JP2020521298A - Anode compositions and methods for prelithiation of anodes - Google Patents

Abstract

Provided are an anode composition and a method of prelithiation of the anode. For a lithium ion battery including a silicon-based active material, a binder selected from polyamic acid and polyimide, and a lithium salt that can be decomposed into lithium oxide and/or lithium peroxide at a temperature of 200 to 400°C. A novel anode composition is provided. Methods of making the anode, prelithiation of the anode, and lithium ion batteries including the anode are also provided.

Description

The present invention includes a silicon-based active material, a binder selected from polyamic acid and polyimide, and a lithium salt that can be decomposed into lithium oxide and/or lithium peroxide at a temperature of 200 to 400°C. It relates to an anode composition for a lithium-ion battery. The invention also relates to a method of making the anode, a method of prelithiating the anode, and a lithium ion battery including the anode.

Lithium-ion batteries are now 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 modest operating voltage. However, during the lithiation/delithiation process, silicon experiences significant expansion and contraction. Such very large volume changes impair the electrochemical performance of lithium-ion batteries. Furthermore, the silicon on the anode surface undesirably reacts with the electrolyte to form a solid electrolyte interface (SEI), causing rapid capacity fading in the lithium-ion battery.

It has been proposed to prelithiate the anode and add lithium oxide or lithium peroxide into the anode to compensate for capacity fade. The pre-lithiated anode is subsequently assembled into a lithium-ion battery. However, due to the high activity of lithium oxide and lithium peroxide, battery manufacturing procedures that follow the prelithiation step require a well-controlled operating environment of humidity, which increases the manufacturing cost of lithium-ion batteries. In addition, lithium oxide and lithium peroxide powders are corrosive or irritating to human skin and mucous membranes and thus require complete protection in industrial production.

There is an ongoing demand for more attractive and reliable lithium-ion batteries.

After intensive research, the inventors
Silicon-based active material,
With a binder selected from polyamic acid and polyimide,
A lithium salt capable of being decomposed to lithium oxide and/or lithium peroxide at a temperature of 200 to 400°C, preferably 300 to 370°C, more preferably 340 to 360°C,
A new anode composition for lithium-ion batteries has been developed.

In some examples, the anode composition further comprises a carbon material.

Mixing all the components of the anode composition according to the present disclosure with a solvent to form a slurry; and
Applying the slurry to the anode current collector,
Also provided is a method of making an anode, the method including:

Also provided is a method of prelithiating an anode made by the method of the present disclosure, which method comprises heating the anode to a temperature of 200 to 400°C, preferably 300 to 370°C, more preferably 340 to 360°C. , Decomposing the lithium salt into lithium oxide and/or lithium peroxide.

Also provided are lithium ion batteries that include an anode made according to the methods of the present disclosure, or an anode prelithiated according to the methods of the present disclosure.

For the first time, the inventors have combined polyimide and/or polyamic acid with specific lithium salts. At the time of in situ heating, the lithium salt may decompose into lithium oxide and/or lithium peroxide. The lithium oxide and/or lithium peroxide thus obtained can provide additional lithium to the anode and compensate for capacity fade, thus significantly improving cell performance (eg initial Coulombic efficiency).

Compared to the known methods of using lithium oxide or lithium peroxide directly, the present disclosure, as a precursor of lithium oxide and/or lithium peroxide, is environmentally friendly, easy to conduct and requires special operating conditions. Not using lithium salt.

In addition, polyimide has good mechanical strength and is stable at the decomposition temperature of lithium salts. Therefore, polyimide is superior to conventional binders used in batteries such as polyvinylidene fluoride (PVDF), and sodium carboxymethyl cellulose (CMC).

Additional features and advantages of the present disclosure will be apparent when the following detailed description is taken in conjunction with the accompanying drawings, which together, by way of example, represent technical features.

Cycle performance is compared between the example cell of the present disclosure and the comparative cell. The discharge/charge profiles are compared between the cells according to the example of the present disclosure and the cells of the comparative example.

Reference will now be made to a number of example embodiments, but specific language is used herein to describe the examples. However, it will be understood that there is no intent to limit the scope of the present disclosure thereby.

Throughout this disclosure, all scientific and technical terms have the same meaning as known to one of ordinary skill in the art, unless otherwise indicated. In case of conflict, the definitions provided in this disclosure should be used.

