Technical Deep Dive — Focusing on High-Temperature Interface Stability to Overcome Key Bottlenecks in Thick-Electrode Wetting Technology

In the first two installments of this special series, we dissected three major pain points of LFP batteries: inadequate fast‑charging performance, rapid capacity fade at elevated temperatures, and the difficulty of wetting high‑density electrode sheets. From the perspective of electrolyte additives, we also detailed solutions to enhance LFP batteries’ high‑rate capability and fast‑charging performance. In this installment, we will continue to explore, from an additive‑based standpoint, how to address the issues of high‑temperature capacity decay and the wetting challenges posed by thick electrodes in LFP battery systems.

I. Additive Solutions to Mitigate High-Temperature Capacity Fade in LFP Batteries

LFP battery capacity fade at elevated temperatures stems primarily from two key factors: first, the dissolution of iron ions from the cathode, leading to structural degradation of the material; second, under high-temperature conditions, the lithium salt LiPF₆ in the electrolyte… ₆ It will accelerate decomposition, generating PF. ₅ , PF ₅ Further hydrolysis of trace water in the electrolyte generates HF. ^[1] . HF exacerbates the Fe in the cathode material ²⁺ Dissolution; meanwhile, high temperatures accelerate the dissolution of LFP cathode material in the electrolyte (though this rate remains far lower than that of lithium manganese oxide materials). ^[2] ), long-term accumulation can still degrade the cathode structure. Second, there is loss of active material. Fe deposited on the surface of the graphite anode… ²⁺ Moreover, the HF generated in the electrolyte can compromise the stability of the SEI film, leading to its repeated rupture, continuous repair, and growth. This process consumes substantial amounts of active lithium, ultimately resulting in irreversible capacity fade. ^[3] 。

LiPF ₆ Decomposition process

To address this pain point, two types of core functional additives can establish a protective system:

1. Cathode‑anode film‑forming additives. Cathode‑specific film‑forming additives undergo oxidative decomposition on the surface of the LFP cathode, forming a dense, stable CEI layer that isolates the electrolyte from direct contact with the cathode material and suppresses Fe… ²⁺ Lithium‑ion batteries employ various additives to enhance their performance. For instance, electrolyte additives can promote the formation of a stable solid electrolyte interphase (SEI) on the electrode surfaces, while anode‑specific film‑forming additives create a dense passivation layer on the graphite anode, thereby suppressing metal‑ion deposition and inhibiting side reactions. Together, these additives ensure superior high‑temperature cycling and storage stability. In LFP systems, common film‑forming additives include carbonate‑based compounds, sulfate esters, sulfonate esters, borate esters, and novel lithium salts. Representative carbonate‑based additives include vinylene carbonate (VC); sulfate‑based additives include ethylene sulfate (DTD) and bis(ethylene sulfate) (BESA); and sulfonate‑based additives include 1,3‑propane sultone (PS) and methyl methanesulfonate (MMDS). These additives collectively improve battery performance in terms of cycle life and high‑temperature operation.

2. Acid- and water‑removal additives. These additives precisely capture trace amounts of HF and water in the electrolyte, preventing their corrosive attack on electrode materials, suppressing the dissolution of transition‑metal ions from the cathode, and slowing down high‑temperature capacity fade, thereby ensuring stable performance of LFP batteries under high‑temperature conditions. The main categories of acid‑ and water‑removal additives include four types: 1) Isocyanate‑containing compounds with the –N=C=O group: In these compounds, the nitrogen atom can scavenge hydrogen from the electrolyte. ⁺ , inhibiting the formation of HF, such as trimethylsilyl isothiocyanate (TMSNCS); 2) Silane/silazane compounds: The Si–O and Si–N bonds in these structures can scavenge HF and phosphorus pentafluoride (PF₃). ₅ ) and H ₂ O, enhance electrolyte stability and prevent electrode corrosion, such as hexamethyldisilazane (HMDS); 3) Nitrogen-containing heterocycles: the nitrogen atom possesses a lone pair of electrons, enabling it to interact with H in the solution. ⁺ Reaction, eliminate H ⁺ , such as propargyloxy carbonylimidazole (IMPC); 4) Novel compound class: its mechanism of action is that it can directly scavenge H⁺ ions from the electrolyte. ⁺ or PF ₅ , in order to reduce the acid content in the electrolyte. ^[4,5]

II. Additive-Based Solution to Overcome the Challenge of Electrolyte Wetting in High-Pressure Compacted Electrode Sheets

To meet the high‑energy‑density demands of the end‑user market, the industry widely employs high‑compaction‑density, thick‑electrode coating processes to boost the capacity of LFP cells; however, this approach increases the diffusion path and resistance of the electrolyte within the electrodes. ^[6] . Increasing the difficulty of electrolyte wetting; if the electrode is not fully浸润 by the electrolyte, it can lead to non-uniform local current densities on the active particles, thereby affecting the utilization rate of the battery’s active materials.

