Guidelines for selecting electric vehicle battery cells

What type of battery cell is good for electric vehicles?

There are three main types of electric vehicle battery cells: lithium-ion batteries, nickel hydrogen batteries, and solid-state batteries. Among them, lithium-ion batteries have become mainstream due to their advantages such as high energy density and long cycle life, and are further subdivided into lithium iron phosphate (LFP), ternary materials (NCM/NCA), lithium manganese oxide (LMO), and lithium titanate (LTO). Lithium iron phosphate batteries are known for their safety and cost advantages, making them suitable for users who value cost-effectiveness; Ternary material battery cells have higher energy density and are suitable for users who pursue long battery life, but the cost is also relatively high. In addition, the shape of the battery cell is also a factor to consider when choosing. Cylindrical battery cells have mature technology and good heat dissipation, but large capacity assembly is complex; Square cells have high energy density and long cycle life, but there may be consistency issues; Soft pack battery cells are lightweight and flexible, but have lower grouping efficiency.

In terms of performance characteristics, different battery cell materials have differences in energy density, cycle life, safety, cost, and low-temperature performance. For example, lithium iron phosphate batteries have low energy density but high safety, while ternary material batteries have high energy density but high cost. At the same time, cells of different shapes also have differences in discharge performance, heat dissipation, and size universality.

In terms of usage scenarios, power cells are suitable for scenarios that require high energy density and high power output, such as electric vehicles; Energy storage cells are suitable for scenarios that require high safety and long cycle life, such as grid energy storage. In addition, different cell shapes are also suitable for different types of devices, such as cylindrical cells for small devices, square cells for medium-sized devices, and soft pack cells for special scenarios.

In terms of brand recommendation, brands such as CATL and BYD have advantages in the field of lithium iron phosphate batteries, making them suitable for users who value safety and cost; Brands such as Panasonic and Tesla have shown outstanding performance in the field of ternary material battery cells, making them suitable for users who pursue high energy density. Meanwhile, brands such as Lishen and AVIC also offer a variety of battery cell specifications to meet different needs.

1、 Comparison of Cell Types and Core Technologies

The current electric vehicle battery cells are mainly divided into three technical routes, each with its own advantages, disadvantages, and applicable scenarios:

Technological Trends:

• Solid state batteries: Toyota, QuantumScape and other companies plan to mass produce them by 2027 with an energy density of over 400Wh/kg, but the cost is high and they will be initially applied to high-end car models.

• Sodium ion battery: Yadea and Chaowei have released sodium battery electric vehicles, with a cost as low as 0.35 yuan/Wh, which may become the mainstream of economical models by 2025.

2、 The Influence of Cell Shape on Performance

The shape of the battery cell directly affects the space utilization, heat dissipation performance, and safety of the battery pack

case

• Tesla 4680 large cylindrical battery: reduces internal resistance and increases charging speed by 30% through the design of stepless ears, but the mass production yield still needs to be optimized.
• CATL CTP 3.0 technology: Square cells are directly integrated into the battery pack, with a volume utilization rate exceeding 72% and an energy density of 255Wh/kg.

3、 Analysis of Key Performance Indicators

1. Energy density:
   • Directly affecting the range, ternary material battery cells are about 30% -50% higher than lithium iron phosphate.
   • Calculation formula: Range ≈ Battery energy (Wh) ÷ Motor power (W) × Average speed (km/h).
2. Cycle life:
   • Lithium iron phosphate can achieve over 3000 cycles, ternary materials can achieve around 1000-1500 cycles, and lithium titanate can achieve over 8000 cycles.
   • Attenuation pattern: The first 80% of the lifespan decays smoothly, while the last 20% decreases rapidly. It is recommended to keep a remaining 20%.
3. Security:
   • The thermal runaway temperature of lithium iron phosphate reaches 800 ℃, while that of ternary materials is about 200-300 ℃.
   • Safety design: CID (current cut-off device), explosion-proof valve, and aluminum shell strength (7000 series aluminum alloy) are key indicators.
4. Cost:
   • Lithium iron phosphate costs about 0.6 yuan/Wh, ternary materials cost about 0.8 yuan/Wh, and the mass production target for sodium ion batteries is 0.35 yuan/Wh.
   • Cost reduction path: CTC (Cell to Chassis) technology reduces structural components and can reduce costs by 15% -20%.

4、 Brand and Product Recommendations

Purchase suggestion:

• Daily commuting: Prioritize choosing lithium iron phosphate or lithium manganese oxide, balancing safety and cost.
• Long distance cycling: Choose ternary materials or sodium ion batteries to balance energy density and low-temperature performance.
• High frequency use: Consider lithium titanate or square battery cells to improve cycle life and fast charging capability.

5、 Future Trends: Prospects for Battery Cell Technology in 2025

1. Material Innovation:
   • Rich lithium manganese based positive electrode: energy density exceeding 350Wh/kg, expected to be applied in small quantities by 2025.
   • Silicon carbon negative electrode: Capacity increased by 10 times, already used in Tesla 4680 battery.
2. Structural innovation:
   • CTC technology: Integration of battery cells and chassis, with a volume utilization rate of over 70%.
   • Blade Battery 2.0: Thickness reduced to 2mm, suitable for more car models.
3. Intelligent management:
   • Battery Health (SOH) Prediction: Real time monitoring through AI algorithms to extend lifespan.
   • Wireless BMS: Reduce wiring harness by 80% and improve reliability.

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