CN116470003A - Pre-lithiated negative electrode piece and lithium ion battery - Google Patents
Pre-lithiated negative electrode piece and lithium ion battery Download PDFInfo
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- CN116470003A CN116470003A CN202310253471.2A CN202310253471A CN116470003A CN 116470003 A CN116470003 A CN 116470003A CN 202310253471 A CN202310253471 A CN 202310253471A CN 116470003 A CN116470003 A CN 116470003A
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 51
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 51
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 115
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 115
- 239000002245 particle Substances 0.000 claims abstract description 66
- 239000000843 powder Substances 0.000 claims abstract description 55
- 239000011248 coating agent Substances 0.000 claims abstract description 30
- 238000000576 coating method Methods 0.000 claims abstract description 30
- 239000007773 negative electrode material Substances 0.000 claims abstract description 26
- 238000009792 diffusion process Methods 0.000 claims abstract description 21
- 239000010405 anode material Substances 0.000 claims abstract description 9
- 239000010406 cathode material Substances 0.000 claims abstract description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 12
- 239000011149 active material Substances 0.000 claims description 7
- 229910021383 artificial graphite Inorganic materials 0.000 claims description 4
- 229910052799 carbon Inorganic materials 0.000 claims description 3
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 2
- HMDDXIMCDZRSNE-UHFFFAOYSA-N [C].[Si] Chemical compound [C].[Si] HMDDXIMCDZRSNE-UHFFFAOYSA-N 0.000 claims description 2
- 239000003575 carbonaceous material Substances 0.000 claims description 2
- 229910021385 hard carbon Inorganic materials 0.000 claims description 2
- 239000004005 microsphere Substances 0.000 claims description 2
- 229910021382 natural graphite Inorganic materials 0.000 claims description 2
- 229910021384 soft carbon Inorganic materials 0.000 claims description 2
- 238000000034 method Methods 0.000 abstract description 21
- 238000006138 lithiation reaction Methods 0.000 description 25
- 229910052751 metal Inorganic materials 0.000 description 17
- 239000002184 metal Substances 0.000 description 17
- 230000008569 process Effects 0.000 description 12
- 238000006243 chemical reaction Methods 0.000 description 9
- 238000005096 rolling process Methods 0.000 description 9
- 230000000052 comparative effect Effects 0.000 description 8
- 230000001276 controlling effect Effects 0.000 description 8
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 7
- 239000011889 copper foil Substances 0.000 description 7
- 238000001556 precipitation Methods 0.000 description 7
- DCAYPVUWAIABOU-UHFFFAOYSA-N hexadecane Chemical compound CCCCCCCCCCCCCCCC DCAYPVUWAIABOU-UHFFFAOYSA-N 0.000 description 6
- 239000007774 positive electrode material Substances 0.000 description 6
- 238000007667 floating Methods 0.000 description 5
- 229910002804 graphite Inorganic materials 0.000 description 5
- 239000010439 graphite Substances 0.000 description 5
- 230000006872 improvement Effects 0.000 description 5
- 238000002347 injection Methods 0.000 description 5
- 239000007924 injection Substances 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 239000003792 electrolyte Substances 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 238000002484 cyclic voltammetry Methods 0.000 description 3
- 230000002427 irreversible effect Effects 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 239000000654 additive Substances 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000005520 cutting process Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000009831 deintercalation Methods 0.000 description 2
- 239000011267 electrode slurry Substances 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 239000011888 foil Substances 0.000 description 2
- 238000009830 intercalation Methods 0.000 description 2
- 230000002687 intercalation Effects 0.000 description 2
- 239000004973 liquid crystal related substance Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 230000001502 supplementing effect Effects 0.000 description 2
- 238000010998 test method Methods 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 239000006183 anode active material Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000012790 confirmation Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 239000002270 dispersing agent Substances 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000007770 graphite material Substances 0.000 description 1
- 230000037427 ion transport Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
- 150000002642 lithium compounds Chemical class 0.000 description 1
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 1
- 229910052976 metal sulfide Inorganic materials 0.000 description 1
- 238000002161 passivation Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000027756 respiratory electron transport chain Effects 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/366—Composites as layered products
-
- 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
Abstract
The invention discloses a pre-lithiated negative electrode piece and a lithium ion battery, comprising a lithium powder layer coated on the surface of the negative electrode piece; which meets the following requirements: (D1×W1)/(D2×εxW2×Ks×10) of 0.1 9 ) Less than or equal to 20; wherein D1 is the granularity D50 of the lithium powder particles, and the unit is mu m; w1 is the coating amount of lithium powder particles in unit area, wherein the coating amount only comprises lithium powder particles, and the unit is g/m 2 The method comprises the steps of carrying out a first treatment on the surface of the D2 is the particle size D50 of the negative electrode material in μm; epsilon is the porosity of the negative electrode plate; w2 is the coating amount of the cathode material per unit area, and the unit is g/m 2 The method comprises the steps of carrying out a first treatment on the surface of the Ks is the lithium ion diffusion coefficient of the anode material, and the unit is m 2 /s。
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a pre-lithiated negative electrode plate and a lithium ion battery.
