CN110679016A - Anode composition and anode prelithiation method - Google Patents

Anode composition and anode prelithiation method Download PDF

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CN110679016A
CN110679016A CN201780091193.8A CN201780091193A CN110679016A CN 110679016 A CN110679016 A CN 110679016A CN 201780091193 A CN201780091193 A CN 201780091193A CN 110679016 A CN110679016 A CN 110679016A
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lithium
anode
silicon
weight
carbon
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蒋蓉蓉
郝小罡
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Robert Bosch GmbH
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    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
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Abstract

The present invention provides a novel anode composition for a lithium ion battery, the novel anode composition comprising: a silicon-based active material, a binder selected from the group consisting of a polyimidic acid and a polyimide, and a lithium salt, wherein the lithium salt is capable of decomposing to lithium oxide and/or lithium peroxide at a temperature of from 200 ℃ to 400 ℃. The invention also provides a method for preparing an anode, a method for prelithiating the anode, and a lithium ion battery comprising the anode.

Description

Anode composition and anode prelithiation method
Technical Field
The present invention relates to an anode composition for a lithium ion battery, the anode composition comprising: a silicon-based active material, a binder selected from the group consisting of a polyimidic acid and a polyimide, and a lithium salt, wherein the lithium salt is capable of decomposing to lithium oxide and/or lithium peroxide at a temperature of 200 ℃ to 400 ℃. The invention also relates to a method for preparing an anode, a method for prelithiating the anode, and a lithium ion battery comprising the anode.
Technical Field
Lithium ion batteries are currently widely used in energy storage systems and electric vehicles.
Silicon is a promising active material for the anode of lithium ion batteries due to its large theoretical capacity and moderate operating voltage. However, during the lithiation/delithiation process, silicon undergoes significant expansion and contraction. This large volume change compromises the electrochemical performance of the lithium ion battery. In addition, silicon at the surface of the anode undesirably reacts with the electrolyte to form a Solid Electrolyte Interface (SEI), resulting in rapid capacity fade of the lithium ion battery.
It has been proposed to add lithium oxide or peroxide to the anode in order to prelithiate the anode and compensate for capacity fade. The prelithiated anode is then assembled into a lithium ion battery. However, due to the high activity of lithium oxide and lithium peroxide, the battery production procedure after the prelithiation step requires an operating environment with well controlled humidity, which increases the manufacturing cost of the lithium ion battery. In addition, since lithium oxide and lithium peroxide powders are corrosive or irritating to human skin and mucous membranes, complete protection is required in industrial production.
There is a continuing need for more attractive and reliable lithium ion batteries.
Disclosure of Invention
After intensive research, the inventors have developed a novel anode composition for lithium ion batteries comprising:
a silicon-based active material;
a binder selected from the group consisting of polyimide acids and polyimides; and
a lithium salt, wherein the lithium salt is capable of decomposing to lithium oxide and/or lithium peroxide at a temperature of from 200 ℃ to 400 ℃, preferably from 300 ℃ to 370 ℃, more preferably about 340 ℃ to 360 ℃.
In some examples, the anode composition further comprises a carbon material.
There is also provided a method for preparing an anode, the method comprising:
mixing all components of an anode composition according to the present disclosure with a solvent to form a slurry; and
the slurry is applied to an anode current collector.
Also provided is a method for prelithiating an anode made according to the method of the present disclosure, the method comprising: the anode is heated to a temperature of from 200 ℃ to 400 ℃, preferably from 300 ℃ to 370 ℃, more preferably about 340 ℃ to 360 ℃ to decompose the lithium salt to lithium oxide and/or peroxide.
Also provided is a lithium ion battery comprising an anode made according to the methods of the present disclosure or a prelithiated anode according to the methods of the present disclosure.
The inventors first specifically combined a polyimide and/or a polyimide acid with a particular lithium salt. Upon heating in situ, the lithium salt may decompose into lithium oxide and/or lithium peroxide. The lithium oxide and/or peroxide thus obtained can provide additional lithium to the anode and compensate for capacity fade, and thus significantly improve battery performance (such as initial coulombic efficiency and cycle stability).
