CN119601590A - Battery cell - Google Patents
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- CN119601590A CN119601590A CN202411888964.4A CN202411888964A CN119601590A CN 119601590 A CN119601590 A CN 119601590A CN 202411888964 A CN202411888964 A CN 202411888964A CN 119601590 A CN119601590 A CN 119601590A
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- H—ELECTRICITY
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- 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
- H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
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- H—ELECTRICITY
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- 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
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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- 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
- H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
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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
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
- H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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- 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
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- 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
- H01M2004/028—Positive electrodes
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- 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
本发明属于锂离子电池技术领域，具体涉及一种电池。本发明通过控制锂离子电池中三价镍元素和四价镍元素的摩尔总量占镍基正极材料中镍元素总摩尔量的百分比、镍基正极材料占正极活性材料的摩尔比以及正极极片的H+增长率可以显著减少电池产气量，保证电池极片和隔膜之间紧密接触，进而降低了电池的内阻，提高了电池的循环性能。The present invention belongs to the technical field of lithium ion batteries, and specifically relates to a battery. The present invention can significantly reduce the gas production of the battery by controlling the percentage of the total molar amount of trivalent nickel elements and tetravalent nickel elements in the lithium ion battery to the total molar amount of nickel elements in the nickel-based positive electrode material, the molar ratio of the nickel-based positive electrode material to the positive electrode active material, and the H + growth rate of the positive electrode plate, thereby ensuring close contact between the battery plate and the diaphragm, thereby reducing the internal resistance of the battery and improving the cycle performance of the battery.
Description
The application is a divisional application of the application with the application number 202411525404.2 and the application name of a battery which is 10/30 of 2024.
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a battery.
Background
The lithium iron manganese phosphate LMFP material consists of manganese (Mn), iron (Fe), phosphorus (P) and lithium (Li), and is used as a lithium battery anode material, and is a material which is of great concern in new energy automobiles and energy storage systems by virtue of the advantages of high performance, stability, economy and the like.
However, the LMFP material has large specific surface area and large contact area with electrolyte, which can aggravate the hydrogen protonation of the electrolyte, and the hydrogen production by reduction of the protonated hydrogen at the negative electrode, so that serious gas production is caused. The produced gas can cause expansion of the pole piece, the contact between the pole piece and the diaphragm is not tight, the impedance is increased, and the pole piece generates black spots.
Therefore, it is a problem to be solved to provide a lithium ion battery that can reduce gas generation.
Disclosure of Invention
In view of the above, the technical problem to be solved by the invention is to provide a battery, which can obviously reduce the gas production, ensure the close contact between the battery pole piece and the diaphragm, further reduce the internal resistance of the battery and improve the cycle performance of the battery.
The invention provides a battery, which comprises a positive plate, wherein the positive plate comprises a positive active material, the positive active material comprises a manganese iron phosphate lithium material and a nickel-based positive material, the nickel-based positive material comprises trivalent nickel element and tetravalent nickel element, the molar ratio of the nickel-based positive material to the positive active material is c, the total molar amount of the trivalent nickel element and the tetravalent nickel element is a in the state of 100% SOC of the battery, the H + growth rate of the positive plate is b, and the a, c and b satisfy the relational expression shown in the formula I:
0.008< (a×c)/b is less than or equal to 8.290, formula I.
Compared with the prior art, the method can obviously reduce the gas yield of the battery by controlling the mole total of trivalent nickel element and tetravalent nickel element in the lithium ion battery to account for the percentage of the total mole of nickel element in the nickel-based positive electrode material, the mole ratio of the nickel-based positive electrode material to the positive electrode active material and the H + growth rate of the positive electrode plate, and ensure the close contact between the battery plate and the diaphragm, thereby reducing the internal resistance of the battery and improving the cycle performance of the battery.
Detailed Description
The invention provides a battery, which comprises a positive plate, wherein the positive plate comprises a positive active material, the positive active material comprises a manganese iron phosphate lithium material and a nickel-based positive material, the molar ratio of the nickel-based positive material to the positive active material is c, in a state of 100% SOC of the battery, the nickel-based positive material comprises trivalent nickel elements and tetravalent nickel elements, the total molar amount of the trivalent nickel elements and the tetravalent nickel elements is a percentage of the total molar amount of the nickel elements in the nickel-based positive material, the H + growth rate of the positive plate is b, and the a, c and b satisfy the relational expression shown in the formula I:
0.008< (a×c)/b is less than or equal to 8.290, formula I.
In the invention, when a, b and c meet the relation formula shown in the formula I, the problems of gas production and expansion of the battery are obviously improved, and the problem of black spots is avoided. The problem of gas production of the battery is comprehensively related to the values of a, b and c, the larger the ion growth rate of H + is, the more serious the gas production is, and at the moment, a proper amount of high-valence Ni ions (a) are introduced, the catalytic oxidation activity of the Ni ions is stronger than that of the Mn ions, so that proton hydrogen can be further oxidized, absorbable gases such as CO, CO 2 and the like are produced, the gas production path is changed, and the production of hydrogen is reduced.
When the calculated value of (a×c)/b exceeds the upper limit of the relation, that is, exceeds the maximum value, the content of tetravalent and trivalent nickel elements may be too much, which may affect the capacity of the battery, the capacity of the battery is reduced, or the increase rate b of H + may be too small, the b value is too small to represent that the active area of the positive electrode surface is smaller, resulting in larger lithium ion diffusion impedance and poorer battery kinetics, and when the calculated value exceeds the lower limit of the relation, that is, exceeds the minimum value, the increase rate of H + ions is too large, the active area of the positive electrode is larger, resulting in serious dissolution of transition metal ions and destruction of SEI, thereby resulting in poorer kinetics, dcR increase, worsening cycle, and also being possible to have the effect of changing the gas production path because the content of trivalent nickel elements and tetravalent nickel elements in the whole positive electrode active material is lower, the hydrogen output is too large, and the safety of the battery is affected.
