CN114242945B - Method for determining ratio of negative electrode capacity to positive electrode capacity and related lithium ion battery - Google Patents

Method for determining ratio of negative electrode capacity to positive electrode capacity and related lithium ion battery Download PDF

Info

Publication number
CN114242945B
CN114242945B CN202210168992.3A CN202210168992A CN114242945B CN 114242945 B CN114242945 B CN 114242945B CN 202210168992 A CN202210168992 A CN 202210168992A CN 114242945 B CN114242945 B CN 114242945B
Authority
CN
China
Prior art keywords
silicon
negative electrode
capacity
positive electrode
ratio
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN202210168992.3A
Other languages
Chinese (zh)
Other versions
CN114242945A (en
Inventor
李康
单旭意
徐鹏飞
刘昕
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
China Lithium Battery Technology Co Ltd
Original Assignee
China Lithium Battery Technology Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by China Lithium Battery Technology Co Ltd filed Critical China Lithium Battery Technology Co Ltd
Priority to CN202210168992.3A priority Critical patent/CN114242945B/en
Publication of CN114242945A publication Critical patent/CN114242945A/en
Application granted granted Critical
Publication of CN114242945B publication Critical patent/CN114242945B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

Disclosed is a method for determining the ratio of the negative electrode capacity to the positive electrode capacity of a silicon-containing negative electrode lithium ion battery, such that the ratio N/P of the capacity N of the negative electrode to the capacity P of the positive electrode satisfies: exp (-pi. c/14) is more than or equal to N/P is less than or equal to 1, wherein c is the proportion of the mole number of silicon elements to the total mole number of all the anode active materials, and c is more than 0 and less than or equal to 1. The lithium ion battery comprises a positive electrode and a silicon-containing negative electrode, wherein the active substance of the silicon-containing negative electrode is a silicon-based material or a mixture of the silicon-based material and a carbon-based material; the ratio N/P between the capacity N of the negative electrode and the capacity P of the positive electrode satisfies: exp (-pi. c/14) is more than or equal to N/P is less than or equal to 1. The N/P ratio is satisfied, the cycle characteristic of the battery can be improved, the coulomb efficiency of the battery for the first charging is improved, the negative electrode is placed for lithium precipitation, and the manufacturing cost of the battery is saved.

