CN113488636A - Composite negative electrode material, negative plate and lithium ion battery - Google Patents

Composite negative electrode material, negative plate and lithium ion battery Download PDF

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CN113488636A
CN113488636A CN202110677123.9A CN202110677123A CN113488636A CN 113488636 A CN113488636 A CN 113488636A CN 202110677123 A CN202110677123 A CN 202110677123A CN 113488636 A CN113488636 A CN 113488636A
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lithium
graphite
soc
voltage
silicon
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CN113488636B (en
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唐文
张传健
刘娇
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Jiangsu Zenio New Energy Battery Technologies Co Ltd
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Dongguan Tafel New Energy Technology Co Ltd
Jiangsu Tafel New Energy Technology Co Ltd
Jiangsu Tafel Power System Co Ltd
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    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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

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Abstract

The invention provides a composite negative electrode material, a negative plate and a lithium ion battery, which comprise a silicon-based material and graphite; voltage S of the silicon-based material at 20% embedded lithium SOC1Voltage G of 20% SOC with said graphite intercalated lithium1A difference of DSG1Said D isSG1The value range is as follows: 0.02V<DSG1<0.15V; voltage S at which the Si-based material has embedded lithium at 80% SOC2Voltage G of 80% SOC with said graphite intercalated lithium2A difference of DSG2Said D isSG2The value range is as follows: -0.01V<DSG2<0.05V. Compared with the prior art, the composite negative electrode material provided by the invention limits the lithium intercalation potential difference between the silicon-based material and graphiteAnd screening out the silicon-based material and graphite with the initial lithium intercalation potential value closer to each other, thereby solving the problem that the compactness of the formed film in the formation stage is influenced by the larger difference of the lithium intercalation potential between the silicon-based material and the graphite at present.

Description

Composite negative electrode material, negative plate and lithium ion battery
Technical Field
The invention relates to the field of lithium batteries, in particular to a composite negative electrode material, a negative plate and a lithium ion battery.
Background
The negative electrode material is a very important component of the lithium ion battery, and directly influences the energy density and the electrochemical performance of the lithium ion battery. The excellent negative electrode material can improve the reversible capacity, the cycle performance and the rate performance of the lithium ion battery; otherwise, the performance of lithium ions is degraded and even the lithium ions cannot work.
The conventional negative electrode material is generally graphite, but the capacity is limited, and the capacity of the silicon oxide material is 1000-. At present, graphite and silicon oxide are mixed to be designed and manufactured into a negative electrode material in the industry.
However, the alloying reaction potential of different silicon oxide materials and lithium has difference due to different raw materials, processes and other physical properties of the silicon oxide materials; the lithium intercalation potential of different graphite materials is different due to different raw materials, processes and other physical properties of the same graphite material; this causes a difference in the reaction potential between different graphites and silicon oxides and lithium. During the charging process, the material with high lithium intercalation potential becomes the main part of the lithium intercalation reaction before charging due to the difference of lithium intercalation potential, and the material with low lithium intercalation potential after recharging contributes to the main capacity. Therefore, in the early stage of formation, if the lithium intercalation potential of the silicon oxide material is low, lithium intercalation reaction mainly occurs at the edge of graphite, and film forming reaction is also biased to the graphite material, so that the silicon oxide material is not enough or not dense in film forming in the formation stage, and further the cycle performance in the later stage is influenced.
In view of the above, it is necessary to provide a technical solution to the above problems.
Disclosure of Invention
One of the objects of the present invention is: the composite negative electrode material is provided, and the problem that the compactness of film forming in a formation stage is influenced due to the large difference of lithium intercalation potentials between the conventional silicon-based material and graphite is solved; so that the composite cathode material has better cycle life.
In order to achieve the purpose, the invention adopts the following technical scheme:
a composite negative electrode material comprises a silicon-based material and graphite;
voltage S of the silicon-based material at 20% embedded lithium SOC1Voltage G of 20% SOC with said graphite intercalated lithium1A difference of DSG1Said D isSG1The value range is as follows: 0.02V<DSG1<0.15V；
Voltage S at which the Si-based material has embedded lithium at 80% SOC2Voltage G of 80% SOC with said graphite intercalated lithium2A difference of DSG2Said D isSG2The value range is as follows: -0.01V<DSG2<0.05V。
Preferably, the voltage S of the silicon-based material at the time of embedding lithium with 20% SOC10.1-0.2V; voltage S at which the Si-based material has embedded lithium at 80% SOC2Is 0.03-0.08V.
