WO2020078308A1 - Secondary battery - Google Patents

Abstract

The present invention provides a secondary battery. The secondary battery comprises a positive electrode piece, a negative electrode piece, an electrolyte, and an isolating film; the positive electrode piece comprises a positive current collector and a positive diaphragm provided on at least one surface of the positive current collector and comprising an positive active material; and the negative electrode piece comprises a negative current collector and a negative diaphragm provided on at least one surface of the negative current collector and comprising a negative active material. The secondary battery also meets: 0.1≤(D50_{negative electrode}×M_{negative electrode})/[(D50_{positive electrode}+4)×(M_{negative electrode}+4)]≤1.5. The secondary battery having the advantages of long cycle life, high energy density, and quick charging and discharging capacity, provided by the present invention, is obtained by reasonably matching a relationship between particle sizes of the positive and negative active materials and capacities of the positive and negative diaphragms.

Description

Secondary battery Technical field

The invention relates to the field of batteries, in particular to a secondary battery.

Background technique

Rechargeable batteries have outstanding characteristics such as light weight, high energy density, no pollution, no memory effect, and long service life, so they are widely used in mobile phones, computers, household appliances, power tools and other fields. Among them, charging time is increasingly valued by end consumers, and is also an important factor limiting the popularity of rechargeable batteries. From the technical principle, the key to determining the charging speed of rechargeable batteries is the negative electrode.

In addition, for rechargeable batteries, the output power, that is, the rapid discharge capacity of the battery, is also an important factor that limits the rapid popularity of rechargeable batteries. From the technical principle, the key to determining the output power of the rechargeable battery is the positive electrode.

Therefore, the matching of the dynamic performance of the positive pole piece and the negative pole piece is crucial to the influence of the rechargeable battery.

Summary of the invention

In view of the problems in the background art, an object of the present invention is to provide a secondary battery that has a long cycle life, high energy density, and rapid charge and discharge capability.

In order to achieve the above object, the present invention provides a secondary battery including a positive electrode tab, a negative electrode tab, an electrolyte, and a separator. The positive electrode tab includes a positive electrode current collector and is provided on at least one surface of the positive electrode current collector and A positive electrode sheet including a positive electrode active material, the negative electrode sheet including a negative electrode current collector and a negative electrode film provided on at least one surface of the negative electrode current collector and including a negative electrode active material. The secondary battery further satisfies: 0.1≤ (D50 _{negative negative} × M) / [(D50 _positive +4) × (M _positive +4)] ≤1.5; wherein, D50 _{of the positive electrode} active material for the positive electrode cumulative volume percentage of 50% corresponding to the particle size, the unit is μm; D50 when the cumulative volume percentage of _{the negative} electrode active material 50% particle diameter corresponding to units of [mu] m; M is a _{positive electrode} capacity per unit area of the positive electrode membrane unit is mAh / cm ^2; M is a _{negative electrode} capacity per unit area of the negative electrode membrane unit is mAh / cm ^2.

Compared with the prior art, the present invention includes at least the following beneficial effects: The present invention obtains a combination of long cycle life, reasonable matching between the positive and negative electrode active material particle sizes, and the positive and negative electrode diaphragm capacitances. Secondary battery with high energy density and fast charge and discharge capability.

detailed description

The secondary battery according to the present invention will be described in detail below.

The secondary battery of the present invention includes a positive electrode tab, a negative electrode tab, an electrolyte, and a separator. The positive electrode tab includes a positive electrode current collector and a positive electrode film provided on at least one surface of the positive electrode current collector and including a positive electrode active material. The negative electrode sheet includes a negative electrode current collector and a negative electrode membrane provided on at least one surface of the negative electrode current collector and including a negative electrode active material.

The secondary battery of the present invention also satisfies: 0.1 ≦ (D50 _{negative electrode} × M _{negative electrode} ) / [(D50 _{positive electrode} + 4) × (M _{positive electrode} + 4)] ≦ 1.5. Wherein _{the positive electrode} D50 cumulative volume percentage of the positive electrode active material reached a particle diameter corresponding to 50%, in units of [mu] m; D50 _{negative electrode} is a negative electrode active material accumulated volume percentage reaches 50% of the particle diameter corresponding to units of [mu] m; _{the positive electrode} M is the capacitance per unit area of the positive electrode film, in units of mAh / cm ^2; M is a _{negative electrode} capacity per unit area of the negative electrode membrane unit is mAh / cm ^2.

