Lithium battery intrinsic safety system and lithium battery

Abstract

The invention relates to the technical field of lithium batteries, and discloses a lithium battery intrinsic safety system and a lithium battery, and the lithium battery intrinsic safety system comprises a first kind of thermosensitive microcapsule which is built in a battery positive electrode and has a critical fracture temperature of Tc1; the second type of thermosensitive microcapsules are arranged in the positive electrode of the battery, and the critical rupture temperature of the second type of thermosensitive microcapsules is Tc2; tc1lt; Tc1lt; tc2, and Tc2-Tc1 is greater than or equal to 10 DEG C; the first kind of thermosensitive microcapsules are configured to be broken when the temperature reaches Tc1, and release the first kind of functional fluid to execute a first kind of safety function; the second kind of thermosensitive microcapsules are configured to break when the temperature reaches Tc2, and release the second kind of functional fluid to execute a second kind of safety function; according to the lithium battery intrinsic safety system, the problem of interference among multiple safety mechanisms is fundamentally solved, and rapid, mild and fundamental blocking in a millisecond-level window in the early stage of thermal runaway is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and more specifically, to intrinsically safe lithium batteries and lithium batteries. Background Art

[0002] For high-energy-density lithium-ion batteries, especially those using high-nickel cathode materials (such as NCA, NCM811), under abusive conditions such as overcharging and overheating, the cathode material will be excessively de-lithiated, resulting in an increase in transition metal elements such as nickel to unstable high valence states (such as ), which is the root cause of inducing the release of lattice oxygen and leading to thermal runaway.

[0003] Currently, battery safety protection mainly relies on the active monitoring and cutting off of the external battery management system (BMS), as well as the structural reinforcement at the system level (such as the double-layer fortification protection and global constant-temperature thermal control architecture adopted by Honeycomb Energy) or fire protection measures (such as the fire extinguishing system verified by the open-door combustion test conducted by Hichen Energy Storage). However, these external systems have a response delay (usually at the second level), making it difficult to cope with the millisecond-level chain reaction in the initial stage of thermal runaway. Some studies have also tried to add chemical substances such as flame retardants to the electrolyte, but these additives often involve continuous side reactions, affecting battery performance, or generating heat and gas during the reaction, bringing secondary risks. Particularly crucial is that if multiple protection mechanisms are triggered disorderly at the same time, the rapidly formed physical high-resistance layer will seriously hinder the subsequent chemical lithium replenishment process, resulting in the failure of safety protection.

[0004] Therefore, there is an urgent need in this field for a built-in safety system that can coordinate the action timing of different mechanisms and achieve efficient and complete blocking in a very short time. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide an intrinsically safe system for lithium batteries and a lithium battery.

[0006] The present invention is implemented as follows. The intrinsically safe system for lithium batteries includes: The first type of thermosensitive microcapsules, which are内置 in the battery cathode and have a critical rupture temperature of Tc1; The second type of thermosensitive microcapsules, which are内置 in the battery cathode and have a critical rupture temperature of Tc2; Wherein, Tc1 < Tc2, and Tc2 - Tc1 ≥ 10°C; The first type of thermosensitive microcapsules are configured to rupture when the temperature reaches Tc1, releasing the first type of functional fluid to perform the first type of safety function; The second type of thermosensitive microcapsules are configured to rupture when the temperature reaches Tc2, releasing the second type of functional fluid to perform the second type of safety function.

[0007] Furthermore, the first type of safety function includes physical adsorption and double-layer reconstruction and / or redox-mediated valence state compensation; the second type of safety function is chemical lithium replenishment and ion intercalation.

[0008] Furthermore, the total molar number n_agent of the active lithium-supplementing component contained in the second type of functional fluid satisfies the following relationship: in, m_cathode is the total mass of the positive electrode active material in the battery; C_theoretical is the theoretical specific capacity of the positive electrode active material; ΔSOC is the change in target SOC before and after triggering, and ΔSOC ≥ 70%; F is the Faraday constant; η is the coulombic efficiency of the lithium replenishment reaction, ranging from 0.8 to 1.0.

[0009] Furthermore, Tc1 is 80°C to 110°C, and Tc2 is 100°C to 150°C.