It should be understood that all detailed descriptions of materials, processes, examples, and figures are presented for purposes of illustration and are not to be construed as limitations of the present disclosure, unless expressly specified otherwise. is there.

As used herein, the terms "cell" and "battery" may be used interchangeably. The term "lithium ion cell (or battery)" may also be abbreviated as "cell" or "battery."

As used herein, the term "comprising" means that other ingredients or other steps that do not affect the final effect can be included. This term encompasses the terms “consisting of” and “consisting essentially of”. Products and processes according to the present disclosure may include essential technical features and/or limitations of the present disclosure described herein, as well as any additional and/or optional ingredients, components, described herein. Steps or limitations can include, consist of, or consist essentially of steps.

In connection with the description of the subject matter of the present application (in particular in connection with the following claims), the terms "a", "an" and "the" and Use of similar referents should be construed to include both singular and plural unless stated otherwise or clearly inconsistent with context.

Unless otherwise specified, all numerical ranges in this context are intended to include both the endpoints and all numerical values and subranges subsumed within that numerical range.

Unless otherwise indicated, all materials and reagents used in this disclosure are commercially available.

Embodiments of the present disclosure will be described in detail below.

Anode The components of the "anode composition" may be mixed with a solvent to form an anode slurry. Subsequently, the anode slurry may be applied onto the anode current collector and dried to form the anode.

In some embodiments,
Silicon-based active material,
With a binder selected from polyamic acid and polyimide,
A lithium salt capable of being decomposed to lithium oxide and/or lithium peroxide at a temperature of 200 to 400°C, preferably 300 to 370°C, more preferably 340 to 360°C,
An anode composition for a lithium ion battery is provided that includes:

In some examples, the anode composition may further include a carbon material.

In some examples, the anode composition is based on the total weight of the anode composition.
5 to 60% by weight, preferably 5 to 40% by weight of a silicon-based active material,
3-15% by weight, preferably 3-10% by weight, of a binder selected from polyamic acids and polyimides,
2 to 30% by weight, preferably 2 to 20% by weight, of a lithium salt which can be decomposed into lithium oxide and/or lithium peroxide at a temperature of 200 to 400° C.,
0-90 wt%, preferably 30-85 wt%, more preferably 40-85 wt% carbon material,
including.

Each component of the disclosed anode composition is described in detail below.

Silicon-Based Active Material The anode composition according to the present disclosure may include a silicon-based active material. Compared with carbon-based active materials, silicon-based active materials have a larger theoretical capacity and more moderate operating voltage.

As used herein, the term "active material" means a material into which lithium ions can be inserted and from which lithium ions can be released during repeated charge/discharge cycles.

The “silicon-based active material” may be an active material containing a silicon element. There is no particular limitation on the silicon-based active material, and materials known to be used in lithium ion batteries may be used. Examples of suitable silicon-based active materials can include, but are not limited to, silicon, silicon alloys, silicon oxides, silicon/carbon composites, silicon oxide/carbon composites, and any combination thereof. .. In some embodiments, 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 powder available from 3M. In some embodiments, the silicon oxide may be a mixture of two or more silicon oxides. For example, silicon oxide may be represented as SiO _x , and the average value of x may be from about 0.5 to about 2.

In some examples, the content of silicon-based active material is 5-60 wt%, preferably 5-40 wt%, based on the total weight of the anode composition. The total weight of the anode composition means the dry weight not including the weight of the solvent.

Binder The anode composition according to the present disclosure may include a binder selected from polyamic acid and polyimide. The binder holds the components of the anode composition together and adheres the anode composition to the anode current collector, ensuring stability and integrity of the anode when volume changes occur during repeated charge/discharge cycles. Properties and, thus, may help improve the electrochemical properties of the final cell, including cycle performance and rate performance.

In addition, polyamic acids and polyimides have high thermal resistance and are stable at the decomposition temperature of lithium salts, as compared to conventional binders that cannot withstand the high decomposition temperatures of lithium salts (eg PVDF and CMC). ing. In some examples, the resulting polyimide is stable at elevated temperatures, even though the polyamic acid can be dehydrated by heating. Furthermore, polyamic acids and polyimides have good mechanical strength, which helps prevent volume changes during repeated charge/discharge cycles, and is thus beneficial to the electrochemical properties of the final cell. is there.

There is no particular limitation on the polyimide and polyamic acid, and commonly known ones may be used.

Polyimides may include aromatic polyimides, aliphatic polyimides, and alicyclic polyimides. The polyimide repeat unit may include -C(O)-NC(O)-, and one or more aromatic, aliphatic and/or cycloaliphatic moieties.

