A battery and energy storage device

Abstract

The application relates to a battery and an energy storage device, which are used for solving the technical problem that the performance of an existing battery seriously decays in a low-temperature environment. The battery comprises a positive pole sheet, a negative pole sheet and an electrolyte, wherein the positive pole sheet comprises a positive pole current collector and a positive pole active material layer arranged on the positive pole current collector, the positive pole active material layer contains a solid-state electrolyte; and the electrolyte contains fluoroethylene carbonate and tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether. Through the above design, the performance of the battery in a low-temperature environment can be effectively improved, so that the battery can maintain normal charging and discharging capacity in a low-temperature environment.

Description

Technical Field

[0001] This invention relates to the field of battery manufacturing technology, and more particularly to a battery and energy storage device. Background Technology

[0002] Lithium-ion batteries are widely used due to their advantages in energy density and power performance. As the application fields of lithium-ion batteries continue to expand, high energy density is no longer sufficient; the ability to operate in special environments, such as low temperatures, has also become an essential performance requirement.

[0003] Under low temperature conditions, the overall performance of lithium batteries will be severely affected, and the charging and discharging capabilities will be greatly reduced. Under extreme low temperatures, lithium batteries may not even be able to charge or discharge, which will seriously affect the user experience.

[0004] Therefore, finding a technical solution that can solve the above-mentioned technical problems has become an important research topic for those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a battery and energy storage device to solve the technical problem of severe performance degradation of existing batteries in low-temperature environments.

[0006] To achieve this objective, the present invention adopts the following technical solution: The present invention provides a battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode comprises a positive current collector and a positive active material layer disposed on the positive current collector, the positive active material layer containing a solid electrolyte; and the electrolyte contains fluoroethylene carbonate and tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0007] Optionally, the solid electrolyte includes one or more of lithium titanium aluminum phosphate, lithium lanthanum zirconium oxide, and lithium germanium phosphorus sulfur.

[0008] Optionally, based on the solid mass of the positive electrode active material layer, the mass fraction of the solid electrolyte is a, wherein a ranges from 1% to 5%.

[0009] Optionally, based on the mass of the electrolyte, the mass fraction of the fluoroethylene carbonate is b, wherein b ranges from 1% to 10%.

[0010] Optionally, based on the mass of the electrolyte, the mass fraction of the tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether is c, wherein c ranges from 1% to 35%.

[0011] Optionally, the mass fraction a of the solid electrolyte, the mass fraction b of the fluoroethylene carbonate, and the mass fraction c of the tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether satisfy the following relationship: a*b*c^(0.6)≥ 10, 0.1

[0012] Optionally, the positive electrode active material layer may further contain ternary materials, lithium iron phosphate, lithium manganese oxide, or lithium cobalt oxide.

[0013] Optionally, the ternary material is Ni, Co, Mn or Ni, Co, Al.

[0014] Optionally, the negative electrode sheet includes a negative current collector and a negative active material layer disposed on the negative current collector, wherein the negative active material layer contains graphite.

[0015] The present invention provides an energy storage device, characterized in that it includes the battery described above.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The battery of the present invention contains a solid electrolyte in the positive electrode active material and fluoroethylene carbonate and tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether in the electrolyte.

[0017] In the above design, the solid electrolyte provides high conductivity, a large specific surface area, and a portion of the capacity. The high conductivity of the solid electrolyte facilitates the construction of an ion-conducting network, shortening the diffusion paths of electrons and ions. The large specific surface area of ​​the solid electrolyte aids in the passage of lithium ions, further accelerating the ion transport rate and thus improving the battery's low-temperature performance. Fluoroethylene carbonate in the electrolyte improves the performance of the resulting SEI film, creating a compact structure without increasing impedance, preventing further electrolyte decomposition, and enhancing the electrolyte's low-temperature performance. Tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether in the electrolyte possesses a strong electron-attracting group. CFn can significantly reduce the electronegativity of oxygen in itself, preventing it from acting as a donor solvent for Li+ coordination. This property helps improve the physical properties of the electrolyte, specifically reducing its viscosity and freezing point, thereby expanding its application range under different temperature conditions.

[0018] In summary, the above design effectively improves the battery's performance in low-temperature environments, enabling it to maintain normal charging and discharging capabilities even at low temperatures. Detailed Implementation

[0019] ​To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions in the embodiments of this invention will be clearly and completely described below. Obviously, the embodiments described below are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0020] On one hand, the present invention provides a battery including a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode includes a positive current collector and a positive active material layer disposed on the positive current collector, the positive active material layer containing a solid electrolyte; and the electrolyte contains fluoroethylene carbonate (FEC) and tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE).

