Temperature self-adjusting electrode and secondary battery

Abstract

The invention relates to the technical field of secondary batteries, in particular to a temperature self-adjusting electrode and a secondary battery. The electrode comprises an active material and a composite phase change material, wherein the composite phase change material comprises a first phase change microcapsule and a second phase change microcapsule; wherein the phase change temperature t1 of the first phase change microcapsule is more than or equal to 5 DEG C and less than or equal to 45 DEG C, and the phase change enthalpy Q1 is 100-235J / g; the phase change temperature t2 of the second phase change microcapsule is 20 DEG C lt; t2-t1 < = 155 DEG C, and the phase change enthalpy Q2 meets the following condition: Q2-Q1 < = 200J / g is greater than or equal to 5J / g. According to the electrode provided by the invention, temperature self-adjustment under different working conditions is realized, temperature change is controlled, the service life of the battery under a wide temperature range working condition is prolonged, and meanwhile, thermal runaway of the battery is prevented.

Description

Technical Field

[0001] This invention relates to the field of secondary battery technology, specifically to a temperature-regulating electrode and a secondary battery. Background Technology

[0002] Temperature is a core environmental factor determining the performance, lifespan, and safety of rechargeable batteries. Against the backdrop of the rapid development of new energy vehicles and large-scale energy storage, optimizing thermal management design, popularizing scientific knowledge about energy storage, and breaking through weather-resistant material technologies are the three guarantees for improving the reliability, safety, and economy of lithium batteries. Temperature control is a core issue in the entire life cycle management of rechargeable batteries.

[0003] The impact of temperature changes on battery performance is one of the core challenges in the field of electrochemical energy storage. When the temperature is higher than the normal operating temperature (25-45℃), the "autocatalytic effect" accelerates, the reaction activity increases, side reactions intensify, SEI decomposition and regeneration cycle accelerate, active lithium loss increases, and capacity decay accelerates. When the battery is abused and the temperature exceeds 80-135℃, the heat generation rate increases exponentially. This is mainly due to SEI rupture, which intensifies the reaction between active materials and electrolyte, leading to a sharp increase in the internal temperature of the battery, increased gas production, battery leakage, smoke, and ultimately thermal runaway, causing safety accidents. When the external environment is below 5℃, the electrolyte viscosity increases dramatically, the migration resistance in the electrolyte and electrode materials (especially graphite anode) increases, the interfacial charge transfer rate decreases, and the discharge capacity can decay to less than 50% of that at room temperature. During high-rate discharge, the voltage drops sharply, causing abnormal shutdown of devices (such as electric vehicles and mobile phones).

[0004] Temperature affects battery performance through multiple dimensions, including chemical reaction rate, electrolyte properties, and material stability. Properly controlling the internal temperature of the battery is crucial for balancing capacity, efficiency, and lifespan. Currently, existing technologies primarily address this issue through external heat dissipation solutions, the development of high- and low-temperature electrolytes, and the introduction of phase change materials into the negative electrode. However, these solutions still have certain limitations. (1) The external heat dissipation system requires complex pipes, pumps, compressors and heat exchangers, which significantly increases the overall weight of the battery module, seriously reduces the energy density of the battery pack, and directly affects the effective load of electric vehicles or energy storage systems.

[0005] (2) Although high and low temperature electrolytes can improve the electrochemical performance of batteries within a certain temperature range, when the internal heat generation accelerates and the heat accumulation exceeds the critical value, there is still a risk of thermal runaway. They cannot solve the safety problems caused by the rise in internal temperature of the battery.

[0006] (3) The phase change material itself has low thermal conductivity and slow response to changes in external heat. Uncoated phase change materials may produce side reactions with the electrolyte, thus deteriorating and failing. Phase change materials are usually insulating, which will hinder electron transport, increase internal resistance, and affect the battery capacity. During phase change, volume changes will occur, and repeated expansion and contraction will generate stress on the electrode structure, affecting the mechanical stability of the electrode and causing battery performance degradation. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems of low efficiency, low energy density, low mechanical stability, low cycle life, and thermal runaway caused by temperature changes in existing secondary batteries, and to provide a temperature self-regulating electrode and a secondary battery.

[0008] To achieve the above objectives, the first aspect of the present invention provides a temperature-self-regulating electrode, the electrode comprising: an active material and a composite phase change material, wherein the composite phase change material comprises: a first phase change microcapsule and a second phase change microcapsule; wherein the phase change temperature t1 of the first phase change microcapsule satisfies 5℃≤t1≤45℃, and the phase change enthalpy Q1 is 100-235J / g; the phase change temperature t2 of the second phase change microcapsule satisfies 20℃≤t2-t1≤155℃, and the phase change enthalpy Q2 satisfies: 5J / g≤Q2-Q1≤200J / g.

[0009] The electrode provided by this invention incorporates a composite phase change material comprising a first phase change microcapsule and a second phase change microcapsule. Through the synergistic effect of the two, the secondary battery can operate at both high and low temperatures, enhancing the versatility of its operating environment, optimizing its electrochemical performance, and improving its safety performance.

[0010] Specifically, the phase transition temperature (t1=5-45℃) of the first phase change microcapsule falls within the normal temperature range. When the battery's internal temperature rises due to an increase in external ambient temperature or self-generated heat, the first phase change microcapsule reaches its phase transition temperature and begins to work. Through its own phase transition process, it absorbs excess heat from the electrode, lowering the internal temperature of the electrode to the normal operating temperature and improving the battery's capacity retention under high-temperature conditions. When the external temperature decreases below the phase transition temperature of the first phase change microcapsule, it undergoes a reversible phase transition, releasing the heat stored under high-temperature conditions to achieve electrode self-heating, thereby increasing the internal temperature of the battery and improving its performance under low-temperature conditions. When the internal temperature of the battery rises sharply, triggering the risk of thermal runaway, the second phase change microcapsule also begins to work. Together, they accelerate heat storage, increase the critical temperature for thermal runaway, and extend the abrupt change time for the battery to reach a thermal runaway state, thereby reducing the occurrence of battery thermal runaway.

[0011] Furthermore, this invention utilizes a double-layered core-shell structure by independently controlling the first and second phase change microcapsules. First, the core-shell structure restricts the changes in state and volume of the phase change material caused by the phase change, reducing damage to the mechanical structure of the electrode. Second, the inner shell material is a thermally conductive material, which enhances the heat exchange between the phase change material and the external environment, improving the thermal response speed. At the same time, it acts as a physical barrier, preventing the core phase change material from exchanging matter with the external environment and inhibiting corrosion. Finally, the outer shell material is a conductive material, avoiding the problem of increased surface resistance of the battery electrode caused by the introduction of phase change microcapsules, and ensuring a good electronic pathway for the electrode.