Generally, when designing a secondary battery, if the dynamic performance of the positive pole piece is much better than that of the negative pole piece, the negative electrode will be charged to a very low potential at a high SOC during the rapid charging of the battery. It will reach 0V in advance, and the active ions will be reduced and precipitated directly on the surface of the negative electrode; if the dynamic performance of the negative pole piece is much better than that of the positive pole piece, the positive electrode will be discharged to a high SOC during the rapid discharge of the battery Very high potential, and the positive pole piece cannot accept a large amount of active ions in a moment, resulting in obvious polarization. The battery reaches the cut-off voltage in advance, the battery capacity cannot be exerted, and during the long-term cycle use of the battery, the positive electrode active material The structural damage is also relatively large, and the cycle life of the battery will also be affected.

After extensive research the inventors found that, when the secondary battery satisfies 0.1≤ (D50 _{negative negative} × M) / [(D50 _{positive electrode} +4) × (M _positive +4)] ≤1.5, the positive electrode sheet and negative electrode sheet The kinetic performance can be well matched, and the resulting secondary battery can have a long cycle life, high energy density and fast charge and discharge capabilities.

In the pole pieces of the positive electrode, the positive electrode active material particle diameter D50 of the larger _{of the positive electrode,} under the same conditions, kinetic properties of the positive electrode sheet is usually worse; _{a positive} electrode larger capacitance per unit area of the membrane M, the energy of the secondary battery The higher the density, the worse the kinetic performance.

Similarly, the negative electrode sheet, negative electrode D50 of the larger particle diameter of _{the negative electrode} active material, under the same conditions, the kinetic performance of the negative electrode sheet is usually worse; the larger the negative electrode capacity per unit area of the diaphragm M _negative, the negative electrode The worse the kinetic performance of the tablets.

After extensive research, the inventor found that when 0.1≤ (D50 _{negative electrode} × M _{negative electrode} ) / [(D50 _{positive electrode} + 4) × (M _{positive electrode} + 4)] ≤1.5, the charge and discharge capabilities of the positive electrode and negative electrode are reasonable The battery can simultaneously have a long cycle life, high energy density and fast charge and discharge capabilities. If (D50 _{negative electrode} × M _{negative electrode} ) / [(D50 _{positive electrode} + 4) × (M _{positive electrode} + 4)] is greater than 1.5, it means that the kinetic performance of the positive pole piece is much better than that of the negative pole piece, and the battery is quickly charged During the process, the negative electrode will be charged to a very low potential at high SOC. The negative electrode potential will reach 0V in advance, and the active ions will be reduced and precipitated directly on the surface of the negative electrode; if (D50 _{negative electrode} × M _{negative electrode} ) / [(D50 _{positive electrode} +4 ) × ( _Mpositive + 4)] less than 0.1, indicating that the dynamic performance of the negative pole piece is much better than that of the positive pole piece. During the rapid discharge of the battery, the positive pole will be discharged to a very high Potential, and the positive pole piece cannot accept a large amount of active ions in a moment, resulting in obvious polarization, the battery reaches the cut-off voltage in advance, the battery capacity cannot be exerted, and the structure of the positive electrode active material is damaged during the long-term cycle use of the battery It is also relatively large, and thus the cycle life of the battery will also be affected.

In some embodiments of the present invention, the lower limit value of (D50 _{negative electrode} × M _{negative electrode} ) / [(D50 _{positive electrode} + 4) × (M _{positive electrode} + 4)] may be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7,0.8, (D50 _{negative negative} × M) / [(D50 _{positive electrode} +4) × _(positive M +4)] the upper limit may be 0.5,0.6,0.7,0.8,0.9,1.0,1.1,1.2, 1.3, 1.4, 1.5.

Preferably, 0.2≤ (D50 _{negative electrode} × M _{negative electrode} ) / [(D50 _{positive electrode} + 4) × (M _{positive electrode} + 4)] ≤1.0; more preferably, 0.3≤ (D50 _{negative electrode} × M _{negative electrode} ) / [(D50 _{positive electrode} + 4) × (M _positive +4)] ≤ 0.7.