In contrast to known methods of directly using lithium oxide or lithium peroxide, the present disclosure uses a lithium salt as a precursor of lithium oxide and/or lithium peroxide, which is environmentally friendly and easy to handle and does not require special handling conditions.
In addition, polyimide has good mechanical strength and is stable at the decomposition temperature of lithium salt. Therefore, polyimide is superior to conventional binders used in batteries, such as polyvinylidene fluoride (PVDF) and sodium carboxymethyl cellulose (CMC).
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Other features and advantages of the present disclosure will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the features of the technology; wherein:
fig. 1 compares the cycle performance of battery cells according to examples of the present disclosure and comparative examples.
Fig. 2 compares discharge/charge curves of battery cells according to examples and comparative examples of the present disclosure.
Reference will now be made to some illustrative examples, and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended.
Detailed Description
Throughout this disclosure, unless otherwise indicated, all scientific and technical terms shall have the same meaning as those known to those skilled in the art. In the event of inconsistencies, the definitions provided in this disclosure shall apply.
It should be understood that the detailed description of all materials, methods, examples, and figures are provided for purposes of illustration and, therefore, should not be construed to limit the present disclosure unless otherwise specifically noted.
Herein, the terms "cell" and "battery" may be used interchangeably. The term "lithium ion battery cell (or battery)" may also be abbreviated as "battery cell" or "battery (battery)".
In this document, the term "comprising" means that other components or other steps which do not affect the final effect may be included. This term encompasses the terms "consisting of … … (the governing of)" and "consisting essentially of … … (the governing of)". Products and methods according to the present disclosure may include, consist of, and consist essentially of: the essential features and/or limitations of the present disclosure described herein, as well as any additional and/or optional ingredients, components, steps, or limitations described herein.
The use of the terms "a" and "an" and "the" and similar referents in the context of describing the subject matter of the present application (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context.
Unless otherwise indicated, each numerical range in this context is intended to include both endpoints and any number and subranges falling within the numerical range.
All materials and reagents used in this disclosure are commercially available unless otherwise specified.
Examples of the present disclosure are described in detail below.
Anode
The components of the "anode composition" may be mixed with a solvent to form an anode slurry. The anode slurry may then be applied to an anode current collector and dried to form an anode.
In some examples, an anode composition for a lithium ion battery is provided, comprising:
a silicon-based active material;
a binder selected from the group consisting of polyimide acids and polyimides; and
a lithium salt, wherein the lithium salt is capable of decomposing to lithium oxide and/or lithium peroxide at a temperature of from 200 ℃ to 400 ℃, preferably from 300 ℃ to 370 ℃, more preferably about 340 ℃ to 360 ℃.
In some examples, the anode composition may further comprise a carbon material.
In some examples, the anode composition comprises: based on the total weight of the anode composition,
from 5 to 60% by weight, preferably from 5 to 40% by weight, of a silicon-based active material;
from 3 to 15% by weight, preferably from 3 to 10% by weight, of a binder selected from the group consisting of polyimide acids and polyimides;
from 2 to 30% by weight, preferably from 2 to 20% by weight, of a lithium salt, wherein the lithium salt is capable of decomposing to lithium oxide and/or lithium peroxide at a temperature of from 200 to 400 ℃; and
from 0 to 90% by weight, preferably from 30 to 85% by weight, more preferably from 40 to 85% by weight of carbon material.
Each component of the anode composition of the present disclosure will be described in detail below.
Silicon-based active materials
Anode compositions according to the present disclosure may include a silicon-based active material. Silicon-based active materials have a larger theoretical capacity and a more moderate operating voltage than carbon-based active materials.
The term "active material" as used herein means a material capable of inserting lithium ions therein and releasing lithium ions therefrom in repeated charge/discharge cycles.
