CN102593508B - Lithium ion battery - Google Patents

Abstract

The present invention provides a lithium ion battery, which has excellent cycle life characteristics and high temperature storage performance. It includes: a cathode containing a cathode active material; an anode containing an anode active material; a separator interposed between the cathode and the anode; and an electrolyte containing: a lithium salt, an organic solvent, a halogenated cyclic carbonate, a cyclic Disulfonate compound; the cathode active material is: _{LiNixCoyM1 -X- YO2 ,} wherein M is selected from one or more of Mn, Al, Ti, Zn, 0.5≤x≤ 1, 0≤y≤0.5, while 1‑x‑y≥0.

Description

Lithium Ion Battery

technical field

The invention relates to the field of electrochemistry, in particular to the field of lithium ion secondary batteries.

Background technique

In recent years, portable electronic products, such as cameras, digital video cameras, mobile phones, and notebook computers, have been widely used in people's daily life, and there is a strong demand for smaller size, lighter weight, and longer life. Therefore, it is required to develop a mobile power source that is compatible with portable electronic products, especially a lightweight secondary battery that can provide high energy density. Compared with lead-acid batteries, nickel-cadmium batteries, and nickel-metal hydride batteries, lithium-ion batteries are widely used in the above-mentioned portable battery products because of their high energy density, high working voltage, long life, and environmental protection.

Lithium-ion batteries are mainly composed of positive and negative electrodes, electrolyte and separator. The positive electrode is mainly lithium metal oxide, and the negative electrode is mainly carbon material. Since the average discharge voltage of a Li-ion battery is approximately 3.6-3.7V, an electrolyte composition that is stable within a charge/discharge voltage of 0-4.2V is required. For this reason, the electrolyte used in lithium-ion batteries must be a non-aqueous electrolyte, such as usually using a solvent containing cyclic carbonate (such as ethylene carbonate) and a linear carbonate solvent (such as dimethyl carbonate, diethyl carbonate, methyl carbonate, etc.) ethyl ester) as the electrolyte.

During the first charging process of lithium-ion batteries, lithium ions are deintercalated from the lithium metal oxide of the cathode active material, migrate to the anode carbon electrode under the drive of voltage, and then sneak into the carbon material. In this process, the electrolyte reacts with the surface of the carbon anode to produce Li ₂ CO ₃ , Li ₂ O, LiOH and other substances, thereby forming a passivation film on the surface of the carbon anode, which is called a solid electrolyte Interfacial (SEI) film. Since lithium ions must pass through this SEI film regardless of charging or discharging, the performance of the SEI film determines many properties of the battery (such as cycle performance, high temperature performance, rate performance).

After the SEI film is formed during the first charge-discharge process, it can further prevent the decomposition of electrolyte solvent molecules and form ion channels in subsequent charge-discharge cycles. However, as the charge and discharge progress, the electrode repeatedly expands and contracts. In this case, the SEI film may rupture or gradually dissolve, and the exposed anode continues to react with the electrolyte while generating gas, thereby increasing the battery capacity. The internal pressure and greatly reduce the cycle life characteristics of the battery. According to the type of carbonate used in the electrolyte and the type of anode active material, the gas produced mainly includes CO, CO ₂ , CH ₄ , C ₂ H ₆ and so on.

Since the electrode surface film affects the initial charge-discharge efficiency, cycle life, and safety of the lithium-ion battery, controlling the formation of the electrode surface film is necessary to realize a high-performance lithium-ion battery. The regulation of the electrode surface film can be achieved by adding certain additives to the electrolyte, because these additive molecules can be preferentially reduced on the anode surface to form a passivation film on the anode surface, which can prevent the electrolyte solvent molecules from Further, the decomposition and co-intercalation of solvent molecules continue on the surface of the anode, and can exist stably in subsequent cycles. During the first charging process, FEC can preferentially reduce the solvent on the surface of the negative electrode, inhibit the further decomposition of the solvent, and improve the stability of the SEI film, thereby improving the cycle performance of the battery.

