CN110649339A - Formation method for improving K value of soft-package battery cell - Google Patents
Formation method for improving K value of soft-package battery cell Download PDFInfo
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- CN110649339A CN110649339A CN201810670476.4A CN201810670476A CN110649339A CN 110649339 A CN110649339 A CN 110649339A CN 201810670476 A CN201810670476 A CN 201810670476A CN 110649339 A CN110649339 A CN 110649339A
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- 230000015572 biosynthetic process Effects 0.000 title claims abstract description 94
- 238000000034 method Methods 0.000 title claims abstract description 58
- 239000011229 interlayer Substances 0.000 claims abstract description 15
- 210000004027 cell Anatomy 0.000 claims description 153
- 238000007600 charging Methods 0.000 claims description 58
- 238000007493 shaping process Methods 0.000 claims description 32
- 238000007599 discharging Methods 0.000 claims description 27
- 238000010277 constant-current charging Methods 0.000 claims description 18
- 238000001816 cooling Methods 0.000 claims description 18
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 abstract description 13
- 229910001416 lithium ion Inorganic materials 0.000 abstract description 13
- 230000005012 migration Effects 0.000 abstract description 10
- 238000013508 migration Methods 0.000 abstract description 10
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 abstract description 5
- 230000000694 effects Effects 0.000 abstract description 5
- 229910052744 lithium Inorganic materials 0.000 abstract description 5
- 238000001556 precipitation Methods 0.000 abstract description 5
- 230000002431 foraging effect Effects 0.000 description 5
- 239000010410 layer Substances 0.000 description 5
- 239000007788 liquid Substances 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 4
- 238000002347 injection Methods 0.000 description 4
- 239000007924 injection Substances 0.000 description 4
- 230000035882 stress Effects 0.000 description 3
- 210000005056 cell body Anatomy 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 230000005489 elastic deformation Effects 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
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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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/44—Methods for charging or discharging
- H01M10/446—Initial charging measures
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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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/058—Construction or manufacture
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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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- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention discloses a formation method for improving a K value of a soft-package battery cell, which solves the problems of poor film formation of an SEI film formed by normal pressure formation of the soft-package battery cell, insufficient deformation and hardness of a battery cell main body, black spots on an interface, lithium precipitation and the like, and also solves the problem of high K value reject ratio caused by high-temperature and high-pressure clamp formation of the soft-package battery cell; in the process of the formation process, a smaller surface pressure is applied to the surface of the battery cell, so that the interlayer spacing between the anode and the cathode and the diaphragm can be reduced, the migration path of lithium ions in the formation process is further reduced, the film forming quality is improved, the internal activity of the battery cell can be improved by controlling the temperature of the clamping plate, and the migration difficulty of the lithium ions is reduced; the invention has the advantages of high SEI film forming quality, difficult deformation of the cell main body and stable cell K value.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a formation method for improving a K value of a soft package battery cell.
Background
As the market demands for high energy density increase day by day, the thickness of the separator of the lithium ion battery also needs to be thinner, but the thin separator has the following problems: on one hand, the thinner diaphragm is subjected to mechanical stress, the generated elastic deformation is larger, the internal stress generated by the diaphragm in the cell winding process is larger, and in the formation process, the internal stress of the cell is further increased due to the expansion of the pole piece, and cannot be released, so that the cell deformation is caused, the interlayer spacing of the positive electrode, the negative electrode and the diaphragm of the cell is increased, and the problems of black spots, lithium precipitation, cell body deformation and the like of an interface are caused; on the other hand, thin membranes are prone to puncture by burrs and dust due to poor mechanical strength, resulting in poor K values.
At present, there are two main formation modes for lithium ion soft-package battery cell: ordinary-temperature normal-pressure common formation and high-temperature high-pressure clamp formation; the problems of poor film forming of an SEI film, deformation of a cell main body, insufficient hardness of the cell main body, black spots on an interface, lithium precipitation and the like easily occur in normal temperature and normal pressure general formation; and the problem of poor K value of the battery cell is easily caused by the formation of the high-temperature and high-pressure clamp.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a formation method for improving the K value of a soft-package battery cell.
