Calculation method for throughput and inventory of cylindrical battery electrolyte

Abstract

The present invention provides a method for calculating the throughput and holding amount of cylindrical battery electrolyte, and relates to the technical field of batteries. The method for calculating the throughput and holding amount of cylindrical battery electrolyte provided by the present invention optimizes the design holding amount mainly according to the electrolyte throughput in the charging state and the discharging state during the battery cell cycle process; the electrolyte holding amount design is more efficient and accurate, which can greatly improve the dynamic performance of the battery cell while avoiding excessive waste of electrolyte.

Description

Technical Field

[0001] The invention relates to the technical field of batteries, and in particular to a method for calculating the throughput and the amount of electrolyte retained in cylindrical batteries. Background Art

[0002] With the rapid development of the industry, the field of lithium batteries is also growing rapidly. Currently, lithium batteries on the market are mainly divided into three types: soft packs, aluminum shells and cylindrical batteries. Cylindrical batteries are highly favored in the energy storage market due to their advantages in high efficiency, high safety and low cost. However, due to their high internal space utilization and poor wettability, there are many considerations for the amount of liquid injection in the battery cell. At this stage, the industry considers the injection problem from many aspects and dimensions (optimizing the electrolyte formula, optimizing the injection method and injection parameters, optimizing the aging time and temperature, etc.). However, the throughput of the electrolyte in the charging and discharging states of the battery cell during the cycle is still ignored, and the electrolyte throughput is directly related to the amount of electrolyte retained during the battery cycle, which has a great impact on the performance of the battery product (such as internal resistance, charge and discharge rate, capacity, cyclability, etc.).

[0003] At present, the electrolyte reserves in most of the production are determined according to the design parameters of the battery cell, such as the calculation of the positive and negative electrode materials and the porosity of the diaphragm, the mass of the active substances in the battery cell, and then the electrolyte reserves are determined. This calculation method is based on an ideal state and ignores the effect of the electrolyte throughput on the reserves during the battery cell cycle. When the battery cell reserves are lower than the throughput, the battery cell reserves will be too low and the dynamic performance will be reduced; when the battery cell reserves are much higher than the throughput, the battery cell reserves will be too high, excessive gas production, and safety will be reduced. Therefore, to ensure the normal use of the electrolyte, the electrolyte throughput needs to be reasonably designed to avoid the occurrence of insufficient or excessive electrolyte.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The first object of the present invention is to provide a method for calculating the electrolyte throughput of a cylindrical battery.

[0006] The second object of the present invention is to provide a method for calculating the amount of electrolyte retained in a cylindrical battery.

[0007] The third object of the present invention is to provide application of the above calculation method in the preparation of cylindrical batteries.

[0008] In order to achieve the above objectives, the following technical solutions are adopted:

[0009] In a first aspect, the present invention provides a method for calculating the electrolyte throughput of a cylindrical battery, and the calculation formula for the electrolyte throughput of the cylindrical battery is as follows:

[0010] M = ΔHt*ρ*k1;

[0011] Ht=Hb-Ha;

[0012] Wherein, M is the electrolyte throughput of the cylindrical battery; ΔHt is the difference between the basic cell thickness at 100% SOC and the basic cell thickness at 0% SOC under the same number of cycles; ρ is the electrolyte density; k1 is the area of ​​the positive electrode sheet; Ha is the basic cell thickness at 0% SOC; Hb is the basic cell thickness at 100% SOC;

[0013] The basic unit is composed of adjacent positive electrode sheets, separators, negative electrode sheets and separators.

[0014] As a further technical solution, the calculation formula of Ha is as follows:

[0015] Ha=Hca+Haa+2*Hs;

[0016] Among them, Hca is the thickness of the positive electrode plate at 0% SOC, Haa is the thickness of the negative electrode plate at 0% SOC, and Hs is the thickness of the separator.

[0017] As a further technical solution, the calculation formula of Hb is as follows:

[0018] Hb=Hcb+Hab+2*Hs;

[0019] Among them, Hcb is the thickness of the positive electrode sheet at 100% SOC, Hab is the thickness of the negative electrode sheet at 100% SOC, and Hs is the thickness of the diaphragm.

[0020] As a further technical solution, the calculation formula of Hcb is as follows:

[0021] Hcb=Hca*(1+η1);

[0022] Among them, η1 is the rebound expansion of the positive electrode during charging and discharging.