Description

Method for determining ratio of negative electrode capacity to positive electrode capacity and related lithium ion battery
Technical Field
The invention relates to the field of lithium ion batteries, in particular to a method for determining the ratio of the negative electrode capacity to the positive electrode capacity of a lithium ion battery, and the lithium ion battery with the ratio of the negative electrode capacity to the positive electrode capacity.
Background
The capacity balance between the negative electrode and the positive electrode is a key factor to be considered when designing the lithium ion battery. Lithium separation can cause aging attenuation and safety degradation of the battery, and in order to avoid lithium separation risk and obtain better safety and electrochemical performance, the negative electrode of the conventional lithium ion battery is generally over-designed, specifically, the over-design comprises the over-size of the negative electrode and the over-capacity in the corresponding areas of the positive electrode and the negative electrode. The ratio N/P of the negative electrode capacity to the positive electrode capacity refers to the ratio of the negative electrode reversible surface capacity to the positive electrode reversible surface capacity in the same stage under the same operation condition, represents the matching of the positive electrode capacity and the negative electrode capacity of the battery cell, and is a key parameter for the design of the battery cell of the lithium battery.
When the battery is designed, if the positive electrode is excessive, redundant lithium ions which are separated from the positive electrode in the charging process are not accommodated in enough vacancies, lithium dendrites are separated out from the surface of the negative electrode to form a short circuit in the battery, so that the cycle life of a battery core is shortened, and the safety risk is improved. Therefore, in the design of lithium ion batteries, N/P >1 is generally used to avoid the above-mentioned problems, but N/P >1 means that there is a margin in the negative electrode, excessive active sites in the negative electrode catalyze decomposition of the electrolyte to cause loss of active lithium, the generated by-products also promote precipitation of metal ions in the positive electrode, and the metal deposits on the negative electrode to further catalyze decomposition of the electrolyte, thereby deteriorating the battery cycle performance. Particularly, when the negative electrode adopts a silicon-carbon system, the silicon-based material has more surface active sites than the carbon-based material, compared with the case that the negative electrode is only the carbon-based material, if the design that N/P is greater than 1 is adopted, more active lithium is consumed, larger irreversible capacity loss of the battery is caused, the overall capacity of the battery is reduced, and meanwhile, the capacities of the positive electrode and the negative electrode are seriously mismatched, and the cycle characteristics of the battery are influenced.
Therefore, for the lithium ion battery with the negative electrode adopting the silicon-based material or the silicon-carbon mixed system, the range of the ratio of the negative electrode capacity to the positive electrode capacity still needs to be further optimized, so that the purposes of reducing the negative electrode active sites and avoiding lithium precipitation can be achieved, and the cycle performance of the battery is improved.
Disclosure of Invention
The present inventors have conducted extensive studies and extensive experiments in order to solve the above problems, and have proposed a method of determining the ratio of negative and positive capacities (N/P) of a silicon-containing negative electrode lithium ion battery, and a lithium ion battery having the range of the ratio of negative and positive capacities on the basis thereof.
Accordingly, in one aspect, the present invention provides a method of determining the ratio of the negative and positive electrode capacities of a silicon-containing negative lithium ion battery such that the ratio N/P of the capacity N of the negative electrode to the capacity P of the positive electrode satisfies: exp (-pi. c/14) is more than or equal to N/P is less than or equal to 1, wherein c is the proportion of the mole number of silicon elements to the total mole number of all the anode active materials, and c is more than 0 and less than or equal to 1.
In another aspect, the present invention provides a lithium ion battery comprising a positive electrode and a silicon-containing negative electrode, wherein an active material of the silicon-containing negative electrode is a silicon-based material or a mixture of the silicon-based material and a carbon-based material; the ratio N/P between the capacity N of the negative electrode and the capacity P of the positive electrode satisfies: exp (-pi. c/14) is more than or equal to N/P is less than or equal to 1, wherein c is the proportion of the mole number of silicon elements to the total mole number of all the anode active materials, and c is more than 0 and less than or equal to 1.
In the lithium ion battery, the capacity of the positive electrode is slightly higher than that of the negative electrode in the initial stage, so that negative electrode active sites can be introduced as little as possible relatively, and the surplus active lithium of the positive electrode is ensured to consume the active sites in the negative electrode in the charging process, so that the actual capacities of the positive electrode and the negative electrode are equivalent, the active sites are eliminated, lithium precipitation caused by the fact that the capacity of the positive electrode is higher than that of the negative electrode can be avoided, and the cycle performance of the battery can be obviously improved.
Drawings
The present application is described in further detail below with reference to the accompanying drawings. The features and advantages of the present application will become more apparent from the description, in which:
fig. 1 is a schematic diagram of active lithium in a positive electrode and active sites and vacancies in a negative electrode;
FIG. 2 is a graph of N/P ratio versus the molar content of silicon in the negative electrode according to the present invention;
FIG. 3 is a graph of positive electrode potential versus negative electrode silicon molar content after a lithium ion battery according to the present invention has been fully charged; and
fig. 4 is a relationship between the potential of the negative electrode after full charge and the molar content of silicon in the negative electrode of the lithium ion battery according to the present invention.
Detailed Description
In the present application, the technical features related to the different embodiments described below may be considered to be combinable with each other as long as they do not conflict with each other.
In the present application, the term "ratio N/P of negative electrode capacity to positive electrode capacity" refers to the ratio of the negative electrode reversible capacity to the positive electrode reversible capacity at the same stage under the same operating conditions.
For example, the negative electrode capacity and the positive electrode capacity can be capacities during charging, newly prepared positive and negative electrode plates can be adopted to form a half-cell with a lithium plate respectively, and the lithium removal capacity of the positive electrode plate and the lithium insertion capacity of the negative electrode plate are obtained under a certain multiplying power; for a non-newly prepared battery, the potential of the positive electrode and the negative electrode can also be determined by adopting a potential monitoring method, such as a three-electrode method, namely, two charge-discharge tests are carried out in a 25 ℃ incubator at the multiplying power of 0.33 ℃, the charge capacity of the positive electrode at the second time is taken as the lithium removal capacity of the positive plate, and the discharge capacity of the negative plate is taken as the lithium insertion capacity of the negative electrode.
