Patent Application
20240356010
This application claims the priority benefit of China application serial no. 202310432269.6, filed on Apr. 20, 2023. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.
The invention specifically relates to a lithium supplement agent and a preparation method thereof, an electrochemical device, and an electronic device.
In a lithium-ion battery, the lower initial coulombic efficiency of the positive and negative electrodes determines the initial efficiency of the entire battery. When the efficiency of the positive and negative electrodes is equal, the utilization rate of active lithium in the battery is the highest. The initial efficiency of current commercial systems is limited by the lower initial efficiency of the negative electrode. Therefore, a lot of active Li provided by the positive electrode is consumed, reducing the overall energy density of the battery.
Several widely studied Li-ion supplementary materials currently exist: Li5FeO4(LFO), Li2NiO2(LNO), and Li6CoO4(LCO), which all have extremely high theoretical capacity and extremely poor reversibility (coulombic efficiency<10%), and are therefore ideal lithium supplement additives (i.e., positive electrode lithium supplement agent). However, LFO, LNO, and LCO are unstable in the air, and readily absorb moisture to form residual alkali (Li2CO3, LiOH), which not only reduces the electrochemical activity thereof, but also causes battery gas to form, causing battery swelling and causing safety hazards.
Based on the above studies, it is necessary to provide a lithium supplement agent that may be used as a positive electrode material to achieve better stability and high theoretical capacity, so as to improve the energy density and cycle stability of the battery.
The technical issue to be solved by the invention is to overcome the instability of existing lithium supplement additives in the air, resulting in a decrease in the electrochemical activity thereof. When existing lithium supplement additives are used in a lithium-ion battery, gas production occurs in the battery, thus causing potential safety hazards. A lithium supplement agent and a preparation method thereof, a positive electrode sheet, an electrochemical device, and an electronic device are thus provided. A positive electrode material containing the lithium-supplement agent of the invention has better stability and high theoretical capacity, and is used in a lithium-ion battery to improve the energy density and cycle stability of the battery.
The invention solves the above technical issues via the following technical solutions.
In the first aspect, the invention provides a lithium supplement agent, including a component A and a component B; a general chemical formula of the component A is: Li6-xM11-yN1yO4-z, wherein 0≤x≤5.95, 0≤y≤1, 0≤z≤2, M1 is selected from one or a plurality of Fe, Ni, Co, Cu, Al, Mn, Ti, and Si; N1 is selected from one or a plurality of Fe, Ni, Co, Cu, Al, Mn, Ti, and Si; a general chemical formula of the component B is: Li1+(a/(2+a))Mn2a/(2+a)M26/(2+a)−2O2, 0.2≤a≤1, M2 is selected from one or a plurality of Fe, Ni, Co, Cu, Al, Mn, Ti, Si, Mg, Zr, Nb, La, Sr, and W; the component B is at least partially located at a surface of the component A.
In the second aspect, the invention also provides a preparation method of the lithium supplement agent, including the following steps: mixing and sintering precursors of the component A and the component B to obtain the lithium supplement agent.
In the third aspect, the invention also provides an electrochemical device, including the positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte.
In the fourth aspect, the invention also provides an electronic device, including the positive electrode material or the lithium-ion secondary battery.
In the fifth aspect, the invention also provides a positive electrode material, including an active substance and a lithium supplement agent, and in the positive electrode material, a mass percentage of the lithium supplement agent is 0.5% to 31%.
The positive progress effect of the invention is:
The positive electrode material containing the lithium-supplement agent of the invention has better stability and high theoretical capacity, and is used in a lithium-ion battery to improve the energy density and cycle stability of the battery.
The invention is further illustrated below by means of examples, but the invention is not limited to the scope of the examples. For the experimental methods that do not specify specific conditions in the following examples, selection is made according to conventional methods and conditions, or according to product instructions.
In the lithium supplement agent of the first aspect of the invention,
Preferably, the M1 is Fe, Ni, Co, Cu, Al, Mn, Ti, or Si.
Preferably, the N1 is Fe, Ni, Co, Cu, Al, Mn, Ti, or Si.
Preferably, the M2 is Fe, Ni, Co, Cu, Al, Mn, Ti, Si, Mg, Zr, Nb, La, Sr, or W.
Preferably, the value range of the x is 0≤x≤5, such as 0.4, 0.5, 0.8, 1, 2, or 4.
