WO2022266799A1

WO2022266799A1 - Electrochemical device and electronic device

Info

Publication number: WO2022266799A1
Application number: PCT/CN2021/101236
Authority: WO
Inventors: 刘茜; 郑席; 杜鹏; 谢远森
Original assignee: 宁德新能源科技有限公司
Priority date: 2021-06-21
Filing date: 2021-06-21
Publication date: 2022-12-29
Also published as: CN114586213A

Abstract

The present application provides an electrochemical device and an electronic device. The discharge capacity of the electrochemical device at 0.2 C at -20°C is A, the discharge capacity of the electrochemical device at 0.2 C at 25°C is B, and 70%≤A/B≤90%. The electrochemical device provided in embodiments of the present application have high low-temperature charge/discharge performance at a low temperature of -20°C.

Description

Electrochemical devices and electronic devices

technical field

The present application relates to the field of electrochemical energy storage, in particular to electrochemical devices and electronic devices.

Background technique

With the development and progress of electrochemical devices (eg, lithium-ion batteries), higher and higher requirements are placed on their low-temperature charge-discharge performance. At present, in order to improve the low-temperature charge-discharge performance of electrochemical devices, although some measures have been taken and some improvements have been made, they are still not satisfactory.

Therefore, improving the low-temperature charge-discharge performance of electrochemical devices is still an urgent problem to be solved.

Contents of the invention

Some embodiments of the present application provide an electrochemical device, the 0.2C discharge capacity of the electrochemical device at -20°C is A, the 0.2C discharge capacity of the electrochemical device at 25°C is B, and 70%≤A/B ≤90%. In some embodiments, 71%≤A/B≤87%. This shows that the electrochemical device proposed in the examples of the present application has better charge and discharge performance at a low temperature of -20°C, can charge and release more energy, and improves the impact on the charge and discharge performance of the electrochemical device at a low temperature. satisfaction.

In some embodiments, the 0.2C discharge capacity of the electrochemical device at 45°C is C, 103%≦C/B≦110%. It shows that the electrochemical device can charge and discharge more energy at medium and high temperature, and has better medium and high temperature charge and discharge performance.

In some embodiments, at least one of the following (a) or (b) is satisfied: (a) the electrochemical device includes a negative electrode, and when the electrochemical device is at a state of charge of 50%, the thickness of the negative electrode is is H ₂ , when the electrochemical device is at 0% state of charge, the thickness of the negative electrode is H ₁ , and (H ₂ -H ₁ )/H ₁ is 0% to 6%; (b) the electrochemical The device includes a negative electrode. When the electrochemical device is in a state of charge of 100%, the thickness of the negative electrode is H ₃ . When the electrochemical device is in a state of charge of 0%, the thickness of the negative electrode is H ₁ , (H ₃ -H ₁ )/H ₁ is 0% to 8%. It represents the thickness growth rate of the negative electrode of the electrochemical device when it is charged from 0% state of charge to 50% state of charge. The thickness growth rate of 0% to 6% means that the negative electrode of the electrochemical device in the embodiment of the application is charging The expansion in the process is small, which is beneficial to improve the charge and discharge performance of the electrochemical device.

In some embodiments, the electrochemical device includes a negative electrode, the negative electrode includes a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector, the porosity of the negative electrode active material layer is 20% to 50%, and optionally, the negative electrode active material layer The porosity is 35% to 50%. If the porosity of the negative electrode active material layer is less than 20%, it means that the space between the negative electrode materials is small, which may lead to insufficient contact between the negative electrode material and the electrolyte, and then the performance of the negative electrode cannot be fully exerted. When the pores of the negative electrode active material layer When the ratio exceeds 50%, it may be because the gap between the particles of the negative electrode material is too large, resulting in poor electrical contact between the particles of the negative electrode material, which affects the performance of the electrochemical device. In some embodiments, the porosity of the negative electrode active material layer is 35% to 50%, and the performance of the electrochemical device is better at this time.

In some embodiments, the electrochemical device includes a negative electrode, the negative electrode includes a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector, the negative electrode active material layer includes a negative electrode material, and the negative electrode material includes hard carbon, And satisfy at least one of the following (c) to (g): (c) the bonding force between the negative electrode active material layer and the negative electrode current collector is 10N/m to 50N/m; preferably, the The bonding force between the negative electrode active material layer and the negative electrode current collector is 10N/m to 48N/m; (d) the compacted density of the negative electrode active material layer is 0.9g/ ^cm3 to 1.25g/cm3 ³ ; (e) the particle breakage rate of the negative electrode material is 10% to 40%, optionally, the particle breakage rate of the negative electrode material is 10% to 25%; (f) the X-ray diffraction of the negative electrode material In the spectrum, there is a diffraction peak between 18 ° and 30 °, and the half-height width of the diffraction peak is 4 ° to 10 °; (g) the microchip layer spacing of the negative electrode material is 0.34nm to 0.4nm, Optionally, the interlayer spacing of the microchips of the negative electrode material is 0.37 nm to 0.39 nm, and optionally, the interlayer spacing of the microchips of the negative electrode material is 0.37 nm to 0.38 nm.

The interlayer spacing of the microchips of the negative electrode material is 0.37nm to 0.39nm. At this time, the dynamic performance of the negative electrode material is better, and the expansion rate of the negative electrode is small. When the interlayer spacing of the microchips of the negative electrode material is too small, ions diffuse between the microchip layers. The resistance is relatively large, and the microchip layer is easily stretched by ions, resulting in the overall expansion of the negative electrode. When the interlayer spacing of the microchips is too large, some solvents may be co-embedded, which will destroy the structure of the negative electrode material and affect the overall electrical performance.

In some embodiments, the electrochemical device satisfies at least one of the following (h) and (i): (h) the 1C discharge capacity of the electrochemical device at 25°C is D, 0.9<D/B<1; (i) The 5C discharge capacity of the electrochemical device at 25°C is E, 99%≤E/B≤105%. In some embodiments, the three-electrode potential is monitored on the electrochemical device, and the voltage is taken as the ordinate and the state of charge is used as the abscissa. The negative electrode delithiation curve is a slope area from 0.3V to 0.8V, and the negative electrode delithiation curve is The state of charge ratio F below 0.2V is 30% to 80%. The delithiation curve of the negative electrode is a slope area from 0.3V to 0.8V (the slope area refers to the angle between the electrochemical curve and the 0V horizontal line is greater than 30°, that is, compared with the initial curve, it is an obvious upward trend), and the delithiation curve of the negative electrode is at 0.2V The following state of charge ratio F is 30% to 80%. In some embodiments, the slope area is an intrinsic characteristic of the hard carbon material, and the state of charge ratio F of the delithiation curve of different negative electrode materials is different below 0.2V. The kinetic performance of the electrochemical device is better when the proportion F is 30% to 80%, but if the charge state proportion F of the negative electrode delithiation curve is below 0.2V is greater than 80%, the overall voltage of the electrochemical device is low, Energy density is reduced.