In the secondary battery of the present invention, it is preferable that 35 ≦ (D50 _{positive electrode} + 4) × (M _{positive electrode} + 4) ≦ 230. Among them, the lower limit value of (D50 _{positive electrode} +4) × (M _{positive electrode} +4) can be 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, (D50 _{positive electrode} +4) × (M _{positive electrode} +4) The upper limit value can be 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230. More preferably, 60 ≦ (D50 _{positive electrode} + 4) × (M _{positive electrode} + 4) ≦ 150. Within the preferred range, the positive pole piece can have both good dynamic performance and high volume energy density.

In the secondary battery of the present invention, preferably, the positive active material of _{positive electrode} particle diameter D50 of 0.2μm ~ 25μm; more preferably, the positive active material of _{positive electrode} particle diameter D50 of 0.4μm ~ 15μm. Within the preferred range, the positive pole piece can have better kinetic performance, which is more conducive to improving the rapid discharge capacity and cycle life of the secondary battery.

In the secondary battery of the present invention, preferably, the positive electrode film capacitance per unit area of _{the positive electrode} M ^{1mAh / cm 2 ~ 10mAh / cm} 2; more preferably, the positive electrode capacitance per unit area of the diaphragm M is a _{positive electrode} ^{2mAh / cm 2 ~ 6mAh / cm} 2. Within the preferred range, the positive pole piece can have better kinetic performance, which is more conducive to improving the rapid discharge capacity and energy density of the secondary battery.

In the secondary battery of the present invention, preferably, 1 ≦ D50 _{negative electrode} × M _{negative electrode} ≦ 100. Among them, the lower limit of D50 _{negative electrode} × M _{negative electrode} can be 1, 2, 4, 6, 8, 8, 10, 12, 14, 16, 18, 20, and the upper limit of D50 _{negative electrode} × M _{negative electrode} can be 18, 20, 22, 24, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100. More preferably, 10 ≦ D50 _{negative electrode} × M _{negative electrode} ≦ 80. Within the preferred range, the negative pole piece can have both good dynamic performance and high volume energy density.

In the secondary battery of the present invention, preferably, the particle diameter of the negative electrode is _{the negative electrode} active material D50 of 0.4μm ~ 30μm; More preferably, the particle diameter D50 of the negative electrode is _{the negative electrode} active material is 0.5μm ~ 16μm. Within the preferred range, the negative pole piece can have better kinetic performance, which is more conducive to improving the rapid charging ability and cycle life of the secondary battery.

In the secondary battery of the present invention, preferably, the negative electrode capacitance per unit area of the diaphragm M of _{the negative electrode} ^{1mAh / cm 2 ~ 10mAh / cm} 2; more preferably, the negative electrode capacitance per unit area of the diaphragm M is _{a negative electrode} ^{2mAh / cm 2 ~ 7mAh / cm} 2. Within the preferred range, the negative pole piece may have better dynamic performance, which is more conducive to improving the rapid charging ability and energy density of the secondary battery.

In the secondary battery of the present invention, the positive electrode diaphragm may be provided on one surface of the positive electrode current collector or on both surfaces of the positive electrode current collector. The positive electrode diaphragm may further include a conductive agent and a binder, wherein the types and contents of the conductive agent and the binder are not specifically limited, and can be selected according to actual needs. The type of the positive electrode current collector is also not specifically limited, and can be selected according to actual needs.

In the secondary battery of the present invention, the negative electrode diaphragm may be provided on one surface of the negative electrode current collector or on both surfaces of the negative electrode current collector. The negative electrode diaphragm may further include a conductive agent and a binder, wherein the types and contents of the conductive agent and the binder are not specifically limited, and can be selected according to actual needs. The type of the negative electrode current collector is also not specifically limited, and can be selected according to actual needs.

It should be noted that when the positive and negative electrode membranes are provided on both surfaces of the positive and negative current collectors, as long as the positive electrode membrane on any one surface of the positive electrode current collector and the negative electrode membrane on any one surface of the negative electrode current collector The sheet satisfies 0.1 ≦ (D50 _{negative electrode} × M _{negative electrode} ) / [(D50 _{positive electrode} + 4) × (M _{positive electrode} + 4)] ≦ 1.5, that is, the battery is considered to fall within the protection scope of the present invention. At the same time, the positive and negative diaphragm parameters given by the present invention also refer to the parameters of the single-sided positive and negative diaphragms.