Preferably, the graphite has a voltage G of 20% SOC intercalated with lithium10.03-0.1V; voltage G of the graphite intercalation 80% SOC2The voltage is 0.008-0.02V.
Preferably, the testing counter electrode with the silicon-based material embedded with lithium at 20% SOC is the same as the testing counter electrode with the graphite material embedded with lithium at 20% SOC; the testing counter electrode of the silicon-based material with the lithium intercalation of 80% SOC is the same as the testing counter electrode of the graphite material with the lithium intercalation of 80% SOC.
Preferably, the counter electrode is any one of metal lithium, lithium cobaltate, lithium nickel cobalt manganese oxide and lithium iron phosphate.
Preferably, the test conditions of the lithium intercalation process are as follows: the charge and discharge test current is 0C-2C of the designed capacity, and the voltage is 0.005V-2V.
Preferably, the mass of the silicon-based material is 0.01-80% of that of the composite negative electrode material.
Preferably, the silicon-based material is SiOxCarbon-containing SiOxSiO containing lithiumxAnd SiO containing magnesiumxAt least one of (1), 0<x<2; wherein the lithium-containing SiOxThe mass ratio of the medium lithium is 0-15%; the SiO containing magnesiumxThe mass percentage of the medium magnesium is 0-15%.
Preferably, the graphite is one or more of artificial graphite, natural graphite, modified graphite, soft carbon and hard carbon.
Another object of the present invention is to provide a negative electrode sheet comprising the composite negative electrode material described above.
The invention also provides a lithium ion battery, which comprises a positive plate, a negative plate and a diaphragm which is arranged between the positive plate and the negative plate, wherein the negative plate is the negative plate.
Compared with the prior art, the invention has the beneficial effects that: according to the composite negative electrode material provided by the invention, the lithium intercalation potential difference of the silicon-based material and the graphite at 20% SOC is limited, so that the difference value is reduced to 0.02-0.15V, and the lithium intercalation potential difference of the silicon-based material and the graphite at 80% SOC is limited, so that the difference value is reduced to-0.01-0.05V, so that the silicon-based material and the graphite with the initial lithium intercalation potential values closer to each other can be compounded into the negative electrode material, and the SEI difference of different negative electrode active materials in formation caused by the larger potential difference is further greatly reduced. Namely, in the early stage and the later stage of formation, because the lithium intercalation potentials of the silicon-based material and the graphite are close, the balance rod of the lithium intercalation reaction is not excessively deviated from one end to influence the film forming performance, so that the problem that the compactness of film forming in the formation stage is influenced due to the large difference of the lithium intercalation potentials between the silicon-based material and the graphite at present is solved, and the composite negative electrode material has a long cycle life.
Drawings
FIG. 1 is a graph showing the voltage and the charged intercalation depth of silicon monoxide and graphite in examples 1 to 3 of the present invention.
Fig. 2 is a 500-cycle curve diagram of the lithium ion batteries of embodiments 1-3 of the present invention.
Detailed Description
As used herein, SOC represents the state of charge of the battery, which may be expressed as a percentage of rated capacity. That is, 20% SOC refers to the state of charge of the material when 20% of full charge is reached; 80% SOC refers to the state of charge of a material when 80% of full charge is reached. For example, the gram capacity of the silica at full charge is 1600mAh/g, 20% SOC means charge to 320 mAh/g; the gram capacity of the graphite when fully charged is 350mAh/g, and 20% SOC means that the graphite is charged to 70 mAh/g. However, in this patent, it should be ensured that the test conditions of the silicon-based material and the graphite are consistent, so as to avoid causing large data errors.