[0012] A second aspect of the present invention provides a secondary battery, wherein the positive electrode and the negative electrode of the secondary battery are each independently selected from the above-mentioned electrodes.

[0013] Compared with the prior art, the present invention has the following advantages: (1) The electrode provided by the present invention uses two phase change microcapsules with different phase change temperatures and phase change enthalpies as composite phase change materials to achieve temperature self-regulation of the electrode under different operating conditions, control temperature changes, improve the cycle life of the battery under normal operating temperature, and prevent the occurrence of battery thermal runaway. (2) The electrode provided by the present invention improves the mechanical structure stability, thermal stability and conductivity of the electrode by adjusting the structure and mass ratio of the first / second phase change microcapsules in the composite phase change material; (3) The battery provided by the present invention improves the electrochemical performance and safety performance of the battery without sacrificing its own performance in a wide temperature range working environment. Attached Figure Description

[0014] Figure 1 This is the DSC test chart of the negative electrode P1 prepared in Example 1; Figure 2 This is a graph showing the cycle performance of the button cell assembled with the negative electrode P1 prepared in Example 1 at 45°C. Detailed Implementation

[0015] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0016] In this invention, unless otherwise specified, "first" and "second" do not indicate a sequence or limit the specific materials or steps; they are merely used to distinguish or indicate that these are not the same material or step. For example, "first phase change microcapsule" and "second phase change microcapsule" are only used to indicate that these are not the same phase change microcapsule.

[0017] The first aspect of the present invention provides a temperature-self-regulating electrode, the electrode comprising: an active material and a composite phase change material, wherein the composite phase change material comprises: a first phase change microcapsule and a second phase change microcapsule; wherein the phase change temperature t1 of the first phase change microcapsule satisfies 5℃≤t1≤45℃, and the phase change enthalpy Q1 is 100-235J / g; the phase change temperature t2 of the second phase change microcapsule satisfies 20℃≤t2-t1≤155℃, and the phase change enthalpy Q2 satisfies: 5J / g≤Q2-Q1≤200J / g.

[0018] In this invention, unless otherwise specified, the phase change enthalpy parameter refers to the amount of heat absorbed or released by a unit mass of a substance when it transforms from one phase to another under isothermal and isobaric conditions. That is, a phase change enthalpy Q1 of 100-235 J / g means that 1g of the first phase change microcapsule absorbs or releases 100-235 J of heat during the phase change.

[0019] In this invention, unless otherwise specified, the phase transition temperature t2 of the second phase change microcapsule is higher than the phase transition temperature t1 of the first phase change microcapsule, and the phase transition enthalpy Q2 of the second phase change microcapsule is higher than the phase transition enthalpy Q1 of the first phase change microcapsule.

[0020] In this invention, the phase transition temperature t1 of the first phase change microcapsule satisfies: 5℃≤t1≤45℃. Within this range, the first phase change microcapsule can release heat to the surroundings at an environment not exceeding 25℃ and absorb energy at an environment exceeding 25℃, thus playing a role in self-regulating the electrode temperature. The second phase change microcapsule, as an infrequently activated phase, has a phase transition temperature t2 that satisfies 20℃≤t2-t1≤155℃. This allows it to promptly curb the internal temperature rise when the battery temperature rises abnormally, even with a relatively small amount added, thereby achieving the purpose of suppressing battery thermal runaway.

[0021] Therefore, the phase change composite materials formed by the two types of phase change microcapsules can work together effectively. They can reduce the electrode temperature by absorbing latent heat when the internal temperature of the battery rises, without losing the electrochemical performance of the electrode, or by releasing latent heat when the battery temperature decreases, thereby enabling the battery to operate in a wide temperature range and improving the battery's safety performance.

[0022] In this invention, the aforementioned phase transition temperature and phase transition enthalpy parameters can be measured using conventional testing methods employed by those skilled in the art, such as differential scanning calorimetry (DSC). DSC is an analytical instrument for measuring the difference in heat flow between a sample and a reference. Specifically, the measurement method involves introducing a phase change material and a reference sample (empty crucible) without phase change or thermal effect under a nitrogen atmosphere at a flow rate of 30-60 mL / min. Heating and cooling are performed within the phase transition temperature range. When the sample undergoes a phase transition, an energy difference is generated between the sample and the reference, reflected as a heat flow versus temperature curve. The heat absorption and release during the phase transition of the phase change material are measured, thereby obtaining the forward and reverse phase transition temperatures and the phase transition enthalpy.

[0023] In some embodiments of the present invention, the phase transition temperature t1 of the first phase transition microcapsule satisfies: 5℃≤t1≤45℃, for example, 5℃, 10℃, 15℃, 20℃, 25℃, 28℃, 30℃, 35℃, 38℃, 40℃, 42℃, and any value in any range of any two values, preferably 28-42℃.

[0024] In some embodiments of the present invention, the phase change enthalpy Q1 of the first phase change microcapsule is 100-235 J / g, for example, 100 J / g, 110 J / g, 120 J / g, 130 J / g, 150 J / g, 155 J / g, 160 J / g, 170 J / g, 180 J / g, 185 J / g, 200 J / g, 235 J / g, and any value within the range of any two values, preferably 120-220 J / g.

[0025] In some embodiments of the present invention, the phase transition temperature t2 of the second phase transition microcapsule satisfies 20℃≤t2-t1≤155℃, for example, 20℃, 30℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 125℃, 155℃, and any value within the range of any two values, preferably satisfying 50℃≤t2-t1≤110℃.

[0026] In some embodiments of the present invention, the phase transition enthalpy Q2 of the second phase change microcapsule satisfies: 5J / g≤Q2-Q1≤200J / g, for example, 20J / g, 25J / g, 30J / g, 40J / g, 50J / g, 60J / g, 80J / g, 90J / g, 100J / g, 120J / g, 150J / g, 180J / g, 200J / g, and any value within the range of any two values, preferably satisfying 5J / g≤Q2-Q1≤150J / g.

[0027] In this invention, preferably, the first phase change microcapsule and the second phase change microcapsule are each independently a core-shell structure with double-layer encapsulation.

[0028] In this invention, unless otherwise specified, a double-layered core-shell structure refers to a structure in which an inner shell material and an outer shell material are sequentially wrapped around the surface of a phase change material as the core, forming an inner shell and an outer shell respectively.

[0029] In some embodiments of the present invention, preferably, the first phase change microcapsule has a first phase change material as its core and is sequentially coated with a first inner shell material and a first outer shell material.