In the secondary battery of the present invention, the specific type of the positive electrode active material is not specifically limited, and can be selected according to actual needs. Preferably, the positive electrode active material may be selected from lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, olivine structure One or more of lithium-containing phosphates. More preferably, the positive electrode active material may be specifically selected from LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (NCM333), LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (NCM523), LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (NCM622), LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (NCM811), LiNi _0.85 Co _0.15 Al _0.05 O ₂ , LiFePO ₄ (LFP), LiMnPO ₄ Or several.

In the secondary battery of the present invention, the specific type of the negative electrode active material is not specifically limited, and can be selected according to actual needs. Preferably, the negative electrode active material may be selected from one or more of carbon materials, silicon-based materials, tin-based materials, and lithium titanate. Wherein, the carbon material may be selected from one or more of graphite, soft carbon, hard carbon, carbon fiber, mesophase carbon microspheres; the graphite may be selected from one or more of artificial graphite and natural graphite ; The silicon-based material may be selected from one or more of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon alloys; the tin-based material may be selected from elemental tin, tin-oxygen compounds, tin alloys One or more. More preferably, the negative electrode active material is selected from one or more of carbon materials and silicon-based materials.

In the secondary battery of the present invention, the separator is provided between the positive pole piece and the negative pole piece to play a role of isolation. The type of the separator is not specifically limited, and may be any separator material used in existing batteries, such as polyethylene, polypropylene, polyvinylidene fluoride, and their multilayer composite membranes, but not limited to These ones.

In the secondary battery of the present invention, the type of the electrolyte is not particularly limited, and may be a liquid electrolyte (also called an electrolyte) or a solid electrolyte. Preferably, the electrolyte uses a liquid electrolyte. Wherein, the liquid electrolyte may include an electrolyte salt and an organic solvent. The specific types of the electrolyte salt and the organic solvent are not subject to specific restrictions, and can be selected according to actual needs. The electrolyte may further include additives, and the types of the additives are not particularly limited. The additives may be negative electrode film-forming additives, positive electrode film-forming additives, or additives that can improve certain performance of the battery, such as improving battery performance. Additives for charging performance, additives for improving high temperature performance of batteries, additives for improving low temperature performance of batteries, etc.

The following uses a lithium-ion battery as an example and combines with specific embodiments to further elaborate the application. It should be understood that these embodiments are only used to illustrate the present application and not to limit the scope of the present application.

Example 1

(1) Preparation of positive pole pieces

The positive electrode active material (see Table 1 for details), the conductive agent Super P, the binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 96: 2: 2, and the solvent N-methylpyrrolidone (NMP) is added in a vacuum Stir until the system is uniform under the action of the mixer to obtain the positive electrode slurry; apply the positive electrode slurry evenly on the positive electrode current collector aluminum foil, then dry the positive electrode current collector coated with the positive electrode slurry at room temperature and transfer to the oven to continue Drying, and then cold pressing and slitting to obtain positive pole pieces.

(2) Preparation of negative pole pieces

Mix the negative electrode active material (see Table 1 for details), the conductive agent Super P, the thickener sodium carboxymethyl cellulose (CMC), and the binder styrene-butadiene rubber (SBR) in a mass ratio of 94.5: 1.5: 1.5: 2.5 , Add solvent deionized water and stir under the action of a vacuum mixer until the system is uniform to obtain a negative electrode slurry; apply the negative electrode slurry uniformly on the negative electrode current collector copper foil, and then apply the negative electrode slurry coated negative electrode slurry The fluid is dried at room temperature and then transferred to an oven to continue drying, and then cold-pressed and slit to obtain a negative pole piece.

(3) Preparation of electrolyte

Ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1: 1: 1 to obtain an organic solvent, and then the fully dried lithium salt LiPF _{6 is} dissolved in the mixture After the organic solvent is prepared, a concentration of 1mol / L electrolyte is prepared.

(4) Preparation of isolation membrane

Polyethylene film is used as isolation film.