In some embodiments, the electrochemical device includes a positive electrode and a negative electrode, the positive electrode includes a positive electrode current collector and a positive electrode active material layer on the positive electrode fluid, and the negative electrode includes a negative electrode current collector and a negative electrode active material layer on the negative electrode current collector. The weight of the single-sided positive electrode active material layer is M ₁ , the weight of the single-sided negative electrode active material layer per unit area is M ₂ , and M ₁ /M ₂ is 2 to 6. In some embodiments, the CB value of the electrochemical device is 0.9 to 1.1, optionally, the CB value is 0.95 to 1.06; wherein, the CB value is the ratio of the negative electrode capacity to the positive electrode capacity under the same area. That is, CB=negative electrode capacity/positive electrode capacity, the negative electrode capacity=CW _{negative electrode} ×gram capacity _{negative electrode} ×active material percentage content _{negative electrode} , the positive electrode capacity=CW _{positive electrode} ×gram capacity _{positive electrode} ×active material percentage content _{positive electrode} . The percentage of active material in the _{positive electrode} and the percentage of active material in the _{negative electrode} respectively represent the mass ratio of the positive electrode material to the positive electrode active material layer and the mass ratio of the negative electrode material to the negative electrode active material layer. By setting the CB value, the performance of the positive electrode material and the negative electrode material can be fully utilized. The positive electrode material and the hard carbon material in the negative electrode material are reasonably matched. When the electrochemical device is a lithium-ion battery, when the CB value is too small, it may cause the positive electrode to provide Too many lithium ions in the negative electrode will cause lithium precipitation, and when the CB value is too large, it may lead to a decrease in energy density.

The present application also proposes an electronic device, including any one of the above electrochemical devices.

In the examples of the present application, the 0.2C discharge capacity of the electrochemical device at -20°C is A, and the 0.2C discharge capacity of the electrochemical device at 25°C is B, and 70%≤A/B≤90%. The electrochemical device proposed in the examples of the present application has better low-temperature charge and discharge performance at a low temperature of -20° C., and can charge and release more energy.

detailed description

The following examples can enable those skilled in the art to understand the present application more comprehensively, but do not limit the present application in any way.

Electrochemical devices, such as lithium-ion batteries, are widely used in various fields and have a wide range of usage scenarios. At low temperatures, the charge-discharge performance of electrochemical devices is often unsatisfactory, and further improvements are expected.

In the description of the present disclosure, "100% state of charge" refers to the state where the electrochemical device is charged to the maximum design voltage with a constant current, and includes the state after standing (generally standing for 10 minutes), which is regarded as Fully charged state, unless otherwise specified, the maximum design voltage includes but not limited to 4.48V, 4.5V, 4.53V or 4.45V, or even higher voltage.

In the description of the present disclosure, "0% state of charge" refers to the state of constant current discharge of the electrochemical device to the minimum design voltage, and includes the state after standing (generally standing for 10 minutes), which is considered to be fully charged. In the discharge state, unless otherwise specified, the maximum design voltage includes but is not limited to 3.0V, 2.8V, 2.6V or 2.0V, or even lower voltage. Similarly, in the description of the present disclosure, the 50% state of charge includes the state after standing (generally standing for 10 minutes).

Some embodiments of the present application provide an electrochemical device, the 0.2C discharge capacity of the electrochemical device at -20°C is A, the 0.2C discharge capacity of the electrochemical device at 25°C is B, and 70%≤A/B ≤90%. In some embodiments, the discharge capacity B of the electrochemical device at 0.2C at 25°C characterizes the charge and discharge performance of the electrochemical device at room temperature, and the discharge capacity A of the electrochemical device at 0.2C at -20°C characterizes the electrochemical device The charge and discharge performance of the device at low temperature, A/B characterizes the retention rate of the charge and discharge performance of the electrochemical device at low temperature, because 70%≤A/B≤90%, this shows that the electrochemical device proposed in the examples of this application The device has better charge and discharge performance at a low temperature of -20°C, can charge and release more energy, and improves the satisfaction with the charge and discharge performance of the electrochemical device at low temperature.

In some embodiments of the present application, the 0.2C discharge capacity of the electrochemical device at 45°C is C, 103%≤C/B≤110%. In some embodiments, the 0.2C discharge capacity of the electrochemical device at 45°C is C, which characterizes the charge and discharge performance of the electrochemical device at medium and high temperatures, and 103%≤C/B≤110% indicates that the electrochemical device can be used in medium and high temperature. Charge and release more energy at high temperature, and have better medium and high temperature charge and discharge performance.

In some embodiments of the present application, the electrochemical device includes a negative electrode, the thickness of the negative electrode is _H2 when the electrochemical device is at a state of charge of 50%, and the thickness of the negative electrode is H1 when the electrochemical device is at _a state of charge of 0%, ( H ₂ -H ₁ )/H ₁ is 0% to 6%. In some embodiments, (H ₂ -H ₁ )/H ₁ represents the thickness growth rate of the negative electrode of the electrochemical device when it is charged from 0% state of charge to 50% state of charge, and the thickness growth rate is 0% to 6 % indicates that the expansion of the negative electrode of the electrochemical device in the embodiment of the present application is small during the charging process, which is conducive to improving the charge and discharge performance of the electrochemical device.

In some embodiments of the present application, the electrochemical device includes a negative electrode, the thickness of the negative electrode is H ₃ when the electrochemical device is in a 100% state of charge, and the thickness of the negative electrode is H ₁ when the electrochemical device is in a 0% state of charge, ( H ₃ -H ₁ )/H ₁ is 0% to 8%. In some embodiments, (H ₃ -H ₁ )/H ₁ represents the thickness growth rate of the negative electrode of the electrochemical device when it is charged from 0% state of charge to 100% state of charge, and the thickness growth rate is 0% to 8 % means that the expansion of the negative electrode of the electrochemical device in the embodiment of the present application is small during the whole charging process, which is beneficial to improve the charge and discharge performance of the electrochemical device.

