates the positive electrode 110 from the negative electrode 120 . Separator 130 does not have electronic conductivity.

Separator 130 is cylindrical. Separator 130 may have a thickness of, for example, 5 μm to 30 μm. The thickness of separator 130 indicates the difference between the outer diameter of separator 130 and the inner diameter of separator 130 . Separator 130 may have a thickness of, for example, 5 μm to 20 μm. Separator 130 may have a thickness of, for example, 12 μm to 20 μm.

Separator 130 may include, for example, particle aggregates. The particle aggregates may contain, for example, insulating particles, binders, and the like. The insulating particles may be, for example, alumina, polyethylene, and the like.

The separator 130 may contain a polymer that swells with the electrolyte. That is, the separator 130 and the electrolyte may form a gel polymer electrolyte. Gel polymer electrolytes can be flexible. Gel polymer electrolytes are expected to absorb and distribute stress.

As the polymer that swells with the electrolytic solution, for example, a copolymer of vinylidene fluoride (VdF) and hexafluoropropylene (HFP) can be considered. A copolymer of VdF and HFP is also denoted as "PVdF-HFP". That is, the separator 130 may contain PVdF-HFP.

《Electrolyte》
Each of the plurality of unit cells 100 is impregnated with an electrolytic solution (not shown). The electrolyte may contain any component as long as it contains Li ions. The electrolytic solution may contain, for example, a supporting salt, a solvent, and the like. The supporting salt may contain, for example, LiPF ₆ or the like. Solvents may include, for example, ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and the like. The electrolytic solution may further contain various additives (for example, film-forming agents, etc.).

《Positive electrode》
The positive electrode 110 covers the surface of the separator 130 . At one end in the z-axis direction in FIG. 2 , the positive electrode 110 is electrically connected to a positive current collector 151 . The positive collector member 151 is electrically connected to a positive terminal (not shown). The positive electrode current collecting member 151 may be, for example, a porous metal sheet, a thin metal plate, or the like.

The positive electrode 110 faces the negative electrode 120 with the separator 130 interposed therebetween. The positive electrode 110 included in one unit cell 100 may be integrated with the positive electrode 110 included in another adjacent unit cell 100 .

The positive electrode 110 includes a positive electrode active material. The positive electrode 110 may consist essentially of the positive electrode active material. The positive electrode 110 may further contain, for example, a conductive material, a binder, etc. in addition to the positive electrode active material. The positive electrode 110 may be composed of, for example, 0.1% to 10% by mass of a conductive material, 0.1% to 10% by mass of a binder, and the balance of the positive electrode active material. The conductive material can contain any component. The conductive material may contain, for example, carbon black. The binder can contain optional ingredients. The binder may include, for example, PVdF or the like.

The positive electrode active material can contain any component. The positive electrode active material is, for example, a group consisting of lithium-nickel-cobalt-manganese composite oxide, lithium-nickel-cobalt-aluminum composite oxide, lithium-manganese composite oxide, lithium-cobalt composite oxide, lithium-nickel composite oxide, and lithium iron phosphate. At least one more selected may be included.

Lithium-nickel-cobalt-manganese composite oxide, for example, the following formula (2):
_{Li1 +zNi1 - xyCoxMnyO2} ( ₂ )
may be represented by x, y and z in formula (2) satisfy the relationships 0<z<0.10, 0<x≦0.3, 0<y<0.5, 1−x>2y.

_The lithium _- nickel _{- cobalt} - _{manganese composite} oxide is selected _{from the group} consisting _{of Li1.05Ni0.5Co0.2Mn0.3O2} , _{Li1.05Ni0.4Co0.3Mn0.3O2} , and _{Li1.05Ni0.8Co0.15Mn0.05O2 ,} for example _. may contain at least one of

Embodiments of the present disclosure (also referred to herein as "the embodiments") are described below. However, the following description does not limit the scope of the claims.

<Production of test battery>
Samples 1 through 22 were prepared as follows.