Therefore, the invention can obviously reduce the gas production of the battery by controlling the values of a, b and c to meet the range of 0.008< (a multiplied by c)/b less than or equal to 8.290, ensure the close contact between the battery pole piece and the diaphragm, further reduce the internal resistance of the battery and improve the cycle performance of the battery. In the present invention, (a×c)/b may be 0.009、0.010、0.02、0.025、0.03、0.05、0.1、0.3、0.5、0.7、0.9、1.0、1.5、2.0、2.5、2.86、3.0、3.5、4.0、4.5、5.0、5.5、6.0、6.5、7.0、7.5、8.0、8.290, or any value between 0.008 to 8.290.
The structural formula of the lithium iron manganese phosphate is LiMn xFeyMz nPO4, wherein M is a doped metal element, 0< x <1,0< y <1, 0.ltoreq.z <1, 2 (x+y) +n×z=2, n is the valence state of the doped metal element M, and the doped element M is at least one selected from Be, ca, mg, ba and Sr. The lithium iron manganese phosphate material used in the embodiment of the invention is exemplified by LiMn 0.6Fe0.4PO4, but is not limited to this type of lithium iron manganese phosphate material.
As a preferred embodiment of the present invention, the percentage of the total mole amount of trivalent nickel element and tetravalent nickel element in the total mole amount of nickel element in the nickel-based positive electrode material, the mole ratio of the nickel-based positive electrode material to the positive electrode active material, and the H + increase rate of the positive electrode sheet satisfy the following relation:
0.025≤(a×c)/b≤2.860
In the invention, the positive electrode active material comprises a lithium manganese iron phosphate material and a nickel-based positive electrode material, the nickel-based positive electrode material comprises trivalent nickel element and tetravalent nickel element in a full charge state of 100% SOC of the battery, the total mole amount of the trivalent nickel element and the tetravalent nickel element accounts for a percentage of the total mole amount of the nickel element in the nickel-based positive electrode material, a is the higher the value of a, the greater the percentage of the total mole amount of the trivalent nickel element and the tetravalent nickel element accounts for the total mole amount of the nickel element in the nickel-based positive electrode material, and the smaller the value of a, the percentage of the total mole amount of the trivalent nickel element and the tetravalent nickel element accounts for the total mole amount of the nickel element in the nickel-based positive electrode material.
Compared with other valence states of nickel element, the catalytic oxidation activities of trivalent nickel element and tetravalent nickel element are higher, the trivalent nickel element and tetravalent nickel element are easier to reduce, the catalytic oxidation activities of ions of trivalent nickel element and tetravalent nickel element are stronger than those of Mn ions, proton hydrogen can be further oxidized, CO 2 and other gases which can be absorbed by the pole piece are generated, and the gas generation path is changed, so that the generation of hydrogen is reduced. The value of a is related to the addition amount of the lithium nickel oxide positive electrode material LNO and the nickel-containing ternary positive electrode material, when the value of a is too high, the preparation cost of the battery becomes high, and when the value of a is too low, the effect of changing the gas production path cannot be achieved.
In the present invention, a is 0.3% or more and 23% or less, and may be any value between 0.3%, 0.5%, 0.7%, 1%, 3%, 5%, 7%, 9%, 10%, 12%, 14%, 15%, 17%, 19%, 20%, 21%, 23%, or 0.3% to 23%. In some preferred embodiments of the invention, 1% or less and 20% or less of a.
Therefore, the invention can ensure that the effect of changing the gas production path of the battery can be achieved under the condition of preparing the battery at low cost by controlling the range of the value of a to be more than or equal to 0.3 percent and less than or equal to 23 percent.
A, the invention is not limited, and a person skilled in the art can detect the percentage of the total mole amount of trivalent nickel element and tetravalent nickel element to the total mole amount of nickel element in the nickel-based positive electrode material according to conventional technical means, and the exemplary method for testing a includes the following steps:
after cleaning the positive plate in a full charge state of 100% SOC of the battery, XPS is used for testing peak areas of nickel element in each valence state in the positive plate, and a is calculated according to a formula shown in a formula II:
a= (S Ni 4++SNi 3+)/S Total area of formula II;
in the formula II, S Ni 4+ represents the area of tetravalent nickel obtained by XPS test;
S Ni 3+ represents the area of trivalent nickel obtained by XPS test;
S Total area of shows the sum of peak areas of the nickel element in each valence state obtained by XPS test.
Specifically, the test method specifically includes the following steps:
And disassembling the positive plate in a full charge state of 100% of SOC of the battery, cleaning the positive plate by adopting DMC (dimethyl carbonate), and then drying to obtain the treated positive plate.
The drying method is not particularly limited, and may be any drying method known to those skilled in the art. In the present invention, vacuum drying is preferably employed, the drying temperature is preferably 25 ℃, and the drying time is preferably 24 hours.
After the processed positive plate is obtained, etching is carried out by an X-ray photoelectron spectroscopy (XPS) method, the etching rate is 0.7nm/s, the etching time is 60s, peak areas of each valence state are fitted according to the binding energy, the sum of the peak areas of the obtained trivalent nickel element and tetravalent nickel element and the total peak area of all valence state nickel elements are tested, and the value of a is calculated according to a formula shown in a formula II, wherein the unit is%.
