Battery cell and method for producing the same, battery device, electric device, energy storage device

Abstract

The application provides a battery monomer, a preparation method thereof, a battery device, a power utilization device and an energy storage device. The application provides a battery monomer, a preparation method thereof, a battery device, a power utilization device and an energy storage device. 30 The application provides a battery monomer, a preparation method thereof, a battery device, a power utilization device and an energy storage device. 30 The application provides a battery monomer, a preparation method thereof, a battery device, a power utilization device and an energy storage device. 3 The application provides a battery monomer, a preparation method thereof, a battery device, a power utilization device and an energy storage device. 4 The application provides a battery monomer, a preparation method thereof, a battery device, a power utilization device and an energy storage device. 4 The application provides a battery monomer, a preparation method thereof, a battery device, a power utilization device and an energy storage device. 5 The application provides a battery monomer, a preparation method thereof, a battery device, a power utilization device and an energy storage device. 3 The application provides a battery monomer, a preparation method thereof, a battery device, a power utilization device and an energy storage device. 6 The application provides a battery monomer, a preparation method thereof, a battery device, a power utilization device and an energy storage device. 3 The application provides a battery monomer, a preparation method thereof, a battery device, a power utilization device and an energy storage device. 4 The application provides a battery monomer, a preparation method thereof, a battery device, a power utilization device and an energy storage device.

Description

Technical Field

[0001] This invention relates to the field of battery manufacturing technology, and more specifically, to a battery cell and its manufacturing method, a battery device, an electrical device, and an energy storage device. Background Technology

[0002] Lithium-ion batteries, as the mainstream electrochemical energy storage devices, have been widely used in consumer electronics, electric vehicles, and grid energy storage. As the energy density requirements of application scenarios continue to increase, cathode material systems are evolving from traditional lithium iron phosphate to high-nickel ternary and high-voltage spinel materials. However, under high-voltage conditions, the oxidation stability of the electrolyte at the cathode interface has become a key bottleneck restricting battery cycle life and safety performance.

[0003] While existing mainstream additives such as tris(trimethylsilyl)phosphite possess a P–O–Si framework and can partially remove HF and form inorganic CEI components, they rely solely on passive sacrificial oxidation and subsequent HF removal, and cannot actively terminate free radical chain reactions. Furthermore, their CEI lacks organic crosslinking components, resulting in a brittle structure that is prone to cracking during long-term cycling.

[0004] Existing technologies often employ the physical mixing of multiple additives to achieve synergistic effects. However, due to the asynchronous reaction timing and spatial distribution between molecules, it is difficult to form a uniform and dense composite CEI. Furthermore, the P–O–Si structure is sensitive to acidic substances such as PF5, exhibiting insufficient chemical stability, and its oxidation initiation potential is difficult to adjust, making it unsuitable for applications ranging from (LiFePO4)LFP (3.65 V) to (LiNi) 0.5 Mn 1.5 O4, LNMO)LNMO (4.7 V) is a wide voltage system; therefore, there is an urgent need for a new type of additive that can achieve free radical scavenging, preferential oxidation film formation and HF scavenging within a single molecule to improve the long-term stability of the cathode interface of high-voltage batteries. Summary of the Invention

[0005] The main objective of this invention is to provide a battery cell and its preparation method, battery device, power device, and energy storage device to solve the problems in the prior art where electrolyte additives in high-voltage lithium-ion batteries have limited functions, cannot actively terminate oxidation chain reactions, have loose CEI structures, poor stability of the P–O–Si framework, and lack intramolecular synergistic film formation mechanisms, resulting in severe gas generation, shortened cycle life, and poor voltage adaptability.

[0006] To achieve the above objectives, according to one aspect of the present invention, a battery cell is provided, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte comprises an additive, an organic solvent, and a lithium salt, and the additive is a compound having a general formula (I).

[0007] R_Ar-LN(R¹)-P(=X) m (Y¹)(Y²)

[0008] General Formula (I)

[0009] Where m is 0 or 1; R_Ar- is selected from substituted or unsubstituted C6~C 30 Aromatic amine groups, substituted or unsubstituted C3~C 30 It consists of any one or more nitrogen-containing heterocyclic groups; L is selected from single bonds, -(CH2) groups, etc. n -、C6~C 12 R¹ is selected from any one or more of the arylene groups, where n is any integer from 1 to 6; R¹ is selected from hydrogen atoms, C1-C6 straight-chain alkyl groups, C3-C6 branched alkyl groups, and -SiR. 2 Any one or more of 3, where R 2 It is a C1-C3 alkyl group; X is an oxygen atom or a sulfur atom; Y¹ and Y² are each independently selected from -NR. 3 -SiR 4 3. -O-SiR 4 3. -OR 5 -NR 3 R 6 Any one or more of Y¹ and Y², and at least one of Y¹ and Y² is -NR. 3 -SiR 4 3; where R 3 R is a hydrogen atom or a C1-C4 alkyl group; 4 It is a C1~C3 alkyl group; R 5 It is a C1~C6 alkyl group or a C6~C 10 aryl; R 6 It is a hydrogen atom, a C1-C6 alkyl group, or a C6-C6 alkyl group. 10 The aryl group; optionally, Y¹, Y² and P atoms can be cyclically synthesized into a 6-membered ring or an 8-membered ring.

[0010] Further, R_Ar- is selected from any one or more of substituted or unsubstituted carbazolyl, substituted or unsubstituted N,N-diarylamino, substituted or unsubstituted phenothiazinyl, and substituted or unsubstituted phenoxazinyl. When R_Ar- has a substituent, the substituent is selected from any one or more of halogen, C1-C6 alkyl, C1-C6 alkoxy, trifluoromethyl and cyano.

[0011] Furthermore, the substituent is selected from any one or more of methyl, methoxy, tert-butyl, fluorine atom, trifluoromethyl and cyano groups.

[0012] Furthermore, L is selected from any one or more of the following: direct bond, methylene, ethylene, propylene, and phenylene.

[0013] Furthermore, both Y¹ and Y² are -NR 3 -SiR 4 3.

[0014] Furthermore, R_Ar- is selected from any one or more of carbazole-9-yl, 3-tert-butylcarbazole-9-yl, N,N-diphenylamino, di(4-methylphenyl)amino and di(4-methoxyphenyl)amino.

[0015] Furthermore, R¹ is selected from any one or more of hydrogen atoms, methyl groups, and -Si(CH3)3.

[0016] Furthermore, Y¹ and Y² are each independently -N(CH3)-Si(CH3)3 or -NH-Si(CH3)3.

[0017] Furthermore, the additive is 9-carbazole-N,N′-bis(methyltrimethylsilylamino)phosphamide or diphenylamino-N,N′-bis(methyltrimethylsilylamino)phosphamide.

[0018] Furthermore, the molecular weight of the additive is 200~800 g / mol.

[0019] Furthermore, the amount of additive added to the electrolyte is 0.01~10 wt%.

[0020] According to another aspect of the present invention, a method for preparing the aforementioned battery cell is provided, comprising stacking or winding a positive electrode sheet, a separator, and a negative electrode sheet in sequence to form an electrode assembly; loading the electrode assembly into an aluminum-plastic film or a metal shell, injecting an electrolyte, and then encapsulating, standing, forming, and aging to obtain a battery cell; the electrolyte includes an additive, and the method for preparing the additive includes: performing a condensation reaction of a raw material comprising a nitrogen-containing aromatic amine compound, a phosphorus-containing chlorine compound, an acid-binding agent, and an anhydrous solvent to form an intermediate; performing a nucleophilic substitution reaction of the intermediate with a raw material comprising a silane-amine compound to obtain the additive; wherein the phosphorus-containing chlorine compound is selected from any one or more of PCl3, POCl3, and R_Ar-LN(R¹)-POCl2; the nitrogen-containing aromatic amine compound is R_Ar-H, wherein the definition of R_Ar- is the same as that defined above; the silane-amine compound is HN(R 3 (SiR) 4 3) and / or HN(SiR) 4 3)2, where R3 and R4 are defined in the same way as in the previous definition; R_Ar-, L and R¹ in R_Ar-LN(R¹)-POCl2 are defined in the same way as in the previous definition.

[0021] Further, the acid-binding agent is triethylamine or diisopropylethylamine; and / or, the anhydrous solvent is selected from any one or more of anhydrous tetrahydrofuran, anhydrous dichloromethane, and anhydrous toluene; and / or, the temperature of the condensation reaction is -20 to 60 °C, preferably 0 to 40 °C, and the time of the condensation reaction is 2 to 24 h; and / or, the temperature of the nucleophilic substitution reaction is 0 to 80 °C, preferably 20 to 60 °C.

[0022] According to another aspect of the present invention, a battery device is provided, the battery device comprising the aforementioned battery cell, and the battery device comprising one or more of the following: battery module, battery pack, and energy storage battery.

[0023] According to another aspect of the present invention, an electrical device is provided, which includes the aforementioned battery device for providing electrical energy.

[0024] According to another aspect of the present invention, an energy storage device is provided, the energy storage device including the aforementioned battery device, the battery device being used to store electrical energy.

[0025] Applying the technical solution of this application, the additive provided by this application has a structure in which an aromatic amine free radical scavenging group, a phosphoramide P=X (oxygen atom or sulfur atom) film-forming center, and a silicon-based HF scavenging center are covalently integrated into a single PN-Si molecular framework. That is, the three functional centers are connected to the same molecular framework by covalent bonds, and synergistically generate a micro-uniform CEI structure within the molecule. Moreover, it can simultaneously participate in the reaction, generate fragments, and deposit films during the oxidation and decomposition process at the positive electrode interface, thereby achieving atomic-scale mixing of phosphorus, silicon, and nitrogen-containing organic components in the CEI. Among them, the aromatic amine group serves as a free radical scavenging and preferential oxidation film-forming center, the phosphoramide P=X serves as an inorganic film-forming precursor center, and the silicon-based group serves as an HF scavenging center. Meanwhile, the aromatic amine groups preferentially undergo electrochemical oxidation in the high-potential range of the positive electrode compared to the host solvent, and their oxidation products participate in the construction of the CEI organic phase. Simultaneously, they capture free radical intermediates generated during the electrolyte oxidation and decomposition process, terminating the chain degradation reaction. Furthermore, the oxidation initiation potential of the aromatic amine groups can be controlled by the electron-donating / electron-pulling effects of substituents, achieving adaptability adjustment of the same framework structure to different operating voltage systems, thus improving the applicability of the battery system. During the oxidation and decomposition of the PN bonds in the PN-Si framework at the positive electrode interface, nitrogen-containing inorganic or organic-inorganic hybrid components such as phosphorus nitrogen compounds and phosphate ammonium salts can be generated. These nitrogen-containing inorganic components can improve the CEI's resistance to Li... + The conductivity selectivity is improved and the adhesion between CEI and the positive electrode surface is enhanced, thereby improving the structural stability of CEI in long-term cycling and solving the problems of severe gas generation, shortened cycle life and poor voltage adaptability of high-voltage lithium-ion batteries. Attached Figure Description

[0026] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0027] Figure 1 A process flow diagram for preparing an additive according to the present invention is shown. Detailed Implementation

[0028] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0029] As analyzed in the background section of this application, in the prior art, electrolyte additives in high-voltage lithium-ion batteries have a single function, cannot actively terminate the oxidation chain reaction, have a loose CEI structure, poor stability of the P–O–Si framework, and lack an intramolecular synergistic film formation mechanism, resulting in serious gas generation, shortened cycle life, and poor voltage adaptability. In order to solve this problem, this application provides a battery cell and its preparation method, a battery device, an electrical device, and an energy storage device.

[0030] In a typical embodiment of this application, a battery cell is provided, including a positive electrode, a negative electrode, a separator, and an electrolyte. The electrolyte includes an additive, an organic solvent, and a lithium salt. The additive is a compound having the general formula (I).

[0031] R_Ar-LN(R¹)-P(=X) m (Y¹)(Y²)

[0032] General Formula (I)

[0033] Where m is 0 or 1; R_Ar- is selected from substituted or unsubstituted C6~C 30 Aromatic amine groups, substituted or unsubstituted C3~C 30 It consists of any one or more nitrogen-containing heterocyclic groups; L is selected from single bonds, -(CH2) groups, etc. n -、C6~C 12 R¹ is selected from any one or more of the arylene groups, where n is any integer from 1 to 6; R¹ is selected from hydrogen atoms, C1-C6 straight-chain alkyl groups, C3-C6 branched alkyl groups, and -SiR. 2 Any one or more of 3, where R 2 It is a C1-C3 alkyl group; X is an oxygen atom or a sulfur atom; Y¹ and Y² are each independently selected from -NR. 3 -SiR 4 3. -O-SiR 4 3. -OR 5 -NR 3 R6 Any one or more of Y¹ and Y², and at least one of Y¹ and Y² is -NR. 3 -SiR 4 3; where R 3 R is a hydrogen atom or a C1-C4 alkyl group; 4 It is a C1~C3 alkyl group; R 5 It is a C1~C6 alkyl group or a C6~C 10 aryl; R 6 It is a hydrogen atom, a C1-C6 alkyl group, or a C6-C6 alkyl group. 10 The aryl group; optionally, Y¹, Y² and P atoms can be cyclically synthesized into a 6-membered ring or an 8-membered ring.

