Calculation method for using amount of conductive agent for positive and negative electrodes of lithium ion battery and application of calculation method in production of lithium ion battery

Abstract

The invention provides a lithium ion battery positive and negative electrode conductive agent dosage calculation method and application thereof in lithium ion battery production, and relates to the technical field of batteries. According to the method for calculating the using amount of the conductive agent for the positive and negative electrodes of the lithium ion battery, the content of the conductive agent can be estimated in advance, the problems that the electrical property of the battery is reduced due to too few conductive agents and the capacity is reduced due to too many conductive agents are solved, meanwhile, trial and error of the content of the conductive agent in cell development and design can be reduced, and efficiency can be improved.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a method for calculating the amount of a positive and negative electrode conductive agent used in a lithium ion battery and an application of the method in lithium ion battery production. Background Art

[0002] During the charging and discharging process of lithium-ion batteries, conductive agents need to be added to improve their performance. The positive and negative electrode materials of the battery often have low electrical conductivity, especially the positive electrode materials such as transition metal oxides or phosphates. In order to ensure that the electrode has good electrical conductivity, conductive agents need to be added to the electrode.

[0003] Conductive agents can collect microcurrents between active materials and between active materials and current collectors to form a conductive network, forming a continuous conductive network inside the electrode, reducing contact resistance and increasing the migration rate of electrons.

[0004] At the same time, the conductive agent also has the function of retaining liquid. It can adsorb the electrolyte in the electrode to prevent its loss or evaporation. At the same time, it helps to evenly distribute the electrolyte in the electrode and improve the utilization rate of the electrolyte, thereby achieving the effect of retaining liquid.

[0005] The content of conductive agent also has a significant impact on the performance of the battery. Too much conductive agent means less active ingredient and low capacity; too little conductive agent means poor conductivity and the battery is prone to polarization. Therefore, adding an appropriate amount of conductive agent is crucial.

[0006] In view of this, the present invention is proposed. Summary of the invention

[0007] The first object of the present invention is to provide a method for calculating the amount of conductive agent used in the positive and negative electrodes of a lithium ion battery to solve the above technical problems.

[0008] The second object of the present invention is to provide application of the above calculation method in lithium ion battery production.

[0009] In order to achieve the above objectives, the following technical solutions are adopted:

[0010] In a first aspect, the present invention provides a method for calculating the amount of conductive agent used in positive and negative electrodes of a lithium ion battery, wherein the positive electrode sheet of the lithium ion battery comprises a positive electrode current collector and a positive electrode slurry layer coated on the positive electrode current collector;

[0011] The positive electrode slurry comprises a positive electrode active material, a positive electrode conductor and a binder;

[0012] In the positive electrode slurry, the calculation formula for the amount of positive electrode conductive agent is as follows:

[0013] m CB正 =K1*m AM正 *Φ 正*2R1*ρ1+α1*(V1 / Ψ1);

[0014] Among them, m CB正 is the weight of the positive electrode conductive agent; K1 is the positive electrode conductivity coefficient; m AM正 is the total active material weight of the positive electrode; Φ 正 is the specific surface area of ​​the positive electrode active material; R1 is the radius of the positive electrode composite conductive agent; ρ1 is the density of the positive electrode conductive agent; V1 is the pore volume of the positive electrode sheet; α1 is the positive electrode liquid retention conversion coefficient; Ψ1 is the oil absorption value of the positive electrode conductive agent;

[0015] The K1 is 0.005-0.02, and α1 is 0.028-0.18;

[0016] The negative electrode sheet of the lithium ion battery comprises a negative electrode current collector and a negative electrode slurry layer coated on the negative electrode current collector;

[0017] The negative electrode slurry comprises a negative electrode active material, a negative electrode conductive agent and a binder;

[0018] In the negative electrode slurry, the calculation formula for the amount of negative electrode conductive agent is as follows:

[0019] m CB负 =K2*m AM负 *Φ 负 *2R2*ρ2+α2*(V2 / Ψ2);

[0020] Among them, m CB负 is the weight of negative electrode conductive agent; K2 is the negative electrode conductivity coefficient; m AM负 is the total active material weight of the negative electrode; Φ 负 is the specific surface area of ​​the negative electrode active material; R2 is the radius of the negative electrode composite conductive agent; ρ2 is the density of the negative electrode conductive agent; V2 is the pore volume of the negative electrode sheet; α2 is the negative electrode liquid retention conversion coefficient; Ψ2 is the oil absorption value of the negative electrode conductive agent;

[0021] The K2 is 0.015-0.15, and the α2 is 0.056-0.16.

[0022] As a further technical solution, the calculation formula for the specific surface area of ​​the positive electrode active material is as follows:

[0023] Φ 正 =(Φ 正1 *λAM 正1 +Φ 正2 *λAM 正2 +…+Φ 正n *λAM 正n );

[0024] Among them, λAM 正1 +λAM 正2 +…+λAM正n =1;λAM 正n is the weight proportion of the nth positive electrode active material; Φ 正n is the specific surface area of ​​the nth positive electrode active material; n is a positive integer.