[0021] It should be noted that the above design systematically solves the core technical problems of lithium batteries such as severe decrease in ion conduction rate, sharp increase in interface impedance and electrolyte freezing failure by introducing a solid electrolyte into the positive electrode active material layer and compounding fluoroethylene carbonate and tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether in the electrolyte.

[0022] On the positive electrode side, the solid electrolyte is uniformly dispersed in particulate form within the positive electrode active material layer, constructing a three-dimensional continuous fast ion conductor network. This significantly shortens the path length for lithium ions to diffuse from the bulk electrolyte to the surface of the positive electrode active material, effectively reducing concentration polarization on the positive electrode side. Especially during high-rate, low-temperature discharge, it can significantly suppress the excessively rapid decay of the voltage plateau. The large specific surface area of ​​the solid electrolyte facilitates lithium ion transport, further accelerating the ion transport rate and thus improving the battery's low-temperature performance.

[0023] On the electrolyte side, fluoroethylene carbonate, as a film-forming additive, preferentially decomposes on the negative electrode surface to form a thin and dense solid electrolyte interface film rich in lithium fluoride. This interface film exhibits extremely low electronic conductivity, excellent mechanical strength, and good flexibility, and can suppress the continuous decomposition of the electrolyte and the cumulative increase in impedance over a long period. Meanwhile, tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, as a non-coordinating fluorinated diluent modified with a strong electron-withdrawing group, weakens the electron cloud density of the ether oxygen atom in its molecular structure through the carbon-fluorine bond, causing it to completely lose its ability to coordinate with lithium ions. This breaks the rigid structure of the lithium salt solvation shell, significantly reducing the activation energy of lithium ion desolvation. This property helps improve the physical properties of the electrolyte, specifically reducing its viscosity and freezing point, thereby expanding its application range under different temperature conditions.

[0024] The positive electrode solid electrolyte network, the low-impedance interface film constructed by fluoroethylene carbonate, and the improvement of bulk electrolyte transport dynamics by tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether belong to three dimensions: the positive electrode interface, the negative electrode interface, and the bulk electrolyte. They form a synergistic optimization mechanism for low-temperature performance, which can effectively improve the battery's performance in low-temperature environments and enable it to maintain normal charge and discharge capabilities in low-temperature environments.

[0025] Furthermore, the solid electrolyte in this invention includes one or more of lithium titanium aluminum phosphate (LATP), lithium lanthanum zirconium oxide (LLZO), and lithium germanium phosphorus sulfur (LGPS).

[0026] It should be noted that the aforementioned lithium titanium aluminum phosphate, lithium lanthanum zirconium oxide, and lithium germanium phosphorus sulfur materials belong to the NASICON type, garnet type, and sulfide type fast ion conductor systems, respectively, each possessing unique performance advantages and adaptable to different process scenarios.

[0027] Lithium titanium aluminum phosphate has a high room temperature ionic conductivity, which allows it to form a good interfacial bond with polyvinylidene fluoride binder during the preparation of positive electrode slurry, thus preventing microcracks from forming on the electrode during drying and rolling. At the same time, it has relatively good tolerance to environmental moisture, making it suitable for direct introduction into existing conventional coating processes.

[0028] Lithium lanthanum zirconium oxide exhibits extremely high chemical stability for lithium metal anodes. When this material is incorporated into the cathode, it can effectively suppress side reactions between the cathode material and the electrolyte, such as the dissolution and migration of transition metal ions, thereby significantly extending the cycle life of the battery. In addition, its wide electrochemical window characteristics enable it to be compatible with high-voltage cathode systems.

[0029] Lithium germanium phosphorus sulfur is one of the solid electrolytes with the highest known room temperature ionic conductivity. When incorporated into the cathode, it can minimize ohmic polarization at low temperatures, making it particularly suitable for low-temperature start-up power supplies or pulse power applications with stringent rate performance requirements.

[0030] When multiple solid electrolytes are used in combination, such as lithium titanium aluminum phosphate combined with lithium lanthanum zirconium oxygen, the dual advantages of high ionic conductivity and wide electrochemical window can be taken into account, further expanding the universality and process compatibility of solid electrolytes in cathode materials of different chemical systems.

