A batch continuous pretreatment electrode device and a method for electrochemically pretreating an electrode

Abstract

The present invention relates to a batch continuous pretreatment electrode device and a method for electrochemically pretreating an electrode, including a raw material electrode winding device (I), an electrolyte infiltration device (II), an electrochemical reaction device (III), an electrode cleaning device (IV), an electrode drying device (V) and a finished product electrode winding device (VI). In the said device, the raw material electrode (1) uses a metal foil as a current collector, and a positive electrode material or a composite positive electrode material that can be pre-reduced by a metal ion battery is coated on the raw material electrode. This device has high production efficiency and can be combined with an electrode coating device to achieve batch continuous production; the electrochemically pretreated electrode can effectively improve the Coulomb efficiency of the first cycle of the battery and increase the energy density.

Description

Technical Field

[0001] The present invention relates to the field of metal ion batteries, and particularly to a method and device for electrochemically pretreating electrodes. Background Art

[0002] Metal ion batteries, including lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, and magnesium-ion batteries, have always been a hot topic in battery technology research. The technology of lithium-ion batteries has developed rapidly and has been widely used in the electrical energy storage of small portable electronic devices. In recent years, to meet the rapid development needs of technologies such as new energy vehicles, smart grids, and distributed energy storage, the development of metal ion batteries with high energy density, high safety, and long life has become a research hotspot in the current energy storage field. The improvement of battery energy density mainly relies on the development of key electrode materials. Taking lithium-ion batteries as an example, there are many studies on various new anode materials for lithium-ion batteries, which have a higher specific capacity compared with traditional carbon anode materials and can greatly improve the energy density of the battery. However, at the same time, these electrode materials generally have a low initial Coulombic efficiency, which will bring many problems to the actual battery production. The same problems will also be encountered in the research and application of other metal ion batteries such as sodium-ion batteries and potassium-ion batteries.

[0003] The low initial Coulombic efficiency is mainly because during the first charging process of the battery, the electrolyte will decompose on the anode side and irreversibly form a solid electrolyte interface (SEI film) or other irreversible compounds at the electrode interface. In the relatively mature field of lithium-ion batteries, the pre-lithiation technology is the most effective method to compensate for lithium loss and improve the initial Coulombic efficiency. The electrochemical pre-lithiation method is one of the commonly used pre-lithiation methods, which can directly pre-lithiate the anode or pre-lithiate the cathode to compensate for the irreversible lithium loss of the anode. By discharging a half-cell composed of the anode and metallic lithium to compensate for lithium, the obtained anode material has poor stability, and lithium may deposit on the electrode, resulting in safety hazards. In contrast, electrochemically pre-lithiating the cathode can accurately control the amount of pre-inserted lithium, and the material is safe and stable, which is an ideal pretreatment method. At the same time, for other metal ion batteries, similar methods can also be applied to their respective corresponding systems to solve the problem of low initial Coulombic efficiency of the battery.

[0004] With the development of various metal ion battery technologies and industries, in order to enable the production of pretreated electrodes to meet the growing actual demand, inventing a method for batch and continuous preparation of pretreated electrodes is an inevitable requirement for the development of the battery industry. Summary of the Invention

[0005] The object of the present invention is to provide a solution for batch production of pretreated cathodes by electrochemical pretreatment method aiming at the problem of the initial Coulombic efficiency of metal ion batteries.

[0006] The present invention provides an electrochemical pretreatment electrode device, comprising a raw material electrode winding device (I), an electrolyte infiltration device (II), an electrochemical reaction device (III), an electrode cleaning device (IV), an electrode drying device (V) and a finished product electrode winding device (VI).

[0007] In the device, the raw material electrode (1) uses a metal foil as a current collector, and a positive electrode material or a composite positive electrode material that can be pre-reduced by a metal ion battery is coated on the raw material electrode.

[0008] Preferably, the reducible positive electrode material includes lithium vanadium phosphate, lithium cobaltate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium vanadium phosphate oxide, lithium titanium phosphate, lithium manganate, lithium nickel manganate, sodium vanadium phosphate, sodium fluorophosphate vanadate, sodium vanadium phosphate oxide, sodium titanium phosphate, potassium vanadium phosphate, potassium titanium phosphate or potassium fluorophosphate vanadate; the composite positive electrode material is a composite material of the above reducible positive electrode material and a positive electrode material, or a composite composite material of one or more of transition metal oxides, transition metal sulfides or transition metal fluorides and a common positive electrode material.

