CN106595823A - Method for quickly evaluating maximum liquid injection amount of lithium ion battery - Google Patents

Abstract

The invention discloses a method for rapidly evaluating the maximum liquid injection volume of a lithium-ion battery. Firstly, the liquid holding rate of the positive electrode sheet, the negative electrode sheet, and the separator is measured; the volume of the electrolyte solution absorbed by them is calculated according to the liquid holding rate; The empty volume _Vyu of the inner cavity of the shell; then detect the correction coefficient η of the void volume that the battery cell can accommodate the electrolyte; finally calculate the total liquid injection volume of the battery m _solution = ( _Vyu + _Vempty × η) × ρ. The evaluation method of the present invention is simple in operation and accurate in results, shortens the debugging time, and avoids the impact of frequent equipment debugging on equipment accuracy and production; and can avoid the decline in the electrical performance of the battery due to insufficient electrolyte injection, and can also be used for battery The liquid injection volume provides accurate design parameters.

Description

A rapid evaluation method for the maximum liquid injection volume of lithium-ion batteries

technical field

The invention relates to the field of lithium ion batteries, in particular to a method for quickly evaluating the maximum liquid injection volume of lithium ion batteries.

Background technique

The liquid injection volume of lithium ion battery is an important factor affecting the electrical performance of lithium ion battery. If the electrolyte injection volume is too small, it will cause large internal resistance, poor rate performance and poor cycle performance of the battery; if the electrolyte injection volume is too large, the It will prolong the production time and waste electrolyte. Usually, the electrolyte injection volume is selected based on two parameters, one is the empirical injection parameter, the unit is g/Ah, that is, the battery injection volume is obtained by multiplying the battery capacity by the corresponding injection parameter, but this empirical parameter It will vary due to different materials, battery models, and battery manufacturing processes. The parameters are complicated and inaccurate, resulting in a large deviation between the calculated liquid injection volume and the actual one. The second is to verify the maximum liquid injection volume of the battery through actual liquid injection. This method is highly dependent on equipment, and the conclusions drawn are not universal. In addition, debugging the liquid injection machine will consume a lot of time and affect the production progress. At the same time, frequent Adjusting equipment parameters will also affect the liquid injection accuracy of the equipment.

The rapid measurement method provided by the invention can calculate the maximum liquid injection volume that can be injected into the battery, and the operation is simple and fast without resorting to complicated equipment.

Contents of the invention

In order to determine the maximum liquid injection volume at the beginning of battery design, the present invention provides a rapid evaluation method for the maximum liquid injection volume of a lithium-ion battery.

The technical scheme of the present invention is as follows: a method for quickly evaluating the maximum liquid injection volume of a lithium-ion battery, comprising the following steps:

(1) First measure the weight and volume of the positive electrode sheet, then completely soak it in the electrolyte, seal it and let it stand, after taking it out, wipe it quickly from the surface once with blotting paper and weigh it immediately; use the electrolyte that the positive electrode sheet can hold The ratio of the volume to its own volume is used to calculate the liquid capacity α of _{the positive} electrode sheet,

Then calculate the liquid capacity α _negative of the negative plate and the liquid capacity α _film of the diaphragm in the same way;

(2) Calculate the volume V of the electrolyte absorbed by the positive plate according to the liquid capacity of the _positive plate = α _positive × V, where V is the volume of the positive plate, and α _is the positive liquid capacity of the positive plate; then use the same The method calculates the liquid absorption volume V _{suction negative} of the negative plate and the liquid suction volume V _{suction film of the diaphragm} ;

(3) First measure the empty volume V of the inner _cavity of the battery case; then detect the correction factor η of the void volume that the cell can accommodate the electrolyte; finally calculate the total liquid injection volume of the battery m _liquid = ( _V + V _empty ×η)×ρ, where V is the _void volume in the cell that can hold the electrolyte, and ρ is the density of the electrolyte.

In a further scheme, the liquid capacity ratio of the positive electrode sheet in the step (1) is _positive α=(m ₁ -m ₀ )/ρ/V, where m ₁ is the mass of the positive electrode sheet after liquid absorption, and m ₀ is the liquid absorption The mass of the positive electrode sheet before, ρ is the density of the electrolyte, and V is the volume of the positive electrode sheet.

In a further solution, the temperature of the electrolyte in the step (1) is 30-55° C., and the time for sealing and standing is 0.5-3 hours.