The invention is realized by the following steps:
step 1, placing a soft-packaged battery cell between clamping plates of a clamp formation cabinet, and setting the surface pressure and the temperature of the battery cell to reduce the interlayer spacing between a positive electrode and a negative electrode of the battery cell and a diaphragm to obtain a first battery cell;
step 2, placing the first battery cell obtained in the step 1 in a clamp formation cabinet for standing for 20min, and sequentially performing first-stage charge and discharge, second-stage charge and discharge and third-stage charge and discharge on the first battery cell by adopting currents with different magnitudes to obtain a second battery cell;
and 3, placing the second battery cell obtained in the step 2 into a shaping clamp, adjusting the battery cell surface pressure of the shaping clamp, placing the shaping clamp with the second battery cell in an oven for baking and shaping, and cooling in the environment after shaping to obtain a formed battery cell.
In the scheme, the cell surface pressure in the step 1 is 0.01-0.05 Mpa.
In the scheme, the temperature of the clamping plate in the step 1 is 45-55 ℃.
In the scheme, the first-stage charging and discharging in the step 2 adopts a current of 0.02C for constant current charging to 3.3V, and the charging cut-off time is 80 min.
In the scheme, the second-stage charging and discharging in the step 2 adopts a current of 0.1C for constant current charging to 3.5V, and the charging cut-off time is 40 min.
In the scheme, the third-stage charging and discharging in the step 2 adopts a current constant current of 0.5C to charge to 3.95V, the charge cut-off time is 80min, and the cut-off current is 0.02C.
In the scheme, the cell surface pressure in the step 3 is 0.8-1.5 Mpa, the baking temperature is 85 ℃, and the baking time is 2.5 hours.
In the scheme, the cooling temperature in the step 3 is 15 ℃, and the cooling time is 2 h.
Compared with the prior art, the invention provides a formation method for improving the K value of a soft package battery cell, which comprises the following steps: step 1, placing a soft-packaged battery cell between clamping plates of a clamp formation cabinet, and controlling interlayer spacing between a positive electrode and a negative electrode of the battery cell and a diaphragm to be reduced to obtain a first battery cell; step 2, placing the first battery cell in a clamp formation cabinet, standing for 20min, and sequentially performing first-stage charge and discharge, second-stage charge and discharge and third-stage charge and discharge on the first battery cell by adopting currents of different magnitudes to obtain a second battery cell; step 3, placing the second battery cell into a shaping fixture, placing the shaping fixture into an oven for baking and shaping, and cooling in the environment after shaping to obtain a formed battery cell; in the formation process, a smaller surface pressure is applied to the surface of the battery cell, so that the interlayer spacing between the positive electrode and the diaphragm, the negative electrode and the diaphragm can be reduced, the migration path of lithium ions in the formation process is further reduced, the film forming quality is improved, the internal activity of the battery cell can be improved by controlling the temperature of the clamping plate, the migration difficulty of the lithium ions is reduced, formation is carried out in three steps, small-current charging is adopted in the early formation stage, namely the first-stage charging and discharging process, a compact SEI film is favorably formed on the surface of a pole piece, the charging current is gradually increased, large-current charging is adopted in the later formation stage, namely the third-stage charging and discharging process, and the formation time can be saved; in addition, by controlling the baking temperature and the cooling temperature, the thickness of the battery cell can be controlled within a specification range while the battery cell is ensured to be smooth in appearance; the invention has the advantages of high SEI film forming quality, difficult deformation of the cell main body and stable cell K value.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The embodiment of the invention provides a formation method for improving a K value of a soft-package battery cell, which is realized by the following steps:
step 1, placing a soft-packaged battery cell between clamping plates of a clamp formation cabinet, setting the temperature of the clamping plates to be 45-55 ℃, applying a battery cell surface pressure of 0.01-0.05 Mpa to the surface of the battery cell, and controlling the interlayer spacing between a positive electrode and a negative electrode of the battery cell and a diaphragm to be reduced to obtain a first battery cell;