[0009] In the device, the electrolyte (2) in the electrolyte infiltration device (II) is a common electrolyte for lithium ion batteries, sodium ion batteries, magnesium ion batteries or potassium ion batteries.

[0010] In the electrochemical reaction device (III) of the device, the negative electrode is a current collector metal negative electrode (3) wound around two parallel rotating shafts. The metal base is one of copper foil tape, aluminum foil tape, foam nickel foil tape and tin foil tape. Preferably, the metal negative electrode is a metal lithium negative electrode, a metal sodium negative electrode or a metal potassium negative electrode.

[0011] The outer layer of the negative electrode is a separator (4). The separator is a polyolefin porous membrane or a gel polymer electrolyte membrane. The gel of the gel electrolyte membrane is one or more of polyethylene oxide (PEO), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVdF), polyvinylidene fluoride - hexafluoropropylene (PVdF - HEP) and polyvinyl acetal (PVB / PVFM). The thickness of the gel polymer electrolyte membrane is 10 - 100 μm, and its width is 2 - 3 mm wider than the negative electrode. The positive electrode is the raw material electrode (1), which is in close contact with the separator (4), and the contact length L is 0.5 - 2 m. The charge and discharge device (5) is connected to the positive and negative rotating shafts.

[0012] In the electrode cleaning device (IV) of the device, the solvent is a carbonate or ether solvent. Preferably, the carbonate solvent is one or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate or ethyl methyl carbonate; the ether solvent is one or more of tetrahydrofuran, ethylene glycol dimethyl ether, dimethoxymethane or 1,2 - dimethoxyethane.

[0013] In the device, the electrode drying equipment (V) is a constant temperature dryer (7), and the drying temperature is set to 60 - 120 °C.

[0014] In the device, the winding speed v of the finished electrode winding equipment (VI) is 1 - 5 m / h, and the discharge current is set according to the electrode active material loading to ensure that the discharge capacity is 90 - 130 mAh / g within a time less than L / v.

[0015] The technical solution adopted in the present invention is as follows: The prepared electrodes are successively connected to the raw material electrode winding equipment (I), the electrolyte infiltration equipment (II), the electrochemical reaction equipment (III), the electrode cleaning equipment (IV), the electrode drying equipment (V), and the finished electrode winding equipment (VI). The current density of the charge and discharge device (5), the drying temperature of the constant temperature dryer (7), and the rotation speed of the shaft of the finished electrode winding equipment (VI) are set to reasonable parameter conditions. The above-mentioned devices are successively started for electrode prelithiation.

[0016] Advantages of the present invention:

[0017] 1. Expand the technical field of electrochemical pretreatment electrode preparation and amplification.

[0018] 2. The device has high production efficiency and can be combined with an electrode coating device to achieve batch continuous production.

[0019] 3. The prepared electrochemical pretreatment electrode can effectively improve the first cycle Coulomb efficiency of the battery and increase the energy density.

[0020] 4. It can simplify the actual manufacturing process of metal ion batteries and reduce costs. Description of the Drawings

[0021] Figure 1 It is a schematic diagram of the device for batch continuous electrochemical pretreatment electrodes designed according to the present invention.

[0022] Among them: (I) Raw material electrode winding equipment; (II) Electrolyte infiltration equipment; (III) Electrochemical reaction equipment; (IV) Electrode cleaning equipment; (V) Electrode drying equipment; (VI) Finished electrode winding equipment; where: 1. Raw material electrode; 2. Metal ion battery electrolyte; 3. Metal negative electrode and current collector metal baseband; 4. Separator; 5. Charge and discharge device; 6. Cleaning solvent; 7. Constant temperature dryer; 8. Finished electrode winding area. Detailed Embodiments

[0023] The present invention provides a preparation method and device for batch continuous production of prelithiated electrodes. The maximum width of the device head in the transverse direction is designed according to the maximum width of the electrodes required for the battery, and the types of electrolyte, the electrochemical reaction voltage window, and the types of cleaning solvents are designed according to the types of electrodes. The following are examples of preparing electrochemically pretreated electrodes using this device.