In some preferred embodiments of the present invention, the molar ratio of trivalent nickel element to tetravalent nickel element is 1:10 to 6:10, and may be 1:10, 1.5:10, 2:10, 2.5:10, 3:10, 3.5:10, 4:10, 4.5:10, 5:10, 5.5:10, 6:10, or any value between 1:10 to 6:10. The molar ratio of the trivalent nickel element to the tetravalent nickel element is too large, which means that the content of the trivalent nickel element is too large, the change effect on the gas production path is poor, the hydrogen production cannot be reduced, the ratio is too small, which means that the content of the trivalent nickel element is too small, the service life of the battery is obviously reduced, and when the molar ratio relationship between the trivalent nickel element and the tetravalent nickel element is in the range of 1:10-6:10, the gas production path of the gas can be effectively changed, namely, the hydrogen production is reduced, meanwhile, the service life of the battery is kept, and the service life of the battery is not reduced too quickly.
In the invention, the nickel-based positive electrode material is selected from one or more of a lithium nickel oxide positive electrode material or a nickel-containing ternary positive electrode material.
In some embodiments of the present invention, the nickel-containing ternary positive electrode material is selected from nickel cobalt manganese ternary positive electrode materials, which is LiNi xCoyMn1-x-yO2, wherein 0.9< x <1,0< y <0.1, and x+y +.1.
In the present invention, the source of the lithium nickel oxide positive electrode material or the nickel-containing ternary positive electrode material is not particularly limited, and may be a commercially available product or may be prepared by a preparation method known to those skilled in the art.
In the invention, the preparation method of the lithium nickel oxide positive electrode material is not limited, and a person skilled in the art can prepare the positive electrode active material according to conventional technical means. The preparation method of the lithium nickel oxide positive electrode material comprises the following steps:
Firstly, weighing a lithium source and a nickel source required by synthesizing a lithium nickel oxide material according to a proportion, adding deionized water, grinding, washing, performing spray drying to obtain dry powder of the lithium nickel oxide material, sintering the dry powder in a protective atmosphere, and cooling to obtain the lithium nickel oxide positive electrode material.
In the invention, the preparation method of the LiNi xCoyMn1-x-yO2 is not limited, and a person skilled in the art can prepare the nickel-based anode material according to a conventional technical means. Illustratively, a nickel-based positive electrode material precursor and a lithium source are mixed and sintered to obtain a nickel-based positive electrode material.
The nickel-based positive electrode material precursor may be one or more of an oxide, hydroxide, and carbonate containing Ni, co, and Mn in a stoichiometric ratio, for example, a hydroxide containing Ni, co, and Mn in a stoichiometric ratio. The positive electrode active material precursor may be obtained by a method known in the art, for example, by a coprecipitation method, a gel method, or a solid phase method.
As an example, ni source, co source and Mn source are dispersed in solvent to obtain mixed solution, the mixed solution, alkali solution and complexing agent solution are pumped into a reaction kettle with stirring at the same time by adopting a continuous parallel flow reaction mode, the pH value of the reaction solution is controlled to be 10-13, the temperature in the reaction kettle is 25-90 ℃, inert gas is introduced for protection during the reaction process, and after the reaction is completed,
Aging, filtering, washing and vacuum drying to obtain hydroxide containing Ni, co and Mn.
In some embodiments of the invention, the Ni source comprises at least one of nickel sulfate, nickel nitrate, nickel chloride, nickel oxalate, or nickel acetate, and/or the Co source comprises at least one of cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt oxalate, or cobalt acetate, and/or the Mn source comprises at least one of manganese sulfate, manganese nitrate, manganese chloride, manganese oxalate, or manganese acetate, and/or the Li source comprises at least one of lithium oxide (Li 2 O), lithium phosphate (Li 3PO4), lithium dihydrogen phosphate (LiH 2PO4), lithium acetate (CH 3 COOLi), lithium hydroxide (LiOH), lithium carbonate (Li 2CO3), or lithium nitrate (LiNO 3).
The positive electrode active material precursor and the lithium source may be mixed using a ball mill mixer or a high-speed mixer. And adding the mixed materials into an atmosphere sintering furnace for sintering. The sintering atmosphere is an oxygen-containing atmosphere, such as an air atmosphere or an oxygen atmosphere.
In addition, the nickel-based positive electrode material can be coated by a coating process, specifically, a dry coating (high-temperature solid phase method) is adopted to coat the surface of the nickel-based positive electrode material, and the surface of the nickel-based positive electrode material is partially or completely coated with a coating layer formed by the coating material. The coating layer contains at least one element (hereinafter, referred to as "coating element") selected from aluminum (Al), titanium (Ti), tungsten (W), boron (B), phosphorus (P), cobalt (Co), yttrium (Y), and silicon (Si).
Further, the particle size of the nickel-based positive electrode material is 40-200 nm.
In the invention, the positive electrode active material further comprises a lithium iron manganese phosphate material, and the particle size of the lithium iron manganese phosphate material is 50-170 nm.
In the present invention, the source of the lithium iron manganese phosphate material is not particularly limited, and may be a commercially available product or may be prepared by a preparation method known to those skilled in the art.
In the invention, the preparation method of the lithium iron manganese phosphate material is not limited, and a person skilled in the art can prepare the lithium iron manganese phosphate material according to conventional technical means. The preparation method of the lithium iron manganese phosphate material comprises the following steps:
Firstly, weighing a lithium source, a manganese source, an iron source and a phosphorus source which are required by synthesizing a lithium iron phosphate material according to proportion, adding deionized water, and grinding to obtain lithium iron phosphate precursor slurry;
Adding a carbon source and lithium iron manganese phosphate precursor slurry, uniformly mixing, grinding, adjusting the solid content, performing spray drying to obtain dry powder, sintering the dry powder in a protective atmosphere, and cooling to obtain the anode active material.