In some embodiments of the present application, the electrochemical device includes a negative electrode, the negative electrode includes a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector, and the porosity of the negative electrode active material layer is 20% to 50%. In some embodiments, if the porosity of the negative electrode active material layer is less than 20%, it means that the space between the negative electrode materials is small, which may lead to insufficient contact between the negative electrode material and the electrolyte, and then cause the performance of the negative electrode to not be fully utilized. When the porosity of the active material layer exceeds 50%, the gap between the particles of the negative electrode material may be too large, resulting in poor electrical contact between the particles of the negative electrode material, which affects the performance of the electrochemical device. In some embodiments, the porosity of the negative electrode active material layer is 35% to 50%, and the performance of the electrochemical device is better at this time.

Porosity test of negative electrode active material layer:

Take a fully charged lithium-ion battery, disassemble it, take out the negative electrode and soak it in DMC (ethylene carbonate) for 20 minutes, then wash it with DMC and acetone in sequence, put it in an oven, and dry it at 80°C for 12 hours. After sample preparation by negative electrode ion milling, observe under SEM, and cut out ten pieces of SEM pictures with the area of A=20μm×20μm, including the cross-section SEM picture of the first active material layer, the cross-section SEM picture of the second active material layer, and the cross-section SEM picture of the entire negative electrode , use the image processing software (Multiphase) to calculate the area B of the darker part of the pore in the cross-sectional view, porosity=B/A×100%, and then calculate the average value of the porosity of ten SEM pictures, which is the negative electrode active material layer porosity.

In some embodiments of the present application, the electrochemical device includes a negative electrode, the negative electrode includes a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector, the negative electrode active material layer includes a negative electrode material, the negative electrode material includes hard carbon, the negative electrode active material layer and The binding force between negative electrode current collectors is 10 N/m to 50 N/m. In some embodiments, if the bonding force between the negative electrode active material layer and the negative electrode current collector is too small, it may cause peeling off or poor contact between the negative electrode active material layer and the negative electrode current collector during the charging and discharging process of the electrochemical device, It is not conducive to electron conduction and affects test performance. If the binding force between the negative electrode active material layer and the negative electrode current collector is too large, it may be necessary to use too much binder, which may be detrimental to the conductivity of the negative electrode and affect the kinetic performance.

Adhesion test between negative electrode active material layer and negative electrode current collector:

The brand of the instrument used for testing the adhesion between the negative electrode active material layer and the negative electrode current collector is Instron, the model is 33652, take the negative electrode (width 30mm × length (100mm to 160mm)), and use double-sided adhesive tape (model: 3M9448A, width 20mm) ×Length (90mm to 150mm)) is fixed on the steel plate, fix the paper tape with the same width as the negative electrode and the negative electrode side with adhesive tape, adjust the limit block of the tension machine to a suitable position, fold the paper tape upwards and slide 40mm , the slip rate is 50mm/min, and the adhesion force between the negative electrode active material layer and the negative electrode current collector is tested under 180° (that is, stretched in the opposite direction).

In some embodiments of the present application, the compacted density of the negative electrode active material layer is 0.9 g/cm ³ to 1.25 g/cm ³ . Test of the compacted density of the negative electrode active material layer:

Take a fully discharged lithium-ion battery, disassemble the negative electrode, wash, dry, use an electronic balance to weigh the negative electrode with a certain area S (both sides of the negative electrode current collector are coated with negative electrode active material layers), and record the weight as W1 , and use a micrometer to measure the thickness T1 of the negative electrode. Use a solvent to wash off the negative electrode active material layer, dry it, measure the weight of the negative electrode current collector, which is recorded as W2, and use a micrometer to measure the thickness T2 of the negative electrode current collector. The weight W0 and the thickness T0 of the negative electrode active material layer arranged on one side of the negative electrode current collector and the compacted density of the negative electrode active material layer are calculated by the following formula:

W0=(W1-W2)/2

T0=(T1-T2)/2

Compacted density=W0/(T0×S).

In some embodiments, if the compaction density of the negative electrode active material layer is too small, it will be unfavorable to the volumetric energy density of the electrochemical device, and it will also be unfavorable to the conduction of electrons in the negative electrode active material layer. If the compaction density of the negative electrode active material layer is too large, the electrolyte may not be able to fully infiltrate the negative electrode active material layer, which is not conducive to fully exerting the performance of the negative electrode.

In some embodiments of the present application, the particle crushing rate of the negative electrode material is 10% to 40%. In some embodiments, the particle crushing rate of the negative electrode material is the ratio of the broken particles of the negative electrode material to the total number of particles of the negative electrode material. In statistics For the particle breakage rate of the negative electrode material, a scanning electron microscope (SEM) can be used to take pictures of the negative electrode active material layer, select at least 10 areas with a predetermined area (10 μm × 10 μm), and count the total number of particles in each predetermined area , and then count the number of broken particles in the predetermined area, the particle breakage rate of the negative electrode material = the number of broken particles / the total number of particles, where the broken particles are visible cracks, that is, the gap where the two parts can completely overlap, indicating that the particles are broken , when the total particle number is counted, the particle diameter is larger than 3 μm, and the particle breakage rate of the negative electrode material in these areas is counted. The negative electrode of the electrochemical device is usually rolled during the manufacturing process, causing the particles of the negative electrode material to be partially broken. A small amount of particle breakage of the negative electrode material is conducive to increasing the contact area with the electrolyte and improving the rate performance. If the rate is too high, the consumption of the electrolyte will be excessively increased. Optionally, the particle breakage rate of the negative electrode material is 10% to 25%. At this time, the overall performance of the electrochemical device is better.

In some embodiments of the present application, in the X-ray diffraction pattern of the negative electrode material, there is a diffraction peak between 18° and 30°, and the half-height width of the diffraction peak is 4° to 10°. In some embodiments, there is only one diffraction peak with a full width at half maximum of 4° to 10° between 18° and 30°. In some embodiments, the negative electrode material may include hard carbon.