[0024] Example 1: Preparation of lithium vanadium phosphate cathode for prelithiated lithium-ion battery

[0025] The pre-coated lithium vanadium phosphate electrode is wound on the raw material electrode winding equipment. The width of the aluminum foil is 20 cm, and the active material loading on the electrode is 5 mg / cm 2 , and the width of the active material blade coating is 16 cm. The aluminum foil reserved at the front end of the lithium vanadium phosphate electrode is wound around each rotating shaft and passes through the electrolyte infiltration equipment, the electrochemical reaction equipment, the electrode cleaning equipment, and the electrode drying equipment, and finally fixed on the finished electrode winding equipment. The effective contact electrode length L in the electrochemical reaction zone is 0.5 m. The thickness of the lithium foil used is 120 μm, and the width is 18 cm. The separator used is a polyethylene oxide (PEO) gel polymer electrolyte membrane. The height of the electrode rotating shaft of the electrochemical reaction equipment is adjusted to make the gel polymer electrolyte membrane in close contact with the lithium vanadium phosphate cathode. The electrolyte used in the electrolyte infiltration equipment is 1 M LiPF6, and the solvent is a 1:1 volume ratio of EC and DMC. The solvent used in the electrode cleaning equipment is DMC. The drying temperature of the electrode dryer is 70 °C. Set the discharge current to 200 - 250 mA, the electrode winding speed to 1 m / h, and the discharge capacity to 100 - 125 mAh / g. Start the device to obtain the required prelithiated lithium vanadium phosphate electrode.

[0026] Example 2: Preparation of lithium manganese oxide cathode for prelithiated lithium-ion battery

[0027] The pre-coated lithium manganese oxide electrode is wound on the raw material electrode winding equipment. The width of the aluminum foil is 20 cm, and the active material loading on the electrode is 5 mg / cm 2, the coating width of the active material is 16 cm. The reserved aluminum foil at the front end of the lithium manganese oxide electrode is wound around each rotating shaft and passes through the electrolyte infiltration device, the electrochemical reaction device, the electrode cleaning device and the electrode drying device, and finally is fixed on the finished electrode winding device. The effective contact electrode length L of the electrochemical reaction device is 0.5 m. The thickness of the used lithium foil is 120 μm and the width is 18 cm. The used separator is a polyacrylonitrile (PAN) gel polymer electrolyte membrane. Adjust the height of the electrochemical reaction device relative to the electrode rotating shaft to make the gel polymer electrolyte in close contact with the lithium manganese oxide positive electrode. The electrolyte used in the electrolyte infiltration device is 1 M LiPF6, and the solvent is EC and DMC with a volume ratio of 1:1. The solvent used in the electrode cleaning device is DMC. The drying temperature of the electrode dryer is 70 °C. Set the discharge current to 100 - 125 mA, the electrode winding speed to 2 m / h, and the discharge capacity to 100 - 125 mAh / g. Start the device to obtain the desired prelithiated lithium manganese oxide electrode.

[0028] Example 3: Preparation of a mixed electrode of lithium vanadium phosphate and lithium iron phosphate for prelithiated lithium-ion batteries

[0029] Replace the lithium vanadium phosphate electrode in Example 1 with a mixed electrode with a molar ratio of lithium vanadium phosphate to lithium iron phosphate of 1:2, and perform electrochemical pretreatment. Keep other processes unchanged, and finally obtain a mixed electrode of prelithiated lithium vanadium phosphate and lithium iron phosphate.

[0030] Example 4: Preparation of a mixed electrode of lithium manganese oxide and 811 nickel cobalt manganese oxide for prelithiated lithium-ion batteries

[0031] Replace the lithium manganese oxide electrode in Example 2 with a mixed electrode with a molar ratio of lithium manganese oxide to 811 nickel cobalt manganese oxide of 1:2, and perform electrochemical pretreatment. Keep other processes unchanged, and finally obtain a mixed electrode of prelithiated lithium manganese oxide and 811 nickel cobalt manganese oxide.