Preferably, the value range of the y is 0≤y≤0.9, such as 0.2, 0.5, 0.6, or 0.8.
Preferably, the value range of the z is 0≤z≤2, such as 0.4, 0.5, 0.8, 1, or 1.5.
Preferably, the value range of the a is 0.22≤a≤1, such as 0.3, 0.5, 0.7, or 0.8.
Preferably, the component B is at least partially coated at the surface of the component A. Preferably, the mass percentage of the component A to the total mass of “the component A and the component B” is 89% to 99.1%, such as 90%, 92%, 95%, 96%, 97%, 98%, or 99%.
Preferably, the lithium supplement is a core-shell structure. The average particle diameter of the core of the core-shell structure may be 0.5 μm to 15 μm. The average thickness of the shell of the core-shell structure may be 20 nm to 200 nm.
In some preferred embodiments of the invention, the chemical formula of the lithium supplement agent is ALi5+eFe1-eCoeO4@(1-A)Li1.33MnO2 or ALi2Ni1-fCufO2@(1-A)Li1.33MnO2;
The A represents the mass percentage of Li5+eFe1-eCoeO4 in Li5+eFe1-eCoeO4@Li1.33MnO2, or the mass percentage of Li2Ni1-fCufO2 in Li2Ni1-fCufO2@Li1.33MnO2.
In some preferred embodiments of the invention, the value range of the A is preferably 0.89≤A≤0.991, such as 0.9, 0.96, 0.97, 0.98, or 0.99.
In some preferred embodiments of the invention, the value range of the e is 0.2≤e≤1, such as 0.5 or 0.4.
In some preferred embodiments of the invention, the value range of the f is 0.5≤f≤1, such as 0.8.
In some preferred embodiments of the invention, the general chemical formula of the component A is: Li6-xM11-yN1yO4-z, wherein 0≤x≤5.95, 0≤y≤1, 0≤z≤2, M1 is Fe, Ni, Co, Cu, Al, Mn, Ti, or Si; N1 is Fe, Ni, Co, Cu, Al, Mn, Ti, or Si; the general chemical formula of the component B is: Li1+(a/(2+a))Mn2a/(2+a)M26/(2+a)−2O2, 0.2≤a≤1, M2 is Fe, Ni, Co, Cu, Al, Mn, Ti, Si, Mg, Zr, Nb, La, Sr, or W; the component B is at least partially coated at the surface of the component A.
In some preferred embodiments of the invention, the chemical formula of the component A is Li2NiO2, Li2Ni0.5Cu0.5O2, Li2Ni0.8Cu0.2O2, Li2Ni0.4Cu0.6O2, Li2Cu2O2, Li5FeO4, Li5.5Fe0.5Co0.5O4, Li5.2Fe0.8Co0.2O4, Li5.6Fe0.4Co0.6O4, or Li6CoO4; the chemical formula of the component B is Li1.33Mn0.67O2, Li1.26Mn0.63Ni0.11O2, Li1.2Mn0.6Ni0.2O2, or Li1.1Mn0.75Ni0.25O2.
In some preferred embodiments of the invention, the chemical formula of the component A is Li2NiO2, Li2Ni0.5Cu0.5O2, Li2Ni0.8Cu0.2O2, Li2Ni0.4Cu0.6O2, Li2Cu2O2, Li5FeO4, Li5.5Fe0.5Co0.5O4, Li5.2Fe0.8Co0.2O4, Li5.6Fe0.4Co0.6O4, or Li6CoO4; the chemical formula of the component B is Li1.33Mn0.67O2.
In some preferred embodiments of the invention, the chemical formula of the component A is Li2NiO2; the chemical formula of the component B is Li1.26Mn0.63Ni0.11O2, Li1.2Mn0.6Ni0.2O2, or Li1.1Mn0.75Ni0.25O2.
In the preparation method of the lithium supplement agent of the second aspect of the invention, Preferably, the precursors of the component A are firstly sintered to obtain the component A and then mixed with the precursors of the component B.
The precursors of the component A may be conventional precursors in the art that may be prepared to satisfy the general chemical formula of the component A as mentioned above, such as Li2O and NiO, or Fe2O3 and LiOH. Generally, for the amount of each component of the component A, the corresponding stoichiometric amount may be selected according to the chemical formula of the component A to be obtained.