In the invention, the lithium source is at least one selected from lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxalate, lithium dihydrogen phosphate, lithium citrate and lithium acetate, the manganese source is at least one selected from manganese carbonate, manganese sulfate, manganese nitrate, manganese chloride, manganese oxalate and manganese acetate, the iron source is at least one selected from ferrous oxalate, ferric hydroxide, ferrous hydroxide, ferric phosphate, ferrous phosphate, ferric acetate, ferrous acetate, ferric carbonate, ferrous carbonate, ferric oxide and ferric oxalate, and the phosphorus source is at least one selected from diammonium hydrogen phosphate, lithium dihydrogen phosphate, ammonium phosphate and lithium phosphate. The present invention preferably employs ferric manganese phosphate as the source of manganese, iron and phosphorus simultaneously, or ferric phosphate as the source of iron and phosphorus simultaneously, the carbon source comprising glucose.
Mixing of the raw materials may be performed using a ball mill mixer or a high speed mixer. And drying the mixed raw materials to obtain a precursor.
And adding the precursor into an atmosphere sintering furnace for sintering. The sintering atmosphere is an oxygen-containing atmosphere, such as an air atmosphere or an oxygen atmosphere.
In addition, the coating process can be carried out on the lithium manganese iron phosphate material, specifically, the surface of the lithium manganese iron phosphate material is coated with the coating material by adopting a dry coating method (high-temperature solid phase method), and the surface of the lithium manganese iron phosphate material is partially or completely coated with the coating layer formed by the coating material. The coating layer contains at least one element (hereinafter, referred to as "coating element") selected from aluminum (Al), titanium (Ti), tungsten (W), boron (B), phosphorus (P), cobalt (Co), yttrium (Y), and silicon (Si).
In the present invention, the molar ratio c of the nickel-based positive electrode material to the positive electrode active material can also affect the gas production of the battery and the performance of the battery.
The larger the c value is, the more the content of the nickel-based material in the whole active material is, the less the content of the LMFP is, although the gas production path of the battery can be changed, and the generation of hydrogen is reduced, the more the capacity of the battery is reduced due to the less the content of the LMFP is, the smaller the c value is, the less the content of the nickel-based material in the whole active material is, the uniform inhibition effect on the gas production of the whole pole piece cannot be achieved, the hydrogen yield is overlarge, and the safety of the battery is affected.
Therefore, the invention can ensure the battery capacity and simultaneously can play a uniform inhibition effect on the gas production of the whole pole piece by controlling the value range of c to be more than or equal to 0.5 percent and less than or equal to 40 percent.
In the present invention, the value of c is in the range of 0.5% -40%, may be 0.5%, 1%, 3%, 5%, 6%, 7%, 10%, 12%, 14%, 15%, 17%, 20%, 22%, 25%, 27%, 30%, 32%, 34%, 35%, 37%, 40%, may be 0.5% -40%, and in some preferred embodiments of the present invention, the value of c is in the range of 5% -30%.
C, the invention is not limited, and a person skilled in the art can detect the molar ratio of the nickel-based positive electrode material to the positive electrode active material according to a conventional technical means, and the exemplary method for testing c includes the following steps:
Discharging the battery from 0.33 to 2.5V at 25 ℃, disassembling the battery to obtain a positive plate and a negative plate, obtaining 2g of positive powder from the positive plate and 2g of negative powder from the negative plate, testing the mole percentage content of Ni element and Mn element in the positive powder and the negative powder by inductively coupled plasma ICP, selecting element detection spectral wavelength (Mn wavelength 257.61nm and Ni wavelength 232.0 nm), setting proper ICP instrument working conditions including gas flow of 0.5L/min and power 1150W according to the characteristics of the sample and the elements to be detected, testing the Mn and Ni content of the elements by ICP, and calculating the mole ratio C of the nickel-based positive electrode material in the positive electrode active material according to a formula shown in a formula VI.
C= (total mole percent of Ni element in positive electrode powder and negative electrode powder/total mole percent of Ni element and mn element in positive electrode powder and negative electrode powder) ×100% formula VI
In the present invention, the H + increase rate b can also affect the gas production of the battery and the performance of the battery.
The growth rate b of H + represents the size of the active area of the pole piece, the larger the growth rate b of H + is, the larger the active area of the pole piece is represented, the smaller the growth rate b of H + is, the smaller the active area of the pole piece is represented, and the larger the growth rate b of H + is related to factors such as carbon coating degree, particle size, distribution mode and the like of the active material. The value of b is high, which indicates that the electrochemical reaction of the pole piece is easier to carry out or the reaction rate is faster, and when the value of b is too high, the reaction degree of the active material and the electrolyte is too high, and excessive side reactions are easy to be initiated, so that the gas production of the battery is excessive and the pole piece is black. When the value b is too low, it is considered that the electrochemical reaction is difficult to proceed effectively, and the kinetics of the battery as a whole is poor, probably because the positive electrode active material particles have a large particle diameter and the carbon layer is too thick to cause a large resistance to solid phase diffusion.
Therefore, in the present invention, it is necessary to control the growth rate b of H + to be in the range of 0.01.ltoreq.b.ltoreq.0.18, and any value between 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, or 0.01 to 0.18 is possible. In some preferred embodiments of the invention, b has a value of 0.02.ltoreq.b.ltoreq.0.15.
When b is controlled to be more than or equal to 0.01 and less than or equal to 0.18, the invention can ensure that the electrochemical reaction is effectively carried out and simultaneously improve the reaction rate as much as possible.
B, the invention is not limited, and a person skilled in the art can detect the H + increase rate according to a conventional technical means, and the exemplary test method of the H + increase rate b includes the following steps:
Two groups of positive pole pieces with the same area of a full charge state of the battery with the same 100% SOC are respectively soaked in the solution with the same volume, one group of positive pole pieces is stored for 48 hours at 60 ℃, the content m1 of H + in the solution is measured, the unit is ppm, the other group of positive pole pieces is stored for 72 hours at 60 ℃, the content m2 of H + in the solution is measured, the unit is ppm, and the growth rate b of H + is calculated according to a formula shown in a formula III:
b= (m 2-m 1)/m 1 formula III;
the test area of the positive electrode plate is 147cm 2, wherein the test area 147cm 2 can be the sum of the areas of the positive electrode plates of a plurality of batteries in a full charge state, and in some specific embodiments of the invention, the test area can be 3 positive electrode plates of the batteries in a 7×7cm 2 full charge state.