Background
The statements herein merely provide background information related to the present disclosure and may not necessarily constitute prior art.
With the use of lithium ion batteries in electric vehicles, smart grids, distributed energy storage and other scenes, people put forward higher requirements on the cycle life of the lithium ion batteries. However, in the first charge and discharge process of the lithium ion battery, serious irreversible capacity loss exists generally, mainly because a large amount of active lithium is consumed by forming an SEI film on the surface of the negative electrode. The most widely used graphite materials at present have the first irreversible lithium loss of more than 6%, and for silicon-based and tin-based alloy cathodes with high specific capacity, the first irreversible lithium loss is even more than 10% -20%. Pre-lithiation compensates for the first capacity loss of the battery by storing lithium ions in the electrode in advance, and can effectively improve the capacity and cycle stability of the battery, so the pre-lithiation technique is considered as an effective solution to solve the negative lithium loss.
The main current prelithiation schemes are mainly divided into positive electrode prelithiation and negative electrode prelithiation. The positive electrode prelithiation mainly adopts a lithium-rich material or a binary lithium compound as a prelithiation additive, but the material generally has the defects of poor stability, high-pressure decomposition requirement, low lithiation efficiency and the like. The negative electrode pre-lithiation mainly comprises a plurality of pre-lithiation modes such as metal lithium physical mixing pre-lithiation, self-discharge lithiation, chemical pre-lithiation, electrochemical lithiation and the like, wherein the research based on the metal lithium physical mixing pre-lithiation technology is relatively extensive. Although the lithium efficiency by the metal lithium prelithiation is higher compared with the positive electrode prelithiation additive, the metal lithium still cannot be fully embedded into the negative electrode material in the prelithiation process, and a passivation layer is formed on the surface of the non-embedded part so as to lose the electronic conductivity, thereby becoming dead lithium and causing serious potential safety hazard.
Disclosure of Invention
Aiming at the defects existing in the prior art, the invention aims to provide a pre-lithiated negative electrode plate and a lithium ion battery.
In order to achieve the above object, the present invention is realized by the following technical scheme:
in a first aspect, the invention provides a pre-lithiated negative electrode sheet comprising a lithium powder layer coated on the surface of the negative electrode sheet; which meets the following requirements:
0.1≤(D1×W1)/(D2×ε×W2×Ks×10 9 )≤20；
wherein D1 is the granularity D50 of the lithium powder particles, and the unit is mu m;
w1 is the coating amount of lithium powder particles in unit area, wherein the coating amount only comprises lithium powder particles, and the unit is g/m 2 ；
D2 is the particle size D50 of the negative electrode material in μm;
epsilon is the porosity of the negative electrode plate;
w2 is the coating amount of the cathode material per unit area, and the unit is g/m 2 ；
Ks is the lithium ion diffusion coefficient of the anode material, and the unit is m 2 /s。
After liquid injection, due to potential difference between metal lithium and the negative electrode material, electrons in the metal lithium are inserted into the negative electrode material under the potential, lithium ions are extracted from lithium metal and migrate to the negative electrode material through electrolyte to reach charge balance, and finally the negative electrode material is pre-lithiated. The larger the particle size of the lithium powder particles is, the lower the efficiency of converting metal lithium into lithium ions in the pre-lithiation process is, the surface of unconverted metal lithium can form a SEI film, the electron transfer function is lost, and the SEI film is remained on the surface of a negative electrode material to further influence the safety performance of the battery cell.