[0032] Example 5: Preparation of a sodium vanadium phosphate positive electrode for prelithiated sodium-ion batteries

[0033] Wind the pre-coated sodium vanadium phosphate electrode on the raw material electrode winding device. The width of the aluminum foil is 18 cm, and the active material loading on the electrode is 5 mg / cm 2, the coating width of the active material is 16 cm. The reserved aluminum foil at the front end of the sodium vanadium phosphate electrode is wound around each rotating shaft, passing through the electrolyte infiltration device, the electrochemical reaction device, the electrode cleaning device and the electrode drying device, and finally fixed on the finished electrode winding device. The effective contact electrode length L of the electrochemical reaction device is 0.5 m. The thickness of the used sodium metal negative electrode is 120 μm and the width is 18 cm. The used separator is a polyacrylonitrile (PAN) gel polymer electrolyte membrane. Adjust the height of the electrochemical reaction device relative to the electrode rotating shaft to make the gel polymer electrolyte in close contact with the sodium vanadium phosphate positive electrode. The electrolyte used in the electrolyte infiltration device is 1 M NaClO4, and the solvent is PC and DEC with a volume ratio of 1:1. The solvent used in the electrode cleaning device is DEC. The drying temperature of the electrode dryer is 70 °C. Set the discharge current to 100 - 125 mA, the electrode winding speed to 2 m / h, and the discharge capacity to 100 - 125 mAh / g. Start the device to obtain the required pre-sodiated sodium vanadium phosphate electrode.

[0034] Example 6: Preparation of a pre-sodiated sodium-ion battery positive electrode of sodium fluorophosphate vanadate

[0035] Replace the sodium vanadium phosphate electrode in Example 5 with a sodium fluorophosphate vanadate electrode and perform electrochemical pretreatment. Keep other processes unchanged, and finally obtain a pre-sodiated sodium fluorophosphate vanadate electrode.

[0036] Example 7: Preparation of a pre-potassiated potassium-ion battery positive electrode of potassium fluorophosphate vanadate

[0037] Wind the pre-coated potassium fluorophosphate vanadate electrode on the raw material electrode winding device. The width of the aluminum foil is 18 cm, and the active material loading on the electrode is 5 mg / cm 2 , the coating width of the active material is 16 cm. The reserved aluminum foil at the front end of the potassium fluorophosphate vanadate electrode is wound around each rotating shaft, passing through the electrolyte infiltration device, the electrochemical reaction device, the electrode cleaning device and the electrode drying device, and finally fixed on the finished electrode winding device. The effective contact electrode length L of the electrochemical reaction device is 0.5 m. The thickness of the used potassium metal negative electrode is 100 μm and the width is 18 cm. The used separator is a polyacrylonitrile (PAN) gel polymer electrolyte membrane. Adjust the height of the electrochemical reaction device relative to the electrode rotating shaft to make the gel polymer electrolyte in close contact with the potassium fluorophosphate vanadate positive electrode. The electrolyte used in the electrolyte infiltration device is 1 M KFP6, and the solvent is EC and DMC with a volume ratio of 1:1. The solvent used in the electrode cleaning device is DEC. The drying temperature of the electrode dryer is 70 °C. Set the discharge current to 100 - 125 mA, the electrode winding speed to 2 m / h, and the discharge capacity to 100 - 125 mAh / g. Start the device to obtain the required pre-potassiated potassium fluorophosphate vanadate electrode.

[0038] Example 8: Preparation of a Li2O / Co / lithium cobaltate composite positive electrode material

[0039] Wind the pre-coated mixed electrode of lithium cobaltate and Co3O4 with a molar ratio of 10:1 on the raw material electrode winding equipment. The width of its aluminum foil is 20 cm, and the active material loading on the electrode is 5 mg / cm 2 , and the width of the active material blade coating is 16 cm. Reserve the aluminum foil at the front end of the lithium manganese oxide electrode and wind it around each rotating shaft through the electrolyte infiltration equipment, electrochemical reaction equipment, electrode cleaning equipment, and electrode drying equipment, and finally fix it on the finished electrode winding equipment. The effective contact electrode length L of the electrochemical reaction equipment is 0.5 m. The thickness of the used lithium foil is 120 μm, and the width is 18 cm. The used separator is a polyacrylonitrile (PAN) gel polymer electrolyte membrane. Adjust the height of the electrochemical reaction equipment for the electrode rotating shaft so that the gel polymer electrolyte is in close contact with the lithium manganese oxide positive electrode. The electrolyte used in the electrolyte infiltration equipment is 1 M LiPF6, and the solvent is EC and DMC with a volume ratio of 1:1. The solvent used in the electrode cleaning equipment is DMC. The drying temperature of the electrode dryer is 70 °C. Set the discharge current to 100 - 125 mA, the electrode winding speed to 2 m / h, and the discharge capacity to 100 - 125 mAh / g. Start the device to obtain the required Li2O / Co / lithium cobaltate composite positive electrode material.