The "silicon-based active material" may be an active material containing silicon element. There is no particular limitation on the silicon-based active material, and those known for use in lithium ion batteries may be used. Examples of suitable silicon-based active materials may include, but are not limited to: silicon, silicon alloys, silicon oxides, silicon/carbon composites, silicon oxide/carbon composites, and any combination thereof. In some examples, the silicon alloy may include silicon and one or more metals selected from the group consisting of: ti, Sn, Al, Sb, Bi, As, Ge and Pb. Commercially available silicon alloys may include, but are not limited to, Si-Fe-Ti alloy powders available from 3M corporation. In some examples, the silicon oxide may be a mixture of oxides of more than one silicon. For example, the silicon oxide may be represented as SiOxWherein x may have an average value of from about 0.5 to about 2.
In some examples, the silicon-based active material is present in an amount of from 5 to 60% by weight, preferably from 5 to 40% by weight, based on the total weight of the anode composition. The total weight of the anode composition means the dry weight excluding the weight of the solvent.
Adhesive agent
An anode composition according to the present disclosure may include a binder selected from the group consisting of a polyimide acid and a polyimide. The binder can hold the components of the anode composition together and attach the anode composition to the anode current collector, helping to maintain good stability and integrity of the anode when volume changes occur during repeated charge/discharge cycles, and thus improving the electrochemical characteristics (including cycle performance and rate capability) of the final cell.
In addition, conventional binders (e.g., PVDF and CMC) cannot withstand the high decomposition temperature of lithium salts, in contrast to polyimide acids and polyimides which have high heat resistance and are stable at the decomposition temperature of lithium salts. In some examples, the resulting polyimide is stable at high temperatures even though the polyimide acid may dehydrate upon heating. In addition, polyimide acid and polyimide have good mechanical strength, which helps prevent volume change during repeated charge/discharge cycles, and thus contributes to the electrochemical characteristics of the final battery cell.
There are no particular limitations on the polyimide and the polyimide acid, and those generally known can be used.
The polyimide may include aromatic polyimides, aliphatic polyimides, and alicyclic polyimides. The repeat units of the polyimide may include-c (o) -N-c (o) -and one or more aromatic, aliphatic, and/or alicyclic moieties.
In some examples, the polyimide may be represented by formula I:
wherein R is1And R2May each independently be C1-C12 alkyl, C1-C12 alkenyl, or C1-C12 alkynyl; preferably C1-C6 alkyl; and m may be an integer from 2 to 50, preferably from 2 to 30.
In some examples, the polyimide may be represented by formula II:
wherein Ar represents a C6-C30 aromatic group; r3May be C1-C12 alkyl, C1-C12 alkenyl or C1-C12 alkynyl; preferably C1-C6 alkyl; and n may be an integer from 2 to 50, preferably from 2 to 30.
In some examples, the polyimide may be represented by formula III:
Figure BDA0002286979760000061
wherein R is3And n each hasHaving the same definitions as described above for formula II; and R is4May independently be C1-C12 alkyl, C1-C12 alkenyl or C1-C12 alkynyl; C1-C6 alkyl is preferred.
The polyimide acid may include aromatic polyimide acid, aliphatic polyimide acid, and alicyclic polyimide acid. The repeating units of the polyimide acid may include carboxyl-C (O) OH, polyamide-C (O) -NH-, and one or more aromatic, aliphatic, and/or cycloaliphatic moieties.
In some examples, the polyimide acid can be represented by formula IV:
wherein Ar, R3And n each have the same definitions as described above for formula II.
In some examples, the polyimide acid can be represented by formula V:
Figure BDA0002286979760000063
wherein R is3、R4And n each have the same definitions as described above for formula III.
To facilitate application of the anode slurry to the anode current collector, the polyimide acid and polyimide are preferably soluble in the solvent used to form the anode slurry (e.g., N-methyl-2-pyrrolidone).
In some examples, the binder is present in an amount of from 3 to 15% by weight, preferably from 3 to 10% by weight, based on the total weight of the anode composition.