The solution is a mixed solution of ethylene carbonate EC, ethylmethyl carbonate EMC and lithium perchlorate, wherein the concentration of the lithium perchlorate in the mixed solution is 1M, the volume ratio of the ethylene carbonate EC to the ethylmethyl carbonate EMC is 3:7, and the dosage of the solution is 20ml.
Specifically, the method for testing the H + content in the 48H storage solution comprises the following steps:
Preparing triethylamine and EMC into a triethylamine titration solution with the concentration of 0.05 mol/L;
mixing EC and EMC according to a volume ratio of 3:7 to obtain 20mL mixed solution, and adding 2.13g of lithium perchlorate into the mixed solution to obtain a soaking solution;
Mixing a positive electrode plate of a battery with a test area of 147cm 2 and a soaking solution, soaking for 48 hours at a temperature of 60 ℃ to obtain a 48-hour positive electrode plate soaking solution, adding 10-30 drops of methyl red into the 48-hour positive electrode plate soaking solution as an indicator, dripping triethylamine titration into the 48-hour positive electrode plate soaking solution containing methyl red, recording the consumption V1 of the triethylamine titration when the 48-hour positive electrode plate soaking solution turns orange, and calculating the content m1 of H + in the 48-hour solution according to a formula IV;
m1=mxv1× 20010/M IV
In the formula IV, M is the concentration of the titration solution, and the unit is mol/L;
V1 is the volume of the consumed titration solution, and the unit is mL;
m is the mass of the soaking liquid, and the unit is g;
Similarly, the method for testing the H + content in the stored 72H solution comprises the following steps:
Preparing triethylamine and EMC into a triethylamine titration solution with the concentration of 0.05 mol/L;
mixing EC and EMC according to a volume ratio of 3:7 to obtain 20mL mixed solution, and adding 2.13g of lithium perchlorate into the mixed solution to obtain a soaking solution;
Mixing a positive electrode plate of a battery with a test area of 147cm 2 and a soaking solution, soaking for 72 hours at a temperature of 60 ℃ to obtain a 72-hour positive electrode plate soaking solution, adding 10-30 drops of methyl red into the 72-hour positive electrode plate soaking solution as an indicator, dripping triethylamine titration into the 72-hour positive electrode plate soaking solution containing methyl red, recording the consumption V2 of the triethylamine titration when the 72-hour positive electrode plate soaking solution turns orange, and calculating the content m2 of H + in the 72-hour solution according to a formula V;
m1=mxv2× 20010/M type V
In the formula IV, M is the concentration of the titration solution, and the unit is mol/L;
v2 is the volume of the consumed titration solution, and the unit is mL;
m is the mass of the soaking solution, and the unit is g.
And substituting the obtained m1 and m2 into a formula III, and calculating to obtain the increase rate b of H +.
In the present invention, the values of a and b are measured at 100% soc for the battery and 0% soc for the battery. Wherein the invention defines the battery to be discharged from 0.33C to 2.5V at 25 ℃ as 0% soc.
In the formula shown in formula I, a×c may reflect the content of trivalent nickel element and tetravalent nickel element in the positive electrode material in the entire positive electrode active material to some extent, the larger the value of a×c, the more the content of trivalent nickel element and tetravalent nickel element, and the smaller the value of a×c, the less the content of trivalent nickel element and tetravalent nickel element in the entire positive electrode active material.
In the invention, the value range of a multiplied by c is controlled to be less than or equal to 0.001 and less than or equal to a multiplied by c and less than or equal to 0.092, when the value of a multiplied by c is less than 0.01, the content of trivalent nickel element and tetravalent nickel element in the pole piece is represented to be less, so that after the nickel-containing material is added into the pole piece, the improvement performance of the nickel-containing material on a gas production path is reduced, namely the performance of the nickel-containing material for inhibiting hydrogen generation is reduced, and when the value of a multiplied by c is more than 2.6, the content of trivalent nickel element and tetravalent nickel element in the pole piece is represented to be excessive. The content of lithium iron manganese phosphate in the positive electrode material is affected, so that the capacity of the battery core is reduced, and the energy density of the battery is reduced.
Therefore, the nickel-containing material can have good performance of changing the gas generating path of the battery, namely reducing the output of hydrogen and ensuring better energy density of the battery by controlling the value range of a multiplied by c to meet the range of a multiplied by 0.001 which is less than or equal to a multiplied by c which is less than or equal to 0.092.
In the present invention, the value 0.001. Ltoreq.aXc.ltoreq.0.092 may be any value of 0.001, 0.002, 0.003, 0.004, 0.005, 0.007, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.092, or 0.001 to 0.092, and in some preferred embodiments of the present invention, 0.003. Ltoreq.aXc.ltoreq.0.06.
In the present invention, the battery includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte.
Wherein the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, the positive electrode active material layer including a positive electrode active material, and the positive electrode active material layer may include a conductive agent and a binder in addition to the above positive electrode active material.
The conductive agent is used to provide conductivity in the electrode, and any conductive agent may be used without particular limitation as long as it has suitable electron conductivity without causing adverse chemical changes in the battery, and carbon fibers such as carbon nanofibers, carbon black such as acetylene black and ketjen black, activated carbon, graphite, mesoporous carbon, fullerenes, and carbon materials such as carbon nanotubes are preferred.