In some embodiments of the present application, the distance between the microchip layers of the negative electrode material is 0.34 nm to 0.4 nm. In some embodiments, the negative electrode material includes carbon material, and the distance between the microchip layers is 0.34 nm to 0.4 nm, indicating that the carbon material is amorphous carbon. Optionally, the microchip layer spacing of the negative electrode material is 0.38nm to 0.39nm. At this time, the dynamic performance of the negative electrode material is better, and the expansion rate of the negative electrode is small. When the microchip layer spacing of the negative electrode material is too small, the ions in the microchip The resistance to diffusion between layers is relatively large, and the microchip layer is easily stretched by ions, resulting in the overall expansion of the negative electrode. When the interlayer spacing of the microchips is too large, some solvents may be co-embedded, which will destroy the structure of the negative electrode material and affect the overall electrical performance.

In some embodiments of the present application, the 1C discharge capacity of the electrochemical device at 25° C. is D, 0.9<D/B<1. In some embodiments, the charge and discharge performance of the electrochemical device at a rate of 1C is almost the same as that at a rate of 0.2C, and the electrochemical device has good rate performance.

In some embodiments of the present application, the 5C discharge capacity of the electrochemical device at 25° C. is E, 99%≤E/B≤105%. In some embodiments, when the temperature of the electrochemical device is 25° C., the discharge capacity at 5C rate is greater than the discharge capacity at 0.2C, which indicates that the electrochemical device has good high-rate charge-discharge performance.

In some embodiments, the three-electrode potential is monitored on the electrochemical device, and the voltage is taken as the ordinate, and the state of charge is used as the abscissa to draw a graph, and the delithiation curve of the negative electrode is a slope area between 0.3V and 0.8V (the slope area refers to the electric The angle between the chemical curve and the 0V horizontal line is greater than 30°, that is, compared with the initial curve, it is an obvious upward trend), and the charge state ratio F of the negative electrode delithiation curve below 0.2V is 30% to 80%. In some embodiments, the slope area is an intrinsic characteristic of the hard carbon material, and the state of charge ratio F of the delithiation curve of different negative electrode materials is different below 0.2V. The kinetic performance of the electrochemical device is better when the proportion F is 30% to 80%, but if the charge state proportion F of the negative electrode delithiation curve is below 0.2V is greater than 80%, the overall voltage of the electrochemical device is low, Energy density is reduced.

In some embodiments, the electrochemical device includes a positive electrode and a negative electrode, the positive electrode includes a positive electrode current collector and a positive electrode active material layer on the positive electrode fluid, and the negative electrode includes a negative electrode current collector and a negative electrode active material layer on the negative electrode current collector. The weight of the single-sided positive electrode active material layer is M ₁ , the weight of the single-sided negative electrode active material layer per unit area is M ₂ , and M ₁ /M ₂ is 2 to 6. In some embodiments, one or both sides of the positive electrode current collector can have a positive electrode active material layer, and M1 is the weight of the positive electrode active material layer per unit area on _one side of the positive electrode current collector. Similarly, one or both sides of the negative electrode current collector have a negative active material layer Material layer, _M2 is the weight of the negative electrode active material layer per unit area on one side of the negative electrode current collector.

In some embodiments, the CB value of the electrochemical device is 0.9 to 1.1, optionally, the CB value is 0.95 to 1.06; wherein, the CB value is the ratio of the negative electrode capacity to the positive electrode capacity under the same area. In some embodiments, by setting the CB value, the performance of the positive electrode material and the negative electrode material can be fully utilized without causing waste. When the electrochemical device is a lithium-ion battery, if the CB value is too small, the lithium ions provided by the positive electrode may be too high. If the value is too large, it will cause the negative electrode to precipitate lithium, and when the CB value is too large, it may lead to a decrease in energy density. Wherein, CB=negative electrode capacity/positive electrode capacity, the negative electrode capacity is (CW _{negative electrode} ×gram capacity _{negative electrode} ×active material percentage content _{negative electrode} ), and the described positive electrode capacity is (CW _{positive electrode} ×gram capacity _{positive electrode} ×active material percentage content _{positive electrode} ), when the CW _{negative electrode} and CW _{positive electrode are} coated, weigh the weight of the negative electrode active material layer and the weight of the positive electrode active material layer on the area of ^1540.25mm , wherein, the acquisition of CW and active material percentage The method is to remove the positive and negative electrodes from the battery, punch small discs (such as ^1540.25mm2 area) on the flat positive and negative electrodes respectively, and weigh the weight of the active material layer, which is CW (weight of coating film area - empty copper and aluminum foil weight obtained). Then the small disc is digested with concentrated hydrochloric acid, filtered, dried, and then the percentage of the active material in the active material layer is calculated (the weight of the sample dried after hydrochloric acid digestion/the weight of the sample before hydrochloric acid digestion).

Gram capacity _{negative electrode} and gram capacity _{positive electrode} test:

Step 1: Make a button-type battery: cut the negative electrode (positive electrode) into Φ (diameter) = 14mm disc as the working electrode, use Φ (diameter) = 18mm metal lithium as the counter electrode and reference electrode, and use it in between Φ (diameter)=20mm PE isolation film is separated, and the electrolytic solution of the present application is added dropwise, assembles and obtains CR2430 button battery.

Step 2: Gram capacity test: Take the assembled button battery to ensure that the open circuit voltage (OCV) is normal, and each group contains at least 4 parallel samples. The voltage window for the coin cell is set from 0V to 2.5V. Let stand at 25°C for 1 hour, and then discharge the battery with a three-stage low current of 0.05C/50μA/20μA. The negative electrode realizes SEI (solid electrolyte interfacial film) film formation and records the lithium intercalation capacity (the positive electrode realizes film formation and records lithium intercalation. capacity). Then charge the battery to 2.5V with a current of 0.1C, and record the delithiation capacity of the negative electrode (positive electrode), which is the gram capacity of the negative electrode material (positive electrode material) _{negative electrode} (gram capacity _{positive electrode} ).

In some embodiments of the present application, the negative electrode material includes carbon materials. The preparation process of the negative electrode material is briefly described below to better understand the present application, but this is only exemplary and not intended to limit the present application. Dissolve raw material 1 (such as phenolic resin) in solvent 1 (such as ethanol) and stir for a period of time to obtain a mixed solution, then transfer the mixed solution to a hydrothermal reaction kettle, perform a hydrothermal reaction at 180°C, and wait for the temperature to cool. Remove the solid part and dry it. And put it into a box-type furnace to sinter the material according to a certain sintering method to obtain the negative electrode material. In some embodiments, the solvent 1 can also be: water, acetone, methanol, dichloromethane, ethyl acetate, hexane, petroleum ether, toluene or N-methylpyrrolidone. In some embodiments, when the raw material 1 is a soluble material, it may be: epoxy resin, urea-formaldehyde resin, amino resin, ether-based resin, polyester resin, sucrose or glucose. When the raw material 1 is an insoluble material, it can directly enter the sintering step. At this time, the raw material 1 includes: biomass such as shells, straw, etc., lignocellulose, starch, polyvinyl chloride, polyethylene, polypropylene, polystyrene ABS Plastic etc. It should be understood that this preparation method is only exemplary, and other suitable preparation methods can also be used. In some embodiments, the electrochemical device using the negative electrode material proposed in the basic application has excellent low-temperature charge and discharge performance, high rate performance and small expansion rate.

