In the field of basic lithium-ion battery research, "unrepeatable experimental data and no basis for electrode selection" have long been key pain points plaguing researchers. Recently, a major breakthrough has been achieved in a study focusing on the standardized parameters of glassy carbon electrodes (GCEs) for lithium-ion batteries. After systematically testing GCEs of different specifications ranging from 2mm to 6mm, the research team has for the first time confirmed that the GCE with a 3mm inner core diameter exhibits optimal performance in lithium-ion transport efficiency, cycle stability, and interface compatibility. Its capacity retention rate reaches 88.6% at a high 5C rate, and the performance attenuation is only 14.3% after 1000 cycles. This achievement provides the first standardized electrode parameter reference for laboratory research on lithium-ion batteries and is expected to significantly improve the research efficiency of the industry.

1. Solving the "Size Chaos": 3mm Inner Core Proves Optimal After Comparing 5 Specifications

"In the past, when selecting GCEs in laboratories, researchers mostly relied on experience or recommendations from suppliers, and data measured by electrodes of different sizes often 'conflicted' with each other," explained Professor Zhang Ming, the leader of the research team and a materials engineering expert. As the "core carrier" for electrochemical testing of lithium-ion batteries, the dimensional parameters of GCEs (inner core diameter, packaging structure, connector specifications) directly affect the efficiency of lithium-ion intercalation/deintercalation and the stability of interface reactions. However, there has long been a lack of systematic research on the correlation between parameters and performance.

To fill this gap, the research team established a comprehensive testing system. They selected five mainstream specifications of GCEs available on the market (with inner core diameters of 2mm, 3mm, 4mm, 5mm, and 6mm, matched with PTFE packaging sizes ranging from 6mm×80mm to 10mm×80mm, and 2mm×15mm/20mm copper connectors) and conducted comparative experiments from three dimensions: microstructure, electrical conductivity, and electrochemical performance.

Scanning Electron Microscopy (SEM) observations showed that the pore structure of the 3mm inner core electrode was "uniform and dense" — the pore size was concentrated between 5nm and 20nm, and the specific surface area reached 326m²/g, which exactly provided an ideal environment of "sufficient channels without congestion" for lithium-ion intercalation/deintercalation. In contrast, the 2mm inner core electrode had smaller pore sizes (2nm-10nm) due to carbonization shrinkage, with its specific surface area dropping to 258m²/g, limiting the diffusion space for lithium ions. The 6mm inner core electrode, on the other hand, experienced pore agglomeration (30nm-50nm) due to uneven heat conduction, resulting in a specific surface area of only 212m²/g and even "lithium ion retention" in local areas.

"The conductivity test further confirmed the advantages of the 3mm specification," Dr. Li Na, a member of the team, said while presenting the experimental data. The room-temperature conductivity of the 3mm inner core electrode reached 285S/cm, significantly higher than that of the 2mm (242S/cm), 4mm (268S/cm), 5mm (255S/cm), and 6mm (231S/cm) specifications. "An excessively small inner core narrows the current collection path, while an excessively large one leads to uneven distribution of internal resistance. Only the 3mm size can balance electron transfer efficiency and structural stability."

2. Impressive Performance in Actual Tests: Meeting Standards for Both High-Rate and Long-Cycle Performance, with More Stable Interface Reactions

In the tests of core performance indicators for lithium-ion batteries, the performance of the 3mm inner core electrode further highlighted its "benchmark status."

In the constant current charge-discharge test, at a 0.1C rate (slow charge-discharge mode), the first discharge specific capacity of the 3mm inner core electrode reached 148mAh/g with a Coulombic efficiency of 89.2%, an increase of more than 30% compared with the 6mm specification (112mAh/g, 82.5%). When the rate was increased to 5C (fast charge-discharge mode), its capacity retention rate was still as high as 88.6%, while the 2mm and 6mm specifications were only 75.3% and 62.1% respectively. This indicates that this specification of electrode is more suitable for research on high-rate lithium-ion batteries.