the small cell surface pressure is adopted for processing, so that the interlayer spacing of the anode, the cathode and the diaphragm can be reduced, and the migration path of lithium ions in the formation process is further shortened, thereby improving the film forming quality; moreover, the smaller interlayer spacing can ensure that the diaphragm is well bonded with the pole piece, so that the hardness and the flatness of the cell body are improved; in addition, the small cell surface pressure can prevent the phenomenon that the K value is bad due to the fact that burrs, particles and the like are extruded by the expansion of the positive pole and the negative pole in the formation process of the cell because the pressure of the clamping plate is too large; the temperature of the clamping plate is 45-55 ℃, the surface temperature of the battery cell can be increased, so that the internal activity of the battery cell is improved, and the migration difficulty of lithium ions is further reduced;
step 2, placing the first battery cell obtained in the step 1 in a clamp formation cabinet for standing for 20min, and sequentially performing first-stage charge and discharge, second-stage charge and discharge and third-stage charge and discharge on the first battery cell by adopting currents with different magnitudes to obtain a second battery cell;
specifically, placing the first battery cell in a clamp formation cabinet and standing for 20 min; the formation process specifically comprises the following steps: firstly, in the first stage of charging and discharging, the constant current charging is carried out to 3.3V by adopting the current with the capacity value of 0.02 time of the battery, and the charging cut-off time is 80 min; then, in the second stage of charging and discharging, the constant current charging is carried out to 3.5V by adopting the current with the capacity value of 0.1 time of the battery, and the charging cut-off time is 40 min; finally, in the third stage, the charging and discharging are carried out by adopting the constant current charging of the current with the capacity value of 0.5 time of the battery to 3.95V, the charging cut-off time is 80min, and the cut-off current is 0.02C;
the formation early stage, namely the first-stage charging and discharging process, adopts low-current charging, which is beneficial to forming a compact SEI film on the surface of the pole piece, and the formation later stage, namely the third-stage charging and discharging process, adopts high-current charging, which can save the formation time;
step 3, placing the second battery cell obtained in the step 2 into a shaping clamp, adjusting the battery cell surface pressure of the shaping clamp to be 0.8-1.5 Mpa, placing the shaping clamp with the second battery cell in an oven, baking for 2.5 hours at the baking temperature of 85 ℃, cooling for 2 hours at the environment of 15 ℃ after shaping, and obtaining a formed battery cell;
through control baking temperature and cooling temperature, can be when guaranteeing that electric core outward appearance is smooth, with electric core thickness control in specification range.
Compared with the prior art, the invention provides a formation method for improving the K value of the soft-package battery cell, solves the problems of poor film formation of an SEI film formed by normal pressure formation of the soft-package battery cell, insufficient deformation and hardness of a battery cell main body, black spots on an interface, lithium precipitation and the like, and also solves the problem of high K value reject ratio caused by formation of a high-temperature high-pressure clamp of the soft-package battery cell; in the process of operation of the formation process, a smaller surface pressure is applied to the surface of the battery cell, so that the interlayer spacing between the anode and the cathode and the diaphragm can be reduced, the migration path of lithium ions in the formation process is further reduced, the film forming quality is improved, the internal activity of the battery cell can be improved by controlling the temperature of the clamping plate, the migration difficulty of the lithium ions is reduced, formation is carried out in three steps, small-current charging is adopted in the early formation stage, namely the first-stage charging and discharging process, a compact SEI film is formed on the surface of a pole piece, the charging current is gradually increased, large-current charging is adopted in the later formation stage, namely the third-stage charging and discharging process, and the formation time can be saved; in addition, by controlling the baking temperature and the cooling temperature, the thickness of the battery cell can be controlled within a specification range while the battery cell is ensured to be smooth in appearance; the invention has the advantages of high SEI film forming quality, difficult deformation of the cell main body and stable cell K value.