Lithium salt
The anode composition according to the present disclosure may comprise a lithium salt capable of decomposing to lithium oxide and/or lithium peroxide at a temperature of from 200 ℃ to 400 ℃, preferably from 300 ℃ to 370 ℃, more preferably about 340 ℃ to 360 ℃.
Upon heating in situ, the lithium salt may decompose into lithium oxide and/or lithium peroxide. The lithium oxide and/or peroxide thus obtained can provide an additional lithium source and compensate for capacity fade, and thus significantly improve battery performance (such as initial coulombic efficiency and cycle stability).
In contrast to known methods of directly using lithium oxide or lithium peroxide, the present disclosure uses a lithium salt as a precursor of lithium oxide, which is environmentally friendly and easy to handle and does not require special handling conditions.
In some examples, the lithium salt is selected from the group consisting of: lithium acetate, lithium oxalate, lithium citrate, and lithium bicarbonate.
The weight ratio of the lithium salt to the silicon-based active material depends on the particular type of lithium salt and silicon-based active material used. Preferably, the weight ratio of lithium in the lithium salt to silicon in the silicon-based active material is from 5:100 to 25:100, preferably from 7:100 to 20: 100. With the ratio of lithium to silicon controlled within these ranges, the battery can be prelithiated to a desired high level while avoiding the introduction of excessive lithium and reducing the mass density of the battery.
In some examples, the lithium salt is present in an amount of from 2 to 30% by weight, preferably from 2 to 20% by weight, based on the total weight of the anode composition.
Solvent(s)
As described above, an anode composition according to the present disclosure may be mixed with a solvent to form an anode slurry. When the anode is heated in a subsequent prelithiation step, the solvent evaporates. Thus, the prelithiated anode contains little or no solvent.
The solvent is not particularly limited, and those known for use in lithium ion batteries may be used. Examples of suitable solvents include N-methyl-2-pyrrolidone (NMP).
Carbon material
The anode composition may further comprise a carbon material. The "carbon material" may be a material containing carbon element. The carbon material may be used as an active material other than a silicon-based active material, or may increase the conductivity and/or dispersibility of the anode composition. There is no particular limitation on the carbon material, and those known for use in lithium ion batteries may be used. In some examples, the carbon material may include, but is not limited to, carbon black, acetylene black, ketjen black, graphite, graphene, carbon nanotubes, carbon fibers, vapor grown carbon fibers, and combinations thereof. In some examples, the carbon black may be Super P (e.g., Super P commercially available from the ultra high Density company (Timcal), particle size: about 20nm or about 40 nm). In some examples, the graphite can be graphite powder (e.g., particle size: 2 to 30 μm), and/or graphite flake (e.g., KS6L commercially available from Tegaku corporation, particle size: about 6 μm). The carbon materials may be used alone or in any combination.
In some examples, graphite powder, Super P, and graphite flakes may be used in combinations of two or three thereof. Graphite powder may be used as the carbon-based active material in the anode to buffer volume changes caused by the silicon-based active material. Super P has a relatively small particle size and good electrical conductivity, and can improve the electrical conductivity and dispersibility of the anode. Graphite flakes have a relatively large particle size and good electrical conductivity, and can improve two-dimensional conductivity, two-dimensional dispersibility, and cycle performance.
In addition to the above components, the anode may optionally contain additives commonly used in electrodes, as long as the additives do not adversely impair the battery performance.
There is no particular limitation on the type, shape, size, and/or content of each component in the anode composition.
In some examples, the content of carbon material is from 0 to 90% by weight, preferably from 30 to 85% by weight, more preferably from 40 to 85% by weight, based on the total weight of the anode composition.
Method for preparing anode
In some examples, there is provided a method for preparing an anode, comprising:
mixing all components of an anode composition according to the present disclosure with a solvent to form a slurry; and
the slurry is applied to an anode current collector.
In some examples, the solvent may include N-methyl-2-pyrrolidone (NMP).