[0025] As a further technical solution, when the number of negative electrode active materials is greater than or equal to 2, the calculation formula for the specific surface area of ​​the negative electrode active material is as follows:

[0026] Φ 负 =(Φ 负1 *βAM 负1 +Φ 负2 *βAM 负2 +…+Φ 负n *βAM 负n );

[0027] Among them, βAM 负1 +βAM 负2 +…+βAM-n=1;βAM 负n is the weight proportion of the nth negative electrode active material; Φ 负n is the specific surface area of ​​the nth negative electrode active material; n is a positive integer.

[0028] As a further technical solution, the positive electrode conductive agent includes: one or more of conductive carbon black and acetylene black.

[0029] The positive electrode active material includes lithium iron phosphate.

[0030] As a further technical solution, the negative electrode conductive agent includes: one or more of conductive carbon black and acetylene black.

[0031] The negative electrode active material includes graphite.

[0032] As a further technical solution, the binder includes PVDF.

[0033] As a further technical solution, the positive electrode current collector includes aluminum foil;

[0034] The negative electrode current collector includes copper foil.

[0035] In a second aspect, the present invention provides application of the above calculation method in lithium ion battery production.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The method for calculating the amount of conductive agent used in the positive and negative electrodes of a lithium-ion battery provided by the present invention can estimate the conductive agent content in advance, thereby avoiding problems such as a decrease in battery electrical performance due to too little conductive agent and a decrease in capacity due to too much conductive agent. At the same time, it can reduce the trial and error of the conductive agent content in the development and design of battery cells, thereby improving efficiency. DETAILED DESCRIPTION

[0038] The embodiments of the present invention will be described in detail below in conjunction with the embodiments and examples, but it will be appreciated by those skilled in the art that the following embodiments and examples are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified, proceed according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0039] In a first aspect, the present invention provides a method for calculating the amount of conductive agent used in positive and negative electrodes of a lithium ion battery, wherein the positive electrode sheet of the lithium ion battery comprises a positive electrode current collector and a positive electrode slurry layer coated on the positive electrode current collector;

[0040] The positive electrode slurry comprises a positive electrode active material, a positive electrode conductor and a binder;

[0041] In the positive electrode slurry, the calculation formula for the amount of positive electrode conductive agent is as follows:

[0042] m CB正 =K1*m AM正 *Φ 正 *2R1*ρ1+α1*(V1 / Ψ1);

[0043] Among them, m CB正 is the weight of the positive electrode conductive agent; K1 is the positive electrode conductivity coefficient; m AM正 is the total active material weight of the positive electrode; Φ 正 is the specific surface area of ​​the positive electrode active material; R1 is the radius of the positive electrode composite conductive agent; ρ1 is the density of the positive electrode conductive agent; V1 is the pore volume of the positive electrode sheet; α1 is the positive electrode liquid retention conversion coefficient; Ψ1 is the oil absorption value of the positive electrode conductive agent;

[0044] The K1 is 0.005-0.02, and α1 is 0.028-0.18;

[0045] The negative electrode sheet of the lithium ion battery comprises a negative electrode current collector and a negative electrode slurry layer coated on the negative electrode current collector;

[0046] The negative electrode slurry comprises a negative electrode active material, a negative electrode conductive agent and a binder;

[0047] In the negative electrode slurry, the calculation formula for the amount of negative electrode conductive agent is as follows:

[0048] m CB负 =K2*m AM负 *Φ 负*2R2*ρ2+α2*(V2 / Ψ2);

[0049] Among them, m CB负 is the weight of negative electrode conductive agent; K2 is the negative electrode conductivity coefficient; m AM负 is the total active material weight of the negative electrode; Φ 负 is the specific surface area of ​​the negative electrode active material; R2 is the radius of the negative electrode composite conductive agent; ρ2 is the density of the negative electrode conductive agent; V2 is the pore volume of the negative electrode sheet; α2 is the negative electrode liquid retention conversion coefficient; Ψ2 is the oil absorption value of the negative electrode conductive agent;

[0050] The K2 is 0.015-0.15, and the α2 is 0.056-0.16.

[0051] The principles of this solution are as follows:

[0052] Ideally, the content of conductive agent in the positive and negative electrodes of the battery = conductive agent required for conductivity (conductive agent attached to the surface of active particles) + conductive agent required for liquid retention (conductive agent uniformly dispersed in the slurry). Assuming m CB is the weight of the conductive agent; K is the conductivity coefficient; m AM is the total active material weight; Φ is the specific surface area of ​​the active material (m 2 / g); R is the radius of the composite conductive agent; ρ is the density of the conductive agent; V is the pore volume of the electrode; α is the liquid retention conversion coefficient; Ψ is the oil absorption value of the conductive agent (mL / 100g); then ①: The volume of the conductive agent in the conductive part is m AM *Φ*2R, the mass of the conductive agent in the conductive part is m AM *Φ*2R*ρ, ②: The conductive agent required for the liquid retention part is V / Ψ. Considering the actual application, the conductivity coefficient K is added to the ① part, and the liquid retention conversion coefficient is added to the ② part. The calculation formula for the total amount of conductive agent is as follows:

[0053] m CB =K*m AM *Φ*2R*ρ+α*(V / Ψ).