The temperature and time of the primary sintering may be conventional temperature and time in the art. Generally, the desired primary sintering temperature and time are also different according to the type of the precursors of the selected component A. For example, when the precursors of the component A are Li2O and NiO, the temperature of the primary sintering is 600° C., and the time of the primary sintering is 12 hours. When the precursors of the component A are Fe2O3 and LiOH, the primary sintering is performed in two stages, wherein the temperature of the first stage is 450° C., the time of the first stage is 12 h, the temperature of the second stage is 600° C., and the time of the second stage is 24 h.
Preferably, the precursors of the component B may be conventional precursors in the art that may be prepared to satisfy the general chemical formula of the component B, such as MnCO3 and Li2CO3. Generally, for the amount of each component of the component B, the corresponding stoichiometric amount may be selected according to the chemical formula of the component B to be obtained.
Preferably, the temperature and time of the sintering may be the conventional temperature and time in the art. Generally, the desired sintering temperature and time are also different according to the type of the precursors of the selected component B. For example, when the precursors of the component B are MnCO3 and Li2CO3, the temperature of the sintering component is 500° C., and the sintering time is 72 h.
Preferably, the mass percentage of the lithium supplement agent to the total mass of the positive electrode sheet is 0.5% to 31%, such as 0.9%, 1%, 2%, 5%, 10%, 15%, 18%, 20% %, 25%, 28%, or 30%.
Preferably, the lithium iron phosphate is LiFePO4.
Preferably, the lithium manganese iron phosphate is LiMn0.6Fe0.4PO4.
Preferably, the nickel-cobalt-manganese ternary material is LiNi0.9Co0.06Mn0.04O2.
Preferably, the lithium cobaltate is LiCoO2.
Preferably, the lithium-rich manganese-based oxide is Li1.1Ni0.4Mn0.6O2.
Preferably, the lithium nickel manganese oxide is LiNi1.5Mn0.5O4.
In some preferred embodiments of the invention, the active substance is lithium iron phosphate, lithium manganese iron phosphate, nickel-cobalt-manganese ternary material, lithium cobaltate, lithium-rich manganese-based oxide, or lithium manganese nickelate; the chemical formula of the lithium supplement agent is ALi5+eFe1-eCoeO4@(1-A)Li1.33MnO2 or ALi2Ni1-f CufO2@(1-A)Li1.33MnO2;
In particular, 0.8≤A<1; 0≤e≤1; 0≤f≤1; the A represents the mass percentage of Li5+eFe1-eCoeO4 in Li5+eFe1-eCoeO4@Li1.33MnO2, or the mass percentage of Li2Ni1-fCufO2 in Li2Ni1-fCufO2@Li1.33MnO2.
In some preferred embodiments of the invention, the active substance is LiMn0.6Fe0.4PO4, the lithium supplement agent is Li2NiO2@Li1.33Mn0.67O2, Li2Ni0.5Cu0.5O2@Li1.33Mn0.67O2, Li2Ni0.8Cu0.2O2@Li1.33Mn0.67O2, Li2Ni0.4Cu0.6O2@Li1.33Mn0.67O2, Li2Cu2O2@Li1.33Mn0.67O2, Li5FeO4@Li1.33Mn0.67O2, Li5.5Fe0.8Co0.5O4@Li1.33Mn0.67O2, Li5.2Fe0.8Co0.2O4@Li1.33Mn0.67O2, Li5.6Fe0.4Co0.6O4@Li1.33Mn0.67O2, Li6CoO4@Li1.33Mn0.67O2, Li2NiO2@Li1.26Mn0.63Ni0.11O2, Li2NiO2@Li1.2Mn0.6Ni0.2O2, or Li2NiO2@Li1.1Mn0.75Ni0.25O2.
In some preferred embodiments of the invention, the active substance is LiMn0.6Fe0.4PO4, LiFePO4, LiNi0.9Co0.06Mn0.04O2, Li1.1Ni0.4Mn0.6O2, LiCoO2, or LiNi1.5Mn0.5O4, the lithium supplement agent is Li2NiO2@Li1.33Mn0.67O2.
In the preparation method of the positive electrode sheet of the fourth aspect of the invention, Preferably, the positive electrode current collector may be a conventional positive electrode current collector in the art, generally aluminum foil.
Preferably, the drying method may be a conventional method in the art.