The invention provides a composite cathode material in a first aspect, which comprises a silicon-based material and graphite; voltage S of the silicon-based material at 20% embedded lithium SOC1Voltage G of 20% SOC with said graphite intercalated lithium1A difference of DSG1Said D isSG1The value range is as follows: 0.02V<DSG1<0.15V; voltage S at which the Si-based material has embedded lithium at 80% SOC2Voltage G of 80% SOC with said graphite intercalated lithium2A difference of DSG2Said D isSG2The value range is as follows: -0.01V<DSG2<0.05V。
In particular, DSG1The value ranges of (a) may be: 0.02V<DSG1<0.05V、0.05V≤DSG1<0.08V、0.08V≤DSG1<0.10V、0.10V≤DSG1<0.12V、0.12V≤DSG1<0.15V。
DSG2The value ranges of (a) may be: -0.01V<DSG2≤0V、0V≤DSG1<0.01V、0.01V≤DSG1<0.02V、0.02V≤DSG1<0.03V、0.03V≤DSG1<0.04V、0.04V≤DSG1<0.05V。
The lithium intercalation potential is determined by the nature of the raw materials, and different materials have different lithium intercalation potentials. Generally, silicon-based materials have different alloying reaction potentials with lithium due to different raw materials, processes and other physical properties, and factors influencing the lithium intercalation potential include but are not limited to the size of silicon crystal, and the lithium intercalation potential of common silicon monoxide is 0.4-0V. Similarly, the intercalation potential of graphite materials is different among different graphites due to different raw materials, processes and other physical properties, and the intercalation potential of common graphite materials is 0.2-0V. The inventor verifies through a large number of experiments that the lithium intercalation potential difference between the silicon-based material and the graphite is limited in the range, so that the initial lithium intercalation potential of the silicon-based material and the graphite is closer, and the SEI difference on different negative electrode active materials caused by potential difference in the battery formation process is solved. The specific operation is as follows: and under the same test condition, performing SOC test on the silicon-based material and the graphite material in advance, preparing the graphite and the silicon-based material which meet the difference range into a composite cathode material, and rejecting the graphite and the silicon-based material which do not meet the difference range to perform adaptive combination again. In the patent test, the capacity data at the end of the first cycle of lithium insertion was selected as the 100% SOC capacity.
Further, the voltage S of the silicon-based material at the time of embedding lithium with 20% SOC1Can be 0.1-0.11V, 0.11-0.12V, 0.12-0.13V, 0.13-0.14V, 0.14-0.15V, 0.15-0.16V, 0.16-0.17V, 0.17-0.18V, 0.18-0.19V, 0.19-0.2V; voltage S at which the Si-based material has embedded lithium at 80% SOC2Can be 0.03-0.04V, 0.04-0.05V, 0.05-0.06V, 0.06-0.07V, 0.07-0.08V.
Further, the voltage G of graphite intercalation 20% SOC10.03-0.04V, 0.04-0.05V, 0.05-0.06V, 0.06-0.07V, 0.07-0.08V, 0.08-0.09V, 0.09-0.1V; voltage G of the graphite intercalation 80% SOC2Can be 0.008-0.009V, 0.009-0.01V, 0.1-0.11V, 0.11-0.12V, 0.12-0.13V, 0.13-0.14V, 0.14-0.15V, 0.15-0.16V, 0.16-0.17V, 0.17-0.18V, 0.18-0.19V, 0.14-0.15V.19～0.2V。
Further, the testing counter electrode with the silicon-based material embedded with lithium at 20% SOC is the same as the testing counter electrode with the graphite material embedded with lithium at 20% SOC; the testing counter electrode of the silicon-based material with the lithium intercalation of 80% SOC is the same as the testing counter electrode of the graphite material with the lithium intercalation of 80% SOC. Because the lithium intercalation potential is the characteristic of the material, although the content of the silicon-based material and the graphite in the full battery has certain influence on the lithium intercalation voltage of the full battery, the lithium intercalation potential of the silicon-based material and the graphite in the material can not be influenced. Therefore, before the silicon-based material and the graphite are compounded into the negative electrode material, the lithium intercalation potentials of the silicon-based material and the graphite are preferentially and respectively measured to judge the suitability of the lithium intercalation potentials of the silicon-based material and the graphite, and the influence of current density and the like on the measurement result of the electrode material in the test process can be reduced as much as possible by adopting the same counter electrode for testing.
Further, the counter electrode is any one of metal lithium, lithium cobaltate, lithium nickel cobalt manganese oxide and lithium iron phosphate. Preferably, the counter electrode is metallic lithium. And metal lithium is adopted as a counter electrode, so that the electrode is purer, and the influence of external factors on a test result in the test process is further ensured.
