Device and method for measuring volume change of anode material of lithium battery

Abstract

The present invention discloses a measuring device and method for the volume change of a lithium battery anode material, including: a housing for placing the anode material sample and injecting electrolyte to provide conditions for the lithium intercalation reaction; a pressing block for compacting the anode material sample; a pressing rod connected to the pressing block, and a length measuring system and a pressure sensing system are also connected to the pressing rod. The length measuring system is used to measure the moving distance of the pressing block, and the pressure sensing system is used to measure the downward pressure of the pressing block. The present invention directly measures the charging volume expansion of the anode material, reduces the cumbersome steps such as pole piece production and battery cell assembly, and can also directly measure the powder compaction density of the material; and the measured data are all real-time data, and the dynamic change of the volume of the anode material can be observed.

Description

Technical Field

[0001] The present invention relates to battery material testing technologies, and more specifically, to a measurement device and method for the volume change of a negative electrode material of a lithium battery. Background Art

[0002] During battery design, the expansion rate of the negative electrode sheet is one of the key parameters to be considered. Especially as the energy density of the battery continues to increase, silicon-carbon composite materials may be used for the negative electrode. In this case, the volume change rate of the negative electrode material during charge and discharge becomes particularly important.

[0003] Currently, in the field of lithium batteries, the volume change of materials during charge and discharge is measured by charging and discharging the battery cells after they are fabricated and then measuring the volume of the battery cells. However, during the charge and discharge process of the battery cells, not only does the volume of the battery material change, but also gas generation occurs, making it impossible to clearly detect the changes in the material itself.

[0004] The main methods for measuring the volume change of battery cells include the liquid displacement method and the internal measurement method, etc.

[0005] The liquid displacement method calculates the volume of the battery cell using information related to liquid buoyancy. For example, in Chinese Patent CN107389148A, a fixture and method for measuring the volume of a battery cell, CN109668603A, a battery cell volume measurement device and method, and CN111256629A, an instrument and method for measuring the volume change of a battery cell, among which CN111256629A can achieve in-situ detection.

[0006] The internal measurement method places sensors inside the battery cell to characterize the changes in the battery cell through the sensors. This method has a high manufacturing cost and is only applicable to hard-shell battery cells.

[0007] The existing methods for measuring the full-charge expansion rate of the negative electrode material generally involve first measuring the initial thickness of the negative electrode sheet, then assembling the battery for charge and discharge, disassembling the battery in the fully charged state, and measuring the thickness of the fully charged negative electrode sheet. The negative electrode expansion rate is calculated by the ratio of the two thicknesses. In Chinese Patent CN109959360A, a measurement system and method for the negative electrode expansion rate of a soft-pack lithium battery calculates the full-charge thickness and expansion rate of the negative electrode by measuring the thickness of the positive and negative electrode sheets after drying, the thickness of the battery cell after electrolyte injection and in the fully charged state. This method avoids disassembling the battery, but still requires battery cell preparation, charge and discharge. Summary of the Invention

[0008] Aiming at the above-mentioned defects existing in the prior art, the purpose of the present invention is to provide a measurement device and method for the volume change of a negative electrode material of a lithium battery, which directly measures the charging volume expansion of the negative electrode material, reduces cumbersome steps such as negative electrode sheet fabrication and battery cell assembly, and can also directly measure the powder compaction density of the material; moreover, the measured data are all real-time data, enabling the observation of the dynamic change of the volume of the negative electrode material.

[0009] To achieve the above object, the present invention adopts the following technical solutions:

[0010] On the one hand, a measuring device for the volume change of a lithium battery anode material, comprising:

[0011] A housing for placing the anode material sample, metallic lithium, and injecting an electrolyte to provide conditions for the lithium intercalation reaction;

[0012] A pressing block for compacting the anode material sample;

[0013] A pressing rod connected to the pressing block, and a length measuring system and a pressure sensing system are also connected to the pressing rod. The length measuring system is used to measure the moving distance of the pressing block, and the pressure sensing system is used to measure the downward pressure of the pressing block.

[0014] Preferably, inside the housing, a lithium filling cavity, a sample cavity, and a liquid injection cavity are sequentially arranged from inside to outside;

[0015] Metallic lithium is placed in the lithium filling cavity;

[0016] The anode material sample is placed in the sample cavity;

[0017] A liquid injection port is provided on the liquid injection cavity for injecting the electrolyte.

