In recent years, the official figures for NEV driving range and battery energy density have been continuously refreshed. However, many may not realize that these improvements do not entirely stem from breakthroughs in electrochemical systems—iterations in cathode materials, anode materials, and electrolytes often take years. More direct changes have occurred at the structural level inside battery packs.
CTM, CTP, CTB, and CTC represent several technological routes where battery integration levels continue to increase. Their common logic is simple: reduce intermediate layers to "stuff" the battery more tightly into the auto body. But the trade-offs between space utilization, manufacturing cost, and repairability vary from one generation to the next.
1. CTM (Cell to Module): The Traditional "Layered Doll" Approach
In the early stages of NEV development, battery pack assembly followed a relatively conservative approach. Battery cells were first assembled into modules, the modules were then arranged into a battery pack, and finally, the battery pack was fixed under the vehicle floor. Battery cell → module → battery pack → auto body formed four independent layers.
The pros and cons of this solution were clear. The advantage was repair convenience—a faulty module could be replaced individually without touching the entire battery pack. Simultaneously, the module casing provided additional protection for the cells, leading to relatively mature structural safety. But the cost was just as direct: module casings, connectors, and cooling pipes took up significant space, resulting in a space utilization rate of only about 40% inside the battery pack. This meant that, for the same volume, the CTM solution could hold the fewest battery cells, limiting its driving range potential.
CTM was the industry's default choice for a long time because it aligned with the traditional automotive supply chain's division of labor—battery enterprises supplied modules, and automakers handled integration. But this division also created a structural ceiling: the volumetric utilization rate of the battery pack was difficult to break through.
2. CTP (Cell to Pack): Eliminating the "Middleman"
The core modification in CTP was skipping the module layer, allowing cells to directly form the battery pack; space utilization improved from around 40% to over 70%. Simultaneously, by reducing module casings, connectors, and fasteners, the number of battery pack parts decreased, leading to lower manufacturing costs.
Two different technological choices for CTP implementation existed in the industry.
One was the thoroughly module-free solution represented by BYD's blade battery. By shaping cells into long strips and arranging them directly into the battery pack, supported by a honeycomb-like structure, it enhanced space utilization while also assuming some structural functions. The other was the highly integrated solution represented by CATL's CTP 3.0 (Qilin battery). It combined cells with multi-functional elastic interlayers into integrated energy units and integrated components like crossbeams, longitudinal beams, water-cooling plates, and thermal pads to further optimize internal layout and thermal management. The Qilin battery achieved a volumetric utilization rate of 72% and a system energy density of 255 Wh/kg.
From a market penetration perspective, CTP has achieved a dominant mainstream position. Mainstream NEV manufacturers in China have launched mass-produced car models equipped with CTP solutions, ranging from independent brands to joint ventures, covering a broad price range from entry-level to high-end products. Meanwhile, the market share of traditional CTM solutions continues to shrink, currently remaining only in some micro-vehicles or specific export models. Overall, CTP has become the most prevalent battery integration technology route at the current stage.
3. CTB and CTC: The Battery Becomes Part of the Auto Body
The concept behind CTB (Cell to Body) is to merge the battery pack's top cover with the vehicle floor. Cells are installed directly onto the vehicle floor, eliminating the need for a separate battery pack top cover. One of the main benefits of this solution is freeing up vertical space, allowing for a more spacious cabin or creating conditions to lower the vehicle's stance. Simultaneously, when the battery pack participates in bearing vehicle loads, torsional stiffness can increase by over 70%.
BYD's Seal series and Xiaomi's Pengcheng series are representative models featuring CTB solutions. BYD officially announced that the Seal's body torsional stiffness reached 40,500 N·m/°. Xiaomi Auto announced a CTB battery volumetric efficiency of 77.8%.
CTC (Cell to Chassis) goes a step further, integrating the battery system more deeply with the chassis or underbody, further blurring the structural boundary of the battery pack as an independent assembly. In some solutions, the battery system is also integrated collaboratively with thermal management, electric drive, and high/low-voltage control modules. Representative examples of this approach include the Tesla Model Y (Texas factory version) and the Leapmotor C10 equipped with the CTC 2.0 Plus solution.
The technical goals of CTB and CTC are aligned—exchanging space utilization and body stiffness through structural integration. The difference between the two routes is more apparent in engineering implementation: CTB simplifies on top of the existing body architecture, retaining a relatively independent chassis frame; CTC treats the chassis and battery as a single whole from the outset, placing higher demands on the vehicle platform's upfront definition.
Market data indicates that while CTB and CTC are still in the relatively early stages of penetrating from the high-end to the mass market, this technological route has begun to filter down to lower price brackets. The 2026 MG4 brought CTB technology down to the price range of 60,000 to 100,000 yuan, showing that structural integration solutions are no longer exclusive to high-end car models.
Concerns Over Structural Integration Solutions
The most direct challenge facing CTB and CTC structural integration solutions is repair economics.
In traditional CTM solutions, some faults could be repaired by replacing the module. After CTP eliminated modules, the battery pack could usually still be removed as an independent assembly, but the smallest repairable unit and repair difficulty on-site depended on the specific structure. CTB and CTC, however, further increase the degree of integration between the battery and auto body, potentially increasing the difficulty of disassembly, detection, and damage assessment.
According to industry estimates, the single-occurrence repair cost for a CTB/CTC solution is 3 to 5 times that of a CTP solution under the same damage conditions. This poses new challenges for insurance companies, the repair system, and the residual value management of used cars. Currently, some automakers, when promoting CTB solutions, simultaneously launch supporting services like "battery-body integrated warranty" or "chassis armor" to alleviate consumer concerns, but this issue has not yet formed a standardized solution at the industry level.
Additionally, CTB and CTC solutions demand significantly higher vehicle manufacturing precision and after-sales detection equipment. Once the battery is integrated with the body, the removal process involves disassembling and reassembling structural body parts, requiring potential upgrades to traditional 4S shops' repair equipment and technical capabilities, involving the restructuring costs of the entire after-sales system.
Evolutionary Direction
From CTM to CTP, and then to CTB and CTC, the evolutionary direction of battery pack integration technology is clear—fewer layers lead to higher space efficiency and greater body stiffness. This is a forward path driven by space efficiency and manufacturing costs.
But this trend is not a linear acceleration. For CTB and CTC to achieve large-scale adoption, besides engineering breakthroughs, simultaneous progress is needed in supporting systems like repair standards, insurance pricing, and used car evaluation. Based on current industry data, CTP will continue to hold its mainstream position, while the penetration rate of CTB/CTC will depend on two variables: the degree of standardization in structural integration solutions and the pace at which repair costs and insurance systems adapt.