A user's smartphone loses its charge rapidly. The user also notices that the phone feels thicker than it was when it was new. Which of the following is the most likely cause of the issue?

The combination of rapid battery discharge and a physical change in the phone's thickness are classic symptoms of a failing lithium-ion battery. As these batteries age or become damaged, their internal chemical components can break down, producing gas. This gas buildup causes the flexible battery pouch to swell or bulge, making the device feel thicker. Concurrently, the battery's ability to hold a charge diminishes significantly, leading to rapid power loss. This condition is a critical failure and poses a safety risk.

B. Malware infection: Malware can cause rapid battery drain by consuming system resources, but it cannot cause the physical swelling of the battery.
C. Damaged charge port: A faulty charge port would prevent or hinder the phone from charging properly but would not cause rapid discharge or physical swelling.
D. Poor connectivity: While a device constantly searching for a cellular or Wi-Fi signal will drain the battery faster, this is a software/reception issue and does not cause the battery to swell.

1. Princeton University

Environmental Health and Safety. "Safety: Lithium-Ion Batteries." This official university safety guide identifies key signs of battery failure. It states

"Signs that a battery may be failing

damaged

and/or unsafe include... Swelling

bulging

or puffiness of the battery or device." This directly links the physical symptom in the question to a bad battery.

Source: Princeton University EHS

Lithium-Ion Batteries Safety Page.

2. Wang

Q.

Mao

B.

Stoliarov

S. I.

& Sun

J. (2019). A review of lithium ion battery failure mechanisms and fire prevention strategies. Progress in Energy and Combustion Science

73

95-131. This peer-reviewed article details battery failure modes. Section 3.1

"Gas generation

" explains that electrochemical side reactions produce gases like H₂

CO

CO₂

and C₂H₄

which "leads to the swelling of the cell and the increase of the internal pressure." This academic source confirms swelling is a direct result of internal battery failure.

DOI: https://doi.org/10.1016/j.pecs.2019.03.002 (Page 99

Section 3.1)

3. University of Michigan

Environment

Health & Safety. "Lithium-Ion Battery Safety." This institutional guide provides safety protocols for handling lithium-ion batteries. Under the section "Signs of a Damaged Battery

" it explicitly lists "A swollen or puffy battery" as a primary indicator of damage

reinforcing that this symptom points directly to a faulty battery.

Source: University of Michigan EHS

Lithium-Ion Battery Safety Guide.