Example 1
Step 1, forming a battery cell with the model of 415879 and the capacity of 3000mAh after liquid injection, placing 4 battery cells on each layer between clamping plates of a clamp forming cabinet, setting the temperature of the clamping plates to be 45 ℃, applying a battery cell surface pressure of 0.01Mpa to the surface of the battery cell, and controlling the interlayer spacing between a positive electrode and a negative electrode of the battery cell and a diaphragm to be reduced to obtain a first battery cell;
step 2, placing the first battery cell obtained in the step 1 in a clamp formation cabinet for standing for 20min, and setting formation process steps to carry out formation, wherein the formation process steps specifically comprise: firstly, in the first stage of charging and discharging, the constant current charging is carried out to 3.3V by adopting the current with the capacity value of 0.02 time of the battery, and the charging cut-off time is 80 min; then, in the second stage of charging and discharging, the constant current charging is carried out to 3.5V by adopting the current with the capacity value of 0.1 time of the battery, and the charging cut-off time is 40 min; finally, in the third stage, the charging and discharging are carried out by adopting the constant current charging of the current with the capacity value of 0.5 time of the battery to 3.95V, the charging cut-off time is 80min, and the cut-off current is 0.02C; operating a formation process step;
and 3, after the formation process is finished, taking out the second battery cell, putting the second battery cell into a shaping clamp, adjusting the surface pressure of the battery cell of the shaping clamp to be 1Mpa, then putting the whole clamp and the battery cell into an oven, baking the whole clamp and the battery cell for 2.5 hours at the baking temperature of 85 ℃, and cooling the whole clamp and the battery cell for 2 hours in the environment of 15 ℃ after shaping to obtain the formed battery cell.
In addition, after the formed battery core is placed in an environment at 45 ℃ for aging for 24 hours, the open-circuit voltage OCV1 of the battery core is tested after the battery core is cooled to room temperature, the open-circuit voltage OCV2 of the battery core is tested after the battery core is placed at the room temperature for 48 hours, and finally the K value of the battery core of the embodiment is calculated.
Example 2
Step 1, forming a battery cell with the model of 415879 and the capacity of 3000mAh after liquid injection, placing 4 battery cells on each layer between clamping plates of a clamp forming cabinet, setting the temperature of the clamping plates to be 45 ℃, applying a battery cell surface pressure of 0.05Mpa to the surface of the battery cell, and controlling the interlayer spacing between a positive electrode and a negative electrode of the battery cell and a diaphragm to be reduced to obtain a first battery cell;
step 2, placing the first battery cell obtained in the step 1 in a clamp formation cabinet for standing for 20min, and setting formation process steps to carry out formation, wherein the formation process steps specifically comprise: firstly, in the first stage of charging and discharging, the constant current charging is carried out to 3.3V by adopting the current with the capacity value of 0.02 time of the battery, and the charging cut-off time is 80 min; then, in the second stage of charging and discharging, the constant current charging is carried out to 3.5V by adopting the current with the capacity value of 0.1 time of the battery, and the charging cut-off time is 40 min; finally, in the third stage, the charging and discharging are carried out by adopting the constant current charging of the current with the capacity value of 0.5 time of the battery to 3.95V, the charging cut-off time is 80min, and the cut-off current is 0.02C; operating a formation process step;
and 3, after the formation process is finished, taking out the second battery cell, putting the second battery cell into a shaping clamp, adjusting the surface pressure of the battery cell of the shaping clamp to be 0.8Mpa, then putting the whole clamp and the battery cell into an oven, baking the whole clamp and the battery cell for 2.5 hours at the baking temperature of 85 ℃, cooling the whole clamp and the battery cell for 2 hours at the environment of 15 ℃ after shaping, and obtaining the formed battery cell.
In addition, after the formed battery core is placed in an environment at 45 ℃ for aging for 24 hours, the open-circuit voltage OCV1 of the battery core is tested after the battery core is cooled to room temperature, the open-circuit voltage OCV2 of the battery core is tested after the battery core is placed at the room temperature for 48 hours, and finally the K value of the battery core of the embodiment is calculated.
Example 3
Step 1, forming a battery cell with the model of 415879 and the capacity of 3000mAh after liquid injection, placing 4 battery cells on each layer between clamping plates of a clamp forming cabinet, setting the temperature of the clamping plates to be 55 ℃, applying a battery cell surface pressure of 0.01Mpa to the surface of the battery cell, and controlling the interlayer spacing between a positive electrode and a negative electrode of the battery cell and a diaphragm to be reduced to obtain a first battery cell;
step 2, placing the first battery cell obtained in the step 1 in a clamp formation cabinet for standing for 20min, and setting formation process steps to carry out formation, wherein the formation process steps specifically comprise: firstly, in the first stage of charging and discharging, the constant current charging is carried out to 3.3V by adopting the current with the capacity value of 0.02 time of the battery, and the charging cut-off time is 80 min; then, in the second stage of charging and discharging, the constant current charging is carried out to 3.5V by adopting the current with the capacity value of 0.1 time of the battery, and the charging cut-off time is 40 min; finally, in the third stage, the charging and discharging are carried out by adopting the constant current charging of the current with the capacity value of 0.5 time of the battery to 3.95V, the charging cut-off time is 80min, and the cut-off current is 0.02C; operating a formation process step;
and 3, after the formation process is finished, taking out the second battery cell, putting the second battery cell into a shaping clamp, adjusting the surface pressure of the battery cell of the shaping clamp to be 1.5Mpa, then putting the whole clamp and the battery cell into an oven, baking the whole clamp and the battery cell for 2.5 hours at the baking temperature of 85 ℃, cooling the whole clamp and the battery cell for 2 hours at the environment of 15 ℃ after shaping, and obtaining the formed battery cell.