(5) Preparation of lithium ion battery

The above positive pole pieces, separators and negative pole pieces are stacked in order, so that the separation membrane is placed between the positive and negative pole pieces to play the role of isolation, and then wound to obtain the bare cell; place the bare cell in the outer packaging In the case, the electrolyte is injected after drying, and the lithium ion battery is obtained through the steps of vacuum packaging, standing, forming, and shaping.

The lithium ion batteries of Examples 2-16 and Comparative Examples 1-6 were all prepared in a similar manner to Example 1, the specific differences are shown in Table 1.

Table 1: Parameters of Examples 1-16 and Comparative Examples 1-6

Next, the test process and test results of the lithium-ion battery will be described.

1. Pole piece test

(1) Particle size test of positive and negative active materials

The particle size of the positive and negative active materials can be obtained by testing with a laser diffraction particle size distribution measuring instrument (Mastersizer 3000).

(2) Capacitance test per unit area of the positive electrode diaphragm

Step 1): Fully discharge the lithium-ion battery containing the positive pole pieces of each embodiment and comparative example, and let it stand for 5 minutes, then charge to the cut-off voltage, where the charging process is to charge at a constant current of 1 / 3C to the cut-off voltage , And then charge to 0.03C with the constant voltage of the cut-off voltage, the charging capacity C ₀ obtained at this time is the discharge capacity of the positive electrode diaphragm.

Step 2): Measure and calculate the total area of the positive electrode diaphragm (the total area here refers to the coating area; if it is double-sided coating, the coating area on both sides needs to be added).

Step 3): According to the capacitance per unit area of the positive electrode membrane = discharge capacity of the positive electrode membrane (mAh) / total area of the positive electrode membrane (cm ² ), calculate the capacitance per unit area of the positive electrode membrane.

(3) Capacitance test per unit area of negative diaphragm:

Step 1): Take the negative pole pieces of the above examples and comparative examples, and use a punching die to obtain a small area of single-sided coated negative electrode wafers. The solution of EC + DMC + DEC (volume ratio 1: 1: 1) with LiPF ₆ as the counter electrode, Celgard membrane as the separation membrane, and LiPF ₆ (concentration 1mol / L) dissolved as the electrolyte is protected by argon gas. Assemble 6 CR2430 button batteries in the glove box. After assembling the coin cell battery, let it stand for 12h, and discharge it at a constant current of 0.05C until the voltage is 5mV, and then discharge it with a 50μA discharge current until the voltage is 5mV, and then use a discharge current of 10μA Carry out constant current discharge until the voltage is 5mV, let stand for 5 minutes, and finally perform constant current charging at a charging current of 0.05C until the final voltage is 2V, and record the charging capacity. The average value of the charging capacity of the six button batteries is the average charging capacity of the negative electrode diaphragm.

Step 2): Use a caliper to measure the diameter d of the negative electrode wafer, and calculate the area of the negative electrode wafer.

Step 3): According to the capacitance per unit area of the negative electrode membrane = the average charging capacity of the negative electrode membrane (mAh) / the area of the negative electrode wafer (cm ² ), the capacitance per unit area of the negative electrode membrane is calculated.

2. Lithium ion battery performance test

(1) Charging performance test:

At 25 ° C, after the lithium ion batteries prepared in the examples and comparative examples were fully charged at xC and fully charged at 1C for 10 times, then the lithium ion batteries were fully charged at xC, and then the negative pole pieces were disassembled , And observe the situation of lithium precipitation on the surface of the negative pole piece. If there is no lithium precipitation on the surface of the negative electrode, the charging rate xC will be tested again in increments of 0.1C until the lithium surface is deposited on the negative electrode surface to stop the test. At this time, the charging rate xC minus 0.1C is the maximum lithium ion battery. Charging rate.

(2) Discharge performance test:

At 25 ° C, the lithium ion batteries prepared in the examples and comparative examples were fully charged at 1C and then discharged at 1C and 4C, respectively, and the ratio of the discharge capacity of 4C to the discharge capacity of 1C was counted. If the ratio is greater than or equal to 95%, it means that the discharge performance of the lithium-ion battery is excellent; if the ratio is between 85% and 95%, it means that the discharge performance of the lithium-ion battery is moderate; if the ratio is less than or equal to 85%, it means that the lithium ion The discharge performance of the battery is poor.