Preferably, the drying temperature may be a conventional temperature in the art, such as 120° C.
Preferably, the drying time may be a conventional time in the art, such as 10 minutes.
Preferably, the slurry generally also contains a conductive agent, a solvent, and a binder.
In particular, the conductive agent may be a conventional conductive agent in the art, such as conductive carbon black (Super P).
In particular, the solvent may be a conventional solvent in the art, preferably nitrogen methylpyrrolidone (NMP).
In particular, the adhesive may be a conventional adhesive in the art, such as polyvinylidene fluoride (PVDF).
Preferably, when the slurry contains the active substance, the lithium supplement agent, the conductive agent, and the binder, the mass ratio of “the positive electrode active substance and the lithium supplement agent”, the conductive agent, and the binder is (93-98):(1-4):(1-4), for example, 97:1.5:1.5.
In some preferred embodiments of the invention, the preparation method of the positive electrode sheet includes the following steps: coating the slurry containing the active substance and the lithium supplement agent on at least one surface of the aluminum foil, and drying at 120° C. for 10 minutes.
In the positive electrode material of the seventh aspect of the invention, Preferably, the value range of the A is 0.89≤A≤0.991, such as 0.9, 0.96, 0.97, 0.98, or 0.99.
Preferably, the value range of the e is 0.2≤e≤1, such as 0.5 or 0.4.
Preferably, the value range of the f is 0.5≤f≤1, such as 0.8.
Preferably, in the positive electrode material, the mass percentage of the lithium supplement agent is 0.9% to 31%, such as 1%, 2%, 5%, 10%, 15%, 18%, 20%, 25%, 28%, or 30%.
Preferably, the lithium iron phosphate is LiFePO4.
Preferably, the lithium manganese iron phosphate is LiMn0.6Fe0.4PO4.
Preferably, the nickel-cobalt-manganese ternary material is LiNi0.9Co0.06Mn0.04O2.
Preferably, the lithium cobaltate is LiCoO2.
Preferably, the lithium-rich manganese-based oxide is Li1.1Ni0.4Mn0.6O2.
Preferably, the lithium nickel manganese oxide is LiNi1.5Mn0.5O4.
In some preferred embodiments of the invention, the active substance is LiMn0.6Fe0.4PO4, the lithium supplement agent is Li2NiO2@Li1.33Mn0.67O2, Li2Ni0.5Cu0.5O2@Li1.33Mn0.67O2, Li2Ni0.8Cu0.2O2@Li1.33Mn0.67O2, Li2Ni0.4Cu0.6O2@Li1.33Mn0.67O2, Li2Cu2O2@Li1.33Mn0.67O2, Li5FeO4@Li1.33Mn0.67O2, Li5.5Fe0.5Co0.5O4@Li1.33Mn0.67O2, Li5.2Fe0.8Co0.2O4@Li1.33Mn0.67O2, Li5.6Fe0.4Co0.6O4@Li1.33Mn0.67O2, Li6CoO4@Li1.33Mn0.67O2, Li2NiO2@Li1.26Mn0.63Ni0.11O2, Li2NiO2@Li1.2Mn0.6Ni0.2O2, or Li2NiO2@Li1.1Mn0.75Ni0.25O2.
In some preferred embodiments of the invention, the active substance is LiMn0.6Fe0.4PO4, LiFePO4, LiNi0.9Co0.06Mn0.04O2, Li1.1Ni0.4Mn0.6O2, LiCoO2, or LiNi1.5Mn0.5O4, the lithium supplement agent is Li2NiO2@Li1.33Mn0.67O2.
On the basis of conforming to common knowledge in the art, the above preferred conditions may be combined arbitrarily to obtain preferred examples of the invention.
The preparation process of the lithium supplement in Example 1 was as follows: first the component A was prepared, then the precursors of the component B were mixed with the component A, and the component B was generated at the surface of the component A. Specifically: Li2O and NiO in a stoichiometric ratio were taken, ground and mixed, and then sintered at 600° C. under N2 for 12 h to obtain the component A (Li2NiO2). Then 0.9 M Li2NiO2 was taken and uniformly mixed with the precursors of the component B (0.02 M MnCO3, 0.02 M Li2CO3) and sintered at 500° C. for 72 h to prepare a lithium supplement agent (wherein the component A was partially coated at the surface of the component B, and the chemical formula is expressed as Li2NiO2@Li1.33Mn0.67O2).