[0034] The additive provided in this application has a structure in which an aromatic amine free radical scavenging group, a phosphoramide P=X (oxygen or sulfur atom) film-forming center, and a silicon-based HF scavenging center are covalently integrated into a single PN-Si molecular framework. That is, the three functional centers are connected to the same molecular framework by covalent bonds, and synergistically generate a micro-uniform CEI structure within the molecule. Moreover, it can participate in the reaction, generate fragments, and deposit films simultaneously during the oxidation and decomposition process at the positive electrode interface, thereby achieving atomic-scale mixing of phosphorus, silicon, and nitrogen-containing organic components in the CEI. Among them, the aromatic amine group serves as a free radical scavenging and preferential oxidation film-forming center, the phosphoramide P=X serves as an inorganic film-forming precursor center, and the silicon-based group serves as an HF scavenging center. Meanwhile, the aromatic amine groups preferentially undergo electrochemical oxidation in the high-potential range of the positive electrode compared to the host solvent, and their oxidation products participate in the construction of the CEI organic phase. Simultaneously, they capture free radical intermediates generated during the electrolyte oxidation and decomposition process, terminating the chain degradation reaction. Furthermore, the oxidation initiation potential of the aromatic amine groups can be controlled by the electron-donating / electron-pulling effects of substituents, achieving adaptability adjustment of the same framework structure to different operating voltage systems, thus improving the applicability of the battery system. During the oxidation and decomposition of the PN bonds in the PN-Si framework at the positive electrode interface, nitrogen-containing inorganic or organic-inorganic hybrid components such as phosphorus nitrogen compounds and phosphate ammonium salts can be generated. These nitrogen-containing inorganic components can improve the CEI's resistance to Li... + The conductivity selectivity is improved and the adhesion between CEI and the positive electrode surface is enhanced, thereby improving the structural stability of CEI in long-term cycling and solving the problems of severe gas generation, shortened cycle life and poor voltage adaptability of high-voltage lithium-ion batteries.

[0035] Specifically, when Y¹ and / or Y² are -NR 3 -SiR 4 At 3, these groups provide silicon-containing active sites through PN-Si linkage, when Y¹ and / or Y² are -O-SiR 4 At 3, these groups provide silicon-containing active sites through PO-Si linkage; at least one of Y¹ and Y² is -NR. 3-SiR 4 3. That is, the molecular structure of the additives in this application will at least form a PN-Si backbone. The introduction of the PN bond in general formula (I) is the core structural feature that distinguishes the compounds of this invention from existing PO-Si additives (TMSPi family) and disclosed PS-Si variants. The PN bond, compared to the PO bond and PS bond, has different structural and functional significance in the following aspects:

[0036] In terms of interfacial decomposition chemistry, the PN bond can generate nitrogen-containing inorganic or organic-inorganic hybrid components such as phosphorus-nitrogen compounds (PNO-based and PN-based) and ammonium phosphates during the oxidative decomposition process at the cathode interface. These nitrogen-containing components are unique CEI components that cannot be provided by PO bond decomposition products (pure phosphates and lithium phosphates) or PS bond decomposition products (sulfur-containing phosphates). Furthermore, nitrogen-containing inorganic components can improve the CEI's resistance to Li. + This improves the conductivity selectivity and enhances the adhesion between the CEI and the positive electrode surface, thereby improving the structural stability of the CEI during long-term cycling.

[0037] In terms of chemical stability, PN bonds are less sensitive to Lewis acidic species (such as PF5) than PO bonds. This is because the pd conjugation effect between the lone pair electrons of the nitrogen atom and the phosphorus center enhances the bond energy of the PN bond, reducing its susceptibility to attack by electrophilic reagents. Therefore, PN-Si framework compounds exhibit better chemical stability than PO-Si framework compounds in LiPF6-containing electrolytes, which helps to prolong the effective operating time of additives in the electrolyte.

[0038] The choice of the R_Ar group determines the E_ox and free radical scavenging efficiency. Introducing electron-donating groups to the R_Ar group reduces E_ox and enhances reducing power, while introducing electron-withdrawing groups increases E_ox and enhances oxidation stability. This correspondence allows researchers to selectively choose appropriate combinations of R_Ar groups and substituents based on the operating voltage window of the target battery system.

[0039] The oxidation state of the P-center determines the balance between chemical stability and film-forming activity. P(V) centers (phosphoramide type) have high chemical stability and long shelf life, but relatively mild reactivity at the interface, making them suitable as long-lasting protective additives. P(III) centers (phosphoramide type) have higher reactivity and can quickly participate in the initial construction of CEI during the first charge cycle, but have lower chemical stability, making them more suitable for scenarios with high initial film formation rate requirements.

[0040] X represents the double-bonded heteroatom in the phosphorus center. When X is an oxygen atom, the compound is a phosphoramide; when X is a sulfur atom, the compound is a thiophosphoramide. Preferably, X is an oxygen atom because the P=O group tends to generate more chemically stable inorganic CEI components such as phosphates and lithium phosphates after interfacial decomposition.

[0041] The type of silicon-based groups in Y¹ / Y² determines the HF scavenging efficiency and silicate tendency. -NR 3 -SiR 4 The reactivity of the N-Si bond in 3 with HF differs from that of the O-Si bond in -O-SiR³3. The differences in reaction rate and product distribution between the two provide additional design freedom for fine-tuning of CEI. The steric hindrance of substituents on the Si atom also affects the reaction rate of HF scavenging—smaller substituents (such as trimethylsilyl-SiMe3) have higher reactivity, while larger substituents (such as triethylsilyl-SiEt3 or tert-butyldimethylsilyl-SiMe2tBu) have lower reactivity but better selectivity.

[0042] The length and rigidity of the connecting arm L affect the effectiveness of intramolecular coordination. A shorter L results in greater spatial proximity between the R_Ar group, the P center, and the Si end group, increasing the probability of fragment co-deposition during interfacial decomposition and improving the microscopic uniformity of the CEI composition. However, an excessively short L may lead to spatial crowding between the large-volume conjugated R_Ar system and the P center, affecting the molecule's geometry and chemical stability. Therefore, the optimal choice for L is a direct bond or a short-chain alkylene group, achieving a balance between spatial proximity and geometric compatibility.

[0043] The functional mechanism by which the above additives exert their protective effect in lithium-ion batteries involves three synergistic mechanisms.

[0044] Mechanism of preferential oxidation film formation at the positive electrode interface (main mechanism):

[0045] During battery charging, when the positive electrode potential rises to near the oxidation initiation potential E_ox of the additive, the aromatic amine groups in the additive preferentially undergo electrochemical oxidation on the positive electrode surface compared to the main carbonate solvent. The aromatic amine groups lose an electron to form a cationic free radical, which exhibits high stability due to the electron delocalization effect of the aromatic ring conjugated system. Simultaneously, the PN bonds and Si-N bonds in the molecule break in the interfacial oxidation environment, generating phosphorus- and nitrogen-containing fragments at the phosphoramide center and silicon-containing fragments at the silicon-based end groups. These three types of fragments—aromatic amine oxidation products (organic crosslinking components), phosphorus- and nitrogen compounds (inorganic phase components), and silicate / silicon-fluorine compounds (inorganic phase components)—are co-deposited in situ on the positive electrode surface, forming a multi-component composite CEI layer containing phosphorus, silicon, nitrogen, and an organic crosslinking matrix. Since the three types of fragments originate from the same molecule, their generation at the interface is spatially and temporally synchronous—the same molecule simultaneously generates all three types of fragments at the same reaction site and deposits them in situ. This microscopic synchronicity ensures uniform mixing of the CEI components at the atomic scale, rather than macroscopic phase separation. In contrast, if three independent additive molecules are used to provide the above three functions respectively, the generation of the three fragments will be asynchronous in time and space due to the adsorption competition, diffusion rate differences, and reaction potential differences of different molecules at the positive electrode interface. The resulting CEI component distribution will inevitably be less uniform than that of the single-molecule scheme. This structural advantage of "intramolecular synergy," which distinguishes it from "intermolecular mixing," is the core value of the technical solution of this invention.

[0046] Free radical chain termination mechanism (auxiliary mechanism):

[0047] During the oxidative decomposition of the electrolyte, the homolytic cleavage of the CH bonds or the breaking of the CO bonds in the carbonate solvent generates reactive intermediates such as alkyl radicals (R·), alkoxy radicals (RO·), and peroxy radicals (ROO·). These radical intermediates initiate chain reactions, leading to continuous electrolyte consumption and gas production. The aromatic amine groups in the additives can terminate the chain reaction through the following mechanisms: the lone pair electrons on the nitrogen atom of the aromatic amine group donate electrons to the reactive radicals (single-electron transfer mechanism), or the aromatic amine group couples with carbon radicals, converting the reactive radicals into stable non-radical products. The stabilizing effect of the cationic free radicals formed after the oxidation of aromatic amines on the tricyclic or polycyclic conjugated system makes it less likely to initiate new side reaction chains. Instead, they tend to deposit at the interface through dimerization or oligomerization, becoming part of the CEI organic phase. This free radical chain termination mechanism and the preferential oxidation film formation mechanism are functionally complementary: the film formation mechanism reduces the direct contact area between the electrolyte and the cathode surface from the perspective of "physical blocking," thus lowering the probability of subsequent oxidative decomposition; the free radical scavenging mechanism terminates the chain reaction that has already occurred from the perspective of "chemical elimination," reducing the propagation and diffusion of generated free radicals. The synergy of the two upgrades cathode interface protection from a single "passive isolation" to a two-layer strategy of "active chemical defense + passive physical barrier."

[0048] HF removal and fluoride management mechanisms:

[0049] The silicon-based groups (-SiR3) in the additive are removed through nucleophilic substitution reactions with HF and PF5 generated from the thermal decomposition of LiPF6 in the electrolyte. Si-N or Si-O bonds react with HF to form Si-F bonds, releasing the corresponding amines or alcohols. The removal of HF reduces the acidity of the electrolyte, mitigating the corrosion of the cathode active material's lattice surface by HF—a significant factor leading to the dissolution of transition metals (Mn, Co, Ni, etc.) from the cathode lattice. Simultaneously, the Si-F reaction products and LiF deposit at the cathode interface, further enriching the inorganic phase component of the CEI and enhancing its compactness and chemical inertness.

[0050] The above additives form a complete functional closed loop across the three parameters of electrochemical activity, interfacial film formation, and performance protection:

[0051] The first parameter is the oxidation initiation potential E_ox. When the electrolyte containing the above additives is tested by linear sweep voltammetry (LSV) on an inert working electrode, a new oxidation peak or current shoulder appears compared to the reference electrolyte without additives. The potential E_ox corresponding to this new characteristic is in the range of 3.8~5.5 V (vs. Li / Li). +Within the range of 4.0 to 5.0 V, more preferably 4.2 to 4.7 V. This parameter confirms that the compound has electrochemical activity that preferentially reacts within the target potential window—the presence of E_ox is a prerequisite for the compound to react "preferentially to the solvent" at the positive electrode interface.

[0052] The second parameter is the compositional characteristics of the coexistence of P and Si in the CEI. After predetermined cycles or high-temperature storage using an electrolyte containing the aforementioned additives, X-ray photoelectron spectroscopy (XPS) analysis of the CEI layer on the cathode surface should simultaneously detect phosphorus-containing components (P 2p characteristic binding energy range) and silicon-containing components (Si 2p characteristic binding energy range), with both atomic percentages showing a statistically significant increase compared to the control group containing only the basic electrolyte. This parameter confirms that "P-Si synergistic film formation" actually occurs at the cathode interface, meaning that phosphorus centers and silicon centers do indeed participate simultaneously in the construction of the CEI, rather than being solely contributed by one element.

[0053] The third parameter is the electrochemical performance improvement index. Under accelerated aging conditions (high-temperature storage and / or high-voltage cycling), batteries containing the above additives show a significant improvement in at least one of the following indicators compared to the control group without additives: improved capacity retention, reduced gas production, reduced AC impedance growth rate, and reduced transition metal dissolution in the cathode material. This parameter links the achievement of the first two parameters (E_ox and CEI composition) to the final engineering performance effect, ensuring that the electrochemical activity and film-forming behavior of the compound truly translate into effective protection of battery performance.

[0054] The technical logic of the three-parameter synergistic constraint is as follows: If E_ox is within the target window but P and Si do not coexist in the CEI—for example, although the compound can be oxidized, the decomposition fragments fail to effectively deposit as CEI components (possibly due to solubility, diffusion, or decomposition pathway issues)—this is not an effective technical solution. Similarly, if P-Si coexist in the CEI but the electrochemical performance is not improved—for example, although film formation occurs, the CEI quality is poor (possibly due to excessive film thickness or inappropriate component ratio leading to excessive impedance)—this is also not an effective technical solution.

[0055] In summary, the structural differences between the compound of this invention and existing phosphorus-silicon additives are reflected in three aspects. First, the bonding type differs: the TMSPi family has a PO-Si backbone, the disclosed thiolated variant has a PS-Si backbone, while this invention has a PN-Si backbone. These three differ in interfacial decomposition chemistry, CEI composition, and chemical stability, with the PN-Si backbone imparting nitrogen-containing components to the CEI. Second, the functional groups differ: existing P-Si additives do not contain specially designed free radical scavenging functional groups, while this invention covalently links aromatic amine groups to the P-Si backbone, forming a "triple functional center" molecular structure. Third, the functional modes differ: existing P-Si additives primarily rely on passive protection through "HF scavenging + sacrificial oxidation," while this invention adds two active protection functions: "active free radical capture" and "preferential oxidation for directional film formation."