As shown in fig. 1, in the present application, the term "vacancy" refers to a spatial site in the negative electrode capable of inserting/extracting active lithium; the term "active site" refers to a defect (e.g., dangling bond, dislocation, etc.) having a higher reaction activity in the phase structure of the negative electrode active material (e.g., silicon-based material and carbon-based material). The active sites not only catalyze the decomposition of the electrolyte to cause partial active lithium deactivation, but also promote the precipitation of metal by-products formed by the reaction, and the metal deposited on the negative electrode further catalyzes the decomposition of the electrolyte to cause vicious circle. Specifically, the active sites catalyze the decomposition of the electrolyte to generate reaction byproducts, the reaction byproducts can cause the precipitation of metal ions in the anode material, the metal ions can be dissolved in the electrolyte firstly after being precipitated and then deposited on the surface of the cathode, and the deposited metal can further catalyze the decomposition of the electrolyte.
The invention provides a method for determining the capacity ratio of a negative electrode and a positive electrode of a silicon-containing negative electrode lithium ion battery, so that the ratio N/P of the capacity N of the negative electrode and the capacity P of the positive electrode meets the following requirements: exp (-pi. c/14) is more than or equal to N/P is less than or equal to 1, wherein c is the proportion of the mole number of silicon elements to the total mole number of all the anode active materials, and c is more than 0 and less than or equal to 1.
Note that pi in the formula exp (-pi. c/14). ltoreq.N/P.ltoreq.1 is a circumferential ratio.
In one embodiment of the method according to the invention, the ratio N/P of the capacity N of the negative electrode and the capacity P of the positive electrode satisfies: exp (-pi × c/30) is more than or equal to N/P is less than or equal to 1.
In another embodiment of the method according to the present invention, the active material of the silicon-containing negative electrode is a silicon-based material or a mixture of a silicon-based material and a carbon-based material.
When the active material of the silicon-containing anode is a silicon-based material, c =1 is a ratio of the number of moles of silicon element to the total number of moles of all anode active materials; when the active material of the silicon-containing anode is a mixture of a silicon-based material and a carbon-based material, c = (the number of moles of the silicon-based material)/(the number of moles of the silicon-based material + the number of moles of the carbon-based material), which is a ratio of the number of moles of silicon element to the total number of moles of the entire anode active material.
In another embodiment of the method according to the invention, the silicon-based material is chosen from the group consisting of elemental silicon, silicon-oxygen-SiOx(0.9<x<1.1), silicon-carbon composite materials and silicon alloys; the carbon-based material is artificial graphite or natural graphite.
In another embodiment of the method according to the present invention, when the active material of the silicon-containing negative electrode is a mixture of a silicon-based material and a carbon-based material, the weight content of the silicon-based material is greater than 0 and equal to or less than 30% based on the total weight of the mixture of the silicon-based material and the carbon-based material. If the content of the silicon-based material is too large, the material particles are more easily broken during the cycle, and thus more active sites are generated, consuming the electrolyte and active lithium, and generating a large expansion force, resulting in deterioration of cycle performance.
The invention also provides a lithium ion battery which comprises a positive electrode and a silicon-containing negative electrode, wherein the active substance of the silicon-containing negative electrode is a silicon-based material or a mixture of the silicon-based material and a carbon-based material; the ratio N/P between the capacity N of the negative electrode and the capacity P of the positive electrode satisfies: exp (-pi. c/14) is more than or equal to N/P is less than or equal to 1, c is the proportion of the mole number of silicon element in the total mole number of all the cathode active materials, and c is more than 0 and less than or equal to 1.
In one embodiment of the lithium ion battery according to the present invention, a ratio N/P of a capacity N of the negative electrode and a capacity P of the positive electrode satisfies: exp (-pi × c/30) is more than or equal to N/P is less than or equal to 1.
In another embodiment of the lithium ion battery according to the present invention, the silicon-based material is selected from the group consisting of elemental silicon, silicon-oxygen-SiOx(0.9<x<1.1), silicon-carbon composite materials and silicon alloys; the carbon-based material is artificial graphite or natural graphite.
In another embodiment of the lithium ion battery according to the invention, the active material of the positive electrode is selected from LiMnO2，LiCoO2，LiNiO2，LiMn2O4，LiFePO4，LiNixCoyMn1-x-yO2(0<x<1、0<y<1、0<x+y<1) One or more of (a).
It is to be noted that the above-described relation for determining the N/P ratio of the present invention is applicable to different types of positive electrodes since the active sites mainly originate from the negative electrode, and therefore the positive electrode active material of the lithium ion battery according to the present invention may be any other positive electrode active material than the above-described one.
In another embodiment of the lithium ion battery according to the present invention, when the active material of the silicon-containing negative electrode is a mixture of a silicon-based material and a carbon-based material, the weight content of the silicon-based material is greater than 0 and equal to or less than 30% based on the total weight of the mixture of the silicon-based material and the carbon-based material. For the same reasons as above.
In one embodiment of the method and the lithium ion battery according to the present invention, when the battery is charged to a cut-off state, the potential of the negative electrode is 0 to 0.05V.
It is to be noted that in the lithium ion battery according to the present invention, any electrolyte and separator commonly used in the art may be used without limitation.
According to the Arrhenius equation of the relation between the reaction rate and the reaction energy barrier and the temperature, under the condition of constant temperature, the reaction amount per unit time only depends on the reaction energy barrier; the inventors found that the energy barrier of the side reaction during charge and discharge is in turn positively correlated with the number of active sites of the negative electrode.
In addition, for a silicon-containing anode, since the number of silicon active sites per unit amount is much greater than that of carbon active sites per unit amount, the number of active sites largely depends on the content of silicon in the anode active material. When the design that the N/P ratio is less than 1 is adopted, the part of the positive electrode with the capacity more than that of the negative electrode is used for reacting with the active sites of the negative electrode, so that the capacities of the positive electrode and the negative electrode are equivalent. This makes it possible to not only improve the cycle characteristics of the battery as described above, but also precisely control the amount of the positive electrode active material containing lithium, thereby saving the manufacturing cost of the battery and expensive lithium resources. Meanwhile, the adaptability of the positive and negative electrode capacities is good, so that the specific energy density of the battery is improved.
After extensive experimentation and fitting analysis, the inventors concluded the following empirical formulas (1) and (2), wherein the minimum or design lower limit (y) of the N/P ratio can be determined according to the following formula (1)min)：
ymin=exp(-π*c/14)(1)
Also, the following formula can be followed(2) Determining an optimal lower bound (y) for the N/P ratioopt)：
