CN117664954A - Method for rapidly evaluating cycle performance of lithium iron phosphate material - Google Patents
Method for rapidly evaluating cycle performance of lithium iron phosphate material Download PDFInfo
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- CN117664954A CN117664954A CN202311735128.8A CN202311735128A CN117664954A CN 117664954 A CN117664954 A CN 117664954A CN 202311735128 A CN202311735128 A CN 202311735128A CN 117664954 A CN117664954 A CN 117664954A
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- iron phosphate
- lithium iron
- phosphate material
- battery
- temperature cycle
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- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 title claims abstract description 71
- 239000000463 material Substances 0.000 title claims abstract description 66
- 238000000034 method Methods 0.000 title claims abstract description 22
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 65
- 238000012360 testing method Methods 0.000 claims abstract description 46
- 125000004122 cyclic group Chemical group 0.000 claims abstract description 13
- 229910052742 iron Inorganic materials 0.000 claims description 28
- 238000010998 test method Methods 0.000 claims description 13
- 230000001351 cycling effect Effects 0.000 claims description 12
- 238000007599 discharging Methods 0.000 claims description 8
- 238000011156 evaluation Methods 0.000 abstract description 3
- 239000006229 carbon black Substances 0.000 description 4
- 238000009472 formulation Methods 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 239000003792 electrolyte Substances 0.000 description 3
- 241000488899 Cephalotaxus Species 0.000 description 2
- 239000002033 PVDF binder Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 101150016402 fsn-1 gene Proteins 0.000 description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
- 238000012216 screening Methods 0.000 description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 1
- 229910001416 lithium ion Inorganic materials 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
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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
The invention relates to a method for rapidly evaluating the cycle performance of a lithium iron phosphate material, which comprises the following steps: (1) Respectively preparing standard lithium iron phosphate and lithium iron phosphate to be tested into a full battery N-B and a full battery T-B, respectively testing high-temperature circulation, then disassembling and taking out a negative plate in the battery, and respectively testing the content of iron element; (2) Taking two fresh batteries N-B, wherein one fresh battery is fully charged to 3.65V, the other fresh battery is discharged to 2.0V, disassembling to obtain positive plates, namely P (full) and P (empty), taking a pole piece P (full) as a positive electrode and a pole piece P (empty) as a negative electrode, assembling the symmetric batteries N-B-symmetrically, and performing normal-temperature cyclic test to obtain cyclic attenuation proportion, wherein the cyclic attenuation proportion of T-B is obtained by adopting the same method; and (3) judging the result: judging and evaluating according to the results of the steps (1) and (2). The method for rapidly evaluating the cycle performance of the lithium iron phosphate material can accelerate the evaluation of the lithium iron phosphate material, shortens the evaluation period and is simple.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a method for rapidly evaluating the cycle performance of a lithium iron phosphate material.
Background
Many factors affecting the cycle life of lithium iron phosphate batteries are currently widely known in the industry to have the greatest effect on cycling, among positive, negative, separator and electrolyte, but positive has an effect on cycling tendencies.
The current method for evaluating the circulation of the lithium iron phosphate material is to make a battery to perform a normal-temperature circulation test, wherein the normal-temperature circulation test is generally as follows: the normal temperature 1C is charged and discharged, the 1-time cycle test requires about 3 hours, and the normal temperature cycle test requires 3000 times of cycle tests, namely about 1 year, to obtain the result of the cycle test. The lithium iron phosphate is evaluated and screened through the cycle performance test result, but the material test time is long, and the whole test period is long.
Therefore, a method for relatively rapidly evaluating the cycling performance of lithium iron phosphate materials is needed.
Disclosure of Invention
The invention aims to provide a method for rapidly evaluating the cycle performance of a lithium iron phosphate material, which can rapidly screen the cycle performance of the lithium iron phosphate material.