[0054] The method for calculating the amount of conductive agent used in the positive and negative electrodes of a lithium-ion battery provided by the present invention can estimate the conductive agent content in advance, thereby avoiding problems such as a decrease in battery electrical performance due to too little conductive agent and a decrease in capacity due to too much conductive agent. At the same time, it can reduce the trial and error of the conductive agent content in the development and design of battery cells, thereby improving efficiency.

[0055] In some optional embodiments, the calculation formula of the specific surface area of ​​the positive electrode active material is as follows:

[0056] Φ 正 =(Φ 正1 *λAM 正1 +Φ 正2 *λAM 正2 +…+Φ正n *λAM 正n );

[0057] Among them, λAM 正1 +λAM 正2 +…+λAM 正n =1;λAM 正n is the weight proportion of the nth positive electrode active material; Φ 正n is the specific surface area of ​​the nth positive electrode active material; n is a positive integer.

[0058] In some optional embodiments, when the amount of the negative electrode active material is greater than or equal to 2, the calculation formula of the specific surface area of ​​the negative electrode active material is as follows:

[0059] Φ 负 =(Φ 负1 *βAM 负1 +Φ 负2 *βAM 负2 +…+Φ 负n *βAM 负n );

[0060] Among them, βAM 负1 +βAM 负2 +…+βAM-n=1;βAM 负n is the weight proportion of the nth negative electrode active material; Φ 负n is the specific surface area of ​​the nth negative electrode active material; n is a positive integer.

[0061] In some optional embodiments, the positive electrode conductive agent includes: one or more of electric carbon black and acetylene black;

[0062] The positive electrode active material includes lithium iron phosphate.

[0063] In some optional embodiments, the negative electrode conductive agent includes: one or more of electric carbon black and acetylene black;

[0064] The negative electrode active material includes graphite.

[0065] In some optional embodiments, the binder includes PVDF.

[0066] In some optional embodiments, the positive electrode current collector comprises aluminum foil;

[0067] The negative electrode current collector includes copper foil.

[0068] In a second aspect, the present invention provides application of the above calculation method in lithium ion battery production.

[0069] The content of the negative electrode conductive agent calculated by the calculation method of the present invention can be used to estimate the content of the conductive agent in advance, thereby avoiding problems such as a decrease in battery electrical performance due to too little conductive agent and a decrease in capacity due to too much conductive agent. At the same time, it can reduce the trial and error of the conductive agent content in the development and design of the battery cell and improve efficiency.

[0070] The present invention is further described below by means of specific examples. However, it should be understood that these examples are only used for more detailed description and should not be construed as limiting the present invention in any form.

[0071] Example 1

[0072] A method for calculating the amount of conductive agent used in the positive and negative electrodes of a lithium-ion battery. The calculation formula for the amount of conductive agent used in the positive electrode is as follows:

[0073] m CB正 =K1*m AM正 *Φ 正 *2R1*ρ1+α1*(V1 / Ψ1);

[0074] Among them, m CB正 is the weight of the positive electrode conductive agent; K1 is the positive electrode conductivity coefficient; m AM正 is the total active material weight of the positive electrode; Φ 正 is the specific surface area of ​​the positive electrode active material; R1 is the radius of the positive electrode composite conductive agent; ρ1 is the density of the positive electrode conductive agent; V1 is the pore volume of the positive electrode sheet; α1 is the positive electrode liquid retention conversion coefficient; Ψ1 is the oil absorption value of the positive electrode conductive agent;

[0075] The K1 is 0.005, and α1 is 0.028;

[0076] The calculation formula for the amount of negative electrode conductive agent is as follows:

[0077] m CB负 =K2*m AM负 *Φ 负 *2R2*ρ2+α2*(V2 / Ψ2);

[0078] Among them, m CB负 is the weight of negative electrode conductive agent; K2 is the negative electrode conductivity coefficient; m AM负 is the total active material weight of the negative electrode; Φ 负 is the specific surface area of ​​the negative electrode active material; R2 is the radius of the negative electrode composite conductive agent; ρ2 is the density of the negative electrode conductive agent; V2 is the pore volume of the negative electrode sheet; α2 is the negative electrode liquid retention conversion coefficient; Ψ2 is the oil absorption value of the negative electrode conductive agent;

[0079] The K2 is 0.015, and α2 is 0.056;

[0080] The calculation formula of the specific surface area of ​​the negative electrode active material is as follows:

[0081] Φ 负 =(Φ 负1 *βAM 负1 +Φ 负2 *βAM 负2 +…+Φ 负n *βAM 负n );

[0082] Among them, βAM 负1 +βAM 负2 +…+βAM-n=1;βAM 负n is the weight proportion of the nth negative electrode active material; Φ 负n is the specific surface area of ​​the nth negative electrode active material; n is a positive integer.