[0023] As a further technical solution, the calculation formula of Hab is as follows:

[0024] Hab=Haa*(1+η2);

[0025] Among them, η2 is the rebound expansion of the negative electrode sheet during charging and discharging.

[0026] In a second aspect, the present invention provides a method for calculating the amount of electrolyte retained in a cylindrical battery, and the calculation formula for the amount of electrolyte retained in the battery is as follows:

[0027] E = E0 + M;

[0028] Among them, E is the electrolyte reserve of the cylindrical battery; Ε0 is the initial electrolyte reserve of the battery cell, and M is the electrolyte throughput of the cylindrical battery.

[0029] As a further technical solution, the calculation formula of E0 is as follows:

[0030] E0=(Vc+Va+Vs+Vt+Vo)*ρ*k2;

[0031] Among them, Vc is the pores of the positive electrode sheet; Va is the pores of the negative electrode sheet; Vt is the interlayer pores; Vo is the pores in the overhang area (the negative electrode exceeds the positive electrode area); Vs is the pores of the diaphragm; ρ is the electrolyte density; k2 is the coefficient, which takes a value of 1-1.05.

[0032] As a further technical solution, the calculation formula of Vc is as follows:

[0033] Vc=σ c *Lc*Wc*Hc;

[0034] Among them, σ c is the porosity of the positive electrode sheet; Lc is the length of the positive electrode sheet; Wc is the width of the positive electrode sheet; Hc is the thickness of the positive electrode sheet;

[0035] The calculation formula of Va is as follows:

[0036] Va=σ a *La*Wa*Ha;

[0037] Among them, σ a is the porosity of the negative electrode sheet; La is the length of the negative electrode sheet; Wa is the width of the negative electrode sheet; Ha is the thickness of the negative electrode sheet;

[0038] The calculation formula of Vs is as follows:

[0039] Vs=σ s *(Ls1+Ls2)*Ws*Hs;

[0040] Among them, σ s is the porosity of the diaphragm; Ls1 is the length of the inner diaphragm, Ls2 is the length of the outer diaphragm, Ws is the width of the diaphragm; Ha is the thickness of the diaphragm;

[0041] The calculation formula of Vt is as follows:

[0042] Vt=La*Wa*Ht;

[0043] Where, Ht is the interlayer gap;

[0044] The calculation formula of Vo is as follows:

[0045] Vo=(Wa-Wc)*Lc*Hc.

[0046] As a further technical solution, the calculation formula of Ht is as follows:

[0047] Ht=D / n-Hc-Ha-2*Hs;

[0048] Where D is the core diameter.

[0049] In a third aspect, the present invention provides application of the above-mentioned calculation method in the preparation of cylindrical batteries.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] The present invention optimizes the design of the holding capacity mainly according to the electrolyte throughput in the charging state and the discharging state during the battery cell cycle process; the electrolyte holding capacity is designed to be more efficient and accurate, which can greatly improve the dynamic performance of the battery cell while avoiding excessive waste of electrolyte. DETAILED DESCRIPTION

[0052] The embodiments of the present invention will be described in detail below in conjunction with the embodiments and examples, but it will be appreciated by those skilled in the art that the following embodiments and examples are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified, proceed according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0053] In a first aspect, the present invention provides a method for calculating the electrolyte throughput of a cylindrical battery, and the calculation formula for the electrolyte throughput of the cylindrical battery is as follows:

[0054] M = ΔHt*ρ*k1;

[0055] Ht=Hb-Ha;

[0056] Wherein, M is the electrolyte throughput of the cylindrical battery; ΔHt is the difference between the basic cell thickness at 100% SOC and the basic cell thickness at 0% SOC under the same number of cycles; ρ is the electrolyte density; k1 is the area of ​​the positive electrode sheet; Ha is the basic cell thickness at 0% SOC; Hb is the basic cell thickness at 100% SOC;

[0057] The basic unit is composed of adjacent positive electrode sheets, separators, negative electrode sheets and separators.

[0058] The present invention optimizes the design of the holding capacity mainly according to the electrolyte throughput in the charging state and the discharging state during the battery cell cycle; the battery cell prepared by this design method has a more scientific and reasonable liquid injection design and greatly improved cycle performance.

[0059] Through this design, the changing trend of the electrolyte throughput can be observed, and the predicted trend is: the throughput increases rapidly in the early stage of the cycle, and gradually tends to balance with the increase of the cycle period.