[0056] In one embodiment of this application, R_Ar- is selected from any one or more of substituted or unsubstituted carbazole group, substituted or unsubstituted N,N-diarylamino group, substituted or unsubstituted phenothiazinyl group, and substituted or unsubstituted phenotoxazinyl group. When R_Ar- has a substituent, the substituent is selected from any one or more of halogen, C1-C6 alkyl group, C1-C6 alkoxy group, trifluoromethyl group, and cyano group.

[0057] The conjugated system of the R-Ar group can stabilize the cationic radical intermediate generated after single-electron oxidation through electron delocalization, thereby endowing the group with radical scavenging function and preferential oxidation film formation function at the cathode interface. The preferred aromatic amine groups are more conducive to stabilizing the oxidation intermediate, efficiently terminating the radical chain reaction, and simultaneously controlling the oxidation potential to adapt to the high voltage system of 4.3~4.7 V, thus enhancing the active interfacial protection.

[0058] When R_Ar is a carbazole group, it is preferred to connect it to the L group through its 9-nitrogen atom or 3-carbon atom;

[0059] When R_Ar is N,N-diarylamino, it includes diphenylamino, di(4-methylphenyl)amino, di(4-methoxyphenyl)amino, etc.

[0060] When R_Ar is a phenothiazine group, it is linked to the L group through its nitrogen atom at the 10-position;

[0061] When R_Ar is a phenoxazine group, it is linked to the L group through its nitrogen atom at the 10-position;

[0062] Furthermore, R_Ar is preferably carbazolyl or N,N-diphenylamino, and more preferably R_Ar is unsubstituted carbazo-9-yl or 3-tert-butylcarbazo-9-yl.

[0063] Furthermore, in one embodiment of this application, the substituent is selected from any one or more of methyl, methoxy, tert-butyl, fluorine, trifluoromethyl, and cyano groups.

[0064] In one embodiment of this application, L is selected from any one or more of direct bond, methylene, ethylene, propylene, and phenylene.

[0065] L is a short-chain linker used to connect the R-Ar group and the nitrogen atom of the phosphoramide center. The length of L affects the spatial distance between the R-Ar group and the P center; the shorter the L, the higher the spatial proximity of the three functional centers during interfacial decomposition, and the higher the efficiency of fragment co-deposition. Preferring the above-mentioned types of L helps to further shorten the distance between functional centers, improve intramolecular synergistic efficiency, promote the atomic-scale co-deposition of P, Si, and N components, and improve CEI uniformity. Further preferred L is a direct bond or a methylene group.

[0066] In one embodiment of this application, both Y¹ and Y² are -NR. 3 -SiR 4 3.

[0067] Both Y¹ and Y² are -NR 3 -SiR 4 3. It can promote the connection of all silicon groups through P–N–Si. At this time, all P-Si connections in the molecule are bridged by nitrogen atoms (PN-Si bond type). Together with the PN bond of R_Ar-L- connected to the P center, it forms a complete PN-Si framework system with nitrogen as the bridging atom, thereby enhancing the HF removal efficiency, generating highly stable silicon nitride oxide, and thus improving the compactness and chemical durability of CEI.

[0068] In one embodiment of this application, R_Ar- is selected from any one or more of carbazole-9-yl, 3-tert-butylcarbazole-9-yl, N,N-diphenylamino, di(4-methylphenyl)amino and di(4-methoxyphenyl)amino.

[0069] Choosing R_Ar- as the above groups allows for better matching with cathodes such as NCM811, thus enabling compounds of general formula (I) to possess both strong free radical scavenging ability and good solubility, achieving a better balance between performance and stability.

[0070] R¹ is a substituent attached to the nitrogen atom at the center of the phosphoramide. In one embodiment of this application, R¹ is selected from any one or more of hydrogen atom, methyl group and -Si(CH3)3.

[0071] The preferred R¹ helps reduce steric hindrance, enhances the reactivity of the P-center, and maintains molecular structural stability, promoting the efficient participation of the additive in interfacial reactions in the electrolyte without easily causing side decomposition reactions. When R¹ is trialkylsilyl, the additional Si group on the nitrogen atom can provide additional HF scavenging active sites.

[0072] Furthermore, in one embodiment of this application, Y¹ and Y² are each independently -N(CH3)-Si(CH3)3 or -NH-Si(CH3)3.

[0073] In one embodiment of this application, the additive is 9-carbazole-N,N′-bis(methyltrimethylsilylamino)phosphamide or diphenylamino-N,N′-bis(methyltrimethylsilylamino)phosphamide.

[0074] In general formula (I), R_Ar is carbazole-9-yl, L is a direct bond, X is O (oxygen atom), and Y¹ and Y² are both -N(CH3)-Si(CH3)3. The compound is then 9-carbazole-N,N′-bis(methyltrimethylsilylamino)phosphoramide. Its molecular structure simultaneously possesses: the radical scavenging function and tunable oxidation potential provided by the carbazole tricyclic conjugated system; the inorganic film-forming precursor function provided by the phosphoramide P=O skeleton; and the HF scavenging and silicate formation functions provided by the two -N(CH3)-Si(CH3)3 end groups. The oxidation initiation potential of the carbazole group can be regulated by the substituents on the ring—the E_ox of unsubstituted carbazole is approximately 3.9~4.4 V (vs. Li / Li). + The range of E_ox is such that introducing electron-donating groups such as tert-butyl can slightly decrease E_ox, while introducing electron-withdrawing groups such as fluorine atoms can increase E_ox.

[0075] In general formula (I), when R_Ar is N,N-diphenylamino, L is a direct bond, X is O, and Y¹ and Y² are both -N(CH3)-Si(CH3)3, the compound is diphenylamino-N,N′-bis(trimethylsilylamino)phosphoramide. The oxidation initiation potential of diphenylamino is typically between 4.0 and 4.5 V (vs. Li / Li). + Within the range, it is compatible with the working voltage window of high-nickel ternary systems.

[0076] In another preferred embodiment, R_Ar is phenothiazine-10-yl or phenotoxazine-10-yl. The sulfur atom in phenothiazine or the oxygen atom in phenotoxazine provides additional electronic effects, making its oxidation initiation potential and radical stabilization ability different from carbazole and diphenylamine. The E_ox of phenothiazine groups is generally low (about 3.5~4.0 V), making them suitable for battery systems with higher reactivity requirements or relatively low operating voltages.

[0077] In one embodiment, X is absent in general formula (I), meaning the phosphorus center is trivalent (P(III)), and the compound has a phosphoramidite structure R_Ar-LN(R¹)-P(Y¹)(Y²). The trivalent phosphorus at the P(III) center has high reducing power and can undergo P(III)→P(V) oxidation conversion at the cathode interface, providing additional sacrificial oxidation consumption function. P(III) has higher reactivity than P(V) and may participate more rapidly in the initial construction of CEI during the first charge cycle. However, the P(III) center is more sensitive to moisture and Lewis acids, and its chemical stability is lower than that of P(V), requiring more stringent anhydrous requirements for electrolyte preparation and storage environments. Therefore, P(III) is suitable for applications with higher requirements for initial film formation rate.

[0078] In another embodiment, phosphorus and silicon atoms in the compound molecule are bridged by two or more nitrogen atoms to form a heterocyclic structure containing PN-Si bonds, such as a six-membered or eight-membered phosphosilicate derivative. Aromatic amine radical scavenging groups are introduced as external substituents on the heterocycle. Cyclic structures offer higher molecular rigidity and more controllable interfacial decomposition modes, but their synthetic complexity is higher than that of open-chain structures.

[0079] The molecular weight of the additive should not be too high to ensure sufficient dissolution in the electrolyte and effective diffusion to the positive electrode interface, nor should it be too low to guarantee the integrity and chemical stability of the three functional centers in the molecule. The selection of the additive's molecular weight needs to balance high solubility and structural stability. In one embodiment of this application, the molecular weight of the additive is 200-800 g / mol, preferably 300-600 g / mol, and more preferably 350-500 g / mol. This is beneficial for improving the efficiency of the additive's diffusion to the positive electrode interface and reducing the risk of increased viscosity and uneven film formation caused by excessively high molecular weight.

[0080] The design of the additive dosage needs to balance the effects of interface protection and electrolyte bulk performance: too low a dosage may result in insufficient accumulation of the synergistic components of the three functional centers in the CEI, failing to form an effective composite protective layer; too high a dosage may cause an increase in electrolyte viscosity and initial interfacial impedance, leading to excessive consumption of the additive during the first charge cycle. In one embodiment of this application, the dosage of the additive in the electrolyte is 0.01~10wt%, preferably 0.1~5wt%, more preferably 0.5~3wt%, thereby achieving significant coexistence of P / Si / N in the CEI, achieving a better balance between the protective effect of the additive and the bulk performance of the battery cell, and thus maximizing the performance improvement of the battery cell.

[0081] In some embodiments of this application, the oxidation initiation potential E_ox of the additive, measured by linear sweep voltammetry (LSV) on an inert working electrode (platinum electrode or glassy carbon electrode), is 3.8~5.5 V (vs. Li / Li). + The preferred voltage for E_ox is 4.0–5.0 V, more preferably 4.2–4.7 V. Setting a lower limit for E_ox ensures that the compound is not significantly consumed within the normal operating voltage range of the battery—for a high-nickel ternary system with a charging cutoff voltage of 4.3 V, E_ox should be at least about 0.1 V higher than the upper limit of the operating potential. Setting an upper limit for E_ox ensures that the compound's oxidation activity is higher than the oxidation initiation potential of the host carbonate solvent, allowing it to preferentially undergo oxidation film formation at the cathode interface compared to the solvent. E_ox can be systematically regulated by the electronic effects of substituents on the R_Ar group: electron-donating substituents (such as methyl, methoxy, tert-butyl) can decrease E_ox, while electron-withdrawing substituents (such as fluorine, trifluoromethyl, cyano) can increase E_ox. This degree of freedom in regulation allows compounds of the same skeleton type to be adapted to battery systems with different operating voltages through substituent design. It should be noted that the above E_ox is an index of the inherent electrochemical properties of the compound measured on an inert electrode; on the surface of the actual battery cathode, catalytic effects and surface chemical environment may cause the effective reaction potential to shift, that is, the E_ox value is used as a reference index for compound screening and molecular design.

[0082] Furthermore, the additive of the present invention is applicable to various lithium-ion battery systems, and the compatible positive electrode material systems, negative electrode material systems, separator material systems, and basic electrolyte systems are as follows:

[0083] Cathode material system:

[0084] The positive electrode active material is selected from layered oxides, polyanionic compounds, and spinel structure materials. Layered oxides include lithium cobalt oxide (LiCoO2), ternary materials (NCM111, NCM523, NCM622, NCM811, etc.), lithium nickel cobalt aluminum oxide (NCA), high-nickel materials (Ni content ≥ 80 mol%), and cobalt-free layered materials. Polyanionic compounds include lithium iron phosphate (LiFePO4), lithium manganese phosphate (LiMnPO4), and lithium vanadium phosphate (Li3V2(PO4)3). Spinel structure materials include lithium manganese oxide (LiMn2O4) and high-voltage spinel (LiNiO2). 0.5 Mn 1.5The positive electrode formulation contains 85-98 wt% active material, 1-10 wt% conductive agent selected from Super P, Ketjen black, carbon nanotubes (CNT), graphene, etc., and 2-8 wt% binder selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), etc. The positive electrode current collector is made of aluminum foil or carbon-coated aluminum foil.

[0085] Anode material system:

[0086] The negative electrode active material is selected from carbon-based materials, silicon-based materials, and lithium metal, among others. Carbon-based materials include artificial graphite, natural graphite, soft carbon, and hard carbon. Silicon-based materials include silicon-carbon composites (Si / C) and silicon suboxide composites (SiO₂). x The anode formulation contains 80-97 wt% active material and 1-5 wt% conductive agent. The binder is selected based on the anode type: graphite anodes commonly use a sodium carboxymethyl cellulose / styrene-butadiene rubber (CMC / SBR) composite system, while silicon-based anodes commonly use high-adhesion binders such as polyacrylic acid (PAA) and polyimide (PI). The anode current collector uses copper foil or carbon-coated copper foil.

[0087] Diaphragm material system:

[0088] The separator is selected from polyolefin separators, ceramic-coated separators, and high-performance polymer separators. Polyolefin separators include polypropylene (PP) single-layer separators, polyethylene (PE) single-layer separators, and PP / PE / PP three-layer composite separators. Ceramic-coated separators use a polyolefin separator as the substrate, coated with ceramic particle layers such as Al2O3, SiO2, TiO2, and boehmite (AlOOH) on one or both sides. High-performance polymer separators are selected from polyimide (PI), polyetheretherketone (PEEK), etc. The electrolyte described in this invention can be used in conjunction with any of the above-mentioned types of separators.