The coating amount W1 of the lithium powder particles and the coating amount W2 of the anode material jointly influence the proportion of active lithium in the anode material after pre-lithiation, and the higher the proportion of the active lithium is, the more obvious the cycle performance improvement is. In the pre-lithiation process, when the coating amount of the negative electrode is fixed, the coating amount W1 of the metal lithium is increased after formation, so that the use amount of active lithium in the lithium ion battery core can be increased, the cycle performance of the battery core is improved, and the cycle performance is not obviously improved due to the excessively small coating amount; however, too large coating amount can cause that lithium ions cannot be timely inserted into the anode material during pre-lithiation, but can cause lithium precipitation, thereby affecting the safety performance of the battery cell. Therefore, the appropriate lithium powder coating amount can balance the cycle performance and the safety performance of the battery cell.
Epsilon represents the porosity of the negative electrode plate, and too high porosity can increase the electronic impedance of the negative electrode material and affect the multiplying power and the cycle performance of the battery cell. Too low a porosity reduces the electron impedance of the anode but reduces the ion transport rate, thereby affecting the prelithiation efficiency. Therefore, the proper porosity can balance the electron transmission and the ion transmission in the pre-lithiation process, and the conversion efficiency of the lithium powder particles is improved.
Ks is the lithium ion diffusion coefficient of the negative electrode material, and the larger Ks is more favorable for the deintercalation of lithium ions, the smaller Ks is less favorable for the deintercalation of lithium ions, and the higher the risk of lithium precipitation on the surface of the negative electrode.
Therefore, the particle size of the lithium powder particles, the lithium supplementing amount per unit area, the particle size of the negative electrode material, the negative electrode coating amount per unit area, the porosity of the negative electrode material layer and the diffusion coefficient of the negative electrode material affect the conversion efficiency of the metal lithium during the pre-lithiation, and have obvious influence on the cycle performance and the interface condition of the battery.
Therefore, in the pre-lithiated negative electrode sheet designed according to the present invention, several of the above-described parameters are comprehensively considered, when 0.1.ltoreq.D1×W1)/(D2×ε×W2×Ks×10 is satisfied 9 ) When the relation is less than or equal to 20, the conversion efficiency of the lithium ion battery subjected to pre-lithiation can be optimally matched, the cycle performance of the lithium ion battery is obviously improved, and meanwhile, the lithium ion battery has better safety.
In some embodiments of the invention, when the pre-lithiated pole piece satisfies 0.1 +.ltoreq.D1×W1)/(D2×εxW2×Ks×10 9 ) When less than 1, the lithium supplementing quantity W1 is smaller and the lithium powder particles D1 are smaller, so that the active lithium participating in the pre-lithiation process is reduced, the probability of generating dead lithium is reduced, and the improvement on the cycle performance is not obvious; when the pre-lithiated pole piece satisfies 15 < (D1×W1)/(D2×εxW2×Ks×10) 9 ) When the lithium addition amount W1 is less than or equal to 20, the lithium powder particles D1 are larger, the circulation performance of the battery cell can be obviously improved by increasing the lithium addition amount W1, the risk of generating dead lithium is increased, and the safety performance of the battery cell is reduced. Therefore, the selection of proper design parameters of the pre-lithiated anode is very important for the safety and cycle performance of the cell.
In some embodiments, the pre-lithiated negative electrode sheet meets the following requirements:
1≤(D1×W1)/(D2×ε×W2×Ks×10 9 )≤15。
more preferably, the method comprises the following steps: (D1×W1)/(D2×εxW2×Ks×10) of 1 or less 9 )≤5。
In some embodiments, the particle size D50 of the lithium powder in the lithium powder layer is 3 to 60 μm. The lithium powder with smaller particle size has larger production difficulty and practical application difficulty, the lithium powder with smaller particle size than 3 mu m has higher activity and higher risk during production.