式中、Ｒ^１及びＲ^２は、それぞれ独立して、Ｃ１〜Ｃ１２アルキル基、Ｃ１〜Ｃ１２アルキレン基、又はＣ１〜Ｃ１２アルキニル基、好ましくは、Ｃ１〜Ｃ６アルキル基であってもよく、ｍは２〜５０、好ましくは２〜３０の整数であってもよい。 In some examples, the polyimide can be represented by Formula I:

In the formula, R ¹ and R ² may be each independently a C1 to C12 alkyl group, a C1 to C12 alkylene group, or a C1 to C12 alkynyl group, preferably a C1 to C6 alkyl group, and m is It may be an integer of 2 to 50, preferably 2 to 30.

式中、ＡｒはＣ６〜Ｃ３０芳香族基を表し、Ｒ^３はＣ１〜Ｃ１２アルキル基、Ｃ１〜Ｃ１２アルケニル基、又はＣ１〜Ｃ１２アルキニル基、好ましくは、Ｃ１〜Ｃ６アルキル基であってもよく、ｎは２〜５０、好ましくは２〜３０の整数であってもよい。 In some examples, the polyimide can be represented by Formula II.

In the formula, Ar represents a C6 to C30 aromatic group, R ³ may be a C1 to C12 alkyl group, a C1 to C12 alkenyl group, or a C1 to C12 alkynyl group, preferably a C1 to C6 alkyl group, n may be an integer of 2 to 50, preferably 2 to 30.

式中、Ｒ^３及びｎはそれぞれ、化学式ＩＩについて上述したものと同じ定義を有し、Ｒ^４は独立してＣ１〜Ｃ１２アルキル基、Ｃ１〜Ｃ１２アルケニル基、又はＣ１〜Ｃ１２アルキニル基、好ましくはＣ１〜Ｃ６アルキル基であってもよい。 In some examples, the polyimide can be represented by Formula III.

Wherein R ³ and n each have the same definition as described above for Formula II, and R ⁴ is independently a C1-C12 alkyl group, a C1-C12 alkenyl group, or a C1-C12 alkynyl group, preferably It may be a C1-C6 alkyl group.

The polyamic acid may include an aromatic polyamic acid, an aliphatic polyamic acid, and an alicyclic polyamic acid. The repeating unit of the polyamic acid may include a carboxy group —C(O)OH, a polyamide group —C(O)—NH—, and one or more aromatic moieties, aliphatic moieties and/or alicyclic moieties. ..

式中、Ａｒ、Ｒ^３、及びｎはそれぞれ、化学式ＩＩについて上述したものと同じ定義を有する。 In some examples, the polyimic acid can be represented by Formula IV.

Wherein Ar, R ³ and n each have the same definition as described above for Formula II.

式中、Ｒ^３、Ｒ^４、及びｎはそれぞれ、化学式ＩＩＩについて上記で説明したものと同じ定義を有する。 In some examples, the polyimic acid can be represented by Formula V:

Wherein R ³ , R ⁴ , and n each have the same definition as described above for Formula III.

To facilitate application of the anode slurry to the anode current collector, the polyamic acid and the polyimide are soluble in the solvent used to form the anode slurry (eg, N-methyl-2-pyrrolidone). preferable.

In some embodiments, the binder content is 3 to 15% by weight, preferably 3 to 10% by weight, based on the total weight of the anode composition.

Lithium Salt The anode composition according to the present disclosure contains a lithium salt that can be decomposed into lithium oxide and/or lithium peroxide at a temperature of 200 to 400° C., preferably 300 to 370° C., more preferably 340 to 360° C. May be included.

At the time of in situ heating, the lithium salt may decompose into lithium oxide and/or lithium peroxide. The lithium oxide and/or lithium peroxide thus obtained can provide an additional source of lithium and compensate for capacity fade, thus significantly improving battery performance (eg initial Coulombic efficiency).

Compared to the known methods of using lithium oxide or lithium peroxide directly, the present disclosure uses a lithium salt as a precursor of lithium oxide, which is environmentally friendly, easy to conduct, and does not require special operating conditions. ing.

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 lithium salt to 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 5:100 to 25:100, preferably 7:100 to 20:100. Controlling the ratio of lithium to silicon within these ranges allows the cells to be pre-lithiated to a desirable high level while at the same time avoiding the excessive introduction of lithium and loss of mass density of the cells. You can

In some examples, the content of lithium salt is 2 to 30% by weight, preferably 2 to 20% by weight, based on the total weight of the anode composition.