[0010] Furthermore, the particle size of both the first type of thermosensitive microcapsule and the second type of thermosensitive microcapsule is 1 μm to 50 μm, the positive electrode of the battery has a positive electrode active material, and the particle size distribution of the first type of thermosensitive microcapsule and the second type of thermosensitive microcapsule matches the particle size distribution of the positive electrode active material.

[0011] Furthermore, the viscosity of both the first type of functional fluid and the second type of functional fluid at 25°C is between 1 mPa·s and 50 mPa·s, so that after the first type of thermosensitive microcapsule and the second type of thermosensitive microcapsule rupture, diffusion and interface coverage are completed within milliseconds.

[0012] Furthermore, the positive electrode of the battery has a positive electrode active material, and the mass percentage of the first type of thermosensitive microcapsule and the second type of thermosensitive microcapsule in the positive electrode active material is 0.5% to 10%.

[0013] The present invention also provides a lithium battery that integrates the aforementioned intrinsic safety system for lithium batteries.

[0014] Compared with existing technologies, the intrinsically safe lithium battery system provided by this invention arranges two types of microcapsules with different critical temperatures in the positive electrode of the battery. The two types of microcapsules contain different functional fluids. When the internal temperature of the lithium battery gradually increases, the first type of thermosensitive microcapsule and the second type of thermosensitive microcapsule rupture sequentially, releasing the first type of functional fluid and the second type of functional fluid. Through the rapid intervention of the first type of safety function, the obstacles to the deep repair of the second type of safety function are cleared, ensuring that the state of charge of the lithium battery can be completely reduced to below the safety threshold and achieving electrical self-locking. This fundamentally solves the problem of interference between multiple safety mechanisms and achieves rapid, gentle and fundamental blocking within a millisecond window in the early stage of thermal runaway. Attached Figure Description

[0015] Figure 1 This is a schematic diagram illustrating the working principle of the intrinsically safe lithium battery system provided by the present invention; Figure 2 This is a simplified structural diagram of the intrinsically safe lithium battery system provided by the present invention; Figure 3 This is a simplified structural diagram of the intrinsically safe lithium battery system provided by the present invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0017] The implementation of the present invention will be described in detail below with reference to specific embodiments.

[0018] In the accompanying drawings of this embodiment, the same or similar reference numerals correspond to the same or similar components. In the description of this invention, it should be understood that if terms such as "upper," "lower," "left," and "right" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting this invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0019] Reference Figure 1-3 The image shows a preferred embodiment of the present invention.

[0020] The intrinsic safety system for lithium batteries includes: The first type of thermosensitive microcapsule 200 is embedded in the positive electrode 100 of the battery, and its critical rupture temperature is Tc1. The second type of thermosensitive microcapsules 300 is内置 in the positive electrode 100 of the battery, and its critical rupture temperature is Tc2; Among them, Tc1 < Tc2, and Tc2 - Tc1 ≥ 10 °C; The first type of thermosensitive microcapsules 200 is configured to rupture when the temperature reaches Tc1, releasing the first type of functional fluid 201 to perform the first type of safety function; The second type of thermosensitive microcapsules 300 is configured to rupture when the temperature reaches Tc2, releasing the second type of functional fluid 301 to perform the second type of safety function.

[0021] In the lithium battery intrinsically safe system provided above, in the positive electrode 100 of the battery, two types of microcapsules with different critical temperatures are arranged, and two different types of microcapsules are equipped with different functional fluids. When the internal temperature of the lithium battery gradually increases, the first type of thermosensitive microcapsules 200 and the second type of thermosensitive microcapsules 300 rupture in sequence, releasing the first type of functional fluid 201 and the second type of functional fluid 301. Through the rapid intervention of the first type of safety function, the obstacles for the in-depth repair of the second type of safety function are cleared, so as to ensure that the state of charge of the lithium battery can be thoroughly reduced to below the safety threshold and electrical self-locking is achieved, fundamentally solving the interference problem between multiple safety mechanisms and achieving rapid, gentle and fundamental blocking within the millisecond-level window in the early stage of thermal runaway.