As a further solution, the empty volume V in the step (3) is the difference between the total _volume of the battery housing cavity and the volume occupied by the battery cells and tabs inside the battery housing; the battery cells can accommodate the volume of the electrolyte The void volume is the sum of the liquid absorption capacity of the positive electrode sheet, the negative electrode sheet and the diaphragm, that is, V _void = V _{suction positive} + V _{suction negative} + V _{suction film} .

Further scheme, the measuring method of the void volume correction factor in the described step (3) is as follows:

(1) detect respectively the _total mass m of the positive electrode sheet, the negative electrode sheet and the separator forming the electric core;

(2) Soak them all in the electrolyte solution at a temperature of 30-55°C, seal them and let them stand for 0.5-3 hours, take them out and quickly wipe their surface once with blotting paper, and immediately weigh them as m _{total 1} , then It _absorbs the mass m of the electrolyte solution = m _{total 1} - m _{total 0} ;

(3) Lay the positive electrode sheet, negative electrode sheet, and separator in step (1) according to the order of cell winding or stacking and clamp them into cells so that the clamping force is equal to the tension force of the battery cell ;

(4) Soak the cell completely in the electrolyte solution at a temperature of 30-55°C and leave it sealed for 0.5-3 hours, take it out and quickly wipe its surface once with blotting paper, and immediately weigh its total weight as m _{total 2} , Then it _absorbs the mass m of electrolyte solution = m _{total 2} - m _{total 0} ;

(5) Void volume correction factor η= _mab2 / _mab1 .

In a further solution, the volumes of the positive electrode sheet, the negative electrode sheet and the diaphragm in the step (1) are calculated by measuring their contour dimensions.

In a further solution, the empty volume V of the inner cavity of the battery case in the step (3) is _measured by a gas replacement method, a liquid replacement method or a three-dimensional simulation software.

In the present invention, the value of the void volume correction coefficient η is determined by the degree of fit between the pole piece and the diaphragm. If one positive electrode sheet, one negative electrode sheet, and two separators are stacked as one unit, there are three units in this embodiment. The more experimental units, the more accurate the void volume correction factor is.

The rapid determination method provided by the invention can calculate the maximum amount of liquid that can be injected into the battery, and the operation is simple and fast without resorting to complicated equipment.

The evaluation method of the present invention is simple in operation and accurate in results, shortens the debugging time, and avoids the impact of frequent equipment debugging on equipment accuracy and production; and can avoid the decline in the electrical performance of the battery due to insufficient electrolyte injection, and can also be used for battery The liquid injection volume provides accurate design parameters.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings.

Figure 1 is a schematic diagram of the composition of the cell for measuring the void volume correction factor η.

detailed description

Example 1:

A method for rapidly evaluating the maximum liquid injection volume of a lithium-ion battery, comprising the following steps:

(1) First measure the weight and volume of the positive electrode sheet, then completely soak it in the electrolyte at a temperature of 30°C and leave it sealed for 3 hours. After taking it out, wipe it quickly from the surface with blotting paper once and weigh it immediately; use the positive electrode The ratio of the electrolyte volume that the sheet can hold to its own volume is used to calculate the liquid capacity of the positive electrode sheet α _positive = (m ₁ -m ₀ )/ρ/V, where m ₁ is the mass of the positive electrode sheet after liquid absorption, m ₀ is the mass of the positive electrode sheet before liquid absorption, ρ is the density of the electrolyte, V is the volume of the positive electrode sheet,

Then calculate the liquid capacity α _negative of the negative plate and the liquid capacity α _film of the diaphragm in the same way;

(2) Calculate the volume V of the electrolyte absorbed by the positive plate according to the liquid capacity of the _positive plate = α _positive × V, where V is the volume of the positive plate, and α _is the positive liquid capacity of the positive plate; then use the same The method calculates the liquid absorption volume V _{suction negative} of the negative plate and the liquid suction volume V _{suction film of the diaphragm} ;

(3) First measure the total volume of the inner cavity of the battery case and the volume occupied by the battery cells and tabs inside the battery case. The difference between the two is the empty volume V of the inner _cavity of the battery case; Void volume correction factor η for containing the electrolyte; finally calculate the total liquid injection volume of the battery m _liquid = (V _remaining + V _empty × η) × ρ, V _empty = V _{suction positive} + V _{suction negative} + V _{suction film} ; formula The _hollow V is the void volume in the cell that can accommodate the electrolyte, and ρ is the density of the electrolyte.