[0018] Preferably, the housing includes a base, and a sample cavity and a liquid injection cavity are sequentially arranged from inside to outside thereon;

[0019] The anode material sample is placed in the sample cavity;

[0020] A liquid injection port is provided on the liquid injection cavity for injecting the electrolyte.

[0021] Preferably, the sample cavity and the liquid injection cavity are separated by ceramics, and the sample cavity and the lithium filling cavity are separated by a ceramic solid electrolyte.

[0022] Preferably, the sample cavity and the liquid injection cavity are separated by a metal material such as stainless steel with holes, and the holes are filled with ceramic materials.

[0023] Preferably, the pressing block is embedded in the sample cavity and is adapted to the sample cavity.

[0024] Preferably, the housing is made of stainless steel.

[0025] On the other hand, a measuring method based on the above-mentioned measuring device for the volume change of a lithium battery anode material, comprising:

[0026] 1) Measurement of the compaction density of the material powder

[0027] In the initial state, the reading of the length measurement system is 0. Lift the pressure rod, take out the pressure block, place the weighed negative electrode material sample in the sample cavity, put in the pressure block, press down the pressure rod, and control the pressure rod to press down slowly. Obtain the real-time pressure value of the negative electrode material sample through the pressure sensing system, and obtain the real-time height value H of the negative electrode material sample through the length measurement system. It can be obtained that:

[0028] The tap density of the negative electrode material sample

[0029] 2) Test on the charging expansion rate of the negative electrode material sample

[0030] Place metallic lithium in the lithium filling cavity with the same height. Place the weighed negative electrode material sample in the sample cavity, put in the pressure block, press down the pressure rod, control the pressure rod to press down slowly, and keep the pressure constant. Inject the electrolyte into the liquid injection cavity, and the height of the electrolyte is higher than the height of the negative electrode material sample;

[0031] The electrolyte completely penetrates the negative electrode material sample and infiltrates into the lithium filling cavity. Obtain the real-time height value H of the negative electrode material sample through the length measurement system. Wait until the lithium insertion reaction is complete and the volume of the negative electrode material sample no longer changes, and obtain the expansion rate of the negative electrode material sample:

[0032] Sample volume V = sample cavity area S × sample height H

[0033]

[0034] On the other hand, a measurement method of a measurement device based on the volume change of the lithium battery negative electrode material includes:

[0035] 1) Measurement of the tap density of the material powder

[0036] In the initial state, the reading of the length measurement system is 0. Lift the pressure rod, take out the pressure block, place the weighed negative electrode material sample in the sample cavity, put in the pressure block, press down the pressure rod, control the pressure rod to press down slowly. Obtain the real-time pressure value of the negative electrode material sample through the pressure sensing system, and obtain the real-time height value H of the negative electrode material sample through the length measurement system. It can be obtained that:

[0037] The tap density of the negative electrode material sample

[0038] 2) Test on the charging expansion rate of the negative electrode material sample

[0039] Place the liquid injection chamber and the sample chamber on the base. Place the metallic lithium and the separator in the sample chamber, insert the pressing block, lower the pressing rod until the pressure reaches P, and the length measurement system measures the height H1 of the metallic lithium and the separator. Remove the pressing block, place the negative electrode material sample on the metallic lithium and the separator, insert the pressing block, lower the pressing rod until the pressure reaches P, and the length measurement system measures the total height H2. Inject the electrolyte into the liquid injection chamber while keeping the pressure P unchanged until the lithium intercalation reaction of the negative electrode material sample is complete and the pressing rod does not move;

[0040] Invert the liquid injection chamber and the sample chamber, remove the base, install the demoulding support tube, slowly increase the downward pressure on the pressing rod until the metallic lithium and the separator are removed, replace the base, apply the pressure P to the pressing rod, and when the pressing rod is stable and no longer moves, the length measurement system measures the height H3 of the negative electrode material sample at this time to obtain the negative electrode expansion rate:

[0041]

[0042] The measuring device and method for the volume change of the negative electrode material of a lithium battery provided by the present invention have the following beneficial effects:

[0043] The present invention can directly measure the lithium intercalation volume expansion of the negative electrode material. Compared with the conventional method of calculating the negative electrode expansion rate by measuring the initial thickness of the negative electrode sheet and then measuring the thickness of the negative electrode sheet after assembling it into a battery and disassembling it under a fully charged state, this method reduces cumbersome steps such as pulping, coating, making positive and negative electrode sheets, assembling the battery cell, drying, injecting liquid, encapsulating, forming, and disassembling the battery, greatly shortening the time required for testing. At the same time, it also avoids the influence of conductive agents and binders added during the pulping and coating processes, and can more truly reflect the lithium intercalation expansion of the negative electrode material itself; and the measured data are all real-time data, and the dynamic change of the volume of the negative electrode material can be observed. At the same time, the equipment involved in this method can also directly measure the powder compaction density of the material. Description of the Drawings

[0044] Figure 1 It is a top view schematic diagram of the housing in the first embodiment of the measuring device of the present invention;

[0045] Figure 2 It is a side view schematic diagram of the first embodiment of the measuring device of the present invention;

[0046] Figure 3 It is a schematic diagram of the pressing block being lifted in the first embodiment of the measuring device of the present invention;

[0047] Figure 4 It is a schematic diagram of removing the pressing block in the first embodiment of the measuring device of the present invention;

[0048] Figure 5 It is a top view schematic diagram of the housing in the second embodiment of the measuring device of the present invention;

[0049] Figure 6 It is a side view schematic diagram of the second embodiment of the measuring device of the present invention;

[0050] Figure 7 It is a schematic diagram of the pressure application of the pressure block in the second embodiment of the measuring device of the present invention;

[0051] Figure 8 It is a schematic diagram of the lithium sheet and the separator coming out in the second embodiment of the measuring device of the present invention. Detailed implementation manners

[0052] In order to better understand the above technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with the drawings and embodiments.

[0053] Combined with Figure 1 and Figure 2 As shown, a measuring device for the volume change of the negative electrode material of a lithium battery provided by the present invention includes:

[0054] A housing 1 for providing conditions to place the negative electrode material sample, metallic lithium, and injecting electrolyte to provide conditions for the lithium intercalation reaction;

[0055] A pressure block 2 for compacting the negative electrode material sample;

[0056] A pressure rod 3 is connected to the pressure block 2. A (high-precision) length measurement system 4 and a (high-precision) pressure sensing system 5 are also connected to the pressure rod 3. The length measurement system 4 is used to measure the moving distance (height) of the pressure block 3, and the pressure sensing system 5 is used to measure the downward pressure of the pressure block 2.

[0057] In the first embodiment of the measuring device of the present invention, a lithium filling cavity 11, a sample cavity 12, and a liquid injection cavity 13 are sequentially arranged inside the housing 1 from the inside to the outside;

[0058] Metallic lithium is placed in the lithium filling cavity 11;

[0059] The negative electrode material sample is placed in the sample cavity 12;

[0060] A liquid injection port 14 is provided on the liquid injection cavity 13 for injecting electrolyte.

[0061] The pressure block 2 is embedded in the sample cavity 12 and is adapted to the size of the sample cavity 12.

[0062] The sample cavity 12 and the liquid injection cavity 13 are separated by ceramics, and the sample cavity 12 and the lithium filling cavity 11 are separated by a ceramic solid electrolyte.

[0063] Combined with Figure 5 and Figure 6As shown in the figure, in the second embodiment of the measurement device of the present invention, the housing 1 includes a base 15, and a sample chamber 12 and a liquid injection chamber 13 are sequentially arranged from the inside to the outside thereon;

[0064] A negative electrode material sample is placed in the sample chamber 12;

[0065] A liquid injection port 14 is provided on the liquid injection chamber 13 for injecting electrolyte.

[0066] The sample chamber 12 and the liquid injection chamber 13 are separated by a metal material such as stainless steel with holes, and the holes are filled with ceramic materials.

[0067] The pressing block 2 is embedded in the sample 12 and is adapted to the sample chamber 12.

[0068] The housing 1 can be of various shapes, such as cylindrical, square columnar or polygonal columnar, etc., and the material is made of stainless steel.

[0069] The present invention also provides a measurement method for a measurement device based on the volume change of a lithium battery negative electrode material:

[0070] Place a certain mass of negative electrode material sample in the sample chamber 12, press down the pressing block 2, the length measurement system 4 measures the moving distance (height) of the pressing block 2, and the pressure sensing system 5 measures the pressing pressure of the pressing block 2 to obtain the compaction density curve of the negative electrode material sample;

[0071] Put in metallic lithium, inject electrolyte into the liquid injection chamber 13, set the pressure of the pressing block 2 as a constant pressure, and obtain the volume change of the negative electrode material sample during the entire lithium insertion reaction under this constant pressure according to the measured moving distance.