In addition, after the formed battery core is placed in an environment at 45 ℃ for aging for 24 hours, the open-circuit voltage OCV1 of the battery core is tested after the battery core is cooled to room temperature, the open-circuit voltage OCV2 of the battery core is tested after the battery core is placed at the room temperature for 48 hours, and finally the K value of the battery core of the embodiment is calculated.
Comparative example 1
Forming by using a liquid-injected battery cell with the model of 415879 and the capacity of 3000mAh, placing 4 battery cells in each layer between clamping plates of a clamp forming cabinet, and forming at the room temperature of 25 ℃; wherein the formation steps are as follows: laying aside for 10 min; ② charging to 3.4V at constant current of 0.02C, and stopping for 240 min; and fourthly, charging to 3.95V at constant current and constant voltage of 0.1C, with the cut-off time of 480min and the cut-off current of 0.02C. After the formation process step operation is finished, the battery core is taken out, the shaping fixture is placed in the shaping fixture, the surface pressure of the battery core is set to be 1Mpa, then the whole fixture and the battery core are placed in an oven at 85 ℃ for shelving for 4 hours, and then the battery core is placed in a cooling chamber at 15 ℃ for cooling for 2 hours.
In addition, after the formed battery core is placed in an environment at 45 ℃ for aging for 24 hours, the open-circuit voltage OCV1 of the battery core is tested after the battery core is cooled to room temperature, the open-circuit voltage OCV2 of the battery core is tested after the battery core is placed at the room temperature for 48 hours, and finally the K value of the battery core of the embodiment is calculated.
Comparative example 2
Step 1, forming a battery cell with the model of 415879 and the capacity of 3000mAh after liquid injection, placing 4 battery cells on each layer between clamping plates of a clamp forming cabinet, setting the temperature of the clamping plates to be 55 ℃, applying a battery cell surface pressure of 1Mpa to the surface of the battery cell, and controlling the interlayer spacing between a positive electrode and a negative electrode of the battery cell and a diaphragm to be reduced to obtain a first battery cell;
step 2, placing the first battery cell obtained in the step 1 in a clamp formation cabinet for standing for 20min, and setting formation process steps to carry out formation, wherein the formation process steps specifically comprise: firstly, in the first stage of charging and discharging, the constant current charging is carried out to 3.3V by adopting the current with the capacity value of 0.02 time of the battery, and the charging cut-off time is 80 min; then, in the second stage of charging and discharging, the constant current charging is carried out to 3.5V by adopting the current with the capacity value of 0.1 time of the battery, and the charging cut-off time is 40 min; finally, in the third stage, the charging and discharging are carried out by adopting the constant current charging of the current with the capacity value of 0.5 time of the battery to 3.95V, the charging cut-off time is 80min, and the cut-off current is 0.02C; operating a formation process step;
and 3, after the formation process is finished, taking out the second battery cell, putting the second battery cell into a shaping clamp, adjusting the surface pressure of the battery cell of the shaping clamp to be 1Mpa, then putting the whole clamp and the battery cell into an oven, baking the whole clamp and the battery cell for 2.5 hours at the baking temperature of 85 ℃, and cooling the whole clamp and the battery cell for 2 hours in the environment of 15 ℃ after shaping to obtain the formed battery cell.
In addition, after the formed battery core is placed in an environment at 45 ℃ for aging for 24 hours, the open-circuit voltage OCV1 of the battery core is tested after the battery core is cooled to room temperature, the open-circuit voltage OCV2 of the battery core is tested after the battery core is placed at the room temperature for 48 hours, and finally the K value of the battery core of the embodiment is calculated.