Further scheme, the measuring method of the void volume correction factor in the described step (3) is as follows:

(1) Detect respectively the total mass m _total of 3 positive pole sheets, 3 negative pole sheets and 6 diaphragms forming the electric core;

(2) Soak them all in the electrolyte solution at a temperature of 30°C and seal them for 3 hours, take them out and quickly wipe their surface once with blotting paper, and immediately weigh their total weight as m _{total 1} , then it absorbs the electrolyte The mass of m _{absorb 1} = m _{total 1} - m _{total 0} ;

(3) The positive electrode sheet 2, the negative electrode sheet 3 and the diaphragm 1 in step (1) are stacked in the order shown in Figure 1, and then clamped with splints 4 on both sides to form a cell, and make Its clamping force is equal to the tension force of the battery cell;

(4) Soak the cell completely in the electrolyte solution at a temperature of 45°C, seal it and let it stand for 1 hour, take it out and quickly wipe its surface once with blotting paper, and immediately weigh its total weight as m _{total 2} , then it absorbs the electrolyte The mass of the liquid m _{absorbs 2} = m _{total 2} - m _{total 0} ;

(5) Void volume correction factor η= _mab2 / _mab1 .

In a further solution, the volumes of the positive electrode sheet, the negative electrode sheet and the separator in the step (1) are calculated by measuring their contour dimensions.

In a further solution, the empty volume V of the inner cavity of the battery case in the step (3) is _measured by a gas replacement method, a liquid replacement method or a three-dimensional simulation software.

Example 2:

A method for rapidly evaluating the maximum liquid injection volume of a lithium-ion battery, comprising the following steps:

(1) First measure the weight and volume of the positive electrode sheet, then completely soak it in the electrolyte solution at a temperature of 55°C and leave it sealed for 0.5 hours. After taking it out, wipe it quickly from the surface once with blotting paper and weigh it immediately; The ratio of the electrolyte volume that the sheet can hold to its own volume is used to calculate the liquid capacity of the _positive electrode sheet αpositive=(m ₁ -m ₀ )/ρ/V=0.08, where the mass of the positive electrode sheet after absorbing liquid m ₁ =315.3 g, the mass of the positive electrode sheet before liquid absorption m ₀ =306.6g, the density of the electrolyte ρ=1.2g/cm ³ , the volume of the positive electrode sheet V=94.3cm ³ ,

Then calculate the liquid capacity of the negative plate α _negative = 0.16 and the liquid capacity of the diaphragm α _film = 0.59 in the same way; the specific data are shown in Table 1 below:

Table 1

m ₀ (g) m ₁ (g) V(cm ³ ) ρ(g/cm ³ ) Positive plate 306.6 315.3 94.3 Negative plate 235.5 258.2 115 diaphragm 23.8 52.3 40.4 Electrolyte 1.2

(2) Calculate the volume of the electrolyte solution absorbed by the positive plate according to the liquid capacity of the positive plate, V _{absorption positive} = α _positive × V = 7.5cm ³ , where V is the volume of the positive plate, and α _positive is the liquid capacity of the positive plate ; Then calculate the negative plate suction volume V _{suction negative} = ^18.4cm3 and diaphragm suction volume V _{suction film} = ^23.8cm3 in the same way;

(3) First measure the total volume of the inner cavity of the battery case and the volume occupied by the battery cells and tabs inside the battery case, the difference between the two is the empty volume V of the inner cavity of the battery case ⁼ _83cm ; then detect The correction factor of the void volume of the cell that can hold the electrolyte is η = 0.85; finally calculate the total liquid injection volume of the battery m _solution = (V _remaining + V _empty × η) × ρ = 150.3g, V _empty = V _{suction positive} + V _{Suction negative} + V _{suction film} = 49.7cm ³ ; where V is the _void volume in the cell that can hold the electrolyte, and ρ is the density of the electrolyte.

Further scheme, the measuring method of the void volume correction factor in the described step (3) is as follows:

(1) Detect respectively the total mass m _{total 0} =58.3g of 3 positive pole pieces, 3 negative pole pieces and 6 diaphragms forming the battery cell;

(2) Soak them all in the electrolyte solution with a temperature of 55°C and seal them for 0.5 hours, take them out and wipe them quickly from the surface once with blotting paper, and immediately claim the total weight as m _{total 1} = 65.8g, then its The mass of the absorbed electrolyte m _{absorb 1} = m _{total 1} - m _{total 0} = 7.5g;

(3) The positive electrode sheet 2, the negative electrode sheet 3 and the diaphragm 1 in step (1) are stacked in the order shown in Figure 1, and then clamped with splints 4 on both sides to form a cell, and make Its clamping force is equal to the tension force of the battery cell;

(4) Soak the cell completely in the electrolyte solution at a temperature of 45°C, seal it and let it stand for 1 hour, take it out and quickly wipe its surface once with blotting paper, and immediately weigh its total weight as m _{total 2} = 64.7g, then The mass of the electrolyte absorbed by it m _{absorb 2} =m _{total 2} -m _{total 0} =6.4g;

(5) Void volume correction factor η= _mab2 / _mab1 =0.85.