"Cycle stability is another key focus in laboratories," Dr. Li Na introduced. The team conducted a 1000-cycle test on the five specifications of electrodes at a 1C rate. The results showed that the capacity retention rate of the 3mm inner core electrode was 85.7%, the charge transfer resistance (Rct) was only 85Ω, and the increase in resistance after cycling was only 15%, far lower than that of other specifications (20%-35%). "This is due to its uniform pore structure, which can inhibit the excessive growth of the SEI film (Solid Electrolyte Interphase film) and reduce the increase in interface impedance. The stability of the SEI film is precisely the key factor affecting the lifespan of lithium-ion batteries."

Cyclic Voltammetry (CV) tests also revealed that the 3mm inner core electrode had the most optimal symmetry of redox peaks, with a peak potential difference of only 0.18V, indicating good reversibility of lithium-ion intercalation/deintercalation kinetics. X-ray Photoelectron Spectroscopy (XPS) analysis further confirmed that its surface oxygen content (4.8%) was moderate, which could promote the uniform formation of the SEI film. The 2mm inner core electrode had a relatively high oxygen content (6.2%), which easily led to excessive oxidation of the SEI film, while the 6mm inner core electrode had a low oxygen content (3.1%), resulting in insufficient stability of the SEI film.

3. Cost-Effective Maintenance: Over 95% Performance Recovery Rate Through Polishing, and Extended Lifespan by Avoiding Ultrasonic Cleaning

In addition to its performance advantages, the "easy maintainability" of the 3mm inner core electrode also provides a new way to reduce costs for laboratories.

The research team applied a polishing and repair process using 0.05μm alumina powder to the 3mm inner core electrode whose performance had deteriorated after 1000 cycles. The results showed that the surface morphology of the electrode was completely restored to its initial state, and the electrical conductivity rebounded to 278S/cm (a recovery rate of 97.5%). At a 1C rate, the first discharge capacity reached 142mAh/g, with a capacity recovery rate of 95.9%, and the capacity retention rate was still 92.3% after 100 cycles.

"In the past, some laboratories were accustomed to cleaning electrodes with ultrasonic waves, but they were unaware that this would damage the porous structure of the glassy carbon inner core," Professor Zhang Ming warned. Experiments have confirmed that the maintenance scheme of "avoiding ultrasonic cleaning + regular polishing" can extend the service life of the 3mm inner core electrode to 2-3 times that of the traditional maintenance method. "Based on the regular usage frequency of laboratories, the annual maintenance cost per electrode can be reduced by more than 60%."

It is worth noting that the study also clarified the applicable scenarios for different specifications of electrodes: for high-rate performance research, priority should be given to the 3mm inner core electrode; for interface reaction mechanism research, the 2mm inner core electrode can be used (due to its high surface oxygen content, which facilitates the observation of SEI film formation); and for high-current testing scenarios, it is recommended to match with a 2mm×20mm copper connector (to enhance mechanical stability). This provides researchers with a clear guide for "selecting electrodes according to needs."

4. Industry Expectations: Promoting Standardized Application and Accelerating the Technological Iteration of Lithium-Ion Batteries

"The core value of this research is to establish a 'unified benchmark' for basic research on lithium-ion batteries," commented Wang Hao, a senior engineer at the China Battery Industry Association. For a long time, the "incomparable experimental data" caused by inconsistent GCE parameters has not only wasted research resources but also may delay the process of technological breakthroughs. "The standardized parameters of the 3mm inner core electrode are expected to become an industry-recommended standard, making the research results of different laboratories comparable and accelerating technological iteration."

At present, the research team has collaborated with a number of domestic electrode manufacturers to develop standardized GCE products based on the research results, which are expected to be supplied to laboratories in bulk in the first quarter of next year. "Next, we will focus on controlling the uniformity of large-size inner core electrodes. By improving the carbonization heating process, we will solve the problem of uneven heat conduction in the 6mm specification. At the same time, we will develop automated polishing equipment to further improve the efficiency of laboratory use," Professor Zhang Ming revealed.