Example 1 the positive electrode material in the positive electrode sheet contained LiMn0.6Fe0.4PO4 (the component C, the active substance) and Li2NiO2@Li1.33MnO2 (the component A+the component B, i.e., the lithium supplement agent), wherein the component C accounted for 92.15% of the total mass of “the component A+the component B+the component C+Super P+PVDF”; the mass percentage of “the component A+the component B” to the total mass of “the component A+the component B+the component C” was 5%. The positive electrode material in the positive electrode sheet also contained conductive carbon black (Super P) and polyvinylidene fluoride (PVDF); LiMn0.6Fe0.4PO4 did not react with Li2NiO2@Li1.33MnO2, and the two were only physically mixed; the mass ratio of “the component A+the component B+the component C”, Super P, and PVDF was 97:1.5:1.5.
The preparation method of Example 1 positive electrode sheet included the following steps: first the active substance, Super P, and PVDF were mixed in the above ratio, and then gradually nitrogen methyl pyrrolidone (NMP) was added with high-speed stirring to prepare a positive electrode slurry with a certain viscosity. Then, the prepared slurry was evenly coated on the aluminum foil, and dried in a blast drying oven at 120° C. for 10 minutes. Lastly, the dried electrode sheet was rolled and cut to make a positive electrode sheet.
The specific preparation process of the lithium supplement agent in Example 24 was: Fe2O3 and LiOH were mixed at a ratio of 1:10, then sintered at 450° C. for 12 hours under N2, and cooled to form. After grinding, the mixture was sintered at 600° C. under N2 for 24 h to obtain LFO, i.e., the component A (Li5FeO4), and then 0.9 M Li5FeO4 was taken and uniformly mixed with the precursors of the component B (0.02 M MnCO3, 0.02 M Li2CO3) and then sintered at 500° C. for 72 h.
In Examples 2 to 6, except for changing the type of the component C in the positive electrode material (as shown in Table 2), other experimental conditions were all the same as in Example 1. The component C may be a conventional commercially available product.
In Examples 7 to 13, except for changing the mass percentage of “the component A+the component B” in the positive electrode material (as shown in Table 2), other experimental conditions were all the same as in Example 1.
In Examples 14 to 19, except for changing the mass percentage of the component A to the total mass of “the component A+the component B” (as shown in Table 2), other experimental conditions were all the same as in Example 1.
In Examples 20 to 28, except for changing the type of the component A (as shown in Table 1), other experimental conditions were all the same as in Example 1. When the component A was LixFeOy, the precursors of the component A were Fe2O3 and LiOH, and the relative mass ratio of the precursors may be adjusted according to the final chemical formula of the component A designed; when the component A was LixNiCuO, the precursors of the component A were NiO, CuO, and Li2O, and the relative proportion of the amount of each precursor may be adjusted according to the chemical formula of the final component A designed.
In Examples 29 to 31, except for changing the type of the component B (as shown in Table 1), other experimental conditions were all the same as in Example 1. The precursors of the component B were Li2CO3, MnCO3, NiCO3, and CoCO3, and the relative proportion of the amount of each precursor may be adjusted according to the chemical formula of the final component B designed.
The lithium supplement agents (the component A+the component B) prepared in Examples 1 to 31 were core-shell structures. In particular, the average particle diameter of the core was 0.5 μm to 15 μm, and the average thickness of the shell was 20 nm to 200 nm.
LiFePO4 (the component C)
Li2NiO2@Li1.33MnO2 (the component A+the component B)
In particular, the component C accounted for 92.15% of the total mass of “the component A+the component B+the component C+Super P+PVDF”; the mass percentage of “the component A+the component B” to the total mass of “the component A+the component B+the component C” was 5%.
LiNi0.9Co0.06Mn0.04O2 (the component C)
Li2NiO2@Li1.33MnO2 (the component A+the component B)
In particular, the component C accounted for 92.15% of the total mass of “the component A+the component B+the component C+Super P+PVDF”; the mass percentage of “the component A+the component B” to the total mass of “the component A+the component B+the component C” was 5%.
LiNi1.5Mn0.5O4 (the component C)
Li2NiO2@Li1.33MnO2 (the component A+the component B)
In particular, the component C accounted for 92.15% of the total mass of “the component A+the component B+the component C+Super P+PVDF”; the mass percentage of “the component A+the component B” to the total mass of “the component A+the component B+the component C” was 5%.