[0030] In some embodiments of the present invention, more preferably, the mass ratio of the first phase change material, the first inner shell material, and the first outer shell material is 100:5-20:0.5-5.

[0031] In this invention, unless otherwise specified, the phase transition temperature t1 of the first phase change microcapsule is equivalent to the phase transition temperature of the first phase change material, and the phase transition enthalpy Q1 depends not only on the type of the first phase change material, but also on the first inner shell material and the first outer shell material.

[0032] In this invention, the phase change enthalpy Q1 of the first phase change microcapsule that is sequentially coated with the first inner shell material and the first outer shell material is lower than the phase change enthalpy of the first phase change material; the phase change enthalpy Q1 of the first phase change microcapsule that is coated with only the first inner shell material remains unchanged, while the phase change enthalpy Q1 of the first phase change microcapsule that is coated with only the first outer shell material decreases.

[0033] In this invention, preferably, the phase transition temperature of the first phase change material is 5-45℃, for example, 5℃, 10℃, 15℃, 20℃, 25℃, 28℃, 30℃, 35℃, 38℃, 40℃, 42℃, or any value within the range of any two values, preferably 28-42℃; the phase transition enthalpy is 100-235 J / g, for example, 100 J / g, 110 J / g, 120 J / g, 130 J / g, 150 J / g, 155 J / g, 160 J / g, 170 J / g, 180 J / g, 185 J / g, 200 J / g, 210 J / g, 220 J / g, 230 J / g, 235 J / g, or any value within the range of any two values, preferably 120-230 J / g.

[0034] In some embodiments of the present invention, preferably, the second phase change microcapsule has a second phase change material as its core and is sequentially coated with a second inner shell material and a second outer shell material.

[0035] In some embodiments of the present invention, more preferably, the mass ratio of the second phase change material, the second inner shell material, and the second outer shell material is 100:5-20:0.5-5.

[0036] Similarly, in this invention, the phase transition temperature t2 of the second phase change microcapsule is equal to the phase transition temperature of the second phase change material, and the phase transition enthalpy Q2 depends not only on the type of the second phase change material, but also on the second inner shell material and the second outer shell material.

[0037] In this invention, similarly, the phase change enthalpy Q2 of the second phase change microcapsule that is sequentially coated with the second inner shell material and the second outer shell material is lower than the phase change enthalpy of the second phase change material; the phase change enthalpy Q2 of the second phase change microcapsule that is coated with only the second inner shell material remains unchanged, while the phase change enthalpy Q2 of the second phase change microcapsule that is coated with only the second outer shell material decreases.

[0038] In this invention, preferably, the phase transition temperature of the second phase change material is 25-200℃, for example, 30℃, 45℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃, 130℃, 135℃, 155℃, 175℃, 200℃, and any value within any range of any two values, preferably 6℃. 0-175℃; phase transition enthalpy of 145-345 J / g, for example, 145 J / g, 150 J / g, 160 J / g, 180 J / g, 205 J / g, 210 J / g, 220 J / g, 250 J / g, 260 J / g, 280 J / g, 300 J / g, 320 J / g, 345 J / g, and any value within any range of any two values, preferably 200-300 J / g.

[0039] In this invention, preferably, the first inner shell material and the second inner shell material are each independently selected from thermally conductive materials; more preferably, the thermal conductivity of the thermally conductive material is 10-500 W / (m·K), for example, 10 W / (m·K), 20 W / (m·K), 50 W / (m·K), 80 W / (m·K), 100 W / (m·K), 120 W / (m·K), 150 W / (m·K), 180 W / (m·K), 200 W / (m·K), 250 W / (m·K), 300 W / (m·K), 400 W / (m·K), 500 W / (m·K), and any value within any range of any two values, preferably 20-300 W / (m·K). This configuration can enhance the heat exchange between the phase change material and the external environment, improve the thermal response speed, and at the same time act as a physical barrier to prevent the core phase change material from exchanging matter with the external environment, thus inhibiting corrosion.

[0040] In this invention, the above-mentioned thermal conductivity parameters can be measured using conventional testing methods for those skilled in the art, such as using a laser flare thermal conductivity tester LFA467 at a test temperature of 25±2℃.

[0041] In this invention, preferably, the first shell material and the second shell material are each independently selected from conductive materials; more preferably, the conductivity of the conductive material is 1-10. 5 S / m, for example, 1S / m, 10S / m, 50S / m, 100S / m, 500S / m, 1000S / m, 5000S / m, 10000S / m, 20000S / m, 50000S / m, 80000S / m, 100000S / m, and any value within the range of any two values, preferably 10-10 5 S / m. This setting avoids the problem of increased electrode resistance caused by the introduction of phase change microcapsules and optimizes the electronic pathway.

[0042] In this invention, the type of the first phase change material can be selected from a wide range, as long as it meets the above-mentioned limitations. Preferably, the first phase change material is selected from at least one of solid alkanes, low-melting-point saturated fatty acids, polyolefins, sodium alginate, soft paraffin, and liquid paraffin.

[0043] In this invention, the aforementioned solid alkanes include, but are not limited to, n-octadecane, isooctadecane, n-eicosane, etc.; the melting point of the low-melting-point saturated fatty acids is 5-45°C, including, but not limited to, decanoic acid, lauric acid, etc.; the aforementioned polyolefins include, but are not limited to, polymethyl methacrylate, polyethylene, etc.; and the melting point of the aforementioned soft paraffin is 25-45°C.

[0044] In this invention, the type of the second phase change material is selected from a wide range, as long as it meets the above-mentioned limitations. The second phase change material is selected from at least one of high-melting-point saturated fatty acids and / or their esters, polyol compounds, and eutectic salts.

[0045] In this invention, the melting point of the high-melting-point saturated fatty acids is 60-180°C, including but not limited to behenic acid, lignosulfonic acid, etc.; the polyol compounds include but are not limited to erythritol, maltitol, polyethylene glycol, etc.; the melting point of the low-melting-point eutectic salt is 100-300°C, including but not limited to nitrate eutectic mixtures, phosphate eutectic mixtures, halogen salt mixtures, etc.

[0046] In this invention, the first inner shell material and the second inner shell material may be the same or different. Preferably, the first inner shell material and the second inner shell material are each independently selected from oxides and / or nitrides.

[0047] In this invention, the oxides include, but are not limited to, silicon dioxide, zinc oxide, titanium oxide, aluminum oxide, magnesium oxide, boron oxide, etc.; the nitrides include, but are not limited to, aluminum nitride, boron nitride, titanium nitride, silicon nitride, etc.