<<Sample 1>>
(Synthesis of titanium oxide)
A raw material powder was prepared by mixing lithium carbonate (Li ₂ CO ₃ ) powder and TiO ₂ (anatase structure) powder. Raw material powder was placed in an electric furnace. The inside of the furnace was an argon (Ar) atmosphere. The set temperature in the furnace was 800°C. Li ₄ Ti ₅ O ₁₂ was synthesized by heating the raw material powder in the furnace.

(Formation of negative electrode)
The following materials were prepared.
Negative electrode active material: Li ₄ Ti ₅ O ₁₂ (synthesized above)
Conductive material: Carbon black Binder: PVdF
Solvent: N-methyl-2-pyrrolidone (NMP)
Metal wire: Cu wire (diameter 50 μm)

A negative electrode slurry was prepared by mixing a negative electrode active material, a conductive material, a binder and a solvent. The mixing ratio of non-volatile components (also referred to as “solid content”) was “negative electrode active material/conductive material/binder=90/7/3 (mass ratio)”. A negative electrode was formed by applying the negative electrode slurry to the surface of the Cu wire and drying it.

(Formation of separator)
A polymer solution was prepared. The solvent in the polymer solution was NMP and the solute was PVdF-HFP. A polymer solution was applied to the surface of the negative electrode. After applying the polymer solution, the polymer solution was dried with a heat gun. This formed a separator. The separator had a thickness of 12 μm.

(Formation of positive electrode)
The following materials were prepared.
Positive _{electrode active material : Li1.05Ni0.5Co0.2Mn0.3O2}
Conductive material: Carbon black Binder: PVdF
Solvent: NMP

A positive electrode slurry was prepared by mixing a positive electrode active material, a conductive material, a binder and a solvent. The mixing ratio of the non-volatile components was "positive electrode active material/conductive material/binder=90/7/3 (mass ratio)". The positive electrode slurry was applied to the surface of the separator and dried to form a positive electrode. A unit cell was thus formed.

(Unity)
Multiple unit cells were prepared. Multiple unit cells were bundled together. Bundles of unit cells were compressed by isostatic pressing. As a result, a plurality of unit cells were bundled.

(sealing)
After binding, lead tabs were connected to the positive and negative electrodes, respectively. A pouch made of Al laminated film was prepared. Multiple unit cells were placed in pouches. The pouch was filled with electrolyte. After injection of the electrolyte, the pouch was sealed with a heat sealer. The electrolytic solution had the following composition.

(Composition of electrolyte)
Support salt: LiPF ₆ (concentration 1 mol/L)
Solvent: EC/DMC/EMC = 3/4/3 (volume ratio)

As described above, a test battery was manufactured. A test battery according to sample 1 had a three-dimensional electrode structure shown in FIGS.

<<Sample 2>>
Similar to sample 1, a negative electrode slurry was prepared. Al foil was prepared. The Al foil had a thickness of 15 μm. The negative electrode raw fabric was formed by applying the negative electrode slurry to the surface of the Al foil and drying it. The negative electrode original fabric was compressed by roll pressing. After the compression, the negative electrode raw fabric was cut into a size of "27 mm width x 42 mm length". As described above, a sheet-like negative electrode was produced.

Similar to Sample 1, a positive electrode slurry was prepared. A positive electrode blank was formed by applying the positive electrode slurry to the surface of the Al foil and drying it. The positive electrode original sheet was compressed by roll pressing. After compression, the original positive electrode sheet was cut into a size of "25 mm width×40 mm length". As described above, a sheet-like positive electrode was produced.

Similar to Sample 1, a polymer solution was prepared. A glass plate was prepared. A polymer film composed of PVdF-HFP was formed by coating the surface of the glass plate with the polymer solution and drying it. The polymer membrane had a thickness of 12 μm. A polymer film was peeled off from the glass plate. As a result, a self-supporting polymer film was recovered.