[0060] The change in throughput can be used to understand the changing trend of the electrolyte during the charge and discharge process of the cylindrical battery: under the macroscopic state, it presents a breathing trend of charging and exhaling, releasing and inhaling, which is specifically manifested as: discharging liquid under charging state and absorbing liquid under discharging state; it is opposite to the breathing trend of the electrolyte in the soft-pack battery; this is because the negative electrode sheet expands during charging, which squeezes the space (the layer gap decreases) to discharge liquid; and at this time, the particles inside the negative electrode sheet expand, and the increase in the particle gap will lead to liquid absorption; but the amount of liquid discharged is greater than the amount of liquid absorbed, and the overall performance is liquid discharge; otherwise, the opposite is true.

[0061] In some optional embodiments, the calculation formula of Ha is as follows:

[0062] Ha=Hca+Haa+2*Hs;

[0063] Among them, Hca is the thickness of the positive electrode plate at 0% SOC, Haa is the thickness of the negative electrode plate at 0% SOC, and Hs is the thickness of the separator.

[0064] In some optional embodiments, the calculation formula of Hb is as follows:

[0065] Hb=Hcb+Hab+2*Hs;

[0066] Among them, Hcb is the thickness of the positive electrode sheet at 100% SOC, Hab is the thickness of the negative electrode sheet at 100% SOC, and Hs is the thickness of the diaphragm.

[0067] In some optional embodiments, the calculation formula of Hcb is as follows:

[0068] Hcb=Hca*(1+η1);

[0069] Among them, η1 is the rebound expansion of the positive electrode during charging and discharging.

[0070] In some optional embodiments, the calculation formula of Hab is as follows:

[0071] Hab=Haa*(1+η2);

[0072] Among them, η2 is the rebound expansion of the negative electrode sheet during charging and discharging.

[0073] In a second aspect, the present invention provides a method for calculating the amount of electrolyte retained in a cylindrical battery, and the calculation formula for the amount of electrolyte retained in the battery is as follows:

[0074] E = E0 + M;

[0075] Among them, E is the electrolyte reserve of the cylindrical battery; Ε0 is the initial electrolyte reserve of the battery cell, and M is the electrolyte throughput of the cylindrical battery.

[0076] In the present invention, EO is composed of the positive electrode sheet pores, the negative electrode sheet pores, the interlayer gap pores, the overhang area pores and the diaphragm pores.

[0077] In some optional implementations, the calculation formula of E0 is as follows:

[0078] E0=(Vc+Va+Vs+Vt+Vo)*ρ*k2;

[0079] Among them, Vc is the pores of the positive electrode sheet; Va is the pores of the negative electrode sheet; Vt is the interlayer pores; Vo is the overhang area pores; Vs is the diaphragm pores; ρ is the electrolyte density; k2 is a coefficient, with a value of 1-1.05, for example, it can be, but not limited to, 1, 1.03 or 1.05.

[0080] In some optional embodiments, the calculation formula of Vc is as follows:

[0081] Vc=σ c *Lc*Wc*Hc;

[0082] Among them, σ c is the porosity of the positive electrode sheet; Lc is the length of the positive electrode sheet; Wc is the width of the positive electrode sheet; Hc is the thickness of the positive electrode sheet;

[0083] The calculation formula of Va is as follows:

[0084] Va=σ a *La*Wa*Ha;

[0085] Among them, σ a is the porosity of the negative electrode sheet; La is the length of the negative electrode sheet; Wa is the width of the negative electrode sheet; Ha is the thickness of the negative electrode sheet;

[0086] The calculation formula of Vs is as follows:

[0087] Vs=σ s *(Ls1+Ls2)*Ws*Hs;

[0088] Among them, σ s is the porosity of the diaphragm; Ls1 is the length of the inner diaphragm, Ls2 is the length of the outer diaphragm, Ws is the width of the diaphragm; Ha is the thickness of the diaphragm;

[0089] The calculation formula of Vt is as follows:

[0090] Vt=La*Wa*Ht;

[0091] Where, Ht is the interlayer gap;

[0092] The calculation formula of Vo is as follows:

[0093] Vo=(Wa-Wc)*Lc*Hc.

[0094] In some optional embodiments, the calculation formula of Ht is as follows:

[0095] Ht=D / n-Hc-Ha-2*Hs;

[0096] Where D is the core diameter.

[0097] In a third aspect, the present invention provides application of the above-mentioned calculation method in the preparation of cylindrical batteries.