To address the challenge of poor electrolyte wetting, the industry typically incorporates electrolyte‑wetting additives—namely, surfactants—which reduce the surface tension of the electrolyte and enhance its wettability and penetration. ^[7] As early as 1989, Asahi Kasei Corporation discovered phosphate ester compounds containing long-chain aliphatic and aromatic moieties that exhibit wetting properties, such as tri(2-ethylhexyl) phosphate, triphenyl phosphite, and fluorobenzene. Around the year 2000, Ube Industries successively reported carbonate esters and tertiary carboxylate esters bearing branched alkyl groups, which likewise enhance the electrolyte’s wettability. In recent years, several novel lithium salts have also been found to serve as electrolyte‑wetting additives, for example, lithium bis(trifluoromethylsulfonyl)imide. Its molecular structure simultaneously incorporates a hydrophilic –SO ₃ - The hydrophobic trifluoroacetyl group can significantly enhance the electrolyte’s wettability toward the electrode active material layer, with a particularly pronounced wetting effect on electrode active material layers exhibiting high compaction density or substantial coating thickness. ^[8] 。

III. Cheerchem Solutions

Addressing two major industry challenges—high‑temperature capacity fade and poor electrolyte wetting in thick electrodes—how can we select the most suitable electrolyte additives? Commercially available additive products today are critical to ensuring long‑term stability and optimal performance. Cheerchem Advanced Material, with years of expertise in lithium‑ion battery additives, offers a comprehensive portfolio of mainstream additive solutions.

The structures and performance characteristics of the aforementioned additives are as follows:

IV. Advantages of Cheerchem Advanced Material

(1) Production Scale

The company leverages three major production bases—Changshu in Jiangsu, Jiaxiang in Shandong, and Lianjiang in Fujian—with a total electrolyte additive capacity of 36,900 tons per year. Among these, core products such as VC (9,000 tons/year), FEC (6,000 tons/year), and DTD (5,000 tons/year) rank among the industry’s highest, ensuring reliable fulfillment of bulk delivery requirements for key customers.

(2) Market Share

Leveraging its deep technological expertise and R&D strengths, Cheerchem Advanced Material ranks first nationwide or at the top of its industry in market share for several mainstream additive products, including DTD, TMSP, and TMSB, and serves as a core supplier to leading downstream electrolyte manufacturers.

(3) Quality

The company has established a rigorous, end-to-end quality control system and holds authoritative certifications including ISO 9001, ISO 14001, ISO 45001, IATF 16949, and Level II safety production standards. It strictly controls key electrolyte parameters such as purity, moisture content, and metal ion levels, effectively ensuring the long-term stability of both the electrolyte and the battery system, thereby earning widespread customer recognition.

(4) Innovation

Cheerchem Advanced Material consistently adheres to a research‑driven growth strategy, continuously increasing its R&D investment, establishing specialized R&D platforms and technical teams, and deeply cultivating cutting‑edge advancements in electrolyte additive technologies. At the same time, guided by a customer‑centric service philosophy, the company maintains close collaboration and joint R&D efforts with leading electrolyte and battery manufacturers across the value chain, precisely addressing the customized development needs of diverse battery chemistries and application scenarios.

Single‑function electrolyte additives struggle to simultaneously meet multiple performance requirements—such as fast charging, high‑temperature cycling, low internal resistance, and long cycle life. Consequently, the industry has increasingly adopted a mainstream approach: formulating multi‑component, multifunctional additive blends that synergistically enhance overall battery performance. Cheerchem Advanced Material is committed to both strengthening its large‑scale production capacity for mainstream additives—leveraging well‑established manufacturing facilities and mature quality‑control systems to ensure stable mass production and timely delivery of standard formulations—and driving innovation through sustained R&D investment. By closely aligning with technological advancements in LFP batteries and the broader new‑energy sector, the company continuously tackles cutting‑edge formulation challenges, iteratively introducing a range of novel functional additives, thereby expanding its product portfolio and pushing the boundaries of technical applications. Looking ahead, Cheerchem will continue to build on its core strengths in independent R&D and scalable manufacturing, deepen collaborative co‑creation with supply‑chain partners, and consistently support technological upgrades in power‑battery and energy‑storage fields, fully contributing to the high‑quality, sustainable development of the lithium‑ion battery industry.

V. References

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[2] Nick Iltchev, Yike Chen, Shigeto Okada, et al. LiFePO ₄ storage at room and elevated temperatures[J]. J. Power Sources, 2003, 19, 749-754．

[3] Ping Liu, John Wang, Jocelyn Hicks-Garner, et al. Aging mechanisms of LiFePO ₄ batteries deduced by electrochemical and structural analyses[J]. J. Electrochem. Soc., 2010,157, A499-A507.

[4] Song Linhu, Li Shiyou, Wang Jie, et al. Research progress on acid- and water‑removal additives for lithium‑ion battery electrolytes [J]. Applied Chemistry, 2022, 5, 697–706.

[5] Shengshui Zhang. Aromatic isocyanate as a new type of electrolyte additive for the improved performance of Li-ion batteries[J]. J. Power Sources, 2006, 163, 567-572.

[6] Sheng Shui Zhang. A review on the separators of liquid electrolyte Li-ion batteries[J]. J. Power Sources, 2007, 164, 351-364.

[7] Hao Zheng, Yong Xie, Hongfa Xiang, et al. A bifunctional electrolyte additive for separator wetting and dendrite suppression in lithium metal batteries[J]. Electrochim. Acta, 2018, 270, 62-69.

[8] Zhang Zhenghua. Research on Electrolyte Regulation and Performance of Lithium Iron Phosphate Batteries [D]. Central South University, 2024.