JP2002313324A - Anode for use in lithium metal dispersed system secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery having high specific capacity and favorable cycling capacity and safely usable. SOLUTION: This secondary battery is manufactured to include a host material capable of adsorbing and desorbing lithium in an electrochemical system such as a carbonaceous material and an anode formed of lithium metal dispersed in this host material, and the newly manufactured anode is combined with a positive electrode containing an activator, a separator to separate the positive electrode and a negative electrode and an electrolyte to communicate the positive electrode with the negative electrode. This invention includes a method to manufacture the newly manufactured anode and a method to actuate the secondary battery including the anode of this invention.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery having a high specific capacity, and more particularly to a host material such as a carbonaceous material capable of adsorbing and desorbing lithium in an electrochemical system, and the host material. And a lithium metal dispersed in the anode.

[0002]

BACKGROUND OF THE INVENTION Lithium and lithium ion secondary batteries or accumulators have recently been used in applications such as cell phones, camcorders and laptop computers, and more recently in higher power applications such as electric vehicles and hybrid electric vehicles. Used in In these applications, the secondary battery has the largest possible specific capacity,
Preferably, high specific capacity is maintained on the next recharge and discharge cycle, providing safe operating conditions and good cycling capability.

[0003] There are various configurations of secondary batteries, and each configuration has a positive electrode (or a cathode), a negative electrode (or an anode), a separator for separating the cathode and the anode, and an electrical connection between the cathode and the anode. Includes a chemically communicating electrolyte. With respect to lithium secondary batteries, when the secondary battery is discharged, ie, used in its particular application, lithium ions are carried through the electrolyte from the anode to the cathode. During this process, electrons are collected from the anode and flow through an external circuit to the cathode. When the secondary battery is charged or recharged, lithium ions are carried from the cathode through the electrolyte to the anode.

[0004]

Conventionally, lithium secondary batteries have been developed using TiS ₂ , MoS ₂ , M
Non-lithiated compounds having a high specific capacity such as nO ₂ and V ₂ O ₅
ds). These cathode activators were combined with lithium metal anodes. When the secondary battery was discharged, lithium ions were carried from the lithium metal anode through the electrolyte to the cathode. Unfortunately, during cycling, lithium metal generated dendrites which eventually caused an unsafe condition in the battery. As a result, production of these types of secondary batteries was discontinued in the early 1990's, preferring lithium-ion batteries.

[0005] Lithium ion batteries generally use LiC as a cathode activator associated with a carbon-based anode.
An oxide of a lithium metal such as oO ₂ and LiNiO ₂ is used. In these batteries, the formation of lithium dendrites on the anode is avoided, thus making the batteries safer. However, the amount of lithium determines the capacity of the battery, and lithium is supplied entirely from the cathode.
This imposes restrictions on the choice of cathode activator since the activator must include desorbable lithium. Furthermore, charging (eg, Li _x CoO ₂ and Li _x N
iO ₂ , where 0.4 <x <1.0) and overcharge (ie, Li _x CoO ₂ and Li _x NiO ₂ , where x <
0.4) LiCoO ₂ and LiNiO ₂ formed during
The delithium product corresponding to
added products) are not stable. In particular, these delithium products tend to react with the electrolyte to generate heat, causing safety issues.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a secondary battery having a high specific capacity and a good cycling ability, and which operates safely. According to the present invention, a newly manufactured secondary battery has an anode composed of a host material capable of adsorbing and desorbing lithium in an electrochemical system, and a lithium metal dispersed in the host material. It has. The lithium metal is preferably a finely ground lithium powder, more preferably having an average particle size of less than about 20 microns. The host material is selected from the group consisting of a carbonaceous material, Si, Sn, tin oxide, a composite tin alloy, a transition metal oxide, a lithium metal nitride, and a lithium metal oxide.
Contains more than one material. The host material preferably contains a carbonaceous material, and more preferably contains graphite.