The invention solves the problems by adopting the following technical scheme: a method for rapidly evaluating the cycle performance of a lithium iron phosphate material, comprising the steps of:
(1) Preparation, testing and disassembly analysis of full cells: preparing a full battery from a standard lithium iron phosphate material N, marking as N-B, testing the high-temperature cycle of the battery N-B, disassembling and taking out a negative plate of the battery N-B after the cycle is carried out for a plurality of times, and testing the content of iron element of the negative plate through ICP, marking as W (iron, N-B-500 times);
preparing a lithium iron phosphate material T to be tested into a full battery, marking as T-B, testing the high-temperature cycle of the battery T-B, disassembling and taking out a negative plate of the battery T-B after the battery T-B is cycled for a plurality of times, testing the content of iron element of the negative plate through ICP, marking as W (iron, T-B-500 times), and the high-temperature cycle test method is the same as the high-temperature cycle test method;
wherein, the N-B and the T-B of the full battery are identical except that the lithium iron phosphate materials are different;
(2) Preparation and testing of symmetrical cells: taking two fresh batteries N-B, fully charging one battery to 3.65V, discharging the other battery to 2.0V, disassembling the two batteries to obtain positive plates, respectively marking the positive plates as P (full) and P (empty), taking the positive plates P (full) as positive poles, taking the positive plates P (empty) as negative poles, assembling the positive plates into symmetrical batteries N-B-symmetrically, performing normal temperature cyclic test, and recording cyclic attenuation proportion after cycling for a plurality of times, and marking the cyclic attenuation proportion as W (N-B-symmetrically);
by adopting the same method, two fresh batteries T-B are prepared to be symmetrical batteries T-B-symmetrically, normal temperature cycle test is carried out, the cycle attenuation proportion is recorded after the two batteries T-B are cycled for a plurality of times and is recorded as W (T-B-symmetry), and the normal temperature cycle test method is the same as the normal temperature cycle test method;
wherein the symmetrical batteries are N-B-symmetrical and T-B-symmetrical, and are identical except for lithium iron phosphate materials;
(3) And (3) judging results: judging according to the results of the steps (1) and (2):
if W (iron, T-B-500 times) is less than or equal to W (iron, N-B-500 times) and W (T-B-symmetry) is less than or equal to W (N-B-symmetry), judging that the cycle performance of the lithium iron phosphate material T to be detected is superior to or equal to that of the standard lithium iron phosphate material N;
if W (iron, T-B-500 times) > W (iron, N-B-500 times) and W (T-B-symmetry) > W (N-B-symmetry), the cycle performance of the lithium iron phosphate material T to be detected can be judged to be worse than that of the standard lithium iron phosphate material N;
if W (iron, T-B-500 times) is less than or equal to W (iron, N-B-500 times) and W (T-B-symmetry) is more than W (N-B-symmetry), judging that the high-temperature cycle performance of the lithium iron phosphate material T to be tested is better than or equal to that of the standard lithium iron phosphate material N, and that the normal-temperature cycle performance of the lithium iron phosphate material T to be tested is worse than that of the standard lithium iron phosphate material N;
if W (iron, T-B-500 times) is more than W (iron, N-B-500 times) and W (T-B-symmetry) is less than or equal to W (N-B-symmetry), the high temperature cycle performance of the lithium iron phosphate material T to be detected is judged to be inferior to that of the standard lithium iron phosphate material N, and the normal temperature cycle performance of the lithium iron phosphate material T to be detected is superior to or equal to that of the standard lithium iron phosphate material N.
Preferably, the number of high temperature cycles in step (1) is 300-500.
Preferably, the normal temperature cycle number in the step (2) is 300-500.
Preferably, the high temperature cycle test in step (1) is specifically: at 45-55deg.C, the charge-discharge current of the battery is 1C, the voltage interval of charge-discharge is set to 2.5-3.65V, and the rest time is 30min after charge and discharge are completed.
Preferably, the normal temperature cycle test in the step (2) specifically includes: the charge and discharge current of the battery is 1C, the voltage interval of charge and discharge is set to 0.5-1.5V, and the battery is kept still for 30min after the charge and the discharge are finished.
Preferably, the cycle-down ratio in step (2) =1-discharge capacity for several cycles/first discharge capacity.
Compared with the prior art, the invention has the advantages that:
the invention provides a method for rapidly evaluating the cycle performance of a lithium iron phosphate material, which shortens the evaluation period of the lithium iron phosphate material, and is simple, easy to operate and realize.
Description of the embodiments
The present invention is described in further detail below with reference to examples.
Example 1
A rapid screening method of lithium iron phosphate materials comprises the following steps:
(1) Preparation, testing and disassembly analysis of full cells: standard lithium iron phosphate materials, defant DY-1, were prepared into 25Ah full cells (positive formulation was 96% lithium iron phosphate Defant DY-1:2% carbon black SP:2% PVDF 5130; negative formulation was 95.5% Cephalotaxus FSN-1:1% carbon black SP:1.5% CMC2200:2% SBR Han Song A301; separator was 16 μm dry Shan Lamo; electrolyte was Tianci E8087), noted DY-1-B, tested for DY-1-B high temperature cycling at 45 ℃ (charge-discharge current was 1C, voltage interval was 2.5-3.65V, charge-discharge ends were all left for 30 min), negative plates of DY-1-B were removed after 500 cycles, and the content of iron element was measured by ICP, noted as W (iron, DY-1-B-500 times) =265 ppm.
The lithium iron phosphate material to be tested is prepared into a 25Ah full battery (Anda B3), the 25Ah full battery is marked as B3-B, the battery B3-B is tested by 45 ℃ high temperature cycle (the high temperature cycle test method is the same as the high temperature cycle test method), the battery B3-B is disassembled and taken out after 500 times of cycle, the negative electrode plate is taken out after disassembly, and the content of iron element is marked as W (iron, B3-B-500 times) =320 ppm by ICP test.