[0072] In the first embodiment of the measurement device of the present invention, a lithium filling chamber 11, a sample chamber 12 and a liquid injection chamber 13 are sequentially arranged from the inside to the outside inside the housing 1;

[0073] The housing 1 is made of stainless steel;

[0074] The pressing block 2 is embedded in the sample 12 and is adapted to the sample chamber 12;

[0075] The sample chamber 12 and the liquid injection chamber 13 are separated by ceramics, and the sample chamber 12 and the lithium filling chamber 11 are separated by a ceramic solid electrolyte.

[0076] The measurement method embodiment one of the measurement device based on the volume change of the lithium battery negative electrode material of the present invention includes:

[0077] 1) Measurement of the compaction density of the material powder

[0078] Combined Figure 2As shown, in the initial state, the reading of the length measurement system 4 is 0, and the reading increases as the pressure bar 3 is lifted; when measuring the compaction density of the material powder, lift the pressure bar 3, remove the compact 3, as Figure 4 shown; place the pre-weighed negative electrode material sample in the sample cavity 12, put in the compact 2, and press down the pressure bar 3, as Figure 3 shown; control the pressure bar 3 to slowly press down, obtain the real-time pressure value of the negative electrode material sample through the pressure sensing system 5, and obtain the real-time height value H of the negative electrode material sample through the length measurement system 4, and it can be obtained that:

[0079] The compaction density of the negative electrode material sample

[0080] If necessary, the system can directly plot in real time to obtain the pressure-compaction density curve;

[0081] Weigh 1 g of the negative electrode material sample, place it in the sample cavity 12, slowly put the compact 2 into the sample cavity to prevent powder splashing. Press the pressure bar 3 down to the position of the compact 2 and start applying pressure, and control the pressure F to continuously and stably rise through the (high-precision) pressure sensing system.

[0082] If the outer diameter of the sample cavity 12 is 2 cm and the inner diameter is 1.6 cm, then the area S of the sample cavity = π×1 2 -π×0.8 2 = 1.131 cm 2 . The real-time compaction density D of the negative electrode material = 1 / (1.131H) g / cm 2 . The real-time pressure-compaction density (F-D) curve can be obtained through real-time data acquisition.

[0083] 2) Test on the charging expansion rate of the negative electrode material sample

[0084] Drop sufficient molten metallic lithium into the lithium filling cavity 11 (or place a lithium column that perfectly fits the lithium filling cavity 11), ensure that its height is not lower than the height of the negative electrode material sample in the sample cavity, place the pre-weighed negative electrode material sample in the sample cavity 12, put in the compact 2, press down the pressure bar 3, control the pressure bar 3 to slowly press down, control the pressure to remain constant, and inject electrolyte into the injection cavity 13, and the height of the electrolyte is higher than the height of the negative electrode material sample;

[0085] The electrolyte can penetrate through the ceramic and ceramic solid electrolyte, completely penetrate the negative electrode material sample and infiltrate into the lithium filling cavity 11. At this time, due to the conductivity of the metal housing 1, a spontaneous reaction occurs between the lithium metal, the electrolyte and the negative electrode material sample, and lithium is embedded in the negative electrode material sample; the real-time height value H of the negative electrode material sample can be obtained through the length measurement system 4 to obtain the real-time volume of the negative electrode material sample. After the lithium insertion reaction is complete, the volume of the negative electrode material sample no longer changes, and the expansion rate of the negative electrode material sample can be obtained:

[0086] The sample volume V = the sample chamber area S × the sample height H

[0087]