The newly manufactured secondary battery of the present invention comprises a positive electrode containing an activator, a host material capable of adsorbing and desorbing lithium in an electrochemical system, and a lithium metal dispersed in the host material. Negative electrode, a separator for separating the positive electrode and the negative electrode, and an electrolytic solution for communicating the positive electrode and the negative electrode. The activator of the cathode is preferably a compound that can be lithiated at an electrochemical potential of 2.0 to 5.0 V with respect to lithium. For example, the active agent of this cathode may be MnO _2, V ₂ O ₅ or mixtures thereof. The lithium metal in the anode is preferably a finely ground lithium powder, more preferably having an average particle size of about 20 microns or less. The host material is a carbonaceous material, Si, S
n, a tin oxide, a composite tin alloy, a transition metal oxide, a lithium metal nitride, and a lithium metal oxide. The host material in the negative electrode preferably contains a carbonaceous material, and more preferably contains graphite. Preferably, the amount of lithium metal present in the negative electrode is less than the maximum amount sufficient to penetrate, form an alloy with, or be adsorbed by the host material in the negative electrode. For example, when the host material is carbon, the amount of lithium is preferably equal to or less than the amount required to produce LiC ₆ .

The present invention comprises providing a host material capable of adsorbing and desorbing lithium in an electrochemical system, dispersing lithium metal in the host material, and dispersing the host material and the host material therein. A method of making a newly fabricated anode for a secondary battery including forming lithium metal in the anode is also included.
The lithium metal and the host material are mixed together with the non-aqueous liquid to form a slurry, which is then added to the current collector,
Further, it is preferable that the anode is formed by drying.
Alternatively, the anode can be formed by chemical means by immersing the host material in a suspension of non-aqueous liquid lithium metal and then forming the anode.

The present invention further includes a method for operating a secondary battery. First, a positive electrode containing an activator, a host material capable of adsorbing and desorbing lithium in an electrochemical system, a negative electrode containing lithium metal dispersed in the host material, a separator for separating the positive electrode from the negative electrode, and a positive electrode A newly manufactured secondary battery is provided that includes an electrolyte that communicates with the anode. In particular, this secondary battery is manufactured using lithium metal dispersed in the anode host material. The freshly assembled battery is in a charged state, and more preferably in a fully charged state (all the removable lithium is in the anode of the newly made battery). Newly made secondary batteries are initially discharged by sending lithium ions from the negative electrode through the electrolyte to the positive electrode. The secondary battery can then be charged or recharged by sending lithium ions from the positive electrode through the electrolyte to the negative electrode, and then by sending lithium ions from the negative electrode through the electrolyte to the positive electrode, It is discharged again. Numerous cycles of charge and discharge steps can be performed while maintaining a high specific capacity of cathode activator and a safe operating condition.

[0010] These and other features and advantages of the present invention will become more readily apparent to those of ordinary skill in the art in view of the following detailed description and accompanying drawings. The drawings illustrate both preferred and alternative embodiments of the invention.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings and the following detailed description, preferred embodiments are described in detail so that the invention may be practiced. While the invention will be described with reference to these specific preferred embodiments, it will be understood that the invention is not limited to these preferred embodiments. On the contrary, however, the present invention includes numerous alternatives, modifications and equivalents which will become apparent in view of the following detailed description and accompanying drawings.

As shown in FIG. 1, the present invention includes a positive electrode or cathode 12, a negative electrode or anode 14, a separator 16 for separating the positive electrode and the negative electrode, and an electrolytic solution for electrochemically connecting the positive electrode and the negative electrode. The secondary battery 10. The secondary battery 10 also includes a current collector 20 that makes electrical contact with the cathode and a current collector 22 that makes electrical contact with the anode. Current collectors 20 and 22 are in electrical contact with each other through an external circuit (not shown). The secondary battery 10
Any configuration known to those skilled in the art, such as a "jelly roll" or stacked configuration, can be used.

[0013] Cathode 12 is formed from an activator that is typically combined with a carbonaceous material and a binder polymer. The activator used in the cathode 12 is preferably a material that can be lithiated at an effective voltage (eg, 2.0-5.0 volts relative to lithium). Preferably, a non-lithiated material such as MnO ₂ , V ₂ O ₅ or MoS ₅ or a mixture thereof can be used as activator, more preferably MnO ₂ is used. However, lithiated materials such as LiMn ₂ O ₄ that can be further lithiated can also be used. Non-lithiated activators generally have higher specific capacities in this configuration than lithiated activators, and thus can provide increased power over secondary batteries containing lithiated activators. Activators are preferred. Further, since anode 14 contains lithium, as described below, cathode 12 need not include a lithiated material for secondary battery 10 to operate. Cathode 1
Preferably, the amount of activator provided in 2 is sufficient to accommodate the removable lithium metal present in anode 14. For example, if MnO ₂ is the activator of the cathode, it is preferred that one mole of MnO ₂ is present in cathode 12 per mole of lithium in anode 14 to generate LiMnO ₂ in the cathode during discharge.