There is no particular limitation on the anode current collector. In some examples, nickel foil, nickel mesh, copper foil, or copper mesh may be used as the anode current collector.
In some examples, the method further comprises a calendering step. During the decomposition of the lithium salt, gas is generated and pores are formed. The porosity of the anode can be well controlled by calendering, lithium oxide and/or lithium peroxide can be uniformly distributed in the anode, and the battery performance can be improved.
Method of prelithiating an anode
In some examples, there is provided a method for prelithiating an anode made according to the method of the present disclosure, the method comprising: the anode is heated to a temperature of from 200 ℃ to 400 ℃, preferably from 300 ℃ to 370 ℃, more preferably about 340 ℃ to 360 ℃ to decompose the lithium salt to lithium oxide and/or peroxide. When the temperature falls within these ranges, the polyimide and/or the polyimide acid exhibits good crosslinking strength, and the electrode current collector is not damaged.
Lithium ion battery
In some examples, a lithium ion battery is provided that includes an anode prepared or prelithiated according to the methods of the present disclosure. In addition, the lithium ion battery also includes a cathode and an electrolyte.
The lithium ion battery according to the present disclosure may be used for an energy storage system and an electric vehicle.
Cathode electrode
The "cathode composition" can be mixed to form a cathode slurry. The cathode slurry may then be applied on a cathode current collector and dried to form a cathode.
According to some examples of the present disclosure, the cathode may include a lithium-based active material. In some examples, the cathode active material may be a material that reversibly releases (desert) and intercalates lithium ions during charge/discharge cycles. During a discharge cycle, lithium ions derived from the lithium-based active material may be transferred from the anode back to the cathode to again form the lithium-based active material.
The lithium-based cathode active material is not particularly limited and mayTo use those cathode active materials that are commonly used in lithium ion battery cells. In some examples, the cathode active material may be selected from the group consisting of: lithium metal oxide, lithium metal phosphate, lithium metal silicate and any combination thereof, preferably lithium transition metal composite oxide, lithium transition metal phosphate, lithium metal silicate and any combination thereof. In some examples, the cathode active material may be selected from the group consisting of: lithium iron phosphate, lithium manganese iron phosphate, and any combination thereof. In some examples, the lithium transition metal composite oxide may be lithium nickel oxide, lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (NCM), lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide/Li2MnO3A composite material (also referred to as a "lithium rich NCM"), or any combination thereof. The transition metal may include any transition metal in groups 3 to 12 of the periodic table, such as titanium, zinc, copper, nickel, molybdenum.
In some examples, the cathode composition may further include a carbon material, a binder, and a solvent in addition to the lithium-based cathode active material.
The binder is not particularly limited, and those known for use in lithium ion batteries may be used. In some examples, the binder may be polyvinylidene fluoride (PVDF), polyacrylic acid (PAA) and derivatives thereof (e.g., LiPAA), sodium carboxymethylcellulose (CMC), and combinations thereof.
The above description of the carbon material and the solvent in the anode is also applicable here. The carbon material and solvent in the cathode may be the same or different from the carbon material and solvent contained in the anode, respectively.
In addition, other additives commonly known for use in lithium ion batteries may optionally be used in the cathode so long as they do not adversely affect the desired performance of the battery.
There is no particular limitation in the type, shape, size and/or content of each component in the cathode composition.
There is no particular limitation on the cathode current collector. In some examples, aluminum foil may be used as the cathode current collector.