PreferablyThe coating amount of the lithium powder layer per unit area is 1-30 g/m 2 。
In some embodiments, the active material of the negative electrode sheet has a particle size D50 of 1 to 25 μm. The negative electrode particles are in the range, so that the contact point between the negative electrode particles and the lithium is increased, the conversion efficiency of lithium in the pre-lithiation process is improved, and dead lithium is not easy to form.
Preferably, the active material of the negative electrode plate has a coating amount ranging from 60 to 120g/m 2 。
In some embodiments, the porosity of the negative electrode sheet is 10% to 45%.
In some embodiments, the negative electrode sheet has a lithium ion diffusion coefficient of 10 -13 ～10 -12 m 2 /s。
In some embodiments, the active material of the negative electrode sheet is selected from one of artificial graphite, natural graphite, activated carbon, silicon carbon material, hard carbon, soft carbon, mesophase carbon microspheres, lithium titanate, or a combination thereof.
The lithium powder particles include any coatable slurry of lithium-containing powder particles.
In a second aspect, the invention provides a lithium ion battery, wherein the negative electrode plate is the pre-lithiated negative electrode plate.
In some embodiments, the lithium ion battery includes a pre-lithiated negative electrode sheet, a positive electrode sheet, a separator, and an electrolyte;
the positive electrode active material is selected from one or a combination of layered positive electrode active material, spinel-type positive electrode active material, olivine-type positive electrode active material and metal sulfide.
The beneficial effects achieved by one or more embodiments of the present invention described above are as follows:
the negative electrode pre-lithiated pole piece meets the requirement of 0.1-D1 xW 1)/(D2 xepsilon xW 2 xKs x 10 by regulating and controlling the relation between physical parameters of the surface lithium powder particle layer and the active material layer 9 ) The contact sites of the lithium powder particles and the anode active material particles are increased by the relational expression less than or equal to 20, so that the metal lithium source can be rapidly oxidized after the injection liquefaction forming process of the lithium ion battery after the pre-lithiation of the lithium powder particlesThe lithium ion battery is embedded into the anode material, so that the utilization rate of metal lithium can be effectively improved, dead lithium residues are reduced, meanwhile, SEI films generated on the surface of the anode material are more uniform, and the lithium ion battery is guaranteed to have good cycle performance and safety performance.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention.
Fig. 1 is a diagram of a negative electrode lithium-ion battery electrode tab structure according to the present invention.
Detailed Description
It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
The embodiment of the invention provides a lithium ion battery, which comprises a pre-lithiated negative electrode plate, a positive electrode plate, a diaphragm and electrolyte. Adding the positive electrode material, conductive carbon black and a binder into a solvent according to a certain proportion to disperse to obtain positive electrode slurry, and then performing procedures such as coating, rolling and the like to obtain a positive electrode plate; adding the negative electrode material, conductive carbon black, a binder and a dispersing agent into a solvent according to a certain proportion to disperse to obtain negative electrode slurry, then performing procedures such as coating, rolling and the like to obtain a negative electrode plate, and then coating lithium powder particles on the surface of the negative electrode plate to obtain a pre-lithiated negative electrode plate; and assembling the prepared positive electrode plate, the pre-lithiated negative electrode plate and the diaphragm into a battery cell through an assembly mode such as winding or lamination, and then performing procedures such as liquid injection, formation, capacity division and the like to obtain the lithium ion battery.
The invention is further illustrated below with reference to examples.
Example 1
A lithium ion battery comprises a positive electrode plate, a negative electrode plate, a diaphragm between the positive electrode plate and the negative electrode plate and electrolyte. Wherein, the liquid crystal display device comprises a liquid crystal display device,the positive pole piece is obtained by coating lithium iron phosphate serving as a positive active material on an aluminum foil; the negative electrode plate adopts D50 of 19 mu m and lithium ion diffusion coefficient Ks of 6 x 10 -13 m 2 Graphite/s as a negative electrode active material was coated on a copper foil with a single-sided area density of 64g/m 2 Obtaining a negative pole piece with the porosity of 25.4% by controlling the rolling thickness; then the lithium powder particles with the D50 of 20 mu m are coated on the surface of the negative electrode plate, and the density of the coated single-sided surface is 2g/m 2 Obtaining a pre-lithiated negative electrode plate; and then the lithium ion battery is obtained after assembly.