[0088] Weigh 1 g of the negative electrode material sample and place it into the sample chamber 12; add a lithium column that perfectly fits the lithium filling chamber 11 into the lithium filling chamber, and ensure that its height is not lower than the height of the material in the sample chamber 12. Slowly place the pressing block 2 into the sample chamber to prevent powder splashing. Press down the pressing rod 3 to the position of the pressing block 2 and start applying pressure. Control the pressure F to rise to the required pressure, such as 10 MPa, through a (high-precision) pressure sensing system and keep it stable. Record the material height H1 at this time. Inject a sufficient amount of electrolyte into the injection chamber 13 through the liquid injection port 14. The electrolyte infiltrates the negative electrode material and metallic lithium through the ceramic and ceramic solid electrolyte layer, ensuring that the electrolyte liquid level is higher than the height of the negative electrode material. At this time, since the housing 1 is made of a conductive metal material, the metallic lithium is electrically connected to the negative electrode material. Therefore, under the action of the ion-conducting electrolyte, lithium will spontaneously embed into the negative electrode material, that is, the lithium intercalation reaction occurs. As the lithium intercalation reaction proceeds, the negative electrode material will expand in volume. When the pressure of the pressing block remains unchanged at 10 Mpa, the material will push the pressing block upward due to volume expansion, and the material height increases. Read the height H in real time. Wait until the lithium intercalation reaction is complete and the volume of the negative electrode material sample no longer changes. At this time, the height is stable at H2.

[0089] If the outer diameter of the sample chamber 12 is 2 cm and the inner diameter is 1.6 cm, then the sample chamber area S = π×1 2 -π×0.8 2 = 1.131 cm 2 .

[0090] The expansion rate of the negative electrode material sample = (H2 - H1) / H1×100%

[0091] The real-time expansion rate of the negative electrode material under 10 MPa pressure = (H - H1) / H1×100%. The time-expansion rate curve can be obtained through real-time data acquisition.

[0092] In the second embodiment of the measuring device of the present invention, the housing 1 includes a base 15 and, successively arranged from the inside outwards thereon, a sample chamber 12 and an injection chamber 13; wherein, the upper surface of the base 15 and the lower surface of the pressing block 2 are both smooth surfaces;

[0093] The housing 1, the pressing block 2 and the pressing rod 3 are made of stainless steel;

[0094] The inner walls of the injection chamber 13 and the sample chamber 12 are smooth. The sample chamber 12 and the injection chamber 13 are separated by a stainless steel material with holes, and the holes are filled with ceramic materials so that the electrolyte can pass through and infiltrate into the negative electrode material sample.

[0095] In addition, a demolding support tube 6 is also provided. The demolding support tube 6 is made of transparent plastic material, which is convenient for observing the demolding situation of the material.

[0096] The second embodiment of the measurement method of the measurement device based on the volume change of the negative electrode material of the lithium battery of the present invention includes:

[0097] 1) Measurement of the tap density of the material powder

[0098] Combined with Figure 6 As shown, in the initial state, the reading of the length measurement system 4 is 0, and the reading increases as the pressing rod 3 is lifted; when measuring the tap density of the material powder, lift the pressing rod 3 and take out the pressing block 2, as Figure 7 shown; place the standard weighed negative electrode material sample in the sample chamber 12, put in the pressing block 2, and press down the pressing rod 3, as Figure 8 shown; control the pressing rod 3 to slowly press down, obtain the real-time pressure value of the negative electrode material sample through the pressure sensing system 5, and obtain the real-time height value H of the negative electrode material sample through the length measurement system 4, and it can be obtained that:

[0099] The tap density of the negative electrode material sample

[0100] If necessary, the system can directly draw a graph in real time to obtain the pressure-tap density curve;

[0101] Weigh 1 g of the negative electrode material sample and place it in the sample chamber 12. Slowly place the pressing block 2 into the sample chamber to prevent powder splashing. Press the pressing rod 3 down to the pressing block 2 and start applying pressure. Control the pressure F to continuously and steadily rise through the (high-precision) pressure sensing system.

[0102] If the inner diameter of the sample chamber 12 is 2 cm, then the area S of the sample chamber = π×1 2 = 3.14 cm 2 . The real-time tap density D of the negative electrode material = 1 / (3.14H) g / cm 2 . The real-time pressure-tap density (F-D) curve can be obtained through real-time data acquisition.