[0089] Basic electrolyte system:

[0090] The organic solvent system of the basic electrolyte is selected from a mixture of carbonate solvents. The organic solvent is selected from two or more of ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), and propylene carbonate (PC). Typical solvent combinations include EC / DMC, EC / DEC, EC / EMC, EC / DMC / DEC, EC / DMC / EMC, etc. The conductive lithium salt is selected from one or more of lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium tetrafluoroborate (LiBF4), with a concentration of 0.5~2.0 mol / L, preferably 0.8~1.5 mol / L, more preferably 1.0~1.2 mol / L, with LiPF6 as the main component. In addition to the additives shown in general formula (I), the basic electrolyte contains one or more synergistic additives selected from the following: fluoroethylene carbonate (FEC), vinylene carbonate (VC), 1,3-propanesulfonate lactone (PS), vinyl sulfate (DTD), lithium difluorooxalate borate (LiDFOB), etc. These synergistic additives mainly function as preferential reduction film-forming agents on the negative electrode side, forming a division of labor and protection at the positive and negative electrode interfaces with the functions of the additives of this invention on the positive electrode side. The total content of the synergistic additives is 0~5 wt%, preferably 0.5~3 wt%. The basic electrolyte is prepared in a dry environment with a dew point below -40 °C, and the moisture content is controlled below 20 ppm. The suitable electrolyte system is mainly a carbonate-based liquid electrolyte.

[0091] In one embodiment of this application, the electrolyte comprises a basic electrolyte component and the aforementioned additives. The basic electrolyte component provides the ion conduction function required for the normal operation of the lithium-ion battery, while the additives provide positive electrode interface protection.

[0092] This invention is particularly suitable for applications with a charging cutoff voltage of not less than 4.3 V (vs. Li / Li). + This invention relates to high-voltage lithium-ion battery systems. In high-voltage systems, the oxidative stress at the cathode interface is more severe, the free radical intermediates generated by electrolyte oxidation and decomposition are more abundant, and the continuous degradation of CEI is more prominent. The synergistic advantages of the additive's three functions—free radical scavenging, synergistic film formation, and HF management—are most significant in this scenario. By regulating the substituents of the R-Ar group to control E-ox, the same backbone type can be adapted to cathode systems with different voltage windows from 4.3 V (high-nickel ternary) to 4.7 V (LNMO).

[0093] The solubility of the additive compound in a standard carbonate electrolyte at 25 °C (1.0 mol / L LiPF6 / ethylene carbonate: methyl ethyl carbonate = 3:7, volume ratio) is not less than 0.5 wt%, preferably not less than 2 wt%, and more preferably not less than 5 wt%. Sufficient solubility is a prerequisite for the additive compound to be uniformly dispersed in the electrolyte and to effectively reach the positive electrode interface through diffusion.

[0094] After being stored in the standard electrolyte at 60 °C for 14 days, the additive compound retains a molecular integrity of not less than 80%, preferably not less than 90%, as determined by liquid chromatography or nuclear magnetic resonance spectroscopy. This chemical stability requirement ensures that the compound does not undergo significant degradation during normal storage in the electrolyte and during the electrolyte injection process.

[0095] In another typical embodiment of this application, a method for preparing the aforementioned battery cell is provided, comprising stacking or winding a positive electrode sheet, a separator, and a negative electrode sheet in sequence to form an electrode assembly; loading the electrode assembly into an aluminum-plastic film or a metal shell, injecting an electrolyte, and then encapsulating, standing, forming, and aging to obtain a battery cell; the electrolyte includes an additive, and the method for preparing the additive includes: performing a condensation reaction on raw materials including a nitrogen-containing aromatic amine compound, a phosphorus-containing chlorine compound, an acid-binding agent, and an anhydrous solvent to form an intermediate; performing a nucleophilic substitution reaction on raw materials including the intermediate and a silicon amine compound to obtain the additive; wherein the phosphorus-containing chlorine compound is selected from any one or more of PCl3, POCl3, and R_Ar-LN(R¹)-POCl2; the nitrogen-containing aromatic amine compound is R_Ar-H, wherein the definition of R_Ar- is the same as that defined above; the silicon amine compound is HN(R 3 (SiR) 4 3) and / or HN(SiR) 4 3)2, where R3 and R4 are defined in the same way as in the previous definition; R_Ar-, L and R¹ in R_Ar-LN(R¹)-POCl2 are defined in the same way as in the previous definition.

[0096] The above preparation method significantly improves the cycle stability and safety performance of batteries by introducing a specially formulated electrolyte additive with a phosphorus-nitrogen-silicon structure. This additive forms a dense and stable SEI / CEI film at the electrode interface, effectively inhibiting electrolyte decomposition and lithium dendrite growth, reducing internal resistance, and enhancing high-temperature storage performance. At the same time, the silicon groups in the additive's molecular structure enhance interfacial wettability, and phosphorus and nitrogen synergistically passivate active sites, reducing gas generation and side reactions.

[0097] Furthermore, in some preferred embodiments of this application, the nitrogen-containing aromatic amine compound R_Ar-H is selected from any one or more of carbazole, 3-tert-butylcarbazole, 3-fluorocarbazole, N,N-diphenylamine, di(4-methylphenyl)amine, di(4-methoxyphenyl)amine, phenothiazine, and phenothiazine; the silane-containing amine compound HN(R3)(SiR 43 ) and / or HN(SiR 43 )2 is selected from any one or more of N-methyltrimethylsilylamine, bis(trimethylsilyl)amine, N-ethyltrimethylsilylamine, and N-methyltriethylsilylamine.

[0098] In one embodiment of this application, the acid-binding agent is triethylamine or diisopropylethylamine; and / or, the anhydrous solvent is selected from any one or more of anhydrous tetrahydrofuran, anhydrous dichloromethane, and anhydrous toluene; and / or, the temperature of the condensation reaction is -20 to 60 °C, preferably 0 to 40 °C, and the time of the condensation reaction is 2 to 24 hours; and / or, the temperature of the nucleophilic substitution reaction is 0 to 80 °C, preferably 20 to 60 °C.

[0099] The preferred acid-binding agent and anhydrous solvent system can effectively suppress side reactions and improve the high selectivity of condensation reaction and nucleophilic substitution reaction; mild temperature control helps to promote the efficient generation of intermediates and the precise grafting of silicon-based functional groups, significantly improving the purity and yield of additives. The resulting electrolyte additives have a uniform structure and excellent interfacial film-forming performance, which greatly improves the cycle stability and safety performance of the battery.

[0100] Furthermore, the synthesis of phosphoramide silane compounds is the core process of this invention. Based on the structural characteristics of general formula (I), the overall strategy of the synthesis process is as follows: first, construct the phosphoramide PN skeleton, then introduce Si groups through a silanization reaction, and finally connect or pre-introduce aromatic amine groups into the initial substrate. The following describes the synthetic route using preferred compounds (carbazole-substituted P(V)-N-Si type compounds) as representatives.

[0101] The first step in the synthetic route is the construction of the phosphoramide skeleton. Starting with phosphoryl chloride (POCl3) or dichlorophosphate (in the form of R_Ar-LN(R¹)-POCl2), a condensation reaction is carried out with an amine containing an aromatic amine group (such as 9-aminocarbazole or the nitrogen anion of carbazole under basic conditions) to form a PN bond. The reaction is carried out under anhydrous conditions, with solvents selected from anhydrous tetrahydrofuran (THF), anhydrous dichloromethane (DCM), or anhydrous toluene. The reaction temperature is -20 to 60 °C, preferably 0 to 40 °C. An organic base such as triethylamine (Et3N) or diisopropylethylamine (DIPEA) is used as an acid-binding agent to capture the HCl released during the reaction. The reaction time is 2 to 24 hours, and the reaction progress is monitored by thin-layer chromatography (TLC) or high-performance liquid chromatography (HPLC).

[0102] The second step involves the introduction of silanine groups. The residual P-Cl bonds in the product from the first step undergo a nucleophilic substitution reaction with silanine-containing compounds (such as N-methyltrimethylsilylamine (an N-methyl analog of HMDS), trimethylsilylamine, etc.) to form PN-Si linkages. The reaction is carried out under anhydrous conditions at a temperature of 0–80 °C, preferably 20–60 °C. Optionally, no additional base may be added (the reaction is driven by the basicity of the reactants themselves), or an organic base may be added as an assisted agent. After the reaction is complete, salt byproducts are removed by filtration, and the target compound is obtained by vacuum distillation or column chromatography purification.

[0103] For the P(III) version of the compound, phosphorus trichloride (PCl3) is used instead of phosphoryl chloride (POCl3) as the starting material. Subsequent operations are similar but must be carried out under strict anaerobic and anhydrous conditions to prevent non-target oxidation of the P(III) center.

[0104] For variants containing cyclic P-Si heterocyclic structures, they can be constructed via cyclization condensation reactions of phosphorosilicon precursors. For example, a linear precursor containing PN and Si-N bonds can be intramolecularly cyclized in the presence of a catalyst to form the target heterocyclic framework, and then aromatic amine groups can be introduced through post-functionalization.

[0105] Product purification and quality control: The crude product is purified by vacuum distillation, recrystallization, or preparative column chromatography. The purity of the target compound is required to be no less than 95%, preferably no less than 98% (determined by HPLC area normalization). Structural confirmation is performed by 1H NMR, 1P NMR, and 1H NMR (¹¹P NMR). 29 The analysis was performed using a combination of Si NMR and high-resolution mass spectrometry (HRMS). The moisture content was controlled to be below 50 ppm by Karl Fischer titration.

[0106] Preparation process of electrolyte containing additives:

[0107] Electrolytes containing phosphoramide silane additives are prepared in a dry environment with a dew point below -40 °C. First, a base electrolyte is prepared using standard procedures, ensuring that the content of each component and the moisture content meet quality standards. Then, the purified phosphoramide silane compound is added to the base electrolyte at the designed dosage and completely dissolved using magnetic stirring or low-speed mechanical stirring. For compounds with low solubility, they can be first dissolved in a small amount of co-solvent (such as EC or DMC) to prepare a concentrated stock solution, which is then diluted into the base electrolyte. Stirring is carried out at room temperature for 0.5–4 hours. The prepared electrolyte is then filtered through a 0.22-micron filter membrane to remove any possible insoluble particles.

[0108] The prepared electrolyte should be sealed and stored in a dry, inert atmosphere at a temperature controlled between 15 and 30 °C. Under recommended storage conditions, the effective shelf life of the electrolyte containing additives should be no less than 6 months, preferably no less than 12 months. During storage, the chemical stability of the additives can be monitored by periodically sampling and performing HPLC analysis.

[0109] Industrialization considerations for the synthesis process:

[0110] The core reactions involved in the synthesis of the compounds of this invention—phosphamide and silanization—are both mature and fundamental reaction types in organic synthetic chemistry, with numerous precedents for industrial application in fields such as pharmaceuticals, agrochemicals, and functional materials. The raw materials used (phosphoryl chloride, silane-containing compounds, carbazole, and other aromatic amine compounds) are all commercially available industrial chemicals, and their prices are within the acceptable cost range for electrolyte additives. The synthesis process does not require precious metal catalysts or extreme reaction conditions and is well-suited to existing fine chemical production equipment. These factors provide a feasible basis for scaling up the preparation of the compounds of this invention from laboratory to industrial production.

[0111] In another typical embodiment of this application, a battery device is provided, which includes the aforementioned battery cell, and the battery device includes one or more of the following: battery module, battery pack, and energy storage battery.

[0112] The aforementioned additives have significant protective properties on the positive electrode interface of high-voltage lithium-ion batteries, and are particularly suitable for battery devices including the aforementioned battery cells.

[0113] In yet another typical embodiment of this application, an electrical device is provided, which includes the aforementioned battery device for providing electrical energy.

[0114] Electrical devices including the above-mentioned battery devices have the advantages of long cycle life and good voltage adaptability.

[0115] In yet another typical embodiment of this application, an energy storage device is provided, which includes the aforementioned battery device for storing electrical energy.

[0116] Energy storage devices, including the above-mentioned battery devices, have advantages such as long cycle life.

[0117] Furthermore, the additive prepared in this application not only significantly improves the electrochemical performance of lithium-ion batteries under high-rate and low-temperature environments, but is also suitable for the needs of long-term energy storage systems. This additive helps improve the battery's cycle stability, high-temperature storage stability, and reduce gas production, making it suitable for energy storage applications requiring long lifespan and low gas production, and meeting the stringent requirements of high-capacity batteries for applications such as grid peak shaving and smooth output of renewable energy.

[0118] The beneficial effects of this application will be explained below with reference to specific embodiments and comparative examples.

[0119] Example 1

[0120] Reference Figure 1 The additive preparation process flow diagram shown is used for the following preparation:

[0121] 9-Carbazolyl-N,N'-bis(methyltrimethylsilylamino)phosphamide: Step 1: Phosphate chloride and carbazole are condensed in anhydrous tetrahydrofuran under alkaline conditions (triethylamine in excess by 3 equivalents to capture HCl generated during the reaction, maintaining the reaction system as weakly alkaline) to form a phosphoramide intermediate. The condensation reaction temperature is 20 °C, and the reaction time is 6 hours. Triethylamine is used as an acid-binding agent. Step 2: The intermediate is reacted with N-methyltrimethylsilylamine in a nucleophilic substitution reaction at 50 °C for 8 hours. The product is then purified by vacuum distillation to obtain the target product. The structure is obtained through... 1 H NMR, 31 P NMR, 29 Confirmed by combined Si NMR and HRMS. Among them: 1 ¹H NMR (CDCl₃, 400 MHz) δ 8.10 (d, J=7.8 Hz, 2H, carbazole-H1 / H8), 7.42 (t, J=7.6 Hz, 2H, carbazole-H3 / H6), 7.32 (d, J=8.0 Hz, 2H, carbazole-H4 / H5), 7.27 (t, J=7.4 Hz, 2H, carbazole-H2 / H7), 2.78 (d, J_PH=8.4 Hz, 6H, PN-CH₃), 0.12 (s, 18H, Si(CH₃)₃); 31 P NMR (CDCl3, 162 MHz) δ 17.8; 29 Si NMR (CDCl3, 79 MHz) δ 4.8; HRMS (ESI + Theoretical value of m / z [M+H] + =418.1900, measured value 418.1903, which is consistent with the target molecule C 20 H 32 N3OPSi2 is consistent. Purity is not less than 98% (HPLC area normalization method). Before use, dry in a vacuum drying oven at 60 ℃ for 12 hours to ensure that the moisture content is less than 50 ppm.

[0122] The R_Ar group is 9-carbazole-N,N′-bis(methyltrimethylsilylamino)phosphamide, with an addition amount of 1.0 wt%.

[0123] Y¹=Y²=-N(CH3)-Si(CH3)3; the positive electrode system is NCM811 / graphite, and the charging cut-off voltage is 4.3 V;

[0124] LSV measured E_ox = 4.15 V (meeting the 4.0-5.0 V effective window); XPS showed that P = 2.5 at%, Si = 1.8 at%, and N = 0.9 at% in CEI, with all three elements present; after 500 cycles at 25°C, the capacity retention rate was 87.2%; after 30 days of storage at 60°C, the capacity retention rate was 91.2% and the recovery rate was 95.5%, with a gas production of only 0.8 mL.

[0125] Example 2

[0126] The difference between Example 2 and Example 1 is that the amount of 9-carbazole-N,N′-bis(methyltrimethylsilylamino)phosphamide added is 0.5 wt%.

[0127] Example 3

[0128] The difference between Example 3 and Example 1 is that the amount of 9-carbazole-N,N′-bis(methyltrimethylsilylamino)phosphamide added is 3 wt%.

[0129] Example 4

[0130] The synthetic route for the additive is similar to that in Example 1, using diphenylamine instead of carbazole as the aromatic amine raw material, with all other synthetic conditions remaining unchanged, and a purity of not less than 98%. The structure is obtained through... 1 H NMR, 31 P NMR, 29 Confirmed by combined Si NMR and HRMS. Among them: 1 1H NMR (CDCl3, 400 MHz) showed that the aromatic ring hydrogens of diphenylamine exhibited a 10H multiplet in the δ 6.95-7.35 range, and the chemical shifts of the N-CH3 and Si(CH3)3 signals were similar to those in Example 1. 31 P NMR (CDCl3, 162 MHz) δ 16.5; HRMS (ESI + )m / z [M+H] + Theoretical value 420.2056, measured value 420.2058, consistent with target molecule C 20 H 34 N3OPSi2 is consistent.

[0131] Example 5

[0132] The synthetic route for the additive is similar to that in Example 1, using 3-tert-butylcarbazole instead of carbazole as the aromatic amine raw material, with all other synthetic conditions remaining unchanged, and a purity of not less than 98%. The structure is obtained through... 1H NMR, 31 P NMR, 29 Confirmed by combined Si NMR and HRMS. Among them: 1 H NMR (CDCl3, 400 MHz) detected a characteristic singlet of tert-butyl at δ 1.42 (s, 9H), and a characteristic multiplet of 3-substituted carbazole appeared in the δ 7.20-8.10 range of the carbazole ring hydrogen. 31 P NMR (CDCl3, 162 MHz) δ 17.9; HRMS (ESI + ) m / z [M+H] + Theoretical value 474.2526, measured value 474.2529, consistent with target molecule C 24 H 40 N3OPSi2 is consistent.

[0133] Example 6

[0134] The synthetic route for the additive is similar to that in Example 1, using 3-fluorocarbazole-9-yl as the R-Ar group, with all other synthetic conditions remaining unchanged, and the purity not less than 98%. The structure is obtained through... 1 H NMR, 19 F NMR, 31 P NMR, 29 Confirmed by combined Si NMR and HRMS. Among them: 1 ¹H NMR (CDCl₃, 400 MHz) showed a slight shift in the chemical shift of the carbazole ring due to fluorine substitution (δ 7.20–8.15). 31 PNMR (CDCl3, 162 MHz) δ 17.6; 19 F NMR (CDCl3, 376 MHz) δ -121.5; HRMS (ESI + ) m / z[M+H] + Theoretical value 436.1806, measured value 436.1808, consistent with target molecule C 20 H 31 The FN3OPSi2 is consistent. The R_Ar group is a fluorinated carbazole compound (E_ox = 4.65 V), the positive electrode system is LNMO / graphite, and the charging cutoff voltage is 4.7 V;

[0135] The retention rate was 82.2% after 500 cycles, 87.8% after storage at 60°C, and the gas production was 1.2 mL, demonstrating that the electron-withdrawing group can be adapted to the high-voltage spinel system.

[0136] Example 7

[0137] The synthetic route for the additive is similar to that in Example 1, except that phenothiazine is used instead of carbazole as the R-Ar group, and the other synthetic conditions remain unchanged, with a purity of not less than 98%. The structure is obtained through... 1 H NMR, 31 P NMR, 29 Confirmed by combined Si NMR and HRMS. Among them: 1 ¹H NMR (CDCl₃, 400 MHz) showed multiple 8H peaks in the phenthiazide ring hydrogen in the δ 6.80–7.10 range; 31 P NMR (CDCl3,162 MHz) δ 18.2; HRMS (ESI + ) m / z [M+H] + The theoretical value is 450.1620, the measured value is 450.1622, and the value is consistent with the target molecule C. 20 H 32 The N3OPSSi2 is consistent. The R_Ar group is a phenothiazine compound (E_ox = 3.85 V), which matches the LFP cathode (3.65 V); the cathode system is LFP / graphite, and the charging cut-off voltage is 3.65 V;

[0138] The retention rate was 96.5% after 500 cycles at 25°C and 97.5% after storage at 60°C, with a gas production of only 0.15 mL and an initial efficiency of 95.8%, proving that the same skeleton can be adapted to low-voltage systems through the R_Ar group.

[0139] Example 8

[0140] The difference between Example 8 and Example 1 is that the amount of 9-carbazole-N,N′-bis(methyltrimethylsilylamino)phosphamide added is 0.1 wt%. After 200 cycles at 25°C, the capacity retention rate was 85.5%, and after 500 cycles, it was 76.8%. After 30 days of storage at 60°C, the capacity retention rate was 84.5%, and the recovery rate was 91.2%. The gas production was 2.0 mL. The CEI contained P=0.6 at%, Si=0.4 at%, and N=0.2 at%. The results indicate that a P / Si coexisting CEI can still be formed at a low addition amount of 0.1 wt%, but due to the limited accumulation of the synergistic components of the three functional centers, the long-term protective efficacy is weaker than the preferred range of 0.5~3 wt%.

[0141] Example 9

[0142] The difference between Example 9 and Example 1 is that the amount of 9-carbazole-N,N′-bis(methyltrimethylsilylamino)phosphamide added is 5 wt%. After 200 cycles at 25°C, the capacity retention rate is 88.5%, and after 500 cycles, it is 79.8%. After 30 days of storage at 60°C, the capacity retention rate is 87.5%, and the recovery rate is 92.5%. The gas production is 1.5 mL. The CEI contains P=6.5 at%, Si=5.2 at%, and N=2.5 at%. The coulombic efficiency in the first cycle is 81.5%. The results indicate that at a 5 wt% addition, the CEI is too thick, leading to an increased initial impedance, and the initial efficiency and the retention rates after 200 / 500 cycles are slightly lower than the 1 wt% baseline.

[0143] Example 10

[0144] The difference between Example 10 and Example 1 is that the amount of 9-carbazole-N,N′-bis(methyltrimethylsilylamino)phosphamide added is 0.01 wt%. After 200 cycles at 25°C, the capacity retention rate is 80.5%, and after 500 cycles, it is 68.5%. After storage at 60°C for 30 days, the capacity retention rate is 81.2%, and the recovery rate is 87.5%. The gas production is 2.8 mL. The P and Si contents in the CEI are only slightly detectable, and N is undetectable. The results indicate that 0.01 wt% is the lower boundary for the functionalization of the additive of this invention. At excessively low addition amounts, the synergistic components of the three functional centers are difficult to form a continuous phase in the CEI, and the interface protection effect is close to that of the blank control.

[0145] Example 11

[0146] The difference between Example 11 and Example 1 is that the amount of 9-carbazole-N,N′-bis(methyltrimethylsilylamino)phosphamide added is 10 wt%. After 200 cycles at 25°C, the capacity retention rate is 82.5%, and after 500 cycles, it is 72.5%. After 30 days of storage at 60°C, the capacity retention rate is 84.5%, and the recovery rate is 90.2%. The gas production is 1.8 mL. In the CEI, P = 8.5 at%, Si = 6.8 at%, and N = 3.2 at%. The first-cycle coulombic efficiency is 76.5%. The results indicate that 10 wt% is the upper limit of the additive of this invention. Excessive film formation in the CEI leads to a significant decrease in initial efficiency and an increase in interfacial impedance, resulting in long-term cycling performance inferior to the 1 wt% baseline. Examples 8 to 11 together with Examples 1 to 3 constitute a gradient series with an addition amount of 0.01 to 10 wt%, verifying that the additive of the present invention can form a protective layer of P / Si coexistence in CEI in this wide range, with 0.5 to 3 wt% as the optimal range.

[0147] The selection of each substituent in general formula (I) of Examples 1 to 11 and Comparative Examples 1 to 7 is shown in Table 1.

[0148] Table 1

[0149]

[0150] Comparative Example 1

[0151] The difference between Comparative Example 1 and Example 1 is that no R-Ar group was added.

[0152] CEI shows no P / Si / N signal; the retention rate is only 64.2% after 500 cycles at 25°C, and the storage retention rate is 79.8% at 60°C, with a gas production rate as high as 3.6 mL.

[0153] Comparative Example 2

[0154] The difference between Comparative Example 2 and Example 1 is that the R_Ar group uses a conventional TMSPi (P–O–Si framework) with an addition amount of 1.0 wt%; and the Y¹ / Y² type is a PO-Si framework.

[0155] XPS detected P / Si but no N; retention rate of 75.8% at 25°C / 500 cycles, gas production of 2.2 mL.

[0156] Comparative Example 3

[0157] The difference between Comparative Example 3 and Example 1 is that the R-Ar group is a physical mixture of TMSPi (0.5 wt%) and 9-ethylcarbazole (0.5 wt%).

[0158] XPS showed N to be only 0.3 at%, far lower than 0.9 at% in Example 1; the retention rate at 25°C / 500 cycles was 78.5%, and the gas production was 1.8 mL.

[0159] Comparative Example 4

[0160] The difference between Comparative Example 4 and Example 1 is that the R_Ar group is a n-butyl group (a non-aromatic amine group) prepared by a condensation reaction. The preparation conditions are the same as the first step of Example 1, and the purity is not less than 98%. The structure is obtained through... 1 H NMR, 31 P NMR, 29 Confirmed by combined Si NMR and HRMS. Among them: 1 ¹H NMR (CDCl₃, 400 MHz) showed characteristic multiplets of n-butyl (δ 0.92, t, 3H; 1.32, m, 2H; 1.50, m, 2H; 2.95, m, 2H), with no detectable aromatic ring hydrogen signal; 31 P NMR (CDCl3, 162 MHz) δ 14.2; HRMS (ESI + ) m / z [M+H] +Theoretical value 324.2056, measured value 324.2058, consistent with target molecule C 12 H 34 N3OPSi2 is consistent.

[0161] LSV showed no new oxidation peaks, and the organic phase was absent in CEI; the gas production reached 2.5 mL, and the capacity retention rate decreased significantly.

[0162] Comparative Example 5

[0163] The difference between Comparative Example 5 and Example 1 is that Y¹=Y²=-O-Si(CH3)3 (P–O–Si structure) is used, and trimethylsilanol is used instead of the silane-containing compound in Example 1 for the second step of the reaction, with a purity of not less than 98%. The structure is obtained through... 1 H NMR, 31 P NMR, 29 Confirmed by combined Si NMR and HRMS. Among them: 1 The H NMR (CDCl3, 400 MHz) signal of carbazole ring hydrogen is basically the same as that in Example 1, but the signal in the -N(CH3)- region disappears and is replaced by a single peak of -OSi(CH3)3 (δ 0.18, s, 18H). 31 P NMR (CDCl3, 162 MHz) δ -8.5 (significantly shifted to higher fields compared to Example 1, reflecting the difference in PO-Si chemical environment); HRMS (ESI) + ) m / z [M+H] + Theoretical value 392.1262, measured value 392.1264, compared with the target molecule C 18 H 26 NO3PSi2 is consistent.

[0164] The N signal almost disappeared in XPS (0.2 at%), and the storage retention rate at 60°C was 86.5%, which is lower than the 91.2% in Example 1.