Example 2
The negative electrode plate adopts D50 of 12 mu m and lithium ion diffusion coefficient Ks of 9 x 10 -13 m 2 Graphite/s as a negative electrode active material was coated on a copper foil with a single-sided area density of 64g/m 2 Obtaining a negative pole piece with the porosity of 25.4% by controlling the rolling thickness; then the lithium powder particles with the D50 of 20 mu m are coated on the surface of the negative electrode plate, and the density of the coated single-sided surface is 3g/m 2 。
Other conditions and parameters are identical to those of embodiment 1, and will not be described again here.
Example 3
The negative electrode plate adopts D50 of 8 mu m and lithium ion diffusion coefficient Ks of 10 x 10 -13 m 2 Graphite/s as a negative electrode active material was coated on a copper foil with a single-sided area density of 64g/m 2 Obtaining a negative pole piece with the porosity of 25.4% by controlling the rolling thickness; then the lithium powder particles with the D50 of 10 mu m are coated on the surface of the negative electrode plate, and the density of the coated single-sided surface is 5g/m 2 。
Other conditions and parameters are identical to those of embodiment 1, and will not be described again here.
Example 4
The negative electrode plate adopts a D50 of 25 mu m and a lithium ion diffusion coefficient Ks of 6 x 10 -13 m 2 Graphite/s as a negative electrode active material was coated on a copper foil with a single-sided area density of 64g/m 2 Obtaining a negative pole piece with the porosity of 22.4% by controlling the rolling thickness; then the lithium powder particles with the D50 of 25 mu m are coated on the surface of the negative electrode plate, and the coated single-sided surface is denseDegree of 5g/m 2 。
Other conditions and parameters are identical to those of embodiment 1, and will not be described again here.
Comparative example 1
The negative electrode plate adopts D50 of 19 mu m and lithium ion diffusion coefficient Ks of 6 x 10 -13 m 2 Graphite/s as a negative electrode active material was coated on a copper foil with a single-sided area density of 64g/m 2 Obtaining a negative pole piece with the porosity of 25.4% by controlling the rolling thickness; then the lithium powder particles with the D50 of 20 mu m are coated on the surface of the negative electrode plate, and the density of the coated single-sided surface is 0.1g/m 2 。
Other conditions and parameters are identical to those of embodiment 1, and will not be described again here.
Comparative example 2
The negative electrode plate adopts D50 of 14 mu m and lithium ion diffusion coefficient Ks of 2 x 10 -13 m 2 Artificial graphite/s as negative electrode active material coated on copper foil with a single-sided surface density of 64g/m 2 Obtaining a negative pole piece with the porosity of 25.4% by controlling the rolling thickness; then the lithium powder particles with the D50 of 30 mu m are coated on the surface of the negative electrode plate, and the density of the coated single-sided surface is 5g/m 2 。
Other conditions and parameters are identical to those of embodiment 1, and will not be described again here.
Comparative example 3
The negative electrode plate adopts a D50 of 16 mu m and a lithium ion diffusion coefficient Ks of 1 x 10 -13 m 2 Artificial graphite/s as negative electrode active material coated on copper foil with a single-sided surface density of 64g/m 2 The negative pole piece with the porosity of 36.7% is obtained by controlling the rolling thickness; then the lithium powder particles with the D50 of 30 mu m are coated on the surface of the negative electrode plate, and the density of the coated single-sided surface is 3g/m 2 。
Other conditions and parameters are identical to those of embodiment 1, and will not be described again here.
Performance test:
porosity testing method
Cutting a proper amount of pole pieces, wherein the mass of the pole pieces is recorded as M 0 The method comprises the steps of carrying out a first treatment on the surface of the Measuring the volume V of the pole piece; the saidThe pole piece is placed in a container, hexadecane is arranged in the container, and the pole piece is completely soaked for a certain time; taking out the pole piece, placing the pole piece on filter paper, sucking and wiping the pole piece to constant weight, and measuring the mass M of the pole piece 1 The method comprises the steps of carrying out a first treatment on the surface of the Epsilon= (M) according to the formula 1 -M 0 ) And (5) calculating the porosity epsilon of the pole piece according to the ratio of rho/V multiplied by 100.