LiCoO2 (the component C)
Li2NiO2@Li1.33MnO2 (the component A+the component B)
In particular, the component C accounted for 92.15% of the total mass of “the component A+the component B+the component C+Super P+PVDF”; the mass percentage of “the component A+the component B” to the total mass of “the component A+the component B+the component C” was 5%.
The main condition parameters involved in the examples are as shown in the following Table 1.
Test objects: the positive electrode sheets prepared in Examples 1 to 31 and Comparative examples 1 to 8.
Test method: the viscosity of the positive electrode slurry was adjusted to 5000±500 mPa s, the actual solid content thereof was tested, and the positive electrode slurry was placed in a 500 mL beaker for 12 h, then the viscosity thereof was tested again.
Test results: as shown in Table 2 below.
The preparation method of the test object batteries in the following effect examples (2) to (4) is as follows:
The prepared positive electrode sheet and the graphite negative electrode sheet were assembled into a 1 Ah soft pack battery. After liquid injection, 4.5 V chemical forming was performed (that is, the first charging process of the battery after liquid injection, this process may activate the active substance in the battery and activate the lithium battery.) And after the aging process, a fresh battery was obtained.
Test method: at 25° C., 2.0 V to 4.2 V, constant current and constant voltage charging (cut-off current 0.05 C) was conducted to the battery cell assembled with the positive electrode prepared in the example at 0.33 C, and constant current discharge was conducted at 0.33 C, and the discharge capacity was the capacity thereof.
Test results: as shown in Table 2 below.
Test method: in the range of 2.5 V to 4.2 V, the battery cell assembled with the positive electrode prepared in the example was charged and discharged for 500 cycles at 45° C. at 1 C, and the capacity ratio of the 500th cycle to the first cycle was recorded as the capacity retention rate thereof.
Test results: as shown in Table 2 below.
Test method: at 60° C. at 4.2 V, the battery cell assembled with the positive electrode prepared in the example was fully charged and stored, the volume difference between the 30th day and the 1st day was recorded, and this value was divided by the volume of the first day to get the storage volume growth rate thereof.
Test results: as shown in Table 2 below.
Analyzing the data in Table 1 to 2 gives:
Compared with Example 1, other conditions were the same, only the mass percentage of “component A+component B” accounting for “total mass of component A+component B+component C” was changed in Examples 7 to 13, thus have varying degrees of impact on gram capacity, cycle capacity retention rate at 45° C., and storage volume growth rate at 60° C. Specifically: when the mass percentage of “component A+component B” in the “total mass of component A+component B+component C” was not more than 5%, for example, 1% to 5%, with the increase of the mass percentage, the gram capacity and the cycle capacity retention rate at 45° C. were also increased, and the storage volume growth rate at 60° C. was decreased. When the mass percentage of “component A+component B” in the “total mass of component A+component B+component C” was greater than 5%, and not greater than 35%, for example, 5% to 31%, with the increase of the mass percentage, the gram capacity and the cycle capacity retention rate at 45° C. were decreased, and the storage volume growth rate at 60° C. was increased.
Compared with Example 1, other conditions were the same, only the mass percentage of the component A in “total mass of component A+component B+component C” was changed in Examples 14 to 19, thus have varying degrees of impact on gram capacity, cycle capacity retention rate at 45° C., and storage volume growth rate at 60° C. Specifically: when the mass percentage of the component A to the “total mass of component A+component B” was greater than 89%, such as 98% to 99.1%, with the increase of the mass percentage, the gram capacity and the cycle capacity retention rate at 45° C. remained basically unchanged, and the storage volume growth rate at 60° C. was increased. When the mass percentage of the component A to the “total mass of component A+component B” was less than 98%, such as 89% to 97%, with the decrease of the mass percentage, the gram capacity and the cycle capacity retention rate at 45° C. were decreased slightly, and the storage volume growth rate at 60° C. was decreased.
Compared with Example 1, other conditions were the same, and only changing the type of the component A of Examples 20 to 28 had varying degrees of impact on the gram capacity, cycle capacity retention rate at 45° C., and storage volume growth rate at 60° C. For example, in Example 23, when the component A was Li2Cu2O2, the gram capacity was 134.8 mAh/g, the cycle capacity retention rate at 45° C. was 92.4%, and the storage volume growth rate at 60° C. was 4.6%. Compared with Examples 1, 20 to 22, and 24 to 28, Example 23 had the smallest storage volume growth rate at 60° C.