[0165] Comparative Example 6

[0166] The difference between Comparative Example 6 and Example 1 is that the compound in Comparative Example 6 is an aromatic amine-type phosphoramide silane compound containing strongly electron-donating substituents. Multiple methoxy or dimethylamino groups, etc., are attached to its R_Ar group, reducing the oxidation initiation potential E_ox to below 3.8 V. This was used in Comparative Example 6 to verify the lower boundary failure of E_ox. The skeletal structure is the same as compound A, only the R_Ar substituents are different. The purity is not less than 98%.

[0167] The R_Ar group is an aromatic amine compound with a strong electron-donating substituent (E_ox = 3.55 V). Its first-efficiency is only 80.5%, the CEI is too thick, and the cycle decay is aggravated. This verifies that E_ox below 3.8 V leads to excessive consumption.

[0168] Comparative Example 7

[0169] The difference between Comparative Example 7 and Example 1 is that the compound in Comparative Example 7 is an aromatic amine-type phosphoramide silane compound containing strongly electron-withdrawing substituents. Multiple fluorine atoms, trifluoromethyl groups, or cyano groups are attached to its R_Ar group, raising the oxidation initiation potential E_ox to above 5.0 V. This was used in Comparative Example 7 to verify the failure of the upper boundary of E_ox. The skeletal structure is the same as compound A, only the R_Ar substituents are different. The purity is not less than 98%.

[0170] The R_Ar group is an aromatic amine compound with a strong electron-withdrawing substituent (E_ox = 5.55 V). It cannot be oxidized at 4.3 V, and the CEI has almost no P / Si / N contribution, with performance close to blank. This verifies that E_ox above 5.0 V is invalid.

[0171] Additives in Comparative Examples 2 and 3:

[0172] Tris(trimethylsilyl)phosphite (TMSPi), with a purity of not less than 99%, was used in Comparative Examples 2 and 3. 9-Ethylcarbazole, with a purity of not less than 98%, was used as an independent aromatic amine radical scavenger physically mixed with TMSPi in Comparative Example 3.

[0173] Basic electrolyte components:

[0174] Ethylene carbonate (EC), battery grade, moisture content less than 20 ppm. Ethyl methyl carbonate (EMC), battery grade, moisture content less than 20 ppm. Lithium hexafluorophosphate (LiPF6), battery grade, purity not less than 99.9%. The basic electrolyte is prepared by dissolving 1.0 mol / L LiPF6 in a mixed solvent of EC / EMC = 3 / 7 (v / v), and the preparation is completed in a glove box with a dew point below -40 °C.

[0175] Electrode and membrane materials:

[0176] NCM811 cathode material (LiNi) 0.8 Co 0.1 Mn 0.1 O2), used for the core verification group and parameter window group. High-voltage spinel cathode material LNMO (LiNi). 0.5 Mn 1.5O4), used in application extension example 6. Lithium iron phosphate cathode material LFP (LiFePO4 / C), carbon-coated type, used in application extension example 7. Artificial graphite anode material. Conductive agent Super P and carbon nanotubes (CNT). Cathode binder PVDF, anode binder CMC / SBR composite system. Cathode current collector is 12 μm thick aluminum foil, anode current collector is 8 μm thick copper foil. The separator is a 16 μm thick PP / PE / PP three-layer composite separator.

[0177] All the chemical reagents mentioned above are analytical grade or battery-grade materials, available commercially, and require necessary purification before use. All operations involving water- and oxygen-sensitive materials were performed in an argon-atmospheric glove box, where the water and oxygen content was controlled below 0.1 ppm.

[0178] Preparation of electrolytes containing additives:

[0179] Electrolytes containing phosphoramide silane additives were prepared in a glove box with a dew point below -40 °C. First, a base electrolyte was prepared according to the above formula, ensuring that the content of each component and the moisture content met the quality standards. Then, the purified additive compound was added to the base electrolyte at the amount specified in the experimental design (0.5–3.0 wt%), and dissolved completely at room temperature using magnetic stirring for 2 hours. The prepared electrolyte was then filtered through a 0.22 μm filter membrane to remove any possible insoluble particles and stored in a sealed glove box for later use.

[0180] For the physical mixing scheme of Comparative Example 3, TMSPi and 9-ethylcarbazole were weighed and added to the basic electrolyte in sequence, each accounting for 0.5 wt%, with a total addition of 1.0 wt%. The stirring conditions were the same as in the example.

[0181] Battery fabrication:

[0182] The core verification group and parameter window group (Examples 1 to 5, 8 to 11, and Comparative Examples 1 to 7) used a 3 Ah NCM811 / graphite stacked pouch cell as the test platform. The positive electrode used NCM811 material with 95 wt% active material, 2 wt% Super P conductive agent, 0.5 wt% carbon nanotubes, and 2.5 wt% PVDF binder, coated on a 12 μm thick aluminum foil current collector. The negative electrode used artificial graphite material with 96 wt% active material, 1 wt% Super P conductive agent, and 3 wt% CMC / SBR composite binder, coated on an 8 μm thick copper foil current collector. The separator was a 16 μm thick PP / PE / PP three-layer composite separator.

[0183] Example 6 of the application extension group uses an LNMO / graphite system, with the positive electrode active material replaced by LNMO. The active material content is 92 wt%, the conductive agent Super P content is 4 wt%, and the binder PVDF content is 4 wt%, with other conditions remaining the same. Example 7 of the application extension group uses an LFP / graphite system, with the positive electrode active material replaced by carbon-coated lithium iron phosphate. The active material content is 93 wt%, the conductive agent Super P content is 4 wt%, and the binder PVDF content is 3 wt%, with other conditions remaining the same.

[0184] Battery assembly employs a standard stacking process, where the positive electrode, separator, and negative electrode are stacked sequentially and encapsulated in an aluminum-plastic film. The assembled batteries are then dried in a vacuum oven at 80°C for 24 hours to ensure the internal moisture content is below 50 ppm. Electrolyte injection is performed in a glove box, using electrolyte prepared according to the experimental design; the injection volume is determined based on the battery capacity. After encapsulation, the batteries are allowed to stand at 25°C for 12 hours to allow for thorough electrolyte saturation before proceeding to the formation and testing phases.

[0185] Performance testing methods:

[0186] All battery performance tests were conducted using the aforementioned standard battery platform. Three parallel samples were prepared for each example and comparative example. All data were taken as the average of the test results of the three parallel samples, with a typical error range of ±3% to ±8%.

[0187] 1) Oxidation initiation potential E_ox test

[0188] The oxidation initiation potentials of each additive compound on the inert working electrode were determined using linear sweep voltammetry (LSV) at 25 °C. A three-electrode cell was assembled, with a platinum disk electrode (2 mm in diameter) as the working electrode, and lithium metal sheets as both the reference and counter electrodes. The electrolytes were electrolytes containing the respective additives and a reference electrolyte without additives, respectively. The open-circuit voltage (OCV) was scanned forward at a rate of 0.5 mV / s from 6.0 V (vs. Li / Li + Record the potential value corresponding to the newly appearing oxidation current peak or current shoulder peak in the electrolyte containing additives compared to the reference electrolyte; this is the oxidation onset potential E_ox of the compound. If no new characteristic peak different from the reference electrolyte is detected within the scanning range, it is marked with a horizontal line; if only a weak shoulder peak is observed and the independent oxidation potential cannot be clearly determined, it is marked as a weak shoulder peak. This parameter is used to verify whether the compound is within the target potential window (3.8 to 5.5 V vs. Li / Li). + It exhibits electrochemical oxidation activity that is preferential over the main carbonate solvent.

[0189] 2) CEI elemental composition analysis

[0190] After cycling the battery 50 times according to the standard charge-discharge regime, the positive electrode was removed in a glove box and cleaned three times with dimethyl carbonate (DMC) to remove residual electrolyte and lithium salt. It was then vacuum-dried in a glove box for 12 hours. X-ray photoelectron spectroscopy (XPS) was used to analyze the elemental composition of the CEI layer on the positive electrode surface. The detection regions included three characteristic binding energy ranges: P 2p (binding energy 128–138 eV), Si 2p (binding energy 98–108 eV), and N 1s (binding energy 394–404 eV). The surface atomic percentage (at%) of each element was recorded, with undetected elements labeled as nd. P and Si were detected simultaneously and showed a statistically significant increase compared to the control group without additives, serving as the criterion for meeting the second parameter of this invention, "the compositional characteristic of P and Si coexisting in the CEI." The detection of the N 1s signal was used as an enhancement term to further distinguish the compositional differences between the PN-Si and PO-Si routes forming the CEI.

[0191] 3) First-lap coulomb efficiency test

[0192] The first cycle of formation serves as the test point for the first-cycle coulombic efficiency. At 25 °C, the batteries, after being filled and allowed to stand, were subjected to their first charge-discharge cycle at a rate of 0.1C. The charging cutoff voltage for the NCM811 / graphite system was 4.3 V, maintained at a constant voltage until 0.01C cutoff, and the discharging cutoff voltage was 2.8 V. The charging cutoff voltage for the LNMO / graphite system was 4.7 V, and the discharging cutoff voltage was 3.5 V. The charging cutoff voltage for the LFP / graphite system was 3.65 V, and the discharging cutoff voltage was 2.5 V. The first-cycle coulombic efficiency = (first discharge capacity / first charge capacity) x 100%. This indicator is used to determine whether the degree of additive sacrifice during the first charge cycle is appropriate. After the first cycle of formation is completed, the second and third charge-discharge cycles are performed at 0.1C to complete activation, followed by formal cycle testing.

[0193] 4) 25 °C Cyclic Capacity Retention Test

[0194] After formation and activation, cycle performance tests were conducted at 25 °C. For the NCM811 / graphite system: constant current charging at 1C to the upper limit voltage of 4.3 V, then constant voltage charging to the current cutoff at 0.05C, followed by constant current discharge at 1C to the lower limit voltage of 2.8 V. For the LNMO / graphite system: constant current charging at 1C to 4.7 V, constant voltage to the cutoff at 0.05C, and then 1C discharge to 3.5 V. For the LFP / graphite system: constant current charging at 1C to 3.65 V, constant voltage to the cutoff at 0.05C, and then 1C discharge to 2.5 V. The discharge capacity was recorded at the 200th and 500th cycles. Capacity retention was calculated as (nth discharge capacity / first discharge capacity) x 100%. Here, the first discharge capacity refers to the first cycle of the formal cycling phase, not the charge-discharge cycle during formation.

[0195] 5) 45 °C High Temperature Cycling Capacity Retention Test

[0196] High-temperature cycling tests were conducted at 45 °C using the same charge-discharge regime as the 25 °C cycle tests described above. The discharge capacity was recorded after the 200th cycle, and the capacity retention rate was calculated. High-temperature conditions accelerate the oxidative decomposition and CEI degradation of the cathode interface, which is beneficial for amplifying the differences in interfacial stability between different additive formulations.

[0197] 6) 60 °C High Temperature Fully Charged Storage Performance Test

[0198] At 25 °C, the battery was charged at a constant current of 0.5C to the upper limit voltage, then charged at a constant voltage until the current cutoff was 0.05C, and then discharged at a constant current of 0.5C to the lower limit voltage. The discharge capacity was recorded as the initial capacity C1. The battery was then fully charged again using the same procedure to ensure it was at 100% SOC. The fully charged battery was stored in a 60 °C constant temperature chamber for 30 days. After storage, the battery was left at room temperature for at least 2 hours, then discharged at a constant current of 0.5C to the lower limit voltage. The capacity C2 was recorded, and the capacity retention rate was calculated as (C2 / C1) x 100%. Subsequently, three charge-discharge cycles were performed at room temperature, and the third discharge capacity C3 was recorded. The capacity recovery rate was calculated as (C3 / C1) x 100%.

[0199] 7) Gas production test

[0200] Using batteries from the same batch as in item 6 (stored fully charged at 60 °C for 30 days), the volume of gas released from the battery was measured using the water displacement method or the airtight syringe method, and the gas production (mL) was recorded. This indicator directly reflects the degree of oxidative decomposition and chain reaction of the electrolyte at the positive electrode interface. The lower the gas production, the better the free radical chain termination and interface protection effect.

[0201] Note: 1. All data are based on the average of three parallel sample tests, with a typical error range of ±3% to ±8%. 2. E_ox was tested using LSV (0.5 mV / s, Pt working electrode, Li / Li). + 3. XPS data is based on surface analysis of the cathode sheet after 50 cycles. 4. The core verification group and parameter window group are based on the NCM811 / graphite system (4.3~2.8 V), and the cycle test adopts 1C / 1C charge-discharge regime. 5. Example 6 of the application expansion group is based on the LNMO / graphite system (4.7~3.5 V), and Example 7 is based on the LFP / graphite system (3.65~2.5 V). Due to the different battery platforms, the absolute performance values ​​are not directly compared with the NCM811 platform. 6. The 60 ℃ storage test and gas production test use the same batch of batteries: the initial capacity C1 is obtained by 0.5C charge-discharge, C2 is measured after 30 days of full charge storage, and C3 is measured after 3 cycles to calculate the recovery rate. The gas production is measured on the same batch of batteries. 7. The first-cycle coulombic efficiency is taken from the data of the first cycle of formation.

