What makes GM's Ultium electric vehicle platform unique

Not only is it compatible with different battery capacities, but it is also compatible with various chemical systems, such as lithium iron phosphate, ternary lithium battery, and future lithium metal battery and solid-state battery.

This article will detail the unique features of the Ultium electric vehicle platform battery system design.

The following is a simple table showing what makes GM’s Ultium electric vehicle platform unique：

Battery structure design

One of the most important features of the Ultium electric vehicle platform’s battery system design is its emphasis on safety.

The battery pack must not only meet the basic requirements of the China’s national standards, but also because in actual use, various extreme scenarios may be encountered. Although these scenarios are rare, they are very dangerous once they occur.

Unique to the Ultium battery platform is the “steel armor” design of the battery pack. This design adopts a high-strength “well”-shaped frame structure, of which ultra-high-strength steel accounts for 37.5%, while high-strength steel accounts for about 61%.

This makes the anti-extrusion performance of the battery pack three times that required by the national standard.

The beam inside the battery pack and the side protection beam of the upper cover assembly are made of 1500MPa ultra-high-strength steel, and the tray assembly is made of 10000MPa bottom protection.

This design not only improves the safety of the battery, but also enhances the torsional stiffness of the vehicle by about 45.8%, making the torsional stiffness of the vehicle with the battery pack reach 35kNm degrees, making the battery pack stronger and safer.

Battery thermal management design

Another key feature of the Ultium electric vehicle platform’s battery system design is its battery thermal management design, which is divided into vehicle thermal management and management in the case of extreme thermal runaway.

The battery system reaches a safe bottom line under extreme working conditions, ensuring not only the safety of the whole vehicle but also the passengers in the vehicle having enough time to evacuate under particularly extreme conditions.

In addition, the Ultium battery platform has many safety-related technologies that have been very successful in the past designs.

The transfer of these technologies is also reflected in the battery packs with new battery formulas, including integrated liquid cooling systems and fast exhaust channels, arc prevention, explosion-proof valve, and battery health intelligent monitoring system combining both ends of “vehicle-cloud”, etc.

Cell design

For automobile companies, power batteries are the core components of electric vehicles.

To design an excellent electric vehicle platform, it is necessary to start from the core technical indicators, usually including capacity, energy, energy density, high and low temperature characteristics, charge and discharge rate and pulse power characteristics, etc.

The Buick E4 uses lithium iron phosphate batteries exclusively for the Ultium electric vehicle platform. The platform’s cell design is optimized for high performance and energy efficiency.

Its positive stage has been optimized, including the use of 0.6μm lithium iron phosphate particles, which are finer than the industry’s common 1μm. This leads to a higher specific surface area, which can reduce the internal resistance by 5% and increase the charge and discharge power.

At the same time, the optimization also includes a newly designed carbon coating technology to improve conductivity and achieve better charging and discharging power. The energy density is increased by 11% by applying the combination technology of large and small particles;

Negative stages have also been optimized. Including the use of high-capacity graphite anode, which can increase the power by 2%. In-situ construction of ion transmission fast channels improves fast charging performance by 15%.

Adopt wide-width multi-point coating process, micron-level whole-process monitoring, and more uniform pole pieces to ensure high consistency of batteries.

SAIC General Motors and PATAC Automotive Technology Center are deeply involved in the formulation and optimization of battery material system formula, manufacturing process, performance evaluation, safety abuse and other aspects.

Based on GM’s globally unified battery safety and performance standards, the Ultium electric vehicle platform exclusive lithium iron phosphate battery cell has been developed.

This cell is famous for its high thermal stability, powerful charging and discharging power, low attenuation and long life, and it also assists lithium battery manufacturers to jointly optimize technical standards and improve product processing technology.

Battery test

Finally, SAIC GM’s extensive testing process ensures the safety and reliability of the battery pack. SAIC GM can test 96 cell samples at the same time in the single battery test laboratory, and 6 test samples at the same time in the battery pack test laboratory.

The test items of the single battery mainly include temperature testing (minus 40°C~85°C C) and charge and discharge test, cycle life, safety, consistency, reliability and other indicators.

In the cell/battery pack test and certification process, 100% cell DCR (DC internal resistance) test, drop test, extrusion test, acupuncture test and other inspections are performed to ensure the safety of the cell/battery pack.

Through these tests, design engineers can know more clearly where the characteristics of a battery are, and how to improve the details.

Summary

In today’s market, in order to achieve the goal of light weight, most of the battery packs of  top 10 power battery companies in the world will choose aluminum as the main structural material; in terms of the structural design goals of the battery pack, energy density is also placed first.

However, SAIC-GM’s Ultium electric vehicle platform adheres to the concept of safety and insists on using steel consistently.

With the popularization of electric vehicles, battery manufacturers and car companies pay more and more attention to the safety performance of batteries, so we foresee that the structural strength of battery packs will also be paid more and more attention.

In addition to being unique in terms of safety, the Ultium electric vehicle platform also features strong compatibility in the design of its battery modules. The introduction of the blade battery further boosts its energy efficiency and safety performance.

SAIC GM’s Ultium electric vehicle platform’s new cell formula battery pack not only demonstrates its safety and comprehensiveness, but also demonstrates its forward-looking and adaptability.