Lithium ion capacitor and preparation method and application thereof

Abstract

The invention provides a lithium ion capacitor and a preparation method and application thereof. The cathode of the lithium ion capacitor comprises a capacitance type cathode material and a battery type cathode material, and the anode of the lithium ion capacitor comprises an anode material; the cathode capacity and the anode capacity of the lithium ion capacitor meet the condition that (m3 * K3) / (m1 * K1 + m2 * K2) is larger than or equal to 0.75 and smaller than or equal to 1.05, m1, m2 and m3 are the unit area loading capacities of a capacitive cathode material, a battery type cathode material and an anode material in the lithium ion capacitor respectively, the unit is g / m < 2 >, and the unit of m1, m2 and m3 is larger than or equal to 0.75 and smaller than or equal to 1.05. K1, K2 and K3 are the specific capacities of a capacitive cathode material, a battery type cathode material and an anode material in the lithium ion capacitor respectively. By designing the relationship between the cathode capacity and the anode capacity in the lithium ion capacitor, the high-temperature stability of the lithium ion capacitor is improved, the gas production problem is improved, and the safety performance of the lithium ion capacitor is improved.

Description

Technical Field

[0001] The present invention relates to the field of energy storage technology, specifically to a lithium ion capacitor, and more particularly to a lithium ion capacitor and a preparation method and application thereof. Background Art

[0002] Lithium-ion capacitors (LICs) are hybrid energy storage devices that combine the high energy density of lithium-ion batteries with the high power density and long cycle life of supercapacitors. They have a wide range of applications, particularly in applications requiring fast charging and discharging, high efficiency, and a long lifespan.

[0003] Conventional lithium-ion capacitor products use cathode lithium replenishment, anode lithium replenishment, or electrolyte organic salt decomposition to replenish lithium to balance the capacity of the capacitor part, increase the capacity contribution of the capacitor part, and improve the performance of the lithium-ion capacitor. However, this usually brings about problems such as complex lithium-ion capacitor preparation process, high cost, many side reactions of lithium-ion capacitors, rapid high-temperature attenuation, and high gas production.

[0004] CN112863898A discloses a lithium-replenishing additive for the positive electrode of a lithium-ion capacitor. The additive is lithium hydride dissolved in an ether solvent. This invention uses lithium hydride as a lithium-replenishing additive to replenish the negative electrode of a lithium-ion supercapacitor through a first-cycle discharge. However, lithium hydride is prone to side reactions with the electrolyte, and the H₂ produced by the decomposition of LiH₂ can increase the internal pressure of the battery, posing a safety hazard.

[0005] CN105374571A discloses a lithium-ion capacitor negative electrode sheet, comprising a pre-lithiation layer disposed on a negative electrode active layer, wherein the material of the pre-lithiation layer comprises passivated lithium powder. In the negative electrode active layer of the lithium-ion capacitor negative electrode sheet, the silicon-based material has a large capacity, and its volume expansion after pre-lithiation of lithium compensates for the space left by the disappearance of the pre-lithiation layer, thereby increasing the power density and service life of the lithium-ion capacitor. However, passivated lithium powder has poor safety and may produce a large number of side reactions with the positive electrode material or the electrolyte.

[0006] Therefore, it is of great significance to provide a lithium ion capacitor with good high-temperature stability, low gas production and high safety. Summary of the Invention

[0007] In response to the shortcomings of the prior art, the present invention aims to provide a lithium-ion capacitor, a method for preparing the same, and its application. By designing the cathode composition and the relationship between cathode and anode capacity in a lithium-ion capacitor, the present invention limits the upper limit of the cathode potential during cycling and storage, thereby inhibiting high-temperature oxidation of the cathode material, improving the high-temperature stability of the lithium-ion capacitor, addressing gassing issues, and enhancing the safety performance of the lithium-ion capacitor.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a lithium ion capacitor, wherein the cathode of the lithium ion capacitor comprises a capacitor-type cathode material and a battery-type cathode material, and the anode of the lithium ion capacitor comprises an anode material;

[0010] The cathode capacity and anode capacity of the lithium ion capacitor satisfy the following requirements: 0.75≤(m3×K3) / (m1×K1+m2×K2)≤1.05, wherein m1, m2 and m3 are the unit area loadings of the capacitive cathode material, battery cathode material and anode material in the lithium ion capacitor, respectively, in g / m 2 , K1, K2 and K3 are the specific capacities of the capacitive cathode material, battery-type cathode material and anode material in the lithium ion capacitor, respectively, in mAh / g.