[0202] The above test methods aim to comprehensively evaluate the overall performance of each embodiment and comparative example, and verify the effectiveness of phosphoramide silane additives containing aromatic amine groups for protecting the positive electrode interface through multi-dimensional performance differences.

[0203] The test results are listed in Tables 2 and 3.

[0204] Table 2

[0205]

[0206] Table 3

[0207]

[0208] Results analysis and discussion:

[0209] Overall effectiveness of phosphoramide silane additives in protecting the cathode interface:

[0210] Experimental results fully demonstrate the significant effect of phosphoramide silane additives containing aromatic amine groups on the interface protection of the positive electrode of high-voltage lithium-ion batteries. By comparing the test data of Example 1 with Comparative Examples 1 and 2, the comprehensive performance improvement brought about by the additives of the present invention can be clearly observed. Example 1 achieved a capacity retention rate of 92.5% after 200 cycles at 25 °C and still maintained 87.2% after 500 cycles, which is an improvement of 15.0 and 23.0 percentage points respectively compared to the blank control Comparative Example 1 without additives (77.5% after 200 cycles and 64.2% after 500 cycles). This significant difference directly verifies the interface protection effectiveness of the technical solution of the present invention under standard cycling conditions.

[0211] More importantly, there is a comparison between Example 1 and Comparative Example 2 (TMSPi, a representative existing PO-Si additive). Comparative Example 2, at the same addition level, maintained a capacity retention rate of 85.5% after 200 cycles and 75.8% after 500 cycles, significantly better than the blank control, Comparative Example 1, but still significantly lower than Example 1. This difference was further amplified under high-temperature conditions: after 200 cycles at 45 °C, the capacity retention rate of Example 1 was 83.5%, while that of Comparative Example 2 was only 72.5%, a difference of 11.0 percentage points. After 30 days of storage at 60 °C, the capacity retention rate of Example 1 was 91.2%, and the recovery rate was 95.5%, while those of Comparative Example 2 were 85.2% and 90.5%, respectively. In terms of gas production, Example 1 produced only 0.8 mL, while Comparative Example 2 produced 2.2 mL, indicating that the gas production inhibition effect of Example 1 was approximately three times that of Comparative Example 2. These multi-dimensional performance advantages demonstrate that the additives of this invention systematically outperform existing TMSPi-type PO-Si additives in terms of interface protection efficacy. This advantage does not stem from accidental fluctuations in a single indicator, but rather reflects the essential improvement in interface protection capability brought about by the design of the PN-Si skeleton combined with the aromatic amine trifunctional center.

[0212] From the perspective of the three-parameter synergistic threshold, Example 1 meets the standard of an effective technical solution at all three parameter levels. Regarding the first parameter, the LSV test is performed at 4.15 V (vs. Li / Li). + A clear oxidation peak was detected at [value missing], falling within the preferred E_ox window (4.0 to 5.0 V), confirming that the compound possesses electrochemical oxidation activity preferential to the host carbonate solvent. Regarding the second parameter, XPS analysis of the cathode surface after 50 cycles simultaneously detected P (2.5 at%), Si (1.8 at%), and N (0.9 at%). The atomic percentages of P and Si were statistically significantly increased compared to the blank control, Comparative Example 1, meeting the criterion requirement of "coexistence of P and Si in CEI composition." The detection of the N 1s signal further confirmed that PN bond decomposition products participated in the construction of the CEI, a unique interfacial component that TMSPi-type PO-Si additives (where N is nd in Comparative Example 2) cannot provide. Regarding the third parameter, Example 1 significantly outperformed the control group in engineering performance indicators such as capacity retention and gas production. The simultaneous achievement of these three parameters formed a complete verification loop of "activity-film formation-performance."

[0213] Experimental evidence that single-molecule functional integration is superior to physical mixing:

[0214] Comparative Example 3 used a physical mixture of TMSPi and 9-ethylcarbazole at 0.5 wt%, with the total addition amount the same as in Example 1. This was used to verify whether adding the P-Si additive and the independent aromatic amine radical scavenger separately to the electrolyte could achieve the same interface protection effect as the single-molecule scheme. Test results showed that while Comparative Example 3's cycling performance and high-temperature storage performance were better than Comparative Example 2 (containing only TMSPi), they were systematically weaker than the single-molecule scheme of Example 1. The capacity retention rate of Comparative Example 3 at 25 °C for 200 cycles was 87.2%, and at 500 cycles it was 78.5%, lower than Example 1's 92.5% and 87.2%, respectively. After 200 cycles at 45 °C, Comparative Example 3's capacity retention rate was 75.2%, lower than Example 1's 83.5%. Regarding gas production, Comparative Example 3 produced 1.8 mL, lower than Comparative Example 2's 2.2 mL, but still more than twice that of Example 1 (0.8 mL).

[0215] The fundamental reason for this performance gap lies in the inability of the reaction timing and spatial distribution of the two independent molecules at the cathode interface to spontaneously match in the physical mixing scheme. TMSPi and 9-ethylcarbazole, as two independent solute molecules, exhibit different adsorption competition, diffusion rates, and oxidation potentials at the cathode interface, leading to asynchronous and uneven deposition and distribution of phosphorus / silicon fragments and aromatic amine oxidation products in the CEI. XPS data supports this analysis: in the CEI of Comparative Example 3, P was 1.8 at% and Si was 1.2 at%, both lower than the 2.5 at% and 1.8 at% of Example 1, and N was only 0.3 at% (0.9 at% in Example 1), indicating that the synergistic deposition efficiency of the functional components at the interface in the physical mixing scheme is significantly lower than that in the single-molecule scheme. The three functional fragments in Example 1 originate from the synchronous decomposition of the same molecule at the same reaction site, and their atomic-scale mixing and spatial homogeneity in the CEI are theoretically impossible to achieve with the physical mixing of independent molecules. This comparison strongly demonstrates the structural advantage of the "intramolecular covalent integration" of this invention over "intermolecular physical mixing."

[0216] The irreplaceable role of aromatic amine radical scavenging centers:

[0217] Comparative Example 4 replaced the R_Ar group from carbazole with n-butyl (a simple alkyl group without an aromatic ring conjugation system), while keeping the PN-Si backbone and Y-side groups unchanged, to verify the irreplaceable nature of the aromatic amine radical scavenging functional center. Test results showed that Comparative Example 4's performance was comprehensively inferior to Example 1, with many indicators even approaching or falling below Comparative Example 2, which only contained TMSPi. The capacity retention rate of Comparative Example 4 at 25 °C for 200 cycles was 83.2%, and at 500 cycles it was 72.5%, lower than Example 1's 92.5% and 87.2%, respectively. The difference in gas production was particularly significant: Comparative Example 4 produced 2.5 mL, higher than Comparative Example 2 (2.2 mL) and Comparative Example 3 (1.8 mL), and significantly higher than Example 1 (0.8 mL).

[0218] The key reason for the poor performance of Comparative Example 4 lies in the lack of two core capabilities provided by the aromatic ring conjugated system of n-butyl. First, n-butyl does not possess preferential oxidation film-forming activity in the high potential range of the positive electrode. The LSV test of Comparative Example 4 did not detect any new characteristic peaks different from the reference electrolyte within the scanning range, indicating that this compound cannot preferentially undergo electrochemical oxidation over the host solvent within the target potential window. Without preferential oxidation, there is no directional film formation, and the organic crosslinking phase component of the CEI is therefore missing. Second, n-butyl cannot stabilize the cationic free radical intermediate after single-electron oxidation through the electron delocalization effect, thus losing the ability to chemically terminate the active free radicals generated during the oxidative decomposition of the electrolyte. The significant increase in gas production directly reflects the consequence that the chain oxidative degradation was not effectively inhibited. It is worth noting that P (1.5 at%) and Si (1.2 at%) were still detected in the CEI of Comparative Example 4, indicating that the PN-Si framework itself still participated in interfacial film formation. However, without the preferential oxidation driven by aromatic amines and free radical scavenging, passive film formation by P / Si alone is insufficient to provide effective interfacial protection. This result demonstrates the irreplaceable role of aromatic amine groups in the "trifunctional center" design of this invention.

[0219] The necessity of PN-Si bonding type compared to PO-Si bonding type:

[0220] Comparative Example 5 retains the design where R_Ar is a carbazole group, X is O, and L is a direct bond, but Y is... 1 and Y 2The -N(CH3)-Si(CH3)3 was replaced with -O-Si(CH3)3, meaning the silicon end groups in the molecule are connected via a PO-Si connection instead of a PN-Si connection. This comparative example was used to verify the necessity of the PN-Si bond type on the Y side while keeping the aromatic amine functional center unchanged. Comparative Example 5 showed a capacity retention of 87.5% at 25 °C for 200 cycles and 78.2% after 500 cycles. While this was better than Comparative Example 4 (83.2%, 72.5%) without aromatic amines, it was significantly lower than Example 1 (92.5%, 87.2%), with a difference of 9.0 percentage points at 500 cycles. After 200 cycles at 45 °C, Comparative Example 5 showed a capacity retention of 74.5%, close to Comparative Example 2 (72.5%), but far lower than Example 1 (83.5%).

[0221] The performance difference between Comparative Example 5 and Example 1 can be explained on two levels. At the level of interfacial decomposition chemistry, the decomposition products of the PO-Si bond at the cathode interface are mainly phosphates and silicates, lacking the nitrogen-containing inorganic or organic-inorganic hybrid CEI components provided by PN bond decomposition. XPS data visually confirm this difference: in Comparative Example 1 of Comparative Example 5, N was only 0.2 at% (close to the detection limit), while in Example 1 it was 0.9 at%. It is believed that the nitrogen-containing components help improve the CEI's resistance to Li. + The conductivity selectivity is improved and the adhesion between the CEI and the positive electrode surface is enhanced, thereby improving the structural stability of the CEI during long-term cycling. In terms of chemical stability, the PO bond is more sensitive to Lewis acidic species (such as PF5 generated from the thermal decomposition of LiPF6) than the PN bond. The effective contact time of Comparative Example 5 in the electrolyte is believed to be shorter than that of Example 1, which is particularly evident in high-temperature long-term storage tests. The storage retention rate of Comparative Example 5 at 60 °C was 86.5%, lower than the 91.2% of Example 1. In summary, even with the retention of aromatic amine radical scavenging function, when the Y side is changed to PO-Si connection, the interface protection effect is still significantly inferior to the PN-Si scheme, which proves the necessity of the PN-Si bond type in the technical solution of this invention.

[0222] The effect of the amount added on performance:

[0223] Examples 2 (0.5 wt%) and 3 (3.0 wt%) together with Example 1 (1.0 wt%) constitute a gradient series of addition amounts, used to verify the effectiveness of the additive of the present invention within the preferred range of 0.5 to 3.0 wt% and the addition amount-performance relationship. The data show that all three addition amounts meet the requirements of the three-parameter synergistic threshold, but exhibit a trade-off relationship between the addition amount and different performance dimensions in specific performance indicators.

[0224] In Example 2, with an addition of 0.5 wt%, XPS still detected the coexistence of P (1.2 at%) and Si (0.8 at%), and the capacity retention rate after 200 cycles was 89.5%, which was better than the comparative examples, demonstrating the effectiveness of the technical solution at low addition levels. However, its 500-cycle retention rate was 83.5%, lower than 87.2% in Example 1, and the gas production was 1.3 mL, higher than 0.8 mL in Example 1, indicating that the accumulation of the synergistic components of the three functional centers in the CEI was low at the 0.5 wt% addition level, and the long-term protective efficacy was weaker than the 1.0 wt% baseline. In Example 3, with an addition of 3.0 wt%, the contents of P (4.2 at%) and Si (3.5 at%) in the CEI were significantly higher than in Example 1, and the gas production decreased to 0.9 mL, which was close to that of Example 1. However, the first-cycle coulombic efficiency of Example 3 was 84.2%, significantly lower than 87.2% of Example 1 and 87.8% of Example 2, reflecting excessive consumption of the additive during the first-cycle charging process under high additive levels. The capacity retention rate of Example 3 at 25 °C / 200 cycles was 91.2%, slightly lower than 92.5% of Example 1, which may be related to the increased impedance caused by the thicker initial CEI layer.

[0225] In summary, the addition amount of 1.0 wt% achieves the optimal balance between interfacial protection effectiveness and the impact on the bulk performance of the electrolyte. It allows sufficient synergistic components of the three functional centers to accumulate in the CEI to form an effective composite protective layer, without causing a decrease in initial efficiency or an increase in impedance due to excessive film formation. Both 0.5 wt% and 3.0 wt% are within the usable range, verifying the broad applicability of this invention in the addition amount range of 0.5 to 3.0 wt%.

[0226] Design verification of R_Ar group type and E_ox regulation:

[0227] The comparison between Examples 4 (N,N-diphenylamino type, E_ox = 4.35 V) and E5 (3-tert-butylcarbazole type, E_ox = 3.95 V) and Example 1 (unsubstituted carbazole type, E_ox = 4.15 V) systematically verifies the design logic of "regulating E_ox through the electron-donating / electron-pulling effect of substituents on the R_Ar group" in the innovation of this invention. The E_ox values ​​of the three examples exhibit a clear substituent effect: the E_ox of Example 5 (3.95 V), which introduces a tert-butyl electron-donating group, is lower than that of the unsubstituted Example 1 (4.15 V), while the E_ox of Example 4 (4.35 V), with the N,N-diphenylamino configuration, is biased towards a higher potential. This trend is completely consistent with the oxidation potential-substituent relationship of aromatic amine compounds in organic electrochemistry, proving the feasibility of regulating E_ox through molecular design using the same PN-Si framework platform.