yopt=exp(-π*c/30)(2)
As shown in fig. 2, y = exp (-pi x/14) determines the lithium extraction boundary of the cell, i.e. the N/P ratio is below this curve at risk of lithium extraction; y = exp (-pi x/30) defines the lower end of the preferred range of cell N/P ratio, which is the boundary of high cycle performance of the battery. In other words, when the N/P ratio is in the region a in the figure, the battery is at risk of lithium extraction; when the N/P ratio is in the B area in the graph, the lithium precipitation risk of the battery can be eliminated; when the N/P ratio is in the region C in the figure, not only is there no risk of lithium precipitation of the battery, but also the cycle performance of the battery, i.e., the preferred range of the N/P ratio, can be improved.
More specifically, in the invention, setting N/P to be less than 1 can avoid the situation that the number of active sites of the negative electrode is too large, so that a large amount of active lithium is consumed by the active sites, and the first coulomb efficiency of the battery is obviously reduced; in addition, the number of active sites on the surface of the silicon-based negative electrode material is larger than that of carbon-based materials such as graphite, so that the lower limit of the N/P ratio is determined according to the silicon content, and the situation that the anode capacity is excessive due to the fact that the N/P is too small, the anode does not have enough vacancy to contain, and lithium is separated out can be avoided.
In addition, by adopting the design of low N/P ratio, after the active site is consumed, the negative electrode potential of the battery is lower than that of the battery designed by high N/P ratio (>1) when the charging is about to cut off, because a low-potential byproduct is generated at the position of the negative electrode active site; the corresponding positive electrode potential is lower than that designed by a high N/P ratio (the charge cut-off potential is fixed), and the positive electrode potential and the negative electrode potential are lower, so that the method is not only characterized by the low N/P ratio design method and the lithium ion battery, but also can be used as the measurement of the consumption degree of the active sites.
Fig. 3 and 4 show the variation of the positive electrode potential and the negative electrode potential with the molar content of silicon in the negative electrode at the time of full charge of the battery, respectively, with the range of fluctuation of ± 10mV in the dotted frame around the solid line. In fig. 3, X is the potential when the positive electrode is charged to full charge, different positive electrode materials have different X, but the positive electrode potential also decreases when the N/P ratio of the same silicon content decreases (the full cell potential remains unchanged, the negative electrode potential decreases, and thus the positive electrode potential also decreases), but not less than X-0.05. In FIG. 4, Y is the potential when the negative electrode is fully charged, and in the case of pure graphite, the full potential of the negative electrode is about 0.05V, and the potential of the negative electrode decreases as the N/P ratio decreases, and the lowest point is Y-0.05 but not less than 0V.
The present invention will be further illustrated by the following examples. It should be noted that the materials used in the examples below are all commercially available products, and see the following table for details.
Name of material For short Source
Graphite C Fibrate-rubicun
Silicone material SiO Signal crossing
Sodium carboxymethylcellulose CMC Japanese paper
Styrene butadiene rubber SBR Rui Weng (Chinese character of 'Rui' type)
Carbon nanotube CNT Tiannai (rhizoma kaempferiae)
Polyvinylidene fluoride PVDF Su Wei
Example 1
Preparing a negative plate: adding graphite, a silica material (SiO), a thickening agent (CMC), a binder (SBR) and a conductive agent (CNT) into a deionized water solvent according to a mass ratio of 86.4:9.6:1.0:2.0:1.0, fully and uniformly mixing to obtain negative electrode slurry, coating the negative electrode slurry on a copper foil, and drying to obtain the negative electrode piece. Preparing a positive plate: adding the high-nickel NCM ternary material, a conductive agent (CNT) and a binder (PVDF) into an NMP solvent according to a mass ratio of 98.0:1.15:0.85, fully and uniformly mixing to obtain positive electrode slurry, coating the positive electrode slurry on an aluminum foil, and drying to obtain the positive electrode piece. The positive and negative pole pieces are rolled, assembled, dried, injected with liquid, formed and subjected to capacity grading to manufacture the lithium ion battery. The designed ratio of negative electrode capacity/positive electrode capacity was 1.0.
Example 2
Preparing a negative plate: adding graphite, a silica material (SiO), a thickening agent (CMC), a binder (SBR) and a conductive agent (CNT) into a deionized water solvent according to a mass ratio of 86.4:9.6:1.0:2.0:1.0, fully and uniformly mixing to obtain negative electrode slurry, coating the negative electrode slurry on a copper foil, and drying to obtain the negative electrode piece. Preparing a positive plate: adding the high-nickel NCM ternary material, a conductive agent (CNT) and a binder (PVDF) into an NMP solvent according to the mass ratio of 98.0:1.15:0.85, fully and uniformly mixing to obtain positive electrode slurry, coating the positive electrode slurry on an aluminum foil, and drying to obtain the positive electrode piece. The designed ratio of negative electrode capacity/positive electrode capacity was 0.99 (upper limit of the preferable range).
Example 3
Preparing a negative plate: adding graphite, a silica material (SiO), a thickening agent (CMC), a binder (SBR) and a conductive agent (CNT) into a deionized water solvent according to the mass ratio of 86.4:9.6:1.0:2.0:1.0, fully and uniformly mixing to obtain negative electrode slurry, coating the negative electrode slurry on a copper foil, and drying to obtain the negative electrode piece. Preparing a positive plate: adding the high-nickel NCM ternary material, a conductive agent (CNT) and a binder (PVDF) into an NMP solvent according to a mass ratio of 98.0:1.15:0.85, fully and uniformly mixing to obtain positive electrode slurry, coating the positive electrode slurry on an aluminum foil, and drying to obtain the positive electrode piece. The designed ratio of negative electrode capacity/positive electrode capacity was 0.978 (minimum).
Comparative example 1
Preparing a negative plate: adding graphite, a silica material (SiO), a thickening agent (CMC), a binder (SBR) and a conductive agent (CNT) into a deionized water solvent according to a mass ratio of 86.4:9.6:1.0:2.0:1.0, fully and uniformly mixing to obtain negative electrode slurry, coating the negative electrode slurry on a copper foil, and drying to obtain the negative electrode piece. Preparing a positive plate: adding the high-nickel NCM ternary material, a conductive agent (CNT) and a binder (PVDF) into an NMP solvent according to the mass ratio of 98.0:1.15:0.85, fully and uniformly mixing to obtain positive electrode slurry, coating the positive electrode slurry on an aluminum foil, and drying to obtain the positive electrode piece. The designed ratio of negative electrode capacity/positive electrode capacity was 1.10.
Comparative example 2
Preparing a negative plate: adding graphite, a silica material (SiO), a thickening agent (CMC), a binder (SBR) and a conductive agent (CNT) into a deionized water solvent according to the mass ratio of 86.4:9.6:1.0:2.0:1.0, fully and uniformly mixing to obtain negative electrode slurry, coating the negative electrode slurry on a copper foil, and drying to obtain the negative electrode piece. Preparing a positive plate: adding the high-nickel NCM ternary material, a conductive agent (CNT) and a binder (PVDF) into an NMP solvent according to the mass ratio of 98.0:1.15:0.85, fully and uniformly mixing to obtain positive electrode slurry, coating the positive electrode slurry on an aluminum foil, and drying to obtain the positive electrode piece. The designed ratio of negative electrode capacity/positive electrode capacity was 0.96.
Example 4