In some embodiments, a conductive agent and a binder may also be included in the negative electrode active material layer. In some embodiments, the conductive agent in the negative electrode active material layer may include at least one of conductive carbon black, Ketjen black, flake graphite, graphene, carbon nanotubes, or carbon fibers. In some embodiments, the binder in the negative active material layer may include carboxymethylcellulose (CMC), polyacrylic acid, polyvinylpyrrolidone, polyaniline, polyimide, polyamideimide, polysilicon At least one of oxane, styrene-butadiene rubber, epoxy resin, polyester resin, polyurethane resin or polyfluorene. In some embodiments, the mass ratio of the negative electrode material, the conductive agent and the binder in the negative electrode active material layer may be (78 to 98.5):(0.1 to 10):(0.1 to 10). The negative electrode material can be a mixture of silicon-based materials and other materials. It should be understood that the above description is only an example, and any other suitable materials and mass ratios may be used. In some embodiments, the negative electrode current collector may use at least one of copper foil, nickel foil, or carbon-based current collector.

In some embodiments, the positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, and the positive electrode active material layer may include a positive electrode material. The positive electrode material includes a positive electrode material capable of absorbing and releasing lithium (Li). Examples of positive electrode materials capable of absorbing/releasing lithium may include lithium cobalt oxide, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium manganate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadyl phosphate, lithium iron phosphate, Lithium titanate and lithium-rich manganese-based materials.

Specifically, the chemical formula of lithium cobalt oxide can be as chemical formula 1:

Li _x Co _a M1 _b O _2-c chemical formula 1

Where M1 means selected from nickel (Ni), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), Copper (Cu), Zinc (Zn), Molybdenum (Mo), Tin (Sn), Calcium (Ca), Strontium (Sr), Tungsten (W), Yttrium (Y), Lanthanum (La), Zirconium (Zr) and At least one of silicon (Si), the values of x, a, b and c are respectively in the following ranges: 0.8≤x≤1.2, 0.8≤a≤1, 0≤b≤0.2, -0.1≤c≤0.2;

The chemical formula of lithium nickel cobalt manganate or lithium nickel cobalt aluminate can be as chemical formula 2:

Li _y Ni _d M2 _e O _2-f chemical formula 2

Wherein M2 means selected from cobalt (Co), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), at least one of copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), tungsten (W), zirconium (Zr), and silicon (Si), The values of y, d, e and f are respectively in the following ranges: 0.8≤y≤1.2, 0.3≤d≤0.98, 0.02≤e≤0.7, -0.1≤f≤0.2;

The chemical formula of lithium manganate can be as chemical formula 3:

Li _z Mn _2-g M3 _g O _4-h chemical formula 3

Where M3 means selected from cobalt (Co), nickel (Ni), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), At least one of copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr) and tungsten (W), the values of z, g and h are respectively in the following ranges Inside: 0.8≤z≤1.2, 0≤g<1.0 and -0.2≤h≤0.2.

In some embodiments, the positive active material layer may further include a conductive agent. In some embodiments, the conductive agent in the positive active material layer may include at least one of conductive carbon black, Ketjen black, flake graphite, graphene, carbon nanotubes, or carbon fibers. In some embodiments, the positive electrode active material layer can also include a binder, and the binder in the positive electrode active material layer can include carboxymethylcellulose (CMC), polyacrylic acid, polyvinylpyrrolidone, polyaniline, polyamide At least one of imine, polyamideimide, polysiloxane, styrene-butadiene rubber, epoxy resin, polyester resin, polyurethane resin or polyfluorene. In some embodiments, the mass ratio of the positive electrode material, the conductive agent and the binder in the positive electrode active material layer may be (80 to 99):(0.1 to 10):(0.1 to 10). In some embodiments, the positive active material layer may have a thickness of 10 μm to 500 μm. It should be understood that the above description is only an example, and any other suitable material, thickness and mass ratio may be used for the positive electrode active material layer. In some embodiments, Al foil may be used as the positive current collector of the positive electrode, and of course, other current collectors commonly used in the art may also be used. In some embodiments, the thickness of the positive current collector of the positive electrode may be 1 μm to 50 μm. In some embodiments, the positive active material layer may be coated only on a partial area of the positive current collector.

In some embodiments, the electrochemical device includes a separator disposed between the positive electrode and the negative electrode. The isolation film includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide or aramid. For example, polyethylene includes at least one selected from high-density polyethylene, low-density polyethylene, or ultra-high molecular weight polyethylene. Especially polyethylene and polypropylene, which have a good effect on preventing short circuits and can improve the stability of the battery through the shutdown effect. In some embodiments, the thickness of the isolation film is in the range of about 5 μm to 50 μm.

In some embodiments, the surface of the isolation membrane may also include a porous layer, the porous layer is arranged on at least one surface of the isolation membrane, the porous layer includes inorganic particles and a binder, and the inorganic particles are selected from alumina (Al ₂ O ₃ ), Silicon oxide (SiO ₂ ), magnesium oxide (MgO), titanium oxide (TiO ₂ ), hafnium oxide (HfO ₂ ), tin oxide (SnO ₂ ), cerium oxide (CeO ₂ ), nickel oxide (NiO), oxide Zinc (ZnO), calcium oxide (CaO), zirconia (ZrO ₂ ), yttrium oxide (Y ₂ O ₃ ), silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or sulfuric acid at least one of barium. In some embodiments, the pores of the isolation membrane have a diameter in the range of about 0.01 μm to 1 μm. The binder of the porous layer is selected from polyvinylidene fluoride, copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, poly At least one of vinylpyrrolidone, polyvinyl ether, polymethylmethacrylate, polytetrafluoroethylene or polyhexafluoropropylene. The porous layer on the surface of the separator can improve the heat resistance, oxidation resistance and electrolyte wettability of the separator, and enhance the adhesion between the separator and the pole piece.