Further, the test conditions of the lithium intercalation process are: the charge and discharge test current is 0C-2C of the designed capacity, and the voltage is 0.005V-2V. Preferably, the charge and discharge test current is 0.01C-0.1C of the designed capacity. Multiple tests of the inventor prove that under the test condition, the influence on the measurement result of the electrode material is minimum, and the method is more suitable for screening out silicon-based materials and graphite with good adaptability.
Further, the mass of the silicon-based material is 0.01-80% of that of the composite negative electrode material. More preferably, the mass of the silicon-based material is 2-5%, 5-10%, 10-15%, 15-20%, 20-25%, 25-30%, 30-35%, 35-40%, 40-50% of the mass of the composite negative electrode material.
Further, the silicon-based material is SiOxCarbon-containing SiOxSiO containing lithiumxAnd SiO containing magnesiumxAt least one of (1), 0<x<2. The arrangement of lithium is additionally added in the silicon-based material,the lithium ion battery can also play a role in supplementing lithium in advance, further compensate lithium ions lost due to volume expansion of the silicon-based material in the first charging and discharging process, and improve the first cycle efficiency of the battery. Wherein the lithium-containing SiOxThe mass ratio of the medium lithium is 0-15%; the SiO containing magnesiumxThe mass percentage of the medium magnesium is 0-15%.
Further, the graphite is one or more of artificial graphite, natural graphite, modified graphite, soft carbon and hard carbon.
The invention provides a negative electrode sheet, which comprises the composite negative electrode material. The negative plate comprises a negative current collector and a negative active substance layer coated on at least one surface of the negative current collector, wherein the negative active substance layer is formed by coating the composite negative material prepared into slurry. The silicon-based material and the graphite in the slurry can be prepared by mixing in a ball-milling stirring mode, a mechanical stirring mode and the like.
The third aspect of the invention provides a lithium ion battery, which comprises a positive plate, a negative plate and a diaphragm spaced between the positive plate and the negative plate, wherein the negative plate is the negative plate.
The positive plate comprises a positive current collector and a positive active material layer coated on at least one surface of the positive current collector. The positive active material layer may be of a chemical formula including, but not limited to, LiaNixCoyMzO2-bNb(wherein a is more than or equal to 0.95 and less than or equal to 1.2, x>0, y is more than or equal to 0, z is more than or equal to 0, and x + y + z is 1,0 is more than or equal to b and less than or equal to 1, M is selected from one or more of Mn and Al, N is selected from one or more of F, P and S), and the positive electrode active material can also be selected from one or more of LiCoO (lithium LiCoO), but not limited to2、LiNiO2、LiVO2、LiCrO2、LiMn2O4、LiCoMnO4、Li2NiMn3O8、LiNi0.5Mn1.5O4、LiCoPO4、LiMnPO4、LiFePO4、LiNiPO4、LiCoFSO4、CuS2、FeS2、MoS2、NiS、TiS2And the like. The positive electrode active material may be further modified, and the method of modifying the positive electrode active material is known to those skilled in the art, for example, the positive electrode active material may be modified by coating, doping, and the like, and the material used in the modification may be one or a combination of more of Al, B, P, Zr, Si, Ti, Ge, Sn, Mg, Ce, W, and the like. The positive electrode current collector adopted by the positive electrode plate is generally a structure or a part for collecting current, and the positive electrode current collector can be various materials suitable for serving as a positive electrode current collector of a lithium ion battery in the field, for example, the positive electrode current collector can include but is not limited to metal foil and the like, and more specifically, can include but is not limited to aluminum foil and the like.
And the separator may be various materials suitable for a lithium ion battery separator in the art, for example, may be one or a combination of more of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, natural fiber, and the like, which include but are not limited thereto.
The lithium ion battery also comprises electrolyte, and the electrolyte comprises an organic solvent, electrolyte lithium salt and an additive. Wherein the electrolyte lithium salt may be LiPF used in a high-temperature electrolyte6And/or LiBOB; or LiBF used in low-temperature electrolyte4、LiBOB、LiPF6At least one of; or LiBF used in anti-overcharge electrolyte4、LiBOB、LiPF6At least one of, LiTFSI; may also be LiClO4、LiAsF6、LiCF3SO3、LiN(CF3SO2)2At least one of (1). And the organic solvent may be a cyclic carbonate including PC, EC, FEC; or chain carbonates, including DEC, DMC, or EMC; and also carboxylic acid esters including MF, MA, EA, MP, etc. And additives include, but are not limited to, film forming additives, conductive additives, flame retardant additives, overcharge prevention additives, control of H in the electrolyte2Additive for O and HF content, improving low temperatureAt least one of a performance additive and a multifunctional additive.