Preparing a negative plate: adding graphite, a silica material (SiO), a thickening agent (CMC), a binder (SBR) and a conductive agent (CNT) into a deionized water solvent according to the mass ratio of 48.0:48.0:1.0:2.0:1.0, fully and uniformly mixing to obtain negative electrode slurry, coating the negative electrode slurry on a copper foil, and drying to obtain the negative electrode piece. Preparing a positive plate: adding the high-nickel NCM ternary material, a conductive agent (CNT) and a binder (PVDF) into an NMP solvent according to the mass ratio of 98.0:1.15:0.85, fully and uniformly mixing to obtain positive electrode slurry, coating the positive electrode slurry on an aluminum foil, and drying to obtain the positive electrode piece. The positive and negative pole pieces are rolled, assembled, dried, injected with liquid, formed and subjected to capacity grading to manufacture the lithium ion battery. The designed ratio of negative electrode capacity/positive electrode capacity was 1.0.
Example 5
Preparing a negative plate: adding graphite, a silica material (SiO), a thickening agent (CMC), a binder (SBR) and a conductive agent (CNT) into a deionized water solvent according to the mass ratio of 48.0:48.0:1.0:2.0:1.0, fully and uniformly mixing to obtain negative electrode slurry, coating the negative electrode slurry on a copper foil, and drying to obtain the negative electrode piece. Preparing a positive plate: adding the high-nickel NCM ternary material, a conductive agent (CNT) and a binder (PVDF) into an NMP solvent according to a mass ratio of 98.0:1.15:0.85, fully and uniformly mixing to obtain positive electrode slurry, coating the positive electrode slurry on an aluminum foil, and drying to obtain the positive electrode piece. The positive and negative pole pieces are rolled, assembled, dried, injected with liquid, formed and subjected to capacity grading to manufacture the lithium ion battery. The designed ratio of negative electrode capacity/positive electrode capacity was 0.952 (upper limit of the preferred range).
Example 6
Preparing a negative plate: adding graphite, a silicon-carbon material (silicon accounts for 30% of the molar ratio of carbon to silicon), a thickening agent (CMC), a binder (SBR) and a conductive agent (CNT) into a deionized water solvent according to the mass ratio of 48.0:48.0:1.0:2.0:1.0, fully and uniformly mixing to obtain negative electrode slurry, coating the negative electrode slurry on a copper foil, and drying to obtain the negative electrode piece. Preparing a positive plate: adding the high-nickel NCM ternary material, a conductive agent (CNT) and a binder (PVDF) into an NMP solvent according to the mass ratio of 98.0:1.15:0.85, fully and uniformly mixing to obtain positive electrode slurry, coating the positive electrode slurry on an aluminum foil, and drying to obtain the positive electrode piece. The positive and negative pole pieces are rolled, assembled, dried, injected with liquid, formed and subjected to capacity grading to manufacture the lithium ion battery. The anode capacity/cathode capacity design ratio was 0.96 (minimum).
Comparative example 3
Preparing a negative plate: adding graphite, a silica material (SiO), a thickening agent (CMC), a binder (SBR) and a conductive agent (CNT) into a deionized water solvent according to the mass ratio of 48.0:48.0:1.0:2.0:1.0, fully and uniformly mixing to obtain negative electrode slurry, coating the negative electrode slurry on a copper foil, and drying to obtain the negative electrode piece. Preparing a positive plate: adding the high-nickel NCM ternary material, a conductive agent (CNT) and a binder (PVDF) into an NMP solvent according to the mass ratio of 98.0:1.15:0.85, fully and uniformly mixing to obtain positive electrode slurry, coating the positive electrode slurry on an aluminum foil, and drying to obtain the positive electrode piece. The positive and negative pole pieces are rolled, assembled, dried, injected with liquid, formed and subjected to capacity grading to manufacture the lithium ion battery. The designed ratio of negative electrode capacity/positive electrode capacity was 1.10.
Comparative example 4
Preparing a negative plate: adding graphite, a silicon-carbon material (silicon accounts for 30% of the molar ratio of carbon to silicon), a thickening agent (CMC), a binder (SBR) and a conductive agent (CNT) into a deionized water solvent according to the mass ratio of 48.0:48.0:1.0:2.0:1.0, fully and uniformly mixing to obtain negative electrode slurry, coating the negative electrode slurry on a copper foil, and drying to obtain the negative electrode piece. Preparing a positive plate: adding the high-nickel NCM ternary material, a conductive agent (CNT) and a binder (PVDF) into an NMP solvent according to a mass ratio of 98.0:1.15:0.85, fully and uniformly mixing to obtain positive electrode slurry, coating the positive electrode slurry on an aluminum foil, and drying to obtain the positive electrode piece. The positive and negative pole pieces are rolled, assembled, dried, injected with liquid, formed and subjected to capacity grading to manufacture the lithium ion battery. The anode capacity/cathode capacity design ratio was 0.94 (below the minimum).
Example 7
Preparing a negative plate: mixing a silicon oxide material (SiO), a thickening agent (CMC), a binder (SBR) and a conductive agent (CNT) according to a ratio of 96.0: adding the mixture into a deionized water solvent according to the mass ratio of 1.0:2.0:1.0, fully and uniformly mixing to obtain negative electrode slurry, coating the negative electrode slurry on copper foil, and drying to obtain a negative electrode plate. Preparing a positive plate: adding the high-nickel NCM ternary material, a conductive agent (CNT) and a binder (PVDF) into an NMP solvent according to the mass ratio of 98.0:1.15:0.85, fully and uniformly mixing to obtain positive electrode slurry, coating the positive electrode slurry on an aluminum foil, and drying to obtain the positive electrode piece. The positive and negative pole pieces are rolled, assembled, dried, injected with liquid, formed and subjected to capacity grading to manufacture the lithium ion battery. The designed ratio of negative electrode capacity/positive electrode capacity was 1.0.
Example 8
Preparing a negative plate: mixing a silicon oxide material (SiO), a thickening agent (CMC), a binder (SBR) and a conductive agent (CNT) according to a ratio of 96.0: adding the mixture into a deionized water solvent according to the mass ratio of 1.0:2.0:1.0, fully and uniformly mixing to obtain negative electrode slurry, coating the negative electrode slurry on copper foil, and drying to obtain a negative electrode plate. Preparing a positive plate: adding the high-nickel NCM ternary material, a conductive agent (CNT) and a binder (PVDF) into an NMP solvent according to the mass ratio of 98.0:1.15:0.85, fully and uniformly mixing to obtain positive electrode slurry, coating the positive electrode slurry on an aluminum foil, and drying to obtain the positive electrode piece. The positive and negative pole pieces are rolled, assembled, dried, injected with liquid, formed and subjected to capacity grading to manufacture the lithium ion battery. The designed ratio of negative electrode capacity/positive electrode capacity was 0.949.
Example 9
Preparing a negative plate: mixing a silicon oxide material (SiO), a thickening agent (CMC), a binder (SBR) and a conductive agent (CNT) according to a ratio of 96.0: adding the mixture into a deionized water solvent according to the mass ratio of 1.0:2.0:1.0, fully and uniformly mixing to obtain negative electrode slurry, coating the negative electrode slurry on copper foil, and drying to obtain a negative electrode plate. Preparing a positive plate: adding the high-nickel NCM ternary material, a conductive agent (CNT) and a binder (PVDF) into an NMP solvent according to a mass ratio of 98.0:1.15:0.85, fully and uniformly mixing to obtain positive electrode slurry, coating the positive electrode slurry on an aluminum foil, and drying to obtain the positive electrode piece. The positive and negative pole pieces are rolled, assembled, dried, injected, formed and subjected to capacity grading to manufacture the lithium ion battery. The designed ratio of negative electrode capacity/positive electrode capacity was 0.884.
Comparative example 5