The binder improves the adhesion between the positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Thus, the binder suitable for use in embodiments is a fluorinated polyolefin-based binder, which may be modified (e.g., carboxylic acid, acrylic acid, acrylonitrile, etc. modified) derivatives including, but not limited to, polyvinylidene fluoride (PVDF), vinylidene fluoride copolymers, or their modified (e.g., carboxylic acid, acrylic acid, acrylonitrile, etc.), and the like.
The present invention is not particularly limited as long as it has conductivity without causing adverse chemical changes in the battery, and may use, for example, stainless steel, aluminum, nickel, titanium, fired carbon, or aluminum or stainless steel surface-treated with one of carbon, nickel, titanium, silver, etc.
In the present invention, the positive electrode sheet may be prepared according to a conventional method in the art. For example, the positive electrode active material, the conductive agent and the binder are dispersed in a solvent, wherein the solvent can be N-methyl pyrrolidone (NMP) or deionized water to form uniform positive electrode slurry, the positive electrode slurry is coated on a positive electrode current collector, and the positive electrode sheet is obtained after procedures such as drying, rolling and the like.
The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer arranged on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material and can also comprise a conductive agent and/or a binder.
The present invention is not particularly limited as long as it has high conductivity without causing adverse chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, copper or stainless steel surface-treated with one of carbon, nickel, titanium, silver, or the like, or an aluminum-cadmium alloy may be used.
As for the anode active material, the kind of the anode active material is not particularly limited in the embodiment of the present invention, and may be selected according to actual demands. As an example, the anode active material may be one or more of natural graphite, artificial graphite, intermediate phase micro carbon spheres (MCMB), hard carbon, soft carbon, silicon-carbon composite, siO m (0 < m <2, such as m=1), spinel structured lithium titanate Li 4Ti5O12.
The types of the conductive agent and the binder in the anode active material layer are not particularly limited in the embodiment of the invention, and can be selected according to actual requirements. The conductive agent is one or more of graphite, superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers, and the binder is one or more of styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl butyral, aqueous acrylic resin and carboxymethyl cellulose. The anode active material layer may further optionally include a thickener such as carboxymethyl cellulose.
The electrolyte of the present invention may be any electrolyte suitable for use in an electrochemical energy storage device in the art. The electrolyte includes an electrolyte, which may generally include a lithium salt, and a solvent.
Specifically, the lithium salt includes at least one of lithium hexafluorophosphate (LiPF 6), lithium tetrafluoroborate (LiBF 4), lithium perchlorate (LiClO 4), lithium hexafluoroarsenate (LiAsF 6), lithium bis (fluorosulfonyl) imide (LiFSI), lithium bis (trifluoromethanesulfonyl) imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalato borate (lidaob), lithium difluoroborate (LiBOB), lithium difluorophosphate (LiPO 2F2), lithium difluorodioxaato phosphate (LiDFOP), and lithium tetrafluorooxalato phosphate (LiTFOP). The concentration of the electrolyte in the electrolyte may be 0.5 to 5mol/L.
Specifically, the solvent includes at least one of Ethylene Carbonate (EC), propylene Carbonate (PC), ethylmethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), butylene Carbonate (BC), fluoroethylene carbonate (FEC), methyl Formate (MF), methyl Acetate (MA), ethyl Acetate (EA), propyl Acetate (PA), methyl Propionate (MP), ethyl Propionate (EP), propyl Propionate (PP), methyl Butyrate (MB), ethyl Butyrate (EB), 1, 4-butyrolactone (GBL), sulfolane (SF), dimethylsulfone (MSM), methylsulfone (EMS) and diethylsulfone (ESE). The solvent may be present in an amount of 70 to 98% by weight based on the weight of the electrolyte.
In addition, additives may be included in the electrolyte. Specifically, the additive may include a negative electrode film-forming additive, a positive electrode film-forming additive, an additive capable of improving certain properties of the battery, such as an additive for improving overcharge properties of the battery, an additive for improving high temperature properties of the battery, an additive for improving low temperature properties of the battery, and the like.
The electrochemical device can further comprise a diaphragm, wherein the diaphragm is positioned between the positive pole piece and the negative pole piece and is used for spacing the positive pole piece and the negative pole piece and preventing the positive pole piece and the negative pole piece from being in contact short circuit. The separator may be any of a variety of materials suitable for use in the art as separator membranes for electrochemical energy storage devices. Specifically, the diaphragm comprises at least one of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester and natural fiber.
The embodiment of the invention provides an electronic device which comprises the battery. The electrochemical device is used as a power supply source of the electronic device.
The electronic device refers to any other device or devices that can utilize electric energy and convert it into mechanical energy, thermal energy, light energy, etc., to form energy, such as an electric motor, an electric heat engine, an electric light source, etc. Specifically, the system can comprise, but is not limited to, mobile equipment, electric vehicles, electric trains, ships, satellites, energy storage systems and the like, wherein the mobile equipment can be mobile phones, notebook computers, unmanned aerial vehicles, sweeping robots, electronic cigarettes and the like, and the electric vehicles can be pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks and the like.
In order to further understand the present invention, the battery provided by the present invention will be described with reference to examples, and the scope of the present invention is not limited by the following examples.
Example 1
1) Preparation of an LMFP positive electrode material:
According to the molar ratio of Li, mn, fe, P elements in the chemical formula of LiMn 0.6Fe0.4PO4, respectively weighing 1moL of lithium carbonate, 0.6moL of manganese carbonate, 0.4moL of ferrous oxalate and 1moL of diammonium hydrogen phosphate, adding deionized water, mixing, ball milling to obtain lithium iron manganese phosphate precursor slurry, then weighing glucose with the mass fraction of 30% and uniformly mixing with the lithium iron manganese phosphate precursor slurry, ball milling for 20 hours, regulating the solid content, spray drying to obtain dry powder, and then performing primary filtration to obtain the precursor. And then placing the precursor into a tube furnace for calcination, wherein the temperature rising speed is 5-600 ℃ for presintering for 300min, then heating to 800 ℃ at the temperature rising speed of 10-720 ℃, calcining for 720min, and naturally cooling to obtain the LiMn 0.6Fe0.4PO4 aggregate. And crushing and grinding the LiMn 0.6Fe0.4PO4 aggregate, crushing for 8 hours, and screening to obtain the LiMn 0.6Fe0.4PO4 anode material.