All batteries DY-1-B and B3-B are identical except for the lithium iron phosphate materials.
(2) Preparation and testing of symmetrical cells: taking two fresh DY-1-B batteries, fully charging one battery to 3.65V, discharging the other battery to 2.0V, disassembling the two batteries to obtain positive plates, respectively marking as P (full) and P (empty), taking the positive plate P (full) as positive electrode, taking the positive plate P (empty) as negative electrode, assembling into a symmetrical battery DY-1-B-symmetrical, performing normal temperature cyclic test (charging and discharging current is 1C, voltage interval is 0.5-1.5V, and the charging and discharging ends are all kept still for 30 min) between 0.5-1.5V, testing 500 times, and recording cyclic attenuation proportion, namely W (DY-1-B-symmetrical) =1.5%.
In the same manner, a symmetric battery B3-B-was obtained, and a normal temperature cycle test (the normal temperature cycle test method was the same as that described above) was performed 500 times, and the cycle decay ratio was recorded as W (B3-B-symmetry) =2.5%.
The symmetric batteries DY-1-B-symmetry and B3-B-symmetry are identical except for the lithium iron phosphate materials.
(3) And (3) judging results: judging according to the results of the steps (1) and (2):
since W (iron, B3-B-500 times) > W (iron, DY-1-B-500 times) and W (B3-B-symmetry) > W (DY-1-B-symmetry), the cycling performance of the lithium iron phosphate material B3 to be tested is inferior to that of the standard lithium iron phosphate material DY-1.
Example 2
A rapid screening method of lithium iron phosphate materials comprises the following steps:
(1) Preparation, testing and disassembly analysis of full cells: standard lithium iron phosphate materials, defant DY-1, were prepared into 25Ah full cells (positive formulation was 96% lithium iron phosphate Defant DY-1:2% carbon black SP:2% PVDF 5130; negative formulation was 95.5% Cephalotaxus FSN-1:1% carbon black SP:1.5% CMC2200:2% SBR Han Song A301; separator was 16 μm dry Shan Lamo; electrolyte was Tianci E8087), noted DY-1-B, tested for DY-1-B at 45℃high temperature cycle (charge-discharge current was 1C, voltage interval was 2.5-3.65V, charge-discharge end was all left for 30 min), tested 500 times, disassembled after 500 cycles to remove negative pole pieces disassembled for DY-1-B, and tested for iron element content by ICP, noted as W (iron, DY-1-B-500 times) =265 ppm.
The lithium iron phosphate material to be tested is prepared into a 25Ah full battery (P600 in North Dali), the 25Ah full battery is marked as P600-B, the battery P600-B is tested for 500 times of testing at 45 ℃ high temperature (the high temperature cycle testing method is the same as the high temperature cycle testing method), the battery P600-B in 500 times of cycles is disassembled to take out a negative plate, and the content of iron element is marked as W (iron, P600-B-500 times) =195 ppm by ICP testing.
Full cells DY-1-B and P600-B are identical except for the lithium iron phosphate materials.
(2) Preparation and testing of symmetrical cells: taking two fresh DY-1-B batteries, fully charging one battery to 3.65V, discharging the other battery to 2.0V, disassembling the two batteries to obtain positive plates, respectively marking as P (full) and P (empty), taking the positive plate P (full) as positive electrode, taking the positive plate P (empty) as negative electrode, assembling into a symmetrical battery DY-1-B-symmetrical, performing normal temperature cyclic test (charging and discharging current is 1C, voltage interval is 0.5-1.5V, and the charging and discharging ends are all kept still for 30 min) between 0.5-1.5V, testing 500 times, and recording cyclic attenuation proportion, namely W (DY-1-B-symmetrical) =1.5%.
In the same manner, a symmetrical battery P600-B-was obtained, and a normal temperature cycle test (the normal temperature cycle test method was the same as the above normal temperature cycle test method) was performed 500 times, and the cycle decay ratio was recorded as W (P600-B-symmetry) =1.2%.
The symmetric batteries DY-1-B-symmetry and P600-B-symmetry are identical except for the lithium iron phosphate materials.
(3) And (3) judging results: judging according to the results of the steps (1) and (2):
since W (iron, P600-B-500 times) < W (iron, DY-1-B-500 times), and W (P600-B-symmetry) < W (DY-1-B-symmetry), the cycle performance of the lithium iron phosphate material P600 to be measured is superior to that of the standard lithium iron phosphate material DY-1.
In addition to the above embodiments, the present invention also includes other embodiments, and all technical solutions that are formed by equivalent transformation or equivalent substitution should fall within the protection scope of the claims of the present invention.