[0103] 2) Test of the charging expansion rate of the negative electrode material sample

[0104] Combined with Figure 7As shown, place the liquid injection chamber 13 and the sample chamber 12 on the base 15. Place the mated lithium metal sheet and separator in the sample chamber 12, put in the pressing block 2, lower the pressing rod 3 to the pressure P, and the length measurement system 4 obtains the height H1 of the lithium metal sheet and the separator; remove the pressing block 2 and the pressing rod 3, place a certain amount of negative electrode material sample on the pressing rod 3, put in the pressing block 2, lower the pressing rod 3 to the pressure P, and obtain the total height H2 through the length measurement system 4; inject electrolyte into the liquid injection chamber 13, keep the pressure P of the pressing rod 3 unchanged until the lithium intercalation reaction of the negative electrode material sample is complete and the pressing rod 3 does not displace;

[0105] Combined with Figure 8 As shown, invert the liquid injection chamber 13 and the sample chamber 12, remove the base 15, install the demolding support tube 6, slowly increase the downward pressure on the pressing rod 3 until the lithium metal sheet and the separator are removed, taking care not to eject the negative electrode material sample; then replace the base 15, as Figure 7 shown, apply the pressure P to the pressing rod 3, and when the pressing rod 2 is stable and no longer moves, obtain the height H3 of the negative electrode material sample at this time through the length measurement system 4 to obtain the negative electrode expansion rate:

[0106]

[0107] If the diameter of the sample chamber is 2 cm, place a lithium sheet with a diameter of 2 cm in the sample chamber, and place a separator with a diameter of 2 cm flat on the lithium sheet; gently place the pressing block 2, lower the pressing rod 3 to the pressing block 2, and start applying pressure. Control its pressure F through a (high-precision) pressure sensing system to rise to the required pressure, such as 10 MPa, and read the height H1 at this time. Lift the pressing rod 3, remove the pressing block 2, weigh 1 g of the negative electrode material sample, and carefully place it in the sample chamber 12; slowly place the pressing block 2 into the sample chamber to prevent powder splashing. Lower the pressing rod 3 to the pressing block 2, and start applying pressure. Control its pressure F to 10 MPa through a (high-precision) pressure sensing system and keep it stable, and record the total height H2 at this time. Inject sufficient electrolyte into the liquid injection chamber 13 through the liquid injection port 14. The electrolyte can pass through the ceramic and infiltrate the negative electrode material and the lithium metal to ensure that the electrolyte liquid level is higher than the height of the materials in the sample chamber. At this time, since the liquid injection chamber 13 and the sample chamber 12 are mainly made of stainless steel metal and have conductivity, the lithium metal is connected to the negative electrode material. Therefore, under the action of the electrolyte conducting ions, lithium will spontaneously intercalate into the negative electrode material, that is, the lithium intercalation reaction occurs. As the lithium intercalation reaction proceeds, the negative electrode material will expand in volume. When the pressure of the pressing block remains unchanged at 10 Mpa, the material will push the pressing block upward due to volume expansion, and the material height increases. When the lithium intercalation reaction is complete, the volume of the negative electrode material sample no longer changes. At this time, invert the housing 1, remove the base 15, place the demolding support tube 6, slowly increase the downward pressure on the pressing rod 3 until the lithium metal sheet and the separator are removed, taking care not to eject the negative electrode material sample; replace the base 15, and place the housing as Figure 7Place it upright as shown, apply a pressure of 10 MPa to the pressure bar 3, wait for the height reading to stabilize, and read the height H3.

[0108] The expansion rate of the negative electrode material sample = (H3 - H2 + H1) / (H2 - H1) × 100%