In order to make the technical solutions and advantages of the present invention clearer, the present invention and its advantages will be described in further detail below with reference to the following detailed description and the accompanying drawings, but the embodiments of the present invention are not limited thereto.
Example 1
A composite negative electrode material comprising 0.5kg of silica and 4.5kg of graphite, wherein the voltage S at which the silica intercalates lithium at 20% SOC1Voltage G at 20% SOC with ink insertion1A difference of DSG1Voltage S at 0.09V, 80% SOC of intercalated lithium in silica2Voltage G of 80% SOC with graphite intercalation2A difference of DSG2It was 0.042V. Specifically, the voltage S at which lithium intercalation into silicon occurs at 20% SOC10.15V, voltage S at 80% SOC with lithium insertion20.05V; voltage G at 20% SOC for graphite intercalation1Voltage G at 0.06V, 80% SOC of lithium intercalation2Is 0.008V.
The preparation method of the composite negative electrode material comprises the following steps: mechanically stirring and mixing the silicon monoxide and the graphite for 2 hours; wherein the stirring revolution speed is 30r/min, and the rotation speed is 300r/min, so as to prepare the composite cathode material.
The utility model provides a negative pole piece, includes the negative pole mass flow body and coat in the negative pole active substance layer of the at least surface of negative pole mass flow body, the coating forms after the thick liquids is made by above-mentioned composite negative electrode material in the negative pole active substance layer.
The preparation method of the negative plate comprises the following steps: mixing the composite negative electrode material, the conductive carbon Super-P, the conductive carbon tube CNT, the binder carboxymethyl cellulose sodium CMC and the binder styrene butadiene rubber SBR according to the mass ratio of 95:1.5:1.4:0.1:2, adding deionized water, stirring in vacuum to obtain uniform slurry, uniformly coating the slurry on a copper foil, and drying to obtain the negative electrode sheet.
A lithium ion battery comprises a positive plate, a negative plate and a diaphragm which is arranged between the positive plate and the negative plate, wherein the negative plate is the negative plate.
The preparation method of the lithium ion battery comprises the following steps:
1) the preparation method of the positive plate comprises the following steps: mixing a positive electrode active material NCM811, conductive carbon Super-P and a binder polyvinylidene fluoride PVDF (polyvinylidene fluoride) according to a mass ratio of 97:2:1, adding a solvent N-methylpyrrolidone NMP, stirring in vacuum to obtain uniform slurry, uniformly coating the slurry on an aluminum foil, and drying to obtain the positive electrode plate.
2) Assembling according to the corresponding relation of the positive plate/the diaphragm/the negative plate, putting into a shell, drying, adding electrolyte, standing in vacuum, forming and grading to obtain the lithium ion battery.
Examples 2 to 13
Referring to the preparation method of example 1, examples 2 to 13 were carried out, and the arrangement of the composite anode material was different from that of example 1, as shown in table 1 below.
TABLE 1
Figure BDA0003121153640000081
Figure BDA0003121153640000091
The lithium ion batteries prepared in the above examples 1 to 13 were subjected to cycle performance detection, and the capacity retention rate after 500 cycles of 1C/1C normal temperature cycle was detected. The results are shown in Table 2 and FIGS. 1-2.
TABLE 2
Group of Capacity retention ratio/%) Group of Capacity retention ratio/%)
Example 1 92.5％ Example 8 90.3％
Example 2 85.3％ Example 9 92.3％
Example 3 89.6％ Example 10 81.6％
Example 4 90.2％ Example 11 93.4％
Example 5 83.1％ Example 12 82.1％
Example 6 93.2％ Example 13 84.5％
Example 7 84.1％
The results show that the graphite and the silicon oxide which meet the lithium intercalation voltage difference defined by the invention are combined by screening the silicon oxide and the graphite in advance, so that the initial lithium intercalation potential difference value of the silicon oxide and the graphite can be greatly reduced, the SEI difference caused by the potential difference is greatly reduced, and the cycle life of the silicon oxide/graphite composite negative electrode material is prolonged.