[0048] In this invention, the first shell material and the second shell material may be the same or different. Preferably, the first shell material and the second shell material are each independently selected from at least one of conductive polymers, one-dimensional conductive carbon, and two-dimensional conductive carbon.

[0049] In this invention, the conductive polymers include, but are not limited to, polyacrylonitrile (PAN), polypyrrole (PPy), polyaniline (PANI), polydopamine (PDA), etc.; the one-dimensional conductive carbons include, but are not limited to, carbon fibers, carbon nanotubes, etc.; and the two-dimensional conductive carbons include, but are not limited to, reduced graphene, soft carbon, hard carbon, amorphous carbon, etc.

[0050] In this invention, the first phase change material and the second phase change material D 50 They can be the same or different. Preferably, the D values ​​of the first phase change material and the second phase change material are... 50 Each has an independent size of 0.7-16µm, preferably 1-10µm.

[0051] In this invention, the above-mentioned D 50 It can be measured using conventional testing methods known to those skilled in the art, such as laser particle size analysis (PSD) / scanning electron microscopy (SEM).

[0052] In some embodiments of the present invention, preferably, the thickness of the first inner shell material is related to the D of the first phase change material. 50 The ratio is 0.01-0.1:1, for example, 0.01:1, 0.015:1, 0.02:1, 0.04:1, 0.05:1, 0.06:1, 0.08:1, 0.1:1, and any value within the range of any two values.

[0053] In this invention, the thickness of the first inner shell material is related to the D of the first phase change material. 50 If the ratio meets this range, it can ensure that the first phase change material does not leak, and that the latent heat released by the first phase change material or the heat change occurring inside the electrode can diffuse instantaneously, maintaining the temperature balance of the electrode. If the ratio is less than 0.01:1, the strength of the first inner shell material cannot withstand the volume change caused by the thermal expansion of the core first phase change material, causing the shell to crack and the core first phase change material to leak, affecting battery performance. If the ratio is greater than 0.1:1, the latent heat released by the first phase change material or the heat change occurring inside the electrode cannot diffuse to each other in time, causing excessive electrode temperature changes and a decrease in temperature regulation capability.

[0054] In some embodiments of the present invention, preferably, the ratio of the thickness of the first outer shell material to the thickness of the first inner shell material is 0.2-0.6:1, for example, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, and any value within the range of any two values.

[0055] In this invention, the ratio of the thickness of the first outer shell material to the thickness of the first inner shell material satisfies this range, which ensures that the first phase change microcapsule has high conductivity without affecting the phase change enthalpy Q1 of the first phase change microcapsule. If the ratio is less than 0.2:1, the conductivity of the first phase change microcapsule may be insufficient. If the ratio is greater than 0.6:1, the phase change enthalpy Q1 of the first phase change microcapsule may decrease, thereby reducing the electrode temperature regulation capability.

[0056] In some embodiments of the present invention, preferably, the thickness of the second inner shell material is related to the D of the second phase change material. 50 The ratio is 0.01-0.1:1, for example, 0.01:1, 0.015:1, 0.02:1, 0.04:1, 0.05:1, 0.06:1, 0.08:1, 0.1:1, and any value within the range of any two values. This setting serves the same purpose as the first phase change microcapsule.

[0057] In some embodiments of the present invention, preferably, the ratio of the thickness of the second outer shell material to the thickness of the second inner shell material is 0.2-0.6:1, for example, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, and any value within a range of any two values. This setting serves the same purpose as the first phase change microcapsule.

[0058] In some embodiments of the present invention, preferably, the mass ratio of the first phase change microcapsule and the second phase change microcapsule is 1.5-5:1, for example, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, and any value within the range of any two values, preferably 2-4.5:1.

[0059] In this invention, when the mass ratio is less than 1.5:1, the amount of the first phase change microcapsule is too low and it cannot achieve good temperature regulation capability; when the mass ratio is greater than 5, the amount of the second phase change microcapsule is too low, and when the battery temperature rises sharply, the total heat storage rate of the two cannot keep up with the heating rate, and it cannot achieve the purpose of suppressing thermal runaway.

[0060] In some embodiments of the present invention, preferably, the D of the first phase change microcapsule and the second phase change microcapsule 50 Each has an independent size of 0.8-20µm, preferably 3-12µm.

[0061] In this invention, unless otherwise specified, the D of phase change microcapsules 50 =Core D 50 +Thickness of inner shell material +Thickness of outer shell material.

[0062] In a preferred embodiment of the present invention, the composite phase change material is preferably composed of the first phase change microcapsule and the second phase change microcapsule.

[0063] In some specific embodiments of the present invention, the composite phase change material is prepared by the following method: (1) Using the first phase change material as the core, the first inner shell material and the first outer shell material are sequentially coated to obtain the first phase change microcapsule; (2) Using the second phase change material as the core, the second inner shell material and the second outer shell material are sequentially coated to obtain the second phase change microcapsule; (3) The first phase change microcapsule and the second phase change microcapsule are mixed to obtain a composite phase change material.

[0064] In this invention, the type of electrode mainly depends on the type of active material; in addition to the active material layer, the electrode also includes a current collector.

[0065] In some embodiments of the present invention, preferably, based on the mass of the active material, the content of the composite phase change material is 0.2-20 wt%, for example, 0.2 wt%, 0.5 wt%, 0.6 wt%, 0.8 wt%, 1 wt%, 1.2 wt%, 1.5 wt%, 2 wt%, 3 wt%, 5 wt%, 8 wt%, 10 wt%, 12 wt%, 15 wt%, 18 wt%, 20 wt%, and any value within any range of any two values, preferably 0.5-10 wt%.

[0066] In this invention, when the above content is less than 0.2 wt%, the heat that the composite phase change material can absorb or release cannot meet the heat change required by the electrode due to temperature rise or fall, and thus cannot achieve the function of regulating electrode temperature; when the above content is greater than 20 wt%, the proportion of inert phase change composite material in the electrode is too high, resulting in a decrease in electrode surface density and sacrificing the energy density of the battery.

[0067] In some embodiments of the present invention, preferably, the content of the active material in the electrode is ≥80wt%, more preferably 85-95wt%, and more preferably 86-92wt%; the content of the composite phase change material is ≤20wt%, preferably 5-10wt%, and more preferably 6-9wt%. The above content ranges are based on the total mass of the active material layer in the electrode.

[0068] In this invention, the active material layer of the electrode contains, in addition to the active material and the composite phase change material, a conductive agent and a binder.

[0069] In this invention, the adhesive includes, but is not limited to, styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS), polyethyleneimine (PEI), polyimide (PI), tert-butyl polyacrylate-triethoxyvinylsilane (TBATEVS), etc.; the conductive agent includes, but is not limited to, acetylene black, conductive carbon black, carbon fiber, carbon nanotubes, Ketjen black, etc.