Preparing a negative plate: a silicone material (SiO), a thickener (CMC), a binder (SBR), and a conductive agent (CNT) were mixed in a ratio of 96.0: adding the mixture into a deionized water solvent according to the mass ratio of 1.0:2.0:1.0, fully and uniformly mixing to obtain negative electrode slurry, coating the negative electrode slurry on copper foil, and drying to obtain a negative electrode plate. Preparing a positive plate: adding the high-nickel NCM ternary material, a conductive agent (CNT) and a binder (PVDF) into an NMP solvent according to the mass ratio of 98.0:1.15:0.85, fully and uniformly mixing to obtain positive electrode slurry, coating the positive electrode slurry on an aluminum foil, and drying to obtain the positive electrode piece. The positive and negative pole pieces are rolled, assembled, dried, injected with liquid, formed and subjected to capacity grading to manufacture the lithium ion battery. The designed ratio of negative electrode capacity/positive electrode capacity was 1.10.
Comparative example 6
Preparing a negative plate: mixing a silicon oxide material (SiO), a thickening agent (CMC), a binder (SBR) and a conductive agent (CNT) according to a ratio of 96.0: adding the mixture into a deionized water solvent according to the mass ratio of 1.0:2.0:1.0, fully and uniformly mixing to obtain negative electrode slurry, coating the negative electrode slurry on copper foil, and drying to obtain a negative electrode plate. Preparing a positive plate: adding the high-nickel NCM ternary material, a conductive agent (CNT) and a binder (PVDF) into an NMP solvent according to a mass ratio of 98.0:1.15:0.85, fully and uniformly mixing to obtain positive electrode slurry, coating the positive electrode slurry on an aluminum foil, and drying to obtain the positive electrode piece. The positive and negative pole pieces are rolled, assembled, dried, injected, formed and subjected to capacity grading to manufacture the lithium ion battery. The designed ratio of negative electrode capacity/positive electrode capacity was 0.79.
In the present application, the capacity retention at the nth cycle is defined as the percentage of the discharge capacity at the nth cycle relative to the discharge capacity at the 1 st full charge discharge (charge first followed by discharge) under the same test conditions and environmental conditions. The specific test method comprises the following steps: 1) placing an upper battery clamping plate into a 25 ℃ high-low temperature box and connecting the upper battery clamping plate with test equipment; 2) standing for 2h to reach thermal equilibrium; 3) the cycle test was performed at a rate of 0.33C/0.33C.
The positive and negative electrode compositions, N/P ratios, and capacity retention rates of 50 cycles, 100 cycles, and 300 cycles of the above examples and comparative examples are shown in Table 1 below.
TABLE 1
Positive electrode Negative electrode N/P Volume 50 times Volume maintenance Rate/%) 100 times (twice) Capacity protection Retention rate/%) 300 times Capacity protection Retention rate/%)
Examples 1 NCM conductive agent: adhesive agent according to 98.0:1.15: 0.85 Graphite, Silica (SiO), alumina Thickening agent (CMC), binder (SBR) And a conductive agent (CNT) according to 86.4:9.6:1.0:2.0:1.0 (molar silicon content: 3.1%) 1 97.96 96.86 94.86
Examples 2 NCM conductive agent: adhesive agent according to 98.0:1.15: 0.85 Graphite, Silica (SiO), alumina Thickening agent (CMC), binder (SBR) And a conductive agent (CNT) according to 86.4:9.6:1.0:2.0:1.0 (the molar content of silicon is 3.1%) 0.99 98.23 97.20 95.20
Examples 3 NCM conductive agent: adhesive agent according to 98.0:1.15: 0.85 Graphite, Silica (SiO), alumina Thickener (CMC), binder (SBR) And a conductive agent (CNT) according to 86.4:9.6:1.0:2.0:1.0 (the molar content of silicon is 3.1%) 0.978 98.15 97.14 95.14
Examples 4 NCM conductive agent: adhesive agent according to 98.0:1.15: 0.85 Graphite, Silica (SiO), alumina Thickener (CMC), binder (SBR) And a conductive agent (CNT) according to 48.0:48.0:1.0:2.0:1.0 (molar silicon content 21.4%) 1 95.00 91.30 89.27
Examples 5 NCM conductive agent: adhesive agent according to 98.0:1.15: 0.85 Graphite, Silica (SiO), alumina Thickener (CMC), binder (SBR) And a conductive agent (CNT) according to 48.0:48.0:1.0:2.0:1.0 (molar silicon content 21.4%) 0.952 95.50 91.74 89.71
Examples 6 NCM conductive agent: adhesive agent according to 98.0:1.15: 0.85 Graphite, Silica (SiO), alumina Thickener (CMC), binder (SBR) And a conductive agent (CNT) according to 48.0:48.0:1.0:2.0:1.0 (molar silicon content 21.4%) 0.96 94.70 91.60 89.4
Examples 7 NCM conductive agent: adhesive agent according to 98.0:1.15: 0.85 Silicon oxide material (SiO), thickening agent (CMC), Binder (SBR) and conductive Electrical agent (CNT) as per 96.0: 1.0:2.0:1.0 1 89 84.27 82.21
examples 8 NCM conductive agent: adhesive agent according to 98.0:1.15: 0.85 Silicon oxide material (SiO), thickening agent (CMC), Binder (SBR), and conductive Electrical agent (CNT) as per 96.0: 1.0:2.0:1.0 0.949 90 84.56 82.53
examples 9 NCM conductive agent: adhesive agent according to 98.0:1.15: 0.85 Silicon oxide material (SiO), thickening agent (CMC), Binder (SBR), and conductive Electrical agent (CNT) as per 96.0: 1.0:2.0:1.0 0.884 89.4 84.4 82.1
comparative example 1 NCM is a conductive agent: adhesive agent according to 98.0:1.15: 0.85 Graphite, Silica (SiO), alumina Thickener (CMC), binder (SBR) And a conductive agent (CNT) according to 86.4:9.6:1.0:2.0:1.0 (molar silicon content: 3.1%) 1.1 97.05 95.06 93.06
Comparative example 2 NCM conductive agent: adhesive agent according to 98.0:1.15: 0.85 Graphite, Silica (SiO), alumina Thickener (CMC), binder (SBR) And a conductive agent (CNT) according to 86.4:9.6:1.0:2.0:1.0 (molar silicon content: 3.1%) 0.96 97.01 95.00 93.00
Comparative example 3 NCM conductive agent: adhesive agent according to 98.0:1.15: 0.85 Graphite, Silica (SiO), alumina Thickener (CMC), binder (SBR) And a conductive agent (CNT) according to 48.0:48.0:1.0:2.0:1.0 (the molar content of silicon is 21.4%) 1.1 91.00 89.00 86.5
Comparative example 4 NCM conductive agent: adhesive agent according to 98.0:1.15: 0.85 Graphite, Silica (SiO), alumina Thickener (CMC), binder (SBR) And a conductive agent (CNT) according to 48.0:48.0:1.0:2.0:1.0 (molar silicon content 21.4%) 0.94 91.55 89.32 87.45
Comparative example 5 NCM conductive agent: adhesive agent according to 98.0:1.15: 0.85 Silicon oxide material (SiO), thickening agent (CMC), Binder (SBR) and conductive Electrical agent (CNT) as per 96.0: 1.0:2.0:1.0 1.1 85 83 81
comparative example 6 NCM conductive agent: adhesive agent according to 98.0:1.15: 0.85 Silicon oxide material (SiO), thickening agent (CMC), Binder (SBR) and conductive Electrical agent (CNT) as per 96.0: 1.0:2.0:1.0 0.79 84 82 80.1
as shown in Table 1, examples 1 to 3 and comparative examples 1 to 2 exemplify cycle performance of different N/P ratios at a silicon molar content of 3.1%, wherein the N/P ratio of example 1 is 1, the N/P ratio of example 2 is in a preferred range, and the N/P ratio of example 3 is between the lower limit of the preferred range and the lower limit of design. The N/P ratio of comparative example 1 is more than 1, and the N/P ratio of comparative example 2 is lower than the design lower limit of the aforementioned N/P ratio; it is clear that examples 1 to 3 have better cycle performance than comparative examples 1 to 2.
Examples 4 to 6 and comparative examples 3 to 4 illustrate the cycling performance at different N/P ratios with silicon molar contents of 21.4% and 30%. Compared with comparative examples 3 to 4, examples 4 to 6 have better cycle performance.
Examples 7 to 9 and comparative examples 5 to 6 illustrate the cycling performance of different N/P ratios when the negative electrode active material is silicon oxide alone. Examples 7 to 9, in which N/P was within the selection range shown in the present application, were superior in cycle performance to comparative examples 5 to 6.
The present application has been described above with reference to preferred embodiments, which are, however, merely exemplary and illustrative. On the basis of the above, the present application can be subjected to various substitutions and modifications, and the present application is in the protection scope of the present application.