When using a lithiable cathode activator as described above, the removable lithium circulated in the cell is sufficiently supplied by the anode 14 and preferably the cell is sufficiently Assembled or manufactured in a charged state. Nevertheless, cathode 12 includes a small amount of one or more lithiated activators (eg, LiCoO ₂ or LiNiO ₂ ) that do not further adsorb lithium at voltages between 2.0 and 5.0 volts. Battery can still be provided in an initially charged state. In this case, the cathode is preferably a lithiated material (eg, LiCo
O ₂ or LiNiO ₂ ) is 50% or less (molar concentration), more preferably 10% or less (molar concentration). LiCo
O ₂ and LiNiO ₂ do not adsorb lithium anymore, so the presence of these materials in the cathode 12 does not reduce the amount of cathode activator needed to accept the removable lithium from the anode 14. .

The anode 14 is formed from a host material 24 capable of adsorbing and desorbing lithium metal 26 dispersed in the host material in the electrochemical system.
For example, lithium present in the anode 14 can penetrate, alloy with, or adsorb to the host material when the battery (and especially the anode) is recharged. The host material is a carbonaceous material; S
i, Sn, a material containing a tin oxide or a composite tin alloy; a transition metal oxide such as CoO; Li3 _- XCo
_x N, where 0 <x <0.5, nitrides of lithium metal and Li ₄ Ti ₅ lithium to adsorption and desorption in an electrochemical system such as oxides of lithium metal, such as O ₁₂ such as Including materials that can. The lithium metal 26 is preferably provided in the anode 14 as finely crushed lithium powder. Further, the average particle size of the lithium metal 26 is preferably about 20 microns or less;
More preferably, it is less than about 10 microns. The lithium metal can be supplied, for example, as a self-combustible powder or a stabilized low-natural powder obtained by treating lithium metal powder with CO ₂ .

The anode 14 can generally be reversibly lithiated and delithiated at an electrochemical potential greater than 0.0 volts and less than 1.5 volts relative to lithium metal. If the electrochemical potential is less than 0.0 volts relative to lithium, lithium metal will not re-enter anode 14 during charging. Alternatively, if the electrochemical potential is greater than 1.5 volts relative to lithium, the battery voltage will be undesirably low. The amount of lithium metal 26 present in anode 14 should be less than the maximum amount sufficient to penetrate, alloy with, or adsorb to host material in anode 14 when the battery is recharged. Preferably, there is. For example,
When the host material is carbon, the amount of lithium is LiC
It is preferably less than the amount required to make ₆ . In other words, the molar ratio of lithium to carbon in the anode is preferably 1: 6 or less.

According to the present invention, a host material capable of adsorbing and desorbing lithium is provided in an electrochemical system, lithium is dispersed in the host material, and the lithium metal dispersed in the host material is dispersed in the host material. Is formed on the anode, whereby the anode 14 can be manufactured. The lithium metal and the host material are preferably mixed with a non-aqueous liquid such as tetrahydrofuran (THF) and a binder to form a slurry. next,
The anode 14 is formed using the slurry, for example, by coating the current collector 22 with the slurry and then drying the slurry. Lithium metal can also be provided in the anode by immersing the host material in a suspension containing a non-aqueous liquid lithium metal such as a hydrocarbon solvent (eg, hexane). The lithium metal used in the suspension is preferably a finely ground lithium powder, as described above. The host material can be formed in the shape of an anode and then immersed in a suspension of lithium metal. Alternatively, the host material can be combined with a suspension of lithium metal to form a slurry, which can then be applied to a current collector and dried to form an anode. Non-aqueous liquids used to make the suspension can be removed by drying the anode (eg, at an elevated temperature). Whatever method is used, it is preferable to disperse the lithium metal in the host material as well as possible. Therefore, as described above,
The average particle size of the lithium metal 26 is preferably about 2
0 microns or less, and more preferably about 10 microns or less.

The host material 24 in the anode 14 comprises carbon
Quality material; Si, Sn, tin oxide or composite tin alloy
Materials containing gold; oxides of transition metals such as CoO; Li
_3-xCo_xN, where lithium such as 0 <x <0.5
Metal nitride and Li_FourTi _FiveO₁₂Lithium metal like
Adsorb lithium in electrochemical systems such as oxides of
Can contain one or more materials that can be
Wear. As described above, the host material 24 is made of graphite.
It is preferable to include Further, the host material 24
A small amount of carbon black (for example, by weight)
(Less than 5%).