[0070] In some embodiments of the present invention, preferably, the electrode contains 0-3 wt% conductive agent, more preferably 0.5-2 wt%; and 0-5 wt% binder, more preferably 1-3 wt%.

[0071] In this invention, the total content of the active material, composite phase change material, conductive agent and binder in the active material layer is 100 wt%.

[0072] In this invention, preferably, when the active material is selected from positive electrode active materials, the electrode is a positive electrode; or, when the active material is selected from negative electrode active materials, the electrode is a negative electrode.

[0073] In this invention, the positive electrode active material includes, but is not limited to, at least one of lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium nickel oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium-rich manganese-based positive electrode material, sodium ion oxide positive electrode material, sodium ion polyanionic positive electrode material, and sodium ion Prussian blue type positive electrode material.

[0074] In this invention, the negative electrode active material includes, but is not limited to, graphite, hard carbon, soft carbon, silicon, SiO, Si / C, metal sulfides, metal oxides, metals and their alloys.

[0075] In one specific embodiment of the present invention, the electrode includes: a positive current collector and a positive active material layer, wherein the positive active material layer contains a positive active material, the aforementioned composite phase change material, an optional conductive agent, and an optional binder.

[0076] In another specific embodiment of the present invention, the electrode includes: a negative current collector and a negative active material layer, wherein the negative active material layer contains a negative active material, the above-mentioned composite phase change material, an optional conductive agent and an optional binder.

[0077] In this invention, preferably, the surface resistance of the electrode is 1-1000mΩ, for example, 1mΩ, 5mΩ, 10mΩ, 20mΩ, 50mΩ, 80mΩ, 100mΩ, 200mΩ, 500mΩ, 600mΩ, 800mΩ, 1000mΩ, and any value within the range of any two values, preferably 10-500mΩ.

[0078] In this invention, preferably, the thermal conductivity of the electrode is 0.09-0.85 W / (m·K), for example, 0.09 W / (m·K), 0.1 W / (m·K), 0.2 W / (m·K), 0.3 W / (m·K), 0.5 W / (m·K), 0.6 W / (m·K), 0.75 W / (m·K), 0.8 W / (m·K), 0.85 W / (m·K), and any value within the range of any two values.

[0079] In this invention, preferably, the temperature change of the electrode ΔT is ≤20℃, for example, 20℃, 18℃, 15℃, 12℃, 10℃, 8℃, 5℃, 2℃, 0℃, and any value in any range of any two values, preferably 0-15℃; wherein, ΔT is the difference between the actual temperature of the battery cell and the ambient temperature.

[0080] In this invention, preferably, the temperature change of the electrode due to cooling ΔT' is ≤22℃, for example, 22℃, 17℃, 15℃, 12℃, 10℃, 8℃, 7℃, 5℃, 2℃, 0℃, and any value within the range of any two values, preferably 0-17℃; wherein, ΔT' is the difference between the actual temperature of the battery cell and the ambient temperature.

[0081] In this invention, preferably, the electrode thermal runaway initiation temperature T1 satisfies: 105 ≤ T1 ≤ 305℃, for example, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 155℃, 175℃, 200℃, 255℃, 280℃, 305℃, and any value within the range of any two values, preferably 125℃ ≤ T1 ≤ 250℃.

[0082] In this invention, the surface resistivity parameter, thermal conductivity parameter, temperature change parameter of the electrode surface, and runaway initiation temperature parameter can be measured using conventional testing methods for those skilled in the art. For example, the surface resistivity parameter is measured using a four-probe resistivity meter, the thermal conductivity parameter and the temperature change parameter of the electrode surface are measured by infrared thermal imaging, and the runaway initiation temperature parameter is measured by ARC testing.

[0083] In some embodiments of the present invention, the electrode is prepared by the following method: mixing an active material, a composite phase change material, an optional conductive agent, an optional binder and a solvent to obtain a slurry with a solid content of 30-60 wt%; coating the slurry onto a current collector, and then drying, cold pressing and slitting the slurry to obtain the electrode.

[0084] A second aspect of the present invention provides a secondary battery, wherein the positive electrode and the negative electrode of the secondary battery are each independently selected from the above-mentioned electrodes.

[0085] According to a particularly preferred embodiment of the present invention, a temperature self-regulating electrode is provided, the electrode comprising: an active material and a composite phase change material, wherein the composite phase change material comprises: a first phase change microcapsule and a second phase change microcapsule; wherein the phase change temperature t1 of the first phase change microcapsule satisfies 5℃≤t1≤45℃, and the phase change enthalpy Q1 is 100-235J / g; the phase change temperature t2 of the second phase change microcapsule satisfies 20℃≤t2-t1≤155℃, and the phase change enthalpy Q2 satisfies: 5J / g≤Q2-Q1≤200J / g; The first phase change microcapsule has a first phase change material as its core and is sequentially encapsulated by a first inner shell material and a first outer shell material; the second phase change microcapsule has a second phase change material as its core and is sequentially encapsulated by a second inner shell material and a second outer shell material. The phase change temperature of the first phase change material is 28-42℃, and the phase change enthalpy is 120-220J / g; the phase change temperature of the second phase change material is 60-175℃, and the phase change enthalpy is 200-300J / g. The first inner shell material and the second inner shell material are each independently selected from thermally conductive materials with a thermal conductivity of 20-300 W / (m·K); the first outer shell material and the second outer shell material are each independently selected from materials with an electrical conductivity of 10-10 W / (m·K). 5 Conductive materials with an S / m ratio.

[0086] The present invention will be described in detail below through embodiments.

[0087] Example 1 S1. Preparation of composite phase change materials The first phase change material (n-octadecane, D) 50 A first phase change microcapsule is obtained by sequentially coating a first inner shell material (silicon nitride, with a thermal conductivity of 162 W / (m·K)) and a first outer shell material (graphene, with an electrical conductivity of 2000 S / m) with a phase change material of 4 μm, a phase change temperature of 28 °C, and a phase change enthalpy of 228 J / g. The thickness of the first inner shell material is 50 nm, and the thickness of the first outer shell material is 10 nm. The mass ratio of the first phase change material, the first inner shell material, and the first outer shell material is 100:10:0.5. With the second phase change material (polyethylene glycol PEG-6000, D) 50 A second phase change microcapsule is obtained by sequentially coating a second inner shell material (silicon nitride, with a thermal conductivity of 162 W / (m·K)) and a second outer shell material (graphene, with an electrical conductivity of 2000 S / m) with a phase change material (4 μm thick, a phase change temperature of 100℃, and a phase change enthalpy of 270 J / g). The thickness of the second inner shell material is 50 nm, and the thickness of the second outer shell material is 10 nm. The mass ratio of the second phase change material, the second inner shell material, and the second outer shell material is 100:10:0.5. The first phase change microcapsule and the second phase change microcapsule were mixed at a mass ratio of 4:1 to obtain the composite phase change material A1. S2, Electrode preparation The negative electrode active material (graphite), the above-mentioned composite phase change material A1, the conductive agent SP and the binder carboxymethyl cellulose CMC were mixed with the solvent water in a mass ratio of 90:6:2:2 to obtain a negative electrode slurry with a solid content of 50wt%. The above negative electrode slurry is coated on copper foil, dried at 80°C, cold-pressed, trimmed, cut into sheets, and slit to obtain negative electrode sheet P1.