[0098] The calculation method of the present invention is used to obtain the battery electrolyte reserve, so that the design of the liquid injection amount in the battery preparation process is more scientific and reasonable, and the cycle performance is greatly improved.

[0099] The present invention is further described below by means of specific examples. However, it should be understood that these examples are only used for more detailed description and should not be construed as limiting the present invention in any form.

[0100] Test Example 1

[0101] In the early stage of the experiment, the existing cylindrical batteries were charged and discharged and disassembled, and the theoretical throughput was calculated according to the following formula:

[0102] M = ΔHt*ρ*k1;

[0103] Ht=Hb-Ha;

[0104] Wherein, M is the electrolyte throughput of the cylindrical battery; ΔHt is the difference between the basic cell thickness at 100% SOC and the basic cell thickness at 0% SOC under the same number of cycles; ρ is the electrolyte density; k1 is the area of ​​the positive electrode sheet; Ha is the basic cell thickness at 0% SOC; Hb is the basic cell thickness at 100% SOC.

[0105] The battery's throughput is preliminarily judged to be 7g.

[0106] Then, cylindrical batteries were prepared using the same raw materials as the above batteries, while taking the throughput factor into account and calculating the injection volume (E) according to the following formula:

[0107] E = E0 + M;

[0108] Among them, E is the electrolyte reserve of the cylindrical battery; Ε0 is the initial electrolyte reserve of the battery cell, and M is the electrolyte throughput of the cylindrical battery.

[0109] The calculation formula of Ε0 is as follows:

[0110] E0=(Vc+Va+Vs+Vt+Vo)*ρ*k2;

[0111] Among them, Vc is the pores of the positive electrode sheet; Va is the pores of the negative electrode sheet; Vt is the interlayer pores; Vo is the overhang area pores; Vs is the diaphragm pores; ρ is the electrolyte density; k2 is a coefficient, with a value of 1-1.05, for example, it can be, but not limited to, 1, 1.03 or 1.05.

[0112] The calculation formula of Vc is as follows:

[0113] Vc=σ c *Lc*Wc*Hc;

[0114] Among them, σ c is the porosity of the positive electrode sheet; Lc is the length of the positive electrode sheet; Wc is the width of the positive electrode sheet; Hc is the thickness of the positive electrode sheet;

[0115] The calculation formula of Va is as follows:

[0116] Va=σ a *La*Wa*Ha;

[0117] Among them, σ a is the porosity of the negative electrode sheet; La is the length of the negative electrode sheet; Wa is the width of the negative electrode sheet; Ha is the thickness of the negative electrode sheet;

[0118] The calculation formula of Vs is as follows:

[0119] Vs=σ s *(Ls1+Ls2)*Ws*Hs;

[0120] Among them, σ s is the porosity of the diaphragm; Ls1 is the length of the inner diaphragm, Ls2 is the length of the outer diaphragm, Ws is the width of the diaphragm; Ha is the thickness of the diaphragm;

[0121] The calculation formula of Vt is as follows:

[0122] Vt=La*Wa*Ht;

[0123] Where, Ht is the interlayer gap;

[0124] The calculation formula of Vo is as follows:

[0125] Vo=(Wa-Wc)*Lc*Hc.

[0126] The design parameters of the battery are shown in Table 1.

[0127] Table 1

[0128]

[0129] The battery prepared above was subjected to charge and discharge cycles and disassembled, and relevant parameters were measured (as shown in Table 2 and Table 3), and then the theoretical throughput was calculated according to the following formula (as shown in Table 2):

[0130] M = ΔHt*ρ*k1;

[0131] Ht=Hb-Ha.

[0132] Table 2 Calculation method of theoretical battery cell throughput

[0133]

[0134] The actual measurement results of the cell throughput are shown in Table 2. It can be seen from Table 2 and Table 3 that the throughput of the electrolyte measured after disassembly is basically consistent with the theoretical throughput, which proves that the method of the present invention is accurate.

[0135] Table 3 Actual cell throughput

[0136]

[0137] Note: The weight before disassembly refers to the weight of the battery, the weight after disassembly refers to the weight after removing the electrolyte between the shell and the core, the dry cell weight refers to the weight of the core after removing the free electrolyte and drying, the core weight is the weight of the core after removing the free electrolyte but not drying, the number of cells = core weight - dry cell weight, the actual throughput M' = the number of cells at 0% SOC - the number of cells at 100% SOC.