A unit cell was formed by laminating the positive electrode, the negative electrode, and the polymer film such that the positive electrode and the negative electrode were opposed to each other with the polymer film interposed therebetween.

As with Sample 1, the unit cell and electrolyte were placed in a pouch, and the pouch was sealed. As described above, a test battery was manufactured. The test battery according to sample 2 had the two-dimensional electrode structure shown in FIG.

<<Sample 3 and Sample 4>>
As shown in Table 1 below, test batteries were manufactured in the same manner as Sample 1, except that the outer diameter of the negative electrode was changed.

<<Sample 5 to Sample 7>>
As shown in Table 1 below, test batteries were each manufactured in the same manner as Sample 1, except that the thickness of the separator was changed.

<<Sample 8 and Sample 9>>
As shown in Table 1 below, test batteries were each manufactured in the same manner as Sample 1, except that the diameter of the metal wire was changed.

<<Sample 10 and Sample 11>>
Li ₄ Ti ₅ O ₁₂ and TiO ₂ (rutile structure) were mixed in a predetermined molar ratio. A raw material powder was thus prepared. Raw material powder was placed in an electric furnace. The inside of the furnace was an Ar atmosphere. The set temperature in the furnace was 1000°C. Li ₂ Ti ₃ O ₇ was synthesized by heating the raw material powder in the furnace.

Similar to Sample 1 (three-dimensional electrode structure) and Sample 2 (two-dimensional electrode structure), except that Li ₂ Ti ₃ O ₇ is used as the negative electrode active material instead of Li ₄ Ti ₅ O ₁₂ . , test batteries were manufactured respectively.

<<Samples 12 and 13>>
Similar to Sample 1 (three-dimensional electrode structure) and Sample 2 (two-dimensional electrode structure), except that TiO ₂ (anatase structure) is used as the negative electrode active material instead of Li ₄ Ti ₅ O ₁₂ . , test batteries were manufactured respectively.

<<Sample 14 and Sample 15>>
_{Sample 1} (three _{- dimensional} electrode _{structure ) and Sample 2 (} Two-dimensional electrode structures), as well as test cells were fabricated respectively.

<<Sample 16 and Sample 17>>
Sample 1 (three _- dimensional _electrode structure) and _Sample 2 (three _{- dimensional} electrode structure ₎ , except that _{Li1.05Ni0.8Co0.15Mn0.05O2 is used} as the positive electrode _active material instead of Li1.05Ni0.5Co0.2Mn0.3O2. Two-dimensional electrode structures), as well as test cells were fabricated respectively.

<<Sample 18 and Sample 19>>
Test batteries were prepared in the same manner as Sample 1 (three-dimensional electrode structure) and Sample 2 (two-dimensional electrode structure), except that MoO ₂ was used as the negative electrode active material instead of Li ₄ Ti ₅ O ₁₂ . were manufactured respectively.

<<Sample 20 and Sample 21>>
Each test battery was manufactured in the same manner as Sample 1, except that the Al wire shown in Table 1 below was used as the metal wire.

<<Sample 22>>
A negative electrode slurry was prepared by mixing graphite, carboxymethylcellulose (CMC), styrene-butadiene rubber (SBR), and ion-exchanged water. The mixing ratio of non-volatile components was "graphite/CMC/SBR=98/1/1 (mass ratio)". A sample battery was manufactured in the same manner as in Sample 1, except that the negative electrode slurry was used to form the negative electrode. Graphite corresponds to a negative electrode active material. CMC and SBR correspond to binders.

<Evaluation>
Under a temperature environment of 25° C., three cycles of constant-current charging and discharging were performed at a current rate of 0.1C. "C" is the unit of current rate. At a current rate of 1C, the rated capacity of the battery is discharged in 1 hour.