Solvent As mentioned above, the anode composition according to the present disclosure may be mixed with a solvent to form an anode slurry. The solvent evaporates when the anode is heated during the subsequent prelithiation step. Therefore, the pre-lithiated anode contains only a small amount of solvent or no solvent.

The solvent is not particularly limited, and those known to be used in lithium ion batteries may be used. An example of a suitable solvent includes N-methyl-2-pyrrolidone (NMP).

Carbon Material The anode composition may further include a carbon material. The “carbon material” may be a material containing elemental carbon. The carbon material may function as an active material different from the silicon-based active material, or may enhance the electrical conductivity and/or dispersibility of the anode composition. There is no particular limitation on the carbon material, and carbon materials known to be used in lithium ion batteries may be used. In some examples, the carbon material can 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. Not limited. In some examples, the carbon black may be Super P (eg, Super P commercially available from Timcal, particle size: about 20 nm or about 40 nm). In some examples, the graphite may be graphite powder (eg, particle size: 2-30 μm), and/or graphite flakes (eg, KS6L commercially available from Timcal, particle size: about 6 μm). The carbon materials may be used individually or in any combination.

In some examples, graphite powder, Super P, and graphite flakes may be used in combinations of two or three of these. The graphite powder functions as a carbon-based active material in the anode, and can thereby buffer the volume change 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 electrical conductivity, two-dimensional dispersibility, and cycle performance.

In addition to the components described above, the anode may optionally contain additives commonly used in electrodes, provided they do not significantly impair cell performance.

There is no particular limitation on the type, shape, size, and/or content of each component of the anode composition.

In some examples, the content of carbon material is 0 to 90% by weight, preferably 30 to 85% by weight, more preferably 40 to 85% by weight, based on the total weight of the anode composition.

Methods of Making Anodes In some embodiments, methods of making an anode are provided, the methods comprising:
Mixing all the components of the anode composition according to the present disclosure with a solvent to form a slurry; and
Applying the slurry to the 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 embodiments, nickel foil, nickel mesh, copper foil, or copper mesh may be used as the anode current collector.

In some embodiments, the method further comprises a calendering step. During decomposition of the lithium salt, gas is generated and porosity is formed. Calendering may provide good control of the porosity of the anode and may evenly distribute lithium oxide and/or lithium peroxide to the anode, which may improve battery performance.

Method of Prelithiating an Anode In some examples, a method of prelithiating an anode made by the methods of the present disclosure is provided, the method comprising: 200 to 400° C., preferably 300 to 370° C. Preferably heating the anode to a temperature of 340-360° C. to decompose the lithium salt into lithium oxide and/or lithium peroxide. When the temperature is within these ranges, the polyimide and/or polyamic acid shows good crosslinking strength and the electrode current collector is not destroyed.

Lithium Ion Batteries In some embodiments, lithium ion batteries are provided, which include an anode made or prelithiated according to the methods of the present disclosure. In addition, lithium-ion batteries also include a cathode and an electrolyte.

Lithium-ion batteries according to the present disclosure may be used in energy storage systems and electric vehicles.

Cathode The "cathode composition" may be mixed to form a cathode slurry. Subsequently, the cathode slurry may be applied onto the cathode current collector and dried to form the cathode.

According to some embodiments of the present disclosure, the cathode may include a lithium-based active material. In some embodiments, the cathode active material can be a material that reversibly desorbs and intercalates lithium ions during charge/discharge cycles. In the discharge cycle, lithium ions derived from the lithium-based active material can return from the anode to the cathode to form the lithium-based active material again.

There is no particular limitation on the lithium-based cathode active material, and a cathode active material generally used in lithium ion cells may be used. In some embodiments, the cathode active material is a lithium metal oxide, a lithium metal phosphate, a lithium metal silicate, and any combination thereof, preferably a lithium transition metal complex oxide, a lithium transition metal phosphorus. May be selected from the group consisting of acid salts, lithium metal silicates, and any combination thereof. In some embodiments, the cathode active material may be selected from the group consisting of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, and any combination thereof. In some embodiments, the lithium transition metal composite oxide is 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/Li ₂ MnO ₃ composite (also referred to as “lithium rich NCM”), or any combination thereof. .. The transition metal may include any transition metal of Groups 3 to 12 of the Periodic Table, such as titanium, zinc, copper, nickel, molybdenum.