Claims (8)

1. A method for determining the ratio of the negative electrode capacity to the positive electrode capacity of a silicon-containing negative electrode lithium ion battery, wherein the minimum lower limit value of the ratio N/P of the capacity N of the negative electrode to the capacity P of the positive electrode is determined by the following formula:
minimum lower limit of N/P = exp (-pi × c/14);
the maximum upper limit value of N/P is 1;
wherein c is the proportion of the mole number of silicon element to the total mole number of all the cathode active materials, and 0< c < 1; wherein the active material of the silicon-containing negative electrode is a mixture of a silicon-based material and a carbon-based material, and the weight content of the silicon-based material is greater than 0 and equal to or less than 30% based on the total weight of the mixture of the silicon-based material and the carbon-based material.
2. The method according to claim 1, wherein the optimum lower limit value of the ratio N/P of the capacity N of the negative electrode and the capacity P of the positive electrode is determined by the following formula:
the optimal lower limit of N/P = exp (-pi × c/30).
3. The method of claim 1, wherein the siliconThe base material is selected from silicon simple substance, silicon oxygen SiOx0.9 of one or more of silicon-carbon composite material and silicon alloy<x<1.1; the carbon-based material is artificial graphite or natural graphite.
4. A lithium ion battery comprises a positive electrode and a silicon-containing negative electrode, wherein the active substance of the silicon-containing negative electrode is a mixture of a silicon-based material and a carbon-based material, and the weight content of the silicon-based material is more than 0 and less than or equal to 30 percent based on the total weight of the mixture of the silicon-based material and the carbon-based material; the minimum lower limit value of the ratio N/P of the capacity N of the negative electrode and the capacity P of the positive electrode is determined by the following formula:
minimum lower limit of N/P = exp (-pi × c/14);
the maximum upper limit value of N/P is 1;
wherein c is a proportion of the mole number of silicon element to the total mole number of all the anode active materials, and 0< c < 1.
5. The lithium ion battery according to claim 4, wherein the optimum lower limit value of the ratio N/P of the capacity N of the negative electrode to the capacity P of the positive electrode is determined by the following formula:
the optimal lower limit of N/P = exp (-pi × c/30).
6. The lithium ion battery of claim 4 or 5, wherein the silicon-based material is selected from the group consisting of elemental silicon, silicon oxygen SiOx0.9, one or more of silicon-carbon composite material and silicon alloy<x<1.1; the carbon-based material is artificial graphite or natural graphite.
7. The lithium ion battery of claim 6, wherein the active material of the positive electrode is selected from LiMnO2，LiCoO2，LiNiO2，LiMn2O4，LiFePO4，LiNixCoyMn1-x-yO2One or more of, 0<x<1、0<y<1、0<x+y<1。
8. The lithium ion battery according to claim 4, wherein the potential of the negative electrode is 0 to 0.05V when the battery is charged in a cutoff state.
CN202210168992.3A 2022-02-24 2022-02-24 Method for determining ratio of negative electrode capacity to positive electrode capacity and related lithium ion battery Active CN114242945B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202210168992.3A CN114242945B (en) 2022-02-24 2022-02-24 Method for determining ratio of negative electrode capacity to positive electrode capacity and related lithium ion battery