[0011] The present invention designs the composition of the lithium ion capacitor, introduces a capacitor-type cathode material and a battery-type cathode material into the cathode of the lithium ion capacitor at the same time, and adjusts the ratio between the cathode capacity and the anode capacity so that the ratio of the anode capacity m3×K3 and the cathode capacity m1×K1+m2×K2 is between 0.75 and 1.05. This can limit the upper limit potential of the cathode during circulation and storage, thereby inhibiting the high-temperature oxidation of the cathode material, improving the cycle life and high-temperature stability of the lithium ion capacitor, improving the gas production problem, and improving the safety performance of the lithium ion capacitor.

[0012] Preferably, the electrolyte concentration of the lithium ion capacitor satisfies:

[0013] During the charge and discharge process, the capacity of the capacitive cathode material and the attenuation ratio of the lithium ion concentration in the electrolyte satisfy: (n×S1×m1×K1) / Q i ≤60%, where Q i is the charge corresponding to the lithium ions in the electrolyte, the unit is C, n is the number of cathode laminate layers, and S1 is the cathode electrode area.

[0014] Preferably, the SOC of the lithium ion capacitor satisfies one of the following conditions:

[0015] a. When the lithium ion capacitor has a laminated structure, 0≤SOC≤m3×K3×S1×n;

[0016] b. When the lithium ion capacitor has a wound structure, 0≤SOC≤m3×K3×S1.

[0017] Preferably, the charging upper limit voltage of the lithium ion capacitor satisfies one of the following conditions:

[0018] c. When the battery-type cathode material comprises lithium iron phosphate, the upper charging voltage limit of the lithium ion capacitor is ≤3.65V;

[0019] d. When the battery-type cathode material is a ternary cathode material or a lithium cobalt oxide material, the upper charging limit voltage of the lithium ion capacitor is ≤4.0V.

[0020] Preferably, the capacitive cathode material comprises any one of activated carbon materials, organic metal framework compounds, covalent organic framework materials or layered double hydroxides, or a combination of at least two thereof.

[0021] Preferably, the battery-type cathode material includes any one or a combination of at least two of lithium iron phosphate material (LFP), NCM ternary positive electrode material, NCA ternary positive electrode material, lithium-rich manganese-based positive electrode material, NCMA ternary positive electrode material or lithium cobalt oxide material (LCO).

[0022] Preferably, the anode material includes any one of graphite, hard carbon, soft carbon, silicon carbon, lithium titanate or niobium tungsten oxide, or a combination of at least two thereof.

[0023] Preferably, the cathode of the lithium ion capacitor further comprises a cathode binder, and the cathode binder comprises PVDF and / or polytetrafluoroethylene.

[0024] Preferably, the anode of the lithium ion capacitor further comprises an anode binder, and the anode binder comprises any one of SBR, PAA, PAN or CMC, or a combination of at least two thereof.

[0025] Preferably, the cathode of the lithium ion capacitor and the anode of the lithium ion capacitor each independently further include a conductive agent, and the conductive agent includes any one of carbon black, carbon nanotubes or graphene, or a combination of at least two of them.

[0026] In a second aspect, the present invention provides a method for preparing the lithium ion capacitor according to the first aspect, the preparation method comprising:

[0027] The lithium ion capacitor is obtained by assembling a lithium ion capacitor cathode, a separator and a lithium ion capacitor anode, wherein the cathode capacity and the anode capacity of the lithium ion capacitor satisfy the following: 0.75≤(m3×K3) / (m1×K1+m2×K2)≤1.05.

[0028] By designing the composition of the lithium-ion capacitor and the ratio of the anode capacity to the cathode capacity, the present invention can significantly improve the cycle life and high-temperature stability of the lithium-ion capacitor without a complex preparation process, effectively improve the gas production problem, and enhance the safety performance of the lithium-ion capacitor.

[0029] Preferably, the method for preparing the lithium ion capacitor cathode comprises:

[0030] A battery-type cathode material, a capacitor-type cathode material, a conductive agent, a binder and a solvent are mixed to prepare a cathode slurry, which is then coated on the surface of an aluminum current collector to prepare a lithium ion capacitor cathode.

[0031] Preferably, the method for preparing the lithium ion capacitor anode comprises:

[0032] An anode material, a conductive agent, a binder and a solvent are mixed to prepare an anode slurry, and the anode slurry is coated on the surface of a copper current collector to prepare a lithium ion capacitor anode.

[0033] In a third aspect, the present invention provides an application of the lithium ion capacitor as described in the first aspect, wherein the lithium ion capacitor is applied in the field of energy storage.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) The present invention designs the composition of the lithium ion capacitor, introduces a capacitor-type cathode material and a battery-type cathode material into the cathode of the lithium ion capacitor at the same time, and adjusts the ratio between the cathode capacity and the anode capacity so that the ratio between the cathode capacity and the anode capacity is between 0.75 and 1.05. This can limit the upper limit potential of the cathode during the cycle and storage process, thereby inhibiting the high-temperature oxidation of the cathode material, improving the high-temperature stability of the lithium ion capacitor, improving the gas production problem, and improving the safety performance of the lithium ion capacitor.

[0036] (2) The present invention designs the composition of the lithium ion capacitor and the ratio of the anode capacity to the cathode capacity, without the need for a complex preparation process, and can significantly improve the cycle life and high-temperature stability of the lithium ion capacitor, effectively improve the gas production problem, and enhance the safety performance of the lithium ion capacitor. DETAILED DESCRIPTION

[0037] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in this application are intended to cover non-exclusive inclusions.

[0039] In the description of this application, the technical terms "first" and "second" are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "multiple" is more than two, unless otherwise clearly defined.

[0040] In one embodiment, the present invention provides a lithium ion capacitor, wherein the cathode of the lithium ion capacitor comprises a capacitor-type cathode material and a battery-type cathode material, and the anode of the lithium ion capacitor comprises an anode material;

[0041] The cathode capacity and anode capacity of the lithium ion capacitor satisfy the following requirements: 0.75≤(m3×K3) / (m1×K1+m2×K2)≤1.05, wherein m1, m2 and m3 are the unit area loadings of the capacitive cathode material, battery cathode material and anode material in the lithium ion capacitor, respectively, in g / m 2 , K1, K2 and K3 are the specific capacities of the capacitive cathode material, battery-type cathode material and anode material in the lithium ion capacitor, respectively, in mAh / g.

[0042] The present invention designs the composition of the lithium ion capacitor, introduces a capacitive cathode material and a battery cathode material into the cathode of the lithium ion capacitor at the same time, and adjusts the ratio between the cathode capacity and the anode capacity so that the ratio of the anode capacity m3×K3 and the cathode capacity m1×K1+m2×K2 is between 0.75 and 1.05, for example, it can be 0.75, 0.8, 0.9, 1 or 1.05, including but not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0043] The present invention controls the ratio between the anode capacity and the cathode capacity to within the range of 0.75-1.05, which can limit the upper limit potential of the cathode during cycling and storage, thereby inhibiting the high-temperature oxidation of the cathode material, improving the cycle life and high-temperature stability of the lithium-ion capacitor, improving the gas production problem, and improving the safety performance of the lithium-ion capacitor.

[0044] In some embodiments, the electrolyte concentration of the lithium ion capacitor satisfies:

[0045] During the charge and discharge process, the capacity of the capacitive cathode material and the attenuation ratio of the lithium ion concentration in the electrolyte satisfy: (n×S1×m1×K1) / Q i ≤60%, where Q i is the charge corresponding to the lithium ions in the electrolyte, the unit is C, n is the number of cathode laminate layers, and S1 is the cathode electrode area.

[0046] During the charge and discharge process of the lithium-ion capacitor provided by the present invention, when the capacitive cathode material absorbs and desorbs anions, the lithium ion decay rate in the electrolyte is below 60%. This can prevent performance degradation caused by excessive fluctuations in the electrolyte ion concentration, thereby improving gassing and enhancing the safety of the lithium-ion capacitor. The lithium ion decay rate in the electrolyte can be, for example, 60%, 59%, 58%, 57%, 56%, or 55%, including but not limited to the values ​​listed above. Other values ​​within the numerical range not listed are also applicable.

[0047] In some embodiments, the SOC of the lithium ion capacitor satisfies one of the following conditions:

[0048] a. When the lithium ion capacitor has a laminated structure, 0≤SOC≤m3×K3×S1×n.

[0049] b. When the lithium ion capacitor has a wound structure, 0≤SOC≤m3×K3×S1.

[0050] In this invention, the SOC of a lithium-ion capacitor refers to its state of charge (SOC), a parameter that reflects the state of charge stored in the capacitor. This invention regulates the SOC of a lithium-ion capacitor based on the available capacity of the anode, effectively preventing gassing and lithium deposition, and ensuring the safety of the lithium-ion capacitor.

[0051] In some embodiments, the upper charging limit voltage of the lithium ion capacitor satisfies one of the following conditions:

[0052] c. When the battery-type cathode material includes lithium iron phosphate, the upper charging limit voltage of the lithium ion capacitor is ≤3.65V, for example, it can be 3.65V, 3.60V, 3.55V, 3.50V, 3.45V or 3.4V, including but not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0053] d. When the battery-type cathode material is a ternary cathode material or a lithium cobalt oxide material, the upper charging limit voltage of the lithium ion capacitor is ≤4.0V, for example, it can be 4.0V, 3.95V, 3.9V, 3.85V, 3.8V or 3.75V, including but not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0054] The present invention can suppress the high-temperature oxidation of the cathode material by regulating the upper charging limit voltage of the lithium-ion capacitor, thereby improving the high-temperature stability and cycle life of the lithium-ion capacitor. By regulating the voltage window, the gas production can be effectively improved.

[0055] In some embodiments, the capacitive cathode material includes any one or a combination of at least two of an activated carbon material, an organometallic framework compound, a covalent organic framework material, or a layered double hydroxide. Typical but non-limiting combinations include a combination of an activated carbon material and an organometallic framework compound, a combination of an activated carbon material and a covalent organic framework material, or a combination of an activated carbon material and a layered double hydroxide.

[0056] In some embodiments, the battery-type cathode material includes any one or a combination of at least two of lithium iron phosphate material (LFP), NCM ternary positive electrode material, NCA ternary positive electrode material, lithium-rich manganese-based positive electrode material, NCMA ternary positive electrode material or lithium cobalt oxide material (LCO), typical but non-limiting combinations include a combination of NCM ternary positive electrode material and NCA ternary positive electrode material, a combination of NCMA ternary positive electrode material and LCO material, a combination of NCA ternary positive electrode material and NCMA ternary positive electrode material or a combination of LCO material and NCM ternary positive electrode material.

[0057] In some embodiments, the anode material includes any one of graphite, hard carbon, soft carbon, silicon carbon, lithium titanate, or niobium tungsten oxide, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of graphite and hard carbon, a combination of soft carbon and silicon carbon, or a combination of lithium titanate and niobium tungsten oxide.

[0058] In some embodiments, the cathode of the lithium ion capacitor further includes a cathode binder, and the cathode binder includes PVDF and / or polytetrafluoroethylene.

[0059] In some embodiments, the anode of the lithium ion capacitor further includes an anode binder, wherein the anode binder includes any one or a combination of at least two of SBR, PAA, PAN, or CMC. Typical but non-limiting combinations include a combination of SBR and CMC, a combination of PAA and CMC, or a combination of PAN and CMC.

[0060] In some embodiments, the cathode of the lithium ion capacitor and the anode of the lithium ion capacitor each independently further include a conductive agent, wherein the conductive agent includes any one or a combination of at least two of carbon black, carbon nanotubes, or graphene. Typical but non-limiting combinations include a combination of carbon black and carbon nanotubes, a combination of graphene and carbon black, or a combination of carbon nanotubes and graphene.

[0061] In another specific embodiment, the present invention provides a method for preparing the lithium ion capacitor as described in the above embodiment, the preparation method comprising:

[0062] The lithium ion capacitor is obtained by assembling a lithium ion capacitor cathode, a separator and a lithium ion capacitor anode, wherein the cathode capacity and the anode capacity of the lithium ion capacitor satisfy the following: 0.75≤(m3×K3) / (m1×K1+m2×K2)≤1.05.

[0063] By designing the composition of the lithium-ion capacitor and the ratio of the anode capacity to the cathode capacity, the present invention can significantly improve the cycle life and high-temperature stability of the lithium-ion capacitor without a complicated preparation process, effectively improve the gas production problem, and enhance the safety performance of the lithium-ion capacitor.

[0064] In some embodiments, the method for preparing the lithium ion capacitor cathode includes:

[0065] A battery-type cathode material, a capacitor-type cathode material, a conductive agent, a binder and a solvent are mixed to prepare a cathode slurry, which is then coated on the surface of an aluminum current collector to prepare a lithium ion capacitor cathode.

[0066] In some embodiments, the method for preparing the lithium ion capacitor anode includes:

[0067] An anode material, a conductive agent, a binder and a solvent are mixed to prepare an anode slurry, and the anode slurry is coated on the surface of a copper current collector to prepare a lithium ion capacitor anode.

[0068] In the present invention, in the method for preparing a lithium ion capacitor cathode and / or a lithium ion capacitor anode, the solvent used is matched to the type of binder and can be, for example, water or NMP (N-methylpyrrolidone). For example, when the cathode binder is PVDF, the solvent is NMP, and when the anode binder is a combination of SBR and CMC, the solvent is water.

[0069] In another specific embodiment, the present invention provides an application of the lithium ion capacitor as described in the above specific embodiment, wherein the lithium ion capacitor is applied in the field of energy storage.

[0070] Example 1

[0071] This embodiment provides a lithium ion capacitor, wherein the cathode material of the lithium ion capacitor includes activated carbon as a capacitor cathode material, LFP as a battery cathode material, and graphite as an anode material. In the lithium ion capacitor, the specific capacity K of the activated carbon is 活性炭 The loading capacity per unit area is 19.5 mAh / g. 活性炭 69.6g / m 2 , the specific capacity K of LFP LFP 160mAh / g, unit area loading capacity m LFP 156.0g / m2 , the specific capacity K of graphite 石墨 The loading capacity per unit area is 367 mAh / g. 石墨 64.6g / m 2 , the charge Q corresponding to the lithium ions in the electrolyte i It is 648.5mAh.

[0072] The lithium ion capacitor provided in this embodiment has a laminated structure, and the area S1 of the cathode plate is 120 cm 2 , the number of lamination layers n is 16, and the upper limit of charging voltage is 3.65V. The anode capacity and cathode capacity meet (m 石墨 ×K 石墨 ) / (m 活性炭 ×K 活性炭 +m LFP ×K LFP )=0.9, the attenuation ratio of the activated carbon capacity and the lithium ion concentration in the electrolyte satisfies: (n×S1×m 活性炭 ×K 活性炭 ) / Q i =40%, SOC=0.95×(m 石墨 ×K 石墨 )×S1×n.

[0073] Example 2

[0074] This embodiment provides a lithium ion capacitor, wherein the cathode material of the lithium ion capacitor includes activated carbon as a capacitor cathode material, NCM as a battery cathode material, and LiNi as a ternary positive electrode material. 0.6 Co 0.2 Mn 0.2 O2, the anode material of the lithium ion capacitor is hard carbon, and in the lithium ion capacitor, the specific capacity K of the activated carbon is 活性炭 The loading capacity per unit area is 19.5 mAh / g. 活性炭 103.2g / m 2 , the specific capacity K of NCM ternary cathode material NCM The loading capacity per unit area is 220 mAh / g. NCM 122.4g / m 2 , the specific capacity K of hard carbon 硬碳 310mAh / g, unit area loading capacity m 硬碳 70.38g / m 2 , the charge Q corresponding to the lithium ions in the electrolyte i It is 643.3mAh.

[0075] The lithium ion capacitor provided in this embodiment has a winding structure, and the area S1 of the cathode plate is 1920 cm 2, the upper limit of charging voltage is 4.0V, the anode capacity and cathode capacity meet m 硬碳 ×K 硬碳 / (m activated carbon × K activated carbon + m NCM ×K NCM )=0.75, the attenuation ratio of activated carbon and lithium ion concentration in electrolyte satisfies: m 活性炭 ×K 活性炭 / Q i =60%, SOC=0.95×m 硬碳 ×K 硬碳 ×S1.

[0076] Example 3

[0077] This embodiment provides a lithium ion capacitor. The components and structure of the lithium ion capacitor are the same as those of Example 1, except that the anode capacity and cathode capacity of this embodiment meet (m 石墨 ×K graphite) / (m activated carbon ×K activated carbon + m LFP ×K LFP )=1.05.

[0078] Example 4

[0079] This embodiment provides a lithium ion capacitor. The components and structure of the lithium ion capacitor are the same as those of Example 1, except that the anode capacity and cathode capacity of this embodiment meet (m 石墨 ×K graphite) / (m activated carbon ×K activated carbon + m LFP ×K LFP )=1.

[0080] Example 5

[0081] This embodiment provides a lithium ion capacitor. The components and structure of the lithium ion capacitor are the same as those of Example 1, except that the anode capacity and cathode capacity of this embodiment meet (m 石墨 ×K graphite) / (m activated carbon ×K activated carbon + m LFP ×K LFP )=1, the attenuation ratio of the activated carbon capacity and the lithium ion concentration in the electrolyte satisfies: (m 活性炭 ×K 活性炭 ) / Q i =20%.

[0082] Example 6

[0083] This embodiment provides a lithium ion capacitor. The components and structure of the lithium ion capacitor are the same as those of Example 1, except that the anode capacity and cathode capacity of this embodiment meet (m 石墨 ×K graphite) / (m activated carbon ×K activated carbon + m LFP ×K LFP)=1, the attenuation ratio of the activated carbon capacity and the lithium ion concentration in the electrolyte satisfies: (m 活性炭 ×K 活性炭 ) / Q i =10%.

[0084] Example 7

[0085] This embodiment provides a lithium ion capacitor. The components and structure of the lithium ion capacitor are the same as those of Example 1, except that the anode capacity and cathode capacity of this embodiment meet (m 石墨 ×K graphite) / (m activated carbon ×K activated carbon + m LFP ×K LFP )=1,SOC=(mgraphite×Kgraphite)×S1×n.

[0086] Example 8

[0087] This embodiment provides a lithium ion capacitor. The components and structure of the lithium ion capacitor are the same as those of Example 1, except that the anode capacity and cathode capacity of this embodiment meet (m 石墨 ×K graphite) / (m activated carbon ×K activated carbon + m LFP ×K LFP )=1, the attenuation ratio of the activated carbon capacity and the lithium ion concentration in the electrolyte satisfies: (m 活性炭 ×K 活性炭 ) / Q i =10%, SOC=0.9×(m 石墨 ×K 石墨 )×S1×n.

[0088] Example 9

[0089] This embodiment provides a lithium ion capacitor. The components and structure of the lithium ion capacitor are the same as those of Example 1, except that the attenuation ratio of the capacity of the activated carbon to the lithium ion concentration in the electrolyte satisfies: (m 活性炭 ×K 活性炭 ) / Q i =70%.

[0090] Comparative Example 1

[0091] This comparative example provides a lithium ion capacitor. The components and structure of the lithium ion capacitor are the same as those of Example 1, except that the anode capacity and cathode capacity in this comparative example meet (m 石墨 ×K graphite) / (m activated carbon ×K activated carbon + m LFP ×K LFP )=1.1.

[0092] The lithium ion capacitors in all the above embodiments and comparative examples were subjected to a 55° C., 1C / 1C cycle test. The test results are shown in Table 1.

[0093] The lithium ion capacitors in all the above embodiments and comparative examples were tested for a 70° C. storage volume change rate ΔV. The test results are shown in Table 2.

[0094] Table 1

[0095]

[0096]

[0097] According to the cycle test results of Examples 1 to 8 in Table 1, the present invention regulates the ratio between the cathode capacity and the anode capacity so that the ratio of the anode capacity to the cathode capacity is between 0.75 and 1.05, thereby limiting the upper limit potential of the cathode during the cycle, thereby inhibiting the high-temperature oxidation of the cathode material and improving the cycle life and high-temperature stability of the lithium-ion capacitor.

[0098] If the ratio of the anode capacity to the cathode capacity is greater than 1.05, according to the test results of Comparative Example 1, when the ratio of the anode capacity to the cathode capacity is 1.1, the cycle capacity retention rate shows a significant decrease, and the downward trend is faster.

[0099] According to the test results of Example 9, when the attenuation ratio of lithium ions in the electrolyte reaches 70%, the electrolyte ion concentration will fluctuate too much, leading to deterioration of the performance of the lithium ion capacitor, gas production, and a significant decrease in capacity retention.

[0100] Table 2

[0101]

[0102] According to the cycle test results of Examples 1 to 8 in Table 2, the present invention regulates the ratio between the cathode capacity and the anode capacity so that the ratio of the anode capacity to the cathode capacity is between 0.75 and 1.05, thereby limiting the upper limit potential of the cathode during the cycle, thereby inhibiting the high-temperature oxidation of the cathode material, improving the gas production problem, and making the 70°C storage volume change rate ΔV within a controllable range, thereby improving the safety performance of the lithium ion capacitor.

[0103] If the ratio of the anode capacity to the cathode capacity is greater than 1.05, according to the test results of Comparative Example 1, when the ratio of the anode capacity to the cathode capacity is 1.1, the 70°C storage volume change rate ΔV is significantly improved.

[0104] According to the test results of Example 9, when the attenuation ratio of lithium ions in the electrolyte reaches 70%, the electrolyte ion concentration will fluctuate too much, which will lead to deterioration of the performance of the lithium ion capacitor, gas production, and a significant increase in the storage volume change rate ΔV at 70°C.

[0105] According to the test results of Example 10, when the capacity of the lithium ion capacitor exceeds the anode capacity, gas generation and lithium deposition will occur, and the 70°C storage volume change rate ΔV will also increase significantly.

[0106] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A lithium ion capacitor, characterized in that: The cathode of the lithium ion capacitor includes a capacitor type cathode material and a battery type cathode material, and the anode of the lithium ion capacitor includes an anode material; The cathode capacity and anode capacity of the lithium ion capacitor satisfy the following requirements: 0.75≤(m3×K3) / (m1×K1+m2×K2)≤1.05, wherein m1, m2 and m3 are the unit area loadings of the capacitive cathode material, battery cathode material and anode material in the lithium ion capacitor, respectively, in g / m 2 , K1, K2 and K3 are the specific capacities of the capacitive cathode material, battery-type cathode material and anode material in the lithium ion capacitor, respectively, in mAh / g.