In some embodiments, the cathode composition may further include a carbon material, a binder, and a solvent in addition to the lithium-based cathode active material.

There is no particular limitation on the binder, and those known to be used in lithium ion batteries may be used. In some embodiments, the binder may be polyvinylidene fluoride (PVDF), polyacrylic acid (PAA) and its derivatives (eg, LiPAA), sodium carboxymethyl cellulose (CMC), and combinations thereof. ..

The above explanations regarding the carbon material and the solvent in the anode also apply here. The carbon material and solvent in the cathode may each be the same as or different from that contained in the anode.

In addition, other additives commonly known for use in lithium-ion batteries may optionally be used at the cathode as long as they do not adversely affect the desired performance of the battery.

There is no particular limitation on the type, shape, size, and/or content of each component of the cathode composition.

There is no particular limitation on the cathode current collector. In some embodiments, aluminum foil may be used as the cathode current collector.

Electrolyte The lithium-ion battery according to the present disclosure may include an electrolyte. According to some embodiments of the present disclosure, the electrolyte may include a lithium salt and a non-aqueous solvent. There is no particular limitation on the lithium salt and non-aqueous solvent, and lithium salt and non-aqueous solvent generally known in the cell may be used. In some examples, the lithium salt in the electrolyte can be different than the lithium-based active material in the cathode and the lithium salt in the anode. According to some embodiments of the present disclosure, the lithium salt may be lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium arsenate (LiAsO ₄ ), LiSbO ₄ , lithium perchlorate. (LiClO ₄ ), LiAlO ₄ , LiGaO ₄ , lithium bis(oxalate)borate (LiBOB), and any combination thereof may be included, but LiPF ₆ is particularly preferable, but not limited thereto.

According to some embodiments of the present disclosure, the non-aqueous solvent in the electrolyte may include carbonate (ie non-fluorinated carbonate) and fluorinated carbonate. According to some embodiments of the present disclosure, carbonates are cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC); dimethyl carbonate (DMC), diethyl carbonate (DEC), A straight or branched chain carbonate such as dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC); and any combination of the aforementioned carbonates. May include, but are not limited to. According to some embodiments of the present disclosure, the fluorinated carbonate may be a fluorinated derivative of the aforementioned carbonates, such as fluoroethylene carbonate (FEC) and difluoroethylene carbonate, difluorinated dimethyl carbonate (DFDMC). ..

Materials NCM-111: Lithium nickel cobalt manganese oxide, cathode active material, D50:12 μm, available from BASF.
Super P: cathode and anode carbon material, 40 nm, available from Timcal.
PVDF: polyvinylidene fluoride, cathode binder, available from Sovey.
Si-Fe-Ti alloy powder: active material of anode, silicon content: 30% by weight, diameter: 50 nm, available from 3M.
Graphite powder: anode active material, diameter: 20 μm, available from Hitachi.
KS6L: Graphite flakes, carbon material of the anode, about 6 μm, available from Timcal.
U-Varnish A: Anode binder, mixture of 20 wt% polyamic acid and 80 wt% N-methyl-2-pyrrolidinone, available from UBE.
Lithium acetate: Lithium salt, source of prelithiation of anode, available from Guoyao.
NMP: N-methyl-2-pyrrolidone, solvent, available from Guoyao.
Celgard 2325: PP/PE/PP Membrane, Separator, available from Celgard.

Example 1 (Ex.1): Cell preparation Cathode preparation At room temperature, 96.5 g NCM-111, 3 g Super P, and 2.5 g PVDF were placed in a 500 mL round bottom flask equipped with a stirrer. Added to 47 g NMP. After stirring for 3 hours, the resulting uniformly dispersed slurry was coated on aluminum foil and then dried at 80° C. for 6 hours. The coated aluminum foil was cut into several Φ12 mm cathodes.

Preparation of Anode At room temperature, 40 g of Si-Fe-Ti alloy powder, 40 g of graphite powder, 10 g of lithium acetate, 10 g of U-Varnish A (dry weight, in the form of 20% by weight solution in NMP), 2 g. Super P, and 8 g KS6L were added to 70 g NMP in a 500 mL round bottom flask equipped with a stirrer. After stirring for 3 hours, the resulting uniformly dispersed slurry was coated on a copper foil and then dried at 60°C for 30 minutes. The coated copper foil was then fired in a nitrogen gas purged tube furnace (RS80/750/11, Nabertherm) at a heating rate of 20°C/min until the temperature reached 350°C. Then, the coated copper foil was taken out from the tubular furnace and cooled to room temperature (about 25° C.). The coated copper foil was cut into several Φ12 mm anodes.