(3) Cycle life test:

At 25 ° C, charge the lithium-ion batteries prepared in the examples and comparative examples at a 3C rate and discharge at a 1C rate, and perform a full-charge discharge cycle test until the capacity of the lithium-ion battery is less than 80% of the initial capacity, and record the cycle time number.

(4) Actual energy density test:

At 25 ℃, the lithium ion batteries prepared in the examples and comparative examples were fully charged at 1 C rate and fully discharged at 1 C rate, and the actual discharge energy at this time was recorded; Weighing, the ratio of the actual discharge energy of the lithium ion battery 1C to the weight of the lithium ion battery is the actual energy density of the lithium ion battery.

Among them, when the actual energy density is less than 80% of the target energy density, the actual energy density of the battery is considered to be very low; when the actual energy density is greater than or equal to 80% of the target energy density and less than 95% of the target energy density, the actual energy density of the battery is considered low When the actual energy density is greater than or equal to 95% of the target energy density and less than 105% of the target energy density, the actual energy density of the battery is considered to be moderate; when the actual energy density is greater than or equal to 105% of the target energy density and less than 120% of the target energy density, It is considered that the actual energy density of the battery is high; when the actual energy density is more than 120% of the target energy density, the actual energy density of the battery is considered to be very high.

Table 2: Test results of Examples 1-16 and Comparative Examples 1-6

A	Maximum charging rate	Discharge performance	Number of cycles	Actual energy density
Example 1	4.0C	Moderate	3520	very high
Example 2	3.6C	Moderate	4200	very high
Example 3	3.6C	Moderate	4350	very high
Example 4	3.6C	Moderate	4500	very high
Example 5	3.3C	Moderate	4600	very high
Example 6	3.6C	Moderate	3680	very high
Example 7	3.0C	Moderate	3000	Higher
Example 8	3.6C	excellent	3400	very high
Example 9	3.3C	excellent	3300	very high
Example 10	3.2C	excellent	3000	Higher
Example 11	3.2C	excellent	3100	Moderate
Example 12	3.0C	excellent	2800	Moderate
Example 13	4.0C	Moderate	4000	very high
Example 14	3.0C	excellent	2000	Moderate
Example 15	4.0C	Moderate	1800	very high
Example 16	3.0C	excellent	1400	Moderate
Comparative Example 1	5.0C	difference	1800	Higher
Comparative Example 2	1.0C	excellent	150	Moderate
Comparative Example 3	5.0C	difference	2700	Higher
Comparative Example 4	1.0C	excellent	300	Moderate
Comparative Example 5	4.5C	difference	1700	Higher
Comparative Example 6	1.0C	excellent	200	Moderate

From the test results in Table 2, it can be seen that the batteries of Examples 1-16 can have both long cycle life, high energy density, and rapid charge and discharge capabilities, because the batteries of Examples 1-16 all satisfy 0.1≤ (D50 _{negative electrode} × M _{negative electrode} ) / [(D50 _{positive electrode} + 4) × (M _{positive electrode} + 4)] ≤1.5, at this time, the dynamic performance of the positive pole piece and the negative pole piece can be well matched, and the resulting battery can have a long Cycle life, high energy density and fast charge and discharge capability.

Comparative Examples 1-6 of dynamic equilibrium of the negative electrode tab and the positive electrode sheet does not match the ratio, (D50 _{negative electrode negative} × M) / _{[(a positive electrode} D50 +4) × (M _positive +4)] are not given in the range In addition, it is difficult for the battery to have a long cycle life, high energy density, and rapid charge and discharge capabilities.

As can be seen from Examples 13-16 and Comparative Examples 3-6, when different positive and negative electrode active materials are used for the battery, as long as 0.1≤ (D50 _{negative electrode} × M _{negative electrode} ) / [(D50 _{positive electrode} + 4) × (M _{positive electrode} +4)] ≤1.5, the obtained batteries can have long cycle life, high energy density and fast charge and discharge ability.