2. The lithium ion capacitor according to claim 1, wherein The electrolyte concentration of the lithium ion capacitor satisfies one: During the charge and discharge process, the capacity of the capacitive cathode material and the attenuation ratio of the lithium ion concentration in the electrolyte satisfy: (n×S1×m1×K1) / Q i ≤60%, where Q i is the charge corresponding to the lithium ions in the electrolyte, the unit is C, n is the number of cathode laminate layers, and S1 is the cathode electrode area.

3. The lithium ion capacitor according to claim 1 or 2, wherein: The SOC of the lithium ion capacitor satisfies one of the following conditions: a. When the lithium ion capacitor has a laminated structure, 0≤SOC≤m3×K3×S1×n; b. When the lithium ion capacitor has a wound structure, 0≤SOC≤m3×K3×S1.

4. The lithium ion capacitor according to any one of claims 1 to 3, wherein: The upper charging limit voltage of the lithium ion capacitor satisfies one of the following conditions: c. When the battery-type cathode material comprises lithium iron phosphate, the upper charging voltage limit of the lithium ion capacitor is ≤3.65V; d. When the battery-type cathode material is a ternary cathode material or a lithium cobalt oxide material, the upper charging limit voltage of the lithium ion capacitor is ≤4.0V.

5. The lithium ion capacitor according to any one of claims 1 to 4, characterized in that: The capacitive cathode material includes any one or a combination of at least two of an activated carbon material, an organic metal framework compound, a covalent organic framework material or a layered double hydroxide; And / or, the battery-type cathode material includes any one or a combination of at least two of lithium iron phosphate material, NCM ternary cathode material, NCA ternary cathode material, lithium-rich manganese-based cathode material, NCMA ternary cathode material or lithium cobalt oxide material; And / or, the anode material includes any one of graphite, hard carbon, soft carbon, silicon carbon, lithium titanate or niobium tungsten oxide, or a combination of at least two thereof.

6. The lithium ion capacitor according to any one of claims 1 to 5, wherein: The cathode of the lithium ion capacitor further includes a cathode binder, and the cathode binder includes PVDF and / or polytetrafluoroethylene; And / or, the anode of the lithium ion capacitor further includes an anode binder, and the anode binder includes any one of SBR, PAA, PAN or CMC, or a combination of at least two of them.

7. The lithium ion capacitor according to any one of claims 1 to 6, wherein: The cathode of the lithium ion capacitor and the anode of the lithium ion capacitor each independently further include a conductive agent, and the conductive agent includes any one of carbon black, carbon nanotubes or graphene, or a combination of at least two of them.

8. A method for preparing a lithium ion capacitor according to any one of claims 1 to 7, characterized in that: The preparation method comprises: The lithium ion capacitor is obtained by assembling a lithium ion capacitor cathode, a separator and a lithium ion capacitor anode, wherein the cathode capacity and the anode capacity of the lithium ion capacitor satisfy the following: 0.75≤(m3×K3) / (m1×K1+m2×K2)≤1.

05.

9. The preparation method according to claim 8, wherein The method for preparing the lithium ion capacitor cathode comprises: Mixing a battery-type cathode material, a capacitor-type cathode material, a conductive agent, a binder, and a solvent to prepare a cathode slurry, and coating the cathode slurry on the surface of an aluminum current collector to prepare a lithium-ion capacitor cathode; And / or, the method for preparing the lithium ion capacitor anode includes: An anode material, a conductive agent, a binder and a solvent are mixed to prepare an anode slurry, and the anode slurry is coated on the surface of a copper current collector to prepare a lithium ion capacitor anode.

10. A use of the lithium ion capacitor according to any one of claims 1 to 7, characterized in that: The lithium ion capacitor is used in the field of energy storage.

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