After 3 cycles, the SOC (state of charge) of the battery was adjusted to 50%. After adjusting the SOC, the test cell was energized for 2 seconds with a current rate of 0.5C. The voltage was measured after 2 seconds. Similarly, at current rates of 1C, 2C, 4C and 6C, the voltage was measured 2 seconds after the start of energization. Measurement results were plotted on two-dimensional coordinates. The horizontal axis of the two-dimensional coordinates is current, and the vertical axis is voltage. The IV resistance was calculated from the slope of the approximate straight line in the two-dimensional coordinates. The IV resistance corresponds to the internal resistance of the battery.

After measurement of the IV resistance, 40 cycles of constant-current charging and discharging were performed at a current rate of 0.5 C in a temperature environment of 40°C. After 40 cycles, IV resistance was measured as above. The resistance increase rate was calculated by the following formula.

Resistance increase rate [%]={(R _cyc −R _ini )/R _ini }×100
In the formula, "R _ini " indicates the IV resistance before 40 cycles (initial).
"R _cyc " in the formula indicates the IV resistance after 40 cycles.

The resistance increase rate is shown in Table 1 below. In this example, the lower the rate of increase in resistance, the lower the increase in resistance due to repeated charging and discharging.

<Results>
In Table 1, for example, in the results of Samples 1 and 2, batteries having a three-dimensional electrode structure tend to exhibit a lower resistance increase rate than batteries having a two-dimensional electrode structure.

For example, in the results of Samples 1, 10, 12, 18, and 22, batteries in which the negative electrode contains titanium oxide tend to have a low resistance increase rate. This is probably because titanium oxide undergoes little change in volume during charging and discharging.

For example, in the results of Samples 1, 10, and 12, when the titanium oxide is Li ₄ Ti ₅ O ₁₂ , the resistance increase rate tends to be low.

For example, in the results of Samples 1, 8, 20, and 21, the resistance increase rate tends to be low when the metal wire is Al wire.

For example, in the results of Samples 1, 3 and 4, there is a tendency that a low resistance increase rate is maintained even when the outer diameter of the negative electrode varies within the range of 100 μm to 300 μm.

For example, the results of Samples 1, 8, and 9 tend to maintain a low resistance increase rate even when the diameter of the metal wire varies within the range of 20 μm to 100 μm.

For example, the results of Samples 1, 5 to 7 show a tendency to maintain a low resistance increase rate even when the thickness of the separator varies within the range of 5 μm to 30 μm.

For example, in _the results of Sample 1, Sample _{14 , and} Sample _{16 , Li1.05Ni0.5Co0.2Mn0.3O2 , Li1.05Ni0.4Co0.3Mn0.3O2, and Li1.05Ni0.8Co0.15Mn were used as the} positive electrode active material _. A low resistance increase rate tends to be maintained when either _0.05 O ₂ is used.

This embodiment and this example are illustrative in all respects. This embodiment and this example are not restrictive. The technical scope determined by the description of the claims includes all changes in the meaning of equivalents to the description of the claims, and all changes within the scope of equivalents to the description of the claims contain.

100,200 unit cell, 101 metal wire, 110,210 positive electrode, 120,220 negative electrode, 130,230 separator, 151 positive current collecting member, 152 negative current collecting member.

Claims (1)

containing multiple unit cells,
each of the plurality of unit cells is rod-shaped,
each of the plurality of unit cells has a hexagonal shape in a cross section orthogonal to the axial direction of the plurality of unit cells,
The plurality of unit cells are bound together,
Each of the plurality of unit cells are arranged parallel to each other,
each of the plurality of unit cells includes a metal wire, a negative electrode, a separator, and a positive electrode;
The negative electrode covers the surface of the metal wire,
The separator covers the surface of the negative electrode,
The positive electrode covers the surface of the separator,
the metal wire is an aluminum wire having a diameter of 20 μm to 50 μm;
the negative electrode comprises titanium oxide,
The titanium oxide has the formula (1):
Li4 ₊ xTi5O12 ( ₁ ) _{_}
is represented by
In the above formula (1), the relationship of -1 ≤ x ≤ 3 is satisfied,
lithium-ion battery.

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