The properties of the cells obtained in example 1, example 2, example 3, comparative example 1 and comparative example 2 were compared as follows:
from the above table, the formation method of the invention can solve the problems of poor film formation of the SEI film formed by normal pressure formation of the soft package battery core, insufficient deformation and hardness of the battery core main body, black spots on the interface, lithium precipitation and poor K value, and can improve the appearance and hardness of the battery core.
In summary, the invention provides a formation method for improving the K value of a soft package battery cell, in the operation process of the formation step, a smaller surface pressure is applied to the surface of the battery cell, so that the interlayer spacing between a positive electrode and a negative electrode and a diaphragm can be reduced, the migration path of lithium ions in the formation process is further reduced, the film formation quality is improved, the internal activity of the battery cell can be improved by controlling the temperature of a clamping plate, the migration difficulty of the lithium ions is reduced, the formation is carried out in three steps, a compact SEI film is formed on the surface of a pole piece in the early formation stage, namely the first-stage charge-discharge process, the charging current is gradually increased, a large current is used for charging in the late formation stage, namely the third-stage charge-discharge process, and the formation time can be saved; in addition, by controlling the baking temperature and the cooling temperature, the thickness of the battery cell can be controlled within a specification range while the battery cell is ensured to be smooth in appearance; the invention has the advantages of high SEI film forming quality, difficult deformation of the cell main body and stable cell K value.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention.
Claims (8)
1. A formation method for improving a K value of a soft package battery cell is characterized by comprising the following steps:
step 1, placing a soft-packaged battery cell between clamping plates of a clamp formation cabinet, setting a battery cell surface pressure and a clamping plate temperature to control the reduction of interlayer spacing between a positive electrode and a negative electrode of the battery cell and a diaphragm, and obtaining a first battery cell;
step 2, placing the first battery cell obtained in the step 1 in a clamp formation cabinet for standing for 20min, and sequentially performing first-stage charge and discharge, second-stage charge and discharge and third-stage charge and discharge on the first battery cell by adopting currents with different magnitudes to obtain a second battery cell;
and 3, placing the second battery cell obtained in the step 2 into a shaping clamp, adjusting the battery cell surface pressure of the shaping clamp, placing the shaping clamp with the second battery cell in an oven for baking and shaping, and cooling in the environment after shaping to obtain a formed battery cell.
2. The formation method for improving the K value of the soft package cell according to claim 1, wherein the cell surface pressure in the step 1 is 0.01 to 0.05 MPa.
3. The formation method for improving the K value of the soft package core according to claim 2, wherein the temperature of the clamping plate in the step 1 is 45-55 ℃.
4. The formation method for improving the K value of the soft package cell according to any one of claims 1 to 3, wherein the first stage of charging and discharging in the step 2 is charging to 3.3V by using a current constant current of 0.02C, and the charge cut-off time is 80 min.
5. The formation method for improving the K value of the soft package cell according to claim 4, wherein the second stage of charging and discharging in the step 2 is performed by constant current charging to 3.5V with a current of 0.1C, and the charge cut-off time is 40 min.
6. The formation method for improving the K value of the soft package cell according to claim 5, wherein the third stage of charging and discharging in the step 2 is charging to 3.95V by using a current constant current of 0.5C, the charge cut-off time is 80min, and the cut-off current is 0.02C.
7. The formation method for improving the K value of the soft package battery cell according to claim 6, wherein the cell surface pressure in the step 3 is 0.8-1.5 Mpa, the baking temperature is 85 ℃, and the baking time is 2.5 h.
8. The formation method for improving the K value of the soft package core according to claim 7, wherein the cooling temperature in the step 3 is 15 ℃ and the cooling time is 2 h.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111384459A (en) * | 2020-03-23 | 2020-07-07 | 时代上汽动力电池有限公司 | Method for judging blockage of negative pressure channel formed by electrical core formation |
| CN111653730A (en) * | 2020-06-12 | 2020-09-11 | 华鼎国联四川动力电池有限公司 | Method for double heat treatment and rapid formation of battery cell coated with artificial SEI film negative pole piece |
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