In some embodiments of the present application, the electrochemical device is wound, stacked or folded. In some embodiments, the positive electrode and/or negative electrode of the electrochemical device may be a wound or stacked multi-layer structure, or a single-layer structure in which a single-layer positive electrode, a separator, and a single-layer negative electrode are stacked.

In some embodiments, the electrochemical device includes a lithium-ion battery, although the present application is not limited thereto. In some embodiments, the electrochemical device may also include an electrolyte. The electrolyte may be one or more of a gel electrolyte, a solid electrolyte and an electrolytic solution, and the electrolytic solution includes a lithium salt and a non-aqueous solvent. The lithium salt is selected from LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiClO ₄ , LiB(C ₆ H ₅ ) ₄ , LiCH ₃ SO ₃ , LiCF ₃ SO ₃ , LiN(SO ₂ CF ₃ ) ₂ , LiC(SO ₂ CF ₃ ) ₃ , LiSiF ₆ , LiBOB or one or more of lithium difluoroborate. For example, LiPF ₆ is selected as a lithium salt because it has high ion conductivity and can improve cycle characteristics. The non-aqueous solvent may be a carbonate compound, an ester-based compound, an ether-based compound, a ketone-based compound, an alcohol-based compound, an aprotic solvent, or a combination thereof. The carbonate compound can be a chain carbonate compound, a cyclic carbonate compound, a fluorocarbonate compound or a combination thereof.

Examples of chain carbonate compounds are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl carbonate Ethyl Ester (MEC) and combinations thereof. Examples of the cyclic carbonate compound are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylethylene carbonate (VEC), or combinations thereof. Examples of the fluorocarbonate compound are fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, Fluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-carbonic acid - Difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, or a combination thereof.

Examples of carboxylate compounds are methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolactone, Valerolactone, mevalonolactone, caprolactone, methyl formate, or combinations thereof.

Examples of ether compounds are dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxy ethyl ethane, 2-methyltetrahydrofuran, tetrahydrofuran or a combination thereof.

Examples of other organic solvents are dimethylsulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, methyl Amides, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters or combinations thereof.

In some embodiments of the present application, taking a lithium-ion battery as an example, the positive electrode, separator, and negative electrode are sequentially wound or stacked into an electrode part, and then packed into an aluminum-plastic film for packaging, injected with an electrolyte, formed, Encapsulation, that is, made of lithium-ion batteries. Then, performance tests were performed on the prepared lithium-ion batteries.

It will be appreciated by those skilled in the art that the above-described fabrication methods of electrochemical devices (eg, lithium-ion batteries) are examples only. Other methods commonly used in the art can be adopted without departing from the content disclosed in the present application.

Embodiments of the present application also provide an electronic device including the above electrochemical device. The electronic device in the embodiment of the present application is not particularly limited, and it may be used in any electronic device known in the prior art. In some embodiments, electronic devices may include, but are not limited to, notebook computers, pen-based computers, mobile computers, e-book players, cellular phones, portable fax machines, portable copiers, portable printers, headsets, VCRs, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, Unmanned aerial vehicles, lighting equipment, toys, game consoles, clocks, electric tools, flashlights, cameras, large household storage batteries and lithium-ion capacitors, etc.

Some specific examples and comparative examples are listed below to better illustrate the present application, wherein a lithium-ion battery is used as an example.

Example 1

Preparation of the positive electrode: mix lithium cobaltate, conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) according to a weight ratio of 97.5:1.0:1.5, add N-methylpyrrolidone (NMP) as a solvent, and stir evenly . The slurry was uniformly coated on the positive electrode current collector aluminum foil with a coating thickness of 80 μm, and the positive electrode was obtained after drying, cold pressing and cutting.

Preparation of negative electrode: Dissolve epoxy resin in ethanol and stir for a period of time to obtain a mixed solution, then add a curing agent (m-phenylenediamine) (epoxy resin: curing agent mass ratio = 10:1) to transfer the mixed solution to the hydrothermal reaction In the still, carry out hydrothermal reaction under the condition of 180°C, wait for the temperature to cool down, and take out the solid part. Put it into a box furnace, raise the temperature to 200°C at 5°C/min for 1 hour under the condition of blowing nitrogen, then raise the temperature to 900°C for 2 hours at 5°C/min, cool naturally, and crush to obtain the negative electrode material. The negative electrode material, conductive carbon black and styrene-butadiene rubber or modified PAA are dissolved in deionized water at a weight ratio of 96:1.5:2.5 to form negative electrode slurry. Copper foil 6 μm is used as the current collector of the negative electrode, and the negative electrode slurry is coated on the current collector of the negative electrode. The thickness of the coated negative electrode active material layer is 50 μm. After drying, it is cooled under the conditions of a pressure of 30 tons and a roll gap of 100 μm Pressing (rolling) and cutting to obtain the negative electrode, and the porosity of the negative electrode active material layer is 30%.

Preparation of the isolation membrane: the isolation membrane is polyethylene (PE) with a thickness of 7 μm.

Electrolyte preparation: In an environment with a water content of less than 10ppm, LiPF ₆ is added to a non-aqueous organic solvent. The non-aqueous organic solvent includes EC, PC and DEC, and the mass ratio of the three organic solvents is: ethylene carbonate (EC) : Propylene Carbonate (PC): Diethyl Carbonate (DEC) = 2: 2: 6, the concentration of LiPF ₆ is 1.15mol/L, mix well to obtain electrolyte solution.

Preparation of lithium-ion battery: stack the positive electrode, separator, and negative electrode in order, so that the separator is in the middle of the positive electrode and the negative electrode to play the role of isolation, and wind up to obtain the electrode assembly. The electrode assembly is placed in the outer packaging aluminum-plastic film, after dehydration at 80°C, the above electrolyte is injected and packaged, and the lithium-ion battery is obtained through chemical formation, degassing, trimming and other processes.

The thickness of the copper foil is 6 μm, which means that the resistance is lower than that of the general copper foil, which is 8 μm to 16 μm. Combined with the hard carbon material in this application, it can achieve a large rate of charge and discharge, and has a higher energy density.

In other embodiments and comparative examples, parameters are changed on the basis of the steps in Example 1, and the specific changed parameters are shown in the table below.

The test method of each parameter of the present application is described below.