Claims (6)
1. A method for rapidly evaluating the cycle performance of a lithium iron phosphate material is characterized by comprising the following steps of: the method comprises the following steps:
(1) Preparation, testing and disassembly analysis of full cells: preparing a full battery from a standard lithium iron phosphate material N, marking as N-B, testing the high-temperature cycle of the battery N-B, disassembling and taking out a negative plate of the battery N-B after the cycle is carried out for a plurality of times, and testing the content of iron element of the negative plate through ICP, marking as W (iron, N-B-500 times);
preparing a lithium iron phosphate material T to be tested into a full battery, marking as T-B, testing the high-temperature cycle of the battery T-B, disassembling and taking out a negative plate of the battery T-B after the battery T-B is cycled for a plurality of times, testing the content of iron element of the negative plate through ICP, marking as W (iron, T-B-500 times), and the high-temperature cycle test method is the same as the high-temperature cycle test method;
wherein, the N-B and the T-B of the full battery are identical except that the lithium iron phosphate materials are different;
(2) Preparation and testing of symmetrical cells: taking two fresh batteries N-B, fully charging one battery to 3.65V, discharging the other battery to 2.0V, disassembling the two batteries to obtain positive plates, respectively marking the positive plates as P (full) and P (empty), taking the positive plates P (full) as positive poles, taking the positive plates P (empty) as negative poles, assembling the positive plates into symmetrical batteries N-B-symmetrically, performing normal temperature cyclic test, and recording cyclic attenuation proportion after cycling for a plurality of times, and marking the cyclic attenuation proportion as W (N-B-symmetrically);
by adopting the same method, two fresh batteries T-B are prepared to be symmetrical batteries T-B-symmetrically, normal temperature cycle test is carried out, the cycle attenuation proportion is recorded after the two batteries T-B are cycled for a plurality of times and is recorded as W (T-B-symmetry), and the normal temperature cycle test method is the same as the normal temperature cycle test method;
wherein the symmetrical batteries are N-B-symmetrical and T-B-symmetrical, and are identical except for lithium iron phosphate materials;
(3) And (3) judging results: judging according to the results of the steps (1) and (2):
if W (iron, T-B-500 times) is less than or equal to W (iron, N-B-500 times) and W (T-B-symmetry) is less than or equal to W (N-B-symmetry), judging that the cycle performance of the lithium iron phosphate material T to be detected is superior to or equal to that of the standard lithium iron phosphate material N;
if W (iron, T-B-500 times) > W (iron, N-B-500 times) and W (T-B-symmetry) > W (N-B-symmetry), the cycle performance of the lithium iron phosphate material T to be detected can be judged to be worse than that of the standard lithium iron phosphate material N;
if W (iron, T-B-500 times) is less than or equal to W (iron, N-B-500 times) and W (T-B-symmetry) is more than W (N-B-symmetry), judging that the high-temperature cycle performance of the lithium iron phosphate material T to be tested is better than or equal to that of the standard lithium iron phosphate material N, and that the normal-temperature cycle performance of the lithium iron phosphate material T to be tested is worse than that of the standard lithium iron phosphate material N;
if W (iron, T-B-500 times) is more than W (iron, N-B-500 times) and W (T-B-symmetry) is less than or equal to W (N-B-symmetry), the high temperature cycle performance of the lithium iron phosphate material T to be detected is judged to be inferior to that of the standard lithium iron phosphate material N, and the normal temperature cycle performance of the lithium iron phosphate material T to be detected is superior to or equal to that of the standard lithium iron phosphate material N.
2. The method for rapidly evaluating the cycling performance of a lithium iron phosphate material according to claim 1, wherein: the high temperature cycle number in the step (1) is 300-500.
3. The method for rapidly evaluating the cycling performance of a lithium iron phosphate material according to claim 1, wherein: the normal temperature cycle time in the step (2) is 300-500 times.
4. The method for rapidly evaluating the cycling performance of a lithium iron phosphate material according to claim 1, wherein: the high-temperature cycle test in the step (1) specifically comprises the following steps: at 45-55deg.C, the charge-discharge current of the battery is 1C, the voltage interval of charge-discharge is set to 2.5-3.65V, and the rest time is 30min after charge and discharge are completed.
5. The method for rapidly evaluating the cycling performance of a lithium iron phosphate material according to claim 1, wherein: the normal temperature cycle test in the step (2) is specifically as follows: the charge and discharge current of the battery is 1C, the voltage interval of charge and discharge is set to 0.5-1.5V, and the battery is kept still for 30min after the charge and the discharge are finished.
6. The method for rapidly evaluating the cycling performance of a lithium iron phosphate material according to claim 1, wherein: the cycle decay ratio=1 in step (2) is the discharge capacity of several cycles/first discharge capacity.
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