The above descriptions are only preferred embodiments of the patent of the present invention, and are not intended to limit the implementation scope of the present invention; that is, all equivalent transformations made according to the scope of the claims of the present invention are within the scope of the claims of the present invention.

Claims (7)

1. A rapid evaluation method for the maximum liquid injection volume of a lithium-ion battery, characterized in that: comprising the following steps: (1) First measure the weight and volume of the positive electrode sheet, then completely soak it in the electrolyte, seal it and let it stand still. After taking it out, wipe it quickly from the surface with blotting paper once and weigh it immediately; use the electrolyte that the positive electrode sheet can hold The ratio of the volume to its own volume is used to calculate the liquid capacity α of _{the positive} electrode sheet, Then calculate the liquid capacity α _negative of the negative plate and the liquid capacity α _film of the diaphragm in the same way; (2) Calculate the volume of the electrolyte absorbed by _{the positive} plate according to the liquid capacity of the _positive plate. The method calculates the liquid absorption volume V _{suction negative} of the negative plate and the liquid suction volume V _{suction film of the diaphragm} ; (3) First measure the empty volume V of the inner cavity of the battery case; then detect the correction factor η of the void volume that the battery cell can accommodate the electrolyte; finally calculate the total liquid _injection volume of the battery m _liquid = (V _Yu + V _empty ×η)×ρ _, where V is the _void volume in the cell that can hold the electrolyte, and ρ is the density of the electrolyte. 2. The rapid evaluation method according to claim 1, characterized in that: the liquid capacity of the positive plate in the step (1) _αpositive =(m ₁ -m ₀ )/ρ/V, where m ₁ is the mass of the positive electrode sheet after liquid absorption, m ₀ is the mass of the positive electrode sheet before liquid absorption, ρ is the density of the electrolyte, and V is the volume of the positive electrode sheet. 3. The rapid evaluation method according to claim 1, characterized in that: the temperature of the electrolyte solution in the step (1) is 30-55°C, and the time for sealing and standing is 0.5-3 hours. 4. The rapid evaluation method according to claim 1, characterized in that: the free volume V in the step (3) is the total volume of the inner _cavity of the battery case and the cells and tabs inside the battery case. The difference in volume; the void volume that can accommodate the electrolyte in the cell is the sum of the liquid absorption of the positive plate, negative plate and diaphragm, that is, V _empty = V _{positive suction} + V _{negative suction} + V _{suction film} . 5. The rapid evaluation method according to claim 1, characterized in that: the measurement method of the void volume correction coefficient in the step (3) is as follows: (1) Detect the total mass m _{total 0} of the positive electrode sheet, negative electrode sheet and diaphragm that make up the battery cell; (2) Soak them all in the electrolyte solution at a temperature of 30-55°C, seal them and let them stand for 0.5-3 hours, take them out and quickly wipe their surface once with blotting paper, and immediately weigh them as m _{total 1} , then It _absorbs the mass m of the electrolyte solution = m _{total 1} - m _{total 0} ; (3) Lay the positive electrode sheet, negative electrode sheet and separator in step (1) according to the order of cell winding or stacking and clamp them into cells so that the clamping force is equal to the tension force of the battery cell ; (4) Soak the cell completely in the electrolyte solution at a temperature of 30-55°C and leave it sealed for 0.5-3 hours, take it out and wipe its surface quickly with blotting paper once, and immediately weigh its total weight as m _{total 2} , Then it _absorbs the mass m of electrolyte solution = m _{total 2} - m _{total 0} ; (5) Void volume correction factor η = m ₂ /m ₁ . 6. The rapid evaluation method according to claim 1, characterized in that the volumes of the positive electrode sheet, negative electrode sheet and separator in the step (1) are calculated by measuring their contour dimensions. 7. The rapid evaluation method according to claim 1, characterized in that: the empty volume V of the inner _cavity of the battery case in the step (3) is measured by gas replacement method, liquid replacement method or three-dimensional simulation software .