[0228] In terms of performance, Examples 4 and 5 were similar to Example 1: Example 4 maintained a capacity retention of 91.8% at 25 °C / 200 cycles, and Example 5 maintained 91.2%, both within 2 percentage points of Example 1 (92.5%). XPS analysis of all three showed coexistence of P, Si, and N elements, with gas production rates all below 1.0 mL, and all three parameters were closed-loop. These data indicate that when E_ox is within the effective window, compounds of different R_Ar types can effectively protect the cathode interface, providing an experimental basis for subsequent targeted adaptation of E_ox to different operating voltage systems.

[0229] Verification of the upper and lower boundaries of the valid window for E_ox:

[0230] Comparative Examples 6 and 7 represent extreme cases where E_ox is too low and too high, respectively, and are used to verify the rationality of the effective window of E_ox (3.8 to 5.5 V vs. Li / Li+) set in this invention.

[0231] Comparative Example 6 used an aromatic amine compound with a strong electron-donating substituent, with an E_ox of only 3.55 V, below the effective window limit of 3.8 V. This compound was prematurely oxidized and consumed in large quantities within the operating potential range of the NCM811 cathode, leading to several adverse consequences: the first-cycle coulombic efficiency dropped sharply to 80.5%, the lowest among all samples, reflecting severe irreversible capacity loss; the capacity retention rate at 25 °C / 200 cycles was 82.5%, and at 500 cycles it was 70.2%, not only far lower than Example 1, but even lower than Comparative Example 2 containing only TMSPi (85.5%, 75.8%). Although the CEI of Comparative Example 6 had a high P / Si / N content (P 3.5 at%, Si 2.8 at%, N 1.3 at%), the excessively thick CEI layer actually increased the interfacial impedance and reduced the Li + Transport efficiency. The gas production was 2.1 mL, significantly higher than the 0.8 mL in Example 1, indicating that the overly reactive aromatic amine could not continue to provide subsequent free radical scavenging protection after initial depletion. These results suggest that excessively low E_ox is not "the more reactive, the better." Too low E_ox leads to premature and excessive consumption of the additive in the first irreversible reaction. Although a thicker initial CEI is formed, the quality of this CEI is inferior to that formed when E_ox is within the appropriate window.

[0232] Comparative Example 7 used an aromatic amine compound with a strong electron-withdrawing substituent, exhibiting an E_ox as high as 5.55 V, far exceeding the upper limit of the effective window. This compound was almost impossible to electrochemically oxidize at a charging cutoff voltage of 4.3 V, thus losing its functional premise of "preferring solvent-based film formation." Performance data from Comparative Example 7 confirmed this analysis: the capacity retention was 79.2% at 25 °C / 200 cycles and 66.5% at 500 cycles, only slightly better than the blank control Comparative Example 1 (77.5%, 64.2%), and far inferior to Example 1 and Comparative Example 2. XPS data showed extremely low P and Si contents in the CEI (0.3 at% and 0.2 at%, respectively), and N was nd, indicating that the additive molecules hardly participated in the construction of the CEI. The gas production was 3.3 mL, close to the 3.6 mL of the blank control Comparative Example 1. The first-cycle coulombic efficiency of Comparative Example 7 was 84.2%, which does not seem very low on the surface. This is because the additive itself did not undergo significant sacrifice or consumption. However, this also means that it failed to perform any interface protection function. The initial effect was "normal" but subsequent protection was lacking, which is in stark contrast to Comparative Example 6.

[0233] The comparison between Comparative Examples 6 and 7 verifies the scientific rationale behind the effective window of E_ox from both positive and negative perspectives: E_ox must be low enough to ensure preferential oxidation over solvent oxidation (excluding Comparative Example 7), but it cannot be too low to avoid excessive consumption (excluding Comparative Example 6). Setting E_ox within the range of 3.8 to 5.5 V, preferably 4.0 to 5.0 V, allows the additive to undergo moderate and controllable preferential oxidation when the positive electrode reaches the target potential, achieving optimal functional output for directional film formation and free radical scavenging.

[0234] Cross-voltage system compatibility verification:

[0235] Examples 6 and 7 respectively used aromatic amine compounds with different E_ox values ​​to match cathode systems with different operating voltages, verifying the design concept of this invention: "achieving cross-voltage system adaptation through the regulation of E_ox by the R_Ar group on the same PN-Si framework platform." The battery platforms used in Examples 6 and 7 are LNMO / graphite (4.7~3.5 V) and LFP / graphite (3.65~2.5 V), respectively, which are different from the NCM811 / graphite platform of the core verification group. Therefore, the absolute performance values ​​are not suitable for direct cross-platform comparison. The focus of their verification is on the effectiveness of the additive schemes within their respective platforms.

[0236] Example 6 uses a fluorinated carbazole compound (E_ox = 4.65 V) paired with an LNMO high-voltage spinel cathode (charge cutoff voltage 4.7 V). Under this extreme high-voltage condition, E6 exhibits a capacity retention of 88.5% at 25 °C / 200 cycles, 82.2% at 500 cycles, 78.5% at 45 °C / 200 cycles, and a storage retention of 87.8% and recovery rate of 92.5% at 60 °C, with a gas production of 1.2 mL. The three-parameter closed-loop condition is met: E_ox is within the effective window, XPS detects the coexistence of P (2.2 at%) and Si (1.6 at%), indicating good cycling and storage performance. This result demonstrates that by introducing electron-withdrawing groups such as fluorine atoms onto the carbazole ring to enhance E_ox, the same PN-Si framework can be effectively adapted to cathode systems with a charge cutoff voltage as high as 4.7 V.

[0237] Example 7 uses a phenothiazine-based compound (E_ox = 3.85 V) with an LFP cathode (charge cutoff voltage 3.65 V). Although the E_ox of the phenothiazine-based additive (3.85 V) is slightly higher than the LFP's charge cutoff voltage (3.65 V), it still preferentially oxidizes and forms a film before the main solvent under the influence of charge polarization and local potential at the cathode interface. Furthermore, its oxidation onset potential is significantly lower than the oxidation decomposition potential of the main solvent, thus achieving preferential film formation and interface protection in the LFP system. The LFP system has a lower operating voltage (platform approximately 3.4 V), and the oxidation stress at the cathode interface is much lower than that of high-nickel ternary and spinel systems. In Example 7, the capacity retention rates at 25 °C / 200 cycles and 500 cycles were 98.2% and 96.5%, respectively; at 45 °C / 200 cycles, it was 96.8%; and at 60 °C, the storage retention rate was 97.5%, the recovery rate was 99.2%, and the gas production was only 0.15 mL. XPS detected the coexistence of P (1.8 at%) and Si (1.3 at%), with a first-cycle coulombic efficiency as high as 95.8%, confirming that the lower E_ox of the phenothiazine-based compound can match the lower operating voltage of the LFP, playing an interface protection function in the system without causing excessive consumption.

[0238] The data from Examples 6 and 7 together demonstrate the broad adaptability of the technical solution of the present invention: spanning a voltage range of more than 1 V from 3.65 V for LFP to 4.7 V for LNMO, the working voltage window of different cathode systems can be matched by adjusting the type of R-Ar group and substituents, and effective cathode interface protection can be achieved on the same PN-Si framework platform.

[0239] Summary of overall technical effects:

[0240] Based on the test data from all embodiments and comparative examples, the phosphoramide silane electrolyte additive containing aromatic amine groups of the present invention exhibits a systematic advantage in protecting the positive electrode interface. Through a step-by-step disassembly and comparison by the core verification group, the necessity and irreplaceability of each key technical feature are clearly demonstrated: the introduction of aromatic amine radical scavenging groups (Example 1 vs. Comparative Example 4), the PN-Si bond type connection mode (Example 1 vs. Comparative Example 5), and the single-molecule three-functional center integrated design (Example 1 vs. Comparative Example 3). These three innovative elements are not simply superimposed, but form a synergistic and complementary functional closed loop. Aromatic amines provide active radical chain termination and preferential oxidation-oriented film formation, the PN-Si framework provides nitrogen-containing CEI components and better chemical stability, and the single-molecule structure ensures the synchronous co-deposition of the three types of fragments at the atomic scale at the interface. All three are indispensable.

[0241] Data from the parameter window verification group further demonstrates that the additives of this invention can meet the requirements of the three-parameter synergistic threshold in an addition range of 0.5 to 3.0 wt%. E_ox can be systematically regulated within a range of approximately 1 V through molecular design using the R_Ar group, and the upper and lower boundaries of the effective E_ox window (3.8 to 5.5 V) are clearly supported by experimental data. Data from the application expansion group demonstrates the cross-voltage system adaptability of the same PN-Si framework platform from 3.65 V for LFP to 4.7 V for LNMO. These experimental results provide sufficient experimental support for the effectiveness and inventiveness of the technical solution of this invention from three aspects: compound electrochemical activity, interfacial film formation, and final engineering performance.

[0242] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A battery cell, characterized in that, The device includes a positive electrode, a negative electrode, a separator, and an electrolyte. The electrolyte includes an additive, an organic solvent, and a lithium salt. The amount of the additive added to the electrolyte is 0.01 to 10 wt%. The additive is a compound having the general formula (I). R_Ar-P(=X)(Y¹)(Y²) General Formula (I) In this case, R_Ar- is directly bonded to the P atom in general formula (I) through its own nitrogen atom; The R_Ar- is selected from any one or more of substituted or unsubstituted carbazole, substituted or unsubstituted N,N-diarylamino, substituted or unsubstituted phenothiazinyl, and substituted or unsubstituted phenotoxazinyl. When the R_Ar- has a substituent, the substituent is selected from any one or more of halogen, C1-C6 alkyl, C1-C6 alkoxy, trifluoromethyl, and cyano. X is an oxygen atom or a sulfur atom; Both Y¹ and Y² are -NR 3 -SiR 4 3; where R 3 R is a hydrogen atom or a C1-C4 alkyl group; 4 It is a C1~C3 alkyl group; The oxidation initiation potential E_ox of the additive, measured by linear scanning voltammetry at a scan rate of 0.5 mV / s, is 3.8~5.5 V, using a platinum electrode as the working electrode and a lithium metal sheet as the reference and counter electrode.

2. The battery cell according to claim 1, characterized in that, The substituent is selected from any one or more of methyl, methoxy, tert-butyl, fluorine, trifluoromethyl, and cyano.

3. The battery cell according to claim 1 or 2, characterized in that, The R_Ar- is selected from any one or more of carbazole-9-yl, 3-tert-butylcarbazole-9-yl, N,N-diphenylamino, di(4-methylphenyl)amino and di(4-methoxyphenyl)amino.

4. The battery cell according to claim 1, characterized in that, The Y¹ and Y² are each independently -N(CH3)-Si(CH3)3 or -NH-Si(CH3)3.

5. The battery cell according to claim 1 or 2, characterized in that, The additive is 9-carbazole-N,N′-bis(methyltrimethylsilylamino)phosphamide or diphenylamino-N,N′-bis(methyltrimethylsilylamino)phosphamide.

6. The battery cell according to claim 1 or 2, characterized in that, The molecular weight of the additive is 200~800 g / mol.

7. A method for preparing a battery cell according to any one of claims 1 to 6, comprising stacking or winding a positive electrode sheet, a separator, and a negative electrode sheet in sequence to form an electrode assembly; inserting the electrode assembly into an aluminum-plastic film or a metal shell, injecting an electrolyte, and then encapsulating, allowing it to stand, forming, and aging to obtain the battery cell; characterized in that, The electrolyte includes an additive, and the method for preparing the additive includes: A condensation reaction is carried out on raw materials including nitrogen-containing aromatic amine compounds, phosphorus-containing chlorine compounds, acid-binding agents and anhydrous solvents to form an intermediate; The additive is obtained by subjecting the intermediate and a silane-containing compound to a nucleophilic substitution reaction. Wherein, the phosphorus-containing chlorine compound is POCl3; the nitrogen-containing aromatic amine compound is R_Ar-H, wherein the definition of R_Ar- is the same as that in claim 1; the silane-containing amine compound is HN(R 3 (SiR) 4 3) and / or HN(SiR) 4 3)2, wherein the definitions of R3 and R4 are the same as their definitions in claim 1.

8. The method for preparing a single battery cell according to claim 7, characterized in that, The acid-binding agent is triethylamine or diisopropylethylamine; And / or, the anhydrous solvent is selected from any one or more of anhydrous tetrahydrofuran, anhydrous dichloromethane, and anhydrous toluene; And / or, the temperature of the condensation reaction is -20 to 60 °C, and the time of the condensation reaction is 2 to 24 hours; And / or, the temperature of the nucleophilic substitution reaction is 0~80 °C.

9. A battery device, characterized in that, The battery device includes the battery cell according to any one of claims 1 to 6, and the battery device includes one or more of the following: battery module, battery pack, and energy storage battery.

10. An electrical appliance, characterized in that, The electrical device includes the battery device of claim 9, the battery device being used to provide electrical energy.

11. An energy storage device, characterized in that, The energy storage device includes the battery device of claim 9, the battery device being used to store electrical energy.

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