[0022] In this embodiment, the first type of safety function includes physical adsorption and double-layer reconstruction and / or redox-mediated valence compensation; the second type of safety function is chemical lithium supplementation and ion intercalation.

[0023] In this embodiment, the total number of moles n_agent of the active lithium-supplementing component contained in the second type of functional fluid 301 satisfies the following relationship: n_agent ≥ (m_cathode × C_theoretical × ΔSOC) / (F × η) Among them, m_cathode is the total mass of the positive electrode active material 101 in the battery; C_theoretical is the theoretical gram capacity of the positive electrode active material; ΔSOC is the change value of the target SOC before and after triggering, and ΔSOC ≥ 70%; F is the Faraday constant; η is the Coulomb efficiency of the lithium supplementation reaction, and its value range is 0.8 to 1.0.

[0024] In this embodiment, Tc1 is 80 °C to 110 °C, and Tc2 is 100 °C to 150 °C.

[0025] The first type of thermosensitive microcapsule 200 contains a first type of functional fluid 201, which is triggered when the temperature reaches Tc1. Through physical adsorption and double-layer reconstruction, or redox-mediated valence state compensation, it achieves rapid preliminary intervention and buffering of the state of charge of the lithium battery. Subsequently, when the temperature reaches Tc2, the second type of thermosensitive microcapsule 300 ruptures and releases the second type of functional fluid 301. Through chemical lithium replenishment and ion intercalation mechanisms, it achieves deep repair and electrical self-locking of the positive electrode active material 101.

[0026] Compared with existing technologies, the intrinsically safe lithium battery system in this embodiment has the following significant advantages: 1) Timing coordination to eliminate interference: Through the orderly interaction between mechanisms, it is ensured that the fast suppression mechanism will not hinder the slow repair mechanism; 2) Precise dosage and reliable safety: Calculations ensure sufficient lithium loading, avoiding protection failure due to insufficient dosage; 3) Rapid response and gentle process: Through fluid release and surface-dominated rapid interaction, the battery's responsiveness is fundamentally limited in a very short time, avoiding violent heat release or gas generation.

[0027] In this embodiment, the particle size of the first type of thermosensitive microcapsule 200 and the second type of thermosensitive microcapsule 300 are both 1 μm to 50 μm. The positive electrode 100 of the battery has a positive electrode active material 101. The particle size distribution of the first type of thermosensitive microcapsule 200 and the second type of thermosensitive microcapsule 300 matches the particle size distribution of the positive electrode active material 101 to ensure that the first type of thermosensitive microcapsule 200 and the second type of thermosensitive microcapsule 300 are uniformly dispersed during the coating process of the positive electrode active material 101.

[0028] In this embodiment, the viscosity of the first type of functional fluid 201 and the second type of functional fluid 301 at 25°C is both 1 mPa·s to 50 mPa·s, so that after the first type of thermosensitive microcapsule 200 and the second type of thermosensitive microcapsule 300 rupture, diffusion and interface coverage are completed within milliseconds.

[0029] In this embodiment, the positive electrode 100 of the battery has a positive electrode active material 101, and the mass percentage of the first type of thermosensitive microcapsule 200 and the second type of thermosensitive microcapsule 300 in the positive electrode active material 101 is 0.5% to 10%, and as a preferred embodiment, it can be 1% to 5%.

[0030] This embodiment also provides a lithium battery that integrates the aforementioned intrinsic safety system for lithium batteries.

[0031] The following are two specific implementation examples: Example 1: Implementation example of the first type of security function.

[0032] Using polystyrene (PS) as the wall material, a first-type thermosensitive microcapsule 200 with a critical rupture temperature Tc1 of 95±2℃ was prepared to encapsulate a first-type functional fluid 201 (e.g., 0.1...). The first type of thermosensitive microcapsules 200 were uniformly mixed into NCM811 positive electrode active material 101 at a mass ratio of 3 wt% (ethanol solution).

[0033] When the temperature reaches Tc1, the first type of thermosensitive microcapsule 200 ruptures, releasing the first type of functional fluid 201. It is oxidized on the surface of the positive electrode. At the same time, for the unstable It plays a restorative role, aiming to quickly consume the initial active species in the process, creating favorable interface conditions and time window for subsequent deep repair.