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202210168992.3A CN114242945B (en) 2022-02-24 2022-02-24 Method for determining ratio of negative electrode capacity to positive electrode capacity and related lithium ion battery

Publications (2)

Publication Number Publication Date
CN114242945A CN114242945A (en) 2022-03-25
CN114242945B true CN114242945B (en) 2022-07-12

Family

ID=80747879

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202210168992.3A Active CN114242945B (en) 2022-02-24 2022-02-24 Method for determining ratio of negative electrode capacity to positive electrode capacity and related lithium ion battery

Country Status (1)

Country Link
CN (1) CN114242945B (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114695968B (en) * 2022-06-01 2022-09-02 四川新能源汽车创新中心有限公司 Lithium ion battery with NP ratio less than 1 and preparation method thereof
CN114965654B (en) * 2022-06-17 2024-02-09 合肥国轩高科动力能源有限公司 Method for evaluating gram capacity and NP ratio of anode and cathode materials in lithium battery

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5219387B2 (en) * 2007-03-12 2013-06-26 三洋電機株式会社 Nonaqueous electrolyte secondary battery
US20120321962A1 (en) * 2010-02-18 2012-12-20 Nec Energy Devices, Ltd. Polymer secondary battery and method for manufacturing the same
CN103794800B (en) * 2012-11-02 2016-12-21 华为技术有限公司 Lithium battery collector, pole piece and lithium battery and preparation method thereof, lithium battery applications
JP6355163B2 (en) * 2014-11-18 2018-07-11 国立研究開発法人産業技術総合研究所 Lithium ion battery
CN110993933A (en) * 2019-10-21 2020-04-10 肇庆遨优动力电池有限公司 Positive electrode material of lithium ion battery, preparation method and lithium ion battery

Also Published As

Publication number Publication date
CN114242945A (en) 2022-03-25

Similar Documents

Publication Publication Date Title
CN110165218B (en) Application of positive electrode sodium supplement agent in sodium ion battery
JP2020064866A (en) Aqueous slurry for battery electrode
CN114242945B (en) Method for determining ratio of negative electrode capacity to positive electrode capacity and related lithium ion battery
KR100280705B1 (en) Electrode active material composition for lithium ion polymer battery and manufacturing method of electrode plate for lithium ion polymer battery using same
KR20190059119A (en) An all solid lithium-polymer secondary battery and method of manufacturing them a secondary battery including a positive electrode
CN110600680A (en) Positive electrode slurry, positive plate comprising positive electrode slurry and lithium ion battery
CN112349953A (en) Lithium ion battery
CN113086978A (en) Negative electrode material, and electrochemical device and electronic device comprising same
JP5279567B2 (en) Nonaqueous electrolyte secondary battery
CN113234403B (en) Adhesive, preparation method and application thereof
CN113903980A (en) Lithium ion battery
CN111009692A (en) Manufacturing method of lithium ion battery and lithium ion battery
CN115663179A (en) Sodium ion battery positive electrode slurry, positive electrode plate, battery and preparation method
JP2002141066A (en) Control valve type lead acid battery
CN112002903B (en) Oily binder and application thereof
CN112993244B (en) Room-temperature full-liquid-state lithium-sulfur battery and preparation method thereof
CN114597350A (en) Calculation method of lithium supplementing time of lithium supplementing electrode, lithium supplementing method and lithium ion battery
JP2005519426A (en) Electrochemical cell with carbonaceous material and molybdenum carbide as anode
CN114204038A (en) Current collector and application thereof
CN113540595A (en) Formation method for improving high-nickel ternary material battery cell interface
CN113097453A (en) Lithium pre-embedding method for positive electrode of lithium ion battery
KR20100117731A (en) Anode active material for lithium secondary battery and lithium secondary battery comprising the same
KR100571457B1 (en) Anode Material in Li-ion Battery for Improving Capacity And Fabrication Method for The Same
CN115632175B (en) Negative electrode lithium supplementing quick-charging pole piece and quick-charging battery
CN116344736A (en) Negative electrode plate, manufacturing method thereof and battery cell

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant