CN108461842B - Method for improving short circuit passing rate of cylindrical lithium titanate energy storage battery cell - Google Patents
Method for improving short circuit passing rate of cylindrical lithium titanate energy storage battery cell Download PDFInfo
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- H—ELECTRICITY
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Abstract
The invention discloses a method for improving the short circuit passing rate of a cylindrical lithium titanate energy storage battery cellThe method comprises the following steps: preparing lithium titanate negative electrode material by adopting a high-temperature solid-phase method, and grinding to obtain D10＝1‑5um，D50＝5‑20um，D90＝10‑40um，(D90‑D10)/D502-6 of negative electrode powder; preparing cathode slurry with solid content of 35-50% and viscosity of 4000-7000mPa & s by using cathode powder as an active substance, superconducting carbon black and carbon nano tubes as conductive agents and polyvinylidene fluoride as a binder; coating the negative electrode slurry on a negative electrode current collector to obtain a lithium titanate negative electrode plate; preparing a positive plate by taking a ternary material as a positive material; and preparing the positive plate and the lithium titanate negative plate into a battery cell according to the N/P of 0.9-0.97. The method for improving the short circuit passing rate of the cylindrical lithium titanate energy storage battery cell is simple and easy to operate, low in cost, and capable of enabling the battery to react smoothly during short circuit and not to lose effectiveness instantly.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a method for improving the short circuit passing rate of a cylindrical lithium titanate energy storage battery core.
Background
Lithium titanate batteries are a special battery in lithium ion batteries, and are getting more and more attention by virtue of excellent cycle performance, ultra-long service life and reliable safety performance. The lithium titanate battery has excellent cycle performance and ultra-long service life of about 30 years, meets the application requirement in the field of industrial energy storage, has obvious cost price advantage in the whole life cycle and high safety, and is a good choice of energy storage batteries. But the defects of the lithium titanate battery are very obvious, such as low energy density, flatulence, high price and the like. What supports the market acceptance of lithium titanate batteries is their safety, long life and low cost of the full life cycle, with safety being a primary consideration for any cell. It has been found experimentally that lithium titanate batteries are not as absolutely safe as people have said, and improper design and cell platform selection can also make them dangerous. In the 32131 cylindrical electrical core system, as mentioned in the present invention, due to poor heat conduction and heat dissipation capabilities, heat generated by the negative electrode cannot be dissipated in time during an external short circuit test, so that the separator melts, and further a large area short circuit between the positive electrode and the negative electrode is caused, and the positive electrode decomposes to release oxygen and generate heat, resulting in thermal runaway explosion of the electrical core. Therefore, the 32131 cylindrical system has a good effect of inhibiting lithium titanate battery cell flatulence, but also has potential safety hazards.
Disclosure of Invention
Based on the technical problems in the prior art, the invention provides a method for improving the short-circuit passing rate of a cylindrical lithium titanate energy storage battery cell, which is simple and easy to operate, low in cost, easy to realize and popularize, relatively gentle in reaction of the battery during short circuit, free of instant failure, and capable of solving the problem of battery cell failure and explosion caused by rapid heat and gas generation of the battery cell during external short circuit of the battery.
The invention provides a method for improving the short circuit passing rate of a cylindrical lithium titanate energy storage battery cell, which comprises the following steps:
s1, preparing a lithium titanate negative electrode material by adopting a high-temperature solid-phase method, and grinding the lithium titanate negative electrode material to obtain negative electrode powder; wherein the particle size distribution of the negative electrode powder material satisfies D10＝1-5um，D50＝5-20um，D90＝10-40um，(D90-D10)/D50＝2-6；
S2, preparing negative electrode slurry by taking the negative electrode powder in the S1 as an active substance, superconducting carbon black and carbon nano tubes as conductive agents and polyvinylidene fluoride as a binder; wherein the weight ratio of the negative electrode powder, the superconducting carbon black, the carbon nano tubes and the polyvinylidene fluoride in S1 is 90-95: 1-3: 2-4: 2-4; the solid content of the negative electrode slurry is 35-50%, and the viscosity is 4000-7000 mPas;
s3, coating the negative electrode slurry in the S2 on a negative electrode current collector to obtain a lithium titanate negative electrode sheet; wherein the single-sided surface density of the negative electrode slurry on the negative electrode current collector is 60-160g/m2The compacted density is 1.8-2.0g/cm3；
S4, preparing a positive plate by taking the ternary material as a positive electrode material; and preparing the positive plate and the lithium titanate negative plate in the S3 into the cylindrical lithium titanate energy storage battery cell according to the N/P ratio of 0.9-0.97.
Preferably, in S1, the pH of the lithium titanate negative electrode material is controlled within a range of 10.5-11.5.
Preferably, in S3, the negative electrode current collector is made of 16+2+2um carbon-coated aluminum foil.
Preferably, in S4, the preparing the positive electrode sheet with the ternary material as the positive electrode material includes preparing a positive electrode slurry and coating the positive electrode slurry on a positive electrode current collector; in the process of preparing the anode slurry, raw materials of the anode slurry comprise a ternary material, superconducting carbon black, carbon nano tubes and polyvinylidene fluoride, and the weight ratio of the ternary material to the superconducting carbon black to the carbon nano tubes to the polyvinylidene fluoride is 92-96: 1-3: 1-4: 1-3.
Preferably, the ternary material is one of NCM111, NCM523, and NCM 622.
Preferably, the solid content of the positive electrode slurry is 60-70%, and the viscosity is 4000-7000mPa s; the single-side surface density of the anode slurry on the anode current collector is controlled to be 60-160g/m2The compacted density is 3.0-3.3g/cm3。
Preferably, the positive current collector is 16um optical aluminum foil.
Preferably, the capacity of the prepared cylindrical lithium titanate energy storage battery cell is distributed in the range of 7-10Ah, and the energy density is distributed in the range of 60-90 Wh/kg.
Preferably, the full battery liquid injection coefficient is controlled between 3.5 and 5.5 g/Ah.
Preferably, the full cell membrane is a 12+4um ceramic membrane.
Preferably, in S1, the lithium titanate negative electrode material is ground by a sand mill, and during the grinding, the particle size of the negative electrode powder is controlled by adjusting the parameters of the sand mill.
The cylindrical lithium titanate energy storage battery cell is a ternary-lithium titanate 32131 type cylindrical-system battery cell.
The method for improving the short circuit passing rate of the cylindrical lithium titanate energy storage battery cell comprises the steps of firstly preparing a required lithium titanate negative electrode material by adopting a high-temperature solid-phase method, and then controlling the granularity of the lithium titanate negative electrode material within a specified range (namely D)10＝1-5um，D50＝5-20um，D90＝10-40um，(D90-D10)/D502-6), the negative electrode powder with larger particle size distribution is obtained, the specific surface area of the LTO (lithium titanate) pole piece is reduced, and the instability caused by overlarge specific surface area and over-strong activity of the negative electrode piece is prevented, namely, the reaction is relatively gentle during short circuit, and the transient failure is avoided; secondly, the large internal resistance is large, the heat is generated more and the gas is generated quickly in the early stage of short circuit, and the battery cell explosion-proof valve can be opened to dissipate heat and release pressure in time, so that the aim of improving the safety is fulfilled; simultaneously controls the single-sided surface density of LTO (lithium titanate) negative plates in the full cell to be 60-160g/m2The compacted density is 1.8-2.0g/cm3The N/P (negative electrode capacity/positive electrode capacity) of the battery cell is in the range of 0.9-0.97, so that the short circuit passing rate of the battery cell can reach 100 percent, and the granularity D of the negative electrode50<When the thickness is 1um, the short circuit passing rate is only 30%, so that the safety of the external short circuit of the battery core is greatly improved;
compared with the prior art, the invention has the beneficial effects that: the process is simple, and the short circuit can be safely passed without adding any structural part design or changing the design of an electric core system; the particle size of LTO can be adjusted only by modifying the parameters of the sand mill, equipment does not need to be replaced or energy consumption is not increased, the particle size distribution is easy to adjust, and extra cost is not generated; the short circuit is ensured to pass by reducing the SOC (state of charge) state, namely sacrificing the capacity without changing the test condition, and the method is easy to realize and popularize and can be applied to actual industrial production.
Drawings
FIG. 1 shows a cylindrical lithium titanate energy storage cell (LTO particle size D) prepared in example 8 of the present invention5015um ternary 622/lithium titanate cylindrical cell) accelerated adiabatic calorimeter test (ARC) failure temperature curve;
FIG. 2 is LTO particle size D50Accelerated adiabatic calorimeter test (ARC) failure temperature profile for 1um ternary 622/lithium titanate cylindrical cells.
Detailed Description
The technical solution of the present invention will be described in detail below with reference to specific examples.
Example 1
The invention provides a method for improving the short circuit passing rate of a cylindrical lithium titanate energy storage battery cell, which comprises the following steps:
s1, preparing a lithium titanate negative electrode material by adopting a high-temperature solid-phase method, and grinding the lithium titanate negative electrode material to obtain negative electrode powder; wherein the particle size distribution of the negative electrode powder material satisfies D10＝5um，D50＝15um，D90＝35um，(D90-D10)/D50＝2；
S2, preparing negative electrode slurry by taking the negative electrode powder in the S1 as an active substance, superconducting carbon black and carbon nano tubes as conductive agents and polyvinylidene fluoride as a binder; wherein the weight ratio of the negative electrode powder, the superconducting carbon black, the carbon nano tubes and the polyvinylidene fluoride in the S1 is 90: 2: 4: 4; the solid content of the negative electrode slurry is 35%, and the viscosity is 7000mPa & s;
s3, coating the negative electrode slurry in the S2 on a negative electrode current collector to obtain a lithium titanate negative electrode sheet; wherein the single-sided surface density of the negative electrode slurry on the negative electrode current collector is 60g/m2The compacted density is 1.8g/cm3；
S4, preparing a positive plate by taking the ternary material as a positive electrode material; and preparing the positive plate and the lithium titanate negative plate in the S3 into the cylindrical lithium titanate energy storage battery cell according to the N/P ratio of 0.9.
Example 2
The invention provides a method for improving the short circuit passing rate of a cylindrical lithium titanate energy storage battery cell, which comprises the following steps:
s1, preparing a lithium titanate negative electrode material by adopting a high-temperature solid-phase method, and grinding the lithium titanate negative electrode material to obtain negative electrode powder; wherein the particle size distribution of the negative electrode powder material satisfies D10＝1um，D50＝6um，D90＝37um，(D90-D10)/D50＝6；
S2, preparing negative electrode slurry by taking the negative electrode powder in the S1 as an active substance, superconducting carbon black and carbon nano tubes as conductive agents and polyvinylidene fluoride as a binder; wherein the weight ratio of the negative electrode powder, the superconducting carbon black, the carbon nano tubes and the polyvinylidene fluoride in S1 is 95: 1: 2: 2; the solid content of the negative electrode slurry is 50%, and the viscosity is 4000mPa & s;
s3, coating the negative electrode slurry in the S2 on a negative electrode current collector to obtain a lithium titanate negative electrode sheet; wherein the single-sided surface density of the negative electrode slurry on the negative electrode current collector is 160g/m2The compacted density is 2.0g/cm3；
S4, preparing a positive plate by taking the ternary material as a positive electrode material; and preparing the positive plate and the lithium titanate negative plate in the S3 into the cylindrical lithium titanate energy storage battery cell according to the N/P ratio of 0.97.
Example 3
The invention provides a method for improving the short circuit passing rate of a cylindrical lithium titanate energy storage battery cell, which comprises the following steps:
s1, preparing a lithium titanate negative electrode material by adopting a high-temperature solid-phase method, and grinding the lithium titanate negative electrode material to obtain negative electrode powder; wherein the particle size distribution of the negative electrode powder material satisfies D10＝4um，D50＝7um，D90＝25um，(D90-D10)/D50＝3；
S2, preparing negative electrode slurry by taking the negative electrode powder in the S1 as an active substance, superconducting carbon black and carbon nano tubes as conductive agents and polyvinylidene fluoride as a binder; wherein the weight ratio of the negative electrode powder, the superconducting carbon black, the carbon nano tubes and the polyvinylidene fluoride in S1 is 91: 3: 3: 3; the solid content of the negative electrode slurry is 38%, and the viscosity is 6600mPa & s;
s3, coating the negative electrode slurry in the S2 on a negative electrode current collector to obtain a lithium titanate negative electrode sheet; wherein the single-sided surface density of the negative electrode slurry on the negative electrode current collector is 80g/m2Compacted density of 1.9g/cm3；
S4, preparing a positive plate by taking the ternary material as a positive electrode material; preparing a positive plate and a lithium titanate negative plate in S3 into a cylindrical lithium titanate energy storage battery cell according to the N/P ratio of 0.92;
wherein in S1, the pH value of the lithium titanate negative electrode material is controlled to be 11.5;
in S3, the negative current collector is made of a 16+2+2um carbon-coated aluminum foil;
in S4, preparing a positive plate by taking the ternary material as the positive material comprises preparing positive slurry and coating the positive slurry on a positive current collector; in the process of preparing the anode slurry, raw materials of the anode slurry comprise a ternary material, superconducting carbon black, a carbon nano tube and polyvinylidene fluoride, and the weight ratio of the ternary material to the superconducting carbon black to the carbon nano tube to the polyvinylidene fluoride is 92: 3: 4: 1;
the ternary material is NCM 523;
the solid content of the positive electrode slurry is 60%, and the viscosity is 4000mPa & s; the single-side surface density of the anode slurry on the anode current collector is controlled to be 86g/m2The compacted density is 3.0g/cm3；
The positive current collector is 16um light aluminum foil;
the capacity of the prepared cylindrical lithium titanate energy storage battery cell is 7Ah, and the energy density is 60 Wh/kg;
the liquid injection coefficient of the full battery is controlled to be 5.5 g/Ah;
the full-cell diaphragm is a ceramic diaphragm of 12+4 um.
Example 4
The invention provides a method for improving the short circuit passing rate of a cylindrical lithium titanate energy storage battery cell, which comprises the following steps:
s1, preparing a lithium titanate negative electrode material by adopting a high-temperature solid-phase method, and grinding the lithium titanate negative electrode material to obtain negative electrode powder; wherein the particle size distribution of the negative electrode powder material satisfies D10＝2um，D50＝7um，D90＝30um，(D90-D10)/D50＝4；
S2, preparing negative electrode slurry by taking the negative electrode powder in the S1 as an active substance, superconducting carbon black and carbon nano tubes as conductive agents and polyvinylidene fluoride as a binder; wherein the weight ratio of the negative electrode powder, the superconducting carbon black, the carbon nano tubes and the polyvinylidene fluoride in S1 is 93: 2: 3: 2; the solid content of the negative electrode slurry is 46%, and the viscosity is 4500mPa & s;
s3, coating the negative electrode slurry in the S2 on a negative electrode current collector to obtain a lithium titanate negative electrode sheet; wherein the single-sided surface density of the negative electrode slurry on the negative electrode current collector is 145g/m2The compacted density is 1.85g/cm3；
S4, preparing a positive plate by taking the ternary material as a positive electrode material; preparing a positive plate and a lithium titanate negative plate in S3 into a cylindrical lithium titanate energy storage battery cell according to the N/P ratio of 0.95;
wherein in S1, the pH value of the lithium titanate negative electrode material is controlled to be 10.5;
in S4, preparing a positive plate by taking the ternary material as the positive material comprises preparing positive slurry and coating the positive slurry on a positive current collector; in the process of preparing the anode slurry, raw materials of the anode slurry comprise a ternary material, superconducting carbon black, a carbon nano tube and polyvinylidene fluoride, and the weight ratio of the ternary material to the superconducting carbon black to the carbon nano tube to the polyvinylidene fluoride is 96: 1: 1: 2;
the ternary material is NCM 111;
the solid content of the positive electrode slurry is 70%, and the viscosity of the positive electrode slurry is 4000mPa & s; the single-side surface density of the positive electrode slurry on the positive electrode current collector is controlled to be 148g/m2The compacted density is 3.3g/cm3；
The positive current collector is 16um light aluminum foil;
the capacity of the prepared cylindrical lithium titanate energy storage battery cell is 10Ah, and the energy density is 90 Wh/kg;
the liquid injection coefficient of the full battery is controlled to be 3.5 g/Ah;
the full-cell diaphragm is a ceramic diaphragm of 12+4 um.
Example 5
The invention provides a method for improving the short circuit passing rate of a cylindrical lithium titanate energy storage battery cell, which comprises the following steps:
s1, preparing a lithium titanate negative electrode material by adopting a high-temperature solid-phase method, and grinding the lithium titanate negative electrode material to obtain negative electrode powder; wherein the particle size distribution of the negative electrode powder material satisfies D10＝3um，D50＝7um，D90＝38um，(D90-D10)/D50(ii) 5; wherein the pH value of the lithium titanate negative electrode material is controlled to be 11;
s2, preparing negative electrode slurry by taking the negative electrode powder in the S1 as an active substance, superconducting carbon black and carbon nano tubes as conductive agents and polyvinylidene fluoride as a binder; wherein the weight ratio of the negative electrode powder, the superconducting carbon black, the carbon nano tubes and the polyvinylidene fluoride in S1 is 93: 2: 2.5: 2.5; the solid content of the negative electrode slurry is 39%, and the viscosity is 5500mPa & s;
s3, coating the negative electrode slurry in the S2 on a negative electrode current collector to obtain a lithium titanate negative electrode sheet; wherein the single-sided surface density of the negative electrode slurry on the negative electrode current collector is 100g/m2Compacted density of 1.9g/cm3；
S4, preparing a positive plate by taking the ternary material as a positive electrode material; preparing a positive plate and a lithium titanate negative plate in S3 into a cylindrical lithium titanate energy storage battery cell according to the N/P ratio of 0.97; preparing a positive plate by taking a ternary material as a positive material, wherein the preparation of the positive plate comprises the steps of preparing positive slurry and coating the positive slurry on a positive current collector; in the process of preparing the anode slurry, raw materials of the anode slurry comprise a ternary material, superconducting carbon black, a carbon nano tube and polyvinylidene fluoride, and the weight ratio of the ternary material to the superconducting carbon black to the carbon nano tube to the polyvinylidene fluoride is 95: 1: 1: 3; the ternary material is NCM 622; the solid content of the positive electrode slurry is 65%, and the viscosity of the positive electrode slurry is 5000mPa & s; the single-side surface density of the anode slurry on the anode current collector is controlled to be 101g/m2The compacted density is 3.2g/cm3；
The capacity of the prepared cylindrical lithium titanate energy storage battery cell is 8.7Ah, and the energy density is 80 Wh/kg;
the liquid injection coefficient of the full battery is controlled to be 4.3 g/Ah;
the full-cell diaphragm is a ceramic diaphragm of 12+4 um.
Example 6
The invention provides a method for improving the short circuit passing rate of a cylindrical lithium titanate energy storage battery cell, which comprises the following steps:
s1, preparing a lithium titanate negative electrode material by adopting a high-temperature solid-phase method, and grinding the lithium titanate negative electrode material to obtain negative electrode powder; wherein the particle size distribution of the negative electrode powder material satisfies D10＝3um，D50＝6um，D90＝30um，(D90-D10)/D50＝4.5；
S2, preparing negative electrode slurry by taking the negative electrode powder in the S1 as an active substance, superconducting carbon black and carbon nano tubes as conductive agents and polyvinylidene fluoride as a binder; wherein the weight ratio of the negative electrode powder, the superconducting carbon black, the carbon nano tubes and the polyvinylidene fluoride in the S1 is 90: 2: 4: 4; the solid content of the negative electrode slurry is 39%, and the viscosity is 5500mPa & s;
s3, coating the negative electrode slurry in the S2 on a negative electrode current collector to obtain a lithium titanate negative electrode sheet; wherein the single-sided surface density of the negative electrode slurry on the negative electrode current collector is 69g/m2Compacted density of 1.9g/cm3；
S4, preparing a positive plate by taking the ternary material as a positive electrode material; preparing a positive plate and a lithium titanate negative plate in S3 into a cylindrical lithium titanate energy storage battery cell according to the N/P ratio of 0.9;
wherein in S1, the pH value of the lithium titanate negative electrode material is controlled to be 11;
in S4, preparing a positive plate by taking the ternary material as the positive material comprises preparing positive slurry and coating the positive slurry on a positive current collector; in the process of preparing the anode slurry, raw materials of the anode slurry comprise a ternary material, superconducting carbon black, a carbon nano tube and polyvinylidene fluoride, and the weight ratio of the ternary material to the superconducting carbon black to the carbon nano tube to the polyvinylidene fluoride is 92: 2: 4: 2;
the ternary material is NCM 111;
the solid content of the positive electrode slurry is 65%, and the viscosity of the positive electrode slurry is 5000mPa & s; the single-side surface density of the anode slurry on the anode current collector is controlled to be 75g/m2The compacted density is 3.1g/cm3；
The capacity of the prepared cylindrical lithium titanate energy storage battery cell is 7Ah, and the energy density is 65 Wh/kg;
the liquid injection coefficient of the full battery is controlled to be 5 g/Ah;
the full-cell diaphragm is a ceramic diaphragm of 12+4 um.