[0083] Example 2

[0084] A method for calculating the amount of conductive agent used in the positive and negative electrodes of a lithium-ion battery. The calculation formula for the amount of conductive agent used in the positive electrode is as follows:

[0085] m CB正 =K1*m AM正 *Φ 正 *2R1*ρ1+α1*(V1 / Ψ1);

[0086] Among them, m CB正 is the weight of the positive electrode conductive agent; K1 is the positive electrode conductivity coefficient; m AM正 is the total active material weight of the positive electrode; Φ 正 is the specific surface area of ​​the positive electrode active material; R1 is the radius of the positive electrode composite conductive agent; ρ1 is the density of the positive electrode conductive agent; V1 is the pore volume of the positive electrode sheet; α1 is the positive electrode liquid retention conversion coefficient; Ψ1 is the oil absorption value of the positive electrode conductive agent;

[0087] The K1 is 0.01, and α1 is 0.09;

[0088] The calculation formula of the specific surface area of ​​the positive electrode active material is as follows:

[0089] Φ 正 =(Φ 正1 *λAM 正1 +Φ 正2 *λAM 正2 +…+Φ 正n *λAM 正n );

[0090] Among them, λAM 正1 +λAM 正2 +…+λAM 正n =1;λAM 正n is the weight proportion of the nth positive electrode active material; Φ 正n is the specific surface area of ​​the nth positive electrode active material; n is a positive integer;

[0091] The calculation formula for the amount of negative electrode conductive agent is as follows:

[0092] m CB负 =K2*m AM负 *Φ 负 *2R2*ρ2+α2*(V2 / Ψ2);

[0093] Among them, m CB负 is the weight of negative electrode conductive agent; K2 is the negative electrode conductivity coefficient; m AM负 is the total active material weight of the negative electrode; Φ 负 is the specific surface area of ​​the negative electrode active material; R2 is the radius of the negative electrode composite conductive agent; ρ2 is the density of the negative electrode conductive agent; V2 is the pore volume of the negative electrode sheet; α2 is the negative electrode liquid retention conversion coefficient; Ψ2 is the oil absorption value of the negative electrode conductive agent;

[0094] The K2 is 0.08, and the α2 is 0.08;

[0095] The calculation formula of the specific surface area of ​​the negative electrode active material is as follows:

[0096] Φ 负 =(Φ 负1 *βAM 负1 +Φ 负2 *βAM 负2 +…+Φ 负n *βAM 负n );

[0097] Among them, βAM 负1 +βAM 负2 +…+βAM-n=1;βAM 负n is the weight proportion of the nth negative electrode active material; Φ 负n is the specific surface area of ​​the nth negative electrode active material; n is a positive integer.

[0098] Example 3

[0099] A method for calculating the amount of conductive agent used in the positive and negative electrodes of a lithium-ion battery. The calculation formula for the amount of conductive agent used in the positive electrode is as follows:

[0100] m CB正 =K1*m AM正 *Φ 正 *2R1*ρ1+α1*(V1 / Ψ1);

[0101] Among them, m CB正 is the weight of the positive electrode conductive agent; K1 is the positive electrode conductivity coefficient; m AM正 is the total active material weight of the positive electrode; Φ 正is the specific surface area of ​​the positive electrode active material; R1 is the radius of the positive electrode composite conductive agent; ρ1 is the density of the positive electrode conductive agent; V1 is the pore volume of the positive electrode sheet; α1 is the positive electrode liquid retention conversion coefficient; Ψ1 is the oil absorption value of the positive electrode conductive agent;

[0102] The K1 is 0.02, and α1 is 0.18;

[0103] The calculation formula of the specific surface area of ​​the positive electrode active material is as follows:

[0104] Φ 正 =(Φ 正1 *λAM 正1 +Φ 正2 *λAM 正2 +…+Φ 正n *λAM 正n );

[0105] Among them, λAM 正1 +λAM 正2 +…+λAM 正n =1;λAM 正n is the weight proportion of the nth positive electrode active material; Φ 正n is the specific surface area of ​​the nth positive electrode active material; n is a positive integer;

[0106] The calculation formula for the amount of negative electrode conductive agent is as follows:

[0107] m CB负 =K2*m AM负 *Φ 负 *2R2*ρ2+α2*(V2 / Ψ2);

[0108] Among them, m CB负 is the weight of negative electrode conductive agent; K2 is the negative electrode conductivity coefficient; m AM负 is the total active material weight of the negative electrode; Φ 负 is the specific surface area of ​​the negative electrode active material; R2 is the radius of the negative electrode composite conductive agent; ρ2 is the density of the negative electrode conductive agent; V2 is the pore volume of the negative electrode sheet; α2 is the negative electrode liquid retention conversion coefficient; Ψ2 is the oil absorption value of the negative electrode conductive agent;