[0138] Afterwards, in order to verify the rationality of the throughput design of the present invention, comparative examples 1 and 2 were designed for the throughput designed by the present invention, and Example 1 was a battery prepared by the method of the present invention. The battery was subjected to charge and discharge cycle tests, and the results are shown in Table 4.

[0139] Table 4

[0140]

[0141] It can be seen from Table 4 that the design method of the present invention is reasonable and the prepared battery has better cycle performance.

[0142] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for calculating the electrolyte throughput of a cylindrical battery, characterized in that: The calculation formula for the cylindrical battery electrolyte throughput is as follows: M = ΔHt*ρ*k1; Ht=Hb-Ha; Wherein, M is the electrolyte throughput of the cylindrical battery; ΔHt is the difference between the basic cell thickness at 100% SOC and the basic cell thickness at 0% SOC under the same number of cycles; ρ is the electrolyte density; k1 is the area of ​​the positive electrode sheet; Ha is the basic cell thickness at 0% SOC; Hb is the basic cell thickness at 100% SOC; The basic unit is composed of adjacent positive electrode sheets, separators, negative electrode sheets and separators.

2. The calculation method according to claim 1, characterized in that: The calculation formula of Ha is as follows: Ha=Hca+Haa+2*Hs; Among them, Hca is the thickness of the positive electrode plate at 0% SOC, Haa is the thickness of the negative electrode plate at 0% SOC, and Hs is the thickness of the separator.

3. The calculation method according to claim 1, characterized in that: The calculation formula of Hb is as follows: Hb=Hcb+Hab+2*Hs; Among them, Hcb is the thickness of the positive electrode sheet at 100% SOC, Hab is the thickness of the negative electrode sheet at 100% SOC, and Hs is the thickness of the diaphragm.

4. The calculation method according to claim 3, characterized in that: The calculation formula of Hcb is as follows: Hcb=Hca*(1+η1); Among them, η1 is the rebound expansion of the positive electrode during charging and discharging.

5. The calculation method according to claim 3, characterized in that: The calculation formula of Hab is as follows: Hab=Haa*(1+η2); Among them, η2 is the rebound expansion of the negative electrode sheet during charging and discharging.

6. A method for calculating the amount of electrolyte in a cylindrical battery, characterized in that: The calculation formula of the battery electrolyte retention is as follows: E = E0 + M; Among them, E is the electrolyte reserve of the cylindrical battery; Ε0 is the initial electrolyte reserve of the battery cell, and M is the electrolyte throughput of the cylindrical battery.

7. The calculation method according to claim 6, characterized in that: The calculation formula of the E0 is as follows: E0=(Vc+Va+Vs+Vt+Vo)*ρ*k2; Among them, Vc is the pores of the positive electrode sheet; Va is the pores of the negative electrode sheet; Vt is the interlayer pores; Vo is the overhang area pores; Vs is the diaphragm pores; ρ is the electrolyte density; k2 is the coefficient, which takes a value of 1-1.

05.

8. The calculation method according to claim 7, characterized in that: The calculation formula of Vc is as follows: Vc=σ c *Lc*Wc*Hc; Among them, σ c is the porosity of the positive electrode sheet; Lc is the length of the positive electrode sheet; Wc is the width of the positive electrode sheet; Hc is the thickness of the positive electrode sheet; The calculation formula of Va is as follows: Va = σ a *La*Wa*Ha; Among them, σ a is the porosity of the negative electrode sheet; La is the length of the negative electrode sheet; Wa is the width of the negative electrode sheet; Ha is the thickness of the negative electrode sheet; The calculation formula of Vs is as follows: Vs=σ s *(Ls1+Ls2)*Ws*Hs; Among them, σ s is the porosity of the diaphragm; Ls1 is the length of the inner diaphragm, Ls2 is the length of the outer diaphragm, Ws is the width of the diaphragm; Ha is the thickness of the diaphragm; The calculation formula of Vt is as follows: Vt=La*Wa*Ht; Where, Ht is the interlayer gap; The calculation formula of Vo is as follows: Vo=(Wa-Wc)*Lc*Hc.

9. The calculation method according to claim 8, characterized in that: The calculation formula of Ht is as follows: Ht=D / n-Hc-Ha-2*Hs; Where D is the core diameter.

10. Application of the calculation method according to any one of claims 6 to 9 in the preparation of cylindrical batteries.

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