[0088] Example 2 The method is the same as in Example 1, except that... In step S1, the type of the first phase change material is replaced with liquid paraffin (D). 50 With a phase transition thickness of 4 μm, a phase transition temperature of 5 °C, and a phase transition enthalpy of 205 J / g, and other conditions remaining the same, composite phase change material A2 was obtained. In step S2, all other conditions remain the same, resulting in the negative electrode plate P2.

[0089] Example 3 The method is the same as in Example 1, except that... In step S1, the type of the first phase change material is replaced with soft paraffin (D). 50 With a phase transition thickness of 4 μm, a phase transition temperature of 34 °C, and a phase transition enthalpy of 180 J / g, and other conditions being the same, composite phase change material A3 was obtained; In step S2, all other conditions remain the same, resulting in the negative electrode plate P3.

[0090] Example 4 The method is the same as in Example 1, except that... In step S1, the type of the first phase change material is replaced with isomeric octadecane (D 50 With a phase transition thickness of 4 μm, a phase transition temperature of 28 °C, and a phase transition enthalpy of 166 J / g, and other conditions being the same, composite phase change material A4 was obtained; In step S2, all other conditions remain the same, resulting in the negative electrode plate P4.

[0091] Example 5 The method is the same as in Example 1, except that... In step S1, the type of the second phase change material is replaced with wood tartaric acid (D... 50 With a phase transition thickness of 4 μm, a phase transition temperature of 60 °C, and a phase transition enthalpy of 245 J / g, and other conditions remaining the same, composite phase change material A5 was obtained; In step S2, all other conditions remain the same, resulting in the negative electrode plate P5.

[0092] Example 6 The method is the same as in Example 1, except that... In step S1, the type of the second phase change material is replaced with a eutectic phosphate, namely a mixture of urea and guanidine phosphate (D... 50 With a phase transition thickness of 4 μm, a phase transition temperature of 135 °C, and a phase transition enthalpy of 240 J / g, and other conditions being the same, composite phase change material A6 was obtained; In step S2, all other conditions remain the same, resulting in the negative electrode plate P6.

[0093] Example 7 The method is the same as in Example 1, except that... In step S1, the type of the second phase change material is replaced with a eutectic halide salt, namely LiCl-LiI (D 50 With a phase transition thickness of 4 μm, a phase transition temperature of 100 °C, and a phase transition enthalpy of 218 J / g, and with all other conditions being the same, composite phase change material A7 was obtained. In step S2, all other conditions remain the same, resulting in the negative electrode plate P7.

[0094] Example 8 The method is the same as in Example 1, except that... In step S1, the first inner shell material is replaced with alumina (thermal conductivity 120 W / (m·K)) and the second inner shell material is replaced with alumina (thermal conductivity 120 W / (m·K)), with the other conditions remaining the same, to obtain composite phase change material A8; In step S2, all other conditions remain the same, and the negative electrode plate P8 is obtained.

[0095] Example 9 The method is the same as in Example 1, except that... In step S1, the type of the first inner shell material is replaced with alumina (thermal conductivity of 120 W / (m·K)) and the thickness of the first inner shell material is adjusted to 200 nm; the type of the second inner shell material is replaced with alumina (thermal conductivity of 120 W / (m·K)) and the thickness of the second inner shell material is adjusted to 200 nm; the other conditions are the same, and the composite phase change material A9 is obtained. In step S2, all other conditions remain the same, resulting in the negative electrode plate P9.

[0096] Example 10 The method is the same as in Example 1, except that... In step S1, the first shell material is replaced with PAN (with an electrical conductivity of 100 S / m), and the second shell material is replaced with PAN (with an electrical conductivity of 100 S / m); all other conditions remain the same, and the composite phase change material A10 is obtained. In step S2, all other conditions remain the same, and the negative electrode plate P10 is obtained.

[0097] Example 11 The method is the same as in Example 1, except that... In step S1, the type of the first outer shell material is replaced with amorphous carbon (with an electrical conductivity of 5 S / m), and the thickness of the first inner shell material is adjusted to 100 nm; the type of the second outer shell material is replaced with amorphous carbon (with an electrical conductivity of 5 S / m), and the thickness of the second inner shell material is adjusted to 100 nm; the other conditions are the same, and the composite phase change material A11 is obtained. In step S2, all other conditions remain the same, and the negative electrode plate P11 is obtained.

[0098] Example 12 The method is the same as in Example 1, except that... In step S1, the mass ratio of the first phase change microcapsule and the second phase change microcapsule is replaced with 1.5:1, and the other conditions are the same, to obtain the composite phase change material A12. In step S2, all other conditions remain the same, resulting in the negative electrode plate P12.

[0099] Example 13 The method is the same as in Example 1, except that... In step S1, the mass ratio of the first phase change microcapsule and the second phase change microcapsule is replaced with 5:1, and the other conditions are the same, to obtain composite phase change material A13. In step S2, all other conditions remain the same, resulting in the negative electrode plate P13.

[0100] Example 14 The method is the same as in Example 1, except that... In step S1, the type of the second inner shell material is replaced with boron nitride (thermal conductivity 33 W / (m·K)), and the thickness of the second inner shell material is adjusted to 100 nm; the type of the second outer shell material is replaced with PPy (electrical conductivity 0.8 S / m), and the thickness of the second outer shell material is adjusted to 20 nm; the other conditions are the same, and the composite phase change material A14 is obtained. In step S2, all other conditions remain the same, resulting in the negative electrode plate P14.

[0101] Example 15 The method is the same as in Example 1, except that... In step S1, the first phase change material only coats the first inner shell material, and the second phase change material only coats the second inner shell material; the other conditions are the same, and the composite phase change material A15 is obtained. In step S2, all other conditions remain the same, resulting in the negative electrode plate P15.