After the cylindrical lithium titanate energy storage battery cell prepared in the embodiment 6 is formed and subjected to capacity grading, according to a standard test of GB/T31485-2015 safety requirement and experimental method for power storage batteries for electric vehicles, the battery cell is charged to 100% SOC, short circuit is connected for 10min, and the internal resistance of an external circuit is less than 5m omega; observing for 1h, and regarding the condition that no explosion or fire occurs as passing; the test shows that the highest temperature on the surface of the battery cell reaches when the battery cell is short-circuitedWhen the temperature is above 120 ℃, but the battery core is not exploded, the explosion-proof valve 40s is opened; in the previous test, when LTO material D was used50<When the temperature is 1um, the battery core can explode when the highest temperature of the battery core reaches about 110 ℃, and the explosion-proof valve is opened for about 1 minute and half minutes; therefore, the cylindrical lithium titanate energy storage battery cell prepared in the example 6 has high external short circuit safety performance, so that the D of the LTO material is increased50The distribution can effectively improve the external short circuit safety performance of the battery cell.
Example 7
The invention provides a method for improving the short circuit passing rate of a cylindrical lithium titanate energy storage battery cell, which comprises the following steps:
s1, preparing a lithium titanate negative electrode material by adopting a high-temperature solid-phase method, and grinding the lithium titanate negative electrode material to obtain negative electrode powder; wherein the particle size distribution of the negative electrode powder material satisfies D10＝5um，D50＝10um，D90＝40um，(D90-D10)/D50＝3.5；
S2, preparing negative electrode slurry by taking the negative electrode powder in the S1 as an active substance, superconducting carbon black and carbon nano tubes as conductive agents and polyvinylidene fluoride as a binder; wherein the weight ratio of the negative electrode powder, the superconducting carbon black, the carbon nano tubes and the polyvinylidene fluoride in S1 is 91: 3: 4: 2; the solid content of the negative electrode slurry is 39%, and the viscosity is 5500mPa & s;
s3, coating the negative electrode slurry in the S2 on a negative electrode current collector to obtain a lithium titanate negative electrode sheet; wherein the single-sided surface density of the negative electrode slurry on the negative electrode current collector is 118g/m2The compacted density is 1.85g/cm3；
S4, preparing a positive plate by taking the ternary material as a positive electrode material; preparing a 32131 cylindrical lithium titanate energy storage battery cell by winding the positive plate and the lithium titanate negative plate in S3 according to the N/P ratio of 0.95;
wherein in S1, the pH value of the lithium titanate negative electrode material is controlled to be 11;
in S4, preparing a positive plate by taking the ternary material as the positive material comprises preparing positive slurry and coating the positive slurry on a positive current collector; in the process of preparing the anode slurry, raw materials of the anode slurry comprise a ternary material, superconducting carbon black, carbon nano tubes and polyvinylidene fluoride, and the weight ratio of the ternary material to the superconducting carbon black to the carbon nano tubes to the polyvinylidene fluoride is 94: 2: 2: 2;
the ternary material is NCM 523;
the solid content of the positive electrode slurry is 65%, and the viscosity of the positive electrode slurry is 5000mPa & s; the single-side surface density of the anode slurry on the anode current collector is controlled to be 120g/m2The compacted density is 3.1g/cm3；
The capacity of the prepared cylindrical lithium titanate energy storage battery cell is 8Ah, and the energy density is 70 Wh/kg;
the liquid injection coefficient of the full battery is controlled to be 4.3 g/Ah;
the full-cell diaphragm is a ceramic diaphragm of 12+4 um.
After the cylindrical lithium titanate energy storage battery cell prepared in the embodiment 7 is formed and subjected to capacity grading, according to a standard test of GB/T31485-2015 safety requirement and experimental method for power storage batteries for electric vehicles, the battery cell is fully charged to 100% SOC, then a short circuit is connected for 10min, and the internal resistance of an external circuit is less than 5m omega; observing for 1h, and regarding the condition that no explosion or fire occurs as passing; through tests, the temperature of the surface of the battery cell reaches over 130 ℃ when the battery cell is in short circuit, but the battery cell can still pass the tests, and the explosion-proof valve 35s is opened; in the previous experiments, when LTO material D50<When the thickness of the battery cell is 1um, the battery cell can explode when the highest temperature of the surface of the battery cell reaches about 100 ℃ when the battery cell is in short circuit; it can be seen that the cylindrical lithium titanate energy storage cell prepared in example 7 has high external short circuit safety, and therefore, the D of the LTO material is increased50The distribution can effectively improve the external short circuit safety performance of the battery cell.
Example 8
The invention provides a method for improving the short circuit passing rate of a cylindrical lithium titanate energy storage battery cell, which comprises the following steps:
s1, preparing a lithium titanate negative electrode material by adopting a high-temperature solid-phase method, and grinding the lithium titanate negative electrode material to obtain negative electrode powder; wherein the particle size distribution of the negative electrode powder material satisfies D10＝2.5um，D50＝15um，D90＝40um，(D90-D10)/D50＝2.5；
S2, preparing negative electrode slurry by taking the negative electrode powder in the S1 as an active substance, superconducting carbon black and carbon nano tubes as conductive agents and polyvinylidene fluoride as a binder; wherein the weight ratio of the negative electrode powder, the superconducting carbon black, the carbon nano tubes and the polyvinylidene fluoride in the S1 is 93.5: 1: 2: 3.5; the solid content of the negative electrode slurry is 39%, and the viscosity is 5500mPa & s;
s3, coating the negative electrode slurry in the S2 on a negative electrode current collector to obtain a lithium titanate negative electrode sheet; wherein the single-sided surface density of the negative electrode slurry on the negative electrode current collector is 129g/m2The compacted density is 1.88g/cm3；
S4, preparing a positive plate by taking the ternary material as a positive electrode material; preparing a positive plate and a lithium titanate negative plate in S3 into a cylindrical lithium titanate energy storage battery cell according to the N/P ratio of 0.97;
wherein in S1, the pH value of the lithium titanate negative electrode material is controlled to be 11;
in S4, preparing a positive plate by taking the ternary material as the positive material comprises preparing positive slurry and coating the positive slurry on a positive current collector; in the process of preparing the anode slurry, raw materials of the anode slurry comprise a ternary material, superconducting carbon black, a carbon nano tube and polyvinylidene fluoride, and the weight ratio of the ternary material to the superconducting carbon black to the carbon nano tube to the polyvinylidene fluoride is 96: 1: 1.5: 1.5;
the ternary material is NCM 622;
the solid content of the positive electrode slurry is 65%, and the viscosity of the positive electrode slurry is 5000mPa & s; the single-sided surface density of the anode slurry on the anode current collector is controlled to be 130g/m2The compacted density is 3.2g/cm3；
The capacity of the prepared cylindrical lithium titanate energy storage battery cell is 9.5Ah, and the energy density is 85 Wh/kg;
the liquid injection coefficient of the full battery is controlled to be 4 g/Ah;
the full-cell diaphragm is a ceramic diaphragm of 12+4 um.
The cylindrical lithium titanate energy storage battery prepared in example 8 is subjected to formation and capacity grading, and then is tested according to GB/T31485-2015 Standard of safety requirements and Experimental methods for Power storage batteries for electric vehiclesFirstly, charging the battery cell to 100% SOC, then switching in a short circuit for 10min, wherein the internal resistance of an external circuit is less than 5m omega; observing for 1h, and regarding the condition that no explosion or fire occurs as passing; the test shows that the temperature of the surface of the battery cell reaches above 120 ℃ when the battery cell is in short circuit, the battery cell passes the test, and the explosion-proof valve 32s is opened; in the previous test, when LTO material D was used50<When the temperature of the battery core is 1um, the battery core can explode when the highest temperature of the battery core reaches about 100 ℃, and most explosion-proof valves cannot be completely opened; therefore, the cylindrical lithium titanate energy storage battery cell prepared in the example 8 has high external short circuit safety performance, and the D of the LTO material is increased50The distribution can effectively improve the short circuit safety performance of the battery cell.
To characterize the cells prepared in example 8 with LTO particle size D50Difference in safety performance between 1um ternary 622/lithium titanate cylindrical cells, cells prepared in example 8 and LTO particle size D, respectively501um ternary 622/lithium titanate cylindrical cell was subjected to accelerated adiabatic calorimetry (ARC) test, and the temperature rise at 5 ℃/min was used as the criterion for failure determination, and fig. 1 is a cylindrical lithium titanate energy storage cell (i.e., LTO particle size D) prepared in example 8 of the present invention5015um ternary 622/lithium titanate cylindrical cell) accelerated adiabatic calorimeter test (ARC) failure temperature curve; FIG. 2 is LTO particle size D50Accelerated adiabatic calorimeter test (ARC) failure temperature profile for 1um ternary 622/lithium titanate cylindrical cells; comparing fig. 1 and fig. 2, it can be seen that the large particle LTO cell failure temperature is 10 ℃ higher, which is safer and consistent with the short circuit test results.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.