Compared with Example 1, other conditions were the same, and only changing the type of the component B of Examples 29 to 31 had varying degrees of impact on the gram capacity, cycle capacity retention rate at 45° C., and storage volume growth rate at 60° C. For example, in Example 1, when the component B was Li1.33Mn0.67O2, the gram capacity (137.6 mAh/g), cycle capacity retention rate at 45° C. (92.8%), and storage volume growth rate at 60° C. (5.3%) were all better than those of Example 29 to 31.
Compared with Example 1, Li2NiO2@Li1.33Mn0.67O2 was not included in Comparative example 1, and the gram capacity and cycle capacity retention rate at 45° C. of Comparative example 1 were both decreased, and the storage volume growth rate at 60° C. thereof was increased.
Compared with Example 2, Li2NiO2@Li1.33Mn0.67O2 was not included in Comparative example 2, and the gram capacity and cycle capacity retention rate at 45° C. of Comparative example 2 were both decreased, and the storage volume growth rate at 60° C. thereof was increased.
Compared with Example 3, Li2NiO2@Li1.33Mn0.67O2 was not included in Comparative example 3, and the gram capacity and cycle capacity retention rate at 45° C. of Comparative example 3 were both decreased, and the storage volume growth rate at 60° C. thereof was increased.
Compared with Example 4, Li2NiO2@Li1.33Mn0.67O2 was not included in Comparative example 4, and the gram capacity and cycle capacity retention rate at 45° C. of Comparative example 4 were both decreased, and the storage volume growth rate at 60° C. thereof was increased.
Compared with Example 5, Li2NiO2@Li1.33Mn0.67O2 was not included in Comparative example 5, and the gram capacity and cycle capacity retention rate at 45° C. of Comparative example 5 were both decreased, and the storage volume growth rate at 60° C. thereof was increased.
Compared with Example 6, Li2NiO2@Li1.33Mn0.67O2 was not included in Comparative example 6, and the gram capacity and cycle capacity retention rate at 45° C. of Comparative example 6 were both decreased, and the storage volume growth rate at 60° C. thereof was increased.
Compared with Examples 1 to 19, Comparative example 7 did not contain “component A+component B”, and the gram capacity and cycle capacity retention rate at 45° C. of Comparative example 7 were both decreased, and the storage volume growth rate at 60° C. thereof was increased.
Compared with Example 24, Comparative example 8 did not contain “component A+component B”, and the gram capacity and cycle capacity retention rate at 45° C. of Comparative example 8 were both significantly decreased, and the storage volume growth rate at 60° C. thereof was significantly increased.
By analyzing the above data, the inventors concluded that the reasons for the above experimental phenomenon may be:
1. The increase in the amount of lithium supplement agent “component A+component B” relative to the active substance component C lead to improved circulation and storage. However, the lithium supplement agent “component A+component B” had poor conductivity, and too much thereof had a negative impact on the electrical properties of the positive electrode material and made them worse.
2. The main effect of the component B was to stabilize the component A, the secondary effect was to supplement lithium, and the main effect of the component A was to supplement lithium. An increase in the amount of the component B improved the stability of the lithium supplement agent “component A+component B”, but too much of the component B reduced the lithium supplement effect of the lithium supplement agent “component A+component B”.
3. Different types of the component A produced different electrochemical properties.
In addition, the inventors have found through experiments that the component B in the lithium supplement agent may be more uniformly coated at the surface of the component A by adjusting the calcination temperature, specifically, the Mn source in the precursors of the component B was first calcined at a low temperature (for example, 300° C. to 500° C.), coated at the surface of the component A, and then calcined at a high temperature (for example, 600° C. to 900° C.), and reacted with the Li source in the precursors of the component B, to better form a lithium supplement agent in which the component B was more uniformly coated at the surface of the component A.
The above specific embodiments have further described the object, technical solutions, and beneficial effects of the invention in detail. It should be understood that the above descriptions are only specific embodiments of the invention and are not intended to limit the invention. Any modifications, equivalent replacements, improvements, etc., made within the spirit and principles of the invention shall all be included within the scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202310432269.6 | Apr 2023 | CN | national |