2) And (3) preparing a positive plate, namely uniformly mixing lithium manganese iron phosphate (LiMn 0.6Fe0.4PO4) and a nickel-based positive material Lithium Nickelate (LNO) positive material according to a molar ratio of 17.01:3.79 as main materials. Uniformly mixing a main material, a conductive agent SP and PVDF glue solution in NMP according to the mass ratio of 96.5:1.5:2, uniformly coating the mixed positive electrode slurry on aluminum foil according to the surface density of 400g/m 2, drying in a 100 ℃ vacuum furnace to obtain a positive electrode plate, slitting, drying in the 100 ℃ vacuum furnace to obtain the positive electrode plate, slitting, rolling and cutting to obtain the positive electrode plate.
3) The preparation method of the negative plate comprises the steps of uniformly mixing artificial graphite, a conductive agent SP and a PVDF glue solution system according to the mass ratio of 96.4:0.6:3, dispersing the mixture in deionized water to obtain negative electrode slurry, uniformly coating the negative electrode slurry on copper foil according to the surface density of 173g/m 2, drying the negative electrode slurry for 12 hours in a vacuum environment at 100 ℃, then carrying out slitting, and carrying out cold pressing treatment according to the compaction density of 1.65g/cm 3 to obtain the negative plate.
4) The electrolyte is prepared by taking EC: EMC=3:7wt% as a solvent system, taking 1.15M LiPF 6 as lithium salt, and selecting 1% VC (vinylene carbonate) and 1% MMDS (methylene methane disulfonate) as film forming additives.
5) And (3) preparing a separation membrane, namely selecting PP as the separation membrane.
6) The battery is assembled, formed and fixed in volume to form SEI/CEI, namely the positive pole piece, the isolating film and the negative pole piece are sequentially stacked, the isolating film is positioned between the positive pole piece and the negative pole piece to play a role of isolation, then the bare cell is obtained by winding, the bare cell is placed in an outer packaging shell, electrolyte is injected after drying, the electrolyte injection coefficient is 0.02-3.5V/0.1-4.25V, stable SEI is formed by measuring the negative pole, more than gas is extracted by two seals, the upper limit voltage is charged by 0.33C, the constant voltage is cut off by 0.05C, the lower limit voltage is 2.5V by 0.C, and the stable CEI is formed by measuring the positive pole.
Examples 2 to 18 and comparative examples 1 to 4
Examples 2 to 18 and comparative examples 1 to 4 respectively provide lithium ion batteries, and the preparation method is similar to that of example 1, except that the types of nickel-based positive electrode materials and the proportions of lithium manganese iron phosphate (LiMn 0.6Fe0.4PO4) and nickel-based positive electrode materials are shown in table 1 when preparing the positive electrode sheet.
For the batteries prepared in each example and comparative example, the test methods for each parameter were as follows:
① The specific test method of the value a is as follows:
disassembling the positive plate in a full charge state of 100% SOC of the battery, cleaning the positive plate by DMC (dimethyl carbonate), and then drying at 25 ℃ for 24 hours to obtain a treated positive plate;
After the processed positive plate is obtained, etching is carried out by an X-ray photoelectron spectroscopy (XPS) method, wherein the specification and the model of an instrument are NEXSA G <2 >, a test beam is set to 400 micrometers in a manual control window of the instrument, the instrument automatically supplements a test energy range according to elements to be tested, the etching residence time is 50ms, the step length is 1eV, the speed is 0.7nm/s, and the etching time is set to 60s. After the test is finished, the instrument automatically gives a test result, and the peak area of each valence state is fitted according to the binding energy.
A is calculated according to the formula shown in formula II:
a= (S Ni 4++SNi 3+)/S Total area of formula II;
in the formula II, S Ni 4+ represents the area of tetravalent nickel obtained by XPS test;
S Ni 3+ represents the area of trivalent nickel obtained by XPS test;
S Total area of shows the sum of peak areas of the nickel element in each valence state obtained by XPS test.
The calculated a values are shown in table 1.
② The test method of the b value is as follows:
Immersing the positive electrode plate of the battery in a full charge state of 100% SOC in the solution, storing for 48 hours at 60 ℃, measuring the content m1 of H + in ppm in the solution, then continuously storing for 72 hours at 60 ℃, measuring the content m2 of H + in ppm in the solution, and calculating the growth rate b of H + according to a formula shown in a formula III:
b= (m 2-m 1)/m 1 formula III;
The test area of the positive electrode plate is 147cm 2, specifically 3 positive electrode plates of a battery in a full charge state of 7 multiplied by 7cm 2;
The solution is a mixed solution of ethylene carbonate EC, ethylmethyl carbonate EMC and lithium perchlorate, wherein the concentration of the lithium perchlorate in the mixed solution is 1M, the volume ratio of the ethylene carbonate EC to the ethylmethyl carbonate EMC is 3:7, and the dosage of the solution is 20ml.
