Battery Fundamentals & Electrochemistry Flashcards
7 cards from real BMS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Battery Fundamentals & Electrochemistry flashcards as text
What is the primary function of the solid electrolyte interphase (SEI) layer on the graphite anode?
Answer: To passivate the anode surface and prevent continued electrolyte decomposition
The SEI forms during initial cycles as electrolyte decomposes on the graphite surface, creating a passivating layer that stabilizes the electrode and prevents further electrolyte reduction.
Which parameter defines the theoretical maximum charge a battery electrode material can store per unit mass?
Answer: Specific capacity (mAh/g)
Specific capacity (mAh/g) is calculated from Faraday's law based on the number of electrons transferred per formula unit and the molecular weight of the active material.
During the charging of a lithium-ion cell, where does oxidation occur?
Answer: At the cathode, which loses lithium ions and electrons
During charging, the cathode is oxidized as it releases Li⁺ ions into the electrolyte and gives up electrons to the external circuit.
What does a flat open-circuit voltage (OCV) curve as a function of state of charge (SOC) indicate about a battery chemistry?
Answer: The cathode material undergoes a two-phase reaction during lithiation
A flat OCV plateau indicates a two-phase coexistence reaction (e.g., LFP) where voltage is thermodynamically pinned until one phase is fully consumed.
What is the significance of the transference number in battery electrolytes?
Answer: It defines the fraction of ionic current carried by lithium ions versus all ions
The lithium transference number (t⁺) indicates what fraction of total ionic current is carried by Li⁺; a higher value reduces concentration polarization and improves rate capability.
Which electrochemical reaction correctly describes the full cell reaction in a nickel-metal hydride (NiMH) battery during discharge?
Answer: MH + NiOOH → M + Ni(OH)₂
During NiMH discharge, the metal hydride (MH) anode is oxidized, releasing H⁺ while NiOOH at the cathode is reduced to Ni(OH)₂, producing usable electrical energy.
What is the purpose of a formation cycle in lithium-ion battery manufacturing?
Answer: To intentionally form the SEI layer and condition the cell to its rated capacity
Formation cycling applies controlled charge-discharge cycles at low C-rates to deliberately grow a stable SEI layer, which determines long-term capacity and cycle life.