[0109] The K2 is 0.15, and the α2 is 0.16;

[0110] The calculation formula of the specific surface area of ​​the negative electrode active material is as follows:

[0111] Φ 负 =(Φ 负1 *βAM 负1 +Φ 负2 *βAM 负2 +…+Φ 负n *βAM 负n );

[0112] Among them, βAM 负1 +βAM 负2 +…+βAM-n=1;βAM 负n is the weight proportion of the nth negative electrode active material; Φ 负n is the specific surface area of ​​the nth negative electrode active material; n is a positive integer.

[0113] Comparative Example 1

[0114] A method for calculating the amount of conductive agent used for positive and negative electrodes of a lithium ion battery, which differs from Example 1 in that K1 is 0.001, α1 is 0.01, K2 is 0.001, and α2 is 0.01.

[0115] Comparative Example 2

[0116] A method for calculating the amount of conductive agent used in positive and negative electrodes of a lithium ion battery, which differs from Example 1 in that K1 is 0.1, α1 is 1, K2 is 0.2, and α2 is 1.

[0117] Test Example 1

[0118] With lithium iron phosphate as the positive electrode active material, conductive carbon black as the conductive agent, and PVDF as the binder, the amount of the positive electrode conductive agent is calculated using the calculation method of Example 1-3 and Comparative Example 1-2:

[0119] m AM正 =0.28471kg; Φ 正 =13.19m 2 / g; R1 = 20nm; ρ1 = 2.2g / m 3 ; V1=47.07cm 3 ;

[0120] Ψ1 = 350 mL / 100 g; active material diameter = 10 microns.

[0121] By calculation, m in Example 1 CB正

[0122] =(0.005*0.28471*1000*13.19*10000*20*2*10^-7*2.2+0.028*(47.07 / 350*100)) / 1000=0.002kg;

[0123] Example 2 m CB正

[0124] =(0.01*0.28471*1000*13.19*10000*20*2*10^-7*2.2+0.09*(47.07 / 350*100)) / 1000=0.0045kg;

[0125] Example 3 m CB正

[0126] =(0.02*0.28471*1000*13.19*10000*20*2*10^-7*2.2+0.18*(47.07 / 350*100)) / 1000=0.009kg;

[0127] m of Comparative Example 1 CB正

[0128] =(0.001*0.28471*1000*13.19*10000*20*2*10^-7*2.2+0.01*(47.07 / 350*100)) / 1000=0.00046kg;

[0129] m of Comparative Example 2 CB正

[0130] =(0.1*0.28471*1000*13.19*10000*20*2*10^-7*2.2+1*(47.07 / 350*100)) / 1000=0.0397kg.

[0131] Then, the positive electrode conductive agent is obtained according to the above calculation, mixed with the positive electrode active material (0.28471 kg) and the binder (0.0065 kg), and coated on the aluminum foil to obtain the positive electrode sheet.

[0132] Negative electrode sheet: Graphite is used as the negative electrode active material, conductive carbon black is used as the conductive agent, CMC+SBR (the mass ratio of CMC to SBR is 1:1) is used as the binder, and the mixture is coated with copper foil to prepare the negative electrode sheet. The amount of the negative electrode conductive agent is calculated using the calculation method in Example 2:

[0133] m AM负 =0.1561kg; Φ 负 =1.3m 2 / g; R2 = 20nm; ρ2 = 2.2g / m 3 ; V2=45.05cm 3 ;

[0134] Ψ2 = 345 mL / 100 g; the diameter of the active substance is 20-30 nm;

[0135] By calculation, m in Example 2 CB负 =

[0136] =(0.08*0.1561*1000*1.3*10000*20*2*10^-7*2.2+0.08*(45.05 / 345*100)) / 1000=0.00247kg;

[0137] Then, the negative electrode conductive agent obtained by the above calculation was mixed with the negative electrode active material (0.1561 kg) and the binder (0.006 kg) and coated on the copper foil to obtain the negative electrode sheet.

[0138] Diaphragm: PP diaphragm.

[0139] Electrolyte: The electrolyte is lithium hexafluorophosphate (1 mol / L), and the solvent is ethylene carbonate and dimethyl carbonate, the ratio of the two is 1:1, and the electrolyte contains 2% by weight of vinylene carbonate.

[0140] The positive electrode sheets prepared in Examples 1-3 and Comparative Examples 1-2 were respectively combined with the above-mentioned negative electrode sheets, separators and electrolytes to prepare lithium-ion batteries, and then the performance of the batteries was tested. The results are as follows:

[0141]

[0142] Note: First efficiency: Coulombic efficiency of the battery in the first charge and discharge cycle; Cycle: Discharge capacity retention rate after 1000 charge and discharge cycles at 0.5C at 25 degrees; Rate: Capacity retention rate when the initial capacity is charged at 0.2C and discharged at 0.2C at 25 degrees, and charged at 0.2C and discharged at 1C; Storage: Capacity retention rate after 30D (30 days) of storage at 100% SOC at 25 degrees.

