Negative electrode, secondary battery, and electric device

Abstract

The application discloses a negative electrode, a secondary battery and a power utilization device. The negative electrode comprises a lithium metal base body, a lithium-nitrogen interface layer on at least one surface of the lithium metal base body, and a nitrogen-based modification layer on the surface of the lithium-nitrogen interface layer. In the application, the lithium-nitrogen interface layer can reduce the impedance value of the contact surface, reduce the interface polarization, thereby enhancing the lithium ion mass transfer efficiency; the nitrogen element in the nitrogen-based modification layer can improve the adsorption capacity of lithium, more easily guide the lithium ion transmission, make the lithium ion deposition process more uniform, and increase the rate of lithium ion in the mass transfer process, thereby inhibiting the generation of lithium dendrites, and enhancing the cycle stability and rate performance of the lithium metal negative electrode.

Description

Technical Field

[0001] This invention relates to the field of batteries, and more particularly to a negative electrode, a secondary battery, and an electrical device. Background Technology

[0002] Lithium metal anodes, with their extremely high theoretical specific capacity (3860 mAh / g) and low redox potential (-3.041 V vs. standard hydrogen electrode), are widely used in rechargeable batteries. However, in practical applications, due to the relatively short diffusion path and strong electric field, lithium ions tend to aggregate at preferentially formed lithium tips, leading to uneven lithium ion distribution and transport. This results in severe dendrite growth, reducing battery cycle life and increasing the risk of separator puncture, causing short circuits and safety issues, thus hindering the commercial application of lithium metal anodes. Therefore, overcoming the problem of uneven lithium dendrite growth during charge-discharge cycles in existing lithium metal anodes is a pressing technical challenge. Summary of the Invention

[0003] This application provides a negative electrode, a secondary battery, and an electrical device, aiming to solve the problem that existing lithium metal negative electrodes are prone to lithium plating during cycling, and the uneven lithium plating results in poor battery cycle life and a tendency to cause battery short circuits.

[0004] In view of this, this application first provides a negative electrode, comprising: a lithium metal substrate; a lithium-nitrogen interface layer disposed on at least one surface of the lithium metal substrate; and a nitrogen-based modification layer disposed on the surface of the lithium-nitrogen interface layer.

[0005] Furthermore, the nitrogen-modified layer includes one or more of g-C3N4, α-C3N4, β-C3N4, and cubic C3N4.

[0006] Furthermore, the density of the nitrogen-modified layer is 12–20 g / cm³. 3 .

[0007] Furthermore, the pore density of the nitrogen-modified layer is 20 ppi to 500 ppi.

[0008] Furthermore, the thickness of the nitrogen-modified layer is 1 μm to 500 μm.

[0009] Furthermore, the thickness of the lithium-nitrogen interface layer is 1 nm to 200 nm.

[0010] Furthermore, the surface of the g-C3N4 contains one or more of graphitic nitrogen, pyridine nitrogen, and pyrrole nitrogen.

[0011] Furthermore, the surface of the g-C3N4 also contains oxygen-containing compounds, which include oxygen-containing functional groups, including at least one of hydroxyl, ether, carbonyl, carboxyl, and ester groups.

[0012] This application also provides a secondary battery, which includes the aforementioned negative electrode.

[0013] This application also provides an electrical device that includes the aforementioned secondary battery, which serves as the power supply for the electrical device.

[0014] Compared with the prior art, this application has the following advantages:

[0015] The negative electrode in this application has a lithium-nitrogen interface layer, which can reduce contact resistance and interfacial polarization, thereby enhancing lithium-ion mass transfer efficiency. The negative electrode also contains a nitrogen-based modification layer, which includes one or more of g-C3N4, α-C3N4, β-C3N4, and cubic C3N4. g-C3N4, α-C3N4, β-C3N4, and cubic C3N4 themselves have a strong ability to adsorb lithium ions. Their surfaces also contain one or more of graphitic nitrogen, pyridine nitrogen, and pyrrole nitrogen, as well as oxygen-containing compounds. Therefore, the adsorption energy for lithium is increased, making it easier to guide lithium-ion transport, increasing the rate of lithium ions in the mass transfer process, thereby suppressing the formation of lithium dendrites, and thus enhancing the cycle stability and rate performance of the lithium metal negative electrode. Detailed Implementation

[0016] The present application will now be described in further detail with reference to specific embodiments. The embodiments given are merely illustrative of the present application and are not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the present application in any way.