[0040] Assemble and test the full cell using the above pre-lithiated electrode and the carbon-based negative electrode. Under the same electrochemical test conditions, its performance is consistent with the results of laboratory small-scale tests. The test results are shown in Table 1:

[0041] Table 1 Comparison table of the performance of the full cell with the positive electrode material before and after pretreatment

[0042]

[0043] In summary, the performance indicators of the pre-lithiated positive electrode material prepared according to the present invention meet the usage requirements. The pre-treated electrodes prepared with a larger area have good uniformity; the device has high production efficiency and can be continuously produced; it provides a basis for solving the practical application of high specific capacity and low Coulomb efficiency negative electrode materials for metal ion batteries.

Claims

1. A batch continuous pretreatment electrode device, comprising a raw material electrode winding device (I), an electrolyte infiltration device (II), an electrochemical reaction device (III), an electrode cleaning device (IV), and a finished product electrode winding device (VI); The raw material electrode winding device (I) comprises a cylindrical or columnar roller A, with a strip-shaped positive electrode sheet wound on the roller surface with the roller center axis as the axis; The electrolyte infiltration device (II) comprises a container containing an electrolyte solution, a cylindrical or columnar roller B is arranged in the container, and the roller B is located in the electrolyte solution; The electrochemical reaction device (III) comprises a current collector metal negative electrode (3), which is a cylindrical structure surrounded by a strip-shaped electrode substrate, and a metal negative electrode layer and a separator layer (4) are arranged in sequence from the inside to the outside on the outer surface of the cylindrical structure to form a cylindrical negative electrode; more than two cylindrical or cylindrical rollers C are arranged inside the cylindrical negative electrode, and the inner wall surface of the cylindrical negative electrode is in contact with the outer surface of the roller C; more than two cylindrical or cylindrical rollers D are arranged outside the cylindrical negative electrode; the central axes of the rollers C and the rollers D are arranged parallel to each other; and the plane where the central axes of at least two of the rollers C are located is parallel to the plane where the central axes of at least two of the rollers D are located; At least one roller C on a parallel plane is placed adjacent to a roller D on another parallel plane to form a roller pair Z, and a second roller C on a parallel plane is placed adjacent to a second roller D on another parallel plane to form a roller pair Y; the positive electrode sheet and the negative electrode are between the roller C and the roller D forming the roller pair Z and the roller pair Y, and the positive electrode sheet and the negative electrode between the roller pair Z and the roller pair Y are in contact with each other; at least one roller C is electrically connected to the negative electrode of a DC power supply, and at least one roller D is electrically connected to the positive electrode of the DC power supply; The electrode cleaning device (IV) comprises a container containing a cleaning solution, a cylindrical or columnar roller E is arranged in the container, and the roller E is located in the cleaning solution; The finished electrode winding device (VI) comprises a cylindrical or columnar roller F, which is used to wind the strip-shaped positive electrode sheet finished product on the roller surface with the roller center axis as the axis; One end of the positive electrode sheet wound on roller A is wound on roller F through the lower end of roller B, between roller pair Z and roller pair Y, and the lower end of roller E in sequence; and roller F is a driving wheel, which can be rotated manually or connected to the output shaft of a DC motor to be driven by the motor to rotate; The positive electrode sheet (1) uses a strip-shaped metal foil as the current collector, and a positive electrode material or a composite positive electrode material that can be pre-reduced by a metal ion battery is coated on the current collector; the loading amount range of the positive electrode material is 1-10 mg / cm 2 ; The metal foil is one of copper foil, nickel foil, aluminum foil and titanium foil; and its thickness is 10-100 microns; The pre-reducible positive electrode material includes one or more of lithium vanadium phosphate, lithium vanadium phosphate, lithium titanium phosphate, lithium manganate, lithium nickel manganate, sodium vanadium phosphate, sodium vanadium fluorophosphate, sodium vanadium phosphate, sodium titanium phosphate, potassium vanadium phosphate, potassium titanium phosphate or potassium vanadium fluorophosphate; The composite positive electrode material is a composite material of the above-mentioned pre-reducible positive electrode material and a positive electrode material, or a composite material of one or more of transition metal oxides, transition metal sulfides or transition metal fluorides and a positive electrode material; The positive electrode material is one or more of lithium iron phosphate, lithium cobaltate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium vanadium phosphate, lithium manganate, lithium nickel manganate, lithium vanadium phosphate oxide, lithium titanium phosphate, sodium manganate, sodium cobaltate, sodium ferrate, sodium iron manganese copperate, sodium vanadium phosphate, sodium fluorovanadate, sodium vanadium phosphate oxide, sodium titanium phosphate, potassium vanadium phosphate, potassium titanium phosphate or potassium fluorovanadate; The transition metal is one or more of iron, cobalt, nickel, manganese, zinc or molybdenum; The mass content of the positive electrode material in the composite positive electrode material is 50-95%.