[0143] It can be seen from the experimental results that if the content of the conductive agent is too little, the cycle performance and rate performance of the battery will be reduced, and if the content of the conductive agent is too much, the first coulombic efficiency of the battery will be reduced.

[0144] Test Example 2

[0145] With lithium iron phosphate as the positive electrode active material, acetylene black as the conductive agent, and PVDF as the binder, the amount of the positive electrode conductive agent is calculated using the calculation method of Example 1-3 and Comparative Example 1-2:

[0146] m AM正 =0.28471kg; Φ 正 =11m 2 / g; R1 = 22nm; ρ1 = 2.2g / m 3 ; V1=47.07cm 3 ;

[0147] Ψ1 = 250 mL / 100 g; active material diameter = 10 microns.

[0148] By calculation, m in Example 1 CB正

[0149] =(0.005*0.28471*1000*11*10000*22*2*10^-7*2.2+0.028*(47.07 / 350*100)) / 1000=0.002kg;

[0150] Example 2 m CB正

[0151] =(0.01*0.28471*1000*11*10000*22*2*10^-7*2.2+0.09*(47.07 / 250*100)) / 1000=0.0047kg;

[0152] Example 3 m CB正

[0153] =(0.02*0.28471*1000*11*10000*22*2*10^-7*2.2+0.18*(47.07 / 250*100)) / 1000=0.0094kg;

[0154] m of Comparative Example 1 CB正

[0155] =(0.001*0.28471*1000*11*10000*22*2*10^-7*2.2+0.01*(47.07 / 250*100)) / 1000=0.00049kg;

[0156] m of Comparative Example 2 CB正

[0157] =(0.1*0.28471*1000*11*10000*22*2*10^-7*2.2+1*(47.07 / 250*100)) / 1000=0.0397kg.

[0158] Then, the positive electrode conductive agent is obtained according to the above calculation, mixed with the positive electrode active material (0.28471 kg) and the binder (binder mass / active material mass = 2.2%), and coated on aluminum foil to obtain the positive electrode sheet.

[0159] Negative electrode sheet: Graphite is used as the negative electrode active material, acetylene black is used as the conductive agent, CMC+SBR (the mass ratio of CMC to SBR is 1:1) is used as the binder, and the mixture is coated with copper foil to prepare the negative electrode sheet. The amount of the negative electrode conductive agent is calculated using the calculation method in Example 2:

[0160] m AM负 =0.1561kg; Φ 负 =1.2m 2 / g; R2 = 22nm; ρ2 = 2.2g / m3 ; V2=45.05cm 3 ;

[0161] Ψ2 = 250 mL / 100 g; the diameter of the active substance is 20-30 nm;

[0162] By calculation, m in Example 2 CB负 ==(0.08*0.1561*1000*1.2*10000*22*2*10^-7*2.2+0.08*(45.05 / 250*100)) / 1000=0.00289kg;

[0163] Then, the negative electrode conductive agent obtained by the above calculation was mixed with the negative electrode active material (0.1561 kg) and the binder (0.006 kg) and coated on the copper foil to obtain the negative electrode sheet.

[0164] Diaphragm: PP diaphragm.

[0165] Electrolyte: The electrolyte is lithium hexafluorophosphate (1 mol / L), and the solvent is ethylene carbonate and dimethyl carbonate, the ratio of the two is 1:1, and the electrolyte contains 2% by weight of vinylene carbonate.

[0166] The positive electrode sheets prepared in Examples 1-3 and Comparative Examples 1-2 were respectively combined with the above-mentioned negative electrode sheets, separators and electrolytes to prepare lithium-ion batteries, and then the performance of the batteries was tested. The results are as follows:

[0167]

[0168] Test Example 3

[0169] With lithium iron phosphate as the positive electrode active material, conductive carbon black as the conductive agent, and PVDF as the binder, the amount of the positive electrode conductive agent is calculated using the calculation method of Example 2:

[0170] m AM正 =0.29225kg; Φ 正 =14(m 2 / g); R1 = 20nm; ρ1 = 2.2g / m 3 ; V1=46.62cm 3 ;

[0171] Ψ1 = 348 mL / 100 g; active material diameter = 10 microns.

[0172] By calculation, m in Example 2 CB正 = = (0.01*0.29225*1000*14*10000*20*2*10^-7*2.2+0.09*(46.62 / 348*100)) / 1000 = 0.0048;

[0173] Then, the positive electrode conductive agent is obtained according to the above calculation, mixed with the positive electrode active material (0.29225 kg) and the binder (0.006 kg), and coated on the aluminum foil to obtain the positive electrode sheet.