As shown in FIG. 1, the cathode 12 is separated from the anode 14 by an electronic insulating separator 16. Generally, this separator 16 is made of polyethylene, polypropylene, or polyvinylidene fluoride (PV
DF).

The secondary battery 10 further includes an electrolyte for electrochemically connecting the cathode 12 and the anode 14. The electrolyte can be a non-aqueous liquid, gel or solid, and preferably contains a lithium salt, for example, LiPF ₆ . The electrolyte is supplied throughout the battery 10 and, in particular, within the cathode 12, anode 14, and separator 16. Generally, the electrolyte is a liquid and the cathode 1
2. The anode 14 and the separator 16 are porous materials that are immersed in an electrolytic solution to provide electrochemical communication between these components.

As mentioned above, the battery 10 includes current collectors 20 and 22, which are used to send electrons to external circuits. Preferably, current collector 20 is made from an aluminum foil and current collector 22 is made from a copper foil.

The battery 10 of the present invention can be fabricated by methods well known to those skilled in the art, and preferably has a layer thickness in the following range (from left to right in FIG. 1).

Layer thickness current collector (20) 20 to 40 μm Cathode (12) 70 to 100 μm Separator (16) 25 to 35 μm Anode (14) 70 to 100 μm Current collector (22) 20 to 40 μm Battery 10 has cathode 12, Also includes an electrolyte dispersed through the anode 14 and the separator 16, and a casing (not shown).

In operation, the newly manufactured rechargeable battery 10 is initially charged, more preferably fully charged, and initially has lithium ions electrolyzed from the anode 14. Cathode 1 through liquid
2 to be discharged. At the same time, electrons flow from the anode 14 to the current collector 22, the external circuit, and the current collector 20.
Through to the cathode 12. Next, the secondary battery 10
Can be charged or recharged by passing lithium ions from the cathode 12 through the electrolyte to the anode 14 and then discharged again, as described above. The charging and discharging steps can generate numerous cycles, while maintaining a high specific capacity of the activator at the cathode and a safe operating state.

The secondary battery 10 can be used for various kinds of applications. For example, secondary batteries can be used in portable electronic devices such as cell phones, camcorders and laptop computers, and in higher power applications such as electric vehicles and hybrid electric vehicles.

After reading the above description of the present invention and reviewing the accompanying drawings, it will be understood that those skilled in the art can make modifications and variations therefrom. Such changes and modifications are included in the claims of the present invention.

[0027]

According to the present invention, it is possible to provide a secondary battery having a high specific capacity, a safe operating state, and a good cycle capability. In particular, since lithium metal is provided in the anode, non-lithiated materials can be used as a preferred cathode activator in secondary batteries. These non-lithiated activators have higher specific capacities than the lithiated materials currently used in lithium ion batteries. Unlike conventional lithium secondary batteries having a non-lithiated cathode activator and a metallic lithium anode, a secondary battery made using a non-lithiated cathode activator in combination with the anode of the present invention is: It has been found that it operates safely and does not generate lithium dendrites when cycling. Further, the secondary battery of the present invention operates more safely than a lithium ion battery, which becomes unstable when lithium is removed from the cathode during charging. In particular, since the activator of the cathode in the secondary battery of the present invention is generally fully charged when the battery is newly manufactured, it is less than the cathode material used in the lithium ion battery. stable. further,
The battery of the present invention can perform a very large number of charges and discharges while maintaining a safe operating state and high specific capacity of the cathode activator.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a simplified configuration of a secondary battery including a cathode, an anode, a separator, and an electrolyte according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Secondary battery 12 Cathode 14 Anode 16 Separator 20 Current collector 22 Current collector 24 Host material 26 Dispersed lithium metal

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor John El Barba, The Third 28216, North Carolina, United States, Charlotte, Inchantment Cove Lane 4351 F-term (reference) 5H029 AJ03 AJ05 AJ12 AK02 AK05 AL01 AL02 AL03 AL04 AL06 AL12 AL18 AM07 CJ13 CJ23 DJ12 DJ16 HJ05 HJ18 5H050 AA07 AA08 AA15 BA17 CA02 CA11 CB02 CB03 CB05 CB08 CB12 CB29 FA08 FA17 FA18 GA13 GA23 HA05 HA18

Claims (30)