The cutting pole piece is a cuboid pole piece, the volume V=length×width×thickness of the pole piece is the thickness of the pole piece minus the thickness of the foil; the hexadecane is analytically pure, and the rho is the density of the hexadecane at normal temperature;
ks test method
For a reversible system controlled by a diffusion step, measuring chemical diffusion coefficient at normal temperature by using a cyclic voltammetry, and assembling negative electrode active material powder into a button cell, wherein the button cell is in a complete delithiation state; cyclic voltammetry (C-V) scanning, scanning speed is 0.1mv/s; and calculated according to the following formula.
Ip＝2.69×10 5 n 3/2 AKs 1/2 v 1/ 2ΔCo (2)
Where Ip is the magnitude of peak current, n is the number of electrons participating in the reaction, a is the electrode area immersed in the solution, ks is the diffusion coefficient of Li in the electrode, v is the scan rate, and Δco is the change in Li concentration before and after the reaction.
Interface effect confirmation: discharging the obtained lithium ion battery to a discharge cut-off voltage at a rate of 0.5C, standing for 30min, then charging to the charge cut-off voltage at a constant current and constant voltage at a rate of 1C, then disassembling the negative electrode plate, and observing the residual floating lithium condition on the surface of the negative electrode plate. The area of the floating lithium area remained on the surface of the negative electrode is less than or equal to 0%, the interface is good, the area of the floating lithium area remained on the surface of the negative electrode is less than 5%, the slight lithium precipitation is considered, the area of the floating lithium area remained on the surface of the negative electrode is 5-50%, the moderate lithium precipitation is considered, and the area of the floating lithium area remained on the surface of the negative electrode is greater than 50%, the serious lithium precipitation is considered.
And (3) cyclic test: and (3) performing a cycle test according to the GB/T31484-2015 'power storage battery cycle life requirement for electric automobile and test method' standard cycle life test requirement.
Specifically, the relevant parameters of examples 1 to 4, comparative examples 1 to 3 and the performance test results under the same conditions are shown in Table 1 below. Wherein, the relation 1 refers to (D1×W1)/(D2×εxW2×Ks×10) 9 ) Is a calculated value of (a).
Table 1 comparison of the comparative properties of examples and comparative examples
As can be seen from table 1, the parameters of the negative electrode active material and the parameters of the lithium powder particle layer in example 1 are satisfied, so that the pre-lithiation effect of the metal lithium powder particles is better (the pre-lithiation effect can be comprehensively determined through the cycle performance and the interface state, and the influence of the influence on the performance is not linear), the full charge interface state of the negative electrode is good, the metal lithium and the negative electrode active material particles have more contact sites, the metal lithium and the negative electrode active material particles can be efficiently and rapidly embedded into the negative electrode particles after liquid injection, the generation of residual dead lithium is obviously reduced, the utilization rate of the metal lithium is effectively improved, the cycle performance of the lithium ion battery is improved, and the safety performance of the battery after pre-lithiation is also improved.
Example 2 reduced the particle size of the anode material particles compared to example 1, increased the utilization of lithium during the prelithiation process, and improved the cycle performance.
Compared with the embodiment 1, the particle sizes of the anode particles and the lithium powder particles are reduced simultaneously, so that the conversion efficiency of the metal lithium is accelerated, the improvement of the cycle performance of the lithium ion battery is facilitated, meanwhile, the coating amount of the lithium powder particles is increased, the available active lithium is increased, and the improvement of the cycle performance of the lithium ion battery is facilitated.
Comparative example 1 compared with example 1, the coating amount of lithium powder particles was reduced, and at the same time, the coating amount of the negative electrode was increased, while the conversion time of metallic lithium was reduced, ensuring good negative electrode interface, but at the same time, the available active lithium was reduced, and the cycle performance of the lithium ion battery could not be effectively improved.