[0174] Negative electrode sheet: Graphite is used as the negative electrode active material, conductive carbon black is used as the conductive agent, CMC+SBR (the mass ratio of CMC to SBR is 1:1) is used as the binder, and the mixture is coated with copper foil to prepare the negative electrode sheet. The amount of the negative electrode conductive agent is calculated using the calculation method of Example 1-3 and Comparative Example 1-2:

[0175] m AM负 =0.1561kg; Φ 负 =1.5m 2 / g; R2 = 20nm; ρ2 = 2.2g / m 2 ; V2=45.05cm 3 ;

[0176] Ψ2 = 350 mL / 100 g; the diameter of the active substance is 20-30 nm;

[0177] By calculation, m in Example 1 CB负 =

[0178] (0.015*0.1561*1000*1.5*10000*20*2*10^-7*2.2+0.056*(45.05 / 350*100)) / 1000=0.0010kg;

[0179] Example 2 m CB负

[0180] =(0.08*0.1561*1000*1.5*10000*20*2*10^-7*2.2+0.08*(45.05 / 350*100)) / 1000=0.0026kg;

[0181] Example 3 m CB负

[0182] =(0.15*0.1561*1000*1.5*10000*20*2*10^-7*2.2+0.16*(45.05 / 350*100)) / 1000=0.0051kg;

[0183] m of Comparative Example 1 CB负

[0184] =(0.001*0.1561*1000*1.5*10000*20*2*10^-7*2.2+0.01*(45.05 / 350*100)) / 1000=0.00014kg;

[0185] m of Comparative Example 2 CB负

[0186] =(0.2*0.1561*1000*1.5*10000*20*2*10^-7*2.2+1*(45.05 / 350*100)) / 1000=0.00169kg;

[0187] Then, the negative electrode conductive agent obtained by the above calculation was mixed with the negative electrode active material (0.1561 kg) and the binder (0.006 kg) and coated on the copper foil to obtain the negative electrode sheet.

[0188] Diaphragm: PP diaphragm.

[0189] Electrolyte: The electrolyte is lithium hexafluorophosphate (1 mol / L), and the solvent is ethylene carbonate and dimethyl carbonate, the ratio of the two is 1:1, and the electrolyte contains 2% by weight of vinylene carbonate.

[0190] The negative electrode sheets prepared in Examples 1-3 and Comparative Examples 1-2 were respectively combined with the positive electrode sheets, separators and electrolytes to prepare lithium-ion batteries, and then the performance of the batteries was tested. The results are as follows:

[0191]

[0192]

[0193] Test Example 4

[0194] With lithium iron phosphate as the positive electrode active material, acetylene black as the conductive agent, and PVDF as the binder, the amount of the positive electrode conductive agent is calculated using the calculation method of Example 2:

[0195] m AM正 =0.29225kg; Φ 正 =14m 2 / g; R1 = 22nm; ρ1 = 2.2g / m 3 ; V1=46.62m 3 ;

[0196] Ψ1 = 343 mL / 100 g; active material diameter = 10 microns;

[0197] By calculation, m in Example 2 CB正= = (0.01*0.29225*1000*14*10000*22*2*10^-7*2.2+0.09*(46.62 / 343*100)) / 1000 = 0.0051;

[0198] Then, the positive electrode conductive agent is obtained according to the above calculation, mixed with the positive electrode active material (0.29225 kg) and the binder (0.0064 kg), and coated on the aluminum foil to obtain the positive electrode sheet.

[0199] Negative electrode sheet: Graphite is used as the negative electrode active material, acetylene black is used as the conductive agent, CMC+SBR (the mass ratio of CMC to SBR is 1:1) is used as the binder, and the mixture is coated with copper foil to prepare the negative electrode sheet. The amount of the negative electrode conductive agent is calculated using the calculation method of Example 1-3 and Comparative Example 1-2:

[0200] m AM负 =0.1561kg; Φ 负 =1.2m 2 / g; R2 = 22nm; ρ2 = 2.2g / m 3 ; V2=45.05m 3 ;

[0201] Ψ2 = 250 mL / 100 g; the diameter of the active substance is 20-30 nm;

[0202] By calculation, m in Example 1 CB负 =

[0203] (0.015*0.1561*1000*1.5*10000*22*2*10^-7*2.2+0.056*(45.05 / 350*100)) / 1000=0.00128kg;

[0204] Example 2 m CB负

[0205] =(0.08*0.1561*1000*1.5*10000*22*2*10^-7*2.2+0.08*(45.05 / 350*100)) / 1000=0.00289kg;

[0206] Example 3 m CB负

[0207] =(0.15*0.1561*1000*1.5*10000*22*2*10^-7*2.2+0.16*(45.05 / 350*100)) / 1000=0.0056kg;

[0208] m of Comparative Example 1 CB负

[0209] =(0.001*0.1561*1000*1.5*10000*22*2*10^-7*2.2+0.01*(45.05 / 350*100)) / 1000=0.00019kg;

[0210] m of Comparative Example 2 CB负

[0211] =(0.2*0.1561*1000*1.5*10000*22*2*10^-7*2.2+1*(45.05 / 350*100)) / 1000=0.0174kg;

[0212] Then, the negative electrode conductive agent obtained by the above calculation was mixed with the negative electrode active material (0.1561 kg) and the binder (0.006 kg) and coated on the copper foil to obtain the negative electrode sheet.

