In the positive electrode sheet of lithium batteries, the aluminum foil current collector is in direct contact with the nickel cobalt manganese ternary positive electrode material. During normal operation, this interface is stable and reliable - aluminum foil for conductivity and active material for energy storage, each performing their respective duties.

But when the battery experiences thermal runaway, the problem arises. The melting point of aluminum foil is only about 650 ℃, while the thermal runaway temperature of ternary lithium batteries can reach over 1000 ℃. At this temperature, the aluminum foil rapidly melts, and liquid aluminum infiltrates into the positive electrode material, undergoing a violent aluminum thermal reaction with nickel cobalt manganese oxide. Related studies have shown that nickel, cobalt, and manganese oxides can undergo aluminum thermal reactions with aluminum under certain conditions, rapidly releasing a large amount of heat. In the military industry, aluminum thermal combustion bombs are usually prepared by mixing nickel oxides, cobalt oxides, and manganese oxides with aluminum powder.

According to statistics on electric vehicle accidents in China, 86% of electric vehicles that have experienced spontaneous combustion accidents use NCM ternary lithium-ion batteries. The aluminum thermal reaction is the fundamental reason for the fast heat release rate and high heat release during the fire process of NCM ternary batteries.

2、 How titanium layer "blocks" aluminum thermal reaction: Understanding the value of titanium plating from the perspective of materials science

Titanium (Ti) is a transition metal with a melting point of up to about 1500 ℃, which is more than twice the melting point of aluminum (about 650 ℃). Adding a titanium plating layer between aluminum foil and nickel cobalt manganese ternary positive electrode material ensures good conductivity of the electrode sheet while utilizing the significantly higher melting point and less melting characteristics of the titanium plating layer. When thermal runaway occurs inside the battery, it effectively isolates the contact between the nickel cobalt manganese ternary positive electrode material and the aluminum foil layer.

Specifically, the protective mechanism of the titanium plating layer includes three levels:

3、 Magnetron Sputtering Titanium Coating: "Growing" Dense Titanium Layer on Aluminum Foil

The preparation of titanium layer on aluminum foil coated with titanium mainly adopts magnetron sputtering process. There are many methods for vacuum coating, including physical vapor deposition (PVD), chemical vapor deposition (CVD), and sputtering deposition. Among them, physical vapor deposition is a commonly used preparation method - coating the film material on the substrate surface under vacuum conditions.

The core issue that needs to be addressed when depositing titanium coatings on aluminum foil by magnetron sputtering is interfacial adhesion. Aluminum is prone to form a dense and insulating natural oxide film (Al ₂ O3) in the air, which cannot form a strong metal bond with the titanium layer. Research has shown that only by using composite ion plasma technology, including ion beam preliminary sputtering of aluminum surfaces, deposition of dense intermediate layers with ion assistance in DC magnetron discharge, and deposition of additional layers in molten cathode magnetron discharge, can corrosion-resistant dense coatings be obtained.

4、 Core properties of aluminum foil coated with titanium

5、 Core application scenarios: from battery safety to electromagnetic protection

6、 Advanced Institute Technology's aluminum foil titanium plating capability

Advanced Institute (Shenzhen) Technology Co., Ltd. was established in 2016 and is a national high-tech enterprise specializing in shielding materials, absorbing materials, flexible substrate coatings, and precious metal pastes. The company has independently built a magnetron sputtering and vacuum evaporation production line, using roll to roll continuous production technology, which can achieve precise deposition of metal layers on the surface of metal substrates such as aluminum foil.

In the field of aluminum foil titanium plating, Advanced Institute Technology provides the following core capabilities:

7、 Conclusion

The essence of aluminum foil coated with titanium is to establish a unified material solution between "lightweight and low-cost aluminum" and "high melting point and corrosion resistance of titanium". It is not replacing aluminum with titanium, but building a high melting point "high-temperature barrier" on the surface of aluminum foil - blocking the aluminum thermal reaction when the battery loses control, resisting oxidation erosion in corrosive environments, and providing a weldable interface in welding scenarios.

From the thermal safety barrier of lithium battery positive electrode current collector to the long-term protection of anti-corrosion packaging, from the conductive substrate of electromagnetic shielding to the high-temperature wear-resistant coating of aerospace - aluminum foil titanium plating is unifying the seemingly contradictory engineering goals of "lightweight" and "high reliability" in one material solution. Understanding the process logic of aluminum foil titanium plating - why plasma pretreatment is needed, why the melting point characteristics of the titanium layer are the core value, and how thickness affects performance - can reveal the technical essence of this material more than simply comparing parameters.