Further, the positive pole piece preferably satisfies 35 ≦ (D50 _{positive electrode} + 4) × (M _{positive electrode} + 4) ≦ 230, and the negative pole piece preferably satisfies 1 ≦ D50 _{negative electrode} × M _{negative electrode} ≦ 100. The sheet and the negative pole piece can maintain better dynamic performance, which is more conducive to improving the cycle life, energy density, fast charging ability and fast discharging ability of the battery. However, when the _{(positive electrode} D50 +4) × _(positive M +4) D50 and a _{negative electrode} or _anode × M two parameters fails to satisfy the requirements, as long as 0.1 ≦ (D50 _{negative negative} × M) / _{[(n-electrode} D50 +4) × (M _{positive electrode} + 4)] ≤1.5, combined with Examples 8-11, the battery can still have long cycle life, high energy density and rapid charge and discharge capability.

Based on the disclosure and teaching of the above description, those skilled in the art can also make changes and modifications to the above-mentioned embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims (10)

1. A secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. The positive electrode sheet includes a positive electrode current collector and a positive electrode membrane provided on at least one surface of the positive electrode current collector and including a positive active material The negative electrode sheet includes a negative electrode current collector and a negative electrode membrane provided on at least one surface of the negative electrode current collector and including a negative electrode active material;

   It is characterized by,

   The secondary battery satisfies: 0.1≤ (D50 _{negative electrode} × M _{negative electrode} ) / [(D50 _{positive electrode} + 4) × (M _{positive electrode} + 4)] ≤1.5;

   among them,

   D50 when the cumulative volume percentage _{of the positive electrode} is the positive electrode active material 50% particle diameter corresponding to units of [mu] m;

   D50 _{negative electrode} is a negative electrode active material accumulated volume percentage reaches 50% of the particle diameter corresponding to units of [mu] m;

   M is a positive electrode _{of the positive electrode} capacity per unit area of the diaphragm, in units of mAh / cm ^2;

   M is a _{negative electrode} capacity per unit area of the negative electrode membrane unit is mAh / cm ^2.
2. The secondary battery according to claim 1, wherein

   The secondary battery satisfies: 0.2≤ (D50 _{negative electrode} × M _{negative electrode} ) / [(D50 _{positive electrode} + 4) × (M _{positive electrode} + 4)] ≤1.0;

   Preferably, the secondary battery satisfies: 0.3 ≦ (D50 _{negative electrode} × M _{negative electrode} ) / [(D50 _{positive electrode} + 4) × (M _{positive electrode} + 4)] ≦ 0.7.
3. The secondary battery according to claim 1 or 2, wherein

   The secondary battery satisfies: 35≤ (D50 _{positive electrode} + 4) × (M _{positive electrode} + 4) ≤230;

   Preferably, the secondary battery satisfies: 60 ≦ (D50 _{positive electrode} + 4) × (M _{positive electrode} + 4) ≦ 150.
4. The secondary battery of claim 1 or claim 2, wherein the positive electrode _{of the positive electrode} active material particle diameter D50 of 0.2μm 25μm ~, preferably 0.4μm ~ 15μm.
5. The secondary battery of claim 1 or claim 2, wherein the positive electrode capacity M _{of the positive electrode} per unit area of membrane ^{1mAh / cm 2 ~ 10mAh / cm} 2, preferably 2mAh / cm ² ~ 6mAh / cm ² .
6. The secondary battery according to claim 1 or 2, wherein

   The secondary battery satisfies: 1≤D50 _{negative electrode} × M _{negative electrode≤100} ;

   Preferably, the secondary battery satisfies: 10 ≦ D50 _{negative electrode} × M _{negative electrode} ≦ 80.
7. The secondary battery of claim 1 or claim 2, wherein said negative electrode is _{the negative electrode} active material particle diameter D50 of 0.4μm ~ 30μm, preferably 0.5μm ~ 16μm.
8. The secondary battery of claim 1 or claim 2, wherein said negative electrode capacity per unit area of membrane M is _negative ^{1mAh / cm 2 ~ 10mAh / cm} 2, preferably 2mAh / cm ² ~ 7mAh / cm ² .
9. The secondary battery according to claim 1, wherein the positive electrode active material is selected from lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, One or more of lithium nickel cobalt aluminum oxide and lithium-containing phosphate with olivine structure.
10. The secondary battery according to claim 1, wherein

    The negative electrode active material is selected from one or more of carbon materials, silicon-based materials, tin-based materials, and lithium titanate;

    Preferably, the negative electrode active material is selected from one or more of carbon materials and silicon-based materials.