[0034] Example 2: Implementation and quantitative design of the second type of safety function.

[0035] Using polymethyl methacrylate (PMMA) as the wall material, a second type of thermosensitive microcapsule 300 with a critical rupture temperature Tc2 of 120±2℃ was prepared, which encapsulated a second type of functional fluid 301 (e.g., 1.5). In ionic liquids (The suspension in the solution).

[0036] Lithium replenishment calculation and system implementation: Taking a 3.5 Ah battery as an example, the mass m_cathode of its positive electrode active material 101 is approximately 17.5 g. To achieve ΔSOC ≥ 70% (i.e., reducing from fully charged to below 30%), the required active lithium replenishment components are calculated based on the aforementioned formula (using...). The total mass percentage of the second type of thermosensitive microcapsules 300 in the positive electrode active material 101 is designed to be no less than 0.101 mol. Based on this, the total mass percentage of the second type of thermosensitive microcapsules 300 in the positive electrode active material 101 is designed to be 6.7%.

[0037] When the temperature reaches Tc2, the second type of thermosensitive microcapsules 300 rupture, and it is expected that the active components in the fluid will, based on the dynamic interface established in the first stage, Irreversible oxidative decomposition occurs on the surface of the high-potential positive electrode: The generated The nitrogen is added to the cathode material through the ion intercalation mechanism, which reduces its average delithiation degree. At the same time, the release of nitrogen helps to dilute local oxygen and suppress side reactions.

[0038] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An intrinsically safe lithium battery system, characterized in that, include: The first type of thermosensitive microcapsule, which is embedded in the positive electrode of the battery, has a critical rupture temperature of Tc1. The second type of thermosensitive microcapsule is embedded in the positive electrode of the battery, and its critical rupture temperature is Tc2. Where Tc1 < Tc2, and Tc2 - Tc1 ≥ 10℃; The first type of thermosensitive microcapsule is configured to rupture when the temperature reaches Tc1, releasing a first type of functional fluid to perform a first type of safety function; The second type of thermosensitive microcapsule is configured to rupture when the temperature reaches Tc2, releasing the second type of functional fluid to perform the second type of safety function.

2. The intrinsically safe lithium battery system according to claim 1, characterized in that, The first type of safety function includes physical adsorption and double-layer reconstruction and / or redox-mediated valence state compensation; the second type of safety function is chemical lithium replenishment and ion intercalation.

3. The intrinsically safe lithium battery system according to claim 2, characterized in that, The total molar number n_agent of the active lithium-supplementing component contained in the second type of functional fluid satisfies the following relationship: in, m_cathode is the total mass of the positive electrode active material in the battery; C_theoretical is the theoretical specific capacity of the positive electrode active material; ΔSOC is the change in target SOC before and after triggering, and ΔSOC ≥ 70%; F is the Faraday constant; η is the coulombic efficiency of the lithium replenishment reaction, ranging from 0.8 to 1.

0.

4. The intrinsically safe lithium battery system according to claim 1, characterized in that, The Tc1 is 80°C to 110°C, and the Tc2 is 100°C to 150°C.

5. The intrinsically safe lithium battery system according to any one of claims 1 to 4, characterized in that, The particle size of both the first type and the second type of thermosensitive microcapsules is 1 μm to 50 μm, and the positive electrode of the battery has a positive electrode active material. The particle size distribution of the first type and the second type of thermosensitive microcapsules matches the particle size distribution of the positive electrode active material.

6. The intrinsically safe lithium battery system according to any one of claims 1 to 4, characterized in that, The viscosity of both the first type of functional fluid and the second type of functional fluid at 25°C is 1 mPa·s to 50 mPa·s, so that after the first type of thermosensitive microcapsule and the second type of thermosensitive microcapsule rupture, diffusion and interface coverage are completed within milliseconds.

7. The intrinsically safe lithium battery system according to claim 1, characterized in that, The positive electrode of the battery has a positive electrode active material, and the mass percentage of the first type of thermosensitive microcapsule and the second type of thermosensitive microcapsule in the positive electrode active material is 0.5% to 10%.

8. A lithium battery, characterized in that, It integrates the intrinsic safety system for lithium batteries as described in any one of claims 1 to 7.

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