[0102] Example 16 The method is the same as in Example 1, except that... In step S1, the first phase change material only coats the first outer shell material, and the second phase change material only coats the second outer shell material; all other conditions are the same, and the composite phase change material A16 is obtained. In step S2, all other conditions remain the same, resulting in the negative electrode plate P16.

[0103] Example 17 The method is the same as in Example 1, except that... In step S2, the mass ratio of the above-mentioned negative electrode active material (graphite), the above-mentioned composite phase change material A1, the conductive agent SP and the binder carboxymethyl cellulose CMC is adjusted to 80:16:2:2. Under the same conditions, the negative electrode P17 was obtained.

[0104] Example 18 The method is the same as in Example 1, except that... In step S2, the mass ratio of the above-mentioned negative electrode active material (graphite), the above-mentioned composite phase change material A1, the conductive agent SP and the binder carboxymethyl cellulose CMC is adjusted to 95:1:2:2. Under the same conditions, the negative electrode P18 was obtained.

[0105] Example 19 The method is the same as in Example 1, except that... In step S2, the above negative electrode active material is replaced with positive electrode active material (NCM811). Under the same conditions, the positive electrode P19 was obtained.

[0106] Comparative Example 1 The method is the same as in Example 1, except that... In step S1, the type of the first phase change material is replaced with hard paraffin (D). 50 With a phase transition thickness of 4 μm, a phase transition temperature of 56 °C, and a phase transition enthalpy of 252 J / g, the composite phase change material DA1 was obtained under the same conditions. In step S2, all other conditions remain the same, and the negative electrode DP1 is obtained.

[0107] Comparative Example 2 The method is the same as in Example 1, except that... In step S1, the type of the second phase change material is replaced with polyphenylene sulfide (DPI). 50 With a phase transition thickness of 4 μm, a phase transition temperature of 220 °C, and a phase transition enthalpy of 240 J / g, the composite phase change material DA2 was obtained under the same conditions. In step S2, all other conditions remain the same, and the negative electrode DP2 is obtained.

[0108] Comparative Example 3 The method is the same as in Example 1, except that... In step S1, the first phase change microcapsule is directly used as the composite phase change material DA3; In step S2, all other conditions remain the same, and the negative electrode DP3 is obtained.

[0109] Comparative Example 4 The method is the same as in Example 1, except that... In step S1, the second phase change microcapsule is directly used as the composite phase change material DA4; In step S2, all other conditions remain the same, and the negative electrode DP4 is obtained.

[0110] Comparative Example 5 The method is the same as in Example 1, except that... In step S1, the first phase change material, the first inner shell material, and the first outer shell material of equal mass are mixed respectively, and then mixed with the second phase change material, the second inner shell material, and the second outer shell material of equal mass to obtain composite phase change material DA5. In step S2, all other conditions remain the same, and the negative electrode DP5 is obtained.

[0111] Comparative Example 6 The method is the same as in Example 1, except that... In step S1, the first phase change material and the second phase change material are directly mixed at a mass ratio of 4:1 to obtain the composite phase change material DA6. In step S2, all other conditions remain the same, and the negative electrode plate DQ6 is obtained.

[0112] Comparative Example 7 The method is the same as in Example 1, except that... Step S1 is missing. In step S2, the negative electrode active material (graphite), conductive agent SP and binder carboxymethyl cellulose CMC are directly mixed in a mass ratio of 96:2:2, and the other conditions are the same, to obtain the negative electrode sheet DP7.

[0113] Table 1

[0114] Note: 1- If the composite phase change material is composed of a first phase change microcapsule and a second phase change microcapsule, it is marked as "√"; otherwise, it is marked as "×". 2- The mass ratio of the first phase change microcapsule to the second phase change microcapsule.

[0115] Table 2

[0116] As can be seen from the results in Table 1-2, compared with Comparative Examples 1-7, Examples 1-19 using the electrodes provided by the present invention have lower sheet resistance, higher thermal conductivity, lower temperature change and higher thermal runaway initiation temperature, thereby improving the mechanical structure stability, thermal stability and conductivity of the electrodes.

[0117] As can be seen from Example 1 and Comparative Examples 1-7, the first phase change material and the second phase change material are not within the protection scope, the electrode temperature change is close to the stability of the external environment, and the battery is prone to thermal runaway; if there is only one phase change material, low temperature change and high thermal runaway temperature cannot be achieved at the same time; if there is no core-shell structure microcapsule or they are not independent, they cannot achieve their respective functions, causing system chaos.

[0118] Therefore, the electrode provided by the present invention uses two phase change microcapsules with different phase change temperatures and phase change enthalpies as composite phase change materials to achieve temperature self-regulation under different operating conditions, control temperature changes, improve the cycle life of the battery at normal operating temperature, and prevent the occurrence of battery thermal runaway.

[0119] Test case Batteries were assembled in Examples 1-19 and Comparative Examples 1-7 respectively, and battery performance was tested. The test results are shown in Table 3.

[0120] Electrode cutting and weighing: Use a stamping machine to stamp the negative electrode sheet into a small round sheet with a diameter of 14mm, and stamp the NCM811 positive electrode sheet into a small round sheet with a diameter of 12mm; use a high-precision balance to weigh the electrode sheet mass and record the data; select electrode sheets with a negative electrode surface capacity / positive electrode surface capacity = 1.1 for later use.

[0121] Battery assembly: (1) Place the positive electrode shell and gasket: The positive electrode shell is placed with the opening facing up and the gasket is placed with the burr side facing down; (2) Place the positive electrode sheet and immerse it: Place the positive electrode sheet with the coating layer facing up in the middle of the positive electrode shell and immerse it with electrolyte; (3) Cover the separator and immerse it: Use tweezers to pick up the separator and cover the positive electrode sheet, and immerse it with electrolyte again; (4) Place the negative electrode sheet and gasket: Place the negative electrode active material side down and place the gasket in alignment; (5) Place the spring sheet and negative electrode shell: Place the spring sheet in alignment and cover it with the negative electrode shell; (6) Seal the battery: Use a sealing machine to press and seal the battery, and observe whether the appearance is complete.

[0122] Test conditions: (1) Calculation of active material mass: active material mass = (electrode mass - foil surface density × electrode area) × surface load; (2) Standing: After the button cell is assembled, it needs to be left to stand for 8 hours before testing; the energy density and initial coulombic efficiency of the battery are measured at 25℃ respectively. The test steps are: charge to 4.2V at 0.1C, discharge to 2.7V at 0.1C; then charge to 4.2V, disassemble the battery, clean the fully charged negative electrode with DMC and perform DSC test; perform cycle test at 0℃ and 45℃ with 0.5C charge and discharge conditions.