Comparative example 2 compared with example 1, the particle size of lithium powder particles was increased, the coating amount of lithium powder was increased, the contact sites between lithium powder particles and negative electrode particles were decreased, and the diffusion coefficient of the negative electrode was low, the metallic lithium was dissolved after injection, an SEI film was formed on the surface of lithium powder particles, and the electron path between the lithium powder particles and the negative electrode particles was disconnected to form "dead lithium", resulting in low utilization rate of the metallic lithium source and lithium precipitation.
Compared with the embodiment 1, the porosity of the cathode pole piece is increased, the diffusion coefficient is lower, the rapid intercalation of lithium ions is not facilitated, serious lithium precipitation is easy to occur in the process of prelithiation, and the safety performance of the battery cell is seriously reduced.
Therefore, the smaller the lithium powder particles and the cathode particles are, the contact point between the lithium powder particles and the cathode particles is increased, the conversion efficiency of lithium in the pre-lithiation process is improved, and dead lithium is not easy to form. The increased coating amount of the lithium powder particles is beneficial to improving the cycle performance of the lithium ion battery, but if the lithium powder particles cannot be converted in time in the pre-lithiation process, dead lithium can be formed, and the cycle performance and the safety performance of the battery are affected. Meanwhile, the porosity and the diffusion coefficient of the negative electrode plate also have influence on the prelithiation, the porosity is larger, the contact points among the negative electrode particles are fewer, and the diffusion coefficient is lower, so that the rapid intercalation of lithium ions is not facilitated, and the cycle performance and the safety performance of the battery are influenced.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The pre-lithiated negative electrode plate is characterized in that: comprises a lithium powder layer coated on the surface of a negative electrode plate; which meets the following requirements:
0.1≤(D1×W1)/(D2×ε×W2×Ks×10 9 )≤20；
wherein D1 is the granularity D50 of the lithium powder particles, and the unit is mu m;
w1 is the coating amount of lithium powder particles in unit area, wherein only the coating amount is containedLithium-containing powder particles in g/m 2 ；
D2 is the particle size D50 of the negative electrode material in μm;
epsilon is the porosity of the negative electrode plate;
w2 is the coating amount of the cathode material per unit area, and the unit is g/m 2 ；
Ks is the lithium ion diffusion coefficient of the anode material, and the unit is m 2 /s。
2. The prelithiated negative electrode tab of claim 1, wherein: the pre-lithiated negative electrode sheet meets the following requirements: (D1×W1)/(D2×εxW2×Ks×10) of 1 or less 9 ) Less than or equal to 15; preferably 1.ltoreq.D1×W1)/(D2×εxW2×Ks.times.10 9 )≤5。
3. The prelithiated anode tab of claim 1 or 2, wherein: the granularity D50 of the lithium powder in the lithium powder layer is 3-60 mu m.
4. The prelithiated anode tab of claim 1 or 2, wherein: the coating amount of the lithium powder layer per unit area is 1-30 g/m 2 。
5. The prelithiated anode tab of claim 1 or 2, wherein: the granularity D50 of the active material of the negative electrode plate is 1-25 mu m.
6. The prelithiated anode tab of claim 1 or 2, wherein: the coating quantity of the active material of the negative electrode plate is 60-120 g/m 2 。
7. The prelithiated anode tab of claim 1 or 2, wherein: the porosity of the negative electrode plate is 10-45%.
8. The prelithiated anode tab of claim 1 or 2, wherein: the lithium ion diffusion coefficient of the negative electrode plate is 10 -13 ～10 -12 m 2 /s。
9. The prelithiated anode tab of claim 1 or 2, wherein: the active material of the negative electrode plate is selected from one or a combination of artificial graphite, natural graphite, active carbon, silicon carbon material, hard carbon, soft carbon, mesophase carbon microsphere and lithium titanate.
10. A lithium ion battery, characterized in that: the negative electrode plate is the pre-lithiated negative electrode plate.
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| CN116960278A (en) * | 2023-09-20 | 2023-10-27 | 苏州清陶新能源科技有限公司 | Negative pole piece and preparation method thereof |
| CN116960278B (en) * | 2023-09-20 | 2024-01-30 | 苏州清陶新能源科技有限公司 | Negative pole piece and preparation method thereof |
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