However, although FEC can improve the cycle performance of the battery, it reduces the high-temperature performance of the battery. When the battery is stored or cycled at high temperature, the battery will swell, which seriously affects the safety performance of the battery. Especially when the cathode material is a composite oxide containing nickel, the high temperature performance is even worse. This is because the surface activity of the nickel-containing composite oxide cathode material is higher in the later stage of charging, and the higher the nickel content, the higher the surface activity, and the decomposition reaction of solvent molecules on the surface causes the battery to bulge.

Therefore, those skilled in the art of lithium-ion batteries are actively looking for suitable additives to improve the performance of lithium batteries. "The Chinese patent application of "disclosed the technical scheme of adding fluorine-containing sulfonate compounds in the electrolyte to suppress the occurrence of gas generation inside the battery, thereby achieving the purpose of improving battery performance.

However, simply adding sulfonate compounds cannot achieve satisfactory technical effects.

Contents of the invention

The object of the present invention is to provide a lithium ion battery which has excellent cycle life characteristics and high temperature storage performance.

In order to achieve the above-mentioned purpose of the invention, the present invention provides a lithium ion battery, which includes:

a cathode comprising a cathode active material;

an anode comprising an anode active material;

a separator placed between the cathode and the anode;

And electrolyte solution, which contains: lithium salt, organic solvent, halogenated cyclic carbonate, cyclic disulfonate compound;

The chemical structure of the cyclic disulfonate compound is shown in structural formula I:

Among them, A is selected from a straight-chain or branched alkylene group, a straight-chain or branched haloalkylene group with 1-5 carbon atoms; B is selected from sulfinyl, carbonyl or the following One of the groups: alkylene, haloalkylene containing 1-5 carbon atoms;

The chemical structure of the halogenated cyclic carbonate is shown in structural formula II:

Wherein, wherein R ₁ , R ₂ , R ₃ and R ₄ are independently selected from a hydrogen atom, a halogen atom, an alkyl group or a haloalkyl group with 1-2 carbon atoms, and R ₁ , R ₂ , R ₃ and R ₄ At least one of them is selected from a halogen atom or a haloalkyl group.

The cathode active material is: LiNi _x Co _y M _1-XY O ₂ , wherein M is selected from one or more of Mn, Al, Ti, Zn, 0.5≤x≤1, 0≤y≤0.5, and at the same time 1-xy ≥ 0.

As a preferred version of the present invention, the cyclic disulfonate compound is selected from one or more of the compounds shown in the following molecular formula 1-molecular formula 5:

In addition, compounds can also be selected from:

As a preferred solution of the present invention, the content of the cyclic disulfonate ester compound in the electrolyte is 0.1%-5% based on the total weight of the electrolyte.

As a preferred solution of the present invention, the content of the cyclic disulfonic acid ester compound in the electrolyte is 1%-5% based on the total weight of the electrolyte.

As a preferred version of the present invention, the halogenated cyclic carbonate is selected from one or more of the compounds shown in the following molecular formula 6-molecular formula 10:

In addition, compounds can also be selected from:

As a preferred solution of the present invention, the content of the halogenated cyclic carbonate in the electrolyte is 0.1-10% by weight based on the total weight of the electrolyte.

As a preferred solution of the present invention, the content of the halogenated cyclic carbonate in the electrolyte is 2-5% by weight based on the total weight of the electrolyte.

As a preferred solution of the present invention, the content of the cyclic disulfonate compound in the electrolyte: the content of the halogenated cyclic carbonate in the electrolyte is 1:1-1:5.

Compared with the traditional lithium ion battery, the lithium ion battery of the present invention has excellent cycle life characteristics and high temperature storage performance.

detailed description

In order to describe in detail the technical content, structural features, achieved objectives and effects of the present invention, the following will be described in detail in conjunction with the embodiments.