Electrolyte
A lithium ion battery according to the present disclosure may include an electrolyte. According to some examples of the present disclosure, the electrolyte may include a lithium salt and a non-aqueous solvent. The lithium salt and the nonaqueous solvent are not particularly limited, and those generally known in battery cells may be used. In some examples, the lithium salt in the electrolyte may be different from the lithium-based active material in the cathode and the lithium salt in the anode. According to some examples of the present disclosure, the lithium salt may include, but is not limited to, lithium hexafluorophosphate (LiPF)6) Lithium tetrafluoroborate (LiBF)4) Lithium arsenate (LiAsO)4)、LiSbO4Lithium perchlorate (LiC 1O)4)、LiAlO4、LiGaO4Lithium bis (oxalato) borate (LiBOB) and any combination thereof, with LiPF being preferred6。
According to some examples of the present disclosure, the non-aqueous solvent in the electrolyte may include a carbonate (i.e., a non-fluorinated carbonate) and a fluorinated carbonate. According to some examples of the present disclosure, carbonates may include, but are not limited to, cyclic carbonates such as Ethylene Carbonate (EC), Propylene Carbonate (PC), Butylene Carbonate (BC); linear or branched carbonates such as dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethylmethyl carbonate (EMC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC); and any combination of the above carbonates. According to some examples of the disclosure, the fluorinated carbonate may be a fluorinated derivative of the above carbonates, such as fluoroethylene carbonate (FEC) and difluoroethylene carbonate, dimethyl carbonate difluoride (DFDMC).
Examples
Material
NCM-111: lithium nickel cobalt manganese oxide, active material of cathode, D50: 12 μm, available from BASF.
Super P: carbon material in the cathode and anode, 40nm, is available from ultra high corporation.
PVDF: polyvinylidene fluoride, a binder in the cathode, is available from Sovey corporation.
Si-Fe-Ti alloy powder: active material of anode, silicon content: 30 wt%, diameter: 50nm, available from 3M company.
Graphite powder: active material of anode, diameter: 20nm, available from Hitachi, Inc.
KS 6L: graphite flakes, the carbon material in the anode, about 6 μm, are available from super dense corporation.
U-Varnish A: the binder in the anode, a mixture of 20 wt% of polyamic acid and 80 wt% of N-methyl-2-pyrrolidone, was obtained from Utsu corporation (UBE).
Lithium acetate: lithium salts, a source of pre-lithiation in the anode, are available from the national drug group (Guoyao).
NMP: n-methyl-2-pyrrolidone, a solvent, available from the national pharmaceutical group.
Celgard 2325: PP/PE/PP films, separator, available from Kargard (Celgard).
Example 1 (ex.1): preparation of a Battery cell
Preparation of the cathode
96.5g NCM-111, 3g Super P and 2.5g PVDF were added to 47g NMP in a 500mL round bottom flask equipped with a stirrer at room temperature. After stirring for 3h, the resulting uniformly dispersed slurry was coated on an aluminum foil and then dried at 80 ℃ for 6 h. The coated aluminum foil was cut into several phi 12mm cathodes.
Preparation of the Anode
40g of Si-Fe-Ti alloy powder, 40g of graphite powder, 10g of lithium acetate, 10g U-Varnish A (dry weight, in the form of a 20 wt% solution in NMP), 2g of Super P and 8g of KS6L were added to 70g of NMP in a 500mL round bottom flask equipped with a stirrer at room temperature. After stirring for 3h, the resulting uniformly dispersed slurry was coated on a copper foil and then dried at 60 ℃ for 30 minutes. The coated Cu foil was then calcined in a tube furnace (RS 80/750/11, Nabertherm (Nabertherm) with a nitrogen purge) at a ramp rate of 20 ℃/min until the temperature reached 350 ℃. Subsequently, the coated Cu foil was taken out of the tube furnace and cooled to room temperature (about 25 ℃). The coated Cu foil was cut into several phi 12mm anodes.
Preparation of a Battery cell
By using the cathode and anode obtained above, a coin cell (CR2016) was assembled in an argon-filled glove box (MB-10compact, braun). Use of 1M LiPF in FEC/EC/EMC (30: 35:35 by volume)6As an electrolyte. Celgard2325 was used as a separator.
COMPARATIVE EXAMPLE 1(Com.Ex.1)
A coin cell was prepared in the manner as described above for example 1, except that lithium acetate was not used.
[ electrochemical measurement ]
The battery performance of each of the battery cells obtained in example 1 and comparative example 1 was measured at 25 ℃ on an Arbin battery test system (model: Arbin BT-G; supplier: Arbin Co.).