[0017] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0018] This application provides a negative electrode, comprising: a lithium metal substrate; a lithium-nitrogen interface layer disposed on at least one surface of the lithium metal substrate; and a nitrogen-based modification layer disposed on the surface of the lithium-nitrogen interface layer. In this embodiment, the lithium-nitrogen interface layer comprises Li x N, where 1 < X ≤ 3.

[0019] In this embodiment, the lithium-nitrogen interface layer can reduce contact impedance and interfacial polarization, thereby enhancing lithium-ion mass transfer efficiency. The nitrogen element in the nitrogen-based modification layer can improve the adsorption capacity for lithium, making it easier to guide lithium-ion transport and guiding the lithium-ion transport path, resulting in a more uniform lithium-ion deposition process. It can also increase the rate of lithium-ion transport during mass transfer, thereby suppressing the formation of lithium dendrites, thus enhancing the cycle stability and rate performance of the lithium metal anode. In some embodiments, the nitrogen-based modification layer can be obtained by carbonizing nitrogen-containing organic matter.

[0020] In another embodiment, the density of the nitrogen-modified layer is 12–20 g / cm³. 3 The nitrogen-based modified layer has a pore density of 20 ppi to 500 ppi and a thickness of 1 μm to 500 μm. The density, porosity, and thickness of the nitrogen-based modified layer determine its ability to regulate lithium flux and density. Higher density, lower porosity, and greater thickness result in a denser and more numerous internal fibrous structure, thus allowing for greater control over (influence on) lithium. However, excessively high pore density leads to a larger direct contact area between the electrolyte and the lithium metal matrix in the negative electrode, increasing the reaction rate and promoting lithium dendrite formation, which negatively impacts battery cycle life. Controlling the pore density within the aforementioned range effectively improves the battery's electrochemical performance and cycle life. Excessive thickness occupies more space, hindering the improvement of battery energy density; conversely, insufficient thickness hinders lithium-ion transport efficiency and overall battery performance.

[0021] In some embodiments, the nitrogen-based modification layer includes one or more of g-C3N4, α-C3N4, β-C3N4, and cubic C3N4. α-C3N4, β-C3N4, and cubic C3N4 have a spatial network crystal structure. In this application, g-C3N4 is preferred. g-C3N4 is a planar two-dimensional sheet structure similar to graphene. It is a network structure formed by infinitely extending triazine rings and 3-S-triazine rings as basic structural units. The g-C3N4 modification layer can significantly homogenize the distribution of lithium ions. Since g-C3N4 has a strong ability to adsorb lithium ions, it can effectively suppress the formation of lithium dendrites and improve the rate of lithium ion deposition / stripping. The presence of g-C3N4 greatly improves the wettability of the electrolyte, reduces the contact angle of the electrolyte on the electrode, and helps to improve the uniformity of lithium ion flux and reduce the non-uniformity of lithium ion transport and deposition.

[0022] In some embodiments, the thickness of the lithium-nitrogen interface layer is 1–200 nm. The thickness of the lithium-nitrogen interface layer directly affects the ability of the nitrogen-based modification layer to regulate the transport of Li ions in the surrounding environment, and thus directly affects the rate performance of the battery. In some embodiments, the Li3N interface layer is generated through a spontaneous reaction between the nitrogen-based modification layer and the lithium metal substrate, which can reduce the contact resistance between the nitrogen-based modification layer and the lithium metal substrate, reduce interfacial polarization, and thereby enhance the lithium-ion mass transfer efficiency.

[0023] In some embodiments, the surface of the g-C3N4 comprises one or more of graphitic nitrogen, pyridine nitrogen, and pyrrole nitrogen. Graphitic nitrogen, pyridine nitrogen, and pyrrole nitrogen have the ability to adsorb ions, which can improve the deposition rate of lithium ions and improve the uniformity of lithium deposition, thereby further suppressing the growth of lithium dendrites in the negative electrode.

[0024] To further enhance the adsorption of lithium ions by the negative electrode, reduce the difficulty of lithium ion mass transfer, decrease ohmic impedance, and increase cycle life, in another embodiment, the mass ratio of pyridine nitrogen, pyrrole nitrogen, and graphite nitrogen is (20-28):(27-32):(50-55). In this embodiment, since pyrrole nitrogen and pyridine nitrogen have stronger adsorption capacity for lithium ions, under the same nitrogen element ratio, the higher the proportion of pyrrole nitrogen and pyridine nitrogen in the nitrogen element, the better the cycle stability and the longer the cycle life.

[0025] In other embodiments, the surface of the g-C3N4 further contains an oxygen-containing compound, which includes oxygen-containing functional groups, including at least one selected from hydroxyl, ether, carbonyl, carboxyl, and ester groups. Because these oxygen-containing functional groups have excellent affinity with the electrolyte, they can improve the wettability of the negative electrode to the electrolyte, reduce the ohmic impedance of the battery, suppress the growth of lithium dendrites, and improve the battery cycle performance.

[0026] In other embodiments, the molar ratio of carbon, nitrogen, and oxygen in the nitrogen-based modification layer is (5–7):(6–8):(0.1–1.5). Within this ratio range, the electrode can exhibit better ability to suppress lithium dendrite growth and better electrolyte wetting performance, resulting in better cycle performance of the battery. Furthermore, the nitrogen-based modification layer containing graphitic nitrogen, pyridine nitrogen, pyrrole nitrogen, and oxygen-containing compounds can more effectively improve the stability of lithium deposition / stripping.

[0027] In another embodiment, this application also provides a method for preparing the above-mentioned negative electrode, the method comprising the following steps:

[0028] Preparation of nitrogen-modified layers;

[0029] The nitrogen-modified layer is stacked on at least one surface of a lithium metal substrate;

[0030] The nitrogen-based modification layer reacts with the lithium metal substrate at the interface to form a lithium-nitrogen interface layer, resulting in a negative electrode in which the lithium metal substrate, the lithium-nitrogen interface layer, and the nitrogen-based modification layer are stacked in sequence.

[0031] In some embodiments of this application, the step of preparing the nitrogen-based modified layer includes: using a nitrogen-containing organic compound as a precursor and performing a carbonization treatment to obtain the nitrogen-based modified layer.

[0032] In some embodiments of this application, the nitrogen-containing organic compounds include melamine, urea, thiourea, and dicyandiamide.

[0033] Preferably, in some embodiments of this application, the nitrogen-containing organic material is melamine foam. The material obtained by carbonizing melamine foam has a richer concentration of nitrogen-containing groups, as well as lower density and higher pore flow rate. This results in the battery exhibiting superior cycle performance and energy density.

[0034] The carbonization process involves placing nitrogen-containing organic matter in a tube furnace within a chemical vapor deposition system, heating it under inert gas protection, maintaining the temperature at 500–650°C for 1–3 hours, cooling it to room temperature, and removing it to obtain a nitrogen-based modified layer.

[0035] The temperature is increased from room temperature to 500–650°C at a rate of 1.0–5.0°C / min.

[0036] In some embodiments of this application, the heating rate is 2°C / min, 3°C / min, or 5°C / min.

[0037] In some embodiments of this application, the temperature is raised to 550°C, 600°C, or 650°C;

[0038] In some embodiments of this application, the holding time at 550°C is 1 hour or 2 hours;

[0039] In this application, the density and porosity of the obtained nitrogen-based modified layer are adjusted by changing the carbonization temperature and the holding time at high temperature;

[0040] Before carbonization, the nitrogen-containing organic matter needs to be cleaned and dried. The cleaning and drying process involves ultrasonically cleaning the nitrogen-containing organic matter in ethanol, deionized water, and ethanol solution, respectively, and then drying it.

[0041] The ultrasonic cleaning time can be 0.5 to 1.5 hours, specifically 1 hour;

[0042] The drying temperature can be 40-70℃, specifically 60℃, and the drying time can be 20-26h, specifically 24h;

[0043] In some embodiments of this application, the method further includes performing an oxygen plasma modification operation on the obtained nitrogen-based modified layer to obtain a nitrogen-based modified layer with oxygen-containing compounds on its surface.

[0044] In some embodiments of this application, the method further includes performing nitrogen plasma modification on the nitrogen-based modified layer containing oxygen-containing compounds on its surface to obtain a nitrogen-based modified layer containing pyridine nitrogen, pyrrole nitrogen, graphitic nitrogen and oxygen-containing compounds in a specific mass ratio on its surface.

[0045] In some embodiments of this application, both oxygen plasma and nitrogen plasma modification are performed within a PECVD system (plasma-enhanced chemistry vapor deposition system).

[0046] The oxygen plasma modification operation is as follows: first, maintain the vacuum level in the PECVD system at 1*10. -3 Below Pa, introduce O2, adjust the system pressure to maintain within the range of 0.1 to 10 Pa, turn on the plasma generator, set the plasma output power to 500 to 1300 W, adjust the plasma radio frequency system reflection power to 1 to 10 W, run the plasma generator for 5 to 30 minutes, turn off the plasma generator, and stop introducing O2.

[0047] In some embodiments of this application, the plasma generator is operated for 5 to 30 minutes after oxygen is introduced, specifically one of 5 minutes, 10 minutes, 20 minutes, or 30 minutes.

[0048] The flow rate of the O2 can be 16–64 sccm;

[0049] The purity of the O2 can be 99% to 99.999%;

[0050] The nitrogen plasma modification operation is as follows: introduce N2, adjust the system pressure to maintain within the range of 0.1 to 10 Pa, turn on the plasma generator, set the plasma output power to 500 to 1300 W, adjust the plasma radio frequency system reflection power to 1 to 10 W, run the plasma generator for 5 to 30 minutes, turn off the plasma generator, and stop introducing N2.

[0051] In some embodiments of this application, the plasma generator is operated for 5 min, 10 min, 20 min, or 30 min after nitrogen gas is introduced;

[0052] The flow rate of N2 can be 16–40 sccm;

[0053] The purity of the N2 can be 99% to 99.999%.

[0054] This application modulates the proportion and distribution of C, N, and O elements on the surface of a nitrogen-based modified layer through simple plasma treatment, especially the proportion of various nitrogen elements on the surface of the nitrogen-based modified layer, such as pyridine nitrogen, pyrrole nitrogen, and graphitic nitrogen, to enhance the ability of the nitrogen-based modified layer surface to adsorb lithium ions.

[0055] The lithium metal matrix includes one or more of lithium metal, lithium alloy, and lithium metal composite oxide. The thickness of the lithium metal matrix is ​​10 μm to 500 μm.

[0056] This application also provides a secondary battery, which includes the above-mentioned negative electrode.

[0057] This application also provides an electrical device, which includes the aforementioned secondary battery, and the secondary battery serves as the power supply for the electrical device.

[0058] In the anode material of this application, the nitrogen-based modification layer itself has a strong ability to adsorb lithium ions. After oxygen plasma modification, the oxygen-containing functional groups formed on the surface of the nitrogen-based modification layer can improve the wettability of the anode to the electrolyte, thereby enhancing the adsorption and guiding ability of the nitrogen-based modification layer for lithium ions, thus enhancing the cycle stability of the lithium metal anode. Furthermore, nitrogen plasma modification can adjust and optimize the type and proportion of nitrogen on the surface of the nitrogen-based modification layer, such as pyridine nitrogen, pyrrole nitrogen, and graphitic nitrogen, making it more attractive to lithium ions, thereby enhancing the adsorption energy of lithium ions, improving the ability of the nitrogen-based modification layer to induce the lithium ion mass transfer process, and enhancing the cycle stability of the lithium metal anode. In addition, the lithium-nitrogen interface layer formed by the spontaneous reaction between the nitrogen-based modification layer and lithium metal in the lithium metal matrix has excellent lithium ion conductivity, improving the lithium ion transport rate. Moreover, the lithium-nitrogen interface layer can also reduce the contact resistance between the nitrogen-based modification layer and lithium metal, reduce interfacial polarization, thereby enhancing the lithium ion mass transfer efficiency and further improving the battery cycle performance.