Example 1

Li-ion battery production:

Positive electrode production: mix positive electrode active material lithium nickel cobalt manganese oxide (LiNi _0.5 Co _0.3 Mn _0.2 O ₂ ), conductive carbon black Super-P and binder polyvinylidene fluoride (PVDF) at a mass ratio of 93:4:3 ), and then they were dispersed in N-methyl-2-pyrrolidone (NMP) to obtain positive electrode slurry. The slurry is uniformly coated on both sides of the aluminum foil, dried, calendered and vacuum-dried, and an aluminum lead-out wire is welded on by an ultrasonic welder to obtain a positive plate with a thickness of 120-150 μm.

Negative electrode production: mix negative electrode active material modified natural graphite, conductive carbon black Super-P, binding agent styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) by the mass ratio of 94: 1: 2.5: 2.5, then They were dispersed in deionized water to obtain negative electrode slurry. The slurry is coated on both sides of the copper foil, dried, calendered and vacuum dried, and a nickel lead wire is welded with an ultrasonic welder to obtain a negative plate, the thickness of which is 120-150 μm.

Preparation of electrolyte: mix ethylene carbonate (EC), diethyl carbonate (DEC) and ethyl methyl carbonate (EMC) in a weight ratio of EC:DEC:EMC=1:1:1, after mixing, Then add lithium hexafluorophosphate (LiPF6) to a molar concentration of 1mol/L, then add 2% of the cyclic disulfonic acid ester compound of the molecular formula 1 by the total mass of the electrolyte and 1% of the compound of the molecular formula 6 by the total mass of the electrolyte Halocarbonate compounds.

Diaphragm production: Polypropylene/polyethylene/polypropylene three-layer isolation film with a thickness of 20 μm is used.

The preparation of the battery core places a polyethylene microporous membrane with a thickness of 20 μm as a separator between the positive plate and the negative plate, and then winds the sandwich structure composed of the positive plate, negative plate and separator, and then flattens the wound body Put it into a square aluminum metal shell, weld the lead wires of the positive and negative electrodes to the corresponding positions of the cover plate, and use a laser welding machine to weld the cover plate and the metal shell into one body to obtain the battery cell to be injected.

The liquid injection and formation of the battery core is in a glove box with a dew point controlled below -40°C. The electrolyte solution prepared above is injected into the battery core through the liquid injection hole. The amount of electrolyte solution must ensure that the gap in the battery core is filled. Then carry out the formation according to the following steps: 0.05C constant current charging for 3 minutes, 0.2C constant current charging for 5 minutes, 0.5C constant current charging for 25 minutes, after shelving for 1 hour and then shaping and sealing, then further charging with a constant current of 0.2C to 4.2V, and shelving at room temperature After 24 hours, discharge to 3.0V with a constant current of 0.2C.

Normal temperature cycle performance test

Charge at a constant current of 1C to 4.2V, then charge at a constant voltage until the current drops to 0.1C, then discharge at a constant current of 1C to 3.0V, and cycle for 200 cycles, record the discharge capacity of the first week and the discharge capacity of the 200th week Discharge capacity, the capacity retention rate is calculated according to the following formula:

Capacity retention rate = discharge capacity in the 200th week / discharge capacity in the first week * 100% high temperature storage performance test

Charge at room temperature with a constant current of 1C to 4.2V, then charge at a constant voltage until the current drops to 0.1C, measure the thickness of the battery, and then store the battery in an oven with a constant temperature of 85°C for 4 hours. After taking it out, let the battery cool down to room temperature , measure the thickness of the battery, and calculate the thickness expansion rate of the battery according to the following formula:

Thickness expansion rate = (battery thickness after storage - battery thickness before storage) / battery thickness before storage * 100%

Example 2

This embodiment is similar to embodiment 1, except that: the cyclic disulfonate compound is of molecular formula 2, and the halogenated carbonate compound is of molecular formula 7.

Example 3

This example is similar to Example 1, except that: the cyclic disulfonate compound is of molecular formula 3, and the halogenated carbonate compound is of molecular formula 8.

Example 4

This example is similar to Example 1, except that: the cyclic disulfonate compound is of molecular formula 4, and the halogenated carbonate compound is of molecular formula 9.