[Claims] An anode fabricated for a secondary battery, comprising: a host material capable of adsorbing and desorbing lithium in an electrochemical system; and lithium metal dispersed in the host material. An anode, comprising: 2. The anode according to claim 1, wherein said lithium metal is finely ground lithium powder. 3. The anode according to claim 2, wherein the lithium powder has an average particle size of about 20 microns or less. 4. An anode according to claim 1, wherein the anode is reversibly lithiated and delithiated at an electrochemical potential greater than 0.0 volts and less than 1.5 volts relative to lithium metal. An anode characterized in that it can be converted into an anode. 5. The anode according to claim 1, wherein the host material is 0.1 to 0.1% of lithium.
An anode comprising one or more materials that can be reversibly lithiated and delithiated at an electrochemical potential greater than 0 volts and less than or equal to 1.5 volts. 6. The anode according to claim 1, wherein the host material is a carbonaceous material, Si, S
An anode comprising one or more materials selected from the group consisting of n, tin oxide, composite tin alloy, transition metal oxide, lithium metal nitride, and lithium metal oxide. 7. The anode according to claim 1, wherein the host material includes a carbonaceous material. 8. The anode according to claim 7, wherein said carbonaceous material is graphite. 9. The anode according to claim 8, wherein said host material further comprises carbon black. 10. The anode according to claim 1, wherein the amount of lithium metal in the anode is:
When the anode is recharged, no more than a maximum amount sufficient to penetrate, alloy with, or adsorb to the host material within the anode. Anode. 11. A secondary battery comprising the anode according to claim 1. 12. A manufactured secondary battery, comprising: a cathode containing an activator; the anode according to claim 1; a separator for separating a positive electrode and a negative electrode; And an electrolyte communicating with the negative electrode. 13. The secondary battery according to claim 12, wherein the positive electrode has a capacity of 2.0 to lithium as an activator.
A secondary battery comprising a compound that can be lithiated at an electrochemical potential of up to 5.0 volts. 14. The secondary battery according to claim 13, wherein the activator in the positive electrode is selected from the group consisting of MnO ₂ , V ₂ O ₅ and MoS ₂ , and a mixture thereof. Features a secondary battery. 15. The secondary battery according to claim 13, wherein the activator in the positive electrode contains MnO ₂ . 16. The secondary battery according to claim 13, wherein the activator in the positive electrode includes LiMn ₂ O ₄ . 17. The secondary battery according to claim 12, wherein an amount of the activator in the cathode is sufficient to receive a detachable lithium metal present in the anode. A secondary battery characterized by the above-mentioned. 18. A secondary battery according to claim 12, wherein the secondary battery is in a fully charged state. 19. A method of fabricating an anode for a secondary battery, comprising the steps of: installing a host material capable of adsorbing and desorbing lithium in an electrochemical system; And forming the host material and the lithium metal dispersed therein on an anode. 20. The method according to claim 19, wherein the dispersing step comprises mixing the lithium metal, the host material and a non-aqueous liquid together to form a slurry. Features method. 21. The method of claim 19 or claim 20, wherein the forming comprises applying the slurry to a current collector and drying the slurry. . 22. The method according to claim 19, wherein the dispersing comprises immersing the host material in a suspension containing lithium metal and a non-aqueous liquid. A method comprising: 23. The method of claim 22, wherein said dispersing comprises immersing said host material in a suspension of lithium metal in a hydrocarbon. . 24. The method according to claim 19, wherein the step of dispersing includes the step of dispersing finely ground lithium metal powder into the host material. Features method. 25. The method of claim 19, wherein the dispersing comprises dispersing lithium metal having an average particle size of about 20 microns or less into the host material. A method comprising: 26. The method according to any of claims 19 to 25, wherein the step of installing is reversible at an electrochemical potential greater than 0.0 volts and less than 1.5 volts relative to lithium. Providing a host material comprising one or more materials that can be selectively lithiated and delithiated. 27. The method according to any of claims 19 to 26, wherein said installing comprises: a carbonaceous material;
Providing a host material including one or more materials selected from the group consisting of Si, Sn, tin oxide, composite tin alloy, transition metal oxide, lithium metal nitride, and lithium metal oxide. A method comprising: 28. The method according to any of claims 19 to 27, wherein said placing comprises providing a host material comprising a carbonaceous material. 29. The method of claim 19, wherein the step of providing includes providing a host material wherein the carbonaceous material is graphite. 30. The method of claim 29, comprising providing a host material wherein said host material further comprises carbon black.