For the first charge cycle, each cell was charged to 4.2V at a current of 0.1C (vs Li/Li)+). Then, for the first discharge cycle, the cell was discharged to 2.5V at a current of 0.1C. The above charge/discharge cycle was repeated in the 2 nd and 3 rd cycles. Subsequently, each cell was charged to 4.2V (vs Li/Li +) at a different rate for the 4 th to 21 st charge cycles. Specifically, the charging rate of the 4 th to 6 th charging cycles was 0.1C, the 7 th to 9 th charging cycles was 1/3C, the 10 th to 12 th charging cycles was 0.5C, the 13 th to 15 th charging cycles was 1C, the 16 th to 18 th charging cycles was 2C, and the 19 th to 21 th charging cycles was 3C. For the 4 th to 21 st discharge cycles, the battery cells were discharged to 2.5V at a current of 0.1C. Finally, each cell was operated at from 2.5 to 4.5V (vs Li/Li)+) And discharged/charged at a rate of 1C (for the following cycle). The mass loading of NCM in each cathode of the cell was about 10mg/cm2. The specific capacity was calculated based on the weight of NCM.
Fig. 1 compares the cycle performance of the battery cells of example 1 and comparative example 1. As can be seen by reference to fig. 1, example 1 exhibited better cycle stability than comparative example 1, which did not use a prelithiation source.
Fig. 2 compares the discharge/charge characteristics of the battery cells in example 1 and comparative example 1. As can be seen by reference to fig. 2, example 1 exhibited a higher initial coulombic efficiency in the first charge/discharge cycle than comparative example 1, which did not use a prelithiation source.

Claims (9)

1. An anode composition for a lithium ion battery, the anode composition comprising:
a silicon-based active material;
a binder selected from the group consisting of polyimide acids and polyimides; and
a lithium salt, wherein the lithium salt is capable of decomposing to lithium oxide and/or lithium peroxide at a temperature of from 200 ℃ to 400 ℃.
2. The anode composition according to claim 1, wherein the binder is soluble in N-methyl-2-pyrrolidone.
3. The anode composition according to claim 1 or 2, wherein the lithium salt is selected from the group consisting of: lithium acetate, lithium oxalate, lithium citrate, and lithium bicarbonate.
4. The anode composition according to any one of the preceding claims, wherein the silicon-based active material is selected from the group consisting of: silicon, silicon alloys, silicon oxides, silicon/carbon composites, and silicon oxide/carbon composites.
5. The anode composition according to any one of the preceding claims, wherein the anode composition further comprises a carbon material, preferably the carbon material is selected from the group consisting of: carbon black, acetylene black, ketjen black, graphite, graphene, carbon nanotubes, carbon fibers, and vapor grown carbon fibers.
6. An anode composition according to any one of the preceding claims, comprising: based on the total weight of the anode composition,
from 5 to 60% by weight, preferably from 5 to 40% by weight, of a silicon-based active material;
from 3 to 15% by weight, preferably from 3 to 10% by weight, of a binder selected from the group consisting of polyimide acids and polyimides;
from 2 to 30% by weight, preferably from 2 to 20% by weight, of a lithium salt, wherein the lithium salt is capable of decomposing to lithium oxide and/or lithium peroxide at a temperature of from 200 to 400 ℃; and
from 0 to 90% by weight, preferably from 30 to 85% by weight, more preferably from 40 to 85% by weight of carbon material.
7. A method for preparing an anode, the method comprising:
mixing all components of the anode composition of any one of claims 1 to 6 with a solvent to form a slurry; and
the slurry is applied to an anode current collector.
8. A method for prelithiating an anode made according to the method of claim 7, the method comprising: the anode is heated to a temperature of from 200 ℃ to 400 ℃ to decompose the lithium salt to lithium oxide and/or lithium peroxide.
9. A lithium ion battery comprising an anode prepared according to the method of claim 7 or a prelithiated anode according to the method of claim 8.
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