[0031] In addition, the solid electrolyte in this invention can also be made of materials other than the three materials mentioned above, which will not be described in detail here.

[0032] Furthermore, based on the solid mass of the positive electrode active material layer, the mass fraction of the solid electrolyte is a, wherein a ranges from 1% to 5%, for example, 1%, 2%, 3%, 4%, 5%, etc.

[0033] It should be noted that in the above design, by effectively controlling the mass fraction 'a' of the solid electrolyte, the solid electrolyte can effectively improve ionic conductivity without significantly reducing the positive electrode energy density within this mass fraction range; if the content is too low, the ion conduction network will be discontinuous, and if the content is too high, it may affect the stability of the positive electrode structure and processing performance.

[0034] Furthermore, based on the mass of the electrolyte, the mass fraction of the fluoroethylene carbonate is b, wherein b ranges from 1% to 10%, for example, 1%, 2%, 3%, 4%, 5%, etc.

[0035] It should be noted that in the above design, by effectively controlling the mass fraction b of fluoroethylene carbonate, fluoroethylene carbonate can form a dense, low-resistance SEI film on the negative electrode surface, effectively inhibiting electrolyte decomposition. Within this mass fraction range, the first coulombic efficiency and cycle life at low temperature are improved; too high or too low a mass fraction will affect the film quality or increase the impedance.

[0036] Furthermore, based on the mass of the electrolyte, the mass fraction of the tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether is c, wherein c ranges from 1% to 35%, for example, 1%, 2%, 3%, 4%, 5%, etc.

[0037] It should be noted that in the above design, by effectively controlling the mass fraction c of tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, fluoroethylene carbonate can form a dense, low-resistance SEI film on the negative electrode surface, effectively inhibiting electrolyte decomposition and improving the first coulombic efficiency and cycle life at low temperature; too high or too low a concentration will affect the film quality or increase the impedance.

[0038] Additionally, it should be noted that b and c are components of the electrolyte and their mass fraction in the total electrolyte. Without any additives or lithium salts, the maximum value of b+c can only be 100, at which point the battery cannot function. In other words, b+c must be less than 100.

[0039] Furthermore, in this invention, the mass fraction a of the solid electrolyte, the mass fraction b of the fluoroethylene carbonate, and the mass fraction c of the tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether satisfy the following relationship: a*b*c^(0.6)≥ 10, 0.1

[0040] It should be noted that by limiting the quantitative synergistic relationship among the three components, the solid electrolyte and electrolyte functional components are ensured to form a synergistic optimization in the positive electrode interface, SEI film structure and solvent system, achieving the best comprehensive balance of low-temperature ion conduction, film stability and low viscosity, and avoiding performance degradation caused by excessive or insufficient single component. ​

[0041] The above relationship is not a simple linear superposition of the components, but rather a profound reflection of the marginal effect balance among the density of the solid-state ion transport pathway at the positive electrode, the quality of the interface film at the negative electrode, and the transport kinetics of the bulk electrolyte. Specifically, the solid electrolyte content *a* mainly contributes to the connectivity of the solid-state ion transport network inside the positive electrode, the fluoroethylene carbonate content *b* contributes to the compactness and low impedance characteristics of the interface film at the negative electrode, and the tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether content *c* (0.6) reflects the diminishing marginal effect of this fluorinated diluent on reducing electrolyte viscosity and promoting desolvation.

[0042] On the other hand, the ratio constraint between b and c ensures a precise balance between film formation and lubrication between fluoroethylene carbonate and tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0043] Furthermore, the positive electrode active material layer in this invention also contains ternary materials, lithium iron phosphate, lithium manganese oxide, or lithium cobalt oxide.

[0044] It should be noted that the above-mentioned positive electrode active material has good compatibility with solid electrolyte. While ensuring high energy density, it can improve the low-temperature lithium-ion diffusion capability with the help of solid electrolyte, thus broadening the low-temperature adaptability of the material system.

[0045] Specifically, the aforementioned ternary material can be Ni, Co, Mn or Ni, Co, Al.

[0046] It should be noted that this type of ternary material has high specific capacity and good structural stability. When combined with solid electrolyte, it can further improve the ionic conductivity and interfacial stability of the cathode, while taking into account both high energy density and low temperature performance.

[0047] Furthermore, the negative electrode sheet of the present invention includes a negative current collector and a negative active material layer disposed on the negative current collector, wherein the negative active material layer contains graphite.

[0048] It should be noted that the graphite anode has a mature lithium intercalation mechanism and a low potential plateau, which matches well with the optimized electrolyte. It can form a stable SEI film under low temperature conditions, ensuring rapid lithium ion insertion / extraction on the anode side and improving the low-temperature cycle performance of the full cell.

[0049] On the other hand, the present invention provides an energy storage device including the battery described above.

[0050] In the battery of the energy storage device of the present invention, the positive electrode active material is added with a solid electrolyte and the electrolyte contains fluoroethylene carbonate and tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0051] In the above design, the solid electrolyte provides high conductivity, a large specific surface area, and a portion of the capacity. The high conductivity of the solid electrolyte facilitates the construction of an ion-conducting network, shortening the diffusion paths of electrons and ions. The large specific surface area of ​​the solid electrolyte aids in the passage of lithium ions, further accelerating the ion transport rate and thus improving the battery's low-temperature performance. Fluoroethylene carbonate in the electrolyte improves the performance of the resulting SEI film, creating a compact structure without increasing impedance, preventing further electrolyte decomposition, and enhancing the electrolyte's low-temperature performance. Tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether in the electrolyte possesses a strong electron-attracting group. CFn significantly reduces the electronegativity of oxygen in itself, preventing it from acting as a donor solvent for Li+ coordination. This property helps improve the physical properties of the electrolyte, specifically reducing its viscosity and freezing point, thereby expanding its application range under different temperature conditions. Through the above design, the battery's performance in low-temperature environments can be effectively improved, enabling it to maintain normal charge and discharge capabilities at low temperatures.

[0052] This energy storage device integrates a battery system with excellent low-temperature adaptability, which can stably output power in low-temperature scenarios such as high-altitude and cold regions, winter outdoor activities, cold chain logistics, and aerospace. It has comprehensive advantages such as high energy density, long life, and high safety, expanding the application range of lithium batteries in extreme environments.

[0053] The above is a detailed description of a battery and energy storage device provided by the present invention. The performance of the battery will be tested below with multiple embodiments and comparative examples to verify the technical effect of the present invention.

[0054] Specifically as follows: First, batteries were manufactured according to the specific parameters shown in the various embodiments and comparative examples in Table 1 below.

[0055] Low-temperature discharge time test method: 1. At room temperature, charge at a current of 0.1C to a full charge voltage of 4.4V. 2. Discharge at a constant current of 0.1C for 9 hours at room temperature; 3. Place the battery cells in a 10℃ incubator for 4 hours; After 4.4 hours, the system was discharged to 3.0V at a current of 1.0C in the temperature chamber, and the discharge time was recorded to characterize the low-temperature performance of the system. The test results are shown in Table 2.

[0056] Table 1 Table 2 in conclusion: As can be clearly seen from the experimental data presented in Table 2, the technical features and parameter ranges defined in this invention have a decisive influence on the low-temperature performance of the battery. The low-temperature discharge times of all embodiments are significantly better than those of the comparative examples. Example 3 achieved a discharge time of 201 seconds, the highest among all tested samples, more than double that of Comparative Example 1. Examples 2 and 4 also achieved discharge times of 181 seconds and 192 seconds, respectively, demonstrating excellent low-temperature discharge capabilities. Even in Example 5, with a low solid electrolyte content (a=1%), the discharge time still reached 163 seconds, significantly higher than all comparative examples that did not fully meet the technical features of this invention.

[0057] Furthermore, Comparative Example 1 showed the lowest low-temperature discharge time at only 89 seconds, indicating that the battery's low-temperature performance was severely inadequate without employing any of the technical features of this invention.

[0058] Comparative Example 2: Discharge time was 103 seconds, slightly improved compared to the control group, but far lower than the Example. Positive electrode ion transport was improved, but the negative electrode SEI film was poor and the electrolyte viscosity was high, resulting in limited improvement in low-temperature performance.

[0059] Comparative Example 3: Discharge time 105 seconds, the negative electrode SEI film is improved, but the positive electrode lacks an ion-conducting network and the electrolyte lacks a low-viscosity diluent, so the low-temperature performance is still poor.

[0060] Comparative Example 4: FEC+TTE added (b=5%, c=8%), no solid electrolyte (a=0). Discharge time was only 93 seconds, close to the blank group. This proves that a solid electrolyte at the positive electrode is indispensable, and optimizing the electrolyte alone cannot achieve a leap in low-temperature performance.