Example 5

This example is similar to Example 1, except that: the cyclic disulfonate compound is of molecular formula 5, and the halogenated carbonate is of molecular formula 10.

Comparative example 1

This comparative example is similar to Example 1, except that the cyclic disulfonate compound is not added to the electrolytic solution.

Comparative example 2

This example is similar to Example 1, except that the halocarbonate is not added to the electrolyte.

Table I:

From the data in Table 1, it can be seen that the battery has excellent cycle performance when halogenated carbonate compounds are added to the electrolyte, but the battery bulges severely when stored at high temperature, and the battery with the addition of cyclic disulfonate compounds can improve the high temperature of the battery. performance. However, the cycle performance is reduced. When the halocarbonate and the cyclic disulfonate compound are added to the electrolyte at the same time, good cycle performance can be maintained without reducing the high temperature performance.

Example 6

This embodiment is similar to Example 1, except that the cyclic disulfonic ester compound is of molecular formula 6, and its content is 5% of the total mass of the electrolyte, and the halogenated carbonate compound is of molecular formula 1, which The content is 0.1% of the total mass of the electrolyte.

Example 7

This embodiment is similar to Example 1, except that the cyclic disulfonate compound is of molecular formula 6, and its content is 0.1% of the total mass of the electrolyte, and the halogenated carbonate compound is of molecular formula 1, which The content is 10% of the total mass of the electrolyte.

Example 8

This embodiment is similar to Example 1, except that the cyclic disulfonic acid ester compound is of molecular formula 6, and its content is 2% of the total mass of the electrolyte, and the halogenated carbonate compound is of molecular formula 1, which The content is 5% of the total mass of the electrolyte.

Example 9

This embodiment is similar to Example 1, except that the cyclic disulfonic acid ester compound is of molecular formula 6, and its content is 2% of the total mass of the electrolyte, and the halogenated carbonate compound is of molecular formula 1, which The content is 2% of the total mass of the electrolyte.

Example 10

This embodiment is similar to Example 1, except that the cyclic disulfonic ester compound is of molecular formula 6, and its content is 1% of the total mass of the electrolyte, and the halogenated carbonate compound is of molecular formula 1, which The content is 3% of the total mass of the electrolyte.

Example 11

This embodiment is similar to Example 1, except that the cyclic disulfonic ester compound is of molecular formula 6, and its content is 5% of the total mass of the electrolyte, and the halogenated carbonate compound is of molecular formula 1, which The content is 3% of the total mass of the electrolyte.

Example 12

This embodiment is similar to Example 1, except that the cyclic disulfonic ester compound is of molecular formula 2, and its content is 3% of the total mass of the electrolyte, and the halogenated carbonate compound is of molecular formula 7, which The content is 0.1% of the total mass of the electrolyte.

Example 13

This embodiment is similar to Example 1, except that the cyclic disulfonic ester compound is of molecular formula 3, and its content is 0.1% of the total mass of the electrolyte, and the halogenated carbonate compound is of molecular formula 8, which The content is 5% of the total mass of the electrolyte.

Example 14

This embodiment is similar to Example 1, except that the cyclic disulfonate compound is of molecular formula 4, and its content is 3% of the total mass of the electrolyte, and the halogenated carbonate compound is of molecular formula 9, which The content is 2% of the total mass of the electrolyte.

Example 15

This embodiment is similar to Example 1, except that the cyclic disulfonic ester compound is of molecular formula 5, and its content is 1% of the total mass of the electrolyte, and the halogenated carbonate compound is of molecular formula 10, which The content is 5% of the total mass of the electrolyte.

Comparative example 3

This comparative example is similar to Example 1, except that: the halogenated carbonate compound is molecular formula 6, its content is 2% of the total amount of the electrolyte, and the cyclic disulfonate compound is not added to the electrolyte. ,

Comparative example 4

This comparative example is similar to Example 1, except that the cyclic disulfonate compound is of molecular formula 3, and its content is 1% of the total amount of the electrolyte, and the halogenated carbonate compound is not added to the electrolyte.