[0109] Those of ordinary skill in the art should recognize that the above embodiments are only used to illustrate the present invention and are not intended to limit the present invention. As long as within the spirit and scope of the present invention, changes and modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A method for measuring the volume change of a lithium battery anode material based on a volume change measurement device for the lithium battery anode material, characterized in that, The device for measuring the volume change of the negative electrode material of the lithium battery includes: A housing for placing the negative electrode material sample, metallic lithium, and injecting electrolyte to provide conditions for the lithium intercalation reaction; A pressing block for compacting the negative electrode material sample and metallic lithium; A pressing rod connected to the pressing block. The pressing rod is also connected with a length measurement system and a pressure sensing system. The length measurement system is used to measure the moving distance of the pressing block, and the pressure sensing system is used to measure the downward pressure of the pressing block. Inside the housing, there are a lithium filling cavity, a sample cavity, and a liquid injection cavity arranged in sequence from the inside to the outside; The metallic lithium is placed in the lithium filling cavity; The negative electrode material sample is placed in the sample cavity; The liquid injection cavity is provided with a liquid injection port for injecting the electrolyte. The measurement method includes: 1) Measurement of the compaction density of the material powder In the initial state, the reading of the length measurement system is 0. Lift the pressing rod, take out the pressing block, place the weighed negative electrode material sample in the sample cavity, put in the pressing block, press down the pressing rod, control the pressing rod to slowly press down, obtain the real-time pressure value of the negative electrode material sample through the pressure sensing system, and obtain the real-time height value H of the negative electrode material sample through the length measurement system. It can be obtained that: The tap density of the negative electrode material sample 2) Test of the charging expansion rate of the negative electrode material sample Place metallic lithium in the lithium filling cavity to ensure that its height is not lower than the height of the negative electrode material sample in the sample cavity. Place the weighed negative electrode material sample in the sample cavity, put in the pressing block, press down the pressing rod, control the pressing rod to slowly press down, control the pressure to be constant, inject the electrolyte into the liquid injection cavity, and the height of the electrolyte is higher than the height of the negative electrode material sample; The electrolyte completely penetrates the negative electrode material sample and seeps into the lithium filling cavity. Obtain the real-time height value H of the negative electrode material sample through the length measurement system. After the lithium intercalation reaction is complete and the volume of the negative electrode material sample no longer changes, obtain the expansion rate of the negative electrode material sample: The volume of the sample V = the area S of the sample cavity × the height H of the sample 2. The method for measuring the volume change of the anode material of a lithium battery according to claim 1, wherein: The sample cavity and the liquid injection cavity are separated by ceramics, and the sample cavity and the lithium filling cavity are separated by a ceramic solid electrolyte.

3. The method for measuring the volume change of the anode material of a lithium battery according to claim 1, wherein: The pressing block is embedded in the sample cavity and is adapted to the sample cavity.

4. The method for measuring the volume change of the anode material of a lithium battery according to claim 1, characterized in that: The housing is made of stainless steel.

5. A method for measuring the volume change of a lithium battery anode material based on a volume change measurement device for the lithium battery anode material, characterized in that, The device for measuring the volume change of the negative electrode material of the lithium battery includes: A housing for placing the negative electrode material sample, metallic lithium, and injecting electrolyte to provide conditions for the lithium intercalation reaction; A pressing block for compacting the negative electrode material sample and metallic lithium; A pressing rod connected to the pressing block. The pressing rod is also connected with a length measurement system and a pressure sensing system. The length measurement system is used to measure the moving distance of the pressing block, and the pressure sensing system is used to measure the downward pressure of the pressing block. The housing includes a base and a sample cavity and a liquid injection cavity arranged in sequence from the inside to the outside thereon; The metallic lithium, separator, and negative electrode material sample are placed in the sample cavity; The liquid injection cavity is provided with a liquid injection port for injecting the electrolyte The method for measuring the volume change of the negative electrode material of the lithium battery includes: 1) Measurement of the compaction density of the material powder In the initial state, the reading of the length measurement system is 0. Lift the pressure rod, remove the pressure block, place the weighed negative electrode material sample in the sample cavity, put in the pressure block, press down the pressure rod, control the pressure rod to slowly press down, obtain the real-time pressure value of the negative electrode material sample through the pressure sensing system, and obtain the real-time height value H of the negative electrode material sample through the length measurement system. It can be obtained that: 2) Test on the charging expansion rate of the negative electrode material sample Place the liquid injection cavity and the sample cavity on the base. Place metallic lithium and a separator in the sample cavity, put in the pressure block, press down the pressure rod to pressure P, and the length measurement system obtains the height H1 of the metallic lithium and the separator. Remove the pressure block, then place the negative electrode material sample on the metallic lithium and the separator, put in the pressure block, press down the pressure rod to pressure P, and obtain the total height H2 through the length measurement system. Inject the electrolyte into the liquid injection cavity, and keep the pressure P unchanged until the lithium intercalation reaction of the negative electrode material sample is complete and the pressure rod does not displace; Invert the liquid injection cavity and the sample cavity, remove the base, install the demoulding support tube, slowly increase the downward pressure on the pressure rod until the metallic lithium and the separator are removed, replace the base again, apply pressure P to the pressure rod, and when the pressure rod is stable and no longer moves, obtain the height H3 of the negative electrode material sample at this time through the length measurement system, and obtain the negative electrode expansion rate:

6. The method for measuring the volume change of the anode material of a lithium battery according to claim 5, wherein: The sample cavity and the liquid injection cavity are separated by stainless steel with holes, and the holes are filled with ceramic materials.

Images