The test method for the H + content in the 48H storage solution comprises the following steps:
Preparing triethylamine and EMC into a triethylamine titration solution with the concentration of 0.05 mol/L;
mixing EC and EMC according to a volume ratio of 3:7 to obtain 20mL mixed solution, and adding 2.13g of lithium perchlorate into the mixed solution to obtain a soaking solution;
Mixing the positive electrode plate of 3 batteries in a full charge state of 7 multiplied by 7cm 2 with a soaking solution, soaking for 48 hours at the temperature of 60 ℃ to obtain a 48-hour positive electrode plate soaking solution, adding 10-30 drops of methyl red into the 48-hour positive electrode plate soaking solution as an indicator, dripping triethylamine titration into the 48-hour positive electrode plate soaking solution containing methyl red, recording the consumption V1 of the triethylamine titration when the 48-hour positive electrode plate soaking solution turns orange, and calculating the content m1 of H + in the 48-hour solution according to a formula IV;
m1=mxv1× 20010/M IV
In the formula IV, M is the concentration of the titration solution, and the unit is mol/L;
V1 is the volume of the consumed titration solution, and the unit is mL;
m is the mass of the soaking liquid, and the unit is g;
Similarly, the method for testing the H + content in the stored 72H solution comprises the following steps:
Preparing triethylamine and EMC into a triethylamine titration solution with the concentration of 0.05 mol/L;
mixing EC and EMC according to a volume ratio of 3:7 to obtain 20mL mixed solution, and adding 2.13g of lithium perchlorate into the mixed solution to obtain a soaking solution;
Mixing the positive electrode plate of 3 batteries in a full charge state of 7 multiplied by 7cm 2 with a soaking liquid, soaking for 72 hours at the temperature of 60 ℃ to obtain a 72-hour positive electrode plate soaking liquid, adding 10-30 drops of methyl red into the 72-hour positive electrode plate soaking liquid as an indicator, dripping triethylamine titration into the 72-hour positive electrode plate soaking liquid containing methyl red, recording the consumption V2 of the triethylamine titration when the 72-hour positive electrode plate soaking liquid turns orange, and calculating the content m2 of H + in the 72-hour solution according to a formula V;
m2=mxv2× 20010/M type V
In the formula IV, M is the concentration of the titration solution, and the unit is mol/L;
v2 is the volume of the consumed titration solution, and the unit is mL;
m is the mass of the soaking solution, and the unit is g.
And substituting the obtained m1 and m2 into a formula III, and calculating to obtain the increase rate b of H +.
③ The test method of the c value is as follows:
Discharging the battery from 0.33 to 2.5V at 25 ℃, disassembling the battery to obtain a positive plate and a negative plate, obtaining 2g of positive powder from the positive plate and 2g of negative powder from the negative plate, testing the mole percentage content of Ni element and Mn element in the positive powder and the negative powder by inductively coupled plasma ICP, and calculating according to a formula shown in a formula VI to obtain the mole ratio C of the nickel-based positive electrode material in the positive electrode active material.
C= (total mole percent of Ni element in positive electrode powder and negative electrode powder/total mole percent of Ni element and mn element in positive electrode powder and negative electrode powder) ×100% formula VI
The lithium ion batteries prepared in the above examples and comparative examples were subjected to performance tests, and specific items and methods are as follows:
① The normal temperature cycle test method comprises the following steps:
After the temperature is 45 ℃, the temperature is charged to 4.3V at 0.33 ℃, the volume is discharged to 2.5V at 0.33 ℃, the constant current and the constant voltage are charged to 4.3V at 1C and the constant current is discharged to 2.5V at the temperature of 45 ℃ after two circles of constant volume, the discharge capacity of the 3 rd circle is recorded as C1 after 200 repeated cycles are finished, and the discharge capacity of the 200 th circle is recorded as C2, and the retention rate of the 200 th circle cycle capacity is= (C2/C1) multiplied by 100%.
② DCR growth rate test method:
Charging at 45 ℃ to 4.3V at 0.33 ℃, discharging at 0.33 ℃ to 2.5V, and after two circles of constant volume, charging at 0.33 ℃ to 4.3V at constant current and constant voltage at 45 ℃, then charging at 80% S0C at 0.33 ℃ in a constant voltage charging mode, standing for two hours, 1C discharging 18S measuring 1C DCR is recorded as R0, charging the battery at 45 ℃ to 2.5V at 0.33 ℃, and continuing to charge the battery at 45 ℃ to 2.5V at 1C constant current and constant voltage, repeating the cycle of charging and discharging at 1C/1C for 200 circles, charging at 0.33 ℃ to 4.3V at 0.33C discharging to 2.5V again at 45 ℃ in a constant volume for two circles, charging at 0.33C to 80% SOC, and 1C 18S measuring 1C DCR 1,200 circles of DCR 1, and increasing the rate of 1C DCR 1 (R1-0) = (R0-100%) in two hours.
The test results are shown in Table 1
TABLE 1
For the lithium ion battery prepared by the embodiment of the invention, the 200cls circulation capacity retention rate is more than or equal to 91.81%, and the DCR growth rate is less than or equal to 10.25%, so that the gas yield of the lithium ion battery is reduced, the internal resistance of the battery is further reduced, and the circulation performance of the battery is improved.
Examples 1 to 5 and examples 10 to 11 in combination with the data of examples 6 to 9, examples 12 to 18 and comparative examples 1 to 4, it can be seen that when a, b, c and a×c satisfy the preferred parameter ranges defined in the present invention, the internal resistance of the lithium ion battery is lower and the cycle performance is relatively better.
From examples 1 to 5 in combination with examples 6 to 9, it can be seen that when the battery satisfies 0.008< (a×c)/b is not more than 8.290, the internal resistance of the lithium ion battery is lower and the cycle performance is relatively higher.
As is clear from the results of comparative examples 1 to 4, even when a, b, c and a.times.c satisfy the parameter ranges defined in the present invention, the lithium ion battery has higher internal resistance and poor cycle performance when the battery does not satisfy the range of 0.008< (a.times.c)/b.ltoreq. 8.290.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
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