Why do Automotive battery aluminum case carry a positive charge? Understand the principle in one article

The lattice structure of aluminum metal is highly matched with the size of lithium ions, making it easy to form lithium aluminum alloys with Li ⁺, thereby causing severe electrochemical corrosion. Once lithium is embedded in the Aluminum shell of a lithium battery, it will gradually generate products such as lithium oxide and lithium hydroxide, which will further react with CO ₂ in the air to produce substances such as lithium carbonate, ultimately leading to battery failure. From the perspective of potential, the lithium insertion potential of aluminum is about 0.3V (vs Li ⁺/Li), which is higher than the 0.01-0.2V of graphite negative electrode. If the potential of Aluminum case for new energy carriers is low, it will preferentially insert lithium than graphite, causing irreversible corrosion of the shell. Therefore, it is necessary to control the aluminum shell potential of lithium batteries above the lithium insertion potential in order to prevent corrosion from the root cause.

From the perspective of standard electrode potential, aluminum has strong reducibility and is easily oxidized and dissolved in electrolyte environment, forming corrosion points that seriously threaten the structure and safety of batteries. However, the positive electrode of lithium-ion batteries is at a high potential of 3V-4.5V or higher during charging. At this potential, the Lithium battery aluminum case will quickly generate a dense, stable, and insulating aluminum oxide passivation film, which can prevent the shell from continuing to be oxidized and dissolved, achieving long-term stable operation. That is to say, placing the aluminum casing of a lithium battery at a high positive potential can actually utilize the passivation effect to achieve self-protection.

If LiFePO4 battery pack do not conduct with the positive electrode, there will be a significant potential difference between the positive electrode and the shell inside the battery. This potential difference will form a weak current through the electrolyte, causing sustained micro short circuits and self discharges, which will reduce the battery capacity and cycle life in the long run. After connecting the New energy aluminum battery cases to the positive electrode equipotential, there is no potential difference between the shell and the positive electrode, which can significantly reduce internal leakage and side reactions, improve battery consistency and service life, and simplify the monitoring and protection logic of the battery management system.

It should be clarified that the Battery shell itself is not "actively positively charged", but is directly connected to the positive terminal of the battery in its structural design, maintaining the same potential. This design comprehensively solves key problems such as lithium insertion in the aluminum shell of lithium batteries, electrochemical corrosion, passivation protection, and potential difference leakage. It not only leverages the advantages of lightweight aluminum, high thermal conductivity, easy molding, and moderate cost, but also maximizes the safety, reliability, and lifespan of the battery. This is also the core reason why square EV car battery housings commonly adopt this solution.

If you need to customize or purchase Automotive battery aluminum cases, please feel free to consult and communicate at any time. We will provide you with professional technical support and product solutions.