1) High and low temperature performance test

In an environment of 25°C, discharge the battery at a constant current to 3V, charge and discharge for the first time, charge at a constant current and constant voltage at a charging current of 0.7C until the upper limit voltage is 4.48V, and then charge at a charging current of 0.2C Carry out constant current discharge under the discharge current until the final voltage is 3V. At this time, record the discharge capacity B at 25°C; then repeat the constant current and constant voltage charge at the charging current of 0.7C until the upper limit voltage is 4.48V, adjust The temperature is -20°C, and then a constant current discharge is performed at a discharge current of 0.2C until the final voltage is 3V, and the discharge capacity A at -20°C is recorded at this time. Adjust the temperature to 25°C, perform constant current and constant voltage charging at a charging current of 0.7C until the upper limit voltage is 4.48V, then adjust the temperature to 45°C, and perform constant current discharge at a discharging current of 0.2C until the final voltage It is 3V, and the discharge capacity C at 45°C is recorded at this time.

Low temperature capacity retention rate A/B=(discharge capacity B at 25°C/discharge capacity A at -20°C)×100%

High temperature capacity retention C/B=(discharge capacity C at 45°C/discharge capacity B at 25°C)×100%

2) Test of rate performance

In an environment of 25°C, discharge the battery at a constant current to 3V, charge and discharge for the first time, charge at a constant current and constant voltage at a charging current of 0.7C until the upper limit voltage is 4.48V, and then charge at a charging current of 0.2C Carry out constant current discharge under the discharge current until the final voltage is 3V. At this time, record the discharge capacity of 0.2C, and then repeat the constant current and constant voltage charge of the battery at the charge current of 0.7C until the upper limit voltage is 4.48V, set in turn The discharge rate is 1C and 5C constant current discharge, until the final voltage is 3V, at this time record the discharge capacity of 1C and 5C

1C capacity retention rate D/B=(0.2C discharge capacity/1C discharge capacity)×100%

5C capacity retention E/B=(0.2C discharge capacity/5C discharge capacity)×100%

The difference between Examples 2 to 8 in Table 1 and Example 1 is to adjust the ratio of curing agent to epoxy resin so that the mass ratio of epoxy resin to curing agent (m-phenylenediamine) is 1:1 to 10:1 respectively Between, and, through the control of rolling pressure, so as to realize the interlayer spacing of material microcrystals as shown in Table 1, and obtain a suitable porosity of the negative electrode active material layer.

Table 1 shows the respective parameters and evaluation results of Examples 1 to 8 and Comparative Examples 1 to 2.

Note: H1 is the thickness _of the negative electrode of the electrochemical device at 0% state of charge, _H2 is the thickness of the negative electrode of the electrochemical device at 50% state of charge, and H3 is the thickness _of the negative electrode of the electrochemical device at 100% state of charge.

Please refer to Table 1. Comparing Example 1 to Example 5 in Table 1, it can be seen that as the distance between the microchip layers of the negative electrode material increases, the A/B value of the electrochemical device increases and the cycle expansion decreases. It can be seen that the microchip layer spacing of the negative electrode material has an impact on the low-temperature charging performance of the electrochemical device. When the microchip layer of the material is small, the performance of the negative electrode material is damaged. The main reason includes the slow ion transport of the electrolyte under low temperature conditions. On this basis, the smaller interlayer spacing of microchips increases the transport resistance of lithium ions, resulting in larger expansion of the negative electrode material. However, the distance between the microcrystals of the negative electrode should not be greater than 0.4nm, because when the distance between the microchips of the negative electrode material is too large, some solvents in the electrolyte may be co-embedded in the negative electrode material, destroying the structure of the negative electrode material and affecting the overall electrical performance of the electrochemical device. At the same time, it is noticed that C/B is also relatively sensitive to the lamellar spacing of the material. When the intercalation resistance increases due to the low interlayer spacing, the lithium intercalation kinetics of the material is poor, and the structural damage is easy to occur during the lithium intercalation process at high temperature, so it is not good for the material. Bad words. In Comparative Example 2, due to the too small interlayer spacing at low temperature, the resulting impedance and polarization are extremely large, resulting in a decrease in low temperature performance.

Comparing Examples 6 to 8 in Table 1, it can be seen that as the porosity of the negative electrode active material layer increases, the A/B of the cell first increases and then decreases. This is because when the porosity is too small, the infiltration of the electrolyte is insufficient, and the material is prone to lithium separation at low temperatures. With the increase of the porosity, the contact between the electrolyte and the material is more sufficient, and the distance between lithium intercalation and delithiation is shortened, making the power of the material Improve academic performance. However, in the process of continuing to increase, compared with Example 1, Comparative Example 1 has a certain improvement in C/B, but its low-temperature performance is poor.

Embodiment 9 to embodiment 12 in table 2, the change of cohesive force is controlled by the change of PAA (polyacrylic acid) adhesive quantity, and the ratio of controlling PAA is 2.8% to 6%, and along with the increase of PAA ratio, active material and The cohesive force between the current collectors increases. The crushing rate of the particles in Examples 13 to 15 is caused by the change of roll pressure during cold pressing, and the roll pressure used is 30 to 50 tons, and the roll pressure used in Comparative Examples 3 to 4 is greater than or equal to 60 tons.

Table 2 shows the respective parameters and evaluation results of Example 4 and Examples 9 to 15 and Comparative Examples 3 to 4.

Please refer to Table 2, adjust the binding force on the basis of Example 4, and in Example 9 to Example 12, as the binding force between the negative electrode active material layer and the negative electrode current collector increases, the particle breakage rate maintains a low level , the low-temperature capacity retention rate of the electrochemical device maintained a stable level, and the capacity retention rate at 1C rate and 5C rate decreased. This is because, when the binding force between the negative electrode active material layer and the negative electrode current collector is too large, the content of the binder in the negative electrode is too high, and the binder is not a non-conductor, which also reduces the conductivity while hindering the migration of lithium ions. The increase of the electronic capacity and the internal resistance of the pole piece affects the kinetic performance of the negative electrode material, thus resulting in a decrease in the capacity retention rate of the electrochemical device at 1C rate and 5C rate. However, the binding force should not be too small. For example, in Comparative Example 3, if the binding force is too small, the negative electrode active material layer and the negative electrode current collector may peel off due to the small binding force, resulting in an increase in internal resistance and a decrease in rate performance.