Claims (8)
1. A method for improving the short circuit passing rate of a cylindrical lithium titanate energy storage battery cell is characterized by comprising the following steps:
s1, preparing the lithium titanate negative electrode material, namely titanium by adopting a high-temperature solid-phase methodGrinding the lithium negative electrode material to obtain negative electrode powder; wherein the particle size distribution of the negative electrode powder material satisfies D10=1-5um，D50=5-20um，D90=10-40um，(D90-D10)/D50=2-6；
S2, preparing negative electrode slurry by taking the negative electrode powder in the S1 as an active substance, superconducting carbon black and carbon nano tubes as conductive agents and polyvinylidene fluoride as a binder; wherein the weight ratio of the negative electrode powder, the superconducting carbon black, the carbon nano tubes and the polyvinylidene fluoride in S1 is 90-95: 1-3: 2-4: 2-4; the solid content of the negative electrode slurry is 35-50%, and the viscosity is 4000-7000 mPas;
s3, coating the negative electrode slurry in the S2 on a negative electrode current collector to obtain a lithium titanate negative electrode sheet; wherein the single-sided surface density of the negative electrode slurry on the negative electrode current collector is 60-160g/m2The compacted density is 1.8-2.0g/cm3；
The negative current collector is a 16+2+2um carbon-coated aluminum foil;
s4, preparing a positive plate by taking the ternary material as a positive electrode material; preparing a positive plate and a lithium titanate negative plate in S3 into a cylindrical lithium titanate energy storage battery cell according to the N/P ratio = 0.9-0.97; the full-cell diaphragm is a ceramic diaphragm of 12+4 um.
2. The method for improving the short circuit passing rate of the cylindrical lithium titanate energy storage battery cell as claimed in claim 1, wherein in S1, the pH of the lithium titanate negative electrode material is controlled within a range of 10.5-11.5.
3. The method for improving the short circuit passing rate of the cylindrical lithium titanate energy storage battery cell according to claim 1, wherein in S4, the step of preparing the positive plate by using the ternary material as the positive electrode material comprises preparing a positive electrode slurry and coating the positive electrode slurry on a positive electrode current collector; in the process of preparing the anode slurry, raw materials of the anode slurry comprise a ternary material, superconducting carbon black, carbon nano tubes and polyvinylidene fluoride, and the weight ratio of the ternary material to the superconducting carbon black to the carbon nano tubes to the polyvinylidene fluoride is 92-96: 1-3: 1-4: 1-3.
4. The method for improving the short circuit passing rate of the cylindrical lithium titanate energy storage battery cell according to claim 1, wherein the ternary material is one of NCM111, NCM523 and NCM 622.
5. The method for improving the short-circuit passing rate of the cylindrical lithium titanate energy storage battery cell according to claim 3, wherein the solid content of the positive electrode slurry is 60% -70%, and the viscosity is 4000-7000mPa s; the single-side surface density of the anode slurry on the anode current collector is controlled to be 60-160g/m2The compacted density is 3.0-3.3g/cm3。
6. The method for improving the short circuit passing rate of the cylindrical lithium titanate energy storage battery cell according to any one of claims 3 or 5, wherein the positive electrode current collector is a 16um optical aluminum foil.
7. The method for improving the short circuit passing rate of a cylindrical lithium titanate energy storage cell according to any one of claims 1 to 5, wherein the capacity distribution of the prepared cylindrical lithium titanate energy storage cell is in the range of 7-10Ah, and the energy density distribution of the prepared cylindrical lithium titanate energy storage cell is in the range of 60-90 Wh/kg.
8. The method for improving the short circuit passing rate of the cylindrical lithium titanate energy storage battery cell according to any one of claims 1 to 5, wherein the full battery liquid injection coefficient is controlled to be 3.5 to 5.5 g/Ah.
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| CN110071292B (en) * | 2019-04-04 | 2022-05-13 | 桑顿新能源科技(长沙)有限公司 | Preparation method of lithium ion battery positive pole piece and positive pole piece |
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