Preparation of Cell A coin cell (CR2016) was assembled using the cathode and anode obtained above in a glove box (MB-10 compact, MBraun) filled with argon. 1M LiPF ₆ in FEC/EC/EMC (volume ratio 30:35:35) was used as electrolyte. Celgard 2325 was used as a separator.

Comparative Example 1 (Com. Ex. 1)
A coin cell was prepared in the same manner as in Example 1 except that lithium acetate was not used.

[Electrochemical measurement]
The battery performance of each cell obtained in Example 1 and Comparative Example 1 was measured at 25° C. with an Arbin battery test system (model: Arbin BT-G; supplier: Arbin).

Each cell was charged to 4.2 V (relative to Li/Li ⁺ ) with a current of 0.1 C in the first charging cycle. Then, in the first discharge cycle, the cell was discharged to 2.5V with a current of 0.1C. The above charge/discharge cycle was repeated for the second and third cycles. Subsequently, in the 4th to 21st charging cycles, each cell was charged to 4.2V (relative to Li/Li ⁺ ) at various rates. Specifically, the charging rate is 0.1C in the 4th to 6th charging cycles, 1/3C in the 7th to 9th charging cycles, 0.5C in the 10th to 12th charging cycles, and 13th. Was 1C in the 15th to 15th charge cycles, 2C in the 16th to 18th charge cycles, and 3C in the 19th to 21st charge cycles. In the 4th to 21st discharge cycles, the cell was discharged to 2.5V with a current of 0.1C. Finally, each cell was discharged/charged in subsequent cycles within a voltage range of 2.5 to 4.5 V (relative to Li/Li ⁺ ) at a rate of 1 C. The NCM mass loading of each cathode of the cell was approximately 10 mg/cm ² . Specific capacity was calculated based on the weight of NCM.

FIG. 1 compares the cycle performances of the cell of Example 1 and the cell of Comparative Example 1. Referring to FIG. 1, it can be seen that Example 1 exhibited better cycle stability as compared to Comparative Example 1 which did not use a pre-lithiated source.

FIG. 2 compares the discharge/charge profiles of the cells of Example 1 and the cells of Comparative Example 1. Referring to FIG. 2, it can be seen that Example 1 exhibited higher initial Coulombic efficiency in the first charge/discharge cycle as compared to Comparative Example 1 which did not use the pre-lithiated source.

Claims (9)

An anode composition for a lithium ion battery, comprising:
Silicon-based active material,
With a binder selected from polyamic acid and polyimide,
A lithium salt capable of being decomposed into lithium oxide and/or lithium peroxide at a temperature of 200 to 400° C.,
An anode composition comprising: The anode composition of claim 1, wherein the binder is soluble in N-methyl-2-pyrrolidone. 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 silicon-based active material according to claim 1, wherein the silicon-based active material is selected from the group consisting of silicon, a silicon alloy, a silicon oxide, a silicon/carbon composite material, and a silicon oxide/carbon composite material. Anode composition. 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. The anode composition according to any one of claims 1 to 4, which is Based on the total weight of the anode composition,
5 to 60% by weight, preferably 5 to 40% by weight of a silicon-based active material,
3 to 15% by weight, preferably 3 to 10% by weight, of a binder selected from polyamic acids and polyimides,
2 to 30% by weight, preferably 2 to 20% by weight, of a lithium salt which can be decomposed into lithium oxide and/or lithium peroxide at a temperature of 200 to 400° C.,
0-90 wt%, preferably 30-85 wt%, more preferably 40-85 wt% carbon material,
The anode composition according to claim 1, which comprises: A method of making an anode, comprising:
Mixing all the components of the anode composition according to any one of claims 1 to 6 with a solvent to form a slurry;
Applying the slurry to an anode current collector;
Including the method. A method of prelithiating an anode made according to the method of claim 7, wherein the anode is heated to a temperature of 200 to 400° C. to decompose the lithium salt into lithium oxide and/or lithium peroxide. A method, including: A lithium ion battery comprising an anode made according to the method of claim 7 or a prelithiated anode according to the method of claim 8.

Images