Wherein, as can be seen from comparison among examples 1 to 5, examples 6 to 10, and examples 11 to 13, even when the lithium intercalation 20% SOC of graphite is set to 0.03 to 0.1V, the lithium intercalation 80% SOC of graphite is set to 0.008 to 0.02V, the lithium intercalation 20% SOC of silicon monoxide is set to 0.1 to 0.2V, and the lithium intercalation 80% SOC of silicon monoxide is set to 0.03 to 0.08V; if the difference between the lithium intercalation potentials of the graphite and the silicon monoxide is asynchronously controlled within the range, the initial lithium intercalation potential difference between the graphite and the silicon monoxide cannot be effectively reduced, and the influence caused by the potential difference is reduced.
The inventor verifies through a large amount of experiments that the voltage S of the silicon-based material at the time of embedding lithium of 20 percent SOC is synchronously limited1Voltage G of 20% SOC with graphite intercalation1Difference D ofSG1A voltage S of 0.02-0.15V when the Si-based material has an embedded lithium of 80% SOC2Voltage G of 80% SOC with said graphite intercalated lithium2Difference D ofSG2When the voltage is-0.01-0.05V, the adaptability of the graphite and the silicon-based material can be improved as much as possible, so that the composite negative electrode material has a good cycle life.
Variations and modifications to the above-described embodiments may also occur to those skilled in the art, which fall within the scope of the invention as disclosed and taught herein. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious improvement, replacement or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims (11)

1. The composite negative electrode material is characterized by comprising a silicon-based material and graphite;
voltage S of the silicon-based material at 20% embedded lithium SOC1Voltage G of 20% SOC with said graphite intercalated lithium1A difference of DSG1Said D isSG1The value range is as follows: 0.02V<DSG1<0.15V；
Voltage S at which the Si-based material has embedded lithium at 80% SOC2Voltage G of 80% SOC with said graphite intercalated lithium2A difference of DSG2Said D isSG2The value range is as follows: -0.01V<DSG2<0.05V。
2. The composite anode material according to claim 1, wherein the Si-based material has a voltage S at an embedded lithium SOC of 20%10.1-0.2V; voltage S at which the Si-based material has embedded lithium at 80% SOC2Is 0.03-0.08V.
3. The composite anode material according to claim 1 or 2, wherein the graphite intercalates lithium at a voltage G of 20% SOC10.03-0.1V; voltage G of the graphite intercalation 80% SOC2The voltage is 0.008-0.02V.
4. The composite anode material of claim 3, wherein the silicon-based material lithium intercalation 20% SOC test counter electrode is the same as the graphite material lithium intercalation 20% SOC test counter electrode; the testing counter electrode of the silicon-based material with the lithium intercalation of 80% SOC is the same as the testing counter electrode of the graphite material with the lithium intercalation of 80% SOC.
5. The composite anode material according to claim 4, wherein the counter electrode is any one of metallic lithium, lithium cobaltate, lithium nickel cobalt manganese oxide and lithium iron phosphate.
6. The composite anode material according to claim 4, wherein the test conditions of the lithium intercalation process are: the charge and discharge test current is 0C-2C of the designed capacity, and the voltage is 0.005V-2V.
7. The composite negative electrode material of claim 1, wherein the mass of the silicon-based material is 0.01-80% of the mass of the composite negative electrode material.
8. The composite anode material of claim 1, wherein the silicon-based material is SiOxCarbon-containing SiOxSiO containing lithiumxAnd SiO containing magnesiumxAt least one of (1), 0<x<2; wherein the lithium-containing SiOxThe mass ratio of the medium lithium is 0-15%; the SiO containing magnesiumxThe mass percentage of the medium magnesium is 0-15%.
9. The composite negative electrode material of claim 1, wherein the graphite is one or more of artificial graphite, natural graphite, modified graphite, soft carbon and hard carbon.
10. A negative electrode sheet comprising the composite negative electrode material according to any one of claims 1 to 9.
11. A lithium ion battery comprising a positive plate, a negative plate and a separator spaced between the positive plate and the negative plate, wherein the negative plate is the negative plate of claim 10.
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