Please refer to Table 2, on the basis of Example 4, adjust the negative electrode particle breakage rate, embodiment 13 to embodiment 15, adjust the particle along with the increase of the particle breakage rate of the negative electrode material, the rate performance is hindered, due to the particle breakage caused by broken The further impact of the electrical contact network, the increase in impedance and the thickening of SEI will further aggravate the polarization, which will easily cause uneven current and lithium precipitation, and make the particles separate from the current collector. With the increase of the breakage rate, the capacity retention rate of 1C rate D/B and 5C The capacity retention ratio E/B at the rate decreases. Therefore, the particle breakage rate of the negative electrode material needs to be controlled below 40%. Comparative Example 4 has a relatively high breakage rate, and the overall rate performance of the material is very poor.

Table 3 shows the respective parameters and evaluation results of Examples 16 to 22.

Please refer to Table 3. Example 16 to Example 19 adjust and adjust the CB value on the basis of Example 4. It can be seen that as the CB value decreases, the low-temperature capacity retention rate of the electrochemical device and 1C, 5C rate The capacity retention rate has a process of first changing little and then decreasing, and the change of CB from 0.95 to 0.9 decreases the fastest. This is because the negative electrode materials in Examples 16 to 19 belong to hard carbon materials, and hard carbon materials have a certain over-intercalation ability, so when the CB value is 0.95, they can still work normally, thereby obtaining a relatively large energy density, but when the CB value is 0.95 When the value is lower than 0.95, due to the excessive lithium ions provided by the positive electrode, the negative electrode material will precipitate lithium, and affect the low-temperature performance and rate performance. When the CB value exceeds 1.1, the energy density of the electrochemical device will decrease due to the excessive CB value. , and the anode potential rises, forcing the cathode potential to rise, which is not conducive to the performance of electrical performance.

Please refer to Table 3, adjust the M ₁ /M ₂ value on the basis of Example 4, as can be seen from Examples 17 to 21, with the weight M ₁ of the single-sided positive electrode active material layer per unit area and the negative electrode activity per unit area As the ratio of the weight M of the material layer increases, the low _- temperature capacity retention rate of the electrochemical device decreases, and the capacity retention rate at 1C rate and 5C rate also decreases. This is because with the increase of M ₁ /M ₂ , the kinetic performance of the cathode material is poor, which will affect the overall electrochemical kinetic performance, and then affect the capacity retention at 1C rate and 5C rate. Therefore, when designing, it is necessary to make a reasonable match according to the capacity of the negative electrode material and the positive electrode material, so that the M ₁ /M ₂ of the cell design is within the preferred range.

The above description is only a preferred embodiment of the present application and an illustration of the applied technical principles. Those skilled in the art should understand that the scope of disclosure involved in this application is not limited to technical solutions formed by a specific combination of the above technical features, but also covers other technical solutions formed by any combination of the above technical features or their equivalent features. Technical solutions. For example, a technical solution formed by replacing the above-mentioned features with technical features with similar functions disclosed in this application.

Claims

An electrochemical device, characterized in that,

The 0.2C discharge capacity of the electrochemical device at -20°C is A, the 0.2C discharge capacity of the electrochemical device at 25°C is B, and 70%≤A/B≤90%.
The electrochemical device according to claim 1, characterized in that the 0.2C discharge capacity of the electrochemical device at 45°C is C, 103%≤C/B≤110%.
The electrochemical device according to claim 1, wherein at least one of the following (a) or (b) is satisfied:

(a) The electrochemical device includes a negative electrode. When the electrochemical device is at a state of charge of 50%, the thickness of the negative electrode is H2 . When the electrochemical device is at a state of charge of 0%, the thickness of the negative electrode is The thickness is H 1 , (H 2 -H 1 )/H 1 is 0% to 6%;

(b) The electrochemical device includes a negative electrode. When the electrochemical device is in a state of charge of 100%, the thickness of the negative electrode is H 3 . When the electrochemical device is in a state of charge of 0%, the thickness of the negative electrode is The thickness is H 1 , and (H 3 -H 1 )/H 1 is 0% to 8%.
The electrochemical device according to claim 1, wherein the electrochemical device comprises a negative electrode, the negative electrode includes a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector, and the negative electrode active material layer of the negative electrode active material layer The porosity is 20% to 50%.
The electrochemical device according to claim 1, wherein the electrochemical device comprises a negative electrode, the negative electrode comprises a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector, and the negative electrode active material layer comprises Negative electrode material, the negative electrode material includes hard carbon, and satisfies at least one of the following (c) to (g):

(c) the bonding force between the negative electrode active material layer and the negative electrode current collector is 10N/m to 50N/m;

(d) the compacted density of the negative electrode active material layer is 0.9g/cm 3 to 1.25g/cm 3 ;

(e) the particle breakage rate of the negative electrode material is 10% to 40%;

(f) In the X-ray diffraction pattern of the negative electrode material, there is a diffraction peak between 18° and 30°, and the half-height width of the diffraction peak is 4° to 10°;

(g) The microchip layer spacing of the negative electrode material is 0.34nm to 0.4nm.
The electrochemical device according to claim 1, wherein at least one of the following (h) or (i) is satisfied:

(h) The 1C discharge capacity of the electrochemical device at 25°C is D, 0.9<D/B<1;

(i) The 5C discharge capacity of the electrochemical device at 25°C is E, 99%≤E/B≤105%.
The electrochemical device according to claim 1, wherein the three-electrode potential is monitored on the electrochemical device, and the voltage is taken as the ordinate, and the state of charge is used as the abscissa to draw a graph, and the negative electrode delithiation curve is at 0.3V From 0.8V to 0.8V is the slope area, and the charge state ratio F of the negative electrode delithiation curve below 0.2V is 30% to 80%.
The electrochemical device according to claim 1, wherein the electrochemical device comprises a positive electrode and a negative electrode, the positive electrode includes a positive electrode current collector and a positive electrode active material layer on the positive electrode fluid, and the negative electrode includes a negative electrode The current collector and the negative active material layer positioned on the negative current collector, the weight of the positive active material layer on one side per unit area is M 1 , and the weight of the negative active material layer on one side per unit area is M 2 , M 1 /M 2 is 2 to 6.
The electrochemical device according to claim 1, wherein the CB value of the electrochemical device is 0.9 to 1.1;

Wherein, CB=negative electrode capacity/positive electrode capacity, said negative electrode capacity=CW negative electrode ×gram capacity negative electrode ×active material percentage content negative electrode , said positive electrode capacity=CW positive electrode ×gram capacity positive electrode ×active material percentage content positive electrode .
An electronic device, characterized by comprising the electrochemical device according to any one of claims 1-9.