1 Core Material System
Positive electrode material
Three element materials (NCM/NCA):
Nickel (Ni) enhances capacity, cobalt (Co) stabilizes structure, and manganese/aluminum (Mn/Al) enhances safety. High nickel content (such as NCM811, NCA) is a trend, but the thermal stability challenge is significant.
Technical difficulty: When the nickel content is greater than 90%, there are significant issues with cycle life and gas production.
Lithium iron phosphate (LFP):
High safety and low cost, but low energy density (~160Wh/kg). BYD blade batteries are a typical structural innovation that improves conductivity through nanotechnology and carbon coating.
Rich lithium manganese base:
The theoretical capacity is greater than 300mAh/g, but the problems of voltage attenuation and low first effect remain to be solved.
Negative electrode material
Graphite: mainstream solution, specific capacity~372mAh/g, close to the theoretical limit.
Silicon based negative electrode: theoretical capacity reaches 4200mAh/g, but volume expansion (>300%) leads to poor cycling. The solution includes nano silicon carbon composite and porous structure design.
Lithium metal negative electrode: a potential option for solid-state batteries, but the dendrite problem is severe.
Electrolyte
Liquid electrolyte: Lithium hexafluorophosphate (LiPF6) is the main component, and additives such as VC and FEC are needed to improve the SEI film.
Solid state electrolytes: oxide (LLZO), sulfide (LGPS), and polymer (PEO), with ion conductivity (10 ⁻³~10 ⁻² S/cm) and interface impedance being key bottlenecks.
Diaphragm
The trend of polyolefin (PE/PP) base film is thinning (<10 μ m)+ceramic coating to enhance heat resistance. The uniformity of pore size in wet process is better than that in dry process.
2 Cell structure design
Cylindrical battery cells (such as 21700, 4680)
The Tesla 4680 adopts a Tabless design, which reduces internal resistance by 50%, but the full pole ear laser welding process is complex.
Square shaped battery cell
Stacking (CATL) vs winding (BYD), stacking has a 5% higher energy density but lower production efficiency. CTP (Cell to Pack) technology eliminates modules and achieves a grouping efficiency of over 75%.
Soft pack battery cell
Aluminum plastic packaging, lightweight but with poor mechanical strength. The General Motors Ultium platform adopts a "flexible" design.
3 Key points of manufacturing process
Electrode coating: The consistency deviation of surface density should be less than ± 1.5%, and dry electrodes (such as QuantumScape) can eliminate solvents.
Polar roller pressing: The compaction density affects ion diffusion, and graphite negative electrodes are usually 1.6-1.8g/cm ³.
Injection and formation: After vacuum injection, the formation of SEI film requires multi-stage charging and discharging (such as 0.02C slow charging).
Drying control: The moisture content should be less than 500ppm to prevent LiPF6 from hydrolyzing and generating HF.
4 Breakthrough in cutting-edge technology
Ultra high nickel positive electrode: Monocrystalline+gradient doping (such as Al/Mg) improves stability.
Composite current collector: PET substrate+copper/aluminum coating (such as CATL), reducing weight by 40% and improving safety.
Pre lithiation technology: positive electrode lithium supplementation (Li ₂ NiO ₂) or negative electrode lithium foil to compensate for first effect loss.
Dry electrode: Tesla's acquisition of Maxwell promotes solvent-free processes, reducing energy consumption by 80%.
5 Challenges and Trends
Energy density: The theoretical limit of liquid batteries is around 350Wh/kg, while solid-state batteries may exceed 500Wh/kg.
Fast charging technology: Silicon negative electrode+superconducting electrolyte can be charged to 80% in 15 minutes, but the risk of lithium precipitation needs to be suppressed.
Recycling economy: The wet recovery efficiency of cobalt and nickel is greater than 98%, but low-cost solutions need to be developed for LFP battery recycling.
6 From the perspective of the industrial chain
Equipment: The precision of the coating machine reaches ± 1 μ m, and the speed of the winding machine is greater than 3m/s (leading intelligent).
Cost: LFP battery cells have been reduced to<80/kWh, while ternary battery cells are around 100/kWh.