[0061] Comparative Example 5: a=2%, b=30% (1%~10% above), c=8%, b / c=3.75 (0.1~0.8 above). a*b*c^(0.6)≥10, but excessive FEC caused SEI film embrittlement and b / c imbalance, with a discharge time of 86 seconds, which was worse than the blank group. This indicates that the b / c ratio is the core constraint, and deviation from it leads to failure.

[0062] Comparative Example 6: a=2%, b=5%, c=100% (over 1%~35%), b / c=0.05 (below 0.1). a*b*c^(0.6)≥10, but excessive TTE caused salting out, and insufficient FEC caused incomplete SEI membrane, with a discharge time of 79 seconds, the worst in the group. This proves that c must be within 1%~35%, and b / c must be ≥0.1.

[0063] Comparative Example 7: a=2%, b=30% (exceeding 1%~10%), c=100% (exceeding 1%~35%), b / c=0.3 (compliant with 0.1~0.8). a*b*c^(0.6)≥10, but b and c are both severely out of range, resulting in double failure of SEI film due to embrittlement and salting out, with a discharge time of 80 seconds. This proves that independent ranges are a prerequisite for the cooperative relationship formula, and neither can be omitted.

[0064] In addition, in Comparative Examples 6 and 7, b and c are components of the electrolyte and their mass fraction in the total electrolyte. Without any additives or lithium salts, the maximum value of b+c can only be 100. At this point, since b+c in Comparative Examples 6 and 7 is greater than 100, the electrolyte ratio is unbalanced, the battery cannot work, and the low-temperature performance is even worse. This proves that b+c must be less than 100.

[0065] The systematic analysis of Comparative Examples 1 to 7 clearly demonstrates that each technical feature defined in the claims of this invention possesses a distinct and irreplaceable technical function, and there is a profound intrinsic correlation and nonlinear synergistic mechanism among these features. The introduction of the positive electrode solid electrolyte constructs a three-dimensional ion-conducting network; fluoroethylene carbonate optimizes the quality of the negative electrode SEI film; and tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether improves the transport kinetics of the bulk electrolyte. These three elements belong to the three dimensions of the positive electrode interface, the negative electrode interface, and the bulk electrolyte, respectively, and none can be omitted. Based on this, the mass fraction ranges of a, b, and c correspond to the percolation threshold of the ion-conducting network, the effective concentration window of the film-forming additive, and the upper limit of compatibility of the fluorinated diluent, respectively. Exceeding any parameter's range will lead to the failure of the corresponding dimension's function. Furthermore, the product condition a*b*c^(0.6) and the ratio condition 0.1 defined in this invention...

[0066] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.​

Claims

1. A battery, characterized in that, The device includes a positive electrode, a negative electrode, and an electrolyte. The positive electrode includes a positive current collector and a positive active material layer disposed on the positive current collector. The positive active material layer contains a solid electrolyte. The electrolyte contains fluoroethylene carbonate and tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

2. The battery according to claim 1, characterized in that, The solid electrolyte includes one or more of lithium titanium aluminum phosphate, lithium lanthanum zirconium oxide, and lithium germanium phosphorus sulfur.

3. The battery according to claim 1, characterized in that, Based on the solid mass of the positive electrode active material layer, the mass fraction of the solid electrolyte is a, where a ranges from 1% to 5%.

4. The battery according to claim 3, characterized in that, Based on the mass of the electrolyte, the mass fraction of the fluoroethylene carbonate is b, wherein b ranges from 1% to 10%.

5. The battery according to claim 4, characterized in that, Based on the mass of the electrolyte, the mass fraction of the tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether is c, wherein c ranges from 1% to 35%.

6. The battery according to claim 5, characterized in that, The mass fraction a of the solid electrolyte, the mass fraction b of the fluoroethylene carbonate, and the mass fraction c of the tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether satisfy the following relationship: a*b*c^(0.6)≥ 10, 0.1 The positive electrode active material layer also contains ternary materials or lithium iron phosphate or lithium manganese oxide or lithium cobalt oxide.

7. The battery according to claim 1, characterized in that, The ternary material is Ni, Co, Mn or Ni, Co, Al.

8. The battery according to claim 7, characterized in that, The negative electrode sheet includes a negative current collector and a negative active material layer disposed on the negative current collector, wherein the negative active material layer contains graphite.

9. The battery according to claim 1, characterized in that, Includes the battery as described in any one of claims 1 to 9.

10. An energy storage device, characterized in that, ​

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