[0123] In Example 1, the DSC of the negative electrode P1 was prepared as follows: Figure 1 As shown, the DSC heat release of the fully charged negative electrode P1 is 1200 J / g.

[0124] The cycling performance of the button cell assembled with negative electrode P1 prepared in Example 1 at 45°C is shown in the figure below. Figure 2 As shown, the capacity retention rate is 96% after 200 cycles at 0.5C and 45℃, which is a high capacity retention rate.

[0125] Table 3

[0126] As can be seen from the results in Table 3, compared with Comparative Examples 1-7, Examples 1-19 using the electrodes provided by the present invention have better high / low temperature cycling performance and lower DSC heat release, and the effect is better.

[0127] As can be seen from Example 1 and Comparative Examples 1-7, the first and second phase change materials are not within the protection scope, resulting in a significant decrease in the high and low temperature performance of the battery and severe heat generation on the electrodes. When only one phase change material exists and the core-shell structured microcapsules are absent or not independent, the battery cannot adapt to temperature changes and operate under wide temperature range conditions, posing safety hazards. Therefore, the battery provided by this invention improves the electrochemical and safety performance of the battery under wide temperature range operating conditions without sacrificing its own performance.

[0128] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A temperature self-regulating electrode, characterized by, The electrode comprises: an active material, a composite phase change material, a conductive agent, and a binder, wherein the composite phase change material comprises: first phase change microcapsules and second phase change microcapsules; wherein the phase change temperature t1 of the first phase change microcapsules satisfies 5℃≤t1≤45℃, and the phase change enthalpy Q1 is 100-235J / g; the phase change temperature t2 of the second phase change microcapsules satisfies 20℃≤t2-t1≤155℃, and the phase change enthalpy Q2 satisfies 5J / g≤Q2-Q1≤200J / g.

2. The electrode of claim 1, wherein, The first phase change microcapsules and the second phase change microcapsules are each independently in a double-layer coated core-shell structure; And / or, the first phase change microcapsules take a first phase change material as a core, and are sequentially coated with a first inner shell material and a first outer shell material; And / or, the second phase change microcapsules take a second phase change material as a core, and are sequentially coated with a second inner shell material and a second outer shell material.

3. The electrode of claim 2, wherein, The mass ratio of the first phase change material, the first inner shell material, and the first outer shell material is 100:5-20:0.5-5; And / or, the mass ratio of the second phase change material, the second inner shell material, and the second outer shell material is 100:5-20:0.5-5.

4. The electrode according to claim 2 or 3, wherein, The phase change temperature of the first phase change material is 5-45℃, preferably 28-42℃; and the phase change enthalpy is 100-235J / g, preferably 120-230J / g; And / or, the phase change temperature of the second phase change material is 25-200℃, preferably 60-175℃; and the phase change enthalpy is 145-345J / g, preferably 200-300J / g; And / or, the first inner shell material and the second inner shell material are each independently selected from a heat-conductive material; preferably, the thermal conductivity of the heat-conductive material is 10-500 W / (m·K), preferably 20-300 W / (m·K); and / or, the first and second shell materials are each independently selected from an electrically conductive material; preferably, the electrically conductive material has an electrical conductivity of 1-10 5 S / m, preferably 10-10 5 S / m.

5. The electrode according to any one of claims 2-4, wherein, The first phase change material is selected from at least one of solid alkanes, low-melting-point saturated fatty acids, polyolefins, sodium alginate, soft paraffin, and liquid paraffin; And / or, the second phase change material is selected from at least one of high-melting-point saturated fatty acids, polyhydric alcohol compounds, and eutectic salts; And / or, the first inner shell material and the second inner shell material are each independently selected from oxides and / or nitrides; And / or, the first outer shell material and the second outer shell material are each independently selected from at least one of conductive polymers, one-dimensional conductive carbon, and two-dimensional conductive carbon.

6. The electrode according to any one of claims 2 to 5, wherein, D of the first and second phase change materials 50 each independently is 0.7-16 µm; and / or the thickness of the first inner shell material is in the range of 0.01-0.1:1 of the D50 of the first phase change material 50 the ratio is 0.01-0.1:1; And / or, the ratio of the thickness of the first outer shell material to the thickness of the first inner shell material is 0.2-0.6:1; and / or the thickness of the second inner shell material is in the range of 0.01-0.1:1 of the D50 of the second phase change material. 50 the ratio is 0.01-0.1:

1. And / or, the ratio of the thickness of the second outer shell material to the thickness of the second inner shell material is 0.2-0.6:

1.

7. The electrode according to any one of claims 1 to 6, wherein, The mass ratio of the first phase change microcapsules to the second phase change microcapsules is 1.5-5:1, preferably 2-4.5:1; and / or the Dv50 of the first and second phase change microcapsules is in the range of 1 to 20 µm. 50 each independently is 0.8 to 20 µm; And / or, the composite phase change material is composed of the first phase change microcapsules and the second phase change microcapsules.

8. The electrode according to any one of claims 1 to 7, wherein, The content of the composite phase change material is 0.2-20wt%, preferably 0.5-10wt%, based on the mass of the active material; And / or, the content of the active material in the electrode is ≥80wt%, preferably 85-95wt%, more preferably 86-92wt%; the content of the composite phase change material is ≤20wt%, preferably 5-10wt%, more preferably 6-9wt%; And / or, the content of the conductive agent in the electrode is 0-3wt%, preferably 0.5-2wt%; the content of the binder is 0-5wt%, preferably 1-3wt%; And / or, when the active material is selected from positive electrode active materials, the electrode is a positive electrode; or, when the active material is selected from negative electrode active materials, the electrode is a negative electrode.

9. The electrode according to any one of claims 1 to 8, wherein, The surface resistance of the electrode is 1-1000mΩ, preferably 10-500mΩ; And / or, the thermal conductivity of the electrode is 0.09-0.85W / (m·K); And / or, the temperature change ΔT of the electrode under heating is ≤20℃, preferably 0-15℃; wherein ΔT is the difference between the actual temperature of the battery cell and the ambient temperature; And / or, the temperature change ΔT' of the electrode under cooling is ≤22℃, preferably 0-17℃; wherein ΔT' is the difference between the actual temperature of the battery cell and the ambient temperature; And / or, the thermal runaway initiation temperature T1 of the electrode satisfies: 105℃≤T1≤305℃, preferably 125℃≤T1≤250℃.

10. A secondary battery characterized by comprising: The positive electrode and the negative electrode of the secondary battery are each independently selected from the electrode of any one of claims 1-9.

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