Table II

It can be known from the data in Table 2 that when the halocarbonate is added too little, the battery cycle performance is poor due to the inability to form an effective passivation film on the surface of the anode; when the halocarbonate is added too much, although the battery cycle performance can be improved, However, the high-temperature performance is reduced, and the battery bulges seriously. When the cyclic disulfonate compound is too small, the battery swelling cannot be effectively suppressed, but when it is added too much, although the battery swelling can be suppressed, the cycle performance of the battery is seriously reduced.

Example 16

This example is similar to Example 1, except that LiNi _0.7 Co _0.15 Mn _0.15 O ₂ is used instead of LiNi _0.5 Co _0.3 Mn _0.2 O ₂ .

Example 17

This embodiment is similar to embodiment 1, except that LiNi _0.8 Co _0.1 Mn _0.1 O ₂ is used instead of LiNi _0.5 Co _0.3 Mn _0.2 O ₂ .

Example 18

This embodiment is similar to embodiment 1, except that LiNi _0.8 Co _0.2 O ₂ is used instead of LiNi _0.5 Co _0.3 Mn _0.2 O ₂ .

Example 19

This embodiment is similar to embodiment 1, except that LiNi _0.5 Co _0.3 Mn _0.2 O ₂ is replaced by LiNi _0.8 Co _0.15 Al _0.55 O ₂ .

Table three

It can be seen from the indicated data that as the nickel content in the cathode material increases, the high temperature performance of the battery decreases, and the battery bulge becomes more serious.

The above is only an embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process conversion made by using the content of the description of the present invention, or directly or indirectly used in other related technical fields, shall be The same reasoning is included in the patent protection scope of the present invention.

Claims (7)

1. A lithium ion battery, characterized in that it comprises: a cathode comprising a cathode active material; an anode comprising an anode active material; a separator placed between the cathode and the anode; And an electrolyte solution, which contains: a lithium salt, an organic solvent, and an electrolyte solution additive consisting of a halogenated cyclic carbonate and a cyclic disulfonate compound; The chemical structure of the cyclic disulfonate compound is shown in structural formula I: Wherein, A is selected from a straight-chain or branched alkylene group, a straight-chain or branched haloalkylene group of 1-5 carbon atoms; B is selected from a sulfinyl group or a carbonyl group; The chemical structure of the halogenated cyclic carbonate is shown in the structural formula II: Wherein, wherein R ₁ , R ₂ , R ₃ and R ₄ are independently selected from a hydrogen atom, a halogen atom, an alkyl group or a haloalkyl group with 1-2 carbon atoms, and R ₁ , R ₂ , R ₃ and R ₄ At least one of them is selected from a halogen atom or a haloalkyl group; The cathode active material is: _LiNix Co _y M _1-XY O ₂ , wherein M is selected from one or more of Al, Ti, Zn, 0.5≤x<1, 0≤y≤0.5, and 1- xy≥0; The content of the cyclic disulfonate compound in the electrolyte: the content of the halogenated cyclic carbonate in the electrolyte is 1:1-1:5. 2. The lithium-ion battery according to claim 1, wherein the cyclic disulfonate compound is selected from one or more of the compounds shown in the following molecular formula 4-molecular formula 5: 3. The lithium-ion battery according to claim 2, wherein the content of the cyclic disulfonate compound in the electrolyte is 0.1%-5% by weight of the electrolyte. 4. The lithium-ion battery according to claim 3, wherein the content of the cyclic disulfonate compound in the electrolyte is 1%-2% by weight of the electrolyte. 5. The lithium ion battery according to claim 1, wherein the halogenated cyclic carbonate is selected from one or more of the compounds shown in the following molecular formula 6-molecular formula 9: 6 . The lithium ion battery according to claim 5 , wherein the content of the halogenated cyclic carbonate in the electrolyte is 0.1-10% by weight based on the total weight of the electrolyte. 7. The lithium ion battery according to claim 6, wherein the content of the halogenated cyclic carbonate in the electrolyte is 2-5% by weight based on the total weight of the electrolyte.