2. The batch continuous preprocessing electrode device according to claim 1, wherein: An electrode drying device (V) is also provided between the electrode cleaning device (IV) and the finished electrode winding device (VI); The electrode drying device (V) includes a container with electric heating parts inside, and an inlet and an outlet for positive electrode sheets are respectively provided at both ends of the container; The positive electrode sheet passes under the lower end of roller E and then enters the container of the electrode drying device through the inlet. The dried positive electrode sheet finished product comes out from the outlet and is directly wound around roller F.

3. The batch continuous pre-treatment electrode device according to claim 1, wherein: The electrolyte (2) in the electrolyte impregnation device (II) in the device is a lithium ion battery electrolyte, a sodium ion battery electrolyte, a magnesium ion battery electrolyte or a potassium ion battery electrolyte; The electrode substrate includes one of a copper foil tape, an aluminum foil tape, a nickel foam foil tape and a tin foil tape; the metal negative electrode is a metal lithium negative electrode, a metal sodium negative electrode, a metal magnesium negative electrode or a metal potassium negative electrode; The separator is a polyolefin porous membrane or a gel polymer electrolyte membrane; the gel of the gel electrolyte membrane is one or more of polyethylene oxide (PEO), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVdF), polyvinylidene fluoride - hexafluoropropylene (PVdF-HEP) and polyvinyl acetal (PVB / PVFM); The thickness of the gel polymer electrolyte membrane is 10-100 μm, and its width is 2-3 mm wider than that of the metal negative electrode.

4. The batch continuous preprocessing electrode device according to claim 1, wherein: The positive electrode sheet is in close contact with the separator (4), and the contact length L is 0.5 - 2 m, that is, the distance between the central axes of roller pair Z and roller pair Y is 0.5 - 2 m.

5. The batch continuous preprocessing electrode device according to claim 4, characterized in that: The current guaranteed by the electrode active material loading is set to ensure a discharge capacity of 90 - 130 mAh g -1 .

6. The batch continuous preprocessing electrode device according to claim 1, characterized in that: The solvent in the electrode cleaning device (IV) in the device is a carbonate solvent or an ether solvent; the carbonate solvent is one or two or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate or ethyl methyl carbonate; the ether solvent is one or two or more of tetrahydrofuran, ethylene glycol dimethyl ether, dimethoxymethane or 1,2-dimethoxyethane.

7. The batch continuous preprocessing electrode device according to claim 1, characterized in that: The electrode drying device (V) in the device is a constant temperature dryer (7), and the drying temperature is set at 60-120 °C.

8. A method for electrochemically pretreating an electrode, characterized in that: Electrochemically pretreat the electrode using the device according to any one of claims 1-7, and the winding speed of the finished electrode winding equipment (VI) in the device v is 1-5 m / h, set the current according to the electrode active material loading, and ensure that the discharge capacity is 90-130 mAh / g within less than L / v of the time

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