1. Definition and calculation logic of surface density

Surface density is a core parameter in the design of lithium-ion battery pole piece, which is defined as the mass of active material per unit surface area of the electrode (unit: mg/cm²).

The calculation formula is: Surface density = compaction density (g/cm³) * pole piece thickness (μm)/1000

The surface density directly determines the content of active materials per unit area of the pole piece and is a regulatory lever for energy density (battery life) and rate performance (charging speed).

2. The impact of surface density on battery life: the "amplifier" of energy density

High surface density improves battery life. The higher the surface density, the more active materials the positive electrode can accommodate per unit surface area, and the energy density increases accordingly.

The cost of battery life: internal resistance and thermal runaway risk. High surface density leads to increased thickness of the pole piece, longer lithium ion diffusion path, increased internal resistance and increased heat generation, which may cause thermal runaway.

3. The impact of surface density on charging speed: the "double-edged sword" of fast charging performance

Low surface density optimizes fast charging capability. When the surface density decreases, the pole piece becomes thinner, the lithium ion diffusion path is shortened, the polarization effect is weakened, and the internal resistance is reduced, which is more suitable for fast charging scenarios.

Hidden dangers of extreme low surface density: Too low surface density will increase the difficulty of coating process, reduce mechanical strength (easy to break), and require more pole piece layers to be stacked, which will increase costs and safety risks.

Theoretically, the smaller the surface density, the more conducive it is to improving rate performance. However, the surface density design also has a lower limit. In addition, the battery has not only rate requirements, but also capacity requirements. Simply reducing the surface density will inevitably increase the number of layers of the pole piece, and the increase in the number of layers also increases the risk.

The balance rule of R&D engineers: How to design the optimal surface density?

Application scenario priority, material and process coordination, dynamic test verification

Bosa Energy

Bosa Energy with 150GWH capacity and over 400,000 electric bus/utility vehicle application experience we are listing first 5 in China power battery industry. We cooperate with Yutong/Geely/Damiler etc.

We are also offering Container ESS systems and delivered 6GWh in 2024(=75,000 Model3 with 80kWh battery). In local market, we are offering OEM service for Changan, CALB, National grid, Ping Gao Electric , Xuji electronics, Ruineng electronics, they are our main Container ESS suppliers in China Market.

We are the most professional supplier of marine lithium batteries in China, and our export volume of marine batteries consistently ranks among the top three in China; We are also the top 1 exporter of lithium battery modules in China, specializing in providing various lithium battery module solutions.

For excellent quality and performance our products are popular in more than 30 countries in the world. We also have established warehouse in Germany and Netherlands to provide safety stock timely delivery for our customers.

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