[0213] Diaphragm: PP diaphragm.

[0214] Electrolyte: The electrolyte is lithium hexafluorophosphate (1 mol / L), and the solvent is ethylene carbonate and dimethyl carbonate, the ratio of the two is 1:1, and the electrolyte contains 2% by weight of vinylene carbonate.

[0215] The negative electrode sheets prepared in Examples 1-3 and Comparative Examples 1-2 were respectively combined with the positive electrode sheets, separators and electrolytes to prepare lithium-ion batteries, and then the performance of the batteries was tested. The results are as follows:

[0216]

[0217] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, but not to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solution of the embodiments of the present invention.

Claims

1. A method for calculating the amount of conductive agent used in positive and negative electrodes of a lithium ion battery, characterized in that: The positive electrode sheet of the lithium-ion battery comprises a positive electrode current collector and a positive electrode slurry layer coated on the positive electrode current collector; The positive electrode slurry comprises a positive electrode active material, a positive electrode conductor and a binder; In the positive electrode slurry, the calculation formula for the amount of positive electrode conductive agent is as follows: m CB正 =K1*m AM正 *F 正 *2R1*ρ1+α1*(V1 / Ψ1); Among them, m CB正 is the weight of the positive electrode conductive agent; K1 is the positive electrode conductivity coefficient; m AM正 is the total active material weight of the positive electrode; Φ 正 is the specific surface area of ​​the positive electrode active material; R1 is the radius of the positive electrode composite conductive agent; ρ1 is the density of the positive electrode conductive agent; V1 is the pore volume of the positive electrode sheet; α1 is the positive electrode liquid retention conversion coefficient; Ψ1 is the oil absorption value of the positive electrode conductive agent; The K1 is 0.005-0.02, and α1 is 0.028-0.18; The negative electrode sheet of the lithium ion battery comprises a negative electrode current collector and a negative electrode slurry layer coated on the negative electrode current collector; The negative electrode slurry comprises a negative electrode active material, a negative electrode conductive agent and a binder; In the negative electrode slurry, the calculation formula for the amount of negative electrode conductive agent is as follows: m CB负 =K2*m AM负 *F 负 *2R2*ρ2+α2*(V2 / Ψ2); Among them, m CB负 is the weight of negative electrode conductive agent; K2 is the negative electrode conductivity coefficient; m AM负 is the total active material weight of the negative electrode; Φ 负 is the specific surface area of ​​the negative electrode active material; R2 is the radius of the negative electrode composite conductive agent; ρ2 is the density of the negative electrode conductive agent; V2 is the pore volume of the negative electrode sheet; α2 is the negative electrode liquid retention conversion coefficient; Ψ2 is the oil absorption value of the negative electrode conductive agent; The K2 is 0.015-0.15, and the α2 is 0.056-0.

16.

2. The calculation method according to claim 1, characterized in that: The calculation formula of the specific surface area of ​​the positive electrode active material is as follows: F 正 =(Φ 正1 *λAM 正1 +F 正2 *λAM 正2 +…+F 正n *λAM 正n ); Among them, λAM 正1 +λAM 正2 +…+λAM 正n =1;λAM 正n is the weight proportion of the nth positive electrode active material; Φ 正n is the specific surface area of ​​the nth positive electrode active material; n is a positive integer.

3. The calculation method according to claim 1, characterized in that: When the number of negative electrode active materials is greater than or equal to 2, the calculation formula for the specific surface area of ​​the negative electrode active material is as follows: F 负 =(Φ 负1 *βAM 负1 +F 负2 *βAM 负2 +…+F 负n *βAM 负n ); Among them, βAM 负1 +βAM 负2 +…+βAM-n=1;βAM 负n is the weight proportion of the nth negative electrode active material; Φ 负n is the specific surface area of ​​the nth negative electrode active material; n is a positive integer.

4. The calculation method according to claim 1, characterized in that: The positive electrode conductive agent includes: one or more of conductive carbon black and acetylene black; The positive electrode active material includes lithium iron phosphate.

5. The calculation method according to claim 1, characterized in that: The negative electrode conductive agent includes: one or more of conductive carbon black and acetylene black; The negative electrode active material includes graphite.

6. The calculation method according to claim 1, characterized in that: The binder includes PVDF.

7. The calculation method according to claim 1, characterized in that: The positive electrode current collector comprises aluminum foil; The negative electrode current collector includes copper foil.

8. Application of the calculation method according to any one of claims 1 to 7 in the production of lithium-ion batteries.

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