[0059] The present application will be further described in detail below with reference to specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0060] Example 1

[0061] Preparation of the above negative electrode:

[0062] 1) A polyurethane foam measuring 5cm x 4cm x 0.8cm (length x width x height) was placed in a tube furnace within a chemical vapor deposition system. Argon gas was introduced into the tube furnace, and the heating rate was adjusted to 2℃ / min, raising the temperature from room temperature (25℃) to 550℃. This temperature was maintained at 550℃ for 2 hours, followed by natural cooling to room temperature. The resulting foam had a density of 16 g / cm³. 3 g-C3N4 foam material (i.e. nitrogen-based modified layer) with a pore density of 250 ppi and a thickness of 250 μm.

[0063] 2) Place the obtained g-C3N4 foam material into the PECVD system, run the vacuum pump system, and maintain the vacuum in the system at 1*10. -3 Below Pa; then introduce O2 (99.999% purity) at a flow rate of 16 sccm, adjust the vacuum pump system to maintain the cavity pressure within the range of 0.1 to 10 Pa, turn on the plasma generator, set the plasma output power to 1000 W, adjust the plasma radio frequency system reflection power to 1 to 10 W, run the plasma generator for 10 min, turn off the plasma generator, and stop introducing O2.

[0064] 3) Introduce N2 (99.999% purity) at a flow rate of 16 sccm, adjust the vacuum pump system to maintain the pressure in the cavity within the range of 0.1-10 Pa, turn on the plasma generator, set the plasma output power to 1000 W, adjust the plasma radio frequency system reflection power to 0-10 W, run the plasma generator for 10 min, turn off the plasma generator, and stop introducing N2; turn off the PECVD system to obtain the modified g-C3N4 foam material (i.e., g-C3N4 foam material with graphitic nitrogen, pyridine nitrogen, pyrrole nitrogen and oxygen-containing compounds on the surface); wherein the molar ratio of C, N, and O in the modified g-C3N4 foam material is 6:7:1, and the mass ratio of pyridine nitrogen, pyrrole nitrogen, and graphitic nitrogen is 25:30:55.

[0065] 4) By contacting the prepared modified g-C3N4 foam material with a lithium sheet with a thickness of 300 μm for 48 hours, a 100 nm thick Li-C3N4 foam material layer can be formed at the contact surface between the lithium sheet and the modified g-C3N4 foam material. x The negative electrode of the N-interface layer.

[0066] Example 2

[0067] Similar to Example 1, except that the temperature in step 1) is increased from room temperature (25°C) to 650°C.

[0068] Example 3

[0069] Similar to Example 1, except that the temperature in step 1) is increased from room temperature (25°C) to 600°C.

[0070] Example 4

[0071] Similar to Example 1, except that the temperature in step 1) is increased from room temperature (25°C) to 520°C.

[0072] Example 5

[0073] Similar to Example 1, except that the size of the melamine foam in step 1) is replaced with 3cm*3cm*0.05cm.

[0074] Example 6

[0075] Similar to Example 1, except that the size of the melamine foam in step 1) is replaced with 4cm*4cm*0.15cm.

[0076] Example 7

[0077] Similar to Example 1, except that the size of the melamine foam in step 1) is replaced with 6cm*5cm*0.5cm.

[0078] Example 8

[0079] Similar to Example 1, except that the size of the melamine foam in step 1) is replaced with 6cm*5cm*1.2cm.

[0080] Example 9

[0081] Similar to Example 1, except that the size of the melamine foam in step 1) is replaced with 6cm*5cm*1.4cm.

[0082] Example 10

[0083] Similar to Example 1, except that the flow rate of O2 in step 2) is adjusted to 2 sccm.

[0084] Example 11

[0085] Similar to Example 1, except that the flow rate of O2 in step 2) is adjusted to 12 sccm.

[0086] Example 12

[0087] Similar to Example 1, except that the flow rate of O2 in step 2) is adjusted to 20 sccm.

[0088] Example 13

[0089] Similar to Example 1, except that the time for introducing O2 into the plasma generator in step 2) is adjusted to 20 minutes.

[0090] Example 14

[0091] Similar to Example 1, except that the flow rate of N2 in step 3) is adjusted to 14 sccm.

[0092] Example 15

[0093] Similar to Example 1, except that the flow rate of N2 in step 3) is adjusted to 10 sccm.

[0094] Example 16

[0095] Similar to Example 1, except that the flow rate of N2 in step 3) is adjusted to 12 sccm.

[0096] Example 17

[0097] Similar to Example 1, except that the thickness of the lithium sheet in step 4) is 10 μm.

[0098] Example 18

[0099] Similar to Example 1, except that the thickness of the lithium sheet in step 4) is 150 μm.

[0100] Example 19

[0101] Similar to Example 1, except that the thickness of the lithium sheet in step 4) is 350 μm.

[0102] Example 20

[0103] Similar to Example 1, except that the thickness of the lithium sheet in step 4) is 500 μm.

[0104] Comparative Example 1

[0105] The provided negative electrode does not have an interface modification layer or a Li3N interface layer.

[0106] Experimental examples (test results are shown in Table 1)

[0107] 1) Cycle life test: The negative electrodes obtained in Examples 1-20 and Comparative Example 1 were used as counter electrodes with lithium metal sheets to fabricate coin cells CR2032. The electrolyte composition of the coin cell CR2032 consisted of solutes of chain ether dimethoxyethane (DME) and cyclic ether 1,3-dioxolane (DOL) in a volume ratio of 1:1, and 2.0% LiNO3. A PP membrane was used as the separator.

[0108] With 1.0mAh cm -2 and 1.0mA cm -2 Lithium was deposited at a high deposition efficiency, and then stripped at the same rate (i.e., 1.0 mAh / cm²). -2 and 1.0mA cm -2 Charge to 1V (vs. Li / Li) + To remove lithium, the CR2032 coin cell battery is cycled through charging and discharging. When the battery fails due to a short circuit, the number of cycles is recorded.

[0109] 2) Wetting performance test of negative electrode: 1 drop (0.2 mL) of electrolyte was dropped onto the negative electrode surface of Examples 1 to 20 and Comparative Example 1, and the contact angle was obtained using a contact angle measuring instrument after 1 second.

[0110] Table 1

[0111]

[0112]

[0113] As shown in Table 1, the experimental data indicates that compared to lithium foil as the negative electrode, the negative electrode with the nitrogen-based modification layer exhibits better electrolyte wetting and better battery cycle performance. The comparative data in Table 1 show that lithium foil, as the negative electrode, has a wetting angle as high as 72°, indicating poor electrolyte wetting performance. This leads to increased polarization of the negative electrode, which is detrimental to battery cycle stability. In contrast, the negative electrode prepared using the embodiments of this application, due to the presence of the modification layer, improves both the wettability of the negative electrode and the cycle life of the battery.

[0114] The present application has been described in detail above. Those skilled in the art will recognize that the present application can be implemented in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope, and without requiring unnecessary experiments. Although specific embodiments are given in this application, it should be understood that further modifications can be made to the present application. In summary, in accordance with the principles of this application, this application is intended to include any changes, uses, or improvements to the present application, including changes made using conventional techniques known in the art that depart from the scope disclosed herein.

Claims

1. A negative electrode, characterized by comprising: Comprising: a lithium metal substrate; a lithium-nitrogen interfacial layer on at least one surface of the lithium metal substrate; a nitrogen-based modification layer on a surface of the lithium-nitrogen interfacial layer; The density of the nitrogen-based modification layer is 12-20 g / cm 3 ; a pore density of the nitrogen-based modification layer is 20 ppi to 500 ppi; the nitrogen-based modification layer comprises g-C3N4; a surface of the g-C3N4 comprises graphitic nitrogen, pyridinic nitrogen, and pyrrolic nitrogen; a mass ratio of the pyridinic nitrogen, pyrrolic nitrogen, and graphitic nitrogen is (20-28):(27-32):(50-55).

2. The negative electrode according to claim 1, characterized by a thickness of the lithium-nitrogen interfacial layer is 1 nm to 200 nm.

3. The negative electrode according to claim 1, characterized by a thickness of the nitrogen-based modification layer is 1 μm to 500 μm.

4. The negative electrode according to claim 1, characterized by the surface of the g-C3N4 further comprises an oxygen-containing compound, the oxygen-containing compound comprises an oxygen-containing functional group, and the oxygen-containing functional group comprises at least one of a hydroxyl group, an ether bond, a carbonyl group, a carboxyl group, and an ester group.

5. A secondary battery characterized by comprising: The negative electrode of any one of claims 1-4.

6. An electric device, characterized by The secondary battery of claim 5, as a power supply for the power-consuming device.

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